linux-kernel - Re: [PATCH 8/8] perf/core: Call perf_prepare

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Date:   Fri, 13 Jan 2023 13:06:42 -0800
From:   Song Liu <song@...nel.org>
To:     Namhyung Kim <namhyung@...nel.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>, bpf@...r.kernel.org
Subject: Re: [PATCH 8/8] perf/core: Call perf_prepare_sample() before running BPF

On Thu, Jan 12, 2023 at 1:40 PM Namhyung Kim <namhyung@...nel.org> wrote:
>
> As BPF can access sample data, it needs to populate the data.  Also
> remove the logic to get the callchain specifically as it's covered by
> the perf_prepare_sample() now.
>
> Cc: Song Liu <song@...nel.org>
> Cc: bpf@...r.kernel.org
> Signed-off-by: Namhyung Kim <namhyung@...nel.org>

Acked-by: Song Liu <song@...nel.org>

> ---
>  kernel/events/core.c | 8 +-------
>  1 file changed, 1 insertion(+), 7 deletions(-)
>
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index 5c4f3fa3d2b7..af8365fb639a 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -10363,13 +10363,7 @@ static void bpf_overflow_handler(struct perf_event *event,
>         rcu_read_lock();
>         prog = READ_ONCE(event->prog);
>         if (prog) {
> -               if (prog->call_get_stack &&
> -                   (event->attr.sample_type & PERF_SAMPLE_CALLCHAIN) &&
> -                   !(data->sample_flags & PERF_SAMPLE_CALLCHAIN)) {
> -                       data->callchain = perf_callchain(event, regs);
> -                       data->sample_flags |= PERF_SAMPLE_CALLCHAIN;
> -               }
> -
> +               perf_prepare_sample(data, event, regs);
>                 ret = bpf_prog_run(prog, &ctx);
>         }
>         rcu_read_unlock();
> --
> 2.39.0.314.g84b9a713c41-goog
>