kernel/bpf/stackmap.c

   1 /* Copyright (c) 2016 Facebook
   2  *
   3  * This program is free software; you can redistribute it and/or
   4  * modify it under the terms of version 2 of the GNU General Public
   5  * License as published by the Free Software Foundation.
   6  */
   7 #include <linux/bpf.h>
   8 #include <linux/jhash.h>
   9 #include <linux/filter.h>
  10 #include <linux/stacktrace.h>
  11 #include <linux/perf_event.h>
  12 #include <linux/elf.h>
  13 #include <linux/pagemap.h>
  14 #include <linux/irq_work.h>
  15 #include "percpu_freelist.h"
  16
  17 #define STACK_CREATE_FLAG_MASK                                  \
  18         (BPF_F_NUMA_NODE | BPF_F_RDONLY | BPF_F_WRONLY |        \
  19          BPF_F_STACK_BUILD_ID)
  20
  21 struct stack_map_bucket {
  22         struct pcpu_freelist_node fnode;
  23         u32 hash;
  24         u32 nr;
  25         u64 data[];
  26 };
  27
  28 struct bpf_stack_map {
  29         struct bpf_map map;
  30         void *elems;
  31         struct pcpu_freelist freelist;
  32         u32 n_buckets;
  33         struct stack_map_bucket *buckets[];
  34 };
  35
  36 /* irq_work to run up_read() for build_id lookup in nmi context */
  37 struct stack_map_irq_work {
  38         struct irq_work irq_work;
  39         struct rw_semaphore *sem;
  40 };
  41
  42 static void do_up_read(struct irq_work *entry)
  43 {
  44         struct stack_map_irq_work *work;
  45
  46         work = container_of(entry, struct stack_map_irq_work, irq_work);
  47         up_read(work->sem);
  48         work->sem = NULL;
  49 }
  50
  51 static DEFINE_PER_CPU(struct stack_map_irq_work, up_read_work);
  52
  53 static inline bool stack_map_use_build_id(struct bpf_map *map)
  54 {
  55         return (map->map_flags & BPF_F_STACK_BUILD_ID);
  56 }
  57
  58 static inline int stack_map_data_size(struct bpf_map *map)
  59 {
  60         return stack_map_use_build_id(map) ?
  61                 sizeof(struct bpf_stack_build_id) : sizeof(u64);
  62 }
  63
  64 static int prealloc_elems_and_freelist(struct bpf_stack_map *smap)
  65 {
  66         u32 elem_size = sizeof(struct stack_map_bucket) + smap->map.value_size;
  67         int err;
  68
  69         smap->elems = bpf_map_area_alloc(elem_size * smap->map.max_entries,
  70                                          smap->map.numa_node);
  71         if (!smap->elems)
  72                 return -ENOMEM;
  73
  74         err = pcpu_freelist_init(&smap->freelist);
  75         if (err)
  76                 goto free_elems;
  77
  78         pcpu_freelist_populate(&smap->freelist, smap->elems, elem_size,
  79                                smap->map.max_entries);
  80         return 0;
  81
  82 free_elems:
  83         bpf_map_area_free(smap->elems);
  84         return err;
  85 }
  86
  87 /* Called from syscall */
  88 static struct bpf_map *stack_map_alloc(union bpf_attr *attr)
  89 {
  90         u32 value_size = attr->value_size;
  91         struct bpf_stack_map *smap;
  92         u64 cost, n_buckets;
  93         int err;
  94
  95         if (!capable(CAP_SYS_ADMIN))
  96                 return ERR_PTR(-EPERM);
  97
  98         if (attr->map_flags & ~STACK_CREATE_FLAG_MASK)
  99                 return ERR_PTR(-EINVAL);
 100
 101         /* check sanity of attributes */
 102         if (attr->max_entries == 0 || attr->key_size != 4 ||
 103             value_size < 8 || value_size % 8)
 104                 return ERR_PTR(-EINVAL);
 105
 106         BUILD_BUG_ON(sizeof(struct bpf_stack_build_id) % sizeof(u64));
 107         if (attr->map_flags & BPF_F_STACK_BUILD_ID) {
 108                 if (value_size % sizeof(struct bpf_stack_build_id) ||
 109                     value_size / sizeof(struct bpf_stack_build_id)
 110                     > sysctl_perf_event_max_stack)
 111                         return ERR_PTR(-EINVAL);
 112         } else if (value_size / 8 > sysctl_perf_event_max_stack)
 113                 return ERR_PTR(-EINVAL);
 114
 115         /* hash table size must be power of 2 */
 116         n_buckets = roundup_pow_of_two(attr->max_entries);
 117
 118         cost = n_buckets * sizeof(struct stack_map_bucket *) + sizeof(*smap);
 119         if (cost >= U32_MAX - PAGE_SIZE)
 120                 return ERR_PTR(-E2BIG);
 121
 122         smap = bpf_map_area_alloc(cost, bpf_map_attr_numa_node(attr));
 123         if (!smap)
 124                 return ERR_PTR(-ENOMEM);
 125
 126         err = -E2BIG;
 127         cost += n_buckets * (value_size + sizeof(struct stack_map_bucket));
 128         if (cost >= U32_MAX - PAGE_SIZE)
 129                 goto free_smap;
 130
 131         bpf_map_init_from_attr(&smap->map, attr);
 132         smap->map.value_size = value_size;
 133         smap->n_buckets = n_buckets;
 134         smap->map.pages = round_up(cost, PAGE_SIZE) >> PAGE_SHIFT;
 135
 136         err = bpf_map_precharge_memlock(smap->map.pages);
 137         if (err)
 138                 goto free_smap;
 139
 140         err = get_callchain_buffers(sysctl_perf_event_max_stack);
 141         if (err)
 142                 goto free_smap;
 143
 144         err = prealloc_elems_and_freelist(smap);
 145         if (err)
 146                 goto put_buffers;
 147
 148         return &smap->map;
 149
 150 put_buffers:
 151         put_callchain_buffers();
 152 free_smap:
 153         bpf_map_area_free(smap);
 154         return ERR_PTR(err);
 155 }
 156
 157 #define BPF_BUILD_ID 3
 158 /*
 159  * Parse build id from the note segment. This logic can be shared between
 160  * 32-bit and 64-bit system, because Elf32_Nhdr and Elf64_Nhdr are
 161  * identical.
 162  */
 163 static inline int stack_map_parse_build_id(void *page_addr,
 164                                            unsigned char *build_id,
 165                                            void *note_start,
 166                                            Elf32_Word note_size)
 167 {
 168         Elf32_Word note_offs = 0, new_offs;
 169
 170         /* check for overflow */
 171         if (note_start < page_addr || note_start + note_size < note_start)
 172                 return -EINVAL;
 173
 174         /* only supports note that fits in the first page */
 175         if (note_start + note_size > page_addr + PAGE_SIZE)
 176                 return -EINVAL;
 177
 178         while (note_offs + sizeof(Elf32_Nhdr) < note_size) {
 179                 Elf32_Nhdr *nhdr = (Elf32_Nhdr *)(note_start + note_offs);
 180
 181                 if (nhdr->n_type == BPF_BUILD_ID &&
 182                     nhdr->n_namesz == sizeof("GNU") &&
 183                     nhdr->n_descsz == BPF_BUILD_ID_SIZE) {
 184                         memcpy(build_id,
 185                                note_start + note_offs +
 186                                ALIGN(sizeof("GNU"), 4) + sizeof(Elf32_Nhdr),
 187                                BPF_BUILD_ID_SIZE);
 188                         return 0;
 189                 }
 190                 new_offs = note_offs + sizeof(Elf32_Nhdr) +
 191                         ALIGN(nhdr->n_namesz, 4) + ALIGN(nhdr->n_descsz, 4);
 192                 if (new_offs <= note_offs)  /* overflow */
 193                         break;
 194                 note_offs = new_offs;
 195         }
 196         return -EINVAL;
 197 }
 198
 199 /* Parse build ID from 32-bit ELF */
 200 static int stack_map_get_build_id_32(void *page_addr,
 201                                      unsigned char *build_id)
 202 {
 203         Elf32_Ehdr *ehdr = (Elf32_Ehdr *)page_addr;
 204         Elf32_Phdr *phdr;
 205         int i;
 206
 207         /* only supports phdr that fits in one page */
 208         if (ehdr->e_phnum >
 209             (PAGE_SIZE - sizeof(Elf32_Ehdr)) / sizeof(Elf32_Phdr))
 210                 return -EINVAL;
 211
 212         phdr = (Elf32_Phdr *)(page_addr + sizeof(Elf32_Ehdr));
 213
 214         for (i = 0; i < ehdr->e_phnum; ++i)
 215                 if (phdr[i].p_type == PT_NOTE)
 216                         return stack_map_parse_build_id(page_addr, build_id,
 217                                         page_addr + phdr[i].p_offset,
 218                                         phdr[i].p_filesz);
 219         return -EINVAL;
 220 }
 221
 222 /* Parse build ID from 64-bit ELF */
 223 static int stack_map_get_build_id_64(void *page_addr,
 224                                      unsigned char *build_id)
 225 {
 226         Elf64_Ehdr *ehdr = (Elf64_Ehdr *)page_addr;
 227         Elf64_Phdr *phdr;
 228         int i;
 229
 230         /* only supports phdr that fits in one page */
 231         if (ehdr->e_phnum >
 232             (PAGE_SIZE - sizeof(Elf64_Ehdr)) / sizeof(Elf64_Phdr))
 233                 return -EINVAL;
 234
 235         phdr = (Elf64_Phdr *)(page_addr + sizeof(Elf64_Ehdr));
 236
 237         for (i = 0; i < ehdr->e_phnum; ++i)
 238                 if (phdr[i].p_type == PT_NOTE)
 239                         return stack_map_parse_build_id(page_addr, build_id,
 240                                         page_addr + phdr[i].p_offset,
 241                                         phdr[i].p_filesz);
 242         return -EINVAL;
 243 }
 244
 245 /* Parse build ID of ELF file mapped to vma */
 246 static int stack_map_get_build_id(struct vm_area_struct *vma,
 247                                   unsigned char *build_id)
 248 {
 249         Elf32_Ehdr *ehdr;
 250         struct page *page;
 251         void *page_addr;
 252         int ret;
 253
 254         /* only works for page backed storage  */
 255         if (!vma->vm_file)
 256                 return -EINVAL;
 257
 258         page = find_get_page(vma->vm_file->f_mapping, 0);
 259         if (!page)
 260                 return -EFAULT; /* page not mapped */
 261
 262         ret = -EINVAL;
 263         page_addr = kmap_atomic(page);
 264         ehdr = (Elf32_Ehdr *)page_addr;
 265
 266         /* compare magic x7f "ELF" */
 267         if (memcmp(ehdr->e_ident, ELFMAG, SELFMAG) != 0)
 268                 goto out;
 269
 270         /* only support executable file and shared object file */
 271         if (ehdr->e_type != ET_EXEC && ehdr->e_type != ET_DYN)
 272                 goto out;
 273
 274         if (ehdr->e_ident[EI_CLASS] == ELFCLASS32)
 275                 ret = stack_map_get_build_id_32(page_addr, build_id);
 276         else if (ehdr->e_ident[EI_CLASS] == ELFCLASS64)
 277                 ret = stack_map_get_build_id_64(page_addr, build_id);
 278 out:
 279         kunmap_atomic(page_addr);
 280         put_page(page);
 281         return ret;
 282 }
 283
 284 static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
 285                                           u64 *ips, u32 trace_nr, bool user)
 286 {
 287         int i;
 288         struct vm_area_struct *vma;
 289         bool irq_work_busy = false;
 290         struct stack_map_irq_work *work = NULL;
 291
 292         if (in_nmi()) {
 293                 work = this_cpu_ptr(&up_read_work);
 294                 if (work->irq_work.flags & IRQ_WORK_BUSY)
 295                         /* cannot queue more up_read, fallback */
 296                         irq_work_busy = true;
 297         }
 298
 299         /*
 300          * We cannot do up_read() in nmi context. To do build_id lookup
 301          * in nmi context, we need to run up_read() in irq_work. We use
 302          * a percpu variable to do the irq_work. If the irq_work is
 303          * already used by another lookup, we fall back to report ips.
 304          *
 305          * Same fallback is used for kernel stack (!user) on a stackmap
 306          * with build_id.
 307          */
 308         if (!user || !current || !current->mm || irq_work_busy ||
 309             down_read_trylock(&current->mm->mmap_sem) == 0) {
 310                 /* cannot access current->mm, fall back to ips */
 311                 for (i = 0; i < trace_nr; i++) {
 312                         id_offs[i].status = BPF_STACK_BUILD_ID_IP;
 313                         id_offs[i].ip = ips[i];
 314                 }
 315                 return;
 316         }
 317
 318         for (i = 0; i < trace_nr; i++) {
 319                 vma = find_vma(current->mm, ips[i]);
 320                 if (!vma || stack_map_get_build_id(vma, id_offs[i].build_id)) {
 321                         /* per entry fall back to ips */
 322                         id_offs[i].status = BPF_STACK_BUILD_ID_IP;
 323                         id_offs[i].ip = ips[i];
 324                         continue;
 325                 }
 326                 id_offs[i].offset = (vma->vm_pgoff << PAGE_SHIFT) + ips[i]
 327                         - vma->vm_start;
 328                 id_offs[i].status = BPF_STACK_BUILD_ID_VALID;
 329         }
 330
 331         if (!work) {
 332                 up_read(&current->mm->mmap_sem);
 333         } else {
 334                 work->sem = &current->mm->mmap_sem;
 335                 irq_work_queue(&work->irq_work);
 336         }
 337 }
 338
 339 BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map,
 340            u64, flags)
 341 {
 342         struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
 343         struct perf_callchain_entry *trace;
 344         struct stack_map_bucket *bucket, *new_bucket, *old_bucket;
 345         u32 max_depth = map->value_size / stack_map_data_size(map);
 346         /* stack_map_alloc() checks that max_depth <= sysctl_perf_event_max_stack */
 347         u32 init_nr = sysctl_perf_event_max_stack - max_depth;
 348         u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
 349         u32 hash, id, trace_nr, trace_len;
 350         bool user = flags & BPF_F_USER_STACK;
 351         bool kernel = !user;
 352         u64 *ips;
 353         bool hash_matches;
 354
 355         if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
 356                                BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
 357                 return -EINVAL;
 358
 359         trace = get_perf_callchain(regs, init_nr, kernel, user,
 360                                    sysctl_perf_event_max_stack, false, false);
 361
 362         if (unlikely(!trace))
 363                 /* couldn't fetch the stack trace */
 364                 return -EFAULT;
 365
 366         /* get_perf_callchain() guarantees that trace->nr >= init_nr
 367          * and trace-nr <= sysctl_perf_event_max_stack, so trace_nr <= max_depth
 368          */
 369         trace_nr = trace->nr - init_nr;
 370
 371         if (trace_nr <= skip)
 372                 /* skipping more than usable stack trace */
 373                 return -EFAULT;
 374
 375         trace_nr -= skip;
 376         trace_len = trace_nr * sizeof(u64);
 377         ips = trace->ip + skip + init_nr;
 378         hash = jhash2((u32 *)ips, trace_len / sizeof(u32), 0);
 379         id = hash & (smap->n_buckets - 1);
 380         bucket = READ_ONCE(smap->buckets[id]);
 381
 382         hash_matches = bucket && bucket->hash == hash;
 383         /* fast cmp */
 384         if (hash_matches && flags & BPF_F_FAST_STACK_CMP)
 385                 return id;
 386
 387         if (stack_map_use_build_id(map)) {
 388                 /* for build_id+offset, pop a bucket before slow cmp */
 389                 new_bucket = (struct stack_map_bucket *)
 390                         pcpu_freelist_pop(&smap->freelist);
 391                 if (unlikely(!new_bucket))
 392                         return -ENOMEM;
 393                 new_bucket->nr = trace_nr;
 394                 stack_map_get_build_id_offset(
 395                         (struct bpf_stack_build_id *)new_bucket->data,
 396                         ips, trace_nr, user);
 397                 trace_len = trace_nr * sizeof(struct bpf_stack_build_id);
 398                 if (hash_matches && bucket->nr == trace_nr &&
 399                     memcmp(bucket->data, new_bucket->data, trace_len) == 0) {
 400                         pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
 401                         return id;
 402                 }
 403                 if (bucket && !(flags & BPF_F_REUSE_STACKID)) {
 404                         pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
 405                         return -EEXIST;
 406                 }
 407         } else {
 408                 if (hash_matches && bucket->nr == trace_nr &&
 409                     memcmp(bucket->data, ips, trace_len) == 0)
 410                         return id;
 411                 if (bucket && !(flags & BPF_F_REUSE_STACKID))
 412                         return -EEXIST;
 413
 414                 new_bucket = (struct stack_map_bucket *)
 415                         pcpu_freelist_pop(&smap->freelist);
 416                 if (unlikely(!new_bucket))
 417                         return -ENOMEM;
 418                 memcpy(new_bucket->data, ips, trace_len);
 419         }
 420
 421         new_bucket->hash = hash;
 422         new_bucket->nr = trace_nr;
 423
 424         old_bucket = xchg(&smap->buckets[id], new_bucket);
 425         if (old_bucket)
 426                 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
 427         return id;
 428 }
 429
 430 const struct bpf_func_proto bpf_get_stackid_proto = {
 431         .func           = bpf_get_stackid,
 432         .gpl_only       = true,
 433         .ret_type       = RET_INTEGER,
 434         .arg1_type      = ARG_PTR_TO_CTX,
 435         .arg2_type      = ARG_CONST_MAP_PTR,
 436         .arg3_type      = ARG_ANYTHING,
 437 };
 438
 439 BPF_CALL_4(bpf_get_stack, struct pt_regs *, regs, void *, buf, u32, size,
 440            u64, flags)
 441 {
 442         u32 init_nr, trace_nr, copy_len, elem_size, num_elem;
 443         bool user_build_id = flags & BPF_F_USER_BUILD_ID;
 444         u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
 445         bool user = flags & BPF_F_USER_STACK;
 446         struct perf_callchain_entry *trace;
 447         bool kernel = !user;
 448         int err = -EINVAL;
 449         u64 *ips;
 450
 451         if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
 452                                BPF_F_USER_BUILD_ID)))
 453                 goto clear;
 454         if (kernel && user_build_id)
 455                 goto clear;
 456
 457         elem_size = (user && user_build_id) ? sizeof(struct bpf_stack_build_id)
 458                                             : sizeof(u64);
 459         if (unlikely(size % elem_size))
 460                 goto clear;
 461
 462         num_elem = size / elem_size;
 463         if (sysctl_perf_event_max_stack < num_elem)
 464                 init_nr = 0;
 465         else
 466                 init_nr = sysctl_perf_event_max_stack - num_elem;
 467         trace = get_perf_callchain(regs, init_nr, kernel, user,
 468                                    sysctl_perf_event_max_stack, false, false);
 469         if (unlikely(!trace))
 470                 goto err_fault;
 471
 472         trace_nr = trace->nr - init_nr;
 473         if (trace_nr < skip)
 474                 goto err_fault;
 475
 476         trace_nr -= skip;
 477         trace_nr = (trace_nr <= num_elem) ? trace_nr : num_elem;
 478         copy_len = trace_nr * elem_size;
 479         ips = trace->ip + skip + init_nr;
 480         if (user && user_build_id)
 481                 stack_map_get_build_id_offset(buf, ips, trace_nr, user);
 482         else
 483                 memcpy(buf, ips, copy_len);
 484
 485         if (size > copy_len)
 486                 memset(buf + copy_len, 0, size - copy_len);
 487         return copy_len;
 488
 489 err_fault:
 490         err = -EFAULT;
 491 clear:
 492         memset(buf, 0, size);
 493         return err;
 494 }
 495
 496 const struct bpf_func_proto bpf_get_stack_proto = {
 497         .func           = bpf_get_stack,
 498         .gpl_only       = true,
 499         .ret_type       = RET_INTEGER,
 500         .arg1_type      = ARG_PTR_TO_CTX,
 501         .arg2_type      = ARG_PTR_TO_UNINIT_MEM,
 502         .arg3_type      = ARG_CONST_SIZE_OR_ZERO,
 503         .arg4_type      = ARG_ANYTHING,
 504 };
 505
 506 /* Called from eBPF program */
 507 static void *stack_map_lookup_elem(struct bpf_map *map, void *key)
 508 {
 509         return ERR_PTR(-EOPNOTSUPP);
 510 }
 511
 512 /* Called from syscall */
 513 int bpf_stackmap_copy(struct bpf_map *map, void *key, void *value)
 514 {
 515         struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
 516         struct stack_map_bucket *bucket, *old_bucket;
 517         u32 id = *(u32 *)key, trace_len;
 518
 519         if (unlikely(id >= smap->n_buckets))
 520                 return -ENOENT;
 521
 522         bucket = xchg(&smap->buckets[id], NULL);
 523         if (!bucket)
 524                 return -ENOENT;
 525
 526         trace_len = bucket->nr * stack_map_data_size(map);
 527         memcpy(value, bucket->data, trace_len);
 528         memset(value + trace_len, 0, map->value_size - trace_len);
 529
 530         old_bucket = xchg(&smap->buckets[id], bucket);
 531         if (old_bucket)
 532                 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
 533         return 0;
 534 }
 535
 536 static int stack_map_get_next_key(struct bpf_map *map, void *key,
 537                                   void *next_key)
 538 {
 539         struct bpf_stack_map *smap = container_of(map,
 540                                                   struct bpf_stack_map, map);
 541         u32 id;
 542
 543         WARN_ON_ONCE(!rcu_read_lock_held());
 544
 545         if (!key) {
 546                 id = 0;
 547         } else {
 548                 id = *(u32 *)key;
 549                 if (id >= smap->n_buckets || !smap->buckets[id])
 550                         id = 0;
 551                 else
 552                         id++;
 553         }
 554
 555         while (id < smap->n_buckets && !smap->buckets[id])
 556                 id++;
 557
 558         if (id >= smap->n_buckets)
 559                 return -ENOENT;
 560
 561         *(u32 *)next_key = id;
 562         return 0;
 563 }
 564
 565 static int stack_map_update_elem(struct bpf_map *map, void *key, void *value,
 566                                  u64 map_flags)
 567 {
 568         return -EINVAL;
 569 }
 570
 571 /* Called from syscall or from eBPF program */
 572 static int stack_map_delete_elem(struct bpf_map *map, void *key)
 573 {
 574         struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
 575         struct stack_map_bucket *old_bucket;
 576         u32 id = *(u32 *)key;
 577
 578         if (unlikely(id >= smap->n_buckets))
 579                 return -E2BIG;
 580
 581         old_bucket = xchg(&smap->buckets[id], NULL);
 582         if (old_bucket) {
 583                 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
 584                 return 0;
 585         } else {
 586                 return -ENOENT;
 587         }
 588 }
 589
 590 /* Called when map->refcnt goes to zero, either from workqueue or from syscall */
 591 static void stack_map_free(struct bpf_map *map)
 592 {
 593         struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
 594
 595         /* wait for bpf programs to complete before freeing stack map */
 596         synchronize_rcu();
 597
 598         bpf_map_area_free(smap->elems);
 599         pcpu_freelist_destroy(&smap->freelist);
 600         bpf_map_area_free(smap);
 601         put_callchain_buffers();
 602 }
 603
 604 const struct bpf_map_ops stack_trace_map_ops = {
 605         .map_alloc = stack_map_alloc,
 606         .map_free = stack_map_free,
 607         .map_get_next_key = stack_map_get_next_key,
 608         .map_lookup_elem = stack_map_lookup_elem,
 609         .map_update_elem = stack_map_update_elem,
 610         .map_delete_elem = stack_map_delete_elem,
 611         .map_check_btf = map_check_no_btf,
 612 };
 613
 614 static int __init stack_map_init(void)
 615 {
 616         int cpu;
 617         struct stack_map_irq_work *work;
 618
 619         for_each_possible_cpu(cpu) {
 620                 work = per_cpu_ptr(&up_read_work, cpu);
 621                 init_irq_work(&work->irq_work, do_up_read);
 622         }
 623         return 0;
 624 }
 625 subsys_initcall(stack_map_init);