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, sizeof(*node),
21			       GFP_ATOMIC | __GFP_NOWARN);
22	if (!node)
23		return ERR_PTR(-ENOMEM);
24
25	bpf_map_inc(&map->map);
26	atomic_inc(&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(&node->map->map);
38	kfree(node);
39	atomic_dec(&map->count);
40}
41
42static void xsk_map_sock_add(struct xdp_sock *xs, struct xsk_map_node *node)
43{
44	spin_lock_bh(&xs->map_list_lock);
45	list_add_tail(&node->node, &xs->map_list);
46	spin_unlock_bh(&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(&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(&n->node);
58			xsk_map_node_free(n);
59		}
60	}
61	spin_unlock_bh(&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(-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(-ENOMEM);
81
82	bpf_map_init_from_attr(&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(&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(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, *(u32 *)key);
154}
155
156static void *xsk_map_lookup_elem_sys_only(struct bpf_map *map, void *key)
157{
158	return ERR_PTR(-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);
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(m, map_entry);
190	if (IS_ERR(node)) {
191		sockfd_put(sock);
192		return PTR_ERR(node);
193	}
194
195	spin_lock_bh(&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(old_xs, map_entry);
211	spin_unlock_bh(&m->lock);
212	sockfd_put(sock);
213	return 0;
214
215out:
216	spin_unlock_bh(&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	int k = *(u32 *)key;
228
229	if (k >= map->max_entries)
230		return -EINVAL;
231
232	spin_lock_bh(&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(old_xs, map_entry);
237	spin_unlock_bh(&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, 0,
245				      __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(&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(&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