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Date:   Thu, 13 Oct 2022 20:43:47 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     wangyufen <wangyufen@...wei.com>
Cc:     quentin@...valent.com, ast@...nel.org, daniel@...earbox.net,
        andrii@...nel.org, martin.lau@...ux.dev, song@...nel.org,
        yhs@...com, john.fastabend@...il.com, kpsingh@...nel.org,
        sdf@...gle.com, haoluo@...gle.com, jolsa@...nel.org,
        davem@...emloft.net, kuba@...nel.org, hawk@...nel.org,
        nathan@...nel.org, ndesaulniers@...gle.com, trix@...hat.com,
        bpf@...r.kernel.org, netdev@...r.kernel.org, llvm@...ts.linux.dev
Subject: Re: [bpf-next v8 1/3] bpftool: Add autoattach for bpf prog load|loadall

On Thu, Oct 13, 2022 at 7:24 PM wangyufen <wangyufen@...wei.com> wrote:
>
>
> 在 2022/10/14 3:47, Andrii Nakryiko 写道:
> > On Mon, Oct 10, 2022 at 3:40 AM Wang Yufen <wangyufen@...wei.com> wrote:
> >> Add autoattach optional to support one-step load-attach-pin_link.
> >>
> >> For example,
> >>     $ bpftool prog loadall test.o /sys/fs/bpf/test autoattach
> >>
> >>     $ bpftool link
> >>     26: tracing  name test1  tag f0da7d0058c00236  gpl
> >>          loaded_at 2022-09-09T21:39:49+0800  uid 0
> >>          xlated 88B  jited 55B  memlock 4096B  map_ids 3
> >>          btf_id 55
> >>     28: kprobe  name test3  tag 002ef1bef0723833  gpl
> >>          loaded_at 2022-09-09T21:39:49+0800  uid 0
> >>          xlated 88B  jited 56B  memlock 4096B  map_ids 3
> >>          btf_id 55
> >>     57: tracepoint  name oncpu  tag 7aa55dfbdcb78941  gpl
> >>          loaded_at 2022-09-09T21:41:32+0800  uid 0
> >>          xlated 456B  jited 265B  memlock 4096B  map_ids 17,13,14,15
> >>          btf_id 82
> >>
> >>     $ bpftool link
> >>     1: tracing  prog 26
> >>          prog_type tracing  attach_type trace_fentry
> >>     3: perf_event  prog 28
> >>     10: perf_event  prog 57
> >>
> >> The autoattach optional can support tracepoints, k(ret)probes,
> >> u(ret)probes.
> >>
> >> Signed-off-by: Wei Yongjun <weiyongjun1@...wei.com>
> >> Signed-off-by: Wang Yufen <wangyufen@...wei.com>
> >> ---
> >>   tools/bpf/bpftool/prog.c | 78 ++++++++++++++++++++++++++++++++++++++++++++++--
> >>   1 file changed, 76 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/tools/bpf/bpftool/prog.c b/tools/bpf/bpftool/prog.c
> >> index c81362a..8f3afce 100644
> >> --- a/tools/bpf/bpftool/prog.c
> >> +++ b/tools/bpf/bpftool/prog.c
> >> @@ -1453,6 +1453,69 @@ static int do_run(int argc, char **argv)
> >>          return ret;
> >>   }
> >>
> >> +static int
> >> +auto_attach_program(struct bpf_program *prog, const char *path)
> >> +{
> >> +       struct bpf_link *link;
> >> +       int err;
> >> +
> >> +       link = bpf_program__attach(prog);
> >> +       if (!link) {
> >> +               p_info("Program %s does not support autoattach, falling back to pinning",
> >> +                      bpf_program__name(prog));
> >> +               return bpf_obj_pin(bpf_program__fd(prog), path);
> >> +       }
> >> +       err = bpf_link__pin(link, path);
> >> +       if (err) {
> >> +               bpf_link__destroy(link);
> >> +               return err;
> >> +       }
> > leaking link here, destroy it unconditionally. If pinning succeeded,
> > you don't need to hold link's FD open anymore.
>
> I got it, will change. Thanks!
>
> >
> >> +       return 0;
> >> +}
> >> +
> >> +static int pathname_concat(const char *path, const char *name, char *buf)
> > why you didn't do the same as in libbpf? Pass buffer size explicitly
> > instead of assuming PATH_MAX
>
> The pathname_concat function is invoked only in one place and is not a
> general function here. So, not modified. Or, can I change the "pathname_concat"
> of libbpf to "LIBBPF_API int libbpf_pathname_concat" and use the
> libbpf_pathname_concat directly?

no need to reuse libbpf's helper, but I do think it's cleaner to
specify not just buffer pointer, but also it's size, just like you do
with any other string buffer API (like snprintf)

>
>
> >
> >> +{
> >> +       int len;
> >> +
> >> +       len = snprintf(buf, PATH_MAX, "%s/%s", path, name);
> >> +       if (len < 0)
> >> +               return -EINVAL;
> >> +       if (len >= PATH_MAX)
> >> +               return -ENAMETOOLONG;
> >> +
> >> +       return 0;
> >> +}
> >> +
> >> +static int
> >> +auto_attach_programs(struct bpf_object *obj, const char *path)
> >> +{
> >> +       struct bpf_program *prog;
> >> +       char buf[PATH_MAX];
> >> +       int err;
> >> +
> >> +       bpf_object__for_each_program(prog, obj) {
> >> +               err = pathname_concat(path, bpf_program__name(prog), buf);
> >> +               if (err)
> >> +                       goto err_unpin_programs;
> >> +
> >> +               err = auto_attach_program(prog, buf);
> >> +               if (err)
> >> +                       goto err_unpin_programs;
> >> +       }
> >> +
> >> +       return 0;
> >> +
> >> +err_unpin_programs:
> >> +       while ((prog = bpf_object__prev_program(obj, prog))) {
> >> +               if (pathname_concat(path, bpf_program__name(prog), buf))
> >> +                       continue;
> >> +
> >> +               bpf_program__unpin(prog, buf);
> >> +       }
> >> +
> >> +       return err;
> >> +}
> >> +
> >>   static int load_with_options(int argc, char **argv, bool first_prog_only)
> >>   {
> >>          enum bpf_prog_type common_prog_type = BPF_PROG_TYPE_UNSPEC;
> >> @@ -1464,6 +1527,7 @@ static int load_with_options(int argc, char **argv, bool first_prog_only)
> >>          struct bpf_program *prog = NULL, *pos;
> >>          unsigned int old_map_fds = 0;
> >>          const char *pinmaps = NULL;
> >> +       bool auto_attach = false;
> >>          struct bpf_object *obj;
> >>          struct bpf_map *map;
> >>          const char *pinfile;
> >> @@ -1583,6 +1647,9 @@ static int load_with_options(int argc, char **argv, bool first_prog_only)
> >>                                  goto err_free_reuse_maps;
> >>
> >>                          pinmaps = GET_ARG();
> >> +               } else if (is_prefix(*argv, "autoattach")) {
> >> +                       auto_attach = true;
> >> +                       NEXT_ARG();
> >>                  } else {
> >>                          p_err("expected no more arguments, 'type', 'map' or 'dev', got: '%s'?",
> >>                                *argv);
> >> @@ -1692,14 +1759,20 @@ static int load_with_options(int argc, char **argv, bool first_prog_only)
> >>                          goto err_close_obj;
> >>                  }
> >>
> >> -               err = bpf_obj_pin(bpf_program__fd(prog), pinfile);
> >> +               if (auto_attach)
> >> +                       err = auto_attach_program(prog, pinfile);
> >> +               else
> >> +                       err = bpf_obj_pin(bpf_program__fd(prog), pinfile);
> >>                  if (err) {
> >>                          p_err("failed to pin program %s",
> >>                                bpf_program__section_name(prog));
> >>                          goto err_close_obj;
> >>                  }
> >>          } else {
> >> -               err = bpf_object__pin_programs(obj, pinfile);
> >> +               if (auto_attach)
> >> +                       err = auto_attach_programs(obj, pinfile);
> >> +               else
> >> +                       err = bpf_object__pin_programs(obj, pinfile);
> >>                  if (err) {
> >>                          p_err("failed to pin all programs");
> >>                          goto err_close_obj;
> >> @@ -2338,6 +2411,7 @@ static int do_help(int argc, char **argv)
> >>                  "                         [type TYPE] [dev NAME] \\\n"
> >>                  "                         [map { idx IDX | name NAME } MAP]\\\n"
> >>                  "                         [pinmaps MAP_DIR]\n"
> >> +               "                         [autoattach]\n"
> >>                  "       %1$s %2$s attach PROG ATTACH_TYPE [MAP]\n"
> >>                  "       %1$s %2$s detach PROG ATTACH_TYPE [MAP]\n"
> >>                  "       %1$s %2$s run PROG \\\n"
> >> --
> >> 1.8.3.1
> >>

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