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/irq_work.h>
  11 #include <linux/btf_ids.h>
  12 #include <linux/buildid.h>
  13 #include "percpu_freelist.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 /* irq_work to run up_read() for build_id lookup in nmi context */
  35 struct stack_map_irq_work {
  36         struct irq_work irq_work;
  37         struct mm_struct *mm;
  38 };
  39
  40 static void do_up_read(struct irq_work *entry)
  41 {
  42         struct stack_map_irq_work *work;
  43
  44         if (WARN_ON_ONCE(IS_ENABLED(CONFIG_PREEMPT_RT)))
  45                 return;
  46
  47         work = container_of(entry, struct stack_map_irq_work, irq_work);
  48         mmap_read_unlock_non_owner(work->mm);
  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         u64 elem_size = sizeof(struct stack_map_bucket) +
  67                         (u64)smap->map.value_size;
  68         int err;
  69
  70         smap->elems = bpf_map_area_alloc(elem_size * smap->map.max_entries,
  71                                          smap->map.numa_node);
  72         if (!smap->elems)
  73                 return -ENOMEM;
  74
  75         err = pcpu_freelist_init(&smap->freelist);
  76         if (err)
  77                 goto free_elems;
  78
  79         pcpu_freelist_populate(&smap->freelist, smap->elems, elem_size,
  80                                smap->map.max_entries);
  81         return 0;
  82
  83 free_elems:
  84         bpf_map_area_free(smap->elems);
  85         return err;
  86 }
  87
  88 /* Called from syscall */
  89 static struct bpf_map *stack_map_alloc(union bpf_attr *attr)
  90 {
  91         u32 value_size = attr->value_size;
  92         struct bpf_stack_map *smap;
  93         u64 cost, n_buckets;
  94         int err;
  95
  96         if (!bpf_capable())
  97                 return ERR_PTR(-EPERM);
  98
  99         if (attr->map_flags & ~STACK_CREATE_FLAG_MASK)
 100                 return ERR_PTR(-EINVAL);
 101
 102         /* check sanity of attributes */
 103         if (attr->max_entries == 0 || attr->key_size != 4 ||
 104             value_size < 8 || value_size % 8)
 105                 return ERR_PTR(-EINVAL);
 106
 107         BUILD_BUG_ON(sizeof(struct bpf_stack_build_id) % sizeof(u64));
 108         if (attr->map_flags & BPF_F_STACK_BUILD_ID) {
 109                 if (value_size % sizeof(struct bpf_stack_build_id) ||
 110                     value_size / sizeof(struct bpf_stack_build_id)
 111                     > sysctl_perf_event_max_stack)
 112                         return ERR_PTR(-EINVAL);
 113         } else if (value_size / 8 > sysctl_perf_event_max_stack)
 114                 return ERR_PTR(-EINVAL);
 115
 116         /* hash table size must be power of 2 */
 117         n_buckets = roundup_pow_of_two(attr->max_entries);
 118         if (!n_buckets)
 119                 return ERR_PTR(-E2BIG);
 120
 121         cost = n_buckets * sizeof(struct stack_map_bucket *) + sizeof(*smap);
 122         smap = bpf_map_area_alloc(cost, bpf_map_attr_numa_node(attr));
 123         if (!smap)
 124                 return ERR_PTR(-ENOMEM);
 125
 126         bpf_map_init_from_attr(&smap->map, attr);
 127         smap->map.value_size = value_size;
 128         smap->n_buckets = n_buckets;
 129
 130         err = get_callchain_buffers(sysctl_perf_event_max_stack);
 131         if (err)
 132                 goto free_smap;
 133
 134         err = prealloc_elems_and_freelist(smap);
 135         if (err)
 136                 goto put_buffers;
 137
 138         return &smap->map;
 139
 140 put_buffers:
 141         put_callchain_buffers();
 142 free_smap:
 143         bpf_map_area_free(smap);
 144         return ERR_PTR(err);
 145 }
 146
 147 static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
 148                                           u64 *ips, u32 trace_nr, bool user)
 149 {
 150         int i;
 151         struct vm_area_struct *vma;
 152         bool irq_work_busy = false;
 153         struct stack_map_irq_work *work = NULL;
 154
 155         if (irqs_disabled()) {
 156                 if (!IS_ENABLED(CONFIG_PREEMPT_RT)) {
 157                         work = this_cpu_ptr(&up_read_work);
 158                         if (irq_work_is_busy(&work->irq_work)) {
 159                                 /* cannot queue more up_read, fallback */
 160                                 irq_work_busy = true;
 161                         }
 162                 } else {
 163                         /*
 164                          * PREEMPT_RT does not allow to trylock mmap sem in
 165                          * interrupt disabled context. Force the fallback code.
 166                          */
 167                         irq_work_busy = true;
 168                 }
 169         }
 170
 171         /*
 172          * We cannot do up_read() when the irq is disabled, because of
 173          * risk to deadlock with rq_lock. To do build_id lookup when the
 174          * irqs are disabled, we need to run up_read() in irq_work. We use
 175          * a percpu variable to do the irq_work. If the irq_work is
 176          * already used by another lookup, we fall back to report ips.
 177          *
 178          * Same fallback is used for kernel stack (!user) on a stackmap
 179          * with build_id.
 180          */
 181         if (!user || !current || !current->mm || irq_work_busy ||
 182             !mmap_read_trylock(current->mm)) {
 183                 /* cannot access current->mm, fall back to ips */
 184                 for (i = 0; i < trace_nr; i++) {
 185                         id_offs[i].status = BPF_STACK_BUILD_ID_IP;
 186                         id_offs[i].ip = ips[i];
 187                         memset(id_offs[i].build_id, 0, BUILD_ID_SIZE_MAX);
 188                 }
 189                 return;
 190         }
 191
 192         for (i = 0; i < trace_nr; i++) {
 193                 vma = find_vma(current->mm, ips[i]);
 194                 if (!vma || build_id_parse(vma, id_offs[i].build_id, NULL)) {
 195                         /* per entry fall back to ips */
 196                         id_offs[i].status = BPF_STACK_BUILD_ID_IP;
 197                         id_offs[i].ip = ips[i];
 198                         memset(id_offs[i].build_id, 0, BUILD_ID_SIZE_MAX);
 199                         continue;
 200                 }
 201                 id_offs[i].offset = (vma->vm_pgoff << PAGE_SHIFT) + ips[i]
 202                         - vma->vm_start;
 203                 id_offs[i].status = BPF_STACK_BUILD_ID_VALID;
 204         }
 205
 206         if (!work) {
 207                 mmap_read_unlock(current->mm);
 208         } else {
 209                 work->mm = current->mm;
 210
 211                 /* The lock will be released once we're out of interrupt
 212                  * context. Tell lockdep that we've released it now so
 213                  * it doesn't complain that we forgot to release it.
 214                  */
 215                 rwsem_release(&current->mm->mmap_lock.dep_map, _RET_IP_);
 216                 irq_work_queue(&work->irq_work);
 217         }
 218 }
 219
 220 static struct perf_callchain_entry *
 221 get_callchain_entry_for_task(struct task_struct *task, u32 max_depth)
 222 {
 223 #ifdef CONFIG_STACKTRACE
 224         struct perf_callchain_entry *entry;
 225         int rctx;
 226
 227         entry = get_callchain_entry(&rctx);
 228
 229         if (!entry)
 230                 return NULL;
 231
 232         entry->nr = stack_trace_save_tsk(task, (unsigned long *)entry->ip,
 233                                          max_depth, 0);
 234
 235         /* stack_trace_save_tsk() works on unsigned long array, while
 236          * perf_callchain_entry uses u64 array. For 32-bit systems, it is
 237          * necessary to fix this mismatch.
 238          */
 239         if (__BITS_PER_LONG != 64) {
 240                 unsigned long *from = (unsigned long *) entry->ip;
 241                 u64 *to = entry->ip;
 242                 int i;
 243
 244                 /* copy data from the end to avoid using extra buffer */
 245                 for (i = entry->nr - 1; i >= 0; i--)
 246                         to[i] = (u64)(from[i]);
 247         }
 248
 249         put_callchain_entry(rctx);
 250
 251         return entry;
 252 #else /* CONFIG_STACKTRACE */
 253         return NULL;
 254 #endif
 255 }
 256
 257 static long __bpf_get_stackid(struct bpf_map *map,
 258                               struct perf_callchain_entry *trace, u64 flags)
 259 {
 260         struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
 261         struct stack_map_bucket *bucket, *new_bucket, *old_bucket;
 262         u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
 263         u32 hash, id, trace_nr, trace_len;
 264         bool user = flags & BPF_F_USER_STACK;
 265         u64 *ips;
 266         bool hash_matches;
 267
 268         if (trace->nr <= skip)
 269                 /* skipping more than usable stack trace */
 270                 return -EFAULT;
 271
 272         trace_nr = trace->nr - skip;
 273         trace_len = trace_nr * sizeof(u64);
 274         ips = trace->ip + skip;
 275         hash = jhash2((u32 *)ips, trace_len / sizeof(u32), 0);
 276         id = hash & (smap->n_buckets - 1);
 277         bucket = READ_ONCE(smap->buckets[id]);
 278
 279         hash_matches = bucket && bucket->hash == hash;
 280         /* fast cmp */
 281         if (hash_matches && flags & BPF_F_FAST_STACK_CMP)
 282                 return id;
 283
 284         if (stack_map_use_build_id(map)) {
 285                 /* for build_id+offset, pop a bucket before slow cmp */
 286                 new_bucket = (struct stack_map_bucket *)
 287                         pcpu_freelist_pop(&smap->freelist);
 288                 if (unlikely(!new_bucket))
 289                         return -ENOMEM;
 290                 new_bucket->nr = trace_nr;
 291                 stack_map_get_build_id_offset(
 292                         (struct bpf_stack_build_id *)new_bucket->data,
 293                         ips, trace_nr, user);
 294                 trace_len = trace_nr * sizeof(struct bpf_stack_build_id);
 295                 if (hash_matches && bucket->nr == trace_nr &&
 296                     memcmp(bucket->data, new_bucket->data, trace_len) == 0) {
 297                         pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
 298                         return id;
 299                 }
 300                 if (bucket && !(flags & BPF_F_REUSE_STACKID)) {
 301                         pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
 302                         return -EEXIST;
 303                 }
 304         } else {
 305                 if (hash_matches && bucket->nr == trace_nr &&
 306                     memcmp(bucket->data, ips, trace_len) == 0)
 307                         return id;
 308                 if (bucket && !(flags & BPF_F_REUSE_STACKID))
 309                         return -EEXIST;
 310
 311                 new_bucket = (struct stack_map_bucket *)
 312                         pcpu_freelist_pop(&smap->freelist);
 313                 if (unlikely(!new_bucket))
 314                         return -ENOMEM;
 315                 memcpy(new_bucket->data, ips, trace_len);
 316         }
 317
 318         new_bucket->hash = hash;
 319         new_bucket->nr = trace_nr;
 320
 321         old_bucket = xchg(&smap->buckets[id], new_bucket);
 322         if (old_bucket)
 323                 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
 324         return id;
 325 }
 326
 327 BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map,
 328            u64, flags)
 329 {
 330         u32 max_depth = map->value_size / stack_map_data_size(map);
 331         u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
 332         bool user = flags & BPF_F_USER_STACK;
 333         struct perf_callchain_entry *trace;
 334         bool kernel = !user;
 335
 336         if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
 337                                BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
 338                 return -EINVAL;
 339
 340         max_depth += skip;
 341         if (max_depth > sysctl_perf_event_max_stack)
 342                 max_depth = sysctl_perf_event_max_stack;
 343
 344         trace = get_perf_callchain(regs, 0, kernel, user, max_depth,
 345                                    false, false);
 346
 347         if (unlikely(!trace))
 348                 /* couldn't fetch the stack trace */
 349                 return -EFAULT;
 350
 351         return __bpf_get_stackid(map, trace, flags);
 352 }
 353
 354 const struct bpf_func_proto bpf_get_stackid_proto = {
 355         .func           = bpf_get_stackid,
 356         .gpl_only       = true,
 357         .ret_type       = RET_INTEGER,
 358         .arg1_type      = ARG_PTR_TO_CTX,
 359         .arg2_type      = ARG_CONST_MAP_PTR,
 360         .arg3_type      = ARG_ANYTHING,
 361 };
 362
 363 static __u64 count_kernel_ip(struct perf_callchain_entry *trace)
 364 {
 365         __u64 nr_kernel = 0;
 366
 367         while (nr_kernel < trace->nr) {
 368                 if (trace->ip[nr_kernel] == PERF_CONTEXT_USER)
 369                         break;
 370                 nr_kernel++;
 371         }
 372         return nr_kernel;
 373 }
 374
 375 BPF_CALL_3(bpf_get_stackid_pe, struct bpf_perf_event_data_kern *, ctx,
 376            struct bpf_map *, map, u64, flags)
 377 {
 378         struct perf_event *event = ctx->event;
 379         struct perf_callchain_entry *trace;
 380         bool kernel, user;
 381         __u64 nr_kernel;
 382         int ret;
 383
 384         /* perf_sample_data doesn't have callchain, use bpf_get_stackid */
 385         if (!(event->attr.sample_type & __PERF_SAMPLE_CALLCHAIN_EARLY))
 386                 return bpf_get_stackid((unsigned long)(ctx->regs),
 387                                        (unsigned long) map, flags, 0, 0);
 388
 389         if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
 390                                BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
 391                 return -EINVAL;
 392
 393         user = flags & BPF_F_USER_STACK;
 394         kernel = !user;
 395
 396         trace = ctx->data->callchain;
 397         if (unlikely(!trace))
 398                 return -EFAULT;
 399
 400         nr_kernel = count_kernel_ip(trace);
 401
 402         if (kernel) {
 403                 __u64 nr = trace->nr;
 404
 405                 trace->nr = nr_kernel;
 406                 ret = __bpf_get_stackid(map, trace, flags);
 407
 408                 /* restore nr */
 409                 trace->nr = nr;
 410         } else { /* user */
 411                 u64 skip = flags & BPF_F_SKIP_FIELD_MASK;
 412
 413                 skip += nr_kernel;
 414                 if (skip > BPF_F_SKIP_FIELD_MASK)
 415                         return -EFAULT;
 416
 417                 flags = (flags & ~BPF_F_SKIP_FIELD_MASK) | skip;
 418                 ret = __bpf_get_stackid(map, trace, flags);
 419         }
 420         return ret;
 421 }
 422
 423 const struct bpf_func_proto bpf_get_stackid_proto_pe = {
 424         .func           = bpf_get_stackid_pe,
 425         .gpl_only       = false,
 426         .ret_type       = RET_INTEGER,
 427         .arg1_type      = ARG_PTR_TO_CTX,
 428         .arg2_type      = ARG_CONST_MAP_PTR,
 429         .arg3_type      = ARG_ANYTHING,
 430 };
 431
 432 static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task,
 433                             struct perf_callchain_entry *trace_in,
 434                             void *buf, u32 size, u64 flags)
 435 {
 436         u32 trace_nr, copy_len, elem_size, num_elem, max_depth;
 437         bool user_build_id = flags & BPF_F_USER_BUILD_ID;
 438         u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
 439         bool user = flags & BPF_F_USER_STACK;
 440         struct perf_callchain_entry *trace;
 441         bool kernel = !user;
 442         int err = -EINVAL;
 443         u64 *ips;
 444
 445         if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
 446                                BPF_F_USER_BUILD_ID)))
 447                 goto clear;
 448         if (kernel && user_build_id)
 449                 goto clear;
 450
 451         elem_size = (user && user_build_id) ? sizeof(struct bpf_stack_build_id)
 452                                             : sizeof(u64);
 453         if (unlikely(size % elem_size))
 454                 goto clear;
 455
 456         /* cannot get valid user stack for task without user_mode regs */
 457         if (task && user && !user_mode(regs))
 458                 goto err_fault;
 459
 460         num_elem = size / elem_size;
 461         max_depth = num_elem + skip;
 462         if (sysctl_perf_event_max_stack < max_depth)
 463                 max_depth = sysctl_perf_event_max_stack;
 464
 465         if (trace_in)
 466                 trace = trace_in;
 467         else if (kernel && task)
 468                 trace = get_callchain_entry_for_task(task, max_depth);
 469         else
 470                 trace = get_perf_callchain(regs, 0, kernel, user, max_depth,
 471                                            false, false);
 472         if (unlikely(!trace))
 473                 goto err_fault;
 474
 475         if (trace->nr < skip)
 476                 goto err_fault;
 477
 478         trace_nr = trace->nr - skip;
 479         trace_nr = (trace_nr <= num_elem) ? trace_nr : num_elem;
 480         copy_len = trace_nr * elem_size;
 481
 482         ips = trace->ip + skip;
 483         if (user && user_build_id)
 484                 stack_map_get_build_id_offset(buf, ips, trace_nr, user);
 485         else
 486                 memcpy(buf, ips, copy_len);
 487
 488         if (size > copy_len)
 489                 memset(buf + copy_len, 0, size - copy_len);
 490         return copy_len;
 491
 492 err_fault:
 493         err = -EFAULT;
 494 clear:
 495         memset(buf, 0, size);
 496         return err;
 497 }
 498
 499 BPF_CALL_4(bpf_get_stack, struct pt_regs *, regs, void *, buf, u32, size,
 500            u64, flags)
 501 {
 502         return __bpf_get_stack(regs, NULL, NULL, buf, size, flags);
 503 }
 504
 505 const struct bpf_func_proto bpf_get_stack_proto = {
 506         .func           = bpf_get_stack,
 507         .gpl_only       = true,
 508         .ret_type       = RET_INTEGER,
 509         .arg1_type      = ARG_PTR_TO_CTX,
 510         .arg2_type      = ARG_PTR_TO_UNINIT_MEM,
 511         .arg3_type      = ARG_CONST_SIZE_OR_ZERO,
 512         .arg4_type      = ARG_ANYTHING,
 513 };
 514
 515 BPF_CALL_4(bpf_get_task_stack, struct task_struct *, task, void *, buf,
 516            u32, size, u64, flags)
 517 {
 518         struct pt_regs *regs;
 519         long res = -EINVAL;
 520
 521         if (!try_get_task_stack(task))
 522                 return -EFAULT;
 523
 524         regs = task_pt_regs(task);
 525         if (regs)
 526                 res = __bpf_get_stack(regs, task, NULL, buf, size, flags);
 527         put_task_stack(task);
 528
 529         return res;
 530 }
 531
 532 const struct bpf_func_proto bpf_get_task_stack_proto = {
 533         .func           = bpf_get_task_stack,
 534         .gpl_only       = false,
 535         .ret_type       = RET_INTEGER,
 536         .arg1_type      = ARG_PTR_TO_BTF_ID,
 537         .arg1_btf_id    = &btf_task_struct_ids[0],
 538         .arg2_type      = ARG_PTR_TO_UNINIT_MEM,
 539         .arg3_type      = ARG_CONST_SIZE_OR_ZERO,
 540         .arg4_type      = ARG_ANYTHING,
 541 };
 542
 543 BPF_CALL_4(bpf_get_stack_pe, struct bpf_perf_event_data_kern *, ctx,
 544            void *, buf, u32, size, u64, flags)
 545 {
 546         struct pt_regs *regs = (struct pt_regs *)(ctx->regs);
 547         struct perf_event *event = ctx->event;
 548         struct perf_callchain_entry *trace;
 549         bool kernel, user;
 550         int err = -EINVAL;
 551         __u64 nr_kernel;
 552
 553         if (!(event->attr.sample_type & __PERF_SAMPLE_CALLCHAIN_EARLY))
 554                 return __bpf_get_stack(regs, NULL, NULL, buf, size, flags);
 555
 556         if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
 557                                BPF_F_USER_BUILD_ID)))
 558                 goto clear;
 559
 560         user = flags & BPF_F_USER_STACK;
 561         kernel = !user;
 562
 563         err = -EFAULT;
 564         trace = ctx->data->callchain;
 565         if (unlikely(!trace))
 566                 goto clear;
 567
 568         nr_kernel = count_kernel_ip(trace);
 569
 570         if (kernel) {
 571                 __u64 nr = trace->nr;
 572
 573                 trace->nr = nr_kernel;
 574                 err = __bpf_get_stack(regs, NULL, trace, buf, size, flags);
 575
 576                 /* restore nr */
 577                 trace->nr = nr;
 578         } else { /* user */
 579                 u64 skip = flags & BPF_F_SKIP_FIELD_MASK;
 580
 581                 skip += nr_kernel;
 582                 if (skip > BPF_F_SKIP_FIELD_MASK)
 583                         goto clear;
 584
 585                 flags = (flags & ~BPF_F_SKIP_FIELD_MASK) | skip;
 586                 err = __bpf_get_stack(regs, NULL, trace, buf, size, flags);
 587         }
 588         return err;
 589
 590 clear:
 591         memset(buf, 0, size);
 592         return err;
 593
 594 }
 595
 596 const struct bpf_func_proto bpf_get_stack_proto_pe = {
 597         .func           = bpf_get_stack_pe,
 598         .gpl_only       = true,
 599         .ret_type       = RET_INTEGER,
 600         .arg1_type      = ARG_PTR_TO_CTX,
 601         .arg2_type      = ARG_PTR_TO_UNINIT_MEM,
 602         .arg3_type      = ARG_CONST_SIZE_OR_ZERO,
 603         .arg4_type      = ARG_ANYTHING,
 604 };
 605
 606 /* Called from eBPF program */
 607 static void *stack_map_lookup_elem(struct bpf_map *map, void *key)
 608 {
 609         return ERR_PTR(-EOPNOTSUPP);
 610 }
 611
 612 /* Called from syscall */
 613 int bpf_stackmap_copy(struct bpf_map *map, void *key, void *value)
 614 {
 615         struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
 616         struct stack_map_bucket *bucket, *old_bucket;
 617         u32 id = *(u32 *)key, trace_len;
 618
 619         if (unlikely(id >= smap->n_buckets))
 620                 return -ENOENT;
 621
 622         bucket = xchg(&smap->buckets[id], NULL);
 623         if (!bucket)
 624                 return -ENOENT;
 625
 626         trace_len = bucket->nr * stack_map_data_size(map);
 627         memcpy(value, bucket->data, trace_len);
 628         memset(value + trace_len, 0, map->value_size - trace_len);
 629
 630         old_bucket = xchg(&smap->buckets[id], bucket);
 631         if (old_bucket)
 632                 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
 633         return 0;
 634 }
 635
 636 static int stack_map_get_next_key(struct bpf_map *map, void *key,
 637                                   void *next_key)
 638 {
 639         struct bpf_stack_map *smap = container_of(map,
 640                                                   struct bpf_stack_map, map);
 641         u32 id;
 642
 643         WARN_ON_ONCE(!rcu_read_lock_held());
 644
 645         if (!key) {
 646                 id = 0;
 647         } else {
 648                 id = *(u32 *)key;
 649                 if (id >= smap->n_buckets || !smap->buckets[id])
 650                         id = 0;
 651                 else
 652                         id++;
 653         }
 654
 655         while (id < smap->n_buckets && !smap->buckets[id])
 656                 id++;
 657
 658         if (id >= smap->n_buckets)
 659                 return -ENOENT;
 660
 661         *(u32 *)next_key = id;
 662         return 0;
 663 }
 664
 665 static int stack_map_update_elem(struct bpf_map *map, void *key, void *value,
 666                                  u64 map_flags)
 667 {
 668         return -EINVAL;
 669 }
 670
 671 /* Called from syscall or from eBPF program */
 672 static int stack_map_delete_elem(struct bpf_map *map, void *key)
 673 {
 674         struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
 675         struct stack_map_bucket *old_bucket;
 676         u32 id = *(u32 *)key;
 677
 678         if (unlikely(id >= smap->n_buckets))
 679                 return -E2BIG;
 680
 681         old_bucket = xchg(&smap->buckets[id], NULL);
 682         if (old_bucket) {
 683                 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
 684                 return 0;
 685         } else {
 686                 return -ENOENT;
 687         }
 688 }
 689
 690 /* Called when map->refcnt goes to zero, either from workqueue or from syscall */
 691 static void stack_map_free(struct bpf_map *map)
 692 {
 693         struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
 694
 695         bpf_map_area_free(smap->elems);
 696         pcpu_freelist_destroy(&smap->freelist);
 697         bpf_map_area_free(smap);
 698         put_callchain_buffers();
 699 }
 700
 701 static int stack_trace_map_btf_id;
 702 const struct bpf_map_ops stack_trace_map_ops = {
 703         .map_meta_equal = bpf_map_meta_equal,
 704         .map_alloc = stack_map_alloc,
 705         .map_free = stack_map_free,
 706         .map_get_next_key = stack_map_get_next_key,
 707         .map_lookup_elem = stack_map_lookup_elem,
 708         .map_update_elem = stack_map_update_elem,
 709         .map_delete_elem = stack_map_delete_elem,
 710         .map_check_btf = map_check_no_btf,
 711         .map_btf_name = "bpf_stack_map",
 712         .map_btf_id = &stack_trace_map_btf_id,
 713 };
 714
 715 static int __init stack_map_init(void)
 716 {
 717         int cpu;
 718         struct stack_map_irq_work *work;
 719
 720         for_each_possible_cpu(cpu) {
 721                 work = per_cpu_ptr(&up_read_work, cpu);
 722                 init_irq_work(&work->irq_work, do_up_read);
 723         }
 724         return 0;
 725 }
 726 subsys_initcall(stack_map_init);