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/irq_work.h>
11 #include <linux/btf_ids.h>
12 #include <linux/buildid.h>
13 #include "percpu_freelist.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
19 struct stack_map_bucket {
20 struct pcpu_freelist_node fnode;
21 u32 hash;
22 u32 nr;
23 u64 data[];
24 };
25
26 struct 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[];
32 };
33
34 /* irq_work to run up_read() for build_id lookup in nmi context */
35 struct stack_map_irq_work {
36 struct irq_work irq_work;
37 struct mm_struct *mm;
38 };
39
do_up_read(struct irq_work * entry)40 static void do_up_read(struct irq_work *entry)
41 {
42 struct stack_map_irq_work *work;
43
44 if (WARN_ON_ONCE(IS_ENABLED(CONFIG_PREEMPT_RT)))
45 return;
46
47 work = container_of(entry, struct stack_map_irq_work, irq_work);
48 mmap_read_unlock_non_owner(work->mm);
49 }
50
51 static DEFINE_PER_CPU(struct stack_map_irq_work, up_read_work);
52
stack_map_use_build_id(struct bpf_map * map)53 static inline bool stack_map_use_build_id(struct bpf_map *map)
54 {
55 return (map->map_flags & BPF_F_STACK_BUILD_ID);
56 }
57
stack_map_data_size(struct bpf_map * map)58 static 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
prealloc_elems_and_freelist(struct bpf_stack_map * smap)64 static int prealloc_elems_and_freelist(struct bpf_stack_map *smap)
65 {
66 u64 elem_size = sizeof(struct stack_map_bucket) +
67 (u64)smap->map.value_size;
68 int err;
69
70 smap->elems = bpf_map_area_alloc(elem_size * smap->map.max_entries,
71 smap->map.numa_node);
72 if (!smap->elems)
73 return -ENOMEM;
74
75 err = pcpu_freelist_init(&smap->freelist);
76 if (err)
77 goto free_elems;
78
79 pcpu_freelist_populate(&smap->freelist, smap->elems, elem_size,
80 smap->map.max_entries);
81 return 0;
82
83 free_elems:
84 bpf_map_area_free(smap->elems);
85 return err;
86 }
87
88 /* Called from syscall */
stack_map_alloc(union bpf_attr * attr)89 static struct bpf_map *stack_map_alloc(union bpf_attr *attr)
90 {
91 u32 value_size = attr->value_size;
92 struct bpf_stack_map *smap;
93 u64 cost, n_buckets;
94 int err;
95
96 if (!bpf_capable())
97 return ERR_PTR(-EPERM);
98
99 if (attr->map_flags & ~STACK_CREATE_FLAG_MASK)
100 return ERR_PTR(-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(-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(-EINVAL);
113 } else if (value_size / 8 > sysctl_perf_event_max_stack)
114 return ERR_PTR(-EINVAL);
115
116 /* hash table size must be power of 2 */
117 n_buckets = roundup_pow_of_two(attr->max_entries);
118 if (!n_buckets)
119 return ERR_PTR(-E2BIG);
120
121 cost = n_buckets * sizeof(struct stack_map_bucket *) + sizeof(*smap);
122 cost += n_buckets * (value_size + sizeof(struct stack_map_bucket));
123 smap = bpf_map_area_alloc(cost, bpf_map_attr_numa_node(attr));
124 if (!smap)
125 return ERR_PTR(-ENOMEM);
126
127 bpf_map_init_from_attr(&smap->map, attr);
128 smap->map.value_size = value_size;
129 smap->n_buckets = n_buckets;
130
131 err = get_callchain_buffers(sysctl_perf_event_max_stack);
132 if (err)
133 goto free_smap;
134
135 err = prealloc_elems_and_freelist(smap);
136 if (err)
137 goto put_buffers;
138
139 return &smap->map;
140
141 put_buffers:
142 put_callchain_buffers();
143 free_smap:
144 bpf_map_area_free(smap);
145 return ERR_PTR(err);
146 }
147
stack_map_get_build_id_offset(struct bpf_stack_build_id * id_offs,u64 * ips,u32 trace_nr,bool user)148 static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
149 u64 *ips, u32 trace_nr, bool user)
150 {
151 int i;
152 struct vm_area_struct *vma;
153 bool irq_work_busy = false;
154 struct stack_map_irq_work *work = NULL;
155
156 if (irqs_disabled()) {
157 if (!IS_ENABLED(CONFIG_PREEMPT_RT)) {
158 work = this_cpu_ptr(&up_read_work);
159 if (irq_work_is_busy(&work->irq_work)) {
160 /* cannot queue more up_read, fallback */
161 irq_work_busy = true;
162 }
163 } else {
164 /*
165 * PREEMPT_RT does not allow to trylock mmap sem in
166 * interrupt disabled context. Force the fallback code.
167 */
168 irq_work_busy = true;
169 }
170 }
171
172 /*
173 * We cannot do up_read() when the irq is disabled, because of
174 * risk to deadlock with rq_lock. To do build_id lookup when the
175 * irqs are disabled, we need to run up_read() in irq_work. We use
176 * a percpu variable to do the irq_work. If the irq_work is
177 * already used by another lookup, we fall back to report ips.
178 *
179 * Same fallback is used for kernel stack (!user) on a stackmap
180 * with build_id.
181 */
182 if (!user || !current || !current->mm || irq_work_busy ||
183 !mmap_read_trylock(current->mm)) {
184 /* cannot access current->mm, fall back to ips */
185 for (i = 0; i < trace_nr; i++) {
186 id_offs[i].status = BPF_STACK_BUILD_ID_IP;
187 id_offs[i].ip = ips[i];
188 memset(id_offs[i].build_id, 0, BUILD_ID_SIZE_MAX);
189 }
190 return;
191 }
192
193 for (i = 0; i < trace_nr; i++) {
194 vma = find_vma(current->mm, ips[i]);
195 if (!vma || build_id_parse(vma, id_offs[i].build_id, NULL)) {
196 /* per entry fall back to ips */
197 id_offs[i].status = BPF_STACK_BUILD_ID_IP;
198 id_offs[i].ip = ips[i];
199 memset(id_offs[i].build_id, 0, BUILD_ID_SIZE_MAX);
200 continue;
201 }
202 id_offs[i].offset = (vma->vm_pgoff << PAGE_SHIFT) + ips[i]
203 - vma->vm_start;
204 id_offs[i].status = BPF_STACK_BUILD_ID_VALID;
205 }
206
207 if (!work) {
208 mmap_read_unlock(current->mm);
209 } else {
210 work->mm = current->mm;
211
212 /* The lock will be released once we're out of interrupt
213 * context. Tell lockdep that we've released it now so
214 * it doesn't complain that we forgot to release it.
215 */
216 rwsem_release(¤t->mm->mmap_lock.dep_map, _RET_IP_);
217 irq_work_queue(&work->irq_work);
218 }
219 }
220
221 static struct perf_callchain_entry *
get_callchain_entry_for_task(struct task_struct * task,u32 init_nr)222 get_callchain_entry_for_task(struct task_struct *task, u32 init_nr)
223 {
224 #ifdef CONFIG_STACKTRACE
225 struct perf_callchain_entry *entry;
226 int rctx;
227
228 entry = get_callchain_entry(&rctx);
229
230 if (!entry)
231 return NULL;
232
233 entry->nr = init_nr +
234 stack_trace_save_tsk(task, (unsigned long *)(entry->ip + init_nr),
235 sysctl_perf_event_max_stack - init_nr, 0);
236
237 /* stack_trace_save_tsk() works on unsigned long array, while
238 * perf_callchain_entry uses u64 array. For 32-bit systems, it is
239 * necessary to fix this mismatch.
240 */
241 if (__BITS_PER_LONG != 64) {
242 unsigned long *from = (unsigned long *) entry->ip;
243 u64 *to = entry->ip;
244 int i;
245
246 /* copy data from the end to avoid using extra buffer */
247 for (i = entry->nr - 1; i >= (int)init_nr; i--)
248 to[i] = (u64)(from[i]);
249 }
250
251 put_callchain_entry(rctx);
252
253 return entry;
254 #else /* CONFIG_STACKTRACE */
255 return NULL;
256 #endif
257 }
258
__bpf_get_stackid(struct bpf_map * map,struct perf_callchain_entry * trace,u64 flags)259 static long __bpf_get_stackid(struct bpf_map *map,
260 struct perf_callchain_entry *trace, u64 flags)
261 {
262 struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
263 struct stack_map_bucket *bucket, *new_bucket, *old_bucket;
264 u32 max_depth = map->value_size / stack_map_data_size(map);
265 /* stack_map_alloc() checks that max_depth <= sysctl_perf_event_max_stack */
266 u32 init_nr = sysctl_perf_event_max_stack - max_depth;
267 u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
268 u32 hash, id, trace_nr, trace_len;
269 bool user = flags & BPF_F_USER_STACK;
270 u64 *ips;
271 bool hash_matches;
272
273 /* get_perf_callchain() guarantees that trace->nr >= init_nr
274 * and trace-nr <= sysctl_perf_event_max_stack, so trace_nr <= max_depth
275 */
276 trace_nr = trace->nr - init_nr;
277
278 if (trace_nr <= skip)
279 /* skipping more than usable stack trace */
280 return -EFAULT;
281
282 trace_nr -= skip;
283 trace_len = trace_nr * sizeof(u64);
284 ips = trace->ip + skip + init_nr;
285 hash = jhash2((u32 *)ips, trace_len / sizeof(u32), 0);
286 id = hash & (smap->n_buckets - 1);
287 bucket = READ_ONCE(smap->buckets[id]);
288
289 hash_matches = bucket && bucket->hash == hash;
290 /* fast cmp */
291 if (hash_matches && flags & BPF_F_FAST_STACK_CMP)
292 return id;
293
294 if (stack_map_use_build_id(map)) {
295 /* for build_id+offset, pop a bucket before slow cmp */
296 new_bucket = (struct stack_map_bucket *)
297 pcpu_freelist_pop(&smap->freelist);
298 if (unlikely(!new_bucket))
299 return -ENOMEM;
300 new_bucket->nr = trace_nr;
301 stack_map_get_build_id_offset(
302 (struct bpf_stack_build_id *)new_bucket->data,
303 ips, trace_nr, user);
304 trace_len = trace_nr * sizeof(struct bpf_stack_build_id);
305 if (hash_matches && bucket->nr == trace_nr &&
306 memcmp(bucket->data, new_bucket->data, trace_len) == 0) {
307 pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
308 return id;
309 }
310 if (bucket && !(flags & BPF_F_REUSE_STACKID)) {
311 pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
312 return -EEXIST;
313 }
314 } else {
315 if (hash_matches && bucket->nr == trace_nr &&
316 memcmp(bucket->data, ips, trace_len) == 0)
317 return id;
318 if (bucket && !(flags & BPF_F_REUSE_STACKID))
319 return -EEXIST;
320
321 new_bucket = (struct stack_map_bucket *)
322 pcpu_freelist_pop(&smap->freelist);
323 if (unlikely(!new_bucket))
324 return -ENOMEM;
325 memcpy(new_bucket->data, ips, trace_len);
326 }
327
328 new_bucket->hash = hash;
329 new_bucket->nr = trace_nr;
330
331 old_bucket = xchg(&smap->buckets[id], new_bucket);
332 if (old_bucket)
333 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
334 return id;
335 }
336
BPF_CALL_3(bpf_get_stackid,struct pt_regs *,regs,struct bpf_map *,map,u64,flags)337 BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map,
338 u64, flags)
339 {
340 u32 max_depth = map->value_size / stack_map_data_size(map);
341 /* stack_map_alloc() checks that max_depth <= sysctl_perf_event_max_stack */
342 u32 init_nr = sysctl_perf_event_max_stack - max_depth;
343 bool user = flags & BPF_F_USER_STACK;
344 struct perf_callchain_entry *trace;
345 bool kernel = !user;
346
347 if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
348 BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
349 return -EINVAL;
350
351 trace = get_perf_callchain(regs, init_nr, kernel, user,
352 sysctl_perf_event_max_stack, false, false);
353
354 if (unlikely(!trace))
355 /* couldn't fetch the stack trace */
356 return -EFAULT;
357
358 return __bpf_get_stackid(map, trace, flags);
359 }
360
361 const struct bpf_func_proto bpf_get_stackid_proto = {
362 .func = bpf_get_stackid,
363 .gpl_only = true,
364 .ret_type = RET_INTEGER,
365 .arg1_type = ARG_PTR_TO_CTX,
366 .arg2_type = ARG_CONST_MAP_PTR,
367 .arg3_type = ARG_ANYTHING,
368 };
369
count_kernel_ip(struct perf_callchain_entry * trace)370 static __u64 count_kernel_ip(struct perf_callchain_entry *trace)
371 {
372 __u64 nr_kernel = 0;
373
374 while (nr_kernel < trace->nr) {
375 if (trace->ip[nr_kernel] == PERF_CONTEXT_USER)
376 break;
377 nr_kernel++;
378 }
379 return nr_kernel;
380 }
381
BPF_CALL_3(bpf_get_stackid_pe,struct bpf_perf_event_data_kern *,ctx,struct bpf_map *,map,u64,flags)382 BPF_CALL_3(bpf_get_stackid_pe, struct bpf_perf_event_data_kern *, ctx,
383 struct bpf_map *, map, u64, flags)
384 {
385 struct perf_event *event = ctx->event;
386 struct perf_callchain_entry *trace;
387 bool kernel, user;
388 __u64 nr_kernel;
389 int ret;
390
391 /* perf_sample_data doesn't have callchain, use bpf_get_stackid */
392 if (!(event->attr.sample_type & __PERF_SAMPLE_CALLCHAIN_EARLY))
393 return bpf_get_stackid((unsigned long)(ctx->regs),
394 (unsigned long) map, flags, 0, 0);
395
396 if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
397 BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
398 return -EINVAL;
399
400 user = flags & BPF_F_USER_STACK;
401 kernel = !user;
402
403 trace = ctx->data->callchain;
404 if (unlikely(!trace))
405 return -EFAULT;
406
407 nr_kernel = count_kernel_ip(trace);
408
409 if (kernel) {
410 __u64 nr = trace->nr;
411
412 trace->nr = nr_kernel;
413 ret = __bpf_get_stackid(map, trace, flags);
414
415 /* restore nr */
416 trace->nr = nr;
417 } else { /* user */
418 u64 skip = flags & BPF_F_SKIP_FIELD_MASK;
419
420 skip += nr_kernel;
421 if (skip > BPF_F_SKIP_FIELD_MASK)
422 return -EFAULT;
423
424 flags = (flags & ~BPF_F_SKIP_FIELD_MASK) | skip;
425 ret = __bpf_get_stackid(map, trace, flags);
426 }
427 return ret;
428 }
429
430 const struct bpf_func_proto bpf_get_stackid_proto_pe = {
431 .func = bpf_get_stackid_pe,
432 .gpl_only = false,
433 .ret_type = RET_INTEGER,
434 .arg1_type = ARG_PTR_TO_CTX,
435 .arg2_type = ARG_CONST_MAP_PTR,
436 .arg3_type = ARG_ANYTHING,
437 };
438
__bpf_get_stack(struct pt_regs * regs,struct task_struct * task,struct perf_callchain_entry * trace_in,void * buf,u32 size,u64 flags)439 static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task,
440 struct perf_callchain_entry *trace_in,
441 void *buf, u32 size, u64 flags)
442 {
443 u32 init_nr, trace_nr, copy_len, elem_size, num_elem;
444 bool user_build_id = flags & BPF_F_USER_BUILD_ID;
445 u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
446 bool user = flags & BPF_F_USER_STACK;
447 struct perf_callchain_entry *trace;
448 bool kernel = !user;
449 int err = -EINVAL;
450 u64 *ips;
451
452 if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
453 BPF_F_USER_BUILD_ID)))
454 goto clear;
455 if (kernel && user_build_id)
456 goto clear;
457
458 elem_size = (user && user_build_id) ? sizeof(struct bpf_stack_build_id)
459 : sizeof(u64);
460 if (unlikely(size % elem_size))
461 goto clear;
462
463 /* cannot get valid user stack for task without user_mode regs */
464 if (task && user && !user_mode(regs))
465 goto err_fault;
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
473 if (trace_in)
474 trace = trace_in;
475 else if (kernel && task)
476 trace = get_callchain_entry_for_task(task, init_nr);
477 else
478 trace = get_perf_callchain(regs, init_nr, kernel, user,
479 sysctl_perf_event_max_stack,
480 false, false);
481 if (unlikely(!trace))
482 goto err_fault;
483
484 trace_nr = trace->nr - init_nr;
485 if (trace_nr < skip)
486 goto err_fault;
487
488 trace_nr -= skip;
489 trace_nr = (trace_nr <= num_elem) ? trace_nr : num_elem;
490 copy_len = trace_nr * elem_size;
491 ips = trace->ip + skip + init_nr;
492 if (user && user_build_id)
493 stack_map_get_build_id_offset(buf, ips, trace_nr, user);
494 else
495 memcpy(buf, ips, copy_len);
496
497 if (size > copy_len)
498 memset(buf + copy_len, 0, size - copy_len);
499 return copy_len;
500
501 err_fault:
502 err = -EFAULT;
503 clear:
504 memset(buf, 0, size);
505 return err;
506 }
507
BPF_CALL_4(bpf_get_stack,struct pt_regs *,regs,void *,buf,u32,size,u64,flags)508 BPF_CALL_4(bpf_get_stack, struct pt_regs *, regs, void *, buf, u32, size,
509 u64, flags)
510 {
511 return __bpf_get_stack(regs, NULL, NULL, buf, size, flags);
512 }
513
514 const struct bpf_func_proto bpf_get_stack_proto = {
515 .func = bpf_get_stack,
516 .gpl_only = true,
517 .ret_type = RET_INTEGER,
518 .arg1_type = ARG_PTR_TO_CTX,
519 .arg2_type = ARG_PTR_TO_UNINIT_MEM,
520 .arg3_type = ARG_CONST_SIZE_OR_ZERO,
521 .arg4_type = ARG_ANYTHING,
522 };
523
BPF_CALL_4(bpf_get_task_stack,struct task_struct *,task,void *,buf,u32,size,u64,flags)524 BPF_CALL_4(bpf_get_task_stack, struct task_struct *, task, void *, buf,
525 u32, size, u64, flags)
526 {
527 struct pt_regs *regs;
528 long res;
529
530 if (!try_get_task_stack(task))
531 return -EFAULT;
532
533 regs = task_pt_regs(task);
534 res = __bpf_get_stack(regs, task, NULL, buf, size, flags);
535 put_task_stack(task);
536
537 return res;
538 }
539
540 const struct bpf_func_proto bpf_get_task_stack_proto = {
541 .func = bpf_get_task_stack,
542 .gpl_only = false,
543 .ret_type = RET_INTEGER,
544 .arg1_type = ARG_PTR_TO_BTF_ID,
545 .arg1_btf_id = &btf_task_struct_ids[0],
546 .arg2_type = ARG_PTR_TO_UNINIT_MEM,
547 .arg3_type = ARG_CONST_SIZE_OR_ZERO,
548 .arg4_type = ARG_ANYTHING,
549 };
550
BPF_CALL_4(bpf_get_stack_pe,struct bpf_perf_event_data_kern *,ctx,void *,buf,u32,size,u64,flags)551 BPF_CALL_4(bpf_get_stack_pe, struct bpf_perf_event_data_kern *, ctx,
552 void *, buf, u32, size, u64, flags)
553 {
554 struct pt_regs *regs = (struct pt_regs *)(ctx->regs);
555 struct perf_event *event = ctx->event;
556 struct perf_callchain_entry *trace;
557 bool kernel, user;
558 int err = -EINVAL;
559 __u64 nr_kernel;
560
561 if (!(event->attr.sample_type & __PERF_SAMPLE_CALLCHAIN_EARLY))
562 return __bpf_get_stack(regs, NULL, NULL, buf, size, flags);
563
564 if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
565 BPF_F_USER_BUILD_ID)))
566 goto clear;
567
568 user = flags & BPF_F_USER_STACK;
569 kernel = !user;
570
571 err = -EFAULT;
572 trace = ctx->data->callchain;
573 if (unlikely(!trace))
574 goto clear;
575
576 nr_kernel = count_kernel_ip(trace);
577
578 if (kernel) {
579 __u64 nr = trace->nr;
580
581 trace->nr = nr_kernel;
582 err = __bpf_get_stack(regs, NULL, trace, buf, size, flags);
583
584 /* restore nr */
585 trace->nr = nr;
586 } else { /* user */
587 u64 skip = flags & BPF_F_SKIP_FIELD_MASK;
588
589 skip += nr_kernel;
590 if (skip > BPF_F_SKIP_FIELD_MASK)
591 goto clear;
592
593 flags = (flags & ~BPF_F_SKIP_FIELD_MASK) | skip;
594 err = __bpf_get_stack(regs, NULL, trace, buf, size, flags);
595 }
596 return err;
597
598 clear:
599 memset(buf, 0, size);
600 return err;
601
602 }
603
604 const struct bpf_func_proto bpf_get_stack_proto_pe = {
605 .func = bpf_get_stack_pe,
606 .gpl_only = true,
607 .ret_type = RET_INTEGER,
608 .arg1_type = ARG_PTR_TO_CTX,
609 .arg2_type = ARG_PTR_TO_UNINIT_MEM,
610 .arg3_type = ARG_CONST_SIZE_OR_ZERO,
611 .arg4_type = ARG_ANYTHING,
612 };
613
614 /* Called from eBPF program */
stack_map_lookup_elem(struct bpf_map * map,void * key)615 static void *stack_map_lookup_elem(struct bpf_map *map, void *key)
616 {
617 return ERR_PTR(-EOPNOTSUPP);
618 }
619
620 /* Called from syscall */
bpf_stackmap_copy(struct bpf_map * map,void * key,void * value)621 int bpf_stackmap_copy(struct bpf_map *map, void *key, void *value)
622 {
623 struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
624 struct stack_map_bucket *bucket, *old_bucket;
625 u32 id = *(u32 *)key, trace_len;
626
627 if (unlikely(id >= smap->n_buckets))
628 return -ENOENT;
629
630 bucket = xchg(&smap->buckets[id], NULL);
631 if (!bucket)
632 return -ENOENT;
633
634 trace_len = bucket->nr * stack_map_data_size(map);
635 memcpy(value, bucket->data, trace_len);
636 memset(value + trace_len, 0, map->value_size - trace_len);
637
638 old_bucket = xchg(&smap->buckets[id], bucket);
639 if (old_bucket)
640 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
641 return 0;
642 }
643
stack_map_get_next_key(struct bpf_map * map,void * key,void * next_key)644 static int stack_map_get_next_key(struct bpf_map *map, void *key,
645 void *next_key)
646 {
647 struct bpf_stack_map *smap = container_of(map,
648 struct bpf_stack_map, map);
649 u32 id;
650
651 WARN_ON_ONCE(!rcu_read_lock_held());
652
653 if (!key) {
654 id = 0;
655 } else {
656 id = *(u32 *)key;
657 if (id >= smap->n_buckets || !smap->buckets[id])
658 id = 0;
659 else
660 id++;
661 }
662
663 while (id < smap->n_buckets && !smap->buckets[id])
664 id++;
665
666 if (id >= smap->n_buckets)
667 return -ENOENT;
668
669 *(u32 *)next_key = id;
670 return 0;
671 }
672
stack_map_update_elem(struct bpf_map * map,void * key,void * value,u64 map_flags)673 static int stack_map_update_elem(struct bpf_map *map, void *key, void *value,
674 u64 map_flags)
675 {
676 return -EINVAL;
677 }
678
679 /* Called from syscall or from eBPF program */
stack_map_delete_elem(struct bpf_map * map,void * key)680 static int stack_map_delete_elem(struct bpf_map *map, void *key)
681 {
682 struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
683 struct stack_map_bucket *old_bucket;
684 u32 id = *(u32 *)key;
685
686 if (unlikely(id >= smap->n_buckets))
687 return -E2BIG;
688
689 old_bucket = xchg(&smap->buckets[id], NULL);
690 if (old_bucket) {
691 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
692 return 0;
693 } else {
694 return -ENOENT;
695 }
696 }
697
698 /* Called when map->refcnt goes to zero, either from workqueue or from syscall */
stack_map_free(struct bpf_map * map)699 static void stack_map_free(struct bpf_map *map)
700 {
701 struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
702
703 bpf_map_area_free(smap->elems);
704 pcpu_freelist_destroy(&smap->freelist);
705 bpf_map_area_free(smap);
706 put_callchain_buffers();
707 }
708
709 static int stack_trace_map_btf_id;
710 const struct bpf_map_ops stack_trace_map_ops = {
711 .map_meta_equal = bpf_map_meta_equal,
712 .map_alloc = stack_map_alloc,
713 .map_free = stack_map_free,
714 .map_get_next_key = stack_map_get_next_key,
715 .map_lookup_elem = stack_map_lookup_elem,
716 .map_update_elem = stack_map_update_elem,
717 .map_delete_elem = stack_map_delete_elem,
718 .map_check_btf = map_check_no_btf,
719 .map_btf_name = "bpf_stack_map",
720 .map_btf_id = &stack_trace_map_btf_id,
721 };
722
stack_map_init(void)723 static int __init stack_map_init(void)
724 {
725 int cpu;
726 struct stack_map_irq_work *work;
727
728 for_each_possible_cpu(cpu) {
729 work = per_cpu_ptr(&up_read_work, cpu);
730 init_irq_work(&work->irq_work, do_up_read);
731 }
732 return 0;
733 }
734 subsys_initcall(stack_map_init);
735
