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Message-ID: <CAEf4BzaP=H_+1Yf8ou2zzmu=h2FtDQh4wSSMgabBrPr_jK7SjA@mail.gmail.com>
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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