libbpf: Add bpf_map__inner_map API

mainline inclusion
from mainline-5.13-rc1
commit b3278099
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I5EUVD
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b3278099b2f6e81771c6c2b70fcf9a56e9ba5d93

-------------------------------------------------

The API gives access to inner map for map in map types (array or
hash of map). It will be used to dynamically set max_entries in it.
Signed-off-by: NYauheni Kaliuta <yauheni.kaliuta@redhat.com>
Signed-off-by: NAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210408061310.95877-7-yauheni.kaliuta@redhat.com
(cherry picked from commit b3278099)
Signed-off-by: NWang Yufen <wangyufen@huawei.com>

tools/lib/bpf/libbpf.c

@@ -2194,6 +2194,7 @@ static int parse_btf_map_def(struct bpf_object *obj,
 			map->inner_map = calloc(1, sizeof(*map->inner_map));
 			if (!map->inner_map)
 				return -ENOMEM;
+			map->inner_map->fd = -1;
 			map->inner_map->sec_idx = obj->efile.btf_maps_shndx;
 			map->inner_map->name = malloc(strlen(map->name) +
 						      sizeof(".inner") + 1);
@@ -3884,6 +3885,14 @@ __u32 bpf_map__max_entries(const struct bpf_map *map)
 	return map->def.max_entries;
 }
 
+struct bpf_map *bpf_map__inner_map(struct bpf_map *map)
+{
+	if (!bpf_map_type__is_map_in_map(map->def.type))
+		return NULL;
+
+	return map->inner_map;
+}
+
 int bpf_map__set_max_entries(struct bpf_map *map, __u32 max_entries)
 {
 	if (map->fd >= 0)
@@ -9545,6 +9554,7 @@ int bpf_map__set_inner_map_fd(struct bpf_map *map, int fd)
 		pr_warn("error: inner_map_fd already specified\n");
 		return -EINVAL;
 	}
+	zfree(&map->inner_map);
 	map->inner_map_fd = fd;
 	return 0;
 }

tools/lib/bpf/libbpf.h

@@ -484,6 +484,7 @@ LIBBPF_API int bpf_map__pin(struct bpf_map *map, const char *path);
 LIBBPF_API int bpf_map__unpin(struct bpf_map *map, const char *path);
 
 LIBBPF_API int bpf_map__set_inner_map_fd(struct bpf_map *map, int fd);
+LIBBPF_API struct bpf_map *bpf_map__inner_map(struct bpf_map *map);
 
 LIBBPF_API long libbpf_get_error(const void *ptr);
 

tools/lib/bpf/libbpf.map

@@ -359,5 +359,6 @@ LIBBPF_0.4.0 {
 		bpf_linker__finalize;
 		bpf_linker__free;
 		bpf_linker__new;
+		bpf_map__inner_map;
 		bpf_object__set_kversion;
 } LIBBPF_0.3.0;