[patch] Ubuntu patch for this problem from GRUB HEAD r803

803_802.diff (text/plain), 1.33 KB, created by Richard Yao (RETIRED) on 2012-01-30 01:05:41 UTC

=== modified file 'ChangeLog'
--- ChangeLog	2010-01-25 19:13:33 +0000
+++ ChangeLog	2011-09-26 09:15:32 +0000
@@ -1,3 +1,10 @@
[phone]  Colin Watson  <[e-mail]>
+
+	* 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  <[e-mail]>
 
 	* stage2/imgact_aout.h: Rewrite using aout.h from GRUB 1.97.2 as

=== modified file 'configure.ac'
--- configure.ac	2010-01-21 17:17:59 +0000
+++ configure.ac	2011-09-26 09:15:32 +0000
@@ -114,6 +114,22 @@
     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