projects/linux·blob v4.19 · refs

624 lines · 16.2 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 == BPF_BUILD_ID_SIZE) {
184 memcpy(build_id,
185 note_start + note_offs +
186 ALIGN(sizeof("GNU"), 4) + sizeof(Elf32_Nhdr),
187 BPF_BUILD_ID_SIZE);
188 return 0;
189 }
190 new_offs = note_offs + sizeof(Elf32_Nhdr) +
191 ALIGN(nhdr->n_namesz, 4) + ALIGN(nhdr->n_descsz, 4);
192 if (new_offs <= note_offs) /* overflow */
193 break;
194 note_offs = new_offs;
195 }
196 return -EINVAL;
197}
198
199/* Parse build ID from 32-bit ELF */
200static int stack_map_get_build_id_32(void *page_addr,
201 unsigned char *build_id)
202{
203 Elf32_Ehdr *ehdr = (Elf32_Ehdr *)page_addr;
204 Elf32_Phdr *phdr;
205 int i;
206
207 /* only supports phdr that fits in one page */
208 if (ehdr->e_phnum >
209 (PAGE_SIZE - sizeof(Elf32_Ehdr)) / sizeof(Elf32_Phdr))
210 return -EINVAL;
211
212 phdr = (Elf32_Phdr *)(page_addr + sizeof(Elf32_Ehdr));
213
214 for (i = 0; i < ehdr->e_phnum; ++i)
215 if (phdr[i].p_type == PT_NOTE)
216 return stack_map_parse_build_id(page_addr, build_id,
217 page_addr + phdr[i].p_offset,
218 phdr[i].p_filesz);
219 return -EINVAL;
220}
221
222/* Parse build ID from 64-bit ELF */
223static int stack_map_get_build_id_64(void *page_addr,
224 unsigned char *build_id)
225{
226 Elf64_Ehdr *ehdr = (Elf64_Ehdr *)page_addr;
227 Elf64_Phdr *phdr;
228 int i;
229
230 /* only supports phdr that fits in one page */
231 if (ehdr->e_phnum >
232 (PAGE_SIZE - sizeof(Elf64_Ehdr)) / sizeof(Elf64_Phdr))
233 return -EINVAL;
234
235 phdr = (Elf64_Phdr *)(page_addr + sizeof(Elf64_Ehdr));
236
237 for (i = 0; i < ehdr->e_phnum; ++i)
238 if (phdr[i].p_type == PT_NOTE)
239 return stack_map_parse_build_id(page_addr, build_id,
240 page_addr + phdr[i].p_offset,
241 phdr[i].p_filesz);
242 return -EINVAL;
243}
244
245/* Parse build ID of ELF file mapped to vma */
246static int stack_map_get_build_id(struct vm_area_struct *vma,
247 unsigned char *build_id)
248{
249 Elf32_Ehdr *ehdr;
250 struct page *page;
251 void *page_addr;
252 int ret;
253
254 /* only works for page backed storage */
255 if (!vma->vm_file)
256 return -EINVAL;
257
258 page = find_get_page(vma->vm_file->f_mapping, 0);
259 if (!page)
260 return -EFAULT; /* page not mapped */
261
262 ret = -EINVAL;
263 page_addr = page_address(page);
264 ehdr = (Elf32_Ehdr *)page_addr;
265
266 /* compare magic x7f "ELF" */
267 if (memcmp(ehdr->e_ident, ELFMAG, SELFMAG) != 0)
268 goto out;
269
270 /* only support executable file and shared object file */
271 if (ehdr->e_type != ET_EXEC && ehdr->e_type != ET_DYN)
272 goto out;
273
274 if (ehdr->e_ident[EI_CLASS] == ELFCLASS32)
275 ret = stack_map_get_build_id_32(page_addr, build_id);
276 else if (ehdr->e_ident[EI_CLASS] == ELFCLASS64)
277 ret = stack_map_get_build_id_64(page_addr, build_id);
278out:
279 put_page(page);
280 return ret;
281}
282
283static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
284 u64 *ips, u32 trace_nr, bool user)
285{
286 int i;
287 struct vm_area_struct *vma;
288 bool irq_work_busy = false;
289 struct stack_map_irq_work *work = NULL;
290
291 if (in_nmi()) {
292 work = this_cpu_ptr(&up_read_work);
293 if (work->irq_work.flags & IRQ_WORK_BUSY)
294 /* cannot queue more up_read, fallback */
295 irq_work_busy = true;
296 }
297
298 /*
299 * We cannot do up_read() in nmi context. To do build_id lookup
300 * in nmi context, we need to run up_read() in irq_work. We use
301 * a percpu variable to do the irq_work. If the irq_work is
302 * already used by another lookup, we fall back to report ips.
303 *
304 * Same fallback is used for kernel stack (!user) on a stackmap
305 * with build_id.
306 */
307 if (!user || !current || !current->mm || irq_work_busy ||
308 down_read_trylock(&current->mm->mmap_sem) == 0) {
309 /* cannot access current->mm, fall back to ips */
310 for (i = 0; i < trace_nr; i++) {
311 id_offs[i].status = BPF_STACK_BUILD_ID_IP;
312 id_offs[i].ip = ips[i];
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 continue;
324 }
325 id_offs[i].offset = (vma->vm_pgoff << PAGE_SHIFT) + ips[i]
326 - vma->vm_start;
327 id_offs[i].status = BPF_STACK_BUILD_ID_VALID;
328 }
329
330 if (!work) {
331 up_read(&current->mm->mmap_sem);
332 } else {
333 work->sem = &current->mm->mmap_sem;
334 irq_work_queue(&work->irq_work);
335 }
336}
337
338BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map,
339 u64, flags)
340{
341 struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
342 struct perf_callchain_entry *trace;
343 struct stack_map_bucket *bucket, *new_bucket, *old_bucket;
344 u32 max_depth = map->value_size / stack_map_data_size(map);
345 /* stack_map_alloc() checks that max_depth <= sysctl_perf_event_max_stack */
346 u32 init_nr = sysctl_perf_event_max_stack - max_depth;
347 u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
348 u32 hash, id, trace_nr, trace_len;
349 bool user = flags & BPF_F_USER_STACK;
350 bool kernel = !user;
351 u64 *ips;
352 bool hash_matches;
353
354 if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
355 BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
356 return -EINVAL;
357
358 trace = get_perf_callchain(regs, init_nr, kernel, user,
359 sysctl_perf_event_max_stack, false, false);
360
361 if (unlikely(!trace))
362 /* couldn't fetch the stack trace */
363 return -EFAULT;
364
365 /* get_perf_callchain() guarantees that trace->nr >= init_nr
366 * and trace-nr <= sysctl_perf_event_max_stack, so trace_nr <= max_depth
367 */
368 trace_nr = trace->nr - init_nr;
369
370 if (trace_nr <= skip)
371 /* skipping more than usable stack trace */
372 return -EFAULT;
373
374 trace_nr -= skip;
375 trace_len = trace_nr * sizeof(u64);
376 ips = trace->ip + skip + init_nr;
377 hash = jhash2((u32 *)ips, trace_len / sizeof(u32), 0);
378 id = hash & (smap->n_buckets - 1);
379 bucket = READ_ONCE(smap->buckets[id]);
380
381 hash_matches = bucket && bucket->hash == hash;
382 /* fast cmp */
383 if (hash_matches && flags & BPF_F_FAST_STACK_CMP)
384 return id;
385
386 if (stack_map_use_build_id(map)) {
387 /* for build_id+offset, pop a bucket before slow cmp */
388 new_bucket = (struct stack_map_bucket *)
389 pcpu_freelist_pop(&smap->freelist);
390 if (unlikely(!new_bucket))
391 return -ENOMEM;
392 new_bucket->nr = trace_nr;
393 stack_map_get_build_id_offset(
394 (struct bpf_stack_build_id *)new_bucket->data,
395 ips, trace_nr, user);
396 trace_len = trace_nr * sizeof(struct bpf_stack_build_id);
397 if (hash_matches && bucket->nr == trace_nr &&
398 memcmp(bucket->data, new_bucket->data, trace_len) == 0) {
399 pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
400 return id;
401 }
402 if (bucket && !(flags & BPF_F_REUSE_STACKID)) {
403 pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
404 return -EEXIST;
405 }
406 } else {
407 if (hash_matches && bucket->nr == trace_nr &&
408 memcmp(bucket->data, ips, trace_len) == 0)
409 return id;
410 if (bucket && !(flags & BPF_F_REUSE_STACKID))
411 return -EEXIST;
412
413 new_bucket = (struct stack_map_bucket *)
414 pcpu_freelist_pop(&smap->freelist);
415 if (unlikely(!new_bucket))
416 return -ENOMEM;
417 memcpy(new_bucket->data, ips, trace_len);
418 }
419
420 new_bucket->hash = hash;
421 new_bucket->nr = trace_nr;
422
423 old_bucket = xchg(&smap->buckets[id], new_bucket);
424 if (old_bucket)
425 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
426 return id;
427}
428
429const struct bpf_func_proto bpf_get_stackid_proto = {
430 .func = bpf_get_stackid,
431 .gpl_only = true,
432 .ret_type = RET_INTEGER,
433 .arg1_type = ARG_PTR_TO_CTX,
434 .arg2_type = ARG_CONST_MAP_PTR,
435 .arg3_type = ARG_ANYTHING,
436};
437
438BPF_CALL_4(bpf_get_stack, struct pt_regs *, regs, void *, buf, u32, size,
439 u64, flags)
440{
441 u32 init_nr, trace_nr, copy_len, elem_size, num_elem;
442 bool user_build_id = flags & BPF_F_USER_BUILD_ID;
443 u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
444 bool user = flags & BPF_F_USER_STACK;
445 struct perf_callchain_entry *trace;
446 bool kernel = !user;
447 int err = -EINVAL;
448 u64 *ips;
449
450 if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
451 BPF_F_USER_BUILD_ID)))
452 goto clear;
453 if (kernel && user_build_id)
454 goto clear;
455
456 elem_size = (user && user_build_id) ? sizeof(struct bpf_stack_build_id)
457 : sizeof(u64);
458 if (unlikely(size % elem_size))
459 goto clear;
460
461 num_elem = size / elem_size;
462 if (sysctl_perf_event_max_stack < num_elem)
463 init_nr = 0;
464 else
465 init_nr = sysctl_perf_event_max_stack - num_elem;
466 trace = get_perf_callchain(regs, init_nr, kernel, user,
467 sysctl_perf_event_max_stack, false, false);
468 if (unlikely(!trace))
469 goto err_fault;
470
471 trace_nr = trace->nr - init_nr;
472 if (trace_nr < skip)
473 goto err_fault;
474
475 trace_nr -= skip;
476 trace_nr = (trace_nr <= num_elem) ? trace_nr : num_elem;
477 copy_len = trace_nr * elem_size;
478 ips = trace->ip + skip + init_nr;
479 if (user && user_build_id)
480 stack_map_get_build_id_offset(buf, ips, trace_nr, user);
481 else
482 memcpy(buf, ips, copy_len);
483
484 if (size > copy_len)
485 memset(buf + copy_len, 0, size - copy_len);
486 return copy_len;
487
488err_fault:
489 err = -EFAULT;
490clear:
491 memset(buf, 0, size);
492 return err;
493}
494
495const struct bpf_func_proto bpf_get_stack_proto = {
496 .func = bpf_get_stack,
497 .gpl_only = true,
498 .ret_type = RET_INTEGER,
499 .arg1_type = ARG_PTR_TO_CTX,
500 .arg2_type = ARG_PTR_TO_UNINIT_MEM,
501 .arg3_type = ARG_CONST_SIZE_OR_ZERO,
502 .arg4_type = ARG_ANYTHING,
503};
504
505/* Called from eBPF program */
506static void *stack_map_lookup_elem(struct bpf_map *map, void *key)
507{
508 return NULL;
509}
510
511/* Called from syscall */
512int bpf_stackmap_copy(struct bpf_map *map, void *key, void *value)
513{
514 struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
515 struct stack_map_bucket *bucket, *old_bucket;
516 u32 id = *(u32 *)key, trace_len;
517
518 if (unlikely(id >= smap->n_buckets))
519 return -ENOENT;
520
521 bucket = xchg(&smap->buckets[id], NULL);
522 if (!bucket)
523 return -ENOENT;
524
525 trace_len = bucket->nr * stack_map_data_size(map);
526 memcpy(value, bucket->data, trace_len);
527 memset(value + trace_len, 0, map->value_size - trace_len);
528
529 old_bucket = xchg(&smap->buckets[id], bucket);
530 if (old_bucket)
531 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
532 return 0;
533}
534
535static int stack_map_get_next_key(struct bpf_map *map, void *key,
536 void *next_key)
537{
538 struct bpf_stack_map *smap = container_of(map,
539 struct bpf_stack_map, map);
540 u32 id;
541
542 WARN_ON_ONCE(!rcu_read_lock_held());
543
544 if (!key) {
545 id = 0;
546 } else {
547 id = *(u32 *)key;
548 if (id >= smap->n_buckets || !smap->buckets[id])
549 id = 0;
550 else
551 id++;
552 }
553
554 while (id < smap->n_buckets && !smap->buckets[id])
555 id++;
556
557 if (id >= smap->n_buckets)
558 return -ENOENT;
559
560 *(u32 *)next_key = id;
561 return 0;
562}
563
564static int stack_map_update_elem(struct bpf_map *map, void *key, void *value,
565 u64 map_flags)
566{
567 return -EINVAL;
568}
569
570/* Called from syscall or from eBPF program */
571static int stack_map_delete_elem(struct bpf_map *map, void *key)
572{
573 struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
574 struct stack_map_bucket *old_bucket;
575 u32 id = *(u32 *)key;
576
577 if (unlikely(id >= smap->n_buckets))
578 return -E2BIG;
579
580 old_bucket = xchg(&smap->buckets[id], NULL);
581 if (old_bucket) {
582 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
583 return 0;
584 } else {
585 return -ENOENT;
586 }
587}
588
589/* Called when map->refcnt goes to zero, either from workqueue or from syscall */
590static void stack_map_free(struct bpf_map *map)
591{
592 struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
593
594 /* wait for bpf programs to complete before freeing stack map */
595 synchronize_rcu();
596
597 bpf_map_area_free(smap->elems);
598 pcpu_freelist_destroy(&smap->freelist);
599 bpf_map_area_free(smap);
600 put_callchain_buffers();
601}
602
603const struct bpf_map_ops stack_map_ops = {
604 .map_alloc = stack_map_alloc,
605 .map_free = stack_map_free,
606 .map_get_next_key = stack_map_get_next_key,
607 .map_lookup_elem = stack_map_lookup_elem,
608 .map_update_elem = stack_map_update_elem,
609 .map_delete_elem = stack_map_delete_elem,
610 .map_check_btf = map_check_no_btf,
611};
612
613static int __init stack_map_init(void)
614{
615 int cpu;
616 struct stack_map_irq_work *work;
617
618 for_each_possible_cpu(cpu) {
619 work = per_cpu_ptr(&up_read_work, cpu);
620 init_irq_work(&work->irq_work, do_up_read);
621 }
622 return 0;
623}
624subsys_initcall(stack_map_init);