startup-serializer.cc

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// 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/startup-serializer.h"
 
#include "src/execution/v8threads.h"
#include "src/handles/global-handles-inl.h"
#include "src/heap/heap-inl.h"
#include "src/heap/read-only-heap.h"
#include "src/objects/contexts.h"
#include "src/objects/objects-inl.h"
#include "src/objects/slots.h"
#include "src/snapshot/read-only-serializer.h"
#include "src/snapshot/shared-heap-serializer.h"
 
namespace v8 {
namespace internal {
 
namespace {
 
// The isolate roots may not point at context-specific objects during
// serialization.
class V8_NODISCARD SanitizeIsolateScope final {
 public:
  SanitizeIsolateScope(Isolate* isolate, bool allow_active_isolate_for_testing,
                       const DisallowGarbageCollection& no_gc)
      : isolate_(isolate),
        feedback_vectors_for_profiling_tools_(
            isolate->heap()->feedback_vectors_for_profiling_tools()),
        detached_contexts_(isolate->heap()->detached_contexts()) {
#ifdef DEBUG
    if (!allow_active_isolate_for_testing) {
      // These should already be empty when creating a real snapshot.
      DCHECK_EQ(feedback_vectors_for_profiling_tools_,
                ReadOnlyRoots(isolate).undefined_value());
      DCHECK_EQ(detached_contexts_,
                ReadOnlyRoots(isolate).empty_weak_array_list());
    }
#endif
 
    isolate->SetFeedbackVectorsForProfilingTools(
        ReadOnlyRoots(isolate).undefined_value());
    isolate->heap()->SetDetachedContexts(
        ReadOnlyRoots(isolate).empty_weak_array_list());
  }
 
  ~SanitizeIsolateScope() {
    // Restore saved fields.
    isolate_->SetFeedbackVectorsForProfilingTools(
        feedback_vectors_for_profiling_tools_);
    isolate_->heap()->SetDetachedContexts(detached_contexts_);
  }
 
 private:
  Isolate* isolate_;
  const Tagged<Object> feedback_vectors_for_profiling_tools_;
  const Tagged<WeakArrayList> detached_contexts_;
};
 
}  // namespace
 
StartupSerializer::StartupSerializer(
    Isolate* isolate, Snapshot::SerializerFlags flags,
    SharedHeapSerializer* shared_heap_serializer)
    : RootsSerializer(isolate, flags, RootIndex::kFirstStrongRoot),
      shared_heap_serializer_(shared_heap_serializer),
      accessor_infos_(isolate->heap()),
      function_template_infos_(isolate->heap()) {
  InitializeCodeAddressMap();
 
  // This serializes any external reference which don't encode to their own
  // index. This is so that the deserializer can verify that any entries that
  // were deduplicated during serialization are also deduplicated in the
  // deserializing binary.
  ExternalReferenceTable* table = isolate->external_reference_table();
  for (uint32_t i = 0; i < ExternalReferenceTable::kSizeIsolateIndependent;
       ++i) {
    ExternalReferenceEncoder::Value encoded_reference =
        EncodeExternalReference(table->address(i));
    if (encoded_reference.index() != i) {
      sink_.PutUint30(i, "expected reference index");
      sink_.PutUint30(encoded_reference.index(), "actual reference index");
    }
  }
  sink_.PutUint30(ExternalReferenceTable::kSizeIsolateIndependent,
                  "end of deduplicated reference indices");
}
 
StartupSerializer::~StartupSerializer() {
  for (DirectHandle<AccessorInfo> info : accessor_infos_) {
    RestoreExternalReferenceRedirector(isolate(), *info);
  }
  for (DirectHandle<FunctionTemplateInfo> info : function_template_infos_) {
    RestoreExternalReferenceRedirector(isolate(), *info);
  }
  OutputStatistics("StartupSerializer");
}
 
void StartupSerializer::SerializeObjectImpl(Handle<HeapObject> obj,
                                            SlotType slot_type) {
  PtrComprCageBase cage_base(isolate());
#ifdef DEBUG
  if (IsJSFunction(*obj, cage_base)) {
    v8::base::OS::PrintError("Reference stack:\n");
    PrintStack(std::cerr);
    Print(*obj, std::cerr);
    FATAL(
        "JSFunction should be added through the context snapshot instead of "
        "the isolate snapshot");
  }
#endif  // DEBUG
  {
    DisallowGarbageCollection no_gc;
    Tagged<HeapObject> raw = *obj;
    DCHECK(!IsInstructionStream(raw));
    if (SerializeHotObject(raw)) return;
    if (IsRootAndHasBeenSerialized(raw) && SerializeRoot(raw)) return;
  }
 
  if (SerializeReadOnlyObjectReference(*obj, &sink_)) return;
  if (SerializeUsingSharedHeapObjectCache(&sink_, obj)) return;
  if (SerializeBackReference(*obj)) return;
 
  if (USE_SIMULATOR_BOOL && IsAccessorInfo(*obj, cage_base)) {
    // Wipe external reference redirects in the accessor info.
    auto info = Cast<AccessorInfo>(obj);
    info->remove_getter_redirection(isolate());
    accessor_infos_.Push(*info);
  } else if (USE_SIMULATOR_BOOL && IsFunctionTemplateInfo(*obj, cage_base)) {
    auto info = Cast<FunctionTemplateInfo>(obj);
    info->remove_callback_redirection(isolate());
    function_template_infos_.Push(*info);
  } else if (IsScript(*obj, cage_base) &&
             Cast<Script>(obj)->IsUserJavaScript()) {
    Cast<Script>(obj)->set_context_data(
        ReadOnlyRoots(isolate()).uninitialized_symbol());
  } else if (IsSharedFunctionInfo(*obj, cage_base)) {
    // Clear inferred name for native functions.
    auto shared = Cast<SharedFunctionInfo>(obj);
    if (!shared->IsSubjectToDebugging() && shared->HasUncompiledData()) {
      shared->uncompiled_data(isolate())->set_inferred_name(
          ReadOnlyRoots(isolate()).empty_string());
    }
  }
 
  CheckRehashability(*obj);
 
  // Object has not yet been serialized.  Serialize it here.
  DCHECK(!ReadOnlyHeap::Contains(*obj));
  ObjectSerializer object_serializer(this, obj, &sink_);
  object_serializer.Serialize(slot_type);
}
 
void StartupSerializer::SerializeWeakReferencesAndDeferred() {
  // This comes right after serialization of the context snapshot, where we
  // add entries to the startup object cache of the startup snapshot. Add
  // one entry with 'undefined' to terminate the startup object cache.
  Tagged<Object> undefined = ReadOnlyRoots(isolate()).undefined_value();
  VisitRootPointer(Root::kStartupObjectCache, nullptr,
                   FullObjectSlot(&undefined));
 
  isolate()->heap()->IterateWeakRoots(
      this, base::EnumSet<SkipRoot>{SkipRoot::kUnserializable});
  SerializeDeferredObjects();
  Pad();
}
 
void StartupSerializer::SerializeStrongReferences(
    const DisallowGarbageCollection& no_gc) {
  Isolate* isolate = this->isolate();
  // No active threads.
  CHECK_NULL(isolate->thread_manager()->FirstThreadStateInUse());
 
  SanitizeIsolateScope sanitize_isolate(
      isolate, allow_active_isolate_for_testing(), no_gc);
 
  // Visit smi roots and immortal immovables first to make sure they end up in
  // the first page.
  isolate->heap()->IterateSmiRoots(this);
  isolate->heap()->IterateRoots(
      this, base::EnumSet<SkipRoot>{SkipRoot::kUnserializable, SkipRoot::kWeak,
                                    SkipRoot::kTracedHandles});
}
 
SerializedHandleChecker::SerializedHandleChecker(
    Isolate* isolate, std::vector<Tagged<Context>>* contexts)
    : isolate_(isolate) {
  AddToSet(Cast<FixedArray>(isolate->heap()->serialized_objects()));
  for (auto const& context : *contexts) {
    AddToSet(Cast<FixedArray>(context->serialized_objects()));
  }
}
 
bool StartupSerializer::SerializeUsingSharedHeapObjectCache(
    SnapshotByteSink* sink, Handle<HeapObject> obj) {
  return shared_heap_serializer_->SerializeUsingSharedHeapObjectCache(sink,
                                                                      obj);
}
 
void StartupSerializer::SerializeUsingStartupObjectCache(
    SnapshotByteSink* sink, Handle<HeapObject> obj) {
  int cache_index = SerializeInObjectCache(obj);
  sink->Put(kStartupObjectCache, "StartupObjectCache");
  sink->PutUint30(cache_index, "startup_object_cache_index");
}
 
void StartupSerializer::CheckNoDirtyFinalizationRegistries() {
  Isolate* isolate = this->isolate();
  CHECK(IsUndefined(isolate->heap()->dirty_js_finalization_registries_list(),
                    isolate));
  CHECK(IsUndefined(
      isolate->heap()->dirty_js_finalization_registries_list_tail(), isolate));
}
 
void SerializedHandleChecker::AddToSet(Tagged<FixedArray> serialized) {
  int length = serialized->length();
  for (int i = 0; i < length; i++) serialized_.insert(serialized->get(i));
}
 
void SerializedHandleChecker::VisitRootPointers(Root root,
                                                const char* description,
                                                FullObjectSlot start,
                                                FullObjectSlot end) {
  for (FullObjectSlot p = start; p < end; ++p) {
    if (serialized_.find(*p) != serialized_.end()) continue;
    PrintF("%s handle not serialized: ",
           root == Root::kGlobalHandles ? "global" : "eternal");
    Print(*p);
    PrintF("\n");
    ok_ = false;
  }
}
 
bool SerializedHandleChecker::CheckGlobalAndEternalHandles() {
  isolate_->global_handles()->IterateAllRoots(this);
  isolate_->traced_handles()->Iterate(this);
  isolate_->eternal_handles()->IterateAllRoots(this);
  return ok_;
}
 
}  // namespace internal
}  // namespace v8