linux-kernel - Re: [RFC] ftrace: Add support to keep some functions out of ftrace

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Message-ID: <CAJ+HfNjLbsDuE4EB_1jwSOnyaUdjejMZJP6U=zcKvZd=iwhhDQ@mail.gmail.com>
Date:   Mon, 15 Aug 2022 13:01:06 +0200
From:   Björn Töpel <bjorn@...nel.org>
To:     Jiri Olsa <olsajiri@...il.com>
Cc:     Chen Zhongjin <chenzhongjin@...wei.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Ingo Molnar <mingo@...hat.com>, bpf <bpf@...r.kernel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...omium.org>,
        Stanislav Fomichev <sdf@...gle.com>,
        Hao Luo <haoluo@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [RFC] ftrace: Add support to keep some functions out of ftrace

On Mon, 15 Aug 2022 at 10:04, Jiri Olsa <olsajiri@...il.com> wrote:
[...]
> > > >
> > > > Today, objtool has also got involved, and added an "--mcount" option
> > > > that will create the section too.
> > > I overlooked that objtool is involved as well,
> > > will check on that
> >
> > objtool --mcount option only involves mcount_loc generation (see
> > annotate_call_site) and other validation check call destination directly
> > (see is_fentry_call).
> >
> > Some simply removing --mcount option dose work for this.
> >
> >
> > Another question, it seems we can export and use DEFINE_BPF_DISPATCHER out
> > of kernel, does that means we should add NO_MCOUNT_FILES for these single
> > uages as well?
>
> yes, cc-ing Björn to make sure it's valid use case for dispatcher
>

Hmm, could you expand a bit on how this would work?