From b6a68a16dc15c65fe76acb7502a806ae415cd3e4 Mon Sep 17 00:00:00 2001 From: Andi Kleen Date: Thu, 28 Jul 2005 21:15:45 -0700 Subject: [PATCH] [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 Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/asm-x86_64/bug.h | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) diff --git a/include/asm-x86_64/bug.h b/include/asm-x86_64/bug.h index 3d2a666a5d..eed7856672 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 -- 2.39.5