kernel/bpf/arraymap.c

   1 /* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com
   2  * Copyright (c) 2016,2017 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/err.h>
  15 #include <linux/slab.h>
  16 #include <linux/mm.h>
  17 #include <linux/filter.h>
  18 #include <linux/perf_event.h>
  19
  20 #include "map_in_map.h"
  21
  22 #define ARRAY_CREATE_FLAG_MASK \
  23         (BPF_F_NUMA_NODE | BPF_F_RDONLY | BPF_F_WRONLY)
  24
  25 static void bpf_array_free_percpu(struct bpf_array *array)
  26 {
  27         int i;
  28
  29         for (i = 0; i < array->map.max_entries; i++)
  30                 free_percpu(array->pptrs[i]);
  31 }
  32
  33 static int bpf_array_alloc_percpu(struct bpf_array *array)
  34 {
  35         void __percpu *ptr;
  36         int i;
  37
  38         for (i = 0; i < array->map.max_entries; i++) {
  39                 ptr = __alloc_percpu_gfp(array->elem_size, 8,
  40                                          GFP_USER | __GFP_NOWARN);
  41                 if (!ptr) {
  42                         bpf_array_free_percpu(array);
  43                         return -ENOMEM;
  44                 }
  45                 array->pptrs[i] = ptr;
  46         }
  47
  48         return 0;
  49 }
  50
  51 /* Called from syscall */
  52 static struct bpf_map *array_map_alloc(union bpf_attr *attr)
  53 {
  54         bool percpu = attr->map_type == BPF_MAP_TYPE_PERCPU_ARRAY;
  55         int numa_node = bpf_map_attr_numa_node(attr);
  56         u32 elem_size, index_mask, max_entries;
  57         bool unpriv = !capable(CAP_SYS_ADMIN);
  58         struct bpf_array *array;
  59         u64 array_size, mask64;
  60
  61         /* check sanity of attributes */
  62         if (attr->max_entries == 0 || attr->key_size != 4 ||
  63             attr->value_size == 0 ||
  64             attr->map_flags & ~ARRAY_CREATE_FLAG_MASK ||
  65             (percpu && numa_node != NUMA_NO_NODE))
  66                 return ERR_PTR(-EINVAL);
  67
  68         if (attr->value_size > KMALLOC_MAX_SIZE)
  69                 /* if value_size is bigger, the user space won't be able to
  70                  * access the elements.
  71                  */
  72                 return ERR_PTR(-E2BIG);
  73
  74         elem_size = round_up(attr->value_size, 8);
  75
  76         max_entries = attr->max_entries;
  77
  78         /* On 32 bit archs roundup_pow_of_two() with max_entries that has
  79          * upper most bit set in u32 space is undefined behavior due to
  80          * resulting 1U << 32, so do it manually here in u64 space.
  81          */
  82         mask64 = fls_long(max_entries - 1);
  83         mask64 = 1ULL << mask64;
  84         mask64 -= 1;
  85
  86         index_mask = mask64;
  87         if (unpriv) {
  88                 /* round up array size to nearest power of 2,
  89                  * since cpu will speculate within index_mask limits
  90                  */
  91                 max_entries = index_mask + 1;
  92                 /* Check for overflows. */
  93                 if (max_entries < attr->max_entries)
  94                         return ERR_PTR(-E2BIG);
  95         }
  96
  97         array_size = sizeof(*array);
  98         if (percpu)
  99                 array_size += (u64) max_entries * sizeof(void *);
 100         else
 101                 array_size += (u64) max_entries * elem_size;
 102
 103         /* make sure there is no u32 overflow later in round_up() */
 104         if (array_size >= U32_MAX - PAGE_SIZE)
 105                 return ERR_PTR(-ENOMEM);
 106
 107         /* allocate all map elements and zero-initialize them */
 108         array = bpf_map_area_alloc(array_size, numa_node);
 109         if (!array)
 110                 return ERR_PTR(-ENOMEM);
 111         array->index_mask = index_mask;
 112         array->map.unpriv_array = unpriv;
 113
 114         /* copy mandatory map attributes */
 115         array->map.map_type = attr->map_type;
 116         array->map.key_size = attr->key_size;
 117         array->map.value_size = attr->value_size;
 118         array->map.max_entries = attr->max_entries;
 119         array->map.map_flags = attr->map_flags;
 120         array->map.numa_node = numa_node;
 121         array->elem_size = elem_size;
 122
 123         if (!percpu)
 124                 goto out;
 125
 126         array_size += (u64) attr->max_entries * elem_size * num_possible_cpus();
 127
 128         if (array_size >= U32_MAX - PAGE_SIZE ||
 129             bpf_array_alloc_percpu(array)) {
 130                 bpf_map_area_free(array);
 131                 return ERR_PTR(-ENOMEM);
 132         }
 133 out:
 134         array->map.pages = round_up(array_size, PAGE_SIZE) >> PAGE_SHIFT;
 135
 136         return &array->map;
 137 }
 138
 139 /* Called from syscall or from eBPF program */
 140 static void *array_map_lookup_elem(struct bpf_map *map, void *key)
 141 {
 142         struct bpf_array *array = container_of(map, struct bpf_array, map);
 143         u32 index = *(u32 *)key;
 144
 145         if (unlikely(index >= array->map.max_entries))
 146                 return NULL;
 147
 148         return array->value + array->elem_size * (index & array->index_mask);
 149 }
 150
 151 /* emit BPF instructions equivalent to C code of array_map_lookup_elem() */
 152 static u32 array_map_gen_lookup(struct bpf_map *map, struct bpf_insn *insn_buf)
 153 {
 154         struct bpf_array *array = container_of(map, struct bpf_array, map);
 155         struct bpf_insn *insn = insn_buf;
 156         u32 elem_size = round_up(map->value_size, 8);
 157         const int ret = BPF_REG_0;
 158         const int map_ptr = BPF_REG_1;
 159         const int index = BPF_REG_2;
 160
 161         *insn++ = BPF_ALU64_IMM(BPF_ADD, map_ptr, offsetof(struct bpf_array, value));
 162         *insn++ = BPF_LDX_MEM(BPF_W, ret, index, 0);
 163         if (map->unpriv_array) {
 164                 *insn++ = BPF_JMP_IMM(BPF_JGE, ret, map->max_entries, 4);
 165                 *insn++ = BPF_ALU32_IMM(BPF_AND, ret, array->index_mask);
 166         } else {
 167                 *insn++ = BPF_JMP_IMM(BPF_JGE, ret, map->max_entries, 3);
 168         }
 169
 170         if (is_power_of_2(elem_size)) {
 171                 *insn++ = BPF_ALU64_IMM(BPF_LSH, ret, ilog2(elem_size));
 172         } else {
 173                 *insn++ = BPF_ALU64_IMM(BPF_MUL, ret, elem_size);
 174         }
 175         *insn++ = BPF_ALU64_REG(BPF_ADD, ret, map_ptr);
 176         *insn++ = BPF_JMP_IMM(BPF_JA, 0, 0, 1);
 177         *insn++ = BPF_MOV64_IMM(ret, 0);
 178         return insn - insn_buf;
 179 }
 180
 181 /* Called from eBPF program */
 182 static void *percpu_array_map_lookup_elem(struct bpf_map *map, void *key)
 183 {
 184         struct bpf_array *array = container_of(map, struct bpf_array, map);
 185         u32 index = *(u32 *)key;
 186
 187         if (unlikely(index >= array->map.max_entries))
 188                 return NULL;
 189
 190         return this_cpu_ptr(array->pptrs[index & array->index_mask]);
 191 }
 192
 193 int bpf_percpu_array_copy(struct bpf_map *map, void *key, void *value)
 194 {
 195         struct bpf_array *array = container_of(map, struct bpf_array, map);
 196         u32 index = *(u32 *)key;
 197         void __percpu *pptr;
 198         int cpu, off = 0;
 199         u32 size;
 200
 201         if (unlikely(index >= array->map.max_entries))
 202                 return -ENOENT;
 203
 204         /* per_cpu areas are zero-filled and bpf programs can only
 205          * access 'value_size' of them, so copying rounded areas
 206          * will not leak any kernel data
 207          */
 208         size = round_up(map->value_size, 8);
 209         rcu_read_lock();
 210         pptr = array->pptrs[index & array->index_mask];
 211         for_each_possible_cpu(cpu) {
 212                 bpf_long_memcpy(value + off, per_cpu_ptr(pptr, cpu), size);
 213                 off += size;
 214         }
 215         rcu_read_unlock();
 216         return 0;
 217 }
 218
 219 /* Called from syscall */
 220 static int array_map_get_next_key(struct bpf_map *map, void *key, void *next_key)
 221 {
 222         struct bpf_array *array = container_of(map, struct bpf_array, map);
 223         u32 index = key ? *(u32 *)key : U32_MAX;
 224         u32 *next = (u32 *)next_key;
 225
 226         if (index >= array->map.max_entries) {
 227                 *next = 0;
 228                 return 0;
 229         }
 230
 231         if (index == array->map.max_entries - 1)
 232                 return -ENOENT;
 233
 234         *next = index + 1;
 235         return 0;
 236 }
 237
 238 /* Called from syscall or from eBPF program */
 239 static int array_map_update_elem(struct bpf_map *map, void *key, void *value,
 240                                  u64 map_flags)
 241 {
 242         struct bpf_array *array = container_of(map, struct bpf_array, map);
 243         u32 index = *(u32 *)key;
 244
 245         if (unlikely(map_flags > BPF_EXIST))
 246                 /* unknown flags */
 247                 return -EINVAL;
 248
 249         if (unlikely(index >= array->map.max_entries))
 250                 /* all elements were pre-allocated, cannot insert a new one */
 251                 return -E2BIG;
 252
 253         if (unlikely(map_flags == BPF_NOEXIST))
 254                 /* all elements already exist */
 255                 return -EEXIST;
 256
 257         if (array->map.map_type == BPF_MAP_TYPE_PERCPU_ARRAY)
 258                 memcpy(this_cpu_ptr(array->pptrs[index & array->index_mask]),
 259                        value, map->value_size);
 260         else
 261                 memcpy(array->value +
 262                        array->elem_size * (index & array->index_mask),
 263                        value, map->value_size);
 264         return 0;
 265 }
 266
 267 int bpf_percpu_array_update(struct bpf_map *map, void *key, void *value,
 268                             u64 map_flags)
 269 {
 270         struct bpf_array *array = container_of(map, struct bpf_array, map);
 271         u32 index = *(u32 *)key;
 272         void __percpu *pptr;
 273         int cpu, off = 0;
 274         u32 size;
 275
 276         if (unlikely(map_flags > BPF_EXIST))
 277                 /* unknown flags */
 278                 return -EINVAL;
 279
 280         if (unlikely(index >= array->map.max_entries))
 281                 /* all elements were pre-allocated, cannot insert a new one */
 282                 return -E2BIG;
 283
 284         if (unlikely(map_flags == BPF_NOEXIST))
 285                 /* all elements already exist */
 286                 return -EEXIST;
 287
 288         /* the user space will provide round_up(value_size, 8) bytes that
 289          * will be copied into per-cpu area. bpf programs can only access
 290          * value_size of it. During lookup the same extra bytes will be
 291          * returned or zeros which were zero-filled by percpu_alloc,
 292          * so no kernel data leaks possible
 293          */
 294         size = round_up(map->value_size, 8);
 295         rcu_read_lock();
 296         pptr = array->pptrs[index & array->index_mask];
 297         for_each_possible_cpu(cpu) {
 298                 bpf_long_memcpy(per_cpu_ptr(pptr, cpu), value + off, size);
 299                 off += size;
 300         }
 301         rcu_read_unlock();
 302         return 0;
 303 }
 304
 305 /* Called from syscall or from eBPF program */
 306 static int array_map_delete_elem(struct bpf_map *map, void *key)
 307 {
 308         return -EINVAL;
 309 }
 310
 311 /* Called when map->refcnt goes to zero, either from workqueue or from syscall */
 312 static void array_map_free(struct bpf_map *map)
 313 {
 314         struct bpf_array *array = container_of(map, struct bpf_array, map);
 315
 316         /* at this point bpf_prog->aux->refcnt == 0 and this map->refcnt == 0,
 317          * so the programs (can be more than one that used this map) were
 318          * disconnected from events. Wait for outstanding programs to complete
 319          * and free the array
 320          */
 321         synchronize_rcu();
 322
 323         if (array->map.map_type == BPF_MAP_TYPE_PERCPU_ARRAY)
 324                 bpf_array_free_percpu(array);
 325
 326         bpf_map_area_free(array);
 327 }
 328
 329 const struct bpf_map_ops array_map_ops = {
 330         .map_alloc = array_map_alloc,
 331         .map_free = array_map_free,
 332         .map_get_next_key = array_map_get_next_key,
 333         .map_lookup_elem = array_map_lookup_elem,
 334         .map_update_elem = array_map_update_elem,
 335         .map_delete_elem = array_map_delete_elem,
 336         .map_gen_lookup = array_map_gen_lookup,
 337 };
 338
 339 const struct bpf_map_ops percpu_array_map_ops = {
 340         .map_alloc = array_map_alloc,
 341         .map_free = array_map_free,
 342         .map_get_next_key = array_map_get_next_key,
 343         .map_lookup_elem = percpu_array_map_lookup_elem,
 344         .map_update_elem = array_map_update_elem,
 345         .map_delete_elem = array_map_delete_elem,
 346 };
 347
 348 static struct bpf_map *fd_array_map_alloc(union bpf_attr *attr)
 349 {
 350         /* only file descriptors can be stored in this type of map */
 351         if (attr->value_size != sizeof(u32))
 352                 return ERR_PTR(-EINVAL);
 353         return array_map_alloc(attr);
 354 }
 355
 356 static void fd_array_map_free(struct bpf_map *map)
 357 {
 358         struct bpf_array *array = container_of(map, struct bpf_array, map);
 359         int i;
 360
 361         synchronize_rcu();
 362
 363         /* make sure it's empty */
 364         for (i = 0; i < array->map.max_entries; i++)
 365                 BUG_ON(array->ptrs[i] != NULL);
 366
 367         bpf_map_area_free(array);
 368 }
 369
 370 static void *fd_array_map_lookup_elem(struct bpf_map *map, void *key)
 371 {
 372         return NULL;
 373 }
 374
 375 /* only called from syscall */
 376 int bpf_fd_array_map_lookup_elem(struct bpf_map *map, void *key, u32 *value)
 377 {
 378         void **elem, *ptr;
 379         int ret =  0;
 380
 381         if (!map->ops->map_fd_sys_lookup_elem)
 382                 return -ENOTSUPP;
 383
 384         rcu_read_lock();
 385         elem = array_map_lookup_elem(map, key);
 386         if (elem && (ptr = READ_ONCE(*elem)))
 387                 *value = map->ops->map_fd_sys_lookup_elem(ptr);
 388         else
 389                 ret = -ENOENT;
 390         rcu_read_unlock();
 391
 392         return ret;
 393 }
 394
 395 /* only called from syscall */
 396 int bpf_fd_array_map_update_elem(struct bpf_map *map, struct file *map_file,
 397                                  void *key, void *value, u64 map_flags)
 398 {
 399         struct bpf_array *array = container_of(map, struct bpf_array, map);
 400         void *new_ptr, *old_ptr;
 401         u32 index = *(u32 *)key, ufd;
 402
 403         if (map_flags != BPF_ANY)
 404                 return -EINVAL;
 405
 406         if (index >= array->map.max_entries)
 407                 return -E2BIG;
 408
 409         ufd = *(u32 *)value;
 410         new_ptr = map->ops->map_fd_get_ptr(map, map_file, ufd);
 411         if (IS_ERR(new_ptr))
 412                 return PTR_ERR(new_ptr);
 413
 414         old_ptr = xchg(array->ptrs + index, new_ptr);
 415         if (old_ptr)
 416                 map->ops->map_fd_put_ptr(old_ptr);
 417
 418         return 0;
 419 }
 420
 421 static int fd_array_map_delete_elem(struct bpf_map *map, void *key)
 422 {
 423         struct bpf_array *array = container_of(map, struct bpf_array, map);
 424         void *old_ptr;
 425         u32 index = *(u32 *)key;
 426
 427         if (index >= array->map.max_entries)
 428                 return -E2BIG;
 429
 430         old_ptr = xchg(array->ptrs + index, NULL);
 431         if (old_ptr) {
 432                 map->ops->map_fd_put_ptr(old_ptr);
 433                 return 0;
 434         } else {
 435                 return -ENOENT;
 436         }
 437 }
 438
 439 static void *prog_fd_array_get_ptr(struct bpf_map *map,
 440                                    struct file *map_file, int fd)
 441 {
 442         struct bpf_array *array = container_of(map, struct bpf_array, map);
 443         struct bpf_prog *prog = bpf_prog_get(fd);
 444
 445         if (IS_ERR(prog))
 446                 return prog;
 447
 448         if (!bpf_prog_array_compatible(array, prog)) {
 449                 bpf_prog_put(prog);
 450                 return ERR_PTR(-EINVAL);
 451         }
 452
 453         return prog;
 454 }
 455
 456 static void prog_fd_array_put_ptr(void *ptr)
 457 {
 458         bpf_prog_put(ptr);
 459 }
 460
 461 static u32 prog_fd_array_sys_lookup_elem(void *ptr)
 462 {
 463         return ((struct bpf_prog *)ptr)->aux->id;
 464 }
 465
 466 /* decrement refcnt of all bpf_progs that are stored in this map */
 467 void bpf_fd_array_map_clear(struct bpf_map *map)
 468 {
 469         struct bpf_array *array = container_of(map, struct bpf_array, map);
 470         int i;
 471
 472         for (i = 0; i < array->map.max_entries; i++)
 473                 fd_array_map_delete_elem(map, &i);
 474 }
 475
 476 const struct bpf_map_ops prog_array_map_ops = {
 477         .map_alloc = fd_array_map_alloc,
 478         .map_free = fd_array_map_free,
 479         .map_get_next_key = array_map_get_next_key,
 480         .map_lookup_elem = fd_array_map_lookup_elem,
 481         .map_delete_elem = fd_array_map_delete_elem,
 482         .map_fd_get_ptr = prog_fd_array_get_ptr,
 483         .map_fd_put_ptr = prog_fd_array_put_ptr,
 484         .map_fd_sys_lookup_elem = prog_fd_array_sys_lookup_elem,
 485 };
 486
 487 static struct bpf_event_entry *bpf_event_entry_gen(struct file *perf_file,
 488                                                    struct file *map_file)
 489 {
 490         struct bpf_event_entry *ee;
 491
 492         ee = kzalloc(sizeof(*ee), GFP_ATOMIC);
 493         if (ee) {
 494                 ee->event = perf_file->private_data;
 495                 ee->perf_file = perf_file;
 496                 ee->map_file = map_file;
 497         }
 498
 499         return ee;
 500 }
 501
 502 static void __bpf_event_entry_free(struct rcu_head *rcu)
 503 {
 504         struct bpf_event_entry *ee;
 505
 506         ee = container_of(rcu, struct bpf_event_entry, rcu);
 507         fput(ee->perf_file);
 508         kfree(ee);
 509 }
 510
 511 static void bpf_event_entry_free_rcu(struct bpf_event_entry *ee)
 512 {
 513         call_rcu(&ee->rcu, __bpf_event_entry_free);
 514 }
 515
 516 static void *perf_event_fd_array_get_ptr(struct bpf_map *map,
 517                                          struct file *map_file, int fd)
 518 {
 519         struct bpf_event_entry *ee;
 520         struct perf_event *event;
 521         struct file *perf_file;
 522         u64 value;
 523
 524         perf_file = perf_event_get(fd);
 525         if (IS_ERR(perf_file))
 526                 return perf_file;
 527
 528         ee = ERR_PTR(-EOPNOTSUPP);
 529         event = perf_file->private_data;
 530         if (perf_event_read_local(event, &value, NULL, NULL) == -EOPNOTSUPP)
 531                 goto err_out;
 532
 533         ee = bpf_event_entry_gen(perf_file, map_file);
 534         if (ee)
 535                 return ee;
 536         ee = ERR_PTR(-ENOMEM);
 537 err_out:
 538         fput(perf_file);
 539         return ee;
 540 }
 541
 542 static void perf_event_fd_array_put_ptr(void *ptr)
 543 {
 544         bpf_event_entry_free_rcu(ptr);
 545 }
 546
 547 static void perf_event_fd_array_release(struct bpf_map *map,
 548                                         struct file *map_file)
 549 {
 550         struct bpf_array *array = container_of(map, struct bpf_array, map);
 551         struct bpf_event_entry *ee;
 552         int i;
 553
 554         rcu_read_lock();
 555         for (i = 0; i < array->map.max_entries; i++) {
 556                 ee = READ_ONCE(array->ptrs[i]);
 557                 if (ee && ee->map_file == map_file)
 558                         fd_array_map_delete_elem(map, &i);
 559         }
 560         rcu_read_unlock();
 561 }
 562
 563 const struct bpf_map_ops perf_event_array_map_ops = {
 564         .map_alloc = fd_array_map_alloc,
 565         .map_free = fd_array_map_free,
 566         .map_get_next_key = array_map_get_next_key,
 567         .map_lookup_elem = fd_array_map_lookup_elem,
 568         .map_delete_elem = fd_array_map_delete_elem,
 569         .map_fd_get_ptr = perf_event_fd_array_get_ptr,
 570         .map_fd_put_ptr = perf_event_fd_array_put_ptr,
 571         .map_release = perf_event_fd_array_release,
 572 };
 573
 574 #ifdef CONFIG_CGROUPS
 575 static void *cgroup_fd_array_get_ptr(struct bpf_map *map,
 576                                      struct file *map_file /* not used */,
 577                                      int fd)
 578 {
 579         return cgroup_get_from_fd(fd);
 580 }
 581
 582 static void cgroup_fd_array_put_ptr(void *ptr)
 583 {
 584         /* cgroup_put free cgrp after a rcu grace period */
 585         cgroup_put(ptr);
 586 }
 587
 588 static void cgroup_fd_array_free(struct bpf_map *map)
 589 {
 590         bpf_fd_array_map_clear(map);
 591         fd_array_map_free(map);
 592 }
 593
 594 const struct bpf_map_ops cgroup_array_map_ops = {
 595         .map_alloc = fd_array_map_alloc,
 596         .map_free = cgroup_fd_array_free,
 597         .map_get_next_key = array_map_get_next_key,
 598         .map_lookup_elem = fd_array_map_lookup_elem,
 599         .map_delete_elem = fd_array_map_delete_elem,
 600         .map_fd_get_ptr = cgroup_fd_array_get_ptr,
 601         .map_fd_put_ptr = cgroup_fd_array_put_ptr,
 602 };
 603 #endif
 604
 605 static struct bpf_map *array_of_map_alloc(union bpf_attr *attr)
 606 {
 607         struct bpf_map *map, *inner_map_meta;
 608
 609         inner_map_meta = bpf_map_meta_alloc(attr->inner_map_fd);
 610         if (IS_ERR(inner_map_meta))
 611                 return inner_map_meta;
 612
 613         map = fd_array_map_alloc(attr);
 614         if (IS_ERR(map)) {
 615                 bpf_map_meta_free(inner_map_meta);
 616                 return map;
 617         }
 618
 619         map->inner_map_meta = inner_map_meta;
 620
 621         return map;
 622 }
 623
 624 static void array_of_map_free(struct bpf_map *map)
 625 {
 626         /* map->inner_map_meta is only accessed by syscall which
 627          * is protected by fdget/fdput.
 628          */
 629         bpf_map_meta_free(map->inner_map_meta);
 630         bpf_fd_array_map_clear(map);
 631         fd_array_map_free(map);
 632 }
 633
 634 static void *array_of_map_lookup_elem(struct bpf_map *map, void *key)
 635 {
 636         struct bpf_map **inner_map = array_map_lookup_elem(map, key);
 637
 638         if (!inner_map)
 639                 return NULL;
 640
 641         return READ_ONCE(*inner_map);
 642 }
 643
 644 static u32 array_of_map_gen_lookup(struct bpf_map *map,
 645                                    struct bpf_insn *insn_buf)
 646 {
 647         struct bpf_array *array = container_of(map, struct bpf_array, map);
 648         u32 elem_size = round_up(map->value_size, 8);
 649         struct bpf_insn *insn = insn_buf;
 650         const int ret = BPF_REG_0;
 651         const int map_ptr = BPF_REG_1;
 652         const int index = BPF_REG_2;
 653
 654         *insn++ = BPF_ALU64_IMM(BPF_ADD, map_ptr, offsetof(struct bpf_array, value));
 655         *insn++ = BPF_LDX_MEM(BPF_W, ret, index, 0);
 656         if (map->unpriv_array) {
 657                 *insn++ = BPF_JMP_IMM(BPF_JGE, ret, map->max_entries, 6);
 658                 *insn++ = BPF_ALU32_IMM(BPF_AND, ret, array->index_mask);
 659         } else {
 660                 *insn++ = BPF_JMP_IMM(BPF_JGE, ret, map->max_entries, 5);
 661         }
 662         if (is_power_of_2(elem_size))
 663                 *insn++ = BPF_ALU64_IMM(BPF_LSH, ret, ilog2(elem_size));
 664         else
 665                 *insn++ = BPF_ALU64_IMM(BPF_MUL, ret, elem_size);
 666         *insn++ = BPF_ALU64_REG(BPF_ADD, ret, map_ptr);
 667         *insn++ = BPF_LDX_MEM(BPF_DW, ret, ret, 0);
 668         *insn++ = BPF_JMP_IMM(BPF_JEQ, ret, 0, 1);
 669         *insn++ = BPF_JMP_IMM(BPF_JA, 0, 0, 1);
 670         *insn++ = BPF_MOV64_IMM(ret, 0);
 671
 672         return insn - insn_buf;
 673 }
 674
 675 const struct bpf_map_ops array_of_maps_map_ops = {
 676         .map_alloc = array_of_map_alloc,
 677         .map_free = array_of_map_free,
 678         .map_get_next_key = array_map_get_next_key,
 679         .map_lookup_elem = array_of_map_lookup_elem,
 680         .map_delete_elem = fd_array_map_delete_elem,
 681         .map_fd_get_ptr = bpf_map_fd_get_ptr,
 682         .map_fd_put_ptr = bpf_map_fd_put_ptr,
 683         .map_fd_sys_lookup_elem = bpf_map_fd_sys_lookup_elem,
 684         .map_gen_lookup = array_of_map_gen_lookup,
 685 };