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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.
#ifndef V8_SNAPSHOT_SERIALIZER_COMMON_H_
#define V8_SNAPSHOT_SERIALIZER_COMMON_H_
#include "src/address-map.h"
#include "src/base/bits.h"
#include "src/external-reference-table.h"
#include "src/globals.h"
#include "src/snapshot/references.h"
#include "src/utils.h"
#include "src/visitors.h"
namespace v8 {
namespace internal {
class CallHandlerInfo;
class Isolate;
class ExternalReferenceEncoder {
public:
class Value {
public:
explicit Value(uint32_t raw) : value_(raw) {}
Value() : value_(0) {}
static uint32_t Encode(uint32_t index, bool is_from_api) {
return Index::encode(index) | IsFromAPI::encode(is_from_api);
}
bool is_from_api() const { return IsFromAPI::decode(value_); }
uint32_t index() const { return Index::decode(value_); }
private:
class Index : public BitField<uint32_t, 0, 31> {};
class IsFromAPI : public BitField<bool, 31, 1> {};
uint32_t value_;
};
explicit ExternalReferenceEncoder(Isolate* isolate);
~ExternalReferenceEncoder();
Value Encode(Address key);
Maybe<Value> TryEncode(Address key);
const char* NameOfAddress(Isolate* isolate, Address address) const;
private:
AddressToIndexHashMap* map_;
#ifdef DEBUG
std::vector<int> count_;
const intptr_t* api_references_;
#endif // DEBUG
DISALLOW_COPY_AND_ASSIGN(ExternalReferenceEncoder);
};
class HotObjectsList {
public:
HotObjectsList() : index_(0) {
for (int i = 0; i < kSize; i++) circular_queue_[i] = nullptr;
}
void Add(HeapObject* object) {
DCHECK(!AllowHeapAllocation::IsAllowed());
circular_queue_[index_] = object;
index_ = (index_ + 1) & kSizeMask;
}
HeapObject* Get(int index) {
DCHECK(!AllowHeapAllocation::IsAllowed());
DCHECK_NOT_NULL(circular_queue_[index]);
return circular_queue_[index];
}
static const int kNotFound = -1;
int Find(HeapObject* object) {
DCHECK(!AllowHeapAllocation::IsAllowed());
for (int i = 0; i < kSize; i++) {
if (circular_queue_[i] == object) return i;
}
return kNotFound;
}
static const int kSize = 8;
private:
static_assert(base::bits::IsPowerOfTwo(kSize), "kSize must be power of two");
static const int kSizeMask = kSize - 1;
HeapObject* circular_queue_[kSize];
int index_;
DISALLOW_COPY_AND_ASSIGN(HotObjectsList);
};
// The Serializer/Deserializer class is a common superclass for Serializer and
// Deserializer which is used to store common constants and methods used by
// both.
class SerializerDeserializer : public RootVisitor {
public:
static void Iterate(Isolate* isolate, RootVisitor* visitor);
// No reservation for large object space necessary.
// We also handle map space differenly.
STATIC_ASSERT(MAP_SPACE == CODE_SPACE + 1);
// We do not support young generation large objects.
STATIC_ASSERT(LAST_SPACE == NEW_LO_SPACE);
STATIC_ASSERT(LAST_SPACE - 1 == LO_SPACE);
static const int kNumberOfPreallocatedSpaces = CODE_SPACE + 1;
static const int kNumberOfSpaces = LO_SPACE + 1;
protected:
static bool CanBeDeferred(HeapObject* o);
void RestoreExternalReferenceRedirectors(
const std::vector<AccessorInfo*>& accessor_infos);
void RestoreExternalReferenceRedirectors(
const std::vector<CallHandlerInfo*>& call_handler_infos);
#define UNUSED_SERIALIZER_BYTE_CODES(V) \
V(0x18) \
V(0x3d) \
V(0x3e) \
V(0x3f) \
V(0x58) \
V(0x59) \
V(0x5a) \
V(0x5b) \
V(0x5c) \
V(0x5d) \
V(0x5e) \
V(0x5f) \
V(0x67) \
V(0x76) \
V(0x78) \
V(0x79) \
V(0x7a) \
V(0x7b) \
V(0x7c) \
V(0x7d)
// ---------- byte code range 0x00..0x7f ----------
// Byte codes in this range represent Where, HowToCode and WhereToPoint.
// Where the pointed-to object can be found:
// The static assert below will trigger when the number of preallocated spaces
// changed. If that happens, update the bytecode ranges in the comments below.
STATIC_ASSERT(6 == kNumberOfSpaces);
enum Where {
// 0x00..0x05 Allocate new object, in specified space.
kNewObject = 0x00,
// 0x08..0x0d Reference to previous object from space.
kBackref = 0x08,
// 0x10..0x15 Reference to previous object from space after skip.
kBackrefWithSkip = 0x10,
// 0x06 Object in the partial snapshot cache.
kPartialSnapshotCache = 0x06,
// 0x07 External reference referenced by id.
kExternalReference = 0x07,
// 0x0e Builtin code referenced by index.
kBuiltin = 0x0e,
// 0x16 Root array item.
kRootArray = 0x16,
// 0x17 Object provided in the attached list.
kAttachedReference = 0x17,
// 0x0f Misc, see below (incl. 0x2f, 0x4f, 0x6f).
// 0x18..0x1f Misc, see below (incl. 0x38..0x3f, 0x58..0x5f, 0x78..0x7f).
};
static const int kWhereMask = 0x1f;
static const int kSpaceMask = 7;
STATIC_ASSERT(kNumberOfSpaces <= kSpaceMask + 1);
// How to code the pointer to the object.
enum HowToCode {
// Straight pointer.
kPlain = 0,
// A pointer inlined in code. What this means depends on the architecture.
kFromCode = 0x20
};
static const int kHowToCodeMask = 0x20;
// Where to point within the object.
enum WhereToPoint {
// Points to start of object
kStartOfObject = 0,
// Points to instruction in code object or payload of cell.
kInnerPointer = 0x40
};
static const int kWhereToPointMask = 0x40;
// ---------- Misc ----------
// Skip.
static const int kSkip = 0x0f;
// Do nothing, used for padding.
static const int kNop = 0x2f;
// Move to next reserved chunk.
static const int kNextChunk = 0x4f;
// Deferring object content.
static const int kDeferred = 0x6f;
// Alignment prefixes 0x19..0x1b
static const int kAlignmentPrefix = 0x19;
// A tag emitted at strategic points in the snapshot to delineate sections.
// If the deserializer does not find these at the expected moments then it
// is an indication that the snapshot and the VM do not fit together.
// Examine the build process for architecture, version or configuration
// mismatches.
static const int kSynchronize = 0x1c;
// Repeats of variable length.
static const int kVariableRepeat = 0x1d;
// Raw data of variable length.
// Used for embedder-allocated backing stores for TypedArrays.
static const int kOffHeapBackingStore = 0x1e;
// Used for embedder-provided serialization data for embedder fields.
static const int kEmbedderFieldsData = 0x1f;
// Used to encode external referenced provided through the API.
static const int kApiReference = 0x38;
static const int kVariableRawCode = 0x39;
static const int kVariableRawData = 0x3a;
static const int kInternalReference = 0x3b;
static const int kInternalReferenceEncoded = 0x3c;
// In-place weak references
static const int kWeakPrefix = 0x7e;
// Encodes an off-heap instruction stream target.
static const int kOffHeapTarget = 0x7f;
// ---------- byte code range 0x80..0xff ----------
// First 32 root array items.
static const int kNumberOfRootArrayConstants = 0x20;
// 0x80..0x9f
static const int kRootArrayConstants = 0x80;
// 0xa0..0xbf
static const int kRootArrayConstantsWithSkip = 0xa0;
static const int kRootArrayConstantsMask = 0x1f;
// 32 common raw data lengths.
static const int kNumberOfFixedRawData = 0x20;
// 0xc0..0xdf
static const int kFixedRawData = 0xc0;
static const int kOnePointerRawData = kFixedRawData;
static const int kFixedRawDataStart = kFixedRawData - 1;
// 16 repeats lengths.
static const int kNumberOfFixedRepeat = 0x10;
// 0xe0..0xef
static const int kFixedRepeat = 0xe0;
static const int kFixedRepeatStart = kFixedRepeat - 1;
// 8 hot (recently seen or back-referenced) objects with optional skip.
static const int kNumberOfHotObjects = 8;
STATIC_ASSERT(kNumberOfHotObjects == HotObjectsList::kSize);
// 0xf0..0xf7
static const int kHotObject = 0xf0;
// 0xf8..0xff
static const int kHotObjectWithSkip = 0xf8;
static const int kHotObjectMask = 0x07;
// ---------- special values ----------
static const int kAnyOldSpace = -1;
// Sentinel after a new object to indicate that double alignment is needed.
static const int kDoubleAlignmentSentinel = 0;
// ---------- member variable ----------
HotObjectsList hot_objects_;
};
class SerializedData {
public:
class Reservation {
public:
Reservation() : reservation_(0) {}
explicit Reservation(uint32_t size)
: reservation_(ChunkSizeBits::encode(size)) {}
uint32_t chunk_size() const { return ChunkSizeBits::decode(reservation_); }
bool is_last() const { return IsLastChunkBits::decode(reservation_); }
void mark_as_last() { reservation_ |= IsLastChunkBits::encode(true); }
private:
uint32_t reservation_;
};
SerializedData(byte* data, int size)
: data_(data), size_(size), owns_data_(false) {}
SerializedData() : data_(nullptr), size_(0), owns_data_(false) {}
SerializedData(SerializedData&& other)
: data_(other.data_), size_(other.size_), owns_data_(other.owns_data_) {
// Ensure |other| will not attempt to destroy our data in destructor.
other.owns_data_ = false;
}
virtual ~SerializedData() {
if (owns_data_) DeleteArray<byte>(data_);
}
uint32_t GetMagicNumber() const { return GetHeaderValue(kMagicNumberOffset); }
class ChunkSizeBits : public BitField<uint32_t, 0, 31> {};
class IsLastChunkBits : public BitField<bool, 31, 1> {};
static uint32_t ComputeMagicNumber(ExternalReferenceTable* table) {
uint32_t external_refs = table->size();
return 0xC0DE0000 ^ external_refs;
}
static const uint32_t kMagicNumberOffset = 0;
protected:
void SetHeaderValue(uint32_t offset, uint32_t value) {
WriteLittleEndianValue(reinterpret_cast<Address>(data_) + offset, value);
}
uint32_t GetHeaderValue(uint32_t offset) const {
return ReadLittleEndianValue<uint32_t>(reinterpret_cast<Address>(data_) +
offset);
}
void AllocateData(uint32_t size);
static uint32_t ComputeMagicNumber(Isolate* isolate);
void SetMagicNumber(Isolate* isolate) {
SetHeaderValue(kMagicNumberOffset, ComputeMagicNumber(isolate));
}
byte* data_;
uint32_t size_;
bool owns_data_;
private:
DISALLOW_COPY_AND_ASSIGN(SerializedData);
};
} // namespace internal
} // namespace v8
#endif // V8_SNAPSHOT_SERIALIZER_COMMON_H_
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