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         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 (!bpf_capable())
  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         if (!n_buckets)
 118                 return ERR_PTR(-E2BIG);
 119
 120         cost = n_buckets * sizeof(struct stack_map_bucket *) + sizeof(*smap);
 121         cost += n_buckets * (value_size + sizeof(struct stack_map_bucket));
 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 init_nr)
 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 = init_nr +
 233                 stack_trace_save_tsk(task, (unsigned long *)(entry->ip + init_nr),
 234                                      sysctl_perf_event_max_stack - init_nr, 0);
 235
 236         /* stack_trace_save_tsk() works on unsigned long array, while
 237          * perf_callchain_entry uses u64 array. For 32-bit systems, it is
 238          * necessary to fix this mismatch.
 239          */
 240         if (__BITS_PER_LONG != 64) {
 241                 unsigned long *from = (unsigned long *) entry->ip;
 242                 u64 *to = entry->ip;
 243                 int i;
 244
 245                 /* copy data from the end to avoid using extra buffer */
 246                 for (i = entry->nr - 1; i >= (int)init_nr; i--)
 247                         to[i] = (u64)(from[i]);
 248         }
 249
 250         put_callchain_entry(rctx);
 251
 252         return entry;
 253 #else /* CONFIG_STACKTRACE */
 254         return NULL;
 255 #endif
 256 }
 257
 258 static long __bpf_get_stackid(struct bpf_map *map,
 259                               struct perf_callchain_entry *trace, u64 flags)
 260 {
 261         struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
 262         struct stack_map_bucket *bucket, *new_bucket, *old_bucket;
 263         u32 max_depth = map->value_size / stack_map_data_size(map);
 264         /* stack_map_alloc() checks that max_depth <= sysctl_perf_event_max_stack */
 265         u32 init_nr = sysctl_perf_event_max_stack - max_depth;
 266         u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
 267         u32 hash, id, trace_nr, trace_len;
 268         bool user = flags & BPF_F_USER_STACK;
 269         u64 *ips;
 270         bool hash_matches;
 271
 272         /* get_perf_callchain() guarantees that trace->nr >= init_nr
 273          * and trace-nr <= sysctl_perf_event_max_stack, so trace_nr <= max_depth
 274          */
 275         trace_nr = trace->nr - init_nr;
 276
 277         if (trace_nr <= skip)
 278                 /* skipping more than usable stack trace */
 279                 return -EFAULT;
 280
 281         trace_nr -= skip;
 282         trace_len = trace_nr * sizeof(u64);
 283         ips = trace->ip + skip + init_nr;
 284         hash = jhash2((u32 *)ips, trace_len / sizeof(u32), 0);
 285         id = hash & (smap->n_buckets - 1);
 286         bucket = READ_ONCE(smap->buckets[id]);
 287
 288         hash_matches = bucket && bucket->hash == hash;
 289         /* fast cmp */
 290         if (hash_matches && flags & BPF_F_FAST_STACK_CMP)
 291                 return id;
 292
 293         if (stack_map_use_build_id(map)) {
 294                 /* for build_id+offset, pop a bucket before slow cmp */
 295                 new_bucket = (struct stack_map_bucket *)
 296                         pcpu_freelist_pop(&smap->freelist);
 297                 if (unlikely(!new_bucket))
 298                         return -ENOMEM;
 299                 new_bucket->nr = trace_nr;
 300                 stack_map_get_build_id_offset(
 301                         (struct bpf_stack_build_id *)new_bucket->data,
 302                         ips, trace_nr, user);
 303                 trace_len = trace_nr * sizeof(struct bpf_stack_build_id);
 304                 if (hash_matches && bucket->nr == trace_nr &&
 305                     memcmp(bucket->data, new_bucket->data, trace_len) == 0) {
 306                         pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
 307                         return id;
 308                 }
 309                 if (bucket && !(flags & BPF_F_REUSE_STACKID)) {
 310                         pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
 311                         return -EEXIST;
 312                 }
 313         } else {
 314                 if (hash_matches && bucket->nr == trace_nr &&
 315                     memcmp(bucket->data, ips, trace_len) == 0)
 316                         return id;
 317                 if (bucket && !(flags & BPF_F_REUSE_STACKID))
 318                         return -EEXIST;
 319
 320                 new_bucket = (struct stack_map_bucket *)
 321                         pcpu_freelist_pop(&smap->freelist);
 322                 if (unlikely(!new_bucket))
 323                         return -ENOMEM;
 324                 memcpy(new_bucket->data, ips, trace_len);
 325         }
 326
 327         new_bucket->hash = hash;
 328         new_bucket->nr = trace_nr;
 329
 330         old_bucket = xchg(&smap->buckets[id], new_bucket);
 331         if (old_bucket)
 332                 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
 333         return id;
 334 }
 335
 336 BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map,
 337            u64, flags)
 338 {
 339         u32 max_depth = map->value_size / stack_map_data_size(map);
 340         /* stack_map_alloc() checks that max_depth <= sysctl_perf_event_max_stack */
 341         u32 init_nr = sysctl_perf_event_max_stack - max_depth;
 342         bool user = flags & BPF_F_USER_STACK;
 343         struct perf_callchain_entry *trace;
 344         bool kernel = !user;
 345
 346         if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
 347                                BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
 348                 return -EINVAL;
 349
 350         trace = get_perf_callchain(regs, init_nr, kernel, user,
 351                                    sysctl_perf_event_max_stack, false, false);
 352
 353         if (unlikely(!trace))
 354                 /* couldn't fetch the stack trace */
 355                 return -EFAULT;
 356
 357         return __bpf_get_stackid(map, trace, flags);
 358 }
 359
 360 const struct bpf_func_proto bpf_get_stackid_proto = {
 361         .func           = bpf_get_stackid,
 362         .gpl_only       = true,
 363         .ret_type       = RET_INTEGER,
 364         .arg1_type      = ARG_PTR_TO_CTX,
 365         .arg2_type      = ARG_CONST_MAP_PTR,
 366         .arg3_type      = ARG_ANYTHING,
 367 };
 368
 369 static __u64 count_kernel_ip(struct perf_callchain_entry *trace)
 370 {
 371         __u64 nr_kernel = 0;
 372
 373         while (nr_kernel < trace->nr) {
 374                 if (trace->ip[nr_kernel] == PERF_CONTEXT_USER)
 375                         break;
 376                 nr_kernel++;
 377         }
 378         return nr_kernel;
 379 }
 380
 381 BPF_CALL_3(bpf_get_stackid_pe, struct bpf_perf_event_data_kern *, ctx,
 382            struct bpf_map *, map, u64, flags)
 383 {
 384         struct perf_event *event = ctx->event;
 385         struct perf_callchain_entry *trace;
 386         bool kernel, user;
 387         __u64 nr_kernel;
 388         int ret;
 389
 390         /* perf_sample_data doesn't have callchain, use bpf_get_stackid */
 391         if (!(event->attr.sample_type & __PERF_SAMPLE_CALLCHAIN_EARLY))
 392                 return bpf_get_stackid((unsigned long)(ctx->regs),
 393                                        (unsigned long) map, flags, 0, 0);
 394
 395         if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
 396                                BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
 397                 return -EINVAL;
 398
 399         user = flags & BPF_F_USER_STACK;
 400         kernel = !user;
 401
 402         trace = ctx->data->callchain;
 403         if (unlikely(!trace))
 404                 return -EFAULT;
 405
 406         nr_kernel = count_kernel_ip(trace);
 407
 408         if (kernel) {
 409                 __u64 nr = trace->nr;
 410
 411                 trace->nr = nr_kernel;
 412                 ret = __bpf_get_stackid(map, trace, flags);
 413
 414                 /* restore nr */
 415                 trace->nr = nr;
 416         } else { /* user */
 417                 u64 skip = flags & BPF_F_SKIP_FIELD_MASK;
 418
 419                 skip += nr_kernel;
 420                 if (skip > BPF_F_SKIP_FIELD_MASK)
 421                         return -EFAULT;
 422
 423                 flags = (flags & ~BPF_F_SKIP_FIELD_MASK) | skip;
 424                 ret = __bpf_get_stackid(map, trace, flags);
 425         }
 426         return ret;
 427 }
 428
 429 const struct bpf_func_proto bpf_get_stackid_proto_pe = {
 430         .func           = bpf_get_stackid_pe,
 431         .gpl_only       = false,
 432         .ret_type       = RET_INTEGER,
 433         .arg1_type      = ARG_PTR_TO_CTX,
 434         .arg2_type      = ARG_CONST_MAP_PTR,
 435         .arg3_type      = ARG_ANYTHING,
 436 };
 437
 438 static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task,
 439                             struct perf_callchain_entry *trace_in,
 440                             void *buf, u32 size, u64 flags)
 441 {
 442         u32 init_nr, trace_nr, copy_len, elem_size, num_elem;
 443         bool user_build_id = flags & BPF_F_USER_BUILD_ID;
 444         u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
 445         bool user = flags & BPF_F_USER_STACK;
 446         struct perf_callchain_entry *trace;
 447         bool kernel = !user;
 448         int err = -EINVAL;
 449         u64 *ips;
 450
 451         if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
 452                                BPF_F_USER_BUILD_ID)))
 453                 goto clear;
 454         if (kernel && user_build_id)
 455                 goto clear;
 456
 457         elem_size = (user && user_build_id) ? sizeof(struct bpf_stack_build_id)
 458                                             : sizeof(u64);
 459         if (unlikely(size % elem_size))
 460                 goto clear;
 461
 462         /* cannot get valid user stack for task without user_mode regs */
 463         if (task && user && !user_mode(regs))
 464                 goto err_fault;
 465
 466         num_elem = size / elem_size;
 467         if (sysctl_perf_event_max_stack < num_elem)
 468                 init_nr = 0;
 469         else
 470                 init_nr = sysctl_perf_event_max_stack - num_elem;
 471
 472         if (trace_in)
 473                 trace = trace_in;
 474         else if (kernel && task)
 475                 trace = get_callchain_entry_for_task(task, init_nr);
 476         else
 477                 trace = get_perf_callchain(regs, init_nr, kernel, user,
 478                                            sysctl_perf_event_max_stack,
 479                                            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 BPF_CALL_4(bpf_get_stack, struct pt_regs *, regs, void *, buf, u32, size,
 508            u64, flags)
 509 {
 510         return __bpf_get_stack(regs, NULL, NULL, buf, size, flags);
 511 }
 512
 513 const struct bpf_func_proto bpf_get_stack_proto = {
 514         .func           = bpf_get_stack,
 515         .gpl_only       = true,
 516         .ret_type       = RET_INTEGER,
 517         .arg1_type      = ARG_PTR_TO_CTX,
 518         .arg2_type      = ARG_PTR_TO_UNINIT_MEM,
 519         .arg3_type      = ARG_CONST_SIZE_OR_ZERO,
 520         .arg4_type      = ARG_ANYTHING,
 521 };
 522
 523 BPF_CALL_4(bpf_get_task_stack, struct task_struct *, task, void *, buf,
 524            u32, size, u64, flags)
 525 {
 526         struct pt_regs *regs;
 527         long res;
 528
 529         if (!try_get_task_stack(task))
 530                 return -EFAULT;
 531
 532         regs = task_pt_regs(task);
 533         res = __bpf_get_stack(regs, task, NULL, buf, size, flags);
 534         put_task_stack(task);
 535
 536         return res;
 537 }
 538
 539 const struct bpf_func_proto bpf_get_task_stack_proto = {
 540         .func           = bpf_get_task_stack,
 541         .gpl_only       = false,
 542         .ret_type       = RET_INTEGER,
 543         .arg1_type      = ARG_PTR_TO_BTF_ID,
 544         .arg1_btf_id    = &btf_task_struct_ids[0],
 545         .arg2_type      = ARG_PTR_TO_UNINIT_MEM,
 546         .arg3_type      = ARG_CONST_SIZE_OR_ZERO,
 547         .arg4_type      = ARG_ANYTHING,
 548 };
 549
 550 BPF_CALL_4(bpf_get_stack_pe, struct bpf_perf_event_data_kern *, ctx,
 551            void *, buf, u32, size, u64, flags)
 552 {
 553         struct pt_regs *regs = (struct pt_regs *)(ctx->regs);
 554         struct perf_event *event = ctx->event;
 555         struct perf_callchain_entry *trace;
 556         bool kernel, user;
 557         int err = -EINVAL;
 558         __u64 nr_kernel;
 559
 560         if (!(event->attr.sample_type & __PERF_SAMPLE_CALLCHAIN_EARLY))
 561                 return __bpf_get_stack(regs, NULL, NULL, buf, size, flags);
 562
 563         if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
 564                                BPF_F_USER_BUILD_ID)))
 565                 goto clear;
 566
 567         user = flags & BPF_F_USER_STACK;
 568         kernel = !user;
 569
 570         err = -EFAULT;
 571         trace = ctx->data->callchain;
 572         if (unlikely(!trace))
 573                 goto clear;
 574
 575         nr_kernel = count_kernel_ip(trace);
 576
 577         if (kernel) {
 578                 __u64 nr = trace->nr;
 579
 580                 trace->nr = nr_kernel;
 581                 err = __bpf_get_stack(regs, NULL, trace, buf, size, flags);
 582
 583                 /* restore nr */
 584                 trace->nr = nr;
 585         } else { /* user */
 586                 u64 skip = flags & BPF_F_SKIP_FIELD_MASK;
 587
 588                 skip += nr_kernel;
 589                 if (skip > BPF_F_SKIP_FIELD_MASK)
 590                         goto clear;
 591
 592                 flags = (flags & ~BPF_F_SKIP_FIELD_MASK) | skip;
 593                 err = __bpf_get_stack(regs, NULL, trace, buf, size, flags);
 594         }
 595         return err;
 596
 597 clear:
 598         memset(buf, 0, size);
 599         return err;
 600
 601 }
 602
 603 const struct bpf_func_proto bpf_get_stack_proto_pe = {
 604         .func           = bpf_get_stack_pe,
 605         .gpl_only       = true,
 606         .ret_type       = RET_INTEGER,
 607         .arg1_type      = ARG_PTR_TO_CTX,
 608         .arg2_type      = ARG_PTR_TO_UNINIT_MEM,
 609         .arg3_type      = ARG_CONST_SIZE_OR_ZERO,
 610         .arg4_type      = ARG_ANYTHING,
 611 };
 612
 613 /* Called from eBPF program */
 614 static void *stack_map_lookup_elem(struct bpf_map *map, void *key)
 615 {
 616         return ERR_PTR(-EOPNOTSUPP);
 617 }
 618
 619 /* Called from syscall */
 620 int bpf_stackmap_copy(struct bpf_map *map, void *key, void *value)
 621 {
 622         struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
 623         struct stack_map_bucket *bucket, *old_bucket;
 624         u32 id = *(u32 *)key, trace_len;
 625
 626         if (unlikely(id >= smap->n_buckets))
 627                 return -ENOENT;
 628
 629         bucket = xchg(&smap->buckets[id], NULL);
 630         if (!bucket)
 631                 return -ENOENT;
 632
 633         trace_len = bucket->nr * stack_map_data_size(map);
 634         memcpy(value, bucket->data, trace_len);
 635         memset(value + trace_len, 0, map->value_size - trace_len);
 636
 637         old_bucket = xchg(&smap->buckets[id], bucket);
 638         if (old_bucket)
 639                 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
 640         return 0;
 641 }
 642
 643 static int stack_map_get_next_key(struct bpf_map *map, void *key,
 644                                   void *next_key)
 645 {
 646         struct bpf_stack_map *smap = container_of(map,
 647                                                   struct bpf_stack_map, map);
 648         u32 id;
 649
 650         WARN_ON_ONCE(!rcu_read_lock_held());
 651
 652         if (!key) {
 653                 id = 0;
 654         } else {
 655                 id = *(u32 *)key;
 656                 if (id >= smap->n_buckets || !smap->buckets[id])
 657                         id = 0;
 658                 else
 659                         id++;
 660         }
 661
 662         while (id < smap->n_buckets && !smap->buckets[id])
 663                 id++;
 664
 665         if (id >= smap->n_buckets)
 666                 return -ENOENT;
 667
 668         *(u32 *)next_key = id;
 669         return 0;
 670 }
 671
 672 static int stack_map_update_elem(struct bpf_map *map, void *key, void *value,
 673                                  u64 map_flags)
 674 {
 675         return -EINVAL;
 676 }
 677
 678 /* Called from syscall or from eBPF program */
 679 static int stack_map_delete_elem(struct bpf_map *map, void *key)
 680 {
 681         struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
 682         struct stack_map_bucket *old_bucket;
 683         u32 id = *(u32 *)key;
 684
 685         if (unlikely(id >= smap->n_buckets))
 686                 return -E2BIG;
 687
 688         old_bucket = xchg(&smap->buckets[id], NULL);
 689         if (old_bucket) {
 690                 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
 691                 return 0;
 692         } else {
 693                 return -ENOENT;
 694         }
 695 }
 696
 697 /* Called when map->refcnt goes to zero, either from workqueue or from syscall */
 698 static void stack_map_free(struct bpf_map *map)
 699 {
 700         struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
 701
 702         bpf_map_area_free(smap->elems);
 703         pcpu_freelist_destroy(&smap->freelist);
 704         bpf_map_area_free(smap);
 705         put_callchain_buffers();
 706 }
 707
 708 static int stack_trace_map_btf_id;
 709 const struct bpf_map_ops stack_trace_map_ops = {
 710         .map_meta_equal = bpf_map_meta_equal,
 711         .map_alloc = stack_map_alloc,
 712         .map_free = stack_map_free,
 713         .map_get_next_key = stack_map_get_next_key,
 714         .map_lookup_elem = stack_map_lookup_elem,
 715         .map_update_elem = stack_map_update_elem,
 716         .map_delete_elem = stack_map_delete_elem,
 717         .map_check_btf = map_check_no_btf,
 718         .map_btf_name = "bpf_stack_map",
 719         .map_btf_id = &stack_trace_map_btf_id,
 720 };
 721
 722 static int __init stack_map_init(void)
 723 {
 724         int cpu;
 725         struct stack_map_irq_work *work;
 726
 727         for_each_possible_cpu(cpu) {
 728                 work = per_cpu_ptr(&up_read_work, cpu);
 729                 init_irq_work(&work->irq_work, do_up_read);
 730         }
 731         return 0;
 732 }
 733 subsys_initcall(stack_map_init);