kernel/bpf/stackmap.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /* Copyright (c) 2016 Facebook
   3  */
   4 #include <linux/bpf.h>
   5 #include <linux/jhash.h>
   6 #include <linux/filter.h>
   7 #include <linux/stacktrace.h>
   8 #include <linux/perf_event.h>
   9 #include <linux/elf.h>
  10 #include <linux/pagemap.h>
  11 #include <linux/irq_work.h>
  12 #include "percpu_freelist.h"
  13
  14 #define STACK_CREATE_FLAG_MASK                                  \
  15         (BPF_F_NUMA_NODE | BPF_F_RDONLY | BPF_F_WRONLY |        \
  16          BPF_F_STACK_BUILD_ID)
  17
  18 struct stack_map_bucket {
  19         struct pcpu_freelist_node fnode;
  20         u32 hash;
  21         u32 nr;
  22         u64 data[];
  23 };
  24
  25 struct bpf_stack_map {
  26         struct bpf_map map;
  27         void *elems;
  28         struct pcpu_freelist freelist;
  29         u32 n_buckets;
  30         struct stack_map_bucket *buckets[];
  31 };
  32
  33 /* irq_work to run up_read() for build_id lookup in nmi context */
  34 struct stack_map_irq_work {
  35         struct irq_work irq_work;
  36         struct rw_semaphore *sem;
  37 };
  38
  39 static void do_up_read(struct irq_work *entry)
  40 {
  41         struct stack_map_irq_work *work;
  42
  43         work = container_of(entry, struct stack_map_irq_work, irq_work);
  44         up_read_non_owner(work->sem);
  45         work->sem = NULL;
  46 }
  47
  48 static DEFINE_PER_CPU(struct stack_map_irq_work, up_read_work);
  49
  50 static inline bool stack_map_use_build_id(struct bpf_map *map)
  51 {
  52         return (map->map_flags & BPF_F_STACK_BUILD_ID);
  53 }
  54
  55 static inline int stack_map_data_size(struct bpf_map *map)
  56 {
  57         return stack_map_use_build_id(map) ?
  58                 sizeof(struct bpf_stack_build_id) : sizeof(u64);
  59 }
  60
  61 static int prealloc_elems_and_freelist(struct bpf_stack_map *smap)
  62 {
  63         u32 elem_size = sizeof(struct stack_map_bucket) + smap->map.value_size;
  64         int err;
  65
  66         smap->elems = bpf_map_area_alloc(elem_size * smap->map.max_entries,
  67                                          smap->map.numa_node);
  68         if (!smap->elems)
  69                 return -ENOMEM;
  70
  71         err = pcpu_freelist_init(&smap->freelist);
  72         if (err)
  73                 goto free_elems;
  74
  75         pcpu_freelist_populate(&smap->freelist, smap->elems, elem_size,
  76                                smap->map.max_entries);
  77         return 0;
  78
  79 free_elems:
  80         bpf_map_area_free(smap->elems);
  81         return err;
  82 }
  83
  84 /* Called from syscall */
  85 static struct bpf_map *stack_map_alloc(union bpf_attr *attr)
  86 {
  87         u32 value_size = attr->value_size;
  88         struct bpf_stack_map *smap;
  89         u64 cost, n_buckets;
  90         int err;
  91
  92         if (!capable(CAP_SYS_ADMIN))
  93                 return ERR_PTR(-EPERM);
  94
  95         if (attr->map_flags & ~STACK_CREATE_FLAG_MASK)
  96                 return ERR_PTR(-EINVAL);
  97
  98         /* check sanity of attributes */
  99         if (attr->max_entries == 0 || attr->key_size != 4 ||
 100             value_size < 8 || value_size % 8)
 101                 return ERR_PTR(-EINVAL);
 102
 103         BUILD_BUG_ON(sizeof(struct bpf_stack_build_id) % sizeof(u64));
 104         if (attr->map_flags & BPF_F_STACK_BUILD_ID) {
 105                 if (value_size % sizeof(struct bpf_stack_build_id) ||
 106                     value_size / sizeof(struct bpf_stack_build_id)
 107                     > sysctl_perf_event_max_stack)
 108                         return ERR_PTR(-EINVAL);
 109         } else if (value_size / 8 > sysctl_perf_event_max_stack)
 110                 return ERR_PTR(-EINVAL);
 111
 112         /* hash table size must be power of 2 */
 113         n_buckets = roundup_pow_of_two(attr->max_entries);
 114
 115         cost = n_buckets * sizeof(struct stack_map_bucket *) + sizeof(*smap);
 116         if (cost >= U32_MAX - PAGE_SIZE)
 117                 return ERR_PTR(-E2BIG);
 118
 119         smap = bpf_map_area_alloc(cost, bpf_map_attr_numa_node(attr));
 120         if (!smap)
 121                 return ERR_PTR(-ENOMEM);
 122
 123         err = -E2BIG;
 124         cost += n_buckets * (value_size + sizeof(struct stack_map_bucket));
 125         if (cost >= U32_MAX - PAGE_SIZE)
 126                 goto free_smap;
 127
 128         bpf_map_init_from_attr(&smap->map, attr);
 129         smap->map.value_size = value_size;
 130         smap->n_buckets = n_buckets;
 131         smap->map.pages = round_up(cost, PAGE_SIZE) >> PAGE_SHIFT;
 132
 133         err = bpf_map_precharge_memlock(smap->map.pages);
 134         if (err)
 135                 goto free_smap;
 136
 137         err = get_callchain_buffers(sysctl_perf_event_max_stack);
 138         if (err)
 139                 goto free_smap;
 140
 141         err = prealloc_elems_and_freelist(smap);
 142         if (err)
 143                 goto put_buffers;
 144
 145         return &smap->map;
 146
 147 put_buffers:
 148         put_callchain_buffers();
 149 free_smap:
 150         bpf_map_area_free(smap);
 151         return ERR_PTR(err);
 152 }
 153
 154 #define BPF_BUILD_ID 3
 155 /*
 156  * Parse build id from the note segment. This logic can be shared between
 157  * 32-bit and 64-bit system, because Elf32_Nhdr and Elf64_Nhdr are
 158  * identical.
 159  */
 160 static inline int stack_map_parse_build_id(void *page_addr,
 161                                            unsigned char *build_id,
 162                                            void *note_start,
 163                                            Elf32_Word note_size)
 164 {
 165         Elf32_Word note_offs = 0, new_offs;
 166
 167         /* check for overflow */
 168         if (note_start < page_addr || note_start + note_size < note_start)
 169                 return -EINVAL;
 170
 171         /* only supports note that fits in the first page */
 172         if (note_start + note_size > page_addr + PAGE_SIZE)
 173                 return -EINVAL;
 174
 175         while (note_offs + sizeof(Elf32_Nhdr) < note_size) {
 176                 Elf32_Nhdr *nhdr = (Elf32_Nhdr *)(note_start + note_offs);
 177
 178                 if (nhdr->n_type == BPF_BUILD_ID &&
 179                     nhdr->n_namesz == sizeof("GNU") &&
 180                     nhdr->n_descsz > 0 &&
 181                     nhdr->n_descsz <= BPF_BUILD_ID_SIZE) {
 182                         memcpy(build_id,
 183                                note_start + note_offs +
 184                                ALIGN(sizeof("GNU"), 4) + sizeof(Elf32_Nhdr),
 185                                nhdr->n_descsz);
 186                         memset(build_id + nhdr->n_descsz, 0,
 187                                BPF_BUILD_ID_SIZE - nhdr->n_descsz);
 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                         memset(id_offs[i].build_id, 0, BPF_BUILD_ID_SIZE);
 315                 }
 316                 return;
 317         }
 318
 319         for (i = 0; i < trace_nr; i++) {
 320                 vma = find_vma(current->mm, ips[i]);
 321                 if (!vma || stack_map_get_build_id(vma, id_offs[i].build_id)) {
 322                         /* per entry fall back to ips */
 323                         id_offs[i].status = BPF_STACK_BUILD_ID_IP;
 324                         id_offs[i].ip = ips[i];
 325                         memset(id_offs[i].build_id, 0, BPF_BUILD_ID_SIZE);
 326                         continue;
 327                 }
 328                 id_offs[i].offset = (vma->vm_pgoff << PAGE_SHIFT) + ips[i]
 329                         - vma->vm_start;
 330                 id_offs[i].status = BPF_STACK_BUILD_ID_VALID;
 331         }
 332
 333         if (!work) {
 334                 up_read(&current->mm->mmap_sem);
 335         } else {
 336                 work->sem = &current->mm->mmap_sem;
 337                 irq_work_queue(&work->irq_work);
 338                 /*
 339                  * The irq_work will release the mmap_sem with
 340                  * up_read_non_owner(). The rwsem_release() is called
 341                  * here to release the lock from lockdep's perspective.
 342                  */
 343                 rwsem_release(&current->mm->mmap_sem.dep_map, 1, _RET_IP_);
 344         }
 345 }
 346
 347 BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map,
 348            u64, flags)
 349 {
 350         struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
 351         struct perf_callchain_entry *trace;
 352         struct stack_map_bucket *bucket, *new_bucket, *old_bucket;
 353         u32 max_depth = map->value_size / stack_map_data_size(map);
 354         /* stack_map_alloc() checks that max_depth <= sysctl_perf_event_max_stack */
 355         u32 init_nr = sysctl_perf_event_max_stack - max_depth;
 356         u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
 357         u32 hash, id, trace_nr, trace_len;
 358         bool user = flags & BPF_F_USER_STACK;
 359         bool kernel = !user;
 360         u64 *ips;
 361         bool hash_matches;
 362
 363         if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
 364                                BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
 365                 return -EINVAL;
 366
 367         trace = get_perf_callchain(regs, init_nr, kernel, user,
 368                                    sysctl_perf_event_max_stack, false, false);
 369
 370         if (unlikely(!trace))
 371                 /* couldn't fetch the stack trace */
 372                 return -EFAULT;
 373
 374         /* get_perf_callchain() guarantees that trace->nr >= init_nr
 375          * and trace-nr <= sysctl_perf_event_max_stack, so trace_nr <= max_depth
 376          */
 377         trace_nr = trace->nr - init_nr;
 378
 379         if (trace_nr <= skip)
 380                 /* skipping more than usable stack trace */
 381                 return -EFAULT;
 382
 383         trace_nr -= skip;
 384         trace_len = trace_nr * sizeof(u64);
 385         ips = trace->ip + skip + init_nr;
 386         hash = jhash2((u32 *)ips, trace_len / sizeof(u32), 0);
 387         id = hash & (smap->n_buckets - 1);
 388         bucket = READ_ONCE(smap->buckets[id]);
 389
 390         hash_matches = bucket && bucket->hash == hash;
 391         /* fast cmp */
 392         if (hash_matches && flags & BPF_F_FAST_STACK_CMP)
 393                 return id;
 394
 395         if (stack_map_use_build_id(map)) {
 396                 /* for build_id+offset, pop a bucket before slow cmp */
 397                 new_bucket = (struct stack_map_bucket *)
 398                         pcpu_freelist_pop(&smap->freelist);
 399                 if (unlikely(!new_bucket))
 400                         return -ENOMEM;
 401                 new_bucket->nr = trace_nr;
 402                 stack_map_get_build_id_offset(
 403                         (struct bpf_stack_build_id *)new_bucket->data,
 404                         ips, trace_nr, user);
 405                 trace_len = trace_nr * sizeof(struct bpf_stack_build_id);
 406                 if (hash_matches && bucket->nr == trace_nr &&
 407                     memcmp(bucket->data, new_bucket->data, trace_len) == 0) {
 408                         pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
 409                         return id;
 410                 }
 411                 if (bucket && !(flags & BPF_F_REUSE_STACKID)) {
 412                         pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
 413                         return -EEXIST;
 414                 }
 415         } else {
 416                 if (hash_matches && bucket->nr == trace_nr &&
 417                     memcmp(bucket->data, ips, trace_len) == 0)
 418                         return id;
 419                 if (bucket && !(flags & BPF_F_REUSE_STACKID))
 420                         return -EEXIST;
 421
 422                 new_bucket = (struct stack_map_bucket *)
 423                         pcpu_freelist_pop(&smap->freelist);
 424                 if (unlikely(!new_bucket))
 425                         return -ENOMEM;
 426                 memcpy(new_bucket->data, ips, trace_len);
 427         }
 428
 429         new_bucket->hash = hash;
 430         new_bucket->nr = trace_nr;
 431
 432         old_bucket = xchg(&smap->buckets[id], new_bucket);
 433         if (old_bucket)
 434                 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
 435         return id;
 436 }
 437
 438 const struct bpf_func_proto bpf_get_stackid_proto = {
 439         .func           = bpf_get_stackid,
 440         .gpl_only       = true,
 441         .ret_type       = RET_INTEGER,
 442         .arg1_type      = ARG_PTR_TO_CTX,
 443         .arg2_type      = ARG_CONST_MAP_PTR,
 444         .arg3_type      = ARG_ANYTHING,
 445 };
 446
 447 BPF_CALL_4(bpf_get_stack, struct pt_regs *, regs, void *, buf, u32, size,
 448            u64, flags)
 449 {
 450         u32 init_nr, trace_nr, copy_len, elem_size, num_elem;
 451         bool user_build_id = flags & BPF_F_USER_BUILD_ID;
 452         u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
 453         bool user = flags & BPF_F_USER_STACK;
 454         struct perf_callchain_entry *trace;
 455         bool kernel = !user;
 456         int err = -EINVAL;
 457         u64 *ips;
 458
 459         if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
 460                                BPF_F_USER_BUILD_ID)))
 461                 goto clear;
 462         if (kernel && user_build_id)
 463                 goto clear;
 464
 465         elem_size = (user && user_build_id) ? sizeof(struct bpf_stack_build_id)
 466                                             : sizeof(u64);
 467         if (unlikely(size % elem_size))
 468                 goto clear;
 469
 470         num_elem = size / elem_size;
 471         if (sysctl_perf_event_max_stack < num_elem)
 472                 init_nr = 0;
 473         else
 474                 init_nr = sysctl_perf_event_max_stack - num_elem;
 475         trace = get_perf_callchain(regs, init_nr, kernel, user,
 476                                    sysctl_perf_event_max_stack, false, false);
 477         if (unlikely(!trace))
 478                 goto err_fault;
 479
 480         trace_nr = trace->nr - init_nr;
 481         if (trace_nr < skip)
 482                 goto err_fault;
 483
 484         trace_nr -= skip;
 485         trace_nr = (trace_nr <= num_elem) ? trace_nr : num_elem;
 486         copy_len = trace_nr * elem_size;
 487         ips = trace->ip + skip + init_nr;
 488         if (user && user_build_id)
 489                 stack_map_get_build_id_offset(buf, ips, trace_nr, user);
 490         else
 491                 memcpy(buf, ips, copy_len);
 492
 493         if (size > copy_len)
 494                 memset(buf + copy_len, 0, size - copy_len);
 495         return copy_len;
 496
 497 err_fault:
 498         err = -EFAULT;
 499 clear:
 500         memset(buf, 0, size);
 501         return err;
 502 }
 503
 504 const struct bpf_func_proto bpf_get_stack_proto = {
 505         .func           = bpf_get_stack,
 506         .gpl_only       = true,
 507         .ret_type       = RET_INTEGER,
 508         .arg1_type      = ARG_PTR_TO_CTX,
 509         .arg2_type      = ARG_PTR_TO_UNINIT_MEM,
 510         .arg3_type      = ARG_CONST_SIZE_OR_ZERO,
 511         .arg4_type      = ARG_ANYTHING,
 512 };
 513
 514 /* Called from eBPF program */
 515 static void *stack_map_lookup_elem(struct bpf_map *map, void *key)
 516 {
 517         return ERR_PTR(-EOPNOTSUPP);
 518 }
 519
 520 /* Called from syscall */
 521 int bpf_stackmap_copy(struct bpf_map *map, void *key, void *value)
 522 {
 523         struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
 524         struct stack_map_bucket *bucket, *old_bucket;
 525         u32 id = *(u32 *)key, trace_len;
 526
 527         if (unlikely(id >= smap->n_buckets))
 528                 return -ENOENT;
 529
 530         bucket = xchg(&smap->buckets[id], NULL);
 531         if (!bucket)
 532                 return -ENOENT;
 533
 534         trace_len = bucket->nr * stack_map_data_size(map);
 535         memcpy(value, bucket->data, trace_len);
 536         memset(value + trace_len, 0, map->value_size - trace_len);
 537
 538         old_bucket = xchg(&smap->buckets[id], bucket);
 539         if (old_bucket)
 540                 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
 541         return 0;
 542 }
 543
 544 static int stack_map_get_next_key(struct bpf_map *map, void *key,
 545                                   void *next_key)
 546 {
 547         struct bpf_stack_map *smap = container_of(map,
 548                                                   struct bpf_stack_map, map);
 549         u32 id;
 550
 551         WARN_ON_ONCE(!rcu_read_lock_held());
 552
 553         if (!key) {
 554                 id = 0;
 555         } else {
 556                 id = *(u32 *)key;
 557                 if (id >= smap->n_buckets || !smap->buckets[id])
 558                         id = 0;
 559                 else
 560                         id++;
 561         }
 562
 563         while (id < smap->n_buckets && !smap->buckets[id])
 564                 id++;
 565
 566         if (id >= smap->n_buckets)
 567                 return -ENOENT;
 568
 569         *(u32 *)next_key = id;
 570         return 0;
 571 }
 572
 573 static int stack_map_update_elem(struct bpf_map *map, void *key, void *value,
 574                                  u64 map_flags)
 575 {
 576         return -EINVAL;
 577 }
 578
 579 /* Called from syscall or from eBPF program */
 580 static int stack_map_delete_elem(struct bpf_map *map, void *key)
 581 {
 582         struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
 583         struct stack_map_bucket *old_bucket;
 584         u32 id = *(u32 *)key;
 585
 586         if (unlikely(id >= smap->n_buckets))
 587                 return -E2BIG;
 588
 589         old_bucket = xchg(&smap->buckets[id], NULL);
 590         if (old_bucket) {
 591                 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
 592                 return 0;
 593         } else {
 594                 return -ENOENT;
 595         }
 596 }
 597
 598 /* Called when map->refcnt goes to zero, either from workqueue or from syscall */
 599 static void stack_map_free(struct bpf_map *map)
 600 {
 601         struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
 602
 603         /* wait for bpf programs to complete before freeing stack map */
 604         synchronize_rcu();
 605
 606         bpf_map_area_free(smap->elems);
 607         pcpu_freelist_destroy(&smap->freelist);
 608         bpf_map_area_free(smap);
 609         put_callchain_buffers();
 610 }
 611
 612 const struct bpf_map_ops stack_trace_map_ops = {
 613         .map_alloc = stack_map_alloc,
 614         .map_free = stack_map_free,
 615         .map_get_next_key = stack_map_get_next_key,
 616         .map_lookup_elem = stack_map_lookup_elem,
 617         .map_update_elem = stack_map_update_elem,
 618         .map_delete_elem = stack_map_delete_elem,
 619         .map_check_btf = map_check_no_btf,
 620 };
 621
 622 static int __init stack_map_init(void)
 623 {
 624         int cpu;
 625         struct stack_map_irq_work *work;
 626
 627         for_each_possible_cpu(cpu) {
 628                 work = per_cpu_ptr(&up_read_work, cpu);
 629                 init_irq_work(&work->irq_work, do_up_read);
 630         }
 631         return 0;
 632 }
 633 subsys_initcall(stack_map_init);