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// Copyright 2023 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef COMPONENTS_GWP_ASAN_CLIENT_THREAD_LOCAL_STATE_H_
#define COMPONENTS_GWP_ASAN_CLIENT_THREAD_LOCAL_STATE_H_
#include "base/check.h"
#include "base/compiler_specific.h"
#include "build/build_config.h"
#if BUILDFLAG(IS_APPLE) || BUILDFLAG(IS_ANDROID)
// On macOS and Android (before Q), the first use of a `thread_local` variable
// on a new thread will cause an allocation, leading to infinite recursion.
// Also, `thread_local` goes through `emutls` on Android, which is slower than
// `pthread_getspecific`.
#define THREAD_LOCAL_STATE_USES_PARTITION_ALLOC_TLS
#elif BUILDFLAG(IS_POSIX) && defined(COMPONENT_BUILD)
// On POSIX platforms when built as component build, use of a `thread_local`
// variable may or may not cause a call to `free()` depending on an
// implementation of TLS. At least in case of glibc/glibc/elf/dl-tls.c,
// `_dl_update_slotinfo()` calls `free()` (as of Apr 2024).
//
// This is a problem for LUD (Lightweight UaF Detector) and ELUD (Extreme LUD)
// as they call `SamplingState::Sample()` inside `free()`, which leads to
// infinite recursion. (See also https://crbug.com/332234169)
//
// Fortunately, statically-linked executables (non-component builds) do not hit
// the problem because they use the "local-exec" model of TLS (i.e. do not call
// any library function).
#define THREAD_LOCAL_STATE_USES_PARTITION_ALLOC_TLS
#endif
#if defined(THREAD_LOCAL_STATE_USES_PARTITION_ALLOC_TLS)
#include "partition_alloc/partition_tls.h"
#endif
namespace gwp_asan::internal {
// Class that provides the optimal thread-local storage implementation depending
// on the platform.
template <typename T>
class ThreadLocalState {
protected:
static void InitIfNeeded() {
#if defined(THREAD_LOCAL_STATE_USES_PARTITION_ALLOC_TLS)
if (!tls_key_) {
partition_alloc::internal::PartitionTlsCreate(&tls_key_, nullptr);
}
#endif
}
#if !defined(THREAD_LOCAL_STATE_USES_PARTITION_ALLOC_TLS)
ALWAYS_INLINE static uintptr_t GetState() { return state_; }
ALWAYS_INLINE static void SetState(uintptr_t value) { state_ = value; }
private:
static thread_local uintptr_t state_
__attribute__((tls_model("initial-exec")));
#else
ALWAYS_INLINE static uintptr_t GetState() {
DCHECK(tls_key_);
return reinterpret_cast<uintptr_t>(
partition_alloc::internal::PartitionTlsGet(tls_key_));
}
ALWAYS_INLINE static void SetState(uintptr_t value) {
DCHECK(tls_key_);
partition_alloc::internal::PartitionTlsSet(tls_key_,
reinterpret_cast<void*>(value));
}
private:
static partition_alloc::internal::PartitionTlsKey tls_key_;
#endif
};
#if !defined(THREAD_LOCAL_STATE_USES_PARTITION_ALLOC_TLS)
template <typename T>
thread_local uintptr_t ThreadLocalState<T>::state_ = 0;
#else
template <typename T>
partition_alloc::internal::PartitionTlsKey ThreadLocalState<T>::tls_key_ = 0;
#endif
} // namespace gwp_asan::internal
#endif // COMPONENTS_GWP_ASAN_CLIENT_THREAD_LOCAL_STATE_H_
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