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// Copyright 2019 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_THREAD_LOCAL_TOP_H_
#define V8_EXECUTION_THREAD_LOCAL_TOP_H_
#include "src/common/globals.h"
#include "src/execution/thread-id.h"
#include "src/objects/contexts.h"
#include "src/utils/utils.h"
namespace v8 {
class TryCatch;
namespace internal {
class ExternalCallbackScope;
class Isolate;
class PromiseOnStack;
class Simulator;
class ThreadLocalTop {
public:
// TODO(all): This is not particularly beautiful. We should probably
// refactor this to really consist of just Addresses and 32-bit
// integer fields.
static constexpr uint32_t kSizeInBytes = 24 * kSystemPointerSize;
// Does early low-level initialization that does not depend on the
// isolate being present.
ThreadLocalTop() = default;
// Initialize the thread data.
void Initialize(Isolate*);
// The top C++ try catch handler or nullptr if none are registered.
//
// This field is not guaranteed to hold an address that can be
// used for comparison with addresses into the JS stack. If such
// an address is needed, use try_catch_handler_address.
v8::TryCatch* try_catch_handler_ = nullptr;
// Get the address of the top C++ try catch handler or nullptr if
// none are registered.
//
// This method always returns an address that can be compared to
// pointers into the JavaScript stack. When running on actual
// hardware, try_catch_handler_address and TryCatchHandler return
// the same pointer. When running on a simulator with a separate JS
// stack, try_catch_handler_address returns a JS stack address that
// corresponds to the place on the JS stack where the C++ handler
// would have been if the stack were not separate.
Address try_catch_handler_address() {
return reinterpret_cast<Address>(
v8::TryCatch::JSStackComparableAddress(try_catch_handler_));
}
// Call depth represents nested v8 api calls. Instead of storing the nesting
// level as an integer, we store the stack height of the last API entry. This
// additional information is used when we decide whether to trigger a debug
// break at a function entry.
template <typename Scope>
void IncrementCallDepth(Scope* stack_allocated_scope) {
stack_allocated_scope->previous_stack_height_ = last_api_entry_;
#if defined(USE_SIMULATOR) || defined(V8_USE_ADDRESS_SANITIZER)
StoreCurrentStackPosition();
#else
last_api_entry_ = reinterpret_cast<i::Address>(stack_allocated_scope);
#endif
}
#if defined(USE_SIMULATOR) || defined(V8_USE_ADDRESS_SANITIZER)
void StoreCurrentStackPosition();
#endif
template <typename Scope>
void DecrementCallDepth(Scope* stack_allocated_scope) {
last_api_entry_ = stack_allocated_scope->previous_stack_height_;
}
bool CallDepthIsZero() const { return last_api_entry_ == kNullAddress; }
void Free();
Isolate* isolate_ = nullptr;
// The context where the current execution method is created and for variable
// lookups.
// TODO(3770): This field is read/written from generated code, so it would
// be cleaner to make it an "Address raw_context_", and construct a Context
// object in the getter. Same for {pending_handler_context_} below. In the
// meantime, assert that the memory layout is the same.
STATIC_ASSERT(sizeof(Context) == kSystemPointerSize);
Context context_;
ThreadId thread_id_ = ThreadId::Invalid();
Object pending_exception_;
// Communication channel between Isolate::FindHandler and the CEntry.
Context pending_handler_context_;
Address pending_handler_entrypoint_ = kNullAddress;
Address pending_handler_constant_pool_ = kNullAddress;
Address pending_handler_fp_ = kNullAddress;
Address pending_handler_sp_ = kNullAddress;
Address last_api_entry_ = kNullAddress;
// Communication channel between Isolate::Throw and message consumers.
Object pending_message_obj_;
bool rethrowing_message_ = false;
// Use a separate value for scheduled exceptions to preserve the
// invariants that hold about pending_exception. We may want to
// unify them later.
bool external_caught_exception_ = false;
Object scheduled_exception_;
// Stack.
// The frame pointer of the top c entry frame.
Address c_entry_fp_ = kNullAddress;
// Try-blocks are chained through the stack.
Address handler_ = kNullAddress;
// C function that was called at c entry.
Address c_function_ = kNullAddress;
// Throwing an exception may cause a Promise rejection. For this purpose
// we keep track of a stack of nested promises and the corresponding
// try-catch handlers.
PromiseOnStack* promise_on_stack_ = nullptr;
// Simulator field is always present to get predictable layout.
Simulator* simulator_ = nullptr;
// The stack pointer of the bottom JS entry frame.
Address js_entry_sp_ = kNullAddress;
// The external callback we're currently in.
ExternalCallbackScope* external_callback_scope_ = nullptr;
StateTag current_vm_state_ = EXTERNAL;
// Call back function to report unsafe JS accesses.
v8::FailedAccessCheckCallback failed_access_check_callback_ = nullptr;
// Address of the thread-local "thread in wasm" flag.
Address thread_in_wasm_flag_address_ = kNullAddress;
};
} // namespace internal
} // namespace v8
#endif // V8_EXECUTION_THREAD_LOCAL_TOP_H_
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