kernel/bpf/hashtab.c

   1 /* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com
   2  * Copyright (c) 2016 Facebook
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of version 2 of the GNU General Public
   6  * License as published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful, but
   9  * WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  11  * General Public License for more details.
  12  */
  13 #include <linux/bpf.h>
  14 #include <linux/jhash.h>
  15 #include <linux/filter.h>
  16 #include <linux/vmalloc.h>
  17 #include "percpu_freelist.h"
  18
  19 struct bucket {
  20         struct hlist_head head;
  21         raw_spinlock_t lock;
  22 };
  23
  24 struct bpf_htab {
  25         struct bpf_map map;
  26         struct bucket *buckets;
  27         void *elems;
  28         struct pcpu_freelist freelist;
  29         atomic_t count; /* number of elements in this hashtable */
  30         u32 n_buckets;  /* number of hash buckets */
  31         u32 elem_size;  /* size of each element in bytes */
  32 };
  33
  34 /* each htab element is struct htab_elem + key + value */
  35 struct htab_elem {
  36         union {
  37                 struct hlist_node hash_node;
  38                 struct bpf_htab *htab;
  39                 struct pcpu_freelist_node fnode;
  40         };
  41         struct rcu_head rcu;
  42         u32 hash;
  43         char key[0] __aligned(8);
  44 };
  45
  46 static inline void htab_elem_set_ptr(struct htab_elem *l, u32 key_size,
  47                                      void __percpu *pptr)
  48 {
  49         *(void __percpu **)(l->key + key_size) = pptr;
  50 }
  51
  52 static inline void __percpu *htab_elem_get_ptr(struct htab_elem *l, u32 key_size)
  53 {
  54         return *(void __percpu **)(l->key + key_size);
  55 }
  56
  57 static struct htab_elem *get_htab_elem(struct bpf_htab *htab, int i)
  58 {
  59         return (struct htab_elem *) (htab->elems + i * htab->elem_size);
  60 }
  61
  62 static void htab_free_elems(struct bpf_htab *htab)
  63 {
  64         int i;
  65
  66         if (htab->map.map_type != BPF_MAP_TYPE_PERCPU_HASH)
  67                 goto free_elems;
  68
  69         for (i = 0; i < htab->map.max_entries; i++) {
  70                 void __percpu *pptr;
  71
  72                 pptr = htab_elem_get_ptr(get_htab_elem(htab, i),
  73                                          htab->map.key_size);
  74                 free_percpu(pptr);
  75         }
  76 free_elems:
  77         vfree(htab->elems);
  78 }
  79
  80 static int prealloc_elems_and_freelist(struct bpf_htab *htab)
  81 {
  82         int err = -ENOMEM, i;
  83
  84         htab->elems = vzalloc(htab->elem_size * htab->map.max_entries);
  85         if (!htab->elems)
  86                 return -ENOMEM;
  87
  88         if (htab->map.map_type != BPF_MAP_TYPE_PERCPU_HASH)
  89                 goto skip_percpu_elems;
  90
  91         for (i = 0; i < htab->map.max_entries; i++) {
  92                 u32 size = round_up(htab->map.value_size, 8);
  93                 void __percpu *pptr;
  94
  95                 pptr = __alloc_percpu_gfp(size, 8, GFP_USER | __GFP_NOWARN);
  96                 if (!pptr)
  97                         goto free_elems;
  98                 htab_elem_set_ptr(get_htab_elem(htab, i), htab->map.key_size,
  99                                   pptr);
 100         }
 101
 102 skip_percpu_elems:
 103         err = pcpu_freelist_init(&htab->freelist);
 104         if (err)
 105                 goto free_elems;
 106
 107         pcpu_freelist_populate(&htab->freelist, htab->elems, htab->elem_size,
 108                                htab->map.max_entries);
 109         return 0;
 110
 111 free_elems:
 112         htab_free_elems(htab);
 113         return err;
 114 }
 115
 116 /* Called from syscall */
 117 static struct bpf_map *htab_map_alloc(union bpf_attr *attr)
 118 {
 119         bool percpu = attr->map_type == BPF_MAP_TYPE_PERCPU_HASH;
 120         struct bpf_htab *htab;
 121         int err, i;
 122         u64 cost;
 123
 124         if (attr->map_flags & ~BPF_F_NO_PREALLOC)
 125                 /* reserved bits should not be used */
 126                 return ERR_PTR(-EINVAL);
 127
 128         htab = kzalloc(sizeof(*htab), GFP_USER);
 129         if (!htab)
 130                 return ERR_PTR(-ENOMEM);
 131
 132         /* mandatory map attributes */
 133         htab->map.map_type = attr->map_type;
 134         htab->map.key_size = attr->key_size;
 135         htab->map.value_size = attr->value_size;
 136         htab->map.max_entries = attr->max_entries;
 137         htab->map.map_flags = attr->map_flags;
 138
 139         /* check sanity of attributes.
 140          * value_size == 0 may be allowed in the future to use map as a set
 141          */
 142         err = -EINVAL;
 143         if (htab->map.max_entries == 0 || htab->map.key_size == 0 ||
 144             htab->map.value_size == 0)
 145                 goto free_htab;
 146
 147         /* hash table size must be power of 2 */
 148         htab->n_buckets = roundup_pow_of_two(htab->map.max_entries);
 149
 150         err = -E2BIG;
 151         if (htab->map.key_size > MAX_BPF_STACK)
 152                 /* eBPF programs initialize keys on stack, so they cannot be
 153                  * larger than max stack size
 154                  */
 155                 goto free_htab;
 156
 157         if (htab->map.value_size >= (1 << (KMALLOC_SHIFT_MAX - 1)) -
 158             MAX_BPF_STACK - sizeof(struct htab_elem))
 159                 /* if value_size is bigger, the user space won't be able to
 160                  * access the elements via bpf syscall. This check also makes
 161                  * sure that the elem_size doesn't overflow and it's
 162                  * kmalloc-able later in htab_map_update_elem()
 163                  */
 164                 goto free_htab;
 165
 166         if (percpu && round_up(htab->map.value_size, 8) > PCPU_MIN_UNIT_SIZE)
 167                 /* make sure the size for pcpu_alloc() is reasonable */
 168                 goto free_htab;
 169
 170         htab->elem_size = sizeof(struct htab_elem) +
 171                           round_up(htab->map.key_size, 8);
 172         if (percpu)
 173                 htab->elem_size += sizeof(void *);
 174         else
 175                 htab->elem_size += round_up(htab->map.value_size, 8);
 176
 177         /* prevent zero size kmalloc and check for u32 overflow */
 178         if (htab->n_buckets == 0 ||
 179             htab->n_buckets > U32_MAX / sizeof(struct bucket))
 180                 goto free_htab;
 181
 182         cost = (u64) htab->n_buckets * sizeof(struct bucket) +
 183                (u64) htab->elem_size * htab->map.max_entries;
 184
 185         if (percpu)
 186                 cost += (u64) round_up(htab->map.value_size, 8) *
 187                         num_possible_cpus() * htab->map.max_entries;
 188
 189         if (cost >= U32_MAX - PAGE_SIZE)
 190                 /* make sure page count doesn't overflow */
 191                 goto free_htab;
 192
 193         htab->map.pages = round_up(cost, PAGE_SIZE) >> PAGE_SHIFT;
 194
 195         /* if map size is larger than memlock limit, reject it early */
 196         err = bpf_map_precharge_memlock(htab->map.pages);
 197         if (err)
 198                 goto free_htab;
 199
 200         err = -ENOMEM;
 201         htab->buckets = kmalloc_array(htab->n_buckets, sizeof(struct bucket),
 202                                       GFP_USER | __GFP_NOWARN);
 203
 204         if (!htab->buckets) {
 205                 htab->buckets = vmalloc(htab->n_buckets * sizeof(struct bucket));
 206                 if (!htab->buckets)
 207                         goto free_htab;
 208         }
 209
 210         for (i = 0; i < htab->n_buckets; i++) {
 211                 INIT_HLIST_HEAD(&htab->buckets[i].head);
 212                 raw_spin_lock_init(&htab->buckets[i].lock);
 213         }
 214
 215         if (!(attr->map_flags & BPF_F_NO_PREALLOC)) {
 216                 err = prealloc_elems_and_freelist(htab);
 217                 if (err)
 218                         goto free_buckets;
 219         }
 220
 221         return &htab->map;
 222
 223 free_buckets:
 224         kvfree(htab->buckets);
 225 free_htab:
 226         kfree(htab);
 227         return ERR_PTR(err);
 228 }
 229
 230 static inline u32 htab_map_hash(const void *key, u32 key_len)
 231 {
 232         return jhash(key, key_len, 0);
 233 }
 234
 235 static inline struct bucket *__select_bucket(struct bpf_htab *htab, u32 hash)
 236 {
 237         return &htab->buckets[hash & (htab->n_buckets - 1)];
 238 }
 239
 240 static inline struct hlist_head *select_bucket(struct bpf_htab *htab, u32 hash)
 241 {
 242         return &__select_bucket(htab, hash)->head;
 243 }
 244
 245 static struct htab_elem *lookup_elem_raw(struct hlist_head *head, u32 hash,
 246                                          void *key, u32 key_size)
 247 {
 248         struct htab_elem *l;
 249
 250         hlist_for_each_entry_rcu(l, head, hash_node)
 251                 if (l->hash == hash && !memcmp(&l->key, key, key_size))
 252                         return l;
 253
 254         return NULL;
 255 }
 256
 257 /* Called from syscall or from eBPF program */
 258 static void *__htab_map_lookup_elem(struct bpf_map *map, void *key)
 259 {
 260         struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
 261         struct hlist_head *head;
 262         struct htab_elem *l;
 263         u32 hash, key_size;
 264
 265         /* Must be called with rcu_read_lock. */
 266         WARN_ON_ONCE(!rcu_read_lock_held());
 267
 268         key_size = map->key_size;
 269
 270         hash = htab_map_hash(key, key_size);
 271
 272         head = select_bucket(htab, hash);
 273
 274         l = lookup_elem_raw(head, hash, key, key_size);
 275
 276         return l;
 277 }
 278
 279 static void *htab_map_lookup_elem(struct bpf_map *map, void *key)
 280 {
 281         struct htab_elem *l = __htab_map_lookup_elem(map, key);
 282
 283         if (l)
 284                 return l->key + round_up(map->key_size, 8);
 285
 286         return NULL;
 287 }
 288
 289 /* Called from syscall */
 290 static int htab_map_get_next_key(struct bpf_map *map, void *key, void *next_key)
 291 {
 292         struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
 293         struct hlist_head *head;
 294         struct htab_elem *l, *next_l;
 295         u32 hash, key_size;
 296         int i;
 297
 298         WARN_ON_ONCE(!rcu_read_lock_held());
 299
 300         key_size = map->key_size;
 301
 302         hash = htab_map_hash(key, key_size);
 303
 304         head = select_bucket(htab, hash);
 305
 306         /* lookup the key */
 307         l = lookup_elem_raw(head, hash, key, key_size);
 308
 309         if (!l) {
 310                 i = 0;
 311                 goto find_first_elem;
 312         }
 313
 314         /* key was found, get next key in the same bucket */
 315         next_l = hlist_entry_safe(rcu_dereference_raw(hlist_next_rcu(&l->hash_node)),
 316                                   struct htab_elem, hash_node);
 317
 318         if (next_l) {
 319                 /* if next elem in this hash list is non-zero, just return it */
 320                 memcpy(next_key, next_l->key, key_size);
 321                 return 0;
 322         }
 323
 324         /* no more elements in this hash list, go to the next bucket */
 325         i = hash & (htab->n_buckets - 1);
 326         i++;
 327
 328 find_first_elem:
 329         /* iterate over buckets */
 330         for (; i < htab->n_buckets; i++) {
 331                 head = select_bucket(htab, i);
 332
 333                 /* pick first element in the bucket */
 334                 next_l = hlist_entry_safe(rcu_dereference_raw(hlist_first_rcu(head)),
 335                                           struct htab_elem, hash_node);
 336                 if (next_l) {
 337                         /* if it's not empty, just return it */
 338                         memcpy(next_key, next_l->key, key_size);
 339                         return 0;
 340                 }
 341         }
 342
 343         /* iterated over all buckets and all elements */
 344         return -ENOENT;
 345 }
 346
 347 static void htab_elem_free(struct bpf_htab *htab, struct htab_elem *l)
 348 {
 349         if (htab->map.map_type == BPF_MAP_TYPE_PERCPU_HASH)
 350                 free_percpu(htab_elem_get_ptr(l, htab->map.key_size));
 351         kfree(l);
 352
 353 }
 354
 355 static void htab_elem_free_rcu(struct rcu_head *head)
 356 {
 357         struct htab_elem *l = container_of(head, struct htab_elem, rcu);
 358         struct bpf_htab *htab = l->htab;
 359
 360         /* must increment bpf_prog_active to avoid kprobe+bpf triggering while
 361          * we're calling kfree, otherwise deadlock is possible if kprobes
 362          * are placed somewhere inside of slub
 363          */
 364         preempt_disable();
 365         __this_cpu_inc(bpf_prog_active);
 366         htab_elem_free(htab, l);
 367         __this_cpu_dec(bpf_prog_active);
 368         preempt_enable();
 369 }
 370
 371 static void free_htab_elem(struct bpf_htab *htab, struct htab_elem *l)
 372 {
 373         if (!(htab->map.map_flags & BPF_F_NO_PREALLOC)) {
 374                 pcpu_freelist_push(&htab->freelist, &l->fnode);
 375         } else {
 376                 atomic_dec(&htab->count);
 377                 l->htab = htab;
 378                 call_rcu(&l->rcu, htab_elem_free_rcu);
 379         }
 380 }
 381
 382 static struct htab_elem *alloc_htab_elem(struct bpf_htab *htab, void *key,
 383                                          void *value, u32 key_size, u32 hash,
 384                                          bool percpu, bool onallcpus)
 385 {
 386         u32 size = htab->map.value_size;
 387         bool prealloc = !(htab->map.map_flags & BPF_F_NO_PREALLOC);
 388         struct htab_elem *l_new;
 389         void __percpu *pptr;
 390
 391         if (prealloc) {
 392                 l_new = (struct htab_elem *)pcpu_freelist_pop(&htab->freelist);
 393                 if (!l_new)
 394                         return ERR_PTR(-E2BIG);
 395         } else {
 396                 if (atomic_inc_return(&htab->count) > htab->map.max_entries) {
 397                         atomic_dec(&htab->count);
 398                         return ERR_PTR(-E2BIG);
 399                 }
 400                 l_new = kmalloc(htab->elem_size, GFP_ATOMIC | __GFP_NOWARN);
 401                 if (!l_new)
 402                         return ERR_PTR(-ENOMEM);
 403         }
 404
 405         memcpy(l_new->key, key, key_size);
 406         if (percpu) {
 407                 /* round up value_size to 8 bytes */
 408                 size = round_up(size, 8);
 409
 410                 if (prealloc) {
 411                         pptr = htab_elem_get_ptr(l_new, key_size);
 412                 } else {
 413                         /* alloc_percpu zero-fills */
 414                         pptr = __alloc_percpu_gfp(size, 8,
 415                                                   GFP_ATOMIC | __GFP_NOWARN);
 416                         if (!pptr) {
 417                                 kfree(l_new);
 418                                 return ERR_PTR(-ENOMEM);
 419                         }
 420                 }
 421
 422                 if (!onallcpus) {
 423                         /* copy true value_size bytes */
 424                         memcpy(this_cpu_ptr(pptr), value, htab->map.value_size);
 425                 } else {
 426                         int off = 0, cpu;
 427
 428                         for_each_possible_cpu(cpu) {
 429                                 bpf_long_memcpy(per_cpu_ptr(pptr, cpu),
 430                                                 value + off, size);
 431                                 off += size;
 432                         }
 433                 }
 434                 if (!prealloc)
 435                         htab_elem_set_ptr(l_new, key_size, pptr);
 436         } else {
 437                 memcpy(l_new->key + round_up(key_size, 8), value, size);
 438         }
 439
 440         l_new->hash = hash;
 441         return l_new;
 442 }
 443
 444 static int check_flags(struct bpf_htab *htab, struct htab_elem *l_old,
 445                        u64 map_flags)
 446 {
 447         if (l_old && map_flags == BPF_NOEXIST)
 448                 /* elem already exists */
 449                 return -EEXIST;
 450
 451         if (!l_old && map_flags == BPF_EXIST)
 452                 /* elem doesn't exist, cannot update it */
 453                 return -ENOENT;
 454
 455         return 0;
 456 }
 457
 458 /* Called from syscall or from eBPF program */
 459 static int htab_map_update_elem(struct bpf_map *map, void *key, void *value,
 460                                 u64 map_flags)
 461 {
 462         struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
 463         struct htab_elem *l_new = NULL, *l_old;
 464         struct hlist_head *head;
 465         unsigned long flags;
 466         struct bucket *b;
 467         u32 key_size, hash;
 468         int ret;
 469
 470         if (unlikely(map_flags > BPF_EXIST))
 471                 /* unknown flags */
 472                 return -EINVAL;
 473
 474         WARN_ON_ONCE(!rcu_read_lock_held());
 475
 476         key_size = map->key_size;
 477
 478         hash = htab_map_hash(key, key_size);
 479
 480         b = __select_bucket(htab, hash);
 481         head = &b->head;
 482
 483         /* bpf_map_update_elem() can be called in_irq() */
 484         raw_spin_lock_irqsave(&b->lock, flags);
 485
 486         l_old = lookup_elem_raw(head, hash, key, key_size);
 487
 488         ret = check_flags(htab, l_old, map_flags);
 489         if (ret)
 490                 goto err;
 491
 492         l_new = alloc_htab_elem(htab, key, value, key_size, hash, false, false);
 493         if (IS_ERR(l_new)) {
 494                 /* all pre-allocated elements are in use or memory exhausted */
 495                 ret = PTR_ERR(l_new);
 496                 goto err;
 497         }
 498
 499         /* add new element to the head of the list, so that
 500          * concurrent search will find it before old elem
 501          */
 502         hlist_add_head_rcu(&l_new->hash_node, head);
 503         if (l_old) {
 504                 hlist_del_rcu(&l_old->hash_node);
 505                 free_htab_elem(htab, l_old);
 506         }
 507         ret = 0;
 508 err:
 509         raw_spin_unlock_irqrestore(&b->lock, flags);
 510         return ret;
 511 }
 512
 513 static int __htab_percpu_map_update_elem(struct bpf_map *map, void *key,
 514                                          void *value, u64 map_flags,
 515                                          bool onallcpus)
 516 {
 517         struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
 518         struct htab_elem *l_new = NULL, *l_old;
 519         struct hlist_head *head;
 520         unsigned long flags;
 521         struct bucket *b;
 522         u32 key_size, hash;
 523         int ret;
 524
 525         if (unlikely(map_flags > BPF_EXIST))
 526                 /* unknown flags */
 527                 return -EINVAL;
 528
 529         WARN_ON_ONCE(!rcu_read_lock_held());
 530
 531         key_size = map->key_size;
 532
 533         hash = htab_map_hash(key, key_size);
 534
 535         b = __select_bucket(htab, hash);
 536         head = &b->head;
 537
 538         /* bpf_map_update_elem() can be called in_irq() */
 539         raw_spin_lock_irqsave(&b->lock, flags);
 540
 541         l_old = lookup_elem_raw(head, hash, key, key_size);
 542
 543         ret = check_flags(htab, l_old, map_flags);
 544         if (ret)
 545                 goto err;
 546
 547         if (l_old) {
 548                 void __percpu *pptr = htab_elem_get_ptr(l_old, key_size);
 549                 u32 size = htab->map.value_size;
 550
 551                 /* per-cpu hash map can update value in-place */
 552                 if (!onallcpus) {
 553                         memcpy(this_cpu_ptr(pptr), value, size);
 554                 } else {
 555                         int off = 0, cpu;
 556
 557                         size = round_up(size, 8);
 558                         for_each_possible_cpu(cpu) {
 559                                 bpf_long_memcpy(per_cpu_ptr(pptr, cpu),
 560                                                 value + off, size);
 561                                 off += size;
 562                         }
 563                 }
 564         } else {
 565                 l_new = alloc_htab_elem(htab, key, value, key_size,
 566                                         hash, true, onallcpus);
 567                 if (IS_ERR(l_new)) {
 568                         ret = PTR_ERR(l_new);
 569                         goto err;
 570                 }
 571                 hlist_add_head_rcu(&l_new->hash_node, head);
 572         }
 573         ret = 0;
 574 err:
 575         raw_spin_unlock_irqrestore(&b->lock, flags);
 576         return ret;
 577 }
 578
 579 static int htab_percpu_map_update_elem(struct bpf_map *map, void *key,
 580                                        void *value, u64 map_flags)
 581 {
 582         return __htab_percpu_map_update_elem(map, key, value, map_flags, false);
 583 }
 584
 585 /* Called from syscall or from eBPF program */
 586 static int htab_map_delete_elem(struct bpf_map *map, void *key)
 587 {
 588         struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
 589         struct hlist_head *head;
 590         struct bucket *b;
 591         struct htab_elem *l;
 592         unsigned long flags;
 593         u32 hash, key_size;
 594         int ret = -ENOENT;
 595
 596         WARN_ON_ONCE(!rcu_read_lock_held());
 597
 598         key_size = map->key_size;
 599
 600         hash = htab_map_hash(key, key_size);
 601         b = __select_bucket(htab, hash);
 602         head = &b->head;
 603
 604         raw_spin_lock_irqsave(&b->lock, flags);
 605
 606         l = lookup_elem_raw(head, hash, key, key_size);
 607
 608         if (l) {
 609                 hlist_del_rcu(&l->hash_node);
 610                 free_htab_elem(htab, l);
 611                 ret = 0;
 612         }
 613
 614         raw_spin_unlock_irqrestore(&b->lock, flags);
 615         return ret;
 616 }
 617
 618 static void delete_all_elements(struct bpf_htab *htab)
 619 {
 620         int i;
 621
 622         for (i = 0; i < htab->n_buckets; i++) {
 623                 struct hlist_head *head = select_bucket(htab, i);
 624                 struct hlist_node *n;
 625                 struct htab_elem *l;
 626
 627                 hlist_for_each_entry_safe(l, n, head, hash_node) {
 628                         hlist_del_rcu(&l->hash_node);
 629                         htab_elem_free(htab, l);
 630                 }
 631         }
 632 }
 633 /* Called when map->refcnt goes to zero, either from workqueue or from syscall */
 634 static void htab_map_free(struct bpf_map *map)
 635 {
 636         struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
 637
 638         /* at this point bpf_prog->aux->refcnt == 0 and this map->refcnt == 0,
 639          * so the programs (can be more than one that used this map) were
 640          * disconnected from events. Wait for outstanding critical sections in
 641          * these programs to complete
 642          */
 643         synchronize_rcu();
 644
 645         /* some of free_htab_elem() callbacks for elements of this map may
 646          * not have executed. Wait for them.
 647          */
 648         rcu_barrier();
 649         if (htab->map.map_flags & BPF_F_NO_PREALLOC) {
 650                 delete_all_elements(htab);
 651         } else {
 652                 htab_free_elems(htab);
 653                 pcpu_freelist_destroy(&htab->freelist);
 654         }
 655         kvfree(htab->buckets);
 656         kfree(htab);
 657 }
 658
 659 static const struct bpf_map_ops htab_ops = {
 660         .map_alloc = htab_map_alloc,
 661         .map_free = htab_map_free,
 662         .map_get_next_key = htab_map_get_next_key,
 663         .map_lookup_elem = htab_map_lookup_elem,
 664         .map_update_elem = htab_map_update_elem,
 665         .map_delete_elem = htab_map_delete_elem,
 666 };
 667
 668 static struct bpf_map_type_list htab_type __read_mostly = {
 669         .ops = &htab_ops,
 670         .type = BPF_MAP_TYPE_HASH,
 671 };
 672
 673 /* Called from eBPF program */
 674 static void *htab_percpu_map_lookup_elem(struct bpf_map *map, void *key)
 675 {
 676         struct htab_elem *l = __htab_map_lookup_elem(map, key);
 677
 678         if (l)
 679                 return this_cpu_ptr(htab_elem_get_ptr(l, map->key_size));
 680         else
 681                 return NULL;
 682 }
 683
 684 int bpf_percpu_hash_copy(struct bpf_map *map, void *key, void *value)
 685 {
 686         struct htab_elem *l;
 687         void __percpu *pptr;
 688         int ret = -ENOENT;
 689         int cpu, off = 0;
 690         u32 size;
 691
 692         /* per_cpu areas are zero-filled and bpf programs can only
 693          * access 'value_size' of them, so copying rounded areas
 694          * will not leak any kernel data
 695          */
 696         size = round_up(map->value_size, 8);
 697         rcu_read_lock();
 698         l = __htab_map_lookup_elem(map, key);
 699         if (!l)
 700                 goto out;
 701         pptr = htab_elem_get_ptr(l, map->key_size);
 702         for_each_possible_cpu(cpu) {
 703                 bpf_long_memcpy(value + off,
 704                                 per_cpu_ptr(pptr, cpu), size);
 705                 off += size;
 706         }
 707         ret = 0;
 708 out:
 709         rcu_read_unlock();
 710         return ret;
 711 }
 712
 713 int bpf_percpu_hash_update(struct bpf_map *map, void *key, void *value,
 714                            u64 map_flags)
 715 {
 716         int ret;
 717
 718         rcu_read_lock();
 719         ret = __htab_percpu_map_update_elem(map, key, value, map_flags, true);
 720         rcu_read_unlock();
 721
 722         return ret;
 723 }
 724
 725 static const struct bpf_map_ops htab_percpu_ops = {
 726         .map_alloc = htab_map_alloc,
 727         .map_free = htab_map_free,
 728         .map_get_next_key = htab_map_get_next_key,
 729         .map_lookup_elem = htab_percpu_map_lookup_elem,
 730         .map_update_elem = htab_percpu_map_update_elem,
 731         .map_delete_elem = htab_map_delete_elem,
 732 };
 733
 734 static struct bpf_map_type_list htab_percpu_type __read_mostly = {
 735         .ops = &htab_percpu_ops,
 736         .type = BPF_MAP_TYPE_PERCPU_HASH,
 737 };
 738
 739 static int __init register_htab_map(void)
 740 {
 741         bpf_register_map_type(&htab_type);
 742         bpf_register_map_type(&htab_percpu_type);
 743         return 0;
 744 }
 745 late_initcall(register_htab_map);