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_non_owner(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 > 0 &&
 184                     nhdr->n_descsz <= BPF_BUILD_ID_SIZE) {
 185                         memcpy(build_id,
 186                                note_start + note_offs +
 187                                ALIGN(sizeof("GNU"), 4) + sizeof(Elf32_Nhdr),
 188                                nhdr->n_descsz);
 189                         memset(build_id + nhdr->n_descsz, 0,
 190                                BPF_BUILD_ID_SIZE - nhdr->n_descsz);
 191                         return 0;
 192                 }
 193                 new_offs = note_offs + sizeof(Elf32_Nhdr) +
 194                         ALIGN(nhdr->n_namesz, 4) + ALIGN(nhdr->n_descsz, 4);
 195                 if (new_offs <= note_offs)  /* overflow */
 196                         break;
 197                 note_offs = new_offs;
 198         }
 199         return -EINVAL;
 200 }
 201
 202 /* Parse build ID from 32-bit ELF */
 203 static int stack_map_get_build_id_32(void *page_addr,
 204                                      unsigned char *build_id)
 205 {
 206         Elf32_Ehdr *ehdr = (Elf32_Ehdr *)page_addr;
 207         Elf32_Phdr *phdr;
 208         int i;
 209
 210         /* only supports phdr that fits in one page */
 211         if (ehdr->e_phnum >
 212             (PAGE_SIZE - sizeof(Elf32_Ehdr)) / sizeof(Elf32_Phdr))
 213                 return -EINVAL;
 214
 215         phdr = (Elf32_Phdr *)(page_addr + sizeof(Elf32_Ehdr));
 216
 217         for (i = 0; i < ehdr->e_phnum; ++i)
 218                 if (phdr[i].p_type == PT_NOTE)
 219                         return stack_map_parse_build_id(page_addr, build_id,
 220                                         page_addr + phdr[i].p_offset,
 221                                         phdr[i].p_filesz);
 222         return -EINVAL;
 223 }
 224
 225 /* Parse build ID from 64-bit ELF */
 226 static int stack_map_get_build_id_64(void *page_addr,
 227                                      unsigned char *build_id)
 228 {
 229         Elf64_Ehdr *ehdr = (Elf64_Ehdr *)page_addr;
 230         Elf64_Phdr *phdr;
 231         int i;
 232
 233         /* only supports phdr that fits in one page */
 234         if (ehdr->e_phnum >
 235             (PAGE_SIZE - sizeof(Elf64_Ehdr)) / sizeof(Elf64_Phdr))
 236                 return -EINVAL;
 237
 238         phdr = (Elf64_Phdr *)(page_addr + sizeof(Elf64_Ehdr));
 239
 240         for (i = 0; i < ehdr->e_phnum; ++i)
 241                 if (phdr[i].p_type == PT_NOTE)
 242                         return stack_map_parse_build_id(page_addr, build_id,
 243                                         page_addr + phdr[i].p_offset,
 244                                         phdr[i].p_filesz);
 245         return -EINVAL;
 246 }
 247
 248 /* Parse build ID of ELF file mapped to vma */
 249 static int stack_map_get_build_id(struct vm_area_struct *vma,
 250                                   unsigned char *build_id)
 251 {
 252         Elf32_Ehdr *ehdr;
 253         struct page *page;
 254         void *page_addr;
 255         int ret;
 256
 257         /* only works for page backed storage  */
 258         if (!vma->vm_file)
 259                 return -EINVAL;
 260
 261         page = find_get_page(vma->vm_file->f_mapping, 0);
 262         if (!page)
 263                 return -EFAULT; /* page not mapped */
 264
 265         ret = -EINVAL;
 266         page_addr = kmap_atomic(page);
 267         ehdr = (Elf32_Ehdr *)page_addr;
 268
 269         /* compare magic x7f "ELF" */
 270         if (memcmp(ehdr->e_ident, ELFMAG, SELFMAG) != 0)
 271                 goto out;
 272
 273         /* only support executable file and shared object file */
 274         if (ehdr->e_type != ET_EXEC && ehdr->e_type != ET_DYN)
 275                 goto out;
 276
 277         if (ehdr->e_ident[EI_CLASS] == ELFCLASS32)
 278                 ret = stack_map_get_build_id_32(page_addr, build_id);
 279         else if (ehdr->e_ident[EI_CLASS] == ELFCLASS64)
 280                 ret = stack_map_get_build_id_64(page_addr, build_id);
 281 out:
 282         kunmap_atomic(page_addr);
 283         put_page(page);
 284         return ret;
 285 }
 286
 287 static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
 288                                           u64 *ips, u32 trace_nr, bool user)
 289 {
 290         int i;
 291         struct vm_area_struct *vma;
 292         bool irq_work_busy = false;
 293         struct stack_map_irq_work *work = NULL;
 294
 295         if (in_nmi()) {
 296                 work = this_cpu_ptr(&up_read_work);
 297                 if (work->irq_work.flags & IRQ_WORK_BUSY)
 298                         /* cannot queue more up_read, fallback */
 299                         irq_work_busy = true;
 300         }
 301
 302         /*
 303          * We cannot do up_read() in nmi context. To do build_id lookup
 304          * in nmi context, we need to run up_read() in irq_work. We use
 305          * a percpu variable to do the irq_work. If the irq_work is
 306          * already used by another lookup, we fall back to report ips.
 307          *
 308          * Same fallback is used for kernel stack (!user) on a stackmap
 309          * with build_id.
 310          */
 311         if (!user || !current || !current->mm || irq_work_busy ||
 312             down_read_trylock(&current->mm->mmap_sem) == 0) {
 313                 /* cannot access current->mm, fall back to ips */
 314                 for (i = 0; i < trace_nr; i++) {
 315                         id_offs[i].status = BPF_STACK_BUILD_ID_IP;
 316                         id_offs[i].ip = ips[i];
 317                         memset(id_offs[i].build_id, 0, BPF_BUILD_ID_SIZE);
 318                 }
 319                 return;
 320         }
 321
 322         for (i = 0; i < trace_nr; i++) {
 323                 vma = find_vma(current->mm, ips[i]);
 324                 if (!vma || stack_map_get_build_id(vma, id_offs[i].build_id)) {
 325                         /* per entry fall back to ips */
 326                         id_offs[i].status = BPF_STACK_BUILD_ID_IP;
 327                         id_offs[i].ip = ips[i];
 328                         memset(id_offs[i].build_id, 0, BPF_BUILD_ID_SIZE);
 329                         continue;
 330                 }
 331                 id_offs[i].offset = (vma->vm_pgoff << PAGE_SHIFT) + ips[i]
 332                         - vma->vm_start;
 333                 id_offs[i].status = BPF_STACK_BUILD_ID_VALID;
 334         }
 335
 336         if (!work) {
 337                 up_read(&current->mm->mmap_sem);
 338         } else {
 339                 work->sem = &current->mm->mmap_sem;
 340                 irq_work_queue(&work->irq_work);
 341                 /*
 342                  * The irq_work will release the mmap_sem with
 343                  * up_read_non_owner(). The rwsem_release() is called
 344                  * here to release the lock from lockdep's perspective.
 345                  */
 346                 rwsem_release(&current->mm->mmap_sem.dep_map, 1, _RET_IP_);
 347         }
 348 }
 349
 350 BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map,
 351            u64, flags)
 352 {
 353         struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
 354         struct perf_callchain_entry *trace;
 355         struct stack_map_bucket *bucket, *new_bucket, *old_bucket;
 356         u32 max_depth = map->value_size / stack_map_data_size(map);
 357         /* stack_map_alloc() checks that max_depth <= sysctl_perf_event_max_stack */
 358         u32 init_nr = sysctl_perf_event_max_stack - max_depth;
 359         u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
 360         u32 hash, id, trace_nr, trace_len;
 361         bool user = flags & BPF_F_USER_STACK;
 362         bool kernel = !user;
 363         u64 *ips;
 364         bool hash_matches;
 365
 366         if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
 367                                BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
 368                 return -EINVAL;
 369
 370         trace = get_perf_callchain(regs, init_nr, kernel, user,
 371                                    sysctl_perf_event_max_stack, false, false);
 372
 373         if (unlikely(!trace))
 374                 /* couldn't fetch the stack trace */
 375                 return -EFAULT;
 376
 377         /* get_perf_callchain() guarantees that trace->nr >= init_nr
 378          * and trace-nr <= sysctl_perf_event_max_stack, so trace_nr <= max_depth
 379          */
 380         trace_nr = trace->nr - init_nr;
 381
 382         if (trace_nr <= skip)
 383                 /* skipping more than usable stack trace */
 384                 return -EFAULT;
 385
 386         trace_nr -= skip;
 387         trace_len = trace_nr * sizeof(u64);
 388         ips = trace->ip + skip + init_nr;
 389         hash = jhash2((u32 *)ips, trace_len / sizeof(u32), 0);
 390         id = hash & (smap->n_buckets - 1);
 391         bucket = READ_ONCE(smap->buckets[id]);
 392
 393         hash_matches = bucket && bucket->hash == hash;
 394         /* fast cmp */
 395         if (hash_matches && flags & BPF_F_FAST_STACK_CMP)
 396                 return id;
 397
 398         if (stack_map_use_build_id(map)) {
 399                 /* for build_id+offset, pop a bucket before slow cmp */
 400                 new_bucket = (struct stack_map_bucket *)
 401                         pcpu_freelist_pop(&smap->freelist);
 402                 if (unlikely(!new_bucket))
 403                         return -ENOMEM;
 404                 new_bucket->nr = trace_nr;
 405                 stack_map_get_build_id_offset(
 406                         (struct bpf_stack_build_id *)new_bucket->data,
 407                         ips, trace_nr, user);
 408                 trace_len = trace_nr * sizeof(struct bpf_stack_build_id);
 409                 if (hash_matches && bucket->nr == trace_nr &&
 410                     memcmp(bucket->data, new_bucket->data, trace_len) == 0) {
 411                         pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
 412                         return id;
 413                 }
 414                 if (bucket && !(flags & BPF_F_REUSE_STACKID)) {
 415                         pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
 416                         return -EEXIST;
 417                 }
 418         } else {
 419                 if (hash_matches && bucket->nr == trace_nr &&
 420                     memcmp(bucket->data, ips, trace_len) == 0)
 421                         return id;
 422                 if (bucket && !(flags & BPF_F_REUSE_STACKID))
 423                         return -EEXIST;
 424
 425                 new_bucket = (struct stack_map_bucket *)
 426                         pcpu_freelist_pop(&smap->freelist);
 427                 if (unlikely(!new_bucket))
 428                         return -ENOMEM;
 429                 memcpy(new_bucket->data, ips, trace_len);
 430         }
 431
 432         new_bucket->hash = hash;
 433         new_bucket->nr = trace_nr;
 434
 435         old_bucket = xchg(&smap->buckets[id], new_bucket);
 436         if (old_bucket)
 437                 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
 438         return id;
 439 }
 440
 441 const struct bpf_func_proto bpf_get_stackid_proto = {
 442         .func           = bpf_get_stackid,
 443         .gpl_only       = true,
 444         .ret_type       = RET_INTEGER,
 445         .arg1_type      = ARG_PTR_TO_CTX,
 446         .arg2_type      = ARG_CONST_MAP_PTR,
 447         .arg3_type      = ARG_ANYTHING,
 448 };
 449
 450 BPF_CALL_4(bpf_get_stack, struct pt_regs *, regs, void *, buf, u32, size,
 451            u64, flags)
 452 {
 453         u32 init_nr, trace_nr, copy_len, elem_size, num_elem;
 454         bool user_build_id = flags & BPF_F_USER_BUILD_ID;
 455         u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
 456         bool user = flags & BPF_F_USER_STACK;
 457         struct perf_callchain_entry *trace;
 458         bool kernel = !user;
 459         int err = -EINVAL;
 460         u64 *ips;
 461
 462         if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
 463                                BPF_F_USER_BUILD_ID)))
 464                 goto clear;
 465         if (kernel && user_build_id)
 466                 goto clear;
 467
 468         elem_size = (user && user_build_id) ? sizeof(struct bpf_stack_build_id)
 469                                             : sizeof(u64);
 470         if (unlikely(size % elem_size))
 471                 goto clear;
 472
 473         num_elem = size / elem_size;
 474         if (sysctl_perf_event_max_stack < num_elem)
 475                 init_nr = 0;
 476         else
 477                 init_nr = sysctl_perf_event_max_stack - num_elem;
 478         trace = get_perf_callchain(regs, init_nr, kernel, user,
 479                                    sysctl_perf_event_max_stack, false, false);
 480         if (unlikely(!trace))
 481                 goto err_fault;
 482
 483         trace_nr = trace->nr - init_nr;
 484         if (trace_nr < skip)
 485                 goto err_fault;
 486
 487         trace_nr -= skip;
 488         trace_nr = (trace_nr <= num_elem) ? trace_nr : num_elem;
 489         copy_len = trace_nr * elem_size;
 490         ips = trace->ip + skip + init_nr;
 491         if (user && user_build_id)
 492                 stack_map_get_build_id_offset(buf, ips, trace_nr, user);
 493         else
 494                 memcpy(buf, ips, copy_len);
 495
 496         if (size > copy_len)
 497                 memset(buf + copy_len, 0, size - copy_len);
 498         return copy_len;
 499
 500 err_fault:
 501         err = -EFAULT;
 502 clear:
 503         memset(buf, 0, size);
 504         return err;
 505 }
 506
 507 const struct bpf_func_proto bpf_get_stack_proto = {
 508         .func           = bpf_get_stack,
 509         .gpl_only       = true,
 510         .ret_type       = RET_INTEGER,
 511         .arg1_type      = ARG_PTR_TO_CTX,
 512         .arg2_type      = ARG_PTR_TO_UNINIT_MEM,
 513         .arg3_type      = ARG_CONST_SIZE_OR_ZERO,
 514         .arg4_type      = ARG_ANYTHING,
 515 };
 516
 517 /* Called from eBPF program */
 518 static void *stack_map_lookup_elem(struct bpf_map *map, void *key)
 519 {
 520         return ERR_PTR(-EOPNOTSUPP);
 521 }
 522
 523 /* Called from syscall */
 524 int bpf_stackmap_copy(struct bpf_map *map, void *key, void *value)
 525 {
 526         struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
 527         struct stack_map_bucket *bucket, *old_bucket;
 528         u32 id = *(u32 *)key, trace_len;
 529
 530         if (unlikely(id >= smap->n_buckets))
 531                 return -ENOENT;
 532
 533         bucket = xchg(&smap->buckets[id], NULL);
 534         if (!bucket)
 535                 return -ENOENT;
 536
 537         trace_len = bucket->nr * stack_map_data_size(map);
 538         memcpy(value, bucket->data, trace_len);
 539         memset(value + trace_len, 0, map->value_size - trace_len);
 540
 541         old_bucket = xchg(&smap->buckets[id], bucket);
 542         if (old_bucket)
 543                 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
 544         return 0;
 545 }
 546
 547 static int stack_map_get_next_key(struct bpf_map *map, void *key,
 548                                   void *next_key)
 549 {
 550         struct bpf_stack_map *smap = container_of(map,
 551                                                   struct bpf_stack_map, map);
 552         u32 id;
 553
 554         WARN_ON_ONCE(!rcu_read_lock_held());
 555
 556         if (!key) {
 557                 id = 0;
 558         } else {
 559                 id = *(u32 *)key;
 560                 if (id >= smap->n_buckets || !smap->buckets[id])
 561                         id = 0;
 562                 else
 563                         id++;
 564         }
 565
 566         while (id < smap->n_buckets && !smap->buckets[id])
 567                 id++;
 568
 569         if (id >= smap->n_buckets)
 570                 return -ENOENT;
 571
 572         *(u32 *)next_key = id;
 573         return 0;
 574 }
 575
 576 static int stack_map_update_elem(struct bpf_map *map, void *key, void *value,
 577                                  u64 map_flags)
 578 {
 579         return -EINVAL;
 580 }
 581
 582 /* Called from syscall or from eBPF program */
 583 static int stack_map_delete_elem(struct bpf_map *map, void *key)
 584 {
 585         struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
 586         struct stack_map_bucket *old_bucket;
 587         u32 id = *(u32 *)key;
 588
 589         if (unlikely(id >= smap->n_buckets))
 590                 return -E2BIG;
 591
 592         old_bucket = xchg(&smap->buckets[id], NULL);
 593         if (old_bucket) {
 594                 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
 595                 return 0;
 596         } else {
 597                 return -ENOENT;
 598         }
 599 }
 600
 601 /* Called when map->refcnt goes to zero, either from workqueue or from syscall */
 602 static void stack_map_free(struct bpf_map *map)
 603 {
 604         struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
 605
 606         /* wait for bpf programs to complete before freeing stack map */
 607         synchronize_rcu();
 608
 609         bpf_map_area_free(smap->elems);
 610         pcpu_freelist_destroy(&smap->freelist);
 611         bpf_map_area_free(smap);
 612         put_callchain_buffers();
 613 }
 614
 615 const struct bpf_map_ops stack_trace_map_ops = {
 616         .map_alloc = stack_map_alloc,
 617         .map_free = stack_map_free,
 618         .map_get_next_key = stack_map_get_next_key,
 619         .map_lookup_elem = stack_map_lookup_elem,
 620         .map_update_elem = stack_map_update_elem,
 621         .map_delete_elem = stack_map_delete_elem,
 622         .map_check_btf = map_check_no_btf,
 623 };
 624
 625 static int __init stack_map_init(void)
 626 {
 627         int cpu;
 628         struct stack_map_irq_work *work;
 629
 630         for_each_possible_cpu(cpu) {
 631                 work = per_cpu_ptr(&up_read_work, cpu);
 632                 init_irq_work(&work->irq_work, do_up_read);
 633         }
 634         return 0;
 635 }
 636 subsys_initcall(stack_map_init);