compiler-rt/lib/asan/asan_thread.cpp

   1 //===-- asan_thread.cpp ---------------------------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This file is a part of AddressSanitizer, an address sanity checker.
  10 //
  11 // Thread-related code.
  12 //===----------------------------------------------------------------------===//
  13 #include "asan_thread.h"
  14
  15 #include "asan_allocator.h"
  16 #include "asan_interceptors.h"
  17 #include "asan_mapping.h"
  18 #include "asan_poisoning.h"
  19 #include "asan_stack.h"
  20 #include "lsan/lsan_common.h"
  21 #include "sanitizer_common/sanitizer_common.h"
  22 #include "sanitizer_common/sanitizer_placement_new.h"
  23 #include "sanitizer_common/sanitizer_stackdepot.h"
  24 #include "sanitizer_common/sanitizer_tls_get_addr.h"
  25
  26 namespace __asan {
  27
  28 // AsanThreadContext implementation.
  29
  30 void AsanThreadContext::OnCreated(void *arg) {
  31   CreateThreadContextArgs *args = static_cast<CreateThreadContextArgs *>(arg);
  32   if (args->stack)
  33     stack_id = StackDepotPut(*args->stack);
  34   thread = args->thread;
  35   thread->set_context(this);
  36 }
  37
  38 void AsanThreadContext::OnFinished() {
  39   // Drop the link to the AsanThread object.
  40   thread = nullptr;
  41 }
  42
  43 static ThreadRegistry *asan_thread_registry;
  44 static ThreadArgRetval *thread_data;
  45
  46 static Mutex mu_for_thread_context;
  47
  48 static ThreadContextBase *GetAsanThreadContext(u32 tid) {
  49   Lock lock(&mu_for_thread_context);
  50   return new (GetGlobalLowLevelAllocator()) AsanThreadContext(tid);
  51 }
  52
  53 static void InitThreads() {
  54   static bool initialized;
  55   // Don't worry about thread_safety - this should be called when there is
  56   // a single thread.
  57   if (LIKELY(initialized))
  58     return;
  59   // Never reuse ASan threads: we store pointer to AsanThreadContext
  60   // in TSD and can't reliably tell when no more TSD destructors will
  61   // be called. It would be wrong to reuse AsanThreadContext for another
  62   // thread before all TSD destructors will be called for it.
  63
  64   // MIPS requires aligned address
  65   static ALIGNED(alignof(
  66       ThreadRegistry)) char thread_registry_placeholder[sizeof(ThreadRegistry)];
  67   static ALIGNED(alignof(
  68       ThreadArgRetval)) char thread_data_placeholder[sizeof(ThreadArgRetval)];
  69
  70   asan_thread_registry =
  71       new (thread_registry_placeholder) ThreadRegistry(GetAsanThreadContext);
  72   thread_data = new (thread_data_placeholder) ThreadArgRetval();
  73   initialized = true;
  74 }
  75
  76 ThreadRegistry &asanThreadRegistry() {
  77   InitThreads();
  78   return *asan_thread_registry;
  79 }
  80
  81 ThreadArgRetval &asanThreadArgRetval() {
  82   InitThreads();
  83   return *thread_data;
  84 }
  85
  86 AsanThreadContext *GetThreadContextByTidLocked(u32 tid) {
  87   return static_cast<AsanThreadContext *>(
  88       asanThreadRegistry().GetThreadLocked(tid));
  89 }
  90
  91 // AsanThread implementation.
  92
  93 AsanThread *AsanThread::Create(const void *start_data, uptr data_size,
  94                                u32 parent_tid, StackTrace *stack,
  95                                bool detached) {
  96   uptr PageSize = GetPageSizeCached();
  97   uptr size = RoundUpTo(sizeof(AsanThread), PageSize);
  98   AsanThread *thread = (AsanThread *)MmapOrDie(size, __func__);
  99   if (data_size) {
 100     uptr availible_size = (uptr)thread + size - (uptr)(thread->start_data_);
 101     CHECK_LE(data_size, availible_size);
 102     internal_memcpy(thread->start_data_, start_data, data_size);
 103   }
 104   AsanThreadContext::CreateThreadContextArgs args = {thread, stack};
 105   asanThreadRegistry().CreateThread(0, detached, parent_tid, &args);
 106
 107   return thread;
 108 }
 109
 110 void AsanThread::GetStartData(void *out, uptr out_size) const {
 111   internal_memcpy(out, start_data_, out_size);
 112 }
 113
 114 void AsanThread::TSDDtor(void *tsd) {
 115   AsanThreadContext *context = (AsanThreadContext *)tsd;
 116   VReport(1, "T%d TSDDtor\n", context->tid);
 117   if (context->thread)
 118     context->thread->Destroy();
 119 }
 120
 121 void AsanThread::Destroy() {
 122   int tid = this->tid();
 123   VReport(1, "T%d exited\n", tid);
 124
 125   bool was_running =
 126       (asanThreadRegistry().FinishThread(tid) == ThreadStatusRunning);
 127   if (was_running) {
 128     if (AsanThread *thread = GetCurrentThread())
 129       CHECK_EQ(this, thread);
 130     malloc_storage().CommitBack();
 131     if (common_flags()->use_sigaltstack)
 132       UnsetAlternateSignalStack();
 133     FlushToDeadThreadStats(&stats_);
 134     // We also clear the shadow on thread destruction because
 135     // some code may still be executing in later TSD destructors
 136     // and we don't want it to have any poisoned stack.
 137     ClearShadowForThreadStackAndTLS();
 138     DeleteFakeStack(tid);
 139   } else {
 140     CHECK_NE(this, GetCurrentThread());
 141   }
 142   uptr size = RoundUpTo(sizeof(AsanThread), GetPageSizeCached());
 143   UnmapOrDie(this, size);
 144   if (was_running)
 145     DTLS_Destroy();
 146 }
 147
 148 void AsanThread::StartSwitchFiber(FakeStack **fake_stack_save, uptr bottom,
 149                                   uptr size) {
 150   if (atomic_load(&stack_switching_, memory_order_relaxed)) {
 151     Report("ERROR: starting fiber switch while in fiber switch\n");
 152     Die();
 153   }
 154
 155   next_stack_bottom_ = bottom;
 156   next_stack_top_ = bottom + size;
 157   atomic_store(&stack_switching_, 1, memory_order_release);
 158
 159   FakeStack *current_fake_stack = fake_stack_;
 160   if (fake_stack_save)
 161     *fake_stack_save = fake_stack_;
 162   fake_stack_ = nullptr;
 163   SetTLSFakeStack(nullptr);
 164   // if fake_stack_save is null, the fiber will die, delete the fakestack
 165   if (!fake_stack_save && current_fake_stack)
 166     current_fake_stack->Destroy(this->tid());
 167 }
 168
 169 void AsanThread::FinishSwitchFiber(FakeStack *fake_stack_save, uptr *bottom_old,
 170                                    uptr *size_old) {
 171   if (!atomic_load(&stack_switching_, memory_order_relaxed)) {
 172     Report("ERROR: finishing a fiber switch that has not started\n");
 173     Die();
 174   }
 175
 176   if (fake_stack_save) {
 177     SetTLSFakeStack(fake_stack_save);
 178     fake_stack_ = fake_stack_save;
 179   }
 180
 181   if (bottom_old)
 182     *bottom_old = stack_bottom_;
 183   if (size_old)
 184     *size_old = stack_top_ - stack_bottom_;
 185   stack_bottom_ = next_stack_bottom_;
 186   stack_top_ = next_stack_top_;
 187   atomic_store(&stack_switching_, 0, memory_order_release);
 188   next_stack_top_ = 0;
 189   next_stack_bottom_ = 0;
 190 }
 191
 192 inline AsanThread::StackBounds AsanThread::GetStackBounds() const {
 193   if (!atomic_load(&stack_switching_, memory_order_acquire)) {
 194     // Make sure the stack bounds are fully initialized.
 195     if (stack_bottom_ >= stack_top_)
 196       return {0, 0};
 197     return {stack_bottom_, stack_top_};
 198   }
 199   char local;
 200   const uptr cur_stack = (uptr)&local;
 201   // Note: need to check next stack first, because FinishSwitchFiber
 202   // may be in process of overwriting stack_top_/bottom_. But in such case
 203   // we are already on the next stack.
 204   if (cur_stack >= next_stack_bottom_ && cur_stack < next_stack_top_)
 205     return {next_stack_bottom_, next_stack_top_};
 206   return {stack_bottom_, stack_top_};
 207 }
 208
 209 uptr AsanThread::stack_top() { return GetStackBounds().top; }
 210
 211 uptr AsanThread::stack_bottom() { return GetStackBounds().bottom; }
 212
 213 uptr AsanThread::stack_size() {
 214   const auto bounds = GetStackBounds();
 215   return bounds.top - bounds.bottom;
 216 }
 217
 218 // We want to create the FakeStack lazily on the first use, but not earlier
 219 // than the stack size is known and the procedure has to be async-signal safe.
 220 FakeStack *AsanThread::AsyncSignalSafeLazyInitFakeStack() {
 221   uptr stack_size = this->stack_size();
 222   if (stack_size == 0)  // stack_size is not yet available, don't use FakeStack.
 223     return nullptr;
 224   uptr old_val = 0;
 225   // fake_stack_ has 3 states:
 226   // 0   -- not initialized
 227   // 1   -- being initialized
 228   // ptr -- initialized
 229   // This CAS checks if the state was 0 and if so changes it to state 1,
 230   // if that was successful, it initializes the pointer.
 231   if (atomic_compare_exchange_strong(
 232           reinterpret_cast<atomic_uintptr_t *>(&fake_stack_), &old_val, 1UL,
 233           memory_order_relaxed)) {
 234     uptr stack_size_log = Log2(RoundUpToPowerOfTwo(stack_size));
 235     CHECK_LE(flags()->min_uar_stack_size_log, flags()->max_uar_stack_size_log);
 236     stack_size_log =
 237         Min(stack_size_log, static_cast<uptr>(flags()->max_uar_stack_size_log));
 238     stack_size_log =
 239         Max(stack_size_log, static_cast<uptr>(flags()->min_uar_stack_size_log));
 240     fake_stack_ = FakeStack::Create(stack_size_log);
 241     DCHECK_EQ(GetCurrentThread(), this);
 242     SetTLSFakeStack(fake_stack_);
 243     return fake_stack_;
 244   }
 245   return nullptr;
 246 }
 247
 248 void AsanThread::Init(const InitOptions *options) {
 249   DCHECK_NE(tid(), kInvalidTid);
 250   next_stack_top_ = next_stack_bottom_ = 0;
 251   atomic_store(&stack_switching_, false, memory_order_release);
 252   CHECK_EQ(this->stack_size(), 0U);
 253   SetThreadStackAndTls(options);
 254   if (stack_top_ != stack_bottom_) {
 255     CHECK_GT(this->stack_size(), 0U);
 256     CHECK(AddrIsInMem(stack_bottom_));
 257     CHECK(AddrIsInMem(stack_top_ - 1));
 258   }
 259   ClearShadowForThreadStackAndTLS();
 260   fake_stack_ = nullptr;
 261   if (__asan_option_detect_stack_use_after_return &&
 262       tid() == GetCurrentTidOrInvalid()) {
 263     // AsyncSignalSafeLazyInitFakeStack makes use of threadlocals and must be
 264     // called from the context of the thread it is initializing, not its parent.
 265     // Most platforms call AsanThread::Init on the newly-spawned thread, but
 266     // Fuchsia calls this function from the parent thread.  To support that
 267     // approach, we avoid calling AsyncSignalSafeLazyInitFakeStack here; it will
 268     // be called by the new thread when it first attempts to access the fake
 269     // stack.
 270     AsyncSignalSafeLazyInitFakeStack();
 271   }
 272   int local = 0;
 273   VReport(1, "T%d: stack [%p,%p) size 0x%zx; local=%p\n", tid(),
 274           (void *)stack_bottom_, (void *)stack_top_, stack_top_ - stack_bottom_,
 275           (void *)&local);
 276 }
 277
 278 // Fuchsia doesn't use ThreadStart.
 279 // asan_fuchsia.c definies CreateMainThread and SetThreadStackAndTls.
 280 #if !SANITIZER_FUCHSIA
 281
 282 void AsanThread::ThreadStart(tid_t os_id) {
 283   Init();
 284   asanThreadRegistry().StartThread(tid(), os_id, ThreadType::Regular, nullptr);
 285
 286   if (common_flags()->use_sigaltstack)
 287     SetAlternateSignalStack();
 288 }
 289
 290 AsanThread *CreateMainThread() {
 291   AsanThread *main_thread = AsanThread::Create(
 292       /* parent_tid */ kMainTid,
 293       /* stack */ nullptr, /* detached */ true);
 294   SetCurrentThread(main_thread);
 295   main_thread->ThreadStart(internal_getpid());
 296   return main_thread;
 297 }
 298
 299 // This implementation doesn't use the argument, which is just passed down
 300 // from the caller of Init (which see, above).  It's only there to support
 301 // OS-specific implementations that need more information passed through.
 302 void AsanThread::SetThreadStackAndTls(const InitOptions *options) {
 303   DCHECK_EQ(options, nullptr);
 304   uptr tls_size = 0;
 305   uptr stack_size = 0;
 306   GetThreadStackAndTls(tid() == kMainTid, &stack_bottom_, &stack_size,
 307                        &tls_begin_, &tls_size);
 308   stack_top_ = RoundDownTo(stack_bottom_ + stack_size, ASAN_SHADOW_GRANULARITY);
 309   stack_bottom_ = RoundDownTo(stack_bottom_, ASAN_SHADOW_GRANULARITY);
 310   tls_end_ = tls_begin_ + tls_size;
 311   dtls_ = DTLS_Get();
 312
 313   if (stack_top_ != stack_bottom_) {
 314     int local;
 315     CHECK(AddrIsInStack((uptr)&local));
 316   }
 317 }
 318
 319 #endif  // !SANITIZER_FUCHSIA
 320
 321 void AsanThread::ClearShadowForThreadStackAndTLS() {
 322   if (stack_top_ != stack_bottom_)
 323     PoisonShadow(stack_bottom_, stack_top_ - stack_bottom_, 0);
 324   if (tls_begin_ != tls_end_) {
 325     uptr tls_begin_aligned = RoundDownTo(tls_begin_, ASAN_SHADOW_GRANULARITY);
 326     uptr tls_end_aligned = RoundUpTo(tls_end_, ASAN_SHADOW_GRANULARITY);
 327     FastPoisonShadow(tls_begin_aligned, tls_end_aligned - tls_begin_aligned, 0);
 328   }
 329 }
 330
 331 bool AsanThread::GetStackFrameAccessByAddr(uptr addr,
 332                                            StackFrameAccess *access) {
 333   if (stack_top_ == stack_bottom_)
 334     return false;
 335
 336   uptr bottom = 0;
 337   if (AddrIsInStack(addr)) {
 338     bottom = stack_bottom();
 339   } else if (FakeStack *fake_stack = get_fake_stack()) {
 340     bottom = fake_stack->AddrIsInFakeStack(addr);
 341     CHECK(bottom);
 342     access->offset = addr - bottom;
 343     access->frame_pc = ((uptr *)bottom)[2];
 344     access->frame_descr = (const char *)((uptr *)bottom)[1];
 345     return true;
 346   }
 347   uptr aligned_addr = RoundDownTo(addr, SANITIZER_WORDSIZE / 8);  // align addr.
 348   uptr mem_ptr = RoundDownTo(aligned_addr, ASAN_SHADOW_GRANULARITY);
 349   u8 *shadow_ptr = (u8 *)MemToShadow(aligned_addr);
 350   u8 *shadow_bottom = (u8 *)MemToShadow(bottom);
 351
 352   while (shadow_ptr >= shadow_bottom &&
 353          *shadow_ptr != kAsanStackLeftRedzoneMagic) {
 354     shadow_ptr--;
 355     mem_ptr -= ASAN_SHADOW_GRANULARITY;
 356   }
 357
 358   while (shadow_ptr >= shadow_bottom &&
 359          *shadow_ptr == kAsanStackLeftRedzoneMagic) {
 360     shadow_ptr--;
 361     mem_ptr -= ASAN_SHADOW_GRANULARITY;
 362   }
 363
 364   if (shadow_ptr < shadow_bottom) {
 365     return false;
 366   }
 367
 368   uptr *ptr = (uptr *)(mem_ptr + ASAN_SHADOW_GRANULARITY);
 369   CHECK(ptr[0] == kCurrentStackFrameMagic);
 370   access->offset = addr - (uptr)ptr;
 371   access->frame_pc = ptr[2];
 372   access->frame_descr = (const char *)ptr[1];
 373   return true;
 374 }
 375
 376 uptr AsanThread::GetStackVariableShadowStart(uptr addr) {
 377   uptr bottom = 0;
 378   if (AddrIsInStack(addr)) {
 379     bottom = stack_bottom();
 380   } else if (FakeStack *fake_stack = get_fake_stack()) {
 381     bottom = fake_stack->AddrIsInFakeStack(addr);
 382     if (bottom == 0) {
 383       return 0;
 384     }
 385   } else {
 386     return 0;
 387   }
 388
 389   uptr aligned_addr = RoundDownTo(addr, SANITIZER_WORDSIZE / 8);  // align addr.
 390   u8 *shadow_ptr = (u8 *)MemToShadow(aligned_addr);
 391   u8 *shadow_bottom = (u8 *)MemToShadow(bottom);
 392
 393   while (shadow_ptr >= shadow_bottom &&
 394          (*shadow_ptr != kAsanStackLeftRedzoneMagic &&
 395           *shadow_ptr != kAsanStackMidRedzoneMagic &&
 396           *shadow_ptr != kAsanStackRightRedzoneMagic))
 397     shadow_ptr--;
 398
 399   return (uptr)shadow_ptr + 1;
 400 }
 401
 402 bool AsanThread::AddrIsInStack(uptr addr) {
 403   const auto bounds = GetStackBounds();
 404   return addr >= bounds.bottom && addr < bounds.top;
 405 }
 406
 407 static bool ThreadStackContainsAddress(ThreadContextBase *tctx_base,
 408                                        void *addr) {
 409   AsanThreadContext *tctx = static_cast<AsanThreadContext *>(tctx_base);
 410   AsanThread *t = tctx->thread;
 411   if (!t)
 412     return false;
 413   if (t->AddrIsInStack((uptr)addr))
 414     return true;
 415   FakeStack *fake_stack = t->get_fake_stack();
 416   if (!fake_stack)
 417     return false;
 418   return fake_stack->AddrIsInFakeStack((uptr)addr);
 419 }
 420
 421 AsanThread *GetCurrentThread() {
 422   AsanThreadContext *context =
 423       reinterpret_cast<AsanThreadContext *>(AsanTSDGet());
 424   if (!context) {
 425     if (SANITIZER_ANDROID) {
 426       // On Android, libc constructor is called _after_ asan_init, and cleans up
 427       // TSD. Try to figure out if this is still the main thread by the stack
 428       // address. We are not entirely sure that we have correct main thread
 429       // limits, so only do this magic on Android, and only if the found thread
 430       // is the main thread.
 431       AsanThreadContext *tctx = GetThreadContextByTidLocked(kMainTid);
 432       if (tctx && ThreadStackContainsAddress(tctx, &context)) {
 433         SetCurrentThread(tctx->thread);
 434         return tctx->thread;
 435       }
 436     }
 437     return nullptr;
 438   }
 439   return context->thread;
 440 }
 441
 442 void SetCurrentThread(AsanThread *t) {
 443   CHECK(t->context());
 444   VReport(2, "SetCurrentThread: %p for thread %p\n", (void *)t->context(),
 445           (void *)GetThreadSelf());
 446   // Make sure we do not reset the current AsanThread.
 447   CHECK_EQ(0, AsanTSDGet());
 448   AsanTSDSet(t->context());
 449   CHECK_EQ(t->context(), AsanTSDGet());
 450 }
 451
 452 u32 GetCurrentTidOrInvalid() {
 453   AsanThread *t = GetCurrentThread();
 454   return t ? t->tid() : kInvalidTid;
 455 }
 456
 457 AsanThread *FindThreadByStackAddress(uptr addr) {
 458   asanThreadRegistry().CheckLocked();
 459   AsanThreadContext *tctx = static_cast<AsanThreadContext *>(
 460       asanThreadRegistry().FindThreadContextLocked(ThreadStackContainsAddress,
 461                                                    (void *)addr));
 462   return tctx ? tctx->thread : nullptr;
 463 }
 464
 465 void EnsureMainThreadIDIsCorrect() {
 466   AsanThreadContext *context =
 467       reinterpret_cast<AsanThreadContext *>(AsanTSDGet());
 468   if (context && (context->tid == kMainTid))
 469     context->os_id = GetTid();
 470 }
 471
 472 __asan::AsanThread *GetAsanThreadByOsIDLocked(tid_t os_id) {
 473   __asan::AsanThreadContext *context = static_cast<__asan::AsanThreadContext *>(
 474       __asan::asanThreadRegistry().FindThreadContextByOsIDLocked(os_id));
 475   if (!context)
 476     return nullptr;
 477   return context->thread;
 478 }
 479 }  // namespace __asan
 480
 481 // --- Implementation of LSan-specific functions --- {{{1
 482 namespace __lsan {
 483 void LockThreads() {
 484   __asan::asanThreadRegistry().Lock();
 485   __asan::asanThreadArgRetval().Lock();
 486 }
 487
 488 void UnlockThreads() {
 489   __asan::asanThreadArgRetval().Unlock();
 490   __asan::asanThreadRegistry().Unlock();
 491 }
 492
 493 static ThreadRegistry *GetAsanThreadRegistryLocked() {
 494   __asan::asanThreadRegistry().CheckLocked();
 495   return &__asan::asanThreadRegistry();
 496 }
 497
 498 void EnsureMainThreadIDIsCorrect() { __asan::EnsureMainThreadIDIsCorrect(); }
 499
 500 bool GetThreadRangesLocked(tid_t os_id, uptr *stack_begin, uptr *stack_end,
 501                            uptr *tls_begin, uptr *tls_end, uptr *cache_begin,
 502                            uptr *cache_end, DTLS **dtls) {
 503   __asan::AsanThread *t = __asan::GetAsanThreadByOsIDLocked(os_id);
 504   if (!t)
 505     return false;
 506   *stack_begin = t->stack_bottom();
 507   *stack_end = t->stack_top();
 508   *tls_begin = t->tls_begin();
 509   *tls_end = t->tls_end();
 510   // ASan doesn't keep allocator caches in TLS, so these are unused.
 511   *cache_begin = 0;
 512   *cache_end = 0;
 513   *dtls = t->dtls();
 514   return true;
 515 }
 516
 517 void GetAllThreadAllocatorCachesLocked(InternalMmapVector<uptr> *caches) {}
 518
 519 void GetThreadExtraStackRangesLocked(tid_t os_id,
 520                                      InternalMmapVector<Range> *ranges) {
 521   __asan::AsanThread *t = __asan::GetAsanThreadByOsIDLocked(os_id);
 522   if (!t)
 523     return;
 524   __asan::FakeStack *fake_stack = t->get_fake_stack();
 525   if (!fake_stack)
 526     return;
 527
 528   fake_stack->ForEachFakeFrame(
 529       [](uptr begin, uptr end, void *arg) {
 530         reinterpret_cast<InternalMmapVector<Range> *>(arg)->push_back(
 531             {begin, end});
 532       },
 533       ranges);
 534 }
 535
 536 void GetThreadExtraStackRangesLocked(InternalMmapVector<Range> *ranges) {
 537   GetAsanThreadRegistryLocked()->RunCallbackForEachThreadLocked(
 538       [](ThreadContextBase *tctx, void *arg) {
 539         GetThreadExtraStackRangesLocked(
 540             tctx->os_id, reinterpret_cast<InternalMmapVector<Range> *>(arg));
 541       },
 542       ranges);
 543 }
 544
 545 void GetAdditionalThreadContextPtrsLocked(InternalMmapVector<uptr> *ptrs) {
 546   __asan::asanThreadArgRetval().GetAllPtrsLocked(ptrs);
 547 }
 548
 549 void GetRunningThreadsLocked(InternalMmapVector<tid_t> *threads) {
 550   GetAsanThreadRegistryLocked()->RunCallbackForEachThreadLocked(
 551       [](ThreadContextBase *tctx, void *threads) {
 552         if (tctx->status == ThreadStatusRunning)
 553           reinterpret_cast<InternalMmapVector<tid_t> *>(threads)->push_back(
 554               tctx->os_id);
 555       },
 556       threads);
 557 }
 558
 559 }  // namespace __lsan
 560
 561 // ---------------------- Interface ---------------- {{{1
 562 using namespace __asan;
 563
 564 extern "C" {
 565 SANITIZER_INTERFACE_ATTRIBUTE
 566 void __sanitizer_start_switch_fiber(void **fakestacksave, const void *bottom,
 567                                     uptr size) {
 568   AsanThread *t = GetCurrentThread();
 569   if (!t) {
 570     VReport(1, "__asan_start_switch_fiber called from unknown thread\n");
 571     return;
 572   }
 573   t->StartSwitchFiber((FakeStack **)fakestacksave, (uptr)bottom, size);
 574 }
 575
 576 SANITIZER_INTERFACE_ATTRIBUTE
 577 void __sanitizer_finish_switch_fiber(void *fakestack, const void **bottom_old,
 578                                      uptr *size_old) {
 579   AsanThread *t = GetCurrentThread();
 580   if (!t) {
 581     VReport(1, "__asan_finish_switch_fiber called from unknown thread\n");
 582     return;
 583   }
 584   t->FinishSwitchFiber((FakeStack *)fakestack, (uptr *)bottom_old,
 585                        (uptr *)size_old);
 586 }
 587 }