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

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

1 files changed, 709 insertions, 0 deletions

diff --git a/dom/script/ScriptSettings.cpp b/dom/script/ScriptSettings.cpp
new file mode 100644
index 0000000000..1f2d92bcb5
--- /dev/null
+++ b/dom/script/ScriptSettings.cpp
@@ -0,0 +1,709 @@
+/* -*- 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/dom/ScriptSettings.h"
+
+#include <utility>
+#include "MainThreadUtils.h"
+#include "js/CharacterEncoding.h"
+#include "js/CompilationAndEvaluation.h"
+#include "js/Conversions.h"
+#include "js/ErrorReport.h"
+#include "js/Exception.h"
+#include "js/GCAPI.h"
+#include "js/PropertyAndElement.h"  // JS_GetProperty
+#include "js/TypeDecls.h"
+#include "js/Value.h"
+#include "js/Warnings.h"
+#include "js/Wrapper.h"
+#include "js/friend/ErrorMessages.h"
+#include "js/loader/LoadedScript.h"
+#include "js/loader/ScriptLoadRequest.h"
+#include "jsapi.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/BasePrincipal.h"
+#include "mozilla/CycleCollectedJSContext.h"
+#include "mozilla/DebugOnly.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/ThreadLocal.h"
+#include "mozilla/dom/AutoEntryScript.h"
+#include "mozilla/dom/BindingUtils.h"
+#include "mozilla/dom/Document.h"
+#include "mozilla/dom/Element.h"
+#include "mozilla/dom/WorkerCommon.h"
+#include "nsContentUtils.h"
+#include "nsDebug.h"
+#include "nsGlobalWindowInner.h"
+#include "nsIGlobalObject.h"
+#include "nsINode.h"
+#include "nsIPrincipal.h"
+#include "nsISupports.h"
+#include "nsJSUtils.h"
+#include "nsPIDOMWindow.h"
+#include "nsString.h"
+#include "nscore.h"
+#include "xpcpublic.h"
+
+namespace mozilla {
+namespace dom {
+
+static MOZ_THREAD_LOCAL(ScriptSettingsStackEntry*) sScriptSettingsTLS;
+
+class ScriptSettingsStack {
+ public:
+  static ScriptSettingsStackEntry* Top() { return sScriptSettingsTLS.get(); }
+
+  static void Push(ScriptSettingsStackEntry* aEntry) {
+    MOZ_ASSERT(!aEntry->mOlder);
+    // Whenever JSAPI use is disabled, the next stack entry pushed must
+    // not be an AutoIncumbentScript.
+    MOZ_ASSERT_IF(!Top() || Top()->NoJSAPI(), !aEntry->IsIncumbentScript());
+    // Whenever the top entry is not an incumbent canidate, the next stack entry
+    // pushed must not be an AutoIncumbentScript.
+    MOZ_ASSERT_IF(Top() && !Top()->IsIncumbentCandidate(),
+                  !aEntry->IsIncumbentScript());
+
+    aEntry->mOlder = Top();
+    sScriptSettingsTLS.set(aEntry);
+  }
+
+  static void Pop(ScriptSettingsStackEntry* aEntry) {
+    MOZ_ASSERT(aEntry == Top());
+    sScriptSettingsTLS.set(aEntry->mOlder);
+  }
+
+  static nsIGlobalObject* IncumbentGlobal() {
+    ScriptSettingsStackEntry* entry = Top();
+    while (entry) {
+      if (entry->IsIncumbentCandidate()) {
+        return entry->mGlobalObject;
+      }
+      entry = entry->mOlder;
+    }
+    return nullptr;
+  }
+
+  static ScriptSettingsStackEntry* EntryPoint() {
+    ScriptSettingsStackEntry* entry = Top();
+    while (entry) {
+      if (entry->IsEntryCandidate()) {
+        return entry;
+      }
+      entry = entry->mOlder;
+    }
+    return nullptr;
+  }
+
+  static nsIGlobalObject* EntryGlobal() {
+    ScriptSettingsStackEntry* entry = EntryPoint();
+    if (!entry) {
+      return nullptr;
+    }
+    return entry->mGlobalObject;
+  }
+
+#ifdef DEBUG
+  static ScriptSettingsStackEntry* TopNonIncumbentScript() {
+    ScriptSettingsStackEntry* entry = Top();
+    while (entry) {
+      if (!entry->IsIncumbentScript()) {
+        return entry;
+      }
+      entry = entry->mOlder;
+    }
+    return nullptr;
+  }
+#endif  // DEBUG
+};
+
+void InitScriptSettings() {
+  bool success = sScriptSettingsTLS.init();
+  if (!success) {
+    MOZ_CRASH();
+  }
+
+  sScriptSettingsTLS.set(nullptr);
+}
+
+void DestroyScriptSettings() {
+  MOZ_ASSERT(sScriptSettingsTLS.get() == nullptr);
+}
+
+ScriptSettingsStackEntry::ScriptSettingsStackEntry(nsIGlobalObject* aGlobal,
+                                                   Type aType)
+    : mGlobalObject(aGlobal), mType(aType), mOlder(nullptr) {
+  MOZ_ASSERT_IF(IsIncumbentCandidate() && !NoJSAPI(), mGlobalObject);
+  MOZ_ASSERT(!mGlobalObject || mGlobalObject->HasJSGlobal(),
+             "Must have an actual JS global for the duration on the stack");
+  MOZ_ASSERT(
+      !mGlobalObject ||
+          JS_IsGlobalObject(mGlobalObject->GetGlobalJSObjectPreserveColor()),
+      "No outer windows allowed");
+}
+
+ScriptSettingsStackEntry::~ScriptSettingsStackEntry() {
+  // We must have an actual JS global for the entire time this is on the stack.
+  MOZ_ASSERT_IF(mGlobalObject, mGlobalObject->HasJSGlobal());
+}
+
+// If the entry or incumbent global ends up being something that the subject
+// principal doesn't subsume, we don't want to use it. This never happens on
+// the web, but can happen with asymmetric privilege relationships (i.e.
+// ExpandedPrincipal and System Principal).
+//
+// The most correct thing to use instead would be the topmost global on the
+// callstack whose principal is subsumed by the subject principal. But that's
+// hard to compute, so we just substitute the global of the current
+// compartment. In practice, this is fine.
+//
+// Note that in particular things like:
+//
+// |SpecialPowers.wrap(crossOriginWindow).eval(open())|
+//
+// trigger this case. Although both the entry global and the current global
+// have normal principals, the use of Gecko-specific System-Principaled JS
+// puts the code from two different origins on the callstack at once, which
+// doesn't happen normally on the web.
+static nsIGlobalObject* ClampToSubject(nsIGlobalObject* aGlobalOrNull) {
+  if (!aGlobalOrNull || !NS_IsMainThread()) {
+    return aGlobalOrNull;
+  }
+
+  nsIPrincipal* globalPrin = aGlobalOrNull->PrincipalOrNull();
+  NS_ENSURE_TRUE(globalPrin, GetCurrentGlobal());
+  if (!nsContentUtils::SubjectPrincipalOrSystemIfNativeCaller()
+           ->SubsumesConsideringDomain(globalPrin)) {
+    return GetCurrentGlobal();
+  }
+
+  return aGlobalOrNull;
+}
+
+nsIGlobalObject* GetEntryGlobal() {
+  return ClampToSubject(ScriptSettingsStack::EntryGlobal());
+}
+
+Document* GetEntryDocument() {
+  nsIGlobalObject* global = GetEntryGlobal();
+  nsCOMPtr<nsPIDOMWindowInner> entryWin = do_QueryInterface(global);
+
+  return entryWin ? entryWin->GetExtantDoc() : nullptr;
+}
+
+nsIGlobalObject* GetIncumbentGlobal() {
+  // We need the current JSContext in order to check the JS for
+  // scripted frames that may have appeared since anyone last
+  // manipulated the stack. If it's null, that means that there
+  // must be no entry global on the stack, and therefore no incumbent
+  // global either.
+  JSContext* cx = nsContentUtils::GetCurrentJSContext();
+  if (!cx) {
+    MOZ_ASSERT(ScriptSettingsStack::EntryGlobal() == nullptr);
+    return nullptr;
+  }
+
+  // See what the JS engine has to say. If we've got a scripted caller
+  // override in place, the JS engine will lie to us and pretend that
+  // there's nothing on the JS stack, which will cause us to check the
+  // incumbent script stack below.
+  if (JSObject* global = JS::GetScriptedCallerGlobal(cx)) {
+    return ClampToSubject(xpc::NativeGlobal(global));
+  }
+
+  // Ok, nothing from the JS engine. Let's use whatever's on the
+  // explicit stack.
+  return ClampToSubject(ScriptSettingsStack::IncumbentGlobal());
+}
+
+nsIGlobalObject* GetCurrentGlobal() {
+  JSContext* cx = nsContentUtils::GetCurrentJSContext();
+  if (!cx) {
+    return nullptr;
+  }
+
+  JSObject* global = JS::CurrentGlobalOrNull(cx);
+  if (!global) {
+    return nullptr;
+  }
+
+  return xpc::NativeGlobal(global);
+}
+
+nsIPrincipal* GetWebIDLCallerPrincipal() {
+  MOZ_ASSERT(NS_IsMainThread());
+  ScriptSettingsStackEntry* entry = ScriptSettingsStack::EntryPoint();
+
+  // If we have an entry point that is not NoJSAPI, we know it must be an
+  // AutoEntryScript.
+  if (!entry || entry->NoJSAPI()) {
+    return nullptr;
+  }
+  AutoEntryScript* aes = static_cast<AutoEntryScript*>(entry);
+
+  return aes->mWebIDLCallerPrincipal;
+}
+
+bool IsJSAPIActive() {
+  ScriptSettingsStackEntry* topEntry = ScriptSettingsStack::Top();
+  return topEntry && !topEntry->NoJSAPI();
+}
+
+namespace danger {
+JSContext* GetJSContext() { return CycleCollectedJSContext::Get()->Context(); }
+}  // namespace danger
+
+JS::RootingContext* RootingCx() {
+  return CycleCollectedJSContext::Get()->RootingCx();
+}
+
+AutoJSAPI::AutoJSAPI()
+    : ScriptSettingsStackEntry(nullptr, eJSAPI),
+      mCx(nullptr),
+      mIsMainThread(false)  // For lack of anything better
+{}
+
+AutoJSAPI::~AutoJSAPI() {
+  if (!mCx) {
+    // No need to do anything here: we never managed to Init, so can't have an
+    // exception on our (nonexistent) JSContext.  We also don't need to restore
+    // any state on it.  Finally, we never made it to pushing ourselves onto the
+    // ScriptSettingsStack, so shouldn't pop.
+    MOZ_ASSERT(ScriptSettingsStack::Top() != this);
+    return;
+  }
+
+  ReportException();
+
+  if (mOldWarningReporter.isSome()) {
+    JS::SetWarningReporter(cx(), mOldWarningReporter.value());
+  }
+
+  ScriptSettingsStack::Pop(this);
+}
+
+void WarningOnlyErrorReporter(JSContext* aCx, JSErrorReport* aRep);
+
+void AutoJSAPI::InitInternal(nsIGlobalObject* aGlobalObject, JSObject* aGlobal,
+                             JSContext* aCx, bool aIsMainThread) {
+  MOZ_ASSERT(aCx);
+  MOZ_ASSERT(aCx == danger::GetJSContext());
+  MOZ_ASSERT(aIsMainThread == NS_IsMainThread());
+  MOZ_ASSERT(bool(aGlobalObject) == bool(aGlobal));
+  MOZ_ASSERT_IF(aGlobalObject,
+                aGlobalObject->GetGlobalJSObjectPreserveColor() == aGlobal);
+#ifdef DEBUG
+  bool haveException = JS_IsExceptionPending(aCx);
+#endif  // DEBUG
+
+  mCx = aCx;
+  mIsMainThread = aIsMainThread;
+  if (aGlobal) {
+    JS::AssertObjectIsNotGray(aGlobal);
+  }
+  mAutoNullableRealm.emplace(mCx, aGlobal);
+  mGlobalObject = aGlobalObject;
+
+  ScriptSettingsStack::Push(this);
+
+  mOldWarningReporter.emplace(JS::GetWarningReporter(aCx));
+
+  JS::SetWarningReporter(aCx, WarningOnlyErrorReporter);
+
+#ifdef DEBUG
+  if (haveException) {
+    JS::Rooted<JS::Value> exn(aCx);
+    JS_GetPendingException(aCx, &exn);
+
+    JS_ClearPendingException(aCx);
+    if (exn.isObject()) {
+      JS::Rooted<JSObject*> exnObj(aCx, &exn.toObject());
+
+      // Make sure we can actually read things from it.  This UncheckedUwrap is
+      // safe because we're only getting data for a debug printf.  In
+      // particular, we do not expose this data to anyone, which is very
+      // important; otherwise it could be a cross-origin information leak.
+      exnObj = js::UncheckedUnwrap(exnObj);
+      JSAutoRealm ar(aCx, exnObj);
+
+      nsAutoJSString stack, filename, name, message;
+      int32_t line;
+
+      JS::Rooted<JS::Value> tmp(aCx);
+      if (!JS_GetProperty(aCx, exnObj, "filename", &tmp)) {
+        JS_ClearPendingException(aCx);
+      }
+      if (tmp.isUndefined()) {
+        if (!JS_GetProperty(aCx, exnObj, "fileName", &tmp)) {
+          JS_ClearPendingException(aCx);
+        }
+      }
+
+      if (!filename.init(aCx, tmp)) {
+        JS_ClearPendingException(aCx);
+      }
+
+      if (!JS_GetProperty(aCx, exnObj, "stack", &tmp) ||
+          !stack.init(aCx, tmp)) {
+        JS_ClearPendingException(aCx);
+      }
+
+      if (!JS_GetProperty(aCx, exnObj, "name", &tmp) || !name.init(aCx, tmp)) {
+        JS_ClearPendingException(aCx);
+      }
+
+      if (!JS_GetProperty(aCx, exnObj, "message", &tmp) ||
+          !message.init(aCx, tmp)) {
+        JS_ClearPendingException(aCx);
+      }
+
+      if (!JS_GetProperty(aCx, exnObj, "lineNumber", &tmp) ||
+          !JS::ToInt32(aCx, tmp, &line)) {
+        JS_ClearPendingException(aCx);
+        line = 0;
+      }
+
+      printf_stderr("PREEXISTING EXCEPTION OBJECT: '%s: %s'\n%s:%d\n%s\n",
+                    NS_ConvertUTF16toUTF8(name).get(),
+                    NS_ConvertUTF16toUTF8(message).get(),
+                    NS_ConvertUTF16toUTF8(filename).get(), line,
+                    NS_ConvertUTF16toUTF8(stack).get());
+    } else {
+      // It's a primitive... not much we can do other than stringify it.
+      nsAutoJSString exnStr;
+      if (!exnStr.init(aCx, exn)) {
+        JS_ClearPendingException(aCx);
+      }
+
+      printf_stderr("PREEXISTING EXCEPTION PRIMITIVE: %s\n",
+                    NS_ConvertUTF16toUTF8(exnStr).get());
+    }
+    MOZ_ASSERT(false, "We had an exception; we should not have");
+  }
+#endif  // DEBUG
+}
+
+AutoJSAPI::AutoJSAPI(nsIGlobalObject* aGlobalObject, bool aIsMainThread,
+                     Type aType)
+    : ScriptSettingsStackEntry(aGlobalObject, aType),
+      mIsMainThread(aIsMainThread) {
+  MOZ_ASSERT(aGlobalObject);
+  MOZ_ASSERT(aGlobalObject->HasJSGlobal(), "Must have a JS global");
+  MOZ_ASSERT(aIsMainThread == NS_IsMainThread());
+
+  InitInternal(aGlobalObject, aGlobalObject->GetGlobalJSObject(),
+               danger::GetJSContext(), aIsMainThread);
+}
+
+void AutoJSAPI::Init() {
+  MOZ_ASSERT(!mCx, "An AutoJSAPI should only be initialised once");
+
+  InitInternal(/* aGlobalObject */ nullptr, /* aGlobal */ nullptr,
+               danger::GetJSContext(), NS_IsMainThread());
+}
+
+bool AutoJSAPI::Init(nsIGlobalObject* aGlobalObject, JSContext* aCx) {
+  MOZ_ASSERT(!mCx, "An AutoJSAPI should only be initialised once");
+  MOZ_ASSERT(aCx);
+
+  if (NS_WARN_IF(!aGlobalObject)) {
+    return false;
+  }
+
+  JSObject* global = aGlobalObject->GetGlobalJSObject();
+  if (NS_WARN_IF(!global)) {
+    return false;
+  }
+
+  InitInternal(aGlobalObject, global, aCx, NS_IsMainThread());
+  return true;
+}
+
+bool AutoJSAPI::Init(nsIGlobalObject* aGlobalObject) {
+  return Init(aGlobalObject, danger::GetJSContext());
+}
+
+bool AutoJSAPI::Init(JSObject* aObject) {
+  MOZ_ASSERT(!js::IsCrossCompartmentWrapper(aObject));
+  return Init(xpc::NativeGlobal(aObject));
+}
+
+bool AutoJSAPI::Init(nsPIDOMWindowInner* aWindow, JSContext* aCx) {
+  return Init(nsGlobalWindowInner::Cast(aWindow), aCx);
+}
+
+bool AutoJSAPI::Init(nsPIDOMWindowInner* aWindow) {
+  return Init(nsGlobalWindowInner::Cast(aWindow));
+}
+
+bool AutoJSAPI::Init(nsGlobalWindowInner* aWindow, JSContext* aCx) {
+  return Init(static_cast<nsIGlobalObject*>(aWindow), aCx);
+}
+
+bool AutoJSAPI::Init(nsGlobalWindowInner* aWindow) {
+  return Init(static_cast<nsIGlobalObject*>(aWindow));
+}
+
+// Even with autoJSAPIOwnsErrorReporting, the JS engine still sends warning
+// reports to the JSErrorReporter as soon as they are generated. These go
+// directly to the console, so we can handle them easily here.
+//
+// Eventually, SpiderMonkey will have a special-purpose callback for warnings
+// only.
+void WarningOnlyErrorReporter(JSContext* aCx, JSErrorReport* aRep) {
+  MOZ_ASSERT(aRep->isWarning());
+  if (!NS_IsMainThread()) {
+    // Reporting a warning on workers is a bit complicated because we have to
+    // climb our parent chain until we get to the main thread.  So go ahead and
+    // just go through the worker or worklet ReportError codepath here.
+    //
+    // That said, it feels like we should be able to short-circuit things a bit
+    // here by posting an appropriate runnable to the main thread directly...
+    // Worth looking into sometime.
+    CycleCollectedJSContext* ccjscx = CycleCollectedJSContext::GetFor(aCx);
+    MOZ_ASSERT(ccjscx);
+
+    ccjscx->ReportError(aRep, JS::ConstUTF8CharsZ());
+    return;
+  }
+
+  RefPtr<xpc::ErrorReport> xpcReport = new xpc::ErrorReport();
+  nsGlobalWindowInner* win = xpc::CurrentWindowOrNull(aCx);
+  xpcReport->Init(aRep, nullptr, nsContentUtils::IsSystemCaller(aCx),
+                  win ? win->WindowID() : 0);
+  xpcReport->LogToConsole();
+}
+
+void AutoJSAPI::ReportException() {
+  if (!HasException()) {
+    return;
+  }
+
+  // AutoJSAPI uses a JSAutoNullableRealm, and may be in a null realm
+  // when the destructor is called. However, the JS engine requires us
+  // to be in a realm when we fetch the pending exception. In this case,
+  // we enter the privileged junk scope and don't dispatch any error events.
+  JS::Rooted<JSObject*> errorGlobal(cx(), JS::CurrentGlobalOrNull(cx()));
+  if (!errorGlobal) {
+    if (mIsMainThread) {
+      errorGlobal = xpc::PrivilegedJunkScope();
+    } else {
+      errorGlobal = GetCurrentThreadWorkerGlobal();
+      if (!errorGlobal) {
+        // We might be reporting an error in debugger code that ran before the
+        // worker's global was created. Use the debugger global instead.
+        errorGlobal = GetCurrentThreadWorkerDebuggerGlobal();
+        if (NS_WARN_IF(!errorGlobal)) {
+          // An exception may have been thrown on attempt to create a global
+          // and now there is no realm from which to fetch the exception.
+          // Give up.
+          ClearException();
+          return;
+        }
+      }
+    }
+  }
+  MOZ_ASSERT(JS_IsGlobalObject(errorGlobal));
+  JSAutoRealm ar(cx(), errorGlobal);
+  JS::ExceptionStack exnStack(cx());
+  JS::ErrorReportBuilder jsReport(cx());
+  if (StealExceptionAndStack(&exnStack) &&
+      jsReport.init(cx(), exnStack, JS::ErrorReportBuilder::WithSideEffects)) {
+    if (mIsMainThread) {
+      RefPtr<xpc::ErrorReport> xpcReport = new xpc::ErrorReport();
+
+      RefPtr<nsGlobalWindowInner> inner = xpc::WindowOrNull(errorGlobal);
+
+      // For WebExtension content script, `WindowOrNull` method will return
+      // null, whereas we would still like to flag the exception with the
+      // related WindowGlobal the content script executed against. So we only
+      // update the `innerWindowID` and not `inner` as we don't want to dispatch
+      // exceptions caused by the content script to the webpage.
+      uint64_t innerWindowID = 0;
+      if (inner) {
+        innerWindowID = inner->WindowID();
+      } else if (nsGlobalWindowInner* win = xpc::SandboxWindowOrNull(
+                     JS::GetNonCCWObjectGlobal(errorGlobal), cx())) {
+        innerWindowID = win->WindowID();
+      }
+
+      bool isChrome =
+          nsContentUtils::ObjectPrincipal(errorGlobal)->IsSystemPrincipal();
+      xpcReport->Init(jsReport.report(), jsReport.toStringResult().c_str(),
+                      isChrome, innerWindowID);
+      if (inner && jsReport.report()->errorNumber != JSMSG_OUT_OF_MEMORY) {
+        JS::RootingContext* rcx = JS::RootingContext::get(cx());
+        DispatchScriptErrorEvent(inner, rcx, xpcReport, exnStack.exception(),
+                                 exnStack.stack());
+      } else {
+        JS::Rooted<JSObject*> stack(cx());
+        JS::Rooted<JSObject*> stackGlobal(cx());
+        xpc::FindExceptionStackForConsoleReport(inner, exnStack.exception(),
+                                                exnStack.stack(), &stack,
+                                                &stackGlobal);
+        // This error is not associated with a specific window,
+        // so omit the exception value to mitigate potential leaks.
+        xpcReport->LogToConsoleWithStack(inner, JS::NothingHandleValue, stack,
+                                         stackGlobal);
+      }
+    } else {
+      // On a worker or worklet, we just use the error reporting mechanism and
+      // don't bother with xpc::ErrorReport.  This will ensure that all the
+      // right worker events (which are a lot more complicated than in the
+      // window case) get fired.
+      CycleCollectedJSContext* ccjscx = CycleCollectedJSContext::GetFor(cx());
+      MOZ_ASSERT(ccjscx);
+      // Before invoking ReportError, put the exception back on the context,
+      // because it may want to put it in its error events and has no other way
+      // to get hold of it.  After we invoke ReportError, clear the exception on
+      // cx(), just in case ReportError didn't.
+      JS::SetPendingExceptionStack(cx(), exnStack);
+      ccjscx->ReportError(jsReport.report(), jsReport.toStringResult());
+      ClearException();
+    }
+  } else {
+    NS_WARNING("OOMed while acquiring uncaught exception from JSAPI");
+    ClearException();
+  }
+}
+
+bool AutoJSAPI::PeekException(JS::MutableHandle<JS::Value> aVal) {
+  MOZ_ASSERT_IF(mIsMainThread, IsStackTop());
+  MOZ_ASSERT(HasException());
+  MOZ_ASSERT(js::GetContextRealm(cx()));
+  return JS_GetPendingException(cx(), aVal);
+}
+
+bool AutoJSAPI::StealException(JS::MutableHandle<JS::Value> aVal) {
+  JS::ExceptionStack exnStack(cx());
+  if (!StealExceptionAndStack(&exnStack)) {
+    return false;
+  }
+  aVal.set(exnStack.exception());
+  return true;
+}
+
+bool AutoJSAPI::StealExceptionAndStack(JS::ExceptionStack* aExnStack) {
+  MOZ_ASSERT_IF(mIsMainThread, IsStackTop());
+  MOZ_ASSERT(HasException());
+  MOZ_ASSERT(js::GetContextRealm(cx()));
+
+  return JS::StealPendingExceptionStack(cx(), aExnStack);
+}
+
+#ifdef DEBUG
+bool AutoJSAPI::IsStackTop() const {
+  return ScriptSettingsStack::TopNonIncumbentScript() == this;
+}
+#endif  // DEBUG
+
+AutoIncumbentScript::AutoIncumbentScript(nsIGlobalObject* aGlobalObject)
+    : ScriptSettingsStackEntry(aGlobalObject, eIncumbentScript),
+      mCallerOverride(nsContentUtils::GetCurrentJSContext()) {
+  ScriptSettingsStack::Push(this);
+}
+
+AutoIncumbentScript::~AutoIncumbentScript() { ScriptSettingsStack::Pop(this); }
+
+AutoNoJSAPI::AutoNoJSAPI(JSContext* aCx)
+    : ScriptSettingsStackEntry(nullptr, eNoJSAPI),
+      JSAutoNullableRealm(aCx, nullptr),
+      mCx(aCx) {
+  // Make sure we don't seem to have an incumbent global due to
+  // whatever script is running right now.
+  JS::HideScriptedCaller(aCx);
+
+  // Make sure the fallback GetIncumbentGlobal() behavior and
+  // GetEntryGlobal() both return null.
+  ScriptSettingsStack::Push(this);
+}
+
+AutoNoJSAPI::~AutoNoJSAPI() {
+  ScriptSettingsStack::Pop(this);
+  JS::UnhideScriptedCaller(mCx);
+}
+
+}  // namespace dom
+
+AutoJSContext::AutoJSContext() : mCx(nullptr) {
+  JS::AutoSuppressGCAnalysis nogc;
+  MOZ_ASSERT(!mCx, "mCx should not be initialized!");
+  MOZ_ASSERT(NS_IsMainThread());
+
+  if (dom::IsJSAPIActive()) {
+    mCx = dom::danger::GetJSContext();
+  } else {
+    mJSAPI.Init();
+    mCx = mJSAPI.cx();
+  }
+}
+
+AutoJSContext::operator JSContext*() const { return mCx; }
+
+AutoSafeJSContext::AutoSafeJSContext() : AutoJSAPI() {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  DebugOnly<bool> ok = Init(xpc::UnprivilegedJunkScope());
+  MOZ_ASSERT(ok,
+             "This is quite odd.  We should have crashed in the "
+             "xpc::NativeGlobal() call if xpc::UnprivilegedJunkScope() "
+             "returned null, and inited correctly otherwise!");
+}
+
+AutoSlowOperation::AutoSlowOperation() : mIsMainThread(NS_IsMainThread()) {
+  if (mIsMainThread) {
+    mScriptActivity.emplace(true);
+  }
+}
+
+void AutoSlowOperation::CheckForInterrupt() {
+  // For now we support only main thread!
+  if (mIsMainThread) {
+    // JS_CheckForInterrupt expects us to be in a realm, so we use a junk scope.
+    // In principle, it doesn't matter which one we use, since we aren't really
+    // running scripts here, and none of our interrupt callbacks can stop
+    // scripts in a junk scope anyway. In practice, though, the privileged junk
+    // scope is the same as the JSM global, and therefore always exists, while
+    // the unprivileged junk scope is created lazily, and may not exist until we
+    // try to use it. So we use the former for the sake of efficiency.
+    dom::AutoJSAPI jsapi;
+    MOZ_ALWAYS_TRUE(jsapi.Init(xpc::PrivilegedJunkScope()));
+    JS_CheckForInterrupt(jsapi.cx());
+  }
+}
+
+AutoAllowLegacyScriptExecution::AutoAllowLegacyScriptExecution() {
+#ifdef DEBUG
+  // no need to do that dance if we are off the main thread,
+  // because we only assert if we are on the main thread!
+  if (!NS_IsMainThread()) {
+    return;
+  }
+  sAutoAllowLegacyScriptExecution++;
+#endif
+}
+
+AutoAllowLegacyScriptExecution::~AutoAllowLegacyScriptExecution() {
+#ifdef DEBUG
+  // no need to do that dance if we are off the main thread,
+  // because we only assert if we are on the main thread!
+  if (!NS_IsMainThread()) {
+    return;
+  }
+  sAutoAllowLegacyScriptExecution--;
+  MOZ_ASSERT(sAutoAllowLegacyScriptExecution >= 0,
+             "how can the stack guard produce a value less than 0?");
+#endif
+}
+
+int AutoAllowLegacyScriptExecution::sAutoAllowLegacyScriptExecution = 0;
+
+/*static*/
+bool AutoAllowLegacyScriptExecution::IsAllowed() {
+  return sAutoAllowLegacyScriptExecution > 0;
+}
+
+}  // namespace mozilla