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[];
 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
 45static int prealloc_elems_and_freelist(struct bpf_stack_map *smap)
 46{
 47	u64 elem_size = sizeof(struct stack_map_bucket) +
 48			(u64)smap->map.value_size;
 49	int err;
 50
 51	smap->elems = bpf_map_area_alloc(elem_size * smap->map.max_entries,
 52					 smap->map.numa_node);
 53	if (!smap->elems)
 54		return -ENOMEM;
 55
 56	err = pcpu_freelist_init(&smap->freelist);
 57	if (err)
 58		goto free_elems;
 59
 60	pcpu_freelist_populate(&smap->freelist, smap->elems, elem_size,
 61			       smap->map.max_entries);
 62	return 0;
 63
 64free_elems:
 65	bpf_map_area_free(smap->elems);
 66	return err;
 67}
 68
 69/* Called from syscall */
 70static struct bpf_map *stack_map_alloc(union bpf_attr *attr)
 71{
 72	u32 value_size = attr->value_size;
 73	struct bpf_stack_map *smap;
 
 74	u64 cost, n_buckets;
 75	int err;
 76
 77	if (!bpf_capable())
 78		return ERR_PTR(-EPERM);
 79
 80	if (attr->map_flags & ~STACK_CREATE_FLAG_MASK)
 81		return ERR_PTR(-EINVAL);
 82
 83	/* check sanity of attributes */
 84	if (attr->max_entries == 0 || attr->key_size != 4 ||
 85	    value_size < 8 || value_size % 8)
 86		return ERR_PTR(-EINVAL);
 87
 88	BUILD_BUG_ON(sizeof(struct bpf_stack_build_id) % sizeof(u64));
 89	if (attr->map_flags & BPF_F_STACK_BUILD_ID) {
 90		if (value_size % sizeof(struct bpf_stack_build_id) ||
 91		    value_size / sizeof(struct bpf_stack_build_id)
 92		    > sysctl_perf_event_max_stack)
 93			return ERR_PTR(-EINVAL);
 94	} else if (value_size / 8 > sysctl_perf_event_max_stack)
 95		return ERR_PTR(-EINVAL);
 96
 97	/* hash table size must be power of 2 */
 98	n_buckets = roundup_pow_of_two(attr->max_entries);
 99	if (!n_buckets)
100		return ERR_PTR(-E2BIG);
101
102	cost = n_buckets * sizeof(struct stack_map_bucket *) + sizeof(*smap);
 
 
 
 
 
103	smap = bpf_map_area_alloc(cost, bpf_map_attr_numa_node(attr));
104	if (!smap)
 
105		return ERR_PTR(-ENOMEM);
 
106
107	bpf_map_init_from_attr(&smap->map, attr);
 
108	smap->n_buckets = n_buckets;
109
110	err = get_callchain_buffers(sysctl_perf_event_max_stack);
111	if (err)
112		goto free_smap;
113
114	err = prealloc_elems_and_freelist(smap);
115	if (err)
116		goto put_buffers;
117
 
 
118	return &smap->map;
119
120put_buffers:
121	put_callchain_buffers();
122free_smap:
 
123	bpf_map_area_free(smap);
124	return ERR_PTR(err);
125}
126
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
127static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
128					  u64 *ips, u32 trace_nr, bool user)
129{
130	int i;
131	struct mmap_unlock_irq_work *work = NULL;
132	bool irq_work_busy = bpf_mmap_unlock_get_irq_work(&work);
133	struct vm_area_struct *vma, *prev_vma = NULL;
134	const char *prev_build_id;
135
136	/* If the irq_work is in use, fall back to report ips. Same
137	 * fallback is used for kernel stack (!user) on a stackmap with
138	 * build_id.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
139	 */
140	if (!user || !current || !current->mm || irq_work_busy ||
141	    !mmap_read_trylock(current->mm)) {
142		/* cannot access current->mm, fall back to ips */
143		for (i = 0; i < trace_nr; i++) {
144			id_offs[i].status = BPF_STACK_BUILD_ID_IP;
145			id_offs[i].ip = ips[i];
146			memset(id_offs[i].build_id, 0, BUILD_ID_SIZE_MAX);
147		}
148		return;
149	}
150
151	for (i = 0; i < trace_nr; i++) {
152		if (range_in_vma(prev_vma, ips[i], ips[i])) {
153			vma = prev_vma;
154			memcpy(id_offs[i].build_id, prev_build_id,
155			       BUILD_ID_SIZE_MAX);
156			goto build_id_valid;
157		}
158		vma = find_vma(current->mm, ips[i]);
159		if (!vma || build_id_parse(vma, id_offs[i].build_id, NULL)) {
160			/* per entry fall back to ips */
161			id_offs[i].status = BPF_STACK_BUILD_ID_IP;
162			id_offs[i].ip = ips[i];
163			memset(id_offs[i].build_id, 0, BUILD_ID_SIZE_MAX);
164			continue;
165		}
166build_id_valid:
167		id_offs[i].offset = (vma->vm_pgoff << PAGE_SHIFT) + ips[i]
168			- vma->vm_start;
169		id_offs[i].status = BPF_STACK_BUILD_ID_VALID;
170		prev_vma = vma;
171		prev_build_id = id_offs[i].build_id;
172	}
173	bpf_mmap_unlock_mm(work, current->mm);
 
 
 
 
 
 
174}
175
176static struct perf_callchain_entry *
177get_callchain_entry_for_task(struct task_struct *task, u32 max_depth)
178{
179#ifdef CONFIG_STACKTRACE
180	struct perf_callchain_entry *entry;
181	int rctx;
182
183	entry = get_callchain_entry(&rctx);
184
185	if (!entry)
186		return NULL;
187
188	entry->nr = stack_trace_save_tsk(task, (unsigned long *)entry->ip,
189					 max_depth, 0);
 
190
191	/* stack_trace_save_tsk() works on unsigned long array, while
192	 * perf_callchain_entry uses u64 array. For 32-bit systems, it is
193	 * necessary to fix this mismatch.
194	 */
195	if (__BITS_PER_LONG != 64) {
196		unsigned long *from = (unsigned long *) entry->ip;
197		u64 *to = entry->ip;
198		int i;
199
200		/* copy data from the end to avoid using extra buffer */
201		for (i = entry->nr - 1; i >= 0; i--)
202			to[i] = (u64)(from[i]);
203	}
204
205	put_callchain_entry(rctx);
206
207	return entry;
208#else /* CONFIG_STACKTRACE */
209	return NULL;
210#endif
211}
212
213static long __bpf_get_stackid(struct bpf_map *map,
214			      struct perf_callchain_entry *trace, u64 flags)
215{
216	struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
217	struct stack_map_bucket *bucket, *new_bucket, *old_bucket;
 
 
 
218	u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
219	u32 hash, id, trace_nr, trace_len;
220	bool user = flags & BPF_F_USER_STACK;
221	u64 *ips;
222	bool hash_matches;
223
224	if (trace->nr <= skip)
 
 
 
 
 
225		/* skipping more than usable stack trace */
226		return -EFAULT;
227
228	trace_nr = trace->nr - skip;
229	trace_len = trace_nr * sizeof(u64);
230	ips = trace->ip + skip;
231	hash = jhash2((u32 *)ips, trace_len / sizeof(u32), 0);
232	id = hash & (smap->n_buckets - 1);
233	bucket = READ_ONCE(smap->buckets[id]);
234
235	hash_matches = bucket && bucket->hash == hash;
236	/* fast cmp */
237	if (hash_matches && flags & BPF_F_FAST_STACK_CMP)
238		return id;
239
240	if (stack_map_use_build_id(map)) {
241		/* for build_id+offset, pop a bucket before slow cmp */
242		new_bucket = (struct stack_map_bucket *)
243			pcpu_freelist_pop(&smap->freelist);
244		if (unlikely(!new_bucket))
245			return -ENOMEM;
246		new_bucket->nr = trace_nr;
247		stack_map_get_build_id_offset(
248			(struct bpf_stack_build_id *)new_bucket->data,
249			ips, trace_nr, user);
250		trace_len = trace_nr * sizeof(struct bpf_stack_build_id);
251		if (hash_matches && bucket->nr == trace_nr &&
252		    memcmp(bucket->data, new_bucket->data, trace_len) == 0) {
253			pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
254			return id;
255		}
256		if (bucket && !(flags & BPF_F_REUSE_STACKID)) {
257			pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
258			return -EEXIST;
259		}
260	} else {
261		if (hash_matches && bucket->nr == trace_nr &&
262		    memcmp(bucket->data, ips, trace_len) == 0)
263			return id;
264		if (bucket && !(flags & BPF_F_REUSE_STACKID))
265			return -EEXIST;
266
267		new_bucket = (struct stack_map_bucket *)
268			pcpu_freelist_pop(&smap->freelist);
269		if (unlikely(!new_bucket))
270			return -ENOMEM;
271		memcpy(new_bucket->data, ips, trace_len);
272	}
273
274	new_bucket->hash = hash;
275	new_bucket->nr = trace_nr;
276
277	old_bucket = xchg(&smap->buckets[id], new_bucket);
278	if (old_bucket)
279		pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
280	return id;
281}
282
283BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map,
284	   u64, flags)
285{
286	u32 max_depth = map->value_size / stack_map_data_size(map);
287	u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
 
288	bool user = flags & BPF_F_USER_STACK;
289	struct perf_callchain_entry *trace;
290	bool kernel = !user;
291
292	if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
293			       BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
294		return -EINVAL;
295
296	max_depth += skip;
297	if (max_depth > sysctl_perf_event_max_stack)
298		max_depth = sysctl_perf_event_max_stack;
299
300	trace = get_perf_callchain(regs, 0, kernel, user, max_depth,
301				   false, false);
302
303	if (unlikely(!trace))
304		/* couldn't fetch the stack trace */
305		return -EFAULT;
306
307	return __bpf_get_stackid(map, trace, flags);
308}
309
310const struct bpf_func_proto bpf_get_stackid_proto = {
311	.func		= bpf_get_stackid,
312	.gpl_only	= true,
313	.ret_type	= RET_INTEGER,
314	.arg1_type	= ARG_PTR_TO_CTX,
315	.arg2_type	= ARG_CONST_MAP_PTR,
316	.arg3_type	= ARG_ANYTHING,
317};
318
319static __u64 count_kernel_ip(struct perf_callchain_entry *trace)
320{
321	__u64 nr_kernel = 0;
322
323	while (nr_kernel < trace->nr) {
324		if (trace->ip[nr_kernel] == PERF_CONTEXT_USER)
325			break;
326		nr_kernel++;
327	}
328	return nr_kernel;
329}
330
331BPF_CALL_3(bpf_get_stackid_pe, struct bpf_perf_event_data_kern *, ctx,
332	   struct bpf_map *, map, u64, flags)
333{
334	struct perf_event *event = ctx->event;
335	struct perf_callchain_entry *trace;
336	bool kernel, user;
337	__u64 nr_kernel;
338	int ret;
339
340	/* perf_sample_data doesn't have callchain, use bpf_get_stackid */
341	if (!(event->attr.sample_type & PERF_SAMPLE_CALLCHAIN))
342		return bpf_get_stackid((unsigned long)(ctx->regs),
343				       (unsigned long) map, flags, 0, 0);
344
345	if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
346			       BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
347		return -EINVAL;
348
349	user = flags & BPF_F_USER_STACK;
350	kernel = !user;
351
352	trace = ctx->data->callchain;
353	if (unlikely(!trace))
354		return -EFAULT;
355
356	nr_kernel = count_kernel_ip(trace);
357
358	if (kernel) {
359		__u64 nr = trace->nr;
360
361		trace->nr = nr_kernel;
362		ret = __bpf_get_stackid(map, trace, flags);
363
364		/* restore nr */
365		trace->nr = nr;
366	} else { /* user */
367		u64 skip = flags & BPF_F_SKIP_FIELD_MASK;
368
369		skip += nr_kernel;
370		if (skip > BPF_F_SKIP_FIELD_MASK)
371			return -EFAULT;
372
373		flags = (flags & ~BPF_F_SKIP_FIELD_MASK) | skip;
374		ret = __bpf_get_stackid(map, trace, flags);
375	}
376	return ret;
377}
378
379const struct bpf_func_proto bpf_get_stackid_proto_pe = {
380	.func		= bpf_get_stackid_pe,
381	.gpl_only	= false,
382	.ret_type	= RET_INTEGER,
383	.arg1_type	= ARG_PTR_TO_CTX,
384	.arg2_type	= ARG_CONST_MAP_PTR,
385	.arg3_type	= ARG_ANYTHING,
386};
387
388static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task,
389			    struct perf_callchain_entry *trace_in,
390			    void *buf, u32 size, u64 flags)
391{
392	u32 trace_nr, copy_len, elem_size, num_elem, max_depth;
393	bool user_build_id = flags & BPF_F_USER_BUILD_ID;
394	u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
395	bool user = flags & BPF_F_USER_STACK;
396	struct perf_callchain_entry *trace;
397	bool kernel = !user;
398	int err = -EINVAL;
399	u64 *ips;
400
401	if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
402			       BPF_F_USER_BUILD_ID)))
403		goto clear;
404	if (kernel && user_build_id)
405		goto clear;
406
407	elem_size = (user && user_build_id) ? sizeof(struct bpf_stack_build_id)
408					    : sizeof(u64);
409	if (unlikely(size % elem_size))
410		goto clear;
411
412	/* cannot get valid user stack for task without user_mode regs */
413	if (task && user && !user_mode(regs))
414		goto err_fault;
415
416	num_elem = size / elem_size;
417	max_depth = num_elem + skip;
418	if (sysctl_perf_event_max_stack < max_depth)
419		max_depth = sysctl_perf_event_max_stack;
 
420
421	if (trace_in)
422		trace = trace_in;
423	else if (kernel && task)
424		trace = get_callchain_entry_for_task(task, max_depth);
425	else
426		trace = get_perf_callchain(regs, 0, kernel, user, max_depth,
 
427					   false, false);
428	if (unlikely(!trace))
429		goto err_fault;
430
431	if (trace->nr < skip)
 
432		goto err_fault;
433
434	trace_nr = trace->nr - skip;
435	trace_nr = (trace_nr <= num_elem) ? trace_nr : num_elem;
436	copy_len = trace_nr * elem_size;
437
438	ips = trace->ip + skip;
439	if (user && user_build_id)
440		stack_map_get_build_id_offset(buf, ips, trace_nr, user);
441	else
442		memcpy(buf, ips, copy_len);
443
444	if (size > copy_len)
445		memset(buf + copy_len, 0, size - copy_len);
446	return copy_len;
447
448err_fault:
449	err = -EFAULT;
450clear:
451	memset(buf, 0, size);
452	return err;
453}
454
455BPF_CALL_4(bpf_get_stack, struct pt_regs *, regs, void *, buf, u32, size,
456	   u64, flags)
457{
458	return __bpf_get_stack(regs, NULL, NULL, buf, size, flags);
459}
460
461const struct bpf_func_proto bpf_get_stack_proto = {
462	.func		= bpf_get_stack,
463	.gpl_only	= true,
464	.ret_type	= RET_INTEGER,
465	.arg1_type	= ARG_PTR_TO_CTX,
466	.arg2_type	= ARG_PTR_TO_UNINIT_MEM,
467	.arg3_type	= ARG_CONST_SIZE_OR_ZERO,
468	.arg4_type	= ARG_ANYTHING,
469};
470
471BPF_CALL_4(bpf_get_task_stack, struct task_struct *, task, void *, buf,
472	   u32, size, u64, flags)
473{
474	struct pt_regs *regs;
475	long res = -EINVAL;
476
477	if (!try_get_task_stack(task))
478		return -EFAULT;
479
480	regs = task_pt_regs(task);
481	if (regs)
482		res = __bpf_get_stack(regs, task, NULL, buf, size, flags);
483	put_task_stack(task);
484
485	return res;
486}
487
 
 
 
488const struct bpf_func_proto bpf_get_task_stack_proto = {
489	.func		= bpf_get_task_stack,
490	.gpl_only	= false,
491	.ret_type	= RET_INTEGER,
492	.arg1_type	= ARG_PTR_TO_BTF_ID,
493	.arg1_btf_id	= &btf_tracing_ids[BTF_TRACING_TYPE_TASK],
494	.arg2_type	= ARG_PTR_TO_UNINIT_MEM,
495	.arg3_type	= ARG_CONST_SIZE_OR_ZERO,
496	.arg4_type	= ARG_ANYTHING,
 
497};
498
499BPF_CALL_4(bpf_get_stack_pe, struct bpf_perf_event_data_kern *, ctx,
500	   void *, buf, u32, size, u64, flags)
501{
502	struct pt_regs *regs = (struct pt_regs *)(ctx->regs);
503	struct perf_event *event = ctx->event;
504	struct perf_callchain_entry *trace;
505	bool kernel, user;
506	int err = -EINVAL;
507	__u64 nr_kernel;
508
509	if (!(event->attr.sample_type & PERF_SAMPLE_CALLCHAIN))
510		return __bpf_get_stack(regs, NULL, NULL, buf, size, flags);
511
512	if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
513			       BPF_F_USER_BUILD_ID)))
514		goto clear;
515
516	user = flags & BPF_F_USER_STACK;
517	kernel = !user;
518
519	err = -EFAULT;
520	trace = ctx->data->callchain;
521	if (unlikely(!trace))
522		goto clear;
523
524	nr_kernel = count_kernel_ip(trace);
525
526	if (kernel) {
527		__u64 nr = trace->nr;
528
529		trace->nr = nr_kernel;
530		err = __bpf_get_stack(regs, NULL, trace, buf, size, flags);
531
532		/* restore nr */
533		trace->nr = nr;
534	} else { /* user */
535		u64 skip = flags & BPF_F_SKIP_FIELD_MASK;
536
537		skip += nr_kernel;
538		if (skip > BPF_F_SKIP_FIELD_MASK)
539			goto clear;
540
541		flags = (flags & ~BPF_F_SKIP_FIELD_MASK) | skip;
542		err = __bpf_get_stack(regs, NULL, trace, buf, size, flags);
543	}
544	return err;
545
546clear:
547	memset(buf, 0, size);
548	return err;
549
550}
551
552const struct bpf_func_proto bpf_get_stack_proto_pe = {
553	.func		= bpf_get_stack_pe,
554	.gpl_only	= true,
555	.ret_type	= RET_INTEGER,
556	.arg1_type	= ARG_PTR_TO_CTX,
557	.arg2_type	= ARG_PTR_TO_UNINIT_MEM,
558	.arg3_type	= ARG_CONST_SIZE_OR_ZERO,
559	.arg4_type	= ARG_ANYTHING,
560};
561
562/* Called from eBPF program */
563static void *stack_map_lookup_elem(struct bpf_map *map, void *key)
564{
565	return ERR_PTR(-EOPNOTSUPP);
566}
567
568/* Called from syscall */
569int bpf_stackmap_copy(struct bpf_map *map, void *key, void *value)
570{
571	struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
572	struct stack_map_bucket *bucket, *old_bucket;
573	u32 id = *(u32 *)key, trace_len;
574
575	if (unlikely(id >= smap->n_buckets))
576		return -ENOENT;
577
578	bucket = xchg(&smap->buckets[id], NULL);
579	if (!bucket)
580		return -ENOENT;
581
582	trace_len = bucket->nr * stack_map_data_size(map);
583	memcpy(value, bucket->data, trace_len);
584	memset(value + trace_len, 0, map->value_size - trace_len);
585
586	old_bucket = xchg(&smap->buckets[id], bucket);
587	if (old_bucket)
588		pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
589	return 0;
590}
591
592static int stack_map_get_next_key(struct bpf_map *map, void *key,
593				  void *next_key)
594{
595	struct bpf_stack_map *smap = container_of(map,
596						  struct bpf_stack_map, map);
597	u32 id;
598
599	WARN_ON_ONCE(!rcu_read_lock_held());
600
601	if (!key) {
602		id = 0;
603	} else {
604		id = *(u32 *)key;
605		if (id >= smap->n_buckets || !smap->buckets[id])
606			id = 0;
607		else
608			id++;
609	}
610
611	while (id < smap->n_buckets && !smap->buckets[id])
612		id++;
613
614	if (id >= smap->n_buckets)
615		return -ENOENT;
616
617	*(u32 *)next_key = id;
618	return 0;
619}
620
621static int stack_map_update_elem(struct bpf_map *map, void *key, void *value,
622				 u64 map_flags)
623{
624	return -EINVAL;
625}
626
627/* Called from syscall or from eBPF program */
628static int stack_map_delete_elem(struct bpf_map *map, void *key)
629{
630	struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
631	struct stack_map_bucket *old_bucket;
632	u32 id = *(u32 *)key;
633
634	if (unlikely(id >= smap->n_buckets))
635		return -E2BIG;
636
637	old_bucket = xchg(&smap->buckets[id], NULL);
638	if (old_bucket) {
639		pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
640		return 0;
641	} else {
642		return -ENOENT;
643	}
644}
645
646/* Called when map->refcnt goes to zero, either from workqueue or from syscall */
647static void stack_map_free(struct bpf_map *map)
648{
649	struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
650
651	bpf_map_area_free(smap->elems);
652	pcpu_freelist_destroy(&smap->freelist);
653	bpf_map_area_free(smap);
654	put_callchain_buffers();
655}
656
657BTF_ID_LIST_SINGLE(stack_trace_map_btf_ids, struct, bpf_stack_map)
658const struct bpf_map_ops stack_trace_map_ops = {
659	.map_meta_equal = bpf_map_meta_equal,
660	.map_alloc = stack_map_alloc,
661	.map_free = stack_map_free,
662	.map_get_next_key = stack_map_get_next_key,
663	.map_lookup_elem = stack_map_lookup_elem,
664	.map_update_elem = stack_map_update_elem,
665	.map_delete_elem = stack_map_delete_elem,
666	.map_check_btf = map_check_no_btf,
667	.map_btf_id = &stack_trace_map_btf_ids[0],
 
668};