[ASan] Fix TLS teardown.

[hctim]

Summary

TLS teardown is currently broken, as we unpoison the shadow a little bit
and to the right of the TLS section, rather than the full TLS section
itself. This currently breaks at -O0, and breaks with some upcoming
globals code that I have.

[vitalybuka]

Thanks!

[eugenis]

Change LGTM but the description does not make any sense to me.

compiler-rt/lib/asan/asan_thread.cpp

 #endif  // !SANITIZER_FUCHSIA
 
 void AsanThread::ClearShadowForThreadStackAndTLS() {
   if (stack_top_ != stack_bottom_)
     PoisonShadow(stack_bottom_, stack_top_ - stack_bottom_, 0);
   if (tls_begin_ != tls_end_) {
     uptr tls_begin_aligned = RoundDownTo(tls_begin_, ASAN_SHADOW_GRANULARITY);
     uptr tls_end_aligned = RoundUpTo(tls_end_, ASAN_SHADOW_GRANULARITY);
-    FastPoisonShadowPartialRightRedzone(tls_begin_aligned,
-                                        tls_end_ - tls_begin_aligned,
-                                        tls_end_aligned - tls_end_, 0);
+    FastPoisonShadow(tls_begin_aligned, tls_end_aligned - tls_begin_aligned, 0);
   }
 }
 
 bool AsanThread::GetStackFrameAccessByAddr(uptr addr,
                                            StackFrameAccess *access) {
   if (stack_top_ == stack_bottom_)
     return false;
 

compiler-rt/test/asan/TestCases/Linux/unpoison_tls.cpp

 // Test that TLS is unpoisoned on thread death.
 // REQUIRES: x86-target-arch && !android
 
+// RUN: %clangxx_asan -O0 %s -pthread -o %t && %run %t 2>&1
 // RUN: %clangxx_asan -O1 %s -pthread -o %t && %run %t 2>&1
 
 #include <assert.h>
 #include <pthread.h>
 #include <stdio.h>
 
 #include <sanitizer/asan_interface.h>