gecko-dev/dom/bindings/CallbackObject.cpp
Bobby Holley e3eca2660e Bug 1070696 - Rename xpc::GetNativeForGlobal to xpc::NativeGlobal and make it accept non-global JSObjects. r=smaug
The method is infallible, and making the callers invoke
js::GetGlobalForObjectCrossCompartment manually is dumb.
2014-09-21 21:31:53 +02:00

317 lines
12 KiB
C++

/* -*- 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 "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::SubjectPrincipal();
}
// 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;
{
// Bug 955660: we cannot do "proper" rooting here because we need the
// global to get a context. Everything here is simple getters that cannot
// GC, so just paper over the necessary dataflow inversion.
JS::AutoSuppressGCAnalysis nogc;
if (mIsMainThread) {
// Now get the global and JSContext for this callback. Note that for the
// case of JS-implemented WebIDL we never have a window here.
nsGlobalWindow* win =
aIsJSImplementedWebIDL ? nullptr : 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::NativeGlobal(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.emplace(globalObject, mIsMainThread, cx);
mAutoEntryScript->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.emplace(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.emplace(cx, aCallback->Callback());
}
// JS-implemented WebIDL is always OK to run, since it runs with Chrome
// privileges anyway.
if (mIsMainThread && !aIsJSImplementedWebIDL) {
// 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.emplace(cx, *mRootedCallable);
// 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.reset();
// Now, if we have a JSContext, report any pending errors on it, unless we
// were told to re-throw them.
if (mCx) {
bool needToDealWithException = JS_IsExceptionPending(mCx);
if ((mCompartment && mExceptionHandling == eRethrowContentExceptions) ||
mExceptionHandling == eRethrowExceptions) {
// Restore the old context options
JS::ContextOptionsRef(mCx) = mSavedJSContextOptions;
mErrorResult.MightThrowJSException();
if (needToDealWithException) {
JS::Rooted<JS::Value> exn(mCx);
if (JS_GetPendingException(mCx, &exn) &&
ShouldRethrowException(exn)) {
mErrorResult.ThrowJSException(mCx, exn);
JS_ClearPendingException(mCx);
needToDealWithException = false;
}
}
}
if (needToDealWithException) {
// 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.reset();
mAutoEntryScript.reset();
// 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