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/filter.h>
8#include <net/xdp_sock.h>
9#include <linux/slab.h>
10#include <linux/sched.h>
11#include <linux/btf_ids.h>
12
13#include "xsk.h"
14
15static struct xsk_map_node *xsk_map_node_alloc(struct xsk_map *map,
16 struct xdp_sock __rcu **map_entry)
17{
18 struct xsk_map_node *node;
19
20 node = bpf_map_kzalloc(map: &map->map, size: sizeof(*node),
21 GFP_ATOMIC | __GFP_NOWARN);
22 if (!node)
23 return ERR_PTR(error: -ENOMEM);
24
25 bpf_map_inc(map: &map->map);
26 atomic_inc(v: &map->count);
27
28 node->map = map;
29 node->map_entry = map_entry;
30 return node;
31}
32
33static void xsk_map_node_free(struct xsk_map_node *node)
34{
35 struct xsk_map *map = node->map;
36
37 bpf_map_put(map: &node->map->map);
38 kfree(objp: node);
39 atomic_dec(v: &map->count);
40}
41
42static void xsk_map_sock_add(struct xdp_sock *xs, struct xsk_map_node *node)
43{
44 spin_lock_bh(lock: &xs->map_list_lock);
45 list_add_tail(new: &node->node, head: &xs->map_list);
46 spin_unlock_bh(lock: &xs->map_list_lock);
47}
48
49static void xsk_map_sock_delete(struct xdp_sock *xs,
50 struct xdp_sock __rcu **map_entry)
51{
52 struct xsk_map_node *n, *tmp;
53
54 spin_lock_bh(lock: &xs->map_list_lock);
55 list_for_each_entry_safe(n, tmp, &xs->map_list, node) {
56 if (map_entry == n->map_entry) {
57 list_del(entry: &n->node);
58 xsk_map_node_free(node: n);
59 }
60 }
61 spin_unlock_bh(lock: &xs->map_list_lock);
62}
63
64static struct bpf_map *xsk_map_alloc(union bpf_attr *attr)
65{
66 struct xsk_map *m;
67 int numa_node;
68 u64 size;
69
70 if (attr->max_entries == 0 || attr->key_size != 4 ||
71 attr->value_size != 4 ||
72 attr->map_flags & ~(BPF_F_NUMA_NODE | BPF_F_RDONLY | BPF_F_WRONLY))
73 return ERR_PTR(error: -EINVAL);
74
75 numa_node = bpf_map_attr_numa_node(attr);
76 size = struct_size(m, xsk_map, attr->max_entries);
77
78 m = bpf_map_area_alloc(size, numa_node);
79 if (!m)
80 return ERR_PTR(error: -ENOMEM);
81
82 bpf_map_init_from_attr(map: &m->map, attr);
83 spin_lock_init(&m->lock);
84
85 return &m->map;
86}
87
88static u64 xsk_map_mem_usage(const struct bpf_map *map)
89{
90 struct xsk_map *m = container_of(map, struct xsk_map, map);
91
92 return struct_size(m, xsk_map, map->max_entries) +
93 (u64)atomic_read(v: &m->count) * sizeof(struct xsk_map_node);
94}
95
96static void xsk_map_free(struct bpf_map *map)
97{
98 struct xsk_map *m = container_of(map, struct xsk_map, map);
99
100 synchronize_net();
101 bpf_map_area_free(base: m);
102}
103
104static int xsk_map_get_next_key(struct bpf_map *map, void *key, void *next_key)
105{
106 struct xsk_map *m = container_of(map, struct xsk_map, map);
107 u32 index = key ? *(u32 *)key : U32_MAX;
108 u32 *next = next_key;
109
110 if (index >= m->map.max_entries) {
111 *next = 0;
112 return 0;
113 }
114
115 if (index == m->map.max_entries - 1)
116 return -ENOENT;
117 *next = index + 1;
118 return 0;
119}
120
121static int xsk_map_gen_lookup(struct bpf_map *map, struct bpf_insn *insn_buf)
122{
123 const int ret = BPF_REG_0, mp = BPF_REG_1, index = BPF_REG_2;
124 struct bpf_insn *insn = insn_buf;
125
126 *insn++ = BPF_LDX_MEM(BPF_W, ret, index, 0);
127 *insn++ = BPF_JMP_IMM(BPF_JGE, ret, map->max_entries, 5);
128 *insn++ = BPF_ALU64_IMM(BPF_LSH, ret, ilog2(sizeof(struct xsk_sock *)));
129 *insn++ = BPF_ALU64_IMM(BPF_ADD, mp, offsetof(struct xsk_map, xsk_map));
130 *insn++ = BPF_ALU64_REG(BPF_ADD, ret, mp);
131 *insn++ = BPF_LDX_MEM(BPF_SIZEOF(struct xsk_sock *), ret, ret, 0);
132 *insn++ = BPF_JMP_IMM(BPF_JA, 0, 0, 1);
133 *insn++ = BPF_MOV64_IMM(ret, 0);
134 return insn - insn_buf;
135}
136
137/* Elements are kept alive by RCU; either by rcu_read_lock() (from syscall) or
138 * by local_bh_disable() (from XDP calls inside NAPI). The
139 * rcu_read_lock_bh_held() below makes lockdep accept both.
140 */
141static void *__xsk_map_lookup_elem(struct bpf_map *map, u32 key)
142{
143 struct xsk_map *m = container_of(map, struct xsk_map, map);
144
145 if (key >= map->max_entries)
146 return NULL;
147
148 return rcu_dereference_check(m->xsk_map[key], rcu_read_lock_bh_held());
149}
150
151static void *xsk_map_lookup_elem(struct bpf_map *map, void *key)
152{
153 return __xsk_map_lookup_elem(map, key: *(u32 *)key);
154}
155
156static void *xsk_map_lookup_elem_sys_only(struct bpf_map *map, void *key)
157{
158 return ERR_PTR(error: -EOPNOTSUPP);
159}
160
161static long xsk_map_update_elem(struct bpf_map *map, void *key, void *value,
162 u64 map_flags)
163{
164 struct xsk_map *m = container_of(map, struct xsk_map, map);
165 struct xdp_sock __rcu **map_entry;
166 struct xdp_sock *xs, *old_xs;
167 u32 i = *(u32 *)key, fd = *(u32 *)value;
168 struct xsk_map_node *node;
169 struct socket *sock;
170 int err;
171
172 if (unlikely(map_flags > BPF_EXIST))
173 return -EINVAL;
174 if (unlikely(i >= m->map.max_entries))
175 return -E2BIG;
176
177 sock = sockfd_lookup(fd, err: &err);
178 if (!sock)
179 return err;
180
181 if (sock->sk->sk_family != PF_XDP) {
182 sockfd_put(sock);
183 return -EOPNOTSUPP;
184 }
185
186 xs = (struct xdp_sock *)sock->sk;
187
188 map_entry = &m->xsk_map[i];
189 node = xsk_map_node_alloc(map: m, map_entry);
190 if (IS_ERR(ptr: node)) {
191 sockfd_put(sock);
192 return PTR_ERR(ptr: node);
193 }
194
195 spin_lock_bh(lock: &m->lock);
196 old_xs = rcu_dereference_protected(*map_entry, lockdep_is_held(&m->lock));
197 if (old_xs == xs) {
198 err = 0;
199 goto out;
200 } else if (old_xs && map_flags == BPF_NOEXIST) {
201 err = -EEXIST;
202 goto out;
203 } else if (!old_xs && map_flags == BPF_EXIST) {
204 err = -ENOENT;
205 goto out;
206 }
207 xsk_map_sock_add(xs, node);
208 rcu_assign_pointer(*map_entry, xs);
209 if (old_xs)
210 xsk_map_sock_delete(xs: old_xs, map_entry);
211 spin_unlock_bh(lock: &m->lock);
212 sockfd_put(sock);
213 return 0;
214
215out:
216 spin_unlock_bh(lock: &m->lock);
217 sockfd_put(sock);
218 xsk_map_node_free(node);
219 return err;
220}
221
222static long xsk_map_delete_elem(struct bpf_map *map, void *key)
223{
224 struct xsk_map *m = container_of(map, struct xsk_map, map);
225 struct xdp_sock __rcu **map_entry;
226 struct xdp_sock *old_xs;
227 u32 k = *(u32 *)key;
228
229 if (k >= map->max_entries)
230 return -EINVAL;
231
232 spin_lock_bh(lock: &m->lock);
233 map_entry = &m->xsk_map[k];
234 old_xs = unrcu_pointer(xchg(map_entry, NULL));
235 if (old_xs)
236 xsk_map_sock_delete(xs: old_xs, map_entry);
237 spin_unlock_bh(lock: &m->lock);
238
239 return 0;
240}
241
242static long xsk_map_redirect(struct bpf_map *map, u64 index, u64 flags)
243{
244 return __bpf_xdp_redirect_map(map, index, flags, flag_mask: 0,
245 lookup_elem: __xsk_map_lookup_elem);
246}
247
248void xsk_map_try_sock_delete(struct xsk_map *map, struct xdp_sock *xs,
249 struct xdp_sock __rcu **map_entry)
250{
251 spin_lock_bh(lock: &map->lock);
252 if (rcu_access_pointer(*map_entry) == xs) {
253 rcu_assign_pointer(*map_entry, NULL);
254 xsk_map_sock_delete(xs, map_entry);
255 }
256 spin_unlock_bh(lock: &map->lock);
257}
258
259static bool xsk_map_meta_equal(const struct bpf_map *meta0,
260 const struct bpf_map *meta1)
261{
262 return meta0->max_entries == meta1->max_entries &&
263 bpf_map_meta_equal(meta0, meta1);
264}
265
266BTF_ID_LIST_SINGLE(xsk_map_btf_ids, struct, xsk_map)
267const struct bpf_map_ops xsk_map_ops = {
268 .map_meta_equal = xsk_map_meta_equal,
269 .map_alloc = xsk_map_alloc,
270 .map_free = xsk_map_free,
271 .map_get_next_key = xsk_map_get_next_key,
272 .map_lookup_elem = xsk_map_lookup_elem,
273 .map_gen_lookup = xsk_map_gen_lookup,
274 .map_lookup_elem_sys_only = xsk_map_lookup_elem_sys_only,
275 .map_update_elem = xsk_map_update_elem,
276 .map_delete_elem = xsk_map_delete_elem,
277 .map_check_btf = map_check_no_btf,
278 .map_mem_usage = xsk_map_mem_usage,
279 .map_btf_id = &xsk_map_btf_ids[0],
280 .map_redirect = xsk_map_redirect,
281};
282

source code of linux/net/xdp/xskmap.c