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Message-ID: <CAEf4Bzaskw74UeufRgKSbGtk5eybD9J+4keAPYb-u=jb5myLjw@mail.gmail.com>
Date: Fri, 23 Sep 2022 14:29:56 -0700
From: Andrii Nakryiko <andrii.nakryiko@...il.com>
To: Wang Yufen <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, 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
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
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?
> + 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).
> + 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"?
> " %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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