From: Markus Trippelsdorf <markus@trippelsdorf.de>
Date: Wed, 16 Nov 2016 11:21:42 +0000 (+0000)
Subject: Fix PR78294 - thread sanitizer broken when using ld.gold
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=8c32ae0e6df1c4dbd2eea98bc56b401d492e8f54;p=gcc.git

Fix PR78294 - thread sanitizer broken when using ld.gold

When one uses ld.gold to build gcc, the thread sanitizer doesn't work,
because gold is more conservative when applying TLS relaxations than
ld.bfd. In this case a missing initial-exec attribute on a declaration
causes gcc to assume the general dynamic model. With ld.bfd this gets
relaxed to initial exec when linking the shared library, so the missing
attribute doesn't matter. But ld.gold doesn't perform this optimization
and this leads to crashes on tsan instrumented binaries.

See: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78294
and: https://sourceware.org/bugzilla/show_bug.cgi?id=20805

The fix is easy, just add the missing attribute.

  PR sanitizer/78294
  * tsan/tsan_rtl.cc: Add missing attribute.

From-SVN: r242480
---

diff --git a/libsanitizer/ChangeLog b/libsanitizer/ChangeLog
index e56cef9c8f4..215c44465bc 100644
--- a/libsanitizer/ChangeLog
+++ b/libsanitizer/ChangeLog
@@ -1,3 +1,8 @@
+2016-11-16  Markus Trippelsdorf  <markus@trippelsdorf.de>
+
+	PR sanitizer/78294
+	* tsan/tsan_rtl.cc: Add missing attribute.
+
 2016-11-16  Maxim Ostapenko  <m.ostapenko@samsung.com>
 
 	* LOCAL_PATCHES: New file.
diff --git a/libsanitizer/tsan/tsan_rtl.cc b/libsanitizer/tsan/tsan_rtl.cc
index 07fa165e939..5be28ce5502 100644
--- a/libsanitizer/tsan/tsan_rtl.cc
+++ b/libsanitizer/tsan/tsan_rtl.cc
@@ -43,6 +43,7 @@ extern "C" void __tsan_resume() {
 namespace __tsan {
 
 #if !SANITIZER_GO && !SANITIZER_MAC
+  __attribute__((tls_model("initial-exec")))
 THREADLOCAL char cur_thread_placeholder[sizeof(ThreadState)] ALIGNED(64);
 #endif
 static char ctx_placeholder[sizeof(Context)] ALIGNED(64);