Re: [RFC bpf-next 09/12] libbpf: Add support to create tracing multi link

[Jiri Olsa <olsajiri@gmail.com>]

On Wed, Feb 04, 2026 at 11:05:16AM -0800, Andrii Nakryiko wrote:
> On Tue, Feb 3, 2026 at 1:40 AM Jiri Olsa <jolsa@kernel.org> wrote:
> >
> > Adding new interface function to attach programs with tracing
> > multi link:
> >
> >   bpf_program__attach_tracing_multi(const struct bpf_program *prog,
> >                                     const char *pattern,
> >                                     const struct bpf_tracing_multi_opts *opts);
> >
> > The program is attach to functions specified by pattern or by
> > btf IDs specified in bpf_tracing_multi_opts object.
> >
> > Adding support for new sections to attach programs with above
> > functions:
> >
> >    fentry.multi/pattern
> >    fexit.multi/pattern
> >
> > Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> > ---
> >  tools/lib/bpf/bpf.c      |  7 ++++
> >  tools/lib/bpf/bpf.h      |  4 ++
> >  tools/lib/bpf/libbpf.c   | 87 ++++++++++++++++++++++++++++++++++++++++
> >  tools/lib/bpf/libbpf.h   | 14 +++++++
> >  tools/lib/bpf/libbpf.map |  1 +
> >  5 files changed, 113 insertions(+)
> 
> [...]
> 
> >  static const char * const map_type_name[] = {
> > @@ -9814,6 +9817,7 @@ static int attach_kprobe_session(const struct bpf_program *prog, long cookie, st
> >  static int attach_uprobe_multi(const struct bpf_program *prog, long cookie, struct bpf_link **link);
> >  static int attach_lsm(const struct bpf_program *prog, long cookie, struct bpf_link **link);
> >  static int attach_iter(const struct bpf_program *prog, long cookie, struct bpf_link **link);
> > +static int attach_tracing_multi(const struct bpf_program *prog, long cookie, struct bpf_link **link);
> >
> >  static const struct bpf_sec_def section_defs[] = {
> >         SEC_DEF("socket",               SOCKET_FILTER, 0, SEC_NONE),
> > @@ -9862,6 +9866,8 @@ static const struct bpf_sec_def section_defs[] = {
> >         SEC_DEF("fexit.s+",             TRACING, BPF_TRACE_FEXIT, SEC_ATTACH_BTF | SEC_SLEEPABLE, attach_trace),
> >         SEC_DEF("fsession+",            TRACING, BPF_TRACE_FSESSION, SEC_ATTACH_BTF, attach_trace),
> >         SEC_DEF("fsession.s+",          TRACING, BPF_TRACE_FSESSION, SEC_ATTACH_BTF | SEC_SLEEPABLE, attach_trace),
> > +       SEC_DEF("fentry.multi+",        TRACING, BPF_TRACE_FENTRY_MULTI, 0, attach_tracing_multi),
> > +       SEC_DEF("fexit.multi+",         TRACING, BPF_TRACE_FEXIT_MULTI, 0, attach_tracing_multi),
> >         SEC_DEF("freplace+",            EXT, 0, SEC_ATTACH_BTF, attach_trace),
> >         SEC_DEF("lsm+",                 LSM, BPF_LSM_MAC, SEC_ATTACH_BTF, attach_lsm),
> >         SEC_DEF("lsm.s+",               LSM, BPF_LSM_MAC, SEC_ATTACH_BTF | SEC_SLEEPABLE, attach_lsm),
> > @@ -12237,6 +12243,87 @@ static int attach_uprobe_multi(const struct bpf_program *prog, long cookie, stru
> >         return ret;
> >  }
> >
> > +struct bpf_link *
> > +bpf_program__attach_tracing_multi(const struct bpf_program *prog, const char *pattern,
> > +                                 const struct bpf_tracing_multi_opts *opts)
> > +{
> > +       LIBBPF_OPTS(bpf_link_create_opts, lopts);
> > +       __u32 *btf_ids, cnt, *free_ids = NULL;
> > +       int prog_fd, link_fd, err;
> > +       struct bpf_link *link;
> > +
> > +       btf_ids = OPTS_GET(opts, btf_ids, false);
> > +       cnt = OPTS_GET(opts, cnt, false);
> > +
> > +       if (!pattern && !btf_ids && !cnt)
> 
> let's check that either both btf_ids and cnt are specified or none
> 
> then we can check that either pattern or btf_ids are specified
> 
> still two checks, but will capture all the bad cases

ok

> 
> > +               return libbpf_err_ptr(-EINVAL);
> > +       if (pattern && (btf_ids || cnt))
> > +               return libbpf_err_ptr(-EINVAL);
> > +
> 
> [...]
> 
> >  struct bpf_uprobe_opts {
> >         /* size of this struct, for forward/backward compatibility */
> >         size_t sz;
> > diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
> > index d18fbcea7578..a3ffb21270e9 100644
> > --- a/tools/lib/bpf/libbpf.map
> > +++ b/tools/lib/bpf/libbpf.map
> > @@ -358,6 +358,7 @@ LIBBPF_1.0.0 {
> >                 bpf_program__attach_ksyscall;
> >                 bpf_program__autoattach;
> >                 bpf_program__set_autoattach;
> > +               bpf_program__attach_tracing_multi;
> 
> stuck in the past? ;) we are in 1.7 cycle

a bit :) will fix, thnx

jirka