From 6737c9f59a523a4813f6e825bfbf3db2dcb00432 Mon Sep 17 00:00:00 2001
From: Paolo Bonzini <pbonzini@redhat.com>
Date: Wed, 15 Jun 2016 22:19:56 +0200
Subject: [PATCH] Use initial-exec tls for libunwind's recursion flag

RH-Author: Paolo Bonzini <pbonzini@redhat.com>
Message-id: <1466029196-19454-1-git-send-email-pbonzini@redhat.com>
Patchwork-id: 70630
O-Subject: [RHEL7.3 PATCH gperftools] Use initial-exec tls for libunwind's recursion flag
Bugzilla: 1339710
RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
RH-Acked-by: Bandan Das <bsd@redhat.com>
RH-Acked-by: Laszlo Ersek <lersek@redhat.com>

From: Aliaksey Kandratsenka <alkondratenko@gmail.com>

Bugzilla: 1339710

Brew build: 11181349

If we don't do it, then reading variable calls to __tls_get_addr, which
uses malloc on first call. initial-exec makes dynamic linker reserve tls
offset for recusion flag early and thus avoid unsafe calls to malloc.

This fixes issue #786.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
(cherry picked from commit 7852eeb75b9375cf52a7da01be044da6e915dd08)
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 src/base/basictypes.h          | 6 ++++++
 src/stacktrace_libunwind-inl.h | 4 +++-
 src/thread_cache.h             | 6 ------
 3 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/src/base/basictypes.h b/src/base/basictypes.h
index 4779611..d7c0f7a 100644
--- a/src/base/basictypes.h
+++ b/src/base/basictypes.h
@@ -192,6 +192,12 @@ struct CompileAssert {
 # define ATTRIBUTE_UNUSED
 #endif
 
+#if defined(HAVE___ATTRIBUTE__) && defined(HAVE_TLS)
+#define ATTR_INITIAL_EXEC __attribute__ ((tls_model ("initial-exec")))
+#else
+#define ATTR_INITIAL_EXEC
+#endif
+
 #define COMPILE_ASSERT(expr, msg)                               \
   typedef CompileAssert<(bool(expr))> msg[bool(expr) ? 1 : -1] ATTRIBUTE_UNUSED
 
diff --git a/src/stacktrace_libunwind-inl.h b/src/stacktrace_libunwind-inl.h
index 8a4a731..6f361ec 100644
--- a/src/stacktrace_libunwind-inl.h
+++ b/src/stacktrace_libunwind-inl.h
@@ -47,6 +47,8 @@ extern "C" {
 #include <libunwind.h>
 }
 #include "gperftools/stacktrace.h"
+
+#include "base/basictypes.h"
 #include "base/logging.h"
 
 // Sometimes, we can try to get a stack trace from within a stack
@@ -56,7 +58,7 @@ extern "C" {
 // recursive request, we'd end up with infinite recursion or deadlock.
 // Luckily, it's safe to ignore those subsequent traces.  In such
 // cases, we return 0 to indicate the situation.
-static __thread int recursive;
+static __thread int recursive ATTR_INITIAL_EXEC;
 
 #if defined(TCMALLOC_ENABLE_UNWIND_FROM_UCONTEXT) && (defined(__i386__) || defined(__x86_64__)) && defined(__GNU_LIBRARY__)
 #define BASE_STACKTRACE_UNW_CONTEXT_IS_UCONTEXT 1
diff --git a/src/thread_cache.h b/src/thread_cache.h
index 5edcdfb..27109af 100644
--- a/src/thread_cache.h
+++ b/src/thread_cache.h
@@ -252,12 +252,6 @@ class ThreadCache {
   // Since we don't really use dlopen in google code -- and using dlopen
   // on a malloc replacement is asking for trouble in any case -- that's
   // a good tradeoff for us.
-#ifdef HAVE___ATTRIBUTE__
-#define ATTR_INITIAL_EXEC __attribute__ ((tls_model ("initial-exec")))
-#else
-#define ATTR_INITIAL_EXEC
-#endif
-
 #ifdef HAVE_TLS
   struct ThreadLocalData {
     ThreadCache* heap;
-- 
1.8.3.1