netdev - Re: [PATCH bpf-next v8 08/11] libbpf: implement bpf_prog_query

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Date:   Fri, 3 Jun 2022 14:34:52 -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 v8 08/11] libbpf: implement bpf_prog_query_opts

On Wed, Jun 1, 2022 at 12:02 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
>
> Signed-off-by: Stanislav Fomichev <sdf@...gle.com>
> ---
>  tools/include/uapi/linux/bpf.h |  3 +++
>  tools/lib/bpf/bpf.c            | 40 +++++++++++++++++++++++++++-------
>  tools/lib/bpf/bpf.h            | 15 +++++++++++++
>  tools/lib/bpf/libbpf.map       |  2 +-
>  4 files changed, 51 insertions(+), 9 deletions(-)
>

Few consistency nits, but otherwise:

Acked-by: Andrii Nakryiko <andrii@...nel.org>


> diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
> index fa64b0b612fd..4271ef3c2afb 100644
> --- a/tools/include/uapi/linux/bpf.h
> +++ b/tools/include/uapi/linux/bpf.h
> @@ -1432,6 +1432,7 @@ union bpf_attr {
>                 __u32           attach_flags;
>                 __aligned_u64   prog_ids;
>                 __u32           prog_cnt;
> +               __aligned_u64   prog_attach_flags; /* output: per-program attach_flags */
>         } query;
>
>         struct { /* anonymous struct used by BPF_RAW_TRACEPOINT_OPEN command */
> @@ -5996,6 +5997,8 @@ struct bpf_prog_info {
>         __u64 run_cnt;
>         __u64 recursion_misses;
>         __u32 verified_insns;
> +       __u32 attach_btf_obj_id;
> +       __u32 attach_btf_id;
>  } __attribute__((aligned(8)));
>
>  struct bpf_map_info {
> diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
> index 240186aac8e6..c7af7db53725 100644
> --- a/tools/lib/bpf/bpf.c
> +++ b/tools/lib/bpf/bpf.c
> @@ -888,28 +888,52 @@ int bpf_iter_create(int link_fd)
>         return libbpf_err_errno(fd);
>  }
>
> -int bpf_prog_query(int target_fd, enum bpf_attach_type type, __u32 query_flags,
> -                  __u32 *attach_flags, __u32 *prog_ids, __u32 *prog_cnt)
> +int bpf_prog_query_opts(int target_fd,
> +                       enum bpf_attach_type type,
> +                       struct bpf_prog_query_opts *opts)
>  {
>         union bpf_attr attr;
>         int ret;
>
>         memset(&attr, 0, sizeof(attr));
> +
> +       if (!OPTS_VALID(opts, bpf_prog_query_opts))
> +               return libbpf_err(-EINVAL);
> +

nit: check input args before you do work (memset), but it's very minor

>         attr.query.target_fd    = target_fd;
>         attr.query.attach_type  = type;
> -       attr.query.query_flags  = query_flags;
> -       attr.query.prog_cnt     = *prog_cnt;
> -       attr.query.prog_ids     = ptr_to_u64(prog_ids);
> +       attr.query.query_flags  = OPTS_GET(opts, query_flags, 0);
> +       attr.query.prog_cnt     = OPTS_GET(opts, prog_cnt, 0);
> +       attr.query.prog_ids     = ptr_to_u64(OPTS_GET(opts, prog_ids, NULL));
> +       attr.query.prog_attach_flags = ptr_to_u64(OPTS_GET(opts, prog_attach_flags, NULL));
>
>         ret = sys_bpf(BPF_PROG_QUERY, &attr, sizeof(attr));
>
> -       if (attach_flags)
> -               *attach_flags = attr.query.attach_flags;
> -       *prog_cnt = attr.query.prog_cnt;
> +       OPTS_SET(opts, attach_flags, attr.query.attach_flags);
> +       OPTS_SET(opts, prog_cnt, attr.query.prog_cnt);
>
>         return libbpf_err_errno(ret);
>  }
>
> +int bpf_prog_query(int target_fd, enum bpf_attach_type type, __u32 query_flags,
> +                  __u32 *attach_flags, __u32 *prog_ids, __u32 *prog_cnt)
> +{
> +       LIBBPF_OPTS(bpf_prog_query_opts, p);

nit: for consistency it would be good to call variable "opts" as we do
pretty much everywhere else?

> +       int ret;
> +
> +       p.query_flags = query_flags;
> +       p.prog_ids = prog_ids;
> +       p.prog_cnt = *prog_cnt;
> +
> +       ret = bpf_prog_query_opts(target_fd, type, &p);
> +
> +       if (attach_flags)
> +               *attach_flags = p.attach_flags;
> +       *prog_cnt = p.prog_cnt;
> +
> +       return ret;

maybe use libbpf_err() here for consistency and just in case we add
something that can clobber errno

> +}
> +
>  int bpf_prog_test_run(int prog_fd, int repeat, void *data, __u32 size,
>                       void *data_out, __u32 *size_out, __u32 *retval,
>                       __u32 *duration)

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