Re: [PATCHv2 bpf-next 1/3] bpf: Add tracing_multi link info support

[Jiri Olsa <olsajiri@gmail.com>]

On Tue, Jun 23, 2026 at 02:01:08PM -0700, Andrii Nakryiko wrote:
> On Tue, Jun 23, 2026 at 7:24 AM Jiri Olsa <jolsa@kernel.org> wrote:
> >
> > Adding BPF_OBJ_GET_INFO_BY_FD support for tracing_multi links.
> >
> > We expose following tracing_multi link data:
> > - attach_type of the program
> > - number of ids
> > - array of BTF ids
> > - array of its related kernel addresses
> > - array of cookies
> >
> > The change follows the kprobe_multi and uprobe_multi link-info convention
> > of optional output arrays with an in/out count,
> >
> > On top of standard tracing link data we also expose addresses, because they
> > are useful info for user (especially when the attachment was done via pattern).
> > This data is hidden when kallsyms does not allow exposing kernel pointer values.
> >
> > Assisted-by: Codex:GPT-5
> > Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> > ---
> >  include/uapi/linux/bpf.h       |  9 ++++++
> >  kernel/trace/bpf_trace.c       | 55 ++++++++++++++++++++++++++++++++++
> >  tools/include/uapi/linux/bpf.h |  9 ++++++
> >  3 files changed, 73 insertions(+)
> >
> > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> > index 89b36de5fdbb..80423ccc6b57 100644
> > --- a/include/uapi/linux/bpf.h
> > +++ b/include/uapi/linux/bpf.h
> > @@ -6839,6 +6839,15 @@ struct bpf_link_info {
> >                         __u32 flags;
> >                         __u32 pid;
> >                 } uprobe_multi;
> > +               struct {
> > +                       __u32 attach_type;
> > +                       __u32 count; /* in/out: tracing_multi target count */
> > +                       __u32 obj_id;
> 
> we have attach_btf_obj_id in bpf_prog_info, but target_obj_id in
> bpf_link_info for tracing programs. The latter, though, is actually
> not always BTF object ID (it can be prog_id for PROG_EXT)...
> 
> So, me personally, I was confused what "obj_id" here mean, it would be
> more obvious if it was called "btf_obj_id", tbh. But that's a minor
> nit/confusion, not feeling strongly.

ok, btf_obj_id si better choice, will change

> 
> everything else LGTM
> 
> Acked-by: Andrii Nakryiko <andrii@kernel.org>

thanks,
jirka