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// Copyright 2021 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.
#include "src/wasm/code-space-access.h"
#include "src/wasm/wasm-code-manager.h"
#include "src/wasm/wasm-engine.h"
namespace v8 {
namespace internal {
namespace wasm {
thread_local int CodeSpaceWriteScope::code_space_write_nesting_level_ = 0;
// The thread-local counter (above) is only valid if a single thread only works
// on one module at a time. This second thread-local checks that.
#if defined(DEBUG) && !V8_HAS_PTHREAD_JIT_WRITE_PROTECT
thread_local NativeModule* CodeSpaceWriteScope::current_native_module_ =
nullptr;
#endif
// TODO(jkummerow): Background threads could permanently stay in
// writable mode; only the main thread has to switch back and forth.
#if V8_HAS_PTHREAD_JIT_WRITE_PROTECT
CodeSpaceWriteScope::CodeSpaceWriteScope(NativeModule*) {
#else // !V8_HAS_PTHREAD_JIT_WRITE_PROTECT
CodeSpaceWriteScope::CodeSpaceWriteScope(NativeModule* native_module)
: native_module_(native_module) {
#ifdef DEBUG
if (code_space_write_nesting_level_ == 0) {
current_native_module_ = native_module;
}
DCHECK_EQ(native_module, current_native_module_);
#endif // DEBUG
#endif // !V8_HAS_PTHREAD_JIT_WRITE_PROTECT
if (code_space_write_nesting_level_ == 0) SetWritable();
code_space_write_nesting_level_++;
}
CodeSpaceWriteScope::~CodeSpaceWriteScope() {
code_space_write_nesting_level_--;
if (code_space_write_nesting_level_ == 0) SetExecutable();
}
#if V8_HAS_PTHREAD_JIT_WRITE_PROTECT
// Ignoring this warning is considered better than relying on
// __builtin_available.
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wunguarded-availability-new"
void CodeSpaceWriteScope::SetWritable() const {
pthread_jit_write_protect_np(0);
}
void CodeSpaceWriteScope::SetExecutable() const {
pthread_jit_write_protect_np(1);
}
#pragma clang diagnostic pop
#else // !V8_HAS_PTHREAD_JIT_WRITE_PROTECT
void CodeSpaceWriteScope::SetWritable() const {
DCHECK_NOT_NULL(native_module_);
auto* code_manager = GetWasmCodeManager();
if (code_manager->MemoryProtectionKeysEnabled()) {
code_manager->SetThreadWritable(true);
} else if (FLAG_wasm_write_protect_code_memory) {
native_module_->AddWriter();
}
}
void CodeSpaceWriteScope::SetExecutable() const {
auto* code_manager = GetWasmCodeManager();
if (code_manager->MemoryProtectionKeysEnabled()) {
DCHECK(FLAG_wasm_memory_protection_keys);
code_manager->SetThreadWritable(false);
} else if (FLAG_wasm_write_protect_code_memory) {
native_module_->RemoveWriter();
}
}
#endif // !V8_HAS_PTHREAD_JIT_WRITE_PROTECT
} // namespace wasm
} // namespace internal
} // namespace v8
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