Commit 08ac454e authored by Mykyta Yatsenko's avatar Mykyta Yatsenko Committed by Andrii Nakryiko
Browse files

libbpf: Auto-attach struct_ops BPF maps in BPF skeleton 



Similarly to `bpf_program`, support `bpf_map` automatic attachment in
`bpf_object__attach_skeleton`. Currently only struct_ops maps could be
attached.

On bpftool side, code-generate links in skeleton struct for struct_ops maps.
Similarly to `bpf_program_skeleton`, set links in `bpf_map_skeleton`.

On libbpf side, extend `bpf_map` with new `autoattach` field to support
enabling or disabling autoattach functionality, introducing
getter/setter for this field.

`bpf_object__(attach|detach)_skeleton` is extended with
attaching/detaching struct_ops maps logic.

Signed-off-by: default avatarMykyta Yatsenko <yatsenko@meta.com>
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20240605175135.117127-1-yatsenko@meta.com
parent b24862ba

tools/bpf/bpftool/gen.c

+32 −4
Original line number Diff line number Diff line
@@ -848,7 +848,7 @@ static int gen_trace(struct bpf_object *obj, const char *obj_name, const char *h 
}



static void

codegen_maps_skeleton(struct bpf_object *obj, size_t map_cnt, bool mmaped)

codegen_maps_skeleton(struct bpf_object *obj, size_t map_cnt, bool mmaped, bool populate_links)

{

	struct bpf_map *map;

	char ident[256];
@@ -888,6 +888,14 @@ codegen_maps_skeleton(struct bpf_object *obj, size_t map_cnt, bool mmaped) 
			printf("\ts->maps[%zu].mmaped = (void **)&obj->%s;\n",

				i, ident);

		}



		if (populate_links && bpf_map__type(map) == BPF_MAP_TYPE_STRUCT_OPS) {

			codegen("\

				\n\

					s->maps[%zu].link = &obj->links.%s;\n\

				",

				i, ident);

		}

		i++;

	}

}
@@ -1141,7 +1149,7 @@ static void gen_st_ops_shadow_init(struct btf *btf, struct bpf_object *obj) 
static int do_skeleton(int argc, char **argv)

{

	char header_guard[MAX_OBJ_NAME_LEN + sizeof("__SKEL_H__")];

	size_t map_cnt = 0, prog_cnt = 0, file_sz, mmap_sz;

	size_t map_cnt = 0, prog_cnt = 0, attach_map_cnt = 0, file_sz, mmap_sz;

	DECLARE_LIBBPF_OPTS(bpf_object_open_opts, opts);

	char obj_name[MAX_OBJ_NAME_LEN] = "", *obj_data;

	struct bpf_object *obj = NULL;
@@ -1225,6 +1233,10 @@ static int do_skeleton(int argc, char **argv) 
			      bpf_map__name(map));

			continue;

		}



		if (bpf_map__type(map) == BPF_MAP_TYPE_STRUCT_OPS)

			attach_map_cnt++;



		map_cnt++;

	}

	bpf_object__for_each_program(prog, obj) {
@@ -1297,6 +1309,9 @@ static int do_skeleton(int argc, char **argv) 
				       bpf_program__name(prog));

		}

		printf("\t} progs;\n");

	}



	if (prog_cnt + attach_map_cnt) {

		printf("\tstruct {\n");

		bpf_object__for_each_program(prog, obj) {

			if (use_loader)
@@ -1306,6 +1321,19 @@ static int do_skeleton(int argc, char **argv) 
				printf("\t\tstruct bpf_link *%s;\n",

				       bpf_program__name(prog));

		}



		bpf_object__for_each_map(map, obj) {

			if (!get_map_ident(map, ident, sizeof(ident)))

				continue;

			if (bpf_map__type(map) != BPF_MAP_TYPE_STRUCT_OPS)

				continue;



			if (use_loader)

				printf("t\tint %s_fd;\n", ident);

			else

				printf("\t\tstruct bpf_link *%s;\n", ident);

		}



		printf("\t} links;\n");

	}
@@ -1448,7 +1476,7 @@ static int do_skeleton(int argc, char **argv) 
		obj_name

	);



	codegen_maps_skeleton(obj, map_cnt, true /*mmaped*/);

	codegen_maps_skeleton(obj, map_cnt, true /*mmaped*/, true /*links*/);

	codegen_progs_skeleton(obj, prog_cnt, true /*populate_links*/);



	codegen("\
@@ -1786,7 +1814,7 @@ static int do_subskeleton(int argc, char **argv) 
		}

	}



	codegen_maps_skeleton(obj, map_cnt, false /*mmaped*/);

	codegen_maps_skeleton(obj, map_cnt, false /*mmaped*/, false /*links*/);

	codegen_progs_skeleton(obj, prog_cnt, false /*links*/);



	codegen("\

tools/lib/bpf/libbpf.c

+61 −3
Original line number Diff line number Diff line
@@ -572,6 +572,7 @@ struct bpf_map { 
	bool pinned;

	bool reused;

	bool autocreate;

	bool autoattach;

	__u64 map_extra;

};
@@ -1400,6 +1401,7 @@ static int init_struct_ops_maps(struct bpf_object *obj, const char *sec_name, 
		map->def.value_size = type->size;

		map->def.max_entries = 1;

		map->def.map_flags = strcmp(sec_name, STRUCT_OPS_LINK_SEC) == 0 ? BPF_F_LINK : 0;

		map->autoattach = true;



		map->st_ops = calloc(1, sizeof(*map->st_ops));

		if (!map->st_ops)
@@ -4819,6 +4821,20 @@ int bpf_map__set_autocreate(struct bpf_map *map, bool autocreate) 
	return 0;

}



int bpf_map__set_autoattach(struct bpf_map *map, bool autoattach)

{

	if (!bpf_map__is_struct_ops(map))

		return libbpf_err(-EINVAL);



	map->autoattach = autoattach;

	return 0;

}



bool bpf_map__autoattach(const struct bpf_map *map)

{

	return map->autoattach;

}



int bpf_map__reuse_fd(struct bpf_map *map, int fd)

{

	struct bpf_map_info info;
@@ -12900,8 +12916,10 @@ struct bpf_link *bpf_map__attach_struct_ops(const struct bpf_map *map) 
	__u32 zero = 0;

	int err, fd;



	if (!bpf_map__is_struct_ops(map))

	if (!bpf_map__is_struct_ops(map)) {

		pr_warn("map '%s': can't attach non-struct_ops map\n", map->name);

		return libbpf_err_ptr(-EINVAL);

	}



	if (map->fd < 0) {

		pr_warn("map '%s': can't attach BPF map without FD (was it created?)\n", map->name);
@@ -13945,6 +13963,35 @@ 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 *map = *s->maps[i].map;

		struct bpf_link **link = s->maps[i].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);



		if (!*link) {

			err = -errno;

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

				bpf_map__name(map), err);

			return libbpf_err(err);

		}

	}



	return 0;

}
@@ -13958,6 +14005,18 @@ void bpf_object__detach_skeleton(struct bpf_object_skeleton *s) 
		bpf_link__destroy(*link);

		*link = NULL;

	}



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

		return;



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

		struct bpf_link **link = s->maps[i].link;



		if (link) {

			bpf_link__destroy(*link);

			*link = NULL;

		}

	}

}



void bpf_object__destroy_skeleton(struct bpf_object_skeleton *s)
@@ -13965,7 +14024,6 @@ void bpf_object__destroy_skeleton(struct bpf_object_skeleton *s) 
	if (!s)

		return;



	if (s->progs)

	bpf_object__detach_skeleton(s);

	if (s->obj)

		bpf_object__close(*s->obj);

tools/lib/bpf/libbpf.h

+18 −0
Original line number Diff line number Diff line
@@ -978,6 +978,23 @@ bpf_object__prev_map(const struct bpf_object *obj, const struct bpf_map *map); 
LIBBPF_API int bpf_map__set_autocreate(struct bpf_map *map, bool autocreate);

LIBBPF_API bool bpf_map__autocreate(const struct bpf_map *map);



/**

 * @brief **bpf_map__set_autoattach()** sets whether libbpf has to auto-attach

 * map during BPF skeleton attach phase.

 * @param map the BPF map instance

 * @param autoattach whether to attach map during BPF skeleton attach phase

 * @return 0 on success; negative error code, otherwise

 */

LIBBPF_API int bpf_map__set_autoattach(struct bpf_map *map, bool autoattach);



/**

 * @brief **bpf_map__autoattach()** returns whether BPF map is configured to

 * auto-attach during BPF skeleton attach phase.

 * @param map the BPF map instance

 * @return true if map is set to auto-attach during skeleton attach phase; false, otherwise

 */

LIBBPF_API bool bpf_map__autoattach(const struct bpf_map *map);



/**

 * @brief **bpf_map__fd()** gets the file descriptor of the passed

 * BPF map
@@ -1672,6 +1689,7 @@ struct bpf_map_skeleton { 
	const char *name;

	struct bpf_map **map;

	void **mmaped;

	struct bpf_link **link;

};



struct bpf_prog_skeleton {

tools/lib/bpf/libbpf.map

+2 −0
Original line number Diff line number Diff line
@@ -419,6 +419,8 @@ LIBBPF_1.4.0 { 


LIBBPF_1.5.0 {

	global:

		bpf_map__autoattach;

		bpf_map__set_autoattach;

		bpf_program__attach_sockmap;

		ring__consume_n;

		ring_buffer__consume_n;