[PATCH bpf-next 2/2] selftests/bpf: add subprog to BPF object file with no entry programs

[Andrii Nakryiko <andrii@kernel.org>]

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@kernel.org>
---
 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";
 
+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