netdev - Re: [PATCH bpf-next v7 07/11] libbpf: implement bpf_prog_query

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Date:   Mon, 23 May 2022 16:22:37 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Stanislav Fomichev <sdf@...gle.com>
Cc:     Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>
Subject: Re: [PATCH bpf-next v7 07/11] libbpf: implement bpf_prog_query_opts

On Wed, May 18, 2022 at 3:55 PM Stanislav Fomichev <sdf@...gle.com> wrote:
>
> Implement bpf_prog_query_opts as a more expendable version of
> bpf_prog_query. Expose new prog_attach_flags and attach_btf_func_id as
> well:
>
> * prog_attach_flags is a per-program attach_type; relevant only for
>   lsm cgroup program which might have different attach_flags
>   per attach_btf_id
> * attach_btf_func_id is a new field expose for prog_query which
>   specifies real btf function id for lsm cgroup attachments
>

just thoughts aloud... Shouldn't bpf_prog_query() also return link_id
if the attachment was done with LINK_CREATE? And then attach flags
could actually be fetched through corresponding struct bpf_link_info.
That is, bpf_prog_query() returns a list of link_ids, and whatever
link-specific information can be fetched by querying individual links.
Seems more logical (and useful overall) to extend struct bpf_link_info
(you can get it more generically from bpftool, by querying fdinfo,
etc).

> Signed-off-by: Stanislav Fomichev <sdf@...gle.com>
> ---
>  tools/include/uapi/linux/bpf.h |  5 ++++
>  tools/lib/bpf/bpf.c            | 42 +++++++++++++++++++++++++++-------
>  tools/lib/bpf/bpf.h            | 15 ++++++++++++
>  tools/lib/bpf/libbpf.map       |  1 +
>  4 files changed, 55 insertions(+), 8 deletions(-)
>

[...]

>         ret = sys_bpf(BPF_PROG_QUERY, &attr, sizeof(attr));
>
> -       if (attach_flags)
> -               *attach_flags = attr.query.attach_flags;
> -       *prog_cnt = attr.query.prog_cnt;
> +       if (OPTS_HAS(opts, prog_cnt))
> +               opts->prog_cnt = attr.query.prog_cnt;

just use OPTS_SET() instead of OPTS_HAS check

> +       if (OPTS_HAS(opts, attach_flags))
> +               opts->attach_flags = attr.query.attach_flags;
>
>         return libbpf_err_errno(ret);
>  }
>

[...]

> diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
> index 6b36f46ab5d8..24f7a5147bf2 100644
> --- a/tools/lib/bpf/libbpf.map
> +++ b/tools/lib/bpf/libbpf.map
> @@ -452,6 +452,7 @@ LIBBPF_0.8.0 {
>                 bpf_map_delete_elem_flags;
>                 bpf_object__destroy_subskeleton;
>                 bpf_object__open_subskeleton;
> +               bpf_prog_query_opts;

please put it into LIBBPF_1.0.0 section, 0.8 is closed now


>                 bpf_program__attach_kprobe_multi_opts;
>                 bpf_program__attach_trace_opts;
>                 bpf_program__attach_usdt;
> --
> 2.36.1.124.g0e6072fb45-goog
>