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         cost += n_buckets * (value_size + sizeof(struct stack_map_bucket));
 123         smap = bpf_map_area_alloc(cost, bpf_map_attr_numa_node(attr));
 124         if (!smap)
 125                 return ERR_PTR(-ENOMEM);
 126
 127         bpf_map_init_from_attr(&smap->map, attr);
 128         smap->map.value_size = value_size;
 129         smap->n_buckets = n_buckets;
 130
 131         err = get_callchain_buffers(sysctl_perf_event_max_stack);
 132         if (err)
 133                 goto free_smap;
 134
 135         err = prealloc_elems_and_freelist(smap);
 136         if (err)
 137                 goto put_buffers;
 138
 139         return &smap->map;
 140
 141 put_buffers:
 142         put_callchain_buffers();
 143 free_smap:
 144         bpf_map_area_free(smap);
 145         return ERR_PTR(err);
 146 }
 147
 148 static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
 149                                           u64 *ips, u32 trace_nr, bool user)
 150 {
 151         int i;
 152         struct vm_area_struct *vma;
 153         bool irq_work_busy = false;
 154         struct stack_map_irq_work *work = NULL;
 155
 156         if (irqs_disabled()) {
 157                 if (!IS_ENABLED(CONFIG_PREEMPT_RT)) {
 158                         work = this_cpu_ptr(&up_read_work);
 159                         if (irq_work_is_busy(&work->irq_work)) {
 160                                 /* cannot queue more up_read, fallback */
 161                                 irq_work_busy = true;
 162                         }
 163                 } else {
 164                         /*
 165                          * PREEMPT_RT does not allow to trylock mmap sem in
 166                          * interrupt disabled context. Force the fallback code.
 167                          */
 168                         irq_work_busy = true;
 169                 }
 170         }
 171
 172         /*
 173          * We cannot do up_read() when the irq is disabled, because of
 174          * risk to deadlock with rq_lock. To do build_id lookup when the
 175          * irqs are disabled, we need to run up_read() in irq_work. We use
 176          * a percpu variable to do the irq_work. If the irq_work is
 177          * already used by another lookup, we fall back to report ips.
 178          *
 179          * Same fallback is used for kernel stack (!user) on a stackmap
 180          * with build_id.
 181          */
 182         if (!user || !current || !current->mm || irq_work_busy ||
 183             !mmap_read_trylock(current->mm)) {
 184                 /* cannot access current->mm, fall back to ips */
 185                 for (i = 0; i < trace_nr; i++) {
 186                         id_offs[i].status = BPF_STACK_BUILD_ID_IP;
 187                         id_offs[i].ip = ips[i];
 188                         memset(id_offs[i].build_id, 0, BUILD_ID_SIZE_MAX);
 189                 }
 190                 return;
 191         }
 192
 193         for (i = 0; i < trace_nr; i++) {
 194                 vma = find_vma(current->mm, ips[i]);
 195                 if (!vma || build_id_parse(vma, id_offs[i].build_id, NULL)) {
 196                         /* per entry fall back to ips */
 197                         id_offs[i].status = BPF_STACK_BUILD_ID_IP;
 198                         id_offs[i].ip = ips[i];
 199                         memset(id_offs[i].build_id, 0, BUILD_ID_SIZE_MAX);
 200                         continue;
 201                 }
 202                 id_offs[i].offset = (vma->vm_pgoff << PAGE_SHIFT) + ips[i]
 203                         - vma->vm_start;
 204                 id_offs[i].status = BPF_STACK_BUILD_ID_VALID;
 205         }
 206
 207         if (!work) {
 208                 mmap_read_unlock(current->mm);
 209         } else {
 210                 work->mm = current->mm;
 211
 212                 /* The lock will be released once we're out of interrupt
 213                  * context. Tell lockdep that we've released it now so
 214                  * it doesn't complain that we forgot to release it.
 215                  */
 216                 rwsem_release(&current->mm->mmap_lock.dep_map, _RET_IP_);
 217                 irq_work_queue(&work->irq_work);
 218         }
 219 }
 220
 221 static struct perf_callchain_entry *
 222 get_callchain_entry_for_task(struct task_struct *task, u32 init_nr)
 223 {
 224 #ifdef CONFIG_STACKTRACE
 225         struct perf_callchain_entry *entry;
 226         int rctx;
 227
 228         entry = get_callchain_entry(&rctx);
 229
 230         if (!entry)
 231                 return NULL;
 232
 233         entry->nr = init_nr +
 234                 stack_trace_save_tsk(task, (unsigned long *)(entry->ip + init_nr),
 235                                      sysctl_perf_event_max_stack - init_nr, 0);
 236
 237         /* stack_trace_save_tsk() works on unsigned long array, while
 238          * perf_callchain_entry uses u64 array. For 32-bit systems, it is
 239          * necessary to fix this mismatch.
 240          */
 241         if (__BITS_PER_LONG != 64) {
 242                 unsigned long *from = (unsigned long *) entry->ip;
 243                 u64 *to = entry->ip;
 244                 int i;
 245
 246                 /* copy data from the end to avoid using extra buffer */
 247                 for (i = entry->nr - 1; i >= (int)init_nr; i--)
 248                         to[i] = (u64)(from[i]);
 249         }
 250
 251         put_callchain_entry(rctx);
 252
 253         return entry;
 254 #else /* CONFIG_STACKTRACE */
 255         return NULL;
 256 #endif
 257 }
 258
 259 static long __bpf_get_stackid(struct bpf_map *map,
 260                               struct perf_callchain_entry *trace, u64 flags)
 261 {
 262         struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
 263         struct stack_map_bucket *bucket, *new_bucket, *old_bucket;
 264         u32 max_depth = map->value_size / stack_map_data_size(map);
 265         /* stack_map_alloc() checks that max_depth <= sysctl_perf_event_max_stack */
 266         u32 init_nr = sysctl_perf_event_max_stack - max_depth;
 267         u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
 268         u32 hash, id, trace_nr, trace_len;
 269         bool user = flags & BPF_F_USER_STACK;
 270         u64 *ips;
 271         bool hash_matches;
 272
 273         /* get_perf_callchain() guarantees that trace->nr >= init_nr
 274          * and trace-nr <= sysctl_perf_event_max_stack, so trace_nr <= max_depth
 275          */
 276         trace_nr = trace->nr - init_nr;
 277
 278         if (trace_nr <= skip)
 279                 /* skipping more than usable stack trace */
 280                 return -EFAULT;
 281
 282         trace_nr -= skip;
 283         trace_len = trace_nr * sizeof(u64);
 284         ips = trace->ip + skip + init_nr;
 285         hash = jhash2((u32 *)ips, trace_len / sizeof(u32), 0);
 286         id = hash & (smap->n_buckets - 1);
 287         bucket = READ_ONCE(smap->buckets[id]);
 288
 289         hash_matches = bucket && bucket->hash == hash;
 290         /* fast cmp */
 291         if (hash_matches && flags & BPF_F_FAST_STACK_CMP)
 292                 return id;
 293
 294         if (stack_map_use_build_id(map)) {
 295                 /* for build_id+offset, pop a bucket before slow cmp */
 296                 new_bucket = (struct stack_map_bucket *)
 297                         pcpu_freelist_pop(&smap->freelist);
 298                 if (unlikely(!new_bucket))
 299                         return -ENOMEM;
 300                 new_bucket->nr = trace_nr;
 301                 stack_map_get_build_id_offset(
 302                         (struct bpf_stack_build_id *)new_bucket->data,
 303                         ips, trace_nr, user);
 304                 trace_len = trace_nr * sizeof(struct bpf_stack_build_id);
 305                 if (hash_matches && bucket->nr == trace_nr &&
 306                     memcmp(bucket->data, new_bucket->data, trace_len) == 0) {
 307                         pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
 308                         return id;
 309                 }
 310                 if (bucket && !(flags & BPF_F_REUSE_STACKID)) {
 311                         pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
 312                         return -EEXIST;
 313                 }
 314         } else {
 315                 if (hash_matches && bucket->nr == trace_nr &&
 316                     memcmp(bucket->data, ips, trace_len) == 0)
 317                         return id;
 318                 if (bucket && !(flags & BPF_F_REUSE_STACKID))
 319                         return -EEXIST;
 320
 321                 new_bucket = (struct stack_map_bucket *)
 322                         pcpu_freelist_pop(&smap->freelist);
 323                 if (unlikely(!new_bucket))
 324                         return -ENOMEM;
 325                 memcpy(new_bucket->data, ips, trace_len);
 326         }
 327
 328         new_bucket->hash = hash;
 329         new_bucket->nr = trace_nr;
 330
 331         old_bucket = xchg(&smap->buckets[id], new_bucket);
 332         if (old_bucket)
 333                 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
 334         return id;
 335 }
 336
 337 BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map,
 338            u64, flags)
 339 {
 340         u32 max_depth = map->value_size / stack_map_data_size(map);
 341         /* stack_map_alloc() checks that max_depth <= sysctl_perf_event_max_stack */
 342         u32 init_nr = sysctl_perf_event_max_stack - max_depth;
 343         bool user = flags & BPF_F_USER_STACK;
 344         struct perf_callchain_entry *trace;
 345         bool kernel = !user;
 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         trace = get_perf_callchain(regs, init_nr, kernel, user,
 352                                    sysctl_perf_event_max_stack, false, false);
 353
 354         if (unlikely(!trace))
 355                 /* couldn't fetch the stack trace */
 356                 return -EFAULT;
 357
 358         return __bpf_get_stackid(map, trace, flags);
 359 }
 360
 361 const struct bpf_func_proto bpf_get_stackid_proto = {
 362         .func           = bpf_get_stackid,
 363         .gpl_only       = true,
 364         .ret_type       = RET_INTEGER,
 365         .arg1_type      = ARG_PTR_TO_CTX,
 366         .arg2_type      = ARG_CONST_MAP_PTR,
 367         .arg3_type      = ARG_ANYTHING,
 368 };
 369
 370 static __u64 count_kernel_ip(struct perf_callchain_entry *trace)
 371 {
 372         __u64 nr_kernel = 0;
 373
 374         while (nr_kernel < trace->nr) {
 375                 if (trace->ip[nr_kernel] == PERF_CONTEXT_USER)
 376                         break;
 377                 nr_kernel++;
 378         }
 379         return nr_kernel;
 380 }
 381
 382 BPF_CALL_3(bpf_get_stackid_pe, struct bpf_perf_event_data_kern *, ctx,
 383            struct bpf_map *, map, u64, flags)
 384 {
 385         struct perf_event *event = ctx->event;
 386         struct perf_callchain_entry *trace;
 387         bool kernel, user;
 388         __u64 nr_kernel;
 389         int ret;
 390
 391         /* perf_sample_data doesn't have callchain, use bpf_get_stackid */
 392         if (!(event->attr.sample_type & __PERF_SAMPLE_CALLCHAIN_EARLY))
 393                 return bpf_get_stackid((unsigned long)(ctx->regs),
 394                                        (unsigned long) map, flags, 0, 0);
 395
 396         if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
 397                                BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
 398                 return -EINVAL;
 399
 400         user = flags & BPF_F_USER_STACK;
 401         kernel = !user;
 402
 403         trace = ctx->data->callchain;
 404         if (unlikely(!trace))
 405                 return -EFAULT;
 406
 407         nr_kernel = count_kernel_ip(trace);
 408
 409         if (kernel) {
 410                 __u64 nr = trace->nr;
 411
 412                 trace->nr = nr_kernel;
 413                 ret = __bpf_get_stackid(map, trace, flags);
 414
 415                 /* restore nr */
 416                 trace->nr = nr;
 417         } else { /* user */
 418                 u64 skip = flags & BPF_F_SKIP_FIELD_MASK;
 419
 420                 skip += nr_kernel;
 421                 if (skip > BPF_F_SKIP_FIELD_MASK)
 422                         return -EFAULT;
 423
 424                 flags = (flags & ~BPF_F_SKIP_FIELD_MASK) | skip;
 425                 ret = __bpf_get_stackid(map, trace, flags);
 426         }
 427         return ret;
 428 }
 429
 430 const struct bpf_func_proto bpf_get_stackid_proto_pe = {
 431         .func           = bpf_get_stackid_pe,
 432         .gpl_only       = false,
 433         .ret_type       = RET_INTEGER,
 434         .arg1_type      = ARG_PTR_TO_CTX,
 435         .arg2_type      = ARG_CONST_MAP_PTR,
 436         .arg3_type      = ARG_ANYTHING,
 437 };
 438
 439 static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task,
 440                             struct perf_callchain_entry *trace_in,
 441                             void *buf, u32 size, u64 flags)
 442 {
 443         u32 init_nr, trace_nr, copy_len, elem_size, num_elem;
 444         bool user_build_id = flags & BPF_F_USER_BUILD_ID;
 445         u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
 446         bool user = flags & BPF_F_USER_STACK;
 447         struct perf_callchain_entry *trace;
 448         bool kernel = !user;
 449         int err = -EINVAL;
 450         u64 *ips;
 451
 452         if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
 453                                BPF_F_USER_BUILD_ID)))
 454                 goto clear;
 455         if (kernel && user_build_id)
 456                 goto clear;
 457
 458         elem_size = (user && user_build_id) ? sizeof(struct bpf_stack_build_id)
 459                                             : sizeof(u64);
 460         if (unlikely(size % elem_size))
 461                 goto clear;
 462
 463         /* cannot get valid user stack for task without user_mode regs */
 464         if (task && user && !user_mode(regs))
 465                 goto err_fault;
 466
 467         num_elem = size / elem_size;
 468         if (sysctl_perf_event_max_stack < num_elem)
 469                 init_nr = 0;
 470         else
 471                 init_nr = sysctl_perf_event_max_stack - num_elem;
 472
 473         if (trace_in)
 474                 trace = trace_in;
 475         else if (kernel && task)
 476                 trace = get_callchain_entry_for_task(task, init_nr);
 477         else
 478                 trace = get_perf_callchain(regs, init_nr, kernel, user,
 479                                            sysctl_perf_event_max_stack,
 480                                            false, false);
 481         if (unlikely(!trace))
 482                 goto err_fault;
 483
 484         trace_nr = trace->nr - init_nr;
 485         if (trace_nr < skip)
 486                 goto err_fault;
 487
 488         trace_nr -= skip;
 489         trace_nr = (trace_nr <= num_elem) ? trace_nr : num_elem;
 490         copy_len = trace_nr * elem_size;
 491         ips = trace->ip + skip + init_nr;
 492         if (user && user_build_id)
 493                 stack_map_get_build_id_offset(buf, ips, trace_nr, user);
 494         else
 495                 memcpy(buf, ips, copy_len);
 496
 497         if (size > copy_len)
 498                 memset(buf + copy_len, 0, size - copy_len);
 499         return copy_len;
 500
 501 err_fault:
 502         err = -EFAULT;
 503 clear:
 504         memset(buf, 0, size);
 505         return err;
 506 }
 507
 508 BPF_CALL_4(bpf_get_stack, struct pt_regs *, regs, void *, buf, u32, size,
 509            u64, flags)
 510 {
 511         return __bpf_get_stack(regs, NULL, NULL, buf, size, flags);
 512 }
 513
 514 const struct bpf_func_proto bpf_get_stack_proto = {
 515         .func           = bpf_get_stack,
 516         .gpl_only       = true,
 517         .ret_type       = RET_INTEGER,
 518         .arg1_type      = ARG_PTR_TO_CTX,
 519         .arg2_type      = ARG_PTR_TO_UNINIT_MEM,
 520         .arg3_type      = ARG_CONST_SIZE_OR_ZERO,
 521         .arg4_type      = ARG_ANYTHING,
 522 };
 523
 524 BPF_CALL_4(bpf_get_task_stack, struct task_struct *, task, void *, buf,
 525            u32, size, u64, flags)
 526 {
 527         struct pt_regs *regs;
 528         long res;
 529
 530         if (!try_get_task_stack(task))
 531                 return -EFAULT;
 532
 533         regs = task_pt_regs(task);
 534         res = __bpf_get_stack(regs, task, NULL, buf, size, flags);
 535         put_task_stack(task);
 536
 537         return res;
 538 }
 539
 540 const struct bpf_func_proto bpf_get_task_stack_proto = {
 541         .func           = bpf_get_task_stack,
 542         .gpl_only       = false,
 543         .ret_type       = RET_INTEGER,
 544         .arg1_type      = ARG_PTR_TO_BTF_ID,
 545         .arg1_btf_id    = &btf_task_struct_ids[0],
 546         .arg2_type      = ARG_PTR_TO_UNINIT_MEM,
 547         .arg3_type      = ARG_CONST_SIZE_OR_ZERO,
 548         .arg4_type      = ARG_ANYTHING,
 549 };
 550
 551 BPF_CALL_4(bpf_get_stack_pe, struct bpf_perf_event_data_kern *, ctx,
 552            void *, buf, u32, size, u64, flags)
 553 {
 554         struct pt_regs *regs = (struct pt_regs *)(ctx->regs);
 555         struct perf_event *event = ctx->event;
 556         struct perf_callchain_entry *trace;
 557         bool kernel, user;
 558         int err = -EINVAL;
 559         __u64 nr_kernel;
 560
 561         if (!(event->attr.sample_type & __PERF_SAMPLE_CALLCHAIN_EARLY))
 562                 return __bpf_get_stack(regs, NULL, NULL, buf, size, flags);
 563
 564         if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
 565                                BPF_F_USER_BUILD_ID)))
 566                 goto clear;
 567
 568         user = flags & BPF_F_USER_STACK;
 569         kernel = !user;
 570
 571         err = -EFAULT;
 572         trace = ctx->data->callchain;
 573         if (unlikely(!trace))
 574                 goto clear;
 575
 576         nr_kernel = count_kernel_ip(trace);
 577
 578         if (kernel) {
 579                 __u64 nr = trace->nr;
 580
 581                 trace->nr = nr_kernel;
 582                 err = __bpf_get_stack(regs, NULL, trace, buf, size, flags);
 583
 584                 /* restore nr */
 585                 trace->nr = nr;
 586         } else { /* user */
 587                 u64 skip = flags & BPF_F_SKIP_FIELD_MASK;
 588
 589                 skip += nr_kernel;
 590                 if (skip > BPF_F_SKIP_FIELD_MASK)
 591                         goto clear;
 592
 593                 flags = (flags & ~BPF_F_SKIP_FIELD_MASK) | skip;
 594                 err = __bpf_get_stack(regs, NULL, trace, buf, size, flags);
 595         }
 596         return err;
 597
 598 clear:
 599         memset(buf, 0, size);
 600         return err;
 601
 602 }
 603
 604 const struct bpf_func_proto bpf_get_stack_proto_pe = {
 605         .func           = bpf_get_stack_pe,
 606         .gpl_only       = true,
 607         .ret_type       = RET_INTEGER,
 608         .arg1_type      = ARG_PTR_TO_CTX,
 609         .arg2_type      = ARG_PTR_TO_UNINIT_MEM,
 610         .arg3_type      = ARG_CONST_SIZE_OR_ZERO,
 611         .arg4_type      = ARG_ANYTHING,
 612 };
 613
 614 /* Called from eBPF program */
 615 static void *stack_map_lookup_elem(struct bpf_map *map, void *key)
 616 {
 617         return ERR_PTR(-EOPNOTSUPP);
 618 }
 619
 620 /* Called from syscall */
 621 int bpf_stackmap_copy(struct bpf_map *map, void *key, void *value)
 622 {
 623         struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
 624         struct stack_map_bucket *bucket, *old_bucket;
 625         u32 id = *(u32 *)key, trace_len;
 626
 627         if (unlikely(id >= smap->n_buckets))
 628                 return -ENOENT;
 629
 630         bucket = xchg(&smap->buckets[id], NULL);
 631         if (!bucket)
 632                 return -ENOENT;
 633
 634         trace_len = bucket->nr * stack_map_data_size(map);
 635         memcpy(value, bucket->data, trace_len);
 636         memset(value + trace_len, 0, map->value_size - trace_len);
 637
 638         old_bucket = xchg(&smap->buckets[id], bucket);
 639         if (old_bucket)
 640                 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
 641         return 0;
 642 }
 643
 644 static int stack_map_get_next_key(struct bpf_map *map, void *key,
 645                                   void *next_key)
 646 {
 647         struct bpf_stack_map *smap = container_of(map,
 648                                                   struct bpf_stack_map, map);
 649         u32 id;
 650
 651         WARN_ON_ONCE(!rcu_read_lock_held());
 652
 653         if (!key) {
 654                 id = 0;
 655         } else {
 656                 id = *(u32 *)key;
 657                 if (id >= smap->n_buckets || !smap->buckets[id])
 658                         id = 0;
 659                 else
 660                         id++;
 661         }
 662
 663         while (id < smap->n_buckets && !smap->buckets[id])
 664                 id++;
 665
 666         if (id >= smap->n_buckets)
 667                 return -ENOENT;
 668
 669         *(u32 *)next_key = id;
 670         return 0;
 671 }
 672
 673 static int stack_map_update_elem(struct bpf_map *map, void *key, void *value,
 674                                  u64 map_flags)
 675 {
 676         return -EINVAL;
 677 }
 678
 679 /* Called from syscall or from eBPF program */
 680 static int stack_map_delete_elem(struct bpf_map *map, void *key)
 681 {
 682         struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
 683         struct stack_map_bucket *old_bucket;
 684         u32 id = *(u32 *)key;
 685
 686         if (unlikely(id >= smap->n_buckets))
 687                 return -E2BIG;
 688
 689         old_bucket = xchg(&smap->buckets[id], NULL);
 690         if (old_bucket) {
 691                 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
 692                 return 0;
 693         } else {
 694                 return -ENOENT;
 695         }
 696 }
 697
 698 /* Called when map->refcnt goes to zero, either from workqueue or from syscall */
 699 static void stack_map_free(struct bpf_map *map)
 700 {
 701         struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
 702
 703         bpf_map_area_free(smap->elems);
 704         pcpu_freelist_destroy(&smap->freelist);
 705         bpf_map_area_free(smap);
 706         put_callchain_buffers();
 707 }
 708
 709 static int stack_trace_map_btf_id;
 710 const struct bpf_map_ops stack_trace_map_ops = {
 711         .map_meta_equal = bpf_map_meta_equal,
 712         .map_alloc = stack_map_alloc,
 713         .map_free = stack_map_free,
 714         .map_get_next_key = stack_map_get_next_key,
 715         .map_lookup_elem = stack_map_lookup_elem,
 716         .map_update_elem = stack_map_update_elem,
 717         .map_delete_elem = stack_map_delete_elem,
 718         .map_check_btf = map_check_no_btf,
 719         .map_btf_name = "bpf_stack_map",
 720         .map_btf_id = &stack_trace_map_btf_id,
 721 };
 722
 723 static int __init stack_map_init(void)
 724 {
 725         int cpu;
 726         struct stack_map_irq_work *work;
 727
 728         for_each_possible_cpu(cpu) {
 729                 work = per_cpu_ptr(&up_read_work, cpu);
 730                 init_irq_work(&work->irq_work, do_up_read);
 731         }
 732         return 0;
 733 }
 734 subsys_initcall(stack_map_init);