Re: [PATCH bpf-next v8 4/5] libbpf: Init kprobe prog expected_attach_type for kfunc probe

[Tao Chen <chen.dylane@xxxxxxxxx>]

在 2025/2/25 09:15, Andrii Nakryiko 写道:
> On Mon, Feb 24, 2025 at 9:03 AM Tao Chen <chen.dylane@xxxxxxxxx> wrote:
> > Kprobe prog type kfuncs like bpf_session_is_return and
> > bpf_session_cookie will check the expected_attach_type,
> > so init the expected_attach_type here.
> >
> > Signed-off-by: Tao Chen <chen.dylane@xxxxxxxxx>
> > ---
> >   tools/lib/bpf/libbpf_probes.c | 1 +
> >   1 file changed, 1 insertion(+)
> >
> > diff --git a/tools/lib/bpf/libbpf_probes.c b/tools/lib/bpf/libbpf_probes.c
> > index 8efebc18a215..bb5b457ddc80 100644
> > --- a/tools/lib/bpf/libbpf_probes.c
> > +++ b/tools/lib/bpf/libbpf_probes.c
> > @@ -126,6 +126,7 @@ static int probe_prog_load(enum bpf_prog_type prog_type,
> >                  break;
> >          case BPF_PROG_TYPE_KPROBE:
> >                  opts.kern_version = get_kernel_version();
> > +               opts.expected_attach_type = BPF_TRACE_KPROBE_SESSION;
>
> so KPROBE_SESSION is relative recent feature, if we unconditionally
> specify this, we'll regress some feature probes for old kernels where
> KPROBE_SESSION isn't supported, no?

Yeah, maybe we can detect the kernel version first, will fix it.

+               if (opts.kern_version >= KERNEL_VERSION(6, 12, 0))
+                       opts.expected_attach_type =BPF_TRACE_KPROBE_SESSION;

> pw-bot: cr
>
> >                  break;
> >          case BPF_PROG_TYPE_LIRC_MODE2:
> >                  opts.expected_attach_type = BPF_LIRC_MODE2;
> > --
> > 2.43.0


--
Best Regards
Tao Chen