On Thu, Oct 10, 2024 at 2:17 PM Andrii Nakryiko <andrii@xxxxxxxxxx> wrote:
>
> Add a subprogram to BPF object file that otherwise has no entry BPF
> programs to validate that libbpf can still load this correctly.
>
> Until this was fixed, user could expect this very confusing error message:
>
> libbpf: prog 'dangling_subprog': missing BPF prog type, check ELF section name '.text'
> libbpf: prog 'dangling_subprog': failed to load: -22
> libbpf: failed to load object 'struct_ops_detach'
> libbpf: failed to load BPF skeleton 'struct_ops_detach': -22
>
> Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
> ---
> tools/testing/selftests/bpf/progs/struct_ops_detach.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/tools/testing/selftests/bpf/progs/struct_ops_detach.c b/tools/testing/selftests/bpf/progs/struct_ops_detach.c
> index 56b787a89876..5222d58592a7 100644
> --- a/tools/testing/selftests/bpf/progs/struct_ops_detach.c
> +++ b/tools/testing/selftests/bpf/progs/struct_ops_detach.c
> @@ -6,5 +6,11 @@
>
> char _license[] SEC("license") = "GPL";
>
argh, I had this comment here, which I missed to amend into this
patch, maybe whoever applies can just add it so I don't spam the
mailing list:
/* This subprogram validates that libbpf handles the situation in which BPF
* object has subprograms in .text section, but has no entry BPF programs.
* At some point that was causing issues due to legacy logic of treating such
* subprogram as entry program (with unknown program type, which would fail).
*/
> +int dangling_subprog(void)
> +{
> + /* do nothing, just be here */
> + return 0;
> +}
> +
> SEC(".struct_ops.link")
> struct bpf_testmod_ops testmod_do_detach;
> --
> 2.43.5
>
