Re: [bpf-next v6 1/3] bpftool: Add auto_attach for bpf prog load|loadall

[wangyufen]

在 2022/9/26 18:46, Quentin Monnet 写道:
> Sat Sep 24 2022 11:13:48 GMT+0100 (British Summer Time) ~ Wang Yufen
> <wangyufen@xxxxxxxxxx>
> > Add auto_attach 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>
> > ---
> > v5 -> v6: skip the programs not supporting auto-attach,
> > 	  and change optional name from "auto_attach" to "autoattach"
> > 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@xxxxxxxxxx/
> > v1: https://patchwork.kernel.org/project/netdevbpf/patch/20220816151725.153343-1-weiyongjun1@xxxxxxxxxx/
> >   tools/bpf/bpftool/prog.c | 76 ++++++++++++++++++++++++++++++++++++++--
> >   1 file changed, 74 insertions(+), 2 deletions(-)
> >
> > diff --git a/tools/bpf/bpftool/prog.c b/tools/bpf/bpftool/prog.c
> > index c81362a001ba..b1cbd06dee19 100644
> > --- a/tools/bpf/bpftool/prog.c
> > +++ b/tools/bpf/bpftool/prog.c
> > @@ -1453,6 +1453,67 @@ get_prog_type_by_name(const char *name, enum bpf_prog_type *prog_type,
> >   	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)
> > +		return -1;
> > +
> > +	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)
> > +{
> > +	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 && errno != EOPNOTSUPP)
> > +			goto err_unpin_programs;
> If I read the above correctly, we skip entirely programs that couldn't
> be auto-attached. I'm not sure what Andrii had in mind exactly, but it
> would make sense to me to fallback to regular program pinning if the
> program couldn't be attached/linked, so we still keep it loaded in the
> kernel after bpftool exits. Probably with a p_info() message to let
> users know?

Thanks for your comment.
I agree with you.
add in v7.

> > +	}
> > +
> > +	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;
> > +}