net/xdp/xskmap.c

   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 };