From 8c32ae0e6df1c4dbd2eea98bc56b401d492e8f54 Mon Sep 17 00:00:00 2001
From: Markus Trippelsdorf <markus@trippelsdorf.de>
Date: Wed, 16 Nov 2016 11:21:42 +0000
Subject: [PATCH] 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
---
libsanitizer/ChangeLog | 5 +++++
libsanitizer/tsan/tsan_rtl.cc | 1 +
2 files changed, 6 insertions(+)
diff --git a/libsanitizer/ChangeLog b/libsanitizer/ChangeLog
index e56cef9c8f43..215c44465bc5 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 07fa165e939c..5be28ce5502e 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);
--
GitLab