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// Copyright 2020 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_DESERIALIZER_H_
#define V8_SNAPSHOT_SERIALIZER_DESERIALIZER_H_
#include "src/objects/visitors.h"
#include "src/snapshot/references.h"
namespace v8 {
namespace internal {
class CallHandlerInfo;
class Isolate;
// 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);
protected:
class HotObjectsList {
public:
HotObjectsList() = default;
void Add(HeapObject object) {
DCHECK(!AllowHeapAllocation::IsAllowed());
circular_queue_[index_] = object;
index_ = (index_ + 1) & kSizeMask;
}
HeapObject Get(int index) {
DCHECK(!AllowHeapAllocation::IsAllowed());
DCHECK(!circular_queue_[index].is_null());
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));
static const int kSizeMask = kSize - 1;
HeapObject circular_queue_[kSize];
int index_ = 0;
DISALLOW_COPY_AND_ASSIGN(HotObjectsList);
};
static bool CanBeDeferred(HeapObject o);
void RestoreExternalReferenceRedirectors(
Isolate* isolate, const std::vector<AccessorInfo>& accessor_infos);
void RestoreExternalReferenceRedirectors(
Isolate* isolate, const std::vector<CallHandlerInfo>& call_handler_infos);
static const int kNumberOfPreallocatedSpaces =
static_cast<int>(SnapshotSpace::kNumberOfPreallocatedSpaces);
static const int kNumberOfSpaces =
static_cast<int>(SnapshotSpace::kNumberOfSpaces);
// clang-format off
#define UNUSED_SERIALIZER_BYTE_CODES(V) \
V(0x06) V(0x07) V(0x0e) V(0x0f) \
/* Free range 0x28..0x2f */ \
V(0x28) V(0x29) V(0x2a) V(0x2b) V(0x2c) V(0x2d) V(0x2e) V(0x2f) \
/* Free range 0x30..0x3f */ \
V(0x30) V(0x31) V(0x32) V(0x33) V(0x34) V(0x35) V(0x36) V(0x37) \
V(0x38) V(0x39) V(0x3a) V(0x3b) V(0x3c) V(0x3d) V(0x3e) V(0x3f) \
/* Free range 0x97..0x9f */ \
V(0x98) V(0x99) V(0x9a) V(0x9b) V(0x9c) V(0x9d) V(0x9e) V(0x9f) \
/* Free range 0xa0..0xaf */ \
V(0xa0) V(0xa1) V(0xa2) V(0xa3) V(0xa4) V(0xa5) V(0xa6) V(0xa7) \
V(0xa8) V(0xa9) V(0xaa) V(0xab) V(0xac) V(0xad) V(0xae) V(0xaf) \
/* Free range 0xb0..0xbf */ \
V(0xb0) V(0xb1) V(0xb2) V(0xb3) V(0xb4) V(0xb5) V(0xb6) V(0xb7) \
V(0xb8) V(0xb9) V(0xba) V(0xbb) V(0xbc) V(0xbd) V(0xbe) V(0xbf) \
/* Free range 0xc0..0xcf */ \
V(0xc0) V(0xc1) V(0xc2) V(0xc3) V(0xc4) V(0xc5) V(0xc6) V(0xc7) \
V(0xc8) V(0xc9) V(0xca) V(0xcb) V(0xcc) V(0xcd) V(0xce) V(0xcf) \
/* Free range 0xd0..0xdf */ \
V(0xd0) V(0xd1) V(0xd2) V(0xd3) V(0xd4) V(0xd5) V(0xd6) V(0xd7) \
V(0xd8) V(0xd9) V(0xda) V(0xdb) V(0xdc) V(0xdd) V(0xde) V(0xdf) \
/* Free range 0xe0..0xef */ \
V(0xe0) V(0xe1) V(0xe2) V(0xe3) V(0xe4) V(0xe5) V(0xe6) V(0xe7) \
V(0xe8) V(0xe9) V(0xea) V(0xeb) V(0xec) V(0xed) V(0xee) V(0xef) \
/* Free range 0xf0..0xff */ \
V(0xf0) V(0xf1) V(0xf2) V(0xf3) V(0xf4) V(0xf5) V(0xf6) V(0xf7) \
V(0xf8) V(0xf9) V(0xfa) V(0xfb) V(0xfc) V(0xfd) V(0xfe) V(0xff)
// clang-format on
// The static assert below will trigger when the number of preallocated spaces
// changed. If that happens, update the kNewObject and kBackref bytecode
// ranges in the comments below.
STATIC_ASSERT(6 == kNumberOfSpaces);
static const int kSpaceMask = 7;
STATIC_ASSERT(kNumberOfSpaces <= kSpaceMask + 1);
// First 32 root array items.
static const int kNumberOfRootArrayConstants = 0x20;
static const int kRootArrayConstantsMask = 0x1f;
// 32 common raw data lengths.
static const int kNumberOfFixedRawData = 0x20;
// 16 repeats lengths.
static const int kNumberOfFixedRepeat = 0x10;
// 8 hot (recently seen or back-referenced) objects with optional skip.
static const int kNumberOfHotObjects = 8;
STATIC_ASSERT(kNumberOfHotObjects == HotObjectsList::kSize);
static const int kHotObjectMask = 0x07;
enum Bytecode {
//
// ---------- byte code range 0x00..0x0f ----------
//
// 0x00..0x05 Allocate new object, in specified space.
kNewObject = 0x00,
// 0x08..0x0d Reference to previous object from specified space.
kBackref = 0x08,
//
// ---------- byte code range 0x10..0x27 ----------
//
// Object in the startup object cache.
kStartupObjectCache = 0x10,
// Root array item.
kRootArray,
// Object provided in the attached list.
kAttachedReference,
// Object in the read-only object cache.
kReadOnlyObjectCache,
// Do nothing, used for padding.
kNop,
// Move to next reserved chunk.
kNextChunk,
// Deferring object content.
kDeferred,
// 3 alignment prefixes 0x17..0x19
kAlignmentPrefix = 0x17,
// 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.
kSynchronize = 0x1a,
// Repeats of variable length.
kVariableRepeat,
// Used for embedder-allocated backing stores for TypedArrays.
kOffHeapBackingStore,
// Used for embedder-provided serialization data for embedder fields.
kEmbedderFieldsData,
// Raw data of variable length.
kVariableRawCode,
kVariableRawData,
// Used to encode external references provided through the API.
kApiReference,
// External reference referenced by id.
kExternalReference,
// Same as two bytecodes above but for serializing sandboxed external
// pointer values.
// TODO(v8:10391): Remove them once all ExternalPointer usages are
// sandbox-ready.
kSandboxedApiReference,
kSandboxedExternalReference,
// Internal reference of a code objects in code stream.
kInternalReference,
// In-place weak references.
kClearedWeakReference,
kWeakPrefix,
// Encodes an off-heap instruction stream target.
kOffHeapTarget,
//
// ---------- byte code range 0x40..0x7f ----------
//
// 0x40..0x5f
kRootArrayConstants = 0x40,
// 0x60..0x7f
kFixedRawData = 0x60,
kFixedRawDataStart = kFixedRawData - 1,
//
// ---------- byte code range 0x80..0x9f ----------
//
// 0x80..0x8f
kFixedRepeat = 0x80,
// 0x90..0x97
kHotObject = 0x90,
};
//
// Some other constants.
//
static const SnapshotSpace kAnyOldSpace = SnapshotSpace::kNumberOfSpaces;
// Sentinel after a new object to indicate that double alignment is needed.
static const int kDoubleAlignmentSentinel = 0;
// Repeat count encoding helpers.
static const int kFirstEncodableRepeatCount = 2;
static const int kLastEncodableFixedRepeatCount =
kFirstEncodableRepeatCount + kNumberOfFixedRepeat - 1;
static const int kFirstEncodableVariableRepeatCount =
kLastEncodableFixedRepeatCount + 1;
// Encodes repeat count into a fixed repeat bytecode.
static int EncodeFixedRepeat(int repeat_count) {
DCHECK(base::IsInRange(repeat_count, kFirstEncodableRepeatCount,
kLastEncodableFixedRepeatCount));
return kFixedRepeat + repeat_count - kFirstEncodableRepeatCount;
}
// Decodes repeat count from a fixed repeat bytecode.
static int DecodeFixedRepeatCount(int bytecode) {
DCHECK(base::IsInRange(bytecode, kFixedRepeat + 0,
kFixedRepeat + kNumberOfFixedRepeat));
return bytecode - kFixedRepeat + kFirstEncodableRepeatCount;
}
// Encodes repeat count into a serialized variable repeat count value.
static int EncodeVariableRepeatCount(int repeat_count) {
DCHECK_LE(kFirstEncodableVariableRepeatCount, repeat_count);
return repeat_count - kFirstEncodableVariableRepeatCount;
}
// Decodes repeat count from a serialized variable repeat count value.
static int DecodeVariableRepeatCount(int value) {
DCHECK_LE(0, value);
return value + kFirstEncodableVariableRepeatCount;
}
// ---------- member variable ----------
HotObjectsList hot_objects_;
};
} // namespace internal
} // namespace v8
#endif // V8_SNAPSHOT_SERIALIZER_DESERIALIZER_H_
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