libbpf: Add "map_extra" as a per-map-type extra flag

This patch adds the libbpf infrastructure for supporting a
per-map-type "map_extra" field, whose definition will be
idiosyncratic depending on map type.

For example, for the bloom filter map, the lower 4 bits of
map_extra is used to denote the number of hash functions.

Please note that until libbpf 1.0 is here, the
"bpf_create_map_params" struct is used as a temporary
means for propagating the map_extra field to the kernel.

Signed-off-by: Joanne Koong <joannekoong@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20211027234504.30744-3-joannekoong@fb.com

tools/lib/bpf/bpf.c

@@ -77,7 +77,7 @@ static inline int sys_bpf_prog_load(union bpf_attr *attr, unsigned int size)
 	return fd;
 }
 
-int bpf_create_map_xattr(const struct bpf_create_map_attr *create_attr)
+int libbpf__bpf_create_map_xattr(const struct bpf_create_map_params *create_attr)
 {
 	union bpf_attr attr;
 	int fd;
@@ -102,11 +102,36 @@ int bpf_create_map_xattr(const struct bpf_create_map_attr *create_attr)
 			create_attr->btf_vmlinux_value_type_id;
 	else
 		attr.inner_map_fd = create_attr->inner_map_fd;
+	attr.map_extra = create_attr->map_extra;
 
 	fd = sys_bpf(BPF_MAP_CREATE, &attr, sizeof(attr));
 	return libbpf_err_errno(fd);
 }
 
+int bpf_create_map_xattr(const struct bpf_create_map_attr *create_attr)
+{
+	struct bpf_create_map_params p = {};
+
+	p.map_type = create_attr->map_type;
+	p.key_size = create_attr->key_size;
+	p.value_size = create_attr->value_size;
+	p.max_entries = create_attr->max_entries;
+	p.map_flags = create_attr->map_flags;
+	p.name = create_attr->name;
+	p.numa_node = create_attr->numa_node;
+	p.btf_fd = create_attr->btf_fd;
+	p.btf_key_type_id = create_attr->btf_key_type_id;
+	p.btf_value_type_id = create_attr->btf_value_type_id;
+	p.map_ifindex = create_attr->map_ifindex;
+	if (p.map_type == BPF_MAP_TYPE_STRUCT_OPS)
+		p.btf_vmlinux_value_type_id =
+			create_attr->btf_vmlinux_value_type_id;
+	else
+		p.inner_map_fd = create_attr->inner_map_fd;
+
+	return libbpf__bpf_create_map_xattr(&p);
+}
+
 int bpf_create_map_node(enum bpf_map_type map_type, const char *name,
 			int key_size, int value_size, int max_entries,
 			__u32 map_flags, int node)

tools/lib/bpf/bpf_gen_internal.h

@@ -43,7 +43,7 @@ void bpf_gen__init(struct bpf_gen *gen, int log_level);
 int bpf_gen__finish(struct bpf_gen *gen);
 void bpf_gen__free(struct bpf_gen *gen);
 void bpf_gen__load_btf(struct bpf_gen *gen, const void *raw_data, __u32 raw_size);
-void bpf_gen__map_create(struct bpf_gen *gen, struct bpf_create_map_attr *map_attr, int map_idx);
+void bpf_gen__map_create(struct bpf_gen *gen, struct bpf_create_map_params *map_attr, int map_idx);
 struct bpf_prog_load_params;
 void bpf_gen__prog_load(struct bpf_gen *gen, struct bpf_prog_load_params *load_attr, int prog_idx);
 void bpf_gen__map_update_elem(struct bpf_gen *gen, int map_idx, void *value, __u32 value_size);

tools/lib/bpf/gen_loader.c

@@ -431,7 +431,7 @@ void bpf_gen__load_btf(struct bpf_gen *gen, const void *btf_raw_data,
 }
 
 void bpf_gen__map_create(struct bpf_gen *gen,
-			 struct bpf_create_map_attr *map_attr, int map_idx)
+			 struct bpf_create_map_params *map_attr, int map_idx)
 {
 	int attr_size = offsetofend(union bpf_attr, btf_vmlinux_value_type_id);
 	bool close_inner_map_fd = false;
@@ -443,6 +443,7 @@ void bpf_gen__map_create(struct bpf_gen *gen,
 	attr.key_size = map_attr->key_size;
 	attr.value_size = map_attr->value_size;
 	attr.map_flags = map_attr->map_flags;
+	attr.map_extra = map_attr->map_extra;
 	memcpy(attr.map_name, map_attr->name,
 	       min((unsigned)strlen(map_attr->name), BPF_OBJ_NAME_LEN - 1));
 	attr.numa_node = map_attr->numa_node;

tools/lib/bpf/libbpf.c

@@ -400,6 +400,7 @@ struct bpf_map {
 	char *pin_path;
 	bool pinned;
 	bool reused;
+	__u64 map_extra;
 };
 
 enum extern_type {
@@ -2324,6 +2325,13 @@ int parse_btf_map_def(const char *map_name, struct btf *btf,
 			}
 			map_def->pinning = val;
 			map_def->parts |= MAP_DEF_PINNING;
+		} else if (strcmp(name, "map_extra") == 0) {
+			__u32 map_extra;
+
+			if (!get_map_field_int(map_name, btf, m, &map_extra))
+				return -EINVAL;
+			map_def->map_extra = map_extra;
+			map_def->parts |= MAP_DEF_MAP_EXTRA;
 		} else {
 			if (strict) {
 				pr_warn("map '%s': unknown field '%s'.\n", map_name, name);
@@ -2348,6 +2356,7 @@ static void fill_map_from_def(struct bpf_map *map, const struct btf_map_def *def
 	map->def.value_size = def->value_size;
 	map->def.max_entries = def->max_entries;
 	map->def.map_flags = def->map_flags;
+	map->map_extra = def->map_extra;
 
 	map->numa_node = def->numa_node;
 	map->btf_key_type_id = def->key_type_id;
@@ -2371,7 +2380,10 @@ static void fill_map_from_def(struct bpf_map *map, const struct btf_map_def *def
 	if (def->parts & MAP_DEF_MAX_ENTRIES)
 		pr_debug("map '%s': found max_entries = %u.\n", map->name, def->max_entries);
 	if (def->parts & MAP_DEF_MAP_FLAGS)
-		pr_debug("map '%s': found map_flags = %u.\n", map->name, def->map_flags);
+		pr_debug("map '%s': found map_flags = 0x%x.\n", map->name, def->map_flags);
+	if (def->parts & MAP_DEF_MAP_EXTRA)
+		pr_debug("map '%s': found map_extra = 0x%llx.\n", map->name,
+			 (unsigned long long)def->map_extra);
 	if (def->parts & MAP_DEF_PINNING)
 		pr_debug("map '%s': found pinning = %u.\n", map->name, def->pinning);
 	if (def->parts & MAP_DEF_NUMA_NODE)
@@ -4210,6 +4222,7 @@ int bpf_map__reuse_fd(struct bpf_map *map, int fd)
 	map->btf_key_type_id = info.btf_key_type_id;
 	map->btf_value_type_id = info.btf_value_type_id;
 	map->reused = true;
+	map->map_extra = info.map_extra;
 
 	return 0;
 
@@ -4724,7 +4737,8 @@ static bool map_is_reuse_compat(const struct bpf_map *map, int map_fd)
 		map_info.key_size == map->def.key_size &&
 		map_info.value_size == map->def.value_size &&
 		map_info.max_entries == map->def.max_entries &&
-		map_info.map_flags == map->def.map_flags);
+		map_info.map_flags == map->def.map_flags &&
+		map_info.map_extra == map->map_extra);
 }
 
 static int
@@ -4807,7 +4821,7 @@ static void bpf_map__destroy(struct bpf_map *map);
 
 static int bpf_object__create_map(struct bpf_object *obj, struct bpf_map *map, bool is_inner)
 {
-	struct bpf_create_map_attr create_attr;
+	struct bpf_create_map_params create_attr;
 	struct bpf_map_def *def = &map->def;
 	int err = 0;
 
@@ -4821,6 +4835,7 @@ static int bpf_object__create_map(struct bpf_object *obj, struct bpf_map *map, b
 	create_attr.key_size = def->key_size;
 	create_attr.value_size = def->value_size;
 	create_attr.numa_node = map->numa_node;
+	create_attr.map_extra = map->map_extra;
 
 	if (def->type == BPF_MAP_TYPE_PERF_EVENT_ARRAY && !def->max_entries) {
 		int nr_cpus;
@@ -4895,7 +4910,7 @@ static int bpf_object__create_map(struct bpf_object *obj, struct bpf_map *map, b
 		 */
 		map->fd = 0;
 	} else {
-		map->fd = bpf_create_map_xattr(&create_attr);
+		map->fd = libbpf__bpf_create_map_xattr(&create_attr);
 	}
 	if (map->fd < 0 && (create_attr.btf_key_type_id ||
 			    create_attr.btf_value_type_id)) {
@@ -4910,7 +4925,7 @@ static int bpf_object__create_map(struct bpf_object *obj, struct bpf_map *map, b
 		create_attr.btf_value_type_id = 0;
 		map->btf_key_type_id = 0;
 		map->btf_value_type_id = 0;
-		map->fd = bpf_create_map_xattr(&create_attr);
+		map->fd = libbpf__bpf_create_map_xattr(&create_attr);
 	}
 
 	err = map->fd < 0 ? -errno : 0;
@@ -8880,6 +8895,19 @@ int bpf_map__set_map_flags(struct bpf_map *map, __u32 flags)
 	return 0;
 }
 
+__u64 bpf_map__map_extra(const struct bpf_map *map)
+{
+	return map->map_extra;
+}
+
+int bpf_map__set_map_extra(struct bpf_map *map, __u64 map_extra)
+{
+	if (map->fd >= 0)
+		return libbpf_err(-EBUSY);
+	map->map_extra = map_extra;
+	return 0;
+}
+
 __u32 bpf_map__numa_node(const struct bpf_map *map)
 {
 	return map->numa_node;

tools/lib/bpf/libbpf.h

@@ -600,6 +600,9 @@ 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);
+/* get/set map map_extra flags */
+LIBBPF_API __u64 bpf_map__map_extra(const struct bpf_map *map);
+LIBBPF_API int bpf_map__set_map_extra(struct bpf_map *map, __u64 map_extra);
 
 typedef void (*bpf_map_clear_priv_t)(struct bpf_map *, void *);
 LIBBPF_API int bpf_map__set_priv(struct bpf_map *map, void *priv,

tools/lib/bpf/libbpf.map

@@ -389,6 +389,8 @@ LIBBPF_0.5.0 {
 
 LIBBPF_0.6.0 {
 	global:
+		bpf_map__map_extra;
+		bpf_map__set_map_extra;
 		bpf_object__next_map;
 		bpf_object__next_program;
 		bpf_object__prev_map;

tools/lib/bpf/libbpf_internal.h

@@ -193,8 +193,9 @@ enum map_def_parts {
 	MAP_DEF_NUMA_NODE	= 0x080,
 	MAP_DEF_PINNING		= 0x100,
 	MAP_DEF_INNER_MAP	= 0x200,
+	MAP_DEF_MAP_EXTRA	= 0x400,
 
-	MAP_DEF_ALL		= 0x3ff, /* combination of all above */
+	MAP_DEF_ALL		= 0x7ff, /* combination of all above */
 };
 
 struct btf_map_def {
@@ -208,6 +209,7 @@ struct btf_map_def {
 	__u32 map_flags;
 	__u32 numa_node;
 	__u32 pinning;
+	__u64 map_extra;
 };
 
 int parse_btf_map_def(const char *map_name, struct btf *btf,
@@ -303,6 +305,27 @@ struct bpf_prog_load_params {
 
 int libbpf__bpf_prog_load(const struct bpf_prog_load_params *load_attr);
 
+struct bpf_create_map_params {
+	const char *name;
+	enum bpf_map_type map_type;
+	__u32 map_flags;
+	__u32 key_size;
+	__u32 value_size;
+	__u32 max_entries;
+	__u32 numa_node;
+	__u32 btf_fd;
+	__u32 btf_key_type_id;
+	__u32 btf_value_type_id;
+	__u32 map_ifindex;
+	union {
+		__u32 inner_map_fd;
+		__u32 btf_vmlinux_value_type_id;
+	};
+	__u64 map_extra;
+};
+
+int libbpf__bpf_create_map_xattr(const struct bpf_create_map_params *create_attr);
+
 struct btf *btf_get_from_fd(int btf_fd, struct btf *base_btf);
 void btf_get_kernel_prefix_kind(enum bpf_attach_type attach_type,
 				const char **prefix, int *kind);