| // Copyright 2016 the V8 project authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #include "src/snapshot/partial-serializer.h" |
| #include "src/snapshot/startup-serializer.h" |
| |
| #include "src/api-inl.h" |
| #include "src/math-random.h" |
| #include "src/objects-inl.h" |
| #include "src/objects/slots.h" |
| |
| namespace v8 { |
| namespace internal { |
| |
| PartialSerializer::PartialSerializer( |
| Isolate* isolate, StartupSerializer* startup_serializer, |
| v8::SerializeEmbedderFieldsCallback callback) |
| : Serializer(isolate), |
| startup_serializer_(startup_serializer), |
| serialize_embedder_fields_(callback), |
| can_be_rehashed_(true) { |
| InitializeCodeAddressMap(); |
| allocator()->UseCustomChunkSize(FLAG_serialization_chunk_size); |
| } |
| |
| PartialSerializer::~PartialSerializer() { |
| OutputStatistics("PartialSerializer"); |
| } |
| |
| void PartialSerializer::Serialize(Context* o, bool include_global_proxy) { |
| context_ = *o; |
| DCHECK(context_->IsNativeContext()); |
| reference_map()->AddAttachedReference(context_->global_proxy()); |
| // The bootstrap snapshot has a code-stub context. When serializing the |
| // partial snapshot, it is chained into the weak context list on the isolate |
| // and it's next context pointer may point to the code-stub context. Clear |
| // it before serializing, it will get re-added to the context list |
| // explicitly when it's loaded. |
| context_->set(Context::NEXT_CONTEXT_LINK, |
| ReadOnlyRoots(isolate()).undefined_value()); |
| DCHECK(!context_->global_object()->IsUndefined()); |
| // Reset math random cache to get fresh random numbers. |
| MathRandom::ResetContext(context_); |
| |
| VisitRootPointer(Root::kPartialSnapshotCache, nullptr, ObjectSlot(o)); |
| SerializeDeferredObjects(); |
| |
| // Add section for embedder-serialized embedder fields. |
| if (!embedder_fields_sink_.data()->empty()) { |
| sink_.Put(kEmbedderFieldsData, "embedder fields data"); |
| sink_.Append(embedder_fields_sink_); |
| sink_.Put(kSynchronize, "Finished with embedder fields data"); |
| } |
| |
| Pad(); |
| } |
| |
| void PartialSerializer::SerializeObject(HeapObject* obj, HowToCode how_to_code, |
| WhereToPoint where_to_point, int skip) { |
| DCHECK(!ObjectIsBytecodeHandler(obj)); // Only referenced in dispatch table. |
| |
| if (SerializeHotObject(obj, how_to_code, where_to_point, skip)) return; |
| |
| if (SerializeRoot(obj, how_to_code, where_to_point, skip)) return; |
| |
| if (SerializeBackReference(obj, how_to_code, where_to_point, skip)) return; |
| |
| if (startup_serializer_->SerializeUsingReadOnlyObjectCache( |
| &sink_, obj, how_to_code, where_to_point, skip)) { |
| return; |
| } |
| |
| if (ShouldBeInThePartialSnapshotCache(obj)) { |
| startup_serializer_->SerializeUsingPartialSnapshotCache( |
| &sink_, obj, how_to_code, where_to_point, skip); |
| return; |
| } |
| |
| // Pointers from the partial snapshot to the objects in the startup snapshot |
| // should go through the root array or through the partial snapshot cache. |
| // If this is not the case you may have to add something to the root array. |
| DCHECK(!startup_serializer_->ReferenceMapContains(obj)); |
| // All the internalized strings that the partial snapshot needs should be |
| // either in the root table or in the partial snapshot cache. |
| DCHECK(!obj->IsInternalizedString()); |
| // Function and object templates are not context specific. |
| DCHECK(!obj->IsTemplateInfo()); |
| // We should not end up at another native context. |
| DCHECK_IMPLIES(obj != context_, !obj->IsNativeContext()); |
| |
| FlushSkip(skip); |
| |
| // Clear literal boilerplates and feedback. |
| if (obj->IsFeedbackVector()) FeedbackVector::cast(obj)->ClearSlots(isolate()); |
| |
| if (SerializeJSObjectWithEmbedderFields(obj, how_to_code, where_to_point)) { |
| return; |
| } |
| |
| if (obj->IsJSFunction()) { |
| // Unconditionally reset the JSFunction to its SFI's code, since we can't |
| // serialize optimized code anyway. |
| JSFunction* closure = JSFunction::cast(obj); |
| if (closure->is_compiled()) closure->set_code(closure->shared()->GetCode()); |
| } |
| |
| CheckRehashability(obj); |
| |
| // Object has not yet been serialized. Serialize it here. |
| ObjectSerializer serializer(this, obj, &sink_, how_to_code, where_to_point); |
| serializer.Serialize(); |
| } |
| |
| bool PartialSerializer::ShouldBeInThePartialSnapshotCache(HeapObject* o) { |
| // Scripts should be referred only through shared function infos. We can't |
| // allow them to be part of the partial snapshot because they contain a |
| // unique ID, and deserializing several partial snapshots containing script |
| // would cause dupes. |
| DCHECK(!o->IsScript()); |
| return o->IsName() || o->IsSharedFunctionInfo() || o->IsHeapNumber() || |
| o->IsCode() || o->IsScopeInfo() || o->IsAccessorInfo() || |
| o->IsTemplateInfo() || |
| o->map() == ReadOnlyRoots(startup_serializer_->isolate()) |
| .fixed_cow_array_map(); |
| } |
| |
| namespace { |
| bool DataIsEmpty(const StartupData& data) { return data.raw_size == 0; } |
| } // anonymous namespace |
| |
| bool PartialSerializer::SerializeJSObjectWithEmbedderFields( |
| Object* obj, HowToCode how_to_code, WhereToPoint where_to_point) { |
| if (!obj->IsJSObject()) return false; |
| JSObject* js_obj = JSObject::cast(obj); |
| int embedder_fields_count = js_obj->GetEmbedderFieldCount(); |
| if (embedder_fields_count == 0) return false; |
| CHECK_GT(embedder_fields_count, 0); |
| DCHECK_NOT_NULL(serialize_embedder_fields_.callback); |
| DCHECK(!js_obj->NeedsRehashing()); |
| |
| DisallowHeapAllocation no_gc; |
| DisallowJavascriptExecution no_js(isolate()); |
| DisallowCompilation no_compile(isolate()); |
| |
| HandleScope scope(isolate()); |
| Handle<JSObject> obj_handle(js_obj, isolate()); |
| v8::Local<v8::Object> api_obj = v8::Utils::ToLocal(obj_handle); |
| |
| std::vector<EmbedderDataSlot::RawData> original_embedder_values; |
| std::vector<StartupData> serialized_data; |
| |
| // 1) Iterate embedder fields. Hold onto the original value of the fields. |
| // Ignore references to heap objects since these are to be handled by the |
| // serializer. For aligned pointers, call the serialize callback. Hold |
| // onto the result. |
| for (int i = 0; i < embedder_fields_count; i++) { |
| EmbedderDataSlot embedder_data_slot(js_obj, i); |
| original_embedder_values.emplace_back(embedder_data_slot.load_raw(no_gc)); |
| Object* object = embedder_data_slot.load_tagged(); |
| if (object->IsHeapObject()) { |
| DCHECK(isolate()->heap()->Contains(HeapObject::cast(object))); |
| serialized_data.push_back({nullptr, 0}); |
| } else { |
| StartupData data = serialize_embedder_fields_.callback( |
| api_obj, i, serialize_embedder_fields_.data); |
| serialized_data.push_back(data); |
| } |
| } |
| |
| // 2) Embedder fields for which the embedder callback produced non-zero |
| // serialized data should be considered aligned pointers to objects owned |
| // by the embedder. Clear these memory addresses to avoid non-determism |
| // in the snapshot. This is done separately to step 1 to no not interleave |
| // with embedder callbacks. |
| for (int i = 0; i < embedder_fields_count; i++) { |
| if (!DataIsEmpty(serialized_data[i])) { |
| EmbedderDataSlot(js_obj, i).store_raw({kNullAddress}, no_gc); |
| } |
| } |
| |
| // 3) Serialize the object. References from embedder fields to heap objects or |
| // smis are serialized regularly. |
| ObjectSerializer(this, js_obj, &sink_, how_to_code, where_to_point) |
| .Serialize(); |
| |
| // 4) Obtain back reference for the serialized object. |
| SerializerReference reference = reference_map()->LookupReference(js_obj); |
| DCHECK(reference.is_back_reference()); |
| |
| // 5) Write data returned by the embedder callbacks into a separate sink, |
| // headed by the back reference. Restore the original embedder fields. |
| for (int i = 0; i < embedder_fields_count; i++) { |
| StartupData data = serialized_data[i]; |
| if (DataIsEmpty(data)) continue; |
| // Restore original values from cleared fields. |
| EmbedderDataSlot(js_obj, i).store_raw(original_embedder_values[i], no_gc); |
| embedder_fields_sink_.Put(kNewObject + reference.space(), |
| "embedder field holder"); |
| embedder_fields_sink_.PutInt(reference.chunk_index(), "BackRefChunkIndex"); |
| embedder_fields_sink_.PutInt(reference.chunk_offset(), |
| "BackRefChunkOffset"); |
| embedder_fields_sink_.PutInt(i, "embedder field index"); |
| embedder_fields_sink_.PutInt(data.raw_size, "embedder fields data size"); |
| embedder_fields_sink_.PutRaw(reinterpret_cast<const byte*>(data.data), |
| data.raw_size, "embedder fields data"); |
| delete[] data.data; |
| } |
| |
| // 6) The content of the separate sink is appended eventually to the default |
| // sink. The ensures that during deserialization, we call the deserializer |
| // callback at the end, and can guarantee that the deserialized objects are |
| // in a consistent state. See PartialSerializer::Serialize. |
| return true; |
| } |
| |
| void PartialSerializer::CheckRehashability(HeapObject* obj) { |
| if (!can_be_rehashed_) return; |
| if (!obj->NeedsRehashing()) return; |
| if (obj->CanBeRehashed()) return; |
| can_be_rehashed_ = false; |
| } |
| |
| } // namespace internal |
| } // namespace v8 |