projects/linux·blob v5.2-rc4 · refs

633 lines · 16.6 KiB

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 u64 cost, n_buckets;
90 int err;
91
92 if (!capable(CAP_SYS_ADMIN))
93 return ERR_PTR(-EPERM);
94
95 if (attr->map_flags & ~STACK_CREATE_FLAG_MASK)
96 return ERR_PTR(-EINVAL);
97
98 /* check sanity of attributes */
99 if (attr->max_entries == 0 || attr->key_size != 4 ||
100 value_size < 8 || value_size % 8)
101 return ERR_PTR(-EINVAL);
102
103 BUILD_BUG_ON(sizeof(struct bpf_stack_build_id) % sizeof(u64));
104 if (attr->map_flags & BPF_F_STACK_BUILD_ID) {
105 if (value_size % sizeof(struct bpf_stack_build_id) ||
106 value_size / sizeof(struct bpf_stack_build_id)
107 > sysctl_perf_event_max_stack)
108 return ERR_PTR(-EINVAL);
109 } else if (value_size / 8 > sysctl_perf_event_max_stack)
110 return ERR_PTR(-EINVAL);
111
112 /* hash table size must be power of 2 */
113 n_buckets = roundup_pow_of_two(attr->max_entries);
114
115 cost = n_buckets * sizeof(struct stack_map_bucket *) + sizeof(*smap);
116 if (cost >= U32_MAX - PAGE_SIZE)
117 return ERR_PTR(-E2BIG);
118
119 smap = bpf_map_area_alloc(cost, bpf_map_attr_numa_node(attr));
120 if (!smap)
121 return ERR_PTR(-ENOMEM);
122
123 err = -E2BIG;
124 cost += n_buckets * (value_size + sizeof(struct stack_map_bucket));
125 if (cost >= U32_MAX - PAGE_SIZE)
126 goto free_smap;
127
128 bpf_map_init_from_attr(&smap->map, attr);
129 smap->map.value_size = value_size;
130 smap->n_buckets = n_buckets;
131 smap->map.pages = round_up(cost, PAGE_SIZE) >> PAGE_SHIFT;
132
133 err = bpf_map_precharge_memlock(smap->map.pages);
134 if (err)
135 goto free_smap;
136
137 err = get_callchain_buffers(sysctl_perf_event_max_stack);
138 if (err)
139 goto free_smap;
140
141 err = prealloc_elems_and_freelist(smap);
142 if (err)
143 goto put_buffers;
144
145 return &smap->map;
146
147put_buffers:
148 put_callchain_buffers();
149free_smap:
150 bpf_map_area_free(smap);
151 return ERR_PTR(err);
152}
153
154#define BPF_BUILD_ID 3
155/*
156 * Parse build id from the note segment. This logic can be shared between
157 * 32-bit and 64-bit system, because Elf32_Nhdr and Elf64_Nhdr are
158 * identical.
159 */
160static inline int stack_map_parse_build_id(void *page_addr,
161 unsigned char *build_id,
162 void *note_start,
163 Elf32_Word note_size)
164{
165 Elf32_Word note_offs = 0, new_offs;
166
167 /* check for overflow */
168 if (note_start < page_addr || note_start + note_size < note_start)
169 return -EINVAL;
170
171 /* only supports note that fits in the first page */
172 if (note_start + note_size > page_addr + PAGE_SIZE)
173 return -EINVAL;
174
175 while (note_offs + sizeof(Elf32_Nhdr) < note_size) {
176 Elf32_Nhdr *nhdr = (Elf32_Nhdr *)(note_start + note_offs);
177
178 if (nhdr->n_type == BPF_BUILD_ID &&
179 nhdr->n_namesz == sizeof("GNU") &&
180 nhdr->n_descsz > 0 &&
181 nhdr->n_descsz <= BPF_BUILD_ID_SIZE) {
182 memcpy(build_id,
183 note_start + note_offs +
184 ALIGN(sizeof("GNU"), 4) + sizeof(Elf32_Nhdr),
185 nhdr->n_descsz);
186 memset(build_id + nhdr->n_descsz, 0,
187 BPF_BUILD_ID_SIZE - nhdr->n_descsz);
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 = kmap_atomic(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 kunmap_atomic(page_addr);
280 put_page(page);
281 return ret;
282}
283
284static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
285 u64 *ips, u32 trace_nr, bool user)
286{
287 int i;
288 struct vm_area_struct *vma;
289 bool irq_work_busy = false;
290 struct stack_map_irq_work *work = NULL;
291
292 if (in_nmi()) {
293 work = this_cpu_ptr(&up_read_work);
294 if (work->irq_work.flags & IRQ_WORK_BUSY)
295 /* cannot queue more up_read, fallback */
296 irq_work_busy = true;
297 }
298
299 /*
300 * We cannot do up_read() in nmi context. To do build_id lookup
301 * in nmi context, we need to run up_read() in irq_work. We use
302 * a percpu variable to do the irq_work. If the irq_work is
303 * already used by another lookup, we fall back to report ips.
304 *
305 * Same fallback is used for kernel stack (!user) on a stackmap
306 * with build_id.
307 */
308 if (!user || !current || !current->mm || irq_work_busy ||
309 down_read_trylock(&current->mm->mmap_sem) == 0) {
310 /* cannot access current->mm, fall back to ips */
311 for (i = 0; i < trace_nr; i++) {
312 id_offs[i].status = BPF_STACK_BUILD_ID_IP;
313 id_offs[i].ip = ips[i];
314 memset(id_offs[i].build_id, 0, BPF_BUILD_ID_SIZE);
315 }
316 return;
317 }
318
319 for (i = 0; i < trace_nr; i++) {
320 vma = find_vma(current->mm, ips[i]);
321 if (!vma || stack_map_get_build_id(vma, id_offs[i].build_id)) {
322 /* per entry fall back to ips */
323 id_offs[i].status = BPF_STACK_BUILD_ID_IP;
324 id_offs[i].ip = ips[i];
325 memset(id_offs[i].build_id, 0, BPF_BUILD_ID_SIZE);
326 continue;
327 }
328 id_offs[i].offset = (vma->vm_pgoff << PAGE_SHIFT) + ips[i]
329 - vma->vm_start;
330 id_offs[i].status = BPF_STACK_BUILD_ID_VALID;
331 }
332
333 if (!work) {
334 up_read(&current->mm->mmap_sem);
335 } else {
336 work->sem = &current->mm->mmap_sem;
337 irq_work_queue(&work->irq_work);
338 /*
339 * The irq_work will release the mmap_sem with
340 * up_read_non_owner(). The rwsem_release() is called
341 * here to release the lock from lockdep's perspective.
342 */
343 rwsem_release(&current->mm->mmap_sem.dep_map, 1, _RET_IP_);
344 }
345}
346
347BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map,
348 u64, flags)
349{
350 struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
351 struct perf_callchain_entry *trace;
352 struct stack_map_bucket *bucket, *new_bucket, *old_bucket;
353 u32 max_depth = map->value_size / stack_map_data_size(map);
354 /* stack_map_alloc() checks that max_depth <= sysctl_perf_event_max_stack */
355 u32 init_nr = sysctl_perf_event_max_stack - max_depth;
356 u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
357 u32 hash, id, trace_nr, trace_len;
358 bool user = flags & BPF_F_USER_STACK;
359 bool kernel = !user;
360 u64 *ips;
361 bool hash_matches;
362
363 if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
364 BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
365 return -EINVAL;
366
367 trace = get_perf_callchain(regs, init_nr, kernel, user,
368 sysctl_perf_event_max_stack, false, false);
369
370 if (unlikely(!trace))
371 /* couldn't fetch the stack trace */
372 return -EFAULT;
373
374 /* get_perf_callchain() guarantees that trace->nr >= init_nr
375 * and trace-nr <= sysctl_perf_event_max_stack, so trace_nr <= max_depth
376 */
377 trace_nr = trace->nr - init_nr;
378
379 if (trace_nr <= skip)
380 /* skipping more than usable stack trace */
381 return -EFAULT;
382
383 trace_nr -= skip;
384 trace_len = trace_nr * sizeof(u64);
385 ips = trace->ip + skip + init_nr;
386 hash = jhash2((u32 *)ips, trace_len / sizeof(u32), 0);
387 id = hash & (smap->n_buckets - 1);
388 bucket = READ_ONCE(smap->buckets[id]);
389
390 hash_matches = bucket && bucket->hash == hash;
391 /* fast cmp */
392 if (hash_matches && flags & BPF_F_FAST_STACK_CMP)
393 return id;
394
395 if (stack_map_use_build_id(map)) {
396 /* for build_id+offset, pop a bucket before slow cmp */
397 new_bucket = (struct stack_map_bucket *)
398 pcpu_freelist_pop(&smap->freelist);
399 if (unlikely(!new_bucket))
400 return -ENOMEM;
401 new_bucket->nr = trace_nr;
402 stack_map_get_build_id_offset(
403 (struct bpf_stack_build_id *)new_bucket->data,
404 ips, trace_nr, user);
405 trace_len = trace_nr * sizeof(struct bpf_stack_build_id);
406 if (hash_matches && bucket->nr == trace_nr &&
407 memcmp(bucket->data, new_bucket->data, trace_len) == 0) {
408 pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
409 return id;
410 }
411 if (bucket && !(flags & BPF_F_REUSE_STACKID)) {
412 pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
413 return -EEXIST;
414 }
415 } else {
416 if (hash_matches && bucket->nr == trace_nr &&
417 memcmp(bucket->data, ips, trace_len) == 0)
418 return id;
419 if (bucket && !(flags & BPF_F_REUSE_STACKID))
420 return -EEXIST;
421
422 new_bucket = (struct stack_map_bucket *)
423 pcpu_freelist_pop(&smap->freelist);
424 if (unlikely(!new_bucket))
425 return -ENOMEM;
426 memcpy(new_bucket->data, ips, trace_len);
427 }
428
429 new_bucket->hash = hash;
430 new_bucket->nr = trace_nr;
431
432 old_bucket = xchg(&smap->buckets[id], new_bucket);
433 if (old_bucket)
434 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
435 return id;
436}
437
438const struct bpf_func_proto bpf_get_stackid_proto = {
439 .func = bpf_get_stackid,
440 .gpl_only = true,
441 .ret_type = RET_INTEGER,
442 .arg1_type = ARG_PTR_TO_CTX,
443 .arg2_type = ARG_CONST_MAP_PTR,
444 .arg3_type = ARG_ANYTHING,
445};
446
447BPF_CALL_4(bpf_get_stack, struct pt_regs *, regs, void *, buf, u32, size,
448 u64, flags)
449{
450 u32 init_nr, trace_nr, copy_len, elem_size, num_elem;
451 bool user_build_id = flags & BPF_F_USER_BUILD_ID;
452 u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
453 bool user = flags & BPF_F_USER_STACK;
454 struct perf_callchain_entry *trace;
455 bool kernel = !user;
456 int err = -EINVAL;
457 u64 *ips;
458
459 if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
460 BPF_F_USER_BUILD_ID)))
461 goto clear;
462 if (kernel && user_build_id)
463 goto clear;
464
465 elem_size = (user && user_build_id) ? sizeof(struct bpf_stack_build_id)
466 : sizeof(u64);
467 if (unlikely(size % elem_size))
468 goto clear;
469
470 num_elem = size / elem_size;
471 if (sysctl_perf_event_max_stack < num_elem)
472 init_nr = 0;
473 else
474 init_nr = sysctl_perf_event_max_stack - num_elem;
475 trace = get_perf_callchain(regs, init_nr, kernel, user,
476 sysctl_perf_event_max_stack, false, false);
477 if (unlikely(!trace))
478 goto err_fault;
479
480 trace_nr = trace->nr - init_nr;
481 if (trace_nr < skip)
482 goto err_fault;
483
484 trace_nr -= skip;
485 trace_nr = (trace_nr <= num_elem) ? trace_nr : num_elem;
486 copy_len = trace_nr * elem_size;
487 ips = trace->ip + skip + init_nr;
488 if (user && user_build_id)
489 stack_map_get_build_id_offset(buf, ips, trace_nr, user);
490 else
491 memcpy(buf, ips, copy_len);
492
493 if (size > copy_len)
494 memset(buf + copy_len, 0, size - copy_len);
495 return copy_len;
496
497err_fault:
498 err = -EFAULT;
499clear:
500 memset(buf, 0, size);
501 return err;
502}
503
504const struct bpf_func_proto bpf_get_stack_proto = {
505 .func = bpf_get_stack,
506 .gpl_only = true,
507 .ret_type = RET_INTEGER,
508 .arg1_type = ARG_PTR_TO_CTX,
509 .arg2_type = ARG_PTR_TO_UNINIT_MEM,
510 .arg3_type = ARG_CONST_SIZE_OR_ZERO,
511 .arg4_type = ARG_ANYTHING,
512};
513
514/* Called from eBPF program */
515static void *stack_map_lookup_elem(struct bpf_map *map, void *key)
516{
517 return ERR_PTR(-EOPNOTSUPP);
518}
519
520/* Called from syscall */
521int bpf_stackmap_copy(struct bpf_map *map, void *key, void *value)
522{
523 struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
524 struct stack_map_bucket *bucket, *old_bucket;
525 u32 id = *(u32 *)key, trace_len;
526
527 if (unlikely(id >= smap->n_buckets))
528 return -ENOENT;
529
530 bucket = xchg(&smap->buckets[id], NULL);
531 if (!bucket)
532 return -ENOENT;
533
534 trace_len = bucket->nr * stack_map_data_size(map);
535 memcpy(value, bucket->data, trace_len);
536 memset(value + trace_len, 0, map->value_size - trace_len);
537
538 old_bucket = xchg(&smap->buckets[id], bucket);
539 if (old_bucket)
540 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
541 return 0;
542}
543
544static int stack_map_get_next_key(struct bpf_map *map, void *key,
545 void *next_key)
546{
547 struct bpf_stack_map *smap = container_of(map,
548 struct bpf_stack_map, map);
549 u32 id;
550
551 WARN_ON_ONCE(!rcu_read_lock_held());
552
553 if (!key) {
554 id = 0;
555 } else {
556 id = *(u32 *)key;
557 if (id >= smap->n_buckets || !smap->buckets[id])
558 id = 0;
559 else
560 id++;
561 }
562
563 while (id < smap->n_buckets && !smap->buckets[id])
564 id++;
565
566 if (id >= smap->n_buckets)
567 return -ENOENT;
568
569 *(u32 *)next_key = id;
570 return 0;
571}
572
573static int stack_map_update_elem(struct bpf_map *map, void *key, void *value,
574 u64 map_flags)
575{
576 return -EINVAL;
577}
578
579/* Called from syscall or from eBPF program */
580static int stack_map_delete_elem(struct bpf_map *map, void *key)
581{
582 struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
583 struct stack_map_bucket *old_bucket;
584 u32 id = *(u32 *)key;
585
586 if (unlikely(id >= smap->n_buckets))
587 return -E2BIG;
588
589 old_bucket = xchg(&smap->buckets[id], NULL);
590 if (old_bucket) {
591 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
592 return 0;
593 } else {
594 return -ENOENT;
595 }
596}
597
598/* Called when map->refcnt goes to zero, either from workqueue or from syscall */
599static void stack_map_free(struct bpf_map *map)
600{
601 struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
602
603 /* wait for bpf programs to complete before freeing stack map */
604 synchronize_rcu();
605
606 bpf_map_area_free(smap->elems);
607 pcpu_freelist_destroy(&smap->freelist);
608 bpf_map_area_free(smap);
609 put_callchain_buffers();
610}
611
612const struct bpf_map_ops stack_trace_map_ops = {
613 .map_alloc = stack_map_alloc,
614 .map_free = stack_map_free,
615 .map_get_next_key = stack_map_get_next_key,
616 .map_lookup_elem = stack_map_lookup_elem,
617 .map_update_elem = stack_map_update_elem,
618 .map_delete_elem = stack_map_delete_elem,
619 .map_check_btf = map_check_no_btf,
620};
621
622static int __init stack_map_init(void)
623{
624 int cpu;
625 struct stack_map_irq_work *work;
626
627 for_each_possible_cpu(cpu) {
628 work = per_cpu_ptr(&up_read_work, cpu);
629 init_irq_work(&work->irq_work, do_up_read);
630 }
631 return 0;
632}
633subsys_initcall(stack_map_init);