unpoison-thread-stacks_clang_10.patch

Enable keyboard shortcuts

[winasan] Unpoison the stack in NtTerminateThread

In long-running builds we've seen some ASan complaints during thread creation

that we suspect are due to leftover poisoning from previous threads whose stacks

occupied that memory. This patch adds a hook that unpoisons the stack just

before the NtTerminateThread syscall.

Differential Revision: https://reviews.llvm.org/D52091

** Update for clang 9 ** : After some backouts, this patch eventually landed

upstream in a different form, as the TLS handler `asan_thread_exit`, but that

variant causes failures in our test suite, so revert the TLS handler in favor of

the interceptor approach from the first patch.

diff --git a/compiler-rt/lib/asan/asan_win.cpp b/compiler-rt/lib/asan/asan_win.cpp

index 417892aaedd..5fe86db44f4 100644

--- a/compiler-rt/lib/asan/asan_win.cpp

+++ b/compiler-rt/lib/asan/asan_win.cpp

@@ -154,6 +154,14 @@ INTERCEPTOR_WINAPI(HANDLE, CreateThread, LPSECURITY_ATTRIBUTES security,

                             thr_flags, tid);

+INTERCEPTOR_WINAPI(void, NtTerminateThread, void *rcx) {

+  // Unpoison the terminating thread's stack because the memory may be re-used.

+  NT_TIB *tib = (NT_TIB *)NtCurrentTeb();

+  uptr stackSize = (uptr)tib->StackBase - (uptr)tib->StackLimit;

+  __asan_unpoison_memory_region(tib->StackLimit, stackSize);

+  return REAL(NtTerminateThread(rcx));

+}

 // }}}

 namespace __asan {

@@ -168,7 +176,9 @@ void InitializePlatformInterceptors() {

   ASAN_INTERCEPT_FUNC(CreateThread);

   ASAN_INTERCEPT_FUNC(SetUnhandledExceptionFilter);

+  CHECK(::__interception::OverrideFunction("NtTerminateThread",

+                                           (uptr)WRAP(NtTerminateThread),

+                                           (uptr *)&REAL(NtTerminateThread)));

 #ifdef _WIN64

   ASAN_INTERCEPT_FUNC(__C_specific_handler);

 #else

@@ -380,19 +390,6 @@ __declspec(allocate(".CRT$XLAB")) void(NTAPI *__asan_tls_init)(

     void *, unsigned long, void *) = asan_thread_init;

 #endif

-static void NTAPI asan_thread_exit(void *module, DWORD reason, void *reserved) {

-  if (reason == DLL_THREAD_DETACH) {

-    // Unpoison the thread's stack because the memory may be re-used.

-    NT_TIB *tib = (NT_TIB *)NtCurrentTeb();

-    uptr stackSize = (uptr)tib->StackBase - (uptr)tib->StackLimit;

-    __asan_unpoison_memory_region(tib->StackLimit, stackSize);

-  }

-}

-#pragma section(".CRT$XLY", long, read)

-__declspec(allocate(".CRT$XLY")) void(NTAPI *__asan_tls_exit)(

-    void *, unsigned long, void *) = asan_thread_exit;

 WIN_FORCE_LINK(__asan_dso_reg_hook)

 // }}}