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Date: Sat, 24 Sep 2022 16:03:49 +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>, <linux-kernel@...r.kernel.org>,
<netdev@...r.kernel.org>, <llvm@...ts.linux.dev>
Subject: Re: [bpf-next v5 1/3] bpftool: Add auto_attach for bpf prog
load|loadall
在 2022/9/24 5:29, Andrii Nakryiko 写道:
> On Wed, Sep 21, 2022 at 12:40 AM Wang Yufen <wangyufen@...wei.com> wrote:
>> Add auto_attach optional to support one-step load-attach-pin_link.
>>
>> For example,
>> $ bpftool prog loadall test.o /sys/fs/bpf/test auto_attach
>>
>> $ 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 auto_attach 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>
>> Reviewed-by: Quentin Monnet <quentin@...valent.com>
>> ---
>> v4 -> v5: some formatting nits of doc
>> v3 -> v4: rename functions, update doc, bash and do_help()
>> v2 -> v3: switch to extend prog load command instead of extend perf
>> v2: https://patchwork.kernel.org/project/netdevbpf/patch/20220824033837.458197-1-weiyongjun1@huawei.com/
>> v1: https://patchwork.kernel.org/project/netdevbpf/patch/20220816151725.153343-1-weiyongjun1@huawei.com/
>> tools/bpf/bpftool/prog.c | 77 ++++++++++++++++++++++++++++++++++++++++++++++--
>> 1 file changed, 75 insertions(+), 2 deletions(-)
>>
>> diff --git a/tools/bpf/bpftool/prog.c b/tools/bpf/bpftool/prog.c
>> index c81362a..aea0b57 100644
>> --- a/tools/bpf/bpftool/prog.c
>> +++ b/tools/bpf/bpftool/prog.c
>> @@ -1453,6 +1453,68 @@ 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);
>> + err = libbpf_get_error(link);
> nit: bpftool uses libbpf 1.0, so no need to use libbpf_get_error()
> anymore, you can just check link for NULL and then look at errno
Thanks, will change in v6
>
> but I wanted to check on desired behavior here. BPF skeleton will skip
> programs that can't be auto-attached because they are of the type that
> can't be declaratively specified to be auto-attachable. For such
> programs bpf_program__attach() will return -EOPNOTSUPP and libbpf's
> skeleton_attach API will silently skip them. Should bpftool be
> stricter about such programs here or should it follow BPF skeleton
> approach?
will change auto_attach_programs() to follow BPF skeleton approach in v6
>> + if (err)
>> + return err;
>> +
>> + err = bpf_link__pin(link, path);
>> + if (err) {
>> + bpf_link__destroy(link);
>> + return err;
>> + }
>> + return 0;
>> +}
>> +
>> +static int pathname_concat(const char *path, const char *name, char *buf)
> you added buffer size in libbpf version of this function, maybe match
> the same signature (I also moved buf and buf_sz to be first two args).
>
>> +{
>> + 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;
>> + }
>> +
> would it be safer to first make sure that all programs are
> auto-attached and then pin links?
>
> also note that not all bpf_links returned by libbpf are actual links
> in kernel (e.g., kprobe/tp bpf_link on older kernels).
will silently skip the unsupport programs as BPF skeleton
approach
>
>> + 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 +1526,7 @@ 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 +1646,9 @@ 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, "auto_attach")) {
>> + auto_attach = true;
>> + NEXT_ARG();
>> } else {
>> p_err("expected no more arguments, 'type', 'map' or 'dev', got: '%s'?",
>> *argv);
>> @@ -1692,14 +1758,20 @@ 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 +2410,7 @@ static int do_help(int argc, char **argv)
>> " [type TYPE] [dev NAME] \\\n"
>> " [map { idx IDX | name NAME } MAP]\\\n"
>> " [pinmaps MAP_DIR]\n"
>> + " [auto_attach]\n"
> looking at "pinmaps" seems like "autoattach" would be more consistent
> naming? Or just "attach"?
will change to "autoattach" in v6
>
>> " %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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