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/elf.h>
  11 #include <linux/pagemap.h>
  12 #include <linux/irq_work.h>
  13 #include <linux/btf_ids.h>
  14 #include "percpu_freelist.h"
  15
  16 #define STACK_CREATE_FLAG_MASK                                  \
  17         (BPF_F_NUMA_NODE | BPF_F_RDONLY | BPF_F_WRONLY |        \
  18          BPF_F_STACK_BUILD_ID)
  19
  20 struct stack_map_bucket {
  21         struct pcpu_freelist_node fnode;
  22         u32 hash;
  23         u32 nr;
  24         u64 data[];
  25 };
  26
  27 struct bpf_stack_map {
  28         struct bpf_map map;
  29         void *elems;
  30         struct pcpu_freelist freelist;
  31         u32 n_buckets;
  32         struct stack_map_bucket *buckets[];
  33 };
  34
  35 /* irq_work to run up_read() for build_id lookup in nmi context */
  36 struct stack_map_irq_work {
  37         struct irq_work irq_work;
  38         struct mm_struct *mm;
  39 };
  40
  41 static void do_up_read(struct irq_work *entry)
  42 {
  43         struct stack_map_irq_work *work;
  44
  45         if (WARN_ON_ONCE(IS_ENABLED(CONFIG_PREEMPT_RT)))
  46                 return;
  47
  48         work = container_of(entry, struct stack_map_irq_work, irq_work);
  49         mmap_read_unlock_non_owner(work->mm);
  50 }
  51
  52 static DEFINE_PER_CPU(struct stack_map_irq_work, up_read_work);
  53
  54 static inline bool stack_map_use_build_id(struct bpf_map *map)
  55 {
  56         return (map->map_flags & BPF_F_STACK_BUILD_ID);
  57 }
  58
  59 static inline int stack_map_data_size(struct bpf_map *map)
  60 {
  61         return stack_map_use_build_id(map) ?
  62                 sizeof(struct bpf_stack_build_id) : sizeof(u64);
  63 }
  64
  65 static int prealloc_elems_and_freelist(struct bpf_stack_map *smap)
  66 {
  67         u32 elem_size = sizeof(struct stack_map_bucket) + 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         struct bpf_map_memory mem;
  94         u64 cost, n_buckets;
  95         int err;
  96
  97         if (!bpf_capable())
  98                 return ERR_PTR(-EPERM);
  99
 100         if (attr->map_flags & ~STACK_CREATE_FLAG_MASK)
 101                 return ERR_PTR(-EINVAL);
 102
 103         /* check sanity of attributes */
 104         if (attr->max_entries == 0 || attr->key_size != 4 ||
 105             value_size < 8 || value_size % 8)
 106                 return ERR_PTR(-EINVAL);
 107
 108         BUILD_BUG_ON(sizeof(struct bpf_stack_build_id) % sizeof(u64));
 109         if (attr->map_flags & BPF_F_STACK_BUILD_ID) {
 110                 if (value_size % sizeof(struct bpf_stack_build_id) ||
 111                     value_size / sizeof(struct bpf_stack_build_id)
 112                     > sysctl_perf_event_max_stack)
 113                         return ERR_PTR(-EINVAL);
 114         } else if (value_size / 8 > sysctl_perf_event_max_stack)
 115                 return ERR_PTR(-EINVAL);
 116
 117         /* hash table size must be power of 2 */
 118         n_buckets = roundup_pow_of_two(attr->max_entries);
 119
 120         cost = n_buckets * sizeof(struct stack_map_bucket *) + sizeof(*smap);
 121         cost += n_buckets * (value_size + sizeof(struct stack_map_bucket));
 122         err = bpf_map_charge_init(&mem, cost);
 123         if (err)
 124                 return ERR_PTR(err);
 125
 126         smap = bpf_map_area_alloc(cost, bpf_map_attr_numa_node(attr));
 127         if (!smap) {
 128                 bpf_map_charge_finish(&mem);
 129                 return ERR_PTR(-ENOMEM);
 130         }
 131
 132         bpf_map_init_from_attr(&smap->map, attr);
 133         smap->map.value_size = value_size;
 134         smap->n_buckets = n_buckets;
 135
 136         err = get_callchain_buffers(sysctl_perf_event_max_stack);
 137         if (err)
 138                 goto free_charge;
 139
 140         err = prealloc_elems_and_freelist(smap);
 141         if (err)
 142                 goto put_buffers;
 143
 144         bpf_map_charge_move(&smap->map.memory, &mem);
 145
 146         return &smap->map;
 147
 148 put_buffers:
 149         put_callchain_buffers();
 150 free_charge:
 151         bpf_map_charge_finish(&mem);
 152         bpf_map_area_free(smap);
 153         return ERR_PTR(err);
 154 }
 155
 156 #define BPF_BUILD_ID 3
 157 /*
 158  * Parse build id from the note segment. This logic can be shared between
 159  * 32-bit and 64-bit system, because Elf32_Nhdr and Elf64_Nhdr are
 160  * identical.
 161  */
 162 static inline int stack_map_parse_build_id(void *page_addr,
 163                                            unsigned char *build_id,
 164                                            void *note_start,
 165                                            Elf32_Word note_size)
 166 {
 167         Elf32_Word note_offs = 0, new_offs;
 168
 169         /* check for overflow */
 170         if (note_start < page_addr || note_start + note_size < note_start)
 171                 return -EINVAL;
 172
 173         /* only supports note that fits in the first page */
 174         if (note_start + note_size > page_addr + PAGE_SIZE)
 175                 return -EINVAL;
 176
 177         while (note_offs + sizeof(Elf32_Nhdr) < note_size) {
 178                 Elf32_Nhdr *nhdr = (Elf32_Nhdr *)(note_start + note_offs);
 179
 180                 if (nhdr->n_type == BPF_BUILD_ID &&
 181                     nhdr->n_namesz == sizeof("GNU") &&
 182                     nhdr->n_descsz > 0 &&
 183                     nhdr->n_descsz <= BPF_BUILD_ID_SIZE) {
 184                         memcpy(build_id,
 185                                note_start + note_offs +
 186                                ALIGN(sizeof("GNU"), 4) + sizeof(Elf32_Nhdr),
 187                                nhdr->n_descsz);
 188                         memset(build_id + nhdr->n_descsz, 0,
 189                                BPF_BUILD_ID_SIZE - nhdr->n_descsz);
 190                         return 0;
 191                 }
 192                 new_offs = note_offs + sizeof(Elf32_Nhdr) +
 193                         ALIGN(nhdr->n_namesz, 4) + ALIGN(nhdr->n_descsz, 4);
 194                 if (new_offs <= note_offs)  /* overflow */
 195                         break;
 196                 note_offs = new_offs;
 197         }
 198         return -EINVAL;
 199 }
 200
 201 /* Parse build ID from 32-bit ELF */
 202 static int stack_map_get_build_id_32(void *page_addr,
 203                                      unsigned char *build_id)
 204 {
 205         Elf32_Ehdr *ehdr = (Elf32_Ehdr *)page_addr;
 206         Elf32_Phdr *phdr;
 207         int i;
 208
 209         /* only supports phdr that fits in one page */
 210         if (ehdr->e_phnum >
 211             (PAGE_SIZE - sizeof(Elf32_Ehdr)) / sizeof(Elf32_Phdr))
 212                 return -EINVAL;
 213
 214         phdr = (Elf32_Phdr *)(page_addr + sizeof(Elf32_Ehdr));
 215
 216         for (i = 0; i < ehdr->e_phnum; ++i) {
 217                 if (phdr[i].p_type == PT_NOTE &&
 218                     !stack_map_parse_build_id(page_addr, build_id,
 219                                               page_addr + phdr[i].p_offset,
 220                                               phdr[i].p_filesz))
 221                         return 0;
 222         }
 223         return -EINVAL;
 224 }
 225
 226 /* Parse build ID from 64-bit ELF */
 227 static int stack_map_get_build_id_64(void *page_addr,
 228                                      unsigned char *build_id)
 229 {
 230         Elf64_Ehdr *ehdr = (Elf64_Ehdr *)page_addr;
 231         Elf64_Phdr *phdr;
 232         int i;
 233
 234         /* only supports phdr that fits in one page */
 235         if (ehdr->e_phnum >
 236             (PAGE_SIZE - sizeof(Elf64_Ehdr)) / sizeof(Elf64_Phdr))
 237                 return -EINVAL;
 238
 239         phdr = (Elf64_Phdr *)(page_addr + sizeof(Elf64_Ehdr));
 240
 241         for (i = 0; i < ehdr->e_phnum; ++i) {
 242                 if (phdr[i].p_type == PT_NOTE &&
 243                     !stack_map_parse_build_id(page_addr, build_id,
 244                                               page_addr + phdr[i].p_offset,
 245                                               phdr[i].p_filesz))
 246                         return 0;
 247         }
 248         return -EINVAL;
 249 }
 250
 251 /* Parse build ID of ELF file mapped to vma */
 252 static int stack_map_get_build_id(struct vm_area_struct *vma,
 253                                   unsigned char *build_id)
 254 {
 255         Elf32_Ehdr *ehdr;
 256         struct page *page;
 257         void *page_addr;
 258         int ret;
 259
 260         /* only works for page backed storage  */
 261         if (!vma->vm_file)
 262                 return -EINVAL;
 263
 264         page = find_get_page(vma->vm_file->f_mapping, 0);
 265         if (!page)
 266                 return -EFAULT; /* page not mapped */
 267
 268         ret = -EINVAL;
 269         page_addr = kmap_atomic(page);
 270         ehdr = (Elf32_Ehdr *)page_addr;
 271
 272         /* compare magic x7f "ELF" */
 273         if (memcmp(ehdr->e_ident, ELFMAG, SELFMAG) != 0)
 274                 goto out;
 275
 276         /* only support executable file and shared object file */
 277         if (ehdr->e_type != ET_EXEC && ehdr->e_type != ET_DYN)
 278                 goto out;
 279
 280         if (ehdr->e_ident[EI_CLASS] == ELFCLASS32)
 281                 ret = stack_map_get_build_id_32(page_addr, build_id);
 282         else if (ehdr->e_ident[EI_CLASS] == ELFCLASS64)
 283                 ret = stack_map_get_build_id_64(page_addr, build_id);
 284 out:
 285         kunmap_atomic(page_addr);
 286         put_page(page);
 287         return ret;
 288 }
 289
 290 static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
 291                                           u64 *ips, u32 trace_nr, bool user)
 292 {
 293         int i;
 294         struct vm_area_struct *vma;
 295         bool irq_work_busy = false;
 296         struct stack_map_irq_work *work = NULL;
 297
 298         if (irqs_disabled()) {
 299                 if (!IS_ENABLED(CONFIG_PREEMPT_RT)) {
 300                         work = this_cpu_ptr(&up_read_work);
 301                         if (atomic_read(&work->irq_work.flags) & IRQ_WORK_BUSY) {
 302                                 /* cannot queue more up_read, fallback */
 303                                 irq_work_busy = true;
 304                         }
 305                 } else {
 306                         /*
 307                          * PREEMPT_RT does not allow to trylock mmap sem in
 308                          * interrupt disabled context. Force the fallback code.
 309                          */
 310                         irq_work_busy = true;
 311                 }
 312         }
 313
 314         /*
 315          * We cannot do up_read() when the irq is disabled, because of
 316          * risk to deadlock with rq_lock. To do build_id lookup when the
 317          * irqs are disabled, we need to run up_read() in irq_work. We use
 318          * a percpu variable to do the irq_work. If the irq_work is
 319          * already used by another lookup, we fall back to report ips.
 320          *
 321          * Same fallback is used for kernel stack (!user) on a stackmap
 322          * with build_id.
 323          */
 324         if (!user || !current || !current->mm || irq_work_busy ||
 325             !mmap_read_trylock_non_owner(current->mm)) {
 326                 /* cannot access current->mm, fall back to ips */
 327                 for (i = 0; i < trace_nr; i++) {
 328                         id_offs[i].status = BPF_STACK_BUILD_ID_IP;
 329                         id_offs[i].ip = ips[i];
 330                         memset(id_offs[i].build_id, 0, BPF_BUILD_ID_SIZE);
 331                 }
 332                 return;
 333         }
 334
 335         for (i = 0; i < trace_nr; i++) {
 336                 vma = find_vma(current->mm, ips[i]);
 337                 if (!vma || stack_map_get_build_id(vma, id_offs[i].build_id)) {
 338                         /* per entry fall back to ips */
 339                         id_offs[i].status = BPF_STACK_BUILD_ID_IP;
 340                         id_offs[i].ip = ips[i];
 341                         memset(id_offs[i].build_id, 0, BPF_BUILD_ID_SIZE);
 342                         continue;
 343                 }
 344                 id_offs[i].offset = (vma->vm_pgoff << PAGE_SHIFT) + ips[i]
 345                         - vma->vm_start;
 346                 id_offs[i].status = BPF_STACK_BUILD_ID_VALID;
 347         }
 348
 349         if (!work) {
 350                 mmap_read_unlock_non_owner(current->mm);
 351         } else {
 352                 work->mm = current->mm;
 353                 irq_work_queue(&work->irq_work);
 354         }
 355 }
 356
 357 static struct perf_callchain_entry *
 358 get_callchain_entry_for_task(struct task_struct *task, u32 init_nr)
 359 {
 360 #ifdef CONFIG_STACKTRACE
 361         struct perf_callchain_entry *entry;
 362         int rctx;
 363
 364         entry = get_callchain_entry(&rctx);
 365
 366         if (!entry)
 367                 return NULL;
 368
 369         entry->nr = init_nr +
 370                 stack_trace_save_tsk(task, (unsigned long *)(entry->ip + init_nr),
 371                                      sysctl_perf_event_max_stack - init_nr, 0);
 372
 373         /* stack_trace_save_tsk() works on unsigned long array, while
 374          * perf_callchain_entry uses u64 array. For 32-bit systems, it is
 375          * necessary to fix this mismatch.
 376          */
 377         if (__BITS_PER_LONG != 64) {
 378                 unsigned long *from = (unsigned long *) entry->ip;
 379                 u64 *to = entry->ip;
 380                 int i;
 381
 382                 /* copy data from the end to avoid using extra buffer */
 383                 for (i = entry->nr - 1; i >= (int)init_nr; i--)
 384                         to[i] = (u64)(from[i]);
 385         }
 386
 387         put_callchain_entry(rctx);
 388
 389         return entry;
 390 #else /* CONFIG_STACKTRACE */
 391         return NULL;
 392 #endif
 393 }
 394
 395 static long __bpf_get_stackid(struct bpf_map *map,
 396                               struct perf_callchain_entry *trace, u64 flags)
 397 {
 398         struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
 399         struct stack_map_bucket *bucket, *new_bucket, *old_bucket;
 400         u32 max_depth = map->value_size / stack_map_data_size(map);
 401         /* stack_map_alloc() checks that max_depth <= sysctl_perf_event_max_stack */
 402         u32 init_nr = sysctl_perf_event_max_stack - max_depth;
 403         u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
 404         u32 hash, id, trace_nr, trace_len;
 405         bool user = flags & BPF_F_USER_STACK;
 406         u64 *ips;
 407         bool hash_matches;
 408
 409         /* get_perf_callchain() guarantees that trace->nr >= init_nr
 410          * and trace-nr <= sysctl_perf_event_max_stack, so trace_nr <= max_depth
 411          */
 412         trace_nr = trace->nr - init_nr;
 413
 414         if (trace_nr <= skip)
 415                 /* skipping more than usable stack trace */
 416                 return -EFAULT;
 417
 418         trace_nr -= skip;
 419         trace_len = trace_nr * sizeof(u64);
 420         ips = trace->ip + skip + init_nr;
 421         hash = jhash2((u32 *)ips, trace_len / sizeof(u32), 0);
 422         id = hash & (smap->n_buckets - 1);
 423         bucket = READ_ONCE(smap->buckets[id]);
 424
 425         hash_matches = bucket && bucket->hash == hash;
 426         /* fast cmp */
 427         if (hash_matches && flags & BPF_F_FAST_STACK_CMP)
 428                 return id;
 429
 430         if (stack_map_use_build_id(map)) {
 431                 /* for build_id+offset, pop a bucket before slow cmp */
 432                 new_bucket = (struct stack_map_bucket *)
 433                         pcpu_freelist_pop(&smap->freelist);
 434                 if (unlikely(!new_bucket))
 435                         return -ENOMEM;
 436                 new_bucket->nr = trace_nr;
 437                 stack_map_get_build_id_offset(
 438                         (struct bpf_stack_build_id *)new_bucket->data,
 439                         ips, trace_nr, user);
 440                 trace_len = trace_nr * sizeof(struct bpf_stack_build_id);
 441                 if (hash_matches && bucket->nr == trace_nr &&
 442                     memcmp(bucket->data, new_bucket->data, trace_len) == 0) {
 443                         pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
 444                         return id;
 445                 }
 446                 if (bucket && !(flags & BPF_F_REUSE_STACKID)) {
 447                         pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
 448                         return -EEXIST;
 449                 }
 450         } else {
 451                 if (hash_matches && bucket->nr == trace_nr &&
 452                     memcmp(bucket->data, ips, trace_len) == 0)
 453                         return id;
 454                 if (bucket && !(flags & BPF_F_REUSE_STACKID))
 455                         return -EEXIST;
 456
 457                 new_bucket = (struct stack_map_bucket *)
 458                         pcpu_freelist_pop(&smap->freelist);
 459                 if (unlikely(!new_bucket))
 460                         return -ENOMEM;
 461                 memcpy(new_bucket->data, ips, trace_len);
 462         }
 463
 464         new_bucket->hash = hash;
 465         new_bucket->nr = trace_nr;
 466
 467         old_bucket = xchg(&smap->buckets[id], new_bucket);
 468         if (old_bucket)
 469                 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
 470         return id;
 471 }
 472
 473 BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map,
 474            u64, flags)
 475 {
 476         u32 max_depth = map->value_size / stack_map_data_size(map);
 477         /* stack_map_alloc() checks that max_depth <= sysctl_perf_event_max_stack */
 478         u32 init_nr = sysctl_perf_event_max_stack - max_depth;
 479         bool user = flags & BPF_F_USER_STACK;
 480         struct perf_callchain_entry *trace;
 481         bool kernel = !user;
 482
 483         if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
 484                                BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
 485                 return -EINVAL;
 486
 487         trace = get_perf_callchain(regs, init_nr, kernel, user,
 488                                    sysctl_perf_event_max_stack, false, false);
 489
 490         if (unlikely(!trace))
 491                 /* couldn't fetch the stack trace */
 492                 return -EFAULT;
 493
 494         return __bpf_get_stackid(map, trace, flags);
 495 }
 496
 497 const struct bpf_func_proto bpf_get_stackid_proto = {
 498         .func           = bpf_get_stackid,
 499         .gpl_only       = true,
 500         .ret_type       = RET_INTEGER,
 501         .arg1_type      = ARG_PTR_TO_CTX,
 502         .arg2_type      = ARG_CONST_MAP_PTR,
 503         .arg3_type      = ARG_ANYTHING,
 504 };
 505
 506 static __u64 count_kernel_ip(struct perf_callchain_entry *trace)
 507 {
 508         __u64 nr_kernel = 0;
 509
 510         while (nr_kernel < trace->nr) {
 511                 if (trace->ip[nr_kernel] == PERF_CONTEXT_USER)
 512                         break;
 513                 nr_kernel++;
 514         }
 515         return nr_kernel;
 516 }
 517
 518 BPF_CALL_3(bpf_get_stackid_pe, struct bpf_perf_event_data_kern *, ctx,
 519            struct bpf_map *, map, u64, flags)
 520 {
 521         struct perf_event *event = ctx->event;
 522         struct perf_callchain_entry *trace;
 523         bool kernel, user;
 524         __u64 nr_kernel;
 525         int ret;
 526
 527         /* perf_sample_data doesn't have callchain, use bpf_get_stackid */
 528         if (!(event->attr.sample_type & __PERF_SAMPLE_CALLCHAIN_EARLY))
 529                 return bpf_get_stackid((unsigned long)(ctx->regs),
 530                                        (unsigned long) map, flags, 0, 0);
 531
 532         if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
 533                                BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
 534                 return -EINVAL;
 535
 536         user = flags & BPF_F_USER_STACK;
 537         kernel = !user;
 538
 539         trace = ctx->data->callchain;
 540         if (unlikely(!trace))
 541                 return -EFAULT;
 542
 543         nr_kernel = count_kernel_ip(trace);
 544
 545         if (kernel) {
 546                 __u64 nr = trace->nr;
 547
 548                 trace->nr = nr_kernel;
 549                 ret = __bpf_get_stackid(map, trace, flags);
 550
 551                 /* restore nr */
 552                 trace->nr = nr;
 553         } else { /* user */
 554                 u64 skip = flags & BPF_F_SKIP_FIELD_MASK;
 555
 556                 skip += nr_kernel;
 557                 if (skip > BPF_F_SKIP_FIELD_MASK)
 558                         return -EFAULT;
 559
 560                 flags = (flags & ~BPF_F_SKIP_FIELD_MASK) | skip;
 561                 ret = __bpf_get_stackid(map, trace, flags);
 562         }
 563         return ret;
 564 }
 565
 566 const struct bpf_func_proto bpf_get_stackid_proto_pe = {
 567         .func           = bpf_get_stackid_pe,
 568         .gpl_only       = false,
 569         .ret_type       = RET_INTEGER,
 570         .arg1_type      = ARG_PTR_TO_CTX,
 571         .arg2_type      = ARG_CONST_MAP_PTR,
 572         .arg3_type      = ARG_ANYTHING,
 573 };
 574
 575 static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task,
 576                             struct perf_callchain_entry *trace_in,
 577                             void *buf, u32 size, u64 flags)
 578 {
 579         u32 init_nr, trace_nr, copy_len, elem_size, num_elem;
 580         bool user_build_id = flags & BPF_F_USER_BUILD_ID;
 581         u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
 582         bool user = flags & BPF_F_USER_STACK;
 583         struct perf_callchain_entry *trace;
 584         bool kernel = !user;
 585         int err = -EINVAL;
 586         u64 *ips;
 587
 588         if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
 589                                BPF_F_USER_BUILD_ID)))
 590                 goto clear;
 591         if (kernel && user_build_id)
 592                 goto clear;
 593
 594         elem_size = (user && user_build_id) ? sizeof(struct bpf_stack_build_id)
 595                                             : sizeof(u64);
 596         if (unlikely(size % elem_size))
 597                 goto clear;
 598
 599         /* cannot get valid user stack for task without user_mode regs */
 600         if (task && user && !user_mode(regs))
 601                 goto err_fault;
 602
 603         num_elem = size / elem_size;
 604         if (sysctl_perf_event_max_stack < num_elem)
 605                 init_nr = 0;
 606         else
 607                 init_nr = sysctl_perf_event_max_stack - num_elem;
 608
 609         if (trace_in)
 610                 trace = trace_in;
 611         else if (kernel && task)
 612                 trace = get_callchain_entry_for_task(task, init_nr);
 613         else
 614                 trace = get_perf_callchain(regs, init_nr, kernel, user,
 615                                            sysctl_perf_event_max_stack,
 616                                            false, false);
 617         if (unlikely(!trace))
 618                 goto err_fault;
 619
 620         trace_nr = trace->nr - init_nr;
 621         if (trace_nr < skip)
 622                 goto err_fault;
 623
 624         trace_nr -= skip;
 625         trace_nr = (trace_nr <= num_elem) ? trace_nr : num_elem;
 626         copy_len = trace_nr * elem_size;
 627         ips = trace->ip + skip + init_nr;
 628         if (user && user_build_id)
 629                 stack_map_get_build_id_offset(buf, ips, trace_nr, user);
 630         else
 631                 memcpy(buf, ips, copy_len);
 632
 633         if (size > copy_len)
 634                 memset(buf + copy_len, 0, size - copy_len);
 635         return copy_len;
 636
 637 err_fault:
 638         err = -EFAULT;
 639 clear:
 640         memset(buf, 0, size);
 641         return err;
 642 }
 643
 644 BPF_CALL_4(bpf_get_stack, struct pt_regs *, regs, void *, buf, u32, size,
 645            u64, flags)
 646 {
 647         return __bpf_get_stack(regs, NULL, NULL, buf, size, flags);
 648 }
 649
 650 const struct bpf_func_proto bpf_get_stack_proto = {
 651         .func           = bpf_get_stack,
 652         .gpl_only       = true,
 653         .ret_type       = RET_INTEGER,
 654         .arg1_type      = ARG_PTR_TO_CTX,
 655         .arg2_type      = ARG_PTR_TO_UNINIT_MEM,
 656         .arg3_type      = ARG_CONST_SIZE_OR_ZERO,
 657         .arg4_type      = ARG_ANYTHING,
 658 };
 659
 660 BPF_CALL_4(bpf_get_task_stack, struct task_struct *, task, void *, buf,
 661            u32, size, u64, flags)
 662 {
 663         struct pt_regs *regs = task_pt_regs(task);
 664
 665         return __bpf_get_stack(regs, task, NULL, buf, size, flags);
 666 }
 667
 668 BTF_ID_LIST_SINGLE(bpf_get_task_stack_btf_ids, struct, task_struct)
 669
 670 const struct bpf_func_proto bpf_get_task_stack_proto = {
 671         .func           = bpf_get_task_stack,
 672         .gpl_only       = false,
 673         .ret_type       = RET_INTEGER,
 674         .arg1_type      = ARG_PTR_TO_BTF_ID,
 675         .arg1_btf_id    = &bpf_get_task_stack_btf_ids[0],
 676         .arg2_type      = ARG_PTR_TO_UNINIT_MEM,
 677         .arg3_type      = ARG_CONST_SIZE_OR_ZERO,
 678         .arg4_type      = ARG_ANYTHING,
 679 };
 680
 681 BPF_CALL_4(bpf_get_stack_pe, struct bpf_perf_event_data_kern *, ctx,
 682            void *, buf, u32, size, u64, flags)
 683 {
 684         struct pt_regs *regs = (struct pt_regs *)(ctx->regs);
 685         struct perf_event *event = ctx->event;
 686         struct perf_callchain_entry *trace;
 687         bool kernel, user;
 688         int err = -EINVAL;
 689         __u64 nr_kernel;
 690
 691         if (!(event->attr.sample_type & __PERF_SAMPLE_CALLCHAIN_EARLY))
 692                 return __bpf_get_stack(regs, NULL, NULL, buf, size, flags);
 693
 694         if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
 695                                BPF_F_USER_BUILD_ID)))
 696                 goto clear;
 697
 698         user = flags & BPF_F_USER_STACK;
 699         kernel = !user;
 700
 701         err = -EFAULT;
 702         trace = ctx->data->callchain;
 703         if (unlikely(!trace))
 704                 goto clear;
 705
 706         nr_kernel = count_kernel_ip(trace);
 707
 708         if (kernel) {
 709                 __u64 nr = trace->nr;
 710
 711                 trace->nr = nr_kernel;
 712                 err = __bpf_get_stack(regs, NULL, trace, buf, size, flags);
 713
 714                 /* restore nr */
 715                 trace->nr = nr;
 716         } else { /* user */
 717                 u64 skip = flags & BPF_F_SKIP_FIELD_MASK;
 718
 719                 skip += nr_kernel;
 720                 if (skip > BPF_F_SKIP_FIELD_MASK)
 721                         goto clear;
 722
 723                 flags = (flags & ~BPF_F_SKIP_FIELD_MASK) | skip;
 724                 err = __bpf_get_stack(regs, NULL, trace, buf, size, flags);
 725         }
 726         return err;
 727
 728 clear:
 729         memset(buf, 0, size);
 730         return err;
 731
 732 }
 733
 734 const struct bpf_func_proto bpf_get_stack_proto_pe = {
 735         .func           = bpf_get_stack_pe,
 736         .gpl_only       = true,
 737         .ret_type       = RET_INTEGER,
 738         .arg1_type      = ARG_PTR_TO_CTX,
 739         .arg2_type      = ARG_PTR_TO_UNINIT_MEM,
 740         .arg3_type      = ARG_CONST_SIZE_OR_ZERO,
 741         .arg4_type      = ARG_ANYTHING,
 742 };
 743
 744 /* Called from eBPF program */
 745 static void *stack_map_lookup_elem(struct bpf_map *map, void *key)
 746 {
 747         return ERR_PTR(-EOPNOTSUPP);
 748 }
 749
 750 /* Called from syscall */
 751 int bpf_stackmap_copy(struct bpf_map *map, void *key, void *value)
 752 {
 753         struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
 754         struct stack_map_bucket *bucket, *old_bucket;
 755         u32 id = *(u32 *)key, trace_len;
 756
 757         if (unlikely(id >= smap->n_buckets))
 758                 return -ENOENT;
 759
 760         bucket = xchg(&smap->buckets[id], NULL);
 761         if (!bucket)
 762                 return -ENOENT;
 763
 764         trace_len = bucket->nr * stack_map_data_size(map);
 765         memcpy(value, bucket->data, trace_len);
 766         memset(value + trace_len, 0, map->value_size - trace_len);
 767
 768         old_bucket = xchg(&smap->buckets[id], bucket);
 769         if (old_bucket)
 770                 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
 771         return 0;
 772 }
 773
 774 static int stack_map_get_next_key(struct bpf_map *map, void *key,
 775                                   void *next_key)
 776 {
 777         struct bpf_stack_map *smap = container_of(map,
 778                                                   struct bpf_stack_map, map);
 779         u32 id;
 780
 781         WARN_ON_ONCE(!rcu_read_lock_held());
 782
 783         if (!key) {
 784                 id = 0;
 785         } else {
 786                 id = *(u32 *)key;
 787                 if (id >= smap->n_buckets || !smap->buckets[id])
 788                         id = 0;
 789                 else
 790                         id++;
 791         }
 792
 793         while (id < smap->n_buckets && !smap->buckets[id])
 794                 id++;
 795
 796         if (id >= smap->n_buckets)
 797                 return -ENOENT;
 798
 799         *(u32 *)next_key = id;
 800         return 0;
 801 }
 802
 803 static int stack_map_update_elem(struct bpf_map *map, void *key, void *value,
 804                                  u64 map_flags)
 805 {
 806         return -EINVAL;
 807 }
 808
 809 /* Called from syscall or from eBPF program */
 810 static int stack_map_delete_elem(struct bpf_map *map, void *key)
 811 {
 812         struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
 813         struct stack_map_bucket *old_bucket;
 814         u32 id = *(u32 *)key;
 815
 816         if (unlikely(id >= smap->n_buckets))
 817                 return -E2BIG;
 818
 819         old_bucket = xchg(&smap->buckets[id], NULL);
 820         if (old_bucket) {
 821                 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
 822                 return 0;
 823         } else {
 824                 return -ENOENT;
 825         }
 826 }
 827
 828 /* Called when map->refcnt goes to zero, either from workqueue or from syscall */
 829 static void stack_map_free(struct bpf_map *map)
 830 {
 831         struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
 832
 833         bpf_map_area_free(smap->elems);
 834         pcpu_freelist_destroy(&smap->freelist);
 835         bpf_map_area_free(smap);
 836         put_callchain_buffers();
 837 }
 838
 839 static int stack_trace_map_btf_id;
 840 const struct bpf_map_ops stack_trace_map_ops = {
 841         .map_meta_equal = bpf_map_meta_equal,
 842         .map_alloc = stack_map_alloc,
 843         .map_free = stack_map_free,
 844         .map_get_next_key = stack_map_get_next_key,
 845         .map_lookup_elem = stack_map_lookup_elem,
 846         .map_update_elem = stack_map_update_elem,
 847         .map_delete_elem = stack_map_delete_elem,
 848         .map_check_btf = map_check_no_btf,
 849         .map_btf_name = "bpf_stack_map",
 850         .map_btf_id = &stack_trace_map_btf_id,
 851 };
 852
 853 static int __init stack_map_init(void)
 854 {
 855         int cpu;
 856         struct stack_map_irq_work *work;
 857
 858         for_each_possible_cpu(cpu) {
 859                 work = per_cpu_ptr(&up_read_work, cpu);
 860                 init_irq_work(&work->irq_work, do_up_read);
 861         }
 862         return 0;
 863 }
 864 subsys_initcall(stack_map_init);