1 files changed, 794 insertions, 0 deletions
diff --git a/toolkit/xre/dllservices/mozglue/nsWindowsDllInterceptor.h b/toolkit/xre/dllservices/mozglue/nsWindowsDllInterceptor.h
new file mode 100644
index 0000000000..1b09f820fa
--- /dev/null
+++ b/toolkit/xre/dllservices/mozglue/nsWindowsDllInterceptor.h
@@ -0,0 +1,794 @@
+/* -*- 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"));
+
+      if (needs10BytePatch) {
+        flags |= DetourFlags::eEnable10BytePatch;
+      }
+#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_ */