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References: <20230201135737.800527-1-jolsa@kernel.org>
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From:   Alexei Starovoitov <alexei.starovoitov@gmail.com>
Date:   Thu, 2 Feb 2023 03:15:39 -0800
Message-ID: <CAADnVQ+im7FwSqDcTLmMvfRcT9unwdHBeWG9Snw7W5Q-bcdWvg@mail.gmail.com>
Subject: Re: [RFC 0/5] mm/bpf/perf: Store build id in file object
To:     Jiri Olsa <jolsa@kernel.org>
Cc:     Alexei Starovoitov <ast@kernel.org>,
        Andrii Nakryiko <andrii@kernel.org>,
        Hao Luo <haoluo@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        bpf <bpf@vger.kernel.org>, linux-mm <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Linux-Fsdevel <linux-fsdevel@vger.kernel.org>,
        "linux-perf-use." <linux-perf-users@vger.kernel.org>,
        Martin KaFai Lau <kafai@fb.com>,
        Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
        John Fastabend <john.fastabend@gmail.com>,
        KP Singh <kpsingh@chromium.org>,
        Stanislav Fomichev <sdf@google.com>,
        Daniel Borkmann <daniel@iogearbox.net>
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On Wed, Feb 1, 2023 at 5:57 AM Jiri Olsa <jolsa@kernel.org> wrote:
>
> hi,
> we have a use cases for bpf programs to use binary file's build id.
>
> After some attempts to add helpers/kfuncs [1] [2] Andrii had an idea [3]
> to store build id directly in the file object. That would solve our use
> case and might be beneficial for other profiling/tracing use cases with
> bpf programs.
>
> This RFC patchset adds new config CONFIG_FILE_BUILD_ID option, which adds
> build id object pointer to the file object when enabled. The build id is
> read/populated when the file is mmap-ed.
>
> I also added bpf and perf changes that would benefit from this.
>
> I'm not sure what's the policy on adding stuff to file object, so apologies
> if that's out of line. I'm open to any feedback or suggestions if there's
> better place or way to do this.

struct file represents all files while build_id is for executables only,
and not all executables, but those currently running, so
I think it's cleaner to put it into vm_area_struct.