Commit a459f4bb authored by Andrii Nakryiko's avatar Andrii Nakryiko Committed by Alexei Starovoitov
Browse files

libbpf: improve old BPF skeleton handling for map auto-attach 



Improve how we handle old BPF skeletons when it comes to BPF map
auto-attachment. Emit one warn-level message per each struct_ops map
that could have been auto-attached, if user provided recent enough BPF
skeleton version. Don't spam log if there are no relevant struct_ops
maps, though.

This should help users realize that they probably need to regenerate BPF
skeleton header with more recent bpftool/libbpf-cargo (or whatever other
means of BPF skeleton generation).

Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Acked-by: default avatarEduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20240708204540.4188946-4-andrii@kernel.org


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 99fb9531

tools/lib/bpf/libbpf.c

+14 −12
Original line number Diff line number Diff line
@@ -13967,32 +13967,34 @@ int bpf_object__attach_skeleton(struct bpf_object_skeleton *s) 
		 */

	}



	/* Skeleton is created with earlier version of bpftool

	 * which does not support auto-attachment

	 */

	if (s->map_skel_sz < sizeof(struct bpf_map_skeleton))

		return 0;



	for (i = 0; i < s->map_cnt; i++) {

		struct bpf_map_skeleton *map_skel = (void *)s->maps + i * s->map_skel_sz;

		struct bpf_map *map = *map_skel->map;

		struct bpf_link **link = map_skel->link;

		struct bpf_link **link;



		if (!map->autocreate || !map->autoattach)

			continue;



		if (*link)

			continue;



		/* only struct_ops maps can be attached */

		if (!bpf_map__is_struct_ops(map))

			continue;

		*link = bpf_map__attach_struct_ops(map);



		/* skeleton is created with earlier version of bpftool, notify user */

		if (s->map_skel_sz < offsetofend(struct bpf_map_skeleton, link)) {

			pr_warn("map '%s': BPF skeleton version is old, skipping map auto-attachment...\n",

				bpf_map__name(map));

			continue;

		}



		link = map_skel->link;

		if (*link)

			continue;



		*link = bpf_map__attach_struct_ops(map);

		if (!*link) {

			err = -errno;

			pr_warn("map '%s': failed to auto-attach: %d\n",

				bpf_map__name(map), err);

			pr_warn("map '%s': failed to auto-attach: %d\n", bpf_map__name(map), err);

			return libbpf_err(err);

		}

	}