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SubjectRe: [BUGFIX PATCH] kprobes: Fix to cancel optimizing/unoptimizing kprobes correctly
On Tue, 7 Jan 2020 18:39:07 -0500
Steven Rostedt <rostedt@goodmis.org> wrote:

> On Tue, 7 Jan 2020 23:42:24 +0900
> Masami Hiramatsu <mhiramat@kernel.org> wrote:
>
> > optimize_kprobe() and unoptimize_kprobe() cancels if given kprobe
> > is on the optimizing_list or unoptimizing_list. However, since
> > commit f66c0447cca1 ("kprobes: Set unoptimized flag after
> > unoptimizing code") modified the update timing of the
> > KPROBE_FLAG_OPTIMIZED, it doesn't work as expected anymore.
> >
> > The optimized_kprobe could be following states.
> >
> > - [optimizing]: Before inserting jump instruction
> > op.kp->flags has KPROBE_FLAG_OPTIMIZED and
> > op->list is not empty.
> >
> > - [optimized]: jump inserted
> > op.kp->flags has KPROBE_FLAG_OPTIMIZED and
> > op->list is empty.
> >
> > - [unoptimizing]: Before removing jump instruction (including unused
> > optprobe)
> > op.kp->flags has KPROBE_FLAG_OPTIMIZED and
> > op->list is not empty.
> >
> > - [unoptimized]: jump removed
> > op.kp->flags doesn't have KPROBE_FLAG_OPTIMIZED and
> > op->list is empty.
> >
> > Current code mis-expects [unoptimizing] state doesn't have
> > KPROBE_FLAG_OPTIMIZED, and that can cause wrong results.
> >
> > This introduces optprobe_queued_unopt() to distinguish [optimizing]
> > and [unoptimizing] states and fixes logics in optimize_kprobe() and
> > unoptimize_kprobe().
> >
> > Fixes: f66c0447cca1 ("kprobes: Set unoptimized flag after unoptimizing code")
> > Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
>
> Looks good.
>
> Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

Thank you!

>
>
> > return;
> > }
> > +
> > /* Optimized kprobe case */
> > - if (force)
> > + if (force) {
> > /* Forcibly update the code: this is a special case */
> > force_unoptimize_kprobe(op);
> > - else {
> > + } else {
> > list_add(&op->list, &unoptimizing_list);
> > kick_kprobe_optimizer();
> > }
>
> I see you added some clean up to this patch.

Yeah, I felt somewhat uncomfortable for that.

>
> -- Steve


--
Masami Hiramatsu <mhiramat@kernel.org>

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