(2015/01/05 21:32), Wang Nan wrote:
> Original code failed to disarm the probed instruction after
>
> echo 0 > /sys/kernel/debug/kprobes/enabled
>
> if OPTPROBE is enabled.
>
> This is caused by a piece of logically inconsistent code:
>
> unoptimize_kprobe(p, false);
> if (!kprobe_queued(p)) {
> ...
> }
>
> unoptimize_kprobe() with 'force' == false queues p onto
> unoptimizing_list, so following kprobe_queued() check always fail unless
> another core schedules optimizer and does the unoptimization very soon.
> This logic causes arch_disarm_kprobe() failed to get execute, lefts a
> breakpoint at the probed address, instead of restoring it.
No, the root cause of this failure comes from the lack of checking
kprobes_all_disarmed in unoptimized_kprobe(). It should check the flag
and return soon if it is set.
So, I Nak this patch.
>
> This patch uses force unoptimize instead.
>
> Signed-off-by: Wang Nan <[email protected]>
> ---
> kernel/kprobes.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> index b185464..9fbe0c3 100644
> --- a/kernel/kprobes.c
> +++ b/kernel/kprobes.c
> @@ -869,7 +869,7 @@ static void __disarm_kprobe(struct kprobe *p, bool reopt)
> {
> struct kprobe *_p;
>
> - unoptimize_kprobe(p, false); /* Try to unoptimize */
> + unoptimize_kprobe(p, true); /* Try to unoptimize */
>
> if (!kprobe_queued(p)) {
> arch_disarm_kprobe(p);
>
--
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Research Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: [email protected]
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