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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/serializer.h"
#include "src/codegen/assembler-inl.h"
#include "src/heap/heap-inl.h" // For Space::identity().
#include "src/heap/memory-chunk-inl.h"
#include "src/heap/read-only-heap.h"
#include "src/interpreter/interpreter.h"
#include "src/objects/code.h"
#include "src/objects/js-array-buffer-inl.h"
#include "src/objects/js-array-inl.h"
#include "src/objects/map.h"
#include "src/objects/slots-inl.h"
#include "src/objects/smi.h"
namespace v8 {
namespace internal {
Serializer::Serializer(Isolate* isolate, Snapshot::SerializerFlags flags)
: isolate_(isolate),
external_reference_encoder_(isolate),
root_index_map_(isolate),
flags_(flags),
allocator_(this) {
#ifdef OBJECT_PRINT
if (FLAG_serialization_statistics) {
for (int space = 0; space < kNumberOfSpaces; ++space) {
// Value-initialized to 0.
instance_type_count_[space] = std::make_unique<int[]>(kInstanceTypes);
instance_type_size_[space] = std::make_unique<size_t[]>(kInstanceTypes);
}
}
#endif // OBJECT_PRINT
}
#ifdef OBJECT_PRINT
void Serializer::CountInstanceType(Map map, int size, SnapshotSpace space) {
const int space_number = static_cast<int>(space);
int instance_type = map.instance_type();
instance_type_count_[space_number][instance_type]++;
instance_type_size_[space_number][instance_type] += size;
}
#endif // OBJECT_PRINT
void Serializer::OutputStatistics(const char* name) {
if (!FLAG_serialization_statistics) return;
PrintF("%s:\n", name);
allocator()->OutputStatistics();
#ifdef OBJECT_PRINT
PrintF(" Instance types (count and bytes):\n");
#define PRINT_INSTANCE_TYPE(Name) \
for (int space = 0; space < kNumberOfSpaces; ++space) { \
if (instance_type_count_[space][Name]) { \
PrintF("%10d %10zu %-10s %s\n", instance_type_count_[space][Name], \
instance_type_size_[space][Name], \
Heap::GetSpaceName(static_cast<AllocationSpace>(space)), #Name); \
} \
}
INSTANCE_TYPE_LIST(PRINT_INSTANCE_TYPE)
#undef PRINT_INSTANCE_TYPE
PrintF("\n");
#endif // OBJECT_PRINT
}
void Serializer::SerializeDeferredObjects() {
while (!deferred_objects_.empty()) {
HeapObject obj = deferred_objects_.back();
deferred_objects_.pop_back();
ObjectSerializer obj_serializer(this, obj, &sink_);
obj_serializer.SerializeDeferred();
}
sink_.Put(kSynchronize, "Finished with deferred objects");
}
bool Serializer::MustBeDeferred(HeapObject object) { return false; }
void Serializer::VisitRootPointers(Root root, const char* description,
FullObjectSlot start, FullObjectSlot end) {
for (FullObjectSlot current = start; current < end; ++current) {
SerializeRootObject(current);
}
}
void Serializer::SerializeRootObject(FullObjectSlot slot) {
Object o = *slot;
if (o.IsSmi()) {
PutSmiRoot(slot);
} else {
SerializeObject(HeapObject::cast(o));
}
}
#ifdef DEBUG
void Serializer::PrintStack() { PrintStack(std::cout); }
void Serializer::PrintStack(std::ostream& out) {
for (const auto o : stack_) {
o.Print(out);
out << "\n";
}
}
#endif // DEBUG
bool Serializer::SerializeRoot(HeapObject obj) {
RootIndex root_index;
// Derived serializers are responsible for determining if the root has
// actually been serialized before calling this.
if (root_index_map()->Lookup(obj, &root_index)) {
PutRoot(root_index, obj);
return true;
}
return false;
}
bool Serializer::SerializeHotObject(HeapObject obj) {
// Encode a reference to a hot object by its index in the working set.
int index = hot_objects_.Find(obj);
if (index == HotObjectsList::kNotFound) return false;
DCHECK(index >= 0 && index < kNumberOfHotObjects);
if (FLAG_trace_serializer) {
PrintF(" Encoding hot object %d:", index);
obj.ShortPrint();
PrintF("\n");
}
sink_.Put(kHotObject + index, "HotObject");
return true;
}
bool Serializer::SerializeBackReference(HeapObject obj) {
SerializerReference reference =
reference_map_.LookupReference(reinterpret_cast<void*>(obj.ptr()));
if (!reference.is_valid()) return false;
// Encode the location of an already deserialized object in order to write
// its location into a later object. We can encode the location as an
// offset fromthe start of the deserialized objects or as an offset
// backwards from thecurrent allocation pointer.
if (reference.is_attached_reference()) {
if (FLAG_trace_serializer) {
PrintF(" Encoding attached reference %d\n",
reference.attached_reference_index());
}
PutAttachedReference(reference);
} else {
DCHECK(reference.is_back_reference());
if (FLAG_trace_serializer) {
PrintF(" Encoding back reference to: ");
obj.ShortPrint();
PrintF("\n");
}
PutAlignmentPrefix(obj);
SnapshotSpace space = reference.space();
sink_.Put(kBackref + static_cast<int>(space), "BackRef");
PutBackReference(obj, reference);
}
return true;
}
bool Serializer::ObjectIsBytecodeHandler(HeapObject obj) const {
if (!obj.IsCode()) return false;
return (Code::cast(obj).kind() == Code::BYTECODE_HANDLER);
}
void Serializer::PutRoot(RootIndex root, HeapObject object) {
int root_index = static_cast<int>(root);
if (FLAG_trace_serializer) {
PrintF(" Encoding root %d:", root_index);
object.ShortPrint();
PrintF("\n");
}
// Assert that the first 32 root array items are a conscious choice. They are
// chosen so that the most common ones can be encoded more efficiently.
STATIC_ASSERT(static_cast<int>(RootIndex::kArgumentsMarker) ==
kNumberOfRootArrayConstants - 1);
// TODO(ulan): Check that it works with young large objects.
if (root_index < kNumberOfRootArrayConstants &&
!Heap::InYoungGeneration(object)) {
sink_.Put(kRootArrayConstants + root_index, "RootConstant");
} else {
sink_.Put(kRootArray, "RootSerialization");
sink_.PutInt(root_index, "root_index");
hot_objects_.Add(object);
}
}
void Serializer::PutSmiRoot(FullObjectSlot slot) {
// Serializing a smi root in compressed pointer builds will serialize the
// full object slot (of kSystemPointerSize) to avoid complications during
// deserialization (endianness or smi sequences).
STATIC_ASSERT(decltype(slot)::kSlotDataSize == sizeof(Address));
STATIC_ASSERT(decltype(slot)::kSlotDataSize == kSystemPointerSize);
static constexpr int bytes_to_output = decltype(slot)::kSlotDataSize;
static constexpr int size_in_tagged = bytes_to_output >> kTaggedSizeLog2;
sink_.PutSection(kFixedRawDataStart + size_in_tagged, "Smi");
Address raw_value = Smi::cast(*slot).ptr();
const byte* raw_value_as_bytes = reinterpret_cast<const byte*>(&raw_value);
for (size_t i = 0; i < bytes_to_output; i++) {
sink_.Put(raw_value_as_bytes[i], "Byte");
}
}
void Serializer::PutBackReference(HeapObject object,
SerializerReference reference) {
DCHECK(allocator()->BackReferenceIsAlreadyAllocated(reference));
switch (reference.space()) {
case SnapshotSpace::kMap:
sink_.PutInt(reference.map_index(), "BackRefMapIndex");
break;
case SnapshotSpace::kLargeObject:
sink_.PutInt(reference.large_object_index(), "BackRefLargeObjectIndex");
break;
default:
sink_.PutInt(reference.chunk_index(), "BackRefChunkIndex");
sink_.PutInt(reference.chunk_offset(), "BackRefChunkOffset");
break;
}
hot_objects_.Add(object);
}
void Serializer::PutAttachedReference(SerializerReference reference) {
DCHECK(reference.is_attached_reference());
sink_.Put(kAttachedReference, "AttachedRef");
sink_.PutInt(reference.attached_reference_index(), "AttachedRefIndex");
}
int Serializer::PutAlignmentPrefix(HeapObject object) {
AllocationAlignment alignment = HeapObject::RequiredAlignment(object.map());
if (alignment != kWordAligned) {
DCHECK(1 <= alignment && alignment <= 3);
byte prefix = (kAlignmentPrefix - 1) + alignment;
sink_.Put(prefix, "Alignment");
return Heap::GetMaximumFillToAlign(alignment);
}
return 0;
}
void Serializer::PutNextChunk(SnapshotSpace space) {
sink_.Put(kNextChunk, "NextChunk");
sink_.Put(static_cast<int>(space), "NextChunkSpace");
}
void Serializer::PutRepeat(int repeat_count) {
if (repeat_count <= kLastEncodableFixedRepeatCount) {
sink_.Put(EncodeFixedRepeat(repeat_count), "FixedRepeat");
} else {
sink_.Put(kVariableRepeat, "VariableRepeat");
sink_.PutInt(EncodeVariableRepeatCount(repeat_count), "repeat count");
}
}
void Serializer::Pad(int padding_offset) {
// The non-branching GetInt will read up to 3 bytes too far, so we need
// to pad the snapshot to make sure we don't read over the end.
for (unsigned i = 0; i < sizeof(int32_t) - 1; i++) {
sink_.Put(kNop, "Padding");
}
// Pad up to pointer size for checksum.
while (!IsAligned(sink_.Position() + padding_offset, kPointerAlignment)) {
sink_.Put(kNop, "Padding");
}
}
void Serializer::InitializeCodeAddressMap() {
isolate_->InitializeLoggingAndCounters();
code_address_map_ = std::make_unique<CodeAddressMap>(isolate_);
}
Code Serializer::CopyCode(Code code) {
code_buffer_.clear(); // Clear buffer without deleting backing store.
int size = code.CodeSize();
code_buffer_.insert(code_buffer_.end(),
reinterpret_cast<byte*>(code.address()),
reinterpret_cast<byte*>(code.address() + size));
// When pointer compression is enabled the checked cast will try to
// decompress map field of off-heap Code object.
return Code::unchecked_cast(HeapObject::FromAddress(
reinterpret_cast<Address>(&code_buffer_.front())));
}
void Serializer::ObjectSerializer::SerializePrologue(SnapshotSpace space,
int size, Map map) {
if (serializer_->code_address_map_) {
const char* code_name =
serializer_->code_address_map_->Lookup(object_.address());
LOG(serializer_->isolate_,
CodeNameEvent(object_.address(), sink_->Position(), code_name));
}
const int space_number = static_cast<int>(space);
SerializerReference back_reference;
if (space == SnapshotSpace::kLargeObject) {
sink_->Put(kNewObject + space_number, "NewLargeObject");
sink_->PutInt(size >> kObjectAlignmentBits, "ObjectSizeInWords");
CHECK(!object_.IsCode());
back_reference = serializer_->allocator()->AllocateLargeObject(size);
} else if (space == SnapshotSpace::kMap) {
DCHECK_EQ(Map::kSize, size);
back_reference = serializer_->allocator()->AllocateMap();
sink_->Put(kNewObject + space_number, "NewMap");
// This is redundant, but we include it anyways.
sink_->PutInt(size >> kObjectAlignmentBits, "ObjectSizeInWords");
} else {
int fill = serializer_->PutAlignmentPrefix(object_);
back_reference = serializer_->allocator()->Allocate(space, size + fill);
sink_->Put(kNewObject + space_number, "NewObject");
sink_->PutInt(size >> kObjectAlignmentBits, "ObjectSizeInWords");
}
#ifdef OBJECT_PRINT
if (FLAG_serialization_statistics) {
serializer_->CountInstanceType(map, size, space);
}
#endif // OBJECT_PRINT
// Mark this object as already serialized.
serializer_->reference_map()->Add(reinterpret_cast<void*>(object_.ptr()),
back_reference);
// Serialize the map (first word of the object).
serializer_->SerializeObject(map);
}
uint32_t Serializer::ObjectSerializer::SerializeBackingStore(
void* backing_store, int32_t byte_length) {
SerializerReference reference =
serializer_->reference_map()->LookupReference(backing_store);
// Serialize the off-heap backing store.
if (!reference.is_valid()) {
sink_->Put(kOffHeapBackingStore, "Off-heap backing store");
sink_->PutInt(byte_length, "length");
sink_->PutRaw(static_cast<byte*>(backing_store), byte_length,
"BackingStore");
reference = serializer_->allocator()->AllocateOffHeapBackingStore();
// Mark this backing store as already serialized.
serializer_->reference_map()->Add(backing_store, reference);
}
return reference.off_heap_backing_store_index();
}
void Serializer::ObjectSerializer::SerializeJSTypedArray() {
JSTypedArray typed_array = JSTypedArray::cast(object_);
if (typed_array.is_on_heap()) {
typed_array.RemoveExternalPointerCompensationForSerialization(
serializer_->isolate());
} else {
if (!typed_array.WasDetached()) {
// Explicitly serialize the backing store now.
JSArrayBuffer buffer = JSArrayBuffer::cast(typed_array.buffer());
CHECK_LE(buffer.byte_length(), Smi::kMaxValue);
CHECK_LE(typed_array.byte_offset(), Smi::kMaxValue);
int32_t byte_length = static_cast<int32_t>(buffer.byte_length());
int32_t byte_offset = static_cast<int32_t>(typed_array.byte_offset());
// We need to calculate the backing store from the data pointer
// because the ArrayBuffer may already have been serialized.
void* backing_store = reinterpret_cast<void*>(
reinterpret_cast<Address>(typed_array.DataPtr()) - byte_offset);
uint32_t ref = SerializeBackingStore(backing_store, byte_length);
typed_array.SetExternalBackingStoreRefForSerialization(ref);
} else {
typed_array.SetExternalBackingStoreRefForSerialization(0);
}
}
SerializeObject();
}
void Serializer::ObjectSerializer::SerializeJSArrayBuffer() {
JSArrayBuffer buffer = JSArrayBuffer::cast(object_);
void* backing_store = buffer.backing_store();
// We cannot store byte_length larger than Smi range in the snapshot.
CHECK_LE(buffer.byte_length(), Smi::kMaxValue);
int32_t byte_length = static_cast<int32_t>(buffer.byte_length());
ArrayBufferExtension* extension = buffer.extension();
// The embedder-allocated backing store only exists for the off-heap case.
if (backing_store != nullptr) {
uint32_t ref = SerializeBackingStore(backing_store, byte_length);
buffer.SetBackingStoreRefForSerialization(ref);
// Ensure deterministic output by setting extension to null during
// serialization.
buffer.set_extension(nullptr);
}
SerializeObject();
buffer.set_backing_store(serializer_->isolate(), backing_store);
buffer.set_extension(extension);
}
void Serializer::ObjectSerializer::SerializeExternalString() {
// For external strings with known resources, we replace the resource field
// with the encoded external reference, which we restore upon deserialize.
// For the rest we serialize them to look like ordinary sequential strings.
ExternalString string = ExternalString::cast(object_);
Address resource = string.resource_as_address();
ExternalReferenceEncoder::Value reference;
if (serializer_->external_reference_encoder_.TryEncode(resource).To(
&reference)) {
DCHECK(reference.is_from_api());
string.set_uint32_as_resource(serializer_->isolate(), reference.index());
SerializeObject();
string.set_address_as_resource(serializer_->isolate(), resource);
} else {
SerializeExternalStringAsSequentialString();
}
}
void Serializer::ObjectSerializer::SerializeExternalStringAsSequentialString() {
// Instead of serializing this as an external string, we serialize
// an imaginary sequential string with the same content.
ReadOnlyRoots roots(serializer_->isolate());
DCHECK(object_.IsExternalString());
ExternalString string = ExternalString::cast(object_);
int length = string.length();
Map map;
int content_size;
int allocation_size;
const byte* resource;
// Find the map and size for the imaginary sequential string.
bool internalized = object_.IsInternalizedString();
if (object_.IsExternalOneByteString()) {
map = internalized ? roots.one_byte_internalized_string_map()
: roots.one_byte_string_map();
allocation_size = SeqOneByteString::SizeFor(length);
content_size = length * kCharSize;
resource = reinterpret_cast<const byte*>(
ExternalOneByteString::cast(string).resource()->data());
} else {
map = internalized ? roots.internalized_string_map() : roots.string_map();
allocation_size = SeqTwoByteString::SizeFor(length);
content_size = length * kShortSize;
resource = reinterpret_cast<const byte*>(
ExternalTwoByteString::cast(string).resource()->data());
}
SnapshotSpace space = (allocation_size > kMaxRegularHeapObjectSize)
? SnapshotSpace::kLargeObject
: SnapshotSpace::kOld;
SerializePrologue(space, allocation_size, map);
// Output the rest of the imaginary string.
int bytes_to_output = allocation_size - HeapObject::kHeaderSize;
DCHECK(IsAligned(bytes_to_output, kTaggedSize));
// Output raw data header. Do not bother with common raw length cases here.
sink_->Put(kVariableRawData, "RawDataForString");
sink_->PutInt(bytes_to_output, "length");
// Serialize string header (except for map).
uint8_t* string_start = reinterpret_cast<uint8_t*>(string.address());
for (int i = HeapObject::kHeaderSize; i < SeqString::kHeaderSize; i++) {
sink_->PutSection(string_start[i], "StringHeader");
}
// Serialize string content.
sink_->PutRaw(resource, content_size, "StringContent");
// Since the allocation size is rounded up to object alignment, there
// maybe left-over bytes that need to be padded.
int padding_size = allocation_size - SeqString::kHeaderSize - content_size;
DCHECK(0 <= padding_size && padding_size < kObjectAlignment);
for (int i = 0; i < padding_size; i++) sink_->PutSection(0, "StringPadding");
}
// Clear and later restore the next link in the weak cell or allocation site.
// TODO(all): replace this with proper iteration of weak slots in serializer.
class UnlinkWeakNextScope {
public:
explicit UnlinkWeakNextScope(Heap* heap, HeapObject object) {
if (object.IsAllocationSite() &&
AllocationSite::cast(object).HasWeakNext()) {
object_ = object;
next_ = AllocationSite::cast(object).weak_next();
AllocationSite::cast(object).set_weak_next(
ReadOnlyRoots(heap).undefined_value());
}
}
~UnlinkWeakNextScope() {
if (!object_.is_null()) {
AllocationSite::cast(object_).set_weak_next(next_,
UPDATE_WEAK_WRITE_BARRIER);
}
}
private:
HeapObject object_;
Object next_;
DISALLOW_HEAP_ALLOCATION(no_gc_)
};
void Serializer::ObjectSerializer::Serialize() {
if (FLAG_trace_serializer) {
PrintF(" Encoding heap object: ");
object_.ShortPrint();
PrintF("\n");
}
if (object_.IsExternalString()) {
SerializeExternalString();
return;
} else if (!ReadOnlyHeap::Contains(object_)) {
// Only clear padding for strings outside the read-only heap. Read-only heap
// should have been cleared elsewhere.
if (object_.IsSeqOneByteString()) {
// Clear padding bytes at the end. Done here to avoid having to do this
// at allocation sites in generated code.
SeqOneByteString::cast(object_).clear_padding();
} else if (object_.IsSeqTwoByteString()) {
SeqTwoByteString::cast(object_).clear_padding();
}
}
if (object_.IsJSTypedArray()) {
SerializeJSTypedArray();
return;
}
if (object_.IsJSArrayBuffer()) {
SerializeJSArrayBuffer();
return;
}
// We don't expect fillers.
DCHECK(!object_.IsFreeSpaceOrFiller());
if (object_.IsScript()) {
// Clear cached line ends.
Object undefined = ReadOnlyRoots(serializer_->isolate()).undefined_value();
Script::cast(object_).set_line_ends(undefined);
}
SerializeObject();
}
namespace {
SnapshotSpace GetSnapshotSpace(HeapObject object) {
if (V8_ENABLE_THIRD_PARTY_HEAP_BOOL) {
if (third_party_heap::Heap::InCodeSpace(object.address())) {
return SnapshotSpace::kCode;
} else if (ReadOnlyHeap::Contains(object)) {
return SnapshotSpace::kReadOnlyHeap;
} else if (object.Size() > kMaxRegularHeapObjectSize) {
return SnapshotSpace::kLargeObject;
} else if (object.IsMap()) {
return SnapshotSpace::kMap;
} else {
return SnapshotSpace::kNew; // avoid new/young distinction in TPH
}
} else if (ReadOnlyHeap::Contains(object)) {
return SnapshotSpace::kReadOnlyHeap;
} else {
AllocationSpace heap_space =
MemoryChunk::FromHeapObject(object)->owner_identity();
// Large code objects are not supported and cannot be expressed by
// SnapshotSpace.
DCHECK_NE(heap_space, CODE_LO_SPACE);
switch (heap_space) {
// Young generation objects are tenured, as objects that have survived
// until snapshot building probably deserve to be considered 'old'.
case NEW_SPACE:
return SnapshotSpace::kOld;
case NEW_LO_SPACE:
return SnapshotSpace::kLargeObject;
default:
return static_cast<SnapshotSpace>(heap_space);
}
}
}
} // namespace
void Serializer::ObjectSerializer::SerializeObject() {
int size = object_.Size();
Map map = object_.map();
SnapshotSpace space = GetSnapshotSpace(object_);
SerializePrologue(space, size, map);
// Serialize the rest of the object.
CHECK_EQ(0, bytes_processed_so_far_);
bytes_processed_so_far_ = kTaggedSize;
RecursionScope recursion(serializer_);
// Objects that are immediately post processed during deserialization
// cannot be deferred, since post processing requires the object content.
if ((recursion.ExceedsMaximum() && CanBeDeferred(object_)) ||
serializer_->MustBeDeferred(object_)) {
serializer_->QueueDeferredObject(object_);
sink_->Put(kDeferred, "Deferring object content");
return;
}
SerializeContent(map, size);
}
void Serializer::ObjectSerializer::SerializeDeferred() {
if (FLAG_trace_serializer) {
PrintF(" Encoding deferred heap object: ");
object_.ShortPrint();
PrintF("\n");
}
int size = object_.Size();
Map map = object_.map();
SerializerReference back_reference =
serializer_->reference_map()->LookupReference(
reinterpret_cast<void*>(object_.ptr()));
DCHECK(back_reference.is_back_reference());
// Serialize the rest of the object.
CHECK_EQ(0, bytes_processed_so_far_);
bytes_processed_so_far_ = kTaggedSize;
serializer_->PutAlignmentPrefix(object_);
sink_->Put(kNewObject + static_cast<int>(back_reference.space()),
"deferred object");
serializer_->PutBackReference(object_, back_reference);
sink_->PutInt(size >> kTaggedSizeLog2, "deferred object size");
SerializeContent(map, size);
}
void Serializer::ObjectSerializer::SerializeContent(Map map, int size) {
UnlinkWeakNextScope unlink_weak_next(serializer_->isolate()->heap(), object_);
if (object_.IsCode()) {
// For code objects, output raw bytes first.
OutputCode(size);
// Then iterate references via reloc info.
object_.IterateBody(map, size, this);
} else {
// For other objects, iterate references first.
object_.IterateBody(map, size, this);
// Then output data payload, if any.
OutputRawData(object_.address() + size);
}
}
void Serializer::ObjectSerializer::VisitPointers(HeapObject host,
ObjectSlot start,
ObjectSlot end) {
VisitPointers(host, MaybeObjectSlot(start), MaybeObjectSlot(end));
}
void Serializer::ObjectSerializer::VisitPointers(HeapObject host,
MaybeObjectSlot start,
MaybeObjectSlot end) {
DisallowHeapAllocation no_gc;
MaybeObjectSlot current = start;
while (current < end) {
while (current < end && (*current)->IsSmi()) {
++current;
}
if (current < end) {
OutputRawData(current.address());
}
// TODO(ishell): Revisit this change once we stick to 32-bit compressed
// tagged values.
while (current < end && (*current)->IsCleared()) {
sink_->Put(kClearedWeakReference, "ClearedWeakReference");
bytes_processed_so_far_ += kTaggedSize;
++current;
}
HeapObject current_contents;
HeapObjectReferenceType reference_type;
while (current < end &&
(*current)->GetHeapObject(¤t_contents, &reference_type)) {
RootIndex root_index;
// Compute repeat count and write repeat prefix if applicable.
// Repeats are not subject to the write barrier so we can only use
// immortal immovable root members. They are never in new space.
MaybeObjectSlot repeat_end = current + 1;
if (repeat_end < end &&
serializer_->root_index_map()->Lookup(current_contents,
&root_index) &&
RootsTable::IsImmortalImmovable(root_index) &&
*current == *repeat_end) {
DCHECK_EQ(reference_type, HeapObjectReferenceType::STRONG);
DCHECK(!Heap::InYoungGeneration(current_contents));
while (repeat_end < end && *repeat_end == *current) {
repeat_end++;
}
int repeat_count = static_cast<int>(repeat_end - current);
current = repeat_end;
bytes_processed_so_far_ += repeat_count * kTaggedSize;
serializer_->PutRepeat(repeat_count);
} else {
bytes_processed_so_far_ += kTaggedSize;
++current;
}
// Now write the object itself.
if (reference_type == HeapObjectReferenceType::WEAK) {
sink_->Put(kWeakPrefix, "WeakReference");
}
serializer_->SerializeObject(current_contents);
}
}
}
void Serializer::ObjectSerializer::VisitEmbeddedPointer(Code host,
RelocInfo* rinfo) {
Object object = rinfo->target_object();
serializer_->SerializeObject(HeapObject::cast(object));
bytes_processed_so_far_ += rinfo->target_address_size();
}
void Serializer::ObjectSerializer::OutputExternalReference(Address target,
int target_size,
bool sandboxify) {
DCHECK_LE(target_size, sizeof(target)); // Must fit in Address.
ExternalReferenceEncoder::Value encoded_reference;
bool encoded_successfully;
if (serializer_->allow_unknown_external_references_for_testing()) {
encoded_successfully =
serializer_->TryEncodeExternalReference(target).To(&encoded_reference);
} else {
encoded_reference = serializer_->EncodeExternalReference(target);
encoded_successfully = true;
}
if (!encoded_successfully) {
// In this case the serialized snapshot will not be used in a different
// Isolate and thus the target address will not change between
// serialization and deserialization. We can serialize seen external
// references verbatim.
CHECK(serializer_->allow_unknown_external_references_for_testing());
CHECK(IsAligned(target_size, kObjectAlignment));
CHECK_LE(target_size, kNumberOfFixedRawData * kTaggedSize);
int size_in_tagged = target_size >> kTaggedSizeLog2;
sink_->PutSection(kFixedRawDataStart + size_in_tagged, "FixedRawData");
sink_->PutRaw(reinterpret_cast<byte*>(&target), target_size, "Bytes");
} else if (encoded_reference.is_from_api()) {
if (V8_HEAP_SANDBOX_BOOL && sandboxify) {
sink_->Put(kSandboxedApiReference, "SandboxedApiRef");
} else {
sink_->Put(kApiReference, "ApiRef");
}
sink_->PutInt(encoded_reference.index(), "reference index");
} else {
if (V8_HEAP_SANDBOX_BOOL && sandboxify) {
sink_->Put(kSandboxedExternalReference, "SandboxedExternalRef");
} else {
sink_->Put(kExternalReference, "ExternalRef");
}
sink_->PutInt(encoded_reference.index(), "reference index");
}
bytes_processed_so_far_ += target_size;
}
void Serializer::ObjectSerializer::VisitExternalReference(Foreign host,
Address* p) {
// "Sandboxify" external reference.
OutputExternalReference(host.foreign_address(), kExternalPointerSize, true);
}
void Serializer::ObjectSerializer::VisitExternalReference(Code host,
RelocInfo* rinfo) {
Address target = rinfo->target_external_reference();
DCHECK_NE(target, kNullAddress); // Code does not reference null.
DCHECK_IMPLIES(serializer_->EncodeExternalReference(target).is_from_api(),
!rinfo->IsCodedSpecially());
// Don't "sandboxify" external references embedded in the code.
OutputExternalReference(target, rinfo->target_address_size(), false);
}
void Serializer::ObjectSerializer::VisitInternalReference(Code host,
RelocInfo* rinfo) {
Address entry = Code::cast(object_).entry();
DCHECK_GE(rinfo->target_internal_reference(), entry);
uintptr_t target_offset = rinfo->target_internal_reference() - entry;
DCHECK_LE(target_offset, Code::cast(object_).raw_instruction_size());
sink_->Put(kInternalReference, "InternalRef");
sink_->PutInt(target_offset, "internal ref value");
}
void Serializer::ObjectSerializer::VisitRuntimeEntry(Code host,
RelocInfo* rinfo) {
// We no longer serialize code that contains runtime entries.
UNREACHABLE();
}
void Serializer::ObjectSerializer::VisitOffHeapTarget(Code host,
RelocInfo* rinfo) {
STATIC_ASSERT(EmbeddedData::kTableSize == Builtins::builtin_count);
Address addr = rinfo->target_off_heap_target();
CHECK_NE(kNullAddress, addr);
Code target = InstructionStream::TryLookupCode(serializer_->isolate(), addr);
CHECK(Builtins::IsIsolateIndependentBuiltin(target));
sink_->Put(kOffHeapTarget, "OffHeapTarget");
sink_->PutInt(target.builtin_index(), "builtin index");
bytes_processed_so_far_ += rinfo->target_address_size();
}
void Serializer::ObjectSerializer::VisitCodeTarget(Code host,
RelocInfo* rinfo) {
#ifdef V8_TARGET_ARCH_ARM
DCHECK(!RelocInfo::IsRelativeCodeTarget(rinfo->rmode()));
#endif
Code object = Code::GetCodeFromTargetAddress(rinfo->target_address());
serializer_->SerializeObject(object);
bytes_processed_so_far_ += rinfo->target_address_size();
}
namespace {
// Similar to OutputRawData, but substitutes the given field with the given
// value instead of reading it from the object.
void OutputRawWithCustomField(SnapshotByteSink* sink, Address object_start,
int written_so_far, int bytes_to_write,
int field_offset, int field_size,
const byte* field_value) {
int offset = field_offset - written_so_far;
if (0 <= offset && offset < bytes_to_write) {
DCHECK_GE(bytes_to_write, offset + field_size);
sink->PutRaw(reinterpret_cast<byte*>(object_start + written_so_far), offset,
"Bytes");
sink->PutRaw(field_value, field_size, "Bytes");
written_so_far += offset + field_size;
bytes_to_write -= offset + field_size;
sink->PutRaw(reinterpret_cast<byte*>(object_start + written_so_far),
bytes_to_write, "Bytes");
} else {
sink->PutRaw(reinterpret_cast<byte*>(object_start + written_so_far),
bytes_to_write, "Bytes");
}
}
} // anonymous namespace
void Serializer::ObjectSerializer::OutputRawData(Address up_to) {
Address object_start = object_.address();
int base = bytes_processed_so_far_;
int up_to_offset = static_cast<int>(up_to - object_start);
int to_skip = up_to_offset - bytes_processed_so_far_;
int bytes_to_output = to_skip;
bytes_processed_so_far_ += to_skip;
DCHECK_GE(to_skip, 0);
if (bytes_to_output != 0) {
DCHECK(to_skip == bytes_to_output);
if (IsAligned(bytes_to_output, kObjectAlignment) &&
bytes_to_output <= kNumberOfFixedRawData * kTaggedSize) {
int size_in_tagged = bytes_to_output >> kTaggedSizeLog2;
sink_->PutSection(kFixedRawDataStart + size_in_tagged, "FixedRawData");
} else {
sink_->Put(kVariableRawData, "VariableRawData");
sink_->PutInt(bytes_to_output, "length");
}
#ifdef MEMORY_SANITIZER
// Check that we do not serialize uninitialized memory.
__msan_check_mem_is_initialized(
reinterpret_cast<void*>(object_start + base), bytes_to_output);
#endif // MEMORY_SANITIZER
if (object_.IsBytecodeArray()) {
// The bytecode age field can be changed by GC concurrently.
byte field_value = BytecodeArray::kNoAgeBytecodeAge;
OutputRawWithCustomField(sink_, object_start, base, bytes_to_output,
BytecodeArray::kBytecodeAgeOffset,
sizeof(field_value), &field_value);
} else if (object_.IsDescriptorArray()) {
// The number of marked descriptors field can be changed by GC
// concurrently.
byte field_value[2];
field_value[0] = 0;
field_value[1] = 0;
OutputRawWithCustomField(
sink_, object_start, base, bytes_to_output,
DescriptorArray::kRawNumberOfMarkedDescriptorsOffset,
sizeof(field_value), field_value);
} else {
sink_->PutRaw(reinterpret_cast<byte*>(object_start + base),
bytes_to_output, "Bytes");
}
}
}
void Serializer::ObjectSerializer::OutputCode(int size) {
DCHECK_EQ(kTaggedSize, bytes_processed_so_far_);
Code on_heap_code = Code::cast(object_);
// To make snapshots reproducible, we make a copy of the code object
// and wipe all pointers in the copy, which we then serialize.
Code off_heap_code = serializer_->CopyCode(on_heap_code);
int mode_mask = RelocInfo::ModeMask(RelocInfo::CODE_TARGET) |
RelocInfo::ModeMask(RelocInfo::FULL_EMBEDDED_OBJECT) |
RelocInfo::ModeMask(RelocInfo::COMPRESSED_EMBEDDED_OBJECT) |
RelocInfo::ModeMask(RelocInfo::EXTERNAL_REFERENCE) |
RelocInfo::ModeMask(RelocInfo::INTERNAL_REFERENCE) |
RelocInfo::ModeMask(RelocInfo::INTERNAL_REFERENCE_ENCODED) |
RelocInfo::ModeMask(RelocInfo::OFF_HEAP_TARGET) |
RelocInfo::ModeMask(RelocInfo::RUNTIME_ENTRY);
// With enabled pointer compression normal accessors no longer work for
// off-heap objects, so we have to get the relocation info data via the
// on-heap code object.
ByteArray relocation_info = on_heap_code.unchecked_relocation_info();
for (RelocIterator it(off_heap_code, relocation_info, mode_mask); !it.done();
it.next()) {
RelocInfo* rinfo = it.rinfo();
rinfo->WipeOut();
}
// We need to wipe out the header fields *after* wiping out the
// relocations, because some of these fields are needed for the latter.
off_heap_code.WipeOutHeader();
Address start = off_heap_code.address() + Code::kDataStart;
int bytes_to_output = size - Code::kDataStart;
DCHECK(IsAligned(bytes_to_output, kTaggedSize));
sink_->Put(kVariableRawCode, "VariableRawCode");
sink_->PutInt(bytes_to_output, "length");
#ifdef MEMORY_SANITIZER
// Check that we do not serialize uninitialized memory.
__msan_check_mem_is_initialized(reinterpret_cast<void*>(start),
bytes_to_output);
#endif // MEMORY_SANITIZER
sink_->PutRaw(reinterpret_cast<byte*>(start), bytes_to_output, "Code");
}
} // namespace internal
} // namespace v8
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