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+/* -*- 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/. */
+
+/* Utilities for managing the script settings object stack defined in webapps */
+
+#ifndef mozilla_dom_ScriptSettings_h
+#define mozilla_dom_ScriptSettings_h
+
+#include "MainThreadUtils.h"
+#include "nsIGlobalObject.h"
+#include "nsIPrincipal.h"
+
+#include "mozilla/Maybe.h"
+
+#include "jsapi.h"
+#include "js/Debug.h"
+
+class nsPIDOMWindowInner;
+class nsGlobalWindow;
+class nsIScriptContext;
+class nsIDocument;
+class nsIDocShell;
+
+namespace mozilla {
+namespace dom {
+
+/*
+ * System-wide setup/teardown routines. Init and Destroy should be invoked
+ * once each, at startup and shutdown (respectively).
+ */
+void InitScriptSettings();
+void DestroyScriptSettings();
+bool ScriptSettingsInitialized();
+
+/*
+ * Static helpers in ScriptSettings which track the number of listeners
+ * of Javascript RunToCompletion events. These should be used by the code in
+ * nsDocShell::SetRecordProfileTimelineMarkers to indicate to script
+ * settings that script run-to-completion needs to be monitored.
+ * SHOULD BE CALLED ONLY BY MAIN THREAD.
+ */
+void UseEntryScriptProfiling();
+void UnuseEntryScriptProfiling();
+
+// To implement a web-compatible browser, it is often necessary to obtain the
+// global object that is "associated" with the currently-running code. This
+// process is made more complicated by the fact that, historically, different
+// algorithms have operated with different definitions of the "associated"
+// global.
+//
+// HTML5 formalizes this into two concepts: the "incumbent global" and the
+// "entry global". The incumbent global corresponds to the global of the
+// current script being executed, whereas the entry global corresponds to the
+// global of the script where the current JS execution began.
+//
+// There is also a potentially-distinct third global that is determined by the
+// current compartment. This roughly corresponds with the notion of Realms in
+// ECMAScript.
+//
+// Suppose some event triggers an event listener in window |A|, which invokes a
+// scripted function in window |B|, which invokes the |window.location.href|
+// setter in window |C|. The entry global would be |A|, the incumbent global
+// would be |B|, and the current compartment would be that of |C|.
+//
+// In general, it's best to use to use the most-closely-associated global
+// unless the spec says to do otherwise. In 95% of the cases, the global of
+// the current compartment (GetCurrentGlobal()) is the right thing. For
+// example, WebIDL constructors (new C.XMLHttpRequest()) are initialized with
+// the global of the current compartment (i.e. |C|).
+//
+// The incumbent global is very similar, but differs in a few edge cases. For
+// example, if window |B| does |C.location.href = "..."|, the incumbent global
+// used for the navigation algorithm is B, because no script from |C| was ever run.
+//
+// The entry global is used for various things like computing base URIs, mostly
+// for historical reasons.
+//
+// Note that all of these functions return bonafide global objects. This means
+// that, for Windows, they always return the inner.
+
+// Returns the global associated with the top-most Candidate Entry Point on
+// the Script Settings Stack. See the HTML spec. This may be null.
+nsIGlobalObject* GetEntryGlobal();
+
+// If the entry global is a window, returns its extant document. Otherwise,
+// returns null.
+nsIDocument* GetEntryDocument();
+
+// Returns the global associated with the top-most entry of the the Script
+// Settings Stack. See the HTML spec. This may be null.
+nsIGlobalObject* GetIncumbentGlobal();
+
+// Returns the global associated with the current compartment. This may be null.
+nsIGlobalObject* GetCurrentGlobal();
+
+// JS-implemented WebIDL presents an interesting situation with respect to the
+// subject principal. A regular C++-implemented API can simply examine the
+// compartment of the most-recently-executed script, and use that to infer the
+// responsible party. However, JS-implemented APIs are run with system
+// principal, and thus clobber the subject principal of the script that
+// invoked the API. So we have to do some extra work to keep track of this
+// information.
+//
+// We therefore implement the following behavior:
+// * Each Script Settings Object has an optional WebIDL Caller Principal field.
+// This defaults to null.
+// * When we push an Entry Point in preparation to run a JS-implemented WebIDL
+// callback, we grab the subject principal at the time of invocation, and
+// store that as the WebIDL Caller Principal.
+// * When non-null, callers can query this principal from script via an API on
+// Components.utils.
+nsIPrincipal* GetWebIDLCallerPrincipal();
+
+// This may be used by callers that know that their incumbent global is non-
+// null (i.e. they know there have been no System Caller pushes since the
+// inner-most script execution).
+inline JSObject& IncumbentJSGlobal()
+{
+ return *GetIncumbentGlobal()->GetGlobalJSObject();
+}
+
+// Returns whether JSAPI is active right now. If it is not, working with a
+// JSContext you grab from somewhere random is not OK and you should be doing
+// AutoJSAPI or AutoEntryScript to get yourself a properly set up JSContext.
+bool IsJSAPIActive();
+
+namespace danger {
+
+// Get the JSContext for this thread. This is in the "danger" namespace because
+// we generally want people using AutoJSAPI instead, unless they really know
+// what they're doing.
+JSContext* GetJSContext();
+
+} // namespace danger
+
+JS::RootingContext* RootingCx();
+
+class ScriptSettingsStack;
+class ScriptSettingsStackEntry {
+ friend class ScriptSettingsStack;
+
+public:
+ ~ScriptSettingsStackEntry();
+
+ bool NoJSAPI() const { return mType == eNoJSAPI; }
+ bool IsEntryCandidate() const {
+ return mType == eEntryScript || mType == eNoJSAPI;
+ }
+ bool IsIncumbentCandidate() { return mType != eJSAPI; }
+ bool IsIncumbentScript() { return mType == eIncumbentScript; }
+
+protected:
+ enum Type {
+ eEntryScript,
+ eIncumbentScript,
+ eJSAPI,
+ eNoJSAPI
+ };
+
+ ScriptSettingsStackEntry(nsIGlobalObject *aGlobal,
+ Type aEntryType);
+
+ nsCOMPtr<nsIGlobalObject> mGlobalObject;
+ Type mType;
+
+private:
+ ScriptSettingsStackEntry *mOlder;
+};
+
+/*
+ * For any interaction with JSAPI, an AutoJSAPI (or one of its subclasses)
+ * must be on the stack.
+ *
+ * This base class should be instantiated as-is when the caller wants to use
+ * JSAPI but doesn't expect to run script. The caller must then call one of its
+ * Init functions before being able to access the JSContext through cx().
+ * Its current duties are as-follows (see individual Init comments for details):
+ *
+ * * Grabbing an appropriate JSContext, and, on the main thread, pushing it onto
+ * the JSContext stack.
+ * * Entering an initial (possibly null) compartment, to ensure that the
+ * previously entered compartment for that JSContext is not used by mistake.
+ * * Reporting any exceptions left on the JSRuntime, unless the caller steals
+ * or silences them.
+ * * On main thread, entering a JSAutoRequest.
+ *
+ * Additionally, the following duties are planned, but not yet implemented:
+ *
+ * * De-poisoning the JSRuntime to allow manipulation of JSAPI. This requires
+ * implementing the poisoning first. For now, this de-poisoning
+ * effectively corresponds to having a non-null cx on the stack.
+ *
+ * In situations where the consumer expects to run script, AutoEntryScript
+ * should be used, which does additional manipulation of the script settings
+ * stack. In bug 991758, we'll add hard invariants to SpiderMonkey, such that
+ * any attempt to run script without an AutoEntryScript on the stack will
+ * fail. This prevents system code from accidentally triggering script
+ * execution at inopportune moments via surreptitious getters and proxies.
+ */
+class MOZ_STACK_CLASS AutoJSAPI : protected ScriptSettingsStackEntry {
+public:
+ // Trivial constructor. One of the Init functions must be called before
+ // accessing the JSContext through cx().
+ AutoJSAPI();
+
+ ~AutoJSAPI();
+
+ // This uses the SafeJSContext (or worker equivalent), and enters a null
+ // compartment, so that the consumer is forced to select a compartment to
+ // enter before manipulating objects.
+ //
+ // This variant will ensure that any errors reported by this AutoJSAPI as it
+ // comes off the stack will not fire error events or be associated with any
+ // particular web-visible global.
+ void Init();
+
+ // This uses the SafeJSContext (or worker equivalent), and enters the
+ // compartment of aGlobalObject.
+ // If aGlobalObject or its associated JS global are null then it returns
+ // false and use of cx() will cause an assertion.
+ //
+ // If aGlobalObject represents a web-visible global, errors reported by this
+ // AutoJSAPI as it comes off the stack will fire the relevant error events and
+ // show up in the corresponding web console.
+ MOZ_MUST_USE bool Init(nsIGlobalObject* aGlobalObject);
+
+ // This is a helper that grabs the native global associated with aObject and
+ // invokes the above Init() with that.
+ MOZ_MUST_USE bool Init(JSObject* aObject);
+
+ // Unsurprisingly, this uses aCx and enters the compartment of aGlobalObject.
+ // If aGlobalObject or its associated JS global are null then it returns
+ // false and use of cx() will cause an assertion.
+ // If aCx is null it will cause an assertion.
+ //
+ // If aGlobalObject represents a web-visible global, errors reported by this
+ // AutoJSAPI as it comes off the stack will fire the relevant error events and
+ // show up in the corresponding web console.
+ MOZ_MUST_USE bool Init(nsIGlobalObject* aGlobalObject, JSContext* aCx);
+
+ // Convenience functions to take an nsPIDOMWindow* or nsGlobalWindow*,
+ // when it is more easily available than an nsIGlobalObject.
+ MOZ_MUST_USE bool Init(nsPIDOMWindowInner* aWindow);
+ MOZ_MUST_USE bool Init(nsPIDOMWindowInner* aWindow, JSContext* aCx);
+
+ MOZ_MUST_USE bool Init(nsGlobalWindow* aWindow);
+ MOZ_MUST_USE bool Init(nsGlobalWindow* aWindow, JSContext* aCx);
+
+ JSContext* cx() const {
+ MOZ_ASSERT(mCx, "Must call Init before using an AutoJSAPI");
+ MOZ_ASSERT(IsStackTop());
+ return mCx;
+ }
+
+#ifdef DEBUG
+ bool IsStackTop() const;
+#endif
+
+ // If HasException, report it. Otherwise, a no-op.
+ void ReportException();
+
+ bool HasException() const {
+ MOZ_ASSERT(IsStackTop());
+ return JS_IsExceptionPending(cx());
+ };
+
+ // Transfers ownership of the current exception from the JS engine to the
+ // caller. Callers must ensure that HasException() is true, and that cx()
+ // is in a non-null compartment.
+ //
+ // Note that this fails if and only if we OOM while wrapping the exception
+ // into the current compartment.
+ MOZ_MUST_USE bool StealException(JS::MutableHandle<JS::Value> aVal);
+
+ // Peek the current exception from the JS engine, without stealing it.
+ // Callers must ensure that HasException() is true, and that cx() is in a
+ // non-null compartment.
+ //
+ // Note that this fails if and only if we OOM while wrapping the exception
+ // into the current compartment.
+ MOZ_MUST_USE bool PeekException(JS::MutableHandle<JS::Value> aVal);
+
+ void ClearException() {
+ MOZ_ASSERT(IsStackTop());
+ JS_ClearPendingException(cx());
+ }
+
+protected:
+ // Protected constructor for subclasses. This constructor initialises the
+ // AutoJSAPI, so Init must NOT be called on subclasses that use this.
+ AutoJSAPI(nsIGlobalObject* aGlobalObject, bool aIsMainThread, Type aType);
+
+private:
+ mozilla::Maybe<JSAutoRequest> mAutoRequest;
+ mozilla::Maybe<JSAutoNullableCompartment> mAutoNullableCompartment;
+ JSContext *mCx;
+
+ // Whether we're mainthread or not; set when we're initialized.
+ bool mIsMainThread;
+ Maybe<JS::WarningReporter> mOldWarningReporter;
+
+ void InitInternal(nsIGlobalObject* aGlobalObject, JSObject* aGlobal,
+ JSContext* aCx, bool aIsMainThread);
+
+ AutoJSAPI(const AutoJSAPI&) = delete;
+ AutoJSAPI& operator= (const AutoJSAPI&) = delete;
+};
+
+/*
+ * A class that represents a new script entry point.
+ *
+ * |aReason| should be a statically-allocated C string naming the reason we're
+ * invoking JavaScript code: "setTimeout", "event", and so on. The devtools use
+ * these strings to label JS execution in timeline and profiling displays.
+ */
+class MOZ_STACK_CLASS AutoEntryScript : public AutoJSAPI {
+public:
+ AutoEntryScript(nsIGlobalObject* aGlobalObject,
+ const char *aReason,
+ bool aIsMainThread = NS_IsMainThread());
+
+ AutoEntryScript(JSObject* aObject, // Any object from the relevant global
+ const char *aReason,
+ bool aIsMainThread = NS_IsMainThread());
+
+ ~AutoEntryScript();
+
+ void SetWebIDLCallerPrincipal(nsIPrincipal *aPrincipal) {
+ mWebIDLCallerPrincipal = aPrincipal;
+ }
+
+private:
+ // A subclass of AutoEntryMonitor that notifies the docshell.
+ class DocshellEntryMonitor final : public JS::dbg::AutoEntryMonitor
+ {
+ public:
+ DocshellEntryMonitor(JSContext* aCx, const char* aReason);
+
+ // Please note that |aAsyncCause| here is owned by the caller, and its
+ // lifetime must outlive the lifetime of the DocshellEntryMonitor object.
+ // In practice, |aAsyncCause| is identical to |aReason| passed into
+ // the AutoEntryScript constructor, so the lifetime requirements are
+ // trivially satisfied by |aReason| being a statically allocated string.
+ void Entry(JSContext* aCx, JSFunction* aFunction,
+ JS::Handle<JS::Value> aAsyncStack,
+ const char* aAsyncCause) override
+ {
+ Entry(aCx, aFunction, nullptr, aAsyncStack, aAsyncCause);
+ }
+
+ void Entry(JSContext* aCx, JSScript* aScript,
+ JS::Handle<JS::Value> aAsyncStack,
+ const char* aAsyncCause) override
+ {
+ Entry(aCx, nullptr, aScript, aAsyncStack, aAsyncCause);
+ }
+
+ void Exit(JSContext* aCx) override;
+
+ private:
+ void Entry(JSContext* aCx, JSFunction* aFunction, JSScript* aScript,
+ JS::Handle<JS::Value> aAsyncStack,
+ const char* aAsyncCause);
+
+ const char* mReason;
+ };
+
+ // It's safe to make this a weak pointer, since it's the subject principal
+ // when we go on the stack, so can't go away until after we're gone. In
+ // particular, this is only used from the CallSetup constructor, and only in
+ // the aIsJSImplementedWebIDL case. And in that case, the subject principal
+ // is the principal of the callee function that is part of the CallArgs just a
+ // bit up the stack, and which will outlive us. So we know the principal
+ // can't go away until then either.
+ nsIPrincipal* MOZ_NON_OWNING_REF mWebIDLCallerPrincipal;
+ friend nsIPrincipal* GetWebIDLCallerPrincipal();
+
+ Maybe<DocshellEntryMonitor> mDocShellEntryMonitor;
+};
+
+/*
+ * A class that can be used to force a particular incumbent script on the stack.
+ */
+class AutoIncumbentScript : protected ScriptSettingsStackEntry {
+public:
+ explicit AutoIncumbentScript(nsIGlobalObject* aGlobalObject);
+ ~AutoIncumbentScript();
+
+private:
+ JS::AutoHideScriptedCaller mCallerOverride;
+};
+
+/*
+ * A class to put the JS engine in an unusable state. The subject principal
+ * will become System, the information on the script settings stack is
+ * rendered inaccessible, and JSAPI may not be manipulated until the class is
+ * either popped or an AutoJSAPI instance is subsequently pushed.
+ *
+ * This class may not be instantiated if an exception is pending.
+ */
+class AutoNoJSAPI : protected ScriptSettingsStackEntry {
+public:
+ explicit AutoNoJSAPI();
+ ~AutoNoJSAPI();
+};
+
+} // namespace dom
+
+/**
+ * Use AutoJSContext when you need a JS context on the stack but don't have one
+ * passed as a parameter. AutoJSContext will take care of finding the most
+ * appropriate JS context and release it when leaving the stack.
+ */
+class MOZ_RAII AutoJSContext {
+public:
+ explicit AutoJSContext(MOZ_GUARD_OBJECT_NOTIFIER_ONLY_PARAM);
+ operator JSContext*() const;
+
+protected:
+ JSContext* mCx;
+ dom::AutoJSAPI mJSAPI;
+ MOZ_DECL_USE_GUARD_OBJECT_NOTIFIER
+};
+
+/**
+ * AutoSafeJSContext is similar to AutoJSContext but will only return the safe
+ * JS context. That means it will never call nsContentUtils::GetCurrentJSContext().
+ *
+ * Note - This is deprecated. Please use AutoJSAPI instead.
+ */
+class MOZ_RAII AutoSafeJSContext : public dom::AutoJSAPI {
+public:
+ explicit AutoSafeJSContext(MOZ_GUARD_OBJECT_NOTIFIER_ONLY_PARAM);
+ operator JSContext*() const
+ {
+ return cx();
+ }
+
+private:
+ MOZ_DECL_USE_GUARD_OBJECT_NOTIFIER
+};
+
+/**
+ * Use AutoSlowOperation when native side calls many JS callbacks in a row
+ * and slow script dialog should be activated if too much time is spent going
+ * through those callbacks.
+ * AutoSlowOperation puts a JSAutoRequest on the stack so that we don't continue
+ * to reset the watchdog and CheckForInterrupt can be then used to check whether
+ * JS execution should be interrupted.
+ */
+class MOZ_RAII AutoSlowOperation : public dom::AutoJSAPI
+{
+public:
+ explicit AutoSlowOperation(MOZ_GUARD_OBJECT_NOTIFIER_ONLY_PARAM);
+ void CheckForInterrupt();
+private:
+ MOZ_DECL_USE_GUARD_OBJECT_NOTIFIER
+};
+
+} // namespace mozilla
+
+#endif // mozilla_dom_ScriptSettings_h