xref: /openbmc/linux/net/xdp/xskmap.c (revision b4a6aaea)
1 // SPDX-License-Identifier: GPL-2.0
2 /* XSKMAP used for AF_XDP sockets
3  * Copyright(c) 2018 Intel Corporation.
4  */
5 
6 #include <linux/bpf.h>
7 #include <linux/capability.h>
8 #include <net/xdp_sock.h>
9 #include <linux/slab.h>
10 #include <linux/sched.h>
11 
12 #include "xsk.h"
13 
14 static struct xsk_map_node *xsk_map_node_alloc(struct xsk_map *map,
15 					       struct xdp_sock __rcu **map_entry)
16 {
17 	struct xsk_map_node *node;
18 
19 	node = bpf_map_kzalloc(&map->map, sizeof(*node),
20 			       GFP_ATOMIC | __GFP_NOWARN);
21 	if (!node)
22 		return ERR_PTR(-ENOMEM);
23 
24 	bpf_map_inc(&map->map);
25 
26 	node->map = map;
27 	node->map_entry = map_entry;
28 	return node;
29 }
30 
31 static void xsk_map_node_free(struct xsk_map_node *node)
32 {
33 	bpf_map_put(&node->map->map);
34 	kfree(node);
35 }
36 
37 static void xsk_map_sock_add(struct xdp_sock *xs, struct xsk_map_node *node)
38 {
39 	spin_lock_bh(&xs->map_list_lock);
40 	list_add_tail(&node->node, &xs->map_list);
41 	spin_unlock_bh(&xs->map_list_lock);
42 }
43 
44 static void xsk_map_sock_delete(struct xdp_sock *xs,
45 				struct xdp_sock __rcu **map_entry)
46 {
47 	struct xsk_map_node *n, *tmp;
48 
49 	spin_lock_bh(&xs->map_list_lock);
50 	list_for_each_entry_safe(n, tmp, &xs->map_list, node) {
51 		if (map_entry == n->map_entry) {
52 			list_del(&n->node);
53 			xsk_map_node_free(n);
54 		}
55 	}
56 	spin_unlock_bh(&xs->map_list_lock);
57 }
58 
59 static struct bpf_map *xsk_map_alloc(union bpf_attr *attr)
60 {
61 	struct xsk_map *m;
62 	int numa_node;
63 	u64 size;
64 
65 	if (!capable(CAP_NET_ADMIN))
66 		return ERR_PTR(-EPERM);
67 
68 	if (attr->max_entries == 0 || attr->key_size != 4 ||
69 	    attr->value_size != 4 ||
70 	    attr->map_flags & ~(BPF_F_NUMA_NODE | BPF_F_RDONLY | BPF_F_WRONLY))
71 		return ERR_PTR(-EINVAL);
72 
73 	numa_node = bpf_map_attr_numa_node(attr);
74 	size = struct_size(m, xsk_map, attr->max_entries);
75 
76 	m = bpf_map_area_alloc(size, numa_node);
77 	if (!m)
78 		return ERR_PTR(-ENOMEM);
79 
80 	bpf_map_init_from_attr(&m->map, attr);
81 	spin_lock_init(&m->lock);
82 
83 	return &m->map;
84 }
85 
86 static void xsk_map_free(struct bpf_map *map)
87 {
88 	struct xsk_map *m = container_of(map, struct xsk_map, map);
89 
90 	synchronize_net();
91 	bpf_map_area_free(m);
92 }
93 
94 static int xsk_map_get_next_key(struct bpf_map *map, void *key, void *next_key)
95 {
96 	struct xsk_map *m = container_of(map, struct xsk_map, map);
97 	u32 index = key ? *(u32 *)key : U32_MAX;
98 	u32 *next = next_key;
99 
100 	if (index >= m->map.max_entries) {
101 		*next = 0;
102 		return 0;
103 	}
104 
105 	if (index == m->map.max_entries - 1)
106 		return -ENOENT;
107 	*next = index + 1;
108 	return 0;
109 }
110 
111 static int xsk_map_gen_lookup(struct bpf_map *map, struct bpf_insn *insn_buf)
112 {
113 	const int ret = BPF_REG_0, mp = BPF_REG_1, index = BPF_REG_2;
114 	struct bpf_insn *insn = insn_buf;
115 
116 	*insn++ = BPF_LDX_MEM(BPF_W, ret, index, 0);
117 	*insn++ = BPF_JMP_IMM(BPF_JGE, ret, map->max_entries, 5);
118 	*insn++ = BPF_ALU64_IMM(BPF_LSH, ret, ilog2(sizeof(struct xsk_sock *)));
119 	*insn++ = BPF_ALU64_IMM(BPF_ADD, mp, offsetof(struct xsk_map, xsk_map));
120 	*insn++ = BPF_ALU64_REG(BPF_ADD, ret, mp);
121 	*insn++ = BPF_LDX_MEM(BPF_SIZEOF(struct xsk_sock *), ret, ret, 0);
122 	*insn++ = BPF_JMP_IMM(BPF_JA, 0, 0, 1);
123 	*insn++ = BPF_MOV64_IMM(ret, 0);
124 	return insn - insn_buf;
125 }
126 
127 /* Elements are kept alive by RCU; either by rcu_read_lock() (from syscall) or
128  * by local_bh_disable() (from XDP calls inside NAPI). The
129  * rcu_read_lock_bh_held() below makes lockdep accept both.
130  */
131 static void *__xsk_map_lookup_elem(struct bpf_map *map, u32 key)
132 {
133 	struct xsk_map *m = container_of(map, struct xsk_map, map);
134 
135 	if (key >= map->max_entries)
136 		return NULL;
137 
138 	return rcu_dereference_check(m->xsk_map[key], rcu_read_lock_bh_held());
139 }
140 
141 static void *xsk_map_lookup_elem(struct bpf_map *map, void *key)
142 {
143 	return __xsk_map_lookup_elem(map, *(u32 *)key);
144 }
145 
146 static void *xsk_map_lookup_elem_sys_only(struct bpf_map *map, void *key)
147 {
148 	return ERR_PTR(-EOPNOTSUPP);
149 }
150 
151 static int xsk_map_update_elem(struct bpf_map *map, void *key, void *value,
152 			       u64 map_flags)
153 {
154 	struct xsk_map *m = container_of(map, struct xsk_map, map);
155 	struct xdp_sock __rcu **map_entry;
156 	struct xdp_sock *xs, *old_xs;
157 	u32 i = *(u32 *)key, fd = *(u32 *)value;
158 	struct xsk_map_node *node;
159 	struct socket *sock;
160 	int err;
161 
162 	if (unlikely(map_flags > BPF_EXIST))
163 		return -EINVAL;
164 	if (unlikely(i >= m->map.max_entries))
165 		return -E2BIG;
166 
167 	sock = sockfd_lookup(fd, &err);
168 	if (!sock)
169 		return err;
170 
171 	if (sock->sk->sk_family != PF_XDP) {
172 		sockfd_put(sock);
173 		return -EOPNOTSUPP;
174 	}
175 
176 	xs = (struct xdp_sock *)sock->sk;
177 
178 	map_entry = &m->xsk_map[i];
179 	node = xsk_map_node_alloc(m, map_entry);
180 	if (IS_ERR(node)) {
181 		sockfd_put(sock);
182 		return PTR_ERR(node);
183 	}
184 
185 	spin_lock_bh(&m->lock);
186 	old_xs = rcu_dereference_protected(*map_entry, lockdep_is_held(&m->lock));
187 	if (old_xs == xs) {
188 		err = 0;
189 		goto out;
190 	} else if (old_xs && map_flags == BPF_NOEXIST) {
191 		err = -EEXIST;
192 		goto out;
193 	} else if (!old_xs && map_flags == BPF_EXIST) {
194 		err = -ENOENT;
195 		goto out;
196 	}
197 	xsk_map_sock_add(xs, node);
198 	rcu_assign_pointer(*map_entry, xs);
199 	if (old_xs)
200 		xsk_map_sock_delete(old_xs, map_entry);
201 	spin_unlock_bh(&m->lock);
202 	sockfd_put(sock);
203 	return 0;
204 
205 out:
206 	spin_unlock_bh(&m->lock);
207 	sockfd_put(sock);
208 	xsk_map_node_free(node);
209 	return err;
210 }
211 
212 static int xsk_map_delete_elem(struct bpf_map *map, void *key)
213 {
214 	struct xsk_map *m = container_of(map, struct xsk_map, map);
215 	struct xdp_sock __rcu **map_entry;
216 	struct xdp_sock *old_xs;
217 	int k = *(u32 *)key;
218 
219 	if (k >= map->max_entries)
220 		return -EINVAL;
221 
222 	spin_lock_bh(&m->lock);
223 	map_entry = &m->xsk_map[k];
224 	old_xs = unrcu_pointer(xchg(map_entry, NULL));
225 	if (old_xs)
226 		xsk_map_sock_delete(old_xs, map_entry);
227 	spin_unlock_bh(&m->lock);
228 
229 	return 0;
230 }
231 
232 static int xsk_map_redirect(struct bpf_map *map, u32 ifindex, u64 flags)
233 {
234 	return __bpf_xdp_redirect_map(map, ifindex, flags, 0,
235 				      __xsk_map_lookup_elem);
236 }
237 
238 void xsk_map_try_sock_delete(struct xsk_map *map, struct xdp_sock *xs,
239 			     struct xdp_sock __rcu **map_entry)
240 {
241 	spin_lock_bh(&map->lock);
242 	if (rcu_access_pointer(*map_entry) == xs) {
243 		rcu_assign_pointer(*map_entry, NULL);
244 		xsk_map_sock_delete(xs, map_entry);
245 	}
246 	spin_unlock_bh(&map->lock);
247 }
248 
249 static bool xsk_map_meta_equal(const struct bpf_map *meta0,
250 			       const struct bpf_map *meta1)
251 {
252 	return meta0->max_entries == meta1->max_entries &&
253 		bpf_map_meta_equal(meta0, meta1);
254 }
255 
256 static int xsk_map_btf_id;
257 const struct bpf_map_ops xsk_map_ops = {
258 	.map_meta_equal = xsk_map_meta_equal,
259 	.map_alloc = xsk_map_alloc,
260 	.map_free = xsk_map_free,
261 	.map_get_next_key = xsk_map_get_next_key,
262 	.map_lookup_elem = xsk_map_lookup_elem,
263 	.map_gen_lookup = xsk_map_gen_lookup,
264 	.map_lookup_elem_sys_only = xsk_map_lookup_elem_sys_only,
265 	.map_update_elem = xsk_map_update_elem,
266 	.map_delete_elem = xsk_map_delete_elem,
267 	.map_check_btf = map_check_no_btf,
268 	.map_btf_name = "xsk_map",
269 	.map_btf_id = &xsk_map_btf_id,
270 	.map_redirect = xsk_map_redirect,
271 };
272