The Tor Browser: dom/bindings/CallbackObject.cpp@6474c204b198 (annotated)

dom/bindings/CallbackObject.cpp@6474c204b198 (annotated)

dom/bindings/CallbackObject.cpp

Wed, 31 Dec 2014 06:09:35 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Wed, 31 Dec 2014 06:09:35 +0100
changeset 0: 6474c204b198
permissions: -rw-r--r--

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

 /* -*- 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 "mozilla/dom/CallbackObject.h"
 #include "mozilla/dom/BindingUtils.h"
 #include "mozilla/dom/DOMError.h"
 #include "mozilla/dom/DOMErrorBinding.h"
 #include "jsfriendapi.h"
 #include "nsIScriptGlobalObject.h"
 #include "nsIXPConnect.h"
 #include "nsIScriptContext.h"
 #include "nsPIDOMWindow.h"
 #include "nsJSUtils.h"
 #include "nsCxPusher.h"
 #include "nsIScriptSecurityManager.h"
 #include "xpcprivate.h"
 #include "WorkerPrivate.h"
 #include "nsGlobalWindow.h"
 #include "WorkerScope.h"
 namespace mozilla {
 namespace dom {
 NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(CallbackObject)
   NS_INTERFACE_MAP_ENTRY(mozilla::dom::CallbackObject)
   NS_INTERFACE_MAP_ENTRY(nsISupports)
 NS_INTERFACE_MAP_END
 NS_IMPL_CYCLE_COLLECTING_ADDREF(CallbackObject)
 NS_IMPL_CYCLE_COLLECTING_RELEASE(CallbackObject)
 NS_IMPL_CYCLE_COLLECTION_CLASS(CallbackObject)
 NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(CallbackObject)
   tmp->DropJSObjects();
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mIncumbentGlobal)
 NS_IMPL_CYCLE_COLLECTION_UNLINK_END
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(CallbackObject)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE_SCRIPT_OBJECTS
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mIncumbentGlobal)
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
 NS_IMPL_CYCLE_COLLECTION_TRACE_BEGIN(CallbackObject)
   NS_IMPL_CYCLE_COLLECTION_TRACE_JS_MEMBER_CALLBACK(mCallback)
   NS_IMPL_CYCLE_COLLECTION_TRACE_JS_MEMBER_CALLBACK(mIncumbentJSGlobal)
 NS_IMPL_CYCLE_COLLECTION_TRACE_END
 CallbackObject::CallSetup::CallSetup(CallbackObject* aCallback,
                                      ErrorResult& aRv,
                                      ExceptionHandling aExceptionHandling,
                                      JSCompartment* aCompartment,
                                      bool aIsJSImplementedWebIDL)
   : mCx(nullptr)
   , mCompartment(aCompartment)
   , mErrorResult(aRv)
   , mExceptionHandling(aExceptionHandling)
   , mIsMainThread(NS_IsMainThread())
 {
   if (mIsMainThread) {
     nsContentUtils::EnterMicroTask();
   }
   // Compute the caller's subject principal (if necessary) early, before we
   // do anything that might perturb the relevant state.
   nsIPrincipal* webIDLCallerPrincipal = nullptr;
   if (aIsJSImplementedWebIDL) {
     webIDLCallerPrincipal = nsContentUtils::GetSubjectPrincipal();
   }
   // We need to produce a useful JSContext here.  Ideally one that the callback
   // is in some sense associated with, so that we can sort of treat it as a
   // "script entry point".  Though once we actually have script entry points,
   // we'll need to do the script entry point bits once we have an actual
   // callable.
   // First, find the real underlying callback.
   JSObject* realCallback = js::UncheckedUnwrap(aCallback->CallbackPreserveColor());
   JSContext* cx = nullptr;
   nsIGlobalObject* globalObject = nullptr;
   {
     JS::AutoAssertNoGC nogc;
     if (mIsMainThread) {
       // Now get the global and JSContext for this callback.
       nsGlobalWindow* win = xpc::WindowGlobalOrNull(realCallback);
       if (win) {
         // Make sure that if this is a window it's the current inner, since the
         // nsIScriptContext and hence JSContext are associated with the outer
         // window.  Which means that if someone holds on to a function from a
         // now-unloaded document we'd have the new document as the script entry
         // point...
         MOZ_ASSERT(win->IsInnerWindow());
         nsPIDOMWindow* outer = win->GetOuterWindow();
         if (!outer || win != outer->GetCurrentInnerWindow()) {
           // Just bail out from here
           return;
         }
         cx = win->GetContext() ? win->GetContext()->GetNativeContext()
                                // This happens - Removing it causes
                                // test_bug293235.xul to go orange.
                                : nsContentUtils::GetSafeJSContext();
         globalObject = win;
       } else {
         // No DOM Window. Store the global and use the SafeJSContext.
         JSObject* glob = js::GetGlobalForObjectCrossCompartment(realCallback);
         globalObject = xpc::GetNativeForGlobal(glob);
         MOZ_ASSERT(globalObject);
         cx = nsContentUtils::GetSafeJSContext();
       }
     } else {
       cx = workers::GetCurrentThreadJSContext();
       globalObject = workers::GetCurrentThreadWorkerPrivate()->GlobalScope();
     }
     // Bail out if there's no useful global. This seems to happen intermittently
     // on gaia-ui tests, probably because nsInProcessTabChildGlobal is returning
     // null in some kind of teardown state.
     if (!globalObject->GetGlobalJSObject()) {
       return;
     }
     mAutoEntryScript.construct(globalObject, mIsMainThread, cx);
     mAutoEntryScript.ref().SetWebIDLCallerPrincipal(webIDLCallerPrincipal);
     nsIGlobalObject* incumbent = aCallback->IncumbentGlobalOrNull();
     if (incumbent) {
       // The callback object traces its incumbent JS global, so in general it
       // should be alive here. However, it's possible that we could run afoul
       // of the same IPC global weirdness described above, wherein the
       // nsIGlobalObject has severed its reference to the JS global. Let's just
       // be safe here, so that nobody has to waste a day debugging gaia-ui tests.
       if (!incumbent->GetGlobalJSObject()) {
         return;
       }
       mAutoIncumbentScript.construct(incumbent);
     }
     // Unmark the callable (by invoking Callback() and not the CallbackPreserveColor()
     // variant), and stick it in a Rooted before it can go gray again.
     // Nothing before us in this function can trigger a CC, so it's safe to wait
     // until here it do the unmark. This allows us to order the following two
     // operations _after_ the Push() above, which lets us take advantage of the
     // JSAutoRequest embedded in the pusher.
     //
     // We can do this even though we're not in the right compartment yet, because
     // Rooted<> does not care about compartments.
     mRootedCallable.construct(cx, aCallback->Callback());
   }
   if (mIsMainThread) {
     // Check that it's ok to run this callback at all.
     // Make sure to use realCallback to get the global of the callback object,
     // not the wrapper.
     bool allowed = nsContentUtils::GetSecurityManager()->
       ScriptAllowed(js::GetGlobalForObjectCrossCompartment(realCallback));
     if (!allowed) {
       return;
     }
   }
   // Enter the compartment of our callback, so we can actually work with it.
   //
   // Note that if the callback is a wrapper, this will not be the same
   // compartment that we ended up in with mAutoEntryScript above, because the
   // entry point is based off of the unwrapped callback (realCallback).
   mAc.construct(cx, mRootedCallable.ref());
   // And now we're ready to go.
   mCx = cx;
   // Make sure the JS engine doesn't report exceptions we want to re-throw
   if ((mCompartment && mExceptionHandling == eRethrowContentExceptions) ||
       mExceptionHandling == eRethrowExceptions) {
     mSavedJSContextOptions = JS::ContextOptionsRef(cx);
     JS::ContextOptionsRef(cx).setDontReportUncaught(true);
   }
 }
 bool
 CallbackObject::CallSetup::ShouldRethrowException(JS::Handle<JS::Value> aException)
 {
   if (mExceptionHandling == eRethrowExceptions) {
     return true;
   }
   MOZ_ASSERT(mExceptionHandling == eRethrowContentExceptions);
   // For eRethrowContentExceptions we only want to throw an exception if the
   // object that was thrown is a DOMError object in the caller compartment
   // (which we stored in mCompartment).
   if (!aException.isObject()) {
     return false;
   }
   JS::Rooted<JSObject*> obj(mCx, &aException.toObject());
   obj = js::UncheckedUnwrap(obj, /* stopAtOuter = */ false);
   if (js::GetObjectCompartment(obj) != mCompartment) {
     return false;
   }
   DOMError* domError;
   return NS_SUCCEEDED(UNWRAP_OBJECT(DOMError, obj, domError));
 }
 CallbackObject::CallSetup::~CallSetup()
 {
   // To get our nesting right we have to destroy our JSAutoCompartment first.
   // In particular, we want to do this before we try reporting any exceptions,
   // so we end up reporting them while in the compartment of our entry point,
   // not whatever cross-compartment wrappper mCallback might be.
   // Be careful: the JSAutoCompartment might not have been constructed at all!
   mAc.destroyIfConstructed();
   // Now, if we have a JSContext, report any pending errors on it, unless we
   // were told to re-throw them.
   if (mCx) {
     bool dealtWithPendingException = false;
     if ((mCompartment && mExceptionHandling == eRethrowContentExceptions) ||
         mExceptionHandling == eRethrowExceptions) {
       // Restore the old context options
       JS::ContextOptionsRef(mCx) = mSavedJSContextOptions;
       mErrorResult.MightThrowJSException();
       if (JS_IsExceptionPending(mCx)) {
         JS::Rooted<JS::Value> exn(mCx);
         if (JS_GetPendingException(mCx, &exn) &&
             ShouldRethrowException(exn)) {
           mErrorResult.ThrowJSException(mCx, exn);
           JS_ClearPendingException(mCx);
           dealtWithPendingException = true;
         }
       }
     }
     if (!dealtWithPendingException) {
       // Either we're supposed to report our exceptions, or we're supposed to
       // re-throw them but we failed to JS_GetPendingException.  Either way,
       // just report the pending exception, if any.
       //
       // We don't use nsJSUtils::ReportPendingException here because all it
       // does at this point is JS_SaveFrameChain and enter a compartment around
       // a JS_ReportPendingException call.  But our mAutoEntryScript should
       // already do a JS_SaveFrameChain and we are already in the compartment
       // we want to be in, so all nsJSUtils::ReportPendingException would do is
       // screw up our compartment, which is exactly what we do not want.
       //
       // XXXbz FIXME: bug 979525 means we don't always JS_SaveFrameChain here,
       // so we need to go ahead and do that.
       JS::Rooted<JSObject*> oldGlobal(mCx, JS::CurrentGlobalOrNull(mCx));
       MOZ_ASSERT(oldGlobal, "How can we not have a global here??");
       bool saved = JS_SaveFrameChain(mCx);
       // Make sure the JSAutoCompartment goes out of scope before the
       // JS_RestoreFrameChain call!
       {
         JSAutoCompartment ac(mCx, oldGlobal);
         MOZ_ASSERT(!JS::DescribeScriptedCaller(mCx),
                    "Our comment above about JS_SaveFrameChain having been "
                    "called is a lie?");
         JS_ReportPendingException(mCx);
       }
       if (saved) {
         JS_RestoreFrameChain(mCx);
       }
     }
   }
   mAutoIncumbentScript.destroyIfConstructed();
   mAutoEntryScript.destroyIfConstructed();
   // It is important that this is the last thing we do, after leaving the
   // compartment and undoing all our entry/incumbent script changes
   if (mIsMainThread) {
     nsContentUtils::LeaveMicroTask();
   }
 }
 already_AddRefed<nsISupports>
 CallbackObjectHolderBase::ToXPCOMCallback(CallbackObject* aCallback,
                                           const nsIID& aIID) const
 {
   MOZ_ASSERT(NS_IsMainThread());
   if (!aCallback) {
     return nullptr;
   }
   AutoSafeJSContext cx;
   JS::Rooted<JSObject*> callback(cx, aCallback->Callback());
   JSAutoCompartment ac(cx, callback);
   nsRefPtr<nsXPCWrappedJS> wrappedJS;
   nsresult rv =
     nsXPCWrappedJS::GetNewOrUsed(callback, aIID, getter_AddRefs(wrappedJS));
   if (NS_FAILED(rv) || !wrappedJS) {
     return nullptr;
   }
   nsCOMPtr<nsISupports> retval;
   rv = wrappedJS->QueryInterface(aIID, getter_AddRefs(retval));
   if (NS_FAILED(rv)) {
     return nullptr;
   }
   return retval.forget();
 }
 } // namespace dom
 } // namespace mozilla

The Tor Browser / annotate

dom/bindings/CallbackObject.cpp@6474c204b198 (annotated)

dom/bindings/CallbackObject.cpp