kernel/bpf/arraymap.c

   1 /* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com
   2  *
   3  * This program is free software; you can redistribute it and/or
   4  * modify it under the terms of version 2 of the GNU General Public
   5  * License as published by the Free Software Foundation.
   6  *
   7  * This program is distributed in the hope that it will be useful, but
   8  * WITHOUT ANY WARRANTY; without even the implied warranty of
   9  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  10  * General Public License for more details.
  11  */
  12 #include <linux/bpf.h>
  13 #include <linux/err.h>
  14 #include <linux/vmalloc.h>
  15 #include <linux/slab.h>
  16 #include <linux/mm.h>
  17 #include <linux/filter.h>
  18
  19 /* Called from syscall */
  20 static struct bpf_map *array_map_alloc(union bpf_attr *attr)
  21 {
  22         struct bpf_array *array;
  23         u32 elem_size, array_size;
  24
  25         /* check sanity of attributes */
  26         if (attr->max_entries == 0 || attr->key_size != 4 ||
  27             attr->value_size == 0)
  28                 return ERR_PTR(-EINVAL);
  29
  30         elem_size = round_up(attr->value_size, 8);
  31
  32         /* check round_up into zero and u32 overflow */
  33         if (elem_size == 0 ||
  34             attr->max_entries > (U32_MAX - sizeof(*array)) / elem_size)
  35                 return ERR_PTR(-ENOMEM);
  36
  37         array_size = sizeof(*array) + attr->max_entries * elem_size;
  38
  39         /* allocate all map elements and zero-initialize them */
  40         array = kzalloc(array_size, GFP_USER | __GFP_NOWARN);
  41         if (!array) {
  42                 array = vzalloc(array_size);
  43                 if (!array)
  44                         return ERR_PTR(-ENOMEM);
  45         }
  46
  47         /* copy mandatory map attributes */
  48         array->map.key_size = attr->key_size;
  49         array->map.value_size = attr->value_size;
  50         array->map.max_entries = attr->max_entries;
  51
  52         array->elem_size = elem_size;
  53
  54         return &array->map;
  55 }
  56
  57 /* Called from syscall or from eBPF program */
  58 static void *array_map_lookup_elem(struct bpf_map *map, void *key)
  59 {
  60         struct bpf_array *array = container_of(map, struct bpf_array, map);
  61         u32 index = *(u32 *)key;
  62
  63         if (index >= array->map.max_entries)
  64                 return NULL;
  65
  66         return array->value + array->elem_size * index;
  67 }
  68
  69 /* Called from syscall */
  70 static int array_map_get_next_key(struct bpf_map *map, void *key, void *next_key)
  71 {
  72         struct bpf_array *array = container_of(map, struct bpf_array, map);
  73         u32 index = *(u32 *)key;
  74         u32 *next = (u32 *)next_key;
  75
  76         if (index >= array->map.max_entries) {
  77                 *next = 0;
  78                 return 0;
  79         }
  80
  81         if (index == array->map.max_entries - 1)
  82                 return -ENOENT;
  83
  84         *next = index + 1;
  85         return 0;
  86 }
  87
  88 /* Called from syscall or from eBPF program */
  89 static int array_map_update_elem(struct bpf_map *map, void *key, void *value,
  90                                  u64 map_flags)
  91 {
  92         struct bpf_array *array = container_of(map, struct bpf_array, map);
  93         u32 index = *(u32 *)key;
  94
  95         if (map_flags > BPF_EXIST)
  96                 /* unknown flags */
  97                 return -EINVAL;
  98
  99         if (index >= array->map.max_entries)
 100                 /* all elements were pre-allocated, cannot insert a new one */
 101                 return -E2BIG;
 102
 103         if (map_flags == BPF_NOEXIST)
 104                 /* all elements already exist */
 105                 return -EEXIST;
 106
 107         memcpy(array->value + array->elem_size * index, value, array->elem_size);
 108         return 0;
 109 }
 110
 111 /* Called from syscall or from eBPF program */
 112 static int array_map_delete_elem(struct bpf_map *map, void *key)
 113 {
 114         return -EINVAL;
 115 }
 116
 117 /* Called when map->refcnt goes to zero, either from workqueue or from syscall */
 118 static void array_map_free(struct bpf_map *map)
 119 {
 120         struct bpf_array *array = container_of(map, struct bpf_array, map);
 121
 122         /* at this point bpf_prog->aux->refcnt == 0 and this map->refcnt == 0,
 123          * so the programs (can be more than one that used this map) were
 124          * disconnected from events. Wait for outstanding programs to complete
 125          * and free the array
 126          */
 127         synchronize_rcu();
 128
 129         kvfree(array);
 130 }
 131
 132 static const struct bpf_map_ops array_ops = {
 133         .map_alloc = array_map_alloc,
 134         .map_free = array_map_free,
 135         .map_get_next_key = array_map_get_next_key,
 136         .map_lookup_elem = array_map_lookup_elem,
 137         .map_update_elem = array_map_update_elem,
 138         .map_delete_elem = array_map_delete_elem,
 139 };
 140
 141 static struct bpf_map_type_list array_type __read_mostly = {
 142         .ops = &array_ops,
 143         .type = BPF_MAP_TYPE_ARRAY,
 144 };
 145
 146 static int __init register_array_map(void)
 147 {
 148         bpf_register_map_type(&array_type);
 149         return 0;
 150 }
 151 late_initcall(register_array_map);
 152
 153 static struct bpf_map *fd_array_map_alloc(union bpf_attr *attr)
 154 {
 155         /* only file descriptors can be stored in this type of map */
 156         if (attr->value_size != sizeof(u32))
 157                 return ERR_PTR(-EINVAL);
 158         return array_map_alloc(attr);
 159 }
 160
 161 static void fd_array_map_free(struct bpf_map *map)
 162 {
 163         struct bpf_array *array = container_of(map, struct bpf_array, map);
 164         int i;
 165
 166         synchronize_rcu();
 167
 168         /* make sure it's empty */
 169         for (i = 0; i < array->map.max_entries; i++)
 170                 BUG_ON(array->ptrs[i] != NULL);
 171         kvfree(array);
 172 }
 173
 174 static void *fd_array_map_lookup_elem(struct bpf_map *map, void *key)
 175 {
 176         return NULL;
 177 }
 178
 179 /* only called from syscall */
 180 static int fd_array_map_update_elem(struct bpf_map *map, void *key,
 181                                     void *value, u64 map_flags)
 182 {
 183         struct bpf_array *array = container_of(map, struct bpf_array, map);
 184         void *new_ptr, *old_ptr;
 185         u32 index = *(u32 *)key, ufd;
 186
 187         if (map_flags != BPF_ANY)
 188                 return -EINVAL;
 189
 190         if (index >= array->map.max_entries)
 191                 return -E2BIG;
 192
 193         ufd = *(u32 *)value;
 194         new_ptr = map->ops->map_fd_get_ptr(map, ufd);
 195         if (IS_ERR(new_ptr))
 196                 return PTR_ERR(new_ptr);
 197
 198         old_ptr = xchg(array->ptrs + index, new_ptr);
 199         if (old_ptr)
 200                 map->ops->map_fd_put_ptr(old_ptr);
 201
 202         return 0;
 203 }
 204
 205 static int fd_array_map_delete_elem(struct bpf_map *map, void *key)
 206 {
 207         struct bpf_array *array = container_of(map, struct bpf_array, map);
 208         void *old_ptr;
 209         u32 index = *(u32 *)key;
 210
 211         if (index >= array->map.max_entries)
 212                 return -E2BIG;
 213
 214         old_ptr = xchg(array->ptrs + index, NULL);
 215         if (old_ptr) {
 216                 map->ops->map_fd_put_ptr(old_ptr);
 217                 return 0;
 218         } else {
 219                 return -ENOENT;
 220         }
 221 }
 222
 223 static void *prog_fd_array_get_ptr(struct bpf_map *map, int fd)
 224 {
 225         struct bpf_array *array = container_of(map, struct bpf_array, map);
 226         struct bpf_prog *prog = bpf_prog_get(fd);
 227         if (IS_ERR(prog))
 228                 return prog;
 229
 230         if (!bpf_prog_array_compatible(array, prog)) {
 231                 bpf_prog_put(prog);
 232                 return ERR_PTR(-EINVAL);
 233         }
 234         return prog;
 235 }
 236
 237 static void prog_fd_array_put_ptr(void *ptr)
 238 {
 239         struct bpf_prog *prog = ptr;
 240
 241         bpf_prog_put_rcu(prog);
 242 }
 243
 244 /* decrement refcnt of all bpf_progs that are stored in this map */
 245 void bpf_fd_array_map_clear(struct bpf_map *map)
 246 {
 247         struct bpf_array *array = container_of(map, struct bpf_array, map);
 248         int i;
 249
 250         for (i = 0; i < array->map.max_entries; i++)
 251                 fd_array_map_delete_elem(map, &i);
 252 }
 253
 254 static const struct bpf_map_ops prog_array_ops = {
 255         .map_alloc = fd_array_map_alloc,
 256         .map_free = fd_array_map_free,
 257         .map_get_next_key = array_map_get_next_key,
 258         .map_lookup_elem = fd_array_map_lookup_elem,
 259         .map_update_elem = fd_array_map_update_elem,
 260         .map_delete_elem = fd_array_map_delete_elem,
 261         .map_fd_get_ptr = prog_fd_array_get_ptr,
 262         .map_fd_put_ptr = prog_fd_array_put_ptr,
 263 };
 264
 265 static struct bpf_map_type_list prog_array_type __read_mostly = {
 266         .ops = &prog_array_ops,
 267         .type = BPF_MAP_TYPE_PROG_ARRAY,
 268 };
 269
 270 static int __init register_prog_array_map(void)
 271 {
 272         bpf_register_map_type(&prog_array_type);
 273         return 0;
 274 }
 275 late_initcall(register_prog_array_map);