On Sat, Oct 05, 2013 at 08:05:58PM -0400, Steven Rostedt wrote:
> > 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) {
> > + /*
> > + * Jump label is enabled for the first time.
> > + * So we expect a default_nop...
> > + */
> > + if (unlikely(memcmp((void *)entry->code, default_nop, 5)
> > + != 0))
> > + bug_at((void *)entry->code, __LINE__);
> > + } else {
> > + /*
> > + * ...otherwise expect an ideal_nop. Otherwise
> > + * something went horribly wrong.
> > + */
> > + if (unlikely(memcmp((void *)entry->code, ideal_nop, 5)
> > + != 0))
> > + bug_at((void *)entry->code, __LINE__);
> > + }
>
> I don't know if I like this change. This is similar to a bug we had
> with the Xen folks, where they didn't realize that jump labels are not
> suppose to be used (or set) before jump_label_init() is called.
>
> I'll have to take a deeper look at this on Monday.
Yes, I understand and saw the commit to call jump_label_init
earlier. Maybe the default could be to insert illegal instructions by
default if we try to replace them with nops or branches afterwards anyway.
insn_sanity programs would have to be tought about that, then.
Greetings,
Hannes
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