// Copyright 2018 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_EXECUTION_ISOLATE_DATA_H_ #define V8_EXECUTION_ISOLATE_DATA_H_ #include "src/builtins/builtins.h" #include "src/codegen/constants-arch.h" #include "src/codegen/external-reference-table.h" #include "src/execution/external-pointer-table.h" #include "src/execution/stack-guard.h" #include "src/execution/thread-local-top.h" #include "src/roots/roots.h" #include "src/utils/utils.h" #include "testing/gtest/include/gtest/gtest_prod.h" namespace v8 { namespace internal { class Isolate; // This class contains a collection of data accessible from both C++ runtime // and compiled code (including assembly stubs, builtins, interpreter bytecode // handlers and optimized code). // In particular, it contains pointer to the V8 heap roots table, external // reference table and builtins array. // The compiled code accesses the isolate data fields indirectly via the root // register. class IsolateData final { public: explicit IsolateData(Isolate* isolate) : stack_guard_(isolate) {} static constexpr intptr_t kIsolateRootBias = kRootRegisterBias; // The value of the kRootRegister. Address isolate_root() const { return reinterpret_cast<Address>(this) + kIsolateRootBias; } // Root-register-relative offset of the roots table. static constexpr int roots_table_offset() { return kRootsTableOffset - kIsolateRootBias; } // Root-register-relative offset of the given root table entry. static constexpr int root_slot_offset(RootIndex root_index) { return roots_table_offset() + RootsTable::offset_of(root_index); } // Root-register-relative offset of the external reference table. static constexpr int external_reference_table_offset() { return kExternalReferenceTableOffset - kIsolateRootBias; } // Root-register-relative offset of the builtin entry table. static constexpr int builtin_entry_table_offset() { return kBuiltinEntryTableOffset - kIsolateRootBias; } static constexpr int builtin_entry_slot_offset(Builtins::Name builtin_index) { CONSTEXPR_DCHECK(Builtins::IsBuiltinId(builtin_index)); return builtin_entry_table_offset() + builtin_index * kSystemPointerSize; } // Root-register-relative offset of the builtins table. static constexpr int builtins_table_offset() { return kBuiltinsTableOffset - kIsolateRootBias; } static constexpr int fast_c_call_caller_fp_offset() { return kFastCCallCallerFPOffset - kIsolateRootBias; } static constexpr int fast_c_call_caller_pc_offset() { return kFastCCallCallerPCOffset - kIsolateRootBias; } // Root-register-relative offset of the given builtin table entry. // TODO(ishell): remove in favour of typified id version. static int builtin_slot_offset(int builtin_index) { DCHECK(Builtins::IsBuiltinId(builtin_index)); return builtins_table_offset() + builtin_index * kSystemPointerSize; } // Root-register-relative offset of the builtin table entry. static int builtin_slot_offset(Builtins::Name id) { return builtins_table_offset() + id * kSystemPointerSize; } // The FP and PC that are saved right before TurboAssembler::CallCFunction. Address* fast_c_call_caller_fp_address() { return &fast_c_call_caller_fp_; } Address* fast_c_call_caller_pc_address() { return &fast_c_call_caller_pc_; } StackGuard* stack_guard() { return &stack_guard_; } uint8_t* stack_is_iterable_address() { return &stack_is_iterable_; } Address fast_c_call_caller_fp() { return fast_c_call_caller_fp_; } Address fast_c_call_caller_pc() { return fast_c_call_caller_pc_; } uint8_t stack_is_iterable() { return stack_is_iterable_; } // Returns true if this address points to data stored in this instance. // If it's the case then the value can be accessed indirectly through the // root register. bool contains(Address address) const { STATIC_ASSERT(std::is_unsigned<Address>::value); Address start = reinterpret_cast<Address>(this); return (address - start) < sizeof(*this); } ThreadLocalTop& thread_local_top() { return thread_local_top_; } ThreadLocalTop const& thread_local_top() const { return thread_local_top_; } RootsTable& roots() { return roots_; } const RootsTable& roots() const { return roots_; } ExternalReferenceTable* external_reference_table() { return &external_reference_table_; } Address* builtin_entry_table() { return builtin_entry_table_; } Address* builtins() { return builtins_; } private: // Static layout definition. // // Note: The location of fields within IsolateData is significant. The // closer they are to the value of kRootRegister (i.e.: isolate_root()), the // cheaper it is to access them. See also: https://crbug.com/993264. // The recommend guideline is to put frequently-accessed fields close to the // beginning of IsolateData. #define FIELDS(V) \ V(kEmbedderDataOffset, Internals::kNumIsolateDataSlots* kSystemPointerSize) \ V(kFastCCallCallerFPOffset, kSystemPointerSize) \ V(kFastCCallCallerPCOffset, kSystemPointerSize) \ V(kStackGuardOffset, StackGuard::kSizeInBytes) \ V(kRootsTableOffset, RootsTable::kEntriesCount* kSystemPointerSize) \ V(kExternalReferenceTableOffset, ExternalReferenceTable::kSizeInBytes) \ V(kThreadLocalTopOffset, ThreadLocalTop::kSizeInBytes) \ V(kBuiltinEntryTableOffset, Builtins::builtin_count* kSystemPointerSize) \ V(kBuiltinsTableOffset, Builtins::builtin_count* kSystemPointerSize) \ FIELDS_HEAP_SANDBOX(V) \ V(kStackIsIterableOffset, kUInt8Size) \ /* This padding aligns IsolateData size by 8 bytes. */ \ V(kPaddingOffset, \ 8 + RoundUp<8>(static_cast<int>(kPaddingOffset)) - kPaddingOffset) \ /* Total size. */ \ V(kSize, 0) #ifdef V8_HEAP_SANDBOX #define FIELDS_HEAP_SANDBOX(V) \ V(kExternalPointerTableOffset, kSystemPointerSize * 3) #else #define FIELDS_HEAP_SANDBOX(V) #endif // V8_HEAP_SANDBOX DEFINE_FIELD_OFFSET_CONSTANTS(0, FIELDS) #undef FIELDS // These fields are accessed through the API, offsets must be kept in sync // with v8::internal::Internals (in include/v8-internal.h) constants. // The layout consitency is verified in Isolate::CheckIsolateLayout() using // runtime checks. void* embedder_data_[Internals::kNumIsolateDataSlots] = {}; // Stores the state of the caller for TurboAssembler::CallCFunction so that // the sampling CPU profiler can iterate the stack during such calls. These // are stored on IsolateData so that they can be stored to with only one move // instruction in compiled code. Address fast_c_call_caller_fp_ = kNullAddress; Address fast_c_call_caller_pc_ = kNullAddress; // Fields related to the system and JS stack. In particular, this contains the // stack limit used by stack checks in generated code. StackGuard stack_guard_; RootsTable roots_; ExternalReferenceTable external_reference_table_; ThreadLocalTop thread_local_top_; // The entry points for all builtins. This corresponds to // Code::InstructionStart() for each Code object in the builtins table below. // The entry table is in IsolateData for easy access through kRootRegister. Address builtin_entry_table_[Builtins::builtin_count] = {}; // The entries in this array are tagged pointers to Code objects. Address builtins_[Builtins::builtin_count] = {}; // Table containing pointers to external objects. #ifdef V8_HEAP_SANDBOX ExternalPointerTable external_pointer_table_; #endif // Whether the SafeStackFrameIterator can successfully iterate the current // stack. Only valid values are 0 or 1. uint8_t stack_is_iterable_ = 1; // Ensure the size is 8-byte aligned in order to make alignment of the field // following the IsolateData field predictable. This solves the issue with // C++ compilers for 32-bit platforms which are not consistent at aligning // int64_t fields. // In order to avoid dealing with zero-size arrays the padding size is always // in the range [8, 15). STATIC_ASSERT(kPaddingOffsetEnd + 1 - kPaddingOffset >= 8); char padding_[kPaddingOffsetEnd + 1 - kPaddingOffset]; V8_INLINE static void AssertPredictableLayout(); friend class Isolate; friend class Heap; FRIEND_TEST(HeapTest, ExternalLimitDefault); FRIEND_TEST(HeapTest, ExternalLimitStaysAboveDefaultForExplicitHandling); DISALLOW_COPY_AND_ASSIGN(IsolateData); }; // IsolateData object must have "predictable" layout which does not change when // cross-compiling to another platform. Otherwise there may be compatibility // issues because of different compilers used for snapshot generator and // actual V8 code. void IsolateData::AssertPredictableLayout() { STATIC_ASSERT(std::is_standard_layout<RootsTable>::value); STATIC_ASSERT(std::is_standard_layout<ThreadLocalTop>::value); STATIC_ASSERT(std::is_standard_layout<ExternalReferenceTable>::value); STATIC_ASSERT(std::is_standard_layout<IsolateData>::value); STATIC_ASSERT(offsetof(IsolateData, roots_) == kRootsTableOffset); STATIC_ASSERT(offsetof(IsolateData, external_reference_table_) == kExternalReferenceTableOffset); STATIC_ASSERT(offsetof(IsolateData, thread_local_top_) == kThreadLocalTopOffset); STATIC_ASSERT(offsetof(IsolateData, builtins_) == kBuiltinsTableOffset); STATIC_ASSERT(offsetof(IsolateData, fast_c_call_caller_fp_) == kFastCCallCallerFPOffset); STATIC_ASSERT(offsetof(IsolateData, fast_c_call_caller_pc_) == kFastCCallCallerPCOffset); STATIC_ASSERT(offsetof(IsolateData, stack_guard_) == kStackGuardOffset); #ifdef V8_HEAP_SANDBOX STATIC_ASSERT(offsetof(IsolateData, external_pointer_table_) == kExternalPointerTableOffset); #endif STATIC_ASSERT(offsetof(IsolateData, stack_is_iterable_) == kStackIsIterableOffset); STATIC_ASSERT(sizeof(IsolateData) == IsolateData::kSize); } } // namespace internal } // namespace v8 #endif // V8_EXECUTION_ISOLATE_DATA_H_