kernel/bpf/bpf_local_storage.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /* Copyright (c) 2019 Facebook  */
   3 #include <linux/rculist.h>
   4 #include <linux/list.h>
   5 #include <linux/hash.h>
   6 #include <linux/types.h>
   7 #include <linux/spinlock.h>
   8 #include <linux/bpf.h>
   9 #include <linux/btf_ids.h>
  10 #include <linux/bpf_local_storage.h>
  11 #include <net/sock.h>
  12 #include <uapi/linux/sock_diag.h>
  13 #include <uapi/linux/btf.h>
  14 #include <linux/rcupdate.h>
  15 #include <linux/rcupdate_trace.h>
  16 #include <linux/rcupdate_wait.h>
  17
  18 #define BPF_LOCAL_STORAGE_CREATE_FLAG_MASK (BPF_F_NO_PREALLOC | BPF_F_CLONE)
  19
  20 static struct bpf_local_storage_map_bucket *
  21 select_bucket(struct bpf_local_storage_map *smap,
  22               struct bpf_local_storage_elem *selem)
  23 {
  24         return &smap->buckets[hash_ptr(selem, smap->bucket_log)];
  25 }
  26
  27 static int mem_charge(struct bpf_local_storage_map *smap, void *owner, u32 size)
  28 {
  29         struct bpf_map *map = &smap->map;
  30
  31         if (!map->ops->map_local_storage_charge)
  32                 return 0;
  33
  34         return map->ops->map_local_storage_charge(smap, owner, size);
  35 }
  36
  37 static void mem_uncharge(struct bpf_local_storage_map *smap, void *owner,
  38                          u32 size)
  39 {
  40         struct bpf_map *map = &smap->map;
  41
  42         if (map->ops->map_local_storage_uncharge)
  43                 map->ops->map_local_storage_uncharge(smap, owner, size);
  44 }
  45
  46 static struct bpf_local_storage __rcu **
  47 owner_storage(struct bpf_local_storage_map *smap, void *owner)
  48 {
  49         struct bpf_map *map = &smap->map;
  50
  51         return map->ops->map_owner_storage_ptr(owner);
  52 }
  53
  54 static bool selem_linked_to_storage(const struct bpf_local_storage_elem *selem)
  55 {
  56         return !hlist_unhashed(&selem->snode);
  57 }
  58
  59 static bool selem_linked_to_map(const struct bpf_local_storage_elem *selem)
  60 {
  61         return !hlist_unhashed(&selem->map_node);
  62 }
  63
  64 struct bpf_local_storage_elem *
  65 bpf_selem_alloc(struct bpf_local_storage_map *smap, void *owner,
  66                 void *value, bool charge_mem)
  67 {
  68         struct bpf_local_storage_elem *selem;
  69
  70         if (charge_mem && mem_charge(smap, owner, smap->elem_size))
  71                 return NULL;
  72
  73         selem = bpf_map_kzalloc(&smap->map, smap->elem_size,
  74                                 GFP_ATOMIC | __GFP_NOWARN);
  75         if (selem) {
  76                 if (value)
  77                         memcpy(SDATA(selem)->data, value, smap->map.value_size);
  78                 return selem;
  79         }
  80
  81         if (charge_mem)
  82                 mem_uncharge(smap, owner, smap->elem_size);
  83
  84         return NULL;
  85 }
  86
  87 void bpf_local_storage_free_rcu(struct rcu_head *rcu)
  88 {
  89         struct bpf_local_storage *local_storage;
  90
  91         local_storage = container_of(rcu, struct bpf_local_storage, rcu);
  92         kfree_rcu(local_storage, rcu);
  93 }
  94
  95 static void bpf_selem_free_rcu(struct rcu_head *rcu)
  96 {
  97         struct bpf_local_storage_elem *selem;
  98
  99         selem = container_of(rcu, struct bpf_local_storage_elem, rcu);
 100         kfree_rcu(selem, rcu);
 101 }
 102
 103 /* local_storage->lock must be held and selem->local_storage == local_storage.
 104  * The caller must ensure selem->smap is still valid to be
 105  * dereferenced for its smap->elem_size and smap->cache_idx.
 106  */
 107 bool bpf_selem_unlink_storage_nolock(struct bpf_local_storage *local_storage,
 108                                      struct bpf_local_storage_elem *selem,
 109                                      bool uncharge_mem)
 110 {
 111         struct bpf_local_storage_map *smap;
 112         bool free_local_storage;
 113         void *owner;
 114
 115         smap = rcu_dereference_check(SDATA(selem)->smap, bpf_rcu_lock_held());
 116         owner = local_storage->owner;
 117
 118         /* All uncharging on the owner must be done first.
 119          * The owner may be freed once the last selem is unlinked
 120          * from local_storage.
 121          */
 122         if (uncharge_mem)
 123                 mem_uncharge(smap, owner, smap->elem_size);
 124
 125         free_local_storage = hlist_is_singular_node(&selem->snode,
 126                                                     &local_storage->list);
 127         if (free_local_storage) {
 128                 mem_uncharge(smap, owner, sizeof(struct bpf_local_storage));
 129                 local_storage->owner = NULL;
 130
 131                 /* After this RCU_INIT, owner may be freed and cannot be used */
 132                 RCU_INIT_POINTER(*owner_storage(smap, owner), NULL);
 133
 134                 /* local_storage is not freed now.  local_storage->lock is
 135                  * still held and raw_spin_unlock_bh(&local_storage->lock)
 136                  * will be done by the caller.
 137                  *
 138                  * Although the unlock will be done under
 139                  * rcu_read_lock(),  it is more intutivie to
 140                  * read if the freeing of the storage is done
 141                  * after the raw_spin_unlock_bh(&local_storage->lock).
 142                  *
 143                  * Hence, a "bool free_local_storage" is returned
 144                  * to the caller which then calls then frees the storage after
 145                  * all the RCU grace periods have expired.
 146                  */
 147         }
 148         hlist_del_init_rcu(&selem->snode);
 149         if (rcu_access_pointer(local_storage->cache[smap->cache_idx]) ==
 150             SDATA(selem))
 151                 RCU_INIT_POINTER(local_storage->cache[smap->cache_idx], NULL);
 152
 153         call_rcu_tasks_trace(&selem->rcu, bpf_selem_free_rcu);
 154         return free_local_storage;
 155 }
 156
 157 static void __bpf_selem_unlink_storage(struct bpf_local_storage_elem *selem)
 158 {
 159         struct bpf_local_storage *local_storage;
 160         bool free_local_storage = false;
 161         unsigned long flags;
 162
 163         if (unlikely(!selem_linked_to_storage(selem)))
 164                 /* selem has already been unlinked from sk */
 165                 return;
 166
 167         local_storage = rcu_dereference_check(selem->local_storage,
 168                                               bpf_rcu_lock_held());
 169         raw_spin_lock_irqsave(&local_storage->lock, flags);
 170         if (likely(selem_linked_to_storage(selem)))
 171                 free_local_storage = bpf_selem_unlink_storage_nolock(
 172                         local_storage, selem, true);
 173         raw_spin_unlock_irqrestore(&local_storage->lock, flags);
 174
 175         if (free_local_storage)
 176                 call_rcu_tasks_trace(&local_storage->rcu,
 177                                      bpf_local_storage_free_rcu);
 178 }
 179
 180 void bpf_selem_link_storage_nolock(struct bpf_local_storage *local_storage,
 181                                    struct bpf_local_storage_elem *selem)
 182 {
 183         RCU_INIT_POINTER(selem->local_storage, local_storage);
 184         hlist_add_head_rcu(&selem->snode, &local_storage->list);
 185 }
 186
 187 void bpf_selem_unlink_map(struct bpf_local_storage_elem *selem)
 188 {
 189         struct bpf_local_storage_map *smap;
 190         struct bpf_local_storage_map_bucket *b;
 191         unsigned long flags;
 192
 193         if (unlikely(!selem_linked_to_map(selem)))
 194                 /* selem has already be unlinked from smap */
 195                 return;
 196
 197         smap = rcu_dereference_check(SDATA(selem)->smap, bpf_rcu_lock_held());
 198         b = select_bucket(smap, selem);
 199         raw_spin_lock_irqsave(&b->lock, flags);
 200         if (likely(selem_linked_to_map(selem)))
 201                 hlist_del_init_rcu(&selem->map_node);
 202         raw_spin_unlock_irqrestore(&b->lock, flags);
 203 }
 204
 205 void bpf_selem_link_map(struct bpf_local_storage_map *smap,
 206                         struct bpf_local_storage_elem *selem)
 207 {
 208         struct bpf_local_storage_map_bucket *b = select_bucket(smap, selem);
 209         unsigned long flags;
 210
 211         raw_spin_lock_irqsave(&b->lock, flags);
 212         RCU_INIT_POINTER(SDATA(selem)->smap, smap);
 213         hlist_add_head_rcu(&selem->map_node, &b->list);
 214         raw_spin_unlock_irqrestore(&b->lock, flags);
 215 }
 216
 217 void bpf_selem_unlink(struct bpf_local_storage_elem *selem)
 218 {
 219         /* Always unlink from map before unlinking from local_storage
 220          * because selem will be freed after successfully unlinked from
 221          * the local_storage.
 222          */
 223         bpf_selem_unlink_map(selem);
 224         __bpf_selem_unlink_storage(selem);
 225 }
 226
 227 struct bpf_local_storage_data *
 228 bpf_local_storage_lookup(struct bpf_local_storage *local_storage,
 229                          struct bpf_local_storage_map *smap,
 230                          bool cacheit_lockit)
 231 {
 232         struct bpf_local_storage_data *sdata;
 233         struct bpf_local_storage_elem *selem;
 234
 235         /* Fast path (cache hit) */
 236         sdata = rcu_dereference_check(local_storage->cache[smap->cache_idx],
 237                                       bpf_rcu_lock_held());
 238         if (sdata && rcu_access_pointer(sdata->smap) == smap)
 239                 return sdata;
 240
 241         /* Slow path (cache miss) */
 242         hlist_for_each_entry_rcu(selem, &local_storage->list, snode,
 243                                   rcu_read_lock_trace_held())
 244                 if (rcu_access_pointer(SDATA(selem)->smap) == smap)
 245                         break;
 246
 247         if (!selem)
 248                 return NULL;
 249
 250         sdata = SDATA(selem);
 251         if (cacheit_lockit) {
 252                 unsigned long flags;
 253
 254                 /* spinlock is needed to avoid racing with the
 255                  * parallel delete.  Otherwise, publishing an already
 256                  * deleted sdata to the cache will become a use-after-free
 257                  * problem in the next bpf_local_storage_lookup().
 258                  */
 259                 raw_spin_lock_irqsave(&local_storage->lock, flags);
 260                 if (selem_linked_to_storage(selem))
 261                         rcu_assign_pointer(local_storage->cache[smap->cache_idx],
 262                                            sdata);
 263                 raw_spin_unlock_irqrestore(&local_storage->lock, flags);
 264         }
 265
 266         return sdata;
 267 }
 268
 269 static int check_flags(const struct bpf_local_storage_data *old_sdata,
 270                        u64 map_flags)
 271 {
 272         if (old_sdata && (map_flags & ~BPF_F_LOCK) == BPF_NOEXIST)
 273                 /* elem already exists */
 274                 return -EEXIST;
 275
 276         if (!old_sdata && (map_flags & ~BPF_F_LOCK) == BPF_EXIST)
 277                 /* elem doesn't exist, cannot update it */
 278                 return -ENOENT;
 279
 280         return 0;
 281 }
 282
 283 int bpf_local_storage_alloc(void *owner,
 284                             struct bpf_local_storage_map *smap,
 285                             struct bpf_local_storage_elem *first_selem)
 286 {
 287         struct bpf_local_storage *prev_storage, *storage;
 288         struct bpf_local_storage **owner_storage_ptr;
 289         int err;
 290
 291         err = mem_charge(smap, owner, sizeof(*storage));
 292         if (err)
 293                 return err;
 294
 295         storage = bpf_map_kzalloc(&smap->map, sizeof(*storage),
 296                                   GFP_ATOMIC | __GFP_NOWARN);
 297         if (!storage) {
 298                 err = -ENOMEM;
 299                 goto uncharge;
 300         }
 301
 302         INIT_HLIST_HEAD(&storage->list);
 303         raw_spin_lock_init(&storage->lock);
 304         storage->owner = owner;
 305
 306         bpf_selem_link_storage_nolock(storage, first_selem);
 307         bpf_selem_link_map(smap, first_selem);
 308
 309         owner_storage_ptr =
 310                 (struct bpf_local_storage **)owner_storage(smap, owner);
 311         /* Publish storage to the owner.
 312          * Instead of using any lock of the kernel object (i.e. owner),
 313          * cmpxchg will work with any kernel object regardless what
 314          * the running context is, bh, irq...etc.
 315          *
 316          * From now on, the owner->storage pointer (e.g. sk->sk_bpf_storage)
 317          * is protected by the storage->lock.  Hence, when freeing
 318          * the owner->storage, the storage->lock must be held before
 319          * setting owner->storage ptr to NULL.
 320          */
 321         prev_storage = cmpxchg(owner_storage_ptr, NULL, storage);
 322         if (unlikely(prev_storage)) {
 323                 bpf_selem_unlink_map(first_selem);
 324                 err = -EAGAIN;
 325                 goto uncharge;
 326
 327                 /* Note that even first_selem was linked to smap's
 328                  * bucket->list, first_selem can be freed immediately
 329                  * (instead of kfree_rcu) because
 330                  * bpf_local_storage_map_free() does a
 331                  * synchronize_rcu_mult (waiting for both sleepable and
 332                  * normal programs) before walking the bucket->list.
 333                  * Hence, no one is accessing selem from the
 334                  * bucket->list under rcu_read_lock().
 335                  */
 336         }
 337
 338         return 0;
 339
 340 uncharge:
 341         kfree(storage);
 342         mem_uncharge(smap, owner, sizeof(*storage));
 343         return err;
 344 }
 345
 346 /* sk cannot be going away because it is linking new elem
 347  * to sk->sk_bpf_storage. (i.e. sk->sk_refcnt cannot be 0).
 348  * Otherwise, it will become a leak (and other memory issues
 349  * during map destruction).
 350  */
 351 struct bpf_local_storage_data *
 352 bpf_local_storage_update(void *owner, struct bpf_local_storage_map *smap,
 353                          void *value, u64 map_flags)
 354 {
 355         struct bpf_local_storage_data *old_sdata = NULL;
 356         struct bpf_local_storage_elem *selem;
 357         struct bpf_local_storage *local_storage;
 358         unsigned long flags;
 359         int err;
 360
 361         /* BPF_EXIST and BPF_NOEXIST cannot be both set */
 362         if (unlikely((map_flags & ~BPF_F_LOCK) > BPF_EXIST) ||
 363             /* BPF_F_LOCK can only be used in a value with spin_lock */
 364             unlikely((map_flags & BPF_F_LOCK) &&
 365                      !map_value_has_spin_lock(&smap->map)))
 366                 return ERR_PTR(-EINVAL);
 367
 368         local_storage = rcu_dereference_check(*owner_storage(smap, owner),
 369                                               bpf_rcu_lock_held());
 370         if (!local_storage || hlist_empty(&local_storage->list)) {
 371                 /* Very first elem for the owner */
 372                 err = check_flags(NULL, map_flags);
 373                 if (err)
 374                         return ERR_PTR(err);
 375
 376                 selem = bpf_selem_alloc(smap, owner, value, true);
 377                 if (!selem)
 378                         return ERR_PTR(-ENOMEM);
 379
 380                 err = bpf_local_storage_alloc(owner, smap, selem);
 381                 if (err) {
 382                         kfree(selem);
 383                         mem_uncharge(smap, owner, smap->elem_size);
 384                         return ERR_PTR(err);
 385                 }
 386
 387                 return SDATA(selem);
 388         }
 389
 390         if ((map_flags & BPF_F_LOCK) && !(map_flags & BPF_NOEXIST)) {
 391                 /* Hoping to find an old_sdata to do inline update
 392                  * such that it can avoid taking the local_storage->lock
 393                  * and changing the lists.
 394                  */
 395                 old_sdata =
 396                         bpf_local_storage_lookup(local_storage, smap, false);
 397                 err = check_flags(old_sdata, map_flags);
 398                 if (err)
 399                         return ERR_PTR(err);
 400                 if (old_sdata && selem_linked_to_storage(SELEM(old_sdata))) {
 401                         copy_map_value_locked(&smap->map, old_sdata->data,
 402                                               value, false);
 403                         return old_sdata;
 404                 }
 405         }
 406
 407         raw_spin_lock_irqsave(&local_storage->lock, flags);
 408
 409         /* Recheck local_storage->list under local_storage->lock */
 410         if (unlikely(hlist_empty(&local_storage->list))) {
 411                 /* A parallel del is happening and local_storage is going
 412                  * away.  It has just been checked before, so very
 413                  * unlikely.  Return instead of retry to keep things
 414                  * simple.
 415                  */
 416                 err = -EAGAIN;
 417                 goto unlock_err;
 418         }
 419
 420         old_sdata = bpf_local_storage_lookup(local_storage, smap, false);
 421         err = check_flags(old_sdata, map_flags);
 422         if (err)
 423                 goto unlock_err;
 424
 425         if (old_sdata && (map_flags & BPF_F_LOCK)) {
 426                 copy_map_value_locked(&smap->map, old_sdata->data, value,
 427                                       false);
 428                 selem = SELEM(old_sdata);
 429                 goto unlock;
 430         }
 431
 432         /* local_storage->lock is held.  Hence, we are sure
 433          * we can unlink and uncharge the old_sdata successfully
 434          * later.  Hence, instead of charging the new selem now
 435          * and then uncharge the old selem later (which may cause
 436          * a potential but unnecessary charge failure),  avoid taking
 437          * a charge at all here (the "!old_sdata" check) and the
 438          * old_sdata will not be uncharged later during
 439          * bpf_selem_unlink_storage_nolock().
 440          */
 441         selem = bpf_selem_alloc(smap, owner, value, !old_sdata);
 442         if (!selem) {
 443                 err = -ENOMEM;
 444                 goto unlock_err;
 445         }
 446
 447         /* First, link the new selem to the map */
 448         bpf_selem_link_map(smap, selem);
 449
 450         /* Second, link (and publish) the new selem to local_storage */
 451         bpf_selem_link_storage_nolock(local_storage, selem);
 452
 453         /* Third, remove old selem, SELEM(old_sdata) */
 454         if (old_sdata) {
 455                 bpf_selem_unlink_map(SELEM(old_sdata));
 456                 bpf_selem_unlink_storage_nolock(local_storage, SELEM(old_sdata),
 457                                                 false);
 458         }
 459
 460 unlock:
 461         raw_spin_unlock_irqrestore(&local_storage->lock, flags);
 462         return SDATA(selem);
 463
 464 unlock_err:
 465         raw_spin_unlock_irqrestore(&local_storage->lock, flags);
 466         return ERR_PTR(err);
 467 }
 468
 469 u16 bpf_local_storage_cache_idx_get(struct bpf_local_storage_cache *cache)
 470 {
 471         u64 min_usage = U64_MAX;
 472         u16 i, res = 0;
 473
 474         spin_lock(&cache->idx_lock);
 475
 476         for (i = 0; i < BPF_LOCAL_STORAGE_CACHE_SIZE; i++) {
 477                 if (cache->idx_usage_counts[i] < min_usage) {
 478                         min_usage = cache->idx_usage_counts[i];
 479                         res = i;
 480
 481                         /* Found a free cache_idx */
 482                         if (!min_usage)
 483                                 break;
 484                 }
 485         }
 486         cache->idx_usage_counts[res]++;
 487
 488         spin_unlock(&cache->idx_lock);
 489
 490         return res;
 491 }
 492
 493 void bpf_local_storage_cache_idx_free(struct bpf_local_storage_cache *cache,
 494                                       u16 idx)
 495 {
 496         spin_lock(&cache->idx_lock);
 497         cache->idx_usage_counts[idx]--;
 498         spin_unlock(&cache->idx_lock);
 499 }
 500
 501 void bpf_local_storage_map_free(struct bpf_local_storage_map *smap,
 502                                 int __percpu *busy_counter)
 503 {
 504         struct bpf_local_storage_elem *selem;
 505         struct bpf_local_storage_map_bucket *b;
 506         unsigned int i;
 507
 508         /* Note that this map might be concurrently cloned from
 509          * bpf_sk_storage_clone. Wait for any existing bpf_sk_storage_clone
 510          * RCU read section to finish before proceeding. New RCU
 511          * read sections should be prevented via bpf_map_inc_not_zero.
 512          */
 513         synchronize_rcu();
 514
 515         /* bpf prog and the userspace can no longer access this map
 516          * now.  No new selem (of this map) can be added
 517          * to the owner->storage or to the map bucket's list.
 518          *
 519          * The elem of this map can be cleaned up here
 520          * or when the storage is freed e.g.
 521          * by bpf_sk_storage_free() during __sk_destruct().
 522          */
 523         for (i = 0; i < (1U << smap->bucket_log); i++) {
 524                 b = &smap->buckets[i];
 525
 526                 rcu_read_lock();
 527                 /* No one is adding to b->list now */
 528                 while ((selem = hlist_entry_safe(
 529                                 rcu_dereference_raw(hlist_first_rcu(&b->list)),
 530                                 struct bpf_local_storage_elem, map_node))) {
 531                         if (busy_counter) {
 532                                 migrate_disable();
 533                                 __this_cpu_inc(*busy_counter);
 534                         }
 535                         bpf_selem_unlink(selem);
 536                         if (busy_counter) {
 537                                 __this_cpu_dec(*busy_counter);
 538                                 migrate_enable();
 539                         }
 540                         cond_resched_rcu();
 541                 }
 542                 rcu_read_unlock();
 543         }
 544
 545         /* While freeing the storage we may still need to access the map.
 546          *
 547          * e.g. when bpf_sk_storage_free() has unlinked selem from the map
 548          * which then made the above while((selem = ...)) loop
 549          * exit immediately.
 550          *
 551          * However, while freeing the storage one still needs to access the
 552          * smap->elem_size to do the uncharging in
 553          * bpf_selem_unlink_storage_nolock().
 554          *
 555          * Hence, wait another rcu grace period for the storage to be freed.
 556          */
 557         synchronize_rcu();
 558
 559         kvfree(smap->buckets);
 560         kfree(smap);
 561 }
 562
 563 int bpf_local_storage_map_alloc_check(union bpf_attr *attr)
 564 {
 565         if (attr->map_flags & ~BPF_LOCAL_STORAGE_CREATE_FLAG_MASK ||
 566             !(attr->map_flags & BPF_F_NO_PREALLOC) ||
 567             attr->max_entries ||
 568             attr->key_size != sizeof(int) || !attr->value_size ||
 569             /* Enforce BTF for userspace sk dumping */
 570             !attr->btf_key_type_id || !attr->btf_value_type_id)
 571                 return -EINVAL;
 572
 573         if (!bpf_capable())
 574                 return -EPERM;
 575
 576         if (attr->value_size > BPF_LOCAL_STORAGE_MAX_VALUE_SIZE)
 577                 return -E2BIG;
 578
 579         return 0;
 580 }
 581
 582 struct bpf_local_storage_map *bpf_local_storage_map_alloc(union bpf_attr *attr)
 583 {
 584         struct bpf_local_storage_map *smap;
 585         unsigned int i;
 586         u32 nbuckets;
 587
 588         smap = kzalloc(sizeof(*smap), GFP_USER | __GFP_NOWARN | __GFP_ACCOUNT);
 589         if (!smap)
 590                 return ERR_PTR(-ENOMEM);
 591         bpf_map_init_from_attr(&smap->map, attr);
 592
 593         nbuckets = roundup_pow_of_two(num_possible_cpus());
 594         /* Use at least 2 buckets, select_bucket() is undefined behavior with 1 bucket */
 595         nbuckets = max_t(u32, 2, nbuckets);
 596         smap->bucket_log = ilog2(nbuckets);
 597
 598         smap->buckets = kvcalloc(sizeof(*smap->buckets), nbuckets,
 599                                  GFP_USER | __GFP_NOWARN | __GFP_ACCOUNT);
 600         if (!smap->buckets) {
 601                 kfree(smap);
 602                 return ERR_PTR(-ENOMEM);
 603         }
 604
 605         for (i = 0; i < nbuckets; i++) {
 606                 INIT_HLIST_HEAD(&smap->buckets[i].list);
 607                 raw_spin_lock_init(&smap->buckets[i].lock);
 608         }
 609
 610         smap->elem_size =
 611                 sizeof(struct bpf_local_storage_elem) + attr->value_size;
 612
 613         return smap;
 614 }
 615
 616 int bpf_local_storage_map_check_btf(const struct bpf_map *map,
 617                                     const struct btf *btf,
 618                                     const struct btf_type *key_type,
 619                                     const struct btf_type *value_type)
 620 {
 621         u32 int_data;
 622
 623         if (BTF_INFO_KIND(key_type->info) != BTF_KIND_INT)
 624                 return -EINVAL;
 625
 626         int_data = *(u32 *)(key_type + 1);
 627         if (BTF_INT_BITS(int_data) != 32 || BTF_INT_OFFSET(int_data))
 628                 return -EINVAL;
 629
 630         return 0;
 631 }