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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 	smap = bpf_map_area_alloc(cost, bpf_map_attr_numa_node(attr));
123 	if (!smap)
124 		return ERR_PTR(-ENOMEM);
125 
126 	bpf_map_init_from_attr(&smap->map, attr);
127 	smap->map.value_size = value_size;
128 	smap->n_buckets = n_buckets;
129 
130 	err = get_callchain_buffers(sysctl_perf_event_max_stack);
131 	if (err)
132 		goto free_smap;
133 
134 	err = prealloc_elems_and_freelist(smap);
135 	if (err)
136 		goto put_buffers;
137 
138 	return &smap->map;
139 
140 put_buffers:
141 	put_callchain_buffers();
142 free_smap:
143 	bpf_map_area_free(smap);
144 	return ERR_PTR(err);
145 }
146 
stack_map_get_build_id_offset(struct bpf_stack_build_id * id_offs,u64 * ips,u32 trace_nr,bool user)147 static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
148 					  u64 *ips, u32 trace_nr, bool user)
149 {
150 	int i;
151 	struct vm_area_struct *vma;
152 	bool irq_work_busy = false;
153 	struct stack_map_irq_work *work = NULL;
154 
155 	if (irqs_disabled()) {
156 		if (!IS_ENABLED(CONFIG_PREEMPT_RT)) {
157 			work = this_cpu_ptr(&up_read_work);
158 			if (irq_work_is_busy(&work->irq_work)) {
159 				/* cannot queue more up_read, fallback */
160 				irq_work_busy = true;
161 			}
162 		} else {
163 			/*
164 			 * PREEMPT_RT does not allow to trylock mmap sem in
165 			 * interrupt disabled context. Force the fallback code.
166 			 */
167 			irq_work_busy = true;
168 		}
169 	}
170 
171 	/*
172 	 * We cannot do up_read() when the irq is disabled, because of
173 	 * risk to deadlock with rq_lock. To do build_id lookup when the
174 	 * irqs are disabled, we need to run up_read() in irq_work. We use
175 	 * a percpu variable to do the irq_work. If the irq_work is
176 	 * already used by another lookup, we fall back to report ips.
177 	 *
178 	 * Same fallback is used for kernel stack (!user) on a stackmap
179 	 * with build_id.
180 	 */
181 	if (!user || !current || !current->mm || irq_work_busy ||
182 	    !mmap_read_trylock(current->mm)) {
183 		/* cannot access current->mm, fall back to ips */
184 		for (i = 0; i < trace_nr; i++) {
185 			id_offs[i].status = BPF_STACK_BUILD_ID_IP;
186 			id_offs[i].ip = ips[i];
187 			memset(id_offs[i].build_id, 0, BUILD_ID_SIZE_MAX);
188 		}
189 		return;
190 	}
191 
192 	for (i = 0; i < trace_nr; i++) {
193 		vma = find_vma(current->mm, ips[i]);
194 		if (!vma || build_id_parse(vma, id_offs[i].build_id, NULL)) {
195 			/* per entry fall back to ips */
196 			id_offs[i].status = BPF_STACK_BUILD_ID_IP;
197 			id_offs[i].ip = ips[i];
198 			memset(id_offs[i].build_id, 0, BUILD_ID_SIZE_MAX);
199 			continue;
200 		}
201 		id_offs[i].offset = (vma->vm_pgoff << PAGE_SHIFT) + ips[i]
202 			- vma->vm_start;
203 		id_offs[i].status = BPF_STACK_BUILD_ID_VALID;
204 	}
205 
206 	if (!work) {
207 		mmap_read_unlock(current->mm);
208 	} else {
209 		work->mm = current->mm;
210 
211 		/* The lock will be released once we're out of interrupt
212 		 * context. Tell lockdep that we've released it now so
213 		 * it doesn't complain that we forgot to release it.
214 		 */
215 		rwsem_release(&current->mm->mmap_lock.dep_map, _RET_IP_);
216 		irq_work_queue(&work->irq_work);
217 	}
218 }
219 
220 static struct perf_callchain_entry *
get_callchain_entry_for_task(struct task_struct * task,u32 max_depth)221 get_callchain_entry_for_task(struct task_struct *task, u32 max_depth)
222 {
223 #ifdef CONFIG_STACKTRACE
224 	struct perf_callchain_entry *entry;
225 	int rctx;
226 
227 	entry = get_callchain_entry(&rctx);
228 
229 	if (!entry)
230 		return NULL;
231 
232 	entry->nr = stack_trace_save_tsk(task, (unsigned long *)entry->ip,
233 					 max_depth, 0);
234 
235 	/* stack_trace_save_tsk() works on unsigned long array, while
236 	 * perf_callchain_entry uses u64 array. For 32-bit systems, it is
237 	 * necessary to fix this mismatch.
238 	 */
239 	if (__BITS_PER_LONG != 64) {
240 		unsigned long *from = (unsigned long *) entry->ip;
241 		u64 *to = entry->ip;
242 		int i;
243 
244 		/* copy data from the end to avoid using extra buffer */
245 		for (i = entry->nr - 1; i >= 0; i--)
246 			to[i] = (u64)(from[i]);
247 	}
248 
249 	put_callchain_entry(rctx);
250 
251 	return entry;
252 #else /* CONFIG_STACKTRACE */
253 	return NULL;
254 #endif
255 }
256 
__bpf_get_stackid(struct bpf_map * map,struct perf_callchain_entry * trace,u64 flags)257 static long __bpf_get_stackid(struct bpf_map *map,
258 			      struct perf_callchain_entry *trace, u64 flags)
259 {
260 	struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
261 	struct stack_map_bucket *bucket, *new_bucket, *old_bucket;
262 	u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
263 	u32 hash, id, trace_nr, trace_len;
264 	bool user = flags & BPF_F_USER_STACK;
265 	u64 *ips;
266 	bool hash_matches;
267 
268 	if (trace->nr <= skip)
269 		/* skipping more than usable stack trace */
270 		return -EFAULT;
271 
272 	trace_nr = trace->nr - skip;
273 	trace_len = trace_nr * sizeof(u64);
274 	ips = trace->ip + skip;
275 	hash = jhash2((u32 *)ips, trace_len / sizeof(u32), 0);
276 	id = hash & (smap->n_buckets - 1);
277 	bucket = READ_ONCE(smap->buckets[id]);
278 
279 	hash_matches = bucket && bucket->hash == hash;
280 	/* fast cmp */
281 	if (hash_matches && flags & BPF_F_FAST_STACK_CMP)
282 		return id;
283 
284 	if (stack_map_use_build_id(map)) {
285 		/* for build_id+offset, pop a bucket before slow cmp */
286 		new_bucket = (struct stack_map_bucket *)
287 			pcpu_freelist_pop(&smap->freelist);
288 		if (unlikely(!new_bucket))
289 			return -ENOMEM;
290 		new_bucket->nr = trace_nr;
291 		stack_map_get_build_id_offset(
292 			(struct bpf_stack_build_id *)new_bucket->data,
293 			ips, trace_nr, user);
294 		trace_len = trace_nr * sizeof(struct bpf_stack_build_id);
295 		if (hash_matches && bucket->nr == trace_nr &&
296 		    memcmp(bucket->data, new_bucket->data, trace_len) == 0) {
297 			pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
298 			return id;
299 		}
300 		if (bucket && !(flags & BPF_F_REUSE_STACKID)) {
301 			pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
302 			return -EEXIST;
303 		}
304 	} else {
305 		if (hash_matches && bucket->nr == trace_nr &&
306 		    memcmp(bucket->data, ips, trace_len) == 0)
307 			return id;
308 		if (bucket && !(flags & BPF_F_REUSE_STACKID))
309 			return -EEXIST;
310 
311 		new_bucket = (struct stack_map_bucket *)
312 			pcpu_freelist_pop(&smap->freelist);
313 		if (unlikely(!new_bucket))
314 			return -ENOMEM;
315 		memcpy(new_bucket->data, ips, trace_len);
316 	}
317 
318 	new_bucket->hash = hash;
319 	new_bucket->nr = trace_nr;
320 
321 	old_bucket = xchg(&smap->buckets[id], new_bucket);
322 	if (old_bucket)
323 		pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
324 	return id;
325 }
326 
BPF_CALL_3(bpf_get_stackid,struct pt_regs *,regs,struct bpf_map *,map,u64,flags)327 BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map,
328 	   u64, flags)
329 {
330 	u32 max_depth = map->value_size / stack_map_data_size(map);
331 	u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
332 	bool user = flags & BPF_F_USER_STACK;
333 	struct perf_callchain_entry *trace;
334 	bool kernel = !user;
335 
336 	if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
337 			       BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
338 		return -EINVAL;
339 
340 	max_depth += skip;
341 	if (max_depth > sysctl_perf_event_max_stack)
342 		max_depth = sysctl_perf_event_max_stack;
343 
344 	trace = get_perf_callchain(regs, 0, kernel, user, max_depth,
345 				   false, false);
346 
347 	if (unlikely(!trace))
348 		/* couldn't fetch the stack trace */
349 		return -EFAULT;
350 
351 	return __bpf_get_stackid(map, trace, flags);
352 }
353 
354 const struct bpf_func_proto bpf_get_stackid_proto = {
355 	.func		= bpf_get_stackid,
356 	.gpl_only	= true,
357 	.ret_type	= RET_INTEGER,
358 	.arg1_type	= ARG_PTR_TO_CTX,
359 	.arg2_type	= ARG_CONST_MAP_PTR,
360 	.arg3_type	= ARG_ANYTHING,
361 };
362 
count_kernel_ip(struct perf_callchain_entry * trace)363 static __u64 count_kernel_ip(struct perf_callchain_entry *trace)
364 {
365 	__u64 nr_kernel = 0;
366 
367 	while (nr_kernel < trace->nr) {
368 		if (trace->ip[nr_kernel] == PERF_CONTEXT_USER)
369 			break;
370 		nr_kernel++;
371 	}
372 	return nr_kernel;
373 }
374 
BPF_CALL_3(bpf_get_stackid_pe,struct bpf_perf_event_data_kern *,ctx,struct bpf_map *,map,u64,flags)375 BPF_CALL_3(bpf_get_stackid_pe, struct bpf_perf_event_data_kern *, ctx,
376 	   struct bpf_map *, map, u64, flags)
377 {
378 	struct perf_event *event = ctx->event;
379 	struct perf_callchain_entry *trace;
380 	bool kernel, user;
381 	__u64 nr_kernel;
382 	int ret;
383 
384 	/* perf_sample_data doesn't have callchain, use bpf_get_stackid */
385 	if (!(event->attr.sample_type & __PERF_SAMPLE_CALLCHAIN_EARLY))
386 		return bpf_get_stackid((unsigned long)(ctx->regs),
387 				       (unsigned long) map, flags, 0, 0);
388 
389 	if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
390 			       BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
391 		return -EINVAL;
392 
393 	user = flags & BPF_F_USER_STACK;
394 	kernel = !user;
395 
396 	trace = ctx->data->callchain;
397 	if (unlikely(!trace))
398 		return -EFAULT;
399 
400 	nr_kernel = count_kernel_ip(trace);
401 
402 	if (kernel) {
403 		__u64 nr = trace->nr;
404 
405 		trace->nr = nr_kernel;
406 		ret = __bpf_get_stackid(map, trace, flags);
407 
408 		/* restore nr */
409 		trace->nr = nr;
410 	} else { /* user */
411 		u64 skip = flags & BPF_F_SKIP_FIELD_MASK;
412 
413 		skip += nr_kernel;
414 		if (skip > BPF_F_SKIP_FIELD_MASK)
415 			return -EFAULT;
416 
417 		flags = (flags & ~BPF_F_SKIP_FIELD_MASK) | skip;
418 		ret = __bpf_get_stackid(map, trace, flags);
419 	}
420 	return ret;
421 }
422 
423 const struct bpf_func_proto bpf_get_stackid_proto_pe = {
424 	.func		= bpf_get_stackid_pe,
425 	.gpl_only	= false,
426 	.ret_type	= RET_INTEGER,
427 	.arg1_type	= ARG_PTR_TO_CTX,
428 	.arg2_type	= ARG_CONST_MAP_PTR,
429 	.arg3_type	= ARG_ANYTHING,
430 };
431 
__bpf_get_stack(struct pt_regs * regs,struct task_struct * task,struct perf_callchain_entry * trace_in,void * buf,u32 size,u64 flags)432 static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task,
433 			    struct perf_callchain_entry *trace_in,
434 			    void *buf, u32 size, u64 flags)
435 {
436 	u32 trace_nr, copy_len, elem_size, num_elem, max_depth;
437 	bool user_build_id = flags & BPF_F_USER_BUILD_ID;
438 	bool crosstask = task && task != current;
439 	u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
440 	bool user = flags & BPF_F_USER_STACK;
441 	struct perf_callchain_entry *trace;
442 	bool kernel = !user;
443 	int err = -EINVAL;
444 	u64 *ips;
445 
446 	if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
447 			       BPF_F_USER_BUILD_ID)))
448 		goto clear;
449 	if (kernel && user_build_id)
450 		goto clear;
451 
452 	elem_size = (user && user_build_id) ? sizeof(struct bpf_stack_build_id)
453 					    : sizeof(u64);
454 	if (unlikely(size % elem_size))
455 		goto clear;
456 
457 	/* cannot get valid user stack for task without user_mode regs */
458 	if (task && user && !user_mode(regs))
459 		goto err_fault;
460 
461 	/* get_perf_callchain does not support crosstask user stack walking
462 	 * but returns an empty stack instead of NULL.
463 	 */
464 	if (crosstask && user) {
465 		err = -EOPNOTSUPP;
466 		goto clear;
467 	}
468 
469 	num_elem = size / elem_size;
470 	max_depth = num_elem + skip;
471 	if (sysctl_perf_event_max_stack < max_depth)
472 		max_depth = sysctl_perf_event_max_stack;
473 
474 	if (trace_in)
475 		trace = trace_in;
476 	else if (kernel && task)
477 		trace = get_callchain_entry_for_task(task, max_depth);
478 	else
479 		trace = get_perf_callchain(regs, 0, kernel, user, max_depth,
480 					   crosstask, false);
481 	if (unlikely(!trace))
482 		goto err_fault;
483 
484 	if (trace->nr < skip)
485 		goto err_fault;
486 
487 	trace_nr = trace->nr - skip;
488 	trace_nr = (trace_nr <= num_elem) ? trace_nr : num_elem;
489 	copy_len = trace_nr * elem_size;
490 
491 	ips = trace->ip + skip;
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 = -EINVAL;
529 
530 	if (!try_get_task_stack(task))
531 		return -EFAULT;
532 
533 	regs = task_pt_regs(task);
534 	if (regs)
535 		res = __bpf_get_stack(regs, task, NULL, buf, size, flags);
536 	put_task_stack(task);
537 
538 	return res;
539 }
540 
541 const struct bpf_func_proto bpf_get_task_stack_proto = {
542 	.func		= bpf_get_task_stack,
543 	.gpl_only	= false,
544 	.ret_type	= RET_INTEGER,
545 	.arg1_type	= ARG_PTR_TO_BTF_ID,
546 	.arg1_btf_id	= &btf_task_struct_ids[0],
547 	.arg2_type	= ARG_PTR_TO_UNINIT_MEM,
548 	.arg3_type	= ARG_CONST_SIZE_OR_ZERO,
549 	.arg4_type	= ARG_ANYTHING,
550 };
551 
BPF_CALL_4(bpf_get_stack_pe,struct bpf_perf_event_data_kern *,ctx,void *,buf,u32,size,u64,flags)552 BPF_CALL_4(bpf_get_stack_pe, struct bpf_perf_event_data_kern *, ctx,
553 	   void *, buf, u32, size, u64, flags)
554 {
555 	struct pt_regs *regs = (struct pt_regs *)(ctx->regs);
556 	struct perf_event *event = ctx->event;
557 	struct perf_callchain_entry *trace;
558 	bool kernel, user;
559 	int err = -EINVAL;
560 	__u64 nr_kernel;
561 
562 	if (!(event->attr.sample_type & __PERF_SAMPLE_CALLCHAIN_EARLY))
563 		return __bpf_get_stack(regs, NULL, NULL, buf, size, flags);
564 
565 	if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
566 			       BPF_F_USER_BUILD_ID)))
567 		goto clear;
568 
569 	user = flags & BPF_F_USER_STACK;
570 	kernel = !user;
571 
572 	err = -EFAULT;
573 	trace = ctx->data->callchain;
574 	if (unlikely(!trace))
575 		goto clear;
576 
577 	nr_kernel = count_kernel_ip(trace);
578 
579 	if (kernel) {
580 		__u64 nr = trace->nr;
581 
582 		trace->nr = nr_kernel;
583 		err = __bpf_get_stack(regs, NULL, trace, buf, size, flags);
584 
585 		/* restore nr */
586 		trace->nr = nr;
587 	} else { /* user */
588 		u64 skip = flags & BPF_F_SKIP_FIELD_MASK;
589 
590 		skip += nr_kernel;
591 		if (skip > BPF_F_SKIP_FIELD_MASK)
592 			goto clear;
593 
594 		flags = (flags & ~BPF_F_SKIP_FIELD_MASK) | skip;
595 		err = __bpf_get_stack(regs, NULL, trace, buf, size, flags);
596 	}
597 	return err;
598 
599 clear:
600 	memset(buf, 0, size);
601 	return err;
602 
603 }
604 
605 const struct bpf_func_proto bpf_get_stack_proto_pe = {
606 	.func		= bpf_get_stack_pe,
607 	.gpl_only	= true,
608 	.ret_type	= RET_INTEGER,
609 	.arg1_type	= ARG_PTR_TO_CTX,
610 	.arg2_type	= ARG_PTR_TO_UNINIT_MEM,
611 	.arg3_type	= ARG_CONST_SIZE_OR_ZERO,
612 	.arg4_type	= ARG_ANYTHING,
613 };
614 
615 /* Called from eBPF program */
stack_map_lookup_elem(struct bpf_map * map,void * key)616 static void *stack_map_lookup_elem(struct bpf_map *map, void *key)
617 {
618 	return ERR_PTR(-EOPNOTSUPP);
619 }
620 
621 /* Called from syscall */
bpf_stackmap_copy(struct bpf_map * map,void * key,void * value)622 int bpf_stackmap_copy(struct bpf_map *map, void *key, void *value)
623 {
624 	struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
625 	struct stack_map_bucket *bucket, *old_bucket;
626 	u32 id = *(u32 *)key, trace_len;
627 
628 	if (unlikely(id >= smap->n_buckets))
629 		return -ENOENT;
630 
631 	bucket = xchg(&smap->buckets[id], NULL);
632 	if (!bucket)
633 		return -ENOENT;
634 
635 	trace_len = bucket->nr * stack_map_data_size(map);
636 	memcpy(value, bucket->data, trace_len);
637 	memset(value + trace_len, 0, map->value_size - trace_len);
638 
639 	old_bucket = xchg(&smap->buckets[id], bucket);
640 	if (old_bucket)
641 		pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
642 	return 0;
643 }
644 
stack_map_get_next_key(struct bpf_map * map,void * key,void * next_key)645 static int stack_map_get_next_key(struct bpf_map *map, void *key,
646 				  void *next_key)
647 {
648 	struct bpf_stack_map *smap = container_of(map,
649 						  struct bpf_stack_map, map);
650 	u32 id;
651 
652 	WARN_ON_ONCE(!rcu_read_lock_held());
653 
654 	if (!key) {
655 		id = 0;
656 	} else {
657 		id = *(u32 *)key;
658 		if (id >= smap->n_buckets || !smap->buckets[id])
659 			id = 0;
660 		else
661 			id++;
662 	}
663 
664 	while (id < smap->n_buckets && !smap->buckets[id])
665 		id++;
666 
667 	if (id >= smap->n_buckets)
668 		return -ENOENT;
669 
670 	*(u32 *)next_key = id;
671 	return 0;
672 }
673 
stack_map_update_elem(struct bpf_map * map,void * key,void * value,u64 map_flags)674 static int stack_map_update_elem(struct bpf_map *map, void *key, void *value,
675 				 u64 map_flags)
676 {
677 	return -EINVAL;
678 }
679 
680 /* Called from syscall or from eBPF program */
stack_map_delete_elem(struct bpf_map * map,void * key)681 static int stack_map_delete_elem(struct bpf_map *map, void *key)
682 {
683 	struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
684 	struct stack_map_bucket *old_bucket;
685 	u32 id = *(u32 *)key;
686 
687 	if (unlikely(id >= smap->n_buckets))
688 		return -E2BIG;
689 
690 	old_bucket = xchg(&smap->buckets[id], NULL);
691 	if (old_bucket) {
692 		pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
693 		return 0;
694 	} else {
695 		return -ENOENT;
696 	}
697 }
698 
699 /* Called when map->refcnt goes to zero, either from workqueue or from syscall */
stack_map_free(struct bpf_map * map)700 static void stack_map_free(struct bpf_map *map)
701 {
702 	struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
703 
704 	bpf_map_area_free(smap->elems);
705 	pcpu_freelist_destroy(&smap->freelist);
706 	bpf_map_area_free(smap);
707 	put_callchain_buffers();
708 }
709 
710 static int stack_trace_map_btf_id;
711 const struct bpf_map_ops stack_trace_map_ops = {
712 	.map_meta_equal = bpf_map_meta_equal,
713 	.map_alloc = stack_map_alloc,
714 	.map_free = stack_map_free,
715 	.map_get_next_key = stack_map_get_next_key,
716 	.map_lookup_elem = stack_map_lookup_elem,
717 	.map_update_elem = stack_map_update_elem,
718 	.map_delete_elem = stack_map_delete_elem,
719 	.map_check_btf = map_check_no_btf,
720 	.map_btf_name = "bpf_stack_map",
721 	.map_btf_id = &stack_trace_map_btf_id,
722 };
723 
stack_map_init(void)724 static int __init stack_map_init(void)
725 {
726 	int cpu;
727 	struct stack_map_irq_work *work;
728 
729 	for_each_possible_cpu(cpu) {
730 		work = per_cpu_ptr(&up_read_work, cpu);
731 		init_irq_work(&work->irq_work, do_up_read);
732 	}
733 	return 0;
734 }
735 subsys_initcall(stack_map_init);
736