Adding upstream version 1:115.7.0.upstream/1%115.7.0upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

213 files changed, 43969 insertions, 0 deletions

diff --git a/toolkit/xre/AssembleCmdLine.h b/toolkit/xre/AssembleCmdLine.h
new file mode 100644
index 0000000000..d969fedfed
--- /dev/null
+++ b/toolkit/xre/AssembleCmdLine.h
@@ -0,0 +1,139 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_AssembleCmdLine_h
+#define mozilla_AssembleCmdLine_h
+
+#if defined(XP_WIN)
+
+#  include "mozilla/UniquePtr.h"
+
+#  include <stdlib.h>
+#  include <windows.h>
+
+#  ifdef MOZILLA_INTERNAL_API
+#    include "nsString.h"
+#  endif  // MOZILLA_INTERNAL_API
+
+namespace mozilla {
+
+// Out param `aWideCmdLine` must be free()d by the caller.
+inline int assembleCmdLine(const char* const* aArgv, wchar_t** aWideCmdLine,
+                           UINT aCodePage) {
+  const char* const* arg;
+  char* p;
+  const char* q;
+  char* cmdLine;
+  int cmdLineSize;
+  int numBackslashes;
+  int i;
+  int argNeedQuotes;
+
+  /*
+   * Find out how large the command line buffer should be.
+   */
+  cmdLineSize = 0;
+  for (arg = aArgv; *arg; ++arg) {
+    /*
+     * \ and " need to be escaped by a \.  In the worst case,
+     * every character is a \ or ", so the string of length
+     * may double.  If we quote an argument, that needs two ".
+     * Finally, we need a space between arguments, and
+     * a null byte at the end of command line.
+     */
+    cmdLineSize += 2 * strlen(*arg) /* \ and " need to be escaped */
+                   + 2              /* we quote every argument */
+                   + 1;             /* space in between, or final null */
+  }
+  p = cmdLine = (char*)malloc(cmdLineSize * sizeof(char));
+  if (!p) {
+    return -1;
+  }
+
+  for (arg = aArgv; *arg; ++arg) {
+    /* Add a space to separates the arguments */
+    if (arg != aArgv) {
+      *p++ = ' ';
+    }
+    q = *arg;
+    numBackslashes = 0;
+    argNeedQuotes = 0;
+
+    /*
+     * If the argument is empty or contains white space, it needs to
+     * be quoted.
+     */
+    if (**arg == '\0' || strpbrk(*arg, " \f\n\r\t\v")) {
+      argNeedQuotes = 1;
+    }
+
+    if (argNeedQuotes) {
+      *p++ = '"';
+    }
+    while (*q) {
+      if (*q == '\\') {
+        numBackslashes++;
+        q++;
+      } else if (*q == '"') {
+        if (numBackslashes) {
+          /*
+           * Double the backslashes since they are followed
+           * by a quote
+           */
+          for (i = 0; i < 2 * numBackslashes; i++) {
+            *p++ = '\\';
+          }
+          numBackslashes = 0;
+        }
+        /* To escape the quote */
+        *p++ = '\\';
+        *p++ = *q++;
+      } else {
+        if (numBackslashes) {
+          /*
+           * Backslashes are not followed by a quote, so
+           * don't need to double the backslashes.
+           */
+          for (i = 0; i < numBackslashes; i++) {
+            *p++ = '\\';
+          }
+          numBackslashes = 0;
+        }
+        *p++ = *q++;
+      }
+    }
+
+    /* Now we are at the end of this argument */
+    if (numBackslashes) {
+      /*
+       * Double the backslashes if we have a quote string
+       * delimiter at the end.
+       */
+      if (argNeedQuotes) {
+        numBackslashes *= 2;
+      }
+      for (i = 0; i < numBackslashes; i++) {
+        *p++ = '\\';
+      }
+    }
+    if (argNeedQuotes) {
+      *p++ = '"';
+    }
+  }
+
+  *p = '\0';
+  int numChars = MultiByteToWideChar(aCodePage, 0, cmdLine, -1, nullptr, 0);
+  *aWideCmdLine = (wchar_t*)malloc(numChars * sizeof(wchar_t));
+  MultiByteToWideChar(aCodePage, 0, cmdLine, -1, *aWideCmdLine, numChars);
+  free(cmdLine);
+  return 0;
+}
+
+}  // namespace mozilla
+
+#endif  // defined(XP_WIN)
+
+#endif  // mozilla_AssembleCmdLine_h
diff --git a/toolkit/xre/AutoSQLiteLifetime.cpp b/toolkit/xre/AutoSQLiteLifetime.cpp
new file mode 100644
index 0000000000..4500ec1bfe
--- /dev/null
+++ b/toolkit/xre/AutoSQLiteLifetime.cpp
@@ -0,0 +1,156 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsDebug.h"
+#include "AutoSQLiteLifetime.h"
+#include "sqlite3.h"
+
+#ifdef MOZ_MEMORY
+#  include "mozmemory.h"
+#  ifdef MOZ_DMD
+#    include "nsIMemoryReporter.h"
+#    include "DMD.h"
+
+namespace mozilla {
+namespace storage {
+extern mozilla::Atomic<size_t> gSqliteMemoryUsed;
+}
+}  // namespace mozilla
+
+using mozilla::storage::gSqliteMemoryUsed;
+
+#  endif
+
+namespace {
+
+// By default, SQLite tracks the size of all its heap blocks by adding an extra
+// 8 bytes at the start of the block to hold the size.  Unfortunately, this
+// causes a lot of 2^N-sized allocations to be rounded up by jemalloc
+// allocator, wasting memory.  For example, a request for 1024 bytes has 8
+// bytes added, becoming a request for 1032 bytes, and jemalloc rounds this up
+// to 2048 bytes, wasting 1012 bytes.  (See bug 676189 for more details.)
+//
+// So we register jemalloc as the malloc implementation, which avoids this
+// 8-byte overhead, and thus a lot of waste.  This requires us to provide a
+// function, sqliteMemRoundup(), which computes the actual size that will be
+// allocated for a given request.  SQLite uses this function before all
+// allocations, and may be able to use any excess bytes caused by the rounding.
+//
+// Note: the wrappers for malloc, realloc and moz_malloc_usable_size are
+// necessary because the sqlite_mem_methods type signatures differ slightly
+// from the standard ones -- they use int instead of size_t.  But we don't need
+// a wrapper for free.
+
+#  ifdef MOZ_DMD
+
+// sqlite does its own memory accounting, and we use its numbers in our memory
+// reporters.  But we don't want sqlite's heap blocks to show up in DMD's
+// output as unreported, so we mark them as reported when they're allocated and
+// mark them as unreported when they are freed.
+//
+// In other words, we are marking all sqlite heap blocks as reported even
+// though we're not reporting them ourselves.  Instead we're trusting that
+// sqlite is fully and correctly accounting for all of its heap blocks via its
+// own memory accounting.  Well, we don't have to trust it entirely, because
+// it's easy to keep track (while doing this DMD-specific marking) of exactly
+// how much memory SQLite is using.  And we can compare that against what
+// SQLite reports it is using.
+
+MOZ_DEFINE_MALLOC_SIZE_OF_ON_ALLOC(SqliteMallocSizeOfOnAlloc)
+MOZ_DEFINE_MALLOC_SIZE_OF_ON_FREE(SqliteMallocSizeOfOnFree)
+
+#  endif
+
+static void* sqliteMemMalloc(int n) {
+  void* p = ::malloc(n);
+#  ifdef MOZ_DMD
+  gSqliteMemoryUsed += SqliteMallocSizeOfOnAlloc(p);
+#  endif
+  return p;
+}
+
+static void sqliteMemFree(void* p) {
+#  ifdef MOZ_DMD
+  gSqliteMemoryUsed -= SqliteMallocSizeOfOnFree(p);
+#  endif
+  ::free(p);
+}
+
+static void* sqliteMemRealloc(void* p, int n) {
+#  ifdef MOZ_DMD
+  gSqliteMemoryUsed -= SqliteMallocSizeOfOnFree(p);
+  void* pnew = ::realloc(p, n);
+  if (pnew) {
+    gSqliteMemoryUsed += SqliteMallocSizeOfOnAlloc(pnew);
+  } else {
+    // realloc failed;  undo the SqliteMallocSizeOfOnFree from above
+    gSqliteMemoryUsed += SqliteMallocSizeOfOnAlloc(p);
+  }
+  return pnew;
+#  else
+  return ::realloc(p, n);
+#  endif
+}
+
+static int sqliteMemSize(void* p) { return ::moz_malloc_usable_size(p); }
+
+static int sqliteMemRoundup(int n) {
+  n = malloc_good_size(n);
+
+  // jemalloc can return blocks of size 2 and 4, but SQLite requires that all
+  // allocations be 8-aligned.  So we round up sub-8 requests to 8.  This
+  // wastes a small amount of memory but is obviously safe.
+  return n <= 8 ? 8 : n;
+}
+
+static int sqliteMemInit(void* p) { return 0; }
+
+static void sqliteMemShutdown(void* p) {}
+
+const sqlite3_mem_methods memMethods = {
+    &sqliteMemMalloc,  &sqliteMemFree, &sqliteMemRealloc,  &sqliteMemSize,
+    &sqliteMemRoundup, &sqliteMemInit, &sqliteMemShutdown, nullptr};
+
+}  // namespace
+
+#endif  // MOZ_MEMORY
+
+namespace mozilla {
+
+AutoSQLiteLifetime::AutoSQLiteLifetime() {
+  if (++AutoSQLiteLifetime::sSingletonEnforcer != 1) {
+    MOZ_CRASH("multiple instances of AutoSQLiteLifetime constructed!");
+  }
+
+#ifdef MOZ_MEMORY
+  sResult = ::sqlite3_config(SQLITE_CONFIG_MALLOC, &memMethods);
+#else
+  sResult = SQLITE_OK;
+#endif
+
+  if (sResult == SQLITE_OK) {
+    // TODO (bug 1191405): do not preallocate the connections caches until we
+    // have figured the impact on our consumers and memory.
+    sqlite3_config(SQLITE_CONFIG_PAGECACHE, NULL, 0, 0);
+
+    // Explicitly initialize sqlite3.  Although this is implicitly called by
+    // various sqlite3 functions (and the sqlite3_open calls in our case),
+    // the documentation suggests calling this directly.  So we do.
+    sResult = ::sqlite3_initialize();
+  }
+}
+
+AutoSQLiteLifetime::~AutoSQLiteLifetime() {
+  // Shutdown the sqlite3 API.  Warn if shutdown did not turn out okay, but
+  // there is nothing actionable we can do in that case.
+  sResult = ::sqlite3_shutdown();
+  NS_WARNING_ASSERTION(sResult == SQLITE_OK,
+                       "sqlite3 did not shutdown cleanly.");
+}
+
+int AutoSQLiteLifetime::sSingletonEnforcer = 0;
+int AutoSQLiteLifetime::sResult = SQLITE_MISUSE;
+
+}  // namespace mozilla
diff --git a/toolkit/xre/AutoSQLiteLifetime.h b/toolkit/xre/AutoSQLiteLifetime.h
new file mode 100644
index 0000000000..26f8d976b2
--- /dev/null
+++ b/toolkit/xre/AutoSQLiteLifetime.h
@@ -0,0 +1,24 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_AutoSQLiteLifetime_h
+#define mozilla_AutoSQLiteLifetime_h
+
+namespace mozilla {
+
+class AutoSQLiteLifetime final {
+ private:
+  static int sSingletonEnforcer;
+  static int sResult;
+
+ public:
+  AutoSQLiteLifetime();
+  ~AutoSQLiteLifetime();
+  static int getInitResult() { return AutoSQLiteLifetime::sResult; }
+};
+
+}  // namespace mozilla
+
+#endif
diff --git a/toolkit/xre/Bootstrap.cpp b/toolkit/xre/Bootstrap.cpp
new file mode 100644
index 0000000000..b81fde839b
--- /dev/null
+++ b/toolkit/xre/Bootstrap.cpp
@@ -0,0 +1,117 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/Bootstrap.h"
+#include "nsXPCOM.h"
+
+#include "AutoSQLiteLifetime.h"
+
+#ifdef MOZ_WIDGET_ANDROID
+#  ifdef MOZ_PROFILE_GENERATE
+extern "C" int __llvm_profile_dump(void);
+#  endif
+#endif
+
+namespace mozilla {
+
+class BootstrapImpl final : public Bootstrap {
+ protected:
+  AutoSQLiteLifetime mSQLLT;
+
+  virtual void Dispose() override { delete this; }
+
+ public:
+  BootstrapImpl() = default;
+
+  ~BootstrapImpl() = default;
+
+  virtual void NS_LogInit() override { ::NS_LogInit(); }
+
+  virtual void NS_LogTerm() override { ::NS_LogTerm(); }
+
+  virtual void XRE_TelemetryAccumulate(int aID, uint32_t aSample) override {
+    ::XRE_TelemetryAccumulate(aID, aSample);
+  }
+
+  virtual void XRE_StartupTimelineRecord(int aEvent,
+                                         mozilla::TimeStamp aWhen) override {
+    ::XRE_StartupTimelineRecord(aEvent, aWhen);
+  }
+
+  virtual int XRE_main(int argc, char* argv[],
+                       const BootstrapConfig& aConfig) override {
+    return ::XRE_main(argc, argv, aConfig);
+  }
+
+  virtual void XRE_StopLateWriteChecks() override {
+    ::XRE_StopLateWriteChecks();
+  }
+
+  virtual int XRE_XPCShellMain(int argc, char** argv, char** envp,
+                               const XREShellData* aShellData) override {
+    return ::XRE_XPCShellMain(argc, argv, envp, aShellData);
+  }
+
+  virtual GeckoProcessType XRE_GetProcessType() override {
+    return ::XRE_GetProcessType();
+  }
+
+  virtual void XRE_SetProcessType(const char* aProcessTypeString) override {
+    ::XRE_SetProcessType(aProcessTypeString);
+  }
+
+  virtual nsresult XRE_InitChildProcess(
+      int argc, char* argv[], const XREChildData* aChildData) override {
+    return ::XRE_InitChildProcess(argc, argv, aChildData);
+  }
+
+  virtual void XRE_EnableSameExecutableForContentProc() override {
+    ::XRE_EnableSameExecutableForContentProc();
+  }
+
+#ifdef MOZ_WIDGET_ANDROID
+  virtual void GeckoStart(JNIEnv* aEnv, char** argv, int argc,
+                          const StaticXREAppData& aAppData, bool xpcshell,
+                          const char* outFilePath) override {
+    ::GeckoStart(aEnv, argv, argc, aAppData, xpcshell, outFilePath);
+  }
+
+  virtual void XRE_SetAndroidChildFds(
+      JNIEnv* aEnv, const XRE_AndroidChildFds& aFds) override {
+    ::XRE_SetAndroidChildFds(aEnv, aFds);
+  }
+
+#  ifdef MOZ_PROFILE_GENERATE
+  virtual void XRE_WriteLLVMProfData() override {
+    __android_log_print(ANDROID_LOG_INFO, "GeckoLibLoad",
+                        "Calling __llvm_profile_dump()");
+    __llvm_profile_dump();
+  }
+#  endif
+#endif
+
+#ifdef LIBFUZZER
+  virtual void XRE_LibFuzzerSetDriver(LibFuzzerDriver aDriver) override {
+    ::XRE_LibFuzzerSetDriver(aDriver);
+  }
+#endif
+
+#ifdef MOZ_ENABLE_FORKSERVER
+  virtual int XRE_ForkServer(int* argc, char*** argv) override {
+    return ::XRE_ForkServer(argc, argv);
+  }
+#endif
+};
+
+extern "C" NS_EXPORT void NS_FROZENCALL
+XRE_GetBootstrap(Bootstrap::UniquePtr& b) {
+  static bool sBootstrapInitialized = false;
+  MOZ_RELEASE_ASSERT(!sBootstrapInitialized);
+
+  sBootstrapInitialized = true;
+  b.reset(new BootstrapImpl());
+}
+
+}  // namespace mozilla
diff --git a/toolkit/xre/Bootstrap.h b/toolkit/xre/Bootstrap.h
new file mode 100644
index 0000000000..9d46bec55b
--- /dev/null
+++ b/toolkit/xre/Bootstrap.h
@@ -0,0 +1,176 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/**
+ * This file represents the only external interface exposed from libxul. It
+ * is used by the various stub binaries (nsBrowserApp, xpcshell,
+ * plugin-container) to initialize XPCOM and start their main loop.
+ */
+
+#ifndef mozilla_Bootstrap_h
+#define mozilla_Bootstrap_h
+
+#include "mozilla/Maybe.h"
+#include "mozilla/ResultVariant.h"
+#include "mozilla/UniquePtr.h"
+#include "mozilla/UniquePtrExtensions.h"
+#include "mozilla/Variant.h"
+#include "nscore.h"
+#include "nsXULAppAPI.h"
+
+#ifdef MOZ_WIDGET_ANDROID
+#  include "jni.h"
+
+namespace mozilla {
+struct StaticXREAppData;
+}
+
+extern "C" NS_EXPORT void GeckoStart(JNIEnv* aEnv, char** argv, int argc,
+                                     const mozilla::StaticXREAppData& aAppData,
+                                     bool xpcshell, const char* outFilePath);
+#endif
+
+#if defined(XP_WIN) && defined(MOZ_SANDBOX)
+namespace sandbox {
+class BrokerServices;
+}
+#endif
+
+namespace mozilla {
+
+struct StaticXREAppData;
+
+struct BootstrapConfig {
+#if defined(XP_WIN) && defined(MOZ_SANDBOX)
+  /* Chromium sandbox BrokerServices. */
+  sandbox::BrokerServices* sandboxBrokerServices;
+#endif
+  /* Pointer to static XRE AppData from application.ini.h */
+  const StaticXREAppData* appData;
+  /* When the pointer above is null, points to the (string) path of an
+   * application.ini file to open and parse.
+   * When the pointer above is non-null, may indicate the directory where
+   * application files are, relative to the XRE. */
+  const char* appDataPath;
+};
+
+/**
+ * This class is virtual abstract so that using it does not require linking
+ * any symbols. The singleton instance of this class is obtained from the
+ * exported method XRE_GetBootstrap.
+ */
+class Bootstrap {
+ protected:
+  Bootstrap() {}
+
+  // Because of allocator mismatches, code outside libxul shouldn't delete a
+  // Bootstrap instance. Use Dispose().
+  virtual ~Bootstrap() {}
+
+  /**
+   * Destroy and deallocate this Bootstrap instance.
+   */
+  virtual void Dispose() = 0;
+
+  /**
+   * Helper class to use with UniquePtr.
+   */
+  class BootstrapDelete {
+   public:
+    constexpr BootstrapDelete() {}
+    void operator()(Bootstrap* aPtr) const { aPtr->Dispose(); }
+  };
+
+ public:
+  typedef mozilla::UniquePtr<Bootstrap, BootstrapDelete> UniquePtr;
+
+  virtual void NS_LogInit() = 0;
+
+  virtual void NS_LogTerm() = 0;
+
+  virtual void XRE_TelemetryAccumulate(int aID, uint32_t aSample) = 0;
+
+  virtual void XRE_StartupTimelineRecord(int aEvent,
+                                         mozilla::TimeStamp aWhen) = 0;
+
+  virtual int XRE_main(int argc, char* argv[],
+                       const BootstrapConfig& aConfig) = 0;
+
+  virtual void XRE_StopLateWriteChecks() = 0;
+
+  virtual int XRE_XPCShellMain(int argc, char** argv, char** envp,
+                               const XREShellData* aShellData) = 0;
+
+  virtual GeckoProcessType XRE_GetProcessType() = 0;
+
+  virtual void XRE_SetProcessType(const char* aProcessTypeString) = 0;
+
+  virtual nsresult XRE_InitChildProcess(int argc, char* argv[],
+                                        const XREChildData* aChildData) = 0;
+
+  virtual void XRE_EnableSameExecutableForContentProc() = 0;
+
+#ifdef MOZ_WIDGET_ANDROID
+  virtual void GeckoStart(JNIEnv* aEnv, char** argv, int argc,
+                          const StaticXREAppData& aAppData, bool xpcshell,
+                          const char* outFilePath) = 0;
+
+  virtual void XRE_SetAndroidChildFds(JNIEnv* aEnv,
+                                      const XRE_AndroidChildFds& fds) = 0;
+#  ifdef MOZ_PROFILE_GENERATE
+  virtual void XRE_WriteLLVMProfData() = 0;
+#  endif
+#endif
+
+#ifdef LIBFUZZER
+  virtual void XRE_LibFuzzerSetDriver(LibFuzzerDriver aDriver) = 0;
+#endif
+
+#ifdef MOZ_ENABLE_FORKSERVER
+  virtual int XRE_ForkServer(int* argc, char*** argv) = 0;
+#endif
+};
+
+enum class LibLoadingStrategy {
+  NoReadAhead,
+  ReadAhead,
+};
+
+#if defined(XP_WIN)
+using DLErrorType = unsigned long;  // (DWORD)
+#else
+using DLErrorType = UniqueFreePtr<char>;
+#endif
+
+using BootstrapError = Variant<nsresult, DLErrorType>;
+
+using BootstrapResult = ::mozilla::Result<Bootstrap::UniquePtr, BootstrapError>;
+
+/**
+ * Creates and returns the singleton instance of the bootstrap object.
+ * @param `b` is an outparam. We use a parameter and not a return value
+ *        because MSVC doesn't let us return a c++ class from a function with
+ *        "C" linkage. On failure this will be null.
+ * @note This function may only be called once and will crash if called again.
+ */
+#ifdef XPCOM_GLUE
+typedef void (*GetBootstrapType)(Bootstrap::UniquePtr&);
+BootstrapResult GetBootstrap(
+    const char* aXPCOMFile = nullptr,
+    LibLoadingStrategy aLibLoadingStrategy = LibLoadingStrategy::NoReadAhead);
+#else
+extern "C" NS_EXPORT void NS_FROZENCALL
+XRE_GetBootstrap(Bootstrap::UniquePtr& b);
+
+inline BootstrapResult GetBootstrap(const char* aXPCOMFile = nullptr) {
+  Bootstrap::UniquePtr bootstrap;
+  XRE_GetBootstrap(bootstrap);
+  return bootstrap;
+}
+#endif
+
+}  // namespace mozilla
+
+#endif  // mozilla_Bootstrap_h
diff --git a/toolkit/xre/CmdLineAndEnvUtils.cpp b/toolkit/xre/CmdLineAndEnvUtils.cpp
new file mode 100644
index 0000000000..634071bc90
--- /dev/null
+++ b/toolkit/xre/CmdLineAndEnvUtils.cpp
@@ -0,0 +1,48 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsCOMPtr.h"
+#include "nsIFile.h"
+#include "nsDependentString.h"
+#include "prenv.h"
+
+#ifdef XP_WIN
+#  include <windows.h>
+#endif
+
+namespace mozilla {
+
+// Load the path of a file saved with SaveFileToEnv
+already_AddRefed<nsIFile> GetFileFromEnv(const char* name) {
+  nsresult rv;
+  nsCOMPtr<nsIFile> file;
+
+#ifdef XP_WIN
+  WCHAR path[_MAX_PATH];
+  if (!GetEnvironmentVariableW(NS_ConvertASCIItoUTF16(name).get(), path,
+                               _MAX_PATH))
+    return nullptr;
+
+  rv = NS_NewLocalFile(nsDependentString(path), true, getter_AddRefs(file));
+  if (NS_FAILED(rv)) return nullptr;
+
+  return file.forget();
+#else
+  const char* arg = PR_GetEnv(name);
+  if (!arg || !*arg) {
+    return nullptr;
+  }
+
+  rv = NS_NewNativeLocalFile(nsDependentCString(arg), true,
+                             getter_AddRefs(file));
+  if (NS_FAILED(rv)) {
+    return nullptr;
+  }
+
+  return file.forget();
+#endif
+}
+
+}  // namespace mozilla
diff --git a/toolkit/xre/CmdLineAndEnvUtils.h b/toolkit/xre/CmdLineAndEnvUtils.h
new file mode 100644
index 0000000000..cad34d2503
--- /dev/null
+++ b/toolkit/xre/CmdLineAndEnvUtils.h
@@ -0,0 +1,732 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_CmdLineAndEnvUtils_h
+#define mozilla_CmdLineAndEnvUtils_h
+
+// NB: This code may be used outside of xul and thus must not depend on XPCOM
+
+#if defined(MOZILLA_INTERNAL_API)
+#  include "prenv.h"
+#  include "prprf.h"
+#  include <string.h>
+#endif
+
+#if defined(XP_WIN)
+#  include "mozilla/UniquePtr.h"
+#  include "mozilla/Vector.h"
+#  include "mozilla/WinHeaderOnlyUtils.h"
+
+#  include <wchar.h>
+#  include <windows.h>
+#endif  // defined(XP_WIN)
+
+#include "mozilla/Maybe.h"
+#include "mozilla/MemoryChecking.h"
+#include "mozilla/TypedEnumBits.h"
+
+#include <ctype.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+#ifndef NS_NO_XPCOM
+#  include "nsIFile.h"
+#  include "mozilla/AlreadyAddRefed.h"
+#endif
+
+// Undo X11/X.h's definition of None
+#undef None
+
+namespace mozilla {
+
+enum ArgResult {
+  ARG_NONE = 0,
+  ARG_FOUND = 1,
+  ARG_BAD = 2  // you wanted a param, but there isn't one
+};
+
+template <typename CharT>
+inline void RemoveArg(int& argc, CharT** argv) {
+  do {
+    *argv = *(argv + 1);
+    ++argv;
+  } while (*argv);
+
+  --argc;
+}
+
+namespace internal {
+
+#if 'a' == '\x61'
+// Valid option characters must have the same representation in every locale
+// (which is true for most of ASCII, barring \x5C and \x7E).
+static inline constexpr bool isValidOptionCharacter(char c) {
+  // We specifically avoid the use of `islower` here; it's locale-dependent, and
+  // may return true for non-ASCII values in some locales.
+  return ('0' <= c && c <= '9') || ('a' <= c && c <= 'z') || c == '-';
+};
+
+// Convert uppercase to lowercase, locale-insensitively.
+static inline constexpr char toLowercase(char c) {
+  // We specifically avoid the use of `tolower` here; it's locale-dependent, and
+  // may output ASCII values for non-ASCII input (or vice versa) in some
+  // locales.
+  return ('A' <= c && c <= 'Z') ? char(c | ' ') : c;
+};
+
+// Convert a CharT to a char, ensuring that no CharT is mapped to any valid
+// option character except the unique CharT naturally corresponding thereto.
+template <typename CharT>
+static inline constexpr char toNarrow(CharT c) {
+  // confirmed to compile down to nothing when `CharT` is `char`
+  return (c & static_cast<CharT>(0xff)) == c ? c : 0xff;
+};
+#else
+// The target system's character set isn't even ASCII-compatible. If you're
+// porting Gecko to such a platform, you'll have to implement these yourself.
+#  error Character conversion functions not implemented for this platform.
+#endif
+
+// Case-insensitively compare a string taken from the command-line (`mixedstr`)
+// to the text of some known command-line option (`lowerstr`).
+template <typename CharT>
+static inline bool strimatch(const char* lowerstr, const CharT* mixedstr) {
+  while (*lowerstr) {
+    if (!*mixedstr) return false;  // mixedstr is shorter
+
+    // Non-ASCII strings may compare incorrectly depending on the user's locale.
+    // Some ASCII-safe characters are also dispermitted for semantic reasons
+    // and simplicity.
+    if (!isValidOptionCharacter(*lowerstr)) return false;
+
+    if (toLowercase(toNarrow(*mixedstr)) != *lowerstr) {
+      return false;  // no match
+    }
+
+    ++lowerstr;
+    ++mixedstr;
+  }
+
+  if (*mixedstr) return false;  // lowerstr is shorter
+
+  return true;
+}
+
+// Given a command-line argument, return Nothing if it isn't structurally a
+// command-line option, and Some(<the option text>) if it is.
+template <typename CharT>
+mozilla::Maybe<const CharT*> ReadAsOption(const CharT* str) {
+  if (!str) {
+    return Nothing();
+  }
+  if (*str == '-') {
+    str++;
+    if (*str == '-') {
+      str++;
+    }
+    return Some(str);
+  }
+#ifdef XP_WIN
+  if (*str == '/') {
+    return Some(str + 1);
+  }
+#endif
+  return Nothing();
+}
+
+}  // namespace internal
+
+using internal::strimatch;
+
+const wchar_t kCommandLineDelimiter[] = L" \t";
+
+enum class CheckArgFlag : uint32_t {
+  None = 0,
+  // (1 << 0) Used to be CheckOSInt
+  RemoveArg = (1 << 1)  // Remove the argument from the argv array.
+};
+
+MOZ_MAKE_ENUM_CLASS_BITWISE_OPERATORS(CheckArgFlag)
+
+/**
+ * Check for a commandline flag. If the flag takes a parameter, the
+ * parameter is returned in aParam. Flags may be in the form -arg or
+ * --arg (or /arg on win32).
+ *
+ * @param aArgc The argc value.
+ * @param aArgv The original argv.
+ * @param aArg the parameter to check. Must be lowercase.
+ * @param aParam if non-null, the -arg <data> will be stored in this pointer.
+ *        This is *not* allocated, but rather a pointer to the argv data.
+ * @param aFlags Flags @see CheckArgFlag
+ */
+template <typename CharT>
+inline ArgResult CheckArg(int& aArgc, CharT** aArgv, const char* aArg,
+                          const CharT** aParam = nullptr,
+                          CheckArgFlag aFlags = CheckArgFlag::RemoveArg) {
+  using internal::ReadAsOption;
+  MOZ_ASSERT(aArgv && aArg);
+
+  CharT** curarg = aArgv + 1;  // skip argv[0]
+  ArgResult ar = ARG_NONE;
+
+  while (*curarg) {
+    if (const auto arg = ReadAsOption(*curarg)) {
+      if (strimatch(aArg, arg.value())) {
+        if (aFlags & CheckArgFlag::RemoveArg) {
+          RemoveArg(aArgc, curarg);
+        } else {
+          ++curarg;
+        }
+
+        if (!aParam) {
+          ar = ARG_FOUND;
+          break;
+        }
+
+        if (*curarg) {
+          if (ReadAsOption(*curarg)) {
+            return ARG_BAD;
+          }
+
+          *aParam = *curarg;
+
+          if (aFlags & CheckArgFlag::RemoveArg) {
+            RemoveArg(aArgc, curarg);
+          }
+
+          ar = ARG_FOUND;
+          break;
+        }
+
+        return ARG_BAD;
+      }
+    }
+
+    ++curarg;
+  }
+
+  return ar;
+}
+
+template <typename CharT>
+inline ArgResult CheckArg(int& aArgc, CharT** aArgv, const char* aArg,
+                          std::nullptr_t,
+                          CheckArgFlag aFlags = CheckArgFlag::RemoveArg) {
+  return CheckArg<CharT>(aArgc, aArgv, aArg,
+                         static_cast<const CharT**>(nullptr), aFlags);
+}
+
+namespace internal {
+// template <typename T>
+// constexpr bool IsStringRange =
+//     std::convertible_to<std::ranges::range_value_t<T>, const char *>;
+
+template <typename CharT, typename ListT>
+// requires IsStringRange<ListT>
+static bool MatchesAnyOf(CharT const* unknown, ListT const& known) {
+  for (const char* k : known) {
+    if (strimatch(k, unknown)) {
+      return true;
+    }
+  }
+  return false;
+}
+
+template <typename CharT, typename ReqContainerT, typename OptContainerT>
+// requires IsStringRange<ReqContainerT> && IsStringRange<OptContainerT>
+inline bool EnsureCommandlineSafeImpl(int aArgc, CharT** aArgv,
+                                      ReqContainerT const& requiredParams,
+                                      OptContainerT const& optionalParams) {
+  // We expect either no -osint, or the full commandline to be:
+  //
+  //   app -osint [<optional-param>...] <required-param> <required-argument>
+  //
+  // Otherwise, we abort to avoid abuse of other command-line handlers from apps
+  // that do a poor job escaping links they give to the OS.
+  //
+  // Note that the above implies that optional parameters do not themselves take
+  // arguments. This is a security feature, to prevent the possible injection of
+  // additional parameters via such arguments. (See, e.g., bug 384384.)
+
+  static constexpr const char* osintLit = "osint";
+
+  // If "-osint" (or the equivalent) is not present, then this is trivially
+  // satisfied.
+  if (CheckArg(aArgc, aArgv, osintLit, nullptr, CheckArgFlag::None) !=
+      ARG_FOUND) {
+    return true;
+  }
+
+  // There should be at least 4 items present:
+  //    <app name> -osint <required param> <arg>.
+  if (aArgc < 4) {
+    return false;
+  }
+
+  // The first parameter must be osint.
+  const auto arg1 = ReadAsOption(aArgv[1]);
+  if (!arg1) return false;
+  if (!strimatch(osintLit, arg1.value())) {
+    return false;
+  }
+  // Following this is any number of optional parameters, terminated by a
+  // required parameter.
+  int pos = 2;
+  while (true) {
+    if (pos >= aArgc) return false;
+
+    auto const arg = ReadAsOption(aArgv[pos]);
+    if (!arg) return false;
+
+    if (MatchesAnyOf(arg.value(), optionalParams)) {
+      ++pos;
+      continue;
+    }
+
+    if (MatchesAnyOf(arg.value(), requiredParams)) {
+      ++pos;
+      break;
+    }
+
+    return false;
+  }
+
+  // There must be one argument remaining...
+  if (pos + 1 != aArgc) return false;
+  // ... which must not be another option.
+  if (ReadAsOption(aArgv[pos])) {
+    return false;
+  }
+
+  // Nothing ill-formed was passed.
+  return true;
+}
+
+// C (and so C++) disallows empty arrays. Rather than require callers to jump
+// through hoops to specify an empty optional-argument list, allow either its
+// omission or its specification as `nullptr`, and do the hoop-jumping here.
+//
+// No such facility is provided for requiredParams, which must have at least one
+// entry.
+template <typename CharT, typename ReqContainerT>
+inline bool EnsureCommandlineSafeImpl(int aArgc, CharT** aArgv,
+                                      ReqContainerT const& requiredParams,
+                                      std::nullptr_t _ = nullptr) {
+  struct {
+    inline const char** begin() const { return nullptr; }
+    inline const char** end() const { return nullptr; }
+  } emptyContainer;
+  return EnsureCommandlineSafeImpl(aArgc, aArgv, requiredParams,
+                                   emptyContainer);
+}
+}  // namespace internal
+
+template <typename CharT, typename ReqContainerT,
+          typename OptContainerT = std::nullptr_t>
+inline void EnsureCommandlineSafe(
+    int aArgc, CharT** aArgv, ReqContainerT const& requiredParams,
+    OptContainerT const& optionalParams = nullptr) {
+  if (!internal::EnsureCommandlineSafeImpl(aArgc, aArgv, requiredParams,
+                                           optionalParams)) {
+    exit(127);
+  }
+}
+
+#if defined(XP_WIN)
+namespace internal {
+/**
+ * Get the length that the string will take and takes into account the
+ * additional length if the string needs to be quoted and if characters need to
+ * be escaped.
+ */
+inline int ArgStrLen(const wchar_t* s) {
+  int backslashes = 0;
+  int i = wcslen(s);
+  bool hasDoubleQuote = wcschr(s, L'"') != nullptr;
+  // Only add doublequotes if the string contains a space or a tab
+  bool addDoubleQuotes = wcspbrk(s, kCommandLineDelimiter) != nullptr;
+
+  if (addDoubleQuotes) {
+    i += 2;  // initial and final duoblequote
+  }
+
+  if (hasDoubleQuote) {
+    while (*s) {
+      if (*s == '\\') {
+        ++backslashes;
+      } else {
+        if (*s == '"') {
+          // Escape the doublequote and all backslashes preceding the
+          // doublequote
+          i += backslashes + 1;
+        }
+
+        backslashes = 0;
+      }
+
+      ++s;
+    }
+  }
+
+  return i;
+}
+
+/**
+ * Copy string "s" to string "d", quoting the argument as appropriate and
+ * escaping doublequotes along with any backslashes that immediately precede
+ * doublequotes.
+ * The CRT parses this to retrieve the original argc/argv that we meant,
+ * see STDARGV.C in the MSVC CRT sources.
+ *
+ * @return the end of the string
+ */
+inline wchar_t* ArgToString(wchar_t* d, const wchar_t* s) {
+  int backslashes = 0;
+  bool hasDoubleQuote = wcschr(s, L'"') != nullptr;
+  // Only add doublequotes if the string contains a space or a tab
+  bool addDoubleQuotes = wcspbrk(s, kCommandLineDelimiter) != nullptr;
+
+  if (addDoubleQuotes) {
+    *d = '"';  // initial doublequote
+    ++d;
+  }
+
+  if (hasDoubleQuote) {
+    int i;
+    while (*s) {
+      if (*s == '\\') {
+        ++backslashes;
+      } else {
+        if (*s == '"') {
+          // Escape the doublequote and all backslashes preceding the
+          // doublequote
+          for (i = 0; i <= backslashes; ++i) {
+            *d = '\\';
+            ++d;
+          }
+        }
+
+        backslashes = 0;
+      }
+
+      *d = *s;
+      ++d;
+      ++s;
+    }
+  } else {
+    wcscpy(d, s);
+    d += wcslen(s);
+  }
+
+  if (addDoubleQuotes) {
+    *d = '"';  // final doublequote
+    ++d;
+  }
+
+  return d;
+}
+
+}  // namespace internal
+
+/**
+ * Creates a command line from a list of arguments.
+ *
+ * @param argc Number of elements in |argv|
+ * @param argv Array of arguments
+ * @param aArgcExtra Number of elements in |aArgvExtra|
+ * @param aArgvExtra Optional array of arguments to be appended to the resulting
+ *                   command line after those provided by |argv|.
+ */
+inline UniquePtr<wchar_t[]> MakeCommandLine(
+    int argc, const wchar_t* const* argv, int aArgcExtra = 0,
+    const wchar_t* const* aArgvExtra = nullptr) {
+  int i;
+  int len = 0;
+
+  // The + 1 for each argument reserves space for either a ' ' or the null
+  // terminator, depending on the position of the argument.
+  for (i = 0; i < argc; ++i) {
+    len += internal::ArgStrLen(argv[i]) + 1;
+  }
+
+  for (i = 0; i < aArgcExtra; ++i) {
+    len += internal::ArgStrLen(aArgvExtra[i]) + 1;
+  }
+
+  // Protect against callers that pass 0 arguments
+  if (len == 0) {
+    len = 1;
+  }
+
+  auto s = MakeUnique<wchar_t[]>(len);
+
+  int totalArgc = argc + aArgcExtra;
+
+  wchar_t* c = s.get();
+  for (i = 0; i < argc; ++i) {
+    c = internal::ArgToString(c, argv[i]);
+    if (i + 1 != totalArgc) {
+      *c = ' ';
+      ++c;
+    }
+  }
+
+  for (i = 0; i < aArgcExtra; ++i) {
+    c = internal::ArgToString(c, aArgvExtra[i]);
+    if (i + 1 != aArgcExtra) {
+      *c = ' ';
+      ++c;
+    }
+  }
+
+  *c = '\0';
+
+  return s;
+}
+
+inline bool SetArgv0ToFullBinaryPath(wchar_t* aArgv[]) {
+  if (!aArgv) {
+    return false;
+  }
+
+  UniquePtr<wchar_t[]> newArgv_0(GetFullBinaryPath());
+  if (!newArgv_0) {
+    return false;
+  }
+
+  // We intentionally leak newArgv_0 into argv[0]
+  aArgv[0] = newArgv_0.release();
+  MOZ_LSAN_INTENTIONALLY_LEAK_OBJECT(aArgv[0]);
+  return true;
+}
+
+#  if defined(MOZILLA_INTERNAL_API)
+// This class converts a command line string into an array of the arguments.
+// It's basically the opposite of MakeCommandLine.  However, the behavior is
+// different from ::CommandLineToArgvW in several ways, such as escaping a
+// backslash or quoting an argument containing whitespaces.  This satisfies
+// the examples at:
+// https://docs.microsoft.com/en-us/cpp/cpp/main-function-command-line-args#results-of-parsing-command-lines
+// https://docs.microsoft.com/en-us/previous-versions/17w5ykft(v=vs.85)
+template <typename T>
+class CommandLineParserWin final {
+  int mArgc;
+  T** mArgv;
+
+  void Release() {
+    if (mArgv) {
+      while (mArgc) {
+        delete[] mArgv[--mArgc];
+      }
+      delete[] mArgv;
+      mArgv = nullptr;
+    }
+  }
+
+ public:
+  CommandLineParserWin() : mArgc(0), mArgv(nullptr) {}
+  ~CommandLineParserWin() { Release(); }
+
+  CommandLineParserWin(const CommandLineParserWin&) = delete;
+  CommandLineParserWin(CommandLineParserWin&&) = delete;
+  CommandLineParserWin& operator=(const CommandLineParserWin&) = delete;
+  CommandLineParserWin& operator=(CommandLineParserWin&&) = delete;
+
+  int Argc() const { return mArgc; }
+  const T* const* Argv() const { return mArgv; }
+
+  // Returns the number of characters handled
+  int HandleCommandLine(const nsTSubstring<T>& aCmdLineString) {
+    Release();
+
+    if (aCmdLineString.IsEmpty()) {
+      return 0;
+    }
+
+    int justCounting = 1;
+    // Flags, etc.
+    int init = 1;
+    int between, quoted, bSlashCount;
+    const T* p;
+    const T* const pEnd = aCmdLineString.EndReading();
+    nsTAutoString<T> arg;
+
+    // We loop if we've not finished the second pass through.
+    while (1) {
+      // Initialize if required.
+      if (init) {
+        p = aCmdLineString.BeginReading();
+        between = 1;
+        mArgc = quoted = bSlashCount = 0;
+
+        init = 0;
+      }
+
+      const T charCurr = (p < pEnd) ? *p : 0;
+      const T charNext = (p + 1 < pEnd) ? *(p + 1) : 0;
+
+      if (between) {
+        // We are traversing whitespace between args.
+        // Check for start of next arg.
+        if (charCurr != 0 && !wcschr(kCommandLineDelimiter, charCurr)) {
+          // Start of another arg.
+          between = 0;
+          arg.Truncate();
+          switch (charCurr) {
+            case '\\':
+              // Count the backslash.
+              bSlashCount = 1;
+              break;
+            case '"':
+              // Remember we're inside quotes.
+              quoted = 1;
+              break;
+            default:
+              // Add character to arg.
+              arg += charCurr;
+              break;
+          }
+        } else {
+          // Another space between args, ignore it.
+        }
+      } else {
+        // We are processing the contents of an argument.
+        // Check for whitespace or end.
+        if (charCurr == 0 ||
+            (!quoted && wcschr(kCommandLineDelimiter, charCurr))) {
+          // Process pending backslashes (interpret them
+          // literally since they're not followed by a ").
+          while (bSlashCount) {
+            arg += '\\';
+            bSlashCount--;
+          }
+          // End current arg.
+          if (!justCounting) {
+            mArgv[mArgc] = new T[arg.Length() + 1];
+            memcpy(mArgv[mArgc], arg.get(), (arg.Length() + 1) * sizeof(T));
+          }
+          mArgc++;
+          // We're now between args.
+          between = 1;
+        } else {
+          // Still inside argument, process the character.
+          switch (charCurr) {
+            case '"':
+              // First, digest preceding backslashes (if any).
+              while (bSlashCount > 1) {
+                // Put one backsplash in arg for each pair.
+                arg += '\\';
+                bSlashCount -= 2;
+              }
+              if (bSlashCount) {
+                // Quote is literal.
+                arg += '"';
+                bSlashCount = 0;
+              } else {
+                // Quote starts or ends a quoted section.
+                if (quoted) {
+                  // Check for special case of consecutive double
+                  // quotes inside a quoted section.
+                  if (charNext == '"') {
+                    // This implies a literal double-quote.  Fake that
+                    // out by causing next double-quote to look as
+                    // if it was preceded by a backslash.
+                    bSlashCount = 1;
+                  } else {
+                    quoted = 0;
+                  }
+                } else {
+                  quoted = 1;
+                }
+              }
+              break;
+            case '\\':
+              // Add to count.
+              bSlashCount++;
+              break;
+            default:
+              // Accept any preceding backslashes literally.
+              while (bSlashCount) {
+                arg += '\\';
+                bSlashCount--;
+              }
+              // Just add next char to the current arg.
+              arg += charCurr;
+              break;
+          }
+        }
+      }
+
+      // Check for end of input.
+      if (charCurr) {
+        // Go to next character.
+        p++;
+      } else {
+        // If on first pass, go on to second.
+        if (justCounting) {
+          // Allocate argv array.
+          mArgv = new T*[mArgc];
+
+          // Start second pass
+          justCounting = 0;
+          init = 1;
+        } else {
+          // Quit.
+          break;
+        }
+      }
+    }
+
+    return p - aCmdLineString.BeginReading();
+  }
+};
+#  endif  // defined(MOZILLA_INTERNAL_API)
+
+#endif  // defined(XP_WIN)
+
+// SaveToEnv and EnvHasValue are only available on Windows or when
+// MOZILLA_INTERNAL_API is defined
+#if defined(MOZILLA_INTERNAL_API) || defined(XP_WIN)
+
+// Save literal putenv string to environment variable.
+MOZ_NEVER_INLINE inline void SaveToEnv(const char* aEnvString) {
+#  if defined(MOZILLA_INTERNAL_API)
+  char* expr = strdup(aEnvString);
+  if (expr) {
+    PR_SetEnv(expr);
+  }
+
+  // We intentionally leak |expr| here since it is required by PR_SetEnv.
+  MOZ_LSAN_INTENTIONALLY_LEAK_OBJECT(expr);
+#  elif defined(XP_WIN)
+  // This is the same as the NSPR implementation
+  // (Note that we don't need to do a strdup for this case; the CRT makes a
+  // copy)
+  _putenv(aEnvString);
+#  endif
+}
+
+inline bool EnvHasValue(const char* aVarName) {
+#  if defined(MOZILLA_INTERNAL_API)
+  const char* val = PR_GetEnv(aVarName);
+  return val && *val;
+#  elif defined(XP_WIN)
+  // This is the same as the NSPR implementation
+  const char* val = getenv(aVarName);
+  return val && *val;
+#  endif
+}
+
+#endif  // end windows/internal_api-only definitions
+
+#ifndef NS_NO_XPCOM
+already_AddRefed<nsIFile> GetFileFromEnv(const char* name);
+#endif
+
+}  // namespace mozilla
+
+#endif  // mozilla_CmdLineAndEnvUtils_h
diff --git a/toolkit/xre/CreateAppData.cpp b/toolkit/xre/CreateAppData.cpp
new file mode 100644
index 0000000000..dda5b37873
--- /dev/null
+++ b/toolkit/xre/CreateAppData.cpp
@@ -0,0 +1,77 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsXULAppAPI.h"
+#include "nsINIParser.h"
+#include "nsIFile.h"
+#include "mozilla/XREAppData.h"
+
+// This include must appear early in the unified cpp file for toolkit/xre to
+// make sure OSX APIs make use of the OSX TextRange before mozilla::TextRange is
+// declared and made a global symbol by a "using namespace mozilla" declaration.
+#ifdef XP_MACOSX
+#  include <Carbon/Carbon.h>
+#endif
+
+using namespace mozilla;
+
+static void ReadString(nsINIParser& parser, const char* section,
+                       const char* key, XREAppData::CharPtr& result) {
+  nsCString str;
+  nsresult rv = parser.GetString(section, key, str);
+  if (NS_SUCCEEDED(rv)) {
+    result = str.get();
+  }
+}
+
+struct ReadFlag {
+  const char* section;
+  const char* key;
+  uint32_t flag;
+};
+
+static void ReadFlag(nsINIParser& parser, const char* section, const char* key,
+                     uint32_t flag, uint32_t& result) {
+  char buf[6];  // large enough to hold "false"
+  nsresult rv = parser.GetString(section, key, buf, sizeof(buf));
+  if (NS_SUCCEEDED(rv) || rv == NS_ERROR_LOSS_OF_SIGNIFICANT_DATA) {
+    if (buf[0] == '1' || buf[0] == 't' || buf[0] == 'T') {
+      result |= flag;
+    }
+    if (buf[0] == '0' || buf[0] == 'f' || buf[0] == 'F') {
+      result &= ~flag;
+    }
+  }
+}
+
+nsresult XRE_ParseAppData(nsIFile* aINIFile, XREAppData& aAppData) {
+  NS_ENSURE_ARG(aINIFile);
+
+  nsresult rv;
+
+  nsINIParser parser;
+  rv = parser.Init(aINIFile);
+  if (NS_FAILED(rv)) return rv;
+
+  ReadString(parser, "App", "Vendor", aAppData.vendor);
+  ReadString(parser, "App", "Name", aAppData.name);
+  ReadString(parser, "App", "RemotingName", aAppData.remotingName);
+  ReadString(parser, "App", "Version", aAppData.version);
+  ReadString(parser, "App", "BuildID", aAppData.buildID);
+  ReadString(parser, "App", "ID", aAppData.ID);
+  ReadString(parser, "App", "Copyright", aAppData.copyright);
+  ReadString(parser, "App", "Profile", aAppData.profile);
+  ReadString(parser, "Gecko", "MinVersion", aAppData.minVersion);
+  ReadString(parser, "Gecko", "MaxVersion", aAppData.maxVersion);
+  ReadString(parser, "Crash Reporter", "ServerURL", aAppData.crashReporterURL);
+  ReadString(parser, "App", "UAName", aAppData.UAName);
+  ReadString(parser, "AppUpdate", "URL", aAppData.updateURL);
+  ReadFlag(parser, "XRE", "EnableProfileMigrator",
+           NS_XRE_ENABLE_PROFILE_MIGRATOR, aAppData.flags);
+  ReadFlag(parser, "Crash Reporter", "Enabled", NS_XRE_ENABLE_CRASH_REPORTER,
+           aAppData.flags);
+
+  return NS_OK;
+}
diff --git a/toolkit/xre/DllPrefetchExperimentRegistryInfo.cpp b/toolkit/xre/DllPrefetchExperimentRegistryInfo.cpp
new file mode 100644
index 0000000000..829999ac45
--- /dev/null
+++ b/toolkit/xre/DllPrefetchExperimentRegistryInfo.cpp
@@ -0,0 +1,112 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#include "DllPrefetchExperimentRegistryInfo.h"
+
+#include "mozilla/Assertions.h"
+#include "mozilla/NativeNt.h"
+#include "mozilla/ResultExtensions.h"
+
+namespace mozilla {
+
+const wchar_t DllPrefetchExperimentRegistryInfo::kExperimentSubKeyPath[] =
+    L"SOFTWARE"
+    L"\\" MOZ_APP_VENDOR L"\\" MOZ_APP_BASENAME L"\\DllPrefetchExperiment";
+
+Result<Ok, nsresult> DllPrefetchExperimentRegistryInfo::Open() {
+  if (!!mRegKey) {
+    return Ok();
+  }
+
+  DWORD disposition;
+  HKEY rawKey;
+  LSTATUS result = ::RegCreateKeyExW(
+      HKEY_CURRENT_USER, kExperimentSubKeyPath, 0, nullptr,
+      REG_OPTION_NON_VOLATILE, KEY_ALL_ACCESS, nullptr, &rawKey, &disposition);
+
+  if (result != ERROR_SUCCESS) {
+    return Err(NS_ERROR_UNEXPECTED);
+  }
+
+  mRegKey.own(rawKey);
+
+  if (disposition == REG_CREATED_NEW_KEY ||
+      disposition == REG_OPENED_EXISTING_KEY) {
+    return Ok();
+  }
+
+  MOZ_ASSERT_UNREACHABLE("Invalid disposition from RegCreateKeyExW");
+  return Err(NS_ERROR_UNEXPECTED);
+}
+
+Result<Ok, nsresult> DllPrefetchExperimentRegistryInfo::ReflectPrefToRegistry(
+    int32_t aVal) {
+  MOZ_TRY(Open());
+
+  mPrefetchMode = aVal;
+
+  LSTATUS status =
+      ::RegSetValueExW(mRegKey.get(), mBinPath.get(), 0, REG_DWORD,
+                       reinterpret_cast<PBYTE>(&aVal), sizeof(aVal));
+
+  if (status != ERROR_SUCCESS) {
+    return Err(NS_ERROR_UNEXPECTED);
+  }
+
+  return Ok();
+}
+
+Result<Ok, nsresult> DllPrefetchExperimentRegistryInfo::ReadRegistryValueData(
+    DWORD expectedType) {
+  MOZ_TRY(Open());
+
+  int32_t data;
+  DWORD dataLen = sizeof((ULONG)data);
+  DWORD type;
+  LSTATUS status =
+      ::RegQueryValueExW(mRegKey.get(), mBinPath.get(), nullptr, &type,
+                         reinterpret_cast<PBYTE>(&data), &dataLen);
+
+  if (status == ERROR_FILE_NOT_FOUND) {
+    // The registry key has not been created, set to default 0
+    mPrefetchMode = 0;
+    return Ok();
+  }
+
+  if (status != ERROR_SUCCESS) {
+    return Err(NS_ERROR_UNEXPECTED);
+  }
+
+  if (type != expectedType) {
+    return Err(NS_ERROR_UNEXPECTED);
+  }
+
+  mPrefetchMode = data;
+  return Ok();
+}
+
+AlteredDllPrefetchMode
+DllPrefetchExperimentRegistryInfo::GetAlteredDllPrefetchMode() {
+  Result<Ok, nsresult> result = ReadRegistryValueData(REG_DWORD);
+  if (!result.isOk()) {
+    MOZ_ASSERT(false);
+    return AlteredDllPrefetchMode::CurrentPrefetch;
+  }
+
+  switch (mPrefetchMode) {
+    case 0:
+      return AlteredDllPrefetchMode::CurrentPrefetch;
+    case 1:
+      return AlteredDllPrefetchMode::NoPrefetch;
+    case 2:
+      return AlteredDllPrefetchMode::OptimizedPrefetch;
+    default:
+      MOZ_ASSERT(false);
+      return AlteredDllPrefetchMode::CurrentPrefetch;
+  }
+}
+
+}  // namespace mozilla
diff --git a/toolkit/xre/DllPrefetchExperimentRegistryInfo.h b/toolkit/xre/DllPrefetchExperimentRegistryInfo.h
new file mode 100644
index 0000000000..26cba51dcf
--- /dev/null
+++ b/toolkit/xre/DllPrefetchExperimentRegistryInfo.h
@@ -0,0 +1,50 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_DllPrefetchExperimentRegistryInfo_h
+#define mozilla_DllPrefetchExperimentRegistryInfo_h
+
+#include "mozilla/Maybe.h"
+#include "mozilla/WinHeaderOnlyUtils.h"
+#include "nsWindowsHelpers.h"
+
+/**
+ * This is a temporary file in order to conduct an experiment on the impact of
+ * startup time on retention (see Bug 1640087).
+ * This was generally adapted from LauncherRegistryInfo.h
+ */
+
+namespace mozilla {
+
+enum class AlteredDllPrefetchMode {
+  CurrentPrefetch,
+  NoPrefetch,
+  OptimizedPrefetch
+};
+
+class DllPrefetchExperimentRegistryInfo final {
+ public:
+  DllPrefetchExperimentRegistryInfo() : mBinPath(GetFullBinaryPath().get()) {}
+  ~DllPrefetchExperimentRegistryInfo() {}
+
+  Result<Ok, nsresult> ReflectPrefToRegistry(int32_t aVal);
+  Result<Ok, nsresult> ReadRegistryValueData(DWORD expectedType);
+
+  AlteredDllPrefetchMode GetAlteredDllPrefetchMode();
+
+ private:
+  Result<Ok, nsresult> Open();
+
+  nsAutoRegKey mRegKey;
+  nsString mBinPath;
+  int32_t mPrefetchMode;
+
+  static const wchar_t kExperimentSubKeyPath[];
+};
+
+}  // namespace mozilla
+
+#endif  // mozilla_DllPrefetchExperimentRegistryInfo_h
diff --git a/toolkit/xre/EventTracer.cpp b/toolkit/xre/EventTracer.cpp
new file mode 100644
index 0000000000..aae3fee8e3
--- /dev/null
+++ b/toolkit/xre/EventTracer.cpp
@@ -0,0 +1,219 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/*
+ * Event loop instrumentation. This code attempts to measure the
+ * latency of the UI-thread event loop by firing native events at it from
+ * a background thread, and measuring how long it takes for them
+ * to be serviced. The measurement interval (kMeasureInterval, below)
+ * is also used as the upper bound of acceptable response time.
+ * When an event takes longer than that interval to be serviced,
+ * a sample will be written to the log.
+ *
+ * Usage:
+ *
+ * Set MOZ_INSTRUMENT_EVENT_LOOP=1 in the environment to enable
+ * this instrumentation. Currently only the UI process is instrumented.
+ *
+ * Set MOZ_INSTRUMENT_EVENT_LOOP_OUTPUT in the environment to a
+ * file path to contain the log output, the default is to log to stdout.
+ *
+ * Set MOZ_INSTRUMENT_EVENT_LOOP_THRESHOLD in the environment to an
+ * integer number of milliseconds to change the threshold for reporting.
+ * The default is 20 milliseconds. Unresponsive periods shorter than this
+ * threshold will not be reported.
+ *
+ * Set MOZ_INSTRUMENT_EVENT_LOOP_INTERVAL in the environment to an
+ * integer number of milliseconds to change the maximum sampling frequency.
+ * This variable controls how often events will be sent to the main
+ * thread's event loop to sample responsiveness. The sampler will not
+ * send events twice within LOOP_INTERVAL milliseconds.
+ * The default is 10 milliseconds.
+ *
+ * All logged output lines start with MOZ_EVENT_TRACE. All timestamps
+ * output are milliseconds since the epoch (PRTime / 1000).
+ *
+ * On startup, a line of the form:
+ *   MOZ_EVENT_TRACE start <timestamp>
+ * will be output.
+ *
+ * On shutdown, a line of the form:
+ *   MOZ_EVENT_TRACE stop <timestamp>
+ * will be output.
+ *
+ * When an event servicing time exceeds the threshold, a line of the form:
+ *   MOZ_EVENT_TRACE sample <timestamp> <duration>
+ * will be output, where <duration> is the number of milliseconds that
+ * it took for the event to be serviced. Duration may contain a fractional
+ * component.
+ */
+
+#include "GeckoProfiler.h"
+
+#include "EventTracer.h"
+
+#include <stdio.h>
+
+#include "mozilla/Preferences.h"
+#include "mozilla/TimeStamp.h"
+#include "mozilla/WidgetTraceEvent.h"
+#include "nsDebug.h"
+#include <limits.h>
+#include <prenv.h>
+#include <prinrval.h>
+#include <prthread.h>
+#include <prtime.h>
+
+#include "nsThreadUtils.h"
+
+using mozilla::FireAndWaitForTracerEvent;
+using mozilla::TimeDuration;
+using mozilla::TimeStamp;
+
+namespace {
+
+PRThread* sTracerThread = nullptr;
+bool sExit = false;
+
+struct TracerStartClosure {
+  bool mLogTracing;
+  int32_t mThresholdInterval;
+};
+
+/*
+ * The tracer thread fires events at the native event loop roughly
+ * every kMeasureInterval. It will sleep to attempt not to send them
+ * more quickly, but if the response time is longer than kMeasureInterval
+ * it will not send another event until the previous response is received.
+ *
+ * The output defaults to stdout, but can be redirected to a file by
+ * settting the environment variable MOZ_INSTRUMENT_EVENT_LOOP_OUTPUT
+ * to the name of a file to use.
+ */
+void TracerThread(void* arg) {
+  AUTO_PROFILER_REGISTER_THREAD("Event Tracer");
+  NS_SetCurrentThreadName("Event Tracer");
+
+  TracerStartClosure* threadArgs = static_cast<TracerStartClosure*>(arg);
+
+  // These are the defaults. They can be overridden by environment vars.
+  // This should be set to the maximum latency we'd like to allow
+  // for responsiveness.
+  int32_t thresholdInterval = threadArgs->mThresholdInterval;
+  PRIntervalTime threshold = PR_MillisecondsToInterval(thresholdInterval);
+  // This is the sampling interval.
+  PRIntervalTime interval = PR_MillisecondsToInterval(thresholdInterval / 2);
+
+  sExit = false;
+  FILE* log = nullptr;
+  char* envfile = PR_GetEnv("MOZ_INSTRUMENT_EVENT_LOOP_OUTPUT");
+  if (envfile) {
+    log = fopen(envfile, "w");
+  }
+  if (log == nullptr) log = stdout;
+
+  char* thresholdenv = PR_GetEnv("MOZ_INSTRUMENT_EVENT_LOOP_THRESHOLD");
+  if (thresholdenv && *thresholdenv) {
+    int val = atoi(thresholdenv);
+    if (val != 0 && val != INT_MAX && val != INT_MIN) {
+      threshold = PR_MillisecondsToInterval(val);
+    }
+  }
+
+  char* intervalenv = PR_GetEnv("MOZ_INSTRUMENT_EVENT_LOOP_INTERVAL");
+  if (intervalenv && *intervalenv) {
+    int val = atoi(intervalenv);
+    if (val != 0 && val != INT_MAX && val != INT_MIN) {
+      interval = PR_MillisecondsToInterval(val);
+    }
+  }
+
+  if (threadArgs->mLogTracing) {
+    long long now = PR_Now() / PR_USEC_PER_MSEC;
+    fprintf(log, "MOZ_EVENT_TRACE start %llu\n", now);
+  }
+
+  while (!sExit) {
+    TimeStamp start(TimeStamp::Now());
+    PRIntervalTime next_sleep = interval;
+
+    // TODO: only wait up to a maximum of interval; return
+    // early if that threshold is exceeded and dump a stack trace
+    // or do something else useful.
+    if (FireAndWaitForTracerEvent()) {
+      TimeDuration duration = TimeStamp::Now() - start;
+      // Only report samples that exceed our measurement threshold.
+      long long now = PR_Now() / PR_USEC_PER_MSEC;
+      if (threadArgs->mLogTracing && duration.ToMilliseconds() > threshold) {
+        fprintf(log, "MOZ_EVENT_TRACE sample %llu %lf\n", now,
+                duration.ToMilliseconds());
+      }
+
+      if (next_sleep > duration.ToMilliseconds()) {
+        next_sleep -= int(duration.ToMilliseconds());
+      } else {
+        // Don't sleep at all if this event took longer than the measure
+        // interval to deliver.
+        next_sleep = 0;
+      }
+    }
+
+    if (next_sleep != 0 && !sExit) {
+      PR_Sleep(next_sleep);
+    }
+  }
+
+  if (threadArgs->mLogTracing) {
+    long long now = PR_Now() / PR_USEC_PER_MSEC;
+    fprintf(log, "MOZ_EVENT_TRACE stop %llu\n", now);
+  }
+
+  if (log != stdout) fclose(log);
+
+  delete threadArgs;
+}
+
+}  // namespace
+
+namespace mozilla {
+
+bool InitEventTracing(bool aLog) {
+  if (sTracerThread) return true;
+
+  // Initialize the widget backend.
+  if (!InitWidgetTracing()) return false;
+
+  // The tracer thread owns the object and will delete it.
+  TracerStartClosure* args = new TracerStartClosure();
+  args->mLogTracing = aLog;
+
+  // Pass the default threshold interval.
+  int32_t thresholdInterval = 20;
+  Preferences::GetInt("devtools.eventlooplag.threshold", &thresholdInterval);
+  args->mThresholdInterval = thresholdInterval;
+
+  // Create a thread that will fire events back at the
+  // main thread to measure responsiveness.
+  MOZ_ASSERT(!sTracerThread, "Event tracing already initialized!");
+  sTracerThread =
+      PR_CreateThread(PR_USER_THREAD, TracerThread, args, PR_PRIORITY_NORMAL,
+                      PR_GLOBAL_THREAD, PR_JOINABLE_THREAD, 0);
+  return sTracerThread != nullptr;
+}
+
+void ShutdownEventTracing() {
+  if (!sTracerThread) return;
+
+  sExit = true;
+  // Ensure that the tracer thread doesn't hang.
+  SignalTracerThread();
+
+  if (sTracerThread) PR_JoinThread(sTracerThread);
+  sTracerThread = nullptr;
+
+  // Allow the widget backend to clean up.
+  CleanUpWidgetTracing();
+}
+
+}  // namespace mozilla
diff --git a/toolkit/xre/EventTracer.h b/toolkit/xre/EventTracer.h
new file mode 100644
index 0000000000..67fa6661dd
--- /dev/null
+++ b/toolkit/xre/EventTracer.h
@@ -0,0 +1,23 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef XRE_EVENTTRACER_H_
+#define XRE_EVENTTRACER_H_
+
+namespace mozilla {
+
+// Create a thread that will fire events back at the
+// main thread to measure responsiveness. Return true
+// if the thread was created successfully.
+//   aLog If the tracing results should be printed to
+//        the console.
+bool InitEventTracing(bool aLog);
+
+// Signal the background thread to stop, and join it.
+// Must be called from the same thread that called InitEventTracing.
+void ShutdownEventTracing();
+
+}  // namespace mozilla
+
+#endif /* XRE_EVENTTRACER_H_ */
diff --git a/toolkit/xre/GeckoArgs.h b/toolkit/xre/GeckoArgs.h
new file mode 100644
index 0000000000..667ddb4ba4
--- /dev/null
+++ b/toolkit/xre/GeckoArgs.h
@@ -0,0 +1,149 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_GeckoArgs_h
+#define mozilla_GeckoArgs_h
+
+#include "mozilla/CmdLineAndEnvUtils.h"
+#include "mozilla/Maybe.h"
+
+#include <array>
+#include <cctype>
+#include <climits>
+#include <string>
+#include <vector>
+
+namespace mozilla {
+
+namespace geckoargs {
+
+template <typename T>
+struct CommandLineArg {
+  Maybe<T> Get(int& aArgc, char** aArgv,
+               const CheckArgFlag aFlags = CheckArgFlag::RemoveArg);
+
+  const char* Name() { return sName; };
+
+  void Put(std::vector<std::string>& aArgs);
+  void Put(T aValue, std::vector<std::string>& aArgs);
+
+  const char* sName;
+  const char* sMatch;
+};
+
+/// Get()
+
+template <>
+inline Maybe<const char*> CommandLineArg<const char*>::Get(
+    int& aArgc, char** aArgv, const CheckArgFlag aFlags) {
+  MOZ_ASSERT(aArgv, "aArgv must be initialized before CheckArg()");
+  const char* rv = nullptr;
+  if (ARG_FOUND == CheckArg(aArgc, aArgv, sMatch, &rv, aFlags)) {
+    return Some(rv);
+  }
+  return Nothing();
+}
+
+template <>
+inline Maybe<bool> CommandLineArg<bool>::Get(int& aArgc, char** aArgv,
+                                             const CheckArgFlag aFlags) {
+  MOZ_ASSERT(aArgv, "aArgv must be initialized before CheckArg()");
+  if (ARG_FOUND ==
+      CheckArg(aArgc, aArgv, sMatch, (const char**)nullptr, aFlags)) {
+    return Some(true);
+  }
+  return Nothing();
+}
+
+template <>
+inline Maybe<uint64_t> CommandLineArg<uint64_t>::Get(
+    int& aArgc, char** aArgv, const CheckArgFlag aFlags) {
+  MOZ_ASSERT(aArgv, "aArgv must be initialized before CheckArg()");
+  const char* rv = nullptr;
+  if (ARG_FOUND == CheckArg(aArgc, aArgv, sMatch, &rv, aFlags)) {
+    errno = 0;
+    char* endptr = nullptr;
+    uint64_t conv = std::strtoull(rv, &endptr, 10);
+    if (errno == 0 && endptr && *endptr == '\0') {
+      return Some(conv);
+    }
+  }
+  return Nothing();
+}
+
+/// Put()
+
+template <>
+inline void CommandLineArg<const char*>::Put(const char* aValue,
+                                             std::vector<std::string>& aArgs) {
+  aArgs.push_back(Name());
+  aArgs.push_back(aValue);
+}
+
+template <>
+inline void CommandLineArg<bool>::Put(bool aValue,
+                                      std::vector<std::string>& aArgs) {
+  if (aValue) {
+    aArgs.push_back(Name());
+  }
+}
+
+template <>
+inline void CommandLineArg<bool>::Put(std::vector<std::string>& aArgs) {
+  Put(true, aArgs);
+}
+
+template <>
+inline void CommandLineArg<uint64_t>::Put(uint64_t aValue,
+                                          std::vector<std::string>& aArgs) {
+  aArgs.push_back(Name());
+  aArgs.push_back(std::to_string(aValue));
+}
+
+#if defined(__GNUC__)
+#  pragma GCC diagnostic push
+#  pragma GCC diagnostic ignored "-Wunused-variable"
+#endif
+
+static CommandLineArg<const char*> sParentBuildID{"-parentBuildID",
+                                                  "parentbuildid"};
+static CommandLineArg<const char*> sAppDir{"-appDir", "appdir"};
+static CommandLineArg<const char*> sProfile{"-profile", "profile"};
+
+static CommandLineArg<uint64_t> sJsInitHandle{"-jsInitHandle", "jsinithandle"};
+static CommandLineArg<uint64_t> sJsInitLen{"-jsInitLen", "jsinitlen"};
+static CommandLineArg<uint64_t> sPrefsHandle{"-prefsHandle", "prefshandle"};
+static CommandLineArg<uint64_t> sPrefsLen{"-prefsLen", "prefslen"};
+static CommandLineArg<uint64_t> sPrefMapHandle{"-prefMapHandle",
+                                               "prefmaphandle"};
+static CommandLineArg<uint64_t> sPrefMapSize{"-prefMapSize", "prefmapsize"};
+
+static CommandLineArg<uint64_t> sChildID{"-childID", "childid"};
+
+static CommandLineArg<uint64_t> sSandboxingKind{"-sandboxingKind",
+                                                "sandboxingkind"};
+
+static CommandLineArg<bool> sSafeMode{"-safeMode", "safemode"};
+
+static CommandLineArg<bool> sIsForBrowser{"-isForBrowser", "isforbrowser"};
+static CommandLineArg<bool> sNotForBrowser{"-notForBrowser", "notforbrowser"};
+
+#if defined(XP_WIN)
+#  if defined(MOZ_SANDBOX)
+static CommandLineArg<bool> sWin32kLockedDown{"-win32kLockedDown",
+                                              "win32klockeddown"};
+#  endif  // defined(MOZ_SANDBOX)
+static CommandLineArg<bool> sDisableDynamicDllBlocklist{
+    "-disableDynamicBlocklist", "disabledynamicblocklist"};
+#endif  // defined(XP_WIN)
+
+#if defined(__GNUC__)
+#  pragma GCC diagnostic pop
+#endif
+
+}  // namespace geckoargs
+
+}  // namespace mozilla
+
+#endif  // mozilla_GeckoArgs_h
diff --git a/toolkit/xre/LauncherRegistryInfo.cpp b/toolkit/xre/LauncherRegistryInfo.cpp
new file mode 100644
index 0000000000..b80ee77f4d
--- /dev/null
+++ b/toolkit/xre/LauncherRegistryInfo.cpp
@@ -0,0 +1,652 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#include "LauncherRegistryInfo.h"
+
+#include "commonupdatedir.h"
+#include "mozilla/ArrayUtils.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/NativeNt.h"
+#include "mozilla/UniquePtr.h"
+
+#include <cwctype>
+#include <shlobj.h>
+#include <string>
+#include <type_traits>
+
+#define EXPAND_STRING_MACRO2(t) t
+#define EXPAND_STRING_MACRO(t) EXPAND_STRING_MACRO2(t)
+
+// This function is copied from Chromium base/time/time_win.cc
+// Returns the current value of the performance counter.
+static uint64_t QPCNowRaw() {
+  LARGE_INTEGER perf_counter_now = {};
+  // According to the MSDN documentation for QueryPerformanceCounter(), this
+  // will never fail on systems that run XP or later.
+  // https://docs.microsoft.com/en-us/windows/win32/api/profileapi/nf-profileapi-queryperformancecounter
+  ::QueryPerformanceCounter(&perf_counter_now);
+  return perf_counter_now.QuadPart;
+}
+
+static mozilla::LauncherResult<DWORD> GetCurrentImageTimestamp() {
+  mozilla::nt::PEHeaders headers(::GetModuleHandleW(nullptr));
+  if (!headers) {
+    return LAUNCHER_ERROR_FROM_WIN32(ERROR_BAD_EXE_FORMAT);
+  }
+
+  DWORD timestamp;
+  if (!headers.GetTimeStamp(timestamp)) {
+    return LAUNCHER_ERROR_FROM_WIN32(ERROR_INVALID_DATA);
+  }
+
+  return timestamp;
+}
+
+template <typename T>
+static mozilla::LauncherResult<mozilla::Maybe<T>> ReadRegistryValueData(
+    const nsAutoRegKey& key, const std::wstring& name, DWORD expectedType) {
+  static_assert(std::is_trivial_v<T> && std::is_standard_layout_v<T>,
+                "Registry value type must be primitive.");
+  T data;
+  DWORD dataLen = sizeof(data);
+  DWORD type;
+  LSTATUS status = ::RegQueryValueExW(key.get(), name.c_str(), nullptr, &type,
+                                      reinterpret_cast<PBYTE>(&data), &dataLen);
+  if (status == ERROR_FILE_NOT_FOUND) {
+    return mozilla::Maybe<T>();
+  }
+
+  if (status != ERROR_SUCCESS) {
+    return LAUNCHER_ERROR_FROM_WIN32(status);
+  }
+
+  if (type != expectedType) {
+    return LAUNCHER_ERROR_FROM_WIN32(ERROR_DATATYPE_MISMATCH);
+  }
+
+  return mozilla::Some(data);
+}
+
+static mozilla::LauncherResult<mozilla::UniquePtr<wchar_t[]>>
+ReadRegistryValueString(const nsAutoRegKey& aKey, const std::wstring& aName) {
+  mozilla::UniquePtr<wchar_t[]> buf;
+  DWORD dataLen;
+  LSTATUS status = ::RegGetValueW(aKey.get(), nullptr, aName.c_str(),
+                                  RRF_RT_REG_SZ, nullptr, nullptr, &dataLen);
+  if (status == ERROR_FILE_NOT_FOUND) {
+    return buf;
+  }
+
+  if (status != ERROR_SUCCESS) {
+    return LAUNCHER_ERROR_FROM_WIN32(status);
+  }
+
+  buf = mozilla::MakeUnique<wchar_t[]>(dataLen / sizeof(wchar_t));
+
+  status = ::RegGetValueW(aKey.get(), nullptr, aName.c_str(), RRF_RT_REG_SZ,
+                          nullptr, buf.get(), &dataLen);
+  if (status != ERROR_SUCCESS) {
+    return LAUNCHER_ERROR_FROM_WIN32(status);
+  }
+
+  return buf;
+}
+
+static mozilla::LauncherVoidResult WriteRegistryValueString(
+    const nsAutoRegKey& aKey, const std::wstring& aName,
+    const std::wstring& aValue) {
+  DWORD dataBytes = (aValue.size() + 1) * sizeof(wchar_t);
+  LSTATUS status = ::RegSetValueExW(
+      aKey.get(), aName.c_str(), /*Reserved*/ 0, REG_SZ,
+      reinterpret_cast<const BYTE*>(aValue.c_str()), dataBytes);
+  if (status != ERROR_SUCCESS) {
+    return LAUNCHER_ERROR_FROM_WIN32(status);
+  }
+
+  return mozilla::Ok();
+}
+
+template <typename T>
+static mozilla::LauncherVoidResult WriteRegistryValueData(
+    const nsAutoRegKey& key, const std::wstring& name, DWORD type, T data) {
+  static_assert(std::is_trivial_v<T> && std::is_standard_layout_v<T>,
+                "Registry value type must be primitive.");
+  LSTATUS status =
+      ::RegSetValueExW(key.get(), name.c_str(), 0, type,
+                       reinterpret_cast<PBYTE>(&data), sizeof(data));
+  if (status != ERROR_SUCCESS) {
+    return LAUNCHER_ERROR_FROM_WIN32(status);
+  }
+
+  return mozilla::Ok();
+}
+
+static mozilla::LauncherResult<bool> DeleteRegistryValueData(
+    const nsAutoRegKey& key, const std::wstring& name) {
+  LSTATUS status = ::RegDeleteValueW(key, name.c_str());
+  if (status == ERROR_FILE_NOT_FOUND) {
+    return false;
+  }
+
+  if (status != ERROR_SUCCESS) {
+    return LAUNCHER_ERROR_FROM_WIN32(status);
+  }
+
+  return true;
+}
+
+namespace mozilla {
+
+const wchar_t LauncherRegistryInfo::kLauncherSubKeyPath[] =
+    L"SOFTWARE\\" EXPAND_STRING_MACRO(MOZ_APP_VENDOR) L"\\" EXPAND_STRING_MACRO(
+        MOZ_APP_BASENAME) L"\\Launcher";
+const wchar_t LauncherRegistryInfo::kLauncherSuffix[] = L"|Launcher";
+const wchar_t LauncherRegistryInfo::kBrowserSuffix[] = L"|Browser";
+const wchar_t LauncherRegistryInfo::kImageTimestampSuffix[] = L"|Image";
+const wchar_t LauncherRegistryInfo::kTelemetrySuffix[] = L"|Telemetry";
+const wchar_t LauncherRegistryInfo::kBlocklistSuffix[] = L"|Blocklist";
+
+bool LauncherRegistryInfo::sAllowCommit = true;
+
+LauncherResult<LauncherRegistryInfo::Disposition> LauncherRegistryInfo::Open() {
+  if (!!mRegKey) {
+    return Disposition::OpenedExisting;
+  }
+
+  DWORD disposition;
+  HKEY rawKey;
+  LSTATUS result = ::RegCreateKeyExW(
+      HKEY_CURRENT_USER, kLauncherSubKeyPath, 0, nullptr,
+      REG_OPTION_NON_VOLATILE, KEY_ALL_ACCESS, nullptr, &rawKey, &disposition);
+  if (result != ERROR_SUCCESS) {
+    return LAUNCHER_ERROR_FROM_WIN32(result);
+  }
+
+  mRegKey.own(rawKey);
+
+  switch (disposition) {
+    case REG_CREATED_NEW_KEY:
+      return Disposition::CreatedNew;
+    case REG_OPENED_EXISTING_KEY:
+      return Disposition::OpenedExisting;
+    default:
+      break;
+  }
+
+  MOZ_ASSERT_UNREACHABLE("Invalid disposition from RegCreateKeyExW");
+  return LAUNCHER_ERROR_GENERIC();
+}
+
+LauncherVoidResult LauncherRegistryInfo::ReflectPrefToRegistry(
+    const bool aEnable) {
+  LauncherResult<EnabledState> curEnabledState = IsEnabled();
+  if (curEnabledState.isErr()) {
+    return curEnabledState.propagateErr();
+  }
+
+  bool isCurrentlyEnabled =
+      curEnabledState.inspect() != EnabledState::ForceDisabled;
+  if (isCurrentlyEnabled == aEnable) {
+    // Don't reflect to the registry unless the new enabled state is actually
+    // changing with respect to the current enabled state.
+    return Ok();
+  }
+
+  // Always delete the launcher timestamp
+  LauncherResult<bool> clearedLauncherTimestamp = ClearLauncherStartTimestamp();
+  MOZ_ASSERT(clearedLauncherTimestamp.isOk());
+  if (clearedLauncherTimestamp.isErr()) {
+    return clearedLauncherTimestamp.propagateErr();
+  }
+
+  // Allow commit when we enable the launcher, otherwise block.
+  sAllowCommit = aEnable;
+
+  if (!aEnable) {
+    // Set the browser timestamp to 0 to indicate force-disabled
+    return WriteBrowserStartTimestamp(0ULL);
+  }
+
+  // Otherwise we delete the browser timestamp to start over fresh
+  LauncherResult<bool> clearedBrowserTimestamp = ClearBrowserStartTimestamp();
+  MOZ_ASSERT(clearedBrowserTimestamp.isOk());
+  if (clearedBrowserTimestamp.isErr()) {
+    return clearedBrowserTimestamp.propagateErr();
+  }
+
+  return Ok();
+}
+
+LauncherVoidResult LauncherRegistryInfo::ReflectTelemetryPrefToRegistry(
+    const bool aEnable) {
+  LauncherResult<Disposition> disposition = Open();
+  if (disposition.isErr()) {
+    return disposition.propagateErr();
+  }
+
+  return WriteRegistryValueData(mRegKey, ResolveTelemetryValueName(), REG_DWORD,
+                                aEnable ? 1UL : 0UL);
+}
+
+LauncherResult<LauncherRegistryInfo::ProcessType> LauncherRegistryInfo::Check(
+    const ProcessType aDesiredType, const CheckOption aOption) {
+  LauncherResult<Disposition> disposition = Open();
+  if (disposition.isErr()) {
+    return disposition.propagateErr();
+  }
+
+  LauncherResult<DWORD> ourImageTimestamp = GetCurrentImageTimestamp();
+  if (ourImageTimestamp.isErr()) {
+    return ourImageTimestamp.propagateErr();
+  }
+
+  LauncherResult<Maybe<DWORD>> savedImageTimestamp = GetSavedImageTimestamp();
+  if (savedImageTimestamp.isErr()) {
+    return savedImageTimestamp.propagateErr();
+  }
+
+  // If we don't have a saved timestamp, or we do but it doesn't match with
+  // our current timestamp, clear previous values unless we're force-disabled.
+  if (savedImageTimestamp.inspect().isNothing() ||
+      savedImageTimestamp.inspect().value() != ourImageTimestamp.inspect()) {
+    LauncherVoidResult clearResult = ClearStartTimestamps();
+    if (clearResult.isErr()) {
+      return clearResult.propagateErr();
+    }
+
+    LauncherVoidResult writeResult =
+        WriteImageTimestamp(ourImageTimestamp.inspect());
+    if (writeResult.isErr()) {
+      return writeResult.propagateErr();
+    }
+  }
+
+  // If we're going to be running as the browser process, or there is no
+  // existing values to check, just write our timestamp and return.
+  if (aDesiredType == ProcessType::Browser) {
+    mBrowserTimestampToWrite = Some(QPCNowRaw());
+    return ProcessType::Browser;
+  }
+
+  if (disposition.inspect() == Disposition::CreatedNew) {
+    mLauncherTimestampToWrite = Some(QPCNowRaw());
+    return ProcessType::Launcher;
+  }
+
+  if (disposition.inspect() != Disposition::OpenedExisting) {
+    MOZ_ASSERT_UNREACHABLE("Invalid |disposition|");
+    return LAUNCHER_ERROR_GENERIC();
+  }
+
+  LauncherResult<Maybe<uint64_t>> lastLauncherTimestampResult =
+      GetLauncherStartTimestamp();
+  if (lastLauncherTimestampResult.isErr()) {
+    return lastLauncherTimestampResult.propagateErr();
+  }
+
+  LauncherResult<Maybe<uint64_t>> lastBrowserTimestampResult =
+      GetBrowserStartTimestamp();
+  if (lastBrowserTimestampResult.isErr()) {
+    return lastBrowserTimestampResult.propagateErr();
+  }
+
+  const Maybe<uint64_t>& lastLauncherTimestamp =
+      lastLauncherTimestampResult.inspect();
+  const Maybe<uint64_t>& lastBrowserTimestamp =
+      lastBrowserTimestampResult.inspect();
+
+  ProcessType typeToRunAs = aDesiredType;
+
+  if (lastLauncherTimestamp.isSome() != lastBrowserTimestamp.isSome()) {
+    // If we have a launcher timestamp but no browser timestamp (or vice versa),
+    // that's bad because it is indicating that the browser can't run with
+    // the launcher process.
+    typeToRunAs = ProcessType::Browser;
+  } else if (lastLauncherTimestamp.isSome()) {
+    // if we have both timestamps, we want to ensure that the launcher timestamp
+    // is earlier than the browser timestamp.
+    if (aDesiredType == ProcessType::Launcher) {
+      bool areTimestampsOk =
+          lastLauncherTimestamp.value() < lastBrowserTimestamp.value();
+      if (!areTimestampsOk) {
+        typeToRunAs = ProcessType::Browser;
+      }
+    }
+  } else {
+    // If we have neither timestamp, then we should try running as suggested
+    // by |aDesiredType|.
+    // We shouldn't really have this scenario unless we're going to be running
+    // as the launcher process.
+    MOZ_ASSERT(typeToRunAs == ProcessType::Launcher);
+    // No change to typeToRunAs
+  }
+
+  // Debugging setting that forces the desired type regardless of the various
+  // tests that have been performed.
+  if (aOption == CheckOption::Force) {
+    typeToRunAs = aDesiredType;
+  }
+
+  switch (typeToRunAs) {
+    case ProcessType::Browser:
+      if (aDesiredType != typeToRunAs) {
+        // We were hoping to run as the launcher, but some failure has caused
+        // us to run as the browser. Set the browser timestamp to zero as an
+        // indicator.
+        mBrowserTimestampToWrite = Some(0ULL);
+      } else {
+        mBrowserTimestampToWrite = Some(QPCNowRaw());
+      }
+      break;
+    case ProcessType::Launcher:
+      mLauncherTimestampToWrite = Some(QPCNowRaw());
+      break;
+    default:
+      MOZ_ASSERT_UNREACHABLE("Invalid |typeToRunAs|");
+      return LAUNCHER_ERROR_GENERIC();
+  }
+
+  return typeToRunAs;
+}
+
+LauncherVoidResult LauncherRegistryInfo::DisableDueToFailure() {
+  LauncherResult<Disposition> disposition = Open();
+  if (disposition.isErr()) {
+    return disposition.propagateErr();
+  }
+  LauncherVoidResult result = WriteBrowserStartTimestamp(0ULL);
+  if (result.isOk()) {
+    // Block commit when we disable the launcher.  It could be allowed
+    // when the image timestamp is updated.
+    sAllowCommit = false;
+  }
+  return result;
+}
+
+LauncherVoidResult LauncherRegistryInfo::Commit() {
+  if (!sAllowCommit) {
+    Abort();
+    return Ok();
+  }
+
+  LauncherResult<Disposition> disposition = Open();
+  if (disposition.isErr()) {
+    return disposition.propagateErr();
+  }
+
+  if (mLauncherTimestampToWrite.isSome()) {
+    LauncherVoidResult writeResult =
+        WriteLauncherStartTimestamp(mLauncherTimestampToWrite.value());
+    if (writeResult.isErr()) {
+      return writeResult.propagateErr();
+    }
+    mLauncherTimestampToWrite = Nothing();
+  }
+
+  if (mBrowserTimestampToWrite.isSome()) {
+    LauncherVoidResult writeResult =
+        WriteBrowserStartTimestamp(mBrowserTimestampToWrite.value());
+    if (writeResult.isErr()) {
+      return writeResult.propagateErr();
+    }
+    mBrowserTimestampToWrite = Nothing();
+  }
+
+  return Ok();
+}
+
+void LauncherRegistryInfo::Abort() {
+  mLauncherTimestampToWrite = mBrowserTimestampToWrite = Nothing();
+}
+
+LauncherRegistryInfo::EnabledState LauncherRegistryInfo::GetEnabledState(
+    const Maybe<uint64_t>& aLauncherTs, const Maybe<uint64_t>& aBrowserTs) {
+  if (aBrowserTs.isSome()) {
+    if (aLauncherTs.isSome()) {
+      if (aLauncherTs.value() < aBrowserTs.value()) {
+        // Both timestamps exist and the browser's timestamp is later.
+        return EnabledState::Enabled;
+      }
+    } else if (aBrowserTs.value() == 0ULL) {
+      // Only browser's timestamp exists and its value is 0.
+      return EnabledState::ForceDisabled;
+    }
+  } else if (aLauncherTs.isNothing()) {
+    // Neither timestamps exist.
+    return EnabledState::Enabled;
+  }
+
+  // Everything else is FailDisabled.
+  return EnabledState::FailDisabled;
+}
+
+LauncherResult<LauncherRegistryInfo::EnabledState>
+LauncherRegistryInfo::IsEnabled() {
+  LauncherResult<Disposition> disposition = Open();
+  if (disposition.isErr()) {
+    return disposition.propagateErr();
+  }
+
+  LauncherResult<Maybe<uint64_t>> lastLauncherTimestamp =
+      GetLauncherStartTimestamp();
+  if (lastLauncherTimestamp.isErr()) {
+    return lastLauncherTimestamp.propagateErr();
+  }
+
+  LauncherResult<Maybe<uint64_t>> lastBrowserTimestamp =
+      GetBrowserStartTimestamp();
+  if (lastBrowserTimestamp.isErr()) {
+    return lastBrowserTimestamp.propagateErr();
+  }
+
+  return GetEnabledState(lastLauncherTimestamp.inspect(),
+                         lastBrowserTimestamp.inspect());
+}
+
+LauncherResult<bool> LauncherRegistryInfo::IsTelemetryEnabled() {
+  LauncherResult<Disposition> disposition = Open();
+  if (disposition.isErr()) {
+    return disposition.propagateErr();
+  }
+
+  LauncherResult<Maybe<DWORD>> result = ReadRegistryValueData<DWORD>(
+      mRegKey, ResolveTelemetryValueName(), REG_DWORD);
+  if (result.isErr()) {
+    return result.propagateErr();
+  }
+
+  if (result.inspect().isNothing()) {
+    // Value does not exist, treat as false
+    return false;
+  }
+
+  return result.inspect().value() != 0;
+}
+
+const std::wstring& LauncherRegistryInfo::ResolveLauncherValueName() {
+  if (mLauncherValueName.empty()) {
+    mLauncherValueName.assign(mBinPath);
+    mLauncherValueName.append(kLauncherSuffix,
+                              ArrayLength(kLauncherSuffix) - 1);
+  }
+
+  return mLauncherValueName;
+}
+
+const std::wstring& LauncherRegistryInfo::ResolveBrowserValueName() {
+  if (mBrowserValueName.empty()) {
+    mBrowserValueName.assign(mBinPath);
+    mBrowserValueName.append(kBrowserSuffix, ArrayLength(kBrowserSuffix) - 1);
+  }
+
+  return mBrowserValueName;
+}
+
+const std::wstring& LauncherRegistryInfo::ResolveImageTimestampValueName() {
+  if (mImageValueName.empty()) {
+    mImageValueName.assign(mBinPath);
+    mImageValueName.append(kImageTimestampSuffix,
+                           ArrayLength(kImageTimestampSuffix) - 1);
+  }
+
+  return mImageValueName;
+}
+
+const std::wstring& LauncherRegistryInfo::ResolveTelemetryValueName() {
+  if (mTelemetryValueName.empty()) {
+    mTelemetryValueName.assign(mBinPath);
+    mTelemetryValueName.append(kTelemetrySuffix,
+                               ArrayLength(kTelemetrySuffix) - 1);
+  }
+
+  return mTelemetryValueName;
+}
+
+const std::wstring& LauncherRegistryInfo::ResolveBlocklistValueName() {
+  if (mBlocklistValueName.empty()) {
+    mBlocklistValueName.assign(mBinPath);
+    mBlocklistValueName.append(kBlocklistSuffix,
+                               ArrayLength(kBlocklistSuffix) - 1);
+  }
+
+  return mBlocklistValueName;
+}
+
+LauncherVoidResult LauncherRegistryInfo::WriteLauncherStartTimestamp(
+    uint64_t aValue) {
+  return WriteRegistryValueData(mRegKey, ResolveLauncherValueName(), REG_QWORD,
+                                aValue);
+}
+
+LauncherVoidResult LauncherRegistryInfo::WriteBrowserStartTimestamp(
+    uint64_t aValue) {
+  return WriteRegistryValueData(mRegKey, ResolveBrowserValueName(), REG_QWORD,
+                                aValue);
+}
+
+LauncherVoidResult LauncherRegistryInfo::WriteImageTimestamp(DWORD aTimestamp) {
+  return WriteRegistryValueData(mRegKey, ResolveImageTimestampValueName(),
+                                REG_DWORD, aTimestamp);
+}
+
+LauncherResult<bool> LauncherRegistryInfo::ClearLauncherStartTimestamp() {
+  return DeleteRegistryValueData(mRegKey, ResolveLauncherValueName());
+}
+
+LauncherResult<bool> LauncherRegistryInfo::ClearBrowserStartTimestamp() {
+  return DeleteRegistryValueData(mRegKey, ResolveBrowserValueName());
+}
+
+LauncherVoidResult LauncherRegistryInfo::ClearStartTimestamps() {
+  LauncherResult<EnabledState> enabled = IsEnabled();
+  if (enabled.isOk() && enabled.inspect() == EnabledState::ForceDisabled) {
+    // We don't clear anything when we're force disabled - we need to maintain
+    // the current registry state in this case.
+    return Ok();
+  }
+
+  LauncherResult<bool> clearedLauncherTimestamp = ClearLauncherStartTimestamp();
+  if (clearedLauncherTimestamp.isErr()) {
+    return clearedLauncherTimestamp.propagateErr();
+  }
+
+  LauncherResult<bool> clearedBrowserTimestamp = ClearBrowserStartTimestamp();
+  if (clearedBrowserTimestamp.isErr()) {
+    return clearedBrowserTimestamp.propagateErr();
+  }
+
+  // Reset both timestamps to align with registry deletion
+  mLauncherTimestampToWrite = mBrowserTimestampToWrite = Nothing();
+
+  // Disablement is gone.  Let's allow commit.
+  sAllowCommit = true;
+
+  return Ok();
+}
+
+LauncherResult<Maybe<DWORD>> LauncherRegistryInfo::GetSavedImageTimestamp() {
+  return ReadRegistryValueData<DWORD>(mRegKey, ResolveImageTimestampValueName(),
+                                      REG_DWORD);
+}
+
+LauncherResult<Maybe<uint64_t>>
+LauncherRegistryInfo::GetLauncherStartTimestamp() {
+  return ReadRegistryValueData<uint64_t>(mRegKey, ResolveLauncherValueName(),
+                                         REG_QWORD);
+}
+
+LauncherResult<Maybe<uint64_t>>
+LauncherRegistryInfo::GetBrowserStartTimestamp() {
+  return ReadRegistryValueData<uint64_t>(mRegKey, ResolveBrowserValueName(),
+                                         REG_QWORD);
+}
+
+LauncherResult<std::wstring>
+LauncherRegistryInfo::BuildDefaultBlocklistFilename() {
+  // These flags are chosen to avoid I/O, see bug 1363398.
+  const DWORD flags =
+      KF_FLAG_SIMPLE_IDLIST | KF_FLAG_DONT_VERIFY | KF_FLAG_NO_ALIAS;
+  PWSTR rawPath = nullptr;
+  HRESULT hr =
+      ::SHGetKnownFolderPath(FOLDERID_RoamingAppData, flags, nullptr, &rawPath);
+  if (FAILED(hr)) {
+    ::CoTaskMemFree(rawPath);
+    return LAUNCHER_ERROR_FROM_HRESULT(hr);
+  }
+
+  UniquePtr<wchar_t, CoTaskMemFreeDeleter> appDataPath(rawPath);
+  std::wstring defaultBlocklistPath(appDataPath.get());
+
+  UniquePtr<NS_tchar[]> hash;
+  std::wstring binPathLower;
+  binPathLower.reserve(mBinPath.size());
+  std::transform(mBinPath.begin(), mBinPath.end(),
+                 std::back_inserter(binPathLower), std::towlower);
+  if (!::GetInstallHash(reinterpret_cast<const char16_t*>(binPathLower.c_str()),
+                        hash)) {
+    return LAUNCHER_ERROR_FROM_WIN32(ERROR_INVALID_DATA);
+  }
+
+  defaultBlocklistPath.append(
+      L"\\" MOZ_APP_VENDOR L"\\" MOZ_APP_BASENAME L"\\blocklist-");
+  defaultBlocklistPath.append(hash.get());
+
+  return defaultBlocklistPath;
+}
+
+LauncherResult<std::wstring> LauncherRegistryInfo::GetBlocklistFileName() {
+  LauncherResult<Disposition> disposition = Open();
+  if (disposition.isErr()) {
+    return disposition.propagateErr();
+  }
+
+  LauncherResult<UniquePtr<wchar_t[]>> readResult =
+      ReadRegistryValueString(mRegKey, ResolveBlocklistValueName());
+  if (readResult.isErr()) {
+    return readResult.propagateErr();
+  }
+
+  if (readResult.inspect()) {
+    UniquePtr<wchar_t[]> buf = readResult.unwrap();
+    return std::wstring(buf.get());
+  }
+
+  LauncherResult<std::wstring> defaultBlocklistPath =
+      BuildDefaultBlocklistFilename();
+  if (defaultBlocklistPath.isErr()) {
+    return defaultBlocklistPath.propagateErr();
+  }
+
+  LauncherVoidResult writeResult = WriteRegistryValueString(
+      mRegKey, ResolveBlocklistValueName(), defaultBlocklistPath.inspect());
+  if (writeResult.isErr()) {
+    return writeResult.propagateErr();
+  }
+
+  return defaultBlocklistPath;
+}
+
+}  // namespace mozilla
diff --git a/toolkit/xre/LauncherRegistryInfo.h b/toolkit/xre/LauncherRegistryInfo.h
new file mode 100644
index 0000000000..c89ed66a69
--- /dev/null
+++ b/toolkit/xre/LauncherRegistryInfo.h
@@ -0,0 +1,104 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_LauncherRegistryInfo_h
+#define mozilla_LauncherRegistryInfo_h
+
+#include "mozilla/Maybe.h"
+#include "mozilla/WinHeaderOnlyUtils.h"
+#include "nsWindowsHelpers.h"
+
+#include <string>
+
+/**
+ * We use std::wstring here because this code must be usable within both the
+ * launcher process and Gecko itself.
+ */
+
+namespace mozilla {
+
+class LauncherRegistryInfo final {
+ public:
+  enum class ProcessType { Launcher, Browser };
+
+  enum class EnabledState {
+    Enabled,
+    FailDisabled,
+    ForceDisabled,
+  };
+
+  enum class CheckOption {
+    Default,
+    Force,
+  };
+
+  LauncherRegistryInfo() : mBinPath(GetFullBinaryPath().get()) {}
+  ~LauncherRegistryInfo() { Abort(); }
+
+  LauncherVoidResult ReflectPrefToRegistry(const bool aEnable);
+  LauncherResult<EnabledState> IsEnabled();
+  LauncherResult<bool> IsTelemetryEnabled();
+  LauncherVoidResult ReflectTelemetryPrefToRegistry(const bool aEnable);
+  LauncherResult<ProcessType> Check(
+      const ProcessType aDesiredType,
+      const CheckOption aOption = CheckOption::Default);
+  LauncherVoidResult DisableDueToFailure();
+  LauncherVoidResult Commit();
+  void Abort();
+  LauncherResult<std::wstring> GetBlocklistFileName();
+
+ private:
+  enum class Disposition { CreatedNew, OpenedExisting };
+
+ private:
+  // This flag is to prevent the disabled state from being accidentally
+  // re-enabled by another instance.
+  static bool sAllowCommit;
+
+  static EnabledState GetEnabledState(const Maybe<uint64_t>& aLauncherTs,
+                                      const Maybe<uint64_t>& aBrowserTs);
+
+  LauncherResult<Disposition> Open();
+  LauncherVoidResult WriteLauncherStartTimestamp(uint64_t aValue);
+  LauncherVoidResult WriteBrowserStartTimestamp(uint64_t aValue);
+  LauncherVoidResult WriteImageTimestamp(DWORD aTimestamp);
+  LauncherResult<bool> ClearLauncherStartTimestamp();
+  LauncherResult<bool> ClearBrowserStartTimestamp();
+  LauncherVoidResult ClearStartTimestamps();
+  LauncherResult<Maybe<DWORD>> GetSavedImageTimestamp();
+  LauncherResult<Maybe<uint64_t>> GetLauncherStartTimestamp();
+  LauncherResult<Maybe<uint64_t>> GetBrowserStartTimestamp();
+  LauncherResult<std::wstring> BuildDefaultBlocklistFilename();
+
+  const std::wstring& ResolveLauncherValueName();
+  const std::wstring& ResolveBrowserValueName();
+  const std::wstring& ResolveImageTimestampValueName();
+  const std::wstring& ResolveTelemetryValueName();
+  const std::wstring& ResolveBlocklistValueName();
+
+ private:
+  Maybe<uint64_t> mLauncherTimestampToWrite;
+  Maybe<uint64_t> mBrowserTimestampToWrite;
+
+  nsAutoRegKey mRegKey;
+  std::wstring mBinPath;
+  std::wstring mImageValueName;
+  std::wstring mBrowserValueName;
+  std::wstring mLauncherValueName;
+  std::wstring mTelemetryValueName;
+  std::wstring mBlocklistValueName;
+
+  static const wchar_t kLauncherSubKeyPath[];
+  static const wchar_t kLauncherSuffix[];
+  static const wchar_t kBrowserSuffix[];
+  static const wchar_t kImageTimestampSuffix[];
+  static const wchar_t kTelemetrySuffix[];
+  static const wchar_t kBlocklistSuffix[];
+};
+
+}  // namespace mozilla
+
+#endif  // mozilla_LauncherRegistryInfo_h
diff --git a/toolkit/xre/MacApplicationDelegate.h b/toolkit/xre/MacApplicationDelegate.h
new file mode 100644
index 0000000000..261cccc122
--- /dev/null
+++ b/toolkit/xre/MacApplicationDelegate.h
@@ -0,0 +1,17 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// This file defines the interface between Cocoa-specific Obj-C++ and generic
+// C++, so it itself cannot have any Obj-C bits in it.
+
+#ifndef MacApplicationDelegate_h_
+#define MacApplicationDelegate_h_
+
+void EnsureUseCocoaDockAPI(void);
+void SetupMacApplicationDelegate(bool* gRestartedByOS);
+void ProcessPendingGetURLAppleEvents(void);
+void DisableAppNap(void);
+
+#endif
diff --git a/toolkit/xre/MacApplicationDelegate.mm b/toolkit/xre/MacApplicationDelegate.mm
new file mode 100644
index 0000000000..215798fa24
--- /dev/null
+++ b/toolkit/xre/MacApplicationDelegate.mm
@@ -0,0 +1,412 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// NSApplication delegate for Mac OS X Cocoa API.
+
+// As of 10.4 Tiger, the system can send six kinds of Apple Events to an application;
+// a well-behaved XUL app should have some kind of handling for all of them.
+//
+// See
+// http://developer.apple.com/documentation/Cocoa/Conceptual/ScriptableCocoaApplications/SApps_handle_AEs/chapter_11_section_3.html
+// for details.
+
+#import <Cocoa/Cocoa.h>
+#include "NativeMenuMac.h"
+#import <Carbon/Carbon.h>
+
+#include "nsCOMPtr.h"
+#include "nsINativeAppSupport.h"
+#include "nsAppRunner.h"
+#include "nsAppShell.h"
+#include "nsComponentManagerUtils.h"
+#include "nsServiceManagerUtils.h"
+#include "nsIAppStartup.h"
+#include "nsIObserverService.h"
+#include "nsISupportsPrimitives.h"
+#include "nsObjCExceptions.h"
+#include "nsIFile.h"
+#include "nsDirectoryServiceDefs.h"
+#include "nsCommandLine.h"
+#include "nsIMacDockSupport.h"
+#include "nsIStandaloneNativeMenu.h"
+#include "nsILocalFileMac.h"
+#include "nsString.h"
+#include "nsCommandLineServiceMac.h"
+#include "nsCommandLine.h"
+#include "nsStandaloneNativeMenu.h"
+#include "nsCocoaUtils.h"
+
+class AutoAutoreleasePool {
+ public:
+  AutoAutoreleasePool() { mLocalPool = [[NSAutoreleasePool alloc] init]; }
+  ~AutoAutoreleasePool() { [mLocalPool release]; }
+
+ private:
+  NSAutoreleasePool* mLocalPool;
+};
+
+@interface MacApplicationDelegate : NSObject <NSApplicationDelegate> {
+}
+
+@end
+
+static bool sProcessedGetURLEvent = false;
+
+// Methods that can be called from non-Objective-C code.
+
+// This is needed, on relaunch, to force the OS to use the "Cocoa Dock API"
+// instead of the "Carbon Dock API".  For more info see bmo bug 377166.
+void EnsureUseCocoaDockAPI() {
+  NS_OBJC_BEGIN_TRY_IGNORE_BLOCK;
+
+  [GeckoNSApplication sharedApplication];
+
+  NS_OBJC_END_TRY_IGNORE_BLOCK;
+}
+
+void DisableAppNap() {
+  // Prevent the parent process from entering App Nap. macOS does not put our
+  // child processes into App Nap and, as a result, when the parent is in
+  // App Nap, child processes continue to run normally generating IPC messages
+  // for the parent which can end up being queued. This can cause the browser
+  // to be unresponsive for a period of time after the App Nap until the parent
+  // process "catches up." NSAppSleepDisabled has to be set early during
+  // startup before the OS reads the value for the process.
+  [[NSUserDefaults standardUserDefaults] registerDefaults:@{
+    @"NSAppSleepDisabled" : @YES,
+  }];
+}
+
+void SetupMacApplicationDelegate(bool* gRestartedByOS) {
+  NS_OBJC_BEGIN_TRY_IGNORE_BLOCK;
+
+  // this is called during startup, outside an event loop, and therefore
+  // needs an autorelease pool to avoid cocoa object leakage (bug 559075)
+  AutoAutoreleasePool pool;
+
+  // Ensure that ProcessPendingGetURLAppleEvents() doesn't regress bug 377166.
+  [GeckoNSApplication sharedApplication];
+
+  // This call makes it so that application:openFile: doesn't get bogus calls
+  // from Cocoa doing its own parsing of the argument string. And yes, we need
+  // to use a string with a boolean value in it. That's just how it works.
+  [[NSUserDefaults standardUserDefaults] setObject:@"NO" forKey:@"NSTreatUnknownArgumentsAsOpen"];
+
+  // Create the delegate. This should be around for the lifetime of the app.
+  id<NSApplicationDelegate> delegate = [[MacApplicationDelegate alloc] init];
+  [[GeckoNSApplication sharedApplication] setDelegate:delegate];
+
+  *gRestartedByOS = !!nsCocoaUtils::ShouldRestoreStateDueToLaunchAtLogin();
+
+  NS_OBJC_END_TRY_IGNORE_BLOCK;
+}
+
+// Indirectly make the OS process any pending GetURL Apple events.  This is
+// done via _DPSNextEvent() (an undocumented AppKit function called from
+// [NSApplication nextEventMatchingMask:untilDate:inMode:dequeue:]).  Apple
+// events are only processed if 'dequeue' is 'YES' -- so we need to call
+// [NSApplication sendEvent:] on any event that gets returned.  'event' will
+// never itself be an Apple event, and it may be 'nil' even when Apple events
+// are processed.
+void ProcessPendingGetURLAppleEvents() {
+  AutoAutoreleasePool pool;
+  bool keepSpinning = true;
+  while (keepSpinning) {
+    sProcessedGetURLEvent = false;
+    NSEvent* event = [NSApp nextEventMatchingMask:NSEventMaskAny
+                                        untilDate:nil
+                                           inMode:NSDefaultRunLoopMode
+                                          dequeue:YES];
+    if (event) [NSApp sendEvent:event];
+    keepSpinning = sProcessedGetURLEvent;
+  }
+}
+
+@implementation MacApplicationDelegate
+
+- (id)init {
+  NS_OBJC_BEGIN_TRY_BLOCK_RETURN;
+
+  if ((self = [super init])) {
+    NSAppleEventManager* aeMgr = [NSAppleEventManager sharedAppleEventManager];
+
+    [aeMgr setEventHandler:self
+               andSelector:@selector(handleAppleEvent:withReplyEvent:)
+             forEventClass:kInternetEventClass
+                andEventID:kAEGetURL];
+
+    [aeMgr setEventHandler:self
+               andSelector:@selector(handleAppleEvent:withReplyEvent:)
+             forEventClass:'WWW!'
+                andEventID:'OURL'];
+
+    [aeMgr setEventHandler:self
+               andSelector:@selector(handleAppleEvent:withReplyEvent:)
+             forEventClass:kCoreEventClass
+                andEventID:kAEOpenDocuments];
+
+    if (![NSApp windowsMenu]) {
+      // If the application has a windows menu, it will keep it up to date and
+      // prepend the window list to the Dock menu automatically.
+      NSMenu* windowsMenu = [[NSMenu alloc] initWithTitle:@"Window"];
+      [NSApp setWindowsMenu:windowsMenu];
+      [windowsMenu release];
+    }
+  }
+  return self;
+
+  NS_OBJC_END_TRY_BLOCK_RETURN(nil);
+}
+
+- (void)dealloc {
+  NS_OBJC_BEGIN_TRY_IGNORE_BLOCK;
+
+  NSAppleEventManager* aeMgr = [NSAppleEventManager sharedAppleEventManager];
+  [aeMgr removeEventHandlerForEventClass:kInternetEventClass andEventID:kAEGetURL];
+  [aeMgr removeEventHandlerForEventClass:'WWW!' andEventID:'OURL'];
+  [aeMgr removeEventHandlerForEventClass:kCoreEventClass andEventID:kAEOpenDocuments];
+  [super dealloc];
+
+  NS_OBJC_END_TRY_IGNORE_BLOCK;
+}
+
+// The method that NSApplication calls upon a request to reopen, such as when
+// the Dock icon is clicked and no windows are open. A "visible" window may be
+// miniaturized, so we can't skip nsCocoaNativeReOpen() if 'flag' is 'true'.
+- (BOOL)applicationShouldHandleReopen:(NSApplication*)theApp hasVisibleWindows:(BOOL)flag {
+  nsCOMPtr<nsINativeAppSupport> nas = NS_GetNativeAppSupport();
+  NS_ENSURE_TRUE(nas, NO);
+
+  // Go to the common Carbon/Cocoa reopen method.
+  nsresult rv = nas->ReOpen();
+  NS_ENSURE_SUCCESS(rv, NO);
+
+  // NO says we don't want NSApplication to do anything else for us.
+  return NO;
+}
+
+// The method that NSApplication calls when documents are requested to be opened.
+// It will be called once for each selected document.
+- (BOOL)application:(NSApplication*)theApplication openFile:(NSString*)filename {
+  NS_OBJC_BEGIN_TRY_BLOCK_RETURN;
+
+  NSURL* url = [NSURL fileURLWithPath:filename];
+  if (!url) return NO;
+
+  NSString* urlString = [url absoluteString];
+  if (!urlString) return NO;
+
+  // Add the URL to any command line we're currently setting up.
+  if (CommandLineServiceMac::AddURLToCurrentCommandLine([urlString UTF8String])) return YES;
+
+  nsCOMPtr<nsILocalFileMac> inFile;
+  nsresult rv = NS_NewLocalFileWithCFURL((CFURLRef)url, true, getter_AddRefs(inFile));
+  if (NS_FAILED(rv)) return NO;
+
+  nsCOMPtr<nsICommandLineRunner> cmdLine(new nsCommandLine());
+
+  nsCString filePath;
+  rv = inFile->GetNativePath(filePath);
+  if (NS_FAILED(rv)) return NO;
+
+  nsCOMPtr<nsIFile> workingDir;
+  rv = NS_GetSpecialDirectory(NS_OS_CURRENT_WORKING_DIR, getter_AddRefs(workingDir));
+  if (NS_FAILED(rv)) {
+    // Couldn't find a working dir. Uh oh. Good job cmdline::Init can cope.
+    workingDir = nullptr;
+  }
+
+  const char* argv[3] = {nullptr, "-file", filePath.get()};
+  rv = cmdLine->Init(3, argv, workingDir, nsICommandLine::STATE_REMOTE_EXPLICIT);
+  if (NS_FAILED(rv)) return NO;
+
+  if (NS_SUCCEEDED(cmdLine->Run())) return YES;
+
+  return NO;
+
+  NS_OBJC_END_TRY_BLOCK_RETURN(NO);
+}
+
+// The method that NSApplication calls when documents are requested to be printed
+// from the Finder (under the "File" menu).
+// It will be called once for each selected document.
+- (BOOL)application:(NSApplication*)theApplication printFile:(NSString*)filename {
+  return NO;
+}
+
+// Create the menu that shows up in the Dock.
+- (NSMenu*)applicationDockMenu:(NSApplication*)sender {
+  NS_OBJC_BEGIN_TRY_BLOCK_RETURN;
+
+  // Create the NSMenu that will contain the dock menu items.
+  NSMenu* menu = [[[NSMenu alloc] initWithTitle:@""] autorelease];
+  [menu setAutoenablesItems:NO];
+
+  // Add application-specific dock menu items. On error, do not insert the
+  // dock menu items.
+  nsresult rv;
+  nsCOMPtr<nsIMacDockSupport> dockSupport =
+      do_GetService("@mozilla.org/widget/macdocksupport;1", &rv);
+  if (NS_FAILED(rv) || !dockSupport) return menu;
+
+  nsCOMPtr<nsIStandaloneNativeMenu> dockMenuInterface;
+  rv = dockSupport->GetDockMenu(getter_AddRefs(dockMenuInterface));
+  if (NS_FAILED(rv) || !dockMenuInterface) return menu;
+
+  RefPtr<mozilla::widget::NativeMenuMac> dockMenu =
+      static_cast<nsStandaloneNativeMenu*>(dockMenuInterface.get())->GetNativeMenu();
+
+  // Give the menu the opportunity to update itself before display.
+  dockMenu->MenuWillOpen();
+
+  // Obtain a copy of the native menu.
+  NSMenu* nativeDockMenu = dockMenu->NativeNSMenu();
+  if (!nativeDockMenu) {
+    return menu;
+  }
+
+  // Loop through the application-specific dock menu and insert its
+  // contents into the dock menu that we are building for Cocoa.
+  int numDockMenuItems = [nativeDockMenu numberOfItems];
+  if (numDockMenuItems > 0) {
+    if ([menu numberOfItems] > 0) [menu addItem:[NSMenuItem separatorItem]];
+
+    for (int i = 0; i < numDockMenuItems; i++) {
+      NSMenuItem* itemCopy = [[nativeDockMenu itemAtIndex:i] copy];
+      [menu addItem:itemCopy];
+      [itemCopy release];
+    }
+  }
+
+  return menu;
+
+  NS_OBJC_END_TRY_BLOCK_RETURN(nil);
+}
+
+- (void)applicationWillFinishLaunching:(NSNotification*)notification {
+  // We provide our own full screen menu item, so we don't want the OS providing
+  // one as well.
+  [[NSUserDefaults standardUserDefaults] setBool:NO forKey:@"NSFullScreenMenuItemEverywhere"];
+}
+
+// If we don't handle applicationShouldTerminate:, a call to [NSApp terminate:]
+// (from the browser or from the OS) can result in an unclean shutdown.
+- (NSApplicationTerminateReply)applicationShouldTerminate:(NSApplication*)sender {
+  nsCOMPtr<nsIObserverService> obsServ = do_GetService("@mozilla.org/observer-service;1");
+  if (!obsServ) return NSTerminateNow;
+
+  nsCOMPtr<nsISupportsPRBool> cancelQuit = do_CreateInstance(NS_SUPPORTS_PRBOOL_CONTRACTID);
+  if (!cancelQuit) return NSTerminateNow;
+
+  cancelQuit->SetData(false);
+  obsServ->NotifyObservers(cancelQuit, "quit-application-requested", nullptr);
+
+  bool abortQuit;
+  cancelQuit->GetData(&abortQuit);
+  if (abortQuit) return NSTerminateCancel;
+
+  nsCOMPtr<nsIAppStartup> appService = do_GetService("@mozilla.org/toolkit/app-startup;1");
+  if (appService) {
+    bool userAllowedQuit = true;
+    appService->Quit(nsIAppStartup::eForceQuit, 0, &userAllowedQuit);
+    if (!userAllowedQuit) {
+      return NSTerminateCancel;
+    }
+  }
+
+  return NSTerminateNow;
+}
+
+- (void)handleAppleEvent:(NSAppleEventDescriptor*)event
+          withReplyEvent:(NSAppleEventDescriptor*)replyEvent {
+  if (!event) return;
+
+  AutoAutoreleasePool pool;
+
+  bool isGetURLEvent = ([event eventClass] == kInternetEventClass && [event eventID] == kAEGetURL);
+  if (isGetURLEvent) sProcessedGetURLEvent = true;
+
+  if (isGetURLEvent || ([event eventClass] == 'WWW!' && [event eventID] == 'OURL')) {
+    NSString* urlString = [[event paramDescriptorForKeyword:keyDirectObject] stringValue];
+    NSURL* url = [NSURL URLWithString:urlString];
+
+    [self openURL:url];
+  } else if ([event eventClass] == kCoreEventClass && [event eventID] == kAEOpenDocuments) {
+    NSAppleEventDescriptor* fileListDescriptor = [event paramDescriptorForKeyword:keyDirectObject];
+    if (!fileListDescriptor) return;
+
+    // Descriptor list indexing is one-based...
+    NSInteger numberOfFiles = [fileListDescriptor numberOfItems];
+    for (NSInteger i = 1; i <= numberOfFiles; i++) {
+      NSString* urlString = [[fileListDescriptor descriptorAtIndex:i] stringValue];
+      if (!urlString) continue;
+
+      // We need a path, not a URL
+      NSURL* url = [NSURL URLWithString:urlString];
+      if (!url) continue;
+
+      [self application:NSApp openFile:[url path]];
+    }
+  }
+}
+
+- (BOOL)application:(NSApplication*)application
+    willContinueUserActivityWithType:(NSString*)userActivityType {
+  return [userActivityType isEqualToString:NSUserActivityTypeBrowsingWeb];
+}
+
+- (BOOL)application:(NSApplication*)application
+    continueUserActivity:(NSUserActivity*)userActivity
+#if defined(MAC_OS_X_VERSION_10_14) && MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_14
+      restorationHandler:(void (^)(NSArray<id<NSUserActivityRestoring>>*))restorationHandler {
+#else
+      restorationHandler:(void (^)(NSArray*))restorationHandler {
+#endif
+  if (![userActivity.activityType isEqualToString:NSUserActivityTypeBrowsingWeb]) {
+    return NO;
+  }
+
+  return [self openURL:userActivity.webpageURL];
+}
+
+- (void)application:(NSApplication*)application
+    didFailToContinueUserActivityWithType:(NSString*)userActivityType
+                                    error:(NSError*)error {
+  NSLog(@"Failed to continue user activity %@: %@", userActivityType, error);
+}
+
+- (BOOL)openURL:(NSURL*)url {
+  if (!url || !url.scheme || [url.scheme caseInsensitiveCompare:@"chrome"] == NSOrderedSame) {
+    return NO;
+  }
+
+  const char* const urlString = [[url absoluteString] UTF8String];
+  // Add the URL to any command line we're currently setting up.
+  if (CommandLineServiceMac::AddURLToCurrentCommandLine(urlString)) {
+    return NO;
+  }
+
+  nsCOMPtr<nsICommandLineRunner> cmdLine(new nsCommandLine());
+  nsCOMPtr<nsIFile> workingDir;
+  nsresult rv = NS_GetSpecialDirectory(NS_OS_CURRENT_WORKING_DIR, getter_AddRefs(workingDir));
+  if (NS_FAILED(rv)) {
+    // Couldn't find a working dir. Uh oh. Good job cmdline::Init can cope.
+    workingDir = nullptr;
+  }
+
+  const char* argv[3] = {nullptr, "-url", urlString};
+  rv = cmdLine->Init(3, argv, workingDir, nsICommandLine::STATE_REMOTE_EXPLICIT);
+  if (NS_FAILED(rv)) {
+    return NO;
+  }
+  rv = cmdLine->Run();
+  if (NS_FAILED(rv)) {
+    return NO;
+  }
+
+  return YES;
+}
+
+@end
diff --git a/toolkit/xre/MacAutoreleasePool.h b/toolkit/xre/MacAutoreleasePool.h
new file mode 100644
index 0000000000..6c574beef2
--- /dev/null
+++ b/toolkit/xre/MacAutoreleasePool.h
@@ -0,0 +1,31 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef MacAutoreleasePool_h_
+#define MacAutoreleasePool_h_
+
+// This needs to be #include-able from non-ObjC code in nsAppRunner.cpp
+#ifdef __OBJC__
+@class NSAutoreleasePool;
+#else
+class NSAutoreleasePool;
+#endif
+
+namespace mozilla {
+
+class MacAutoreleasePool {
+ public:
+  MacAutoreleasePool();
+  ~MacAutoreleasePool();
+
+ private:
+  NSAutoreleasePool* mPool;
+
+  MacAutoreleasePool(const MacAutoreleasePool&);
+  void operator=(const MacAutoreleasePool&);
+};
+
+}  // namespace mozilla
+
+#endif  // MacAutoreleasePool_h_
diff --git a/toolkit/xre/MacAutoreleasePool.mm b/toolkit/xre/MacAutoreleasePool.mm
new file mode 100644
index 0000000000..0d2a47b3d8
--- /dev/null
+++ b/toolkit/xre/MacAutoreleasePool.mm
@@ -0,0 +1,17 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "MacAutoreleasePool.h"
+#include "nsDebug.h"
+
+#import <Foundation/Foundation.h>
+
+using mozilla::MacAutoreleasePool;
+
+MacAutoreleasePool::MacAutoreleasePool() {
+  mPool = [[NSAutoreleasePool alloc] init];
+  NS_ASSERTION(mPool != nullptr, "failed to create pool, objects will leak");
+}
+
+MacAutoreleasePool::~MacAutoreleasePool() { [mPool release]; }
diff --git a/toolkit/xre/MacLaunchHelper.h b/toolkit/xre/MacLaunchHelper.h
new file mode 100644
index 0000000000..a4a8fb1666
--- /dev/null
+++ b/toolkit/xre/MacLaunchHelper.h
@@ -0,0 +1,25 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef MacLaunchHelper_h_
+#define MacLaunchHelper_h_
+
+#include <stdint.h>
+
+#include <unistd.h>
+
+extern "C" {
+/**
+ * Passing an aPid parameter to LaunchChildMac will wait for the launched
+ * process to terminate. When the process terminates, aPid will be set to the
+ * pid of the terminated process to confirm that it executed successfully.
+ */
+void LaunchChildMac(int aArgc, char** aArgv, pid_t* aPid = 0);
+bool LaunchElevatedUpdate(int aArgc, char** aArgv, pid_t* aPid = 0);
+bool InstallPrivilegedHelper();
+void AbortElevatedUpdate();
+}
+
+#endif
diff --git a/toolkit/xre/MacLaunchHelper.mm b/toolkit/xre/MacLaunchHelper.mm
new file mode 100644
index 0000000000..555e15d084
--- /dev/null
+++ b/toolkit/xre/MacLaunchHelper.mm
@@ -0,0 +1,117 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "MacLaunchHelper.h"
+
+#include "MacAutoreleasePool.h"
+#include "mozilla/UniquePtr.h"
+
+#include <Cocoa/Cocoa.h>
+#include <crt_externs.h>
+#include <ServiceManagement/ServiceManagement.h>
+#include <Security/Authorization.h>
+#include <spawn.h>
+#include <stdio.h>
+
+using namespace mozilla;
+
+void LaunchChildMac(int aArgc, char** aArgv, pid_t* aPid) {
+  MacAutoreleasePool pool;
+
+  @try {
+    NSString* launchPath = [NSString stringWithUTF8String:aArgv[0]];
+    NSMutableArray* arguments = [NSMutableArray arrayWithCapacity:aArgc - 1];
+    for (int i = 1; i < aArgc; i++) {
+      [arguments addObject:[NSString stringWithUTF8String:aArgv[i]]];
+    }
+    NSTask* child = [NSTask launchedTaskWithLaunchPath:launchPath arguments:arguments];
+    if (aPid) {
+      *aPid = [child processIdentifier];
+      // We used to use waitpid to wait for the process to terminate. This is
+      // incompatible with NSTask and we wait for the process to exit here
+      // instead.
+      [child waitUntilExit];
+    }
+  } @catch (NSException* e) {
+    NSLog(@"%@: %@", e.name, e.reason);
+  }
+}
+
+bool InstallPrivilegedHelper() {
+  AuthorizationRef authRef = NULL;
+  OSStatus status = AuthorizationCreate(
+      NULL, kAuthorizationEmptyEnvironment,
+      kAuthorizationFlagDefaults | kAuthorizationFlagInteractionAllowed, &authRef);
+  if (status != errAuthorizationSuccess) {
+    // AuthorizationCreate really shouldn't fail.
+    NSLog(@"AuthorizationCreate failed! NSOSStatusErrorDomain / %d", (int)status);
+    return NO;
+  }
+
+  BOOL result = NO;
+  AuthorizationItem authItem = {kSMRightBlessPrivilegedHelper, 0, NULL, 0};
+  AuthorizationRights authRights = {1, &authItem};
+  AuthorizationFlags flags = kAuthorizationFlagDefaults | kAuthorizationFlagInteractionAllowed |
+                             kAuthorizationFlagPreAuthorize | kAuthorizationFlagExtendRights;
+
+  // Obtain the right to install our privileged helper tool.
+  status =
+      AuthorizationCopyRights(authRef, &authRights, kAuthorizationEmptyEnvironment, flags, NULL);
+  if (status != errAuthorizationSuccess) {
+    NSLog(@"AuthorizationCopyRights failed! NSOSStatusErrorDomain / %d", (int)status);
+  } else {
+    CFErrorRef cfError;
+    // This does all the work of verifying the helper tool against the
+    // application and vice-versa. Once verification has passed, the embedded
+    // launchd.plist is extracted and placed in /Library/LaunchDaemons and then
+    // loaded. The executable is placed in /Library/PrivilegedHelperTools.
+    result = (BOOL)SMJobBless(kSMDomainSystemLaunchd, (CFStringRef) @"org.mozilla.updater", authRef,
+                              &cfError);
+    if (!result) {
+      NSLog(@"Unable to install helper!");
+      CFRelease(cfError);
+    }
+  }
+
+  return result;
+}
+
+void AbortElevatedUpdate() {
+  mozilla::MacAutoreleasePool pool;
+
+  id updateServer = nil;
+  int currTry = 0;
+  const int numRetries = 10;  // Number of IPC connection retries before
+                              // giving up.
+  while (currTry < numRetries) {
+    @try {
+      updateServer = (id)[NSConnection
+          rootProxyForConnectionWithRegisteredName:@"org.mozilla.updater.server"
+                                              host:nil
+                                   usingNameServer:[NSSocketPortNameServer sharedInstance]];
+      if (updateServer && [updateServer respondsToSelector:@selector(abort)]) {
+        [updateServer performSelector:@selector(abort)];
+        return;
+      }
+      NSLog(@"Server doesn't exist or doesn't provide correct selectors.");
+      sleep(1);  // Wait 1 second.
+      currTry++;
+    } @catch (NSException* e) {
+      NSLog(@"Encountered exception, retrying: %@: %@", e.name, e.reason);
+      sleep(1);  // Wait 1 second.
+      currTry++;
+    }
+  }
+  NSLog(@"Unable to clean up updater.");
+}
+
+bool LaunchElevatedUpdate(int aArgc, char** aArgv, pid_t* aPid) {
+  LaunchChildMac(aArgc, aArgv, aPid);
+  bool didSucceed = InstallPrivilegedHelper();
+  if (!didSucceed) {
+    AbortElevatedUpdate();
+  }
+  return didSucceed;
+}
diff --git a/toolkit/xre/MacRunFromDmgUtils.h b/toolkit/xre/MacRunFromDmgUtils.h
new file mode 100644
index 0000000000..d93e6445b1
--- /dev/null
+++ b/toolkit/xre/MacRunFromDmgUtils.h
@@ -0,0 +1,33 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// This file defines the interface between Cocoa-specific Obj-C++ and generic
+// C++, so it itself cannot have any Obj-C bits in it.
+
+#ifndef MacRunFromDmgUtils_h_
+#define MacRunFromDmgUtils_h_
+
+namespace mozilla::MacRunFromDmgUtils {
+
+/**
+ * Returns true if the app is running from the read-only filesystem of a
+ * mounted .dmg.  Returns false if not, or if we fail to determine whether it
+ * is.
+ */
+bool IsAppRunningFromDmg();
+
+/**
+ * Checks whether the app is running from a read-only .dmg image or a read-only
+ * app translocated location and, if so, asks the user for permission before
+ * attempting to install the app and launch it.
+ *
+ * Returns true if the app has been installed and relaunched, in which case
+ * this instance of the app should exit.
+ */
+bool MaybeInstallAndRelaunch();
+
+}  // namespace mozilla::MacRunFromDmgUtils
+
+#endif
diff --git a/toolkit/xre/MacRunFromDmgUtils.mm b/toolkit/xre/MacRunFromDmgUtils.mm
new file mode 100644
index 0000000000..38381b5c48
--- /dev/null
+++ b/toolkit/xre/MacRunFromDmgUtils.mm
@@ -0,0 +1,513 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <AppKit/AppKit.h>
+#include <ApplicationServices/ApplicationServices.h>
+#include <CoreFoundation/CoreFoundation.h>
+#include <CoreServices/CoreServices.h>
+#include <IOKit/IOKitLib.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/mount.h>
+#include <sys/param.h>
+
+#include "MacRunFromDmgUtils.h"
+#include "MacLaunchHelper.h"
+
+#include "mozilla/ErrorResult.h"
+#include "mozilla/glean/GleanMetrics.h"
+#include "mozilla/intl/Localization.h"
+#include "mozilla/Telemetry.h"
+#include "nsCocoaFeatures.h"
+#include "nsCocoaUtils.h"
+#include "nsCommandLine.h"
+#include "nsCommandLineServiceMac.h"
+#include "nsILocalFileMac.h"
+#include "nsIMacDockSupport.h"
+#include "nsObjCExceptions.h"
+#include "prenv.h"
+#include "nsString.h"
+#ifdef MOZ_UPDATER
+#  include "nsUpdateDriver.h"
+#endif
+#include "SDKDeclarations.h"
+
+// For IOKit docs, see:
+// https://developer.apple.com/documentation/iokit
+// https://developer.apple.com/library/archive/documentation/DeviceDrivers/Conceptual/IOKitFundamentals/
+
+namespace mozilla::MacRunFromDmgUtils {
+
+/**
+ * Opens a dialog to ask the user whether the existing app in the Applications
+ * folder should be launched, or if the user wants to proceed with launching
+ * the app from the .dmg.
+ * Returns true if the dialog is successfully opened and the user chooses to
+ * launch the app from the Applications folder, otherwise returns false.
+ */
+static bool AskUserIfWeShouldLaunchExistingInstall() {
+  NS_OBJC_BEGIN_TRY_BLOCK_RETURN;
+
+  // Try to get the localized strings:
+  nsTArray<nsCString> resIds = {
+      "branding/brand.ftl"_ns,
+      "toolkit/global/run-from-dmg.ftl"_ns,
+  };
+  RefPtr<intl::Localization> l10n = intl::Localization::Create(resIds, true);
+
+  ErrorResult rv;
+  nsAutoCString mozTitle, mozMessage, mozLaunchExisting, mozLaunchFromDMG;
+  l10n->FormatValueSync("prompt-to-launch-existing-app-title"_ns, {}, mozTitle, rv);
+  if (rv.Failed()) {
+    return false;
+  }
+  l10n->FormatValueSync("prompt-to-launch-existing-app-message"_ns, {}, mozMessage, rv);
+  if (rv.Failed()) {
+    return false;
+  }
+  l10n->FormatValueSync("prompt-to-launch-existing-app-yes-button"_ns, {}, mozLaunchExisting, rv);
+  if (rv.Failed()) {
+    return false;
+  }
+  l10n->FormatValueSync("prompt-to-launch-existing-app-no-button"_ns, {}, mozLaunchFromDMG, rv);
+  if (rv.Failed()) {
+    return false;
+  }
+
+  NSString* title = [NSString stringWithUTF8String:reinterpret_cast<const char*>(mozTitle.get())];
+  NSString* message =
+      [NSString stringWithUTF8String:reinterpret_cast<const char*>(mozMessage.get())];
+  NSString* launchExisting =
+      [NSString stringWithUTF8String:reinterpret_cast<const char*>(mozLaunchExisting.get())];
+  NSString* launchFromDMG =
+      [NSString stringWithUTF8String:reinterpret_cast<const char*>(mozLaunchFromDMG.get())];
+
+  NSAlert* alert = [[[NSAlert alloc] init] autorelease];
+
+  // Note that we don't set an icon since the app icon is used by default.
+  [alert setAlertStyle:NSAlertStyleInformational];
+  [alert setMessageText:title];
+  [alert setInformativeText:message];
+  // Note that if the user hits 'Enter' the "Install" button is activated,
+  // whereas if they hit  'Space' the "Don't Install" button is activated.
+  // That's standard behavior so probably desirable.
+  [alert addButtonWithTitle:launchExisting];
+  NSButton* launchFromDMGButton = [alert addButtonWithTitle:launchFromDMG];
+  // Since the "Don't Install" button doesn't have the title "Cancel" we need
+  // to map the Escape key to it manually:
+  [launchFromDMGButton setKeyEquivalent:@"\e"];
+
+  __block NSInteger result = -1;
+  dispatch_async(dispatch_get_main_queue(), ^{
+    result = [alert runModal];
+    [NSApp stop:nil];
+  });
+
+  // We need to call run on NSApp here for accessibility. See
+  // AskUserIfWeShouldInstall for a detailed explanation.
+  [NSApp run];
+  MOZ_ASSERT(result != -1);
+
+  return result == NSAlertFirstButtonReturn;
+
+  NS_OBJC_END_TRY_BLOCK_RETURN(false);
+}
+
+/**
+ * Opens a dialog to ask the user whether the app should be installed to their
+ * Applications folder.  Returns true if the dialog is successfully opened and
+ * the user accept, otherwise returns false.
+ */
+static bool AskUserIfWeShouldInstall() {
+  NS_OBJC_BEGIN_TRY_BLOCK_RETURN;
+
+  // Try to get the localized strings:
+  nsTArray<nsCString> resIds = {
+      "branding/brand.ftl"_ns,
+      "toolkit/global/run-from-dmg.ftl"_ns,
+  };
+  RefPtr<intl::Localization> l10n = intl::Localization::Create(resIds, true);
+
+  ErrorResult rv;
+  nsAutoCString mozTitle, mozMessage, mozInstall, mozDontInstall;
+  l10n->FormatValueSync("prompt-to-install-title"_ns, {}, mozTitle, rv);
+  if (rv.Failed()) {
+    return false;
+  }
+  l10n->FormatValueSync("prompt-to-install-message"_ns, {}, mozMessage, rv);
+  if (rv.Failed()) {
+    return false;
+  }
+  l10n->FormatValueSync("prompt-to-install-yes-button"_ns, {}, mozInstall, rv);
+  if (rv.Failed()) {
+    return false;
+  }
+  l10n->FormatValueSync("prompt-to-install-no-button"_ns, {}, mozDontInstall, rv);
+  if (rv.Failed()) {
+    return false;
+  }
+
+  NSString* title = [NSString stringWithUTF8String:reinterpret_cast<const char*>(mozTitle.get())];
+  NSString* message =
+      [NSString stringWithUTF8String:reinterpret_cast<const char*>(mozMessage.get())];
+  NSString* install =
+      [NSString stringWithUTF8String:reinterpret_cast<const char*>(mozInstall.get())];
+  NSString* dontInstall =
+      [NSString stringWithUTF8String:reinterpret_cast<const char*>(mozDontInstall.get())];
+
+  NSAlert* alert = [[[NSAlert alloc] init] autorelease];
+
+  // Note that we don't set an icon since the app icon is used by default.
+  [alert setAlertStyle:NSAlertStyleInformational];
+  [alert setMessageText:title];
+  [alert setInformativeText:message];
+  // Note that if the user hits 'Enter' the "Install" button is activated,
+  // whereas if they hit  'Space' the "Don't Install" button is activated.
+  // That's standard behavior so probably desirable.
+  [alert addButtonWithTitle:install];
+  NSButton* dontInstallButton = [alert addButtonWithTitle:dontInstall];
+  // Since the "Don't Install" button doesn't have the title "Cancel" we need
+  // to map the Escape key to it manually:
+  [dontInstallButton setKeyEquivalent:@"\e"];
+
+  // We need to call run on NSApp to allow accessibility. We only run it
+  // for this specific alert which blocks the app's loop until the user
+  // responds, it then subsequently stops the app's loop.
+  //
+  // AskUserIfWeShouldInstall
+  //          |
+  //          | ---> [NSApp run]
+  //          |          |
+  //          |          | -----> task
+  //          |          |          | -----------> [alert runModal]
+  //          |          |          |                     | (User selects button)
+  //          |          |          | <---------------   done
+  //          |          |          |
+  //          |          |          | -----------> [NSApp stop:nil]
+  //          |          |          | <-----------
+  //          |          | <--------
+  //          | <-------
+  //        done
+  __block NSInteger result = -1;
+  dispatch_async(dispatch_get_main_queue(), ^{
+    result = [alert runModal];
+    [NSApp stop:nil];
+  });
+
+  [NSApp run];
+  MOZ_ASSERT(result != -1);
+
+  return result == NSAlertFirstButtonReturn;
+
+  NS_OBJC_END_TRY_BLOCK_RETURN(false);
+}
+
+static void ShowInstallFailedDialog() {
+  NS_OBJC_BEGIN_TRY_IGNORE_BLOCK;
+
+  // Try to get the localized strings:
+  nsTArray<nsCString> resIds = {
+      "branding/brand.ftl"_ns,
+      "toolkit/global/run-from-dmg.ftl"_ns,
+  };
+  RefPtr<intl::Localization> l10n = intl::Localization::Create(resIds, true);
+
+  ErrorResult rv;
+  nsAutoCString mozTitle, mozMessage;
+  l10n->FormatValueSync("install-failed-title"_ns, {}, mozTitle, rv);
+  if (rv.Failed()) {
+    return;
+  }
+  l10n->FormatValueSync("install-failed-message"_ns, {}, mozMessage, rv);
+  if (rv.Failed()) {
+    return;
+  }
+
+  NSString* title = [NSString stringWithUTF8String:reinterpret_cast<const char*>(mozTitle.get())];
+  NSString* message =
+      [NSString stringWithUTF8String:reinterpret_cast<const char*>(mozMessage.get())];
+
+  NSAlert* alert = [[[NSAlert alloc] init] autorelease];
+
+  [alert setAlertStyle:NSAlertStyleWarning];
+  [alert setMessageText:title];
+  [alert setInformativeText:message];
+
+  __block NSInteger result = -1;
+  dispatch_async(dispatch_get_main_queue(), ^{
+    result = [alert runModal];
+    [NSApp stop:nil];
+  });
+
+  // We need to call run on NSApp here for accessibility. See
+  // AskUserIfWeShouldInstall for a detailed explanation.
+  [NSApp run];
+  MOZ_ASSERT(result != -1);
+  (void)result;
+
+  NS_OBJC_END_TRY_IGNORE_BLOCK;
+}
+
+/**
+ * Helper to launch macOS tasks via NSTask.
+ */
+static void LaunchTask(NSString* aPath, NSArray* aArguments) {
+  if (@available(macOS 10.13, *)) {
+    NSTask* task = [[NSTask alloc] init];
+    [task setExecutableURL:[NSURL fileURLWithPath:aPath]];
+    if (aArguments) {
+      [task setArguments:aArguments];
+    }
+    [task launchAndReturnError:nil];
+    [task release];
+  } else {
+    NSArray* arguments = aArguments;
+    if (!arguments) {
+      arguments = @[];
+    }
+    [NSTask launchedTaskWithLaunchPath:aPath arguments:arguments];
+  }
+}
+
+static void LaunchInstalledApp(NSString* aBundlePath) {
+  LaunchTask([[NSBundle bundleWithPath:aBundlePath] executablePath], nil);
+}
+
+static void RegisterAppWithLaunchServices(NSString* aBundlePath) {
+  NSArray* arguments = @[ @"-f", aBundlePath ];
+  LaunchTask(@"/System/Library/Frameworks/CoreServices.framework/Frameworks/"
+             @"LaunchServices.framework/Support/lsregister",
+             arguments);
+}
+
+static void StripQuarantineBit(NSString* aBundlePath) {
+  NSArray* arguments = @[ @"-d", @"com.apple.quarantine", aBundlePath ];
+  LaunchTask(@"/usr/bin/xattr", arguments);
+}
+
+#ifdef MOZ_UPDATER
+bool LaunchElevatedDmgInstall(NSString* aBundlePath, NSArray* aArguments) {
+  NSTask* task;
+  if (@available(macOS 10.13, *)) {
+    task = [[NSTask alloc] init];
+    [task setExecutableURL:[NSURL fileURLWithPath:aBundlePath]];
+    if (aArguments) {
+      [task setArguments:aArguments];
+    }
+    [task launchAndReturnError:nil];
+  } else {
+    NSArray* arguments = aArguments;
+    if (!arguments) {
+      arguments = @[];
+    }
+    task = [NSTask launchedTaskWithLaunchPath:aBundlePath arguments:arguments];
+  }
+
+  bool didSucceed = InstallPrivilegedHelper();
+  [task waitUntilExit];
+  if (@available(macOS 10.13, *)) {
+    [task release];
+  }
+  if (!didSucceed) {
+    AbortElevatedUpdate();
+  }
+
+  return didSucceed;
+}
+#endif
+
+// Note: both arguments are expected to contain the app name (to end with
+// '.app').
+static bool InstallFromPath(NSString* aBundlePath, NSString* aDestPath) {
+  bool installSuccessful = false;
+  NSFileManager* fileManager = [NSFileManager defaultManager];
+  if ([fileManager copyItemAtPath:aBundlePath toPath:aDestPath error:nil]) {
+    RegisterAppWithLaunchServices(aDestPath);
+    StripQuarantineBit(aDestPath);
+    installSuccessful = true;
+  }
+
+#ifdef MOZ_UPDATER
+  // The installation may have been unsuccessful if the user did not have the
+  // rights to write to the Applications directory. Check for this situation and
+  // launch an elevated installation if necessary. Rather than creating a new,
+  // dedicated executable for this installation and incurring the
+  // added maintenance burden of yet another executable, we are using the
+  // updater binary. Since bug 394984 landed, the updater has the ability to
+  // install and launch itself as a Privileged Helper tool, which is what is
+  // necessary here.
+  NSString* destDir = [aDestPath stringByDeletingLastPathComponent];
+  if (!installSuccessful && ![fileManager isWritableFileAtPath:destDir]) {
+    NSString* updaterBinPath = [NSString pathWithComponents:@[
+      aBundlePath, @"Contents", @"MacOS", [NSString stringWithUTF8String:UPDATER_APP], @"Contents",
+      @"MacOS", [NSString stringWithUTF8String:UPDATER_BIN]
+    ]];
+
+    NSArray* arguments = @[ @"-dmgInstall", aBundlePath, aDestPath ];
+    LaunchElevatedDmgInstall(updaterBinPath, arguments);
+    installSuccessful = [fileManager fileExistsAtPath:aDestPath];
+  }
+#endif
+
+  if (!installSuccessful) {
+    return false;
+  }
+
+  // Pin to dock:
+  nsresult rv;
+  nsCOMPtr<nsIMacDockSupport> dockSupport =
+      do_GetService("@mozilla.org/widget/macdocksupport;1", &rv);
+  if (NS_SUCCEEDED(rv) && dockSupport) {
+    bool isInDock;
+    nsAutoString appPath, appToReplacePath;
+    nsCocoaUtils::GetStringForNSString(aDestPath, appPath);
+    nsCocoaUtils::GetStringForNSString(aBundlePath, appToReplacePath);
+    dockSupport->EnsureAppIsPinnedToDock(appPath, appToReplacePath, &isInDock);
+  }
+
+  return true;
+}
+
+bool IsAppRunningFromDmg() {
+  NS_OBJC_BEGIN_TRY_BLOCK_RETURN;
+
+  const char* path = [[[NSBundle mainBundle] bundlePath] fileSystemRepresentation];
+
+  struct statfs statfsBuf;
+  if (statfs(path, &statfsBuf) != 0) {
+    return false;
+  }
+
+  // Optimization to minimize impact on startup time:
+  if (!(statfsBuf.f_flags & MNT_RDONLY)) {
+    return false;
+  }
+
+  // Get the "BSD device name" ("diskXsY", as found in /dev) of the filesystem
+  // our app is on so we can use IOKit to get its IOMedia object:
+  const char devDirPath[] = "/dev/";
+  const int devDirPathLength = strlen(devDirPath);
+  if (strncmp(statfsBuf.f_mntfromname, devDirPath, devDirPathLength) != 0) {
+    // This has been observed to happen under App Translocation. In this case,
+    // path is the translocated path, and f_mntfromname is the path under
+    // /Volumes. Do another stat on that path.
+    nsCString volumesPath(statfsBuf.f_mntfromname);
+    if (statfs(volumesPath.get(), &statfsBuf) != 0) {
+      return false;
+    }
+
+    if (strncmp(statfsBuf.f_mntfromname, devDirPath, devDirPathLength) != 0) {
+      // It still doesn't begin with /dev/, bail out.
+      return false;
+    }
+  }
+  const char* bsdDeviceName = statfsBuf.f_mntfromname + devDirPathLength;
+
+  // Get the IOMedia object:
+  // (Note: IOServiceGetMatchingServices takes ownership of serviceDict's ref.)
+  CFMutableDictionaryRef serviceDict = IOBSDNameMatching(kIOMasterPortDefault, 0, bsdDeviceName);
+  if (!serviceDict) {
+    return false;
+  }
+  io_service_t media = IOServiceGetMatchingService(kIOMasterPortDefault, serviceDict);
+  if (!media || !IOObjectConformsTo(media, "IOMedia")) {
+    return false;
+  }
+
+  // Search the parent chain for a service implementing the disk image class
+  // (taking care to start with `media` itself):
+  io_service_t imageDrive = IO_OBJECT_NULL;
+  io_iterator_t iter;
+  if (IORegistryEntryCreateIterator(media, kIOServicePlane,
+                                    kIORegistryIterateRecursively | kIORegistryIterateParents,
+                                    &iter) != KERN_SUCCESS) {
+    IOObjectRelease(media);
+    return false;
+  }
+  const char* imageClass =
+      nsCocoaFeatures::OnMontereyOrLater() ? "AppleDiskImageDevice" : "IOHDIXHDDrive";
+  for (imageDrive = media; imageDrive; imageDrive = IOIteratorNext(iter)) {
+    if (IOObjectConformsTo(imageDrive, imageClass)) {
+      break;
+    }
+    IOObjectRelease(imageDrive);
+  }
+  IOObjectRelease(iter);
+
+  if (imageDrive) {
+    IOObjectRelease(imageDrive);
+    return true;
+  }
+  return false;
+
+  NS_OBJC_END_TRY_BLOCK_RETURN(false);
+}
+
+bool MaybeInstallAndRelaunch() {
+  NS_OBJC_BEGIN_TRY_BLOCK_RETURN;
+
+  @autoreleasepool {
+    bool isFromDmg = IsAppRunningFromDmg();
+    bool isTranslocated = false;
+    if (!isFromDmg) {
+      NSString* bundlePath = [[NSBundle mainBundle] bundlePath];
+      if ([bundlePath containsString:@"/AppTranslocation/"]) {
+        isTranslocated = true;
+      }
+    }
+
+    if (!isFromDmg && !isTranslocated) {
+      return false;
+    }
+
+    // The Applications directory may not be at /Applications, although in
+    // practice we're unlikely to encounter since run-from-.dmg is really an
+    // issue with novice mac users. Still, look it up correctly:
+    NSArray* applicationsDirs =
+        NSSearchPathForDirectoriesInDomains(NSApplicationDirectory, NSLocalDomainMask, YES);
+    NSString* applicationsDir = applicationsDirs[0];
+
+    // Sanity check dir exists
+    NSFileManager* fileManager = [NSFileManager defaultManager];
+    BOOL isDir;
+    if (![fileManager fileExistsAtPath:applicationsDir isDirectory:&isDir] || !isDir) {
+      return false;
+    }
+
+    NSString* bundlePath = [[NSBundle mainBundle] bundlePath];
+    NSString* appName = [bundlePath lastPathComponent];
+    NSString* destPath = [applicationsDir stringByAppendingPathComponent:appName];
+
+    // If the app (an app of the same name) is already installed we can't really
+    // tell without asking if we're dealing with the edge case of an
+    // inexperienced user running from .dmg by mistake, or if we're dealing with
+    // a more sophisticated user intentionally running from .dmg.
+    if ([fileManager fileExistsAtPath:destPath]) {
+      if (AskUserIfWeShouldLaunchExistingInstall()) {
+        StripQuarantineBit(destPath);
+        LaunchInstalledApp(destPath);
+        return true;
+      }
+      return false;
+    }
+
+    if (!AskUserIfWeShouldInstall()) {
+      return false;
+    }
+
+    if (!InstallFromPath(bundlePath, destPath)) {
+      ShowInstallFailedDialog();
+      return false;
+    }
+
+    LaunchInstalledApp(destPath);
+
+    return true;
+  }
+
+  NS_OBJC_END_TRY_BLOCK_RETURN(false);
+}
+
+}  // namespace mozilla::MacRunFromDmgUtils
diff --git a/toolkit/xre/MultiInstanceLock.cpp b/toolkit/xre/MultiInstanceLock.cpp
new file mode 100644
index 0000000000..eb4db6367a
--- /dev/null
+++ b/toolkit/xre/MultiInstanceLock.cpp
@@ -0,0 +1,297 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sw=2 sts=2 et cindent: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "MultiInstanceLock.h"
+
+#include "commonupdatedir.h"  // for GetInstallHash
+#include "mozilla/UniquePtr.h"
+#include "nsPrintfCString.h"
+#include "nsPromiseFlatString.h"
+#include "nsXULAppAPI.h"
+#include "updatedefines.h"  // for NS_t* definitions
+
+#ifdef XP_WIN
+#  include <shlwapi.h>
+#else
+#  include <fcntl.h>
+#  include <sys/stat.h>
+#  include <sys/types.h>
+#endif
+
+#ifdef XP_WIN
+#  include "WinUtils.h"
+#endif
+
+#ifdef MOZ_WIDGET_COCOA
+#  include "nsILocalFileMac.h"
+#endif
+
+namespace mozilla {
+
+bool GetMultiInstanceLockFileName(const char* nameToken,
+                                  const char16_t* installPath,
+                                  nsCString& filePath) {
+#ifdef XP_WIN
+  // On Windows, the lock file is placed at the path
+  // [updateDirectory]\[nameToken]-[pathHash], so first we need to get the
+  // update directory path and then append the file name.
+
+  // Note: This will return something like
+  //   C:\ProgramData\Mozilla-1de4eec8-1241-4177-a864-e594e8d1fb38\updates\<hash>
+  // But we actually are going to want to return the root update directory,
+  // the grandparent of this directory, which will look something like this:
+  //   C:\ProgramData\Mozilla-1de4eec8-1241-4177-a864-e594e8d1fb38
+  mozilla::UniquePtr<wchar_t[]> updateDir;
+  HRESULT hr = GetCommonUpdateDirectory(
+      reinterpret_cast<const wchar_t*>(installPath), updateDir);
+  if (FAILED(hr)) {
+    return false;
+  }
+
+  // For the path manipulation that we are about to do, it is important that
+  // the update directory have no trailing slash.
+  size_t len = wcslen(updateDir.get());
+  if (len == 0) {
+    return false;
+  }
+  if (updateDir.get()[len - 1] == '/' || updateDir.get()[len - 1] == '\\') {
+    updateDir.get()[len - 1] = '\0';
+  }
+
+  wchar_t* hashPtr = PathFindFileNameW(updateDir.get());
+  // PathFindFileNameW returns a pointer to the beginning of the string on
+  // failure.
+  if (hashPtr == updateDir.get()) {
+    return false;
+  }
+
+  // We need to make a copy of the hash before we modify updateDir to get the
+  // root update dir.
+  size_t hashSize = wcslen(hashPtr) + 1;
+  mozilla::UniquePtr<wchar_t[]> hash = mozilla::MakeUnique<wchar_t[]>(hashSize);
+  errno_t error = wcscpy_s(hash.get(), hashSize, hashPtr);
+  if (error != 0) {
+    return false;
+  }
+
+  // Get the root update dir from the update dir.
+  BOOL success = PathRemoveFileSpecW(updateDir.get());
+  if (!success) {
+    return false;
+  }
+  success = PathRemoveFileSpecW(updateDir.get());
+  if (!success) {
+    return false;
+  }
+
+  filePath =
+      nsPrintfCString("%s\\%s-%s", NS_ConvertUTF16toUTF8(updateDir.get()).get(),
+                      nameToken, NS_ConvertUTF16toUTF8(hash.get()).get());
+
+#else
+  mozilla::UniquePtr<NS_tchar[]> pathHash;
+  if (!GetInstallHash(installPath, pathHash)) {
+    return false;
+  }
+
+  // On POSIX platforms the base path is /tmp/[vendor][nameToken]-[pathHash].
+  filePath = nsPrintfCString("/tmp/%s%s-%s", MOZ_APP_VENDOR, nameToken,
+                             pathHash.get());
+
+#endif
+
+  return true;
+}
+
+MultiInstLockHandle OpenMultiInstanceLock(const char* nameToken,
+                                          const char16_t* installPath) {
+  nsCString filePath;
+  if (!GetMultiInstanceLockFileName(nameToken, installPath, filePath)) {
+    return MULTI_INSTANCE_LOCK_HANDLE_ERROR;
+  }
+
+  // Open a file handle with full privileges and sharing, and then attempt to
+  // take a shared (nonexclusive, read-only) lock on it.
+#ifdef XP_WIN
+  HANDLE h =
+      ::CreateFileW(PromiseFlatString(NS_ConvertUTF8toUTF16(filePath)).get(),
+                    GENERIC_READ | GENERIC_WRITE,
+                    FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE,
+                    nullptr, OPEN_ALWAYS, 0, nullptr);
+  if (h != INVALID_HANDLE_VALUE) {
+    // The LockFileEx functions always require an OVERLAPPED structure even
+    // though we did not open the lock file for overlapped I/O.
+    OVERLAPPED o = {0};
+    if (!::LockFileEx(h, LOCKFILE_FAIL_IMMEDIATELY, 0, 1, 0, &o)) {
+      CloseHandle(h);
+      h = INVALID_HANDLE_VALUE;
+    }
+  }
+  return h;
+
+#else
+  int fd = ::open(PromiseFlatCString(filePath).get(),
+                  O_CLOEXEC | O_CREAT | O_NOFOLLOW,
+                  S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH);
+  if (fd != -1) {
+    // We would like to ensure that the lock file is deleted when we are done
+    // with it. The normal way to do that would be to call unlink on it right
+    // now, but that would immediately delete the name from the file system, and
+    // we need other instances to be able to open that name and get the same
+    // inode, so we can't unlink the file before we're done with it. This means
+    // we accept some unreliability in getting the file deleted, but it's a zero
+    // byte file in the tmp directory, so having it stay around isn't the worst.
+    struct flock l = {0};
+    l.l_start = 0;
+    l.l_len = 0;
+    l.l_type = F_RDLCK;
+    if (::fcntl(fd, F_SETLK, &l)) {
+      ::close(fd);
+      fd = -1;
+    }
+  }
+  return fd;
+
+#endif
+}
+
+void ReleaseMultiInstanceLock(MultiInstLockHandle lock) {
+  if (lock != MULTI_INSTANCE_LOCK_HANDLE_ERROR) {
+#ifdef XP_WIN
+    OVERLAPPED o = {0};
+    ::UnlockFileEx(lock, 0, 1, 0, &o);
+    ::CloseHandle(lock);
+
+#else
+    // If we're the last instance, then unlink the lock file. There is a race
+    // condition here that may cause an instance to fail to open the same inode
+    // as another even though they use the same path, but there's no reasonable
+    // way to avoid that without skipping deleting the file at all, so we accept
+    // that risk.
+    bool otherInstance = true;
+    if (IsOtherInstanceRunning(lock, &otherInstance) && !otherInstance) {
+      // Recover the file's path so we can unlink it.
+      // There's no error checking in here because we're content to let the file
+      // hang around if any of this fails (which can happen if for example we're
+      // on a system where /proc/self/fd does not exist); this is a zero-byte
+      // file in the tmp directory after all.
+      UniquePtr<NS_tchar[]> linkPath = MakeUnique<NS_tchar[]>(MAXPATHLEN + 1);
+      NS_tsnprintf(linkPath.get(), MAXPATHLEN + 1, "/proc/self/fd/%d", lock);
+      UniquePtr<NS_tchar[]> lockFilePath =
+          MakeUnique<NS_tchar[]>(MAXPATHLEN + 1);
+      if (::readlink(linkPath.get(), lockFilePath.get(), MAXPATHLEN + 1) !=
+          -1) {
+        ::unlink(lockFilePath.get());
+      }
+    }
+    // Now close the lock file, which will release the lock.
+    ::close(lock);
+#endif
+  }
+}
+
+bool IsOtherInstanceRunning(MultiInstLockHandle lock, bool* aResult) {
+  // Every running instance has opened a readonly lock, and read locks prevent
+  // write locks from being opened, so to see if we are the only instance, we
+  // attempt to take a write lock, and if it succeeds then that must mean there
+  // are no other read locks open and therefore no other instances.
+  if (lock == MULTI_INSTANCE_LOCK_HANDLE_ERROR) {
+    return false;
+  }
+
+#ifdef XP_WIN
+  // We need to release the lock we're holding before we would be allowed to
+  // take an exclusive lock, and if that succeeds we need to release it too
+  // in order to get our shared lock back. This procedure is not atomic, so we
+  // accept the risk of the scheduler deciding to ruin our day between these
+  // operations; we'd get a false negative in a different instance's check.
+  OVERLAPPED o = {0};
+  // Release our current shared lock.
+  if (!::UnlockFileEx(lock, 0, 1, 0, &o)) {
+    return false;
+  }
+  // Attempt to take an exclusive lock.
+  bool rv = false;
+  if (::LockFileEx(lock, LOCKFILE_EXCLUSIVE_LOCK | LOCKFILE_FAIL_IMMEDIATELY, 0,
+                   1, 0, &o)) {
+    // We got the exclusive lock, so now release it.
+    ::UnlockFileEx(lock, 0, 1, 0, &o);
+    *aResult = false;
+    rv = true;
+  } else if (::GetLastError() == ERROR_LOCK_VIOLATION) {
+    // We didn't get the exclusive lock because of outstanding shared locks.
+    *aResult = true;
+    rv = true;
+  }
+  // Attempt to reclaim the shared lock we released at the beginning.
+  if (!::LockFileEx(lock, LOCKFILE_FAIL_IMMEDIATELY, 0, 1, 0, &o)) {
+    rv = false;
+  }
+  return rv;
+
+#else
+  // See if we would be allowed to set a write lock (no need to actually do so).
+  struct flock l = {0};
+  l.l_start = 0;
+  l.l_len = 0;
+  l.l_type = F_WRLCK;
+  if (::fcntl(lock, F_GETLK, &l)) {
+    return false;
+  }
+  *aResult = l.l_type != F_UNLCK;
+  return true;
+
+#endif
+}
+
+already_AddRefed<nsIFile> GetNormalizedAppFile(nsIFile* aAppFile) {
+  // If we're given an app file, use it; otherwise, get it from the ambient
+  // directory service.
+  nsresult rv;
+  nsCOMPtr<nsIFile> appFile;
+  if (aAppFile) {
+    rv = aAppFile->Clone(getter_AddRefs(appFile));
+    NS_ENSURE_SUCCESS(rv, nullptr);
+  } else {
+    nsCOMPtr<nsIProperties> dirSvc =
+        do_GetService(NS_DIRECTORY_SERVICE_CONTRACTID);
+    NS_ENSURE_TRUE(dirSvc, nullptr);
+
+    rv = dirSvc->Get(XRE_EXECUTABLE_FILE, NS_GET_IID(nsIFile),
+                     getter_AddRefs(appFile));
+    NS_ENSURE_SUCCESS(rv, nullptr);
+  }
+
+  // It is possible that the path we have is on a case insensitive
+  // filesystem in which case the path may vary depending on how the
+  // application is called. We want to normalize the case somehow.
+  // On Linux XRE_EXECUTABLE_FILE already seems to be set to the correct path.
+  //
+  // See similar nsXREDirProvider::GetInstallHash. The main difference here is
+  // to allow lookup to fail on OSX, because some tests use a nonexistent
+  // appFile.
+#ifdef XP_WIN
+  // Windows provides a way to get the correct case.
+  if (!mozilla::widget::WinUtils::ResolveJunctionPointsAndSymLinks(appFile)) {
+    NS_WARNING("Failed to resolve install directory.");
+  }
+#elif defined(MOZ_WIDGET_COCOA)
+  // On OSX roundtripping through an FSRef fixes the case.
+  FSRef ref;
+  nsCOMPtr<nsILocalFileMac> macFile = do_QueryInterface(appFile);
+  if (macFile && NS_SUCCEEDED(macFile->GetFSRef(&ref)) &&
+      NS_SUCCEEDED(
+          NS_NewLocalFileWithFSRef(&ref, true, getter_AddRefs(macFile)))) {
+    appFile = static_cast<nsIFile*>(macFile);
+  } else {
+    NS_WARNING("Failed to resolve install directory.");
+  }
+#endif
+
+  return appFile.forget();
+}
+
+};  // namespace mozilla
diff --git a/toolkit/xre/MultiInstanceLock.h b/toolkit/xre/MultiInstanceLock.h
new file mode 100644
index 0000000000..1d6a93e7a8
--- /dev/null
+++ b/toolkit/xre/MultiInstanceLock.h
@@ -0,0 +1,99 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sw=2 sts=2 et cindent: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef MULTIINSTANCELOCK_H
+#define MULTIINSTANCELOCK_H
+
+#ifdef XP_WIN
+#  include <windows.h>
+#endif
+#include "nsIFile.h"
+
+// These functions manage "multi-instance locks", which are a type of lock
+// specifically designed to allow instances of an application, process, or other
+// task to detect when other instances relevant to them are running. Each
+// instance opens a lock and holds it for the duration of the task of interest
+// (which may be the lifetime of the process, or a shorter period). Then while
+// the lock is open, it can be used to check whether any other instances of the
+// same task are currently running out of the same copy of the binary, in the
+// context of any OS user. A process can open any number of locks, so long as
+// they use different names. It is necessary for the process to have permission
+// to create files in /tmp/ on POSIX systems or ProgramData\[vendor]\ on
+// Windows, so this mechanism may not work for sandboxed processes.
+
+// The implementation is based on file locking. An empty file is created in a
+// systemwide (not per-user) location, and a shared (read) lock is taken on that
+// file; the value that OpenMultiInstanceLock() returns is the file
+// handle/descriptor. When you call IsOtherInstanceRunning(), it will attempt to
+// convert that shared lock into an exclusive (write) lock. If that operation
+// would succeed, it means that there must not be any other shared locks
+// currently taken on that file, so we know there are no other instances
+// running. This is a more complex design than most file locks or most other
+// concurrency mechanisms, but it is necessary for this use case because of the
+// requirement that an instance must be able to detect other instances that were
+// started later than it was. If, say, a mutex were used, or another kind of
+// exclusive lock, then the first instance that tried to take it would succeed,
+// and be unable to tell that another instance had tried to take it later and
+// failed. This mechanism allows any number of instances started at any time in
+// relation to one another to always be able to detect that the others exist
+// (although it does not allow you to know how many others exist). The lock is
+// guaranteed to be released if the process holding it crashes or is exec'd into
+// something else, because the file is closed when that happens. The file itself
+// is not necessarily always deleted on POSIX, because it isn't possible (within
+// reason) to guarantee that unlink() is called, but the file is empty and
+// created in the /tmp directory, so should not be a serious problem.
+
+namespace mozilla {
+
+#ifdef XP_WIN
+using MultiInstLockHandle = HANDLE;
+#  define MULTI_INSTANCE_LOCK_HANDLE_ERROR INVALID_HANDLE_VALUE
+#else
+using MultiInstLockHandle = int;
+#  define MULTI_INSTANCE_LOCK_HANDLE_ERROR -1
+#endif
+
+/*
+ * nameToken should be a string very briefly naming the lock you are creating
+ * creating, and it should be unique except for across multiple instances of the
+ * same application. The vendor name is included in the generated path, so it
+ * doesn't need to be present in your supplied name. Try to keep this name sort
+ * of short, ideally under about 64 characters, because creating the lock will
+ * fail if the final path string (the token + the path hash + the vendor name)
+ * is longer than the platform's maximum path and/or path component length.
+ *
+ * installPath should be the path to the directory containing the application,
+ * which will be used to form a path specific to that installation.
+ *
+ * Returns MULTI_INSTANCE_LOCK_HANDLE_ERROR upon failure, or a handle which can
+ * later be passed to the other functions declared here upon success.
+ */
+MultiInstLockHandle OpenMultiInstanceLock(const char* nameToken,
+                                          const char16_t* installPath);
+
+void ReleaseMultiInstanceLock(MultiInstLockHandle lock);
+
+// aResult will be set to true if another instance *was* found, false if not.
+// Return value is true on success, false on error (and aResult won't be set).
+bool IsOtherInstanceRunning(MultiInstLockHandle lock, bool* aResult);
+
+// It is possible that the path we have is on a case insensitive
+// filesystem in which case the path may vary depending on how the
+// application is called. We want to normalize the case somehow.
+// When aAppFile is NULL, this function returns a nsIFile with a normalized
+// path for the currently running binary. When aAppFile is not null,
+// this function ensures the file path is properly normalized.
+already_AddRefed<nsIFile> GetNormalizedAppFile(nsIFile* aAppFile);
+
+// Computes the file path of multi instance lock
+// Returns true when successful - false otherwise
+bool GetMultiInstanceLockFileName(const char* nameToken,
+                                  const char16_t* installPath,
+                                  nsCString& filePath);
+
+};  // namespace mozilla
+
+#endif  // MULTIINSTANCELOCK_H
diff --git a/toolkit/xre/PolicyChecks.h b/toolkit/xre/PolicyChecks.h
new file mode 100644
index 0000000000..a876ff917d
--- /dev/null
+++ b/toolkit/xre/PolicyChecks.h
@@ -0,0 +1,66 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_PolicyChecks_h
+#define mozilla_PolicyChecks_h
+
+#if defined(XP_WIN)
+
+#  include <windows.h>
+#  include "mozilla/Maybe.h"
+
+#  define POLICY_REGKEY_NAME L"SOFTWARE\\Policies\\Mozilla\\" MOZ_APP_BASENAME
+
+// NB: This code must be able to run apart from XPCOM
+
+namespace mozilla {
+
+// Returns Some(true) if the registry value is 1
+// Returns Some(false) if the registry value is not 1
+// Returns Nothing() if the registry value is not present
+inline Maybe<bool> PolicyHasRegValueOfOne(HKEY aKey, LPCWSTR aName) {
+  {
+    DWORD len = sizeof(DWORD);
+    DWORD value;
+    LONG ret = ::RegGetValueW(aKey, POLICY_REGKEY_NAME, aName, RRF_RT_DWORD,
+                              nullptr, &value, &len);
+    if (ret == ERROR_SUCCESS) {
+      return Some(value == 1);
+    }
+  }
+  {
+    ULONGLONG value;
+    DWORD len = sizeof(ULONGLONG);
+    LONG ret = ::RegGetValueW(aKey, POLICY_REGKEY_NAME, aName, RRF_RT_QWORD,
+                              nullptr, &value, &len);
+    if (ret == ERROR_SUCCESS) {
+      return Some(value == 1);
+    }
+  }
+  return Nothing();
+}
+
+inline bool PolicyCheckBoolean(LPCWSTR aPolicyName) {
+  Maybe<bool> localMachineResult =
+      PolicyHasRegValueOfOne(HKEY_LOCAL_MACHINE, aPolicyName);
+  if (localMachineResult.isSome()) {
+    return localMachineResult.value();
+  }
+
+  Maybe<bool> currentUserResult =
+      PolicyHasRegValueOfOne(HKEY_CURRENT_USER, aPolicyName);
+  if (currentUserResult.isSome()) {
+    return currentUserResult.value();
+  }
+
+  return false;
+}
+
+}  // namespace mozilla
+
+#endif  // defined(XP_WIN)
+
+#endif  // mozilla_PolicyChecks_h
diff --git a/toolkit/xre/ProfileReset.cpp b/toolkit/xre/ProfileReset.cpp
new file mode 100644
index 0000000000..8ed01e6535
--- /dev/null
+++ b/toolkit/xre/ProfileReset.cpp
@@ -0,0 +1,146 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsIAppStartup.h"
+#include "nsIFile.h"
+#include "nsIStringBundle.h"
+#include "nsIToolkitProfile.h"
+#include "nsIWindowWatcher.h"
+
+#include "ProfileReset.h"
+
+#include "nsDirectoryServiceDefs.h"
+#include "nsDirectoryServiceUtils.h"
+#include "nsPIDOMWindow.h"
+#include "nsString.h"
+#include "mozilla/Components.h"
+#include "mozilla/XREAppData.h"
+
+#include "mozilla/SpinEventLoopUntil.h"
+#include "mozilla/Unused.h"
+
+using namespace mozilla;
+
+extern const XREAppData* gAppData;
+
+static const char kProfileProperties[] =
+    "chrome://mozapps/locale/profile/profileSelection.properties";
+
+/**
+ * Spin up a thread to backup the old profile's main directory and delete the
+ * profile's local directory. Once complete have the profile service remove the
+ * old profile and if necessary make the new profile the default.
+ */
+nsresult ProfileResetCleanup(nsToolkitProfileService* aService,
+                             nsIToolkitProfile* aOldProfile) {
+  nsresult rv;
+  nsCOMPtr<nsIFile> profileDir;
+  rv = aOldProfile->GetRootDir(getter_AddRefs(profileDir));
+  if (NS_FAILED(rv)) return rv;
+
+  nsCOMPtr<nsIFile> profileLocalDir;
+  rv = aOldProfile->GetLocalDir(getter_AddRefs(profileLocalDir));
+  if (NS_FAILED(rv)) return rv;
+
+  // Get the friendly name for the backup directory.
+  nsCOMPtr<nsIStringBundleService> sbs =
+      mozilla::components::StringBundle::Service();
+  if (!sbs) return NS_ERROR_FAILURE;
+
+  nsCOMPtr<nsIStringBundle> sb;
+  Unused << sbs->CreateBundle(kProfileProperties, getter_AddRefs(sb));
+  if (!sb) return NS_ERROR_FAILURE;
+
+  NS_ConvertUTF8toUTF16 appName(gAppData->name);
+  AutoTArray<nsString, 2> params = {appName, appName};
+
+  nsAutoString resetBackupDirectoryName;
+
+  static const char* kResetBackupDirectory = "resetBackupDirectory";
+  rv = sb->FormatStringFromName(kResetBackupDirectory, params,
+                                resetBackupDirectoryName);
+  if (NS_FAILED(rv)) return rv;
+
+  // Get info to copy the old root profile dir to the desktop as a backup.
+  nsCOMPtr<nsIFile> backupDest, containerDest, profileDest;
+  rv = NS_GetSpecialDirectory(NS_OS_DESKTOP_DIR, getter_AddRefs(backupDest));
+  if (NS_FAILED(rv)) {
+    // Fall back to the home directory if the desktop is not available.
+    rv = NS_GetSpecialDirectory(NS_OS_HOME_DIR, getter_AddRefs(backupDest));
+    if (NS_FAILED(rv)) return rv;
+  }
+
+  // Try to create a directory for all the backups
+  backupDest->Clone(getter_AddRefs(containerDest));
+  containerDest->Append(resetBackupDirectoryName);
+  rv = containerDest->Create(nsIFile::DIRECTORY_TYPE, 0700);
+  // It's OK if it already exists, if and only if it is a directory
+  if (rv == NS_ERROR_FILE_ALREADY_EXISTS) {
+    bool containerIsDir;
+    rv = containerDest->IsDirectory(&containerIsDir);
+    if (NS_FAILED(rv) || !containerIsDir) {
+      return rv;
+    }
+  } else if (NS_FAILED(rv)) {
+    return rv;
+  }
+
+  // Get the name of the profile
+  nsAutoString leafName;
+  rv = profileDir->GetLeafName(leafName);
+  if (NS_FAILED(rv)) return rv;
+
+  // Try to create a unique directory for the profile:
+  containerDest->Clone(getter_AddRefs(profileDest));
+  profileDest->Append(leafName);
+  rv = profileDest->CreateUnique(nsIFile::DIRECTORY_TYPE, 0700);
+  if (NS_FAILED(rv)) return rv;
+
+  // Get the unique profile name
+  rv = profileDest->GetLeafName(leafName);
+  if (NS_FAILED(rv)) return rv;
+
+  // Delete the empty directory that CreateUnique just created.
+  rv = profileDest->Remove(false);
+  if (NS_FAILED(rv)) return rv;
+
+  // Show a progress window while the cleanup happens since the disk I/O can
+  // take time.
+  nsCOMPtr<nsIWindowWatcher> windowWatcher(
+      do_GetService(NS_WINDOWWATCHER_CONTRACTID));
+  if (!windowWatcher) return NS_ERROR_FAILURE;
+
+  nsCOMPtr<nsIAppStartup> appStartup(components::AppStartup::Service());
+  if (!appStartup) return NS_ERROR_FAILURE;
+
+  nsCOMPtr<mozIDOMWindowProxy> progressWindow;
+  rv = windowWatcher->OpenWindow(nullptr, nsDependentCString(kResetProgressURL),
+                                 "_blank"_ns, "centerscreen,chrome,titlebar"_ns,
+                                 nullptr, getter_AddRefs(progressWindow));
+  if (NS_FAILED(rv)) return rv;
+
+  // Create a new thread to do the bulk of profile cleanup to stay responsive.
+  nsCOMPtr<nsIThread> cleanupThread;
+  rv = NS_NewNamedThread("ResetCleanup", getter_AddRefs(cleanupThread));
+  if (NS_SUCCEEDED(rv)) {
+    nsCOMPtr<nsIRunnable> runnable = new ProfileResetCleanupAsyncTask(
+        profileDir, profileLocalDir, containerDest, leafName);
+    cleanupThread->Dispatch(runnable, nsIThread::DISPATCH_NORMAL);
+    // The result callback will shut down the worker thread.
+
+    // Wait for the cleanup thread to complete.
+    SpinEventLoopUntil("xre:ProfileResetCreateBackup"_ns,
+                       [&]() { return gProfileResetCleanupCompleted; });
+  } else {
+    gProfileResetCleanupCompleted = true;
+    NS_WARNING("Cleanup thread creation failed");
+    return rv;
+  }
+  // Close the progress window now that the cleanup thread is done.
+  auto* piWindow = nsPIDOMWindowOuter::From(progressWindow);
+  piWindow->Close();
+
+  return aService->ApplyResetProfile(aOldProfile);
+}
diff --git a/toolkit/xre/ProfileReset.h b/toolkit/xre/ProfileReset.h
new file mode 100644
index 0000000000..71a52e7252
--- /dev/null
+++ b/toolkit/xre/ProfileReset.h
@@ -0,0 +1,84 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsToolkitProfileService.h"
+#include "nsIFile.h"
+#include "nsIThread.h"
+#include "nsThreadUtils.h"
+
+static bool gProfileResetCleanupCompleted = false;
+static const char kResetProgressURL[] =
+    "chrome://global/content/resetProfileProgress.xhtml";
+
+nsresult ProfileResetCleanup(nsToolkitProfileService* aService,
+                             nsIToolkitProfile* aOldProfile);
+
+class ProfileResetCleanupResultTask : public mozilla::Runnable {
+ public:
+  ProfileResetCleanupResultTask()
+      : mozilla::Runnable("ProfileResetCleanupResultTask"),
+        mWorkerThread(do_GetCurrentThread()) {
+    MOZ_ASSERT(!NS_IsMainThread());
+  }
+
+  NS_IMETHOD Run() override {
+    MOZ_ASSERT(NS_IsMainThread());
+    mWorkerThread->Shutdown();
+    return NS_OK;
+  }
+
+ private:
+  nsCOMPtr<nsIThread> mWorkerThread;
+};
+
+class ProfileResetCleanupAsyncTask : public mozilla::Runnable {
+ public:
+  ProfileResetCleanupAsyncTask(nsIFile* aProfileDir, nsIFile* aProfileLocalDir,
+                               nsIFile* aTargetDir, const nsAString& aLeafName)
+      : mozilla::Runnable("ProfileResetCleanupAsyncTask"),
+        mProfileDir(aProfileDir),
+        mProfileLocalDir(aProfileLocalDir),
+        mTargetDir(aTargetDir),
+        mLeafName(aLeafName) {}
+
+  /**
+   * Copy a root profile to a backup folder before deleting it.  Then delete the
+   * local profile dir.
+   */
+  NS_IMETHOD Run() override {
+    // Copy profile's files to the destination. The profile folder will be
+    // removed after the changes to the known profiles have been flushed to disk
+    // in nsToolkitProfileService::ApplyResetProfile which isn't called until
+    // after this thread finishes copying the files.
+    nsresult rv = mProfileDir->CopyToFollowingLinks(mTargetDir, mLeafName);
+    // I guess we just warn if we fail to make the backup?
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      NS_WARNING("Could not backup the root profile directory");
+    }
+
+    // If we have a separate local cache profile directory, just delete it.
+    // Don't return an error if this fails so that reset can proceed if it can't
+    // be deleted.
+    bool sameDir;
+    nsresult rvLocal = mProfileDir->Equals(mProfileLocalDir, &sameDir);
+    if (NS_SUCCEEDED(rvLocal) && !sameDir) {
+      rvLocal = mProfileLocalDir->Remove(true);
+      if (NS_FAILED(rvLocal)) {
+        NS_WARNING("Could not remove the old local profile directory (cache)");
+      }
+    }
+    gProfileResetCleanupCompleted = true;
+
+    nsCOMPtr<nsIRunnable> resultRunnable = new ProfileResetCleanupResultTask();
+    NS_DispatchToMainThread(resultRunnable);
+    return NS_OK;
+  }
+
+ private:
+  nsCOMPtr<nsIFile> mProfileDir;
+  nsCOMPtr<nsIFile> mProfileLocalDir;
+  nsCOMPtr<nsIFile> mTargetDir;
+  nsString mLeafName;
+};
diff --git a/toolkit/xre/SafeMode.h b/toolkit/xre/SafeMode.h
new file mode 100644
index 0000000000..9323ff1a9c
--- /dev/null
+++ b/toolkit/xre/SafeMode.h
@@ -0,0 +1,90 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_SafeMode_h
+#define mozilla_SafeMode_h
+
+// NB: This code must be able to run apart from XPCOM
+
+#include "mozilla/CmdLineAndEnvUtils.h"
+#include "mozilla/Maybe.h"
+
+#if defined(XP_WIN)
+#  include "mozilla/PolicyChecks.h"
+#  include <windows.h>
+#endif  // defined(XP_WIN)
+
+// Undo X11/X.h's definition of None
+#undef None
+
+namespace mozilla {
+
+enum class SafeModeFlag : uint32_t {
+  None = 0,
+  Unset = (1 << 0),
+  NoKeyPressCheck = (1 << 1),
+};
+
+MOZ_MAKE_ENUM_CLASS_BITWISE_OPERATORS(SafeModeFlag)
+
+template <typename CharT>
+inline Maybe<bool> IsSafeModeRequested(
+    int& aArgc, CharT* aArgv[],
+    const SafeModeFlag aFlags = SafeModeFlag::Unset) {
+  CheckArgFlag checkArgFlags = CheckArgFlag::None;
+  if (aFlags & SafeModeFlag::Unset) {
+    checkArgFlags |= CheckArgFlag::RemoveArg;
+  }
+
+  ArgResult ar = CheckArg(aArgc, aArgv, "safe-mode", nullptr, checkArgFlags);
+  if (ar == ARG_BAD) {
+    return Nothing();
+  }
+
+  bool result = ar == ARG_FOUND;
+
+#if defined(XP_WIN)
+  // If the shift key is pressed and the ctrl and / or alt keys are not pressed
+  // during startup, start in safe mode. GetKeyState returns a short and the
+  // high order bit will be 1 if the key is pressed. By masking the returned
+  // short with 0x8000 the result will be 0 if the key is not pressed and
+  // non-zero otherwise.
+  if (!(aFlags & SafeModeFlag::NoKeyPressCheck) &&
+      (GetKeyState(VK_SHIFT) & 0x8000) && !(GetKeyState(VK_CONTROL) & 0x8000) &&
+      !(GetKeyState(VK_MENU) & 0x8000) &&
+      !EnvHasValue("MOZ_DISABLE_SAFE_MODE_KEY")) {
+    result = true;
+  }
+
+  if (result && PolicyCheckBoolean(L"DisableSafeMode")) {
+    result = false;
+  }
+#endif  // defined(XP_WIN)
+
+#if defined(XP_MACOSX)
+  if (!(aFlags & SafeModeFlag::NoKeyPressCheck) &&
+      (GetCurrentEventKeyModifiers() & optionKey) &&
+      !EnvHasValue("MOZ_DISABLE_SAFE_MODE_KEY")) {
+    result = true;
+  }
+#endif  // defined(XP_MACOSX)
+
+  // The Safe Mode Policy should not be enforced for the env var case
+  // (used by updater and crash-recovery).
+  if (EnvHasValue("MOZ_SAFE_MODE_RESTART")) {
+    result = true;
+    if (aFlags & SafeModeFlag::Unset) {
+      // unset the env variable
+      SaveToEnv("MOZ_SAFE_MODE_RESTART=");
+    }
+  }
+
+  return Some(result);
+}
+
+}  // namespace mozilla
+
+#endif  // mozilla_SafeMode_h
diff --git a/toolkit/xre/UIKitDirProvider.h b/toolkit/xre/UIKitDirProvider.h
new file mode 100644
index 0000000000..ff7ad6b3b9
--- /dev/null
+++ b/toolkit/xre/UIKitDirProvider.h
@@ -0,0 +1,13 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef TOOLKIT_XRE_UIKITDIRPROVIDER_H_
+#define TOOLKIT_XRE_UIKITDIRPROVIDER_H_
+
+#include "nsString.h"
+
+bool GetUIKitDirectory(bool aLocal, nsACString& aUserDir);
+
+#endif  // TOOLKIT_XRE_UIKITDIRPROVIDER_H_
diff --git a/toolkit/xre/UIKitDirProvider.mm b/toolkit/xre/UIKitDirProvider.mm
new file mode 100644
index 0000000000..043ecbe2ec
--- /dev/null
+++ b/toolkit/xre/UIKitDirProvider.mm
@@ -0,0 +1,18 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <Foundation/Foundation.h>
+
+#include "UIKitDirProvider.h"
+
+bool GetUIKitDirectory(bool aLocal, nsACString& aUserDir) {
+  NSSearchPathDirectory directory = aLocal ? NSCachesDirectory : NSApplicationSupportDirectory;
+  NSArray* paths = NSSearchPathForDirectoriesInDomains(directory, NSUserDomainMask, YES);
+  if ([paths count] == 0) {
+    return false;
+  }
+  aUserDir = [[paths objectAtIndex:0] UTF8String];
+  return true;
+}
diff --git a/toolkit/xre/WinTokenUtils.cpp b/toolkit/xre/WinTokenUtils.cpp
new file mode 100644
index 0000000000..4774ec6dad
--- /dev/null
+++ b/toolkit/xre/WinTokenUtils.cpp
@@ -0,0 +1,72 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#include "WinTokenUtils.h"
+#include "nsWindowsHelpers.h"
+
+using namespace mozilla;
+
+// If |aToken| is nullptr, CheckTokenMembership uses the calling thread's
+// primary token to check membership for.
+static LauncherResult<bool> IsMemberOfAdministrators(
+    const nsAutoHandle& aToken) {
+  BYTE adminsGroupSid[SECURITY_MAX_SID_SIZE];
+  DWORD adminsGroupSidSize = sizeof(adminsGroupSid);
+  if (!CreateWellKnownSid(WinBuiltinAdministratorsSid, nullptr, adminsGroupSid,
+                          &adminsGroupSidSize)) {
+    return LAUNCHER_ERROR_FROM_LAST();
+  }
+
+  BOOL isMember;
+  if (!CheckTokenMembership(aToken, adminsGroupSid, &isMember)) {
+    return LAUNCHER_ERROR_FROM_LAST();
+  }
+  return !!isMember;
+}
+
+static LauncherResult<bool> IsUacEnabled() {
+  DWORD len = sizeof(DWORD);
+  DWORD value;
+  LSTATUS status = RegGetValueW(
+      HKEY_LOCAL_MACHINE,
+      L"SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Policies\\System",
+      L"EnableLUA", RRF_RT_DWORD, nullptr, &value, &len);
+  if (status != ERROR_SUCCESS) {
+    return LAUNCHER_ERROR_FROM_WIN32(status);
+  }
+
+  // UAC is disabled only when EnableLUA is 0.
+  return (value != 0);
+}
+
+namespace mozilla {
+
+LauncherResult<bool> IsAdminWithoutUac() {
+  // To check whether the process was launched with Administrator priviledges
+  // or not, we cannot simply check the integrity level of the current process
+  // because the launcher process spawns the browser process with the medium
+  // integrity level even though the launcher process is high integrity level.
+  // We check whether the thread's token contains Administratos SID or not
+  // instead.
+  LauncherResult<bool> containsAdminGroup =
+      IsMemberOfAdministrators(nsAutoHandle());
+  if (containsAdminGroup.isErr()) {
+    return containsAdminGroup.propagateErr();
+  }
+
+  if (!containsAdminGroup.unwrap()) {
+    return false;
+  }
+
+  LauncherResult<bool> isUacEnabled = IsUacEnabled();
+  if (isUacEnabled.isErr()) {
+    return isUacEnabled.propagateErr();
+  }
+
+  return !isUacEnabled.unwrap();
+}
+
+}  // namespace mozilla
diff --git a/toolkit/xre/WinTokenUtils.h b/toolkit/xre/WinTokenUtils.h
new file mode 100644
index 0000000000..48b9ec5a8b
--- /dev/null
+++ b/toolkit/xre/WinTokenUtils.h
@@ -0,0 +1,18 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_WinTokenUtils_h
+#define mozilla_WinTokenUtils_h
+
+#include "mozilla/WinHeaderOnlyUtils.h"
+
+namespace mozilla {
+
+LauncherResult<bool> IsAdminWithoutUac();
+
+}  // namespace mozilla
+
+#endif  // mozilla_WinTokenUtils_h
diff --git a/toolkit/xre/components.conf b/toolkit/xre/components.conf
new file mode 100644
index 0000000000..b59964e794
--- /dev/null
+++ b/toolkit/xre/components.conf
@@ -0,0 +1,71 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+if defined('MOZ_CRASHREPORTER'):
+    crash_reporter = ['@mozilla.org/toolkit/crash-reporter;1']
+else:
+    crash_reporter = []
+
+Classes = [
+    {
+        'name': 'XULRuntime',
+        'js_name': 'appinfo',
+        'cid': '{95d89e3e-a169-41a3-8e56-719978e15b12}',
+        'contract_ids': [
+            '@mozilla.org/xre/app-info;1',
+            '@mozilla.org/xre/runtime;1',
+        ] + crash_reporter,
+        'interfaces': ['nsIXULRuntime', 'nsIXULAppInfo', 'nsICrashReporter'],
+        'legacy_constructor': 'mozilla::AppInfoConstructor',
+        'headers': ['nsAppRunner.h'],
+        'processes': ProcessSelector.ALLOW_IN_SOCKET_PROCESS,
+        'overridable': True,
+    },
+    {
+        'cid': '{471f4944-1dd2-11b2-87ac-90be0a51d609}',
+        'contract_ids': ['@mozilla.org/embedcomp/rangefind;1'],
+        'type': 'nsFind',
+        'headers': ['/toolkit/components/find/nsFind.h'],
+    },
+    {
+        'cid': '{7e677795-c582-4cd1-9e8d-8271b3474d2a}',
+        'contract_ids': ['@mozilla.org/embedding/browser/nsWebBrowserPersist;1'],
+        'type': 'nsWebBrowserPersist',
+        'headers': ['/dom/webbrowserpersist/nsWebBrowserPersist.h'],
+    },
+    {
+        'js_name': 'ww',
+        'cid': '{a21bfa01-f349-4394-a84c-8de5cf0737d0}',
+        'contract_ids': ['@mozilla.org/embedcomp/window-watcher;1'],
+        'interfaces': ['nsIWindowWatcher'],
+        'type': 'nsWindowWatcher',
+        'headers': ['nsWindowWatcher.h'],
+        'init_method': 'Init',
+        'overridable': True,
+    },
+    {
+        'cid': '{5573967d-f6cf-4c63-8e0e-9ac06e04d62b}',
+        'contract_ids': ['@mozilla.org/xre/directory-provider;1'],
+        'singleton': True,
+        'type': 'nsXREDirProvider',
+        'constructor': 'nsXREDirProvider::GetSingleton',
+        'headers': ['/toolkit/xre/nsXREDirProvider.h'],
+    },
+    {
+        'cid': '{4e4aae11-8901-46cc-8217-dad7c5415873}',
+        'contract_ids': ['@mozilla.org/embedcomp/dialogparam;1'],
+        'type': 'nsDialogParamBlock',
+        'headers': ['/toolkit/components/windowwatcher/nsDialogParamBlock.h'],
+    },
+    {
+        'cid': '{5f5e59ce-27bc-47eb-9d1f-b09ca9049836}',
+        'contract_ids': ['@mozilla.org/toolkit/profile-service;1'],
+        'singleton': True,
+        'constructor': 'NS_GetToolkitProfileService',
+        'type': 'nsToolkitProfileService',
+        'headers': ['/toolkit/profile/nsToolkitProfileService.h'],
+    },
+]
diff --git a/toolkit/xre/detect_win32k_conflicts.h b/toolkit/xre/detect_win32k_conflicts.h
new file mode 100644
index 0000000000..62ff737bcd
--- /dev/null
+++ b/toolkit/xre/detect_win32k_conflicts.h
@@ -0,0 +1,20 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#ifndef TOOLKIT_XRE_DETECT_WIN32K_CONFLICTS_H
+#define TOOLKIT_XRE_DETECT_WIN32K_CONFLICTS_H
+#include <cinttypes>
+
+// C interface for the `detect_win32k_conflicts` Rust crate
+
+struct ConflictingMitigationStatus {
+  bool caller_check;
+  bool sim_exec;
+  bool stack_pivot;
+};
+
+extern "C" bool detect_win32k_conflicting_mitigations(
+    ConflictingMitigationStatus* aConflictingMitigationStatus);
+
+#endif  // TOOLKIT_XRE_DETECT_WIN32K_CONFLICTS_H
diff --git a/toolkit/xre/detect_win32k_conflicts/.gitignore b/toolkit/xre/detect_win32k_conflicts/.gitignore
new file mode 100644
index 0000000000..869df07dae
--- /dev/null
+++ b/toolkit/xre/detect_win32k_conflicts/.gitignore
@@ -0,0 +1,2 @@
+/target
+Cargo.lock
\ No newline at end of file
diff --git a/toolkit/xre/detect_win32k_conflicts/Cargo.toml b/toolkit/xre/detect_win32k_conflicts/Cargo.toml
new file mode 100644
index 0000000000..a94402df9e
--- /dev/null
+++ b/toolkit/xre/detect_win32k_conflicts/Cargo.toml
@@ -0,0 +1,10 @@
+[package]
+name = "detect_win32k_conflicts"
+version = "0.1.0"
+edition = "2021"
+license = "MPL-2.0"
+
+[dependencies]
+log = "0.4"
+thiserror = "1"
+winapi = { version = "0.3", features = ["winerror", "winreg"] }
diff --git a/toolkit/xre/detect_win32k_conflicts/src/detect.rs b/toolkit/xre/detect_win32k_conflicts/src/detect.rs
new file mode 100644
index 0000000000..e21c80e157
--- /dev/null
+++ b/toolkit/xre/detect_win32k_conflicts/src/detect.rs
@@ -0,0 +1,165 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+//! This module contains the actual functions that explore the registry for the status
+//! of the conflicting mitigations.
+
+use super::error::DetectConflictError;
+use super::registry::{RegKey, RegValue};
+
+use std::ffi::OsStr;
+
+/// Subkey that the Windows Exploit Protection status is located in
+const EXPLOIT_PROTECTION_SUBKEY: &str =
+    "SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion\\Image File Execution Options";
+
+/// Name of the value within that subkey that contains the exploit protection status
+const MITIGATION_VALUE_NAME: &str = "MitigationOptions";
+
+/// The bit number within the value with the StackPivot status
+const STACK_PIVOT_BIT: usize = 80;
+
+/// The bit number within the value with the CallerCheck status
+const CALLER_CHECK_BIT: usize = 84;
+
+/// The bit number within the value with the SimExec status
+const SIM_EXEC_BIT: usize = 88;
+
+/// Printable, FFI-safe structure containing the status of the conflicting mitigations
+#[repr(C)]
+#[derive(Clone, Copy, Debug, Default, PartialEq)]
+pub struct ConflictingMitigationStatus {
+    /// The status of the CallerCheck feature. 0 = disabled, 1 = enabled
+    caller_check: bool,
+    /// The status of the SimExec feature. 0 = disabled, 1 = enabled
+    sim_exec: bool,
+    /// The status of the StackPivot feature. 0 = disabled, 1 = enabled
+    stack_pivot: bool,
+}
+
+impl std::fmt::Display for ConflictingMitigationStatus {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> Result<(), std::fmt::Error> {
+        use std::fmt::Write;
+        write_status(f, "CallerCheck", self.caller_check)?;
+        f.write_char(' ')?;
+        write_status(f, "SimExec", self.sim_exec)?;
+        f.write_char(' ')?;
+        write_status(f, "StackPivot", self.stack_pivot)
+    }
+}
+
+/// Search the registry for win32k-conflicting mitigations for the given process
+///
+/// `process_name` is the name of the process that will be checked for conflicting mitigations
+/// It uses the same case-insensitive algorithm that the Windows Registry uses itself to detect
+/// whether a process needs mitigations or not
+///
+/// (This will usually be `firefox.exe`)
+///
+/// # Caveat
+///
+/// Windows allows an arbitrary number of "filters", which are subkeys of the main key
+/// that also have a `MitigationOptions` value. They are used to allow filtering by path.
+///
+/// For simplicity, we "flatten" the path filters when we figure this out, and so the
+/// returned value will be the logical "OR" of all mitigations enabled with any filter
+///
+/// So if there are two entries for "C:\Firefox\firefox.exe" with mitigations `A` and `B` enabled
+/// and another entry for "C:\Program Files\Mozilla Firefox\firefox.exe" with mitigation `C`
+/// enabled, we will return that `A`, `B`, and `C` are all enabled
+pub fn get_conflicting_mitigations(
+    process_name: impl AsRef<OsStr>,
+) -> Result<ConflictingMitigationStatus, DetectConflictError> {
+    let process_name = process_name.as_ref();
+
+    let key = RegKey::root_local_machine()
+        .try_open_subkey(EXPLOIT_PROTECTION_SUBKEY)?
+        .ok_or(DetectConflictError::ExploitProtectionKeyMissing)?;
+
+    let process_key = match key.try_open_subkey(process_name)? {
+        Some(key) => key,
+        None => {
+            log::info!(
+                "process name {:?} not found in exploit protection",
+                process_name
+            );
+            return Ok(ConflictingMitigationStatus::default());
+        }
+    };
+
+    // First get mitigation status for the root key
+    let mut status = get_conflicting_mitigations_for_key(&process_key)?;
+
+    // Then get mitigation status for each subkey and logical-or them all together
+    for subkey_name in process_key.subkey_names() {
+        let subkey_name = subkey_name?;
+
+        let subkey = process_key
+            .try_open_subkey(subkey_name)?
+            .expect("a subkey somehow doesn't exist after enumerating it");
+
+        let subkey_status = get_conflicting_mitigations_for_key(&subkey)?;
+        status.caller_check |= subkey_status.caller_check;
+        status.sim_exec |= subkey_status.sim_exec;
+        status.stack_pivot |= subkey_status.stack_pivot;
+    }
+
+    log::info!(
+        "process name {:?} has mitigation status {:?}",
+        process_name,
+        status
+    );
+
+    Ok(status)
+}
+
+/// Check a key to see if it has a "MitigationOptions" value with any conflicting mitigations
+/// enabled
+fn get_conflicting_mitigations_for_key(
+    key: &RegKey,
+) -> Result<ConflictingMitigationStatus, DetectConflictError> {
+    let value = match key.try_get_value(MITIGATION_VALUE_NAME)? {
+        Some(value) => value,
+        None => return Ok(ConflictingMitigationStatus::default()),
+    };
+
+    let bits = match value {
+        RegValue::Binary(bits) => bits,
+        _ => return Ok(ConflictingMitigationStatus::default()),
+    };
+
+    Ok(ConflictingMitigationStatus {
+        caller_check: get_bit(&bits, CALLER_CHECK_BIT)?,
+        sim_exec: get_bit(&bits, SIM_EXEC_BIT)?,
+        stack_pivot: get_bit(&bits, STACK_PIVOT_BIT)?,
+    })
+}
+
+/// Retrieve a bit from a vector-of-bitflags, which is what will be returned by the registry
+/// entry for exploit protection. The bits are numbered first by increasing value within a byte,
+/// and then by increasing index within the slice.
+///
+/// Ex: bit 0 = (index 0, mask 0x01), bit 7 = (index 0, mask 0x80), bit 8 = (index 1, mask 0x01)
+fn get_bit(bytes: &[u8], bit_idx: usize) -> Result<bool, DetectConflictError> {
+    let byte = bytes
+        .get(bit_idx / 8)
+        .ok_or(DetectConflictError::RegValueTooShort)?;
+
+    Ok(if byte & (1 << (bit_idx % 8)) != 0 {
+        true
+    } else {
+        false
+    })
+}
+
+/// Write the status of a feature to the given formatter. `bit == 0` means feature is disabled,
+/// `bit == 1` means enabled
+fn write_status(
+    f: &mut std::fmt::Formatter<'_>,
+    name: &str,
+    bit: bool,
+) -> Result<(), std::fmt::Error> {
+    let status_str = if bit { "enabled" } else { "disabled" };
+    write!(f, "{} is {}.", name, status_str)
+}
diff --git a/toolkit/xre/detect_win32k_conflicts/src/error.rs b/toolkit/xre/detect_win32k_conflicts/src/error.rs
new file mode 100644
index 0000000000..cc73d04b2d
--- /dev/null
+++ b/toolkit/xre/detect_win32k_conflicts/src/error.rs
@@ -0,0 +1,36 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+//! Contains the error type for this crate
+
+use thiserror::Error;
+
+/// The error type for this crate
+#[derive(Debug, Error)]
+pub enum DetectConflictError {
+    /// An exploit protection key was not found in the registry
+    #[error("exploit protection key missing")]
+    ExploitProtectionKeyMissing,
+    /// Failed to enumerate the next registry subkey
+    #[error("failed to enumerate next registry subkey. code: {0}")]
+    RegEnumKeyFailed(u32),
+    /// Failed to get a value from the registry
+    #[error("failed to get registry value. code: {0}")]
+    RegGetValueFailed(u32),
+    /// Failed to get the length of a value from the registry
+    #[error("failed to get registry value length. code: {0}")]
+    RegGetValueLenFailed(u32),
+    /// Failed to open a registry key
+    #[error("failed to open registry key. code: {0}")]
+    RegOpenKeyFailed(u32),
+    /// Exploit Protection registry value was too short
+    #[error("exploit protection registry value too short")]
+    RegValueTooShort,
+    /// Failed to query key for subkey length
+    #[error("failed to query key for max subkey length. code: {0}")]
+    RegQueryInfoKeyFailed(u32),
+    /// A registry value had an unsupported type
+    #[error("key has unsupported value type: {0}")]
+    UnsupportedValueType(u32),
+}
diff --git a/toolkit/xre/detect_win32k_conflicts/src/ffi.rs b/toolkit/xre/detect_win32k_conflicts/src/ffi.rs
new file mode 100644
index 0000000000..826f452726
--- /dev/null
+++ b/toolkit/xre/detect_win32k_conflicts/src/ffi.rs
@@ -0,0 +1,57 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+//! C foreign-function interface for this crate
+
+use super::detect::{get_conflicting_mitigations, ConflictingMitigationStatus};
+
+/// C FFI for `get_conflicting_mitigations`
+///
+/// Checks the current process to see if any conflicting mitigations would be enabled
+/// by Windows Exploit Protection
+///
+/// `conflicting_mitigations` is an out pointer that will receive the status of the
+/// Win32k conflicting mitigations
+///
+/// On success, returns `1`. On failure, returns `0` and `conflicting_mitigations` is left
+/// untouched
+///
+/// # Safety
+///
+/// `conflicting_mitigations` must not be a non-const, non-null ptr and **must be initialized**
+///
+/// # Example
+///
+/// ```C++
+/// void myFunc() {
+///     ConflictingMitigationStatus status = {}; // GOOD - value-initializes the object
+///     if(!detect_win32k_conflicting_mitigations(&status)) {
+///         // error
+///     }
+/// }
+/// ```
+#[no_mangle]
+pub unsafe extern "C" fn detect_win32k_conflicting_mitigations(
+    conflicting_mitigations: &mut ConflictingMitigationStatus,
+) -> bool {
+    let process_path =
+        std::env::current_exe().expect("unable to determine the path of our executable");
+    let file_name = process_path
+        .file_name()
+        .expect("executable doesn't have a file name");
+
+    match get_conflicting_mitigations(file_name) {
+        Ok(status) => {
+            *conflicting_mitigations = status;
+            true
+        }
+        Err(e) => {
+            log::error!(
+                "Failed to get Win32k Lockdown conflicting mitigation status: {}",
+                e
+            );
+            false
+        }
+    }
+}
diff --git a/toolkit/xre/detect_win32k_conflicts/src/lib.rs b/toolkit/xre/detect_win32k_conflicts/src/lib.rs
new file mode 100644
index 0000000000..4333603b92
--- /dev/null
+++ b/toolkit/xre/detect_win32k_conflicts/src/lib.rs
@@ -0,0 +1,18 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+//! Crate to detect Windows Exploit Protection mitigations that may interfere with Win32k
+//! Lockdown
+
+#![deny(missing_docs)]
+
+mod detect;
+mod error;
+mod ffi;
+mod registry;
+
+pub use self::detect::get_conflicting_mitigations;
+pub use self::detect::ConflictingMitigationStatus;
+pub use self::error::DetectConflictError;
+pub use self::ffi::detect_win32k_conflicting_mitigations;
diff --git a/toolkit/xre/detect_win32k_conflicts/src/registry.rs b/toolkit/xre/detect_win32k_conflicts/src/registry.rs
new file mode 100644
index 0000000000..f375a64284
--- /dev/null
+++ b/toolkit/xre/detect_win32k_conflicts/src/registry.rs
@@ -0,0 +1,360 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+//! This module contains helpers for exploring the Windows Registry
+
+use super::error::DetectConflictError;
+
+use std::ffi::{OsStr, OsString};
+use std::os::windows::ffi::{OsStrExt, OsStringExt};
+
+use winapi::{
+    shared::{
+        minwindef::HKEY,
+        winerror::{ERROR_FILE_NOT_FOUND, ERROR_NO_MORE_ITEMS, ERROR_SUCCESS},
+    },
+    um::{
+        winnt::{KEY_READ, REG_BINARY, REG_DWORD, REG_SZ},
+        winreg::{
+            RegCloseKey, RegEnumKeyExW, RegGetValueW, RegOpenKeyExW, RegQueryInfoKeyW,
+            HKEY_LOCAL_MACHINE, RRF_RT_REG_BINARY, RRF_RT_REG_DWORD, RRF_RT_REG_SZ,
+        },
+    },
+};
+
+/// An open key in the Windows Registry
+///
+/// (Note that Windows ref-counts keys internally, so we don't need subkeys to "hang on" to
+/// their parents)
+#[derive(Debug)]
+pub struct RegKey {
+    /// The Win32 handle of the open key
+    handle: HKEY,
+}
+
+impl RegKey {
+    /// Open the global HKEY_LOCAL_MACHINE handle
+    pub fn root_local_machine() -> RegKey {
+        RegKey {
+            handle: HKEY_LOCAL_MACHINE,
+        }
+    }
+    /// Try to open a subkey relative to this key with read-only access rights
+    ///
+    /// Returns `None` if the subkey doesn't exist
+    pub fn try_open_subkey(
+        &self,
+        subkey: impl AsRef<OsStr>,
+    ) -> Result<Option<RegKey>, DetectConflictError> {
+        let win32_subkey = to_win32_string(subkey.as_ref());
+
+        let mut subkey_handle = std::ptr::null_mut();
+        let rv = unsafe {
+            RegOpenKeyExW(
+                self.handle,
+                win32_subkey.as_ptr(),
+                0, // options
+                KEY_READ,
+                &mut subkey_handle,
+            )
+        }
+        .try_into()
+        .unwrap();
+
+        match rv {
+            ERROR_SUCCESS => {
+                assert!(!subkey_handle.is_null());
+
+                Ok(Some(RegKey {
+                    handle: subkey_handle,
+                }))
+            }
+            ERROR_FILE_NOT_FOUND => Ok(None),
+            _ => Err(DetectConflictError::RegOpenKeyFailed(rv)),
+        }
+    }
+    /// Try to get a value with the given name
+    ///
+    /// Returns `None` if there is no value with that name
+    ///
+    /// Note that you can pass the empty string to get the default value
+    pub fn try_get_value(
+        &self,
+        value_name: impl AsRef<OsStr>,
+    ) -> Result<Option<RegValue>, DetectConflictError> {
+        let win32_value_name = to_win32_string(value_name.as_ref());
+
+        // First we query the value's length and type so we know how to create the data buffer
+        let mut value_type = 0;
+        let mut value_len = 0;
+
+        let rv = unsafe {
+            RegGetValueW(
+                self.handle,
+                std::ptr::null(), // subkey
+                win32_value_name.as_ptr(),
+                RRF_RT_REG_BINARY | RRF_RT_REG_DWORD | RRF_RT_REG_SZ,
+                &mut value_type,
+                std::ptr::null_mut(), // no data ptr, just query length & type
+                &mut value_len,
+            )
+        }
+        .try_into()
+        .unwrap();
+
+        if rv == ERROR_FILE_NOT_FOUND {
+            return Ok(None);
+        }
+
+        if rv != ERROR_SUCCESS || value_len == 0 {
+            return Err(DetectConflictError::RegGetValueLenFailed(rv));
+        }
+
+        if value_type == REG_SZ {
+            // buffer length is in wide characters
+            let buffer_len = value_len / 2;
+
+            assert_eq!(buffer_len * 2, value_len);
+
+            let mut buffer = vec![0u16; buffer_len.try_into().unwrap()];
+
+            let rv = unsafe {
+                RegGetValueW(
+                    self.handle,
+                    std::ptr::null(), // subkey
+                    win32_value_name.as_ptr(),
+                    RRF_RT_REG_SZ,
+                    std::ptr::null_mut(), // no need to query type again
+                    buffer.as_mut_ptr().cast(),
+                    &mut value_len,
+                )
+            }
+            .try_into()
+            .unwrap();
+
+            if rv != ERROR_SUCCESS {
+                return Err(DetectConflictError::RegGetValueFailed(rv));
+            }
+
+            Ok(Some(RegValue::String(from_win32_string(&buffer))))
+        } else if value_type == REG_BINARY {
+            let mut buffer = vec![0u8; value_len.try_into().unwrap()];
+
+            let rv = unsafe {
+                RegGetValueW(
+                    self.handle,
+                    std::ptr::null(), // subkey
+                    win32_value_name.as_ptr(),
+                    RRF_RT_REG_BINARY,
+                    std::ptr::null_mut(), // no need to query type again
+                    buffer.as_mut_ptr().cast(),
+                    &mut value_len,
+                )
+            }
+            .try_into()
+            .unwrap();
+
+            if rv != ERROR_SUCCESS {
+                return Err(DetectConflictError::RegGetValueFailed(rv));
+            }
+
+            Ok(Some(RegValue::Binary(buffer)))
+        } else if value_type == REG_DWORD {
+            assert_eq!(value_len, 4);
+
+            let mut buffer = 0u32;
+
+            let rv = unsafe {
+                RegGetValueW(
+                    self.handle,
+                    std::ptr::null(), // subkey
+                    win32_value_name.as_ptr(),
+                    RRF_RT_REG_DWORD,
+                    std::ptr::null_mut(), // no need to query type again
+                    (&mut buffer as *mut u32).cast(),
+                    &mut value_len,
+                )
+            }
+            .try_into()
+            .unwrap();
+
+            if rv != ERROR_SUCCESS {
+                return Err(DetectConflictError::RegGetValueFailed(rv));
+            }
+
+            Ok(Some(RegValue::Dword(buffer)))
+        } else {
+            Err(DetectConflictError::UnsupportedValueType(value_type))
+        }
+    }
+    /// Get an iterator that returns the names of all the subkeys of this key
+    pub fn subkey_names(&self) -> SubkeyNames<'_> {
+        SubkeyNames::new(self)
+    }
+}
+
+impl Drop for RegKey {
+    fn drop(&mut self) {
+        assert!(!self.handle.is_null());
+
+        if self.handle == HKEY_LOCAL_MACHINE {
+            return;
+        }
+
+        let rv: u32 = unsafe { RegCloseKey(self.handle) }.try_into().unwrap();
+
+        if rv != ERROR_SUCCESS {
+            log::warn!("failed to close opened registry key");
+        }
+    }
+}
+
+/// An iterator through the subkeys of a key
+///
+/// Returns items of type `Result<OsString, DetectConflictError>`. If an error occurs, calling `next()` again
+/// will likely just continue to result in errors, so it's best to just abandon ship at that
+/// point
+#[derive(Debug)]
+pub struct SubkeyNames<'a> {
+    /// The key that is being iterated
+    key: &'a RegKey,
+    /// The current index of the subkey -- Incremented each successful call to `next()`
+    index: u32,
+    /// A buffer that is large enough to hold the longest subkey name
+    buffer: Option<Vec<u16>>,
+}
+
+impl<'a> SubkeyNames<'a> {
+    /// Create a new subkey name iterator
+    fn new(key: &'a RegKey) -> SubkeyNames<'a> {
+        SubkeyNames {
+            key,
+            index: 0,
+            buffer: None,
+        }
+    }
+    /// Initialize `self.buffer` with a vector that's long enough to hold the longest subkey name
+    /// (if it isn't already)
+    fn create_buffer_if_needed(&mut self) -> Result<(), DetectConflictError> {
+        if self.buffer.is_some() {
+            return Ok(());
+        }
+
+        let mut max_key_length = 0;
+
+        let rv = unsafe {
+            RegQueryInfoKeyW(
+                self.key.handle,
+                std::ptr::null_mut(), // class ptr
+                std::ptr::null_mut(), // class len ptr
+                std::ptr::null_mut(), // reserved
+                std::ptr::null_mut(), // num of subkeys ptr
+                &mut max_key_length,
+                std::ptr::null_mut(), // max class length ptr
+                std::ptr::null_mut(), // number of values ptr
+                std::ptr::null_mut(), // longest value name ptr
+                std::ptr::null_mut(), // longest value data ptr
+                std::ptr::null_mut(), // DACL ptr
+                std::ptr::null_mut(), // last write time ptr
+            )
+        }
+        .try_into()
+        .unwrap();
+
+        if rv != ERROR_SUCCESS {
+            return Err(DetectConflictError::RegQueryInfoKeyFailed(rv));
+        }
+
+        // +1 for the null terminator
+        let max_key_length = usize::try_from(max_key_length).unwrap() + 1;
+
+        self.buffer = Some(vec![0u16; max_key_length]);
+
+        Ok(())
+    }
+}
+
+impl<'a> Iterator for SubkeyNames<'a> {
+    type Item = Result<OsString, DetectConflictError>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        if let Err(e) = self.create_buffer_if_needed() {
+            return Some(Err(e));
+        }
+
+        let buffer = self.buffer.as_mut().unwrap();
+        let mut name_len = u32::try_from(buffer.len()).unwrap();
+
+        let rv = unsafe {
+            RegEnumKeyExW(
+                self.key.handle,
+                self.index,
+                buffer.as_mut_ptr(),
+                &mut name_len,
+                std::ptr::null_mut(), // reserved
+                std::ptr::null_mut(), // class ptr
+                std::ptr::null_mut(), // class len ptr
+                std::ptr::null_mut(), // last write time ptr
+            )
+        }
+        .try_into()
+        .unwrap();
+
+        if rv == ERROR_NO_MORE_ITEMS {
+            return None;
+        }
+
+        if rv != ERROR_SUCCESS {
+            return Some(Err(DetectConflictError::RegEnumKeyFailed(rv)));
+        }
+
+        self.index += 1;
+
+        // +1 for the null terminator
+        let name_len = usize::try_from(name_len).unwrap() + 1;
+
+        Some(Ok(from_win32_string(&buffer[0..name_len])))
+    }
+}
+
+/// A single value in the registry
+#[derive(Clone, Debug, PartialEq)]
+pub enum RegValue {
+    /// A REG_BINARY value
+    Binary(Vec<u8>),
+    /// A REG_DWORD value
+    Dword(u32),
+    /// A REG_SZ value
+    String(OsString),
+}
+
+/// Convert an OsStr to a null-terminated wide character string
+///
+/// The input string must not contain any interior null values, and the resulting wide
+/// character array will have a null terminator appended
+fn to_win32_string(s: &OsStr) -> Vec<u16> {
+    // +1 for the null terminator
+    let mut result = Vec::with_capacity(s.len() + 1);
+
+    for wc in s.encode_wide() {
+        assert_ne!(wc, 0);
+        result.push(wc);
+    }
+
+    result.push(0);
+    result
+}
+
+/// Convert a null-terminated wide character string into an OsString
+///
+/// The passed-in slice must have exactly one wide null character as the last element
+fn from_win32_string(s: &[u16]) -> OsString {
+    for (idx, wc) in s.iter().enumerate() {
+        if *wc == 0 {
+            assert_eq!(idx, s.len() - 1);
+            return OsString::from_wide(&s[0..idx]);
+        }
+    }
+    panic!("missing null terminator at end of win32 string");
+}
diff --git a/toolkit/xre/detect_win32k_conflicts/tests/basic.rs b/toolkit/xre/detect_win32k_conflicts/tests/basic.rs
new file mode 100644
index 0000000000..d16a0bd976
--- /dev/null
+++ b/toolkit/xre/detect_win32k_conflicts/tests/basic.rs
@@ -0,0 +1,14 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use detect_win32k_conflicts::{detect_win32k_conflicting_mitigations, ConflictingMitigationStatus};
+
+#[test]
+fn basic() {
+    let mut status = ConflictingMitigationStatus::default();
+
+    let result = unsafe { detect_win32k_conflicting_mitigations(&mut status) };
+
+    assert!(result);
+}
diff --git a/toolkit/xre/dllservices/DynamicBlocklist.h b/toolkit/xre/dllservices/DynamicBlocklist.h
new file mode 100644
index 0000000000..a8db60d4ea
--- /dev/null
+++ b/toolkit/xre/dllservices/DynamicBlocklist.h
@@ -0,0 +1,291 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_DynamicBlocklist_h
+#define mozilla_DynamicBlocklist_h
+
+#include <winternl.h>
+
+#include "nsWindowsHelpers.h"
+#include "mozilla/CheckedInt.h"
+#include "mozilla/NativeNt.h"
+#include "mozilla/UniquePtr.h"
+#include "mozilla/Unused.h"
+#include "mozilla/Vector.h"
+
+#if defined(MOZILLA_INTERNAL_API)
+#  include "mozilla/dom/Promise.h"
+#  include "nsIOutputStream.h"
+#  include "nsTHashSet.h"
+#endif  // defined(MOZILLA_INTERNAL_API)
+
+#include "mozilla/WindowsDllBlocklistInfo.h"
+
+#if !defined(MOZILLA_INTERNAL_API) && defined(ENABLE_TESTS)
+#  include "mozilla/CmdLineAndEnvUtils.h"
+#  define BLOCKLIST_INSERT_TEST_ENTRY
+#endif  // !defined(MOZILLA_INTERNAL_API) && defined(ENABLE_TESTS)
+
+namespace mozilla {
+using DllBlockInfo = DllBlockInfoT<UNICODE_STRING>;
+
+struct DynamicBlockListBase {
+  static constexpr uint32_t kSignature = 'FFBL';  // Firefox Blocklist
+  static constexpr uint32_t kCurrentVersion = 1;
+
+  struct FileHeader {
+    uint32_t mSignature;
+    uint32_t mFileVersion;
+    uint32_t mPayloadSize;
+  };
+};
+// Define this class in a header so that TestCrossProcessWin
+// can include and test it.
+class DynamicBlockList final : public DynamicBlockListBase {
+  uint32_t mPayloadSize;
+  UniquePtr<uint8_t[]> mPayload;
+
+#ifdef ENABLE_TESTS
+  // These two definitions are needed for the DynamicBlocklistWriter to avoid
+  // writing this test entry out to the blocklist file, so compile these in
+  // even if MOZILLA_INTERNAL_API is defined.
+ public:
+  static constexpr wchar_t kTestDll[] = L"TestDllBlocklist_UserBlocked.dll";
+  // kTestDll is null-terminated, but we don't want that for the blocklist
+  // file
+  static constexpr size_t kTestDllBytes = sizeof(kTestDll) - sizeof(wchar_t);
+
+ private:
+#  ifdef BLOCKLIST_INSERT_TEST_ENTRY
+  // Set up a test entry in the blocklist, used for testing purposes.
+  void AssignTestEntry(DllBlockInfo* testEntry, uint32_t nameOffset) {
+    testEntry->mName.Length = kTestDllBytes;
+    testEntry->mName.MaximumLength = kTestDllBytes;
+    testEntry->mName.Buffer = reinterpret_cast<PWSTR>(nameOffset);
+    testEntry->mMaxVersion = DllBlockInfo::ALL_VERSIONS;
+    testEntry->mFlags = DllBlockInfoFlags::FLAGS_DEFAULT;
+  }
+
+  void CreateListWithTestEntry() {
+    mPayloadSize = sizeof(DllBlockInfo) * 2 + kTestDllBytes;
+    mPayload = MakeUnique<uint8_t[]>(mPayloadSize);
+    DllBlockInfo* entry = reinterpret_cast<DllBlockInfo*>(mPayload.get());
+    AssignTestEntry(entry, sizeof(DllBlockInfo) * 2);
+    memcpy(mPayload.get() + sizeof(DllBlockInfo) * 2, kTestDll, kTestDllBytes);
+    ++entry;
+    entry->mName.Length = 0;
+    entry->mName.MaximumLength = 0;
+  }
+#  endif  // BLOCKLIST_INSERT_TEST_ENTRY
+#endif    // ENABLE_TESTS
+
+  bool LoadFile(const wchar_t* aPath) {
+#ifdef BLOCKLIST_INSERT_TEST_ENTRY
+    const bool shouldInsertBlocklistTestEntry =
+        MOZ_UNLIKELY(mozilla::EnvHasValue("MOZ_DISABLE_NONLOCAL_CONNECTIONS") ||
+                     mozilla::EnvHasValue("MOZ_RUN_GTEST"));
+#endif
+
+    nsAutoHandle file(
+        ::CreateFileW(aPath, GENERIC_READ,
+                      FILE_SHARE_READ | FILE_SHARE_DELETE | FILE_SHARE_WRITE,
+                      nullptr, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, nullptr));
+    if (!file) {
+#ifdef BLOCKLIST_INSERT_TEST_ENTRY
+      if (shouldInsertBlocklistTestEntry) {
+        // If the blocklist file doesn't exist, we still want to include a test
+        // entry for testing purposes.
+        CreateListWithTestEntry();
+        return true;
+      }
+#endif
+      return false;
+    }
+
+    DWORD bytesRead = 0;
+    FileHeader header;
+    BOOL ok =
+        ::ReadFile(file.get(), &header, sizeof(header), &bytesRead, nullptr);
+    if (!ok) {
+#ifdef BLOCKLIST_INSERT_TEST_ENTRY
+      if (shouldInsertBlocklistTestEntry) {
+        // If we have a problem reading the blocklist file, we still want to
+        // include a test entry for testing purposes.
+        CreateListWithTestEntry();
+        return true;
+      }
+#endif
+      return false;
+    }
+    if (bytesRead != sizeof(header)) {
+      return false;
+    }
+
+    if (header.mSignature != kSignature ||
+        header.mFileVersion != kCurrentVersion) {
+      return false;
+    }
+
+    uint32_t destinationPayloadSize = header.mPayloadSize;
+#ifdef BLOCKLIST_INSERT_TEST_ENTRY
+    if (shouldInsertBlocklistTestEntry) {
+      // Write an extra entry for testing purposes
+      destinationPayloadSize += sizeof(DllBlockInfo) + kTestDllBytes;
+    }
+#endif
+    UniquePtr<uint8_t[]> payload =
+        MakeUnique<uint8_t[]>(destinationPayloadSize);
+    ok = ::ReadFile(file.get(), payload.get(), header.mPayloadSize, &bytesRead,
+                    nullptr);
+    if (!ok || bytesRead != header.mPayloadSize) {
+      return false;
+    }
+
+    uint32_t sizeOfPayloadToIterateOver = header.mPayloadSize;
+#ifdef BLOCKLIST_INSERT_TEST_ENTRY
+    bool haveWrittenTestEntry = false;
+    UNICODE_STRING testUnicodeString;
+    // Cast the const-ness away since we're only going to use
+    // this to compare against strings.
+    testUnicodeString.Buffer = const_cast<PWSTR>(kTestDll);
+    testUnicodeString.Length = kTestDllBytes;
+    testUnicodeString.MaximumLength = kTestDllBytes;
+#endif
+    for (uint32_t offset = 0; offset < sizeOfPayloadToIterateOver;
+         offset += sizeof(DllBlockInfo)) {
+      DllBlockInfo* entry =
+          reinterpret_cast<DllBlockInfo*>(payload.get() + offset);
+      if (!entry->mName.Length) {
+#ifdef BLOCKLIST_INSERT_TEST_ENTRY
+        if (shouldInsertBlocklistTestEntry && !haveWrittenTestEntry) {
+          // Shift everything forward
+          memmove(payload.get() + offset + sizeof(DllBlockInfo),
+                  payload.get() + offset, header.mPayloadSize - offset);
+          AssignTestEntry(entry, destinationPayloadSize - kTestDllBytes);
+          haveWrittenTestEntry = true;
+        }
+#endif
+        break;
+      }
+
+      size_t stringOffset = reinterpret_cast<size_t>(entry->mName.Buffer);
+      if (stringOffset + entry->mName.Length > header.mPayloadSize) {
+        entry->mName.Length = 0;
+        break;
+      }
+      entry->mName.MaximumLength = entry->mName.Length;
+#ifdef BLOCKLIST_INSERT_TEST_ENTRY
+      if (shouldInsertBlocklistTestEntry && !haveWrittenTestEntry) {
+        UNICODE_STRING currentUnicodeString;
+        currentUnicodeString.Buffer =
+            reinterpret_cast<PWSTR>(payload.get() + stringOffset);
+        currentUnicodeString.Length = entry->mName.Length;
+        currentUnicodeString.MaximumLength = entry->mName.Length;
+        if (RtlCompareUnicodeString(&currentUnicodeString, &testUnicodeString,
+                                    TRUE) > 0) {
+          // Shift everything forward
+          memmove(payload.get() + offset + sizeof(DllBlockInfo),
+                  payload.get() + offset, header.mPayloadSize - offset);
+          AssignTestEntry(entry, destinationPayloadSize - kTestDllBytes);
+          haveWrittenTestEntry = true;
+          // Now we have expanded the area of valid memory, so there is more
+          // allowable space to iterate over.
+          sizeOfPayloadToIterateOver = destinationPayloadSize;
+          offset += sizeof(DllBlockInfo);
+          ++entry;
+        }
+        // The start of the string section will be moving ahead (or has already
+        // moved ahead) to make room for the test entry
+        entry->mName.Buffer +=
+            sizeof(DllBlockInfo) / sizeof(entry->mName.Buffer[0]);
+      }
+#endif
+    }
+#ifdef BLOCKLIST_INSERT_TEST_ENTRY
+    if (shouldInsertBlocklistTestEntry) {
+      memcpy(payload.get() + destinationPayloadSize - kTestDllBytes, kTestDll,
+             kTestDllBytes);
+    }
+#endif
+
+    mPayloadSize = destinationPayloadSize;
+    mPayload = std::move(payload);
+    return true;
+  }
+
+ public:
+  DynamicBlockList() : mPayloadSize(0) {}
+  explicit DynamicBlockList(const wchar_t* aPath) : mPayloadSize(0) {
+    LoadFile(aPath);
+  }
+
+  DynamicBlockList(DynamicBlockList&&) = default;
+  DynamicBlockList& operator=(DynamicBlockList&&) = default;
+  DynamicBlockList(const DynamicBlockList&) = delete;
+  DynamicBlockList& operator=(const DynamicBlockList&) = delete;
+
+  constexpr uint32_t GetPayloadSize() const { return mPayloadSize; }
+
+  // Return the number of bytes copied
+  size_t CopyTo(void* aBuffer, size_t aBufferLength) const {
+    if (mPayloadSize > aBufferLength) {
+      return 0;
+    }
+    memcpy(aBuffer, mPayload.get(), mPayloadSize);
+    return mPayloadSize;
+  }
+};
+
+#if defined(MOZILLA_INTERNAL_API) && defined(MOZ_LAUNCHER_PROCESS)
+
+class DynamicBlocklistWriter final : public DynamicBlockListBase {
+  template <typename T>
+  static nsresult WriteValue(nsIOutputStream* aOutputStream, const T& aValue) {
+    uint32_t written;
+    return aOutputStream->Write(reinterpret_cast<const char*>(&aValue),
+                                sizeof(T), &written);
+  }
+
+  template <typename T>
+  static nsresult WriteBuffer(nsIOutputStream* aOutputStream, const T* aBuffer,
+                              uint32_t aBufferSize) {
+    uint32_t written;
+    return aOutputStream->Write(reinterpret_cast<const char*>(aBuffer),
+                                aBufferSize, &written);
+  }
+
+  RefPtr<dom::Promise> mPromise;
+  Vector<DllBlockInfo> mArray;
+  // All strings are packed in this buffer without null characters
+  UniquePtr<uint8_t[]> mStringBuffer;
+
+  size_t mArraySize;
+  size_t mStringBufferSize;
+
+  nsresult WriteToFile(const nsAString& aName) const;
+
+ public:
+  DynamicBlocklistWriter(
+      RefPtr<dom::Promise> aPromise,
+      const nsTHashSet<nsStringCaseInsensitiveHashKey>& aBlocklist);
+  ~DynamicBlocklistWriter() = default;
+
+  DynamicBlocklistWriter(DynamicBlocklistWriter&&) = default;
+  DynamicBlocklistWriter& operator=(DynamicBlocklistWriter&&) = default;
+  DynamicBlocklistWriter(const DynamicBlocklistWriter&) = delete;
+  DynamicBlocklistWriter& operator=(const DynamicBlocklistWriter&) = delete;
+
+  bool IsReady() const { return mStringBuffer.get(); }
+
+  void Run();
+  void Cancel();
+};
+
+#endif  // defined(MOZILLA_INTERNAL_API) && defined(MOZ_LAUNCHER_PROCESS)
+
+}  // namespace mozilla
+
+#endif  //  mozilla_DynamicBlocklist_h
diff --git a/toolkit/xre/dllservices/DynamicBlocklistWriter.cpp b/toolkit/xre/dllservices/DynamicBlocklistWriter.cpp
new file mode 100644
index 0000000000..38a9972e94
--- /dev/null
+++ b/toolkit/xre/dllservices/DynamicBlocklistWriter.cpp
@@ -0,0 +1,139 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/DynamicBlocklist.h"
+#include "mozilla/LauncherRegistryInfo.h"
+
+#include "nsISafeOutputStream.h"
+#include "nsNetUtil.h"
+
+namespace mozilla {
+#if ENABLE_TESTS
+nsDependentString testEntryString(DynamicBlockList::kTestDll,
+                                  DynamicBlockList::kTestDllBytes /
+                                      sizeof(DynamicBlockList::kTestDll[0]));
+#endif
+
+bool ShouldWriteEntry(const nsAString& name) {
+#if ENABLE_TESTS
+  return name != testEntryString;
+#else
+  return true;
+#endif
+}
+
+DynamicBlocklistWriter::DynamicBlocklistWriter(
+    RefPtr<dom::Promise> aPromise,
+    const nsTHashSet<nsStringCaseInsensitiveHashKey>& aBlocklist)
+    : mPromise(aPromise), mArraySize(0), mStringBufferSize(0) {
+  CheckedUint32 payloadSize;
+  bool hasTestEntry = false;
+  for (const nsAString& name : aBlocklist) {
+    if (ShouldWriteEntry(name)) {
+      payloadSize += name.Length() * sizeof(char16_t);
+      if (!payloadSize.isValid()) {
+        return;
+      }
+    } else {
+      hasTestEntry = true;
+    }
+  }
+
+  uint32_t entriesToWrite = aBlocklist.Count();
+  if (hasTestEntry) {
+    entriesToWrite -= 1;
+  }
+
+  mStringBufferSize = payloadSize.value();
+  mArraySize = (entriesToWrite + 1) * sizeof(DllBlockInfo);
+
+  payloadSize += mArraySize;
+  if (!payloadSize.isValid()) {
+    return;
+  }
+
+  mStringBuffer = MakeUnique<uint8_t[]>(mStringBufferSize);
+  Unused << mArray.resize(entriesToWrite + 1);  // aBlockEntries + sentinel
+
+  size_t currentStringOffset = 0;
+  size_t i = 0;
+  for (const nsAString& name : aBlocklist) {
+    if (!ShouldWriteEntry(name)) {
+      continue;
+    }
+    const uint32_t nameSize = name.Length() * sizeof(char16_t);
+
+    mArray[i].mMaxVersion = DllBlockInfo::ALL_VERSIONS;
+    mArray[i].mFlags = DllBlockInfoFlags::FLAGS_DEFAULT;
+
+    // Copy the module's name to the string buffer and store its offset
+    // in mName.Buffer
+    memcpy(mStringBuffer.get() + currentStringOffset, name.BeginReading(),
+           nameSize);
+    mArray[i].mName.Buffer =
+        reinterpret_cast<wchar_t*>(mArraySize + currentStringOffset);
+    // Only keep mName.Length and leave mName.MaximumLength to be zero
+    mArray[i].mName.Length = nameSize;
+
+    currentStringOffset += nameSize;
+    ++i;
+  }
+}
+
+nsresult DynamicBlocklistWriter::WriteToFile(const nsAString& aName) const {
+  nsCOMPtr<nsIFile> file;
+  MOZ_TRY(NS_NewLocalFile(aName, true, getter_AddRefs(file)));
+
+  nsCOMPtr<nsIOutputStream> stream;
+  MOZ_TRY(NS_NewSafeLocalFileOutputStream(getter_AddRefs(stream), file));
+
+  MOZ_TRY(WriteValue(stream, kSignature));
+  MOZ_TRY(WriteValue(stream, kCurrentVersion));
+  MOZ_TRY(WriteValue(stream,
+                     static_cast<uint32_t>(mArraySize + mStringBufferSize)));
+  MOZ_TRY(WriteBuffer(stream, mArray.begin(), mArraySize));
+  MOZ_TRY(WriteBuffer(stream, mStringBuffer.get(), mStringBufferSize));
+
+  nsresult rv;
+  nsCOMPtr<nsISafeOutputStream> safeStream = do_QueryInterface(stream, &rv);
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+
+  return safeStream->Finish();
+}
+
+void DynamicBlocklistWriter::Run() {
+  MOZ_ASSERT(!NS_IsMainThread());
+
+  nsresult rv = NS_ERROR_ABORT;
+
+  LauncherRegistryInfo regInfo;
+  LauncherResult<std::wstring> blocklistFile = regInfo.GetBlocklistFileName();
+  if (blocklistFile.isOk()) {
+    const wchar_t* rawBuffer = blocklistFile.inspect().c_str();
+    rv = WriteToFile(nsDependentString(rawBuffer));
+  }
+
+  NS_DispatchToMainThread(
+      // Don't capture mPromise by copy because we're not in the main thread
+      NS_NewRunnableFunction(__func__, [promise = std::move(mPromise), rv]() {
+        if (NS_SUCCEEDED(rv)) {
+          promise->MaybeResolve(JS::NullHandleValue);
+        } else {
+          promise->MaybeReject(rv);
+        }
+      }));
+}
+
+void DynamicBlocklistWriter::Cancel() {
+  MOZ_ASSERT(NS_IsMainThread());
+  if (mPromise) {
+    mPromise->MaybeReject(NS_ERROR_ABORT);
+  }
+}
+
+}  // namespace mozilla
diff --git a/toolkit/xre/dllservices/ModuleEvaluator.cpp b/toolkit/xre/dllservices/ModuleEvaluator.cpp
new file mode 100644
index 0000000000..6e8a3c3493
--- /dev/null
+++ b/toolkit/xre/dllservices/ModuleEvaluator.cpp
@@ -0,0 +1,251 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#include "ModuleEvaluator.h"
+
+#include <algorithm>  // For std::find()
+#include <type_traits>
+
+#include <windows.h>
+#include <shlobj.h>
+
+#include "mozilla/ArrayUtils.h"
+#include "mozilla/ModuleVersionInfo.h"
+#include "mozilla/UniquePtr.h"
+#include "mozilla/Unused.h"
+#include "mozilla/WinDllServices.h"
+#include "mozilla/WinHeaderOnlyUtils.h"
+#include "nsReadableUtils.h"
+#include "nsWindowsHelpers.h"
+#include "nsXULAppAPI.h"
+
+namespace mozilla {
+
+// Fills a Vector with keyboard layout DLLs found in the registry.
+// These are leaf names only, not full paths. Here we will convert them to
+// lowercase before returning, to facilitate case-insensitive searches.
+// On error, this may return partial results.
+static Vector<nsString> GetKeyboardLayoutDlls() {
+  Vector<nsString> result;
+
+  HKEY rawKey;
+  if (::RegOpenKeyExW(HKEY_LOCAL_MACHINE,
+                      L"SYSTEM\\CurrentControlSet\\Control\\Keyboard Layouts",
+                      0, KEY_ENUMERATE_SUB_KEYS, &rawKey) != ERROR_SUCCESS) {
+    return result;
+  }
+  nsAutoRegKey key(rawKey);
+
+  DWORD iKey = 0;
+  wchar_t strTemp[MAX_PATH] = {};
+  while (true) {
+    DWORD strTempSize = ArrayLength(strTemp);
+    if (RegEnumKeyExW(rawKey, iKey, strTemp, &strTempSize, nullptr, nullptr,
+                      nullptr, nullptr) != ERROR_SUCCESS) {
+      // ERROR_NO_MORE_ITEMS or a real error: bail with what we have.
+      return result;
+    }
+    iKey++;
+
+    strTempSize = sizeof(strTemp);
+    if (::RegGetValueW(rawKey, strTemp, L"Layout File", RRF_RT_REG_SZ, nullptr,
+                       strTemp, &strTempSize) == ERROR_SUCCESS &&
+        strTempSize) {
+      nsString ws(strTemp, ((strTempSize + 1) / sizeof(wchar_t)) - 1);
+      ToLowerCase(ws);  // To facilitate case-insensitive searches
+      Unused << result.emplaceBack(std::move(ws));
+    }
+  }
+}
+
+/* static */
+bool ModuleEvaluator::ResolveKnownFolder(REFKNOWNFOLDERID aFolderId,
+                                         nsIFile** aOutFile) {
+  if (!aOutFile) {
+    return false;
+  }
+
+  *aOutFile = nullptr;
+
+  // Since we're running off main thread, we can't use NS_GetSpecialDirectory
+  PWSTR rawPath = nullptr;
+  HRESULT hr =
+      ::SHGetKnownFolderPath(aFolderId, KF_FLAG_DEFAULT, nullptr, &rawPath);
+  if (FAILED(hr)) {
+    return false;
+  }
+
+  using ShellStringUniquePtr =
+      UniquePtr<std::remove_pointer_t<PWSTR>, CoTaskMemFreeDeleter>;
+
+  ShellStringUniquePtr path(rawPath);
+
+  nsresult rv = NS_NewLocalFile(nsDependentString(path.get()), false, aOutFile);
+  return NS_SUCCEEDED(rv);
+}
+
+ModuleEvaluator::ModuleEvaluator()
+    : mKeyboardLayoutDlls(GetKeyboardLayoutDlls()) {
+  MOZ_ASSERT(XRE_IsParentProcess());
+
+#if defined(_M_IX86)
+  // We want to resolve to SYSWOW64 when applicable
+  REFKNOWNFOLDERID systemFolderId = FOLDERID_SystemX86;
+#else
+  REFKNOWNFOLDERID systemFolderId = FOLDERID_System;
+#endif  // defined(_M_IX86)
+
+  bool resolveOk =
+      ResolveKnownFolder(systemFolderId, getter_AddRefs(mSysDirectory));
+  MOZ_ASSERT(resolveOk);
+  if (!resolveOk) {
+    return;
+  }
+
+  nsCOMPtr<nsIFile> winSxSDir;
+  resolveOk = ResolveKnownFolder(FOLDERID_Windows, getter_AddRefs(winSxSDir));
+  MOZ_ASSERT(resolveOk);
+  if (!resolveOk) {
+    return;
+  }
+
+  nsresult rv = winSxSDir->Append(u"WinSxS"_ns);
+  MOZ_ASSERT(NS_SUCCEEDED(rv));
+  if (NS_FAILED(rv)) {
+    return;
+  }
+
+  mWinSxSDirectory = std::move(winSxSDir);
+
+  nsCOMPtr<nsIFile> exeFile;
+  rv = XRE_GetBinaryPath(getter_AddRefs(exeFile));
+  MOZ_ASSERT(NS_SUCCEEDED(rv));
+  if (NS_FAILED(rv)) {
+    return;
+  }
+
+  rv = exeFile->GetParent(getter_AddRefs(mExeDirectory));
+  MOZ_ASSERT(NS_SUCCEEDED(rv));
+  if (NS_FAILED(rv)) {
+    return;
+  }
+
+  nsAutoString exePath;
+  rv = exeFile->GetPath(exePath);
+  MOZ_ASSERT(NS_SUCCEEDED(rv));
+  if (NS_FAILED(rv)) {
+    return;
+  }
+
+  ModuleVersionInfo exeVi;
+  if (!exeVi.GetFromImage(exePath)) {
+    return;
+  }
+
+  mExeVersion = Some(ModuleVersion(exeVi.mFileVersion.Version64()));
+}
+
+ModuleEvaluator::operator bool() const {
+  return mExeVersion.isSome() && mExeDirectory && mSysDirectory &&
+         mWinSxSDirectory;
+}
+
+Maybe<ModuleTrustFlags> ModuleEvaluator::GetTrust(
+    const ModuleRecord& aModuleRecord) const {
+  MOZ_ASSERT(XRE_IsParentProcess());
+
+  // We start by checking authenticode signatures, as the presence of any
+  // signature will produce an immediate pass/fail.
+  if (aModuleRecord.mVendorInfo.isSome() &&
+      aModuleRecord.mVendorInfo.ref().mSource ==
+          VendorInfo::Source::Signature) {
+    const nsString& signedBy = aModuleRecord.mVendorInfo.ref().mVendor;
+
+    if (signedBy.EqualsLiteral("Microsoft Windows")) {
+      return Some(ModuleTrustFlags::MicrosoftWindowsSignature);
+    } else if (signedBy.EqualsLiteral("Microsoft Corporation")) {
+      return Some(ModuleTrustFlags::MicrosoftWindowsSignature);
+    } else if (signedBy.EqualsLiteral("Mozilla Corporation")) {
+      return Some(ModuleTrustFlags::MozillaSignature);
+    } else {
+      // Being signed by somebody who is neither Microsoft nor us is an
+      // automatic and immediate disqualification.
+      return Some(ModuleTrustFlags::None);
+    }
+  }
+
+  const nsCOMPtr<nsIFile>& dllFile = aModuleRecord.mResolvedDosName;
+  MOZ_ASSERT(!!dllFile);
+  if (!dllFile) {
+    return Nothing();
+  }
+
+  nsAutoString dllLeafLower;
+  if (NS_FAILED(dllFile->GetLeafName(dllLeafLower))) {
+    return Nothing();
+  }
+
+  ToLowerCase(dllLeafLower);  // To facilitate case-insensitive searching
+
+  // The JIT profiling module doesn't really have any other practical way to
+  // match; hard-code it as being trusted.
+  if (dllLeafLower.EqualsLiteral("jitpi.dll")) {
+    return Some(ModuleTrustFlags::JitPI);
+  }
+
+  ModuleTrustFlags result = ModuleTrustFlags::None;
+
+  nsresult rv;
+  bool contained;
+
+  // Is the DLL in the system directory?
+  rv = mSysDirectory->Contains(dllFile, &contained);
+  if (NS_SUCCEEDED(rv) && contained) {
+    result |= ModuleTrustFlags::SystemDirectory;
+  }
+
+  // Is the DLL in the WinSxS directory? Some Microsoft DLLs (e.g. comctl32) are
+  // loaded from here and don't have digital signatures. So while this is not a
+  // guarantee of trustworthiness, but is at least as valid as system32.
+  rv = mWinSxSDirectory->Contains(dllFile, &contained);
+  if (NS_SUCCEEDED(rv) && contained) {
+    result |= ModuleTrustFlags::WinSxSDirectory;
+  }
+
+  // Is it a keyboard layout DLL?
+  if (std::find(mKeyboardLayoutDlls.begin(), mKeyboardLayoutDlls.end(),
+                dllLeafLower) != mKeyboardLayoutDlls.end()) {
+    result |= ModuleTrustFlags::KeyboardLayout;
+    // This doesn't guarantee trustworthiness by itself. Keyboard layouts also
+    // must be in the system directory.
+  }
+
+  if (aModuleRecord.mVendorInfo.isSome() &&
+      aModuleRecord.mVendorInfo.ref().mSource ==
+          VendorInfo::Source::VersionInfo) {
+    const nsString& companyName = aModuleRecord.mVendorInfo.ref().mVendor;
+
+    if (companyName.EqualsLiteral("Microsoft Corporation")) {
+      result |= ModuleTrustFlags::MicrosoftVersion;
+    }
+  }
+
+  rv = mExeDirectory->Contains(dllFile, &contained);
+  if (NS_SUCCEEDED(rv) && contained) {
+    result |= ModuleTrustFlags::FirefoxDirectory;
+
+    // If the DLL is in the Firefox directory, does it also share the Firefox
+    // version info?
+    if (mExeVersion.isSome() && aModuleRecord.mVersion.isSome() &&
+        mExeVersion.value() == aModuleRecord.mVersion.value()) {
+      result |= ModuleTrustFlags::FirefoxDirectoryAndVersion;
+    }
+  }
+
+  return Some(result);
+}
+
+}  // namespace mozilla
diff --git a/toolkit/xre/dllservices/ModuleEvaluator.h b/toolkit/xre/dllservices/ModuleEvaluator.h
new file mode 100644
index 0000000000..565b5d4da4
--- /dev/null
+++ b/toolkit/xre/dllservices/ModuleEvaluator.h
@@ -0,0 +1,50 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_ModuleEvaluator_h
+#define mozilla_ModuleEvaluator_h
+
+#include "mozilla/Attributes.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/UntrustedModulesData.h"
+#include "mozilla/Vector.h"
+#include "mozilla/WinHeaderOnlyUtils.h"
+#include "nsCOMPtr.h"
+#include "nsIFile.h"
+#include "nsString.h"
+
+#include <shtypes.h>
+
+namespace mozilla {
+
+class ModuleRecord;
+
+/**
+ * This class performs trustworthiness evaluation for incoming DLLs.
+ */
+class MOZ_RAII ModuleEvaluator final {
+ public:
+  ModuleEvaluator();
+
+  explicit operator bool() const;
+
+  Maybe<ModuleTrustFlags> GetTrust(const ModuleRecord& aModuleRecord) const;
+
+ private:
+  static bool ResolveKnownFolder(REFKNOWNFOLDERID aFolderId,
+                                 nsIFile** aOutFile);
+
+ private:
+  Maybe<ModuleVersion> mExeVersion;  // Version number of the running EXE image
+  nsCOMPtr<nsIFile> mExeDirectory;
+  nsCOMPtr<nsIFile> mSysDirectory;
+  nsCOMPtr<nsIFile> mWinSxSDirectory;
+  Vector<nsString> mKeyboardLayoutDlls;
+};
+
+}  // namespace mozilla
+
+#endif  // mozilla_ModuleEvaluator_h
diff --git a/toolkit/xre/dllservices/ModuleVersionInfo.cpp b/toolkit/xre/dllservices/ModuleVersionInfo.cpp
new file mode 100644
index 0000000000..c8c2956a74
--- /dev/null
+++ b/toolkit/xre/dllservices/ModuleVersionInfo.cpp
@@ -0,0 +1,111 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#include "ModuleVersionInfo.h"
+
+#include "mozilla/UniquePtr.h"
+
+namespace mozilla {
+
+/**
+ * Gets a string value from a version info block with the specified translation
+ * and field name.
+ *
+ * @param  aBlock       [in] The binary version resource block
+ * @param  aTranslation [in] The translation ID as obtained in the version
+ *                      translation list.
+ * @param  aFieldName   [in] Null-terminated name of the desired field
+ * @param  aResult      [out] Receives the string value, if successful.
+ * @return true if successful. aResult is unchanged upon failure.
+ */
+static bool QueryStringValue(const void* aBlock, DWORD aTranslation,
+                             const wchar_t* aFieldName, nsAString& aResult) {
+  nsAutoString path;
+  path.AppendPrintf("\\StringFileInfo\\%02lX%02lX%02lX%02lX\\%S",
+                    (aTranslation & 0x0000ff00) >> 8,
+                    (aTranslation & 0x000000ff),
+                    (aTranslation & 0xff000000) >> 24,
+                    (aTranslation & 0x00ff0000) >> 16, aFieldName);
+
+  wchar_t* lpBuffer = nullptr;
+  UINT len = 0;
+  if (!::VerQueryValueW(aBlock, path.get(), (PVOID*)&lpBuffer, &len)) {
+    return false;
+  }
+  aResult.Assign(lpBuffer, (size_t)len - 1);
+  return true;
+}
+
+/**
+ * Searches through translations in the version resource for the requested
+ * field. English(US) is preferred, otherwise we take the first translation
+ * that succeeds.
+ *
+ * @param  aBlock        [in] The binary version resource block
+ * @param  aTranslations [in] The list of translation IDs available
+ * @param  aNumTrans     [in] Number of items in aTranslations
+ * @param  aFieldName    [in] Null-terminated name of the desired field
+ * @param  aResult       [in] Receives the string value, if successful.
+ * @return true if successful. aResult is unchanged upon failure.
+ */
+static bool QueryStringValue(const void* aBlock, const DWORD* aTranslations,
+                             size_t aNumTrans, const wchar_t* aFieldName,
+                             nsAString& aResult) {
+  static const DWORD kPreferredTranslation =
+      0x04b00409;  // English (US), Unicode
+  if (QueryStringValue(aBlock, kPreferredTranslation, aFieldName, aResult)) {
+    return true;
+  }
+  for (size_t i = 0; i < aNumTrans; ++i) {
+    if (QueryStringValue(aBlock, aTranslations[i], aFieldName, aResult)) {
+      return true;
+    }
+  }
+  return false;
+}
+
+bool ModuleVersionInfo::GetFromImage(const nsAString& aPath) {
+  nsString path(aPath);
+  DWORD infoSize = GetFileVersionInfoSizeW(path.get(), nullptr);
+  if (!infoSize) {
+    return false;
+  }
+
+  auto verInfo = MakeUnique<BYTE[]>(infoSize);
+  if (!::GetFileVersionInfoW(path.get(), 0, infoSize, verInfo.get())) {
+    return false;
+  }
+
+  VS_FIXEDFILEINFO* vInfo = nullptr;
+  UINT vInfoLen = 0;
+  if (::VerQueryValueW(verInfo.get(), L"\\", (LPVOID*)&vInfo, &vInfoLen)) {
+    mFileVersion =
+        VersionNumber(vInfo->dwFileVersionMS, vInfo->dwFileVersionLS);
+    mProductVersion =
+        VersionNumber(vInfo->dwProductVersionMS, vInfo->dwProductVersionLS);
+  }
+
+  // Note that regardless the character set indicated, strings are always
+  // returned as Unicode by the Windows APIs.
+  DWORD* pTrans = nullptr;
+  UINT cbTrans = 0;
+  if (::VerQueryValueW(verInfo.get(), L"\\VarFileInfo\\Translation",
+                       (PVOID*)&pTrans, &cbTrans)) {
+    size_t numTrans = cbTrans / sizeof(DWORD);
+    QueryStringValue(verInfo.get(), pTrans, numTrans, L"CompanyName",
+                     mCompanyName);
+    QueryStringValue(verInfo.get(), pTrans, numTrans, L"ProductName",
+                     mProductName);
+    QueryStringValue(verInfo.get(), pTrans, numTrans, L"LegalCopyright",
+                     mLegalCopyright);
+    QueryStringValue(verInfo.get(), pTrans, numTrans, L"FileDescription",
+                     mFileDescription);
+  }
+
+  return true;
+}
+
+}  // namespace mozilla
diff --git a/toolkit/xre/dllservices/ModuleVersionInfo.h b/toolkit/xre/dllservices/ModuleVersionInfo.h
new file mode 100644
index 0000000000..2b46817417
--- /dev/null
+++ b/toolkit/xre/dllservices/ModuleVersionInfo.h
@@ -0,0 +1,71 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_ModuleVersionInfo_h
+#define mozilla_ModuleVersionInfo_h
+
+#include <windows.h>
+#include "nsString.h"
+
+namespace mozilla {
+
+// Obtains basic version info from a module image's version info resource.
+class ModuleVersionInfo {
+ public:
+  // We favor English(US) for these fields, otherwise we take the first
+  // translation provided in the version resource.
+  nsString mCompanyName;
+  nsString mProductName;
+  nsString mLegalCopyright;
+  nsString mFileDescription;
+
+  // Represents an A.B.C.D style version number, internally stored as a uint64_t
+  class VersionNumber {
+    uint64_t mVersion64 = 0;
+
+   public:
+    VersionNumber() = default;
+
+    VersionNumber(DWORD aMostSig, DWORD aLeastSig)
+        : mVersion64((uint64_t)aMostSig << 32 | aLeastSig) {}
+
+    uint16_t A() const {
+      return (uint16_t)((mVersion64 & 0xffff000000000000) >> 48);
+    }
+
+    uint16_t B() const {
+      return (uint16_t)((mVersion64 & 0x0000ffff00000000) >> 32);
+    }
+
+    uint16_t C() const {
+      return (uint16_t)((mVersion64 & 0x00000000ffff0000) >> 16);
+    }
+
+    uint16_t D() const { return (uint16_t)(mVersion64 & 0x000000000000ffff); }
+
+    uint64_t Version64() const { return mVersion64; }
+
+    bool operator==(const VersionNumber& aOther) const {
+      return mVersion64 == aOther.mVersion64;
+    }
+
+    nsCString ToString() const {
+      nsCString ret;
+      ret.AppendPrintf("%d.%d.%d.%d", (int)A(), (int)B(), (int)C(), (int)D());
+      return ret;
+    }
+  };
+
+  VersionNumber mFileVersion;
+  VersionNumber mProductVersion;
+
+  // Returns false if it has no version resource or has no fixed version info.
+  bool GetFromImage(const nsAString& aPath);
+};
+
+}  // namespace mozilla
+
+#endif  // mozilla_ModuleVersionInfo_h
diff --git a/toolkit/xre/dllservices/UntrustedModulesData.cpp b/toolkit/xre/dllservices/UntrustedModulesData.cpp
new file mode 100644
index 0000000000..297dbac554
--- /dev/null
+++ b/toolkit/xre/dllservices/UntrustedModulesData.cpp
@@ -0,0 +1,453 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#include "UntrustedModulesData.h"
+
+#include <windows.h>
+
+#include "mozilla/CmdLineAndEnvUtils.h"
+#include "mozilla/DynamicallyLinkedFunctionPtr.h"
+#include "mozilla/FileUtilsWin.h"
+#include "mozilla/Likely.h"
+#include "mozilla/MathAlgorithms.h"
+#include "mozilla/UniquePtr.h"
+#include "mozilla/Unused.h"
+#include "mozilla/WinDllServices.h"
+#include "ModuleEvaluator.h"
+#include "ModuleVersionInfo.h"
+#include "nsCOMPtr.h"
+#include "nsDebug.h"
+#include "nsXULAppAPI.h"
+#include "WinUtils.h"
+
+// Some utility functions
+
+static LONGLONG GetQPCFreq() {
+  static const LONGLONG sFreq = []() -> LONGLONG {
+    LARGE_INTEGER freq;
+    ::QueryPerformanceFrequency(&freq);
+    return freq.QuadPart;
+  }();
+
+  return sFreq;
+}
+
+template <typename ReturnT>
+static ReturnT QPCToTimeUnits(const LONGLONG aTimeStamp,
+                              const LONGLONG aUnitsPerSec) {
+  return ReturnT(aTimeStamp * aUnitsPerSec) / ReturnT(GetQPCFreq());
+}
+
+template <typename ReturnT>
+static ReturnT QPCToMilliseconds(const LONGLONG aTimeStamp) {
+  const LONGLONG kMillisecondsPerSec = 1000;
+  return QPCToTimeUnits<ReturnT>(aTimeStamp, kMillisecondsPerSec);
+}
+
+template <typename ReturnT>
+static ReturnT QPCToMicroseconds(const LONGLONG aTimeStamp) {
+  const LONGLONG kMicrosecondsPerSec = 1000000;
+  return QPCToTimeUnits<ReturnT>(aTimeStamp, kMicrosecondsPerSec);
+}
+
+static LONGLONG TimeUnitsToQPC(const LONGLONG aTimeStamp,
+                               const LONGLONG aUnitsPerSec) {
+  MOZ_ASSERT(aUnitsPerSec != 0);
+
+  LONGLONG result = aTimeStamp;
+  result *= GetQPCFreq();
+  result /= aUnitsPerSec;
+  return result;
+}
+
+namespace mozilla {
+
+static Maybe<double> QPCLoadDurationToMilliseconds(
+    const ModuleLoadInfo& aNtInfo) {
+  if (aNtInfo.IsBare()) {
+    return Nothing();
+  }
+
+  return Some(QPCToMilliseconds<double>(aNtInfo.mLoadTimeInfo.QuadPart));
+}
+
+ModuleRecord::ModuleRecord() : mTrustFlags(ModuleTrustFlags::None) {}
+
+ModuleRecord::ModuleRecord(const nsAString& aResolvedNtPath)
+    : mResolvedNtName(aResolvedNtPath), mTrustFlags(ModuleTrustFlags::None) {
+  if (aResolvedNtPath.IsEmpty()) {
+    return;
+  }
+
+  MOZ_ASSERT(XRE_IsParentProcess());
+
+  nsAutoString resolvedDosPath;
+  if (!NtPathToDosPath(aResolvedNtPath, resolvedDosPath)) {
+#if defined(DEBUG)
+    nsAutoCString msg;
+    msg.AppendLiteral("NtPathToDosPath failed for path \"");
+    msg.Append(NS_ConvertUTF16toUTF8(aResolvedNtPath));
+    msg.AppendLiteral("\"");
+    NS_WARNING(msg.get());
+#endif  // defined(DEBUG)
+    return;
+  }
+
+  nsresult rv =
+      NS_NewLocalFile(resolvedDosPath, false, getter_AddRefs(mResolvedDosName));
+  if (NS_FAILED(rv) || !mResolvedDosName) {
+    return;
+  }
+
+  GetVersionAndVendorInfo(resolvedDosPath);
+
+  // Now sanitize the resolved DLL name. If we cannot sanitize this then this
+  // record must not be considered valid.
+  nsAutoString strSanitizedPath(resolvedDosPath);
+  if (!widget::WinUtils::PreparePathForTelemetry(strSanitizedPath)) {
+    return;
+  }
+
+  mSanitizedDllName = strSanitizedPath;
+}
+
+void ModuleRecord::GetVersionAndVendorInfo(const nsAString& aPath) {
+  RefPtr<DllServices> dllSvc(DllServices::Get());
+
+  // WinVerifyTrust is too slow and of limited utility for our purposes, so
+  // we pass SkipTrustVerification here to avoid it.
+  UniquePtr<wchar_t[]> signedBy(
+      dllSvc->GetBinaryOrgName(PromiseFlatString(aPath).get(),
+                               AuthenticodeFlags::SkipTrustVerification));
+  if (signedBy) {
+    mVendorInfo = Some(VendorInfo(VendorInfo::Source::Signature,
+                                  nsDependentString(signedBy.get())));
+  }
+
+  ModuleVersionInfo verInfo;
+  if (!verInfo.GetFromImage(aPath)) {
+    return;
+  }
+
+  if (verInfo.mFileVersion.Version64()) {
+    mVersion = Some(ModuleVersion(verInfo.mFileVersion.Version64()));
+  }
+
+  if (!mVendorInfo && !verInfo.mCompanyName.IsEmpty()) {
+    mVendorInfo =
+        Some(VendorInfo(VendorInfo::Source::VersionInfo, verInfo.mCompanyName));
+  }
+}
+
+bool ModuleRecord::IsXUL() const {
+  if (!mResolvedDosName) {
+    return false;
+  }
+
+  nsAutoString leafName;
+  nsresult rv = mResolvedDosName->GetLeafName(leafName);
+  if (NS_FAILED(rv)) {
+    return false;
+  }
+
+  return leafName.EqualsIgnoreCase("xul.dll");
+}
+
+int32_t ModuleRecord::GetScoreThreshold() const {
+#ifdef ENABLE_TESTS
+  // Check whether we are running as an xpcshell test.
+  if (MOZ_UNLIKELY(mozilla::EnvHasValue("XPCSHELL_TEST_PROFILE_DIR"))) {
+    nsAutoString dllLeaf;
+    if (NS_SUCCEEDED(mResolvedDosName->GetLeafName(dllLeaf))) {
+      // During xpcshell tests, this DLL is hard-coded to pass through all
+      // criteria checks and still result in "untrusted" status, so it shows up
+      // in the untrusted modules ping for the test to examine.
+      // Setting the threshold very high ensures the test will cover all
+      // criteria.
+      if (dllLeaf.EqualsIgnoreCase("modules-test.dll")) {
+        return 99999;
+      }
+    }
+  }
+#endif
+
+  return 100;
+}
+
+bool ModuleRecord::IsTrusted() const {
+  if (mTrustFlags == ModuleTrustFlags::None) {
+    return false;
+  }
+
+  // These flags are immediate passes
+  if (mTrustFlags &
+      (ModuleTrustFlags::MicrosoftWindowsSignature |
+       ModuleTrustFlags::MozillaSignature | ModuleTrustFlags::JitPI)) {
+    return true;
+  }
+
+  // The remaining flags, when set, each count for 50 points toward a
+  // trustworthiness score.
+  int32_t score = static_cast<int32_t>(
+                      CountPopulation32(static_cast<uint32_t>(mTrustFlags))) *
+                  50;
+  return score >= GetScoreThreshold();
+}
+
+ProcessedModuleLoadEvent::ProcessedModuleLoadEvent()
+    : mProcessUptimeMS(0ULL),
+      mThreadId(0UL),
+      mBaseAddress(0U),
+      mIsDependent(false),
+      mLoadStatus(0) {}
+
+ProcessedModuleLoadEvent::ProcessedModuleLoadEvent(
+    glue::EnhancedModuleLoadInfo&& aModLoadInfo,
+    RefPtr<ModuleRecord>&& aModuleRecord)
+    : mProcessUptimeMS(QPCTimeStampToProcessUptimeMilliseconds(
+          aModLoadInfo.mNtLoadInfo.mBeginTimestamp)),
+      mLoadDurationMS(QPCLoadDurationToMilliseconds(aModLoadInfo.mNtLoadInfo)),
+      mThreadId(aModLoadInfo.mNtLoadInfo.mThreadId),
+      mThreadName(std::move(aModLoadInfo.mThreadName)),
+      mBaseAddress(
+          reinterpret_cast<uintptr_t>(aModLoadInfo.mNtLoadInfo.mBaseAddr)),
+      mModule(std::move(aModuleRecord)),
+      mIsDependent(aModLoadInfo.mNtLoadInfo.mIsDependent),
+      mLoadStatus(static_cast<uint32_t>(aModLoadInfo.mNtLoadInfo.mStatus)) {
+  if (!mModule || !(*mModule)) {
+    return;
+  }
+
+  mRequestedDllName = aModLoadInfo.mNtLoadInfo.mRequestedDllName.AsString();
+
+  // If we're in the main process, sanitize the requested DLL name here.
+  // If not, we cannot use PreparePathForTelemetry because it may try to
+  // delayload shlwapi.dll and could fail if the process is sandboxed.
+  // We leave mRequestedDllName unsanitized here and sanitize it when
+  // transferring it to the main process.
+  // (See ParamTraits<mozilla::UntrustedModulesData>::ReadEvent)
+  if (XRE_IsParentProcess()) {
+    SanitizeRequestedDllName();
+  }
+}
+
+void ProcessedModuleLoadEvent::SanitizeRequestedDllName() {
+  if (!mRequestedDllName.IsEmpty() &&
+      !widget::WinUtils::PreparePathForTelemetry(mRequestedDllName)) {
+    // If we cannot sanitize a path, we simply do not provide that field to
+    // Telemetry.
+    mRequestedDllName.Truncate();
+  }
+}
+
+/* static */
+Maybe<LONGLONG>
+ProcessedModuleLoadEvent::ComputeQPCTimeStampForProcessCreation() {
+  // This is similar to the algorithm used by TimeStamp::ProcessCreation:
+
+  // 1. Get the process creation timestamp as FILETIME;
+  FILETIME creationTime, exitTime, kernelTime, userTime;
+  if (!::GetProcessTimes(::GetCurrentProcess(), &creationTime, &exitTime,
+                         &kernelTime, &userTime)) {
+    return Nothing();
+  }
+
+  // 2. Get current timestamps as both QPC and FILETIME;
+  LARGE_INTEGER nowQPC;
+  ::QueryPerformanceCounter(&nowQPC);
+
+  static const StaticDynamicallyLinkedFunctionPtr<void(WINAPI*)(LPFILETIME)>
+      pGetSystemTimePreciseAsFileTime(L"kernel32.dll",
+                                      "GetSystemTimePreciseAsFileTime");
+
+  FILETIME nowFile;
+  if (pGetSystemTimePreciseAsFileTime) {
+    pGetSystemTimePreciseAsFileTime(&nowFile);
+  } else {
+    ::GetSystemTimeAsFileTime(&nowFile);
+  }
+
+  // 3. Take the difference between the FILETIMEs from (1) and (2),
+  //    respectively, yielding the elapsed process uptime in microseconds.
+  ULARGE_INTEGER ulCreation = {
+      {creationTime.dwLowDateTime, creationTime.dwHighDateTime}};
+  ULARGE_INTEGER ulNow = {{nowFile.dwLowDateTime, nowFile.dwHighDateTime}};
+
+  ULONGLONG timeSinceCreationMicroSec =
+      (ulNow.QuadPart - ulCreation.QuadPart) / 10ULL;
+
+  // 4. Convert the QPC timestamp from (1) to microseconds.
+  LONGLONG nowQPCMicroSec = QPCToMicroseconds<LONGLONG>(nowQPC.QuadPart);
+
+  // 5. Convert the elapsed uptime to an absolute timestamp by subtracting
+  //    from (4), which yields the absolute timestamp for process creation.
+  //    We convert back to QPC units before returning.
+  const LONGLONG kMicrosecondsPerSec = 1000000;
+  return Some(TimeUnitsToQPC(nowQPCMicroSec - timeSinceCreationMicroSec,
+                             kMicrosecondsPerSec));
+}
+
+/* static */
+uint64_t ProcessedModuleLoadEvent::QPCTimeStampToProcessUptimeMilliseconds(
+    const LARGE_INTEGER& aTimeStamp) {
+  static const Maybe<LONGLONG> sProcessCreationTimeStamp =
+      ComputeQPCTimeStampForProcessCreation();
+
+  if (!sProcessCreationTimeStamp) {
+    return 0ULL;
+  }
+
+  LONGLONG diff = aTimeStamp.QuadPart - sProcessCreationTimeStamp.value();
+  return QPCToMilliseconds<uint64_t>(diff);
+}
+
+bool ProcessedModuleLoadEvent::IsXULLoad() const {
+  if (!mModule) {
+    return false;
+  }
+
+  return mModule->IsXUL();
+}
+
+bool ProcessedModuleLoadEvent::IsTrusted() const {
+  if (!mModule) {
+    return false;
+  }
+
+  return mModule->IsTrusted();
+}
+
+void UntrustedModulesData::AddNewLoads(
+    const ModulesMap& aModules, UntrustedModuleLoadingEvents&& aEvents,
+    Vector<Telemetry::ProcessedStack>&& aStacks) {
+  MOZ_ASSERT(aEvents.length() == aStacks.length());
+  for (const auto& entry : aModules) {
+    if (entry.GetData()->IsTrusted()) {
+      // Filter out trusted module records
+      continue;
+    }
+
+    Unused << mModules.LookupOrInsert(entry.GetKey(), entry.GetData());
+  }
+
+  MOZ_ASSERT(mEvents.length() <= kMaxEvents);
+
+  mNumEvents += aStacks.length();
+  mEvents.extendBack(std::move(aEvents));
+  for (auto&& stack : aStacks) {
+    mStacks.AddStack(stack);
+  }
+  Truncate(false);
+}
+
+void UntrustedModulesData::MergeModules(UntrustedModulesData& aNewData) {
+  for (auto item : aNewData.mEvents) {
+    mModules.WithEntryHandle(item->mEvent.mModule->mResolvedNtName,
+                             [&](auto&& addPtr) {
+                               if (addPtr) {
+                                 // Even though the path of a ModuleRecord
+                                 // matches, the object of ModuleRecord can be
+                                 // different. Make sure the event's mModule
+                                 // points to an object in mModules.
+                                 item->mEvent.mModule = addPtr.Data();
+                               } else {
+                                 addPtr.Insert(item->mEvent.mModule);
+                               }
+                             });
+  }
+}
+
+void UntrustedModulesData::Merge(UntrustedModulesData&& aNewData) {
+  // Don't merge loading events of a different process
+  MOZ_ASSERT((mProcessType == aNewData.mProcessType) &&
+             (mPid == aNewData.mPid));
+
+  UntrustedModulesData newData(std::move(aNewData));
+
+  if (!mNumEvents) {
+    mNumEvents = newData.mNumEvents;
+    mModules = std::move(newData.mModules);
+    mEvents = std::move(newData.mEvents);
+    mStacks = std::move(newData.mStacks);
+    return;
+  }
+
+  MergeModules(newData);
+  mNumEvents += newData.mNumEvents;
+  mEvents.extendBack(std::move(newData.mEvents));
+  mStacks.AddStacks(newData.mStacks);
+  Truncate(false);
+}
+
+void UntrustedModulesData::Truncate(bool aDropCallstackData) {
+  if (aDropCallstackData) {
+    mStacks.Clear();
+  }
+
+  if (mNumEvents <= kMaxEvents) {
+    return;
+  }
+
+  UntrustedModuleLoadingEvents events;
+  events.splice(0, mEvents, mNumEvents - kMaxEvents, kMaxEvents);
+  std::swap(events, mEvents);
+  mNumEvents = kMaxEvents;
+  // mStacks only keeps the latest kMaxEvents stacks, so mEvents will
+  // still be lined up with mStacks.
+}
+
+void UntrustedModulesData::MergeWithoutStacks(UntrustedModulesData&& aNewData) {
+  // Don't merge loading events of a different process
+  MOZ_ASSERT((mProcessType == aNewData.mProcessType) &&
+             (mPid == aNewData.mPid));
+  MOZ_ASSERT(!mStacks.GetStackCount());
+
+  UntrustedModulesData newData(std::move(aNewData));
+
+  if (mNumEvents > 0) {
+    MergeModules(newData);
+  } else {
+    mModules = std::move(newData.mModules);
+  }
+
+  mNumEvents += newData.mNumEvents;
+  mEvents.extendBack(std::move(newData.mEvents));
+
+  Truncate(true);
+}
+
+void UntrustedModulesData::Swap(UntrustedModulesData& aOther) {
+  GeckoProcessType tmpProcessType = mProcessType;
+  mProcessType = aOther.mProcessType;
+  aOther.mProcessType = tmpProcessType;
+
+  DWORD tmpPid = mPid;
+  mPid = aOther.mPid;
+  aOther.mPid = tmpPid;
+
+  TimeDuration tmpElapsed = mElapsed;
+  mElapsed = aOther.mElapsed;
+  aOther.mElapsed = tmpElapsed;
+
+  mModules.SwapElements(aOther.mModules);
+  std::swap(mNumEvents, aOther.mNumEvents);
+  std::swap(mEvents, aOther.mEvents);
+  mStacks.Swap(aOther.mStacks);
+
+  Maybe<double> tmpXULLoadDurationMS = mXULLoadDurationMS;
+  mXULLoadDurationMS = aOther.mXULLoadDurationMS;
+  aOther.mXULLoadDurationMS = tmpXULLoadDurationMS;
+
+  uint32_t tmpSanitizationFailures = mSanitizationFailures;
+  mSanitizationFailures = aOther.mSanitizationFailures;
+  aOther.mSanitizationFailures = tmpSanitizationFailures;
+
+  uint32_t tmpTrustTestFailures = mTrustTestFailures;
+  mTrustTestFailures = aOther.mTrustTestFailures;
+  aOther.mTrustTestFailures = tmpTrustTestFailures;
+}
+
+}  // namespace mozilla
diff --git a/toolkit/xre/dllservices/UntrustedModulesData.h b/toolkit/xre/dllservices/UntrustedModulesData.h
new file mode 100644
index 0000000000..158cc24746
--- /dev/null
+++ b/toolkit/xre/dllservices/UntrustedModulesData.h
@@ -0,0 +1,653 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_UntrustedModulesData_h
+#define mozilla_UntrustedModulesData_h
+
+#if defined(XP_WIN)
+
+#  include "ipc/IPCMessageUtils.h"
+#  include "mozilla/CombinedStacks.h"
+#  include "mozilla/DebugOnly.h"
+#  include "mozilla/LinkedList.h"
+#  include "mozilla/Maybe.h"
+#  include "mozilla/RefPtr.h"
+#  include "mozilla/TypedEnumBits.h"
+#  include "mozilla/Unused.h"
+#  include "mozilla/Variant.h"
+#  include "mozilla/Vector.h"
+#  include "mozilla/WinHeaderOnlyUtils.h"
+#  include "nsCOMPtr.h"
+#  include "nsHashKeys.h"
+#  include "nsIFile.h"
+#  include "nsISupportsImpl.h"
+#  include "nsRefPtrHashtable.h"
+#  include "nsString.h"
+#  include "nsXULAppAPI.h"
+
+namespace mozilla {
+namespace glue {
+struct EnhancedModuleLoadInfo;
+}  // namespace glue
+
+enum class ModuleTrustFlags : uint32_t {
+  None = 0,
+  MozillaSignature = 1,
+  MicrosoftWindowsSignature = 2,
+  MicrosoftVersion = 4,
+  FirefoxDirectory = 8,
+  FirefoxDirectoryAndVersion = 0x10,
+  SystemDirectory = 0x20,
+  KeyboardLayout = 0x40,
+  JitPI = 0x80,
+  WinSxSDirectory = 0x100,
+};
+
+MOZ_MAKE_ENUM_CLASS_BITWISE_OPERATORS(ModuleTrustFlags);
+
+class VendorInfo final {
+ public:
+  enum class Source : uint32_t {
+    None,
+    Signature,
+    VersionInfo,
+  };
+
+  VendorInfo() : mSource(Source::None) {}
+  VendorInfo(const Source aSource, const nsAString& aVendor)
+      : mSource(aSource), mVendor(aVendor) {
+    MOZ_ASSERT(aSource != Source::None && !aVendor.IsEmpty());
+  }
+
+  Source mSource;
+  nsString mVendor;
+};
+
+class ModulesMap;
+
+class ModuleRecord final {
+ public:
+  explicit ModuleRecord(const nsAString& aResolvedNtPath);
+
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(ModuleRecord)
+
+  nsString mResolvedNtName;
+  nsCOMPtr<nsIFile> mResolvedDosName;
+  nsString mSanitizedDllName;
+  Maybe<ModuleVersion> mVersion;
+  Maybe<VendorInfo> mVendorInfo;
+  ModuleTrustFlags mTrustFlags;
+
+  explicit operator bool() const { return !mSanitizedDllName.IsEmpty(); }
+  bool IsXUL() const;
+  bool IsTrusted() const;
+
+  ModuleRecord(const ModuleRecord&) = delete;
+  ModuleRecord(ModuleRecord&&) = delete;
+
+  ModuleRecord& operator=(const ModuleRecord&) = delete;
+  ModuleRecord& operator=(ModuleRecord&&) = delete;
+
+ private:
+  ModuleRecord();
+  ~ModuleRecord() = default;
+  void GetVersionAndVendorInfo(const nsAString& aPath);
+  int32_t GetScoreThreshold() const;
+
+  friend struct ::IPC::ParamTraits<ModulesMap>;
+};
+
+/**
+ * This type holds module path data using one of two internal representations.
+ * It may be created from either a nsTHashtable or a Vector, and may be
+ * serialized from either representation into a common format over the wire.
+ * Deserialization always uses the Vector representation.
+ */
+struct ModulePaths final {
+  using SetType = nsTHashtable<nsStringCaseInsensitiveHashKey>;
+  using VecType = Vector<nsString>;
+
+  Variant<SetType, VecType> mModuleNtPaths;
+
+  template <typename T>
+  explicit ModulePaths(T&& aPaths)
+      : mModuleNtPaths(AsVariant(std::forward<T>(aPaths))) {}
+
+  ModulePaths() : mModuleNtPaths(VecType()) {}
+
+  ModulePaths(const ModulePaths& aOther) = delete;
+  ModulePaths(ModulePaths&& aOther) = default;
+  ModulePaths& operator=(const ModulePaths&) = delete;
+  ModulePaths& operator=(ModulePaths&&) = default;
+};
+
+class ProcessedModuleLoadEvent final {
+ public:
+  ProcessedModuleLoadEvent();
+  ProcessedModuleLoadEvent(glue::EnhancedModuleLoadInfo&& aModLoadInfo,
+                           RefPtr<ModuleRecord>&& aModuleRecord);
+
+  explicit operator bool() const { return mModule && *mModule; }
+  bool IsXULLoad() const;
+  bool IsTrusted() const;
+
+  uint64_t mProcessUptimeMS;
+  Maybe<double> mLoadDurationMS;
+  DWORD mThreadId;
+  nsCString mThreadName;
+  nsString mRequestedDllName;
+  // We intentionally store mBaseAddress as part of the event and not the
+  // module, as relocation may cause it to change between loads. If so, we want
+  // to know about it.
+  uintptr_t mBaseAddress;
+  RefPtr<ModuleRecord> mModule;
+  bool mIsDependent;
+  uint32_t mLoadStatus;  // corresponding to enum ModuleLoadInfo::Status
+
+  ProcessedModuleLoadEvent(const ProcessedModuleLoadEvent&) = delete;
+  ProcessedModuleLoadEvent& operator=(const ProcessedModuleLoadEvent&) = delete;
+
+  ProcessedModuleLoadEvent(ProcessedModuleLoadEvent&&) = default;
+  ProcessedModuleLoadEvent& operator=(ProcessedModuleLoadEvent&&) = default;
+
+  void SanitizeRequestedDllName();
+
+ private:
+  static Maybe<LONGLONG> ComputeQPCTimeStampForProcessCreation();
+  static uint64_t QPCTimeStampToProcessUptimeMilliseconds(
+      const LARGE_INTEGER& aTimeStamp);
+};
+
+// Declaring ModulesMap this way makes it much easier to forward declare than
+// if we had used |using| or |typedef|.
+class ModulesMap final
+    : public nsRefPtrHashtable<nsStringCaseInsensitiveHashKey, ModuleRecord> {
+ public:
+  ModulesMap()
+      : nsRefPtrHashtable<nsStringCaseInsensitiveHashKey, ModuleRecord>() {}
+};
+
+struct ProcessedModuleLoadEventContainer final
+    : public LinkedListElement<ProcessedModuleLoadEventContainer> {
+  ProcessedModuleLoadEvent mEvent;
+  ProcessedModuleLoadEventContainer() = default;
+  explicit ProcessedModuleLoadEventContainer(ProcessedModuleLoadEvent&& aEvent)
+      : mEvent(std::move(aEvent)) {}
+
+  ProcessedModuleLoadEventContainer(ProcessedModuleLoadEventContainer&&) =
+      default;
+  ProcessedModuleLoadEventContainer& operator=(
+      ProcessedModuleLoadEventContainer&&) = default;
+  ProcessedModuleLoadEventContainer(const ProcessedModuleLoadEventContainer&) =
+      delete;
+  ProcessedModuleLoadEventContainer& operator=(
+      const ProcessedModuleLoadEventContainer&) = delete;
+};
+using UntrustedModuleLoadingEvents =
+    AutoCleanLinkedList<ProcessedModuleLoadEventContainer>;
+
+class UntrustedModulesData final {
+  // Merge aNewData.mEvents into this->mModules and also
+  // make module entries in aNewData point to items in this->mModules.
+  void MergeModules(UntrustedModulesData& aNewData);
+
+ public:
+  // Ensure mEvents will never retain more than kMaxEvents events.
+  // This constant matches the maximum in Telemetry::CombinedStacks.
+  // Truncate() relies on these being the same.
+  static constexpr size_t kMaxEvents = 50;
+
+  UntrustedModulesData()
+      : mProcessType(XRE_GetProcessType()),
+        mPid(::GetCurrentProcessId()),
+        mNumEvents(0),
+        mSanitizationFailures(0),
+        mTrustTestFailures(0) {
+    MOZ_ASSERT(kMaxEvents == mStacks.GetMaxStacksCount());
+  }
+
+  UntrustedModulesData(UntrustedModulesData&&) = default;
+  UntrustedModulesData& operator=(UntrustedModulesData&&) = default;
+
+  UntrustedModulesData(const UntrustedModulesData&) = delete;
+  UntrustedModulesData& operator=(const UntrustedModulesData&) = delete;
+
+  explicit operator bool() const {
+    return !mEvents.isEmpty() || mSanitizationFailures || mTrustTestFailures ||
+           mXULLoadDurationMS.isSome();
+  }
+
+  void AddNewLoads(const ModulesMap& aModulesMap,
+                   UntrustedModuleLoadingEvents&& aEvents,
+                   Vector<Telemetry::ProcessedStack>&& aStacks);
+  void Merge(UntrustedModulesData&& aNewData);
+  void MergeWithoutStacks(UntrustedModulesData&& aNewData);
+  void Swap(UntrustedModulesData& aOther);
+
+  // Drop callstack data and old loading events.
+  void Truncate(bool aDropCallstackData);
+
+  GeckoProcessType mProcessType;
+  DWORD mPid;
+  TimeDuration mElapsed;
+  ModulesMap mModules;
+  uint32_t mNumEvents;
+  UntrustedModuleLoadingEvents mEvents;
+  Telemetry::CombinedStacks mStacks;
+  Maybe<double> mXULLoadDurationMS;
+  uint32_t mSanitizationFailures;
+  uint32_t mTrustTestFailures;
+};
+
+class ModulesMapResult final {
+ public:
+  ModulesMapResult() : mTrustTestFailures(0) {}
+
+  ModulesMapResult(const ModulesMapResult& aOther) = delete;
+  ModulesMapResult(ModulesMapResult&& aOther) = default;
+  ModulesMapResult& operator=(const ModulesMapResult& aOther) = delete;
+  ModulesMapResult& operator=(ModulesMapResult&& aOther) = default;
+
+  ModulesMap mModules;
+  uint32_t mTrustTestFailures;
+};
+
+}  // namespace mozilla
+
+namespace IPC {
+
+template <>
+struct ParamTraits<mozilla::ModuleVersion> {
+  typedef mozilla::ModuleVersion paramType;
+
+  static void Write(MessageWriter* aWriter, const paramType& aParam) {
+    aWriter->WriteUInt64(aParam.AsInteger());
+  }
+
+  static bool Read(MessageReader* aReader, paramType* aResult) {
+    uint64_t ver;
+    if (!aReader->ReadUInt64(&ver)) {
+      return false;
+    }
+
+    *aResult = ver;
+    return true;
+  }
+};
+
+template <>
+struct ParamTraits<mozilla::VendorInfo> {
+  typedef mozilla::VendorInfo paramType;
+
+  static void Write(MessageWriter* aWriter, const paramType& aParam) {
+    aWriter->WriteUInt32(static_cast<uint32_t>(aParam.mSource));
+    WriteParam(aWriter, aParam.mVendor);
+  }
+
+  static bool Read(MessageReader* aReader, paramType* aResult) {
+    uint32_t source;
+    if (!aReader->ReadUInt32(&source)) {
+      return false;
+    }
+
+    aResult->mSource = static_cast<mozilla::VendorInfo::Source>(source);
+
+    if (!ReadParam(aReader, &aResult->mVendor)) {
+      return false;
+    }
+
+    return true;
+  }
+};
+
+template <>
+struct ParamTraits<mozilla::ModuleRecord> {
+  typedef mozilla::ModuleRecord paramType;
+
+  static void Write(MessageWriter* aWriter, const paramType& aParam) {
+    WriteParam(aWriter, aParam.mResolvedNtName);
+
+    nsAutoString resolvedDosName;
+    if (aParam.mResolvedDosName) {
+      mozilla::DebugOnly<nsresult> rv =
+          aParam.mResolvedDosName->GetPath(resolvedDosName);
+      MOZ_ASSERT(NS_SUCCEEDED(rv));
+    }
+
+    WriteParam(aWriter, resolvedDosName);
+    WriteParam(aWriter, aParam.mSanitizedDllName);
+    WriteParam(aWriter, aParam.mVersion);
+    WriteParam(aWriter, aParam.mVendorInfo);
+    aWriter->WriteUInt32(static_cast<uint32_t>(aParam.mTrustFlags));
+  }
+
+  static bool Read(MessageReader* aReader, paramType* aResult) {
+    if (!ReadParam(aReader, &aResult->mResolvedNtName)) {
+      return false;
+    }
+
+    nsAutoString resolvedDosName;
+    if (!ReadParam(aReader, &resolvedDosName)) {
+      return false;
+    }
+
+    if (resolvedDosName.IsEmpty()) {
+      aResult->mResolvedDosName = nullptr;
+    } else if (NS_FAILED(NS_NewLocalFile(
+                   resolvedDosName, false,
+                   getter_AddRefs(aResult->mResolvedDosName)))) {
+      return false;
+    }
+
+    if (!ReadParam(aReader, &aResult->mSanitizedDllName)) {
+      return false;
+    }
+
+    if (!ReadParam(aReader, &aResult->mVersion)) {
+      return false;
+    }
+
+    if (!ReadParam(aReader, &aResult->mVendorInfo)) {
+      return false;
+    }
+
+    uint32_t trustFlags;
+    if (!aReader->ReadUInt32(&trustFlags)) {
+      return false;
+    }
+
+    aResult->mTrustFlags = static_cast<mozilla::ModuleTrustFlags>(trustFlags);
+    return true;
+  }
+};
+
+template <>
+struct ParamTraits<mozilla::ModulesMap> {
+  typedef mozilla::ModulesMap paramType;
+
+  static void Write(MessageWriter* aWriter, const paramType& aParam) {
+    aWriter->WriteUInt32(aParam.Count());
+
+    for (const auto& entry : aParam) {
+      MOZ_RELEASE_ASSERT(entry.GetData());
+      WriteParam(aWriter, entry.GetKey());
+      WriteParam(aWriter, *(entry.GetData()));
+    }
+  }
+
+  static bool Read(MessageReader* aReader, paramType* aResult) {
+    uint32_t count;
+    if (!ReadParam(aReader, &count)) {
+      return false;
+    }
+
+    for (uint32_t current = 0; current < count; ++current) {
+      nsAutoString key;
+      if (!ReadParam(aReader, &key) || key.IsEmpty()) {
+        return false;
+      }
+
+      RefPtr<mozilla::ModuleRecord> rec(new mozilla::ModuleRecord());
+      if (!ReadParam(aReader, rec.get())) {
+        return false;
+      }
+
+      aResult->InsertOrUpdate(key, std::move(rec));
+    }
+
+    return true;
+  }
+};
+
+template <>
+struct ParamTraits<mozilla::ModulePaths> {
+  typedef mozilla::ModulePaths paramType;
+
+  static void Write(MessageWriter* aWriter, const paramType& aParam) {
+    aParam.mModuleNtPaths.match(
+        [aWriter](const paramType::SetType& aSet) { WriteSet(aWriter, aSet); },
+        [aWriter](const paramType::VecType& aVec) {
+          WriteVector(aWriter, aVec);
+        });
+  }
+
+  static bool Read(MessageReader* aReader, paramType* aResult) {
+    uint32_t len;
+    if (!aReader->ReadUInt32(&len)) {
+      return false;
+    }
+
+    // As noted in the comments for ModulePaths, we only deserialize using the
+    // Vector representation.
+    auto& vec = aResult->mModuleNtPaths.as<paramType::VecType>();
+    if (!vec.reserve(len)) {
+      return false;
+    }
+
+    for (uint32_t idx = 0; idx < len; ++idx) {
+      nsString str;
+      if (!ReadParam(aReader, &str)) {
+        return false;
+      }
+
+      if (!vec.emplaceBack(std::move(str))) {
+        return false;
+      }
+    }
+
+    return true;
+  }
+
+ private:
+  // NB: This function must write out the set in the same format as WriteVector
+  static void WriteSet(MessageWriter* aWriter, const paramType::SetType& aSet) {
+    aWriter->WriteUInt32(aSet.Count());
+    for (const auto& key : aSet.Keys()) {
+      WriteParam(aWriter, key);
+    }
+  }
+
+  // NB: This function must write out the vector in the same format as WriteSet
+  static void WriteVector(MessageWriter* aWriter,
+                          const paramType::VecType& aVec) {
+    aWriter->WriteUInt32(aVec.length());
+    for (auto const& item : aVec) {
+      WriteParam(aWriter, item);
+    }
+  }
+};
+
+template <>
+struct ParamTraits<mozilla::UntrustedModulesData> {
+  typedef mozilla::UntrustedModulesData paramType;
+
+  static void Write(MessageWriter* aWriter, const paramType& aParam) {
+    aWriter->WriteUInt32(aParam.mProcessType);
+    aWriter->WriteULong(aParam.mPid);
+    WriteParam(aWriter, aParam.mElapsed);
+    WriteParam(aWriter, aParam.mModules);
+
+    aWriter->WriteUInt32(aParam.mNumEvents);
+    for (auto event : aParam.mEvents) {
+      WriteEvent(aWriter, event->mEvent);
+    }
+
+    WriteParam(aWriter, aParam.mStacks);
+    WriteParam(aWriter, aParam.mXULLoadDurationMS);
+    aWriter->WriteUInt32(aParam.mSanitizationFailures);
+    aWriter->WriteUInt32(aParam.mTrustTestFailures);
+  }
+
+  static bool Read(MessageReader* aReader, paramType* aResult) {
+    uint32_t processType;
+    if (!aReader->ReadUInt32(&processType)) {
+      return false;
+    }
+
+    aResult->mProcessType = static_cast<GeckoProcessType>(processType);
+
+    if (!aReader->ReadULong(&aResult->mPid)) {
+      return false;
+    }
+
+    if (!ReadParam(aReader, &aResult->mElapsed)) {
+      return false;
+    }
+
+    if (!ReadParam(aReader, &aResult->mModules)) {
+      return false;
+    }
+
+    // We read mEvents manually so that we can use ReadEvent defined below.
+    if (!ReadParam(aReader, &aResult->mNumEvents)) {
+      return false;
+    }
+
+    for (uint32_t curEventIdx = 0; curEventIdx < aResult->mNumEvents;
+         ++curEventIdx) {
+      auto newEvent =
+          mozilla::MakeUnique<mozilla::ProcessedModuleLoadEventContainer>();
+      if (!ReadEvent(aReader, &newEvent->mEvent, aResult->mModules)) {
+        return false;
+      }
+      aResult->mEvents.insertBack(newEvent.release());
+    }
+
+    if (!ReadParam(aReader, &aResult->mStacks)) {
+      return false;
+    }
+
+    if (!ReadParam(aReader, &aResult->mXULLoadDurationMS)) {
+      return false;
+    }
+
+    if (!aReader->ReadUInt32(&aResult->mSanitizationFailures)) {
+      return false;
+    }
+
+    if (!aReader->ReadUInt32(&aResult->mTrustTestFailures)) {
+      return false;
+    }
+
+    return true;
+  }
+
+ private:
+  // Because ProcessedModuleLoadEvent depends on a hash table from
+  // UntrustedModulesData, we do its serialization as part of this
+  // specialization.
+  static void WriteEvent(MessageWriter* aWriter,
+                         const mozilla::ProcessedModuleLoadEvent& aParam) {
+    aWriter->WriteUInt64(aParam.mProcessUptimeMS);
+    WriteParam(aWriter, aParam.mLoadDurationMS);
+    aWriter->WriteULong(aParam.mThreadId);
+    WriteParam(aWriter, aParam.mThreadName);
+    WriteParam(aWriter, aParam.mRequestedDllName);
+    WriteParam(aWriter, aParam.mBaseAddress);
+    WriteParam(aWriter, aParam.mIsDependent);
+    WriteParam(aWriter, aParam.mLoadStatus);
+
+    // We don't write the ModuleRecord directly; we write its key into the
+    // UntrustedModulesData::mModules hash table.
+    MOZ_ASSERT(aParam.mModule && !aParam.mModule->mResolvedNtName.IsEmpty());
+    WriteParam(aWriter, aParam.mModule->mResolvedNtName);
+  }
+
+  // Because ProcessedModuleLoadEvent depends on a hash table from
+  // UntrustedModulesData, we do its deserialization as part of this
+  // specialization.
+  static bool ReadEvent(MessageReader* aReader,
+                        mozilla::ProcessedModuleLoadEvent* aResult,
+                        const mozilla::ModulesMap& aModulesMap) {
+    if (!aReader->ReadUInt64(&aResult->mProcessUptimeMS)) {
+      return false;
+    }
+
+    if (!ReadParam(aReader, &aResult->mLoadDurationMS)) {
+      return false;
+    }
+
+    if (!aReader->ReadULong(&aResult->mThreadId)) {
+      return false;
+    }
+
+    if (!ReadParam(aReader, &aResult->mThreadName)) {
+      return false;
+    }
+
+    if (!ReadParam(aReader, &aResult->mRequestedDllName)) {
+      return false;
+    }
+
+    // When ProcessedModuleLoadEvent was constructed in a child process, we left
+    // mRequestedDllName unsanitized, so now is a good time to sanitize it.
+    aResult->SanitizeRequestedDllName();
+
+    if (!ReadParam(aReader, &aResult->mBaseAddress)) {
+      return false;
+    }
+
+    if (!ReadParam(aReader, &aResult->mIsDependent)) {
+      return false;
+    }
+
+    if (!ReadParam(aReader, &aResult->mLoadStatus)) {
+      return false;
+    }
+
+    nsAutoString resolvedNtName;
+    if (!ReadParam(aReader, &resolvedNtName)) {
+      return false;
+    }
+
+    // NB: While bad data integrity might for some reason result in a null
+    // mModule, we do not fail the deserialization; this is a data error,
+    // rather than an IPC error. The error is detected and dealt with in
+    // telemetry.
+    aResult->mModule = aModulesMap.Get(resolvedNtName);
+
+    return true;
+  }
+};
+
+template <>
+struct ParamTraits<mozilla::ModulesMapResult> {
+  typedef mozilla::ModulesMapResult paramType;
+
+  static void Write(MessageWriter* aWriter, const paramType& aParam) {
+    WriteParam(aWriter, aParam.mModules);
+    aWriter->WriteUInt32(aParam.mTrustTestFailures);
+  }
+
+  static bool Read(MessageReader* aReader, paramType* aResult) {
+    if (!ReadParam(aReader, &aResult->mModules)) {
+      return false;
+    }
+
+    if (!aReader->ReadUInt32(&aResult->mTrustTestFailures)) {
+      return false;
+    }
+
+    return true;
+  }
+};
+
+}  // namespace IPC
+
+#else  // defined(XP_WIN)
+
+namespace mozilla {
+
+// For compiling IPDL on non-Windows platforms
+using UntrustedModulesData = uint32_t;
+using ModulePaths = uint32_t;
+using ModulesMapResult = uint32_t;
+
+}  // namespace mozilla
+
+#endif  // defined(XP_WIN)
+
+#endif  // mozilla_UntrustedModulesData_h
diff --git a/toolkit/xre/dllservices/UntrustedModulesProcessor.cpp b/toolkit/xre/dllservices/UntrustedModulesProcessor.cpp
new file mode 100644
index 0000000000..4deb920a52
--- /dev/null
+++ b/toolkit/xre/dllservices/UntrustedModulesProcessor.cpp
@@ -0,0 +1,1063 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#include "UntrustedModulesProcessor.h"
+
+#include <windows.h>
+
+#include "mozilla/CmdLineAndEnvUtils.h"
+#include "mozilla/DebugOnly.h"
+#include "mozilla/dom/ContentChild.h"
+#include "mozilla/dom/ContentParent.h"
+#include "mozilla/Likely.h"
+#include "mozilla/net/SocketProcessChild.h"
+#include "mozilla/net/SocketProcessParent.h"
+#include "mozilla/ipc/UtilityProcessParent.h"
+#include "mozilla/ipc/UtilityProcessChild.h"
+#include "mozilla/RDDChild.h"
+#include "mozilla/RDDParent.h"
+#include "mozilla/RDDProcessManager.h"
+#include "mozilla/ScopeExit.h"
+#include "mozilla/Services.h"
+#include "mozilla/Telemetry.h"
+#include "mozilla/Unused.h"
+#include "ModuleEvaluator.h"
+#include "nsCOMPtr.h"
+#include "nsHashKeys.h"
+#include "nsIObserverService.h"
+#include "nsTHashtable.h"
+#include "nsThreadUtils.h"
+#include "nsXULAppAPI.h"
+#include "private/prpriv.h"  // For PR_GetThreadID
+
+namespace mozilla {
+
+class MOZ_RAII BackgroundPriorityRegion final {
+ public:
+  BackgroundPriorityRegion()
+      : mIsBackground(
+            ::SetThreadPriority(::GetCurrentThread(), THREAD_PRIORITY_IDLE)) {}
+
+  ~BackgroundPriorityRegion() {
+    if (!mIsBackground) {
+      return;
+    }
+
+    Clear(::GetCurrentThread());
+  }
+
+  static void Clear(const nsAutoHandle& aThread) {
+    if (!aThread) {
+      return;
+    }
+
+    Clear(aThread.get());
+  }
+
+  BackgroundPriorityRegion(const BackgroundPriorityRegion&) = delete;
+  BackgroundPriorityRegion(BackgroundPriorityRegion&&) = delete;
+  BackgroundPriorityRegion& operator=(const BackgroundPriorityRegion&) = delete;
+  BackgroundPriorityRegion& operator=(BackgroundPriorityRegion&&) = delete;
+
+ private:
+  static void Clear(HANDLE aThread) {
+    DebugOnly<BOOL> ok = ::SetThreadPriority(aThread, THREAD_PRIORITY_NORMAL);
+    MOZ_ASSERT(ok);
+  }
+
+ private:
+  const BOOL mIsBackground;
+};
+
+/* static */
+bool UntrustedModulesProcessor::IsSupportedProcessType() {
+  switch (XRE_GetProcessType()) {
+    case GeckoProcessType_Default:
+    case GeckoProcessType_Content:
+    case GeckoProcessType_Socket:
+      return Telemetry::CanRecordReleaseData();
+    case GeckoProcessType_RDD:
+    case GeckoProcessType_Utility:
+      // For RDD and Utility process, we check the telemetry settings in
+      // RDDChild::Init() / UtilityProcessChild::Init() running in the browser
+      // process because CanRecordReleaseData() always returns false here.
+      return true;
+    default:
+      return false;
+  }
+}
+
+/* static */
+RefPtr<UntrustedModulesProcessor> UntrustedModulesProcessor::Create(
+    bool aIsReadyForBackgroundProcessing) {
+  if (!IsSupportedProcessType()) {
+    return nullptr;
+  }
+
+  RefPtr<UntrustedModulesProcessor> result(
+      new UntrustedModulesProcessor(aIsReadyForBackgroundProcessing));
+  return result.forget();
+}
+
+NS_IMPL_ISUPPORTS(UntrustedModulesProcessor, nsIObserver, nsIThreadPoolListener)
+
+static const uint32_t kThreadTimeoutMS = 120000;  // 2 minutes
+
+UntrustedModulesProcessor::UntrustedModulesProcessor(
+    bool aIsReadyForBackgroundProcessing)
+    : mThread(new LazyIdleThread(kThreadTimeoutMS, "Untrusted Modules",
+                                 LazyIdleThread::ManualShutdown)),
+      mThreadHandleMutex(
+          "mozilla::UntrustedModulesProcessor::mThreadHandleMutex"),
+      mUnprocessedMutex(
+          "mozilla::UntrustedModulesProcessor::mUnprocessedMutex"),
+      mModuleCacheMutex(
+          "mozilla::UntrustedModulesProcessor::mModuleCacheMutex"),
+      mStatus(aIsReadyForBackgroundProcessing ? Status::Allowed
+                                              : Status::StartingUp) {
+  AddObservers();
+}
+
+void UntrustedModulesProcessor::AddObservers() {
+  nsCOMPtr<nsIObserverService> obsServ(services::GetObserverService());
+  obsServ->AddObserver(this, NS_XPCOM_WILL_SHUTDOWN_OBSERVER_ID, false);
+  obsServ->AddObserver(this, "xpcom-shutdown-threads", false);
+  obsServ->AddObserver(this, "unblock-untrusted-modules-thread", false);
+  if (XRE_IsContentProcess()) {
+    obsServ->AddObserver(this, "content-child-will-shutdown", false);
+  }
+  mThread->SetListener(this);
+}
+
+bool UntrustedModulesProcessor::IsReadyForBackgroundProcessing() const {
+  return mStatus == Status::Allowed;
+}
+
+void UntrustedModulesProcessor::Disable() {
+  // Ensure that mThread cannot run at low priority anymore
+  {
+    MutexAutoLock lock(mThreadHandleMutex);
+    BackgroundPriorityRegion::Clear(mThreadHandle);
+  }
+
+  // No more background processing allowed beyond this point
+  if (mStatus.exchange(Status::ShuttingDown) != Status::Allowed) {
+    return;
+  }
+
+  MutexAutoLock lock(mUnprocessedMutex);
+  CancelScheduledProcessing(lock);
+}
+
+NS_IMETHODIMP UntrustedModulesProcessor::Observe(nsISupports* aSubject,
+                                                 const char* aTopic,
+                                                 const char16_t* aData) {
+  if (!strcmp(aTopic, NS_XPCOM_WILL_SHUTDOWN_OBSERVER_ID) ||
+      !strcmp(aTopic, "content-child-will-shutdown")) {
+    Disable();
+    return NS_OK;
+  }
+
+  if (!strcmp(aTopic, "xpcom-shutdown-threads")) {
+    Disable();
+    mThread->Shutdown();
+
+    RemoveObservers();
+
+    mThread = nullptr;
+    return NS_OK;
+  }
+
+  if (!strcmp(aTopic, "unblock-untrusted-modules-thread")) {
+    nsCOMPtr<nsIObserverService> obs(services::GetObserverService());
+    obs->RemoveObserver(this, "unblock-untrusted-modules-thread");
+
+    mStatus.compareExchange(Status::StartingUp, Status::Allowed);
+
+    if (!IsReadyForBackgroundProcessing()) {
+      // If we're shutting down, stop here.
+      return NS_OK;
+    }
+
+    if (XRE_IsParentProcess()) {
+      // Propagate notification to child processes
+      nsTArray<dom::ContentParent*> contentProcesses;
+      dom::ContentParent::GetAll(contentProcesses);
+      for (auto* proc : contentProcesses) {
+        Unused << proc->SendUnblockUntrustedModulesThread();
+      }
+      if (auto* proc = net::SocketProcessParent::GetSingleton()) {
+        Unused << proc->SendUnblockUntrustedModulesThread();
+      }
+      if (auto* rddMgr = RDDProcessManager::Get()) {
+        if (auto* proc = rddMgr->GetRDDChild()) {
+          Unused << proc->SendUnblockUntrustedModulesThread();
+        }
+      }
+    }
+
+    return NS_OK;
+  }
+
+  MOZ_ASSERT_UNREACHABLE("Not reachable");
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP UntrustedModulesProcessor::OnThreadCreated() {
+  // Whenever a backing lazy thread is created, record a thread handle to it.
+  HANDLE threadHandle;
+  if (!::DuplicateHandle(
+          ::GetCurrentProcess(), ::GetCurrentThread(), ::GetCurrentProcess(),
+          &threadHandle,
+          THREAD_QUERY_LIMITED_INFORMATION | THREAD_SET_LIMITED_INFORMATION,
+          FALSE, 0)) {
+    MOZ_ASSERT_UNREACHABLE("DuplicateHandle failed on GetCurrentThread()?");
+    threadHandle = nullptr;
+  }
+  MutexAutoLock lock(mThreadHandleMutex);
+  mThreadHandle.own(threadHandle);
+  return NS_OK;
+}
+
+NS_IMETHODIMP UntrustedModulesProcessor::OnThreadShuttingDown() {
+  // When a lazy thread shuts down, clean up the thread handle reference unless
+  // it's already been replaced.
+  MutexAutoLock lock(mThreadHandleMutex);
+  if (mThreadHandle && ::GetCurrentThreadId() == ::GetThreadId(mThreadHandle)) {
+    mThreadHandle.reset();
+  }
+  return NS_OK;
+}
+
+void UntrustedModulesProcessor::RemoveObservers() {
+  nsCOMPtr<nsIObserverService> obsServ(services::GetObserverService());
+  obsServ->RemoveObserver(this, NS_XPCOM_WILL_SHUTDOWN_OBSERVER_ID);
+  obsServ->RemoveObserver(this, "xpcom-shutdown-threads");
+  obsServ->RemoveObserver(this, "unblock-untrusted-modules-thread");
+  if (XRE_IsContentProcess()) {
+    obsServ->RemoveObserver(this, "content-child-will-shutdown");
+  }
+  mThread->SetListener(nullptr);
+}
+
+void UntrustedModulesProcessor::ScheduleNonEmptyQueueProcessing(
+    const MutexAutoLock& aProofOfLock) {
+  // In case something tried to load a DLL during shutdown
+  if (!mThread) {
+    return;
+  }
+
+#if defined(ENABLE_TESTS)
+  // Don't bother scheduling background processing in short-lived xpcshell
+  // processes; it makes the test suites take too long.
+  if (MOZ_UNLIKELY(mozilla::EnvHasValue("XPCSHELL_TEST_PROFILE_DIR"))) {
+    return;
+  }
+#endif  // defined(ENABLE_TESTS)
+
+  if (mIdleRunnable) {
+    return;
+  }
+
+  if (!IsReadyForBackgroundProcessing()) {
+    return;
+  }
+
+  // Schedule a runnable to trigger background processing once the main thread
+  // has gone idle. We do it this way to ensure that we don't start doing a
+  // bunch of processing during periods of heavy main thread activity.
+  nsCOMPtr<nsIRunnable> idleRunnable(NewCancelableRunnableMethod(
+      "UntrustedModulesProcessor::DispatchBackgroundProcessing", this,
+      &UntrustedModulesProcessor::DispatchBackgroundProcessing));
+
+  if (NS_FAILED(NS_DispatchToMainThreadQueue(do_AddRef(idleRunnable),
+                                             EventQueuePriority::Idle))) {
+    return;
+  }
+
+  mIdleRunnable = std::move(idleRunnable);
+}
+
+void UntrustedModulesProcessor::CancelScheduledProcessing(
+    const MutexAutoLock& aProofOfLock) {
+  if (!mIdleRunnable) {
+    return;
+  }
+
+  nsCOMPtr<nsICancelableRunnable> cancelable(do_QueryInterface(mIdleRunnable));
+  if (cancelable) {
+    // Stop the pending idle runnable from doing anything
+    cancelable->Cancel();
+  }
+
+  mIdleRunnable = nullptr;
+}
+
+void UntrustedModulesProcessor::DispatchBackgroundProcessing() {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  if (!IsReadyForBackgroundProcessing()) {
+    return;
+  }
+
+  nsCOMPtr<nsIRunnable> runnable(NewRunnableMethod(
+      "UntrustedModulesProcessor::BackgroundProcessModuleLoadQueue", this,
+      &UntrustedModulesProcessor::BackgroundProcessModuleLoadQueue));
+
+  mThread->Dispatch(runnable.forget(), NS_DISPATCH_NORMAL);
+}
+
+void UntrustedModulesProcessor::Enqueue(
+    glue::EnhancedModuleLoadInfo&& aModLoadInfo) {
+  if (mStatus == Status::ShuttingDown) {
+    return;
+  }
+
+  {
+    MutexAutoLock lock(mThreadHandleMutex);
+    DWORD bgThreadId = ::GetThreadId(mThreadHandle);
+    if (aModLoadInfo.mNtLoadInfo.mThreadId == bgThreadId) {
+      // Exclude loads that were caused by our own background thread
+      return;
+    }
+  }
+
+  MutexAutoLock lock(mUnprocessedMutex);
+
+  mUnprocessedModuleLoads.insertBack(
+      new UnprocessedModuleLoadInfoContainer(std::move(aModLoadInfo)));
+
+  ScheduleNonEmptyQueueProcessing(lock);
+}
+
+void UntrustedModulesProcessor::Enqueue(ModuleLoadInfoVec&& aEvents) {
+  if (mStatus == Status::ShuttingDown) {
+    return;
+  }
+
+  // We do not need to attempt to exclude our background thread in this case
+  // because |aEvents| was accumulated prior to |mThread|'s existence.
+
+  MutexAutoLock lock(mUnprocessedMutex);
+
+  for (auto& event : aEvents) {
+    mUnprocessedModuleLoads.insertBack(
+        new UnprocessedModuleLoadInfoContainer(std::move(event)));
+  }
+
+  ScheduleNonEmptyQueueProcessing(lock);
+}
+
+void UntrustedModulesProcessor::AssertRunningOnLazyIdleThread() {
+#if defined(DEBUG)
+  MOZ_ASSERT(mThread->IsOnCurrentThread());
+#endif  // defined(DEBUG)
+}
+
+RefPtr<UntrustedModulesPromise> UntrustedModulesProcessor::GetProcessedData() {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  // Clear any background priority in case background processing is running.
+  {
+    MutexAutoLock lock(mThreadHandleMutex);
+    BackgroundPriorityRegion::Clear(mThreadHandle);
+  }
+
+  RefPtr<UntrustedModulesProcessor> self(this);
+  return InvokeAsync(mThread, __func__, [self = std::move(self)]() {
+    return self->GetProcessedDataInternal();
+  });
+}
+
+RefPtr<ModulesTrustPromise> UntrustedModulesProcessor::GetModulesTrust(
+    ModulePaths&& aModPaths, bool aRunAtNormalPriority) {
+  MOZ_ASSERT(XRE_IsParentProcess() && NS_IsMainThread());
+
+  if (!IsReadyForBackgroundProcessing()) {
+    return ModulesTrustPromise::CreateAndReject(
+        NS_ERROR_ILLEGAL_DURING_SHUTDOWN, __func__);
+  }
+
+  RefPtr<UntrustedModulesProcessor> self(this);
+  auto run = [self = std::move(self), modPaths = std::move(aModPaths),
+              runNormal = aRunAtNormalPriority]() mutable {
+    return self->GetModulesTrustInternal(std::move(modPaths), runNormal);
+  };
+
+  if (aRunAtNormalPriority) {
+    // Clear any background priority in case background processing is running.
+    {
+      MutexAutoLock lock(mThreadHandleMutex);
+      BackgroundPriorityRegion::Clear(mThreadHandle);
+    }
+
+    return InvokeAsync(mThread, __func__, std::move(run));
+  }
+
+  RefPtr<ModulesTrustPromise::Private> p(
+      new ModulesTrustPromise::Private(__func__));
+  nsCOMPtr<nsISerialEventTarget> evtTarget(mThread);
+  const char* source = __func__;
+
+  auto runWrap = [evtTarget = std::move(evtTarget), p, source,
+                  run = std::move(run)]() mutable -> void {
+    InvokeAsync(evtTarget, source, std::move(run))->ChainTo(p.forget(), source);
+  };
+
+  nsCOMPtr<nsIRunnable> idleRunnable(
+      NS_NewRunnableFunction(source, std::move(runWrap)));
+
+  nsresult rv = NS_DispatchToMainThreadQueue(idleRunnable.forget(),
+                                             EventQueuePriority::Idle);
+  if (NS_FAILED(rv)) {
+    p->Reject(rv, source);
+  }
+
+  return p;
+}
+
+RefPtr<UntrustedModulesPromise>
+UntrustedModulesProcessor::GetProcessedDataInternal() {
+  AssertRunningOnLazyIdleThread();
+  if (!XRE_IsParentProcess()) {
+    return GetProcessedDataInternalChildProcess();
+  }
+
+  ProcessModuleLoadQueue();
+
+  return GetAllProcessedData(__func__);
+}
+
+RefPtr<UntrustedModulesPromise> UntrustedModulesProcessor::GetAllProcessedData(
+    const char* aSource) {
+  AssertRunningOnLazyIdleThread();
+
+  UntrustedModulesData result;
+
+  if (!mProcessedModuleLoads) {
+    return UntrustedModulesPromise::CreateAndResolve(Nothing(), aSource);
+  }
+
+  result.Swap(mProcessedModuleLoads);
+
+  result.mElapsed = TimeStamp::Now() - TimeStamp::ProcessCreation();
+
+  return UntrustedModulesPromise::CreateAndResolve(
+      Some(UntrustedModulesData(std::move(result))), aSource);
+}
+
+RefPtr<UntrustedModulesPromise>
+UntrustedModulesProcessor::GetProcessedDataInternalChildProcess() {
+  AssertRunningOnLazyIdleThread();
+  MOZ_ASSERT(!XRE_IsParentProcess());
+
+  RefPtr<GetModulesTrustPromise> whenProcessed(
+      ProcessModuleLoadQueueChildProcess(Priority::Default));
+
+  RefPtr<UntrustedModulesProcessor> self(this);
+  RefPtr<UntrustedModulesPromise::Private> p(
+      new UntrustedModulesPromise::Private(__func__));
+  nsCOMPtr<nsISerialEventTarget> evtTarget(mThread);
+
+  const char* source = __func__;
+  auto completionRoutine = [evtTarget = std::move(evtTarget), p,
+                            self = std::move(self), source,
+                            whenProcessed = std::move(whenProcessed)]() {
+    MOZ_ASSERT(NS_IsMainThread());
+    if (!self->IsReadyForBackgroundProcessing()) {
+      // We can't do any more work, just reject all the things
+      whenProcessed->Then(
+          GetMainThreadSerialEventTarget(), source,
+          [p, source](Maybe<ModulesMapResultWithLoads>&& aResult) {
+            p->Reject(NS_ERROR_ILLEGAL_DURING_SHUTDOWN, source);
+          },
+          [p, source](nsresult aRv) { p->Reject(aRv, source); });
+      return;
+    }
+
+    whenProcessed->Then(
+        evtTarget, source,
+        [p, self = std::move(self),
+         source](Maybe<ModulesMapResultWithLoads>&& aResult) mutable {
+          if (aResult.isSome()) {
+            self->CompleteProcessing(std::move(aResult.ref()));
+          }
+          self->GetAllProcessedData(source)->ChainTo(p.forget(), source);
+        },
+        [p, source](nsresult aRv) { p->Reject(aRv, source); });
+  };
+
+  // We always send |completionRoutine| on a trip through the main thread
+  // due to some subtlety with |mThread| being a LazyIdleThread: we can only
+  // Dispatch or Then to |mThread| from its creating thread, which is the
+  // main thread. Hopefully we can get rid of this in the future and just
+  // invoke whenProcessed->Then() directly.
+  nsresult rv = NS_DispatchToMainThread(
+      NS_NewRunnableFunction(__func__, std::move(completionRoutine)));
+  MOZ_ASSERT(NS_SUCCEEDED(rv));
+  if (NS_FAILED(rv)) {
+    p->Reject(rv, __func__);
+  }
+
+  return p;
+}
+
+void UntrustedModulesProcessor::BackgroundProcessModuleLoadQueue() {
+  if (!IsReadyForBackgroundProcessing()) {
+    return;
+  }
+
+  BackgroundPriorityRegion bgRgn;
+
+  if (!IsReadyForBackgroundProcessing()) {
+    return;
+  }
+
+  ProcessModuleLoadQueue();
+}
+
+RefPtr<ModuleRecord> UntrustedModulesProcessor::GetOrAddModuleRecord(
+    const ModuleEvaluator& aModEval, const nsAString& aResolvedNtPath) {
+  MOZ_ASSERT(XRE_IsParentProcess());
+
+  MutexAutoLock lock(mModuleCacheMutex);
+  return mGlobalModuleCache.WithEntryHandle(
+      aResolvedNtPath, [&](auto&& addPtr) -> RefPtr<ModuleRecord> {
+        if (addPtr) {
+          return addPtr.Data();
+        }
+
+        RefPtr<ModuleRecord> newMod(new ModuleRecord(aResolvedNtPath));
+        if (!(*newMod)) {
+          return nullptr;
+        }
+
+        Maybe<ModuleTrustFlags> maybeTrust = aModEval.GetTrust(*newMod);
+        if (maybeTrust.isNothing()) {
+          return nullptr;
+        }
+
+        newMod->mTrustFlags = maybeTrust.value();
+
+        return addPtr.Insert(std::move(newMod));
+      });
+}
+
+RefPtr<ModuleRecord> UntrustedModulesProcessor::GetModuleRecord(
+    const ModulesMap& aModules,
+    const glue::EnhancedModuleLoadInfo& aModuleLoadInfo) {
+  MOZ_ASSERT(!XRE_IsParentProcess());
+
+  return aModules.Get(aModuleLoadInfo.mNtLoadInfo.mSectionName.AsString());
+}
+
+void UntrustedModulesProcessor::BackgroundProcessModuleLoadQueueChildProcess() {
+  RefPtr<GetModulesTrustPromise> whenProcessed(
+      ProcessModuleLoadQueueChildProcess(Priority::Background));
+
+  RefPtr<UntrustedModulesProcessor> self(this);
+  nsCOMPtr<nsISerialEventTarget> evtTarget(mThread);
+
+  const char* source = __func__;
+  auto completionRoutine = [evtTarget = std::move(evtTarget),
+                            self = std::move(self), source,
+                            whenProcessed = std::move(whenProcessed)]() {
+    MOZ_ASSERT(NS_IsMainThread());
+    if (!self->IsReadyForBackgroundProcessing()) {
+      // We can't do any more work, just no-op
+      whenProcessed->Then(
+          GetMainThreadSerialEventTarget(), source,
+          [](Maybe<ModulesMapResultWithLoads>&& aResult) {},
+          [](nsresult aRv) {});
+      return;
+    }
+
+    whenProcessed->Then(
+        evtTarget, source,
+        [self = std::move(self)](Maybe<ModulesMapResultWithLoads>&& aResult) {
+          if (aResult.isNothing() || !self->IsReadyForBackgroundProcessing()) {
+            // Nothing to do
+            return;
+          }
+
+          BackgroundPriorityRegion bgRgn;
+          self->CompleteProcessing(std::move(aResult.ref()));
+        },
+        [](nsresult aRv) {});
+  };
+
+  // We always send |completionRoutine| on a trip through the main thread
+  // due to some subtlety with |mThread| being a LazyIdleThread: we can only
+  // Dispatch or Then to |mThread| from its creating thread, which is the
+  // main thread. Hopefully we can get rid of this in the future and just
+  // invoke whenProcessed->Then() directly.
+  DebugOnly<nsresult> rv = NS_DispatchToMainThread(
+      NS_NewRunnableFunction(__func__, std::move(completionRoutine)));
+  MOZ_ASSERT(NS_SUCCEEDED(rv));
+}
+
+UnprocessedModuleLoads UntrustedModulesProcessor::ExtractLoadingEventsToProcess(
+    size_t aMaxLength) {
+  UnprocessedModuleLoads loadsToProcess;
+
+  MutexAutoLock lock(mUnprocessedMutex);
+  CancelScheduledProcessing(lock);
+
+  loadsToProcess.splice(0, mUnprocessedModuleLoads, 0, aMaxLength);
+  return loadsToProcess;
+}
+
+// This function contains multiple IsReadyForBackgroundProcessing() checks so
+// that we can quickly bail out at the first sign of shutdown. This may be
+// important when the current thread is running under background priority.
+void UntrustedModulesProcessor::ProcessModuleLoadQueue() {
+  AssertRunningOnLazyIdleThread();
+  if (!XRE_IsParentProcess()) {
+    BackgroundProcessModuleLoadQueueChildProcess();
+    return;
+  }
+
+  UnprocessedModuleLoads loadsToProcess =
+      ExtractLoadingEventsToProcess(UntrustedModulesData::kMaxEvents);
+  if (!IsReadyForBackgroundProcessing() || loadsToProcess.isEmpty()) {
+    return;
+  }
+
+  ModuleEvaluator modEval;
+  MOZ_ASSERT(!!modEval);
+  if (!modEval) {
+    return;
+  }
+
+  Telemetry::BatchProcessedStackGenerator stackProcessor;
+  Maybe<double> maybeXulLoadDuration;
+  Vector<Telemetry::ProcessedStack> processedStacks;
+  UntrustedModuleLoadingEvents processedEvents;
+  uint32_t sanitizationFailures = 0;
+  uint32_t trustTestFailures = 0;
+
+  for (UnprocessedModuleLoadInfoContainer* container : loadsToProcess) {
+    glue::EnhancedModuleLoadInfo& entry = container->mInfo;
+
+    if (!IsReadyForBackgroundProcessing()) {
+      return;
+    }
+
+    RefPtr<ModuleRecord> module(GetOrAddModuleRecord(
+        modEval, entry.mNtLoadInfo.mSectionName.AsString()));
+    if (!module) {
+      // We failed to obtain trust information about the module.
+      // Don't include test failures in the ping to avoid flooding it.
+      ++trustTestFailures;
+      continue;
+    }
+
+    if (!IsReadyForBackgroundProcessing()) {
+      return;
+    }
+
+    glue::EnhancedModuleLoadInfo::BacktraceType backtrace =
+        std::move(entry.mNtLoadInfo.mBacktrace);
+    ProcessedModuleLoadEvent event(std::move(entry), std::move(module));
+
+    if (!event) {
+      // We don't have a sanitized DLL path, so we cannot include this event
+      // for privacy reasons.
+      ++sanitizationFailures;
+      continue;
+    }
+
+    if (!IsReadyForBackgroundProcessing()) {
+      return;
+    }
+
+    if (event.IsTrusted()) {
+      if (event.IsXULLoad()) {
+        maybeXulLoadDuration = event.mLoadDurationMS;
+      }
+
+      // Trusted modules are not included in the ping
+      continue;
+    }
+
+    mProcessedModuleLoads.mModules.LookupOrInsert(
+        event.mModule->mResolvedNtName, event.mModule);
+
+    if (!IsReadyForBackgroundProcessing()) {
+      return;
+    }
+
+    Telemetry::ProcessedStack processedStack =
+        stackProcessor.GetStackAndModules(backtrace);
+
+    if (!IsReadyForBackgroundProcessing()) {
+      return;
+    }
+
+    Unused << processedStacks.emplaceBack(std::move(processedStack));
+    processedEvents.insertBack(
+        new ProcessedModuleLoadEventContainer(std::move(event)));
+  }
+
+  if (processedStacks.empty() && processedEvents.isEmpty() &&
+      !sanitizationFailures && !trustTestFailures) {
+    // Nothing to save
+    return;
+  }
+
+  if (!IsReadyForBackgroundProcessing()) {
+    return;
+  }
+
+  // Modules have been added to mProcessedModuleLoads.mModules
+  // in the loop above.  Passing an empty ModulesMap to AddNewLoads.
+  mProcessedModuleLoads.AddNewLoads(ModulesMap{}, std::move(processedEvents),
+                                    std::move(processedStacks));
+  if (maybeXulLoadDuration) {
+    MOZ_ASSERT(!mProcessedModuleLoads.mXULLoadDurationMS);
+    mProcessedModuleLoads.mXULLoadDurationMS = maybeXulLoadDuration;
+  }
+
+  mProcessedModuleLoads.mSanitizationFailures += sanitizationFailures;
+  mProcessedModuleLoads.mTrustTestFailures += trustTestFailures;
+}
+
+template <typename ActorT>
+static RefPtr<GetModulesTrustIpcPromise> SendGetModulesTrust(
+    ActorT* aActor, ModulePaths&& aModPaths, bool aRunAtNormalPriority) {
+  MOZ_ASSERT(NS_IsMainThread());
+  return aActor->SendGetModulesTrust(std::move(aModPaths),
+                                     aRunAtNormalPriority);
+}
+
+RefPtr<GetModulesTrustIpcPromise>
+UntrustedModulesProcessor::SendGetModulesTrust(ModulePaths&& aModules,
+                                               Priority aPriority) {
+  MOZ_ASSERT(NS_IsMainThread());
+  bool runNormal = aPriority == Priority::Default;
+
+  switch (XRE_GetProcessType()) {
+    case GeckoProcessType_Content: {
+      return ::mozilla::SendGetModulesTrust(dom::ContentChild::GetSingleton(),
+                                            std::move(aModules), runNormal);
+    }
+    case GeckoProcessType_RDD: {
+      return ::mozilla::SendGetModulesTrust(RDDParent::GetSingleton(),
+                                            std::move(aModules), runNormal);
+    }
+    case GeckoProcessType_Socket: {
+      return ::mozilla::SendGetModulesTrust(
+          net::SocketProcessChild::GetSingleton(), std::move(aModules),
+          runNormal);
+    }
+    case GeckoProcessType_Utility: {
+      return ::mozilla::SendGetModulesTrust(
+          ipc::UtilityProcessChild::GetSingleton().get(), std::move(aModules),
+          runNormal);
+    }
+    default: {
+      MOZ_ASSERT_UNREACHABLE("Unsupported process type");
+      return GetModulesTrustIpcPromise::CreateAndReject(
+          ipc::ResponseRejectReason::SendError, __func__);
+    }
+  }
+}
+
+/**
+ * This method works very similarly to ProcessModuleLoadQueue, with the
+ * exception that a sandboxed child process does not have sufficient rights to
+ * be able to evaluate a module's trustworthiness. Instead, we accumulate the
+ * resolved paths for all of the modules in this batch and send them to the
+ * parent to determine trustworthiness.
+ *
+ * The parent process returns a list of untrusted modules and invokes
+ * CompleteProcessing to handle the remainder of the process.
+ *
+ * By doing it this way, we minimize the amount of data that needs to be sent
+ * over IPC and avoid the need to process every load's metadata only
+ * to throw most of it away (since most modules will be trusted).
+ */
+RefPtr<UntrustedModulesProcessor::GetModulesTrustPromise>
+UntrustedModulesProcessor::ProcessModuleLoadQueueChildProcess(
+    UntrustedModulesProcessor::Priority aPriority) {
+  AssertRunningOnLazyIdleThread();
+  MOZ_ASSERT(!XRE_IsParentProcess());
+
+  UnprocessedModuleLoads loadsToProcess =
+      ExtractLoadingEventsToProcess(UntrustedModulesData::kMaxEvents);
+  if (loadsToProcess.isEmpty()) {
+    // Nothing to process
+    return GetModulesTrustPromise::CreateAndResolve(Nothing(), __func__);
+  }
+
+  if (!IsReadyForBackgroundProcessing()) {
+    return GetModulesTrustPromise::CreateAndReject(
+        NS_ERROR_ILLEGAL_DURING_SHUTDOWN, __func__);
+  }
+
+  nsTHashtable<nsStringCaseInsensitiveHashKey> moduleNtPathSet;
+
+  // Build a set of modules to be processed by the parent
+  for (UnprocessedModuleLoadInfoContainer* container : loadsToProcess) {
+    glue::EnhancedModuleLoadInfo& entry = container->mInfo;
+
+    if (!IsReadyForBackgroundProcessing()) {
+      return GetModulesTrustPromise::CreateAndReject(
+          NS_ERROR_ILLEGAL_DURING_SHUTDOWN, __func__);
+    }
+
+    moduleNtPathSet.PutEntry(entry.mNtLoadInfo.mSectionName.AsString());
+  }
+
+  if (!IsReadyForBackgroundProcessing()) {
+    return GetModulesTrustPromise::CreateAndReject(
+        NS_ERROR_ILLEGAL_DURING_SHUTDOWN, __func__);
+  }
+
+  MOZ_ASSERT(!moduleNtPathSet.IsEmpty());
+  if (moduleNtPathSet.IsEmpty()) {
+    // Nothing to process
+    return GetModulesTrustPromise::CreateAndResolve(Nothing(), __func__);
+  }
+
+  ModulePaths moduleNtPaths(std::move(moduleNtPathSet));
+
+  if (!IsReadyForBackgroundProcessing()) {
+    return GetModulesTrustPromise::CreateAndReject(
+        NS_ERROR_ILLEGAL_DURING_SHUTDOWN, __func__);
+  }
+
+  RefPtr<UntrustedModulesProcessor> self(this);
+
+  auto invoker = [self = std::move(self),
+                  moduleNtPaths = std::move(moduleNtPaths),
+                  priority = aPriority]() mutable {
+    return self->SendGetModulesTrust(std::move(moduleNtPaths), priority);
+  };
+
+  RefPtr<GetModulesTrustPromise::Private> p(
+      new GetModulesTrustPromise::Private(__func__));
+
+  if (!IsReadyForBackgroundProcessing()) {
+    p->Reject(NS_ERROR_ILLEGAL_DURING_SHUTDOWN, __func__);
+    return p;
+  }
+
+  // Send the IPC request via the main thread
+  InvokeAsync(GetMainThreadSerialEventTarget(), __func__, std::move(invoker))
+      ->Then(
+          GetMainThreadSerialEventTarget(), __func__,
+          [p, loads = std::move(loadsToProcess)](
+              Maybe<ModulesMapResult>&& aResult) mutable {
+            ModulesMapResultWithLoads result(std::move(aResult),
+                                             std::move(loads));
+            p->Resolve(Some(ModulesMapResultWithLoads(std::move(result))),
+                       __func__);
+          },
+          [p](ipc::ResponseRejectReason aReason) {
+            p->Reject(NS_ERROR_FAILURE, __func__);
+          });
+
+  return p;
+}
+
+void UntrustedModulesProcessor::CompleteProcessing(
+    UntrustedModulesProcessor::ModulesMapResultWithLoads&& aModulesAndLoads) {
+  MOZ_ASSERT(!XRE_IsParentProcess());
+  AssertRunningOnLazyIdleThread();
+
+  if (!IsReadyForBackgroundProcessing()) {
+    return;
+  }
+
+  if (aModulesAndLoads.mModMapResult.isNothing()) {
+    // No untrusted modules in this batch, nothing to save.
+    return;
+  }
+
+  // This map only contains information about modules deemed to be untrusted,
+  // plus xul.dll. Any module referenced by load requests that is *not* in the
+  // map is deemed to be trusted.
+  ModulesMap& modules = aModulesAndLoads.mModMapResult.ref().mModules;
+  const uint32_t& trustTestFailures =
+      aModulesAndLoads.mModMapResult.ref().mTrustTestFailures;
+  UnprocessedModuleLoads& loads = aModulesAndLoads.mLoads;
+
+  if (modules.IsEmpty() && !trustTestFailures) {
+    // No data, nothing to save.
+    return;
+  }
+
+  if (!IsReadyForBackgroundProcessing()) {
+    return;
+  }
+
+  Telemetry::BatchProcessedStackGenerator stackProcessor;
+
+  Maybe<double> maybeXulLoadDuration;
+  Vector<Telemetry::ProcessedStack> processedStacks;
+  UntrustedModuleLoadingEvents processedEvents;
+  uint32_t sanitizationFailures = 0;
+
+  if (!modules.IsEmpty()) {
+    for (UnprocessedModuleLoadInfoContainer* container : loads) {
+      glue::EnhancedModuleLoadInfo& item = container->mInfo;
+      if (!IsReadyForBackgroundProcessing()) {
+        return;
+      }
+
+      RefPtr<ModuleRecord> module(GetModuleRecord(modules, item));
+      if (!module) {
+        // If module is null then |item| is trusted
+        continue;
+      }
+
+      if (!IsReadyForBackgroundProcessing()) {
+        return;
+      }
+
+      glue::EnhancedModuleLoadInfo::BacktraceType backtrace =
+          std::move(item.mNtLoadInfo.mBacktrace);
+      ProcessedModuleLoadEvent event(std::move(item), std::move(module));
+
+      if (!IsReadyForBackgroundProcessing()) {
+        return;
+      }
+
+      if (!event) {
+        // We don't have a sanitized DLL path, so we cannot include this event
+        // for privacy reasons.
+        ++sanitizationFailures;
+        continue;
+      }
+
+      if (!IsReadyForBackgroundProcessing()) {
+        return;
+      }
+
+      if (event.IsXULLoad()) {
+        maybeXulLoadDuration = event.mLoadDurationMS;
+        // We saved the XUL load duration, but it is still trusted, so we
+        // continue.
+        continue;
+      }
+
+      if (!IsReadyForBackgroundProcessing()) {
+        return;
+      }
+
+      Telemetry::ProcessedStack processedStack =
+          stackProcessor.GetStackAndModules(backtrace);
+
+      Unused << processedStacks.emplaceBack(std::move(processedStack));
+      processedEvents.insertBack(
+          new ProcessedModuleLoadEventContainer(std::move(event)));
+    }
+  }
+
+  if (processedStacks.empty() && processedEvents.isEmpty() &&
+      !sanitizationFailures && !trustTestFailures) {
+    // Nothing to save
+    return;
+  }
+
+  if (!IsReadyForBackgroundProcessing()) {
+    return;
+  }
+
+  mProcessedModuleLoads.AddNewLoads(modules, std::move(processedEvents),
+                                    std::move(processedStacks));
+  if (maybeXulLoadDuration) {
+    MOZ_ASSERT(!mProcessedModuleLoads.mXULLoadDurationMS);
+    mProcessedModuleLoads.mXULLoadDurationMS = maybeXulLoadDuration;
+  }
+
+  mProcessedModuleLoads.mSanitizationFailures += sanitizationFailures;
+  mProcessedModuleLoads.mTrustTestFailures += trustTestFailures;
+}
+
+// The thread priority of this job should match the priority that the child
+// process is running with, as specified by |aRunAtNormalPriority|.
+RefPtr<ModulesTrustPromise> UntrustedModulesProcessor::GetModulesTrustInternal(
+    ModulePaths&& aModPaths, bool aRunAtNormalPriority) {
+  MOZ_ASSERT(XRE_IsParentProcess());
+  AssertRunningOnLazyIdleThread();
+
+  if (!IsReadyForBackgroundProcessing()) {
+    return ModulesTrustPromise::CreateAndReject(
+        NS_ERROR_ILLEGAL_DURING_SHUTDOWN, __func__);
+  }
+
+  if (aRunAtNormalPriority) {
+    return GetModulesTrustInternal(std::move(aModPaths));
+  }
+
+  BackgroundPriorityRegion bgRgn;
+  return GetModulesTrustInternal(std::move(aModPaths));
+}
+
+// For each module in |aModPaths|, evaluate its trustworthiness and only send
+// ModuleRecords for untrusted modules back to the child process. We also save
+// XUL's ModuleRecord so that the child process may report XUL's load time.
+RefPtr<ModulesTrustPromise> UntrustedModulesProcessor::GetModulesTrustInternal(
+    ModulePaths&& aModPaths) {
+  MOZ_ASSERT(XRE_IsParentProcess());
+  AssertRunningOnLazyIdleThread();
+
+  ModulesMapResult result;
+
+  ModulesMap& modMap = result.mModules;
+  uint32_t& trustTestFailures = result.mTrustTestFailures;
+
+  ModuleEvaluator modEval;
+  MOZ_ASSERT(!!modEval);
+  if (!modEval) {
+    return ModulesTrustPromise::CreateAndReject(NS_ERROR_FAILURE, __func__);
+  }
+
+  for (auto& resolvedNtPath :
+       aModPaths.mModuleNtPaths.as<ModulePaths::VecType>()) {
+    if (!IsReadyForBackgroundProcessing()) {
+      return ModulesTrustPromise::CreateAndReject(
+          NS_ERROR_ILLEGAL_DURING_SHUTDOWN, __func__);
+    }
+
+    MOZ_ASSERT(!resolvedNtPath.IsEmpty());
+    if (resolvedNtPath.IsEmpty()) {
+      continue;
+    }
+
+    RefPtr<ModuleRecord> module(GetOrAddModuleRecord(modEval, resolvedNtPath));
+    if (!module) {
+      // We failed to obtain trust information.
+      ++trustTestFailures;
+      continue;
+    }
+
+    if (!IsReadyForBackgroundProcessing()) {
+      return ModulesTrustPromise::CreateAndReject(
+          NS_ERROR_ILLEGAL_DURING_SHUTDOWN, __func__);
+    }
+
+    if (module->IsTrusted() && !module->IsXUL()) {
+      // If the module is trusted we exclude it from results, unless it's XUL.
+      // (We save XUL so that the child process may report XUL's load time)
+      continue;
+    }
+
+    if (!IsReadyForBackgroundProcessing()) {
+      return ModulesTrustPromise::CreateAndReject(
+          NS_ERROR_ILLEGAL_DURING_SHUTDOWN, __func__);
+    }
+
+    modMap.InsertOrUpdate(resolvedNtPath, std::move(module));
+  }
+
+  return ModulesTrustPromise::CreateAndResolve(std::move(result), __func__);
+}
+
+}  // namespace mozilla
diff --git a/toolkit/xre/dllservices/UntrustedModulesProcessor.h b/toolkit/xre/dllservices/UntrustedModulesProcessor.h
new file mode 100644
index 0000000000..b91d88961a
--- /dev/null
+++ b/toolkit/xre/dllservices/UntrustedModulesProcessor.h
@@ -0,0 +1,185 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_UntrustedModulesProcessor_h
+#define mozilla_UntrustedModulesProcessor_h
+
+#include "mozilla/Atomics.h"
+#include "mozilla/DebugOnly.h"
+#include "mozilla/glue/WindowsDllServices.h"
+#include "mozilla/LazyIdleThread.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/MozPromise.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/UntrustedModulesData.h"
+#include "mozilla/Vector.h"
+#include "mozilla/WinHeaderOnlyUtils.h"
+#include "nsCOMPtr.h"
+#include "nsIObserver.h"
+#include "nsIRunnable.h"
+#include "nsISupportsImpl.h"
+#include "nsString.h"
+
+namespace mozilla {
+
+class ModuleEvaluator;
+
+using UntrustedModulesPromise =
+    MozPromise<Maybe<UntrustedModulesData>, nsresult, true>;
+
+using ModulesTrustPromise = MozPromise<ModulesMapResult, nsresult, true>;
+
+using GetModulesTrustIpcPromise =
+    MozPromise<Maybe<ModulesMapResult>, ipc::ResponseRejectReason, true>;
+
+struct UnprocessedModuleLoadInfoContainer final
+    : public LinkedListElement<UnprocessedModuleLoadInfoContainer> {
+  glue::EnhancedModuleLoadInfo mInfo;
+
+  template <typename T>
+  explicit UnprocessedModuleLoadInfoContainer(T&& aInfo)
+      : mInfo(std::move(aInfo)) {}
+
+  UnprocessedModuleLoadInfoContainer(
+      const UnprocessedModuleLoadInfoContainer&) = delete;
+  UnprocessedModuleLoadInfoContainer& operator=(
+      const UnprocessedModuleLoadInfoContainer&) = delete;
+};
+using UnprocessedModuleLoads =
+    AutoCleanLinkedList<UnprocessedModuleLoadInfoContainer>;
+
+class UntrustedModulesProcessor final : public nsIObserver,
+                                        public nsIThreadPoolListener {
+ public:
+  static RefPtr<UntrustedModulesProcessor> Create(
+      bool aIsReadyForBackgroundProcessing);
+
+  NS_DECL_THREADSAFE_ISUPPORTS
+  NS_DECL_NSIOBSERVER
+  NS_DECL_NSITHREADPOOLLISTENER
+
+  // Called to check if the parent process is ready when a child process
+  // is spanwed
+  bool IsReadyForBackgroundProcessing() const;
+
+  // Called by DLL Services to explicitly begin shutting down
+  void Disable();
+
+  // Called by DLL Services to submit module load data to the processor
+  void Enqueue(glue::EnhancedModuleLoadInfo&& aModLoadInfo);
+  void Enqueue(ModuleLoadInfoVec&& aEvents);
+
+  // Called by telemetry to retrieve the processed data
+  RefPtr<UntrustedModulesPromise> GetProcessedData();
+
+  // Called by IPC actors in the parent process to evaluate module trust
+  // on behalf of child processes
+  RefPtr<ModulesTrustPromise> GetModulesTrust(ModulePaths&& aModPaths,
+                                              bool aRunAtNormalPriority);
+
+  UntrustedModulesProcessor(const UntrustedModulesProcessor&) = delete;
+  UntrustedModulesProcessor(UntrustedModulesProcessor&&) = delete;
+  UntrustedModulesProcessor& operator=(const UntrustedModulesProcessor&) =
+      delete;
+  UntrustedModulesProcessor& operator=(UntrustedModulesProcessor&&) = delete;
+
+ private:
+  ~UntrustedModulesProcessor() = default;
+  explicit UntrustedModulesProcessor(bool aIsReadyForBackgroundProcessing);
+
+  static bool IsSupportedProcessType();
+
+  void AddObservers();
+  void RemoveObservers();
+
+  void ScheduleNonEmptyQueueProcessing(const MutexAutoLock& aProofOfLock)
+      MOZ_REQUIRES(mUnprocessedMutex);
+  void CancelScheduledProcessing(const MutexAutoLock& aProofOfLock)
+      MOZ_REQUIRES(mUnprocessedMutex);
+  void DispatchBackgroundProcessing();
+
+  void BackgroundProcessModuleLoadQueue();
+  void ProcessModuleLoadQueue();
+
+  // Extract the loading events from mUnprocessedModuleLoads to process and
+  // move to mProcessedModuleLoads.  It's guaranteed that the total length of
+  // mProcessedModuleLoads will not exceed |aMaxLength|.
+  UnprocessedModuleLoads ExtractLoadingEventsToProcess(size_t aMaxLength);
+
+  class ModulesMapResultWithLoads final {
+   public:
+    ModulesMapResultWithLoads(Maybe<ModulesMapResult>&& aModMapResult,
+                              UnprocessedModuleLoads&& aLoads)
+        : mModMapResult(std::move(aModMapResult)), mLoads(std::move(aLoads)) {}
+    Maybe<ModulesMapResult> mModMapResult;
+    UnprocessedModuleLoads mLoads;
+  };
+
+  using GetModulesTrustPromise =
+      MozPromise<Maybe<ModulesMapResultWithLoads>, nsresult, true>;
+
+  enum class Priority { Default, Background };
+
+  RefPtr<GetModulesTrustPromise> ProcessModuleLoadQueueChildProcess(
+      Priority aPriority);
+  void BackgroundProcessModuleLoadQueueChildProcess();
+
+  void AssertRunningOnLazyIdleThread();
+
+  RefPtr<UntrustedModulesPromise> GetProcessedDataInternal();
+  RefPtr<UntrustedModulesPromise> GetProcessedDataInternalChildProcess();
+
+  RefPtr<ModulesTrustPromise> GetModulesTrustInternal(
+      ModulePaths&& aModPaths, bool aRunAtNormalPriority);
+  RefPtr<ModulesTrustPromise> GetModulesTrustInternal(ModulePaths&& aModPaths);
+
+  // This function is only called by the parent process
+  RefPtr<ModuleRecord> GetOrAddModuleRecord(const ModuleEvaluator& aModEval,
+                                            const nsAString& aResolvedNtPath);
+
+  // Only called by child processes
+  RefPtr<ModuleRecord> GetModuleRecord(
+      const ModulesMap& aModules,
+      const glue::EnhancedModuleLoadInfo& aModuleLoadInfo);
+
+  RefPtr<GetModulesTrustIpcPromise> SendGetModulesTrust(ModulePaths&& aModules,
+                                                        Priority aPriority);
+
+  void CompleteProcessing(ModulesMapResultWithLoads&& aModulesAndLoads);
+  RefPtr<UntrustedModulesPromise> GetAllProcessedData(const char* aSource);
+
+ private:
+  RefPtr<LazyIdleThread> mThread;
+
+  Mutex mThreadHandleMutex;
+  Mutex mUnprocessedMutex;
+  Mutex mModuleCacheMutex;
+
+  // Windows HANDLE for the currently active mThread, if active.
+  nsAutoHandle mThreadHandle MOZ_GUARDED_BY(mThreadHandleMutex);
+
+  // The members in this group are protected by mUnprocessedMutex
+  UnprocessedModuleLoads mUnprocessedModuleLoads
+      MOZ_GUARDED_BY(mUnprocessedMutex);
+  nsCOMPtr<nsIRunnable> mIdleRunnable MOZ_GUARDED_BY(mUnprocessedMutex);
+
+  // This member must only be touched on mThread
+  UntrustedModulesData mProcessedModuleLoads;
+
+  enum class Status { StartingUp, Allowed, ShuttingDown };
+
+  // This member may be touched by any thread
+  Atomic<Status> mStatus;
+
+  // Cache all module records, including ones trusted and ones loaded in
+  // child processes, in the browser process to avoid evaluating the same
+  // module multiple times
+  ModulesMap mGlobalModuleCache MOZ_GUARDED_BY(mModuleCacheMutex);
+};
+
+}  // namespace mozilla
+
+#endif  // mozilla_UntrustedModulesProcessor_h
diff --git a/toolkit/xre/dllservices/WinDllServices.cpp b/toolkit/xre/dllservices/WinDllServices.cpp
new file mode 100644
index 0000000000..b98a15252b
--- /dev/null
+++ b/toolkit/xre/dllservices/WinDllServices.cpp
@@ -0,0 +1,142 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/WinDllServices.h"
+
+#include <windows.h>
+#include <psapi.h>
+
+#include "mozilla/ClearOnShutdown.h"
+#include "mozilla/SchedulerGroup.h"
+#include "mozilla/Services.h"
+#include "mozilla/StaticLocalPtr.h"
+#include "mozilla/UntrustedModulesProcessor.h"
+#include "nsCOMPtr.h"
+#include "nsIObserverService.h"
+#include "nsString.h"
+#include "nsXULAppAPI.h"
+
+namespace mozilla {
+
+const char* DllServices::kTopicDllLoadedMainThread = "dll-loaded-main-thread";
+const char* DllServices::kTopicDllLoadedNonMainThread =
+    "dll-loaded-non-main-thread";
+
+/* static */
+DllServices* DllServices::Get() {
+  static StaticLocalRefPtr<DllServices> sInstance(
+      []() -> already_AddRefed<DllServices> {
+        RefPtr<DllServices> dllSvc(new DllServices());
+        // Full DLL services require XPCOM, which GMP doesn't have
+        if (XRE_IsGMPluginProcess()) {
+          dllSvc->EnableBasic();
+        } else {
+          dllSvc->EnableFull();
+        }
+
+        auto setClearOnShutdown = [ptr = &sInstance]() -> void {
+          ClearOnShutdown(ptr);
+        };
+
+        if (NS_IsMainThread()) {
+          setClearOnShutdown();
+          return dllSvc.forget();
+        }
+
+        SchedulerGroup::Dispatch(
+            TaskCategory::Other,
+            NS_NewRunnableFunction("mozilla::DllServices::Get",
+                                   std::move(setClearOnShutdown)));
+
+        return dllSvc.forget();
+      }());
+
+  return sInstance;
+}
+
+DllServices::~DllServices() { DisableFull(); }
+
+void DllServices::StartUntrustedModulesProcessor(bool aIsStartingUp) {
+  MOZ_ASSERT(NS_IsMainThread());
+  MOZ_ASSERT(!mUntrustedModulesProcessor);
+  mUntrustedModulesProcessor = UntrustedModulesProcessor::Create(aIsStartingUp);
+}
+
+bool DllServices::IsReadyForBackgroundProcessing() const {
+  return mUntrustedModulesProcessor &&
+         mUntrustedModulesProcessor->IsReadyForBackgroundProcessing();
+}
+
+RefPtr<UntrustedModulesPromise> DllServices::GetUntrustedModulesData() {
+  if (!mUntrustedModulesProcessor) {
+    return UntrustedModulesPromise::CreateAndReject(NS_ERROR_NOT_IMPLEMENTED,
+                                                    __func__);
+  }
+
+  return mUntrustedModulesProcessor->GetProcessedData();
+}
+
+void DllServices::DisableFull() {
+  if (XRE_IsGMPluginProcess()) {
+    return;
+  }
+
+  if (mUntrustedModulesProcessor) {
+    mUntrustedModulesProcessor->Disable();
+  }
+
+  glue::DllServices::DisableFull();
+}
+
+RefPtr<ModulesTrustPromise> DllServices::GetModulesTrust(
+    ModulePaths&& aModPaths, bool aRunAtNormalPriority) {
+  if (!mUntrustedModulesProcessor) {
+    return ModulesTrustPromise::CreateAndReject(NS_ERROR_NOT_IMPLEMENTED,
+                                                __func__);
+  }
+
+  return mUntrustedModulesProcessor->GetModulesTrust(std::move(aModPaths),
+                                                     aRunAtNormalPriority);
+}
+
+void DllServices::NotifyDllLoad(glue::EnhancedModuleLoadInfo&& aModLoadInfo) {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  const char* topic;
+
+  if (aModLoadInfo.mNtLoadInfo.mThreadId == ::GetCurrentThreadId()) {
+    topic = kTopicDllLoadedMainThread;
+  } else {
+    topic = kTopicDllLoadedNonMainThread;
+  }
+
+  // We save the path to a nsAutoString because once we have submitted
+  // aModLoadInfo for processing there is no guarantee that the original
+  // buffer will continue to be valid.
+  nsAutoString dllFilePath(aModLoadInfo.GetSectionName());
+
+  if (mUntrustedModulesProcessor) {
+    mUntrustedModulesProcessor->Enqueue(std::move(aModLoadInfo));
+  }
+
+  nsCOMPtr<nsIObserverService> obsServ(mozilla::services::GetObserverService());
+  if (!obsServ) {
+    return;
+  }
+
+  obsServ->NotifyObservers(nullptr, topic, dllFilePath.get());
+}
+
+void DllServices::NotifyModuleLoadBacklog(ModuleLoadInfoVec&& aEvents) {
+  MOZ_ASSERT(NS_IsMainThread());
+  if (!mUntrustedModulesProcessor) {
+    return;
+  }
+
+  mUntrustedModulesProcessor->Enqueue(std::move(aEvents));
+}
+
+}  // namespace mozilla
diff --git a/toolkit/xre/dllservices/WinDllServices.h b/toolkit/xre/dllservices/WinDllServices.h
new file mode 100644
index 0000000000..a5d4f9b363
--- /dev/null
+++ b/toolkit/xre/dllservices/WinDllServices.h
@@ -0,0 +1,57 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_WinDllServices_h
+#define mozilla_WinDllServices_h
+
+#include "mozilla/glue/WindowsDllServices.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/MozPromise.h"
+#include "mozilla/RefPtr.h"
+
+namespace mozilla {
+
+class UntrustedModulesData;
+class UntrustedModulesProcessor;
+
+using UntrustedModulesPromise =
+    MozPromise<Maybe<UntrustedModulesData>, nsresult, true>;
+
+struct ModulePaths;
+class ModulesMapResult;
+
+using ModulesTrustPromise = MozPromise<ModulesMapResult, nsresult, true>;
+
+class DllServices final : public glue::DllServices {
+ public:
+  static DllServices* Get();
+
+  virtual void DisableFull() override;
+
+  static const char* kTopicDllLoadedMainThread;
+  static const char* kTopicDllLoadedNonMainThread;
+
+  void StartUntrustedModulesProcessor(bool aIsReadyForBackgroundProcessing);
+  bool IsReadyForBackgroundProcessing() const;
+
+  RefPtr<UntrustedModulesPromise> GetUntrustedModulesData();
+
+  RefPtr<ModulesTrustPromise> GetModulesTrust(ModulePaths&& aModPaths,
+                                              bool aRunAtNormalPriority);
+
+ private:
+  DllServices() = default;
+  ~DllServices();
+
+  void NotifyDllLoad(glue::EnhancedModuleLoadInfo&& aModLoadInfo) override;
+  void NotifyModuleLoadBacklog(ModuleLoadInfoVec&& aEvents) override;
+
+  RefPtr<UntrustedModulesProcessor> mUntrustedModulesProcessor;
+};
+
+}  // namespace mozilla
+
+#endif  // mozilla_WinDllServices_h
diff --git a/toolkit/xre/dllservices/moz.build b/toolkit/xre/dllservices/moz.build
new file mode 100644
index 0000000000..9fb82f6c23
--- /dev/null
+++ b/toolkit/xre/dllservices/moz.build
@@ -0,0 +1,43 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+with Files("**"):
+    BUG_COMPONENT = ("Core", "DLL Services")
+
+Library("dllservices")
+
+FINAL_LIBRARY = "xul"
+
+EXPORTS.mozilla += [
+    "DynamicBlocklist.h",
+    "ModuleVersionInfo.h",
+    "UntrustedModulesData.h",
+    "UntrustedModulesProcessor.h",
+    "WinDllServices.h",
+]
+
+DIRS += [
+    "mozglue",
+]
+
+UNIFIED_SOURCES += [
+    "ModuleEvaluator.cpp",
+    "ModuleVersionInfo.cpp",
+    "UntrustedModulesData.cpp",
+    "UntrustedModulesProcessor.cpp",
+    "WinDllServices.cpp",
+]
+
+if CONFIG["MOZ_LAUNCHER_PROCESS"]:
+    UNIFIED_SOURCES += [
+        "DynamicBlocklistWriter.cpp",
+    ]
+
+TEST_DIRS += [
+    "tests",
+]
+
+include("/ipc/chromium/chromium-config.mozbuild")
diff --git a/toolkit/xre/dllservices/mozglue/Authenticode.cpp b/toolkit/xre/dllservices/mozglue/Authenticode.cpp
new file mode 100644
index 0000000000..ee702b2ac6
--- /dev/null
+++ b/toolkit/xre/dllservices/mozglue/Authenticode.cpp
@@ -0,0 +1,439 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// We need Windows 8 functions and structures to be able to verify SHA-256.
+#if defined(_WIN32_WINNT)
+#  undef _WIN32_WINNT
+#  define _WIN32_WINNT _WIN32_WINNT_WIN8
+#endif  // defined(_WIN32_WINNT)
+#if defined(NTDDI_VERSION)
+#  undef NTDDI_VERSION
+#  define NTDDI_VERSION NTDDI_WIN8
+#endif  // defined(NTDDI_VERSION)
+
+#include "Authenticode.h"
+
+#include "mozilla/ArrayUtils.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/DynamicallyLinkedFunctionPtr.h"
+#include "mozilla/ScopeExit.h"
+#include "mozilla/UniquePtr.h"
+#include "mozilla/WindowsVersion.h"
+#include "nsWindowsHelpers.h"
+
+#include <windows.h>
+#include <softpub.h>
+#include <wincrypt.h>
+#include <wintrust.h>
+#include <mscat.h>
+
+#include <string.h>
+
+namespace {
+
+struct CertStoreDeleter {
+  typedef HCERTSTORE pointer;
+  void operator()(pointer aStore) { ::CertCloseStore(aStore, 0); }
+};
+
+struct CryptMsgDeleter {
+  typedef HCRYPTMSG pointer;
+  void operator()(pointer aMsg) { ::CryptMsgClose(aMsg); }
+};
+
+struct CertContextDeleter {
+  void operator()(PCCERT_CONTEXT aCertContext) {
+    ::CertFreeCertificateContext(aCertContext);
+  }
+};
+
+struct CATAdminContextDeleter {
+  typedef HCATADMIN pointer;
+  void operator()(pointer aCtx) {
+    static const mozilla::StaticDynamicallyLinkedFunctionPtr<
+        decltype(&::CryptCATAdminReleaseContext)>
+        pCryptCATAdminReleaseContext(L"wintrust.dll",
+                                     "CryptCATAdminReleaseContext");
+
+    MOZ_ASSERT(!!pCryptCATAdminReleaseContext);
+    if (!pCryptCATAdminReleaseContext) {
+      return;
+    }
+
+    pCryptCATAdminReleaseContext(aCtx, 0);
+  }
+};
+
+typedef mozilla::UniquePtr<HCERTSTORE, CertStoreDeleter> CertStoreUniquePtr;
+typedef mozilla::UniquePtr<HCRYPTMSG, CryptMsgDeleter> CryptMsgUniquePtr;
+typedef mozilla::UniquePtr<const CERT_CONTEXT, CertContextDeleter>
+    CertContextUniquePtr;
+typedef mozilla::UniquePtr<HCATADMIN, CATAdminContextDeleter>
+    CATAdminContextUniquePtr;
+
+static const DWORD kEncodingTypes = X509_ASN_ENCODING | PKCS_7_ASN_ENCODING;
+
+class SignedBinary final {
+ public:
+  SignedBinary(const wchar_t* aFilePath, mozilla::AuthenticodeFlags aFlags);
+
+  explicit operator bool() const { return mCertStore && mCryptMsg && mCertCtx; }
+
+  mozilla::UniquePtr<wchar_t[]> GetOrgName();
+
+  SignedBinary(const SignedBinary&) = delete;
+  SignedBinary(SignedBinary&&) = delete;
+  SignedBinary& operator=(const SignedBinary&) = delete;
+  SignedBinary& operator=(SignedBinary&&) = delete;
+
+ private:
+  bool VerifySignature(const wchar_t* aFilePath);
+  bool QueryObject(const wchar_t* aFilePath);
+  static bool VerifySignatureInternal(WINTRUST_DATA& aTrustData);
+
+ private:
+  enum class TrustSource { eNone, eEmbedded, eCatalog };
+
+ private:
+  const mozilla::AuthenticodeFlags mFlags;
+  TrustSource mTrustSource;
+  CertStoreUniquePtr mCertStore;
+  CryptMsgUniquePtr mCryptMsg;
+  CertContextUniquePtr mCertCtx;
+};
+
+SignedBinary::SignedBinary(const wchar_t* aFilePath,
+                           mozilla::AuthenticodeFlags aFlags)
+    : mFlags(aFlags), mTrustSource(TrustSource::eNone) {
+  if (!VerifySignature(aFilePath)) {
+    return;
+  }
+
+  DWORD certInfoLen = 0;
+  BOOL ok = CryptMsgGetParam(mCryptMsg.get(), CMSG_SIGNER_CERT_INFO_PARAM, 0,
+                             nullptr, &certInfoLen);
+  if (!ok) {
+    return;
+  }
+
+  auto certInfoBuf = mozilla::MakeUnique<char[]>(certInfoLen);
+
+  ok = CryptMsgGetParam(mCryptMsg.get(), CMSG_SIGNER_CERT_INFO_PARAM, 0,
+                        certInfoBuf.get(), &certInfoLen);
+  if (!ok) {
+    return;
+  }
+
+  auto certInfo = reinterpret_cast<CERT_INFO*>(certInfoBuf.get());
+
+  PCCERT_CONTEXT certCtx =
+      CertFindCertificateInStore(mCertStore.get(), kEncodingTypes, 0,
+                                 CERT_FIND_SUBJECT_CERT, certInfo, nullptr);
+  if (!certCtx) {
+    return;
+  }
+
+  mCertCtx.reset(certCtx);
+}
+
+bool SignedBinary::QueryObject(const wchar_t* aFilePath) {
+  DWORD encodingType, contentType, formatType;
+  HCERTSTORE rawCertStore;
+  HCRYPTMSG rawCryptMsg;
+  BOOL result = ::CryptQueryObject(CERT_QUERY_OBJECT_FILE, aFilePath,
+                                   CERT_QUERY_CONTENT_FLAG_PKCS7_SIGNED_EMBED,
+                                   CERT_QUERY_FORMAT_FLAG_BINARY, 0,
+                                   &encodingType, &contentType, &formatType,
+                                   &rawCertStore, &rawCryptMsg, nullptr);
+  if (!result) {
+    return false;
+  }
+
+  mCertStore.reset(rawCertStore);
+  mCryptMsg.reset(rawCryptMsg);
+
+  return true;
+}
+
+/**
+ * @param aTrustData must be a WINTRUST_DATA structure that has been zeroed out
+ *                   and then populated at least with its |cbStruct|,
+ *                   |dwUnionChoice|, and appropriate union field. This function
+ *                   will then populate the remaining fields as appropriate.
+ */
+/* static */
+bool SignedBinary::VerifySignatureInternal(WINTRUST_DATA& aTrustData) {
+  static const mozilla::StaticDynamicallyLinkedFunctionPtr<
+      decltype(&::WinVerifyTrust)>
+      pWinVerifyTrust(L"wintrust.dll", "WinVerifyTrust");
+  if (!pWinVerifyTrust) {
+    return false;
+  }
+
+  aTrustData.dwUIChoice = WTD_UI_NONE;
+  aTrustData.fdwRevocationChecks = WTD_REVOKE_NONE;
+  aTrustData.dwStateAction = WTD_STATEACTION_VERIFY;
+  aTrustData.dwProvFlags = WTD_CACHE_ONLY_URL_RETRIEVAL;
+
+  const HWND hwnd = (HWND)INVALID_HANDLE_VALUE;
+  GUID policyGUID = WINTRUST_ACTION_GENERIC_VERIFY_V2;
+  LONG result = pWinVerifyTrust(hwnd, &policyGUID, &aTrustData);
+
+  aTrustData.dwStateAction = WTD_STATEACTION_CLOSE;
+  pWinVerifyTrust(hwnd, &policyGUID, &aTrustData);
+
+  return result == ERROR_SUCCESS;
+}
+
+bool SignedBinary::VerifySignature(const wchar_t* aFilePath) {
+  // First, try the binary itself
+  if (QueryObject(aFilePath)) {
+    mTrustSource = TrustSource::eEmbedded;
+    if (mFlags & mozilla::AuthenticodeFlags::SkipTrustVerification) {
+      return true;
+    }
+
+    WINTRUST_FILE_INFO fileInfo = {sizeof(fileInfo)};
+    fileInfo.pcwszFilePath = aFilePath;
+
+    WINTRUST_DATA trustData = {sizeof(trustData)};
+    trustData.dwUnionChoice = WTD_CHOICE_FILE;
+    trustData.pFile = &fileInfo;
+
+    return VerifySignatureInternal(trustData);
+  }
+
+  // We didn't find anything in the binary, so now try a catalog file.
+
+  // First, we open a catalog admin context.
+  HCATADMIN rawCatAdmin;
+
+  // Windows 7 also exports the CryptCATAdminAcquireContext2 API, but it does
+  // *not* sign its binaries with SHA-256, so we use the old API in that case.
+  if (mozilla::IsWin8OrLater()) {
+    static const mozilla::StaticDynamicallyLinkedFunctionPtr<
+        decltype(&::CryptCATAdminAcquireContext2)>
+        pCryptCATAdminAcquireContext2(L"wintrust.dll",
+                                      "CryptCATAdminAcquireContext2");
+    if (!pCryptCATAdminAcquireContext2) {
+      return false;
+    }
+
+    CERT_STRONG_SIGN_PARA policy = {sizeof(policy)};
+    policy.dwInfoChoice = CERT_STRONG_SIGN_OID_INFO_CHOICE;
+    policy.pszOID = const_cast<char*>(
+        szOID_CERT_STRONG_SIGN_OS_CURRENT);  // -Wwritable-strings
+
+    if (!pCryptCATAdminAcquireContext2(&rawCatAdmin, nullptr,
+                                       BCRYPT_SHA256_ALGORITHM, &policy, 0)) {
+      return false;
+    }
+  } else {
+    static const mozilla::StaticDynamicallyLinkedFunctionPtr<
+        decltype(&::CryptCATAdminAcquireContext)>
+        pCryptCATAdminAcquireContext(L"wintrust.dll",
+                                     "CryptCATAdminAcquireContext");
+
+    if (!pCryptCATAdminAcquireContext ||
+        !pCryptCATAdminAcquireContext(&rawCatAdmin, nullptr, 0)) {
+      return false;
+    }
+  }
+
+  CATAdminContextUniquePtr catAdmin(rawCatAdmin);
+
+  // Now we need to hash the file at aFilePath.
+  // Since we're hashing this file, let's open it with a sequential scan hint.
+  HANDLE rawFile =
+      ::CreateFileW(aFilePath, GENERIC_READ,
+                    FILE_SHARE_READ | FILE_SHARE_DELETE | FILE_SHARE_WRITE,
+                    nullptr, OPEN_EXISTING, FILE_FLAG_SEQUENTIAL_SCAN, nullptr);
+  if (rawFile == INVALID_HANDLE_VALUE) {
+    return false;
+  }
+
+  nsAutoHandle file(rawFile);
+  DWORD hashLen = 0;
+  mozilla::UniquePtr<BYTE[]> hashBuf;
+
+  static const mozilla::StaticDynamicallyLinkedFunctionPtr<
+      decltype(&::CryptCATAdminCalcHashFromFileHandle2)>
+      pCryptCATAdminCalcHashFromFileHandle2(
+          L"wintrust.dll", "CryptCATAdminCalcHashFromFileHandle2");
+  if (pCryptCATAdminCalcHashFromFileHandle2) {
+    if (!pCryptCATAdminCalcHashFromFileHandle2(rawCatAdmin, rawFile, &hashLen,
+                                               nullptr, 0) &&
+        ::GetLastError() != ERROR_INSUFFICIENT_BUFFER) {
+      return false;
+    }
+
+    hashBuf = mozilla::MakeUnique<BYTE[]>(hashLen);
+
+    if (!pCryptCATAdminCalcHashFromFileHandle2(rawCatAdmin, rawFile, &hashLen,
+                                               hashBuf.get(), 0)) {
+      return false;
+    }
+  } else {
+    static const mozilla::StaticDynamicallyLinkedFunctionPtr<
+        decltype(&::CryptCATAdminCalcHashFromFileHandle)>
+        pCryptCATAdminCalcHashFromFileHandle(
+            L"wintrust.dll", "CryptCATAdminCalcHashFromFileHandle");
+
+    if (!pCryptCATAdminCalcHashFromFileHandle) {
+      return false;
+    }
+
+    if (!pCryptCATAdminCalcHashFromFileHandle(rawFile, &hashLen, nullptr, 0) &&
+        ::GetLastError() != ERROR_INSUFFICIENT_BUFFER) {
+      return false;
+    }
+
+    hashBuf = mozilla::MakeUnique<BYTE[]>(hashLen);
+
+    if (!pCryptCATAdminCalcHashFromFileHandle(rawFile, &hashLen, hashBuf.get(),
+                                              0)) {
+      return false;
+    }
+  }
+
+  // Now that we've hashed the file, query the catalog system to see if any
+  // catalogs reference a binary with our hash.
+
+  static const mozilla::StaticDynamicallyLinkedFunctionPtr<
+      decltype(&::CryptCATAdminEnumCatalogFromHash)>
+      pCryptCATAdminEnumCatalogFromHash(L"wintrust.dll",
+                                        "CryptCATAdminEnumCatalogFromHash");
+  if (!pCryptCATAdminEnumCatalogFromHash) {
+    return false;
+  }
+
+  static const mozilla::StaticDynamicallyLinkedFunctionPtr<
+      decltype(&::CryptCATAdminReleaseCatalogContext)>
+      pCryptCATAdminReleaseCatalogContext(L"wintrust.dll",
+                                          "CryptCATAdminReleaseCatalogContext");
+  if (!pCryptCATAdminReleaseCatalogContext) {
+    return false;
+  }
+
+  HCATINFO catInfoHdl = pCryptCATAdminEnumCatalogFromHash(
+      rawCatAdmin, hashBuf.get(), hashLen, 0, nullptr);
+  if (!catInfoHdl) {
+    return false;
+  }
+
+  // We can't use UniquePtr for this because the deleter function requires two
+  // parameters.
+  auto cleanCatInfoHdl =
+      mozilla::MakeScopeExit([rawCatAdmin, catInfoHdl]() -> void {
+        pCryptCATAdminReleaseCatalogContext(rawCatAdmin, catInfoHdl, 0);
+      });
+
+  // We found a catalog! Now query for the path to the catalog file.
+
+  static const mozilla::StaticDynamicallyLinkedFunctionPtr<
+      decltype(&::CryptCATCatalogInfoFromContext)>
+      pCryptCATCatalogInfoFromContext(L"wintrust.dll",
+                                      "CryptCATCatalogInfoFromContext");
+  if (!pCryptCATCatalogInfoFromContext) {
+    return false;
+  }
+
+  CATALOG_INFO_ catInfo = {sizeof(catInfo)};
+  if (!pCryptCATCatalogInfoFromContext(catInfoHdl, &catInfo, 0)) {
+    return false;
+  }
+
+  if (!QueryObject(catInfo.wszCatalogFile)) {
+    return false;
+  }
+
+  mTrustSource = TrustSource::eCatalog;
+
+  if (mFlags & mozilla::AuthenticodeFlags::SkipTrustVerification) {
+    return true;
+  }
+
+  // WINTRUST_CATALOG_INFO::pcwszMemberTag is commonly set to the string
+  // representation of the file hash, so we build that here.
+
+  DWORD strHashBufLen = (hashLen * 2) + 1;
+  auto strHashBuf = mozilla::MakeUnique<wchar_t[]>(strHashBufLen);
+  if (!::CryptBinaryToStringW(hashBuf.get(), hashLen,
+                              CRYPT_STRING_HEXRAW | CRYPT_STRING_NOCRLF,
+                              strHashBuf.get(), &strHashBufLen)) {
+    return false;
+  }
+
+  // Ensure that the tag is uppercase for WinVerifyTrust
+  // NB: CryptBinaryToStringW overwrites strHashBufLen with the length excluding
+  //     the null terminator, so we need to add it back for this call.
+  if (_wcsupr_s(strHashBuf.get(), strHashBufLen + 1)) {
+    return false;
+  }
+
+  // Now, given the path to the catalog, and the path to the member (ie, the
+  // binary whose hash we are validating), we may now validate. If the
+  // validation is successful, we then QueryObject on the *catalog file*
+  // instead of the binary.
+
+  WINTRUST_CATALOG_INFO wtCatInfo = {sizeof(wtCatInfo)};
+  wtCatInfo.pcwszCatalogFilePath = catInfo.wszCatalogFile;
+  wtCatInfo.pcwszMemberTag = strHashBuf.get();
+  wtCatInfo.pcwszMemberFilePath = aFilePath;
+  wtCatInfo.hMemberFile = rawFile;
+  if (mozilla::IsWin8OrLater()) {
+    wtCatInfo.hCatAdmin = rawCatAdmin;
+  }
+
+  WINTRUST_DATA trustData = {sizeof(trustData)};
+  trustData.dwUnionChoice = WTD_CHOICE_CATALOG;
+  trustData.pCatalog = &wtCatInfo;
+
+  return VerifySignatureInternal(trustData);
+}
+
+mozilla::UniquePtr<wchar_t[]> SignedBinary::GetOrgName() {
+  DWORD charCount = CertGetNameStringW(
+      mCertCtx.get(), CERT_NAME_SIMPLE_DISPLAY_TYPE, 0, nullptr, nullptr, 0);
+  if (charCount <= 1) {
+    // Not found
+    return nullptr;
+  }
+
+  auto result = mozilla::MakeUnique<wchar_t[]>(charCount);
+  charCount = CertGetNameStringW(mCertCtx.get(), CERT_NAME_SIMPLE_DISPLAY_TYPE,
+                                 0, nullptr, result.get(), charCount);
+  MOZ_ASSERT(charCount > 1);
+
+  return result;
+}
+
+}  // anonymous namespace
+
+namespace mozilla {
+
+class AuthenticodeImpl : public Authenticode {
+ public:
+  virtual UniquePtr<wchar_t[]> GetBinaryOrgName(
+      const wchar_t* aFilePath,
+      AuthenticodeFlags aFlags = AuthenticodeFlags::Default) override;
+};
+
+UniquePtr<wchar_t[]> AuthenticodeImpl::GetBinaryOrgName(
+    const wchar_t* aFilePath, AuthenticodeFlags aFlags) {
+  SignedBinary bin(aFilePath, aFlags);
+  if (!bin) {
+    return nullptr;
+  }
+
+  return bin.GetOrgName();
+}
+
+static AuthenticodeImpl sAuthenticodeImpl;
+
+Authenticode* GetAuthenticode() { return &sAuthenticodeImpl; }
+
+}  // namespace mozilla
diff --git a/toolkit/xre/dllservices/mozglue/Authenticode.h b/toolkit/xre/dllservices/mozglue/Authenticode.h
new file mode 100644
index 0000000000..182512da2c
--- /dev/null
+++ b/toolkit/xre/dllservices/mozglue/Authenticode.h
@@ -0,0 +1,32 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_Authenticode_h
+#define mozilla_Authenticode_h
+
+#include "mozilla/Maybe.h"
+#include "mozilla/TypedEnumBits.h"
+#include "mozilla/UniquePtr.h"
+
+namespace mozilla {
+
+enum class AuthenticodeFlags : uint32_t {
+  Default = 0,
+  SkipTrustVerification = 1,
+};
+
+MOZ_MAKE_ENUM_CLASS_BITWISE_OPERATORS(AuthenticodeFlags)
+
+class Authenticode {
+ public:
+  virtual UniquePtr<wchar_t[]> GetBinaryOrgName(
+      const wchar_t* aFilePath,
+      AuthenticodeFlags aFlags = AuthenticodeFlags::Default) = 0;
+};
+
+}  // namespace mozilla
+
+#endif  // mozilla_Authenticode_h
diff --git a/toolkit/xre/dllservices/mozglue/CacheNtDllThunk.cpp b/toolkit/xre/dllservices/mozglue/CacheNtDllThunk.cpp
new file mode 100644
index 0000000000..f3eef13504
--- /dev/null
+++ b/toolkit/xre/dllservices/mozglue/CacheNtDllThunk.cpp
@@ -0,0 +1,60 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "CacheNtDllThunk.h"
+
+#include "mozilla/Maybe.h"
+#include "mozilla/Span.h"
+#include "mozilla/StaticPtr.h"
+
+namespace mozilla {
+
+static StaticAutoPtr<Buffer<IMAGE_THUNK_DATA>> sCachedNtDllThunk;
+
+// This static method initializes sCachedNtDllThunk.  Because it's called in
+// XREMain::XRE_main, which happens long before WindowsProcessLauncher's ctor
+// accesses sCachedNtDllThunk, there is no race on sCachedNtDllThunk, thus
+// no mutex is needed.
+static void CacheNtDllThunk() {
+  if (sCachedNtDllThunk) {
+    return;
+  }
+
+  do {
+    nt::PEHeaders ourExeImage(::GetModuleHandleW(nullptr));
+    if (!ourExeImage) {
+      break;
+    }
+
+    nt::PEHeaders ntdllImage(::GetModuleHandleW(L"ntdll.dll"));
+    if (!ntdllImage) {
+      break;
+    }
+
+    Maybe<Range<const uint8_t>> ntdllBoundaries = ntdllImage.GetBounds();
+    if (!ntdllBoundaries) {
+      break;
+    }
+
+    Maybe<Span<IMAGE_THUNK_DATA>> maybeNtDllThunks =
+        ourExeImage.GetIATThunksForModule("ntdll.dll", ntdllBoundaries.ptr());
+    if (maybeNtDllThunks.isNothing()) {
+      break;
+    }
+
+    sCachedNtDllThunk = new Buffer<IMAGE_THUNK_DATA>(maybeNtDllThunks.value());
+    return;
+  } while (false);
+
+  // Failed to cache IAT.  Initializing the variable with nullptr.
+  sCachedNtDllThunk = new Buffer<IMAGE_THUNK_DATA>();
+}
+
+static Buffer<IMAGE_THUNK_DATA>* GetCachedNtDllThunk() {
+  return sCachedNtDllThunk;
+}
+
+}  // namespace mozilla
diff --git a/toolkit/xre/dllservices/mozglue/CacheNtDllThunk.h b/toolkit/xre/dllservices/mozglue/CacheNtDllThunk.h
new file mode 100644
index 0000000000..403e001afc
--- /dev/null
+++ b/toolkit/xre/dllservices/mozglue/CacheNtDllThunk.h
@@ -0,0 +1,21 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_CacheNtDllThunk_h
+#define mozilla_CacheNtDllThunk_h
+
+#include "mozilla/Types.h"
+#include "mozilla/Buffer.h"
+#include "mozilla/NativeNt.h"
+
+namespace mozilla {
+
+MFBT_API void CacheNtDllThunk();
+MFBT_API Buffer<IMAGE_THUNK_DATA>* GetCachedNtDllThunk();
+
+};  // namespace mozilla
+
+#endif  // mozilla_CacheNtDllThunk_h
diff --git a/toolkit/xre/dllservices/mozglue/LoaderAPIInterfaces.h b/toolkit/xre/dllservices/mozglue/LoaderAPIInterfaces.h
new file mode 100644
index 0000000000..67871b0c7a
--- /dev/null
+++ b/toolkit/xre/dllservices/mozglue/LoaderAPIInterfaces.h
@@ -0,0 +1,126 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_LoaderAPIInterfaces_h
+#define mozilla_LoaderAPIInterfaces_h
+
+#include "nscore.h"
+#include "mozilla/glue/SharedSection.h"
+#include "mozilla/ModuleLoadInfo.h"
+#include "mozilla/ProcessType.h"
+
+namespace mozilla {
+namespace nt {
+
+class NS_NO_VTABLE LoaderObserver {
+ public:
+  /**
+   * Notification that a DLL load has begun.
+   *
+   * @param aContext Outparam that allows this observer to store any context
+   *                 information pertaining to the current load.
+   * @param aRequestedDllName The DLL name requested by whatever invoked the
+   *                          loader. This name may not match the effective
+   *                          name of the DLL once the loader has completed
+   *                          its path search.
+   */
+  virtual void OnBeginDllLoad(void** aContext,
+                              PCUNICODE_STRING aRequestedDllName) = 0;
+
+  /**
+   * Query the observer to determine whether the DLL named |aLSPLeafName| needs
+   * to be substituted with another module, and substitute the module handle
+   * when necessary.
+   *
+   * @return true when substitution occurs, otherwise false
+   */
+  virtual bool SubstituteForLSP(PCUNICODE_STRING aLSPLeafName,
+                                PHANDLE aOutHandle) = 0;
+
+  /**
+   * Notification that a DLL load has ended.
+   *
+   * @param aContext The context that was set by the corresponding call to
+   *                 OnBeginDllLoad
+   * @param aNtStatus The NTSTATUS returned by LdrLoadDll
+   * @param aModuleLoadInfo Telemetry information that was gathered about the
+   *                        load.
+   */
+  virtual void OnEndDllLoad(void* aContext, NTSTATUS aNtStatus,
+                            ModuleLoadInfo&& aModuleLoadInfo) = 0;
+
+  /**
+   * Called to inform the observer that it is no longer active and, if
+   * necessary, call aNext->OnForward() with any accumulated telemetry
+   * information.
+   */
+  virtual void Forward(LoaderObserver* aNext) = 0;
+
+  /**
+   * Receives a vector of module load telemetry from a previous LoaderObserver.
+   */
+  virtual void OnForward(ModuleLoadInfoVec&& aInfo) = 0;
+};
+
+class NS_NO_VTABLE LoaderAPI {
+ public:
+  /**
+   * Construct a new ModuleLoadInfo structure and notify the LoaderObserver
+   * that a library load is beginning.
+   */
+  virtual ModuleLoadInfo ConstructAndNotifyBeginDllLoad(
+      void** aContext, PCUNICODE_STRING aRequestedDllName) = 0;
+
+  /**
+   * Query to determine whether the DLL named |aLSPLeafName| needs to be
+   * substituted with another module, and substitute the module handle when
+   * necessary.
+   *
+   * @return true when substitution occurs, otherwise false
+   */
+  virtual bool SubstituteForLSP(PCUNICODE_STRING aLSPLeafName,
+                                PHANDLE aOutHandle) = 0;
+
+  /**
+   * Notification that a DLL load has ended.
+   */
+  virtual void NotifyEndDllLoad(void* aContext, NTSTATUS aLoadNtStatus,
+                                ModuleLoadInfo&& aModuleLoadInfo) = 0;
+
+  /**
+   * Given the address of a mapped section, obtain the name of the file that is
+   * backing it.
+   */
+  virtual AllocatedUnicodeString GetSectionName(void* aSectionAddr) = 0;
+
+  using InitDllBlocklistOOPFnPtr = LauncherVoidResultWithLineInfo (*)(
+      const wchar_t*, HANDLE, const IMAGE_THUNK_DATA*, const GeckoProcessType);
+  using HandleLauncherErrorFnPtr = void (*)(const LauncherError&, const char*);
+
+  /**
+   * Return a pointer to winlauncher's function.
+   * Used by sandboxBroker::LaunchApp.
+   */
+  virtual InitDllBlocklistOOPFnPtr GetDllBlocklistInitFn() = 0;
+  virtual HandleLauncherErrorFnPtr GetHandleLauncherErrorFn() = 0;
+  virtual SharedSection* GetSharedSection() = 0;
+};
+
+struct WinLauncherServices final {
+  nt::LoaderAPI::InitDllBlocklistOOPFnPtr mInitDllBlocklistOOP;
+  nt::LoaderAPI::HandleLauncherErrorFnPtr mHandleLauncherError;
+  SharedSection* mSharedSection;
+
+  WinLauncherServices()
+      : mInitDllBlocklistOOP(nullptr),
+        mHandleLauncherError(nullptr),
+        mSharedSection(nullptr) {}
+};
+
+}  // namespace nt
+}  // namespace mozilla
+
+#endif  // mozilla_LoaderAPIInterfaces_h
diff --git a/toolkit/xre/dllservices/mozglue/LoaderObserver.cpp b/toolkit/xre/dllservices/mozglue/LoaderObserver.cpp
new file mode 100644
index 0000000000..d2014365c4
--- /dev/null
+++ b/toolkit/xre/dllservices/mozglue/LoaderObserver.cpp
@@ -0,0 +1,149 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "LoaderObserver.h"
+
+#include "mozilla/AutoProfilerLabel.h"
+#include "mozilla/BaseProfilerMarkers.h"
+#include "mozilla/glue/WindowsUnicode.h"
+#include "mozilla/StackWalk_windows.h"
+#include "mozilla/TimeStamp.h"
+
+namespace mozilla {
+
+extern glue::Win32SRWLock gDllServicesLock;
+extern glue::detail::DllServicesBase* gDllServices;
+
+namespace glue {
+
+void LoaderObserver::OnBeginDllLoad(void** aContext,
+                                    PCUNICODE_STRING aRequestedDllName) {
+  MOZ_ASSERT(aContext);
+  if (IsProfilerPresent()) {
+    UniquePtr<char[]> utf8RequestedDllName(WideToUTF8(aRequestedDllName));
+    BASE_PROFILER_MARKER_TEXT(
+        "DllLoad", OTHER, MarkerTiming::IntervalStart(),
+        mozilla::ProfilerString8View::WrapNullTerminatedString(
+            utf8RequestedDllName.get()));
+    *aContext = utf8RequestedDllName.release();
+  }
+
+#ifdef _M_AMD64
+  // Prevent the stack walker from suspending this thread when LdrLoadDll
+  // holds the RtlLookupFunctionEntry lock.
+  SuppressStackWalking();
+#endif
+}
+
+bool LoaderObserver::SubstituteForLSP(PCUNICODE_STRING aLSPLeafName,
+                                      PHANDLE aOutHandle) {
+  // Currently unsupported
+  return false;
+}
+
+void LoaderObserver::OnEndDllLoad(void* aContext, NTSTATUS aNtStatus,
+                                  ModuleLoadInfo&& aModuleLoadInfo) {
+#ifdef _M_AMD64
+  DesuppressStackWalking();
+#endif
+
+  if (aContext) {
+    UniquePtr<char[]> utf8RequestedDllName{static_cast<char*>(aContext)};
+    BASE_PROFILER_MARKER_TEXT(
+        "DllLoad", OTHER, MarkerTiming::IntervalEnd(),
+        mozilla::ProfilerString8View::WrapNullTerminatedString(
+            utf8RequestedDllName.get()));
+  }
+
+  // We want to record a denied DLL load regardless of |aNtStatus| because
+  // |aNtStatus| is set to access-denied when DLL load was blocked.
+  if ((!NT_SUCCESS(aNtStatus) && !aModuleLoadInfo.WasDenied()) ||
+      !aModuleLoadInfo.WasMapped()) {
+    return;
+  }
+
+  {  // Scope for lock
+    AutoSharedLock lock(gDllServicesLock);
+    if (gDllServices) {
+      gDllServices->DispatchDllLoadNotification(std::move(aModuleLoadInfo));
+      return;
+    }
+  }
+
+  // No dll services, save for later
+  AutoExclusiveLock lock(mLock);
+  if (!mEnabled) {
+    return;
+  }
+
+  if (!mModuleLoads) {
+    mModuleLoads = new ModuleLoadInfoVec();
+  }
+
+  Unused << mModuleLoads->emplaceBack(
+      std::forward<ModuleLoadInfo>(aModuleLoadInfo));
+}
+
+void LoaderObserver::Forward(nt::LoaderObserver* aNext) {
+  MOZ_ASSERT_UNREACHABLE(
+      "This implementation does not forward to any more "
+      "nt::LoaderObserver objects");
+}
+
+void LoaderObserver::Forward(detail::DllServicesBase* aNext) {
+  MOZ_ASSERT(aNext);
+  if (!aNext) {
+    return;
+  }
+
+  ModuleLoadInfoVec* moduleLoads = nullptr;
+
+  {  // Scope for lock
+    AutoExclusiveLock lock(mLock);
+    moduleLoads = mModuleLoads;
+    mModuleLoads = nullptr;
+  }
+
+  if (!moduleLoads) {
+    return;
+  }
+
+  aNext->DispatchModuleLoadBacklogNotification(std::move(*moduleLoads));
+  delete moduleLoads;
+}
+
+void LoaderObserver::Disable() {
+  ModuleLoadInfoVec* moduleLoads = nullptr;
+
+  {  // Scope for lock
+    AutoExclusiveLock lock(mLock);
+    moduleLoads = mModuleLoads;
+    mModuleLoads = nullptr;
+    mEnabled = false;
+  }
+
+  delete moduleLoads;
+}
+
+void LoaderObserver::OnForward(ModuleLoadInfoVec&& aInfo) {
+  AutoExclusiveLock lock(mLock);
+  if (!mModuleLoads) {
+    mModuleLoads = new ModuleLoadInfoVec();
+  }
+
+  MOZ_ASSERT(mModuleLoads->empty());
+  if (mModuleLoads->empty()) {
+    *mModuleLoads = std::move(aInfo);
+  } else {
+    // This should not happen, but we can handle it
+    for (auto&& item : aInfo) {
+      Unused << mModuleLoads->append(std::move(item));
+    }
+  }
+}
+
+}  // namespace glue
+}  // namespace mozilla
diff --git a/toolkit/xre/dllservices/mozglue/LoaderObserver.h b/toolkit/xre/dllservices/mozglue/LoaderObserver.h
new file mode 100644
index 0000000000..39b13035a3
--- /dev/null
+++ b/toolkit/xre/dllservices/mozglue/LoaderObserver.h
@@ -0,0 +1,45 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_glue_LoaderObserver_h
+#define mozilla_glue_LoaderObserver_h
+
+#include "mozilla/Attributes.h"
+#include "mozilla/LoaderAPIInterfaces.h"
+#include "mozilla/glue/WindowsDllServices.h"
+#include "mozilla/glue/WinUtils.h"
+#include "mozilla/UniquePtr.h"
+
+namespace mozilla {
+namespace glue {
+
+class MOZ_ONLY_USED_TO_AVOID_STATIC_CONSTRUCTORS LoaderObserver final
+    : public nt::LoaderObserver {
+ public:
+  constexpr LoaderObserver() : mModuleLoads(nullptr), mEnabled(true) {}
+
+  void OnBeginDllLoad(void** aContext,
+                      PCUNICODE_STRING aPreliminaryDllName) final;
+  bool SubstituteForLSP(PCUNICODE_STRING aLspLeafName,
+                        PHANDLE aOutHandle) final;
+  void OnEndDllLoad(void* aContext, NTSTATUS aNtStatus,
+                    ModuleLoadInfo&& aModuleLoadInfo) final;
+  void Forward(nt::LoaderObserver* aNext) final;
+  void OnForward(ModuleLoadInfoVec&& aInfo) final;
+
+  void Forward(mozilla::glue::detail::DllServicesBase* aSvc);
+  void Disable();
+
+ private:
+  Win32SRWLock mLock;
+  ModuleLoadInfoVec* mModuleLoads;
+  bool mEnabled;
+};
+
+}  // namespace glue
+}  // namespace mozilla
+
+#endif  // mozilla_glue_LoaderObserver_h
diff --git a/toolkit/xre/dllservices/mozglue/ModuleLoadFrame.cpp b/toolkit/xre/dllservices/mozglue/ModuleLoadFrame.cpp
new file mode 100644
index 0000000000..a49505adbc
--- /dev/null
+++ b/toolkit/xre/dllservices/mozglue/ModuleLoadFrame.cpp
@@ -0,0 +1,104 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "ModuleLoadFrame.h"
+#include "mozilla/NativeNt.h"
+#include "mozilla/UniquePtr.h"
+#include "NtLoaderAPI.h"
+
+#include <string.h>
+
+#include "WindowsFallbackLoaderAPI.h"
+
+static bool IsNullTerminated(PCUNICODE_STRING aStr) {
+  return aStr && (aStr->MaximumLength >= (aStr->Length + sizeof(WCHAR))) &&
+         aStr->Buffer && aStr->Buffer[aStr->Length / sizeof(WCHAR)] == 0;
+}
+
+static mozilla::FallbackLoaderAPI gFallbackLoaderAPI;
+
+namespace mozilla {
+namespace glue {
+
+nt::LoaderAPI* ModuleLoadFrame::sLoaderAPI;
+
+using GetNtLoaderAPIFn = decltype(&mozilla::GetNtLoaderAPI);
+
+/* static */
+void ModuleLoadFrame::StaticInit(nt::LoaderObserver* aNewObserver,
+                                 nt::WinLauncherServices* aOutWinLauncher) {
+  const auto pGetNtLoaderAPI = reinterpret_cast<GetNtLoaderAPIFn>(
+      ::GetProcAddress(::GetModuleHandleW(nullptr), "GetNtLoaderAPI"));
+  if (!pGetNtLoaderAPI) {
+    // This case occurs in processes other than firefox.exe that do not contain
+    // the launcher process blocklist.
+    gFallbackLoaderAPI.SetObserver(aNewObserver);
+    sLoaderAPI = &gFallbackLoaderAPI;
+
+    if (aOutWinLauncher) {
+      aOutWinLauncher->mHandleLauncherError = [](const mozilla::LauncherError&,
+                                                 const char*) {};
+      // We intentionally leave mInitDllBlocklistOOP null to make sure calling
+      // mInitDllBlocklistOOP in non-Firefox hits MOZ_RELEASE_ASSERT.
+    }
+    return;
+  }
+
+  sLoaderAPI = pGetNtLoaderAPI(aNewObserver);
+  MOZ_ASSERT(sLoaderAPI);
+
+  if (aOutWinLauncher) {
+    aOutWinLauncher->mInitDllBlocklistOOP = sLoaderAPI->GetDllBlocklistInitFn();
+    aOutWinLauncher->mHandleLauncherError =
+        sLoaderAPI->GetHandleLauncherErrorFn();
+    aOutWinLauncher->mSharedSection = sLoaderAPI->GetSharedSection();
+  }
+}
+
+ModuleLoadFrame::ModuleLoadFrame(PCUNICODE_STRING aRequestedDllName)
+    : mAlreadyLoaded(false),
+      mContext(nullptr),
+      mDllLoadStatus(STATUS_UNSUCCESSFUL),
+      mLoadInfo(sLoaderAPI->ConstructAndNotifyBeginDllLoad(&mContext,
+                                                           aRequestedDllName)) {
+  if (!aRequestedDllName) {
+    return;
+  }
+
+  UniquePtr<WCHAR[]> nameBuf;
+  const WCHAR* name = nullptr;
+
+  if (IsNullTerminated(aRequestedDllName)) {
+    name = aRequestedDllName->Buffer;
+  } else {
+    USHORT charLenExclNul = aRequestedDllName->Length / sizeof(WCHAR);
+    USHORT charLenInclNul = charLenExclNul + 1;
+    nameBuf = MakeUnique<WCHAR[]>(charLenInclNul);
+    if (!wcsncpy_s(nameBuf.get(), charLenInclNul, aRequestedDllName->Buffer,
+                   charLenExclNul)) {
+      name = nameBuf.get();
+    }
+  }
+
+  mAlreadyLoaded = name && !!::GetModuleHandleW(name);
+}
+
+ModuleLoadFrame::~ModuleLoadFrame() {
+  sLoaderAPI->NotifyEndDllLoad(mContext, mDllLoadStatus, std::move(mLoadInfo));
+}
+
+void ModuleLoadFrame::SetLoadStatus(NTSTATUS aNtStatus, HANDLE aHandle) {
+  mDllLoadStatus = aNtStatus;
+  void* baseAddr = mozilla::nt::PEHeaders::HModuleToBaseAddr<void*>(
+      reinterpret_cast<HMODULE>(aHandle));
+  mLoadInfo.mBaseAddr = baseAddr;
+  if (!mAlreadyLoaded) {
+    mLoadInfo.mSectionName = sLoaderAPI->GetSectionName(baseAddr);
+  }
+}
+
+}  // namespace glue
+}  // namespace mozilla
diff --git a/toolkit/xre/dllservices/mozglue/ModuleLoadFrame.h b/toolkit/xre/dllservices/mozglue/ModuleLoadFrame.h
new file mode 100644
index 0000000000..d47e42ab0c
--- /dev/null
+++ b/toolkit/xre/dllservices/mozglue/ModuleLoadFrame.h
@@ -0,0 +1,44 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_glue_ModuleLoadFrame_h
+#define mozilla_glue_ModuleLoadFrame_h
+
+#include "mozilla/Attributes.h"
+#include "mozilla/LoaderAPIInterfaces.h"
+
+namespace mozilla {
+namespace glue {
+
+class MOZ_RAII ModuleLoadFrame final {
+ public:
+  explicit ModuleLoadFrame(PCUNICODE_STRING aRequestedDllName);
+  ~ModuleLoadFrame();
+
+  void SetLoadStatus(NTSTATUS aNtStatus, HANDLE aHandle);
+
+  ModuleLoadFrame(const ModuleLoadFrame&) = delete;
+  ModuleLoadFrame(ModuleLoadFrame&&) = delete;
+  ModuleLoadFrame& operator=(const ModuleLoadFrame&) = delete;
+  ModuleLoadFrame& operator=(ModuleLoadFrame&&) = delete;
+
+  static void StaticInit(nt::LoaderObserver* aNewObserver,
+                         nt::WinLauncherServices* aOutWinLauncher);
+
+ private:
+  bool mAlreadyLoaded;
+  void* mContext;
+  NTSTATUS mDllLoadStatus;
+  ModuleLoadInfo mLoadInfo;
+
+ private:
+  static nt::LoaderAPI* sLoaderAPI;
+};
+
+}  // namespace glue
+}  // namespace mozilla
+
+#endif  // mozilla_glue_ModuleLoadFrame_h
diff --git a/toolkit/xre/dllservices/mozglue/ModuleLoadInfo.h b/toolkit/xre/dllservices/mozglue/ModuleLoadInfo.h
new file mode 100644
index 0000000000..683586a5b0
--- /dev/null
+++ b/toolkit/xre/dllservices/mozglue/ModuleLoadInfo.h
@@ -0,0 +1,179 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_ModuleLoadInfo_h
+#define mozilla_ModuleLoadInfo_h
+
+#include "mozilla/NativeNt.h"
+#include "mozilla/Vector.h"
+#include "mozilla/Unused.h"
+
+namespace mozilla {
+
+struct ModuleLoadInfo final {
+  enum class Status : uint32_t {
+    Loaded = 0,
+    Blocked,
+    Redirected,
+  };
+
+  // We do not provide these methods inside Gecko proper.
+#if !defined(MOZILLA_INTERNAL_API)
+
+  /**
+   * This constructor is for use by the LdrLoadDll hook.
+   */
+  explicit ModuleLoadInfo(PCUNICODE_STRING aRequestedDllName)
+      : mLoadTimeInfo(),
+        mThreadId(nt::RtlGetCurrentThreadId()),
+        mRequestedDllName(aRequestedDllName),
+        mBaseAddr(nullptr),
+        mStatus(Status::Loaded),
+        mIsDependent(false) {
+#  if defined(IMPL_MFBT)
+    ::QueryPerformanceCounter(&mBeginTimestamp);
+#  else
+    ::RtlQueryPerformanceCounter(&mBeginTimestamp);
+#  endif  // defined(IMPL_MFBT)
+  }
+
+  /**
+   * This constructor is used by the NtMapViewOfSection hook IF AND ONLY IF
+   * the LdrLoadDll hook did not already construct a ModuleLoadInfo for the
+   * current DLL load. This may occur while the loader is loading dependencies
+   * of another library.
+   */
+  ModuleLoadInfo(nt::AllocatedUnicodeString&& aSectionName,
+                 const void* aBaseAddr, Status aLoadStatus, bool aIsDependent)
+      : mLoadTimeInfo(),
+        mThreadId(nt::RtlGetCurrentThreadId()),
+        mSectionName(std::move(aSectionName)),
+        mBaseAddr(aBaseAddr),
+        mStatus(aLoadStatus),
+        mIsDependent(aIsDependent) {
+#  if defined(IMPL_MFBT)
+    ::QueryPerformanceCounter(&mBeginTimestamp);
+#  else
+    ::RtlQueryPerformanceCounter(&mBeginTimestamp);
+#  endif  // defined(IMPL_MFBT)
+  }
+
+  /**
+   * Marks the time that LdrLoadDll began loading this library.
+   */
+  void SetBeginLoadTimeStamp() {
+#  if defined(IMPL_MFBT)
+    ::QueryPerformanceCounter(&mLoadTimeInfo);
+#  else
+    ::RtlQueryPerformanceCounter(&mLoadTimeInfo);
+#  endif  // defined(IMPL_MFBT)
+  }
+
+  /**
+   * Marks the time that LdrLoadDll finished loading this library.
+   */
+  void SetEndLoadTimeStamp() {
+    LARGE_INTEGER endTimeStamp;
+#  if defined(IMPL_MFBT)
+    ::QueryPerformanceCounter(&endTimeStamp);
+#  else
+    ::RtlQueryPerformanceCounter(&endTimeStamp);
+#  endif  // defined(IMPL_MFBT)
+
+    LONGLONG& timeInfo = mLoadTimeInfo.QuadPart;
+    if (!timeInfo) {
+      return;
+    }
+
+    timeInfo = endTimeStamp.QuadPart - timeInfo;
+  }
+
+  /**
+   * Saves the current thread's call stack.
+   */
+  void CaptureBacktrace() {
+    const DWORD kMaxBacktraceSize = 512;
+
+    if (!mBacktrace.resize(kMaxBacktraceSize)) {
+      return;
+    }
+
+    // We don't use a Win32 variant here because Win32's CaptureStackBackTrace
+    // is just a macro that resolve to this function anyway.
+    WORD numCaptured = ::RtlCaptureStackBackTrace(2, kMaxBacktraceSize,
+                                                  mBacktrace.begin(), nullptr);
+    Unused << mBacktrace.resize(numCaptured);
+    // These backtraces might stick around for a while, so let's trim any
+    // excess memory.
+    mBacktrace.shrinkStorageToFit();
+  }
+
+#endif  // !defined(MOZILLA_INTERNAL_API)
+
+  ModuleLoadInfo(ModuleLoadInfo&&) = default;
+  ModuleLoadInfo& operator=(ModuleLoadInfo&&) = default;
+
+  ModuleLoadInfo() = delete;
+  ModuleLoadInfo(const ModuleLoadInfo&) = delete;
+  ModuleLoadInfo& operator=(const ModuleLoadInfo&) = delete;
+
+  /**
+   * A "bare" module load is one that was mapped without the code passing
+   * through a call to ntdll!LdrLoadDll.
+   */
+  bool IsBare() const {
+    // SetBeginLoadTimeStamp() and SetEndLoadTimeStamp() are only called by the
+    // LdrLoadDll hook, so when mLoadTimeInfo == 0, we know that we are bare.
+    return !mLoadTimeInfo.QuadPart;
+  }
+
+  /**
+   * Returns true for DLL loads where LdrLoadDll was called but
+   * NtMapViewOfSection was not. This will happen for DLL requests where the DLL
+   * was already mapped into memory by a previous request.
+   */
+  bool WasMapped() const { return !mSectionName.IsEmpty(); }
+
+  /**
+   * Returns true for DLL load which was denied by our blocklist.
+   */
+  bool WasDenied() const {
+    return mStatus == ModuleLoadInfo::Status::Blocked ||
+           mStatus == ModuleLoadInfo::Status::Redirected;
+  }
+
+  /**
+   * Returns true for a DLL load which was blocked by our blocklist.
+   */
+  bool WasBlocked() const { return mStatus == ModuleLoadInfo::Status::Blocked; }
+
+  // Timestamp for the creation of this event
+  LARGE_INTEGER mBeginTimestamp;
+  // Duration of the LdrLoadDll call
+  LARGE_INTEGER mLoadTimeInfo;
+  // Thread ID of this DLL load
+  DWORD mThreadId;
+  // The name requested of LdrLoadDll by its caller
+  nt::AllocatedUnicodeString mRequestedDllName;
+  // The name of the DLL that backs section that was mapped by the loader. This
+  // string is the effective name of the DLL that was resolved by the loader's
+  // path search algorithm.
+  nt::AllocatedUnicodeString mSectionName;
+  // The base address of the module's mapped section
+  const void* mBaseAddr;
+  // If the module was successfully loaded, stack trace of the DLL load request
+  Vector<PVOID, 0, nt::RtlAllocPolicy> mBacktrace;
+  // The status of DLL load
+  Status mStatus;
+  // Whether the module is one of the executables's dependent modules or not
+  bool mIsDependent;
+};
+
+using ModuleLoadInfoVec = Vector<ModuleLoadInfo, 0, nt::RtlAllocPolicy>;
+
+}  // namespace mozilla
+
+#endif  // mozilla_ModuleLoadInfo_h
diff --git a/toolkit/xre/dllservices/mozglue/NtLoaderAPI.h b/toolkit/xre/dllservices/mozglue/NtLoaderAPI.h
new file mode 100644
index 0000000000..628609092b
--- /dev/null
+++ b/toolkit/xre/dllservices/mozglue/NtLoaderAPI.h
@@ -0,0 +1,23 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_NtLoaderAPI_h
+#define mozilla_NtLoaderAPI_h
+
+#include "mozilla/LoaderAPIInterfaces.h"
+
+#if !defined(IMPL_MFBT)
+#  error "This should only be included from mozglue!"
+#endif  // !defined(IMPL_MFBT)
+
+namespace mozilla {
+
+extern "C" MOZ_IMPORT_API nt::LoaderAPI* GetNtLoaderAPI(
+    nt::LoaderObserver* aNewObserver);
+
+}  // namespace mozilla
+
+#endif  // mozilla_NtLoaderAPI_h
diff --git a/toolkit/xre/dllservices/mozglue/SharedSection.h b/toolkit/xre/dllservices/mozglue/SharedSection.h
new file mode 100644
index 0000000000..162c8e8343
--- /dev/null
+++ b/toolkit/xre/dllservices/mozglue/SharedSection.h
@@ -0,0 +1,28 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_glue_SharedSection_h
+#define mozilla_glue_SharedSection_h
+
+#include <winternl.h>
+#include "nscore.h"
+#include "mozilla/Span.h"
+#include "mozilla/WindowsDllBlocklistInfo.h"
+
+namespace mozilla::nt {
+
+// This interface provides a way to access winlauncher's shared section
+// through DllServices.
+struct NS_NO_VTABLE SharedSection {
+  virtual Span<const wchar_t> GetDependentModules() = 0;
+  // Returns a span of the whole space for dynamic blocklist entries.
+  // Use IsValidDynamicBlocklistEntry() to determine the end of the list.
+  virtual Span<const DllBlockInfoT<UNICODE_STRING>> GetDynamicBlocklist() = 0;
+};
+
+}  // namespace mozilla::nt
+
+#endif  // mozilla_glue_SharedSection_h
diff --git a/toolkit/xre/dllservices/mozglue/WindowsBCryptInitialization.cpp b/toolkit/xre/dllservices/mozglue/WindowsBCryptInitialization.cpp
new file mode 100644
index 0000000000..e643a096ab
--- /dev/null
+++ b/toolkit/xre/dllservices/mozglue/WindowsBCryptInitialization.cpp
@@ -0,0 +1,24 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/WindowsBCryptInitialization.h"
+
+#include "mozilla/RandomNum.h"
+#include "nsWindowsDllInterceptor.h"
+
+#include <bcrypt.h>
+#pragma comment(lib, "bcrypt.lib")
+
+namespace mozilla {
+
+bool WindowsBCryptInitialization() {
+  UCHAR buffer[32];
+  NTSTATUS status = ::BCryptGenRandom(nullptr, buffer, sizeof(buffer),
+                                      BCRYPT_USE_SYSTEM_PREFERRED_RNG);
+  return NT_SUCCESS(status);
+}
+
+}  // namespace mozilla
diff --git a/toolkit/xre/dllservices/mozglue/WindowsBCryptInitialization.h b/toolkit/xre/dllservices/mozglue/WindowsBCryptInitialization.h
new file mode 100644
index 0000000000..b67e5016fb
--- /dev/null
+++ b/toolkit/xre/dllservices/mozglue/WindowsBCryptInitialization.h
@@ -0,0 +1,24 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_WindowsBCryptInitialization_h
+#define mozilla_WindowsBCryptInitialization_h
+
+#include "mozilla/Types.h"
+
+namespace mozilla {
+
+// This functions ensures that calling BCryptGenRandom will work later. It
+// triggers a first call to BCryptGenRandom() to pre-load bcryptPrimitives.dll.
+// In sandboxed processes, this must happen while the current thread still has
+// an unrestricted impersonation token. We need to perform that operation to
+// warmup the BCryptGenRandom() calls is used by others, especially Rust. See
+// bug 1746524, bug 1751094, bug 1751177, bug 1788004.
+MFBT_API bool WindowsBCryptInitialization();
+
+}  // namespace mozilla
+
+#endif  // mozilla_WindowsBCryptInitialization_h
diff --git a/toolkit/xre/dllservices/mozglue/WindowsDllBlocklist.cpp b/toolkit/xre/dllservices/mozglue/WindowsDllBlocklist.cpp
new file mode 100644
index 0000000000..5ac3af4559
--- /dev/null
+++ b/toolkit/xre/dllservices/mozglue/WindowsDllBlocklist.cpp
@@ -0,0 +1,811 @@
+/* -*- Mode: C++; tab-width: 40; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <windows.h>
+#include <winternl.h>
+
+#pragma warning(push)
+#pragma warning(disable : 4275 4530)  // See msvc-stl-wrapper.template.h
+#include <map>
+#pragma warning(pop)
+
+#include "Authenticode.h"
+#include "BaseProfiler.h"
+#include "nsWindowsDllInterceptor.h"
+#include "mozilla/CmdLineAndEnvUtils.h"
+#include "mozilla/DebugOnly.h"
+#include "mozilla/StackWalk_windows.h"
+#include "mozilla/TimeStamp.h"
+#include "mozilla/UniquePtr.h"
+#include "mozilla/Vector.h"
+#include "mozilla/WindowsProcessMitigations.h"
+#include "mozilla/WindowsVersion.h"
+#include "mozilla/WinHeaderOnlyUtils.h"
+#include "nsWindowsHelpers.h"
+#include "WindowsDllBlocklist.h"
+#include "mozilla/AutoProfilerLabel.h"
+#include "mozilla/glue/Debug.h"
+#include "mozilla/glue/WindowsDllServices.h"
+#include "mozilla/glue/WinUtils.h"
+
+// Start new implementation
+#include "LoaderObserver.h"
+#include "ModuleLoadFrame.h"
+#include "mozilla/glue/WindowsUnicode.h"
+
+namespace mozilla {
+
+glue::Win32SRWLock gDllServicesLock;
+glue::detail::DllServicesBase* gDllServices;
+
+}  // namespace mozilla
+
+using namespace mozilla;
+
+using CrashReporter::Annotation;
+using CrashReporter::AnnotationWriter;
+
+#define DLL_BLOCKLIST_ENTRY(name, ...) {name, __VA_ARGS__},
+#define DLL_BLOCKLIST_STRING_TYPE const char*
+#include "mozilla/WindowsDllBlocklistLegacyDefs.h"
+
+// define this for very verbose dll load debug spew
+#undef DEBUG_very_verbose
+
+static uint32_t sInitFlags;
+static bool sBlocklistInitAttempted;
+static bool sBlocklistInitFailed;
+static bool sUser32BeforeBlocklist;
+
+typedef MOZ_NORETURN_PTR void(__fastcall* BaseThreadInitThunk_func)(
+    BOOL aIsInitialThread, void* aStartAddress, void* aThreadParam);
+static WindowsDllInterceptor::FuncHookType<BaseThreadInitThunk_func>
+    stub_BaseThreadInitThunk;
+
+typedef NTSTATUS(NTAPI* LdrLoadDll_func)(PWCHAR filePath, PULONG flags,
+                                         PUNICODE_STRING moduleFileName,
+                                         PHANDLE handle);
+static WindowsDllInterceptor::FuncHookType<LdrLoadDll_func> stub_LdrLoadDll;
+
+#ifdef _M_AMD64
+typedef decltype(RtlInstallFunctionTableCallback)*
+    RtlInstallFunctionTableCallback_func;
+static WindowsDllInterceptor::FuncHookType<RtlInstallFunctionTableCallback_func>
+    stub_RtlInstallFunctionTableCallback;
+
+extern uint8_t* sMsMpegJitCodeRegionStart;
+extern size_t sMsMpegJitCodeRegionSize;
+
+BOOLEAN WINAPI patched_RtlInstallFunctionTableCallback(
+    DWORD64 TableIdentifier, DWORD64 BaseAddress, DWORD Length,
+    PGET_RUNTIME_FUNCTION_CALLBACK Callback, PVOID Context,
+    PCWSTR OutOfProcessCallbackDll) {
+  // msmpeg2vdec.dll sets up a function table callback for their JIT code that
+  // just terminates the process, because their JIT doesn't have unwind info.
+  // If we see this callback being registered, record the region address, so
+  // that StackWalk.cpp can avoid unwinding addresses in this region.
+  //
+  // To keep things simple I'm not tracking unloads of msmpeg2vdec.dll.
+  // Worst case the stack walker will needlessly avoid a few pages of memory.
+
+  // Tricky: GetModuleHandleExW adds a ref by default; GetModuleHandleW doesn't.
+  HMODULE callbackModule = nullptr;
+  DWORD moduleFlags = GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS |
+                      GET_MODULE_HANDLE_EX_FLAG_UNCHANGED_REFCOUNT;
+
+  // These GetModuleHandle calls enter a critical section on Win7.
+  AutoSuppressStackWalking suppress;
+
+  if (GetModuleHandleExW(moduleFlags, (LPWSTR)Callback, &callbackModule) &&
+      GetModuleHandleW(L"msmpeg2vdec.dll") == callbackModule) {
+    sMsMpegJitCodeRegionStart = (uint8_t*)BaseAddress;
+    sMsMpegJitCodeRegionSize = Length;
+  }
+
+  return stub_RtlInstallFunctionTableCallback(TableIdentifier, BaseAddress,
+                                              Length, Callback, Context,
+                                              OutOfProcessCallbackDll);
+}
+#endif
+
+template <class T>
+struct RVAMap {
+  RVAMap(HANDLE map, DWORD offset) {
+    SYSTEM_INFO info;
+    GetSystemInfo(&info);
+
+    DWORD alignedOffset =
+        (offset / info.dwAllocationGranularity) * info.dwAllocationGranularity;
+
+    MOZ_ASSERT(offset - alignedOffset < info.dwAllocationGranularity, "Wtf");
+
+    mRealView = ::MapViewOfFile(map, FILE_MAP_READ, 0, alignedOffset,
+                                sizeof(T) + (offset - alignedOffset));
+
+    mMappedView =
+        mRealView
+            ? reinterpret_cast<T*>((char*)mRealView + (offset - alignedOffset))
+            : nullptr;
+  }
+  ~RVAMap() {
+    if (mRealView) {
+      ::UnmapViewOfFile(mRealView);
+    }
+  }
+  operator const T*() const { return mMappedView; }
+  const T* operator->() const { return mMappedView; }
+
+ private:
+  const T* mMappedView;
+  void* mRealView;
+};
+
+static DWORD GetTimestamp(const wchar_t* path) {
+  DWORD timestamp = 0;
+
+  HANDLE file = ::CreateFileW(path, GENERIC_READ, FILE_SHARE_READ, nullptr,
+                              OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, nullptr);
+  if (file != INVALID_HANDLE_VALUE) {
+    HANDLE map =
+        ::CreateFileMappingW(file, nullptr, PAGE_READONLY, 0, 0, nullptr);
+    if (map) {
+      RVAMap<IMAGE_DOS_HEADER> peHeader(map, 0);
+      if (peHeader) {
+        RVAMap<IMAGE_NT_HEADERS> ntHeader(map, peHeader->e_lfanew);
+        if (ntHeader) {
+          timestamp = ntHeader->FileHeader.TimeDateStamp;
+        }
+      }
+      ::CloseHandle(map);
+    }
+    ::CloseHandle(file);
+  }
+
+  return timestamp;
+}
+
+// This lock protects both the reentrancy sentinel and the crash reporter
+// data structures.
+static CRITICAL_SECTION sLock;
+
+/**
+ * Some versions of Windows call LoadLibraryEx to get the version information
+ * for a DLL, which causes our patched LdrLoadDll implementation to re-enter
+ * itself and cause infinite recursion and a stack-exhaustion crash. We protect
+ * against reentrancy by allowing recursive loads of the same DLL.
+ *
+ * Note that we don't use __declspec(thread) because that doesn't work in DLLs
+ * loaded via LoadLibrary and there can be a limited number of TLS slots, so
+ * we roll our own.
+ */
+class ReentrancySentinel {
+ public:
+  explicit ReentrancySentinel(const char* dllName) {
+    DWORD currentThreadId = GetCurrentThreadId();
+    AutoCriticalSection lock(&sLock);
+    mPreviousDllName = (*sThreadMap)[currentThreadId];
+
+    // If there is a DLL currently being loaded and it has the same name
+    // as the current attempt, we're re-entering.
+    mReentered = mPreviousDllName && !stricmp(mPreviousDllName, dllName);
+    (*sThreadMap)[currentThreadId] = dllName;
+  }
+
+  ~ReentrancySentinel() {
+    DWORD currentThreadId = GetCurrentThreadId();
+    AutoCriticalSection lock(&sLock);
+    (*sThreadMap)[currentThreadId] = mPreviousDllName;
+  }
+
+  bool BailOut() const { return mReentered; };
+
+  static void InitializeStatics() {
+    InitializeCriticalSection(&sLock);
+    sThreadMap = new std::map<DWORD, const char*>;
+  }
+
+ private:
+  static std::map<DWORD, const char*>* sThreadMap;
+
+  const char* mPreviousDllName;
+  bool mReentered;
+};
+
+std::map<DWORD, const char*>* ReentrancySentinel::sThreadMap;
+
+using WritableBuffer = mozilla::glue::detail::WritableBuffer<1024>;
+
+/**
+ * This is a linked list of DLLs that have been blocked. It doesn't use
+ * mozilla::LinkedList because this is an append-only list and doesn't need
+ * to be doubly linked.
+ */
+class DllBlockSet {
+ public:
+  static void Add(const char* name, unsigned long long version);
+
+  // Write the list of blocked DLLs to a WritableBuffer object. This method is
+  // run after a crash occurs and must therefore not use the heap, etc.
+  static void Write(WritableBuffer& buffer);
+
+ private:
+  DllBlockSet(const char* name, unsigned long long version)
+      : mName(name), mVersion(version), mNext(nullptr) {}
+
+  const char* mName;  // points into the gWindowsDllBlocklist string
+  unsigned long long mVersion;
+  DllBlockSet* mNext;
+
+  static DllBlockSet* gFirst;
+};
+
+DllBlockSet* DllBlockSet::gFirst;
+
+void DllBlockSet::Add(const char* name, unsigned long long version) {
+  AutoCriticalSection lock(&sLock);
+  for (DllBlockSet* b = gFirst; b; b = b->mNext) {
+    if (0 == strcmp(b->mName, name) && b->mVersion == version) {
+      return;
+    }
+  }
+  // Not already present
+  DllBlockSet* n = new DllBlockSet(name, version);
+  n->mNext = gFirst;
+  gFirst = n;
+}
+
+void DllBlockSet::Write(WritableBuffer& buffer) {
+  // It would be nicer to use AutoCriticalSection here. However, its destructor
+  // might not run if an exception occurs, in which case we would never leave
+  // the critical section. (MSVC warns about this possibility.) So we
+  // enter and leave manually.
+  ::EnterCriticalSection(&sLock);
+
+  // Because this method is called after a crash occurs, and uses heap memory,
+  // protect this entire block with a structured exception handler.
+  MOZ_SEH_TRY {
+    for (DllBlockSet* b = gFirst; b; b = b->mNext) {
+      // write name[,v.v.v.v];
+      buffer.Write(b->mName, strlen(b->mName));
+      if (b->mVersion != DllBlockInfo::ALL_VERSIONS) {
+        buffer.Write(",", 1);
+        uint16_t parts[4];
+        parts[0] = b->mVersion >> 48;
+        parts[1] = (b->mVersion >> 32) & 0xFFFF;
+        parts[2] = (b->mVersion >> 16) & 0xFFFF;
+        parts[3] = b->mVersion & 0xFFFF;
+        for (int p = 0; p < 4; ++p) {
+          char buf[32];
+          _ltoa_s(parts[p], buf, sizeof(buf), 10);
+          buffer.Write(buf, strlen(buf));
+          if (p != 3) {
+            buffer.Write(".", 1);
+          }
+        }
+      }
+      buffer.Write(";", 1);
+    }
+  }
+  MOZ_SEH_EXCEPT(EXCEPTION_EXECUTE_HANDLER) {}
+
+  ::LeaveCriticalSection(&sLock);
+}
+
+static UniquePtr<wchar_t[]> getFullPath(PWCHAR filePath, wchar_t* fname) {
+  // In Windows 8, the first parameter seems to be used for more than just the
+  // path name.  For example, its numerical value can be 1.  Passing a non-valid
+  // pointer to SearchPathW will cause a crash, so we need to check to see if we
+  // are handed a valid pointer, and otherwise just pass nullptr to SearchPathW.
+  PWCHAR sanitizedFilePath = nullptr;
+  if ((uintptr_t(filePath) >= 65536) && ((uintptr_t(filePath) & 1) == 0)) {
+    sanitizedFilePath = filePath;
+  }
+
+  // figure out the length of the string that we need
+  DWORD pathlen =
+      SearchPathW(sanitizedFilePath, fname, L".dll", 0, nullptr, nullptr);
+  if (pathlen == 0) {
+    return nullptr;
+  }
+
+  auto full_fname = MakeUnique<wchar_t[]>(pathlen + 1);
+  if (!full_fname) {
+    // couldn't allocate memory?
+    return nullptr;
+  }
+
+  // now actually grab it
+  SearchPathW(sanitizedFilePath, fname, L".dll", pathlen + 1, full_fname.get(),
+              nullptr);
+  return full_fname;
+}
+
+// No builtin function to find the last character matching a set
+static wchar_t* lastslash(wchar_t* s, int len) {
+  for (wchar_t* c = s + len - 1; c >= s; --c) {
+    if (*c == L'\\' || *c == L'/') {
+      return c;
+    }
+  }
+  return nullptr;
+}
+
+static bool ShouldBlockBasedOnBlockInfo(const DllBlockInfo& info,
+                                        const char* dllName, PWCHAR filePath,
+                                        wchar_t* fname,
+                                        unsigned long long* fVersion) {
+#ifdef DEBUG_very_verbose
+  printf_stderr("LdrLoadDll: info->mName: '%s'\n", info->mName);
+#endif
+
+  if (info.mFlags & DllBlockInfoFlags::REDIRECT_TO_NOOP_ENTRYPOINT) {
+    printf_stderr(
+        "LdrLoadDll: "
+        "Ignoring the REDIRECT_TO_NOOP_ENTRYPOINT flag\n");
+  }
+
+  if ((info.mFlags & DllBlockInfoFlags::BLOCK_WIN8_AND_OLDER) &&
+      IsWin8Point1OrLater()) {
+    return false;
+  }
+
+  if ((info.mFlags & DllBlockInfoFlags::BLOCK_WIN7_AND_OLDER) &&
+      IsWin8OrLater()) {
+    return false;
+  }
+
+  if ((info.mFlags & DllBlockInfoFlags::CHILD_PROCESSES_ONLY) &&
+      !(sInitFlags & eDllBlocklistInitFlagIsChildProcess)) {
+    return false;
+  }
+
+  if ((info.mFlags & DllBlockInfoFlags::UTILITY_PROCESSES_ONLY) &&
+      !(sInitFlags & eDllBlocklistInitFlagIsUtilityProcess)) {
+    return false;
+  }
+
+  if ((info.mFlags & DllBlockInfoFlags::SOCKET_PROCESSES_ONLY) &&
+      !(sInitFlags & eDllBlocklistInitFlagIsSocketProcess)) {
+    return false;
+  }
+
+  if ((info.mFlags & DllBlockInfoFlags::GPU_PROCESSES_ONLY) &&
+      !(sInitFlags & eDllBlocklistInitFlagIsGPUProcess)) {
+    return false;
+  }
+
+  if ((info.mFlags & DllBlockInfoFlags::BROWSER_PROCESS_ONLY) &&
+      (sInitFlags & eDllBlocklistInitFlagIsChildProcess)) {
+    return false;
+  }
+
+  if ((info.mFlags & DllBlockInfoFlags::GMPLUGIN_PROCESSES_ONLY) &&
+      !(sInitFlags & eDllBlocklistInitFlagIsGMPluginProcess)) {
+    return false;
+  }
+
+  *fVersion = DllBlockInfo::ALL_VERSIONS;
+
+  if (info.mMaxVersion != DllBlockInfo::ALL_VERSIONS) {
+    ReentrancySentinel sentinel(dllName);
+    if (sentinel.BailOut()) {
+      return false;
+    }
+
+    UniquePtr<wchar_t[]> full_fname = getFullPath(filePath, fname);
+    if (!full_fname) {
+      // uh, we couldn't find the DLL at all, so...
+      printf_stderr(
+          "LdrLoadDll: Blocking load of '%s' (SearchPathW didn't find "
+          "it?)\n",
+          dllName);
+      return true;
+    }
+
+    if (info.mFlags & DllBlockInfoFlags::USE_TIMESTAMP) {
+      *fVersion = GetTimestamp(full_fname.get());
+      if (*fVersion > info.mMaxVersion) {
+        return false;
+      }
+    } else {
+      LauncherResult<ModuleVersion> version =
+          GetModuleVersion(full_fname.get());
+      // If we failed to get the version information, we block.
+      if (version.isOk()) {
+        return info.IsVersionBlocked(version.unwrap());
+      }
+    }
+  }
+  // Falling through to here means we should block.
+  return true;
+}
+
+struct CaseSensitiveStringComparator {
+  explicit CaseSensitiveStringComparator(const char* aTarget)
+      : mTarget(aTarget) {}
+
+  int operator()(const DllBlockInfo& aVal) const {
+    return strcmp(mTarget, aVal.mName);
+  }
+
+  const char* mTarget;
+};
+
+static NTSTATUS NTAPI patched_LdrLoadDll(PWCHAR filePath, PULONG flags,
+                                         PUNICODE_STRING moduleFileName,
+                                         PHANDLE handle) {
+  // We have UCS2 (UTF16?), we want ASCII, but we also just want the filename
+  // portion
+#define DLLNAME_MAX 128
+  char dllName[DLLNAME_MAX + 1];
+  wchar_t* dll_part;
+  char* dot;
+
+  int len = moduleFileName->Length / 2;
+  wchar_t* fname = moduleFileName->Buffer;
+
+  // The filename isn't guaranteed to be null terminated, but in practice
+  // it always will be; ensure that this is so, and bail if not.
+  // This is done instead of the more robust approach because of bug 527122,
+  // where lots of weird things were happening when we tried to make a copy.
+  if (moduleFileName->MaximumLength < moduleFileName->Length + 2 ||
+      fname[len] != 0) {
+#ifdef DEBUG
+    printf_stderr("LdrLoadDll: non-null terminated string found!\n");
+#endif
+    goto continue_loading;
+  }
+
+  dll_part = lastslash(fname, len);
+  if (dll_part) {
+    dll_part = dll_part + 1;
+    len -= dll_part - fname;
+  } else {
+    dll_part = fname;
+  }
+
+#ifdef DEBUG_very_verbose
+  printf_stderr("LdrLoadDll: dll_part '%S' %d\n", dll_part, len);
+#endif
+
+  // if it's too long, then, we assume we won't want to block it,
+  // since DLLNAME_MAX should be at least long enough to hold the longest
+  // entry in our blocklist.
+  if (len > DLLNAME_MAX) {
+#ifdef DEBUG
+    printf_stderr("LdrLoadDll: len too long! %d\n", len);
+#endif
+    goto continue_loading;
+  }
+
+  // copy over to our char byte buffer, lowercasing ASCII as we go
+  for (int i = 0; i < len; i++) {
+    wchar_t c = dll_part[i];
+
+    if (c > 0x7f) {
+      // welp, it's not ascii; if we need to add non-ascii things to
+      // our blocklist, we'll have to remove this limitation.
+      goto continue_loading;
+    }
+
+    // ensure that dll name is all lowercase
+    if (c >= 'A' && c <= 'Z') c += 'a' - 'A';
+
+    dllName[i] = (char)c;
+  }
+
+  dllName[len] = 0;
+
+#ifdef DEBUG_very_verbose
+  printf_stderr("LdrLoadDll: dll name '%s'\n", dllName);
+#endif
+
+  if (!(sInitFlags & eDllBlocklistInitFlagWasBootstrapped)) {
+    // Block a suspicious binary that uses various 12-digit hex strings
+    // e.g. MovieMode.48CA2AEFA22D.dll (bug 973138)
+    dot = strchr(dllName, '.');
+    if (dot && (strchr(dot + 1, '.') == dot + 13)) {
+      char* end = nullptr;
+      _strtoui64(dot + 1, &end, 16);
+      if (end == dot + 13) {
+        return STATUS_DLL_NOT_FOUND;
+      }
+    }
+    // Block binaries where the filename is at least 16 hex digits
+    if (dot && ((dot - dllName) >= 16)) {
+      char* current = dllName;
+      while (current < dot && isxdigit(*current)) {
+        current++;
+      }
+      if (current == dot) {
+        return STATUS_DLL_NOT_FOUND;
+      }
+    }
+
+    // then compare to everything on the blocklist
+    DECLARE_POINTER_TO_FIRST_DLL_BLOCKLIST_ENTRY(info);
+    DECLARE_DLL_BLOCKLIST_NUM_ENTRIES(infoNumEntries);
+    CaseSensitiveStringComparator comp(dllName);
+    size_t match = LowerBound(info, 0, infoNumEntries, comp);
+    if (match != infoNumEntries) {
+      // There may be multiple entries on the list. Since LowerBound() returns
+      // the first entry that matches (if there are any matches),
+      // search forward from there.
+      while (match < infoNumEntries && (comp(info[match]) == 0)) {
+        unsigned long long fVersion;
+        if (ShouldBlockBasedOnBlockInfo(info[match], dllName, filePath, fname,
+                                        &fVersion)) {
+          printf_stderr(
+              "LdrLoadDll: Blocking load of '%s' -- see "
+              "http://www.mozilla.com/en-US/blocklist/\n",
+              dllName);
+          DllBlockSet::Add(info[match].mName, fVersion);
+          return STATUS_DLL_NOT_FOUND;
+        }
+        ++match;
+      }
+    }
+  }
+
+continue_loading:
+#ifdef DEBUG_very_verbose
+  printf_stderr("LdrLoadDll: continuing load... ('%S')\n",
+                moduleFileName->Buffer);
+#endif
+
+  glue::ModuleLoadFrame loadFrame(moduleFileName);
+
+  NTSTATUS ret;
+  HANDLE myHandle;
+
+  {
+#if defined(_M_AMD64) || defined(_M_ARM64)
+    AutoSuppressStackWalking suppress;
+#endif
+    ret = stub_LdrLoadDll(filePath, flags, moduleFileName, &myHandle);
+  }
+
+  if (handle) {
+    *handle = myHandle;
+  }
+
+  loadFrame.SetLoadStatus(ret, myHandle);
+
+  return ret;
+}
+
+#if defined(NIGHTLY_BUILD)
+// Map of specific thread proc addresses we should block. In particular,
+// LoadLibrary* APIs which indicate DLL injection
+static void* gStartAddressesToBlock[4];
+#endif  // defined(NIGHTLY_BUILD)
+
+static bool ShouldBlockThread(void* aStartAddress) {
+  // Allows crashfirefox.exe to continue to work. Also if your threadproc is
+  // null, this crash is intentional.
+  if (aStartAddress == nullptr) {
+    return false;
+  }
+
+#if defined(NIGHTLY_BUILD)
+  for (auto p : gStartAddressesToBlock) {
+    if (p == aStartAddress) {
+      return true;
+    }
+  }
+#endif
+
+  bool shouldBlock = false;
+  MEMORY_BASIC_INFORMATION startAddressInfo = {0};
+  if (VirtualQuery(aStartAddress, &startAddressInfo,
+                   sizeof(startAddressInfo))) {
+    shouldBlock |= startAddressInfo.State != MEM_COMMIT;
+    shouldBlock |= startAddressInfo.Protect != PAGE_EXECUTE_READ;
+  }
+
+  return shouldBlock;
+}
+
+// Allows blocked threads to still run normally through BaseThreadInitThunk, in
+// case there's any magic there that we shouldn't skip.
+static DWORD WINAPI NopThreadProc(void* /* aThreadParam */) { return 0; }
+
+static MOZ_NORETURN void __fastcall patched_BaseThreadInitThunk(
+    BOOL aIsInitialThread, void* aStartAddress, void* aThreadParam) {
+  if (ShouldBlockThread(aStartAddress)) {
+    aStartAddress = (void*)NopThreadProc;
+  }
+
+  stub_BaseThreadInitThunk(aIsInitialThread, aStartAddress, aThreadParam);
+}
+
+static WindowsDllInterceptor NtDllIntercept;
+static WindowsDllInterceptor Kernel32Intercept;
+
+static void GetNativeNtBlockSetWriter();
+
+static glue::LoaderObserver gMozglueLoaderObserver;
+static nt::WinLauncherServices gWinLauncher;
+
+MFBT_API void DllBlocklist_Initialize(uint32_t aInitFlags) {
+  if (sBlocklistInitAttempted) {
+    return;
+  }
+  sBlocklistInitAttempted = true;
+
+  sInitFlags = aInitFlags;
+
+  glue::ModuleLoadFrame::StaticInit(&gMozglueLoaderObserver, &gWinLauncher);
+
+#ifdef _M_AMD64
+  if (!IsWin8OrLater()) {
+    Kernel32Intercept.Init(L"kernel32.dll");
+    // The crash that this hook works around is only seen on Win7.
+    stub_RtlInstallFunctionTableCallback.Set(
+        Kernel32Intercept, "RtlInstallFunctionTableCallback",
+        &patched_RtlInstallFunctionTableCallback);
+  }
+#endif
+
+  // Bug 1361410: WRusr.dll will overwrite our hook and cause a crash.
+  // Workaround: If we detect WRusr.dll, don't hook.
+  if (!GetModuleHandleW(L"WRusr.dll")) {
+    Kernel32Intercept.Init(L"kernel32.dll");
+    if (!stub_BaseThreadInitThunk.SetDetour(Kernel32Intercept,
+                                            "BaseThreadInitThunk",
+                                            &patched_BaseThreadInitThunk)) {
+#ifdef DEBUG
+      printf_stderr("BaseThreadInitThunk hook failed\n");
+#endif
+    }
+  }
+
+#if defined(NIGHTLY_BUILD)
+  // Populate a list of thread start addresses to block.
+  HMODULE hKernel = GetModuleHandleW(L"kernel32.dll");
+  if (hKernel) {
+    void* pProc;
+
+    pProc = (void*)GetProcAddress(hKernel, "LoadLibraryA");
+    gStartAddressesToBlock[0] = pProc;
+
+    pProc = (void*)GetProcAddress(hKernel, "LoadLibraryW");
+    gStartAddressesToBlock[1] = pProc;
+
+    pProc = (void*)GetProcAddress(hKernel, "LoadLibraryExA");
+    gStartAddressesToBlock[2] = pProc;
+
+    pProc = (void*)GetProcAddress(hKernel, "LoadLibraryExW");
+    gStartAddressesToBlock[3] = pProc;
+  }
+#endif
+
+  if (aInitFlags & eDllBlocklistInitFlagWasBootstrapped) {
+    GetNativeNtBlockSetWriter();
+    return;
+  }
+
+  // There are a couple of exceptional cases where we skip user32.dll check.
+  // - If the the process was bootstrapped by the launcher process, AppInit
+  //   DLLs will be intercepted by the new DllBlockList.  No need to check
+  //   here.
+  // - The code to initialize the base profiler loads winmm.dll which
+  //   statically links user32.dll on an older Windows.  This means if the base
+  //   profiler is active before coming here, we cannot fully intercept AppInit
+  //   DLLs.  Given that the base profiler is used outside the typical use
+  //   cases, it's ok not to check user32.dll in this scenario.
+  const bool skipUser32Check =
+      (sInitFlags & eDllBlocklistInitFlagWasBootstrapped) ||
+      (!IsWin10AnniversaryUpdateOrLater() &&
+       baseprofiler::profiler_is_active());
+
+  // In order to be effective against AppInit DLLs, the blocklist must be
+  // initialized before user32.dll is loaded into the process (bug 932100).
+  if (!skipUser32Check && GetModuleHandleW(L"user32.dll")) {
+    sUser32BeforeBlocklist = true;
+#ifdef DEBUG
+    printf_stderr("DLL blocklist was unable to intercept AppInit DLLs.\n");
+#endif
+  }
+
+  NtDllIntercept.Init("ntdll.dll");
+
+  ReentrancySentinel::InitializeStatics();
+
+  // We specifically use a detour, because there are cases where external
+  // code also tries to hook LdrLoadDll, and doesn't know how to relocate our
+  // nop space patches. (Bug 951827)
+  bool ok = stub_LdrLoadDll.SetDetour(NtDllIntercept, "LdrLoadDll",
+                                      &patched_LdrLoadDll);
+
+  if (!ok) {
+    sBlocklistInitFailed = true;
+#ifdef DEBUG
+    printf_stderr("LdrLoadDll hook failed, no dll blocklisting active\n");
+#endif
+  }
+
+  // If someone injects a thread early that causes user32.dll to load off the
+  // main thread this causes issues, so load it as soon as we've initialized
+  // the block-list. (See bug 1400637)
+  if (!sUser32BeforeBlocklist && !IsWin32kLockedDown()) {
+    ::LoadLibraryW(L"user32.dll");
+  }
+}
+
+#ifdef DEBUG
+MFBT_API void DllBlocklist_Shutdown() {}
+#endif  // DEBUG
+
+static void InternalWriteNotes(AnnotationWriter& aWriter) {
+  WritableBuffer buffer;
+  DllBlockSet::Write(buffer);
+
+  aWriter.Write(Annotation::BlockedDllList, buffer.Data(), buffer.Length());
+
+  if (sBlocklistInitFailed) {
+    aWriter.Write(Annotation::BlocklistInitFailed, "1");
+  }
+
+  if (sUser32BeforeBlocklist) {
+    aWriter.Write(Annotation::User32BeforeBlocklist, "1");
+  }
+}
+
+using WriterFn = void (*)(AnnotationWriter&);
+static WriterFn gWriterFn = &InternalWriteNotes;
+
+static void GetNativeNtBlockSetWriter() {
+  auto nativeWriter = reinterpret_cast<WriterFn>(
+      ::GetProcAddress(::GetModuleHandleW(nullptr), "NativeNtBlockSet_Write"));
+  if (nativeWriter) {
+    gWriterFn = nativeWriter;
+  }
+}
+
+MFBT_API void DllBlocklist_WriteNotes(AnnotationWriter& aWriter) {
+  MOZ_ASSERT(gWriterFn);
+  gWriterFn(aWriter);
+}
+
+MFBT_API bool DllBlocklist_CheckStatus() {
+  if (sBlocklistInitFailed || sUser32BeforeBlocklist) return false;
+  return true;
+}
+
+// ============================================================================
+// This section is for DLL Services
+// ============================================================================
+
+namespace mozilla {
+Authenticode* GetAuthenticode();
+}  // namespace mozilla
+
+/**
+ * Please note that DllBlocklist_SetFullDllServices is called with
+ * aSvc = nullptr to de-initialize the resources even though they
+ * have been initialized via DllBlocklist_SetBasicDllServices.
+ */
+MFBT_API void DllBlocklist_SetFullDllServices(
+    mozilla::glue::detail::DllServicesBase* aSvc) {
+  glue::AutoExclusiveLock lock(gDllServicesLock);
+  if (aSvc) {
+    aSvc->SetAuthenticodeImpl(GetAuthenticode());
+    aSvc->SetWinLauncherServices(gWinLauncher);
+    gMozglueLoaderObserver.Forward(aSvc);
+  }
+
+  gDllServices = aSvc;
+}
+
+MFBT_API void DllBlocklist_SetBasicDllServices(
+    mozilla::glue::detail::DllServicesBase* aSvc) {
+  if (!aSvc) {
+    return;
+  }
+
+  aSvc->SetAuthenticodeImpl(GetAuthenticode());
+  gMozglueLoaderObserver.Disable();
+}
diff --git a/toolkit/xre/dllservices/mozglue/WindowsDllBlocklist.h b/toolkit/xre/dllservices/mozglue/WindowsDllBlocklist.h
new file mode 100644
index 0000000000..1b43e6d1fc
--- /dev/null
+++ b/toolkit/xre/dllservices/mozglue/WindowsDllBlocklist.h
@@ -0,0 +1,95 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_windowsdllblocklist_h
+#define mozilla_windowsdllblocklist_h
+
+#if (defined(_MSC_VER) || defined(__MINGW32__)) && \
+    (defined(_M_IX86) || defined(_M_X64) || defined(_M_ARM64))
+
+#  include <windows.h>
+#  include "CrashAnnotations.h"
+#  include "mozilla/Attributes.h"
+#  include "mozilla/ProcessType.h"
+#  include "mozilla/Types.h"
+
+#  define HAS_DLL_BLOCKLIST
+
+enum DllBlocklistInitFlags {
+  eDllBlocklistInitFlagDefault = 0,
+  eDllBlocklistInitFlagIsChildProcess = 1 << 0,
+  eDllBlocklistInitFlagWasBootstrapped = 1 << 1,
+  eDllBlocklistInitFlagIsUtilityProcess = 1 << 2,
+  eDllBlocklistInitFlagIsSocketProcess = 1 << 3,
+  eDllBlocklistInitFlagIsGPUProcess = 1 << 4,
+  eDllBlocklistInitFlagIsGMPluginProcess = 1 << 5,
+};
+
+inline void SetDllBlocklistProcessTypeFlags(uint32_t& aFlags,
+                                            GeckoProcessType aProcessType) {
+  if (aProcessType == GeckoProcessType_Utility) {
+    aFlags |= eDllBlocklistInitFlagIsUtilityProcess;
+  } else if (aProcessType == GeckoProcessType_Socket) {
+    aFlags |= eDllBlocklistInitFlagIsSocketProcess;
+  } else if (aProcessType == GeckoProcessType_GPU) {
+    aFlags |= eDllBlocklistInitFlagIsGPUProcess;
+  } else if (aProcessType == GeckoProcessType_GMPlugin) {
+    aFlags |= eDllBlocklistInitFlagIsGMPluginProcess;
+  }
+}
+
+// Only available from within firefox.exe
+#  if !defined(IMPL_MFBT) && !defined(MOZILLA_INTERNAL_API)
+extern uint32_t gBlocklistInitFlags;
+#  endif  // !defined(IMPL_MFBT) && !defined(MOZILLA_INTERNAL_API)
+
+MFBT_API void DllBlocklist_Initialize(
+    uint32_t aInitFlags = eDllBlocklistInitFlagDefault);
+MFBT_API void DllBlocklist_WriteNotes(CrashReporter::AnnotationWriter& aWriter);
+MFBT_API bool DllBlocklist_CheckStatus();
+
+// This export intends to clean up after DllBlocklist_Initialize().
+// It's disabled in release builds for performance and to limit callers' ability
+// to interfere with dll blocking.
+#  ifdef DEBUG
+MFBT_API void DllBlocklist_Shutdown();
+#  endif  // DEBUG
+
+namespace mozilla {
+namespace glue {
+namespace detail {
+// Forward declaration
+class DllServicesBase;
+
+template <size_t N>
+class WritableBuffer {
+  char mBuffer[N];
+  size_t mLen;
+
+  size_t Available() const { return sizeof(mBuffer) - mLen; }
+
+ public:
+  WritableBuffer() : mBuffer{0}, mLen(0) {}
+
+  void Write(const char* aData, size_t aLen) {
+    size_t writable_len = std::min(aLen, Available());
+    memcpy(mBuffer + mLen, aData, writable_len);
+    mLen += writable_len;
+  }
+
+  size_t Length() const { return mLen; }
+  const char* Data() const { return mBuffer; }
+};
+}  // namespace detail
+}  // namespace glue
+}  // namespace mozilla
+
+MFBT_API void DllBlocklist_SetFullDllServices(
+    mozilla::glue::detail::DllServicesBase* aSvc);
+MFBT_API void DllBlocklist_SetBasicDllServices(
+    mozilla::glue::detail::DllServicesBase* aSvc);
+
+#endif  // defined(_MSC_VER) && (defined(_M_IX86) || defined(_M_X64))
+#endif  // mozilla_windowsdllblocklist_h
diff --git a/toolkit/xre/dllservices/mozglue/WindowsDllBlocklistCommon.h b/toolkit/xre/dllservices/mozglue/WindowsDllBlocklistCommon.h
new file mode 100644
index 0000000000..b9f176ac02
--- /dev/null
+++ b/toolkit/xre/dllservices/mozglue/WindowsDllBlocklistCommon.h
@@ -0,0 +1,46 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_WindowsDllBlocklistCommon_h
+#define mozilla_WindowsDllBlocklistCommon_h
+
+#include "mozilla/ArrayUtils.h"
+#include "mozilla/WindowsDllBlocklistInfo.h"
+
+#if !defined(DLL_BLOCKLIST_STRING_TYPE)
+#  error "You must define DLL_BLOCKLIST_STRING_TYPE"
+#endif  // !defined(DLL_BLOCKLIST_STRING_TYPE)
+
+#define DLL_BLOCKLIST_DEFINITIONS_BEGIN_NAMED(name)                       \
+  using DllBlockInfo = mozilla::DllBlockInfoT<DLL_BLOCKLIST_STRING_TYPE>; \
+  static const DllBlockInfo name[] = {
+#define DLL_BLOCKLIST_DEFINITIONS_BEGIN \
+  DLL_BLOCKLIST_DEFINITIONS_BEGIN_NAMED(gWindowsDllBlocklist)
+
+#define DLL_BLOCKLIST_DEFINITIONS_END \
+  {}                                  \
+  }                                   \
+  ;
+
+#define DECLARE_POINTER_TO_FIRST_DLL_BLOCKLIST_ENTRY_FOR(name, list) \
+  const DllBlockInfo* name = &list[0]
+
+#define DECLARE_POINTER_TO_FIRST_DLL_BLOCKLIST_ENTRY(name) \
+  DECLARE_POINTER_TO_FIRST_DLL_BLOCKLIST_ENTRY_FOR(name, gWindowsDllBlocklist)
+
+#define DECLARE_POINTER_TO_LAST_DLL_BLOCKLIST_ENTRY_FOR(name, list) \
+  const DllBlockInfo* name = &list[mozilla::ArrayLength(list) - 1]
+
+#define DECLARE_POINTER_TO_LAST_DLL_BLOCKLIST_ENTRY(name) \
+  DECLARE_POINTER_TO_LAST_DLL_BLOCKLIST_ENTRY_FOR(name, gWindowsDllBlocklist)
+
+#define DECLARE_DLL_BLOCKLIST_NUM_ENTRIES_FOR(name, list) \
+  const size_t name = mozilla::ArrayLength(list) - 1
+
+#define DECLARE_DLL_BLOCKLIST_NUM_ENTRIES(name) \
+  DECLARE_DLL_BLOCKLIST_NUM_ENTRIES_FOR(name, gWindowsDllBlocklist)
+
+#endif  // mozilla_WindowsDllBlocklistCommon_h
diff --git a/toolkit/xre/dllservices/mozglue/WindowsDllBlocklistDefs.in b/toolkit/xre/dllservices/mozglue/WindowsDllBlocklistDefs.in
new file mode 100644
index 0000000000..eaeee1b870
--- /dev/null
+++ b/toolkit/xre/dllservices/mozglue/WindowsDllBlocklistDefs.in
@@ -0,0 +1,434 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# This file exposes these lists:
+# ALL_PROCESSES, BROWSER_PROCESS, CHILD_PROCESSES, GMPLUGIN_PROCESSES,
+# GPU_PROCESSES, UTILITY_PROCESSES, and SOCKET_PROCESSES
+#
+# In addition, each of those lists supports a special variant for test-only
+# entries:
+# ALL_PROCESSES_TESTS, BROWSER_PROCESS_TESTS, CHILD_PROCESSES_TESTS,
+# GMPLUGIN_PROCESSES_TESTS, GPU_PROCESSES_TESTS, UTILITY_PROCESSES_TESTS, and
+# SOCKET_PROCESSES_TESTS
+#
+# Choose the list that is applicable to the applicable process type(s) for your
+# DLL block.
+#
+# The currently supported blocklist entry types are:
+# DllBlocklistEntry, A11yBlocklistEntry, LspBlocklistEntry,
+# RedirectToNoOpEntryPoint
+# (See gen_dll_blocklist_defs.py for their documentation.)
+#
+# Example:
+# ALL_PROCESSES += [
+#     DllBlocklistEntry("foo.dll", (1, 2, 3, 4)),
+#     DllBlocklistEntry("foo.dll", ALL_VERSIONS),
+#     DllBlocklistEntry("foo.dll", UNVERSIONED),
+#     DllBlocklistEntry("foo.dll", 0x0000123400000000),
+#     DllBlocklistEntry("foo.dll", PETimeStamp(0x12345678)),
+# ]
+#
+# The version parameter the "last bad" version, that is, we block anything that
+# is less-than or equal to that version.
+
+ALL_PROCESSES += [
+    # NPFFAddon - Known malware
+    DllBlocklistEntry("npffaddon.dll", ALL_VERSIONS),
+
+    # AVG 8 - Antivirus vendor AVG, old version, plugin already blocklisted
+    DllBlocklistEntry("avgrsstx.dll", (8,5,0,401)),
+
+    # calc.dll - Suspected malware
+    DllBlocklistEntry("calc.dll", (1,0,0,1)),
+
+    # hook.dll - Suspected malware
+    DllBlocklistEntry("hook.dll", ALL_VERSIONS),
+
+    # GoogleDesktopNetwork3.dll - Extremely old, unversioned instances
+    # of this DLL cause crashes
+    # GoogleDesktopNetwork3.dll - Discontinued product but seems to crash at
+    # least on Win7 32-bits
+    #
+    # Since it was already blocked for all processes but unversioned DLLs, it
+    # looks like one cannot have this and a second block declaration for
+    # utility processes but limiting versions / windows targets
+    DllBlocklistEntry("googledesktopnetwork3.dll", ALL_VERSIONS),
+
+    # rdolib.dll - Suspected malware
+    DllBlocklistEntry("rdolib.dll", (6,0,88,4)),
+
+    # fgjk4wvb.dll - Suspected malware
+    DllBlocklistEntry("fgjk4wvb.dll", (8,8,8,8)),
+
+    # radhslib.dll - Naomi internet filter - unmaintained since 2006
+    DllBlocklistEntry("radhslib.dll", UNVERSIONED),
+
+    # Music download filter for vkontakte.ru - old instances
+    # of this DLL cause crashes
+    DllBlocklistEntry("vksaver.dll", (2,2,2,0)),
+
+    # Topcrash in Firefox 4.0b1
+    DllBlocklistEntry("rlxf.dll", (1,2,323,1)),
+
+    # psicon.dll - Topcrashes in Thunderbird, and some crashes in Firefox
+    # Adobe photoshop library, now redundant in later installations
+    DllBlocklistEntry("psicon.dll", ALL_VERSIONS),
+
+    # Topcrash in Firefox 4 betas (bug 618899),
+    DllBlocklistEntry("accelerator.dll", (3,2,1,6)),
+
+    # Topcrash with Roboform in Firefox 8 (bug 699134),
+    DllBlocklistEntry("rf-firefox.dll", (7,6,1,0)),
+    DllBlocklistEntry("roboform.dll", (7,6,1,0)),
+
+    # Topcrash with Babylon Toolbar on FF16+ (bug 721264),
+    DllBlocklistEntry("babyfox.dll", ALL_VERSIONS),
+
+    # sprotector.dll crashes, bug 957258
+    DllBlocklistEntry("sprotector.dll", ALL_VERSIONS),
+
+    # Windows Media Foundation FLAC decoder and type sniffer (bug 839031).
+    DllBlocklistEntry("mfflac.dll", ALL_VERSIONS),
+
+    # Older Relevant Knowledge DLLs cause us to crash (bug 904001).
+    DllBlocklistEntry("rlnx.dll", (1, 3, 334, 9)),
+    DllBlocklistEntry("pmnx.dll", (1, 3, 334, 9)),
+    DllBlocklistEntry("opnx.dll", (1, 3, 334, 9)),
+    DllBlocklistEntry("prnx.dll", (1, 3, 334, 9)),
+
+    # Older belgian ID card software causes Firefox to crash or hang on
+    # shutdown, bug 831285 and 918399.
+    DllBlocklistEntry("beid35cardlayer.dll", (3, 5, 6, 6968)),
+
+    # bug 925459, bitguard crashes
+    DllBlocklistEntry("bitguard.dll", ALL_VERSIONS),
+
+    # bug 812683 - crashes in Windows library when Asus Gamer OSD is installed
+    # Software is discontinued/unsupported
+    DllBlocklistEntry("atkdx11disp.dll", ALL_VERSIONS),
+
+    # Topcrash with Conduit SearchProtect, bug 944542
+    DllBlocklistEntry("spvc32.dll", ALL_VERSIONS),
+
+    # Topcrash with V-bates, bug 1002748 and bug 1023239
+    DllBlocklistEntry("libinject.dll", UNVERSIONED),
+    DllBlocklistEntry("libinject2.dll", PETimeStamp(0x537DDC93)),
+    DllBlocklistEntry("libredir2.dll", PETimeStamp(0x5385B7ED)),
+
+    # Crashes with RoboForm2Go written against old SDK, bug 988311/1196859
+    DllBlocklistEntry("rf-firefox-22.dll", ALL_VERSIONS),
+    DllBlocklistEntry("rf-firefox-40.dll", ALL_VERSIONS),
+
+    # Crashes with DesktopTemperature, bug 1046382
+    DllBlocklistEntry("dtwxsvc.dll", PETimeStamp(0x53153234)),
+
+    # Startup crashes with Lenovo Onekey Theater, bug 1123778
+    DllBlocklistEntry("activedetect32.dll", UNVERSIONED),
+    DllBlocklistEntry("activedetect64.dll", UNVERSIONED),
+    DllBlocklistEntry("windowsapihookdll32.dll", UNVERSIONED),
+    DllBlocklistEntry("windowsapihookdll64.dll", UNVERSIONED),
+
+    # Flash crashes with RealNetworks RealDownloader, bug 1132663
+    DllBlocklistEntry("rndlnpshimswf.dll", ALL_VERSIONS),
+    DllBlocklistEntry("rndlmainbrowserrecordplugin.dll", ALL_VERSIONS),
+
+    # Startup crashes with RealNetworks Browser Record Plugin, bug 1170141
+    DllBlocklistEntry("nprpffbrowserrecordext.dll", ALL_VERSIONS),
+    DllBlocklistEntry("nprndlffbrowserrecordext.dll", ALL_VERSIONS),
+
+    # Crashes with CyberLink YouCam, bug 1136968
+    DllBlocklistEntry("ycwebcamerasource.ax", (2, 0, 0, 1611)),
+
+    # Old version of WebcamMax crashes WebRTC, bug 1130061
+    DllBlocklistEntry("vwcsource.ax", (1, 5, 0, 0)),
+
+    # NetOp School, discontinued product, bug 763395
+    DllBlocklistEntry("nlsp.dll", (6, 23, 2012, 19)),
+
+    # Orbit Downloader, bug 1222819
+    DllBlocklistEntry("grabdll.dll", (2, 6, 1, 0)),
+    DllBlocklistEntry("grabkernel.dll", (1, 0, 0, 1)),
+
+    # ESET, bug 1229252
+    DllBlocklistEntry("eoppmonitor.dll", ALL_VERSIONS),
+
+    # SS2OSD, bug 1262348
+    DllBlocklistEntry("ss2osd.dll", ALL_VERSIONS),
+    DllBlocklistEntry("ss2devprops.dll", ALL_VERSIONS),
+
+    # NHASUSSTRIXOSD.DLL, bug 1269244
+    DllBlocklistEntry("nhasusstrixosd.dll", ALL_VERSIONS),
+    DllBlocklistEntry("nhasusstrixdevprops.dll", ALL_VERSIONS),
+
+    # Crashes with PremierOpinion/RelevantKnowledge, bug 1277846
+    DllBlocklistEntry("opls.dll", ALL_VERSIONS),
+    DllBlocklistEntry("opls64.dll", ALL_VERSIONS),
+    DllBlocklistEntry("pmls.dll", ALL_VERSIONS),
+    DllBlocklistEntry("pmls64.dll", ALL_VERSIONS),
+    DllBlocklistEntry("prls.dll", ALL_VERSIONS),
+    DllBlocklistEntry("prls64.dll", ALL_VERSIONS),
+    DllBlocklistEntry("rlls.dll", ALL_VERSIONS),
+    DllBlocklistEntry("rlls64.dll", ALL_VERSIONS),
+
+    # Vorbis DirectShow filters, bug 1239690.
+    DllBlocklistEntry("vorbis.acm", (0, 0, 3, 6)),
+
+    # AhnLab Internet Security, bug 1311969
+    DllBlocklistEntry("nzbrcom.dll", ALL_VERSIONS),
+
+    # K7TotalSecurity, bug 1339083 and bug 1694489.
+    DllBlocklistEntry("k7pswsen.dll", (15, 2, 2, 102)),
+
+    # smci*.dll - goobzo crashware (bug 1339908),
+    DllBlocklistEntry("smci32.dll", ALL_VERSIONS),
+    DllBlocklistEntry("smci64.dll", ALL_VERSIONS),
+
+    # Crashes with Internet Download Manager, bug 1333486
+    DllBlocklistEntry("idmcchandler7.dll", ALL_VERSIONS),
+    DllBlocklistEntry("idmcchandler7_64.dll", ALL_VERSIONS),
+    DllBlocklistEntry("idmcchandler5.dll", ALL_VERSIONS),
+    DllBlocklistEntry("idmcchandler5_64.dll", ALL_VERSIONS),
+
+    # Nahimic 2 breaks applicaton update (bug 1356637),
+    DllBlocklistEntry("nahimic2devprops.dll", (2, 5, 19, 0xffff)),
+    # Nahimic is causing crashes, bug 1233556
+    DllBlocklistEntry("nahimicmsiosd.dll", UNVERSIONED),
+    # Nahimic is causing crashes, bug 1360029
+    DllBlocklistEntry("nahimicvrdevprops.dll", UNVERSIONED),
+    DllBlocklistEntry("nahimic2osd.dll", (2, 5, 19, 0xffff)),
+    DllBlocklistEntry("nahimicmsidevprops.dll", UNVERSIONED),
+
+    # Bug 1268470 - crashes with Kaspersky Lab on Windows 8
+    DllBlocklistEntry("klsihk64.dll", (14, 0, 456, 0xffff),
+                      BLOCK_WIN8_AND_OLDER),
+
+    # Bug 1579758, crashes with OpenSC nightly version 0.19.0.448 and lower
+    DllBlocklistEntry("onepin-opensc-pkcs11.dll", (0, 19, 0, 448)),
+
+    # Avecto Privilege Guard causes crashes, bug 1385542
+    DllBlocklistEntry("pghook.dll", ALL_VERSIONS),
+
+    # Old versions of G DATA BankGuard, bug 1421991
+    DllBlocklistEntry("banksafe64.dll", (1, 2, 15299, 65535)),
+
+    # Old versions of G DATA, bug 1043775
+    DllBlocklistEntry("gdkbfltdll64.dll", (1, 0, 14141, 240)),
+
+    # Dell Backup and Recovery tool causes crashes, bug 1433408
+    DllBlocklistEntry("dbroverlayiconnotbackuped.dll", (1, 8, 0, 9)),
+    DllBlocklistEntry("dbroverlayiconbackuped.dll", (1, 8, 0, 9)),
+
+    # NVIDIA nView Desktop Management causes crashes, bug 1465787
+    DllBlocklistEntry("nviewh64.dll", (6, 14, 10, 14847)),
+
+    # Ivanti Endpoint Security, bug 1553776
+    DllBlocklistEntry("sxwmon.dll", ALL_VERSIONS),
+    DllBlocklistEntry("sxwmon64.dll", ALL_VERSIONS),
+
+    # 360 Safeguard/360 Total Security causes a11y crashes, bug 1536227.
+    DllBlocklistEntry("safemon64.dll", ALL_VERSIONS),
+
+    # Old versions of Digital Guardian, bug 1318858, bug 1603974,
+    # and bug 1672367
+    RedirectToNoOpEntryPoint("dgapi.dll", (7, 5, 0xffff, 0xffff)),
+    RedirectToNoOpEntryPoint("dgapi64.dll", (7, 5, 0xffff, 0xffff)),
+
+    # Old versions of COMODO Internet Security, bug 1608048
+    DllBlocklistEntry("IseGuard32.dll", (1, 6, 13835, 184)),
+    DllBlocklistEntry("IseGuard64.dll", (1, 6, 13835, 184)),
+
+    # Old version of COMODO Firewall, bug 1407712 and bug 1624336
+    DllBlocklistEntry("guard64.dll", (8, 4, 0, 65535)),
+
+    # Old version of Panda Security, bug 1637984 and bug 1705125
+    DllBlocklistEntry("PavLspHook64.dll", (9, 2, 2, 1), BLOCK_WIN7_AND_OLDER),
+    DllBlocklistEntry("PavSHook64.dll", (9, 2, 2, 1), BLOCK_WIN7_AND_OLDER),
+
+    # Webroot SecureAnywhere causes crashes, bug 1700281
+    DllBlocklistEntry("WRDll.x64.dll", (1, 1, 0, 227)),
+    DllBlocklistEntry("WRDll.x86.dll", (1, 1, 0, 227)),
+
+    # Webroot SecureAnywhere causes deadlocks, bug 1752466
+    DllBlocklistEntry("WRusr.dll", (9, 0, 32, 49)),
+
+    # InfoWatch Device Monitor causes crashes, bug 1704276
+    DllBlocklistEntry("iwprn.dll", (6, 9, 11, 360)),
+    DllBlocklistEntry("iwprn_x86.dll", (6, 9, 11, 360)),
+
+    # Forcepoint DLLs causing crashes, bug 1767993
+    DllBlocklistEntry("qipcap.dll", (7, 7, 819, 1)),
+    DllBlocklistEntry("qipcap64.dll", (7, 7, 819, 1)),
+
+    # Cylance, bug 1756190 and bug 1799562
+    DllBlocklistEntry("CylanceMemDef64.dll", ALL_VERSIONS),
+
+    # ESET security (bug 1833793)
+    DllBlocklistEntry("eoppbrowser.dll", (1, 0, 88, 0), BLOCK_WIN7_AND_OLDER),
+]
+
+ALL_PROCESSES_TESTS += [
+    # DLLs used by TestDllBlocklist* gTests
+    DllBlocklistEntry("testdllblocklist_matchbyname.dll", ALL_VERSIONS),
+    DllBlocklistEntry("testdllblocklist_matchbyversion.dll", (5, 5, 5, 5)),
+    DllBlocklistEntry("testdllblocklist_allowbyversion.dll", (5, 5, 5, 5)),
+    RedirectToNoOpEntryPoint("testdllblocklist_noopentrypoint.dll",
+                             (5, 5, 5, 5)),
+    DllBlocklistEntry("testdllblocklist_singlenotification1.dll", ALL_VERSIONS),
+    DllBlocklistEntry("testdllblocklist_singlenotification2.dll", (5, 5, 5, 5)),
+    DllBlocklistEntry("testdllblocklist_multipleentries_differentprocesses.dll", UNVERSIONED),
+    # Multiple entries so that search is required to account for each one
+    DllBlocklistEntry("testdllblocklist_multipleentries_sameprocessbackward.dll", (5, 5, 5, 5)),
+    DllBlocklistEntry("testdllblocklist_multipleentries_sameprocessbackward.dll", (1, 1, 1, 1)),
+    DllBlocklistEntry("testdllblocklist_multipleentries_sameprocessbackward.dll", (1, 1, 1, 1)),
+    DllBlocklistEntry("testdllblocklist_multipleentries_sameprocessbackward.dll", (1, 1, 1, 1)),
+    DllBlocklistEntry("testdllblocklist_multipleentries_sameprocessbackward.dll", (1, 1, 1, 1)),
+    DllBlocklistEntry("testdllblocklist_multipleentries_sameprocessbackward.dll", (1, 1, 1, 1)),
+    DllBlocklistEntry("testdllblocklist_multipleentries_sameprocessbackward.dll", (1, 1, 1, 1)),
+    # Multiple entries so that search is required to account for each one
+    DllBlocklistEntry("testdllblocklist_multipleentries_sameprocessforward.dll", (1, 1, 1, 1)),
+    DllBlocklistEntry("testdllblocklist_multipleentries_sameprocessforward.dll", (1, 1, 1, 1)),
+    DllBlocklistEntry("testdllblocklist_multipleentries_sameprocessforward.dll", (1, 1, 1, 1)),
+    DllBlocklistEntry("testdllblocklist_multipleentries_sameprocessforward.dll", (1, 1, 1, 1)),
+    DllBlocklistEntry("testdllblocklist_multipleentries_sameprocessforward.dll", (1, 1, 1, 1)),
+    DllBlocklistEntry("testdllblocklist_multipleentries_sameprocessforward.dll", (1, 1, 1, 1)),
+    DllBlocklistEntry("testdllblocklist_multipleentries_sameprocessforward.dll", (1, 1, 1, 1)),
+    DllBlocklistEntry("testdllblocklist_multipleentries_sameprocessforward.dll", (5, 5, 5, 5)),
+]
+
+BROWSER_PROCESS += [
+    # RealPlayer, bug 1418535, bug 1437417
+    # Versions before 18.1.11.0 cause severe performance problems.
+    A11yBlocklistEntry("dtvhooks.dll", (18, 1, 10, 0xffff)),
+    A11yBlocklistEntry("dtvhooks64.dll", (18, 1, 10, 0xffff)),
+
+    # SolidWorks Windows Explorer integration causes crashes, bug 1566109
+    # and bug 1468250
+    DllBlocklistEntry("Database.dll", ALL_VERSIONS),
+
+    # Hancom Office shell extension causes crashes when the file picker is
+    # opened. See bug 1581092.
+    DllBlocklistEntry("hncshellext64.dll", (1, 0, 0 ,3)),
+
+    # Cambridge Silicon Radio, bug 1634538
+    DllBlocklistEntry("BLEtokenCredentialProvider.dll", (2, 1, 63, 0)),
+
+    # FYunZip and PuddingZip, loaded as shell extension, cause crashes
+    # bug 1576728
+    DllBlocklistEntry("oly64.dll", (1, 1, 3, 19920)),
+    DllBlocklistEntry("oly.dll", (1, 1, 3, 19920)),
+    DllBlocklistEntry("pdzipmenu64.dll", (1, 4, 4, 20103)),
+    DllBlocklistEntry("pdzipmenu32.dll", (1, 4, 4, 20103)),
+
+    # McAfee Data Loss Prevention causes crashs with multiple signatures,
+    # bug 1634090, bug 1717676
+    DllBlocklistEntry("fcagff.dll", (11, 6, 300, 2)),
+    DllBlocklistEntry("fcagff64.dll", (11, 6, 300, 2)),
+
+    # AVerMedia's virtual camera module causes crashes (bug 1692908)
+    DllBlocklistEntry("avmvirtualsource.ax", (1, 0, 0, 3)),
+
+    # Avast (bug 1794064)
+    DllBlocklistEntry("aswJsFlt.dll", (18, 0, 1473, 0)),
+
+    # ASUS Web Storage (bug 1714940)
+    DllBlocklistEntry("asuswsshellext64.dll", (1, 1, 0, 27)),
+
+    # ExplorerPatcher (bug 1798707)
+    DllBlocklistEntry("explorerpatcher.amd64.dll", ALL_VERSIONS),
+
+    # Sonic Studio 3 (bug 1540883)
+    DllBlocklistEntry("ss3devprops.dll", ALL_VERSIONS),
+
+    # Nahimic audio driver (bug 1540883)
+    DllBlocklistEntry("audiodevprops2.dll", (2, 6, 14, 0)),
+
+    # Kingsoft internet security (bug 1837242)
+    DllBlocklistEntry("kisfdpro64.dll", ALL_VERSIONS),
+
+    # Kingsoft internet security (bug 1837246)
+    DllBlocklistEntry("dghmpg64.dll", ALL_VERSIONS),
+
+    # Legacy DLL for digital signatures with ID cards from Spain (bug 1709082),
+    # up-to-date setups use DNIe_P11_x64.dll instead
+    DllBlocklistEntry("UsrDNIeCertStore.dll", ALL_VERSIONS),
+]
+
+CHILD_PROCESSES += [
+    # Causes crashes in the GPU process with WebRender enabled, bug 1544435
+    DllBlocklistEntry("wbload.dll", ALL_VERSIONS),
+
+    # Causes crashes in the content process with win32k lockdown, bug 1766022
+    DllBlocklistEntry("videocapturer.dll", ALL_VERSIONS),
+    DllBlocklistEntry("videocapturerhk32.dll", ALL_VERSIONS),
+    DllBlocklistEntry("videocapturerhk64.dll", ALL_VERSIONS),
+
+    # Causes crashes in the content process with win32k lockdown, bug 1766029
+    # The crash seems to be in the *_m module which has been unloaded.
+    DllBlocklistEntry("safaweb.dll", (3, 0, 21, 3181)),
+    DllBlocklistEntry("safaweb_m.dll", (3, 0, 21, 3181)),
+    DllBlocklistEntry("safaweb64.dll", (3, 0, 21, 3181)),
+    DllBlocklistEntry("safaweb64_m.dll", (3, 0, 21, 3181)),
+
+    # Causes crashes in the content process with win32k lockdown, bug 1769309
+    DllBlocklistEntry("hmpalert.dll", (3, 8, 8, 889)),
+]
+
+GPU_PROCESSES += [
+    # MSI Nahimic audio driver causes crashes in the GPU process, bug 1804023
+    DllBlocklistEntry("nahimicosd.dll", (2, 2, 25, 0)),
+]
+
+GPU_PROCESSES_TESTS += [
+    # DLLs used by TestDllBlocklist* gTests
+    DllBlocklistEntry("testdllblocklist_gpuprocessonly.dll", ALL_VERSIONS),
+    DllBlocklistEntry("testdllblocklist_multipleentries_differentprocesses.dll", ALL_VERSIONS)
+]
+
+SOCKET_PROCESSES += [
+    # Causes crashes in the socket process, bug 1760668
+    DllBlocklistEntry("ipseng64.dll", (17, 2, 6, 25)),
+    DllBlocklistEntry("ipseng32.dll", (17, 2, 6, 25)),
+
+    # Causes crashes in the socket process, bug 1807038 and bug 1845111
+    DllBlocklistEntry("kwsui64.dll", ALL_VERSIONS),
+]
+
+SOCKET_PROCESSES_TESTS += [
+    # DLLs used by TestDllBlocklist* gTests
+    DllBlocklistEntry("testdllblocklist_socketprocessonly.dll", ALL_VERSIONS),
+]
+
+UTILITY_PROCESSES += [
+    # Generated dynamic code that we block
+    DllBlocklistEntry("cyinjct.dll", ALL_VERSIONS),
+
+    # Causes crashes in the utility process, bug 1826393
+    DllBlocklistEntry("ipseng64.dll", ALL_VERSIONS),
+    DllBlocklistEntry("ipseng32.dll", ALL_VERSIONS),
+    DllBlocklistEntry("ks3rdhmpg.dll", ALL_VERSIONS),
+    DllBlocklistEntry("kwsui64.dll", ALL_VERSIONS),
+
+    # Messes with user32 and breaks Utility on Win7 x86
+    DllBlocklistEntry("aswhook.dll", ALL_VERSIONS, BLOCK_WIN7_AND_OLDER),
+]
+
+UTILITY_PROCESSES_TESTS += [
+    # DLLs used by TestDllBlocklist* gTests
+    DllBlocklistEntry("testdllblocklist_utilityprocessonly.dll", ALL_VERSIONS),
+]
+
+GMPLUGIN_PROCESSES += [
+    # Causes crashes in the plugin process, bug 1830950
+    DllBlocklistEntry("ipseng64.dll", ALL_VERSIONS),
+    DllBlocklistEntry("ipseng32.dll", ALL_VERSIONS),
+    DllBlocklistEntry("ks3rdhmpg.dll", ALL_VERSIONS),
+    DllBlocklistEntry("kwsui64.dll", ALL_VERSIONS),
+]
+
+GMPLUGIN_PROCESSES_TESTS += [
+    # DLLs used by TestDllBlocklist* gTests
+    DllBlocklistEntry("testdllblocklist_gmpluginprocessonly.dll", ALL_VERSIONS),
+]
diff --git a/toolkit/xre/dllservices/mozglue/WindowsDllBlocklistInfo.h b/toolkit/xre/dllservices/mozglue/WindowsDllBlocklistInfo.h
new file mode 100644
index 0000000000..3607c3049e
--- /dev/null
+++ b/toolkit/xre/dllservices/mozglue/WindowsDllBlocklistInfo.h
@@ -0,0 +1,106 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_WindowsDllBlocklistInfo_h
+#define mozilla_WindowsDllBlocklistInfo_h
+
+#include <stdint.h>
+
+namespace mozilla {
+
+// If the USE_TIMESTAMP flag is set, then we use the timestamp from
+// the IMAGE_FILE_HEADER in lieu of a version number.
+//
+// If the UTILITY_PROCESSES_ONLY, SOCKET_PROCESSES_ONLY, GPU_PROCESSES_ONLY,
+// or GMPLUGIN_PROCESSES_ONLY flags are set, the dll will only be blocked for
+// these specific child processes. Note that these are a subset of
+// CHILD_PROCESSES_ONLY.
+enum DllBlockInfoFlags : uint32_t {
+  FLAGS_DEFAULT = 0,
+  BLOCK_WIN7_AND_OLDER = 1 << 0,
+  BLOCK_WIN8_AND_OLDER = 1 << 1,
+  USE_TIMESTAMP = 1 << 2,
+  CHILD_PROCESSES_ONLY = 1 << 3,
+  BROWSER_PROCESS_ONLY = 1 << 4,
+  REDIRECT_TO_NOOP_ENTRYPOINT = 1 << 5,
+  UTILITY_PROCESSES_ONLY = 1 << 6,
+  SOCKET_PROCESSES_ONLY = 1 << 7,
+  GPU_PROCESSES_ONLY = 1 << 8,
+  GMPLUGIN_PROCESSES_ONLY = 1 << 9,
+};
+
+constexpr DllBlockInfoFlags operator|(const DllBlockInfoFlags a,
+                                      const DllBlockInfoFlags b) {
+  return static_cast<DllBlockInfoFlags>(static_cast<uint32_t>(a) |
+                                        static_cast<uint32_t>(b));
+}
+
+template <typename StrType>
+struct DllBlockInfoT {
+  // The name of the DLL -- in LOWERCASE!  It will be compared to
+  // a lowercase version of the DLL name only.
+  StrType mName;
+
+  // If mMaxVersion is ALL_VERSIONS, we'll block all versions of this
+  // dll.  Otherwise, we'll block all versions less than or equal to
+  // the given version, as queried by GetFileVersionInfo and
+  // VS_FIXEDFILEINFO's dwFileVersionMS and dwFileVersionLS fields.
+  //
+  // Note that the version is usually 4 components, which is A.B.C.D
+  // encoded as 0x AAAA BBBB CCCC DDDD ULL (spaces added for clarity),
+  // but it's not required to be of that format.
+  uint64_t mMaxVersion;
+
+  // If the USE_TIMESTAMP flag is set, then we use the timestamp from
+  // the IMAGE_FILE_HEADER in lieu of a version number.
+  //
+  // If the UTILITY_PROCESSES_ONLY, SOCKET_PROCESSES_ONLY, GPU_PROCESSES_ONLY,
+  // or GMPLUGIN_PROCESSES_ONLY flags are set, the dll will only be blocked for
+  // these specific child processes. Note that these are a subset of
+  // CHILD_PROCESSES_ONLY. These flags cannot be combined.
+  DllBlockInfoFlags mFlags;
+
+  bool IsVersionBlocked(const uint64_t aOther) const {
+    if (mMaxVersion == ALL_VERSIONS) {
+      return true;
+    }
+
+    return aOther <= mMaxVersion;
+  }
+
+  bool IsValidDynamicBlocklistEntry() const;
+
+  static const uint64_t ALL_VERSIONS = (uint64_t)-1LL;
+
+  // DLLs sometimes ship without a version number, particularly early
+  // releases. Blocking "version <= 0" has the effect of blocking unversioned
+  // DLLs (since the call to get version info fails), but not blocking
+  // any versioned instance.
+  static const uint64_t UNVERSIONED = 0ULL;
+};
+
+}  // namespace mozilla
+
+// Convert the 4 (decimal) components of a DLL version number into a
+// single unsigned long long, as needed by the blocklist
+#if defined(_MSC_VER) && !defined(__clang__)
+
+// MSVC does not properly handle the constexpr MAKE_VERSION, so we use a macro
+// instead (ugh).
+#  define MAKE_VERSION(a, b, c, d) \
+    ((a##ULL << 48) + (b##ULL << 32) + (c##ULL << 16) + d##ULL)
+
+#else
+
+static inline constexpr uint64_t MAKE_VERSION(uint16_t a, uint16_t b,
+                                              uint16_t c, uint16_t d) {
+  return static_cast<uint64_t>(a) << 48 | static_cast<uint64_t>(b) << 32 |
+         static_cast<uint64_t>(c) << 16 | static_cast<uint64_t>(d);
+}
+
+#endif
+
+#endif  // mozilla_WindowsDllBlocklistInfo_h
diff --git a/toolkit/xre/dllservices/mozglue/WindowsDllServices.h b/toolkit/xre/dllservices/mozglue/WindowsDllServices.h
new file mode 100644
index 0000000000..70ba5e98b0
--- /dev/null
+++ b/toolkit/xre/dllservices/mozglue/WindowsDllServices.h
@@ -0,0 +1,234 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_glue_WindowsDllServices_h
+#define mozilla_glue_WindowsDllServices_h
+
+#include <utility>
+
+#include "mozilla/Assertions.h"
+#include "mozilla/Authenticode.h"
+#include "mozilla/LoaderAPIInterfaces.h"
+#include "mozilla/UniquePtr.h"
+#include "mozilla/Vector.h"
+#include "mozilla/WinHeaderOnlyUtils.h"
+#include "mozilla/WindowsDllBlocklist.h"
+#include "mozilla/mozalloc.h"
+
+#if defined(MOZILLA_INTERNAL_API)
+#  include "MainThreadUtils.h"
+#  include "nsISupportsImpl.h"
+#  include "nsString.h"
+#  include "nsThreadUtils.h"
+#  include "prthread.h"
+#  include "mozilla/SchedulerGroup.h"
+#endif  // defined(MOZILLA_INTERNAL_API)
+
+// For PCUNICODE_STRING
+#include <winternl.h>
+
+namespace mozilla {
+namespace glue {
+namespace detail {
+
+class DllServicesBase : public Authenticode {
+ public:
+  /**
+   * WARNING: This method is called from within an unsafe context that holds
+   *          multiple locks inside the Windows loader. The only thing that
+   *          this function should be used for is dispatching the event to our
+   *          event loop so that it may be handled in a safe context.
+   */
+  virtual void DispatchDllLoadNotification(ModuleLoadInfo&& aModLoadInfo) = 0;
+
+  /**
+   * This function accepts module load events to be processed later for
+   * the untrusted modules telemetry ping.
+   *
+   * WARNING: This method is run from within the Windows loader and should
+   *          only perform trivial, loader-friendly operations.
+   */
+  virtual void DispatchModuleLoadBacklogNotification(
+      ModuleLoadInfoVec&& aEvents) = 0;
+
+  void SetAuthenticodeImpl(Authenticode* aAuthenticode) {
+    mAuthenticode = aAuthenticode;
+  }
+
+  void SetWinLauncherServices(const nt::WinLauncherServices& aWinLauncher) {
+    mWinLauncher = aWinLauncher;
+  }
+
+  template <typename... Args>
+  LauncherVoidResultWithLineInfo InitDllBlocklistOOP(Args&&... aArgs) {
+    MOZ_RELEASE_ASSERT(mWinLauncher.mInitDllBlocklistOOP);
+    return mWinLauncher.mInitDllBlocklistOOP(std::forward<Args>(aArgs)...);
+  }
+
+  template <typename... Args>
+  void HandleLauncherError(Args&&... aArgs) {
+    MOZ_RELEASE_ASSERT(mWinLauncher.mHandleLauncherError);
+    mWinLauncher.mHandleLauncherError(std::forward<Args>(aArgs)...);
+  }
+
+  nt::SharedSection* GetSharedSection() { return mWinLauncher.mSharedSection; }
+
+  // In debug builds we override GetBinaryOrgName to add a Gecko-specific
+  // assertion. OTOH, we normally do not want people overriding this function,
+  // so we'll make it final in the release case, thus covering all bases.
+#if defined(DEBUG)
+  UniquePtr<wchar_t[]> GetBinaryOrgName(
+      const wchar_t* aFilePath,
+      AuthenticodeFlags aFlags = AuthenticodeFlags::Default) override
+#else
+  UniquePtr<wchar_t[]> GetBinaryOrgName(
+      const wchar_t* aFilePath,
+      AuthenticodeFlags aFlags = AuthenticodeFlags::Default) final
+#endif  // defined(DEBUG)
+  {
+    if (!mAuthenticode) {
+      return nullptr;
+    }
+
+    return mAuthenticode->GetBinaryOrgName(aFilePath, aFlags);
+  }
+
+  virtual void DisableFull() { DllBlocklist_SetFullDllServices(nullptr); }
+
+  DllServicesBase(const DllServicesBase&) = delete;
+  DllServicesBase(DllServicesBase&&) = delete;
+  DllServicesBase& operator=(const DllServicesBase&) = delete;
+  DllServicesBase& operator=(DllServicesBase&&) = delete;
+
+ protected:
+  DllServicesBase() : mAuthenticode(nullptr) {}
+
+  virtual ~DllServicesBase() = default;
+
+  void EnableFull() { DllBlocklist_SetFullDllServices(this); }
+  void EnableBasic() { DllBlocklist_SetBasicDllServices(this); }
+
+ private:
+  Authenticode* mAuthenticode;
+  nt::WinLauncherServices mWinLauncher;
+};
+
+}  // namespace detail
+
+#if defined(MOZILLA_INTERNAL_API)
+
+struct EnhancedModuleLoadInfo final {
+  explicit EnhancedModuleLoadInfo(ModuleLoadInfo&& aModLoadInfo)
+      : mNtLoadInfo(std::move(aModLoadInfo)) {
+    // Only populate mThreadName when we're on the same thread as the event
+    if (mNtLoadInfo.mThreadId == ::GetCurrentThreadId()) {
+      mThreadName = PR_GetThreadName(PR_GetCurrentThread());
+    }
+    MOZ_ASSERT(!mNtLoadInfo.mSectionName.IsEmpty());
+  }
+
+  EnhancedModuleLoadInfo(EnhancedModuleLoadInfo&&) = default;
+  EnhancedModuleLoadInfo& operator=(EnhancedModuleLoadInfo&&) = default;
+
+  EnhancedModuleLoadInfo(const EnhancedModuleLoadInfo&) = delete;
+  EnhancedModuleLoadInfo& operator=(const EnhancedModuleLoadInfo&) = delete;
+
+  nsDependentString GetSectionName() const {
+    return mNtLoadInfo.mSectionName.AsString();
+  }
+
+  using BacktraceType = decltype(ModuleLoadInfo::mBacktrace);
+
+  ModuleLoadInfo mNtLoadInfo;
+  nsCString mThreadName;
+};
+
+class DllServices : public detail::DllServicesBase {
+ public:
+  void DispatchDllLoadNotification(ModuleLoadInfo&& aModLoadInfo) final {
+    // We only notify one blocked DLL load event per blocked DLL for the main
+    // thread, because dispatching a notification can trigger a new blocked
+    // DLL load if the DLL is registered as a WH_GETMESSAGE hook. In that case,
+    // dispatching a notification with every load results in an infinite cycle,
+    // see bug 1823412.
+    if (aModLoadInfo.WasBlocked() && NS_IsMainThread()) {
+      nsDependentString sectionName(aModLoadInfo.mSectionName.AsString());
+
+      for (const auto& blockedModule : mMainThreadBlockedModules) {
+        if (sectionName == blockedModule) {
+          return;
+        }
+      }
+
+      MOZ_ALWAYS_TRUE(mMainThreadBlockedModules.append(sectionName));
+    }
+
+    nsCOMPtr<nsIRunnable> runnable(
+        NewRunnableMethod<StoreCopyPassByRRef<EnhancedModuleLoadInfo>>(
+            "DllServices::NotifyDllLoad", this, &DllServices::NotifyDllLoad,
+            std::move(aModLoadInfo)));
+
+    SchedulerGroup::Dispatch(TaskCategory::Other, runnable.forget());
+  }
+
+  void DispatchModuleLoadBacklogNotification(
+      ModuleLoadInfoVec&& aEvents) final {
+    nsCOMPtr<nsIRunnable> runnable(
+        NewRunnableMethod<StoreCopyPassByRRef<ModuleLoadInfoVec>>(
+            "DllServices::NotifyModuleLoadBacklog", this,
+            &DllServices::NotifyModuleLoadBacklog, std::move(aEvents)));
+
+    SchedulerGroup::Dispatch(TaskCategory::Other, runnable.forget());
+  }
+
+#  if defined(DEBUG)
+  UniquePtr<wchar_t[]> GetBinaryOrgName(
+      const wchar_t* aFilePath,
+      AuthenticodeFlags aFlags = AuthenticodeFlags::Default) final {
+    // This function may perform disk I/O, so we should never call it on the
+    // main thread.
+    MOZ_ASSERT(!NS_IsMainThread());
+    return detail::DllServicesBase::GetBinaryOrgName(aFilePath, aFlags);
+  }
+#  endif  // defined(DEBUG)
+
+  NS_INLINE_DECL_THREADSAFE_VIRTUAL_REFCOUNTING(DllServices)
+
+ protected:
+  DllServices() = default;
+  ~DllServices() = default;
+
+  virtual void NotifyDllLoad(EnhancedModuleLoadInfo&& aModLoadInfo) = 0;
+  virtual void NotifyModuleLoadBacklog(ModuleLoadInfoVec&& aEvents) = 0;
+
+ private:
+  // This vector has no associated lock. It must only be used on the main
+  // thread.
+  Vector<nsString> mMainThreadBlockedModules;
+};
+
+#else
+
+class BasicDllServices final : public detail::DllServicesBase {
+ public:
+  BasicDllServices() { EnableBasic(); }
+
+  ~BasicDllServices() = default;
+
+  // Not useful in this class, so provide a default implementation
+  virtual void DispatchDllLoadNotification(
+      ModuleLoadInfo&& aModLoadInfo) override {}
+
+  virtual void DispatchModuleLoadBacklogNotification(
+      ModuleLoadInfoVec&& aEvents) override {}
+};
+
+#endif  // defined(MOZILLA_INTERNAL_API)
+
+}  // namespace glue
+}  // namespace mozilla
+
+#endif  // mozilla_glue_WindowsDllServices_h
diff --git a/toolkit/xre/dllservices/mozglue/WindowsFallbackLoaderAPI.cpp b/toolkit/xre/dllservices/mozglue/WindowsFallbackLoaderAPI.cpp
new file mode 100644
index 0000000000..bda309d499
--- /dev/null
+++ b/toolkit/xre/dllservices/mozglue/WindowsFallbackLoaderAPI.cpp
@@ -0,0 +1,91 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#include "WindowsFallbackLoaderAPI.h"
+
+namespace mozilla {
+
+ModuleLoadInfo FallbackLoaderAPI::ConstructAndNotifyBeginDllLoad(
+    void** aContext, PCUNICODE_STRING aRequestedDllName) {
+  ModuleLoadInfo loadInfo(aRequestedDllName);
+
+  MOZ_ASSERT(mLoaderObserver);
+  if (mLoaderObserver) {
+    mLoaderObserver->OnBeginDllLoad(aContext, aRequestedDllName);
+  }
+
+  return loadInfo;
+}
+
+bool FallbackLoaderAPI::SubstituteForLSP(PCUNICODE_STRING aLSPLeafName,
+                                         PHANDLE aOutHandle) {
+  MOZ_ASSERT(mLoaderObserver);
+  if (!mLoaderObserver) {
+    return false;
+  }
+
+  return mLoaderObserver->SubstituteForLSP(aLSPLeafName, aOutHandle);
+}
+
+void FallbackLoaderAPI::NotifyEndDllLoad(void* aContext, NTSTATUS aLoadNtStatus,
+                                         ModuleLoadInfo&& aModuleLoadInfo) {
+  aModuleLoadInfo.SetEndLoadTimeStamp();
+
+  if (NT_SUCCESS(aLoadNtStatus)) {
+    aModuleLoadInfo.CaptureBacktrace();
+  }
+
+  MOZ_ASSERT(mLoaderObserver);
+  if (mLoaderObserver) {
+    mLoaderObserver->OnEndDllLoad(aContext, aLoadNtStatus,
+                                  std::move(aModuleLoadInfo));
+  }
+}
+
+nt::AllocatedUnicodeString FallbackLoaderAPI::GetSectionName(
+    void* aSectionAddr) {
+  static const StaticDynamicallyLinkedFunctionPtr<
+      decltype(&::NtQueryVirtualMemory)>
+      pNtQueryVirtualMemory(L"ntdll.dll", "NtQueryVirtualMemory");
+  MOZ_ASSERT(pNtQueryVirtualMemory);
+
+  if (!pNtQueryVirtualMemory) {
+    return nt::AllocatedUnicodeString();
+  }
+
+  nt::MemorySectionNameBuf buf;
+  NTSTATUS ntStatus =
+      pNtQueryVirtualMemory(::GetCurrentProcess(), aSectionAddr,
+                            MemorySectionName, &buf, sizeof(buf), nullptr);
+  if (!NT_SUCCESS(ntStatus)) {
+    return nt::AllocatedUnicodeString();
+  }
+
+  return nt::AllocatedUnicodeString(&buf.mSectionFileName);
+}
+
+nt::LoaderAPI::InitDllBlocklistOOPFnPtr
+FallbackLoaderAPI::GetDllBlocklistInitFn() {
+  MOZ_ASSERT_UNREACHABLE("This should not be called so soon!");
+  return nullptr;
+}
+
+nt::LoaderAPI::HandleLauncherErrorFnPtr
+FallbackLoaderAPI::GetHandleLauncherErrorFn() {
+  MOZ_ASSERT_UNREACHABLE("This should not be called so soon!");
+  return nullptr;
+}
+
+nt::SharedSection* FallbackLoaderAPI::GetSharedSection() {
+  MOZ_ASSERT_UNREACHABLE("This should not be called so soon!");
+  return nullptr;
+}
+
+void FallbackLoaderAPI::SetObserver(nt::LoaderObserver* aLoaderObserver) {
+  mLoaderObserver = aLoaderObserver;
+}
+
+}  // namespace mozilla
diff --git a/toolkit/xre/dllservices/mozglue/WindowsFallbackLoaderAPI.h b/toolkit/xre/dllservices/mozglue/WindowsFallbackLoaderAPI.h
new file mode 100644
index 0000000000..8d6fcb2f0c
--- /dev/null
+++ b/toolkit/xre/dllservices/mozglue/WindowsFallbackLoaderAPI.h
@@ -0,0 +1,39 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_WindowsFallbackLoaderAPI_h
+#define mozilla_WindowsFallbackLoaderAPI_h
+
+#include "mozilla/Attributes.h"
+#include "NtLoaderAPI.h"
+
+namespace mozilla {
+
+class MOZ_ONLY_USED_TO_AVOID_STATIC_CONSTRUCTORS FallbackLoaderAPI final
+    : public nt::LoaderAPI {
+ public:
+  constexpr FallbackLoaderAPI() : mLoaderObserver(nullptr) {}
+
+  ModuleLoadInfo ConstructAndNotifyBeginDllLoad(
+      void** aContext, PCUNICODE_STRING aRequestedDllName) final;
+  bool SubstituteForLSP(PCUNICODE_STRING aLSPLeafName,
+                        PHANDLE aOutHandle) final;
+  void NotifyEndDllLoad(void* aContext, NTSTATUS aLoadNtStatus,
+                        ModuleLoadInfo&& aModuleLoadInfo) final;
+  nt::AllocatedUnicodeString GetSectionName(void* aSectionAddr) final;
+  nt::LoaderAPI::InitDllBlocklistOOPFnPtr GetDllBlocklistInitFn() final;
+  nt::LoaderAPI::HandleLauncherErrorFnPtr GetHandleLauncherErrorFn() final;
+  nt::SharedSection* GetSharedSection() final;
+
+  void SetObserver(nt::LoaderObserver* aLoaderObserver);
+
+ private:
+  nt::LoaderObserver* mLoaderObserver;
+};
+
+}  // namespace mozilla
+
+#endif  // mozilla_WindowsFallbackLoaderAPI_h
diff --git a/toolkit/xre/dllservices/mozglue/gen_dll_blocklist_defs.py b/toolkit/xre/dllservices/mozglue/gen_dll_blocklist_defs.py
new file mode 100644
index 0000000000..35e1cc300d
--- /dev/null
+++ b/toolkit/xre/dllservices/mozglue/gen_dll_blocklist_defs.py
@@ -0,0 +1,755 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import os
+from copy import deepcopy
+from struct import unpack
+from uuid import UUID
+
+from six import iteritems
+
+H_HEADER = """/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This file was auto-generated from {0} by gen_dll_blocklist_data.py.  */
+
+#ifndef mozilla_{1}_h
+#define mozilla_{1}_h
+
+"""
+
+H_FOOTER = """#endif  // mozilla_{1}_h
+
+"""
+
+H_DEFS_BEGIN_DEFAULT = """#include "mozilla/WindowsDllBlocklistCommon.h"
+
+DLL_BLOCKLIST_DEFINITIONS_BEGIN
+
+"""
+
+H_DEFS_END_DEFAULT = """
+DLL_BLOCKLIST_DEFINITIONS_END
+
+"""
+
+H_BEGIN_LSP = """#include <guiddef.h>
+
+static const GUID gLayerGuids[] = {
+
+"""
+
+H_END_LSP = """
+};
+
+"""
+
+H_BEGIN_A11Y = """#include "mozilla/WindowsDllBlocklistCommon.h"
+
+DLL_BLOCKLIST_DEFINITIONS_BEGIN_NAMED(gBlockedInprocDlls)
+
+"""
+
+# These flag names should match the ones defined in WindowsDllBlocklistInfo.h
+FLAGS_DEFAULT = "FLAGS_DEFAULT"
+BLOCK_WIN8_AND_OLDER = "BLOCK_WIN8_AND_OLDER"
+BLOCK_WIN7_AND_OLDER = "BLOCK_WIN7_AND_OLDER"
+USE_TIMESTAMP = "USE_TIMESTAMP"
+CHILD_PROCESSES_ONLY = "CHILD_PROCESSES_ONLY"
+BROWSER_PROCESS_ONLY = "BROWSER_PROCESS_ONLY"
+SUBSTITUTE_LSP_PASSTHROUGH = "SUBSTITUTE_LSP_PASSTHROUGH"
+REDIRECT_TO_NOOP_ENTRYPOINT = "REDIRECT_TO_NOOP_ENTRYPOINT"
+UTILITY_PROCESSES_ONLY = "UTILITY_PROCESSES_ONLY"
+SOCKET_PROCESSES_ONLY = "SOCKET_PROCESSES_ONLY"
+GPU_PROCESSES_ONLY = "GPU_PROCESSES_ONLY"
+GMPLUGIN_PROCESSES_ONLY = "GMPLUGIN_PROCESSES_ONLY"
+
+# Only these flags are available in the input script
+INPUT_ONLY_FLAGS = {
+    BLOCK_WIN8_AND_OLDER,
+    BLOCK_WIN7_AND_OLDER,
+}
+
+
+def FILTER_ALLOW_ALL(entry):
+    # A11y entries are special, so we always exclude those by default
+    # (so it's not really allowing 'all', but it is simpler to reason about by
+    #  pretending that it is allowing all.)
+    return not isinstance(entry, A11yBlocklistEntry)
+
+
+def FILTER_DENY_ALL(entry):
+    return False
+
+
+def FILTER_ALLOW_ONLY_A11Y(entry):
+    return isinstance(entry, A11yBlocklistEntry)
+
+
+def FILTER_ALLOW_ONLY_LSP(entry):
+    return isinstance(entry, LspBlocklistEntry)
+
+
+def FILTER_TESTS_ONLY(entry):
+    return not isinstance(entry, A11yBlocklistEntry) and entry.is_test()
+
+
+def derive_test_key(key):
+    return key + "_TESTS"
+
+
+ALL_DEFINITION_LISTS = (
+    "ALL_PROCESSES",
+    "BROWSER_PROCESS",
+    "CHILD_PROCESSES",
+    "GMPLUGIN_PROCESSES",
+    "GPU_PROCESSES",
+    "UTILITY_PROCESSES",
+    "SOCKET_PROCESSES",
+)
+
+
+class BlocklistDescriptor(object):
+    """This class encapsulates every file that is output from this script.
+    Each instance has a name, an "input specification", and optional "flag
+    specification" and "output specification" entries.
+    """
+
+    DEFAULT_OUTSPEC = {
+        "mode": "",
+        "filter": FILTER_ALLOW_ALL,
+        "begin": H_DEFS_BEGIN_DEFAULT,
+        "end": H_DEFS_END_DEFAULT,
+    }
+
+    FILE_NAME_TPL = "WindowsDllBlocklist{0}Defs"
+
+    OutputDir = None
+    ExistingFd = None
+    ExistingFdLeafName = None
+
+    def __init__(self, name, inspec, **kwargs):
+        """Positional arguments:
+
+        name -- String containing the name of the output list.
+
+        inspec -- One or more members of ALL_DEFINITION_LISTS. The input used
+        for this blocklist file is the union of all lists specified by this
+        variable.
+
+        Keyword arguments:
+
+        outspec -- an optional list of dicts that specify how the lists output
+        will be written out to a file. Each dict may contain the following keys:
+
+            'mode' -- a string that specifies a mode that is used when writing
+            out list entries to this particular output. This is passed in as the
+            mode argument to DllBlocklistEntry's write method.
+
+            'filter' -- a function that, given a blocklist entry, decides
+            whether or not that entry shall be included in this output file.
+
+            'begin' -- a string that is written to the output file after writing
+            the file's header, but prior to writing out any blocklist entries.
+
+            'end' -- a string that is written to the output file after writing
+            out any blocklist entries but before the file's footer.
+
+        Any unspecified keys will be assigned default values.
+
+        flagspec -- an optional dict whose keys consist of one or more of the
+        list names from inspec. Each corresponding value is a set of flags that
+        should be applied to each entry from that list. For example, the
+        flagspec:
+
+            {'CHILD_PROCESSES': {CHILD_PROCESSES_ONLY}}
+
+        causes any blocklist entries from the CHILD_PROCESSES list to be output
+        with the CHILD_PROCESSES_ONLY flag set.
+
+        """
+
+        self._name = name
+
+        # inspec's elements must all come from ALL_DEFINITION_LISTS
+        assert not (set(inspec).difference(set(ALL_DEFINITION_LISTS)))
+
+        # Internally to the descriptor, we store input specifications as a dict
+        # that maps each input blocklist name to the set of flags to be applied
+        # to each entry in that blocklist.
+        self._inspec = {blocklist: set() for blocklist in inspec}
+
+        self._outspecs = kwargs.get("outspec", BlocklistDescriptor.DEFAULT_OUTSPEC)
+        if isinstance(self._outspecs, dict):
+            # _outspecs should always be stored as a list of dicts
+            self._outspecs = [self._outspecs]
+
+        flagspecs = kwargs.get("flagspec", dict())
+        # flagspec's keys must all come from ALL_DEFINITION_LISTS
+        assert not (set(flagspecs.keys()).difference(set(self._inspec.keys())))
+
+        # Merge the flags from flagspec into _inspec's sets
+        for blocklist, flagspec in iteritems(flagspecs):
+            spec = self._inspec[blocklist]
+            if not isinstance(spec, set):
+                raise TypeError("Flag spec for list %s must be a set!" % blocklist)
+            spec.update(flagspec)
+
+    @staticmethod
+    def set_output_fd(fd):
+        """The build system has already provided an open file descriptor for
+        one of our outputs. We save that here so that we may use that fd once
+        we're ready to process that fd's file. We also obtain the output dir for
+        use as the base directory for the other output files that we open.
+        """
+        BlocklistDescriptor.ExistingFd = fd
+        (
+            BlocklistDescriptor.OutputDir,
+            BlocklistDescriptor.ExistingFdLeafName,
+        ) = os.path.split(fd.name)
+
+    @staticmethod
+    def ensure_no_dupes(defs):
+        """Ensure that defs does not contain any dupes. We raise a ValueError
+        because this is a bug in the input and requires developer intervention.
+        """
+        seen = set()
+        for e in defs:
+            name = e.get_name()
+            if name not in seen:
+                seen.add(name)
+            else:
+                raise ValueError("Duplicate entry found: %s" % name)
+
+    @staticmethod
+    def get_test_entries(exec_env, blocklist):
+        """Obtains all test entries for the corresponding blocklist, and also
+        ensures that each entry has its test flag set.
+
+        Positional arguments:
+
+        exec_env -- dict containing the globals that were passed to exec to
+        when the input script was run.
+
+        blocklist -- The name of the blocklist to obtain tests from. This
+        should be one of the members of ALL_DEFINITION_LISTS
+        """
+        test_key = derive_test_key(blocklist)
+
+        def set_is_test(elem):
+            elem.set_is_test()
+            return elem
+
+        return map(set_is_test, exec_env[test_key])
+
+    def gen_list(self, exec_env, filter_func):
+        """Generates a sorted list of blocklist entries from the input script,
+        filtered via filter_func.
+
+        Positional arguments:
+
+        exec_env -- dict containing the globals that were passed to exec to
+        when the input script was run. This function expects exec_env to
+        contain lists of blocklist entries, keyed using one of the members of
+        ALL_DEFINITION_LISTS.
+
+        filter_func -- a filter function that evaluates each blocklist entry
+        to determine whether or not it should be included in the results.
+        """
+
+        # This list contains all the entries across all blocklists that we
+        # potentially want to process
+        unified_list = []
+
+        # For each blocklist specified in the _inspec, we query the globals
+        # for their entries, add any flags, and then add them to the
+        # unified_list.
+        for blocklist, listflags in iteritems(self._inspec):
+
+            def add_list_flags(elem):
+                # We deep copy so that flags set for an entry in one blocklist
+                # do not interfere with flags set for an entry in a different
+                # list.
+                result = deepcopy(elem)
+                result.add_flags(listflags)
+                return result
+
+            # We add list flags *before* filtering because the filters might
+            # want to access flags as part of their operation.
+            unified_list.extend(map(add_list_flags, exec_env[blocklist]))
+
+            # We also add any test entries for the lists specified by _inspec
+            unified_list.extend(
+                map(add_list_flags, self.get_test_entries(exec_env, blocklist))
+            )
+
+        # Now we filter out any unwanted list entries
+        filtered_list = filter(filter_func, unified_list)
+
+        # Sort the list on entry name so that the blocklist code may use
+        # binary search if it so chooses.
+        return sorted(filtered_list, key=lambda e: e.get_name())
+
+    @staticmethod
+    def get_fd(outspec_leaf_name):
+        """If BlocklistDescriptor.ExistingFd corresponds to outspec_leaf_name,
+        then we return that. Otherwise, we construct a new absolute path to
+        outspec_leaf_name and open a new file descriptor for writing.
+        """
+        if (
+            not BlocklistDescriptor.ExistingFd
+            or BlocklistDescriptor.ExistingFdLeafName != outspec_leaf_name
+        ):
+            new_name = os.path.join(BlocklistDescriptor.OutputDir, outspec_leaf_name)
+            return open(new_name, "w")
+
+        fd = BlocklistDescriptor.ExistingFd
+        BlocklistDescriptor.ExistingFd = None
+        return fd
+
+    def write(self, src_file, exec_env):
+        """Write out all output files that are specified by this descriptor.
+
+        Positional arguments:
+
+        src_file -- name of the input file from which the lists were generated.
+
+        exec_env -- dictionary containing the lists that were parsed from the
+        input file when it was executed.
+        """
+
+        for outspec in self._outspecs:
+            # Use DEFAULT_OUTSPEC to supply defaults for any unused outspec keys
+            effective_outspec = BlocklistDescriptor.DEFAULT_OUTSPEC.copy()
+            effective_outspec.update(outspec)
+
+            entries = self.gen_list(exec_env, effective_outspec["filter"])
+            if not entries:
+                continue
+
+            mode = effective_outspec["mode"]
+
+            # Since each output descriptor may generate output across multiple
+            # modes, each list is uniquified via the concatenation of our name
+            # and the mode.
+            listname = self._name + mode
+            leafname_no_ext = BlocklistDescriptor.FILE_NAME_TPL.format(listname)
+            leafname = leafname_no_ext + ".h"
+
+            with self.get_fd(leafname) as output:
+                print(H_HEADER.format(src_file, leafname_no_ext), file=output, end="")
+                print(effective_outspec["begin"], file=output, end="")
+
+                for e in entries:
+                    e.write(output, mode)
+
+                print(effective_outspec["end"], file=output, end="")
+                print(H_FOOTER.format(src_file, leafname_no_ext), file=output, end="")
+
+
+A11Y_OUTPUT_SPEC = {
+    "filter": FILTER_ALLOW_ONLY_A11Y,
+    "begin": H_BEGIN_A11Y,
+}
+
+LSP_MODE_GUID = "Guid"
+
+LSP_OUTPUT_SPEC = [
+    {
+        "mode": LSP_MODE_GUID,
+        "filter": FILTER_ALLOW_ONLY_LSP,
+        "begin": H_BEGIN_LSP,
+        "end": H_END_LSP,
+    },
+]
+
+GENERATED_BLOCKLIST_FILES = [
+    BlocklistDescriptor("A11y", ["BROWSER_PROCESS"], outspec=A11Y_OUTPUT_SPEC),
+    BlocklistDescriptor(
+        "Launcher",
+        ALL_DEFINITION_LISTS,
+        flagspec={
+            "BROWSER_PROCESS": {BROWSER_PROCESS_ONLY},
+            "CHILD_PROCESSES": {CHILD_PROCESSES_ONLY},
+            "GMPLUGIN_PROCESSES": {GMPLUGIN_PROCESSES_ONLY},
+            "GPU_PROCESSES": {GPU_PROCESSES_ONLY},
+            "UTILITY_PROCESSES": {UTILITY_PROCESSES_ONLY},
+            "SOCKET_PROCESSES": {SOCKET_PROCESSES_ONLY},
+        },
+    ),
+    BlocklistDescriptor(
+        "Legacy",
+        ALL_DEFINITION_LISTS,
+        flagspec={
+            "BROWSER_PROCESS": {BROWSER_PROCESS_ONLY},
+            "CHILD_PROCESSES": {CHILD_PROCESSES_ONLY},
+            "GMPLUGIN_PROCESSES": {GMPLUGIN_PROCESSES_ONLY},
+            "GPU_PROCESSES": {GPU_PROCESSES_ONLY},
+            "UTILITY_PROCESSES": {UTILITY_PROCESSES_ONLY},
+            "SOCKET_PROCESSES": {SOCKET_PROCESSES_ONLY},
+        },
+    ),
+    # Roughed-in for the moment; we'll enable this in bug 1238735
+    # BlocklistDescriptor('LSP', ALL_DEFINITION_LISTS, outspec=LSP_OUTPUT_SPEC),
+    BlocklistDescriptor(
+        "Test", ALL_DEFINITION_LISTS, outspec={"filter": FILTER_TESTS_ONLY}
+    ),
+]
+
+
+class PETimeStamp(object):
+    def __init__(self, ts):
+        max_timestamp = (2 ** 32) - 1
+        if ts < 0 or ts > max_timestamp:
+            raise ValueError("Invalid timestamp value")
+        self._value = ts
+
+    def __str__(self):
+        return "0x%08XU" % self._value
+
+
+class Version(object):
+    """Encapsulates a DLL version."""
+
+    ALL_VERSIONS = 0xFFFFFFFFFFFFFFFF
+    UNVERSIONED = 0
+
+    def __init__(self, *args):
+        """There are multiple ways to construct a Version:
+
+        As a tuple containing four elements (recommended);
+        As four integral arguments;
+        As a PETimeStamp;
+        As a long integer.
+
+        The tuple and list formats require the value of each element to be
+        between 0 and 0xFFFF, inclusive.
+        """
+
+        self._ver = Version.UNVERSIONED
+
+        if len(args) == 1:
+            if isinstance(args[0], tuple):
+                self.validate_iterable(args[0])
+
+                self._ver = "MAKE_VERSION%r" % (args[0],)
+            elif isinstance(args[0], PETimeStamp):
+                self._ver = args[0]
+            else:
+                self._ver = int(args[0])
+        elif len(args) == 4:
+            self.validate_iterable(args)
+
+            self._ver = "MAKE_VERSION%r" % (tuple(args),)
+        else:
+            raise ValueError("Bad arguments to Version constructor")
+
+    def validate_iterable(self, arg):
+        if len(arg) != 4:
+            raise ValueError("Versions must be a 4-tuple")
+
+        for component in arg:
+            if not isinstance(component, int) or component < 0 or component > 0xFFFF:
+                raise ValueError(
+                    "Each version component must be a 16-bit " "unsigned integer"
+                )
+
+    def build_long(self, args):
+        self.validate_iterable(args)
+        return (
+            (int(args[0]) << 48)
+            | (int(args[1]) << 32)
+            | (int(args[2]) << 16)
+            | int(args[3])
+        )
+
+    def is_timestamp(self):
+        return isinstance(self._ver, PETimeStamp)
+
+    def __str__(self):
+        if isinstance(self._ver, int):
+            if self._ver == Version.ALL_VERSIONS:
+                return "DllBlockInfo::ALL_VERSIONS"
+
+            if self._ver == Version.UNVERSIONED:
+                return "DllBlockInfo::UNVERSIONED"
+
+            return "0x%016XULL" % self._ver
+
+        return str(self._ver)
+
+
+class DllBlocklistEntry(object):
+    TEST_CONDITION = "defined(ENABLE_TESTS)"
+
+    def __init__(self, name, ver, flags=(), **kwargs):
+        """Positional arguments:
+
+        name -- The leaf name of the DLL.
+
+        ver -- The maximum version to be blocked. NB: The comparison used by the
+        blocklist is <=, so you should specify the last bad version, as opposed
+        to the first good version.
+
+        flags -- iterable containing the flags that should be applicable to
+        this blocklist entry.
+
+        Keyword arguments:
+
+        condition -- a string containing a C++ preprocessor expression. This
+        condition is written as a condition for an #if/#endif block that is
+        generated around the entry during output.
+        """
+
+        self.check_ascii(name)
+        self._name = name.lower()
+        self._ver = Version(ver)
+
+        self._flags = set()
+        self.add_flags(flags)
+        if self._ver.is_timestamp():
+            self._flags.add(USE_TIMESTAMP)
+
+        self._cond = kwargs.get("condition", set())
+        if isinstance(self._cond, str):
+            self._cond = {self._cond}
+
+    @staticmethod
+    def check_ascii(name):
+        try:
+            # Supported in Python 3.7
+            if not name.isascii():
+                raise ValueError('DLL name "%s" must be ASCII!' % name)
+            return
+        except AttributeError:
+            pass
+
+        try:
+            name.encode("ascii")
+        except UnicodeEncodeError:
+            raise ValueError('DLL name "%s" must be ASCII!' % name)
+
+    def get_name(self):
+        return self._name
+
+    def set_condition(self, cond):
+        self._cond.add(cond)
+
+    def get_condition(self):
+        if len(self._cond) == 1:
+            fmt = "{0}"
+        else:
+            fmt = "({0})"
+
+        return " && ".join([fmt.format(c) for c in self._cond])
+
+    def set_is_test(self):
+        self.set_condition(DllBlocklistEntry.TEST_CONDITION)
+
+    def is_test(self):
+        return self._cond and DllBlocklistEntry.TEST_CONDITION in self._cond
+
+    def add_flags(self, new_flags):
+        if isinstance(new_flags, str):
+            self._flags.add(new_flags)
+        else:
+            self._flags.update(new_flags)
+
+    @staticmethod
+    def get_flag_string(flag):
+        return "mozilla::DllBlockInfoFlags::" + flag
+
+    def get_flags_list(self):
+        return self._flags
+
+    def write(self, output, mode):
+        if self._cond:
+            print("#if %s" % self.get_condition(), file=output)
+
+        flags_str = ""
+
+        flags = self.get_flags_list()
+        if flags:
+            flags_str = ", " + " | ".join(map(self.get_flag_string, flags))
+
+        entry_str = '  DLL_BLOCKLIST_ENTRY("%s", %s%s)' % (
+            self._name,
+            str(self._ver),
+            flags_str,
+        )
+        print(entry_str, file=output)
+
+        if self._cond:
+            print("#endif  // %s" % self.get_condition(), file=output)
+
+
+class A11yBlocklistEntry(DllBlocklistEntry):
+    """Represents a blocklist entry for injected a11y DLLs. This class does
+    not need to do anything special compared to a DllBlocklistEntry; we just
+    use this type to distinguish a11y entries from "regular" blocklist entries.
+    """
+
+    def __init__(self, name, ver, flags=(), **kwargs):
+        """These arguments are identical to DllBlocklistEntry.__init__"""
+
+        super(A11yBlocklistEntry, self).__init__(name, ver, flags, **kwargs)
+
+
+class RedirectToNoOpEntryPoint(DllBlocklistEntry):
+    """Represents a blocklist entry to hook the entrypoint into a function
+    just returning TRUE to keep a module alive and harmless.
+    This entry is intended to block a DLL which is injected by IAT patching
+    which is planted by a kernel callback routine for LoadImage because
+    blocking such a DLL makes a process fail to launch.
+    """
+
+    def __init__(self, name, ver, flags=(), **kwargs):
+        """These arguments are identical to DllBlocklistEntry.__init__"""
+
+        super(RedirectToNoOpEntryPoint, self).__init__(name, ver, flags, **kwargs)
+
+    def get_flags_list(self):
+        flags = super(RedirectToNoOpEntryPoint, self).get_flags_list()
+        # RedirectToNoOpEntryPoint items always include the following flag
+        flags.add(REDIRECT_TO_NOOP_ENTRYPOINT)
+        return flags
+
+
+class LspBlocklistEntry(DllBlocklistEntry):
+    """Represents a blocklist entry for a WinSock Layered Service Provider (LSP)."""
+
+    GUID_UNPACK_FMT_LE = "<IHHBBBBBBBB"
+    Guids = dict()
+
+    def __init__(self, name, ver, guids, flags=(), **kwargs):
+        """Positional arguments:
+
+        name -- The leaf name of the DLL.
+
+        ver -- The maximum version to be blocked. NB: The comparison used by the
+        blocklist is <=, so you should specify the last bad version, as opposed
+        to the first good version.
+
+        guids -- Either a string or list of strings containing the GUIDs that
+        uniquely identify the LSP. These GUIDs are generated by the developer of
+        the LSP and are registered with WinSock alongside the LSP. We record
+        this GUID as part of the "Winsock_LSP" annotation in our crash reports.
+
+        flags -- iterable containing the flags that should be applicable to
+        this blocklist entry.
+
+        Keyword arguments:
+
+        condition -- a string containing a C++ preprocessor expression. This
+        condition is written as a condition for an #if/#endif block that is
+        generated around the entry during output.
+        """
+
+        super(LspBlocklistEntry, self).__init__(name, ver, flags, **kwargs)
+        if not guids:
+            raise ValueError("Missing GUID(s)!")
+
+        if isinstance(guids, str):
+            self.insert(UUID(guids), name)
+        else:
+            for guid in guids:
+                self.insert(UUID(guid), name)
+
+    def insert(self, guid, name):
+        # Some explanation here: Multiple DLLs (and thus multiple instances of
+        # LspBlocklistEntry) may share the same GUIDs. To ensure that we do not
+        # have any duplicates, we store each GUID in a class variable, Guids.
+        # We include the original DLL name from the blocklist definitions so
+        # that we may output a comment above each GUID indicating which entries
+        # correspond to which GUID.
+        LspBlocklistEntry.Guids.setdefault(guid, []).append(name)
+
+    def get_flags_list(self):
+        flags = super(LspBlocklistEntry, self).get_flags_list()
+        # LSP entries always include the following flag
+        flags.add(SUBSTITUTE_LSP_PASSTHROUGH)
+        return flags
+
+    @staticmethod
+    def as_c_struct(guid, names):
+        parts = unpack(LspBlocklistEntry.GUID_UNPACK_FMT_LE, guid.bytes_le)
+        str_guid = (
+            "  // %r\n  // {%s}\n  { 0x%08x, 0x%04x, 0x%04x, "
+            "{ 0x%02x, 0x%02x, 0x%02x, 0x%02x, 0x%02x, 0x%02x, 0x%02x, 0x%02x }"
+            " }"
+            % (
+                names,
+                str(guid),
+                parts[0],
+                parts[1],
+                parts[2],
+                parts[3],
+                parts[4],
+                parts[5],
+                parts[6],
+                parts[7],
+                parts[8],
+                parts[9],
+                parts[10],
+            )
+        )
+        return str_guid
+
+    def write(self, output, mode):
+        if mode != LSP_MODE_GUID:
+            super(LspBlocklistEntry, self).write(output, mode)
+            return
+
+        # We dump the entire contents of Guids on the first call, and then
+        # clear it. Remaining invocations of this method are no-ops.
+        if LspBlocklistEntry.Guids:
+            result = ",\n".join(
+                [
+                    self.as_c_struct(guid, names)
+                    for guid, names in iteritems(LspBlocklistEntry.Guids)
+                ]
+            )
+            print(result, file=output)
+            LspBlocklistEntry.Guids.clear()
+
+
+def exec_script_file(script_name, globals):
+    with open(script_name) as script:
+        exec(compile(script.read(), script_name, "exec"), globals)
+
+
+def gen_blocklists(first_fd, defs_filename):
+
+    BlocklistDescriptor.set_output_fd(first_fd)
+
+    # exec_env defines the global variables that will be present in the
+    # execution environment when defs_filename is run by exec.
+    exec_env = {
+        # Add the blocklist entry types
+        "A11yBlocklistEntry": A11yBlocklistEntry,
+        "DllBlocklistEntry": DllBlocklistEntry,
+        "LspBlocklistEntry": LspBlocklistEntry,
+        "RedirectToNoOpEntryPoint": RedirectToNoOpEntryPoint,
+        # Add the special version types
+        "ALL_VERSIONS": Version.ALL_VERSIONS,
+        "UNVERSIONED": Version.UNVERSIONED,
+        "PETimeStamp": PETimeStamp,
+    }
+
+    # Import definition lists into exec_env
+    for defname in ALL_DEFINITION_LISTS:
+        exec_env[defname] = []
+        # For each defname, add a special list for test-only entries
+        exec_env[derive_test_key(defname)] = []
+
+    # Import flags into exec_env
+    exec_env.update({flag: flag for flag in INPUT_ONLY_FLAGS})
+
+    # Now execute the input script with exec_env providing the globals
+    exec_script_file(defs_filename, exec_env)
+
+    # Tell the output descriptors to write out the output files.
+    for desc in GENERATED_BLOCKLIST_FILES:
+        desc.write(defs_filename, exec_env)
diff --git a/toolkit/xre/dllservices/mozglue/interceptor/Arm64.cpp b/toolkit/xre/dllservices/mozglue/interceptor/Arm64.cpp
new file mode 100644
index 0000000000..81d8e6d09b
--- /dev/null
+++ b/toolkit/xre/dllservices/mozglue/interceptor/Arm64.cpp
@@ -0,0 +1,89 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#include "Arm64.h"
+
+#include "mozilla/ResultVariant.h"
+
+namespace mozilla {
+namespace interceptor {
+namespace arm64 {
+
+struct PCRelativeLoadTest {
+  // Bitmask to be ANDed with the instruction to isolate the bits that this
+  // instance is interested in
+  uint32_t mTestMask;
+  // The desired bits that we want to see after masking
+  uint32_t mMatchBits;
+  // If we match, mDecodeFn provide the code to decode the instruction.
+  LoadOrBranch (*mDecodeFn)(const uintptr_t aPC, const uint32_t aInst);
+};
+
+static LoadOrBranch ADRPDecode(const uintptr_t aPC, const uint32_t aInst) {
+  // Keep in mind that on Windows aarch64, uint32_t is little-endian
+  const uint32_t kMaskDataProcImmPcRelativeImmLo = 0x60000000;
+  const uint32_t kMaskDataProcImmPcRelativeImmHi = 0x00FFFFE0;
+
+  uintptr_t base = aPC;
+  intptr_t offset = SignExtend<intptr_t>(
+      ((aInst & kMaskDataProcImmPcRelativeImmHi) >> 3) |
+          ((aInst & kMaskDataProcImmPcRelativeImmLo) >> 29),
+      21);
+
+  base &= ~0xFFFULL;
+  offset <<= 12;
+
+  uint8_t reg = aInst & 0x1F;
+
+  return LoadOrBranch(base + offset, reg);
+}
+
+MFBT_API LoadOrBranch BUncondImmDecode(const uintptr_t aPC,
+                                       const uint32_t aInst) {
+  int32_t offset = SignExtend<int32_t>(aInst & 0x03FFFFFFU, 26);
+  return LoadOrBranch(aPC + offset);
+}
+
+// Order is important here; more specific encoding tests must be placed before
+// less specific encoding tests.
+static const PCRelativeLoadTest gPCRelTests[] = {
+    {0x9FC00000, 0x10000000, nullptr},      // ADR
+    {0x9FC00000, 0x90000000, &ADRPDecode},  // ADRP
+    {0xFF000000, 0x58000000, nullptr},      // LDR (literal) 64-bit GPR
+    {0x3B000000, 0x18000000, nullptr},      // LDR (literal) (remaining forms)
+    {0x7C000000, 0x14000000, nullptr},      // B (unconditional immediate)
+    {0xFE000000, 0x54000000, nullptr},      // B.Cond
+    {0x7E000000, 0x34000000, nullptr},      // Compare and branch (imm)
+    {0x7E000000, 0x36000000, nullptr},      // Test and branch (imm)
+    {0xFE000000, 0xD6000000, nullptr}       // Unconditional branch (reg)
+};
+
+/**
+ * In this function we interate through each entry in |gPCRelTests|, AND
+ * |aInst| with |test.mTestMask| to isolate the bits that we're interested in,
+ * then compare that result against |test.mMatchBits|. If we have a match,
+ * then that particular entry is applicable to |aInst|. If |test.mDecodeFn| is
+ * present, then we call it to decode the instruction. If it is not present,
+ * then we assume that this particular instruction is unsupported.
+ */
+MFBT_API Result<LoadOrBranch, PCRelCheckError> CheckForPCRel(
+    const uintptr_t aPC, const uint32_t aInst) {
+  for (auto&& test : gPCRelTests) {
+    if ((aInst & test.mTestMask) == test.mMatchBits) {
+      if (!test.mDecodeFn) {
+        return Err(PCRelCheckError::NoDecoderAvailable);
+      }
+
+      return test.mDecodeFn(aPC, aInst);
+    }
+  }
+
+  return Err(PCRelCheckError::InstructionNotPCRel);
+}
+
+}  // namespace arm64
+}  // namespace interceptor
+}  // namespace mozilla
diff --git a/toolkit/xre/dllservices/mozglue/interceptor/Arm64.h b/toolkit/xre/dllservices/mozglue/interceptor/Arm64.h
new file mode 100644
index 0000000000..4070fbf99f
--- /dev/null
+++ b/toolkit/xre/dllservices/mozglue/interceptor/Arm64.h
@@ -0,0 +1,221 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_interceptor_Arm64_h
+#define mozilla_interceptor_Arm64_h
+
+#include <type_traits>
+
+#include "mozilla/Assertions.h"
+#include "mozilla/CheckedInt.h"
+#include "mozilla/MathAlgorithms.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/Result.h"
+#include "mozilla/Saturate.h"
+#include "mozilla/Types.h"
+
+namespace mozilla {
+namespace interceptor {
+namespace arm64 {
+
+// clang-format off
+enum class IntegerConditionCode : uint8_t {
+  // From the ARMv8 Architectural Reference Manual, Section C1.2.4
+  //               Description           Condition Flags
+  EQ = 0b0000,  // ==                    Z == 1
+  NE = 0b0001,  // !=                    Z == 0
+  CS = 0b0010,  // carry set             C == 1
+  HS = 0b0010,  // carry set (alias)     C == 1
+  CC = 0b0011,  // carry clear           C == 0
+  LO = 0b0011,  // carry clear (alias)   C == 0
+  MI = 0b0100,  // < 0                   N == 1
+  PL = 0b0101,  // >= 0                  N == 0
+  VS = 0b0110,  // overflow              V == 1
+  VC = 0b0111,  // no overflow           V == 0
+  HI = 0b1000,  // unsigned >            C == 1 && Z == 0
+  LS = 0b1001,  // unsigned <=           !(C == 1 && Z == 0)
+  GE = 0b1010,  // signed >=             N == V
+  LT = 0b1011,  // signed <              N != V
+  GT = 0b1100,  // signed >              Z == 0 && N == V
+  LE = 0b1101,  // signed <=             !(Z == 0 && N == V)
+  AL = 0b1110,  // unconditional         <Any>
+  NV = 0b1111   // unconditional (but AL is the preferred encoding)
+};
+// clang-format on
+
+struct LoadOrBranch {
+  enum class Type {
+    Load,
+    Branch,
+  };
+
+  // Load constructor
+  LoadOrBranch(const uintptr_t aAbsAddress, const uint8_t aDestReg)
+      : mType(Type::Load), mAbsAddress(aAbsAddress), mDestReg(aDestReg) {
+    MOZ_ASSERT(aDestReg < 32);
+  }
+
+  // Unconditional branch constructor
+  explicit LoadOrBranch(const uintptr_t aAbsAddress)
+      : mType(Type::Branch),
+        mAbsAddress(aAbsAddress),
+        mCond(IntegerConditionCode::AL) {}
+
+  // Conditional branch constructor
+  LoadOrBranch(const uintptr_t aAbsAddress, const IntegerConditionCode aCond)
+      : mType(Type::Branch), mAbsAddress(aAbsAddress), mCond(aCond) {}
+
+  Type mType;
+
+  // The absolute address to be loaded into a register, or branched to
+  uintptr_t mAbsAddress;
+
+  union {
+    // The destination register for the load
+    uint8_t mDestReg;
+
+    // The condition code for the branch
+    IntegerConditionCode mCond;
+  };
+};
+
+enum class PCRelCheckError {
+  InstructionNotPCRel,
+  NoDecoderAvailable,
+};
+
+MFBT_API Result<LoadOrBranch, PCRelCheckError> CheckForPCRel(
+    const uintptr_t aPC, const uint32_t aInst);
+
+/**
+ * Casts |aValue| to a |ResultT| via sign extension.
+ *
+ * This function should be used when extracting signed immediate values from
+ * an instruction.
+ *
+ * @param aValue The value to be sign extended. This value should already be
+ *               isolated from the remainder of the instruction's bits and
+ *               shifted all the way to the right.
+ * @param aNumValidBits The number of bits in |aValue| that contain the
+ *                      immediate signed value, including the sign bit.
+ */
+template <typename ResultT>
+inline ResultT SignExtend(const uint32_t aValue, const uint8_t aNumValidBits) {
+  static_assert(std::is_integral_v<ResultT> && std::is_signed_v<ResultT>,
+                "ResultT must be a signed integral type");
+  MOZ_ASSERT(aNumValidBits < 32U && aNumValidBits > 1);
+
+  using UnsignedResultT = std::decay_t<std::make_unsigned_t<ResultT>>;
+
+  const uint8_t kResultWidthBits = sizeof(ResultT) * 8;
+
+  // Shift left unsigned
+  const uint8_t shiftAmt = kResultWidthBits - aNumValidBits;
+  UnsignedResultT shiftedLeft = static_cast<UnsignedResultT>(aValue)
+                                << shiftAmt;
+
+  // Now shift right signed
+  auto result = static_cast<ResultT>(shiftedLeft);
+  result >>= shiftAmt;
+
+  return result;
+}
+
+inline static uint32_t BuildUnconditionalBranchToRegister(const uint32_t aReg) {
+  MOZ_ASSERT(aReg < 32);
+  // BR aReg
+  return 0xD61F0000 | (aReg << 5);
+}
+
+MFBT_API LoadOrBranch BUncondImmDecode(const uintptr_t aPC,
+                                       const uint32_t aInst);
+
+/**
+ * If |aTarget| is more than 128MB away from |aPC|, we need to use a veneer.
+ */
+inline static bool IsVeneerRequired(const uintptr_t aPC,
+                                    const uintptr_t aTarget) {
+  detail::Saturate<intptr_t> saturated(aTarget);
+  saturated -= aPC;
+
+  uintptr_t absDiff = Abs(saturated.value());
+
+  return absDiff >= 0x08000000U;
+}
+
+inline static bool IsUnconditionalBranchImm(const uint32_t aInst) {
+  return (aInst & 0xFC000000U) == 0x14000000U;
+}
+
+inline static Maybe<uint32_t> BuildUnconditionalBranchImm(
+    const uintptr_t aPC, const uintptr_t aTarget) {
+  detail::Saturate<intptr_t> saturated(aTarget);
+  saturated -= aPC;
+
+  CheckedInt<int32_t> offset(saturated.value());
+  if (!offset.isValid()) {
+    return Nothing();
+  }
+
+  // offset should be a multiple of 4
+  MOZ_ASSERT(offset.value() % 4 == 0);
+  if (offset.value() % 4) {
+    return Nothing();
+  }
+
+  offset /= 4;
+  if (!offset.isValid()) {
+    return Nothing();
+  }
+
+  uint32_t signbits = static_cast<uint32_t>(offset.value()) & 0xFE000000;
+  // Ensure that offset is small enough to fit into the 26 bit region.
+  // We check that the sign bits are either all ones or all zeros.
+  MOZ_ASSERT(signbits == 0xFE000000 || !signbits);
+  if (signbits && signbits != 0xFE000000) {
+    return Nothing();
+  }
+
+  uint32_t masked = static_cast<uint32_t>(offset.value()) & 0x03FFFFFF;
+
+  // B imm26
+  return Some(0x14000000U | masked);
+}
+
+/**
+ * Allocate and construct a veneer that provides an absolute 64-bit branch to
+ * the hook function.
+ */
+template <typename TrampPoolT>
+inline static uintptr_t MakeVeneer(TrampPoolT& aTrampPool, void* aPrimaryTramp,
+                                   const uintptr_t aDestAddress) {
+  auto maybeVeneer = aTrampPool.GetNextTrampoline();
+  if (!maybeVeneer) {
+    return 0;
+  }
+
+  Trampoline<typename TrampPoolT::MMPolicyT> veneer(
+      std::move(maybeVeneer.ref()));
+
+  // Write the same header information that is used for trampolines
+  veneer.WriteEncodedPointer(nullptr);
+  veneer.WriteEncodedPointer(aPrimaryTramp);
+
+  veneer.StartExecutableCode();
+
+  // Register 16 is explicitly intended for veneers in ARM64, so we use that
+  // register without fear of clobbering anything important.
+  veneer.WriteLoadLiteral(aDestAddress, 16);
+  veneer.WriteInstruction(BuildUnconditionalBranchToRegister(16));
+
+  return reinterpret_cast<uintptr_t>(veneer.EndExecutableCode());
+}
+
+}  // namespace arm64
+}  // namespace interceptor
+}  // namespace mozilla
+
+#endif  // mozilla_interceptor_Arm64_h
diff --git a/toolkit/xre/dllservices/mozglue/interceptor/MMPolicies.h b/toolkit/xre/dllservices/mozglue/interceptor/MMPolicies.h
new file mode 100644
index 0000000000..0a309a1065
--- /dev/null
+++ b/toolkit/xre/dllservices/mozglue/interceptor/MMPolicies.h
@@ -0,0 +1,1031 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_interceptor_MMPolicies_h
+#define mozilla_interceptor_MMPolicies_h
+
+#include "mozilla/Assertions.h"
+#include "mozilla/CheckedInt.h"
+#include "mozilla/DynamicallyLinkedFunctionPtr.h"
+#include "mozilla/MathAlgorithms.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/Span.h"
+#include "mozilla/TypedEnumBits.h"
+#include "mozilla/Types.h"
+#include "mozilla/WindowsMapRemoteView.h"
+#include "mozilla/WindowsUnwindInfo.h"
+
+#include <windows.h>
+
+#if (NTDDI_VERSION < NTDDI_WIN10_RS4) || defined(__MINGW32__)
+PVOID WINAPI VirtualAlloc2(HANDLE Process, PVOID BaseAddress, SIZE_T Size,
+                           ULONG AllocationType, ULONG PageProtection,
+                           MEM_EXTENDED_PARAMETER* ExtendedParameters,
+                           ULONG ParameterCount);
+PVOID WINAPI MapViewOfFile3(HANDLE FileMapping, HANDLE Process,
+                            PVOID BaseAddress, ULONG64 Offset, SIZE_T ViewSize,
+                            ULONG AllocationType, ULONG PageProtection,
+                            MEM_EXTENDED_PARAMETER* ExtendedParameters,
+                            ULONG ParameterCount);
+#endif  // (NTDDI_VERSION < NTDDI_WIN10_RS4) || defined(__MINGW32__)
+
+// _CRT_RAND_S is not defined everywhere, but we need it.
+#if !defined(_CRT_RAND_S)
+extern "C" errno_t rand_s(unsigned int* randomValue);
+#endif  // !defined(_CRT_RAND_S)
+
+// Declaring only the functions we need in NativeNt.h.  To include the entire
+// NativeNt.h causes circular dependency.
+namespace mozilla {
+namespace nt {
+SIZE_T WINAPI VirtualQueryEx(HANDLE aProcess, LPCVOID aAddress,
+                             PMEMORY_BASIC_INFORMATION aMemInfo,
+                             SIZE_T aMemInfoLen);
+
+SIZE_T WINAPI VirtualQuery(LPCVOID aAddress, PMEMORY_BASIC_INFORMATION aMemInfo,
+                           SIZE_T aMemInfoLen);
+}  // namespace nt
+}  // namespace mozilla
+
+namespace mozilla {
+namespace interceptor {
+
+// This class implements memory operations not involving any kernel32's
+// functions, so that derived classes can use them.
+class MOZ_TRIVIAL_CTOR_DTOR MMPolicyInProcessPrimitive {
+ protected:
+  bool ProtectInternal(decltype(&::VirtualProtect) aVirtualProtect,
+                       void* aVAddress, size_t aSize, uint32_t aProtFlags,
+                       uint32_t* aPrevProtFlags) const {
+    MOZ_ASSERT(aPrevProtFlags);
+    BOOL ok = aVirtualProtect(aVAddress, aSize, aProtFlags,
+                              reinterpret_cast<PDWORD>(aPrevProtFlags));
+    if (!ok && aPrevProtFlags) {
+      // VirtualProtect can fail but still set valid protection flags.
+      // Let's clear those upon failure.
+      *aPrevProtFlags = 0;
+    }
+
+    return !!ok;
+  }
+
+ public:
+  bool Read(void* aToPtr, const void* aFromPtr, size_t aLen) const {
+    ::memcpy(aToPtr, aFromPtr, aLen);
+    return true;
+  }
+
+  bool Write(void* aToPtr, const void* aFromPtr, size_t aLen) const {
+    ::memcpy(aToPtr, aFromPtr, aLen);
+    return true;
+  }
+
+  /**
+   * @return true if the page that hosts aVAddress is accessible.
+   */
+  bool IsPageAccessible(uintptr_t aVAddress) const {
+    MEMORY_BASIC_INFORMATION mbi;
+    SIZE_T result = nt::VirtualQuery(reinterpret_cast<LPCVOID>(aVAddress), &mbi,
+                                     sizeof(mbi));
+
+    return result && mbi.AllocationProtect && mbi.State == MEM_COMMIT &&
+           mbi.Protect != PAGE_NOACCESS;
+  }
+};
+
+class MOZ_TRIVIAL_CTOR_DTOR MMPolicyBase {
+ protected:
+  static uintptr_t AlignDown(const uintptr_t aUnaligned,
+                             const uintptr_t aAlignTo) {
+    MOZ_ASSERT(IsPowerOfTwo(aAlignTo));
+#pragma warning(suppress : 4146)
+    return aUnaligned & (-aAlignTo);
+  }
+
+  static uintptr_t AlignUp(const uintptr_t aUnaligned,
+                           const uintptr_t aAlignTo) {
+    MOZ_ASSERT(IsPowerOfTwo(aAlignTo));
+#pragma warning(suppress : 4146)
+    return aUnaligned + ((-aUnaligned) & (aAlignTo - 1));
+  }
+
+  static PVOID AlignUpToRegion(PVOID aUnaligned, uintptr_t aAlignTo,
+                               size_t aLen, size_t aDesiredLen) {
+    uintptr_t unaligned = reinterpret_cast<uintptr_t>(aUnaligned);
+    uintptr_t aligned = AlignUp(unaligned, aAlignTo);
+    MOZ_ASSERT(aligned >= unaligned);
+
+    if (aLen < aligned - unaligned) {
+      return nullptr;
+    }
+
+    aLen -= (aligned - unaligned);
+    return reinterpret_cast<PVOID>((aLen >= aDesiredLen) ? aligned : 0);
+  }
+
+ public:
+#if defined(NIGHTLY_BUILD)
+  Maybe<DetourError> mLastError;
+  const Maybe<DetourError>& GetLastDetourError() const { return mLastError; }
+  template <typename... Args>
+  void SetLastDetourError(Args&&... aArgs) {
+    mLastError = Some(DetourError(std::forward<Args>(aArgs)...));
+  }
+#else
+  template <typename... Args>
+  void SetLastDetourError(Args&&... aArgs) {}
+#endif  // defined(NIGHTLY_BUILD)
+
+  DWORD ComputeAllocationSize(const uint32_t aRequestedSize) const {
+    MOZ_ASSERT(aRequestedSize);
+    DWORD result = aRequestedSize;
+
+    const uint32_t granularity = GetAllocGranularity();
+
+    uint32_t mod = aRequestedSize % granularity;
+    if (mod) {
+      result += (granularity - mod);
+    }
+
+    return result;
+  }
+
+  DWORD GetAllocGranularity() const {
+    static const DWORD kAllocGranularity = []() -> DWORD {
+      SYSTEM_INFO sysInfo;
+      ::GetSystemInfo(&sysInfo);
+      return sysInfo.dwAllocationGranularity;
+    }();
+
+    return kAllocGranularity;
+  }
+
+  DWORD GetPageSize() const {
+    static const DWORD kPageSize = []() -> DWORD {
+      SYSTEM_INFO sysInfo;
+      ::GetSystemInfo(&sysInfo);
+      return sysInfo.dwPageSize;
+    }();
+
+    return kPageSize;
+  }
+
+  uintptr_t GetMaxUserModeAddress() const {
+    static const uintptr_t kMaxUserModeAddr = []() -> uintptr_t {
+      SYSTEM_INFO sysInfo;
+      ::GetSystemInfo(&sysInfo);
+      return reinterpret_cast<uintptr_t>(sysInfo.lpMaximumApplicationAddress);
+    }();
+
+    return kMaxUserModeAddr;
+  }
+
+  static const uint8_t* GetLowerBound(const Span<const uint8_t>& aBounds) {
+    return &(*aBounds.cbegin());
+  }
+
+  static const uint8_t* GetUpperBoundIncl(const Span<const uint8_t>& aBounds) {
+    // We return an upper bound that is inclusive.
+    return &(*(aBounds.cend() - 1));
+  }
+
+  static const uint8_t* GetUpperBoundExcl(const Span<const uint8_t>& aBounds) {
+    // We return an upper bound that is exclusive by adding 1 to the inclusive
+    // upper bound.
+    return GetUpperBoundIncl(aBounds) + 1;
+  }
+
+  /**
+   * It is convenient for us to provide address range information based on a
+   * "pivot" and a distance from that pivot, as branch instructions operate
+   * within a range of the program counter. OTOH, to actually manage the
+   * regions of memory, it is easier to think about them in terms of their
+   * lower and upper bounds. This function converts from the former format to
+   * the latter format.
+   */
+  Maybe<Span<const uint8_t>> SpanFromPivotAndDistance(
+      const uint32_t aSize, const uintptr_t aPivotAddr,
+      const uint32_t aMaxDistanceFromPivot) const {
+    if (!aPivotAddr || !aMaxDistanceFromPivot) {
+      return Nothing();
+    }
+
+    // We don't allow regions below 1MB so that we're not allocating near any
+    // sensitive areas in our address space.
+    const uintptr_t kMinAllowableAddress = 0x100000;
+
+    const uintptr_t kGranularity(GetAllocGranularity());
+
+    // We subtract the max distance from the pivot to determine our lower bound.
+    CheckedInt<uintptr_t> lowerBound(aPivotAddr);
+    lowerBound -= aMaxDistanceFromPivot;
+    if (lowerBound.isValid()) {
+      // In this case, the subtraction has not underflowed, but we still want
+      // the lower bound to be at least kMinAllowableAddress.
+      lowerBound = std::max(lowerBound.value(), kMinAllowableAddress);
+    } else {
+      // In this case, we underflowed. Forcibly set the lower bound to
+      // kMinAllowableAddress.
+      lowerBound = CheckedInt<uintptr_t>(kMinAllowableAddress);
+    }
+
+    // Align up to the next unit of allocation granularity when necessary.
+    lowerBound = AlignUp(lowerBound.value(), kGranularity);
+    MOZ_ASSERT(lowerBound.isValid());
+    if (!lowerBound.isValid()) {
+      return Nothing();
+    }
+
+    // We must ensure that our region is below the maximum allowable user-mode
+    // address, or our reservation will fail.
+    const uintptr_t kMaxUserModeAddr = GetMaxUserModeAddress();
+
+    // We add the max distance from the pivot to determine our upper bound.
+    CheckedInt<uintptr_t> upperBound(aPivotAddr);
+    upperBound += aMaxDistanceFromPivot;
+    if (upperBound.isValid()) {
+      // In this case, the addition has not overflowed, but we still want
+      // the upper bound to be at most kMaxUserModeAddr.
+      upperBound = std::min(upperBound.value(), kMaxUserModeAddr);
+    } else {
+      // In this case, we overflowed. Forcibly set the upper bound to
+      // kMaxUserModeAddr.
+      upperBound = CheckedInt<uintptr_t>(kMaxUserModeAddr);
+    }
+
+    // Subtract the desired allocation size so that any chunk allocated in the
+    // region will be reachable.
+    upperBound -= aSize;
+    if (!upperBound.isValid()) {
+      return Nothing();
+    }
+
+    // Align down to the next unit of allocation granularity when necessary.
+    upperBound = AlignDown(upperBound.value(), kGranularity);
+    if (!upperBound.isValid()) {
+      return Nothing();
+    }
+
+    MOZ_ASSERT(lowerBound.value() < upperBound.value());
+    if (lowerBound.value() >= upperBound.value()) {
+      return Nothing();
+    }
+
+    // Return the result as a Span
+    return Some(Span(reinterpret_cast<const uint8_t*>(lowerBound.value()),
+                     upperBound.value() - lowerBound.value()));
+  }
+
+  /**
+   * This function locates a virtual memory region of |aDesiredBytesLen| that
+   * resides in the interval [aRangeMin, aRangeMax). We do this by scanning the
+   * virtual memory space for a block of unallocated memory that is sufficiently
+   * large.
+   */
+  PVOID FindRegion(HANDLE aProcess, const size_t aDesiredBytesLen,
+                   const uint8_t* aRangeMin, const uint8_t* aRangeMax) {
+    // Convert the given pointers to uintptr_t because we should not
+    // compare two pointers unless they are from the same array or object.
+    uintptr_t rangeMin = reinterpret_cast<uintptr_t>(aRangeMin);
+    uintptr_t rangeMax = reinterpret_cast<uintptr_t>(aRangeMax);
+
+    const DWORD kGranularity = GetAllocGranularity();
+    if (!aDesiredBytesLen) {
+      SetLastDetourError(MMPOLICY_RESERVE_FINDREGION_INVALIDLEN);
+      return nullptr;
+    }
+
+    MOZ_ASSERT(rangeMin < rangeMax);
+    if (rangeMin >= rangeMax) {
+      SetLastDetourError(MMPOLICY_RESERVE_FINDREGION_INVALIDRANGE);
+      return nullptr;
+    }
+
+    // Generate a randomized base address that falls within the interval
+    // [aRangeMin, aRangeMax - aDesiredBytesLen]
+    unsigned int rnd = 0;
+    rand_s(&rnd);
+
+    // Reduce rnd to a value that falls within the acceptable range
+    uintptr_t maxOffset =
+        (rangeMax - rangeMin - aDesiredBytesLen) / kGranularity;
+    // Divide by maxOffset + 1 because maxOffset * kGranularity is acceptable.
+    uintptr_t offset = (uintptr_t(rnd) % (maxOffset + 1)) * kGranularity;
+
+    // Start searching at this address
+    const uintptr_t searchStart = rangeMin + offset;
+    // The max address needs to incorporate the desired length
+    const uintptr_t kMaxPtr = rangeMax - aDesiredBytesLen;
+
+    MOZ_DIAGNOSTIC_ASSERT(searchStart <= kMaxPtr);
+
+    MEMORY_BASIC_INFORMATION mbi;
+    SIZE_T len = sizeof(mbi);
+
+    // Scan the range for a free chunk that is at least as large as
+    // aDesiredBytesLen
+    // Scan [searchStart, kMaxPtr]
+    for (uintptr_t address = searchStart; address <= kMaxPtr;) {
+      if (nt::VirtualQueryEx(aProcess, reinterpret_cast<uint8_t*>(address),
+                             &mbi, len) != len) {
+        SetLastDetourError(MMPOLICY_RESERVE_FINDREGION_VIRTUALQUERY_ERROR,
+                           ::GetLastError());
+        return nullptr;
+      }
+
+      if (mbi.State == MEM_FREE) {
+        // |mbi.BaseAddress| is aligned with the page granularity, but may not
+        // be aligned with the allocation granularity.  VirtualAlloc does not
+        // accept such a non-aligned address unless the corresponding allocation
+        // region is free.  So we get the next boundary's start address.
+        PVOID regionStart = AlignUpToRegion(mbi.BaseAddress, kGranularity,
+                                            mbi.RegionSize, aDesiredBytesLen);
+        if (regionStart) {
+          return regionStart;
+        }
+      }
+
+      address = reinterpret_cast<uintptr_t>(mbi.BaseAddress) + mbi.RegionSize;
+    }
+
+    // Scan [aRangeMin, searchStart)
+    for (uintptr_t address = rangeMin; address < searchStart;) {
+      if (nt::VirtualQueryEx(aProcess, reinterpret_cast<uint8_t*>(address),
+                             &mbi, len) != len) {
+        SetLastDetourError(MMPOLICY_RESERVE_FINDREGION_VIRTUALQUERY_ERROR,
+                           ::GetLastError());
+        return nullptr;
+      }
+
+      if (mbi.State == MEM_FREE) {
+        PVOID regionStart = AlignUpToRegion(mbi.BaseAddress, kGranularity,
+                                            mbi.RegionSize, aDesiredBytesLen);
+        if (regionStart) {
+          return regionStart;
+        }
+      }
+
+      address = reinterpret_cast<uintptr_t>(mbi.BaseAddress) + mbi.RegionSize;
+    }
+
+    SetLastDetourError(MMPOLICY_RESERVE_FINDREGION_NO_FREE_REGION,
+                       ::GetLastError());
+    return nullptr;
+  }
+
+  /**
+   * This function reserves a |aSize| block of virtual memory.
+   *
+   * When |aBounds| is Nothing, it just calls |aReserveFn| and lets Windows
+   * choose the base address.
+   *
+   * Otherwise, it tries to call |aReserveRangeFn| to reserve the memory within
+   * the bounds provided by |aBounds|. It is advantageous to use this function
+   * because the OS's VM manager has better information as to which base
+   * addresses are the best to use.
+   *
+   * If |aReserveRangeFn| retuns Nothing, this means that the platform support
+   * is not available. In that case, we fall back to manually computing a region
+   * to use for reserving the memory by calling |FindRegion|.
+   */
+  template <typename ReserveFnT, typename ReserveRangeFnT>
+  PVOID Reserve(HANDLE aProcess, const uint32_t aSize,
+                const ReserveFnT& aReserveFn,
+                const ReserveRangeFnT& aReserveRangeFn,
+                const Maybe<Span<const uint8_t>>& aBounds) {
+    if (!aBounds) {
+      // No restrictions, let the OS choose the base address
+      PVOID ret = aReserveFn(aProcess, nullptr, aSize);
+      if (!ret) {
+        SetLastDetourError(MMPOLICY_RESERVE_NOBOUND_RESERVE_ERROR,
+                           ::GetLastError());
+      }
+      return ret;
+    }
+
+    const uint8_t* lowerBound = GetLowerBound(aBounds.ref());
+    const uint8_t* upperBoundExcl = GetUpperBoundExcl(aBounds.ref());
+
+    Maybe<PVOID> result =
+        aReserveRangeFn(aProcess, aSize, lowerBound, upperBoundExcl);
+    if (result) {
+      return result.value();
+    }
+
+    // aReserveRangeFn is not available on this machine. We'll do a manual
+    // search.
+
+    size_t curAttempt = 0;
+    const size_t kMaxAttempts = 8;
+
+    // We loop here because |FindRegion| may return a base address that
+    // is reserved elsewhere before we have had a chance to reserve it
+    // ourselves.
+    while (curAttempt < kMaxAttempts) {
+      PVOID base = FindRegion(aProcess, aSize, lowerBound, upperBoundExcl);
+      if (!base) {
+        return nullptr;
+      }
+
+      result = Some(aReserveFn(aProcess, base, aSize));
+      if (result.value()) {
+        return result.value();
+      }
+
+      ++curAttempt;
+    }
+
+    // If we run out of attempts, we fall through to the default case where
+    // the system chooses any base address it wants. In that case, the hook
+    // will be set on a best-effort basis.
+    PVOID ret = aReserveFn(aProcess, nullptr, aSize);
+    if (!ret) {
+      SetLastDetourError(MMPOLICY_RESERVE_FINAL_RESERVE_ERROR,
+                         ::GetLastError());
+    }
+    return ret;
+  }
+};
+
+class MOZ_TRIVIAL_CTOR_DTOR MMPolicyInProcess
+    : public MMPolicyInProcessPrimitive,
+      public MMPolicyBase {
+ public:
+  typedef MMPolicyInProcess MMPolicyT;
+
+  constexpr MMPolicyInProcess()
+      : mBase(nullptr), mReservationSize(0), mCommitOffset(0) {}
+
+  MMPolicyInProcess(const MMPolicyInProcess&) = delete;
+  MMPolicyInProcess& operator=(const MMPolicyInProcess&) = delete;
+
+  MMPolicyInProcess(MMPolicyInProcess&& aOther)
+      : mBase(nullptr), mReservationSize(0), mCommitOffset(0) {
+    *this = std::move(aOther);
+  }
+
+  MMPolicyInProcess& operator=(MMPolicyInProcess&& aOther) {
+    mBase = aOther.mBase;
+    aOther.mBase = nullptr;
+
+    mCommitOffset = aOther.mCommitOffset;
+    aOther.mCommitOffset = 0;
+
+    mReservationSize = aOther.mReservationSize;
+    aOther.mReservationSize = 0;
+
+    return *this;
+  }
+
+  explicit operator bool() const { return !!mBase; }
+
+  /**
+   * Should we unhook everything upon destruction?
+   */
+  bool ShouldUnhookUponDestruction() const { return true; }
+
+#if defined(_M_IX86)
+  bool WriteAtomic(void* aDestPtr, const uint16_t aValue) const {
+    *static_cast<uint16_t*>(aDestPtr) = aValue;
+    return true;
+  }
+#endif  // defined(_M_IX86)
+
+  bool Protect(void* aVAddress, size_t aSize, uint32_t aProtFlags,
+               uint32_t* aPrevProtFlags) const {
+    return ProtectInternal(::VirtualProtect, aVAddress, aSize, aProtFlags,
+                           aPrevProtFlags);
+  }
+
+  bool FlushInstructionCache() const {
+    return !!::FlushInstructionCache(::GetCurrentProcess(), nullptr, 0);
+  }
+
+  static DWORD GetTrampWriteProtFlags() { return PAGE_EXECUTE_READWRITE; }
+
+#if defined(_M_X64)
+  bool IsTrampolineSpaceInLowest2GB() const {
+    return (mBase + mReservationSize) <=
+           reinterpret_cast<uint8_t*>(0x0000000080000000ULL);
+  }
+
+  static constexpr bool kSupportsUnwindInfo = true;
+
+  mozilla::UniquePtr<uint8_t[]> LookupUnwindInfo(
+      uintptr_t aOrigFuncAddr, uint32_t* aOffsetFromBeginAddr,
+      uint32_t* aOffsetToEndAddr, uintptr_t* aOrigImageBase) const {
+    DWORD64 origImageBase = 0;
+    auto origFuncEntry =
+        RtlLookupFunctionEntry(aOrigFuncAddr, &origImageBase, nullptr);
+    if (!origFuncEntry) {
+      return nullptr;
+    }
+
+    if (aOffsetFromBeginAddr) {
+      *aOffsetFromBeginAddr =
+          aOrigFuncAddr - (origImageBase + origFuncEntry->BeginAddress);
+    }
+    if (aOffsetToEndAddr) {
+      *aOffsetToEndAddr =
+          (origImageBase + origFuncEntry->EndAddress) - aOrigFuncAddr;
+    }
+    if (aOrigImageBase) {
+      *aOrigImageBase = origImageBase;
+    }
+    return reinterpret_cast<const UnwindInfo*>(origImageBase +
+                                               origFuncEntry->UnwindData)
+        ->Copy();
+  }
+
+  bool AddFunctionTable(uintptr_t aFunctionTable, uint32_t aEntryCount,
+                        uintptr_t aBaseAddress) const {
+    return bool(
+        RtlAddFunctionTable(reinterpret_cast<PRUNTIME_FUNCTION>(aFunctionTable),
+                            aEntryCount, aBaseAddress));
+  }
+#endif  // defined(_M_X64)
+
+ protected:
+  uint8_t* GetLocalView() const { return mBase; }
+
+  uintptr_t GetRemoteView() const {
+    // Same as local view for in-process
+    return reinterpret_cast<uintptr_t>(mBase);
+  }
+
+  /**
+   * @return the effective number of bytes reserved, or 0 on failure
+   */
+  uint32_t Reserve(const uint32_t aSize,
+                   const Maybe<Span<const uint8_t>>& aBounds) {
+    if (!aSize) {
+      return 0;
+    }
+
+    if (mBase) {
+      MOZ_ASSERT(mReservationSize >= aSize);
+      return mReservationSize;
+    }
+
+    mReservationSize = ComputeAllocationSize(aSize);
+
+    auto reserveFn = [](HANDLE aProcess, PVOID aBase, uint32_t aSize) -> PVOID {
+      return ::VirtualAlloc(aBase, aSize, MEM_RESERVE, PAGE_NOACCESS);
+    };
+
+    auto reserveWithinRangeFn =
+        [](HANDLE aProcess, uint32_t aSize, const uint8_t* aRangeMin,
+           const uint8_t* aRangeMaxExcl) -> Maybe<PVOID> {
+      static const StaticDynamicallyLinkedFunctionPtr<
+          decltype(&::VirtualAlloc2)>
+          pVirtualAlloc2(L"kernelbase.dll", "VirtualAlloc2");
+      if (!pVirtualAlloc2) {
+        return Nothing();
+      }
+
+      // NB: MEM_ADDRESS_REQUIREMENTS::HighestEndingAddress is *inclusive*
+      MEM_ADDRESS_REQUIREMENTS memReq = {
+          const_cast<uint8_t*>(aRangeMin),
+          const_cast<uint8_t*>(aRangeMaxExcl - 1)};
+
+      MEM_EXTENDED_PARAMETER memParam = {};
+      memParam.Type = MemExtendedParameterAddressRequirements;
+      memParam.Pointer = &memReq;
+
+      return Some(pVirtualAlloc2(aProcess, nullptr, aSize, MEM_RESERVE,
+                                 PAGE_NOACCESS, &memParam, 1));
+    };
+
+    mBase = static_cast<uint8_t*>(
+        MMPolicyBase::Reserve(::GetCurrentProcess(), mReservationSize,
+                              reserveFn, reserveWithinRangeFn, aBounds));
+
+    if (!mBase) {
+      return 0;
+    }
+
+    return mReservationSize;
+  }
+
+  bool MaybeCommitNextPage(const uint32_t aRequestedOffset,
+                           const uint32_t aRequestedLength) {
+    if (!(*this)) {
+      return false;
+    }
+
+    uint32_t limit = aRequestedOffset + aRequestedLength - 1;
+    if (limit < mCommitOffset) {
+      // No commit required
+      return true;
+    }
+
+    MOZ_DIAGNOSTIC_ASSERT(mCommitOffset < mReservationSize);
+    if (mCommitOffset >= mReservationSize) {
+      return false;
+    }
+
+    PVOID local = ::VirtualAlloc(mBase + mCommitOffset, GetPageSize(),
+                                 MEM_COMMIT, PAGE_EXECUTE_READ);
+    if (!local) {
+      return false;
+    }
+
+    mCommitOffset += GetPageSize();
+    return true;
+  }
+
+ private:
+  uint8_t* mBase;
+  uint32_t mReservationSize;
+  uint32_t mCommitOffset;
+};
+
+// This class manages in-process memory access without using functions
+// imported from kernel32.dll.  Instead, it uses functions in its own
+// function table that are provided from outside.
+class MMPolicyInProcessEarlyStage : public MMPolicyInProcessPrimitive {
+ public:
+  struct Kernel32Exports {
+    decltype(&::FlushInstructionCache) mFlushInstructionCache;
+    decltype(&::GetModuleHandleW) mGetModuleHandleW;
+    decltype(&::GetSystemInfo) mGetSystemInfo;
+    decltype(&::VirtualProtect) mVirtualProtect;
+  };
+
+ private:
+  static DWORD GetPageSize(const Kernel32Exports& aK32Exports) {
+    SYSTEM_INFO sysInfo;
+    aK32Exports.mGetSystemInfo(&sysInfo);
+    return sysInfo.dwPageSize;
+  }
+
+  const Kernel32Exports& mK32Exports;
+  const DWORD mPageSize;
+
+ public:
+  explicit MMPolicyInProcessEarlyStage(const Kernel32Exports& aK32Exports)
+      : mK32Exports(aK32Exports), mPageSize(GetPageSize(mK32Exports)) {}
+
+  // The pattern of constructing a local static variable with a lambda,
+  // which can be seen in MMPolicyBase, is compiled into code with the
+  // critical section APIs like EnterCriticalSection imported from kernel32.dll.
+  // Because this class needs to be able to run in a process's early stage
+  // when IAT is not yet resolved, we cannot use that patten, thus simply
+  // caching a value as a local member in the class.
+  DWORD GetPageSize() const { return mPageSize; }
+
+  bool Protect(void* aVAddress, size_t aSize, uint32_t aProtFlags,
+               uint32_t* aPrevProtFlags) const {
+    return ProtectInternal(mK32Exports.mVirtualProtect, aVAddress, aSize,
+                           aProtFlags, aPrevProtFlags);
+  }
+
+  bool FlushInstructionCache() const {
+    const HANDLE kCurrentProcess = reinterpret_cast<HANDLE>(-1);
+    return !!mK32Exports.mFlushInstructionCache(kCurrentProcess, nullptr, 0);
+  }
+};
+
+class MMPolicyOutOfProcess : public MMPolicyBase {
+ public:
+  typedef MMPolicyOutOfProcess MMPolicyT;
+
+  explicit MMPolicyOutOfProcess(HANDLE aProcess)
+      : mProcess(nullptr),
+        mMapping(nullptr),
+        mLocalView(nullptr),
+        mRemoteView(nullptr),
+        mReservationSize(0),
+        mCommitOffset(0) {
+    MOZ_ASSERT(aProcess);
+    ::DuplicateHandle(::GetCurrentProcess(), aProcess, ::GetCurrentProcess(),
+                      &mProcess, kAccessFlags, FALSE, 0);
+    MOZ_ASSERT(mProcess);
+  }
+
+  explicit MMPolicyOutOfProcess(DWORD aPid)
+      : mProcess(::OpenProcess(kAccessFlags, FALSE, aPid)),
+        mMapping(nullptr),
+        mLocalView(nullptr),
+        mRemoteView(nullptr),
+        mReservationSize(0),
+        mCommitOffset(0) {
+    MOZ_ASSERT(mProcess);
+  }
+
+  ~MMPolicyOutOfProcess() { Destroy(); }
+
+  MMPolicyOutOfProcess(MMPolicyOutOfProcess&& aOther)
+      : mProcess(nullptr),
+        mMapping(nullptr),
+        mLocalView(nullptr),
+        mRemoteView(nullptr),
+        mReservationSize(0),
+        mCommitOffset(0) {
+    *this = std::move(aOther);
+  }
+
+  MMPolicyOutOfProcess(const MMPolicyOutOfProcess& aOther) = delete;
+  MMPolicyOutOfProcess& operator=(const MMPolicyOutOfProcess&) = delete;
+
+  MMPolicyOutOfProcess& operator=(MMPolicyOutOfProcess&& aOther) {
+    Destroy();
+
+    mProcess = aOther.mProcess;
+    aOther.mProcess = nullptr;
+
+    mMapping = aOther.mMapping;
+    aOther.mMapping = nullptr;
+
+    mLocalView = aOther.mLocalView;
+    aOther.mLocalView = nullptr;
+
+    mRemoteView = aOther.mRemoteView;
+    aOther.mRemoteView = nullptr;
+
+    mReservationSize = aOther.mReservationSize;
+    aOther.mReservationSize = 0;
+
+    mCommitOffset = aOther.mCommitOffset;
+    aOther.mCommitOffset = 0;
+
+    return *this;
+  }
+
+  explicit operator bool() const {
+    return mProcess && mMapping && mLocalView && mRemoteView;
+  }
+
+  bool ShouldUnhookUponDestruction() const {
+    // We don't clean up hooks for remote processes; they are expected to
+    // outlive our process.
+    return false;
+  }
+
+  // This function reads as many bytes as |aLen| from the target process and
+  // succeeds only when the entire area to be read is accessible.
+  bool Read(void* aToPtr, const void* aFromPtr, size_t aLen) const {
+    MOZ_ASSERT(mProcess);
+    if (!mProcess) {
+      return false;
+    }
+
+    SIZE_T numBytes = 0;
+    BOOL ok = ::ReadProcessMemory(mProcess, aFromPtr, aToPtr, aLen, &numBytes);
+    return ok && numBytes == aLen;
+  }
+
+  // This function reads as many bytes as possible from the target process up
+  // to |aLen| bytes and returns the number of bytes which was actually read.
+  size_t TryRead(void* aToPtr, const void* aFromPtr, size_t aLen) const {
+    MOZ_ASSERT(mProcess);
+    if (!mProcess) {
+      return 0;
+    }
+
+    uint32_t pageSize = GetPageSize();
+    uintptr_t pageMask = pageSize - 1;
+
+    auto rangeStart = reinterpret_cast<uintptr_t>(aFromPtr);
+    auto rangeEnd = rangeStart + aLen;
+
+    while (rangeStart < rangeEnd) {
+      SIZE_T numBytes = 0;
+      BOOL ok = ::ReadProcessMemory(mProcess, aFromPtr, aToPtr,
+                                    rangeEnd - rangeStart, &numBytes);
+      if (ok) {
+        return numBytes;
+      }
+
+      // If ReadProcessMemory fails, try to read up to each page boundary from
+      // the end of the requested area one by one.
+      if (rangeEnd & pageMask) {
+        rangeEnd &= ~pageMask;
+      } else {
+        rangeEnd -= pageSize;
+      }
+    }
+
+    return 0;
+  }
+
+  bool Write(void* aToPtr, const void* aFromPtr, size_t aLen) const {
+    MOZ_ASSERT(mProcess);
+    if (!mProcess) {
+      return false;
+    }
+
+    SIZE_T numBytes = 0;
+    BOOL ok = ::WriteProcessMemory(mProcess, aToPtr, aFromPtr, aLen, &numBytes);
+    return ok && numBytes == aLen;
+  }
+
+  bool Protect(void* aVAddress, size_t aSize, uint32_t aProtFlags,
+               uint32_t* aPrevProtFlags) const {
+    MOZ_ASSERT(mProcess);
+    if (!mProcess) {
+      return false;
+    }
+
+    MOZ_ASSERT(aPrevProtFlags);
+    BOOL ok = ::VirtualProtectEx(mProcess, aVAddress, aSize, aProtFlags,
+                                 reinterpret_cast<PDWORD>(aPrevProtFlags));
+    if (!ok && aPrevProtFlags) {
+      // VirtualProtectEx can fail but still set valid protection flags.
+      // Let's clear those upon failure.
+      *aPrevProtFlags = 0;
+    }
+
+    return !!ok;
+  }
+
+  /**
+   * @return true if the page that hosts aVAddress is accessible.
+   */
+  bool IsPageAccessible(uintptr_t aVAddress) const {
+    MEMORY_BASIC_INFORMATION mbi;
+    SIZE_T result = nt::VirtualQueryEx(
+        mProcess, reinterpret_cast<LPCVOID>(aVAddress), &mbi, sizeof(mbi));
+
+    return result && mbi.AllocationProtect && mbi.State == MEM_COMMIT &&
+           mbi.Protect != PAGE_NOACCESS;
+  }
+
+  bool FlushInstructionCache() const {
+    return !!::FlushInstructionCache(mProcess, nullptr, 0);
+  }
+
+  static DWORD GetTrampWriteProtFlags() { return PAGE_READWRITE; }
+
+#if defined(_M_X64)
+  bool IsTrampolineSpaceInLowest2GB() const {
+    return (GetRemoteView() + mReservationSize) <= 0x0000000080000000ULL;
+  }
+
+  // TODO: We should also implement unwind info for our out-of-process policy.
+  static constexpr bool kSupportsUnwindInfo = false;
+
+  inline mozilla::UniquePtr<uint8_t[]> LookupUnwindInfo(
+      uintptr_t aOrigFuncAddr, uint32_t* aOffsetFromBeginAddr,
+      uint32_t* aOffsetToEndAddr, uintptr_t* aOrigImageBase) const {
+    return nullptr;
+  }
+
+  inline bool AddFunctionTable(uintptr_t aNewTable, uint32_t aEntryCount,
+                               uintptr_t aBaseAddress) const {
+    return false;
+  }
+#endif  // defined(_M_X64)
+
+ protected:
+  uint8_t* GetLocalView() const { return mLocalView; }
+
+  uintptr_t GetRemoteView() const {
+    return reinterpret_cast<uintptr_t>(mRemoteView);
+  }
+
+  /**
+   * @return the effective number of bytes reserved, or 0 on failure
+   */
+  uint32_t Reserve(const uint32_t aSize,
+                   const Maybe<Span<const uint8_t>>& aBounds) {
+    if (!aSize || !mProcess) {
+      SetLastDetourError(MMPOLICY_RESERVE_INVALIDARG);
+      return 0;
+    }
+
+    if (mRemoteView) {
+      MOZ_ASSERT(mReservationSize >= aSize);
+      SetLastDetourError(MMPOLICY_RESERVE_ZERO_RESERVATIONSIZE);
+      return mReservationSize;
+    }
+
+    mReservationSize = ComputeAllocationSize(aSize);
+
+    mMapping = ::CreateFileMappingW(INVALID_HANDLE_VALUE, nullptr,
+                                    PAGE_EXECUTE_READWRITE | SEC_RESERVE, 0,
+                                    mReservationSize, nullptr);
+    if (!mMapping) {
+      SetLastDetourError(MMPOLICY_RESERVE_CREATEFILEMAPPING, ::GetLastError());
+      return 0;
+    }
+
+    mLocalView = static_cast<uint8_t*>(
+        ::MapViewOfFile(mMapping, FILE_MAP_WRITE, 0, 0, 0));
+    if (!mLocalView) {
+      SetLastDetourError(MMPOLICY_RESERVE_MAPVIEWOFFILE, ::GetLastError());
+      return 0;
+    }
+
+    auto reserveFn = [mapping = mMapping](HANDLE aProcess, PVOID aBase,
+                                          uint32_t aSize) -> PVOID {
+      return mozilla::MapRemoteViewOfFile(mapping, aProcess, 0ULL, aBase, 0, 0,
+                                          PAGE_EXECUTE_READ);
+    };
+
+    auto reserveWithinRangeFn =
+        [mapping = mMapping](HANDLE aProcess, uint32_t aSize,
+                             const uint8_t* aRangeMin,
+                             const uint8_t* aRangeMaxExcl) -> Maybe<PVOID> {
+      static const StaticDynamicallyLinkedFunctionPtr<
+          decltype(&::MapViewOfFile3)>
+          pMapViewOfFile3(L"kernelbase.dll", "MapViewOfFile3");
+      if (!pMapViewOfFile3) {
+        return Nothing();
+      }
+
+      // NB: MEM_ADDRESS_REQUIREMENTS::HighestEndingAddress is *inclusive*
+      MEM_ADDRESS_REQUIREMENTS memReq = {
+          const_cast<uint8_t*>(aRangeMin),
+          const_cast<uint8_t*>(aRangeMaxExcl - 1)};
+
+      MEM_EXTENDED_PARAMETER memParam = {};
+      memParam.Type = MemExtendedParameterAddressRequirements;
+      memParam.Pointer = &memReq;
+
+      return Some(pMapViewOfFile3(mapping, aProcess, nullptr, 0, aSize, 0,
+                                  PAGE_EXECUTE_READ, &memParam, 1));
+    };
+
+    mRemoteView = MMPolicyBase::Reserve(mProcess, mReservationSize, reserveFn,
+                                        reserveWithinRangeFn, aBounds);
+    if (!mRemoteView) {
+      return 0;
+    }
+
+    return mReservationSize;
+  }
+
+  bool MaybeCommitNextPage(const uint32_t aRequestedOffset,
+                           const uint32_t aRequestedLength) {
+    if (!(*this)) {
+      return false;
+    }
+
+    uint32_t limit = aRequestedOffset + aRequestedLength - 1;
+    if (limit < mCommitOffset) {
+      // No commit required
+      return true;
+    }
+
+    MOZ_DIAGNOSTIC_ASSERT(mCommitOffset < mReservationSize);
+    if (mCommitOffset >= mReservationSize) {
+      return false;
+    }
+
+    PVOID local = ::VirtualAlloc(mLocalView + mCommitOffset, GetPageSize(),
+                                 MEM_COMMIT, PAGE_READWRITE);
+    if (!local) {
+      return false;
+    }
+
+    PVOID remote = ::VirtualAllocEx(
+        mProcess, static_cast<uint8_t*>(mRemoteView) + mCommitOffset,
+        GetPageSize(), MEM_COMMIT, PAGE_EXECUTE_READ);
+    if (!remote) {
+      return false;
+    }
+
+    mCommitOffset += GetPageSize();
+    return true;
+  }
+
+ private:
+  void Destroy() {
+    // We always leak the remote view
+    if (mLocalView) {
+      ::UnmapViewOfFile(mLocalView);
+      mLocalView = nullptr;
+    }
+
+    if (mMapping) {
+      ::CloseHandle(mMapping);
+      mMapping = nullptr;
+    }
+
+    if (mProcess) {
+      ::CloseHandle(mProcess);
+      mProcess = nullptr;
+    }
+  }
+
+ private:
+  HANDLE mProcess;
+  HANDLE mMapping;
+  uint8_t* mLocalView;
+  PVOID mRemoteView;
+  uint32_t mReservationSize;
+  uint32_t mCommitOffset;
+
+  static const DWORD kAccessFlags = PROCESS_QUERY_INFORMATION |
+                                    PROCESS_VM_OPERATION | PROCESS_VM_READ |
+                                    PROCESS_VM_WRITE;
+};
+
+}  // namespace interceptor
+}  // namespace mozilla
+
+#endif  // mozilla_interceptor_MMPolicies_h
diff --git a/toolkit/xre/dllservices/mozglue/interceptor/PatcherBase.h b/toolkit/xre/dllservices/mozglue/interceptor/PatcherBase.h
new file mode 100644
index 0000000000..e39a38fafd
--- /dev/null
+++ b/toolkit/xre/dllservices/mozglue/interceptor/PatcherBase.h
@@ -0,0 +1,141 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_interceptor_PatcherBase_h
+#define mozilla_interceptor_PatcherBase_h
+
+#include "mozilla/interceptor/TargetFunction.h"
+
+namespace mozilla {
+namespace interceptor {
+
+template <typename MMPolicy>
+struct GetProcAddressSelector;
+
+template <>
+struct GetProcAddressSelector<MMPolicyOutOfProcess> {
+  FARPROC operator()(HMODULE aModule, const char* aName,
+                     const MMPolicyOutOfProcess& aMMPolicy) const {
+    auto exportSection =
+        mozilla::nt::PEExportSection<MMPolicyOutOfProcess>::Get(aModule,
+                                                                aMMPolicy);
+    return exportSection.GetProcAddress(aName);
+  }
+};
+
+template <>
+struct GetProcAddressSelector<MMPolicyInProcess> {
+  FARPROC operator()(HMODULE aModule, const char* aName,
+                     const MMPolicyInProcess&) const {
+    // PEExportSection works for MMPolicyInProcess, too, but the native
+    // GetProcAddress is still better because PEExportSection does not
+    // solve a forwarded entry.
+    return ::GetProcAddress(aModule, aName);
+  }
+};
+
+template <typename VMPolicy>
+class WindowsDllPatcherBase {
+ protected:
+  typedef typename VMPolicy::MMPolicyT MMPolicyT;
+
+  template <typename... Args>
+  explicit WindowsDllPatcherBase(Args&&... aArgs)
+      : mVMPolicy(std::forward<Args>(aArgs)...) {}
+
+  ReadOnlyTargetFunction<MMPolicyT> ResolveRedirectedAddress(
+      FARPROC aOriginalFunction) {
+    uintptr_t currAddr = reinterpret_cast<uintptr_t>(aOriginalFunction);
+
+#if defined(_M_IX86) || defined(_M_X64)
+    uintptr_t prevAddr = 0;
+    while (prevAddr != currAddr) {
+      ReadOnlyTargetFunction<MMPolicyT> currFunc(mVMPolicy, currAddr);
+      prevAddr = currAddr;
+
+      // If function entry is jmp rel8 stub to the internal implementation, we
+      // resolve redirected address from the jump target.
+      uintptr_t nextAddr = 0;
+      if (currFunc.IsRelativeShortJump(&nextAddr)) {
+        int8_t offset = nextAddr - currFunc.GetAddress() - 2;
+
+#  if defined(_M_X64)
+        // We redirect to the target of a short jump backwards if the target
+        // is another jump (only 32-bit displacement is currently supported).
+        // This case is used by GetFileAttributesW in Win7 x64.
+        if ((offset < 0) && (currFunc.IsValidAtOffset(2 + offset))) {
+          ReadOnlyTargetFunction<MMPolicyT> redirectFn(mVMPolicy, nextAddr);
+          if (redirectFn.IsIndirectNearJump(&nextAddr)) {
+            return redirectFn;
+          }
+        }
+#  endif
+
+        // We check the downstream has enough nop-space only when the offset is
+        // positive.  Otherwise we stop chasing redirects and let the caller
+        // fail to hook.
+        if (offset > 0) {
+          bool isNopSpace = true;
+          for (int8_t i = 0; i < offset; i++) {
+            if (currFunc[2 + i] != 0x90) {
+              isNopSpace = false;
+              break;
+            }
+          }
+
+          if (isNopSpace) {
+            currAddr = nextAddr;
+          }
+        }
+#  if defined(_M_X64)
+      } else if (currFunc.IsIndirectNearJump(&nextAddr) ||
+                 currFunc.IsRelativeNearJump(&nextAddr)) {
+#  else
+      } else if (currFunc.IsIndirectNearJump(&nextAddr)) {
+#  endif
+        // If function entry is jmp [disp32] such as used by kernel32, we
+        // resolve redirected address from import table. For x64, we resolve
+        // a relative near jump for TestDllInterceptor with --disable-optimize.
+        currAddr = nextAddr;
+      }
+    }
+#endif  // defined(_M_IX86) || defined(_M_X64)
+
+    if (currAddr != reinterpret_cast<uintptr_t>(aOriginalFunction) &&
+        !mVMPolicy.IsPageAccessible(currAddr)) {
+      currAddr = reinterpret_cast<uintptr_t>(aOriginalFunction);
+    }
+    return ReadOnlyTargetFunction<MMPolicyT>(mVMPolicy, currAddr);
+  }
+
+ public:
+  FARPROC GetProcAddress(HMODULE aModule, const char* aName) const {
+    GetProcAddressSelector<MMPolicyT> selector;
+    return selector(aModule, aName, mVMPolicy);
+  }
+
+  bool IsPageAccessible(uintptr_t aAddress) const {
+    return mVMPolicy.IsPageAccessible(aAddress);
+  }
+
+#if defined(NIGHTLY_BUILD)
+  const Maybe<DetourError>& GetLastDetourError() const {
+    return mVMPolicy.GetLastDetourError();
+  }
+#endif  // defined(NIGHTLY_BUILD)
+  template <typename... Args>
+  void SetLastDetourError(Args&&... aArgs) {
+    mVMPolicy.SetLastDetourError(std::forward<Args>(aArgs)...);
+  }
+
+ protected:
+  VMPolicy mVMPolicy;
+};
+
+}  // namespace interceptor
+}  // namespace mozilla
+
+#endif  // mozilla_interceptor_PatcherBase_h
diff --git a/toolkit/xre/dllservices/mozglue/interceptor/PatcherDetour.h b/toolkit/xre/dllservices/mozglue/interceptor/PatcherDetour.h
new file mode 100644
index 0000000000..e0b33c7add
--- /dev/null
+++ b/toolkit/xre/dllservices/mozglue/interceptor/PatcherDetour.h
@@ -0,0 +1,1739 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_interceptor_PatcherDetour_h
+#define mozilla_interceptor_PatcherDetour_h
+
+#if defined(_M_ARM64)
+#  include "mozilla/interceptor/Arm64.h"
+#endif  // defined(_M_ARM64)
+#include <utility>
+
+#include "mozilla/Maybe.h"
+#include "mozilla/NativeNt.h"
+#include "mozilla/ScopeExit.h"
+#include "mozilla/TypedEnumBits.h"
+#include "mozilla/Types.h"
+#include "mozilla/Unused.h"
+#include "mozilla/interceptor/PatcherBase.h"
+#include "mozilla/interceptor/Trampoline.h"
+#include "mozilla/interceptor/VMSharingPolicies.h"
+
+#define COPY_CODES(NBYTES)                           \
+  do {                                               \
+    tramp.CopyCodes(origBytes.GetAddress(), NBYTES); \
+    origBytes += NBYTES;                             \
+  } while (0)
+
+namespace mozilla {
+namespace interceptor {
+
+enum class DetourFlags : uint32_t {
+  eDefault = 0,
+  eEnable10BytePatch = 1,  // Allow 10-byte patches when conditions allow
+  eTestOnlyForceShortPatch =
+      2,  // Force short patches at all times (x86-64 and arm64 testing only)
+  eDontResolveRedirection =
+      4,  // Don't resolve the redirection of JMP (e.g. kernel32 -> kernelbase)
+};
+
+MOZ_MAKE_ENUM_CLASS_BITWISE_OPERATORS(DetourFlags)
+
+// This class is responsible to do tasks which depend on MMPolicy, decoupled
+// from VMPolicy.  We already have WindowsDllPatcherBase, but it needs to
+// depend on VMPolicy to hold an instance of VMPolicy as a member.
+template <typename MMPolicyT>
+class WindowsDllDetourPatcherPrimitive {
+ protected:
+#if defined(_M_ARM64)
+  // LDR x16, .+8
+  static const uint32_t kLdrX16Plus8 = 0x58000050U;
+#endif  // defined(_M_ARM64)
+
+  static void ApplyDefaultPatch(WritableTargetFunction<MMPolicyT>& target,
+                                intptr_t aDest) {
+#if defined(_M_IX86)
+    target.WriteByte(0xe9);     // jmp
+    target.WriteDisp32(aDest);  // hook displacement
+#elif defined(_M_X64)
+    // mov r11, address
+    target.WriteByte(0x49);
+    target.WriteByte(0xbb);
+    target.WritePointer(aDest);
+
+    // jmp r11
+    target.WriteByte(0x41);
+    target.WriteByte(0xff);
+    target.WriteByte(0xe3);
+#elif defined(_M_ARM64)
+    // The default patch requires 16 bytes
+    // LDR x16, .+8
+    target.WriteLong(kLdrX16Plus8);
+    // BR x16
+    target.WriteLong(arm64::BuildUnconditionalBranchToRegister(16));
+    target.WritePointer(aDest);
+#else
+#  error "Unsupported processor architecture"
+#endif
+  }
+
+ public:
+  constexpr static uint32_t GetWorstCaseRequiredBytesToPatch() {
+#if defined(_M_IX86)
+    return 5;
+#elif defined(_M_X64)
+    return 13;
+#elif defined(_M_ARM64)
+    return 16;
+#else
+#  error "Unsupported processor architecture"
+#endif
+  }
+
+  WindowsDllDetourPatcherPrimitive() = default;
+
+  WindowsDllDetourPatcherPrimitive(const WindowsDllDetourPatcherPrimitive&) =
+      delete;
+  WindowsDllDetourPatcherPrimitive(WindowsDllDetourPatcherPrimitive&&) = delete;
+  WindowsDllDetourPatcherPrimitive& operator=(
+      const WindowsDllDetourPatcherPrimitive&) = delete;
+  WindowsDllDetourPatcherPrimitive& operator=(
+      WindowsDllDetourPatcherPrimitive&&) = delete;
+
+  bool AddIrreversibleHook(const MMPolicyT& aMMPolicy, FARPROC aTargetFn,
+                           intptr_t aHookDest) {
+    ReadOnlyTargetFunction<MMPolicyT> targetReadOnly(aMMPolicy, aTargetFn);
+
+    WritableTargetFunction<MMPolicyT> targetWritable(
+        targetReadOnly.Promote(GetWorstCaseRequiredBytesToPatch()));
+    if (!targetWritable) {
+      return false;
+    }
+
+    ApplyDefaultPatch(targetWritable, aHookDest);
+
+    return targetWritable.Commit();
+  }
+};
+
+template <typename VMPolicy>
+class WindowsDllDetourPatcher final
+    : public WindowsDllDetourPatcherPrimitive<typename VMPolicy::MMPolicyT>,
+      public WindowsDllPatcherBase<VMPolicy> {
+  using MMPolicyT = typename VMPolicy::MMPolicyT;
+  using TrampPoolT = typename VMPolicy::PoolType;
+  using PrimitiveT = WindowsDllDetourPatcherPrimitive<MMPolicyT>;
+  Maybe<DetourFlags> mFlags;
+
+ public:
+  template <typename... Args>
+  explicit WindowsDllDetourPatcher(Args&&... aArgs)
+      : WindowsDllPatcherBase<VMPolicy>(std::forward<Args>(aArgs)...) {}
+
+  ~WindowsDllDetourPatcher() { Clear(); }
+
+  WindowsDllDetourPatcher(const WindowsDllDetourPatcher&) = delete;
+  WindowsDllDetourPatcher(WindowsDllDetourPatcher&&) = delete;
+  WindowsDllDetourPatcher& operator=(const WindowsDllDetourPatcher&) = delete;
+  WindowsDllDetourPatcher& operator=(WindowsDllDetourPatcher&&) = delete;
+
+  void Clear() {
+    if (!this->mVMPolicy.ShouldUnhookUponDestruction()) {
+      return;
+    }
+
+#if defined(_M_IX86)
+    size_t nBytes = 1 + sizeof(intptr_t);
+#elif defined(_M_X64)
+    size_t nBytes = 2 + sizeof(intptr_t);
+#elif defined(_M_ARM64)
+    size_t nBytes = 2 * sizeof(uint32_t) + sizeof(uintptr_t);
+#else
+#  error "Unknown processor type"
+#endif
+
+    const auto& tramps = this->mVMPolicy.Items();
+    for (auto&& tramp : tramps) {
+      // First we read the pointer to the interceptor instance.
+      Maybe<uintptr_t> instance = tramp.ReadEncodedPointer();
+      if (!instance) {
+        continue;
+      }
+
+      if (instance.value() != reinterpret_cast<uintptr_t>(this)) {
+        // tramp does not belong to this interceptor instance.
+        continue;
+      }
+
+      auto clearInstance = MakeScopeExit([&tramp]() -> void {
+        // Clear the instance pointer so that no future instances with the same
+        // |this| pointer will attempt to reset its hook.
+        tramp.Rewind();
+        tramp.WriteEncodedPointer(nullptr);
+      });
+
+      // Now we read the pointer to the intercepted function.
+      Maybe<uintptr_t> interceptedFn = tramp.ReadEncodedPointer();
+      if (!interceptedFn) {
+        continue;
+      }
+
+      WritableTargetFunction<MMPolicyT> origBytes(
+          this->mVMPolicy, interceptedFn.value(), nBytes);
+      if (!origBytes) {
+        continue;
+      }
+
+#if defined(_M_IX86) || defined(_M_X64)
+
+      Maybe<uint8_t> maybeOpcode1 = origBytes.ReadByte();
+      if (!maybeOpcode1) {
+        continue;
+      }
+
+      uint8_t opcode1 = maybeOpcode1.value();
+
+#  if defined(_M_IX86)
+      // Ensure the JMP from CreateTrampoline is where we expect it to be.
+      MOZ_ASSERT(opcode1 == 0xE9);
+      if (opcode1 != 0xE9) {
+        continue;
+      }
+
+      intptr_t startOfTrampInstructions =
+          static_cast<intptr_t>(tramp.GetCurrentRemoteAddress());
+
+      origBytes.WriteDisp32(startOfTrampInstructions);
+      if (!origBytes) {
+        continue;
+      }
+
+      origBytes.Commit();
+#  elif defined(_M_X64)
+      // Note: At the moment we clear 13-byte patches by replacing the jump to
+      //       the patched function by a jump to the stub code. The original
+      //       bytes of the original function are *not* restored. This implies
+      //       that the stub code outlives our cleaning, so unwind information
+      //       remains useful and must not be removed here.
+      if (opcode1 == 0x49) {
+        if (!Clear13BytePatch(origBytes, tramp.GetCurrentRemoteAddress())) {
+          continue;
+        }
+      } else if (opcode1 == 0xB8) {
+        if (!Clear10BytePatch(origBytes)) {
+          continue;
+        }
+      } else if (opcode1 == 0x48) {
+        // The original function was just a different trampoline
+        if (!ClearTrampolinePatch(origBytes, tramp.GetCurrentRemoteAddress())) {
+          continue;
+        }
+      } else {
+        MOZ_ASSERT_UNREACHABLE("Unrecognized patch!");
+        continue;
+      }
+#  endif
+
+#elif defined(_M_ARM64)
+
+      // Ensure that we see the instruction that we expect
+      Maybe<uint32_t> inst1 = origBytes.ReadLong();
+      if (!inst1) {
+        continue;
+      }
+
+      if (inst1.value() == this->kLdrX16Plus8) {
+        if (!Clear16BytePatch(origBytes, tramp.GetCurrentRemoteAddress())) {
+          continue;
+        }
+      } else if (arm64::IsUnconditionalBranchImm(inst1.value())) {
+        if (!Clear4BytePatch(inst1.value(), origBytes)) {
+          continue;
+        }
+      } else {
+        MOZ_ASSERT_UNREACHABLE("Unrecognized patch!");
+        continue;
+      }
+
+#else
+#  error "Unknown processor type"
+#endif
+    }
+
+    this->mVMPolicy.Clear();
+  }
+
+#if defined(_M_X64)
+  bool Clear13BytePatch(WritableTargetFunction<MMPolicyT>& aOrigBytes,
+                        const uintptr_t aResetToAddress) {
+    Maybe<uint8_t> maybeOpcode2 = aOrigBytes.ReadByte();
+    if (!maybeOpcode2) {
+      return false;
+    }
+
+    uint8_t opcode2 = maybeOpcode2.value();
+    if (opcode2 != 0xBB) {
+      return false;
+    }
+
+    aOrigBytes.WritePointer(aResetToAddress);
+    if (!aOrigBytes) {
+      return false;
+    }
+
+    return aOrigBytes.Commit();
+  }
+
+  bool ClearTrampolinePatch(WritableTargetFunction<MMPolicyT>& aOrigBytes,
+                            const uintptr_t aPtrToResetToAddress) {
+    // The target of the trampoline we replaced is stored at
+    // aPtrToResetToAddress. We simply put it back where we got it from.
+    Maybe<uint8_t> maybeOpcode2 = aOrigBytes.ReadByte();
+    if (!maybeOpcode2) {
+      return false;
+    }
+
+    uint8_t opcode2 = maybeOpcode2.value();
+    if (opcode2 != 0xB8) {
+      return false;
+    }
+
+    auto oldPtr = *(reinterpret_cast<const uintptr_t*>(aPtrToResetToAddress));
+
+    aOrigBytes.WritePointer(oldPtr);
+    if (!aOrigBytes) {
+      return false;
+    }
+
+    return aOrigBytes.Commit();
+  }
+
+  bool Clear10BytePatch(WritableTargetFunction<MMPolicyT>& aOrigBytes) {
+    Maybe<uint32_t> maybePtr32 = aOrigBytes.ReadLong();
+    if (!maybePtr32) {
+      return false;
+    }
+
+    uint32_t ptr32 = maybePtr32.value();
+    // We expect the high bit to be clear
+    if (ptr32 & 0x80000000) {
+      return false;
+    }
+
+    uintptr_t trampPtr = ptr32;
+
+    // trampPtr points to an intermediate trampoline that contains a 13-byte
+    // patch. We back up by sizeof(uintptr_t) so that we can access the pointer
+    // to the stub trampoline.
+    WritableTargetFunction<MMPolicyT> writableIntermediate(
+        this->mVMPolicy, trampPtr - sizeof(uintptr_t), 13 + sizeof(uintptr_t));
+    if (!writableIntermediate) {
+      return false;
+    }
+
+    Maybe<uintptr_t> stubTramp = writableIntermediate.ReadEncodedPtr();
+    if (!stubTramp || !stubTramp.value()) {
+      return false;
+    }
+
+    Maybe<uint8_t> maybeOpcode1 = writableIntermediate.ReadByte();
+    if (!maybeOpcode1) {
+      return false;
+    }
+
+    // We expect this opcode to be the beginning of our normal mov r11, ptr
+    // patch sequence.
+    uint8_t opcode1 = maybeOpcode1.value();
+    if (opcode1 != 0x49) {
+      return false;
+    }
+
+    // Now we can just delegate the rest to our normal 13-byte patch clearing.
+    return Clear13BytePatch(writableIntermediate, stubTramp.value());
+  }
+#endif  // defined(_M_X64)
+
+#if defined(_M_ARM64)
+  bool Clear4BytePatch(const uint32_t aBranchImm,
+                       WritableTargetFunction<MMPolicyT>& aOrigBytes) {
+    MOZ_ASSERT(arm64::IsUnconditionalBranchImm(aBranchImm));
+
+    arm64::LoadOrBranch decoded = arm64::BUncondImmDecode(
+        aOrigBytes.GetCurrentAddress() - sizeof(uint32_t), aBranchImm);
+
+    uintptr_t trampPtr = decoded.mAbsAddress;
+
+    // trampPtr points to an intermediate trampoline that contains a veneer.
+    // We back up by sizeof(uintptr_t) so that we can access the pointer to the
+    // stub trampoline.
+
+    // We want trampLen to be the size of the veneer, plus one pointer (since
+    // we are backing up trampPtr by one pointer)
+    size_t trampLen = 16 + sizeof(uintptr_t);
+
+    WritableTargetFunction<MMPolicyT> writableIntermediate(
+        this->mVMPolicy, trampPtr - sizeof(uintptr_t), trampLen);
+    if (!writableIntermediate) {
+      return false;
+    }
+
+    Maybe<uintptr_t> stubTramp = writableIntermediate.ReadEncodedPtr();
+    if (!stubTramp || !stubTramp.value()) {
+      return false;
+    }
+
+    Maybe<uint32_t> inst1 = writableIntermediate.ReadLong();
+    if (!inst1 || inst1.value() != this->kLdrX16Plus8) {
+      return false;
+    }
+
+    return Clear16BytePatch(writableIntermediate, stubTramp.value());
+  }
+
+  bool Clear16BytePatch(WritableTargetFunction<MMPolicyT>& aOrigBytes,
+                        const uintptr_t aResetToAddress) {
+    Maybe<uint32_t> inst2 = aOrigBytes.ReadLong();
+    if (!inst2) {
+      return false;
+    }
+
+    if (inst2.value() != arm64::BuildUnconditionalBranchToRegister(16)) {
+      MOZ_ASSERT_UNREACHABLE("Unrecognized patch!");
+      return false;
+    }
+
+    // Clobber the pointer to our hook function with a pointer to the
+    // start of the trampoline.
+    aOrigBytes.WritePointer(aResetToAddress);
+    aOrigBytes.Commit();
+
+    return true;
+  }
+#endif  // defined(_M_ARM64)
+
+  void Init(DetourFlags aFlags = DetourFlags::eDefault) {
+    if (Initialized()) {
+      return;
+    }
+
+#if defined(_M_X64)
+    if (aFlags & DetourFlags::eTestOnlyForceShortPatch) {
+      aFlags |= DetourFlags::eEnable10BytePatch;
+    }
+#endif  // defined(_M_X64)
+
+    mFlags = Some(aFlags);
+  }
+
+  bool Initialized() const { return mFlags.isSome(); }
+
+  bool AddHook(FARPROC aTargetFn, intptr_t aHookDest, void** aOrigFunc) {
+    ReadOnlyTargetFunction<MMPolicyT> target(
+        (mFlags.value() & DetourFlags::eDontResolveRedirection)
+            ? ReadOnlyTargetFunction<MMPolicyT>(
+                  this->mVMPolicy, reinterpret_cast<uintptr_t>(aTargetFn))
+            : this->ResolveRedirectedAddress(aTargetFn));
+
+    TrampPoolT* trampPool = nullptr;
+
+#if defined(_M_ARM64)
+    // ARM64 uses two passes to build its trampoline. The first pass uses a
+    // null tramp to determine how many bytes are needed. Once that is known,
+    // CreateTrampoline calls itself recursively with a "real" tramp.
+    Trampoline<MMPolicyT> tramp(nullptr);
+#else
+    Maybe<TrampPoolT> maybeTrampPool = DoReserve();
+    MOZ_ASSERT(maybeTrampPool);
+    if (!maybeTrampPool) {
+      return false;
+    }
+
+    trampPool = maybeTrampPool.ptr();
+
+    Maybe<Trampoline<MMPolicyT>> maybeTramp(trampPool->GetNextTrampoline());
+    if (!maybeTramp) {
+      this->SetLastDetourError(
+          DetourResultCode::DETOUR_PATCHER_NEXT_TRAMPOLINE_ERROR);
+      return false;
+    }
+
+    Trampoline<MMPolicyT> tramp(std::move(maybeTramp.ref()));
+#endif
+
+    CreateTrampoline(target, trampPool, tramp, aHookDest, aOrigFunc);
+    if (!*aOrigFunc) {
+      return false;
+    }
+
+    return true;
+  }
+
+ private:
+  /**
+   * This function returns a maximum distance that can be reached by a single
+   * unconditional jump instruction. This is dependent on the processor ISA.
+   * Note that this distance is *exclusive* when added to the pivot, so the
+   * distance returned by this function is actually
+   * (maximum_absolute_offset + 1).
+   */
+  static uint32_t GetDefaultPivotDistance() {
+#if defined(_M_ARM64)
+    // Immediate unconditional branch allows for +/- 128MB
+    return 0x08000000U;
+#elif defined(_M_IX86) || defined(_M_X64)
+    // For these ISAs, our distance will assume the use of an unconditional jmp
+    // with a 32-bit signed displacement.
+    return 0x80000000U;
+#else
+#  error "Not defined for this processor arch"
+#endif
+  }
+
+  /**
+   * If we're reserving trampoline space for a specific module, we base the
+   * pivot off of the median address of the module's .text section. While this
+   * may not be precise, it should be accurate enough for our purposes: To
+   * ensure that the trampoline space is reachable by any executable code in the
+   * module.
+   */
+  Maybe<TrampPoolT> ReserveForModule(HMODULE aModule) {
+    nt::PEHeaders moduleHeaders(aModule);
+    if (!moduleHeaders) {
+      this->SetLastDetourError(
+          DetourResultCode::DETOUR_PATCHER_RESERVE_FOR_MODULE_PE_ERROR);
+      return Nothing();
+    }
+
+    Maybe<Span<const uint8_t>> textSectionInfo =
+        moduleHeaders.GetTextSectionInfo();
+    if (!textSectionInfo) {
+      this->SetLastDetourError(
+          DetourResultCode::DETOUR_PATCHER_RESERVE_FOR_MODULE_TEXT_ERROR);
+      return Nothing();
+    }
+
+    const uint8_t* median = textSectionInfo.value().data() +
+                            (textSectionInfo.value().LengthBytes() / 2);
+
+    Maybe<TrampPoolT> maybeTrampPool = this->mVMPolicy.Reserve(
+        reinterpret_cast<uintptr_t>(median), GetDefaultPivotDistance());
+    if (!maybeTrampPool) {
+      this->SetLastDetourError(
+          DetourResultCode::DETOUR_PATCHER_RESERVE_FOR_MODULE_RESERVE_ERROR);
+    }
+    return maybeTrampPool;
+  }
+
+  Maybe<TrampPoolT> DoReserve(HMODULE aModule = nullptr) {
+    if (aModule) {
+      return ReserveForModule(aModule);
+    }
+
+    uintptr_t pivot = 0;
+    uint32_t distance = 0;
+
+#if defined(_M_X64)
+    if (mFlags.value() & DetourFlags::eEnable10BytePatch) {
+      // We must stay below the 2GB mark because a 10-byte patch uses movsxd
+      // (ie, sign extension) to expand the pointer to 64-bits, so bit 31 of any
+      // pointers into the reserved region must be 0.
+      pivot = 0x40000000U;
+      distance = 0x40000000U;
+    }
+#endif  // defined(_M_X64)
+
+    Maybe<TrampPoolT> maybeTrampPool = this->mVMPolicy.Reserve(pivot, distance);
+#if defined(NIGHTLY_BUILD)
+    if (!maybeTrampPool && this->GetLastDetourError().isNothing()) {
+      this->SetLastDetourError(
+          DetourResultCode::DETOUR_PATCHER_DO_RESERVE_ERROR);
+    }
+#endif  // defined(NIGHTLY_BUILD)
+    return maybeTrampPool;
+  }
+
+ protected:
+#if !defined(_M_ARM64)
+
+  const static int kPageSize = 4096;
+
+  // rex bits
+  static const BYTE kMaskHighNibble = 0xF0;
+  static const BYTE kRexOpcode = 0x40;
+  static const BYTE kMaskRexW = 0x08;
+  static const BYTE kMaskRexR = 0x04;
+  static const BYTE kMaskRexX = 0x02;
+  static const BYTE kMaskRexB = 0x01;
+
+  // mod r/m bits
+  static const BYTE kRegFieldShift = 3;
+  static const BYTE kMaskMod = 0xC0;
+  static const BYTE kMaskReg = 0x38;
+  static const BYTE kMaskRm = 0x07;
+  static const BYTE kRmNeedSib = 0x04;
+  static const BYTE kModReg = 0xC0;
+  static const BYTE kModDisp32 = 0x80;
+  static const BYTE kModDisp8 = 0x40;
+  static const BYTE kModNoRegDisp = 0x00;
+  static const BYTE kRmNoRegDispDisp32 = 0x05;
+
+  // sib bits
+  static const BYTE kMaskSibScale = 0xC0;
+  static const BYTE kMaskSibIndex = 0x38;
+  static const BYTE kMaskSibBase = 0x07;
+  static const BYTE kSibBaseEbp = 0x05;
+
+  // Register bit IDs.
+  static const BYTE kRegAx = 0x0;
+  static const BYTE kRegCx = 0x1;
+  static const BYTE kRegDx = 0x2;
+  static const BYTE kRegBx = 0x3;
+  static const BYTE kRegSp = 0x4;
+  static const BYTE kRegBp = 0x5;
+  static const BYTE kRegSi = 0x6;
+  static const BYTE kRegDi = 0x7;
+
+  // Special ModR/M codes.  These indicate operands that cannot be simply
+  // memcpy-ed.
+  // Operand is a 64-bit RIP-relative address.
+  static const int kModOperand64 = -2;
+  // Operand is not yet handled by our trampoline.
+  static const int kModUnknown = -1;
+
+  /**
+   * Returns the number of bytes taken by the ModR/M byte, SIB (if present)
+   * and the instruction's operand.  In special cases, the special MODRM codes
+   * above are returned.
+   * aModRm points to the ModR/M byte of the instruction.
+   * On return, aSubOpcode (if present) is filled with the subopcode/register
+   * code found in the ModR/M byte.
+   */
+  int CountModRmSib(const ReadOnlyTargetFunction<MMPolicyT>& aModRm,
+                    BYTE* aSubOpcode = nullptr) {
+    int numBytes = 1;  // Start with 1 for mod r/m byte itself
+    switch (*aModRm & kMaskMod) {
+      case kModReg:
+        return numBytes;
+      case kModDisp8:
+        numBytes += 1;
+        break;
+      case kModDisp32:
+        numBytes += 4;
+        break;
+      case kModNoRegDisp:
+        if ((*aModRm & kMaskRm) == kRmNoRegDispDisp32) {
+#  if defined(_M_X64)
+          if (aSubOpcode) {
+            *aSubOpcode = (*aModRm & kMaskReg) >> kRegFieldShift;
+          }
+          return kModOperand64;
+#  else
+          // On IA-32, all ModR/M instruction modes address memory relative to 0
+          numBytes += 4;
+#  endif
+        } else if (((*aModRm & kMaskRm) == kRmNeedSib &&
+                    (*(aModRm + 1) & kMaskSibBase) == kSibBaseEbp)) {
+          numBytes += 4;
+        }
+        break;
+      default:
+        // This should not be reachable
+        MOZ_ASSERT_UNREACHABLE("Impossible value for modr/m byte mod bits");
+        return kModUnknown;
+    }
+    if ((*aModRm & kMaskRm) == kRmNeedSib) {
+      // SIB byte
+      numBytes += 1;
+    }
+    if (aSubOpcode) {
+      *aSubOpcode = (*aModRm & kMaskReg) >> kRegFieldShift;
+    }
+    return numBytes;
+  }
+
+#  if defined(_M_X64)
+  enum class JumpType{Je, Jne, Jae, Jmp, Call};
+
+  static bool GenerateJump(Trampoline<MMPolicyT>& aTramp,
+                           uintptr_t aAbsTargetAddress, const JumpType aType) {
+    // Near call, absolute indirect, address given in r/m32
+    if (aType == JumpType::Call) {
+      // CALL [RIP+0]
+      aTramp.WriteByte(0xff);
+      aTramp.WriteByte(0x15);
+      // The offset to jump destination -- 2 bytes after the current position.
+      aTramp.WriteInteger(2);
+      aTramp.WriteByte(0xeb);  // JMP + 8 (jump over target address)
+      aTramp.WriteByte(8);
+      aTramp.WritePointer(aAbsTargetAddress);
+      return !!aTramp;
+    }
+
+    // Write an opposite conditional jump because the destination branches
+    // are swapped.
+    if (aType == JumpType::Je) {
+      // JNE RIP+14
+      aTramp.WriteByte(0x75);
+      aTramp.WriteByte(14);
+    } else if (aType == JumpType::Jne) {
+      // JE RIP+14
+      aTramp.WriteByte(0x74);
+      aTramp.WriteByte(14);
+    } else if (aType == JumpType::Jae) {
+      // JB RIP+14
+      aTramp.WriteByte(0x72);
+      aTramp.WriteByte(14);
+    }
+
+    // Near jmp, absolute indirect, address given in r/m32
+    // JMP [RIP+0]
+    aTramp.WriteByte(0xff);
+    aTramp.WriteByte(0x25);
+    // The offset to jump destination is 0
+    aTramp.WriteInteger(0);
+    aTramp.WritePointer(aAbsTargetAddress);
+
+    return !!aTramp;
+  }
+#  endif
+
+  enum ePrefixGroupBits{eNoPrefixes = 0, ePrefixGroup1 = (1 << 0),
+                        ePrefixGroup2 = (1 << 1), ePrefixGroup3 = (1 << 2),
+                        ePrefixGroup4 = (1 << 3)};
+
+  int CountPrefixBytes(const ReadOnlyTargetFunction<MMPolicyT>& aBytes,
+                       unsigned char* aOutGroupBits) {
+    unsigned char& groupBits = *aOutGroupBits;
+    groupBits = eNoPrefixes;
+    int index = 0;
+    while (true) {
+      switch (aBytes[index]) {
+        // Group 1
+        case 0xF0:  // LOCK
+        case 0xF2:  // REPNZ
+        case 0xF3:  // REP / REPZ
+          if (groupBits & ePrefixGroup1) {
+            return -1;
+          }
+          groupBits |= ePrefixGroup1;
+          ++index;
+          break;
+
+        // Group 2
+        case 0x2E:  // CS override / branch not taken
+        case 0x36:  // SS override
+        case 0x3E:  // DS override / branch taken
+        case 0x64:  // FS override
+        case 0x65:  // GS override
+          if (groupBits & ePrefixGroup2) {
+            return -1;
+          }
+          groupBits |= ePrefixGroup2;
+          ++index;
+          break;
+
+        // Group 3
+        case 0x66:  // operand size override
+          if (groupBits & ePrefixGroup3) {
+            return -1;
+          }
+          groupBits |= ePrefixGroup3;
+          ++index;
+          break;
+
+        // Group 4
+        case 0x67:  // Address size override
+          if (groupBits & ePrefixGroup4) {
+            return -1;
+          }
+          groupBits |= ePrefixGroup4;
+          ++index;
+          break;
+
+        default:
+          return index;
+      }
+    }
+  }
+
+  // Return a ModR/M byte made from the 2 Mod bits, the register used for the
+  // reg bits and the register used for the R/M bits.
+  BYTE BuildModRmByte(BYTE aModBits, BYTE aReg, BYTE aRm) {
+    MOZ_ASSERT((aRm & kMaskRm) == aRm);
+    MOZ_ASSERT((aModBits & kMaskMod) == aModBits);
+    MOZ_ASSERT(((aReg << kRegFieldShift) & kMaskReg) ==
+               (aReg << kRegFieldShift));
+    return aModBits | (aReg << kRegFieldShift) | aRm;
+  }
+
+#endif  // !defined(_M_ARM64)
+
+  // If originalFn is a recognized trampoline then patch it to call aDest,
+  // set *aTramp and *aOutTramp to that trampoline's target and return true.
+  bool PatchIfTargetIsRecognizedTrampoline(
+      Trampoline<MMPolicyT>& aTramp,
+      ReadOnlyTargetFunction<MMPolicyT>& aOriginalFn, intptr_t aDest,
+      void** aOutTramp) {
+#if defined(_M_X64)
+    // Variation 1:
+    // 48 b8 imm64  mov rax, imm64
+    // ff e0        jmp rax
+    //
+    // Variation 2:
+    // 48 b8 imm64  mov rax, imm64
+    // 50           push rax
+    // c3           ret
+    if ((aOriginalFn[0] == 0x48) && (aOriginalFn[1] == 0xB8) &&
+        ((aOriginalFn[10] == 0xFF && aOriginalFn[11] == 0xE0) ||
+         (aOriginalFn[10] == 0x50 && aOriginalFn[11] == 0xC3))) {
+      uintptr_t originalTarget =
+          (aOriginalFn + 2).template ChasePointer<uintptr_t>();
+
+      // Skip the first two bytes (48 b8) so that we can overwrite the imm64
+      WritableTargetFunction<MMPolicyT> target(aOriginalFn.Promote(8, 2));
+      if (!target) {
+        return false;
+      }
+
+      // Write the new JMP target address.
+      target.WritePointer(aDest);
+      if (!target.Commit()) {
+        return false;
+      }
+
+      // Store the old target address so we can restore it when we're cleared
+      aTramp.WritePointer(originalTarget);
+      if (!aTramp) {
+        return false;
+      }
+
+      *aOutTramp = reinterpret_cast<void*>(originalTarget);
+      return true;
+    }
+#endif  // defined(_M_X64)
+
+    return false;
+  }
+
+#if defined(_M_ARM64)
+  bool Apply4BytePatch(TrampPoolT* aTrampPool, void* aTrampPtr,
+                       WritableTargetFunction<MMPolicyT>& target,
+                       intptr_t aDest) {
+    MOZ_ASSERT(aTrampPool);
+    if (!aTrampPool) {
+      return false;
+    }
+
+    uintptr_t hookDest = arm64::MakeVeneer(*aTrampPool, aTrampPtr, aDest);
+    if (!hookDest) {
+      return false;
+    }
+
+    Maybe<uint32_t> branchImm = arm64::BuildUnconditionalBranchImm(
+        target.GetCurrentAddress(), hookDest);
+    if (!branchImm) {
+      return false;
+    }
+
+    target.WriteLong(branchImm.value());
+
+    return true;
+  }
+#endif  // defined(_M_ARM64)
+
+#if defined(_M_X64)
+  bool Apply10BytePatch(TrampPoolT* aTrampPool, void* aTrampPtr,
+                        WritableTargetFunction<MMPolicyT>& target,
+                        intptr_t aDest) {
+    // Note: Even if the target function is also below 2GB, we still use an
+    // intermediary trampoline so that we consistently have a 64-bit pointer
+    // that we can use to reset the trampoline upon interceptor shutdown.
+    Maybe<Trampoline<MMPolicyT>> maybeCallTramp(
+        aTrampPool->GetNextTrampoline());
+    if (!maybeCallTramp) {
+      return false;
+    }
+
+    Trampoline<MMPolicyT> callTramp(std::move(maybeCallTramp.ref()));
+
+    // Write a null instance so that Clear() does not consider this tramp to
+    // be a normal tramp to be torn down.
+    callTramp.WriteEncodedPointer(nullptr);
+    // Use the second pointer slot to store a pointer to the primary tramp
+    callTramp.WriteEncodedPointer(aTrampPtr);
+    callTramp.StartExecutableCode();
+
+    // mov r11, address
+    callTramp.WriteByte(0x49);
+    callTramp.WriteByte(0xbb);
+    callTramp.WritePointer(aDest);
+
+    // jmp r11
+    callTramp.WriteByte(0x41);
+    callTramp.WriteByte(0xff);
+    callTramp.WriteByte(0xe3);
+
+    void* callTrampStart = callTramp.EndExecutableCode();
+    if (!callTrampStart) {
+      return false;
+    }
+
+    target.WriteByte(0xB8);  // MOV EAX, IMM32
+
+    // Assert that the topmost 33 bits are 0
+    MOZ_ASSERT(
+        !(reinterpret_cast<uintptr_t>(callTrampStart) & (~0x7FFFFFFFULL)));
+
+    target.WriteLong(static_cast<uint32_t>(
+        reinterpret_cast<uintptr_t>(callTrampStart) & 0x7FFFFFFFU));
+    target.WriteByte(0x48);  // REX.W
+    target.WriteByte(0x63);  // MOVSXD r64, r/m32
+    // dest: rax, src: eax
+    target.WriteByte(BuildModRmByte(kModReg, kRegAx, kRegAx));
+    target.WriteByte(0xFF);                                // JMP /4
+    target.WriteByte(BuildModRmByte(kModReg, 4, kRegAx));  // rax
+
+    return true;
+  }
+#endif  // defined(_M_X64)
+
+  void CreateTrampoline(ReadOnlyTargetFunction<MMPolicyT>& origBytes,
+                        TrampPoolT* aTrampPool, Trampoline<MMPolicyT>& aTramp,
+                        intptr_t aDest, void** aOutTramp) {
+    *aOutTramp = nullptr;
+
+    Trampoline<MMPolicyT>& tramp = aTramp;
+    if (!tramp) {
+      this->SetLastDetourError(
+          DetourResultCode::DETOUR_PATCHER_INVALID_TRAMPOLINE);
+      return;
+    }
+
+    // The beginning of the trampoline contains two pointer-width slots:
+    // [0]: |this|, so that we know whether the trampoline belongs to us;
+    // [1]: Pointer to original function, so that we can reset the hooked
+    // function to its original behavior upon destruction.  In rare cases
+    // where the function was already a different trampoline, this is
+    // just a pointer to that trampoline's target address.
+    tramp.WriteEncodedPointer(this);
+    if (!tramp) {
+      this->SetLastDetourError(
+          DetourResultCode::DETOUR_PATCHER_WRITE_POINTER_ERROR);
+      return;
+    }
+
+    auto clearInstanceOnFailure = MakeScopeExit([this, aOutTramp, &tramp,
+                                                 &origBytes]() -> void {
+      // *aOutTramp is not set until CreateTrampoline has completed
+      // successfully, so we can use that to check for success.
+      if (*aOutTramp) {
+        return;
+      }
+
+      // Clear the instance pointer so that we don't try to reset a
+      // nonexistent hook.
+      tramp.Rewind();
+      tramp.WriteEncodedPointer(nullptr);
+
+#if defined(NIGHTLY_BUILD)
+      origBytes.Rewind();
+      this->SetLastDetourError(
+          DetourResultCode::DETOUR_PATCHER_CREATE_TRAMPOLINE_ERROR);
+      DetourError& lastError = *this->mVMPolicy.mLastError;
+      size_t bytesToCapture = std::min(
+          ArrayLength(lastError.mOrigBytes),
+          static_cast<size_t>(PrimitiveT::GetWorstCaseRequiredBytesToPatch()));
+#  if defined(_M_ARM64)
+      size_t numInstructionsToCapture = bytesToCapture / sizeof(uint32_t);
+      auto origBytesDst = reinterpret_cast<uint32_t*>(lastError.mOrigBytes);
+      for (size_t i = 0; i < numInstructionsToCapture; ++i) {
+        origBytesDst[i] = origBytes.ReadNextInstruction();
+      }
+#  else
+      for (size_t i = 0; i < bytesToCapture; ++i) {
+        lastError.mOrigBytes[i] = origBytes[i];
+      }
+#  endif  // defined(_M_ARM64)
+#else
+      // Silence -Wunused-lambda-capture in non-Nightly.
+      Unused << this;
+      Unused << origBytes;
+#endif  // defined(NIGHTLY_BUILD)
+    });
+
+    tramp.WritePointer(origBytes.AsEncodedPtr());
+    if (!tramp) {
+      return;
+    }
+
+    if (PatchIfTargetIsRecognizedTrampoline(tramp, origBytes, aDest,
+                                            aOutTramp)) {
+      return;
+    }
+
+    tramp.StartExecutableCode();
+
+    constexpr uint32_t kWorstCaseBytesRequired =
+        PrimitiveT::GetWorstCaseRequiredBytesToPatch();
+
+#if defined(_M_IX86)
+    int pJmp32 = -1;
+    while (origBytes.GetOffset() < kWorstCaseBytesRequired) {
+      // Understand some simple instructions that might be found in a
+      // prologue; we might need to extend this as necessary.
+      //
+      // Note!  If we ever need to understand jump instructions, we'll
+      // need to rewrite the displacement argument.
+      unsigned char prefixGroups;
+      int numPrefixBytes = CountPrefixBytes(origBytes, &prefixGroups);
+      if (numPrefixBytes < 0 ||
+          (prefixGroups & (ePrefixGroup3 | ePrefixGroup4))) {
+        // Either the prefix sequence was bad, or there are prefixes that
+        // we don't currently support (groups 3 and 4)
+        MOZ_ASSERT_UNREACHABLE("Unrecognized opcode sequence");
+        return;
+      }
+
+      origBytes += numPrefixBytes;
+      if (*origBytes >= 0x88 && *origBytes <= 0x8B) {
+        // various MOVs
+        ++origBytes;
+        int len = CountModRmSib(origBytes);
+        if (len < 0) {
+          MOZ_ASSERT_UNREACHABLE("Unrecognized MOV opcode sequence");
+          return;
+        }
+        origBytes += len;
+      } else if (*origBytes == 0x0f &&
+                 (origBytes[1] == 0x10 || origBytes[1] == 0x11)) {
+        // SSE: movups xmm, xmm/m128
+        //      movups xmm/m128, xmm
+        origBytes += 2;
+        int len = CountModRmSib(origBytes);
+        if (len < 0) {
+          MOZ_ASSERT_UNREACHABLE("Unrecognized MOV opcode sequence");
+          return;
+        }
+        origBytes += len;
+      } else if (*origBytes == 0xA1) {
+        // MOV eax, [seg:offset]
+        origBytes += 5;
+      } else if (*origBytes == 0xB8) {
+        // MOV 0xB8: http://ref.x86asm.net/coder32.html#xB8
+        origBytes += 5;
+      } else if (*origBytes == 0x33 && (origBytes[1] & kMaskMod) == kModReg) {
+        // XOR r32, r32
+        origBytes += 2;
+      } else if ((*origBytes & 0xf8) == 0x40) {
+        // INC r32
+        origBytes += 1;
+      } else if (*origBytes == 0x83) {
+        uint8_t mod = static_cast<uint8_t>(origBytes[1]) & kMaskMod;
+        uint8_t rm = static_cast<uint8_t>(origBytes[1]) & kMaskRm;
+        if (mod == kModReg) {
+          // ADD|OR|ADC|SBB|AND|SUB|XOR|CMP r, imm8
+          origBytes += 3;
+        } else if (mod == kModDisp8 && rm != kRmNeedSib) {
+          // ADD|OR|ADC|SBB|AND|SUB|XOR|CMP [r+disp8], imm8
+          origBytes += 4;
+        } else {
+          // bail
+          MOZ_ASSERT_UNREACHABLE("Unrecognized bit opcode sequence");
+          return;
+        }
+      } else if (*origBytes == 0x68) {
+        // PUSH with 4-byte operand
+        origBytes += 5;
+      } else if ((*origBytes & 0xf0) == 0x50) {
+        // 1-byte PUSH/POP
+        ++origBytes;
+      } else if (*origBytes == 0x6A) {
+        // PUSH imm8
+        origBytes += 2;
+      } else if (*origBytes == 0xe9) {
+        pJmp32 = origBytes.GetOffset();
+        // jmp 32bit offset
+        origBytes += 5;
+      } else if (*origBytes == 0xff && origBytes[1] == 0x25) {
+        // jmp [disp32]
+        origBytes += 6;
+      } else if (*origBytes == 0xc2) {
+        // ret imm16.  We can't handle this but it happens.  We don't ASSERT but
+        // we do fail to hook.
+#  if defined(MOZILLA_INTERNAL_API)
+        NS_WARNING("Cannot hook method -- RET opcode found");
+#  endif
+        return;
+      } else {
+        // printf ("Unknown x86 instruction byte 0x%02x, aborting trampoline\n",
+        // *origBytes);
+        MOZ_ASSERT_UNREACHABLE("Unrecognized opcode sequence");
+        return;
+      }
+    }
+
+    // The trampoline is a copy of the instructions that we just traced,
+    // followed by a jump that we add below.
+    tramp.CopyFrom(origBytes.GetBaseAddress(), origBytes.GetOffset());
+    if (!tramp) {
+      return;
+    }
+#elif defined(_M_X64)
+    bool foundJmp = false;
+    // |use10BytePatch| should always default to |false| in production. It is
+    // not set to true unless we detect that a 10-byte patch is necessary.
+    // OTOH, for testing purposes, if we want to force a 10-byte patch, we
+    // always initialize |use10BytePatch| to |true|.
+    bool use10BytePatch =
+        (mFlags.value() & DetourFlags::eTestOnlyForceShortPatch) ==
+        DetourFlags::eTestOnlyForceShortPatch;
+    const uint32_t bytesRequired =
+        use10BytePatch ? 10 : kWorstCaseBytesRequired;
+
+    while (origBytes.GetOffset() < bytesRequired) {
+      // If we found JMP 32bit offset, we require that the next bytes must
+      // be NOP or INT3.  There is no reason to copy them.
+      // TODO: This used to trigger for Je as well.  Now that I allow
+      // instructions after CALL and JE, I don't think I need that.
+      // The only real value of this condition is that if code follows a JMP
+      // then its _probably_ the target of a JMP somewhere else and we
+      // will be overwriting it, which would be tragic.  This seems
+      // highly unlikely.
+      if (foundJmp) {
+        if (*origBytes == 0x90 || *origBytes == 0xcc) {
+          ++origBytes;
+          continue;
+        }
+
+        // If our trampoline space is located in the lowest 2GB, we can do a ten
+        // byte patch instead of a thirteen byte patch.
+        if (aTrampPool && aTrampPool->IsInLowest2GB() &&
+            origBytes.GetOffset() >= 10) {
+          use10BytePatch = true;
+          break;
+        }
+
+        MOZ_ASSERT_UNREACHABLE("Opcode sequence includes commands after JMP");
+        return;
+      }
+      if (*origBytes == 0x0f) {
+        COPY_CODES(1);
+        if (*origBytes == 0x1f) {
+          // nop (multibyte)
+          COPY_CODES(1);
+          if ((*origBytes & 0xc0) == 0x40 && (*origBytes & 0x7) == 0x04) {
+            COPY_CODES(3);
+          } else {
+            MOZ_ASSERT_UNREACHABLE("Unrecognized opcode sequence");
+            return;
+          }
+        } else if (*origBytes == 0x05) {
+          // syscall
+          COPY_CODES(1);
+        } else if (*origBytes == 0x10 || *origBytes == 0x11) {
+          // SSE: movups xmm, xmm/m128
+          //      movups xmm/m128, xmm
+          COPY_CODES(1);
+          int nModRmSibBytes = CountModRmSib(origBytes);
+          if (nModRmSibBytes < 0) {
+            MOZ_ASSERT_UNREACHABLE("Unrecognized opcode sequence");
+            return;
+          } else {
+            COPY_CODES(nModRmSibBytes);
+          }
+        } else if (*origBytes >= 0x83 && *origBytes <= 0x85) {
+          // 0f 83 cd    JAE rel32
+          // 0f 84 cd    JE  rel32
+          // 0f 85 cd    JNE rel32
+          const JumpType kJumpTypes[] = {JumpType::Jae, JumpType::Je,
+                                         JumpType::Jne};
+          auto jumpType = kJumpTypes[*origBytes - 0x83];
+          ++origBytes;
+          --tramp;  // overwrite the 0x0f we copied above
+
+          if (!GenerateJump(tramp, origBytes.ReadDisp32AsAbsolute(),
+                            jumpType)) {
+            return;
+          }
+        } else {
+          MOZ_ASSERT_UNREACHABLE("Unrecognized opcode sequence");
+          return;
+        }
+      } else if (*origBytes >= 0x88 && *origBytes <= 0x8B) {
+        // various 32-bit MOVs
+        COPY_CODES(1);
+        int len = CountModRmSib(origBytes);
+        if (len < 0) {
+          MOZ_ASSERT_UNREACHABLE("Unrecognized MOV opcode sequence");
+          return;
+        }
+        COPY_CODES(len);
+      } else if (*origBytes == 0x40 || *origBytes == 0x41) {
+        // Plain REX or REX.B
+        COPY_CODES(1);
+        if ((*origBytes & 0xf0) == 0x50) {
+          // push/pop with Rx register
+          COPY_CODES(1);
+        } else if (*origBytes >= 0xb8 && *origBytes <= 0xbf) {
+          // mov r32, imm32
+          COPY_CODES(5);
+        } else if (*origBytes == 0x8b && (origBytes[1] & kMaskMod) == kModReg) {
+          // 8B /r: mov r32, r/m32
+          COPY_CODES(2);
+        } else if (*origBytes == 0xf7 &&
+                   (origBytes[1] & (kMaskMod | kMaskReg)) ==
+                       (kModReg | (0 << kRegFieldShift))) {
+          // F7 /0 id: test r/m32, imm32
+          COPY_CODES(6);
+        } else {
+          MOZ_ASSERT_UNREACHABLE("Unrecognized opcode sequence");
+          return;
+        }
+      } else if (*origBytes == 0x44) {
+        // REX.R
+        COPY_CODES(1);
+
+        // TODO: Combine with the "0x89" case below in the REX.W section
+        if (*origBytes == 0x89) {
+          // mov r/m32, r32
+          COPY_CODES(1);
+          int len = CountModRmSib(origBytes);
+          if (len < 0) {
+            MOZ_ASSERT_UNREACHABLE("Unrecognized opcode sequence");
+            return;
+          }
+          COPY_CODES(len);
+        } else {
+          MOZ_ASSERT_UNREACHABLE("Unrecognized opcode sequence");
+          return;
+        }
+      } else if (*origBytes == 0x45) {
+        // REX.R & REX.B
+        COPY_CODES(1);
+
+        if (*origBytes == 0x33) {
+          // xor r32, r32
+          COPY_CODES(2);
+        } else {
+          MOZ_ASSERT_UNREACHABLE("Unrecognized opcode sequence");
+          return;
+        }
+      } else if ((*origBytes & 0xfa) == 0x48) {
+        // REX.W | REX.WR | REX.WRB | REX.WB
+        COPY_CODES(1);
+
+        if (*origBytes == 0x81 && (origBytes[1] & 0xf8) == 0xe8) {
+          // sub r, dword
+          COPY_CODES(6);
+        } else if (*origBytes == 0x83 && (origBytes[1] & 0xf8) == 0xe8) {
+          // sub r, byte
+          COPY_CODES(3);
+        } else if (*origBytes == 0x83 &&
+                   (origBytes[1] & (kMaskMod | kMaskReg)) == kModReg) {
+          // add r, byte
+          COPY_CODES(3);
+        } else if (*origBytes == 0x83 && (origBytes[1] & 0xf8) == 0x60) {
+          // and [r+d], imm8
+          COPY_CODES(5);
+        } else if (*origBytes == 0x2b && (origBytes[1] & kMaskMod) == kModReg) {
+          // sub r64, r64
+          COPY_CODES(2);
+        } else if (*origBytes == 0x85) {
+          // 85 /r => TEST r/m32, r32
+          if ((origBytes[1] & 0xc0) == 0xc0) {
+            COPY_CODES(2);
+          } else {
+            MOZ_ASSERT_UNREACHABLE("Unrecognized opcode sequence");
+            return;
+          }
+        } else if ((*origBytes & 0xfd) == 0x89) {
+          // MOV r/m64, r64 | MOV r64, r/m64
+          BYTE reg;
+          int len = CountModRmSib(origBytes + 1, &reg);
+          if (len < 0) {
+            MOZ_ASSERT(len == kModOperand64);
+            if (len != kModOperand64) {
+              return;
+            }
+            origBytes += 2;  // skip the MOV and MOD R/M bytes
+
+            // The instruction MOVs 64-bit data from a RIP-relative memory
+            // address (determined with a 32-bit offset from RIP) into a
+            // 64-bit register.
+            uintptr_t absAddr = origBytes.ReadDisp32AsAbsolute();
+
+            if (reg == kRegAx) {
+              // Destination is RAX.  Encode instruction as MOVABS with a
+              // 64-bit absolute address as its immediate operand.
+              tramp.WriteByte(0xa1);
+              tramp.WritePointer(absAddr);
+            } else {
+              // The MOV must be done in two steps.  First, we MOVABS the
+              // absolute 64-bit address into our target register.
+              // Then, we MOV from that address into the register
+              // using register-indirect addressing.
+              tramp.WriteByte(0xb8 + reg);
+              tramp.WritePointer(absAddr);
+              tramp.WriteByte(0x48);
+              tramp.WriteByte(0x8b);
+              tramp.WriteByte(BuildModRmByte(kModNoRegDisp, reg, reg));
+            }
+          } else {
+            COPY_CODES(len + 1);
+          }
+        } else if ((*origBytes & 0xf8) == 0xb8) {
+          // MOV r64, imm64
+          COPY_CODES(9);
+        } else if (*origBytes == 0xc7) {
+          // MOV r/m64, imm32
+          if (origBytes[1] == 0x44) {
+            // MOV [r64+disp8], imm32
+            // ModR/W + SIB + disp8 + imm32
+            COPY_CODES(8);
+          } else {
+            MOZ_ASSERT_UNREACHABLE("Unrecognized opcode sequence");
+            return;
+          }
+        } else if (*origBytes == 0xff) {
+          // JMP/4 or CALL/2
+          if ((origBytes[1] & 0xc0) == 0x0 && (origBytes[1] & 0x07) == 0x5 &&
+              ((origBytes[1] & 0x38) == 0x20 ||
+               (origBytes[1] & 0x38) == 0x10)) {
+            origBytes += 2;
+            --tramp;  // overwrite the REX.W/REX.RW we copied above
+
+            foundJmp = (origBytes[1] & 0x38) == 0x20;
+            if (!GenerateJump(tramp, origBytes.ChasePointerFromDisp(),
+                              foundJmp ? JumpType::Jmp : JumpType::Call)) {
+              return;
+            }
+          } else {
+            // not support yet!
+            MOZ_ASSERT_UNREACHABLE("Unrecognized opcode sequence");
+            return;
+          }
+        } else if (*origBytes == 0x8d) {
+          // LEA reg, addr
+          if ((origBytes[1] & kMaskMod) == 0x0 &&
+              (origBytes[1] & kMaskRm) == 0x5) {
+            // [rip+disp32]
+            // convert 32bit offset to 64bit direct and convert instruction
+            // to a simple 64-bit mov
+            BYTE reg = (origBytes[1] & kMaskReg) >> kRegFieldShift;
+            origBytes += 2;
+            uintptr_t absAddr = origBytes.ReadDisp32AsAbsolute();
+            tramp.WriteByte(0xb8 + reg);  // move
+            tramp.WritePointer(absAddr);
+          } else {
+            // Above we dealt with RIP-relative instructions.  Any other
+            // operand form can simply be copied.
+            int len = CountModRmSib(origBytes + 1);
+            // We handled the kModOperand64 -- ie RIP-relative -- case above
+            MOZ_ASSERT(len > 0);
+            COPY_CODES(len + 1);
+          }
+        } else if (*origBytes == 0x63 && (origBytes[1] & kMaskMod) == kModReg) {
+          // movsxd r64, r32 (move + sign extend)
+          COPY_CODES(2);
+        } else {
+          // not support yet!
+          MOZ_ASSERT_UNREACHABLE("Unrecognized opcode sequence");
+          return;
+        }
+      } else if (*origBytes == 0x66) {
+        // operand override prefix
+        COPY_CODES(1);
+        // This is the same as the x86 version
+        if (*origBytes >= 0x88 && *origBytes <= 0x8B) {
+          // various MOVs
+          unsigned char b = origBytes[1];
+          if (((b & 0xc0) == 0xc0) ||
+              (((b & 0xc0) == 0x00) && ((b & 0x07) != 0x04) &&
+               ((b & 0x07) != 0x05))) {
+            // REG=r, R/M=r or REG=r, R/M=[r]
+            COPY_CODES(2);
+          } else if ((b & 0xc0) == 0x40) {
+            if ((b & 0x07) == 0x04) {
+              // REG=r, R/M=[SIB + disp8]
+              COPY_CODES(4);
+            } else {
+              // REG=r, R/M=[r + disp8]
+              COPY_CODES(3);
+            }
+          } else {
+            // complex MOV, bail
+            MOZ_ASSERT_UNREACHABLE("Unrecognized MOV opcode sequence");
+            return;
+          }
+        } else if (*origBytes == 0x44 && origBytes[1] == 0x89) {
+          // mov word ptr [reg+disp8], reg
+          COPY_CODES(2);
+          int len = CountModRmSib(origBytes);
+          if (len < 0) {
+            // no way to support this yet.
+            MOZ_ASSERT_UNREACHABLE("Unrecognized opcode sequence");
+            return;
+          }
+          COPY_CODES(len);
+        }
+      } else if ((*origBytes & 0xf0) == 0x50) {
+        // 1-byte push/pop
+        COPY_CODES(1);
+      } else if (*origBytes == 0x65) {
+        // GS prefix
+        //
+        // The entry of GetKeyState on Windows 10 has the following code.
+        // 65 48 8b 04 25 30 00 00 00    mov   rax,qword ptr gs:[30h]
+        // (GS prefix + REX + MOV (0x8b) ...)
+        if (origBytes[1] == 0x48 &&
+            (origBytes[2] >= 0x88 && origBytes[2] <= 0x8b)) {
+          COPY_CODES(3);
+          int len = CountModRmSib(origBytes);
+          if (len < 0) {
+            // no way to support this yet.
+            MOZ_ASSERT_UNREACHABLE("Unrecognized opcode sequence");
+            return;
+          }
+          COPY_CODES(len);
+        } else {
+          MOZ_ASSERT_UNREACHABLE("Unrecognized opcode sequence");
+          return;
+        }
+      } else if (*origBytes == 0x80 && origBytes[1] == 0x3d) {
+        origBytes += 2;
+
+        // cmp byte ptr [rip-relative address], imm8
+        // We'll compute the absolute address and do the cmp in r11
+
+        // push r11 (to save the old value)
+        tramp.WriteByte(0x49);
+        tramp.WriteByte(0x53);
+
+        uintptr_t absAddr = origBytes.ReadDisp32AsAbsolute();
+
+        // mov r11, absolute address
+        tramp.WriteByte(0x49);
+        tramp.WriteByte(0xbb);
+        tramp.WritePointer(absAddr);
+
+        // cmp byte ptr [r11],...
+        tramp.WriteByte(0x41);
+        tramp.WriteByte(0x80);
+        tramp.WriteByte(0x3b);
+
+        // ...imm8
+        COPY_CODES(1);
+
+        // pop r11 (doesn't affect the flags from the cmp)
+        tramp.WriteByte(0x49);
+        tramp.WriteByte(0x5b);
+      } else if (*origBytes == 0x90) {
+        // nop
+        COPY_CODES(1);
+      } else if ((*origBytes & 0xf8) == 0xb8) {
+        // MOV r32, imm32
+        COPY_CODES(5);
+      } else if (*origBytes == 0x33) {
+        // xor r32, r/m32
+        COPY_CODES(2);
+      } else if (*origBytes == 0xf6) {
+        // test r/m8, imm8 (used by ntdll on Windows 10 x64)
+        // (no flags are affected by near jmp since there is no task switch,
+        // so it is ok for a jmp to be written immediately after a test)
+        BYTE subOpcode = 0;
+        int nModRmSibBytes = CountModRmSib(origBytes + 1, &subOpcode);
+        if (nModRmSibBytes < 0 || subOpcode != 0) {
+          // Unsupported
+          MOZ_ASSERT_UNREACHABLE("Unrecognized opcode sequence");
+          return;
+        }
+        COPY_CODES(2 + nModRmSibBytes);
+      } else if (*origBytes == 0x85) {
+        // test r/m32, r32
+        int nModRmSibBytes = CountModRmSib(origBytes + 1);
+        if (nModRmSibBytes < 0) {
+          MOZ_ASSERT_UNREACHABLE("Unrecognized opcode sequence");
+          return;
+        }
+        COPY_CODES(1 + nModRmSibBytes);
+      } else if (*origBytes == 0xd1 && (origBytes[1] & kMaskMod) == kModReg) {
+        // bit shifts/rotates : (SA|SH|RO|RC)(R|L) r32
+        // (e.g. 0xd1 0xe0 is SAL, 0xd1 0xc8 is ROR)
+        COPY_CODES(2);
+      } else if (*origBytes == 0x83 && (origBytes[1] & kMaskMod) == kModReg) {
+        // ADD|OR|ADC|SBB|AND|SUB|XOR|CMP r, imm8
+        COPY_CODES(3);
+      } else if (*origBytes == 0xc3) {
+        // ret
+        COPY_CODES(1);
+      } else if (*origBytes == 0xcc) {
+        // int 3
+        COPY_CODES(1);
+      } else if (*origBytes == 0xe8 || *origBytes == 0xe9) {
+        // CALL (0xe8) or JMP (0xe9) 32bit offset
+        foundJmp = *origBytes == 0xe9;
+        ++origBytes;
+
+        if (!GenerateJump(tramp, origBytes.ReadDisp32AsAbsolute(),
+                          foundJmp ? JumpType::Jmp : JumpType::Call)) {
+          return;
+        }
+      } else if (*origBytes >= 0x73 && *origBytes <= 0x75) {
+        // 73 cb    JAE rel8
+        // 74 cb    JE  rel8
+        // 75 cb    JNE rel8
+        const JumpType kJumpTypes[] = {JumpType::Jae, JumpType::Je,
+                                       JumpType::Jne};
+        auto jumpType = kJumpTypes[*origBytes - 0x73];
+        uint8_t offset = origBytes[1];
+
+        origBytes += 2;
+
+        if (!GenerateJump(tramp, origBytes.OffsetToAbsolute(offset),
+                          jumpType)) {
+          return;
+        }
+      } else if (*origBytes == 0xff) {
+        uint8_t mod = origBytes[1] & kMaskMod;
+        uint8_t reg = (origBytes[1] & kMaskReg) >> kRegFieldShift;
+        uint8_t rm = origBytes[1] & kMaskRm;
+        if (mod == kModReg && (reg == 0 || reg == 1 || reg == 2 || reg == 6)) {
+          // INC|DEC|CALL|PUSH r64
+          COPY_CODES(2);
+        } else if (mod == kModNoRegDisp && reg == 2 &&
+                   rm == kRmNoRegDispDisp32) {
+          // FF 15    CALL [disp32]
+          origBytes += 2;
+          if (!GenerateJump(tramp, origBytes.ChasePointerFromDisp(),
+                            JumpType::Call)) {
+            return;
+          }
+        } else if (reg == 4) {
+          // FF /4 (Opcode=ff, REG=4): JMP r/m
+          if (mod == kModNoRegDisp && rm == kRmNoRegDispDisp32) {
+            // FF 25    JMP [disp32]
+            foundJmp = true;
+
+            origBytes += 2;
+
+            uintptr_t jmpDest = origBytes.ChasePointerFromDisp();
+
+            if (!GenerateJump(tramp, jmpDest, JumpType::Jmp)) {
+              return;
+            }
+          } else {
+            // JMP r/m except JMP [disp32]
+            int len = CountModRmSib(origBytes + 1);
+            if (len < 0) {
+              // RIP-relative not yet supported
+              MOZ_ASSERT_UNREACHABLE("Unrecognized opcode sequence");
+              return;
+            }
+
+            COPY_CODES(len + 1);
+
+            foundJmp = true;
+          }
+        } else {
+          MOZ_ASSERT_UNREACHABLE("Unrecognized opcode sequence");
+          return;
+        }
+      } else if (*origBytes == 0x83 && (origBytes[1] & 0xf8) == 0x60) {
+        // and [r+d], imm8
+        COPY_CODES(5);
+      } else if (*origBytes == 0xc6) {
+        // mov [r+d], imm8
+        int len = CountModRmSib(origBytes + 1);
+        if (len < 0) {
+          // RIP-relative not yet supported
+          MOZ_ASSERT_UNREACHABLE("Unrecognized opcode sequence");
+          return;
+        }
+        COPY_CODES(len + 2);
+      } else {
+        MOZ_ASSERT_UNREACHABLE("Unrecognized opcode sequence");
+        return;
+      }
+    }
+#elif defined(_M_ARM64)
+
+    // The number of bytes required to facilitate a detour depends on the
+    // proximity of the hook function to the target function. In the best case,
+    // we can branch within +/- 128MB of the current location, requiring only
+    // 4 bytes. In the worst case, we need 16 bytes to load an absolute address
+    // into a register and then branch to it.
+    const uint32_t bytesRequiredFromDecode =
+        (mFlags.value() & DetourFlags::eTestOnlyForceShortPatch)
+            ? 4
+            : kWorstCaseBytesRequired;
+
+    while (origBytes.GetOffset() < bytesRequiredFromDecode) {
+      uintptr_t curPC = origBytes.GetCurrentAbsolute();
+      uint32_t curInst = origBytes.ReadNextInstruction();
+
+      Result<arm64::LoadOrBranch, arm64::PCRelCheckError> pcRelInfo =
+          arm64::CheckForPCRel(curPC, curInst);
+      if (pcRelInfo.isErr()) {
+        if (pcRelInfo.unwrapErr() ==
+            arm64::PCRelCheckError::InstructionNotPCRel) {
+          // Instruction is not PC-relative, we can just copy it verbatim
+          tramp.WriteInstruction(curInst);
+          continue;
+        }
+
+        // At this point we have determined that there is no decoder available
+        // for the current, PC-relative, instruction.
+
+        // origBytes is now pointing one instruction past the one that we
+        // need the trampoline to jump back to.
+        if (!origBytes.BackUpOneInstruction()) {
+          return;
+        }
+
+        break;
+      }
+
+      // We need to load an absolute address into a particular register
+      tramp.WriteLoadLiteral(pcRelInfo.inspect().mAbsAddress,
+                             pcRelInfo.inspect().mDestReg);
+    }
+
+#else
+#  error "Unknown processor type"
+#endif
+
+    if (origBytes.GetOffset() > 100) {
+      // printf ("Too big!");
+      return;
+    }
+
+#if defined(_M_IX86)
+    if (pJmp32 >= 0) {
+      // Jump directly to the original target of the jump instead of jumping to
+      // the original function. Adjust jump target displacement to jump location
+      // in the trampoline.
+      tramp.AdjustDisp32AtOffset(pJmp32 + 1, origBytes.GetBaseAddress());
+    } else {
+      tramp.WriteByte(0xe9);  // jmp
+      tramp.WriteDisp32(origBytes.GetAddress());
+    }
+#elif defined(_M_X64)
+    // If we found a Jmp, we don't need to add another instruction. However,
+    // if we found a _conditional_ jump or a CALL (or no control operations
+    // at all) then we still need to run the rest of aOriginalFunction.
+    if (!foundJmp) {
+      if (!GenerateJump(tramp, origBytes.GetAddress(), JumpType::Jmp)) {
+        return;
+      }
+    }
+#elif defined(_M_ARM64)
+    // Let's find out how many bytes we have available to us for patching
+    uint32_t numBytesForPatching = tramp.GetCurrentExecutableCodeLen();
+
+    if (!numBytesForPatching) {
+      // There's nothing we can do
+      return;
+    }
+
+    if (tramp.IsNull()) {
+      // Recursive case
+      HMODULE targetModule = nullptr;
+
+      if (numBytesForPatching < kWorstCaseBytesRequired) {
+        if (!::GetModuleHandleExW(
+                GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS |
+                    GET_MODULE_HANDLE_EX_FLAG_UNCHANGED_REFCOUNT,
+                reinterpret_cast<LPCWSTR>(origBytes.GetBaseAddress()),
+                &targetModule)) {
+          return;
+        }
+      }
+
+      Maybe<TrampPoolT> maybeTrampPool = DoReserve(targetModule);
+      MOZ_ASSERT(maybeTrampPool);
+      if (!maybeTrampPool) {
+        return;
+      }
+
+      Maybe<Trampoline<MMPolicyT>> maybeRealTramp(
+          maybeTrampPool.ref().GetNextTrampoline());
+      if (!maybeRealTramp) {
+        return;
+      }
+
+      origBytes.Rewind();
+      CreateTrampoline(origBytes, maybeTrampPool.ptr(), maybeRealTramp.ref(),
+                       aDest, aOutTramp);
+      return;
+    }
+
+    // Write the branch from the trampoline back to the original code
+
+    tramp.WriteLoadLiteral(origBytes.GetAddress(), 16);
+    tramp.WriteInstruction(arm64::BuildUnconditionalBranchToRegister(16));
+#else
+#  error "Unsupported processor architecture"
+#endif
+
+    // The trampoline is now complete.
+    void* trampPtr = tramp.EndExecutableCode();
+    if (!trampPtr) {
+      return;
+    }
+
+#ifdef _M_X64
+    if constexpr (MMPolicyT::kSupportsUnwindInfo) {
+      DebugOnly<bool> unwindInfoAdded = tramp.AddUnwindInfo(
+          origBytes.GetBaseAddress(), origBytes.GetOffset());
+      MOZ_ASSERT(unwindInfoAdded);
+    }
+#endif  // _M_X64
+
+    WritableTargetFunction<MMPolicyT> target(origBytes.Promote());
+    if (!target) {
+      return;
+    }
+
+    do {
+      // Now patch the original function.
+      // When we're instructed to apply a non-default patch, apply it and exit.
+      // If non-default patching fails, bail out, no fallback.
+      // Otherwise, we go straight to the default patch.
+
+#if defined(_M_X64)
+      if (use10BytePatch) {
+        if (!Apply10BytePatch(aTrampPool, trampPtr, target, aDest)) {
+          return;
+        }
+        break;
+      }
+#elif defined(_M_ARM64)
+      if (numBytesForPatching < kWorstCaseBytesRequired) {
+        if (!Apply4BytePatch(aTrampPool, trampPtr, target, aDest)) {
+          return;
+        }
+        break;
+      }
+#endif
+
+      PrimitiveT::ApplyDefaultPatch(target, aDest);
+    } while (false);
+
+    // Output the trampoline, thus signalling that this call was a success. This
+    // must happen before our patched function can be reached from another
+    // thread, so before we commit the target code (bug 1838286).
+    *aOutTramp = trampPtr;
+
+    if (!target.Commit()) {
+      *aOutTramp = nullptr;
+    }
+  }
+};
+
+}  // namespace interceptor
+}  // namespace mozilla
+
+#endif  // mozilla_interceptor_PatcherDetour_h
diff --git a/toolkit/xre/dllservices/mozglue/interceptor/PatcherNopSpace.h b/toolkit/xre/dllservices/mozglue/interceptor/PatcherNopSpace.h
new file mode 100644
index 0000000000..deee87e0f8
--- /dev/null
+++ b/toolkit/xre/dllservices/mozglue/interceptor/PatcherNopSpace.h
@@ -0,0 +1,205 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_interceptor_PatcherNopSpace_h
+#define mozilla_interceptor_PatcherNopSpace_h
+
+#if defined(_M_IX86)
+
+#  include "mozilla/interceptor/PatcherBase.h"
+
+namespace mozilla {
+namespace interceptor {
+
+template <typename VMPolicy>
+class WindowsDllNopSpacePatcher final : public WindowsDllPatcherBase<VMPolicy> {
+  typedef typename VMPolicy::MMPolicyT MMPolicyT;
+
+  // For remembering the addresses of functions we've patched.
+  mozilla::Vector<void*> mPatchedFns;
+
+ public:
+  template <typename... Args>
+  explicit WindowsDllNopSpacePatcher(Args&&... aArgs)
+      : WindowsDllPatcherBase<VMPolicy>(std::forward<Args>(aArgs)...) {}
+
+  ~WindowsDllNopSpacePatcher() { Clear(); }
+
+  WindowsDllNopSpacePatcher(const WindowsDllNopSpacePatcher&) = delete;
+  WindowsDllNopSpacePatcher(WindowsDllNopSpacePatcher&&) = delete;
+  WindowsDllNopSpacePatcher& operator=(const WindowsDllNopSpacePatcher&) =
+      delete;
+  WindowsDllNopSpacePatcher& operator=(WindowsDllNopSpacePatcher&&) = delete;
+
+  void Clear() {
+    // Restore the mov edi, edi to the beginning of each function we patched.
+
+    for (auto&& ptr : mPatchedFns) {
+      WritableTargetFunction<MMPolicyT> fn(
+          this->mVMPolicy, reinterpret_cast<uintptr_t>(ptr), sizeof(uint16_t));
+      if (!fn) {
+        continue;
+      }
+
+      // mov edi, edi
+      fn.CommitAndWriteShort(0xff8b);
+    }
+
+    mPatchedFns.clear();
+  }
+
+  /**
+   * NVIDIA Optimus drivers utilize Microsoft Detours 2.x to patch functions
+   * in our address space. There is a bug in Detours 2.x that causes it to
+   * patch at the wrong address when attempting to detour code that is already
+   * NOP space patched. This function is an effort to detect the presence of
+   * this NVIDIA code in our address space and disable NOP space patching if it
+   * is. We also check AppInit_DLLs since this is the mechanism that the Optimus
+   * drivers use to inject into our process.
+   */
+  static bool IsCompatible() {
+    // These DLLs are known to have bad interactions with this style of patching
+    const wchar_t* kIncompatibleDLLs[] = {L"detoured.dll", L"_etoured.dll",
+                                          L"nvd3d9wrap.dll", L"nvdxgiwrap.dll"};
+    // See if the infringing DLLs are already loaded
+    for (unsigned int i = 0; i < mozilla::ArrayLength(kIncompatibleDLLs); ++i) {
+      if (GetModuleHandleW(kIncompatibleDLLs[i])) {
+        return false;
+      }
+    }
+    if (GetModuleHandleW(L"user32.dll")) {
+      // user32 is loaded but the infringing DLLs are not, assume we're safe to
+      // proceed.
+      return true;
+    }
+    // If user32 has not loaded yet, check AppInit_DLLs to ensure that Optimus
+    // won't be loaded once user32 is initialized.
+    HKEY hkey = NULL;
+    if (!RegOpenKeyExW(
+            HKEY_LOCAL_MACHINE,
+            L"SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion\\Windows", 0,
+            KEY_QUERY_VALUE, &hkey)) {
+      nsAutoRegKey key(hkey);
+      DWORD numBytes = 0;
+      const wchar_t kAppInitDLLs[] = L"AppInit_DLLs";
+      // Query for required buffer size
+      LONG status = RegQueryValueExW(hkey, kAppInitDLLs, nullptr, nullptr,
+                                     nullptr, &numBytes);
+      mozilla::UniquePtr<wchar_t[]> data;
+      if (!status) {
+        // Allocate the buffer and query for the actual data
+        data = mozilla::MakeUnique<wchar_t[]>((numBytes + 1) / sizeof(wchar_t));
+        status = RegQueryValueExW(hkey, kAppInitDLLs, nullptr, nullptr,
+                                  (LPBYTE)data.get(), &numBytes);
+      }
+      if (!status) {
+        // For each token, split up the filename components and then check the
+        // name of the file.
+        const wchar_t kDelimiters[] = L", ";
+        wchar_t* tokenContext = nullptr;
+        wchar_t* token = wcstok_s(data.get(), kDelimiters, &tokenContext);
+        while (token) {
+          wchar_t fname[_MAX_FNAME] = {0};
+          if (!_wsplitpath_s(token, nullptr, 0, nullptr, 0, fname,
+                             mozilla::ArrayLength(fname), nullptr, 0)) {
+            // nvinit.dll is responsible for bootstrapping the DLL injection, so
+            // that is the library that we check for here
+            const wchar_t kNvInitName[] = L"nvinit";
+            if (!_wcsnicmp(fname, kNvInitName,
+                           mozilla::ArrayLength(kNvInitName))) {
+              return false;
+            }
+          }
+          token = wcstok_s(nullptr, kDelimiters, &tokenContext);
+        }
+      }
+    }
+    return true;
+  }
+
+  bool AddHook(FARPROC aTargetFn, intptr_t aHookDest, void** aOrigFunc) {
+    if (!IsCompatible()) {
+#  if defined(MOZILLA_INTERNAL_API)
+      NS_WARNING("NOP space patching is unavailable for compatibility reasons");
+#  endif
+      return false;
+    }
+
+    MOZ_ASSERT(aTargetFn);
+    if (!aTargetFn) {
+      return false;
+    }
+
+    ReadOnlyTargetFunction<MMPolicyT> readOnlyTargetFn(
+        this->ResolveRedirectedAddress(aTargetFn));
+
+    if (!WriteHook(readOnlyTargetFn, aHookDest, aOrigFunc)) {
+      return false;
+    }
+
+    return mPatchedFns.append(
+        reinterpret_cast<void*>(readOnlyTargetFn.GetBaseAddress()));
+  }
+
+  bool WriteHook(const ReadOnlyTargetFunction<MMPolicyT>& aFn,
+                 intptr_t aHookDest, void** aOrigFunc) {
+    // Ensure we can read and write starting at fn - 5 (for the long jmp we're
+    // going to write) and ending at fn + 2 (for the short jmp up to the long
+    // jmp). These bytes may span two pages with different protection.
+    WritableTargetFunction<MMPolicyT> writableFn(aFn.Promote(7, -5));
+    if (!writableFn) {
+      return false;
+    }
+
+    // Check that the 5 bytes before the function are NOP's or INT 3's,
+    const uint8_t nopOrBp[] = {0x90, 0xCC};
+    if (!writableFn.template VerifyValuesAreOneOf<uint8_t, 5>(nopOrBp)) {
+      return false;
+    }
+
+    // ... and that the first 2 bytes of the function are mov(edi, edi).
+    // There are two ways to encode the same thing:
+    //
+    //   0x89 0xff == mov r/m, r
+    //   0x8b 0xff == mov r, r/m
+    //
+    // where "r" is register and "r/m" is register or memory.
+    // Windows seems to use 0x8B 0xFF. We include 0x89 0xFF out of paranoia.
+
+    // (These look backwards because little-endian)
+    const uint16_t possibleEncodings[] = {0xFF8B, 0xFF89};
+    if (!writableFn.template VerifyValuesAreOneOf<uint16_t, 1>(
+            possibleEncodings, 5)) {
+      return false;
+    }
+
+    // Write a long jump into the space above the function.
+    writableFn.WriteByte(0xe9);  // jmp
+    if (!writableFn) {
+      return false;
+    }
+
+    writableFn.WriteDisp32(aHookDest);  // target
+    if (!writableFn) {
+      return false;
+    }
+
+    // Set aOrigFunc here, because after this point, aHookDest might be called,
+    // and aHookDest might use the aOrigFunc pointer.
+    *aOrigFunc = reinterpret_cast<void*>(writableFn.GetCurrentAddress() +
+                                         sizeof(uint16_t));
+
+    // Short jump up into our long jump.
+    return writableFn.CommitAndWriteShort(0xF9EB);  // jmp $-5
+  }
+};
+
+}  // namespace interceptor
+}  // namespace mozilla
+
+#endif  // defined(_M_IX86)
+
+#endif  // mozilla_interceptor_PatcherNopSpace_h
diff --git a/toolkit/xre/dllservices/mozglue/interceptor/RangeMap.h b/toolkit/xre/dllservices/mozglue/interceptor/RangeMap.h
new file mode 100644
index 0000000000..d45d031613
--- /dev/null
+++ b/toolkit/xre/dllservices/mozglue/interceptor/RangeMap.h
@@ -0,0 +1,142 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_interceptor_RangeMap_h
+#define mozilla_interceptor_RangeMap_h
+
+#include "mozilla/Attributes.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/mozalloc.h"
+#include "mozilla/Span.h"
+#include "mozilla/UniquePtr.h"
+#include "mozilla/Vector.h"
+
+#include <algorithm>
+
+namespace mozilla {
+namespace interceptor {
+
+/**
+ * This class maintains a vector of VMSharingPolicyUnique objects, sorted on
+ * the memory range that is used for reserving each object.
+ *
+ * This is used by VMSharingPolicyShared for creating and looking up VM regions
+ * that are within proximity of the applicable range.
+ *
+ * VMSharingPolicyUnique objects managed by this class are reused whenever
+ * possible. If no range is required, we just return the first available
+ * policy.
+ *
+ * If no range is required and no policies have yet been allocated, we create
+ * a new one with a null range as a default.
+ */
+template <typename MMPolicyT>
+class RangeMap final {
+ private:
+  /**
+   * This class is used as the comparison key for sorting and insertion.
+   */
+  class Range {
+   public:
+    constexpr Range() : mBase(0), mLimit(0) {}
+
+    explicit Range(const Maybe<Span<const uint8_t>>& aBounds)
+        : mBase(aBounds ? reinterpret_cast<const uintptr_t>(
+                              MMPolicyT::GetLowerBound(aBounds.ref()))
+                        : 0),
+          mLimit(aBounds ? reinterpret_cast<const uintptr_t>(
+                               MMPolicyT::GetUpperBoundIncl(aBounds.ref()))
+                         : 0) {}
+
+    Range& operator=(const Range&) = default;
+    Range(const Range&) = default;
+    Range(Range&&) = default;
+    Range& operator=(Range&&) = default;
+
+    bool operator<(const Range& aOther) const {
+      return mBase < aOther.mBase ||
+             (mBase == aOther.mBase && mLimit < aOther.mLimit);
+    }
+
+    bool Contains(const Range& aOther) const {
+      return mBase <= aOther.mBase && mLimit >= aOther.mLimit;
+    }
+
+   private:
+    uintptr_t mBase;
+    uintptr_t mLimit;
+  };
+
+  class PolicyInfo final : public Range {
+   public:
+    explicit PolicyInfo(const Range& aRange)
+        : Range(aRange),
+          mPolicy(MakeUnique<VMSharingPolicyUnique<MMPolicyT>>()) {}
+
+    PolicyInfo(const PolicyInfo&) = delete;
+    PolicyInfo& operator=(const PolicyInfo&) = delete;
+
+    PolicyInfo(PolicyInfo&& aOther) = default;
+    PolicyInfo& operator=(PolicyInfo&& aOther) = default;
+
+    VMSharingPolicyUnique<MMPolicyT>* GetPolicy() { return mPolicy.get(); }
+
+   private:
+    UniquePtr<VMSharingPolicyUnique<MMPolicyT>> mPolicy;
+  };
+
+  using VectorType = Vector<PolicyInfo, 0, InfallibleAllocPolicy>;
+
+ public:
+  constexpr RangeMap() : mPolicies(nullptr) {}
+
+  VMSharingPolicyUnique<MMPolicyT>* GetPolicy(
+      const Maybe<Span<const uint8_t>>& aBounds) {
+    Range testRange(aBounds);
+
+    if (!mPolicies) {
+      mPolicies = new VectorType();
+    }
+
+    // If no bounds are specified, we just use the first available policy
+    if (!aBounds) {
+      if (mPolicies->empty()) {
+        if (!mPolicies->append(PolicyInfo(testRange))) {
+          return nullptr;
+        }
+      }
+
+      return GetFirstPolicy();
+    }
+
+    // mPolicies is sorted, so we search
+    auto itr =
+        std::lower_bound(mPolicies->begin(), mPolicies->end(), testRange);
+    if (itr != mPolicies->end() && itr->Contains(testRange)) {
+      return itr->GetPolicy();
+    }
+
+    itr = mPolicies->insert(itr, PolicyInfo(testRange));
+
+    MOZ_ASSERT(std::is_sorted(mPolicies->begin(), mPolicies->end()));
+
+    return itr->GetPolicy();
+  }
+
+ private:
+  VMSharingPolicyUnique<MMPolicyT>* GetFirstPolicy() {
+    MOZ_RELEASE_ASSERT(mPolicies && !mPolicies->empty());
+    return mPolicies->begin()->GetPolicy();
+  }
+
+ private:
+  VectorType* mPolicies;
+};
+
+}  // namespace interceptor
+}  // namespace mozilla
+
+#endif  // mozilla_interceptor_RangeMap_h
diff --git a/toolkit/xre/dllservices/mozglue/interceptor/TargetFunction.h b/toolkit/xre/dllservices/mozglue/interceptor/TargetFunction.h
new file mode 100644
index 0000000000..b79867edcd
--- /dev/null
+++ b/toolkit/xre/dllservices/mozglue/interceptor/TargetFunction.h
@@ -0,0 +1,1000 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_interceptor_TargetFunction_h
+#define mozilla_interceptor_TargetFunction_h
+
+#include "mozilla/Assertions.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/BinarySearch.h"
+#include "mozilla/CheckedInt.h"
+#include "mozilla/Maybe.h"
+
+#include "mozilla/Types.h"
+#include "mozilla/Unused.h"
+#include "mozilla/Vector.h"
+
+#include <memory>
+#include <type_traits>
+
+namespace mozilla {
+namespace interceptor {
+
+#if defined(_M_IX86)
+
+template <typename T>
+bool CommitAndWriteShortInternal(const T& aMMPolicy, void* aDest,
+                                 uint16_t aValue);
+
+template <>
+inline bool CommitAndWriteShortInternal<MMPolicyInProcess>(
+    const MMPolicyInProcess& aMMPolicy, void* aDest, uint16_t aValue) {
+  return aMMPolicy.WriteAtomic(aDest, aValue);
+}
+
+template <>
+inline bool CommitAndWriteShortInternal<MMPolicyOutOfProcess>(
+    const MMPolicyOutOfProcess& aMMPolicy, void* aDest, uint16_t aValue) {
+  return aMMPolicy.Write(aDest, &aValue, sizeof(uint16_t));
+}
+
+#endif  // defined(_M_IX86)
+
+// Forward declaration
+template <typename MMPolicy>
+class ReadOnlyTargetFunction;
+
+template <typename MMPolicy>
+class MOZ_STACK_CLASS WritableTargetFunction final {
+  class AutoProtect final {
+    using ProtectParams = std::tuple<uintptr_t, uint32_t>;
+
+   public:
+    explicit AutoProtect(const MMPolicy& aMMPolicy) : mMMPolicy(aMMPolicy) {}
+
+    AutoProtect(const MMPolicy& aMMPolicy, uintptr_t aAddr, size_t aNumBytes,
+                uint32_t aNewProt)
+        : mMMPolicy(aMMPolicy) {
+      const uint32_t pageSize = mMMPolicy.GetPageSize();
+      const uintptr_t limit = aAddr + aNumBytes - 1;
+      const uintptr_t limitPageNum = limit / pageSize;
+      const uintptr_t basePageNum = aAddr / pageSize;
+      const uintptr_t numPagesToChange = limitPageNum - basePageNum + 1;
+
+      // We'll use the base address of the page instead of aAddr
+      uintptr_t curAddr = basePageNum * pageSize;
+
+      // Now change the protection on each page
+      for (uintptr_t curPage = 0; curPage < numPagesToChange;
+           ++curPage, curAddr += pageSize) {
+        uint32_t prevProt;
+        if (!aMMPolicy.Protect(reinterpret_cast<void*>(curAddr), pageSize,
+                               aNewProt, &prevProt)) {
+          Clear();
+          return;
+        }
+
+        // Save the previous protection for curAddr so that we can revert this
+        // in the destructor.
+        if (!mProtects.append(std::make_tuple(curAddr, prevProt))) {
+          Clear();
+          return;
+        }
+      }
+    }
+
+    AutoProtect(AutoProtect&& aOther)
+        : mMMPolicy(aOther.mMMPolicy), mProtects(std::move(aOther.mProtects)) {
+      aOther.mProtects.clear();
+    }
+
+    ~AutoProtect() { Clear(); }
+
+    explicit operator bool() const { return !mProtects.empty(); }
+
+    AutoProtect(const AutoProtect&) = delete;
+    AutoProtect& operator=(const AutoProtect&) = delete;
+    AutoProtect& operator=(AutoProtect&&) = delete;
+
+   private:
+    void Clear() {
+      const uint32_t pageSize = mMMPolicy.GetPageSize();
+      for (auto&& entry : mProtects) {
+        uint32_t prevProt;
+        DebugOnly<bool> ok =
+            mMMPolicy.Protect(reinterpret_cast<void*>(std::get<0>(entry)),
+                              pageSize, std::get<1>(entry), &prevProt);
+        MOZ_ASSERT(ok);
+      }
+
+      mProtects.clear();
+    }
+
+   private:
+    const MMPolicy& mMMPolicy;
+    // We include two entries of inline storage as that is most common in the
+    // worst case.
+    Vector<ProtectParams, 2> mProtects;
+  };
+
+ public:
+  /**
+   * Used to initialize an invalid WritableTargetFunction, thus signalling an
+   * error.
+   */
+  explicit WritableTargetFunction(const MMPolicy& aMMPolicy)
+      : mMMPolicy(aMMPolicy),
+        mFunc(0),
+        mNumBytes(0),
+        mOffset(0),
+        mStartWriteOffset(0),
+        mAccumulatedStatus(false),
+        mProtect(aMMPolicy) {}
+
+  WritableTargetFunction(const MMPolicy& aMMPolicy, uintptr_t aFunc,
+                         size_t aNumBytes)
+      : mMMPolicy(aMMPolicy),
+        mFunc(aFunc),
+        mNumBytes(aNumBytes),
+        mOffset(0),
+        mStartWriteOffset(0),
+        mAccumulatedStatus(true),
+        mProtect(aMMPolicy, aFunc, aNumBytes, PAGE_EXECUTE_READWRITE) {}
+
+  WritableTargetFunction(WritableTargetFunction&& aOther)
+      : mMMPolicy(aOther.mMMPolicy),
+        mFunc(aOther.mFunc),
+        mNumBytes(aOther.mNumBytes),
+        mOffset(aOther.mOffset),
+        mStartWriteOffset(aOther.mStartWriteOffset),
+        mLocalBytes(std::move(aOther.mLocalBytes)),
+        mAccumulatedStatus(aOther.mAccumulatedStatus),
+        mProtect(std::move(aOther.mProtect)) {
+    aOther.mAccumulatedStatus = false;
+  }
+
+  ~WritableTargetFunction() {
+    MOZ_ASSERT(mLocalBytes.empty(), "Did you forget to call Commit?");
+  }
+
+  WritableTargetFunction(const WritableTargetFunction&) = delete;
+  WritableTargetFunction& operator=(const WritableTargetFunction&) = delete;
+  WritableTargetFunction& operator=(WritableTargetFunction&&) = delete;
+
+  /**
+   * @return true if data was successfully committed.
+   */
+  bool Commit() {
+    if (!(*this)) {
+      return false;
+    }
+
+    if (mLocalBytes.empty()) {
+      // Nothing to commit, treat like success
+      return true;
+    }
+
+    bool ok =
+        mMMPolicy.Write(reinterpret_cast<void*>(mFunc + mStartWriteOffset),
+                        mLocalBytes.begin(), mLocalBytes.length());
+    if (!ok) {
+      return false;
+    }
+
+    mMMPolicy.FlushInstructionCache();
+
+    mStartWriteOffset += mLocalBytes.length();
+
+    mLocalBytes.clear();
+    return true;
+  }
+
+  explicit operator bool() const { return mProtect && mAccumulatedStatus; }
+
+  void WriteByte(const uint8_t& aValue) {
+    if (!mLocalBytes.append(aValue)) {
+      mAccumulatedStatus = false;
+      return;
+    }
+
+    mOffset += sizeof(uint8_t);
+  }
+
+  Maybe<uint8_t> ReadByte() {
+    // Reading is only permitted prior to any writing
+    MOZ_ASSERT(mOffset == mStartWriteOffset);
+    if (mOffset > mStartWriteOffset) {
+      mAccumulatedStatus = false;
+      return Nothing();
+    }
+
+    uint8_t value;
+    if (!mMMPolicy.Read(&value, reinterpret_cast<const void*>(mFunc + mOffset),
+                        sizeof(uint8_t))) {
+      mAccumulatedStatus = false;
+      return Nothing();
+    }
+
+    mOffset += sizeof(uint8_t);
+    mStartWriteOffset += sizeof(uint8_t);
+    return Some(value);
+  }
+
+  Maybe<uintptr_t> ReadEncodedPtr() {
+    // Reading is only permitted prior to any writing
+    MOZ_ASSERT(mOffset == mStartWriteOffset);
+    if (mOffset > mStartWriteOffset) {
+      mAccumulatedStatus = false;
+      return Nothing();
+    }
+
+    uintptr_t value;
+    if (!mMMPolicy.Read(&value, reinterpret_cast<const void*>(mFunc + mOffset),
+                        sizeof(uintptr_t))) {
+      mAccumulatedStatus = false;
+      return Nothing();
+    }
+
+    mOffset += sizeof(uintptr_t);
+    mStartWriteOffset += sizeof(uintptr_t);
+    return Some(ReadOnlyTargetFunction<MMPolicy>::DecodePtr(value));
+  }
+
+  Maybe<uint32_t> ReadLong() {
+    // Reading is only permitted prior to any writing
+    MOZ_ASSERT(mOffset == mStartWriteOffset);
+    if (mOffset > mStartWriteOffset) {
+      mAccumulatedStatus = false;
+      return Nothing();
+    }
+
+    uint32_t value;
+    if (!mMMPolicy.Read(&value, reinterpret_cast<const void*>(mFunc + mOffset),
+                        sizeof(uint32_t))) {
+      mAccumulatedStatus = false;
+      return Nothing();
+    }
+
+    mOffset += sizeof(uint32_t);
+    mStartWriteOffset += sizeof(uint32_t);
+    return Some(value);
+  }
+
+  void WriteShort(const uint16_t& aValue) {
+    if (!mLocalBytes.append(reinterpret_cast<const uint8_t*>(&aValue),
+                            sizeof(uint16_t))) {
+      mAccumulatedStatus = false;
+      return;
+    }
+
+    mOffset += sizeof(uint16_t);
+  }
+
+#if defined(_M_IX86)
+ public:
+  /**
+   * Commits any dirty writes, and then writes a short, atomically if possible.
+   * This call may succeed in both inproc and outproc cases, but atomicity
+   * is only guaranteed in the inproc case.
+   */
+  bool CommitAndWriteShort(const uint16_t aValue) {
+    // First, commit everything that has been written until now
+    if (!Commit()) {
+      return false;
+    }
+
+    // Now immediately write the short, atomically if inproc
+    bool ok = CommitAndWriteShortInternal(
+        mMMPolicy, reinterpret_cast<void*>(mFunc + mStartWriteOffset), aValue);
+    if (!ok) {
+      return false;
+    }
+
+    mMMPolicy.FlushInstructionCache();
+    mStartWriteOffset += sizeof(uint16_t);
+    return true;
+  }
+#endif  // defined(_M_IX86)
+
+  void WriteDisp32(const uintptr_t aAbsTarget) {
+    intptr_t diff = static_cast<intptr_t>(aAbsTarget) -
+                    static_cast<intptr_t>(mFunc + mOffset + sizeof(int32_t));
+
+    CheckedInt<int32_t> checkedDisp(diff);
+    MOZ_ASSERT(checkedDisp.isValid());
+    if (!checkedDisp.isValid()) {
+      mAccumulatedStatus = false;
+      return;
+    }
+
+    int32_t disp = checkedDisp.value();
+    if (!mLocalBytes.append(reinterpret_cast<uint8_t*>(&disp),
+                            sizeof(int32_t))) {
+      mAccumulatedStatus = false;
+      return;
+    }
+
+    mOffset += sizeof(int32_t);
+  }
+
+#if defined(_M_X64) || defined(_M_ARM64)
+  void WriteLong(const uint32_t aValue) {
+    if (!mLocalBytes.append(reinterpret_cast<const uint8_t*>(&aValue),
+                            sizeof(uint32_t))) {
+      mAccumulatedStatus = false;
+      return;
+    }
+
+    mOffset += sizeof(uint32_t);
+  }
+#endif  // defined(_M_X64)
+
+  void WritePointer(const uintptr_t aAbsTarget) {
+    if (!mLocalBytes.append(reinterpret_cast<const uint8_t*>(&aAbsTarget),
+                            sizeof(uintptr_t))) {
+      mAccumulatedStatus = false;
+      return;
+    }
+
+    mOffset += sizeof(uintptr_t);
+  }
+
+  /**
+   * @param aValues N-sized array of type T that specifies the set of values
+   *                that are permissible in the first M bytes of the target
+   *                function at aOffset.
+   * @return true if M values of type T in the function are members of the
+   *         set specified by aValues.
+   */
+  template <typename T, size_t M, size_t N>
+  bool VerifyValuesAreOneOf(const T (&aValues)[N], const uint8_t aOffset = 0) {
+    T buf[M];
+    if (!mMMPolicy.Read(
+            buf, reinterpret_cast<const void*>(mFunc + mOffset + aOffset),
+            M * sizeof(T))) {
+      return false;
+    }
+
+    for (auto&& fnValue : buf) {
+      bool match = false;
+      for (auto&& testValue : aValues) {
+        match |= (fnValue == testValue);
+      }
+
+      if (!match) {
+        return false;
+      }
+    }
+
+    return true;
+  }
+
+  uintptr_t GetCurrentAddress() const { return mFunc + mOffset; }
+
+ private:
+  const MMPolicy& mMMPolicy;
+  const uintptr_t mFunc;
+  const size_t mNumBytes;
+  uint32_t mOffset;
+  uint32_t mStartWriteOffset;
+
+  // In an ideal world, we'd only read 5 bytes on 32-bit and 13 bytes on 64-bit,
+  // to match the minimum bytes that we need to write in in order to patch the
+  // target function. Since the actual opcodes will often require us to pull in
+  // extra bytes above that minimum, we set the inline storage to be larger than
+  // those minima in an effort to give the Vector extra wiggle room before it
+  // needs to touch the heap.
+#if defined(_M_IX86)
+  static const size_t kInlineStorage = 16;
+#elif defined(_M_X64) || defined(_M_ARM64)
+  static const size_t kInlineStorage = 32;
+#endif
+  Vector<uint8_t, kInlineStorage> mLocalBytes;
+  bool mAccumulatedStatus;
+  AutoProtect mProtect;
+};
+
+template <typename MMPolicy>
+class ReadOnlyTargetBytes {
+ public:
+  ReadOnlyTargetBytes(const MMPolicy& aMMPolicy, const void* aBase)
+      : mMMPolicy(aMMPolicy), mBase(reinterpret_cast<const uint8_t*>(aBase)) {}
+
+  ReadOnlyTargetBytes(ReadOnlyTargetBytes&& aOther)
+      : mMMPolicy(aOther.mMMPolicy), mBase(aOther.mBase) {}
+
+  ReadOnlyTargetBytes(const ReadOnlyTargetBytes& aOther,
+                      const uint32_t aOffsetFromOther = 0)
+      : mMMPolicy(aOther.mMMPolicy), mBase(aOther.mBase + aOffsetFromOther) {}
+
+  void EnsureLimit(uint32_t aDesiredLimit) {
+    // In the out-proc case we use this function to read the target function's
+    // bytes in the other process into a local buffer. We don't need that for
+    // the in-process case because we already have direct access to our target
+    // function's bytes.
+  }
+
+  uint32_t TryEnsureLimit(uint32_t aDesiredLimit) {
+    // Same as EnsureLimit above.  We don't need to ensure for the in-process.
+    return aDesiredLimit;
+  }
+
+  bool IsValidAtOffset(const int8_t aOffset) const {
+    if (!aOffset) {
+      return true;
+    }
+
+    uintptr_t base = reinterpret_cast<uintptr_t>(mBase);
+    uintptr_t adjusted = base + aOffset;
+    uint32_t pageSize = mMMPolicy.GetPageSize();
+
+    // If |adjusted| is within the same page as |mBase|, we're still valid
+    if ((base / pageSize) == (adjusted / pageSize)) {
+      return true;
+    }
+
+    // Otherwise, let's query |adjusted|
+    return mMMPolicy.IsPageAccessible(adjusted);
+  }
+
+  /**
+   * This returns a pointer to a *potentially local copy* of the target
+   * function's bytes. The returned pointer should not be used for any
+   * pointer arithmetic relating to the target function.
+   */
+  const uint8_t* GetLocalBytes() const { return mBase; }
+
+  /**
+   * This returns a pointer to the target function's bytes. The returned pointer
+   * may possibly belong to another process, so while it should be used for
+   * pointer arithmetic, it *must not* be dereferenced.
+   */
+  uintptr_t GetBase() const { return reinterpret_cast<uintptr_t>(mBase); }
+
+  const MMPolicy& GetMMPolicy() const { return mMMPolicy; }
+
+  ReadOnlyTargetBytes& operator=(const ReadOnlyTargetBytes&) = delete;
+  ReadOnlyTargetBytes& operator=(ReadOnlyTargetBytes&&) = delete;
+
+ private:
+  const MMPolicy& mMMPolicy;
+  uint8_t const* const mBase;
+};
+
+template <>
+class ReadOnlyTargetBytes<MMPolicyOutOfProcess> {
+ public:
+  ReadOnlyTargetBytes(const MMPolicyOutOfProcess& aMMPolicy, const void* aBase)
+      : mMMPolicy(aMMPolicy), mBase(reinterpret_cast<const uint8_t*>(aBase)) {}
+
+  ReadOnlyTargetBytes(ReadOnlyTargetBytes&& aOther)
+      : mMMPolicy(aOther.mMMPolicy),
+        mLocalBytes(std::move(aOther.mLocalBytes)),
+        mBase(aOther.mBase) {}
+
+  ReadOnlyTargetBytes(const ReadOnlyTargetBytes& aOther)
+      : mMMPolicy(aOther.mMMPolicy), mBase(aOther.mBase) {
+    Unused << mLocalBytes.appendAll(aOther.mLocalBytes);
+  }
+
+  ReadOnlyTargetBytes(const ReadOnlyTargetBytes& aOther,
+                      const uint32_t aOffsetFromOther)
+      : mMMPolicy(aOther.mMMPolicy), mBase(aOther.mBase + aOffsetFromOther) {
+    if (aOffsetFromOther >= aOther.mLocalBytes.length()) {
+      return;
+    }
+
+    Unused << mLocalBytes.append(aOther.mLocalBytes.begin() + aOffsetFromOther,
+                                 aOther.mLocalBytes.end());
+  }
+
+  void EnsureLimit(uint32_t aDesiredLimit) {
+    size_t prevSize = mLocalBytes.length();
+    if (aDesiredLimit < prevSize) {
+      return;
+    }
+
+    size_t newSize = aDesiredLimit + 1;
+    if (newSize < kInlineStorage) {
+      // Always try to read as much memory as we can at once
+      newSize = kInlineStorage;
+    }
+
+    bool resizeOk = mLocalBytes.resize(newSize);
+    MOZ_RELEASE_ASSERT(resizeOk);
+
+    bool ok = mMMPolicy.Read(&mLocalBytes[prevSize], mBase + prevSize,
+                             newSize - prevSize);
+    if (ok) {
+      return;
+    }
+
+    // We couldn't pull more bytes than needed (which may happen if those extra
+    // bytes are not accessible). In this case, we try just to get the bare
+    // minimum.
+    newSize = aDesiredLimit + 1;
+    resizeOk = mLocalBytes.resize(newSize);
+    MOZ_RELEASE_ASSERT(resizeOk);
+
+    ok = mMMPolicy.Read(&mLocalBytes[prevSize], mBase + prevSize,
+                        newSize - prevSize);
+    MOZ_RELEASE_ASSERT(ok);
+  }
+
+  // This function tries to ensure as many bytes as possible up to
+  // |aDesiredLimit| bytes, returning how many bytes were actually ensured.
+  // As EnsureLimit does, we allocate an extra byte in local to make sure
+  // mLocalBytes always has at least one byte even though the target memory
+  // was inaccessible at all.
+  uint32_t TryEnsureLimit(uint32_t aDesiredLimit) {
+    size_t prevSize = mLocalBytes.length();
+    if (aDesiredLimit < prevSize) {
+      return aDesiredLimit;
+    }
+
+    size_t newSize = aDesiredLimit;
+    if (newSize < kInlineStorage) {
+      // Always try to read as much memory as we can at once
+      newSize = kInlineStorage;
+    }
+
+    bool resizeOk = mLocalBytes.resize(newSize);
+    MOZ_RELEASE_ASSERT(resizeOk);
+
+    size_t bytesRead = mMMPolicy.TryRead(&mLocalBytes[prevSize],
+                                         mBase + prevSize, newSize - prevSize);
+
+    newSize = prevSize + bytesRead;
+
+    resizeOk = mLocalBytes.resize(newSize + 1);
+    MOZ_RELEASE_ASSERT(resizeOk);
+
+    mLocalBytes[newSize] = 0;
+    return newSize;
+  }
+
+  bool IsValidAtOffset(const int8_t aOffset) const {
+    if (!aOffset) {
+      return true;
+    }
+
+    uintptr_t base = reinterpret_cast<uintptr_t>(mBase);
+    uintptr_t adjusted = base + aOffset;
+    uint32_t pageSize = mMMPolicy.GetPageSize();
+
+    // If |adjusted| is within the same page as |mBase|, we're still valid
+    if ((base / pageSize) == (adjusted / pageSize)) {
+      return true;
+    }
+
+    // Otherwise, let's query |adjusted|
+    return mMMPolicy.IsPageAccessible(adjusted);
+  }
+
+  /**
+   * This returns a pointer to a *potentially local copy* of the target
+   * function's bytes. The returned pointer should not be used for any
+   * pointer arithmetic relating to the target function.
+   */
+  const uint8_t* GetLocalBytes() const {
+    if (mLocalBytes.empty()) {
+      return nullptr;
+    }
+
+    return mLocalBytes.begin();
+  }
+
+  /**
+   * This returns a pointer to the target function's bytes. The returned pointer
+   * may possibly belong to another process, so while it should be used for
+   * pointer arithmetic, it *must not* be dereferenced.
+   */
+  uintptr_t GetBase() const { return reinterpret_cast<uintptr_t>(mBase); }
+
+  const MMPolicyOutOfProcess& GetMMPolicy() const { return mMMPolicy; }
+
+  ReadOnlyTargetBytes& operator=(const ReadOnlyTargetBytes&) = delete;
+  ReadOnlyTargetBytes& operator=(ReadOnlyTargetBytes&&) = delete;
+
+ private:
+  // In an ideal world, we'd only read 5 bytes on 32-bit and 13 bytes on 64-bit,
+  // to match the minimum bytes that we need to write in in order to patch the
+  // target function. Since the actual opcodes will often require us to pull in
+  // extra bytes above that minimum, we set the inline storage to be larger than
+  // those minima in an effort to give the Vector extra wiggle room before it
+  // needs to touch the heap.
+#if defined(_M_IX86)
+  static const size_t kInlineStorage = 16;
+#elif defined(_M_X64) || defined(_M_ARM64)
+  static const size_t kInlineStorage = 32;
+#endif
+
+  const MMPolicyOutOfProcess& mMMPolicy;
+  Vector<uint8_t, kInlineStorage> mLocalBytes;
+  uint8_t const* const mBase;
+};
+
+template <typename MMPolicy>
+class TargetBytesPtr {
+ public:
+  typedef TargetBytesPtr<MMPolicy> Type;
+
+  static Type Make(const MMPolicy& aMMPolicy, const void* aFunc) {
+    return TargetBytesPtr(aMMPolicy, aFunc);
+  }
+
+  static Type CopyFromOffset(const TargetBytesPtr& aOther,
+                             const uint32_t aOffsetFromOther) {
+    return TargetBytesPtr(aOther, aOffsetFromOther);
+  }
+
+  ReadOnlyTargetBytes<MMPolicy>* operator->() { return &mTargetBytes; }
+
+  TargetBytesPtr(TargetBytesPtr&& aOther)
+      : mTargetBytes(std::move(aOther.mTargetBytes)) {}
+
+  TargetBytesPtr(const TargetBytesPtr& aOther)
+      : mTargetBytes(aOther.mTargetBytes) {}
+
+  TargetBytesPtr& operator=(const TargetBytesPtr&) = delete;
+  TargetBytesPtr& operator=(TargetBytesPtr&&) = delete;
+
+ private:
+  TargetBytesPtr(const MMPolicy& aMMPolicy, const void* aFunc)
+      : mTargetBytes(aMMPolicy, aFunc) {}
+
+  TargetBytesPtr(const TargetBytesPtr& aOther, const uint32_t aOffsetFromOther)
+      : mTargetBytes(aOther.mTargetBytes, aOffsetFromOther) {}
+
+  ReadOnlyTargetBytes<MMPolicy> mTargetBytes;
+};
+
+template <>
+class TargetBytesPtr<MMPolicyOutOfProcess> {
+ public:
+  typedef std::shared_ptr<ReadOnlyTargetBytes<MMPolicyOutOfProcess>> Type;
+
+  static Type Make(const MMPolicyOutOfProcess& aMMPolicy, const void* aFunc) {
+    return std::make_shared<ReadOnlyTargetBytes<MMPolicyOutOfProcess>>(
+        aMMPolicy, aFunc);
+  }
+
+  static Type CopyFromOffset(const Type& aOther,
+                             const uint32_t aOffsetFromOther) {
+    return std::make_shared<ReadOnlyTargetBytes<MMPolicyOutOfProcess>>(
+        *aOther, aOffsetFromOther);
+  }
+};
+
+template <typename MMPolicy>
+class MOZ_STACK_CLASS ReadOnlyTargetFunction final {
+ public:
+  ReadOnlyTargetFunction(const MMPolicy& aMMPolicy, const void* aFunc)
+      : mTargetBytes(TargetBytesPtr<MMPolicy>::Make(aMMPolicy, aFunc)),
+        mOffset(0) {}
+
+  ReadOnlyTargetFunction(const MMPolicy& aMMPolicy, FARPROC aFunc)
+      : mTargetBytes(TargetBytesPtr<MMPolicy>::Make(
+            aMMPolicy, reinterpret_cast<const void*>(aFunc))),
+        mOffset(0) {}
+
+  ReadOnlyTargetFunction(const MMPolicy& aMMPolicy, uintptr_t aFunc)
+      : mTargetBytes(TargetBytesPtr<MMPolicy>::Make(
+            aMMPolicy, reinterpret_cast<const void*>(aFunc))),
+        mOffset(0) {}
+
+  ReadOnlyTargetFunction(ReadOnlyTargetFunction&& aOther)
+      : mTargetBytes(std::move(aOther.mTargetBytes)), mOffset(aOther.mOffset) {}
+
+  ReadOnlyTargetFunction& operator=(const ReadOnlyTargetFunction&) = delete;
+  ReadOnlyTargetFunction& operator=(ReadOnlyTargetFunction&&) = delete;
+
+  ~ReadOnlyTargetFunction() = default;
+
+  ReadOnlyTargetFunction operator+(const uint32_t aOffset) const {
+    return ReadOnlyTargetFunction(*this, mOffset + aOffset);
+  }
+
+  uintptr_t GetBaseAddress() const { return mTargetBytes->GetBase(); }
+
+  uintptr_t GetAddress() const { return mTargetBytes->GetBase() + mOffset; }
+
+  uintptr_t AsEncodedPtr() const {
+    return EncodePtr(
+        reinterpret_cast<void*>(mTargetBytes->GetBase() + mOffset));
+  }
+
+  static uintptr_t EncodePtr(void* aPtr) {
+    return reinterpret_cast<uintptr_t>(::EncodePointer(aPtr));
+  }
+
+  static uintptr_t DecodePtr(uintptr_t aEncodedPtr) {
+    return reinterpret_cast<uintptr_t>(
+        ::DecodePointer(reinterpret_cast<PVOID>(aEncodedPtr)));
+  }
+
+  bool IsValidAtOffset(const int8_t aOffset) const {
+    return mTargetBytes->IsValidAtOffset(aOffset);
+  }
+
+#if defined(_M_ARM64)
+
+  uint32_t ReadNextInstruction() {
+    mTargetBytes->EnsureLimit(mOffset + sizeof(uint32_t));
+    uint32_t instruction = *reinterpret_cast<const uint32_t*>(
+        mTargetBytes->GetLocalBytes() + mOffset);
+    mOffset += sizeof(uint32_t);
+    return instruction;
+  }
+
+  bool BackUpOneInstruction() {
+    if (mOffset < sizeof(uint32_t)) {
+      return false;
+    }
+
+    mOffset -= sizeof(uint32_t);
+    return true;
+  }
+
+#else
+
+  uint8_t const& operator*() const {
+    mTargetBytes->EnsureLimit(mOffset);
+    return *(mTargetBytes->GetLocalBytes() + mOffset);
+  }
+
+  uint8_t const& operator[](uint32_t aIndex) const {
+    mTargetBytes->EnsureLimit(mOffset + aIndex);
+    return *(mTargetBytes->GetLocalBytes() + mOffset + aIndex);
+  }
+
+  ReadOnlyTargetFunction& operator++() {
+    ++mOffset;
+    return *this;
+  }
+
+  ReadOnlyTargetFunction& operator+=(uint32_t aDelta) {
+    mOffset += aDelta;
+    return *this;
+  }
+
+  uintptr_t ReadDisp32AsAbsolute() {
+    mTargetBytes->EnsureLimit(mOffset + sizeof(int32_t));
+    int32_t disp = *reinterpret_cast<const int32_t*>(
+        mTargetBytes->GetLocalBytes() + mOffset);
+    uintptr_t result =
+        mTargetBytes->GetBase() + mOffset + sizeof(int32_t) + disp;
+    mOffset += sizeof(int32_t);
+    return result;
+  }
+
+  bool IsRelativeShortJump(uintptr_t* aOutTarget) {
+    if ((*this)[0] == 0xeb) {
+      int8_t offset = static_cast<int8_t>((*this)[1]);
+      *aOutTarget = GetAddress() + 2 + offset;
+      return true;
+    }
+    return false;
+  }
+
+#  if defined(_M_X64)
+  // Currently this function is used only in x64.
+  bool IsRelativeNearJump(uintptr_t* aOutTarget) {
+    if ((*this)[0] == 0xe9) {
+      *aOutTarget = (*this + 1).ReadDisp32AsAbsolute();
+      return true;
+    }
+    return false;
+  }
+#  endif  // defined(_M_X64)
+
+  bool IsIndirectNearJump(uintptr_t* aOutTarget) {
+    if ((*this)[0] == 0xff && (*this)[1] == 0x25) {
+#  if defined(_M_X64)
+      *aOutTarget = (*this + 2).ChasePointerFromDisp();
+#  else
+      *aOutTarget = (*this + 2).template ChasePointer<uintptr_t*>();
+#  endif  // defined(_M_X64)
+      return true;
+    }
+#  if defined(_M_X64)
+    else if ((*this)[0] == 0x48 && (*this)[1] == 0xff && (*this)[2] == 0x25) {
+      // According to Intel SDM, JMP does not have REX.W except JMP m16:64,
+      // but CPU can execute JMP r/m32 with REX.W.  We handle it just in case.
+      *aOutTarget = (*this + 3).ChasePointerFromDisp();
+      return true;
+    }
+#  endif  // defined(_M_X64)
+    return false;
+  }
+
+#endif  // defined(_M_ARM64)
+
+  void Rewind() { mOffset = 0; }
+
+  uint32_t GetOffset() const { return mOffset; }
+
+  uintptr_t OffsetToAbsolute(const uint8_t aOffset) const {
+    return mTargetBytes->GetBase() + mOffset + aOffset;
+  }
+
+  uintptr_t GetCurrentAbsolute() const { return OffsetToAbsolute(0); }
+
+  /**
+   * This method promotes the code referenced by this object to be writable.
+   *
+   * @param aLen    The length of the function's code to make writable. If set
+   *                to zero, this object's current offset is used as the length.
+   * @param aOffset The result's base address will be offset from this
+   *                object's base address by |aOffset| bytes. This value may be
+   *                negative.
+   */
+  WritableTargetFunction<MMPolicy> Promote(const uint32_t aLen = 0,
+                                           const int8_t aOffset = 0) const {
+    const uint32_t effectiveLength = aLen ? aLen : mOffset;
+    MOZ_RELEASE_ASSERT(effectiveLength,
+                       "Cannot Promote a zero-length function");
+
+    if (!mTargetBytes->IsValidAtOffset(aOffset)) {
+      return WritableTargetFunction<MMPolicy>(mTargetBytes->GetMMPolicy());
+    }
+
+    WritableTargetFunction<MMPolicy> result(mTargetBytes->GetMMPolicy(),
+                                            mTargetBytes->GetBase() + aOffset,
+                                            effectiveLength);
+
+    return result;
+  }
+
+ private:
+  template <typename T>
+  struct ChasePointerHelper {
+    template <typename MMPolicy_>
+    static T Result(const MMPolicy_&, T aValue) {
+      return aValue;
+    }
+  };
+
+  template <typename T>
+  struct ChasePointerHelper<T*> {
+    template <typename MMPolicy_>
+    static auto Result(const MMPolicy_& aPolicy, T* aValue) {
+      ReadOnlyTargetFunction<MMPolicy_> ptr(aPolicy, aValue);
+      return ptr.template ChasePointer<T>();
+    }
+  };
+
+ public:
+  // Keep chasing pointers until T is not a pointer type anymore
+  template <typename T>
+  auto ChasePointer() {
+    mTargetBytes->EnsureLimit(mOffset + sizeof(T));
+    const std::remove_cv_t<T> result =
+        *reinterpret_cast<const std::remove_cv_t<T>*>(
+            mTargetBytes->GetLocalBytes() + mOffset);
+    return ChasePointerHelper<std::remove_cv_t<T>>::Result(
+        mTargetBytes->GetMMPolicy(), result);
+  }
+
+  uintptr_t ChasePointerFromDisp() {
+    uintptr_t ptrFromDisp = ReadDisp32AsAbsolute();
+    ReadOnlyTargetFunction<MMPolicy> ptr(
+        mTargetBytes->GetMMPolicy(),
+        reinterpret_cast<const void*>(ptrFromDisp));
+    return ptr.template ChasePointer<uintptr_t>();
+  }
+
+ private:
+  ReadOnlyTargetFunction(const ReadOnlyTargetFunction& aOther)
+      : mTargetBytes(aOther.mTargetBytes), mOffset(aOther.mOffset) {}
+
+  ReadOnlyTargetFunction(const ReadOnlyTargetFunction& aOther,
+                         const uint32_t aOffsetFromOther)
+      : mTargetBytes(TargetBytesPtr<MMPolicy>::CopyFromOffset(
+            aOther.mTargetBytes, aOffsetFromOther)),
+        mOffset(0) {}
+
+ private:
+  mutable typename TargetBytesPtr<MMPolicy>::Type mTargetBytes;
+  uint32_t mOffset;
+};
+
+template <typename MMPolicy, typename T>
+class MOZ_STACK_CLASS TargetObject {
+  mutable typename TargetBytesPtr<MMPolicy>::Type mTargetBytes;
+
+  TargetObject(const MMPolicy& aMMPolicy, const void* aBaseAddress)
+      : mTargetBytes(TargetBytesPtr<MMPolicy>::Make(aMMPolicy, aBaseAddress)) {
+    mTargetBytes->EnsureLimit(sizeof(T));
+  }
+
+ public:
+  explicit TargetObject(const MMPolicy& aMMPolicy)
+      : mTargetBytes(TargetBytesPtr<MMPolicy>::Make(aMMPolicy, nullptr)) {}
+
+  TargetObject(const MMPolicy& aMMPolicy, uintptr_t aBaseAddress)
+      : TargetObject(aMMPolicy, reinterpret_cast<const void*>(aBaseAddress)) {}
+
+  TargetObject(const TargetObject&) = delete;
+  TargetObject(TargetObject&&) = delete;
+  TargetObject& operator=(const TargetObject&) = delete;
+  TargetObject& operator=(TargetObject&&) = delete;
+
+  explicit operator bool() const {
+    return mTargetBytes->GetBase() && mTargetBytes->GetLocalBytes();
+  }
+
+  const T* operator->() const {
+    return reinterpret_cast<const T*>(mTargetBytes->GetLocalBytes());
+  }
+
+  const T* GetLocalBase() const {
+    return reinterpret_cast<const T*>(mTargetBytes->GetLocalBytes());
+  }
+};
+
+template <typename MMPolicy, typename T>
+class MOZ_STACK_CLASS TargetObjectArray {
+  mutable typename TargetBytesPtr<MMPolicy>::Type mTargetBytes;
+  size_t mNumOfItems;
+
+  TargetObjectArray(const MMPolicy& aMMPolicy, const void* aBaseAddress,
+                    size_t aNumOfItems)
+      : mTargetBytes(TargetBytesPtr<MMPolicy>::Make(aMMPolicy, aBaseAddress)),
+        mNumOfItems(aNumOfItems) {
+    uint32_t itemsRead =
+        mTargetBytes->TryEnsureLimit(sizeof(T) * mNumOfItems) / sizeof(T);
+    // itemsRead may be bigger than the requested amount because of buffering,
+    // but mNumOfItems should not include extra bytes of buffering.
+    if (itemsRead < mNumOfItems) {
+      mNumOfItems = itemsRead;
+    }
+  }
+
+  const T* GetLocalBase() const {
+    return reinterpret_cast<const T*>(mTargetBytes->GetLocalBytes());
+  }
+
+ public:
+  explicit TargetObjectArray(const MMPolicy& aMMPolicy)
+      : mTargetBytes(TargetBytesPtr<MMPolicy>::Make(aMMPolicy, nullptr)),
+        mNumOfItems(0) {}
+
+  TargetObjectArray(const MMPolicy& aMMPolicy, uintptr_t aBaseAddress,
+                    size_t aNumOfItems)
+      : TargetObjectArray(aMMPolicy,
+                          reinterpret_cast<const void*>(aBaseAddress),
+                          aNumOfItems) {}
+
+  TargetObjectArray(const TargetObjectArray&) = delete;
+  TargetObjectArray(TargetObjectArray&&) = delete;
+  TargetObjectArray& operator=(const TargetObjectArray&) = delete;
+  TargetObjectArray& operator=(TargetObjectArray&&) = delete;
+
+  explicit operator bool() const {
+    return mTargetBytes->GetBase() && mNumOfItems;
+  }
+
+  const T* operator[](size_t aIndex) const {
+    if (aIndex >= mNumOfItems) {
+      return nullptr;
+    }
+
+    return &GetLocalBase()[aIndex];
+  }
+
+  template <typename Comparator>
+  bool BinarySearchIf(const Comparator& aCompare,
+                      size_t* aMatchOrInsertionPoint) const {
+    return mozilla::BinarySearchIf(GetLocalBase(), 0, mNumOfItems, aCompare,
+                                   aMatchOrInsertionPoint);
+  }
+};
+
+}  // namespace interceptor
+}  // namespace mozilla
+
+#endif  // mozilla_interceptor_TargetFunction_h
diff --git a/toolkit/xre/dllservices/mozglue/interceptor/Trampoline.h b/toolkit/xre/dllservices/mozglue/interceptor/Trampoline.h
new file mode 100644
index 0000000000..befbd47215
--- /dev/null
+++ b/toolkit/xre/dllservices/mozglue/interceptor/Trampoline.h
@@ -0,0 +1,773 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_interceptor_Trampoline_h
+#define mozilla_interceptor_Trampoline_h
+
+#include "mozilla/Assertions.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/CheckedInt.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/Types.h"
+#include "mozilla/WindowsProcessMitigations.h"
+#include "mozilla/WindowsUnwindInfo.h"
+
+namespace mozilla {
+namespace interceptor {
+
+template <typename MMPolicy>
+class MOZ_STACK_CLASS Trampoline final {
+ public:
+  Trampoline(const MMPolicy* aMMPolicy, uint8_t* const aLocalBase,
+             const uintptr_t aRemoteBase, const uint32_t aChunkSize)
+      : mMMPolicy(aMMPolicy),
+        mPrevLocalProt(0),
+        mLocalBase(aLocalBase),
+        mRemoteBase(aRemoteBase),
+        mOffset(0),
+        mExeOffset(0),
+#ifdef _M_X64
+        mCopyCodesEndOffset(0),
+        mExeEndOffset(0),
+#endif  // _M_X64
+        mMaxOffset(aChunkSize),
+        mAccumulatedStatus(true) {
+    if (!::VirtualProtect(aLocalBase, aChunkSize,
+                          MMPolicy::GetTrampWriteProtFlags(),
+                          &mPrevLocalProt)) {
+      mPrevLocalProt = 0;
+    }
+  }
+
+  Trampoline(Trampoline&& aOther)
+      : mMMPolicy(aOther.mMMPolicy),
+        mPrevLocalProt(aOther.mPrevLocalProt),
+        mLocalBase(aOther.mLocalBase),
+        mRemoteBase(aOther.mRemoteBase),
+        mOffset(aOther.mOffset),
+        mExeOffset(aOther.mExeOffset),
+#ifdef _M_X64
+        mCopyCodesEndOffset(aOther.mCopyCodesEndOffset),
+        mExeEndOffset(aOther.mExeEndOffset),
+#endif  // _M_X64
+        mMaxOffset(aOther.mMaxOffset),
+        mAccumulatedStatus(aOther.mAccumulatedStatus) {
+    aOther.mPrevLocalProt = 0;
+    aOther.mAccumulatedStatus = false;
+  }
+
+  MOZ_IMPLICIT Trampoline(decltype(nullptr))
+      : mMMPolicy(nullptr),
+        mPrevLocalProt(0),
+        mLocalBase(nullptr),
+        mRemoteBase(0),
+        mOffset(0),
+        mExeOffset(0),
+#ifdef _M_X64
+        mCopyCodesEndOffset(0),
+        mExeEndOffset(0),
+#endif  // _M_X64
+        mMaxOffset(0),
+        mAccumulatedStatus(false) {
+  }
+
+  Trampoline(const Trampoline&) = delete;
+  Trampoline& operator=(const Trampoline&) = delete;
+
+  Trampoline& operator=(Trampoline&& aOther) {
+    Clear();
+
+    mMMPolicy = aOther.mMMPolicy;
+    mPrevLocalProt = aOther.mPrevLocalProt;
+    mLocalBase = aOther.mLocalBase;
+    mRemoteBase = aOther.mRemoteBase;
+    mOffset = aOther.mOffset;
+    mExeOffset = aOther.mExeOffset;
+#ifdef _M_X64
+    mCopyCodesEndOffset = aOther.mCopyCodesEndOffset;
+    mExeEndOffset = aOther.mExeEndOffset;
+#endif  // _M_X64
+    mMaxOffset = aOther.mMaxOffset;
+    mAccumulatedStatus = aOther.mAccumulatedStatus;
+
+    aOther.mPrevLocalProt = 0;
+    aOther.mAccumulatedStatus = false;
+
+    return *this;
+  }
+
+  ~Trampoline() { Clear(); }
+
+  explicit operator bool() const {
+    return IsNull() ||
+           (mLocalBase && mRemoteBase && mPrevLocalProt && mAccumulatedStatus);
+  }
+
+  bool IsNull() const { return !mMMPolicy; }
+
+#if defined(_M_ARM64)
+
+  void WriteInstruction(uint32_t aInstruction) {
+    const uint32_t kDelta = sizeof(uint32_t);
+
+    if (!mMMPolicy) {
+      // Null tramp, just track offset
+      mOffset += kDelta;
+      return;
+    }
+
+    if (mOffset + kDelta > mMaxOffset) {
+      mAccumulatedStatus = false;
+      return;
+    }
+
+    *reinterpret_cast<uint32_t*>(mLocalBase + mOffset) = aInstruction;
+    mOffset += kDelta;
+  }
+
+  void WriteLoadLiteral(const uintptr_t aAddress, const uint8_t aReg) {
+    const uint32_t kDelta = sizeof(uint32_t) + sizeof(uintptr_t);
+
+    if (!mMMPolicy) {
+      // Null tramp, just track offset
+      mOffset += kDelta;
+      return;
+    }
+
+    // We grow the literal pool from the *end* of the tramp,
+    // so we need to ensure that there is enough room for both an instruction
+    // and a pointer
+    if (mOffset + kDelta > mMaxOffset) {
+      mAccumulatedStatus = false;
+      return;
+    }
+
+    mMaxOffset -= sizeof(uintptr_t);
+    *reinterpret_cast<uintptr_t*>(mLocalBase + mMaxOffset) = aAddress;
+
+    CheckedInt<intptr_t> pc(GetCurrentRemoteAddress());
+    if (!pc.isValid()) {
+      mAccumulatedStatus = false;
+      return;
+    }
+
+    CheckedInt<intptr_t> literal(reinterpret_cast<uintptr_t>(mLocalBase) +
+                                 mMaxOffset);
+    if (!literal.isValid()) {
+      mAccumulatedStatus = false;
+      return;
+    }
+
+    CheckedInt<intptr_t> ptrOffset = (literal - pc);
+    if (!ptrOffset.isValid()) {
+      mAccumulatedStatus = false;
+      return;
+    }
+
+    // ptrOffset must be properly aligned
+    MOZ_ASSERT((ptrOffset.value() % 4) == 0);
+    ptrOffset /= 4;
+
+    CheckedInt<int32_t> offset(ptrOffset.value());
+    if (!offset.isValid()) {
+      mAccumulatedStatus = false;
+      return;
+    }
+
+    // Ensure that offset falls within the range of a signed 19-bit value
+    if (offset.value() < -0x40000 || offset.value() > 0x3FFFF) {
+      mAccumulatedStatus = false;
+      return;
+    }
+
+    const int32_t kimm19Mask = 0x7FFFF;
+    int32_t masked = offset.value() & kimm19Mask;
+
+    MOZ_ASSERT(aReg < 32);
+    uint32_t loadInstr = 0x58000000 | (masked << 5) | aReg;
+    WriteInstruction(loadInstr);
+  }
+
+#else
+
+  void WriteByte(uint8_t aValue) {
+    const uint32_t kDelta = sizeof(uint8_t);
+
+    if (!mMMPolicy) {
+      // Null tramp, just track offset
+      mOffset += kDelta;
+      return;
+    }
+
+    if (mOffset >= mMaxOffset) {
+      mAccumulatedStatus = false;
+      return;
+    }
+
+    *(mLocalBase + mOffset) = aValue;
+    ++mOffset;
+  }
+
+  void WriteInteger(int32_t aValue) {
+    const uint32_t kDelta = sizeof(int32_t);
+
+    if (!mMMPolicy) {
+      // Null tramp, just track offset
+      mOffset += kDelta;
+      return;
+    }
+
+    if (mOffset + kDelta > mMaxOffset) {
+      mAccumulatedStatus = false;
+      return;
+    }
+
+    *reinterpret_cast<int32_t*>(mLocalBase + mOffset) = aValue;
+    mOffset += kDelta;
+  }
+
+  void WriteDisp32(uintptr_t aAbsTarget) {
+    const uint32_t kDelta = sizeof(int32_t);
+
+    if (!mMMPolicy) {
+      // Null tramp, just track offset
+      mOffset += kDelta;
+      return;
+    }
+
+    if (mOffset + kDelta > mMaxOffset) {
+      mAccumulatedStatus = false;
+      return;
+    }
+
+    // This needs to be computed from the remote location
+    intptr_t remoteTrampPosition = static_cast<intptr_t>(mRemoteBase + mOffset);
+
+    intptr_t diff =
+        static_cast<intptr_t>(aAbsTarget) - (remoteTrampPosition + kDelta);
+
+    CheckedInt<int32_t> checkedDisp(diff);
+    MOZ_ASSERT(checkedDisp.isValid());
+    if (!checkedDisp.isValid()) {
+      mAccumulatedStatus = false;
+      return;
+    }
+
+    int32_t disp = checkedDisp.value();
+    *reinterpret_cast<int32_t*>(mLocalBase + mOffset) = disp;
+    mOffset += kDelta;
+  }
+
+  void WriteBytes(void* aAddr, size_t aSize) {
+    if (!mMMPolicy) {
+      // Null tramp, just track offset
+      mOffset += aSize;
+      return;
+    }
+
+    if (mOffset + aSize > mMaxOffset) {
+      mAccumulatedStatus = false;
+      return;
+    }
+
+    std::memcpy(reinterpret_cast<void*>(mLocalBase + mOffset), aAddr, aSize);
+    mOffset += aSize;
+  }
+
+#endif
+
+  void WritePointer(uintptr_t aValue) {
+    const uint32_t kDelta = sizeof(uintptr_t);
+
+    if (!mMMPolicy) {
+      // Null tramp, just track offset
+      mOffset += kDelta;
+      return;
+    }
+
+    if (mOffset + kDelta > mMaxOffset) {
+      mAccumulatedStatus = false;
+      return;
+    }
+
+    *reinterpret_cast<uintptr_t*>(mLocalBase + mOffset) = aValue;
+    mOffset += kDelta;
+  }
+
+  void WriteEncodedPointer(void* aValue) {
+    uintptr_t encoded = ReadOnlyTargetFunction<MMPolicy>::EncodePtr(aValue);
+    WritePointer(encoded);
+  }
+
+  Maybe<uintptr_t> ReadPointer() {
+    if (mOffset + sizeof(uintptr_t) > mMaxOffset) {
+      mAccumulatedStatus = false;
+      return Nothing();
+    }
+
+    auto result = Some(*reinterpret_cast<uintptr_t*>(mLocalBase + mOffset));
+    mOffset += sizeof(uintptr_t);
+    return std::move(result);
+  }
+
+  Maybe<uintptr_t> ReadEncodedPointer() {
+    Maybe<uintptr_t> encoded(ReadPointer());
+    if (!encoded) {
+      return encoded;
+    }
+
+    return Some(ReadOnlyTargetFunction<MMPolicy>::DecodePtr(encoded.value()));
+  }
+
+#if defined(_M_IX86)
+  // 32-bit only
+  void AdjustDisp32AtOffset(uint32_t aOffset, uintptr_t aAbsTarget) {
+    uint32_t effectiveOffset = mExeOffset + aOffset;
+
+    if (effectiveOffset + sizeof(int32_t) > mMaxOffset) {
+      mAccumulatedStatus = false;
+      return;
+    }
+
+    intptr_t diff = static_cast<intptr_t>(aAbsTarget) -
+                    static_cast<intptr_t>(mRemoteBase + mExeOffset);
+    *reinterpret_cast<int32_t*>(mLocalBase + effectiveOffset) += diff;
+  }
+#endif  // defined(_M_IX86)
+
+  void CopyFrom(uintptr_t aOrigBytes, uint32_t aNumBytes) {
+    if (!mMMPolicy) {
+      // Null tramp, just track offset
+      mOffset += aNumBytes;
+      return;
+    }
+
+    if (!mMMPolicy || mOffset + aNumBytes > mMaxOffset) {
+      mAccumulatedStatus = false;
+      return;
+    }
+
+    if (!mMMPolicy->Read(mLocalBase + mOffset,
+                         reinterpret_cast<void*>(aOrigBytes), aNumBytes)) {
+      mAccumulatedStatus = false;
+      return;
+    }
+
+    mOffset += aNumBytes;
+  }
+
+  void CopyCodes(uintptr_t aOrigBytes, uint32_t aNumBytes) {
+#ifdef _M_X64
+    if (mOffset == mCopyCodesEndOffset) {
+      mCopyCodesEndOffset += aNumBytes;
+    }
+#endif  // _M_X64
+    CopyFrom(aOrigBytes, aNumBytes);
+  }
+
+  void Rewind() { mOffset = 0; }
+
+  uintptr_t GetCurrentRemoteAddress() const { return mRemoteBase + mOffset; }
+
+  void StartExecutableCode() {
+    MOZ_ASSERT(!mExeOffset);
+    mExeOffset = mOffset;
+#ifdef _M_X64
+    mCopyCodesEndOffset = mOffset;
+#endif  // _M_X64
+  }
+
+  void* EndExecutableCode() {
+    if (!mAccumulatedStatus || !mMMPolicy) {
+      return nullptr;
+    }
+
+#ifdef _M_X64
+    mExeEndOffset = mOffset;
+#endif  // _M_X64
+
+    // This must always return the start address the executable code
+    // *in the target process*
+    return reinterpret_cast<void*>(mRemoteBase + mExeOffset);
+  }
+
+  uint32_t GetCurrentExecutableCodeLen() const { return mOffset - mExeOffset; }
+
+#ifdef _M_X64
+
+  void Align(uint32_t aAlignment) {
+    // aAlignment should be a power of 2
+    MOZ_ASSERT(!(aAlignment & (aAlignment - 1)));
+
+    uint32_t alignedOffset = (mOffset + aAlignment - 1) & ~(aAlignment - 1);
+    if (alignedOffset > mMaxOffset) {
+      mAccumulatedStatus = false;
+      return;
+    }
+    mOffset = alignedOffset;
+  }
+
+  // We assume that all instructions that are part of the prologue are left
+  // intact by detouring code, i.e. that they are copied using CopyCodes. This
+  // is not true for calls and jumps for example, but calls and jumps cannot be
+  // part of the prologue. This assumption allows us to copy unwind information
+  // as-is, because unwind information only refers to instructions within the
+  // prologue.
+  bool AddUnwindInfo(uintptr_t aOrigFuncAddr, uintptr_t aOrigFuncStopOffset) {
+    if constexpr (!MMPolicy::kSupportsUnwindInfo) {
+      return false;
+    }
+
+    if (!mMMPolicy) {
+      return false;
+    }
+
+    uint32_t origFuncOffsetFromBeginAddr = 0;
+    uint32_t origFuncOffsetToEndAddr = 0;
+    uintptr_t origImageBase = 0;
+    auto unwindInfoData =
+        mMMPolicy->LookupUnwindInfo(aOrigFuncAddr, &origFuncOffsetFromBeginAddr,
+                                    &origFuncOffsetToEndAddr, &origImageBase);
+    if (!unwindInfoData) {
+      // If the original function does not have unwind info, there is nothing
+      // more to do.
+      return true;
+    }
+
+    // We do not support hooking at a location that isn't the beginning of a
+    // function.
+    MOZ_ASSERT(origFuncOffsetFromBeginAddr == 0);
+    if (origFuncOffsetFromBeginAddr != 0) {
+      return false;
+    }
+
+    IterableUnwindInfo unwindInfoIt(unwindInfoData.get());
+    auto& unwindInfo = unwindInfoIt.Info();
+
+    // The prologue should contain only instructions that we detour using
+    // CopyCodes. If not, there is most likely a mismatch between the unwind
+    // information and the actual code we are detouring, so we stop here. This
+    // is a best-effort safeguard intended to detect situations where e.g.
+    // third-party injected code would have altered the function we are
+    // detouring.
+    if (mCopyCodesEndOffset < aOrigFuncStopOffset &&
+        unwindInfo.size_of_prolog > mCopyCodesEndOffset) {
+      return false;
+    }
+
+    // According to the documentation, the array is sorted by descending order
+    // of offset in the prologue. Let's double check this assumption if in
+    // debug. This also checks that the full unwind information isn't
+    // ill-formed, thanks to all the MOZ_ASSERT in iteration code.
+#  ifdef DEBUG
+    uint8_t previousOffset = 0xFF;
+    for (const auto& unwindCode : unwindInfoIt) {
+      MOZ_ASSERT(unwindCode.offset_in_prolog <= previousOffset);
+      previousOffset = unwindCode.offset_in_prolog;
+    }
+#  endif  // DEBUG
+
+    // We skip entries that are not part of the code we have detoured.
+    // This code relies on the array being sorted by descending order of offset
+    // in the prolog.
+    uint8_t firstRelevantCode = 0;
+    uint8_t countOfCodes = 0;
+    auto it = unwindInfoIt.begin();
+    for (; it != unwindInfoIt.end(); ++it) {
+      const auto& unwindCode = *it;
+      if (unwindCode.offset_in_prolog <= aOrigFuncStopOffset) {
+        // Found a relevant entry
+        firstRelevantCode = it.Index();
+        countOfCodes = unwindInfo.count_of_codes - firstRelevantCode;
+        break;
+      }
+    }
+
+    // Check that we encountered no ill-formed unwind codes.
+    if (!it.IsValid() && !it.IsAtEnd()) {
+      return false;
+    }
+
+    // We do not support chained unwind info. We should add support for chained
+    // unwind info if we ever reach this assert. Since we hook functions at
+    // their start address, this should not happen.
+    if (unwindInfo.flags & UNW_FLAG_CHAININFO) {
+      MOZ_ASSERT(
+          false,
+          "Tried to detour at a location with chained unwind information");
+      return false;
+    }
+
+    // We do not support exception handler info either. This could be a problem
+    // if we detour code that does not belong to the prologue and contains a
+    // call instruction, as this handler would then not be found if unwinding
+    // from callees. The following assert checks that this does not happen.
+    //
+    // Our current assumption is that all the functions we hook either have no
+    // associated exception handlers, or it is __GSHandlerCheck. This handler
+    // is the most commonly found, for example it is present in LdrLoadDll,
+    // SendMessageTimeoutW, GetWindowInfo. It is added to functions that use
+    // stack buffers, in order to mitigate stack buffer overflows. We explain
+    // below why it is not a problem that we do not preserve __GSHandlerCheck
+    // information when we detour code.
+    //
+    // Preserving exception handler information would raise two challenges:
+    //
+    // (1) if the exception handler was not written in a generic way, it may
+    //     behave differently when called for our detoured code compared to
+    //     what it would do if called from the original location of the code;
+    // (2) the exception handler can be followed by handler-specific data,
+    //     which we cannot copy because we do not know its size.
+    //
+    // __GSHandlerCheck checks that the stack cookie value wasn't overwritten
+    // before continuing to unwind and call further handlers. That is a
+    // security feature that we want to preserve. However, since these
+    // functions allocate stack space and write the stack cookie as part of
+    // their prologue, the 13 bytes that we detour are necessarily part of
+    // their prologue, which must contain at least the following instructions:
+    //
+    //   48 81 ec XX XX XX XX     sub rsp, 0xXXXXXXXX
+    //   48 8b 05 XX XX XX XX     mov rax, qword ptr [rip+__security_cookie]
+    //   48 33 c4                 xor rax, rsp
+    //   48 89 84 24 XX XX XX XX  mov qword ptr [RSP + 0xXXXXXXXX],RAX
+    //
+    // As a consequence, code associated with __GSHandlerCheck will necessarily
+    // satisfy (aOrigFuncStopOffset <= unwindInfo.size_of_prolog), and it is OK
+    // to not preserve handler info in that case.
+#  ifdef DEBUG
+    if (aOrigFuncStopOffset > unwindInfo.size_of_prolog) {
+      MOZ_ASSERT(!(unwindInfo.flags & (UNW_FLAG_EHANDLER | UNW_FLAG_UHANDLER)));
+    }
+#  endif  // DEBUG
+
+    // The unwind info must be DWORD-aligned
+    Align(sizeof(uint32_t));
+    if (!mAccumulatedStatus) {
+      return false;
+    }
+    uintptr_t unwindInfoOffset = mOffset;
+
+    unwindInfo.flags &=
+        ~(UNW_FLAG_CHAININFO | UNW_FLAG_EHANDLER | UNW_FLAG_UHANDLER);
+    unwindInfo.count_of_codes = countOfCodes;
+    if (aOrigFuncStopOffset < unwindInfo.size_of_prolog) {
+      unwindInfo.size_of_prolog = aOrigFuncStopOffset;
+    }
+
+    WriteBytes(reinterpret_cast<void*>(&unwindInfo),
+               offsetof(UnwindInfo, unwind_code));
+    if (!mAccumulatedStatus) {
+      return false;
+    }
+
+    WriteBytes(
+        reinterpret_cast<void*>(&unwindInfo.unwind_code[firstRelevantCode]),
+        countOfCodes * sizeof(UnwindCode));
+    if (!mAccumulatedStatus) {
+      return false;
+    }
+
+    // The function table must be DWORD-aligned
+    Align(sizeof(uint32_t));
+    if (!mAccumulatedStatus) {
+      return false;
+    }
+    uintptr_t functionTableOffset = mOffset;
+
+    WriteInteger(mExeOffset);
+    if (!mAccumulatedStatus) {
+      return false;
+    }
+
+    WriteInteger(mExeEndOffset);
+    if (!mAccumulatedStatus) {
+      return false;
+    }
+
+    WriteInteger(unwindInfoOffset);
+    if (!mAccumulatedStatus) {
+      return false;
+    }
+
+    return mMMPolicy->AddFunctionTable(mRemoteBase + functionTableOffset, 1,
+                                       mRemoteBase);
+  }
+
+#endif  // _M_X64
+
+  Trampoline<MMPolicy>& operator--() {
+    MOZ_ASSERT(mOffset);
+    --mOffset;
+    return *this;
+  }
+
+ private:
+  void Clear() {
+    if (!mLocalBase || !mPrevLocalProt) {
+      return;
+    }
+
+    DebugOnly<bool> ok = !!::VirtualProtect(mLocalBase, mMaxOffset,
+                                            mPrevLocalProt, &mPrevLocalProt);
+    MOZ_ASSERT(ok);
+
+    mLocalBase = nullptr;
+    mRemoteBase = 0;
+    mPrevLocalProt = 0;
+    mAccumulatedStatus = false;
+  }
+
+ private:
+  const MMPolicy* mMMPolicy;
+  DWORD mPrevLocalProt;
+  uint8_t* mLocalBase;
+  uintptr_t mRemoteBase;
+  uint32_t mOffset;
+  uint32_t mExeOffset;
+#ifdef _M_X64
+  uint32_t mCopyCodesEndOffset;
+  uint32_t mExeEndOffset;
+#endif  // _M_X64
+  uint32_t mMaxOffset;
+  bool mAccumulatedStatus;
+};
+
+template <typename MMPolicy>
+class MOZ_STACK_CLASS TrampolineCollection final {
+ public:
+  class MOZ_STACK_CLASS TrampolineIterator final {
+   public:
+    Trampoline<MMPolicy> operator*() {
+      uint32_t offset = mCurTramp * mCollection.mTrampSize;
+      return Trampoline<MMPolicy>(
+          &mCollection.mMMPolicy, mCollection.mLocalBase + offset,
+          mCollection.mRemoteBase + offset, mCollection.mTrampSize);
+    }
+
+    TrampolineIterator& operator++() {
+      ++mCurTramp;
+      return *this;
+    }
+
+    bool operator!=(const TrampolineIterator& aOther) const {
+      return mCurTramp != aOther.mCurTramp;
+    }
+
+   private:
+    explicit TrampolineIterator(
+        const TrampolineCollection<MMPolicy>& aCollection,
+        const uint32_t aCurTramp = 0)
+        : mCollection(aCollection), mCurTramp(aCurTramp) {}
+
+    const TrampolineCollection<MMPolicy>& mCollection;
+    uint32_t mCurTramp;
+
+    friend class TrampolineCollection<MMPolicy>;
+  };
+
+  explicit TrampolineCollection(const MMPolicy& aMMPolicy)
+      : mMMPolicy(aMMPolicy),
+        mLocalBase(0),
+        mRemoteBase(0),
+        mTrampSize(0),
+        mNumTramps(0),
+        mPrevProt(0),
+        mCS(nullptr) {}
+
+  TrampolineCollection(const MMPolicy& aMMPolicy, uint8_t* const aLocalBase,
+                       const uintptr_t aRemoteBase, const uint32_t aTrampSize,
+                       const uint32_t aNumTramps)
+      : mMMPolicy(aMMPolicy),
+        mLocalBase(aLocalBase),
+        mRemoteBase(aRemoteBase),
+        mTrampSize(aTrampSize),
+        mNumTramps(aNumTramps),
+        mPrevProt(0),
+        mCS(nullptr) {
+    if (!aNumTramps) {
+      return;
+    }
+
+    BOOL ok = mMMPolicy.Protect(aLocalBase, aNumTramps * aTrampSize,
+                                PAGE_EXECUTE_READWRITE, &mPrevProt);
+    if (!ok) {
+      // When destroying a sandboxed process that uses
+      // MITIGATION_DYNAMIC_CODE_DISABLE, we won't be allowed to write to our
+      // executable memory so we just do nothing.  If we fail to get access
+      // to memory for any other reason, we still don't want to crash but we
+      // do assert.
+      MOZ_ASSERT(IsDynamicCodeDisabled());
+      mNumTramps = 0;
+      mPrevProt = 0;
+    }
+  }
+
+  ~TrampolineCollection() {
+    if (!mPrevProt) {
+      return;
+    }
+
+    mMMPolicy.Protect(mLocalBase, mNumTramps * mTrampSize, mPrevProt,
+                      &mPrevProt);
+
+    if (mCS) {
+      ::LeaveCriticalSection(mCS);
+    }
+  }
+
+  void Lock(CRITICAL_SECTION& aCS) {
+    if (!mPrevProt || mCS) {
+      return;
+    }
+
+    mCS = &aCS;
+    ::EnterCriticalSection(&aCS);
+  }
+
+  TrampolineIterator begin() const {
+    if (!mPrevProt) {
+      return end();
+    }
+
+    return TrampolineIterator(*this);
+  }
+
+  TrampolineIterator end() const {
+    return TrampolineIterator(*this, mNumTramps);
+  }
+
+  TrampolineCollection(const TrampolineCollection&) = delete;
+  TrampolineCollection& operator=(const TrampolineCollection&) = delete;
+  TrampolineCollection& operator=(TrampolineCollection&&) = delete;
+
+  TrampolineCollection(TrampolineCollection&& aOther)
+      : mMMPolicy(aOther.mMMPolicy),
+        mLocalBase(aOther.mLocalBase),
+        mRemoteBase(aOther.mRemoteBase),
+        mTrampSize(aOther.mTrampSize),
+        mNumTramps(aOther.mNumTramps),
+        mPrevProt(aOther.mPrevProt),
+        mCS(aOther.mCS) {
+    aOther.mPrevProt = 0;
+    aOther.mCS = nullptr;
+  }
+
+ private:
+  const MMPolicy& mMMPolicy;
+  uint8_t* const mLocalBase;
+  const uintptr_t mRemoteBase;
+  const uint32_t mTrampSize;
+  uint32_t mNumTramps;
+  uint32_t mPrevProt;
+  CRITICAL_SECTION* mCS;
+
+  friend class TrampolineIterator;
+};
+
+}  // namespace interceptor
+}  // namespace mozilla
+
+#endif  // mozilla_interceptor_Trampoline_h
diff --git a/toolkit/xre/dllservices/mozglue/interceptor/VMSharingPolicies.h b/toolkit/xre/dllservices/mozglue/interceptor/VMSharingPolicies.h
new file mode 100644
index 0000000000..8f93f5c1ad
--- /dev/null
+++ b/toolkit/xre/dllservices/mozglue/interceptor/VMSharingPolicies.h
@@ -0,0 +1,285 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_interceptor_VMSharingPolicies_h
+#define mozilla_interceptor_VMSharingPolicies_h
+
+#include "mozilla/Assertions.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/Types.h"
+
+namespace mozilla {
+namespace interceptor {
+
+/**
+ * This class is an abstraction of a reservation of virtual address space that
+ * has been obtained from a VMSharingPolicy via the policy's |Reserve| method.
+ *
+ * TrampolinePool allows us to obtain a trampoline without needing to concern
+ * ourselves with the underlying implementation of the VM sharing policy.
+ *
+ * For example, VMSharingPolicyShared delegates to VMSharingPolicyUnique, but
+ * also requires taking a lock before doing so. By invoking |GetNextTrampoline|
+ * on a TrampolinePool, the caller does not need to concern themselves with
+ * that detail.
+ *
+ * We accompolish this with a recursive implementation that provides an inner
+ * TrampolinePool that is provided by the delegated VMSharingPolicy.
+ */
+template <typename VMPolicyT, typename InnerT>
+class MOZ_STACK_CLASS TrampolinePool final {
+ public:
+  TrampolinePool(TrampolinePool&& aOther) = default;
+
+  TrampolinePool(VMPolicyT& aVMPolicy, InnerT&& aInner)
+      : mVMPolicy(aVMPolicy), mInner(std::move(aInner)) {}
+
+  TrampolinePool& operator=(TrampolinePool&& aOther) = delete;
+  TrampolinePool(const TrampolinePool&) = delete;
+  TrampolinePool& operator=(const TrampolinePool&) = delete;
+
+  using MMPolicyT = typename VMPolicyT::MMPolicyT;
+
+  Maybe<Trampoline<MMPolicyT>> GetNextTrampoline() {
+    return mVMPolicy.GetNextTrampoline(mInner);
+  }
+
+#if defined(_M_X64)
+  bool IsInLowest2GB() const {
+    return mVMPolicy.IsTrampolineSpaceInLowest2GB(mInner);
+  }
+#endif  // defined(_M_X64)
+
+ private:
+  VMPolicyT& mVMPolicy;
+  InnerT mInner;
+};
+
+/**
+ * This specialization is the base case for TrampolinePool, and is used by
+ * VMSharingPolicyUnique (since that policy does not delegate anything).
+ */
+template <typename VMPolicyT>
+class MOZ_STACK_CLASS TrampolinePool<VMPolicyT, decltype(nullptr)> final {
+ public:
+  explicit TrampolinePool(VMPolicyT& aVMPolicy) : mVMPolicy(aVMPolicy) {}
+
+  TrampolinePool(TrampolinePool&& aOther) = default;
+
+  TrampolinePool& operator=(TrampolinePool&& aOther) = delete;
+  TrampolinePool(const TrampolinePool&) = delete;
+  TrampolinePool& operator=(const TrampolinePool&) = delete;
+
+  using MMPolicyT = typename VMPolicyT::MMPolicyT;
+
+  Maybe<Trampoline<MMPolicyT>> GetNextTrampoline() {
+    return mVMPolicy.GetNextTrampoline();
+  }
+
+#if defined(_M_X64)
+  bool IsInLowest2GB() const {
+    return mVMPolicy.IsTrampolineSpaceInLowest2GB();
+  }
+#endif  // defined(_M_X64)
+
+ private:
+  VMPolicyT& mVMPolicy;
+};
+
+template <typename MMPolicy>
+class VMSharingPolicyUnique : public MMPolicy {
+  using ThisType = VMSharingPolicyUnique<MMPolicy>;
+
+ public:
+  using PoolType = TrampolinePool<ThisType, decltype(nullptr)>;
+
+  template <typename... Args>
+  explicit VMSharingPolicyUnique(Args&&... aArgs)
+      : MMPolicy(std::forward<Args>(aArgs)...), mNextChunkIndex(0) {}
+
+  Maybe<PoolType> Reserve(const uintptr_t aPivotAddr,
+                          const uint32_t aMaxDistanceFromPivot) {
+    // Win32 allocates VM addresses at a 64KiB granularity, so we might as well
+    // utilize that entire 64KiB reservation.
+    uint32_t len = MMPolicy::GetAllocGranularity();
+
+    Maybe<Span<const uint8_t>> maybeBounds = MMPolicy::SpanFromPivotAndDistance(
+        len, aPivotAddr, aMaxDistanceFromPivot);
+
+    return Reserve(len, maybeBounds);
+  }
+
+  Maybe<PoolType> Reserve(const uint32_t aSize,
+                          const Maybe<Span<const uint8_t>>& aBounds) {
+    uint32_t bytesReserved = MMPolicy::Reserve(aSize, aBounds);
+    if (!bytesReserved) {
+      return Nothing();
+    }
+
+    return Some(PoolType(*this));
+  }
+
+  TrampolineCollection<MMPolicy> Items() const {
+    return TrampolineCollection<MMPolicy>(*this, this->GetLocalView(),
+                                          this->GetRemoteView(), kChunkSize,
+                                          mNextChunkIndex);
+  }
+
+  void Clear() { mNextChunkIndex = 0; }
+
+  ~VMSharingPolicyUnique() = default;
+
+  VMSharingPolicyUnique(const VMSharingPolicyUnique&) = delete;
+  VMSharingPolicyUnique& operator=(const VMSharingPolicyUnique&) = delete;
+
+  VMSharingPolicyUnique(VMSharingPolicyUnique&& aOther)
+      : MMPolicy(std::move(aOther)), mNextChunkIndex(aOther.mNextChunkIndex) {
+    aOther.mNextChunkIndex = 0;
+  }
+
+  VMSharingPolicyUnique& operator=(VMSharingPolicyUnique&& aOther) {
+    static_cast<MMPolicy&>(*this) = std::move(aOther);
+    mNextChunkIndex = aOther.mNextChunkIndex;
+    aOther.mNextChunkIndex = 0;
+    return *this;
+  }
+
+ protected:
+  // In VMSharingPolicyUnique we do not implement the overload that accepts
+  // an inner trampoline pool, as this policy is expected to be the
+  // implementation of the base case.
+  Maybe<Trampoline<MMPolicy>> GetNextTrampoline() {
+    uint32_t offset = mNextChunkIndex * kChunkSize;
+    if (!this->MaybeCommitNextPage(offset, kChunkSize)) {
+      return Nothing();
+    }
+
+    Trampoline<MMPolicy> result(this, this->GetLocalView() + offset,
+                                this->GetRemoteView() + offset, kChunkSize);
+    if (!!result) {
+      ++mNextChunkIndex;
+    }
+
+    return Some(std::move(result));
+  }
+
+ private:
+  uint32_t mNextChunkIndex;
+  static const uint32_t kChunkSize = 128;
+
+  template <typename VMPolicyT, typename FriendT>
+  friend class TrampolinePool;
+};
+
+}  // namespace interceptor
+}  // namespace mozilla
+
+// We don't include RangeMap.h until this point because it depends on the
+// TrampolinePool definitions from above.
+#include "mozilla/interceptor/RangeMap.h"
+
+namespace mozilla {
+namespace interceptor {
+
+// We only support this policy for in-proc MMPolicy.
+class MOZ_TRIVIAL_CTOR_DTOR VMSharingPolicyShared : public MMPolicyInProcess {
+  typedef VMSharingPolicyUnique<MMPolicyInProcess> UniquePolicyT;
+  typedef VMSharingPolicyShared ThisType;
+
+ public:
+  using PoolType = TrampolinePool<ThisType, UniquePolicyT::PoolType>;
+  using MMPolicyT = MMPolicyInProcess;
+
+  constexpr VMSharingPolicyShared() {}
+
+  bool ShouldUnhookUponDestruction() const { return false; }
+
+  Maybe<PoolType> Reserve(const uintptr_t aPivotAddr,
+                          const uint32_t aMaxDistanceFromPivot) {
+    // Win32 allocates VM addresses at a 64KiB granularity, so we might as well
+    // utilize that entire 64KiB reservation.
+    uint32_t len = this->GetAllocGranularity();
+
+    Maybe<Span<const uint8_t>> maybeBounds =
+        MMPolicyInProcess::SpanFromPivotAndDistance(len, aPivotAddr,
+                                                    aMaxDistanceFromPivot);
+
+    AutoCriticalSection lock(GetCS());
+    VMSharingPolicyUnique<MMPolicyT>* uniquePol = sVMMap.GetPolicy(maybeBounds);
+    MOZ_ASSERT(uniquePol);
+    if (!uniquePol) {
+      return Nothing();
+    }
+
+    Maybe<UniquePolicyT::PoolType> maybeUnique =
+        uniquePol->Reserve(len, maybeBounds);
+    if (!maybeUnique) {
+      return Nothing();
+    }
+
+    return Some(PoolType(*this, std::move(maybeUnique.ref())));
+  }
+
+  TrampolineCollection<MMPolicyInProcess> Items() const {
+    // Since ShouldUnhookUponDestruction returns false, this can be empty
+    return TrampolineCollection<MMPolicyInProcess>(*this);
+  }
+
+  void Clear() {
+    // This must be a no-op for shared VM policy; we can't have one interceptor
+    // wiping out trampolines for all interceptors in the process.
+  }
+
+  VMSharingPolicyShared(const VMSharingPolicyShared&) = delete;
+  VMSharingPolicyShared(VMSharingPolicyShared&&) = delete;
+  VMSharingPolicyShared& operator=(const VMSharingPolicyShared&) = delete;
+  VMSharingPolicyShared& operator=(VMSharingPolicyShared&&) = delete;
+
+ private:
+  static CRITICAL_SECTION* GetCS() {
+    static const bool isAlloc = []() -> bool {
+      DWORD flags = 0;
+#if defined(RELEASE_OR_BETA)
+      flags |= CRITICAL_SECTION_NO_DEBUG_INFO;
+#endif  // defined(RELEASE_OR_BETA)
+      ::InitializeCriticalSectionEx(&sCS, 4000, flags);
+      return true;
+    }();
+    Unused << isAlloc;
+
+    return &sCS;
+  }
+
+  // In VMSharingPolicyShared, we only implement the overload that accepts
+  // a VMSharingPolicyUnique trampoline pool as |aInner|, since we require the
+  // former policy to wrap the latter.
+  Maybe<Trampoline<MMPolicyInProcess>> GetNextTrampoline(
+      UniquePolicyT::PoolType& aInner) {
+    AutoCriticalSection lock(GetCS());
+    return aInner.GetNextTrampoline();
+  }
+
+#if defined(_M_X64)
+  bool IsTrampolineSpaceInLowest2GB(
+      const UniquePolicyT::PoolType& aInner) const {
+    AutoCriticalSection lock(GetCS());
+    return aInner.IsInLowest2GB();
+  }
+#endif  // defined(_M_X64)
+
+ private:
+  template <typename VMPolicyT, typename InnerT>
+  friend class TrampolinePool;
+
+  inline static RangeMap<MMPolicyInProcess> sVMMap;
+  inline static CRITICAL_SECTION sCS;
+};
+
+}  // namespace interceptor
+}  // namespace mozilla
+
+#endif  // mozilla_interceptor_VMSharingPolicies_h
diff --git a/toolkit/xre/dllservices/mozglue/interceptor/moz.build b/toolkit/xre/dllservices/mozglue/interceptor/moz.build
new file mode 100644
index 0000000000..561e33b147
--- /dev/null
+++ b/toolkit/xre/dllservices/mozglue/interceptor/moz.build
@@ -0,0 +1,26 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+EXPORTS.mozilla.interceptor += [
+    "Arm64.h",
+    "MMPolicies.h",
+    "PatcherBase.h",
+    "PatcherDetour.h",
+    "PatcherNopSpace.h",
+    "RangeMap.h",
+    "TargetFunction.h",
+    "Trampoline.h",
+    "VMSharingPolicies.h",
+]
+
+if CONFIG["CPU_ARCH"] == "aarch64":
+    Library("interceptor")
+
+    FINAL_LIBRARY = "mozglue"
+
+    UNIFIED_SOURCES += [
+        "Arm64.cpp",
+    ]
diff --git a/toolkit/xre/dllservices/mozglue/moz.build b/toolkit/xre/dllservices/mozglue/moz.build
new file mode 100644
index 0000000000..72b39a6b8a
--- /dev/null
+++ b/toolkit/xre/dllservices/mozglue/moz.build
@@ -0,0 +1,80 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+Library("dllservices_mozglue")
+
+if CONFIG["MOZ_WIDGET_TOOLKIT"]:
+    SOURCES += [
+        # This file contains a |using namespace mozilla;| statement
+        "WindowsDllBlocklist.cpp",
+    ]
+
+    UNIFIED_SOURCES += [
+        "Authenticode.cpp",
+        "LoaderObserver.cpp",
+        "ModuleLoadFrame.cpp",
+        "WindowsBCryptInitialization.cpp",
+        "WindowsFallbackLoaderAPI.cpp",
+    ]
+
+if not CONFIG["JS_STANDALONE"]:
+    UNIFIED_SOURCES += [
+        "CacheNtDllThunk.cpp",
+    ]
+
+OS_LIBS += [
+    "crypt32",
+    "ntdll",
+    "version",
+    "wintrust",
+]
+
+DELAYLOAD_DLLS += [
+    "crypt32.dll",
+    "wintrust.dll",
+]
+
+EXPORTS += [
+    "nsWindowsDllInterceptor.h",
+]
+
+EXPORTS.mozilla += [
+    "Authenticode.h",
+    "CacheNtDllThunk.h",
+    "LoaderAPIInterfaces.h",
+    "ModuleLoadInfo.h",
+    "WindowsBCryptInitialization.h",
+    "WindowsDllBlocklist.h",
+    "WindowsDllBlocklistCommon.h",
+    "WindowsDllBlocklistInfo.h",
+]
+
+EXPORTS.mozilla.glue += [
+    "SharedSection.h",
+    "WindowsDllServices.h",
+]
+
+# Generate DLL Blocklists
+blocklist_header_types = ["A11y", "Launcher", "Legacy", "Test"]
+blocklist_file_leaf_tpl = "WindowsDllBlocklist{0}Defs.h"
+blocklist_files = tuple(
+    [blocklist_file_leaf_tpl.format(type) for type in blocklist_header_types]
+)
+
+GeneratedFile(
+    *blocklist_files,
+    script="gen_dll_blocklist_defs.py",
+    entry_point="gen_blocklists",
+    inputs=["WindowsDllBlocklistDefs.in"]
+)
+
+EXPORTS.mozilla += ["!" + hdr for hdr in blocklist_files]
+
+DIRS += [
+    "interceptor",
+]
+
+FINAL_LIBRARY = "mozglue"
diff --git a/toolkit/xre/dllservices/mozglue/nsWindowsDllInterceptor.h b/toolkit/xre/dllservices/mozglue/nsWindowsDllInterceptor.h
new file mode 100644
index 0000000000..1211b49526
--- /dev/null
+++ b/toolkit/xre/dllservices/mozglue/nsWindowsDllInterceptor.h
@@ -0,0 +1,819 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef NS_WINDOWS_DLL_INTERCEPTOR_H_
+#define NS_WINDOWS_DLL_INTERCEPTOR_H_
+
+#include <wchar.h>
+#include <windows.h>
+#include <winternl.h>
+
+#include <utility>
+
+#include "mozilla/ArrayUtils.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/Atomics.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/CheckedInt.h"
+#include "mozilla/DebugOnly.h"
+#include "mozilla/NativeNt.h"
+
+#include "mozilla/Types.h"
+#include "mozilla/UniquePtr.h"
+#include "mozilla/Vector.h"
+#include "mozilla/interceptor/MMPolicies.h"
+#include "mozilla/interceptor/PatcherDetour.h"
+#include "mozilla/interceptor/PatcherNopSpace.h"
+#include "mozilla/interceptor/VMSharingPolicies.h"
+#include "nsWindowsHelpers.h"
+
+/*
+ * Simple function interception.
+ *
+ * We have two separate mechanisms for intercepting a function: We can use the
+ * built-in nop space, if it exists, or we can create a detour.
+ *
+ * Using the built-in nop space works as follows: On x86-32, DLL functions
+ * begin with a two-byte nop (mov edi, edi) and are preceeded by five bytes of
+ * NOP instructions.
+ *
+ * When we detect a function with this prelude, we do the following:
+ *
+ * 1. Write a long jump to our interceptor function into the five bytes of NOPs
+ *    before the function.
+ *
+ * 2. Write a short jump -5 into the two-byte nop at the beginning of the
+ *    function.
+ *
+ * This mechanism is nice because it's thread-safe.  It's even safe to do if
+ * another thread is currently running the function we're modifying!
+ *
+ * When the WindowsDllNopSpacePatcher is destroyed, we overwrite the short jump
+ * but not the long jump, so re-intercepting the same function won't work,
+ * because its prelude won't match.
+ *
+ *
+ * Unfortunately nop space patching doesn't work on functions which don't have
+ * this magic prelude (and in particular, x86-64 never has the prelude).  So
+ * when we can't use the built-in nop space, we fall back to using a detour,
+ * which works as follows:
+ *
+ * 1. Save first N bytes of OrigFunction to trampoline, where N is a
+ *    number of bytes >= 5 that are instruction aligned.
+ *
+ * 2. Replace first 5 bytes of OrigFunction with a jump to the Hook
+ *    function.
+ *
+ * 3. After N bytes of the trampoline, add a jump to OrigFunction+N to
+ *    continue original program flow.
+ *
+ * 4. Hook function needs to call the trampoline during its execution,
+ *    to invoke the original function (so address of trampoline is
+ *    returned).
+ *
+ * When the WindowsDllDetourPatcher object is destructed, OrigFunction is
+ * patched again to jump directly to the trampoline instead of going through
+ * the hook function. As such, re-intercepting the same function won't work, as
+ * jump instructions are not supported.
+ *
+ * Note that this is not thread-safe.  Sad day.
+ *
+ */
+
+#if defined(_M_IX86) && defined(__clang__) && __has_declspec_attribute(guard)
+// On x86, nop-space patches return to the second instruction of their target.
+// This is a deliberate violation of Control Flow Guard, so disable the check.
+#  define INTERCEPTOR_DISABLE_CFGUARD __declspec(guard(nocf))
+#else
+#  define INTERCEPTOR_DISABLE_CFGUARD /* nothing */
+#endif
+
+namespace mozilla {
+namespace interceptor {
+
+template <typename T>
+struct OriginalFunctionPtrTraits;
+
+template <typename R, typename... Args>
+struct OriginalFunctionPtrTraits<R (*)(Args...)> {
+  using ReturnType = R;
+};
+
+#if defined(_M_IX86)
+template <typename R, typename... Args>
+struct OriginalFunctionPtrTraits<R(__stdcall*)(Args...)> {
+  using ReturnType = R;
+};
+
+template <typename R, typename... Args>
+struct OriginalFunctionPtrTraits<R(__fastcall*)(Args...)> {
+  using ReturnType = R;
+};
+#endif  // defined(_M_IX86)
+
+template <typename InterceptorT, typename FuncPtrT>
+class FuncHook final {
+ public:
+  using ThisType = FuncHook<InterceptorT, FuncPtrT>;
+  using ReturnType = typename OriginalFunctionPtrTraits<FuncPtrT>::ReturnType;
+
+  constexpr FuncHook() : mOrigFunc(nullptr), mInitOnce(INIT_ONCE_STATIC_INIT) {}
+
+  ~FuncHook() = default;
+
+  bool Set(InterceptorT& aInterceptor, const char* aName, FuncPtrT aHookDest) {
+    LPVOID addHookOk = nullptr;
+    InitOnceContext ctx(this, &aInterceptor, aName, aHookDest, false);
+
+    return ::InitOnceExecuteOnce(&mInitOnce, &InitOnceCallback, &ctx,
+                                 &addHookOk) &&
+           addHookOk;
+  }
+
+  bool SetDetour(InterceptorT& aInterceptor, const char* aName,
+                 FuncPtrT aHookDest) {
+    LPVOID addHookOk = nullptr;
+    InitOnceContext ctx(this, &aInterceptor, aName, aHookDest, true);
+
+    return ::InitOnceExecuteOnce(&mInitOnce, &InitOnceCallback, &ctx,
+                                 &addHookOk) &&
+           addHookOk;
+  }
+
+  explicit operator bool() const { return !!mOrigFunc; }
+
+  template <typename... ArgsType>
+  INTERCEPTOR_DISABLE_CFGUARD ReturnType operator()(ArgsType&&... aArgs) const {
+    return mOrigFunc(std::forward<ArgsType>(aArgs)...);
+  }
+
+  FuncPtrT GetStub() const { return mOrigFunc; }
+
+  // One-time init stuff cannot be moved or copied
+  FuncHook(const FuncHook&) = delete;
+  FuncHook(FuncHook&&) = delete;
+  FuncHook& operator=(const FuncHook&) = delete;
+  FuncHook& operator=(FuncHook&& aOther) = delete;
+
+ private:
+  struct MOZ_RAII InitOnceContext final {
+    InitOnceContext(ThisType* aHook, InterceptorT* aInterceptor,
+                    const char* aName, FuncPtrT aHookDest, bool aForceDetour)
+        : mHook(aHook),
+          mInterceptor(aInterceptor),
+          mName(aName),
+          mHookDest(reinterpret_cast<void*>(aHookDest)),
+          mForceDetour(aForceDetour) {}
+
+    ThisType* mHook;
+    InterceptorT* mInterceptor;
+    const char* mName;
+    void* mHookDest;
+    bool mForceDetour;
+  };
+
+ private:
+  bool Apply(InterceptorT* aInterceptor, const char* aName, void* aHookDest) {
+    return aInterceptor->AddHook(aName, reinterpret_cast<intptr_t>(aHookDest),
+                                 reinterpret_cast<void**>(&mOrigFunc));
+  }
+
+  bool ApplyDetour(InterceptorT* aInterceptor, const char* aName,
+                   void* aHookDest) {
+    return aInterceptor->AddDetour(aName, reinterpret_cast<intptr_t>(aHookDest),
+                                   reinterpret_cast<void**>(&mOrigFunc));
+  }
+
+  static BOOL CALLBACK InitOnceCallback(PINIT_ONCE aInitOnce, PVOID aParam,
+                                        PVOID* aOutContext) {
+    MOZ_ASSERT(aOutContext);
+
+    bool result;
+    auto ctx = reinterpret_cast<InitOnceContext*>(aParam);
+    if (ctx->mForceDetour) {
+      result = ctx->mHook->ApplyDetour(ctx->mInterceptor, ctx->mName,
+                                       ctx->mHookDest);
+    } else {
+      result = ctx->mHook->Apply(ctx->mInterceptor, ctx->mName, ctx->mHookDest);
+    }
+
+    *aOutContext =
+        result ? reinterpret_cast<PVOID>(1U << INIT_ONCE_CTX_RESERVED_BITS)
+               : nullptr;
+    return TRUE;
+  }
+
+ private:
+  FuncPtrT mOrigFunc;
+  INIT_ONCE mInitOnce;
+};
+
+template <typename InterceptorT, typename FuncPtrT>
+class MOZ_ONLY_USED_TO_AVOID_STATIC_CONSTRUCTORS FuncHookCrossProcess final {
+ public:
+  using ThisType = FuncHookCrossProcess<InterceptorT, FuncPtrT>;
+  using ReturnType = typename OriginalFunctionPtrTraits<FuncPtrT>::ReturnType;
+
+#if defined(DEBUG)
+  FuncHookCrossProcess() {}
+#endif  // defined(DEBUG)
+
+  bool Set(nt::CrossExecTransferManager& aTransferMgr,
+           InterceptorT& aInterceptor, const char* aName, FuncPtrT aHookDest) {
+    FuncPtrT origFunc;
+    if (!aInterceptor.AddHook(aName, reinterpret_cast<intptr_t>(aHookDest),
+                              reinterpret_cast<void**>(&origFunc))) {
+      return false;
+    }
+
+    return CopyStubToChildProcess(aTransferMgr, aInterceptor, origFunc);
+  }
+
+  bool SetDetour(nt::CrossExecTransferManager& aTransferMgr,
+                 InterceptorT& aInterceptor, const char* aName,
+                 FuncPtrT aHookDest) {
+    FuncPtrT origFunc;
+    if (!aInterceptor.AddDetour(aName, reinterpret_cast<intptr_t>(aHookDest),
+                                reinterpret_cast<void**>(&origFunc))) {
+      return false;
+    }
+
+    return CopyStubToChildProcess(aTransferMgr, aInterceptor, origFunc);
+  }
+
+  explicit operator bool() const { return !!mOrigFunc; }
+
+  /**
+   * NB: This operator is only meaningful when invoked in the target process!
+   */
+  template <typename... ArgsType>
+  ReturnType operator()(ArgsType&&... aArgs) const {
+    return mOrigFunc(std::forward<ArgsType>(aArgs)...);
+  }
+
+#if defined(DEBUG)
+  FuncHookCrossProcess(const FuncHookCrossProcess&) = delete;
+  FuncHookCrossProcess(FuncHookCrossProcess&&) = delete;
+  FuncHookCrossProcess& operator=(const FuncHookCrossProcess&) = delete;
+  FuncHookCrossProcess& operator=(FuncHookCrossProcess&& aOther) = delete;
+#endif  // defined(DEBUG)
+
+ private:
+  bool CopyStubToChildProcess(nt::CrossExecTransferManager& aTransferMgr,
+                              InterceptorT& aInterceptor, FuncPtrT aStub) {
+    LauncherVoidResult writeResult =
+        aTransferMgr.Transfer(&mOrigFunc, &aStub, sizeof(FuncPtrT));
+    if (writeResult.isErr()) {
+#ifdef MOZ_USE_LAUNCHER_ERROR
+      const mozilla::WindowsError& err = writeResult.inspectErr().mError;
+#else
+      const mozilla::WindowsError& err = writeResult.inspectErr();
+#endif
+      aInterceptor.SetLastDetourError(FUNCHOOKCROSSPROCESS_COPYSTUB_ERROR,
+                                      err.AsHResult());
+      return false;
+    }
+    return true;
+  }
+
+ private:
+  FuncPtrT mOrigFunc;
+};
+
+template <typename MMPolicyT, typename InterceptorT>
+struct TypeResolver;
+
+template <typename InterceptorT>
+struct TypeResolver<mozilla::interceptor::MMPolicyInProcess, InterceptorT> {
+  template <typename FuncPtrT>
+  using FuncHookType = FuncHook<InterceptorT, FuncPtrT>;
+};
+
+template <typename InterceptorT>
+struct TypeResolver<mozilla::interceptor::MMPolicyOutOfProcess, InterceptorT> {
+  template <typename FuncPtrT>
+  using FuncHookType = FuncHookCrossProcess<InterceptorT, FuncPtrT>;
+};
+
+template <typename VMPolicy = mozilla::interceptor::VMSharingPolicyShared>
+class WindowsDllInterceptor final
+    : public TypeResolver<typename VMPolicy::MMPolicyT,
+                          WindowsDllInterceptor<VMPolicy>> {
+  typedef WindowsDllInterceptor<VMPolicy> ThisType;
+
+  interceptor::WindowsDllDetourPatcher<VMPolicy> mDetourPatcher;
+#if defined(_M_IX86)
+  interceptor::WindowsDllNopSpacePatcher<typename VMPolicy::MMPolicyT>
+      mNopSpacePatcher;
+#endif  // defined(_M_IX86)
+
+  HMODULE mModule;
+
+ public:
+  template <typename... Args>
+  explicit WindowsDllInterceptor(Args&&... aArgs)
+      : mDetourPatcher(std::forward<Args>(aArgs)...)
+#if defined(_M_IX86)
+        ,
+        mNopSpacePatcher(std::forward<Args>(aArgs)...)
+#endif  // defined(_M_IX86)
+        ,
+        mModule(nullptr) {
+  }
+
+  WindowsDllInterceptor(const WindowsDllInterceptor&) = delete;
+  WindowsDllInterceptor(WindowsDllInterceptor&&) = delete;
+  WindowsDllInterceptor& operator=(const WindowsDllInterceptor&) = delete;
+  WindowsDllInterceptor& operator=(WindowsDllInterceptor&&) = delete;
+
+  ~WindowsDllInterceptor() { Clear(); }
+
+  template <size_t N>
+  void Init(const char (&aModuleName)[N]) {
+    wchar_t moduleName[N];
+
+    for (size_t i = 0; i < N; ++i) {
+      MOZ_ASSERT(!(aModuleName[i] & 0x80),
+                 "Use wide-character overload for non-ASCII module names");
+      moduleName[i] = aModuleName[i];
+    }
+
+    Init(moduleName);
+  }
+
+  void Init(const wchar_t* aModuleName) {
+    if (mModule) {
+      return;
+    }
+
+    mModule = ::LoadLibraryW(aModuleName);
+  }
+
+  /** Force a specific configuration for testing purposes. NOT to be used in
+      production code! **/
+  void TestOnlyDetourInit(const wchar_t* aModuleName, DetourFlags aFlags) {
+    Init(aModuleName);
+    mDetourPatcher.Init(aFlags);
+  }
+
+  void Clear() {
+    if (!mModule) {
+      return;
+    }
+
+#if defined(_M_IX86)
+    mNopSpacePatcher.Clear();
+#endif  // defined(_M_IX86)
+    mDetourPatcher.Clear();
+
+    // NB: We intentionally leak mModule
+  }
+
+#if defined(NIGHTLY_BUILD)
+  const Maybe<DetourError>& GetLastDetourError() const {
+    return mDetourPatcher.GetLastDetourError();
+  }
+#endif  // defined(NIGHTLY_BUILD)
+  template <typename... Args>
+  void SetLastDetourError(Args&&... aArgs) {
+    return mDetourPatcher.SetLastDetourError(std::forward<Args>(aArgs)...);
+  }
+
+  constexpr static uint32_t GetWorstCaseRequiredBytesToPatch() {
+    return WindowsDllDetourPatcherPrimitive<
+        typename VMPolicy::MMPolicyT>::GetWorstCaseRequiredBytesToPatch();
+  }
+
+ private:
+  /**
+   * Hook/detour the method aName from the DLL we set in Init so that it calls
+   * aHookDest instead.  Returns the original method pointer in aOrigFunc
+   * and returns true if successful.
+   *
+   * IMPORTANT: If you use this method, please add your case to the
+   * TestDllInterceptor in order to detect future failures.  Even if this
+   * succeeds now, updates to the hooked DLL could cause it to fail in
+   * the future.
+   */
+  bool AddHook(const char* aName, intptr_t aHookDest, void** aOrigFunc) {
+    // Use a nop space patch if possible, otherwise fall back to a detour.
+    // This should be the preferred method for adding hooks.
+    if (!mModule) {
+      mDetourPatcher.SetLastDetourError(DetourResultCode::INTERCEPTOR_MOD_NULL);
+      return false;
+    }
+
+    if (!mDetourPatcher.IsPageAccessible(
+            nt::PEHeaders::HModuleToBaseAddr<uintptr_t>(mModule))) {
+      mDetourPatcher.SetLastDetourError(
+          DetourResultCode::INTERCEPTOR_MOD_INACCESSIBLE);
+      return false;
+    }
+
+    FARPROC proc = mDetourPatcher.GetProcAddress(mModule, aName);
+    if (!proc) {
+      mDetourPatcher.SetLastDetourError(
+          DetourResultCode::INTERCEPTOR_PROC_NULL);
+      return false;
+    }
+
+    if (!mDetourPatcher.IsPageAccessible(reinterpret_cast<uintptr_t>(proc))) {
+      mDetourPatcher.SetLastDetourError(
+          DetourResultCode::INTERCEPTOR_PROC_INACCESSIBLE);
+      return false;
+    }
+
+#if defined(_M_IX86)
+    if (mNopSpacePatcher.AddHook(proc, aHookDest, aOrigFunc)) {
+      return true;
+    }
+#endif  // defined(_M_IX86)
+
+    return AddDetour(proc, aHookDest, aOrigFunc);
+  }
+
+  /**
+   * Detour the method aName from the DLL we set in Init so that it calls
+   * aHookDest instead.  Returns the original method pointer in aOrigFunc
+   * and returns true if successful.
+   *
+   * IMPORTANT: If you use this method, please add your case to the
+   * TestDllInterceptor in order to detect future failures.  Even if this
+   * succeeds now, updates to the detoured DLL could cause it to fail in
+   * the future.
+   */
+  bool AddDetour(const char* aName, intptr_t aHookDest, void** aOrigFunc) {
+    // Generally, code should not call this method directly. Use AddHook unless
+    // there is a specific need to avoid nop space patches.
+    if (!mModule) {
+      mDetourPatcher.SetLastDetourError(DetourResultCode::INTERCEPTOR_MOD_NULL);
+      return false;
+    }
+
+    if (!mDetourPatcher.IsPageAccessible(
+            nt::PEHeaders::HModuleToBaseAddr<uintptr_t>(mModule))) {
+      mDetourPatcher.SetLastDetourError(
+          DetourResultCode::INTERCEPTOR_MOD_INACCESSIBLE);
+      return false;
+    }
+
+    FARPROC proc = mDetourPatcher.GetProcAddress(mModule, aName);
+    if (!proc) {
+      mDetourPatcher.SetLastDetourError(
+          DetourResultCode::INTERCEPTOR_PROC_NULL);
+      return false;
+    }
+
+    if (!mDetourPatcher.IsPageAccessible(reinterpret_cast<uintptr_t>(proc))) {
+      mDetourPatcher.SetLastDetourError(
+          DetourResultCode::INTERCEPTOR_PROC_INACCESSIBLE);
+      return false;
+    }
+
+    return AddDetour(proc, aHookDest, aOrigFunc);
+  }
+
+  bool AddDetour(FARPROC aProc, intptr_t aHookDest, void** aOrigFunc) {
+    MOZ_ASSERT(mModule && aProc);
+
+    if (!mDetourPatcher.Initialized()) {
+      DetourFlags flags = DetourFlags::eDefault;
+#if defined(_M_X64)
+      // NTDLL hooks should attempt to use a 10-byte patch because some
+      // injected DLLs do the same and interfere with our stuff.
+      bool needs10BytePatch = (mModule == ::GetModuleHandleW(L"ntdll.dll"));
+
+      bool isWin8Or81 = IsWin8OrLater() && (!IsWin10OrLater());
+      bool isWin8 = IsWin8OrLater() && (!IsWin8Point1OrLater());
+
+      bool isKernel32Dll = (mModule == ::GetModuleHandleW(L"kernel32.dll"));
+
+      bool isDuplicateHandle = (reinterpret_cast<void*>(aProc) ==
+                                reinterpret_cast<void*>(&::DuplicateHandle));
+
+      // CloseHandle on Windows 8/8.1 only accomodates 10-byte patches.
+      needs10BytePatch |= isWin8Or81 && isKernel32Dll &&
+                          (reinterpret_cast<void*>(aProc) ==
+                           reinterpret_cast<void*>(&CloseHandle));
+
+      // CreateFileA and DuplicateHandle on Windows 8 require 10-byte patches.
+      needs10BytePatch |= isWin8 && isKernel32Dll &&
+                          ((reinterpret_cast<void*>(aProc) ==
+                            reinterpret_cast<void*>(&::CreateFileA)) ||
+                           isDuplicateHandle);
+
+      if (needs10BytePatch) {
+        flags |= DetourFlags::eEnable10BytePatch;
+      }
+
+      if (isWin8 && isDuplicateHandle) {
+        // Because we can't detour Win8's KERNELBASE!DuplicateHandle,
+        // we detour kernel32!DuplicateHandle (See bug 1659398).
+        flags |= DetourFlags::eDontResolveRedirection;
+      }
+#endif  // defined(_M_X64)
+
+      mDetourPatcher.Init(flags);
+    }
+
+    return mDetourPatcher.AddHook(aProc, aHookDest, aOrigFunc);
+  }
+
+ private:
+  template <typename InterceptorT, typename FuncPtrT>
+  friend class FuncHook;
+
+  template <typename InterceptorT, typename FuncPtrT>
+  friend class FuncHookCrossProcess;
+};
+
+/**
+ * IAT patching is intended for use when we only want to intercept a function
+ * call originating from a specific module.
+ */
+class WindowsIATPatcher final {
+ public:
+  template <typename FuncPtrT>
+  using FuncHookType = FuncHook<WindowsIATPatcher, FuncPtrT>;
+
+ private:
+  static bool CheckASCII(const char* aInStr) {
+    while (*aInStr) {
+      if (*aInStr & 0x80) {
+        return false;
+      }
+      ++aInStr;
+    }
+    return true;
+  }
+
+  static bool AddHook(HMODULE aFromModule, const char* aToModuleName,
+                      const char* aTargetFnName, void* aHookDest,
+                      Atomic<void*>* aOutOrigFunc) {
+    if (!aFromModule || !aToModuleName || !aTargetFnName || !aOutOrigFunc) {
+      return false;
+    }
+
+    // PE Spec requires ASCII names for imported module names
+    const bool isModuleNameAscii = CheckASCII(aToModuleName);
+    MOZ_ASSERT(isModuleNameAscii);
+    if (!isModuleNameAscii) {
+      return false;
+    }
+
+    // PE Spec requires ASCII names for imported function names
+    const bool isTargetFnNameAscii = CheckASCII(aTargetFnName);
+    MOZ_ASSERT(isTargetFnNameAscii);
+    if (!isTargetFnNameAscii) {
+      return false;
+    }
+
+    nt::PEHeaders headers(aFromModule);
+    if (!headers) {
+      return false;
+    }
+
+    PIMAGE_IMPORT_DESCRIPTOR impDesc =
+        headers.GetImportDescriptor(aToModuleName);
+    if (!nt::PEHeaders::IsValid(impDesc)) {
+      // Either aFromModule does not import aToModuleName at load-time, or
+      // aToModuleName is a (currently unsupported) delay-load import.
+      return false;
+    }
+
+    // Resolve the import name table (INT).
+    auto firstINTThunk = headers.template RVAToPtr<PIMAGE_THUNK_DATA>(
+        impDesc->OriginalFirstThunk);
+    if (!nt::PEHeaders::IsValid(firstINTThunk)) {
+      return false;
+    }
+
+    Maybe<ptrdiff_t> thunkIndex;
+
+    // Scan the INT for the location of the thunk for the function named
+    // 'aTargetFnName'.
+    for (PIMAGE_THUNK_DATA curINTThunk = firstINTThunk;
+         nt::PEHeaders::IsValid(curINTThunk); ++curINTThunk) {
+      if (IMAGE_SNAP_BY_ORDINAL(curINTThunk->u1.Ordinal)) {
+        // Currently not supporting import by ordinal; this isn't hard to add,
+        // but we won't bother unless necessary.
+        continue;
+      }
+
+      PIMAGE_IMPORT_BY_NAME curThunkFnName =
+          headers.template RVAToPtr<PIMAGE_IMPORT_BY_NAME>(
+              curINTThunk->u1.AddressOfData);
+      MOZ_ASSERT(curThunkFnName);
+      if (!curThunkFnName) {
+        // Looks like we have a bad name descriptor. Try to continue.
+        continue;
+      }
+
+      // Function name checks MUST be case-sensitive!
+      if (!strcmp(aTargetFnName, curThunkFnName->Name)) {
+        // We found the thunk. Save the index of this thunk, as the IAT thunk
+        // is located at the same index in that table as in the INT.
+        thunkIndex = Some(curINTThunk - firstINTThunk);
+        break;
+      }
+    }
+
+    if (thunkIndex.isNothing()) {
+      // We never found a thunk for that function. Perhaps it's not imported?
+      return false;
+    }
+
+    if (thunkIndex.value() < 0) {
+      // That's just wrong.
+      return false;
+    }
+
+    auto firstIATThunk =
+        headers.template RVAToPtr<PIMAGE_THUNK_DATA>(impDesc->FirstThunk);
+    if (!nt::PEHeaders::IsValid(firstIATThunk)) {
+      return false;
+    }
+
+    // Resolve the IAT thunk for the function we want
+    PIMAGE_THUNK_DATA targetThunk = &firstIATThunk[thunkIndex.value()];
+    if (!nt::PEHeaders::IsValid(targetThunk)) {
+      return false;
+    }
+
+    auto fnPtr = reinterpret_cast<Atomic<void*>*>(&targetThunk->u1.Function);
+
+    // Now we can just change out its pointer with our hook function.
+    AutoVirtualProtect prot(fnPtr, sizeof(void*), PAGE_EXECUTE_READWRITE);
+    if (!prot) {
+      return false;
+    }
+
+    // We do the exchange this way to ensure that *aOutOrigFunc is always valid
+    // once the atomic exchange has taken place.
+    void* tmp;
+
+    do {
+      tmp = *fnPtr;
+      *aOutOrigFunc = tmp;
+    } while (!fnPtr->compareExchange(tmp, aHookDest));
+
+    return true;
+  }
+
+  template <typename InterceptorT, typename FuncPtrT>
+  friend class FuncHook;
+};
+
+template <typename FuncPtrT>
+class MOZ_ONLY_USED_TO_AVOID_STATIC_CONSTRUCTORS
+    FuncHook<WindowsIATPatcher, FuncPtrT>
+        final {
+ public:
+  using ThisType = FuncHook<WindowsIATPatcher, FuncPtrT>;
+  using ReturnType = typename OriginalFunctionPtrTraits<FuncPtrT>::ReturnType;
+
+  constexpr FuncHook()
+      : mInitOnce(INIT_ONCE_STATIC_INIT),
+        mFromModule(nullptr),
+        mOrigFunc(nullptr) {}
+
+#if defined(DEBUG)
+  ~FuncHook() = default;
+#endif  // defined(DEBUG)
+
+  bool Set(const wchar_t* aFromModuleName, const char* aToModuleName,
+           const char* aFnName, FuncPtrT aHookDest) {
+    nsModuleHandle fromModule(::LoadLibraryW(aFromModuleName));
+    if (!fromModule) {
+      return false;
+    }
+
+    return Set(fromModule, aToModuleName, aFnName, aHookDest);
+  }
+
+  // We offer this overload in case the client wants finer-grained control over
+  // loading aFromModule.
+  bool Set(nsModuleHandle& aFromModule, const char* aToModuleName,
+           const char* aFnName, FuncPtrT aHookDest) {
+    LPVOID addHookOk = nullptr;
+    InitOnceContext ctx(this, aFromModule, aToModuleName, aFnName, aHookDest);
+
+    bool result = ::InitOnceExecuteOnce(&mInitOnce, &InitOnceCallback, &ctx,
+                                        &addHookOk) &&
+                  addHookOk;
+    if (!result) {
+      return result;
+    }
+
+    // If we successfully set the hook then we must retain a strong reference
+    // to the module that we modified.
+    mFromModule = aFromModule.disown();
+    return result;
+  }
+
+  explicit operator bool() const { return !!mOrigFunc; }
+
+  template <typename... ArgsType>
+  ReturnType operator()(ArgsType&&... aArgs) const {
+    return mOrigFunc(std::forward<ArgsType>(aArgs)...);
+  }
+
+  FuncPtrT GetStub() const { return mOrigFunc; }
+
+#if defined(DEBUG)
+  // One-time init stuff cannot be moved or copied
+  FuncHook(const FuncHook&) = delete;
+  FuncHook(FuncHook&&) = delete;
+  FuncHook& operator=(const FuncHook&) = delete;
+  FuncHook& operator=(FuncHook&& aOther) = delete;
+#endif  // defined(DEBUG)
+
+ private:
+  struct MOZ_RAII InitOnceContext final {
+    InitOnceContext(ThisType* aHook, const nsModuleHandle& aFromModule,
+                    const char* aToModuleName, const char* aFnName,
+                    FuncPtrT aHookDest)
+        : mHook(aHook),
+          mFromModule(aFromModule),
+          mToModuleName(aToModuleName),
+          mFnName(aFnName),
+          mHookDest(reinterpret_cast<void*>(aHookDest)) {}
+
+    ThisType* mHook;
+    const nsModuleHandle& mFromModule;
+    const char* mToModuleName;
+    const char* mFnName;
+    void* mHookDest;
+  };
+
+ private:
+  bool Apply(const nsModuleHandle& aFromModule, const char* aToModuleName,
+             const char* aFnName, void* aHookDest) {
+    return WindowsIATPatcher::AddHook(
+        aFromModule, aToModuleName, aFnName, aHookDest,
+        reinterpret_cast<Atomic<void*>*>(&mOrigFunc));
+  }
+
+  static BOOL CALLBACK InitOnceCallback(PINIT_ONCE aInitOnce, PVOID aParam,
+                                        PVOID* aOutContext) {
+    MOZ_ASSERT(aOutContext);
+
+    auto ctx = reinterpret_cast<InitOnceContext*>(aParam);
+    bool result = ctx->mHook->Apply(ctx->mFromModule, ctx->mToModuleName,
+                                    ctx->mFnName, ctx->mHookDest);
+
+    *aOutContext =
+        result ? reinterpret_cast<PVOID>(1U << INIT_ONCE_CTX_RESERVED_BITS)
+               : nullptr;
+    return TRUE;
+  }
+
+ private:
+  INIT_ONCE mInitOnce;
+  HMODULE mFromModule;  // never freed
+  FuncPtrT mOrigFunc;
+};
+
+/**
+ * This class applies an irreversible patch to jump to a target function
+ * without backing up the original function.
+ */
+class WindowsDllEntryPointInterceptor final {
+  using DllMainFn = BOOL(WINAPI*)(HINSTANCE, DWORD, LPVOID);
+  using MMPolicyT = MMPolicyInProcessEarlyStage;
+
+  MMPolicyT mMMPolicy;
+
+ public:
+  explicit WindowsDllEntryPointInterceptor(
+      const MMPolicyT::Kernel32Exports& aK32Exports)
+      : mMMPolicy(aK32Exports) {}
+
+  bool Set(const nt::PEHeaders& aHeaders, DllMainFn aDestination) {
+    if (!aHeaders) {
+      return false;
+    }
+
+    WindowsDllDetourPatcherPrimitive<MMPolicyT> patcher;
+    return patcher.AddIrreversibleHook(
+        mMMPolicy, aHeaders.GetEntryPoint(),
+        reinterpret_cast<uintptr_t>(aDestination));
+  }
+};
+
+}  // namespace interceptor
+
+using WindowsDllInterceptor = interceptor::WindowsDllInterceptor<>;
+
+using CrossProcessDllInterceptor = interceptor::WindowsDllInterceptor<
+    mozilla::interceptor::VMSharingPolicyUnique<
+        mozilla::interceptor::MMPolicyOutOfProcess>>;
+
+using WindowsIATPatcher = interceptor::WindowsIATPatcher;
+
+}  // namespace mozilla
+
+#endif /* NS_WINDOWS_DLL_INTERCEPTOR_H_ */
diff --git a/toolkit/xre/dllservices/tests/AssemblyPayloads.h b/toolkit/xre/dllservices/tests/AssemblyPayloads.h
new file mode 100644
index 0000000000..4dcbcc5fbf
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/AssemblyPayloads.h
@@ -0,0 +1,238 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+/* These assembly functions represent patterns that were already hooked by
+ * another application before our detour.
+ */
+
+#ifndef mozilla_AssemblyPayloads_h
+#define mozilla_AssemblyPayloads_h
+
+#include <cstdint>
+
+#define PADDING_256_NOP                                              \
+  "nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;" \
+  "nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;" \
+  "nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;" \
+  "nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;" \
+  "nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;" \
+  "nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;" \
+  "nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;" \
+  "nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;" \
+  "nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;" \
+  "nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;" \
+  "nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;" \
+  "nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;" \
+  "nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;" \
+  "nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;" \
+  "nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;" \
+  "nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;"
+
+extern "C" {
+
+#if defined(__clang__)
+#  if defined(_M_X64)
+constexpr uintptr_t JumpDestination = 0x7fff00000000;
+
+__declspec(dllexport) __attribute__((naked)) void MovPushRet() {
+  asm volatile(
+      "mov %0, %%rax;"
+      "push %%rax;"
+      "ret;"
+      :
+      : "i"(JumpDestination));
+}
+
+__declspec(dllexport) __attribute__((naked)) void MovRaxJump() {
+  asm volatile(
+      "mov %0, %%rax;"
+      "jmpq *%%rax;"
+      :
+      : "i"(JumpDestination));
+}
+
+__declspec(dllexport) __attribute__((naked)) void DoubleJump() {
+  asm volatile(
+      "jmp label1;"
+
+      "label2:"
+      "mov %0, %%rax;"
+      "jmpq *%%rax;"
+
+      // 0x100 bytes padding to generate jmp rel32 instead of jmp rel8
+      PADDING_256_NOP
+
+      "label1:"
+      "jmp label2;"
+      :
+      : "i"(JumpDestination));
+}
+
+__declspec(dllexport) __attribute__((naked)) void NearJump() {
+  asm volatile(
+      "jae label3;"
+      "je  label3;"
+      "jne label3;"
+
+      "label4:"
+      "mov %0, %%rax;"
+      "jmpq *%%rax;"
+
+      // 0x100 bytes padding to generate jae rel32 instead of jae rel8
+      PADDING_256_NOP
+
+      "label3:"
+      "jmp label4;"
+      :
+      : "i"(JumpDestination));
+}
+
+__declspec(dllexport) __attribute__((naked)) void OpcodeFF() {
+  // Skip PUSH (FF /6) because clang prefers Opcode 50+rd
+  // to translate PUSH r64 rather than Opcode FF.
+  asm volatile(
+      "incl %eax;"
+      "decl %ebx;"
+      "call *%rcx;"
+      "jmp *(%rip);"  // Indirect jump to 0xcccccccc`cccccccc
+      "int $3;int $3;int $3;int $3;"
+      "int $3;int $3;int $3;int $3;");
+}
+
+__declspec(dllexport) __attribute__((naked)) void IndirectCall() {
+  asm volatile(
+      "call *(%rip);"  // Indirect call to 0x90909090`90909090
+      "nop;nop;nop;nop;nop;nop;nop;nop;"
+      "ret;");
+}
+
+__declspec(dllexport) __attribute__((naked)) void MovImm64() {
+  asm volatile(
+      "mov $0x1234567812345678, %r10;"
+      "nop;nop;nop");
+}
+
+#    if !defined(MOZ_CODE_COVERAGE)
+// This code reproduces bug 1798787: it uses the same prologue, the same unwind
+// info, and it has a call instruction that starts within the 13 first bytes.
+__attribute__((naked)) void DetouredCallCode(uintptr_t aCallee) {
+  asm volatile(
+      "subq $0x28, %rsp;"
+      "testq %rcx, %rcx;"
+      "jz exit;"
+      "callq *%rcx;"
+      "exit:"
+      "addq $0x28, %rsp;"
+      "retq;");
+}
+constexpr uint8_t gDetouredCallCodeSize = 16;  // size of function in bytes
+alignas(uint32_t) uint8_t gDetouredCallUnwindInfo[] = {
+    0x01,  // Version (1), Flags (0)
+    0x04,  // SizeOfProlog (4)
+    0x01,  // CountOfUnwindCodes (1)
+    0x00,  // FrameRegister (0), FrameOffset (0)
+    // UnwindCodes[0]
+    0x04,  // .OffsetInProlog (4)
+    0x42,  // .UnwindOpCode(UWOP_ALLOC_SMALL=2), .UnwindInfo (4)
+};
+
+// This points to the same code as DetouredCallCode, but dynamically generated
+// so that it can have custom unwinding info. See TestDllInterceptor.cpp.
+extern decltype(&DetouredCallCode) gDetouredCall;
+
+// This is just a jumper: our hooking code will thus detour the jump target
+// -- it will not detour DetouredCallJumper. We need to do this to point our
+// hooking code to the dynamic code, because our hooking API works with an
+// exported function name.
+__attribute__((naked)) __declspec(dllexport noinline) void DetouredCallJumper(
+    uintptr_t aCallee) {
+  // Ideally we would want this to be:
+  //   jmp qword ptr [rip + offset gDetouredCall]
+  // Unfortunately, it is unclear how to do that with inline assembly, so we
+  // use a zero offset and patch it before the test.
+  asm volatile("jmpq *0(%rip)");
+}
+#    endif  // !defined(MOZ_CODE_COVERAGE)
+
+#  elif defined(_M_IX86)
+constexpr uintptr_t JumpDestination = 0x7fff0000;
+
+__declspec(dllexport) __attribute__((naked)) void PushRet() {
+  asm volatile(
+      "push %0;"
+      "ret;"
+      :
+      : "i"(JumpDestination));
+}
+
+__declspec(dllexport) __attribute__((naked)) void MovEaxJump() {
+  asm volatile(
+      "mov %0, %%eax;"
+      "jmp *%%eax;"
+      :
+      : "i"(JumpDestination));
+}
+
+__declspec(dllexport) __attribute__((naked)) void Opcode83() {
+  asm volatile(
+      "xor $0x42, %eax;"
+      "cmpl $1, 0xc(%ebp);");
+}
+
+__declspec(dllexport) __attribute__((naked)) void LockPrefix() {
+  // Test an instruction with a LOCK prefix (0xf0) at a non-zero offset
+  asm volatile(
+      "push $0x7c;"
+      "lock push $0x7c;");
+}
+
+__declspec(dllexport) __attribute__((naked)) void LooksLikeLockPrefix() {
+  // This is for a regression scenario of bug 1625452, where we double-counted
+  // the offset in CountPrefixBytes.  When we count prefix bytes in front of
+  // the 2nd PUSH located at offset 2, we mistakenly started counting from
+  // the byte 0xf0 at offset 4, which is considered as LOCK, thus we try to
+  // detour the next byte 0xcc and it fails.
+  //
+  // 0: 6a7c       push 7Ch
+  // 2: 68ccf00000 push 0F0CCh
+  //
+  asm volatile(
+      "push $0x7c;"
+      "push $0x0000f0cc;");
+}
+
+__declspec(dllexport) __attribute__((naked)) void DoubleJump() {
+  asm volatile(
+      "jmp label1;"
+
+      "label2:"
+      "mov %0, %%eax;"
+      "jmp *%%eax;"
+
+      // 0x100 bytes padding to generate jmp rel32 instead of jmp rel8
+      PADDING_256_NOP
+
+      "label1:"
+      "jmp label2;"
+      :
+      : "i"(JumpDestination));
+}
+#  endif
+
+#  if !defined(_M_ARM64)
+__declspec(dllexport) __attribute__((naked)) void UnsupportedOp() {
+  asm volatile(
+      "ud2;"
+      "nop;nop;nop;nop;nop;nop;nop;nop;"
+      "nop;nop;nop;nop;nop;nop;nop;nop;");
+}
+#  endif  // !defined(_M_ARM64)
+
+#endif  // defined(__clang__)
+
+}  // extern "C"
+
+#endif  // mozilla_AssemblyPayloads_h
diff --git a/toolkit/xre/dllservices/tests/TestDllBlocklistAssumptions.cpp b/toolkit/xre/dllservices/tests/TestDllBlocklistAssumptions.cpp
new file mode 100644
index 0000000000..17c68f26dc
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/TestDllBlocklistAssumptions.cpp
@@ -0,0 +1,344 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <windows.h>
+#include <tlhelp32.h>
+
+#include <stdio.h>
+
+#include "mozilla/Assertions.h"
+#include "mozilla/NativeNt.h"
+#include "mozilla/Vector.h"
+
+#include "nsWindowsDllInterceptor.h"
+
+NTSTATUS NTAPI NtMapViewOfSection(
+    HANDLE aSection, HANDLE aProcess, PVOID* aBaseAddress, ULONG_PTR aZeroBits,
+    SIZE_T aCommitSize, PLARGE_INTEGER aSectionOffset, PSIZE_T aViewSize,
+    SECTION_INHERIT aInheritDisposition, ULONG aAllocationType,
+    ULONG aProtectionFlags);
+
+using namespace mozilla;
+
+static WindowsDllInterceptor NtdllIntercept;
+
+static WindowsDllInterceptor::FuncHookType<decltype(&::NtMapViewOfSection)>
+    stub_NtMapViewOfSection;
+
+static constexpr auto kDllUsedForLoadLibraryTests = L"dbghelp.dll";
+
+class MappedViewsInfoCollector {
+ public:
+  struct MappedViewInfo {
+    PVOID BaseAddress;
+    HANDLE aSection;
+    PUBLIC_OBJECT_BASIC_INFORMATION obiSection;
+    MEMORY_BASIC_INFORMATION mbiVirtualMemory;
+  };
+
+  MappedViewsInfoCollector() = default;
+  ~MappedViewsInfoCollector() = default;
+
+  const MappedViewInfo* begin() const { return mMappedViewsInfo.begin(); }
+  const MappedViewInfo* end() const { return mMappedViewsInfo.end(); }
+
+  const MappedViewInfo* GetInfo(PVOID aBaseAddress) const {
+    for (const auto& mappedView : mMappedViewsInfo) {
+      if (mappedView.BaseAddress == aBaseAddress) {
+        return &mappedView;
+      }
+    }
+    return nullptr;
+  }
+
+  void Add(PVOID aBaseAddress, HANDLE aSection) {
+    auto existingMappedViewInfo = GetInfo(aBaseAddress);
+    if (existingMappedViewInfo) {
+      MOZ_RELEASE_ASSERT(existingMappedViewInfo->BaseAddress == aBaseAddress);
+      MOZ_RELEASE_ASSERT(existingMappedViewInfo->aSection == aSection);
+      return;
+    }
+
+    MappedViewInfo mappedViewInfo{aBaseAddress, aSection};
+    MOZ_RELEASE_ASSERT(NT_SUCCESS(::NtQueryObject(
+        aSection, ObjectBasicInformation, &mappedViewInfo.obiSection,
+        sizeof(mappedViewInfo.obiSection), nullptr)));
+    MOZ_RELEASE_ASSERT(NT_SUCCESS(::NtQueryVirtualMemory(
+        ::GetCurrentProcess(), aBaseAddress, MemoryBasicInformation,
+        &mappedViewInfo.mbiVirtualMemory,
+        sizeof(mappedViewInfo.mbiVirtualMemory), nullptr)));
+    MOZ_RELEASE_ASSERT(mMappedViewsInfo.append(std::move(mappedViewInfo)));
+  }
+
+  void Reset() { MOZ_RELEASE_ASSERT(mMappedViewsInfo.resize(0)); }
+
+ private:
+  Vector<MappedViewInfo> mMappedViewsInfo;
+};
+
+static bool sIsTestRunning = false;
+static MappedViewsInfoCollector sMappedViewsInfoCollector;
+
+NTSTATUS NTAPI patched_NtMapViewOfSection(
+    HANDLE aSection, HANDLE aProcess, PVOID* aBaseAddress, ULONG_PTR aZeroBits,
+    SIZE_T aCommitSize, PLARGE_INTEGER aSectionOffset, PSIZE_T aViewSize,
+    SECTION_INHERIT aInheritDisposition, ULONG aAllocationType,
+    ULONG aProtectionFlags) {
+  NTSTATUS result = stub_NtMapViewOfSection(
+      aSection, aProcess, aBaseAddress, aZeroBits, aCommitSize, aSectionOffset,
+      aViewSize, aInheritDisposition, aAllocationType, aProtectionFlags);
+  if (sIsTestRunning && NT_SUCCESS(result)) {
+    MOZ_RELEASE_ASSERT(aBaseAddress);
+    sMappedViewsInfoCollector.Add(*aBaseAddress, aSection);
+  }
+  return result;
+}
+
+bool InitializeTests() {
+  NtdllIntercept.Init(L"ntdll.dll");
+
+  bool success = stub_NtMapViewOfSection.Set(
+      NtdllIntercept, "NtMapViewOfSection", patched_NtMapViewOfSection);
+  if (!success) {
+    printf(
+        "TEST-UNEXPECTED-FAIL | TestDllBlocklistAssumptions | "
+        "Failed to hook NtMapViewOfSection.\n");
+    fflush(stdout);
+    return false;
+  }
+
+  printf(
+      "TEST-PASS | TestDllBlocklistAssumptions | "
+      "Successfully hooked NtMapViewOfSection.\n");
+  fflush(stdout);
+  return true;
+}
+
+bool CheckMappedViewAssumptions(const char* aTestDescription, PVOID baseAddress,
+                                bool aExpectExecutableSection,
+                                bool aExpectImageTypeMemory) {
+  auto mappedViewInfo = sMappedViewsInfoCollector.GetInfo(baseAddress);
+  if (!mappedViewInfo) {
+    printf(
+        "TEST-UNEXPECTED-FAIL | TestDllBlocklistAssumptions | "
+        "Failed to find mapped view information while testing %s.\n",
+        aTestDescription);
+    fflush(stdout);
+    return false;
+  }
+
+  MOZ_RELEASE_ASSERT(mappedViewInfo->BaseAddress == baseAddress);
+
+  if (aExpectExecutableSection !=
+      bool(mappedViewInfo->obiSection.GrantedAccess & SECTION_MAP_EXECUTE)) {
+    printf(
+        "TEST-UNEXPECTED-FAIL | TestDllBlocklistAssumptions | "
+        "Mismatch in assumptions regarding section executablity while testing "
+        "%s.\n",
+        aTestDescription);
+    fflush(stdout);
+    return false;
+  }
+
+  if (aExpectImageTypeMemory !=
+      bool(mappedViewInfo->mbiVirtualMemory.Type & MEM_IMAGE)) {
+    printf(
+        "TEST-UNEXPECTED-FAIL | TestDllBlocklistAssumptions | "
+        "Mismatch in assumptions regarding virtual memory type while testing "
+        "%s.\n",
+        aTestDescription);
+    fflush(stdout);
+    return false;
+  }
+  return true;
+}
+
+// Assumptions used to block normal DLL loads:
+//  - section handle was granted SECTION_MAP_EXECUTE access;
+//  - virtual memory is tagged as MEM_IMAGE type.
+bool TestDllLoad() {
+  sMappedViewsInfoCollector.Reset();
+
+  auto module = ::LoadLibraryW(kDllUsedForLoadLibraryTests);
+  if (!module) {
+    printf(
+        "TEST-UNEXPECTED-FAIL | TestDllBlocklistAssumptions | "
+        "Call to LoadLibraryW failed with error %lu.\n",
+        ::GetLastError());
+    fflush(stdout);
+    return false;
+  }
+
+  auto baseAddress = nt::PEHeaders::HModuleToBaseAddr<PVOID>(module);
+  bool result =
+      CheckMappedViewAssumptions("LoadLibraryW", baseAddress, true, true);
+  FreeLibrary(module);
+
+  if (result) {
+    printf(
+        "TEST-PASS | TestDllBlocklistAssumptions | "
+        "DLL loading works as expected.\n");
+    fflush(stdout);
+  }
+  return result;
+}
+
+// Assumptions used to avoid blocking DLL loads when loading as data file:
+//  - section handle was *not* granted SECTION_MAP_EXECUTE access;
+//  - virtual memory is *not* tagged as MEM_IMAGE type.
+bool TestDllLoadAsDataFile() {
+  sMappedViewsInfoCollector.Reset();
+
+  auto module = ::LoadLibraryExW(kDllUsedForLoadLibraryTests, nullptr,
+                                 LOAD_LIBRARY_AS_DATAFILE);
+  if (!module) {
+    printf(
+        "TEST-UNEXPECTED-FAIL | TestDllBlocklistAssumptions | "
+        "Call to LoadLibraryExW failed with error %lu.\n",
+        ::GetLastError());
+    fflush(stdout);
+    return false;
+  }
+
+  auto baseAddress = nt::PEHeaders::HModuleToBaseAddr<PVOID>(module);
+  bool result = CheckMappedViewAssumptions(
+      "LoadLibraryExW(LOAD_LIBRARY_AS_DATAFILE)", baseAddress, false, false);
+  FreeLibrary(module);
+
+  if (result) {
+    printf(
+        "TEST-PASS | TestDllBlocklistAssumptions | "
+        "DLL loading as data file works as expected.\n");
+    fflush(stdout);
+  }
+  return result;
+}
+
+// Assumptions used to avoid blocking DLL loads when loading as image resource:
+//  - section handle was *not* granted SECTION_MAP_EXECUTE access;
+//  - virtual memory is tagged as MEM_IMAGE type, however.
+bool TestDllLoadAsImageResource() {
+  sMappedViewsInfoCollector.Reset();
+
+  auto module = ::LoadLibraryExW(kDllUsedForLoadLibraryTests, nullptr,
+                                 LOAD_LIBRARY_AS_IMAGE_RESOURCE);
+  if (!module) {
+    printf(
+        "TEST-UNEXPECTED-FAIL | TestDllBlocklistAssumptions | "
+        "Call to LoadLibraryExW failed with error %lu.\n",
+        ::GetLastError());
+    fflush(stdout);
+    return false;
+  }
+
+  auto baseAddress = nt::PEHeaders::HModuleToBaseAddr<PVOID>(module);
+  bool result = CheckMappedViewAssumptions(
+      "LoadLibraryExW(LOAD_LIBRARY_AS_IMAGE_RESOURCE)", baseAddress, false,
+      true);
+  FreeLibrary(module);
+
+  if (result) {
+    printf(
+        "TEST-PASS | TestDllBlocklistAssumptions | "
+        "DLL loading as image resource works as expected.\n");
+    fflush(stdout);
+  }
+  return result;
+}
+
+// Assumptions used to avoid crashing when using Thread32Next (bug 1733532):
+//  - section handle was *not* granted SECTION_MAP_EXECUTE access;
+//  - virtual memory is *not* tagged as MEM_IMAGE type.
+bool TestThreadIteration() {
+  sMappedViewsInfoCollector.Reset();
+
+  HANDLE snapshot = ::CreateToolhelp32Snapshot(TH32CS_SNAPTHREAD, 0);
+  if (snapshot == INVALID_HANDLE_VALUE) {
+    printf(
+        "TEST-UNEXPECTED-FAIL | TestDllBlocklistAssumptions | "
+        "Call toCreateToolhelp32Snapshot failed with error %lu.\n",
+        ::GetLastError());
+    fflush(stdout);
+    return false;
+  }
+
+  THREADENTRY32 entry{};
+  entry.dwSize = sizeof(entry);
+  if (!::Thread32First(snapshot, &entry)) {
+    printf(
+        "TEST-UNEXPECTED-FAIL | TestDllBlocklistAssumptions | "
+        "Call to Thread32First failed with error %lu.\n",
+        ::GetLastError());
+    fflush(stdout);
+    return false;
+  }
+
+  while (::Thread32Next(snapshot, &entry)) {
+  }
+  auto error = GetLastError();
+  if (error != ERROR_NO_MORE_FILES) {
+    printf(
+        "TEST-UNEXPECTED-FAIL | TestDllBlocklistAssumptions | "
+        "Call to Thread32Next failed with unexpected error %lu.\n",
+        error);
+    fflush(stdout);
+    return false;
+  }
+
+  uint32_t count = 0;
+  for (const auto& mappedViewInfo : sMappedViewsInfoCollector) {
+    if (!CheckMappedViewAssumptions("Thread32Next", mappedViewInfo.BaseAddress,
+                                    false, false)) {
+      return false;
+    }
+    ++count;
+  }
+
+  if (!count) {
+    printf(
+        "TEST-UNEXPECTED-FAIL | TestDllBlocklistAssumptions | "
+        "Unexpectedly found no mappings after iterating threads with "
+        "Thread32Next.\n");
+    fflush(stdout);
+    return false;
+  }
+
+  printf(
+      "TEST-PASS | TestDllBlocklistAssumptions | "
+      "Iterating threads with Thread32Next works as expected.\n");
+  fflush(stdout);
+  return true;
+}
+
+extern "C" int wmain(int argc, wchar_t* argv[]) {
+  LARGE_INTEGER start;
+  QueryPerformanceCounter(&start);
+
+  sIsTestRunning = true;
+  if (InitializeTests() && TestDllLoad() && TestDllLoadAsDataFile() &&
+      TestDllLoadAsImageResource() && TestThreadIteration()) {
+    sIsTestRunning = false;
+
+    printf("TEST-PASS | TestDllBlocklistAssumptions | all checks passed\n");
+
+    LARGE_INTEGER end, freq;
+    QueryPerformanceCounter(&end);
+
+    QueryPerformanceFrequency(&freq);
+
+    LARGE_INTEGER result;
+    result.QuadPart = end.QuadPart - start.QuadPart;
+    result.QuadPart *= 1000000;
+    result.QuadPart /= freq.QuadPart;
+
+    printf("Elapsed time: %lld microseconds\n", result.QuadPart);
+
+    return 0;
+  }
+
+  sIsTestRunning = false;
+  return 1;
+}
diff --git a/toolkit/xre/dllservices/tests/TestDllInterceptor.cpp b/toolkit/xre/dllservices/tests/TestDllInterceptor.cpp
new file mode 100644
index 0000000000..2b70c9bcd4
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/TestDllInterceptor.cpp
@@ -0,0 +1,1475 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <shlobj.h>
+#include <stdio.h>
+#include <commdlg.h>
+#define SECURITY_WIN32
+#include <security.h>
+#include <wininet.h>
+#include <schnlsp.h>
+#include <winternl.h>
+#include <processthreadsapi.h>
+
+#include <bcrypt.h>
+#pragma comment(lib, "bcrypt.lib")
+
+#include "AssemblyPayloads.h"
+#include "mozilla/DynamicallyLinkedFunctionPtr.h"
+#include "mozilla/UniquePtr.h"
+#include "mozilla/WindowsVersion.h"
+#include "nsWindowsDllInterceptor.h"
+#include "nsWindowsHelpers.h"
+
+NTSTATUS NTAPI NtFlushBuffersFile(HANDLE, PIO_STATUS_BLOCK);
+NTSTATUS NTAPI NtReadFile(HANDLE, HANDLE, PIO_APC_ROUTINE, PVOID,
+                          PIO_STATUS_BLOCK, PVOID, ULONG, PLARGE_INTEGER,
+                          PULONG);
+NTSTATUS NTAPI NtReadFileScatter(HANDLE, HANDLE, PIO_APC_ROUTINE, PVOID,
+                                 PIO_STATUS_BLOCK, PFILE_SEGMENT_ELEMENT, ULONG,
+                                 PLARGE_INTEGER, PULONG);
+NTSTATUS NTAPI NtWriteFile(HANDLE, HANDLE, PIO_APC_ROUTINE, PVOID,
+                           PIO_STATUS_BLOCK, PVOID, ULONG, PLARGE_INTEGER,
+                           PULONG);
+NTSTATUS NTAPI NtWriteFileGather(HANDLE, HANDLE, PIO_APC_ROUTINE, PVOID,
+                                 PIO_STATUS_BLOCK, PFILE_SEGMENT_ELEMENT, ULONG,
+                                 PLARGE_INTEGER, PULONG);
+NTSTATUS NTAPI NtQueryFullAttributesFile(POBJECT_ATTRIBUTES, PVOID);
+NTSTATUS NTAPI LdrLoadDll(PWCHAR filePath, PULONG flags,
+                          PUNICODE_STRING moduleFileName, PHANDLE handle);
+NTSTATUS NTAPI LdrUnloadDll(HMODULE);
+
+NTSTATUS NTAPI NtMapViewOfSection(
+    HANDLE aSection, HANDLE aProcess, PVOID* aBaseAddress, ULONG_PTR aZeroBits,
+    SIZE_T aCommitSize, PLARGE_INTEGER aSectionOffset, PSIZE_T aViewSize,
+    SECTION_INHERIT aInheritDisposition, ULONG aAllocationType,
+    ULONG aProtectionFlags);
+
+// These pointers are disguised as PVOID to avoid pulling in obscure headers
+PVOID NTAPI LdrResolveDelayLoadedAPI(PVOID, PVOID, PVOID, PVOID, PVOID, ULONG);
+void CALLBACK ProcessCaretEvents(HWINEVENTHOOK, DWORD, HWND, LONG, LONG, DWORD,
+                                 DWORD);
+void __fastcall BaseThreadInitThunk(BOOL aIsInitialThread, void* aStartAddress,
+                                    void* aThreadParam);
+
+BOOL WINAPI ApiSetQueryApiSetPresence(PCUNICODE_STRING, PBOOLEAN);
+
+#if (_WIN32_WINNT < 0x0602)
+BOOL WINAPI
+SetProcessMitigationPolicy(PROCESS_MITIGATION_POLICY aMitigationPolicy,
+                           PVOID aBuffer, SIZE_T aBufferLen);
+#endif  // (_WIN32_WINNT < 0x0602)
+
+#define RtlGenRandom SystemFunction036
+extern "C" BOOLEAN NTAPI RtlGenRandom(PVOID aRandomBuffer,
+                                      ULONG aRandomBufferLength);
+
+using namespace mozilla;
+
+struct payload {
+  UINT64 a;
+  UINT64 b;
+  UINT64 c;
+
+  bool operator==(const payload& other) const {
+    return (a == other.a && b == other.b && c == other.c);
+  }
+};
+
+extern "C" __declspec(dllexport) __declspec(noinline) payload
+    rotatePayload(payload p) {
+  UINT64 tmp = p.a;
+  p.a = p.b;
+  p.b = p.c;
+  p.c = tmp;
+  return p;
+}
+
+// payloadNotHooked is a target function for a test to expect a negative result.
+// We cannot use rotatePayload for that purpose because our detour cannot hook
+// a function detoured already.  Please keep this function always unhooked.
+extern "C" __declspec(dllexport) __declspec(noinline) payload
+    payloadNotHooked(payload p) {
+  // Do something different from rotatePayload to avoid ICF.
+  p.a ^= p.b;
+  p.b ^= p.c;
+  p.c ^= p.a;
+  return p;
+}
+
+// Declared as volatile to prevent optimizers from incorrectly eliding accesses
+// to it. (See bug 1769001 for a motivating example.)
+static volatile bool patched_func_called = false;
+
+static WindowsDllInterceptor::FuncHookType<decltype(&rotatePayload)>
+    orig_rotatePayload;
+
+static WindowsDllInterceptor::FuncHookType<decltype(&payloadNotHooked)>
+    orig_payloadNotHooked;
+
+static payload patched_rotatePayload(payload p) {
+  patched_func_called = true;
+  return orig_rotatePayload(p);
+}
+
+// Invoke aFunc by taking aArg's contents and using them as aFunc's arguments
+template <typename OrigFuncT, typename... Args,
+          typename ArgTuple = std::tuple<Args...>, size_t... Indices>
+decltype(auto) Apply(OrigFuncT& aFunc, ArgTuple&& aArgs,
+                     std::index_sequence<Indices...>) {
+  return std::apply(aFunc, aArgs);
+}
+
+#define DEFINE_TEST_FUNCTION(calling_convention)                               \
+  template <typename R, typename... Args, typename... TestArgs>                \
+  bool TestFunction(R(calling_convention* aFunc)(Args...), bool (*aPred)(R),   \
+                    TestArgs&&... aArgs) {                                     \
+    using ArgTuple = std::tuple<Args...>;                                      \
+    using Indices = std::index_sequence_for<Args...>;                          \
+    ArgTuple fakeArgs{std::forward<TestArgs>(aArgs)...};                       \
+    patched_func_called = false;                                               \
+    return aPred(Apply(aFunc, std::forward<ArgTuple>(fakeArgs), Indices())) && \
+           patched_func_called;                                                \
+  }                                                                            \
+                                                                               \
+  /* Specialization for functions returning void */                            \
+  template <typename PredT, typename... Args, typename... TestArgs>            \
+  bool TestFunction(void(calling_convention * aFunc)(Args...), PredT,          \
+                    TestArgs&&... aArgs) {                                     \
+    using ArgTuple = std::tuple<Args...>;                                      \
+    using Indices = std::index_sequence_for<Args...>;                          \
+    ArgTuple fakeArgs{std::forward<TestArgs>(aArgs)...};                       \
+    patched_func_called = false;                                               \
+    Apply(aFunc, std::forward<ArgTuple>(fakeArgs), Indices());                 \
+    return patched_func_called;                                                \
+  }
+
+// C++11 allows empty arguments to macros. clang works just fine. MSVC does the
+// right thing, but it also throws up warning C4003.
+#if defined(_MSC_VER) && !defined(__clang__)
+DEFINE_TEST_FUNCTION(__cdecl)
+#else
+DEFINE_TEST_FUNCTION()
+#endif
+
+#ifdef _M_IX86
+DEFINE_TEST_FUNCTION(__stdcall)
+DEFINE_TEST_FUNCTION(__fastcall)
+#endif  // _M_IX86
+
+// Test the hooked function against the supplied predicate
+template <typename OrigFuncT, typename PredicateT, typename... Args>
+bool CheckHook(OrigFuncT& aOrigFunc, const char* aDllName,
+               const char* aFuncName, PredicateT&& aPred, Args&&... aArgs) {
+  if (TestFunction(aOrigFunc, std::forward<PredicateT>(aPred),
+                   std::forward<Args>(aArgs)...)) {
+    printf(
+        "TEST-PASS | WindowsDllInterceptor | "
+        "Executed hooked function %s from %s\n",
+        aFuncName, aDllName);
+    fflush(stdout);
+    return true;
+  }
+  printf(
+      "TEST-FAILED | WindowsDllInterceptor | "
+      "Failed to execute hooked function %s from %s\n",
+      aFuncName, aDllName);
+  return false;
+}
+
+struct InterceptorFunction {
+  static const size_t EXEC_MEMBLOCK_SIZE = 64 * 1024;  // 64K
+
+  static InterceptorFunction& Create() {
+    // Make sure the executable memory is allocated
+    if (!sBlock) {
+      Init();
+    }
+    MOZ_ASSERT(sBlock);
+
+    // Make sure we aren't making more functions than we allocated room for
+    MOZ_RELEASE_ASSERT((sNumInstances + 1) * sizeof(InterceptorFunction) <=
+                       EXEC_MEMBLOCK_SIZE);
+
+    // Grab the next InterceptorFunction from executable memory
+    InterceptorFunction& ret = *reinterpret_cast<InterceptorFunction*>(
+        sBlock + (sNumInstances++ * sizeof(InterceptorFunction)));
+
+    // Set the InterceptorFunction to the code template.
+    auto funcCode = &ret[0];
+    memcpy(funcCode, sInterceptorTemplate, TemplateLength);
+
+    // Fill in the patched_func_called pointer in the template.
+    auto pfPtr =
+        reinterpret_cast<volatile bool**>(&ret[PatchedFuncCalledIndex]);
+    *pfPtr = &patched_func_called;
+    return ret;
+  }
+
+  uint8_t& operator[](size_t i) { return mFuncCode[i]; }
+
+  uint8_t* GetFunction() { return mFuncCode; }
+
+  void SetStub(uintptr_t aStub) {
+    auto pfPtr = reinterpret_cast<uintptr_t*>(&mFuncCode[StubFuncIndex]);
+    *pfPtr = aStub;
+  }
+
+ private:
+  // We intercept functions with short machine-code functions that set a boolean
+  // and run the stub that launches the original function.  Each entry in the
+  // array is the code for one of those interceptor functions.  We cannot
+  // free this memory until the test shuts down.
+  // The templates have spots for the address of patched_func_called
+  // and for the address of the stub function.  Their indices in the byte
+  // array are given as constants below and they appear as blocks of
+  // 0xff bytes in the templates.
+#if defined(_M_X64)
+  //  0: 48 b8 ff ff ff ff ff ff ff ff    movabs rax, &patched_func_called
+  //  a: c6 00 01                         mov    BYTE PTR [rax],0x1
+  //  d: 48 b8 ff ff ff ff ff ff ff ff    movabs rax, &stub_func_ptr
+  // 17: ff e0                            jmp    rax
+  static constexpr uint8_t sInterceptorTemplate[] = {
+      0x48, 0xB8, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
+      0xFF, 0xC6, 0x00, 0x01, 0x48, 0xB8, 0xFF, 0xFF, 0xFF,
+      0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xE0};
+  static const size_t PatchedFuncCalledIndex = 0x2;
+  static const size_t StubFuncIndex = 0xf;
+#elif defined(_M_IX86)
+  // 0: c6 05 ff ff ff ff 01     mov    BYTE PTR &patched_func_called, 0x1
+  // 7: 68 ff ff ff ff           push   &stub_func_ptr
+  // c: c3                       ret
+  static constexpr uint8_t sInterceptorTemplate[] = {
+      0xC6, 0x05, 0xFF, 0xFF, 0xFF, 0xFF, 0x01,
+      0x68, 0xFF, 0xFF, 0xFF, 0xFF, 0xC3};
+  static const size_t PatchedFuncCalledIndex = 0x2;
+  static const size_t StubFuncIndex = 0x8;
+#elif defined(_M_ARM64)
+  //  0: 31 00 80 52    movz w17, #0x1
+  //  4: 90 00 00 58    ldr  x16, #16
+  //  8: 11 02 00 39    strb w17, [x16]
+  //  c: 90 00 00 58    ldr  x16, #16
+  // 10: 00 02 1F D6    br   x16
+  // 14: &patched_func_called
+  // 1c: &stub_func_ptr
+  static constexpr uint8_t sInterceptorTemplate[] = {
+      0x31, 0x00, 0x80, 0x52, 0x90, 0x00, 0x00, 0x58, 0x11, 0x02, 0x00, 0x39,
+      0x90, 0x00, 0x00, 0x58, 0x00, 0x02, 0x1F, 0xD6, 0xFF, 0xFF, 0xFF, 0xFF,
+      0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF};
+  static const size_t PatchedFuncCalledIndex = 0x14;
+  static const size_t StubFuncIndex = 0x1c;
+#else
+#  error "Missing template for architecture"
+#endif
+
+  static const size_t TemplateLength = sizeof(sInterceptorTemplate);
+  uint8_t mFuncCode[TemplateLength];
+
+  InterceptorFunction() = delete;
+  InterceptorFunction(const InterceptorFunction&) = delete;
+  InterceptorFunction& operator=(const InterceptorFunction&) = delete;
+
+  static void Init() {
+    MOZ_ASSERT(!sBlock);
+    sBlock = reinterpret_cast<uint8_t*>(
+        ::VirtualAlloc(nullptr, EXEC_MEMBLOCK_SIZE, MEM_RESERVE | MEM_COMMIT,
+                       PAGE_EXECUTE_READWRITE));
+  }
+
+  static uint8_t* sBlock;
+  static size_t sNumInstances;
+};
+
+uint8_t* InterceptorFunction::sBlock = nullptr;
+size_t InterceptorFunction::sNumInstances = 0;
+
+constexpr uint8_t InterceptorFunction::sInterceptorTemplate[];
+
+#ifdef _M_X64
+
+// To check that unwind information propagates from hooked functions to their
+// stubs, we need to find the real address where the detoured code lives.
+class RedirectionResolver : public interceptor::WindowsDllPatcherBase<
+                                interceptor::VMSharingPolicyShared> {
+ public:
+  uintptr_t ResolveRedirectedAddressForTest(FARPROC aFunc) {
+    bool isWin8 = IsWin8OrLater() && (!IsWin8Point1OrLater());
+
+    bool isDuplicateHandle = (reinterpret_cast<void*>(aFunc) ==
+                              reinterpret_cast<void*>(&::DuplicateHandle));
+
+    // We need to reproduce the behavior of WindowsDllInterceptor::AddDetour
+    // with respect to redirection, including the corner case for bug 1659398.
+    if (isWin8 && isDuplicateHandle) {
+      return reinterpret_cast<uintptr_t>(aFunc);
+    }
+
+    return ResolveRedirectedAddress(aFunc).GetAddress();
+  }
+};
+
+#endif  // _M_X64
+
+// Hook the function and optionally attempt calling it
+template <typename OrigFuncT, size_t N, typename PredicateT, typename... Args>
+bool TestHook(const char (&dll)[N], const char* func, PredicateT&& aPred,
+              Args&&... aArgs) {
+  auto orig_func(
+      mozilla::MakeUnique<WindowsDllInterceptor::FuncHookType<OrigFuncT>>());
+  wchar_t dllW[N];
+  std::copy(std::begin(dll), std::end(dll), std::begin(dllW));
+
+  HMODULE module = ::LoadLibraryW(dllW);
+  FARPROC funcAddr = ::GetProcAddress(module, func);
+  if (!funcAddr) {
+    printf(
+        "TEST-UNEXPECTED-FAIL | WindowsDllInterceptor | Failed to find %s from "
+        "%s\n",
+        func, dll);
+    fflush(stdout);
+    return false;
+  }
+
+#ifdef _M_X64
+
+  // Resolve what is the actual address of the code that will be detoured, as
+  // that's the code we want to compare with when we check for unwind
+  // information. Do that *before* detouring, although the address will only be
+  // used after detouring.
+  RedirectionResolver resolver;
+  auto detouredCodeAddr = resolver.ResolveRedirectedAddressForTest(funcAddr);
+
+#endif  // _M_X64
+
+  bool successful = false;
+  WindowsDllInterceptor TestIntercept;
+  TestIntercept.Init(dll);
+
+  InterceptorFunction& interceptorFunc = InterceptorFunction::Create();
+  successful = orig_func->Set(
+      TestIntercept, func,
+      reinterpret_cast<OrigFuncT>(interceptorFunc.GetFunction()));
+
+  if (successful) {
+    auto stub = reinterpret_cast<uintptr_t>(orig_func->GetStub());
+    interceptorFunc.SetStub(stub);
+    printf("TEST-PASS | WindowsDllInterceptor | Could hook %s from %s\n", func,
+           dll);
+    fflush(stdout);
+
+#ifdef _M_X64
+
+    // Check that unwind information has been added if and only if it was
+    // present for the original detoured code.
+    uintptr_t funcImageBase = 0;
+    auto funcEntry =
+        RtlLookupFunctionEntry(detouredCodeAddr, &funcImageBase, nullptr);
+    bool funcHasUnwindInfo = bool(funcEntry);
+
+    uintptr_t stubImageBase = 0;
+    auto stubEntry = RtlLookupFunctionEntry(stub, &stubImageBase, nullptr);
+    bool stubHasUnwindInfo = bool(stubEntry);
+
+    if (funcHasUnwindInfo == stubHasUnwindInfo) {
+      printf(
+          "TEST-PASS | WindowsDllInterceptor | The hook for %s from %s and "
+          "the original function are coherent with respect to unwind info: "
+          "funcHasUnwindInfo (%d) == stubHasUnwindInfo (%d).\n",
+          func, dll, funcHasUnwindInfo, stubHasUnwindInfo);
+      fflush(stdout);
+    } else {
+      printf(
+          "TEST-UNEXPECTED-FAIL | WindowsDllInterceptor | Hook for %s from %s "
+          "and the original function are not coherent with respect to unwind "
+          "info: "
+          "funcHasUnwindInfo (%d) != stubHasUnwindInfo (%d).\n",
+          func, dll, funcHasUnwindInfo, stubHasUnwindInfo);
+      fflush(stdout);
+      return false;
+    }
+
+    if (stubHasUnwindInfo) {
+      if (stub == (stubImageBase + stubEntry->BeginAddress)) {
+        printf(
+            "TEST-PASS | WindowsDllInterceptor | The hook for %s from %s has "
+            "coherent unwind info.\n",
+            func, dll);
+        fflush(stdout);
+      } else {
+        printf(
+            "TEST-UNEXPECTED-FAIL | WindowsDllInterceptor | The hook for %s "
+            " from %s has incoherent unwind info.\n",
+            func, dll);
+        fflush(stdout);
+        return false;
+      }
+    }
+
+#endif  // _M_X64
+
+    if (!aPred) {
+      printf(
+          "TEST-SKIPPED | WindowsDllInterceptor | "
+          "Will not attempt to execute patched %s.\n",
+          func);
+      fflush(stdout);
+      return true;
+    }
+
+    // Test the DLL function we just hooked.
+    return CheckHook(reinterpret_cast<OrigFuncT&>(funcAddr), dll, func,
+                     std::forward<PredicateT>(aPred),
+                     std::forward<Args>(aArgs)...);
+  } else {
+    printf(
+        "TEST-UNEXPECTED-FAIL | WindowsDllInterceptor | Failed to hook %s from "
+        "%s\n",
+        func, dll);
+    fflush(stdout);
+
+    // Print out the function's bytes so that we can easily analyze the error.
+    nsModuleHandle mod(::LoadLibraryW(dllW));
+    FARPROC funcAddr = ::GetProcAddress(mod, func);
+    if (funcAddr) {
+      const uint32_t kNumBytesToDump =
+          WindowsDllInterceptor::GetWorstCaseRequiredBytesToPatch();
+
+      printf("\tFirst %u bytes of function:\n\t", kNumBytesToDump);
+
+      auto code = reinterpret_cast<const uint8_t*>(funcAddr);
+      for (uint32_t i = 0; i < kNumBytesToDump; ++i) {
+        char suffix = (i < (kNumBytesToDump - 1)) ? ' ' : '\n';
+        printf("%02hhX%c", code[i], suffix);
+      }
+
+      fflush(stdout);
+    }
+    return false;
+  }
+}
+
+// Detour the function and optionally attempt calling it
+template <typename OrigFuncT, size_t N, typename PredicateT>
+bool TestDetour(const char (&dll)[N], const char* func, PredicateT&& aPred) {
+  auto orig_func(
+      mozilla::MakeUnique<WindowsDllInterceptor::FuncHookType<OrigFuncT>>());
+  wchar_t dllW[N];
+  std::copy(std::begin(dll), std::end(dll), std::begin(dllW));
+
+  bool successful = false;
+  WindowsDllInterceptor TestIntercept;
+  TestIntercept.Init(dll);
+
+  InterceptorFunction& interceptorFunc = InterceptorFunction::Create();
+  successful = orig_func->Set(
+      TestIntercept, func,
+      reinterpret_cast<OrigFuncT>(interceptorFunc.GetFunction()));
+
+  if (successful) {
+    interceptorFunc.SetStub(reinterpret_cast<uintptr_t>(orig_func->GetStub()));
+    printf("TEST-PASS | WindowsDllInterceptor | Could detour %s from %s\n",
+           func, dll);
+    fflush(stdout);
+    if (!aPred) {
+      printf(
+          "TEST-SKIPPED | WindowsDllInterceptor | "
+          "Will not attempt to execute patched %s.\n",
+          func);
+      fflush(stdout);
+      return true;
+    }
+
+    // Test the DLL function we just hooked.
+    HMODULE module = ::LoadLibraryW(dllW);
+    FARPROC funcAddr = ::GetProcAddress(module, func);
+    if (!funcAddr) {
+      return false;
+    }
+
+    return CheckHook(reinterpret_cast<OrigFuncT&>(funcAddr), dll, func,
+                     std::forward<PredicateT>(aPred));
+  } else {
+    printf(
+        "TEST-UNEXPECTED-FAIL | WindowsDllInterceptor | Failed to detour %s "
+        "from %s\n",
+        func, dll);
+    fflush(stdout);
+    return false;
+  }
+}
+
+// If a function pointer's type returns void*, this template converts that type
+// to return uintptr_t instead, for the purposes of predicates.
+template <typename FuncT>
+struct SubstituteForVoidPtr {
+  using Type = FuncT;
+};
+
+template <typename... Args>
+struct SubstituteForVoidPtr<void* (*)(Args...)> {
+  using Type = uintptr_t (*)(Args...);
+};
+
+#ifdef _M_IX86
+template <typename... Args>
+struct SubstituteForVoidPtr<void*(__stdcall*)(Args...)> {
+  using Type = uintptr_t(__stdcall*)(Args...);
+};
+
+template <typename... Args>
+struct SubstituteForVoidPtr<void*(__fastcall*)(Args...)> {
+  using Type = uintptr_t(__fastcall*)(Args...);
+};
+#endif  // _M_IX86
+
+// Determines the function's return type
+template <typename FuncT>
+struct ReturnType;
+
+template <typename R, typename... Args>
+struct ReturnType<R (*)(Args...)> {
+  using Type = R;
+};
+
+#ifdef _M_IX86
+template <typename R, typename... Args>
+struct ReturnType<R(__stdcall*)(Args...)> {
+  using Type = R;
+};
+
+template <typename R, typename... Args>
+struct ReturnType<R(__fastcall*)(Args...)> {
+  using Type = R;
+};
+#endif  // _M_IX86
+
+// Predicates that may be supplied during tests
+template <typename FuncT>
+struct Predicates {
+  using ArgType = typename ReturnType<FuncT>::Type;
+
+  template <ArgType CompVal>
+  static bool Equals(ArgType aValue) {
+    return CompVal == aValue;
+  }
+
+  template <ArgType CompVal>
+  static bool NotEquals(ArgType aValue) {
+    return CompVal != aValue;
+  }
+
+  template <ArgType CompVal>
+  static bool Ignore(ArgType aValue) {
+    return true;
+  }
+};
+
+// Functions that return void should be ignored, so we specialize the
+// Ignore predicate for that case. Use nullptr as the value to compare against.
+template <typename... Args>
+struct Predicates<void (*)(Args...)> {
+  template <nullptr_t DummyVal>
+  static bool Ignore() {
+    return true;
+  }
+};
+
+#ifdef _M_IX86
+template <typename... Args>
+struct Predicates<void(__stdcall*)(Args...)> {
+  template <nullptr_t DummyVal>
+  static bool Ignore() {
+    return true;
+  }
+};
+
+template <typename... Args>
+struct Predicates<void(__fastcall*)(Args...)> {
+  template <nullptr_t DummyVal>
+  static bool Ignore() {
+    return true;
+  }
+};
+#endif  // _M_IX86
+
+// The standard test. Hook |func|, and then try executing it with all zero
+// arguments, using |pred| and |comp| to determine whether the call successfully
+// executed. In general, you want set pred and comp such that they return true
+// when the function is returning whatever value is expected with all-zero
+// arguments.
+//
+// Note: When |func| returns void, you must supply |Ignore| and |nullptr| as the
+// |pred| and |comp| arguments, respectively.
+#define TEST_HOOK_HELPER(dll, func, pred, comp) \
+  TestHook<decltype(&func)>(dll, #func,         \
+                            &Predicates<decltype(&func)>::pred<comp>)
+
+#define TEST_HOOK(dll, func, pred, comp) TEST_HOOK_HELPER(dll, func, pred, comp)
+
+// We need to special-case functions that return INVALID_HANDLE_VALUE
+// (ie, CreateFile). Our template machinery for comparing values doesn't work
+// with integer constants passed as pointers (well, it works on MSVC, but not
+// clang, because that is not standard-compliant).
+#define TEST_HOOK_FOR_INVALID_HANDLE_VALUE(dll, func)                   \
+  TestHook<SubstituteForVoidPtr<decltype(&func)>::Type>(                \
+      dll, #func,                                                       \
+      &Predicates<SubstituteForVoidPtr<decltype(&func)>::Type>::Equals< \
+          uintptr_t(-1)>)
+
+// This variant allows you to explicitly supply arguments to the hooked function
+// during testing. You want to provide arguments that produce the conditions
+// that induce the function to return a value that is accepted by your
+// predicate.
+#define TEST_HOOK_PARAMS(dll, func, pred, comp, ...) \
+  TestHook<decltype(&func)>(                         \
+      dll, #func, &Predicates<decltype(&func)>::pred<comp>, __VA_ARGS__)
+
+// This is for cases when we want to hook |func|, but it is unsafe to attempt
+// to execute the function in the context of a test.
+#define TEST_HOOK_SKIP_EXEC(dll, func)                                        \
+  TestHook<decltype(&func)>(                                                  \
+      dll, #func,                                                             \
+      reinterpret_cast<bool (*)(typename ReturnType<decltype(&func)>::Type)>( \
+          NULL))
+
+// The following three variants are identical to the previous macros,
+// however the forcibly use a Detour on 32-bit Windows. On 64-bit Windows,
+// these macros are identical to their TEST_HOOK variants.
+#define TEST_DETOUR(dll, func, pred, comp) \
+  TestDetour<decltype(&func)>(dll, #func,  \
+                              &Predicates<decltype(&func)>::pred<comp>)
+
+#define TEST_DETOUR_PARAMS(dll, func, pred, comp, ...) \
+  TestDetour<decltype(&func)>(                         \
+      dll, #func, &Predicates<decltype(&func)>::pred<comp>, __VA_ARGS__)
+
+#define TEST_DETOUR_SKIP_EXEC(dll, func)                                      \
+  TestDetour<decltype(&func)>(                                                \
+      dll, #func,                                                             \
+      reinterpret_cast<bool (*)(typename ReturnType<decltype(&func)>::Type)>( \
+          NULL))
+
+template <typename OrigFuncT, size_t N, typename PredicateT, typename... Args>
+bool MaybeTestHook(const bool cond, const char (&dll)[N], const char* func,
+                   PredicateT&& aPred, Args&&... aArgs) {
+  if (!cond) {
+    printf(
+        "TEST-SKIPPED | WindowsDllInterceptor | Skipped hook test for %s from "
+        "%s\n",
+        func, dll);
+    fflush(stdout);
+    return true;
+  }
+
+  return TestHook<OrigFuncT>(dll, func, std::forward<PredicateT>(aPred),
+                             std::forward<Args>(aArgs)...);
+}
+
+// Like TEST_HOOK, but the test is only executed when cond is true.
+#define MAYBE_TEST_HOOK(cond, dll, func, pred, comp) \
+  MaybeTestHook<decltype(&func)>(cond, dll, #func,   \
+                                 &Predicates<decltype(&func)>::pred<comp>)
+
+#define MAYBE_TEST_HOOK_PARAMS(cond, dll, func, pred, comp, ...) \
+  MaybeTestHook<decltype(&func)>(                                \
+      cond, dll, #func, &Predicates<decltype(&func)>::pred<comp>, __VA_ARGS__)
+
+#define MAYBE_TEST_HOOK_SKIP_EXEC(cond, dll, func)                            \
+  MaybeTestHook<decltype(&func)>(                                             \
+      cond, dll, #func,                                                       \
+      reinterpret_cast<bool (*)(typename ReturnType<decltype(&func)>::Type)>( \
+          NULL))
+
+bool ShouldTestTipTsf() {
+  if (!IsWin8OrLater()) {
+    return false;
+  }
+
+  mozilla::DynamicallyLinkedFunctionPtr<decltype(&SHGetKnownFolderPath)>
+      pSHGetKnownFolderPath(L"shell32.dll", "SHGetKnownFolderPath");
+  if (!pSHGetKnownFolderPath) {
+    return false;
+  }
+
+  PWSTR commonFilesPath = nullptr;
+  if (FAILED(pSHGetKnownFolderPath(FOLDERID_ProgramFilesCommon, 0, nullptr,
+                                   &commonFilesPath))) {
+    return false;
+  }
+
+  wchar_t fullPath[MAX_PATH + 1] = {};
+  wcscpy(fullPath, commonFilesPath);
+  wcscat(fullPath, L"\\Microsoft Shared\\Ink\\tiptsf.dll");
+  CoTaskMemFree(commonFilesPath);
+
+  if (!LoadLibraryW(fullPath)) {
+    return false;
+  }
+
+  // Leak the module so that it's loaded for the interceptor test
+  return true;
+}
+
+static const wchar_t gEmptyUnicodeStringLiteral[] = L"";
+static UNICODE_STRING gEmptyUnicodeString;
+static BOOLEAN gIsPresent;
+
+bool HasApiSetQueryApiSetPresence() {
+  mozilla::DynamicallyLinkedFunctionPtr<decltype(&ApiSetQueryApiSetPresence)>
+      func(L"Api-ms-win-core-apiquery-l1-1-0.dll", "ApiSetQueryApiSetPresence");
+  if (!func) {
+    return false;
+  }
+
+  // Prepare gEmptyUnicodeString for the test
+  ::RtlInitUnicodeString(&gEmptyUnicodeString, gEmptyUnicodeStringLiteral);
+
+  return true;
+}
+
+// Set this to true to test function unhooking (currently broken).
+const bool ShouldTestUnhookFunction = false;
+
+#if defined(_M_X64) || defined(_M_ARM64)
+
+// Use VMSharingPolicyUnique for the ShortInterceptor, as it needs to
+// reserve its trampoline memory in a special location.
+using ShortInterceptor = mozilla::interceptor::WindowsDllInterceptor<
+    mozilla::interceptor::VMSharingPolicyUnique<
+        mozilla::interceptor::MMPolicyInProcess>>;
+
+static ShortInterceptor::FuncHookType<decltype(&::NtMapViewOfSection)>
+    orig_NtMapViewOfSection;
+
+#endif  // defined(_M_X64) || defined(_M_ARM64)
+
+bool TestShortDetour() {
+#if defined(_M_X64) || defined(_M_ARM64)
+  auto pNtMapViewOfSection = reinterpret_cast<decltype(&::NtMapViewOfSection)>(
+      ::GetProcAddress(::GetModuleHandleW(L"ntdll.dll"), "NtMapViewOfSection"));
+  if (!pNtMapViewOfSection) {
+    printf(
+        "TEST-FAILED | WindowsDllInterceptor | "
+        "Failed to resolve ntdll!NtMapViewOfSection\n");
+    fflush(stdout);
+    return false;
+  }
+
+  {  // Scope for shortInterceptor
+    ShortInterceptor shortInterceptor;
+    shortInterceptor.TestOnlyDetourInit(
+        L"ntdll.dll",
+        mozilla::interceptor::DetourFlags::eTestOnlyForceShortPatch);
+
+    InterceptorFunction& interceptorFunc = InterceptorFunction::Create();
+    if (!orig_NtMapViewOfSection.SetDetour(
+            shortInterceptor, "NtMapViewOfSection",
+            reinterpret_cast<decltype(&::NtMapViewOfSection)>(
+                interceptorFunc.GetFunction()))) {
+      printf(
+          "TEST-FAILED | WindowsDllInterceptor | "
+          "Failed to hook ntdll!NtMapViewOfSection via 10-byte patch\n");
+      fflush(stdout);
+      return false;
+    }
+
+    interceptorFunc.SetStub(
+        reinterpret_cast<uintptr_t>(orig_NtMapViewOfSection.GetStub()));
+
+    auto pred =
+        &Predicates<decltype(&::NtMapViewOfSection)>::Ignore<((NTSTATUS)0)>;
+
+    if (!CheckHook(pNtMapViewOfSection, "ntdll.dll", "NtMapViewOfSection",
+                   pred)) {
+      // CheckHook has already printed the error message for us
+      return false;
+    }
+  }
+
+  // Now ensure that our hook cleanup worked
+  if (ShouldTestUnhookFunction) {
+    NTSTATUS status =
+        pNtMapViewOfSection(nullptr, nullptr, nullptr, 0, 0, nullptr, nullptr,
+                            ((SECTION_INHERIT)0), 0, 0);
+    if (NT_SUCCESS(status)) {
+      printf(
+          "TEST-FAILED | WindowsDllInterceptor | "
+          "Unexpected successful call to ntdll!NtMapViewOfSection after "
+          "removing short-patched hook\n");
+      fflush(stdout);
+      return false;
+    }
+
+    printf(
+        "TEST-PASS | WindowsDllInterceptor | "
+        "Successfully unhooked ntdll!NtMapViewOfSection via short patch\n");
+    fflush(stdout);
+  }
+
+  return true;
+#else
+  return true;
+#endif
+}
+
+constexpr uintptr_t NoStubAddressCheck = 0;
+constexpr uintptr_t ExpectedFail = 1;
+struct TestCase {
+  const char* mFunctionName;
+  uintptr_t mExpectedStub;
+  bool mPatchedOnce;
+  explicit TestCase(const char* aFunctionName, uintptr_t aExpectedStub)
+      : mFunctionName(aFunctionName),
+        mExpectedStub(aExpectedStub),
+        mPatchedOnce(false) {}
+} g_AssemblyTestCases[] = {
+#if defined(__clang__)
+// We disable these testcases because the code coverage instrumentation injects
+// code in a way that WindowsDllInterceptor doesn't understand.
+#  ifndef MOZ_CODE_COVERAGE
+#    if defined(_M_X64)
+    // Since we have PatchIfTargetIsRecognizedTrampoline for x64, we expect the
+    // original jump destination is returned as a stub.
+    TestCase("MovPushRet", JumpDestination),
+    TestCase("MovRaxJump", JumpDestination),
+    TestCase("DoubleJump", JumpDestination),
+
+    // Passing NoStubAddressCheck as the following testcases return
+    // a trampoline address instead of the original destination.
+    TestCase("NearJump", NoStubAddressCheck),
+    TestCase("OpcodeFF", NoStubAddressCheck),
+    TestCase("IndirectCall", NoStubAddressCheck),
+    TestCase("MovImm64", NoStubAddressCheck),
+#    elif defined(_M_IX86)
+    // Skip the stub address check as we always generate a trampoline for x86.
+    TestCase("PushRet", NoStubAddressCheck),
+    TestCase("MovEaxJump", NoStubAddressCheck),
+    TestCase("DoubleJump", NoStubAddressCheck),
+    TestCase("Opcode83", NoStubAddressCheck),
+    TestCase("LockPrefix", NoStubAddressCheck),
+    TestCase("LooksLikeLockPrefix", NoStubAddressCheck),
+#    endif
+#    if !defined(DEBUG)
+    // Skip on Debug build because it hits MOZ_ASSERT_UNREACHABLE.
+    TestCase("UnsupportedOp", ExpectedFail),
+#    endif  // !defined(DEBUG)
+#  endif    // MOZ_CODE_COVERAGE
+#endif      // defined(__clang__)
+};
+
+template <typename InterceptorType>
+bool TestAssemblyFunctions() {
+  static const auto patchedFunction = []() { patched_func_called = true; };
+
+  InterceptorType interceptor;
+  interceptor.Init("TestDllInterceptor.exe");
+
+  for (auto& testCase : g_AssemblyTestCases) {
+    if (testCase.mExpectedStub == NoStubAddressCheck && testCase.mPatchedOnce) {
+      // For the testcases with NoStubAddressCheck, we revert a hook by
+      // jumping into the original stub, which is not detourable again.
+      continue;
+    }
+
+    typename InterceptorType::template FuncHookType<void (*)()> hook;
+    bool result =
+        hook.Set(interceptor, testCase.mFunctionName, patchedFunction);
+    if (testCase.mExpectedStub == ExpectedFail) {
+      if (result) {
+        printf(
+            "TEST-FAILED | WindowsDllInterceptor | "
+            "Unexpectedly succeeded to detour %s.\n",
+            testCase.mFunctionName);
+        return false;
+      }
+#if defined(NIGHTLY_BUILD)
+      const Maybe<DetourError>& maybeError = interceptor.GetLastDetourError();
+      if (maybeError.isNothing()) {
+        printf(
+            "TEST-FAILED | WindowsDllInterceptor | "
+            "DetourError was not set on detour error.\n");
+        return false;
+      }
+      if (maybeError.ref().mErrorCode !=
+          DetourResultCode::DETOUR_PATCHER_CREATE_TRAMPOLINE_ERROR) {
+        printf(
+            "TEST-FAILED | WindowsDllInterceptor | "
+            "A wrong detour errorcode was set on detour error.\n");
+        return false;
+      }
+#endif  // defined(NIGHTLY_BUILD)
+      printf("TEST-PASS | WindowsDllInterceptor | %s\n",
+             testCase.mFunctionName);
+      continue;
+    }
+
+    if (!result) {
+      printf(
+          "TEST-FAILED | WindowsDllInterceptor | "
+          "Failed to detour %s.\n",
+          testCase.mFunctionName);
+      return false;
+    }
+
+    testCase.mPatchedOnce = true;
+
+    const auto actualStub = reinterpret_cast<uintptr_t>(hook.GetStub());
+    if (testCase.mExpectedStub != NoStubAddressCheck &&
+        actualStub != testCase.mExpectedStub) {
+      printf(
+          "TEST-FAILED | WindowsDllInterceptor | "
+          "Wrong stub was backed up for %s: %zx\n",
+          testCase.mFunctionName, actualStub);
+      return false;
+    }
+
+    patched_func_called = false;
+
+    auto originalFunction = reinterpret_cast<void (*)()>(
+        GetProcAddress(GetModuleHandleW(nullptr), testCase.mFunctionName));
+    originalFunction();
+
+    if (!patched_func_called) {
+      printf(
+          "TEST-FAILED | WindowsDllInterceptor | "
+          "Hook from %s was not called\n",
+          testCase.mFunctionName);
+      return false;
+    }
+
+    printf("TEST-PASS | WindowsDllInterceptor | %s\n", testCase.mFunctionName);
+  }
+
+  return true;
+}
+
+#if defined(_M_X64) && !defined(MOZ_CODE_COVERAGE)
+// We want to test hooking and unhooking with unwind information, so we need:
+//  - a VMSharingPolicy such that ShouldUnhookUponDestruction() is true and
+//    Items() is implemented;
+//  - a MMPolicy such that ShouldUnhookUponDestruction() is true and
+//    kSupportsUnwindInfo is true.
+using DetouredCallInterceptor = mozilla::interceptor::WindowsDllInterceptor<
+    mozilla::interceptor::VMSharingPolicyUnique<
+        mozilla::interceptor::MMPolicyInProcess>>;
+
+struct DetouredCallChunk {
+  alignas(uint32_t) RUNTIME_FUNCTION functionTable[1];
+  alignas(uint32_t) uint8_t unwindInfo[sizeof(gDetouredCallUnwindInfo)];
+  uint8_t code[gDetouredCallCodeSize];
+};
+
+// Unfortunately using RtlAddFunctionTable for static code that lives within
+// a module doesn't seem to work. Presumably it conflicts with the static
+// function tables. So we recreate gDetouredCall as dynamic code to be able to
+// associate it with unwind information.
+decltype(&DetouredCallCode) gDetouredCall =
+    []() -> decltype(&DetouredCallCode) {
+  // We first adjust the detoured call jumper from:
+  //   ff 25 00 00 00 00    jmp qword ptr [rip + 0]
+  // to:
+  //   ff 25 XX XX XX XX    jmp qword ptr [rip + offset gDetouredCall]
+  uint8_t bytes[6]{0xff, 0x25, 0, 0, 0, 0};
+  if (0 != memcmp(bytes, reinterpret_cast<void*>(DetouredCallJumper),
+                  sizeof bytes)) {
+    return nullptr;
+  }
+
+  DWORD oldProtect{};
+  if (!VirtualProtect(reinterpret_cast<void*>(DetouredCallJumper), sizeof bytes,
+                      PAGE_READWRITE, &oldProtect)) {
+    return nullptr;
+  }
+
+  *reinterpret_cast<uint32_t*>(&bytes[2]) = static_cast<uint32_t>(
+      reinterpret_cast<uintptr_t>(&gDetouredCall) -
+      (reinterpret_cast<uintptr_t>(DetouredCallJumper) + sizeof bytes));
+  memcpy(reinterpret_cast<void*>(DetouredCallJumper), bytes, sizeof bytes);
+
+  if (!VirtualProtect(reinterpret_cast<void*>(DetouredCallJumper), sizeof bytes,
+                      oldProtect, &oldProtect)) {
+    return nullptr;
+  }
+
+  auto detouredCallChunk = reinterpret_cast<DetouredCallChunk*>(
+      VirtualAlloc(nullptr, sizeof(DetouredCallChunk), MEM_RESERVE | MEM_COMMIT,
+                   PAGE_READWRITE));
+  if (!detouredCallChunk) {
+    return nullptr;
+  }
+
+  detouredCallChunk->functionTable[0].BeginAddress =
+      offsetof(DetouredCallChunk, code);
+  detouredCallChunk->functionTable[0].EndAddress =
+      offsetof(DetouredCallChunk, code) + gDetouredCallCodeSize;
+  detouredCallChunk->functionTable[0].UnwindData =
+      offsetof(DetouredCallChunk, unwindInfo);
+  memcpy(reinterpret_cast<void*>(&detouredCallChunk->unwindInfo),
+         reinterpret_cast<void*>(gDetouredCallUnwindInfo),
+         sizeof(detouredCallChunk->unwindInfo));
+  memcpy(reinterpret_cast<void*>(&detouredCallChunk->code[0]),
+         reinterpret_cast<void*>(DetouredCallCode),
+         sizeof(detouredCallChunk->code));
+
+  if (!VirtualProtect(reinterpret_cast<void*>(detouredCallChunk),
+                      sizeof(DetouredCallChunk), PAGE_EXECUTE_READ,
+                      &oldProtect)) {
+    VirtualFree(detouredCallChunk, 0, MEM_RELEASE);
+    return nullptr;
+  }
+
+  if (!RtlAddFunctionTable(detouredCallChunk->functionTable, 1,
+                           reinterpret_cast<uintptr_t>(detouredCallChunk))) {
+    VirtualFree(detouredCallChunk, 0, MEM_RELEASE);
+    return nullptr;
+  }
+
+  return reinterpret_cast<decltype(&DetouredCallCode)>(detouredCallChunk->code);
+}();
+
+// We use our own variable instead of patched_func_called because the callee of
+// gDetouredCall could end up calling other, already hooked functions could
+// change patched_func_called.
+static volatile bool sCalledPatchedDetouredCall = false;
+static volatile bool sCalledDetouredCallCallee = false;
+static volatile bool sCouldUnwindFromDetouredCallCallee = false;
+void DetouredCallCallee() {
+  sCalledDetouredCallCallee = true;
+
+  // Check that we can fully unwind the stack
+  CONTEXT contextRecord{};
+  RtlCaptureContext(&contextRecord);
+  if (!contextRecord.Rip) {
+    printf(
+        "TEST-UNEXPECTED-FAIL | WindowsDllInterceptor | "
+        "DetouredCallCallee was unable to get an initial context to work "
+        "with\n");
+    fflush(stdout);
+    return;
+  }
+  while (contextRecord.Rip) {
+    DWORD64 imageBase = 0;
+    auto FunctionEntry =
+        RtlLookupFunctionEntry(contextRecord.Rip, &imageBase, nullptr);
+    if (!FunctionEntry) {
+      printf(
+          "TEST-UNEXPECTED-FAIL | WindowsDllInterceptor | "
+          "DetouredCallCallee was unable to get unwind info for ControlPc=%p\n",
+          reinterpret_cast<void*>(contextRecord.Rip));
+      fflush(stdout);
+      return;
+    }
+    printf(
+        "TEST-PASS | WindowsDllInterceptor | "
+        "DetouredCallCallee was able to get unwind info for ControlPc=%p\n",
+        reinterpret_cast<void*>(contextRecord.Rip));
+    fflush(stdout);
+    void* handlerData = nullptr;
+    DWORD64 establisherFrame = 0;
+    RtlVirtualUnwind(UNW_FLAG_NHANDLER, imageBase, contextRecord.Rip,
+                     FunctionEntry, &contextRecord, &handlerData,
+                     &establisherFrame, nullptr);
+  }
+  sCouldUnwindFromDetouredCallCallee = true;
+}
+
+static DetouredCallInterceptor::FuncHookType<decltype(&DetouredCallCode)>
+    orig_DetouredCall;
+
+static void patched_DetouredCall(uintptr_t aCallee) {
+  sCalledPatchedDetouredCall = true;
+  return orig_DetouredCall(aCallee);
+}
+
+bool TestCallingDetouredCall(const char* aTestDescription,
+                             bool aExpectCalledPatchedDetouredCall) {
+  sCalledPatchedDetouredCall = false;
+  sCalledDetouredCallCallee = false;
+  sCouldUnwindFromDetouredCallCallee = false;
+  DetouredCallJumper(reinterpret_cast<uintptr_t>(DetouredCallCallee));
+
+  if (aExpectCalledPatchedDetouredCall != sCalledPatchedDetouredCall) {
+    printf(
+        "TEST-UNEXPECTED-FAIL | WindowsDllInterceptor | "
+        "%s: expectCalledPatchedDetouredCall (%d) differs from "
+        "sCalledPatchedDetouredCall (%d)\n",
+        aTestDescription, aExpectCalledPatchedDetouredCall,
+        sCalledPatchedDetouredCall);
+    fflush(stdout);
+    return false;
+  }
+
+  printf(
+      "TEST-PASS | WindowsDllInterceptor | "
+      "%s: expectCalledPatchedDetouredCall (%d) matches with "
+      "sCalledPatchedDetouredCall (%d)\n",
+      aTestDescription, aExpectCalledPatchedDetouredCall,
+      sCalledPatchedDetouredCall);
+  fflush(stdout);
+
+  if (!sCalledDetouredCallCallee) {
+    printf(
+        "TEST-UNEXPECTED-FAIL | WindowsDllInterceptor | "
+        "%s: gDetouredCall failed to call its callee\n",
+        aTestDescription);
+    fflush(stdout);
+    return false;
+  }
+
+  printf(
+      "TEST-PASS | WindowsDllInterceptor | "
+      "%s: gDetouredCall successfully called its callee\n",
+      aTestDescription);
+  fflush(stdout);
+
+  if (!sCouldUnwindFromDetouredCallCallee) {
+    printf(
+        "TEST-UNEXPECTED-FAIL | WindowsDllInterceptor | "
+        "%s: the callee of gDetouredCall failed to unwind\n",
+        aTestDescription);
+    fflush(stdout);
+    return false;
+  }
+
+  printf(
+      "TEST-PASS | WindowsDllInterceptor | "
+      "%s: the callee of gDetouredCall successfully unwinded\n",
+      aTestDescription);
+  fflush(stdout);
+  return true;
+}
+
+// Test that detouring a call preserves unwind information (bug 1798787).
+bool TestDetouredCallUnwindInfo() {
+  if (!gDetouredCall) {
+    printf(
+        "TEST-UNEXPECTED-FAIL | WindowsDllInterceptor | "
+        "Failed to generate dynamic gDetouredCall code\n");
+    fflush(stdout);
+    return false;
+  }
+
+  uintptr_t imageBase = 0;
+  if (!RtlLookupFunctionEntry(reinterpret_cast<uintptr_t>(gDetouredCall),
+                              &imageBase, nullptr)) {
+    printf(
+        "TEST-UNEXPECTED-FAIL | WindowsDllInterceptor | "
+        "Failed to find unwind information for dynamic gDetouredCall code\n");
+    fflush(stdout);
+    return false;
+  }
+
+  // We first double check that we manage to unwind when we *do not* detour
+  if (!TestCallingDetouredCall("Before hooking", false)) {
+    return false;
+  }
+
+  uintptr_t StubAddress = 0;
+
+  // The real test starts here: let's detour and check if we can still unwind
+  {
+    DetouredCallInterceptor ExeIntercept;
+    ExeIntercept.Init("TestDllInterceptor.exe");
+    if (!orig_DetouredCall.Set(ExeIntercept, "DetouredCallJumper",
+                               &patched_DetouredCall)) {
+      printf(
+          "TEST-UNEXPECTED-FAIL | WindowsDllInterceptor | "
+          "Failed to hook the detoured call jumper.\n");
+      fflush(stdout);
+      return false;
+    }
+
+    printf(
+        "TEST-PASS | WindowsDllInterceptor | "
+        "Successfully hooked the detoured call jumper.\n");
+    fflush(stdout);
+
+    StubAddress = reinterpret_cast<uintptr_t>(orig_DetouredCall.GetStub());
+    if (!RtlLookupFunctionEntry(StubAddress, &imageBase, nullptr)) {
+      printf(
+          "TEST-UNEXPECTED-FAIL | WindowsDllInterceptor | "
+          "Failed to find unwind information for detoured code of "
+          "gDetouredCall\n");
+      fflush(stdout);
+      return false;
+    }
+
+    TestCallingDetouredCall("After hooking", true);
+  }
+
+  // Check that we can still unwind after clearing the hook.
+  return TestCallingDetouredCall("After unhooking", false);
+}
+#endif  // defined(_M_X64) && !defined(MOZ_CODE_COVERAGE)
+
+bool TestDynamicCodePolicy() {
+  if (!IsWin8Point1OrLater()) {
+    // Skip if a platform does not support this policy.
+    return true;
+  }
+
+  PROCESS_MITIGATION_DYNAMIC_CODE_POLICY policy = {};
+  policy.ProhibitDynamicCode = true;
+
+  mozilla::DynamicallyLinkedFunctionPtr<decltype(&SetProcessMitigationPolicy)>
+      pSetProcessMitigationPolicy(L"kernel32.dll",
+                                  "SetProcessMitigationPolicy");
+  if (!pSetProcessMitigationPolicy) {
+    printf(
+        "TEST-UNEXPECTED-FAIL | WindowsDllInterceptor | "
+        "SetProcessMitigationPolicy does not exist.\n");
+    fflush(stdout);
+    return false;
+  }
+
+  if (!pSetProcessMitigationPolicy(ProcessDynamicCodePolicy, &policy,
+                                   sizeof(policy))) {
+    printf(
+        "TEST-UNEXPECTED-FAIL | WindowsDllInterceptor | "
+        "Fail to enable ProcessDynamicCodePolicy.\n");
+    fflush(stdout);
+    return false;
+  }
+
+  WindowsDllInterceptor ExeIntercept;
+  ExeIntercept.Init("TestDllInterceptor.exe");
+
+  // Make sure we fail to hook a function if ProcessDynamicCodePolicy is on
+  // because we cannot create an executable trampoline region.
+  if (orig_payloadNotHooked.Set(ExeIntercept, "payloadNotHooked",
+                                &patched_rotatePayload)) {
+    printf(
+        "TEST-UNEXPECTED-FAIL | WindowsDllInterceptor | "
+        "ProcessDynamicCodePolicy is not working.\n");
+    fflush(stdout);
+    return false;
+  }
+
+  printf(
+      "TEST-PASS | WindowsDllInterceptor | "
+      "Successfully passed TestDynamicCodePolicy.\n");
+  fflush(stdout);
+  return true;
+}
+
+extern "C" int wmain(int argc, wchar_t* argv[]) {
+  LARGE_INTEGER start;
+  QueryPerformanceCounter(&start);
+
+  // We disable this part of the test because the code coverage instrumentation
+  // injects code in rotatePayload in a way that WindowsDllInterceptor doesn't
+  // understand.
+#ifndef MOZ_CODE_COVERAGE
+  payload initial = {0x12345678, 0xfc4e9d31, 0x87654321};
+  payload p0, p1;
+  ZeroMemory(&p0, sizeof(p0));
+  ZeroMemory(&p1, sizeof(p1));
+
+  p0 = rotatePayload(initial);
+
+  {
+    WindowsDllInterceptor ExeIntercept;
+    ExeIntercept.Init("TestDllInterceptor.exe");
+    if (orig_rotatePayload.Set(ExeIntercept, "rotatePayload",
+                               &patched_rotatePayload)) {
+      printf("TEST-PASS | WindowsDllInterceptor | Hook added\n");
+      fflush(stdout);
+    } else {
+      printf(
+          "TEST-UNEXPECTED-FAIL | WindowsDllInterceptor | Failed to add "
+          "hook\n");
+      fflush(stdout);
+      return 1;
+    }
+
+    p1 = rotatePayload(initial);
+
+    if (patched_func_called) {
+      printf("TEST-PASS | WindowsDllInterceptor | Hook called\n");
+      fflush(stdout);
+    } else {
+      printf(
+          "TEST-UNEXPECTED-FAIL | WindowsDllInterceptor | Hook was not "
+          "called\n");
+      fflush(stdout);
+      return 1;
+    }
+
+    if (p0 == p1) {
+      printf("TEST-PASS | WindowsDllInterceptor | Hook works properly\n");
+      fflush(stdout);
+    } else {
+      printf(
+          "TEST-UNEXPECTED-FAIL | WindowsDllInterceptor | Hook didn't return "
+          "the right information\n");
+      fflush(stdout);
+      return 1;
+    }
+  }
+
+  patched_func_called = false;
+  ZeroMemory(&p1, sizeof(p1));
+
+  p1 = rotatePayload(initial);
+
+  if (ShouldTestUnhookFunction != patched_func_called) {
+    printf(
+        "TEST-PASS | WindowsDllInterceptor | Hook was %scalled after "
+        "unregistration\n",
+        ShouldTestUnhookFunction ? "not " : "");
+    fflush(stdout);
+  } else {
+    printf(
+        "TEST-UNEXPECTED-FAIL | WindowsDllInterceptor | Hook was %scalled "
+        "after unregistration\n",
+        ShouldTestUnhookFunction ? "" : "not ");
+    fflush(stdout);
+    return 1;
+  }
+
+  if (p0 == p1) {
+    printf(
+        "TEST-PASS | WindowsDllInterceptor | Original function worked "
+        "properly\n");
+    fflush(stdout);
+  } else {
+    printf(
+        "TEST-UNEXPECTED-FAIL | WindowsDllInterceptor | Original function "
+        "didn't return the right information\n");
+    fflush(stdout);
+    return 1;
+  }
+#endif
+
+  CredHandle credHandle;
+  memset(&credHandle, 0, sizeof(CredHandle));
+  OBJECT_ATTRIBUTES attributes = {};
+
+  // NB: These tests should be ordered such that lower-level APIs are tested
+  // before higher-level APIs.
+  if (TestShortDetour() &&
+  // Run <ShortInterceptor> first because <WindowsDllInterceptor>
+  // does not clean up hooks.
+#if defined(_M_X64)
+      TestAssemblyFunctions<ShortInterceptor>() &&
+#endif
+      TestAssemblyFunctions<WindowsDllInterceptor>() &&
+#ifdef _M_IX86
+      // We keep this test to hook complex code on x86. (Bug 850957)
+      TEST_HOOK("ntdll.dll", NtFlushBuffersFile, NotEquals, 0) &&
+#endif
+      TEST_HOOK("ntdll.dll", NtCreateFile, NotEquals, 0) &&
+      TEST_HOOK("ntdll.dll", NtReadFile, NotEquals, 0) &&
+      TEST_HOOK("ntdll.dll", NtReadFileScatter, NotEquals, 0) &&
+      TEST_HOOK("ntdll.dll", NtWriteFile, NotEquals, 0) &&
+      TEST_HOOK("ntdll.dll", NtWriteFileGather, NotEquals, 0) &&
+      TEST_HOOK_PARAMS("ntdll.dll", NtQueryFullAttributesFile, NotEquals, 0,
+                       &attributes, nullptr) &&
+      TEST_DETOUR_SKIP_EXEC("ntdll.dll", LdrLoadDll) &&
+      TEST_HOOK("ntdll.dll", LdrUnloadDll, NotEquals, 0) &&
+      MAYBE_TEST_HOOK_SKIP_EXEC(IsWin8OrLater(), "ntdll.dll",
+                                LdrResolveDelayLoadedAPI) &&
+      MAYBE_TEST_HOOK_PARAMS(HasApiSetQueryApiSetPresence(),
+                             "Api-ms-win-core-apiquery-l1-1-0.dll",
+                             ApiSetQueryApiSetPresence, Equals, FALSE,
+                             &gEmptyUnicodeString, &gIsPresent) &&
+      TEST_HOOK("kernelbase.dll", QueryDosDeviceW, Equals, 0) &&
+      TEST_HOOK("kernel32.dll", GetFileAttributesW, Equals,
+                INVALID_FILE_ATTRIBUTES) &&
+#if !defined(_M_ARM64)
+#  ifndef MOZ_ASAN
+      // Bug 733892: toolkit/crashreporter/nsExceptionHandler.cpp
+      // This fails on ASan because the ASan runtime already hooked this
+      // function
+      TEST_HOOK("kernel32.dll", SetUnhandledExceptionFilter, Ignore, nullptr) &&
+#  endif
+#endif  // !defined(_M_ARM64)
+#ifdef _M_IX86
+      TEST_HOOK_FOR_INVALID_HANDLE_VALUE("kernel32.dll", CreateFileW) &&
+#endif
+#if !defined(_M_ARM64)
+      TEST_HOOK_FOR_INVALID_HANDLE_VALUE("kernel32.dll", CreateFileA) &&
+#endif  // !defined(_M_ARM64)
+#if !defined(_M_ARM64)
+      TEST_HOOK("kernel32.dll", TlsAlloc, NotEquals, TLS_OUT_OF_INDEXES) &&
+      TEST_HOOK_PARAMS("kernel32.dll", TlsFree, Equals, FALSE,
+                       TLS_OUT_OF_INDEXES) &&
+      TEST_HOOK("kernel32.dll", CloseHandle, Equals, FALSE) &&
+      TEST_HOOK("kernel32.dll", DuplicateHandle, Equals, FALSE) &&
+#endif  // !defined(_M_ARM64)
+      TEST_DETOUR_SKIP_EXEC("kernel32.dll", BaseThreadInitThunk) &&
+#if defined(_M_X64) || defined(_M_ARM64)
+      MAYBE_TEST_HOOK(!IsWin8OrLater(), "kernel32.dll",
+                      RtlInstallFunctionTableCallback, Equals, FALSE) &&
+      TEST_HOOK("user32.dll", GetKeyState, Ignore, 0) &&  // see Bug 1316415
+#endif
+      TEST_HOOK("user32.dll", GetWindowInfo, Equals, FALSE) &&
+      TEST_HOOK("user32.dll", TrackPopupMenu, Equals, FALSE) &&
+      TEST_DETOUR("user32.dll", CreateWindowExW, Equals, nullptr) &&
+      TEST_HOOK("user32.dll", InSendMessageEx, Equals, ISMEX_NOSEND) &&
+      TEST_HOOK("user32.dll", SendMessageTimeoutW, Equals, 0) &&
+      TEST_HOOK("user32.dll", SetCursorPos, NotEquals, FALSE) &&
+      TEST_HOOK("bcrypt.dll", BCryptGenRandom, Equals,
+                static_cast<NTSTATUS>(STATUS_INVALID_HANDLE)) &&
+      TEST_HOOK("advapi32.dll", RtlGenRandom, Equals, TRUE) &&
+#if !defined(_M_ARM64)
+      TEST_HOOK("imm32.dll", ImmGetContext, Equals, nullptr) &&
+#endif  // !defined(_M_ARM64)
+      TEST_HOOK("imm32.dll", ImmGetCompositionStringW, Ignore, 0) &&
+      TEST_HOOK_SKIP_EXEC("imm32.dll", ImmSetCandidateWindow) &&
+      TEST_HOOK("imm32.dll", ImmNotifyIME, Equals, 0) &&
+      TEST_HOOK("comdlg32.dll", GetSaveFileNameW, Ignore, FALSE) &&
+      TEST_HOOK("comdlg32.dll", GetOpenFileNameW, Ignore, FALSE) &&
+#if defined(_M_X64)
+      TEST_HOOK("comdlg32.dll", PrintDlgW, Ignore, 0) &&
+#endif
+      MAYBE_TEST_HOOK(ShouldTestTipTsf(), "tiptsf.dll", ProcessCaretEvents,
+                      Ignore, nullptr) &&
+      TEST_HOOK("wininet.dll", InternetOpenA, NotEquals, nullptr) &&
+      TEST_HOOK("wininet.dll", InternetCloseHandle, Equals, FALSE) &&
+      TEST_HOOK("wininet.dll", InternetConnectA, Equals, nullptr) &&
+      TEST_HOOK("wininet.dll", InternetQueryDataAvailable, Equals, FALSE) &&
+      TEST_HOOK("wininet.dll", InternetReadFile, Equals, FALSE) &&
+      TEST_HOOK("wininet.dll", InternetWriteFile, Equals, FALSE) &&
+      TEST_HOOK("wininet.dll", InternetSetOptionA, Equals, FALSE) &&
+      TEST_HOOK("wininet.dll", HttpAddRequestHeadersA, Equals, FALSE) &&
+      TEST_HOOK("wininet.dll", HttpOpenRequestA, Equals, nullptr) &&
+      TEST_HOOK("wininet.dll", HttpQueryInfoA, Equals, FALSE) &&
+      TEST_HOOK("wininet.dll", HttpSendRequestA, Equals, FALSE) &&
+      TEST_HOOK("wininet.dll", HttpSendRequestExA, Equals, FALSE) &&
+      TEST_HOOK("wininet.dll", HttpEndRequestA, Equals, FALSE) &&
+      TEST_HOOK("wininet.dll", InternetQueryOptionA, Equals, FALSE) &&
+      TEST_HOOK("sspicli.dll", AcquireCredentialsHandleA, NotEquals,
+                SEC_E_OK) &&
+      TEST_HOOK_PARAMS("sspicli.dll", QueryCredentialsAttributesA, Equals,
+                       SEC_E_INVALID_HANDLE, &credHandle, 0, nullptr) &&
+      TEST_HOOK_PARAMS("sspicli.dll", FreeCredentialsHandle, Equals,
+                       SEC_E_INVALID_HANDLE, &credHandle) &&
+#if defined(_M_X64) && !defined(MOZ_CODE_COVERAGE)
+      TestDetouredCallUnwindInfo() &&
+#endif  // defined(_M_X64) && !defined(MOZ_CODE_COVERAGE)
+      // Run TestDynamicCodePolicy() at the end because the policy is
+      // irreversible.
+      TestDynamicCodePolicy()) {
+    printf("TEST-PASS | WindowsDllInterceptor | all checks passed\n");
+
+    LARGE_INTEGER end, freq;
+    QueryPerformanceCounter(&end);
+
+    QueryPerformanceFrequency(&freq);
+
+    LARGE_INTEGER result;
+    result.QuadPart = end.QuadPart - start.QuadPart;
+    result.QuadPart *= 1000000;
+    result.QuadPart /= freq.QuadPart;
+
+    printf("Elapsed time: %lld microseconds\n", result.QuadPart);
+
+    return 0;
+  }
+
+  return 1;
+}
diff --git a/toolkit/xre/dllservices/tests/TestDllInterceptor.exe.manifest b/toolkit/xre/dllservices/tests/TestDllInterceptor.exe.manifest
new file mode 100644
index 0000000000..11287012c5
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/TestDllInterceptor.exe.manifest
@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<assembly xmlns="urn:schemas-microsoft-com:asm.v1"
+          manifestVersion="1.0"
+          xmlns:asmv3="urn:schemas-microsoft-com:asm.v3">
+  <assemblyIdentity type="win32"
+                    name="TestDllInterceptor"
+                    version="1.0.0.0" />
+  <compatibility xmlns="urn:schemas-microsoft-com:compatibility.v1">
+    <application>
+      <!-- Need this to use functions in WindowsVersion.h -->
+      <supportedOS Id="{8e0f7a12-bfb3-4fe8-b9a5-48fd50a15a9a}"/> <!-- Win10 -->
+      <supportedOS Id="{1f676c76-80e1-4239-95bb-83d0f6d0da78}"/> <!-- Win8.1 -->
+      <supportedOS Id="{4a2f28e3-53b9-4441-ba9c-d69d4a4a6e38}"/> <!-- Win8 -->
+      <supportedOS Id="{35138b9a-5d96-4fbd-8e2d-a2440225f93a}"/> <!-- Win7 -->
+    </application>
+  </compatibility>
+</assembly>
diff --git a/toolkit/xre/dllservices/tests/TestDllInterceptorCrossProcess.cpp b/toolkit/xre/dllservices/tests/TestDllInterceptorCrossProcess.cpp
new file mode 100644
index 0000000000..32cf90bac1
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/TestDllInterceptorCrossProcess.cpp
@@ -0,0 +1,159 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/Attributes.h"
+#include "mozilla/ArrayUtils.h"
+#include "mozilla/CmdLineAndEnvUtils.h"
+#include "nsWindowsDllInterceptor.h"
+#include "nsWindowsHelpers.h"
+
+#include <string>
+
+using std::wstring;
+
+extern "C" __declspec(dllexport) int ReturnResult() { return 2; }
+
+static mozilla::CrossProcessDllInterceptor::FuncHookType<
+    decltype(&ReturnResult)>
+    gOrigReturnResult;
+
+static int ReturnResultHook() {
+  if (gOrigReturnResult() != 2) {
+    return 3;
+  }
+
+  return 0;
+}
+
+int ParentMain(int argc, wchar_t* argv[]) {
+  mozilla::SetArgv0ToFullBinaryPath(argv);
+
+  // We'll add the child process to a job so that, in the event of a failure in
+  // this parent process, the child process will be automatically terminated.
+  nsAutoHandle job(::CreateJobObjectW(nullptr, nullptr));
+  if (!job) {
+    printf(
+        "TEST-UNEXPECTED-FAIL | DllInterceptorCrossProcess | Job creation "
+        "failed\n");
+    return 1;
+  }
+
+  JOBOBJECT_EXTENDED_LIMIT_INFORMATION jobInfo = {};
+  jobInfo.BasicLimitInformation.LimitFlags = JOB_OBJECT_LIMIT_KILL_ON_JOB_CLOSE;
+
+  if (!::SetInformationJobObject(job.get(), JobObjectExtendedLimitInformation,
+                                 &jobInfo, sizeof(jobInfo))) {
+    printf(
+        "TEST-UNEXPECTED-FAIL | DllInterceptorCrossProcess | Job config "
+        "failed\n");
+    return 1;
+  }
+
+  wchar_t childArgv_1[] = L"-child";
+
+  wchar_t* childArgv[] = {argv[0], childArgv_1};
+
+  mozilla::UniquePtr<wchar_t[]> cmdLine(
+      mozilla::MakeCommandLine(mozilla::ArrayLength(childArgv), childArgv));
+
+  STARTUPINFOW si = {sizeof(si)};
+  PROCESS_INFORMATION pi;
+  if (!::CreateProcessW(argv[0], cmdLine.get(), nullptr, nullptr, FALSE,
+                        CREATE_SUSPENDED, nullptr, nullptr, &si, &pi)) {
+    printf(
+        "TEST-UNEXPECTED-FAIL | DllInterceptorCrossProcess | Failed to spawn "
+        "child process\n");
+    return 1;
+  }
+
+  nsAutoHandle childProcess(pi.hProcess);
+  nsAutoHandle childMainThread(pi.hThread);
+
+  if (!::AssignProcessToJobObject(job.get(), childProcess.get())) {
+    printf(
+        "TEST-UNEXPECTED-FAIL | DllInterceptorCrossProcess | Failed to assign "
+        "child process to job\n");
+    ::TerminateProcess(childProcess.get(), 1);
+    return 1;
+  }
+
+  mozilla::nt::CrossExecTransferManager transferMgr(childProcess);
+  if (!transferMgr) {
+    printf(
+        "TEST-UNEXPECTED-FAIL | DllInterceptorCrossProcess | "
+        "CrossExecTransferManager instantiation failed.\n");
+    return 1;
+  }
+
+  mozilla::CrossProcessDllInterceptor intcpt(childProcess.get());
+  intcpt.Init("TestDllInterceptorCrossProcess.exe");
+
+  if (!gOrigReturnResult.Set(transferMgr, intcpt, "ReturnResult",
+                             &ReturnResultHook)) {
+    printf(
+        "TEST-UNEXPECTED-FAIL | DllInterceptorCrossProcess | Failed to add "
+        "hook\n");
+    return 1;
+  }
+
+  printf("TEST-PASS | DllInterceptorCrossProcess | Hook added\n");
+
+  if (::ResumeThread(childMainThread.get()) == static_cast<DWORD>(-1)) {
+    printf(
+        "TEST-UNEXPECTED-FAIL | DllInterceptorCrossProcess | Failed to resume "
+        "child thread\n");
+    return 1;
+  }
+
+  BOOL remoteDebugging;
+  bool debugging =
+      ::IsDebuggerPresent() ||
+      (::CheckRemoteDebuggerPresent(childProcess.get(), &remoteDebugging) &&
+       remoteDebugging);
+
+  DWORD waitResult =
+      ::WaitForSingleObject(childProcess.get(), debugging ? INFINITE : 60000);
+  if (waitResult != WAIT_OBJECT_0) {
+    printf(
+        "TEST-UNEXPECTED-FAIL | DllInterceptorCrossProcess | Child process "
+        "failed to finish\n");
+    return 1;
+  }
+
+  DWORD childExitCode;
+  if (!::GetExitCodeProcess(childProcess.get(), &childExitCode)) {
+    printf(
+        "TEST-UNEXPECTED-FAIL | DllInterceptorCrossProcess | Failed to obtain "
+        "child process exit code\n");
+    return 1;
+  }
+
+  if (childExitCode) {
+    printf(
+        "TEST-UNEXPECTED-FAIL | DllInterceptorCrossProcess | Child process "
+        "exit code is %lu instead of 0\n",
+        childExitCode);
+    return 1;
+  }
+
+  printf(
+      "TEST-PASS | DllInterceptorCrossProcess | Child process exit code is "
+      "zero\n");
+  return 0;
+}
+
+extern "C" int wmain(int argc, wchar_t* argv[]) {
+  if (argc > 1) {
+    // clang keeps inlining this call despite every attempt to force it to do
+    // otherwise. We'll use GetProcAddress and call its function pointer
+    // instead.
+    auto pReturnResult = reinterpret_cast<decltype(&ReturnResult)>(
+        ::GetProcAddress(::GetModuleHandleW(nullptr), "ReturnResult"));
+    return pReturnResult();
+  }
+
+  return ParentMain(argc, argv);
+}
diff --git a/toolkit/xre/dllservices/tests/TestIATPatcher.cpp b/toolkit/xre/dllservices/tests/TestIATPatcher.cpp
new file mode 100644
index 0000000000..2f84c0541a
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/TestIATPatcher.cpp
@@ -0,0 +1,121 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/Assertions.h"
+#include "mozilla/DynamicallyLinkedFunctionPtr.h"
+#include "nsWindowsDllInterceptor.h"
+#include "nsWindowsHelpers.h"
+
+#include <shlwapi.h>
+
+static int NormalImport() { return ::GetSystemMetrics(SM_CYCAPTION); }
+
+static bool DelayLoadImport() {
+  return !!::UrlIsW(L"http://example.com/", URLIS_FILEURL);
+}
+
+static mozilla::WindowsIATPatcher::FuncHookType<decltype(&::GetSystemMetrics)>
+    gGetSystemMetricsHook;
+
+static mozilla::WindowsIATPatcher::FuncHookType<decltype(&::MessageBoxA)>
+    gMessageBoxAHook;
+
+static mozilla::WindowsIATPatcher::FuncHookType<decltype(&::UrlIsW)> gUrlIsHook;
+
+static bool gGetSystemMetricsHookCalled = false;
+
+static int WINAPI GetSystemMetricsHook(int aIndex) {
+  MOZ_DIAGNOSTIC_ASSERT(aIndex == SM_CYCAPTION);
+  gGetSystemMetricsHookCalled = true;
+  return 0;
+}
+
+static bool gUrlIsHookCalled = false;
+
+static BOOL WINAPI UrlIsWHook(PCWSTR aUrl, URLIS aFlags) {
+  gUrlIsHookCalled = true;
+  return TRUE;
+}
+
+static HMODULE GetStrongReferenceToExeModule() {
+  HMODULE result;
+  if (!::GetModuleHandleExW(0, nullptr, &result)) {
+    return nullptr;
+  }
+
+  return result;
+}
+
+#define PRINT_FAIL(msg) printf("TEST-UNEXPECTED-FAIL | IATPatcher | " msg "\n")
+
+extern "C" int wmain(int argc, wchar_t* argv[]) {
+  nsModuleHandle ourModule1(GetStrongReferenceToExeModule());
+  if (!ourModule1) {
+    PRINT_FAIL("Failed obtaining HMODULE for executable");
+    return 1;
+  }
+
+  if (!gGetSystemMetricsHook.Set(ourModule1, "user32.dll", "GetSystemMetrics",
+                                 &GetSystemMetricsHook)) {
+    PRINT_FAIL("Failed setting GetSystemMetrics hook");
+    return 1;
+  }
+
+  if (NormalImport() || !gGetSystemMetricsHookCalled) {
+    PRINT_FAIL("GetSystemMetrics hook was not called");
+    return 1;
+  }
+
+  static const mozilla::StaticDynamicallyLinkedFunctionPtr<
+      decltype(&::GetSystemMetrics)>
+      pRealGetSystemMetrics(L"user32.dll", "GetSystemMetrics");
+  if (!pRealGetSystemMetrics) {
+    PRINT_FAIL("Failed resolving real GetSystemMetrics pointer");
+    return 1;
+  }
+
+  if (gGetSystemMetricsHook.GetStub() != pRealGetSystemMetrics) {
+    PRINT_FAIL(
+        "GetSystemMetrics hook stub pointer does not match real "
+        "GetSystemMetrics pointer");
+    return 1;
+  }
+
+  nsModuleHandle ourModule2(GetStrongReferenceToExeModule());
+  if (!ourModule2) {
+    PRINT_FAIL("Failed obtaining HMODULE for executable");
+    return 1;
+  }
+
+  // This should fail becuase the test never calls, and thus never imports,
+  // MessageBoxA
+  if (gMessageBoxAHook.Set(ourModule2, "user32.dll", "MessageBoxA", nullptr)) {
+    PRINT_FAIL("Setting MessageBoxA hook succeeded when it should have failed");
+    return 1;
+  }
+
+  nsModuleHandle ourModule3(GetStrongReferenceToExeModule());
+  if (!ourModule3) {
+    PRINT_FAIL("Failed obtaining HMODULE for executable");
+    return 1;
+  }
+
+  // These tests involve a delay-loaded import, which are not supported; we
+  // expect these tests to FAIL.
+
+  if (gUrlIsHook.Set(ourModule3, "shlwapi.dll", "UrlIsW", &UrlIsWHook)) {
+    PRINT_FAIL("gUrlIsHook.Set should have failed");
+    return 1;
+  }
+
+  if (DelayLoadImport() || gUrlIsHookCalled) {
+    PRINT_FAIL("gUrlIsHook should not have been called");
+    return 1;
+  }
+
+  printf("TEST-PASS | IATPatcher | All tests passed.\n");
+  return 0;
+}
diff --git a/toolkit/xre/dllservices/tests/TestMMPolicy.cpp b/toolkit/xre/dllservices/tests/TestMMPolicy.cpp
new file mode 100644
index 0000000000..1ae93a4ed1
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/TestMMPolicy.cpp
@@ -0,0 +1,204 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsWindowsDllInterceptor.h"
+
+#include <functional>
+
+mozilla::interceptor::MMPolicyInProcess gPolicy;
+
+void DepleteVirtualAddress(
+    uint8_t* aStart, size_t aSize,
+    const std::function<void(void*)>& aPostAllocCallback) {
+  const DWORD granularity = gPolicy.GetAllocGranularity();
+  if (aStart == 0 || aSize < granularity) {
+    return;
+  }
+
+  uint8_t* alignedStart = reinterpret_cast<uint8_t*>(
+      (((reinterpret_cast<uintptr_t>(aStart) - 1) / granularity) + 1) *
+      granularity);
+  aSize -= (alignedStart - aStart);
+  if (auto p = VirtualAlloc(alignedStart, aSize, MEM_RESERVE, PAGE_NOACCESS)) {
+    aPostAllocCallback(p);
+    return;
+  }
+
+  uintptr_t mask = ~(static_cast<uintptr_t>(granularity) - 1);
+  size_t halfSize = (aSize >> 1) & mask;
+  if (halfSize == 0) {
+    return;
+  }
+
+  DepleteVirtualAddress(aStart, halfSize, aPostAllocCallback);
+  DepleteVirtualAddress(aStart + halfSize, aSize - halfSize,
+                        aPostAllocCallback);
+}
+
+bool ValidateFreeRegion(LPVOID aRegion, size_t aDesiredLen) {
+  MEMORY_BASIC_INFORMATION mbi;
+  if (VirtualQuery(aRegion, &mbi, sizeof(mbi)) != sizeof(mbi)) {
+    printf(
+        "TEST-FAILED | TestMMPolicy | "
+        "VirtualQuery(%p) failed - %08lx\n",
+        aRegion, GetLastError());
+    return false;
+  }
+
+  if (mbi.State != MEM_FREE) {
+    printf(
+        "TEST-FAILED | TestMMPolicy | "
+        "%p is not within a free region\n",
+        aRegion);
+    return false;
+  }
+
+  if (aRegion != mbi.BaseAddress ||
+      reinterpret_cast<uintptr_t>(mbi.BaseAddress) %
+          gPolicy.GetAllocGranularity()) {
+    printf(
+        "TEST-FAILED | TestMMPolicy | "
+        "%p is not a region's start address\n",
+        aRegion);
+    return false;
+  }
+
+  LPVOID allocated = VirtualAlloc(aRegion, aDesiredLen,
+                                  MEM_RESERVE | MEM_COMMIT, PAGE_READWRITE);
+  if (!allocated) {
+    printf(
+        "TEST-FAILED | TestMMPolicy | "
+        "VirtualAlloc(%p) failed - %08lx\n",
+        aRegion, GetLastError());
+    return false;
+  }
+
+  if (!VirtualFree(allocated, 0, MEM_RELEASE)) {
+    printf(
+        "TEST-FAILED | TestMMPolicy | "
+        "VirtualFree(%p) failed - %08lx\n",
+        allocated, GetLastError());
+    return false;
+  }
+
+  return true;
+}
+
+bool TestFindRegion() {
+  // Skip the near-null addresses
+  uint8_t* minAddr = reinterpret_cast<uint8_t*>(
+      std::max(gPolicy.GetAllocGranularity(), 0x1000000ul));
+  // 64bit address space is too large to deplete.  32bit space is enough.
+  uint8_t* maxAddr = reinterpret_cast<uint8_t*>(std::min(
+      gPolicy.GetMaxUserModeAddress(), static_cast<uintptr_t>(0xffffffff)));
+
+  // Keep one of the regions we allocate so that we can release it later.
+  void* lastResort = nullptr;
+
+  // Reserve all free regions in the range [minAddr, maxAddr]
+  for (uint8_t* address = minAddr; address <= maxAddr;) {
+    MEMORY_BASIC_INFORMATION mbi;
+    if (VirtualQuery(address, &mbi, sizeof(mbi)) != sizeof(mbi)) {
+      printf(
+          "TEST-FAILED | TestMMPolicy | "
+          "VirtualQuery(%p) failed - %08lx\n",
+          address, GetLastError());
+      break;
+    }
+
+    address = reinterpret_cast<uint8_t*>(mbi.BaseAddress);
+    if (mbi.State == MEM_FREE) {
+      DepleteVirtualAddress(address, mbi.RegionSize,
+                            [&lastResort](void* aAllocated) {
+                              // Pick the first address we allocate to make sure
+                              // FindRegion scans the full range.
+                              if (!lastResort) {
+                                lastResort = aAllocated;
+                              }
+                            });
+    }
+
+    address += mbi.RegionSize;
+  }
+
+  if (!lastResort) {
+    printf(
+        "TEST-SKIPPED | TestMMPolicy | "
+        "No free region in [%p - %p].  Skipping the testcase.\n",
+        minAddr, maxAddr);
+    return true;
+  }
+
+  // Make sure there are no free regions
+  PVOID freeRegion =
+      gPolicy.FindRegion(GetCurrentProcess(), 1, minAddr, maxAddr);
+  if (freeRegion) {
+    if (reinterpret_cast<uintptr_t>(freeRegion) %
+        gPolicy.GetAllocGranularity()) {
+      printf(
+          "TEST-FAILED | TestMMPolicy | "
+          "MMPolicyBase::FindRegion returned an unaligned address %p.\n",
+          freeRegion);
+      return false;
+    }
+
+    printf(
+        "TEST-SKIPPED | TestMMPolicy | "
+        "%p was freed after depletion.  Skipping the testcase.\n",
+        freeRegion);
+    return true;
+  }
+
+  // Free one region, and thus we can expect FindRegion finds this region
+  if (!VirtualFree(lastResort, 0, MEM_RELEASE)) {
+    printf(
+        "TEST-FAILED | TestMMPolicy | "
+        "VirtualFree(%p) failed - %08lx\n",
+        lastResort, GetLastError());
+    return false;
+  }
+  printf("The region starting from %p has been freed.\n", lastResort);
+
+  // Run the function several times because it uses a randon number inside
+  // and its result is nondeterministic.
+  for (int i = 0; i < 50; ++i) {
+    // Because one region was freed, a desire up to one region
+    // should be fulfilled.
+    const size_t desiredLengths[] = {1, gPolicy.GetAllocGranularity()};
+
+    for (auto desiredLen : desiredLengths) {
+      freeRegion =
+          gPolicy.FindRegion(GetCurrentProcess(), desiredLen, minAddr, maxAddr);
+      if (!freeRegion) {
+        printf(
+            "TEST-FAILED | TestMMPolicy | "
+            "Failed to find a free region.\n");
+        return false;
+      }
+
+      if (!ValidateFreeRegion(freeRegion, desiredLen)) {
+        return false;
+      }
+    }
+  }
+
+  return true;
+}
+
+extern "C" int wmain(int argc, wchar_t* argv[]) {
+  // Preload delayload modules (e.g. advapi32.dll, bcryptPrimitives.dll, etc.)
+  // by calling rand_s(), which is used in MMPolicy::FindRegion, before
+  // depleting the process memory during the test.
+  unsigned int rnd = 0;
+  rand_s(&rnd);
+
+  if (!TestFindRegion()) {
+    return 1;
+  }
+
+  printf("TEST-PASS | TestMMPolicy | All tests passed.\n");
+  return 0;
+}
diff --git a/toolkit/xre/dllservices/tests/gtest/TestDLLBlocklist.cpp b/toolkit/xre/dllservices/tests/gtest/TestDLLBlocklist.cpp
new file mode 100644
index 0000000000..938f63a524
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/gtest/TestDLLBlocklist.cpp
@@ -0,0 +1,475 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <windows.h>
+#include <winternl.h>
+
+#include <process.h>
+
+#include <array>
+#include <functional>
+
+#include "gtest/gtest.h"
+
+#include "mozilla/ArrayUtils.h"
+#include "mozilla/Char16.h"
+#include "mozilla/gtest/MozAssertions.h"
+#include "mozilla/Services.h"
+#include "mozilla/WinDllServices.h"
+#include "mozilla/WindowsStackCookie.h"
+#include "nsDirectoryServiceDefs.h"
+#include "nsDirectoryServiceUtils.h"
+#include "nsIObserver.h"
+#include "nsIObserverService.h"
+#include "nsIThread.h"
+#include "nsReadableUtils.h"
+#include "nsString.h"
+#include "nsTArray.h"
+#include "nsUnicharUtils.h"
+#include "nsWindowsHelpers.h"
+
+static nsString GetFullPath(const nsAString& aLeaf) {
+  nsCOMPtr<nsIFile> f;
+
+  EXPECT_TRUE(NS_SUCCEEDED(
+      NS_GetSpecialDirectory(NS_OS_CURRENT_WORKING_DIR, getter_AddRefs(f))));
+
+  EXPECT_NS_SUCCEEDED(f->Append(aLeaf));
+
+  bool exists;
+  EXPECT_TRUE(NS_SUCCEEDED(f->Exists(&exists)) && exists);
+
+  nsString ret;
+  EXPECT_NS_SUCCEEDED(f->GetPath(ret));
+  return ret;
+}
+
+void FlushMainThreadLoop() {
+  nsCOMPtr<nsIThread> mainThread;
+  nsresult rv = NS_GetMainThread(getter_AddRefs(mainThread));
+  ASSERT_NS_SUCCEEDED(rv);
+
+  rv = NS_OK;
+  bool processed = true;
+  while (processed && NS_SUCCEEDED(rv)) {
+    rv = mainThread->ProcessNextEvent(false, &processed);
+  }
+}
+
+class TestDLLLoadObserver : public nsIObserver {
+ public:
+  using DLLFilter = std::function<bool(const char16_t*)>;
+
+  explicit TestDLLLoadObserver(DLLFilter dllFilter)
+      : mDllFilter(std::move(dllFilter)),
+        mMainThreadNotificationsCount(0),
+        mNonMainThreadNotificationsCount(0){};
+
+  NS_DECL_THREADSAFE_ISUPPORTS
+
+  NS_IMETHOD Observe(nsISupports* aSubject, const char* aTopic,
+                     const char16_t* aData) override {
+    if (!mDllFilter(aData)) {
+      return NS_OK;
+    }
+    if (0 == strcmp(aTopic, mozilla::DllServices::kTopicDllLoadedMainThread)) {
+      ++mMainThreadNotificationsCount;
+    } else {
+      EXPECT_TRUE(
+          0 ==
+          strcmp(aTopic, mozilla::DllServices::kTopicDllLoadedNonMainThread));
+      ++mNonMainThreadNotificationsCount;
+    }
+    return NS_OK;
+  }
+
+  void Init() {
+    nsCOMPtr<nsIObserverService> obsServ(
+        mozilla::services::GetObserverService());
+
+    EXPECT_TRUE(obsServ);
+
+    obsServ->AddObserver(this, mozilla::DllServices::kTopicDllLoadedMainThread,
+                         false);
+    obsServ->AddObserver(
+        this, mozilla::DllServices::kTopicDllLoadedNonMainThread, false);
+  }
+
+  void Exit() {
+    // Observe only gets called if/when we flush the main thread loop.
+    FlushMainThreadLoop();
+
+    nsCOMPtr<nsIObserverService> obsServ(
+        mozilla::services::GetObserverService());
+
+    EXPECT_TRUE(obsServ);
+
+    obsServ->RemoveObserver(this,
+                            mozilla::DllServices::kTopicDllLoadedMainThread);
+    obsServ->RemoveObserver(this,
+                            mozilla::DllServices::kTopicDllLoadedNonMainThread);
+  }
+
+  int MainThreadNotificationsCount() { return mMainThreadNotificationsCount; }
+
+  int NonMainThreadNotificationsCount() {
+    return mNonMainThreadNotificationsCount;
+  }
+
+ private:
+  virtual ~TestDLLLoadObserver() = default;
+
+  DLLFilter mDllFilter;
+  int mMainThreadNotificationsCount;
+  int mNonMainThreadNotificationsCount;
+};
+
+NS_IMPL_ISUPPORTS(TestDLLLoadObserver, nsIObserver)
+
+TEST(TestDllBlocklist, BlockDllByName)
+{
+  // The DLL name has capital letters, so this also tests that the comparison
+  // is case-insensitive.
+  constexpr auto kLeafName = u"TestDllBlocklist_MatchByName.dll"_ns;
+  nsString dllPath = GetFullPath(kLeafName);
+
+  nsModuleHandle hDll(::LoadLibraryW(dllPath.get()));
+
+  EXPECT_TRUE(!hDll);
+  EXPECT_TRUE(!::GetModuleHandleW(kLeafName.get()));
+
+  hDll.own(::LoadLibraryExW(dllPath.get(), nullptr, LOAD_LIBRARY_AS_DATAFILE));
+  // Mapped as MEM_MAPPED + PAGE_READONLY
+  EXPECT_TRUE(hDll);
+}
+
+TEST(TestDllBlocklist, BlockDllByVersion)
+{
+  constexpr auto kLeafName = u"TestDllBlocklist_MatchByVersion.dll"_ns;
+  nsString dllPath = GetFullPath(kLeafName);
+
+  nsModuleHandle hDll(::LoadLibraryW(dllPath.get()));
+
+  EXPECT_TRUE(!hDll);
+  EXPECT_TRUE(!::GetModuleHandleW(kLeafName.get()));
+
+  hDll.own(
+      ::LoadLibraryExW(dllPath.get(), nullptr, LOAD_LIBRARY_AS_IMAGE_RESOURCE));
+  // Mapped as MEM_IMAGE + PAGE_READONLY
+  EXPECT_TRUE(hDll);
+}
+
+TEST(TestDllBlocklist, AllowDllByVersion)
+{
+  constexpr auto kLeafName = u"TestDllBlocklist_AllowByVersion.dll"_ns;
+  nsString dllPath = GetFullPath(kLeafName);
+
+  nsModuleHandle hDll(::LoadLibraryW(dllPath.get()));
+
+  EXPECT_TRUE(!!hDll);
+  EXPECT_TRUE(!!::GetModuleHandleW(kLeafName.get()));
+}
+
+TEST(TestDllBlocklist, GPUProcessOnly_AllowInMainProcess)
+{
+  constexpr auto kLeafName = u"TestDllBlocklist_GPUProcessOnly.dll"_ns;
+  nsString dllPath = GetFullPath(kLeafName);
+
+  nsModuleHandle hDll(::LoadLibraryW(dllPath.get()));
+
+  EXPECT_TRUE(!!hDll);
+  EXPECT_TRUE(!!::GetModuleHandleW(kLeafName.get()));
+}
+
+TEST(TestDllBlocklist, SocketProcessOnly_AllowInMainProcess)
+{
+  constexpr auto kLeafName = u"TestDllBlocklist_SocketProcessOnly.dll"_ns;
+  nsString dllPath = GetFullPath(kLeafName);
+
+  nsModuleHandle hDll(::LoadLibraryW(dllPath.get()));
+
+  EXPECT_TRUE(!!hDll);
+  EXPECT_TRUE(!!::GetModuleHandleW(kLeafName.get()));
+}
+
+TEST(TestDllBlocklist, UtilityProcessOnly_AllowInMainProcess)
+{
+  constexpr auto kLeafName = u"TestDllBlocklist_UtilityProcessOnly.dll"_ns;
+  nsString dllPath = GetFullPath(kLeafName);
+
+  nsModuleHandle hDll(::LoadLibraryW(dllPath.get()));
+
+  EXPECT_TRUE(!!hDll);
+  EXPECT_TRUE(!!::GetModuleHandleW(kLeafName.get()));
+}
+
+TEST(TestDllBlocklist, GMPluginProcessOnly_AllowInMainProcess)
+{
+  constexpr auto kLeafName = u"TestDllBlocklist_GMPluginProcessOnly.dll"_ns;
+  nsString dllPath = GetFullPath(kLeafName);
+
+  nsModuleHandle hDll(::LoadLibraryW(dllPath.get()));
+
+  EXPECT_TRUE(!!hDll);
+  EXPECT_TRUE(!!::GetModuleHandleW(kLeafName.get()));
+}
+
+// This DLL has two entries; it's blocked for unversioned (i.e. DLLs that
+// have no version information) everywhere and blocked for versions 5.5.5.5 and
+// earlier only in the GPU process. Since the version we're trying to load
+// is 5.5.5.5, it should load in the main process.
+TEST(TestDllBlocklist, MultipleEntriesDifferentProcesses_AllowInMainProcess)
+{
+  constexpr auto kLeafName =
+      u"TestDllBlocklist_MultipleEntries_DifferentProcesses.dll"_ns;
+  nsString dllPath = GetFullPath(kLeafName);
+
+  nsModuleHandle hDll(::LoadLibraryW(dllPath.get()));
+
+  EXPECT_TRUE(!!hDll);
+  EXPECT_TRUE(!!::GetModuleHandleW(kLeafName.get()));
+}
+
+TEST(TestDllBlocklist, MultipleEntriesSameProcessBackward_Block)
+{
+  // One entry matches by version and many others do not, so
+  // we should block.
+  constexpr auto kLeafName =
+      u"TestDllBlocklist_MultipleEntries_SameProcessBackward.dll"_ns;
+  nsString dllPath = GetFullPath(kLeafName);
+
+  nsModuleHandle hDll(::LoadLibraryW(dllPath.get()));
+
+  EXPECT_TRUE(!hDll);
+  EXPECT_TRUE(!::GetModuleHandleW(kLeafName.get()));
+
+  hDll.own(
+      ::LoadLibraryExW(dllPath.get(), nullptr, LOAD_LIBRARY_AS_IMAGE_RESOURCE));
+  // Mapped as MEM_IMAGE + PAGE_READONLY
+  EXPECT_TRUE(hDll);
+}
+
+TEST(TestDllBlocklist, MultipleEntriesSameProcessForward_Block)
+{
+  // One entry matches by version and many others do not, so
+  // we should block.
+  constexpr auto kLeafName =
+      u"TestDllBlocklist_MultipleEntries_SameProcessForward.dll"_ns;
+  nsString dllPath = GetFullPath(kLeafName);
+
+  nsModuleHandle hDll(::LoadLibraryW(dllPath.get()));
+
+  EXPECT_TRUE(!hDll);
+  EXPECT_TRUE(!::GetModuleHandleW(kLeafName.get()));
+
+  hDll.own(
+      ::LoadLibraryExW(dllPath.get(), nullptr, LOAD_LIBRARY_AS_IMAGE_RESOURCE));
+  // Mapped as MEM_IMAGE + PAGE_READONLY
+  EXPECT_TRUE(hDll);
+}
+
+#if defined(MOZ_LAUNCHER_PROCESS)
+// RedirectToNoOpEntryPoint needs the launcher process.
+// This test will fail in debug x64 if we mistakenly reintroduce stack buffers
+// in patched_NtMapViewOfSection (see bug 1733532).
+TEST(TestDllBlocklist, NoOpEntryPoint)
+{
+  // DllMain of this dll has MOZ_RELEASE_ASSERT.  This test makes sure we load
+  // the module successfully without running DllMain.
+  constexpr auto kLeafName = u"TestDllBlocklist_NoOpEntryPoint.dll"_ns;
+  nsString dllPath = GetFullPath(kLeafName);
+
+  nsModuleHandle hDll(::LoadLibraryW(dllPath.get()));
+
+#  if defined(MOZ_ASAN)
+  // With ASAN, the test uses mozglue's blocklist where
+  // REDIRECT_TO_NOOP_ENTRYPOINT is ignored.  So LoadLibraryW
+  // is expected to fail.
+  EXPECT_TRUE(!hDll);
+  EXPECT_TRUE(!::GetModuleHandleW(kLeafName.get()));
+#  else
+  EXPECT_TRUE(!!hDll);
+  EXPECT_TRUE(!!::GetModuleHandleW(kLeafName.get()));
+#  endif
+}
+
+// User blocklist needs the launcher process.
+// This test will fail in debug x64 if we mistakenly reintroduce stack buffers
+// in patched_NtMapViewOfSection (see bug 1733532).
+TEST(TestDllBlocklist, UserBlocked)
+{
+  constexpr auto kLeafName = u"TestDllBlocklist_UserBlocked.dll"_ns;
+  nsString dllPath = GetFullPath(kLeafName);
+
+  nsModuleHandle hDll(::LoadLibraryW(dllPath.get()));
+
+// With ASAN, the test uses mozglue's blocklist where
+// the user blocklist is not used.
+#  if !defined(MOZ_ASAN)
+  EXPECT_TRUE(!hDll);
+  EXPECT_TRUE(!::GetModuleHandleW(kLeafName.get()));
+#  endif
+  hDll.own(::LoadLibraryExW(dllPath.get(), nullptr, LOAD_LIBRARY_AS_DATAFILE));
+  // Mapped as MEM_MAPPED + PAGE_READONLY
+  EXPECT_TRUE(hDll);
+}
+#endif  // defined(MOZ_LAUNCHER_PROCESS)
+
+#define DLL_BLOCKLIST_ENTRY(name, ...) {name, __VA_ARGS__},
+#define DLL_BLOCKLIST_STRING_TYPE const char*
+#include "mozilla/WindowsDllBlocklistLegacyDefs.h"
+
+TEST(TestDllBlocklist, BlocklistIntegrity)
+{
+  DECLARE_POINTER_TO_FIRST_DLL_BLOCKLIST_ENTRY(pFirst);
+  DECLARE_POINTER_TO_LAST_DLL_BLOCKLIST_ENTRY(pLast);
+
+  EXPECT_FALSE(pLast->mName || pLast->mMaxVersion || pLast->mFlags);
+
+  for (size_t i = 0; i < mozilla::ArrayLength(gWindowsDllBlocklist) - 1; ++i) {
+    auto pEntry = pFirst + i;
+
+    // Validate name
+    EXPECT_TRUE(!!pEntry->mName);
+    EXPECT_GT(strlen(pEntry->mName), 3U);
+
+    // Check the filename for valid characters.
+    for (auto pch = pEntry->mName; *pch != 0; ++pch) {
+      EXPECT_FALSE(*pch >= 'A' && *pch <= 'Z');
+    }
+  }
+}
+
+TEST(TestDllBlocklist, BlockThreadWithLoadLibraryEntryPoint)
+{
+  // Only supported on Nightly
+#if defined(NIGHTLY_BUILD)
+  using ThreadProc = unsigned(__stdcall*)(void*);
+
+  constexpr auto kLeafNameW = u"TestDllBlocklist_MatchByVersion.dll"_ns;
+
+  nsString fullPathW = GetFullPath(kLeafNameW);
+  EXPECT_FALSE(fullPathW.IsEmpty());
+
+  nsAutoHandle threadW(reinterpret_cast<HANDLE>(
+      _beginthreadex(nullptr, 0, reinterpret_cast<ThreadProc>(&::LoadLibraryW),
+                     (void*)fullPathW.get(), 0, nullptr)));
+
+  EXPECT_TRUE(!!threadW);
+  EXPECT_EQ(::WaitForSingleObject(threadW, INFINITE), WAIT_OBJECT_0);
+
+#  if !defined(MOZ_ASAN)
+  // ASAN builds under Windows 11 can have unexpected thread exit codes.
+  // See bug 1798796
+  DWORD exitCode;
+  EXPECT_TRUE(::GetExitCodeThread(threadW, &exitCode) && !exitCode);
+#  endif  // !defined(MOZ_ASAN)
+  EXPECT_TRUE(!::GetModuleHandleW(kLeafNameW.get()));
+
+  const NS_LossyConvertUTF16toASCII fullPathA(fullPathW);
+  EXPECT_FALSE(fullPathA.IsEmpty());
+
+  nsAutoHandle threadA(reinterpret_cast<HANDLE>(
+      _beginthreadex(nullptr, 0, reinterpret_cast<ThreadProc>(&::LoadLibraryA),
+                     (void*)fullPathA.get(), 0, nullptr)));
+
+  EXPECT_TRUE(!!threadA);
+  EXPECT_EQ(::WaitForSingleObject(threadA, INFINITE), WAIT_OBJECT_0);
+#  if !defined(MOZ_ASAN)
+  // ASAN builds under Windows 11 can have unexpected thread exit codes.
+  // See bug 1798796
+  EXPECT_TRUE(::GetExitCodeThread(threadA, &exitCode) && !exitCode);
+#  endif  // !defined(MOZ_ASAN)
+  EXPECT_TRUE(!::GetModuleHandleW(kLeafNameW.get()));
+#endif  // defined(NIGHTLY_BUILD)
+}
+
+constexpr auto kSingleNotificationDll1Loads = 4;
+constexpr auto kSingleNotificationDll2Loads = 3;
+using DllFullPathsArray =
+    std::array<nsString,
+               kSingleNotificationDll1Loads + kSingleNotificationDll2Loads>;
+
+DWORD __stdcall LoadSingleNotificationModules(LPVOID aThreadParameter) {
+  auto* dllFullPaths = reinterpret_cast<DllFullPathsArray*>(aThreadParameter);
+
+  for (const auto& dllFullPath : *dllFullPaths) {
+    nsModuleHandle hDll(::LoadLibraryW(dllFullPath.get()));
+    EXPECT_TRUE(!hDll);
+    EXPECT_TRUE(!::GetModuleHandleW(dllFullPath.get()));
+  }
+
+  return 0;
+}
+
+// The next test is only relevant if we hook LdrLoadDll, so we reflect the
+// hooking condition from browser/app/winlauncher/DllBlocklistInit.cpp.
+#if !defined(MOZ_ASAN) && !defined(_M_ARM64)
+
+// This test relies on the fact that blocked DLL loads generate a DLL load
+// notification.
+TEST(TestDllBlocklist, SingleNotification)
+{
+  // We will block-load the two DLLs multiple times, with variations on case.
+  std::array<nsLiteralString, kSingleNotificationDll1Loads> dll1Variations{
+      u"TestDllBlocklist_SingleNotification1.dll"_ns,
+      u"TestDllBlocklist_SingleNotification1.dll"_ns,
+      u"testdllblocklist_singlenotification1.dll"_ns,
+      u"TeStDlLbLoCkLiSt_SiNgLeNoTiFiCaTiOn1.DlL"_ns,
+  };
+  std::array<nsLiteralString, kSingleNotificationDll2Loads> dll2Variations{
+      u"TestDllBlocklist_SingleNotification2.dll"_ns,
+      u"testdllblocklist_singlenotification2.dll"_ns,
+      u"TESTDLLBLOCKLIST_SINGLENOTIFICATION2.dll"_ns,
+  };
+  DllFullPathsArray dllFullPaths;
+  size_t i = 0;
+  for (const auto& dllName : dll1Variations) {
+    dllFullPaths[i] = GetFullPath(dllName);
+    ++i;
+  }
+  for (const auto& dllName : dll2Variations) {
+    dllFullPaths[i] = GetFullPath(dllName);
+    ++i;
+  }
+
+  // Register our observer.
+  TestDLLLoadObserver::DLLFilter dllFilter(
+      [](const char16_t* aLoadedPath) -> bool {
+        nsDependentString loadedPath(aLoadedPath);
+        return StringEndsWith(loadedPath,
+                              u"\\testdllblocklist_singlenotification1.dll"_ns,
+                              nsCaseInsensitiveStringComparator) ||
+               StringEndsWith(loadedPath,
+                              u"\\testdllblocklist_singlenotification2.dll"_ns,
+                              nsCaseInsensitiveStringComparator);
+      });
+  RefPtr<TestDLLLoadObserver> obs(new TestDLLLoadObserver(dllFilter));
+  obs->Init();
+
+  // Load DllServices. This is required for notifications to get dispatched.
+  RefPtr<mozilla::DllServices> dllSvc(mozilla::DllServices::Get());
+  EXPECT_TRUE(dllSvc);
+
+  // Block-load the two DLLs multiple times on the main thread.
+  LoadSingleNotificationModules(reinterpret_cast<void*>(&dllFullPaths));
+
+  // Block-load the two DLLs multiple times on a different thread.
+  HANDLE thread =
+      ::CreateThread(nullptr, 0, LoadSingleNotificationModules,
+                     reinterpret_cast<void*>(&dllFullPaths), 0, nullptr);
+  EXPECT_EQ(::WaitForSingleObject(thread, 5000), WAIT_OBJECT_0);
+
+  // Unregister our observer and flush the main thread loop.
+  obs->Exit();
+
+  // Check how many notifications we received
+  EXPECT_EQ(obs->MainThreadNotificationsCount(), 2);
+  EXPECT_EQ(obs->NonMainThreadNotificationsCount(),
+            kSingleNotificationDll1Loads + kSingleNotificationDll2Loads);
+}
+
+#endif  // !defined(MOZ_ASAN) && !defined(_M_ARM64)
diff --git a/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_AllowByVersion/TestDllBlocklist_AllowByVersion.cpp b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_AllowByVersion/TestDllBlocklist_AllowByVersion.cpp
new file mode 100644
index 0000000000..7bd936296e
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_AllowByVersion/TestDllBlocklist_AllowByVersion.cpp
@@ -0,0 +1,7 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <windows.h>
+
+BOOL WINAPI DllMain(HINSTANCE hInstance, DWORD aReason, LPVOID) { return TRUE; }
diff --git a/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_AllowByVersion/TestDllBlocklist_AllowByVersion.rc b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_AllowByVersion/TestDllBlocklist_AllowByVersion.rc
new file mode 100644
index 0000000000..f56aa099ff
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_AllowByVersion/TestDllBlocklist_AllowByVersion.rc
@@ -0,0 +1,42 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <winver.h>
+
+/////////////////////////////////////////////////////////////////////////////
+//
+// Version
+//
+
+VS_VERSION_INFO VERSIONINFO
+  FILEVERSION    5,5,5,6
+  PRODUCTVERSION 5,5,5,1
+  FILEFLAGSMASK 0x3fL
+#ifdef _DEBUG
+  FILEFLAGS 0x1L
+#else
+  FILEFLAGS 0x0L
+#endif
+  FILEOS VOS__WINDOWS32
+  FILETYPE VFT_DLL
+  FILESUBTYPE 0x0L
+BEGIN
+  BLOCK "StringFileInfo"
+  BEGIN
+    BLOCK "040904e4"
+    BEGIN
+      VALUE "CompanyName", "mozilla.org"
+      VALUE "FileDescription", L"Test DLL"
+      VALUE "FileVersion", "1.0"
+      VALUE "InternalName", "Test DLL"
+      VALUE "OriginalFilename", "TestDllBlocklist_AllowByVersion.dll"
+      VALUE "ProductName", "Test DLL"
+      VALUE "ProductVersion", "1.0"
+    END
+  END
+  BLOCK "VarFileInfo"
+  BEGIN
+    VALUE "Translation", 0x0409, 1252
+  END
+END
diff --git a/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_AllowByVersion/moz.build b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_AllowByVersion/moz.build
new file mode 100644
index 0000000000..0987cdde1a
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_AllowByVersion/moz.build
@@ -0,0 +1,17 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+DIST_INSTALL = False
+
+SharedLibrary("TestDllBlocklist_AllowByVersion")
+
+UNIFIED_SOURCES = [
+    "TestDllBlocklist_AllowByVersion.cpp",
+]
+
+RCFILE = "TestDllBlocklist_AllowByVersion.rc"
+
+if CONFIG["COMPILE_ENVIRONMENT"]:
+    TEST_HARNESS_FILES.gtest += ["!TestDllBlocklist_AllowByVersion.dll"]
diff --git a/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_GMPluginProcessOnly/TestDllBlocklist_GMPluginProcessOnly.cpp b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_GMPluginProcessOnly/TestDllBlocklist_GMPluginProcessOnly.cpp
new file mode 100644
index 0000000000..7bd936296e
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_GMPluginProcessOnly/TestDllBlocklist_GMPluginProcessOnly.cpp
@@ -0,0 +1,7 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <windows.h>
+
+BOOL WINAPI DllMain(HINSTANCE hInstance, DWORD aReason, LPVOID) { return TRUE; }
diff --git a/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_GMPluginProcessOnly/moz.build b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_GMPluginProcessOnly/moz.build
new file mode 100644
index 0000000000..a5c89c2b8e
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_GMPluginProcessOnly/moz.build
@@ -0,0 +1,15 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+DIST_INSTALL = False
+
+SharedLibrary("TestDllBlocklist_GMPluginProcessOnly")
+
+UNIFIED_SOURCES = [
+    "TestDllBlocklist_GMPluginProcessOnly.cpp",
+]
+
+if CONFIG["COMPILE_ENVIRONMENT"]:
+    TEST_HARNESS_FILES.gtest += ["!TestDllBlocklist_GMPluginProcessOnly.dll"]
diff --git a/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_GPUProcessOnly/TestDllBlocklist_GPUProcessOnly.cpp b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_GPUProcessOnly/TestDllBlocklist_GPUProcessOnly.cpp
new file mode 100644
index 0000000000..7bd936296e
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_GPUProcessOnly/TestDllBlocklist_GPUProcessOnly.cpp
@@ -0,0 +1,7 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <windows.h>
+
+BOOL WINAPI DllMain(HINSTANCE hInstance, DWORD aReason, LPVOID) { return TRUE; }
diff --git a/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_GPUProcessOnly/moz.build b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_GPUProcessOnly/moz.build
new file mode 100644
index 0000000000..748e9cf22c
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_GPUProcessOnly/moz.build
@@ -0,0 +1,15 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+DIST_INSTALL = False
+
+SharedLibrary("TestDllBlocklist_GPUProcessOnly")
+
+UNIFIED_SOURCES = [
+    "TestDllBlocklist_GPUProcessOnly.cpp",
+]
+
+if CONFIG["COMPILE_ENVIRONMENT"]:
+    TEST_HARNESS_FILES.gtest += ["!TestDllBlocklist_GPUProcessOnly.dll"]
diff --git a/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_MatchByName/TestDllBlocklist_MatchByName.cpp b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_MatchByName/TestDllBlocklist_MatchByName.cpp
new file mode 100644
index 0000000000..7bd936296e
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_MatchByName/TestDllBlocklist_MatchByName.cpp
@@ -0,0 +1,7 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <windows.h>
+
+BOOL WINAPI DllMain(HINSTANCE hInstance, DWORD aReason, LPVOID) { return TRUE; }
diff --git a/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_MatchByName/moz.build b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_MatchByName/moz.build
new file mode 100644
index 0000000000..f34931898a
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_MatchByName/moz.build
@@ -0,0 +1,15 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+DIST_INSTALL = False
+
+SharedLibrary("TestDllBlocklist_MatchByName")
+
+UNIFIED_SOURCES = [
+    "TestDllBlocklist_MatchByName.cpp",
+]
+
+if CONFIG["COMPILE_ENVIRONMENT"]:
+    TEST_HARNESS_FILES.gtest += ["!TestDllBlocklist_MatchByName.dll"]
diff --git a/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_MatchByVersion/TestDllBlocklist_MatchByVersion.cpp b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_MatchByVersion/TestDllBlocklist_MatchByVersion.cpp
new file mode 100644
index 0000000000..7bd936296e
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_MatchByVersion/TestDllBlocklist_MatchByVersion.cpp
@@ -0,0 +1,7 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <windows.h>
+
+BOOL WINAPI DllMain(HINSTANCE hInstance, DWORD aReason, LPVOID) { return TRUE; }
diff --git a/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_MatchByVersion/TestDllBlocklist_MatchByVersion.rc b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_MatchByVersion/TestDllBlocklist_MatchByVersion.rc
new file mode 100644
index 0000000000..7390c1cb34
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_MatchByVersion/TestDllBlocklist_MatchByVersion.rc
@@ -0,0 +1,42 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <winver.h>
+
+/////////////////////////////////////////////////////////////////////////////
+//
+// Version
+//
+
+VS_VERSION_INFO VERSIONINFO
+  FILEVERSION    5,5,5,5
+  PRODUCTVERSION 5,5,5,1
+  FILEFLAGSMASK 0x3fL
+#ifdef _DEBUG
+  FILEFLAGS 0x1L
+#else
+  FILEFLAGS 0x0L
+#endif
+  FILEOS VOS__WINDOWS32
+  FILETYPE VFT_DLL
+  FILESUBTYPE 0x0L
+BEGIN
+  BLOCK "StringFileInfo"
+  BEGIN
+    BLOCK "040904e4"
+    BEGIN
+      VALUE "CompanyName", "mozilla.org"
+      VALUE "FileDescription", L"Test DLL"
+      VALUE "FileVersion", "1.0"
+      VALUE "InternalName", "Test DLL"
+      VALUE "OriginalFilename", "TestDllBlocklist_MatchByVersion.dll"
+      VALUE "ProductName", "Test DLL"
+      VALUE "ProductVersion", "1.0"
+    END
+  END
+  BLOCK "VarFileInfo"
+  BEGIN
+    VALUE "Translation", 0x0409, 1252
+  END
+END
diff --git a/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_MatchByVersion/moz.build b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_MatchByVersion/moz.build
new file mode 100644
index 0000000000..38e10524c7
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_MatchByVersion/moz.build
@@ -0,0 +1,17 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+DIST_INSTALL = False
+
+SharedLibrary("TestDllBlocklist_MatchByVersion")
+
+UNIFIED_SOURCES = [
+    "TestDllBlocklist_MatchByVersion.cpp",
+]
+
+RCFILE = "TestDllBlocklist_MatchByVersion.rc"
+
+if CONFIG["COMPILE_ENVIRONMENT"]:
+    TEST_HARNESS_FILES.gtest += ["!TestDllBlocklist_MatchByVersion.dll"]
diff --git a/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_MultipleEntries_DifferentProcesses/TestDllBlocklist_MultipleEntries_DifferentProcesses.cpp b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_MultipleEntries_DifferentProcesses/TestDllBlocklist_MultipleEntries_DifferentProcesses.cpp
new file mode 100644
index 0000000000..7bd936296e
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_MultipleEntries_DifferentProcesses/TestDllBlocklist_MultipleEntries_DifferentProcesses.cpp
@@ -0,0 +1,7 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <windows.h>
+
+BOOL WINAPI DllMain(HINSTANCE hInstance, DWORD aReason, LPVOID) { return TRUE; }
diff --git a/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_MultipleEntries_DifferentProcesses/TestDllBlocklist_MultipleEntries_DifferentProcesses.rc b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_MultipleEntries_DifferentProcesses/TestDllBlocklist_MultipleEntries_DifferentProcesses.rc
new file mode 100644
index 0000000000..2b5b81406e
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_MultipleEntries_DifferentProcesses/TestDllBlocklist_MultipleEntries_DifferentProcesses.rc
@@ -0,0 +1,42 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <winver.h>
+
+/////////////////////////////////////////////////////////////////////////////
+//
+// Version
+//
+
+VS_VERSION_INFO VERSIONINFO
+  FILEVERSION    5,5,5,5
+  PRODUCTVERSION 5,5,5,1
+  FILEFLAGSMASK 0x3fL
+#ifdef _DEBUG
+  FILEFLAGS 0x1L
+#else
+  FILEFLAGS 0x0L
+#endif
+  FILEOS VOS__WINDOWS32
+  FILETYPE VFT_DLL
+  FILESUBTYPE 0x0L
+BEGIN
+  BLOCK "StringFileInfo"
+  BEGIN
+    BLOCK "040904e4"
+    BEGIN
+      VALUE "CompanyName", "mozilla.org"
+      VALUE "FileDescription", L"Test DLL"
+      VALUE "FileVersion", "1.0"
+      VALUE "InternalName", "Test DLL"
+      VALUE "OriginalFilename", "TestDllBlocklist_MultipleEntries_DifferentProcesses.dll"
+      VALUE "ProductName", "Test DLL"
+      VALUE "ProductVersion", "1.0"
+    END
+  END
+  BLOCK "VarFileInfo"
+  BEGIN
+    VALUE "Translation", 0x0409, 1252
+  END
+END
diff --git a/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_MultipleEntries_DifferentProcesses/moz.build b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_MultipleEntries_DifferentProcesses/moz.build
new file mode 100644
index 0000000000..cf2f745a28
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_MultipleEntries_DifferentProcesses/moz.build
@@ -0,0 +1,19 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+DIST_INSTALL = False
+
+SharedLibrary("TestDllBlocklist_MultipleEntries_DifferentProcesses")
+
+UNIFIED_SOURCES = [
+    "TestDllBlocklist_MultipleEntries_DifferentProcesses.cpp",
+]
+
+RCFILE = "TestDllBlocklist_MultipleEntries_DifferentProcesses.rc"
+
+if CONFIG["COMPILE_ENVIRONMENT"]:
+    TEST_HARNESS_FILES.gtest += [
+        "!TestDllBlocklist_MultipleEntries_DifferentProcesses.dll"
+    ]
diff --git a/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_MultipleEntries_SameProcessBackward/TestDllBlocklist_MultipleEntries_SameProcessBackward.cpp b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_MultipleEntries_SameProcessBackward/TestDllBlocklist_MultipleEntries_SameProcessBackward.cpp
new file mode 100644
index 0000000000..7bd936296e
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_MultipleEntries_SameProcessBackward/TestDllBlocklist_MultipleEntries_SameProcessBackward.cpp
@@ -0,0 +1,7 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <windows.h>
+
+BOOL WINAPI DllMain(HINSTANCE hInstance, DWORD aReason, LPVOID) { return TRUE; }
diff --git a/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_MultipleEntries_SameProcessBackward/TestDllBlocklist_MultipleEntries_SameProcessBackward.rc b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_MultipleEntries_SameProcessBackward/TestDllBlocklist_MultipleEntries_SameProcessBackward.rc
new file mode 100644
index 0000000000..0b2431c343
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_MultipleEntries_SameProcessBackward/TestDllBlocklist_MultipleEntries_SameProcessBackward.rc
@@ -0,0 +1,42 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <winver.h>
+
+/////////////////////////////////////////////////////////////////////////////
+//
+// Version
+//
+
+VS_VERSION_INFO VERSIONINFO
+  FILEVERSION    5,5,5,5
+  PRODUCTVERSION 5,5,5,1
+  FILEFLAGSMASK 0x3fL
+#ifdef _DEBUG
+  FILEFLAGS 0x1L
+#else
+  FILEFLAGS 0x0L
+#endif
+  FILEOS VOS__WINDOWS32
+  FILETYPE VFT_DLL
+  FILESUBTYPE 0x0L
+BEGIN
+  BLOCK "StringFileInfo"
+  BEGIN
+    BLOCK "040904e4"
+    BEGIN
+      VALUE "CompanyName", "mozilla.org"
+      VALUE "FileDescription", L"Test DLL"
+      VALUE "FileVersion", "1.0"
+      VALUE "InternalName", "Test DLL"
+      VALUE "OriginalFilename", "TestDllBlocklist_MultipleEntries_SameProcessBackward.dll"
+      VALUE "ProductName", "Test DLL"
+      VALUE "ProductVersion", "1.0"
+    END
+  END
+  BLOCK "VarFileInfo"
+  BEGIN
+    VALUE "Translation", 0x0409, 1252
+  END
+END
diff --git a/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_MultipleEntries_SameProcessBackward/moz.build b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_MultipleEntries_SameProcessBackward/moz.build
new file mode 100644
index 0000000000..21ab229245
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_MultipleEntries_SameProcessBackward/moz.build
@@ -0,0 +1,19 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+DIST_INSTALL = False
+
+SharedLibrary("TestDllBlocklist_MultipleEntries_SameProcessBackward")
+
+UNIFIED_SOURCES = [
+    "TestDllBlocklist_MultipleEntries_SameProcessBackward.cpp",
+]
+
+RCFILE = "TestDllBlocklist_MultipleEntries_SameProcessBackward.rc"
+
+if CONFIG["COMPILE_ENVIRONMENT"]:
+    TEST_HARNESS_FILES.gtest += [
+        "!TestDllBlocklist_MultipleEntries_SameProcessBackward.dll"
+    ]
diff --git a/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_MultipleEntries_SameProcessForward/TestDllBlocklist_MultipleEntries_SameProcessForward.cpp b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_MultipleEntries_SameProcessForward/TestDllBlocklist_MultipleEntries_SameProcessForward.cpp
new file mode 100644
index 0000000000..7bd936296e
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_MultipleEntries_SameProcessForward/TestDllBlocklist_MultipleEntries_SameProcessForward.cpp
@@ -0,0 +1,7 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <windows.h>
+
+BOOL WINAPI DllMain(HINSTANCE hInstance, DWORD aReason, LPVOID) { return TRUE; }
diff --git a/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_MultipleEntries_SameProcessForward/TestDllBlocklist_MultipleEntries_SameProcessForward.rc b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_MultipleEntries_SameProcessForward/TestDllBlocklist_MultipleEntries_SameProcessForward.rc
new file mode 100644
index 0000000000..20d14e24d7
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_MultipleEntries_SameProcessForward/TestDllBlocklist_MultipleEntries_SameProcessForward.rc
@@ -0,0 +1,42 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <winver.h>
+
+/////////////////////////////////////////////////////////////////////////////
+//
+// Version
+//
+
+VS_VERSION_INFO VERSIONINFO
+  FILEVERSION    5,5,5,5
+  PRODUCTVERSION 5,5,5,1
+  FILEFLAGSMASK 0x3fL
+#ifdef _DEBUG
+  FILEFLAGS 0x1L
+#else
+  FILEFLAGS 0x0L
+#endif
+  FILEOS VOS__WINDOWS32
+  FILETYPE VFT_DLL
+  FILESUBTYPE 0x0L
+BEGIN
+  BLOCK "StringFileInfo"
+  BEGIN
+    BLOCK "040904e4"
+    BEGIN
+      VALUE "CompanyName", "mozilla.org"
+      VALUE "FileDescription", L"Test DLL"
+      VALUE "FileVersion", "1.0"
+      VALUE "InternalName", "Test DLL"
+      VALUE "OriginalFilename", "TestDllBlocklist_MultipleEntries_SameProcessForward.dll"
+      VALUE "ProductName", "Test DLL"
+      VALUE "ProductVersion", "1.0"
+    END
+  END
+  BLOCK "VarFileInfo"
+  BEGIN
+    VALUE "Translation", 0x0409, 1252
+  END
+END
diff --git a/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_MultipleEntries_SameProcessForward/moz.build b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_MultipleEntries_SameProcessForward/moz.build
new file mode 100644
index 0000000000..1546489efb
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_MultipleEntries_SameProcessForward/moz.build
@@ -0,0 +1,19 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+DIST_INSTALL = False
+
+SharedLibrary("TestDllBlocklist_MultipleEntries_SameProcessForward")
+
+UNIFIED_SOURCES = [
+    "TestDllBlocklist_MultipleEntries_SameProcessForward.cpp",
+]
+
+RCFILE = "TestDllBlocklist_MultipleEntries_SameProcessForward.rc"
+
+if CONFIG["COMPILE_ENVIRONMENT"]:
+    TEST_HARNESS_FILES.gtest += [
+        "!TestDllBlocklist_MultipleEntries_SameProcessForward.dll"
+    ]
diff --git a/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_NoOpEntryPoint/TestDllBlocklist_NoOpEntryPoint.cpp b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_NoOpEntryPoint/TestDllBlocklist_NoOpEntryPoint.cpp
new file mode 100644
index 0000000000..2505b8b700
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_NoOpEntryPoint/TestDllBlocklist_NoOpEntryPoint.cpp
@@ -0,0 +1,12 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <windows.h>
+
+#include "mozilla/Assertions.h"
+
+BOOL WINAPI DllMain(HINSTANCE hInstance, DWORD aReason, LPVOID) {
+  MOZ_RELEASE_ASSERT(0);
+  return TRUE;
+}
diff --git a/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_NoOpEntryPoint/TestDllBlocklist_NoOpEntryPoint.rc b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_NoOpEntryPoint/TestDllBlocklist_NoOpEntryPoint.rc
new file mode 100644
index 0000000000..7c79dac373
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_NoOpEntryPoint/TestDllBlocklist_NoOpEntryPoint.rc
@@ -0,0 +1,42 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <winver.h>
+
+/////////////////////////////////////////////////////////////////////////////
+//
+// Version
+//
+
+VS_VERSION_INFO VERSIONINFO
+  FILEVERSION    5,5,5,5
+  PRODUCTVERSION 5,5,5,1
+  FILEFLAGSMASK 0x3fL
+#ifdef _DEBUG
+  FILEFLAGS 0x1L
+#else
+  FILEFLAGS 0x0L
+#endif
+  FILEOS VOS__WINDOWS32
+  FILETYPE VFT_DLL
+  FILESUBTYPE 0x0L
+BEGIN
+  BLOCK "StringFileInfo"
+  BEGIN
+    BLOCK "040904e4"
+    BEGIN
+      VALUE "CompanyName", "mozilla.org"
+      VALUE "FileDescription", L"Test DLL"
+      VALUE "FileVersion", "1.0"
+      VALUE "InternalName", "Test DLL"
+      VALUE "OriginalFilename", "TestDllBlocklist_NoOpEntryPoint.dll"
+      VALUE "ProductName", "Test DLL"
+      VALUE "ProductVersion", "1.0"
+    END
+  END
+  BLOCK "VarFileInfo"
+  BEGIN
+    VALUE "Translation", 0x0409, 1252
+  END
+END
diff --git a/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_NoOpEntryPoint/moz.build b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_NoOpEntryPoint/moz.build
new file mode 100644
index 0000000000..e9a10a150a
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_NoOpEntryPoint/moz.build
@@ -0,0 +1,21 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+DIST_INSTALL = False
+
+SharedLibrary("TestDllBlocklist_NoOpEntryPoint")
+
+UNIFIED_SOURCES = [
+    "TestDllBlocklist_NoOpEntryPoint.cpp",
+]
+
+RCFILE = "TestDllBlocklist_NoOpEntryPoint.rc"
+
+if CONFIG["COMPILE_ENVIRONMENT"]:
+    TEST_HARNESS_FILES.gtest += ["!TestDllBlocklist_NoOpEntryPoint.dll"]
+
+OS_LIBS += [
+    "uuid",
+]
diff --git a/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_SingleNotification1/TestDllBlocklist_SingleNotification1.cpp b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_SingleNotification1/TestDllBlocklist_SingleNotification1.cpp
new file mode 100644
index 0000000000..4f6ce877eb
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_SingleNotification1/TestDllBlocklist_SingleNotification1.cpp
@@ -0,0 +1,7 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <windows.h>
+
+BOOL WINAPI DllMain(HINSTANCE, DWORD, LPVOID) { return TRUE; }
diff --git a/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_SingleNotification1/TestDllBlocklist_SingleNotification1.rc b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_SingleNotification1/TestDllBlocklist_SingleNotification1.rc
new file mode 100644
index 0000000000..90f098b1b9
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_SingleNotification1/TestDllBlocklist_SingleNotification1.rc
@@ -0,0 +1,42 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public

+ * License, v. 2.0. If a copy of the MPL was not distributed with this

+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

+

+#include <winver.h>

+

+/////////////////////////////////////////////////////////////////////////////

+//

+// Version

+//

+

+VS_VERSION_INFO VERSIONINFO

+  FILEVERSION    5,5,5,5

+  PRODUCTVERSION 5,5,5,1

+  FILEFLAGSMASK 0x3fL

+#ifdef _DEBUG

+  FILEFLAGS 0x1L

+#else

+  FILEFLAGS 0x0L

+#endif

+  FILEOS VOS__WINDOWS32

+  FILETYPE VFT_DLL

+  FILESUBTYPE 0x0L

+BEGIN

+  BLOCK "StringFileInfo"

+  BEGIN

+    BLOCK "040904e4"

+    BEGIN

+      VALUE "CompanyName", "mozilla.org"

+      VALUE "FileDescription", L"Test DLL"

+      VALUE "FileVersion", "1.0"

+      VALUE "InternalName", "Test DLL"

+      VALUE "OriginalFilename", "TestDllBlocklist_SingleNotification1.dll"

+      VALUE "ProductName", "Test DLL"

+      VALUE "ProductVersion", "1.0"

+    END

+  END

+  BLOCK "VarFileInfo"

+  BEGIN

+    VALUE "Translation", 0x0409, 1252

+  END

+END

diff --git a/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_SingleNotification1/moz.build b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_SingleNotification1/moz.build
new file mode 100644
index 0000000000..79139b2b6e
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_SingleNotification1/moz.build
@@ -0,0 +1,17 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+DIST_INSTALL = False
+
+SharedLibrary("TestDllBlocklist_SingleNotification1")
+
+UNIFIED_SOURCES = [
+    "TestDllBlocklist_SingleNotification1.cpp",
+]
+
+RCFILE = "TestDllBlocklist_SingleNotification1.rc"
+
+if CONFIG["COMPILE_ENVIRONMENT"]:
+    TEST_HARNESS_FILES.gtest += ["!TestDllBlocklist_SingleNotification1.dll"]
diff --git a/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_SingleNotification2/TestDllBlocklist_SingleNotification2.cpp b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_SingleNotification2/TestDllBlocklist_SingleNotification2.cpp
new file mode 100644
index 0000000000..4f6ce877eb
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_SingleNotification2/TestDllBlocklist_SingleNotification2.cpp
@@ -0,0 +1,7 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <windows.h>
+
+BOOL WINAPI DllMain(HINSTANCE, DWORD, LPVOID) { return TRUE; }
diff --git a/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_SingleNotification2/TestDllBlocklist_SingleNotification2.rc b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_SingleNotification2/TestDllBlocklist_SingleNotification2.rc
new file mode 100644
index 0000000000..0cd44b2f9b
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_SingleNotification2/TestDllBlocklist_SingleNotification2.rc
@@ -0,0 +1,42 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public

+ * License, v. 2.0. If a copy of the MPL was not distributed with this

+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

+

+#include <winver.h>

+

+/////////////////////////////////////////////////////////////////////////////

+//

+// Version

+//

+

+VS_VERSION_INFO VERSIONINFO

+  FILEVERSION    5,5,5,5

+  PRODUCTVERSION 5,5,5,1

+  FILEFLAGSMASK 0x3fL

+#ifdef _DEBUG

+  FILEFLAGS 0x1L

+#else

+  FILEFLAGS 0x0L

+#endif

+  FILEOS VOS__WINDOWS32

+  FILETYPE VFT_DLL

+  FILESUBTYPE 0x0L

+BEGIN

+  BLOCK "StringFileInfo"

+  BEGIN

+    BLOCK "040904e4"

+    BEGIN

+      VALUE "CompanyName", "mozilla.org"

+      VALUE "FileDescription", L"Test DLL"

+      VALUE "FileVersion", "1.0"

+      VALUE "InternalName", "Test DLL"

+      VALUE "OriginalFilename", "TestDllBlocklist_SingleNotification2.dll"

+      VALUE "ProductName", "Test DLL"

+      VALUE "ProductVersion", "1.0"

+    END

+  END

+  BLOCK "VarFileInfo"

+  BEGIN

+    VALUE "Translation", 0x0409, 1252

+  END

+END

diff --git a/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_SingleNotification2/moz.build b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_SingleNotification2/moz.build
new file mode 100644
index 0000000000..64d551f480
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_SingleNotification2/moz.build
@@ -0,0 +1,17 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+DIST_INSTALL = False
+
+SharedLibrary("TestDllBlocklist_SingleNotification2")
+
+UNIFIED_SOURCES = [
+    "TestDllBlocklist_SingleNotification2.cpp",
+]
+
+RCFILE = "TestDllBlocklist_SingleNotification2.rc"
+
+if CONFIG["COMPILE_ENVIRONMENT"]:
+    TEST_HARNESS_FILES.gtest += ["!TestDllBlocklist_SingleNotification2.dll"]
diff --git a/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_SocketProcessOnly/TestDllBlocklist_SocketProcessOnly.cpp b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_SocketProcessOnly/TestDllBlocklist_SocketProcessOnly.cpp
new file mode 100644
index 0000000000..7bd936296e
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_SocketProcessOnly/TestDllBlocklist_SocketProcessOnly.cpp
@@ -0,0 +1,7 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <windows.h>
+
+BOOL WINAPI DllMain(HINSTANCE hInstance, DWORD aReason, LPVOID) { return TRUE; }
diff --git a/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_SocketProcessOnly/moz.build b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_SocketProcessOnly/moz.build
new file mode 100644
index 0000000000..dc93544e1b
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_SocketProcessOnly/moz.build
@@ -0,0 +1,15 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+DIST_INSTALL = False
+
+SharedLibrary("TestDllBlocklist_SocketProcessOnly")
+
+UNIFIED_SOURCES = [
+    "TestDllBlocklist_SocketProcessOnly.cpp",
+]
+
+if CONFIG["COMPILE_ENVIRONMENT"]:
+    TEST_HARNESS_FILES.gtest += ["!TestDllBlocklist_SocketProcessOnly.dll"]
diff --git a/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_UserBlocked/TestDllBlocklist_UserBlocked.cpp b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_UserBlocked/TestDllBlocklist_UserBlocked.cpp
new file mode 100644
index 0000000000..7bd936296e
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_UserBlocked/TestDllBlocklist_UserBlocked.cpp
@@ -0,0 +1,7 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <windows.h>
+
+BOOL WINAPI DllMain(HINSTANCE hInstance, DWORD aReason, LPVOID) { return TRUE; }
diff --git a/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_UserBlocked/moz.build b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_UserBlocked/moz.build
new file mode 100644
index 0000000000..31996c5cb2
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_UserBlocked/moz.build
@@ -0,0 +1,15 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+DIST_INSTALL = False
+
+SharedLibrary("TestDllBlocklist_UserBlocked")
+
+UNIFIED_SOURCES = [
+    "TestDllBlocklist_UserBlocked.cpp",
+]
+
+if CONFIG["COMPILE_ENVIRONMENT"]:
+    TEST_HARNESS_FILES.gtest += ["!TestDllBlocklist_UserBlocked.dll"]
diff --git a/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_UtilityProcessOnly/TestDllBlocklist_UtilityProcessOnly.cpp b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_UtilityProcessOnly/TestDllBlocklist_UtilityProcessOnly.cpp
new file mode 100644
index 0000000000..7bd936296e
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_UtilityProcessOnly/TestDllBlocklist_UtilityProcessOnly.cpp
@@ -0,0 +1,7 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <windows.h>
+
+BOOL WINAPI DllMain(HINSTANCE hInstance, DWORD aReason, LPVOID) { return TRUE; }
diff --git a/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_UtilityProcessOnly/moz.build b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_UtilityProcessOnly/moz.build
new file mode 100644
index 0000000000..913d0f155c
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/gtest/TestDllBlocklist_UtilityProcessOnly/moz.build
@@ -0,0 +1,15 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+DIST_INSTALL = False
+
+SharedLibrary("TestDllBlocklist_UtilityProcessOnly")
+
+UNIFIED_SOURCES = [
+    "TestDllBlocklist_UtilityProcessOnly.cpp",
+]
+
+if CONFIG["COMPILE_ENVIRONMENT"]:
+    TEST_HARNESS_FILES.gtest += ["!TestDllBlocklist_UtilityProcessOnly.dll"]
diff --git a/toolkit/xre/dllservices/tests/gtest/TestUntrustedModules.cpp b/toolkit/xre/dllservices/tests/gtest/TestUntrustedModules.cpp
new file mode 100644
index 0000000000..ba4d1a8df8
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/gtest/TestUntrustedModules.cpp
@@ -0,0 +1,462 @@
+/* vim:set ts=2 sw=2 sts=2 et: */
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+#include "gtest/gtest.h"
+
+#include "js/RegExp.h"
+#include "mozilla/BinarySearch.h"
+#include "mozilla/gtest/MozAssertions.h"
+#include "mozilla/SpinEventLoopUntil.h"
+#include "mozilla/UntrustedModulesProcessor.h"
+#include "mozilla/WinDllServices.h"
+#include "nsContentUtils.h"
+#include "nsDirectoryServiceDefs.h"
+#include "TelemetryFixture.h"
+#include "UntrustedModulesBackupService.h"
+#include "UntrustedModulesDataSerializer.h"
+
+using namespace mozilla;
+
+class ModuleLoadCounter final {
+  nsTHashMap<nsStringCaseInsensitiveHashKey, int> mCounters;
+
+ public:
+  template <size_t N>
+  ModuleLoadCounter(const nsString (&aNames)[N], const int (&aCounts)[N])
+      : mCounters(N) {
+    for (size_t i = 0; i < N; ++i) {
+      mCounters.InsertOrUpdate(aNames[i], aCounts[i]);
+    }
+  }
+
+  template <size_t N>
+  bool Remains(const nsString (&aNames)[N], const int (&aCounts)[N]) {
+    EXPECT_EQ(mCounters.Count(), N);
+    if (mCounters.Count() != N) {
+      return false;
+    }
+
+    bool result = true;
+    for (size_t i = 0; i < N; ++i) {
+      auto entry = mCounters.Lookup(aNames[i]);
+      if (!entry) {
+        wprintf(L"%s is not registered.\n",
+                static_cast<const wchar_t*>(aNames[i].get()));
+        result = false;
+      } else if (*entry != aCounts[i]) {
+        // We can return false, but let's print out all unmet modules
+        // which may be helpful to investigate test failures.
+        wprintf(L"%s:%4d\n", static_cast<const wchar_t*>(aNames[i].get()),
+                *entry);
+        result = false;
+      }
+    }
+    return result;
+  }
+
+  bool IsDone() const {
+    bool allZero = true;
+    for (const auto& data : mCounters.Values()) {
+      if (data < 0) {
+        // If any counter is negative, we know the test fails.
+        // No need to continue.
+        return true;
+      }
+      if (data > 0) {
+        allZero = false;
+      }
+    }
+    // If all counters are zero, the test finished nicely.  Otherwise, those
+    // counters are expected to be decremented later.  Let's continue.
+    return allZero;
+  }
+
+  void Decrement(const nsString& aName) {
+    if (auto entry = mCounters.Lookup(aName)) {
+      --(*entry);
+    }
+  }
+};
+
+class UntrustedModulesCollector {
+  static constexpr int kMaximumAttempts = 500;
+  Vector<UntrustedModulesData> mData;
+  ModuleLoadCounter* mChecker = nullptr;
+  Maybe<nsresult> mRv;
+  int mAttempts = 0;
+
+  void PollUntrustedModulesData() {
+    RefPtr<DllServices> dllSvc(DllServices::Get());
+    dllSvc->GetUntrustedModulesData()->Then(
+        GetMainThreadSerialEventTarget(), __func__,
+        [this](Maybe<UntrustedModulesData>&& aResult) {
+          // Some of expected loaded modules are still missing after
+          // kMaximumAttempts queries were submitted.
+          // Giving up here to avoid an infinite loop.
+          if (++mAttempts > kMaximumAttempts) {
+            mRv = Some(NS_ERROR_ABORT);
+            return;
+          }
+
+          if (aResult.isSome()) {
+            wprintf(L"Received data. (attempts=%d)\n", mAttempts);
+            for (auto item : aResult.ref().mEvents) {
+              mChecker->Decrement(item->mEvent.mRequestedDllName);
+            }
+            EXPECT_TRUE(mData.emplaceBack(std::move(aResult.ref())));
+          }
+
+          if (mChecker->IsDone()) {
+            mRv = Some(NS_OK);
+            return;
+          }
+
+          PollUntrustedModulesData();
+        },
+        [this](nsresult aReason) {
+          wprintf(L"GetUntrustedModulesData() failed - %08x\n", aReason);
+          EXPECT_TRUE(false);
+          mRv = Some(aReason);
+        });
+  }
+
+ public:
+  Vector<UntrustedModulesData>& Data() { return mData; }
+
+  nsresult Collect(ModuleLoadCounter& aChecker) {
+    mRv = Nothing();
+    mChecker = &aChecker;
+    mAttempts = 0;
+    mData.clear();
+
+    PollUntrustedModulesData();
+
+    EXPECT_TRUE(SpinEventLoopUntil("xre:UntrustedModulesCollector"_ns,
+                                   [this]() { return mRv.isSome(); }));
+
+    mChecker = nullptr;
+    return *mRv;
+  }
+};
+
+class UntrustedModulesFixture : public TelemetryTestFixture {
+  static constexpr int kLoadCountBeforeDllServices = 5;
+  static constexpr int kLoadCountAfterDllServices = 5;
+  static constexpr uint32_t kMaxModulesArrayLen = 10;
+
+  // One of the important test scenarios is to load modules before DllServices
+  // is initialized and to make sure those loading events are forwarded when
+  // DllServices is initialized.
+  // However, GTest instantiates a Fixture class every testcase and there is
+  // no way to re-enable DllServices and UntrustedModulesProcessor once it's
+  // disabled, which means no matter how many testcases we have, only the
+  // first testcase exercises that scenario.  That's why we implement that
+  // test scenario in InitialModuleLoadOnce as a static member and runs it
+  // in the first testcase to be executed.
+  static INIT_ONCE sInitLoadOnce;
+  static UntrustedModulesCollector sInitLoadDataCollector;
+
+  static nsString PrependWorkingDir(const nsAString& aLeaf) {
+    nsCOMPtr<nsIFile> file;
+    EXPECT_TRUE(NS_SUCCEEDED(NS_GetSpecialDirectory(NS_OS_CURRENT_WORKING_DIR,
+                                                    getter_AddRefs(file))));
+    EXPECT_NS_SUCCEEDED(file->Append(aLeaf));
+    bool exists;
+    EXPECT_TRUE(NS_SUCCEEDED(file->Exists(&exists)) && exists);
+    nsString fullPath;
+    EXPECT_NS_SUCCEEDED(file->GetPath(fullPath));
+    return fullPath;
+  }
+
+  static BOOL CALLBACK InitialModuleLoadOnce(PINIT_ONCE, void*, void**);
+
+ protected:
+  static constexpr int kInitLoadCount =
+      kLoadCountBeforeDllServices + kLoadCountAfterDllServices;
+  static const nsString kTestModules[];
+
+  static void ValidateUntrustedModules(const UntrustedModulesData& aData,
+                                       bool aIsTruncatedData = false);
+
+  static void LoadAndFree(const nsAString& aLeaf) {
+    nsModuleHandle dll(::LoadLibraryW(PrependWorkingDir(aLeaf).get()));
+    EXPECT_TRUE(!!dll);
+  }
+
+  virtual void SetUp() override {
+    TelemetryTestFixture::SetUp();
+    ::InitOnceExecuteOnce(&sInitLoadOnce, InitialModuleLoadOnce, nullptr,
+                          nullptr);
+  }
+
+  static const Vector<UntrustedModulesData>& GetInitLoadData() {
+    return sInitLoadDataCollector.Data();
+  }
+
+  // This method is useful if we want a new instance of UntrustedModulesData
+  // which is not copyable.
+  static UntrustedModulesData CollectSingleData() {
+    // If we call LoadAndFree more than once, those loading events are
+    // likely to be merged into an instance of UntrustedModulesData,
+    // meaning the length of the collector's vector is at least one but
+    // the exact number is unknown.
+    LoadAndFree(kTestModules[0]);
+
+    UntrustedModulesCollector collector;
+    ModuleLoadCounter waitForOne({kTestModules[0]}, {1});
+    EXPECT_NS_SUCCEEDED(collector.Collect(waitForOne));
+    EXPECT_TRUE(waitForOne.Remains({kTestModules[0]}, {0}));
+    EXPECT_EQ(collector.Data().length(), 1U);
+
+    // Cannot "return collector.Data()[0]" as copy ctor is deleted.
+    return UntrustedModulesData(std::move(collector.Data()[0]));
+  }
+
+  template <typename DataFetcherT>
+  void ValidateJSValue(const char16_t* aPattern, size_t aPatternLength,
+                       DataFetcherT&& aDataFetcher) {
+    AutoJSContextWithGlobal cx(mCleanGlobal);
+    mozilla::Telemetry::UntrustedModulesDataSerializer serializer(
+        cx.GetJSContext(), kMaxModulesArrayLen);
+    EXPECT_TRUE(!!serializer);
+    aDataFetcher(serializer);
+
+    JS::Rooted<JS::Value> jsval(cx.GetJSContext());
+    serializer.GetObject(&jsval);
+
+    nsAutoString json;
+    EXPECT_TRUE(nsContentUtils::StringifyJSON(
+        cx.GetJSContext(), jsval, json, dom::UndefinedIsNullStringLiteral));
+
+    JS::Rooted<JSObject*> re(
+        cx.GetJSContext(),
+        JS::NewUCRegExpObject(cx.GetJSContext(), aPattern, aPatternLength,
+                              JS::RegExpFlag::Global));
+    EXPECT_TRUE(!!re);
+
+    JS::Rooted<JS::Value> matchResult(cx.GetJSContext(), JS::NullValue());
+    size_t idx = 0;
+    EXPECT_TRUE(JS::ExecuteRegExpNoStatics(cx.GetJSContext(), re, json.get(),
+                                           json.Length(), &idx, true,
+                                           &matchResult));
+    // On match, with aOnlyMatch = true, ExecuteRegExpNoStatics returns boolean
+    // true.  If no match, ExecuteRegExpNoStatics returns Null.
+    EXPECT_TRUE(matchResult.isBoolean() && matchResult.toBoolean());
+    if (!matchResult.isBoolean() || !matchResult.toBoolean()) {
+      // If match failed, print out the actual JSON kindly.
+      wprintf(L"JSON: %s\n", static_cast<const wchar_t*>(json.get()));
+      wprintf(L"RE: %s\n", aPattern);
+    }
+  }
+};
+
+const nsString UntrustedModulesFixture::kTestModules[] = {
+    // Sorted for binary-search
+    u"TestUntrustedModules_Dll1.dll"_ns,
+    u"TestUntrustedModules_Dll2.dll"_ns,
+};
+
+INIT_ONCE UntrustedModulesFixture::sInitLoadOnce = INIT_ONCE_STATIC_INIT;
+UntrustedModulesCollector UntrustedModulesFixture::sInitLoadDataCollector;
+
+void UntrustedModulesFixture::ValidateUntrustedModules(
+    const UntrustedModulesData& aData, bool aIsTruncatedData) {
+  // This defines a list of modules which are listed on our blocklist and
+  // thus its loading status is not expected to be Status::Loaded.
+  // Although the UntrustedModulesFixture test does not touch any of them,
+  // the current process might have run a test like TestDllBlocklist where
+  // we try to load and block them.
+  const struct {
+    const wchar_t* mName;
+    ModuleLoadInfo::Status mStatus;
+  } kKnownModules[] = {
+    // Sorted by mName for binary-search
+    {L"TestDllBlocklist_MatchByName.dll", ModuleLoadInfo::Status::Blocked},
+    {L"TestDllBlocklist_MatchByVersion.dll", ModuleLoadInfo::Status::Blocked},
+    {L"TestDllBlocklist_NoOpEntryPoint.dll",
+     ModuleLoadInfo::Status::Redirected},
+#if !defined(MOZ_ASAN)
+    // With ASAN, the test uses mozglue's blocklist where
+    // the user blocklist is not used. So only check for this
+    // DLL in the non-ASAN case.
+    {L"TestDllBlocklist_UserBlocked.dll", ModuleLoadInfo::Status::Blocked},
+#endif  // !defined(MOZ_ASAN)
+  };
+
+  EXPECT_EQ(aData.mProcessType, GeckoProcessType_Default);
+  EXPECT_EQ(aData.mPid, ::GetCurrentProcessId());
+
+  nsTHashtable<nsPtrHashKey<void>> moduleSet;
+  for (const RefPtr<ModuleRecord>& module : aData.mModules.Values()) {
+    moduleSet.PutEntry(module);
+  }
+
+  size_t numBlockedEvents = 0;
+  for (auto item : aData.mEvents) {
+    const auto& evt = item->mEvent;
+    const nsDependentSubstring leafName =
+        nt::GetLeafName(evt.mModule->mResolvedNtName);
+    const nsAutoString leafNameStr(leafName.Data(), leafName.Length());
+    const ModuleLoadInfo::Status loadStatus =
+        static_cast<ModuleLoadInfo::Status>(evt.mLoadStatus);
+    if (loadStatus == ModuleLoadInfo::Status::Blocked) {
+      ++numBlockedEvents;
+    }
+
+    size_t match;
+    if (BinarySearchIf(
+            kKnownModules, 0, ArrayLength(kKnownModules),
+            [&leafNameStr](const auto& aVal) {
+              return _wcsicmp(leafNameStr.get(), aVal.mName);
+            },
+            &match)) {
+      EXPECT_EQ(loadStatus, kKnownModules[match].mStatus);
+    } else {
+      EXPECT_EQ(evt.mLoadStatus, 0U);
+    }
+
+    if (BinarySearchIf(
+            kTestModules, 0, ArrayLength(kTestModules),
+            [&leafNameStr](const auto& aVal) {
+              return _wcsicmp(leafNameStr.get(), aVal.get());
+            },
+            &match)) {
+      // We know the test modules are loaded in the main thread,
+      // but we don't know about other modules.
+      EXPECT_EQ(evt.mThreadId, ::GetCurrentThreadId());
+    }
+
+    // Make sure mModule is pointing to an entry of mModules.
+    EXPECT_TRUE(moduleSet.Contains(evt.mModule));
+    EXPECT_FALSE(evt.mIsDependent);
+  }
+
+  // No check for the mXULLoadDurationMS field because the field has a value
+  // in CCov build GTest, but it is empty in non-CCov build (bug 1681936).
+  EXPECT_EQ(aData.mNumEvents, aData.mEvents.length());
+  EXPECT_GT(aData.mNumEvents, 0U);
+  if (aIsTruncatedData) {
+    EXPECT_EQ(aData.mStacks.GetModuleCount(), 0U);
+    EXPECT_LE(aData.mNumEvents, UntrustedModulesData::kMaxEvents);
+  } else if (numBlockedEvents == aData.mNumEvents) {
+    // If all loading events were blocked or aData is truncated,
+    // the stacks are empty.
+    EXPECT_EQ(aData.mStacks.GetModuleCount(), 0U);
+  } else {
+    EXPECT_GT(aData.mStacks.GetModuleCount(), 0U);
+  }
+  EXPECT_EQ(aData.mSanitizationFailures, 0U);
+  EXPECT_EQ(aData.mTrustTestFailures, 0U);
+}
+
+BOOL CALLBACK UntrustedModulesFixture::InitialModuleLoadOnce(PINIT_ONCE, void*,
+                                                             void**) {
+  for (int i = 0; i < kLoadCountBeforeDllServices; ++i) {
+    for (const auto& mod : kTestModules) {
+      LoadAndFree(mod);
+    }
+  }
+
+  RefPtr<DllServices> dllSvc(DllServices::Get());
+  dllSvc->StartUntrustedModulesProcessor(true);
+
+  for (int i = 0; i < kLoadCountAfterDllServices; ++i) {
+    for (const auto& mod : kTestModules) {
+      LoadAndFree(mod);
+    }
+  }
+
+  ModuleLoadCounter waitForTwo(kTestModules, {kInitLoadCount, kInitLoadCount});
+  EXPECT_EQ(sInitLoadDataCollector.Collect(waitForTwo), NS_OK);
+  EXPECT_TRUE(waitForTwo.Remains(kTestModules, {0, 0}));
+
+  for (const auto& event : GetInitLoadData()) {
+    ValidateUntrustedModules(event);
+  }
+
+  // Data was removed when retrieved.  No data is retrieved again.
+  UntrustedModulesCollector collector;
+  ModuleLoadCounter waitOnceForEach(kTestModules, {1, 1});
+  EXPECT_EQ(collector.Collect(waitOnceForEach), NS_ERROR_ABORT);
+  EXPECT_TRUE(waitOnceForEach.Remains(kTestModules, {1, 1}));
+
+  return TRUE;
+}
+
+#define PROCESS_OBJ(TYPE, PID) \
+  u"\"" TYPE u"\\." PID u"\":{" \
+    u"\"processType\":\"" TYPE u"\",\"elapsed\":\\d+\\.\\d+," \
+    u"\"sanitizationFailures\":0,\"trustTestFailures\":0," \
+    u"\"events\":\\[{" \
+      u"\"processUptimeMS\":\\d+,\"loadDurationMS\":\\d+\\.\\d+," \
+      u"\"threadID\":\\d+,\"threadName\":\"Main Thread\"," \
+      u"\"baseAddress\":\"0x[0-9a-f]+\",\"moduleIndex\":0," \
+      u"\"isDependent\":false,\"loadStatus\":0}\\]," \
+    u"\"combinedStacks\":{" \
+      u"\"memoryMap\":\\[\\[\"\\w+\\.\\w+\",\"[0-9A-Z]+\"\\]" \
+        u"(,\\[\"\\w+\\.\\w+\",\"[0-9A-Z]+\\\"\\])*\\]," \
+      u"\"stacks\":\\[\\[\\[(-1|\\d+),\\d+\\]" \
+        u"(,\\[(-1|\\d+),\\d+\\])*\\]\\]}}"
+
+TEST_F(UntrustedModulesFixture, Serialize) {
+  // clang-format off
+  const char16_t kPattern[] = u"{\"structVersion\":1,"
+    u"\"modules\":\\[{"
+      u"\"resolvedDllName\":\"TestUntrustedModules_Dll1\\.dll\","
+      u"\"fileVersion\":\"1\\.2\\.3\\.4\","
+      // It would be nice to hard-code this, but this might change with
+      // compiler versions, etc.
+      u"\"debugID\":\"[0-9A-F]{33}\","
+      u"\"companyName\":\"Mozilla Corporation\",\"trustFlags\":0}\\],"
+    u"\"blockedModules\":\\[.*?\\]," // allow for the case where there are some blocked modules
+    u"\"processes\":{"
+      PROCESS_OBJ(u"browser", u"0xabc") u","
+      PROCESS_OBJ(u"browser", u"0x4") u","
+      PROCESS_OBJ(u"rdd", u"0x4")
+  u"}}";
+  // clang-format on
+
+  UntrustedModulesBackupData backup1, backup2;
+  {
+    UntrustedModulesData data1 = CollectSingleData();
+    UntrustedModulesData data2 = CollectSingleData();
+    UntrustedModulesData data3 = CollectSingleData();
+
+    data1.mPid = 0xabc;
+    data2.mPid = 0x4;
+    data2.mProcessType = GeckoProcessType_RDD;
+    data3.mPid = 0x4;
+
+    backup1.Add(std::move(data1));
+    backup2.Add(std::move(data2));
+    backup1.Add(std::move(data3));
+  }
+
+  ValidateJSValue(kPattern, ArrayLength(kPattern) - 1,
+                  [&backup1, &backup2](
+                      Telemetry::UntrustedModulesDataSerializer& aSerializer) {
+                    EXPECT_NS_SUCCEEDED(aSerializer.Add(backup1));
+                    EXPECT_NS_SUCCEEDED(aSerializer.Add(backup2));
+                  });
+}
+
+TEST_F(UntrustedModulesFixture, Backup) {
+  RefPtr<UntrustedModulesBackupService> backupSvc(
+      UntrustedModulesBackupService::Get());
+  for (int i = 0; i < 100; ++i) {
+    backupSvc->Backup(CollectSingleData());
+  }
+
+  backupSvc->SettleAllStagingData();
+  EXPECT_TRUE(backupSvc->Staging().IsEmpty());
+
+  for (const auto& entry : backupSvc->Settled()) {
+    const RefPtr<UntrustedModulesDataContainer>& container = entry.GetData();
+    EXPECT_TRUE(!!container);
+    const UntrustedModulesData& data = container->mData;
+    EXPECT_EQ(entry.GetKey(), ProcessHashKey(data.mProcessType, data.mPid));
+    ValidateUntrustedModules(data, /*aIsTruncatedData*/ true);
+  }
+}
diff --git a/toolkit/xre/dllservices/tests/gtest/TestUntrustedModules_Dll1/TestUntrustedModules_Dll1.cpp b/toolkit/xre/dllservices/tests/gtest/TestUntrustedModules_Dll1/TestUntrustedModules_Dll1.cpp
new file mode 100644
index 0000000000..4f6ce877eb
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/gtest/TestUntrustedModules_Dll1/TestUntrustedModules_Dll1.cpp
@@ -0,0 +1,7 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <windows.h>
+
+BOOL WINAPI DllMain(HINSTANCE, DWORD, LPVOID) { return TRUE; }
diff --git a/toolkit/xre/dllservices/tests/gtest/TestUntrustedModules_Dll1/TestUntrustedModules_Dll1.rc b/toolkit/xre/dllservices/tests/gtest/TestUntrustedModules_Dll1/TestUntrustedModules_Dll1.rc
new file mode 100644
index 0000000000..2358b88b93
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/gtest/TestUntrustedModules_Dll1/TestUntrustedModules_Dll1.rc
@@ -0,0 +1,38 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public

+ * License, v. 2.0. If a copy of the MPL was not distributed with this

+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

+

+#include <winver.h>

+

+/////////////////////////////////////////////////////////////////////////////

+//

+// Version

+//

+

+VS_VERSION_INFO VERSIONINFO

+  FILEVERSION    1,2,3,4  // This field will be collected

+  PRODUCTVERSION 5,6,7,8

+  FILEFLAGSMASK 0x3fL

+#ifdef _DEBUG

+  FILEFLAGS 0x1L

+#else

+  FILEFLAGS 0x0L

+#endif

+  FILEOS VOS__WINDOWS32

+  FILETYPE VFT_DLL

+  FILESUBTYPE 0x0L

+BEGIN

+  BLOCK "StringFileInfo"

+  BEGIN

+    BLOCK "040904e4"

+    BEGIN

+      VALUE "CompanyName", "Mozilla Corporation"

+      VALUE "OriginalFilename", "TestUntrustedModules_Dll1.dll"

+      VALUE "ProductName", "Test DLL"

+    END

+  END

+  BLOCK "VarFileInfo"

+  BEGIN

+    VALUE "Translation", 0x0409, 1252

+  END

+END

diff --git a/toolkit/xre/dllservices/tests/gtest/TestUntrustedModules_Dll1/moz.build b/toolkit/xre/dllservices/tests/gtest/TestUntrustedModules_Dll1/moz.build
new file mode 100644
index 0000000000..57fc59ca8a
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/gtest/TestUntrustedModules_Dll1/moz.build
@@ -0,0 +1,17 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+DIST_INSTALL = False
+
+SharedLibrary("TestUntrustedModules_Dll1")
+
+UNIFIED_SOURCES = [
+    "TestUntrustedModules_Dll1.cpp",
+]
+
+RCFILE = "TestUntrustedModules_Dll1.rc"
+
+if CONFIG["COMPILE_ENVIRONMENT"]:
+    TEST_HARNESS_FILES.gtest += ["!TestUntrustedModules_Dll1.dll"]
diff --git a/toolkit/xre/dllservices/tests/gtest/TestUntrustedModules_Dll2/TestUntrustedModules_Dll2.cpp b/toolkit/xre/dllservices/tests/gtest/TestUntrustedModules_Dll2/TestUntrustedModules_Dll2.cpp
new file mode 100644
index 0000000000..4f6ce877eb
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/gtest/TestUntrustedModules_Dll2/TestUntrustedModules_Dll2.cpp
@@ -0,0 +1,7 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <windows.h>
+
+BOOL WINAPI DllMain(HINSTANCE, DWORD, LPVOID) { return TRUE; }
diff --git a/toolkit/xre/dllservices/tests/gtest/TestUntrustedModules_Dll2/moz.build b/toolkit/xre/dllservices/tests/gtest/TestUntrustedModules_Dll2/moz.build
new file mode 100644
index 0000000000..fcefe41329
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/gtest/TestUntrustedModules_Dll2/moz.build
@@ -0,0 +1,15 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+DIST_INSTALL = False
+
+SharedLibrary("TestUntrustedModules_Dll2")
+
+UNIFIED_SOURCES = [
+    "TestUntrustedModules_Dll2.cpp",
+]
+
+if CONFIG["COMPILE_ENVIRONMENT"]:
+    TEST_HARNESS_FILES.gtest += ["!TestUntrustedModules_Dll2.dll"]
diff --git a/toolkit/xre/dllservices/tests/gtest/moz.build b/toolkit/xre/dllservices/tests/gtest/moz.build
new file mode 100644
index 0000000000..92f341841a
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/gtest/moz.build
@@ -0,0 +1,39 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+Library("dllservicestest")
+
+UNIFIED_SOURCES += [
+    "TestDLLBlocklist.cpp",
+    "TestUntrustedModules.cpp",
+]
+
+LOCAL_INCLUDES += [
+    "/toolkit/components/telemetry/other",
+    "/toolkit/components/telemetry/tests/gtest",
+]
+
+TEST_DIRS += [
+    "rust",
+    "TestDllBlocklist_AllowByVersion",
+    "TestDllBlocklist_GMPluginProcessOnly",
+    "TestDllBlocklist_GPUProcessOnly",
+    "TestDllBlocklist_MatchByName",
+    "TestDllBlocklist_MatchByVersion",
+    "TestDllBlocklist_MultipleEntries_DifferentProcesses",
+    "TestDllBlocklist_MultipleEntries_SameProcessBackward",
+    "TestDllBlocklist_MultipleEntries_SameProcessForward",
+    "TestDllBlocklist_NoOpEntryPoint",
+    "TestDllBlocklist_SingleNotification1",
+    "TestDllBlocklist_SingleNotification2",
+    "TestDllBlocklist_SocketProcessOnly",
+    "TestDllBlocklist_UserBlocked",
+    "TestDllBlocklist_UtilityProcessOnly",
+    "TestUntrustedModules_Dll1",
+    "TestUntrustedModules_Dll2",
+]
+
+include("/ipc/chromium/chromium-config.mozbuild")
+
+FINAL_LIBRARY = "xul-gtest"
diff --git a/toolkit/xre/dllservices/tests/gtest/rust/Cargo.toml b/toolkit/xre/dllservices/tests/gtest/rust/Cargo.toml
new file mode 100644
index 0000000000..a342fb8bf2
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/gtest/rust/Cargo.toml
@@ -0,0 +1,12 @@
+[package]

+name = "dllservices-gtest"

+version = "0.1.0"

+authors = ["nobody@mozilla.com"]

+license = "MPL-2.0"

+description = "Tests for dllservices"

+

+[dependencies]

+uuid = { version = "1.0", features = ["v4"] }

+

+[lib]

+path = "test.rs"

diff --git a/toolkit/xre/dllservices/tests/gtest/rust/TestBCryptFallback.cpp b/toolkit/xre/dllservices/tests/gtest/rust/TestBCryptFallback.cpp
new file mode 100644
index 0000000000..ca4dbde3ab
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/gtest/rust/TestBCryptFallback.cpp
@@ -0,0 +1,113 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <windows.h>
+#include <ntstatus.h>
+
+#include <bcrypt.h>
+#pragma comment(lib, "bcrypt.lib")
+
+#include "gtest/gtest.h"
+
+#include "nsWindowsDllInterceptor.h"
+
+#define RtlGenRandom SystemFunction036
+extern "C" BOOLEAN NTAPI RtlGenRandom(PVOID aRandomBuffer,
+                                      ULONG aRandomBufferLength);
+
+static mozilla::WindowsDllInterceptor BCryptIntercept;
+static mozilla::WindowsDllInterceptor::FuncHookType<
+    decltype(&::BCryptGenRandom)>
+    stub_BCryptGenRandom;
+
+static mozilla::WindowsDllInterceptor AdvApiIntercept;
+static mozilla::WindowsDllInterceptor::FuncHookType<decltype(&RtlGenRandom)>
+    stub_RtlGenRandom;
+
+volatile bool gAreHooksActive = false;
+volatile bool gHasPanicked = false;
+volatile bool gHasReachedBCryptGenRandom = false;
+volatile bool gHasReachedRtlGenRandom = false;
+
+NTSTATUS WINAPI patched_BCryptGenRandom(BCRYPT_ALG_HANDLE aAlgorithm,
+                                        PUCHAR aBuffer, ULONG aSize,
+                                        ULONG aFlags) {
+  if (gAreHooksActive) {
+    gHasReachedBCryptGenRandom = true;
+    // Force BCryptGenRandom failures when the hook is active.
+    return STATUS_UNSUCCESSFUL;
+  }
+  return stub_BCryptGenRandom(aAlgorithm, aBuffer, aSize, aFlags);
+}
+
+BOOLEAN NTAPI patched_RtlGenRandom(PVOID aRandomBuffer,
+                                   ULONG aRandomBufferLength) {
+  if (gAreHooksActive) {
+    gHasReachedRtlGenRandom = true;
+  }
+  return stub_RtlGenRandom(aRandomBuffer, aRandomBufferLength);
+}
+
+bool InitInterception() {
+  static bool sSuccess = []() {
+    BCryptIntercept.Init(L"bcrypt.dll");
+    AdvApiIntercept.Init(L"advapi32.dll");
+    return stub_BCryptGenRandom.SetDetour(BCryptIntercept, "BCryptGenRandom",
+                                          patched_BCryptGenRandom) &&
+           stub_RtlGenRandom.SetDetour(AdvApiIntercept, "SystemFunction036",
+                                       patched_RtlGenRandom);
+  }();
+  gAreHooksActive = true;
+  return sSuccess;
+}
+
+void ExitInterception() { gAreHooksActive = false; }
+
+DWORD WINAPI TestIsFallbackTriggeredThreadProc(LPVOID aParameter) {
+  auto testedFunction = reinterpret_cast<void (*)()>(aParameter);
+  EXPECT_TRUE(InitInterception());
+  MOZ_SEH_TRY { testedFunction(); }
+  MOZ_SEH_EXCEPT(EXCEPTION_EXECUTE_HANDLER) {
+    // Catch a potential Rust panic
+    gHasPanicked = true;
+  }
+  ExitInterception();
+  return 0;
+}
+
+// This function hooks BCryptGenRandom to make it fail, and hooks RtlGenRandom
+// to allow us to ensure that it gets visited as a fallback for
+// BCryptGenRandom.
+void TestIsFallbackTriggered(void (*aTestedFunction)()) {
+  gHasPanicked = false;
+  gHasReachedBCryptGenRandom = false;
+  gHasReachedRtlGenRandom = false;
+
+  // The HashMap test must run on a new thread, because some random bytes have
+  // already been collected but not used on the current thread by previous
+  // calls to HashMap::new in various locations of the code base. These bytes
+  // would be recycled instead of calling into BCryptGenRandom and RtlGenRandom
+  // if running the HashMap test on the current thread.
+  auto thread =
+      ::CreateThread(nullptr, 0, TestIsFallbackTriggeredThreadProc,
+                     reinterpret_cast<void*>(aTestedFunction), 0, nullptr);
+  EXPECT_TRUE(bool(thread));
+  EXPECT_EQ(::WaitForSingleObject(thread, 5000),
+            static_cast<DWORD>(WAIT_OBJECT_0));
+
+  EXPECT_FALSE(gHasPanicked);
+  EXPECT_TRUE(gHasReachedBCryptGenRandom);
+  EXPECT_TRUE(gHasReachedRtlGenRandom);
+}
+
+extern "C" void Rust_TriggerGenRandomFromHashMap();
+extern "C" void Rust_TriggerGenRandomFromUuid();
+
+TEST(TestBCryptFallback, HashMapTriggersFallback)
+{ TestIsFallbackTriggered(Rust_TriggerGenRandomFromHashMap); }
+
+TEST(TestBCryptFallback, UuidTriggersFallback)
+{ TestIsFallbackTriggered(Rust_TriggerGenRandomFromUuid); }
diff --git a/toolkit/xre/dllservices/tests/gtest/rust/moz.build b/toolkit/xre/dllservices/tests/gtest/rust/moz.build
new file mode 100644
index 0000000000..eea8b9e978
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/gtest/rust/moz.build
@@ -0,0 +1,11 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+Library("dllservicestest")
+
+UNIFIED_SOURCES += [
+    "TestBCryptFallback.cpp",
+]
+
+FINAL_LIBRARY = "xul-gtest"
diff --git a/toolkit/xre/dllservices/tests/gtest/rust/test.rs b/toolkit/xre/dllservices/tests/gtest/rust/test.rs
new file mode 100644
index 0000000000..51c2a6e156
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/gtest/rust/test.rs
@@ -0,0 +1,19 @@
+/* -*- Mode: rust; rust-indent-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use std::collections::HashMap;
+
+extern crate uuid;
+use uuid::Uuid;
+
+#[no_mangle]
+pub extern "C" fn Rust_TriggerGenRandomFromHashMap() -> () {
+    let _: HashMap<u32, u32> = HashMap::new();
+}
+
+#[no_mangle]
+pub extern "C" fn Rust_TriggerGenRandomFromUuid() -> () {
+    let _: Uuid = Uuid::new_v4();
+}
diff --git a/toolkit/xre/dllservices/tests/moz.build b/toolkit/xre/dllservices/tests/moz.build
new file mode 100644
index 0000000000..957243a476
--- /dev/null
+++ b/toolkit/xre/dllservices/tests/moz.build
@@ -0,0 +1,47 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+GeckoCppUnitTests(
+    [
+        "TestDllBlocklistAssumptions",
+        "TestDllInterceptor",
+        "TestIATPatcher",
+        "TestMMPolicy",
+    ],
+    linkage=None,
+)
+
+if CONFIG["CPU_ARCH"] in ("x86", "x86_64"):
+    # Cross-process interceptors not yet supported on aarch64
+    GeckoCppUnitTests(
+        [
+            "TestDllInterceptorCrossProcess",
+        ],
+        linkage=None,
+    )
+
+OS_LIBS += [
+    "advapi32",
+    "ntdll",
+    "ole32",
+    "shlwapi",
+    "user32",
+    "uuid",
+]
+
+DELAYLOAD_DLLS += [
+    "shlwapi.dll",
+]
+
+if CONFIG["CC_TYPE"] in ("gcc", "clang"):
+    # This allows us to use wmain as the entry point on mingw
+    LDFLAGS += [
+        "-municode",
+    ]
+
+TEST_DIRS += [
+    "gtest",
+]
diff --git a/toolkit/xre/glxtest/glxtest.cpp b/toolkit/xre/glxtest/glxtest.cpp
new file mode 100644
index 0000000000..33a21c11f7
--- /dev/null
+++ b/toolkit/xre/glxtest/glxtest.cpp
@@ -0,0 +1,1034 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: sw=2 ts=8 et :
+ */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+//////////////////////////////////////////////////////////////////////////////
+//
+// Explanation: See bug 639842. Safely getting GL driver info on X11 is hard,
+// because the only way to do that is to create a GL context and call
+// glGetString(), but with bad drivers, just creating a GL context may crash.
+//
+// This file implements the idea to do that in a separate process.
+//
+// The only non-static function here is fire_glxtest_process(). It creates a
+// pipe, publishes its 'read' end as the mozilla::widget::glxtest_pipe global
+// variable, forks, and runs that GLX probe in the child process, which runs the
+// childgltest() static function. This creates a X connection, a GLX context,
+// calls glGetString, and writes that to the 'write' end of the pipe.
+
+#include <cstdio>
+#include <cstdlib>
+#include <dlfcn.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <getopt.h>
+#include <vector>
+#include <stdint.h>
+#include <string.h>
+#include <stdarg.h>
+
+#ifdef MOZ_WAYLAND
+#  include <gdk/gdk.h>
+#endif
+
+#if defined(MOZ_ASAN) || defined(FUZZING)
+#  include <signal.h>
+#endif
+
+#ifdef __SUNPRO_CC
+#  include <stdio.h>
+#endif
+
+#ifdef MOZ_X11
+#  include "X11/Xlib.h"
+#  include "X11/Xutil.h"
+#  include <X11/extensions/Xrandr.h>
+#endif
+
+#include <vector>
+#include <sys/wait.h>
+#include "mozilla/ScopeExit.h"
+#include "mozilla/Types.h"
+
+#include "mozilla/GfxInfoUtils.h"
+
+#ifdef MOZ_X11
+// stuff from glx.h
+typedef struct __GLXcontextRec* GLXContext;
+typedef XID GLXPixmap;
+typedef XID GLXDrawable;
+/* GLX 1.3 and later */
+typedef struct __GLXFBConfigRec* GLXFBConfig;
+typedef XID GLXFBConfigID;
+typedef XID GLXContextID;
+typedef XID GLXWindow;
+typedef XID GLXPbuffer;
+#  define GLX_RGBA 4
+#  define GLX_RED_SIZE 8
+#  define GLX_GREEN_SIZE 9
+#  define GLX_BLUE_SIZE 10
+#  define GLX_DOUBLEBUFFER 5
+#endif
+
+// stuff from gl.h
+typedef uint8_t GLubyte;
+typedef uint32_t GLenum;
+#define GL_VENDOR 0x1F00
+#define GL_RENDERER 0x1F01
+#define GL_VERSION 0x1F02
+
+// GLX_MESA_query_renderer
+// clang-format off
+#define GLX_RENDERER_VENDOR_ID_MESA                            0x8183
+#define GLX_RENDERER_DEVICE_ID_MESA                            0x8184
+#define GLX_RENDERER_VERSION_MESA                              0x8185
+#define GLX_RENDERER_ACCELERATED_MESA                          0x8186
+#define GLX_RENDERER_VIDEO_MEMORY_MESA                         0x8187
+#define GLX_RENDERER_UNIFIED_MEMORY_ARCHITECTURE_MESA          0x8188
+#define GLX_RENDERER_PREFERRED_PROFILE_MESA                    0x8189
+#define GLX_RENDERER_OPENGL_CORE_PROFILE_VERSION_MESA          0x818A
+#define GLX_RENDERER_OPENGL_COMPATIBILITY_PROFILE_VERSION_MESA 0x818B
+#define GLX_RENDERER_OPENGL_ES_PROFILE_VERSION_MESA            0x818C
+#define GLX_RENDERER_OPENGL_ES2_PROFILE_VERSION_MESA           0x818D
+#define GLX_RENDERER_ID_MESA                                   0x818E
+// clang-format on
+
+// stuff from egl.h
+typedef intptr_t EGLAttrib;
+typedef int EGLBoolean;
+typedef void* EGLConfig;
+typedef void* EGLContext;
+typedef void* EGLDeviceEXT;
+typedef void* EGLDisplay;
+typedef unsigned int EGLenum;
+typedef int EGLint;
+typedef void* EGLNativeDisplayType;
+typedef void* EGLSurface;
+typedef void* (*PFNEGLGETPROCADDRESS)(const char*);
+
+#define EGL_NO_CONTEXT nullptr
+#define EGL_NO_SURFACE nullptr
+#define EGL_FALSE 0
+#define EGL_TRUE 1
+#define EGL_OPENGL_ES2_BIT 0x0004
+#define EGL_BLUE_SIZE 0x3022
+#define EGL_GREEN_SIZE 0x3023
+#define EGL_RED_SIZE 0x3024
+#define EGL_NONE 0x3038
+#define EGL_RENDERABLE_TYPE 0x3040
+#define EGL_VENDOR 0x3053
+#define EGL_EXTENSIONS 0x3055
+#define EGL_CONTEXT_MAJOR_VERSION 0x3098
+#define EGL_OPENGL_ES_API 0x30A0
+#define EGL_OPENGL_API 0x30A2
+#define EGL_DEVICE_EXT 0x322C
+#define EGL_DRM_DEVICE_FILE_EXT 0x3233
+#define EGL_DRM_RENDER_NODE_FILE_EXT 0x3377
+
+// stuff from xf86drm.h
+#define DRM_NODE_RENDER 2
+#define DRM_NODE_MAX 3
+
+typedef struct _drmPciDeviceInfo {
+  uint16_t vendor_id;
+  uint16_t device_id;
+  uint16_t subvendor_id;
+  uint16_t subdevice_id;
+  uint8_t revision_id;
+} drmPciDeviceInfo, *drmPciDeviceInfoPtr;
+
+typedef struct _drmDevice {
+  char** nodes;
+  int available_nodes;
+  int bustype;
+  union {
+    void* pci;
+    void* usb;
+    void* platform;
+    void* host1x;
+  } businfo;
+  union {
+    drmPciDeviceInfoPtr pci;
+    void* usb;
+    void* platform;
+    void* host1x;
+  } deviceinfo;
+} drmDevice, *drmDevicePtr;
+
+// Open libGL and load needed symbols
+#if defined(__OpenBSD__) || defined(__NetBSD__)
+#  define LIBGL_FILENAME "libGL.so"
+#  define LIBGLES_FILENAME "libGLESv2.so"
+#  define LIBEGL_FILENAME "libEGL.so"
+#  define LIBDRM_FILENAME "libdrm.so"
+#else
+#  define LIBGL_FILENAME "libGL.so.1"
+#  define LIBGLES_FILENAME "libGLESv2.so.2"
+#  define LIBEGL_FILENAME "libEGL.so.1"
+#  define LIBDRM_FILENAME "libdrm.so.2"
+#endif
+
+#ifdef MOZ_X11
+static int x_error_handler(Display*, XErrorEvent* ev) {
+  record_value(
+      "ERROR\nX error, error_code=%d, "
+      "request_code=%d, minor_code=%d\n",
+      ev->error_code, ev->request_code, ev->minor_code);
+  record_flush();
+  _exit(EXIT_FAILURE);
+}
+#endif
+
+// childgltest is declared inside extern "C" so that the name is not mangled.
+// The name is used in build/valgrind/x86_64-pc-linux-gnu.sup to suppress
+// memory leak errors because we run it inside a short lived fork and we don't
+// care about leaking memory
+extern "C" {
+
+#define PCI_FILL_IDENT 0x0001
+#define PCI_FILL_CLASS 0x0020
+#define PCI_BASE_CLASS_DISPLAY 0x03
+
+static void get_pci_status() {
+  log("GLX_TEST: get_pci_status start\n");
+
+  if (access("/sys/bus/pci/", F_OK) != 0 &&
+      access("/sys/bus/pci_express/", F_OK) != 0) {
+    record_warning("cannot access /sys/bus/pci");
+    return;
+  }
+
+  void* libpci = dlopen("libpci.so.3", RTLD_LAZY);
+  if (!libpci) {
+    libpci = dlopen("libpci.so", RTLD_LAZY);
+  }
+  if (!libpci) {
+    record_warning("libpci missing");
+    return;
+  }
+  auto release = mozilla::MakeScopeExit([&] { dlclose(libpci); });
+
+  typedef struct pci_dev {
+    struct pci_dev* next;
+    uint16_t domain_16;
+    uint8_t bus, dev, func;
+    unsigned int known_fields;
+    uint16_t vendor_id, device_id;
+    uint16_t device_class;
+  } pci_dev;
+
+  typedef struct pci_access {
+    unsigned int method;
+    int writeable;
+    int buscentric;
+    char* id_file_name;
+    int free_id_name;
+    int numeric_ids;
+    unsigned int id_lookup_mode;
+    int debugging;
+    void* error;
+    void* warning;
+    void* debug;
+    pci_dev* devices;
+  } pci_access;
+
+  typedef pci_access* (*PCIALLOC)(void);
+  PCIALLOC pci_alloc = cast<PCIALLOC>(dlsym(libpci, "pci_alloc"));
+
+  typedef void (*PCIINIT)(pci_access*);
+  PCIINIT pci_init = cast<PCIINIT>(dlsym(libpci, "pci_init"));
+
+  typedef void (*PCICLEANUP)(pci_access*);
+  PCICLEANUP pci_cleanup = cast<PCICLEANUP>(dlsym(libpci, "pci_cleanup"));
+
+  typedef void (*PCISCANBUS)(pci_access*);
+  PCISCANBUS pci_scan_bus = cast<PCISCANBUS>(dlsym(libpci, "pci_scan_bus"));
+
+  typedef void (*PCIFILLINFO)(pci_dev*, int);
+  PCIFILLINFO pci_fill_info = cast<PCIFILLINFO>(dlsym(libpci, "pci_fill_info"));
+
+  if (!pci_alloc || !pci_cleanup || !pci_scan_bus || !pci_fill_info) {
+    dlclose(libpci);
+    record_warning("libpci missing methods");
+    return;
+  }
+
+  pci_access* pacc = pci_alloc();
+  if (!pacc) {
+    record_warning("libpci alloc failed");
+    return;
+  }
+
+  pci_init(pacc);
+  pci_scan_bus(pacc);
+
+  for (pci_dev* dev = pacc->devices; dev; dev = dev->next) {
+    pci_fill_info(dev, PCI_FILL_IDENT | PCI_FILL_CLASS);
+    if (dev->device_class >> 8 == PCI_BASE_CLASS_DISPLAY && dev->vendor_id &&
+        dev->device_id) {
+      record_value("PCI_VENDOR_ID\n0x%04x\nPCI_DEVICE_ID\n0x%04x\n",
+                   dev->vendor_id, dev->device_id);
+    }
+  }
+
+  pci_cleanup(pacc);
+
+  log("GLX_TEST: get_pci_status finished\n");
+}
+
+#ifdef MOZ_WAYLAND
+static void set_render_device_path(const char* render_device_path) {
+  record_value("DRM_RENDERDEVICE\n%s\n", render_device_path);
+}
+
+static bool device_has_name(const drmDevice* device, const char* name) {
+  for (size_t i = 0; i < DRM_NODE_MAX; i++) {
+    if (!(device->available_nodes & (1 << i))) {
+      continue;
+    }
+    if (strcmp(device->nodes[i], name) == 0) {
+      return true;
+    }
+  }
+  return false;
+}
+
+static bool get_render_name(const char* name) {
+  void* libdrm = dlopen(LIBDRM_FILENAME, RTLD_LAZY);
+  if (!libdrm) {
+    record_warning("Failed to open libdrm");
+    return false;
+  }
+  auto release = mozilla::MakeScopeExit([&] { dlclose(libdrm); });
+
+  typedef int (*DRMGETDEVICES2)(uint32_t, drmDevicePtr*, int);
+  DRMGETDEVICES2 drmGetDevices2 =
+      cast<DRMGETDEVICES2>(dlsym(libdrm, "drmGetDevices2"));
+
+  typedef void (*DRMFREEDEVICE)(drmDevicePtr*);
+  DRMFREEDEVICE drmFreeDevice =
+      cast<DRMFREEDEVICE>(dlsym(libdrm, "drmFreeDevice"));
+
+  if (!drmGetDevices2 || !drmFreeDevice) {
+    record_warning(
+        "libdrm missing methods for drmGetDevices2 or drmFreeDevice");
+    return false;
+  }
+
+  uint32_t flags = 0;
+  int devices_len = drmGetDevices2(flags, nullptr, 0);
+  if (devices_len < 0) {
+    record_warning("drmGetDevices2 failed");
+    return false;
+  }
+  drmDevice** devices = (drmDevice**)calloc(devices_len, sizeof(drmDevice*));
+  if (!devices) {
+    record_warning("Allocation error");
+    return false;
+  }
+  devices_len = drmGetDevices2(flags, devices, devices_len);
+  if (devices_len < 0) {
+    free(devices);
+    record_warning("drmGetDevices2 failed");
+    return false;
+  }
+
+  const drmDevice* match = nullptr;
+  for (int i = 0; i < devices_len; i++) {
+    if (device_has_name(devices[i], name)) {
+      match = devices[i];
+      break;
+    }
+  }
+
+  // Fallback path for split kms/render devices - if only one drm render node
+  // exists it's most likely the one we're looking for.
+  if (match && !(match->available_nodes & (1 << DRM_NODE_RENDER))) {
+    match = nullptr;
+    for (int i = 0; i < devices_len; i++) {
+      if (devices[i]->available_nodes & (1 << DRM_NODE_RENDER)) {
+        if (!match) {
+          match = devices[i];
+        } else {
+          // more than one candidate found, stop trying.
+          match = nullptr;
+          break;
+        }
+      }
+    }
+    if (match) {
+      record_warning(
+          "DRM render node not clearly detectable. Falling back to using the "
+          "only one that was found.");
+    } else {
+      record_warning("DRM device has no render node");
+    }
+  }
+
+  bool result = false;
+  if (!match) {
+    record_warning("Cannot find DRM device");
+  } else {
+    set_render_device_path(match->nodes[DRM_NODE_RENDER]);
+    record_value(
+        "MESA_VENDOR_ID\n0x%04x\n"
+        "MESA_DEVICE_ID\n0x%04x\n",
+        match->deviceinfo.pci->vendor_id, match->deviceinfo.pci->device_id);
+    result = true;
+  }
+
+  for (int i = 0; i < devices_len; i++) {
+    drmFreeDevice(&devices[i]);
+  }
+  free(devices);
+  return result;
+}
+#endif
+
+static bool get_egl_gl_status(EGLDisplay dpy,
+                              PFNEGLGETPROCADDRESS eglGetProcAddress) {
+  typedef EGLBoolean (*PFNEGLCHOOSECONFIGPROC)(
+      EGLDisplay dpy, EGLint const* attrib_list, EGLConfig* configs,
+      EGLint config_size, EGLint* num_config);
+  PFNEGLCHOOSECONFIGPROC eglChooseConfig =
+      cast<PFNEGLCHOOSECONFIGPROC>(eglGetProcAddress("eglChooseConfig"));
+
+  typedef EGLBoolean (*PFNEGLBINDAPIPROC)(EGLint api);
+  PFNEGLBINDAPIPROC eglBindAPI =
+      cast<PFNEGLBINDAPIPROC>(eglGetProcAddress("eglBindAPI"));
+
+  typedef EGLContext (*PFNEGLCREATECONTEXTPROC)(
+      EGLDisplay dpy, EGLConfig config, EGLContext share_context,
+      EGLint const* attrib_list);
+  PFNEGLCREATECONTEXTPROC eglCreateContext =
+      cast<PFNEGLCREATECONTEXTPROC>(eglGetProcAddress("eglCreateContext"));
+
+  typedef EGLBoolean (*PFNEGLDESTROYCONTEXTPROC)(EGLDisplay dpy,
+                                                 EGLContext ctx);
+  PFNEGLDESTROYCONTEXTPROC eglDestroyContext =
+      cast<PFNEGLDESTROYCONTEXTPROC>(eglGetProcAddress("eglDestroyContext"));
+
+  typedef EGLBoolean (*PFNEGLMAKECURRENTPROC)(
+      EGLDisplay dpy, EGLSurface draw, EGLSurface read, EGLContext context);
+  PFNEGLMAKECURRENTPROC eglMakeCurrent =
+      cast<PFNEGLMAKECURRENTPROC>(eglGetProcAddress("eglMakeCurrent"));
+
+  typedef const char* (*PFNEGLQUERYDEVICESTRINGEXTPROC)(EGLDeviceEXT device,
+                                                        EGLint name);
+  PFNEGLQUERYDEVICESTRINGEXTPROC eglQueryDeviceStringEXT =
+      cast<PFNEGLQUERYDEVICESTRINGEXTPROC>(
+          eglGetProcAddress("eglQueryDeviceStringEXT"));
+
+  typedef EGLBoolean (*PFNEGLQUERYDISPLAYATTRIBEXTPROC)(
+      EGLDisplay dpy, EGLint name, EGLAttrib* value);
+  PFNEGLQUERYDISPLAYATTRIBEXTPROC eglQueryDisplayAttribEXT =
+      cast<PFNEGLQUERYDISPLAYATTRIBEXTPROC>(
+          eglGetProcAddress("eglQueryDisplayAttribEXT"));
+
+  log("GLX_TEST: get_egl_gl_status start\n");
+
+  if (!eglChooseConfig || !eglCreateContext || !eglDestroyContext ||
+      !eglMakeCurrent || !eglQueryDeviceStringEXT) {
+    record_warning("libEGL missing methods for GL test");
+    return false;
+  }
+
+  typedef GLubyte* (*PFNGLGETSTRING)(GLenum);
+  PFNGLGETSTRING glGetString =
+      cast<PFNGLGETSTRING>(eglGetProcAddress("glGetString"));
+
+#if defined(__arm__) || defined(__aarch64__)
+  bool useGles = true;
+#else
+  bool useGles = false;
+#endif
+
+  std::vector<EGLint> attribs;
+  attribs.push_back(EGL_RED_SIZE);
+  attribs.push_back(8);
+  attribs.push_back(EGL_GREEN_SIZE);
+  attribs.push_back(8);
+  attribs.push_back(EGL_BLUE_SIZE);
+  attribs.push_back(8);
+  if (useGles) {
+    attribs.push_back(EGL_RENDERABLE_TYPE);
+    attribs.push_back(EGL_OPENGL_ES2_BIT);
+  }
+  attribs.push_back(EGL_NONE);
+
+  EGLConfig config;
+  EGLint num_config;
+  if (eglChooseConfig(dpy, attribs.data(), &config, 1, &num_config) ==
+      EGL_FALSE) {
+    record_warning("eglChooseConfig returned an error");
+    return false;
+  }
+
+  EGLenum api = useGles ? EGL_OPENGL_ES_API : EGL_OPENGL_API;
+  if (eglBindAPI(api) == EGL_FALSE) {
+    record_warning("eglBindAPI returned an error");
+    return false;
+  }
+
+  EGLint ctx_attrs[] = {EGL_CONTEXT_MAJOR_VERSION, 3, EGL_NONE};
+  EGLContext ectx = eglCreateContext(dpy, config, EGL_NO_CONTEXT, ctx_attrs);
+  if (!ectx) {
+    EGLint ctx_attrs_fallback[] = {EGL_CONTEXT_MAJOR_VERSION, 2, EGL_NONE};
+    ectx = eglCreateContext(dpy, config, EGL_NO_CONTEXT, ctx_attrs_fallback);
+    if (!ectx) {
+      record_warning("eglCreateContext returned an error");
+      return false;
+    }
+  }
+
+  if (eglMakeCurrent(dpy, EGL_NO_SURFACE, EGL_NO_SURFACE, ectx) == EGL_FALSE) {
+    eglDestroyContext(dpy, ectx);
+    record_warning("eglMakeCurrent returned an error");
+    return false;
+  }
+  eglDestroyContext(dpy, ectx);
+
+  // Implementations disagree about whether eglGetProcAddress or dlsym
+  // should be used for getting functions from the actual API, see
+  // https://github.com/anholt/libepoxy/commit/14f24485e33816139398d1bd170d617703473738
+  void* libgl = nullptr;
+  if (!glGetString) {
+    libgl = dlopen(LIBGL_FILENAME, RTLD_LAZY);
+    if (!libgl) {
+      libgl = dlopen(LIBGLES_FILENAME, RTLD_LAZY);
+      if (!libgl) {
+        record_warning(LIBGL_FILENAME " and " LIBGLES_FILENAME " missing");
+        return false;
+      }
+    }
+
+    glGetString = cast<PFNGLGETSTRING>(dlsym(libgl, "glGetString"));
+    if (!glGetString) {
+      dlclose(libgl);
+      record_warning("libEGL, libGL and libGLESv2 are missing glGetString");
+      return false;
+    }
+  }
+  auto release = mozilla::MakeScopeExit([&] {
+    if (libgl) {
+      dlclose(libgl);
+    }
+  });
+
+  const GLubyte* versionString = glGetString(GL_VERSION);
+  const GLubyte* vendorString = glGetString(GL_VENDOR);
+  const GLubyte* rendererString = glGetString(GL_RENDERER);
+
+  if (versionString && vendorString && rendererString) {
+    record_value("VENDOR\n%s\nRENDERER\n%s\nVERSION\n%s\nTFP\nTRUE\n",
+                 vendorString, rendererString, versionString);
+  } else {
+    record_warning("EGL glGetString returned null");
+    return false;
+  }
+
+  EGLDeviceEXT device;
+  if (eglQueryDisplayAttribEXT(dpy, EGL_DEVICE_EXT, (EGLAttrib*)&device) ==
+      EGL_TRUE) {
+    const char* deviceExtensions =
+        eglQueryDeviceStringEXT(device, EGL_EXTENSIONS);
+    if (deviceExtensions &&
+        strstr(deviceExtensions, "EGL_MESA_device_software")) {
+      record_value("MESA_ACCELERATED\nFALSE\n");
+    } else {
+#ifdef MOZ_WAYLAND
+      const char* deviceString =
+          eglQueryDeviceStringEXT(device, EGL_DRM_DEVICE_FILE_EXT);
+      if (!deviceString || !get_render_name(deviceString)) {
+        const char* renderNodeString =
+            eglQueryDeviceStringEXT(device, EGL_DRM_RENDER_NODE_FILE_EXT);
+        if (renderNodeString) {
+          set_render_device_path(renderNodeString);
+        }
+      }
+#endif
+    }
+  }
+
+  log("GLX_TEST: get_egl_gl_status finished\n");
+  return true;
+}
+
+static bool get_egl_status(EGLNativeDisplayType native_dpy) {
+  log("GLX_TEST: get_egl_status start\n");
+
+  EGLDisplay dpy = nullptr;
+
+  typedef EGLBoolean (*PFNEGLTERMINATEPROC)(EGLDisplay dpy);
+  PFNEGLTERMINATEPROC eglTerminate = nullptr;
+
+  void* libegl = dlopen(LIBEGL_FILENAME, RTLD_LAZY);
+  if (!libegl) {
+    record_warning("libEGL missing");
+    return false;
+  }
+  auto release = mozilla::MakeScopeExit([&] {
+    if (dpy) {
+      eglTerminate(dpy);
+    }
+    // Unload libegl here causes ASAN/MemLeaks failures on Linux
+    // as libegl may not be meant to be unloaded runtime.
+    // See 1304156 for reference.
+    // dlclose(libegl);
+  });
+
+  PFNEGLGETPROCADDRESS eglGetProcAddress =
+      cast<PFNEGLGETPROCADDRESS>(dlsym(libegl, "eglGetProcAddress"));
+
+  if (!eglGetProcAddress) {
+    record_warning("no eglGetProcAddress");
+    return false;
+  }
+
+  typedef EGLDisplay (*PFNEGLGETDISPLAYPROC)(void* native_display);
+  PFNEGLGETDISPLAYPROC eglGetDisplay =
+      cast<PFNEGLGETDISPLAYPROC>(eglGetProcAddress("eglGetDisplay"));
+
+  typedef EGLBoolean (*PFNEGLINITIALIZEPROC)(EGLDisplay dpy, EGLint* major,
+                                             EGLint* minor);
+  PFNEGLINITIALIZEPROC eglInitialize =
+      cast<PFNEGLINITIALIZEPROC>(eglGetProcAddress("eglInitialize"));
+  eglTerminate = cast<PFNEGLTERMINATEPROC>(eglGetProcAddress("eglTerminate"));
+
+  if (!eglGetDisplay || !eglInitialize || !eglTerminate) {
+    record_warning("libEGL missing methods");
+    return false;
+  }
+
+  dpy = eglGetDisplay(native_dpy);
+  if (!dpy) {
+    record_warning("libEGL no display");
+    return false;
+  }
+
+  EGLint major, minor;
+  if (!eglInitialize(dpy, &major, &minor)) {
+    record_warning("libEGL initialize failed");
+    return false;
+  }
+
+  typedef const char* (*PFNEGLGETDISPLAYDRIVERNAMEPROC)(EGLDisplay dpy);
+  PFNEGLGETDISPLAYDRIVERNAMEPROC eglGetDisplayDriverName =
+      cast<PFNEGLGETDISPLAYDRIVERNAMEPROC>(
+          eglGetProcAddress("eglGetDisplayDriverName"));
+  if (eglGetDisplayDriverName) {
+    const char* driDriver = eglGetDisplayDriverName(dpy);
+    if (driDriver) {
+      record_value("DRI_DRIVER\n%s\n", driDriver);
+    }
+  }
+
+  bool ret = get_egl_gl_status(dpy, eglGetProcAddress);
+  log("GLX_TEST: get_egl_status finished with return: %d\n", ret);
+
+  return ret;
+}
+
+#ifdef MOZ_X11
+static void get_xrandr_info(Display* dpy) {
+  log("GLX_TEST: get_xrandr_info start\n");
+
+  // When running on remote X11 the xrandr version may be stuck on an ancient
+  // version. There are still setups using remote X11 out there, so make sure we
+  // don't crash.
+  int eventBase, errorBase, major, minor;
+  if (!XRRQueryExtension(dpy, &eventBase, &errorBase) ||
+      !XRRQueryVersion(dpy, &major, &minor) ||
+      !(major > 1 || (major == 1 && minor >= 4))) {
+    log("GLX_TEST: get_xrandr_info failed, old version.\n");
+    return;
+  }
+
+  Window root = RootWindow(dpy, DefaultScreen(dpy));
+  XRRProviderResources* pr = XRRGetProviderResources(dpy, root);
+  if (!pr) {
+    return;
+  }
+  XRRScreenResources* res = XRRGetScreenResourcesCurrent(dpy, root);
+  if (!res) {
+    XRRFreeProviderResources(pr);
+    return;
+  }
+  if (pr->nproviders != 0) {
+    record_value("DDX_DRIVER\n");
+    for (int i = 0; i < pr->nproviders; i++) {
+      XRRProviderInfo* info = XRRGetProviderInfo(dpy, res, pr->providers[i]);
+      if (info) {
+        record_value("%s%s", info->name, i == pr->nproviders - 1 ? ";\n" : ";");
+        XRRFreeProviderInfo(info);
+      }
+    }
+  }
+  XRRFreeScreenResources(res);
+  XRRFreeProviderResources(pr);
+
+  log("GLX_TEST: get_xrandr_info finished\n");
+}
+
+void glxtest() {
+  log("GLX_TEST: glxtest start\n");
+
+  Display* dpy = nullptr;
+  void* libgl = dlopen(LIBGL_FILENAME, RTLD_LAZY);
+  if (!libgl) {
+    record_error(LIBGL_FILENAME " missing");
+    return;
+  }
+  auto release = mozilla::MakeScopeExit([&] {
+    if (dpy) {
+#  ifdef MOZ_ASAN
+      XCloseDisplay(dpy);
+#  else
+      // This XSync call wanted to be instead:
+      //   XCloseDisplay(dpy);
+      // but this can cause 1-minute stalls on certain setups using Nouveau, see
+      // bug 973192
+      XSync(dpy, False);
+#  endif
+    }
+    dlclose(libgl);
+  });
+
+  typedef void* (*PFNGLXGETPROCADDRESS)(const char*);
+  PFNGLXGETPROCADDRESS glXGetProcAddress =
+      cast<PFNGLXGETPROCADDRESS>(dlsym(libgl, "glXGetProcAddress"));
+
+  if (!glXGetProcAddress) {
+    record_error("no glXGetProcAddress");
+    return;
+  }
+
+  typedef GLXFBConfig* (*PFNGLXQUERYEXTENSION)(Display*, int*, int*);
+  PFNGLXQUERYEXTENSION glXQueryExtension =
+      cast<PFNGLXQUERYEXTENSION>(glXGetProcAddress("glXQueryExtension"));
+
+  typedef GLXFBConfig* (*PFNGLXQUERYVERSION)(Display*, int*, int*);
+  PFNGLXQUERYVERSION glXQueryVersion =
+      cast<PFNGLXQUERYVERSION>(dlsym(libgl, "glXQueryVersion"));
+
+  typedef XVisualInfo* (*PFNGLXCHOOSEVISUAL)(Display*, int, int*);
+  PFNGLXCHOOSEVISUAL glXChooseVisual =
+      cast<PFNGLXCHOOSEVISUAL>(glXGetProcAddress("glXChooseVisual"));
+
+  typedef GLXContext (*PFNGLXCREATECONTEXT)(Display*, XVisualInfo*, GLXContext,
+                                            Bool);
+  PFNGLXCREATECONTEXT glXCreateContext =
+      cast<PFNGLXCREATECONTEXT>(glXGetProcAddress("glXCreateContext"));
+
+  typedef Bool (*PFNGLXMAKECURRENT)(Display*, GLXDrawable, GLXContext);
+  PFNGLXMAKECURRENT glXMakeCurrent =
+      cast<PFNGLXMAKECURRENT>(glXGetProcAddress("glXMakeCurrent"));
+
+  typedef void (*PFNGLXDESTROYCONTEXT)(Display*, GLXContext);
+  PFNGLXDESTROYCONTEXT glXDestroyContext =
+      cast<PFNGLXDESTROYCONTEXT>(glXGetProcAddress("glXDestroyContext"));
+
+  typedef GLubyte* (*PFNGLGETSTRING)(GLenum);
+  PFNGLGETSTRING glGetString =
+      cast<PFNGLGETSTRING>(glXGetProcAddress("glGetString"));
+
+  if (!glXQueryExtension || !glXQueryVersion || !glXChooseVisual ||
+      !glXCreateContext || !glXMakeCurrent || !glXDestroyContext ||
+      !glGetString) {
+    record_error(LIBGL_FILENAME " missing methods");
+    return;
+  }
+
+  ///// Open a connection to the X server /////
+  dpy = XOpenDisplay(nullptr);
+  if (!dpy) {
+    record_error("Unable to open a connection to the X server");
+    return;
+  }
+
+  ///// Check that the GLX extension is present /////
+  if (!glXQueryExtension(dpy, nullptr, nullptr)) {
+    record_error("GLX extension missing");
+    return;
+  }
+
+  XSetErrorHandler(x_error_handler);
+
+  ///// Get a visual /////
+  int attribs[] = {GLX_RGBA, GLX_RED_SIZE,  1, GLX_GREEN_SIZE,
+                   1,        GLX_BLUE_SIZE, 1, None};
+  XVisualInfo* vInfo = glXChooseVisual(dpy, DefaultScreen(dpy), attribs);
+  if (!vInfo) {
+    int attribs2[] = {GLX_RGBA, GLX_RED_SIZE,  1, GLX_GREEN_SIZE,
+                      1,        GLX_BLUE_SIZE, 1, GLX_DOUBLEBUFFER,
+                      None};
+    vInfo = glXChooseVisual(dpy, DefaultScreen(dpy), attribs2);
+    if (!vInfo) {
+      record_error("No visuals found");
+      return;
+    }
+  }
+
+  // using a X11 Window instead of a GLXPixmap does not crash
+  // fglrx in indirect rendering. bug 680644
+  Window window;
+  XSetWindowAttributes swa;
+  swa.colormap = XCreateColormap(dpy, RootWindow(dpy, vInfo->screen),
+                                 vInfo->visual, AllocNone);
+
+  swa.border_pixel = 0;
+  window = XCreateWindow(dpy, RootWindow(dpy, vInfo->screen), 0, 0, 16, 16, 0,
+                         vInfo->depth, InputOutput, vInfo->visual,
+                         CWBorderPixel | CWColormap, &swa);
+
+  ///// Get a GL context and make it current //////
+  GLXContext context = glXCreateContext(dpy, vInfo, nullptr, True);
+  glXMakeCurrent(dpy, window, context);
+
+  ///// Look for this symbol to determine texture_from_pixmap support /////
+  void* glXBindTexImageEXT = glXGetProcAddress("glXBindTexImageEXT");
+
+  ///// Get GL vendor/renderer/versions strings /////
+  const GLubyte* versionString = glGetString(GL_VERSION);
+  const GLubyte* vendorString = glGetString(GL_VENDOR);
+  const GLubyte* rendererString = glGetString(GL_RENDERER);
+
+  if (versionString && vendorString && rendererString) {
+    record_value("VENDOR\n%s\nRENDERER\n%s\nVERSION\n%s\nTFP\n%s\n",
+                 vendorString, rendererString, versionString,
+                 glXBindTexImageEXT ? "TRUE" : "FALSE");
+  } else {
+    record_error("glGetString returned null");
+  }
+
+  // If GLX_MESA_query_renderer is available, populate additional data.
+  typedef Bool (*PFNGLXQUERYCURRENTRENDERERINTEGERMESAPROC)(
+      int attribute, unsigned int* value);
+  PFNGLXQUERYCURRENTRENDERERINTEGERMESAPROC
+  glXQueryCurrentRendererIntegerMESAProc =
+      cast<PFNGLXQUERYCURRENTRENDERERINTEGERMESAPROC>(
+          glXGetProcAddress("glXQueryCurrentRendererIntegerMESA"));
+  if (glXQueryCurrentRendererIntegerMESAProc) {
+    unsigned int vendorId, deviceId, accelerated, videoMemoryMB;
+    glXQueryCurrentRendererIntegerMESAProc(GLX_RENDERER_VENDOR_ID_MESA,
+                                           &vendorId);
+    glXQueryCurrentRendererIntegerMESAProc(GLX_RENDERER_DEVICE_ID_MESA,
+                                           &deviceId);
+    glXQueryCurrentRendererIntegerMESAProc(GLX_RENDERER_ACCELERATED_MESA,
+                                           &accelerated);
+    glXQueryCurrentRendererIntegerMESAProc(GLX_RENDERER_VIDEO_MEMORY_MESA,
+                                           &videoMemoryMB);
+
+    // Truncate IDs to 4 digits- that's all PCI IDs are.
+    vendorId &= 0xFFFF;
+    deviceId &= 0xFFFF;
+
+    record_value(
+        "MESA_VENDOR_ID\n0x%04x\n"
+        "MESA_DEVICE_ID\n0x%04x\n"
+        "MESA_ACCELERATED\n%s\n"
+        "MESA_VRAM\n%dMB\n",
+        vendorId, deviceId, accelerated ? "TRUE" : "FALSE", videoMemoryMB);
+  }
+
+  // From Mesa's GL/internal/dri_interface.h, to be used by DRI clients.
+  typedef const char* (*PFNGLXGETSCREENDRIVERPROC)(Display* dpy, int scrNum);
+  PFNGLXGETSCREENDRIVERPROC glXGetScreenDriverProc =
+      cast<PFNGLXGETSCREENDRIVERPROC>(glXGetProcAddress("glXGetScreenDriver"));
+  if (glXGetScreenDriverProc) {
+    const char* driDriver = glXGetScreenDriverProc(dpy, DefaultScreen(dpy));
+    if (driDriver) {
+      record_value("DRI_DRIVER\n%s\n", driDriver);
+    }
+  }
+
+  // Get monitor and DDX driver information
+  get_xrandr_info(dpy);
+
+  ///// Clean up. Indeed, the parent process might fail to kill us (e.g. if it
+  ///// doesn't need to check GL info) so we might be staying alive for longer
+  ///// than expected, so it's important to consume as little memory as
+  ///// possible. Also we want to check that we're able to do that too without
+  ///// generating X errors.
+  glXMakeCurrent(dpy, None,
+                 nullptr);  // must release the GL context before destroying it
+  glXDestroyContext(dpy, context);
+  XDestroyWindow(dpy, window);
+  XFreeColormap(dpy, swa.colormap);
+  XFree(vInfo);
+
+  record_value("TEST_TYPE\nGLX\n");
+  log("GLX_TEST: glxtest finished\n");
+}
+
+bool x11_egltest() {
+  log("GLX_TEST: x11_egltest start\n");
+
+  Display* dpy = XOpenDisplay(nullptr);
+  if (!dpy) {
+    return false;
+  }
+#  ifdef MOZ_ASAN
+  auto release = mozilla::MakeScopeExit([&] {
+    // Bug 1715245: Closing the display connection here crashes on NV prop.
+    // drivers. Just leave it open, the process will exit shortly after anyway.
+    XCloseDisplay(dpy);
+  });
+#  endif
+
+  XSetErrorHandler(x_error_handler);
+
+  if (!get_egl_status(dpy)) {
+    return false;
+  }
+
+  // Bug 1667621: 30bit "Deep Color" is broken on EGL on Mesa (as of 2021/10).
+  // Disable all non-standard depths for the initial EGL roleout.
+  int screenCount = ScreenCount(dpy);
+  for (int idx = 0; idx < screenCount; idx++) {
+    if (DefaultDepth(dpy, idx) != 24) {
+      return false;
+    }
+  }
+
+  // Get monitor and DDX driver information
+  get_xrandr_info(dpy);
+
+  record_value("TEST_TYPE\nEGL\n");
+
+  log("GLX_TEST: x11_egltest finished\n");
+  return true;
+}
+#endif
+
+#ifdef MOZ_WAYLAND
+void wayland_egltest() {
+  log("GLX_TEST: wayland_egltest start\n");
+
+  static auto sWlDisplayConnect = (struct wl_display * (*)(const char*))
+      dlsym(RTLD_DEFAULT, "wl_display_connect");
+  static auto sWlDisplayRoundtrip =
+      (int (*)(struct wl_display*))dlsym(RTLD_DEFAULT, "wl_display_roundtrip");
+  static auto sWlDisplayDisconnect = (void (*)(struct wl_display*))dlsym(
+      RTLD_DEFAULT, "wl_display_disconnect");
+
+  if (!sWlDisplayConnect || !sWlDisplayRoundtrip || !sWlDisplayDisconnect) {
+    record_error("Missing Wayland libraries");
+    return;
+  }
+
+  // NOTE: returns false to fall back to X11 when the Wayland socket doesn't
+  // exist but fails with record_error if something actually went wrong
+  struct wl_display* dpy = sWlDisplayConnect(nullptr);
+  if (!dpy) {
+    record_error("Could not connect to wayland socket");
+    return;
+  }
+
+  if (!get_egl_status((EGLNativeDisplayType)dpy)) {
+    record_error("EGL test failed");
+  }
+
+  // This is enough to crash some broken NVIDIA prime + Wayland setups, see
+  // https://github.com/NVIDIA/egl-wayland/issues/41 and bug 1768260.
+  sWlDisplayRoundtrip(dpy);
+
+  sWlDisplayDisconnect(dpy);
+  record_value("TEST_TYPE\nEGL\n");
+  log("GLX_TEST: wayland_egltest finished\n");
+}
+#endif
+
+int childgltest(bool aWayland) {
+  log("GLX_TEST: childgltest start\n");
+
+  // Get a list of all GPUs from the PCI bus.
+  get_pci_status();
+
+#ifdef MOZ_WAYLAND
+  if (aWayland) {
+    wayland_egltest();
+  }
+#endif
+#ifdef MOZ_X11
+  if (!aWayland) {
+    // TODO: --display command line argument is not properly handled
+    if (!x11_egltest()) {
+      glxtest();
+    }
+  }
+#endif
+  // Finally write buffered data to the pipe.
+  record_flush();
+
+  log("GLX_TEST: childgltest finished\n");
+  return EXIT_SUCCESS;
+}
+
+}  // extern "C"
+
+static void PrintUsage() {
+  printf(
+      "Firefox OpenGL probe utility\n"
+      "\n"
+      "usage: glxtest [options]\n"
+      "\n"
+      "Options:\n"
+      "\n"
+      "  -h --help                 show this message\n"
+      "  -f --fd num               where to print output, default it stdout\n"
+      "  -w --wayland              probe OpenGL/EGL on Wayland (default is "
+      "X11)\n"
+      "\n");
+}
+
+int main(int argc, char** argv) {
+  struct option longOptions[] = {{"help", no_argument, nullptr, 'h'},
+                                 {"fd", required_argument, nullptr, 'f'},
+                                 {"wayland", no_argument, nullptr, 'w'},
+                                 {nullptr, 0, nullptr, 0}};
+  const char* shortOptions = "hf:w";
+  int c;
+  bool wayland = false;
+  while ((c = getopt_long(argc, argv, shortOptions, longOptions, nullptr)) !=
+         -1) {
+    switch (c) {
+      case 'w':
+        wayland = true;
+        break;
+      case 'f':
+        output_pipe = atoi(optarg);
+        break;
+      case 'h':
+#ifdef MOZ_WAYLAND
+        // Dummy call to mozgtk to prevent the linker from removing
+        // the dependency with --as-needed.
+        // see toolkit/library/moz.build for details.
+        gdk_display_get_default();
+#endif
+        PrintUsage();
+        return 0;
+      default:
+        break;
+    }
+  }
+  if (getenv("MOZ_AVOID_OPENGL_ALTOGETHER")) {
+    const char* msg = "ERROR\nMOZ_AVOID_OPENGL_ALTOGETHER envvar set";
+    MOZ_UNUSED(write(output_pipe, msg, strlen(msg)));
+    exit(EXIT_FAILURE);
+  }
+  const char* env = getenv("MOZ_GFX_DEBUG");
+  enable_logging = env && *env == '1';
+  if (!enable_logging) {
+    close_logging();
+  }
+#if defined(MOZ_ASAN) || defined(FUZZING)
+  // If handle_segv=1 (default), then glxtest crash will print a sanitizer
+  // report which can confuse the harness in fuzzing automation.
+  signal(SIGSEGV, SIG_DFL);
+#endif
+  return childgltest(wayland);
+}
diff --git a/toolkit/xre/glxtest/moz.build b/toolkit/xre/glxtest/moz.build
new file mode 100644
index 0000000000..bc7365582b
--- /dev/null
+++ b/toolkit/xre/glxtest/moz.build
@@ -0,0 +1,26 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+with Files("**"):
+    BUG_COMPONENT = ("Core", "Widget: Gtk")
+
+Program("glxtest")
+SOURCES += [
+    "glxtest.cpp",
+]
+
+if CONFIG["MOZ_ASAN"]:
+    SOURCES += [
+        "../../../mozglue/build/AsanOptions.cpp",
+    ]
+
+CXXFLAGS += CONFIG["MOZ_GTK3_CFLAGS"]
+CXXFLAGS += CONFIG["MOZ_PANGO_CFLAGS"]
+OS_LIBS += CONFIG["MOZ_X11_LIBS"]
+OS_LIBS += CONFIG["MOZ_GTK3_LIBS"]
+
+NO_PGO = True
+DisableStlWrapping()
diff --git a/toolkit/xre/metrics.yaml b/toolkit/xre/metrics.yaml
new file mode 100644
index 0000000000..c53ee95ecd
--- /dev/null
+++ b/toolkit/xre/metrics.yaml
@@ -0,0 +1,11 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# Adding a new metric? We have docs for that!
+# https://firefox-source-docs.mozilla.org/toolkit/components/glean/user/new_definitions_file.html
+
+---
+$schema: moz://mozilla.org/schemas/glean/metrics/2-0-0
+$tags:
+  - "Toolkit :: Startup and Profile System"
diff --git a/toolkit/xre/moz.build b/toolkit/xre/moz.build
new file mode 100644
index 0000000000..dc7695e7ac
--- /dev/null
+++ b/toolkit/xre/moz.build
@@ -0,0 +1,277 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+include("../components/telemetry/telemetry-constants.mozbuild")
+
+with Files("**"):
+    BUG_COMPONENT = ("Toolkit", "Startup and Profile System")
+
+if CONFIG["OS_ARCH"] == "WINNT":
+    TEST_DIRS += ["test/win"]
+
+MOCHITEST_MANIFESTS += ["test/mochitest.ini"]
+BROWSER_CHROME_MANIFESTS += ["test/browser.ini"]
+XPCSHELL_TESTS_MANIFESTS += ["test/xpcshell.ini"]
+MARIONETTE_UNIT_MANIFESTS += ["test/marionette/marionette.ini"]
+
+XPIDL_SOURCES += [
+    "nsINativeAppSupport.idl",
+    "nsIXREDirProvider.idl",
+]
+
+if CONFIG["OS_ARCH"] == "WINNT":
+    XPIDL_SOURCES += [
+        "nsIWinAppHelper.idl",
+    ]
+
+XPIDL_MODULE = "xulapp"
+
+EXPORTS += [
+    "nsAppRunner.h",
+]
+
+EXPORTS.mozilla += [
+    "AutoSQLiteLifetime.h",
+    "Bootstrap.h",
+    "CmdLineAndEnvUtils.h",
+    "GeckoArgs.h",
+    "MultiInstanceLock.h",
+    "SafeMode.h",
+]
+
+if CONFIG["MOZ_INSTRUMENT_EVENT_LOOP"]:
+    EXPORTS += ["EventTracer.h"]
+
+if CONFIG["MOZ_WIDGET_TOOLKIT"] == "windows":
+    EXPORTS.mozilla += [
+        "AssembleCmdLine.h",
+        "DllPrefetchExperimentRegistryInfo.h",
+        "PolicyChecks.h",
+        "WinTokenUtils.h",
+    ]
+    UNIFIED_SOURCES += [
+        "/toolkit/mozapps/update/common/pathhash.cpp",
+        "/toolkit/mozapps/update/common/updateutils_win.cpp",
+        "DllPrefetchExperimentRegistryInfo.cpp",
+        "nsNativeAppSupportWin.cpp",
+        "WinTokenUtils.cpp",
+    ]
+    DEFINES["PROXY_PRINTING"] = 1
+    LOCAL_INCLUDES += [
+        "../components/printingui",
+    ]
+    if CONFIG["MOZ_LAUNCHER_PROCESS"]:
+        EXPORTS.mozilla += [
+            "LauncherRegistryInfo.h",
+        ]
+        UNIFIED_SOURCES += [
+            "LauncherRegistryInfo.cpp",
+        ]
+    DIRS += [
+        "dllservices",
+    ]
+elif CONFIG["MOZ_WIDGET_TOOLKIT"] == "cocoa":
+    EXPORTS.mozilla += [
+        "MacRunFromDmgUtils.h",
+    ]
+    UNIFIED_SOURCES += [
+        "MacApplicationDelegate.mm",
+        "MacAutoreleasePool.mm",
+        "MacLaunchHelper.mm",
+        "MacRunFromDmgUtils.mm",
+        "nsCommandLineServiceMac.mm",
+        "nsNativeAppSupportCocoa.mm",
+        "updaterfileutils_osx.mm",
+    ]
+    DEFINES["PROXY_PRINTING"] = 1
+    LOCAL_INCLUDES += [
+        "../components/printingui",
+    ]
+elif CONFIG["MOZ_WIDGET_TOOLKIT"] == "uikit":
+    UNIFIED_SOURCES += [
+        "nsNativeAppSupportDefault.cpp",
+        "UIKitDirProvider.mm",
+    ]
+elif CONFIG["MOZ_WIDGET_TOOLKIT"] == "gtk":
+    UNIFIED_SOURCES += [
+        "nsNativeAppSupportUnix.cpp",
+    ]
+    CXXFLAGS += CONFIG["MOZ_X11_SM_CFLAGS"]
+else:
+    UNIFIED_SOURCES += [
+        "nsNativeAppSupportDefault.cpp",
+    ]
+
+if CONFIG["MOZ_HAS_REMOTE"]:
+    LOCAL_INCLUDES += [
+        "../components/remote",
+    ]
+
+if CONFIG["MOZ_WIDGET_TOOLKIT"] == "gtk":
+    UNIFIED_SOURCES += [
+        "nsGDKErrorHandler.cpp",
+    ]
+
+if CONFIG["MOZ_X11"]:
+    EXPORTS += ["nsX11ErrorHandler.h"]
+    UNIFIED_SOURCES += [
+        "nsX11ErrorHandler.cpp",
+    ]
+
+if CONFIG["MOZ_WIDGET_TOOLKIT"] == "android":
+    UNIFIED_SOURCES += [
+        "nsAndroidStartup.cpp",
+    ]
+
+if CONFIG["MOZ_WIDGET_TOOLKIT"] != "android":
+    UNIFIED_SOURCES += [
+        "MultiInstanceLock.cpp",
+    ]
+
+UNIFIED_SOURCES += [
+    "/toolkit/mozapps/update/common/commonupdatedir.cpp",
+    "AutoSQLiteLifetime.cpp",
+    "Bootstrap.cpp",
+    "CmdLineAndEnvUtils.cpp",
+    "CreateAppData.cpp",
+    "nsConsoleWriter.cpp",
+    "nsNativeAppSupportBase.cpp",
+    "nsSigHandlers.cpp",
+    "nsXREDirProvider.cpp",
+]
+
+# nsAppRunner.cpp and ProfileReset.cpp cannot be built in unified mode because
+# they pull in OS X system headers.
+# nsEmbedFunctions.cpp cannot be built in unified mode because it pulls in X11 headers.
+SOURCES += [
+    "../../other-licenses/nsis/Contrib/CityHash/cityhash/city.cpp",
+    "nsAppRunner.cpp",
+    "nsEmbedFunctions.cpp",
+    "ProfileReset.cpp",
+]
+
+if CONFIG["MOZ_INSTRUMENT_EVENT_LOOP"]:
+    UNIFIED_SOURCES += [
+        "EventTracer.cpp",
+    ]
+
+if CONFIG["MOZ_UPDATER"]:
+    if CONFIG["MOZ_WIDGET_TOOLKIT"] != "android":
+        UNIFIED_SOURCES += [
+            "nsUpdateDriver.cpp",
+            "nsUpdateSyncManager.cpp",
+        ]
+
+if CONFIG["MOZ_PDF_PRINTING"]:
+    DEFINES["PROXY_PRINTING"] = 1
+    LOCAL_INCLUDES += [
+        "../components/printingui",
+    ]
+
+XPCOM_MANIFESTS += [
+    "components.conf",
+]
+
+include("/ipc/chromium/chromium-config.mozbuild")
+
+FINAL_LIBRARY = "xul"
+
+if CONFIG["MOZ_X11"] or CONFIG["MOZ_WAYLAND"]:
+    DEFINES["USE_GLX_TEST"] = True
+    DIRS += ["glxtest"]
+
+for var in (
+    "MOZ_APP_NAME",
+    "MOZ_APP_BASENAME",
+    "MOZ_APP_DISPLAYNAME",
+    "MOZ_APP_VENDOR",
+    "MOZ_APP_VERSION",
+    "OS_TARGET",
+    "MOZ_WIDGET_TOOLKIT",
+):
+    DEFINES[var] = '"%s"' % CONFIG[var]
+
+if CONFIG["MOZ_DEFAULT_BROWSER_AGENT"] and CONFIG["OS_ARCH"] == "WINNT":
+    DEFINES["MOZ_DEFAULT_BROWSER_AGENT"] = CONFIG["MOZ_DEFAULT_BROWSER_AGENT"]
+
+if CONFIG["MOZ_UPDATER"] and CONFIG["MOZ_WIDGET_TOOLKIT"] != "android":
+    DEFINES["MOZ_UPDATER"] = True
+
+if CONFIG["MOZ_WIDGET_TOOLKIT"] == "windows":
+    DEFINES["WIN32_LEAN_AND_MEAN"] = True
+    DEFINES["UNICODE"] = True
+    DEFINES["_UNICODE"] = True
+
+if CONFIG["MOZ_WIDGET_TOOLKIT"] == "android":
+    DEFINES["ANDROID_PACKAGE_NAME"] = '"%s"' % CONFIG["ANDROID_PACKAGE_NAME"]
+
+DEFINES["MOZ_DISTRIBUTION_ID"] = '"%s"' % CONFIG["MOZ_DISTRIBUTION_ID"]
+
+if CONFIG["TARGET_XPCOM_ABI"]:
+    DEFINES["TARGET_OS_ABI"] = '"%s_%s"' % (
+        CONFIG["OS_TARGET"],
+        CONFIG["TARGET_XPCOM_ABI"],
+    )
+
+if CONFIG["OS_ARCH"] == "Linux" and "lib64" in CONFIG["libdir"]:
+    DEFINES["HAVE_USR_LIB64_DIR"] = True
+
+DEFINES["GRE_MILESTONE"] = CONFIG["GRE_MILESTONE"]
+DEFINES["MOZ_APP_VERSION_DISPLAY"] = CONFIG["MOZ_APP_VERSION_DISPLAY"]
+
+for var in ("APP_VERSION", "APP_ID"):
+    DEFINES[var] = CONFIG["MOZ_%s" % var]
+
+if CONFIG["MOZ_BUILD_APP"] == "browser":
+    DEFINES["MOZ_BUILD_APP_IS_BROWSER"] = True
+
+LOCAL_INCLUDES += [
+    "../../other-licenses/nsis/Contrib/CityHash/cityhash",
+    "../components/find",
+    "../components/printingui/ipc",
+    "../components/windowwatcher",
+    "../mozapps/update/common",
+    "../profile",
+    "/config",
+    "/dom/base",
+    "/dom/commandhandler",
+    "/dom/ipc",
+    "/dom/webbrowserpersist",
+    "/testing/gtest/mozilla",
+    "/toolkit/crashreporter",
+    "/xpcom/build",
+]
+
+if CONFIG["MOZ_SANDBOX"] and CONFIG["OS_ARCH"] == "WINNT":
+    LOCAL_INCLUDES += [
+        "/security/sandbox/chromium",
+        "/security/sandbox/chromium-shim",
+    ]
+
+if CONFIG["MOZ_SANDBOX"] and CONFIG["OS_ARCH"] == "Linux":
+    USE_LIBS += [
+        "mozsandbox",
+    ]
+
+if CONFIG["MOZ_WIDGET_TOOLKIT"] == "cocoa":
+    LOCAL_INCLUDES += [
+        "/widget",
+        "/widget/cocoa",
+        "/xpcom/base",
+    ]
+
+CXXFLAGS += CONFIG["MOZ_DBUS_CFLAGS"]
+CXXFLAGS += CONFIG["MOZ_DBUS_GLIB_CFLAGS"]
+
+if CONFIG["MOZ_WIDGET_TOOLKIT"] == "gtk":
+    CXXFLAGS += CONFIG["MOZ_GTK3_CFLAGS"]
+    CXXFLAGS += CONFIG["MOZ_PANGO_CFLAGS"]
+
+DEFINES["TOPOBJDIR"] = TOPOBJDIR
+FINAL_TARGET_PP_FILES += ["platform.ini"]
+
+if CONFIG["ENABLE_TESTS"]:
+    DIRS += ["test/gtest"]
diff --git a/toolkit/xre/nsAndroidStartup.cpp b/toolkit/xre/nsAndroidStartup.cpp
new file mode 100644
index 0000000000..d581dc47a4
--- /dev/null
+++ b/toolkit/xre/nsAndroidStartup.cpp
@@ -0,0 +1,57 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <android/log.h>
+
+#include <jni.h>
+
+#include <stdlib.h>
+#include <string.h>
+#include <pthread.h>
+
+#include "mozilla/jni/Utils.h"
+#include "nsTArray.h"
+#include "nsString.h"
+#include "nsAppRunner.h"
+#include "mozilla/Bootstrap.h"
+#include "XREShellData.h"
+
+#define LOG(args...) __android_log_print(ANDROID_LOG_INFO, MOZ_APP_NAME, args)
+
+using namespace mozilla;
+
+extern "C" NS_EXPORT void GeckoStart(JNIEnv* env, char** argv, int argc,
+                                     const StaticXREAppData& aAppData,
+                                     bool xpcshell, const char* outFilePath) {
+  mozilla::jni::SetGeckoThreadEnv(env);
+
+  if (!argv) {
+    LOG("Failed to get arguments for GeckoStart\n");
+    return;
+  }
+
+  if (xpcshell) {
+    XREShellData shellData;
+    FILE* outFile = fopen(outFilePath, "w");
+    if (!outFile) {
+      LOG("XRE_XPCShellMain cannot open %s", outFilePath);
+      return;
+    }
+    // We redirect both stdout and stderr to the same file, to conform with
+    // what runxpcshell.py does on Desktop.
+    shellData.outFile = outFile;
+    shellData.errFile = outFile;
+    int result = XRE_XPCShellMain(argc, argv, nullptr, &shellData);
+    fclose(shellData.outFile);
+    if (result) LOG("XRE_XPCShellMain returned %d", result);
+  } else {
+    BootstrapConfig config;
+    config.appData = &aAppData;
+    config.appDataPath = nullptr;
+
+    int result = XRE_main(argc, argv, config);
+    if (result) LOG("XRE_main returned %d", result);
+  }
+}
diff --git a/toolkit/xre/nsAppRunner.cpp b/toolkit/xre/nsAppRunner.cpp
new file mode 100644
index 0000000000..14b8c98dc8
--- /dev/null
+++ b/toolkit/xre/nsAppRunner.cpp
@@ -0,0 +1,6153 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/dom/ContentParent.h"
+#include "mozilla/dom/ContentChild.h"
+#include "mozilla/ipc/GeckoChildProcessHost.h"
+
+#include "mozilla/AppShutdown.h"
+#include "mozilla/ArrayUtils.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/Components.h"
+#include "mozilla/FilePreferences.h"
+#include "mozilla/ChaosMode.h"
+#include "mozilla/CmdLineAndEnvUtils.h"
+#include "mozilla/IOInterposer.h"
+#include "mozilla/ipc/UtilityProcessChild.h"
+#include "mozilla/Likely.h"
+#include "mozilla/MemoryChecking.h"
+#include "mozilla/Poison.h"
+#include "mozilla/Preferences.h"
+#include "mozilla/Printf.h"
+#include "mozilla/ProcessType.h"
+#include "mozilla/ResultExtensions.h"
+#include "mozilla/RuntimeExceptionModule.h"
+#include "mozilla/ScopeExit.h"
+#include "mozilla/StaticPrefs_browser.h"
+#include "mozilla/StaticPrefs_fission.h"
+#include "mozilla/StaticPrefs_webgl.h"
+#include "mozilla/StaticPrefs_widget.h"
+#include "mozilla/Telemetry.h"
+#include "mozilla/Utf8.h"
+#include "mozilla/intl/LocaleService.h"
+#include "mozilla/JSONWriter.h"
+#include "mozilla/gfx/gfxVars.h"
+#include "mozilla/glean/GleanPings.h"
+#include "mozilla/widget/TextRecognition.h"
+#include "BaseProfiler.h"
+
+#include "nsAppRunner.h"
+#include "mozilla/XREAppData.h"
+#include "mozilla/Bootstrap.h"
+#if defined(MOZ_UPDATER) && !defined(MOZ_WIDGET_ANDROID)
+#  include "nsUpdateDriver.h"
+#  include "nsUpdateSyncManager.h"
+#endif
+#include "ProfileReset.h"
+
+#ifdef MOZ_INSTRUMENT_EVENT_LOOP
+#  include "EventTracer.h"
+#endif
+
+#ifdef XP_MACOSX
+#  include "nsVersionComparator.h"
+#  include "MacLaunchHelper.h"
+#  include "MacApplicationDelegate.h"
+#  include "MacAutoreleasePool.h"
+#  include "MacRunFromDmgUtils.h"
+// these are needed for sysctl
+#  include <sys/types.h>
+#  include <sys/sysctl.h>
+#endif
+
+#include "prnetdb.h"
+#include "prprf.h"
+#include "prproces.h"
+#include "prenv.h"
+#include "prtime.h"
+
+#include "nsIAppStartup.h"
+#include "nsCategoryManagerUtils.h"
+#include "nsIMutableArray.h"
+#include "nsCommandLine.h"
+#include "nsIComponentRegistrar.h"
+#include "nsIDialogParamBlock.h"
+#include "mozilla/ModuleUtils.h"
+#include "nsIIOService.h"
+#include "nsIObserverService.h"
+#include "nsINativeAppSupport.h"
+#include "nsIPlatformInfo.h"
+#include "nsIProcess.h"
+#include "nsIProfileUnlocker.h"
+#include "nsIPromptService.h"
+#include "nsIPropertyBag2.h"
+#include "nsIServiceManager.h"
+#include "nsIStringBundle.h"
+#include "nsISupportsPrimitives.h"
+#include "nsIToolkitProfile.h"
+#include "nsToolkitProfileService.h"
+#include "nsIURI.h"
+#include "nsIURL.h"
+#include "nsIWindowCreator.h"
+#include "nsIWindowWatcher.h"
+#include "nsIXULAppInfo.h"
+#include "nsIXULRuntime.h"
+#include "nsPIDOMWindow.h"
+#include "nsIWidget.h"
+#include "nsAppShellCID.h"
+#include "mozilla/dom/quota/QuotaManager.h"
+#include "mozilla/scache/StartupCache.h"
+#include "gfxPlatform.h"
+#include "PDMFactory.h"
+#ifdef XP_MACOSX
+#  include "gfxPlatformMac.h"
+#endif
+
+#include "mozilla/Unused.h"
+
+#ifdef XP_WIN
+#  include "nsIWinAppHelper.h"
+#  include <windows.h>
+#  include <intrin.h>
+#  include <math.h>
+#  include "cairo/cairo-features.h"
+#  include "detect_win32k_conflicts.h"
+#  include "mozilla/PreXULSkeletonUI.h"
+#  include "mozilla/DllPrefetchExperimentRegistryInfo.h"
+#  include "mozilla/WindowsBCryptInitialization.h"
+#  include "mozilla/WindowsDllBlocklist.h"
+#  include "mozilla/WindowsProcessMitigations.h"
+#  include "mozilla/WinHeaderOnlyUtils.h"
+#  include "mozilla/mscom/ProcessRuntime.h"
+#  include "mozilla/mscom/ProfilerMarkers.h"
+#  include "WinTokenUtils.h"
+
+#  if defined(MOZ_LAUNCHER_PROCESS)
+#    include "mozilla/LauncherRegistryInfo.h"
+#  endif
+
+#  if defined(MOZ_DEFAULT_BROWSER_AGENT)
+#    include "nsIWindowsRegKey.h"
+#  endif
+
+#  ifndef PROCESS_DEP_ENABLE
+#    define PROCESS_DEP_ENABLE 0x1
+#  endif
+#endif
+
+#if defined(MOZ_SANDBOX)
+#  include "mozilla/SandboxSettings.h"
+#endif
+
+#ifdef ACCESSIBILITY
+#  include "nsAccessibilityService.h"
+#  if defined(XP_WIN)
+#    include "mozilla/a11y/Compatibility.h"
+#    include "mozilla/a11y/Platform.h"
+#  endif
+#endif
+
+#include "nsCRT.h"
+#include "nsCOMPtr.h"
+#include "nsDirectoryServiceDefs.h"
+#include "nsDirectoryServiceUtils.h"
+#include "nsEmbedCID.h"
+#include "nsIDUtils.h"
+#include "nsNetUtil.h"
+#include "nsReadableUtils.h"
+#include "nsXPCOM.h"
+#include "nsXPCOMCIDInternal.h"
+#include "nsString.h"
+#include "nsPrintfCString.h"
+#include "nsVersionComparator.h"
+
+#include "nsAppDirectoryServiceDefs.h"
+#include "nsXULAppAPI.h"
+#include "nsXREDirProvider.h"
+
+#include "nsINIParser.h"
+#include "mozilla/Omnijar.h"
+#include "mozilla/StartupTimeline.h"
+#include "mozilla/LateWriteChecks.h"
+
+#include <stdlib.h>
+#include <locale.h>
+
+#ifdef XP_UNIX
+#  include <errno.h>
+#  include <pwd.h>
+#  include <string.h>
+#  include <sys/resource.h>
+#  include <sys/stat.h>
+#  include <unistd.h>
+#endif
+
+#ifdef XP_WIN
+#  include <process.h>
+#  include <shlobj.h>
+#  include "mozilla/WinDllServices.h"
+#  include "nsThreadUtils.h"
+#  include "WinUtils.h"
+#endif
+
+#ifdef XP_MACOSX
+#  include "nsILocalFileMac.h"
+#  include "nsCommandLineServiceMac.h"
+#endif
+
+// for X remote support
+#if defined(MOZ_HAS_REMOTE)
+#  include "nsRemoteService.h"
+#endif
+
+#if defined(DEBUG) && defined(XP_WIN)
+#  include <malloc.h>
+#endif
+
+#if defined(XP_MACOSX)
+#  include <Carbon/Carbon.h>
+#endif
+
+#ifdef DEBUG
+#  include "mozilla/Logging.h"
+#endif
+
+#ifdef MOZ_JPROF
+#  include "jprof.h"
+#endif
+
+#include "nsExceptionHandler.h"
+#include "nsICrashReporter.h"
+#include "nsIPrefService.h"
+#include "nsIMemoryInfoDumper.h"
+#if defined(XP_LINUX) && !defined(ANDROID)
+#  include "mozilla/widget/LSBUtils.h"
+#endif
+
+#include "base/command_line.h"
+#include "GTestRunner.h"
+
+#ifdef MOZ_WIDGET_ANDROID
+#  include "mozilla/java/GeckoAppShellWrappers.h"
+#endif
+
+#if defined(MOZ_SANDBOX)
+#  if defined(XP_LINUX) && !defined(ANDROID)
+#    include "mozilla/SandboxInfo.h"
+#  elif defined(XP_WIN)
+#    include "sandboxBroker.h"
+#  endif
+#endif
+
+#ifdef MOZ_CODE_COVERAGE
+#  include "mozilla/CodeCoverageHandler.h"
+#endif
+
+#include "SafeMode.h"
+
+#ifdef MOZ_BACKGROUNDTASKS
+#  include "mozilla/BackgroundTasks.h"
+#  include "nsIPowerManagerService.h"
+#  include "nsIStringBundle.h"
+#endif
+
+#ifdef USE_GLX_TEST
+#  include "mozilla/GUniquePtr.h"
+#  include "mozilla/GfxInfo.h"
+#endif
+
+extern uint32_t gRestartMode;
+extern void InstallSignalHandlers(const char* ProgramName);
+
+#define FILE_COMPATIBILITY_INFO "compatibility.ini"_ns
+#define FILE_INVALIDATE_CACHES ".purgecaches"_ns
+#define FILE_STARTUP_INCOMPLETE u".startup-incomplete"_ns
+
+#if defined(MOZ_BLOCK_PROFILE_DOWNGRADE) || defined(MOZ_LAUNCHER_PROCESS) || \
+    defined(MOZ_DEFAULT_BROWSER_AGENT)
+static const char kPrefHealthReportUploadEnabled[] =
+    "datareporting.healthreport.uploadEnabled";
+#endif  // defined(MOZ_BLOCK_PROFILE_DOWNGRADE) || defined(MOZ_LAUNCHER_PROCESS)
+        // || defined(MOZ_DEFAULT_BROWSER_AGENT)
+#if defined(MOZ_DEFAULT_BROWSER_AGENT)
+static const char kPrefDefaultAgentEnabled[] = "default-browser-agent.enabled";
+
+static const char kPrefServicesSettingsServer[] = "services.settings.server";
+static const char kPrefSecurityContentSignatureRootHash[] =
+    "security.content.signature.root_hash";
+static const char kPrefSetDefaultBrowserUserChoicePref[] =
+    "browser.shell.setDefaultBrowserUserChoice";
+#endif  // defined(MOZ_DEFAULT_BROWSER_AGENT)
+
+#if defined(XP_WIN)
+static const char kPrefThemeId[] = "extensions.activeThemeID";
+static const char kPrefBrowserStartupBlankWindow[] =
+    "browser.startup.blankWindow";
+static const char kPrefPreXulSkeletonUI[] = "browser.startup.preXulSkeletonUI";
+#endif  // defined(XP_WIN)
+
+#if defined(MOZ_WIDGET_GTK)
+constexpr nsLiteralCString kStartupTokenNames[] = {
+    "XDG_ACTIVATION_TOKEN"_ns,
+    "DESKTOP_STARTUP_ID"_ns,
+};
+#endif
+
+int gArgc;
+char** gArgv;
+
+static const char gToolkitVersion[] = MOZ_STRINGIFY(GRE_MILESTONE);
+// The gToolkitBuildID global is defined to MOZ_BUILDID via gen_buildid.py
+// in toolkit/library. See related comment in toolkit/library/moz.build.
+extern const char gToolkitBuildID[];
+
+static nsIProfileLock* gProfileLock;
+#if defined(MOZ_HAS_REMOTE)
+static nsRemoteService* gRemoteService;
+bool gRestartWithoutRemote = false;
+#endif
+
+int gRestartArgc;
+char** gRestartArgv;
+
+// If gRestartedByOS is set, we were automatically restarted by the OS.
+bool gRestartedByOS = false;
+
+bool gIsGtest = false;
+
+nsString gAbsoluteArgv0Path;
+
+#if defined(XP_WIN)
+nsString gProcessStartupShortcut;
+#endif
+
+#if defined(MOZ_WIDGET_GTK)
+#  include <glib.h>
+#  include "mozilla/WidgetUtilsGtk.h"
+#  include <gtk/gtk.h>
+#  ifdef MOZ_WAYLAND
+#    include <gdk/gdkwayland.h>
+#    include "mozilla/widget/nsWaylandDisplay.h"
+#  endif
+#  ifdef MOZ_X11
+#    include <gdk/gdkx.h>
+#  endif /* MOZ_X11 */
+#endif
+#include "BinaryPath.h"
+
+#ifdef MOZ_LINKER
+extern "C" MFBT_API bool IsSignalHandlingBroken();
+#endif
+
+#ifdef FUZZING
+#  include "FuzzerRunner.h"
+
+namespace mozilla {
+FuzzerRunner* fuzzerRunner = 0;
+}  // namespace mozilla
+
+#  ifdef LIBFUZZER
+void XRE_LibFuzzerSetDriver(LibFuzzerDriver aDriver) {
+  mozilla::fuzzerRunner->setParams(aDriver);
+}
+#  endif
+#endif  // FUZZING
+
+// Undo X11/X.h's definition of None
+#undef None
+
+namespace mozilla {
+int (*RunGTest)(int*, char**) = 0;
+
+bool RunningGTest() { return RunGTest; }
+}  // namespace mozilla
+
+using namespace mozilla;
+using namespace mozilla::widget;
+using namespace mozilla::startup;
+using mozilla::Unused;
+using mozilla::dom::ContentChild;
+using mozilla::dom::ContentParent;
+using mozilla::dom::quota::QuotaManager;
+using mozilla::intl::LocaleService;
+using mozilla::scache::StartupCache;
+
+// Save the given word to the specified environment variable.
+static void MOZ_NEVER_INLINE SaveWordToEnv(const char* name,
+                                           const nsACString& word) {
+  char* expr =
+      Smprintf("%s=%s", name, PromiseFlatCString(word).get()).release();
+  if (expr) PR_SetEnv(expr);
+  // We intentionally leak |expr| here since it is required by PR_SetEnv.
+}
+
+// Save the path of the given file to the specified environment variable.
+static void SaveFileToEnv(const char* name, nsIFile* file) {
+#ifdef XP_WIN
+  nsAutoString path;
+  file->GetPath(path);
+  SetEnvironmentVariableW(NS_ConvertASCIItoUTF16(name).get(), path.get());
+#else
+  nsAutoCString path;
+  file->GetNativePath(path);
+  SaveWordToEnv(name, path);
+#endif
+}
+
+static bool gIsExpectedExit = false;
+
+void MozExpectedExit() { gIsExpectedExit = true; }
+
+/**
+ * Runs atexit() to catch unexpected exit from 3rd party libraries like the
+ * Intel graphics driver calling exit in an error condition. When they
+ * call exit() to report an error we won't shutdown correctly and wont catch
+ * the issue with our crash reporter.
+ */
+static void UnexpectedExit() {
+  if (!gIsExpectedExit) {
+    gIsExpectedExit = true;  // Don't risk re-entrency issues when crashing.
+    MOZ_CRASH("Exit called by third party code.");
+  }
+}
+
+#if defined(MOZ_WAYLAND)
+bool IsWaylandEnabled() {
+  static bool isWaylandEnabled = []() {
+    const char* waylandDisplay = PR_GetEnv("WAYLAND_DISPLAY");
+    if (!waylandDisplay) {
+      return false;
+    }
+    if (!PR_GetEnv("DISPLAY")) {
+      // No X11 display, so try to run wayland.
+      return true;
+    }
+    // MOZ_ENABLE_WAYLAND is our primary Wayland on/off switch.
+    if (const char* waylandPref = PR_GetEnv("MOZ_ENABLE_WAYLAND")) {
+      return *waylandPref == '1';
+    }
+    if (const char* backendPref = PR_GetEnv("GDK_BACKEND")) {
+      if (!strncmp(backendPref, "wayland", 7)) {
+        NS_WARNING(
+            "Wayland backend should be enabled by MOZ_ENABLE_WAYLAND=1."
+            "GDK_BACKEND is a Gtk3 debug variable and may cause issues.");
+        return true;
+      }
+    }
+#  ifdef EARLY_BETA_OR_EARLIER
+    // Enable by default when we're running on a recent enough GTK version. We'd
+    // like to check further details like compositor version and so on ideally
+    // to make sure we don't enable it on old Mutter or what not, but we can't,
+    // so let's assume that if the user is running on a Wayland session by
+    // default we're ok, since either the distro has enabled Wayland by default,
+    // or the user has gone out of their way to use Wayland.
+    //
+    // TODO(emilio): If users hit problems, we might be able to restrict it to
+    // GNOME / KDE  / known-good-desktop environments by checking
+    // XDG_CURRENT_DESKTOP or so...
+    return !gtk_check_version(3, 24, 30);
+#  else
+    return false;
+#  endif
+  }();
+  return isWaylandEnabled;
+}
+#else
+bool IsWaylandEnabled() { return false; }
+#endif
+
+/**
+ * Output a string to the user.  This method is really only meant to be used to
+ * output last-ditch error messages designed for developers NOT END USERS.
+ *
+ * @param isError
+ *        Pass true to indicate severe errors.
+ * @param fmt
+ *        printf-style format string followed by arguments.
+ */
+static MOZ_FORMAT_PRINTF(2, 3) void Output(bool isError, const char* fmt, ...) {
+  va_list ap;
+  va_start(ap, fmt);
+
+#if defined(XP_WIN) && !MOZ_WINCONSOLE
+  SmprintfPointer msg = mozilla::Vsmprintf(fmt, ap);
+  if (msg) {
+    UINT flags = MB_OK;
+    if (isError)
+      flags |= MB_ICONERROR;
+    else
+      flags |= MB_ICONINFORMATION;
+
+    wchar_t wide_msg[1024];
+    MultiByteToWideChar(CP_ACP, 0, msg.get(), -1, wide_msg,
+                        sizeof(wide_msg) / sizeof(wchar_t));
+
+    MessageBoxW(nullptr, wide_msg, L"XULRunner", flags);
+  }
+#elif defined(MOZ_WIDGET_ANDROID)
+  SmprintfPointer msg = mozilla::Vsmprintf(fmt, ap);
+  if (msg) {
+    __android_log_print(isError ? ANDROID_LOG_ERROR : ANDROID_LOG_INFO,
+                        "GeckoRuntime", "%s", msg.get());
+  }
+#else
+  vfprintf(stderr, fmt, ap);
+#endif
+
+  va_end(ap);
+}
+
+/**
+ * Check for a commandline flag. If the flag takes a parameter, the
+ * parameter is returned in aParam. Flags may be in the form -arg or
+ * --arg (or /arg on win32).
+ *
+ * @param aArg the parameter to check. Must be lowercase.
+ * @param aParam if non-null, the -arg <data> will be stored in this pointer.
+ *        This is *not* allocated, but rather a pointer to the argv data.
+ * @param aFlags flags @see CheckArgFlag
+ */
+static ArgResult CheckArg(const char* aArg, const char** aParam = nullptr,
+                          CheckArgFlag aFlags = CheckArgFlag::RemoveArg) {
+  MOZ_ASSERT(gArgv, "gArgv must be initialized before CheckArg()");
+  return CheckArg(gArgc, gArgv, aArg, aParam, aFlags);
+}
+
+/**
+ * Check for a commandline flag. Ignore data that's passed in with the flag.
+ * Flags may be in the form -arg or --arg (or /arg on win32).
+ * Will not remove flag if found.
+ *
+ * @param aArg the parameter to check. Must be lowercase.
+ */
+static ArgResult CheckArgExists(const char* aArg) {
+  return CheckArg(aArg, nullptr, CheckArgFlag::None);
+}
+
+bool gSafeMode = false;
+bool gFxREmbedded = false;
+
+enum E10sStatus {
+  kE10sEnabledByDefault,
+  kE10sDisabledByUser,
+  kE10sForceDisabled,
+};
+
+static bool gBrowserTabsRemoteAutostart = false;
+static E10sStatus gBrowserTabsRemoteStatus;
+static bool gBrowserTabsRemoteAutostartInitialized = false;
+
+namespace mozilla {
+
+bool BrowserTabsRemoteAutostart() {
+  if (gBrowserTabsRemoteAutostartInitialized) {
+    return gBrowserTabsRemoteAutostart;
+  }
+  gBrowserTabsRemoteAutostartInitialized = true;
+
+  // If we're not in the parent process, we are running E10s.
+  if (!XRE_IsParentProcess()) {
+    gBrowserTabsRemoteAutostart = true;
+    return gBrowserTabsRemoteAutostart;
+  }
+
+#if defined(MOZILLA_OFFICIAL) && MOZ_BUILD_APP_IS_BROWSER
+  bool allowSingleProcessOutsideAutomation = false;
+#else
+  bool allowSingleProcessOutsideAutomation = true;
+#endif
+
+  E10sStatus status = kE10sEnabledByDefault;
+  // We use "are non-local connections disabled" as a proxy for
+  // "are we running some kind of automated test". It would be nicer to use
+  // xpc::IsInAutomation(), but that depends on some prefs being set, which
+  // they are not in (at least) gtests (where we can't) and xpcshell.
+  // Long-term, hopefully we can make tests switch to environment variables
+  // to disable e10s and then we can get rid of this.
+  if (allowSingleProcessOutsideAutomation ||
+      xpc::AreNonLocalConnectionsDisabled()) {
+    bool optInPref =
+        Preferences::GetBool("browser.tabs.remote.autostart", true);
+
+    if (optInPref) {
+      gBrowserTabsRemoteAutostart = true;
+    } else {
+      status = kE10sDisabledByUser;
+    }
+  } else {
+    gBrowserTabsRemoteAutostart = true;
+  }
+
+  // Uber override pref for emergency blocking
+  if (gBrowserTabsRemoteAutostart) {
+    const char* forceDisable = PR_GetEnv("MOZ_FORCE_DISABLE_E10S");
+#if defined(MOZ_WIDGET_ANDROID)
+    // We need this for xpcshell on Android
+    if (forceDisable && *forceDisable) {
+#else
+    // The environment variable must match the application version to apply.
+    if (forceDisable && gAppData && !strcmp(forceDisable, gAppData->version)) {
+#endif
+      gBrowserTabsRemoteAutostart = false;
+      status = kE10sForceDisabled;
+    }
+  }
+
+  gBrowserTabsRemoteStatus = status;
+
+  return gBrowserTabsRemoteAutostart;
+}
+
+}  // namespace mozilla
+
+// Win32k Infrastructure ==============================================
+
+// This bool tells us if we have initialized the following two statics
+// upon startup.
+
+static bool gWin32kInitialized = false;
+
+// Win32k Lockdown for the current session is determined once, at startup,
+// and then remains the same for the duration of the session.
+
+static nsIXULRuntime::ContentWin32kLockdownState gWin32kStatus;
+
+// The status of the win32k experiment. It is determined once, at startup,
+// and then remains the same for the duration of the session.
+
+static nsIXULRuntime::ExperimentStatus gWin32kExperimentStatus =
+    nsIXULRuntime::eExperimentStatusUnenrolled;
+
+#ifdef XP_WIN
+// The states for win32k lockdown can be generalized to:
+//  - User doesn't meet requirements (bad OS, webrender, remotegl) aka
+//  PersistentRequirement
+//  - User has Safe Mode enabled, Win32k Disabled by Env Var, or E10S disabled
+//  by Env Var aka TemporaryRequirement
+//  - User has set the win32k pref to something non-default aka NonDefaultPref
+//  - User has been enrolled in the experiment and does what it says aka
+//  Enrolled
+//  - User does the default aka Default
+//
+// We expect the below behvaior.  In the code, there may be references to these
+//     behaviors (e.g. [A]) but not always.
+//
+// [A] Becoming enrolled in the experiment while NonDefaultPref disqualifies
+//     you upon next browser start
+// [B] Becoming enrolled in the experiment while PersistentRequirement
+//     disqualifies you upon next browser start
+// [C] Becoming enrolled in the experiment while TemporaryRequirement does not
+//     disqualify you
+// [D] Becoming enrolled in the experiment will only take effect after restart
+// [E] While enrolled, becoming PersistentRequirement will not disqualify you
+//     until browser restart, but if the state is present at browser start,
+//     will disqualify you. Additionally, it will not affect the session value
+//     of gWin32kStatus.
+//     XXX(bobowen): I hope both webrender and wbgl.out-of-process require a
+//                   restart to take effect!
+// [F] While enrolled, becoming NonDefaultPref will disqualify you upon next
+//     browser start
+// [G] While enrolled, becoming TemporaryRequirement will _not_ disqualify you,
+//     but the session status will prevent win32k lockdown from taking effect.
+
+// The win32k pref
+static const char kPrefWin32k[] = "security.sandbox.content.win32k-disable";
+
+// The current enrollment status as controlled by Normandy. This value is only
+// stored in the default preference branch, and is not persisted across
+// sessions by the preference service. It therefore isn't available early
+// enough at startup, and needs to be synced to a preference in the user
+// branch which is persisted across sessions.
+static const char kPrefWin32kExperimentEnrollmentStatus[] =
+    "security.sandbox.content.win32k-experiment.enrollmentStatus";
+
+// The enrollment status to be used at browser startup. This automatically
+// synced from the above enrollmentStatus preference whenever the latter is
+// changed. We reused the Fission experiment enum - it can have any of the
+// values defined in the `nsIXULRuntime_ExperimentStatus` enum _except_ rollout.
+// Meanings are documented in the declaration of
+// `nsIXULRuntime.fissionExperimentStatus`
+static const char kPrefWin32kExperimentStartupEnrollmentStatus[] =
+    "security.sandbox.content.win32k-experiment.startupEnrollmentStatus";
+
+namespace mozilla {
+
+bool Win32kExperimentEnrolled() {
+  MOZ_ASSERT(XRE_IsParentProcess());
+  return gWin32kExperimentStatus == nsIXULRuntime::eExperimentStatusControl ||
+         gWin32kExperimentStatus == nsIXULRuntime::eExperimentStatusTreatment;
+}
+
+}  // namespace mozilla
+
+static bool Win32kRequirementsUnsatisfied(
+    nsIXULRuntime::ContentWin32kLockdownState aStatus) {
+  return aStatus == nsIXULRuntime::ContentWin32kLockdownState::
+                        OperatingSystemNotSupported ||
+         aStatus ==
+             nsIXULRuntime::ContentWin32kLockdownState::MissingWebRender ||
+         aStatus ==
+             nsIXULRuntime::ContentWin32kLockdownState::MissingRemoteWebGL ||
+         aStatus ==
+             nsIXULRuntime::ContentWin32kLockdownState::DecodersArentRemote;
+}
+
+static void Win32kExperimentDisqualify() {
+  MOZ_ASSERT(XRE_IsParentProcess());
+  Preferences::SetUint(kPrefWin32kExperimentEnrollmentStatus,
+                       nsIXULRuntime::eExperimentStatusDisqualified);
+}
+
+static void OnWin32kEnrollmentStatusChanged(const char* aPref, void* aData) {
+  auto newStatusInt =
+      Preferences::GetUint(kPrefWin32kExperimentEnrollmentStatus,
+                           nsIXULRuntime::eExperimentStatusUnenrolled);
+  auto newStatus = newStatusInt < nsIXULRuntime::eExperimentStatusCount
+                       ? nsIXULRuntime::ExperimentStatus(newStatusInt)
+                       : nsIXULRuntime::eExperimentStatusDisqualified;
+
+  // Set the startup pref for next browser start [D]
+  Preferences::SetUint(kPrefWin32kExperimentStartupEnrollmentStatus, newStatus);
+}
+
+namespace {
+// This observer is notified during `profile-before-change`, and ensures that
+// the experiment enrollment status is synced over before the browser shuts
+// down, even if it was not modified since win32k was initialized.
+class Win32kEnrollmentStatusShutdownObserver final : public nsIObserver {
+ public:
+  NS_DECL_ISUPPORTS
+
+  NS_IMETHOD Observe(nsISupports* aSubject, const char* aTopic,
+                     const char16_t* aData) override {
+    MOZ_ASSERT(!strcmp("profile-before-change", aTopic));
+    OnWin32kEnrollmentStatusChanged(kPrefWin32kExperimentEnrollmentStatus,
+                                    nullptr);
+    return NS_OK;
+  }
+
+ private:
+  ~Win32kEnrollmentStatusShutdownObserver() = default;
+};
+NS_IMPL_ISUPPORTS(Win32kEnrollmentStatusShutdownObserver, nsIObserver)
+}  // namespace
+
+static void OnWin32kChanged(const char* aPref, void* aData) {
+  // If we're actively enrolled in the Win32k experiment, disqualify the user
+  // from the experiment if the Win32k pref is modified. [F]
+  if (Win32kExperimentEnrolled() && Preferences::HasUserValue(kPrefWin32k)) {
+    Win32kExperimentDisqualify();
+  }
+}
+
+#endif  // XP_WIN
+
+namespace mozilla {
+void EnsureWin32kInitialized();
+}
+
+nsIXULRuntime::ContentWin32kLockdownState GetLiveWin32kLockdownState() {
+#ifdef XP_WIN
+
+  // HasUserValue The Pref functions can only be called on main thread
+  MOZ_ASSERT(NS_IsMainThread());
+
+#  ifdef MOZ_BACKGROUNDTASKS
+  if (BackgroundTasks::IsBackgroundTaskMode()) {
+    // Let's bail out before loading all the graphics libs.
+    return nsIXULRuntime::ContentWin32kLockdownState::DisabledByDefault;
+  }
+#  endif
+
+  mozilla::EnsureWin32kInitialized();
+  gfxPlatform::GetPlatform();
+
+  if (gSafeMode) {
+    return nsIXULRuntime::ContentWin32kLockdownState::DisabledBySafeMode;
+  }
+
+  if (EnvHasValue("MOZ_ENABLE_WIN32K")) {
+    return nsIXULRuntime::ContentWin32kLockdownState::DisabledByEnvVar;
+  }
+
+  if (!mozilla::BrowserTabsRemoteAutostart()) {
+    return nsIXULRuntime::ContentWin32kLockdownState::DisabledByE10S;
+  }
+
+  // Win32k lockdown is available on Win8+, but we are initially limiting it to
+  // Windows 10 v1709 (build 16299) or later. Before this COM initialization
+  // currently fails if user32.dll has loaded before it is called.
+  if (!IsWin10FallCreatorsUpdateOrLater()) {
+    return nsIXULRuntime::ContentWin32kLockdownState::
+        OperatingSystemNotSupported;
+  }
+
+  {
+    ConflictingMitigationStatus conflictingMitigationStatus = {};
+    if (!detect_win32k_conflicting_mitigations(&conflictingMitigationStatus)) {
+      return nsIXULRuntime::ContentWin32kLockdownState::
+          IncompatibleMitigationPolicy;
+    }
+    if (conflictingMitigationStatus.caller_check ||
+        conflictingMitigationStatus.sim_exec ||
+        conflictingMitigationStatus.stack_pivot) {
+      return nsIXULRuntime::ContentWin32kLockdownState::
+          IncompatibleMitigationPolicy;
+    }
+  }
+
+  // Non-native theming is required as well
+  if (!StaticPrefs::widget_non_native_theme_enabled()) {
+    return nsIXULRuntime::ContentWin32kLockdownState::MissingNonNativeTheming;
+  }
+
+  // Win32k Lockdown requires Remote WebGL, but it may be disabled on
+  // certain hardware or virtual machines.
+  if (!gfx::gfxVars::AllowWebglOop() || !StaticPrefs::webgl_out_of_process()) {
+    return nsIXULRuntime::ContentWin32kLockdownState::MissingRemoteWebGL;
+  }
+
+  // Some (not sure exactly which) decoders are not compatible
+  if (!PDMFactory::AllDecodersAreRemote()) {
+    return nsIXULRuntime::ContentWin32kLockdownState::DecodersArentRemote;
+  }
+
+  bool prefSetByUser =
+      Preferences::HasUserValue("security.sandbox.content.win32k-disable");
+  bool prefValue = Preferences::GetBool(
+      "security.sandbox.content.win32k-disable", false, PrefValueKind::User);
+  bool defaultValue = Preferences::GetBool(
+      "security.sandbox.content.win32k-disable", false, PrefValueKind::Default);
+
+  if (prefSetByUser) {
+    if (prefValue) {
+      return nsIXULRuntime::ContentWin32kLockdownState::EnabledByUserPref;
+    } else {
+      return nsIXULRuntime::ContentWin32kLockdownState::DisabledByUserPref;
+    }
+  }
+
+  if (gWin32kExperimentStatus ==
+      nsIXULRuntime::ExperimentStatus::eExperimentStatusControl) {
+    return nsIXULRuntime::ContentWin32kLockdownState::DisabledByControlGroup;
+  } else if (gWin32kExperimentStatus ==
+             nsIXULRuntime::ExperimentStatus::eExperimentStatusTreatment) {
+    return nsIXULRuntime::ContentWin32kLockdownState::EnabledByTreatmentGroup;
+  }
+
+  if (defaultValue) {
+    return nsIXULRuntime::ContentWin32kLockdownState::EnabledByDefault;
+  } else {
+    return nsIXULRuntime::ContentWin32kLockdownState::DisabledByDefault;
+  }
+
+#else
+
+  return nsIXULRuntime::ContentWin32kLockdownState::OperatingSystemNotSupported;
+
+#endif
+}
+
+namespace mozilla {
+
+void EnsureWin32kInitialized() {
+  if (gWin32kInitialized) {
+    return;
+  }
+  gWin32kInitialized = true;
+
+#ifdef XP_WIN
+
+  // Initialize the Win32k experiment, configuring win32k's
+  // default, before checking other overrides. This allows opting-out of a
+  // Win32k experiment through about:preferences or about:config from a
+  // safemode session.
+  uint32_t experimentRaw =
+      Preferences::GetUint(kPrefWin32kExperimentStartupEnrollmentStatus,
+                           nsIXULRuntime::eExperimentStatusUnenrolled);
+  gWin32kExperimentStatus =
+      experimentRaw < nsIXULRuntime::eExperimentStatusCount
+          ? nsIXULRuntime::ExperimentStatus(experimentRaw)
+          : nsIXULRuntime::eExperimentStatusDisqualified;
+
+  // Watch the experiment enrollment status pref to detect experiment
+  // disqualification, and ensure it is propagated for the next restart.
+  Preferences::RegisterCallback(&OnWin32kEnrollmentStatusChanged,
+                                kPrefWin32kExperimentEnrollmentStatus);
+  if (nsCOMPtr<nsIObserverService> observerService =
+          mozilla::services::GetObserverService()) {
+    nsCOMPtr<nsIObserver> shutdownObserver =
+        new Win32kEnrollmentStatusShutdownObserver();
+    observerService->AddObserver(shutdownObserver, "profile-before-change",
+                                 false);
+  }
+
+  // If the user no longer qualifies because they edited a required pref, check
+  // that. [B] [E]
+  auto tmpStatus = GetLiveWin32kLockdownState();
+  if (Win32kExperimentEnrolled() && Win32kRequirementsUnsatisfied(tmpStatus)) {
+    Win32kExperimentDisqualify();
+    gWin32kExperimentStatus = nsIXULRuntime::eExperimentStatusDisqualified;
+  }
+
+  // If the user has overridden an active experiment by setting a user value for
+  // "security.sandbox.content.win32k-disable", disqualify the user from the
+  // experiment. [A] [F]
+  if (Preferences::HasUserValue(kPrefWin32k) && Win32kExperimentEnrolled()) {
+    Win32kExperimentDisqualify();
+    gWin32kExperimentStatus = nsIXULRuntime::eExperimentStatusDisqualified;
+  }
+
+  // Unlike Fission, we do not configure the default branch based on experiment
+  // enrollment status.  Instead we check the startupEnrollmentPref in
+  // GetContentWin32kLockdownState()
+
+  Preferences::RegisterCallback(&OnWin32kChanged, kPrefWin32k);
+
+  // Set the state
+  gWin32kStatus = GetLiveWin32kLockdownState();
+
+#else
+  gWin32kStatus =
+      nsIXULRuntime::ContentWin32kLockdownState::OperatingSystemNotSupported;
+  gWin32kExperimentStatus = nsIXULRuntime::eExperimentStatusUnenrolled;
+
+#endif  // XP_WIN
+}
+
+nsIXULRuntime::ContentWin32kLockdownState GetWin32kLockdownState() {
+#ifdef XP_WIN
+
+  mozilla::EnsureWin32kInitialized();
+  return gWin32kStatus;
+
+#else
+
+  return nsIXULRuntime::ContentWin32kLockdownState::OperatingSystemNotSupported;
+
+#endif
+}
+
+}  // namespace mozilla
+
+// End Win32k Infrastructure ==========================================
+
+// Fission Infrastructure =============================================
+
+// Fission enablement for the current session is determined once, at startup,
+// and then remains the same for the duration of the session.
+//
+// The following factors determine whether or not Fission is enabled for a
+// session, in order of precedence:
+//
+// - Safe mode: In safe mode, Fission is never enabled.
+//
+// - The MOZ_FORCE_ENABLE_FISSION environment variable: If set to any value,
+//   Fission will be enabled.
+//
+// - The 'fission.autostart' preference, if it has been configured by the user.
+static const char kPrefFissionAutostart[] = "fission.autostart";
+
+// The computed FissionAutostart value for the session, read by content
+// processes to initialize gFissionAutostart.
+//
+// This pref is locked, and only configured on the default branch, so should
+// never be persisted in a profile.
+static const char kPrefFissionAutostartSession[] = "fission.autostart.session";
+
+//
+// The computed FissionAutostart value for the session, read by content
+// processes to initialize gFissionAutostart.
+
+static bool gFissionAutostart = false;
+static bool gFissionAutostartInitialized = false;
+static nsIXULRuntime::FissionDecisionStatus gFissionDecisionStatus;
+static void EnsureFissionAutostartInitialized() {
+  if (gFissionAutostartInitialized) {
+    return;
+  }
+  gFissionAutostartInitialized = true;
+
+  if (!XRE_IsParentProcess()) {
+    // This pref is configured for the current session by the parent process.
+    gFissionAutostart = Preferences::GetBool(kPrefFissionAutostartSession,
+                                             false, PrefValueKind::Default);
+    return;
+  }
+
+  if (!BrowserTabsRemoteAutostart()) {
+    gFissionAutostart = false;
+    if (gBrowserTabsRemoteStatus == kE10sForceDisabled) {
+      gFissionDecisionStatus = nsIXULRuntime::eFissionDisabledByE10sEnv;
+    } else {
+      gFissionDecisionStatus = nsIXULRuntime::eFissionDisabledByE10sOther;
+    }
+  } else if (EnvHasValue("MOZ_FORCE_ENABLE_FISSION")) {
+    gFissionAutostart = true;
+    gFissionDecisionStatus = nsIXULRuntime::eFissionEnabledByEnv;
+  } else if (EnvHasValue("MOZ_FORCE_DISABLE_FISSION")) {
+    gFissionAutostart = false;
+    gFissionDecisionStatus = nsIXULRuntime::eFissionDisabledByEnv;
+  } else {
+    // NOTE: This will take into account changes to the default due to
+    // `InitializeFissionExperimentStatus`.
+    gFissionAutostart = Preferences::GetBool(kPrefFissionAutostart, false);
+    if (Preferences::HasUserValue(kPrefFissionAutostart)) {
+      gFissionDecisionStatus = gFissionAutostart
+                                   ? nsIXULRuntime::eFissionEnabledByUserPref
+                                   : nsIXULRuntime::eFissionDisabledByUserPref;
+    } else {
+      gFissionDecisionStatus = gFissionAutostart
+                                   ? nsIXULRuntime::eFissionEnabledByDefault
+                                   : nsIXULRuntime::eFissionDisabledByDefault;
+    }
+  }
+
+  // Content processes cannot run the same logic as we're running in the parent
+  // process, as the current value of various preferences may have changed
+  // between launches. Instead, the content process will read the default branch
+  // of the locked `fission.autostart.session` preference to determine the value
+  // determined by this method.
+  Preferences::Unlock(kPrefFissionAutostartSession);
+  Preferences::ClearUser(kPrefFissionAutostartSession);
+  Preferences::SetBool(kPrefFissionAutostartSession, gFissionAutostart,
+                       PrefValueKind::Default);
+  Preferences::Lock(kPrefFissionAutostartSession);
+}
+
+namespace mozilla {
+
+bool FissionAutostart() {
+  EnsureFissionAutostartInitialized();
+  return gFissionAutostart;
+}
+
+}  // namespace mozilla
+
+// End Fission Infrastructure =========================================
+
+namespace mozilla {
+
+bool SessionHistoryInParent() {
+  return FissionAutostart() ||
+         !StaticPrefs::
+             fission_disableSessionHistoryInParent_AtStartup_DoNotUseDirectly();
+}
+
+bool BFCacheInParent() {
+  return SessionHistoryInParent() &&
+         StaticPrefs::fission_bfcacheInParent_DoNotUseDirectly();
+}
+
+}  // namespace mozilla
+
+/**
+ * The nsXULAppInfo object implements nsIFactory so that it can be its own
+ * singleton.
+ */
+class nsXULAppInfo : public nsIXULAppInfo,
+#ifdef XP_WIN
+                     public nsIWinAppHelper,
+#endif
+                     public nsICrashReporter,
+                     public nsIFinishDumpingCallback,
+                     public nsIXULRuntime
+
+{
+ public:
+  constexpr nsXULAppInfo() = default;
+  NS_DECL_ISUPPORTS_INHERITED
+  NS_DECL_NSIPLATFORMINFO
+  NS_DECL_NSIXULAPPINFO
+  NS_DECL_NSIXULRUNTIME
+  NS_DECL_NSICRASHREPORTER
+  NS_DECL_NSIFINISHDUMPINGCALLBACK
+#ifdef XP_WIN
+  NS_DECL_NSIWINAPPHELPER
+#endif
+};
+
+NS_INTERFACE_MAP_BEGIN(nsXULAppInfo)
+  NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsISupports, nsIXULRuntime)
+  NS_INTERFACE_MAP_ENTRY(nsIXULRuntime)
+#ifdef XP_WIN
+  NS_INTERFACE_MAP_ENTRY(nsIWinAppHelper)
+#endif
+  NS_INTERFACE_MAP_ENTRY(nsICrashReporter)
+  NS_INTERFACE_MAP_ENTRY(nsIFinishDumpingCallback)
+  NS_INTERFACE_MAP_ENTRY(nsIPlatformInfo)
+  NS_INTERFACE_MAP_ENTRY_CONDITIONAL(nsIXULAppInfo,
+                                     gAppData || XRE_IsContentProcess())
+NS_INTERFACE_MAP_END
+
+NS_IMETHODIMP_(MozExternalRefCountType)
+nsXULAppInfo::AddRef() { return 1; }
+
+NS_IMETHODIMP_(MozExternalRefCountType)
+nsXULAppInfo::Release() { return 1; }
+
+NS_IMETHODIMP
+nsXULAppInfo::GetVendor(nsACString& aResult) {
+  if (XRE_IsContentProcess()) {
+    ContentChild* cc = ContentChild::GetSingleton();
+    aResult = cc->GetAppInfo().vendor;
+    return NS_OK;
+  }
+  aResult.Assign(gAppData->vendor);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::GetName(nsACString& aResult) {
+  if (XRE_IsContentProcess()) {
+    ContentChild* cc = ContentChild::GetSingleton();
+    aResult = cc->GetAppInfo().name;
+    return NS_OK;
+  }
+
+#ifdef MOZ_WIDGET_ANDROID
+  nsCString name = java::GeckoAppShell::GetAppName()->ToCString();
+  aResult.Assign(std::move(name));
+#else
+  aResult.Assign(gAppData->name);
+#endif
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::GetID(nsACString& aResult) {
+  if (XRE_IsContentProcess()) {
+    ContentChild* cc = ContentChild::GetSingleton();
+    aResult = cc->GetAppInfo().ID;
+    return NS_OK;
+  }
+  aResult.Assign(gAppData->ID);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::GetVersion(nsACString& aResult) {
+  if (XRE_IsContentProcess()) {
+    ContentChild* cc = ContentChild::GetSingleton();
+    aResult = cc->GetAppInfo().version;
+    return NS_OK;
+  }
+  aResult.Assign(gAppData->version);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::GetPlatformVersion(nsACString& aResult) {
+  aResult.Assign(gToolkitVersion);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::GetAppBuildID(nsACString& aResult) {
+  if (XRE_IsContentProcess()) {
+    ContentChild* cc = ContentChild::GetSingleton();
+    aResult = cc->GetAppInfo().buildID;
+    return NS_OK;
+  }
+  aResult.Assign(gAppData->buildID);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::GetPlatformBuildID(nsACString& aResult) {
+  aResult.Assign(gToolkitBuildID);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::GetUAName(nsACString& aResult) {
+  if (XRE_IsContentProcess()) {
+    ContentChild* cc = ContentChild::GetSingleton();
+    aResult = cc->GetAppInfo().UAName;
+    return NS_OK;
+  }
+  aResult.Assign(gAppData->UAName);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::GetSourceURL(nsACString& aResult) {
+  if (XRE_IsContentProcess()) {
+    ContentChild* cc = ContentChild::GetSingleton();
+    aResult = cc->GetAppInfo().sourceURL;
+    return NS_OK;
+  }
+  aResult.Assign(gAppData->sourceURL);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::GetUpdateURL(nsACString& aResult) {
+  if (XRE_IsContentProcess()) {
+    ContentChild* cc = ContentChild::GetSingleton();
+    aResult = cc->GetAppInfo().updateURL;
+    return NS_OK;
+  }
+  aResult.Assign(gAppData->updateURL);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::GetLogConsoleErrors(bool* aResult) {
+  *aResult = gLogConsoleErrors;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::SetLogConsoleErrors(bool aValue) {
+  gLogConsoleErrors = aValue;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::GetInSafeMode(bool* aResult) {
+  *aResult = gSafeMode;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::GetOS(nsACString& aResult) {
+  aResult.AssignLiteral(OS_TARGET);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::GetXPCOMABI(nsACString& aResult) {
+#ifdef TARGET_XPCOM_ABI
+  aResult.AssignLiteral(TARGET_XPCOM_ABI);
+  return NS_OK;
+#else
+  return NS_ERROR_NOT_AVAILABLE;
+#endif
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::GetWidgetToolkit(nsACString& aResult) {
+  aResult.AssignLiteral(MOZ_WIDGET_TOOLKIT);
+  return NS_OK;
+}
+
+// Ensure that the GeckoProcessType enum, defined in xpcom/build/nsXULAppAPI.h,
+// is synchronized with the const unsigned longs defined in
+// xpcom/system/nsIXULRuntime.idl.
+#define GECKO_PROCESS_TYPE(enum_value, enum_name, string_name, proc_typename, \
+                           process_bin_type, procinfo_typename,               \
+                           webidl_typename, allcaps_name)                     \
+  static_assert(nsIXULRuntime::PROCESS_TYPE_##allcaps_name ==                 \
+                    static_cast<int>(GeckoProcessType_##enum_name),           \
+                "GeckoProcessType in nsXULAppAPI.h not synchronized with "    \
+                "nsIXULRuntime.idl");
+#include "mozilla/GeckoProcessTypes.h"
+#undef GECKO_PROCESS_TYPE
+
+// .. and ensure that that is all of them:
+static_assert(GeckoProcessType_Utility + 1 == GeckoProcessType_End,
+              "Did not find the final GeckoProcessType");
+
+NS_IMETHODIMP
+nsXULAppInfo::GetProcessType(uint32_t* aResult) {
+  NS_ENSURE_ARG_POINTER(aResult);
+  *aResult = XRE_GetProcessType();
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::GetProcessID(uint32_t* aResult) {
+#ifdef XP_WIN
+  *aResult = GetCurrentProcessId();
+#else
+  *aResult = getpid();
+#endif
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::GetUniqueProcessID(uint64_t* aResult) {
+  if (XRE_IsContentProcess()) {
+    ContentChild* cc = ContentChild::GetSingleton();
+    *aResult = cc->GetID();
+  } else {
+    *aResult = 0;
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::GetRemoteType(nsACString& aRemoteType) {
+  if (XRE_IsContentProcess()) {
+    aRemoteType = ContentChild::GetSingleton()->GetRemoteType();
+  } else {
+    aRemoteType = NOT_REMOTE_TYPE;
+  }
+
+  return NS_OK;
+}
+
+static nsCString gLastAppVersion;
+static nsCString gLastAppBuildID;
+
+NS_IMETHODIMP
+nsXULAppInfo::GetLastAppVersion(nsACString& aResult) {
+  if (XRE_IsContentProcess()) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  if (!gLastAppVersion.IsVoid() && gLastAppVersion.IsEmpty()) {
+    NS_WARNING("Attempt to retrieve lastAppVersion before it has been set.");
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  aResult.Assign(gLastAppVersion);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::GetLastAppBuildID(nsACString& aResult) {
+  if (XRE_IsContentProcess()) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  if (!gLastAppBuildID.IsVoid() && gLastAppBuildID.IsEmpty()) {
+    NS_WARNING("Attempt to retrieve lastAppBuildID before it has been set.");
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  aResult.Assign(gLastAppBuildID);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::GetFissionAutostart(bool* aResult) {
+  *aResult = FissionAutostart();
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::GetWin32kExperimentStatus(ExperimentStatus* aResult) {
+  if (!XRE_IsParentProcess()) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  EnsureWin32kInitialized();
+  *aResult = gWin32kExperimentStatus;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::GetWin32kLiveStatusTestingOnly(
+    nsIXULRuntime::ContentWin32kLockdownState* aResult) {
+  if (!XRE_IsParentProcess()) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  EnsureWin32kInitialized();
+  *aResult = GetLiveWin32kLockdownState();
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::GetWin32kSessionStatus(
+    nsIXULRuntime::ContentWin32kLockdownState* aResult) {
+  if (!XRE_IsParentProcess()) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  EnsureWin32kInitialized();
+  *aResult = gWin32kStatus;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::GetFissionDecisionStatus(FissionDecisionStatus* aResult) {
+  if (!XRE_IsParentProcess()) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  EnsureFissionAutostartInitialized();
+
+  MOZ_ASSERT(gFissionDecisionStatus != eFissionStatusUnknown);
+  *aResult = gFissionDecisionStatus;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::GetFissionDecisionStatusString(nsACString& aResult) {
+  if (!XRE_IsParentProcess()) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  EnsureFissionAutostartInitialized();
+  switch (gFissionDecisionStatus) {
+    case eFissionExperimentControl:
+      aResult = "experimentControl";
+      break;
+    case eFissionExperimentTreatment:
+      aResult = "experimentTreatment";
+      break;
+    case eFissionDisabledByE10sEnv:
+      aResult = "disabledByE10sEnv";
+      break;
+    case eFissionEnabledByEnv:
+      aResult = "enabledByEnv";
+      break;
+    case eFissionDisabledByEnv:
+      aResult = "disabledByEnv";
+      break;
+    case eFissionEnabledByDefault:
+      aResult = "enabledByDefault";
+      break;
+    case eFissionDisabledByDefault:
+      aResult = "disabledByDefault";
+      break;
+    case eFissionEnabledByUserPref:
+      aResult = "enabledByUserPref";
+      break;
+    case eFissionDisabledByUserPref:
+      aResult = "disabledByUserPref";
+      break;
+    case eFissionDisabledByE10sOther:
+      aResult = "disabledByE10sOther";
+      break;
+    case eFissionEnabledByRollout:
+      aResult = "enabledByRollout";
+      break;
+    default:
+      MOZ_ASSERT_UNREACHABLE("Unexpected enum value");
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::GetSessionHistoryInParent(bool* aResult) {
+  *aResult = SessionHistoryInParent();
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::GetBrowserTabsRemoteAutostart(bool* aResult) {
+  *aResult = BrowserTabsRemoteAutostart();
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::GetMaxWebProcessCount(uint32_t* aResult) {
+  *aResult = mozilla::GetMaxWebProcessCount();
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::GetAccessibilityEnabled(bool* aResult) {
+#ifdef ACCESSIBILITY
+  *aResult = GetAccService() != nullptr;
+#else
+  *aResult = false;
+#endif
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::GetAccessibilityInstantiator(nsAString& aInstantiator) {
+#if defined(ACCESSIBILITY) && defined(XP_WIN)
+  if (!GetAccService()) {
+    aInstantiator.Truncate();
+    return NS_OK;
+  }
+  nsAutoString ipClientInfo;
+  a11y::Compatibility::GetHumanReadableConsumersStr(ipClientInfo);
+  aInstantiator.Append(ipClientInfo);
+  aInstantiator.AppendLiteral("|");
+
+  nsCOMPtr<nsIFile> oopClientExe;
+  if (a11y::GetInstantiator(getter_AddRefs(oopClientExe))) {
+    nsAutoString oopClientInfo;
+    if (NS_SUCCEEDED(oopClientExe->GetPath(oopClientInfo))) {
+      aInstantiator.Append(oopClientInfo);
+    }
+  }
+#else
+  aInstantiator.Truncate();
+#endif
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::GetShouldBlockIncompatJaws(bool* aResult) {
+  *aResult = false;
+#if defined(ACCESSIBILITY) && defined(XP_WIN)
+  *aResult = mozilla::a11y::Compatibility::IsOldJAWS();
+#endif
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::GetIs64Bit(bool* aResult) {
+#ifdef HAVE_64BIT_BUILD
+  *aResult = true;
+#else
+  *aResult = false;
+#endif
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::GetIsTextRecognitionSupported(bool* aResult) {
+  *aResult = widget::TextRecognition::IsSupported();
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::EnsureContentProcess() {
+  if (!XRE_IsParentProcess()) return NS_ERROR_NOT_AVAILABLE;
+
+  RefPtr<ContentParent> unused =
+      ContentParent::GetNewOrUsedBrowserProcess(DEFAULT_REMOTE_TYPE);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::InvalidateCachesOnRestart() {
+  nsCOMPtr<nsIFile> file;
+  nsresult rv =
+      NS_GetSpecialDirectory(NS_APP_PROFILE_DIR_STARTUP, getter_AddRefs(file));
+  if (NS_FAILED(rv)) return rv;
+  if (!file) return NS_ERROR_NOT_AVAILABLE;
+
+  file->AppendNative(FILE_COMPATIBILITY_INFO);
+
+  nsINIParser parser;
+  rv = parser.Init(file);
+  if (NS_FAILED(rv)) {
+    // This fails if compatibility.ini is not there, so we'll
+    // flush the caches on the next restart anyways.
+    return NS_OK;
+  }
+
+  nsAutoCString buf;
+  rv = parser.GetString("Compatibility", "InvalidateCaches", buf);
+
+  if (NS_FAILED(rv)) {
+    PRFileDesc* fd;
+    rv = file->OpenNSPRFileDesc(PR_RDWR | PR_APPEND, 0600, &fd);
+    if (NS_FAILED(rv)) {
+      NS_ERROR("could not create output stream");
+      return NS_ERROR_NOT_AVAILABLE;
+    }
+    static const char kInvalidationHeader[] =
+        NS_LINEBREAK "InvalidateCaches=1" NS_LINEBREAK;
+    PR_Write(fd, kInvalidationHeader, sizeof(kInvalidationHeader) - 1);
+    PR_Close(fd);
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::GetReplacedLockTime(PRTime* aReplacedLockTime) {
+  if (!gProfileLock) return NS_ERROR_NOT_AVAILABLE;
+  gProfileLock->GetReplacedLockTime(aReplacedLockTime);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::GetDefaultUpdateChannel(nsACString& aResult) {
+  aResult.AssignLiteral(MOZ_STRINGIFY(MOZ_UPDATE_CHANNEL));
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::GetDistributionID(nsACString& aResult) {
+  aResult.AssignLiteral(MOZ_DISTRIBUTION_ID);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::GetWindowsDLLBlocklistStatus(bool* aResult) {
+#if defined(HAS_DLL_BLOCKLIST)
+  *aResult = DllBlocklist_CheckStatus();
+#else
+  *aResult = false;
+#endif
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::GetRestartedByOS(bool* aResult) {
+  *aResult = gRestartedByOS;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::GetChromeColorSchemeIsDark(bool* aResult) {
+  LookAndFeel::EnsureColorSchemesInitialized();
+  *aResult = LookAndFeel::ColorSchemeForChrome() == ColorScheme::Dark;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::GetContentThemeDerivedColorSchemeIsDark(bool* aResult) {
+  *aResult =
+      LookAndFeel::ThemeDerivedColorSchemeForContent() == ColorScheme::Dark;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::GetPrefersReducedMotion(bool* aResult) {
+  *aResult =
+      LookAndFeel::GetInt(LookAndFeel::IntID::PrefersReducedMotion, 0) == 1;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::GetDrawInTitlebar(bool* aResult) {
+  *aResult = LookAndFeel::DrawInTitlebar();
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::GetDesktopEnvironment(nsACString& aDesktopEnvironment) {
+#ifdef MOZ_WIDGET_GTK
+  aDesktopEnvironment.Assign(GetDesktopEnvironmentIdentifier());
+#endif
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::GetProcessStartupShortcut(nsAString& aShortcut) {
+#if defined(XP_WIN)
+  if (XRE_IsParentProcess()) {
+    aShortcut.Assign(gProcessStartupShortcut);
+    return NS_OK;
+  }
+#endif
+  return NS_ERROR_NOT_AVAILABLE;
+}
+
+#if defined(XP_WIN) && defined(MOZ_LAUNCHER_PROCESS)
+// Forward declaration
+void SetupLauncherProcessPref();
+
+static Maybe<LauncherRegistryInfo::EnabledState> gLauncherProcessState;
+#endif  // defined(XP_WIN) && defined(MOZ_LAUNCHER_PROCESS)
+
+NS_IMETHODIMP
+nsXULAppInfo::GetLauncherProcessState(uint32_t* aResult) {
+#if defined(XP_WIN) && defined(MOZ_LAUNCHER_PROCESS)
+  SetupLauncherProcessPref();
+
+  if (!gLauncherProcessState) {
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  *aResult = static_cast<uint32_t>(gLauncherProcessState.value());
+  return NS_OK;
+#else
+  return NS_ERROR_NOT_AVAILABLE;
+#endif
+}
+
+#ifdef XP_WIN
+NS_IMETHODIMP
+nsXULAppInfo::GetUserCanElevate(bool* aUserCanElevate) {
+  HANDLE rawToken;
+  if (!::OpenProcessToken(::GetCurrentProcess(), TOKEN_QUERY, &rawToken)) {
+    *aUserCanElevate = false;
+    return NS_OK;
+  }
+
+  nsAutoHandle token(rawToken);
+  LauncherResult<TOKEN_ELEVATION_TYPE> elevationType = GetElevationType(token);
+  if (elevationType.isErr()) {
+    *aUserCanElevate = false;
+    return NS_OK;
+  }
+
+  // The possible values returned for elevationType and their meanings are:
+  //   TokenElevationTypeDefault: The token does not have a linked token
+  //     (e.g. UAC disabled or a standard user, so they can't be elevated)
+  //   TokenElevationTypeFull: The token is linked to an elevated token
+  //     (e.g. UAC is enabled and the user is already elevated so they can't
+  //      be elevated again)
+  //   TokenElevationTypeLimited: The token is linked to a limited token
+  //     (e.g. UAC is enabled and the user is not elevated, so they can be
+  //      elevated)
+  *aUserCanElevate = (elevationType.inspect() == TokenElevationTypeLimited);
+  return NS_OK;
+}
+#endif
+
+NS_IMETHODIMP
+nsXULAppInfo::GetCrashReporterEnabled(bool* aEnabled) {
+  *aEnabled = CrashReporter::GetEnabled();
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::SetEnabled(bool aEnabled) {
+  if (aEnabled) {
+    if (CrashReporter::GetEnabled()) {
+      // no point in erroring for double-enabling
+      return NS_OK;
+    }
+
+    nsCOMPtr<nsIFile> greBinDir;
+    NS_GetSpecialDirectory(NS_GRE_BIN_DIR, getter_AddRefs(greBinDir));
+    if (!greBinDir) {
+      return NS_ERROR_FAILURE;
+    }
+
+    nsCOMPtr<nsIFile> xreBinDirectory = greBinDir;
+    if (!xreBinDirectory) {
+      return NS_ERROR_FAILURE;
+    }
+
+    return CrashReporter::SetExceptionHandler(xreBinDirectory, true);
+  }
+
+  if (!CrashReporter::GetEnabled()) {
+    // no point in erroring for double-disabling
+    return NS_OK;
+  }
+
+  return CrashReporter::UnsetExceptionHandler();
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::GetServerURL(nsIURL** aServerURL) {
+  NS_ENSURE_ARG_POINTER(aServerURL);
+  if (!CrashReporter::GetEnabled()) return NS_ERROR_NOT_INITIALIZED;
+
+  nsAutoCString data;
+  if (!CrashReporter::GetServerURL(data)) {
+    return NS_ERROR_FAILURE;
+  }
+  nsCOMPtr<nsIURI> uri;
+  NS_NewURI(getter_AddRefs(uri), data);
+  if (!uri) return NS_ERROR_FAILURE;
+
+  nsCOMPtr<nsIURL> url;
+  url = do_QueryInterface(uri);
+  NS_ADDREF(*aServerURL = url);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::SetServerURL(nsIURL* aServerURL) {
+  // Only allow https or http URLs
+  if (!aServerURL->SchemeIs("http") && !aServerURL->SchemeIs("https")) {
+    return NS_ERROR_INVALID_ARG;
+  }
+
+  nsAutoCString spec;
+  nsresult rv = aServerURL->GetSpec(spec);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  return CrashReporter::SetServerURL(spec);
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::GetMinidumpPath(nsIFile** aMinidumpPath) {
+  if (!CrashReporter::GetEnabled()) return NS_ERROR_NOT_INITIALIZED;
+
+  nsAutoString path;
+  if (!CrashReporter::GetMinidumpPath(path)) return NS_ERROR_FAILURE;
+
+  nsresult rv = NS_NewLocalFile(path, false, aMinidumpPath);
+  NS_ENSURE_SUCCESS(rv, rv);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::SetMinidumpPath(nsIFile* aMinidumpPath) {
+  nsAutoString path;
+  nsresult rv = aMinidumpPath->GetPath(path);
+  NS_ENSURE_SUCCESS(rv, rv);
+  return CrashReporter::SetMinidumpPath(path);
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::GetMinidumpForID(const nsAString& aId, nsIFile** aMinidump) {
+  if (!CrashReporter::GetMinidumpForID(aId, aMinidump)) {
+    return NS_ERROR_FILE_NOT_FOUND;
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::GetExtraFileForID(const nsAString& aId, nsIFile** aExtraFile) {
+  if (!CrashReporter::GetExtraFileForID(aId, aExtraFile)) {
+    return NS_ERROR_FILE_NOT_FOUND;
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::AnnotateCrashReport(const nsACString& key,
+                                  const nsACString& data) {
+  CrashReporter::Annotation annotation;
+
+  if (!AnnotationFromString(annotation, PromiseFlatCString(key).get())) {
+    return NS_ERROR_INVALID_ARG;
+  }
+
+  return CrashReporter::AnnotateCrashReport(annotation, data);
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::RemoveCrashReportAnnotation(const nsACString& key) {
+  CrashReporter::Annotation annotation;
+
+  if (!AnnotationFromString(annotation, PromiseFlatCString(key).get())) {
+    return NS_ERROR_INVALID_ARG;
+  }
+
+  return CrashReporter::RemoveCrashReportAnnotation(annotation);
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::IsAnnotationAllowlistedForPing(const nsACString& aValue,
+                                             bool* aIsAllowlisted) {
+  CrashReporter::Annotation annotation;
+
+  if (!AnnotationFromString(annotation, PromiseFlatCString(aValue).get())) {
+    return NS_ERROR_INVALID_ARG;
+  }
+
+  *aIsAllowlisted = CrashReporter::IsAnnotationAllowlistedForPing(annotation);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::AppendAppNotesToCrashReport(const nsACString& data) {
+  return CrashReporter::AppendAppNotesToCrashReport(data);
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::RegisterAppMemory(uint64_t pointer, uint64_t len) {
+  return CrashReporter::RegisterAppMemory((void*)pointer, len);
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::WriteMinidumpForException(void* aExceptionInfo) {
+#ifdef XP_WIN
+  return CrashReporter::WriteMinidumpForException(
+      static_cast<EXCEPTION_POINTERS*>(aExceptionInfo));
+#else
+  return NS_ERROR_NOT_IMPLEMENTED;
+#endif
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::AppendObjCExceptionInfoToAppNotes(void* aException) {
+#ifdef XP_MACOSX
+  return CrashReporter::AppendObjCExceptionInfoToAppNotes(aException);
+#else
+  return NS_ERROR_NOT_IMPLEMENTED;
+#endif
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::GetSubmitReports(bool* aEnabled) {
+  return CrashReporter::GetSubmitReports(aEnabled);
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::SetSubmitReports(bool aEnabled) {
+  return CrashReporter::SetSubmitReports(aEnabled);
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::UpdateCrashEventsDir() {
+  CrashReporter::UpdateCrashEventsDir();
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXULAppInfo::SaveMemoryReport() {
+  if (!CrashReporter::GetEnabled()) {
+    return NS_ERROR_NOT_INITIALIZED;
+  }
+  nsCOMPtr<nsIFile> file;
+  nsresult rv = CrashReporter::GetDefaultMemoryReportFile(getter_AddRefs(file));
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  nsString path;
+  file->GetPath(path);
+
+  nsCOMPtr<nsIMemoryInfoDumper> dumper =
+      do_GetService("@mozilla.org/memory-info-dumper;1");
+  if (NS_WARN_IF(!dumper)) {
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  rv = dumper->DumpMemoryReportsToNamedFile(
+      path, this, file, true /* anonymize */, false /* minimizeMemoryUsage */);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+  return NS_OK;
+}
+
+// This method is from nsIFInishDumpingCallback.
+NS_IMETHODIMP
+nsXULAppInfo::Callback(nsISupports* aData) {
+  nsCOMPtr<nsIFile> file = do_QueryInterface(aData);
+  MOZ_ASSERT(file);
+
+  CrashReporter::SetMemoryReportFile(file);
+  return NS_OK;
+}
+
+static const nsXULAppInfo kAppInfo;
+namespace mozilla {
+nsresult AppInfoConstructor(REFNSIID aIID, void** aResult) {
+  return const_cast<nsXULAppInfo*>(&kAppInfo)->QueryInterface(aIID, aResult);
+}
+}  // namespace mozilla
+
+bool gLogConsoleErrors = false;
+
+#define NS_ENSURE_TRUE_LOG(x, ret)               \
+  PR_BEGIN_MACRO                                 \
+  if (MOZ_UNLIKELY(!(x))) {                      \
+    NS_WARNING("NS_ENSURE_TRUE(" #x ") failed"); \
+    gLogConsoleErrors = true;                    \
+    return ret;                                  \
+  }                                              \
+  PR_END_MACRO
+
+#define NS_ENSURE_SUCCESS_LOG(res, ret) \
+  NS_ENSURE_TRUE_LOG(NS_SUCCEEDED(res), ret)
+
+/**
+ * Because we're starting/stopping XPCOM several times in different scenarios,
+ * this class is a stack-based critter that makes sure that XPCOM is shut down
+ * during early returns.
+ */
+
+class ScopedXPCOMStartup {
+ public:
+  ScopedXPCOMStartup() : mServiceManager(nullptr) {}
+  ~ScopedXPCOMStartup();
+
+  nsresult Initialize(bool aInitJSContext = true);
+  nsresult SetWindowCreator(nsINativeAppSupport* native);
+
+ private:
+  nsIServiceManager* mServiceManager;
+  static nsINativeAppSupport* gNativeAppSupport;
+
+  friend already_AddRefed<nsINativeAppSupport> NS_GetNativeAppSupport();
+};
+
+ScopedXPCOMStartup::~ScopedXPCOMStartup() {
+  NS_IF_RELEASE(gNativeAppSupport);
+
+  if (mServiceManager) {
+#ifdef XP_MACOSX
+    // On OS X, we need a pool to catch cocoa objects that are autoreleased
+    // during teardown.
+    mozilla::MacAutoreleasePool pool;
+#endif
+
+    nsCOMPtr<nsIAppStartup> appStartup(components::AppStartup::Service());
+    if (appStartup) appStartup->DestroyHiddenWindow();
+
+    gDirServiceProvider->DoShutdown();
+    PROFILER_MARKER_UNTYPED("Shutdown early", OTHER);
+
+    WriteConsoleLog();
+
+    NS_ShutdownXPCOM(mServiceManager);
+    mServiceManager = nullptr;
+  }
+}
+
+nsresult ScopedXPCOMStartup::Initialize(bool aInitJSContext) {
+  NS_ASSERTION(gDirServiceProvider, "Should not get here!");
+
+  nsresult rv;
+
+  rv = NS_InitXPCOM(&mServiceManager, gDirServiceProvider->GetAppDir(),
+                    gDirServiceProvider, aInitJSContext);
+  if (NS_FAILED(rv)) {
+    NS_ERROR("Couldn't start xpcom!");
+    mServiceManager = nullptr;
+  } else {
+#ifdef DEBUG
+    nsCOMPtr<nsIComponentRegistrar> reg = do_QueryInterface(mServiceManager);
+    NS_ASSERTION(reg, "Service Manager doesn't QI to Registrar.");
+#endif
+  }
+
+  return rv;
+}
+
+/**
+ * This is a little factory class that serves as a singleton-service-factory
+ * for the nativeappsupport object.
+ */
+class nsSingletonFactory final : public nsIFactory {
+ public:
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIFACTORY
+
+  explicit nsSingletonFactory(nsISupports* aSingleton);
+
+ private:
+  ~nsSingletonFactory() = default;
+  nsCOMPtr<nsISupports> mSingleton;
+};
+
+nsSingletonFactory::nsSingletonFactory(nsISupports* aSingleton)
+    : mSingleton(aSingleton) {
+  NS_ASSERTION(mSingleton, "Singleton was null!");
+}
+
+NS_IMPL_ISUPPORTS(nsSingletonFactory, nsIFactory)
+
+NS_IMETHODIMP
+nsSingletonFactory::CreateInstance(const nsIID& aIID, void** aResult) {
+  return mSingleton->QueryInterface(aIID, aResult);
+}
+
+/**
+ * Set our windowcreator on the WindowWatcher service.
+ */
+nsresult ScopedXPCOMStartup::SetWindowCreator(nsINativeAppSupport* native) {
+  nsresult rv;
+
+  NS_IF_ADDREF(gNativeAppSupport = native);
+
+  nsCOMPtr<nsIWindowCreator> creator(components::AppStartup::Service());
+  if (!creator) return NS_ERROR_UNEXPECTED;
+
+  nsCOMPtr<nsIWindowWatcher> wwatch(
+      do_GetService(NS_WINDOWWATCHER_CONTRACTID, &rv));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  return wwatch->SetWindowCreator(creator);
+}
+
+/* static */ already_AddRefed<nsINativeAppSupport> NS_GetNativeAppSupport() {
+  if (!ScopedXPCOMStartup::gNativeAppSupport) {
+    return nullptr;
+  }
+
+  return do_AddRef(ScopedXPCOMStartup::gNativeAppSupport);
+}
+
+nsINativeAppSupport* ScopedXPCOMStartup::gNativeAppSupport;
+
+static void DumpArbitraryHelp() {
+  nsresult rv;
+
+  ScopedLogging log;
+
+  {
+    ScopedXPCOMStartup xpcom;
+    xpcom.Initialize();
+
+    nsCOMPtr<nsICommandLineRunner> cmdline(new nsCommandLine());
+
+    nsCString text;
+    rv = cmdline->GetHelpText(text);
+    if (NS_SUCCEEDED(rv)) printf("%s", text.get());
+  }
+}
+
+// English text needs to go into a dtd file.
+// But when this is called we have no components etc. These strings must either
+// be here, or in a native resource file.
+static void DumpHelp() {
+  printf(
+      "Usage: %s [ options ... ] [URL]\n"
+      "       where options include:\n\n",
+      gArgv[0]);
+
+#ifdef MOZ_X11
+  printf(
+      "X11 options\n"
+      "  --display=DISPLAY  X display to use\n"
+      "  --sync             Make X calls synchronous\n");
+#endif
+#ifdef XP_UNIX
+  printf(
+      "  --g-fatal-warnings Make all warnings fatal\n"
+      "\n%s options\n",
+      (const char*)gAppData->name);
+#endif
+
+  printf(
+      "  -h or --help       Print this message.\n"
+      "  -v or --version    Print %s version.\n"
+      "  --full-version     Print %s version, build and platform build ids.\n"
+      "  -P <profile>       Start with <profile>.\n"
+      "  --profile <path>   Start with profile at <path>.\n"
+      "  --migration        Start with migration wizard.\n"
+      "  --ProfileManager   Start with ProfileManager.\n"
+#ifdef MOZ_HAS_REMOTE
+      "  --no-remote        Do not accept or send remote commands; implies\n"
+      "                     --new-instance.\n"
+      "  --new-instance     Open new instance, not a new window in running "
+      "instance.\n"
+#endif
+      "  --safe-mode        Disables extensions and themes for this session.\n"
+#ifdef MOZ_BLOCK_PROFILE_DOWNGRADE
+      "  --allow-downgrade  Allows downgrading a profile.\n"
+#endif
+      "  --MOZ_LOG=<modules> Treated as MOZ_LOG=<modules> environment "
+      "variable,\n"
+      "                     overrides it.\n"
+      "  --MOZ_LOG_FILE=<file> Treated as MOZ_LOG_FILE=<file> environment "
+      "variable,\n"
+      "                     overrides it. If MOZ_LOG_FILE is not specified as "
+      "an\n"
+      "                     argument or as an environment variable, logging "
+      "will be\n"
+      "                     written to stdout.\n",
+      (const char*)gAppData->name, (const char*)gAppData->name);
+
+#if defined(XP_WIN)
+  printf("  --console          Start %s with a debugging console.\n",
+         (const char*)gAppData->name);
+#endif
+
+#if defined(XP_WIN) || defined(MOZ_WIDGET_GTK) || defined(XP_MACOSX)
+  printf("  --headless         Run without a GUI.\n");
+#endif
+
+  // this works, but only after the components have registered.  so if you drop
+  // in a new command line handler, --help won't not until the second run. out
+  // of the bug, because we ship a component.reg file, it works correctly.
+  DumpArbitraryHelp();
+}
+
+static inline void DumpVersion() {
+  if (gAppData->vendor && *gAppData->vendor) {
+    printf("%s ", (const char*)gAppData->vendor);
+  }
+  printf("%s ", (const char*)gAppData->name);
+
+  // Use the displayed version
+  // For example, for beta, we would display 42.0b2 instead of 42.0
+  printf("%s", MOZ_STRINGIFY(MOZ_APP_VERSION_DISPLAY));
+
+  if (gAppData->copyright && *gAppData->copyright) {
+    printf(", %s", (const char*)gAppData->copyright);
+  }
+  printf("\n");
+}
+
+static inline void DumpFullVersion() {
+  if (gAppData->vendor && *gAppData->vendor) {
+    printf("%s ", (const char*)gAppData->vendor);
+  }
+  printf("%s ", (const char*)gAppData->name);
+
+  // Use the displayed version
+  // For example, for beta, we would display 42.0b2 instead of 42.0
+  printf("%s ", MOZ_STRINGIFY(MOZ_APP_VERSION_DISPLAY));
+
+  printf("%s ", (const char*)gAppData->buildID);
+  printf("%s ", (const char*)PlatformBuildID());
+  if (gAppData->copyright && *gAppData->copyright) {
+    printf(", %s", (const char*)gAppData->copyright);
+  }
+  printf("\n");
+}
+
+void XRE_InitOmnijar(nsIFile* greOmni, nsIFile* appOmni) {
+  mozilla::Omnijar::Init(greOmni, appOmni);
+}
+
+nsresult XRE_GetBinaryPath(nsIFile** aResult) {
+  return mozilla::BinaryPath::GetFile(aResult);
+}
+
+#ifdef XP_WIN
+#  include "nsWindowsRestart.cpp"
+#  include <shellapi.h>
+
+typedef BOOL(WINAPI* SetProcessDEPPolicyFunc)(DWORD dwFlags);
+
+static void RegisterApplicationRestartChanged(const char* aPref, void* aData) {
+  DWORD cchCmdLine = 0;
+  HRESULT rc = ::GetApplicationRestartSettings(::GetCurrentProcess(), nullptr,
+                                               &cchCmdLine, nullptr);
+  bool wasRegistered = false;
+  if (rc == S_OK) {
+    wasRegistered = true;
+  }
+
+  if (Preferences::GetBool(PREF_WIN_REGISTER_APPLICATION_RESTART, false) &&
+      !wasRegistered) {
+    // Make the command line to use when restarting.
+    // Excludes argv[0] because RegisterApplicationRestart adds the
+    // executable name, replace that temporarily with -os-restarted
+    char* exeName = gRestartArgv[0];
+    gRestartArgv[0] = const_cast<char*>("-os-restarted");
+    wchar_t** restartArgvConverted =
+        AllocConvertUTF8toUTF16Strings(gRestartArgc, gRestartArgv);
+    gRestartArgv[0] = exeName;
+
+    mozilla::UniquePtr<wchar_t[]> restartCommandLine;
+    if (restartArgvConverted) {
+      restartCommandLine =
+          mozilla::MakeCommandLine(gRestartArgc, restartArgvConverted);
+      FreeAllocStrings(gRestartArgc, restartArgvConverted);
+    }
+
+    if (restartCommandLine) {
+      // Flags RESTART_NO_PATCH and RESTART_NO_REBOOT are not set, so we
+      // should be restarted if terminated by an update or restart.
+      ::RegisterApplicationRestart(restartCommandLine.get(),
+                                   RESTART_NO_CRASH | RESTART_NO_HANG);
+    }
+  } else if (wasRegistered) {
+    ::UnregisterApplicationRestart();
+  }
+}
+
+static void OnAlteredPrefetchPrefChanged(const char* aPref, void* aData) {
+  int32_t prefVal = Preferences::GetInt(PREF_WIN_ALTERED_DLL_PREFETCH, 0);
+
+  mozilla::DllPrefetchExperimentRegistryInfo prefetchRegInfo;
+  mozilla::DebugOnly<mozilla::Result<Ok, nsresult>> reflectResult =
+      prefetchRegInfo.ReflectPrefToRegistry(prefVal);
+
+  MOZ_ASSERT(reflectResult.value.isOk());
+}
+
+static void SetupAlteredPrefetchPref() {
+  mozilla::DllPrefetchExperimentRegistryInfo prefetchRegInfo;
+
+  mozilla::DebugOnly<mozilla::Result<Ok, nsresult>> reflectResult =
+      prefetchRegInfo.ReflectPrefToRegistry(
+          Preferences::GetInt(PREF_WIN_ALTERED_DLL_PREFETCH, 0));
+  MOZ_ASSERT(reflectResult.value.isOk());
+
+  Preferences::RegisterCallback(&OnAlteredPrefetchPrefChanged,
+                                PREF_WIN_ALTERED_DLL_PREFETCH);
+}
+
+static void ReflectSkeletonUIPrefToRegistry(const char* aPref, void* aData) {
+  Unused << aPref;
+  Unused << aData;
+
+  bool shouldBeEnabled =
+      Preferences::GetBool(kPrefPreXulSkeletonUI, false) &&
+      Preferences::GetBool(kPrefBrowserStartupBlankWindow, false) &&
+      LookAndFeel::DrawInTitlebar();
+  if (shouldBeEnabled && Preferences::HasUserValue(kPrefThemeId)) {
+    nsCString themeId;
+    Preferences::GetCString(kPrefThemeId, themeId);
+    if (themeId.EqualsLiteral("default-theme@mozilla.org")) {
+      Unused << SetPreXULSkeletonUIThemeId(ThemeMode::Default);
+    } else if (themeId.EqualsLiteral("firefox-compact-dark@mozilla.org")) {
+      Unused << SetPreXULSkeletonUIThemeId(ThemeMode::Dark);
+    } else if (themeId.EqualsLiteral("firefox-compact-light@mozilla.org")) {
+      Unused << SetPreXULSkeletonUIThemeId(ThemeMode::Light);
+    } else {
+      shouldBeEnabled = false;
+    }
+  } else if (shouldBeEnabled) {
+    Unused << SetPreXULSkeletonUIThemeId(ThemeMode::Default);
+  }
+
+  if (GetPreXULSkeletonUIEnabled() != shouldBeEnabled) {
+    Unused << SetPreXULSkeletonUIEnabledIfAllowed(shouldBeEnabled);
+  }
+}
+
+static void SetupSkeletonUIPrefs() {
+  ReflectSkeletonUIPrefToRegistry(nullptr, nullptr);
+  Preferences::RegisterCallback(&ReflectSkeletonUIPrefToRegistry,
+                                kPrefPreXulSkeletonUI);
+  Preferences::RegisterCallback(&ReflectSkeletonUIPrefToRegistry,
+                                kPrefBrowserStartupBlankWindow);
+  Preferences::RegisterCallback(&ReflectSkeletonUIPrefToRegistry, kPrefThemeId);
+  Preferences::RegisterCallback(
+      &ReflectSkeletonUIPrefToRegistry,
+      nsDependentCString(StaticPrefs::GetPrefName_browser_tabs_inTitlebar()));
+}
+
+#  if defined(MOZ_LAUNCHER_PROCESS)
+
+static void OnLauncherPrefChanged(const char* aPref, void* aData) {
+  bool prefVal = Preferences::GetBool(PREF_WIN_LAUNCHER_PROCESS_ENABLED, true);
+
+  mozilla::LauncherRegistryInfo launcherRegInfo;
+  mozilla::DebugOnly<mozilla::LauncherVoidResult> reflectResult =
+      launcherRegInfo.ReflectPrefToRegistry(prefVal);
+  MOZ_ASSERT(reflectResult.inspect().isOk());
+}
+
+static void OnLauncherTelemetryPrefChanged(const char* aPref, void* aData) {
+  bool prefVal = Preferences::GetBool(kPrefHealthReportUploadEnabled, true);
+
+  mozilla::LauncherRegistryInfo launcherRegInfo;
+  mozilla::DebugOnly<mozilla::LauncherVoidResult> reflectResult =
+      launcherRegInfo.ReflectTelemetryPrefToRegistry(prefVal);
+  MOZ_ASSERT(reflectResult.inspect().isOk());
+}
+
+static void SetupLauncherProcessPref() {
+  if (gLauncherProcessState) {
+    // We've already successfully run
+    return;
+  }
+
+  mozilla::LauncherRegistryInfo launcherRegInfo;
+
+  mozilla::LauncherResult<mozilla::LauncherRegistryInfo::EnabledState>
+      enabledState = launcherRegInfo.IsEnabled();
+
+  if (enabledState.isOk()) {
+    gLauncherProcessState = Some(enabledState.unwrap());
+
+    CrashReporter::AnnotateCrashReport(
+        CrashReporter::Annotation::LauncherProcessState,
+        static_cast<uint32_t>(enabledState.unwrap()));
+
+    // Reflect the launcher process registry state into user prefs
+    Preferences::SetBool(
+        PREF_WIN_LAUNCHER_PROCESS_ENABLED,
+        enabledState.unwrap() !=
+            mozilla::LauncherRegistryInfo::EnabledState::ForceDisabled);
+  }
+
+  mozilla::DebugOnly<mozilla::LauncherVoidResult> reflectResult =
+      launcherRegInfo.ReflectTelemetryPrefToRegistry(
+          Preferences::GetBool(kPrefHealthReportUploadEnabled, true));
+  MOZ_ASSERT(reflectResult.inspect().isOk());
+
+  Preferences::RegisterCallback(&OnLauncherPrefChanged,
+                                PREF_WIN_LAUNCHER_PROCESS_ENABLED);
+  Preferences::RegisterCallback(&OnLauncherTelemetryPrefChanged,
+                                kPrefHealthReportUploadEnabled);
+}
+
+#  endif  // defined(MOZ_LAUNCHER_PROCESS)
+
+#  if defined(MOZ_DEFAULT_BROWSER_AGENT)
+
+#    define DEFAULT_BROWSER_AGENT_KEY_NAME \
+      "SOFTWARE\\" MOZ_APP_VENDOR "\\" MOZ_APP_NAME "\\Default Browser Agent"
+
+static nsresult PrependRegistryValueName(nsAutoString& aValueName) {
+  nsresult rv;
+
+  nsCOMPtr<nsIFile> binaryPath;
+  rv = XRE_GetBinaryPath(getter_AddRefs(binaryPath));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsCOMPtr<nsIFile> binaryDir;
+  rv = binaryPath->GetParent(getter_AddRefs(binaryDir));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsAutoString prefix;
+  rv = binaryDir->GetPath(prefix);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  prefix.AppendLiteral("|");
+  aValueName.Insert(prefix, 0);
+
+  return NS_OK;
+}
+
+static void OnDefaultAgentTelemetryPrefChanged(const char* aPref, void* aData) {
+  nsresult rv;
+  nsAutoString valueName;
+  if (strcmp(aPref, kPrefHealthReportUploadEnabled) == 0) {
+    valueName.AssignLiteral("DisableTelemetry");
+  } else if (strcmp(aPref, kPrefDefaultAgentEnabled) == 0) {
+    valueName.AssignLiteral("DisableDefaultBrowserAgent");
+  } else {
+    return;
+  }
+  rv = PrependRegistryValueName(valueName);
+  NS_ENSURE_SUCCESS_VOID(rv);
+
+  nsCOMPtr<nsIWindowsRegKey> regKey =
+      do_CreateInstance("@mozilla.org/windows-registry-key;1", &rv);
+  NS_ENSURE_SUCCESS_VOID(rv);
+
+  nsAutoString keyName;
+  keyName.AppendLiteral(DEFAULT_BROWSER_AGENT_KEY_NAME);
+  rv = regKey->Create(nsIWindowsRegKey::ROOT_KEY_CURRENT_USER, keyName,
+                      nsIWindowsRegKey::ACCESS_WRITE);
+
+  bool prefVal = Preferences::GetBool(aPref, true);
+
+  // We're recording whether the pref is *disabled*, so invert the value.
+  rv = regKey->WriteIntValue(valueName, prefVal ? 0 : 1);
+  NS_ENSURE_SUCCESS_VOID(rv);
+}
+
+static void OnSetDefaultBrowserUserChoicePrefChanged(const char* aPref,
+                                                     void* aData) {
+  nsresult rv;
+  if (strcmp(aPref, kPrefSetDefaultBrowserUserChoicePref) != 0) {
+    return;
+  }
+  nsAutoString valueName;
+  valueName.AssignLiteral("SetDefaultBrowserUserChoice");
+  rv = PrependRegistryValueName(valueName);
+  NS_ENSURE_SUCCESS_VOID(rv);
+
+  nsCOMPtr<nsIWindowsRegKey> regKey =
+      do_CreateInstance("@mozilla.org/windows-registry-key;1", &rv);
+  NS_ENSURE_SUCCESS_VOID(rv);
+
+  nsAutoString keyName;
+  keyName.AppendLiteral(DEFAULT_BROWSER_AGENT_KEY_NAME);
+  rv = regKey->Create(nsIWindowsRegKey::ROOT_KEY_CURRENT_USER, keyName,
+                      nsIWindowsRegKey::ACCESS_WRITE);
+
+  bool prefVal = Preferences::GetBool(aPref, true);
+
+  rv = regKey->WriteIntValue(valueName, prefVal);
+  NS_ENSURE_SUCCESS_VOID(rv);
+}
+
+static void OnDefaultAgentRemoteSettingsPrefChanged(const char* aPref,
+                                                    void* aData) {
+  nsresult rv;
+  nsAutoString valueName;
+  if (strcmp(aPref, kPrefServicesSettingsServer) == 0) {
+    valueName.AssignLiteral("ServicesSettingsServer");
+  } else if (strcmp(aPref, kPrefSecurityContentSignatureRootHash) == 0) {
+    valueName.AssignLiteral("SecurityContentSignatureRootHash");
+  } else {
+    return;
+  }
+  rv = PrependRegistryValueName(valueName);
+  NS_ENSURE_SUCCESS_VOID(rv);
+
+  nsCOMPtr<nsIWindowsRegKey> regKey =
+      do_CreateInstance("@mozilla.org/windows-registry-key;1", &rv);
+  NS_ENSURE_SUCCESS_VOID(rv);
+
+  nsAutoString keyName;
+  keyName.AppendLiteral(DEFAULT_BROWSER_AGENT_KEY_NAME);
+  rv = regKey->Create(nsIWindowsRegKey::ROOT_KEY_CURRENT_USER, keyName,
+                      nsIWindowsRegKey::ACCESS_WRITE);
+
+  NS_ENSURE_SUCCESS_VOID(rv);
+
+  nsAutoString prefVal;
+  rv = Preferences::GetString(aPref, prefVal);
+  NS_ENSURE_SUCCESS_VOID(rv);
+
+  if (prefVal.IsEmpty()) {
+    rv = regKey->RemoveValue(valueName);
+  } else {
+    rv = regKey->WriteStringValue(valueName, prefVal);
+  }
+  NS_ENSURE_SUCCESS_VOID(rv);
+}
+
+static void SetDefaultAgentLastRunTime() {
+  nsresult rv;
+  nsAutoString valueName;
+  valueName.AppendLiteral("AppLastRunTime");
+  rv = PrependRegistryValueName(valueName);
+  NS_ENSURE_SUCCESS_VOID(rv);
+
+  nsCOMPtr<nsIWindowsRegKey> regKey =
+      do_CreateInstance("@mozilla.org/windows-registry-key;1", &rv);
+  NS_ENSURE_SUCCESS_VOID(rv);
+
+  nsAutoString keyName;
+  keyName.AppendLiteral(DEFAULT_BROWSER_AGENT_KEY_NAME);
+  rv = regKey->Create(nsIWindowsRegKey::ROOT_KEY_CURRENT_USER, keyName,
+                      nsIWindowsRegKey::ACCESS_WRITE);
+  NS_ENSURE_SUCCESS_VOID(rv);
+
+  FILETIME fileTime;
+  GetSystemTimeAsFileTime(&fileTime);
+
+  ULARGE_INTEGER integerTime;
+  integerTime.u.LowPart = fileTime.dwLowDateTime;
+  integerTime.u.HighPart = fileTime.dwHighDateTime;
+
+  rv = regKey->WriteInt64Value(valueName, integerTime.QuadPart);
+  NS_ENSURE_SUCCESS_VOID(rv);
+}
+
+#  endif  // defined(MOZ_DEFAULT_BROWSER_AGENT)
+
+#endif  // XP_WIN
+
+void UnlockProfile() {
+  if (gProfileLock) {
+    gProfileLock->Unlock();
+  }
+}
+
+nsresult LaunchChild(bool aBlankCommandLine, bool aTryExec) {
+  // Restart this process by exec'ing it into the current process
+  // if supported by the platform.  Otherwise, use NSPR.
+
+#ifdef MOZ_JPROF
+  // make sure JPROF doesn't think we're E10s
+  unsetenv("JPROF_ISCHILD");
+#endif
+
+  if (aBlankCommandLine) {
+    gRestartArgc = 1;
+    gRestartArgv[gRestartArgc] = nullptr;
+  }
+
+#if defined(MOZ_HAS_REMOTE)
+  if (gRestartWithoutRemote) {
+    SaveToEnv("MOZ_NO_REMOTE=1");
+  }
+#endif
+
+  SaveToEnv("MOZ_LAUNCHED_CHILD=1");
+#if defined(MOZ_LAUNCHER_PROCESS)
+  SaveToEnv("MOZ_LAUNCHER_PROCESS=1");
+#endif  // defined(MOZ_LAUNCHER_PROCESS)
+
+#if !defined(MOZ_WIDGET_ANDROID)  // Android has separate restart code.
+#  if defined(XP_MACOSX)
+  CommandLineServiceMac::SetupMacCommandLine(gRestartArgc, gRestartArgv, true);
+  LaunchChildMac(gRestartArgc, gRestartArgv);
+#  else
+  nsCOMPtr<nsIFile> lf;
+  nsresult rv = XRE_GetBinaryPath(getter_AddRefs(lf));
+  if (NS_FAILED(rv)) return rv;
+
+#    if defined(XP_WIN)
+  nsAutoString exePath;
+  rv = lf->GetPath(exePath);
+  if (NS_FAILED(rv)) return rv;
+
+  HANDLE hProcess;
+  if (!WinLaunchChild(exePath.get(), gRestartArgc, gRestartArgv, nullptr,
+                      &hProcess))
+    return NS_ERROR_FAILURE;
+  // Keep the current process around until the restarted process has created
+  // its message queue, to avoid the launched process's windows being forced
+  // into the background.
+  mozilla::WaitForInputIdle(hProcess);
+  ::CloseHandle(hProcess);
+
+#    else
+  nsAutoCString exePath;
+  rv = lf->GetNativePath(exePath);
+  if (NS_FAILED(rv)) return rv;
+
+#      if defined(XP_UNIX)
+  if (aTryExec) {
+    execv(exePath.get(), gRestartArgv);
+
+    // If execv returns we know it's because it failed.
+    return NS_ERROR_FAILURE;
+  }
+#      endif
+  if (PR_CreateProcessDetached(exePath.get(), gRestartArgv, nullptr, nullptr) ==
+      PR_FAILURE) {
+    return NS_ERROR_FAILURE;
+  }
+
+  // Note that we don't know if the child process starts okay, if it
+  // immediately returns non-zero then we may mask that by returning a zero
+  // exit status.
+
+#    endif  // WP_WIN
+#  endif    // WP_MACOSX
+#endif      // MOZ_WIDGET_ANDROID
+
+  return NS_ERROR_LAUNCHED_CHILD_PROCESS;
+}
+
+static const char kProfileProperties[] =
+    "chrome://mozapps/locale/profile/profileSelection.properties";
+
+namespace {
+
+/**
+ * This class, instead of a raw nsresult, should be the return type of any
+ * function called by SelectProfile that initializes XPCOM.
+ */
+class ReturnAbortOnError {
+ public:
+  MOZ_IMPLICIT ReturnAbortOnError(nsresult aRv) { mRv = ConvertRv(aRv); }
+
+  operator nsresult() { return mRv; }
+
+ private:
+  inline nsresult ConvertRv(nsresult aRv) {
+    if (NS_SUCCEEDED(aRv) || aRv == NS_ERROR_LAUNCHED_CHILD_PROCESS) {
+      return aRv;
+    }
+#ifdef MOZ_BACKGROUNDTASKS
+    // A background task that fails to lock its profile will return
+    // NS_ERROR_UNEXPECTED and this will allow the task to exit with a
+    // non-zero exit code.
+    if (aRv == NS_ERROR_UNEXPECTED && BackgroundTasks::IsBackgroundTaskMode()) {
+      return aRv;
+    }
+#endif
+    return NS_ERROR_ABORT;
+  }
+
+  nsresult mRv;
+};
+
+}  // namespace
+
+static nsresult ProfileMissingDialog(nsINativeAppSupport* aNative) {
+#ifdef MOZ_WIDGET_ANDROID
+  // We cannot really do anything this early during initialization, so we just
+  // return as this is likely the effect of misconfiguration on the test side.
+  // Non-test code paths cannot set the profile folder, which is always the
+  // default one.
+  Output(true, "Could not find profile folder.\n");
+  return NS_ERROR_ABORT;
+#else
+#  ifdef MOZ_BACKGROUNDTASKS
+  if (BackgroundTasks::IsBackgroundTaskMode()) {
+    // We should never get to this point in background task mode.
+    Output(false,
+           "Could not determine any profile running in backgroundtask mode!\n");
+    return NS_ERROR_ABORT;
+  }
+#  endif  // MOZ_BACKGROUNDTASKS
+
+  nsresult rv;
+
+  ScopedXPCOMStartup xpcom;
+  rv = xpcom.Initialize();
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  rv = xpcom.SetWindowCreator(aNative);
+  NS_ENSURE_SUCCESS(rv, NS_ERROR_FAILURE);
+
+  {  // extra scoping is needed so we release these components before xpcom
+     // shutdown
+    nsCOMPtr<nsIStringBundleService> sbs =
+        mozilla::components::StringBundle::Service();
+    NS_ENSURE_TRUE(sbs, NS_ERROR_FAILURE);
+
+    nsCOMPtr<nsIStringBundle> sb;
+    sbs->CreateBundle(kProfileProperties, getter_AddRefs(sb));
+    NS_ENSURE_TRUE_LOG(sbs, NS_ERROR_FAILURE);
+
+    NS_ConvertUTF8toUTF16 appName(gAppData->name);
+    AutoTArray<nsString, 2> params = {appName, appName};
+
+    // profileMissing
+    nsAutoString missingMessage;
+    rv = sb->FormatStringFromName("profileMissing", params, missingMessage);
+    NS_ENSURE_SUCCESS(rv, NS_ERROR_ABORT);
+
+    nsAutoString missingTitle;
+    params.SetLength(1);
+    rv = sb->FormatStringFromName("profileMissingTitle", params, missingTitle);
+    NS_ENSURE_SUCCESS(rv, NS_ERROR_ABORT);
+
+    nsCOMPtr<nsIPromptService> ps(do_GetService(NS_PROMPTSERVICE_CONTRACTID));
+    NS_ENSURE_TRUE(ps, NS_ERROR_FAILURE);
+
+    ps->Alert(nullptr, missingTitle.get(), missingMessage.get());
+
+    return NS_ERROR_ABORT;
+  }
+#endif    // MOZ_WIDGET_ANDROID
+}
+
+static ReturnAbortOnError ProfileLockedDialog(nsIFile* aProfileDir,
+                                              nsIFile* aProfileLocalDir,
+                                              nsIProfileUnlocker* aUnlocker,
+                                              nsINativeAppSupport* aNative,
+                                              nsIProfileLock** aResult) {
+  nsresult rv;
+
+  bool exists;
+  aProfileDir->Exists(&exists);
+  if (!exists) {
+    return ProfileMissingDialog(aNative);
+  }
+
+  ScopedXPCOMStartup xpcom;
+  rv = xpcom.Initialize();
+  NS_ENSURE_SUCCESS(rv, rv);
+
+#if defined(MOZ_TELEMETRY_REPORTING)
+  // We cannot check if telemetry has been disabled by the user, yet.
+  // So, rely on the build time settings, instead.
+  mozilla::Telemetry::WriteFailedProfileLock(aProfileDir);
+#endif
+
+  rv = xpcom.SetWindowCreator(aNative);
+  NS_ENSURE_SUCCESS(rv, NS_ERROR_FAILURE);
+
+  {  // extra scoping is needed so we release these components before xpcom
+     // shutdown
+    nsCOMPtr<nsIStringBundleService> sbs =
+        mozilla::components::StringBundle::Service();
+    NS_ENSURE_TRUE(sbs, NS_ERROR_FAILURE);
+
+    nsCOMPtr<nsIStringBundle> sb;
+    sbs->CreateBundle(kProfileProperties, getter_AddRefs(sb));
+    NS_ENSURE_TRUE_LOG(sbs, NS_ERROR_FAILURE);
+
+    NS_ConvertUTF8toUTF16 appName(gAppData->name);
+    AutoTArray<nsString, 3> params = {appName, appName, appName};
+
+    nsAutoString killMessage;
+#ifndef XP_MACOSX
+    rv = sb->FormatStringFromName(
+        aUnlocker ? "restartMessageUnlocker" : "restartMessageNoUnlocker2",
+        params, killMessage);
+#else
+    rv = sb->FormatStringFromName(
+        aUnlocker ? "restartMessageUnlockerMac" : "restartMessageNoUnlockerMac",
+        params, killMessage);
+#endif
+    NS_ENSURE_SUCCESS(rv, NS_ERROR_FAILURE);
+
+    params.SetLength(1);
+    nsAutoString killTitle;
+    rv = sb->FormatStringFromName("restartTitle", params, killTitle);
+    NS_ENSURE_SUCCESS(rv, NS_ERROR_FAILURE);
+
+#ifdef MOZ_BACKGROUNDTASKS
+    if (BackgroundTasks::IsBackgroundTaskMode()) {
+      // This error is handled specially to exit with a non-zero exit code.
+      printf_stderr("%s\n", NS_LossyConvertUTF16toASCII(killMessage).get());
+      return NS_ERROR_UNEXPECTED;
+    }
+#endif
+
+    if (gfxPlatform::IsHeadless()) {
+      // TODO: make a way to turn off all dialogs when headless.
+      Output(true, "%s\n", NS_LossyConvertUTF16toASCII(killMessage).get());
+      return NS_ERROR_FAILURE;
+    }
+
+    nsCOMPtr<nsIPromptService> ps(do_GetService(NS_PROMPTSERVICE_CONTRACTID));
+    NS_ENSURE_TRUE(ps, NS_ERROR_FAILURE);
+
+    if (aUnlocker) {
+      int32_t button;
+#ifdef MOZ_WIDGET_ANDROID
+      // On Android we always kill the process if the lock is still being held
+      button = 0;
+#else
+      const uint32_t flags = (nsIPromptService::BUTTON_TITLE_IS_STRING *
+                              nsIPromptService::BUTTON_POS_0) +
+                             (nsIPromptService::BUTTON_TITLE_CANCEL *
+                              nsIPromptService::BUTTON_POS_1);
+
+      bool checkState = false;
+      rv = ps->ConfirmEx(nullptr, killTitle.get(), killMessage.get(), flags,
+                         killTitle.get(), nullptr, nullptr, nullptr,
+                         &checkState, &button);
+      NS_ENSURE_SUCCESS_LOG(rv, rv);
+#endif
+
+      if (button == 0) {
+        rv = aUnlocker->Unlock(nsIProfileUnlocker::FORCE_QUIT);
+        if (NS_FAILED(rv)) {
+          return rv;
+        }
+
+        SaveFileToEnv("XRE_PROFILE_PATH", aProfileDir);
+        SaveFileToEnv("XRE_PROFILE_LOCAL_PATH", aProfileLocalDir);
+
+#if defined(MOZ_HAS_REMOTE)
+        if (gRemoteService) {
+          gRemoteService->UnlockStartup();
+          gRemoteService = nullptr;
+        }
+#endif
+        return LaunchChild(false, true);
+      }
+    } else {
+      rv = ps->Alert(nullptr, killTitle.get(), killMessage.get());
+      NS_ENSURE_SUCCESS_LOG(rv, rv);
+    }
+
+    return NS_ERROR_ABORT;
+  }
+}
+
+static const char kProfileManagerURL[] =
+    "chrome://mozapps/content/profile/profileSelection.xhtml";
+
+static ReturnAbortOnError ShowProfileManager(
+    nsIToolkitProfileService* aProfileSvc, nsINativeAppSupport* aNative) {
+  nsresult rv;
+
+  nsCOMPtr<nsIFile> profD, profLD;
+  bool offline = false;
+  int32_t dialogReturn;
+
+  {
+    ScopedXPCOMStartup xpcom;
+    rv = xpcom.Initialize();
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    rv = xpcom.SetWindowCreator(aNative);
+    NS_ENSURE_SUCCESS(rv, NS_ERROR_FAILURE);
+
+#ifdef XP_MACOSX
+    CommandLineServiceMac::SetupMacCommandLine(gRestartArgc, gRestartArgv,
+                                               true);
+#endif
+
+    {  // extra scoping is needed so we release these components before xpcom
+       // shutdown
+      nsCOMPtr<nsIWindowWatcher> windowWatcher(
+          do_GetService(NS_WINDOWWATCHER_CONTRACTID));
+      nsCOMPtr<nsIDialogParamBlock> ioParamBlock(
+          do_CreateInstance(NS_DIALOGPARAMBLOCK_CONTRACTID));
+      nsCOMPtr<nsIMutableArray> dlgArray(
+          do_CreateInstance(NS_ARRAY_CONTRACTID));
+      NS_ENSURE_TRUE(windowWatcher && ioParamBlock && dlgArray,
+                     NS_ERROR_FAILURE);
+
+      ioParamBlock->SetObjects(dlgArray);
+
+      nsCOMPtr<nsIAppStartup> appStartup(components::AppStartup::Service());
+      NS_ENSURE_TRUE(appStartup, NS_ERROR_FAILURE);
+
+      nsAutoCString features("centerscreen,chrome,modal,titlebar");
+      // If we're launching a private browsing window make sure to set that
+      // feature for the Profile Manager window as well, so it groups correctly
+      // on the Windows taskbar.
+      if (CheckArgExists("private-window") == ARG_FOUND) {
+        features.AppendLiteral(",private");
+      }
+      nsCOMPtr<mozIDOMWindowProxy> newWindow;
+      rv = windowWatcher->OpenWindow(
+          nullptr, nsDependentCString(kProfileManagerURL), "_blank"_ns,
+          features, ioParamBlock, getter_AddRefs(newWindow));
+
+      NS_ENSURE_SUCCESS_LOG(rv, rv);
+
+      rv = ioParamBlock->GetInt(0, &dialogReturn);
+      if (NS_FAILED(rv) || dialogReturn == nsIToolkitProfileService::exit) {
+        return NS_ERROR_ABORT;
+      }
+
+      int32_t startOffline;
+      rv = ioParamBlock->GetInt(1, &startOffline);
+      offline = NS_SUCCEEDED(rv) && startOffline == 1;
+
+      rv = dlgArray->QueryElementAt(0, NS_GET_IID(nsIFile),
+                                    getter_AddRefs(profD));
+      NS_ENSURE_SUCCESS_LOG(rv, rv);
+
+      rv = dlgArray->QueryElementAt(1, NS_GET_IID(nsIFile),
+                                    getter_AddRefs(profLD));
+      NS_ENSURE_SUCCESS_LOG(rv, rv);
+    }
+  }
+
+  if (offline) {
+    SaveToEnv("XRE_START_OFFLINE=1");
+  }
+
+  // User requested that we restart back into the profile manager.
+  if (dialogReturn == nsIToolkitProfileService::restart) {
+    SaveToEnv("XRE_RESTART_TO_PROFILE_MANAGER=1");
+    SaveToEnv("XRE_RESTARTED_BY_PROFILE_MANAGER=1");
+  } else {
+    MOZ_ASSERT(dialogReturn == nsIToolkitProfileService::launchWithProfile);
+    SaveFileToEnv("XRE_PROFILE_PATH", profD);
+    SaveFileToEnv("XRE_PROFILE_LOCAL_PATH", profLD);
+    SaveToEnv("XRE_RESTARTED_BY_PROFILE_MANAGER=1");
+  }
+
+  if (gRestartedByOS) {
+    // Re-add this argument when actually starting the application.
+    char** newArgv =
+        (char**)realloc(gRestartArgv, sizeof(char*) * (gRestartArgc + 2));
+    NS_ENSURE_TRUE(newArgv, NS_ERROR_OUT_OF_MEMORY);
+    gRestartArgv = newArgv;
+    gRestartArgv[gRestartArgc++] = const_cast<char*>("-os-restarted");
+    gRestartArgv[gRestartArgc] = nullptr;
+  }
+#if defined(MOZ_HAS_REMOTE)
+  if (gRemoteService) {
+    gRemoteService->UnlockStartup();
+    gRemoteService = nullptr;
+  }
+#endif
+  return LaunchChild(false, true);
+}
+
+static bool gDoMigration = false;
+static bool gDoProfileReset = false;
+static nsCOMPtr<nsIToolkitProfile> gResetOldProfile;
+
+static nsresult LockProfile(nsINativeAppSupport* aNative, nsIFile* aRootDir,
+                            nsIFile* aLocalDir, nsIToolkitProfile* aProfile,
+                            nsIProfileLock** aResult) {
+  // If you close Firefox and very quickly reopen it, the old Firefox may
+  // still be closing down. Rather than immediately showing the
+  // "Firefox is running but is not responding" message, we spend a few
+  // seconds retrying first.
+
+  static const int kLockRetrySeconds = 5;
+  static const int kLockRetrySleepMS = 100;
+
+  nsresult rv;
+  nsCOMPtr<nsIProfileUnlocker> unlocker;
+  const TimeStamp start = TimeStamp::Now();
+  do {
+    if (aProfile) {
+      rv = aProfile->Lock(getter_AddRefs(unlocker), aResult);
+    } else {
+      rv = NS_LockProfilePath(aRootDir, aLocalDir, getter_AddRefs(unlocker),
+                              aResult);
+    }
+    if (NS_SUCCEEDED(rv)) {
+      StartupTimeline::Record(StartupTimeline::AFTER_PROFILE_LOCKED);
+      return NS_OK;
+    }
+    PR_Sleep(kLockRetrySleepMS);
+  } while (TimeStamp::Now() - start <
+           TimeDuration::FromSeconds(kLockRetrySeconds));
+
+  return ProfileLockedDialog(aRootDir, aLocalDir, unlocker, aNative, aResult);
+}
+
+// Pick a profile. We need to end up with a profile root dir, local dir and
+// potentially an nsIToolkitProfile instance.
+//
+// 1) check for --profile <path>
+// 2) check for -P <name>
+// 3) check for --ProfileManager
+// 4) use the default profile, if there is one
+// 5) if there are *no* profiles, set up profile-migration
+// 6) display the profile-manager UI
+static nsresult SelectProfile(nsToolkitProfileService* aProfileSvc,
+                              nsINativeAppSupport* aNative, nsIFile** aRootDir,
+                              nsIFile** aLocalDir, nsIToolkitProfile** aProfile,
+                              bool* aWasDefaultSelection) {
+  StartupTimeline::Record(StartupTimeline::SELECT_PROFILE);
+
+  nsresult rv;
+
+  if (EnvHasValue("MOZ_RESET_PROFILE_RESTART")) {
+    gDoProfileReset = true;
+    gDoMigration = true;
+  }
+
+  // reset-profile and migration args need to be checked before any profiles are
+  // chosen below.
+  ArgResult ar = CheckArg("reset-profile");
+  if (ar == ARG_FOUND) {
+    gDoProfileReset = true;
+  }
+
+  ar = CheckArg("migration");
+  if (ar == ARG_FOUND) {
+    gDoMigration = true;
+  }
+
+#if defined(XP_WIN)
+  // This arg is only used to indicate to telemetry that a profile refresh
+  // (reset+migration) was requested from the uninstaller, pass this along
+  // via an environment variable for simplicity.
+  ar = CheckArg("uninstaller-profile-refresh");
+  if (ar == ARG_FOUND) {
+    SaveToEnv("MOZ_UNINSTALLER_PROFILE_REFRESH=1");
+  }
+#endif
+
+  if (EnvHasValue("XRE_RESTART_TO_PROFILE_MANAGER")) {
+    return ShowProfileManager(aProfileSvc, aNative);
+  }
+
+  // Ask the profile manager to select the profile directories to use.
+  bool didCreate = false;
+  rv = aProfileSvc->SelectStartupProfile(&gArgc, gArgv, gDoProfileReset,
+                                         aRootDir, aLocalDir, aProfile,
+                                         &didCreate, aWasDefaultSelection);
+
+  if (rv == NS_ERROR_SHOW_PROFILE_MANAGER) {
+    return ShowProfileManager(aProfileSvc, aNative);
+  }
+
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  if (didCreate) {
+    // For a fresh install, we would like to let users decide
+    // to do profile migration on their own later after using.
+    gDoProfileReset = false;
+    gDoMigration = false;
+  }
+
+  if (gDoProfileReset && !*aProfile) {
+    NS_WARNING("Profile reset is only supported for named profiles.");
+    return NS_ERROR_ABORT;
+  }
+
+  // No profile could be found. This generally shouldn't happen, a new profile
+  // should be created in all cases except for profile reset which is covered
+  // above, but just in case...
+  if (!*aRootDir) {
+    NS_WARNING("Failed to select or create profile.");
+    return NS_ERROR_ABORT;
+  }
+
+  return NS_OK;
+}
+
+#ifdef MOZ_BLOCK_PROFILE_DOWNGRADE
+struct FileWriteFunc final : public JSONWriteFunc {
+  FILE* mFile;
+  explicit FileWriteFunc(FILE* aFile) : mFile(aFile) {}
+
+  void Write(const Span<const char>& aStr) final {
+    fprintf(mFile, "%.*s", int(aStr.size()), aStr.data());
+  }
+};
+
+static void SubmitDowngradeTelemetry(const nsCString& aLastVersion,
+                                     bool aHasSync, int32_t aButton) {
+  nsCOMPtr<nsIPrefService> prefSvc =
+      do_GetService("@mozilla.org/preferences-service;1");
+  NS_ENSURE_TRUE_VOID(prefSvc);
+
+  nsCOMPtr<nsIPrefBranch> prefBranch = do_QueryInterface(prefSvc);
+  NS_ENSURE_TRUE_VOID(prefBranch);
+
+  bool enabled;
+  nsresult rv =
+      prefBranch->GetBoolPref(kPrefHealthReportUploadEnabled, &enabled);
+  NS_ENSURE_SUCCESS_VOID(rv);
+  if (!enabled) {
+    return;
+  }
+
+  nsCString server;
+  rv = prefBranch->GetCharPref("toolkit.telemetry.server", server);
+  NS_ENSURE_SUCCESS_VOID(rv);
+
+  nsCString clientId;
+  rv = prefBranch->GetCharPref("toolkit.telemetry.cachedClientID", clientId);
+  NS_ENSURE_SUCCESS_VOID(rv);
+
+  rv = prefSvc->GetDefaultBranch(nullptr, getter_AddRefs(prefBranch));
+  NS_ENSURE_SUCCESS_VOID(rv);
+
+  nsCString channel("default");
+  rv = prefBranch->GetCharPref("app.update.channel", channel);
+  NS_ENSURE_SUCCESS_VOID(rv);
+
+  nsID uuid;
+  rv = nsID::GenerateUUIDInPlace(uuid);
+  NS_ENSURE_SUCCESS_VOID(rv);
+
+  nsCString arch("null");
+  nsCOMPtr<nsIPropertyBag2> sysInfo =
+      do_GetService("@mozilla.org/system-info;1");
+  NS_ENSURE_TRUE_VOID(sysInfo);
+  sysInfo->GetPropertyAsACString(u"arch"_ns, arch);
+
+  time_t now;
+  time(&now);
+  char date[sizeof "YYYY-MM-DDThh:mm:ss.000Z"];
+  strftime(date, sizeof date, "%FT%T.000Z", gmtime(&now));
+
+  NSID_TrimBracketsASCII pingId(uuid);
+  constexpr auto pingType = "downgrade"_ns;
+
+  int32_t pos = aLastVersion.Find("_");
+  if (pos == kNotFound) {
+    return;
+  }
+
+  const nsDependentCSubstring lastVersion = Substring(aLastVersion, 0, pos);
+  const nsDependentCSubstring lastBuildId =
+      Substring(aLastVersion, pos + 1, 14);
+
+  nsPrintfCString url("%s/submit/telemetry/%s/%s/%s/%s/%s/%s?v=%d",
+                      server.get(), PromiseFlatCString(pingId).get(),
+                      pingType.get(), (const char*)gAppData->name,
+                      (const char*)gAppData->version, channel.get(),
+                      (const char*)gAppData->buildID,
+                      TELEMETRY_PING_FORMAT_VERSION);
+
+  nsCOMPtr<nsIFile> pingFile;
+  rv = NS_GetSpecialDirectory(XRE_USER_APP_DATA_DIR, getter_AddRefs(pingFile));
+  NS_ENSURE_SUCCESS_VOID(rv);
+  rv = pingFile->Append(u"Pending Pings"_ns);
+  NS_ENSURE_SUCCESS_VOID(rv);
+  rv = pingFile->Create(nsIFile::DIRECTORY_TYPE, 0755);
+  if (NS_FAILED(rv) && rv != NS_ERROR_FILE_ALREADY_EXISTS) {
+    return;
+  }
+  rv = pingFile->Append(NS_ConvertUTF8toUTF16(pingId));
+  NS_ENSURE_SUCCESS_VOID(rv);
+
+  nsCOMPtr<nsIFile> pingSender;
+  rv = NS_GetSpecialDirectory(NS_GRE_BIN_DIR, getter_AddRefs(pingSender));
+  NS_ENSURE_SUCCESS_VOID(rv);
+#  ifdef XP_WIN
+  pingSender->Append(u"pingsender.exe"_ns);
+#  else
+  pingSender->Append(u"pingsender"_ns);
+#  endif
+
+  bool exists;
+  rv = pingSender->Exists(&exists);
+  NS_ENSURE_SUCCESS_VOID(rv);
+  if (!exists) {
+    return;
+  }
+
+  FILE* file;
+  rv = pingFile->OpenANSIFileDesc("w", &file);
+  NS_ENSURE_SUCCESS_VOID(rv);
+
+  JSONWriter w(MakeUnique<FileWriteFunc>(file));
+  w.Start();
+  {
+    w.StringProperty("type",
+                     Span<const char>(pingType.Data(), pingType.Length()));
+    w.StringProperty("id", PromiseFlatCString(pingId));
+    w.StringProperty("creationDate", MakeStringSpan(date));
+    w.IntProperty("version", TELEMETRY_PING_FORMAT_VERSION);
+    w.StringProperty("clientId", clientId);
+    w.StartObjectProperty("application");
+    {
+      w.StringProperty("architecture", arch);
+      w.StringProperty(
+          "buildId",
+          MakeStringSpan(static_cast<const char*>(gAppData->buildID)));
+      w.StringProperty(
+          "name", MakeStringSpan(static_cast<const char*>(gAppData->name)));
+      w.StringProperty(
+          "version",
+          MakeStringSpan(static_cast<const char*>(gAppData->version)));
+      w.StringProperty("displayVersion",
+                       MOZ_STRINGIFY(MOZ_APP_VERSION_DISPLAY));
+      w.StringProperty(
+          "vendor", MakeStringSpan(static_cast<const char*>(gAppData->vendor)));
+      w.StringProperty("platformVersion", gToolkitVersion);
+#  ifdef TARGET_XPCOM_ABI
+      w.StringProperty("xpcomAbi", TARGET_XPCOM_ABI);
+#  else
+      w.StringProperty("xpcomAbi", "unknown");
+#  endif
+      w.StringProperty("channel", channel);
+    }
+    w.EndObject();
+    w.StartObjectProperty("payload");
+    {
+      w.StringProperty("lastVersion", PromiseFlatCString(lastVersion));
+      w.StringProperty("lastBuildId", PromiseFlatCString(lastBuildId));
+      w.BoolProperty("hasSync", aHasSync);
+      w.IntProperty("button", aButton);
+    }
+    w.EndObject();
+  }
+  w.End();
+
+  fclose(file);
+
+  PathString filePath = pingFile->NativePath();
+  const filesystem::Path::value_type* args[2];
+#  ifdef XP_WIN
+  nsString urlw = NS_ConvertUTF8toUTF16(url);
+  args[0] = urlw.get();
+#  else
+  args[0] = url.get();
+#  endif
+  args[1] = filePath.get();
+
+  nsCOMPtr<nsIProcess> process =
+      do_CreateInstance("@mozilla.org/process/util;1");
+  NS_ENSURE_TRUE_VOID(process);
+  process->Init(pingSender);
+  process->SetStartHidden(true);
+  process->SetNoShell(true);
+
+#  ifdef XP_WIN
+  process->Runw(false, args, 2);
+#  else
+  process->Run(false, args, 2);
+#  endif
+}
+
+static const char kProfileDowngradeURL[] =
+    "chrome://mozapps/content/profile/profileDowngrade.xhtml";
+
+static ReturnAbortOnError CheckDowngrade(nsIFile* aProfileDir,
+                                         nsINativeAppSupport* aNative,
+                                         nsIToolkitProfileService* aProfileSvc,
+                                         const nsCString& aLastVersion) {
+  int32_t result = 0;
+  nsresult rv;
+
+  {
+    if (gfxPlatform::IsHeadless()) {
+      // TODO: make a way to turn off all dialogs when headless.
+      Output(true,
+             "This profile was last used with a newer version of this "
+             "application. Please create a new profile.\n");
+      return NS_ERROR_ABORT;
+    }
+
+    ScopedXPCOMStartup xpcom;
+    rv = xpcom.Initialize();
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    rv = xpcom.SetWindowCreator(aNative);
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    {  // extra scoping is needed so we release these components before xpcom
+       // shutdown
+      bool hasSync = false;
+      nsCOMPtr<nsIPrefService> prefSvc =
+          do_GetService("@mozilla.org/preferences-service;1");
+      NS_ENSURE_TRUE(prefSvc, rv);
+
+      nsCOMPtr<nsIFile> prefsFile;
+      rv = aProfileDir->Clone(getter_AddRefs(prefsFile));
+      NS_ENSURE_SUCCESS(rv, rv);
+
+      rv = prefsFile->Append(u"prefs.js"_ns);
+      NS_ENSURE_SUCCESS(rv, rv);
+
+      rv = prefSvc->ReadUserPrefsFromFile(prefsFile);
+      if (NS_SUCCEEDED(rv)) {
+        nsCOMPtr<nsIPrefBranch> prefBranch = do_QueryInterface(prefSvc);
+
+        rv = prefBranch->PrefHasUserValue("services.sync.username", &hasSync);
+        NS_ENSURE_SUCCESS(rv, rv);
+      }
+
+      nsCOMPtr<nsIWindowWatcher> windowWatcher =
+          do_GetService(NS_WINDOWWATCHER_CONTRACTID);
+      NS_ENSURE_TRUE(windowWatcher, NS_ERROR_ABORT);
+
+      nsCOMPtr<nsIAppStartup> appStartup(components::AppStartup::Service());
+      NS_ENSURE_TRUE(appStartup, NS_ERROR_FAILURE);
+
+      nsCOMPtr<nsIDialogParamBlock> paramBlock =
+          do_CreateInstance(NS_DIALOGPARAMBLOCK_CONTRACTID);
+      NS_ENSURE_TRUE(paramBlock, NS_ERROR_ABORT);
+
+      uint8_t flags = 0;
+      if (hasSync) {
+        flags |= nsIToolkitProfileService::hasSync;
+      }
+
+      paramBlock->SetInt(0, flags);
+
+      nsAutoCString features("centerscreen,chrome,modal,titlebar");
+      // If we're launching a private browsing window make sure to set that
+      // feature for the Profile Manager window as well, so it groups correctly
+      // on the Windows taskbar.
+      if (CheckArgExists("private-window") == ARG_FOUND) {
+        features.AppendLiteral(",private");
+      }
+      nsCOMPtr<mozIDOMWindowProxy> newWindow;
+      rv = windowWatcher->OpenWindow(
+          nullptr, nsDependentCString(kProfileDowngradeURL), "_blank"_ns,
+          features, paramBlock, getter_AddRefs(newWindow));
+      NS_ENSURE_SUCCESS(rv, rv);
+
+      paramBlock->GetInt(1, &result);
+
+      SubmitDowngradeTelemetry(aLastVersion, hasSync, result);
+    }
+  }
+
+  if (result == nsIToolkitProfileService::createNewProfile) {
+    // Create a new profile and start it.
+    nsCString profileName;
+    profileName.AssignLiteral("default");
+#  ifdef MOZ_DEDICATED_PROFILES
+    profileName.Append("-" MOZ_STRINGIFY(MOZ_UPDATE_CHANNEL));
+#  endif
+    nsCOMPtr<nsIToolkitProfile> newProfile;
+    rv = aProfileSvc->CreateUniqueProfile(nullptr, profileName,
+                                          getter_AddRefs(newProfile));
+    NS_ENSURE_SUCCESS(rv, rv);
+    rv = aProfileSvc->SetDefaultProfile(newProfile);
+    NS_ENSURE_SUCCESS(rv, rv);
+    rv = aProfileSvc->Flush();
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    nsCOMPtr<nsIFile> profD, profLD;
+    rv = newProfile->GetRootDir(getter_AddRefs(profD));
+    NS_ENSURE_SUCCESS(rv, rv);
+    rv = newProfile->GetLocalDir(getter_AddRefs(profLD));
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    SaveFileToEnv("XRE_PROFILE_PATH", profD);
+    SaveFileToEnv("XRE_PROFILE_LOCAL_PATH", profLD);
+
+    return LaunchChild(false, true);
+  }
+
+  // Cancel
+  return NS_ERROR_ABORT;
+}
+#endif
+
+/**
+ * Extracts the various parts of a compatibility version string.
+ *
+ * Compatibility versions are of the form
+ * "<appversion>_<appbuildid>/<platformbuildid>". The toolkit version comparator
+ * can only handle 32-bit numbers and in the normal case build IDs are larger
+ * than this. So if the build ID is numeric we split it into two version parts.
+ */
+static void ExtractCompatVersionInfo(const nsACString& aCompatVersion,
+                                     nsACString& aAppVersion,
+                                     nsACString& aAppBuildID) {
+  int32_t underscorePos = aCompatVersion.FindChar('_');
+  int32_t slashPos = aCompatVersion.FindChar('/');
+
+  if (underscorePos == kNotFound || slashPos == kNotFound ||
+      slashPos < underscorePos) {
+    NS_WARNING(
+        "compatibility.ini Version string does not match the expected format.");
+
+    // Fall back to just using the entire string as the version.
+    aAppVersion = aCompatVersion;
+    aAppBuildID.Truncate(0);
+    return;
+  }
+
+  aAppVersion = Substring(aCompatVersion, 0, underscorePos);
+  aAppBuildID = Substring(aCompatVersion, underscorePos + 1,
+                          slashPos - (underscorePos + 1));
+}
+
+/**
+ * Compares the provided compatibility versions. Returns 0 if they match,
+ * < 0 if the new version is considered an upgrade from the old version and
+ * > 0 if the new version is considered a downgrade from the old version.
+ */
+int32_t CompareCompatVersions(const nsACString& aOldCompatVersion,
+                              const nsACString& aNewCompatVersion) {
+  // Hardcode the case where the last run was in safe mode (Bug 1556612). We
+  // cannot tell if this is a downgrade or not so just assume it isn't and let
+  // the user proceed.
+  if (aOldCompatVersion.EqualsLiteral("Safe Mode")) {
+    return -1;
+  }
+
+  // Extract the major version part from the version string and only use that
+  // for version comparison.
+  int32_t index = aOldCompatVersion.FindChar('.');
+  const nsACString& oldMajorVersion = Substring(
+      aOldCompatVersion, 0, index < 0 ? aOldCompatVersion.Length() : index);
+  index = aNewCompatVersion.FindChar('.');
+  const nsACString& newMajorVersion = Substring(
+      aNewCompatVersion, 0, index < 0 ? aNewCompatVersion.Length() : index);
+
+  return CompareVersions(PromiseFlatCString(oldMajorVersion).get(),
+                         PromiseFlatCString(newMajorVersion).get());
+}
+
+/**
+ * Checks the compatibility.ini file to see if we have updated our application
+ * or otherwise invalidated our caches. If the application has been updated,
+ * we return false; otherwise, we return true.
+ *
+ * We also write the status of the caches (valid/invalid) into the return param
+ * aCachesOK. The aCachesOK is always invalid if the application has been
+ * updated.
+ *
+ * Finally, aIsDowngrade is set to true if the current application is older
+ * than that previously used by the profile.
+ */
+static bool CheckCompatibility(nsIFile* aProfileDir, const nsCString& aVersion,
+                               const nsCString& aOSABI, nsIFile* aXULRunnerDir,
+                               nsIFile* aAppDir, nsIFile* aFlagFile,
+                               bool* aCachesOK, bool* aIsDowngrade,
+                               nsCString& aLastVersion) {
+  *aCachesOK = false;
+  *aIsDowngrade = false;
+  gLastAppVersion.SetIsVoid(true);
+  gLastAppBuildID.SetIsVoid(true);
+
+  nsCOMPtr<nsIFile> file;
+  aProfileDir->Clone(getter_AddRefs(file));
+  if (!file) return false;
+  file->AppendNative(FILE_COMPATIBILITY_INFO);
+
+  nsINIParser parser;
+  nsresult rv = parser.Init(file);
+  if (NS_FAILED(rv)) return false;
+
+  rv = parser.GetString("Compatibility", "LastVersion", aLastVersion);
+  if (NS_FAILED(rv)) {
+    return false;
+  }
+
+  if (!aLastVersion.Equals(aVersion)) {
+    // The version is not the same. Whether it's a downgrade depends on an
+    // actual comparison:
+    *aIsDowngrade = 0 < CompareCompatVersions(aLastVersion, aVersion);
+    ExtractCompatVersionInfo(aLastVersion, gLastAppVersion, gLastAppBuildID);
+    return false;
+  }
+
+  // If we get here, the version matched, but there may still be other
+  // differences between us and the build that the profile last ran under.
+
+  gLastAppVersion.Assign(gAppData->version);
+  gLastAppBuildID.Assign(gAppData->buildID);
+
+  nsAutoCString buf;
+  rv = parser.GetString("Compatibility", "LastOSABI", buf);
+  if (NS_FAILED(rv) || !aOSABI.Equals(buf)) return false;
+
+  rv = parser.GetString("Compatibility", "LastPlatformDir", buf);
+  if (NS_FAILED(rv)) return false;
+
+  nsCOMPtr<nsIFile> lf;
+  rv = NS_NewNativeLocalFile(""_ns, false, getter_AddRefs(lf));
+  if (NS_FAILED(rv)) return false;
+
+  rv = lf->SetPersistentDescriptor(buf);
+  if (NS_FAILED(rv)) return false;
+
+  bool eq;
+  rv = lf->Equals(aXULRunnerDir, &eq);
+  if (NS_FAILED(rv) || !eq) return false;
+
+  if (aAppDir) {
+    rv = parser.GetString("Compatibility", "LastAppDir", buf);
+    if (NS_FAILED(rv)) return false;
+
+    rv = NS_NewNativeLocalFile(""_ns, false, getter_AddRefs(lf));
+    if (NS_FAILED(rv)) return false;
+
+    rv = lf->SetPersistentDescriptor(buf);
+    if (NS_FAILED(rv)) return false;
+
+    rv = lf->Equals(aAppDir, &eq);
+    if (NS_FAILED(rv) || !eq) return false;
+  }
+
+  // If we see this flag, caches are invalid.
+  rv = parser.GetString("Compatibility", "InvalidateCaches", buf);
+  *aCachesOK = (NS_FAILED(rv) || !buf.EqualsLiteral("1"));
+
+  bool purgeCaches = false;
+  if (aFlagFile && NS_SUCCEEDED(aFlagFile->Exists(&purgeCaches)) &&
+      purgeCaches) {
+    *aCachesOK = false;
+  }
+
+  return true;
+}
+
+void BuildCompatVersion(const char* aAppVersion, const char* aAppBuildID,
+                        const char* aToolkitBuildID, nsACString& aBuf) {
+  aBuf.Assign(aAppVersion);
+  aBuf.Append('_');
+  aBuf.Append(aAppBuildID);
+  aBuf.Append('/');
+  aBuf.Append(aToolkitBuildID);
+}
+
+static void BuildVersion(nsCString& aBuf) {
+  BuildCompatVersion(gAppData->version, gAppData->buildID, gToolkitBuildID,
+                     aBuf);
+}
+
+static void WriteVersion(nsIFile* aProfileDir, const nsCString& aVersion,
+                         const nsCString& aOSABI, nsIFile* aXULRunnerDir,
+                         nsIFile* aAppDir, bool invalidateCache) {
+  nsCOMPtr<nsIFile> file;
+  aProfileDir->Clone(getter_AddRefs(file));
+  if (!file) return;
+  file->AppendNative(FILE_COMPATIBILITY_INFO);
+
+  nsAutoCString platformDir;
+  Unused << aXULRunnerDir->GetPersistentDescriptor(platformDir);
+
+  nsAutoCString appDir;
+  if (aAppDir) Unused << aAppDir->GetPersistentDescriptor(appDir);
+
+  PRFileDesc* fd;
+  nsresult rv = file->OpenNSPRFileDesc(PR_WRONLY | PR_CREATE_FILE | PR_TRUNCATE,
+                                       0600, &fd);
+  if (NS_FAILED(rv)) {
+    NS_ERROR("could not create output stream");
+    return;
+  }
+
+  static const char kHeader[] = "[Compatibility]" NS_LINEBREAK "LastVersion=";
+
+  PR_Write(fd, kHeader, sizeof(kHeader) - 1);
+  PR_Write(fd, aVersion.get(), aVersion.Length());
+
+  static const char kOSABIHeader[] = NS_LINEBREAK "LastOSABI=";
+  PR_Write(fd, kOSABIHeader, sizeof(kOSABIHeader) - 1);
+  PR_Write(fd, aOSABI.get(), aOSABI.Length());
+
+  static const char kPlatformDirHeader[] = NS_LINEBREAK "LastPlatformDir=";
+
+  PR_Write(fd, kPlatformDirHeader, sizeof(kPlatformDirHeader) - 1);
+  PR_Write(fd, platformDir.get(), platformDir.Length());
+
+  static const char kAppDirHeader[] = NS_LINEBREAK "LastAppDir=";
+  if (aAppDir) {
+    PR_Write(fd, kAppDirHeader, sizeof(kAppDirHeader) - 1);
+    PR_Write(fd, appDir.get(), appDir.Length());
+  }
+
+  static const char kInvalidationHeader[] = NS_LINEBREAK "InvalidateCaches=1";
+  if (invalidateCache)
+    PR_Write(fd, kInvalidationHeader, sizeof(kInvalidationHeader) - 1);
+
+  static const char kNL[] = NS_LINEBREAK;
+  PR_Write(fd, kNL, sizeof(kNL) - 1);
+
+  PR_Close(fd);
+}
+
+/**
+ * Returns true if the startup cache file was successfully removed.
+ * Returns false if file->Clone fails at any point (OOM) or if unable
+ * to remove the startup cache file. Note in particular the return value
+ * is unaffected by a failure to remove extensions.ini
+ */
+static bool RemoveComponentRegistries(nsIFile* aProfileDir,
+                                      nsIFile* aLocalProfileDir,
+                                      bool aRemoveEMFiles) {
+  nsCOMPtr<nsIFile> file;
+  aProfileDir->Clone(getter_AddRefs(file));
+  if (!file) return false;
+
+  if (aRemoveEMFiles) {
+    file->SetNativeLeafName("extensions.ini"_ns);
+    file->Remove(false);
+  }
+
+  aLocalProfileDir->Clone(getter_AddRefs(file));
+  if (!file) return false;
+
+  file->AppendNative("startupCache"_ns);
+  nsresult rv = file->Remove(true);
+  return NS_SUCCEEDED(rv) || rv == NS_ERROR_FILE_NOT_FOUND;
+}
+
+// When we first initialize the crash reporter we don't have a profile,
+// so we set the minidump path to $TEMP.  Once we have a profile,
+// we set it to $PROFILE/minidumps, creating the directory
+// if needed.
+static void MakeOrSetMinidumpPath(nsIFile* profD) {
+  nsCOMPtr<nsIFile> dumpD;
+  profD->Clone(getter_AddRefs(dumpD));
+
+  if (dumpD) {
+    bool fileExists;
+    // XXX: do some more error checking here
+    dumpD->Append(u"minidumps"_ns);
+    dumpD->Exists(&fileExists);
+    if (!fileExists) {
+      nsresult rv = dumpD->Create(nsIFile::DIRECTORY_TYPE, 0700);
+      NS_ENSURE_SUCCESS_VOID(rv);
+    }
+
+    nsAutoString pathStr;
+    if (NS_SUCCEEDED(dumpD->GetPath(pathStr)))
+      CrashReporter::SetMinidumpPath(pathStr);
+  }
+}
+
+const XREAppData* gAppData = nullptr;
+
+/**
+ * NSPR will search for the "nspr_use_zone_allocator" symbol throughout
+ * the process and use it to determine whether the application defines its own
+ * memory allocator or not.
+ *
+ * Since most applications (e.g. Firefox and Thunderbird) don't use any special
+ * allocators and therefore don't define this symbol, NSPR must search the
+ * entire process, which reduces startup performance.
+ *
+ * By defining the symbol here, we can avoid the wasted lookup and hopefully
+ * improve startup performance.
+ */
+NS_VISIBILITY_DEFAULT PRBool nspr_use_zone_allocator = PR_FALSE;
+
+#ifdef CAIRO_HAS_DWRITE_FONT
+
+#  include <dwrite.h>
+#  include "nsWindowsHelpers.h"
+
+#  ifdef DEBUG_DWRITE_STARTUP
+
+#    define LOGREGISTRY(msg) LogRegistryEvent(msg)
+
+// for use when monitoring process
+static void LogRegistryEvent(const wchar_t* msg) {
+  HKEY dummyKey;
+  HRESULT hr;
+  wchar_t buf[512];
+
+  wsprintf(buf, L" log %s", msg);
+  hr = RegOpenKeyEx(HKEY_LOCAL_MACHINE, buf, 0, KEY_READ, &dummyKey);
+  if (SUCCEEDED(hr)) {
+    RegCloseKey(dummyKey);
+  }
+}
+#  else
+
+#    define LOGREGISTRY(msg)
+
+#  endif
+
+static DWORD WINAPI InitDwriteBG(LPVOID lpdwThreadParam) {
+  SetThreadPriority(GetCurrentThread(), THREAD_MODE_BACKGROUND_BEGIN);
+  LOGREGISTRY(L"loading dwrite.dll");
+  HMODULE dwdll = LoadLibrarySystem32(L"dwrite.dll");
+  if (dwdll) {
+    decltype(DWriteCreateFactory)* createDWriteFactory =
+        (decltype(DWriteCreateFactory)*)GetProcAddress(dwdll,
+                                                       "DWriteCreateFactory");
+    if (createDWriteFactory) {
+      LOGREGISTRY(L"creating dwrite factory");
+      IDWriteFactory* factory;
+      HRESULT hr = createDWriteFactory(DWRITE_FACTORY_TYPE_SHARED,
+                                       __uuidof(IDWriteFactory),
+                                       reinterpret_cast<IUnknown**>(&factory));
+      if (SUCCEEDED(hr)) {
+        LOGREGISTRY(L"dwrite factory done");
+        factory->Release();
+        LOGREGISTRY(L"freed factory");
+      } else {
+        LOGREGISTRY(L"failed to create factory");
+      }
+    }
+  }
+  SetThreadPriority(GetCurrentThread(), THREAD_MODE_BACKGROUND_END);
+  return 0;
+}
+#endif
+
+#include "GeckoProfiler.h"
+#include "ProfilerControl.h"
+
+// Encapsulates startup and shutdown state for XRE_main
+class XREMain {
+ public:
+  XREMain() = default;
+
+  ~XREMain() {
+    mScopedXPCOM = nullptr;
+    mAppData = nullptr;
+  }
+
+  int XRE_main(int argc, char* argv[], const BootstrapConfig& aConfig);
+  int XRE_mainInit(bool* aExitFlag);
+  int XRE_mainStartup(bool* aExitFlag);
+  nsresult XRE_mainRun();
+
+  bool CheckLastStartupWasCrash();
+
+  nsCOMPtr<nsINativeAppSupport> mNativeApp;
+  RefPtr<nsToolkitProfileService> mProfileSvc;
+  nsCOMPtr<nsIFile> mProfD;
+  nsCOMPtr<nsIFile> mProfLD;
+  nsCOMPtr<nsIProfileLock> mProfileLock;
+#if defined(MOZ_HAS_REMOTE)
+  RefPtr<nsRemoteService> mRemoteService;
+#endif
+
+  UniquePtr<ScopedXPCOMStartup> mScopedXPCOM;
+  UniquePtr<XREAppData> mAppData;
+
+  nsXREDirProvider mDirProvider;
+
+#ifdef MOZ_WIDGET_GTK
+  nsAutoCString mXDGActivationToken;
+  nsAutoCString mDesktopStartupID;
+#endif
+
+  bool mStartOffline = false;
+#if defined(MOZ_HAS_REMOTE)
+  bool mDisableRemoteClient = false;
+  bool mDisableRemoteServer = false;
+#endif
+};
+
+#if defined(XP_UNIX) && !defined(ANDROID)
+static SmprintfPointer FormatUid(uid_t aId) {
+  if (const auto pw = getpwuid(aId)) {
+    return mozilla::Smprintf("%s", pw->pw_name);
+  }
+  return mozilla::Smprintf("uid %d", static_cast<int>(aId));
+}
+
+// Bug 1323302: refuse to run under sudo or similar.
+static bool CheckForUserMismatch() {
+  static char const* const kVars[] = {
+      "HOME",
+#  ifdef MOZ_WIDGET_GTK
+      "XDG_RUNTIME_DIR",
+#  endif
+#  ifdef MOZ_X11
+      "XAUTHORITY",
+#  endif
+  };
+
+  const uid_t euid = geteuid();
+  if (euid != 0) {
+    // On Linux it's possible to have superuser capabilities with a
+    // nonzero uid, but anyone who knows enough to make that happen
+    // probably knows enough to debug the resulting problems.
+    // Otherwise, a non-root user can't cause the problems we're
+    // concerned about.
+    return false;
+  }
+
+  for (const auto var : kVars) {
+    if (const auto path = PR_GetEnv(var)) {
+      struct stat st;
+      if (stat(path, &st) == 0) {
+        if (st.st_uid != euid) {
+          const auto owner = FormatUid(st.st_uid);
+          Output(true,
+                 "Running " MOZ_APP_DISPLAYNAME
+                 " as root in a regular"
+                 " user's session is not supported.  ($%s is %s which is"
+                 " owned by %s.)\n",
+                 var, path, owner.get());
+          return true;
+        }
+      }
+    }
+  }
+  return false;
+}
+#else  // !XP_UNIX || ANDROID
+static bool CheckForUserMismatch() { return false; }
+#endif
+
+void mozilla::startup::IncreaseDescriptorLimits() {
+#ifdef XP_UNIX
+  // Increase the fd limit to accomodate IPC resources like shared memory.
+  // See also the Darwin case in config/external/nspr/pr/moz.build
+  static const rlim_t kFDs = 4096;
+  struct rlimit rlim;
+
+  if (getrlimit(RLIMIT_NOFILE, &rlim) != 0) {
+    Output(false, "getrlimit: %s\n", strerror(errno));
+    return;
+  }
+  // Don't decrease the limit if it's already high enough, but don't
+  // try to go over the hard limit.  (RLIM_INFINITY isn't required to
+  // be the numerically largest rlim_t, so don't assume that.)
+  if (rlim.rlim_cur != RLIM_INFINITY && rlim.rlim_cur < kFDs &&
+      rlim.rlim_cur < rlim.rlim_max) {
+    if (rlim.rlim_max != RLIM_INFINITY && rlim.rlim_max < kFDs) {
+      rlim.rlim_cur = rlim.rlim_max;
+    } else {
+      rlim.rlim_cur = kFDs;
+    }
+    if (setrlimit(RLIMIT_NOFILE, &rlim) != 0) {
+      Output(false, "setrlimit: %s\n", strerror(errno));
+    }
+  }
+#endif
+}
+
+#ifdef XP_WIN
+
+static uint32_t GetMicrocodeVersionByVendor(HKEY key, DWORD upper,
+                                            DWORD lower) {
+  WCHAR data[13];  // The CPUID vendor string is 12 characters long plus null
+  DWORD len = sizeof(data);
+  DWORD vtype;
+
+  if (RegQueryValueExW(key, L"VendorIdentifier", nullptr, &vtype,
+                       reinterpret_cast<LPBYTE>(data), &len) == ERROR_SUCCESS) {
+    if (wcscmp(L"GenuineIntel", data) == 0) {
+      // Intel reports the microcode version in the upper 32 bits of the MSR
+      return upper;
+    }
+
+    if (wcscmp(L"AuthenticAMD", data) == 0) {
+      // AMD reports the microcode version in the lower 32 bits of the MSR
+      return lower;
+    }
+
+    // Unknown CPU vendor, return whatever half is non-zero
+    return lower ? lower : upper;
+  }
+
+  return 0;  // No clue
+}
+
+#endif  // XP_WIN
+
+static void MaybeAddCPUMicrocodeCrashAnnotation() {
+#ifdef XP_WIN
+  // Add CPU microcode version to the crash report as "CPUMicrocodeVersion".
+  // It feels like this code may belong in nsSystemInfo instead.
+  uint32_t cpuUpdateRevision = 0;
+  HKEY key;
+  static const WCHAR keyName[] =
+      L"HARDWARE\\DESCRIPTION\\System\\CentralProcessor\\0";
+
+  if (RegOpenKeyEx(HKEY_LOCAL_MACHINE, keyName, 0, KEY_QUERY_VALUE, &key) ==
+      ERROR_SUCCESS) {
+    DWORD updateRevision[2];
+    DWORD len = sizeof(updateRevision);
+    DWORD vtype;
+
+    // Windows 7 uses "Update Signature", 8 uses "Update Revision".
+    // For AMD CPUs, "CurrentPatchLevel" is sometimes used.
+    // Take the first one we find.
+    LPCWSTR choices[] = {L"Update Signature", L"Update Revision",
+                         L"CurrentPatchLevel"};
+    for (const auto& oneChoice : choices) {
+      if (RegQueryValueExW(key, oneChoice, nullptr, &vtype,
+                           reinterpret_cast<LPBYTE>(updateRevision),
+                           &len) == ERROR_SUCCESS) {
+        if (vtype == REG_BINARY && len == sizeof(updateRevision)) {
+          cpuUpdateRevision = GetMicrocodeVersionByVendor(
+              key, updateRevision[1], updateRevision[0]);
+          break;
+        }
+
+        if (vtype == REG_DWORD && len == sizeof(updateRevision[0])) {
+          cpuUpdateRevision = static_cast<int>(updateRevision[0]);
+          break;
+        }
+      }
+    }
+  }
+
+  if (cpuUpdateRevision > 0) {
+    CrashReporter::AnnotateCrashReport(
+        CrashReporter::Annotation::CPUMicrocodeVersion,
+        nsPrintfCString("0x%" PRIx32, cpuUpdateRevision));
+  }
+#endif
+}
+
+#if defined(MOZ_BACKGROUNDTASKS)
+static void SetupConsoleForBackgroundTask(
+    const nsCString& aBackgroundTaskName) {
+  // We do not suppress output on Windows because:
+  // 1. Background task subprocesses launched via LaunchApp() does not attach to
+  //    the console.
+  // 2. Suppressing output intermittently causes failures on when running
+  //    multiple tasks (see bug 1831631)
+#  ifndef XP_WIN
+  if (BackgroundTasks::IsNoOutputTaskName(aBackgroundTaskName) &&
+      !CheckArg("attach-console") &&
+      !EnvHasValue("MOZ_BACKGROUNDTASKS_IGNORE_NO_OUTPUT")) {
+    // Suppress output, somewhat crudely.  We need to suppress stderr as well
+    // as stdout because assertions, of which there are many, write to stderr.
+    Unused << freopen("/dev/null", "w", stdout);
+    Unused << freopen("/dev/null", "w", stderr);
+    return;
+  }
+#  endif
+  printf_stderr("*** You are running in background task mode. ***\n");
+}
+#endif
+
+/*
+ * XRE_mainInit - Initial setup and command line parameter processing.
+ * Main() will exit early if either return value != 0 or if aExitFlag is
+ * true.
+ */
+int XREMain::XRE_mainInit(bool* aExitFlag) {
+  if (!aExitFlag) return 1;
+  *aExitFlag = false;
+
+  atexit(UnexpectedExit);
+  auto expectedShutdown = mozilla::MakeScopeExit([&] { MozExpectedExit(); });
+
+  StartupTimeline::Record(StartupTimeline::MAIN);
+
+  if (CheckForUserMismatch()) {
+    return 1;
+  }
+
+#ifdef XP_MACOSX
+  mozilla::MacAutoreleasePool pool;
+
+  DisableAppNap();
+#endif
+
+#ifdef MOZ_BACKGROUNDTASKS
+  Maybe<nsCString> backgroundTask = Nothing();
+  const char* backgroundTaskName = nullptr;
+  if (ARG_FOUND ==
+      CheckArg("backgroundtask", &backgroundTaskName, CheckArgFlag::None)) {
+    backgroundTask = Some(backgroundTaskName);
+
+    SetupConsoleForBackgroundTask(backgroundTask.ref());
+  }
+
+  BackgroundTasks::Init(backgroundTask);
+#endif
+
+#ifndef ANDROID
+  if (PR_GetEnv("MOZ_RUN_GTEST")
+#  ifdef FUZZING
+      || PR_GetEnv("FUZZER")
+#  endif
+#  ifdef MOZ_BACKGROUNDTASKS
+      || BackgroundTasks::IsBackgroundTaskMode()
+#  endif
+  ) {
+    // Enable headless mode and assert that it worked, since gfxPlatform
+    // uses a static bool set after the first call to `IsHeadless`.
+    // Note: Android gtests seem to require an Activity and fail to start
+    // with headless mode enabled.
+    PR_SetEnv("MOZ_HEADLESS=1");
+    MOZ_ASSERT(gfxPlatform::IsHeadless());
+  }
+#endif  // ANDROID
+
+  if (PR_GetEnv("MOZ_CHAOSMODE")) {
+    ChaosFeature feature = ChaosFeature::Any;
+    long featureInt = strtol(PR_GetEnv("MOZ_CHAOSMODE"), nullptr, 16);
+    if (featureInt) {
+      // NOTE: MOZ_CHAOSMODE=0 or a non-hex value maps to Any feature.
+      feature = static_cast<ChaosFeature>(featureInt);
+    }
+    ChaosMode::SetChaosFeature(feature);
+  }
+
+  if (CheckArgExists("fxr")) {
+    gFxREmbedded = true;
+  }
+
+  if (ChaosMode::isActive(ChaosFeature::Any)) {
+    printf_stderr(
+        "*** You are running in chaos test mode. See ChaosMode.h. ***\n");
+  }
+
+  if (CheckArg("headless") || CheckArgExists("screenshot")) {
+    PR_SetEnv("MOZ_HEADLESS=1");
+  }
+
+  if (gfxPlatform::IsHeadless()) {
+#if defined(XP_WIN) || defined(MOZ_WIDGET_GTK) || defined(XP_MACOSX)
+    printf_stderr("*** You are running in headless mode.\n");
+#else
+    Output(
+        true,
+        "Error: headless mode is not currently supported on this platform.\n");
+    return 1;
+#endif
+
+#ifdef XP_MACOSX
+    // To avoid taking focus when running in headless mode immediately
+    // transition Firefox to a background application.
+    ProcessSerialNumber psn = {0, kCurrentProcess};
+    OSStatus transformStatus =
+        TransformProcessType(&psn, kProcessTransformToBackgroundApplication);
+    if (transformStatus != noErr) {
+      NS_ERROR("Failed to make process a background application.");
+      return 1;
+    }
+#endif
+  }
+
+  nsresult rv;
+  ArgResult ar;
+
+#ifdef DEBUG
+  if (PR_GetEnv("XRE_MAIN_BREAK")) NS_BREAK();
+#endif
+
+  mozilla::startup::IncreaseDescriptorLimits();
+
+  SetupErrorHandling(gArgv[0]);
+
+#ifdef CAIRO_HAS_DWRITE_FONT
+  {
+    // Bug 602792 - when DWriteCreateFactory is called the dwrite client dll
+    // starts the FntCache service if it isn't already running (it's set
+    // to manual startup by default in Windows 7 RTM).  Subsequent DirectWrite
+    // calls cause the IDWriteFactory object to communicate with the FntCache
+    // service with a timeout; if there's no response after the timeout, the
+    // DirectWrite client library will assume the service isn't around and do
+    // manual font file I/O on _all_ system fonts.  To avoid this, load the
+    // dwrite library and create a factory as early as possible so that the
+    // FntCache service is ready by the time it's needed.
+
+    CreateThread(nullptr, 0, &InitDwriteBG, nullptr, 0, nullptr);
+  }
+#endif
+
+#ifdef XP_UNIX
+  const char* home = PR_GetEnv("HOME");
+  if (!home || !*home) {
+    struct passwd* pw = getpwuid(geteuid());
+    if (!pw || !pw->pw_dir) {
+      Output(true, "Could not determine HOME directory");
+      return 1;
+    }
+    SaveWordToEnv("HOME", nsDependentCString(pw->pw_dir));
+  }
+#endif
+
+#ifdef MOZ_ACCESSIBILITY_ATK
+  // Suppress atk-bridge init at startup, until mozilla accessibility is
+  // initialized.  This works after gnome 2.24.2.
+  SaveToEnv("NO_AT_BRIDGE=1");
+#endif
+
+  // Check for application.ini overrides
+  const char* override = nullptr;
+  ar = CheckArg("override", &override);
+  if (ar == ARG_BAD) {
+    Output(true, "Incorrect number of arguments passed to --override");
+    return 1;
+  }
+  if (ar == ARG_FOUND) {
+    nsCOMPtr<nsIFile> overrideLF;
+    rv = XRE_GetFileFromPath(override, getter_AddRefs(overrideLF));
+    if (NS_FAILED(rv)) {
+      Output(true, "Error: unrecognized override.ini path.\n");
+      return 1;
+    }
+
+    rv = XRE_ParseAppData(overrideLF, *mAppData);
+    if (NS_FAILED(rv)) {
+      Output(true, "Couldn't read override.ini");
+      return 1;
+    }
+  }
+
+  // Check sanity and correctness of app data.
+
+  if (!mAppData->name) {
+    Output(true, "Error: App:Name not specified in application.ini\n");
+    return 1;
+  }
+  if (!mAppData->buildID) {
+    Output(true, "Error: App:BuildID not specified in application.ini\n");
+    return 1;
+  }
+
+  // XXX Originally ScopedLogging was here? Now it's in XRE_main above
+  // XRE_mainInit.
+
+  if (!mAppData->minVersion) {
+    Output(true, "Error: Gecko:MinVersion not specified in application.ini\n");
+    return 1;
+  }
+
+  if (!mAppData->maxVersion) {
+    // If no maxVersion is specified, we assume the app is only compatible
+    // with the initial preview release. Do not increment this number ever!
+    mAppData->maxVersion = "1.*";
+  }
+
+  if (mozilla::Version(mAppData->minVersion) > gToolkitVersion ||
+      mozilla::Version(mAppData->maxVersion) < gToolkitVersion) {
+    Output(true,
+           "Error: Platform version '%s' is not compatible with\n"
+           "minVersion >= %s\nmaxVersion <= %s\n",
+           (const char*)gToolkitVersion, (const char*)mAppData->minVersion,
+           (const char*)mAppData->maxVersion);
+    return 1;
+  }
+
+  rv = mDirProvider.Initialize(mAppData->directory, mAppData->xreDirectory);
+  if (NS_FAILED(rv)) return 1;
+
+  if (EnvHasValue("MOZ_CRASHREPORTER")) {
+    mAppData->flags |= NS_XRE_ENABLE_CRASH_REPORTER;
+  }
+
+  nsCOMPtr<nsIFile> xreBinDirectory;
+  xreBinDirectory = mDirProvider.GetGREBinDir();
+
+  if ((mAppData->flags & NS_XRE_ENABLE_CRASH_REPORTER) &&
+      NS_SUCCEEDED(CrashReporter::SetExceptionHandler(xreBinDirectory))) {
+    nsCOMPtr<nsIFile> file;
+    rv = nsXREDirProvider::GetUserAppDataDirectory(getter_AddRefs(file));
+    if (NS_SUCCEEDED(rv)) {
+      CrashReporter::SetUserAppDataDirectory(file);
+    }
+    if (mAppData->crashReporterURL)
+      CrashReporter::SetServerURL(
+          nsDependentCString(mAppData->crashReporterURL));
+
+    // We overwrite this once we finish starting up.
+    CrashReporter::AnnotateCrashReport(CrashReporter::Annotation::StartupCrash,
+                                       true);
+
+    // pass some basic info from the app data
+    if (mAppData->vendor)
+      CrashReporter::AnnotateCrashReport(CrashReporter::Annotation::Vendor,
+                                         nsDependentCString(mAppData->vendor));
+    if (mAppData->name)
+      CrashReporter::AnnotateCrashReport(CrashReporter::Annotation::ProductName,
+                                         nsDependentCString(mAppData->name));
+    if (mAppData->ID)
+      CrashReporter::AnnotateCrashReport(CrashReporter::Annotation::ProductID,
+                                         nsDependentCString(mAppData->ID));
+    if (mAppData->version)
+      CrashReporter::AnnotateCrashReport(CrashReporter::Annotation::Version,
+                                         nsDependentCString(mAppData->version));
+    if (mAppData->buildID)
+      CrashReporter::AnnotateCrashReport(CrashReporter::Annotation::BuildID,
+                                         nsDependentCString(mAppData->buildID));
+
+    nsDependentCString releaseChannel(MOZ_STRINGIFY(MOZ_UPDATE_CHANNEL));
+    CrashReporter::AnnotateCrashReport(
+        CrashReporter::Annotation::ReleaseChannel, releaseChannel);
+#ifdef MOZ_LINKER
+    CrashReporter::AnnotateCrashReport(
+        CrashReporter::Annotation::CrashAddressLikelyWrong,
+        IsSignalHandlingBroken());
+#endif
+
+#ifdef XP_WIN
+    nsAutoString appInitDLLs;
+    if (widget::WinUtils::GetAppInitDLLs(appInitDLLs)) {
+      CrashReporter::AnnotateCrashReport(CrashReporter::Annotation::AppInitDLLs,
+                                         NS_ConvertUTF16toUTF8(appInitDLLs));
+    }
+
+    nsString packageFamilyName = widget::WinUtils::GetPackageFamilyName();
+    if (StringBeginsWith(packageFamilyName, u"Mozilla."_ns) ||
+        StringBeginsWith(packageFamilyName, u"MozillaCorporation."_ns)) {
+      CrashReporter::AnnotateCrashReport(
+          CrashReporter::Annotation::WindowsPackageFamilyName,
+          NS_ConvertUTF16toUTF8(packageFamilyName));
+    }
+#endif
+
+    bool isBackgroundTaskMode = false;
+#ifdef MOZ_BACKGROUNDTASKS
+    Maybe<nsCString> backgroundTasks = BackgroundTasks::GetBackgroundTasks();
+    if (backgroundTasks.isSome()) {
+      isBackgroundTaskMode = true;
+      CrashReporter::AnnotateCrashReport(
+          CrashReporter::Annotation::BackgroundTaskName, backgroundTasks.ref());
+    }
+#endif
+    CrashReporter::AnnotateCrashReport(
+        CrashReporter::Annotation::BackgroundTaskMode, isBackgroundTaskMode);
+
+    CrashReporter::AnnotateCrashReport(CrashReporter::Annotation::HeadlessMode,
+                                       gfxPlatform::IsHeadless());
+
+    CrashReporter::SetRestartArgs(gArgc, gArgv);
+
+    // annotate other data (user id etc)
+    nsCOMPtr<nsIFile> userAppDataDir;
+    if (NS_SUCCEEDED(mDirProvider.GetUserAppDataDirectory(
+            getter_AddRefs(userAppDataDir)))) {
+      CrashReporter::SetupExtraData(userAppDataDir,
+                                    nsDependentCString(mAppData->buildID));
+
+      // see if we have a crashreporter-override.ini in the application
+      // directory
+      nsCOMPtr<nsIFile> overrideini;
+      if (NS_SUCCEEDED(
+              mDirProvider.GetAppDir()->Clone(getter_AddRefs(overrideini))) &&
+          NS_SUCCEEDED(
+              overrideini->AppendNative("crashreporter-override.ini"_ns))) {
+#ifdef XP_WIN
+        nsAutoString overridePathW;
+        overrideini->GetPath(overridePathW);
+        NS_ConvertUTF16toUTF8 overridePath(overridePathW);
+#else
+        nsAutoCString overridePath;
+        overrideini->GetNativePath(overridePath);
+#endif
+
+        SaveWordToEnv("MOZ_CRASHREPORTER_STRINGS_OVERRIDE", overridePath);
+      }
+    }
+  } else {
+    // We might have registered a runtime exception module very early in process
+    // startup to catch early crashes. This is before we have access to ini file
+    // data, so unregister here if it turns out the crash reporter is disabled.
+    CrashReporter::UnregisterRuntimeExceptionModule();
+  }
+
+#if defined(MOZ_SANDBOX) && defined(XP_WIN)
+  if (mAppData->sandboxBrokerServices) {
+    SandboxBroker::Initialize(mAppData->sandboxBrokerServices);
+  } else {
+#  if defined(MOZ_SANDBOX)
+    // If we're sandboxing content and we fail to initialize, then crashing here
+    // seems like the sensible option.
+    if (BrowserTabsRemoteAutostart()) {
+      MOZ_CRASH("Failed to initialize broker services, can't continue.");
+    }
+#  endif
+    // Otherwise just warn for the moment, as most things will work.
+    NS_WARNING(
+        "Failed to initialize broker services, sandboxed processes will "
+        "fail to start.");
+  }
+#endif
+
+#ifdef XP_MACOSX
+  // Set up ability to respond to system (Apple) events. This must occur before
+  // ProcessUpdates to ensure that links clicked in external applications aren't
+  // lost when updates are pending.
+  SetupMacApplicationDelegate(&gRestartedByOS);
+
+  if (EnvHasValue("MOZ_LAUNCHED_CHILD")) {
+    // This is needed, on relaunch, to force the OS to use the "Cocoa Dock
+    // API".  Otherwise the call to ReceiveNextEvent() below will make it
+    // use the "Carbon Dock API".  For more info see bmo bug 377166.
+    EnsureUseCocoaDockAPI();
+
+    // When the app relaunches, the original process exits.  This causes
+    // the dock tile to stop bouncing, lose the "running" triangle, and
+    // if the tile does not permanently reside in the Dock, even disappear.
+    // This can be confusing to the user, who is expecting the app to launch.
+    // Calling ReceiveNextEvent without requesting any event is enough to
+    // cause a dock tile for the child process to appear.
+    const EventTypeSpec kFakeEventList[] = {{INT_MAX, INT_MAX}};
+    EventRef event;
+    ::ReceiveNextEvent(GetEventTypeCount(kFakeEventList), kFakeEventList,
+                       kEventDurationNoWait, false, &event);
+  }
+
+  if (CheckArg("foreground")) {
+    // The original process communicates that it was in the foreground by
+    // adding this argument.  This new process, which is taking over for
+    // the old one, should make itself the active application.
+    ProcessSerialNumber psn;
+    if (::GetCurrentProcess(&psn) == noErr) ::SetFrontProcess(&psn);
+  }
+#endif
+
+  SaveToEnv("MOZ_LAUNCHED_CHILD=");
+
+  // On Windows, the -os-restarted command line switch lets us know when we are
+  // restarted via RegisterApplicationRestart. May be used for other OSes later.
+  if (CheckArg("os-restarted", nullptr, CheckArgFlag::RemoveArg) == ARG_FOUND) {
+    gRestartedByOS = true;
+  }
+
+  gRestartArgc = gArgc;
+  gRestartArgv =
+      (char**)malloc(sizeof(char*) * (gArgc + 1 + (override ? 2 : 0)));
+  if (!gRestartArgv) {
+    return 1;
+  }
+
+  int i;
+  for (i = 0; i < gArgc; ++i) {
+    gRestartArgv[i] = gArgv[i];
+  }
+
+  // Add the -override argument back (it is removed automatically be CheckArg)
+  // if there is one
+  if (override) {
+    gRestartArgv[gRestartArgc++] = const_cast<char*>("-override");
+    gRestartArgv[gRestartArgc++] = const_cast<char*>(override);
+  }
+
+  gRestartArgv[gRestartArgc] = nullptr;
+
+  Maybe<bool> safeModeRequested = IsSafeModeRequested(gArgc, gArgv);
+  if (!safeModeRequested) {
+    return 1;
+  }
+#ifdef MOZ_BACKGROUNDTASKS
+  if (BackgroundTasks::IsBackgroundTaskMode()) {
+    safeModeRequested = Some(false);
+
+    // Remove the --backgroundtask arg now that it has been saved in
+    // gRestartArgv.
+    const char* tmpBackgroundTaskName = nullptr;
+    Unused << CheckArg("backgroundtask", &tmpBackgroundTaskName,
+                       CheckArgFlag::RemoveArg);
+  }
+#endif
+
+  gSafeMode = safeModeRequested.value();
+
+  MaybeAddCPUMicrocodeCrashAnnotation();
+  CrashReporter::AnnotateCrashReport(CrashReporter::Annotation::SafeMode,
+                                     gSafeMode);
+
+#if defined(MOZ_HAS_REMOTE)
+  // Handle --no-remote and --new-instance command line arguments. Setup
+  // the environment to better accommodate other components and various
+  // restart scenarios.
+  ar = CheckArg("no-remote");
+  if (ar == ARG_FOUND || EnvHasValue("MOZ_NO_REMOTE")) {
+    mDisableRemoteClient = true;
+    mDisableRemoteServer = true;
+    gRestartWithoutRemote = true;
+    // We don't want to propagate MOZ_NO_REMOTE to potential child
+    // process.
+    SaveToEnv("MOZ_NO_REMOTE=");
+  }
+
+  ar = CheckArg("new-instance");
+  if (ar == ARG_FOUND || EnvHasValue("MOZ_NEW_INSTANCE")) {
+    mDisableRemoteClient = true;
+  }
+#else
+  // These arguments do nothing in platforms with no remoting support but we
+  // should remove them from the command line anyway.
+  CheckArg("no-remote");
+  CheckArg("new-instance");
+#endif
+
+  ar = CheckArg("offline");
+  if (ar || EnvHasValue("XRE_START_OFFLINE")) {
+    mStartOffline = true;
+  }
+
+  // On Windows, to get working console arrangements so help/version/etc
+  // print something, we need to initialize the native app support.
+  rv = NS_CreateNativeAppSupport(getter_AddRefs(mNativeApp));
+  if (NS_FAILED(rv)) return 1;
+
+  // Handle --help, --full-version and --version command line arguments.
+  // They should return quickly, so we deal with them here.
+  if (CheckArg("h") || CheckArg("help") || CheckArg("?")) {
+    DumpHelp();
+    *aExitFlag = true;
+    return 0;
+  }
+
+  if (CheckArg("v") || CheckArg("version")) {
+    DumpVersion();
+    *aExitFlag = true;
+    return 0;
+  }
+
+  if (CheckArg("full-version")) {
+    DumpFullVersion();
+    *aExitFlag = true;
+    return 0;
+  }
+
+  rv = XRE_InitCommandLine(gArgc, gArgv);
+  NS_ENSURE_SUCCESS(rv, 1);
+
+  return 0;
+}
+
+#if defined(XP_LINUX) && !defined(ANDROID)
+
+static void AnnotateLSBRelease(void*) {
+  nsCString dist, desc, release, codename;
+  if (widget::lsb::GetLSBRelease(dist, desc, release, codename)) {
+    CrashReporter::AppendAppNotesToCrashReport(desc);
+  }
+}
+
+#endif  // defined(XP_LINUX) && !defined(ANDROID)
+
+#ifdef XP_WIN
+static void ReadAheadSystemDll(const wchar_t* dllName) {
+  wchar_t dllPath[MAX_PATH];
+  if (ConstructSystem32Path(dllName, dllPath, MAX_PATH)) {
+    ReadAheadLib(dllPath);
+  }
+}
+
+static void ReadAheadPackagedDll(const wchar_t* dllName,
+                                 const wchar_t* aGREDir) {
+  wchar_t dllPath[MAX_PATH];
+  swprintf(dllPath, MAX_PATH, L"%s\\%s", aGREDir, dllName);
+  ReadAheadLib(dllPath);
+}
+
+static void PR_CALLBACK ReadAheadDlls_ThreadStart(void* arg) {
+  UniquePtr<wchar_t[]> greDir(static_cast<wchar_t*>(arg));
+
+  // In Bug 1628903, we investigated which DLLs we should prefetch in
+  // order to reduce disk I/O and improve startup on Windows machines.
+  // Our ultimate goal is to measure the impact of these improvements on
+  // retention (see Bug 1640087). Before we place this within a pref,
+  // we should ensure this feature only ships to the nightly channel
+  // and monitor results from that subset.
+  if (greDir) {
+    // Prefetch the DLLs shipped with firefox
+    ReadAheadPackagedDll(L"libegl.dll", greDir.get());
+    ReadAheadPackagedDll(L"libGLESv2.dll", greDir.get());
+    ReadAheadPackagedDll(L"nssckbi.dll", greDir.get());
+    ReadAheadPackagedDll(L"freebl3.dll", greDir.get());
+    ReadAheadPackagedDll(L"softokn3.dll", greDir.get());
+
+    // Prefetch the system DLLs
+    ReadAheadSystemDll(L"DWrite.dll");
+    ReadAheadSystemDll(L"D3DCompiler_47.dll");
+  } else {
+    // Load DataExchange.dll and twinapi.appcore.dll for
+    // nsWindow::EnableDragDrop
+    ReadAheadSystemDll(L"DataExchange.dll");
+    ReadAheadSystemDll(L"twinapi.appcore.dll");
+
+    // Load twinapi.dll for WindowsUIUtils::UpdateTabletModeState
+    ReadAheadSystemDll(L"twinapi.dll");
+
+    // Load explorerframe.dll for WinTaskbar::Initialize
+    ReadAheadSystemDll(L"ExplorerFrame.dll");
+
+    // Load WinTypes.dll for nsOSHelperAppService::GetApplicationDescription
+    ReadAheadSystemDll(L"WinTypes.dll");
+  }
+}
+#endif
+
+#if defined(MOZ_UPDATER) && !defined(MOZ_WIDGET_ANDROID)
+enum struct ShouldNotProcessUpdatesReason {
+  DevToolsLaunching,
+  NotAnUpdatingTask,
+  OtherInstanceRunning,
+};
+
+const char* ShouldNotProcessUpdatesReasonAsString(
+    ShouldNotProcessUpdatesReason aReason) {
+  switch (aReason) {
+    case ShouldNotProcessUpdatesReason::DevToolsLaunching:
+      return "DevToolsLaunching";
+    case ShouldNotProcessUpdatesReason::NotAnUpdatingTask:
+      return "NotAnUpdatingTask";
+    case ShouldNotProcessUpdatesReason::OtherInstanceRunning:
+      return "OtherInstanceRunning";
+    default:
+      MOZ_CRASH("impossible value for ShouldNotProcessUpdatesReason");
+  }
+}
+
+Maybe<ShouldNotProcessUpdatesReason> ShouldNotProcessUpdates(
+    nsXREDirProvider& aDirProvider) {
+  // Do not process updates if we're launching devtools, as evidenced by
+  // "--chrome ..." with the browser toolbox chrome document URL.
+
+  // Keep this synchronized with the value of the same name in
+  // devtools/client/framework/browser-toolbox/Launcher.sys.mjs.  Or, for bonus
+  // points, lift this value to nsIXulRuntime or similar, so that it can be
+  // accessed in both locations.  (The prefs service isn't available at this
+  // point so the simplest manner of sharing the value is not available to us.)
+  const char* BROWSER_TOOLBOX_WINDOW_URL =
+      "chrome://devtools/content/framework/browser-toolbox/window.html";
+
+  const char* chromeParam = nullptr;
+  if (ARG_FOUND == CheckArg("chrome", &chromeParam, CheckArgFlag::None)) {
+    if (!chromeParam || !strcmp(BROWSER_TOOLBOX_WINDOW_URL, chromeParam)) {
+      NS_WARNING("ShouldNotProcessUpdates(): DevToolsLaunching");
+      return Some(ShouldNotProcessUpdatesReason::DevToolsLaunching);
+    }
+  }
+
+#  ifdef MOZ_BACKGROUNDTASKS
+  // Do not process updates if we're running a background task mode and another
+  // instance is already running.  This avoids periodic maintenance updating
+  // underneath a browsing session.
+  Maybe<nsCString> backgroundTasks = BackgroundTasks::GetBackgroundTasks();
+  if (backgroundTasks.isSome()) {
+    // Only process updates for specific tasks: at this time, the
+    // `backgroundupdate` task and the test-only `shouldprocessupdates` task.
+    //
+    // Background tasks can be sparked by Firefox instances that are shutting
+    // down, which can cause races between the task startup trying to update and
+    // Firefox trying to invoke the updater.  This happened when converting
+    // `pingsender` to a background task, since it is launched to send pings at
+    // shutdown: Bug 1736373.
+    //
+    // We'd prefer to have this be a property of the task definition sibling to
+    // `backgroundTaskTimeoutSec`, but when we reach this code we're well before
+    // we can load the task JSM.
+    if (!BackgroundTasks::IsUpdatingTaskName(backgroundTasks.ref())) {
+      NS_WARNING("ShouldNotProcessUpdates(): NotAnUpdatingTask");
+      return Some(ShouldNotProcessUpdatesReason::NotAnUpdatingTask);
+    }
+
+    // At this point we have a dir provider but no XPCOM directory service.  We
+    // launch the update sync manager using that information so that it doesn't
+    // need to ask for (and fail to find) the directory service.
+    nsCOMPtr<nsIFile> anAppFile;
+    bool persistent;
+    nsresult rv = aDirProvider.GetFile(XRE_EXECUTABLE_FILE, &persistent,
+                                       getter_AddRefs(anAppFile));
+    if (NS_FAILED(rv) || !anAppFile) {
+      // Strange, but not a reason to skip processing updates.
+      return Nothing();
+    }
+
+    auto updateSyncManager = new nsUpdateSyncManager(anAppFile);
+
+    bool otherInstance = false;
+    updateSyncManager->IsOtherInstanceRunning(&otherInstance);
+    if (otherInstance) {
+      NS_WARNING("ShouldNotProcessUpdates(): OtherInstanceRunning");
+      return Some(ShouldNotProcessUpdatesReason::OtherInstanceRunning);
+    }
+  }
+#  endif
+
+  return Nothing();
+}
+#endif
+
+namespace mozilla::startup {
+Result<nsCOMPtr<nsIFile>, nsresult> GetIncompleteStartupFile(nsIFile* aProfLD) {
+  nsCOMPtr<nsIFile> crashFile;
+  MOZ_TRY(aProfLD->Clone(getter_AddRefs(crashFile)));
+  MOZ_TRY(crashFile->Append(FILE_STARTUP_INCOMPLETE));
+  return std::move(crashFile);
+}
+}  // namespace mozilla::startup
+
+// Check whether the last startup attempt resulted in a crash or hang.
+// This is distinct from the definition of a startup crash from
+// nsAppStartup::TrackStartupCrashBegin.
+bool XREMain::CheckLastStartupWasCrash() {
+  Result<nsCOMPtr<nsIFile>, nsresult> crashFile =
+      GetIncompleteStartupFile(mProfLD);
+  if (crashFile.isErr()) {
+    return true;
+  }
+
+  // Attempt to create the incomplete startup canary file. If the file already
+  // exists, this fails, and we know the last startup was a crash. If it
+  // doesn't already exist, it is created, and will be removed at the end of
+  // the startup crash detection window.
+  AutoFDClose fd;
+  Unused << crashFile.inspect()->OpenNSPRFileDesc(
+      PR_WRONLY | PR_CREATE_FILE | PR_EXCL, 0666, &fd.rwget());
+  return !fd;
+}
+
+/*
+ * XRE_mainStartup - Initializes the profile and various other services.
+ * Main() will exit early if either return value != 0 or if aExitFlag is
+ * true.
+ */
+int XREMain::XRE_mainStartup(bool* aExitFlag) {
+  nsresult rv;
+
+  if (!aExitFlag) return 1;
+  *aExitFlag = false;
+
+#ifdef XP_MACOSX
+  mozilla::MacAutoreleasePool pool;
+#endif
+
+  // Enable Telemetry IO Reporting on DEBUG, nightly and local builds,
+  // but disable it on FUZZING builds and for ANDROID.
+#ifndef FUZZING
+#  ifndef ANDROID
+#    ifdef DEBUG
+  mozilla::Telemetry::InitIOReporting(gAppData->xreDirectory);
+#    else
+  {
+    const char* releaseChannel = MOZ_STRINGIFY(MOZ_UPDATE_CHANNEL);
+    if (strcmp(releaseChannel, "nightly") == 0 ||
+        strcmp(releaseChannel, "default") == 0) {
+      mozilla::Telemetry::InitIOReporting(gAppData->xreDirectory);
+    }
+  }
+#    endif /* DEBUG */
+#  endif   /* ANDROID */
+#endif     /* FUZZING */
+
+#if defined(XP_WIN)
+  // Enable the HeapEnableTerminationOnCorruption exploit mitigation. We ignore
+  // the return code because it always returns success, although it has no
+  // effect on Windows older than XP SP3.
+  HeapSetInformation(NULL, HeapEnableTerminationOnCorruption, NULL, 0);
+#endif /* XP_WIN */
+
+#ifdef MOZ_WIDGET_GTK
+  // Stash startup token in owned memory because gtk_init will clear
+  // DESKTOP_STARTUP_ID it.
+  if (const char* v = PR_GetEnv("DESKTOP_STARTUP_ID")) {
+    mDesktopStartupID.Assign(v);
+  }
+  if (const char* v = PR_GetEnv("XDG_ACTIVATION_TOKEN")) {
+    mXDGActivationToken.Assign(v);
+  }
+#endif
+
+#if defined(XP_WIN)
+  {
+    // Save the shortcut path before lpTitle is replaced by an AUMID,
+    // such as by WinTaskbar
+    STARTUPINFOW si;
+    GetStartupInfoW(&si);
+    if (si.dwFlags & STARTF_TITLEISAPPID) {
+      NS_WARNING("AUMID was already set, shortcut may have been lost.");
+    } else if ((si.dwFlags & STARTF_TITLEISLINKNAME) && si.lpTitle) {
+      gProcessStartupShortcut.Assign(si.lpTitle);
+    }
+  }
+#endif /* XP_WIN */
+
+#if defined(MOZ_WIDGET_GTK)
+  // setup for private colormap.  Ideally we'd like to do this
+  // in nsAppShell::Create, but we need to get in before gtk
+  // has been initialized to make sure everything is running
+  // consistently.
+
+  // Set program name to the one defined in application.ini.
+  g_set_prgname(gAppData->remotingName);
+
+  // Initialize GTK here for splash.
+
+#  if defined(MOZ_WIDGET_GTK) && defined(MOZ_X11)
+  // Disable XInput2 multidevice support due to focus bugginess.
+  // See bugs 1182700, 1170342.
+  // gdk_disable_multidevice() affects Gdk X11 backend only,
+  // the multidevice support is always enabled on Wayland backend.
+  const char* useXI2 = PR_GetEnv("MOZ_USE_XINPUT2");
+  if (!useXI2 || (*useXI2 == '0')) gdk_disable_multidevice();
+#  endif
+
+  // Open the display ourselves instead of using gtk_init, so that we can
+  // close it without fear that one day gtk might clean up the display it
+  // opens.
+  if (!gtk_parse_args(&gArgc, &gArgv)) return 1;
+#endif /* MOZ_WIDGET_GTK */
+
+#ifdef FUZZING
+  if (PR_GetEnv("FUZZER")) {
+    *aExitFlag = true;
+    return mozilla::fuzzerRunner->Run(&gArgc, &gArgv);
+  }
+#endif
+
+  if (PR_GetEnv("MOZ_RUN_GTEST")) {
+    int result;
+#ifdef XP_WIN
+    UseParentConsole();
+#endif
+    // RunGTest will only be set if we're in xul-unit
+    if (mozilla::RunGTest) {
+      gIsGtest = true;
+      result = mozilla::RunGTest(&gArgc, gArgv);
+      gIsGtest = false;
+    } else {
+      result = 1;
+      printf("TEST-UNEXPECTED-FAIL | gtest | Not compiled with enable-tests\n");
+    }
+    *aExitFlag = true;
+    return result;
+  }
+
+  bool isBackgroundTaskMode = false;
+#ifdef MOZ_BACKGROUNDTASKS
+  isBackgroundTaskMode = BackgroundTasks::IsBackgroundTaskMode();
+#endif
+
+#ifdef MOZ_HAS_REMOTE
+  if (gfxPlatform::IsHeadless()) {
+    mDisableRemoteClient = true;
+    mDisableRemoteServer = true;
+  }
+#endif
+
+#ifdef MOZ_X11
+  // Init X11 in thread-safe mode. Must be called prior to the first call to
+  // XOpenDisplay (called inside gdk_display_open). This is a requirement for
+  // off main tread compositing.
+  if (!isBackgroundTaskMode && !gfxPlatform::IsHeadless()) {
+    XInitThreads();
+  }
+#endif
+#if defined(MOZ_WIDGET_GTK)
+  if (!isBackgroundTaskMode && !gfxPlatform::IsHeadless()) {
+    const char* display_name = nullptr;
+    bool saveDisplayArg = false;
+
+    // display_name is owned by gdk.
+    display_name = gdk_get_display_arg_name();
+    // if --display argument is given make sure it's
+    // also passed to ContentChild::Init() by MOZ_GDK_DISPLAY.
+    if (display_name) {
+      SaveWordToEnv("MOZ_GDK_DISPLAY", nsDependentCString(display_name));
+      saveDisplayArg = true;
+    }
+
+    bool waylandEnabled = IsWaylandEnabled();
+    // On Wayland disabled builds read X11 DISPLAY env exclusively
+    // and don't care about different displays.
+    if (!waylandEnabled && !display_name) {
+      display_name = PR_GetEnv("DISPLAY");
+      if (!display_name) {
+        PR_fprintf(PR_STDERR,
+                   "Error: no DISPLAY environment variable specified\n");
+        return 1;
+      }
+    }
+
+    if (display_name) {
+      GdkDisplay* disp = gdk_display_open(display_name);
+      if (!disp) {
+        PR_fprintf(PR_STDERR, "Error: cannot open display: %s\n", display_name);
+        return 1;
+      }
+      if (saveDisplayArg) {
+        if (GdkIsX11Display(disp)) {
+          SaveWordToEnv("DISPLAY", nsDependentCString(display_name));
+        }
+#  ifdef MOZ_WAYLAND
+        else if (GdkIsWaylandDisplay(disp)) {
+          SaveWordToEnv("WAYLAND_DISPLAY", nsDependentCString(display_name));
+        }
+#  endif
+      }
+    }
+#  ifdef MOZ_WIDGET_GTK
+    else {
+      gdk_display_manager_open_display(gdk_display_manager_get(), nullptr);
+    }
+#  endif
+  }
+#endif
+#if defined(MOZ_HAS_REMOTE)
+  // handle --remote now that xpcom is fired up
+  mRemoteService = new nsRemoteService(gAppData->remotingName);
+  if (mRemoteService && !mDisableRemoteServer) {
+    mRemoteService->LockStartup();
+    gRemoteService = mRemoteService;
+  }
+#endif
+#if defined(MOZ_WIDGET_GTK)
+  g_set_application_name(mAppData->name);
+
+#endif /* defined(MOZ_WIDGET_GTK) */
+#ifdef MOZ_X11
+  // Do this after initializing GDK, or GDK will install its own handler.
+  XRE_InstallX11ErrorHandler();
+#endif
+
+  // Call the code to install our handler
+#ifdef MOZ_JPROF
+  setupProfilingStuff();
+#endif
+
+  bool canRun = false;
+  rv = mNativeApp->Start(&canRun);
+  if (NS_FAILED(rv) || !canRun) {
+    return 1;
+  }
+
+#ifdef MOZ_WIDGET_GTK
+  // startup token might be cleared now, we recover it in case we need a
+  // restart.
+  if (!mDesktopStartupID.IsEmpty()) {
+    // Leak it with extreme prejudice!
+    PR_SetEnv(ToNewCString("DESKTOP_STARTUP_ID="_ns + mDesktopStartupID));
+  }
+
+  if (!mXDGActivationToken.IsEmpty()) {
+    // Leak it with extreme prejudice!
+    PR_SetEnv(ToNewCString("XDG_ACTIVATION_TOKEN="_ns + mXDGActivationToken));
+  }
+#endif
+
+  // Support exiting early for testing startup sequence. Bug 1360493
+  if (CheckArg("test-launch-without-hang")) {
+    *aExitFlag = true;
+    return 0;
+  }
+
+  mProfileSvc = NS_GetToolkitProfileService();
+  if (!mProfileSvc) {
+    // We failed to choose or create profile - notify user and quit
+    ProfileMissingDialog(mNativeApp);
+    return 1;
+  }
+
+  bool wasDefaultSelection;
+  nsCOMPtr<nsIToolkitProfile> profile;
+  rv = SelectProfile(mProfileSvc, mNativeApp, getter_AddRefs(mProfD),
+                     getter_AddRefs(mProfLD), getter_AddRefs(profile),
+                     &wasDefaultSelection);
+  if (rv == NS_ERROR_LAUNCHED_CHILD_PROCESS || rv == NS_ERROR_ABORT) {
+    *aExitFlag = true;
+    return 0;
+  }
+
+  if (NS_FAILED(rv)) {
+    // We failed to choose or create profile - notify user and quit
+    ProfileMissingDialog(mNativeApp);
+    return 1;
+  }
+
+#if defined(MOZ_HAS_REMOTE)
+  if (mRemoteService) {
+    // We want a unique profile name to identify the remote instance.
+    nsCString profileName;
+    if (profile) {
+      rv = profile->GetName(profileName);
+    }
+    if (!profile || NS_FAILED(rv) || profileName.IsEmpty()) {
+      // Couldn't get a name from the profile. Use the directory name?
+      nsString leafName;
+      rv = mProfD->GetLeafName(leafName);
+      if (NS_SUCCEEDED(rv)) {
+        CopyUTF16toUTF8(leafName, profileName);
+      }
+    }
+
+    mRemoteService->SetProfile(profileName);
+
+    if (!mDisableRemoteClient) {
+      // Try to remote the entire command line. If this fails, start up
+      // normally.
+#  ifdef MOZ_WIDGET_GTK
+      const auto& startupToken =
+          GdkIsWaylandDisplay() ? mXDGActivationToken : mDesktopStartupID;
+#  else
+      const nsCString startupToken;
+#  endif
+      RemoteResult rr = mRemoteService->StartClient(
+          startupToken.IsEmpty() ? nullptr : startupToken.get());
+      if (rr == REMOTE_FOUND) {
+        *aExitFlag = true;
+        mRemoteService->UnlockStartup();
+        return 0;
+      }
+      if (rr == REMOTE_ARG_BAD) {
+        mRemoteService->UnlockStartup();
+        return 1;
+      }
+    }
+  }
+#endif
+
+#if defined(MOZ_UPDATER) && !defined(MOZ_WIDGET_ANDROID)
+  Maybe<ShouldNotProcessUpdatesReason> shouldNotProcessUpdatesReason =
+      ShouldNotProcessUpdates(mDirProvider);
+  if (shouldNotProcessUpdatesReason.isNothing()) {
+    // Check for and process any available updates
+    nsCOMPtr<nsIFile> updRoot;
+    bool persistent;
+    rv = mDirProvider.GetFile(XRE_UPDATE_ROOT_DIR, &persistent,
+                              getter_AddRefs(updRoot));
+    // XRE_UPDATE_ROOT_DIR may fail. Fallback to appDir if failed
+    if (NS_FAILED(rv)) {
+      updRoot = mDirProvider.GetAppDir();
+    }
+
+    // If the MOZ_TEST_PROCESS_UPDATES environment variable already exists, then
+    // we are being called from the callback application.
+    if (EnvHasValue("MOZ_TEST_PROCESS_UPDATES")) {
+      // If the caller has asked us to log our arguments, do so.  This is used
+      // to make sure that the maintenance service successfully launches the
+      // callback application.
+      const char* logFile = nullptr;
+      if (ARG_FOUND == CheckArg("dump-args", &logFile)) {
+        FILE* logFP = fopen(logFile, "wb");
+        if (logFP) {
+          for (int i = 1; i < gRestartArgc; ++i) {
+            fprintf(logFP, "%s\n", gRestartArgv[i]);
+          }
+          fclose(logFP);
+        }
+      }
+      *aExitFlag = true;
+      return 0;
+    }
+
+    // Support for processing an update and exiting. The
+    // MOZ_TEST_PROCESS_UPDATES environment variable will be part of the
+    // updater's environment and the application that is relaunched by the
+    // updater. When the application is relaunched by the updater it will be
+    // removed below and the application will exit.
+    if (CheckArg("test-process-updates")) {
+      SaveToEnv("MOZ_TEST_PROCESS_UPDATES=1");
+    }
+    nsCOMPtr<nsIFile> exeFile, exeDir;
+    rv = mDirProvider.GetFile(XRE_EXECUTABLE_FILE, &persistent,
+                              getter_AddRefs(exeFile));
+    NS_ENSURE_SUCCESS(rv, 1);
+    rv = exeFile->GetParent(getter_AddRefs(exeDir));
+    NS_ENSURE_SUCCESS(rv, 1);
+    ProcessUpdates(mDirProvider.GetGREDir(), exeDir, updRoot, gRestartArgc,
+                   gRestartArgv, mAppData->version);
+    if (EnvHasValue("MOZ_TEST_PROCESS_UPDATES")) {
+      SaveToEnv("MOZ_TEST_PROCESS_UPDATES=");
+      *aExitFlag = true;
+      return 0;
+    }
+  } else {
+    if (CheckArg("test-process-updates") ||
+        EnvHasValue("MOZ_TEST_PROCESS_UPDATES")) {
+      // Support for testing *not* processing an update.  The launched process
+      // can witness this environment variable and conclude that its runtime
+      // environment resulted in not processing updates.
+
+      SaveToEnv(nsPrintfCString(
+                    "MOZ_TEST_PROCESS_UPDATES=ShouldNotProcessUpdates(): %s",
+                    ShouldNotProcessUpdatesReasonAsString(
+                        shouldNotProcessUpdatesReason.value()))
+                    .get());
+    }
+  }
+#endif
+
+  // We now know there is no existing instance using the selected profile. If
+  // the profile wasn't selected by specific command line arguments and the
+  // user has chosen to show the profile manager on startup then do that.
+  if (wasDefaultSelection) {
+    bool useSelectedProfile;
+    rv = mProfileSvc->GetStartWithLastProfile(&useSelectedProfile);
+    NS_ENSURE_SUCCESS(rv, 1);
+
+    if (!useSelectedProfile) {
+      rv = ShowProfileManager(mProfileSvc, mNativeApp);
+      if (rv == NS_ERROR_LAUNCHED_CHILD_PROCESS || rv == NS_ERROR_ABORT) {
+        *aExitFlag = true;
+        return 0;
+      }
+      if (NS_FAILED(rv)) {
+        return 1;
+      }
+    }
+  }
+
+  // We always want to lock the profile even if we're actually going to reset
+  // it later.
+  rv = LockProfile(mNativeApp, mProfD, mProfLD, profile,
+                   getter_AddRefs(mProfileLock));
+  if (rv == NS_ERROR_LAUNCHED_CHILD_PROCESS || rv == NS_ERROR_ABORT) {
+    *aExitFlag = true;
+    return 0;
+  } else if (NS_FAILED(rv)) {
+    return 1;
+  }
+
+  if (gDoProfileReset) {
+    if (EnvHasValue("MOZ_RESET_PROFILE_RESTART")) {
+      SaveToEnv("MOZ_RESET_PROFILE_RESTART=");
+      // We only want to restore the previous session if the profile refresh was
+      // triggered by user. And if it was a user-triggered profile refresh
+      // through, say, the safeMode dialog or the troubleshooting page, the
+      // MOZ_RESET_PROFILE_RESTART env variable would be set. Hence we set
+      // MOZ_RESET_PROFILE_MIGRATE_SESSION here so that Firefox profile migrator
+      // would migrate old session data later.
+      SaveToEnv("MOZ_RESET_PROFILE_MIGRATE_SESSION=1");
+    }
+    // Unlock the source profile.
+    mProfileLock->Unlock();
+
+    // If we're resetting a profile, create a new one and use it to startup.
+    gResetOldProfile = profile;
+    rv = mProfileSvc->CreateResetProfile(getter_AddRefs(profile));
+    if (NS_SUCCEEDED(rv)) {
+      rv = profile->GetRootDir(getter_AddRefs(mProfD));
+      NS_ENSURE_SUCCESS(rv, 1);
+      SaveFileToEnv("XRE_PROFILE_PATH", mProfD);
+
+      rv = profile->GetLocalDir(getter_AddRefs(mProfLD));
+      NS_ENSURE_SUCCESS(rv, 1);
+      SaveFileToEnv("XRE_PROFILE_LOCAL_PATH", mProfLD);
+
+      // Lock the new profile
+      rv = LockProfile(mNativeApp, mProfD, mProfLD, profile,
+                       getter_AddRefs(mProfileLock));
+      if (rv == NS_ERROR_LAUNCHED_CHILD_PROCESS || rv == NS_ERROR_ABORT) {
+        *aExitFlag = true;
+        return 0;
+      } else if (NS_FAILED(rv)) {
+        return 1;
+      }
+    } else {
+      NS_WARNING("Profile reset failed.");
+      return 1;
+    }
+  }
+
+  gProfileLock = mProfileLock;
+
+  nsAutoCString version;
+  BuildVersion(version);
+
+#ifdef TARGET_OS_ABI
+  constexpr auto osABI = nsLiteralCString{TARGET_OS_ABI};
+#else
+  // No TARGET_XPCOM_ABI, but at least the OS is known
+  constexpr auto osABI = nsLiteralCString{OS_TARGET "_UNKNOWN"};
+#endif
+
+  // Check for version compatibility with the last version of the app this
+  // profile was started with.  The format of the version stamp is defined
+  // by the BuildVersion function.
+  // Also check to see if something has happened to invalidate our
+  // fastload caches, like an app upgrade.
+
+  // If we see .purgecaches, that means someone did a make.
+  // Re-register components to catch potential changes.
+  nsCOMPtr<nsIFile> flagFile;
+  if (mAppData->directory) {
+    Unused << mAppData->directory->Clone(getter_AddRefs(flagFile));
+  }
+  if (flagFile) {
+    flagFile->AppendNative(FILE_INVALIDATE_CACHES);
+  }
+
+  bool cachesOK;
+  bool isDowngrade;
+  nsCString lastVersion;
+  bool versionOK = CheckCompatibility(
+      mProfD, version, osABI, mDirProvider.GetGREDir(), mAppData->directory,
+      flagFile, &cachesOK, &isDowngrade, lastVersion);
+
+  MOZ_RELEASE_ASSERT(!cachesOK || lastVersion.Equals(version),
+                     "Caches cannot be good if the version has changed.");
+
+#ifdef MOZ_BLOCK_PROFILE_DOWNGRADE
+  // The argument check must come first so the argument is always removed from
+  // the command line regardless of whether this is a downgrade or not.
+  if (!CheckArg("allow-downgrade") && isDowngrade &&
+      !EnvHasValue("MOZ_ALLOW_DOWNGRADE")) {
+    rv = CheckDowngrade(mProfD, mNativeApp, mProfileSvc, lastVersion);
+    if (rv == NS_ERROR_LAUNCHED_CHILD_PROCESS || rv == NS_ERROR_ABORT) {
+      *aExitFlag = true;
+      return 0;
+    }
+  }
+#endif
+
+  rv = mDirProvider.SetProfile(mProfD, mProfLD);
+  NS_ENSURE_SUCCESS(rv, 1);
+
+  //////////////////////// NOW WE HAVE A PROFILE ////////////////////////
+
+  mozilla::Telemetry::SetProfileDir(mProfD);
+
+  if (mAppData->flags & NS_XRE_ENABLE_CRASH_REPORTER) {
+    MakeOrSetMinidumpPath(mProfD);
+  }
+
+  CrashReporter::SetProfileDirectory(mProfD);
+
+#ifdef MOZ_ASAN_REPORTER
+  // In ASan reporter builds, we need to set ASan's log_path as early as
+  // possible, so it dumps its errors into files there instead of using
+  // the default stderr location. Since this is crucial for ASan reporter
+  // to work at all (and we don't want people to use a non-functional
+  // ASan reporter build), all failures while setting log_path are fatal.
+  setASanReporterPath(mProfD);
+
+  // Export to env for child processes
+  SaveFileToEnv("ASAN_REPORTER_PATH", mProfD);
+#endif
+
+  bool lastStartupWasCrash = CheckLastStartupWasCrash();
+
+  CrashReporter::AnnotateCrashReport(
+      CrashReporter::Annotation::LastStartupWasCrash, lastStartupWasCrash);
+
+  if (CheckArg("purgecaches") || PR_GetEnv("MOZ_PURGE_CACHES") ||
+      lastStartupWasCrash || gSafeMode) {
+    cachesOK = false;
+  }
+
+  CrashReporter::AnnotateCrashReport(
+      CrashReporter::Annotation::StartupCacheValid, cachesOK && versionOK);
+
+  // Every time a profile is loaded by a build with a different version,
+  // it updates the compatibility.ini file saying what version last wrote
+  // the fastload caches.  On subsequent launches if the version matches,
+  // there is no need for re-registration.  If the user loads the same
+  // profile in different builds the component registry must be
+  // re-generated to prevent mysterious component loading failures.
+  //
+  bool startupCacheValid = true;
+
+  if (!cachesOK || !versionOK) {
+    QuotaManager::InvalidateQuotaCache();
+
+    startupCacheValid = RemoveComponentRegistries(mProfD, mProfLD, false);
+
+    // Rewrite compatibility.ini to match the current build. The next run
+    // should attempt to invalidate the caches if either this run is safe mode
+    // or the attempt to invalidate the caches this time failed.
+    WriteVersion(mProfD, version, osABI, mDirProvider.GetGREDir(),
+                 mAppData->directory, gSafeMode || !startupCacheValid);
+  }
+
+  if (!startupCacheValid) StartupCache::IgnoreDiskCache();
+
+  if (flagFile) {
+    flagFile->Remove(true);
+  }
+
+  // Flush any pending page load events.
+  mozilla::glean_pings::Pageload.Submit("startup"_ns);
+
+  if (!isBackgroundTaskMode) {
+#ifdef USE_GLX_TEST
+    GfxInfo::FireGLXTestProcess();
+#endif
+#ifdef MOZ_WAYLAND
+    // Make sure we have wayland connection for main thread.
+    // It's used as template to create display connections
+    // for different threads.
+    if (IsWaylandEnabled()) {
+      MOZ_UNUSED(WaylandDisplayGet());
+    }
+#endif
+  }
+
+  return 0;
+}
+
+#if defined(MOZ_SANDBOX)
+void AddSandboxAnnotations() {
+  {
+    // Include the sandbox content level, regardless of platform
+    int level = GetEffectiveContentSandboxLevel();
+
+    nsAutoCString levelString;
+    levelString.AppendInt(level);
+
+    CrashReporter::AnnotateCrashReport(
+        CrashReporter::Annotation::ContentSandboxLevel, levelString);
+  }
+
+  {
+    int level = GetEffectiveGpuSandboxLevel();
+
+    nsAutoCString levelString;
+    levelString.AppendInt(level);
+
+    CrashReporter::AnnotateCrashReport(
+        CrashReporter::Annotation::GpuSandboxLevel, levelString);
+  }
+
+  // Include whether or not this instance is capable of content sandboxing
+  bool sandboxCapable = false;
+
+#  if defined(XP_WIN)
+  // All supported Windows versions support some level of content sandboxing
+  sandboxCapable = true;
+#  elif defined(XP_MACOSX)
+  // All supported OS X versions are capable
+  sandboxCapable = true;
+#  elif defined(XP_LINUX)
+  sandboxCapable = SandboxInfo::Get().CanSandboxContent();
+#  elif defined(__OpenBSD__)
+  sandboxCapable = true;
+  StartOpenBSDSandbox(GeckoProcessType_Default);
+#  endif
+
+  CrashReporter::AnnotateCrashReport(
+      CrashReporter::Annotation::ContentSandboxCapable, sandboxCapable);
+}
+#endif /* MOZ_SANDBOX */
+
+/*
+ * XRE_mainRun - Command line startup, profile migration, and
+ * the calling of appStartup->Run().
+ */
+nsresult XREMain::XRE_mainRun() {
+  nsresult rv = NS_OK;
+  NS_ASSERTION(mScopedXPCOM, "Scoped xpcom not initialized.");
+
+#if defined(XP_WIN)
+  RefPtr<mozilla::DllServices> dllServices(mozilla::DllServices::Get());
+  dllServices->StartUntrustedModulesProcessor(false);
+  auto dllServicesDisable =
+      MakeScopeExit([&dllServices]() { dllServices->DisableFull(); });
+
+  mozilla::mscom::InitProfilerMarkers();
+#endif  // defined(XP_WIN)
+
+  // We need the appStartup pointer to span multiple scopes, so we declare
+  // it here.
+  nsCOMPtr<nsIAppStartup> appStartup;
+  // Ditto with the command line.
+  nsCOMPtr<nsICommandLineRunner> cmdLine;
+
+  {
+#ifdef XP_MACOSX
+    // In this scope, create an autorelease pool that will leave scope with
+    // it just before entering our event loop.
+    mozilla::MacAutoreleasePool pool;
+#endif
+
+    rv = mScopedXPCOM->SetWindowCreator(mNativeApp);
+    NS_ENSURE_SUCCESS(rv, NS_ERROR_FAILURE);
+
+    // tell the crash reporter to also send the release channel
+    nsCOMPtr<nsIPrefService> prefs =
+        do_GetService("@mozilla.org/preferences-service;1", &rv);
+    if (NS_SUCCEEDED(rv)) {
+      nsCOMPtr<nsIPrefBranch> defaultPrefBranch;
+      rv = prefs->GetDefaultBranch(nullptr, getter_AddRefs(defaultPrefBranch));
+
+      if (NS_SUCCEEDED(rv)) {
+        nsAutoCString sval;
+        rv = defaultPrefBranch->GetCharPref("app.update.channel", sval);
+        if (NS_SUCCEEDED(rv)) {
+          CrashReporter::AnnotateCrashReport(
+              CrashReporter::Annotation::ReleaseChannel, sval);
+        }
+      }
+    }
+    // Needs to be set after xpcom initialization.
+    bool includeContextHeap = Preferences::GetBool(
+        "toolkit.crashreporter.include_context_heap", false);
+    CrashReporter::SetIncludeContextHeap(includeContextHeap);
+
+#if defined(XP_LINUX) && !defined(ANDROID)
+    PR_CreateThread(PR_USER_THREAD, AnnotateLSBRelease, 0, PR_PRIORITY_LOW,
+                    PR_GLOBAL_THREAD, PR_UNJOINABLE_THREAD, 0);
+#endif
+
+    if (mStartOffline) {
+      nsCOMPtr<nsIIOService> io(
+          do_GetService("@mozilla.org/network/io-service;1"));
+      NS_ENSURE_TRUE(io, NS_ERROR_FAILURE);
+      io->SetManageOfflineStatus(false);
+      io->SetOffline(true);
+    }
+
+#ifdef XP_WIN
+    mozilla::DllPrefetchExperimentRegistryInfo prefetchRegInfo;
+    mozilla::AlteredDllPrefetchMode dllPrefetchMode =
+        prefetchRegInfo.GetAlteredDllPrefetchMode();
+
+    if (!PR_GetEnv("XRE_NO_DLL_READAHEAD") &&
+        dllPrefetchMode != mozilla::AlteredDllPrefetchMode::NoPrefetch) {
+      nsCOMPtr<nsIFile> greDir = mDirProvider.GetGREDir();
+      nsAutoString path;
+      rv = greDir->GetPath(path);
+      if (NS_SUCCEEDED(rv)) {
+        PRThread* readAheadThread;
+        wchar_t* pathRaw;
+
+        // We use the presence of a path argument inside the thread to determine
+        // which list of Dlls to use. The old list does not need access to the
+        // GRE dir, so the path argument is set to a null pointer.
+        if (dllPrefetchMode ==
+            mozilla::AlteredDllPrefetchMode::OptimizedPrefetch) {
+          pathRaw = new wchar_t[MAX_PATH];
+          wcscpy_s(pathRaw, MAX_PATH, path.get());
+        } else {
+          pathRaw = nullptr;
+        }
+        readAheadThread = PR_CreateThread(
+            PR_USER_THREAD, ReadAheadDlls_ThreadStart, (void*)pathRaw,
+            PR_PRIORITY_NORMAL, PR_GLOBAL_THREAD, PR_UNJOINABLE_THREAD, 0);
+        if (readAheadThread == NULL) {
+          delete[] pathRaw;
+        }
+      }
+    }
+#endif
+
+    if (gDoMigration) {
+      nsCOMPtr<nsIFile> file;
+      mDirProvider.GetAppDir()->Clone(getter_AddRefs(file));
+      file->AppendNative("override.ini"_ns);
+      nsINIParser parser;
+      nsresult rv = parser.Init(file);
+      // if override.ini doesn't exist, also check for distribution.ini
+      if (NS_FAILED(rv)) {
+        bool persistent;
+        mDirProvider.GetFile(XRE_APP_DISTRIBUTION_DIR, &persistent,
+                             getter_AddRefs(file));
+        file->AppendNative("distribution.ini"_ns);
+        rv = parser.Init(file);
+      }
+      if (NS_SUCCEEDED(rv)) {
+        nsAutoCString buf;
+        rv = parser.GetString("XRE", "EnableProfileMigrator", buf);
+        if (NS_SUCCEEDED(rv)) {
+          if (buf[0] == '0' || buf[0] == 'f' || buf[0] == 'F') {
+            gDoMigration = false;
+          }
+        }
+      }
+    }
+
+    // We'd like to initialize the JSContext *after* reading the user prefs.
+    // Unfortunately that's not possible if we have to do profile migration
+    // because that requires us to execute JS before reading user prefs.
+    // Restarting the browser after profile migration would fix this. See
+    // bug 1592523.
+    bool initializedJSContext = false;
+
+    {
+      // Profile Migration
+      if (mAppData->flags & NS_XRE_ENABLE_PROFILE_MIGRATOR && gDoMigration) {
+        gDoMigration = false;
+
+        xpc::InitializeJSContext();
+        initializedJSContext = true;
+
+        nsCOMPtr<nsIProfileMigrator> pm(
+            do_CreateInstance(NS_PROFILEMIGRATOR_CONTRACTID));
+        if (pm) {
+          nsAutoCString aKey;
+          nsAutoCString aName;
+          if (gDoProfileReset) {
+            // Automatically migrate from the current application if we just
+            // reset the profile.
+            aKey = MOZ_APP_NAME;
+            gResetOldProfile->GetName(aName);
+          }
+          pm->Migrate(&mDirProvider, aKey, aName);
+        }
+      }
+
+      if (gDoProfileReset) {
+        if (!initializedJSContext) {
+          xpc::InitializeJSContext();
+          initializedJSContext = true;
+        }
+
+        nsresult backupCreated =
+            ProfileResetCleanup(mProfileSvc, gResetOldProfile);
+        if (NS_FAILED(backupCreated)) {
+          NS_WARNING("Could not cleanup the profile that was reset");
+        }
+      }
+    }
+
+    // Initialize user preferences before notifying startup observers so they're
+    // ready in time for early consumers, such as the component loader.
+    mDirProvider.InitializeUserPrefs();
+
+    // Now that all (user) prefs have been loaded we can initialize the main
+    // thread's JSContext.
+    if (!initializedJSContext) {
+      xpc::InitializeJSContext();
+    }
+
+    // Finally, now that JS has been initialized, we can finish pref loading.
+    // This needs to happen after JS and XPConnect initialization because
+    // AutoConfig files require JS execution. Note that this means AutoConfig
+    // files can't override JS engine start-up prefs.
+    mDirProvider.FinishInitializingUserPrefs();
+
+#if defined(MOZ_SANDBOX) && defined(XP_WIN)
+    // Now that we have preferences and the directory provider, we can
+    // finish initializing SandboxBroker. This must happen before the GFX
+    // platform is initialized (which will launch the GPU process), which
+    // occurs when the "app-startup" category is started up below
+    //
+    // After this completes, we are ready to launch sandboxed processes
+    mozilla::SandboxBroker::GeckoDependentInitialize();
+#endif
+
+    nsCOMPtr<nsIFile> workingDir;
+    rv = NS_GetSpecialDirectory(NS_OS_CURRENT_WORKING_DIR,
+                                getter_AddRefs(workingDir));
+    if (NS_FAILED(rv)) {
+      // No working dir? This can happen if it gets deleted before we start.
+      workingDir = nullptr;
+    }
+
+    cmdLine = new nsCommandLine();
+
+    rv = cmdLine->Init(gArgc, gArgv, workingDir,
+                       nsICommandLine::STATE_INITIAL_LAUNCH);
+    NS_ENSURE_SUCCESS(rv, NS_ERROR_FAILURE);
+
+    // "app-startup" is the name of both the category and the event
+    NS_CreateServicesFromCategory("app-startup", cmdLine, "app-startup",
+                                  nullptr);
+
+    appStartup = components::AppStartup::Service();
+    NS_ENSURE_TRUE(appStartup, NS_ERROR_FAILURE);
+
+    mDirProvider.DoStartup();
+
+#ifdef XP_WIN
+    // It needs to be called on the main thread because it has to use
+    // nsObserverService.
+    EnsureWin32kInitialized();
+#endif
+
+    // As FilePreferences need the profile directory, we must initialize right
+    // here.
+    mozilla::FilePreferences::InitDirectoriesAllowlist();
+    mozilla::FilePreferences::InitPrefs();
+
+    OverrideDefaultLocaleIfNeeded();
+
+    nsCString userAgentLocale;
+    LocaleService::GetInstance()->GetAppLocaleAsBCP47(userAgentLocale);
+    CrashReporter::AnnotateCrashReport(
+        CrashReporter::Annotation::useragent_locale, userAgentLocale);
+
+    if (!AppShutdown::IsInOrBeyond(ShutdownPhase::AppShutdownConfirmed)) {
+      /* Special-case services that need early access to the command
+          line. */
+      nsCOMPtr<nsIObserverService> obsService =
+          mozilla::services::GetObserverService();
+      if (obsService) {
+        obsService->NotifyObservers(cmdLine, "command-line-startup", nullptr);
+      }
+    }
+
+#ifdef XP_WIN
+    // Hack to sync up the various environment storages. XUL_APP_FILE is special
+    // in that it comes from a different CRT (firefox.exe's static-linked copy).
+    // Ugly details in http://bugzil.la/1175039#c27
+    char appFile[MAX_PATH];
+    if (GetEnvironmentVariableA("XUL_APP_FILE", appFile, sizeof(appFile))) {
+      SmprintfPointer saved = mozilla::Smprintf("XUL_APP_FILE=%s", appFile);
+      // We intentionally leak the string here since it is required by
+      // PR_SetEnv.
+      PR_SetEnv(saved.release());
+    }
+#endif
+
+    mozilla::AppShutdown::SaveEnvVarsForPotentialRestart();
+
+    // clear out any environment variables which may have been set
+    // during the relaunch process now that we know we won't be relaunching.
+    SaveToEnv("XRE_PROFILE_PATH=");
+    SaveToEnv("XRE_PROFILE_LOCAL_PATH=");
+    SaveToEnv("XRE_START_OFFLINE=");
+    SaveToEnv("XUL_APP_FILE=");
+    SaveToEnv("XRE_BINARY_PATH=");
+    SaveToEnv("XRE_RESTARTED_BY_PROFILE_MANAGER=");
+
+    if (!AppShutdown::IsInOrBeyond(ShutdownPhase::AppShutdownConfirmed)) {
+#ifdef XP_MACOSX
+      bool lazyHiddenWindow = false;
+#else
+      bool lazyHiddenWindow =
+          Preferences::GetBool("toolkit.lazyHiddenWindow", false);
+#endif
+
+#ifdef MOZ_BACKGROUNDTASKS
+      if (BackgroundTasks::IsBackgroundTaskMode()) {
+        // Background tasks aren't going to load a chrome XUL document.
+        lazyHiddenWindow = true;
+      }
+#endif
+
+      if (!lazyHiddenWindow) {
+        rv = appStartup->CreateHiddenWindow();
+        NS_ENSURE_SUCCESS(rv, NS_ERROR_FAILURE);
+      }
+
+#ifdef XP_WIN
+      Preferences::RegisterCallbackAndCall(
+          RegisterApplicationRestartChanged,
+          PREF_WIN_REGISTER_APPLICATION_RESTART);
+      SetupAlteredPrefetchPref();
+      SetupSkeletonUIPrefs();
+#  if defined(MOZ_LAUNCHER_PROCESS)
+      SetupLauncherProcessPref();
+#  endif  // defined(MOZ_LAUNCHER_PROCESS)
+#  if defined(MOZ_DEFAULT_BROWSER_AGENT)
+#    if defined(MOZ_BACKGROUNDTASKS)
+      // The backgroundtask profile is not a browsing profile, let alone the new
+      // default profile, so don't mirror its properties into the registry.
+      if (!BackgroundTasks::IsBackgroundTaskMode())
+#    endif  // defined(MOZ_BACKGROUNDTASKS)
+      {
+        Preferences::RegisterCallbackAndCall(
+            &OnDefaultAgentTelemetryPrefChanged,
+            kPrefHealthReportUploadEnabled);
+        Preferences::RegisterCallbackAndCall(
+            &OnDefaultAgentTelemetryPrefChanged, kPrefDefaultAgentEnabled);
+
+        Preferences::RegisterCallbackAndCall(
+            &OnDefaultAgentRemoteSettingsPrefChanged,
+            kPrefServicesSettingsServer);
+        Preferences::RegisterCallbackAndCall(
+            &OnDefaultAgentRemoteSettingsPrefChanged,
+            kPrefSecurityContentSignatureRootHash);
+
+        Preferences::RegisterCallbackAndCall(
+            &OnSetDefaultBrowserUserChoicePrefChanged,
+            kPrefSetDefaultBrowserUserChoicePref);
+
+        SetDefaultAgentLastRunTime();
+      }
+#  endif  // defined(MOZ_DEFAULT_BROWSER_AGENT)
+#endif
+
+#if defined(MOZ_WIDGET_GTK)
+      // Clear the environment variables so they won't be inherited by child
+      // processes and confuse things.
+      for (const auto& name : kStartupTokenNames) {
+        g_unsetenv(name.get());
+      }
+#endif
+
+#ifdef XP_MACOSX
+      // we re-initialize the command-line service and do appleevents munging
+      // after we are sure that we're not restarting
+      cmdLine = new nsCommandLine();
+
+      char** tempArgv = static_cast<char**>(malloc(gArgc * sizeof(char*)));
+      for (int i = 0; i < gArgc; i++) {
+        tempArgv[i] = strdup(gArgv[i]);
+      }
+      CommandLineServiceMac::SetupMacCommandLine(gArgc, tempArgv, false);
+      rv = cmdLine->Init(gArgc, tempArgv, workingDir,
+                         nsICommandLine::STATE_INITIAL_LAUNCH);
+      free(tempArgv);
+      NS_ENSURE_SUCCESS(rv, NS_ERROR_FAILURE);
+
+#  ifdef MOZILLA_OFFICIAL
+      // Check if we're running from a DMG or an app translocated location and
+      // allow the user to install to the Applications directory.
+      if (MacRunFromDmgUtils::MaybeInstallAndRelaunch()) {
+        bool userAllowedQuit = true;
+        appStartup->Quit(nsIAppStartup::eForceQuit, 0, &userAllowedQuit);
+      }
+#  endif
+#endif
+
+      nsCOMPtr<nsIObserverService> obsService =
+          mozilla::services::GetObserverService();
+      if (obsService)
+        obsService->NotifyObservers(nullptr, "final-ui-startup", nullptr);
+
+      (void)appStartup->DoneStartingUp();
+
+      CrashReporter::AnnotateCrashReport(
+          CrashReporter::Annotation::StartupCrash, false);
+
+      AppShutdown::IsInOrBeyond(ShutdownPhase::AppShutdownConfirmed);
+    }
+
+    if (!AppShutdown::IsInOrBeyond(ShutdownPhase::AppShutdownConfirmed)) {
+      rv = cmdLine->Run();
+      NS_ENSURE_SUCCESS_LOG(rv, NS_ERROR_FAILURE);
+    }
+
+    if (!AppShutdown::IsInOrBeyond(ShutdownPhase::AppShutdownConfirmed)) {
+#if defined(MOZ_HAS_REMOTE)
+      // if we have X remote support, start listening for requests on the
+      // proxy window.
+      if (mRemoteService && !mDisableRemoteServer) {
+        mRemoteService->StartupServer();
+        mRemoteService->UnlockStartup();
+        gRemoteService = nullptr;
+      }
+#endif /* MOZ_WIDGET_GTK */
+
+      mNativeApp->Enable();
+    }
+
+#ifdef MOZ_INSTRUMENT_EVENT_LOOP
+    if (PR_GetEnv("MOZ_INSTRUMENT_EVENT_LOOP")) {
+      bool logToConsole = true;
+      mozilla::InitEventTracing(logToConsole);
+    }
+#endif /* MOZ_INSTRUMENT_EVENT_LOOP */
+
+    // Send Telemetry about Gecko version and buildid
+    Telemetry::ScalarSet(Telemetry::ScalarID::GECKO_VERSION,
+                         NS_ConvertASCIItoUTF16(gAppData->version));
+    Telemetry::ScalarSet(Telemetry::ScalarID::GECKO_BUILD_ID,
+                         NS_ConvertASCIItoUTF16(gAppData->buildID));
+
+#if defined(MOZ_SANDBOX) && defined(XP_LINUX)
+    // If we're on Linux, we now have information about the OS capabilities
+    // available to us.
+    SandboxInfo sandboxInfo = SandboxInfo::Get();
+    Telemetry::Accumulate(Telemetry::SANDBOX_HAS_SECCOMP_BPF,
+                          sandboxInfo.Test(SandboxInfo::kHasSeccompBPF));
+    Telemetry::Accumulate(Telemetry::SANDBOX_HAS_SECCOMP_TSYNC,
+                          sandboxInfo.Test(SandboxInfo::kHasSeccompTSync));
+    Telemetry::Accumulate(
+        Telemetry::SANDBOX_HAS_USER_NAMESPACES_PRIVILEGED,
+        sandboxInfo.Test(SandboxInfo::kHasPrivilegedUserNamespaces));
+    Telemetry::Accumulate(Telemetry::SANDBOX_HAS_USER_NAMESPACES,
+                          sandboxInfo.Test(SandboxInfo::kHasUserNamespaces));
+    Telemetry::Accumulate(Telemetry::SANDBOX_CONTENT_ENABLED,
+                          sandboxInfo.Test(SandboxInfo::kEnabledForContent));
+    Telemetry::Accumulate(Telemetry::SANDBOX_MEDIA_ENABLED,
+                          sandboxInfo.Test(SandboxInfo::kEnabledForMedia));
+    nsAutoCString flagsString;
+    flagsString.AppendInt(sandboxInfo.AsInteger());
+
+    CrashReporter::AnnotateCrashReport(
+        CrashReporter::Annotation::ContentSandboxCapabilities, flagsString);
+#endif /* MOZ_SANDBOX && XP_LINUX */
+
+#if defined(XP_WIN)
+    LauncherResult<bool> isAdminWithoutUac = IsAdminWithoutUac();
+    if (isAdminWithoutUac.isOk()) {
+      Telemetry::ScalarSet(
+          Telemetry::ScalarID::OS_ENVIRONMENT_IS_ADMIN_WITHOUT_UAC,
+          isAdminWithoutUac.unwrap());
+    }
+#endif /* XP_WIN */
+
+#if defined(MOZ_SANDBOX)
+    AddSandboxAnnotations();
+#endif /* MOZ_SANDBOX */
+
+    mProfileSvc->CompleteStartup();
+  }
+
+#ifdef MOZ_BACKGROUNDTASKS
+  if (BackgroundTasks::IsBackgroundTaskMode()) {
+    // In background task mode, we don't fire various delayed initialization
+    // notifications, which in the regular browser is how startup crash tracking
+    // is marked as finished.  Here, getting this far means we don't have a
+    // startup crash.
+    rv = appStartup->TrackStartupCrashEnd();
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    // We never open a window, but don't want to exit immediately.
+    rv = appStartup->EnterLastWindowClosingSurvivalArea();
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    // Avoid some small differences in initialization order across platforms.
+    nsCOMPtr<nsIPowerManagerService> powerManagerService =
+        do_GetService(POWERMANAGERSERVICE_CONTRACTID);
+    nsCOMPtr<nsIStringBundleService> stringBundleService =
+        do_GetService(NS_STRINGBUNDLE_CONTRACTID);
+
+    rv = BackgroundTasks::RunBackgroundTask(cmdLine);
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+#endif
+
+  {
+    rv = appStartup->Run();
+    if (NS_FAILED(rv)) {
+      NS_ERROR("failed to run appstartup");
+      gLogConsoleErrors = true;
+    }
+  }
+
+  return rv;
+}
+
+#if defined(MOZ_WIDGET_ANDROID)
+static already_AddRefed<nsIFile> GreOmniPath(int argc, char** argv) {
+  nsresult rv;
+
+  const char* path = nullptr;
+  ArgResult ar = CheckArg(argc, argv, "greomni", &path, CheckArgFlag::None);
+  if (ar == ARG_BAD) {
+    PR_fprintf(PR_STDERR,
+               "Error: argument --greomni requires a path argument\n");
+    return nullptr;
+  }
+
+  if (!path) return nullptr;
+
+  nsCOMPtr<nsIFile> greOmni;
+  rv = XRE_GetFileFromPath(path, getter_AddRefs(greOmni));
+  if (NS_FAILED(rv)) {
+    PR_fprintf(PR_STDERR, "Error: argument --greomni requires a valid path\n");
+    return nullptr;
+  }
+
+  return greOmni.forget();
+}
+#endif
+
+/*
+ * XRE_main - A class based main entry point used by most platforms.
+ *            Note that on OSX, aAppData->xreDirectory will point to
+ *            .app/Contents/Resources.
+ */
+int XREMain::XRE_main(int argc, char* argv[], const BootstrapConfig& aConfig) {
+  gArgc = argc;
+  gArgv = argv;
+
+  ScopedLogging log;
+
+  mozilla::LogModule::Init(gArgc, gArgv);
+
+#ifndef XP_LINUX
+  NS_SetCurrentThreadName("MainThread");
+#endif
+
+  AUTO_BASE_PROFILER_LABEL("XREMain::XRE_main (around Gecko Profiler)", OTHER);
+  AUTO_PROFILER_INIT;
+  AUTO_PROFILER_LABEL("XREMain::XRE_main", OTHER);
+
+#ifdef XP_MACOSX
+  // We call this early because it will kick off a background-thread task
+  // to register the fonts, and we'd like it to have a chance to complete
+  // before gfxPlatform initialization actually requires it.
+  gfxPlatformMac::RegisterSupplementalFonts();
+#endif
+
+#ifdef MOZ_CODE_COVERAGE
+  CodeCoverageHandler::Init();
+#endif
+
+  nsresult rv = NS_OK;
+
+  if (aConfig.appData) {
+    mAppData = MakeUnique<XREAppData>(*aConfig.appData);
+  } else {
+    MOZ_RELEASE_ASSERT(aConfig.appDataPath);
+    nsCOMPtr<nsIFile> appini;
+    rv = XRE_GetFileFromPath(aConfig.appDataPath, getter_AddRefs(appini));
+    if (NS_FAILED(rv)) {
+      Output(true, "Error: unrecognized path: %s\n", aConfig.appDataPath);
+      return 1;
+    }
+
+    mAppData = MakeUnique<XREAppData>();
+    rv = XRE_ParseAppData(appini, *mAppData);
+    if (NS_FAILED(rv)) {
+      Output(true, "Couldn't read application.ini");
+      return 1;
+    }
+
+    appini->GetParent(getter_AddRefs(mAppData->directory));
+  }
+
+  if (!mAppData->remotingName) {
+    mAppData->remotingName = mAppData->name;
+  }
+  // used throughout this file
+  gAppData = mAppData.get();
+
+  nsCOMPtr<nsIFile> binFile;
+  rv = XRE_GetBinaryPath(getter_AddRefs(binFile));
+  NS_ENSURE_SUCCESS(rv, 1);
+
+  rv = binFile->GetPath(gAbsoluteArgv0Path);
+  NS_ENSURE_SUCCESS(rv, 1);
+
+  if (!mAppData->xreDirectory) {
+    nsCOMPtr<nsIFile> greDir;
+
+#if defined(MOZ_WIDGET_ANDROID)
+    greDir = GreOmniPath(argc, argv);
+    if (!greDir) {
+      return 2;
+    }
+#else
+    rv = binFile->GetParent(getter_AddRefs(greDir));
+    if (NS_FAILED(rv)) return 2;
+#endif
+
+#ifdef XP_MACOSX
+    nsCOMPtr<nsIFile> parent;
+    greDir->GetParent(getter_AddRefs(parent));
+    greDir = parent.forget();
+    greDir->AppendNative("Resources"_ns);
+#endif
+
+    mAppData->xreDirectory = greDir;
+  }
+
+#if defined(MOZ_WIDGET_ANDROID)
+  nsCOMPtr<nsIFile> dataDir;
+  rv = binFile->GetParent(getter_AddRefs(dataDir));
+  if (NS_FAILED(rv)) return 2;
+
+  mAppData->directory = dataDir;
+#else
+  if (aConfig.appData && aConfig.appDataPath) {
+    mAppData->xreDirectory->Clone(getter_AddRefs(mAppData->directory));
+    mAppData->directory->AppendNative(nsDependentCString(aConfig.appDataPath));
+  }
+#endif
+
+  if (!mAppData->directory) {
+    mAppData->directory = mAppData->xreDirectory;
+  }
+
+#if defined(XP_WIN)
+#  if defined(MOZ_SANDBOX)
+  mAppData->sandboxBrokerServices = aConfig.sandboxBrokerServices;
+#  endif  // defined(MOZ_SANDBOX)
+
+  {
+    DebugOnly<bool> result = WindowsBCryptInitialization();
+    MOZ_ASSERT(result);
+  }
+#endif  // defined(XP_WIN)
+
+  // Once we unset the exception handler, we lose the ability to properly
+  // detect hangs -- they show up as crashes.  We do this as late as possible.
+  // In particular, after ProcessRuntime is destroyed on Windows.
+  auto unsetExceptionHandler = MakeScopeExit([&] {
+    if (mAppData->flags & NS_XRE_ENABLE_CRASH_REPORTER)
+      return CrashReporter::UnsetExceptionHandler();
+    return NS_OK;
+  });
+
+  mozilla::IOInterposerInit ioInterposerGuard;
+
+#if defined(XP_WIN)
+  // We should have already done this when we created the skeleton UI. However,
+  // there is code in here which needs xul in order to work, like EnsureMTA. It
+  // should be setup that running it again is safe.
+  mozilla::mscom::ProcessRuntime msCOMRuntime;
+#endif
+
+  // init
+  bool exit = false;
+  int result = XRE_mainInit(&exit);
+  if (result != 0 || exit) return result;
+
+  // If we exit gracefully, remove the startup crash canary file.
+  auto cleanup = MakeScopeExit([&]() -> nsresult {
+    if (mProfLD) {
+      nsCOMPtr<nsIFile> crashFile;
+      MOZ_TRY_VAR(crashFile, GetIncompleteStartupFile(mProfLD));
+      crashFile->Remove(false);
+    }
+    return NS_OK;
+  });
+
+  // startup
+  result = XRE_mainStartup(&exit);
+  if (result != 0 || exit) return result;
+
+  // Start the real application. We use |aInitJSContext = false| because
+  // XRE_mainRun wants to initialize the JSContext after reading user prefs.
+
+  mScopedXPCOM = MakeUnique<ScopedXPCOMStartup>();
+
+  rv = mScopedXPCOM->Initialize(/* aInitJSContext = */ false);
+  NS_ENSURE_SUCCESS(rv, 1);
+
+  // run!
+  rv = XRE_mainRun();
+
+#ifdef MOZ_X11
+  XRE_CleanupX11ErrorHandler();
+#endif
+
+#ifdef MOZ_INSTRUMENT_EVENT_LOOP
+  mozilla::ShutdownEventTracing();
+#endif
+
+  gAbsoluteArgv0Path.Truncate();
+
+#if defined(MOZ_HAS_REMOTE)
+  // Shut down the remote service. We must do this before calling LaunchChild
+  // if we're restarting because otherwise the new instance will attempt to
+  // remote to this instance.
+  if (mRemoteService && !mDisableRemoteServer) {
+    mRemoteService->ShutdownServer();
+  }
+#endif /* MOZ_WIDGET_GTK */
+
+  mScopedXPCOM = nullptr;
+
+  // unlock the profile after ScopedXPCOMStartup object (xpcom)
+  // has gone out of scope.  see bug #386739 for more details
+  mProfileLock->Unlock();
+  gProfileLock = nullptr;
+
+  gLastAppVersion.Truncate();
+  gLastAppBuildID.Truncate();
+
+  mozilla::AppShutdown::MaybeDoRestart();
+
+#ifdef MOZ_WIDGET_GTK
+  // gdk_display_close also calls gdk_display_manager_set_default_display
+  // appropriately when necessary.
+  if (!gfxPlatform::IsHeadless()) {
+#  ifdef MOZ_WAYLAND
+    WaylandDisplayRelease();
+#  endif
+  }
+#endif
+
+  XRE_DeinitCommandLine();
+
+  if (NS_FAILED(rv)) {
+    return 1;
+  }
+  return mozilla::AppShutdown::GetExitCode();
+}
+
+void XRE_StopLateWriteChecks(void) { mozilla::StopLateWriteChecks(); }
+
+int XRE_main(int argc, char* argv[], const BootstrapConfig& aConfig) {
+  XREMain main;
+
+  int result = main.XRE_main(argc, argv, aConfig);
+  mozilla::RecordShutdownEndTimeStamp();
+#ifdef MOZ_BACKGROUNDTASKS
+  // This is well after the profile has been unlocked, so it's okay if this does
+  // delete this background task's temporary profile.
+  mozilla::BackgroundTasks::Shutdown();
+#endif
+  return result;
+}
+
+nsresult XRE_InitCommandLine(int aArgc, char* aArgv[]) {
+  nsresult rv = NS_OK;
+
+#if defined(OS_WIN)
+  CommandLine::Init(aArgc, aArgv);
+#else
+
+  // these leak on error, but that's OK: we'll just exit()
+  char** canonArgs = new char*[aArgc];
+
+  // get the canonical version of the binary's path
+  nsCOMPtr<nsIFile> binFile;
+  rv = XRE_GetBinaryPath(getter_AddRefs(binFile));
+  if (NS_FAILED(rv)) return NS_ERROR_FAILURE;
+
+  nsAutoCString canonBinPath;
+  rv = binFile->GetNativePath(canonBinPath);
+  if (NS_FAILED(rv)) return NS_ERROR_FAILURE;
+
+  canonArgs[0] = strdup(canonBinPath.get());
+
+  for (int i = 1; i < aArgc; ++i) {
+    if (aArgv[i]) {
+      canonArgs[i] = strdup(aArgv[i]);
+    }
+  }
+
+  NS_ASSERTION(!CommandLine::IsInitialized(), "Bad news!");
+  CommandLine::Init(aArgc, canonArgs);
+
+  for (int i = 0; i < aArgc; ++i) free(canonArgs[i]);
+  delete[] canonArgs;
+#endif
+
+#if defined(MOZ_WIDGET_ANDROID)
+  nsCOMPtr<nsIFile> greOmni =
+      gAppData ? gAppData->xreDirectory : GreOmniPath(aArgc, aArgv);
+  if (!greOmni) {
+    return NS_ERROR_FAILURE;
+  }
+  mozilla::Omnijar::Init(greOmni, greOmni);
+#endif
+
+  return rv;
+}
+
+nsresult XRE_DeinitCommandLine() {
+  nsresult rv = NS_OK;
+
+  CommandLine::Terminate();
+
+  return rv;
+}
+
+GeckoProcessType XRE_GetProcessType() { return GetGeckoProcessType(); }
+
+const char* XRE_GetProcessTypeString() {
+  return XRE_GeckoProcessTypeToString(XRE_GetProcessType());
+}
+
+bool XRE_IsE10sParentProcess() {
+#ifdef MOZ_WIDGET_ANDROID
+  return XRE_IsParentProcess() && BrowserTabsRemoteAutostart() &&
+         mozilla::jni::IsAvailable();
+#else
+  return XRE_IsParentProcess() && BrowserTabsRemoteAutostart();
+#endif
+}
+
+#define GECKO_PROCESS_TYPE(enum_value, enum_name, string_name, proc_typename, \
+                           process_bin_type, procinfo_typename,               \
+                           webidl_typename, allcaps_name)                     \
+  bool XRE_Is##proc_typename##Process() {                                     \
+    return XRE_GetProcessType() == GeckoProcessType_##enum_name;              \
+  }
+#include "mozilla/GeckoProcessTypes.h"
+#undef GECKO_PROCESS_TYPE
+
+bool XRE_UseNativeEventProcessing() {
+  switch (XRE_GetProcessType()) {
+#if defined(XP_MACOSX) || defined(XP_WIN)
+    case GeckoProcessType_RDD:
+    case GeckoProcessType_Socket:
+      return false;
+    case GeckoProcessType_Utility: {
+#  if defined(XP_WIN)
+      auto upc = mozilla::ipc::UtilityProcessChild::Get();
+      MOZ_ASSERT(upc);
+      // WindowsUtils is for Windows APIs, which typically require a Windows
+      // native event loop.
+      return upc->mSandbox == mozilla::ipc::SandboxingKind::WINDOWS_UTILS;
+#  else
+      return false;
+#  endif  // defined(XP_WIN)
+    }
+#endif  // defined(XP_MACOSX) || defined(XP_WIN)
+    case GeckoProcessType_Content:
+      return StaticPrefs::dom_ipc_useNativeEventProcessing_content();
+    default:
+      return true;
+  }
+}
+
+namespace mozilla {
+
+uint32_t GetMaxWebProcessCount() {
+  // multiOptOut is in int to allow us to run multiple experiments without
+  // introducing multiple prefs a la the autostart.N prefs.
+  if (Preferences::GetInt("dom.ipc.multiOptOut", 0) >=
+      nsIXULRuntime::E10S_MULTI_EXPERIMENT) {
+    return 1;
+  }
+
+  const char* optInPref = "dom.ipc.processCount";
+  uint32_t optInPrefValue = Preferences::GetInt(optInPref, 1);
+  return std::max(1u, optInPrefValue);
+}
+
+const char* PlatformBuildID() { return gToolkitBuildID; }
+
+}  // namespace mozilla
+
+void SetupErrorHandling(const char* progname) {
+#ifdef XP_WIN
+  /* On Windows XPSP3 and Windows Vista if DEP is configured off-by-default
+     we still want DEP protection: enable it explicitly and programmatically.
+
+     This function is not available on WinXPSP2 so we dynamically load it.
+  */
+
+  HMODULE kernel32 = GetModuleHandleW(L"kernel32.dll");
+  SetProcessDEPPolicyFunc _SetProcessDEPPolicy =
+      (SetProcessDEPPolicyFunc)GetProcAddress(kernel32, "SetProcessDEPPolicy");
+  if (_SetProcessDEPPolicy) _SetProcessDEPPolicy(PROCESS_DEP_ENABLE);
+#endif
+
+#ifdef XP_WIN
+  // Suppress the "DLL Foo could not be found" dialog, such that if dependent
+  // libraries (such as GDI+) are not preset, we gracefully fail to load those
+  // XPCOM components, instead of being ungraceful.
+  UINT realMode = SetErrorMode(0);
+  realMode |= SEM_FAILCRITICALERRORS;
+  // If XRE_NO_WINDOWS_CRASH_DIALOG is set, suppress displaying the "This
+  // application has crashed" dialog box.  This is mainly useful for
+  // automated testing environments, e.g. tinderbox, where there's no need
+  // for a dozen of the dialog boxes to litter the console
+  if (getenv("XRE_NO_WINDOWS_CRASH_DIALOG"))
+    realMode |= SEM_NOGPFAULTERRORBOX | SEM_NOOPENFILEERRORBOX;
+
+  SetErrorMode(realMode);
+
+#endif
+
+  InstallSignalHandlers(progname);
+
+  // Unbuffer stdout, needed for tinderbox tests.
+  setbuf(stdout, 0);
+}
+
+// Note: This function should not be needed anymore. See Bug 818634 for details.
+void OverrideDefaultLocaleIfNeeded() {
+  // Read pref to decide whether to override default locale with US English.
+  if (mozilla::Preferences::GetBool("javascript.use_us_english_locale",
+                                    false)) {
+    // Set the application-wide C-locale. Needed to resist fingerprinting
+    // of Date.toLocaleFormat(). We use the locale to "C.UTF-8" if possible,
+    // to avoid interfering with non-ASCII keyboard input on some Linux
+    // desktops. Otherwise fall back to the "C" locale, which is available on
+    // all platforms.
+    setlocale(LC_ALL, "C.UTF-8") || setlocale(LC_ALL, "C");
+  }
+}
+
+static bool gRunSelfAsContentProc = false;
+
+void XRE_EnableSameExecutableForContentProc() {
+  if (!PR_GetEnv("MOZ_SEPARATE_CHILD_PROCESS")) {
+    gRunSelfAsContentProc = true;
+  }
+}
+
+mozilla::BinPathType XRE_GetChildProcBinPathType(
+    GeckoProcessType aProcessType) {
+  MOZ_ASSERT(aProcessType != GeckoProcessType_Default);
+
+  if (!gRunSelfAsContentProc) {
+    return BinPathType::PluginContainer;
+  }
+
+  switch (aProcessType) {
+#define GECKO_PROCESS_TYPE(enum_value, enum_name, string_name, proc_typename, \
+                           process_bin_type, procinfo_typename,               \
+                           webidl_typename, allcaps_name)                     \
+  case GeckoProcessType_##enum_name:                                          \
+    return BinPathType::process_bin_type;
+#include "mozilla/GeckoProcessTypes.h"
+#undef GECKO_PROCESS_TYPE
+    default:
+      return BinPathType::PluginContainer;
+  }
+}
+
+// From mozglue/static/rust/lib.rs
+extern "C" void install_rust_hooks();
+
+struct InstallRustHooks {
+  InstallRustHooks() { install_rust_hooks(); }
+};
+
+InstallRustHooks sInstallRustHooks;
+
+#ifdef MOZ_ASAN_REPORTER
+void setASanReporterPath(nsIFile* aDir) {
+  nsCOMPtr<nsIFile> dir;
+  aDir->Clone(getter_AddRefs(dir));
+
+  dir->Append(u"asan"_ns);
+  nsresult rv = dir->Create(nsIFile::DIRECTORY_TYPE, 0700);
+  if (NS_WARN_IF(NS_FAILED(rv) && rv != NS_ERROR_FILE_ALREADY_EXISTS)) {
+    MOZ_CRASH("[ASan Reporter] Unable to create crash directory.");
+  }
+
+  dir->Append(u"ff_asan_log"_ns);
+
+#  ifdef XP_WIN
+  nsAutoString nspathW;
+  rv = dir->GetPath(nspathW);
+  NS_ConvertUTF16toUTF8 nspath(nspathW);
+#  else
+  nsAutoCString nspath;
+  rv = dir->GetNativePath(nspath);
+#  endif
+  if (NS_FAILED(rv)) {
+    MOZ_CRASH("[ASan Reporter] Unable to get native path for crash directory.");
+  }
+
+  __sanitizer_set_report_path(nspath.get());
+}
+#endif
diff --git a/toolkit/xre/nsAppRunner.h b/toolkit/xre/nsAppRunner.h
new file mode 100644
index 0000000000..2b0315f3a3
--- /dev/null
+++ b/toolkit/xre/nsAppRunner.h
@@ -0,0 +1,166 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef nsAppRunner_h__
+#define nsAppRunner_h__
+
+#ifdef XP_WIN
+#  include <windows.h>
+#  include "mozilla/WindowsConsole.h"
+#else
+#  include <limits.h>
+#endif
+
+#ifndef MAXPATHLEN
+#  ifdef PATH_MAX
+#    define MAXPATHLEN PATH_MAX
+#  elif defined(_MAX_PATH)
+#    define MAXPATHLEN _MAX_PATH
+#  elif defined(CCHMAXPATH)
+#    define MAXPATHLEN CCHMAXPATH
+#  else
+#    define MAXPATHLEN 1024
+#  endif
+#endif
+
+#include "nsCOMPtr.h"
+#include "nsStringFwd.h"
+#include "nsXULAppAPI.h"
+
+class nsINativeAppSupport;
+class nsXREDirProvider;
+class nsIToolkitProfileService;
+class nsIFile;
+class nsIProfileLock;
+class nsIProfileUnlocker;
+class nsIFactory;
+
+extern nsXREDirProvider* gDirServiceProvider;
+
+// NOTE: gAppData will be null in embedded contexts.
+extern const mozilla::XREAppData* gAppData;
+extern bool gSafeMode;
+extern bool gFxREmbedded;
+
+extern int gArgc;
+extern char** gArgv;
+extern int gRestartArgc;
+extern char** gRestartArgv;
+extern bool gRestartedByOS;
+extern bool gLogConsoleErrors;
+extern nsString gAbsoluteArgv0Path;
+
+extern bool gIsGtest;
+
+namespace mozilla {
+nsresult AppInfoConstructor(const nsID& aIID, void** aResult);
+}  // namespace mozilla
+
+// Exported for gtests.
+void BuildCompatVersion(const char* aAppVersion, const char* aAppBuildID,
+                        const char* aToolkitBuildID, nsACString& aBuf);
+
+/**
+ * Compares the provided compatibility versions. Returns 0 if they match,
+ * < 0 if the new version is considered an upgrade from the old version and
+ * > 0 if the new version is considered a downgrade from the old version.
+ */
+int32_t CompareCompatVersions(const nsACString& aOldCompatVersion,
+                              const nsACString& aNewCompatVersion);
+
+/**
+ * Create the nativeappsupport implementation.
+ *
+ * @note XPCOMInit has not happened yet.
+ */
+nsresult NS_CreateNativeAppSupport(nsINativeAppSupport** aResult);
+already_AddRefed<nsINativeAppSupport> NS_GetNativeAppSupport();
+
+/**
+ * Try to acquire exclusive access to the specified profile directory.
+ *
+ * @param aPath
+ *        The profile directory to lock.
+ * @param aTempPath
+ *        The corresponding profile temporary directory.
+ * @param aUnlocker
+ *        A callback interface used to attempt to unlock a profile that
+ *        appears to be locked.
+ * @param aResult
+ *        The resulting profile lock object (or null if the profile could
+ *        not be locked).
+ *
+ * @return NS_ERROR_FILE_ACCESS_DENIED to indicate that the profile
+ *         directory cannot be unlocked.
+ */
+nsresult NS_LockProfilePath(nsIFile* aPath, nsIFile* aTempPath,
+                            nsIProfileUnlocker** aUnlocker,
+                            nsIProfileLock** aResult);
+
+void WriteConsoleLog();
+
+void OverrideDefaultLocaleIfNeeded();
+
+/**
+ * Allow exit() calls to complete. This should be done from a proper Gecko
+ * shutdown path. Otherwise we aim to catch improper shutdowns.
+ */
+void MozExpectedExit();
+
+class nsINativeAppSupport;
+
+// If aBlankCommandLine is true, then the application will be launched with a
+// blank command line instead of being launched with the same command line that
+// it was initially started with.
+// If aTryExec is true then we use exec on platforms that support it to
+// remain in the foreground.
+nsresult LaunchChild(bool aBlankCommandLine, bool aTryExec = false);
+
+void UnlockProfile();
+
+#ifdef XP_WIN
+
+BOOL WinLaunchChild(const wchar_t* exePath, int argc, char** argv,
+                    HANDLE userToken = nullptr, HANDLE* hProcess = nullptr);
+
+#  define PREF_WIN_REGISTER_APPLICATION_RESTART \
+    "toolkit.winRegisterApplicationRestart"
+
+#  define PREF_WIN_ALTERED_DLL_PREFETCH "startup.experiments.alteredDllPrefetch"
+
+#  if defined(MOZ_LAUNCHER_PROCESS)
+#    define PREF_WIN_LAUNCHER_PROCESS_ENABLED "browser.launcherProcess.enabled"
+#  endif  // defined(MOZ_LAUNCHER_PROCESS)
+#endif
+
+namespace mozilla {
+namespace startup {
+Result<nsCOMPtr<nsIFile>, nsresult> GetIncompleteStartupFile(nsIFile* aProfLD);
+
+void IncreaseDescriptorLimits();
+}  // namespace startup
+
+const char* PlatformBuildID();
+
+bool RunningGTest();
+
+}  // namespace mozilla
+
+/**
+ * Set up platform specific error handling such as suppressing DLL load dialog
+ * and the JIT debugger on Windows, and install unix signal handlers.
+ */
+void SetupErrorHandling(const char* progname);
+
+#ifdef MOZ_ASAN_REPORTER
+extern "C" {
+void MOZ_EXPORT __sanitizer_set_report_path(const char* path);
+}
+void setASanReporterPath(nsIFile* aDir);
+#endif
+
+bool IsWaylandEnabled();
+
+#endif  // nsAppRunner_h__
diff --git a/toolkit/xre/nsCommandLineServiceMac.h b/toolkit/xre/nsCommandLineServiceMac.h
new file mode 100644
index 0000000000..caa37fdc52
--- /dev/null
+++ b/toolkit/xre/nsCommandLineServiceMac.h
@@ -0,0 +1,20 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef nsCommandLineServiceMac_h_
+#define nsCommandLineServiceMac_h_
+
+#include "nscore.h"
+
+namespace CommandLineServiceMac {
+void SetupMacCommandLine(int& argc, char**& argv, bool forRestart);
+
+// Add a URL to the command line currently being set up via
+// SetupMacCommandLine. Returns false if no command line is
+// being set up or the addition fails for any other reason.
+bool AddURLToCurrentCommandLine(const char* aURL);
+}  // namespace CommandLineServiceMac
+
+#endif  // nsCommandLineServiceMac_h_
diff --git a/toolkit/xre/nsCommandLineServiceMac.mm b/toolkit/xre/nsCommandLineServiceMac.mm
new file mode 100644
index 0000000000..e143a41fad
--- /dev/null
+++ b/toolkit/xre/nsCommandLineServiceMac.mm
@@ -0,0 +1,94 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsCommandLineServiceMac.h"
+#include "MacApplicationDelegate.h"
+#include <cstring>
+#include <Cocoa/Cocoa.h>
+
+namespace CommandLineServiceMac {
+
+static const int kArgsGrowSize = 20;
+
+static char** sArgs = nullptr;
+static int sArgsAllocated = 0;
+static int sArgsUsed = 0;
+
+static bool sBuildingCommandLine = false;
+
+void AddToCommandLine(const char* inArgText) {
+  if (sArgsUsed >= sArgsAllocated - 1) {
+    // realloc does not free the given pointer if allocation fails
+    char** temp =
+        static_cast<char**>(realloc(sArgs, (sArgsAllocated + kArgsGrowSize) * sizeof(char*)));
+    if (!temp) return;
+    sArgs = temp;
+    sArgsAllocated += kArgsGrowSize;
+  }
+
+  char* temp2 = strdup(inArgText);
+  if (!temp2) return;
+
+  sArgs[sArgsUsed++] = temp2;
+  sArgs[sArgsUsed] = nullptr;
+
+  return;
+}
+
+// Caller has ownership of argv and is responsible for freeing the allocated
+// memory.
+void SetupMacCommandLine(int& argc, char**& argv, bool forRestart) {
+  sArgs = static_cast<char**>(malloc(kArgsGrowSize * sizeof(char*)));
+  if (!sArgs) return;
+  sArgsAllocated = kArgsGrowSize;
+  sArgs[0] = nullptr;
+  sArgsUsed = 0;
+
+  sBuildingCommandLine = true;
+
+  // Copy args, stripping anything we don't want.
+  for (int arg = 0; arg < argc; arg++) {
+    char* flag = argv[arg];
+    // Don't pass on the psn (Process Serial Number) flag from the OS, or
+    // the "-foreground" flag since it will be set below if necessary.
+    if (strncmp(flag, "-psn_", 5) != 0 && strncmp(flag, "-foreground", 11) != 0)
+      AddToCommandLine(flag);
+  }
+
+  // Force processing of any pending Apple GetURL Events while we're building
+  // the command line. The handlers will append to the command line rather than
+  // act directly so there is no chance we'll process them during a XUL window
+  // load and accidentally open unnecessary windows and home pages.
+  ProcessPendingGetURLAppleEvents();
+
+  // If the process will be relaunched, the child should be in the foreground
+  // if the parent is in the foreground.  This will be communicated in a
+  // command-line argument to the child.
+  if (forRestart) {
+    NSRunningApplication* frontApp = [[NSWorkspace sharedWorkspace] frontmostApplication];
+    if ([frontApp isEqual:[NSRunningApplication currentApplication]]) {
+      AddToCommandLine("-foreground");
+    }
+  }
+
+  sBuildingCommandLine = false;
+
+  free(argv);
+  argc = sArgsUsed;
+  argv = sArgs;
+}
+
+bool AddURLToCurrentCommandLine(const char* aURL) {
+  if (!sBuildingCommandLine) {
+    return false;
+  }
+
+  AddToCommandLine("-url");
+  AddToCommandLine(aURL);
+
+  return true;
+}
+
+}  // namespace CommandLineServiceMac
diff --git a/toolkit/xre/nsConsoleWriter.cpp b/toolkit/xre/nsConsoleWriter.cpp
new file mode 100644
index 0000000000..d89ea3bde3
--- /dev/null
+++ b/toolkit/xre/nsConsoleWriter.cpp
@@ -0,0 +1,80 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsAppRunner.h"
+
+#include "prio.h"
+#include "prprf.h"
+#include "prenv.h"
+
+#include "nsCRT.h"
+#include "nsNativeCharsetUtils.h"
+#include "nsString.h"
+#include "nsXREDirProvider.h"
+#include "nsXULAppAPI.h"
+
+#include "nsIConsoleService.h"
+#include "nsIConsoleMessage.h"
+
+void WriteConsoleLog() {
+  nsresult rv;
+
+  nsCOMPtr<nsIFile> lfile;
+
+  char* logFileEnv = PR_GetEnv("XRE_CONSOLE_LOG");
+  if (logFileEnv && *logFileEnv) {
+    rv = XRE_GetFileFromPath(logFileEnv, getter_AddRefs(lfile));
+    if (NS_FAILED(rv)) return;
+  } else {
+    if (!gLogConsoleErrors) return;
+
+    rv = nsXREDirProvider::GetUserAppDataDirectory(getter_AddRefs(lfile));
+    if (NS_FAILED(rv)) return;
+
+    lfile->AppendNative("console.log"_ns);
+  }
+
+  PRFileDesc* file;
+  rv = lfile->OpenNSPRFileDesc(PR_WRONLY | PR_APPEND | PR_CREATE_FILE, 0660,
+                               &file);
+  if (NS_FAILED(rv)) return;
+
+  nsCOMPtr<nsIConsoleService> csrv(do_GetService(NS_CONSOLESERVICE_CONTRACTID));
+  if (!csrv) {
+    PR_Close(file);
+    return;
+  }
+
+  nsTArray<RefPtr<nsIConsoleMessage>> messages;
+
+  rv = csrv->GetMessageArray(messages);
+  if (NS_FAILED(rv)) {
+    PR_Close(file);
+    return;
+  }
+
+  if (!messages.IsEmpty()) {
+    PRExplodedTime etime;
+    PR_ExplodeTime(PR_Now(), PR_LocalTimeParameters, &etime);
+    char datetime[512];
+    PR_FormatTimeUSEnglish(datetime, sizeof(datetime), "%Y-%m-%d %H:%M:%S",
+                           &etime);
+
+    PR_fprintf(file, NS_LINEBREAK "*** Console log: %s ***" NS_LINEBREAK,
+               datetime);
+  }
+
+  nsString msg;
+  nsAutoCString nativemsg;
+
+  for (auto& message : messages) {
+    rv = message->GetMessageMoz(msg);
+    if (NS_SUCCEEDED(rv)) {
+      NS_CopyUnicodeToNative(msg, nativemsg);
+      PR_fprintf(file, "%s" NS_LINEBREAK, nativemsg.get());
+    }
+  }
+
+  PR_Close(file);
+}
diff --git a/toolkit/xre/nsEmbedFunctions.cpp b/toolkit/xre/nsEmbedFunctions.cpp
new file mode 100644
index 0000000000..fa236e0f86
--- /dev/null
+++ b/toolkit/xre/nsEmbedFunctions.cpp
@@ -0,0 +1,833 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/DebugOnly.h"
+
+#include "nsXULAppAPI.h"
+
+#include <stdlib.h>
+#if defined(MOZ_WIDGET_GTK)
+#  include <glib.h>
+#endif
+
+#include "prenv.h"
+
+#include "nsIAppShell.h"
+#include "nsIToolkitProfile.h"
+
+#ifdef XP_WIN
+#  include <process.h>
+#  include <shobjidl.h>
+#  include "mozilla/ipc/WindowsMessageLoop.h"
+#  ifdef MOZ_SANDBOX
+#    include "mozilla/RandomNum.h"
+#  endif
+#  include "mozilla/ScopeExit.h"
+#  include "mozilla/WinDllServices.h"
+#  include "mozilla/WindowsBCryptInitialization.h"
+#  include "WinUtils.h"
+#endif
+
+#include "nsAppRunner.h"
+#include "nsExceptionHandler.h"
+#include "mozilla/RuntimeExceptionModule.h"
+#include "nsThreadUtils.h"
+#include "nsJSUtils.h"
+#include "nsWidgetsCID.h"
+#include "nsXREDirProvider.h"
+#ifdef MOZ_ASAN_REPORTER
+#  include "CmdLineAndEnvUtils.h"
+#  include "nsIFile.h"
+#endif
+
+#include "mozilla/Omnijar.h"
+#if defined(XP_MACOSX)
+#  include <mach/mach.h>
+#  include <servers/bootstrap.h>
+#  include "nsVersionComparator.h"
+#  include "chrome/common/mach_ipc_mac.h"
+#  include "gfxPlatformMac.h"
+#endif
+#include "nsX11ErrorHandler.h"
+#include "nsGDKErrorHandler.h"
+#include "base/at_exit.h"
+#include "base/message_loop.h"
+#include "base/process_util.h"
+#if defined(MOZ_WIDGET_ANDROID)
+#  include "chrome/common/ipc_channel.h"
+#  include "mozilla/jni/Utils.h"
+#  include "mozilla/ipc/ProcessUtils.h"
+#endif  //  defined(MOZ_WIDGET_ANDROID)
+
+#include "mozilla/AbstractThread.h"
+#include "mozilla/FilePreferences.h"
+#include "mozilla/IOInterposer.h"
+#include "mozilla/ProcessType.h"
+#include "mozilla/RDDProcessImpl.h"
+#include "mozilla/ipc/UtilityProcessImpl.h"
+#include "mozilla/UniquePtr.h"
+
+#include "mozilla/ipc/BrowserProcessSubThread.h"
+#include "mozilla/ipc/IOThreadChild.h"
+#include "mozilla/ipc/ProcessChild.h"
+
+#include "mozilla/dom/ContentProcess.h"
+#include "mozilla/dom/ContentParent.h"
+
+#include "mozilla/ipc/TestShellParent.h"
+#if defined(XP_WIN)
+#  include "mozilla/WindowsConsole.h"
+#  include "mozilla/WindowsDllBlocklist.h"
+#endif
+
+#include "GMPProcessChild.h"
+#include "mozilla/gfx/GPUProcessImpl.h"
+#include "mozilla/net/SocketProcessImpl.h"
+
+#include "ProfilerControl.h"
+
+#if defined(MOZ_SANDBOX) && defined(XP_WIN)
+#  include "mozilla/sandboxTarget.h"
+#  include "mozilla/sandboxing/loggingCallbacks.h"
+#  include "mozilla/RemoteSandboxBrokerProcessChild.h"
+#endif
+
+#if defined(MOZ_SANDBOX)
+#  include "XREChildData.h"
+#  include "mozilla/SandboxSettings.h"
+#endif
+
+#if defined(XP_LINUX) && defined(MOZ_SANDBOX)
+#  include "mozilla/Sandbox.h"
+#endif
+
+#if defined(XP_LINUX)
+#  include <sys/prctl.h>
+#  ifndef PR_SET_PTRACER
+#    define PR_SET_PTRACER 0x59616d61
+#  endif
+#  ifndef PR_SET_PTRACER_ANY
+#    define PR_SET_PTRACER_ANY ((unsigned long)-1)
+#  endif
+#endif
+
+#ifdef MOZ_JPROF
+#  include "jprof.h"
+#endif
+
+#if defined(XP_WIN) && defined(MOZ_SANDBOX)
+#  include "mozilla/sandboxing/SandboxInitialization.h"
+#  include "mozilla/sandboxing/sandboxLogging.h"
+#endif
+
+#if defined(MOZ_ENABLE_FORKSERVER)
+#  include "mozilla/ipc/ForkServer.h"
+#endif
+
+#if defined(MOZ_X11)
+#  include <X11/Xlib.h>
+#endif
+
+#include "VRProcessChild.h"
+
+using namespace mozilla;
+
+using mozilla::ipc::BrowserProcessSubThread;
+using mozilla::ipc::GeckoChildProcessHost;
+using mozilla::ipc::IOThreadChild;
+using mozilla::ipc::ProcessChild;
+
+using mozilla::dom::ContentParent;
+using mozilla::dom::ContentProcess;
+
+using mozilla::gmp::GMPProcessChild;
+
+using mozilla::ipc::TestShellCommandParent;
+using mozilla::ipc::TestShellParent;
+
+namespace mozilla::_ipdltest {
+// Set in IPDLUnitTest.cpp when running gtests.
+UniquePtr<mozilla::ipc::ProcessChild> (*gMakeIPDLUnitTestProcessChild)(
+    base::ProcessId, const nsID&) = nullptr;
+}  // namespace mozilla::_ipdltest
+
+static NS_DEFINE_CID(kAppShellCID, NS_APPSHELL_CID);
+
+const char* XRE_GeckoProcessTypeToString(GeckoProcessType aProcessType) {
+  switch (aProcessType) {
+#define GECKO_PROCESS_TYPE(enum_value, enum_name, string_name, proc_typename, \
+                           process_bin_type, procinfo_typename,               \
+                           webidl_typename, allcaps_name)                     \
+  case GeckoProcessType::GeckoProcessType_##enum_name:                        \
+    return string_name;
+#include "mozilla/GeckoProcessTypes.h"
+#undef GECKO_PROCESS_TYPE
+    default:
+      return "invalid";
+  }
+}
+
+const char* XRE_ChildProcessTypeToAnnotation(GeckoProcessType aProcessType) {
+  switch (aProcessType) {
+    case GeckoProcessType_GMPlugin:
+      return "plugin";
+    case GeckoProcessType_Default:
+      return "";
+    case GeckoProcessType_Content:
+      return "content";
+    default:
+      return XRE_GeckoProcessTypeToString(aProcessType);
+  }
+}
+
+#if defined(MOZ_WIDGET_ANDROID)
+void XRE_SetAndroidChildFds(JNIEnv* env, const XRE_AndroidChildFds& fds) {
+  mozilla::jni::SetGeckoThreadEnv(env);
+  mozilla::ipc::SetPrefsFd(fds.mPrefsFd);
+  mozilla::ipc::SetPrefMapFd(fds.mPrefMapFd);
+  IPC::Channel::SetClientChannelFd(fds.mIpcFd);
+  CrashReporter::SetNotificationPipeForChild(fds.mCrashFd);
+  CrashReporter::SetCrashAnnotationPipeForChild(fds.mCrashAnnotationFd);
+}
+#endif  // defined(MOZ_WIDGET_ANDROID)
+
+void XRE_SetProcessType(const char* aProcessTypeString) {
+  SetGeckoProcessType(aProcessTypeString);
+}
+
+#if defined(XP_WIN)
+void SetTaskbarGroupId(const nsString& aId) {
+  if (FAILED(SetCurrentProcessExplicitAppUserModelID(aId.get()))) {
+    NS_WARNING(
+        "SetCurrentProcessExplicitAppUserModelID failed for child process.");
+  }
+}
+#endif
+
+#if defined(MOZ_SANDBOX)
+void AddContentSandboxLevelAnnotation() {
+  if (XRE_GetProcessType() == GeckoProcessType_Content) {
+    int level = GetEffectiveContentSandboxLevel();
+    CrashReporter::AnnotateCrashReport(
+        CrashReporter::Annotation::ContentSandboxLevel, level);
+  } else if (XRE_GetProcessType() == GeckoProcessType_GPU) {
+    int level = GetEffectiveGpuSandboxLevel();
+    CrashReporter::AnnotateCrashReport(
+        CrashReporter::Annotation::GpuSandboxLevel, level);
+  }
+}
+#endif /* MOZ_SANDBOX */
+
+namespace {
+
+int GetDebugChildPauseTime() {
+  auto pauseStr = PR_GetEnv("MOZ_DEBUG_CHILD_PAUSE");
+  if (pauseStr && *pauseStr) {
+    int pause = atoi(pauseStr);
+    if (pause != 1) {  // must be !=1 since =1 enables the default pause time
+#if defined(OS_WIN)
+      pause *= 1000;  // convert to ms
+#endif
+      return pause;
+    }
+  }
+#ifdef OS_POSIX
+  return 30;  // seconds
+#elif defined(OS_WIN)
+  return 10000;  // milliseconds
+#else
+  return 0;
+#endif
+}
+
+static bool IsCrashReporterEnabled(const char* aArg) {
+  // on windows and mac, |aArg| is the named pipe on which the server is
+  // listening for requests, or "-" if crash reporting is disabled.
+#if defined(XP_MACOSX) || defined(XP_WIN)
+  return 0 != strcmp("-", aArg);
+#else
+  // on POSIX, |aArg| is "true" if crash reporting is enabled, false otherwise
+  return 0 != strcmp("false", aArg);
+#endif
+}
+
+}  // namespace
+
+nsresult XRE_InitChildProcess(int aArgc, char* aArgv[],
+                              const XREChildData* aChildData) {
+  NS_ENSURE_ARG_MIN(aArgc, 2);
+  NS_ENSURE_ARG_POINTER(aArgv);
+  NS_ENSURE_ARG_POINTER(aArgv[0]);
+  MOZ_ASSERT(aChildData);
+
+  NS_SetCurrentThreadName("MainThread");
+
+#ifdef MOZ_ASAN_REPORTER
+  // In ASan reporter builds, we need to set ASan's log_path as early as
+  // possible, so it dumps its errors into files there instead of using
+  // the default stderr location. Since this is crucial for ASan reporter
+  // to work at all (and we don't want people to use a non-functional
+  // ASan reporter build), all failures while setting log_path are fatal.
+  //
+  // We receive this log_path via the ASAN_REPORTER_PATH environment variable
+  // because there is no other way to generically get the necessary profile
+  // directory in all child types without adding support for that in each
+  // child process type class (at the risk of missing this in a child).
+  //
+  // In certain cases (e.g. child startup through xpcshell or gtests), this
+  // code needs to remain disabled, as no ASAN_REPORTER_PATH would be available.
+  if (!PR_GetEnv("MOZ_DISABLE_ASAN_REPORTER") && !PR_GetEnv("MOZ_RUN_GTEST")) {
+    nsCOMPtr<nsIFile> asanReporterPath = GetFileFromEnv("ASAN_REPORTER_PATH");
+    if (!asanReporterPath) {
+      MOZ_CRASH("Child did not receive ASAN_REPORTER_PATH!");
+    }
+    setASanReporterPath(asanReporterPath);
+  }
+#endif
+
+#if defined(XP_LINUX) && defined(MOZ_SANDBOX)
+  // This has to happen before glib thread pools are started.
+  mozilla::SandboxEarlyInit();
+  // This just needs to happen before sandboxing, to initialize the
+  // cached value, but libmozsandbox can't see this symbol.
+  mozilla::GetNumberOfProcessors();
+#endif
+
+#ifdef MOZ_JPROF
+  // Call the code to install our handler
+  setupProfilingStuff();
+#endif
+
+#if defined(XP_WIN)
+  // From the --attach-console support in nsNativeAppSupportWin.cpp, but
+  // here we are a content child process, so we always attempt to attach
+  // to the parent's (ie, the browser's) console.
+  // Try to attach console to the parent process.
+  // It will succeed when the parent process is a command line,
+  // so that stdio will be displayed in it.
+  UseParentConsole();
+
+#  if defined(MOZ_SANDBOX)
+  if (aChildData->sandboxTargetServices) {
+    SandboxTarget::Instance()->SetTargetServices(
+        aChildData->sandboxTargetServices);
+  }
+#  endif
+#endif
+
+  // NB: This must be called before profiler_init
+  ScopedLogging logger;
+
+  mozilla::LogModule::Init(aArgc, aArgv);
+
+  AUTO_BASE_PROFILER_LABEL("XRE_InitChildProcess (around Gecko Profiler)",
+                           OTHER);
+  AUTO_PROFILER_INIT;
+  AUTO_PROFILER_LABEL("XRE_InitChildProcess", OTHER);
+
+#ifdef XP_MACOSX
+  gfxPlatformMac::RegisterSupplementalFonts();
+#endif
+
+  // Ensure AbstractThread is minimally setup, so async IPC messages
+  // work properly.
+  AbstractThread::InitTLS();
+
+  // Complete 'task_t' exchange for Mac OS X. This structure has the same size
+  // regardless of architecture so we don't have any cross-arch issues here.
+#ifdef XP_MACOSX
+  if (aArgc < 1) return NS_ERROR_FAILURE;
+
+#  if defined(MOZ_SANDBOX)
+  // Save the original number of arguments to pass to the sandbox
+  // setup routine which also uses the crash server argument.
+  int allArgc = aArgc;
+#  endif /* MOZ_SANDBOX */
+
+  // Acquire the mach bootstrap port name from our command line, and send our
+  // task_t to the parent process.
+  const char* const mach_port_name = aArgv[--aArgc];
+
+  const int kTimeoutMs = 1000;
+
+  UniqueMachSendRight task_sender;
+  kern_return_t kr = bootstrap_look_up(bootstrap_port, mach_port_name,
+                                       getter_Transfers(task_sender));
+  if (kr != KERN_SUCCESS) {
+    NS_WARNING(nsPrintfCString("child bootstrap_look_up failed: %s",
+                               mach_error_string(kr))
+                   .get());
+    return NS_ERROR_FAILURE;
+  }
+
+  kr = MachSendPortSendRight(task_sender.get(), mach_task_self(),
+                             Some(kTimeoutMs));
+  if (kr != KERN_SUCCESS) {
+    NS_WARNING(nsPrintfCString("child MachSendPortSendRight failed: %s",
+                               mach_error_string(kr))
+                   .get());
+    return NS_ERROR_FAILURE;
+  }
+
+#  if defined(MOZ_SANDBOX)
+  std::string sandboxError;
+  if (!GeckoChildProcessHost::StartMacSandbox(allArgc, aArgv, sandboxError)) {
+    printf_stderr("Sandbox error: %s\n", sandboxError.c_str());
+    MOZ_CRASH("Sandbox initialization failed");
+  }
+#  endif /* MOZ_SANDBOX */
+
+#endif /* XP_MACOSX */
+
+  SetupErrorHandling(aArgv[0]);
+
+  bool exceptionHandlerIsSet = false;
+  if (!CrashReporter::IsDummy()) {
+    CrashReporter::FileHandle crashTimeAnnotationFile =
+        CrashReporter::kInvalidFileHandle;
+#if defined(XP_WIN)
+    if (aArgc < 1) {
+      return NS_ERROR_FAILURE;
+    }
+    // Pop the first argument, this is used by the WER runtime exception module
+    // which reads it from the command-line so we can just discard it here.
+    --aArgc;
+
+    const char* const crashTimeAnnotationArg = aArgv[--aArgc];
+    crashTimeAnnotationFile = reinterpret_cast<CrashReporter::FileHandle>(
+        std::stoul(std::string(crashTimeAnnotationArg)));
+#endif
+
+    if (aArgc < 1) return NS_ERROR_FAILURE;
+    const char* const crashReporterArg = aArgv[--aArgc];
+
+    if (IsCrashReporterEnabled(crashReporterArg)) {
+      exceptionHandlerIsSet = CrashReporter::SetRemoteExceptionHandler(
+          crashReporterArg, crashTimeAnnotationFile);
+      MOZ_ASSERT(exceptionHandlerIsSet,
+                 "Should have been able to set remote exception handler");
+
+      if (!exceptionHandlerIsSet) {
+        // Bug 684322 will add better visibility into this condition
+        NS_WARNING("Could not setup crash reporting\n");
+      }
+    } else {
+      // We might have registered a runtime exception module very early in
+      // process startup to catch early crashes. This is before we process the
+      // crash reporter arg, so unregister here if it turns out the crash
+      // reporter is disabled.
+      CrashReporter::UnregisterRuntimeExceptionModule();
+    }
+  }
+
+  gArgv = aArgv;
+  gArgc = aArgc;
+
+#ifdef MOZ_X11
+  XInitThreads();
+#endif
+#ifdef MOZ_WIDGET_GTK
+  // Setting the name here avoids the need to pass this through to gtk_init().
+  g_set_prgname(aArgv[0]);
+#endif
+
+#ifdef OS_POSIX
+  if (PR_GetEnv("MOZ_DEBUG_CHILD_PROCESS") ||
+      PR_GetEnv("MOZ_DEBUG_CHILD_PAUSE")) {
+#  if defined(XP_LINUX) && defined(DEBUG)
+    if (prctl(PR_SET_PTRACER, PR_SET_PTRACER_ANY, 0, 0, 0) != 0) {
+      printf_stderr("Could not allow ptrace from any process.\n");
+    }
+#  endif
+    printf_stderr(
+        "\n\nCHILDCHILDCHILDCHILD (process type %s)\n  debug me @ %d\n\n",
+        XRE_GetProcessTypeString(), base::GetCurrentProcId());
+    sleep(GetDebugChildPauseTime());
+  }
+#elif defined(OS_WIN)
+  if (PR_GetEnv("MOZ_DEBUG_CHILD_PROCESS")) {
+    NS_DebugBreak(NS_DEBUG_BREAK,
+                  "Invoking NS_DebugBreak() to debug child process", nullptr,
+                  __FILE__, __LINE__);
+  } else if (PR_GetEnv("MOZ_DEBUG_CHILD_PAUSE")) {
+    printf_stderr(
+        "\n\nCHILDCHILDCHILDCHILD (process type %s)\n  debug me @ %lu\n\n",
+        XRE_GetProcessTypeString(), base::GetCurrentProcId());
+    ::Sleep(GetDebugChildPauseTime());
+  }
+#endif
+
+#ifdef MOZ_WIDGET_ANDROID
+  // The parent process already did this, but Gecko child processes on
+  // Android aren't descendants of the parent process, so they don't
+  // inherit its rlimits.
+  mozilla::startup::IncreaseDescriptorLimits();
+#endif
+
+  // child processes launched by GeckoChildProcessHost get this magic
+  // argument appended to their command lines
+  const char* const parentPIDString = aArgv[aArgc - 1];
+  MOZ_ASSERT(parentPIDString, "NULL parent PID");
+  --aArgc;
+
+  char* end = 0;
+  base::ProcessId parentPID = strtol(parentPIDString, &end, 10);
+  MOZ_ASSERT(!*end, "invalid parent PID");
+
+  // They also get the initial message channel ID passed in the same manner.
+  const char* const messageChannelIdString = aArgv[aArgc - 1];
+  MOZ_ASSERT(messageChannelIdString, "NULL MessageChannel Id");
+  --aArgc;
+
+  nsID messageChannelId{};
+  if (!messageChannelId.Parse(messageChannelIdString)) {
+    return NS_ERROR_FAILURE;
+  }
+
+#if defined(XP_WIN)
+  // On Win7+, when not running as an MSIX package, register the application
+  // user model id passed in by parent. This ensures windows created by the
+  // container properly group with the parent app on the Win7 taskbar.
+  // MSIX packages explicitly do not support setting the appid from within
+  // the app, as it is set in the package manifest instead.
+  const char* const appModelUserId = aArgv[--aArgc];
+  if (appModelUserId && !mozilla::widget::WinUtils::HasPackageIdentity()) {
+    // '-' implies no support
+    if (*appModelUserId != '-') {
+      nsString appId;
+      CopyASCIItoUTF16(nsDependentCString(appModelUserId), appId);
+      // The version string is encased in quotes
+      appId.Trim("\"");
+      // Set the id
+      SetTaskbarGroupId(appId);
+    }
+  }
+#endif
+
+  base::AtExitManager exitManager;
+
+  nsresult rv = XRE_InitCommandLine(aArgc, aArgv);
+  if (NS_FAILED(rv)) {
+    return NS_ERROR_FAILURE;
+  }
+
+  MessageLoop::Type uiLoopType;
+  switch (XRE_GetProcessType()) {
+    case GeckoProcessType_Content:
+    case GeckoProcessType_GPU:
+    case GeckoProcessType_IPDLUnitTest:
+    case GeckoProcessType_VR:
+    case GeckoProcessType_RDD:
+    case GeckoProcessType_Socket:
+    case GeckoProcessType_Utility:
+      // Content processes need the XPCOM/chromium frankenventloop
+      uiLoopType = MessageLoop::TYPE_MOZILLA_CHILD;
+      break;
+    case GeckoProcessType_GMPlugin:
+    case GeckoProcessType_RemoteSandboxBroker:
+      uiLoopType = MessageLoop::TYPE_DEFAULT;
+      break;
+    default:
+      uiLoopType = MessageLoop::TYPE_UI;
+      break;
+  }
+
+#if defined(XP_WIN)
+#  if defined(MOZ_SANDBOX)
+  if (aChildData->sandboxBrokerServices) {
+    SandboxBroker::Initialize(aChildData->sandboxBrokerServices);
+    SandboxBroker::GeckoDependentInitialize();
+  }
+#  endif  // defined(MOZ_SANDBOX)
+
+  {
+    DebugOnly<bool> result = mozilla::WindowsBCryptInitialization();
+    MOZ_ASSERT(result);
+  }
+#endif  // defined(XP_WIN)
+
+  {
+    // This is a lexical scope for the MessageLoop below.  We want it
+    // to go out of scope before NS_LogTerm() so that we don't get
+    // spurious warnings about XPCOM objects being destroyed from a
+    // static context.
+
+    Maybe<IOInterposerInit> ioInterposerGuard;
+
+    // Associate this thread with a UI MessageLoop
+    MessageLoop uiMessageLoop(uiLoopType);
+    {
+      UniquePtr<ProcessChild> process;
+      switch (XRE_GetProcessType()) {
+        case GeckoProcessType_Default:
+          MOZ_CRASH("This makes no sense");
+          break;
+
+        case GeckoProcessType_Content:
+          ioInterposerGuard.emplace();
+          process = MakeUnique<ContentProcess>(parentPID, messageChannelId);
+          break;
+
+        case GeckoProcessType_IPDLUnitTest:
+          MOZ_RELEASE_ASSERT(mozilla::_ipdltest::gMakeIPDLUnitTestProcessChild,
+                             "xul-gtest not loaded!");
+          process = mozilla::_ipdltest::gMakeIPDLUnitTestProcessChild(
+              parentPID, messageChannelId);
+          break;
+
+        case GeckoProcessType_GMPlugin:
+          process =
+              MakeUnique<gmp::GMPProcessChild>(parentPID, messageChannelId);
+          break;
+
+        case GeckoProcessType_GPU:
+          process =
+              MakeUnique<gfx::GPUProcessImpl>(parentPID, messageChannelId);
+          break;
+
+        case GeckoProcessType_VR:
+          process =
+              MakeUnique<gfx::VRProcessChild>(parentPID, messageChannelId);
+          break;
+
+        case GeckoProcessType_RDD:
+          process = MakeUnique<RDDProcessImpl>(parentPID, messageChannelId);
+          break;
+
+        case GeckoProcessType_Socket:
+          ioInterposerGuard.emplace();
+          process =
+              MakeUnique<net::SocketProcessImpl>(parentPID, messageChannelId);
+          break;
+
+        case GeckoProcessType_Utility:
+          process =
+              MakeUnique<ipc::UtilityProcessImpl>(parentPID, messageChannelId);
+          break;
+
+#if defined(MOZ_SANDBOX) && defined(XP_WIN)
+        case GeckoProcessType_RemoteSandboxBroker:
+          process = MakeUnique<RemoteSandboxBrokerProcessChild>(
+              parentPID, messageChannelId);
+          break;
+#endif
+
+#if defined(MOZ_ENABLE_FORKSERVER)
+        case GeckoProcessType_ForkServer:
+          MOZ_CRASH("Fork server should not go here");
+          break;
+#endif
+        default:
+          MOZ_CRASH("Unknown main thread class");
+      }
+
+      if (!process->Init(aArgc, aArgv)) {
+        return NS_ERROR_FAILURE;
+      }
+
+#if defined(XP_WIN)
+      // Set child processes up such that they will get killed after the
+      // chrome process is killed in cases where the user shuts the system
+      // down or logs off.
+      ::SetProcessShutdownParameters(0x280 - 1, SHUTDOWN_NORETRY);
+
+      RefPtr<DllServices> dllSvc(DllServices::Get());
+      auto dllSvcDisable =
+          MakeScopeExit([&dllSvc]() { dllSvc->DisableFull(); });
+#endif
+
+#if defined(MOZ_SANDBOX) && defined(XP_WIN)
+      // We need to do this after the process has been initialised, as
+      // InitLoggingIfRequired may need access to prefs.
+      mozilla::sandboxing::InitLoggingIfRequired(
+          aChildData->ProvideLogFunction);
+#endif
+      if (XRE_GetProcessType() != GeckoProcessType_RemoteSandboxBroker) {
+        // Remote sandbox launcher process doesn't have prerequisites for
+        // these...
+        mozilla::FilePreferences::InitDirectoriesAllowlist();
+        mozilla::FilePreferences::InitPrefs();
+        OverrideDefaultLocaleIfNeeded();
+      }
+
+#if defined(MOZ_SANDBOX)
+      AddContentSandboxLevelAnnotation();
+#endif
+
+      // Run the UI event loop on the main thread.
+      uiMessageLoop.MessageLoop::Run();
+
+      // Allow ProcessChild to clean up after itself before going out of
+      // scope and being deleted
+      process->CleanUp();
+      mozilla::Omnijar::CleanUp();
+    }
+  }
+
+  CrashReporter::UnsetRemoteExceptionHandler(exceptionHandlerIsSet);
+
+  return XRE_DeinitCommandLine();
+}
+
+MessageLoop* XRE_GetIOMessageLoop() {
+  if (GetGeckoProcessType() == GeckoProcessType_Default) {
+    return BrowserProcessSubThread::GetMessageLoop(BrowserProcessSubThread::IO);
+  }
+  return IOThreadChild::message_loop();
+}
+
+nsresult XRE_RunAppShell() {
+  nsCOMPtr<nsIAppShell> appShell(do_GetService(kAppShellCID));
+  NS_ENSURE_TRUE(appShell, NS_ERROR_FAILURE);
+#if defined(XP_MACOSX)
+  if (XRE_UseNativeEventProcessing()) {
+    // In content processes that want XPCOM (and hence want
+    // AppShell), we usually run our hybrid event loop through
+    // MessagePump::Run(), by way of nsBaseAppShell::Run().  The
+    // Cocoa nsAppShell impl, however, implements its own Run()
+    // that's unaware of MessagePump.  That's all rather suboptimal,
+    // but oddly enough not a problem... usually.
+    //
+    // The problem with this setup comes during startup.
+    // XPCOM-in-subprocesses depends on IPC, e.g. to init the pref
+    // service, so we have to init IPC first.  But, IPC also
+    // indirectly kinda-depends on XPCOM, because MessagePump
+    // schedules work from off-main threads (e.g. IO thread) by
+    // using NS_DispatchToMainThread().  If the IO thread receives a
+    // Message from the parent before nsThreadManager is
+    // initialized, then DispatchToMainThread() will fail, although
+    // MessagePump will remember the task.  This race condition
+    // isn't a problem when appShell->Run() ends up in
+    // MessagePump::Run(), because MessagePump will immediate see it
+    // has work to do.  It *is* a problem when we end up in [NSApp
+    // run], because it's not aware that MessagePump has work that
+    // needs to be processed; that was supposed to be signaled by
+    // nsIRunnable(s).
+    //
+    // So instead of hacking Cocoa nsAppShell or rewriting the
+    // event-loop system, we compromise here by processing any tasks
+    // that might have been enqueued on MessagePump, *before*
+    // MessagePump::ScheduleWork was able to successfully
+    // DispatchToMainThread().
+    MessageLoop* loop = MessageLoop::current();
+    bool couldNest = loop->NestableTasksAllowed();
+
+    loop->SetNestableTasksAllowed(true);
+    RefPtr<Runnable> task = new MessageLoop::QuitTask();
+    loop->PostTask(task.forget());
+    loop->Run();
+
+    loop->SetNestableTasksAllowed(couldNest);
+  }
+#endif  // XP_MACOSX
+  return appShell->Run();
+}
+
+void XRE_ShutdownChildProcess() {
+  MOZ_ASSERT(NS_IsMainThread(), "Wrong thread!");
+
+  mozilla::DebugOnly<MessageLoop*> ioLoop = XRE_GetIOMessageLoop();
+  MOZ_ASSERT(!!ioLoop, "Bad shutdown order");
+
+  // Quit() sets off the following chain of events
+  //  (1) UI loop starts quitting
+  //  (2) UI loop returns from Run() in XRE_InitChildProcess()
+  //  (3) ProcessChild goes out of scope and terminates the IO thread
+  //  (4) ProcessChild joins the IO thread
+  //  (5) exit()
+  MessageLoop::current()->Quit();
+
+#if defined(XP_MACOSX)
+  nsCOMPtr<nsIAppShell> appShell(do_GetService(kAppShellCID));
+  if (appShell) {
+    // On Mac, we might be only above nsAppShell::Run(), not
+    // MessagePump::Run().  See XRE_RunAppShell(). To account for
+    // that case, we fire off an Exit() here.  If we were indeed
+    // above MessagePump::Run(), this Exit() is just superfluous.
+    appShell->Exit();
+  }
+#endif  // XP_MACOSX
+}
+
+namespace {
+ContentParent* gContentParent;  // long-lived, manually refcounted
+TestShellParent* GetOrCreateTestShellParent() {
+  if (!gContentParent) {
+    // Use a "web" child process by default.  File a bug if you don't like
+    // this and you're sure you wouldn't be better off writing a "browser"
+    // chrome mochitest where you can have multiple types of content
+    // processes.
+    RefPtr<ContentParent> parent =
+        ContentParent::GetNewOrUsedBrowserProcess(DEFAULT_REMOTE_TYPE);
+    parent.forget(&gContentParent);
+  } else if (gContentParent->IsShuttingDown()) {
+    return nullptr;
+  }
+  TestShellParent* tsp = gContentParent->GetTestShellSingleton();
+  if (!tsp) {
+    tsp = gContentParent->CreateTestShell();
+  }
+  return tsp;
+}
+
+}  // namespace
+
+bool XRE_SendTestShellCommand(JSContext* aCx, JSString* aCommand,
+                              JS::Value* aCallback) {
+  JS::Rooted<JSString*> cmd(aCx, aCommand);
+  TestShellParent* tsp = GetOrCreateTestShellParent();
+  NS_ENSURE_TRUE(tsp, false);
+
+  nsAutoJSString command;
+  NS_ENSURE_TRUE(command.init(aCx, cmd), false);
+
+  if (!aCallback) {
+    return tsp->SendExecuteCommand(command);
+  }
+
+  TestShellCommandParent* callback = static_cast<TestShellCommandParent*>(
+      tsp->SendPTestShellCommandConstructor(command));
+  NS_ENSURE_TRUE(callback, false);
+
+  NS_ENSURE_TRUE(callback->SetCallback(aCx, *aCallback), false);
+
+  return true;
+}
+
+bool XRE_ShutdownTestShell() {
+  if (!gContentParent) {
+    return true;
+  }
+  bool ret = true;
+  if (gContentParent->IsAlive()) {
+    ret = gContentParent->DestroyTestShell(
+        gContentParent->GetTestShellSingleton());
+  }
+  NS_RELEASE(gContentParent);
+  return ret;
+}
+
+#ifdef MOZ_X11
+void XRE_InstallX11ErrorHandler() {
+#  ifdef MOZ_WIDGET_GTK
+  InstallGdkErrorHandler();
+#  endif
+
+  // Ensure our X11 error handler overrides the default GDK error handler such
+  // that errors are ignored by default. GDK will install its own error handler
+  // temporarily when pushing error traps internally as needed. This avoids us
+  // otherwise having to frequently override the error handler merely to trap
+  // errors in multiple places that would otherwise contend with GDK or other
+  // libraries that might also override the handler.
+  InstallX11ErrorHandler();
+}
+
+void XRE_CleanupX11ErrorHandler() { CleanupX11ErrorHandler(); }
+#endif
+
+#ifdef MOZ_ENABLE_FORKSERVER
+int XRE_ForkServer(int* aArgc, char*** aArgv) {
+  return mozilla::ipc::ForkServer::RunForkServer(aArgc, aArgv) ? 1 : 0;
+}
+#endif
diff --git a/toolkit/xre/nsGDKErrorHandler.cpp b/toolkit/xre/nsGDKErrorHandler.cpp
new file mode 100644
index 0000000000..19895cff0a
--- /dev/null
+++ b/toolkit/xre/nsGDKErrorHandler.cpp
@@ -0,0 +1,117 @@
+/* -*- Mode: C++; tab-width: 40; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsGDKErrorHandler.h"
+
+#include <gtk/gtk.h>
+#ifdef MOZ_X11
+#  include <gdk/gdkx.h>
+#endif
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "nsDebug.h"
+#include "nsString.h"
+#ifdef MOZ_X11
+#  include "nsX11ErrorHandler.h"
+#endif
+
+#include "prenv.h"
+
+/* See https://bugzilla.gnome.org/show_bug.cgi?id=629608#c8
+ *
+ * GDK implements X11 error traps to ignore X11 errors.
+ * Unfortunatelly We don't know which X11 events can be ignored
+ * so we have to utilize the Gdk error handler to avoid
+ * false alarms in Gtk3.
+ */
+static void GdkErrorHandler(const gchar* log_domain, GLogLevelFlags log_level,
+                            const gchar* message, gpointer user_data) {
+#ifdef MOZ_X11
+  if (strstr(message, "X Window System error")) {
+    XErrorEvent event;
+    nsDependentCString buffer(message);
+    char* endptr;
+
+    /* Parse Gdk X Window error message which has this format:
+     * (Details: serial XXXX error_code XXXX request_code XXXX (XXXX) minor_code
+     * XXXX)
+     */
+    constexpr auto serialString = "(Details: serial "_ns;
+    int32_t start = buffer.Find(serialString);
+    if (start == kNotFound) {
+      MOZ_CRASH_UNSAFE(message);
+    }
+
+    start += serialString.Length();
+    errno = 0;
+    event.serial = strtol(buffer.BeginReading() + start, &endptr, 10);
+    if (errno) {
+      MOZ_CRASH_UNSAFE(message);
+    }
+
+    constexpr auto errorCodeString = " error_code "_ns;
+    if (!StringBeginsWith(Substring(endptr, buffer.EndReading()),
+                          errorCodeString)) {
+      MOZ_CRASH_UNSAFE(message);
+    }
+
+    errno = 0;
+    event.error_code = strtol(endptr + errorCodeString.Length(), &endptr, 10);
+    if (errno) {
+      MOZ_CRASH_UNSAFE(message);
+    }
+
+    constexpr auto requestCodeString = " request_code "_ns;
+    if (!StringBeginsWith(Substring(endptr, buffer.EndReading()),
+                          requestCodeString)) {
+      MOZ_CRASH_UNSAFE(message);
+    }
+
+    errno = 0;
+    event.request_code =
+        strtol(endptr + requestCodeString.Length(), &endptr, 10);
+    if (errno) {
+      MOZ_CRASH_UNSAFE(message);
+    }
+
+    constexpr auto minorCodeString = " minor_code "_ns;
+    start = buffer.Find(minorCodeString, endptr - buffer.BeginReading());
+    if (!start) {
+      MOZ_CRASH_UNSAFE(message);
+    }
+
+    errno = 0;
+    event.minor_code = strtol(
+        buffer.BeginReading() + start + minorCodeString.Length(), nullptr, 10);
+    if (errno) {
+      MOZ_CRASH_UNSAFE(message);
+    }
+
+    event.display = GDK_DISPLAY_XDISPLAY(gdk_display_get_default());
+    // Gdk does not provide resource ID
+    event.resourceid = 0;
+
+    X11Error(event.display, &event);
+  } else
+#endif
+  {
+    g_log_default_handler(log_domain, log_level, message, user_data);
+    MOZ_CRASH_UNSAFE(message);
+  }
+}
+
+void InstallGdkErrorHandler() {
+  g_log_set_handler("Gdk",
+                    (GLogLevelFlags)(G_LOG_LEVEL_ERROR | G_LOG_FLAG_FATAL |
+                                     G_LOG_FLAG_RECURSION),
+                    GdkErrorHandler, nullptr);
+#ifdef MOZ_X11
+  if (PR_GetEnv("MOZ_X_SYNC")) {
+    XSynchronize(GDK_DISPLAY_XDISPLAY(gdk_display_get_default()), X11True);
+  }
+#endif
+}
diff --git a/toolkit/xre/nsGDKErrorHandler.h b/toolkit/xre/nsGDKErrorHandler.h
new file mode 100644
index 0000000000..7c6cdce41f
--- /dev/null
+++ b/toolkit/xre/nsGDKErrorHandler.h
@@ -0,0 +1,8 @@
+/* -*- Mode: C++; tab-width: 40; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifdef MOZ_WIDGET_GTK
+void InstallGdkErrorHandler();
+#endif
diff --git a/toolkit/xre/nsINativeAppSupport.idl b/toolkit/xre/nsINativeAppSupport.idl
new file mode 100644
index 0000000000..7cfce02ab4
--- /dev/null
+++ b/toolkit/xre/nsINativeAppSupport.idl
@@ -0,0 +1,55 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsISupports.idl"
+
+/* nsINativeAppSupport
+ *
+ * This "pseudo" (in the XPCOM sense) interface provides for
+ * platform-specific general application support
+ *
+ * Due to the nature of the beast, this interface is not a full-blown
+ * XPCOM component.  The primary reason is that objects that implement
+ * this interface generally must be operational *before* XPCOM (or any
+ * of the rest of Mozilla) are initialized.  As a result, this
+ * interface is instantiated by somewhat unconventional means.
+ *
+ * To create the implementor of this interface, you call the function
+ * NS_CreateNativeAppSupport.  This is done in the startup code
+ * in nsAppRunner.cpp
+ *
+ * The interface provides these functions:
+ *  start - You call this to inform the native app support that the
+ *          application is starting.  In addition, it serves as a
+ *          query as to whether the application should continue to
+ *          run.
+ *
+ *          If the returned boolean result is PR_FALSE, then the
+ *          application should exit without further processing.  In
+ *          such cases, the returned nsresult indicates whether the
+ *          reason to exit is due to an error or not.
+ *
+ *          Win32 Note: In the case of starting a second instance
+ *                      of this executable, this function will return
+ *                      PR_FALSE and nsresult==NS_OK.  This means that
+ *                      the command line arguments have been
+ *                      successfully passed to the instance of the
+ *                      application acting as a remote server.
+ *  quit - Informs the native app support that the application is stopping. The
+ *         app support should disable any functionality enabled by start.
+ *
+ *  onLastWindowClosing -  Called when the last window is closed. Used as a
+ *                         "soft" shutdown, passwords are flushed.
+ */
+
+[scriptable, uuid(5fdf8480-1f98-11d4-8077-00600811a9c3)]
+interface nsINativeAppSupport : nsISupports {
+    // Startup/shutdown.
+    boolean start();
+    void    enable();
+
+    void onLastWindowClosing();
+    void ReOpen();
+};
diff --git a/toolkit/xre/nsIWinAppHelper.idl b/toolkit/xre/nsIWinAppHelper.idl
new file mode 100644
index 0000000000..c8a602977c
--- /dev/null
+++ b/toolkit/xre/nsIWinAppHelper.idl
@@ -0,0 +1,19 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsISupports.idl"
+
+/**
+ * A scriptable interface used on Windows only to do some work from
+ * a special process that gets created with elevated privileges.
+ *
+ * @status UNSTABLE - This interface is not frozen and will probably change in
+ *                    future releases.
+ */
+
+[scriptable, uuid(dc263ca8-b257-47eb-b5b7-339d9e0b90f7)]
+interface nsIWinAppHelper : nsISupports
+{
+  readonly attribute boolean userCanElevate;
+};
diff --git a/toolkit/xre/nsIXREDirProvider.idl b/toolkit/xre/nsIXREDirProvider.idl
new file mode 100644
index 0000000000..ce599a83bc
--- /dev/null
+++ b/toolkit/xre/nsIXREDirProvider.idl
@@ -0,0 +1,23 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsISupports.idl"
+
+interface nsIFile;
+
+[scriptable, uuid(f6ee3c0a-5119-47fc-b1a7-ace9e1111fff)]
+interface nsIXREDirProvider : nsISupports
+{
+  /**
+   * Only intended to be used from xpcshell tests. Allows setting the local
+   * and normal profile data directories. Calling this after something using
+   * them has started up will cause problems.
+   */
+  void setUserDataDirectory(in nsIFile aFile, in boolean aLocal);
+
+  /**
+   * Gets the hash for the current installation directory.
+   */
+  AString getInstallHash();
+};
diff --git a/toolkit/xre/nsNativeAppSupportBase.cpp b/toolkit/xre/nsNativeAppSupportBase.cpp
new file mode 100644
index 0000000000..43c329ec86
--- /dev/null
+++ b/toolkit/xre/nsNativeAppSupportBase.cpp
@@ -0,0 +1,28 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsNativeAppSupportBase.h"
+
+nsNativeAppSupportBase::nsNativeAppSupportBase() = default;
+
+nsNativeAppSupportBase::~nsNativeAppSupportBase() = default;
+
+NS_IMPL_ISUPPORTS(nsNativeAppSupportBase, nsINativeAppSupport)
+
+// Start answer defaults to OK.
+NS_IMETHODIMP
+nsNativeAppSupportBase::Start(bool* result) {
+  *result = true;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsNativeAppSupportBase::Enable() { return NS_OK; }
+
+NS_IMETHODIMP
+nsNativeAppSupportBase::ReOpen() { return NS_OK; }
+
+NS_IMETHODIMP
+nsNativeAppSupportBase::OnLastWindowClosing() { return NS_OK; }
diff --git a/toolkit/xre/nsNativeAppSupportBase.h b/toolkit/xre/nsNativeAppSupportBase.h
new file mode 100644
index 0000000000..851ea358fe
--- /dev/null
+++ b/toolkit/xre/nsNativeAppSupportBase.h
@@ -0,0 +1,28 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef nsNativeAppSupportBase_h__
+#define nsNativeAppSupportBase_h__
+
+#include "nsAppRunner.h"
+#include "nsINativeAppSupport.h"
+
+// nsNativeAppSupportBase
+//
+// This is a default implementation of the nsINativeAppSupport interface
+// declared in mozilla/xpfe/appshell/public/nsINativeAppSupport.h.
+
+class nsNativeAppSupportBase : public nsINativeAppSupport {
+ public:
+  nsNativeAppSupportBase();
+
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSINATIVEAPPSUPPORT
+
+ protected:
+  virtual ~nsNativeAppSupportBase();
+};
+
+#endif
diff --git a/toolkit/xre/nsNativeAppSupportCocoa.mm b/toolkit/xre/nsNativeAppSupportCocoa.mm
new file mode 100644
index 0000000000..1fe480b699
--- /dev/null
+++ b/toolkit/xre/nsNativeAppSupportCocoa.mm
@@ -0,0 +1,178 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsString.h"
+
+#import <CoreServices/CoreServices.h>
+#import <Cocoa/Cocoa.h>
+
+#include "nsCOMPtr.h"
+#include "nsCocoaFeatures.h"
+#include "nsNativeAppSupportBase.h"
+#include "nsServiceManagerUtils.h"
+
+#include "nsIBaseWindow.h"
+#include "nsCommandLine.h"
+#include "mozIDOMWindow.h"
+#include "nsIWebNavigation.h"
+#include "nsIWidget.h"
+#include "nsIWindowMediator.h"
+#include "nsPIDOMWindow.h"
+#include "WidgetUtils.h"
+
+// This must be included last:
+#include "nsObjCExceptions.h"
+
+using mozilla::widget::WidgetUtils;
+
+nsresult GetNativeWindowPointerFromDOMWindow(mozIDOMWindowProxy* a_window,
+                                             NSWindow** a_nativeWindow) {
+  *a_nativeWindow = nil;
+  if (!a_window) return NS_ERROR_INVALID_ARG;
+
+  nsPIDOMWindowOuter* win = nsPIDOMWindowOuter::From(a_window);
+  nsCOMPtr<nsIWidget> widget = WidgetUtils::DOMWindowToWidget(win);
+  if (!widget) {
+    return NS_ERROR_FAILURE;
+  }
+
+  *a_nativeWindow = (NSWindow*)widget->GetNativeData(NS_NATIVE_WINDOW);
+
+  return NS_OK;
+}
+
+class nsNativeAppSupportCocoa : public nsNativeAppSupportBase {
+ public:
+  nsNativeAppSupportCocoa() : mCanShowUI(false) {}
+
+  NS_IMETHOD Start(bool* aRetVal) override;
+  NS_IMETHOD ReOpen() override;
+  NS_IMETHOD Enable() override;
+
+ private:
+  bool mCanShowUI;
+};
+
+NS_IMETHODIMP
+nsNativeAppSupportCocoa::Enable() {
+  mCanShowUI = true;
+  return NS_OK;
+}
+
+NS_IMETHODIMP nsNativeAppSupportCocoa::Start(bool* _retval) {
+  int major, minor, bugfix;
+  nsCocoaFeatures::GetSystemVersion(major, minor, bugfix);
+
+  NS_OBJC_BEGIN_TRY_BLOCK_RETURN;
+
+  // Check that the OS version is supported, if not return false,
+  // which will make the browser quit.  In principle we could display an
+  // alert here.  But the alert's message and buttons would require custom
+  // localization.  So (for now at least) we just log an English message
+  // to the console before quitting.
+  if (major < 10 || (major == 10 && minor < 12)) {
+    NSLog(@"Minimum OS version requirement not met!");
+    return NS_OK;
+  }
+
+  *_retval = true;
+
+  return NS_OK;
+
+  NS_OBJC_END_TRY_BLOCK_RETURN(NS_ERROR_FAILURE);
+}
+
+NS_IMETHODIMP
+nsNativeAppSupportCocoa::ReOpen() {
+  NS_OBJC_BEGIN_TRY_BLOCK_RETURN;
+
+  if (!mCanShowUI) return NS_ERROR_FAILURE;
+
+  bool haveNonMiniaturized = false;
+  bool haveOpenWindows = false;
+  bool done = false;
+
+  nsCOMPtr<nsIWindowMediator> wm(do_GetService(NS_WINDOWMEDIATOR_CONTRACTID));
+  if (!wm) {
+    return NS_ERROR_FAILURE;
+  } else {
+    nsCOMPtr<nsISimpleEnumerator> windowList;
+    wm->GetAppWindowEnumerator(nullptr, getter_AddRefs(windowList));
+    bool more;
+    windowList->HasMoreElements(&more);
+    while (more) {
+      nsCOMPtr<nsISupports> nextWindow = nullptr;
+      windowList->GetNext(getter_AddRefs(nextWindow));
+      nsCOMPtr<nsIBaseWindow> baseWindow(do_QueryInterface(nextWindow));
+      if (!baseWindow) {
+        windowList->HasMoreElements(&more);
+        continue;
+      } else {
+        haveOpenWindows = true;
+      }
+
+      nsCOMPtr<nsIWidget> widget = nullptr;
+      baseWindow->GetMainWidget(getter_AddRefs(widget));
+      if (!widget || !widget->IsVisible()) {
+        windowList->HasMoreElements(&more);
+        continue;
+      }
+      NSWindow* cocoaWindow = (NSWindow*)widget->GetNativeData(NS_NATIVE_WINDOW);
+      if (![cocoaWindow isMiniaturized]) {
+        haveNonMiniaturized = true;
+        break;  // have un-minimized windows, nothing to do
+      }
+      windowList->HasMoreElements(&more);
+    }  // end while
+
+    if (!haveNonMiniaturized) {
+      // Prioritize browser windows for deminiaturization
+      nsCOMPtr<mozIDOMWindowProxy> mru;
+      wm->GetMostRecentBrowserWindow(getter_AddRefs(mru));
+
+      // Failing that, deminiaturize the most recently used window
+      if (!mru) {
+        wm->GetMostRecentWindow(nullptr, getter_AddRefs(mru));
+      }
+
+      if (mru) {
+        NSWindow* cocoaMru = nil;
+        GetNativeWindowPointerFromDOMWindow(mru, &cocoaMru);
+        if (cocoaMru) {
+          [cocoaMru deminiaturize:nil];
+          done = true;
+        }
+      }
+    }  // end if have non miniaturized
+
+    if (!haveOpenWindows && !done) {
+      char* argv[] = {nullptr};
+
+      // use an empty command line to make the right kind(s) of window open
+      nsCOMPtr<nsICommandLineRunner> cmdLine(new nsCommandLine());
+
+      nsresult rv;
+      rv = cmdLine->Init(0, argv, nullptr, nsICommandLine::STATE_REMOTE_EXPLICIT);
+      NS_ENSURE_SUCCESS(rv, rv);
+
+      return cmdLine->Run();
+    }
+
+  }  // got window mediator
+  return NS_OK;
+
+  NS_OBJC_END_TRY_BLOCK_RETURN(NS_ERROR_FAILURE);
+}
+
+#pragma mark -
+
+// Create and return an instance of class nsNativeAppSupportCocoa.
+nsresult NS_CreateNativeAppSupport(nsINativeAppSupport** aResult) {
+  *aResult = new nsNativeAppSupportCocoa;
+  if (!*aResult) return NS_ERROR_OUT_OF_MEMORY;
+
+  NS_ADDREF(*aResult);
+  return NS_OK;
+}
diff --git a/toolkit/xre/nsNativeAppSupportDefault.cpp b/toolkit/xre/nsNativeAppSupportDefault.cpp
new file mode 100644
index 0000000000..a65ac4e1a5
--- /dev/null
+++ b/toolkit/xre/nsNativeAppSupportDefault.cpp
@@ -0,0 +1,15 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsNativeAppSupportBase.h"
+
+nsresult NS_CreateNativeAppSupport(nsINativeAppSupport** aResult) {
+  nsNativeAppSupportBase* native = new nsNativeAppSupportBase();
+  if (!native) return NS_ERROR_OUT_OF_MEMORY;
+
+  *aResult = native;
+  NS_ADDREF(*aResult);
+
+  return NS_OK;
+}
diff --git a/toolkit/xre/nsNativeAppSupportUnix.cpp b/toolkit/xre/nsNativeAppSupportUnix.cpp
new file mode 100644
index 0000000000..bed9e546db
--- /dev/null
+++ b/toolkit/xre/nsNativeAppSupportUnix.cpp
@@ -0,0 +1,662 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsNativeAppSupportBase.h"
+#include "nsComponentManagerUtils.h"
+#include "nsCOMPtr.h"
+#include "nsXPCOM.h"
+#include "nsISupportsPrimitives.h"
+#include "nsIObserverService.h"
+#include "nsIAppStartup.h"
+#include "nsServiceManagerUtils.h"
+#include "prlink.h"
+#include "nsXREDirProvider.h"
+#include "nsReadableUtils.h"
+
+#include "nsIFile.h"
+#include "nsDirectoryServiceDefs.h"
+#include "nsPIDOMWindow.h"
+#include "nsIWidget.h"
+#include "mozilla/Logging.h"
+#include "mozilla/Services.h"
+#include "mozilla/XREAppData.h"
+
+#include <stdlib.h>
+#include <glib.h>
+#include <glib-object.h>
+#include <gtk/gtk.h>
+
+#ifdef MOZ_X11
+#  include <gdk/gdkx.h>
+#  include <X11/ICE/ICElib.h>
+#  include <X11/SM/SMlib.h>
+#  include <fcntl.h>
+#  include "nsThreadUtils.h"
+
+#  include <pwd.h>
+#endif
+
+#ifdef MOZ_ENABLE_DBUS
+#  include <dbus/dbus.h>
+#endif
+
+#define MIN_GTK_MAJOR_VERSION 2
+#define MIN_GTK_MINOR_VERSION 10
+#define UNSUPPORTED_GTK_MSG \
+  "We're sorry, this application requires a version of the GTK+ library that is not installed on your computer.\n\n\
+You have GTK+ %d.%d.\nThis application requires GTK+ %d.%d or newer.\n\n\
+Please upgrade your GTK+ library if you wish to use this application."
+
+#if MOZ_X11
+#  undef IceSetIOErrorHandler
+#  undef IceAddConnectionWatch
+#  undef IceConnectionNumber
+#  undef IceProcessMessages
+#  undef IceGetConnectionContext
+#  undef SmcInteractDone
+#  undef SmcSaveYourselfDone
+#  undef SmcInteractRequest
+#  undef SmcCloseConnection
+#  undef SmcOpenConnection
+#  undef SmcSetProperties
+
+typedef IceIOErrorHandler (*IceSetIOErrorHandlerFn)(IceIOErrorHandler);
+typedef int (*IceAddConnectionWatchFn)(IceWatchProc, IcePointer);
+typedef int (*IceConnectionNumberFn)(IceConn);
+typedef IceProcessMessagesStatus (*IceProcessMessagesFn)(IceConn,
+                                                         IceReplyWaitInfo*,
+                                                         Bool*);
+typedef IcePointer (*IceGetConnectionContextFn)(IceConn);
+
+typedef void (*SmcInteractDoneFn)(SmcConn, Bool);
+typedef void (*SmcSaveYourselfDoneFn)(SmcConn, Bool);
+typedef int (*SmcInteractRequestFn)(SmcConn, int, SmcInteractProc, SmPointer);
+typedef SmcCloseStatus (*SmcCloseConnectionFn)(SmcConn, int, char**);
+typedef SmcConn (*SmcOpenConnectionFn)(char*, SmPointer, int, int,
+                                       unsigned long, SmcCallbacks*,
+                                       const char*, char**, int, char*);
+typedef void (*SmcSetPropertiesFn)(SmcConn, int, SmProp**);
+
+static IceSetIOErrorHandlerFn IceSetIOErrorHandlerPtr;
+static IceAddConnectionWatchFn IceAddConnectionWatchPtr;
+static IceConnectionNumberFn IceConnectionNumberPtr;
+static IceProcessMessagesFn IceProcessMessagesPtr;
+static IceGetConnectionContextFn IceGetConnectionContextPtr;
+static SmcInteractDoneFn SmcInteractDonePtr;
+static SmcSaveYourselfDoneFn SmcSaveYourselfDonePtr;
+static SmcInteractRequestFn SmcInteractRequestPtr;
+static SmcCloseConnectionFn SmcCloseConnectionPtr;
+static SmcOpenConnectionFn SmcOpenConnectionPtr;
+static SmcSetPropertiesFn SmcSetPropertiesPtr;
+
+#  define IceSetIOErrorHandler IceSetIOErrorHandlerPtr
+#  define IceAddConnectionWatch IceAddConnectionWatchPtr
+#  define IceConnectionNumber IceConnectionNumberPtr
+#  define IceProcessMessages IceProcessMessagesPtr
+#  define IceGetConnectionContext IceGetConnectionContextPtr
+#  define SmcInteractDone SmcInteractDonePtr
+#  define SmcSaveYourselfDone SmcSaveYourselfDonePtr
+#  define SmcInteractRequest SmcInteractRequestPtr
+#  define SmcCloseConnection SmcCloseConnectionPtr
+#  define SmcOpenConnection SmcOpenConnectionPtr
+#  define SmcSetProperties SmcSetPropertiesPtr
+
+enum ClientState {
+  STATE_DISCONNECTED,
+  STATE_REGISTERING,
+  STATE_IDLE,
+  STATE_INTERACTING,
+  STATE_SHUTDOWN_CANCELLED
+};
+
+using namespace mozilla;
+
+static const char* gClientStateTable[] = {"DISCONNECTED", "REGISTERING", "IDLE",
+                                          "INTERACTING", "SHUTDOWN_CANCELLED"};
+
+static LazyLogModule sMozSMLog("MozSM");
+#endif /* MOZ_X11 */
+
+class nsNativeAppSupportUnix : public nsNativeAppSupportBase {
+ public:
+#if MOZ_X11
+  nsNativeAppSupportUnix()
+      : mSessionConnection(nullptr), mClientState(STATE_DISCONNECTED){};
+  ~nsNativeAppSupportUnix() {
+    // this goes out of scope after "web-workers-shutdown" async shutdown phase
+    // so it's safe to disconnect here (i.e. the application won't lose data)
+    DisconnectFromSM();
+  };
+
+  void DisconnectFromSM();
+#endif
+  NS_IMETHOD Start(bool* aRetVal) override;
+  NS_IMETHOD Enable() override;
+
+ private:
+#if MOZ_X11
+  static void SaveYourselfCB(SmcConn smc_conn, SmPointer client_data,
+                             int save_style, Bool shutdown, int interact_style,
+                             Bool fast);
+  static void DieCB(SmcConn smc_conn, SmPointer client_data);
+  static void InteractCB(SmcConn smc_conn, SmPointer client_data);
+  static void SaveCompleteCB(SmcConn smc_conn, SmPointer client_data){};
+  static void ShutdownCancelledCB(SmcConn smc_conn, SmPointer client_data);
+  void DoInteract();
+  void SetClientState(ClientState aState) {
+    mClientState = aState;
+    MOZ_LOG(sMozSMLog, LogLevel::Debug,
+            ("New state = %s\n", gClientStateTable[aState]));
+  }
+
+  SmcConn mSessionConnection;
+  ClientState mClientState;
+#endif
+};
+
+#if MOZ_X11
+static gboolean process_ice_messages(IceConn connection) {
+  IceProcessMessagesStatus status;
+
+  status = IceProcessMessages(connection, nullptr, nullptr);
+
+  switch (status) {
+    case IceProcessMessagesSuccess:
+      return TRUE;
+
+    case IceProcessMessagesIOError: {
+      nsNativeAppSupportUnix* native = static_cast<nsNativeAppSupportUnix*>(
+          IceGetConnectionContext(connection));
+      native->DisconnectFromSM();
+    }
+      return FALSE;
+
+    case IceProcessMessagesConnectionClosed:
+      return FALSE;
+
+    default:
+      g_assert_not_reached();
+  }
+}
+
+static gboolean ice_iochannel_watch(GIOChannel* channel, GIOCondition condition,
+                                    gpointer client_data) {
+  return process_ice_messages(static_cast<IceConn>(client_data));
+}
+
+static void ice_connection_watch(IceConn connection, IcePointer client_data,
+                                 Bool opening, IcePointer* watch_data) {
+  guint watch_id;
+
+  if (opening) {
+    GIOChannel* channel;
+    int fd = IceConnectionNumber(connection);
+
+    fcntl(fd, F_SETFD, fcntl(fd, F_GETFD, 0) | FD_CLOEXEC);
+    channel = g_io_channel_unix_new(fd);
+    watch_id =
+        g_io_add_watch(channel, static_cast<GIOCondition>(G_IO_IN | G_IO_ERR),
+                       ice_iochannel_watch, connection);
+    g_io_channel_unref(channel);
+
+    *watch_data = GUINT_TO_POINTER(watch_id);
+  } else {
+    watch_id = GPOINTER_TO_UINT(*watch_data);
+    g_source_remove(watch_id);
+  }
+}
+
+static void ice_io_error_handler(IceConn connection) {
+  // override the default handler which would exit the application;
+  // do nothing and let ICELib handle the failure of the connection gracefully.
+}
+
+static void ice_init(void) {
+  static bool initted = false;
+
+  if (!initted) {
+    IceSetIOErrorHandler(ice_io_error_handler);
+    IceAddConnectionWatch(ice_connection_watch, nullptr);
+    initted = true;
+  }
+}
+
+void nsNativeAppSupportUnix::InteractCB(SmcConn smc_conn,
+                                        SmPointer client_data) {
+  nsNativeAppSupportUnix* self =
+      static_cast<nsNativeAppSupportUnix*>(client_data);
+
+  self->SetClientState(STATE_INTERACTING);
+
+  // We do this asynchronously, as we spin the event loop recursively if
+  // a dialog is displayed. If we do this synchronously, we don't finish
+  // processing the current ICE event whilst the dialog is displayed, which
+  // means we won't process any more. libsm hates us if we do the InteractDone
+  // with a pending ShutdownCancelled, and we would certainly like to handle Die
+  // whilst a dialog is displayed
+  NS_DispatchToCurrentThread(
+      NewRunnableMethod("nsNativeAppSupportUnix::DoInteract", self,
+                        &nsNativeAppSupportUnix::DoInteract));
+}
+
+void nsNativeAppSupportUnix::DoInteract() {
+  nsCOMPtr<nsIObserverService> obsServ =
+      mozilla::services::GetObserverService();
+  if (!obsServ) {
+    SmcInteractDone(mSessionConnection, False);
+    SmcSaveYourselfDone(mSessionConnection, True);
+    SetClientState(STATE_IDLE);
+    return;
+  }
+
+  nsCOMPtr<nsISupportsPRBool> cancelQuit =
+      do_CreateInstance(NS_SUPPORTS_PRBOOL_CONTRACTID);
+
+  bool abortQuit = false;
+  if (cancelQuit) {
+    cancelQuit->SetData(false);
+    obsServ->NotifyObservers(cancelQuit, "quit-application-requested", nullptr);
+
+    cancelQuit->GetData(&abortQuit);
+  }
+
+  if (!abortQuit && mClientState == STATE_DISCONNECTED) {
+    // The session manager disappeared, whilst we were interacting, so
+    // quit now
+    nsCOMPtr<nsIAppStartup> appService =
+        do_GetService("@mozilla.org/toolkit/app-startup;1");
+
+    if (appService) {
+      bool userAllowedQuit = true;
+      appService->Quit(nsIAppStartup::eForceQuit, 0, &userAllowedQuit);
+    }
+  } else {
+    if (mClientState != STATE_SHUTDOWN_CANCELLED) {
+      // Only do this if the shutdown wasn't cancelled
+      SmcInteractDone(mSessionConnection, !!abortQuit);
+      SmcSaveYourselfDone(mSessionConnection, !abortQuit);
+    }
+
+    SetClientState(STATE_IDLE);
+  }
+}
+
+void nsNativeAppSupportUnix::SaveYourselfCB(SmcConn smc_conn,
+                                            SmPointer client_data,
+                                            int save_style, Bool shutdown,
+                                            int interact_style, Bool fast) {
+  nsNativeAppSupportUnix* self =
+      static_cast<nsNativeAppSupportUnix*>(client_data);
+
+  // Expect a SaveYourselfCB if we're registering a new client.
+  // All properties are already set in Start() so just reply with
+  // SmcSaveYourselfDone if the callback matches the expected signature.
+  //
+  // Ancient versions (?) of xsm do not follow such an early SaveYourself with
+  // SaveComplete. This is a problem if the application freezes interaction
+  // while waiting for a response to SmcSaveYourselfDone. So never freeze
+  // interaction when in STATE_REGISTERING.
+  //
+  // That aside, we could treat each combination of flags appropriately and not
+  // special-case this.
+  if (self->mClientState == STATE_REGISTERING) {
+    self->SetClientState(STATE_IDLE);
+
+    if (save_style == SmSaveLocal && interact_style == SmInteractStyleNone &&
+        !shutdown && !fast) {
+      SmcSaveYourselfDone(self->mSessionConnection, True);
+      return;
+    }
+  }
+
+  if (self->mClientState == STATE_SHUTDOWN_CANCELLED) {
+    // The last shutdown request was cancelled whilst we were interacting,
+    // and we haven't finished interacting yet. Switch the state back again
+    self->SetClientState(STATE_INTERACTING);
+  }
+
+  nsCOMPtr<nsIObserverService> obsServ =
+      mozilla::services::GetObserverService();
+  if (!obsServ) {
+    SmcSaveYourselfDone(smc_conn, True);
+    return;
+  }
+
+  bool status = false;
+  nsCOMPtr<nsISupportsPRBool> didSaveSession =
+      do_CreateInstance(NS_SUPPORTS_PRBOOL_CONTRACTID);
+
+  if (!didSaveSession) {
+    SmcSaveYourselfDone(smc_conn, True);
+    return;
+  }
+
+  // Notify observers to save the session state
+  didSaveSession->SetData(false);
+  obsServ->NotifyObservers(didSaveSession, "session-save", nullptr);
+
+  didSaveSession->GetData(&status);
+
+  // If the interact style permits us to, we are shutting down and we didn't
+  // manage to (or weren't asked to) save the local state, then notify the user
+  // in advance that we are doing to quit (assuming that we aren't already
+  // doing so)
+  if (!status && shutdown && interact_style != SmInteractStyleNone) {
+    if (self->mClientState != STATE_INTERACTING) {
+      SmcInteractRequest(smc_conn, SmDialogNormal,
+                         nsNativeAppSupportUnix::InteractCB, client_data);
+    }
+  } else {
+    SmcSaveYourselfDone(smc_conn, True);
+  }
+}
+
+void nsNativeAppSupportUnix::DieCB(SmcConn smc_conn, SmPointer client_data) {
+  nsCOMPtr<nsIAppStartup> appService =
+      do_GetService("@mozilla.org/toolkit/app-startup;1");
+
+  if (appService) {
+    bool userAllowedQuit = false;
+    appService->Quit(nsIAppStartup::eForceQuit, 0, &userAllowedQuit);
+  }
+  // Quit causes the shutdown to begin but the shutdown process is asynchronous
+  // so we can't DisconnectFromSM() yet
+}
+
+void nsNativeAppSupportUnix::ShutdownCancelledCB(SmcConn smc_conn,
+                                                 SmPointer client_data) {
+  nsNativeAppSupportUnix* self =
+      static_cast<nsNativeAppSupportUnix*>(client_data);
+
+  // Interacting is the only time when we wouldn't already have called
+  // SmcSaveYourselfDone. Do that now, then set the state to make sure we
+  // don't send it again after finishing interacting
+  if (self->mClientState == STATE_INTERACTING) {
+    SmcSaveYourselfDone(smc_conn, False);
+    self->SetClientState(STATE_SHUTDOWN_CANCELLED);
+  }
+}
+
+void nsNativeAppSupportUnix::DisconnectFromSM() {
+  // the SM is free to exit any time after we disconnect, so callers must be
+  // sure to have reached a sufficiently advanced phase of shutdown that there
+  // is no risk of data loss:
+  // e.g. all async writes are complete by the end of "profile-before-change"
+  if (mSessionConnection) {
+    SetClientState(STATE_DISCONNECTED);
+    SmcCloseConnection(mSessionConnection, 0, nullptr);
+    mSessionConnection = nullptr;
+    gdk_x11_set_sm_client_id(nullptr);  // follow gnome-client behaviour
+  }
+}
+
+static void SetSMValue(SmPropValue& val, const nsCString& data) {
+  val.value = static_cast<SmPointer>(const_cast<char*>(data.get()));
+  val.length = data.Length();
+}
+
+static void SetSMProperty(SmProp& prop, const char* name, const char* type,
+                          int numVals, SmPropValue vals[]) {
+  prop.name = const_cast<char*>(name);
+  prop.type = const_cast<char*>(type);
+  prop.num_vals = numVals;
+  prop.vals = vals;
+}
+#endif /* MOZ_X11 */
+
+static void RemoveArg(char** argv) {
+  do {
+    *argv = *(argv + 1);
+    ++argv;
+  } while (*argv);
+
+  --gArgc;
+}
+
+NS_IMETHODIMP
+nsNativeAppSupportUnix::Start(bool* aRetVal) {
+  NS_ASSERTION(gAppData, "gAppData must not be null.");
+
+// The dbus library is used by both nsWifiScannerDBus and BluetoothDBusService,
+// from diffrent threads. This could lead to race conditions if the dbus is not
+// initialized before making any other library calls.
+#ifdef MOZ_ENABLE_DBUS
+  dbus_threads_init_default();
+#endif
+
+  *aRetVal = true;
+
+#ifdef MOZ_X11
+  gboolean sm_disable = FALSE;
+  if (!getenv("SESSION_MANAGER")) {
+    sm_disable = TRUE;
+  }
+
+  nsAutoCString prev_client_id;
+
+  char** curarg = gArgv + 1;
+  while (*curarg) {
+    char* arg = *curarg;
+    if (arg[0] == '-' && arg[1] == '-') {
+      arg += 2;
+      if (!strcmp(arg, "sm-disable")) {
+        RemoveArg(curarg);
+        sm_disable = TRUE;
+        continue;
+      } else if (!strcmp(arg, "sm-client-id")) {
+        RemoveArg(curarg);
+        if (*curarg[0] != '-') {
+          prev_client_id = *curarg;
+          RemoveArg(curarg);
+        }
+        continue;
+      }
+    }
+
+    ++curarg;
+  }
+
+  if (prev_client_id.IsEmpty()) {
+    prev_client_id = getenv("DESKTOP_AUTOSTART_ID");
+  }
+
+  // We don't want child processes to use the same ID
+  unsetenv("DESKTOP_AUTOSTART_ID");
+
+  char* client_id = nullptr;
+  if (!sm_disable) {
+    PRLibrary* iceLib = PR_LoadLibrary("libICE.so.6");
+    if (!iceLib) {
+      return NS_OK;
+    }
+
+    PRLibrary* smLib = PR_LoadLibrary("libSM.so.6");
+    if (!smLib) {
+      PR_UnloadLibrary(iceLib);
+      return NS_OK;
+    }
+
+    IceSetIOErrorHandler = (IceSetIOErrorHandlerFn)PR_FindFunctionSymbol(
+        iceLib, "IceSetIOErrorHandler");
+    IceAddConnectionWatch = (IceAddConnectionWatchFn)PR_FindFunctionSymbol(
+        iceLib, "IceAddConnectionWatch");
+    IceConnectionNumber = (IceConnectionNumberFn)PR_FindFunctionSymbol(
+        iceLib, "IceConnectionNumber");
+    IceProcessMessages = (IceProcessMessagesFn)PR_FindFunctionSymbol(
+        iceLib, "IceProcessMessages");
+    IceGetConnectionContext = (IceGetConnectionContextFn)PR_FindFunctionSymbol(
+        iceLib, "IceGetConnectionContext");
+    if (!IceSetIOErrorHandler || !IceAddConnectionWatch ||
+        !IceConnectionNumber || !IceProcessMessages ||
+        !IceGetConnectionContext) {
+      PR_UnloadLibrary(iceLib);
+      PR_UnloadLibrary(smLib);
+      return NS_OK;
+    }
+
+    SmcInteractDone =
+        (SmcInteractDoneFn)PR_FindFunctionSymbol(smLib, "SmcInteractDone");
+    SmcSaveYourselfDone = (SmcSaveYourselfDoneFn)PR_FindFunctionSymbol(
+        smLib, "SmcSaveYourselfDone");
+    SmcInteractRequest = (SmcInteractRequestFn)PR_FindFunctionSymbol(
+        smLib, "SmcInteractRequest");
+    SmcCloseConnection = (SmcCloseConnectionFn)PR_FindFunctionSymbol(
+        smLib, "SmcCloseConnection");
+    SmcOpenConnection =
+        (SmcOpenConnectionFn)PR_FindFunctionSymbol(smLib, "SmcOpenConnection");
+    SmcSetProperties =
+        (SmcSetPropertiesFn)PR_FindFunctionSymbol(smLib, "SmcSetProperties");
+    if (!SmcInteractDone || !SmcSaveYourselfDone || !SmcInteractRequest ||
+        !SmcCloseConnection || !SmcOpenConnection || !SmcSetProperties) {
+      PR_UnloadLibrary(iceLib);
+      PR_UnloadLibrary(smLib);
+      return NS_OK;
+    }
+
+    ice_init();
+
+    // all callbacks are mandatory in libSM 1.0, so listen even if we don't
+    // care.
+    unsigned long mask = SmcSaveYourselfProcMask | SmcDieProcMask |
+                         SmcSaveCompleteProcMask | SmcShutdownCancelledProcMask;
+
+    SmcCallbacks callbacks;
+    callbacks.save_yourself.callback = nsNativeAppSupportUnix::SaveYourselfCB;
+    callbacks.save_yourself.client_data = static_cast<SmPointer>(this);
+
+    callbacks.die.callback = nsNativeAppSupportUnix::DieCB;
+    callbacks.die.client_data = static_cast<SmPointer>(this);
+
+    callbacks.save_complete.callback = nsNativeAppSupportUnix::SaveCompleteCB;
+    callbacks.save_complete.client_data = nullptr;
+
+    callbacks.shutdown_cancelled.callback =
+        nsNativeAppSupportUnix::ShutdownCancelledCB;
+    callbacks.shutdown_cancelled.client_data = static_cast<SmPointer>(this);
+
+    char errbuf[256];
+    mSessionConnection = SmcOpenConnection(
+        nullptr, this, SmProtoMajor, SmProtoMinor, mask, &callbacks,
+        prev_client_id.get(), &client_id, sizeof(errbuf), errbuf);
+  }
+
+  if (!mSessionConnection) {
+    return NS_OK;
+  }
+
+  LogModule::Init(
+      gArgc, gArgv);  // need to make sure initialized before SetClientState
+  if (prev_client_id.IsEmpty() ||
+      (client_id && !prev_client_id.Equals(client_id))) {
+    SetClientState(STATE_REGISTERING);
+  } else {
+    SetClientState(STATE_IDLE);
+  }
+
+  gdk_x11_set_sm_client_id(client_id);
+
+  // Set SM Properties
+  // SmCloneCommand, SmProgram, SmRestartCommand, SmUserID are required
+  // properties so must be set, and must have a sensible fallback value.
+
+  // Determine executable path to use for XSMP session restore
+
+  // Is there a request to suppress default binary launcher?
+  nsAutoCString path(getenv("MOZ_APP_LAUNCHER"));
+
+  if (path.IsEmpty()) {
+    NS_ASSERTION(gDirServiceProvider,
+                 "gDirServiceProvider is NULL! This shouldn't happen!");
+    nsCOMPtr<nsIFile> executablePath;
+    nsresult rv;
+
+    bool dummy;
+    rv = gDirServiceProvider->GetFile(XRE_EXECUTABLE_FILE, &dummy,
+                                      getter_AddRefs(executablePath));
+
+    if (NS_SUCCEEDED(rv)) {
+      // Strip off the -bin suffix to get the shell script we should run; this
+      // is what Breakpad does
+      nsAutoCString leafName;
+      rv = executablePath->GetNativeLeafName(leafName);
+      if (NS_SUCCEEDED(rv) && StringEndsWith(leafName, "-bin"_ns)) {
+        leafName.SetLength(leafName.Length() - strlen("-bin"));
+        executablePath->SetNativeLeafName(leafName);
+      }
+
+      executablePath->GetNativePath(path);
+    }
+  }
+
+  if (path.IsEmpty()) {
+    // can't determine executable path. Best fallback is name from
+    // application.ini but it might not resolve to the same executable at
+    // launch time.
+    path = gAppData->name;  // will always be set
+    ToLowerCase(path);
+    MOZ_LOG(sMozSMLog, LogLevel::Warning,
+            ("Could not determine executable path. Falling back to %s.",
+             path.get()));
+  }
+
+  SmProp propRestart, propClone, propProgram, propUser, *props[4];
+  SmPropValue valsRestart[3], valsClone[1], valsProgram[1], valsUser[1];
+  int n = 0;
+
+  constexpr auto kClientIDParam = "--sm-client-id"_ns;
+
+  SetSMValue(valsRestart[0], path);
+  SetSMValue(valsRestart[1], kClientIDParam);
+  SetSMValue(valsRestart[2], nsDependentCString(client_id));
+  SetSMProperty(propRestart, SmRestartCommand, SmLISTofARRAY8, 3, valsRestart);
+  props[n++] = &propRestart;
+
+  SetSMValue(valsClone[0], path);
+  SetSMProperty(propClone, SmCloneCommand, SmLISTofARRAY8, 1, valsClone);
+  props[n++] = &propClone;
+
+  nsAutoCString appName(gAppData->name);  // will always be set
+  ToLowerCase(appName);
+
+  SetSMValue(valsProgram[0], appName);
+  SetSMProperty(propProgram, SmProgram, SmARRAY8, 1, valsProgram);
+  props[n++] = &propProgram;
+
+  nsAutoCString userName;  // username that started the program
+  struct passwd* pw = getpwuid(getuid());
+  if (pw && pw->pw_name) {
+    userName = pw->pw_name;
+  } else {
+    userName = "nobody"_ns;
+    MOZ_LOG(
+        sMozSMLog, LogLevel::Warning,
+        ("Could not determine user-name. Falling back to %s.", userName.get()));
+  }
+
+  SetSMValue(valsUser[0], userName);
+  SetSMProperty(propUser, SmUserID, SmARRAY8, 1, valsUser);
+  props[n++] = &propUser;
+
+  SmcSetProperties(mSessionConnection, n, props);
+
+  g_free(client_id);
+#endif /* MOZ_X11 */
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsNativeAppSupportUnix::Enable() { return NS_OK; }
+
+nsresult NS_CreateNativeAppSupport(nsINativeAppSupport** aResult) {
+  nsNativeAppSupportBase* native = new nsNativeAppSupportUnix();
+  if (!native) return NS_ERROR_OUT_OF_MEMORY;
+
+  *aResult = native;
+  NS_ADDREF(*aResult);
+
+  return NS_OK;
+}
diff --git a/toolkit/xre/nsNativeAppSupportWin.cpp b/toolkit/xre/nsNativeAppSupportWin.cpp
new file mode 100644
index 0000000000..8c4b43b3f6
--- /dev/null
+++ b/toolkit/xre/nsNativeAppSupportWin.cpp
@@ -0,0 +1,66 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsNativeAppSupportBase.h"
+#include "nsNativeAppSupportWin.h"
+
+#include "mozilla/CmdLineAndEnvUtils.h"
+#include "mozilla/WindowsConsole.h"
+
+using namespace mozilla;
+
+/*
+ * This code attaches the process to the appropriate console.
+ */
+
+class nsNativeAppSupportWin : public nsNativeAppSupportBase {
+ public:
+  // Utility function to handle a Win32-specific command line
+  // option: "--console", which dynamically creates a Windows
+  // console.
+  void CheckConsole();
+
+ private:
+  ~nsNativeAppSupportWin() {}
+};  // nsNativeAppSupportWin
+
+void nsNativeAppSupportWin::CheckConsole() {
+  if (CheckArg(gArgc, gArgv, "attach-console") == ARG_FOUND) {
+    UseParentConsole();
+  }
+
+  if (CheckArg(gArgc, gArgv, "console") == ARG_FOUND) {
+    if (AllocConsole()) {
+      // Redirect the standard streams to the new console, but
+      // only if they haven't been redirected to a valid file.
+      // Visual Studio's _fileno() returns -2 for the standard
+      // streams if they aren't associated with an output stream.
+      if (_fileno(stdout) == -2) {
+        freopen("CONOUT$", "w", stdout);
+      }
+      // There is no CONERR$, so use CONOUT$ for stderr as well.
+      if (_fileno(stderr) == -2) {
+        freopen("CONOUT$", "w", stderr);
+      }
+      if (_fileno(stdin) == -2) {
+        freopen("CONIN$", "r", stdin);
+      }
+    }
+  }
+}
+
+// Create and return an instance of class nsNativeAppSupportWin.
+nsresult NS_CreateNativeAppSupport(nsINativeAppSupport** aResult) {
+  nsNativeAppSupportWin* pNative = new nsNativeAppSupportWin;
+  if (!pNative) return NS_ERROR_OUT_OF_MEMORY;
+
+  // Check for dynamic console creation request.
+  pNative->CheckConsole();
+
+  *aResult = pNative;
+  NS_ADDREF(*aResult);
+
+  return NS_OK;
+}
diff --git a/toolkit/xre/nsNativeAppSupportWin.h b/toolkit/xre/nsNativeAppSupportWin.h
new file mode 100644
index 0000000000..4bf01e1bb5
--- /dev/null
+++ b/toolkit/xre/nsNativeAppSupportWin.h
@@ -0,0 +1,29 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* This file has *public* stuff needed for the Win32 implementation of
+ * the nsINativeAppSupport interface.  It has to be broken out into a
+ * separate file in order to ensure that the generated .h file can be
+ * used in a Win32 .rc file.  See /mozilla/xpfe/bootstrap/splash.rc.
+ *
+ * This file, and the generated .h, are only needed on Win32 platforms.
+ */
+
+// Constants identifying Win32 "native" resources.
+
+#define IDI_APPICON 1
+#define IDI_DOCUMENT 2
+#define IDI_NEWWINDOW 3
+#define IDI_NEWTAB 4
+// If IDI_PBMODE's index changes, PRIVATE_BROWSING_ICON_INDEX
+// in BrowserContentHandler.sys.mjs must also be updated.
+#define IDI_PBMODE 5
+#define IDI_DOCUMENT_PDF 6
+#ifndef IDI_APPLICATION
+#  define IDI_APPLICATION 32512
+#endif
+
+// String that goes in the WinXP Start Menu.
+#define IDS_STARTMENU_APPNAME 103
diff --git a/toolkit/xre/nsSigHandlers.cpp b/toolkit/xre/nsSigHandlers.cpp
new file mode 100644
index 0000000000..f28a21fce4
--- /dev/null
+++ b/toolkit/xre/nsSigHandlers.cpp
@@ -0,0 +1,402 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/*
+ * This module is supposed to abstract signal handling away from the other
+ * platforms that do not support it.
+ */
+
+#include "nsSigHandlers.h"
+
+#ifdef XP_UNIX
+
+#  include <signal.h>
+#  include <stdio.h>
+#  include <string.h>
+#  include "prthread.h"
+#  include "prenv.h"
+#  include "nsDebug.h"
+#  include "nsString.h"
+#  include "nsXULAppAPI.h"
+
+#  if defined(LINUX)
+#    include <sys/time.h>
+#    include <sys/resource.h>
+#    include <unistd.h>
+#    include <stdlib.h>  // atoi
+#    include <sys/prctl.h>
+#    ifndef ANDROID  // no Android impl
+#      include <ucontext.h>
+#    endif
+#  endif
+
+#  if defined(SOLARIS)
+#    include <sys/resource.h>
+#    include <ucontext.h>
+#  endif
+
+// Note: some tests manipulate this value.
+unsigned int _gdb_sleep_duration = 300;
+
+#  if defined(LINUX) && !defined(ANDROID) && defined(DEBUG) && \
+      (defined(__i386) || defined(__x86_64) || defined(PPC))
+#    define CRAWL_STACK_ON_SIGSEGV
+#  endif
+
+#  ifndef PR_SET_PTRACER
+#    define PR_SET_PTRACER 0x59616d61
+#  endif
+#  ifndef PR_SET_PTRACER_ANY
+#    define PR_SET_PTRACER_ANY ((unsigned long)-1)
+#  endif
+
+#  if defined(CRAWL_STACK_ON_SIGSEGV)
+
+#    include <unistd.h>
+#    include "nsISupportsUtils.h"
+#    include "mozilla/Attributes.h"
+#    include "mozilla/StackWalk.h"
+
+static const char* gProgname = "huh?";
+
+// NB: keep me up to date with the same variable in
+// ipc/chromium/chrome/common/ipc_channel_posix.cc
+static const int kClientChannelFd = 3;
+
+extern "C" {
+
+static void PrintStackFrame(uint32_t aFrameNumber, void* aPC, void* aSP,
+                            void* aClosure) {
+  char buf[1024];
+  MozCodeAddressDetails details;
+
+  MozDescribeCodeAddress(aPC, &details);
+  MozFormatCodeAddressDetails(buf, sizeof(buf), aFrameNumber, aPC, &details);
+  fprintf(stdout, "%s\n", buf);
+  fflush(stdout);
+}
+}
+
+void common_crap_handler(int signum, const void* aFirstFramePC) {
+  printf("\nProgram %s (pid = %d) received signal %d.\n", gProgname, getpid(),
+         signum);
+
+  printf("Stack:\n");
+  MozStackWalk(PrintStackFrame, aFirstFramePC, /* maxFrames */ 0, nullptr);
+
+  printf("Sleeping for %d seconds.\n", _gdb_sleep_duration);
+  printf("Type 'gdb %s %d' to attach your debugger to this thread.\n",
+         gProgname, getpid());
+
+  // Allow us to be ptraced by gdb on Linux with Yama restrictions enabled.
+  prctl(PR_SET_PTRACER, PR_SET_PTRACER_ANY);
+
+  sleep(_gdb_sleep_duration);
+
+  printf("Done sleeping...\n");
+
+  _exit(signum);
+}
+
+MOZ_NEVER_INLINE void ah_crap_handler(int signum) {
+  common_crap_handler(signum, CallerPC());
+}
+
+MOZ_NEVER_INLINE void child_ah_crap_handler(int signum) {
+  if (!getenv("MOZ_DONT_UNBLOCK_PARENT_ON_CHILD_CRASH"))
+    close(kClientChannelFd);
+  common_crap_handler(signum, CallerPC());
+}
+
+#  endif  // CRAWL_STACK_ON_SIGSEGV
+
+#  ifdef MOZ_WIDGET_GTK
+// Need this include for version test below.
+#    include <glib.h>
+#  endif
+
+#  if defined(MOZ_WIDGET_GTK) && \
+      (GLIB_MAJOR_VERSION > 2 || \
+       (GLIB_MAJOR_VERSION == 2 && GLIB_MINOR_VERSION >= 6))
+
+static GLogFunc orig_log_func = nullptr;
+
+extern "C" {
+static void glib_log_func(const gchar* log_domain, GLogLevelFlags log_level,
+                          const gchar* message, gpointer user_data);
+}
+
+// GDK sometimes avoids calling exit handlers, but we still want to know when we
+// crash, see https://gitlab.gnome.org/GNOME/gtk/-/issues/4514 and bug 1743144.
+static bool IsCrashyGtkMessage(const nsACString& aMessage) {
+  if (aMessage.EqualsLiteral("Lost connection to Wayland compositor.")) {
+    // https://gitlab.gnome.org/GNOME/gtk/-/blob/gtk-3-24/gdk/wayland/gdkeventsource.c#L210
+    return true;
+  }
+  if (StringBeginsWith(aMessage, "Error flushing display: "_ns)) {
+    // https://gitlab.gnome.org/GNOME/gtk/-/blob/gtk-3-24/gdk/wayland/gdkeventsource.c#L68
+    return true;
+  }
+  if (StringBeginsWith(aMessage, "Error reading events from display: "_ns)) {
+    // https://gitlab.gnome.org/GNOME/gtk/-/blob/gtk-3-24/gdk/wayland/gdkeventsource.c#L97
+    return true;
+  }
+  if (StringBeginsWith(aMessage, "Error "_ns) &&
+      StringEndsWith(aMessage, " dispatching to Wayland display."_ns)) {
+    // https://gitlab.gnome.org/GNOME/gtk/-/blob/gtk-3-24/gdk/wayland/gdkeventsource.c#L205
+    return true;
+  }
+  return false;
+}
+
+/* static */ void glib_log_func(const gchar* log_domain,
+                                GLogLevelFlags log_level, const gchar* message,
+                                gpointer user_data) {
+  if (MOZ_UNLIKELY(IsCrashyGtkMessage(nsDependentCString(message)))) {
+    MOZ_CRASH_UNSAFE(strdup(message));
+  }
+
+  if (log_level &
+      (G_LOG_LEVEL_ERROR | G_LOG_FLAG_FATAL | G_LOG_FLAG_RECURSION)) {
+    NS_DebugBreak(NS_DEBUG_ASSERTION, message, "glib assertion", __FILE__,
+                  __LINE__);
+  } else if (log_level & (G_LOG_LEVEL_CRITICAL | G_LOG_LEVEL_WARNING)) {
+    NS_DebugBreak(NS_DEBUG_WARNING, message, "glib warning", __FILE__,
+                  __LINE__);
+  }
+
+  orig_log_func(log_domain, log_level, message, nullptr);
+}
+
+#  endif
+
+#  ifdef SA_SIGINFO
+static void fpehandler(int signum, siginfo_t* si, void* context) {
+  /* Integer divide by zero or integer overflow. */
+  /* Note: FPE_INTOVF is ignored on Intel, PowerPC and SPARC systems. */
+  if (si->si_code == FPE_INTDIV || si->si_code == FPE_INTOVF) {
+    NS_DebugBreak(NS_DEBUG_ABORT, "Divide by zero", nullptr, __FILE__,
+                  __LINE__);
+  }
+
+#    ifdef XP_MACOSX
+#      if defined(__i386__) || defined(__amd64__)
+  ucontext_t* uc = (ucontext_t*)context;
+
+  _STRUCT_FP_CONTROL* ctrl = &uc->uc_mcontext->__fs.__fpu_fcw;
+  ctrl->__invalid = ctrl->__denorm = ctrl->__zdiv = ctrl->__ovrfl =
+      ctrl->__undfl = ctrl->__precis = 1;
+
+  _STRUCT_FP_STATUS* status = &uc->uc_mcontext->__fs.__fpu_fsw;
+  status->__invalid = status->__denorm = status->__zdiv = status->__ovrfl =
+      status->__undfl = status->__precis = status->__stkflt =
+          status->__errsumm = 0;
+
+  uint32_t* mxcsr = &uc->uc_mcontext->__fs.__fpu_mxcsr;
+  *mxcsr |= SSE_EXCEPTION_MASK; /* disable all SSE exceptions */
+  *mxcsr &= ~SSE_STATUS_FLAGS;  /* clear all pending SSE exceptions */
+#      endif
+#    endif
+#    if defined(LINUX) && !defined(ANDROID)
+
+#      if defined(__i386__)
+  ucontext_t* uc = (ucontext_t*)context;
+  /*
+   * It seems that we have no access to mxcsr on Linux. libc
+   * seems to be translating cw/sw to mxcsr.
+   */
+  unsigned long int* cw = &uc->uc_mcontext.fpregs->cw;
+  *cw |= FPU_EXCEPTION_MASK;
+
+  unsigned long int* sw = &uc->uc_mcontext.fpregs->sw;
+  *sw &= ~FPU_STATUS_FLAGS;
+#      endif
+#      if defined(__amd64__)
+  ucontext_t* uc = (ucontext_t*)context;
+
+  uint16_t* cw = &uc->uc_mcontext.fpregs->cwd;
+  *cw |= FPU_EXCEPTION_MASK;
+
+  uint16_t* sw = &uc->uc_mcontext.fpregs->swd;
+  *sw &= ~FPU_STATUS_FLAGS;
+
+  uint32_t* mxcsr = &uc->uc_mcontext.fpregs->mxcsr;
+  *mxcsr |= SSE_EXCEPTION_MASK; /* disable all SSE exceptions */
+  *mxcsr &= ~SSE_STATUS_FLAGS;  /* clear all pending SSE exceptions */
+#      endif
+#    endif
+#    ifdef SOLARIS
+  ucontext_t* uc = (ucontext_t*)context;
+
+#      if defined(__i386)
+  uint32_t* cw = &uc->uc_mcontext.fpregs.fp_reg_set.fpchip_state.state[0];
+  *cw |= FPU_EXCEPTION_MASK;
+
+  uint32_t* sw = &uc->uc_mcontext.fpregs.fp_reg_set.fpchip_state.state[1];
+  *sw &= ~FPU_STATUS_FLAGS;
+
+  /* address of the instruction that caused the exception */
+  uint32_t* ip = &uc->uc_mcontext.fpregs.fp_reg_set.fpchip_state.state[3];
+  uc->uc_mcontext.gregs[REG_PC] = *ip;
+#      endif
+#      if defined(__amd64__)
+  uint16_t* cw = &uc->uc_mcontext.fpregs.fp_reg_set.fpchip_state.cw;
+  *cw |= FPU_EXCEPTION_MASK;
+
+  uint16_t* sw = &uc->uc_mcontext.fpregs.fp_reg_set.fpchip_state.sw;
+  *sw &= ~FPU_STATUS_FLAGS;
+
+  uint32_t* mxcsr = &uc->uc_mcontext.fpregs.fp_reg_set.fpchip_state.mxcsr;
+  *mxcsr |= SSE_EXCEPTION_MASK; /* disable all SSE exceptions */
+  *mxcsr &= ~SSE_STATUS_FLAGS;  /* clear all pending SSE exceptions */
+#      endif
+#    endif
+}
+#  endif
+
+void InstallSignalHandlers(const char* aProgname) {
+#  if defined(CRAWL_STACK_ON_SIGSEGV)
+  if (aProgname) {
+    const char* tmp = strdup(aProgname);
+    if (tmp) {
+      gProgname = tmp;
+    }
+  }
+#  endif  // CRAWL_STACK_ON_SIGSEGV
+
+  const char* gdbSleep = PR_GetEnv("MOZ_GDB_SLEEP");
+  if (gdbSleep && *gdbSleep) {
+    unsigned int s;
+    if (1 == sscanf(gdbSleep, "%u", &s)) {
+      _gdb_sleep_duration = s;
+    }
+  }
+
+#  if defined(CRAWL_STACK_ON_SIGSEGV)
+  if (!getenv("XRE_NO_WINDOWS_CRASH_DIALOG")) {
+    void (*crap_handler)(int) = GeckoProcessType_Default != XRE_GetProcessType()
+                                    ? child_ah_crap_handler
+                                    : ah_crap_handler;
+    signal(SIGSEGV, crap_handler);
+    signal(SIGILL, crap_handler);
+    signal(SIGABRT, crap_handler);
+  }
+#  endif  // CRAWL_STACK_ON_SIGSEGV
+
+#  ifdef SA_SIGINFO
+  /* Install a handler for floating point exceptions and disable them if they
+   * occur. */
+  struct sigaction sa, osa;
+  sa.sa_flags = SA_ONSTACK | SA_RESTART | SA_SIGINFO;
+  sa.sa_sigaction = fpehandler;
+  sigemptyset(&sa.sa_mask);
+  sigaction(SIGFPE, &sa, &osa);
+#  endif
+
+  if (!XRE_IsParentProcess()) {
+    /*
+     * If the user is debugging a Gecko parent process in gdb and hits ^C to
+     * suspend, a SIGINT signal will be sent to the child. We ignore this signal
+     * so the child isn't killed.
+     */
+    signal(SIGINT, SIG_IGN);
+  }
+
+#  if defined(DEBUG) && defined(LINUX)
+  const char* memLimit = PR_GetEnv("MOZ_MEM_LIMIT");
+  if (memLimit && *memLimit) {
+    long m = atoi(memLimit);
+    m *= (1024 * 1024);
+    struct rlimit r;
+    r.rlim_cur = m;
+    r.rlim_max = m;
+    setrlimit(RLIMIT_AS, &r);
+  }
+#  endif
+
+#  if defined(MOZ_WIDGET_GTK) && \
+      (GLIB_MAJOR_VERSION > 2 || \
+       (GLIB_MAJOR_VERSION == 2 && GLIB_MINOR_VERSION >= 6))
+  // Override the default glib logging function to intercept some crashes that
+  // are uninterceptable otherwise.
+  // Also, when XPCOM_DEBUG_BREAK is set, we can also get stacks for them.
+  // so we get stacks for it too.
+  orig_log_func = g_log_set_default_handler(glib_log_func, nullptr);
+#  endif
+}
+
+#elif XP_WIN
+
+#  include <windows.h>
+
+#  ifdef _M_IX86
+/*
+ * WinNT.h prior to SDK7 does not expose the structure of the ExtendedRegisters
+ * for ia86. We known that MxCsr is at offset 0x18 and is a DWORD.
+ */
+#    define MXCSR(ctx) (*(DWORD*)(((BYTE*)(ctx)->ExtendedRegisters) + 0x18))
+#  endif
+
+#  ifdef _M_X64
+#    define MXCSR(ctx) (ctx)->MxCsr
+#  endif
+
+#  if defined(_M_IX86) || defined(_M_X64)
+
+#    ifdef _M_X64
+#      define X87CW(ctx) (ctx)->FltSave.ControlWord
+#      define X87SW(ctx) (ctx)->FltSave.StatusWord
+#    else
+#      define X87CW(ctx) (ctx)->FloatSave.ControlWord
+#      define X87SW(ctx) (ctx)->FloatSave.StatusWord
+#    endif
+
+static LPTOP_LEVEL_EXCEPTION_FILTER gFPEPreviousFilter;
+
+LONG __stdcall FpeHandler(PEXCEPTION_POINTERS pe) {
+  PEXCEPTION_RECORD e = (PEXCEPTION_RECORD)pe->ExceptionRecord;
+  CONTEXT* c = (CONTEXT*)pe->ContextRecord;
+
+  switch (e->ExceptionCode) {
+    case STATUS_FLOAT_DENORMAL_OPERAND:
+    case STATUS_FLOAT_DIVIDE_BY_ZERO:
+    case STATUS_FLOAT_INEXACT_RESULT:
+    case STATUS_FLOAT_INVALID_OPERATION:
+    case STATUS_FLOAT_OVERFLOW:
+    case STATUS_FLOAT_STACK_CHECK:
+    case STATUS_FLOAT_UNDERFLOW:
+    case STATUS_FLOAT_MULTIPLE_FAULTS:
+    case STATUS_FLOAT_MULTIPLE_TRAPS:
+      X87CW(c) |= FPU_EXCEPTION_MASK; /* disable all FPU exceptions */
+      X87SW(c) &= ~FPU_STATUS_FLAGS;  /* clear all pending FPU exceptions */
+#    ifdef _M_IX86
+      if (c->ContextFlags & CONTEXT_EXTENDED_REGISTERS) {
+#    endif
+        MXCSR(c) |= SSE_EXCEPTION_MASK; /* disable all SSE exceptions */
+        MXCSR(c) &= ~SSE_STATUS_FLAGS;  /* clear all pending SSE exceptions */
+#    ifdef _M_IX86
+      }
+#    endif
+      return EXCEPTION_CONTINUE_EXECUTION;
+  }
+  LONG action = EXCEPTION_CONTINUE_SEARCH;
+  if (gFPEPreviousFilter) action = gFPEPreviousFilter(pe);
+
+  return action;
+}
+
+void InstallSignalHandlers(const char* aProgname) {
+  gFPEPreviousFilter = SetUnhandledExceptionFilter(FpeHandler);
+}
+
+#  else
+
+void InstallSignalHandlers(const char* aProgname) {}
+
+#  endif
+
+#else
+#  error No signal handling implementation for this platform.
+#endif
diff --git a/toolkit/xre/nsSigHandlers.h b/toolkit/xre/nsSigHandlers.h
new file mode 100644
index 0000000000..f7424c026a
--- /dev/null
+++ b/toolkit/xre/nsSigHandlers.h
@@ -0,0 +1,40 @@
+/* -*- Mode: C++; tab-width: 40; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#if defined(_M_IX86) || defined(_M_X64) || defined(__i386__) || \
+    defined(__i386) || defined(__amd64__)
+
+/*
+ * x87 FPU Control Word:
+ *
+ * 0 -> IM  Invalid Operation
+ * 1 -> DM  Denormalized Operand
+ * 2 -> ZM  Zero Divide
+ * 3 -> OM  Overflow
+ * 4 -> UM  Underflow
+ * 5 -> PM  Precision
+ */
+#  define FPU_EXCEPTION_MASK 0x3f
+
+/*
+ * x86 FPU Status Word:
+ *
+ * 0..5  ->      Exception flags  (see x86 FPU Control Word)
+ * 6     -> SF   Stack Fault
+ * 7     -> ES   Error Summary Status
+ */
+#  define FPU_STATUS_FLAGS 0xff
+
+/*
+ * MXCSR Control and Status Register:
+ *
+ * 0..5  ->      Exception flags (see x86 FPU Control Word)
+ * 6     -> DAZ  Denormals Are Zero
+ * 7..12 ->      Exception mask (see x86 FPU Control Word)
+ */
+#  define SSE_STATUS_FLAGS FPU_EXCEPTION_MASK
+#  define SSE_EXCEPTION_MASK (FPU_EXCEPTION_MASK << 7)
+
+#endif
diff --git a/toolkit/xre/nsUpdateDriver.cpp b/toolkit/xre/nsUpdateDriver.cpp
new file mode 100644
index 0000000000..c355741c76
--- /dev/null
+++ b/toolkit/xre/nsUpdateDriver.cpp
@@ -0,0 +1,955 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sw=2 sts=2 et cindent: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <stdlib.h>
+#include <stdio.h>
+#include "nsUpdateDriver.h"
+
+#include "nsDebug.h"
+#include "nsXULAppAPI.h"
+#include "nsAppRunner.h"
+#include "nsIFile.h"
+#include "nsVariant.h"
+#include "nsCOMPtr.h"
+#include "nsString.h"
+#include "prproces.h"
+#include "mozilla/Logging.h"
+#include "prenv.h"
+#include "nsVersionComparator.h"
+#include "nsDirectoryServiceDefs.h"
+#include "nsThreadUtils.h"
+#include "nsIXULAppInfo.h"
+#include "mozilla/Preferences.h"
+#include "nsPrintfCString.h"
+#include "mozilla/DebugOnly.h"
+#include "mozilla/ErrorNames.h"
+#include "mozilla/Printf.h"
+#include "mozilla/UniquePtr.h"
+#include "nsIObserverService.h"
+#include "nsNetCID.h"
+#include "mozilla/ScopeExit.h"
+#include "mozilla/Services.h"
+#include "mozilla/dom/Promise.h"
+
+#ifdef XP_MACOSX
+#  include "nsILocalFileMac.h"
+#  include "nsCommandLineServiceMac.h"
+#  include "MacLaunchHelper.h"
+#  include "updaterfileutils_osx.h"
+#  include "mozilla/Monitor.h"
+#  include "gfxPlatformMac.h"
+#endif
+
+#if defined(XP_WIN)
+#  include <direct.h>
+#  include <process.h>
+#  include <windows.h>
+#  include <shlwapi.h>
+#  include <strsafe.h>
+#  include "commonupdatedir.h"
+#  include "nsWindowsHelpers.h"
+#  include "pathhash.h"
+#  include "WinUtils.h"
+#  define getcwd(path, size) _getcwd(path, size)
+#  define getpid() GetCurrentProcessId()
+#elif defined(XP_UNIX)
+#  include <unistd.h>
+#  include <sys/wait.h>
+#endif
+
+using namespace mozilla;
+
+static LazyLogModule sUpdateLog("updatedriver");
+// Some other file in our unified batch might have defined LOG already.
+#ifdef LOG
+#  undef LOG
+#endif
+#define LOG(args) MOZ_LOG(sUpdateLog, mozilla::LogLevel::Debug, args)
+
+#ifdef XP_MACOSX
+static void UpdateDriverSetupMacCommandLine(int& argc, char**& argv,
+                                            bool restart) {
+  if (NS_IsMainThread()) {
+    CommandLineServiceMac::SetupMacCommandLine(argc, argv, restart);
+    return;
+  }
+  // Bug 1335916: SetupMacCommandLine calls a CoreFoundation function that
+  // asserts that it was called from the main thread, so if we are not the main
+  // thread, we have to dispatch that call to there. But we also have to get the
+  // result from it, so we can't just dispatch and return, we have to wait
+  // until the dispatched operation actually completes. So we also set up a
+  // monitor to signal us when that happens, and block until then.
+  Monitor monitor MOZ_UNANNOTATED("nsUpdateDriver SetupMacCommandLine");
+
+  nsresult rv = NS_DispatchToMainThread(NS_NewRunnableFunction(
+      "UpdateDriverSetupMacCommandLine",
+      [&argc, &argv, restart, &monitor]() -> void {
+        CommandLineServiceMac::SetupMacCommandLine(argc, argv, restart);
+        MonitorAutoLock(monitor).Notify();
+      }));
+
+  if (NS_FAILED(rv)) {
+    LOG(
+        ("Update driver error dispatching SetupMacCommandLine to main thread: "
+         "%d\n",
+         rv));
+    return;
+  }
+
+  // The length of this wait is arbitrary, but should be long enough that having
+  // it expire means something is seriously wrong.
+  CVStatus status =
+      MonitorAutoLock(monitor).Wait(TimeDuration::FromSeconds(60));
+  if (status == CVStatus::Timeout) {
+    LOG(("Update driver timed out waiting for SetupMacCommandLine\n"));
+  }
+}
+#endif
+
+static nsresult GetCurrentWorkingDir(nsACString& aOutPath) {
+  // Cannot use NS_GetSpecialDirectory because XPCOM is not yet initialized.
+  // This code is duplicated from xpcom/io/SpecialSystemDirectory.cpp:
+
+  aOutPath.Truncate();
+
+#if defined(XP_WIN)
+  wchar_t wpath[MAX_PATH];
+  if (!_wgetcwd(wpath, ArrayLength(wpath))) {
+    return NS_ERROR_FAILURE;
+  }
+  CopyUTF16toUTF8(nsDependentString(wpath), aOutPath);
+#else
+  char path[MAXPATHLEN];
+  if (!getcwd(path, ArrayLength(path))) {
+    return NS_ERROR_FAILURE;
+  }
+  aOutPath = path;
+#endif
+
+  return NS_OK;
+}
+
+/**
+ * Get the path to the installation directory. For Mac OS X this will be the
+ * bundle directory.
+ *
+ * @param appDir         the application directory file object
+ * @param installDirPath the path to the installation directory
+ */
+static nsresult GetInstallDirPath(nsIFile* appDir, nsACString& installDirPath) {
+  nsresult rv;
+#ifdef XP_MACOSX
+  nsCOMPtr<nsIFile> parentDir1, parentDir2;
+  rv = appDir->GetParent(getter_AddRefs(parentDir1));
+  NS_ENSURE_SUCCESS(rv, rv);
+  rv = parentDir1->GetParent(getter_AddRefs(parentDir2));
+  NS_ENSURE_SUCCESS(rv, rv);
+  rv = parentDir2->GetNativePath(installDirPath);
+  NS_ENSURE_SUCCESS(rv, rv);
+#elif XP_WIN
+  nsAutoString installDirPathW;
+  rv = appDir->GetPath(installDirPathW);
+  NS_ENSURE_SUCCESS(rv, rv);
+  CopyUTF16toUTF8(installDirPathW, installDirPath);
+#else
+  rv = appDir->GetNativePath(installDirPath);
+  NS_ENSURE_SUCCESS(rv, rv);
+#endif
+  return NS_OK;
+}
+
+static bool GetFile(nsIFile* dir, const nsACString& name,
+                    nsCOMPtr<nsIFile>& result) {
+  nsresult rv;
+
+  nsCOMPtr<nsIFile> file;
+  rv = dir->Clone(getter_AddRefs(file));
+  if (NS_FAILED(rv)) {
+    return false;
+  }
+
+  rv = file->AppendNative(name);
+  if (NS_FAILED(rv)) {
+    return false;
+  }
+
+  result = file;
+  return true;
+}
+
+static bool GetStatusFile(nsIFile* dir, nsCOMPtr<nsIFile>& result) {
+  return GetFile(dir, "update.status"_ns, result);
+}
+
+/**
+ * Get the contents of the update.status file when the update.status file can
+ * be opened with read and write access. The reason it is opened for both read
+ * and write is to prevent trying to update when the user doesn't have write
+ * access to the update directory.
+ *
+ * @param statusFile the status file object.
+ * @param buf        the buffer holding the file contents
+ *
+ * @return true if successful, false otherwise.
+ */
+template <size_t Size>
+static bool GetStatusFileContents(nsIFile* statusFile, char (&buf)[Size]) {
+  static_assert(
+      Size > 16,
+      "Buffer needs to be large enough to hold the known status codes");
+
+  PRFileDesc* fd = nullptr;
+  nsresult rv = statusFile->OpenNSPRFileDesc(PR_RDWR, 0660, &fd);
+  if (NS_FAILED(rv)) {
+    return false;
+  }
+
+  const int32_t n = PR_Read(fd, buf, Size);
+  PR_Close(fd);
+
+  return (n >= 0);
+}
+
+enum UpdateStatus {
+  eNoUpdateAction,
+  ePendingUpdate,
+  ePendingService,
+  ePendingElevate,
+  eAppliedUpdate,
+  eAppliedService,
+};
+
+/**
+ * Returns a value indicating what needs to be done in order to handle an
+ * update.
+ *
+ * @param dir the directory in which we should look for an update.status file.
+ * @param statusFile the update.status file found in the directory.
+ *
+ * @return the update action to be performed.
+ */
+static UpdateStatus GetUpdateStatus(nsIFile* dir,
+                                    nsCOMPtr<nsIFile>& statusFile) {
+  if (GetStatusFile(dir, statusFile)) {
+    char buf[32];
+    if (GetStatusFileContents(statusFile, buf)) {
+      const char kPending[] = "pending";
+      const char kPendingService[] = "pending-service";
+      const char kPendingElevate[] = "pending-elevate";
+      const char kApplied[] = "applied";
+      const char kAppliedService[] = "applied-service";
+      if (!strncmp(buf, kPendingElevate, sizeof(kPendingElevate) - 1)) {
+        return ePendingElevate;
+      }
+      if (!strncmp(buf, kPendingService, sizeof(kPendingService) - 1)) {
+        return ePendingService;
+      }
+      if (!strncmp(buf, kPending, sizeof(kPending) - 1)) {
+        return ePendingUpdate;
+      }
+      if (!strncmp(buf, kAppliedService, sizeof(kAppliedService) - 1)) {
+        return eAppliedService;
+      }
+      if (!strncmp(buf, kApplied, sizeof(kApplied) - 1)) {
+        return eAppliedUpdate;
+      }
+    }
+  }
+  return eNoUpdateAction;
+}
+
+static bool GetVersionFile(nsIFile* dir, nsCOMPtr<nsIFile>& result) {
+  return GetFile(dir, "update.version"_ns, result);
+}
+
+// Compares the current application version with the update's application
+// version.
+static bool IsOlderVersion(nsIFile* versionFile, const char* appVersion) {
+  PRFileDesc* fd = nullptr;
+  nsresult rv = versionFile->OpenNSPRFileDesc(PR_RDONLY, 0660, &fd);
+  if (NS_FAILED(rv)) {
+    return true;
+  }
+
+  char buf[32];
+  const int32_t n = PR_Read(fd, buf, sizeof(buf));
+  PR_Close(fd);
+
+  if (n < 0) {
+    return false;
+  }
+
+  // Trim off the trailing newline
+  if (buf[n - 1] == '\n') {
+    buf[n - 1] = '\0';
+  }
+
+  // If the update xml doesn't provide the application version the file will
+  // contain the string "null" and it is assumed that the update is not older.
+  const char kNull[] = "null";
+  if (strncmp(buf, kNull, sizeof(kNull) - 1) == 0) {
+    return false;
+  }
+
+  return mozilla::Version(appVersion) > buf;
+}
+
+/**
+ * Applies, switches, or stages an update.
+ *
+ * @param greDir       the GRE directory
+ * @param updateDir    the update root directory
+ * @param appDir       the application directory
+ * @param appArgc      the number of args passed to the application
+ * @param appArgv      the args passed to the application
+ *                     (used for restarting the application when necessary)
+ * @param restart      true when a restart is necessary.
+ * @param isStaged     true when the update has already been staged
+ * @param outpid (out) parameter holding the handle to the updater application
+ *                     when staging updates
+ */
+static void ApplyUpdate(nsIFile* greDir, nsIFile* updateDir, nsIFile* appDir,
+                        int appArgc, char** appArgv, bool restart,
+                        bool isStaged, ProcessType* outpid) {
+  // The following determines the update operation to perform.
+  // 1. When restart is false the update will be staged.
+  // 2. When restart is true and isStaged is false the update will apply the mar
+  //    file to the installation directory.
+  // 3. When restart is true and isStaged is true the update will switch the
+  //    staged update with the installation directory.
+
+  nsresult rv;
+
+  nsCOMPtr<nsIFile> updater;
+  nsAutoCString updaterPath;
+  nsAutoCString updateDirPath;
+#if defined(XP_WIN)
+  // Get an nsIFile reference for the updater in the installation dir.
+  if (!GetFile(greDir, nsLiteralCString(UPDATER_BIN), updater)) {
+    return;
+  }
+
+  // Get the path to the updater.
+  nsAutoString updaterPathW;
+  rv = updater->GetPath(updaterPathW);
+  if (NS_FAILED(rv)) {
+    return;
+  }
+  CopyUTF16toUTF8(updaterPathW, updaterPath);
+
+  // Get the path to the update dir.
+  nsAutoString updateDirPathW;
+  rv = updateDir->GetPath(updateDirPathW);
+  if (NS_FAILED(rv)) {
+    return;
+  }
+  CopyUTF16toUTF8(updateDirPathW, updateDirPath);
+#elif defined(XP_MACOSX)
+  // Get an nsIFile reference for the updater in the installation dir.
+  if (!GetFile(appDir, nsLiteralCString(UPDATER_APP), updater)) {
+    return;
+  }
+  rv = updater->AppendNative("Contents"_ns);
+  if (NS_FAILED(rv)) {
+    return;
+  }
+  rv = updater->AppendNative("MacOS"_ns);
+  if (NS_FAILED(rv)) {
+    return;
+  }
+  rv = updater->AppendNative(nsLiteralCString(UPDATER_BIN));
+  if (NS_FAILED(rv)) {
+    return;
+  }
+
+  // Get the path to the updater.
+  rv = updater->GetNativePath(updaterPath);
+  if (NS_FAILED(rv)) {
+    return;
+  }
+
+  // Get the path to the update dir.
+  rv = updateDir->GetNativePath(updateDirPath);
+  if (NS_FAILED(rv)) {
+    return;
+  }
+#else
+  // Get an nsIFile reference for the updater in the installation dir.
+  if (!GetFile(greDir, nsLiteralCString(UPDATER_BIN), updater)) {
+    return;
+  }
+
+  // Get the path to the updater.
+  rv = updater->GetNativePath(updaterPath);
+  if (NS_FAILED(rv)) {
+    return;
+  }
+
+  // Get the path to the update dir.
+  rv = updateDir->GetNativePath(updateDirPath);
+  if (NS_FAILED(rv)) {
+    return;
+  }
+#endif
+
+  // appFilePath and workingDirPath are only used when the application will be
+  // restarted.
+  nsAutoCString appFilePath;
+  nsAutoCString workingDirPath;
+  if (restart) {
+    // Get the path to the current working directory.
+    rv = GetCurrentWorkingDir(workingDirPath);
+    if (NS_FAILED(rv)) {
+      return;
+    }
+
+    // Get the application file path used by the updater to restart the
+    // application after the update has finished.
+    nsCOMPtr<nsIFile> appFile;
+    XRE_GetBinaryPath(getter_AddRefs(appFile));
+    if (!appFile) {
+      return;
+    }
+
+#if defined(XP_WIN)
+    nsAutoString appFilePathW;
+    rv = appFile->GetPath(appFilePathW);
+    if (NS_FAILED(rv)) {
+      return;
+    }
+    CopyUTF16toUTF8(appFilePathW, appFilePath);
+#else
+    rv = appFile->GetNativePath(appFilePath);
+    if (NS_FAILED(rv)) {
+      return;
+    }
+#endif
+  }
+
+  // Get the installation directory path.
+  nsAutoCString installDirPath;
+  rv = GetInstallDirPath(appDir, installDirPath);
+  if (NS_FAILED(rv)) {
+    return;
+  }
+
+#if defined(XP_MACOSX)
+  // If we're going to do a restart, we need to make sure the font registration
+  // thread has finished before this process exits (bug 1777332).
+  if (restart) {
+    gfxPlatformMac::WaitForFontRegistration();
+  }
+
+  // We need to detect whether elevation is required for this update. This can
+  // occur when an admin user installs the application, but another admin
+  // user attempts to update (see bug 394984).
+  // We only check if we need elevation if we are restarting. We don't attempt
+  // to stage if elevation is required. Staging happens without the user knowing
+  // about it, and we don't want to ask for elevation for seemingly no reason.
+  bool needElevation = false;
+  if (restart) {
+    needElevation = !IsRecursivelyWritable(installDirPath.get());
+    if (needElevation) {
+      // Normally we would check this via nsIAppStartup::wasSilentlyStarted,
+      // but nsIAppStartup isn't available yet.
+      char* mozAppSilentStart = PR_GetEnv("MOZ_APP_SILENT_START");
+      bool wasSilentlyStarted =
+          mozAppSilentStart && (strcmp(mozAppSilentStart, "") != 0);
+      if (wasSilentlyStarted) {
+        // Elevation always requires prompting for credentials on macOS. If we
+        // are trying to restart silently, we must not display UI such as this
+        // prompt.
+        // We make this check here rather than in the updater, because it is
+        // actually Firefox that shows the elevation prompt (via
+        // InstallPrivilegedHelper), not the updater.
+        return;
+      }
+    }
+  }
+#endif
+
+  nsAutoCString applyToDirPath;
+  nsCOMPtr<nsIFile> updatedDir;
+  if (restart && !isStaged) {
+    // The install directory is the same as the apply to directory.
+    applyToDirPath.Assign(installDirPath);
+  } else {
+    // Get the directory where the update is staged or will be staged. This is
+    // `updateDir` for macOS and `appDir` for all other platforms. macOS cannot
+    // stage updates inside the .app bundle (`appDir`) without breaking the code
+    // signature on the bundle, so we use `updateDir` instead.
+#if defined(XP_MACOSX)
+    if (!GetFile(updateDir, "Updated.app"_ns, updatedDir)) {
+#else
+    if (!GetFile(appDir, "updated"_ns, updatedDir)) {
+#endif
+      return;
+    }
+#if defined(XP_WIN)
+    nsAutoString applyToDirPathW;
+    rv = updatedDir->GetPath(applyToDirPathW);
+    if (NS_FAILED(rv)) {
+      return;
+    }
+    CopyUTF16toUTF8(applyToDirPathW, applyToDirPath);
+#else
+    rv = updatedDir->GetNativePath(applyToDirPath);
+#endif
+  }
+  if (NS_FAILED(rv)) {
+    return;
+  }
+
+  if (restart && isStaged) {
+    // When the update should already be staged make sure that the updated
+    // directory exists.
+    bool updatedDirExists = false;
+    if (NS_FAILED(updatedDir->Exists(&updatedDirExists)) || !updatedDirExists) {
+      return;
+    }
+  }
+
+  // On platforms where we are not calling execv, we may need to make the
+  // updater executable wait for the calling process to exit.  Otherwise, the
+  // updater may have trouble modifying our executable image (because it might
+  // still be in use).  This is accomplished by passing our PID to the updater
+  // so that it can wait for us to exit.  This is not perfect as there is a race
+  // condition that could bite us.  It's possible that the calling process could
+  // exit before the updater waits on the specified PID, and in the meantime a
+  // new process with the same PID could be created.  This situation is
+  // unlikely, however, given the way most operating systems recycle PIDs. We'll
+  // take our chances ;-) Construct the PID argument for this process to pass to
+  // the updater.
+  nsAutoCString pid;
+  if (restart) {
+#if defined(XP_UNIX) & !defined(XP_MACOSX)
+    // When execv is used for an update that requires a restart 0 is passed
+    // which is ignored by the updater.
+    pid.AssignLiteral("0");
+#else
+    pid.AppendInt((int32_t)getpid());
+#endif
+    if (isStaged) {
+      // Append a special token to the PID in order to inform the updater that
+      // it should replace install with the updated directory.
+      pid.AppendLiteral("/replace");
+    }
+  } else {
+    // Signal the updater application that it should stage the update.
+    pid.AssignLiteral("-1");
+  }
+
+  int argc = 5;
+  if (restart) {
+    argc = appArgc + 6;
+    if (gRestartedByOS) {
+      argc += 1;
+    }
+  }
+  char** argv = static_cast<char**>(malloc((argc + 1) * sizeof(char*)));
+  if (!argv) {
+    return;
+  }
+  argv[0] = (char*)updaterPath.get();
+  argv[1] = (char*)updateDirPath.get();
+  argv[2] = (char*)installDirPath.get();
+  argv[3] = (char*)applyToDirPath.get();
+  argv[4] = (char*)pid.get();
+  if (restart && appArgc) {
+    argv[5] = (char*)workingDirPath.get();
+    argv[6] = (char*)appFilePath.get();
+    for (int i = 1; i < appArgc; ++i) {
+      argv[6 + i] = appArgv[i];
+    }
+    if (gRestartedByOS) {
+      // We haven't truly started up, restore this argument so that we will have
+      // it upon restart.
+      argv[6 + appArgc] = const_cast<char*>("-os-restarted");
+    }
+  }
+  argv[argc] = nullptr;
+
+  if (restart && gSafeMode) {
+    PR_SetEnv("MOZ_SAFE_MODE_RESTART=1");
+  }
+
+  LOG(("spawning updater process [%s]\n", updaterPath.get()));
+
+#if defined(XP_UNIX) && !defined(XP_MACOSX)
+  // We use execv to spawn the updater process on all UNIX systems except Mac
+  // OSX since it is known to cause problems on the Mac.  Windows has execv, but
+  // it is a faked implementation that doesn't really replace the current
+  // process. Instead it spawns a new process, so we gain nothing from using
+  // execv on Windows.
+  if (restart) {
+    int execResult = execv(updaterPath.get(), argv);
+    free(argv);
+    exit(execResult);
+  }
+  *outpid = fork();
+  if (*outpid == -1) {
+    free(argv);
+    return;
+  }
+  if (*outpid == 0) {
+    int execResult = execv(updaterPath.get(), argv);
+    free(argv);
+    exit(execResult);
+  }
+#elif defined(XP_WIN)
+  if (isStaged) {
+    // Launch the updater to replace the installation with the staged updated.
+    if (!WinLaunchChild(updaterPathW.get(), argc, argv)) {
+      free(argv);
+      return;
+    }
+  } else {
+    // Launch the updater to either stage or apply an update.
+    if (!WinLaunchChild(updaterPathW.get(), argc, argv, nullptr, outpid)) {
+      free(argv);
+      return;
+    }
+  }
+#elif defined(XP_MACOSX)
+UpdateDriverSetupMacCommandLine(argc, argv, restart);
+if (restart && needElevation) {
+  bool hasLaunched = LaunchElevatedUpdate(argc, argv, outpid);
+  free(argv);
+  if (!hasLaunched) {
+    LOG(("Failed to launch elevated update!"));
+    exit(1);
+  }
+  exit(0);
+}
+
+if (isStaged) {
+  // Launch the updater to replace the installation with the staged updated.
+  LaunchChildMac(argc, argv);
+} else {
+  // Launch the updater to either stage or apply an update.
+  LaunchChildMac(argc, argv, outpid);
+}
+#else
+if (isStaged) {
+  // Launch the updater to replace the installation with the staged updated.
+  PR_CreateProcessDetached(updaterPath.get(), argv, nullptr, nullptr);
+} else {
+  // Launch the updater to either stage or apply an update.
+  *outpid = PR_CreateProcess(updaterPath.get(), argv, nullptr, nullptr);
+}
+#endif
+  free(argv);
+  if (restart) {
+    exit(0);
+  }
+}
+
+#if !defined(XP_WIN)
+/**
+ * Wait briefly to see if a process terminates, then return true if it has.
+ *
+ * (Not implemented on Windows, where HandleWatcher is used instead.)
+ */
+static bool ProcessHasTerminated(ProcessType pt) {
+#  if defined(XP_MACOSX)
+  // We're waiting for the process to terminate in LaunchChildMac.
+  return true;
+#  elif defined(XP_UNIX)
+  int exitStatus;
+  pid_t exited = waitpid(pt, &exitStatus, WNOHANG);
+  if (exited == 0) {
+    // Process is still running.
+    sleep(1);
+    return false;
+  }
+  if (exited == -1) {
+    LOG(("Error while checking if the updater process is finished"));
+    // This shouldn't happen, but if it does, the updater process is lost to us,
+    // so the best we can do is pretend that it's exited.
+    return true;
+  }
+  // If we get here, the process has exited; make sure it exited normally.
+  if (WIFEXITED(exitStatus) && (WEXITSTATUS(exitStatus) != 0)) {
+    LOG(("Error while running the updater process, check update.log"));
+  }
+  return true;
+#  else
+  // No way to have a non-blocking implementation on these platforms,
+  // because we're using NSPR and it only provides a blocking wait.
+  int32_t exitCode;
+  PR_WaitProcess(pt, &exitCode);
+  if (exitCode != 0) {
+    LOG(("Error while running the updater process, check update.log"));
+  }
+  return true;
+#  endif
+}
+#endif
+
+nsresult ProcessUpdates(nsIFile* greDir, nsIFile* appDir, nsIFile* updRootDir,
+                        int argc, char** argv, const char* appVersion,
+                        bool restart, ProcessType* pid) {
+  nsresult rv;
+
+#ifdef XP_WIN
+  // If we're in a package, we know any updates that we find are not for us.
+  if (mozilla::widget::WinUtils::HasPackageIdentity()) {
+    return NS_OK;
+  }
+#endif
+
+  nsCOMPtr<nsIFile> updatesDir;
+  rv = updRootDir->Clone(getter_AddRefs(updatesDir));
+  NS_ENSURE_SUCCESS(rv, rv);
+  rv = updatesDir->AppendNative("updates"_ns);
+  NS_ENSURE_SUCCESS(rv, rv);
+  rv = updatesDir->AppendNative("0"_ns);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // Return early since there isn't a valid update when the update application
+  // version file doesn't exist or if the update's application version is less
+  // than the current application version. The cleanup of the update will happen
+  // during post update processing in nsUpdateService.js.
+  nsCOMPtr<nsIFile> versionFile;
+  if (!GetVersionFile(updatesDir, versionFile) ||
+      IsOlderVersion(versionFile, appVersion)) {
+    return NS_OK;
+  }
+
+  nsCOMPtr<nsIFile> statusFile;
+  UpdateStatus status = GetUpdateStatus(updatesDir, statusFile);
+  switch (status) {
+    case ePendingUpdate:
+    case ePendingService: {
+      ApplyUpdate(greDir, updatesDir, appDir, argc, argv, restart, false, pid);
+      break;
+    }
+    case eAppliedUpdate:
+    case eAppliedService:
+      // An update was staged and needs to be switched so the updated
+      // application is used.
+      ApplyUpdate(greDir, updatesDir, appDir, argc, argv, restart, true, pid);
+      break;
+    case ePendingElevate:
+      // No action should be performed since the user hasn't opted into
+      // elevating for the update so continue application startup.
+    case eNoUpdateAction:
+      // We don't need to do any special processing here, we'll just continue to
+      // startup the application.
+      break;
+  }
+
+  return NS_OK;
+}
+
+NS_IMPL_ISUPPORTS(nsUpdateProcessor, nsIUpdateProcessor)
+
+nsUpdateProcessor::nsUpdateProcessor() : mUpdaterPID(0) {}
+
+#ifdef XP_WIN
+nsUpdateProcessor::~nsUpdateProcessor() { mProcessWatcher.Stop(); }
+#else
+nsUpdateProcessor::~nsUpdateProcessor() = default;
+#endif
+
+NS_IMETHODIMP
+nsUpdateProcessor::ProcessUpdate() {
+  nsresult rv;
+
+  nsCOMPtr<nsIProperties> ds =
+      do_GetService(NS_DIRECTORY_SERVICE_CONTRACTID, &rv);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsCOMPtr<nsIFile> exeFile;
+  rv = ds->Get(XRE_EXECUTABLE_FILE, NS_GET_IID(nsIFile),
+               getter_AddRefs(exeFile));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsCOMPtr<nsIFile> appDir;
+  rv = exeFile->GetParent(getter_AddRefs(appDir));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsCOMPtr<nsIFile> greDir;
+  rv = ds->Get(NS_GRE_DIR, NS_GET_IID(nsIFile), getter_AddRefs(greDir));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsCOMPtr<nsIFile> updRoot;
+  rv = ds->Get(XRE_UPDATE_ROOT_DIR, NS_GET_IID(nsIFile),
+               getter_AddRefs(updRoot));
+  NS_ASSERTION(NS_SUCCEEDED(rv), "Can't get the UpdRootD dir");
+
+  // XRE_UPDATE_ROOT_DIR should not fail but if it does fallback to the
+  // application directory just to be safe.
+  if (NS_FAILED(rv)) {
+    rv = appDir->Clone(getter_AddRefs(updRoot));
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+
+  nsCOMPtr<nsIXULAppInfo> appInfo =
+      do_GetService("@mozilla.org/xre/app-info;1", &rv);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsAutoCString appVersion;
+  rv = appInfo->GetVersion(appVersion);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // Copy the parameters to the StagedUpdateInfo structure shared with the
+  // worker thread.
+  mInfo.mGREDir = greDir;
+  mInfo.mAppDir = appDir;
+  mInfo.mUpdateRoot = updRoot;
+  mInfo.mArgc = 0;
+  mInfo.mArgv = nullptr;
+  mInfo.mAppVersion = appVersion;
+
+  MOZ_ASSERT(NS_IsMainThread(), "not main thread");
+  nsCOMPtr<nsIRunnable> r =
+      NewRunnableMethod("nsUpdateProcessor::StartStagedUpdate", this,
+                        &nsUpdateProcessor::StartStagedUpdate);
+  return NS_NewNamedThread("UpdateProcessor", getter_AddRefs(mWorkerThread), r);
+}
+
+void nsUpdateProcessor::StartStagedUpdate() {
+  MOZ_ASSERT(!NS_IsMainThread(), "main thread");
+
+  // If we fail to launch the updater process or its monitor for some reason, we
+  // need to shut down the worker thread, as there isn't anything more for us to
+  // do.
+  auto onExitStopThread = mozilla::MakeScopeExit([&] {
+    nsresult rv = NS_DispatchToMainThread(
+        NewRunnableMethod("nsUpdateProcessor::ShutdownWorkerThread", this,
+                          &nsUpdateProcessor::ShutdownWorkerThread));
+    NS_ENSURE_SUCCESS_VOID(rv);
+  });
+
+  // Launch updater. (We do this on a worker thread to avoid blocking the main
+  // thread with file I/O.)
+  nsresult rv = ProcessUpdates(mInfo.mGREDir, mInfo.mAppDir, mInfo.mUpdateRoot,
+                               mInfo.mArgc, mInfo.mArgv,
+                               mInfo.mAppVersion.get(), false, &mUpdaterPID);
+  if (NS_FAILED(rv)) {
+    MOZ_LOG(sUpdateLog, mozilla::LogLevel::Error,
+            ("could not start updater process: %s", GetStaticErrorName(rv)));
+    return;
+  }
+
+  if (!mUpdaterPID) {
+    // not an error
+    MOZ_LOG(sUpdateLog, mozilla::LogLevel::Verbose,
+            ("ProcessUpdates() indicated nothing to do"));
+    return;
+  }
+
+#ifdef WIN32
+  // Set up a HandleWatcher to report to the main thread when we're done.
+  RefPtr<nsIThread> mainThread;
+  NS_GetMainThread(getter_AddRefs(mainThread));
+  mProcessWatcher.Watch(mUpdaterPID, mainThread,
+                        NewRunnableMethod("nsUpdateProcessor::UpdateDone", this,
+                                          &nsUpdateProcessor::UpdateDone));
+
+// On Windows, that's all we need the worker thread for. Let
+// `onExitStopThread` shut us down.
+#else
+  // Monitor the state of the updater process while it is staging an update.
+  rv = NS_DispatchToCurrentThread(
+      NewRunnableMethod("nsUpdateProcessor::WaitForProcess", this,
+                        &nsUpdateProcessor::WaitForProcess));
+  if (NS_FAILED(rv)) {
+    MOZ_LOG(sUpdateLog, mozilla::LogLevel::Error,
+            ("could not start updater process poll: error %s",
+             GetStaticErrorName(rv)));
+    return;
+  }
+
+  // Leave the worker thread alive to run WaitForProcess. Either it or its
+  // successors will be responsible for shutting down the worker thread.
+  onExitStopThread.release();
+#endif
+}
+
+void nsUpdateProcessor::ShutdownWorkerThread() {
+  MOZ_ASSERT(NS_IsMainThread(), "not main thread");
+  mWorkerThread->Shutdown();
+  mWorkerThread = nullptr;
+}
+
+#ifndef WIN32
+void nsUpdateProcessor::WaitForProcess() {
+  MOZ_ASSERT(!NS_IsMainThread(), "main thread");
+  if (ProcessHasTerminated(mUpdaterPID)) {
+    NS_DispatchToMainThread(NewRunnableMethod(
+        "nsUpdateProcessor::UpdateDone", this, &nsUpdateProcessor::UpdateDone));
+  } else {
+    NS_DispatchToCurrentThread(
+        NewRunnableMethod("nsUpdateProcessor::WaitForProcess", this,
+                          &nsUpdateProcessor::WaitForProcess));
+  }
+}
+#endif
+
+void nsUpdateProcessor::UpdateDone() {
+  MOZ_ASSERT(NS_IsMainThread(), "not main thread");
+
+  nsCOMPtr<nsIUpdateManager> um =
+      do_GetService("@mozilla.org/updates/update-manager;1");
+  if (um) {
+    // This completes asynchronously, but nothing else that we are doing in this
+    // function requires waiting for this to complete.
+    RefPtr<mozilla::dom::Promise> outPromise;
+    um->RefreshUpdateStatus(getter_AddRefs(outPromise));
+  }
+
+// On Windows, shutting down the worker thread is taken care of by another task.
+// (Which may not have run yet, so we can't assert.)
+#ifndef XP_WIN
+  ShutdownWorkerThread();
+#endif
+}
+
+NS_IMETHODIMP
+nsUpdateProcessor::GetServiceRegKeyExists(bool* aResult) {
+#ifndef XP_WIN
+  return NS_ERROR_NOT_IMPLEMENTED;
+#else   // #ifdef XP_WIN
+  nsCOMPtr<nsIProperties> dirSvc(
+      do_GetService("@mozilla.org/file/directory_service;1"));
+  NS_ENSURE_TRUE(dirSvc, NS_ERROR_SERVICE_NOT_AVAILABLE);
+
+  nsCOMPtr<nsIFile> installBin;
+  nsresult rv = dirSvc->Get(XRE_EXECUTABLE_FILE, NS_GET_IID(nsIFile),
+                            getter_AddRefs(installBin));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsCOMPtr<nsIFile> installDir;
+  rv = installBin->GetParent(getter_AddRefs(installDir));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsAutoString installPath;
+  rv = installDir->GetPath(installPath);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  wchar_t maintenanceServiceKey[MAX_PATH + 1];
+  BOOL success = CalculateRegistryPathFromFilePath(
+      PromiseFlatString(installPath).get(), maintenanceServiceKey);
+  NS_ENSURE_TRUE(success, NS_ERROR_FAILURE);
+
+  HKEY regHandle;
+  LSTATUS ls = RegOpenKeyExW(HKEY_LOCAL_MACHINE, maintenanceServiceKey, 0,
+                             KEY_QUERY_VALUE | KEY_WOW64_64KEY, &regHandle);
+  if (ls == ERROR_SUCCESS) {
+    RegCloseKey(regHandle);
+    *aResult = true;
+    return NS_OK;
+  }
+  if (ls == ERROR_FILE_NOT_FOUND) {
+    *aResult = false;
+    return NS_OK;
+  }
+  // We got an error we weren't expecting reading the registry.
+  return NS_ERROR_NOT_AVAILABLE;
+#endif  // #ifdef XP_WIN
+}
diff --git a/toolkit/xre/nsUpdateDriver.h b/toolkit/xre/nsUpdateDriver.h
new file mode 100644
index 0000000000..24a20f3f76
--- /dev/null
+++ b/toolkit/xre/nsUpdateDriver.h
@@ -0,0 +1,112 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sw=2 sts=2 et cindent: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef nsUpdateDriver_h__
+#define nsUpdateDriver_h__
+
+#include "nscore.h"
+#include "nsIUpdateService.h"
+#include "nsIThread.h"
+#include "nsCOMPtr.h"
+#include "nsString.h"
+#include "mozilla/Attributes.h"
+
+class nsIFile;
+
+#if defined(XP_WIN)
+#  include <windows.h>
+#  include "mozilla/WinHandleWatcher.h"
+typedef HANDLE ProcessType;
+#elif defined(XP_UNIX)
+typedef pid_t ProcessType;
+#else
+#  include "prproces.h"
+typedef PRProcess* ProcessType;
+#endif
+
+#ifdef XP_WIN
+#  define UPDATER_BIN "updater.exe"
+#  define MAINTENANCE_SVC_NAME L"MozillaMaintenance"
+#elif XP_MACOSX
+#  define UPDATER_APP "updater.app"
+#  define UPDATER_BIN "org.mozilla.updater"
+#else
+#  define UPDATER_BIN "updater"
+#endif
+
+/**
+ * This function processes any available updates.  As part of that process, it
+ * may exit the current process and relaunch it at a later time.
+ *
+ * Two directories are passed to this function: greDir (where the actual
+ * binary resides) and appDir (which contains application.ini for XULRunner
+ * apps). If this is not a XULRunner app then appDir is identical to greDir.
+ *
+ * The argc and argv passed to this function should be what is needed to
+ * relaunch the current process.
+ *
+ * The appVersion param passed to this function is the current application's
+ * version and is used to determine if an update's version is older than the
+ * current application version.
+ *
+ * If you want the update to be processed without restarting, set the restart
+ * parameter to false.
+ *
+ * This function does not modify appDir.
+ */
+nsresult ProcessUpdates(nsIFile* greDir, nsIFile* appDir, nsIFile* updRootDir,
+                        int argc, char** argv, const char* appVersion,
+                        bool restart = true, ProcessType* pid = nullptr);
+
+// The implementation of the update processor handles the task of loading the
+// updater application for staging an update.
+// XXX ehsan this is living in this file in order to make use of the existing
+// stuff here, we might want to move it elsewhere in the future.
+class nsUpdateProcessor final : public nsIUpdateProcessor {
+ public:
+  nsUpdateProcessor();
+
+  NS_DECL_THREADSAFE_ISUPPORTS
+  NS_DECL_NSIUPDATEPROCESSOR
+
+ private:
+  ~nsUpdateProcessor();
+
+  struct StagedUpdateInfo {
+    StagedUpdateInfo() : mArgc(0), mArgv(nullptr) {}
+    ~StagedUpdateInfo() {
+      for (int i = 0; i < mArgc; ++i) {
+        delete[] mArgv[i];
+      }
+      delete[] mArgv;
+    }
+
+    nsCOMPtr<nsIFile> mGREDir;
+    nsCOMPtr<nsIFile> mAppDir;
+    nsCOMPtr<nsIFile> mUpdateRoot;
+    int mArgc;
+    char** mArgv;
+    nsCString mAppVersion;
+  };
+
+ private:
+  void StartStagedUpdate();
+  void UpdateDone();
+  void ShutdownWorkerThread();
+
+#ifndef XP_WIN
+  void WaitForProcess();
+#endif
+
+ private:
+  ProcessType mUpdaterPID;
+  nsCOMPtr<nsIThread> mWorkerThread;
+#ifdef XP_WIN
+  mozilla::HandleWatcher mProcessWatcher;
+#endif
+  StagedUpdateInfo mInfo;
+};
+#endif  // nsUpdateDriver_h__
diff --git a/toolkit/xre/nsUpdateSyncManager.cpp b/toolkit/xre/nsUpdateSyncManager.cpp
new file mode 100644
index 0000000000..b2f6d4247b
--- /dev/null
+++ b/toolkit/xre/nsUpdateSyncManager.cpp
@@ -0,0 +1,129 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sw=2 sts=2 et cindent: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsUpdateSyncManager.h"
+
+#include "mozilla/Unused.h"
+#include "mozilla/Services.h"
+#include "nsComponentManagerUtils.h"
+#include "nsCRT.h"
+#include "nsIFile.h"
+#include "nsIObserverService.h"
+#include "nsIProperties.h"
+#include "nsString.h"
+#include "nsXULAppAPI.h"
+
+// The lock code generates a path that already includes the vendor name,
+// so this only needs to name the specific lock.
+#define UPDATE_LOCK_NAME_TOKEN "UpdateLock"
+
+nsUpdateSyncManager* gUpdateSyncManager = nullptr;
+
+NS_IMPL_ISUPPORTS(nsUpdateSyncManager, nsIUpdateSyncManager, nsIObserver)
+
+nsUpdateSyncManager::nsUpdateSyncManager(nsIFile* anAppFile /* = nullptr */) {
+  gUpdateSyncManager = this;
+  OpenLock(anAppFile);
+}
+
+nsUpdateSyncManager::~nsUpdateSyncManager() {
+  ReleaseLock();
+  gUpdateSyncManager = nullptr;
+}
+
+already_AddRefed<nsUpdateSyncManager> nsUpdateSyncManager::GetSingleton() {
+  if (!gUpdateSyncManager) {
+    new nsUpdateSyncManager();  // This sets gUpdateSyncManager.
+  }
+  return do_AddRef(gUpdateSyncManager);
+}
+
+NS_IMETHODIMP nsUpdateSyncManager::Observe(nsISupports* aSubject,
+                                           const char* aTopic,
+                                           const char16_t* aData) {
+  mozilla::Unused << aSubject;
+  mozilla::Unused << aData;
+
+  // We want to hold the lock for as much of the lifetime of the app as we can,
+  // so we observe xpcom-startup so we get constructed as early as possible,
+  // which triggers constructing the singleton.
+  if (!nsCRT::strcmp(aTopic, NS_XPCOM_STARTUP_OBSERVER_ID)) {
+    nsCOMPtr<nsIObserverService> observerService =
+        mozilla::services::GetObserverService();
+    if (observerService) {
+      return observerService->AddObserver(this, NS_XPCOM_SHUTDOWN_OBSERVER_ID,
+                                          false);
+    }
+    return NS_ERROR_SERVICE_NOT_AVAILABLE;
+  }
+  if (!nsCRT::strcmp(aTopic, NS_XPCOM_SHUTDOWN_OBSERVER_ID)) {
+    ReleaseLock();
+  }
+
+  return NS_OK;
+}
+
+nsresult nsUpdateSyncManager::OpenLock(nsIFile* anAppFile) {
+  nsresult rv;
+  if (mLock != MULTI_INSTANCE_LOCK_HANDLE_ERROR) {
+    // Lock is already open.
+    return NS_OK;
+  }
+
+  // Our component registration should already have made sure of this.
+  if (NS_WARN_IF(XRE_GetProcessType() != GeckoProcessType_Default)) {
+    return NS_OK;
+  }
+
+  nsCOMPtr<nsIFile> appFile = mozilla::GetNormalizedAppFile(anAppFile);
+  if (!appFile) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  nsCOMPtr<nsIFile> appDirFile;
+  rv = appFile->GetParent(getter_AddRefs(appDirFile));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsAutoString appDirPath;
+  rv = appDirFile->GetPath(appDirPath);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  mLock =
+      mozilla::OpenMultiInstanceLock(UPDATE_LOCK_NAME_TOKEN, appDirPath.get());
+  NS_ENSURE_TRUE(mLock, NS_ERROR_FAILURE);
+
+  return NS_OK;
+}
+
+void nsUpdateSyncManager::ReleaseLock() {
+  if (mLock == MULTI_INSTANCE_LOCK_HANDLE_ERROR) {
+    // Lock is already released.
+    return;
+  }
+
+  mozilla::ReleaseMultiInstanceLock(mLock);
+  mLock = MULTI_INSTANCE_LOCK_HANDLE_ERROR;
+}
+
+NS_IMETHODIMP nsUpdateSyncManager::IsOtherInstanceRunning(bool* aResult) {
+  if (NS_WARN_IF(XRE_GetProcessType() != GeckoProcessType_Default)) {
+    return NS_ERROR_SERVICE_NOT_AVAILABLE;
+  }
+
+  if (mLock == MULTI_INSTANCE_LOCK_HANDLE_ERROR) {
+    return NS_ERROR_NOT_INITIALIZED;
+  }
+
+  bool rv = mozilla::IsOtherInstanceRunning(mLock, aResult);
+  NS_ENSURE_TRUE(rv, NS_ERROR_FAILURE);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP nsUpdateSyncManager::ResetLock(nsIFile* anAppFile = nullptr) {
+  ReleaseLock();
+  return OpenLock(anAppFile);
+}
diff --git a/toolkit/xre/nsUpdateSyncManager.h b/toolkit/xre/nsUpdateSyncManager.h
new file mode 100644
index 0000000000..4c24cde8d4
--- /dev/null
+++ b/toolkit/xre/nsUpdateSyncManager.h
@@ -0,0 +1,49 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sw=2 sts=2 et cindent: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef nsUpdateSyncManager_h__
+#define nsUpdateSyncManager_h__
+
+#include "mozilla/AlreadyAddRefed.h"
+#include "nsIObserver.h"
+#include "nsIUpdateService.h"
+#include "MultiInstanceLock.h"
+
+// The update sync manager is responsible for making sure that only one
+// instance of the application is running at the time we want to start updating
+// it. It does this by taking a multi-instance lock very early during the
+// application's startup process. Then, when app update tasks are ready to run,
+// the update service asks us whether anything else has also taken that lock,
+// which, if true, would mean another instance of the application is currently
+// running and performing update tasks should be avoided (the update service
+// also runs a timeout and eventually goes ahead with the update in order to
+// prevent an external program from effectively disabling updates).
+class nsUpdateSyncManager final : public nsIUpdateSyncManager,
+                                  public nsIObserver {
+ public:
+  explicit nsUpdateSyncManager(nsIFile* anAppFile = nullptr);
+
+  NS_DECL_THREADSAFE_ISUPPORTS
+  NS_DECL_NSIUPDATESYNCMANAGER
+  NS_DECL_NSIOBSERVER
+
+  static already_AddRefed<nsUpdateSyncManager> GetSingleton();
+
+ private:
+  ~nsUpdateSyncManager();
+
+  nsUpdateSyncManager(nsUpdateSyncManager&) = delete;
+  nsUpdateSyncManager(nsUpdateSyncManager&&) = delete;
+  nsUpdateSyncManager& operator=(nsUpdateSyncManager&) = delete;
+  nsUpdateSyncManager& operator=(nsUpdateSyncManager&&) = delete;
+
+  nsresult OpenLock(nsIFile* anAppFile = nullptr);
+  void ReleaseLock();
+
+  mozilla::MultiInstLockHandle mLock = MULTI_INSTANCE_LOCK_HANDLE_ERROR;
+};
+
+#endif  // nsUpdateSyncManager_h__
diff --git a/toolkit/xre/nsWindowsRestart.cpp b/toolkit/xre/nsWindowsRestart.cpp
new file mode 100644
index 0000000000..869ca7c92c
--- /dev/null
+++ b/toolkit/xre/nsWindowsRestart.cpp
@@ -0,0 +1,197 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// This file is not build directly. Instead, it is included in multiple
+// shared objects.
+
+#ifdef nsWindowsRestart_cpp
+#  error \
+      "nsWindowsRestart.cpp is not a header file, and must only be included once."
+#else
+#  define nsWindowsRestart_cpp
+#endif
+
+#include "mozilla/CmdLineAndEnvUtils.h"
+#include "nsUTF8Utils.h"
+
+#include <shellapi.h>
+
+// Needed for CreateEnvironmentBlock
+#include <userenv.h>
+#ifndef __MINGW32__
+#  pragma comment(lib, "userenv.lib")
+#endif
+
+/**
+ * Convert UTF8 to UTF16 without using the normal XPCOM goop, which we
+ * can't link to updater.exe.
+ */
+static char16_t* AllocConvertUTF8toUTF16(const char* arg) {
+  // UTF16 can't be longer in units than UTF8
+  size_t len = strlen(arg);
+  char16_t* s = new char16_t[(len + 1) * sizeof(char16_t)];
+  if (!s) return nullptr;
+
+  size_t dstLen = ::MultiByteToWideChar(CP_UTF8, 0, arg, len,
+                                        reinterpret_cast<wchar_t*>(s), len);
+  s[dstLen] = 0;
+
+  return s;
+}
+
+static void FreeAllocStrings(int argc, wchar_t** argv) {
+  while (argc) {
+    --argc;
+    delete[] argv[argc];
+  }
+
+  delete[] argv;
+}
+
+static wchar_t** AllocConvertUTF8toUTF16Strings(int argc, char** argv) {
+  wchar_t** argvConverted = new wchar_t*[argc];
+  if (!argvConverted) return nullptr;
+
+  for (int i = 0; i < argc; ++i) {
+    argvConverted[i] =
+        reinterpret_cast<wchar_t*>(AllocConvertUTF8toUTF16(argv[i]));
+    if (!argvConverted[i]) {
+      FreeAllocStrings(i, argvConverted);
+      return nullptr;
+    }
+  }
+  return argvConverted;
+}
+
+/**
+ * Return true if we are in a job with JOB_OBJECT_LIMIT_KILL_ON_JOB_CLOSE and
+ * we can break away from it.
+ * CreateProcess fails if we try to break away from a job but it's not allowed.
+ * So if we cannot determine the result due to a failure, we assume we don't
+ * need to break away and this returns false.
+ */
+static bool NeedToBreakAwayFromJob() {
+  // If we can't determine if we are in a job, we assume we're not in a job.
+  BOOL inJob = FALSE;
+  if (!::IsProcessInJob(::GetCurrentProcess(), nullptr, &inJob)) {
+    return false;
+  }
+
+  // If there is no job, there is nothing to worry about.
+  if (!inJob) {
+    return false;
+  }
+
+  // If we can't get the job object flags, we assume no need to break away from
+  // it.
+  JOBOBJECT_EXTENDED_LIMIT_INFORMATION job_info = {};
+  if (!::QueryInformationJobObject(nullptr, JobObjectExtendedLimitInformation,
+                                   &job_info, sizeof(job_info), nullptr)) {
+    return false;
+  }
+
+  // If JOB_OBJECT_LIMIT_KILL_ON_JOB_CLOSE is not set, no need to worry about
+  // the job.
+  if (!(job_info.BasicLimitInformation.LimitFlags &
+        JOB_OBJECT_LIMIT_KILL_ON_JOB_CLOSE)) {
+    return false;
+  }
+
+  // If we can't break away from the current job, there is nothing we can do.
+  if (!(job_info.BasicLimitInformation.LimitFlags &
+        JOB_OBJECT_LIMIT_BREAKAWAY_OK)) {
+    return false;
+  }
+
+  // We can and need to break away from the job.
+  return true;
+}
+
+/**
+ * Launch a child process with the specified arguments.
+ * @note argv[0] is ignored
+ * @note The form of this function that takes char **argv expects UTF-8
+ */
+
+BOOL WinLaunchChild(const wchar_t* exePath, int argc, wchar_t** argv,
+                    HANDLE userToken = nullptr, HANDLE* hProcess = nullptr);
+
+BOOL WinLaunchChild(const wchar_t* exePath, int argc, char** argv,
+                    HANDLE userToken, HANDLE* hProcess) {
+  wchar_t** argvConverted = AllocConvertUTF8toUTF16Strings(argc, argv);
+  if (!argvConverted) return FALSE;
+
+  BOOL ok = WinLaunchChild(exePath, argc, argvConverted, userToken, hProcess);
+  FreeAllocStrings(argc, argvConverted);
+  return ok;
+}
+
+BOOL WinLaunchChild(const wchar_t* exePath, int argc, wchar_t** argv,
+                    HANDLE userToken, HANDLE* hProcess) {
+  BOOL ok;
+
+  mozilla::UniquePtr<wchar_t[]> cl(mozilla::MakeCommandLine(argc, argv));
+  if (!cl) {
+    return FALSE;
+  }
+
+  DWORD creationFlags =
+      NeedToBreakAwayFromJob() ? CREATE_BREAKAWAY_FROM_JOB : 0;
+
+  STARTUPINFOW si = {0};
+  si.cb = sizeof(STARTUPINFOW);
+  si.lpDesktop = const_cast<LPWSTR>(L"winsta0\\Default");
+  PROCESS_INFORMATION pi = {0};
+
+  if (userToken == nullptr) {
+    ok = CreateProcessW(exePath, cl.get(),
+                        nullptr,  // no special security attributes
+                        nullptr,  // no special thread attributes
+                        FALSE,    // don't inherit filehandles
+                        creationFlags,
+                        nullptr,  // inherit my environment
+                        nullptr,  // use my current directory
+                        &si, &pi);
+  } else {
+    // Create an environment block for the process we're about to start using
+    // the user's token.
+    LPVOID environmentBlock = nullptr;
+    if (!CreateEnvironmentBlock(&environmentBlock, userToken, TRUE)) {
+      environmentBlock = nullptr;
+    }
+
+    ok = CreateProcessAsUserW(userToken, exePath, cl.get(),
+                              nullptr,  // no special security attributes
+                              nullptr,  // no special thread attributes
+                              FALSE,    // don't inherit filehandles
+                              creationFlags, environmentBlock,
+                              nullptr,  // use my current directory
+                              &si, &pi);
+
+    if (environmentBlock) {
+      DestroyEnvironmentBlock(environmentBlock);
+    }
+  }
+
+  if (ok) {
+    if (hProcess) {
+      *hProcess = pi.hProcess;  // the caller now owns the HANDLE
+    } else {
+      CloseHandle(pi.hProcess);
+    }
+    CloseHandle(pi.hThread);
+  } else {
+    LPVOID lpMsgBuf = nullptr;
+    FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM |
+                      FORMAT_MESSAGE_IGNORE_INSERTS,
+                  nullptr, GetLastError(),
+                  MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), (LPTSTR)&lpMsgBuf,
+                  0, nullptr);
+    wprintf(L"Error restarting: %s\n",
+            lpMsgBuf ? static_cast<const wchar_t*>(lpMsgBuf) : L"(null)");
+    if (lpMsgBuf) LocalFree(lpMsgBuf);
+  }
+
+  return ok;
+}
diff --git a/toolkit/xre/nsWindowsWMain.cpp b/toolkit/xre/nsWindowsWMain.cpp
new file mode 100644
index 0000000000..ea14a59b80
--- /dev/null
+++ b/toolkit/xre/nsWindowsWMain.cpp
@@ -0,0 +1,176 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef nsWindowsWMain_cpp
+#define nsWindowsWMain_cpp
+
+// This file is a .cpp file meant to be included in nsBrowserApp.cpp and other
+// similar bootstrap code. It converts wide-character windows wmain into UTF-8
+// narrow-character strings.
+
+#ifndef XP_WIN
+#  error This file only makes sense on Windows.
+#endif
+
+#include "mozilla/Char16.h"
+#include "nsUTF8Utils.h"
+#include "nsWindowsHelpers.h"
+
+#include <windows.h>
+#include <versionhelpers.h>
+
+#ifdef __MINGW32__
+
+/* MingW currently does not implement a wide version of the
+   startup routines.  Workaround is to implement something like
+   it ourselves.  See bug 411826 */
+
+#  include <shellapi.h>
+
+int wmain(int argc, WCHAR** argv);
+
+int main(int argc, char** argv) {
+  LPWSTR commandLine = GetCommandLineW();
+  int argcw = 0;
+  LPWSTR* argvw = CommandLineToArgvW(commandLine, &argcw);
+  if (!argvw) return 127;
+
+  int result = wmain(argcw, argvw);
+  LocalFree(argvw);
+  return result;
+}
+#endif /* __MINGW32__ */
+
+#define main NS_internal_main
+
+#ifndef XRE_WANT_ENVIRON
+int main(int argc, char** argv);
+#else
+int main(int argc, char** argv, char** envp);
+#endif
+
+// SanitizeEnvironmentVariables()
+//
+// Mitigate CVE-2007-6753 (binary planting via unexpanded environment variable
+// references) by forcibly expanding all environment variable references in
+// %PATH%.
+//
+// CVE-2007-6753 is documented to have affected all active mainline Windows
+// versions at the time of its announcement (i.e., up to Windows 7). Microsoft
+// has never formally stated that later versions of Windows are free of this
+// issue; out of an abundance of caution, we continue to mitigate it on Windows
+// 8 and beyond.
+static void SanitizeEnvironmentVariables() {
+  DWORD bufferSize = GetEnvironmentVariableW(L"PATH", nullptr, 0);
+  if (bufferSize) {
+    wchar_t* originalPath = new wchar_t[bufferSize];
+    if (bufferSize - 1 ==
+        GetEnvironmentVariableW(L"PATH", originalPath, bufferSize)) {
+      bufferSize = ExpandEnvironmentStringsW(originalPath, nullptr, 0);
+      // The maximum length of a Windows environment variable and the maximum
+      // length of a string returned by ExpandEnvironmentStringsW are both
+      // documented to be 32,767 characters. Under some versions of Windows,
+      // however, both may be longer, with delayed but deleterious consequences.
+      //
+      // We therefore cap the size manually, in case the user has a sufficiently
+      // problematic %PATH%. (See bug 1753910.) This is unlikely to occur unless
+      // there is some form of recursive referencing involved, in which case
+      // expansion is no mitigation anyway.
+      if (bufferSize && bufferSize < 32768) {
+        wchar_t* newPath = new wchar_t[bufferSize];
+        if (ExpandEnvironmentStringsW(originalPath, newPath, bufferSize)) {
+          SetEnvironmentVariableW(L"PATH", newPath);
+        }
+        delete[] newPath;
+      }
+    }
+    delete[] originalPath;
+  }
+}
+
+static char* AllocConvertUTF16toUTF8(char16ptr_t arg) {
+  // be generous... UTF16 units can expand up to 3 UTF8 units
+  size_t len = wcslen(arg);
+  // ConvertUTF16toUTF8 requires +1. Let's do that here, too, lacking
+  // knowledge of Windows internals.
+  size_t dstLen = len * 3 + 1;
+  char* s = new char[dstLen + 1];  // Another +1 for zero terminator
+  if (!s) return nullptr;
+
+  int written =
+      ::WideCharToMultiByte(CP_UTF8, 0, arg, len, s, dstLen, nullptr, nullptr);
+  s[written] = 0;
+  return s;
+}
+
+static void FreeAllocStrings(int argc, char** argv) {
+  while (argc) {
+    --argc;
+    delete[] argv[argc];
+  }
+
+  delete[] argv;
+}
+
+int wmain(int argc, WCHAR** argv) {
+  // In Windows 7 32-bit, user32.dll must be mapped to the same virtual
+  // address in all processes.  Otherwise, win32k's user-mode callback causes
+  // crash.  Since we delayload user32.dll, if our code or injected code
+  // reserves the user32 address before user32.dll is loaded, it is loaded
+  // to a new address and we crash.  To mitigate this problem, we explicitly
+  // load user32.dll as early as possible. See bug 1730033 for details.
+  if (!IsWindows8OrGreater()) {
+    SYSTEM_INFO sysInfo;
+    ::GetNativeSystemInfo(&sysInfo);
+    if (sysInfo.wProcessorArchitecture == PROCESSOR_ARCHITECTURE_INTEL) {
+      LoadLibrarySystem32(L"user32.dll");
+    }
+  }
+
+  SanitizeEnvironmentVariables();
+  SetDllDirectoryW(L"");
+
+  // Only run this code if LauncherProcessWin.h was included beforehand, thus
+  // signalling that the hosting process should support launcher mode.
+#if defined(mozilla_LauncherProcessWin_h)
+  mozilla::Maybe<int> launcherResult =
+      mozilla::LauncherMain(argc, argv, sAppData);
+  if (launcherResult) {
+    return launcherResult.value();
+  }
+#endif  // defined(mozilla_LauncherProcessWin_h)
+
+  char** argvConverted = new char*[argc + 1];
+  if (!argvConverted) return 127;
+
+  for (int i = 0; i < argc; ++i) {
+    argvConverted[i] = AllocConvertUTF16toUTF8(argv[i]);
+    if (!argvConverted[i]) {
+      return 127;
+    }
+  }
+  argvConverted[argc] = nullptr;
+
+  // need to save argvConverted copy for later deletion.
+  char** deleteUs = new char*[argc + 1];
+  if (!deleteUs) {
+    FreeAllocStrings(argc, argvConverted);
+    return 127;
+  }
+  for (int i = 0; i < argc; i++) deleteUs[i] = argvConverted[i];
+#ifndef XRE_WANT_ENVIRON
+  int result = main(argc, argvConverted);
+#else
+  // Force creation of the multibyte _environ variable.
+  getenv("PATH");
+  int result = main(argc, argvConverted, _environ);
+#endif
+
+  delete[] argvConverted;
+  FreeAllocStrings(argc, deleteUs);
+
+  return result;
+}
+
+#endif  // nsWindowsWMain_cpp
diff --git a/toolkit/xre/nsX11ErrorHandler.cpp b/toolkit/xre/nsX11ErrorHandler.cpp
new file mode 100644
index 0000000000..77f71db8f9
--- /dev/null
+++ b/toolkit/xre/nsX11ErrorHandler.cpp
@@ -0,0 +1,156 @@
+/* -*- Mode: C++; tab-width: 40; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsX11ErrorHandler.h"
+
+#include "prenv.h"
+#include "nsXULAppAPI.h"
+#include "nsExceptionHandler.h"
+#include "nsDebug.h"
+#include "nsString.h"
+#include "nsTArray.h"
+
+#include "mozilla/X11Util.h"
+#include <X11/Xlib.h>
+
+#define BUFSIZE 2048  // What Xlib uses with XGetErrorDatabaseText
+
+struct XExtension {
+  nsCString name;
+  int major_opcode;
+
+  XExtension(const char* aName, int aCode) : name(aName), major_opcode(aCode) {}
+};
+
+static nsTArray<XExtension> sXExtensions;
+
+// man XSetErrorHandler says "the error handler should not call any
+// functions (directly or indirectly) on the display that will generate
+// protocol requests or that will look for input events" so we query the
+// extension list early to avoid problems.
+static void QueryXExtensions(Display* aDisplay) {
+  if (!sXExtensions.IsEmpty() || !aDisplay) {
+    return;
+  }
+  int nExts = 0;
+  char** extNames = XListExtensions(aDisplay, &nExts);
+  if (!extNames) {
+    return;
+  }
+  for (int i = 0; i < nExts; ++i) {
+    int major_opcode, first_event, first_error;
+    if (XQueryExtension(aDisplay, extNames[i], &major_opcode, &first_event,
+                        &first_error)) {
+      sXExtensions.EmplaceBack(extNames[i], major_opcode);
+    }
+  }
+  XFreeExtensionList(extNames);
+}
+
+extern "C" {
+int X11Error(Display* display, XErrorEvent* event) {
+#ifdef DEBUG
+  // Get an indication of how long ago the request that caused the error was
+  // made.
+  unsigned long age = NextRequest(display) - event->serial;
+#endif
+
+  // Get a string to represent the request that caused the error.
+  nsAutoCString message;
+  if (event->request_code < 128) {
+    // Core protocol request
+    message.AppendInt(event->request_code);
+  } else {
+    // Extension request
+    for (XExtension& ext : sXExtensions) {
+      if (ext.major_opcode == event->request_code) {
+        message.Append(ext.name);
+        message.Append('.');
+        message.AppendInt(event->minor_code);
+        break;
+      }
+    }
+  }
+
+  char buffer[BUFSIZE];
+  if (message.IsEmpty()) {
+    buffer[0] = '\0';
+  } else {
+    XGetErrorDatabaseText(display, "XRequest", message.get(), "", buffer,
+                          sizeof(buffer));
+  }
+
+  nsAutoCString notes;
+  if (buffer[0]) {
+    notes.Append(buffer);
+  } else {
+    notes.AppendLiteral("Request ");
+    notes.AppendInt(event->request_code);
+    notes.Append('.');
+    notes.AppendInt(event->minor_code);
+  }
+
+  notes.AppendLiteral(": ");
+
+  // Get a string to describe the error.
+  XGetErrorText(display, event->error_code, buffer, sizeof(buffer));
+  notes.Append(buffer);
+
+#ifdef DEBUG
+  // For requests where Xlib gets the reply synchronously, |age| will be 1
+  // and the stack will include the function making the request.  For
+  // asynchronous requests, the current stack will often be unrelated to the
+  // point of making the request, even if |age| is 1, but sometimes this may
+  // help us count back to the point of the request.  With XSynchronize on,
+  // the stack will include the function making the request, even though
+  // |age| will be 2 for asynchronous requests because XSynchronize is
+  // implemented by an empty request from an XSync, which has not yet been
+  // processed.
+  if (age > 1) {
+    // XSynchronize returns the previous "after function".  If a second
+    // XSynchronize call returns the same function after an enable call then
+    // synchronization must have already been enabled.
+    if (XSynchronize(display, X11True) == XSynchronize(display, X11False)) {
+      notes.AppendLiteral("; sync");
+    } else {
+      notes.AppendLiteral("; ");
+      notes.AppendInt(uint32_t(age));
+      notes.AppendLiteral(" requests ago");
+    }
+  }
+
+  // The resource id is unlikely to be useful in a crash report without
+  // context of other ids, but add it to the debug console output.
+  notes.AppendLiteral("; id=0x");
+  notes.AppendInt(uint32_t(event->resourceid), 16);
+#  ifdef MOZ_X11
+  // Actually, for requests where Xlib gets the reply synchronously,
+  // MOZ_X_SYNC=1 will not be necessary, but we don't have a table to tell us
+  // which requests get a synchronous reply.
+  if (!PR_GetEnv("MOZ_X_SYNC")) {
+    notes.AppendLiteral(
+        "\nRe-running with MOZ_X_SYNC=1 in the environment may give a more "
+        "helpful backtrace.");
+  }
+#  endif
+#endif
+
+  NS_WARNING(notes.get());
+  return 0;
+}
+}
+
+void InstallX11ErrorHandler() {
+  XSetErrorHandler(X11Error);
+
+  if (Display* display = mozilla::DefaultXDisplay()) {
+    QueryXExtensions(display);
+    if (PR_GetEnv("MOZ_X_SYNC")) {
+      XSynchronize(display, X11True);
+    }
+  }
+}
+
+void CleanupX11ErrorHandler() { sXExtensions.Clear(); }
diff --git a/toolkit/xre/nsX11ErrorHandler.h b/toolkit/xre/nsX11ErrorHandler.h
new file mode 100644
index 0000000000..bd7ac59154
--- /dev/null
+++ b/toolkit/xre/nsX11ErrorHandler.h
@@ -0,0 +1,20 @@
+/* -*- Mode: C++; tab-width: 40; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifdef MOZ_X11
+#  include <X11/Xlib.h>
+#  include "X11UndefineNone.h"  // Unset some macros defined by X.h included by Xlib.h
+
+/**
+ * InstallX11ErrorHandler is not suitable for processes running with GTK3 as
+ * GDK3 will replace the handler.  This is still used for the plugin process,
+ * which runs with GTK2.
+ **/
+void InstallX11ErrorHandler();
+
+void CleanupX11ErrorHandler();
+
+extern "C" int X11Error(Display* display, XErrorEvent* event);
+#endif
diff --git a/toolkit/xre/nsXREDirProvider.cpp b/toolkit/xre/nsXREDirProvider.cpp
new file mode 100644
index 0000000000..41d2353fe8
--- /dev/null
+++ b/toolkit/xre/nsXREDirProvider.cpp
@@ -0,0 +1,1512 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsAppRunner.h"
+#include "nsXREDirProvider.h"
+#ifndef ANDROID
+#  include "commonupdatedir.h"
+#endif
+
+#include "jsapi.h"
+#include "xpcpublic.h"
+#include "prprf.h"
+
+#include "nsIAppStartup.h"
+#include "nsIFile.h"
+#include "nsIObserver.h"
+#include "nsIObserverService.h"
+#include "nsISimpleEnumerator.h"
+#include "nsIToolkitProfileService.h"
+#include "nsIXULRuntime.h"
+#include "commonupdatedir.h"
+
+#include "nsAppDirectoryServiceDefs.h"
+#include "nsDirectoryServiceDefs.h"
+#include "nsDirectoryServiceUtils.h"
+#include "nsXULAppAPI.h"
+#include "nsCategoryManagerUtils.h"
+
+#include "nsDependentString.h"
+#include "nsCOMArray.h"
+#include "nsArrayEnumerator.h"
+#include "nsEnumeratorUtils.h"
+#include "nsReadableUtils.h"
+
+#include "SpecialSystemDirectory.h"
+
+#include "mozilla/dom/ScriptSettings.h"
+
+#include "mozilla/AppShutdown.h"
+#include "mozilla/AutoRestore.h"
+#ifdef MOZ_BACKGROUNDTASKS
+#  include "mozilla/BackgroundTasks.h"
+#endif
+#include "mozilla/Components.h"
+#include "mozilla/Services.h"
+#include "mozilla/Omnijar.h"
+#include "mozilla/Preferences.h"
+#include "mozilla/ProfilerLabels.h"
+#include "mozilla/Telemetry.h"
+#include "mozilla/XREAppData.h"
+#include "nsPrintfCString.h"
+
+#ifdef MOZ_THUNDERBIRD
+#  include "nsIPK11TokenDB.h"
+#  include "nsIPK11Token.h"
+#endif
+
+#include <stdlib.h>
+
+#ifdef XP_WIN
+#  include <windows.h>
+#  include <shlobj.h>
+#  include "WinUtils.h"
+#endif
+#ifdef XP_MACOSX
+#  include "nsILocalFileMac.h"
+// for chflags()
+#  include <sys/stat.h>
+#  include <unistd.h>
+#endif
+#ifdef XP_UNIX
+#  include <ctype.h>
+#endif
+#ifdef XP_IOS
+#  include "UIKitDirProvider.h"
+#endif
+
+#if defined(MOZ_CONTENT_TEMP_DIR)
+#  include "mozilla/SandboxSettings.h"
+#  include "nsID.h"
+#  include "mozilla/Unused.h"
+#endif
+
+#if defined(XP_MACOSX)
+#  define APP_REGISTRY_NAME "Application Registry"
+#elif defined(XP_WIN)
+#  define APP_REGISTRY_NAME "registry.dat"
+#else
+#  define APP_REGISTRY_NAME "appreg"
+#endif
+
+#define PREF_OVERRIDE_DIRNAME "preferences"
+
+#if defined(MOZ_CONTENT_TEMP_DIR)
+static already_AddRefed<nsIFile> GetProcessSandboxTempDir(
+    GeckoProcessType type);
+static nsresult DeleteDirIfExists(nsIFile* dir);
+static bool IsContentSandboxDisabled();
+static const char* GetProcessTempBaseDirKey();
+static already_AddRefed<nsIFile> CreateProcessSandboxTempDir(
+    GeckoProcessType procType);
+#endif
+
+nsXREDirProvider* gDirServiceProvider = nullptr;
+nsIFile* gDataDirHomeLocal = nullptr;
+nsIFile* gDataDirHome = nullptr;
+nsCOMPtr<nsIFile> gDataDirProfileLocal = nullptr;
+nsCOMPtr<nsIFile> gDataDirProfile = nullptr;
+
+// These are required to allow nsXREDirProvider to be usable in xpcshell tests.
+// where gAppData is null.
+#if defined(XP_MACOSX) || defined(XP_UNIX)
+static const char* GetAppName() {
+  if (gAppData) {
+    return gAppData->name;
+  }
+  return nullptr;
+}
+#endif
+
+#ifdef XP_MACOSX
+static const char* GetAppVendor() {
+  if (gAppData) {
+    return gAppData->vendor;
+  }
+  return nullptr;
+}
+#endif
+
+nsXREDirProvider::nsXREDirProvider() { gDirServiceProvider = this; }
+
+nsXREDirProvider::~nsXREDirProvider() {
+  gDirServiceProvider = nullptr;
+  gDataDirHomeLocal = nullptr;
+  gDataDirHome = nullptr;
+}
+
+already_AddRefed<nsXREDirProvider> nsXREDirProvider::GetSingleton() {
+  if (!gDirServiceProvider) {
+    new nsXREDirProvider();  // This sets gDirServiceProvider
+  }
+  return do_AddRef(gDirServiceProvider);
+}
+
+nsresult nsXREDirProvider::Initialize(nsIFile* aXULAppDir, nsIFile* aGREDir) {
+  NS_ENSURE_ARG(aXULAppDir);
+  NS_ENSURE_ARG(aGREDir);
+
+  mXULAppDir = aXULAppDir;
+  mGREDir = aGREDir;
+  nsCOMPtr<nsIFile> binaryPath;
+  nsresult rv = XRE_GetBinaryPath(getter_AddRefs(binaryPath));
+  NS_ENSURE_SUCCESS(rv, rv);
+  return binaryPath->GetParent(getter_AddRefs(mGREBinDir));
+}
+
+nsresult nsXREDirProvider::SetProfile(nsIFile* aDir, nsIFile* aLocalDir) {
+  MOZ_ASSERT(aDir && aLocalDir, "We don't support no-profile apps!");
+  MOZ_ASSERT(!mProfileDir && !mProfileLocalDir,
+             "You may only set the profile directories once");
+
+  nsresult rv = EnsureDirectoryExists(aDir);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  rv = EnsureDirectoryExists(aLocalDir);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+#ifndef XP_WIN
+  nsAutoCString profilePath;
+  rv = aDir->GetNativePath(profilePath);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsAutoCString localProfilePath;
+  rv = aLocalDir->GetNativePath(localProfilePath);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  if (!mozilla::IsUtf8(profilePath) || !mozilla::IsUtf8(localProfilePath)) {
+    PR_fprintf(
+        PR_STDERR,
+        "Error: The profile path is not valid UTF-8. Unable to continue.\n");
+    return NS_ERROR_FAILURE;
+  }
+#endif
+
+#ifdef XP_MACOSX
+  bool same;
+  if (NS_SUCCEEDED(aDir->Equals(aLocalDir, &same)) && !same) {
+    // Ensure that the cache directory is not indexed by Spotlight
+    // (bug 718910).  At least on OS X, the cache directory (under
+    // ~/Library/Caches/) is always the "local" user profile
+    // directory.  This is confusing, since *both* user profile
+    // directories are "local" (they both exist under the user's
+    // home directory).  But this usage dates back at least as far
+    // as the patch for bug 291033, where "local" seems to mean
+    // "suitable for temporary storage".  Don't hide the cache
+    // directory if by some chance it and the "non-local" profile
+    // directory are the same -- there are bad side effects from
+    // hiding a profile directory under /Library/Application Support/
+    // (see bug 801883).
+    nsAutoCString cacheDir;
+    if (NS_SUCCEEDED(aLocalDir->GetNativePath(cacheDir))) {
+      if (chflags(cacheDir.get(), UF_HIDDEN)) {
+        NS_WARNING("Failed to set Cache directory to HIDDEN.");
+      }
+    }
+  }
+#endif
+
+  mProfileDir = aDir;
+  mProfileLocalDir = aLocalDir;
+  return NS_OK;
+}
+
+NS_IMPL_QUERY_INTERFACE(nsXREDirProvider, nsIDirectoryServiceProvider,
+                        nsIDirectoryServiceProvider2, nsIXREDirProvider,
+                        nsIProfileStartup)
+
+NS_IMETHODIMP_(MozExternalRefCountType)
+nsXREDirProvider::AddRef() { return 1; }
+
+NS_IMETHODIMP_(MozExternalRefCountType)
+nsXREDirProvider::Release() { return 0; }
+
+nsresult nsXREDirProvider::GetUserProfilesRootDir(nsIFile** aResult) {
+  nsCOMPtr<nsIFile> file;
+  nsresult rv = GetUserDataDirectory(getter_AddRefs(file), false);
+
+  if (NS_SUCCEEDED(rv)) {
+#if !defined(XP_UNIX) || defined(XP_MACOSX)
+    rv = file->AppendNative("Profiles"_ns);
+#endif
+    // We must create the profile directory here if it does not exist.
+    nsresult tmp = EnsureDirectoryExists(file);
+    if (NS_FAILED(tmp)) {
+      rv = tmp;
+    }
+  }
+  file.swap(*aResult);
+  return rv;
+}
+
+nsresult nsXREDirProvider::GetUserProfilesLocalDir(nsIFile** aResult) {
+  nsCOMPtr<nsIFile> file;
+  nsresult rv = GetUserDataDirectory(getter_AddRefs(file), true);
+
+  if (NS_SUCCEEDED(rv)) {
+#if !defined(XP_UNIX) || defined(XP_MACOSX)
+    rv = file->AppendNative("Profiles"_ns);
+#endif
+    // We must create the profile directory here if it does not exist.
+    nsresult tmp = EnsureDirectoryExists(file);
+    if (NS_FAILED(tmp)) {
+      rv = tmp;
+    }
+  }
+  file.swap(*aResult);
+  return NS_OK;
+}
+
+#ifdef MOZ_BACKGROUNDTASKS
+nsresult nsXREDirProvider::GetBackgroundTasksProfilesRootDir(
+    nsIFile** aResult) {
+  nsCOMPtr<nsIFile> file;
+  nsresult rv = GetUserDataDirectory(getter_AddRefs(file), false);
+
+  if (NS_SUCCEEDED(rv)) {
+#  if !defined(XP_UNIX) || defined(XP_MACOSX)
+    // Sibling to regular user "Profiles" directory.
+    rv = file->AppendNative("Background Tasks Profiles"_ns);
+#  endif
+    // We must create the directory here if it does not exist.
+    nsresult tmp = EnsureDirectoryExists(file);
+    if (NS_FAILED(tmp)) {
+      rv = tmp;
+    }
+  }
+  file.swap(*aResult);
+  return rv;
+}
+#endif
+
+#if defined(XP_UNIX) || defined(XP_MACOSX)
+/**
+ * Get the directory that is the parent of the system-wide directories
+ * for extensions and native manifests.
+ *
+ * On OSX this is /Library/Application Support/Mozilla
+ * On Linux this is /usr/{lib,lib64}/mozilla
+ *   (for 32- and 64-bit systems respsectively)
+ */
+static nsresult GetSystemParentDirectory(nsIFile** aFile) {
+  nsresult rv;
+  nsCOMPtr<nsIFile> localDir;
+#  if defined(XP_MACOSX)
+  rv = GetOSXFolderType(kOnSystemDisk, kApplicationSupportFolderType,
+                        getter_AddRefs(localDir));
+  if (NS_SUCCEEDED(rv)) {
+    rv = localDir->AppendNative("Mozilla"_ns);
+  }
+#  else
+  constexpr auto dirname =
+#    ifdef HAVE_USR_LIB64_DIR
+      "/usr/lib64/mozilla"_ns
+#    elif defined(__OpenBSD__) || defined(__FreeBSD__)
+      "/usr/local/lib/mozilla"_ns
+#    else
+      "/usr/lib/mozilla"_ns
+#    endif
+      ;
+  rv = NS_NewNativeLocalFile(dirname, false, getter_AddRefs(localDir));
+#  endif
+
+  if (NS_SUCCEEDED(rv)) {
+    localDir.forget(aFile);
+  }
+  return rv;
+}
+#endif
+
+NS_IMETHODIMP
+nsXREDirProvider::GetFile(const char* aProperty, bool* aPersistent,
+                          nsIFile** aFile) {
+  *aPersistent = true;
+  nsresult rv = NS_ERROR_FAILURE;
+
+  nsCOMPtr<nsIFile> file;
+
+  if (!strcmp(aProperty, NS_APP_USER_PROFILE_LOCAL_50_DIR) ||
+      !strcmp(aProperty, NS_APP_PROFILE_LOCAL_DIR_STARTUP)) {
+    if (mProfileLocalDir) {
+      rv = mProfileLocalDir->Clone(getter_AddRefs(file));
+    } else {
+      // Profile directories are only set up in the parent process.
+      // We don't expect every caller to check if they are in the right process,
+      // so fail immediately to avoid warning spam.
+      NS_WARNING_ASSERTION(!XRE_IsParentProcess(),
+                           "tried to get profile in parent too early");
+      return NS_ERROR_FAILURE;
+    }
+  } else if (!strcmp(aProperty, NS_APP_USER_PROFILE_50_DIR) ||
+             !strcmp(aProperty, NS_APP_PROFILE_DIR_STARTUP)) {
+    if (mProfileDir) {
+      rv = mProfileDir->Clone(getter_AddRefs(file));
+    } else {
+      // Profile directories are only set up in the parent process.
+      // We don't expect every caller to check if they are in the right process,
+      // so fail immediately to avoid warning spam.
+      NS_WARNING_ASSERTION(!XRE_IsParentProcess(),
+                           "tried to get profile in parent too early");
+      return NS_ERROR_FAILURE;
+    }
+  } else if (!strcmp(aProperty, NS_GRE_DIR)) {
+    // On Android, internal files are inside the APK, a zip file, so this
+    // folder doesn't really make sense.
+#if !defined(MOZ_WIDGET_ANDROID)
+    rv = mGREDir->Clone(getter_AddRefs(file));
+#endif  // !defined(MOZ_WIDGET_ANDROID)
+  } else if (!strcmp(aProperty, NS_GRE_BIN_DIR)) {
+    rv = mGREBinDir->Clone(getter_AddRefs(file));
+  } else if (!strcmp(aProperty, NS_OS_CURRENT_PROCESS_DIR) ||
+             !strcmp(aProperty, NS_APP_INSTALL_CLEANUP_DIR)) {
+    rv = GetAppDir()->Clone(getter_AddRefs(file));
+  } else if (!strcmp(aProperty, NS_APP_PREF_DEFAULTS_50_DIR)) {
+    // Same as NS_GRE_DIR
+#if !defined(MOZ_WIDGET_ANDROID)
+    // return the GRE default prefs directory here, and the app default prefs
+    // directory (if applicable) in NS_APP_PREFS_DEFAULTS_DIR_LIST.
+    rv = mGREDir->Clone(getter_AddRefs(file));
+    NS_ENSURE_SUCCESS(rv, rv);
+    rv = file->AppendNative("defaults"_ns);
+    NS_ENSURE_SUCCESS(rv, rv);
+    rv = file->AppendNative("pref"_ns);
+#endif  // !defined(MOZ_WIDGET_ANDROID)
+  } else if (!strcmp(aProperty, NS_APP_APPLICATION_REGISTRY_DIR) ||
+             !strcmp(aProperty, XRE_USER_APP_DATA_DIR)) {
+    rv = GetUserAppDataDirectory(getter_AddRefs(file));
+  }
+#if defined(XP_UNIX) || defined(XP_MACOSX)
+  else if (!strcmp(aProperty, XRE_SYS_NATIVE_MANIFESTS)) {
+    rv = ::GetSystemParentDirectory(getter_AddRefs(file));
+  } else if (!strcmp(aProperty, XRE_USER_NATIVE_MANIFESTS)) {
+    rv = GetUserDataDirectoryHome(getter_AddRefs(file), false);
+    NS_ENSURE_SUCCESS(rv, rv);
+#  if defined(XP_MACOSX)
+    rv = file->AppendNative("Mozilla"_ns);
+#  else   // defined(XP_MACOSX)
+    rv = file->AppendNative(".mozilla"_ns);
+#  endif  // defined(XP_MACOSX)
+  }
+#endif  // defined(XP_UNIX) || defined(XP_MACOSX)
+  else if (!strcmp(aProperty, XRE_UPDATE_ROOT_DIR)) {
+    rv = GetUpdateRootDir(getter_AddRefs(file));
+  } else if (!strcmp(aProperty, XRE_OLD_UPDATE_ROOT_DIR)) {
+    rv = GetUpdateRootDir(getter_AddRefs(file), true);
+  } else if (!strcmp(aProperty, NS_APP_APPLICATION_REGISTRY_FILE)) {
+    rv = GetUserAppDataDirectory(getter_AddRefs(file));
+    NS_ENSURE_SUCCESS(rv, rv);
+    rv = file->AppendNative(nsLiteralCString(APP_REGISTRY_NAME));
+  } else if (!strcmp(aProperty, NS_APP_USER_PROFILES_ROOT_DIR)) {
+    rv = GetUserProfilesRootDir(getter_AddRefs(file));
+  } else if (!strcmp(aProperty, NS_APP_USER_PROFILES_LOCAL_ROOT_DIR)) {
+    rv = GetUserProfilesLocalDir(getter_AddRefs(file));
+  } else if (!strcmp(aProperty, XRE_EXECUTABLE_FILE)) {
+    rv = XRE_GetBinaryPath(getter_AddRefs(file));
+  }
+#if defined(XP_UNIX) || defined(XP_MACOSX)
+  else if (!strcmp(aProperty, XRE_SYS_LOCAL_EXTENSION_PARENT_DIR)) {
+#  ifdef ENABLE_SYSTEM_EXTENSION_DIRS
+    rv = GetSystemExtensionsDirectory(getter_AddRefs(file));
+#  endif
+  }
+#endif  // defined(XP_UNIX) || defined(XP_MACOSX)
+#if defined(XP_UNIX) && !defined(XP_MACOSX)
+  else if (!strcmp(aProperty, XRE_SYS_SHARE_EXTENSION_PARENT_DIR)) {
+#  ifdef ENABLE_SYSTEM_EXTENSION_DIRS
+#    if defined(__OpenBSD__) || defined(__FreeBSD__)
+    static const char* const sysLExtDir = "/usr/local/share/mozilla/extensions";
+#    else
+    static const char* const sysLExtDir = "/usr/share/mozilla/extensions";
+#    endif
+    rv = NS_NewNativeLocalFile(nsDependentCString(sysLExtDir), false,
+                               getter_AddRefs(file));
+#  endif
+  }
+#endif  // defined(XP_UNIX) && !defined(XP_MACOSX)
+  else if (!strcmp(aProperty, XRE_USER_SYS_EXTENSION_DIR)) {
+#ifdef ENABLE_SYSTEM_EXTENSION_DIRS
+    rv = GetSysUserExtensionsDirectory(getter_AddRefs(file));
+#endif
+  } else if (!strcmp(aProperty, XRE_USER_RUNTIME_DIR)) {
+#if defined(XP_UNIX)
+    nsPrintfCString path("/run/user/%d/%s/", getuid(), GetAppName());
+    ToLowerCase(path);
+    rv = NS_NewNativeLocalFile(path, false, getter_AddRefs(file));
+#endif
+  } else if (!strcmp(aProperty, XRE_APP_DISTRIBUTION_DIR)) {
+    bool persistent = false;
+    rv = GetFile(NS_GRE_DIR, &persistent, getter_AddRefs(file));
+    NS_ENSURE_SUCCESS(rv, rv);
+    rv = file->AppendNative("distribution"_ns);
+  } else if (!strcmp(aProperty, XRE_APP_FEATURES_DIR)) {
+    rv = GetAppDir()->Clone(getter_AddRefs(file));
+    NS_ENSURE_SUCCESS(rv, rv);
+    rv = file->AppendNative("features"_ns);
+  } else if (!strcmp(aProperty, XRE_ADDON_APP_DIR)) {
+    nsCOMPtr<nsIDirectoryServiceProvider> dirsvc(
+        do_GetService("@mozilla.org/file/directory_service;1", &rv));
+    NS_ENSURE_SUCCESS(rv, rv);
+    bool unused;
+    rv = dirsvc->GetFile("XCurProcD", &unused, getter_AddRefs(file));
+  }
+#if defined(MOZ_CONTENT_TEMP_DIR)
+  else if (!strcmp(aProperty, NS_APP_CONTENT_PROCESS_TEMP_DIR)) {
+    if (!mContentTempDir) {
+      rv = LoadContentProcessTempDir();
+      NS_ENSURE_SUCCESS(rv, rv);
+    }
+    rv = mContentTempDir->Clone(getter_AddRefs(file));
+  }
+#endif  // defined(MOZ_CONTENT_TEMP_DIR)
+  else if (!strcmp(aProperty, NS_APP_USER_CHROME_DIR)) {
+    // We need to allow component, xpt, and chrome registration to
+    // occur prior to the profile-after-change notification.
+    rv = GetProfileStartupDir(getter_AddRefs(file));
+    NS_ENSURE_SUCCESS(rv, rv);
+    rv = file->AppendNative("chrome"_ns);
+  } else if (!strcmp(aProperty, NS_APP_PREFS_50_DIR)) {
+    rv = GetProfileDir(getter_AddRefs(file));
+  } else if (!strcmp(aProperty, NS_APP_PREFS_50_FILE)) {
+    rv = GetProfileDir(getter_AddRefs(file));
+    NS_ENSURE_SUCCESS(rv, rv);
+    rv = file->AppendNative("prefs.js"_ns);
+  } else if (!strcmp(aProperty, NS_APP_PREFS_OVERRIDE_DIR)) {
+    rv = GetProfileDir(getter_AddRefs(file));
+    NS_ENSURE_SUCCESS(rv, rv);
+    rv = file->AppendNative(nsLiteralCString(PREF_OVERRIDE_DIRNAME));
+    NS_ENSURE_SUCCESS(rv, rv);
+    rv = EnsureDirectoryExists(file);
+  } else {
+    // We don't know anything about this property. Fail without warning, because
+    // otherwise we'll get too much warning spam due to
+    // nsDirectoryService::Get() trying everything it gets with every provider.
+    return NS_ERROR_FAILURE;
+  }
+
+  NS_ENSURE_SUCCESS(rv, rv);
+  NS_ENSURE_TRUE(file, NS_ERROR_FAILURE);
+
+  file.forget(aFile);
+  return NS_OK;
+}
+
+static void LoadDirIntoArray(nsIFile* dir, const char* const* aAppendList,
+                             nsCOMArray<nsIFile>& aDirectories) {
+  if (!dir) return;
+
+  nsCOMPtr<nsIFile> subdir;
+  dir->Clone(getter_AddRefs(subdir));
+  if (!subdir) return;
+
+  for (const char* const* a = aAppendList; *a; ++a) {
+    subdir->AppendNative(nsDependentCString(*a));
+  }
+
+  bool exists;
+  if (NS_SUCCEEDED(subdir->Exists(&exists)) && exists) {
+    aDirectories.AppendObject(subdir);
+  }
+}
+
+#if defined(MOZ_CONTENT_TEMP_DIR)
+
+static const char* GetProcessTempBaseDirKey() { return NS_OS_TEMP_DIR; }
+
+//
+// Sets mContentTempDir so that it refers to the appropriate temp dir.
+// If the sandbox is enabled, NS_APP_CONTENT_PROCESS_TEMP_DIR, otherwise
+// NS_OS_TEMP_DIR is used.
+//
+nsresult nsXREDirProvider::LoadContentProcessTempDir() {
+  // The parent is responsible for creating the sandbox temp dir.
+  if (XRE_IsParentProcess()) {
+    mContentProcessSandboxTempDir =
+        CreateProcessSandboxTempDir(GeckoProcessType_Content);
+    mContentTempDir = mContentProcessSandboxTempDir;
+  } else {
+    mContentTempDir = !IsContentSandboxDisabled()
+                          ? GetProcessSandboxTempDir(GeckoProcessType_Content)
+                          : nullptr;
+  }
+
+  if (!mContentTempDir) {
+    nsresult rv =
+        NS_GetSpecialDirectory(NS_OS_TEMP_DIR, getter_AddRefs(mContentTempDir));
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+  }
+
+  return NS_OK;
+}
+
+static bool IsContentSandboxDisabled() {
+  return !mozilla::BrowserTabsRemoteAutostart() ||
+         (!mozilla::IsContentSandboxEnabled());
+}
+
+//
+// If a process sandbox temp dir is to be used, returns an nsIFile
+// for the directory. Returns null if an error occurs.
+//
+static already_AddRefed<nsIFile> GetProcessSandboxTempDir(
+    GeckoProcessType type) {
+  nsCOMPtr<nsIFile> localFile;
+
+  nsresult rv = NS_GetSpecialDirectory(GetProcessTempBaseDirKey(),
+                                       getter_AddRefs(localFile));
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return nullptr;
+  }
+
+  MOZ_ASSERT(type == GeckoProcessType_Content);
+
+  const char* prefKey = "security.sandbox.content.tempDirSuffix";
+  nsAutoString tempDirSuffix;
+  rv = mozilla::Preferences::GetString(prefKey, tempDirSuffix);
+  if (NS_WARN_IF(NS_FAILED(rv)) || tempDirSuffix.IsEmpty()) {
+    return nullptr;
+  }
+
+  rv = localFile->Append(u"Temp-"_ns + tempDirSuffix);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return nullptr;
+  }
+
+  return localFile.forget();
+}
+
+//
+// Create a temporary directory for use from sandboxed processes.
+// Only called in the parent. The path is derived from a UUID stored in a
+// pref which is available to content processes. Returns null
+// if the content sandbox is disabled or if an error occurs.
+//
+static already_AddRefed<nsIFile> CreateProcessSandboxTempDir(
+    GeckoProcessType procType) {
+  if ((procType == GeckoProcessType_Content) && IsContentSandboxDisabled()) {
+    return nullptr;
+  }
+
+  MOZ_ASSERT(procType == GeckoProcessType_Content);
+
+  // Get (and create if blank) temp directory suffix pref.
+  const char* pref = "security.sandbox.content.tempDirSuffix";
+
+  nsresult rv;
+  nsAutoString tempDirSuffix;
+  mozilla::Preferences::GetString(pref, tempDirSuffix);
+
+  if (tempDirSuffix.IsEmpty()) {
+    nsID uuid;
+    rv = nsID::GenerateUUIDInPlace(uuid);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return nullptr;
+    }
+
+    char uuidChars[NSID_LENGTH];
+    uuid.ToProvidedString(uuidChars);
+    tempDirSuffix.AssignASCII(uuidChars, NSID_LENGTH);
+#  ifdef XP_UNIX
+    // Braces in a path are somewhat annoying to deal with
+    // and pretty alien on Unix
+    tempDirSuffix.StripChars(u"{}");
+#  endif
+
+    // Save the pref
+    rv = mozilla::Preferences::SetString(pref, tempDirSuffix);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      // If we fail to save the pref we don't want to create the temp dir,
+      // because we won't be able to clean it up later.
+      return nullptr;
+    }
+
+    nsCOMPtr<nsIPrefService> prefsvc = mozilla::Preferences::GetService();
+    if (!prefsvc || NS_FAILED((rv = prefsvc->SavePrefFile(nullptr)))) {
+      // Again, if we fail to save the pref file we might not be able to clean
+      // up the temp directory, so don't create one.  Note that in the case
+      // the preference values allows an off main thread save, the successful
+      // return from the call doesn't mean we actually saved the file.  See
+      // bug 1364496 for details.
+      NS_WARNING("Failed to save pref file, cannot create temp dir.");
+      return nullptr;
+    }
+  }
+
+  nsCOMPtr<nsIFile> sandboxTempDir = GetProcessSandboxTempDir(procType);
+  if (!sandboxTempDir) {
+    NS_WARNING("Failed to determine sandbox temp dir path.");
+    return nullptr;
+  }
+
+  // Remove the directory. It may exist due to a previous crash.
+  if (NS_FAILED(DeleteDirIfExists(sandboxTempDir))) {
+    NS_WARNING("Failed to reset sandbox temp dir.");
+    return nullptr;
+  }
+
+  // Create the directory
+  rv = sandboxTempDir->Create(nsIFile::DIRECTORY_TYPE, 0700);
+  if (NS_FAILED(rv)) {
+    NS_WARNING("Failed to create sandbox temp dir.");
+    return nullptr;
+  }
+
+  return sandboxTempDir.forget();
+}
+
+static nsresult DeleteDirIfExists(nsIFile* dir) {
+  if (dir) {
+    // Don't return an error if the directory doesn't exist.
+    nsresult rv = dir->Remove(/* aRecursive */ true);
+    if (NS_FAILED(rv) && rv != NS_ERROR_FILE_NOT_FOUND) {
+      return rv;
+    }
+  }
+  return NS_OK;
+}
+
+#endif  // defined(MOZ_CONTENT_TEMP_DIR)
+
+static const char* const kAppendPrefDir[] = {"defaults", "preferences",
+                                             nullptr};
+#ifdef MOZ_BACKGROUNDTASKS
+static const char* const kAppendBackgroundTasksPrefDir[] = {
+    "defaults", "backgroundtasks", nullptr};
+#endif
+
+NS_IMETHODIMP
+nsXREDirProvider::GetFiles(const char* aProperty,
+                           nsISimpleEnumerator** aResult) {
+  nsresult rv = NS_ERROR_FAILURE;
+  *aResult = nullptr;
+
+  if (!strcmp(aProperty, NS_APP_PREFS_DEFAULTS_DIR_LIST)) {
+    nsCOMArray<nsIFile> directories;
+
+    LoadDirIntoArray(mXULAppDir, kAppendPrefDir, directories);
+#ifdef MOZ_BACKGROUNDTASKS
+    if (mozilla::BackgroundTasks::IsBackgroundTaskMode()) {
+      LoadDirIntoArray(mGREDir, kAppendBackgroundTasksPrefDir, directories);
+      LoadDirIntoArray(mXULAppDir, kAppendBackgroundTasksPrefDir, directories);
+    }
+#endif
+
+    rv = NS_NewArrayEnumerator(aResult, directories, NS_GET_IID(nsIFile));
+  } else if (!strcmp(aProperty, NS_APP_CHROME_DIR_LIST)) {
+    // NS_APP_CHROME_DIR_LIST is only used to get default (native) icons
+    // for OS window decoration.
+
+    static const char* const kAppendChromeDir[] = {"chrome", nullptr};
+    nsCOMArray<nsIFile> directories;
+    LoadDirIntoArray(mXULAppDir, kAppendChromeDir, directories);
+
+    rv = NS_NewArrayEnumerator(aResult, directories, NS_GET_IID(nsIFile));
+  }
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  return NS_SUCCESS_AGGREGATE_RESULT;
+}
+
+NS_IMETHODIMP
+nsXREDirProvider::GetDirectory(nsIFile** aResult) {
+  NS_ENSURE_TRUE(mProfileDir, NS_ERROR_NOT_INITIALIZED);
+  return mProfileDir->Clone(aResult);
+}
+
+void nsXREDirProvider::InitializeUserPrefs() {
+  if (!mPrefsInitialized) {
+    mozilla::Preferences::InitializeUserPrefs();
+  }
+}
+
+void nsXREDirProvider::FinishInitializingUserPrefs() {
+  if (!mPrefsInitialized) {
+    mozilla::Preferences::FinishInitializingUserPrefs();
+    mPrefsInitialized = true;
+  }
+}
+
+NS_IMETHODIMP
+nsXREDirProvider::DoStartup() {
+  nsresult rv;
+
+  if (!mAppStarted) {
+    nsCOMPtr<nsIObserverService> obsSvc =
+        mozilla::services::GetObserverService();
+    if (!obsSvc) return NS_ERROR_FAILURE;
+
+    mAppStarted = true;
+
+    /*
+       Make sure we've setup prefs before profile-do-change to be able to use
+       them to track crashes and because we want to begin crash tracking before
+       other code run from this notification since they may cause crashes.
+    */
+    MOZ_ASSERT(mPrefsInitialized);
+
+    bool safeModeNecessary = false;
+    nsCOMPtr<nsIAppStartup> appStartup(
+        mozilla::components::AppStartup::Service());
+    if (appStartup) {
+      rv = appStartup->TrackStartupCrashBegin(&safeModeNecessary);
+      if (NS_FAILED(rv) && rv != NS_ERROR_NOT_AVAILABLE)
+        NS_WARNING("Error while beginning startup crash tracking");
+
+      if (!gSafeMode && safeModeNecessary) {
+        appStartup->RestartInSafeMode(nsIAppStartup::eForceQuit);
+        return NS_OK;
+      }
+    }
+
+    static const char16_t kStartup[] = {'s', 't', 'a', 'r',
+                                        't', 'u', 'p', '\0'};
+    obsSvc->NotifyObservers(nullptr, "profile-do-change", kStartup);
+
+    // Initialize the Enterprise Policies service in the parent process
+    // In the content process it's loaded on demand when needed
+    if (XRE_IsParentProcess()) {
+      nsCOMPtr<nsIObserver> policies(
+          do_GetService("@mozilla.org/enterprisepolicies;1"));
+      if (policies) {
+        policies->Observe(nullptr, "policies-startup", nullptr);
+      }
+    }
+
+#ifdef MOZ_THUNDERBIRD
+    bool bgtaskMode = false;
+#  ifdef MOZ_BACKGROUNDTASKS
+    bgtaskMode = mozilla::BackgroundTasks::IsBackgroundTaskMode();
+#  endif
+    if (!bgtaskMode &&
+        mozilla::Preferences::GetBool(
+            "security.prompt_for_master_password_on_startup", false)) {
+      // Prompt for the master password prior to opening application windows,
+      // to avoid the race that triggers multiple prompts (see bug 177175).
+      // We use this code until we have a better solution, possibly as
+      // described in bug 177175 comment 384.
+      nsCOMPtr<nsIPK11TokenDB> db =
+          do_GetService("@mozilla.org/security/pk11tokendb;1");
+      if (db) {
+        nsCOMPtr<nsIPK11Token> token;
+        if (NS_SUCCEEDED(db->GetInternalKeyToken(getter_AddRefs(token)))) {
+          mozilla::Unused << token->Login(false);
+        }
+      } else {
+        NS_WARNING("Failed to get nsIPK11TokenDB service.");
+      }
+    }
+#endif
+
+    bool initExtensionManager =
+#ifdef MOZ_BACKGROUNDTASKS
+        !mozilla::BackgroundTasks::IsBackgroundTaskMode();
+#else
+        true;
+#endif
+    if (initExtensionManager) {
+      // Init the Extension Manager
+      nsCOMPtr<nsIObserver> em =
+          do_GetService("@mozilla.org/addons/integration;1");
+      if (em) {
+        em->Observe(nullptr, "addons-startup", nullptr);
+      } else {
+        NS_WARNING("Failed to create Addons Manager.");
+      }
+    }
+
+    obsSvc->NotifyObservers(nullptr, "profile-after-change", kStartup);
+
+    // Any component that has registered for the profile-after-change category
+    // should also be created at this time.
+    (void)NS_CreateServicesFromCategory("profile-after-change", nullptr,
+                                        "profile-after-change");
+
+    if (gSafeMode && safeModeNecessary) {
+      static const char16_t kCrashed[] = {'c', 'r', 'a', 's',
+                                          'h', 'e', 'd', '\0'};
+      obsSvc->NotifyObservers(nullptr, "safemode-forced", kCrashed);
+    }
+
+    // 1 = Regular mode, 2 = Safe mode, 3 = Safe mode forced
+    int mode = 1;
+    if (gSafeMode) {
+      if (safeModeNecessary)
+        mode = 3;
+      else
+        mode = 2;
+    }
+    mozilla::Telemetry::Accumulate(mozilla::Telemetry::SAFE_MODE_USAGE, mode);
+
+    obsSvc->NotifyObservers(nullptr, "profile-initial-state", nullptr);
+
+#if defined(MOZ_CONTENT_TEMP_DIR)
+    // Makes sure the content temp dir has been loaded if it hasn't been
+    // already. In the parent this ensures it has been created before we attempt
+    // to start any content processes.
+    if (!mContentTempDir) {
+      mozilla::Unused << NS_WARN_IF(NS_FAILED(LoadContentProcessTempDir()));
+    }
+#endif
+  }
+  return NS_OK;
+}
+
+void nsXREDirProvider::DoShutdown() {
+  AUTO_PROFILER_LABEL("nsXREDirProvider::DoShutdown", OTHER);
+
+  if (mAppStarted) {
+    mozilla::AppShutdown::AdvanceShutdownPhase(
+        mozilla::ShutdownPhase::AppShutdownNetTeardown, nullptr);
+    mozilla::AppShutdown::AdvanceShutdownPhase(
+        mozilla::ShutdownPhase::AppShutdownTeardown, nullptr);
+
+#ifdef DEBUG
+    // Not having this causes large intermittent leaks. See bug 1340425.
+    if (JSContext* cx = mozilla::dom::danger::GetJSContext()) {
+      JS_GC(cx);
+    }
+#endif
+
+    mozilla::AppShutdown::AdvanceShutdownPhase(
+        mozilla::ShutdownPhase::AppShutdown, nullptr);
+    mozilla::AppShutdown::AdvanceShutdownPhase(
+        mozilla::ShutdownPhase::AppShutdownQM, nullptr);
+    mozilla::AppShutdown::AdvanceShutdownPhase(
+        mozilla::ShutdownPhase::AppShutdownTelemetry, nullptr);
+    mAppStarted = false;
+  }
+
+  gDataDirProfileLocal = nullptr;
+  gDataDirProfile = nullptr;
+
+#if defined(MOZ_CONTENT_TEMP_DIR)
+  if (XRE_IsParentProcess()) {
+    mozilla::Unused << DeleteDirIfExists(mContentProcessSandboxTempDir);
+  }
+#endif
+}
+
+#ifdef XP_WIN
+static nsresult GetShellFolderPath(KNOWNFOLDERID folder, nsAString& _retval) {
+  DWORD flags = KF_FLAG_SIMPLE_IDLIST | KF_FLAG_DONT_VERIFY | KF_FLAG_NO_ALIAS;
+  PWSTR path = nullptr;
+
+  if (!SUCCEEDED(SHGetKnownFolderPath(folder, flags, NULL, &path))) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  _retval = nsDependentString(path);
+  CoTaskMemFree(path);
+  return NS_OK;
+}
+
+/**
+ * Provides a fallback for getting the path to APPDATA or LOCALAPPDATA by
+ * querying the registry when the call to SHGetSpecialFolderLocation or
+ * SHGetPathFromIDListW is unable to provide these paths (Bug 513958).
+ */
+static nsresult GetRegWindowsAppDataFolder(bool aLocal, nsAString& _retval) {
+  HKEY key;
+  LPCWSTR keyName =
+      L"Software\\Microsoft\\Windows\\CurrentVersion\\Explorer\\Shell Folders";
+  DWORD res = ::RegOpenKeyExW(HKEY_CURRENT_USER, keyName, 0, KEY_READ, &key);
+  if (res != ERROR_SUCCESS) {
+    _retval.SetLength(0);
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  DWORD type, size;
+  res = RegQueryValueExW(key, (aLocal ? L"Local AppData" : L"AppData"), nullptr,
+                         &type, nullptr, &size);
+  // The call to RegQueryValueExW must succeed, the type must be REG_SZ, the
+  // buffer size must not equal 0, and the buffer size be a multiple of 2.
+  if (res != ERROR_SUCCESS || type != REG_SZ || size == 0 || size % 2 != 0) {
+    ::RegCloseKey(key);
+    _retval.SetLength(0);
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  // |size| may or may not include room for the terminating null character
+  DWORD resultLen = size / 2;
+
+  if (!_retval.SetLength(resultLen, mozilla::fallible)) {
+    ::RegCloseKey(key);
+    _retval.SetLength(0);
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  auto begin = _retval.BeginWriting();
+
+  res = RegQueryValueExW(key, (aLocal ? L"Local AppData" : L"AppData"), nullptr,
+                         nullptr, (LPBYTE)begin, &size);
+  ::RegCloseKey(key);
+  if (res != ERROR_SUCCESS) {
+    _retval.SetLength(0);
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  if (!_retval.CharAt(resultLen - 1)) {
+    // It was already null terminated.
+    _retval.Truncate(resultLen - 1);
+  }
+
+  return NS_OK;
+}
+#endif
+
+static nsresult HashInstallPath(nsAString& aInstallPath, nsAString& aPathHash) {
+  mozilla::UniquePtr<NS_tchar[]> hash;
+  bool success = ::GetInstallHash(PromiseFlatString(aInstallPath).get(), hash);
+  if (!success) {
+    return NS_ERROR_FAILURE;
+  }
+
+  // The hash string is a NS_tchar*, which is wchar* in Windows and char*
+  // elsewhere.
+#ifdef XP_WIN
+  aPathHash.Assign(hash.get());
+#else
+  aPathHash.AssignASCII(hash.get());
+#endif
+  return NS_OK;
+}
+
+/**
+ * Gets a hash of the installation directory.
+ */
+nsresult nsXREDirProvider::GetInstallHash(nsAString& aPathHash) {
+  nsAutoString stringToHash;
+
+#ifdef XP_WIN
+  if (mozilla::widget::WinUtils::HasPackageIdentity()) {
+    // For packages, the install path includes the version number, so it isn't
+    // a stable or consistent identifier for the installation. The package
+    // family name is though, so use that instead of the path.
+    stringToHash = mozilla::widget::WinUtils::GetPackageFamilyName();
+  } else
+#endif
+  {
+    nsCOMPtr<nsIFile> installDir;
+    nsCOMPtr<nsIFile> appFile;
+    bool per = false;
+    nsresult rv = GetFile(XRE_EXECUTABLE_FILE, &per, getter_AddRefs(appFile));
+    NS_ENSURE_SUCCESS(rv, rv);
+    rv = appFile->GetParent(getter_AddRefs(installDir));
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    // It is possible that the path we have is on a case insensitive
+    // filesystem in which case the path may vary depending on how the
+    // application is called. We want to normalize the case somehow.
+#ifdef XP_WIN
+    // Windows provides a way to get the correct case.
+    if (!mozilla::widget::WinUtils::ResolveJunctionPointsAndSymLinks(
+            installDir)) {
+      NS_WARNING("Failed to resolve install directory.");
+    }
+#elif defined(MOZ_WIDGET_COCOA)
+    // On OSX roundtripping through an FSRef fixes the case.
+    FSRef ref;
+    nsCOMPtr<nsILocalFileMac> macFile = do_QueryInterface(installDir);
+    rv = macFile->GetFSRef(&ref);
+    NS_ENSURE_SUCCESS(rv, rv);
+    rv = NS_NewLocalFileWithFSRef(&ref, true, getter_AddRefs(macFile));
+    NS_ENSURE_SUCCESS(rv, rv);
+    installDir = static_cast<nsIFile*>(macFile);
+#endif
+    // On linux XRE_EXECUTABLE_FILE already seems to be set to the correct path.
+
+    rv = installDir->GetPath(stringToHash);
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+
+  // If we somehow failed to get an actual value, hashing an empty string could
+  // potentially cause some serious problems given all the things this hash is
+  // used for. So we don't allow that.
+  if (stringToHash.IsEmpty()) {
+    return NS_ERROR_FAILURE;
+  }
+
+  return HashInstallPath(stringToHash, aPathHash);
+}
+
+/**
+ * Before bug 1555319 the directory hashed can have had an incorrect case.
+ * Access to that hash is still available through this function. It is needed so
+ * we can migrate users who may have an incorrect hash in profiles.ini. This
+ * support can probably be removed in a few releases time.
+ */
+nsresult nsXREDirProvider::GetLegacyInstallHash(nsAString& aPathHash) {
+  nsCOMPtr<nsIFile> installDir;
+  nsCOMPtr<nsIFile> appFile;
+  bool per = false;
+  nsresult rv = GetFile(XRE_EXECUTABLE_FILE, &per, getter_AddRefs(appFile));
+  NS_ENSURE_SUCCESS(rv, rv);
+  rv = appFile->GetParent(getter_AddRefs(installDir));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsAutoString installPath;
+  rv = installDir->GetPath(installPath);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+#ifdef XP_WIN
+#  if defined(MOZ_THUNDERBIRD) || defined(MOZ_SUITE)
+  // Convert a 64-bit install path to what would have been the 32-bit install
+  // path to allow users to migrate their profiles from one to the other.
+  PWSTR pathX86 = nullptr;
+  HRESULT hres =
+      SHGetKnownFolderPath(FOLDERID_ProgramFilesX86, 0, nullptr, &pathX86);
+  if (SUCCEEDED(hres)) {
+    nsDependentString strPathX86(pathX86);
+    if (!StringBeginsWith(installPath, strPathX86,
+                          nsCaseInsensitiveStringComparator)) {
+      PWSTR path = nullptr;
+      hres = SHGetKnownFolderPath(FOLDERID_ProgramFiles, 0, nullptr, &path);
+      if (SUCCEEDED(hres)) {
+        if (StringBeginsWith(installPath, nsDependentString(path),
+                             nsCaseInsensitiveStringComparator)) {
+          installPath.Replace(0, wcslen(path), strPathX86);
+        }
+      }
+      CoTaskMemFree(path);
+    }
+  }
+  CoTaskMemFree(pathX86);
+#  endif
+#endif
+  return HashInstallPath(installPath, aPathHash);
+}
+
+nsresult nsXREDirProvider::GetUpdateRootDir(nsIFile** aResult,
+                                            bool aGetOldLocation) {
+#ifndef XP_WIN
+  // There is no old update location on platforms other than Windows. Windows is
+  // the only platform for which we migrated the update directory.
+  if (aGetOldLocation) {
+    return NS_ERROR_NOT_IMPLEMENTED;
+  }
+#endif
+  nsCOMPtr<nsIFile> updRoot;
+  nsCOMPtr<nsIFile> appFile;
+  bool per = false;
+  nsresult rv = GetFile(XRE_EXECUTABLE_FILE, &per, getter_AddRefs(appFile));
+  NS_ENSURE_SUCCESS(rv, rv);
+  rv = appFile->GetParent(getter_AddRefs(updRoot));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+#ifdef XP_MACOSX
+  nsCOMPtr<nsIFile> appRootDirFile;
+  nsCOMPtr<nsIFile> localDir;
+  nsAutoString appDirPath;
+  if (NS_FAILED(appFile->GetParent(getter_AddRefs(appRootDirFile))) ||
+      NS_FAILED(appRootDirFile->GetPath(appDirPath)) ||
+      NS_FAILED(GetUserDataDirectoryHome(getter_AddRefs(localDir), true))) {
+    return NS_ERROR_FAILURE;
+  }
+
+  int32_t dotIndex = appDirPath.RFind(u".app");
+  if (dotIndex == kNotFound) {
+    dotIndex = appDirPath.Length();
+  }
+  appDirPath = Substring(appDirPath, 1, dotIndex - 1);
+
+  bool hasVendor = GetAppVendor() && strlen(GetAppVendor()) != 0;
+  if (hasVendor || GetAppName()) {
+    if (NS_FAILED(localDir->AppendNative(
+            nsDependentCString(hasVendor ? GetAppVendor() : GetAppName())))) {
+      return NS_ERROR_FAILURE;
+    }
+  } else if (NS_FAILED(localDir->AppendNative("Mozilla"_ns))) {
+    return NS_ERROR_FAILURE;
+  }
+
+  if (NS_FAILED(localDir->Append(u"updates"_ns)) ||
+      NS_FAILED(localDir->AppendRelativePath(appDirPath))) {
+    return NS_ERROR_FAILURE;
+  }
+
+  localDir.forget(aResult);
+  return NS_OK;
+
+#elif XP_WIN
+  nsAutoString installPath;
+  rv = updRoot->GetPath(installPath);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  mozilla::UniquePtr<wchar_t[]> updatePath;
+  HRESULT hrv;
+  if (aGetOldLocation) {
+    hrv =
+        GetOldUpdateDirectory(PromiseFlatString(installPath).get(), updatePath);
+  } else {
+    hrv = GetCommonUpdateDirectory(PromiseFlatString(installPath).get(),
+                                   updatePath);
+  }
+  if (FAILED(hrv)) {
+    return NS_ERROR_FAILURE;
+  }
+  nsAutoString updatePathStr;
+  updatePathStr.Assign(updatePath.get());
+  updRoot->InitWithPath(updatePathStr);
+  updRoot.forget(aResult);
+  return NS_OK;
+#else
+  updRoot.forget(aResult);
+  return NS_OK;
+#endif  // XP_WIN
+}
+
+nsresult nsXREDirProvider::GetProfileStartupDir(nsIFile** aResult) {
+  NS_ENSURE_TRUE(mProfileDir, NS_ERROR_FAILURE);
+  return mProfileDir->Clone(aResult);
+}
+
+nsresult nsXREDirProvider::GetProfileDir(nsIFile** aResult) {
+  if (!mProfileDir) {
+    nsresult rv = NS_GetSpecialDirectory(NS_APP_USER_PROFILE_50_DIR,
+                                         getter_AddRefs(mProfileDir));
+    NS_ENSURE_SUCCESS(rv, rv);
+    NS_ENSURE_TRUE(mProfileDir, NS_ERROR_FAILURE);
+  }
+  return mProfileDir->Clone(aResult);
+}
+
+NS_IMETHODIMP
+nsXREDirProvider::SetUserDataDirectory(nsIFile* aFile, bool aLocal) {
+  if (aLocal) {
+    NS_IF_RELEASE(gDataDirHomeLocal);
+    NS_IF_ADDREF(gDataDirHomeLocal = aFile);
+  } else {
+    NS_IF_RELEASE(gDataDirHome);
+    NS_IF_ADDREF(gDataDirHome = aFile);
+  }
+
+  return NS_OK;
+}
+
+/* static */
+nsresult nsXREDirProvider::SetUserDataProfileDirectory(nsCOMPtr<nsIFile>& aFile,
+                                                       bool aLocal) {
+  if (aLocal) {
+    gDataDirProfileLocal = aFile;
+  } else {
+    gDataDirProfile = aFile;
+  }
+
+  return NS_OK;
+}
+
+nsresult nsXREDirProvider::GetUserDataDirectoryHome(nsIFile** aFile,
+                                                    bool aLocal) {
+  // Copied from nsAppFileLocationProvider (more or less)
+  nsresult rv;
+  nsCOMPtr<nsIFile> localDir;
+
+  if (aLocal && gDataDirHomeLocal) {
+    return gDataDirHomeLocal->Clone(aFile);
+  }
+  if (!aLocal && gDataDirHome) {
+    return gDataDirHome->Clone(aFile);
+  }
+
+#if defined(XP_MACOSX)
+  FSRef fsRef;
+  OSType folderType;
+  if (aLocal) {
+    folderType = kCachedDataFolderType;
+  } else {
+#  ifdef MOZ_THUNDERBIRD
+    folderType = kDomainLibraryFolderType;
+#  else
+    folderType = kApplicationSupportFolderType;
+#  endif
+  }
+  OSErr err = ::FSFindFolder(kUserDomain, folderType, kCreateFolder, &fsRef);
+  NS_ENSURE_FALSE(err, NS_ERROR_FAILURE);
+
+  rv = NS_NewNativeLocalFile(""_ns, true, getter_AddRefs(localDir));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsCOMPtr<nsILocalFileMac> dirFileMac = do_QueryInterface(localDir);
+  NS_ENSURE_TRUE(dirFileMac, NS_ERROR_UNEXPECTED);
+
+  rv = dirFileMac->InitWithFSRef(&fsRef);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  localDir = dirFileMac;
+#elif defined(XP_IOS)
+  nsAutoCString userDir;
+  if (GetUIKitDirectory(aLocal, userDir)) {
+    rv = NS_NewNativeLocalFile(userDir, true, getter_AddRefs(localDir));
+  } else {
+    rv = NS_ERROR_FAILURE;
+  }
+  NS_ENSURE_SUCCESS(rv, rv);
+#elif defined(XP_WIN)
+  nsString path;
+  if (aLocal) {
+    rv = GetShellFolderPath(FOLDERID_LocalAppData, path);
+    if (NS_FAILED(rv)) rv = GetRegWindowsAppDataFolder(aLocal, path);
+  }
+  if (!aLocal || NS_FAILED(rv)) {
+    rv = GetShellFolderPath(FOLDERID_RoamingAppData, path);
+    if (NS_FAILED(rv)) {
+      if (!aLocal) rv = GetRegWindowsAppDataFolder(aLocal, path);
+    }
+  }
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  rv = NS_NewLocalFile(path, true, getter_AddRefs(localDir));
+#elif defined(XP_UNIX)
+  const char* homeDir = getenv("HOME");
+  if (!homeDir || !*homeDir) return NS_ERROR_FAILURE;
+
+#  ifdef ANDROID /* We want (ProfD == ProfLD) on Android. */
+  aLocal = false;
+#  endif
+
+  if (aLocal) {
+    // If $XDG_CACHE_HOME is defined use it, otherwise use $HOME/.cache.
+    const char* cacheHome = getenv("XDG_CACHE_HOME");
+    if (cacheHome && *cacheHome) {
+      rv = NS_NewNativeLocalFile(nsDependentCString(cacheHome), true,
+                                 getter_AddRefs(localDir));
+    } else {
+      rv = NS_NewNativeLocalFile(nsDependentCString(homeDir), true,
+                                 getter_AddRefs(localDir));
+      if (NS_SUCCEEDED(rv)) rv = localDir->AppendNative(".cache"_ns);
+    }
+  } else {
+    rv = NS_NewNativeLocalFile(nsDependentCString(homeDir), true,
+                               getter_AddRefs(localDir));
+  }
+#else
+#  error "Don't know how to get product dir on your platform"
+#endif
+
+  NS_IF_ADDREF(*aFile = localDir);
+  return rv;
+}
+
+nsresult nsXREDirProvider::GetSysUserExtensionsDirectory(nsIFile** aFile) {
+  nsCOMPtr<nsIFile> localDir;
+  nsresult rv = GetUserDataDirectoryHome(getter_AddRefs(localDir), false);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  rv = AppendSysUserExtensionPath(localDir);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  rv = EnsureDirectoryExists(localDir);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  localDir.forget(aFile);
+  return NS_OK;
+}
+
+#if defined(XP_UNIX) || defined(XP_MACOSX)
+nsresult nsXREDirProvider::GetSystemExtensionsDirectory(nsIFile** aFile) {
+  nsresult rv;
+  nsCOMPtr<nsIFile> localDir;
+
+  rv = GetSystemParentDirectory(getter_AddRefs(localDir));
+  if (NS_SUCCEEDED(rv)) {
+    constexpr auto sExtensions =
+#  if defined(XP_MACOSX)
+        "Extensions"_ns
+#  else
+        "extensions"_ns
+#  endif
+        ;
+
+    rv = localDir->AppendNative(sExtensions);
+    if (NS_SUCCEEDED(rv)) {
+      localDir.forget(aFile);
+    }
+  }
+  return rv;
+}
+#endif
+
+nsresult nsXREDirProvider::GetUserDataDirectory(nsIFile** aFile, bool aLocal) {
+  nsCOMPtr<nsIFile> localDir;
+
+  if (aLocal && gDataDirProfileLocal) {
+    return gDataDirProfileLocal->Clone(aFile);
+  }
+  if (!aLocal && gDataDirProfile) {
+    return gDataDirProfile->Clone(aFile);
+  }
+
+  nsresult rv = GetUserDataDirectoryHome(getter_AddRefs(localDir), aLocal);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  rv = AppendProfilePath(localDir, aLocal);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  rv = EnsureDirectoryExists(localDir);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsXREDirProvider::SetUserDataProfileDirectory(localDir, aLocal);
+
+  localDir.forget(aFile);
+  return NS_OK;
+}
+
+nsresult nsXREDirProvider::EnsureDirectoryExists(nsIFile* aDirectory) {
+  nsresult rv = aDirectory->Create(nsIFile::DIRECTORY_TYPE, 0700);
+
+  if (rv == NS_ERROR_FILE_ALREADY_EXISTS) {
+    rv = NS_OK;
+  }
+  return rv;
+}
+
+nsresult nsXREDirProvider::AppendSysUserExtensionPath(nsIFile* aFile) {
+  NS_ASSERTION(aFile, "Null pointer!");
+
+  nsresult rv;
+
+#if defined(XP_MACOSX) || defined(XP_WIN)
+
+  static const char* const sXR = "Mozilla";
+  rv = aFile->AppendNative(nsDependentCString(sXR));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  static const char* const sExtensions = "Extensions";
+  rv = aFile->AppendNative(nsDependentCString(sExtensions));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+#elif defined(XP_UNIX)
+
+  static const char* const sXR = ".mozilla";
+  rv = aFile->AppendNative(nsDependentCString(sXR));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  static const char* const sExtensions = "extensions";
+  rv = aFile->AppendNative(nsDependentCString(sExtensions));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+#else
+#  error "Don't know how to get XRE user extension path on your platform"
+#endif
+  return NS_OK;
+}
+
+nsresult nsXREDirProvider::AppendProfilePath(nsIFile* aFile, bool aLocal) {
+  NS_ASSERTION(aFile, "Null pointer!");
+
+  // If there is no XREAppData then there is no information to use to build
+  // the profile path so just do nothing. This should only happen in xpcshell
+  // tests.
+  if (!gAppData) {
+    return NS_OK;
+  }
+
+  nsAutoCString profile;
+  nsAutoCString appName;
+  nsAutoCString vendor;
+  if (gAppData->profile) {
+    profile = gAppData->profile;
+  } else {
+    appName = gAppData->name;
+    vendor = gAppData->vendor;
+  }
+
+  nsresult rv = NS_OK;
+
+#if defined(XP_MACOSX)
+  if (!profile.IsEmpty()) {
+    rv = AppendProfileString(aFile, profile.get());
+  } else {
+    // Note that MacOS ignores the vendor when creating the profile hierarchy -
+    // all application preferences directories live alongside one another in
+    // ~/Library/Application Support/
+    rv = aFile->AppendNative(appName);
+  }
+  NS_ENSURE_SUCCESS(rv, rv);
+
+#elif defined(XP_WIN)
+  if (!profile.IsEmpty()) {
+    rv = AppendProfileString(aFile, profile.get());
+  } else {
+    if (!vendor.IsEmpty()) {
+      rv = aFile->AppendNative(vendor);
+      NS_ENSURE_SUCCESS(rv, rv);
+    }
+    rv = aFile->AppendNative(appName);
+  }
+  NS_ENSURE_SUCCESS(rv, rv);
+
+#elif defined(ANDROID)
+  // The directory used for storing profiles
+  // The parent of this directory is set in GetUserDataDirectoryHome
+  // XXX: handle gAppData->profile properly
+  // XXXsmaug ...and the rest of the profile creation!
+  rv = aFile->AppendNative(nsDependentCString("mozilla"));
+  NS_ENSURE_SUCCESS(rv, rv);
+#elif defined(XP_UNIX)
+  nsAutoCString folder;
+  // Make it hidden (by starting with "."), except when local (the
+  // profile is already under ~/.cache or XDG_CACHE_HOME).
+  if (!aLocal) folder.Assign('.');
+
+  if (!profile.IsEmpty()) {
+    // Skip any leading path characters
+    const char* profileStart = profile.get();
+    while (*profileStart == '/' || *profileStart == '\\') profileStart++;
+
+    // On the off chance that someone wanted their folder to be hidden don't
+    // let it become ".."
+    if (*profileStart == '.' && !aLocal) profileStart++;
+
+    folder.Append(profileStart);
+    ToLowerCase(folder);
+
+    rv = AppendProfileString(aFile, folder.BeginReading());
+  } else {
+    if (!vendor.IsEmpty()) {
+      folder.Append(vendor);
+      ToLowerCase(folder);
+
+      rv = aFile->AppendNative(folder);
+      NS_ENSURE_SUCCESS(rv, rv);
+
+      folder.Truncate();
+    }
+
+    // This can be the case in tests.
+    if (!appName.IsEmpty()) {
+      folder.Append(appName);
+      ToLowerCase(folder);
+
+      rv = aFile->AppendNative(folder);
+    }
+  }
+  NS_ENSURE_SUCCESS(rv, rv);
+
+#else
+#  error "Don't know how to get profile path on your platform"
+#endif
+  return NS_OK;
+}
+
+nsresult nsXREDirProvider::AppendProfileString(nsIFile* aFile,
+                                               const char* aPath) {
+  NS_ASSERTION(aFile, "Null file!");
+  NS_ASSERTION(aPath, "Null path!");
+
+  nsAutoCString pathDup(aPath);
+
+  char* path = pathDup.BeginWriting();
+
+  nsresult rv;
+  char* subdir;
+  while ((subdir = NS_strtok("/\\", &path))) {
+    rv = aFile->AppendNative(nsDependentCString(subdir));
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+
+  return NS_OK;
+}
diff --git a/toolkit/xre/nsXREDirProvider.h b/toolkit/xre/nsXREDirProvider.h
new file mode 100644
index 0000000000..e25fccda22
--- /dev/null
+++ b/toolkit/xre/nsXREDirProvider.h
@@ -0,0 +1,158 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef _nsXREDirProvider_h__
+#define _nsXREDirProvider_h__
+
+#include "nsIDirectoryService.h"
+#include "nsIProfileMigrator.h"
+#include "nsIFile.h"
+#include "nsIXREDirProvider.h"
+
+#include "nsCOMPtr.h"
+#include "nsCOMArray.h"
+#include "mozilla/Attributes.h"
+#ifdef MOZ_BACKGROUNDTASKS
+#  include "mozilla/BackgroundTasks.h"
+#endif
+
+// {5573967d-f6cf-4c63-8e0e-9ac06e04d62b}
+#define NS_XREDIRPROVIDER_CID                        \
+  {                                                  \
+    0x5573967d, 0xf6cf, 0x4c63, {                    \
+      0x8e, 0x0e, 0x9a, 0xc0, 0x6e, 0x04, 0xd6, 0x2b \
+    }                                                \
+  }
+#define NS_XREDIRPROVIDER_CONTRACTID "@mozilla.org/xre/directory-provider;1"
+
+class nsXREDirProvider final : public nsIDirectoryServiceProvider2,
+                               public nsIXREDirProvider,
+                               public nsIProfileStartup {
+ public:
+  // we use a custom isupports implementation (no refcount)
+  NS_IMETHOD QueryInterface(REFNSIID aIID, void** aInstancePtr) override;
+  NS_IMETHOD_(MozExternalRefCountType) AddRef(void) override;
+  NS_IMETHOD_(MozExternalRefCountType) Release(void) override;
+
+  NS_DECL_NSIDIRECTORYSERVICEPROVIDER
+  NS_DECL_NSIDIRECTORYSERVICEPROVIDER2
+  NS_DECL_NSIXREDIRPROVIDER
+  NS_DECL_NSIPROFILESTARTUP
+
+  nsXREDirProvider();
+
+  nsresult Initialize(nsIFile* aXULAppDir, nsIFile* aGREDir);
+  ~nsXREDirProvider();
+
+  static already_AddRefed<nsXREDirProvider> GetSingleton();
+
+  nsresult GetUserProfilesRootDir(nsIFile** aResult);
+  nsresult GetUserProfilesLocalDir(nsIFile** aResult);
+#ifdef MOZ_BACKGROUNDTASKS
+  // A special location for non-ephemeral background tasks profiles,
+  // distinct from user profiles.
+  nsresult GetBackgroundTasksProfilesRootDir(nsIFile** aResult);
+#endif
+
+  nsresult GetLegacyInstallHash(nsAString& aPathHash);
+
+  nsresult SetProfile(nsIFile* aProfileDir, nsIFile* aProfileLocalDir);
+
+  void InitializeUserPrefs();
+  void FinishInitializingUserPrefs();
+
+  void DoShutdown();
+
+  static nsresult GetUserAppDataDirectory(nsIFile** aFile) {
+    return GetUserDataDirectory(aFile, false);
+  }
+  static nsresult GetUserLocalDataDirectory(nsIFile** aFile) {
+    return GetUserDataDirectory(aFile, true);
+  }
+
+  static nsresult GetUserDataDirectory(nsIFile** aFile, bool aLocal);
+
+  /* make sure you clone it, if you need to do stuff to it */
+  nsIFile* GetGREDir() { return mGREDir; }
+  nsIFile* GetGREBinDir() { return mGREBinDir; }
+  nsIFile* GetAppDir() {
+    if (mXULAppDir) return mXULAppDir;
+    return mGREDir;
+  }
+
+  /**
+   * Get the directory under which update directory is created.
+   * This method may be called before XPCOM is started. aResult
+   * is a clone, it may be modified.
+   *
+   * If aGetOldLocation is true, this function will return the location of
+   * the update directory before it was moved from the user profile directory
+   * to a per-installation directory. This functionality is only meant to be
+   * used for migration of the update directory to the new location. It is only
+   * valid to request the old update location on Windows, since that is the only
+   * platform on which the update directory was migrated.
+   */
+  nsresult GetUpdateRootDir(nsIFile** aResult, bool aGetOldLocation = false);
+
+  /**
+   * Get the profile startup directory.
+   * This method may be called before XPCOM is started. aResult
+   * is a clone, it may be modified.
+   */
+  nsresult GetProfileStartupDir(nsIFile** aResult);
+
+  /**
+   * Get the profile directory. Only call this method
+   * when XPCOM is initialized! aResult is a clone, it may be modified.
+   */
+  nsresult GetProfileDir(nsIFile** aResult);
+
+ private:
+  nsresult GetFilesInternal(const char* aProperty,
+                            nsISimpleEnumerator** aResult);
+  static nsresult GetUserDataDirectoryHome(nsIFile** aFile, bool aLocal);
+  static nsresult GetSysUserExtensionsDirectory(nsIFile** aFile);
+#if defined(XP_UNIX) || defined(XP_MACOSX)
+  static nsresult GetSystemExtensionsDirectory(nsIFile** aFile);
+#endif
+  static nsresult EnsureDirectoryExists(nsIFile* aDirectory);
+
+  // Determine the profile path within the UAppData directory. This is different
+  // on every major platform.
+  static nsresult AppendProfilePath(nsIFile* aFile, bool aLocal);
+
+  static nsresult AppendSysUserExtensionPath(nsIFile* aFile);
+
+  // Internal helper that splits a path into components using the '/' and '\\'
+  // delimiters.
+  static inline nsresult AppendProfileString(nsIFile* aFile, const char* aPath);
+
+  static nsresult SetUserDataProfileDirectory(nsCOMPtr<nsIFile>& aFile,
+                                              bool aLocal);
+
+#if defined(MOZ_CONTENT_TEMP_DIR)
+  // Load the temp directory for sandboxed content processes
+  nsresult LoadContentProcessTempDir();
+#endif
+
+  void Append(nsIFile* aDirectory);
+
+  // On OSX, mGREDir points to .app/Contents/Resources
+  nsCOMPtr<nsIFile> mGREDir;
+  // On OSX, mGREBinDir points to .app/Contents/MacOS
+  nsCOMPtr<nsIFile> mGREBinDir;
+  // On OSX, mXULAppDir points to .app/Contents/Resources/browser
+  nsCOMPtr<nsIFile> mXULAppDir;
+  nsCOMPtr<nsIFile> mProfileDir;
+  nsCOMPtr<nsIFile> mProfileLocalDir;
+  bool mAppStarted = false;
+  bool mPrefsInitialized = false;
+#if defined(MOZ_CONTENT_TEMP_DIR)
+  nsCOMPtr<nsIFile> mContentTempDir;
+  nsCOMPtr<nsIFile> mContentProcessSandboxTempDir;
+#endif
+};
+
+#endif
diff --git a/toolkit/xre/platform.ini b/toolkit/xre/platform.ini
new file mode 100644
index 0000000000..01c8b741a1
--- /dev/null
+++ b/toolkit/xre/platform.ini
@@ -0,0 +1,17 @@
+#if 0
+; This Source Code Form is subject to the terms of the Mozilla Public
+; License, v. 2.0. If a copy of the MPL was not distributed with this
+; file, You can obtain one at http://mozilla.org/MPL/2.0/.
+#endif
+#filter substitution
+#include @TOPOBJDIR@/buildid.h
+#include @TOPOBJDIR@/source-repo.h
+[Build]
+BuildID=@MOZ_BUILDID@
+Milestone=@GRE_MILESTONE@
+#ifdef MOZ_SOURCE_REPO
+SourceRepository=@MOZ_SOURCE_REPO@
+#endif
+#ifdef MOZ_SOURCE_STAMP
+SourceStamp=@MOZ_SOURCE_STAMP@
+#endif
diff --git a/toolkit/xre/test/browser.ini b/toolkit/xre/test/browser.ini
new file mode 100644
index 0000000000..7f6eaced59
--- /dev/null
+++ b/toolkit/xre/test/browser.ini
@@ -0,0 +1,4 @@
+[DEFAULT]
+
+[browser_checkdllblockliststate.js]
+skip-if = os != "win" || ccov # Bug 1531789
diff --git a/toolkit/xre/test/browser_checkdllblockliststate.js b/toolkit/xre/test/browser_checkdllblockliststate.js
new file mode 100644
index 0000000000..759c9b3635
--- /dev/null
+++ b/toolkit/xre/test/browser_checkdllblockliststate.js
@@ -0,0 +1,17 @@
+// Any copyright is dedicated to the Public Domain.
+// http://creativecommons.org/publicdomain/zero/1.0/
+
+// Tests that the dll blocklist initializes correctly during test runs.
+add_task(async function test() {
+  await BrowserTestUtils.withNewTab(
+    { gBrowser, url: "about:blank" },
+    function (browser) {
+      ok(
+        Services.appinfo.windowsDLLBlocklistStatus,
+        "Windows dll blocklist status should be true, indicating it is " +
+          "running properly. A failure in this test is considered a " +
+          "release blocker."
+      );
+    }
+  );
+});
diff --git a/toolkit/xre/test/gtest/TestAssembleCommandLineWin.cpp b/toolkit/xre/test/gtest/TestAssembleCommandLineWin.cpp
new file mode 100644
index 0000000000..e36c62e0db
--- /dev/null
+++ b/toolkit/xre/test/gtest/TestAssembleCommandLineWin.cpp
@@ -0,0 +1,227 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "gtest/gtest.h"
+
+#include "mozilla/AssembleCmdLine.h"
+#include "mozilla/CmdLineAndEnvUtils.h"
+#include "mozilla/gtest/MozAssertions.h"
+#include "mozilla/UniquePtrExtensions.h"
+#include "WinRemoteMessage.h"
+
+using namespace mozilla;
+
+template <typename T>
+struct TestCase {
+  const T* mArgs[4];
+  const wchar_t* mExpected;
+};
+
+#define ALPHA_IN_UTF8 "\xe3\x82\xa2\xe3\x83\xab\xe3\x83\x95\xe3\x82\xa1"
+#define OMEGA_IN_UTF8 "\xe3\x82\xaa\xe3\x83\xa1\xe3\x82\xac"
+#define ALPHA_IN_UTF16 L"\u30A2\u30EB\u30D5\u30A1"
+#define OMEGA_IN_UTF16 L"\u30AA\u30E1\u30AC"
+#define UPPER_CYRILLIC_P_IN_UTF8 "\xd0\xa0"
+#define LOWER_CYRILLIC_P_IN_UTF8 "\xd1\x80"
+#define UPPER_CYRILLIC_P_IN_UTF16 L"\u0420"
+#define LOWER_CYRILLIC_P_IN_UTF16 L"\u0440"
+
+TestCase<char> testCases[] = {
+    // Copied from TestXREMakeCommandLineWin.ini
+    {{"a:\\", nullptr}, L"a:\\"},
+    {{"a:\"", nullptr}, L"a:\\\""},
+    {{"a:\\b c", nullptr}, L"\"a:\\b c\""},
+    {{"a:\\b c\"", nullptr}, L"\"a:\\b c\\\"\""},
+    {{"a:\\b c\\d e", nullptr}, L"\"a:\\b c\\d e\""},
+    {{"a:\\b c\\d e\"", nullptr}, L"\"a:\\b c\\d e\\\"\""},
+    {{"a:\\", nullptr}, L"a:\\"},
+    {{"a:\"", "b:\\c d", nullptr}, L"a:\\\" \"b:\\c d\""},
+    {{"a", "b:\" c:\\d", "e", nullptr}, L"a \"b:\\\" c:\\d\" e"},
+    {{"abc", "d", "e", nullptr}, L"abc d e"},
+    {{"a b c", "d", "e", nullptr}, L"\"a b c\" d e"},
+    {{"a\\\\\\b", "de fg", "h", nullptr}, L"a\\\\\\b \"de fg\" h"},
+    {{"a", "b", nullptr}, L"a b"},
+    {{"a\tb", nullptr}, L"\"a\tb\""},
+    {{"a\\\"b", "c", "d", nullptr}, L"a\\\\\\\"b c d"},
+    {{"a\\\"b", "c", nullptr}, L"a\\\\\\\"b c"},
+    {{"a\\\\\\b c", nullptr}, L"\"a\\\\\\b c\""},
+    {{"\"a", nullptr}, L"\\\"a"},
+    {{"\\a", nullptr}, L"\\a"},
+    {{"\\\\\\a", nullptr}, L"\\\\\\a"},
+    {{"\\\\\\\"a", nullptr}, L"\\\\\\\\\\\\\\\"a"},
+    {{"a\\\"b c\" d e", nullptr}, L"\"a\\\\\\\"b c\\\" d e\""},
+    {{"a\\\\\"b", "c d e", nullptr}, L"a\\\\\\\\\\\"b \"c d e\""},
+    {{"a:\\b", "c\\" ALPHA_IN_UTF8, OMEGA_IN_UTF8 "\\d", nullptr},
+     L"a:\\b c\\" ALPHA_IN_UTF16 L" " OMEGA_IN_UTF16 L"\\d"},
+    {{"a:\\b", "c\\" ALPHA_IN_UTF8 " " OMEGA_IN_UTF8 "\\d", nullptr},
+     L"a:\\b \"c\\" ALPHA_IN_UTF16 L" " OMEGA_IN_UTF16 L"\\d\""},
+    {{ALPHA_IN_UTF8, OMEGA_IN_UTF8, nullptr},
+     ALPHA_IN_UTF16 L" " OMEGA_IN_UTF16},
+
+    // More single-argument cases
+    {{"a\fb", nullptr}, L"\"a\fb\""},
+    {{"a\nb", nullptr}, L"\"a\nb\""},
+    {{"a\rb", nullptr}, L"\"a\rb\""},
+    {{"a\vb", nullptr}, L"\"a\vb\""},
+    {{"\"a\" \"b\"", nullptr}, L"\"\\\"a\\\" \\\"b\\\"\""},
+    {{"\"a\\b\" \"c\\d\"", nullptr}, L"\"\\\"a\\b\\\" \\\"c\\d\\\"\""},
+    {{"\\\\ \\\\", nullptr}, L"\"\\\\ \\\\\\\\\""},
+    {{"\"\" \"\"", nullptr}, L"\"\\\"\\\" \\\"\\\"\""},
+    {{ALPHA_IN_UTF8 "\\" OMEGA_IN_UTF8, nullptr},
+     ALPHA_IN_UTF16 L"\\" OMEGA_IN_UTF16},
+    {{ALPHA_IN_UTF8 " " OMEGA_IN_UTF8, nullptr},
+     L"\"" ALPHA_IN_UTF16 L" " OMEGA_IN_UTF16 L"\""},
+
+    // Empty string cases
+    {{"", nullptr}, L"\"\""},
+    {{"foo", "", nullptr}, L"foo \"\""},
+    {{"", "bar", nullptr}, L"\"\" bar"},
+    {{"foo", "", "bar", nullptr}, L"foo \"\" bar"},
+};
+
+TEST(AssembleCommandLineWin, assembleCmdLine)
+{
+  for (const auto& testCase : testCases) {
+    UniqueFreePtr<wchar_t> assembled;
+    wchar_t* assembledRaw = nullptr;
+    EXPECT_EQ(assembleCmdLine(testCase.mArgs, &assembledRaw, CP_UTF8), 0);
+    assembled.reset(assembledRaw);
+
+    EXPECT_STREQ(assembled.get(), testCase.mExpected);
+  }
+}
+
+TEST(CommandLineParserWin, HandleCommandLine)
+{
+  CommandLineParserWin<char> parser;
+  for (const auto& testCase : testCases) {
+    NS_ConvertUTF16toUTF8 utf8(testCase.mExpected);
+    parser.HandleCommandLine(utf8);
+
+    if (utf8.Length() == 0) {
+      EXPECT_EQ(parser.Argc(), 0);
+      continue;
+    }
+
+    for (int i = 0; i < parser.Argc(); ++i) {
+      EXPECT_NE(testCase.mArgs[i], nullptr);
+      EXPECT_STREQ(parser.Argv()[i], testCase.mArgs[i]);
+    }
+    EXPECT_EQ(testCase.mArgs[parser.Argc()], nullptr);
+  }
+}
+
+TEST(WinRemoteMessage, SendReceive)
+{
+  const char kCommandline[] =
+      "dummy.exe /arg1 --arg2 \"3rd arg\" "
+      "4th=\"" UPPER_CYRILLIC_P_IN_UTF8 " " LOWER_CYRILLIC_P_IN_UTF8 "\"";
+  const wchar_t kCommandlineW[] =
+      L"dummy.exe /arg1 --arg2 \"3rd arg\" "
+      L"4th=\"" UPPER_CYRILLIC_P_IN_UTF16 L" " LOWER_CYRILLIC_P_IN_UTF16 L"\"";
+  const wchar_t* kExpectedArgsW[] = {
+      L"-arg1", L"-arg2", L"3rd arg",
+      L"4th=" UPPER_CYRILLIC_P_IN_UTF16 L" " LOWER_CYRILLIC_P_IN_UTF16};
+
+  char workingDirA[MAX_PATH];
+  wchar_t workingDirW[MAX_PATH];
+  EXPECT_NE(getcwd(workingDirA, MAX_PATH), nullptr);
+  EXPECT_NE(_wgetcwd(workingDirW, MAX_PATH), nullptr);
+
+  WinRemoteMessageSender v0(kCommandline);
+  WinRemoteMessageSender v1(kCommandline, workingDirA);
+  WinRemoteMessageSender v2(kCommandlineW, workingDirW);
+
+  WinRemoteMessageReceiver receiver;
+  int32_t len;
+  nsAutoString arg;
+  nsCOMPtr<nsIFile> workingDir;
+
+  receiver.Parse(v0.CopyData());
+  EXPECT_NS_SUCCEEDED(receiver.CommandLineRunner()->GetLength(&len));
+  EXPECT_EQ(static_cast<size_t>(len), ArrayLength(kExpectedArgsW));
+  for (size_t i = 0; i < ArrayLength(kExpectedArgsW); ++i) {
+    EXPECT_TRUE(
+        NS_SUCCEEDED(receiver.CommandLineRunner()->GetArgument(i, arg)));
+    EXPECT_STREQ(arg.get(), kExpectedArgsW[i]);
+  }
+  EXPECT_EQ(receiver.CommandLineRunner()->GetWorkingDirectory(
+                getter_AddRefs(workingDir)),
+            NS_ERROR_NOT_INITIALIZED);
+
+  receiver.Parse(v1.CopyData());
+  EXPECT_NS_SUCCEEDED(receiver.CommandLineRunner()->GetLength(&len));
+  EXPECT_EQ(static_cast<size_t>(len), ArrayLength(kExpectedArgsW));
+  for (size_t i = 0; i < ArrayLength(kExpectedArgsW); ++i) {
+    EXPECT_TRUE(
+        NS_SUCCEEDED(receiver.CommandLineRunner()->GetArgument(i, arg)));
+    EXPECT_STREQ(arg.get(), kExpectedArgsW[i]);
+  }
+  EXPECT_TRUE(NS_SUCCEEDED(receiver.CommandLineRunner()->GetWorkingDirectory(
+      getter_AddRefs(workingDir))));
+  EXPECT_NS_SUCCEEDED(workingDir->GetPath(arg));
+  EXPECT_STREQ(arg.get(), workingDirW);
+
+  receiver.Parse(v2.CopyData());
+  EXPECT_NS_SUCCEEDED(receiver.CommandLineRunner()->GetLength(&len));
+  EXPECT_EQ(static_cast<size_t>(len), ArrayLength(kExpectedArgsW));
+  for (size_t i = 0; i < ArrayLength(kExpectedArgsW); ++i) {
+    EXPECT_TRUE(
+        NS_SUCCEEDED(receiver.CommandLineRunner()->GetArgument(i, arg)));
+    EXPECT_STREQ(arg.get(), kExpectedArgsW[i]);
+  }
+  EXPECT_TRUE(NS_SUCCEEDED(receiver.CommandLineRunner()->GetWorkingDirectory(
+      getter_AddRefs(workingDir))));
+  EXPECT_NS_SUCCEEDED(workingDir->GetPath(arg));
+  EXPECT_STREQ(arg.get(), workingDirW);
+}
+
+TEST(WinRemoteMessage, NonNullTerminatedBuffer)
+{
+  // Reserve two pages and commit the first one
+  const uint32_t kPageSize = 4096;
+  UniquePtr<void, VirtualFreeDeleter> pages(
+      ::VirtualAlloc(nullptr, kPageSize * 2, MEM_RESERVE, PAGE_NOACCESS));
+  EXPECT_TRUE(pages);
+  EXPECT_TRUE(
+      ::VirtualAlloc(pages.get(), kPageSize, MEM_COMMIT, PAGE_READWRITE));
+
+  // Test strings with lengths between 0 and |kMaxBufferSize| bytes
+  const int kMaxBufferSize = 10;
+
+  // Set a string just before the boundary between the two pages.
+  uint8_t* bufferEnd = reinterpret_cast<uint8_t*>(pages.get()) + kPageSize;
+  memset(bufferEnd - kMaxBufferSize, '$', kMaxBufferSize);
+
+  nsCOMPtr<nsIFile> workingDir;
+  COPYDATASTRUCT copyData = {};
+  for (int i = 0; i < kMaxBufferSize; ++i) {
+    WinRemoteMessageReceiver receiver;
+
+    copyData.cbData = i;
+    copyData.lpData = bufferEnd - i;
+
+    copyData.dwData =
+        static_cast<ULONG_PTR>(WinRemoteMessageVersion::CommandLineOnly);
+    EXPECT_NS_SUCCEEDED(receiver.Parse(&copyData));
+    EXPECT_EQ(receiver.CommandLineRunner()->GetWorkingDirectory(
+                  getter_AddRefs(workingDir)),
+              NS_ERROR_NOT_INITIALIZED);
+
+    copyData.dwData = static_cast<ULONG_PTR>(
+        WinRemoteMessageVersion::CommandLineAndWorkingDir);
+    EXPECT_NS_SUCCEEDED(receiver.Parse(&copyData));
+    EXPECT_EQ(receiver.CommandLineRunner()->GetWorkingDirectory(
+                  getter_AddRefs(workingDir)),
+              NS_ERROR_NOT_INITIALIZED);
+
+    copyData.dwData = static_cast<ULONG_PTR>(
+        WinRemoteMessageVersion::CommandLineAndWorkingDirInUtf16);
+    EXPECT_NS_SUCCEEDED(receiver.Parse(&copyData));
+    EXPECT_EQ(receiver.CommandLineRunner()->GetWorkingDirectory(
+                  getter_AddRefs(workingDir)),
+              NS_ERROR_NOT_INITIALIZED);
+  }
+}
diff --git a/toolkit/xre/test/gtest/TestCmdLineAndEnvUtils.cpp b/toolkit/xre/test/gtest/TestCmdLineAndEnvUtils.cpp
new file mode 100644
index 0000000000..a5f8a19a9c
--- /dev/null
+++ b/toolkit/xre/test/gtest/TestCmdLineAndEnvUtils.cpp
@@ -0,0 +1,372 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <memory>
+#include <ostream>
+#include <string>
+#include <string_view>
+#include <type_traits>
+#include <vector>
+
+#include "gtest/gtest.h"
+
+#include "mozilla/CmdLineAndEnvUtils.h"
+
+// Insulate these test-classes from the outside world.
+//
+// (In particular, distinguish this `CommandLine` from the one in ipc/chromium.
+// The compiler has no issues here, but the MSVC debugger gets somewhat
+// confused.)
+namespace testzilla {
+
+// Auxiliary class to simplify the declaration of test-cases for
+// EnsureCommandlineSafe.
+class CommandLine {
+  const size_t size;
+  std::vector<std::string> _data_8;
+  std::vector<std::wstring> _data_16;
+  // _should_ be const all the way through, but...
+  char const** argv_8;
+  wchar_t const** argv_16;
+
+ public:
+  inline int argc() const { return (int)(unsigned int)(size); }
+
+  template <typename CharT>
+  CharT const** argv() const;
+
+  CommandLine(CommandLine const&) = delete;
+  CommandLine(CommandLine&& that) = delete;
+
+  template <typename Container>
+  explicit CommandLine(Container const& container)
+      : size{std::size(container) + 1},     // plus one for argv[0]
+        argv_8(new const char*[size + 1]),  // plus one again for argv[argc]
+        argv_16(new const wchar_t*[size + 1]) {
+    _data_8.reserve(size + 1);
+    _data_16.reserve(size + 1);
+    size_t pos = 0;
+
+    const auto append = [&](const char* val) {
+      size_t const len = ::strlen(val);
+      _data_8.emplace_back(val, val + len);
+      _data_16.emplace_back(val, val + len);
+      argv_8[pos] = _data_8.back().data();
+      argv_16[pos] = _data_16.back().data();
+      ++pos;
+    };
+
+    append("GECKOAPP.COM");  // argv[0] may be anything
+    for (const char* item : container) {
+      append(item);
+    }
+    assert(pos == size);
+
+    // C99 §5.1.2.2.1 states "argv[argc] shall be a null pointer", and
+    // `CheckArg` implicitly relies on this.
+    argv_8[pos] = nullptr;
+    argv_16[pos] = nullptr;
+  }
+
+  // debug output
+  friend std::ostream& operator<<(std::ostream& o, CommandLine const& cl) {
+    for (const auto& item : cl._data_8) {
+      o << '"';
+      for (const char c : item) {
+        if (c == '"') {
+          o << "\\\"";
+        } else {
+          o << c;
+        }
+      }
+      o << "\", ";
+    }
+    return o;
+  }
+};
+
+template <>
+char const** CommandLine::argv<char>() const {
+  return argv_8;
+}
+template <>
+wchar_t const** CommandLine::argv<wchar_t>() const {
+  return argv_16;
+}
+
+enum TestCaseState : bool {
+  FAIL = false,
+  PASS = true,
+};
+constexpr TestCaseState operator!(TestCaseState s) {
+  return TestCaseState(!bool(s));
+}
+
+#ifdef XP_WIN
+constexpr static const TestCaseState WIN_ONLY = PASS;
+#else
+constexpr static const TestCaseState WIN_ONLY = FAIL;
+#endif
+
+using NarrowTestCase = std::pair<const char*, const char*>;
+constexpr std::pair<TestCaseState, NarrowTestCase> kStrMatches8[] = {
+    {PASS, {"", ""}},
+
+    {PASS, {"i", "i"}},
+    {PASS, {"i", "I"}},
+
+    {FAIL, {"", "i"}},
+    {FAIL, {"i", ""}},
+    {FAIL, {"i", "j"}},
+
+    {PASS, {"mozilla", "mozilla"}},
+    {PASS, {"mozilla", "Mozilla"}},
+    {PASS, {"mozilla", "MOZILLA"}},
+    {PASS, {"mozilla", "mOZILLA"}},
+    {PASS, {"mozilla", "mOZIlLa"}},
+    {PASS, {"mozilla", "MoZiLlA"}},
+
+    {FAIL, {"mozilla", ""}},
+    {FAIL, {"mozilla", "mozill"}},
+    {FAIL, {"mozilla", "mozillo"}},
+    {FAIL, {"mozilla", "mozillam"}},
+    {FAIL, {"mozilla", "mozilla-"}},
+    {FAIL, {"mozilla", "-mozilla"}},
+    {FAIL, {"-mozilla", "mozilla"}},
+
+    // numbers are permissible
+    {PASS, {"m0zi11a", "m0zi11a"}},
+    {PASS, {"m0zi11a", "M0ZI11A"}},
+    {PASS, {"m0zi11a", "m0Zi11A"}},
+
+    {FAIL, {"mozilla", "m0zi11a"}},
+    {FAIL, {"m0zi11a", "mozilla"}},
+
+    // capital letters are not accepted in the left comparand
+    {FAIL, {"I", "i"}},
+    {FAIL, {"I", "i"}},
+    {FAIL, {"Mozilla", "mozilla"}},
+    {FAIL, {"Mozilla", "Mozilla"}},
+
+    // punctuation other than `-` is rejected
+    {FAIL, {"*", "*"}},
+    {FAIL, {"*", "word"}},
+    {FAIL, {".", "."}},
+    {FAIL, {".", "a"}},
+    {FAIL, {"_", "_"}},
+
+    // spaces are rejected
+    {FAIL, {" ", " "}},
+    {FAIL, {"two words", "two words"}},
+
+    // non-ASCII characters are rejected
+    //
+    // (the contents of this test case may differ depending on the source and
+    // execution character sets, but the result should always be failure)
+    {FAIL, {"à", "a"}},
+    {FAIL, {"a", "à"}},
+    {FAIL, {"à", "à"}},
+};
+
+#ifdef XP_WIN
+using WideTestCase = std::pair<const char*, const wchar_t*>;
+std::pair<TestCaseState, WideTestCase> kStrMatches16[] = {
+    // (Turkish 'İ' may lowercase to 'i' in some locales, but
+    // we explicitly prevent that from being relevant)
+    {FAIL, {"i", L"İ"}},
+    {FAIL, {"mozilla", L"ṁozilla"}},
+};
+#endif
+
+constexpr const char* kRequiredArgs[] = {"aleph", "beth"};
+
+std::pair<TestCaseState, std::vector<const char*>> const kCommandLines[] = {
+    // the basic admissible forms
+    {PASS, {"-osint", "-aleph", "http://www.example.com/"}},
+    {PASS, {"-osint", "-beth", "http://www.example.com/"}},
+
+    // GNU-style double-dashes are also allowed
+    {PASS, {"--osint", "-aleph", "http://www.example.com/"}},
+    {PASS, {"--osint", "-beth", "http://www.example.com/"}},
+    {PASS, {"--osint", "--aleph", "http://www.example.com/"}},
+    {PASS, {"--osint", "--beth", "http://www.example.com/"}},
+
+    // on Windows, slashes are also permitted
+    {WIN_ONLY, {"-osint", "/aleph", "http://www.example.com/"}},
+    {WIN_ONLY, {"--osint", "/aleph", "http://www.example.com/"}},
+    // - These should pass on Windows because they're well-formed.
+    // - These should pass elsewhere because the first parameter is
+    //     just a local filesystem path, not an option.
+    {PASS, {"/osint", "/aleph", "http://www.example.com/"}},
+    {PASS, {"/osint", "-aleph", "http://www.example.com/"}},
+    {PASS, {"/osint", "--aleph", "http://www.example.com/"}},
+
+    // the required argument's argument may not itself be a flag
+    {FAIL, {"-osint", "-aleph", "-anything"}},
+    {FAIL, {"-osint", "-aleph", "--anything"}},
+    // - On Windows systems this is a switch and should be rejected.
+    // - On non-Windows systems this is potentially a valid local path.
+    {!WIN_ONLY, {"-osint", "-aleph", "/anything"}},
+
+    // wrong order
+    {FAIL, {"-osint", "http://www.example.com/", "-aleph"}},
+    {FAIL, {"-aleph", "-osint", "http://www.example.com/"}},
+    {FAIL, {"-aleph", "http://www.example.com/", "-osint"}},
+    {FAIL, {"http://www.example.com/", "-osint", "-aleph"}},
+    {FAIL, {"http://www.example.com/", "-aleph", "-osint"}},
+
+    // missing arguments
+    {FAIL, {"-osint", "http://www.example.com/"}},
+    {FAIL, {"-osint", "-aleph"}},
+    {FAIL, {"-osint"}},
+
+    // improper arguments
+    {FAIL, {"-osint", "-other-argument", "http://www.example.com/"}},
+    {FAIL, {"-osint", "", "http://www.example.com/"}},
+
+    // additional arguments
+    {FAIL, {"-osint", "-aleph", "http://www.example.com/", "-other-argument"}},
+    {FAIL, {"-osint", "-other-argument", "-aleph", "http://www.example.com/"}},
+    {FAIL, {"-osint", "-aleph", "-other-argument", "http://www.example.com/"}},
+    {FAIL, {"-osint", "-aleph", "http://www.example.com/", "-a", "-b"}},
+    {FAIL, {"-osint", "-aleph", "-a", "http://www.example.com/", "-b"}},
+    {FAIL, {"-osint", "-a", "-aleph", "http://www.example.com/", "-b"}},
+
+    // multiply-occurring otherwise-licit arguments
+    {FAIL, {"-osint", "-aleph", "-beth", "http://www.example.com/"}},
+    {FAIL, {"-osint", "-aleph", "-aleph", "http://www.example.com/"}},
+
+    // if -osint is not supplied, anything goes
+    {PASS, {}},
+    {PASS, {"http://www.example.com"}},
+    {PASS, {"-aleph", "http://www.example.com/"}},
+    {PASS, {"-beth", "http://www.example.com/"}},
+    {PASS, {"-aleph", "http://www.example.com/", "-other-argument"}},
+    {PASS, {"-aleph", "-aleph", "http://www.example.com/"}},
+};
+
+constexpr static char const* const kOptionalArgs[] = {"mozilla", "allizom"};
+
+// Additional test cases for optional parameters.
+//
+// Test cases marked PASS should pass iff the above optional parameters are
+// permitted. (Test cases marked FAIL should fail regardless, and are only
+// grouped here for convenience and semantic coherence.)
+std::pair<TestCaseState, std::vector<const char*>> kCommandLinesOpt[] = {
+    // one permitted optional argument
+    {PASS, {"-osint", "-mozilla", "-aleph", "http://www.example.com/"}},
+    {PASS, {"-osint", "-allizom", "-aleph", "http://www.example.com/"}},
+
+    // multiple permitted optional arguments
+    {PASS,
+     {"-osint", "-mozilla", "-allizom", "-aleph", "http://www.example.com/"}},
+    {PASS,
+     {"-osint", "-allizom", "-mozilla", "-aleph", "http://www.example.com/"}},
+
+    // optional arguments in the wrong place
+    {FAIL, {"-mozilla", "-osint", "-aleph", "http://www.example.com/"}},
+    {FAIL, {"-osint", "-aleph", "-mozilla", "http://www.example.com/"}},
+    {FAIL, {"-osint", "-aleph", "http://www.example.com/", "-mozilla"}},
+
+    // optional arguments in both right and wrong places
+    {FAIL,
+     {"-mozilla", "-osint", "-allizom", "-aleph", "http://www.example.com/"}},
+    {FAIL,
+     {"-osint", "-allizom", "-aleph", "-mozilla", "http://www.example.com/"}},
+    {FAIL,
+     {"-osint", "-allizom", "-aleph", "http://www.example.com/", "-mozilla"}},
+};
+
+enum WithOptionalState : bool {
+  NoOptionalArgs = false,
+  WithOptionalArgs = true,
+};
+
+template <typename CharT>
+bool TestCommandLineImpl(CommandLine const& cl,
+                         WithOptionalState withOptional) {
+  int argc = cl.argc();
+  // EnsureCommandlineSafe's signature isn't const-correct here for annoying
+  // reasons, but it is indeed non-mutating.
+  CharT** argv = const_cast<CharT**>(cl.argv<CharT>());
+  if (withOptional) {
+    return mozilla::internal::EnsureCommandlineSafeImpl(
+        argc, argv, kRequiredArgs, kOptionalArgs);
+  }
+  return mozilla::internal::EnsureCommandlineSafeImpl(argc, argv,
+                                                      kRequiredArgs);
+}
+
+// Test that `args` produces `expectation`. On Windows, test against both
+// wide-character and narrow-character implementations.
+void TestCommandLine(TestCaseState expectation, CommandLine const& cl,
+                     WithOptionalState withOptional) {
+  EXPECT_EQ(TestCommandLineImpl<char>(cl, withOptional), expectation)
+      << "cl is: " << cl << std::endl
+      << "withOptional is: " << bool(withOptional);
+#ifdef XP_WIN
+  EXPECT_EQ(TestCommandLineImpl<wchar_t>(cl, withOptional), expectation)
+      << "cl is: " << cl << std::endl
+      << "withOptional is: " << bool(withOptional);
+#endif
+}
+}  // namespace testzilla
+
+/***********************
+ * Test cases
+ */
+
+TEST(CmdLineAndEnvUtils, strimatch)
+{
+  using namespace testzilla;
+  using mozilla::strimatch;
+  for (auto const& [result, data] : kStrMatches8) {
+    auto const& [left, right] = data;
+    EXPECT_EQ(strimatch(left, right), result)
+        << '<' << left << "> !~ <" << right << '>';
+
+#ifdef XP_WIN
+    wchar_t right_wide[200];
+    ::mbstowcs(right_wide, right, 200);
+    EXPECT_EQ(strimatch(left, right_wide), result)
+        << '<' << left << "> !~ L<" << right << '>';
+#endif
+  }
+
+#ifdef XP_WIN
+  for (auto const& [result, data] : kStrMatches16) {
+    auto const& [left, right] = data;
+    EXPECT_EQ(strimatch(left, right), result)
+        << '<' << left << "> !~ L<" << right << '>';
+  }
+#endif
+}
+
+TEST(CmdLineAndEnvUtils, ensureSafe)
+{
+  using namespace testzilla;
+  for (auto const& [result, data] : kCommandLines) {
+    CommandLine const cl(data);
+    TestCommandLine(result, cl, NoOptionalArgs);
+  }
+  for (auto const& [_unused, data] : kCommandLinesOpt) {
+    MOZ_UNUSED(_unused);  // silence gcc
+    CommandLine const cl(data);
+    TestCommandLine(FAIL, cl, NoOptionalArgs);
+  }
+}
+
+TEST(CmdLineAndEnvUtils, ensureSafeWithOptional)
+{
+  using namespace testzilla;
+  for (auto const& [result, data] : kCommandLines) {
+    CommandLine const cl(data);
+    TestCommandLine(result, cl, WithOptionalArgs);
+  }
+  for (auto const& [result, data] : kCommandLinesOpt) {
+    CommandLine const cl(data);
+    TestCommandLine(result, cl, WithOptionalArgs);
+  }
+}
diff --git a/toolkit/xre/test/gtest/TestCompatVersionCompare.cpp b/toolkit/xre/test/gtest/TestCompatVersionCompare.cpp
new file mode 100644
index 0000000000..bce64aacd5
--- /dev/null
+++ b/toolkit/xre/test/gtest/TestCompatVersionCompare.cpp
@@ -0,0 +1,53 @@
+/* vim:set ts=2 sw=2 sts=2 et: */
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+#include "gtest/gtest.h"
+#include "nsAppRunner.h"
+#include "nsString.h"
+
+void CheckCompatVersionCompare(const nsCString& aOldCompatVersion,
+                               const nsCString& aNewCompatVersion,
+                               bool aExpectedSame, bool aExpectedDowngrade) {
+  printf("Comparing '%s' to '%s'.\n", aOldCompatVersion.get(),
+         aNewCompatVersion.get());
+
+  int32_t result = CompareCompatVersions(aOldCompatVersion, aNewCompatVersion);
+
+  ASSERT_EQ(aExpectedSame, result == 0)
+      << "Version sameness check should match.";
+  ASSERT_EQ(aExpectedDowngrade, result > 0)
+      << "Version downgrade check should match.";
+}
+
+void CheckExpectedResult(const char* aOldAppVersion, const char* aNewAppVersion,
+                         bool aExpectedSame, bool aExpectedDowngrade) {
+  nsCString oldCompatVersion;
+  BuildCompatVersion(aOldAppVersion, "", "", oldCompatVersion);
+
+  nsCString newCompatVersion;
+  BuildCompatVersion(aNewAppVersion, "", "", newCompatVersion);
+
+  CheckCompatVersionCompare(oldCompatVersion, newCompatVersion, aExpectedSame,
+                            aExpectedDowngrade);
+}
+
+TEST(CompatVersionCompare, CompareVersionChange)
+{
+  // Identical
+  CheckExpectedResult("67.0", "67.0", true, false);
+
+  // Version changes
+  CheckExpectedResult("67.0", "68.0", false, false);
+  CheckExpectedResult("68.0", "67.0", false, true);
+  CheckExpectedResult("67.0", "67.0.1", true, false);
+  CheckExpectedResult("67.0.1", "67.0", true, false);
+  CheckExpectedResult("67.0.1", "67.0.1", true, false);
+  CheckExpectedResult("67.0.1", "67.0.2", true, false);
+  CheckExpectedResult("67.0.2", "67.0.1", true, false);
+
+  // Check that if the last run was safe mode then we consider this an upgrade.
+  CheckCompatVersionCompare(
+      "Safe Mode"_ns, "67.0.1_20000000000000/20000000000000"_ns, false, false);
+}
diff --git a/toolkit/xre/test/gtest/TestGeckoArgs.cpp b/toolkit/xre/test/gtest/TestGeckoArgs.cpp
new file mode 100644
index 0000000000..42c7a41b2b
--- /dev/null
+++ b/toolkit/xre/test/gtest/TestGeckoArgs.cpp
@@ -0,0 +1,179 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "gtest/gtest.h"
+
+#include "mozilla/ArrayUtils.h"
+#include "mozilla/GeckoArgs.h"
+
+using namespace mozilla;
+using namespace mozilla::geckoargs;
+
+static CommandLineArg<const char*> kCharParam{"-charParam", "charparam"};
+static CommandLineArg<uint64_t> kUint64Param{"-Uint64Param", "uint64param"};
+static CommandLineArg<bool> kFlag{"-Flag", "flag"};
+
+template <size_t N>
+bool CheckArgv(char** aArgv, const char* const (&aExpected)[N]) {
+  for (size_t i = 0; i < N; ++i) {
+    if (aArgv[i] == nullptr && aExpected[i] == nullptr) {
+      return true;
+    }
+    if (aArgv[i] == nullptr || aExpected[i] == nullptr) {
+      return false;
+    }
+    if (strcmp(aArgv[i], aExpected[i]) != 0) {
+      return false;
+    }
+  }
+  return true;
+}
+
+char kFirefox[] = "$HOME/bin/firefox/firefox-bin";
+
+TEST(GeckoArgs, const_char_ptr)
+{
+  char kCharParamStr[] = "-charParam";
+  char kCharParamValue[] = "paramValue";
+
+  {
+    char* argv[] = {kFirefox, kCharParamStr, kCharParamValue, nullptr};
+    int argc = ArrayLength(argv);
+    EXPECT_EQ(argc, 4);
+
+    Maybe<const char*> charParam = kCharParam.Get(argc, argv);
+    EXPECT_TRUE(charParam.isSome());
+    EXPECT_EQ(*charParam, kCharParamValue);
+
+    const char* const expArgv[] = {kFirefox, nullptr};
+    EXPECT_TRUE(CheckArgv(argv, expArgv));
+  }
+  {
+    char kBlahBlah[] = "-blahblah";
+    char* argv[] = {kFirefox, kCharParamStr, kBlahBlah, nullptr};
+    int argc = ArrayLength(argv);
+    EXPECT_EQ(argc, 4);
+
+    Maybe<const char*> charParam = kCharParam.Get(argc, argv);
+    EXPECT_TRUE(charParam.isNothing());
+
+    const char* const expArgv[] = {kFirefox, kBlahBlah, nullptr};
+    EXPECT_TRUE(CheckArgv(argv, expArgv));
+  }
+  {
+    std::vector<std::string> extraArgs;
+    EXPECT_EQ(extraArgs.size(), 0U);
+    kCharParam.Put("ParamValue", extraArgs);
+    EXPECT_EQ(extraArgs.size(), 2U);
+    EXPECT_EQ(extraArgs[0], "-charParam");
+    EXPECT_EQ(extraArgs[1], "ParamValue");
+  }
+  { EXPECT_EQ(kCharParam.Name(), "-charParam"); }
+}
+
+TEST(GeckoArgs, uint64)
+{
+  char kUint64ParamStr[] = "-Uint64Param";
+
+  {
+    char* argv[] = {kFirefox, kUint64ParamStr, nullptr};
+    int argc = ArrayLength(argv);
+    EXPECT_EQ(argc, 3);
+
+    Maybe<uint64_t> uint64Param = kUint64Param.Get(argc, argv);
+    EXPECT_TRUE(uint64Param.isNothing());
+
+    const char* const expArgv[] = {kFirefox, nullptr};
+    EXPECT_TRUE(CheckArgv(argv, expArgv));
+  }
+  {
+    char* argv[] = {kFirefox, nullptr};
+    int argc = ArrayLength(argv);
+    EXPECT_EQ(argc, 2);
+
+    Maybe<uint64_t> uint64Param = kUint64Param.Get(argc, argv);
+    EXPECT_TRUE(uint64Param.isNothing());
+
+    const char* const expArgv[] = {kFirefox, nullptr};
+    EXPECT_TRUE(CheckArgv(argv, expArgv));
+  }
+  {
+    char kUint64ParamValue[] = "42";
+    char* argv[] = {kFirefox, kUint64ParamStr, kUint64ParamValue, nullptr};
+    int argc = ArrayLength(argv);
+    EXPECT_EQ(argc, 4);
+
+    Maybe<uint64_t> uint64Param = kUint64Param.Get(argc, argv);
+    EXPECT_TRUE(uint64Param.isSome());
+    EXPECT_EQ(*uint64Param, 42U);
+
+    const char* const expArgv[] = {kFirefox, nullptr};
+    EXPECT_TRUE(CheckArgv(argv, expArgv));
+  }
+  {
+    char kUint64ParamValue[] = "aa";
+    char* argv[] = {kFirefox, kUint64ParamStr, kUint64ParamValue, nullptr};
+    int argc = ArrayLength(argv);
+    EXPECT_EQ(argc, 4);
+
+    Maybe<uint64_t> uint64Param = kUint64Param.Get(argc, argv);
+    EXPECT_TRUE(uint64Param.isNothing());
+
+    const char* const expArgv[] = {kFirefox, nullptr};
+    EXPECT_TRUE(CheckArgv(argv, expArgv));
+  }
+  {
+    std::vector<std::string> extraArgs;
+    EXPECT_EQ(extraArgs.size(), 0U);
+    kUint64Param.Put(1234, extraArgs);
+    EXPECT_EQ(extraArgs.size(), 2U);
+    EXPECT_EQ(extraArgs[0], "-Uint64Param");
+    EXPECT_EQ(extraArgs[1], "1234");
+  }
+  { EXPECT_EQ(kUint64Param.Name(), "-Uint64Param"); }
+}
+
+TEST(GeckoArgs, bool)
+{
+  char kFlagStr[] = "-Flag";
+
+  {
+    char* argv[] = {kFirefox, kFlagStr, nullptr};
+    int argc = ArrayLength(argv);
+    EXPECT_EQ(argc, 3);
+
+    Maybe<bool> Flag = kFlag.Get(argc, argv);
+    EXPECT_TRUE(Flag.isSome());
+    EXPECT_TRUE(*Flag);
+
+    const char* const expArgv[] = {kFirefox, nullptr};
+    EXPECT_TRUE(CheckArgv(argv, expArgv));
+  }
+  {
+    char* argv[] = {kFirefox, nullptr};
+    int argc = ArrayLength(argv);
+    EXPECT_EQ(argc, 2);
+
+    Maybe<bool> Flag = kFlag.Get(argc, argv);
+    EXPECT_TRUE(Flag.isNothing());
+
+    const char* const expArgv[] = {kFirefox, nullptr};
+    EXPECT_TRUE(CheckArgv(argv, expArgv));
+  }
+  {
+    std::vector<std::string> extraArgs;
+    EXPECT_EQ(extraArgs.size(), 0U);
+    kFlag.Put(true, extraArgs);
+    EXPECT_EQ(extraArgs.size(), 1U);
+    EXPECT_EQ(extraArgs[0], "-Flag");
+  }
+  {
+    std::vector<std::string> extraArgs;
+    EXPECT_EQ(extraArgs.size(), 0U);
+    kFlag.Put(false, extraArgs);
+    EXPECT_EQ(extraArgs.size(), 0U);
+  }
+  { EXPECT_EQ(kFlag.Name(), "-Flag"); }
+}
diff --git a/toolkit/xre/test/gtest/moz.build b/toolkit/xre/test/gtest/moz.build
new file mode 100644
index 0000000000..bec881fa72
--- /dev/null
+++ b/toolkit/xre/test/gtest/moz.build
@@ -0,0 +1,24 @@
+# -*- Mode: python; c-basic-offset: 4; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, you can obtain one at http://mozilla.org/MPL/2.0/.
+
+Library("xretest")
+
+UNIFIED_SOURCES = [
+    "TestCmdLineAndEnvUtils.cpp",
+    "TestCompatVersionCompare.cpp",
+    "TestGeckoArgs.cpp",
+]
+
+LOCAL_INCLUDES += [
+    "/toolkit/components/remote",
+]
+
+if CONFIG["OS_TARGET"] == "WINNT":
+    UNIFIED_SOURCES += [
+        "TestAssembleCommandLineWin.cpp",
+    ]
+
+FINAL_LIBRARY = "xul-gtest"
diff --git a/toolkit/xre/test/marionette/gen_win32k_tests.py b/toolkit/xre/test/marionette/gen_win32k_tests.py
new file mode 100644
index 0000000000..e0a39776db
--- /dev/null
+++ b/toolkit/xre/test/marionette/gen_win32k_tests.py
@@ -0,0 +1,212 @@
+#!/usr/bin/env python3
+
+import re
+
+RE_DEFAULT = re.compile(r"\[D=([TF])\] ")
+RE_TRANSITION = re.compile(r"([a-zA-Z0-9 \[\]=#_-]+) *->(.*)")
+RE_ASSERTION = re.compile(
+    r"\[A S=([a-zA-Z01_]+) SS=([a-zA-Z01_]+) ES=([a-zA-Z01_]+) P=([a-zA-Z_]+) ESP=([a-zA-Z_]+)\]"
+)
+RE_ASSERTION_SHORTHAND = re.compile(r"\[A#([0-9T]+)\]")
+
+# ======================================================================
+# ======================================================================
+
+testnum = 1
+
+
+def start_test(line):
+    global testnum
+    output.write(
+        """
+    def test_{0}(self):
+        # {1}...\n""".format(
+            testnum, line[0:80]
+        )
+    )
+    testnum += 1
+
+
+def set_default(d):
+    output.write(
+        """
+        if self.default_is is not {0}:
+            return\n""".format(
+            "True" if d == "T" else "False"
+        )
+    )
+
+
+def enroll(e):
+    if e.endswith("-C"):
+        e = e[:-2]
+        output.write("\n        # Re-set enrollment pref, like Normandy would do\n")
+    output.write(
+        "        self.set_enrollment_status(ExperimentStatus.ENROLLED_{0})\n".format(
+            e.upper()
+        )
+    )
+
+
+def set_pref(enabled):
+    output.write(
+        "\n        self.marionette.set_pref(Prefs.WIN32K, {0})\n".format(str(enabled))
+    )
+
+
+def set_e10s(enable):
+    if enable:
+        output.write(
+            """
+        app_version = self.execute_script("return Services.appinfo.version")
+        self.restart(env={ENV_DISABLE_E10S: app_version})
+        self.set_env(ENV_DISABLE_E10S, "null")\n"""
+        )
+    else:
+        raise Exception("Not implemented")
+
+
+def set_header(enable):
+    if enable:
+        output.write(
+            """
+        self.restart(env={ENV_DISABLE_WIN32K: "1"})\n"""
+        )
+    else:
+        output.write(
+            """
+        self.set_env(ENV_DISABLE_WIN32K, "")\n"""
+        )
+
+
+def set_bad_requirements(enabled):
+    output.write(
+        """
+        self.marionette.set_pref(Prefs.WEBGL, {0})\n""".format(
+            "False" if enabled else "True"
+        )
+    )
+
+
+def restart():
+    output.write("\n        self.restart()\n")
+
+
+def print_assertion(assertion):
+    if not assertion:
+        return
+    output.write(
+        """
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.{0},
+            sessionStatus=ContentWin32kLockdownState.{1},
+            experimentStatus=ExperimentStatus.{2},
+            pref={3},
+            enrollmentStatusPref=ExperimentStatus.{4},
+        )\n""".format(
+            *assertion
+        )
+    )
+
+
+# ======================================================================
+# ======================================================================
+
+TESTS = open("win32k_tests.txt", "r").readlines()
+
+output = open("test_win32k_enrollment.py", "w", newline="\n")
+header = open("test_win32k_enrollment.template.py", "r")
+for l in header:
+    output.write(l)
+
+mappings = {}
+for line in TESTS:
+    line = line.strip()
+    if not line:
+        continue
+
+    if line.startswith("#"):
+        continue
+    elif line.startswith("> "):
+        line = line[2:]
+        key, value = line.split(":")
+        mappings[key.strip()] = value.strip()
+        continue
+    elif line.startswith("-"):
+        line = line[1:].strip()
+    elif line.startswith("+"):
+        line = line[1:].strip()
+        import pdb
+
+        pdb.set_trace()
+    else:
+        raise Exception("unknown line type: " + line)
+
+    # We can't handle Safe Mode right now
+    if "Safe Mode" in line:
+        continue
+
+    # If we have no assertions defined, skip the test entirely
+    if "[A" not in line:
+        continue
+
+    if not RE_DEFAULT.match(line):
+        raise Exception("'{0}' does not match the default regex".format(line))
+    default = RE_DEFAULT.search(line).groups(1)[0]
+
+    start_test(line)
+
+    set_default(default)
+
+    line = line[6:]
+
+    while line:
+        # this is a horrible hack for the line ending to avoid making the
+        # regex more complicated and having to fix it
+        if not line.endswith(" ->"):
+            line += " ->"
+
+        groups = RE_TRANSITION.search(line).groups()
+        start = groups[0].strip()
+        end = groups[1].strip()
+
+        if RE_ASSERTION.search(start):
+            assertion = RE_ASSERTION.search(start).groups()
+            start = start[0 : start.index("[")].strip()
+        elif RE_ASSERTION_SHORTHAND.search(start):
+            key = RE_ASSERTION_SHORTHAND.search(start).groups()[0]
+            assertion = RE_ASSERTION.search(mappings[key]).groups()
+            start = start[0 : start.index("[")].strip()
+        else:
+            assertion = ""
+
+        if start == "Nothing":
+            pass
+        elif start.startswith("Enrolled "):
+            enroll(start[9:])
+        elif start == "E10S":
+            set_e10s(True)
+        elif start == "Header-On":
+            set_header(True)
+        elif start == "Header-Off":
+            set_header(False)
+        elif start == "Bad Requirements":
+            set_bad_requirements(True)
+        elif start == "Restart":
+            restart()
+        elif start == "On":
+            set_pref(True)
+        elif start == "Off":
+            set_pref(False)
+        else:
+            raise Exception("Unknown Action: " + start)
+
+        print_assertion(assertion)
+
+        line = end.strip()
+
+    if RE_ASSERTION.match(line):
+        print_assertion(RE_ASSERTION.search(line).groups())
+    elif RE_ASSERTION_SHORTHAND.search(line):
+        key = RE_ASSERTION_SHORTHAND.search(line).groups()[0]
+        print_assertion(RE_ASSERTION.search(mappings[key]).groups())
diff --git a/toolkit/xre/test/marionette/marionette.ini b/toolkit/xre/test/marionette/marionette.ini
new file mode 100644
index 0000000000..bb49d6c5de
--- /dev/null
+++ b/toolkit/xre/test/marionette/marionette.ini
@@ -0,0 +1,6 @@
+[test_fission_autostart.py]
+[test_win32k_enrollment.py]
+skip-if =
+  os != 'win'
+  ccov  # Bug 1757102
+[test_exitcode.py]
diff --git a/toolkit/xre/test/marionette/test_exitcode.py b/toolkit/xre/test/marionette/test_exitcode.py
new file mode 100644
index 0000000000..4ce7306122
--- /dev/null
+++ b/toolkit/xre/test/marionette/test_exitcode.py
@@ -0,0 +1,31 @@
+from marionette_harness import MarionetteTestCase
+
+
+class TestFissionAutostart(MarionetteTestCase):
+    def test_normal_exit(self):
+        self.marionette.set_context(self.marionette.CONTEXT_CHROME)
+
+        def call_quit():
+            self.marionette.execute_script(
+                """
+                Services.startup.quit(Ci.nsIAppStartup.eAttemptQuit);
+                """,
+                sandbox="system",
+            )
+
+        self.marionette.quit(callback=call_quit)
+        self.assertEqual(self.marionette.instance.runner.returncode, 0)
+
+    def test_exit_code(self):
+        self.marionette.set_context(self.marionette.CONTEXT_CHROME)
+
+        def call_quit():
+            self.marionette.execute_script(
+                """
+                Services.startup.quit(Ci.nsIAppStartup.eAttemptQuit, 5);
+                """,
+                sandbox="system",
+            )
+
+        self.marionette.quit(callback=call_quit)
+        self.assertEqual(self.marionette.instance.runner.returncode, 5)
diff --git a/toolkit/xre/test/marionette/test_fission_autostart.py b/toolkit/xre/test/marionette/test_fission_autostart.py
new file mode 100644
index 0000000000..e34087aca9
--- /dev/null
+++ b/toolkit/xre/test/marionette/test_fission_autostart.py
@@ -0,0 +1,247 @@
+from contextlib import contextmanager
+
+from marionette_harness import MarionetteTestCase
+
+
+class ExperimentStatus:
+    UNENROLLED = 0
+    ENROLLED_CONTROL = 1
+    ENROLLED_TREATMENT = 2
+    DISQUALIFIED = 3
+
+
+class Prefs:
+    FISSION_AUTOSTART = "fission.autostart"
+    FISSION_AUTOSTART_SESSION = "fission.autostart.session"
+
+
+ENV_ENABLE_FISSION = "MOZ_FORCE_ENABLE_FISSION"
+ENV_DISABLE_FISSION = "MOZ_FORCE_DISABLE_FISSION"
+ENV_DISABLE_E10S = "MOZ_FORCE_DISABLE_E10S"
+
+
+DECISION_STATUS = {
+    "experimentControl": 1,
+    "experimentTreatment": 2,
+    "disabledByE10sEnv": 3,
+    "enabledByEnv": 4,
+    "disabledByEnv": 5,
+    "enabledByDefault": 7,
+    "disabledByDefault": 8,
+    "enabledByUserPref": 9,
+    "disabledByUserPref": 10,
+    "disabledByE10sOther": 11,
+}
+
+
+class TestFissionAutostart(MarionetteTestCase):
+    SANDBOX_NAME = "fission-autostart"
+
+    def execute_script(self, code, *args, **kwargs):
+        with self.marionette.using_context(self.marionette.CONTEXT_CHROME):
+            return self.marionette.execute_script(
+                code, new_sandbox=False, sandbox=self.SANDBOX_NAME, *args, **kwargs
+            )
+
+    def get_fission_status(self):
+        return self.execute_script(
+            r"""
+          let win = Services.wm.getMostRecentWindow("navigator:browser");
+          return {
+            fissionAutostart: Services.appinfo.fissionAutostart,
+            decisionStatus: Services.appinfo.fissionDecisionStatus,
+            decisionStatusString: Services.appinfo.fissionDecisionStatusString,
+            useRemoteSubframes: win.docShell.nsILoadContext.useRemoteSubframes,
+            fissionAutostartSession: Services.prefs.getBoolPref("fission.autostart.session"),
+            dynamicFissionAutostart: Services.prefs.getBoolPref("fission.autostart"),
+          };
+        """
+        )
+
+    def check_fission_status(self, enabled, decision, dynamic=None):
+        if dynamic is None:
+            dynamic = enabled
+
+        expected = {
+            "fissionAutostart": enabled,
+            "decisionStatus": DECISION_STATUS[decision],
+            "decisionStatusString": decision,
+            "useRemoteSubframes": enabled,
+            "fissionAutostartSession": enabled,
+            "dynamicFissionAutostart": dynamic,
+        }
+
+        status = self.get_fission_status()
+
+        for prop, value in expected.items():
+            self.assertEqual(
+                status[prop],
+                value,
+                "%s should have the value `%r`, but has `%r`"
+                % (prop, value, status[prop]),
+            )
+
+    def set_env(self, env, value):
+        self.execute_script(
+            "env.set(arguments[0], arguments[1]);", script_args=(env, value)
+        )
+
+    def get_env(self, env):
+        return self.execute_script("return env.get(arguments[0]);", script_args=(env,))
+
+    def restart(self, prefs=None, env=None):
+        if prefs:
+            self.marionette.set_prefs(prefs)
+
+        if env:
+            for name, value in env.items():
+                self.set_env(name, value)
+
+        self.marionette.restart(in_app=True, clean=False)
+        self.setUpSession()
+
+        # Sanity check our environment.
+        if prefs:
+            for key, val in prefs.items():
+                if val is not None:
+                    self.assertEqual(self.marionette.get_pref(key), val)
+        if env:
+            for key, val in env.items():
+                self.assertEqual(self.get_env(key), val or "")
+
+    def setUpSession(self):
+        self.marionette.set_context(self.marionette.CONTEXT_CHROME)
+
+        self.execute_script(
+            r"""
+          // We're running in a function, in a sandbox, that inherits from an
+          // X-ray wrapped window. Anything we want to be globally available
+          // needs to be defined on that window.
+          window.env = Services.env;
+        """
+        )
+
+    @contextmanager
+    def full_restart(self):
+        profile = self.marionette.instance.profile
+        try:
+            self.marionette.quit()
+            yield profile
+        finally:
+            self.marionette.start_session()
+            self.setUpSession()
+
+    def setUp(self):
+        super(TestFissionAutostart, self).setUp()
+
+        # If we have configured marionette to require a particular value for
+        # `fission.autostart`, remove it as a forced pref until `tearDown`, and
+        # perform a clean restart, so we run this test without the pref
+        # pre-configured.
+        self.fissionRequired = None
+        if Prefs.FISSION_AUTOSTART in self.marionette.instance.required_prefs:
+            self.fissionRequired = self.marionette.instance.required_prefs[
+                Prefs.FISSION_AUTOSTART
+            ]
+            del self.marionette.instance.required_prefs[Prefs.FISSION_AUTOSTART]
+            self.marionette.restart(in_app=False, clean=True)
+
+        self.setUpSession()
+
+        # Fission status must start out with `enabledByDefault`
+        self.check_fission_status(
+            enabled=True,
+            decision="enabledByDefault",
+        )
+
+    def tearDown(self):
+        if self.fissionRequired is not None:
+            self.marionette.instance.required_prefs[
+                Prefs.FISSION_AUTOSTART
+            ] = self.fissionRequired
+        self.marionette.restart(in_app=False, clean=True)
+
+        super(TestFissionAutostart, self).tearDown()
+
+    def test_runtime_changes(self):
+        """Tests that changes to preferences during runtime do not have any
+        effect on the current session."""
+
+        self.check_fission_status(
+            enabled=True,
+            decision="enabledByDefault",
+        )
+
+        self.restart(prefs={Prefs.FISSION_AUTOSTART: False})
+
+        self.check_fission_status(
+            enabled=False,
+            decision="disabledByUserPref",
+        )
+
+        self.marionette.set_pref(Prefs.FISSION_AUTOSTART, True)
+        self.check_fission_status(
+            enabled=False,
+            decision="disabledByUserPref",
+            dynamic=True,
+        )
+
+        self.marionette.clear_pref(Prefs.FISSION_AUTOSTART)
+        self.check_fission_status(
+            enabled=False,
+            decision="disabledByUserPref",
+            dynamic=True,
+        )
+
+        self.restart()
+        self.check_fission_status(
+            enabled=True,
+            decision="enabledByDefault",
+        )
+
+    def test_fission_precedence(self):
+        self.check_fission_status(
+            enabled=True,
+            decision="enabledByDefault",
+        )
+
+        self.restart(
+            prefs={Prefs.FISSION_AUTOSTART: False}, env={ENV_ENABLE_FISSION: "1"}
+        )
+        self.check_fission_status(
+            enabled=True,
+            decision="enabledByEnv",
+            dynamic=False,
+        )
+
+        self.restart(
+            prefs={Prefs.FISSION_AUTOSTART: True},
+            env={ENV_DISABLE_FISSION: "1", ENV_ENABLE_FISSION: ""},
+        )
+        self.check_fission_status(
+            enabled=False,
+            decision="disabledByEnv",
+            dynamic=True,
+        )
+
+        self.restart(
+            prefs={Prefs.FISSION_AUTOSTART: False}, env={ENV_DISABLE_FISSION: ""}
+        )
+        self.check_fission_status(
+            enabled=False,
+            decision="disabledByUserPref",
+        )
+
+        self.restart(prefs={Prefs.FISSION_AUTOSTART: None})
+        self.check_fission_status(
+            enabled=True,
+            decision="enabledByDefault",
+        )
+
+        app_version = self.execute_script("return Services.appinfo.version")
+        self.restart(env={ENV_DISABLE_E10S: app_version})
+        self.check_fission_status(
+            enabled=False,
+            decision="disabledByE10sEnv",
+            dynamic=True,
+        )
diff --git a/toolkit/xre/test/marionette/test_win32k_enrollment.py b/toolkit/xre/test/marionette/test_win32k_enrollment.py
new file mode 100644
index 0000000000..d09331319b
--- /dev/null
+++ b/toolkit/xre/test/marionette/test_win32k_enrollment.py
@@ -0,0 +1,2506 @@
+from contextlib import contextmanager
+
+from marionette_harness import MarionetteTestCase
+
+
+class ExperimentStatus:
+    UNENROLLED = 0
+    ENROLLED_CONTROL = 1
+    ENROLLED_TREATMENT = 2
+    DISQUALIFIED = 3
+
+
+class ContentWin32kLockdownState:
+    LockdownEnabled = 1
+    MissingWebRender = 2
+    OperatingSystemNotSupported = 3
+    PrefNotSet = 4
+    MissingRemoteWebGL = 5
+    MissingNonNativeTheming = 6
+    DisabledByEnvVar = 7
+    DisabledBySafeMode = 8
+    DisabledByE10S = 9
+    DisabledByUserPref = 10
+    EnabledByUserPref = 11
+    DisabledByControlGroup = 12
+    EnabledByTreatmentGroup = 13
+    DisabledByDefault = 14
+    EnabledByDefault = 15
+
+
+class Prefs:
+    ENROLLMENT_STATUS = "security.sandbox.content.win32k-experiment.enrollmentStatus"
+    STARTUP_ENROLLMENT_STATUS = (
+        "security.sandbox.content.win32k-experiment.startupEnrollmentStatus"
+    )
+    WIN32K = "security.sandbox.content.win32k-disable"
+    WEBGL = "webgl.out-of-process"
+
+
+ENV_DISABLE_WIN32K = "MOZ_ENABLE_WIN32K"
+ENV_DISABLE_E10S = "MOZ_FORCE_DISABLE_E10S"
+
+
+class TestWin32kAutostart(MarionetteTestCase):
+    SANDBOX_NAME = "win32k-autostart"
+
+    def execute_script(self, code, *args, **kwargs):
+        with self.marionette.using_context(self.marionette.CONTEXT_CHROME):
+            return self.marionette.execute_script(
+                code, new_sandbox=False, sandbox=self.SANDBOX_NAME, *args, **kwargs
+            )
+
+    def get_win32k_status(self):
+        return self.execute_script(
+            r"""
+          let win = Services.wm.getMostRecentWindow("navigator:browser");
+          let ses = "security.sandbox.content.win32k-experiment.startupEnrollmentStatus";
+          return {
+            win32kSessionStatus: Services.appinfo.win32kSessionStatus,
+            win32kStatus: Services.appinfo.win32kLiveStatusTestingOnly,
+            win32kExperimentStatus: Services.appinfo.win32kExperimentStatus,
+            win32kPref: Services.prefs.getBoolPref("security.sandbox.content.win32k-disable"),
+            win32kStartupEnrollmentStatusPref: Services.prefs.getIntPref(ses),
+          };
+        """
+        )
+
+    def check_win32k_status(
+        self, status, sessionStatus, experimentStatus, pref, enrollmentStatusPref
+    ):
+        # We CANNOT check win32kEnrollmentStatusPref after a restart because we only set this
+        # pref on the default branch, and it goes away after a restart, so we only check
+        # the startupEnrollmentStatusPref
+        expected = {
+            "win32kSessionStatus": sessionStatus,
+            "win32kStatus": status,
+            "win32kExperimentStatus": experimentStatus,
+            "win32kPref": pref,
+            "win32kStartupEnrollmentStatusPref": enrollmentStatusPref,
+        }
+
+        status = self.get_win32k_status()
+
+        for prop, value in expected.items():
+            self.assertEqual(
+                status[prop],
+                value,
+                "%s should have the value `%r`, but has `%r`"
+                % (prop, value, status[prop]),
+            )
+
+    def set_env(self, env, value):
+        self.execute_script(
+            "env.set(arguments[0], arguments[1]);", script_args=(env, value)
+        )
+
+    def get_env(self, env):
+        return self.execute_script("return env.get(arguments[0]);", script_args=(env,))
+
+    def set_enrollment_status(self, status):
+        self.marionette.set_pref(Prefs.ENROLLMENT_STATUS, status, default_branch=True)
+
+        updated_status = self.marionette.get_pref(Prefs.ENROLLMENT_STATUS)
+        self.assertTrue(
+            status == updated_status or updated_status == ExperimentStatus.DISQUALIFIED
+        )
+        startup_status = self.marionette.get_pref(Prefs.STARTUP_ENROLLMENT_STATUS)
+        self.assertEqual(
+            startup_status,
+            updated_status,
+            "Startup enrollment status (%r) should match "
+            "session status (%r)" % (startup_status, updated_status),
+        )
+
+    def restart(self, prefs=None, env=None):
+        if prefs:
+            self.marionette.set_prefs(prefs)
+
+        if env:
+            for name, value in env.items():
+                self.set_env(name, value)
+
+        self.marionette.restart(in_app=True, clean=False)
+        self.setUpSession()
+
+        # Sanity check our environment.
+        if prefs:
+            for key, val in prefs.items():
+                if val is not None:
+                    self.assertEqual(self.marionette.get_pref(key), val)
+        if env:
+            for key, val in env.items():
+                self.assertEqual(self.get_env(key), val or "")
+
+    def setUpSession(self):
+        self.marionette.set_context(self.marionette.CONTEXT_CHROME)
+
+        self.execute_script(
+            r"""
+          // We're running in a function, in a sandbox, that inherits from an
+          // X-ray wrapped window. Anything we want to be globally available
+          // needs to be defined on that window.
+          window.env = Services.env;
+        """
+        )
+
+    @contextmanager
+    def full_restart(self):
+        profile = self.marionette.instance.profile
+        try:
+            self.marionette.quit()
+            yield profile
+        finally:
+            self.marionette.start_session()
+            self.setUpSession()
+
+    def setUp(self):
+        super(TestWin32kAutostart, self).setUp()
+
+        # If we have configured marionette to require a particular value for
+        # `win32k.autostart`, remove it as a forced pref until `tearDown`, and
+        # perform a clean restart, so we run this test without the pref
+        # pre-configured.
+        self.win32kRequired = None
+        if Prefs.WIN32K in self.marionette.instance.required_prefs:
+            self.win32kRequired = self.marionette.instance.required_prefs[Prefs.WIN32K]
+            del self.marionette.instance.required_prefs[Prefs.WIN32K]
+            self.marionette.restart(in_app=False, clean=True)
+
+        self.setUpSession()
+
+        # Marionette doesn't let you set preferences on the default branch before startup
+        # so we can't test the default=False and default=True scenarios in one test
+        # What we can do is generate all the tests, and then only run the runs for which
+        # the default is.  (And run the other ones locally to make sure they work before
+        # we land it.)
+        prefJS = 'return Services.prefs.getBoolPref("security.sandbox.content.win32k-disable");'
+        self.default_is = self.execute_script(prefJS)
+
+        if self.default_is is False:
+            # Win32k status must start out with `disabledByDefault`
+            self.check_win32k_status(
+                status=ContentWin32kLockdownState.DisabledByDefault,
+                sessionStatus=ContentWin32kLockdownState.DisabledByDefault,
+                experimentStatus=ExperimentStatus.UNENROLLED,
+                pref=False,
+                enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+            )
+        else:
+            # Win32k status must start out with `enabledByDefault`
+            self.check_win32k_status(
+                status=ContentWin32kLockdownState.EnabledByDefault,
+                sessionStatus=ContentWin32kLockdownState.EnabledByDefault,
+                experimentStatus=ExperimentStatus.UNENROLLED,
+                pref=True,
+                enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+            )
+
+    def tearDown(self):
+        if self.win32kRequired is not None:
+            self.marionette.instance.required_prefs[Prefs.WIN32K] = self.win32kRequired
+        self.marionette.restart(in_app=False, clean=True)
+
+        super(TestWin32kAutostart, self).tearDown()
+
+    def test_1(self):
+        # [D=F] Nothing [A#1] -> Enrolled Control [A S=DisabledByDefault SS=DisabledByDefa...
+
+        if self.default_is is not False:
+            return
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.DisabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_CONTROL)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.DisabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_CONTROL,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByControlGroup,
+            sessionStatus=ContentWin32kLockdownState.DisabledByControlGroup,
+            experimentStatus=ExperimentStatus.ENROLLED_CONTROL,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_CONTROL,
+        )
+
+    def test_2(self):
+        # [D=F] Nothing [A#1] -> Enrolled Treatment [A S=DisabledByDefault SS=DisabledByDe...
+
+        if self.default_is is not False:
+            return
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.DisabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_TREATMENT)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.DisabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_TREATMENT,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByTreatmentGroup,
+            sessionStatus=ContentWin32kLockdownState.EnabledByTreatmentGroup,
+            experimentStatus=ExperimentStatus.ENROLLED_TREATMENT,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_TREATMENT,
+        )
+
+    def test_3(self):
+        # [D=F] Nothing [A#1] -> On [A S=EnabledByUserPref SS=DisabledByDefault ES=UNENROL...
+
+        if self.default_is is not False:
+            return
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.DisabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        self.marionette.set_pref(Prefs.WIN32K, True)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByUserPref,
+            sessionStatus=ContentWin32kLockdownState.DisabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByUserPref,
+            sessionStatus=ContentWin32kLockdownState.EnabledByUserPref,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+    def test_4(self):
+        # [D=F] Nothing [A#1] -> Off [A#1] -> Restart [A#1]...
+
+        if self.default_is is not False:
+            return
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.DisabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        self.marionette.set_pref(Prefs.WIN32K, False)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.DisabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.DisabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+    def test_5(self):
+        # [D=F] Nothing [A#1] -> On -> Bad Requirements [A S=MissingRemoteWebGL SS=Disable...
+
+        if self.default_is is not False:
+            return
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.DisabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        self.marionette.set_pref(Prefs.WIN32K, True)
+
+        self.marionette.set_pref(Prefs.WEBGL, False)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.MissingRemoteWebGL,
+            sessionStatus=ContentWin32kLockdownState.DisabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.MissingRemoteWebGL,
+            sessionStatus=ContentWin32kLockdownState.MissingRemoteWebGL,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+    def test_6(self):
+        # [D=F] Nothing [A#1] -> On -> E10S [A S=DisabledByE10S SS=DisabledByE10S ES=UNENR...
+
+        if self.default_is is not False:
+            return
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.DisabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        self.marionette.set_pref(Prefs.WIN32K, True)
+
+        app_version = self.execute_script("return Services.appinfo.version")
+        self.restart(env={ENV_DISABLE_E10S: app_version})
+        self.set_env(ENV_DISABLE_E10S, "null")
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByE10S,
+            sessionStatus=ContentWin32kLockdownState.DisabledByE10S,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+    def test_7(self):
+        # [D=F] Nothing [A#1] -> On -> Header-On [A S=DisabledByEnvVar SS=DisabledByEnvVar...
+
+        if self.default_is is not False:
+            return
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.DisabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        self.marionette.set_pref(Prefs.WIN32K, True)
+
+        self.restart(env={ENV_DISABLE_WIN32K: "1"})
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByEnvVar,
+            sessionStatus=ContentWin32kLockdownState.DisabledByEnvVar,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        self.set_env(ENV_DISABLE_WIN32K, "")
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByUserPref,
+            sessionStatus=ContentWin32kLockdownState.DisabledByEnvVar,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+    def test_8(self):
+        # [D=T] Nothing [A#1T] -> Enrolled Control [A S=EnabledByDefault SS=EnabledByDefau...
+
+        if self.default_is is not True:
+            return
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.EnabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_CONTROL)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.EnabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_CONTROL,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByControlGroup,
+            sessionStatus=ContentWin32kLockdownState.DisabledByControlGroup,
+            experimentStatus=ExperimentStatus.ENROLLED_CONTROL,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_CONTROL,
+        )
+
+    def test_9(self):
+        # [D=T] Nothing [A#1T] -> Enrolled Treatment [A S=EnabledByDefault SS=EnabledByDef...
+
+        if self.default_is is not True:
+            return
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.EnabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_TREATMENT)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.EnabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_TREATMENT,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByTreatmentGroup,
+            sessionStatus=ContentWin32kLockdownState.EnabledByTreatmentGroup,
+            experimentStatus=ExperimentStatus.ENROLLED_TREATMENT,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_TREATMENT,
+        )
+
+    def test_10(self):
+        # [D=T] Nothing [A#1T] -> On [A S=EnabledByDefault SS=EnabledByDefault ES=UNENROLL...
+
+        if self.default_is is not True:
+            return
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.EnabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        self.marionette.set_pref(Prefs.WIN32K, True)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.EnabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.EnabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+    def test_11(self):
+        # [D=T] Nothing [A#1T] -> Off [A S=DisabledByUserPref SS=EnabledByDefault ES=UNENR...
+
+        if self.default_is is not True:
+            return
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.EnabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        self.marionette.set_pref(Prefs.WIN32K, False)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByUserPref,
+            sessionStatus=ContentWin32kLockdownState.EnabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByUserPref,
+            sessionStatus=ContentWin32kLockdownState.DisabledByUserPref,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+    def test_12(self):
+        # [D=T] Nothing [A#1T] -> On -> Bad Requirements [A S=MissingRemoteWebGL SS=Enable...
+
+        if self.default_is is not True:
+            return
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.EnabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        self.marionette.set_pref(Prefs.WIN32K, True)
+
+        self.marionette.set_pref(Prefs.WEBGL, False)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.MissingRemoteWebGL,
+            sessionStatus=ContentWin32kLockdownState.EnabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.MissingRemoteWebGL,
+            sessionStatus=ContentWin32kLockdownState.MissingRemoteWebGL,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+    def test_13(self):
+        # [D=T] Nothing [A#1T] -> On -> E10S [A S=DisabledByE10S SS=DisabledByE10S ES=UNEN...
+
+        if self.default_is is not True:
+            return
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.EnabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        self.marionette.set_pref(Prefs.WIN32K, True)
+
+        app_version = self.execute_script("return Services.appinfo.version")
+        self.restart(env={ENV_DISABLE_E10S: app_version})
+        self.set_env(ENV_DISABLE_E10S, "null")
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByE10S,
+            sessionStatus=ContentWin32kLockdownState.DisabledByE10S,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+    def test_14(self):
+        # [D=T] Nothing [A#1T] -> On -> Header-On [A S=DisabledByEnvVar SS=DisabledByEnvVa...
+
+        if self.default_is is not True:
+            return
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.EnabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        self.marionette.set_pref(Prefs.WIN32K, True)
+
+        self.restart(env={ENV_DISABLE_WIN32K: "1"})
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByEnvVar,
+            sessionStatus=ContentWin32kLockdownState.DisabledByEnvVar,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        self.set_env(ENV_DISABLE_WIN32K, "")
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.DisabledByEnvVar,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+    def test_15(self):
+        # [D=F] On [A#3] -> Restart [A#4] -> Enrolled Control [A S=EnabledByUserPref SS=En...
+
+        if self.default_is is not False:
+            return
+
+        self.marionette.set_pref(Prefs.WIN32K, True)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByUserPref,
+            sessionStatus=ContentWin32kLockdownState.DisabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByUserPref,
+            sessionStatus=ContentWin32kLockdownState.EnabledByUserPref,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_CONTROL)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByUserPref,
+            sessionStatus=ContentWin32kLockdownState.EnabledByUserPref,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_CONTROL,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByUserPref,
+            sessionStatus=ContentWin32kLockdownState.EnabledByUserPref,
+            experimentStatus=ExperimentStatus.DISQUALIFIED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.DISQUALIFIED,
+        )
+
+    def test_16(self):
+        # [D=F] On [A#3] -> Restart [A#4] -> Enrolled Treatment [A S=EnabledByUserPref SS=...
+
+        if self.default_is is not False:
+            return
+
+        self.marionette.set_pref(Prefs.WIN32K, True)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByUserPref,
+            sessionStatus=ContentWin32kLockdownState.DisabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByUserPref,
+            sessionStatus=ContentWin32kLockdownState.EnabledByUserPref,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_TREATMENT)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByUserPref,
+            sessionStatus=ContentWin32kLockdownState.EnabledByUserPref,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_TREATMENT,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByUserPref,
+            sessionStatus=ContentWin32kLockdownState.EnabledByUserPref,
+            experimentStatus=ExperimentStatus.DISQUALIFIED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.DISQUALIFIED,
+        )
+
+    def test_17(self):
+        # [D=F] On [A#3] -> Restart [A#4] -> Off [A S=DisabledByDefault SS=EnabledByUserPr...
+
+        if self.default_is is not False:
+            return
+
+        self.marionette.set_pref(Prefs.WIN32K, True)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByUserPref,
+            sessionStatus=ContentWin32kLockdownState.DisabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByUserPref,
+            sessionStatus=ContentWin32kLockdownState.EnabledByUserPref,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        self.marionette.set_pref(Prefs.WIN32K, False)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.EnabledByUserPref,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.DisabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+    def test_18(self):
+        # [D=F] On [A#3] -> Restart [A#4] -> Bad Requirements [A S=MissingRemoteWebGL SS=E...
+
+        if self.default_is is not False:
+            return
+
+        self.marionette.set_pref(Prefs.WIN32K, True)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByUserPref,
+            sessionStatus=ContentWin32kLockdownState.DisabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByUserPref,
+            sessionStatus=ContentWin32kLockdownState.EnabledByUserPref,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        self.marionette.set_pref(Prefs.WEBGL, False)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.MissingRemoteWebGL,
+            sessionStatus=ContentWin32kLockdownState.EnabledByUserPref,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+    def test_19(self):
+        # [D=F] On [A#3] -> Restart [A#4] -> E10S [A S=DisabledByE10S SS=DisabledByE10S ES...
+
+        if self.default_is is not False:
+            return
+
+        self.marionette.set_pref(Prefs.WIN32K, True)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByUserPref,
+            sessionStatus=ContentWin32kLockdownState.DisabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByUserPref,
+            sessionStatus=ContentWin32kLockdownState.EnabledByUserPref,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        app_version = self.execute_script("return Services.appinfo.version")
+        self.restart(env={ENV_DISABLE_E10S: app_version})
+        self.set_env(ENV_DISABLE_E10S, "null")
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByE10S,
+            sessionStatus=ContentWin32kLockdownState.DisabledByE10S,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByUserPref,
+            sessionStatus=ContentWin32kLockdownState.EnabledByUserPref,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+    def test_20(self):
+        # [D=F] On [A#3] -> Restart [A#4] -> Header-On [A S=DisabledByEnvVar SS=DisabledBy...
+
+        if self.default_is is not False:
+            return
+
+        self.marionette.set_pref(Prefs.WIN32K, True)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByUserPref,
+            sessionStatus=ContentWin32kLockdownState.DisabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByUserPref,
+            sessionStatus=ContentWin32kLockdownState.EnabledByUserPref,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        self.restart(env={ENV_DISABLE_WIN32K: "1"})
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByEnvVar,
+            sessionStatus=ContentWin32kLockdownState.DisabledByEnvVar,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        self.set_env(ENV_DISABLE_WIN32K, "")
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByUserPref,
+            sessionStatus=ContentWin32kLockdownState.EnabledByUserPref,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+    def test_21(self):
+        # [D=T] On [A#3T] -> Restart [A#4T] -> Enrolled Control [A S=EnabledByDefault SS=E...
+
+        if self.default_is is not True:
+            return
+
+        self.marionette.set_pref(Prefs.WIN32K, True)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.EnabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.EnabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_CONTROL)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.EnabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_CONTROL,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByControlGroup,
+            sessionStatus=ContentWin32kLockdownState.DisabledByControlGroup,
+            experimentStatus=ExperimentStatus.ENROLLED_CONTROL,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_CONTROL,
+        )
+
+    def test_22(self):
+        # [D=T] On [A#3T] -> Restart [A#4T] -> Enrolled Treatment [A S=EnabledByDefault SS...
+
+        if self.default_is is not True:
+            return
+
+        self.marionette.set_pref(Prefs.WIN32K, True)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.EnabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.EnabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_TREATMENT)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.EnabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_TREATMENT,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByTreatmentGroup,
+            sessionStatus=ContentWin32kLockdownState.EnabledByTreatmentGroup,
+            experimentStatus=ExperimentStatus.ENROLLED_TREATMENT,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_TREATMENT,
+        )
+
+    def test_23(self):
+        # [D=T] On [A#3T] -> Restart [A#4T] -> Off [A S=DisabledByUserPref SS=EnabledByDef...
+
+        if self.default_is is not True:
+            return
+
+        self.marionette.set_pref(Prefs.WIN32K, True)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.EnabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.EnabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        self.marionette.set_pref(Prefs.WIN32K, False)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByUserPref,
+            sessionStatus=ContentWin32kLockdownState.EnabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByUserPref,
+            sessionStatus=ContentWin32kLockdownState.DisabledByUserPref,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+    def test_24(self):
+        # [D=T] On [A#3T] -> Restart [A#4T] -> Bad Requirements [A S=MissingRemoteWebGL SS...
+
+        if self.default_is is not True:
+            return
+
+        self.marionette.set_pref(Prefs.WIN32K, True)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.EnabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.EnabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        self.marionette.set_pref(Prefs.WEBGL, False)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.MissingRemoteWebGL,
+            sessionStatus=ContentWin32kLockdownState.EnabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+    def test_25(self):
+        # [D=T] On [A#3T] -> Restart [A#4T] -> E10S [A S=DisabledByE10S SS=DisabledByE10S ...
+
+        if self.default_is is not True:
+            return
+
+        self.marionette.set_pref(Prefs.WIN32K, True)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.EnabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.EnabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        app_version = self.execute_script("return Services.appinfo.version")
+        self.restart(env={ENV_DISABLE_E10S: app_version})
+        self.set_env(ENV_DISABLE_E10S, "null")
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByE10S,
+            sessionStatus=ContentWin32kLockdownState.DisabledByE10S,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.EnabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+    def test_26(self):
+        # [D=T] On [A#3T] -> Restart [A#4T] -> Header-On [A S=DisabledByEnvVar SS=Disabled...
+
+        if self.default_is is not True:
+            return
+
+        self.marionette.set_pref(Prefs.WIN32K, True)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.EnabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.EnabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        self.restart(env={ENV_DISABLE_WIN32K: "1"})
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByEnvVar,
+            sessionStatus=ContentWin32kLockdownState.DisabledByEnvVar,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        self.set_env(ENV_DISABLE_WIN32K, "")
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.EnabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+    def test_27(self):
+        # [D=F] Enrolled Control [A#5] -> Restart [A#6] -> Enrolled Control-C -> On [A S=E...
+
+        if self.default_is is not False:
+            return
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_CONTROL)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.DisabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_CONTROL,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByControlGroup,
+            sessionStatus=ContentWin32kLockdownState.DisabledByControlGroup,
+            experimentStatus=ExperimentStatus.ENROLLED_CONTROL,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_CONTROL,
+        )
+
+        # Re-set enrollment pref, like Normandy would do
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_CONTROL)
+
+        self.marionette.set_pref(Prefs.WIN32K, True)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByUserPref,
+            sessionStatus=ContentWin32kLockdownState.DisabledByControlGroup,
+            experimentStatus=ExperimentStatus.ENROLLED_CONTROL,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.DISQUALIFIED,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByUserPref,
+            sessionStatus=ContentWin32kLockdownState.EnabledByUserPref,
+            experimentStatus=ExperimentStatus.DISQUALIFIED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.DISQUALIFIED,
+        )
+
+    def test_28(self):
+        # [D=F] Enrolled Control [A#5] -> Restart [A#6] -> Off [A#6]...
+
+        if self.default_is is not False:
+            return
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_CONTROL)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.DisabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_CONTROL,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByControlGroup,
+            sessionStatus=ContentWin32kLockdownState.DisabledByControlGroup,
+            experimentStatus=ExperimentStatus.ENROLLED_CONTROL,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_CONTROL,
+        )
+
+        self.marionette.set_pref(Prefs.WIN32K, False)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByControlGroup,
+            sessionStatus=ContentWin32kLockdownState.DisabledByControlGroup,
+            experimentStatus=ExperimentStatus.ENROLLED_CONTROL,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_CONTROL,
+        )
+
+    def test_29(self):
+        # [D=F] Enrolled Control [A#5] -> Restart [A#6] -> Enrolled Control-C -> Bad Requi...
+
+        if self.default_is is not False:
+            return
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_CONTROL)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.DisabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_CONTROL,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByControlGroup,
+            sessionStatus=ContentWin32kLockdownState.DisabledByControlGroup,
+            experimentStatus=ExperimentStatus.ENROLLED_CONTROL,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_CONTROL,
+        )
+
+        # Re-set enrollment pref, like Normandy would do
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_CONTROL)
+
+        self.marionette.set_pref(Prefs.WEBGL, False)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.MissingRemoteWebGL,
+            sessionStatus=ContentWin32kLockdownState.DisabledByControlGroup,
+            experimentStatus=ExperimentStatus.ENROLLED_CONTROL,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_CONTROL,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.MissingRemoteWebGL,
+            sessionStatus=ContentWin32kLockdownState.MissingRemoteWebGL,
+            experimentStatus=ExperimentStatus.DISQUALIFIED,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.DISQUALIFIED,
+        )
+
+    def test_30(self):
+        # [D=F] Enrolled Control [A#5] -> Restart [A#6] -> Enrolled Control-C -> E10S [A S...
+
+        if self.default_is is not False:
+            return
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_CONTROL)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.DisabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_CONTROL,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByControlGroup,
+            sessionStatus=ContentWin32kLockdownState.DisabledByControlGroup,
+            experimentStatus=ExperimentStatus.ENROLLED_CONTROL,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_CONTROL,
+        )
+
+        # Re-set enrollment pref, like Normandy would do
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_CONTROL)
+
+        app_version = self.execute_script("return Services.appinfo.version")
+        self.restart(env={ENV_DISABLE_E10S: app_version})
+        self.set_env(ENV_DISABLE_E10S, "null")
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByE10S,
+            sessionStatus=ContentWin32kLockdownState.DisabledByE10S,
+            experimentStatus=ExperimentStatus.ENROLLED_CONTROL,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_CONTROL,
+        )
+
+        # Re-set enrollment pref, like Normandy would do
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_CONTROL)
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByControlGroup,
+            sessionStatus=ContentWin32kLockdownState.DisabledByControlGroup,
+            experimentStatus=ExperimentStatus.ENROLLED_CONTROL,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_CONTROL,
+        )
+
+    def test_31(self):
+        # [D=F] Enrolled Control [A#5] -> Restart [A#6] -> Enrolled Control-C -> Header-On...
+
+        if self.default_is is not False:
+            return
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_CONTROL)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.DisabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_CONTROL,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByControlGroup,
+            sessionStatus=ContentWin32kLockdownState.DisabledByControlGroup,
+            experimentStatus=ExperimentStatus.ENROLLED_CONTROL,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_CONTROL,
+        )
+
+        # Re-set enrollment pref, like Normandy would do
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_CONTROL)
+
+        self.restart(env={ENV_DISABLE_WIN32K: "1"})
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByEnvVar,
+            sessionStatus=ContentWin32kLockdownState.DisabledByEnvVar,
+            experimentStatus=ExperimentStatus.ENROLLED_CONTROL,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_CONTROL,
+        )
+
+        self.set_env(ENV_DISABLE_WIN32K, "")
+
+        # Re-set enrollment pref, like Normandy would do
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_CONTROL)
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByControlGroup,
+            sessionStatus=ContentWin32kLockdownState.DisabledByControlGroup,
+            experimentStatus=ExperimentStatus.ENROLLED_CONTROL,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_CONTROL,
+        )
+
+    def test_32(self):
+        # [D=T] Enrolled Control [A#5T] -> Restart [A#6T] -> Enrolled Control-C -> On [A S...
+
+        if self.default_is is not True:
+            return
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_CONTROL)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.EnabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_CONTROL,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByControlGroup,
+            sessionStatus=ContentWin32kLockdownState.DisabledByControlGroup,
+            experimentStatus=ExperimentStatus.ENROLLED_CONTROL,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_CONTROL,
+        )
+
+        # Re-set enrollment pref, like Normandy would do
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_CONTROL)
+
+        self.marionette.set_pref(Prefs.WIN32K, True)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByControlGroup,
+            sessionStatus=ContentWin32kLockdownState.DisabledByControlGroup,
+            experimentStatus=ExperimentStatus.ENROLLED_CONTROL,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_CONTROL,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByControlGroup,
+            sessionStatus=ContentWin32kLockdownState.DisabledByControlGroup,
+            experimentStatus=ExperimentStatus.ENROLLED_CONTROL,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_CONTROL,
+        )
+
+    def test_33(self):
+        # [D=T] Enrolled Control [A#5T] -> Restart [A#6T] -> Off [A S=DisabledByUserPref S...
+
+        if self.default_is is not True:
+            return
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_CONTROL)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.EnabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_CONTROL,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByControlGroup,
+            sessionStatus=ContentWin32kLockdownState.DisabledByControlGroup,
+            experimentStatus=ExperimentStatus.ENROLLED_CONTROL,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_CONTROL,
+        )
+
+        self.marionette.set_pref(Prefs.WIN32K, False)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByUserPref,
+            sessionStatus=ContentWin32kLockdownState.DisabledByControlGroup,
+            experimentStatus=ExperimentStatus.ENROLLED_CONTROL,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.DISQUALIFIED,
+        )
+
+    def test_34(self):
+        # [D=T] Enrolled Control [A#5T] -> Restart [A#6T] -> Enrolled Control-C -> Bad Req...
+
+        if self.default_is is not True:
+            return
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_CONTROL)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.EnabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_CONTROL,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByControlGroup,
+            sessionStatus=ContentWin32kLockdownState.DisabledByControlGroup,
+            experimentStatus=ExperimentStatus.ENROLLED_CONTROL,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_CONTROL,
+        )
+
+        # Re-set enrollment pref, like Normandy would do
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_CONTROL)
+
+        self.marionette.set_pref(Prefs.WEBGL, False)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.MissingRemoteWebGL,
+            sessionStatus=ContentWin32kLockdownState.DisabledByControlGroup,
+            experimentStatus=ExperimentStatus.ENROLLED_CONTROL,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_CONTROL,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.MissingRemoteWebGL,
+            sessionStatus=ContentWin32kLockdownState.MissingRemoteWebGL,
+            experimentStatus=ExperimentStatus.DISQUALIFIED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.DISQUALIFIED,
+        )
+
+    def test_35(self):
+        # [D=T] Enrolled Control [A#5T] -> Restart [A#6T] -> Enrolled Control-C -> E10S [A...
+
+        if self.default_is is not True:
+            return
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_CONTROL)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.EnabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_CONTROL,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByControlGroup,
+            sessionStatus=ContentWin32kLockdownState.DisabledByControlGroup,
+            experimentStatus=ExperimentStatus.ENROLLED_CONTROL,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_CONTROL,
+        )
+
+        # Re-set enrollment pref, like Normandy would do
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_CONTROL)
+
+        app_version = self.execute_script("return Services.appinfo.version")
+        self.restart(env={ENV_DISABLE_E10S: app_version})
+        self.set_env(ENV_DISABLE_E10S, "null")
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByE10S,
+            sessionStatus=ContentWin32kLockdownState.DisabledByE10S,
+            experimentStatus=ExperimentStatus.ENROLLED_CONTROL,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_CONTROL,
+        )
+
+        # Re-set enrollment pref, like Normandy would do
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_CONTROL)
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByControlGroup,
+            sessionStatus=ContentWin32kLockdownState.DisabledByControlGroup,
+            experimentStatus=ExperimentStatus.ENROLLED_CONTROL,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_CONTROL,
+        )
+
+    def test_36(self):
+        # [D=T] Enrolled Control [A#5T] -> Restart [A#6T] -> Enrolled Control-C -> Header-...
+
+        if self.default_is is not True:
+            return
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_CONTROL)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.EnabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_CONTROL,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByControlGroup,
+            sessionStatus=ContentWin32kLockdownState.DisabledByControlGroup,
+            experimentStatus=ExperimentStatus.ENROLLED_CONTROL,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_CONTROL,
+        )
+
+        # Re-set enrollment pref, like Normandy would do
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_CONTROL)
+
+        self.restart(env={ENV_DISABLE_WIN32K: "1"})
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByEnvVar,
+            sessionStatus=ContentWin32kLockdownState.DisabledByEnvVar,
+            experimentStatus=ExperimentStatus.ENROLLED_CONTROL,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_CONTROL,
+        )
+
+        self.set_env(ENV_DISABLE_WIN32K, "")
+
+        # Re-set enrollment pref, like Normandy would do
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_CONTROL)
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByControlGroup,
+            sessionStatus=ContentWin32kLockdownState.DisabledByControlGroup,
+            experimentStatus=ExperimentStatus.ENROLLED_CONTROL,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_CONTROL,
+        )
+
+    def test_37(self):
+        # [D=F] Enrolled Treatment [A#7] -> Restart [A#8] -> Enrolled Treatment-C -> On [A...
+
+        if self.default_is is not False:
+            return
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_TREATMENT)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.DisabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_TREATMENT,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByTreatmentGroup,
+            sessionStatus=ContentWin32kLockdownState.EnabledByTreatmentGroup,
+            experimentStatus=ExperimentStatus.ENROLLED_TREATMENT,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_TREATMENT,
+        )
+
+        # Re-set enrollment pref, like Normandy would do
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_TREATMENT)
+
+        self.marionette.set_pref(Prefs.WIN32K, True)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByUserPref,
+            sessionStatus=ContentWin32kLockdownState.EnabledByTreatmentGroup,
+            experimentStatus=ExperimentStatus.ENROLLED_TREATMENT,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.DISQUALIFIED,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByUserPref,
+            sessionStatus=ContentWin32kLockdownState.EnabledByUserPref,
+            experimentStatus=ExperimentStatus.DISQUALIFIED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.DISQUALIFIED,
+        )
+
+    def test_38(self):
+        # [D=F] Enrolled Treatment [A#7] -> Restart [A#8] -> Enrolled Treatment-C -> Off [...
+
+        if self.default_is is not False:
+            return
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_TREATMENT)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.DisabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_TREATMENT,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByTreatmentGroup,
+            sessionStatus=ContentWin32kLockdownState.EnabledByTreatmentGroup,
+            experimentStatus=ExperimentStatus.ENROLLED_TREATMENT,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_TREATMENT,
+        )
+
+        # Re-set enrollment pref, like Normandy would do
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_TREATMENT)
+
+        self.marionette.set_pref(Prefs.WIN32K, False)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByTreatmentGroup,
+            sessionStatus=ContentWin32kLockdownState.EnabledByTreatmentGroup,
+            experimentStatus=ExperimentStatus.ENROLLED_TREATMENT,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_TREATMENT,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByTreatmentGroup,
+            sessionStatus=ContentWin32kLockdownState.EnabledByTreatmentGroup,
+            experimentStatus=ExperimentStatus.ENROLLED_TREATMENT,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_TREATMENT,
+        )
+
+    def test_39(self):
+        # [D=F] Enrolled Treatment [A#7] -> Restart [A#8] -> Enrolled Treatment-C -> Bad R...
+
+        if self.default_is is not False:
+            return
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_TREATMENT)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.DisabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_TREATMENT,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByTreatmentGroup,
+            sessionStatus=ContentWin32kLockdownState.EnabledByTreatmentGroup,
+            experimentStatus=ExperimentStatus.ENROLLED_TREATMENT,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_TREATMENT,
+        )
+
+        # Re-set enrollment pref, like Normandy would do
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_TREATMENT)
+
+        self.marionette.set_pref(Prefs.WEBGL, False)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.MissingRemoteWebGL,
+            sessionStatus=ContentWin32kLockdownState.EnabledByTreatmentGroup,
+            experimentStatus=ExperimentStatus.ENROLLED_TREATMENT,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_TREATMENT,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.MissingRemoteWebGL,
+            sessionStatus=ContentWin32kLockdownState.MissingRemoteWebGL,
+            experimentStatus=ExperimentStatus.DISQUALIFIED,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.DISQUALIFIED,
+        )
+
+    def test_40(self):
+        # [D=F] Enrolled Treatment [A#7] -> Restart [A#8] -> Enrolled Treatment-C -> E10S ...
+
+        if self.default_is is not False:
+            return
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_TREATMENT)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.DisabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_TREATMENT,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByTreatmentGroup,
+            sessionStatus=ContentWin32kLockdownState.EnabledByTreatmentGroup,
+            experimentStatus=ExperimentStatus.ENROLLED_TREATMENT,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_TREATMENT,
+        )
+
+        # Re-set enrollment pref, like Normandy would do
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_TREATMENT)
+
+        app_version = self.execute_script("return Services.appinfo.version")
+        self.restart(env={ENV_DISABLE_E10S: app_version})
+        self.set_env(ENV_DISABLE_E10S, "null")
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByE10S,
+            sessionStatus=ContentWin32kLockdownState.DisabledByE10S,
+            experimentStatus=ExperimentStatus.ENROLLED_TREATMENT,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_TREATMENT,
+        )
+
+        # Re-set enrollment pref, like Normandy would do
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_TREATMENT)
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByTreatmentGroup,
+            sessionStatus=ContentWin32kLockdownState.EnabledByTreatmentGroup,
+            experimentStatus=ExperimentStatus.ENROLLED_TREATMENT,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_TREATMENT,
+        )
+
+    def test_41(self):
+        # [D=F] Enrolled Treatment [A#7] -> Restart [A#8] -> Enrolled Treatment-C -> Heade...
+
+        if self.default_is is not False:
+            return
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_TREATMENT)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.DisabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_TREATMENT,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByTreatmentGroup,
+            sessionStatus=ContentWin32kLockdownState.EnabledByTreatmentGroup,
+            experimentStatus=ExperimentStatus.ENROLLED_TREATMENT,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_TREATMENT,
+        )
+
+        # Re-set enrollment pref, like Normandy would do
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_TREATMENT)
+
+        self.restart(env={ENV_DISABLE_WIN32K: "1"})
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByEnvVar,
+            sessionStatus=ContentWin32kLockdownState.DisabledByEnvVar,
+            experimentStatus=ExperimentStatus.ENROLLED_TREATMENT,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_TREATMENT,
+        )
+
+        self.set_env(ENV_DISABLE_WIN32K, "")
+
+        # Re-set enrollment pref, like Normandy would do
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_TREATMENT)
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByTreatmentGroup,
+            sessionStatus=ContentWin32kLockdownState.EnabledByTreatmentGroup,
+            experimentStatus=ExperimentStatus.ENROLLED_TREATMENT,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_TREATMENT,
+        )
+
+    def test_42(self):
+        # [D=T] Enrolled Treatment [A#7T] -> Restart [A#8T] -> Enrolled Treatment-C -> On ...
+
+        if self.default_is is not True:
+            return
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_TREATMENT)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.EnabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_TREATMENT,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByTreatmentGroup,
+            sessionStatus=ContentWin32kLockdownState.EnabledByTreatmentGroup,
+            experimentStatus=ExperimentStatus.ENROLLED_TREATMENT,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_TREATMENT,
+        )
+
+        # Re-set enrollment pref, like Normandy would do
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_TREATMENT)
+
+        self.marionette.set_pref(Prefs.WIN32K, True)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByTreatmentGroup,
+            sessionStatus=ContentWin32kLockdownState.EnabledByTreatmentGroup,
+            experimentStatus=ExperimentStatus.ENROLLED_TREATMENT,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_TREATMENT,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByTreatmentGroup,
+            sessionStatus=ContentWin32kLockdownState.EnabledByTreatmentGroup,
+            experimentStatus=ExperimentStatus.ENROLLED_TREATMENT,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_TREATMENT,
+        )
+
+    def test_43(self):
+        # [D=T] Enrolled Treatment [A#7T] -> Restart [A#8T] -> Enrolled Treatment-C -> Off...
+
+        if self.default_is is not True:
+            return
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_TREATMENT)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.EnabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_TREATMENT,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByTreatmentGroup,
+            sessionStatus=ContentWin32kLockdownState.EnabledByTreatmentGroup,
+            experimentStatus=ExperimentStatus.ENROLLED_TREATMENT,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_TREATMENT,
+        )
+
+        # Re-set enrollment pref, like Normandy would do
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_TREATMENT)
+
+        self.marionette.set_pref(Prefs.WIN32K, False)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByUserPref,
+            sessionStatus=ContentWin32kLockdownState.EnabledByTreatmentGroup,
+            experimentStatus=ExperimentStatus.ENROLLED_TREATMENT,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.DISQUALIFIED,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByUserPref,
+            sessionStatus=ContentWin32kLockdownState.DisabledByUserPref,
+            experimentStatus=ExperimentStatus.DISQUALIFIED,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.DISQUALIFIED,
+        )
+
+    def test_44(self):
+        # [D=T] Enrolled Treatment [A#7T] -> Restart [A#8T] -> Enrolled Treatment-C -> Bad...
+
+        if self.default_is is not True:
+            return
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_TREATMENT)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.EnabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_TREATMENT,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByTreatmentGroup,
+            sessionStatus=ContentWin32kLockdownState.EnabledByTreatmentGroup,
+            experimentStatus=ExperimentStatus.ENROLLED_TREATMENT,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_TREATMENT,
+        )
+
+        # Re-set enrollment pref, like Normandy would do
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_TREATMENT)
+
+        self.marionette.set_pref(Prefs.WEBGL, False)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.MissingRemoteWebGL,
+            sessionStatus=ContentWin32kLockdownState.EnabledByTreatmentGroup,
+            experimentStatus=ExperimentStatus.ENROLLED_TREATMENT,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_TREATMENT,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.MissingRemoteWebGL,
+            sessionStatus=ContentWin32kLockdownState.MissingRemoteWebGL,
+            experimentStatus=ExperimentStatus.DISQUALIFIED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.DISQUALIFIED,
+        )
+
+    def test_45(self):
+        # [D=T] Enrolled Treatment [A#7T] -> Restart [A#8T] -> Enrolled Treatment-C -> E10...
+
+        if self.default_is is not True:
+            return
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_TREATMENT)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.EnabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_TREATMENT,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByTreatmentGroup,
+            sessionStatus=ContentWin32kLockdownState.EnabledByTreatmentGroup,
+            experimentStatus=ExperimentStatus.ENROLLED_TREATMENT,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_TREATMENT,
+        )
+
+        # Re-set enrollment pref, like Normandy would do
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_TREATMENT)
+
+        app_version = self.execute_script("return Services.appinfo.version")
+        self.restart(env={ENV_DISABLE_E10S: app_version})
+        self.set_env(ENV_DISABLE_E10S, "null")
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByE10S,
+            sessionStatus=ContentWin32kLockdownState.DisabledByE10S,
+            experimentStatus=ExperimentStatus.ENROLLED_TREATMENT,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_TREATMENT,
+        )
+
+        # Re-set enrollment pref, like Normandy would do
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_TREATMENT)
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByTreatmentGroup,
+            sessionStatus=ContentWin32kLockdownState.EnabledByTreatmentGroup,
+            experimentStatus=ExperimentStatus.ENROLLED_TREATMENT,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_TREATMENT,
+        )
+
+    def test_46(self):
+        # [D=T] Enrolled Treatment [A#7T] -> Restart [A#8T] -> Enrolled Treatment-C -> Hea...
+
+        if self.default_is is not True:
+            return
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_TREATMENT)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByDefault,
+            sessionStatus=ContentWin32kLockdownState.EnabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_TREATMENT,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByTreatmentGroup,
+            sessionStatus=ContentWin32kLockdownState.EnabledByTreatmentGroup,
+            experimentStatus=ExperimentStatus.ENROLLED_TREATMENT,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_TREATMENT,
+        )
+
+        # Re-set enrollment pref, like Normandy would do
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_TREATMENT)
+
+        self.restart(env={ENV_DISABLE_WIN32K: "1"})
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.DisabledByEnvVar,
+            sessionStatus=ContentWin32kLockdownState.DisabledByEnvVar,
+            experimentStatus=ExperimentStatus.ENROLLED_TREATMENT,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_TREATMENT,
+        )
+
+        self.set_env(ENV_DISABLE_WIN32K, "")
+
+        # Re-set enrollment pref, like Normandy would do
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_TREATMENT)
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.EnabledByTreatmentGroup,
+            sessionStatus=ContentWin32kLockdownState.EnabledByTreatmentGroup,
+            experimentStatus=ExperimentStatus.ENROLLED_TREATMENT,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_TREATMENT,
+        )
+
+    def test_47(self):
+        # [D=F] Bad Requirements [A#9] -> Restart [A#10] -> Enrolled Control [A S=MissingR...
+
+        if self.default_is is not False:
+            return
+
+        self.marionette.set_pref(Prefs.WEBGL, False)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.MissingRemoteWebGL,
+            sessionStatus=ContentWin32kLockdownState.DisabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.MissingRemoteWebGL,
+            sessionStatus=ContentWin32kLockdownState.MissingRemoteWebGL,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_CONTROL)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.MissingRemoteWebGL,
+            sessionStatus=ContentWin32kLockdownState.MissingRemoteWebGL,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_CONTROL,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.MissingRemoteWebGL,
+            sessionStatus=ContentWin32kLockdownState.MissingRemoteWebGL,
+            experimentStatus=ExperimentStatus.DISQUALIFIED,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.DISQUALIFIED,
+        )
+
+    def test_48(self):
+        # [D=F] Bad Requirements [A#9] -> Restart [A#10] -> Enrolled Treatment [A S=Missin...
+
+        if self.default_is is not False:
+            return
+
+        self.marionette.set_pref(Prefs.WEBGL, False)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.MissingRemoteWebGL,
+            sessionStatus=ContentWin32kLockdownState.DisabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.MissingRemoteWebGL,
+            sessionStatus=ContentWin32kLockdownState.MissingRemoteWebGL,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_TREATMENT)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.MissingRemoteWebGL,
+            sessionStatus=ContentWin32kLockdownState.MissingRemoteWebGL,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_TREATMENT,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.MissingRemoteWebGL,
+            sessionStatus=ContentWin32kLockdownState.MissingRemoteWebGL,
+            experimentStatus=ExperimentStatus.DISQUALIFIED,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.DISQUALIFIED,
+        )
+
+    def test_49(self):
+        # [D=F] Bad Requirements [A#9] -> Restart [A#10] -> On [A S=MissingRemoteWebGL SS=...
+
+        if self.default_is is not False:
+            return
+
+        self.marionette.set_pref(Prefs.WEBGL, False)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.MissingRemoteWebGL,
+            sessionStatus=ContentWin32kLockdownState.DisabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.MissingRemoteWebGL,
+            sessionStatus=ContentWin32kLockdownState.MissingRemoteWebGL,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        self.marionette.set_pref(Prefs.WIN32K, True)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.MissingRemoteWebGL,
+            sessionStatus=ContentWin32kLockdownState.MissingRemoteWebGL,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+    def test_50(self):
+        # [D=F] Bad Requirements [A#9] -> Restart [A#10] -> Off [A S=MissingRemoteWebGL SS...
+
+        if self.default_is is not False:
+            return
+
+        self.marionette.set_pref(Prefs.WEBGL, False)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.MissingRemoteWebGL,
+            sessionStatus=ContentWin32kLockdownState.DisabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.MissingRemoteWebGL,
+            sessionStatus=ContentWin32kLockdownState.MissingRemoteWebGL,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        self.marionette.set_pref(Prefs.WIN32K, False)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.MissingRemoteWebGL,
+            sessionStatus=ContentWin32kLockdownState.MissingRemoteWebGL,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+    def test_51(self):
+        # [D=T] Bad Requirements [A#9T] -> Restart [A#10T] -> Enrolled Control [A S=Missin...
+
+        if self.default_is is not True:
+            return
+
+        self.marionette.set_pref(Prefs.WEBGL, False)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.MissingRemoteWebGL,
+            sessionStatus=ContentWin32kLockdownState.EnabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.MissingRemoteWebGL,
+            sessionStatus=ContentWin32kLockdownState.MissingRemoteWebGL,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_CONTROL)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.MissingRemoteWebGL,
+            sessionStatus=ContentWin32kLockdownState.MissingRemoteWebGL,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_CONTROL,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.MissingRemoteWebGL,
+            sessionStatus=ContentWin32kLockdownState.MissingRemoteWebGL,
+            experimentStatus=ExperimentStatus.DISQUALIFIED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.DISQUALIFIED,
+        )
+
+    def test_52(self):
+        # [D=T] Bad Requirements [A#9T] -> Restart [A#10T] -> Enrolled Treatment [A S=Miss...
+
+        if self.default_is is not True:
+            return
+
+        self.marionette.set_pref(Prefs.WEBGL, False)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.MissingRemoteWebGL,
+            sessionStatus=ContentWin32kLockdownState.EnabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.MissingRemoteWebGL,
+            sessionStatus=ContentWin32kLockdownState.MissingRemoteWebGL,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+        self.set_enrollment_status(ExperimentStatus.ENROLLED_TREATMENT)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.MissingRemoteWebGL,
+            sessionStatus=ContentWin32kLockdownState.MissingRemoteWebGL,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.ENROLLED_TREATMENT,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.MissingRemoteWebGL,
+            sessionStatus=ContentWin32kLockdownState.MissingRemoteWebGL,
+            experimentStatus=ExperimentStatus.DISQUALIFIED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.DISQUALIFIED,
+        )
+
+    def test_53(self):
+        # [D=T] Bad Requirements [A#9T] -> Restart [A#10T] -> On [A S=MissingRemoteWebGL S...
+
+        if self.default_is is not True:
+            return
+
+        self.marionette.set_pref(Prefs.WEBGL, False)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.MissingRemoteWebGL,
+            sessionStatus=ContentWin32kLockdownState.EnabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.MissingRemoteWebGL,
+            sessionStatus=ContentWin32kLockdownState.MissingRemoteWebGL,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        self.marionette.set_pref(Prefs.WIN32K, True)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.MissingRemoteWebGL,
+            sessionStatus=ContentWin32kLockdownState.MissingRemoteWebGL,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+    def test_54(self):
+        # [D=T] Bad Requirements [A#9T] -> Restart [A#10T] -> Off [A S=MissingRemoteWebGL ...
+
+        if self.default_is is not True:
+            return
+
+        self.marionette.set_pref(Prefs.WEBGL, False)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.MissingRemoteWebGL,
+            sessionStatus=ContentWin32kLockdownState.EnabledByDefault,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        self.restart()
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.MissingRemoteWebGL,
+            sessionStatus=ContentWin32kLockdownState.MissingRemoteWebGL,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=True,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
+
+        self.marionette.set_pref(Prefs.WIN32K, False)
+
+        self.check_win32k_status(
+            status=ContentWin32kLockdownState.MissingRemoteWebGL,
+            sessionStatus=ContentWin32kLockdownState.MissingRemoteWebGL,
+            experimentStatus=ExperimentStatus.UNENROLLED,
+            pref=False,
+            enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+        )
diff --git a/toolkit/xre/test/marionette/test_win32k_enrollment.template.py b/toolkit/xre/test/marionette/test_win32k_enrollment.template.py
new file mode 100644
index 0000000000..30dc7fed33
--- /dev/null
+++ b/toolkit/xre/test/marionette/test_win32k_enrollment.template.py
@@ -0,0 +1,204 @@
+from contextlib import contextmanager
+
+from marionette_harness import MarionetteTestCase
+
+
+class ExperimentStatus:
+    UNENROLLED = 0
+    ENROLLED_CONTROL = 1
+    ENROLLED_TREATMENT = 2
+    DISQUALIFIED = 3
+
+
+class ContentWin32kLockdownState:
+    LockdownEnabled = 1
+    MissingWebRender = 2
+    OperatingSystemNotSupported = 3
+    PrefNotSet = 4
+    MissingRemoteWebGL = 5
+    MissingNonNativeTheming = 6
+    DisabledByEnvVar = 7
+    DisabledBySafeMode = 8
+    DisabledByE10S = 9
+    DisabledByUserPref = 10
+    EnabledByUserPref = 11
+    DisabledByControlGroup = 12
+    EnabledByTreatmentGroup = 13
+    DisabledByDefault = 14
+    EnabledByDefault = 15
+
+
+class Prefs:
+    ENROLLMENT_STATUS = "security.sandbox.content.win32k-experiment.enrollmentStatus"
+    STARTUP_ENROLLMENT_STATUS = (
+        "security.sandbox.content.win32k-experiment.startupEnrollmentStatus"
+    )
+    WIN32K = "security.sandbox.content.win32k-disable"
+    WEBGL = "webgl.out-of-process"
+
+
+ENV_DISABLE_WIN32K = "MOZ_ENABLE_WIN32K"
+ENV_DISABLE_E10S = "MOZ_FORCE_DISABLE_E10S"
+
+
+class TestWin32kAutostart(MarionetteTestCase):
+    SANDBOX_NAME = "win32k-autostart"
+
+    def execute_script(self, code, *args, **kwargs):
+        with self.marionette.using_context(self.marionette.CONTEXT_CHROME):
+            return self.marionette.execute_script(
+                code, new_sandbox=False, sandbox=self.SANDBOX_NAME, *args, **kwargs
+            )
+
+    def get_win32k_status(self):
+        return self.execute_script(
+            r"""
+          let win = Services.wm.getMostRecentWindow("navigator:browser");
+          let ses = "security.sandbox.content.win32k-experiment.startupEnrollmentStatus";
+          return {
+            win32kSessionStatus: Services.appinfo.win32kSessionStatus,
+            win32kStatus: Services.appinfo.win32kLiveStatusTestingOnly,
+            win32kExperimentStatus: Services.appinfo.win32kExperimentStatus,
+            win32kPref: Services.prefs.getBoolPref("security.sandbox.content.win32k-disable"),
+            win32kStartupEnrollmentStatusPref: Services.prefs.getIntPref(ses),
+          };
+        """
+        )
+
+    def check_win32k_status(
+        self, status, sessionStatus, experimentStatus, pref, enrollmentStatusPref
+    ):
+        # We CANNOT check win32kEnrollmentStatusPref after a restart because we only set this
+        # pref on the default branch, and it goes away after a restart, so we only check
+        # the startupEnrollmentStatusPref
+        expected = {
+            "win32kSessionStatus": sessionStatus,
+            "win32kStatus": status,
+            "win32kExperimentStatus": experimentStatus,
+            "win32kPref": pref,
+            "win32kStartupEnrollmentStatusPref": enrollmentStatusPref,
+        }
+
+        status = self.get_win32k_status()
+
+        for prop, value in expected.items():
+            self.assertEqual(
+                status[prop],
+                value,
+                "%s should have the value `%r`, but has `%r`"
+                % (prop, value, status[prop]),
+            )
+
+    def set_env(self, env, value):
+        self.execute_script(
+            "env.set(arguments[0], arguments[1]);", script_args=(env, value)
+        )
+
+    def get_env(self, env):
+        return self.execute_script("return env.get(arguments[0]);", script_args=(env,))
+
+    def set_enrollment_status(self, status):
+        self.marionette.set_pref(Prefs.ENROLLMENT_STATUS, status, default_branch=True)
+
+        updated_status = self.marionette.get_pref(Prefs.ENROLLMENT_STATUS)
+        self.assertTrue(
+            status == updated_status or updated_status == ExperimentStatus.DISQUALIFIED
+        )
+        startup_status = self.marionette.get_pref(Prefs.STARTUP_ENROLLMENT_STATUS)
+        self.assertEqual(
+            startup_status,
+            updated_status,
+            "Startup enrollment status (%r) should match "
+            "session status (%r)" % (startup_status, updated_status),
+        )
+
+    def restart(self, prefs=None, env=None):
+        if prefs:
+            self.marionette.set_prefs(prefs)
+
+        if env:
+            for name, value in env.items():
+                self.set_env(name, value)
+
+        self.marionette.restart(in_app=True, clean=False)
+        self.setUpSession()
+
+        # Sanity check our environment.
+        if prefs:
+            for key, val in prefs.items():
+                if val is not None:
+                    self.assertEqual(self.marionette.get_pref(key), val)
+        if env:
+            for key, val in env.items():
+                self.assertEqual(self.get_env(key), val or "")
+
+    def setUpSession(self):
+        self.marionette.set_context(self.marionette.CONTEXT_CHROME)
+
+        self.execute_script(
+            r"""
+          // We're running in a function, in a sandbox, that inherits from an
+          // X-ray wrapped window. Anything we want to be globally available
+          // needs to be defined on that window.
+          window.env = Services.env;
+        """
+        )
+
+    @contextmanager
+    def full_restart(self):
+        profile = self.marionette.instance.profile
+        try:
+            self.marionette.quit()
+            yield profile
+        finally:
+            self.marionette.start_session()
+            self.setUpSession()
+
+    def setUp(self):
+        super(TestWin32kAutostart, self).setUp()
+
+        # If we have configured marionette to require a particular value for
+        # `win32k.autostart`, remove it as a forced pref until `tearDown`, and
+        # perform a clean restart, so we run this test without the pref
+        # pre-configured.
+        self.win32kRequired = None
+        if Prefs.WIN32K in self.marionette.instance.required_prefs:
+            self.win32kRequired = self.marionette.instance.required_prefs[Prefs.WIN32K]
+            del self.marionette.instance.required_prefs[Prefs.WIN32K]
+            self.marionette.restart(in_app=False, clean=True)
+
+        self.setUpSession()
+
+        # Marionette doesn't let you set preferences on the default branch before startup
+        # so we can't test the default=False and default=True scenarios in one test
+        # What we can do is generate all the tests, and then only run the runs for which
+        # the default is.  (And run the other ones locally to make sure they work before
+        # we land it.)
+        prefJS = 'return Services.prefs.getBoolPref("security.sandbox.content.win32k-disable");'
+        self.default_is = self.execute_script(prefJS)
+
+        if self.default_is is False:
+            # Win32k status must start out with `disabledByDefault`
+            self.check_win32k_status(
+                status=ContentWin32kLockdownState.DisabledByDefault,
+                sessionStatus=ContentWin32kLockdownState.DisabledByDefault,
+                experimentStatus=ExperimentStatus.UNENROLLED,
+                pref=False,
+                enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+            )
+        else:
+            # Win32k status must start out with `enabledByDefault`
+            self.check_win32k_status(
+                status=ContentWin32kLockdownState.EnabledByDefault,
+                sessionStatus=ContentWin32kLockdownState.EnabledByDefault,
+                experimentStatus=ExperimentStatus.UNENROLLED,
+                pref=True,
+                enrollmentStatusPref=ExperimentStatus.UNENROLLED,
+            )
+
+    def tearDown(self):
+        if self.win32kRequired is not None:
+            self.marionette.instance.required_prefs[Prefs.WIN32K] = self.win32kRequired
+        self.marionette.restart(in_app=False, clean=True)
+
+        super(TestWin32kAutostart, self).tearDown()
diff --git a/toolkit/xre/test/marionette/win32k_tests.txt b/toolkit/xre/test/marionette/win32k_tests.txt
new file mode 100644
index 0000000000..76068de268
--- /dev/null
+++ b/toolkit/xre/test/marionette/win32k_tests.txt
@@ -0,0 +1,167 @@
+#############################################

+# This file serves as the test case list for gen_win32k_tests.py

+

+#############################################

+# Only here for reference:

+

+# MissingWebRender = 2

+# OperatingSystemNotSupported = 3

+# MissingRemoteWebGL = 5

+# DisabledByEnvVar = 7

+# DisabledBySafeMode = 8

+# DisabledByE10S = 9

+# DisabledByUserPref = 10

+# EnabledByUserPref = 11

+# DisabledByControlGroup = 12

+# EnabledByTreatmentGroup = 13

+# DisabledByDefault = 14

+# EnabledByDefault = 15

+

+# UNENROLLED

+# ENROLLED_CONTROL

+# ENROLLED_TREATMENT

+# DISQUALIFIED

+

+#############################################

+# Assertion Mappings

+# Shorthand values for the test cases below.  Instead of writing out the whole thing

+# you can just do [A#5]

+

+ > 1  : [A S=DisabledByDefault SS=DisabledByDefault ES=UNENROLLED P=False ESP=UNENROLLED]

+ > 1T : [A S=EnabledByDefault SS=EnabledByDefault ES=UNENROLLED P=True ESP=UNENROLLED]

+ > 2  : [A S=EnabledByDefault SS=EnabledByDefault ES=UNENROLLED P=True ESP=UNENROLLED]

+ > 3  : [A S=EnabledByUserPref SS=DisabledByDefault ES=UNENROLLED P=True ESP=UNENROLLED]

+ > 3T : [A S=EnabledByDefault SS=EnabledByDefault ES=UNENROLLED P=True ESP=UNENROLLED]

+ > 4  : [A S=EnabledByUserPref SS=EnabledByUserPref ES=UNENROLLED P=True ESP=UNENROLLED]

+ > 4T : [A S=EnabledByDefault SS=EnabledByDefault ES=UNENROLLED P=True ESP=UNENROLLED]

+ > 5  : [A S=DisabledByDefault SS=DisabledByDefault ES=UNENROLLED P=False ESP=ENROLLED_CONTROL]

+ > 5T : [A S=EnabledByDefault SS=EnabledByDefault ES=UNENROLLED P=True ESP=ENROLLED_CONTROL]

+ > 6  : [A S=DisabledByControlGroup SS=DisabledByControlGroup ES=ENROLLED_CONTROL P=False ESP=ENROLLED_CONTROL]

+ > 6T : [A S=DisabledByControlGroup SS=DisabledByControlGroup ES=ENROLLED_CONTROL P=True ESP=ENROLLED_CONTROL]

+ > 7  : [A S=DisabledByDefault SS=DisabledByDefault ES=UNENROLLED P=False ESP=ENROLLED_TREATMENT]

+ > 7T : [A S=EnabledByDefault SS=EnabledByDefault ES=UNENROLLED P=True ESP=ENROLLED_TREATMENT]

+ > 8  : [A S=EnabledByTreatmentGroup SS=EnabledByTreatmentGroup ES=ENROLLED_TREATMENT P=False ESP=ENROLLED_TREATMENT]

+ > 8T : [A S=EnabledByTreatmentGroup SS=EnabledByTreatmentGroup ES=ENROLLED_TREATMENT P=True ESP=ENROLLED_TREATMENT]

+ > 9  : [A S=MissingRemoteWebGL SS=DisabledByDefault ES=UNENROLLED P=False ESP=UNENROLLED]

+ > 9T : [A S=MissingRemoteWebGL SS=EnabledByDefault ES=UNENROLLED P=True ESP=UNENROLLED]

+ > 10 : [A S=MissingRemoteWebGL SS=MissingRemoteWebGL ES=UNENROLLED P=False ESP=UNENROLLED]

+ > 10T: [A S=MissingRemoteWebGL SS=MissingRemoteWebGL ES=UNENROLLED P=True ESP=UNENROLLED]

+ 

+

+# TODO

+# - win32k env var tests

+

+

+#############################################

+# Tests

+

+# Syntax:

+#   [D=T] - is the default value for win32k lockdown pref 'false' or 'true'

+#   Action -> Action

+#       Valid Actions: 

+#             Nothing

+#             Enrolled Control/Treatment

+#             On/Off (changes win32k pref)

+#             Restart

+#             E10s (Restarts with E10s disabled)

+#             Header-On - Restart with MOZ_ENABLE_WIN32K set

+#             Header-Off - unset MOZ_ENABLE_WIN32K but do not restart

+#             Bad Requirements - sets webg out of process to false, invalidating win32k

+#             Enrolled /Control/Treatment]-C:

+#                   The enrollment pref is set by normandy on _every_ startup on the

+#                   default branch, where it doesn't persist.

+#                   This action represents normandy doing its normal set that

+#                   occurs after a restart.  If Normandy doesn't do it, the

+#                   startupEnrollmentPref is set back to 0 after restart, which is expected.

+#   [A S= SS= ES= P= ESP=] - trigger an assertion check for the listed values

+#        S  - 'Status' or the current value of calculating GetWin32kLockdownState()

+#        SS - 'Session Status' or the current value of set-once-at-startup static variable gWin32kStatus

+#        ES - 'Experiment Status' or the value of gWin32kExperimentStatus

+#        P  - 'Pref' or the value of security.sandbox.content.win32k-disable

+#        ESP- 'Enrollment Status Pref' or the value of security.sandbox.content.win32k-experiment.startupEnrollmentStatus

+#   [A#5] - trigger an assertion check from the mapping table above

+

+

+# Safe Mode tests are currently not generated, as I don't know how to make marionette restart in safe mode

+

+#################

+ - [D=F] Nothing [A#1] -> Enrolled Control [A S=DisabledByDefault SS=DisabledByDefault ES=UNENROLLED P=False ESP=ENROLLED_CONTROL] -> Restart [A S=DisabledByControlGroup SS=DisabledByControlGroup ES=ENROLLED_CONTROL P=False ESP=ENROLLED_CONTROL]

+ - [D=F] Nothing [A#1] -> Enrolled Treatment [A S=DisabledByDefault SS=DisabledByDefault ES=UNENROLLED P=False ESP=ENROLLED_TREATMENT] -> Restart [A S=EnabledByTreatmentGroup SS=EnabledByTreatmentGroup ES=ENROLLED_TREATMENT P=False ESP=ENROLLED_TREATMENT]

+ - [D=F] Nothing [A#1] -> On [A S=EnabledByUserPref SS=DisabledByDefault ES=UNENROLLED P=True ESP=UNENROLLED] -> Restart [A S=EnabledByUserPref SS=EnabledByUserPref ES=UNENROLLED P=True ESP=UNENROLLED]

+ - [D=F] Nothing [A#1] -> Off [A#1] -> Restart [A#1]

+ - [D=F] Nothing [A#1] -> On -> Bad Requirements [A S=MissingRemoteWebGL SS=DisabledByDefault ES=UNENROLLED P=True ESP=UNENROLLED] -> Restart [A S=MissingRemoteWebGL SS=MissingRemoteWebGL ES=UNENROLLED P=True ESP=UNENROLLED]

+ - [D=F] Nothing [A#1] -> On -> E10S [A S=DisabledByE10S SS=DisabledByE10S ES=UNENROLLED P=True ESP=UNENROLLED]

+ - [D=F] Nothing [A#1] -> On -> Header-On [A S=DisabledByEnvVar SS=DisabledByEnvVar ES=UNENROLLED P=True ESP=UNENROLLED] -> Header-Off [A S=EnabledByUserPref SS=DisabledByEnvVar ES=UNENROLLED P=True ESP=UNENROLLED]

+ - [D=F] Nothing [A#1] -> Safe Mode -> Restart

+

+#################

+ - [D=T] Nothing [A#1T] -> Enrolled Control [A S=EnabledByDefault SS=EnabledByDefault ES=UNENROLLED P=True ESP=ENROLLED_CONTROL] -> Restart [A S=DisabledByControlGroup SS=DisabledByControlGroup ES=ENROLLED_CONTROL P=True ESP=ENROLLED_CONTROL]

+ - [D=T] Nothing [A#1T] -> Enrolled Treatment [A S=EnabledByDefault SS=EnabledByDefault ES=UNENROLLED P=True ESP=ENROLLED_TREATMENT] -> Restart [A S=EnabledByTreatmentGroup SS=EnabledByTreatmentGroup ES=ENROLLED_TREATMENT P=True ESP=ENROLLED_TREATMENT]

+ - [D=T] Nothing [A#1T] -> On [A S=EnabledByDefault SS=EnabledByDefault ES=UNENROLLED P=True ESP=UNENROLLED] -> Restart [A S=EnabledByDefault SS=EnabledByDefault ES=UNENROLLED P=True ESP=UNENROLLED]

+ - [D=T] Nothing [A#1T] -> Off [A S=DisabledByUserPref SS=EnabledByDefault ES=UNENROLLED P=False ESP=UNENROLLED] -> Restart [A S=DisabledByUserPref SS=DisabledByUserPref ES=UNENROLLED P=False ESP=UNENROLLED]

+ - [D=T] Nothing [A#1T] -> On -> Bad Requirements [A S=MissingRemoteWebGL SS=EnabledByDefault ES=UNENROLLED P=True ESP=UNENROLLED] -> Restart [A S=MissingRemoteWebGL SS=MissingRemoteWebGL ES=UNENROLLED P=True ESP=UNENROLLED]

+ - [D=T] Nothing [A#1T] -> On -> E10S [A S=DisabledByE10S SS=DisabledByE10S ES=UNENROLLED P=True ESP=UNENROLLED]

+ - [D=T] Nothing [A#1T] -> On -> Header-On [A S=DisabledByEnvVar SS=DisabledByEnvVar ES=UNENROLLED P=True ESP=UNENROLLED] -> Header-Off [A S=EnabledByDefault SS=DisabledByEnvVar ES=UNENROLLED P=True ESP=UNENROLLED]

+ - [D=T] Nothing [A#1T] -> Safe Mode -> Restart

+

+#################

+ - [D=F] On [A#3] -> Restart [A#4] -> Enrolled Control [A S=EnabledByUserPref SS=EnabledByUserPref ES=UNENROLLED P=True ESP=ENROLLED_CONTROL] -> Restart [A S=EnabledByUserPref SS=EnabledByUserPref ES=DISQUALIFIED P=True ESP=DISQUALIFIED]

+ - [D=F] On [A#3] -> Restart [A#4] -> Enrolled Treatment [A S=EnabledByUserPref SS=EnabledByUserPref ES=UNENROLLED P=True ESP=ENROLLED_TREATMENT] -> Restart [A S=EnabledByUserPref SS=EnabledByUserPref ES=DISQUALIFIED P=True ESP=DISQUALIFIED]

+ - [D=F] On [A#3] -> Restart [A#4] -> Off [A S=DisabledByDefault SS=EnabledByUserPref ES=UNENROLLED P=False ESP=UNENROLLED] -> Restart [A S=DisabledByDefault SS=DisabledByDefault ES=UNENROLLED P=False ESP=UNENROLLED]

+ - [D=F] On [A#3] -> Restart [A#4] -> Bad Requirements [A S=MissingRemoteWebGL SS=EnabledByUserPref ES=UNENROLLED P=True ESP=UNENROLLED]

+ - [D=F] On [A#3] -> Restart [A#4] -> E10S [A S=DisabledByE10S SS=DisabledByE10S ES=UNENROLLED P=True ESP=UNENROLLED] -> Restart [A#4]

+ - [D=F] On [A#3] -> Restart [A#4] -> Header-On [A S=DisabledByEnvVar SS=DisabledByEnvVar ES=UNENROLLED P=True ESP=UNENROLLED] -> Header-Off -> Restart [A#4]

+ - [D=F] On [A#3] -> Restart [A#4] -> Safe Mode

+

+#################

+ - [D=T] On [A#3T] -> Restart [A#4T] -> Enrolled Control [A S=EnabledByDefault SS=EnabledByDefault ES=UNENROLLED P=True ESP=ENROLLED_CONTROL] -> Restart [A S=DisabledByControlGroup SS=DisabledByControlGroup ES=ENROLLED_CONTROL P=True ESP=ENROLLED_CONTROL]

+ - [D=T] On [A#3T] -> Restart [A#4T] -> Enrolled Treatment [A S=EnabledByDefault SS=EnabledByDefault ES=UNENROLLED P=True ESP=ENROLLED_TREATMENT] -> Restart [A S=EnabledByTreatmentGroup SS=EnabledByTreatmentGroup ES=ENROLLED_TREATMENT P=True ESP=ENROLLED_TREATMENT]

+ - [D=T] On [A#3T] -> Restart [A#4T] -> Off [A S=DisabledByUserPref SS=EnabledByDefault ES=UNENROLLED P=False ESP=UNENROLLED] -> Restart [A S=DisabledByUserPref SS=DisabledByUserPref ES=UNENROLLED P=False ESP=UNENROLLED]

+ - [D=T] On [A#3T] -> Restart [A#4T] -> Bad Requirements [A S=MissingRemoteWebGL SS=EnabledByDefault ES=UNENROLLED P=True ESP=UNENROLLED]

+ - [D=T] On [A#3T] -> Restart [A#4T] -> E10S [A S=DisabledByE10S SS=DisabledByE10S ES=UNENROLLED P=True ESP=UNENROLLED] -> Restart [A#4T]

+ - [D=T] On [A#3T] -> Restart [A#4T] -> Header-On [A S=DisabledByEnvVar SS=DisabledByEnvVar ES=UNENROLLED P=True ESP=UNENROLLED] -> Header-Off -> Restart [A#4T]

+ - [D=T] On [A#3T] -> Restart [A#4T] -> Safe Mode

+

+#################

+ - [D=F] Enrolled Control [A#5] -> Restart [A#6] -> Enrolled Control-C -> On [A S=EnabledByUserPref SS=DisabledByControlGroup ES=ENROLLED_CONTROL P=True ESP=DISQUALIFIED] -> Restart [A S=EnabledByUserPref SS=EnabledByUserPref ES=DISQUALIFIED P=True ESP=DISQUALIFIED]

+ - [D=F] Enrolled Control [A#5] -> Restart [A#6] -> Off [A#6]

+ - [D=F] Enrolled Control [A#5] -> Restart [A#6] -> Enrolled Control-C -> Bad Requirements [A S=MissingRemoteWebGL SS=DisabledByControlGroup ES=ENROLLED_CONTROL P=False ESP=ENROLLED_CONTROL] -> Restart [A S=MissingRemoteWebGL SS=MissingRemoteWebGL ES=DISQUALIFIED P=False ESP=DISQUALIFIED]

+ - [D=F] Enrolled Control [A#5] -> Restart [A#6] -> Enrolled Control-C -> E10S [A S=DisabledByE10S SS=DisabledByE10S ES=ENROLLED_CONTROL P=False ESP=ENROLLED_CONTROL] -> Enrolled Control-C -> Restart [A#6]

+ - [D=F] Enrolled Control [A#5] -> Restart [A#6] -> Enrolled Control-C -> Header-On [A S=DisabledByEnvVar SS=DisabledByEnvVar ES=ENROLLED_CONTROL P=False ESP=ENROLLED_CONTROL] -> Header-Off -> Enrolled Control-C -> Restart [A#6]

+ - [D=F] Enrolled Control [A#5] -> Restart [A#6] -> Safe Mode -> 

+

+#################

+ - [D=T] Enrolled Control [A#5T] -> Restart [A#6T] -> Enrolled Control-C -> On [A S=DisabledByControlGroup SS=DisabledByControlGroup ES=ENROLLED_CONTROL P=True ESP=ENROLLED_CONTROL] -> Restart [A S=DisabledByControlGroup SS=DisabledByControlGroup ES=ENROLLED_CONTROL P=True ESP=ENROLLED_CONTROL]

+ - [D=T] Enrolled Control [A#5T] -> Restart [A#6T] -> Off [A S=DisabledByUserPref SS=DisabledByControlGroup ES=ENROLLED_CONTROL P=False ESP=DISQUALIFIED]

+ - [D=T] Enrolled Control [A#5T] -> Restart [A#6T] -> Enrolled Control-C -> Bad Requirements [A S=MissingRemoteWebGL SS=DisabledByControlGroup ES=ENROLLED_CONTROL P=True ESP=ENROLLED_CONTROL] -> Restart [A S=MissingRemoteWebGL SS=MissingRemoteWebGL ES=DISQUALIFIED P=True ESP=DISQUALIFIED]

+ - [D=T] Enrolled Control [A#5T] -> Restart [A#6T] -> Enrolled Control-C -> E10S [A S=DisabledByE10S SS=DisabledByE10S ES=ENROLLED_CONTROL P=True ESP=ENROLLED_CONTROL] -> Enrolled Control-C -> Restart [A#6T]

+ - [D=T] Enrolled Control [A#5T] -> Restart [A#6T] -> Enrolled Control-C -> Header-On [A S=DisabledByEnvVar SS=DisabledByEnvVar ES=ENROLLED_CONTROL P=True ESP=ENROLLED_CONTROL] -> Header-Off -> Enrolled Control-C -> Restart [A#6T]

+ - [D=T] Enrolled Control [A#5T] -> Restart [A#6T] -> Safe Mode -> 

+

+#################

+ - [D=F] Enrolled Treatment [A#7] -> Restart [A#8] -> Enrolled Treatment-C -> On [A S=EnabledByUserPref SS=EnabledByTreatmentGroup ES=ENROLLED_TREATMENT P=True ESP=DISQUALIFIED] -> Restart [A S=EnabledByUserPref SS=EnabledByUserPref ES=DISQUALIFIED P=True ESP=DISQUALIFIED]

+ - [D=F] Enrolled Treatment [A#7] -> Restart [A#8] -> Enrolled Treatment-C -> Off [A#8] -> Restart [A#8]

+ - [D=F] Enrolled Treatment [A#7] -> Restart [A#8] -> Enrolled Treatment-C -> Bad Requirements [A S=MissingRemoteWebGL SS=EnabledByTreatmentGroup ES=ENROLLED_TREATMENT P=False ESP=ENROLLED_TREATMENT] -> Restart [A S=MissingRemoteWebGL SS=MissingRemoteWebGL ES=DISQUALIFIED P=False ESP=DISQUALIFIED]

+ - [D=F] Enrolled Treatment [A#7] -> Restart [A#8] -> Enrolled Treatment-C -> E10S [A S=DisabledByE10S SS=DisabledByE10S ES=ENROLLED_TREATMENT P=False ESP=ENROLLED_TREATMENT] -> Enrolled Treatment-C -> Restart [A#8]

+ - [D=F] Enrolled Treatment [A#7] -> Restart [A#8] -> Enrolled Treatment-C -> Header-On [A S=DisabledByEnvVar SS=DisabledByEnvVar ES=ENROLLED_TREATMENT P=False ESP=ENROLLED_TREATMENT] -> Header-Off -> Enrolled Treatment-C -> Restart [A#8]

+ - [D=F] Enrolled Treatment [A#7] -> Restart [A#8] -> Safe Mode ->

+

+#################

+ - [D=T] Enrolled Treatment [A#7T] -> Restart [A#8T] -> Enrolled Treatment-C -> On [A S=EnabledByTreatmentGroup SS=EnabledByTreatmentGroup ES=ENROLLED_TREATMENT P=True ESP=ENROLLED_TREATMENT] -> Restart [A S=EnabledByTreatmentGroup SS=EnabledByTreatmentGroup ES=ENROLLED_TREATMENT P=True ESP=ENROLLED_TREATMENT]

+ - [D=T] Enrolled Treatment [A#7T] -> Restart [A#8T] -> Enrolled Treatment-C -> Off [A S=DisabledByUserPref SS=EnabledByTreatmentGroup ES=ENROLLED_TREATMENT P=False ESP=DISQUALIFIED] -> Restart [A S=DisabledByUserPref SS=DisabledByUserPref ES=DISQUALIFIED P=False ESP=DISQUALIFIED]

+ - [D=T] Enrolled Treatment [A#7T] -> Restart [A#8T] -> Enrolled Treatment-C -> Bad Requirements [A S=MissingRemoteWebGL SS=EnabledByTreatmentGroup ES=ENROLLED_TREATMENT P=True ESP=ENROLLED_TREATMENT] -> Restart [A S=MissingRemoteWebGL SS=MissingRemoteWebGL ES=DISQUALIFIED P=True ESP=DISQUALIFIED]

+ - [D=T] Enrolled Treatment [A#7T] -> Restart [A#8T] -> Enrolled Treatment-C -> E10S [A S=DisabledByE10S SS=DisabledByE10S ES=ENROLLED_TREATMENT P=True ESP=ENROLLED_TREATMENT] -> Enrolled Treatment-C -> Restart [A#8T]

+ - [D=T] Enrolled Treatment [A#7T] -> Restart [A#8T] -> Enrolled Treatment-C -> Header-On [A S=DisabledByEnvVar SS=DisabledByEnvVar ES=ENROLLED_TREATMENT P=True ESP=ENROLLED_TREATMENT] -> Header-Off -> Enrolled Treatment-C -> Restart [A#8T]

+ - [D=T] Enrolled Treatment [A#7T] -> Restart [A#8T] -> Safe Mode ->

+

+#################

+ - [D=F] Bad Requirements [A#9] -> Restart [A#10] -> Enrolled Control [A S=MissingRemoteWebGL SS=MissingRemoteWebGL ES=UNENROLLED P=False ESP=ENROLLED_CONTROL] -> Restart [A S=MissingRemoteWebGL SS=MissingRemoteWebGL ES=DISQUALIFIED P=False ESP=DISQUALIFIED] 

+ - [D=F] Bad Requirements [A#9] -> Restart [A#10] -> Enrolled Treatment [A S=MissingRemoteWebGL SS=MissingRemoteWebGL ES=UNENROLLED P=False ESP=ENROLLED_TREATMENT] -> Restart [A S=MissingRemoteWebGL SS=MissingRemoteWebGL ES=DISQUALIFIED P=False ESP=DISQUALIFIED] 

+ - [D=F] Bad Requirements [A#9] -> Restart [A#10] -> On [A S=MissingRemoteWebGL SS=MissingRemoteWebGL ES=UNENROLLED P=True ESP=UNENROLLED]

+ - [D=F] Bad Requirements [A#9] -> Restart [A#10] -> Off [A S=MissingRemoteWebGL SS=MissingRemoteWebGL ES=UNENROLLED P=False ESP=UNENROLLED]

+

+#################

+ - [D=T] Bad Requirements [A#9T] -> Restart [A#10T] -> Enrolled Control [A S=MissingRemoteWebGL SS=MissingRemoteWebGL ES=UNENROLLED P=True ESP=ENROLLED_CONTROL] -> Restart [A S=MissingRemoteWebGL SS=MissingRemoteWebGL ES=DISQUALIFIED P=True ESP=DISQUALIFIED] 

+ - [D=T] Bad Requirements [A#9T] -> Restart [A#10T] -> Enrolled Treatment [A S=MissingRemoteWebGL SS=MissingRemoteWebGL ES=UNENROLLED P=True ESP=ENROLLED_TREATMENT] -> Restart [A S=MissingRemoteWebGL SS=MissingRemoteWebGL ES=DISQUALIFIED P=True ESP=DISQUALIFIED] 

+ - [D=T] Bad Requirements [A#9T] -> Restart [A#10T] -> On [A S=MissingRemoteWebGL SS=MissingRemoteWebGL ES=UNENROLLED P=True ESP=UNENROLLED]

+ - [D=T] Bad Requirements [A#9T] -> Restart [A#10T] -> Off [A S=MissingRemoteWebGL SS=MissingRemoteWebGL ES=UNENROLLED P=False ESP=UNENROLLED]

diff --git a/toolkit/xre/test/mochitest.ini b/toolkit/xre/test/mochitest.ini
new file mode 100644
index 0000000000..ccbb08ed97
--- /dev/null
+++ b/toolkit/xre/test/mochitest.ini
@@ -0,0 +1,3 @@
+[DEFAULT]
+
+[test_fpuhandler.html]
diff --git a/toolkit/xre/test/show_hash.js b/toolkit/xre/test/show_hash.js
new file mode 100644
index 0000000000..28674e6840
--- /dev/null
+++ b/toolkit/xre/test/show_hash.js
@@ -0,0 +1,4 @@
+const xre = Cc["@mozilla.org/xre/directory-provider;1"].getService(
+  Ci.nsIXREDirProvider
+);
+dump(`${xre.getInstallHash(false)}\n`);
diff --git a/toolkit/xre/test/test_fpuhandler.html b/toolkit/xre/test/test_fpuhandler.html
new file mode 100644
index 0000000000..a3869f2ecf
--- /dev/null
+++ b/toolkit/xre/test/test_fpuhandler.html
@@ -0,0 +1,36 @@
+<head>
+  <title>Floating-point exception handler test</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+
+<body onload="runTest()">
+  <embed id="plugin1" type="application/x-test" width="400" height="400"></embed>
+
+  <script class="testbody" type="application/javascript">
+  SimpleTest.waitForExplicitFinish();
+
+  function doDiv(x, y) {
+    var z;
+    z = x / y;
+
+    for (let i = 0 + x; i < 1000; ++i)
+      z = y / x;
+
+    z = x / y;
+    return z;
+  }
+
+  function runTest() {
+    ok(isNaN(doDiv(0.0, 0.0)), "Undefined division-by-zero doesn't crash");
+
+    try {
+      document.getElementById("plugin1").enableFPExceptions();
+    } catch (e) {
+      ok(true, "No special code to set the FPU bit in the testplugin.");
+      SimpleTest.finish();
+      return;
+    }
+
+    ok(isNaN(doDiv(0.0, 0.0)), "Undefined division-by-zero doesn't crash again.");
+    SimpleTest.finish();
+  }
+  </script>
diff --git a/toolkit/xre/test/test_install_hash.js b/toolkit/xre/test/test_install_hash.js
new file mode 100644
index 0000000000..9dc331fac5
--- /dev/null
+++ b/toolkit/xre/test/test_install_hash.js
@@ -0,0 +1,146 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+/**
+ * This runs the xpcshell binary with different cases for the executable path.
+ * They should all result in the same installation hash.
+ */
+
+const { Subprocess } = ChromeUtils.importESModule(
+  "resource://gre/modules/Subprocess.sys.mjs"
+);
+
+const XRE = Cc["@mozilla.org/xre/directory-provider;1"].getService(
+  Ci.nsIXREDirProvider
+);
+const HASH = XRE.getInstallHash(false);
+const EXE = Services.dirsvc.get("XREExeF", Ci.nsIFile);
+const SCRIPT = do_get_file("show_hash.js", false);
+
+async function getHash(bin) {
+  try {
+    // If this test is running through firefox.exe -xpcshell, we need
+    // to make sure to execute the script through it as well.
+    let args = [];
+    if (!bin.leafName.startsWith("xpcshell")) {
+      args.push("-xpcshell");
+    }
+    args.push(SCRIPT.path);
+
+    let proc = await Subprocess.call({
+      command: bin.path,
+      arguments: args,
+    });
+
+    let result = "";
+    let string;
+    while ((string = await proc.stdout.readString())) {
+      result += string;
+    }
+
+    return result.trim();
+  } catch (e) {
+    if (e.errorCode == Subprocess.ERROR_BAD_EXECUTABLE) {
+      return null;
+    }
+    throw e;
+  }
+}
+
+// Walks through a path's entries and calls a mutator function to change the
+// case of each.
+function mutatePath(path, mutator) {
+  let parts = [];
+  let index = 0;
+  while (path.parent != null) {
+    parts.push(mutator(path.leafName, index++));
+    path = path.parent;
+  }
+
+  while (parts.length) {
+    path.append(parts.pop());
+  }
+
+  return path;
+}
+
+// Counts how many path parts a mutator will be called for.
+function countParts(path) {
+  let index = 0;
+  while (path.parent != null) {
+    path = path.parent;
+    index++;
+  }
+  return index;
+}
+
+add_task(async function testSameBinary() {
+  // Running with the same binary path should definitely work and give the same
+  // hash.
+  Assert.equal(
+    await getHash(EXE),
+    HASH,
+    "Should have the same hash when running the same binary."
+  );
+});
+
+add_task(async function testUpperCase() {
+  let upper = mutatePath(EXE, p => p.toLocaleUpperCase());
+  let hash = await getHash(upper);
+
+  // We may not get a hash if any part of the filesystem is case sensitive.
+  if (hash) {
+    Assert.equal(
+      hash,
+      HASH,
+      `Should have seen the same hash from ${upper.path}.`
+    );
+  }
+});
+
+add_task(async function testLowerCase() {
+  let lower = mutatePath(EXE, p => p.toLocaleLowerCase());
+  let hash = await getHash(lower);
+
+  // We may not get a hash if any part of the filesystem is case sensitive.
+  if (hash) {
+    Assert.equal(
+      hash,
+      HASH,
+      `Should have seen the same hash from ${lower.path}.`
+    );
+  }
+});
+
+add_task(async function testEachPart() {
+  // We need to check the case where only some of the directories in the path
+  // are case insensitive.
+
+  let count = countParts(EXE);
+  for (let i = 0; i < count; i++) {
+    let upper = mutatePath(EXE, (p, index) =>
+      index == i ? p.toLocaleUpperCase() : p
+    );
+    let lower = mutatePath(EXE, (p, index) =>
+      index == i ? p.toLocaleLowerCase() : p
+    );
+
+    let upperHash = await getHash(upper);
+    if (upperHash) {
+      Assert.equal(
+        upperHash,
+        HASH,
+        `Should have seen the same hash from ${upper.path}.`
+      );
+    }
+
+    let lowerHash = await getHash(lower);
+    if (lowerHash) {
+      Assert.equal(
+        lowerHash,
+        HASH,
+        `Should have seen the same hash from ${lower.path}.`
+      );
+    }
+  }
+});
diff --git a/toolkit/xre/test/test_launch_without_hang.js b/toolkit/xre/test/test_launch_without_hang.js
new file mode 100644
index 0000000000..feacae36d4
--- /dev/null
+++ b/toolkit/xre/test/test_launch_without_hang.js
@@ -0,0 +1,256 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+// bug 1360493
+// Launch the browser a number of times, testing startup hangs.
+
+"use strict";
+
+const { AppConstants } = ChromeUtils.importESModule(
+  "resource://gre/modules/AppConstants.sys.mjs"
+);
+
+const APP_TIMER_TIMEOUT_MS = 1000 * 15;
+const TRY_COUNT = 50;
+
+// Sets a group of environment variables, returning the old values.
+// newVals AND return value is an array of { key: "", value: "" }
+function setEnvironmentVariables(newVals) {
+  let oldVals = [];
+  for (let i = 0; i < newVals.length; ++i) {
+    let key = newVals[i].key;
+    let value = newVals[i].value;
+    let oldObj = { key };
+    if (Services.env.exists(key)) {
+      oldObj.value = Services.env.get(key);
+    } else {
+      oldObj.value = null;
+    }
+
+    Services.env.set(key, value);
+    oldVals.push(oldObj);
+  }
+  return oldVals;
+}
+
+function getFirefoxExecutableFilename() {
+  if (AppConstants.platform === "win") {
+    return AppConstants.MOZ_APP_NAME + ".exe";
+  }
+  return AppConstants.MOZ_APP_NAME;
+}
+
+// Returns a nsIFile to the firefox.exe executable file
+function getFirefoxExecutableFile() {
+  let file = Cc["@mozilla.org/file/local;1"].createInstance(Ci.nsIFile);
+  file = Services.dirsvc.get("GreBinD", Ci.nsIFile);
+
+  file.append(getFirefoxExecutableFilename());
+  return file;
+}
+
+// Takes an executable and arguments, and wraps it in a call to the system shell.
+// Technique adapted from \toolkit\mozapps\update\tests\unit_service_updater\xpcshellUtilsAUS.js
+// to avoid child process console output polluting the xpcshell log.
+// returns { file: (nsIFile), args: [] }
+function wrapLaunchInShell(file, args) {
+  let ret = {};
+
+  if (AppConstants.platform === "win") {
+    ret.file = Services.dirsvc.get("WinD", Ci.nsIFile);
+    ret.file.append("System32");
+    ret.file.append("cmd.exe");
+    ret.args = ["/D", "/Q", "/C", file.path].concat(args).concat([">nul"]);
+  } else {
+    ret.file = Cc["@mozilla.org/file/local;1"].createInstance(Ci.nsIFile);
+    ret.file.initWithPath("/usr/bin/env");
+    ret.args = [file.path].concat(args).concat(["> /dev/null"]);
+  }
+
+  Assert.ok(
+    ret.file.exists(),
+    "Executable file should exist: " + ret.file.path
+  );
+
+  return ret;
+}
+
+// Needed because process.kill() kills the console, not its child process, firefox.
+function terminateFirefox(completion) {
+  let executableName = getFirefoxExecutableFilename();
+  let file;
+  let args;
+
+  if (AppConstants.platform === "win") {
+    file = Services.dirsvc.get("WinD", Ci.nsIFile);
+    file.append("System32");
+    file.append("taskkill.exe");
+    args = ["/F", "/IM", executableName];
+  } else {
+    file = Cc["@mozilla.org/file/local;1"].createInstance(Ci.nsIFile);
+    file.initWithPath("/usr/bin/killall");
+    args = [executableName];
+  }
+
+  info("launching application: " + file.path);
+  info("            with args: " + args.join(" "));
+
+  let process = Cc["@mozilla.org/process/util;1"].createInstance(Ci.nsIProcess);
+  process.init(file);
+
+  let processObserver = {
+    observe: function PO_observe(aSubject, aTopic, aData) {
+      info("topic: " + aTopic + ", process exitValue: " + process.exitValue);
+
+      Assert.equal(
+        process.exitValue,
+        0,
+        "Terminate firefox process exit value should be 0"
+      );
+      Assert.equal(
+        aTopic,
+        "process-finished",
+        "Terminate firefox observer topic should be process-finished"
+      );
+
+      if (completion) {
+        completion();
+      }
+    },
+    QueryInterface: ChromeUtils.generateQI(["nsIObserver"]),
+  };
+
+  process.runAsync(args, args.length, processObserver);
+
+  info("             with pid: " + process.pid);
+}
+
+// Launches file with args asynchronously, failing if the process did not
+// exit within timeoutMS milliseconds. If a timeout occurs, handler()
+// is called.
+function launchProcess(file, args, env, timeoutMS, handler, attemptCount) {
+  let state = {};
+
+  state.attempt = attemptCount;
+
+  state.processObserver = {
+    observe: function PO_observe(aSubject, aTopic, aData) {
+      if (!state.appTimer) {
+        // the app timer has been canceled; this process has timed out already so don't process further.
+        handler(false);
+        return;
+      }
+
+      info(
+        "topic: " + aTopic + ", process exitValue: " + state.process.exitValue
+      );
+
+      info("Restoring environment variables");
+      setEnvironmentVariables(state.oldEnv);
+
+      state.appTimer.cancel();
+      state.appTimer = null;
+
+      Assert.equal(
+        state.process.exitValue,
+        0,
+        "the application process exit value should be 0"
+      );
+      Assert.equal(
+        aTopic,
+        "process-finished",
+        "the application process observer topic should be process-finished"
+      );
+
+      handler(true);
+    },
+    QueryInterface: ChromeUtils.generateQI(["nsIObserver"]),
+  };
+
+  // The timer callback to kill the process if it takes too long.
+  state.appTimerCallback = {
+    notify: function TC_notify(aTimer) {
+      state.appTimer = null;
+
+      info("Restoring environment variables");
+      setEnvironmentVariables(state.oldEnv);
+
+      if (state.process.isRunning) {
+        info("attempting to kill process");
+
+        // This will cause the shell process to exit as well, triggering our process observer.
+        terminateFirefox(function terminateFirefoxCompletion() {
+          Assert.ok(false, "Launch application timer expired");
+        });
+      }
+    },
+    QueryInterface: ChromeUtils.generateQI(["nsITimerCallback"]),
+  };
+
+  info("launching application: " + file.path);
+  info("            with args: " + args.join(" "));
+  info("     with environment: ");
+  for (let i = 0; i < env.length; ++i) {
+    info("             " + env[i].key + "=" + env[i].value);
+  }
+
+  state.process = Cc["@mozilla.org/process/util;1"].createInstance(
+    Ci.nsIProcess
+  );
+  state.process.init(file);
+
+  state.appTimer = Cc["@mozilla.org/timer;1"].createInstance(Ci.nsITimer);
+  state.appTimer.initWithCallback(
+    state.appTimerCallback,
+    timeoutMS,
+    Ci.nsITimer.TYPE_ONE_SHOT
+  );
+
+  state.oldEnv = setEnvironmentVariables(env);
+
+  state.process.runAsync(args, args.length, state.processObserver);
+
+  info("             with pid: " + state.process.pid);
+}
+
+function run_test() {
+  do_test_pending();
+
+  let env = [
+    { key: "MOZ_CRASHREPORTER_DISABLE", value: null },
+    { key: "MOZ_CRASHREPORTER", value: "1" },
+    { key: "MOZ_CRASHREPORTER_NO_REPORT", value: "1" },
+    { key: "MOZ_CRASHREPORTER_SHUTDOWN", value: "1" },
+    { key: "XPCOM_DEBUG_BREAK", value: "stack-and-abort" },
+  ];
+
+  let triesStarted = 1;
+
+  let handler = function launchFirefoxHandler(okToContinue) {
+    triesStarted++;
+    if (triesStarted <= TRY_COUNT && okToContinue) {
+      testTry();
+    } else {
+      do_test_finished();
+    }
+  };
+
+  let testTry = function testTry() {
+    let shell = wrapLaunchInShell(getFirefoxExecutableFile(), [
+      "-no-remote",
+      "-test-launch-without-hang",
+    ]);
+    info("Try attempt #" + triesStarted);
+    launchProcess(
+      shell.file,
+      shell.args,
+      env,
+      APP_TIMER_TIMEOUT_MS,
+      handler,
+      triesStarted
+    );
+  };
+
+  testTry();
+}
diff --git a/toolkit/xre/test/win/Makefile.in b/toolkit/xre/test/win/Makefile.in
new file mode 100644
index 0000000000..5a67b8eac8
--- /dev/null
+++ b/toolkit/xre/test/win/Makefile.in
@@ -0,0 +1,11 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+MOZ_WINCONSOLE = 1
+
+include $(topsrcdir)/config/rules.mk
+
+check::
+	@echo 'Running TestXREMakeCommandLineWin tests'
+	@$(RUN_TEST_PROGRAM) $(FINAL_TARGET)/TestXREMakeCommandLineWin.exe
diff --git a/toolkit/xre/test/win/TestLauncherRegistryInfo.cpp b/toolkit/xre/test/win/TestLauncherRegistryInfo.cpp
new file mode 100644
index 0000000000..ab5edcf1ca
--- /dev/null
+++ b/toolkit/xre/test/win/TestLauncherRegistryInfo.cpp
@@ -0,0 +1,783 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#define MOZ_USE_LAUNCHER_ERROR
+
+#include "mozilla/LauncherRegistryInfo.h"
+#include "mozilla/NativeNt.h"
+#include "mozilla/ScopeExit.h"
+#include "mozilla/Unused.h"
+#include "nsWindowsHelpers.h"
+
+#include "LauncherRegistryInfo.cpp"
+
+#include <string>
+
+static const char kMsgStart[] = "TEST-FAILED | LauncherRegistryInfo | ";
+
+static const wchar_t kRegKeyPath[] = L"SOFTWARE\\" EXPAND_STRING_MACRO(
+    MOZ_APP_VENDOR) L"\\" EXPAND_STRING_MACRO(MOZ_APP_BASENAME) L"\\Launcher";
+static const wchar_t kBrowserSuffix[] = L"|Browser";
+static const wchar_t kLauncherSuffix[] = L"|Launcher";
+static const wchar_t kImageSuffix[] = L"|Image";
+static const wchar_t kTelemetrySuffix[] = L"|Telemetry";
+
+static std::wstring gBrowserValue;
+static std::wstring gLauncherValue;
+static std::wstring gImageValue;
+static std::wstring gTelemetryValue;
+
+static DWORD gMyImageTimestamp;
+
+#define RUN_TEST(result, fn)                                                 \
+  if ((result = fn()).isErr()) {                                             \
+    const mozilla::LauncherError& err = result.inspectErr();                 \
+    printf("%s%s | %08lx (%s:%d)\n", kMsgStart, #fn, err.mError.AsHResult(), \
+           err.mFile, err.mLine);                                            \
+    return 1;                                                                \
+  }
+
+#define EXPECT_COMMIT_IS_OK()                        \
+  do {                                               \
+    mozilla::LauncherVoidResult vr2 = info.Commit(); \
+    if (vr2.isErr()) {                               \
+      return vr2;                                    \
+    }                                                \
+  } while (0)
+
+#define EXPECT_CHECK_RESULT_IS(desired, expected)                       \
+  do {                                                                  \
+    mozilla::LauncherResult<mozilla::LauncherRegistryInfo::ProcessType> \
+        result = info.Check(mozilla::LauncherRegistryInfo::desired);    \
+    if (result.isErr()) {                                               \
+      return result.propagateErr();                                     \
+    }                                                                   \
+    if (result.unwrap() != mozilla::LauncherRegistryInfo::expected) {   \
+      return LAUNCHER_ERROR_FROM_HRESULT(E_FAIL);                       \
+    }                                                                   \
+  } while (0)
+
+#define EXPECT_ENABLED_STATE_IS(expected)                                \
+  do {                                                                   \
+    mozilla::LauncherResult<mozilla::LauncherRegistryInfo::EnabledState> \
+        enabled = info.IsEnabled();                                      \
+    if (enabled.isErr()) {                                               \
+      return enabled.propagateErr();                                     \
+    }                                                                    \
+    if (enabled.unwrap() != mozilla::LauncherRegistryInfo::expected) {   \
+      return LAUNCHER_ERROR_FROM_HRESULT(E_UNEXPECTED);                  \
+    }                                                                    \
+  } while (0)
+
+#define EXPECT_TELEMETRY_IS_ENABLED(expected)                          \
+  do {                                                                 \
+    mozilla::LauncherResult<bool> enabled = info.IsTelemetryEnabled(); \
+    if (enabled.isErr()) {                                             \
+      return enabled.propagateErr();                                   \
+    }                                                                  \
+    if (enabled.unwrap() != expected) {                                \
+      return LAUNCHER_ERROR_FROM_HRESULT(E_UNEXPECTED);                \
+    }                                                                  \
+  } while (0)
+
+#define EXPECT_REG_DWORD_EXISTS_AND_EQ(name, expected)      \
+  do {                                                      \
+    mozilla::LauncherResult<mozilla::Maybe<DWORD>> result = \
+        ReadRegistryValueData<DWORD>(name, REG_DWORD);      \
+    if (result.isErr()) {                                   \
+      return result.propagateErr();                         \
+    }                                                       \
+    if (result.inspect().isNothing() ||                     \
+        result.inspect().value() != expected) {             \
+      return LAUNCHER_ERROR_FROM_HRESULT(E_UNEXPECTED);     \
+    }                                                       \
+  } while (0)
+
+#define EXPECT_REG_QWORD_EXISTS(name)                          \
+  do {                                                         \
+    mozilla::LauncherResult<mozilla::Maybe<uint64_t>> result = \
+        ReadRegistryValueData<uint64_t>(name, REG_QWORD);      \
+    if (result.isErr()) {                                      \
+      return result.propagateErr();                            \
+    }                                                          \
+    if (result.inspect().isNothing()) {                        \
+      return LAUNCHER_ERROR_FROM_HRESULT(E_UNEXPECTED);        \
+    }                                                          \
+  } while (0)
+
+#define EXPECT_REG_QWORD_EXISTS_AND_EQ(name, expected)         \
+  do {                                                         \
+    mozilla::LauncherResult<mozilla::Maybe<uint64_t>> result = \
+        ReadRegistryValueData<uint64_t>(name, REG_QWORD);      \
+    if (result.isErr()) {                                      \
+      return result.propagateErr();                            \
+    }                                                          \
+    if (result.inspect().isNothing() ||                        \
+        result.inspect().value() != expected) {                \
+      return LAUNCHER_ERROR_FROM_HRESULT(E_UNEXPECTED);        \
+    }                                                          \
+  } while (0)
+
+#define EXPECT_REG_DWORD_DOES_NOT_EXIST(name)               \
+  do {                                                      \
+    mozilla::LauncherResult<mozilla::Maybe<DWORD>> result = \
+        ReadRegistryValueData<DWORD>(name, REG_DWORD);      \
+    if (result.isErr()) {                                   \
+      return result.propagateErr();                         \
+    }                                                       \
+    if (result.inspect().isSome()) {                        \
+      return LAUNCHER_ERROR_FROM_HRESULT(E_UNEXPECTED);     \
+    }                                                       \
+  } while (0)
+
+#define EXPECT_REG_QWORD_DOES_NOT_EXIST(name)                  \
+  do {                                                         \
+    mozilla::LauncherResult<mozilla::Maybe<uint64_t>> result = \
+        ReadRegistryValueData<uint64_t>(name, REG_QWORD);      \
+    if (result.isErr()) {                                      \
+      return result.propagateErr();                            \
+    }                                                          \
+    if (result.inspect().isSome()) {                           \
+      return LAUNCHER_ERROR_FROM_HRESULT(E_UNEXPECTED);        \
+    }                                                          \
+  } while (0)
+
+template <typename T>
+static mozilla::LauncherResult<mozilla::Maybe<T>> ReadRegistryValueData(
+    const std::wstring& name, DWORD expectedType) {
+  T data;
+  DWORD dataLen = sizeof(data);
+  DWORD type;
+  LSTATUS status = ::RegGetValueW(HKEY_CURRENT_USER, kRegKeyPath, name.c_str(),
+                                  RRF_RT_ANY, &type, &data, &dataLen);
+  if (status == ERROR_FILE_NOT_FOUND) {
+    return mozilla::Maybe<T>();
+  }
+
+  if (status != ERROR_SUCCESS) {
+    return LAUNCHER_ERROR_FROM_WIN32(status);
+  }
+
+  if (type != expectedType) {
+    return LAUNCHER_ERROR_FROM_WIN32(ERROR_DATATYPE_MISMATCH);
+  }
+
+  return mozilla::Some(data);
+}
+
+template <typename T>
+static mozilla::LauncherVoidResult WriteRegistryValueData(
+    const std::wstring& name, DWORD type, T data) {
+  LSTATUS status = ::RegSetKeyValueW(HKEY_CURRENT_USER, kRegKeyPath,
+                                     name.c_str(), type, &data, sizeof(T));
+  if (status != ERROR_SUCCESS) {
+    return LAUNCHER_ERROR_FROM_WIN32(status);
+  }
+
+  return mozilla::Ok();
+}
+
+static mozilla::LauncherVoidResult DeleteRegistryValueData(
+    const std::wstring& name) {
+  LSTATUS status =
+      ::RegDeleteKeyValueW(HKEY_CURRENT_USER, kRegKeyPath, name.c_str());
+  if (status == ERROR_SUCCESS || status == ERROR_FILE_NOT_FOUND) {
+    return mozilla::Ok();
+  }
+
+  return LAUNCHER_ERROR_FROM_WIN32(status);
+}
+
+static mozilla::LauncherVoidResult DeleteAllRegstryValues() {
+  // Unblock commit via ReflectPrefToRegistry
+  // (We need to set false, and then true to bypass the early return)
+  mozilla::LauncherRegistryInfo info;
+  mozilla::LauncherVoidResult vr = info.ReflectPrefToRegistry(false);
+  vr = info.ReflectPrefToRegistry(true);
+  if (vr.isErr()) {
+    return vr;
+  }
+
+  vr = DeleteRegistryValueData(gImageValue);
+  if (vr.isErr()) {
+    return vr;
+  }
+
+  vr = DeleteRegistryValueData(gLauncherValue);
+  if (vr.isErr()) {
+    return vr;
+  }
+
+  vr = DeleteRegistryValueData(gBrowserValue);
+  if (vr.isErr()) {
+    return vr;
+  }
+
+  return DeleteRegistryValueData(gTelemetryValue);
+}
+
+bool GetInstallHash(const char16_t*, mozilla::UniquePtr<NS_tchar[]>& result) {
+  return true;
+}
+
+static mozilla::LauncherVoidResult SetupEnabledScenario() {
+  // Reset the registry state to an enabled state. First, we delete all existing
+  // registry values (if any).
+  mozilla::LauncherVoidResult vr = DeleteAllRegstryValues();
+  if (vr.isErr()) {
+    return vr;
+  }
+
+  // Now we run Check(Launcher)...
+  mozilla::LauncherRegistryInfo info;
+  EXPECT_CHECK_RESULT_IS(ProcessType::Launcher, ProcessType::Launcher);
+  EXPECT_COMMIT_IS_OK();
+  // ...and Check(Browser)
+  EXPECT_CHECK_RESULT_IS(ProcessType::Browser, ProcessType::Browser);
+  EXPECT_COMMIT_IS_OK();
+
+  // By this point we are considered to be fully enabled.
+  return mozilla::Ok();
+}
+
+static mozilla::LauncherVoidResult TestEmptyRegistry() {
+  mozilla::LauncherVoidResult vr = DeleteAllRegstryValues();
+  if (vr.isErr()) {
+    return vr;
+  }
+
+  mozilla::LauncherRegistryInfo info;
+  EXPECT_CHECK_RESULT_IS(ProcessType::Launcher, ProcessType::Launcher);
+  EXPECT_COMMIT_IS_OK();
+
+  // LauncherRegistryInfo should have created Launcher and Image values
+  EXPECT_REG_DWORD_EXISTS_AND_EQ(gImageValue, gMyImageTimestamp);
+  EXPECT_REG_QWORD_EXISTS(gLauncherValue);
+  EXPECT_REG_QWORD_DOES_NOT_EXIST(gBrowserValue);
+
+  EXPECT_ENABLED_STATE_IS(EnabledState::FailDisabled);
+
+  return mozilla::Ok();
+}
+
+static mozilla::LauncherVoidResult TestNormal() {
+  mozilla::LauncherVoidResult vr = DeleteAllRegstryValues();
+  if (vr.isErr()) {
+    return vr;
+  }
+  vr = WriteRegistryValueData<DWORD>(gImageValue, REG_DWORD, gMyImageTimestamp);
+  if (vr.isErr()) {
+    return vr;
+  }
+  vr = WriteRegistryValueData<uint64_t>(gLauncherValue, REG_QWORD, QPCNowRaw());
+  if (vr.isErr()) {
+    return vr;
+  }
+
+  mozilla::LauncherRegistryInfo info;
+  EXPECT_CHECK_RESULT_IS(ProcessType::Browser, ProcessType::Browser);
+  EXPECT_COMMIT_IS_OK();
+
+  // Make sure the browser timestamp is newer than the launcher's
+  mozilla::LauncherResult<mozilla::Maybe<uint64_t>> launcherTs =
+      ReadRegistryValueData<uint64_t>(gLauncherValue, REG_QWORD);
+  if (launcherTs.isErr()) {
+    return launcherTs.propagateErr();
+  }
+  mozilla::LauncherResult<mozilla::Maybe<uint64_t>> browserTs =
+      ReadRegistryValueData<uint64_t>(gBrowserValue, REG_QWORD);
+  if (browserTs.isErr()) {
+    return browserTs.propagateErr();
+  }
+  if (launcherTs.inspect().isNothing() || browserTs.inspect().isNothing() ||
+      browserTs.inspect().value() <= launcherTs.inspect().value()) {
+    return LAUNCHER_ERROR_FROM_HRESULT(E_FAIL);
+  }
+
+  EXPECT_ENABLED_STATE_IS(EnabledState::Enabled);
+
+  return mozilla::Ok();
+}
+
+static mozilla::LauncherVoidResult TestBrowserNoLauncher() {
+  mozilla::LauncherVoidResult vr = SetupEnabledScenario();
+  if (vr.isErr()) {
+    return vr;
+  }
+  vr = DeleteRegistryValueData(gLauncherValue);
+  if (vr.isErr()) {
+    return vr;
+  }
+
+  mozilla::LauncherRegistryInfo info;
+  EXPECT_CHECK_RESULT_IS(ProcessType::Launcher, ProcessType::Browser);
+  EXPECT_COMMIT_IS_OK();
+
+  // Verify that we still don't have a launcher timestamp
+  EXPECT_REG_QWORD_DOES_NOT_EXIST(gLauncherValue);
+  // Verify that the browser timestamp is now zero
+  EXPECT_REG_QWORD_EXISTS_AND_EQ(gBrowserValue, 0ULL);
+
+  EXPECT_ENABLED_STATE_IS(EnabledState::ForceDisabled);
+
+  return mozilla::Ok();
+}
+
+static mozilla::LauncherVoidResult TestLauncherNoBrowser() {
+  constexpr uint64_t launcherTs = 0x77777777;
+  mozilla::LauncherVoidResult vr = DeleteAllRegstryValues();
+  if (vr.isErr()) {
+    return vr;
+  }
+  vr = WriteRegistryValueData<DWORD>(gImageValue, REG_DWORD, gMyImageTimestamp);
+  if (vr.isErr()) {
+    return vr;
+  }
+  vr = WriteRegistryValueData<uint64_t>(gLauncherValue, REG_QWORD, launcherTs);
+  if (vr.isErr()) {
+    return vr;
+  }
+
+  mozilla::LauncherRegistryInfo info;
+  EXPECT_CHECK_RESULT_IS(ProcessType::Launcher, ProcessType::Browser);
+  EXPECT_COMMIT_IS_OK();
+
+  // Launcher's timestamps is kept intact while browser's is set to 0.
+  EXPECT_REG_QWORD_EXISTS_AND_EQ(gLauncherValue, launcherTs);
+  EXPECT_REG_QWORD_EXISTS_AND_EQ(gBrowserValue, 0ULL);
+
+  EXPECT_ENABLED_STATE_IS(EnabledState::FailDisabled);
+
+  return mozilla::Ok();
+}
+
+static mozilla::LauncherVoidResult TestBrowserLessThanLauncher() {
+  constexpr uint64_t launcherTs = 0x77777777, browserTs = 0x66666666;
+  mozilla::LauncherVoidResult vr = DeleteAllRegstryValues();
+  if (vr.isErr()) {
+    return vr;
+  }
+  vr = WriteRegistryValueData<DWORD>(gImageValue, REG_DWORD, gMyImageTimestamp);
+  if (vr.isErr()) {
+    return vr;
+  }
+  vr = WriteRegistryValueData<uint64_t>(gLauncherValue, REG_QWORD, launcherTs);
+  if (vr.isErr()) {
+    return vr;
+  }
+  vr = WriteRegistryValueData<uint64_t>(gBrowserValue, REG_QWORD, browserTs);
+  if (vr.isErr()) {
+    return vr;
+  }
+
+  mozilla::LauncherRegistryInfo info;
+  EXPECT_CHECK_RESULT_IS(ProcessType::Launcher, ProcessType::Browser);
+  EXPECT_COMMIT_IS_OK();
+
+  // Launcher's timestamps is kept intact while browser's is set to 0.
+  EXPECT_REG_QWORD_EXISTS_AND_EQ(gLauncherValue, launcherTs);
+  EXPECT_REG_QWORD_EXISTS_AND_EQ(gBrowserValue, 0ULL);
+
+  EXPECT_ENABLED_STATE_IS(EnabledState::FailDisabled);
+
+  return mozilla::Ok();
+}
+
+static mozilla::LauncherVoidResult TestImageTimestampChange() {
+  // This should reset the timestamps and then essentially run like
+  // TestEmptyRegistry
+  mozilla::LauncherVoidResult vr = DeleteAllRegstryValues();
+  if (vr.isErr()) {
+    return vr;
+  }
+  vr = WriteRegistryValueData<DWORD>(gImageValue, REG_DWORD, 0x12345678);
+  if (vr.isErr()) {
+    return vr;
+  }
+  vr = WriteRegistryValueData<uint64_t>(gLauncherValue, REG_QWORD, 1ULL);
+  if (vr.isErr()) {
+    return vr;
+  }
+  vr = WriteRegistryValueData<uint64_t>(gBrowserValue, REG_QWORD, 2ULL);
+  if (vr.isErr()) {
+    return vr;
+  }
+
+  mozilla::LauncherRegistryInfo info;
+  EXPECT_CHECK_RESULT_IS(ProcessType::Launcher, ProcessType::Launcher);
+  EXPECT_COMMIT_IS_OK();
+
+  EXPECT_REG_DWORD_EXISTS_AND_EQ(gImageValue, gMyImageTimestamp);
+  EXPECT_REG_QWORD_EXISTS(gLauncherValue);
+  EXPECT_REG_QWORD_DOES_NOT_EXIST(gBrowserValue);
+
+  return mozilla::Ok();
+}
+
+static mozilla::LauncherVoidResult TestImageTimestampChangeWhenDisabled() {
+  mozilla::LauncherVoidResult vr = DeleteAllRegstryValues();
+  if (vr.isErr()) {
+    return vr;
+  }
+  vr = WriteRegistryValueData<DWORD>(gImageValue, REG_DWORD, 0x12345678);
+  if (vr.isErr()) {
+    return vr;
+  }
+  vr = WriteRegistryValueData<uint64_t>(gBrowserValue, REG_QWORD, 0ULL);
+  if (vr.isErr()) {
+    return vr;
+  }
+
+  mozilla::LauncherRegistryInfo info;
+  EXPECT_CHECK_RESULT_IS(ProcessType::Launcher, ProcessType::Browser);
+  EXPECT_COMMIT_IS_OK();
+
+  EXPECT_REG_DWORD_EXISTS_AND_EQ(gImageValue, gMyImageTimestamp);
+  EXPECT_REG_QWORD_DOES_NOT_EXIST(gLauncherValue);
+  EXPECT_REG_QWORD_EXISTS_AND_EQ(gBrowserValue, 0);
+
+  EXPECT_ENABLED_STATE_IS(EnabledState::ForceDisabled);
+
+  return mozilla::Ok();
+}
+
+static mozilla::LauncherVoidResult TestDisableDueToFailure() {
+  mozilla::LauncherVoidResult vr = SetupEnabledScenario();
+  if (vr.isErr()) {
+    return vr;
+  }
+
+  // Check that we are indeed enabled.
+  mozilla::LauncherRegistryInfo info;
+  EXPECT_ENABLED_STATE_IS(EnabledState::Enabled);
+
+  // Now call DisableDueToFailure
+  mozilla::LauncherVoidResult lvr = info.DisableDueToFailure();
+  if (lvr.isErr()) {
+    return lvr.propagateErr();
+  }
+
+  // We should now be FailDisabled
+  EXPECT_ENABLED_STATE_IS(EnabledState::FailDisabled);
+
+  // If we delete the launcher timestamp, IsEnabled should then return
+  // ForceDisabled.
+  vr = DeleteRegistryValueData(gLauncherValue);
+  if (vr.isErr()) {
+    return vr;
+  }
+  EXPECT_ENABLED_STATE_IS(EnabledState::ForceDisabled);
+
+  return mozilla::Ok();
+}
+
+static mozilla::LauncherVoidResult TestPrefReflection() {
+  // Reset the registry to a known good state.
+  mozilla::LauncherVoidResult vr = SetupEnabledScenario();
+  if (vr.isErr()) {
+    return vr;
+  }
+
+  // Let's see what happens when we flip the pref to OFF.
+  mozilla::LauncherRegistryInfo info;
+  mozilla::LauncherVoidResult reflectOk = info.ReflectPrefToRegistry(false);
+  if (reflectOk.isErr()) {
+    return reflectOk.propagateErr();
+  }
+
+  // Launcher timestamp should be non-existent.
+  EXPECT_REG_QWORD_DOES_NOT_EXIST(gLauncherValue);
+  // Browser timestamp should be zero
+  EXPECT_REG_QWORD_EXISTS_AND_EQ(gBrowserValue, 0ULL);
+  // IsEnabled should give us ForceDisabled
+  EXPECT_ENABLED_STATE_IS(EnabledState::ForceDisabled);
+
+  // Now test to see what happens when the pref is set to ON.
+  reflectOk = info.ReflectPrefToRegistry(true);
+  if (reflectOk.isErr()) {
+    return reflectOk.propagateErr();
+  }
+
+  // Launcher and browser timestamps should be non-existent.
+  EXPECT_REG_QWORD_DOES_NOT_EXIST(gLauncherValue);
+  EXPECT_REG_QWORD_DOES_NOT_EXIST(gBrowserValue);
+
+  // IsEnabled should give us Enabled.
+  EXPECT_ENABLED_STATE_IS(EnabledState::Enabled);
+
+  return mozilla::Ok();
+}
+
+static mozilla::LauncherVoidResult TestTelemetryConfig() {
+  mozilla::LauncherVoidResult vr = DeleteAllRegstryValues();
+  if (vr.isErr()) {
+    return vr;
+  }
+
+  mozilla::LauncherRegistryInfo info;
+  EXPECT_TELEMETRY_IS_ENABLED(false);
+
+  mozilla::LauncherVoidResult reflectOk =
+      info.ReflectTelemetryPrefToRegistry(false);
+  if (reflectOk.isErr()) {
+    return reflectOk.propagateErr();
+  }
+  EXPECT_TELEMETRY_IS_ENABLED(false);
+
+  reflectOk = info.ReflectTelemetryPrefToRegistry(true);
+  if (reflectOk.isErr()) {
+    return reflectOk.propagateErr();
+  }
+  EXPECT_TELEMETRY_IS_ENABLED(true);
+
+  return mozilla::Ok();
+}
+
+static mozilla::LauncherVoidResult TestCommitAbort() {
+  mozilla::LauncherVoidResult vr = SetupEnabledScenario();
+  if (vr.isErr()) {
+    return vr;
+  }
+
+  // Retrieve the current timestamps to compare later
+  mozilla::LauncherResult<mozilla::Maybe<uint64_t>> launcherValue =
+      ReadRegistryValueData<uint64_t>(gLauncherValue, REG_QWORD);
+  if (launcherValue.isErr() || launcherValue.inspect().isNothing()) {
+    return launcherValue.propagateErr();
+  }
+  mozilla::LauncherResult<mozilla::Maybe<uint64_t>> browserValue =
+      ReadRegistryValueData<uint64_t>(gBrowserValue, REG_QWORD);
+  if (browserValue.isErr() || browserValue.inspect().isNothing()) {
+    return browserValue.propagateErr();
+  }
+  uint64_t launcherTs = launcherValue.inspect().value();
+  uint64_t browserTs = browserValue.inspect().value();
+
+  vr = []() -> mozilla::LauncherVoidResult {
+    mozilla::LauncherRegistryInfo info;
+    EXPECT_CHECK_RESULT_IS(ProcessType::Launcher, ProcessType::Launcher);
+    // No commit
+    return mozilla::Ok();
+  }();
+  if (vr.isErr()) {
+    return vr;
+  }
+
+  // Exiting the scope discards the change.
+  mozilla::LauncherRegistryInfo info;
+  EXPECT_REG_DWORD_EXISTS_AND_EQ(gImageValue, gMyImageTimestamp);
+  EXPECT_REG_QWORD_EXISTS_AND_EQ(gLauncherValue, launcherTs);
+  EXPECT_REG_QWORD_EXISTS_AND_EQ(gBrowserValue, browserTs);
+
+  // Commit -> Check -> Abort -> Commit
+  EXPECT_COMMIT_IS_OK();
+  EXPECT_CHECK_RESULT_IS(ProcessType::Launcher, ProcessType::Launcher);
+  info.Abort();
+  EXPECT_COMMIT_IS_OK();
+
+  // Nothing is changed.
+  EXPECT_REG_DWORD_EXISTS_AND_EQ(gImageValue, gMyImageTimestamp);
+  EXPECT_REG_QWORD_EXISTS_AND_EQ(gLauncherValue, launcherTs);
+  EXPECT_REG_QWORD_EXISTS_AND_EQ(gBrowserValue, browserTs);
+  EXPECT_ENABLED_STATE_IS(EnabledState::Enabled);
+
+  return mozilla::Ok();
+}
+
+static mozilla::LauncherVoidResult TestDisableDuringLauncherLaunch() {
+  mozilla::LauncherVoidResult vr = SetupEnabledScenario();
+  if (vr.isErr()) {
+    return vr;
+  }
+
+  mozilla::LauncherResult<mozilla::Maybe<uint64_t>> launcherTs =
+      ReadRegistryValueData<uint64_t>(gLauncherValue, REG_QWORD);
+  if (launcherTs.isErr()) {
+    return launcherTs.propagateErr();
+  }
+  if (launcherTs.inspect().isNothing()) {
+    return LAUNCHER_ERROR_FROM_HRESULT(E_UNEXPECTED);
+  }
+
+  vr = []() -> mozilla::LauncherVoidResult {
+    mozilla::LauncherRegistryInfo info;
+    EXPECT_CHECK_RESULT_IS(ProcessType::Launcher, ProcessType::Launcher);
+
+    // Call DisableDueToFailure with a different instance
+    mozilla::LauncherVoidResult vr = []() -> mozilla::LauncherVoidResult {
+      mozilla::LauncherRegistryInfo info;
+      mozilla::LauncherVoidResult vr = info.DisableDueToFailure();
+      if (vr.isErr()) {
+        return vr.propagateErr();
+      }
+      return mozilla::Ok();
+    }();
+    if (vr.isErr()) {
+      return vr;
+    }
+
+    // Commit after disable.
+    EXPECT_COMMIT_IS_OK();
+
+    return mozilla::Ok();
+  }();
+  if (vr.isErr()) {
+    return vr;
+  }
+
+  // Make sure we're still FailDisabled and the launcher's timestamp is not
+  // updated
+  mozilla::LauncherRegistryInfo info;
+  EXPECT_ENABLED_STATE_IS(EnabledState::FailDisabled);
+  EXPECT_REG_QWORD_EXISTS_AND_EQ(gLauncherValue, launcherTs.inspect().value());
+
+  return mozilla::Ok();
+}
+
+static mozilla::LauncherVoidResult TestDisableDuringBrowserLaunch() {
+  mozilla::LauncherVoidResult vr = SetupEnabledScenario();
+  if (vr.isErr()) {
+    return vr;
+  }
+
+  mozilla::LauncherRegistryInfo info;
+  EXPECT_CHECK_RESULT_IS(ProcessType::Launcher, ProcessType::Launcher);
+  EXPECT_COMMIT_IS_OK();
+
+  vr = []() -> mozilla::LauncherVoidResult {
+    mozilla::LauncherRegistryInfo info;
+    EXPECT_CHECK_RESULT_IS(ProcessType::Browser, ProcessType::Browser);
+
+    // Call DisableDueToFailure with a different instance
+    mozilla::LauncherVoidResult vr = []() -> mozilla::LauncherVoidResult {
+      mozilla::LauncherRegistryInfo info;
+      mozilla::LauncherVoidResult vr = info.DisableDueToFailure();
+      if (vr.isErr()) {
+        return vr.propagateErr();
+      }
+      return mozilla::Ok();
+    }();
+    if (vr.isErr()) {
+      return vr;
+    }
+
+    // Commit after disable.
+    EXPECT_COMMIT_IS_OK();
+
+    return mozilla::Ok();
+  }();
+  if (vr.isErr()) {
+    return vr;
+  }
+
+  // Make sure we're still FailDisabled
+  EXPECT_ENABLED_STATE_IS(EnabledState::FailDisabled);
+
+  return mozilla::Ok();
+}
+
+static mozilla::LauncherVoidResult TestReEnable() {
+  mozilla::LauncherVoidResult vr = SetupEnabledScenario();
+  if (vr.isErr()) {
+    return vr;
+  }
+
+  // Make FailDisabled
+  mozilla::LauncherRegistryInfo info;
+  vr = info.DisableDueToFailure();
+  if (vr.isErr()) {
+    return vr.propagateErr();
+  }
+  EXPECT_ENABLED_STATE_IS(EnabledState::FailDisabled);
+
+  // Attempt to launch when FailDisabled: Still be FailDisabled
+  EXPECT_CHECK_RESULT_IS(ProcessType::Launcher, ProcessType::Browser);
+  EXPECT_COMMIT_IS_OK();
+  EXPECT_ENABLED_STATE_IS(EnabledState::FailDisabled);
+
+  // Change the timestamp
+  vr = WriteRegistryValueData<DWORD>(gImageValue, REG_DWORD, 0x12345678);
+  if (vr.isErr()) {
+    return vr;
+  }
+
+  // Attempt to launch again: Launcher comes back
+  EXPECT_CHECK_RESULT_IS(ProcessType::Launcher, ProcessType::Launcher);
+  EXPECT_COMMIT_IS_OK();
+
+  // Make ForceDisabled
+  vr = info.ReflectPrefToRegistry(false);
+  if (vr.isErr()) {
+    return vr.propagateErr();
+  }
+  EXPECT_ENABLED_STATE_IS(EnabledState::ForceDisabled);
+
+  // Attempt to launch when ForceDisabled: Still be ForceDisabled
+  EXPECT_CHECK_RESULT_IS(ProcessType::Launcher, ProcessType::Browser);
+  EXPECT_COMMIT_IS_OK();
+  EXPECT_ENABLED_STATE_IS(EnabledState::ForceDisabled);
+
+  // Change the timestamp
+  vr = WriteRegistryValueData<DWORD>(gImageValue, REG_DWORD, 0x12345678);
+  if (vr.isErr()) {
+    return vr;
+  }
+
+  // Attempt to launch again: Still be ForceDisabled
+  EXPECT_CHECK_RESULT_IS(ProcessType::Launcher, ProcessType::Browser);
+  EXPECT_COMMIT_IS_OK();
+  EXPECT_ENABLED_STATE_IS(EnabledState::ForceDisabled);
+
+  return mozilla::Ok();
+}
+
+int main(int argc, char* argv[]) {
+  auto fullPath = mozilla::GetFullBinaryPath();
+  if (!fullPath) {
+    return 1;
+  }
+
+  // Global setup for all tests
+  gBrowserValue = fullPath.get();
+  gBrowserValue += kBrowserSuffix;
+
+  gLauncherValue = fullPath.get();
+  gLauncherValue += kLauncherSuffix;
+
+  gImageValue = fullPath.get();
+  gImageValue += kImageSuffix;
+
+  gTelemetryValue = fullPath.get();
+  gTelemetryValue += kTelemetrySuffix;
+
+  mozilla::LauncherResult<DWORD> timestamp = 0;
+  RUN_TEST(timestamp, GetCurrentImageTimestamp);
+  gMyImageTimestamp = timestamp.unwrap();
+
+  auto onExit = mozilla::MakeScopeExit(
+      []() { mozilla::Unused << DeleteAllRegstryValues(); });
+
+  mozilla::LauncherVoidResult vr = mozilla::Ok();
+
+  // All testcases should call SetupEnabledScenario() or
+  // DeleteAllRegstryValues() to be order-independent
+  RUN_TEST(vr, TestEmptyRegistry);
+  RUN_TEST(vr, TestNormal);
+  RUN_TEST(vr, TestBrowserNoLauncher);
+  RUN_TEST(vr, TestLauncherNoBrowser);
+  RUN_TEST(vr, TestBrowserLessThanLauncher);
+  RUN_TEST(vr, TestImageTimestampChange);
+  RUN_TEST(vr, TestImageTimestampChangeWhenDisabled);
+  RUN_TEST(vr, TestDisableDueToFailure);
+  RUN_TEST(vr, TestPrefReflection);
+  RUN_TEST(vr, TestTelemetryConfig);
+  RUN_TEST(vr, TestCommitAbort);
+  RUN_TEST(vr, TestDisableDuringLauncherLaunch);
+  RUN_TEST(vr, TestDisableDuringBrowserLaunch);
+  RUN_TEST(vr, TestReEnable);
+
+  return 0;
+}
diff --git a/toolkit/xre/test/win/TestXREMakeCommandLineWin.cpp b/toolkit/xre/test/win/TestXREMakeCommandLineWin.cpp
new file mode 100644
index 0000000000..c12550c3d6
--- /dev/null
+++ b/toolkit/xre/test/win/TestXREMakeCommandLineWin.cpp
@@ -0,0 +1,266 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <windows.h>
+// Support for _setmode
+#include <fcntl.h>
+#include <io.h>
+
+#include "nsWindowsRestart.cpp"
+
+// CommandLineToArgvW may return different values for argv[0] since it contains
+// the path to the binary that was executed so we prepend an argument that is
+// quoted with a space to prevent argv[1] being appended to argv[0].
+#define DUMMY_ARG1 L"\"arg 1\" "
+
+#ifndef MAXPATHLEN
+#  ifdef PATH_MAX
+#    define MAXPATHLEN PATH_MAX
+#  elif defined(MAX_PATH)
+#    define MAXPATHLEN MAX_PATH
+#  elif defined(_MAX_PATH)
+#    define MAXPATHLEN _MAX_PATH
+#  elif defined(CCHMAXPATH)
+#    define MAXPATHLEN CCHMAXPATH
+#  else
+#    define MAXPATHLEN 1024
+#  endif
+#endif
+
+#define TEST_NAME L"XRE MakeCommandLine"
+#define MAX_TESTS 100
+
+// Verbose output can be enabled by defining VERBOSE 1
+#define VERBOSE 0
+
+// Compares compareCmdLine with the output of MakeCommandLine. This is
+// accomplished by converting inCmdLine to an argument list with
+// CommandLineToArgvW and converting it back to a command line with
+// MakeCommandLine.
+static int verifyCmdLineCreation(wchar_t* inCmdLine, wchar_t* compareCmdLine,
+                                 bool passes, int testNum) {
+  int rv = 0;
+  int i;
+  int inArgc;
+  int outArgc;
+  bool isEqual;
+
+  // When debugging with command lines containing Unicode characters greater
+  // than 255 you can set the mode for stdout to Unicode so the console will
+  // receive the correct characters though it won't display them properly unless
+  // the console's font has been set to one that can display the characters. You
+  // can also redirect the console output to a file that has been saved as
+  // Unicode to view the characters.
+  //  _setmode(_fileno(stdout), _O_WTEXT);
+
+  // Prepend an additional argument to the command line. CommandLineToArgvW
+  // handles argv[0] differently than other arguments since argv[0] is the path
+  // to the binary being executed and MakeCommandLine only handles argv[1] and
+  // larger.
+  wchar_t* inCmdLineNew = (wchar_t*)malloc(
+      (wcslen(DUMMY_ARG1) + wcslen(inCmdLine) + 1) * sizeof(wchar_t));
+  wcscpy(inCmdLineNew, DUMMY_ARG1);
+  wcscat(inCmdLineNew, inCmdLine);
+  LPWSTR* inArgv = CommandLineToArgvW(inCmdLineNew, &inArgc);
+
+  auto outCmdLine = mozilla::MakeCommandLine(inArgc - 1, inArgv + 1);
+  wchar_t* outCmdLineNew = (wchar_t*)malloc(
+      (wcslen(DUMMY_ARG1) + wcslen(outCmdLine.get()) + 1) * sizeof(wchar_t));
+  wcscpy(outCmdLineNew, DUMMY_ARG1);
+  wcscat(outCmdLineNew, outCmdLine.get());
+  LPWSTR* outArgv = CommandLineToArgvW(outCmdLineNew, &outArgc);
+
+  if (VERBOSE) {
+    wprintf(L"\n");
+    wprintf(L"Verbose Output\n");
+    wprintf(L"--------------\n");
+    wprintf(L"Input command line   : >%s<\n", inCmdLine);
+    wprintf(L"MakeComandLine output: >%s<\n", outCmdLine.get());
+    wprintf(L"Expected command line: >%s<\n", compareCmdLine);
+
+    wprintf(L"input argc : %d\n", inArgc - 1);
+    wprintf(L"output argc: %d\n", outArgc - 1);
+
+    for (i = 1; i < inArgc; ++i) {
+      wprintf(L"input argv[%d] : >%s<\n", i - 1, inArgv[i]);
+    }
+
+    for (i = 1; i < outArgc; ++i) {
+      wprintf(L"output argv[%d]: >%s<\n", i - 1, outArgv[i]);
+    }
+    wprintf(L"\n");
+  }
+
+  isEqual = (inArgc == outArgc);
+  if (!isEqual) {
+    wprintf(L"TEST-%s-FAIL | %s | ARGC Comparison (check %2d)\n",
+            passes ? L"UNEXPECTED" : L"KNOWN", TEST_NAME, testNum);
+    if (passes) {
+      rv = 1;
+    }
+    LocalFree(inArgv);
+    LocalFree(outArgv);
+    free(inCmdLineNew);
+    free(outCmdLineNew);
+    return rv;
+  }
+
+  for (i = 1; i < inArgc; ++i) {
+    isEqual = (wcscmp(inArgv[i], outArgv[i]) == 0);
+    if (!isEqual) {
+      wprintf(L"TEST-%s-FAIL | %s | ARGV Comparison (check %2d)\n",
+              passes ? L"UNEXPECTED" : L"KNOWN", TEST_NAME, testNum);
+      if (passes) {
+        rv = 1;
+      }
+      LocalFree(inArgv);
+      LocalFree(outArgv);
+      free(inCmdLineNew);
+      free(outCmdLineNew);
+      return rv;
+    }
+  }
+
+  isEqual = (wcscmp(outCmdLine.get(), compareCmdLine) == 0);
+  if (!isEqual) {
+    wprintf(L"TEST-%s-FAIL | %s | Command Line Comparison (check %2d)\n",
+            passes ? L"UNEXPECTED" : L"KNOWN", TEST_NAME, testNum);
+    if (passes) {
+      rv = 1;
+    }
+    LocalFree(inArgv);
+    LocalFree(outArgv);
+    free(inCmdLineNew);
+    free(outCmdLineNew);
+    return rv;
+  }
+
+  if (rv == 0) {
+    if (passes) {
+      wprintf(L"TEST-PASS | %s | check %2d\n", TEST_NAME, testNum);
+    } else {
+      wprintf(L"TEST-UNEXPECTED-PASS | %s | check %2d\n", TEST_NAME, testNum);
+      rv = 1;
+    }
+  }
+
+  LocalFree(inArgv);
+  LocalFree(outArgv);
+  free(inCmdLineNew);
+  free(outCmdLineNew);
+  return rv;
+}
+
+int wmain(int argc, wchar_t* argv[]) {
+  int i;
+  int rv = 0;
+
+  if (argc > 1 && (_wcsicmp(argv[1], L"-check-one") != 0 || argc != 3)) {
+    fwprintf(stderr,
+             L"Displays and validates output from MakeCommandLine.\n\n");
+    fwprintf(stderr, L"Usage: %s -check-one <test number>\n\n", argv[0]);
+    fwprintf(stderr,
+             L"  <test number>\tSpecifies the test number to run from the\n");
+    fwprintf(stderr, L"\t\tTestXREMakeCommandLineWin.ini file.\n");
+    return 255;
+  }
+
+  wchar_t inifile[MAXPATHLEN];
+  if (!::GetModuleFileNameW(0, inifile, MAXPATHLEN)) {
+    wprintf(L"TEST-UNEXPECTED-FAIL | %s | GetModuleFileNameW\n", TEST_NAME);
+    return 2;
+  }
+
+  WCHAR* slash = wcsrchr(inifile, '\\');
+  if (!slash) {
+    wprintf(L"TEST-UNEXPECTED-FAIL | %s | wcsrchr\n", TEST_NAME);
+    return 3;
+  }
+
+  wcscpy(slash + 1, L"TestXREMakeCommandLineWin.ini\0");
+
+  for (i = 0; i < MAX_TESTS; ++i) {
+    wchar_t sInputVal[MAXPATHLEN];
+    wchar_t sOutputVal[MAXPATHLEN];
+    wchar_t sPassesVal[MAXPATHLEN];
+    wchar_t sInputKey[MAXPATHLEN];
+    wchar_t sOutputKey[MAXPATHLEN];
+    wchar_t sPassesKey[MAXPATHLEN];
+
+    if (argc > 2 && _wcsicmp(argv[1], L"-check-one") == 0 && argc == 3) {
+      i = _wtoi(argv[2]);
+    }
+
+    _snwprintf(sInputKey, MAXPATHLEN, L"input_%d", i);
+    _snwprintf(sOutputKey, MAXPATHLEN, L"output_%d", i);
+    _snwprintf(sPassesKey, MAXPATHLEN, L"passes_%d", i);
+
+    if (!GetPrivateProfileStringW(L"MakeCommandLineTests", sInputKey, nullptr,
+                                  sInputVal, MAXPATHLEN, inifile)) {
+      if (i == 0 || (argc > 2 && _wcsicmp(argv[1], L"-check-one") == 0)) {
+        wprintf(L"TEST-UNEXPECTED-FAIL | %s | see following explanation:\n",
+                TEST_NAME);
+        wprintf(
+            L"ERROR: Either the TestXREMakeCommandLineWin.ini file doesn't "
+            L"exist\n");
+        if (argc > 1 && _wcsicmp(argv[1], L"-check-one") == 0 && argc == 3) {
+          wprintf(
+              L"ERROR: or the test is not defined in the MakeCommandLineTests "
+              L"section.\n");
+        } else {
+          wprintf(
+              L"ERROR: or it has no tests defined in the MakeCommandLineTests "
+              L"section.\n");
+        }
+        wprintf(L"ERROR: File: %s\n", inifile);
+        return 4;
+      }
+      break;
+    }
+
+    GetPrivateProfileStringW(L"MakeCommandLineTests", sOutputKey, nullptr,
+                             sOutputVal, MAXPATHLEN, inifile);
+    GetPrivateProfileStringW(L"MakeCommandLineTests", sPassesKey, nullptr,
+                             sPassesVal, MAXPATHLEN, inifile);
+
+    rv |= verifyCmdLineCreation(
+        sInputVal, sOutputVal,
+        (_wcsicmp(sPassesVal, L"false") == 0) ? FALSE : TRUE, i);
+
+    if (argc > 2 && _wcsicmp(argv[1], L"-check-one") == 0) {
+      break;
+    }
+  }
+
+  if (rv == 0) {
+    wprintf(L"TEST-PASS | %s | all checks passed\n", TEST_NAME);
+  } else {
+    wprintf(L"TEST-UNEXPECTED-FAIL | %s | some checks failed\n", TEST_NAME);
+  }
+
+  return rv;
+}
+
+#ifdef __MINGW32__
+
+/* MingW currently does not implement a wide version of the
+   startup routines.  Workaround is to implement something like
+   it ourselves.  See bug 411826 */
+
+#  include <shellapi.h>
+
+int main(int argc, char** argv) {
+  LPWSTR commandLine = GetCommandLineW();
+  int argcw = 0;
+  LPWSTR* argvw = CommandLineToArgvW(commandLine, &argcw);
+  if (!argvw) return 127;
+
+  int result = wmain(argcw, argvw);
+  LocalFree(argvw);
+  return result;
+}
+#endif /* __MINGW32__ */
diff --git a/toolkit/xre/test/win/TestXREMakeCommandLineWin.ini b/toolkit/xre/test/win/TestXREMakeCommandLineWin.ini
new file mode 100644
index 0000000000..dbb529d1b1
--- /dev/null
+++ b/toolkit/xre/test/win/TestXREMakeCommandLineWin.ini
@@ -0,0 +1,94 @@
+; A typical MakeCommandLine test will contain an input and an output name value
+; pair. The value for input_xx is the input command line and the value for
+; output_xx is the expected output command line.
+;
+; A test that is known to fail can be added as follows. If the passes_xx name
+; value pair doesn't exist it defaults to true.
+; input_99=yabadaba
+; output_99=doo
+; passes_99=false
+;
+; If a value starts and ends with single or double quotation marks then it must
+; be enclosed in single or double quotation marks due to GetPrivateProfileString
+; discarding the outmost quotation marks. See GetPrivateProfileString on MSDN
+; for more information.
+; http://msdn.microsoft.com/en-us/library/ms724353.aspx
+
+[MakeCommandLineTests]
+input_0=a:\
+output_0=a:\
+
+input_1=""a:\""
+output_1=a:\"
+
+input_2=""a:\b c""
+output_2=""a:\b c""
+
+input_3=""a:\b c\""
+output_3=""a:\b c\"""
+
+input_4=""a:\b c\d e""
+output_4=""a:\b c\d e""
+
+input_5=""a:\b c\d e\""
+output_5=""a:\b c\d e\"""
+
+input_6=""a:\\""
+output_6=a:\
+
+input_7="a:\" "b:\c d"
+output_7=a:\" "b:\c d"
+
+input_8="a "b:\" "c:\d e""
+output_8="a "b:\" c:\d" e"
+
+input_9="abc" d e
+output_9=abc d e
+
+input_10="a b c" d e
+output_10="a b c" d e
+
+input_11=a\\\b d"e f"g h
+output_11=a\\\b "de fg" h
+
+input_12=a	b
+output_12=a b
+
+input_13=""a	b""
+output_13=""a	b""
+
+input_14=a\\\"b c d
+output_14=a\\\"b c d
+
+input_15=a\\\"b c"
+output_15=a\\\"b c
+
+input_16=""a\\\b c"
+output_16=""a\\\b c""
+
+input_17=\"a
+output_17=\"a
+
+input_18=\\"a
+output_18=\a
+
+input_19=\\"\\\\"a
+output_19=\\\a
+
+input_20=\\"\\\\\"a
+output_20=\\\\\\\"a
+
+input_21="a\\\"b c\" d e
+output_21=""a\\\"b c\" d e""
+
+input_22=a\\\\\"b c" d e"
+output_22=a\\\\\"b "c d e"
+
+input_23=a:\b c\アルファ オメガ\d
+output_23=a:\b c\アルファ オメガ\d
+
+input_24=a:\b "c\アルファ オメガ\d"
+output_24=a:\b "c\アルファ オメガ\d"
+
+input_25=アルファ オメガ
+output_25=アルファ オメガ
diff --git a/toolkit/xre/test/win/mochitest/browser_env_path_long.ini b/toolkit/xre/test/win/mochitest/browser_env_path_long.ini
new file mode 100644
index 0000000000..9eb5a7b6e4
--- /dev/null
+++ b/toolkit/xre/test/win/mochitest/browser_env_path_long.ini
@@ -0,0 +1,7 @@
+[DEFAULT]
+# This path should expand to >32K characters. See bug 1753910.
+environment =
+  PATH="C:/loremipsumdolorsitamet/adipiscingconsectetuerelit/;C:/loremipsumdolorsitamet/adipiscingconsectetuerelit/;C:/loremipsumdolorsitamet/adipiscingconsectetuerelit/;C:/loremipsumdolorsitamet/adipiscingconsectetuerelit/;C:/loremipsumdolorsitamet/adipiscingconsectetuerelit/;C:/loremipsumdolorsitamet/adipiscingconsectetuerelit/;C:/loremipsumdolorsitamet/adipiscingconsectetuerelit/;C:/loremipsumdolorsitamet/adipiscingconsectetuerelit/;C:/loremipsumdolorsitamet/adipiscingconsectetuerelit/;C:/loremipsumdolorsitamet/adipiscingconsectetuerelit/;C:/loremipsumdolorsitamet/adipiscingconsectetuerelit/;C:/loremipsumdolorsitamet/adipiscingconsectetuerelit/;C:/loremipsumdolorsitamet/adipiscingconsectetuerelit/;C:/loremipsumdolorsitamet/adipiscingconsectetuerelit/;C:/loremipsumdolorsitamet/adipiscingconsectetuerelit/;C:/loremipsumdolorsitamet/adipiscingconsectetuerelit/;%PATH%;%PATH%;%PATH%;%PATH%;%PATH%;%PATH%;%PATH%;%PATH%;%PATH%;%PATH%;%PATH%;%PATH%;%PATH%;%PATH%;%PATH%;%PATH%;%PATH%;%PATH%;%PATH%;%PATH%;%PATH%;%PATH%;%PATH%;%PATH%;%PATH%;%PATH%;%PATH%;%PATH%;%PATH%;%PATH%"
+
+[browser_env_path_long.js]
+skip-if = os != "win"
diff --git a/toolkit/xre/test/win/mochitest/browser_env_path_long.js b/toolkit/xre/test/win/mochitest/browser_env_path_long.js
new file mode 100644
index 0000000000..9bc63214b0
--- /dev/null
+++ b/toolkit/xre/test/win/mochitest/browser_env_path_long.js
@@ -0,0 +1,16 @@
+// Any copyright is dedicated to the Public Domain.
+// http://creativecommons.org/publicdomain/zero/1.0/
+
+// Test that the browser starts even when PATH would expand to a detrimentally
+// long value.
+add_task(async function test() {
+  await BrowserTestUtils.withNewTab(
+    { gBrowser, url: "about:blank" },
+    function (browser) {
+      ok(
+        true,
+        "Browser should start even with potentially pathologically long PATH."
+      );
+    }
+  );
+});
diff --git a/toolkit/xre/test/win/moz.build b/toolkit/xre/test/win/moz.build
new file mode 100644
index 0000000000..8744f70698
--- /dev/null
+++ b/toolkit/xre/test/win/moz.build
@@ -0,0 +1,55 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+BROWSER_CHROME_MANIFESTS += [
+    "mochitest/browser_env_path_long.ini",
+]
+
+GeckoCppUnitTests(
+    [
+        "TestXREMakeCommandLineWin",
+    ],
+    linkage=None,
+)
+
+# This needs to be installed alongside the above unit test.
+FINAL_TARGET_FILES += [
+    "TestXREMakeCommandLineWin.ini",
+]
+
+DEFINES["NS_NO_XPCOM"] = True
+
+LOCAL_INCLUDES += [
+    "/config",
+    "/toolkit/xre",
+]
+
+DisableStlWrapping()
+USE_STATIC_LIBS = True
+
+OS_LIBS += [
+    "advapi32",
+    "comctl32",
+    "ole32",
+    "shell32",
+    "uuid",
+    "userenv",
+    "ws2_32",
+]
+
+if CONFIG["MOZ_LAUNCHER_PROCESS"]:
+    LOCAL_INCLUDES += [
+        "/toolkit/mozapps/update/common",
+    ]
+    GeckoCppUnitTests(
+        [
+            "TestLauncherRegistryInfo",
+        ],
+        linkage=None,
+    )
+    # Needed for TestLauncherRegistryInfo
+    for var in ("MOZ_APP_BASENAME", "MOZ_APP_VENDOR"):
+        DEFINES[var] = '"%s"' % CONFIG[var]
diff --git a/toolkit/xre/test/xpcshell.ini b/toolkit/xre/test/xpcshell.ini
new file mode 100644
index 0000000000..acf84f715e
--- /dev/null
+++ b/toolkit/xre/test/xpcshell.ini
@@ -0,0 +1,19 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+[DEFAULT]
+tags = native
+
+[test_launch_without_hang.js]
+run-sequentially = Has to launch application binary
+skip-if = toolkit == 'android'
+requesttimeoutfactor = 2
+[test_install_hash.js]
+# Android doesn't ship Subprocess.sys.mjs and debug builds output garbage that the
+# test cannot handle.
+skip-if =
+  toolkit == 'android'
+  debug
+support-files =
+  show_hash.js
diff --git a/toolkit/xre/updaterfileutils_osx.h b/toolkit/xre/updaterfileutils_osx.h
new file mode 100644
index 0000000000..1fa0db1f4e
--- /dev/null
+++ b/toolkit/xre/updaterfileutils_osx.h
@@ -0,0 +1,13 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef updaterfileutils_osx_h_
+#define updaterfileutils_osx_h_
+
+extern "C" {
+bool IsRecursivelyWritable(const char* aPath);
+}
+
+#endif
diff --git a/toolkit/xre/updaterfileutils_osx.mm b/toolkit/xre/updaterfileutils_osx.mm
new file mode 100644
index 0000000000..15a4b3a5ba
--- /dev/null
+++ b/toolkit/xre/updaterfileutils_osx.mm
@@ -0,0 +1,46 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "updaterfileutils_osx.h"
+
+#include <Cocoa/Cocoa.h>
+
+bool IsRecursivelyWritable(const char* aPath) {
+  NSAutoreleasePool* pool = [[NSAutoreleasePool alloc] init];
+
+  NSString* rootPath = [NSString stringWithUTF8String:aPath];
+  NSFileManager* fileManager = [NSFileManager defaultManager];
+  NSError* error = nil;
+  NSArray* subPaths = [fileManager subpathsOfDirectoryAtPath:rootPath error:&error];
+  NSMutableArray* paths = [NSMutableArray arrayWithCapacity:[subPaths count] + 1];
+  [paths addObject:@""];
+  [paths addObjectsFromArray:subPaths];
+
+  if (error) {
+    [pool drain];
+    return false;
+  }
+
+  for (NSString* currPath in paths) {
+    NSString* child = [rootPath stringByAppendingPathComponent:currPath];
+
+    NSDictionary* attributes = [fileManager attributesOfItemAtPath:child error:&error];
+    if (error) {
+      [pool drain];
+      return false;
+    }
+
+    // Don't check for writability of files pointed to by symlinks, as they may
+    // not be descendants of the root path.
+    if ([attributes fileType] != NSFileTypeSymbolicLink &&
+        [fileManager isWritableFileAtPath:child] == NO) {
+      [pool drain];
+      return false;
+    }
+  }
+
+  [pool drain];
+  return true;
+}