// Copyright 2006-2008 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. // The common functionality when building with or without snapshots. #include "src/snapshot/snapshot.h" #include "src/base/platform/platform.h" #include "src/common/assert-scope.h" #include "src/execution/isolate-inl.h" #include "src/heap/safepoint.h" #include "src/init/bootstrapper.h" #include "src/logging/runtime-call-stats-scope.h" #include "src/objects/code-kind.h" #include "src/objects/js-regexp-inl.h" #include "src/snapshot/context-deserializer.h" #include "src/snapshot/context-serializer.h" #include "src/snapshot/read-only-deserializer.h" #include "src/snapshot/read-only-serializer.h" #include "src/snapshot/shared-heap-deserializer.h" #include "src/snapshot/shared-heap-serializer.h" #include "src/snapshot/snapshot-utils.h" #include "src/snapshot/startup-deserializer.h" #include "src/snapshot/startup-serializer.h" #include "src/utils/memcopy.h" #include "src/utils/version.h" #ifdef V8_SNAPSHOT_COMPRESSION #include "src/snapshot/snapshot-compression.h" #endif namespace v8 { namespace internal { namespace { class SnapshotImpl : public AllStatic { public: static v8::StartupData CreateSnapshotBlob( const SnapshotData* startup_snapshot_in, const SnapshotData* read_only_snapshot_in, const SnapshotData* shared_heap_snapshot_in, const std::vector<SnapshotData*>& context_snapshots_in, bool can_be_rehashed); static uint32_t ExtractNumContexts(const v8::StartupData* data); static uint32_t ExtractContextOffset(const v8::StartupData* data, uint32_t index); static base::Vector<const byte> ExtractStartupData( const v8::StartupData* data); static base::Vector<const byte> ExtractReadOnlyData( const v8::StartupData* data); static base::Vector<const byte> ExtractSharedHeapData( const v8::StartupData* data); static base::Vector<const byte> ExtractContextData( const v8::StartupData* data, uint32_t index); static uint32_t GetHeaderValue(const v8::StartupData* data, uint32_t offset) { return base::ReadLittleEndianValue<uint32_t>( reinterpret_cast<Address>(data->data) + offset); } static void SetHeaderValue(char* data, uint32_t offset, uint32_t value) { base::WriteLittleEndianValue(reinterpret_cast<Address>(data) + offset, value); } static void CheckVersion(const v8::StartupData* data); // Snapshot blob layout: // [0] number of contexts N // [1] rehashability // [2] checksum // [3] (64 bytes) version string // [4] offset to readonly // [5] offset to shared heap // [6] offset to context 0 // [7] offset to context 1 // ... // ... offset to context N - 1 // ... startup snapshot data // ... read-only snapshot data // ... shared heap snapshot data // ... context 0 snapshot data // ... context 1 snapshot data static const uint32_t kNumberOfContextsOffset = 0; // TODO(yangguo): generalize rehashing, and remove this flag. static const uint32_t kRehashabilityOffset = kNumberOfContextsOffset + kUInt32Size; static const uint32_t kChecksumOffset = kRehashabilityOffset + kUInt32Size; static const uint32_t kVersionStringOffset = kChecksumOffset + kUInt32Size; static const uint32_t kVersionStringLength = 64; static const uint32_t kReadOnlyOffsetOffset = kVersionStringOffset + kVersionStringLength; static const uint32_t kSharedHeapOffsetOffset = kReadOnlyOffsetOffset + kUInt32Size; static const uint32_t kFirstContextOffsetOffset = kSharedHeapOffsetOffset + kUInt32Size; static base::Vector<const byte> ChecksummedContent( const v8::StartupData* data) { static_assert(kVersionStringOffset == kChecksumOffset + kUInt32Size); const uint32_t kChecksumStart = kVersionStringOffset; return base::Vector<const byte>( reinterpret_cast<const byte*>(data->data + kChecksumStart), data->raw_size - kChecksumStart); } static uint32_t StartupSnapshotOffset(int num_contexts) { return POINTER_SIZE_ALIGN(kFirstContextOffsetOffset + num_contexts * kInt32Size); } static uint32_t ContextSnapshotOffsetOffset(int index) { return kFirstContextOffsetOffset + index * kInt32Size; } }; } // namespace SnapshotData MaybeDecompress(Isolate* isolate, const base::Vector<const byte>& snapshot_data) { #ifdef V8_SNAPSHOT_COMPRESSION TRACE_EVENT0("v8", "V8.SnapshotDecompress"); RCS_SCOPE(isolate, RuntimeCallCounterId::kSnapshotDecompress); return SnapshotCompression::Decompress(snapshot_data); #else return SnapshotData(snapshot_data); #endif } #ifdef DEBUG bool Snapshot::SnapshotIsValid(const v8::StartupData* snapshot_blob) { return SnapshotImpl::ExtractNumContexts(snapshot_blob) > 0; } #endif // DEBUG bool Snapshot::HasContextSnapshot(Isolate* isolate, size_t index) { // Do not use snapshots if the isolate is used to create snapshots. const v8::StartupData* blob = isolate->snapshot_blob(); if (blob == nullptr) return false; if (blob->data == nullptr) return false; size_t num_contexts = static_cast<size_t>(SnapshotImpl::ExtractNumContexts(blob)); return index < num_contexts; } bool Snapshot::VersionIsValid(const v8::StartupData* data) { char version[SnapshotImpl::kVersionStringLength]; memset(version, 0, SnapshotImpl::kVersionStringLength); CHECK_LT( SnapshotImpl::kVersionStringOffset + SnapshotImpl::kVersionStringLength, static_cast<uint32_t>(data->raw_size)); Version::GetString( base::Vector<char>(version, SnapshotImpl::kVersionStringLength)); return strncmp(version, data->data + SnapshotImpl::kVersionStringOffset, SnapshotImpl::kVersionStringLength) == 0; } bool Snapshot::Initialize(Isolate* isolate) { if (!isolate->snapshot_available()) return false; TRACE_EVENT0("v8", "V8.DeserializeIsolate"); RCS_SCOPE(isolate, RuntimeCallCounterId::kDeserializeIsolate); base::ElapsedTimer timer; if (FLAG_profile_deserialization) timer.Start(); const v8::StartupData* blob = isolate->snapshot_blob(); SnapshotImpl::CheckVersion(blob); if (Snapshot::ShouldVerifyChecksum(blob)) { CHECK(VerifyChecksum(blob)); } base::Vector<const byte> startup_data = SnapshotImpl::ExtractStartupData(blob); base::Vector<const byte> read_only_data = SnapshotImpl::ExtractReadOnlyData(blob); base::Vector<const byte> shared_heap_data = SnapshotImpl::ExtractSharedHeapData(blob); SnapshotData startup_snapshot_data(MaybeDecompress(isolate, startup_data)); SnapshotData read_only_snapshot_data( MaybeDecompress(isolate, read_only_data)); SnapshotData shared_heap_snapshot_data( MaybeDecompress(isolate, shared_heap_data)); bool success = isolate->InitWithSnapshot( &startup_snapshot_data, &read_only_snapshot_data, &shared_heap_snapshot_data, ExtractRehashability(blob)); if (FLAG_profile_deserialization) { double ms = timer.Elapsed().InMillisecondsF(); int bytes = startup_data.length(); PrintF("[Deserializing isolate (%d bytes) took %0.3f ms]\n", bytes, ms); } return success; } MaybeHandle<Context> Snapshot::NewContextFromSnapshot( Isolate* isolate, Handle<JSGlobalProxy> global_proxy, size_t context_index, v8::DeserializeEmbedderFieldsCallback embedder_fields_deserializer) { if (!isolate->snapshot_available()) return Handle<Context>(); TRACE_EVENT0("v8", "V8.DeserializeContext"); RCS_SCOPE(isolate, RuntimeCallCounterId::kDeserializeContext); base::ElapsedTimer timer; if (FLAG_profile_deserialization) timer.Start(); const v8::StartupData* blob = isolate->snapshot_blob(); bool can_rehash = ExtractRehashability(blob); base::Vector<const byte> context_data = SnapshotImpl::ExtractContextData( blob, static_cast<uint32_t>(context_index)); SnapshotData snapshot_data(MaybeDecompress(isolate, context_data)); MaybeHandle<Context> maybe_result = ContextDeserializer::DeserializeContext( isolate, &snapshot_data, can_rehash, global_proxy, embedder_fields_deserializer); Handle<Context> result; if (!maybe_result.ToHandle(&result)) return MaybeHandle<Context>(); if (FLAG_profile_deserialization) { double ms = timer.Elapsed().InMillisecondsF(); int bytes = context_data.length(); PrintF("[Deserializing context #%zu (%d bytes) took %0.3f ms]\n", context_index, bytes, ms); } return result; } // static void Snapshot::ClearReconstructableDataForSerialization( Isolate* isolate, bool clear_recompilable_data) { // Clear SFIs and JSRegExps. PtrComprCageBase cage_base(isolate); if (clear_recompilable_data) { HandleScope scope(isolate); std::vector<i::Handle<i::SharedFunctionInfo>> sfis_to_clear; { i::HeapObjectIterator it(isolate->heap()); for (i::HeapObject o = it.Next(); !o.is_null(); o = it.Next()) { if (o.IsSharedFunctionInfo(cage_base)) { i::SharedFunctionInfo shared = i::SharedFunctionInfo::cast(o); if (shared.script(cage_base).IsScript(cage_base) && Script::cast(shared.script(cage_base)).type() == Script::TYPE_EXTENSION) { continue; // Don't clear extensions, they cannot be recompiled. } if (shared.CanDiscardCompiled()) { sfis_to_clear.emplace_back(shared, isolate); } } else if (o.IsJSRegExp(cage_base)) { i::JSRegExp regexp = i::JSRegExp::cast(o); if (regexp.HasCompiledCode()) { regexp.DiscardCompiledCodeForSerialization(); } } } } // Must happen after heap iteration since SFI::DiscardCompiled may allocate. for (i::Handle<i::SharedFunctionInfo> shared : sfis_to_clear) { if (shared->CanDiscardCompiled()) { i::SharedFunctionInfo::DiscardCompiled(isolate, shared); } } } // Clear JSFunctions. i::HeapObjectIterator it(isolate->heap()); for (i::HeapObject o = it.Next(); !o.is_null(); o = it.Next()) { if (!o.IsJSFunction(cage_base)) continue; i::JSFunction fun = i::JSFunction::cast(o); fun.CompleteInobjectSlackTrackingIfActive(); i::SharedFunctionInfo shared = fun.shared(); if (shared.script(cage_base).IsScript(cage_base) && Script::cast(shared.script(cage_base)).type() == Script::TYPE_EXTENSION) { continue; // Don't clear extensions, they cannot be recompiled. } // Also, clear out feedback vectors and recompilable code. if (fun.CanDiscardCompiled()) { fun.set_code(*BUILTIN_CODE(isolate, CompileLazy)); } if (!fun.raw_feedback_cell(cage_base).value(cage_base).IsUndefined()) { fun.raw_feedback_cell(cage_base).set_value( i::ReadOnlyRoots(isolate).undefined_value()); } #ifdef DEBUG if (clear_recompilable_data) { #if V8_ENABLE_WEBASSEMBLY DCHECK(fun.shared().HasWasmExportedFunctionData() || fun.shared().HasBuiltinId() || fun.shared().IsApiFunction() || fun.shared().HasUncompiledDataWithoutPreparseData()); #else DCHECK(fun.shared().HasBuiltinId() || fun.shared().IsApiFunction() || fun.shared().HasUncompiledDataWithoutPreparseData()); #endif // V8_ENABLE_WEBASSEMBLY } #endif // DEBUG } } // static void Snapshot::SerializeDeserializeAndVerifyForTesting( Isolate* isolate, Handle<Context> default_context) { StartupData serialized_data; std::unique_ptr<const char[]> auto_delete_serialized_data; isolate->heap()->CollectAllAvailableGarbage( i::GarbageCollectionReason::kSnapshotCreator); // Test serialization. { GlobalSafepointScope global_safepoint(isolate); DisallowGarbageCollection no_gc; Snapshot::SerializerFlags flags( Snapshot::kAllowUnknownExternalReferencesForTesting | Snapshot::kAllowActiveIsolateForTesting | ((isolate->shared_isolate() || ReadOnlyHeap::IsReadOnlySpaceShared()) ? Snapshot::kReconstructReadOnlyAndSharedObjectCachesForTesting : 0)); serialized_data = Snapshot::Create(isolate, *default_context, global_safepoint, no_gc, flags); auto_delete_serialized_data.reset(serialized_data.data); } // Test deserialization. Isolate* new_isolate = Isolate::New(); { // Set serializer_enabled() to not install extensions and experimental // natives on the new isolate. // TODO(v8:10416): This should be a separate setting on the isolate. new_isolate->enable_serializer(); new_isolate->Enter(); new_isolate->set_snapshot_blob(&serialized_data); new_isolate->set_array_buffer_allocator( v8::ArrayBuffer::Allocator::NewDefaultAllocator()); if (Isolate* shared_isolate = isolate->shared_isolate()) { new_isolate->set_shared_isolate(shared_isolate); } CHECK(Snapshot::Initialize(new_isolate)); HandleScope scope(new_isolate); Handle<Context> new_native_context = new_isolate->bootstrapper()->CreateEnvironmentForTesting(); CHECK(new_native_context->IsNativeContext()); #ifdef VERIFY_HEAP if (FLAG_verify_heap) new_isolate->heap()->Verify(); #endif // VERIFY_HEAP } new_isolate->Exit(); Isolate::Delete(new_isolate); } // static constexpr Snapshot::SerializerFlags Snapshot::kDefaultSerializerFlags; // static v8::StartupData Snapshot::Create( Isolate* isolate, std::vector<Context>* contexts, const std::vector<SerializeInternalFieldsCallback>& embedder_fields_serializers, const GlobalSafepointScope& global_safepoint, const DisallowGarbageCollection& no_gc, SerializerFlags flags) { TRACE_EVENT0("v8", "V8.SnapshotCreate"); DCHECK_EQ(contexts->size(), embedder_fields_serializers.size()); DCHECK_GT(contexts->size(), 0); HandleScope scope(isolate); // The GlobalSafepointScope ensures we are in a safepoint scope so that the // string table is safe to iterate. Unlike mksnapshot, embedders may have // background threads running. ReadOnlySerializer read_only_serializer(isolate, flags); read_only_serializer.SerializeReadOnlyRoots(); SharedHeapSerializer shared_heap_serializer(isolate, flags, &read_only_serializer); StartupSerializer startup_serializer(isolate, flags, &read_only_serializer, &shared_heap_serializer); startup_serializer.SerializeStrongReferences(no_gc); // Serialize each context with a new serializer. const int num_contexts = static_cast<int>(contexts->size()); std::vector<SnapshotData*> context_snapshots; context_snapshots.reserve(num_contexts); // TODO(v8:6593): generalize rehashing, and remove this flag. bool can_be_rehashed = true; std::vector<int> context_allocation_sizes; for (int i = 0; i < num_contexts; i++) { ContextSerializer context_serializer(isolate, flags, &startup_serializer, embedder_fields_serializers[i]); context_serializer.Serialize(&contexts->at(i), no_gc); can_be_rehashed = can_be_rehashed && context_serializer.can_be_rehashed(); context_snapshots.push_back(new SnapshotData(&context_serializer)); if (FLAG_serialization_statistics) { context_allocation_sizes.push_back( context_serializer.TotalAllocationSize()); } } startup_serializer.SerializeWeakReferencesAndDeferred(); can_be_rehashed = can_be_rehashed && startup_serializer.can_be_rehashed(); startup_serializer.CheckNoDirtyFinalizationRegistries(); shared_heap_serializer.FinalizeSerialization(); can_be_rehashed = can_be_rehashed && shared_heap_serializer.can_be_rehashed(); read_only_serializer.FinalizeSerialization(); can_be_rehashed = can_be_rehashed && read_only_serializer.can_be_rehashed(); if (FLAG_serialization_statistics) { // These prints should match the regexp in test/memory/Memory.json DCHECK_NE(read_only_serializer.TotalAllocationSize(), 0); DCHECK_NE(shared_heap_serializer.TotalAllocationSize(), 0); DCHECK_NE(startup_serializer.TotalAllocationSize(), 0); PrintF("Deserialization will allocate:\n"); PrintF("%10d bytes per isolate\n", read_only_serializer.TotalAllocationSize() + startup_serializer.TotalAllocationSize()); for (int i = 0; i < num_contexts; i++) { DCHECK_NE(context_allocation_sizes[i], 0); PrintF("%10d bytes per context #%d\n", context_allocation_sizes[i], i); } PrintF("\n"); } SnapshotData read_only_snapshot(&read_only_serializer); SnapshotData shared_heap_snapshot(&shared_heap_serializer); SnapshotData startup_snapshot(&startup_serializer); v8::StartupData result = SnapshotImpl::CreateSnapshotBlob( &startup_snapshot, &read_only_snapshot, &shared_heap_snapshot, context_snapshots, can_be_rehashed); for (const SnapshotData* ptr : context_snapshots) delete ptr; CHECK(Snapshot::VerifyChecksum(&result)); return result; } // static v8::StartupData Snapshot::Create(Isolate* isolate, Context default_context, const GlobalSafepointScope& global_safepoint, const DisallowGarbageCollection& no_gc, SerializerFlags flags) { std::vector<Context> contexts{default_context}; std::vector<SerializeInternalFieldsCallback> callbacks{{}}; return Snapshot::Create(isolate, &contexts, callbacks, global_safepoint, no_gc, flags); } v8::StartupData SnapshotImpl::CreateSnapshotBlob( const SnapshotData* startup_snapshot_in, const SnapshotData* read_only_snapshot_in, const SnapshotData* shared_heap_snapshot_in, const std::vector<SnapshotData*>& context_snapshots_in, bool can_be_rehashed) { TRACE_EVENT0("v8", "V8.SnapshotCompress"); // Have these separate from snapshot_in for compression, since we need to // access the compressed data as well as the uncompressed reservations. const SnapshotData* startup_snapshot; const SnapshotData* read_only_snapshot; const SnapshotData* shared_heap_snapshot; const std::vector<SnapshotData*>* context_snapshots; #ifdef V8_SNAPSHOT_COMPRESSION SnapshotData startup_compressed( SnapshotCompression::Compress(startup_snapshot_in)); SnapshotData read_only_compressed( SnapshotCompression::Compress(read_only_snapshot_in)); SnapshotData shared_heap_compressed( SnapshotCompression::Compress(shared_heap_snapshot_in)); startup_snapshot = &startup_compressed; read_only_snapshot = &read_only_compressed; shared_heap_snapshot = &shared_heap_compressed; std::vector<SnapshotData> context_snapshots_compressed; context_snapshots_compressed.reserve(context_snapshots_in.size()); std::vector<SnapshotData*> context_snapshots_compressed_ptrs; for (unsigned int i = 0; i < context_snapshots_in.size(); ++i) { context_snapshots_compressed.push_back( SnapshotCompression::Compress(context_snapshots_in[i])); context_snapshots_compressed_ptrs.push_back( &context_snapshots_compressed[i]); } context_snapshots = &context_snapshots_compressed_ptrs; #else startup_snapshot = startup_snapshot_in; read_only_snapshot = read_only_snapshot_in; shared_heap_snapshot = shared_heap_snapshot_in; context_snapshots = &context_snapshots_in; #endif uint32_t num_contexts = static_cast<uint32_t>(context_snapshots->size()); uint32_t startup_snapshot_offset = SnapshotImpl::StartupSnapshotOffset(num_contexts); uint32_t total_length = startup_snapshot_offset; total_length += static_cast<uint32_t>(startup_snapshot->RawData().length()); total_length += static_cast<uint32_t>(read_only_snapshot->RawData().length()); total_length += static_cast<uint32_t>(shared_heap_snapshot->RawData().length()); for (const auto context_snapshot : *context_snapshots) { total_length += static_cast<uint32_t>(context_snapshot->RawData().length()); } char* data = new char[total_length]; // Zero out pre-payload data. Part of that is only used for padding. memset(data, 0, SnapshotImpl::StartupSnapshotOffset(num_contexts)); SnapshotImpl::SetHeaderValue(data, SnapshotImpl::kNumberOfContextsOffset, num_contexts); SnapshotImpl::SetHeaderValue(data, SnapshotImpl::kRehashabilityOffset, can_be_rehashed ? 1 : 0); // Write version string into snapshot data. memset(data + SnapshotImpl::kVersionStringOffset, 0, SnapshotImpl::kVersionStringLength); Version::GetString( base::Vector<char>(data + SnapshotImpl::kVersionStringOffset, SnapshotImpl::kVersionStringLength)); // Startup snapshot (isolate-specific data). uint32_t payload_offset = startup_snapshot_offset; uint32_t payload_length = static_cast<uint32_t>(startup_snapshot->RawData().length()); CopyBytes(data + payload_offset, reinterpret_cast<const char*>(startup_snapshot->RawData().begin()), payload_length); if (FLAG_serialization_statistics) { PrintF("Snapshot blob consists of:\n%10d bytes for startup\n", payload_length); } payload_offset += payload_length; // Read-only. SnapshotImpl::SetHeaderValue(data, SnapshotImpl::kReadOnlyOffsetOffset, payload_offset); payload_length = read_only_snapshot->RawData().length(); CopyBytes( data + payload_offset, reinterpret_cast<const char*>(read_only_snapshot->RawData().begin()), payload_length); if (FLAG_serialization_statistics) { PrintF("%10d bytes for read-only\n", payload_length); } payload_offset += payload_length; // Shared heap. SnapshotImpl::SetHeaderValue(data, SnapshotImpl::kSharedHeapOffsetOffset, payload_offset); payload_length = shared_heap_snapshot->RawData().length(); CopyBytes( data + payload_offset, reinterpret_cast<const char*>(shared_heap_snapshot->RawData().begin()), payload_length); if (FLAG_serialization_statistics) { PrintF("%10d bytes for shared heap\n", payload_length); } payload_offset += payload_length; // Context snapshots (context-specific data). for (uint32_t i = 0; i < num_contexts; i++) { SnapshotImpl::SetHeaderValue( data, SnapshotImpl::ContextSnapshotOffsetOffset(i), payload_offset); SnapshotData* context_snapshot = (*context_snapshots)[i]; payload_length = context_snapshot->RawData().length(); CopyBytes( data + payload_offset, reinterpret_cast<const char*>(context_snapshot->RawData().begin()), payload_length); if (FLAG_serialization_statistics) { PrintF("%10d bytes for context #%d\n", payload_length, i); } payload_offset += payload_length; } if (FLAG_serialization_statistics) PrintF("\n"); DCHECK_EQ(total_length, payload_offset); v8::StartupData result = {data, static_cast<int>(total_length)}; SnapshotImpl::SetHeaderValue( data, SnapshotImpl::kChecksumOffset, Checksum(SnapshotImpl::ChecksummedContent(&result))); return result; } uint32_t SnapshotImpl::ExtractNumContexts(const v8::StartupData* data) { CHECK_LT(kNumberOfContextsOffset, data->raw_size); uint32_t num_contexts = GetHeaderValue(data, kNumberOfContextsOffset); return num_contexts; } uint32_t Snapshot::GetExpectedChecksum(const v8::StartupData* data) { return SnapshotImpl::GetHeaderValue(data, SnapshotImpl::kChecksumOffset); } uint32_t Snapshot::CalculateChecksum(const v8::StartupData* data) { return Checksum(SnapshotImpl::ChecksummedContent(data)); } bool Snapshot::VerifyChecksum(const v8::StartupData* data) { base::ElapsedTimer timer; if (FLAG_profile_deserialization) timer.Start(); uint32_t expected = GetExpectedChecksum(data); uint32_t result = CalculateChecksum(data); if (FLAG_profile_deserialization) { double ms = timer.Elapsed().InMillisecondsF(); PrintF("[Verifying snapshot checksum took %0.3f ms]\n", ms); } return result == expected; } uint32_t SnapshotImpl::ExtractContextOffset(const v8::StartupData* data, uint32_t index) { // Extract the offset of the context at a given index from the StartupData, // and check that it is within bounds. uint32_t context_offset = GetHeaderValue(data, ContextSnapshotOffsetOffset(index)); CHECK_LT(context_offset, static_cast<uint32_t>(data->raw_size)); return context_offset; } bool Snapshot::ExtractRehashability(const v8::StartupData* data) { CHECK_LT(SnapshotImpl::kRehashabilityOffset, static_cast<uint32_t>(data->raw_size)); uint32_t rehashability = SnapshotImpl::GetHeaderValue(data, SnapshotImpl::kRehashabilityOffset); CHECK_IMPLIES(rehashability != 0, rehashability == 1); return rehashability != 0; } namespace { base::Vector<const byte> ExtractData(const v8::StartupData* snapshot, uint32_t start_offset, uint32_t end_offset) { CHECK_LT(start_offset, end_offset); CHECK_LT(end_offset, snapshot->raw_size); uint32_t length = end_offset - start_offset; const byte* data = reinterpret_cast<const byte*>(snapshot->data + start_offset); return base::Vector<const byte>(data, length); } } // namespace base::Vector<const byte> SnapshotImpl::ExtractStartupData( const v8::StartupData* data) { DCHECK(Snapshot::SnapshotIsValid(data)); uint32_t num_contexts = ExtractNumContexts(data); return ExtractData(data, StartupSnapshotOffset(num_contexts), GetHeaderValue(data, kReadOnlyOffsetOffset)); } base::Vector<const byte> SnapshotImpl::ExtractReadOnlyData( const v8::StartupData* data) { DCHECK(Snapshot::SnapshotIsValid(data)); return ExtractData(data, GetHeaderValue(data, kReadOnlyOffsetOffset), GetHeaderValue(data, kSharedHeapOffsetOffset)); } base::Vector<const byte> SnapshotImpl::ExtractSharedHeapData( const v8::StartupData* data) { DCHECK(Snapshot::SnapshotIsValid(data)); return ExtractData(data, GetHeaderValue(data, kSharedHeapOffsetOffset), GetHeaderValue(data, ContextSnapshotOffsetOffset(0))); } base::Vector<const byte> SnapshotImpl::ExtractContextData( const v8::StartupData* data, uint32_t index) { uint32_t num_contexts = ExtractNumContexts(data); CHECK_LT(index, num_contexts); uint32_t context_offset = ExtractContextOffset(data, index); uint32_t next_context_offset; if (index == num_contexts - 1) { next_context_offset = data->raw_size; } else { next_context_offset = ExtractContextOffset(data, index + 1); CHECK_LT(next_context_offset, data->raw_size); } const byte* context_data = reinterpret_cast<const byte*>(data->data + context_offset); uint32_t context_length = next_context_offset - context_offset; return base::Vector<const byte>(context_data, context_length); } void SnapshotImpl::CheckVersion(const v8::StartupData* data) { if (!Snapshot::VersionIsValid(data)) { char version[kVersionStringLength]; memset(version, 0, kVersionStringLength); CHECK_LT(kVersionStringOffset + kVersionStringLength, static_cast<uint32_t>(data->raw_size)); Version::GetString(base::Vector<char>(version, kVersionStringLength)); FATAL( "Version mismatch between V8 binary and snapshot.\n" "# V8 binary version: %.*s\n" "# Snapshot version: %.*s\n" "# The snapshot consists of %d bytes and contains %d context(s).", kVersionStringLength, version, kVersionStringLength, data->data + kVersionStringOffset, data->raw_size, ExtractNumContexts(data)); } } namespace { bool RunExtraCode(v8::Isolate* isolate, v8::Local<v8::Context> context, const char* utf8_source, const char* name) { v8::Context::Scope context_scope(context); v8::TryCatch try_catch(isolate); v8::Local<v8::String> source_string; if (!v8::String::NewFromUtf8(isolate, utf8_source).ToLocal(&source_string)) { return false; } v8::Local<v8::String> resource_name = v8::String::NewFromUtf8(isolate, name).ToLocalChecked(); v8::ScriptOrigin origin(isolate, resource_name); v8::ScriptCompiler::Source source(source_string, origin); v8::Local<v8::Script> script; if (!v8::ScriptCompiler::Compile(context, &source).ToLocal(&script)) return false; if (script->Run(context).IsEmpty()) return false; CHECK(!try_catch.HasCaught()); return true; } } // namespace v8::StartupData CreateSnapshotDataBlobInternal( v8::SnapshotCreator::FunctionCodeHandling function_code_handling, const char* embedded_source, v8::Isolate* isolate) { // If no isolate is passed in, create it (and a new context) from scratch. if (isolate == nullptr) isolate = v8::Isolate::Allocate(); // Optionally run a script to embed, and serialize to create a snapshot blob. v8::SnapshotCreator snapshot_creator(isolate); { v8::HandleScope scope(isolate); v8::Local<v8::Context> context = v8::Context::New(isolate); if (embedded_source != nullptr && !RunExtraCode(isolate, context, embedded_source, "<embedded>")) { return {}; } snapshot_creator.SetDefaultContext(context); } return snapshot_creator.CreateBlob(function_code_handling); } v8::StartupData WarmUpSnapshotDataBlobInternal( v8::StartupData cold_snapshot_blob, const char* warmup_source) { CHECK(cold_snapshot_blob.raw_size > 0 && cold_snapshot_blob.data != nullptr); CHECK_NOT_NULL(warmup_source); // Use following steps to create a warmed up snapshot blob from a cold one: // - Create a new isolate from the cold snapshot. // - Create a new context to run the warmup script. This will trigger // compilation of executed functions. // - Create a new context. This context will be unpolluted. // - Serialize the isolate and the second context into a new snapshot blob. v8::SnapshotCreator snapshot_creator(nullptr, &cold_snapshot_blob); v8::Isolate* isolate = snapshot_creator.GetIsolate(); { v8::HandleScope scope(isolate); v8::Local<v8::Context> context = v8::Context::New(isolate); if (!RunExtraCode(isolate, context, warmup_source, "<warm-up>")) { return {}; } } { v8::HandleScope handle_scope(isolate); isolate->ContextDisposedNotification(false); v8::Local<v8::Context> context = v8::Context::New(isolate); snapshot_creator.SetDefaultContext(context); } return snapshot_creator.CreateBlob( v8::SnapshotCreator::FunctionCodeHandling::kKeep); } } // namespace internal } // namespace v8