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SubjectRe: Regression :-) Re: [GIT PULL RESEND] x86/jumpmplabel changes for v3.12-rc1
> It seems to imply line 53 is the originating bug, so that would be:
>
> 47 if (type == JUMP_LABEL_ENABLE) {
> 48 /*
> 49 * We are enabling this jump label. If it is not a nop
> 50 * then something must have gone wrong.
> 51 */
> 52 if (unlikely(memcmp((void *)entry->code, ideal_nop, 5) != 0))
> 53 bug_at((void *)entry->code, __LINE__);
>
> But it is a NOP isn't it? The code is
>
> Unexpected op at trace_clock_global+0x6b/0x120 [ffffffff8113a21b] (0f 1f 44 00 00) 53
>
> Perhaps the ideal_nop has not been set yet?
>

And this looks to fix it for me.

diff --git a/arch/x86/kernel/jump_label.c b/arch/x86/kernel/jump_label.c
index ee11b7d..d688348 100644
--- a/arch/x86/kernel/jump_label.c
+++ b/arch/x86/kernel/jump_label.c
@@ -44,13 +44,20 @@ static void __jump_label_transform(struct jump_entry *entry,
union jump_code_union code;
const unsigned char *ideal_nop = ideal_nops[NOP_ATOMIC5];

+ if (init) {
+ const unsigned char default_nop[] = { STATIC_KEY_INIT_NOP };
+ if (unlikely(memcmp((void *)entry->code, default_nop, 5) != 0))
+ bug_at((void *)entry->code, __LINE__);
+ }
if (type == JUMP_LABEL_ENABLE) {
/*
* We are enabling this jump label. If it is not a nop
* then something must have gone wrong.
*/
- if (unlikely(memcmp((void *)entry->code, ideal_nop, 5) != 0))
- bug_at((void *)entry->code, __LINE__);
+ if (!init) {
+ if (unlikely(memcmp((void *)entry->code, ideal_nop, 5) != 0))
+ bug_at((void *)entry->code, __LINE__);
+ }

code.jump = 0xe9;
code.offset = entry->target -
@@ -62,11 +69,7 @@ static void __jump_label_transform(struct jump_entry *entry,
* If this is the first initialization call, then we
* are converting the default nop to the ideal nop.
*/
- if (init) {
- const unsigned char default_nop[] = { STATIC_KEY_INIT_NOP };
- if (unlikely(memcmp((void *)entry->code, default_nop, 5) != 0))
- bug_at((void *)entry->code, __LINE__);
- } else {
+ if (!init) {
code.jump = 0xe9;
code.offset = entry->target -
(entry->code + JUMP_LABEL_NOP_SIZE);

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