From: Colin Watson <cjwatson@ubuntu.com>
Date: Mon, 26 Sep 2011 09:15:32 +0000 (+0100)
Subject: * configure.ac: Build stage2 with -fno-reorder-functions to prevent
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=3af093a503f2fd305facd313b7005fa8878fcf55;p=thirdparty%2Fgrub.git

* configure.ac: Build stage2 with -fno-reorder-functions to prevent
unlikely-to-be-executed functions being reordered before _start with
GCC 4.6.
Fixes Ubuntu bug #837815.
---

diff --git a/ChangeLog b/ChangeLog
index 565a4325b..3f51b8b37 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2011-09-26  Colin Watson  <cjwatson@ubuntu.com>
+
+	* configure.ac: Build stage2 with -fno-reorder-functions to prevent
+	unlikely-to-be-executed functions being reordered before _start with
+	GCC 4.6.
+	Fixes Ubuntu bug #837815.
+
 2010-01-25  Robert Millan  <rmh.grub@aybabtu.com>
 
 	* stage2/imgact_aout.h: Rewrite using aout.h from GRUB 1.97.2 as
diff --git a/configure.ac b/configure.ac
index f462677a6..c862eb2e6 100644
--- a/configure.ac
+++ b/configure.ac
@@ -114,6 +114,22 @@ if test "x$ac_cv_prog_gcc" = xyes; then
     if test "x$grub_cv_cc_no_stack_protector" = xyes; then
       STAGE2_CFLAGS="$STAGE2_CFLAGS -fno-stack-protector"
     fi
+    # GCC >= 3.3 supports -fno-reorder-functions; this defends us against
+    # unlikely-to-be-executed functions being linked before _start with GCC
+    # >= 4.6.
+    AC_CACHE_CHECK([whether gcc has -fno-reorder-functions],
+		   no_reorder_functions_flag, [
+      saved_CFLAGS=$CFLAGS
+      CFLAGS="-fno-reorder-functions"
+      AC_TRY_COMPILE(,
+		     ,
+		     no_reorder_functions_flag=yes,
+		     no_reorder_functions_flag=no)
+      CFLAGS=$saved_CFLAGS
+    ])
+    if test "x$no_reorder_functions_flag" = xyes; then
+      STAGE2_CFLAGS="$STAGE2_CFLAGS -fno-reorder-functions"
+    fi
   fi
 fi