[hwasan] Add a (almost) no-interceptor mode.

[eugenis]

Summary

The idea behind this change is to allow sanitization of libc. We are prototyping on Bionic,
but the tool interface will be general enough (or at least generalizable) to support any other libc.

When libc depends on libclang_rt.hwasan, the latter can not interpose libc functions.
In fact, majority of interceptors become unnecessary when libc code is instrumented.

This change gets rid of most hwasan interceptors and provides interface for libc to notify
hwasan about thread creation and destruction events. Some interceptors (pthread_create)
are kept under #ifdef to enable testing with uninstrumented libc. They are expressed in
terms of the new libc interface.

The new cmake switch, COMPILER_RT_HWASAN_WITH_INTERCEPTORS, ON by default, builds testing
version of the library with the aforementioned pthread_create interceptor.
With the OFF setting, the library becomes more of a libc plugin.

[kcc]

LGTM,
but please consider moving the code around (in a separate CL) to reduce the number of #ifdefs

[eugenis]

Sure. Eventually the entire hwasan_interceptors.cc would be under one big ifdef, if things go as planned.

compiler-rt/trunk/CMakeLists.txt

if (NOT COMPILER_RT_ASAN_SHADOW_SCALE STREQUAL "")
   set(COMPILER_RT_ASAN_SHADOW_SCALE_LLVM_FLAG
       -mllvm -asan-mapping-scale=${COMPILER_RT_ASAN_SHADOW_SCALE})
   set(COMPILER_RT_ASAN_SHADOW_SCALE_DEFINITION
       ASAN_SHADOW_SCALE=${COMPILER_RT_ASAN_SHADOW_SCALE})
   set(COMPILER_RT_ASAN_SHADOW_SCALE_FLAG
       -D${COMPILER_RT_ASAN_SHADOW_SCALE_DEFINITION})
 endif()
 
+set(COMPILER_RT_HWASAN_WITH_INTERCEPTORS ON CACHE BOOLEAN
+    "Enable libc interceptors in HWASan (testing mode)")
+
 set(COMPILER_RT_BAREMETAL_BUILD OFF CACHE BOOLEAN
   "Build for a bare-metal target.")
 
 if (COMPILER_RT_STANDALONE_BUILD)
   load_llvm_config()
   if (TARGET intrinsics_gen)
     # Loading the llvm config causes this target to be imported so place it
     # under the appropriate folder in an IDE.

compiler-rt/trunk/include/sanitizer/hwasan_interface.h

#endif
 
   // Set memory tag from the current SP address to the given address to zero.
   // This is meant to annotate longjmp and other non-local jumps.
   // This function needs to know the (almost) exact destination frame address;
   // clearing shadow for the entire thread stack like __asan_handle_no_return
   // does would cause false reports.
   void __hwasan_handle_longjmp(const void *sp_dst);
 
+  // Libc hook for thread creation. Should be called in the child thread before
+  // any instrumented code.
+  void __hwasan_thread_enter();
+
+  // Libc hook for thread destruction. No instrumented code should run after
+  // this call.
+  void __hwasan_thread_exit();
+
   // Print shadow and origin for the memory range to stderr in a human-readable
   // format.
   void __hwasan_print_shadow(const volatile void *x, size_t size);
 
   int __sanitizer_posix_memalign(void **memptr, size_t alignment, size_t size);
   void * __sanitizer_memalign(size_t alignment, size_t size);
   void * __sanitizer_aligned_alloc(size_t alignment, size_t size);
   void * __sanitizer___libc_memalign(size_t alignment, size_t size);

compiler-rt/trunk/lib/hwasan/CMakeLists.txt

set(HWASAN_RTL_HEADERS
   hwasan_flags.inc
   hwasan_interface_internal.h
   hwasan_mapping.h
   hwasan_poisoning.h
   hwasan_report.h
   hwasan_thread.h)
 
 
+set(HWASAN_DEFINITIONS)
+append_list_if(COMPILER_RT_HWASAN_WITH_INTERCEPTORS HWASAN_WITH_INTERCEPTORS=1 HWASAN_DEFINITIONS)
+
 set(HWASAN_RTL_CFLAGS ${SANITIZER_COMMON_CFLAGS})
 append_rtti_flag(OFF HWASAN_RTL_CFLAGS)
 append_list_if(COMPILER_RT_HAS_FPIC_FLAG -fPIC HWASAN_RTL_CFLAGS)
 # Prevent clang from generating libc calls.
 append_list_if(COMPILER_RT_HAS_FFREESTANDING_FLAG -ffreestanding HWASAN_RTL_CFLAGS)
 
 set(HWASAN_DYNAMIC_LINK_FLAGS ${SANITIZER_COMMON_LINK_FLAGS})
 

 
 # Static runtime library.
 add_compiler_rt_component(hwasan)
 
 add_compiler_rt_object_libraries(RTHwasan
   ARCHS ${HWASAN_SUPPORTED_ARCH}
   SOURCES ${HWASAN_RTL_SOURCES}
   ADDITIONAL_HEADERS ${HWASAN_RTL_HEADERS}
-  CFLAGS ${HWASAN_RTL_CFLAGS})
+  CFLAGS ${HWASAN_RTL_CFLAGS}
+  DEFS ${HWASAN_DEFINITIONS})
 add_compiler_rt_object_libraries(RTHwasan_cxx
   ARCHS ${HWASAN_SUPPORTED_ARCH}
   SOURCES ${HWASAN_RTL_CXX_SOURCES}
   ADDITIONAL_HEADERS ${HWASAN_RTL_HEADERS}
-  CFLAGS ${HWASAN_RTL_CFLAGS})
+  CFLAGS ${HWASAN_RTL_CFLAGS}
+  DEFS ${HWASAN_DEFINITIONS})
 add_compiler_rt_object_libraries(RTHwasan_dynamic
   ARCHS ${HWASAN_SUPPORTED_ARCH}
   SOURCES ${HWASAN_RTL_SOURCES} ${HWASAN_RTL_CXX_SOURCES}
   ADDITIONAL_HEADERS ${HWASAN_RTL_HEADERS}
-  CFLAGS ${HWASAN_DYNAMIC_CFLAGS})
+  CFLAGS ${HWASAN_DYNAMIC_CFLAGS}
+  DEFS ${HWASAN_DEFINITIONS})
 
 file(WRITE ${CMAKE_CURRENT_BINARY_DIR}/dummy.cc "")
 add_compiler_rt_object_libraries(RTHwasan_dynamic_version_script_dummy
   ARCHS ${HWASAN_SUPPORTED_ARCH}
   SOURCES ${CMAKE_CURRENT_BINARY_DIR}/dummy.cc
-  CFLAGS ${HWASAN_DYNAMIC_CFLAGS})
+  CFLAGS ${HWASAN_DYNAMIC_CFLAGS}
+  DEFS ${HWASAN_DEFINITIONS})
 
 foreach(arch ${HWASAN_SUPPORTED_ARCH})
   add_compiler_rt_runtime(clang_rt.hwasan
     STATIC
     ARCHS ${arch}
     OBJECT_LIBS RTHwasan
                 RTInterception
                 RTSanitizerCommon

compiler-rt/trunk/lib/hwasan/hwasan.h

 #ifndef HWASAN_REPLACE_OPERATORS_NEW_AND_DELETE
 # define HWASAN_REPLACE_OPERATORS_NEW_AND_DELETE 1
 #endif
 
 #ifndef HWASAN_CONTAINS_UBSAN
 # define HWASAN_CONTAINS_UBSAN CAN_SANITIZE_UB
 #endif
 
+#ifndef HWASAN_WITH_INTERCEPTORS
+#define HWASAN_WITH_INTERCEPTORS 0
+#endif
+
 typedef u8 tag_t;
 
 // TBI (Top Byte Ignore) feature of AArch64: bits [63:56] are ignored in address
 // translation and can be used to store a tag.
 const unsigned kAddressTagShift = 56;
 const uptr kAddressTagMask = 0xFFUL << kAddressTagShift;
 
 static inline tag_t GetTagFromPointer(uptr p) {
public:
   ScopedThreadLocalStateBackup() { Backup(); }
   ~ScopedThreadLocalStateBackup() { Restore(); }
   void Backup();
   void Restore();
  private:
   u64 va_arg_overflow_size_tls;
 };
 
-void HwasanTSDInit(void (*destructor)(void *tsd));
-void *HwasanTSDGet();
-void HwasanTSDSet(void *tsd);
-void HwasanTSDDtor(void *tsd);
+void HwasanTSDInit();
 
 void HwasanOnDeadlySignal(int signo, void *info, void *context);
 
 }  // namespace __hwasan
 
 #define HWASAN_MALLOC_HOOK(ptr, size)       \
   do {                                    \
     if (&__sanitizer_malloc_hook) {       \

compiler-rt/trunk/lib/hwasan/hwasan.cc

void __hwasan_init() {
   InitializeInterceptors();
   InstallDeadlySignalHandlers(HwasanOnDeadlySignal);
   InstallAtExitHandler(); // Needs __cxa_atexit interceptor.
 
   Symbolizer::GetOrInit()->AddHooks(EnterSymbolizer, ExitSymbolizer);
 
   InitializeCoverage(common_flags()->coverage, common_flags()->coverage_dir);
 
-  HwasanTSDInit(HwasanTSDDtor);
+  HwasanTSDInit();
 
   HwasanAllocatorInit();
 
   HwasanThread *main_thread = HwasanThread::Create(nullptr, nullptr);
   SetCurrentThread(main_thread);
-  main_thread->ThreadStart();
+  main_thread->Init();
 
 #if HWASAN_CONTAINS_UBSAN
   __ubsan::InitAsPlugin();
 #endif
 
   VPrintf(1, "HWAddressSanitizer init done\n");
 
   hwasan_init_is_running = 0;

compiler-rt/trunk/lib/hwasan/hwasan_interceptors.cc

 // aarch64 (which uses a different register for sret value).  We have a test
 // to confirm that.
 INTERCEPTOR(void, mallinfo, __sanitizer_struct_mallinfo *sret) {
 #ifdef __aarch64__
   uptr r8;
   asm volatile("mov %0,x8" : "=r" (r8));
   sret = reinterpret_cast<__sanitizer_struct_mallinfo*>(r8);
 #endif
-  REAL(memset)(sret, 0, sizeof(*sret));
+  internal_memset(sret, 0, sizeof(*sret));
 }
 #define HWASAN_MAYBE_INTERCEPT_MALLINFO INTERCEPT_FUNCTION(mallinfo)
 #else
 #define HWASAN_MAYBE_INTERCEPT_MALLINFO
 #endif
 
 #if !SANITIZER_FREEBSD && !SANITIZER_NETBSD
 INTERCEPTOR(int, mallopt, int cmd, int value) {
INTERCEPTOR(void *, malloc, SIZE_T size) {
   if (UNLIKELY(!hwasan_init_is_running))
     ENSURE_HWASAN_INITED();
   if (UNLIKELY(!hwasan_inited))
     // Hack: dlsym calls malloc before REAL(malloc) is retrieved from dlsym.
     return AllocateFromLocalPool(size);
   return hwasan_malloc(size, &stack);
 }
 
-template <class Mmap>
-static void *mmap_interceptor(Mmap real_mmap, void *addr, SIZE_T sz, int prot,
-                              int flags, int fd, OFF64_T off) {
-  if (addr && !MEM_IS_APP(addr)) {
-    if (flags & map_fixed) {
-      errno = errno_EINVAL;
-      return (void *)-1;
-    } else {
-      addr = nullptr;
-    }
-  }
-  return real_mmap(addr, sz, prot, flags, fd, off);
-}
-
+#if HWASAN_WITH_INTERCEPTORS
 extern "C" int pthread_attr_init(void *attr);
 extern "C" int pthread_attr_destroy(void *attr);
 
 static void *HwasanThreadStartFunc(void *arg) {
-  HwasanThread *t = (HwasanThread *)arg;
-  SetCurrentThread(t);
-  return t->ThreadStart();
+  __hwasan_thread_enter();
+  return ((HwasanThread *)arg)->ThreadStart();
 }
 
 INTERCEPTOR(int, pthread_create, void *th, void *attr, void *(*callback)(void*),
             void * param) {
   ENSURE_HWASAN_INITED(); // for GetTlsSize()
   __sanitizer_pthread_attr_t myattr;
   if (!attr) {
     pthread_attr_init(&myattr);
     attr = &myattr;
   }
 
   AdjustStackSize(attr);
 
   HwasanThread *t = HwasanThread::Create(callback, param);
 
   int res = REAL(pthread_create)(th, attr, HwasanThreadStartFunc, t);
 
   if (attr == &myattr)
     pthread_attr_destroy(&myattr);
   return res;
 }
+#endif // HWASAN_WITH_INTERCEPTORS
 
 static void BeforeFork() {
   StackDepotLockAll();
 }
 
 static void AfterFork() {
   StackDepotUnlockAll();
 }

 
 int OnExit() {
   // FIXME: ask frontend whether we need to return failure.
   return 0;
 }
 
 } // namespace __hwasan
 
-// A version of CHECK_UNPOISONED using a saved scope value. Used in common
-// interceptors.
-#define CHECK_UNPOISONED_CTX(ctx, x, n)                         \
-  do {                                                          \
-    if (!((HwasanInterceptorContext *)ctx)->in_interceptor_scope) \
-      CHECK_UNPOISONED_0(x, n);                                 \
-  } while (0)
-
-#define HWASAN_INTERCEPT_FUNC(name)                                       \
-  do {                                                                  \
-    if ((!INTERCEPT_FUNCTION(name) || !REAL(name)))                     \
-      VReport(1, "HWAddressSanitizer: failed to intercept '" #name "'\n"); \
-  } while (0)
-
-#define HWASAN_INTERCEPT_FUNC_VER(name, ver)                                    \
-  do {                                                                        \
-    if ((!INTERCEPT_FUNCTION_VER(name, ver) || !REAL(name)))                  \
-      VReport(                                                                \
-          1, "HWAddressSanitizer: failed to intercept '" #name "@@" #ver "'\n"); \
-  } while (0)
-
-#define COMMON_INTERCEPT_FUNCTION(name) HWASAN_INTERCEPT_FUNC(name)
-#define COMMON_INTERCEPT_FUNCTION_VER(name, ver)                          \
-  HWASAN_INTERCEPT_FUNC_VER(name, ver)
-#define COMMON_INTERCEPTOR_WRITE_RANGE(ctx, ptr, size) \
-  CHECK_UNPOISONED_CTX(ctx, ptr, size)
-#define COMMON_INTERCEPTOR_READ_RANGE(ctx, ptr, size) \
-  CHECK_UNPOISONED_CTX(ctx, ptr, size)
-#define COMMON_INTERCEPTOR_INITIALIZE_RANGE(ptr, size) \
-  HWASAN_WRITE_RANGE(ctx, ptr, size)
-#define COMMON_INTERCEPTOR_ENTER(ctx, func, ...)                  \
-  if (hwasan_init_is_running) return REAL(func)(__VA_ARGS__);       \
-  ENSURE_HWASAN_INITED();                                           \
-  HwasanInterceptorContext hwasan_ctx = {IsInInterceptorScope()};     \
-  ctx = (void *)&hwasan_ctx;                                        \
-  (void)ctx;                                                      \
-  InterceptorScope interceptor_scope;
-#define COMMON_INTERCEPTOR_DIR_ACQUIRE(ctx, path) \
-  do {                                            \
-  } while (false)
-#define COMMON_INTERCEPTOR_FD_ACQUIRE(ctx, fd) \
-  do {                                         \
-  } while (false)
-#define COMMON_INTERCEPTOR_FD_RELEASE(ctx, fd) \
-  do {                                         \
-  } while (false)
-#define COMMON_INTERCEPTOR_FD_SOCKET_ACCEPT(ctx, fd, newfd) \
-  do {                                                      \
-  } while (false)
-#define COMMON_INTERCEPTOR_SET_THREAD_NAME(ctx, name) \
-  do {                                                \
-  } while (false)  // FIXME
-#define COMMON_INTERCEPTOR_SET_PTHREAD_NAME(ctx, thread, name) \
-  do {                                                         \
-  } while (false)  // FIXME
-#define COMMON_INTERCEPTOR_BLOCK_REAL(name) REAL(name)
-#define COMMON_INTERCEPTOR_ON_EXIT(ctx) OnExit()
-
-#define COMMON_INTERCEPTOR_GET_TLS_RANGE(begin, end)                           \
-  if (HwasanThread *t = GetCurrentThread()) {                                    \
-    *begin = t->tls_begin();                                                   \
-    *end = t->tls_end();                                                       \
-  } else {                                                                     \
-    *begin = *end = 0;                                                         \
-  }
-
-// AArch64 has TBI and can (and must!) pass the pointer to system memset as-is.
-// Other platforms need to remove the tag.
-#if defined(__aarch64__)
-#define COMMON_INTERCEPTOR_MEMSET_IMPL(ctx, dst, v, size)     \
-  {                                                           \
-    COMMON_INTERCEPTOR_ENTER(ctx, memset, dst, v, size);      \
-    if (common_flags()->intercept_intrin &&                   \
-        MEM_IS_APP(GetAddressFromPointer(dst)))               \
-      COMMON_INTERCEPTOR_WRITE_RANGE(ctx, dst, size);         \
-    return REAL(memset)(dst, v, size); \
-  }
-#else
-#define COMMON_INTERCEPTOR_MEMSET_IMPL(ctx, dst, v, size)     \
-  {                                                           \
-    COMMON_INTERCEPTOR_ENTER(ctx, memset, dst, v, size);      \
-    if (common_flags()->intercept_intrin &&                   \
-        MEM_IS_APP(GetAddressFromPointer(dst)))               \
-      COMMON_INTERCEPTOR_WRITE_RANGE(ctx, dst, size);         \
-    return REAL(memset)(GetAddressFromPointer(dst), v, size); \
-  }
-#endif
-
-#define COMMON_INTERCEPTOR_MMAP_IMPL(ctx, mmap, addr, length, prot, flags, fd, \
-                                     offset)                                   \
-  do {                                                                         \
-    return mmap_interceptor(REAL(mmap), addr, length, prot, flags, fd,         \
-                            offset);                                           \
-  } while (false)
-
-#include "sanitizer_common/sanitizer_platform_interceptors.h"
-#include "sanitizer_common/sanitizer_common_interceptors.inc"
-#include "sanitizer_common/sanitizer_signal_interceptors.inc"
-
-#define COMMON_SYSCALL_PRE_READ_RANGE(p, s) CHECK_UNPOISONED(p, s)
-#define COMMON_SYSCALL_PRE_WRITE_RANGE(p, s) \
-  do {                                       \
-    (void)(p);                               \
-    (void)(s);                               \
-  } while (false)
-#define COMMON_SYSCALL_POST_READ_RANGE(p, s) \
-  do {                                       \
-    (void)(p);                               \
-    (void)(s);                               \
-  } while (false)
-#define COMMON_SYSCALL_POST_WRITE_RANGE(p, s) \
-  do {                                        \
-    (void)(p);                                \
-    (void)(s);                                \
-  } while (false)
-#include "sanitizer_common/sanitizer_common_syscalls.inc"
-#include "sanitizer_common/sanitizer_syscalls_netbsd.inc"
-
-
-
 namespace __hwasan {
 
 void InitializeInterceptors() {
   static int inited = 0;
   CHECK_EQ(inited, 0);
-  InitializeCommonInterceptors();
-  InitializeSignalInterceptors();
 
+  // FIXME: disable interceptors for allocator functions, keep only __sanitizer
+  // aliases unless HWASAN_WITH_INTERCEPTORS=1.
   INTERCEPT_FUNCTION(posix_memalign);
   HWASAN_MAYBE_INTERCEPT_MEMALIGN;
   INTERCEPT_FUNCTION(__libc_memalign);
   INTERCEPT_FUNCTION(valloc);
   HWASAN_MAYBE_INTERCEPT_PVALLOC;
   INTERCEPT_FUNCTION(malloc);
   INTERCEPT_FUNCTION(calloc);
   INTERCEPT_FUNCTION(realloc);
   INTERCEPT_FUNCTION(free);
   HWASAN_MAYBE_INTERCEPT_CFREE;
   INTERCEPT_FUNCTION(malloc_usable_size);
   HWASAN_MAYBE_INTERCEPT_MALLINFO;
   HWASAN_MAYBE_INTERCEPT_MALLOPT;
   HWASAN_MAYBE_INTERCEPT_MALLOC_STATS;
-  INTERCEPT_FUNCTION(pthread_create);
   INTERCEPT_FUNCTION(fork);
 
+#if HWASAN_WITH_INTERCEPTORS
+  INTERCEPT_FUNCTION(pthread_create);
+#endif
+
   inited = 1;
 }
 } // namespace __hwasan

compiler-rt/trunk/lib/hwasan/hwasan_interface_internal.h

 void __sanitizer_unaligned_store64(uu64 *p, u64 x);
 
 SANITIZER_INTERFACE_ATTRIBUTE
 void __hwasan_enable_allocator_tagging();
 
 SANITIZER_INTERFACE_ATTRIBUTE
 void __hwasan_disable_allocator_tagging();
 
+SANITIZER_INTERFACE_ATTRIBUTE
+void __hwasan_thread_enter();
+
+SANITIZER_INTERFACE_ATTRIBUTE
+void __hwasan_thread_exit();
+
 }  // extern "C"
 
 #endif  // HWASAN_INTERFACE_INTERNAL_H

compiler-rt/trunk/lib/hwasan/hwasan_linux.cc

 }
 
 void InstallAtExitHandler() {
   atexit(HwasanAtExit);
 }
 
 // ---------------------- TSD ---------------- {{{1
 
+extern "C" void __hwasan_thread_enter() {
+  HwasanThread *t = HwasanThread::Create(nullptr, nullptr);
+  SetCurrentThread(t);
+  t->Init();
+}
+
+extern "C" void __hwasan_thread_exit() {
+  HwasanThread *t = GetCurrentThread();
+  // Make sure that signal handler can not see a stale current thread pointer.
+  atomic_signal_fence(memory_order_seq_cst);
+  if (t)
+    t->Destroy();
+}
+
+#if HWASAN_WITH_INTERCEPTORS
 static pthread_key_t tsd_key;
 static bool tsd_key_inited = false;
 
-void HwasanTSDInit(void (*destructor)(void *tsd)) {
+void HwasanTSDDtor(void *tsd) {
+  HwasanThread *t = (HwasanThread*)tsd;
+  if (t->destructor_iterations_ > 1) {
+    t->destructor_iterations_--;
+    CHECK_EQ(0, pthread_setspecific(tsd_key, tsd));
+    return;
+  }
+  __hwasan_thread_exit();
+}
+
+void HwasanTSDInit() {
   CHECK(!tsd_key_inited);
   tsd_key_inited = true;
-  CHECK_EQ(0, pthread_key_create(&tsd_key, destructor));
+  CHECK_EQ(0, pthread_key_create(&tsd_key, HwasanTSDDtor));
 }
 
 HwasanThread *GetCurrentThread() {
-  return (HwasanThread*)pthread_getspecific(tsd_key);
+  return (HwasanThread *)pthread_getspecific(tsd_key);
 }
 
 void SetCurrentThread(HwasanThread *t) {
   // Make sure that HwasanTSDDtor gets called at the end.
   CHECK(tsd_key_inited);
   // Make sure we do not reset the current HwasanThread.
   CHECK_EQ(0, pthread_getspecific(tsd_key));
   pthread_setspecific(tsd_key, (void *)t);
 }
-
-void HwasanTSDDtor(void *tsd) {
-  HwasanThread *t = (HwasanThread*)tsd;
-  if (t->destructor_iterations_ > 1) {
-    t->destructor_iterations_--;
-    CHECK_EQ(0, pthread_setspecific(tsd_key, tsd));
-    return;
-  }
-  // Make sure that signal handler can not see a stale current thread pointer.
-  atomic_signal_fence(memory_order_seq_cst);
-  HwasanThread::TSDDtor(tsd);
+#elif SANITIZER_ANDROID
+void HwasanTSDInit() {}
+HwasanThread *GetCurrentThread() {
+  return (HwasanThread*)*get_android_tls_ptr();
+
+void SetCurrentThread(HwasanThread *t) {
+  *get_android_tls_ptr() = (uptr)t;
 }
+#else
+#error unsupported configuration !HWASAN_WITH_INTERCEPTORS && !SANITIZER_ANDROID
+#endif
 
 struct AccessInfo {
   uptr addr;
   uptr size;
   bool is_store;
   bool is_load;
   bool recover;
 };

compiler-rt/trunk/lib/hwasan/hwasan_thread.h

 #include "hwasan_allocator.h"
 #include "sanitizer_common/sanitizer_common.h"
 
 namespace __hwasan {
 
 class HwasanThread {
  public:
   static HwasanThread *Create(thread_callback_t start_routine, void *arg);
-  static void TSDDtor(void *tsd);
   void Destroy();
 
-  void Init();  // Should be called from the thread itself.
+  void Init();
   thread_return_t ThreadStart();
 
   uptr stack_top() { return stack_top_; }
   uptr stack_bottom() { return stack_bottom_; }
   uptr tls_begin() { return tls_begin_; }
   uptr tls_end() { return tls_end_; }
   bool IsMainThread() { return start_routine_ == nullptr; }
 

compiler-rt/trunk/lib/hwasan/hwasan_thread.cc

 void HwasanThread::Init() {
   SetThreadStackAndTls();
   if (stack_bottom_) {
     CHECK(MEM_IS_APP(stack_bottom_));
     CHECK(MEM_IS_APP(stack_top_ - 1));
   }
 }
 
-void HwasanThread::TSDDtor(void *tsd) {
-  HwasanThread *t = (HwasanThread*)tsd;
-  t->Destroy();
-}
-
 void HwasanThread::ClearShadowForThreadStackAndTLS() {
   if (stack_top_ != stack_bottom_)
     TagMemory(stack_bottom_, stack_top_ - stack_bottom_, 0);
   if (tls_begin_ != tls_end_)
     TagMemory(tls_begin_, tls_end_ - tls_begin_, 0);
 }
 
 void HwasanThread::Destroy() {
   malloc_storage().CommitBack();
   ClearShadowForThreadStackAndTLS();
   uptr size = RoundUpTo(sizeof(HwasanThread), GetPageSizeCached());
   UnmapOrDie(this, size);
   DTLS_Destroy();
 }
 
 thread_return_t HwasanThread::ThreadStart() {
-  Init();
-
-  if (!start_routine_) {
-    // start_routine_ == 0 if we're on the main thread or on one of the
-    // OS X libdispatch worker threads. But nobody is supposed to call
-    // ThreadStart() for the worker threads.
-    return 0;
-  }
-
-  thread_return_t res = start_routine_(arg_);
-
-  return res;
+  return start_routine_(arg_);
 }
 
 static u32 xorshift(u32 state) {
   state ^= state << 13;
   state ^= state >> 17;
   state ^= state << 5;
   return state;
 }

compiler-rt/trunk/test/hwasan/TestCases/longjmp.c

 // RUN: %clang_hwasan -O0 -DNEGATIVE %s -o %t && %run %t 2>&1
 // RUN: %clang_hwasan -O0 %s -o %t && not %run %t 2>&1 | FileCheck %s
 
 // REQUIRES: stable-runtime
 
 #include <stdlib.h>
 #include <assert.h>
 #include <sanitizer/hwasan_interface.h>
 
 __attribute__((noinline))
 int f(void *caller_frame) {
-  char z[32] = {};
-  char *volatile p = z;
+  int z = 0;
+  int *volatile p = &z;
   // Tag of local is never zero.
   assert(__hwasan_tag_pointer(p, 0) != p);
 #ifndef NEGATIVE
   // This will destroy shadow of "z", and the following load will crash.
   __hwasan_handle_longjmp(caller_frame);
 #endif
   return p[0];
 }
 
 int main() {
   return f(__builtin_frame_address(0));
   // CHECK: READ of size 8
   // CHECK: pointer tag
   // CHECK: memory tag 0x0
 }