Re: [RFC PATCH bpf-next v2 3/7] libbpf: Add support for rstat flush progs

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On Sat, May 14, 2022 at 7:35 PM Yosry Ahmed <yosryahmed@xxxxxxxxxx> wrote:
>
> Add support to attach RSTAT_FLUSH programs.
>
> Signed-off-by: Yosry Ahmed <yosryahmed@xxxxxxxxxx>
> ---
>  tools/lib/bpf/bpf.c      |  1 -
>  tools/lib/bpf/libbpf.c   | 40 ++++++++++++++++++++++++++++++++++++++++
>  tools/lib/bpf/libbpf.h   |  3 +++
>  tools/lib/bpf/libbpf.map |  1 +
>  4 files changed, 44 insertions(+), 1 deletion(-)
>
> diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
> index 5660268e103f..9e3cb0d1eb99 100644
> --- a/tools/lib/bpf/bpf.c
> +++ b/tools/lib/bpf/bpf.c
> @@ -870,7 +870,6 @@ int bpf_link_create(int prog_fd, int target_fd,
>                 attr.link_create.tracing.cookie = OPTS_GET(opts, tracing.cookie, 0);
>                 if (!OPTS_ZEROED(opts, tracing))
>                         return libbpf_err(-EINVAL);
> -               break;

This is a mistake, a remnant of RFC V1. Will remove it in the next version.

>         default:
>                 if (!OPTS_ZEROED(opts, flags))
>                         return libbpf_err(-EINVAL);
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index 4867a930628b..b7fc64ebf8dd 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -8998,6 +8998,7 @@ static int attach_trace(const struct bpf_program *prog, long cookie, struct bpf_
>  static int attach_kprobe_multi(const struct bpf_program *prog, long cookie, struct bpf_link **link);
>  static int attach_lsm(const struct bpf_program *prog, long cookie, struct bpf_link **link);
>  static int attach_iter(const struct bpf_program *prog, long cookie, struct bpf_link **link);
> +static int attach_rstat(const struct bpf_program *prog, long cookie, struct bpf_link **link);
>
>  static const struct bpf_sec_def section_defs[] = {
>         SEC_DEF("socket",               SOCKET_FILTER, 0, SEC_NONE | SEC_SLOPPY_PFX),
> @@ -9078,6 +9079,7 @@ static const struct bpf_sec_def section_defs[] = {
>         SEC_DEF("cgroup/setsockopt",    CGROUP_SOCKOPT, BPF_CGROUP_SETSOCKOPT, SEC_ATTACHABLE | SEC_SLOPPY_PFX),
>         SEC_DEF("struct_ops+",          STRUCT_OPS, 0, SEC_NONE),
>         SEC_DEF("sk_lookup",            SK_LOOKUP, BPF_SK_LOOKUP, SEC_ATTACHABLE | SEC_SLOPPY_PFX),
> +       SEC_DEF("rstat/flush",          RSTAT_FLUSH, 0, SEC_NONE, attach_rstat),
>  };
>
>  static size_t custom_sec_def_cnt;
> @@ -11784,6 +11786,44 @@ static int attach_iter(const struct bpf_program *prog, long cookie, struct bpf_l
>         return libbpf_get_error(*link);
>  }
>
> +struct bpf_link *bpf_program__attach_rstat(const struct bpf_program *prog)
> +{
> +       struct bpf_link *link = NULL;
> +       char errmsg[STRERR_BUFSIZE];
> +       int err, prog_fd, link_fd;
> +
> +       prog_fd = bpf_program__fd(prog);
> +       if (prog_fd < 0) {
> +               pr_warn("prog '%s': can't attach before loaded\n", prog->name);
> +               return libbpf_err_ptr(-EINVAL);
> +       }
> +
> +       link = calloc(1, sizeof(*link));
> +       if (!link)
> +               return libbpf_err_ptr(-ENOMEM);
> +       link->detach = &bpf_link__detach_fd;
> +
> +       /* rstat flushers are currently the only supported rstat programs */
> +       link_fd = bpf_link_create(prog_fd, 0, BPF_RSTAT_FLUSH, NULL);
> +       if (link_fd < 0) {
> +               err = -errno;
> +               pr_warn("prog '%s': failed to attach: %s\n",
> +                       prog->name, libbpf_strerror_r(err, errmsg,
> +                                                     sizeof(errmsg)));
> +               free(link);
> +               return libbpf_err_ptr(err);
> +       }
> +
> +       link->fd = link_fd;
> +       return link;
> +}
> +
> +static int attach_rstat(const struct bpf_program *prog, long cookie, struct bpf_link **link)
> +{
> +       *link = bpf_program__attach_rstat(prog);
> +       return libbpf_get_error(*link);
> +}
> +
>  struct bpf_link *bpf_program__attach(const struct bpf_program *prog)
>  {
>         struct bpf_link *link = NULL;
> diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
> index 21984dcd6dbe..f8b6827d5550 100644
> --- a/tools/lib/bpf/libbpf.h
> +++ b/tools/lib/bpf/libbpf.h
> @@ -662,6 +662,9 @@ LIBBPF_API struct bpf_link *
>  bpf_program__attach_iter(const struct bpf_program *prog,
>                          const struct bpf_iter_attach_opts *opts);
>
> +LIBBPF_API struct bpf_link *
> +bpf_program__attach_rstat(const struct bpf_program *prog);
> +
>  /*
>   * Libbpf allows callers to adjust BPF programs before being loaded
>   * into kernel. One program in an object file can be transformed into
> diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
> index 008da8db1d94..f945c6265cb5 100644
> --- a/tools/lib/bpf/libbpf.map
> +++ b/tools/lib/bpf/libbpf.map
> @@ -449,6 +449,7 @@ LIBBPF_0.8.0 {
>                 bpf_program__attach_kprobe_multi_opts;
>                 bpf_program__attach_trace_opts;
>                 bpf_program__attach_usdt;
> +               bpf_program__attach_rstat;
>                 bpf_program__set_insns;
>                 libbpf_register_prog_handler;
>                 libbpf_unregister_prog_handler;
> --
> 2.36.0.550.gb090851708-goog
>



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