[PATCH net-next v3 2/2] bpf: remove struct bpf_map_type_list

[Johannes Berg <johannes@sipsolutions.net>]

From: Johannes Berg <johannes.berg@intel.com>

There's no need to have struct bpf_map_type_list since
it just contains a list_head, the type, and the ops
pointer. Since the types are densely packed and not
actually dynamically registered, it's much easier and
smaller to have an array of type->ops pointer. Also
initialize this array statically to remove code needed
to initialize it.

In order to save duplicating the list, move it to the
types header file added by the previous patch and
include it in the same fashion.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
---
 include/linux/bpf.h       | 11 ++-----
 include/linux/bpf_types.h | 16 ++++++++++
 kernel/bpf/arraymap.c     | 78 ++++-------------------------------------------
 kernel/bpf/hashtab.c      | 46 +++-------------------------
 kernel/bpf/lpm_trie.c     | 14 +--------
 kernel/bpf/stackmap.c     | 14 +--------
 kernel/bpf/syscall.c      | 37 +++++++++++-----------
 7 files changed, 51 insertions(+), 165 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 07fc02bb38e4..6bb38d76faf4 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -53,12 +53,6 @@ struct bpf_map {
 	struct bpf_map *inner_map_meta;
 };
 
-struct bpf_map_type_list {
-	struct list_head list_node;
-	const struct bpf_map_ops *ops;
-	enum bpf_map_type type;
-};
-
 /* function argument constraints */
 enum bpf_arg_type {
 	ARG_DONTCARE = 0,	/* unused argument in helper function */
@@ -239,10 +233,11 @@ DECLARE_PER_CPU(int, bpf_prog_active);
 
 #define BPF_PROG_TYPE(_id, _ops) \
 	extern const struct bpf_verifier_ops _ops;
+#define BPF_MAP_TYPE(_id, _ops) \
+	extern const struct bpf_map_ops _ops;
 #include <linux/bpf_types.h>
 #undef BPF_PROG_TYPE
-
-void bpf_register_map_type(struct bpf_map_type_list *tl);
+#undef BPF_MAP_TYPE
 
 struct bpf_prog *bpf_prog_get(u32 ufd);
 struct bpf_prog *bpf_prog_get_type(u32 ufd, enum bpf_prog_type type);
diff --git a/include/linux/bpf_types.h b/include/linux/bpf_types.h
index 68b0a9811216..42eacfe0630e 100644
--- a/include/linux/bpf_types.h
+++ b/include/linux/bpf_types.h
@@ -16,3 +16,19 @@ BPF_PROG_TYPE(BPF_PROG_TYPE_KPROBE, kprobe_prog_ops)
 BPF_PROG_TYPE(BPF_PROG_TYPE_TRACEPOINT, tracepoint_prog_ops)
 BPF_PROG_TYPE(BPF_PROG_TYPE_PERF_EVENT, perf_event_prog_ops)
 #endif
+
+BPF_MAP_TYPE(BPF_MAP_TYPE_ARRAY, array_map_ops)
+BPF_MAP_TYPE(BPF_MAP_TYPE_PERCPU_ARRAY, percpu_array_map_ops)
+BPF_MAP_TYPE(BPF_MAP_TYPE_PROG_ARRAY, prog_array_map_ops)
+BPF_MAP_TYPE(BPF_MAP_TYPE_PERF_EVENT_ARRAY, perf_event_array_map_ops)
+#ifdef CONFIG_CGROUPS
+BPF_MAP_TYPE(BPF_MAP_TYPE_CGROUP_ARRAY, cgroup_array_map_ops)
+#endif
+BPF_MAP_TYPE(BPF_MAP_TYPE_HASH, htab_map_ops)
+BPF_MAP_TYPE(BPF_MAP_TYPE_PERCPU_HASH, htab_percpu_map_ops)
+BPF_MAP_TYPE(BPF_MAP_TYPE_LRU_HASH, htab_lru_map_ops)
+BPF_MAP_TYPE(BPF_MAP_TYPE_LRU_PERCPU_HASH, htab_lru_percpu_map_ops)
+BPF_MAP_TYPE(BPF_MAP_TYPE_LPM_TRIE, trie_map_ops)
+BPF_MAP_TYPE(BPF_MAP_TYPE_STACK_TRACE, stack_map_ops)
+BPF_MAP_TYPE(BPF_MAP_TYPE_ARRAY_OF_MAPS, array_of_maps_map_ops)
+BPF_MAP_TYPE(BPF_MAP_TYPE_HASH_OF_MAPS, htab_of_maps_map_ops)
diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
index bc9da93db403..ec621df5a97a 100644
--- a/kernel/bpf/arraymap.c
+++ b/kernel/bpf/arraymap.c
@@ -287,7 +287,7 @@ static void array_map_free(struct bpf_map *map)
 	bpf_map_area_free(array);
 }
 
-static const struct bpf_map_ops array_ops = {
+const struct bpf_map_ops array_map_ops = {
 	.map_alloc = array_map_alloc,
 	.map_free = array_map_free,
 	.map_get_next_key = array_map_get_next_key,
@@ -297,12 +297,7 @@ static const struct bpf_map_ops array_ops = {
 	.map_gen_lookup = array_map_gen_lookup,
 };
 
-static struct bpf_map_type_list array_type __ro_after_init = {
-	.ops = &array_ops,
-	.type = BPF_MAP_TYPE_ARRAY,
-};
-
-static const struct bpf_map_ops percpu_array_ops = {
+const struct bpf_map_ops percpu_array_map_ops = {
 	.map_alloc = array_map_alloc,
 	.map_free = array_map_free,
 	.map_get_next_key = array_map_get_next_key,
@@ -311,19 +306,6 @@ static const struct bpf_map_ops percpu_array_ops = {
 	.map_delete_elem = array_map_delete_elem,
 };
 
-static struct bpf_map_type_list percpu_array_type __ro_after_init = {
-	.ops = &percpu_array_ops,
-	.type = BPF_MAP_TYPE_PERCPU_ARRAY,
-};
-
-static int __init register_array_map(void)
-{
-	bpf_register_map_type(&array_type);
-	bpf_register_map_type(&percpu_array_type);
-	return 0;
-}
-late_initcall(register_array_map);
-
 static struct bpf_map *fd_array_map_alloc(union bpf_attr *attr)
 {
 	/* only file descriptors can be stored in this type of map */
@@ -427,7 +409,7 @@ void bpf_fd_array_map_clear(struct bpf_map *map)
 		fd_array_map_delete_elem(map, &i);
 }
 
-static const struct bpf_map_ops prog_array_ops = {
+const struct bpf_map_ops prog_array_map_ops = {
 	.map_alloc = fd_array_map_alloc,
 	.map_free = fd_array_map_free,
 	.map_get_next_key = array_map_get_next_key,
@@ -437,18 +419,6 @@ static const struct bpf_map_ops prog_array_ops = {
 	.map_fd_put_ptr = prog_fd_array_put_ptr,
 };
 
-static struct bpf_map_type_list prog_array_type __ro_after_init = {
-	.ops = &prog_array_ops,
-	.type = BPF_MAP_TYPE_PROG_ARRAY,
-};
-
-static int __init register_prog_array_map(void)
-{
-	bpf_register_map_type(&prog_array_type);
-	return 0;
-}
-late_initcall(register_prog_array_map);
-
 static struct bpf_event_entry *bpf_event_entry_gen(struct file *perf_file,
 						   struct file *map_file)
 {
@@ -539,7 +509,7 @@ static void perf_event_fd_array_release(struct bpf_map *map,
 	rcu_read_unlock();
 }
 
-static const struct bpf_map_ops perf_event_array_ops = {
+const struct bpf_map_ops perf_event_array_map_ops = {
 	.map_alloc = fd_array_map_alloc,
 	.map_free = fd_array_map_free,
 	.map_get_next_key = array_map_get_next_key,
@@ -550,18 +520,6 @@ static const struct bpf_map_ops perf_event_array_ops = {
 	.map_release = perf_event_fd_array_release,
 };
 
-static struct bpf_map_type_list perf_event_array_type __ro_after_init = {
-	.ops = &perf_event_array_ops,
-	.type = BPF_MAP_TYPE_PERF_EVENT_ARRAY,
-};
-
-static int __init register_perf_event_array_map(void)
-{
-	bpf_register_map_type(&perf_event_array_type);
-	return 0;
-}
-late_initcall(register_perf_event_array_map);
-
 #ifdef CONFIG_CGROUPS
 static void *cgroup_fd_array_get_ptr(struct bpf_map *map,
 				     struct file *map_file /* not used */,
@@ -582,7 +540,7 @@ static void cgroup_fd_array_free(struct bpf_map *map)
 	fd_array_map_free(map);
 }
 
-static const struct bpf_map_ops cgroup_array_ops = {
+const struct bpf_map_ops cgroup_array_map_ops = {
 	.map_alloc = fd_array_map_alloc,
 	.map_free = cgroup_fd_array_free,
 	.map_get_next_key = array_map_get_next_key,
@@ -591,18 +549,6 @@ static const struct bpf_map_ops cgroup_array_ops = {
 	.map_fd_get_ptr = cgroup_fd_array_get_ptr,
 	.map_fd_put_ptr = cgroup_fd_array_put_ptr,
 };
-
-static struct bpf_map_type_list cgroup_array_type __ro_after_init = {
-	.ops = &cgroup_array_ops,
-	.type = BPF_MAP_TYPE_CGROUP_ARRAY,
-};
-
-static int __init register_cgroup_array_map(void)
-{
-	bpf_register_map_type(&cgroup_array_type);
-	return 0;
-}
-late_initcall(register_cgroup_array_map);
 #endif
 
 static struct bpf_map *array_of_map_alloc(union bpf_attr *attr)
@@ -644,7 +590,7 @@ static void *array_of_map_lookup_elem(struct bpf_map *map, void *key)
 	return READ_ONCE(*inner_map);
 }
 
-static const struct bpf_map_ops array_of_map_ops = {
+const struct bpf_map_ops array_of_maps_map_ops = {
 	.map_alloc = array_of_map_alloc,
 	.map_free = array_of_map_free,
 	.map_get_next_key = array_map_get_next_key,
@@ -653,15 +599,3 @@ static const struct bpf_map_ops array_of_map_ops = {
 	.map_fd_get_ptr = bpf_map_fd_get_ptr,
 	.map_fd_put_ptr = bpf_map_fd_put_ptr,
 };
-
-static struct bpf_map_type_list array_of_map_type __ro_after_init = {
-	.ops = &array_of_map_ops,
-	.type = BPF_MAP_TYPE_ARRAY_OF_MAPS,
-};
-
-static int __init register_array_of_map(void)
-{
-	bpf_register_map_type(&array_of_map_type);
-	return 0;
-}
-late_initcall(register_array_of_map);
diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
index d5b0623ce87d..bc80c038e430 100644
--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c
@@ -1096,7 +1096,7 @@ static void htab_map_free(struct bpf_map *map)
 	kfree(htab);
 }
 
-static const struct bpf_map_ops htab_ops = {
+const struct bpf_map_ops htab_map_ops = {
 	.map_alloc = htab_map_alloc,
 	.map_free = htab_map_free,
 	.map_get_next_key = htab_map_get_next_key,
@@ -1106,12 +1106,7 @@ static const struct bpf_map_ops htab_ops = {
 	.map_gen_lookup = htab_map_gen_lookup,
 };
 
-static struct bpf_map_type_list htab_type __ro_after_init = {
-	.ops = &htab_ops,
-	.type = BPF_MAP_TYPE_HASH,
-};
-
-static const struct bpf_map_ops htab_lru_ops = {
+const struct bpf_map_ops htab_lru_map_ops = {
 	.map_alloc = htab_map_alloc,
 	.map_free = htab_map_free,
 	.map_get_next_key = htab_map_get_next_key,
@@ -1120,11 +1115,6 @@ static const struct bpf_map_ops htab_lru_ops = {
 	.map_delete_elem = htab_lru_map_delete_elem,
 };
 
-static struct bpf_map_type_list htab_lru_type __ro_after_init = {
-	.ops = &htab_lru_ops,
-	.type = BPF_MAP_TYPE_LRU_HASH,
-};
-
 /* Called from eBPF program */
 static void *htab_percpu_map_lookup_elem(struct bpf_map *map, void *key)
 {
@@ -1198,7 +1188,7 @@ int bpf_percpu_hash_update(struct bpf_map *map, void *key, void *value,
 	return ret;
 }
 
-static const struct bpf_map_ops htab_percpu_ops = {
+const struct bpf_map_ops htab_percpu_map_ops = {
 	.map_alloc = htab_map_alloc,
 	.map_free = htab_map_free,
 	.map_get_next_key = htab_map_get_next_key,
@@ -1207,12 +1197,7 @@ static const struct bpf_map_ops htab_percpu_ops = {
 	.map_delete_elem = htab_map_delete_elem,
 };
 
-static struct bpf_map_type_list htab_percpu_type __ro_after_init = {
-	.ops = &htab_percpu_ops,
-	.type = BPF_MAP_TYPE_PERCPU_HASH,
-};
-
-static const struct bpf_map_ops htab_lru_percpu_ops = {
+const struct bpf_map_ops htab_lru_percpu_map_ops = {
 	.map_alloc = htab_map_alloc,
 	.map_free = htab_map_free,
 	.map_get_next_key = htab_map_get_next_key,
@@ -1221,11 +1206,6 @@ static const struct bpf_map_ops htab_lru_percpu_ops = {
 	.map_delete_elem = htab_lru_map_delete_elem,
 };
 
-static struct bpf_map_type_list htab_lru_percpu_type __ro_after_init = {
-	.ops = &htab_lru_percpu_ops,
-	.type = BPF_MAP_TYPE_LRU_PERCPU_HASH,
-};
-
 static struct bpf_map *fd_htab_map_alloc(union bpf_attr *attr)
 {
 	struct bpf_map *map;
@@ -1316,7 +1296,7 @@ static void htab_of_map_free(struct bpf_map *map)
 	fd_htab_map_free(map);
 }
 
-static const struct bpf_map_ops htab_of_map_ops = {
+const struct bpf_map_ops htab_of_maps_map_ops = {
 	.map_alloc = htab_of_map_alloc,
 	.map_free = htab_of_map_free,
 	.map_get_next_key = htab_map_get_next_key,
@@ -1325,19 +1305,3 @@ static const struct bpf_map_ops htab_of_map_ops = {
 	.map_fd_get_ptr = bpf_map_fd_get_ptr,
 	.map_fd_put_ptr = bpf_map_fd_put_ptr,
 };
-
-static struct bpf_map_type_list htab_of_map_type __ro_after_init = {
-	.ops = &htab_of_map_ops,
-	.type = BPF_MAP_TYPE_HASH_OF_MAPS,
-};
-
-static int __init register_htab_map(void)
-{
-	bpf_register_map_type(&htab_type);
-	bpf_register_map_type(&htab_percpu_type);
-	bpf_register_map_type(&htab_lru_type);
-	bpf_register_map_type(&htab_lru_percpu_type);
-	bpf_register_map_type(&htab_of_map_type);
-	return 0;
-}
-late_initcall(register_htab_map);
diff --git a/kernel/bpf/lpm_trie.c b/kernel/bpf/lpm_trie.c
index b37bd9ab7f57..39cfafd895b8 100644
--- a/kernel/bpf/lpm_trie.c
+++ b/kernel/bpf/lpm_trie.c
@@ -505,7 +505,7 @@ static int trie_get_next_key(struct bpf_map *map, void *key, void *next_key)
 	return -ENOTSUPP;
 }
 
-static const struct bpf_map_ops trie_ops = {
+const struct bpf_map_ops trie_map_ops = {
 	.map_alloc = trie_alloc,
 	.map_free = trie_free,
 	.map_get_next_key = trie_get_next_key,
@@ -513,15 +513,3 @@ static const struct bpf_map_ops trie_ops = {
 	.map_update_elem = trie_update_elem,
 	.map_delete_elem = trie_delete_elem,
 };
-
-static struct bpf_map_type_list trie_type __ro_after_init = {
-	.ops = &trie_ops,
-	.type = BPF_MAP_TYPE_LPM_TRIE,
-};
-
-static int __init register_trie_map(void)
-{
-	bpf_register_map_type(&trie_type);
-	return 0;
-}
-late_initcall(register_trie_map);
diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c
index 22aa45cd0324..4dfd6f2ec2f9 100644
--- a/kernel/bpf/stackmap.c
+++ b/kernel/bpf/stackmap.c
@@ -264,7 +264,7 @@ static void stack_map_free(struct bpf_map *map)
 	put_callchain_buffers();
 }
 
-static const struct bpf_map_ops stack_map_ops = {
+const struct bpf_map_ops stack_map_ops = {
 	.map_alloc = stack_map_alloc,
 	.map_free = stack_map_free,
 	.map_get_next_key = stack_map_get_next_key,
@@ -272,15 +272,3 @@ static const struct bpf_map_ops stack_map_ops = {
 	.map_update_elem = stack_map_update_elem,
 	.map_delete_elem = stack_map_delete_elem,
 };
-
-static struct bpf_map_type_list stack_map_type __ro_after_init = {
-	.ops = &stack_map_ops,
-	.type = BPF_MAP_TYPE_STACK_TRACE,
-};
-
-static int __init register_stack_map(void)
-{
-	bpf_register_map_type(&stack_map_type);
-	return 0;
-}
-late_initcall(register_stack_map);
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index ea55691cbf5e..b89288e2b589 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -27,30 +27,29 @@ DEFINE_PER_CPU(int, bpf_prog_active);
 
 int sysctl_unprivileged_bpf_disabled __read_mostly;
 
-static LIST_HEAD(bpf_map_types);
+static const struct bpf_map_ops * const bpf_map_types[] = {
+#define BPF_PROG_TYPE(_id, _ops)
+#define BPF_MAP_TYPE(_id, _ops) \
+	[_id] = &_ops,
+#include <linux/bpf_types.h>
+#undef BPF_PROG_TYPE
+#undef BPF_MAP_TYPE
+};
 
 static struct bpf_map *find_and_alloc_map(union bpf_attr *attr)
 {
-	struct bpf_map_type_list *tl;
 	struct bpf_map *map;
 
-	list_for_each_entry(tl, &bpf_map_types, list_node) {
-		if (tl->type == attr->map_type) {
-			map = tl->ops->map_alloc(attr);
-			if (IS_ERR(map))
-				return map;
-			map->ops = tl->ops;
-			map->map_type = attr->map_type;
-			return map;
-		}
-	}
-	return ERR_PTR(-EINVAL);
-}
+	if (attr->map_type >= ARRAY_SIZE(bpf_map_types) ||
+	    !bpf_map_types[attr->map_type])
+		return ERR_PTR(-EINVAL);
 
-/* boot time registration of different map implementations */
-void bpf_register_map_type(struct bpf_map_type_list *tl)
-{
-	list_add(&tl->list_node, &bpf_map_types);
+	map = bpf_map_types[attr->map_type]->map_alloc(attr);
+	if (IS_ERR(map))
+		return map;
+	map->ops = bpf_map_types[attr->map_type];
+	map->map_type = attr->map_type;
+	return map;
 }
 
 void *bpf_map_area_alloc(size_t size)
@@ -576,8 +575,10 @@ static int map_get_next_key(union bpf_attr *attr)
 static const struct bpf_verifier_ops * const bpf_prog_types[] = {
 #define BPF_PROG_TYPE(_id, _ops) \
 	[_id] = &_ops,
+#define BPF_MAP_TYPE(_id, _ops)
 #include <linux/bpf_types.h>
 #undef BPF_PROG_TYPE
+#undef BPF_MAP_TYPE
 };
 
 static int find_prog_type(enum bpf_prog_type type, struct bpf_prog *prog)
-- 
2.11.0