linux-kernel - Re: [PATCH 2/8] perf bpf filter: Implement event sample filtering

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Message-ID: <CAM9d7chrbQ+79HRJF=e3DLA7rDL-LdNw2fVW3enjJjY+E-ESsQ@mail.gmail.com>
Date:   Sun, 19 Feb 2023 08:48:42 -0800
From:   Namhyung Kim <namhyung@...nel.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Jiri Olsa <jolsa@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Ian Rogers <irogers@...gle.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Song Liu <song@...nel.org>,
        Stephane Eranian <eranian@...gle.com>,
        Ravi Bangoria <ravi.bangoria@....com>,
        Leo Yan <leo.yan@...aro.org>,
        James Clark <james.clark@....com>, Hao Luo <haoluo@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-perf-users@...r.kernel.org, bpf@...r.kernel.org
Subject: Re: [PATCH 2/8] perf bpf filter: Implement event sample filtering

On Sun, Feb 19, 2023 at 3:14 AM Arnaldo Carvalho de Melo
<acme@...nel.org> wrote:
>
> Em Sat, Feb 18, 2023 at 10:13:23PM -0800, Namhyung Kim escreveu:
> > The BPF program will be attached to a perf_event and be triggered when
> > it overflows.  It'd iterate the filters map and compare the sample
> > value according to the expression.  If any of them fails, the sample
> > would be dropped.
> >
> > Also it needs to have the corresponding sample data for the expression
> > so it compares data->sample_flags with the given value.  To access the
> > sample data, it uses the bpf_cast_to_kern_ctx() kfunc which was added
> > in v6.2 kernel.
>
>   CLANG   /tmp/build/perf/util/bpf_skel/.tmp/sample_filter.bpf.o
> util/bpf_skel/sample_filter.bpf.c:26:19: error: no member named 'sample_flags' in 'struct perf_sample_data'
>         if ((kctx->data->sample_flags & entry->flags) == 0)
>              ~~~~~~~~~~  ^
> 1 error generated.
> make[2]: *** [Makefile.perf:1078: /tmp/build/perf/util/bpf_skel/.tmp/sample_filter.bpf.o] Error 1
> make[1]: *** [Makefile.perf:236: sub-make] Error 2
> make: *** [Makefile:113: install-bin] Error 2
> make: Leaving directory '/var/home/acme/git/perf/tools/perf'
>
>  Performance counter stats for 'make -k BUILD_BPF_SKEL=1 CORESIGHT=1 O=/tmp/build/perf -C tools/perf install-bin':

Hmm.. strange.  In the include/linux/perf_event.h, the
perf_sample_data has sample_flags, but vmlinux.h doesn't.

Thanks,
Namhyung