Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Fri, 30 Dec 2022 20:10:20 +0800
From:   Changbin Du <changbin.du@gmail.com>
To:     Leo Yan <leo.yan@linaro.org>
Cc:     Andrii Nakryiko <andrii.nakryiko@gmail.com>,
        Quentin Monnet <quentin@isovalent.com>,
        Changbin Du <changbin.du@gmail.com>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Andrii Nakryiko <andrii@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Shuah Khan <shuah@kernel.org>,
        Martin KaFai Lau <martin.lau@linux.dev>,
        Song Liu <song@kernel.org>, Yonghong Song <yhs@fb.com>,
        John Fastabend <john.fastabend@gmail.com>,
        KP Singh <kpsingh@kernel.org>,
        Stanislav Fomichev <sdf@google.com>,
        Hao Luo <haoluo@google.com>, Jiri Olsa <jolsa@kernel.org>,
        bpf@vger.kernel.org, linux-kernel@vger.kernel.org,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Namhyung Kim <namhyung@kernel.org>,
        Mykola Lysenko <mykolal@fb.com>,
        linux-perf-users@vger.kernel.org, linux-kselftest@vger.kernel.org
Subject: Re: [PATCH v3 1/2] libbpf: show error info about missing ".BTF"
 section
Message-ID: <20221230121020.boqhrujywruq3oi2@mail.google.com>
References: <20221217223509.88254-1-changbin.du@gmail.com>
 <20221217223509.88254-2-changbin.du@gmail.com>
 <Y5/eE+ds+e+k3VJO@leoy-yangtze.lan>
 <20221220013114.zkkxkqh7orahxbzh@mail.google.com>
 <Y6GdofET0gHQzRX6@leoy-yangtze.lan>
 <CAEf4Bzb_XOEoG9anNdzQVJRqd3G4yKJTSa9Dgc9xkMXqn-xdFg@mail.gmail.com>
 <Y6KDrELoIfPbh3VN@leoy-yangtze.lan>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <Y6KDrELoIfPbh3VN@leoy-yangtze.lan>
Precedence: bulk

On Wed, Dec 21, 2022 at 11:55:24AM +0800, Leo Yan wrote:
> On Tue, Dec 20, 2022 at 04:13:13PM -0800, Andrii Nakryiko wrote:
> 
> [...]
> 
> > > > > > @@ -990,6 +990,7 @@ static struct btf *btf_parse_elf(const char *path, struct btf *base_btf,
> > > > > >   err = 0;
> > > > > >
> > > > > >   if (!btf_data) {
> > > > > > +         pr_warn("failed to find '%s' ELF section in %s\n", BTF_ELF_SEC, path);
> > > > > >           err = -ENOENT;
> > >
> > > btf_parse_elf() returns -ENOENT when ELF file doesn't contain BTF
> > > section, therefore, bpftool dumps error string "No such file or
> > > directory".  It's confused that actually vmlinux is existed.
> > >
> > > I am wondering if we can use error -LIBBPF_ERRNO__FORMAT (or any
> > > better choice?) to replace -ENOENT at here, this can avoid bpftool to
> > > outputs "No such file or directory" in this case.
> > 
> > The only really meaningful error code would be -ESRCH, which
> > strerror() will translate to "No such process", which is also
> > completely confusing.
> 
> Or maybe -ENODATA (No data available) is a better choice?
> 
> Thanks,
> Leo
>
Yan, will you have a patch for this suggestion?

[snip]

-- 
Cheers,
Changbin Du