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//===-- hwasan_fuchsia.cpp --------------------------------------*- C++ -*-===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
/// \file
/// This file is a part of HWAddressSanitizer and contains Fuchsia-specific
/// code.
#include "sanitizer_common/sanitizer_fuchsia.h"
#include <zircon/features.h>
#include <zircon/syscalls.h>
#include "hwasan.h"
#include "hwasan_interface_internal.h"
#include "hwasan_report.h"
#include "hwasan_thread.h"
#include "hwasan_thread_list.h"
// This TLS variable contains the location of the stack ring buffer and can be
// used to always find the hwasan thread object associated with the current
// running thread.
THREADLOCAL uptr __hwasan_tls;
namespace __hwasan {
bool InitShadow() {
CHECK_NE(__sanitizer::ShadowBounds.shadow_limit, 0);
// These variables are used by MemIsShadow for asserting we have a correct
// shadow address. On Fuchsia, we only have one region of shadow, so the
// bounds of Low shadow can be zero while High shadow represents the true
// bounds. Note that these are inclusive ranges.
kLowShadowStart = 0;
kLowShadowEnd = 0;
kHighShadowStart = __sanitizer::ShadowBounds.shadow_base;
kHighShadowEnd = __sanitizer::ShadowBounds.shadow_limit - 1;
return true;
bool MemIsApp(uptr p) {
CHECK(GetTagFromPointer(p) == 0);
return __sanitizer::ShadowBounds.shadow_limit <= p &&
p <= (__sanitizer::ShadowBounds.memory_limit - 1);
// These are known parameters passed to the hwasan runtime on thread creation.
struct Thread::InitState {
uptr stack_bottom, stack_top;
static void FinishThreadInitialization(Thread *thread);
void InitThreads() {
// This is the minimal alignment needed for the storage where hwasan threads
// and their stack ring buffers are placed. This alignment is necessary so the
// stack ring buffer can perform a simple calculation to get the next element
// in the RB. The instructions for this calculation are emitted by the
// compiler. (Full explanation in hwasan_thread_list.h.)
uptr alloc_size = UINT64_C(1) << kShadowBaseAlignment;
uptr thread_start = reinterpret_cast<uptr>(
MmapAlignedOrDieOnFatalError(alloc_size, alloc_size, __func__));
InitThreadList(thread_start, alloc_size);
// Create the hwasan thread object for the current (main) thread. Stack info
// for this thread is known from information passed via
// __sanitizer_startup_hook.
const Thread::InitState state = {
.stack_bottom = __sanitizer::MainThreadStackBase,
.stack_top =
__sanitizer::MainThreadStackBase + __sanitizer::MainThreadStackSize,
uptr *GetCurrentThreadLongPtr() { return &__hwasan_tls; }
// This is called from the parent thread before the new thread is created. Here
// we can propagate known info like the stack bounds to Thread::Init before
// jumping into the thread. We cannot initialize the stack ring buffer yet since
// we have not entered the new thread.
static void *BeforeThreadCreateHook(uptr user_id, bool detached,
const char *name, uptr stack_bottom,
uptr stack_size) {
const Thread::InitState state = {
.stack_bottom = stack_bottom,
.stack_top = stack_bottom + stack_size,
return hwasanThreadList().CreateCurrentThread(&state);
// This sets the stack top and bottom according to the InitState passed to
// CreateCurrentThread above.
void Thread::InitStackAndTls(const InitState *state) {
CHECK_NE(state->stack_bottom, 0);
CHECK_NE(state->stack_top, 0);
stack_bottom_ = state->stack_bottom;
stack_top_ = state->stack_top;
tls_end_ = tls_begin_ = 0;
// This is called after creating a new thread with the pointer returned by
// BeforeThreadCreateHook. We are still in the creating thread and should check
// if it was actually created correctly.
static void ThreadCreateHook(void *hook, bool aborted) {
Thread *thread = static_cast<Thread *>(hook);
if (!aborted) {
// The thread was created successfully.
// ThreadStartHook can already be running in the new thread.
} else {
// The thread wasn't created after all.
// Clean up everything we set up in BeforeThreadCreateHook.
// This is called in the newly-created thread before it runs anything else,
// with the pointer returned by BeforeThreadCreateHook (above). Here we can
// setup the stack ring buffer.
static void ThreadStartHook(void *hook, thrd_t self) {
Thread *thread = static_cast<Thread *>(hook);
// This is the function that sets up the stack ring buffer and enables us to use
// GetCurrentThread. This function should only be called while IN the thread
// that we want to create the hwasan thread object for so __hwasan_tls can be
// properly referenced.
static void FinishThreadInitialization(Thread *thread) {
CHECK_NE(thread, nullptr);
// The ring buffer is located immediately before the thread object.
uptr stack_buffer_size = hwasanThreadList().GetRingBufferSize();
uptr stack_buffer_start = reinterpret_cast<uptr>(thread) - stack_buffer_size;
thread->InitStackRingBuffer(stack_buffer_start, stack_buffer_size);
static void ThreadExitHook(void *hook, thrd_t self) {
Thread *thread = static_cast<Thread *>(hook);
uptr TagMemoryAligned(uptr p, uptr size, tag_t tag) {
CHECK(IsAligned(p, kShadowAlignment));
CHECK(IsAligned(size, kShadowAlignment));
__sanitizer_fill_shadow(p, size, tag,
return AddTagToPointer(p, tag);
// Not implemented because Fuchsia does not use signal handlers.
void HwasanOnDeadlySignal(int signo, void *info, void *context) {}
// Not implemented because Fuchsia does not use interceptors.
void InitializeInterceptors() {}
// Not implemented because this is only relevant for Android.
void AndroidTestTlsSlot() {}
// TSD was normally used on linux as a means of calling the hwasan thread exit
// handler passed to pthread_key_create. This is not needed on Fuchsia because
// we will be using __sanitizer_thread_exit_hook.
void HwasanTSDInit() {}
void HwasanTSDThreadInit() {}
// On linux, this just would call `atexit(HwasanAtExit)`. The functions in
// HwasanAtExit are unimplemented for Fuchsia and effectively no-ops, so this
// function is unneeded.
void InstallAtExitHandler() {}
void HwasanInstallAtForkHandler() {}
void InitializeOsSupport() {
#ifdef __aarch64__
uint32_t features = 0;
CHECK_EQ(zx_system_get_features(ZX_FEATURE_KIND_ADDRESS_TAGGING, &features),
flags()->fail_without_syscall_abi) {
"FATAL: HWAddressSanitizer requires "
} // namespace __hwasan
extern "C" {
void *__sanitizer_before_thread_create_hook(thrd_t thread, bool detached,
const char *name, void *stack_base,
size_t stack_size) {
return __hwasan::BeforeThreadCreateHook(
reinterpret_cast<uptr>(thread), detached, name,
reinterpret_cast<uptr>(stack_base), stack_size);
void __sanitizer_thread_create_hook(void *hook, thrd_t thread, int error) {
__hwasan::ThreadCreateHook(hook, error != thrd_success);
void __sanitizer_thread_start_hook(void *hook, thrd_t self) {
__hwasan::ThreadStartHook(hook, reinterpret_cast<uptr>(self));
void __sanitizer_thread_exit_hook(void *hook, thrd_t self) {
__hwasan::ThreadExitHook(hook, self);
} // extern "C"