[Xen-devel] [PATCH] x86_emulate: fix side-effect macro call

[Samuel Thibault <samuel.thibault@xxxxxxxxxxxxx>]

x86_emulate: fix side-effect macro call
Both jmp_rel and insn_fetch_type increment eip, so it's not
compiler-safe to nest the calls.

Signed-off-by: Samuel Thibault <samuel.thibault@xxxxxxxxxxxxx>

---
Yes, I actually got a bug because of this, with debian's gcc 4.2.3.

diff -r 52f222b319ef xen/arch/x86/x86_emulate.c
--- a/xen/arch/x86/x86_emulate.c        Tue Feb 05 11:21:22 2008 +0000
+++ b/xen/arch/x86/x86_emulate.c        Tue Feb 05 15:30:48 2008 +0000
@@ -2644,9 +2644,11 @@
         break;
     }
 
-    case 0xeb: /* jmp (short) */
-        jmp_rel(insn_fetch_type(int8_t));
+    case 0xeb: /* jmp (short) */ {
+        int8_t rel = insn_fetch_type(int8_t);
+        jmp_rel(rel);
         break;
+    }
 
     case 0xf1: /* int1 (icebp) */
         src.val = EXC_DB;

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel