[PATCH] x86_64: Turn BUG data into valid instruction
This avoids confusing the disassembler. Costs 2 bytes per BUG.
Thanks to Suresh Siddha and Jan Beulich for suggesting suitable instructions.
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/include/asm-x86_64/bug.h b/include/asm-x86_64/bug.h
index 3d2a666..eed7856 100644
--- a/include/asm-x86_64/bug.h
+++ b/include/asm-x86_64/bug.h
@@ -8,17 +8,24 @@
* this frame.
*/
struct bug_frame {
- unsigned char ud2[2];
+ unsigned char ud2[2];
+ unsigned char mov;
/* should use 32bit offset instead, but the assembler doesn't
like it */
char *filename;
+ unsigned char ret;
unsigned short line;
} __attribute__((packed));
#ifdef CONFIG_BUG
#define HAVE_ARCH_BUG
-#define BUG() \
- asm volatile("ud2 ; .quad %c1 ; .short %c0" :: \
+/* We turn the bug frame into valid instructions to not confuse
+ the disassembler. Thanks to Jan Beulich & Suresh Siddha
+ for nice instruction selection.
+ The magic numbers generate mov $64bitimm,%eax ; ret $offset. */
+#define BUG() \
+ asm volatile( \
+ "ud2 ; .byte 0xa3 ; .quad %c1 ; .byte 0xc2 ; .short %c0" :: \
"i"(__LINE__), "i" (__stringify(__FILE__)))
void out_of_line_bug(void);
#else
