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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/stacktrace.h>
8#include <linux/perf_event.h>
9#include <linux/elf.h>
10#include <linux/pagemap.h>
11#include <linux/irq_work.h>
12#include "percpu_freelist.h"
13
14#define STACK_CREATE_FLAG_MASK \
15 (BPF_F_NUMA_NODE | BPF_F_RDONLY | BPF_F_WRONLY | \
16 BPF_F_STACK_BUILD_ID)
17
18struct stack_map_bucket {
19 struct pcpu_freelist_node fnode;
20 u32 hash;
21 u32 nr;
22 u64 data[];
23};
24
25struct bpf_stack_map {
26 struct bpf_map map;
27 void *elems;
28 struct pcpu_freelist freelist;
29 u32 n_buckets;
30 struct stack_map_bucket *buckets[];
31};
32
33/* irq_work to run up_read() for build_id lookup in nmi context */
34struct stack_map_irq_work {
35 struct irq_work irq_work;
36 struct rw_semaphore *sem;
37};
38
39static void do_up_read(struct irq_work *entry)
40{
41 struct stack_map_irq_work *work;
42
43 work = container_of(entry, struct stack_map_irq_work, irq_work);
44 up_read_non_owner(work->sem);
45 work->sem = NULL;
46}
47
48static DEFINE_PER_CPU(struct stack_map_irq_work, up_read_work);
49
50static inline bool stack_map_use_build_id(struct bpf_map *map)
51{
52 return (map->map_flags & BPF_F_STACK_BUILD_ID);
53}
54
55static inline int stack_map_data_size(struct bpf_map *map)
56{
57 return stack_map_use_build_id(map) ?
58 sizeof(struct bpf_stack_build_id) : sizeof(u64);
59}
60
61static int prealloc_elems_and_freelist(struct bpf_stack_map *smap)
62{
63 u32 elem_size = sizeof(struct stack_map_bucket) + smap->map.value_size;
64 int err;
65
66 smap->elems = bpf_map_area_alloc(elem_size * smap->map.max_entries,
67 smap->map.numa_node);
68 if (!smap->elems)
69 return -ENOMEM;
70
71 err = pcpu_freelist_init(&smap->freelist);
72 if (err)
73 goto free_elems;
74
75 pcpu_freelist_populate(&smap->freelist, smap->elems, elem_size,
76 smap->map.max_entries);
77 return 0;
78
79free_elems:
80 bpf_map_area_free(smap->elems);
81 return err;
82}
83
84/* Called from syscall */
85static struct bpf_map *stack_map_alloc(union bpf_attr *attr)
86{
87 u32 value_size = attr->value_size;
88 struct bpf_stack_map *smap;
89 struct bpf_map_memory mem;
90 u64 cost, n_buckets;
91 int err;
92
93 if (!capable(CAP_SYS_ADMIN))
94 return ERR_PTR(-EPERM);
95
96 if (attr->map_flags & ~STACK_CREATE_FLAG_MASK)
97 return ERR_PTR(-EINVAL);
98
99 /* check sanity of attributes */
100 if (attr->max_entries == 0 || attr->key_size != 4 ||
101 value_size < 8 || value_size % 8)
102 return ERR_PTR(-EINVAL);
103
104 BUILD_BUG_ON(sizeof(struct bpf_stack_build_id) % sizeof(u64));
105 if (attr->map_flags & BPF_F_STACK_BUILD_ID) {
106 if (value_size % sizeof(struct bpf_stack_build_id) ||
107 value_size / sizeof(struct bpf_stack_build_id)
108 > sysctl_perf_event_max_stack)
109 return ERR_PTR(-EINVAL);
110 } else if (value_size / 8 > sysctl_perf_event_max_stack)
111 return ERR_PTR(-EINVAL);
112
113 /* hash table size must be power of 2 */
114 n_buckets = roundup_pow_of_two(attr->max_entries);
115
116 cost = n_buckets * sizeof(struct stack_map_bucket *) + sizeof(*smap);
117 cost += n_buckets * (value_size + sizeof(struct stack_map_bucket));
118 err = bpf_map_charge_init(&mem, cost);
119 if (err)
120 return ERR_PTR(err);
121
122 smap = bpf_map_area_alloc(cost, bpf_map_attr_numa_node(attr));
123 if (!smap) {
124 bpf_map_charge_finish(&mem);
125 return ERR_PTR(-ENOMEM);
126 }
127
128 bpf_map_init_from_attr(&smap->map, attr);
129 smap->map.value_size = value_size;
130 smap->n_buckets = n_buckets;
131
132 err = get_callchain_buffers(sysctl_perf_event_max_stack);
133 if (err)
134 goto free_charge;
135
136 err = prealloc_elems_and_freelist(smap);
137 if (err)
138 goto put_buffers;
139
140 bpf_map_charge_move(&smap->map.memory, &mem);
141
142 return &smap->map;
143
144put_buffers:
145 put_callchain_buffers();
146free_charge:
147 bpf_map_charge_finish(&mem);
148 bpf_map_area_free(smap);
149 return ERR_PTR(err);
150}
151
152#define BPF_BUILD_ID 3
153/*
154 * Parse build id from the note segment. This logic can be shared between
155 * 32-bit and 64-bit system, because Elf32_Nhdr and Elf64_Nhdr are
156 * identical.
157 */
158static inline int stack_map_parse_build_id(void *page_addr,
159 unsigned char *build_id,
160 void *note_start,
161 Elf32_Word note_size)
162{
163 Elf32_Word note_offs = 0, new_offs;
164
165 /* check for overflow */
166 if (note_start < page_addr || note_start + note_size < note_start)
167 return -EINVAL;
168
169 /* only supports note that fits in the first page */
170 if (note_start + note_size > page_addr + PAGE_SIZE)
171 return -EINVAL;
172
173 while (note_offs + sizeof(Elf32_Nhdr) < note_size) {
174 Elf32_Nhdr *nhdr = (Elf32_Nhdr *)(note_start + note_offs);
175
176 if (nhdr->n_type == BPF_BUILD_ID &&
177 nhdr->n_namesz == sizeof("GNU") &&
178 nhdr->n_descsz > 0 &&
179 nhdr->n_descsz <= BPF_BUILD_ID_SIZE) {
180 memcpy(build_id,
181 note_start + note_offs +
182 ALIGN(sizeof("GNU"), 4) + sizeof(Elf32_Nhdr),
183 nhdr->n_descsz);
184 memset(build_id + nhdr->n_descsz, 0,
185 BPF_BUILD_ID_SIZE - nhdr->n_descsz);
186 return 0;
187 }
188 new_offs = note_offs + sizeof(Elf32_Nhdr) +
189 ALIGN(nhdr->n_namesz, 4) + ALIGN(nhdr->n_descsz, 4);
190 if (new_offs <= note_offs) /* overflow */
191 break;
192 note_offs = new_offs;
193 }
194 return -EINVAL;
195}
196
197/* Parse build ID from 32-bit ELF */
198static int stack_map_get_build_id_32(void *page_addr,
199 unsigned char *build_id)
200{
201 Elf32_Ehdr *ehdr = (Elf32_Ehdr *)page_addr;
202 Elf32_Phdr *phdr;
203 int i;
204
205 /* only supports phdr that fits in one page */
206 if (ehdr->e_phnum >
207 (PAGE_SIZE - sizeof(Elf32_Ehdr)) / sizeof(Elf32_Phdr))
208 return -EINVAL;
209
210 phdr = (Elf32_Phdr *)(page_addr + sizeof(Elf32_Ehdr));
211
212 for (i = 0; i < ehdr->e_phnum; ++i)
213 if (phdr[i].p_type == PT_NOTE)
214 return stack_map_parse_build_id(page_addr, build_id,
215 page_addr + phdr[i].p_offset,
216 phdr[i].p_filesz);
217 return -EINVAL;
218}
219
220/* Parse build ID from 64-bit ELF */
221static int stack_map_get_build_id_64(void *page_addr,
222 unsigned char *build_id)
223{
224 Elf64_Ehdr *ehdr = (Elf64_Ehdr *)page_addr;
225 Elf64_Phdr *phdr;
226 int i;
227
228 /* only supports phdr that fits in one page */
229 if (ehdr->e_phnum >
230 (PAGE_SIZE - sizeof(Elf64_Ehdr)) / sizeof(Elf64_Phdr))
231 return -EINVAL;
232
233 phdr = (Elf64_Phdr *)(page_addr + sizeof(Elf64_Ehdr));
234
235 for (i = 0; i < ehdr->e_phnum; ++i)
236 if (phdr[i].p_type == PT_NOTE)
237 return stack_map_parse_build_id(page_addr, build_id,
238 page_addr + phdr[i].p_offset,
239 phdr[i].p_filesz);
240 return -EINVAL;
241}
242
243/* Parse build ID of ELF file mapped to vma */
244static int stack_map_get_build_id(struct vm_area_struct *vma,
245 unsigned char *build_id)
246{
247 Elf32_Ehdr *ehdr;
248 struct page *page;
249 void *page_addr;
250 int ret;
251
252 /* only works for page backed storage */
253 if (!vma->vm_file)
254 return -EINVAL;
255
256 page = find_get_page(vma->vm_file->f_mapping, 0);
257 if (!page)
258 return -EFAULT; /* page not mapped */
259
260 ret = -EINVAL;
261 page_addr = kmap_atomic(page);
262 ehdr = (Elf32_Ehdr *)page_addr;
263
264 /* compare magic x7f "ELF" */
265 if (memcmp(ehdr->e_ident, ELFMAG, SELFMAG) != 0)
266 goto out;
267
268 /* only support executable file and shared object file */
269 if (ehdr->e_type != ET_EXEC && ehdr->e_type != ET_DYN)
270 goto out;
271
272 if (ehdr->e_ident[EI_CLASS] == ELFCLASS32)
273 ret = stack_map_get_build_id_32(page_addr, build_id);
274 else if (ehdr->e_ident[EI_CLASS] == ELFCLASS64)
275 ret = stack_map_get_build_id_64(page_addr, build_id);
276out:
277 kunmap_atomic(page_addr);
278 put_page(page);
279 return ret;
280}
281
282static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
283 u64 *ips, u32 trace_nr, bool user)
284{
285 int i;
286 struct vm_area_struct *vma;
287 bool irq_work_busy = false;
288 struct stack_map_irq_work *work = NULL;
289
290 if (in_nmi()) {
291 work = this_cpu_ptr(&up_read_work);
292 if (work->irq_work.flags & IRQ_WORK_BUSY)
293 /* cannot queue more up_read, fallback */
294 irq_work_busy = true;
295 }
296
297 /*
298 * We cannot do up_read() in nmi context. To do build_id lookup
299 * in nmi context, we need to run up_read() in irq_work. We use
300 * a percpu variable to do the irq_work. If the irq_work is
301 * already used by another lookup, we fall back to report ips.
302 *
303 * Same fallback is used for kernel stack (!user) on a stackmap
304 * with build_id.
305 */
306 if (!user || !current || !current->mm || irq_work_busy ||
307 down_read_trylock(¤t->mm->mmap_sem) == 0) {
308 /* cannot access current->mm, fall back to ips */
309 for (i = 0; i < trace_nr; i++) {
310 id_offs[i].status = BPF_STACK_BUILD_ID_IP;
311 id_offs[i].ip = ips[i];
312 memset(id_offs[i].build_id, 0, BPF_BUILD_ID_SIZE);
313 }
314 return;
315 }
316
317 for (i = 0; i < trace_nr; i++) {
318 vma = find_vma(current->mm, ips[i]);
319 if (!vma || stack_map_get_build_id(vma, id_offs[i].build_id)) {
320 /* per entry fall back to ips */
321 id_offs[i].status = BPF_STACK_BUILD_ID_IP;
322 id_offs[i].ip = ips[i];
323 memset(id_offs[i].build_id, 0, BPF_BUILD_ID_SIZE);
324 continue;
325 }
326 id_offs[i].offset = (vma->vm_pgoff << PAGE_SHIFT) + ips[i]
327 - vma->vm_start;
328 id_offs[i].status = BPF_STACK_BUILD_ID_VALID;
329 }
330
331 if (!work) {
332 up_read(¤t->mm->mmap_sem);
333 } else {
334 work->sem = ¤t->mm->mmap_sem;
335 irq_work_queue(&work->irq_work);
336 /*
337 * The irq_work will release the mmap_sem with
338 * up_read_non_owner(). The rwsem_release() is called
339 * here to release the lock from lockdep's perspective.
340 */
341 rwsem_release(¤t->mm->mmap_sem.dep_map, 1, _RET_IP_);
342 }
343}
344
345BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map,
346 u64, flags)
347{
348 struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
349 struct perf_callchain_entry *trace;
350 struct stack_map_bucket *bucket, *new_bucket, *old_bucket;
351 u32 max_depth = map->value_size / stack_map_data_size(map);
352 /* stack_map_alloc() checks that max_depth <= sysctl_perf_event_max_stack */
353 u32 init_nr = sysctl_perf_event_max_stack - max_depth;
354 u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
355 u32 hash, id, trace_nr, trace_len;
356 bool user = flags & BPF_F_USER_STACK;
357 bool kernel = !user;
358 u64 *ips;
359 bool hash_matches;
360
361 if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
362 BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
363 return -EINVAL;
364
365 trace = get_perf_callchain(regs, init_nr, kernel, user,
366 sysctl_perf_event_max_stack, false, false);
367
368 if (unlikely(!trace))
369 /* couldn't fetch the stack trace */
370 return -EFAULT;
371
372 /* get_perf_callchain() guarantees that trace->nr >= init_nr
373 * and trace-nr <= sysctl_perf_event_max_stack, so trace_nr <= max_depth
374 */
375 trace_nr = trace->nr - init_nr;
376
377 if (trace_nr <= skip)
378 /* skipping more than usable stack trace */
379 return -EFAULT;
380
381 trace_nr -= skip;
382 trace_len = trace_nr * sizeof(u64);
383 ips = trace->ip + skip + init_nr;
384 hash = jhash2((u32 *)ips, trace_len / sizeof(u32), 0);
385 id = hash & (smap->n_buckets - 1);
386 bucket = READ_ONCE(smap->buckets[id]);
387
388 hash_matches = bucket && bucket->hash == hash;
389 /* fast cmp */
390 if (hash_matches && flags & BPF_F_FAST_STACK_CMP)
391 return id;
392
393 if (stack_map_use_build_id(map)) {
394 /* for build_id+offset, pop a bucket before slow cmp */
395 new_bucket = (struct stack_map_bucket *)
396 pcpu_freelist_pop(&smap->freelist);
397 if (unlikely(!new_bucket))
398 return -ENOMEM;
399 new_bucket->nr = trace_nr;
400 stack_map_get_build_id_offset(
401 (struct bpf_stack_build_id *)new_bucket->data,
402 ips, trace_nr, user);
403 trace_len = trace_nr * sizeof(struct bpf_stack_build_id);
404 if (hash_matches && bucket->nr == trace_nr &&
405 memcmp(bucket->data, new_bucket->data, trace_len) == 0) {
406 pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
407 return id;
408 }
409 if (bucket && !(flags & BPF_F_REUSE_STACKID)) {
410 pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
411 return -EEXIST;
412 }
413 } else {
414 if (hash_matches && bucket->nr == trace_nr &&
415 memcmp(bucket->data, ips, trace_len) == 0)
416 return id;
417 if (bucket && !(flags & BPF_F_REUSE_STACKID))
418 return -EEXIST;
419
420 new_bucket = (struct stack_map_bucket *)
421 pcpu_freelist_pop(&smap->freelist);
422 if (unlikely(!new_bucket))
423 return -ENOMEM;
424 memcpy(new_bucket->data, ips, trace_len);
425 }
426
427 new_bucket->hash = hash;
428 new_bucket->nr = trace_nr;
429
430 old_bucket = xchg(&smap->buckets[id], new_bucket);
431 if (old_bucket)
432 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
433 return id;
434}
435
436const struct bpf_func_proto bpf_get_stackid_proto = {
437 .func = bpf_get_stackid,
438 .gpl_only = true,
439 .ret_type = RET_INTEGER,
440 .arg1_type = ARG_PTR_TO_CTX,
441 .arg2_type = ARG_CONST_MAP_PTR,
442 .arg3_type = ARG_ANYTHING,
443};
444
445BPF_CALL_4(bpf_get_stack, struct pt_regs *, regs, void *, buf, u32, size,
446 u64, flags)
447{
448 u32 init_nr, trace_nr, copy_len, elem_size, num_elem;
449 bool user_build_id = flags & BPF_F_USER_BUILD_ID;
450 u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
451 bool user = flags & BPF_F_USER_STACK;
452 struct perf_callchain_entry *trace;
453 bool kernel = !user;
454 int err = -EINVAL;
455 u64 *ips;
456
457 if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
458 BPF_F_USER_BUILD_ID)))
459 goto clear;
460 if (kernel && user_build_id)
461 goto clear;
462
463 elem_size = (user && user_build_id) ? sizeof(struct bpf_stack_build_id)
464 : sizeof(u64);
465 if (unlikely(size % elem_size))
466 goto clear;
467
468 num_elem = size / elem_size;
469 if (sysctl_perf_event_max_stack < num_elem)
470 init_nr = 0;
471 else
472 init_nr = sysctl_perf_event_max_stack - num_elem;
473 trace = get_perf_callchain(regs, init_nr, kernel, user,
474 sysctl_perf_event_max_stack, false, false);
475 if (unlikely(!trace))
476 goto err_fault;
477
478 trace_nr = trace->nr - init_nr;
479 if (trace_nr < skip)
480 goto err_fault;
481
482 trace_nr -= skip;
483 trace_nr = (trace_nr <= num_elem) ? trace_nr : num_elem;
484 copy_len = trace_nr * elem_size;
485 ips = trace->ip + skip + init_nr;
486 if (user && user_build_id)
487 stack_map_get_build_id_offset(buf, ips, trace_nr, user);
488 else
489 memcpy(buf, ips, copy_len);
490
491 if (size > copy_len)
492 memset(buf + copy_len, 0, size - copy_len);
493 return copy_len;
494
495err_fault:
496 err = -EFAULT;
497clear:
498 memset(buf, 0, size);
499 return err;
500}
501
502const struct bpf_func_proto bpf_get_stack_proto = {
503 .func = bpf_get_stack,
504 .gpl_only = true,
505 .ret_type = RET_INTEGER,
506 .arg1_type = ARG_PTR_TO_CTX,
507 .arg2_type = ARG_PTR_TO_UNINIT_MEM,
508 .arg3_type = ARG_CONST_SIZE_OR_ZERO,
509 .arg4_type = ARG_ANYTHING,
510};
511
512/* Called from eBPF program */
513static void *stack_map_lookup_elem(struct bpf_map *map, void *key)
514{
515 return ERR_PTR(-EOPNOTSUPP);
516}
517
518/* Called from syscall */
519int bpf_stackmap_copy(struct bpf_map *map, void *key, void *value)
520{
521 struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
522 struct stack_map_bucket *bucket, *old_bucket;
523 u32 id = *(u32 *)key, trace_len;
524
525 if (unlikely(id >= smap->n_buckets))
526 return -ENOENT;
527
528 bucket = xchg(&smap->buckets[id], NULL);
529 if (!bucket)
530 return -ENOENT;
531
532 trace_len = bucket->nr * stack_map_data_size(map);
533 memcpy(value, bucket->data, trace_len);
534 memset(value + trace_len, 0, map->value_size - trace_len);
535
536 old_bucket = xchg(&smap->buckets[id], bucket);
537 if (old_bucket)
538 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
539 return 0;
540}
541
542static int stack_map_get_next_key(struct bpf_map *map, void *key,
543 void *next_key)
544{
545 struct bpf_stack_map *smap = container_of(map,
546 struct bpf_stack_map, map);
547 u32 id;
548
549 WARN_ON_ONCE(!rcu_read_lock_held());
550
551 if (!key) {
552 id = 0;
553 } else {
554 id = *(u32 *)key;
555 if (id >= smap->n_buckets || !smap->buckets[id])
556 id = 0;
557 else
558 id++;
559 }
560
561 while (id < smap->n_buckets && !smap->buckets[id])
562 id++;
563
564 if (id >= smap->n_buckets)
565 return -ENOENT;
566
567 *(u32 *)next_key = id;
568 return 0;
569}
570
571static int stack_map_update_elem(struct bpf_map *map, void *key, void *value,
572 u64 map_flags)
573{
574 return -EINVAL;
575}
576
577/* Called from syscall or from eBPF program */
578static int stack_map_delete_elem(struct bpf_map *map, void *key)
579{
580 struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
581 struct stack_map_bucket *old_bucket;
582 u32 id = *(u32 *)key;
583
584 if (unlikely(id >= smap->n_buckets))
585 return -E2BIG;
586
587 old_bucket = xchg(&smap->buckets[id], NULL);
588 if (old_bucket) {
589 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
590 return 0;
591 } else {
592 return -ENOENT;
593 }
594}
595
596/* Called when map->refcnt goes to zero, either from workqueue or from syscall */
597static void stack_map_free(struct bpf_map *map)
598{
599 struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
600
601 /* wait for bpf programs to complete before freeing stack map */
602 synchronize_rcu();
603
604 bpf_map_area_free(smap->elems);
605 pcpu_freelist_destroy(&smap->freelist);
606 bpf_map_area_free(smap);
607 put_callchain_buffers();
608}
609
610const struct bpf_map_ops stack_trace_map_ops = {
611 .map_alloc = stack_map_alloc,
612 .map_free = stack_map_free,
613 .map_get_next_key = stack_map_get_next_key,
614 .map_lookup_elem = stack_map_lookup_elem,
615 .map_update_elem = stack_map_update_elem,
616 .map_delete_elem = stack_map_delete_elem,
617 .map_check_btf = map_check_no_btf,
618};
619
620static int __init stack_map_init(void)
621{
622 int cpu;
623 struct stack_map_irq_work *work;
624
625 for_each_possible_cpu(cpu) {
626 work = per_cpu_ptr(&up_read_work, cpu);
627 init_irq_work(&work->irq_work, do_up_read);
628 }
629 return 0;
630}
631subsys_initcall(stack_map_init);
1/* Copyright (c) 2016 Facebook
2 *
3 * This program is free software; you can redistribute it and/or
4 * modify it under the terms of version 2 of the GNU General Public
5 * License as published by the Free Software Foundation.
6 */
7#include <linux/bpf.h>
8#include <linux/jhash.h>
9#include <linux/filter.h>
10#include <linux/stacktrace.h>
11#include <linux/perf_event.h>
12#include <linux/elf.h>
13#include <linux/pagemap.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
20struct stack_map_bucket {
21 struct pcpu_freelist_node fnode;
22 u32 hash;
23 u32 nr;
24 u64 data[];
25};
26
27struct 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
35static inline bool stack_map_use_build_id(struct bpf_map *map)
36{
37 return (map->map_flags & BPF_F_STACK_BUILD_ID);
38}
39
40static inline int stack_map_data_size(struct bpf_map *map)
41{
42 return stack_map_use_build_id(map) ?
43 sizeof(struct bpf_stack_build_id) : sizeof(u64);
44}
45
46static int prealloc_elems_and_freelist(struct bpf_stack_map *smap)
47{
48 u32 elem_size = sizeof(struct stack_map_bucket) + smap->map.value_size;
49 int err;
50
51 smap->elems = bpf_map_area_alloc(elem_size * smap->map.max_entries,
52 smap->map.numa_node);
53 if (!smap->elems)
54 return -ENOMEM;
55
56 err = pcpu_freelist_init(&smap->freelist);
57 if (err)
58 goto free_elems;
59
60 pcpu_freelist_populate(&smap->freelist, smap->elems, elem_size,
61 smap->map.max_entries);
62 return 0;
63
64free_elems:
65 bpf_map_area_free(smap->elems);
66 return err;
67}
68
69/* Called from syscall */
70static struct bpf_map *stack_map_alloc(union bpf_attr *attr)
71{
72 u32 value_size = attr->value_size;
73 struct bpf_stack_map *smap;
74 u64 cost, n_buckets;
75 int err;
76
77 if (!capable(CAP_SYS_ADMIN))
78 return ERR_PTR(-EPERM);
79
80 if (attr->map_flags & ~STACK_CREATE_FLAG_MASK)
81 return ERR_PTR(-EINVAL);
82
83 /* check sanity of attributes */
84 if (attr->max_entries == 0 || attr->key_size != 4 ||
85 value_size < 8 || value_size % 8)
86 return ERR_PTR(-EINVAL);
87
88 BUILD_BUG_ON(sizeof(struct bpf_stack_build_id) % sizeof(u64));
89 if (attr->map_flags & BPF_F_STACK_BUILD_ID) {
90 if (value_size % sizeof(struct bpf_stack_build_id) ||
91 value_size / sizeof(struct bpf_stack_build_id)
92 > sysctl_perf_event_max_stack)
93 return ERR_PTR(-EINVAL);
94 } else if (value_size / 8 > sysctl_perf_event_max_stack)
95 return ERR_PTR(-EINVAL);
96
97 /* hash table size must be power of 2 */
98 n_buckets = roundup_pow_of_two(attr->max_entries);
99
100 cost = n_buckets * sizeof(struct stack_map_bucket *) + sizeof(*smap);
101 if (cost >= U32_MAX - PAGE_SIZE)
102 return ERR_PTR(-E2BIG);
103
104 smap = bpf_map_area_alloc(cost, bpf_map_attr_numa_node(attr));
105 if (!smap)
106 return ERR_PTR(-ENOMEM);
107
108 err = -E2BIG;
109 cost += n_buckets * (value_size + sizeof(struct stack_map_bucket));
110 if (cost >= U32_MAX - PAGE_SIZE)
111 goto free_smap;
112
113 bpf_map_init_from_attr(&smap->map, attr);
114 smap->map.value_size = value_size;
115 smap->n_buckets = n_buckets;
116 smap->map.pages = round_up(cost, PAGE_SIZE) >> PAGE_SHIFT;
117
118 err = bpf_map_precharge_memlock(smap->map.pages);
119 if (err)
120 goto free_smap;
121
122 err = get_callchain_buffers(sysctl_perf_event_max_stack);
123 if (err)
124 goto free_smap;
125
126 err = prealloc_elems_and_freelist(smap);
127 if (err)
128 goto put_buffers;
129
130 return &smap->map;
131
132put_buffers:
133 put_callchain_buffers();
134free_smap:
135 bpf_map_area_free(smap);
136 return ERR_PTR(err);
137}
138
139#define BPF_BUILD_ID 3
140/*
141 * Parse build id from the note segment. This logic can be shared between
142 * 32-bit and 64-bit system, because Elf32_Nhdr and Elf64_Nhdr are
143 * identical.
144 */
145static inline int stack_map_parse_build_id(void *page_addr,
146 unsigned char *build_id,
147 void *note_start,
148 Elf32_Word note_size)
149{
150 Elf32_Word note_offs = 0, new_offs;
151
152 /* check for overflow */
153 if (note_start < page_addr || note_start + note_size < note_start)
154 return -EINVAL;
155
156 /* only supports note that fits in the first page */
157 if (note_start + note_size > page_addr + PAGE_SIZE)
158 return -EINVAL;
159
160 while (note_offs + sizeof(Elf32_Nhdr) < note_size) {
161 Elf32_Nhdr *nhdr = (Elf32_Nhdr *)(note_start + note_offs);
162
163 if (nhdr->n_type == BPF_BUILD_ID &&
164 nhdr->n_namesz == sizeof("GNU") &&
165 nhdr->n_descsz == BPF_BUILD_ID_SIZE) {
166 memcpy(build_id,
167 note_start + note_offs +
168 ALIGN(sizeof("GNU"), 4) + sizeof(Elf32_Nhdr),
169 BPF_BUILD_ID_SIZE);
170 return 0;
171 }
172 new_offs = note_offs + sizeof(Elf32_Nhdr) +
173 ALIGN(nhdr->n_namesz, 4) + ALIGN(nhdr->n_descsz, 4);
174 if (new_offs <= note_offs) /* overflow */
175 break;
176 note_offs = new_offs;
177 }
178 return -EINVAL;
179}
180
181/* Parse build ID from 32-bit ELF */
182static int stack_map_get_build_id_32(void *page_addr,
183 unsigned char *build_id)
184{
185 Elf32_Ehdr *ehdr = (Elf32_Ehdr *)page_addr;
186 Elf32_Phdr *phdr;
187 int i;
188
189 /* only supports phdr that fits in one page */
190 if (ehdr->e_phnum >
191 (PAGE_SIZE - sizeof(Elf32_Ehdr)) / sizeof(Elf32_Phdr))
192 return -EINVAL;
193
194 phdr = (Elf32_Phdr *)(page_addr + sizeof(Elf32_Ehdr));
195
196 for (i = 0; i < ehdr->e_phnum; ++i)
197 if (phdr[i].p_type == PT_NOTE)
198 return stack_map_parse_build_id(page_addr, build_id,
199 page_addr + phdr[i].p_offset,
200 phdr[i].p_filesz);
201 return -EINVAL;
202}
203
204/* Parse build ID from 64-bit ELF */
205static int stack_map_get_build_id_64(void *page_addr,
206 unsigned char *build_id)
207{
208 Elf64_Ehdr *ehdr = (Elf64_Ehdr *)page_addr;
209 Elf64_Phdr *phdr;
210 int i;
211
212 /* only supports phdr that fits in one page */
213 if (ehdr->e_phnum >
214 (PAGE_SIZE - sizeof(Elf64_Ehdr)) / sizeof(Elf64_Phdr))
215 return -EINVAL;
216
217 phdr = (Elf64_Phdr *)(page_addr + sizeof(Elf64_Ehdr));
218
219 for (i = 0; i < ehdr->e_phnum; ++i)
220 if (phdr[i].p_type == PT_NOTE)
221 return stack_map_parse_build_id(page_addr, build_id,
222 page_addr + phdr[i].p_offset,
223 phdr[i].p_filesz);
224 return -EINVAL;
225}
226
227/* Parse build ID of ELF file mapped to vma */
228static int stack_map_get_build_id(struct vm_area_struct *vma,
229 unsigned char *build_id)
230{
231 Elf32_Ehdr *ehdr;
232 struct page *page;
233 void *page_addr;
234 int ret;
235
236 /* only works for page backed storage */
237 if (!vma->vm_file)
238 return -EINVAL;
239
240 page = find_get_page(vma->vm_file->f_mapping, 0);
241 if (!page)
242 return -EFAULT; /* page not mapped */
243
244 ret = -EINVAL;
245 page_addr = page_address(page);
246 ehdr = (Elf32_Ehdr *)page_addr;
247
248 /* compare magic x7f "ELF" */
249 if (memcmp(ehdr->e_ident, ELFMAG, SELFMAG) != 0)
250 goto out;
251
252 /* only support executable file and shared object file */
253 if (ehdr->e_type != ET_EXEC && ehdr->e_type != ET_DYN)
254 goto out;
255
256 if (ehdr->e_ident[EI_CLASS] == ELFCLASS32)
257 ret = stack_map_get_build_id_32(page_addr, build_id);
258 else if (ehdr->e_ident[EI_CLASS] == ELFCLASS64)
259 ret = stack_map_get_build_id_64(page_addr, build_id);
260out:
261 put_page(page);
262 return ret;
263}
264
265static void stack_map_get_build_id_offset(struct bpf_map *map,
266 struct stack_map_bucket *bucket,
267 u64 *ips, u32 trace_nr, bool user)
268{
269 int i;
270 struct vm_area_struct *vma;
271 struct bpf_stack_build_id *id_offs;
272
273 bucket->nr = trace_nr;
274 id_offs = (struct bpf_stack_build_id *)bucket->data;
275
276 /*
277 * We cannot do up_read() in nmi context, so build_id lookup is
278 * only supported for non-nmi events. If at some point, it is
279 * possible to run find_vma() without taking the semaphore, we
280 * would like to allow build_id lookup in nmi context.
281 *
282 * Same fallback is used for kernel stack (!user) on a stackmap
283 * with build_id.
284 */
285 if (!user || !current || !current->mm || in_nmi() ||
286 down_read_trylock(¤t->mm->mmap_sem) == 0) {
287 /* cannot access current->mm, fall back to ips */
288 for (i = 0; i < trace_nr; i++) {
289 id_offs[i].status = BPF_STACK_BUILD_ID_IP;
290 id_offs[i].ip = ips[i];
291 }
292 return;
293 }
294
295 for (i = 0; i < trace_nr; i++) {
296 vma = find_vma(current->mm, ips[i]);
297 if (!vma || stack_map_get_build_id(vma, id_offs[i].build_id)) {
298 /* per entry fall back to ips */
299 id_offs[i].status = BPF_STACK_BUILD_ID_IP;
300 id_offs[i].ip = ips[i];
301 continue;
302 }
303 id_offs[i].offset = (vma->vm_pgoff << PAGE_SHIFT) + ips[i]
304 - vma->vm_start;
305 id_offs[i].status = BPF_STACK_BUILD_ID_VALID;
306 }
307 up_read(¤t->mm->mmap_sem);
308}
309
310BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map,
311 u64, flags)
312{
313 struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
314 struct perf_callchain_entry *trace;
315 struct stack_map_bucket *bucket, *new_bucket, *old_bucket;
316 u32 max_depth = map->value_size / stack_map_data_size(map);
317 /* stack_map_alloc() checks that max_depth <= sysctl_perf_event_max_stack */
318 u32 init_nr = sysctl_perf_event_max_stack - max_depth;
319 u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
320 u32 hash, id, trace_nr, trace_len;
321 bool user = flags & BPF_F_USER_STACK;
322 bool kernel = !user;
323 u64 *ips;
324 bool hash_matches;
325
326 if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
327 BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
328 return -EINVAL;
329
330 trace = get_perf_callchain(regs, init_nr, kernel, user,
331 sysctl_perf_event_max_stack, false, false);
332
333 if (unlikely(!trace))
334 /* couldn't fetch the stack trace */
335 return -EFAULT;
336
337 /* get_perf_callchain() guarantees that trace->nr >= init_nr
338 * and trace-nr <= sysctl_perf_event_max_stack, so trace_nr <= max_depth
339 */
340 trace_nr = trace->nr - init_nr;
341
342 if (trace_nr <= skip)
343 /* skipping more than usable stack trace */
344 return -EFAULT;
345
346 trace_nr -= skip;
347 trace_len = trace_nr * sizeof(u64);
348 ips = trace->ip + skip + init_nr;
349 hash = jhash2((u32 *)ips, trace_len / sizeof(u32), 0);
350 id = hash & (smap->n_buckets - 1);
351 bucket = READ_ONCE(smap->buckets[id]);
352
353 hash_matches = bucket && bucket->hash == hash;
354 /* fast cmp */
355 if (hash_matches && flags & BPF_F_FAST_STACK_CMP)
356 return id;
357
358 if (stack_map_use_build_id(map)) {
359 /* for build_id+offset, pop a bucket before slow cmp */
360 new_bucket = (struct stack_map_bucket *)
361 pcpu_freelist_pop(&smap->freelist);
362 if (unlikely(!new_bucket))
363 return -ENOMEM;
364 stack_map_get_build_id_offset(map, new_bucket, ips,
365 trace_nr, user);
366 trace_len = trace_nr * sizeof(struct bpf_stack_build_id);
367 if (hash_matches && bucket->nr == trace_nr &&
368 memcmp(bucket->data, new_bucket->data, trace_len) == 0) {
369 pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
370 return id;
371 }
372 if (bucket && !(flags & BPF_F_REUSE_STACKID)) {
373 pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
374 return -EEXIST;
375 }
376 } else {
377 if (hash_matches && bucket->nr == trace_nr &&
378 memcmp(bucket->data, ips, trace_len) == 0)
379 return id;
380 if (bucket && !(flags & BPF_F_REUSE_STACKID))
381 return -EEXIST;
382
383 new_bucket = (struct stack_map_bucket *)
384 pcpu_freelist_pop(&smap->freelist);
385 if (unlikely(!new_bucket))
386 return -ENOMEM;
387 memcpy(new_bucket->data, ips, trace_len);
388 }
389
390 new_bucket->hash = hash;
391 new_bucket->nr = trace_nr;
392
393 old_bucket = xchg(&smap->buckets[id], new_bucket);
394 if (old_bucket)
395 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
396 return id;
397}
398
399const struct bpf_func_proto bpf_get_stackid_proto = {
400 .func = bpf_get_stackid,
401 .gpl_only = true,
402 .ret_type = RET_INTEGER,
403 .arg1_type = ARG_PTR_TO_CTX,
404 .arg2_type = ARG_CONST_MAP_PTR,
405 .arg3_type = ARG_ANYTHING,
406};
407
408/* Called from eBPF program */
409static void *stack_map_lookup_elem(struct bpf_map *map, void *key)
410{
411 return NULL;
412}
413
414/* Called from syscall */
415int bpf_stackmap_copy(struct bpf_map *map, void *key, void *value)
416{
417 struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
418 struct stack_map_bucket *bucket, *old_bucket;
419 u32 id = *(u32 *)key, trace_len;
420
421 if (unlikely(id >= smap->n_buckets))
422 return -ENOENT;
423
424 bucket = xchg(&smap->buckets[id], NULL);
425 if (!bucket)
426 return -ENOENT;
427
428 trace_len = bucket->nr * stack_map_data_size(map);
429 memcpy(value, bucket->data, trace_len);
430 memset(value + trace_len, 0, map->value_size - trace_len);
431
432 old_bucket = xchg(&smap->buckets[id], bucket);
433 if (old_bucket)
434 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
435 return 0;
436}
437
438static int stack_map_get_next_key(struct bpf_map *map, void *key,
439 void *next_key)
440{
441 struct bpf_stack_map *smap = container_of(map,
442 struct bpf_stack_map, map);
443 u32 id;
444
445 WARN_ON_ONCE(!rcu_read_lock_held());
446
447 if (!key) {
448 id = 0;
449 } else {
450 id = *(u32 *)key;
451 if (id >= smap->n_buckets || !smap->buckets[id])
452 id = 0;
453 else
454 id++;
455 }
456
457 while (id < smap->n_buckets && !smap->buckets[id])
458 id++;
459
460 if (id >= smap->n_buckets)
461 return -ENOENT;
462
463 *(u32 *)next_key = id;
464 return 0;
465}
466
467static int stack_map_update_elem(struct bpf_map *map, void *key, void *value,
468 u64 map_flags)
469{
470 return -EINVAL;
471}
472
473/* Called from syscall or from eBPF program */
474static int stack_map_delete_elem(struct bpf_map *map, void *key)
475{
476 struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
477 struct stack_map_bucket *old_bucket;
478 u32 id = *(u32 *)key;
479
480 if (unlikely(id >= smap->n_buckets))
481 return -E2BIG;
482
483 old_bucket = xchg(&smap->buckets[id], NULL);
484 if (old_bucket) {
485 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
486 return 0;
487 } else {
488 return -ENOENT;
489 }
490}
491
492/* Called when map->refcnt goes to zero, either from workqueue or from syscall */
493static void stack_map_free(struct bpf_map *map)
494{
495 struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
496
497 /* wait for bpf programs to complete before freeing stack map */
498 synchronize_rcu();
499
500 bpf_map_area_free(smap->elems);
501 pcpu_freelist_destroy(&smap->freelist);
502 bpf_map_area_free(smap);
503 put_callchain_buffers();
504}
505
506const struct bpf_map_ops stack_map_ops = {
507 .map_alloc = stack_map_alloc,
508 .map_free = stack_map_free,
509 .map_get_next_key = stack_map_get_next_key,
510 .map_lookup_elem = stack_map_lookup_elem,
511 .map_update_elem = stack_map_update_elem,
512 .map_delete_elem = stack_map_delete_elem,
513};