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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.
#if !V8_ENABLE_WEBASSEMBLY
#error This header should only be included if WebAssembly is enabled.
#endif // !V8_ENABLE_WEBASSEMBLY
#ifndef V8_WASM_CODE_SPACE_ACCESS_H_
#define V8_WASM_CODE_SPACE_ACCESS_H_
#include "src/base/build_config.h"
#include "src/base/macros.h"
#include "src/common/globals.h"
namespace v8 {
namespace internal {
#if defined(V8_OS_MACOSX) && defined(V8_HOST_ARCH_ARM64)
// Ignoring this warning is considered better than relying on
// __builtin_available.
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wunguarded-availability-new"
inline void SwitchMemoryPermissionsToWritable() {
pthread_jit_write_protect_np(0);
}
inline void SwitchMemoryPermissionsToExecutable() {
pthread_jit_write_protect_np(1);
}
#pragma clang diagnostic pop
namespace wasm {
class V8_NODISCARD CodeSpaceWriteScope {
public:
// TODO(jkummerow): Background threads could permanently stay in
// writable mode; only the main thread has to switch back and forth.
CodeSpaceWriteScope() {
if (code_space_write_nesting_level_ == 0) {
SwitchMemoryPermissionsToWritable();
}
code_space_write_nesting_level_++;
}
~CodeSpaceWriteScope() {
code_space_write_nesting_level_--;
if (code_space_write_nesting_level_ == 0) {
SwitchMemoryPermissionsToExecutable();
}
}
private:
static thread_local int code_space_write_nesting_level_;
};
#define CODE_SPACE_WRITE_SCOPE CodeSpaceWriteScope _write_access_;
} // namespace wasm
#else // Not Mac-on-arm64.
// Nothing to do, we map code memory with rwx permissions.
inline void SwitchMemoryPermissionsToWritable() {}
inline void SwitchMemoryPermissionsToExecutable() {}
#define CODE_SPACE_WRITE_SCOPE
#endif // V8_OS_MACOSX && V8_HOST_ARCH_ARM64
} // namespace internal
} // namespace v8
#endif // V8_WASM_CODE_SPACE_ACCESS_H_
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