firefox-main/js/src/vm/ProxyObject.cpp (file symbol)

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/* 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 "vm/ProxyObject.h"
#include "gc/GC.h"
#include "gc/GCProbes.h"
#include "gc/Marking.h"
#include "gc/Zone.h"
#include "proxy/DeadObjectProxy.h"
#include "vm/Compartment.h"
#include "vm/Realm.h"
#include "gc/ObjectKind-inl.h"
#include "gc/StableCellHasher-inl.h" // gc::MaybeGetUniqueId, gc::GetUniqueIdInfallible
#include "vm/JSContext-inl.h"
using namespace js;
static gc::AllocKind GetProxyGCObjectKind(const JSClass* clasp,
const BaseProxyHandler* handler,
const Value& priv) {
MOZ_ASSERT(clasp->isProxyObject());
uint32_t nreserved = JSCLASS_RESERVED_SLOTS(clasp);
// For now assert each Proxy Class has at least 1 reserved slot. This is
// not a hard requirement, but helps catch Classes that need an explicit
// JSCLASS_HAS_RESERVED_SLOTS since bug 1360523.
MOZ_ASSERT(nreserved > 0);
uint32_t nslots = detail::ProxyValueArray::allocCount(nreserved);
MOZ_ASSERT(nslots <= NativeObject::MAX_FIXED_SLOTS);
gc::AllocKind kind = gc::GetGCObjectKind(nslots);
gc::FinalizeKind finalizeKind;
// Bug 1957589: Support non-finalized proxies as well.
if (handler->finalizeInBackground(priv)) {
finalizeKind = gc::FinalizeKind::Background;
} else {
finalizeKind = gc::FinalizeKind::Foreground;
}
return gc::GetFinalizedAllocKind(kind, finalizeKind);
}
void ProxyObject::init(const BaseProxyHandler* handler, HandleValue priv,
JSContext* cx) {
data.init(handler, numReservedSlots());
if (IsCrossCompartmentWrapper(this)) {
MOZ_ASSERT(cx->global() == &cx->compartment()->globalForNewCCW());
setCrossCompartmentPrivate(priv);
} else {
setSameCompartmentPrivate(priv);
}
}
/* static */
ProxyObject* ProxyObject::New(JSContext* cx, const BaseProxyHandler* handler,
HandleValue priv, TaggedProto proto_,
const JSClass* clasp) {
Rooted<TaggedProto> proto(cx, proto_);
MOZ_ASSERT(!clasp->isNativeObject());
MOZ_ASSERT(clasp->isProxyObject());
MOZ_ASSERT(isValidProxyClass(clasp));
MOZ_ASSERT(clasp->shouldDelayMetadataBuilder());
MOZ_ASSERT_IF(proto.isObject(),
cx->compartment() == proto.toObject()->compartment());
MOZ_ASSERT(clasp->hasFinalize());
#ifdef DEBUG
if (priv.isGCThing()) {
JS::AssertCellIsNotGray(priv.toGCThing());
}
#endif
gc::AllocKind allocKind = GetProxyGCObjectKind(clasp, handler, priv);
Realm* realm = cx->realm();
AutoSetNewObjectMetadata metadata(cx);
// Try to look up the shape in the NewProxyCache.
Rooted<Shape*> shape(cx);
if (!realm->newProxyCache.lookup(clasp, proto, shape.address())) {
shape = ProxyShape::getShape(cx, clasp, realm, proto, ObjectFlags());
if (!shape) {
return nullptr;
}
realm->newProxyCache.add(shape);
}
MOZ_ASSERT(shape->realm() == realm);
MOZ_ASSERT(!IsAboutToBeFinalizedUnbarriered(shape.get()));
// Ensure that the wrapper has the same lifetime assumptions as the
// wrappee. Prefer to allocate in the nursery, when possible.
gc::Heap heap;
if ((priv.isGCThing() && priv.toGCThing()->isTenured()) ||
!handler->canNurseryAllocate()) {
heap = gc::Heap::Tenured;
} else {
heap = gc::Heap::Default;
}
debugCheckNewObject(shape, allocKind, heap);
ProxyObject* proxy = cx->newCell<ProxyObject>(allocKind, heap, clasp);
if (!proxy) {
return nullptr;
}
proxy->initShape(shape);
MOZ_ASSERT(clasp->shouldDelayMetadataBuilder());
realm->setObjectPendingMetadata(proxy);
gc::gcprobes::CreateObject(proxy);
proxy->init(handler, priv, cx);
return proxy;
}
gc::AllocKind ProxyObject::allocKindForTenure() const {
Value priv = private_();
return GetProxyGCObjectKind(getClass(), data.handler, priv);
}
void ProxyObject::setCrossCompartmentPrivate(const Value& priv) {
setPrivate(priv);
}
void ProxyObject::setSameCompartmentPrivate(const Value& priv) {
MOZ_ASSERT(IsObjectValueInCompartment(priv, compartment()));
setPrivate(priv);
}
inline void ProxyObject::setPrivate(const Value& priv) {
#ifdef DEBUG
JS::AssertValueIsNotGray(priv);
#endif
*slotOfPrivate() = priv;
}
void ProxyObject::setExpando(JSObject* expando) {
// Ensure we're in the same compartment as the proxy object: Don't want the
// expando to end up as a CCW.
MOZ_ASSERT_IF(expando, expando->compartment() == compartment());
// Ensure that we don't accidentally end up pointing to a
// grey object, which would violate GC invariants.
MOZ_ASSERT_IF(!zone()->isGCPreparing() && isMarkedBlack() && expando,
!JS::GCThingIsMarkedGray(JS::GCCellPtr(expando)));
*expandoPtr() = expando;
}
void ProxyObject::nuke() {
// Notify the zone that a delegate is no longer a delegate. Be careful not to
// expose this pointer, because it has already been removed from the wrapper
// map yet we have assertions during tracing that will verify that it is
// still present.
JSObject* delegate = UncheckedUnwrapWithoutExpose(this);
if (delegate != this) {
delegate->zone()->beforeClearDelegate(this, delegate);
}
// Clear the target reference and replaced it with a value that encodes
// various information about the original target.
setSameCompartmentPrivate(DeadProxyTargetValue(this));
// Clear out the expando
setExpando(nullptr);
// Update the handler to make this a DeadObjectProxy.
setHandler(&DeadObjectProxy::singleton);
// The proxy's reserved slots are not cleared and will continue to be
// traced. This avoids the possibility of triggering write barriers while
// nuking proxies in dead compartments which could otherwise cause those
// compartments to be kept alive. Note that these are slots cannot hold
// cross compartment pointers, so this cannot cause the target compartment
// to leak.
}
// Use this method with extreme caution. It trades the guts of two proxies.
/* static */
void ProxyObject::swap(JSContext* cx, Handle<ProxyObject*> a,
Handle<ProxyObject*> b,
AutoEnterOOMUnsafeRegion& oomUnsafe) {
// Only proxies with SwappableProxyReservedSlots and the same AllocKind may be
// swapped.
MOZ_RELEASE_ASSERT(JSCLASS_RESERVED_SLOTS(a->getClass()) ==
js::SwappableProxyReservedSlots);
MOZ_RELEASE_ASSERT(JSCLASS_RESERVED_SLOTS(b->getClass()) ==
js::SwappableProxyReservedSlots);
MOZ_RELEASE_ASSERT(a->allocKind() == b->allocKind());
MOZ_RELEASE_ASSERT(a->compartment() == b->compartment());
// You must have entered the objects' compartment before calling this.
MOZ_RELEASE_ASSERT(cx->compartment() == a->compartment());
// Only certain types of objects are allowed to be swapped. This allows the
// JITs to better optimize objects that can never swap and rules out most
// builtin objects that have special behaviour.
MOZ_RELEASE_ASSERT(js::ObjectMayBeSwapped(a));
MOZ_RELEASE_ASSERT(js::ObjectMayBeSwapped(b));
// Don't allow a GC which may observe intermediate state or run before we
// execute all necessary barriers.
gc::AutoSuppressGC nogc(cx);
if (a->isTenured() || b->isTenured()) {
if (a->zone()->wasGCStarted()) {
cx->runtime()->gc.storeBuffer().setMayHavePointersToDeadCells();
}
}
unsigned r = NotifyGCPreSwap(a, b);
bool aIsUsedAsPrototype = a->isUsedAsPrototype();
bool bIsUsedAsPrototype = b->isUsedAsPrototype();
// Verify that swapping does not result in an object becoming its own proto.
if (aIsUsedAsPrototype && b->hasStaticPrototype()) {
MOZ_RELEASE_ASSERT(b->staticPrototype() != a);
}
if (bIsUsedAsPrototype && a->hasStaticPrototype()) {
MOZ_RELEASE_ASSERT(a->staticPrototype() != b);
}
#ifdef DEBUG
// Record any associated unique IDs.
//
// Note that unique IDs are NOT swapped but remain associated with the
// original address.
uint64_t aid = 0;
uint64_t bid = 0;
(void)gc::MaybeGetUniqueId(a, &aid);
(void)gc::MaybeGetUniqueId(b, &bid);
#endif
// Swap shape.
Shape* shapeA = a->shape();
a->setShapeForProxySwap(b->shape());
b->setShapeForProxySwap(shapeA);
// Swap handler.
const BaseProxyHandler* handlerA = a->handler();
a->setHandler(b->handler());
b->setHandler(handlerA);
// Swap expando objects.
JSObject* expandoA = a->expando();
a->setExpando(b->expando());
b->setExpando(expandoA);
// Swap private slot.
Value privateA = GetProxyPrivate(a);
SetProxyPrivate(a, GetProxyPrivate(b));
SetProxyPrivate(b, privateA);
// Swap reserved slots.
for (size_t i = 0; i < SwappableProxyReservedSlots; i++) {
Value slotA = GetProxyReservedSlot(a, i);
SetProxyReservedSlot(a, i, GetProxyReservedSlot(b, i));
SetProxyReservedSlot(b, i, slotA);
}
MOZ_ASSERT_IF(aid, gc::GetUniqueIdInfallible(a) == aid);
MOZ_ASSERT_IF(bid, gc::GetUniqueIdInfallible(b) == bid);
// Preserve the IsUsedAsPrototype flag on the objects.
if (aIsUsedAsPrototype) {
if (!JSObject::setIsUsedAsPrototype(cx, a)) {
oomUnsafe.crash("setIsUsedAsPrototype");
}
}
if (bIsUsedAsPrototype) {
if (!JSObject::setIsUsedAsPrototype(cx, b)) {
oomUnsafe.crash("setIsUsedAsPrototype");
}
}
NotifyGCPostSwap(a, b, r);
}
JS_PUBLIC_API void js::detail::SetValueInProxy(Value* slot,
const Value& value) {
// Slots in proxies are not GCPtr<Value>s, so do a cast whenever assigning
// values to them which might trigger a barrier.
*reinterpret_cast<GCPtr<Value>*>(slot) = value;
}