netdev - Re: [PATCH bpf-next v4 5/5] selftests/bpf: Test load and dump metadata with btftool and skel

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Date:   Fri, 11 Sep 2020 08:57:37 -0700
From:   Stanislav Fomichev <sdf@...gle.com>
To:     Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc:     Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        YiFei Zhu <zhuyifei@...gle.com>,
        YiFei Zhu <zhuyifei1999@...il.com>
Subject: Re: [PATCH bpf-next v4 5/5] selftests/bpf: Test load and dump
 metadata with btftool and skel

On Thu, Sep 10, 2020 at 12:59 PM Andrii Nakryiko
<andrii.nakryiko@...il.com> wrote:
>
> On Wed, Sep 9, 2020 at 11:25 AM Stanislav Fomichev <sdf@...gle.com> wrote:
> >
> > From: YiFei Zhu <zhuyifei@...gle.com>
> >
> > This is a simple test to check that loading and dumping metadata
> > in btftool works, whether or not metadata contents are used by the
> > program.
> >
> > A C test is also added to make sure the skeleton code can read the
> > metadata values.
> >
> > Cc: YiFei Zhu <zhuyifei1999@...il.com>
> > Signed-off-by: YiFei Zhu <zhuyifei@...gle.com>
> > Signed-off-by: Stanislav Fomichev <sdf@...gle.com>
> > ---
>
> It would be good to test that libbpf does bind .rodata even if BPF
> program doesn't use it. So for metadata_unused you can get
> bpf_prog_info and check that it does contain the id of .rodata?
Good idea, will add that.

> > +const char bpf_metadata_a[] SEC(".rodata") = "foo";
> > +const int bpf_metadata_b SEC(".rodata") = 1;
>
> please add volatile to ensure these are not optimized away
Ack, ty!