Re: [PATCH 2/3] libbpf: Add helper to extract perf fd from bpf_link

[Song Liu <liu.song.a23@gmail.com>]

On Tue, Aug 6, 2019 at 4:42 PM Daniel Xu <dxu@dxuuu.xyz> wrote:
>
> It is sometimes necessary to perform ioctl's on the underlying perf fd.
> There is not currently a way to extract the fd given a bpf_link, so add a
> helper for it.

Missing "Signed-off-by" tag. Please run scripts/checkpatch.pl on the patches.

Otherwise, looks good to me.

Acked-by: Song Liu <songliubraving@fb.com>

> ---
>  tools/lib/bpf/libbpf.c   | 13 +++++++++++++
>  tools/lib/bpf/libbpf.h   |  1 +
>  tools/lib/bpf/libbpf.map |  5 +++++
>  3 files changed, 19 insertions(+)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index ead915aec349..8469d69448ae 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -4004,6 +4004,19 @@ static int bpf_link__destroy_perf_event(struct bpf_link *link)
>         return err;
>  }
>
> +int bpf_link__get_perf_fd(struct bpf_link *link)
> +{
> +       struct bpf_link_fd *l = (void *)link;
> +
> +       if (!link)
> +               return -1;
> +
> +       if (link->destroy != &bpf_link__destroy_perf_event)
> +               return -1;
> +
> +       return l->fd;
> +}
> +
>  struct bpf_link *bpf_program__attach_perf_event(struct bpf_program *prog,
>                                                 int pfd)
>  {
> diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
> index 8a9d462a6f6d..5391ac95e4fa 100644
> --- a/tools/lib/bpf/libbpf.h
> +++ b/tools/lib/bpf/libbpf.h
> @@ -168,6 +168,7 @@ LIBBPF_API void bpf_program__unload(struct bpf_program *prog);
>  struct bpf_link;
>
>  LIBBPF_API int bpf_link__destroy(struct bpf_link *link);
> +LIBBPF_API int bpf_link__get_perf_fd(struct bpf_link *link);
>
>  LIBBPF_API struct bpf_link *
>  bpf_program__attach_perf_event(struct bpf_program *prog, int pfd);
> diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
> index f9d316e873d8..0f844ce29b04 100644
> --- a/tools/lib/bpf/libbpf.map
> +++ b/tools/lib/bpf/libbpf.map
> @@ -184,3 +184,8 @@ LIBBPF_0.0.4 {
>                 perf_buffer__new_raw;
>                 perf_buffer__poll;
>  } LIBBPF_0.0.3;
> +
> +LIBBPF_0.0.5 {
> +       global:
> +               bpf_link__get_perf_fd;
> +} LIBBPF_0.0.4;
> --
> 2.20.1
>