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/btf_ids.h>
11#include <linux/buildid.h>
12#include "percpu_freelist.h"
13#include "mmap_unlock_work.h"
14
15#define STACK_CREATE_FLAG_MASK \
16 (BPF_F_NUMA_NODE | BPF_F_RDONLY | BPF_F_WRONLY | \
17 BPF_F_STACK_BUILD_ID)
18
19struct stack_map_bucket {
20 struct pcpu_freelist_node fnode;
21 u32 hash;
22 u32 nr;
23 u64 data[];
24};
25
26struct bpf_stack_map {
27 struct bpf_map map;
28 void *elems;
29 struct pcpu_freelist freelist;
30 u32 n_buckets;
31 struct stack_map_bucket *buckets[] __counted_by(n_buckets);
32};
33
34static inline bool stack_map_use_build_id(struct bpf_map *map)
35{
36 return (map->map_flags & BPF_F_STACK_BUILD_ID);
37}
38
39static inline int stack_map_data_size(struct bpf_map *map)
40{
41 return stack_map_use_build_id(map) ?
42 sizeof(struct bpf_stack_build_id) : sizeof(u64);
43}
44
45/**
46 * stack_map_calculate_max_depth - Calculate maximum allowed stack trace depth
47 * @size: Size of the buffer/map value in bytes
48 * @elem_size: Size of each stack trace element
49 * @flags: BPF stack trace flags (BPF_F_USER_STACK, BPF_F_USER_BUILD_ID, ...)
50 *
51 * Return: Maximum number of stack trace entries that can be safely stored
52 */
53static u32 stack_map_calculate_max_depth(u32 size, u32 elem_size, u64 flags)
54{
55 u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
56 u32 max_depth;
57 u32 curr_sysctl_max_stack = READ_ONCE(sysctl_perf_event_max_stack);
58
59 max_depth = size / elem_size;
60 max_depth += skip;
61 if (max_depth > curr_sysctl_max_stack)
62 return curr_sysctl_max_stack;
63
64 return max_depth;
65}
66
67static int prealloc_elems_and_freelist(struct bpf_stack_map *smap)
68{
69 u64 elem_size = sizeof(struct stack_map_bucket) +
70 (u64)smap->map.value_size;
71 int err;
72
73 smap->elems = bpf_map_area_alloc(size: elem_size * smap->map.max_entries,
74 numa_node: smap->map.numa_node);
75 if (!smap->elems)
76 return -ENOMEM;
77
78 err = pcpu_freelist_init(&smap->freelist);
79 if (err)
80 goto free_elems;
81
82 pcpu_freelist_populate(s: &smap->freelist, buf: smap->elems, elem_size,
83 nr_elems: smap->map.max_entries);
84 return 0;
85
86free_elems:
87 bpf_map_area_free(base: smap->elems);
88 return err;
89}
90
91/* Called from syscall */
92static struct bpf_map *stack_map_alloc(union bpf_attr *attr)
93{
94 u32 value_size = attr->value_size;
95 struct bpf_stack_map *smap;
96 u64 cost, n_buckets;
97 int err;
98
99 if (attr->map_flags & ~STACK_CREATE_FLAG_MASK)
100 return ERR_PTR(error: -EINVAL);
101
102 /* check sanity of attributes */
103 if (attr->max_entries == 0 || attr->key_size != 4 ||
104 value_size < 8 || value_size % 8)
105 return ERR_PTR(error: -EINVAL);
106
107 BUILD_BUG_ON(sizeof(struct bpf_stack_build_id) % sizeof(u64));
108 if (attr->map_flags & BPF_F_STACK_BUILD_ID) {
109 if (value_size % sizeof(struct bpf_stack_build_id) ||
110 value_size / sizeof(struct bpf_stack_build_id)
111 > sysctl_perf_event_max_stack)
112 return ERR_PTR(error: -EINVAL);
113 } else if (value_size / 8 > sysctl_perf_event_max_stack)
114 return ERR_PTR(error: -EINVAL);
115
116 /* hash table size must be power of 2; roundup_pow_of_two() can overflow
117 * into UB on 32-bit arches, so check that first
118 */
119 if (attr->max_entries > 1UL << 31)
120 return ERR_PTR(error: -E2BIG);
121
122 n_buckets = roundup_pow_of_two(attr->max_entries);
123
124 cost = n_buckets * sizeof(struct stack_map_bucket *) + sizeof(*smap);
125 smap = bpf_map_area_alloc(size: cost, numa_node: bpf_map_attr_numa_node(attr));
126 if (!smap)
127 return ERR_PTR(error: -ENOMEM);
128
129 bpf_map_init_from_attr(map: &smap->map, attr);
130 smap->n_buckets = n_buckets;
131
132 err = get_callchain_buffers(max_stack: sysctl_perf_event_max_stack);
133 if (err)
134 goto free_smap;
135
136 err = prealloc_elems_and_freelist(smap);
137 if (err)
138 goto put_buffers;
139
140 return &smap->map;
141
142put_buffers:
143 put_callchain_buffers();
144free_smap:
145 bpf_map_area_free(base: smap);
146 return ERR_PTR(error: err);
147}
148
149static int fetch_build_id(struct vm_area_struct *vma, unsigned char *build_id, bool may_fault)
150{
151 return may_fault ? build_id_parse(vma, build_id, NULL)
152 : build_id_parse_nofault(vma, build_id, NULL);
153}
154
155/*
156 * Expects all id_offs[i].ip values to be set to correct initial IPs.
157 * They will be subsequently:
158 * - either adjusted in place to a file offset, if build ID fetching
159 * succeeds; in this case id_offs[i].build_id is set to correct build ID,
160 * and id_offs[i].status is set to BPF_STACK_BUILD_ID_VALID;
161 * - or IP will be kept intact, if build ID fetching failed; in this case
162 * id_offs[i].build_id is zeroed out and id_offs[i].status is set to
163 * BPF_STACK_BUILD_ID_IP.
164 */
165static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
166 u32 trace_nr, bool user, bool may_fault)
167{
168 int i;
169 struct mmap_unlock_irq_work *work = NULL;
170 bool irq_work_busy = bpf_mmap_unlock_get_irq_work(work_ptr: &work);
171 struct vm_area_struct *vma, *prev_vma = NULL;
172 const char *prev_build_id;
173
174 /* If the irq_work is in use, fall back to report ips. Same
175 * fallback is used for kernel stack (!user) on a stackmap with
176 * build_id.
177 */
178 if (!user || !current || !current->mm || irq_work_busy ||
179 !mmap_read_trylock(current->mm)) {
180 /* cannot access current->mm, fall back to ips */
181 for (i = 0; i < trace_nr; i++) {
182 id_offs[i].status = BPF_STACK_BUILD_ID_IP;
183 memset(id_offs[i].build_id, 0, BUILD_ID_SIZE_MAX);
184 }
185 return;
186 }
187
188 for (i = 0; i < trace_nr; i++) {
189 u64 ip = READ_ONCE(id_offs[i].ip);
190
191 if (range_in_vma(vma: prev_vma, start: ip, end: ip)) {
192 vma = prev_vma;
193 memcpy(id_offs[i].build_id, prev_build_id, BUILD_ID_SIZE_MAX);
194 goto build_id_valid;
195 }
196 vma = find_vma(current->mm, addr: ip);
197 if (!vma || fetch_build_id(vma, build_id: id_offs[i].build_id, may_fault)) {
198 /* per entry fall back to ips */
199 id_offs[i].status = BPF_STACK_BUILD_ID_IP;
200 memset(id_offs[i].build_id, 0, BUILD_ID_SIZE_MAX);
201 continue;
202 }
203build_id_valid:
204 id_offs[i].offset = (vma->vm_pgoff << PAGE_SHIFT) + ip - vma->vm_start;
205 id_offs[i].status = BPF_STACK_BUILD_ID_VALID;
206 prev_vma = vma;
207 prev_build_id = id_offs[i].build_id;
208 }
209 bpf_mmap_unlock_mm(work, current->mm);
210}
211
212static struct perf_callchain_entry *
213get_callchain_entry_for_task(struct task_struct *task, u32 max_depth)
214{
215#ifdef CONFIG_STACKTRACE
216 struct perf_callchain_entry *entry;
217 int rctx;
218
219 entry = get_callchain_entry(rctx: &rctx);
220
221 if (!entry)
222 return NULL;
223
224 entry->nr = stack_trace_save_tsk(task, store: (unsigned long *)entry->ip,
225 size: max_depth, skipnr: 0);
226
227 /* stack_trace_save_tsk() works on unsigned long array, while
228 * perf_callchain_entry uses u64 array. For 32-bit systems, it is
229 * necessary to fix this mismatch.
230 */
231 if (__BITS_PER_LONG != 64) {
232 unsigned long *from = (unsigned long *) entry->ip;
233 u64 *to = entry->ip;
234 int i;
235
236 /* copy data from the end to avoid using extra buffer */
237 for (i = entry->nr - 1; i >= 0; i--)
238 to[i] = (u64)(from[i]);
239 }
240
241 put_callchain_entry(rctx);
242
243 return entry;
244#else /* CONFIG_STACKTRACE */
245 return NULL;
246#endif
247}
248
249static long __bpf_get_stackid(struct bpf_map *map,
250 struct perf_callchain_entry *trace, u64 flags)
251{
252 struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
253 struct stack_map_bucket *bucket, *new_bucket, *old_bucket;
254 u32 hash, id, trace_nr, trace_len, i, max_depth;
255 u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
256 bool user = flags & BPF_F_USER_STACK;
257 u64 *ips;
258 bool hash_matches;
259
260 if (trace->nr <= skip)
261 /* skipping more than usable stack trace */
262 return -EFAULT;
263
264 max_depth = stack_map_calculate_max_depth(size: map->value_size, elem_size: stack_map_data_size(map), flags);
265 trace_nr = min_t(u32, trace->nr - skip, max_depth - skip);
266 trace_len = trace_nr * sizeof(u64);
267 ips = trace->ip + skip;
268 hash = jhash2(k: (u32 *)ips, length: trace_len / sizeof(u32), initval: 0);
269 id = hash & (smap->n_buckets - 1);
270 bucket = READ_ONCE(smap->buckets[id]);
271
272 hash_matches = bucket && bucket->hash == hash;
273 /* fast cmp */
274 if (hash_matches && flags & BPF_F_FAST_STACK_CMP)
275 return id;
276
277 if (stack_map_use_build_id(map)) {
278 struct bpf_stack_build_id *id_offs;
279
280 /* for build_id+offset, pop a bucket before slow cmp */
281 new_bucket = (struct stack_map_bucket *)
282 pcpu_freelist_pop(&smap->freelist);
283 if (unlikely(!new_bucket))
284 return -ENOMEM;
285 new_bucket->nr = trace_nr;
286 id_offs = (struct bpf_stack_build_id *)new_bucket->data;
287 for (i = 0; i < trace_nr; i++)
288 id_offs[i].ip = ips[i];
289 stack_map_get_build_id_offset(id_offs, trace_nr, user, may_fault: false /* !may_fault */);
290 trace_len = trace_nr * sizeof(struct bpf_stack_build_id);
291 if (hash_matches && bucket->nr == trace_nr &&
292 memcmp(p: bucket->data, q: new_bucket->data, size: trace_len) == 0) {
293 pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
294 return id;
295 }
296 if (bucket && !(flags & BPF_F_REUSE_STACKID)) {
297 pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
298 return -EEXIST;
299 }
300 } else {
301 if (hash_matches && bucket->nr == trace_nr &&
302 memcmp(p: bucket->data, q: ips, size: trace_len) == 0)
303 return id;
304 if (bucket && !(flags & BPF_F_REUSE_STACKID))
305 return -EEXIST;
306
307 new_bucket = (struct stack_map_bucket *)
308 pcpu_freelist_pop(&smap->freelist);
309 if (unlikely(!new_bucket))
310 return -ENOMEM;
311 memcpy(new_bucket->data, ips, trace_len);
312 }
313
314 new_bucket->hash = hash;
315 new_bucket->nr = trace_nr;
316
317 old_bucket = xchg(&smap->buckets[id], new_bucket);
318 if (old_bucket)
319 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
320 return id;
321}
322
323BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map,
324 u64, flags)
325{
326 u32 elem_size = stack_map_data_size(map);
327 bool user = flags & BPF_F_USER_STACK;
328 struct perf_callchain_entry *trace;
329 bool kernel = !user;
330 u32 max_depth;
331
332 if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
333 BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
334 return -EINVAL;
335
336 max_depth = stack_map_calculate_max_depth(size: map->value_size, elem_size, flags);
337 trace = get_perf_callchain(regs, kernel, user, max_stack: max_depth,
338 crosstask: false, add_mark: false, defer_cookie: 0);
339
340 if (unlikely(!trace))
341 /* couldn't fetch the stack trace */
342 return -EFAULT;
343
344 return __bpf_get_stackid(map, trace, flags);
345}
346
347const struct bpf_func_proto bpf_get_stackid_proto = {
348 .func = bpf_get_stackid,
349 .gpl_only = true,
350 .ret_type = RET_INTEGER,
351 .arg1_type = ARG_PTR_TO_CTX,
352 .arg2_type = ARG_CONST_MAP_PTR,
353 .arg3_type = ARG_ANYTHING,
354};
355
356static __u64 count_kernel_ip(struct perf_callchain_entry *trace)
357{
358 __u64 nr_kernel = 0;
359
360 while (nr_kernel < trace->nr) {
361 if (trace->ip[nr_kernel] == PERF_CONTEXT_USER)
362 break;
363 nr_kernel++;
364 }
365 return nr_kernel;
366}
367
368BPF_CALL_3(bpf_get_stackid_pe, struct bpf_perf_event_data_kern *, ctx,
369 struct bpf_map *, map, u64, flags)
370{
371 struct perf_event *event = ctx->event;
372 struct perf_callchain_entry *trace;
373 bool kernel, user;
374 __u64 nr_kernel;
375 int ret;
376
377 /* perf_sample_data doesn't have callchain, use bpf_get_stackid */
378 if (!(event->attr.sample_type & PERF_SAMPLE_CALLCHAIN))
379 return bpf_get_stackid(regs: (unsigned long)(ctx->regs),
380 map: (unsigned long) map, flags, ur_1: 0, ur_2: 0);
381
382 if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
383 BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
384 return -EINVAL;
385
386 user = flags & BPF_F_USER_STACK;
387 kernel = !user;
388
389 trace = ctx->data->callchain;
390 if (unlikely(!trace))
391 return -EFAULT;
392
393 nr_kernel = count_kernel_ip(trace);
394 __u64 nr = trace->nr; /* save original */
395
396 if (kernel) {
397 trace->nr = nr_kernel;
398 ret = __bpf_get_stackid(map, trace, flags);
399 } else { /* user */
400 u64 skip = flags & BPF_F_SKIP_FIELD_MASK;
401
402 skip += nr_kernel;
403 if (skip > BPF_F_SKIP_FIELD_MASK)
404 return -EFAULT;
405
406 flags = (flags & ~BPF_F_SKIP_FIELD_MASK) | skip;
407 ret = __bpf_get_stackid(map, trace, flags);
408 }
409
410 /* restore nr */
411 trace->nr = nr;
412
413 return ret;
414}
415
416const struct bpf_func_proto bpf_get_stackid_proto_pe = {
417 .func = bpf_get_stackid_pe,
418 .gpl_only = false,
419 .ret_type = RET_INTEGER,
420 .arg1_type = ARG_PTR_TO_CTX,
421 .arg2_type = ARG_CONST_MAP_PTR,
422 .arg3_type = ARG_ANYTHING,
423};
424
425static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task,
426 struct perf_callchain_entry *trace_in,
427 void *buf, u32 size, u64 flags, bool may_fault)
428{
429 u32 trace_nr, copy_len, elem_size, max_depth;
430 bool user_build_id = flags & BPF_F_USER_BUILD_ID;
431 bool crosstask = task && task != current;
432 u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
433 bool user = flags & BPF_F_USER_STACK;
434 struct perf_callchain_entry *trace;
435 bool kernel = !user;
436 int err = -EINVAL;
437 u64 *ips;
438
439 if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
440 BPF_F_USER_BUILD_ID)))
441 goto clear;
442 if (kernel && user_build_id)
443 goto clear;
444
445 elem_size = user_build_id ? sizeof(struct bpf_stack_build_id) : sizeof(u64);
446 if (unlikely(size % elem_size))
447 goto clear;
448
449 /* cannot get valid user stack for task without user_mode regs */
450 if (task && user && !user_mode(regs))
451 goto err_fault;
452
453 /* get_perf_callchain does not support crosstask user stack walking
454 * but returns an empty stack instead of NULL.
455 */
456 if (crosstask && user) {
457 err = -EOPNOTSUPP;
458 goto clear;
459 }
460
461 max_depth = stack_map_calculate_max_depth(size, elem_size, flags);
462
463 if (may_fault)
464 rcu_read_lock(); /* need RCU for perf's callchain below */
465
466 if (trace_in) {
467 trace = trace_in;
468 trace->nr = min_t(u32, trace->nr, max_depth);
469 } else if (kernel && task) {
470 trace = get_callchain_entry_for_task(task, max_depth);
471 } else {
472 trace = get_perf_callchain(regs, kernel, user, max_stack: max_depth,
473 crosstask, add_mark: false, defer_cookie: 0);
474 }
475
476 if (unlikely(!trace) || trace->nr < skip) {
477 if (may_fault)
478 rcu_read_unlock();
479 goto err_fault;
480 }
481
482 trace_nr = trace->nr - skip;
483 copy_len = trace_nr * elem_size;
484
485 ips = trace->ip + skip;
486 if (user_build_id) {
487 struct bpf_stack_build_id *id_offs = buf;
488 u32 i;
489
490 for (i = 0; i < trace_nr; i++)
491 id_offs[i].ip = ips[i];
492 } else {
493 memcpy(buf, ips, copy_len);
494 }
495
496 /* trace/ips should not be dereferenced after this point */
497 if (may_fault)
498 rcu_read_unlock();
499
500 if (user_build_id)
501 stack_map_get_build_id_offset(id_offs: buf, trace_nr, user, may_fault);
502
503 if (size > copy_len)
504 memset(buf + copy_len, 0, size - copy_len);
505 return copy_len;
506
507err_fault:
508 err = -EFAULT;
509clear:
510 memset(buf, 0, size);
511 return err;
512}
513
514BPF_CALL_4(bpf_get_stack, struct pt_regs *, regs, void *, buf, u32, size,
515 u64, flags)
516{
517 return __bpf_get_stack(regs, NULL, NULL, buf, size, flags, may_fault: false /* !may_fault */);
518}
519
520const struct bpf_func_proto bpf_get_stack_proto = {
521 .func = bpf_get_stack,
522 .gpl_only = true,
523 .ret_type = RET_INTEGER,
524 .arg1_type = ARG_PTR_TO_CTX,
525 .arg2_type = ARG_PTR_TO_UNINIT_MEM,
526 .arg3_type = ARG_CONST_SIZE_OR_ZERO,
527 .arg4_type = ARG_ANYTHING,
528};
529
530BPF_CALL_4(bpf_get_stack_sleepable, struct pt_regs *, regs, void *, buf, u32, size,
531 u64, flags)
532{
533 return __bpf_get_stack(regs, NULL, NULL, buf, size, flags, may_fault: true /* may_fault */);
534}
535
536const struct bpf_func_proto bpf_get_stack_sleepable_proto = {
537 .func = bpf_get_stack_sleepable,
538 .gpl_only = true,
539 .ret_type = RET_INTEGER,
540 .arg1_type = ARG_PTR_TO_CTX,
541 .arg2_type = ARG_PTR_TO_UNINIT_MEM,
542 .arg3_type = ARG_CONST_SIZE_OR_ZERO,
543 .arg4_type = ARG_ANYTHING,
544};
545
546static long __bpf_get_task_stack(struct task_struct *task, void *buf, u32 size,
547 u64 flags, bool may_fault)
548{
549 struct pt_regs *regs;
550 long res = -EINVAL;
551
552 if (!try_get_task_stack(tsk: task))
553 return -EFAULT;
554
555 regs = task_pt_regs(task);
556 if (regs)
557 res = __bpf_get_stack(regs, task, NULL, buf, size, flags, may_fault);
558 put_task_stack(tsk: task);
559
560 return res;
561}
562
563BPF_CALL_4(bpf_get_task_stack, struct task_struct *, task, void *, buf,
564 u32, size, u64, flags)
565{
566 return __bpf_get_task_stack(task, buf, size, flags, may_fault: false /* !may_fault */);
567}
568
569const struct bpf_func_proto bpf_get_task_stack_proto = {
570 .func = bpf_get_task_stack,
571 .gpl_only = false,
572 .ret_type = RET_INTEGER,
573 .arg1_type = ARG_PTR_TO_BTF_ID,
574 .arg1_btf_id = &btf_tracing_ids[BTF_TRACING_TYPE_TASK],
575 .arg2_type = ARG_PTR_TO_UNINIT_MEM,
576 .arg3_type = ARG_CONST_SIZE_OR_ZERO,
577 .arg4_type = ARG_ANYTHING,
578};
579
580BPF_CALL_4(bpf_get_task_stack_sleepable, struct task_struct *, task, void *, buf,
581 u32, size, u64, flags)
582{
583 return __bpf_get_task_stack(task, buf, size, flags, may_fault: true /* !may_fault */);
584}
585
586const struct bpf_func_proto bpf_get_task_stack_sleepable_proto = {
587 .func = bpf_get_task_stack_sleepable,
588 .gpl_only = false,
589 .ret_type = RET_INTEGER,
590 .arg1_type = ARG_PTR_TO_BTF_ID,
591 .arg1_btf_id = &btf_tracing_ids[BTF_TRACING_TYPE_TASK],
592 .arg2_type = ARG_PTR_TO_UNINIT_MEM,
593 .arg3_type = ARG_CONST_SIZE_OR_ZERO,
594 .arg4_type = ARG_ANYTHING,
595};
596
597BPF_CALL_4(bpf_get_stack_pe, struct bpf_perf_event_data_kern *, ctx,
598 void *, buf, u32, size, u64, flags)
599{
600 struct pt_regs *regs = (struct pt_regs *)(ctx->regs);
601 struct perf_event *event = ctx->event;
602 struct perf_callchain_entry *trace;
603 bool kernel, user;
604 int err = -EINVAL;
605 __u64 nr_kernel;
606
607 if (!(event->attr.sample_type & PERF_SAMPLE_CALLCHAIN))
608 return __bpf_get_stack(regs, NULL, NULL, buf, size, flags, may_fault: false /* !may_fault */);
609
610 if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
611 BPF_F_USER_BUILD_ID)))
612 goto clear;
613
614 user = flags & BPF_F_USER_STACK;
615 kernel = !user;
616
617 err = -EFAULT;
618 trace = ctx->data->callchain;
619 if (unlikely(!trace))
620 goto clear;
621
622 nr_kernel = count_kernel_ip(trace);
623
624 if (kernel) {
625 __u64 nr = trace->nr;
626
627 trace->nr = nr_kernel;
628 err = __bpf_get_stack(regs, NULL, trace_in: trace, buf, size, flags, may_fault: false /* !may_fault */);
629
630 /* restore nr */
631 trace->nr = nr;
632 } else { /* user */
633 u64 skip = flags & BPF_F_SKIP_FIELD_MASK;
634
635 skip += nr_kernel;
636 if (skip > BPF_F_SKIP_FIELD_MASK)
637 goto clear;
638
639 flags = (flags & ~BPF_F_SKIP_FIELD_MASK) | skip;
640 err = __bpf_get_stack(regs, NULL, trace_in: trace, buf, size, flags, may_fault: false /* !may_fault */);
641 }
642 return err;
643
644clear:
645 memset(buf, 0, size);
646 return err;
647
648}
649
650const struct bpf_func_proto bpf_get_stack_proto_pe = {
651 .func = bpf_get_stack_pe,
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/* Called from eBPF program */
661static void *stack_map_lookup_elem(struct bpf_map *map, void *key)
662{
663 return ERR_PTR(error: -EOPNOTSUPP);
664}
665
666/* Called from syscall */
667static int stack_map_lookup_and_delete_elem(struct bpf_map *map, void *key,
668 void *value, u64 flags)
669{
670 return bpf_stackmap_extract(map, key, value, delete: true);
671}
672
673/* Called from syscall */
674int bpf_stackmap_extract(struct bpf_map *map, void *key, void *value,
675 bool delete)
676{
677 struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
678 struct stack_map_bucket *bucket, *old_bucket;
679 u32 id = *(u32 *)key, trace_len;
680
681 if (unlikely(id >= smap->n_buckets))
682 return -ENOENT;
683
684 bucket = xchg(&smap->buckets[id], NULL);
685 if (!bucket)
686 return -ENOENT;
687
688 trace_len = bucket->nr * stack_map_data_size(map);
689 memcpy(value, bucket->data, trace_len);
690 memset(value + trace_len, 0, map->value_size - trace_len);
691
692 if (delete)
693 old_bucket = bucket;
694 else
695 old_bucket = xchg(&smap->buckets[id], bucket);
696 if (old_bucket)
697 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
698 return 0;
699}
700
701static int stack_map_get_next_key(struct bpf_map *map, void *key,
702 void *next_key)
703{
704 struct bpf_stack_map *smap = container_of(map,
705 struct bpf_stack_map, map);
706 u32 id;
707
708 WARN_ON_ONCE(!rcu_read_lock_held());
709
710 if (!key) {
711 id = 0;
712 } else {
713 id = *(u32 *)key;
714 if (id >= smap->n_buckets || !smap->buckets[id])
715 id = 0;
716 else
717 id++;
718 }
719
720 while (id < smap->n_buckets && !smap->buckets[id])
721 id++;
722
723 if (id >= smap->n_buckets)
724 return -ENOENT;
725
726 *(u32 *)next_key = id;
727 return 0;
728}
729
730static long stack_map_update_elem(struct bpf_map *map, void *key, void *value,
731 u64 map_flags)
732{
733 return -EINVAL;
734}
735
736/* Called from syscall or from eBPF program */
737static long stack_map_delete_elem(struct bpf_map *map, void *key)
738{
739 struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
740 struct stack_map_bucket *old_bucket;
741 u32 id = *(u32 *)key;
742
743 if (unlikely(id >= smap->n_buckets))
744 return -E2BIG;
745
746 old_bucket = xchg(&smap->buckets[id], NULL);
747 if (old_bucket) {
748 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
749 return 0;
750 } else {
751 return -ENOENT;
752 }
753}
754
755/* Called when map->refcnt goes to zero, either from workqueue or from syscall */
756static void stack_map_free(struct bpf_map *map)
757{
758 struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
759
760 bpf_map_area_free(base: smap->elems);
761 pcpu_freelist_destroy(s: &smap->freelist);
762 bpf_map_area_free(base: smap);
763 put_callchain_buffers();
764}
765
766static u64 stack_map_mem_usage(const struct bpf_map *map)
767{
768 struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
769 u64 value_size = map->value_size;
770 u64 n_buckets = smap->n_buckets;
771 u64 enties = map->max_entries;
772 u64 usage = sizeof(*smap);
773
774 usage += n_buckets * sizeof(struct stack_map_bucket *);
775 usage += enties * (sizeof(struct stack_map_bucket) + value_size);
776 return usage;
777}
778
779BTF_ID_LIST_SINGLE(stack_trace_map_btf_ids, struct, bpf_stack_map)
780const struct bpf_map_ops stack_trace_map_ops = {
781 .map_meta_equal = bpf_map_meta_equal,
782 .map_alloc = stack_map_alloc,
783 .map_free = stack_map_free,
784 .map_get_next_key = stack_map_get_next_key,
785 .map_lookup_elem = stack_map_lookup_elem,
786 .map_lookup_and_delete_elem = stack_map_lookup_and_delete_elem,
787 .map_update_elem = stack_map_update_elem,
788 .map_delete_elem = stack_map_delete_elem,
789 .map_check_btf = map_check_no_btf,
790 .map_mem_usage = stack_map_mem_usage,
791 .map_btf_id = &stack_trace_map_btf_ids[0],
792};
793

source code of linux/kernel/bpf/stackmap.c