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 
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 
stack_map_use_build_id(struct bpf_map * map)34 static inline bool stack_map_use_build_id(struct bpf_map *map)
35 {
36 	return (map->map_flags & BPF_F_STACK_BUILD_ID);
37 }
38 
stack_map_data_size(struct bpf_map * map)39 static 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 
prealloc_elems_and_freelist(struct bpf_stack_map * smap)45 static 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 
64 free_elems:
65 	bpf_map_area_free(smap->elems);
66 	return err;
67 }
68 
69 /* Called from syscall */
stack_map_alloc(union bpf_attr * attr)70 static 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 (attr->map_flags & ~STACK_CREATE_FLAG_MASK)
78 		return ERR_PTR(-EINVAL);
79 
80 	/* check sanity of attributes */
81 	if (attr->max_entries == 0 || attr->key_size != 4 ||
82 	    value_size < 8 || value_size % 8)
83 		return ERR_PTR(-EINVAL);
84 
85 	BUILD_BUG_ON(sizeof(struct bpf_stack_build_id) % sizeof(u64));
86 	if (attr->map_flags & BPF_F_STACK_BUILD_ID) {
87 		if (value_size % sizeof(struct bpf_stack_build_id) ||
88 		    value_size / sizeof(struct bpf_stack_build_id)
89 		    > sysctl_perf_event_max_stack)
90 			return ERR_PTR(-EINVAL);
91 	} else if (value_size / 8 > sysctl_perf_event_max_stack)
92 		return ERR_PTR(-EINVAL);
93 
94 	/* hash table size must be power of 2 */
95 	n_buckets = roundup_pow_of_two(attr->max_entries);
96 	if (!n_buckets)
97 		return ERR_PTR(-E2BIG);
98 
99 	cost = n_buckets * sizeof(struct stack_map_bucket *) + sizeof(*smap);
100 	smap = bpf_map_area_alloc(cost, bpf_map_attr_numa_node(attr));
101 	if (!smap)
102 		return ERR_PTR(-ENOMEM);
103 
104 	bpf_map_init_from_attr(&smap->map, attr);
105 	smap->n_buckets = n_buckets;
106 
107 	err = get_callchain_buffers(sysctl_perf_event_max_stack);
108 	if (err)
109 		goto free_smap;
110 
111 	err = prealloc_elems_and_freelist(smap);
112 	if (err)
113 		goto put_buffers;
114 
115 	return &smap->map;
116 
117 put_buffers:
118 	put_callchain_buffers();
119 free_smap:
120 	bpf_map_area_free(smap);
121 	return ERR_PTR(err);
122 }
123 
stack_map_get_build_id_offset(struct bpf_stack_build_id * id_offs,u64 * ips,u32 trace_nr,bool user)124 static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
125 					  u64 *ips, u32 trace_nr, bool user)
126 {
127 	int i;
128 	struct mmap_unlock_irq_work *work = NULL;
129 	bool irq_work_busy = bpf_mmap_unlock_get_irq_work(&work);
130 	struct vm_area_struct *vma, *prev_vma = NULL;
131 	const char *prev_build_id;
132 
133 	/* If the irq_work is in use, fall back to report ips. Same
134 	 * fallback is used for kernel stack (!user) on a stackmap with
135 	 * build_id.
136 	 */
137 	if (!user || !current || !current->mm || irq_work_busy ||
138 	    !mmap_read_trylock(current->mm)) {
139 		/* cannot access current->mm, fall back to ips */
140 		for (i = 0; i < trace_nr; i++) {
141 			id_offs[i].status = BPF_STACK_BUILD_ID_IP;
142 			id_offs[i].ip = ips[i];
143 			memset(id_offs[i].build_id, 0, BUILD_ID_SIZE_MAX);
144 		}
145 		return;
146 	}
147 
148 	for (i = 0; i < trace_nr; i++) {
149 		if (range_in_vma(prev_vma, ips[i], ips[i])) {
150 			vma = prev_vma;
151 			memcpy(id_offs[i].build_id, prev_build_id,
152 			       BUILD_ID_SIZE_MAX);
153 			goto build_id_valid;
154 		}
155 		vma = find_vma(current->mm, ips[i]);
156 		if (!vma || build_id_parse(vma, id_offs[i].build_id, NULL)) {
157 			/* per entry fall back to ips */
158 			id_offs[i].status = BPF_STACK_BUILD_ID_IP;
159 			id_offs[i].ip = ips[i];
160 			memset(id_offs[i].build_id, 0, BUILD_ID_SIZE_MAX);
161 			continue;
162 		}
163 build_id_valid:
164 		id_offs[i].offset = (vma->vm_pgoff << PAGE_SHIFT) + ips[i]
165 			- vma->vm_start;
166 		id_offs[i].status = BPF_STACK_BUILD_ID_VALID;
167 		prev_vma = vma;
168 		prev_build_id = id_offs[i].build_id;
169 	}
170 	bpf_mmap_unlock_mm(work, current->mm);
171 }
172 
173 static struct perf_callchain_entry *
get_callchain_entry_for_task(struct task_struct * task,u32 max_depth)174 get_callchain_entry_for_task(struct task_struct *task, u32 max_depth)
175 {
176 #ifdef CONFIG_STACKTRACE
177 	struct perf_callchain_entry *entry;
178 	int rctx;
179 
180 	entry = get_callchain_entry(&rctx);
181 
182 	if (!entry)
183 		return NULL;
184 
185 	entry->nr = stack_trace_save_tsk(task, (unsigned long *)entry->ip,
186 					 max_depth, 0);
187 
188 	/* stack_trace_save_tsk() works on unsigned long array, while
189 	 * perf_callchain_entry uses u64 array. For 32-bit systems, it is
190 	 * necessary to fix this mismatch.
191 	 */
192 	if (__BITS_PER_LONG != 64) {
193 		unsigned long *from = (unsigned long *) entry->ip;
194 		u64 *to = entry->ip;
195 		int i;
196 
197 		/* copy data from the end to avoid using extra buffer */
198 		for (i = entry->nr - 1; i >= 0; i--)
199 			to[i] = (u64)(from[i]);
200 	}
201 
202 	put_callchain_entry(rctx);
203 
204 	return entry;
205 #else /* CONFIG_STACKTRACE */
206 	return NULL;
207 #endif
208 }
209 
__bpf_get_stackid(struct bpf_map * map,struct perf_callchain_entry * trace,u64 flags)210 static long __bpf_get_stackid(struct bpf_map *map,
211 			      struct perf_callchain_entry *trace, u64 flags)
212 {
213 	struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
214 	struct stack_map_bucket *bucket, *new_bucket, *old_bucket;
215 	u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
216 	u32 hash, id, trace_nr, trace_len;
217 	bool user = flags & BPF_F_USER_STACK;
218 	u64 *ips;
219 	bool hash_matches;
220 
221 	if (trace->nr <= skip)
222 		/* skipping more than usable stack trace */
223 		return -EFAULT;
224 
225 	trace_nr = trace->nr - skip;
226 	trace_len = trace_nr * sizeof(u64);
227 	ips = trace->ip + skip;
228 	hash = jhash2((u32 *)ips, trace_len / sizeof(u32), 0);
229 	id = hash & (smap->n_buckets - 1);
230 	bucket = READ_ONCE(smap->buckets[id]);
231 
232 	hash_matches = bucket && bucket->hash == hash;
233 	/* fast cmp */
234 	if (hash_matches && flags & BPF_F_FAST_STACK_CMP)
235 		return id;
236 
237 	if (stack_map_use_build_id(map)) {
238 		/* for build_id+offset, pop a bucket before slow cmp */
239 		new_bucket = (struct stack_map_bucket *)
240 			pcpu_freelist_pop(&smap->freelist);
241 		if (unlikely(!new_bucket))
242 			return -ENOMEM;
243 		new_bucket->nr = trace_nr;
244 		stack_map_get_build_id_offset(
245 			(struct bpf_stack_build_id *)new_bucket->data,
246 			ips, trace_nr, user);
247 		trace_len = trace_nr * sizeof(struct bpf_stack_build_id);
248 		if (hash_matches && bucket->nr == trace_nr &&
249 		    memcmp(bucket->data, new_bucket->data, trace_len) == 0) {
250 			pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
251 			return id;
252 		}
253 		if (bucket && !(flags & BPF_F_REUSE_STACKID)) {
254 			pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
255 			return -EEXIST;
256 		}
257 	} else {
258 		if (hash_matches && bucket->nr == trace_nr &&
259 		    memcmp(bucket->data, ips, trace_len) == 0)
260 			return id;
261 		if (bucket && !(flags & BPF_F_REUSE_STACKID))
262 			return -EEXIST;
263 
264 		new_bucket = (struct stack_map_bucket *)
265 			pcpu_freelist_pop(&smap->freelist);
266 		if (unlikely(!new_bucket))
267 			return -ENOMEM;
268 		memcpy(new_bucket->data, ips, trace_len);
269 	}
270 
271 	new_bucket->hash = hash;
272 	new_bucket->nr = trace_nr;
273 
274 	old_bucket = xchg(&smap->buckets[id], new_bucket);
275 	if (old_bucket)
276 		pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
277 	return id;
278 }
279 
BPF_CALL_3(bpf_get_stackid,struct pt_regs *,regs,struct bpf_map *,map,u64,flags)280 BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map,
281 	   u64, flags)
282 {
283 	u32 max_depth = map->value_size / stack_map_data_size(map);
284 	u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
285 	bool user = flags & BPF_F_USER_STACK;
286 	struct perf_callchain_entry *trace;
287 	bool kernel = !user;
288 
289 	if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
290 			       BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
291 		return -EINVAL;
292 
293 	max_depth += skip;
294 	if (max_depth > sysctl_perf_event_max_stack)
295 		max_depth = sysctl_perf_event_max_stack;
296 
297 	trace = get_perf_callchain(regs, 0, kernel, user, max_depth,
298 				   false, false);
299 
300 	if (unlikely(!trace))
301 		/* couldn't fetch the stack trace */
302 		return -EFAULT;
303 
304 	return __bpf_get_stackid(map, trace, flags);
305 }
306 
307 const struct bpf_func_proto bpf_get_stackid_proto = {
308 	.func		= bpf_get_stackid,
309 	.gpl_only	= true,
310 	.ret_type	= RET_INTEGER,
311 	.arg1_type	= ARG_PTR_TO_CTX,
312 	.arg2_type	= ARG_CONST_MAP_PTR,
313 	.arg3_type	= ARG_ANYTHING,
314 };
315 
count_kernel_ip(struct perf_callchain_entry * trace)316 static __u64 count_kernel_ip(struct perf_callchain_entry *trace)
317 {
318 	__u64 nr_kernel = 0;
319 
320 	while (nr_kernel < trace->nr) {
321 		if (trace->ip[nr_kernel] == PERF_CONTEXT_USER)
322 			break;
323 		nr_kernel++;
324 	}
325 	return nr_kernel;
326 }
327 
BPF_CALL_3(bpf_get_stackid_pe,struct bpf_perf_event_data_kern *,ctx,struct bpf_map *,map,u64,flags)328 BPF_CALL_3(bpf_get_stackid_pe, struct bpf_perf_event_data_kern *, ctx,
329 	   struct bpf_map *, map, u64, flags)
330 {
331 	struct perf_event *event = ctx->event;
332 	struct perf_callchain_entry *trace;
333 	bool kernel, user;
334 	__u64 nr_kernel;
335 	int ret;
336 
337 	/* perf_sample_data doesn't have callchain, use bpf_get_stackid */
338 	if (!(event->attr.sample_type & PERF_SAMPLE_CALLCHAIN))
339 		return bpf_get_stackid((unsigned long)(ctx->regs),
340 				       (unsigned long) map, flags, 0, 0);
341 
342 	if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
343 			       BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
344 		return -EINVAL;
345 
346 	user = flags & BPF_F_USER_STACK;
347 	kernel = !user;
348 
349 	trace = ctx->data->callchain;
350 	if (unlikely(!trace))
351 		return -EFAULT;
352 
353 	nr_kernel = count_kernel_ip(trace);
354 
355 	if (kernel) {
356 		__u64 nr = trace->nr;
357 
358 		trace->nr = nr_kernel;
359 		ret = __bpf_get_stackid(map, trace, flags);
360 
361 		/* restore nr */
362 		trace->nr = nr;
363 	} else { /* user */
364 		u64 skip = flags & BPF_F_SKIP_FIELD_MASK;
365 
366 		skip += nr_kernel;
367 		if (skip > BPF_F_SKIP_FIELD_MASK)
368 			return -EFAULT;
369 
370 		flags = (flags & ~BPF_F_SKIP_FIELD_MASK) | skip;
371 		ret = __bpf_get_stackid(map, trace, flags);
372 	}
373 	return ret;
374 }
375 
376 const struct bpf_func_proto bpf_get_stackid_proto_pe = {
377 	.func		= bpf_get_stackid_pe,
378 	.gpl_only	= false,
379 	.ret_type	= RET_INTEGER,
380 	.arg1_type	= ARG_PTR_TO_CTX,
381 	.arg2_type	= ARG_CONST_MAP_PTR,
382 	.arg3_type	= ARG_ANYTHING,
383 };
384 
__bpf_get_stack(struct pt_regs * regs,struct task_struct * task,struct perf_callchain_entry * trace_in,void * buf,u32 size,u64 flags)385 static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task,
386 			    struct perf_callchain_entry *trace_in,
387 			    void *buf, u32 size, u64 flags)
388 {
389 	u32 trace_nr, copy_len, elem_size, num_elem, max_depth;
390 	bool user_build_id = flags & BPF_F_USER_BUILD_ID;
391 	bool crosstask = task && task != current;
392 	u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
393 	bool user = flags & BPF_F_USER_STACK;
394 	struct perf_callchain_entry *trace;
395 	bool kernel = !user;
396 	int err = -EINVAL;
397 	u64 *ips;
398 
399 	if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
400 			       BPF_F_USER_BUILD_ID)))
401 		goto clear;
402 	if (kernel && user_build_id)
403 		goto clear;
404 
405 	elem_size = (user && user_build_id) ? sizeof(struct bpf_stack_build_id)
406 					    : sizeof(u64);
407 	if (unlikely(size % elem_size))
408 		goto clear;
409 
410 	/* cannot get valid user stack for task without user_mode regs */
411 	if (task && user && !user_mode(regs))
412 		goto err_fault;
413 
414 	/* get_perf_callchain does not support crosstask user stack walking
415 	 * but returns an empty stack instead of NULL.
416 	 */
417 	if (crosstask && user) {
418 		err = -EOPNOTSUPP;
419 		goto clear;
420 	}
421 
422 	num_elem = size / elem_size;
423 	max_depth = num_elem + skip;
424 	if (sysctl_perf_event_max_stack < max_depth)
425 		max_depth = sysctl_perf_event_max_stack;
426 
427 	if (trace_in)
428 		trace = trace_in;
429 	else if (kernel && task)
430 		trace = get_callchain_entry_for_task(task, max_depth);
431 	else
432 		trace = get_perf_callchain(regs, 0, kernel, user, max_depth,
433 					   crosstask, false);
434 	if (unlikely(!trace))
435 		goto err_fault;
436 
437 	if (trace->nr < skip)
438 		goto err_fault;
439 
440 	trace_nr = trace->nr - skip;
441 	trace_nr = (trace_nr <= num_elem) ? trace_nr : num_elem;
442 	copy_len = trace_nr * elem_size;
443 
444 	ips = trace->ip + skip;
445 	if (user && user_build_id)
446 		stack_map_get_build_id_offset(buf, ips, trace_nr, user);
447 	else
448 		memcpy(buf, ips, copy_len);
449 
450 	if (size > copy_len)
451 		memset(buf + copy_len, 0, size - copy_len);
452 	return copy_len;
453 
454 err_fault:
455 	err = -EFAULT;
456 clear:
457 	memset(buf, 0, size);
458 	return err;
459 }
460 
BPF_CALL_4(bpf_get_stack,struct pt_regs *,regs,void *,buf,u32,size,u64,flags)461 BPF_CALL_4(bpf_get_stack, struct pt_regs *, regs, void *, buf, u32, size,
462 	   u64, flags)
463 {
464 	return __bpf_get_stack(regs, NULL, NULL, buf, size, flags);
465 }
466 
467 const struct bpf_func_proto bpf_get_stack_proto = {
468 	.func		= bpf_get_stack,
469 	.gpl_only	= true,
470 	.ret_type	= RET_INTEGER,
471 	.arg1_type	= ARG_PTR_TO_CTX,
472 	.arg2_type	= ARG_PTR_TO_UNINIT_MEM,
473 	.arg3_type	= ARG_CONST_SIZE_OR_ZERO,
474 	.arg4_type	= ARG_ANYTHING,
475 };
476 
BPF_CALL_4(bpf_get_task_stack,struct task_struct *,task,void *,buf,u32,size,u64,flags)477 BPF_CALL_4(bpf_get_task_stack, struct task_struct *, task, void *, buf,
478 	   u32, size, u64, flags)
479 {
480 	struct pt_regs *regs;
481 	long res = -EINVAL;
482 
483 	if (!try_get_task_stack(task))
484 		return -EFAULT;
485 
486 	regs = task_pt_regs(task);
487 	if (regs)
488 		res = __bpf_get_stack(regs, task, NULL, buf, size, flags);
489 	put_task_stack(task);
490 
491 	return res;
492 }
493 
494 const struct bpf_func_proto bpf_get_task_stack_proto = {
495 	.func		= bpf_get_task_stack,
496 	.gpl_only	= false,
497 	.ret_type	= RET_INTEGER,
498 	.arg1_type	= ARG_PTR_TO_BTF_ID,
499 	.arg1_btf_id	= &btf_tracing_ids[BTF_TRACING_TYPE_TASK],
500 	.arg2_type	= ARG_PTR_TO_UNINIT_MEM,
501 	.arg3_type	= ARG_CONST_SIZE_OR_ZERO,
502 	.arg4_type	= ARG_ANYTHING,
503 };
504 
BPF_CALL_4(bpf_get_stack_pe,struct bpf_perf_event_data_kern *,ctx,void *,buf,u32,size,u64,flags)505 BPF_CALL_4(bpf_get_stack_pe, struct bpf_perf_event_data_kern *, ctx,
506 	   void *, buf, u32, size, u64, flags)
507 {
508 	struct pt_regs *regs = (struct pt_regs *)(ctx->regs);
509 	struct perf_event *event = ctx->event;
510 	struct perf_callchain_entry *trace;
511 	bool kernel, user;
512 	int err = -EINVAL;
513 	__u64 nr_kernel;
514 
515 	if (!(event->attr.sample_type & PERF_SAMPLE_CALLCHAIN))
516 		return __bpf_get_stack(regs, NULL, NULL, buf, size, flags);
517 
518 	if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
519 			       BPF_F_USER_BUILD_ID)))
520 		goto clear;
521 
522 	user = flags & BPF_F_USER_STACK;
523 	kernel = !user;
524 
525 	err = -EFAULT;
526 	trace = ctx->data->callchain;
527 	if (unlikely(!trace))
528 		goto clear;
529 
530 	nr_kernel = count_kernel_ip(trace);
531 
532 	if (kernel) {
533 		__u64 nr = trace->nr;
534 
535 		trace->nr = nr_kernel;
536 		err = __bpf_get_stack(regs, NULL, trace, buf, size, flags);
537 
538 		/* restore nr */
539 		trace->nr = nr;
540 	} else { /* user */
541 		u64 skip = flags & BPF_F_SKIP_FIELD_MASK;
542 
543 		skip += nr_kernel;
544 		if (skip > BPF_F_SKIP_FIELD_MASK)
545 			goto clear;
546 
547 		flags = (flags & ~BPF_F_SKIP_FIELD_MASK) | skip;
548 		err = __bpf_get_stack(regs, NULL, trace, buf, size, flags);
549 	}
550 	return err;
551 
552 clear:
553 	memset(buf, 0, size);
554 	return err;
555 
556 }
557 
558 const struct bpf_func_proto bpf_get_stack_proto_pe = {
559 	.func		= bpf_get_stack_pe,
560 	.gpl_only	= true,
561 	.ret_type	= RET_INTEGER,
562 	.arg1_type	= ARG_PTR_TO_CTX,
563 	.arg2_type	= ARG_PTR_TO_UNINIT_MEM,
564 	.arg3_type	= ARG_CONST_SIZE_OR_ZERO,
565 	.arg4_type	= ARG_ANYTHING,
566 };
567 
568 /* Called from eBPF program */
stack_map_lookup_elem(struct bpf_map * map,void * key)569 static void *stack_map_lookup_elem(struct bpf_map *map, void *key)
570 {
571 	return ERR_PTR(-EOPNOTSUPP);
572 }
573 
574 /* Called from syscall */
bpf_stackmap_copy(struct bpf_map * map,void * key,void * value)575 int bpf_stackmap_copy(struct bpf_map *map, void *key, void *value)
576 {
577 	struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
578 	struct stack_map_bucket *bucket, *old_bucket;
579 	u32 id = *(u32 *)key, trace_len;
580 
581 	if (unlikely(id >= smap->n_buckets))
582 		return -ENOENT;
583 
584 	bucket = xchg(&smap->buckets[id], NULL);
585 	if (!bucket)
586 		return -ENOENT;
587 
588 	trace_len = bucket->nr * stack_map_data_size(map);
589 	memcpy(value, bucket->data, trace_len);
590 	memset(value + trace_len, 0, map->value_size - trace_len);
591 
592 	old_bucket = xchg(&smap->buckets[id], bucket);
593 	if (old_bucket)
594 		pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
595 	return 0;
596 }
597 
stack_map_get_next_key(struct bpf_map * map,void * key,void * next_key)598 static int stack_map_get_next_key(struct bpf_map *map, void *key,
599 				  void *next_key)
600 {
601 	struct bpf_stack_map *smap = container_of(map,
602 						  struct bpf_stack_map, map);
603 	u32 id;
604 
605 	WARN_ON_ONCE(!rcu_read_lock_held());
606 
607 	if (!key) {
608 		id = 0;
609 	} else {
610 		id = *(u32 *)key;
611 		if (id >= smap->n_buckets || !smap->buckets[id])
612 			id = 0;
613 		else
614 			id++;
615 	}
616 
617 	while (id < smap->n_buckets && !smap->buckets[id])
618 		id++;
619 
620 	if (id >= smap->n_buckets)
621 		return -ENOENT;
622 
623 	*(u32 *)next_key = id;
624 	return 0;
625 }
626 
stack_map_update_elem(struct bpf_map * map,void * key,void * value,u64 map_flags)627 static long stack_map_update_elem(struct bpf_map *map, void *key, void *value,
628 				  u64 map_flags)
629 {
630 	return -EINVAL;
631 }
632 
633 /* Called from syscall or from eBPF program */
stack_map_delete_elem(struct bpf_map * map,void * key)634 static long stack_map_delete_elem(struct bpf_map *map, void *key)
635 {
636 	struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
637 	struct stack_map_bucket *old_bucket;
638 	u32 id = *(u32 *)key;
639 
640 	if (unlikely(id >= smap->n_buckets))
641 		return -E2BIG;
642 
643 	old_bucket = xchg(&smap->buckets[id], NULL);
644 	if (old_bucket) {
645 		pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
646 		return 0;
647 	} else {
648 		return -ENOENT;
649 	}
650 }
651 
652 /* Called when map->refcnt goes to zero, either from workqueue or from syscall */
stack_map_free(struct bpf_map * map)653 static void stack_map_free(struct bpf_map *map)
654 {
655 	struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
656 
657 	bpf_map_area_free(smap->elems);
658 	pcpu_freelist_destroy(&smap->freelist);
659 	bpf_map_area_free(smap);
660 	put_callchain_buffers();
661 }
662 
stack_map_mem_usage(const struct bpf_map * map)663 static u64 stack_map_mem_usage(const struct bpf_map *map)
664 {
665 	struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
666 	u64 value_size = map->value_size;
667 	u64 n_buckets = smap->n_buckets;
668 	u64 enties = map->max_entries;
669 	u64 usage = sizeof(*smap);
670 
671 	usage += n_buckets * sizeof(struct stack_map_bucket *);
672 	usage += enties * (sizeof(struct stack_map_bucket) + value_size);
673 	return usage;
674 }
675 
676 BTF_ID_LIST_SINGLE(stack_trace_map_btf_ids, struct, bpf_stack_map)
677 const struct bpf_map_ops stack_trace_map_ops = {
678 	.map_meta_equal = bpf_map_meta_equal,
679 	.map_alloc = stack_map_alloc,
680 	.map_free = stack_map_free,
681 	.map_get_next_key = stack_map_get_next_key,
682 	.map_lookup_elem = stack_map_lookup_elem,
683 	.map_update_elem = stack_map_update_elem,
684 	.map_delete_elem = stack_map_delete_elem,
685 	.map_check_btf = map_check_no_btf,
686 	.map_mem_usage = stack_map_mem_usage,
687 	.map_btf_id = &stack_trace_map_btf_ids[0],
688 };
689