build/build-clang/unpoison-thread-stacks.patch

   1 [winasan] Unpoison the stack in NtTerminateThread
   2
   3 In long-running builds we've seen some ASan complaints during thread creation
   4 that we suspect are due to leftover poisoning from previous threads whose stacks
   5 occupied that memory. This patch adds a hook that unpoisons the stack just
   6 before the NtTerminateThread syscall.
   7
   8 Differential Revision: https://reviews.llvm.org/D52091
   9
  10 ** Update for clang 9 ** : After some backouts, this patch eventually landed
  11 upstream in a different form, as the TLS handler `asan_thread_exit`, but that
  12 variant causes failures in our test suite, so revert the TLS handler in favor of
  13 the interceptor approach from the first patch.
  14
  15 --- a/compiler-rt/lib/asan/asan_win.cc
  16 +++ b/compiler-rt/lib/asan/asan_win.cc
  17 @@ -154,6 +154,14 @@
  18                              thr_flags, tid);
  19  }
  20
  21 +INTERCEPTOR_WINAPI(void, NtTerminateThread, void *rcx) {
  22 +  // Unpoison the terminating thread's stack because the memory may be re-used.
  23 +  NT_TIB *tib = (NT_TIB *)NtCurrentTeb();
  24 +  uptr stackSize = (uptr)tib->StackBase - (uptr)tib->StackLimit;
  25 +  __asan_unpoison_memory_region(tib->StackLimit, stackSize);
  26 +  return REAL(NtTerminateThread(rcx));
  27 +}
  28 +
  29  // }}}
  30
  31  namespace __asan {
  32 @@ -168,7 +176,9 @@
  33
  34    ASAN_INTERCEPT_FUNC(CreateThread);
  35    ASAN_INTERCEPT_FUNC(SetUnhandledExceptionFilter);
  36 -
  37 +  CHECK(::__interception::OverrideFunction("NtTerminateThread",
  38 +                                           (uptr)WRAP(NtTerminateThread),
  39 +                                           (uptr *)&REAL(NtTerminateThread)));
  40  #ifdef _WIN64
  41    ASAN_INTERCEPT_FUNC(__C_specific_handler);
  42  #else
  43 @@ -380,19 +390,6 @@
  44      void *, unsigned long, void *) = asan_thread_init;
  45  #endif
  46
  47 -static void NTAPI asan_thread_exit(void *module, DWORD reason, void *reserved) {
  48 -  if (reason == DLL_THREAD_DETACH) {
  49 -    // Unpoison the thread's stack because the memory may be re-used.
  50 -    NT_TIB *tib = (NT_TIB *)NtCurrentTeb();
  51 -    uptr stackSize = (uptr)tib->StackBase - (uptr)tib->StackLimit;
  52 -    __asan_unpoison_memory_region(tib->StackLimit, stackSize);
  53 -  }
  54 -}
  55 -
  56 -#pragma section(".CRT$XLY", long, read)  // NOLINT
  57 -__declspec(allocate(".CRT$XLY")) void(NTAPI *__asan_tls_exit)(
  58 -    void *, unsigned long, void *) = asan_thread_exit;
  59 -
  60  WIN_FORCE_LINK(__asan_dso_reg_hook)
  61
  62  // }}}