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/rculist_nulls.h>
  17 #include "percpu_freelist.h"
  18 #include "bpf_lru_list.h"
  19 #include "map_in_map.h"
  20
  21 #define HTAB_CREATE_FLAG_MASK                                           \
  22         (BPF_F_NO_PREALLOC | BPF_F_NO_COMMON_LRU | BPF_F_NUMA_NODE |    \
  23          BPF_F_RDONLY | BPF_F_WRONLY)
  24
  25 struct bucket {
  26         struct hlist_nulls_head head;
  27         raw_spinlock_t lock;
  28 };
  29
  30 struct bpf_htab {
  31         struct bpf_map map;
  32         struct bucket *buckets;
  33         void *elems;
  34         union {
  35                 struct pcpu_freelist freelist;
  36                 struct bpf_lru lru;
  37         };
  38         struct htab_elem *__percpu *extra_elems;
  39         atomic_t count; /* number of elements in this hashtable */
  40         u32 n_buckets;  /* number of hash buckets */
  41         u32 elem_size;  /* size of each element in bytes */
  42 };
  43
  44 /* each htab element is struct htab_elem + key + value */
  45 struct htab_elem {
  46         union {
  47                 struct hlist_nulls_node hash_node;
  48                 struct {
  49                         void *padding;
  50                         union {
  51                                 struct bpf_htab *htab;
  52                                 struct pcpu_freelist_node fnode;
  53                         };
  54                 };
  55         };
  56         union {
  57                 struct rcu_head rcu;
  58                 struct bpf_lru_node lru_node;
  59         };
  60         u32 hash;
  61         char key[0] __aligned(8);
  62 };
  63
  64 static bool htab_lru_map_delete_node(void *arg, struct bpf_lru_node *node);
  65
  66 static bool htab_is_lru(const struct bpf_htab *htab)
  67 {
  68         return htab->map.map_type == BPF_MAP_TYPE_LRU_HASH ||
  69                 htab->map.map_type == BPF_MAP_TYPE_LRU_PERCPU_HASH;
  70 }
  71
  72 static bool htab_is_percpu(const struct bpf_htab *htab)
  73 {
  74         return htab->map.map_type == BPF_MAP_TYPE_PERCPU_HASH ||
  75                 htab->map.map_type == BPF_MAP_TYPE_LRU_PERCPU_HASH;
  76 }
  77
  78 static bool htab_is_prealloc(const struct bpf_htab *htab)
  79 {
  80         return !(htab->map.map_flags & BPF_F_NO_PREALLOC);
  81 }
  82
  83 static inline void htab_elem_set_ptr(struct htab_elem *l, u32 key_size,
  84                                      void __percpu *pptr)
  85 {
  86         *(void __percpu **)(l->key + key_size) = pptr;
  87 }
  88
  89 static inline void __percpu *htab_elem_get_ptr(struct htab_elem *l, u32 key_size)
  90 {
  91         return *(void __percpu **)(l->key + key_size);
  92 }
  93
  94 static void *fd_htab_map_get_ptr(const struct bpf_map *map, struct htab_elem *l)
  95 {
  96         return *(void **)(l->key + roundup(map->key_size, 8));
  97 }
  98
  99 static struct htab_elem *get_htab_elem(struct bpf_htab *htab, int i)
 100 {
 101         return (struct htab_elem *) (htab->elems + i * htab->elem_size);
 102 }
 103
 104 static void htab_free_elems(struct bpf_htab *htab)
 105 {
 106         int i;
 107
 108         if (!htab_is_percpu(htab))
 109                 goto free_elems;
 110
 111         for (i = 0; i < htab->map.max_entries; i++) {
 112                 void __percpu *pptr;
 113
 114                 pptr = htab_elem_get_ptr(get_htab_elem(htab, i),
 115                                          htab->map.key_size);
 116                 free_percpu(pptr);
 117                 cond_resched();
 118         }
 119 free_elems:
 120         bpf_map_area_free(htab->elems);
 121 }
 122
 123 static struct htab_elem *prealloc_lru_pop(struct bpf_htab *htab, void *key,
 124                                           u32 hash)
 125 {
 126         struct bpf_lru_node *node = bpf_lru_pop_free(&htab->lru, hash);
 127         struct htab_elem *l;
 128
 129         if (node) {
 130                 l = container_of(node, struct htab_elem, lru_node);
 131                 memcpy(l->key, key, htab->map.key_size);
 132                 return l;
 133         }
 134
 135         return NULL;
 136 }
 137
 138 static int prealloc_init(struct bpf_htab *htab)
 139 {
 140         u32 num_entries = htab->map.max_entries;
 141         int err = -ENOMEM, i;
 142
 143         if (!htab_is_percpu(htab) && !htab_is_lru(htab))
 144                 num_entries += num_possible_cpus();
 145
 146         htab->elems = bpf_map_area_alloc(htab->elem_size * num_entries,
 147                                          htab->map.numa_node);
 148         if (!htab->elems)
 149                 return -ENOMEM;
 150
 151         if (!htab_is_percpu(htab))
 152                 goto skip_percpu_elems;
 153
 154         for (i = 0; i < num_entries; i++) {
 155                 u32 size = round_up(htab->map.value_size, 8);
 156                 void __percpu *pptr;
 157
 158                 pptr = __alloc_percpu_gfp(size, 8, GFP_USER | __GFP_NOWARN);
 159                 if (!pptr)
 160                         goto free_elems;
 161                 htab_elem_set_ptr(get_htab_elem(htab, i), htab->map.key_size,
 162                                   pptr);
 163                 cond_resched();
 164         }
 165
 166 skip_percpu_elems:
 167         if (htab_is_lru(htab))
 168                 err = bpf_lru_init(&htab->lru,
 169                                    htab->map.map_flags & BPF_F_NO_COMMON_LRU,
 170                                    offsetof(struct htab_elem, hash) -
 171                                    offsetof(struct htab_elem, lru_node),
 172                                    htab_lru_map_delete_node,
 173                                    htab);
 174         else
 175                 err = pcpu_freelist_init(&htab->freelist);
 176
 177         if (err)
 178                 goto free_elems;
 179
 180         if (htab_is_lru(htab))
 181                 bpf_lru_populate(&htab->lru, htab->elems,
 182                                  offsetof(struct htab_elem, lru_node),
 183                                  htab->elem_size, num_entries);
 184         else
 185                 pcpu_freelist_populate(&htab->freelist,
 186                                        htab->elems + offsetof(struct htab_elem, fnode),
 187                                        htab->elem_size, num_entries);
 188
 189         return 0;
 190
 191 free_elems:
 192         htab_free_elems(htab);
 193         return err;
 194 }
 195
 196 static void prealloc_destroy(struct bpf_htab *htab)
 197 {
 198         htab_free_elems(htab);
 199
 200         if (htab_is_lru(htab))
 201                 bpf_lru_destroy(&htab->lru);
 202         else
 203                 pcpu_freelist_destroy(&htab->freelist);
 204 }
 205
 206 static int alloc_extra_elems(struct bpf_htab *htab)
 207 {
 208         struct htab_elem *__percpu *pptr, *l_new;
 209         struct pcpu_freelist_node *l;
 210         int cpu;
 211
 212         pptr = __alloc_percpu_gfp(sizeof(struct htab_elem *), 8,
 213                                   GFP_USER | __GFP_NOWARN);
 214         if (!pptr)
 215                 return -ENOMEM;
 216
 217         for_each_possible_cpu(cpu) {
 218                 l = pcpu_freelist_pop(&htab->freelist);
 219                 /* pop will succeed, since prealloc_init()
 220                  * preallocated extra num_possible_cpus elements
 221                  */
 222                 l_new = container_of(l, struct htab_elem, fnode);
 223                 *per_cpu_ptr(pptr, cpu) = l_new;
 224         }
 225         htab->extra_elems = pptr;
 226         return 0;
 227 }
 228
 229 /* Called from syscall */
 230 static int htab_map_alloc_check(union bpf_attr *attr)
 231 {
 232         bool percpu = (attr->map_type == BPF_MAP_TYPE_PERCPU_HASH ||
 233                        attr->map_type == BPF_MAP_TYPE_LRU_PERCPU_HASH);
 234         bool lru = (attr->map_type == BPF_MAP_TYPE_LRU_HASH ||
 235                     attr->map_type == BPF_MAP_TYPE_LRU_PERCPU_HASH);
 236         /* percpu_lru means each cpu has its own LRU list.
 237          * it is different from BPF_MAP_TYPE_PERCPU_HASH where
 238          * the map's value itself is percpu.  percpu_lru has
 239          * nothing to do with the map's value.
 240          */
 241         bool percpu_lru = (attr->map_flags & BPF_F_NO_COMMON_LRU);
 242         bool prealloc = !(attr->map_flags & BPF_F_NO_PREALLOC);
 243         int numa_node = bpf_map_attr_numa_node(attr);
 244
 245         BUILD_BUG_ON(offsetof(struct htab_elem, htab) !=
 246                      offsetof(struct htab_elem, hash_node.pprev));
 247         BUILD_BUG_ON(offsetof(struct htab_elem, fnode.next) !=
 248                      offsetof(struct htab_elem, hash_node.pprev));
 249
 250         if (lru && !capable(CAP_SYS_ADMIN))
 251                 /* LRU implementation is much complicated than other
 252                  * maps.  Hence, limit to CAP_SYS_ADMIN for now.
 253                  */
 254                 return -EPERM;
 255
 256         if (attr->map_flags & ~HTAB_CREATE_FLAG_MASK)
 257                 /* reserved bits should not be used */
 258                 return -EINVAL;
 259
 260         if (!lru && percpu_lru)
 261                 return -EINVAL;
 262
 263         if (lru && !prealloc)
 264                 return -ENOTSUPP;
 265
 266         if (numa_node != NUMA_NO_NODE && (percpu || percpu_lru))
 267                 return -EINVAL;
 268
 269         /* check sanity of attributes.
 270          * value_size == 0 may be allowed in the future to use map as a set
 271          */
 272         if (attr->max_entries == 0 || attr->key_size == 0 ||
 273             attr->value_size == 0)
 274                 return -EINVAL;
 275
 276         if (attr->key_size > MAX_BPF_STACK)
 277                 /* eBPF programs initialize keys on stack, so they cannot be
 278                  * larger than max stack size
 279                  */
 280                 return -E2BIG;
 281
 282         if (attr->value_size >= KMALLOC_MAX_SIZE -
 283             MAX_BPF_STACK - sizeof(struct htab_elem))
 284                 /* if value_size is bigger, the user space won't be able to
 285                  * access the elements via bpf syscall. This check also makes
 286                  * sure that the elem_size doesn't overflow and it's
 287                  * kmalloc-able later in htab_map_update_elem()
 288                  */
 289                 return -E2BIG;
 290
 291         return 0;
 292 }
 293
 294 static struct bpf_map *htab_map_alloc(union bpf_attr *attr)
 295 {
 296         bool percpu = (attr->map_type == BPF_MAP_TYPE_PERCPU_HASH ||
 297                        attr->map_type == BPF_MAP_TYPE_LRU_PERCPU_HASH);
 298         bool lru = (attr->map_type == BPF_MAP_TYPE_LRU_HASH ||
 299                     attr->map_type == BPF_MAP_TYPE_LRU_PERCPU_HASH);
 300         /* percpu_lru means each cpu has its own LRU list.
 301          * it is different from BPF_MAP_TYPE_PERCPU_HASH where
 302          * the map's value itself is percpu.  percpu_lru has
 303          * nothing to do with the map's value.
 304          */
 305         bool percpu_lru = (attr->map_flags & BPF_F_NO_COMMON_LRU);
 306         bool prealloc = !(attr->map_flags & BPF_F_NO_PREALLOC);
 307         struct bpf_htab *htab;
 308         int err, i;
 309         u64 cost;
 310
 311         htab = kzalloc(sizeof(*htab), GFP_USER);
 312         if (!htab)
 313                 return ERR_PTR(-ENOMEM);
 314
 315         bpf_map_init_from_attr(&htab->map, attr);
 316
 317         if (percpu_lru) {
 318                 /* ensure each CPU's lru list has >=1 elements.
 319                  * since we are at it, make each lru list has the same
 320                  * number of elements.
 321                  */
 322                 htab->map.max_entries = roundup(attr->max_entries,
 323                                                 num_possible_cpus());
 324                 if (htab->map.max_entries < attr->max_entries)
 325                         htab->map.max_entries = rounddown(attr->max_entries,
 326                                                           num_possible_cpus());
 327         }
 328
 329         /* hash table size must be power of 2 */
 330         htab->n_buckets = roundup_pow_of_two(htab->map.max_entries);
 331
 332         htab->elem_size = sizeof(struct htab_elem) +
 333                           round_up(htab->map.key_size, 8);
 334         if (percpu)
 335                 htab->elem_size += sizeof(void *);
 336         else
 337                 htab->elem_size += round_up(htab->map.value_size, 8);
 338
 339         err = -E2BIG;
 340         /* prevent zero size kmalloc and check for u32 overflow */
 341         if (htab->n_buckets == 0 ||
 342             htab->n_buckets > U32_MAX / sizeof(struct bucket))
 343                 goto free_htab;
 344
 345         cost = (u64) htab->n_buckets * sizeof(struct bucket) +
 346                (u64) htab->elem_size * htab->map.max_entries;
 347
 348         if (percpu)
 349                 cost += (u64) round_up(htab->map.value_size, 8) *
 350                         num_possible_cpus() * htab->map.max_entries;
 351         else
 352                cost += (u64) htab->elem_size * num_possible_cpus();
 353
 354         if (cost >= U32_MAX - PAGE_SIZE)
 355                 /* make sure page count doesn't overflow */
 356                 goto free_htab;
 357
 358         htab->map.pages = round_up(cost, PAGE_SIZE) >> PAGE_SHIFT;
 359
 360         /* if map size is larger than memlock limit, reject it early */
 361         err = bpf_map_precharge_memlock(htab->map.pages);
 362         if (err)
 363                 goto free_htab;
 364
 365         err = -ENOMEM;
 366         htab->buckets = bpf_map_area_alloc(htab->n_buckets *
 367                                            sizeof(struct bucket),
 368                                            htab->map.numa_node);
 369         if (!htab->buckets)
 370                 goto free_htab;
 371
 372         for (i = 0; i < htab->n_buckets; i++) {
 373                 INIT_HLIST_NULLS_HEAD(&htab->buckets[i].head, i);
 374                 raw_spin_lock_init(&htab->buckets[i].lock);
 375         }
 376
 377         if (prealloc) {
 378                 err = prealloc_init(htab);
 379                 if (err)
 380                         goto free_buckets;
 381
 382                 if (!percpu && !lru) {
 383                         /* lru itself can remove the least used element, so
 384                          * there is no need for an extra elem during map_update.
 385                          */
 386                         err = alloc_extra_elems(htab);
 387                         if (err)
 388                                 goto free_prealloc;
 389                 }
 390         }
 391
 392         return &htab->map;
 393
 394 free_prealloc:
 395         prealloc_destroy(htab);
 396 free_buckets:
 397         bpf_map_area_free(htab->buckets);
 398 free_htab:
 399         kfree(htab);
 400         return ERR_PTR(err);
 401 }
 402
 403 static inline u32 htab_map_hash(const void *key, u32 key_len)
 404 {
 405         return jhash(key, key_len, 0);
 406 }
 407
 408 static inline struct bucket *__select_bucket(struct bpf_htab *htab, u32 hash)
 409 {
 410         return &htab->buckets[hash & (htab->n_buckets - 1)];
 411 }
 412
 413 static inline struct hlist_nulls_head *select_bucket(struct bpf_htab *htab, u32 hash)
 414 {
 415         return &__select_bucket(htab, hash)->head;
 416 }
 417
 418 /* this lookup function can only be called with bucket lock taken */
 419 static struct htab_elem *lookup_elem_raw(struct hlist_nulls_head *head, u32 hash,
 420                                          void *key, u32 key_size)
 421 {
 422         struct hlist_nulls_node *n;
 423         struct htab_elem *l;
 424
 425         hlist_nulls_for_each_entry_rcu(l, n, head, hash_node)
 426                 if (l->hash == hash && !memcmp(&l->key, key, key_size))
 427                         return l;
 428
 429         return NULL;
 430 }
 431
 432 /* can be called without bucket lock. it will repeat the loop in
 433  * the unlikely event when elements moved from one bucket into another
 434  * while link list is being walked
 435  */
 436 static struct htab_elem *lookup_nulls_elem_raw(struct hlist_nulls_head *head,
 437                                                u32 hash, void *key,
 438                                                u32 key_size, u32 n_buckets)
 439 {
 440         struct hlist_nulls_node *n;
 441         struct htab_elem *l;
 442
 443 again:
 444         hlist_nulls_for_each_entry_rcu(l, n, head, hash_node)
 445                 if (l->hash == hash && !memcmp(&l->key, key, key_size))
 446                         return l;
 447
 448         if (unlikely(get_nulls_value(n) != (hash & (n_buckets - 1))))
 449                 goto again;
 450
 451         return NULL;
 452 }
 453
 454 /* Called from syscall or from eBPF program directly, so
 455  * arguments have to match bpf_map_lookup_elem() exactly.
 456  * The return value is adjusted by BPF instructions
 457  * in htab_map_gen_lookup().
 458  */
 459 static void *__htab_map_lookup_elem(struct bpf_map *map, void *key)
 460 {
 461         struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
 462         struct hlist_nulls_head *head;
 463         struct htab_elem *l;
 464         u32 hash, key_size;
 465
 466         /* Must be called with rcu_read_lock. */
 467         WARN_ON_ONCE(!rcu_read_lock_held());
 468
 469         key_size = map->key_size;
 470
 471         hash = htab_map_hash(key, key_size);
 472
 473         head = select_bucket(htab, hash);
 474
 475         l = lookup_nulls_elem_raw(head, hash, key, key_size, htab->n_buckets);
 476
 477         return l;
 478 }
 479
 480 static void *htab_map_lookup_elem(struct bpf_map *map, void *key)
 481 {
 482         struct htab_elem *l = __htab_map_lookup_elem(map, key);
 483
 484         if (l)
 485                 return l->key + round_up(map->key_size, 8);
 486
 487         return NULL;
 488 }
 489
 490 /* inline bpf_map_lookup_elem() call.
 491  * Instead of:
 492  * bpf_prog
 493  *   bpf_map_lookup_elem
 494  *     map->ops->map_lookup_elem
 495  *       htab_map_lookup_elem
 496  *         __htab_map_lookup_elem
 497  * do:
 498  * bpf_prog
 499  *   __htab_map_lookup_elem
 500  */
 501 static u32 htab_map_gen_lookup(struct bpf_map *map, struct bpf_insn *insn_buf)
 502 {
 503         struct bpf_insn *insn = insn_buf;
 504         const int ret = BPF_REG_0;
 505
 506         *insn++ = BPF_EMIT_CALL((u64 (*)(u64, u64, u64, u64, u64))__htab_map_lookup_elem);
 507         *insn++ = BPF_JMP_IMM(BPF_JEQ, ret, 0, 1);
 508         *insn++ = BPF_ALU64_IMM(BPF_ADD, ret,
 509                                 offsetof(struct htab_elem, key) +
 510                                 round_up(map->key_size, 8));
 511         return insn - insn_buf;
 512 }
 513
 514 static void *htab_lru_map_lookup_elem(struct bpf_map *map, void *key)
 515 {
 516         struct htab_elem *l = __htab_map_lookup_elem(map, key);
 517
 518         if (l) {
 519                 bpf_lru_node_set_ref(&l->lru_node);
 520                 return l->key + round_up(map->key_size, 8);
 521         }
 522
 523         return NULL;
 524 }
 525
 526 static u32 htab_lru_map_gen_lookup(struct bpf_map *map,
 527                                    struct bpf_insn *insn_buf)
 528 {
 529         struct bpf_insn *insn = insn_buf;
 530         const int ret = BPF_REG_0;
 531         const int ref_reg = BPF_REG_1;
 532
 533         *insn++ = BPF_EMIT_CALL((u64 (*)(u64, u64, u64, u64, u64))__htab_map_lookup_elem);
 534         *insn++ = BPF_JMP_IMM(BPF_JEQ, ret, 0, 4);
 535         *insn++ = BPF_LDX_MEM(BPF_B, ref_reg, ret,
 536                               offsetof(struct htab_elem, lru_node) +
 537                               offsetof(struct bpf_lru_node, ref));
 538         *insn++ = BPF_JMP_IMM(BPF_JNE, ref_reg, 0, 1);
 539         *insn++ = BPF_ST_MEM(BPF_B, ret,
 540                              offsetof(struct htab_elem, lru_node) +
 541                              offsetof(struct bpf_lru_node, ref),
 542                              1);
 543         *insn++ = BPF_ALU64_IMM(BPF_ADD, ret,
 544                                 offsetof(struct htab_elem, key) +
 545                                 round_up(map->key_size, 8));
 546         return insn - insn_buf;
 547 }
 548
 549 /* It is called from the bpf_lru_list when the LRU needs to delete
 550  * older elements from the htab.
 551  */
 552 static bool htab_lru_map_delete_node(void *arg, struct bpf_lru_node *node)
 553 {
 554         struct bpf_htab *htab = (struct bpf_htab *)arg;
 555         struct htab_elem *l = NULL, *tgt_l;
 556         struct hlist_nulls_head *head;
 557         struct hlist_nulls_node *n;
 558         unsigned long flags;
 559         struct bucket *b;
 560
 561         tgt_l = container_of(node, struct htab_elem, lru_node);
 562         b = __select_bucket(htab, tgt_l->hash);
 563         head = &b->head;
 564
 565         raw_spin_lock_irqsave(&b->lock, flags);
 566
 567         hlist_nulls_for_each_entry_rcu(l, n, head, hash_node)
 568                 if (l == tgt_l) {
 569                         hlist_nulls_del_rcu(&l->hash_node);
 570                         break;
 571                 }
 572
 573         raw_spin_unlock_irqrestore(&b->lock, flags);
 574
 575         return l == tgt_l;
 576 }
 577
 578 /* Called from syscall */
 579 static int htab_map_get_next_key(struct bpf_map *map, void *key, void *next_key)
 580 {
 581         struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
 582         struct hlist_nulls_head *head;
 583         struct htab_elem *l, *next_l;
 584         u32 hash, key_size;
 585         int i = 0;
 586
 587         WARN_ON_ONCE(!rcu_read_lock_held());
 588
 589         key_size = map->key_size;
 590
 591         if (!key)
 592                 goto find_first_elem;
 593
 594         hash = htab_map_hash(key, key_size);
 595
 596         head = select_bucket(htab, hash);
 597
 598         /* lookup the key */
 599         l = lookup_nulls_elem_raw(head, hash, key, key_size, htab->n_buckets);
 600
 601         if (!l)
 602                 goto find_first_elem;
 603
 604         /* key was found, get next key in the same bucket */
 605         next_l = hlist_nulls_entry_safe(rcu_dereference_raw(hlist_nulls_next_rcu(&l->hash_node)),
 606                                   struct htab_elem, hash_node);
 607
 608         if (next_l) {
 609                 /* if next elem in this hash list is non-zero, just return it */
 610                 memcpy(next_key, next_l->key, key_size);
 611                 return 0;
 612         }
 613
 614         /* no more elements in this hash list, go to the next bucket */
 615         i = hash & (htab->n_buckets - 1);
 616         i++;
 617
 618 find_first_elem:
 619         /* iterate over buckets */
 620         for (; i < htab->n_buckets; i++) {
 621                 head = select_bucket(htab, i);
 622
 623                 /* pick first element in the bucket */
 624                 next_l = hlist_nulls_entry_safe(rcu_dereference_raw(hlist_nulls_first_rcu(head)),
 625                                           struct htab_elem, hash_node);
 626                 if (next_l) {
 627                         /* if it's not empty, just return it */
 628                         memcpy(next_key, next_l->key, key_size);
 629                         return 0;
 630                 }
 631         }
 632
 633         /* iterated over all buckets and all elements */
 634         return -ENOENT;
 635 }
 636
 637 static void htab_elem_free(struct bpf_htab *htab, struct htab_elem *l)
 638 {
 639         if (htab->map.map_type == BPF_MAP_TYPE_PERCPU_HASH)
 640                 free_percpu(htab_elem_get_ptr(l, htab->map.key_size));
 641         kfree(l);
 642 }
 643
 644 static void htab_elem_free_rcu(struct rcu_head *head)
 645 {
 646         struct htab_elem *l = container_of(head, struct htab_elem, rcu);
 647         struct bpf_htab *htab = l->htab;
 648
 649         /* must increment bpf_prog_active to avoid kprobe+bpf triggering while
 650          * we're calling kfree, otherwise deadlock is possible if kprobes
 651          * are placed somewhere inside of slub
 652          */
 653         preempt_disable();
 654         __this_cpu_inc(bpf_prog_active);
 655         htab_elem_free(htab, l);
 656         __this_cpu_dec(bpf_prog_active);
 657         preempt_enable();
 658 }
 659
 660 static void free_htab_elem(struct bpf_htab *htab, struct htab_elem *l)
 661 {
 662         struct bpf_map *map = &htab->map;
 663
 664         if (map->ops->map_fd_put_ptr) {
 665                 void *ptr = fd_htab_map_get_ptr(map, l);
 666
 667                 map->ops->map_fd_put_ptr(ptr);
 668         }
 669
 670         if (htab_is_prealloc(htab)) {
 671                 pcpu_freelist_push(&htab->freelist, &l->fnode);
 672         } else {
 673                 atomic_dec(&htab->count);
 674                 l->htab = htab;
 675                 call_rcu(&l->rcu, htab_elem_free_rcu);
 676         }
 677 }
 678
 679 static void pcpu_copy_value(struct bpf_htab *htab, void __percpu *pptr,
 680                             void *value, bool onallcpus)
 681 {
 682         if (!onallcpus) {
 683                 /* copy true value_size bytes */
 684                 memcpy(this_cpu_ptr(pptr), value, htab->map.value_size);
 685         } else {
 686                 u32 size = round_up(htab->map.value_size, 8);
 687                 int off = 0, cpu;
 688
 689                 for_each_possible_cpu(cpu) {
 690                         bpf_long_memcpy(per_cpu_ptr(pptr, cpu),
 691                                         value + off, size);
 692                         off += size;
 693                 }
 694         }
 695 }
 696
 697 static bool fd_htab_map_needs_adjust(const struct bpf_htab *htab)
 698 {
 699         return htab->map.map_type == BPF_MAP_TYPE_HASH_OF_MAPS &&
 700                BITS_PER_LONG == 64;
 701 }
 702
 703 static u32 htab_size_value(const struct bpf_htab *htab, bool percpu)
 704 {
 705         u32 size = htab->map.value_size;
 706
 707         if (percpu || fd_htab_map_needs_adjust(htab))
 708                 size = round_up(size, 8);
 709         return size;
 710 }
 711
 712 static struct htab_elem *alloc_htab_elem(struct bpf_htab *htab, void *key,
 713                                          void *value, u32 key_size, u32 hash,
 714                                          bool percpu, bool onallcpus,
 715                                          struct htab_elem *old_elem)
 716 {
 717         u32 size = htab_size_value(htab, percpu);
 718         bool prealloc = htab_is_prealloc(htab);
 719         struct htab_elem *l_new, **pl_new;
 720         void __percpu *pptr;
 721
 722         if (prealloc) {
 723                 if (old_elem) {
 724                         /* if we're updating the existing element,
 725                          * use per-cpu extra elems to avoid freelist_pop/push
 726                          */
 727                         pl_new = this_cpu_ptr(htab->extra_elems);
 728                         l_new = *pl_new;
 729                         *pl_new = old_elem;
 730                 } else {
 731                         struct pcpu_freelist_node *l;
 732
 733                         l = pcpu_freelist_pop(&htab->freelist);
 734                         if (!l)
 735                                 return ERR_PTR(-E2BIG);
 736                         l_new = container_of(l, struct htab_elem, fnode);
 737                 }
 738         } else {
 739                 if (atomic_inc_return(&htab->count) > htab->map.max_entries)
 740                         if (!old_elem) {
 741                                 /* when map is full and update() is replacing
 742                                  * old element, it's ok to allocate, since
 743                                  * old element will be freed immediately.
 744                                  * Otherwise return an error
 745                                  */
 746                                 atomic_dec(&htab->count);
 747                                 return ERR_PTR(-E2BIG);
 748                         }
 749                 l_new = kmalloc_node(htab->elem_size, GFP_ATOMIC | __GFP_NOWARN,
 750                                      htab->map.numa_node);
 751                 if (!l_new)
 752                         return ERR_PTR(-ENOMEM);
 753         }
 754
 755         memcpy(l_new->key, key, key_size);
 756         if (percpu) {
 757                 if (prealloc) {
 758                         pptr = htab_elem_get_ptr(l_new, key_size);
 759                 } else {
 760                         /* alloc_percpu zero-fills */
 761                         pptr = __alloc_percpu_gfp(size, 8,
 762                                                   GFP_ATOMIC | __GFP_NOWARN);
 763                         if (!pptr) {
 764                                 kfree(l_new);
 765                                 return ERR_PTR(-ENOMEM);
 766                         }
 767                 }
 768
 769                 pcpu_copy_value(htab, pptr, value, onallcpus);
 770
 771                 if (!prealloc)
 772                         htab_elem_set_ptr(l_new, key_size, pptr);
 773         } else {
 774                 memcpy(l_new->key + round_up(key_size, 8), value, size);
 775         }
 776
 777         l_new->hash = hash;
 778         return l_new;
 779 }
 780
 781 static int check_flags(struct bpf_htab *htab, struct htab_elem *l_old,
 782                        u64 map_flags)
 783 {
 784         if (l_old && map_flags == BPF_NOEXIST)
 785                 /* elem already exists */
 786                 return -EEXIST;
 787
 788         if (!l_old && map_flags == BPF_EXIST)
 789                 /* elem doesn't exist, cannot update it */
 790                 return -ENOENT;
 791
 792         return 0;
 793 }
 794
 795 /* Called from syscall or from eBPF program */
 796 static int htab_map_update_elem(struct bpf_map *map, void *key, void *value,
 797                                 u64 map_flags)
 798 {
 799         struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
 800         struct htab_elem *l_new = NULL, *l_old;
 801         struct hlist_nulls_head *head;
 802         unsigned long flags;
 803         struct bucket *b;
 804         u32 key_size, hash;
 805         int ret;
 806
 807         if (unlikely(map_flags > BPF_EXIST))
 808                 /* unknown flags */
 809                 return -EINVAL;
 810
 811         WARN_ON_ONCE(!rcu_read_lock_held());
 812
 813         key_size = map->key_size;
 814
 815         hash = htab_map_hash(key, key_size);
 816
 817         b = __select_bucket(htab, hash);
 818         head = &b->head;
 819
 820         /* bpf_map_update_elem() can be called in_irq() */
 821         raw_spin_lock_irqsave(&b->lock, flags);
 822
 823         l_old = lookup_elem_raw(head, hash, key, key_size);
 824
 825         ret = check_flags(htab, l_old, map_flags);
 826         if (ret)
 827                 goto err;
 828
 829         l_new = alloc_htab_elem(htab, key, value, key_size, hash, false, false,
 830                                 l_old);
 831         if (IS_ERR(l_new)) {
 832                 /* all pre-allocated elements are in use or memory exhausted */
 833                 ret = PTR_ERR(l_new);
 834                 goto err;
 835         }
 836
 837         /* add new element to the head of the list, so that
 838          * concurrent search will find it before old elem
 839          */
 840         hlist_nulls_add_head_rcu(&l_new->hash_node, head);
 841         if (l_old) {
 842                 hlist_nulls_del_rcu(&l_old->hash_node);
 843                 if (!htab_is_prealloc(htab))
 844                         free_htab_elem(htab, l_old);
 845         }
 846         ret = 0;
 847 err:
 848         raw_spin_unlock_irqrestore(&b->lock, flags);
 849         return ret;
 850 }
 851
 852 static int htab_lru_map_update_elem(struct bpf_map *map, void *key, void *value,
 853                                     u64 map_flags)
 854 {
 855         struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
 856         struct htab_elem *l_new, *l_old = NULL;
 857         struct hlist_nulls_head *head;
 858         unsigned long flags;
 859         struct bucket *b;
 860         u32 key_size, hash;
 861         int ret;
 862
 863         if (unlikely(map_flags > BPF_EXIST))
 864                 /* unknown flags */
 865                 return -EINVAL;
 866
 867         WARN_ON_ONCE(!rcu_read_lock_held());
 868
 869         key_size = map->key_size;
 870
 871         hash = htab_map_hash(key, key_size);
 872
 873         b = __select_bucket(htab, hash);
 874         head = &b->head;
 875
 876         /* For LRU, we need to alloc before taking bucket's
 877          * spinlock because getting free nodes from LRU may need
 878          * to remove older elements from htab and this removal
 879          * operation will need a bucket lock.
 880          */
 881         l_new = prealloc_lru_pop(htab, key, hash);
 882         if (!l_new)
 883                 return -ENOMEM;
 884         memcpy(l_new->key + round_up(map->key_size, 8), value, map->value_size);
 885
 886         /* bpf_map_update_elem() can be called in_irq() */
 887         raw_spin_lock_irqsave(&b->lock, flags);
 888
 889         l_old = lookup_elem_raw(head, hash, key, key_size);
 890
 891         ret = check_flags(htab, l_old, map_flags);
 892         if (ret)
 893                 goto err;
 894
 895         /* add new element to the head of the list, so that
 896          * concurrent search will find it before old elem
 897          */
 898         hlist_nulls_add_head_rcu(&l_new->hash_node, head);
 899         if (l_old) {
 900                 bpf_lru_node_set_ref(&l_new->lru_node);
 901                 hlist_nulls_del_rcu(&l_old->hash_node);
 902         }
 903         ret = 0;
 904
 905 err:
 906         raw_spin_unlock_irqrestore(&b->lock, flags);
 907
 908         if (ret)
 909                 bpf_lru_push_free(&htab->lru, &l_new->lru_node);
 910         else if (l_old)
 911                 bpf_lru_push_free(&htab->lru, &l_old->lru_node);
 912
 913         return ret;
 914 }
 915
 916 static int __htab_percpu_map_update_elem(struct bpf_map *map, void *key,
 917                                          void *value, u64 map_flags,
 918                                          bool onallcpus)
 919 {
 920         struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
 921         struct htab_elem *l_new = NULL, *l_old;
 922         struct hlist_nulls_head *head;
 923         unsigned long flags;
 924         struct bucket *b;
 925         u32 key_size, hash;
 926         int ret;
 927
 928         if (unlikely(map_flags > BPF_EXIST))
 929                 /* unknown flags */
 930                 return -EINVAL;
 931
 932         WARN_ON_ONCE(!rcu_read_lock_held());
 933
 934         key_size = map->key_size;
 935
 936         hash = htab_map_hash(key, key_size);
 937
 938         b = __select_bucket(htab, hash);
 939         head = &b->head;
 940
 941         /* bpf_map_update_elem() can be called in_irq() */
 942         raw_spin_lock_irqsave(&b->lock, flags);
 943
 944         l_old = lookup_elem_raw(head, hash, key, key_size);
 945
 946         ret = check_flags(htab, l_old, map_flags);
 947         if (ret)
 948                 goto err;
 949
 950         if (l_old) {
 951                 /* per-cpu hash map can update value in-place */
 952                 pcpu_copy_value(htab, htab_elem_get_ptr(l_old, key_size),
 953                                 value, onallcpus);
 954         } else {
 955                 l_new = alloc_htab_elem(htab, key, value, key_size,
 956                                         hash, true, onallcpus, NULL);
 957                 if (IS_ERR(l_new)) {
 958                         ret = PTR_ERR(l_new);
 959                         goto err;
 960                 }
 961                 hlist_nulls_add_head_rcu(&l_new->hash_node, head);
 962         }
 963         ret = 0;
 964 err:
 965         raw_spin_unlock_irqrestore(&b->lock, flags);
 966         return ret;
 967 }
 968
 969 static int __htab_lru_percpu_map_update_elem(struct bpf_map *map, void *key,
 970                                              void *value, u64 map_flags,
 971                                              bool onallcpus)
 972 {
 973         struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
 974         struct htab_elem *l_new = NULL, *l_old;
 975         struct hlist_nulls_head *head;
 976         unsigned long flags;
 977         struct bucket *b;
 978         u32 key_size, hash;
 979         int ret;
 980
 981         if (unlikely(map_flags > BPF_EXIST))
 982                 /* unknown flags */
 983                 return -EINVAL;
 984
 985         WARN_ON_ONCE(!rcu_read_lock_held());
 986
 987         key_size = map->key_size;
 988
 989         hash = htab_map_hash(key, key_size);
 990
 991         b = __select_bucket(htab, hash);
 992         head = &b->head;
 993
 994         /* For LRU, we need to alloc before taking bucket's
 995          * spinlock because LRU's elem alloc may need
 996          * to remove older elem from htab and this removal
 997          * operation will need a bucket lock.
 998          */
 999         if (map_flags != BPF_EXIST) {
1000                 l_new = prealloc_lru_pop(htab, key, hash);
1001                 if (!l_new)
1002                         return -ENOMEM;
1003         }
1004
1005         /* bpf_map_update_elem() can be called in_irq() */
1006         raw_spin_lock_irqsave(&b->lock, flags);
1007
1008         l_old = lookup_elem_raw(head, hash, key, key_size);
1009
1010         ret = check_flags(htab, l_old, map_flags);
1011         if (ret)
1012                 goto err;
1013
1014         if (l_old) {
1015                 bpf_lru_node_set_ref(&l_old->lru_node);
1016
1017                 /* per-cpu hash map can update value in-place */
1018                 pcpu_copy_value(htab, htab_elem_get_ptr(l_old, key_size),
1019                                 value, onallcpus);
1020         } else {
1021                 pcpu_copy_value(htab, htab_elem_get_ptr(l_new, key_size),
1022                                 value, onallcpus);
1023                 hlist_nulls_add_head_rcu(&l_new->hash_node, head);
1024                 l_new = NULL;
1025         }
1026         ret = 0;
1027 err:
1028         raw_spin_unlock_irqrestore(&b->lock, flags);
1029         if (l_new)
1030                 bpf_lru_push_free(&htab->lru, &l_new->lru_node);
1031         return ret;
1032 }
1033
1034 static int htab_percpu_map_update_elem(struct bpf_map *map, void *key,
1035                                        void *value, u64 map_flags)
1036 {
1037         return __htab_percpu_map_update_elem(map, key, value, map_flags, false);
1038 }
1039
1040 static int htab_lru_percpu_map_update_elem(struct bpf_map *map, void *key,
1041                                            void *value, u64 map_flags)
1042 {
1043         return __htab_lru_percpu_map_update_elem(map, key, value, map_flags,
1044                                                  false);
1045 }
1046
1047 /* Called from syscall or from eBPF program */
1048 static int htab_map_delete_elem(struct bpf_map *map, void *key)
1049 {
1050         struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
1051         struct hlist_nulls_head *head;
1052         struct bucket *b;
1053         struct htab_elem *l;
1054         unsigned long flags;
1055         u32 hash, key_size;
1056         int ret = -ENOENT;
1057
1058         WARN_ON_ONCE(!rcu_read_lock_held());
1059
1060         key_size = map->key_size;
1061
1062         hash = htab_map_hash(key, key_size);
1063         b = __select_bucket(htab, hash);
1064         head = &b->head;
1065
1066         raw_spin_lock_irqsave(&b->lock, flags);
1067
1068         l = lookup_elem_raw(head, hash, key, key_size);
1069
1070         if (l) {
1071                 hlist_nulls_del_rcu(&l->hash_node);
1072                 free_htab_elem(htab, l);
1073                 ret = 0;
1074         }
1075
1076         raw_spin_unlock_irqrestore(&b->lock, flags);
1077         return ret;
1078 }
1079
1080 static int htab_lru_map_delete_elem(struct bpf_map *map, void *key)
1081 {
1082         struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
1083         struct hlist_nulls_head *head;
1084         struct bucket *b;
1085         struct htab_elem *l;
1086         unsigned long flags;
1087         u32 hash, key_size;
1088         int ret = -ENOENT;
1089
1090         WARN_ON_ONCE(!rcu_read_lock_held());
1091
1092         key_size = map->key_size;
1093
1094         hash = htab_map_hash(key, key_size);
1095         b = __select_bucket(htab, hash);
1096         head = &b->head;
1097
1098         raw_spin_lock_irqsave(&b->lock, flags);
1099
1100         l = lookup_elem_raw(head, hash, key, key_size);
1101
1102         if (l) {
1103                 hlist_nulls_del_rcu(&l->hash_node);
1104                 ret = 0;
1105         }
1106
1107         raw_spin_unlock_irqrestore(&b->lock, flags);
1108         if (l)
1109                 bpf_lru_push_free(&htab->lru, &l->lru_node);
1110         return ret;
1111 }
1112
1113 static void delete_all_elements(struct bpf_htab *htab)
1114 {
1115         int i;
1116
1117         for (i = 0; i < htab->n_buckets; i++) {
1118                 struct hlist_nulls_head *head = select_bucket(htab, i);
1119                 struct hlist_nulls_node *n;
1120                 struct htab_elem *l;
1121
1122                 hlist_nulls_for_each_entry_safe(l, n, head, hash_node) {
1123                         hlist_nulls_del_rcu(&l->hash_node);
1124                         htab_elem_free(htab, l);
1125                 }
1126         }
1127 }
1128
1129 /* Called when map->refcnt goes to zero, either from workqueue or from syscall */
1130 static void htab_map_free(struct bpf_map *map)
1131 {
1132         struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
1133
1134         /* at this point bpf_prog->aux->refcnt == 0 and this map->refcnt == 0,
1135          * so the programs (can be more than one that used this map) were
1136          * disconnected from events. Wait for outstanding critical sections in
1137          * these programs to complete
1138          */
1139         synchronize_rcu();
1140
1141         /* some of free_htab_elem() callbacks for elements of this map may
1142          * not have executed. Wait for them.
1143          */
1144         rcu_barrier();
1145         if (!htab_is_prealloc(htab))
1146                 delete_all_elements(htab);
1147         else
1148                 prealloc_destroy(htab);
1149
1150         free_percpu(htab->extra_elems);
1151         bpf_map_area_free(htab->buckets);
1152         kfree(htab);
1153 }
1154
1155 const struct bpf_map_ops htab_map_ops = {
1156         .map_alloc_check = htab_map_alloc_check,
1157         .map_alloc = htab_map_alloc,
1158         .map_free = htab_map_free,
1159         .map_get_next_key = htab_map_get_next_key,
1160         .map_lookup_elem = htab_map_lookup_elem,
1161         .map_update_elem = htab_map_update_elem,
1162         .map_delete_elem = htab_map_delete_elem,
1163         .map_gen_lookup = htab_map_gen_lookup,
1164 };
1165
1166 const struct bpf_map_ops htab_lru_map_ops = {
1167         .map_alloc_check = htab_map_alloc_check,
1168         .map_alloc = htab_map_alloc,
1169         .map_free = htab_map_free,
1170         .map_get_next_key = htab_map_get_next_key,
1171         .map_lookup_elem = htab_lru_map_lookup_elem,
1172         .map_update_elem = htab_lru_map_update_elem,
1173         .map_delete_elem = htab_lru_map_delete_elem,
1174         .map_gen_lookup = htab_lru_map_gen_lookup,
1175 };
1176
1177 /* Called from eBPF program */
1178 static void *htab_percpu_map_lookup_elem(struct bpf_map *map, void *key)
1179 {
1180         struct htab_elem *l = __htab_map_lookup_elem(map, key);
1181
1182         if (l)
1183                 return this_cpu_ptr(htab_elem_get_ptr(l, map->key_size));
1184         else
1185                 return NULL;
1186 }
1187
1188 static void *htab_lru_percpu_map_lookup_elem(struct bpf_map *map, void *key)
1189 {
1190         struct htab_elem *l = __htab_map_lookup_elem(map, key);
1191
1192         if (l) {
1193                 bpf_lru_node_set_ref(&l->lru_node);
1194                 return this_cpu_ptr(htab_elem_get_ptr(l, map->key_size));
1195         }
1196
1197         return NULL;
1198 }
1199
1200 int bpf_percpu_hash_copy(struct bpf_map *map, void *key, void *value)
1201 {
1202         struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
1203         struct htab_elem *l;
1204         void __percpu *pptr;
1205         int ret = -ENOENT;
1206         int cpu, off = 0;
1207         u32 size;
1208
1209         /* per_cpu areas are zero-filled and bpf programs can only
1210          * access 'value_size' of them, so copying rounded areas
1211          * will not leak any kernel data
1212          */
1213         size = round_up(map->value_size, 8);
1214         rcu_read_lock();
1215         l = __htab_map_lookup_elem(map, key);
1216         if (!l)
1217                 goto out;
1218         if (htab_is_lru(htab))
1219                 bpf_lru_node_set_ref(&l->lru_node);
1220         pptr = htab_elem_get_ptr(l, map->key_size);
1221         for_each_possible_cpu(cpu) {
1222                 bpf_long_memcpy(value + off,
1223                                 per_cpu_ptr(pptr, cpu), size);
1224                 off += size;
1225         }
1226         ret = 0;
1227 out:
1228         rcu_read_unlock();
1229         return ret;
1230 }
1231
1232 int bpf_percpu_hash_update(struct bpf_map *map, void *key, void *value,
1233                            u64 map_flags)
1234 {
1235         struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
1236         int ret;
1237
1238         rcu_read_lock();
1239         if (htab_is_lru(htab))
1240                 ret = __htab_lru_percpu_map_update_elem(map, key, value,
1241                                                         map_flags, true);
1242         else
1243                 ret = __htab_percpu_map_update_elem(map, key, value, map_flags,
1244                                                     true);
1245         rcu_read_unlock();
1246
1247         return ret;
1248 }
1249
1250 const struct bpf_map_ops htab_percpu_map_ops = {
1251         .map_alloc_check = htab_map_alloc_check,
1252         .map_alloc = htab_map_alloc,
1253         .map_free = htab_map_free,
1254         .map_get_next_key = htab_map_get_next_key,
1255         .map_lookup_elem = htab_percpu_map_lookup_elem,
1256         .map_update_elem = htab_percpu_map_update_elem,
1257         .map_delete_elem = htab_map_delete_elem,
1258 };
1259
1260 const struct bpf_map_ops htab_lru_percpu_map_ops = {
1261         .map_alloc_check = htab_map_alloc_check,
1262         .map_alloc = htab_map_alloc,
1263         .map_free = htab_map_free,
1264         .map_get_next_key = htab_map_get_next_key,
1265         .map_lookup_elem = htab_lru_percpu_map_lookup_elem,
1266         .map_update_elem = htab_lru_percpu_map_update_elem,
1267         .map_delete_elem = htab_lru_map_delete_elem,
1268 };
1269
1270 static int fd_htab_map_alloc_check(union bpf_attr *attr)
1271 {
1272         if (attr->value_size != sizeof(u32))
1273                 return -EINVAL;
1274         return htab_map_alloc_check(attr);
1275 }
1276
1277 static void fd_htab_map_free(struct bpf_map *map)
1278 {
1279         struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
1280         struct hlist_nulls_node *n;
1281         struct hlist_nulls_head *head;
1282         struct htab_elem *l;
1283         int i;
1284
1285         for (i = 0; i < htab->n_buckets; i++) {
1286                 head = select_bucket(htab, i);
1287
1288                 hlist_nulls_for_each_entry_safe(l, n, head, hash_node) {
1289                         void *ptr = fd_htab_map_get_ptr(map, l);
1290
1291                         map->ops->map_fd_put_ptr(ptr);
1292                 }
1293         }
1294
1295         htab_map_free(map);
1296 }
1297
1298 /* only called from syscall */
1299 int bpf_fd_htab_map_lookup_elem(struct bpf_map *map, void *key, u32 *value)
1300 {
1301         void **ptr;
1302         int ret = 0;
1303
1304         if (!map->ops->map_fd_sys_lookup_elem)
1305                 return -ENOTSUPP;
1306
1307         rcu_read_lock();
1308         ptr = htab_map_lookup_elem(map, key);
1309         if (ptr)
1310                 *value = map->ops->map_fd_sys_lookup_elem(READ_ONCE(*ptr));
1311         else
1312                 ret = -ENOENT;
1313         rcu_read_unlock();
1314
1315         return ret;
1316 }
1317
1318 /* only called from syscall */
1319 int bpf_fd_htab_map_update_elem(struct bpf_map *map, struct file *map_file,
1320                                 void *key, void *value, u64 map_flags)
1321 {
1322         void *ptr;
1323         int ret;
1324         u32 ufd = *(u32 *)value;
1325
1326         ptr = map->ops->map_fd_get_ptr(map, map_file, ufd);
1327         if (IS_ERR(ptr))
1328                 return PTR_ERR(ptr);
1329
1330         ret = htab_map_update_elem(map, key, &ptr, map_flags);
1331         if (ret)
1332                 map->ops->map_fd_put_ptr(ptr);
1333
1334         return ret;
1335 }
1336
1337 static struct bpf_map *htab_of_map_alloc(union bpf_attr *attr)
1338 {
1339         struct bpf_map *map, *inner_map_meta;
1340
1341         inner_map_meta = bpf_map_meta_alloc(attr->inner_map_fd);
1342         if (IS_ERR(inner_map_meta))
1343                 return inner_map_meta;
1344
1345         map = htab_map_alloc(attr);
1346         if (IS_ERR(map)) {
1347                 bpf_map_meta_free(inner_map_meta);
1348                 return map;
1349         }
1350
1351         map->inner_map_meta = inner_map_meta;
1352
1353         return map;
1354 }
1355
1356 static void *htab_of_map_lookup_elem(struct bpf_map *map, void *key)
1357 {
1358         struct bpf_map **inner_map  = htab_map_lookup_elem(map, key);
1359
1360         if (!inner_map)
1361                 return NULL;
1362
1363         return READ_ONCE(*inner_map);
1364 }
1365
1366 static u32 htab_of_map_gen_lookup(struct bpf_map *map,
1367                                   struct bpf_insn *insn_buf)
1368 {
1369         struct bpf_insn *insn = insn_buf;
1370         const int ret = BPF_REG_0;
1371
1372         *insn++ = BPF_EMIT_CALL((u64 (*)(u64, u64, u64, u64, u64))__htab_map_lookup_elem);
1373         *insn++ = BPF_JMP_IMM(BPF_JEQ, ret, 0, 2);
1374         *insn++ = BPF_ALU64_IMM(BPF_ADD, ret,
1375                                 offsetof(struct htab_elem, key) +
1376                                 round_up(map->key_size, 8));
1377         *insn++ = BPF_LDX_MEM(BPF_DW, ret, ret, 0);
1378
1379         return insn - insn_buf;
1380 }
1381
1382 static void htab_of_map_free(struct bpf_map *map)
1383 {
1384         bpf_map_meta_free(map->inner_map_meta);
1385         fd_htab_map_free(map);
1386 }
1387
1388 const struct bpf_map_ops htab_of_maps_map_ops = {
1389         .map_alloc_check = fd_htab_map_alloc_check,
1390         .map_alloc = htab_of_map_alloc,
1391         .map_free = htab_of_map_free,
1392         .map_get_next_key = htab_map_get_next_key,
1393         .map_lookup_elem = htab_of_map_lookup_elem,
1394         .map_delete_elem = htab_map_delete_elem,
1395         .map_fd_get_ptr = bpf_map_fd_get_ptr,
1396         .map_fd_put_ptr = bpf_map_fd_put_ptr,
1397         .map_fd_sys_lookup_elem = bpf_map_fd_sys_lookup_elem,
1398         .map_gen_lookup = htab_of_map_gen_lookup,
1399 };