// 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/api-inl.h" #include "src/execution/microtask-queue.h" #include "src/heap/combined-heap.h" #include "src/numbers/math-random.h" #include "src/objects/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( reinterpret_cast<void*>(context_.global_proxy().ptr())); // 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_); #ifdef DEBUG MicrotaskQueue* microtask_queue = context_.native_context().microtask_queue(); DCHECK_EQ(0, microtask_queue->size()); DCHECK(!microtask_queue->HasMicrotasksSuppressions()); DCHECK_EQ(0, microtask_queue->GetMicrotasksScopeDepth()); DCHECK(microtask_queue->DebugMicrotasksScopeDepthIsZero()); #endif context_.native_context().set_microtask_queue(nullptr); VisitRootPointer(Root::kPartialSnapshotCache, nullptr, FullObjectSlot(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) { DCHECK(!ObjectIsBytecodeHandler(obj)); // Only referenced in dispatch table. if (SerializeHotObject(obj)) return; if (SerializeRoot(obj)) return; if (SerializeBackReference(obj)) return; if (startup_serializer_->SerializeUsingReadOnlyObjectCache(&sink_, obj)) { return; } if (ShouldBeInThePartialSnapshotCache(obj)) { startup_serializer_->SerializeUsingPartialSnapshotCache(&sink_, obj); 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()); // Clear literal boilerplates and feedback. if (obj.IsFeedbackVector()) FeedbackVector::cast(obj).ClearSlots(isolate()); // Clear InterruptBudget when serializing FeedbackCell. if (obj.IsFeedbackCell()) { FeedbackCell::cast(obj).set_interrupt_budget( FeedbackCell::GetInitialInterruptBudget()); } if (SerializeJSObjectWithEmbedderFields(obj)) { 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); closure.ResetIfBytecodeFlushed(); 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_); 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.IsClassPositions() || 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) { 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(!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(IsValidHeapObject(isolate()->heap(), HeapObject::cast(object))); serialized_data.push_back({nullptr, 0}); } else { // If no serializer is provided and the field was empty, we serialize it // by default to nullptr. if (serialize_embedder_fields_.callback == nullptr && object.ptr() == 0) { serialized_data.push_back({nullptr, 0}); } else { DCHECK_NOT_NULL(serialize_embedder_fields_.callback); 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_).Serialize(); // 4) Obtain back reference for the serialized object. SerializerReference reference = reference_map()->LookupReference(reinterpret_cast<void*>(js_obj.ptr())); 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 + static_cast<int>(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