linux-kernel - Re: BTF, pahole and static functions (was Re: [PATCH] libbpf: resolve kernel function name optimization for kprobe)

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Date:   Tue, 24 Jan 2023 04:25:46 -0800
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Yonghong Song <yhs@...a.com>
Cc:     Alan Maguire <alan.maguire@...cle.com>,
        Menglong Dong <menglong8.dong@...il.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        Song Liu <song@...nel.org>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Stanislav Fomichev <sdf@...gle.com>,
        Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
        bpf <bpf@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>,
        Menglong Dong <imagedong@...cent.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>
Subject: Re: BTF, pahole and static functions (was Re: [PATCH] libbpf: resolve
 kernel function name optimization for kprobe)

On Mon, Jan 23, 2023 at 11:18 PM Yonghong Song <yhs@...a.com> wrote:
site.
> >>> So perhaps the best approach is to eliminate such inconsistent static
> >>> function descriptions? The actual amount is small, ~100 functions.
> >>
> >> Removing these inconsistent static functions could be a simpler
> >> approach.
> >
> > I took that approach with
> >
> > https://github.com/acmel/dwarves/commit/80eaecdb00b3d79becc2133b854593277093b115
> >
> > Static functions with inconsistent prototypes are left out of
> > BTF encoding. Given that the numbers here are pretty low (around
> > 100 or so, not including .isra functions which have inconsistent
> > prototypes due to optimizations), that seems to be the simplest
> > solution for now.
>
> Yes, I am okay with this approach. This will prevent user mistaking
> kprobe a wrong function and this is what we want for now.

Let's proceed with the fix first and then discuss improvements on top.