linux-kernel - Re: [PATCHv2 0/3] perf/bpf: Replace deprecated code

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Date:   Thu, 17 Feb 2022 13:55:13 -0800
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Jiri Olsa <jolsa@...nel.org>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Ingo Molnar <mingo@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Ian Rogers <irogers@...gle.com>,
        "linux-perf-use." <linux-perf-users@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>, Andrii Nakryiko <andrii@...nel.org>
Subject: Re: [PATCHv2 0/3] perf/bpf: Replace deprecated code

On Thu, Feb 17, 2022 at 5:19 AM Jiri Olsa <jolsa@...nel.org> wrote:
>
> hi,
> the original patchset [1] removed the whole perf functionality
> with the hope nobody's using that. But it turned out there's
> actually bpf script using prologue functionality, so there
> might be users of this.
>
> This patchset gets rid of and adds workaround (and keeps the
> current functionality) for following deprecated libbpf
> functions/struct:
>
>   bpf_program__set_priv
>   bpf_program__priv
>   bpf_map__set_priv
>   bpf_map__priv
>   bpf_program__set_prep
>   bpf_program__nth_fd
>   struct bpf_prog_prep_result
>
> Basically it implements workarounds suggested by Andrii in [2].
>
> I tested with script from examples/bpf that are working for me:
>
>   examples/bpf/hello.c
>   examples/bpf/5sec.c
>
> The rest seem to fail for various reasons even without this
> change..  they seem unmaintained for some time now, but I might
> have wrong setup.
>
> Also available in here:
>   git://git.kernel.org/pub/scm/linux/kernel/git/jolsa/perf.git
>   perf/depre
>
> thanks,
> jirka
>
>
> [1] https://lore.kernel.org/linux-perf-users/YgoPxhE3OEEmZqla@krava/T/#t
> [2] https://lore.kernel.org/linux-perf-users/YgoPxhE3OEEmZqla@krava/T/#md3ccab9fe70a4583e94603b1a562e369bd67b17d
> ---
> Jiri Olsa (3):
>       perf tools: Remove bpf_program__set_priv/bpf_program__priv usage
>       perf tools: Remove bpf_map__set_priv/bpf_map__priv usage
>       perf tools: Rework prologue generation code
>

It's great that you are deprecating these, thanks a lot for that! I
suggest to also doing libbpf_set_strict_mode(LIBBPF_STRICT_ALL) to
check that libbpf 1.0 won't break anything. For example, you'll need
to use a custom SEC() handler to handle those quirky sections that
perf allows. This patch set has landed in bpf-next, so you should be
good to go.


>  tools/perf/util/bpf-loader.c | 267 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-----------------
>  1 file changed, 230 insertions(+), 37 deletions(-)