projects/linux·blob v5.0-rc5 · refs

630 lines · 16.5 KiB

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