Re: [PATCH bpf-next 2/3] bpf: Show precise rejected function when attaching to __btf_id functions

[KaFai Wan <mannkafai@gmail.com>]

On Thu, 2025-07-10 at 10:19 -0700, Alexei Starovoitov wrote:
> On Thu, Jul 10, 2025 at 9:27 AM KaFai Wan <mannkafai@gmail.com>
> wrote:
> > 
> > Show the precise rejected function name when attaching tracing to
> > __btf_id functions.
> > 
> > $ ./fentry
> > libbpf: prog 'migrate_disable': BPF program load failed: -EINVAL
> > libbpf: prog 'migrate_disable': -- BEGIN PROG LOAD LOG --
> > Attaching tracing to __btf_id function 'migrate_disable' is
> > rejected.
> > 
> > Signed-off-by: KaFai Wan <mannkafai@gmail.com>
> > ---
> >  kernel/bpf/verifier.c | 2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> > index 275d82fb1a1a..2779d63e1f8b 100644
> > --- a/kernel/bpf/verifier.c
> > +++ b/kernel/bpf/verifier.c
> > @@ -23938,6 +23938,8 @@ static int check_attach_btf_id(struct
> > bpf_verifier_env *env)
> >                         return ret;
> >         } else if (prog->type == BPF_PROG_TYPE_TRACING &&
> >                    btf_id_set_contains(&btf_id_deny, btf_id)) {
> > +               verbose(env, "Attaching tracing to __btf_id
> > function '%s' is rejected.\n",
> > +                       tgt_info.tgt_name);
> 
> "Attaching tracing to __btf_id" ?! What does it mean?
> Drop "__btf_id" and "tracing" bits.
> 

My fault, I mean "Attaching tracing programs to function" in
'btf_id_deny'.

I will change it in v2.

> --
> pw-bot: cr

-- 
Thanks,
KaFai