netdev - Re: [PATCH bpf-next] selftests/bpf: Fix stat probe in d

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Date:   Fri, 18 Sep 2020 12:22:31 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:     Jiri Olsa <jolsa@...nel.org>, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andriin@...com>,
        Network Development <netdev@...r.kernel.org>,
        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>
Subject: Re: [PATCH bpf-next] selftests/bpf: Fix stat probe in d_path test

On Thu, Sep 17, 2020 at 02:14:38PM -0700, Alexei Starovoitov wrote:
> On Thu, Sep 17, 2020 at 1:25 AM Jiri Olsa <jolsa@...hat.com> wrote:
> >
> > > Ideally resolve_btfids would parse dwarf info and check
> > > whether any of the funcs in allowlist were inlined.
> > > That would be more reliable, but not pretty to drag libdw
> > > dependency into resolve_btfids.
> >
> > hm, we could add some check to perf|bpftrace that would
> > show you all the places where function is called from and
> > if it was inlined or is a regular call.. so user is aware
> > what probe calls to expect
> 
> The check like this belongs in some library,
> but making libbpf depend on dwarf is not great.
> I think we're at the point where we need to break libbpf
> into many libraries. This one could be called libbpftrace.
> It would potentially include symbolizer and other dwarf
> related operations.

ok

> Such inlining check would be good to do not only for d_path
> allowlist, but for any kprobe/fentry function.

yes, that's what I meant

jirka