linux-kernel - Re: [PATCH 1/2] perf bpf-filter: Fix sample flag check with ||

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Date:   Tue, 15 Aug 2023 01:16:48 -0700
From:   Ian Rogers <irogers@...gle.com>
To:     Namhyung Kim <namhyung@...nel.org>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-perf-users@...r.kernel.org
Subject: Re: [PATCH 1/2] perf bpf-filter: Fix sample flag check with ||

On Thu, Aug 10, 2023 at 7:58 PM Namhyung Kim <namhyung@...nel.org> wrote:
>
> For logical OR operator, the actual sample_flags are in the 'groups'
> list so it needs to check entries in the list instead.  Otherwise it
> would show the following error message.
>
>   $ sudo perf record -a -e cycles:p --filter 'period > 100 || weight > 0' sleep 1
>   Error: cycles:p event does not have sample flags 0
>   failed to set filter "BPF" on event cycles:p with 2 (No such file or directory)
>
> Actually it should warn on 'weight' is used without WEIGHT flag.
>
>   Error: cycles:p event does not have PERF_SAMPLE_WEIGHT
>    Hint: please add -W option to perf record
>   failed to set filter "BPF" on event cycles:p with 2 (No such file or directory)
>
> Fixes: 4310551b76e0 ("perf bpf filter: Show warning for missing sample flags")
> Signed-off-by: Namhyung Kim <namhyung@...nel.org>

Reviewed-by: Ian Rogers <irogers@...gle.com>

Thanks,
Ian

> ---
>  tools/perf/util/bpf-filter.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
>
> diff --git a/tools/perf/util/bpf-filter.c b/tools/perf/util/bpf-filter.c
> index 47f01df658d9..b51544996046 100644
> --- a/tools/perf/util/bpf-filter.c
> +++ b/tools/perf/util/bpf-filter.c
> @@ -62,6 +62,16 @@ static int check_sample_flags(struct evsel *evsel, struct perf_bpf_filter_expr *
>         if (evsel->core.attr.sample_type & expr->sample_flags)
>                 return 0;
>
> +       if (expr->op == PBF_OP_GROUP_BEGIN) {
> +               struct perf_bpf_filter_expr *group;
> +
> +               list_for_each_entry(group, &expr->groups, list) {
> +                       if (check_sample_flags(evsel, group) < 0)
> +                               return -1;
> +               }
> +               return 0;
> +       }
> +
>         info = get_sample_info(expr->sample_flags);
>         if (info == NULL) {
>                 pr_err("Error: %s event does not have sample flags %lx\n",
> --
> 2.41.0.640.ga95def55d0-goog
>