summaryrefslogtreecommitdiff
path: root/kernel/bpf/hashtab.c
blob: fff3650d52fc774f7efdf2d289e879a916f44c60 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
/* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com
 * Copyright (c) 2016 Facebook
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of version 2 of the GNU General Public
 * License as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License for more details.
 */
#include <linux/bpf.h>
#include <linux/jhash.h>
#include <linux/filter.h>
#include <linux/vmalloc.h>
#include "percpu_freelist.h"

struct bucket {
	struct hlist_head head;
	raw_spinlock_t lock;
};

struct bpf_htab {
	struct bpf_map map;
	struct bucket *buckets;
	void *elems;
	struct pcpu_freelist freelist;
	atomic_t count;	/* number of elements in this hashtable */
	u32 n_buckets;	/* number of hash buckets */
	u32 elem_size;	/* size of each element in bytes */
};

/* each htab element is struct htab_elem + key + value */
struct htab_elem {
	union {
		struct hlist_node hash_node;
		struct bpf_htab *htab;
		struct pcpu_freelist_node fnode;
	};
	struct rcu_head rcu;
	u32 hash;
	char key[0] __aligned(8);
};

static inline void htab_elem_set_ptr(struct htab_elem *l, u32 key_size,
				     void __percpu *pptr)
{
	*(void __percpu **)(l->key + key_size) = pptr;
}

static inline void __percpu *htab_elem_get_ptr(struct htab_elem *l, u32 key_size)
{
	return *(void __percpu **)(l->key + key_size);
}

static struct htab_elem *get_htab_elem(struct bpf_htab *htab, int i)
{
	return (struct htab_elem *) (htab->elems + i * htab->elem_size);
}

static void htab_free_elems(struct bpf_htab *htab)
{
	int i;

	if (htab->map.map_type != BPF_MAP_TYPE_PERCPU_HASH)
		goto free_elems;

	for (i = 0; i < htab->map.max_entries; i++) {
		void __percpu *pptr;

		pptr = htab_elem_get_ptr(get_htab_elem(htab, i),
					 htab->map.key_size);
		free_percpu(pptr);
	}
free_elems:
	vfree(htab->elems);
}

static int prealloc_elems_and_freelist(struct bpf_htab *htab)
{
	int err = -ENOMEM, i;

	htab->elems = vzalloc(htab->elem_size * htab->map.max_entries);
	if (!htab->elems)
		return -ENOMEM;

	if (htab->map.map_type != BPF_MAP_TYPE_PERCPU_HASH)
		goto skip_percpu_elems;

	for (i = 0; i < htab->map.max_entries; i++) {
		u32 size = round_up(htab->map.value_size, 8);
		void __percpu *pptr;

		pptr = __alloc_percpu_gfp(size, 8, GFP_USER | __GFP_NOWARN);
		if (!pptr)
			goto free_elems;
		htab_elem_set_ptr(get_htab_elem(htab, i), htab->map.key_size,
				  pptr);
	}

skip_percpu_elems:
	err = pcpu_freelist_init(&htab->freelist);
	if (err)
		goto free_elems;

	pcpu_freelist_populate(&htab->freelist, htab->elems, htab->elem_size,
			       htab->map.max_entries);
	return 0;

free_elems:
	htab_free_elems(htab);
	return err;
}

/* Called from syscall */
static struct bpf_map *htab_map_alloc(union bpf_attr *attr)
{
	bool percpu = attr->map_type == BPF_MAP_TYPE_PERCPU_HASH;
	struct bpf_htab *htab;
	int err, i;
	u64 cost;

	if (attr->map_flags & ~BPF_F_NO_PREALLOC)
		/* reserved bits should not be used */
		return ERR_PTR(-EINVAL);

	htab = kzalloc(sizeof(*htab), GFP_USER);
	if (!htab)
		return ERR_PTR(-ENOMEM);

	/* mandatory map attributes */
	htab->map.map_type = attr->map_type;
	htab->map.key_size = attr->key_size;
	htab->map.value_size = attr->value_size;
	htab->map.max_entries = attr->max_entries;
	htab->map.map_flags = attr->map_flags;

	/* check sanity of attributes.
	 * value_size == 0 may be allowed in the future to use map as a set
	 */
	err = -EINVAL;
	if (htab->map.max_entries == 0 || htab->map.key_size == 0 ||
	    htab->map.value_size == 0)
		goto free_htab;

	/* hash table size must be power of 2 */
	htab->n_buckets = roundup_pow_of_two(htab->map.max_entries);

	err = -E2BIG;
	if (htab->map.key_size > MAX_BPF_STACK)
		/* eBPF programs initialize keys on stack, so they cannot be
		 * larger than max stack size
		 */
		goto free_htab;

	if (htab->map.value_size >= (1 << (KMALLOC_SHIFT_MAX - 1)) -
	    MAX_BPF_STACK - sizeof(struct htab_elem))
		/* if value_size is bigger, the user space won't be able to
		 * access the elements via bpf syscall. This check also makes
		 * sure that the elem_size doesn't overflow and it's
		 * kmalloc-able later in htab_map_update_elem()
		 */
		goto free_htab;

	if (percpu && round_up(htab->map.value_size, 8) > PCPU_MIN_UNIT_SIZE)
		/* make sure the size for pcpu_alloc() is reasonable */
		goto free_htab;

	htab->elem_size = sizeof(struct htab_elem) +
			  round_up(htab->map.key_size, 8);
	if (percpu)
		htab->elem_size += sizeof(void *);
	else
		htab->elem_size += round_up(htab->map.value_size, 8);

	/* prevent zero size kmalloc and check for u32 overflow */
	if (htab->n_buckets == 0 ||
	    htab->n_buckets > U32_MAX / sizeof(struct bucket))
		goto free_htab;

	cost = (u64) htab->n_buckets * sizeof(struct bucket) +
	       (u64) htab->elem_size * htab->map.max_entries;

	if (percpu)
		cost += (u64) round_up(htab->map.value_size, 8) *
			num_possible_cpus() * htab->map.max_entries;

	if (cost >= U32_MAX - PAGE_SIZE)
		/* make sure page count doesn't overflow */
		goto free_htab;

	htab->map.pages = round_up(cost, PAGE_SIZE) >> PAGE_SHIFT;

	/* if map size is larger than memlock limit, reject it early */
	err = bpf_map_precharge_memlock(htab->map.pages);
	if (err)
		goto free_htab;

	err = -ENOMEM;
	htab->buckets = kmalloc_array(htab->n_buckets, sizeof(struct bucket),
				      GFP_USER | __GFP_NOWARN);

	if (!htab->buckets) {
		htab->buckets = vmalloc(htab->n_buckets * sizeof(struct bucket));
		if (!htab->buckets)
			goto free_htab;
	}

	for (i = 0; i < htab->n_buckets; i++) {
		INIT_HLIST_HEAD(&htab->buckets[i].head);
		raw_spin_lock_init(&htab->buckets[i].lock);
	}

	if (!(attr->map_flags & BPF_F_NO_PREALLOC)) {
		err = prealloc_elems_and_freelist(htab);
		if (err)
			goto free_buckets;
	}

	return &htab->map;

free_buckets:
	kvfree(htab->buckets);
free_htab:
	kfree(htab);
	return ERR_PTR(err);
}

static inline u32 htab_map_hash(const void *key, u32 key_len)
{
	return jhash(key, key_len, 0);
}

static inline struct bucket *__select_bucket(struct bpf_htab *htab, u32 hash)
{
	return &htab->buckets[hash & (htab->n_buckets - 1)];
}

static inline struct hlist_head *select_bucket(struct bpf_htab *htab, u32 hash)
{
	return &__select_bucket(htab, hash)->head;
}

static struct htab_elem *lookup_elem_raw(struct hlist_head *head, u32 hash,
					 void *key, u32 key_size)
{
	struct htab_elem *l;

	hlist_for_each_entry_rcu(l, head, hash_node)
		if (l->hash == hash && !memcmp(&l->key, key, key_size))
			return l;

	return NULL;
}

/* Called from syscall or from eBPF program */
static void *__htab_map_lookup_elem(struct bpf_map *map, void *key)
{
	struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
	struct hlist_head *head;
	struct htab_elem *l;
	u32 hash, key_size;

	/* Must be called with rcu_read_lock. */
	WARN_ON_ONCE(!rcu_read_lock_held());

	key_size = map->key_size;

	hash = htab_map_hash(key, key_size);

	head = select_bucket(htab, hash);

	l = lookup_elem_raw(head, hash, key, key_size);

	return l;
}

static void *htab_map_lookup_elem(struct bpf_map *map, void *key)
{
	struct htab_elem *l = __htab_map_lookup_elem(map, key);

	if (l)
		return l->key + round_up(map->key_size, 8);

	return NULL;
}

/* Called from syscall */
static int htab_map_get_next_key(struct bpf_map *map, void *key, void *next_key)
{
	struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
	struct hlist_head *head;
	struct htab_elem *l, *next_l;
	u32 hash, key_size;
	int i;

	WARN_ON_ONCE(!rcu_read_lock_held());

	key_size = map->key_size;

	hash = htab_map_hash(key, key_size);

	head = select_bucket(htab, hash);

	/* lookup the key */
	l = lookup_elem_raw(head, hash, key, key_size);

	if (!l) {
		i = 0;
		goto find_first_elem;
	}

	/* key was found, get next key in the same bucket */
	next_l = hlist_entry_safe(rcu_dereference_raw(hlist_next_rcu(&l->hash_node)),
				  struct htab_elem, hash_node);

	if (next_l) {
		/* if next elem in this hash list is non-zero, just return it */
		memcpy(next_key, next_l->key, key_size);
		return 0;
	}

	/* no more elements in this hash list, go to the next bucket */
	i = hash & (htab->n_buckets - 1);
	i++;

find_first_elem:
	/* iterate over buckets */
	for (; i < htab->n_buckets; i++) {
		head = select_bucket(htab, i);

		/* pick first element in the bucket */
		next_l = hlist_entry_safe(rcu_dereference_raw(hlist_first_rcu(head)),
					  struct htab_elem, hash_node);
		if (next_l) {
			/* if it's not empty, just return it */
			memcpy(next_key, next_l->key, key_size);
			return 0;
		}
	}

	/* iterated over all buckets and all elements */
	return -ENOENT;
}

static void htab_elem_free(struct bpf_htab *htab, struct htab_elem *l)
{
	if (htab->map.map_type == BPF_MAP_TYPE_PERCPU_HASH)
		free_percpu(htab_elem_get_ptr(l, htab->map.key_size));
	kfree(l);

}

static void htab_elem_free_rcu(struct rcu_head *head)
{
	struct htab_elem *l = container_of(head, struct htab_elem, rcu);
	struct bpf_htab *htab = l->htab;

	/* must increment bpf_prog_active to avoid kprobe+bpf triggering while
	 * we're calling kfree, otherwise deadlock is possible if kprobes
	 * are placed somewhere inside of slub
	 */
	preempt_disable();
	__this_cpu_inc(bpf_prog_active);
	htab_elem_free(htab, l);
	__this_cpu_dec(bpf_prog_active);
	preempt_enable();
}

static void free_htab_elem(struct bpf_htab *htab, struct htab_elem *l)
{
	if (!(htab->map.map_flags & BPF_F_NO_PREALLOC)) {
		pcpu_freelist_push(&htab->freelist, &l->fnode);
	} else {
		atomic_dec(&htab->count);
		l->htab = htab;
		call_rcu(&l->rcu, htab_elem_free_rcu);
	}
}

static struct htab_elem *alloc_htab_elem(struct bpf_htab *htab, void *key,
					 void *value, u32 key_size, u32 hash,
					 bool percpu, bool onallcpus)
{
	u32 size = htab->map.value_size;
	bool prealloc = !(htab->map.map_flags & BPF_F_NO_PREALLOC);
	struct htab_elem *l_new;
	void __percpu *pptr;

	if (prealloc) {
		l_new = (struct htab_elem *)pcpu_freelist_pop(&htab->freelist);
		if (!l_new)
			return ERR_PTR(-E2BIG);
	} else {
		if (atomic_inc_return(&htab->count) > htab->map.max_entries) {
			atomic_dec(&htab->count);
			return ERR_PTR(-E2BIG);
		}
		l_new = kmalloc(htab->elem_size, GFP_ATOMIC | __GFP_NOWARN);
		if (!l_new)
			return ERR_PTR(-ENOMEM);
	}

	memcpy(l_new->key, key, key_size);
	if (percpu) {
		/* round up value_size to 8 bytes */
		size = round_up(size, 8);

		if (prealloc) {
			pptr = htab_elem_get_ptr(l_new, key_size);
		} else {
			/* alloc_percpu zero-fills */
			pptr = __alloc_percpu_gfp(size, 8,
						  GFP_ATOMIC | __GFP_NOWARN);
			if (!pptr) {
				kfree(l_new);
				return ERR_PTR(-ENOMEM);
			}
		}

		if (!onallcpus) {
			/* copy true value_size bytes */
			memcpy(this_cpu_ptr(pptr), value, htab->map.value_size);
		} else {
			int off = 0, cpu;

			for_each_possible_cpu(cpu) {
				bpf_long_memcpy(per_cpu_ptr(pptr, cpu),
						value + off, size);
				off += size;
			}
		}
		if (!prealloc)
			htab_elem_set_ptr(l_new, key_size, pptr);
	} else {
		memcpy(l_new->key + round_up(key_size, 8), value, size);
	}

	l_new->hash = hash;
	return l_new;
}

static int check_flags(struct bpf_htab *htab, struct htab_elem *l_old,
		       u64 map_flags)
{
	if (l_old && map_flags == BPF_NOEXIST)
		/* elem already exists */
		return -EEXIST;

	if (!l_old && map_flags == BPF_EXIST)
		/* elem doesn't exist, cannot update it */
		return -ENOENT;

	return 0;
}

/* Called from syscall or from eBPF program */
static int htab_map_update_elem(struct bpf_map *map, void *key, void *value,
				u64 map_flags)
{
	struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
	struct htab_elem *l_new = NULL, *l_old;
	struct hlist_head *head;
	unsigned long flags;
	struct bucket *b;
	u32 key_size, hash;
	int ret;

	if (unlikely(map_flags > BPF_EXIST))
		/* unknown flags */
		return -EINVAL;

	WARN_ON_ONCE(!rcu_read_lock_held());

	key_size = map->key_size;

	hash = htab_map_hash(key, key_size);

	b = __select_bucket(htab, hash);
	head = &b->head;

	/* bpf_map_update_elem() can be called in_irq() */
	raw_spin_lock_irqsave(&b->lock, flags);

	l_old = lookup_elem_raw(head, hash, key, key_size);

	ret = check_flags(htab, l_old, map_flags);
	if (ret)
		goto err;

	l_new = alloc_htab_elem(htab, key, value, key_size, hash, false, false);
	if (IS_ERR(l_new)) {
		/* all pre-allocated elements are in use or memory exhausted */
		ret = PTR_ERR(l_new);
		goto err;
	}

	/* add new element to the head of the list, so that
	 * concurrent search will find it before old elem
	 */
	hlist_add_head_rcu(&l_new->hash_node, head);
	if (l_old) {
		hlist_del_rcu(&l_old->hash_node);
		free_htab_elem(htab, l_old);
	}
	ret = 0;
err:
	raw_spin_unlock_irqrestore(&b->lock, flags);
	return ret;
}

static int __htab_percpu_map_update_elem(struct bpf_map *map, void *key,
					 void *value, u64 map_flags,
					 bool onallcpus)
{
	struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
	struct htab_elem *l_new = NULL, *l_old;
	struct hlist_head *head;
	unsigned long flags;
	struct bucket *b;
	u32 key_size, hash;
	int ret;

	if (unlikely(map_flags > BPF_EXIST))
		/* unknown flags */
		return -EINVAL;

	WARN_ON_ONCE(!rcu_read_lock_held());

	key_size = map->key_size;

	hash = htab_map_hash(key, key_size);

	b = __select_bucket(htab, hash);
	head = &b->head;

	/* bpf_map_update_elem() can be called in_irq() */
	raw_spin_lock_irqsave(&b->lock, flags);

	l_old = lookup_elem_raw(head, hash, key, key_size);

	ret = check_flags(htab, l_old, map_flags);
	if (ret)
		goto err;

	if (l_old) {
		void __percpu *pptr = htab_elem_get_ptr(l_old, key_size);
		u32 size = htab->map.value_size;

		/* per-cpu hash map can update value in-place */
		if (!onallcpus) {
			memcpy(this_cpu_ptr(pptr), value, size);
		} else {
			int off = 0, cpu;

			size = round_up(size, 8);
			for_each_possible_cpu(cpu) {
				bpf_long_memcpy(per_cpu_ptr(pptr, cpu),
						value + off, size);
				off += size;
			}
		}
	} else {
		l_new = alloc_htab_elem(htab, key, value, key_size,
					hash, true, onallcpus);
		if (IS_ERR(l_new)) {
			ret = PTR_ERR(l_new);
			goto err;
		}
		hlist_add_head_rcu(&l_new->hash_node, head);
	}
	ret = 0;
err:
	raw_spin_unlock_irqrestore(&b->lock, flags);
	return ret;
}

static int htab_percpu_map_update_elem(struct bpf_map *map, void *key,
				       void *value, u64 map_flags)
{
	return __htab_percpu_map_update_elem(map, key, value, map_flags, false);
}

/* Called from syscall or from eBPF program */
static int htab_map_delete_elem(struct bpf_map *map, void *key)
{
	struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
	struct hlist_head *head;
	struct bucket *b;
	struct htab_elem *l;
	unsigned long flags;
	u32 hash, key_size;
	int ret = -ENOENT;

	WARN_ON_ONCE(!rcu_read_lock_held());

	key_size = map->key_size;

	hash = htab_map_hash(key, key_size);
	b = __select_bucket(htab, hash);
	head = &b->head;

	raw_spin_lock_irqsave(&b->lock, flags);

	l = lookup_elem_raw(head, hash, key, key_size);

	if (l) {
		hlist_del_rcu(&l->hash_node);
		free_htab_elem(htab, l);
		ret = 0;
	}

	raw_spin_unlock_irqrestore(&b->lock, flags);
	return ret;
}

static void delete_all_elements(struct bpf_htab *htab)
{
	int i;

	for (i = 0; i < htab->n_buckets; i++) {
		struct hlist_head *head = select_bucket(htab, i);
		struct hlist_node *n;
		struct htab_elem *l;

		hlist_for_each_entry_safe(l, n, head, hash_node) {
			hlist_del_rcu(&l->hash_node);
			htab_elem_free(htab, l);
		}
	}
}
/* Called when map->refcnt goes to zero, either from workqueue or from syscall */
static void htab_map_free(struct bpf_map *map)
{
	struct bpf_htab *htab = container_of(map, struct bpf_htab, map);

	/* at this point bpf_prog->aux->refcnt == 0 and this map->refcnt == 0,
	 * so the programs (can be more than one that used this map) were
	 * disconnected from events. Wait for outstanding critical sections in
	 * these programs to complete
	 */
	synchronize_rcu();

	/* some of free_htab_elem() callbacks for elements of this map may
	 * not have executed. Wait for them.
	 */
	rcu_barrier();
	if (htab->map.map_flags & BPF_F_NO_PREALLOC) {
		delete_all_elements(htab);
	} else {
		htab_free_elems(htab);
		pcpu_freelist_destroy(&htab->freelist);
	}
	kvfree(htab->buckets);
	kfree(htab);
}

static const struct bpf_map_ops htab_ops = {
	.map_alloc = htab_map_alloc,
	.map_free = htab_map_free,
	.map_get_next_key = htab_map_get_next_key,
	.map_lookup_elem = htab_map_lookup_elem,
	.map_update_elem = htab_map_update_elem,
	.map_delete_elem = htab_map_delete_elem,
};

static struct bpf_map_type_list htab_type __read_mostly = {
	.ops = &htab_ops,
	.type = BPF_MAP_TYPE_HASH,
};

/* Called from eBPF program */
static void *htab_percpu_map_lookup_elem(struct bpf_map *map, void *key)
{
	struct htab_elem *l = __htab_map_lookup_elem(map, key);

	if (l)
		return this_cpu_ptr(htab_elem_get_ptr(l, map->key_size));
	else
		return NULL;
}

int bpf_percpu_hash_copy(struct bpf_map *map, void *key, void *value)
{
	struct htab_elem *l;
	void __percpu *pptr;
	int ret = -ENOENT;
	int cpu, off = 0;
	u32 size;

	/* per_cpu areas are zero-filled and bpf programs can only
	 * access 'value_size' of them, so copying rounded areas
	 * will not leak any kernel data
	 */
	size = round_up(map->value_size, 8);
	rcu_read_lock();
	l = __htab_map_lookup_elem(map, key);
	if (!l)
		goto out;
	pptr = htab_elem_get_ptr(l, map->key_size);
	for_each_possible_cpu(cpu) {
		bpf_long_memcpy(value + off,
				per_cpu_ptr(pptr, cpu), size);
		off += size;
	}
	ret = 0;
out:
	rcu_read_unlock();
	return ret;
}

int bpf_percpu_hash_update(struct bpf_map *map, void *key, void *value,
			   u64 map_flags)
{
	int ret;

	rcu_read_lock();
	ret = __htab_percpu_map_update_elem(map, key, value, map_flags, true);
	rcu_read_unlock();

	return ret;
}

static const struct bpf_map_ops htab_percpu_ops = {
	.map_alloc = htab_map_alloc,
	.map_free = htab_map_free,
	.map_get_next_key = htab_map_get_next_key,
	.map_lookup_elem = htab_percpu_map_lookup_elem,
	.map_update_elem = htab_percpu_map_update_elem,
	.map_delete_elem = htab_map_delete_elem,
};

static struct bpf_map_type_list htab_percpu_type __read_mostly = {
	.ops = &htab_percpu_ops,
	.type = BPF_MAP_TYPE_PERCPU_HASH,
};

static int __init register_htab_map(void)
{
	bpf_register_map_type(&htab_type);
	bpf_register_map_type(&htab_percpu_type);
	return 0;
}
late_initcall(register_htab_map);