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-rw-r--r--arch/x86/include/asm/bug.h15
-rw-r--r--arch/x86/kernel/traps.c2
2 files changed, 7 insertions, 10 deletions
diff --git a/arch/x86/include/asm/bug.h b/arch/x86/include/asm/bug.h
index 71e6f4bf9161..6804d6642767 100644
--- a/arch/x86/include/asm/bug.h
+++ b/arch/x86/include/asm/bug.h
@@ -5,23 +5,20 @@
#include <linux/stringify.h>
/*
- * Since some emulators terminate on UD2, we cannot use it for WARN.
- * Since various instruction decoders disagree on the length of UD1,
- * we cannot use it either. So use UD0 for WARN.
+ * Despite that some emulators terminate on UD2, we use it for WARN().
*
- * (binutils knows about "ud1" but {en,de}codes it as 2 bytes, whereas
- * our kernel decoder thinks it takes a ModRM byte, which seems consistent
- * with various things like the Intel SDM instruction encoding rules)
+ * Since various instruction decoders/specs disagree on the encoding of
+ * UD0/UD1.
*/
-#define ASM_UD0 ".byte 0x0f, 0xff"
+#define ASM_UD0 ".byte 0x0f, 0xff" /* + ModRM (for Intel) */
#define ASM_UD1 ".byte 0x0f, 0xb9" /* + ModRM */
#define ASM_UD2 ".byte 0x0f, 0x0b"
#define INSN_UD0 0xff0f
#define INSN_UD2 0x0b0f
-#define LEN_UD0 2
+#define LEN_UD2 2
#ifdef CONFIG_GENERIC_BUG
@@ -79,7 +76,7 @@ do { \
#define __WARN_FLAGS(flags) \
do { \
- _BUG_FLAGS(ASM_UD0, BUGFLAG_WARNING|(flags)); \
+ _BUG_FLAGS(ASM_UD2, BUGFLAG_WARNING|(flags)); \
annotate_reachable(); \
} while (0)
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 446c9ef8cfc3..3d9b2308e7fa 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -181,7 +181,7 @@ int fixup_bug(struct pt_regs *regs, int trapnr)
break;
case BUG_TRAP_TYPE_WARN:
- regs->ip += LEN_UD0;
+ regs->ip += LEN_UD2;
return 1;
}