libbpf: Add a bunch of attribute getters/setters for map definitions

Add a bunch of getter for various aspects of BPF map. Some of these attribute
(e.g., key_size, value_size, type, etc) are available right now in struct
bpf_map_def, but this patch adds getter allowing to fetch them individually.
bpf_map_def approach isn't very scalable, when ABI stability requirements are
taken into account. It's much easier to extend libbpf and add support for new
features, when each aspect of BPF map has separate getter/setter.

Getters follow the common naming convention of not explicitly having "get" in
its name: bpf_map__type() returns map type, bpf_map__key_size() returns
key_size. Setters, though, explicitly have set in their name:
bpf_map__set_type(), bpf_map__set_key_size().

This patch ensures we now have a getter and a setter for the following
map attributes:
  - type;
  - max_entries;
  - map_flags;
  - numa_node;
  - key_size;
  - value_size;
  - ifindex.

bpf_map__resize() enforces unnecessary restriction of max_entries > 0. It is
unnecessary, because libbpf actually supports zero max_entries for some cases
(e.g., for PERF_EVENT_ARRAY map) and treats it specially during map creation
time. To allow setting max_entries=0, new bpf_map__set_max_entries() setter is
added. bpf_map__resize()'s behavior is preserved for backwards compatibility
reasons.

Map ifindex getter is added as well. There is a setter already, but no
corresponding getter. Fix this assymetry as well. bpf_map__set_ifindex()
itself is converted from void function into error-returning one, similar to
other setters. The only error returned right now is -EBUSY, if BPF map is
already loaded and has corresponding FD.

One lacking attribute with no ability to get/set or even specify it
declaratively is numa_node. This patch fixes this gap and both adds
programmatic getter/setter, as well as adds support for numa_node field in
BTF-defined map.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Toke Høiland-Jørgensen <toke@redhat.com>
Link: https://lore.kernel.org/bpf/20200621062112.3006313-1-andriin@fb.com

tools/lib/bpf/libbpf.c

@@ -310,6 +310,7 @@ struct bpf_map {
 	int map_ifindex;
 	int inner_map_fd;
 	struct bpf_map_def def;
+	__u32 numa_node;
 	__u32 btf_var_idx;
 	__u32 btf_key_type_id;
 	__u32 btf_value_type_id;
@@ -1957,6 +1958,10 @@ static int parse_btf_map_def(struct bpf_object *obj,
 				return -EINVAL;
 			pr_debug("map '%s': found map_flags = %u.\n",
 				 map->name, map->def.map_flags);
+		} else if (strcmp(name, "numa_node") == 0) {
+			if (!get_map_field_int(map->name, obj->btf, m, &map->numa_node))
+				return -EINVAL;
+			pr_debug("map '%s': found numa_node = %u.\n", map->name, map->numa_node);
 		} else if (strcmp(name, "key_size") == 0) {
 			__u32 sz;
 
@@ -3222,20 +3227,27 @@ int bpf_map__reuse_fd(struct bpf_map *map, int fd)
 	return err;
 }
 
-int bpf_map__resize(struct bpf_map *map, __u32 max_entries)
+__u32 bpf_map__max_entries(const struct bpf_map *map)
 {
-	if (!map || !max_entries)
-		return -EINVAL;
+	return map->def.max_entries;
+}
 
-	/* If map already created, its attributes can't be changed. */
+int bpf_map__set_max_entries(struct bpf_map *map, __u32 max_entries)
+{
 	if (map->fd >= 0)
 		return -EBUSY;
-
 	map->def.max_entries = max_entries;
-
 	return 0;
 }
 
+int bpf_map__resize(struct bpf_map *map, __u32 max_entries)
+{
+	if (!map || !max_entries)
+		return -EINVAL;
+
+	return bpf_map__set_max_entries(map, max_entries);
+}
+
 static int
 bpf_object__probe_loading(struct bpf_object *obj)
 {
@@ -3603,6 +3615,7 @@ static int bpf_object__create_map(struct bpf_object *obj, struct bpf_map *map)
 	create_attr.map_flags = def->map_flags;
 	create_attr.key_size = def->key_size;
 	create_attr.value_size = def->value_size;
+	create_attr.numa_node = map->numa_node;
 
 	if (def->type == BPF_MAP_TYPE_PERF_EVENT_ARRAY && !def->max_entries) {
 		int nr_cpus;
@@ -7088,6 +7101,71 @@ const char *bpf_map__name(const struct bpf_map *map)
 	return map ? map->name : NULL;
 }
 
+enum bpf_map_type bpf_map__type(const struct bpf_map *map)
+{
+	return map->def.type;
+}
+
+int bpf_map__set_type(struct bpf_map *map, enum bpf_map_type type)
+{
+	if (map->fd >= 0)
+		return -EBUSY;
+	map->def.type = type;
+	return 0;
+}
+
+__u32 bpf_map__map_flags(const struct bpf_map *map)
+{
+	return map->def.map_flags;
+}
+
+int bpf_map__set_map_flags(struct bpf_map *map, __u32 flags)
+{
+	if (map->fd >= 0)
+		return -EBUSY;
+	map->def.map_flags = flags;
+	return 0;
+}
+
+__u32 bpf_map__numa_node(const struct bpf_map *map)
+{
+	return map->numa_node;
+}
+
+int bpf_map__set_numa_node(struct bpf_map *map, __u32 numa_node)
+{
+	if (map->fd >= 0)
+		return -EBUSY;
+	map->numa_node = numa_node;
+	return 0;
+}
+
+__u32 bpf_map__key_size(const struct bpf_map *map)
+{
+	return map->def.key_size;
+}
+
+int bpf_map__set_key_size(struct bpf_map *map, __u32 size)
+{
+	if (map->fd >= 0)
+		return -EBUSY;
+	map->def.key_size = size;
+	return 0;
+}
+
+__u32 bpf_map__value_size(const struct bpf_map *map)
+{
+	return map->def.value_size;
+}
+
+int bpf_map__set_value_size(struct bpf_map *map, __u32 size)
+{
+	if (map->fd >= 0)
+		return -EBUSY;
+	map->def.value_size = size;
+	return 0;
+}
+
 __u32 bpf_map__btf_key_type_id(const struct bpf_map *map)
 {
 	return map ? map->btf_key_type_id : 0;
@@ -7140,9 +7218,17 @@ bool bpf_map__is_internal(const struct bpf_map *map)
 	return map->libbpf_type != LIBBPF_MAP_UNSPEC;
 }
 
-void bpf_map__set_ifindex(struct bpf_map *map, __u32 ifindex)
+__u32 bpf_map__ifindex(const struct bpf_map *map)
+{
+	return map->map_ifindex;
+}
+
+int bpf_map__set_ifindex(struct bpf_map *map, __u32 ifindex)
 {
+	if (map->fd >= 0)
+		return -EBUSY;
 	map->map_ifindex = ifindex;
+	return 0;
 }
 
 int bpf_map__set_inner_map_fd(struct bpf_map *map, int fd)

tools/lib/bpf/libbpf.h

@@ -418,11 +418,38 @@ bpf_map__next(const struct bpf_map *map, const struct bpf_object *obj);
 LIBBPF_API struct bpf_map *
 bpf_map__prev(const struct bpf_map *map, const struct bpf_object *obj);
 
+/* get/set map FD */
 LIBBPF_API int bpf_map__fd(const struct bpf_map *map);
+LIBBPF_API int bpf_map__reuse_fd(struct bpf_map *map, int fd);
+/* get map definition */
 LIBBPF_API const struct bpf_map_def *bpf_map__def(const struct bpf_map *map);
+/* get map name */
 LIBBPF_API const char *bpf_map__name(const struct bpf_map *map);
+/* get/set map type */
+LIBBPF_API enum bpf_map_type bpf_map__type(const struct bpf_map *map);
+LIBBPF_API int bpf_map__set_type(struct bpf_map *map, enum bpf_map_type type);
+/* get/set map size (max_entries) */
+LIBBPF_API __u32 bpf_map__max_entries(const struct bpf_map *map);
+LIBBPF_API int bpf_map__set_max_entries(struct bpf_map *map, __u32 max_entries);
+LIBBPF_API int bpf_map__resize(struct bpf_map *map, __u32 max_entries);
+/* get/set map flags */
+LIBBPF_API __u32 bpf_map__map_flags(const struct bpf_map *map);
+LIBBPF_API int bpf_map__set_map_flags(struct bpf_map *map, __u32 flags);
+/* get/set map NUMA node */
+LIBBPF_API __u32 bpf_map__numa_node(const struct bpf_map *map);
+LIBBPF_API int bpf_map__set_numa_node(struct bpf_map *map, __u32 numa_node);
+/* get/set map key size */
+LIBBPF_API __u32 bpf_map__key_size(const struct bpf_map *map);
+LIBBPF_API int bpf_map__set_key_size(struct bpf_map *map, __u32 size);
+/* get/set map value size */
+LIBBPF_API __u32 bpf_map__value_size(const struct bpf_map *map);
+LIBBPF_API int bpf_map__set_value_size(struct bpf_map *map, __u32 size);
+/* get map key/value BTF type IDs */
 LIBBPF_API __u32 bpf_map__btf_key_type_id(const struct bpf_map *map);
 LIBBPF_API __u32 bpf_map__btf_value_type_id(const struct bpf_map *map);
+/* get/set map if_index */
+LIBBPF_API __u32 bpf_map__ifindex(const struct bpf_map *map);
+LIBBPF_API int bpf_map__set_ifindex(struct bpf_map *map, __u32 ifindex);
 
 typedef void (*bpf_map_clear_priv_t)(struct bpf_map *, void *);
 LIBBPF_API int bpf_map__set_priv(struct bpf_map *map, void *priv,
@@ -430,11 +457,8 @@ LIBBPF_API int bpf_map__set_priv(struct bpf_map *map, void *priv,
 LIBBPF_API void *bpf_map__priv(const struct bpf_map *map);
 LIBBPF_API int bpf_map__set_initial_value(struct bpf_map *map,
 					  const void *data, size_t size);
-LIBBPF_API int bpf_map__reuse_fd(struct bpf_map *map, int fd);
-LIBBPF_API int bpf_map__resize(struct bpf_map *map, __u32 max_entries);
 LIBBPF_API bool bpf_map__is_offload_neutral(const struct bpf_map *map);
 LIBBPF_API bool bpf_map__is_internal(const struct bpf_map *map);
-LIBBPF_API void bpf_map__set_ifindex(struct bpf_map *map, __u32 ifindex);
 LIBBPF_API int bpf_map__set_pin_path(struct bpf_map *map, const char *path);
 LIBBPF_API const char *bpf_map__get_pin_path(const struct bpf_map *map);
 LIBBPF_API bool bpf_map__is_pinned(const struct bpf_map *map);

tools/lib/bpf/libbpf.map

@@ -272,4 +272,18 @@ LIBBPF_0.0.9 {
 } LIBBPF_0.0.8;
 
 LIBBPF_0.1.0 {
+	global:
+		bpf_map__ifindex;
+		bpf_map__key_size;
+		bpf_map__map_flags;
+		bpf_map__max_entries;
+		bpf_map__numa_node;
+		bpf_map__set_key_size;
+		bpf_map__set_map_flags;
+		bpf_map__set_max_entries;
+		bpf_map__set_numa_node;
+		bpf_map__set_type;
+		bpf_map__set_value_size;
+		bpf_map__type;
+		bpf_map__value_size;
 } LIBBPF_0.0.9;