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All rights reserved. // Use of this source code is governed by a BSD-style license that can be // found in the LICENSE file. #ifndef INCLUDE_V8_INTERNAL_H_ #define INCLUDE_V8_INTERNAL_H_ #include #include #include #include #include "v8-version.h" // NOLINT(build/include_directory) #include "v8config.h" // NOLINT(build/include_directory) namespace v8 { class Array; class Context; class Data; class Isolate; template class Local; namespace internal { class Isolate; typedef uintptr_t Address; static const Address kNullAddress = 0; /** * Configuration of tagging scheme. */ const int kApiSystemPointerSize = sizeof(void*); const int kApiDoubleSize = sizeof(double); const int kApiInt32Size = sizeof(int32_t); const int kApiInt64Size = sizeof(int64_t); // Tag information for HeapObject. const int kHeapObjectTag = 1; const int kWeakHeapObjectTag = 3; const int kHeapObjectTagSize = 2; const intptr_t kHeapObjectTagMask = (1 << kHeapObjectTagSize) - 1; // Tag information for fowarding pointers stored in object headers. // 0b00 at the lowest 2 bits in the header indicates that the map word is a // forwarding pointer. const int kForwardingTag = 0; const int kForwardingTagSize = 2; const intptr_t kForwardingTagMask = (1 << kForwardingTagSize) - 1; // Tag information for Smi. const int kSmiTag = 0; const int kSmiTagSize = 1; const intptr_t kSmiTagMask = (1 << kSmiTagSize) - 1; template struct SmiTagging; constexpr intptr_t kIntptrAllBitsSet = intptr_t{-1}; constexpr uintptr_t kUintptrAllBitsSet = static_cast(kIntptrAllBitsSet); // Smi constants for systems where tagged pointer is a 32-bit value. template <> struct SmiTagging<4> { enum { kSmiShiftSize = 0, kSmiValueSize = 31 }; static constexpr intptr_t kSmiMinValue = static_cast(kUintptrAllBitsSet << (kSmiValueSize - 1)); static constexpr intptr_t kSmiMaxValue = -(kSmiMinValue + 1); V8_INLINE static int SmiToInt(const internal::Address value) { int shift_bits = kSmiTagSize + kSmiShiftSize; // Truncate and shift down (requires >> to be sign extending). return static_cast(static_cast(value)) >> shift_bits; } V8_INLINE static constexpr bool IsValidSmi(intptr_t value) { // Is value in range [kSmiMinValue, kSmiMaxValue]. // Use unsigned operations in order to avoid undefined behaviour in case of // signed integer overflow. return (static_cast(value) - static_cast(kSmiMinValue)) <= (static_cast(kSmiMaxValue) - static_cast(kSmiMinValue)); } }; // Smi constants for systems where tagged pointer is a 64-bit value. template <> struct SmiTagging<8> { enum { kSmiShiftSize = 31, kSmiValueSize = 32 }; static constexpr intptr_t kSmiMinValue = static_cast(kUintptrAllBitsSet << (kSmiValueSize - 1)); static constexpr intptr_t kSmiMaxValue = -(kSmiMinValue + 1); V8_INLINE static int SmiToInt(const internal::Address value) { int shift_bits = kSmiTagSize + kSmiShiftSize; // Shift down and throw away top 32 bits. return static_cast(static_cast(value) >> shift_bits); } V8_INLINE static constexpr bool IsValidSmi(intptr_t value) { // To be representable as a long smi, the value must be a 32-bit integer. return (value == static_cast(value)); } }; #ifdef V8_COMPRESS_POINTERS static_assert( kApiSystemPointerSize == kApiInt64Size, "Pointer compression can be enabled only for 64-bit architectures"); const int kApiTaggedSize = kApiInt32Size; #else const int kApiTaggedSize = kApiSystemPointerSize; #endif constexpr bool PointerCompressionIsEnabled() { return kApiTaggedSize != kApiSystemPointerSize; } constexpr bool HeapSandboxIsEnabled() { #ifdef V8_HEAP_SANDBOX return true; #else return false; #endif } using ExternalPointer_t = Address; // If the heap sandbox is enabled, these tag values will be ORed with the // external pointers in the external pointer table to prevent use of pointers of // the wrong type. When a pointer is loaded, it is ANDed with the inverse of the // expected type's tag. The tags are constructed in a way that guarantees that a // failed type check will result in one or more of the top bits of the pointer // to be set, rendering the pointer inacessible. This construction allows // performing the type check and removing GC marking bits from the pointer at // the same time. enum ExternalPointerTag : uint64_t { kExternalPointerNullTag = 0x0000000000000000, kArrayBufferBackingStoreTag = 0x00ff000000000000, // 0b000000011111111 kTypedArrayExternalPointerTag = 0x017f000000000000, // 0b000000101111111 kDataViewDataPointerTag = 0x01bf000000000000, // 0b000000110111111 kExternalStringResourceTag = 0x01df000000000000, // 0b000000111011111 kExternalStringResourceDataTag = 0x01ef000000000000, // 0b000000111101111 kForeignForeignAddressTag = 0x01f7000000000000, // 0b000000111110111 kNativeContextMicrotaskQueueTag = 0x01fb000000000000, // 0b000000111111011 kEmbedderDataSlotPayloadTag = 0x01fd000000000000, // 0b000000111111101 kCodeEntryPointTag = 0x01fe000000000000, // 0b000000111111110 }; constexpr uint64_t kExternalPointerTagMask = 0xffff000000000000; #ifdef V8_31BIT_SMIS_ON_64BIT_ARCH using PlatformSmiTagging = SmiTagging; #else using PlatformSmiTagging = SmiTagging; #endif // TODO(ishell): Consinder adding kSmiShiftBits = kSmiShiftSize + kSmiTagSize // since it's used much more often than the inividual constants. const int kSmiShiftSize = PlatformSmiTagging::kSmiShiftSize; const int kSmiValueSize = PlatformSmiTagging::kSmiValueSize; const int kSmiMinValue = static_cast(PlatformSmiTagging::kSmiMinValue); const int kSmiMaxValue = static_cast(PlatformSmiTagging::kSmiMaxValue); constexpr bool SmiValuesAre31Bits() { return kSmiValueSize == 31; } constexpr bool SmiValuesAre32Bits() { return kSmiValueSize == 32; } V8_INLINE static constexpr internal::Address IntToSmi(int value) { return (static_cast
(value) << (kSmiTagSize + kSmiShiftSize)) | kSmiTag; } // Converts encoded external pointer to address. V8_EXPORT Address DecodeExternalPointerImpl(const Isolate* isolate, ExternalPointer_t pointer, ExternalPointerTag tag); // {obj} must be the raw tagged pointer representation of a HeapObject // that's guaranteed to never be in ReadOnlySpace. V8_EXPORT internal::Isolate* IsolateFromNeverReadOnlySpaceObject(Address obj); // Returns if we need to throw when an error occurs. This infers the language // mode based on the current context and the closure. This returns true if the // language mode is strict. V8_EXPORT bool ShouldThrowOnError(v8::internal::Isolate* isolate); /** * This class exports constants and functionality from within v8 that * is necessary to implement inline functions in the v8 api. Don't * depend on functions and constants defined here. */ class Internals { #ifdef V8_MAP_PACKING V8_INLINE static constexpr internal::Address UnpackMapWord( internal::Address mapword) { // TODO(wenyuzhao): Clear header metadata. return mapword ^ kMapWordXorMask; } #endif public: // These values match non-compiler-dependent values defined within // the implementation of v8. static const int kHeapObjectMapOffset = 0; static const int kMapInstanceTypeOffset = 1 * kApiTaggedSize + kApiInt32Size; static const int kStringResourceOffset = 1 * kApiTaggedSize + 2 * kApiInt32Size; static const int kOddballKindOffset = 4 * kApiTaggedSize + kApiDoubleSize; static const int kJSObjectHeaderSize = 3 * kApiTaggedSize; static const int kFixedArrayHeaderSize = 2 * kApiTaggedSize; static const int kEmbedderDataArrayHeaderSize = 2 * kApiTaggedSize; static const int kEmbedderDataSlotSize = kApiSystemPointerSize; #ifdef V8_HEAP_SANDBOX static const int kEmbedderDataSlotRawPayloadOffset = kApiTaggedSize; #endif static const int kNativeContextEmbedderDataOffset = 6 * kApiTaggedSize; static const int kFullStringRepresentationMask = 0x0f; static const int kStringEncodingMask = 0x8; static const int kExternalTwoByteRepresentationTag = 0x02; static const int kExternalOneByteRepresentationTag = 0x0a; static const uint32_t kNumIsolateDataSlots = 4; // IsolateData layout guarantees. static const int kIsolateEmbedderDataOffset = 0; static const int kIsolateFastCCallCallerFpOffset = kNumIsolateDataSlots * kApiSystemPointerSize; static const int kIsolateFastCCallCallerPcOffset = kIsolateFastCCallCallerFpOffset + kApiSystemPointerSize; static const int kIsolateFastApiCallTargetOffset = kIsolateFastCCallCallerPcOffset + kApiSystemPointerSize; static const int kIsolateStackGuardOffset = kIsolateFastApiCallTargetOffset + kApiSystemPointerSize; static const int kIsolateRootsOffset = kIsolateStackGuardOffset + 7 * kApiSystemPointerSize; static const int kExternalPointerTableBufferOffset = 0; static const int kExternalPointerTableLengthOffset = kExternalPointerTableBufferOffset + kApiSystemPointerSize; static const int kExternalPointerTableCapacityOffset = kExternalPointerTableLengthOffset + kApiInt32Size; static const int kUndefinedValueRootIndex = 4; static const int kTheHoleValueRootIndex = 5; static const int kNullValueRootIndex = 6; static const int kTrueValueRootIndex = 7; static const int kFalseValueRootIndex = 8; static const int kEmptyStringRootIndex = 9; static const int kNodeClassIdOffset = 1 * kApiSystemPointerSize; static const int kNodeFlagsOffset = 1 * kApiSystemPointerSize + 3; static const int kNodeStateMask = 0x7; static const int kNodeStateIsWeakValue = 2; static const int kNodeStateIsPendingValue = 3; static const int kFirstNonstringType = 0x40; static const int kOddballType = 0x43; static const int kForeignType = 0x46; static const int kJSSpecialApiObjectType = 0x410; static const int kJSApiObjectType = 0x420; static const int kJSObjectType = 0x421; static const int kUndefinedOddballKind = 5; static const int kNullOddballKind = 3; // Constants used by PropertyCallbackInfo to check if we should throw when an // error occurs. static const int kThrowOnError = 0; static const int kDontThrow = 1; static const int kInferShouldThrowMode = 2; // Soft limit for AdjustAmountofExternalAllocatedMemory. Trigger an // incremental GC once the external memory reaches this limit. static constexpr int kExternalAllocationSoftLimit = 64 * 1024 * 1024; #ifdef V8_MAP_PACKING static const uintptr_t kMapWordMetadataMask = 0xffffULL << 48; // The lowest two bits of mapwords are always `0b10` static const uintptr_t kMapWordSignature = 0b10; // XORing a (non-compressed) map with this mask ensures that the two // low-order bits are 0b10. The 0 at the end makes this look like a Smi, // although real Smis have all lower 32 bits unset. We only rely on these // values passing as Smis in very few places. static const int kMapWordXorMask = 0b11; #endif V8_EXPORT static void CheckInitializedImpl(v8::Isolate* isolate); V8_INLINE static void CheckInitialized(v8::Isolate* isolate) { #ifdef V8_ENABLE_CHECKS CheckInitializedImpl(isolate); #endif } V8_INLINE static bool HasHeapObjectTag(const internal::Address value) { return (value & kHeapObjectTagMask) == static_cast
(kHeapObjectTag); } V8_INLINE static int SmiValue(const internal::Address value) { return PlatformSmiTagging::SmiToInt(value); } V8_INLINE static constexpr internal::Address IntToSmi(int value) { return internal::IntToSmi(value); } V8_INLINE static constexpr bool IsValidSmi(intptr_t value) { return PlatformSmiTagging::IsValidSmi(value); } V8_INLINE static int GetInstanceType(const internal::Address obj) { typedef internal::Address A; A map = ReadTaggedPointerField(obj, kHeapObjectMapOffset); #ifdef V8_MAP_PACKING map = UnpackMapWord(map); #endif return ReadRawField(map, kMapInstanceTypeOffset); } V8_INLINE static int GetOddballKind(const internal::Address obj) { return SmiValue(ReadTaggedSignedField(obj, kOddballKindOffset)); } V8_INLINE static bool IsExternalTwoByteString(int instance_type) { int representation = (instance_type & kFullStringRepresentationMask); return representation == kExternalTwoByteRepresentationTag; } V8_INLINE static uint8_t GetNodeFlag(internal::Address* obj, int shift) { uint8_t* addr = reinterpret_cast(obj) + kNodeFlagsOffset; return *addr & static_cast(1U << shift); } V8_INLINE static void UpdateNodeFlag(internal::Address* obj, bool value, int shift) { uint8_t* addr = reinterpret_cast(obj) + kNodeFlagsOffset; uint8_t mask = static_cast(1U << shift); *addr = static_cast((*addr & ~mask) | (value << shift)); } V8_INLINE static uint8_t GetNodeState(internal::Address* obj) { uint8_t* addr = reinterpret_cast(obj) + kNodeFlagsOffset; return *addr & kNodeStateMask; } V8_INLINE static void UpdateNodeState(internal::Address* obj, uint8_t value) { uint8_t* addr = reinterpret_cast(obj) + kNodeFlagsOffset; *addr = static_cast((*addr & ~kNodeStateMask) | value); } V8_INLINE static void SetEmbedderData(v8::Isolate* isolate, uint32_t slot, void* data) { internal::Address addr = reinterpret_cast(isolate) + kIsolateEmbedderDataOffset + slot * kApiSystemPointerSize; *reinterpret_cast(addr) = data; } V8_INLINE static void* GetEmbedderData(const v8::Isolate* isolate, uint32_t slot) { internal::Address addr = reinterpret_cast(isolate) + kIsolateEmbedderDataOffset + slot * kApiSystemPointerSize; return *reinterpret_cast(addr); } V8_INLINE static internal::Address* GetRoot(v8::Isolate* isolate, int index) { internal::Address addr = reinterpret_cast(isolate) + kIsolateRootsOffset + index * kApiSystemPointerSize; return reinterpret_cast(addr); } template V8_INLINE static T ReadRawField(internal::Address heap_object_ptr, int offset) { internal::Address addr = heap_object_ptr + offset - kHeapObjectTag; #ifdef V8_COMPRESS_POINTERS if (sizeof(T) > kApiTaggedSize) { // TODO(ishell, v8:8875): When pointer compression is enabled 8-byte size // fields (external pointers, doubles and BigInt data) are only // kTaggedSize aligned so we have to use unaligned pointer friendly way of // accessing them in order to avoid undefined behavior in C++ code. T r; memcpy(&r, reinterpret_cast(addr), sizeof(T)); return r; } #endif return *reinterpret_cast(addr); } V8_INLINE static internal::Address ReadTaggedPointerField( internal::Address heap_object_ptr, int offset) { #ifdef V8_COMPRESS_POINTERS uint32_t value = ReadRawField(heap_object_ptr, offset); internal::Address base = GetPtrComprCageBaseFromOnHeapAddress(heap_object_ptr); return base + static_cast(static_cast(value)); #else return ReadRawField(heap_object_ptr, offset); #endif } V8_INLINE static internal::Address ReadTaggedSignedField( internal::Address heap_object_ptr, int offset) { #ifdef V8_COMPRESS_POINTERS uint32_t value = ReadRawField(heap_object_ptr, offset); return static_cast(static_cast(value)); #else return ReadRawField(heap_object_ptr, offset); #endif } V8_INLINE static internal::Isolate* GetIsolateForHeapSandbox( internal::Address obj) { #ifdef V8_HEAP_SANDBOX return internal::IsolateFromNeverReadOnlySpaceObject(obj); #else // Not used in non-sandbox mode. return nullptr; #endif } V8_INLINE static Address DecodeExternalPointer( const Isolate* isolate, ExternalPointer_t encoded_pointer, ExternalPointerTag tag) { #ifdef V8_HEAP_SANDBOX return internal::DecodeExternalPointerImpl(isolate, encoded_pointer, tag); #else return encoded_pointer; #endif } V8_INLINE static internal::Address ReadExternalPointerField( internal::Isolate* isolate, internal::Address heap_object_ptr, int offset, ExternalPointerTag tag) { #ifdef V8_HEAP_SANDBOX internal::ExternalPointer_t encoded_value = ReadRawField(heap_object_ptr, offset); // We currently have to treat zero as nullptr in embedder slots. return encoded_value ? DecodeExternalPointer(isolate, encoded_value, tag) : 0; #else return ReadRawField
(heap_object_ptr, offset); #endif } #ifdef V8_COMPRESS_POINTERS // See v8:7703 or src/ptr-compr.* for details about pointer compression. static constexpr size_t kPtrComprCageReservationSize = size_t{1} << 32; static constexpr size_t kPtrComprCageBaseAlignment = size_t{1} << 32; V8_INLINE static internal::Address GetPtrComprCageBaseFromOnHeapAddress( internal::Address addr) { return addr & -static_cast(kPtrComprCageBaseAlignment); } V8_INLINE static internal::Address DecompressTaggedAnyField( internal::Address heap_object_ptr, uint32_t value) { internal::Address base = GetPtrComprCageBaseFromOnHeapAddress(heap_object_ptr); return base + static_cast(static_cast(value)); } #endif // V8_COMPRESS_POINTERS }; // Only perform cast check for types derived from v8::Data since // other types do not implement the Cast method. template struct CastCheck { template static void Perform(T* data); }; template <> template void CastCheck::Perform(T* data) { T::Cast(data); } template <> template void CastCheck::Perform(T* data) {} template V8_INLINE void PerformCastCheck(T* data) { CastCheck::value && !std::is_same>::value>::Perform(data); } // A base class for backing stores, which is needed due to vagaries of // how static casts work with std::shared_ptr. class BackingStoreBase {}; } // namespace internal V8_EXPORT bool CopyAndConvertArrayToCppBufferInt32(Local src, int32_t* dst, uint32_t max_length); V8_EXPORT bool CopyAndConvertArrayToCppBufferFloat64(Local src, double* dst, uint32_t max_length); } // namespace v8 #endif // INCLUDE_V8_INTERNAL_H_