Re: [bpf-next v8 1/3] bpftool: Add autoattach for bpf prog load|loadall

[wangyufen <wangyufen@xxxxxxxxxx>]

在 2022/10/14 3:47, Andrii Nakryiko 写道:
> On Mon, Oct 10, 2022 at 3:40 AM Wang Yufen <wangyufen@xxxxxxxxxx> 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@xxxxxxxxxx>
> > Signed-off-by: Wang Yufen <wangyufen@xxxxxxxxxx>
> > ---
> >   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?


> > +{
> > +       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