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Date:   Fri, 14 Oct 2022 10:24:39 +0800
From:   wangyufen <wangyufen@...wei.com>
To:     Andrii Nakryiko <andrii.nakryiko@...il.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


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?


>
>> +{
>> +       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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