netdev - Re: [PATCH bpf-next v5 3/5] libbpf: Add BPF_PROG_BIND_MAP syscall and use it on .rodata section

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Date:   Tue, 15 Sep 2020 15:03:05 -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 <zhuyifei1999@...il.com>
Subject: Re: [PATCH bpf-next v5 3/5] libbpf: Add BPF_PROG_BIND_MAP syscall and
 use it on .rodata section

On Mon, Sep 14, 2020 at 4:28 PM Andrii Nakryiko
<andrii.nakryiko@...il.com> wrote:
>
> On Mon, Sep 14, 2020 at 11:37 AM Stanislav Fomichev <sdf@...gle.com> wrote:
> >
> > +       if (!kernel_supports(FEAT_GLOBAL_DATA))
> > +               return 0;
>
> TBH, I don't think this check is needed, and it's actually coupling
> two independent features together. probe_prog_bind_map() probes
> PROG_BIND_MAP, it has nothing to do with global data itself. It's all
> cached now, so there is no problem with that, it just feels unclean.
> If someone is using .rodata and the kernel doesn't support global
> data, we'll fail way sooner. On the other hand, if there will be
> another use case where PROG_BIND_MAP is needed for something else, why
> would we care about global data support? I know that in the real world
> it will be hard to find a kernel with PROG_BIND_MAP and no global data
> support, due to the latter being so much older, but still, unnecessary
> coupling.
>
> Would be nice to follow up and remove this, thanks.
Agreed, will respin, thanks!