ebpf: constify various function pointer structs

We can move bpf_map_ops and bpf_verifier_ops and other structs into ro
section, bpf_map_type_list and bpf_prog_type_list into read mostly.
Signed-off-by: NDaniel Borkmann <daniel@iogearbox.net>
Acked-by: NAlexei Starovoitov <ast@plumgrid.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/linux/bpf.h

@@ -32,13 +32,13 @@ struct bpf_map {
 	u32 key_size;
 	u32 value_size;
 	u32 max_entries;
-	struct bpf_map_ops *ops;
+	const struct bpf_map_ops *ops;
 	struct work_struct work;
 };
 
 struct bpf_map_type_list {
 	struct list_head list_node;
-	struct bpf_map_ops *ops;
+	const struct bpf_map_ops *ops;
 	enum bpf_map_type type;
 };
 
@@ -109,7 +109,7 @@ struct bpf_verifier_ops {
 
 struct bpf_prog_type_list {
 	struct list_head list_node;
-	struct bpf_verifier_ops *ops;
+	const struct bpf_verifier_ops *ops;
 	enum bpf_prog_type type;
 };
 
@@ -121,7 +121,7 @@ struct bpf_prog_aux {
 	atomic_t refcnt;
 	bool is_gpl_compatible;
 	enum bpf_prog_type prog_type;
-	struct bpf_verifier_ops *ops;
+	const struct bpf_verifier_ops *ops;
 	struct bpf_map **used_maps;
 	u32 used_map_cnt;
 	struct bpf_prog *prog;
@@ -138,8 +138,8 @@ struct bpf_prog *bpf_prog_get(u32 ufd);
 int bpf_check(struct bpf_prog *fp, union bpf_attr *attr);
 
 /* verifier prototypes for helper functions called from eBPF programs */
-extern struct bpf_func_proto bpf_map_lookup_elem_proto;
-extern struct bpf_func_proto bpf_map_update_elem_proto;
-extern struct bpf_func_proto bpf_map_delete_elem_proto;
+extern const struct bpf_func_proto bpf_map_lookup_elem_proto;
+extern const struct bpf_func_proto bpf_map_update_elem_proto;
+extern const struct bpf_func_proto bpf_map_delete_elem_proto;
 
 #endif /* _LINUX_BPF_H */

kernel/bpf/arraymap.c

@@ -134,7 +134,7 @@ static void array_map_free(struct bpf_map *map)
 	kvfree(array);
 }
 
-static struct bpf_map_ops array_ops = {
+static const struct bpf_map_ops array_ops = {
 	.map_alloc = array_map_alloc,
 	.map_free = array_map_free,
 	.map_get_next_key = array_map_get_next_key,
@@ -143,14 +143,14 @@ static struct bpf_map_ops array_ops = {
 	.map_delete_elem = array_map_delete_elem,
 };
 
-static struct bpf_map_type_list tl = {
+static struct bpf_map_type_list array_type __read_mostly = {
 	.ops = &array_ops,
 	.type = BPF_MAP_TYPE_ARRAY,
 };
 
 static int __init register_array_map(void)
 {
-	bpf_register_map_type(&tl);
+	bpf_register_map_type(&array_type);
 	return 0;
 }
 late_initcall(register_array_map);

kernel/bpf/hashtab.c

@@ -345,7 +345,7 @@ static void htab_map_free(struct bpf_map *map)
 	kfree(htab);
 }
 
-static struct bpf_map_ops htab_ops = {
+static const struct bpf_map_ops htab_ops = {
 	.map_alloc = htab_map_alloc,
 	.map_free = htab_map_free,
 	.map_get_next_key = htab_map_get_next_key,
@@ -354,14 +354,14 @@ static struct bpf_map_ops htab_ops = {
 	.map_delete_elem = htab_map_delete_elem,
 };
 
-static struct bpf_map_type_list tl = {
+static struct bpf_map_type_list htab_type __read_mostly = {
 	.ops = &htab_ops,
 	.type = BPF_MAP_TYPE_HASH,
 };
 
 static int __init register_htab_map(void)
 {
-	bpf_register_map_type(&tl);
+	bpf_register_map_type(&htab_type);
 	return 0;
 }
 late_initcall(register_htab_map);

kernel/bpf/helpers.c

@@ -41,7 +41,7 @@ static u64 bpf_map_lookup_elem(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
 	return (unsigned long) value;
 }
 
-struct bpf_func_proto bpf_map_lookup_elem_proto = {
+const struct bpf_func_proto bpf_map_lookup_elem_proto = {
 	.func = bpf_map_lookup_elem,
 	.gpl_only = false,
 	.ret_type = RET_PTR_TO_MAP_VALUE_OR_NULL,
@@ -60,7 +60,7 @@ static u64 bpf_map_update_elem(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
 	return map->ops->map_update_elem(map, key, value, r4);
 }
 
-struct bpf_func_proto bpf_map_update_elem_proto = {
+const struct bpf_func_proto bpf_map_update_elem_proto = {
 	.func = bpf_map_update_elem,
 	.gpl_only = false,
 	.ret_type = RET_INTEGER,
@@ -80,7 +80,7 @@ static u64 bpf_map_delete_elem(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
 	return map->ops->map_delete_elem(map, key);
 }
 
-struct bpf_func_proto bpf_map_delete_elem_proto = {
+const struct bpf_func_proto bpf_map_delete_elem_proto = {
 	.func = bpf_map_delete_elem,
 	.gpl_only = false,
 	.ret_type = RET_INTEGER,

net/core/filter.c

@@ -1159,19 +1159,19 @@ static bool sock_filter_is_valid_access(int off, int size, enum bpf_access_type
 	return false;
 }
 
-static struct bpf_verifier_ops sock_filter_ops = {
+static const struct bpf_verifier_ops sock_filter_ops = {
 	.get_func_proto = sock_filter_func_proto,
 	.is_valid_access = sock_filter_is_valid_access,
 };
 
-static struct bpf_prog_type_list tl = {
+static struct bpf_prog_type_list sock_filter_type __read_mostly = {
 	.ops = &sock_filter_ops,
 	.type = BPF_PROG_TYPE_SOCKET_FILTER,
 };
 
 static int __init register_sock_filter_ops(void)
 {
-	bpf_register_prog_type(&tl);
+	bpf_register_prog_type(&sock_filter_type);
 	return 0;
 }
 late_initcall(register_sock_filter_ops);