[PATCH bpf-next 2/2] bpftool: Reject non-autoload programs for light skeletons

[Thiébaud Weksteen]

When generating a light skeleton (bpftool gen skeleton -L), there is no
libbpf runtime object or bpf_program__set_autoload() API available to
enable/disable the autoloading of programs. If a BPF program in the
object has autoload disabled (e.g. via SEC("?...")), bpf_object__load()
silently skips loading it. bpftool still generates struct bpf_prog_desc
fields and attach functions in the light skeleton header, leaving
skel->progs.<name>.prog_fd uninitialized (0).

Explicitly reject non-autoloaded programs when use_loader is true with
an error message, preventing the generation of broken light skeleton
headers.

Signed-off-by: Thiébaud Weksteen <tweek@xxxxxxxxxx>
---
 tools/bpf/bpftool/gen.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/tools/bpf/bpftool/gen.c b/tools/bpf/bpftool/gen.c
index a50540ef6521..1583150241c8 100644
--- a/tools/bpf/bpftool/gen.c
+++ b/tools/bpf/bpftool/gen.c
@@ -1340,6 +1340,12 @@ static int do_skeleton(int argc, char **argv)
 	}
 	bpf_object__for_each_program(prog, obj) {
 		prog_cnt++;
+
+		if (use_loader && !bpf_program__autoload(prog)) {
+			p_err("program '%s' is marked as non-autoload, which is not supported for light skeletons",
+			      bpf_program__name(prog));
+			return -1;
+		}
 	}
 
 	get_header_guard(header_guard, obj_name, "SKEL_H");
-- 
2.55.0.979.g7e5102b832-goog