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From ea723210a76778c7e86b8df21cb284fc2665ee4f Mon Sep 17 00:00:00 2001
From: mancha <mancha1 AT zoho DOT com>
Date: Wed, 22 Oct 2014
Subject: Fix unsafe compiler optimization
GCC 4.8 enables -ftree-loop-distribute-patterns at -O3 by default and
this optimization may transform loops into memset/memmove calls. Without
proper handling this may generate unexpected PLT calls on GLIBC.
This patch fixes by creating memset/memmove aliases to internal GLIBC
__GI_memset/__GI_memmove symbols.
This fix for use on glibc 2.17 is based on the following upstream
commits:
https://sourceware.org/git/?p=glibc.git;h=6a97b62a5b4f
https://sourceware.org/git/?p=glibc.git;h=4959e284ca9c
---
sysdeps/generic/symbol-hacks.h | 7 ++++++-
sysdeps/wordsize-32/symbol-hacks.h | 2 ++
sysdeps/x86_64/x32/symbol-hacks.h | 2 +-
3 files changed, 9 insertions(+), 2 deletions(-)
--- a/sysdeps/generic/symbol-hacks.h
+++ b/sysdeps/generic/symbol-hacks.h
@@ -1 +1,6 @@
-/* Fortunately nothing to do. */
+/* Some compiler optimizations may transform loops into memset/memmove
+ calls and without proper declaration it may generate PLT calls. */
+#if !defined __ASSEMBLER__ && !defined NOT_IN_libc && defined SHARED
+asm ("memmove = __GI_memmove");
+asm ("memset = __GI_memset");
+#endif
--- a/sysdeps/wordsize-32/symbol-hacks.h
+++ b/sysdeps/wordsize-32/symbol-hacks.h
@@ -16,6 +16,8 @@
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
+#include_next "symbol-hacks.h"
+
/* A very dirty trick: gcc emits references to __divdi3, __udivdi3,
__moddi3, and __umoddi3. These functions are exported and
therefore we get PLTs. Unnecessarily so. Changing gcc is a big
--- a/sysdeps/x86_64/x32/symbol-hacks.h
+++ b/sysdeps/x86_64/x32/symbol-hacks.h
@@ -1 +1 @@
-/* Fortunately nothing to do. */
+#include <sysdeps/generic/symbol-hacks.h>
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