Re: [PATCH v2 2/3] perf/bpf: Allow a bpf program to suppress all sample side effects.

[Andrii Nakryiko]

On Thu, Dec 7, 2023 at 8:35 AM Kyle Huey <me@xxxxxxxxxxxx> wrote:
>
> Returning zero from a bpf program attached to a perf event already
> suppresses any data output. By clearing pending_kill, returning zero from a
> bpf program will effectively pretend the sample never happened for all
> userspace purposes.
>
> Signed-off-by: Kyle Huey <khuey@xxxxxxxxxxxx>
> ---
>  kernel/events/core.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>

LGTM

Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx>

> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index 19fddfc27a4a..6cda05a4969d 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -10421,8 +10421,10 @@ static void bpf_overflow_handler(struct perf_event *event,
>         rcu_read_unlock();
>  out:
>         __this_cpu_dec(bpf_prog_active);
> -       if (!ret)
> +       if (!ret) {
> +               event->pending_kill = 0;
>                 return;
> +       }
>
>         event->orig_overflow_handler(event, data, regs);
>  }
> --
> 2.34.1
>