tools/libbpf: Add support for BPF_MODIFY_RETURN

Signed-off-by: KP Singh <kpsingh@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200304191853.1529-6-kpsingh@chromium.org

tools/lib/bpf/libbpf.c

@@ -6288,6 +6288,10 @@ static const struct bpf_sec_def section_defs[] = {
 		.expected_attach_type = BPF_TRACE_FENTRY,
 		.is_attach_btf = true,
 		.attach_fn = attach_trace),
+	SEC_DEF("fmod_ret/", TRACING,
+		.expected_attach_type = BPF_MODIFY_RETURN,
+		.is_attach_btf = true,
+		.attach_fn = attach_trace),
 	SEC_DEF("fexit/", TRACING,
 		.expected_attach_type = BPF_TRACE_FEXIT,
 		.is_attach_btf = true,