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/kernel.h>
   8 #include <linux/stacktrace.h>
   9 #include <linux/perf_event.h>
  10 #include <linux/btf_ids.h>
  11 #include <linux/buildid.h>
  12 #include "percpu_freelist.h"
  13 #include "mmap_unlock_work.h"
  14
  15 #define STACK_CREATE_FLAG_MASK                                  \
  16         (BPF_F_NUMA_NODE | BPF_F_RDONLY | BPF_F_WRONLY |        \
  17          BPF_F_STACK_BUILD_ID)
  18
  19 struct stack_map_bucket {
  20         struct pcpu_freelist_node fnode;
  21         u32 hash;
  22         u32 nr;
  23         u64 data[];
  24 };
  25
  26 struct bpf_stack_map {
  27         struct bpf_map map;
  28         void *elems;
  29         struct pcpu_freelist freelist;
  30         u32 n_buckets;
  31         struct stack_map_bucket *buckets[];
  32 };
  33
  34 static inline bool stack_map_use_build_id(struct bpf_map *map)
  35 {
  36         return (map->map_flags & BPF_F_STACK_BUILD_ID);
  37 }
  38
  39 static inline int stack_map_data_size(struct bpf_map *map)
  40 {
  41         return stack_map_use_build_id(map) ?
  42                 sizeof(struct bpf_stack_build_id) : sizeof(u64);
  43 }
  44
  45 static int prealloc_elems_and_freelist(struct bpf_stack_map *smap)
  46 {
  47         u64 elem_size = sizeof(struct stack_map_bucket) +
  48                         (u64)smap->map.value_size;
  49         int err;
  50
  51         smap->elems = bpf_map_area_alloc(elem_size * smap->map.max_entries,
  52                                          smap->map.numa_node);
  53         if (!smap->elems)
  54                 return -ENOMEM;
  55
  56         err = pcpu_freelist_init(&smap->freelist);
  57         if (err)
  58                 goto free_elems;
  59
  60         pcpu_freelist_populate(&smap->freelist, smap->elems, elem_size,
  61                                smap->map.max_entries);
  62         return 0;
  63
  64 free_elems:
  65         bpf_map_area_free(smap->elems);
  66         return err;
  67 }
  68
  69 /* Called from syscall */
  70 static struct bpf_map *stack_map_alloc(union bpf_attr *attr)
  71 {
  72         u32 value_size = attr->value_size;
  73         struct bpf_stack_map *smap;
  74         u64 cost, n_buckets;
  75         int err;
  76
  77         if (!bpf_capable())
  78                 return ERR_PTR(-EPERM);
  79
  80         if (attr->map_flags & ~STACK_CREATE_FLAG_MASK)
  81                 return ERR_PTR(-EINVAL);
  82
  83         /* check sanity of attributes */
  84         if (attr->max_entries == 0 || attr->key_size != 4 ||
  85             value_size < 8 || value_size % 8)
  86                 return ERR_PTR(-EINVAL);
  87
  88         BUILD_BUG_ON(sizeof(struct bpf_stack_build_id) % sizeof(u64));
  89         if (attr->map_flags & BPF_F_STACK_BUILD_ID) {
  90                 if (value_size % sizeof(struct bpf_stack_build_id) ||
  91                     value_size / sizeof(struct bpf_stack_build_id)
  92                     > sysctl_perf_event_max_stack)
  93                         return ERR_PTR(-EINVAL);
  94         } else if (value_size / 8 > sysctl_perf_event_max_stack)
  95                 return ERR_PTR(-EINVAL);
  96
  97         /* hash table size must be power of 2 */
  98         n_buckets = roundup_pow_of_two(attr->max_entries);
  99         if (!n_buckets)
 100                 return ERR_PTR(-E2BIG);
 101
 102         cost = n_buckets * sizeof(struct stack_map_bucket *) + sizeof(*smap);
 103         cost += n_buckets * (value_size + sizeof(struct stack_map_bucket));
 104         smap = bpf_map_area_alloc(cost, bpf_map_attr_numa_node(attr));
 105         if (!smap)
 106                 return ERR_PTR(-ENOMEM);
 107
 108         bpf_map_init_from_attr(&smap->map, attr);
 109         smap->map.value_size = value_size;
 110         smap->n_buckets = n_buckets;
 111
 112         err = get_callchain_buffers(sysctl_perf_event_max_stack);
 113         if (err)
 114                 goto free_smap;
 115
 116         err = prealloc_elems_and_freelist(smap);
 117         if (err)
 118                 goto put_buffers;
 119
 120         return &smap->map;
 121
 122 put_buffers:
 123         put_callchain_buffers();
 124 free_smap:
 125         bpf_map_area_free(smap);
 126         return ERR_PTR(err);
 127 }
 128
 129 static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
 130                                           u64 *ips, u32 trace_nr, bool user)
 131 {
 132         int i;
 133         struct mmap_unlock_irq_work *work = NULL;
 134         bool irq_work_busy = bpf_mmap_unlock_get_irq_work(&work);
 135         struct vm_area_struct *vma, *prev_vma = NULL;
 136         const char *prev_build_id;
 137
 138         /* If the irq_work is in use, fall back to report ips. Same
 139          * fallback is used for kernel stack (!user) on a stackmap with
 140          * build_id.
 141          */
 142         if (!user || !current || !current->mm || irq_work_busy ||
 143             !mmap_read_trylock(current->mm)) {
 144                 /* cannot access current->mm, fall back to ips */
 145                 for (i = 0; i < trace_nr; i++) {
 146                         id_offs[i].status = BPF_STACK_BUILD_ID_IP;
 147                         id_offs[i].ip = ips[i];
 148                         memset(id_offs[i].build_id, 0, BUILD_ID_SIZE_MAX);
 149                 }
 150                 return;
 151         }
 152
 153         for (i = 0; i < trace_nr; i++) {
 154                 if (range_in_vma(prev_vma, ips[i], ips[i])) {
 155                         vma = prev_vma;
 156                         memcpy(id_offs[i].build_id, prev_build_id,
 157                                BUILD_ID_SIZE_MAX);
 158                         goto build_id_valid;
 159                 }
 160                 vma = find_vma(current->mm, ips[i]);
 161                 if (!vma || build_id_parse(vma, id_offs[i].build_id, NULL)) {
 162                         /* per entry fall back to ips */
 163                         id_offs[i].status = BPF_STACK_BUILD_ID_IP;
 164                         id_offs[i].ip = ips[i];
 165                         memset(id_offs[i].build_id, 0, BUILD_ID_SIZE_MAX);
 166                         continue;
 167                 }
 168 build_id_valid:
 169                 id_offs[i].offset = (vma->vm_pgoff << PAGE_SHIFT) + ips[i]
 170                         - vma->vm_start;
 171                 id_offs[i].status = BPF_STACK_BUILD_ID_VALID;
 172                 prev_vma = vma;
 173                 prev_build_id = id_offs[i].build_id;
 174         }
 175         bpf_mmap_unlock_mm(work, current->mm);
 176 }
 177
 178 static struct perf_callchain_entry *
 179 get_callchain_entry_for_task(struct task_struct *task, u32 max_depth)
 180 {
 181 #ifdef CONFIG_STACKTRACE
 182         struct perf_callchain_entry *entry;
 183         int rctx;
 184
 185         entry = get_callchain_entry(&rctx);
 186
 187         if (!entry)
 188                 return NULL;
 189
 190         entry->nr = stack_trace_save_tsk(task, (unsigned long *)entry->ip,
 191                                          max_depth, 0);
 192
 193         /* stack_trace_save_tsk() works on unsigned long array, while
 194          * perf_callchain_entry uses u64 array. For 32-bit systems, it is
 195          * necessary to fix this mismatch.
 196          */
 197         if (__BITS_PER_LONG != 64) {
 198                 unsigned long *from = (unsigned long *) entry->ip;
 199                 u64 *to = entry->ip;
 200                 int i;
 201
 202                 /* copy data from the end to avoid using extra buffer */
 203                 for (i = entry->nr - 1; i >= 0; i--)
 204                         to[i] = (u64)(from[i]);
 205         }
 206
 207         put_callchain_entry(rctx);
 208
 209         return entry;
 210 #else /* CONFIG_STACKTRACE */
 211         return NULL;
 212 #endif
 213 }
 214
 215 static long __bpf_get_stackid(struct bpf_map *map,
 216                               struct perf_callchain_entry *trace, u64 flags)
 217 {
 218         struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
 219         struct stack_map_bucket *bucket, *new_bucket, *old_bucket;
 220         u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
 221         u32 hash, id, trace_nr, trace_len;
 222         bool user = flags & BPF_F_USER_STACK;
 223         u64 *ips;
 224         bool hash_matches;
 225
 226         if (trace->nr <= skip)
 227                 /* skipping more than usable stack trace */
 228                 return -EFAULT;
 229
 230         trace_nr = trace->nr - skip;
 231         trace_len = trace_nr * sizeof(u64);
 232         ips = trace->ip + skip;
 233         hash = jhash2((u32 *)ips, trace_len / sizeof(u32), 0);
 234         id = hash & (smap->n_buckets - 1);
 235         bucket = READ_ONCE(smap->buckets[id]);
 236
 237         hash_matches = bucket && bucket->hash == hash;
 238         /* fast cmp */
 239         if (hash_matches && flags & BPF_F_FAST_STACK_CMP)
 240                 return id;
 241
 242         if (stack_map_use_build_id(map)) {
 243                 /* for build_id+offset, pop a bucket before slow cmp */
 244                 new_bucket = (struct stack_map_bucket *)
 245                         pcpu_freelist_pop(&smap->freelist);
 246                 if (unlikely(!new_bucket))
 247                         return -ENOMEM;
 248                 new_bucket->nr = trace_nr;
 249                 stack_map_get_build_id_offset(
 250                         (struct bpf_stack_build_id *)new_bucket->data,
 251                         ips, trace_nr, user);
 252                 trace_len = trace_nr * sizeof(struct bpf_stack_build_id);
 253                 if (hash_matches && bucket->nr == trace_nr &&
 254                     memcmp(bucket->data, new_bucket->data, trace_len) == 0) {
 255                         pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
 256                         return id;
 257                 }
 258                 if (bucket && !(flags & BPF_F_REUSE_STACKID)) {
 259                         pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
 260                         return -EEXIST;
 261                 }
 262         } else {
 263                 if (hash_matches && bucket->nr == trace_nr &&
 264                     memcmp(bucket->data, ips, trace_len) == 0)
 265                         return id;
 266                 if (bucket && !(flags & BPF_F_REUSE_STACKID))
 267                         return -EEXIST;
 268
 269                 new_bucket = (struct stack_map_bucket *)
 270                         pcpu_freelist_pop(&smap->freelist);
 271                 if (unlikely(!new_bucket))
 272                         return -ENOMEM;
 273                 memcpy(new_bucket->data, ips, trace_len);
 274         }
 275
 276         new_bucket->hash = hash;
 277         new_bucket->nr = trace_nr;
 278
 279         old_bucket = xchg(&smap->buckets[id], new_bucket);
 280         if (old_bucket)
 281                 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
 282         return id;
 283 }
 284
 285 BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map,
 286            u64, flags)
 287 {
 288         u32 max_depth = map->value_size / stack_map_data_size(map);
 289         u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
 290         bool user = flags & BPF_F_USER_STACK;
 291         struct perf_callchain_entry *trace;
 292         bool kernel = !user;
 293
 294         if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
 295                                BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
 296                 return -EINVAL;
 297
 298         max_depth += skip;
 299         if (max_depth > sysctl_perf_event_max_stack)
 300                 max_depth = sysctl_perf_event_max_stack;
 301
 302         trace = get_perf_callchain(regs, 0, kernel, user, max_depth,
 303                                    false, false);
 304
 305         if (unlikely(!trace))
 306                 /* couldn't fetch the stack trace */
 307                 return -EFAULT;
 308
 309         return __bpf_get_stackid(map, trace, flags);
 310 }
 311
 312 const struct bpf_func_proto bpf_get_stackid_proto = {
 313         .func           = bpf_get_stackid,
 314         .gpl_only       = true,
 315         .ret_type       = RET_INTEGER,
 316         .arg1_type      = ARG_PTR_TO_CTX,
 317         .arg2_type      = ARG_CONST_MAP_PTR,
 318         .arg3_type      = ARG_ANYTHING,
 319 };
 320
 321 static __u64 count_kernel_ip(struct perf_callchain_entry *trace)
 322 {
 323         __u64 nr_kernel = 0;
 324
 325         while (nr_kernel < trace->nr) {
 326                 if (trace->ip[nr_kernel] == PERF_CONTEXT_USER)
 327                         break;
 328                 nr_kernel++;
 329         }
 330         return nr_kernel;
 331 }
 332
 333 BPF_CALL_3(bpf_get_stackid_pe, struct bpf_perf_event_data_kern *, ctx,
 334            struct bpf_map *, map, u64, flags)
 335 {
 336         struct perf_event *event = ctx->event;
 337         struct perf_callchain_entry *trace;
 338         bool kernel, user;
 339         __u64 nr_kernel;
 340         int ret;
 341
 342         /* perf_sample_data doesn't have callchain, use bpf_get_stackid */
 343         if (!(event->attr.sample_type & __PERF_SAMPLE_CALLCHAIN_EARLY))
 344                 return bpf_get_stackid((unsigned long)(ctx->regs),
 345                                        (unsigned long) map, flags, 0, 0);
 346
 347         if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
 348                                BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
 349                 return -EINVAL;
 350
 351         user = flags & BPF_F_USER_STACK;
 352         kernel = !user;
 353
 354         trace = ctx->data->callchain;
 355         if (unlikely(!trace))
 356                 return -EFAULT;
 357
 358         nr_kernel = count_kernel_ip(trace);
 359
 360         if (kernel) {
 361                 __u64 nr = trace->nr;
 362
 363                 trace->nr = nr_kernel;
 364                 ret = __bpf_get_stackid(map, trace, flags);
 365
 366                 /* restore nr */
 367                 trace->nr = nr;
 368         } else { /* user */
 369                 u64 skip = flags & BPF_F_SKIP_FIELD_MASK;
 370
 371                 skip += nr_kernel;
 372                 if (skip > BPF_F_SKIP_FIELD_MASK)
 373                         return -EFAULT;
 374
 375                 flags = (flags & ~BPF_F_SKIP_FIELD_MASK) | skip;
 376                 ret = __bpf_get_stackid(map, trace, flags);
 377         }
 378         return ret;
 379 }
 380
 381 const struct bpf_func_proto bpf_get_stackid_proto_pe = {
 382         .func           = bpf_get_stackid_pe,
 383         .gpl_only       = false,
 384         .ret_type       = RET_INTEGER,
 385         .arg1_type      = ARG_PTR_TO_CTX,
 386         .arg2_type      = ARG_CONST_MAP_PTR,
 387         .arg3_type      = ARG_ANYTHING,
 388 };
 389
 390 static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task,
 391                             struct perf_callchain_entry *trace_in,
 392                             void *buf, u32 size, u64 flags)
 393 {
 394         u32 trace_nr, copy_len, elem_size, num_elem, max_depth;
 395         bool user_build_id = flags & BPF_F_USER_BUILD_ID;
 396         u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
 397         bool user = flags & BPF_F_USER_STACK;
 398         struct perf_callchain_entry *trace;
 399         bool kernel = !user;
 400         int err = -EINVAL;
 401         u64 *ips;
 402
 403         if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
 404                                BPF_F_USER_BUILD_ID)))
 405                 goto clear;
 406         if (kernel && user_build_id)
 407                 goto clear;
 408
 409         elem_size = (user && user_build_id) ? sizeof(struct bpf_stack_build_id)
 410                                             : sizeof(u64);
 411         if (unlikely(size % elem_size))
 412                 goto clear;
 413
 414         /* cannot get valid user stack for task without user_mode regs */
 415         if (task && user && !user_mode(regs))
 416                 goto err_fault;
 417
 418         num_elem = size / elem_size;
 419         max_depth = num_elem + skip;
 420         if (sysctl_perf_event_max_stack < max_depth)
 421                 max_depth = sysctl_perf_event_max_stack;
 422
 423         if (trace_in)
 424                 trace = trace_in;
 425         else if (kernel && task)
 426                 trace = get_callchain_entry_for_task(task, max_depth);
 427         else
 428                 trace = get_perf_callchain(regs, 0, kernel, user, max_depth,
 429                                            false, false);
 430         if (unlikely(!trace))
 431                 goto err_fault;
 432
 433         if (trace->nr < skip)
 434                 goto err_fault;
 435
 436         trace_nr = trace->nr - skip;
 437         trace_nr = (trace_nr <= num_elem) ? trace_nr : num_elem;
 438         copy_len = trace_nr * elem_size;
 439
 440         ips = trace->ip + skip;
 441         if (user && user_build_id)
 442                 stack_map_get_build_id_offset(buf, ips, trace_nr, user);
 443         else
 444                 memcpy(buf, ips, copy_len);
 445
 446         if (size > copy_len)
 447                 memset(buf + copy_len, 0, size - copy_len);
 448         return copy_len;
 449
 450 err_fault:
 451         err = -EFAULT;
 452 clear:
 453         memset(buf, 0, size);
 454         return err;
 455 }
 456
 457 BPF_CALL_4(bpf_get_stack, struct pt_regs *, regs, void *, buf, u32, size,
 458            u64, flags)
 459 {
 460         return __bpf_get_stack(regs, NULL, NULL, buf, size, flags);
 461 }
 462
 463 const struct bpf_func_proto bpf_get_stack_proto = {
 464         .func           = bpf_get_stack,
 465         .gpl_only       = true,
 466         .ret_type       = RET_INTEGER,
 467         .arg1_type      = ARG_PTR_TO_CTX,
 468         .arg2_type      = ARG_PTR_TO_UNINIT_MEM,
 469         .arg3_type      = ARG_CONST_SIZE_OR_ZERO,
 470         .arg4_type      = ARG_ANYTHING,
 471 };
 472
 473 BPF_CALL_4(bpf_get_task_stack, struct task_struct *, task, void *, buf,
 474            u32, size, u64, flags)
 475 {
 476         struct pt_regs *regs;
 477         long res = -EINVAL;
 478
 479         if (!try_get_task_stack(task))
 480                 return -EFAULT;
 481
 482         regs = task_pt_regs(task);
 483         if (regs)
 484                 res = __bpf_get_stack(regs, task, NULL, buf, size, flags);
 485         put_task_stack(task);
 486
 487         return res;
 488 }
 489
 490 const struct bpf_func_proto bpf_get_task_stack_proto = {
 491         .func           = bpf_get_task_stack,
 492         .gpl_only       = false,
 493         .ret_type       = RET_INTEGER,
 494         .arg1_type      = ARG_PTR_TO_BTF_ID,
 495         .arg1_btf_id    = &btf_tracing_ids[BTF_TRACING_TYPE_TASK],
 496         .arg2_type      = ARG_PTR_TO_UNINIT_MEM,
 497         .arg3_type      = ARG_CONST_SIZE_OR_ZERO,
 498         .arg4_type      = ARG_ANYTHING,
 499 };
 500
 501 BPF_CALL_4(bpf_get_stack_pe, struct bpf_perf_event_data_kern *, ctx,
 502            void *, buf, u32, size, u64, flags)
 503 {
 504         struct pt_regs *regs = (struct pt_regs *)(ctx->regs);
 505         struct perf_event *event = ctx->event;
 506         struct perf_callchain_entry *trace;
 507         bool kernel, user;
 508         int err = -EINVAL;
 509         __u64 nr_kernel;
 510
 511         if (!(event->attr.sample_type & __PERF_SAMPLE_CALLCHAIN_EARLY))
 512                 return __bpf_get_stack(regs, NULL, NULL, buf, size, flags);
 513
 514         if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
 515                                BPF_F_USER_BUILD_ID)))
 516                 goto clear;
 517
 518         user = flags & BPF_F_USER_STACK;
 519         kernel = !user;
 520
 521         err = -EFAULT;
 522         trace = ctx->data->callchain;
 523         if (unlikely(!trace))
 524                 goto clear;
 525
 526         nr_kernel = count_kernel_ip(trace);
 527
 528         if (kernel) {
 529                 __u64 nr = trace->nr;
 530
 531                 trace->nr = nr_kernel;
 532                 err = __bpf_get_stack(regs, NULL, trace, buf, size, flags);
 533
 534                 /* restore nr */
 535                 trace->nr = nr;
 536         } else { /* user */
 537                 u64 skip = flags & BPF_F_SKIP_FIELD_MASK;
 538
 539                 skip += nr_kernel;
 540                 if (skip > BPF_F_SKIP_FIELD_MASK)
 541                         goto clear;
 542
 543                 flags = (flags & ~BPF_F_SKIP_FIELD_MASK) | skip;
 544                 err = __bpf_get_stack(regs, NULL, trace, buf, size, flags);
 545         }
 546         return err;
 547
 548 clear:
 549         memset(buf, 0, size);
 550         return err;
 551
 552 }
 553
 554 const struct bpf_func_proto bpf_get_stack_proto_pe = {
 555         .func           = bpf_get_stack_pe,
 556         .gpl_only       = true,
 557         .ret_type       = RET_INTEGER,
 558         .arg1_type      = ARG_PTR_TO_CTX,
 559         .arg2_type      = ARG_PTR_TO_UNINIT_MEM,
 560         .arg3_type      = ARG_CONST_SIZE_OR_ZERO,
 561         .arg4_type      = ARG_ANYTHING,
 562 };
 563
 564 /* Called from eBPF program */
 565 static void *stack_map_lookup_elem(struct bpf_map *map, void *key)
 566 {
 567         return ERR_PTR(-EOPNOTSUPP);
 568 }
 569
 570 /* Called from syscall */
 571 int bpf_stackmap_copy(struct bpf_map *map, void *key, void *value)
 572 {
 573         struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
 574         struct stack_map_bucket *bucket, *old_bucket;
 575         u32 id = *(u32 *)key, trace_len;
 576
 577         if (unlikely(id >= smap->n_buckets))
 578                 return -ENOENT;
 579
 580         bucket = xchg(&smap->buckets[id], NULL);
 581         if (!bucket)
 582                 return -ENOENT;
 583
 584         trace_len = bucket->nr * stack_map_data_size(map);
 585         memcpy(value, bucket->data, trace_len);
 586         memset(value + trace_len, 0, map->value_size - trace_len);
 587
 588         old_bucket = xchg(&smap->buckets[id], bucket);
 589         if (old_bucket)
 590                 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
 591         return 0;
 592 }
 593
 594 static int stack_map_get_next_key(struct bpf_map *map, void *key,
 595                                   void *next_key)
 596 {
 597         struct bpf_stack_map *smap = container_of(map,
 598                                                   struct bpf_stack_map, map);
 599         u32 id;
 600
 601         WARN_ON_ONCE(!rcu_read_lock_held());
 602
 603         if (!key) {
 604                 id = 0;
 605         } else {
 606                 id = *(u32 *)key;
 607                 if (id >= smap->n_buckets || !smap->buckets[id])
 608                         id = 0;
 609                 else
 610                         id++;
 611         }
 612
 613         while (id < smap->n_buckets && !smap->buckets[id])
 614                 id++;
 615
 616         if (id >= smap->n_buckets)
 617                 return -ENOENT;
 618
 619         *(u32 *)next_key = id;
 620         return 0;
 621 }
 622
 623 static int stack_map_update_elem(struct bpf_map *map, void *key, void *value,
 624                                  u64 map_flags)
 625 {
 626         return -EINVAL;
 627 }
 628
 629 /* Called from syscall or from eBPF program */
 630 static int stack_map_delete_elem(struct bpf_map *map, void *key)
 631 {
 632         struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
 633         struct stack_map_bucket *old_bucket;
 634         u32 id = *(u32 *)key;
 635
 636         if (unlikely(id >= smap->n_buckets))
 637                 return -E2BIG;
 638
 639         old_bucket = xchg(&smap->buckets[id], NULL);
 640         if (old_bucket) {
 641                 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
 642                 return 0;
 643         } else {
 644                 return -ENOENT;
 645         }
 646 }
 647
 648 /* Called when map->refcnt goes to zero, either from workqueue or from syscall */
 649 static void stack_map_free(struct bpf_map *map)
 650 {
 651         struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
 652
 653         bpf_map_area_free(smap->elems);
 654         pcpu_freelist_destroy(&smap->freelist);
 655         bpf_map_area_free(smap);
 656         put_callchain_buffers();
 657 }
 658
 659 static int stack_trace_map_btf_id;
 660 const struct bpf_map_ops stack_trace_map_ops = {
 661         .map_meta_equal = bpf_map_meta_equal,
 662         .map_alloc = stack_map_alloc,
 663         .map_free = stack_map_free,
 664         .map_get_next_key = stack_map_get_next_key,
 665         .map_lookup_elem = stack_map_lookup_elem,
 666         .map_update_elem = stack_map_update_elem,
 667         .map_delete_elem = stack_map_delete_elem,
 668         .map_check_btf = map_check_no_btf,
 669         .map_btf_name = "bpf_stack_map",
 670         .map_btf_id = &stack_trace_map_btf_id,
 671 };