[winasan] Unpoison stack memory when threads exit (redux)

[dmajor]

Summary

This is a second attempt at r342652 using a TLS callback instead of an interceptor.

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 callback that unpoisons the stack memory when a thread exits.

[dmajor]

@rnk would you be able to test this out on the nacl browser_tests before landing?

[rnk]

lgtm

Thanks for asking about the test, but honestly it's quite a lot of trouble for me to reproduce that build configuration. If you commit it, we'll know if it works by tomorrow, and I won't have to do anything.

If this approach doesn't work going forward, my next idea would be to unpoison the thread stack during thread creation. We already have a CreateThread interceptor that wraps thread startup, so this wouldn't be too hard.

asan_win.cc

366 ↗

(On Diff #188229)

Let's use .CRT$XLX or Y instead. There is no guarantee that this XLZ section sorts before the XLZ section that the is used to find the bounds for thread destructors.

compiler-rt/trunk/lib/asan/asan_win.cc

static void NTAPI asan_thread_init(void *module, DWORD reason, void *reserved) {
   if (reason == DLL_PROCESS_ATTACH) __asan_init();
 }
 
 #pragma section(".CRT$XLAB", long, read)  // NOLINT
 __declspec(allocate(".CRT$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$XLY", long, read)  // NOLINT
+__declspec(allocate(".CRT$XLY")) void (NTAPI *__asan_tls_exit)(void *,
+    unsigned long, void *) = asan_thread_exit;
+
 WIN_FORCE_LINK(__asan_dso_reg_hook)
 
 // }}}
 }  // namespace __asan
 
 #endif  // SANITIZER_WINDOWS