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

[Andrii Nakryiko <andrii.nakryiko@xxxxxxxxx>]

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?

pw-bot: cr

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