aboutsummaryrefslogtreecommitdiff
path: root/mm/util.c
blob: 669397235787b90e0b7cd44cc8257dcfb0847fd9 (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
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
// SPDX-License-Identifier: GPL-2.0-only
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/compiler.h>
#include <linux/export.h>
#include <linux/err.h>
#include <linux/sched.h>
#include <linux/sched/mm.h>
#include <linux/sched/signal.h>
#include <linux/sched/task_stack.h>
#include <linux/security.h>
#include <linux/swap.h>
#include <linux/swapops.h>
#include <linux/mman.h>
#include <linux/hugetlb.h>
#include <linux/vmalloc.h>
#include <linux/userfaultfd_k.h>
#include <linux/elf.h>
#include <linux/elf-randomize.h>
#include <linux/personality.h>
#include <linux/random.h>
#include <linux/processor.h>
#include <linux/sizes.h>
#include <linux/compat.h>

#include <linux/uaccess.h>

#include "internal.h"
#include "swap.h"

/**
 * kfree_const - conditionally free memory
 * @x: pointer to the memory
 *
 * Function calls kfree only if @x is not in .rodata section.
 */
void kfree_const(const void *x)
{
	if (!is_kernel_rodata((unsigned long)x))
		kfree(x);
}
EXPORT_SYMBOL(kfree_const);

/**
 * kstrdup - allocate space for and copy an existing string
 * @s: the string to duplicate
 * @gfp: the GFP mask used in the kmalloc() call when allocating memory
 *
 * Return: newly allocated copy of @s or %NULL in case of error
 */
noinline
char *kstrdup(const char *s, gfp_t gfp)
{
	size_t len;
	char *buf;

	if (!s)
		return NULL;

	len = strlen(s) + 1;
	buf = kmalloc_track_caller(len, gfp);
	if (buf)
		memcpy(buf, s, len);
	return buf;
}
EXPORT_SYMBOL(kstrdup);

/**
 * kstrdup_const - conditionally duplicate an existing const string
 * @s: the string to duplicate
 * @gfp: the GFP mask used in the kmalloc() call when allocating memory
 *
 * Note: Strings allocated by kstrdup_const should be freed by kfree_const and
 * must not be passed to krealloc().
 *
 * Return: source string if it is in .rodata section otherwise
 * fallback to kstrdup.
 */
const char *kstrdup_const(const char *s, gfp_t gfp)
{
	if (is_kernel_rodata((unsigned long)s))
		return s;

	return kstrdup(s, gfp);
}
EXPORT_SYMBOL(kstrdup_const);

/**
 * kstrndup - allocate space for and copy an existing string
 * @s: the string to duplicate
 * @max: read at most @max chars from @s
 * @gfp: the GFP mask used in the kmalloc() call when allocating memory
 *
 * Note: Use kmemdup_nul() instead if the size is known exactly.
 *
 * Return: newly allocated copy of @s or %NULL in case of error
 */
char *kstrndup(const char *s, size_t max, gfp_t gfp)
{
	size_t len;
	char *buf;

	if (!s)
		return NULL;

	len = strnlen(s, max);
	buf = kmalloc_track_caller(len+1, gfp);
	if (buf) {
		memcpy(buf, s, len);
		buf[len] = '\0';
	}
	return buf;
}
EXPORT_SYMBOL(kstrndup);

/**
 * kmemdup - duplicate region of memory
 *
 * @src: memory region to duplicate
 * @len: memory region length
 * @gfp: GFP mask to use
 *
 * Return: newly allocated copy of @src or %NULL in case of error,
 * result is physically contiguous. Use kfree() to free.
 */
void *kmemdup(const void *src, size_t len, gfp_t gfp)
{
	void *p;

	p = kmalloc_track_caller(len, gfp);
	if (p)
		memcpy(p, src, len);
	return p;
}
EXPORT_SYMBOL(kmemdup);

/**
 * kmemdup_array - duplicate a given array.
 *
 * @src: array to duplicate.
 * @element_size: size of each element of array.
 * @count: number of elements to duplicate from array.
 * @gfp: GFP mask to use.
 *
 * Return: duplicated array of @src or %NULL in case of error,
 * result is physically contiguous. Use kfree() to free.
 */
void *kmemdup_array(const void *src, size_t element_size, size_t count, gfp_t gfp)
{
	return kmemdup(src, size_mul(element_size, count), gfp);
}
EXPORT_SYMBOL(kmemdup_array);

/**
 * kvmemdup - duplicate region of memory
 *
 * @src: memory region to duplicate
 * @len: memory region length
 * @gfp: GFP mask to use
 *
 * Return: newly allocated copy of @src or %NULL in case of error,
 * result may be not physically contiguous. Use kvfree() to free.
 */
void *kvmemdup(const void *src, size_t len, gfp_t gfp)
{
	void *p;

	p = kvmalloc(len, gfp);
	if (p)
		memcpy(p, src, len);
	return p;
}
EXPORT_SYMBOL(kvmemdup);

/**
 * kmemdup_nul - Create a NUL-terminated string from unterminated data
 * @s: The data to stringify
 * @len: The size of the data
 * @gfp: the GFP mask used in the kmalloc() call when allocating memory
 *
 * Return: newly allocated copy of @s with NUL-termination or %NULL in
 * case of error
 */
char *kmemdup_nul(const char *s, size_t len, gfp_t gfp)
{
	char *buf;

	if (!s)
		return NULL;

	buf = kmalloc_track_caller(len + 1, gfp);
	if (buf) {
		memcpy(buf, s, len);
		buf[len] = '\0';
	}
	return buf;
}
EXPORT_SYMBOL(kmemdup_nul);

/**
 * memdup_user - duplicate memory region from user space
 *
 * @src: source address in user space
 * @len: number of bytes to copy
 *
 * Return: an ERR_PTR() on failure.  Result is physically
 * contiguous, to be freed by kfree().
 */
void *memdup_user(const void __user *src, size_t len)
{
	void *p;

	p = kmalloc_track_caller(len, GFP_USER | __GFP_NOWARN);
	if (!p)
		return ERR_PTR(-ENOMEM);

	if (copy_from_user(p, src, len)) {
		kfree(p);
		return ERR_PTR(-EFAULT);
	}

	return p;
}
EXPORT_SYMBOL(memdup_user);

/**
 * vmemdup_user - duplicate memory region from user space
 *
 * @src: source address in user space
 * @len: number of bytes to copy
 *
 * Return: an ERR_PTR() on failure.  Result may be not
 * physically contiguous.  Use kvfree() to free.
 */
void *vmemdup_user(const void __user *src, size_t len)
{
	void *p;

	p = kvmalloc(len, GFP_USER);
	if (!p)
		return ERR_PTR(-ENOMEM);

	if (copy_from_user(p, src, len)) {
		kvfree(p);
		return ERR_PTR(-EFAULT);
	}

	return p;
}
EXPORT_SYMBOL(vmemdup_user);

/**
 * strndup_user - duplicate an existing string from user space
 * @s: The string to duplicate
 * @n: Maximum number of bytes to copy, including the trailing NUL.
 *
 * Return: newly allocated copy of @s or an ERR_PTR() in case of error
 */
char *strndup_user(const char __user *s, long n)
{
	char *p;
	long length;

	length = strnlen_user(s, n);

	if (!length)
		return ERR_PTR(-EFAULT);

	if (length > n)
		return ERR_PTR(-EINVAL);

	p = memdup_user(s, length);

	if (IS_ERR(p))
		return p;

	p[length - 1] = '\0';

	return p;
}
EXPORT_SYMBOL(strndup_user);

/**
 * memdup_user_nul - duplicate memory region from user space and NUL-terminate
 *
 * @src: source address in user space
 * @len: number of bytes to copy
 *
 * Return: an ERR_PTR() on failure.
 */
void *memdup_user_nul(const void __user *src, size_t len)
{
	char *p;

	/*
	 * Always use GFP_KERNEL, since copy_from_user() can sleep and
	 * cause pagefault, which makes it pointless to use GFP_NOFS
	 * or GFP_ATOMIC.
	 */
	p = kmalloc_track_caller(len + 1, GFP_KERNEL);
	if (!p)
		return ERR_PTR(-ENOMEM);

	if (copy_from_user(p, src, len)) {
		kfree(p);
		return ERR_PTR(-EFAULT);
	}
	p[len] = '\0';

	return p;
}
EXPORT_SYMBOL(memdup_user_nul);

/* Check if the vma is being used as a stack by this task */
int vma_is_stack_for_current(struct vm_area_struct *vma)
{
	struct task_struct * __maybe_unused t = current;

	return (vma->vm_start <= KSTK_ESP(t) && vma->vm_end >= KSTK_ESP(t));
}

/*
 * Change backing file, only valid to use during initial VMA setup.
 */
void vma_set_file(struct vm_area_struct *vma, struct file *file)
{
	/* Changing an anonymous vma with this is illegal */
	get_file(file);
	swap(vma->vm_file, file);
	fput(file);
}
EXPORT_SYMBOL(vma_set_file);

#ifndef STACK_RND_MASK
#define STACK_RND_MASK (0x7ff >> (PAGE_SHIFT - 12))     /* 8MB of VA */
#endif

unsigned long randomize_stack_top(unsigned long stack_top)
{
	unsigned long random_variable = 0;

	if (current->flags & PF_RANDOMIZE) {
		random_variable = get_random_long();
		random_variable &= STACK_RND_MASK;
		random_variable <<= PAGE_SHIFT;
	}
#ifdef CONFIG_STACK_GROWSUP
	return PAGE_ALIGN(stack_top) + random_variable;
#else
	return PAGE_ALIGN(stack_top) - random_variable;
#endif
}

/**
 * randomize_page - Generate a random, page aligned address
 * @start:	The smallest acceptable address the caller will take.
 * @range:	The size of the area, starting at @start, within which the
 *		random address must fall.
 *
 * If @start + @range would overflow, @range is capped.
 *
 * NOTE: Historical use of randomize_range, which this replaces, presumed that
 * @start was already page aligned.  We now align it regardless.
 *
 * Return: A page aligned address within [start, start + range).  On error,
 * @start is returned.
 */
unsigned long randomize_page(unsigned long start, unsigned long range)
{
	if (!PAGE_ALIGNED(start)) {
		range -= PAGE_ALIGN(start) - start;
		start = PAGE_ALIGN(start);
	}

	if (start > ULONG_MAX - range)
		range = ULONG_MAX - start;

	range >>= PAGE_SHIFT;

	if (range == 0)
		return start;

	return start + (get_random_long() % range << PAGE_SHIFT);
}

#ifdef CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
unsigned long __weak arch_randomize_brk(struct mm_struct *mm)
{
	/* Is the current task 32bit ? */
	if (!IS_ENABLED(CONFIG_64BIT) || is_compat_task())
		return randomize_page(mm->brk, SZ_32M);

	return randomize_page(mm->brk, SZ_1G);
}

unsigned long arch_mmap_rnd(void)
{
	unsigned long rnd;

#ifdef CONFIG_HAVE_ARCH_MMAP_RND_COMPAT_BITS
	if (is_compat_task())
		rnd = get_random_long() & ((1UL << mmap_rnd_compat_bits) - 1);
	else
#endif /* CONFIG_HAVE_ARCH_MMAP_RND_COMPAT_BITS */
		rnd = get_random_long() & ((1UL << mmap_rnd_bits) - 1);

	return rnd << PAGE_SHIFT;
}

static int mmap_is_legacy(struct rlimit *rlim_stack)
{
	if (current->personality & ADDR_COMPAT_LAYOUT)
		return 1;

	/* On parisc the stack always grows up - so a unlimited stack should
	 * not be an indicator to use the legacy memory layout. */
	if (rlim_stack->rlim_cur == RLIM_INFINITY &&
		!IS_ENABLED(CONFIG_STACK_GROWSUP))
		return 1;

	return sysctl_legacy_va_layout;
}

/*
 * Leave enough space between the mmap area and the stack to honour ulimit in
 * the face of randomisation.
 */
#define MIN_GAP		(SZ_128M)
#define MAX_GAP		(STACK_TOP / 6 * 5)

static unsigned long mmap_base(unsigned long rnd, struct rlimit *rlim_stack)
{
#ifdef CONFIG_STACK_GROWSUP
	/*
	 * For an upwards growing stack the calculation is much simpler.
	 * Memory for the maximum stack size is reserved at the top of the
	 * task. mmap_base starts directly below the stack and grows
	 * downwards.
	 */
	return PAGE_ALIGN_DOWN(mmap_upper_limit(rlim_stack) - rnd);
#else
	unsigned long gap = rlim_stack->rlim_cur;
	unsigned long pad = stack_guard_gap;

	/* Account for stack randomization if necessary */
	if (current->flags & PF_RANDOMIZE)
		pad += (STACK_RND_MASK << PAGE_SHIFT);

	/* Values close to RLIM_INFINITY can overflow. */
	if (gap + pad > gap)
		gap += pad;

	if (gap < MIN_GAP)
		gap = MIN_GAP;
	else if (gap > MAX_GAP)
		gap = MAX_GAP;

	return PAGE_ALIGN(STACK_TOP - gap - rnd);
#endif
}

void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
{
	unsigned long random_factor = 0UL;

	if (current->flags & PF_RANDOMIZE)
		random_factor = arch_mmap_rnd();

	if (mmap_is_legacy(rlim_stack)) {
		mm->mmap_base = TASK_UNMAPPED_BASE + random_factor;
		mm->get_unmapped_area = arch_get_unmapped_area;
	} else {
		mm->mmap_base = mmap_base(random_factor, rlim_stack);
		mm->get_unmapped_area = arch_get_unmapped_area_topdown;
	}
}
#elif defined(CONFIG_MMU) && !defined(HAVE_ARCH_PICK_MMAP_LAYOUT)
void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
{
	mm->mmap_base = TASK_UNMAPPED_BASE;
	mm->get_unmapped_area = arch_get_unmapped_area;
}
#endif

/**
 * __account_locked_vm - account locked pages to an mm's locked_vm
 * @mm:          mm to account against
 * @pages:       number of pages to account
 * @inc:         %true if @pages should be considered positive, %false if not
 * @task:        task used to check RLIMIT_MEMLOCK
 * @bypass_rlim: %true if checking RLIMIT_MEMLOCK should be skipped
 *
 * Assumes @task and @mm are valid (i.e. at least one reference on each), and
 * that mmap_lock is held as writer.
 *
 * Return:
 * * 0       on success
 * * -ENOMEM if RLIMIT_MEMLOCK would be exceeded.
 */
int __account_locked_vm(struct mm_struct *mm, unsigned long pages, bool inc,
			struct task_struct *task, bool bypass_rlim)
{
	unsigned long locked_vm, limit;
	int ret = 0;

	mmap_assert_write_locked(mm);

	locked_vm = mm->locked_vm;
	if (inc) {
		if (!bypass_rlim) {
			limit = task_rlimit(task, RLIMIT_MEMLOCK) >> PAGE_SHIFT;
			if (locked_vm + pages > limit)
				ret = -ENOMEM;
		}
		if (!ret)
			mm->locked_vm = locked_vm + pages;
	} else {
		WARN_ON_ONCE(pages > locked_vm);
		mm->locked_vm = locked_vm - pages;
	}

	pr_debug("%s: [%d] caller %ps %c%lu %lu/%lu%s\n", __func__, task->pid,
		 (void *)_RET_IP_, (inc) ? '+' : '-', pages << PAGE_SHIFT,
		 locked_vm << PAGE_SHIFT, task_rlimit(task, RLIMIT_MEMLOCK),
		 ret ? " - exceeded" : "");

	return ret;
}
EXPORT_SYMBOL_GPL(__account_locked_vm);

/**
 * account_locked_vm - account locked pages to an mm's locked_vm
 * @mm:          mm to account against, may be NULL
 * @pages:       number of pages to account
 * @inc:         %true if @pages should be considered positive, %false if not
 *
 * Assumes a non-NULL @mm is valid (i.e. at least one reference on it).
 *
 * Return:
 * * 0       on success, or if mm is NULL
 * * -ENOMEM if RLIMIT_MEMLOCK would be exceeded.
 */
int account_locked_vm(struct mm_struct *mm, unsigned long pages, bool inc)
{
	int ret;

	if (pages == 0 || !mm)
		return 0;

	mmap_write_lock(mm);
	ret = __account_locked_vm(mm, pages, inc, current,
				  capable(CAP_IPC_LOCK));
	mmap_write_unlock(mm);

	return ret;
}
EXPORT_SYMBOL_GPL(account_locked_vm);

unsigned long vm_mmap_pgoff(struct file *file, unsigned long addr,
	unsigned long len, unsigned long prot,
	unsigned long flag, unsigned long pgoff)
{
	unsigned long ret;
	struct mm_struct *mm = current->mm;
	unsigned long populate;
	LIST_HEAD(uf);

	ret = security_mmap_file(file, prot, flag);
	if (!ret) {
		if (mmap_write_lock_killable(mm))
			return -EINTR;
		ret = do_mmap(file, addr, len, prot, flag, 0, pgoff, &populate,
			      &uf);
		mmap_write_unlock(mm);
		userfaultfd_unmap_complete(mm, &uf);
		if (populate)
			mm_populate(ret, populate);
	}
	return ret;
}

unsigned long vm_mmap(struct file *file, unsigned long addr,
	unsigned long len, unsigned long prot,
	unsigned long flag, unsigned long offset)
{
	if (unlikely(offset + PAGE_ALIGN(len) < offset))
		return -EINVAL;
	if (unlikely(offset_in_page(offset)))
		return -EINVAL;

	return vm_mmap_pgoff(file, addr, len, prot, flag, offset >> PAGE_SHIFT);
}
EXPORT_SYMBOL(vm_mmap);

/**
 * kvmalloc_node - attempt to allocate physically contiguous memory, but upon
 * failure, fall back to non-contiguous (vmalloc) allocation.
 * @size: size of the request.
 * @flags: gfp mask for the allocation - must be compatible (superset) with GFP_KERNEL.
 * @node: numa node to allocate from
 *
 * Uses kmalloc to get the memory but if the allocation fails then falls back
 * to the vmalloc allocator. Use kvfree for freeing the memory.
 *
 * GFP_NOWAIT and GFP_ATOMIC are not supported, neither is the __GFP_NORETRY modifier.
 * __GFP_RETRY_MAYFAIL is supported, and it should be used only if kmalloc is
 * preferable to the vmalloc fallback, due to visible performance drawbacks.
 *
 * Return: pointer to the allocated memory of %NULL in case of failure
 */
void *kvmalloc_node(size_t size, gfp_t flags, int node)
{
	gfp_t kmalloc_flags = flags;
	void *ret;

	/*
	 * We want to attempt a large physically contiguous block first because
	 * it is less likely to fragment multiple larger blocks and therefore
	 * contribute to a long term fragmentation less than vmalloc fallback.
	 * However make sure that larger requests are not too disruptive - no
	 * OOM killer and no allocation failure warnings as we have a fallback.
	 */
	if (size > PAGE_SIZE) {
		kmalloc_flags |= __GFP_NOWARN;

		if (!(kmalloc_flags & __GFP_RETRY_MAYFAIL))
			kmalloc_flags |= __GFP_NORETRY;

		/* nofail semantic is implemented by the vmalloc fallback */
		kmalloc_flags &= ~__GFP_NOFAIL;
	}

	ret = kmalloc_node(size, kmalloc_flags, node);

	/*
	 * It doesn't really make sense to fallback to vmalloc for sub page
	 * requests
	 */
	if (ret || size <= PAGE_SIZE)
		return ret;

	/* non-sleeping allocations are not supported by vmalloc */
	if (!gfpflags_allow_blocking(flags))
		return NULL;

	/* Don't even allow crazy sizes */
	if (unlikely(size > INT_MAX)) {
		WARN_ON_ONCE(!(flags & __GFP_NOWARN));
		return NULL;
	}

	/*
	 * kvmalloc() can always use VM_ALLOW_HUGE_VMAP,
	 * since the callers already cannot assume anything
	 * about the resulting pointer, and cannot play
	 * protection games.
	 */
	return __vmalloc_node_range(size, 1, VMALLOC_START, VMALLOC_END,
			flags, PAGE_KERNEL, VM_ALLOW_HUGE_VMAP,
			node, __builtin_return_address(0));
}
EXPORT_SYMBOL(kvmalloc_node);

/**
 * kvfree() - Free memory.
 * @addr: Pointer to allocated memory.
 *
 * kvfree frees memory allocated by any of vmalloc(), kmalloc() or kvmalloc().
 * It is slightly more efficient to use kfree() or vfree() if you are certain
 * that you know which one to use.
 *
 * Context: Either preemptible task context or not-NMI interrupt.
 */
void kvfree(const void *addr)
{
	if (is_vmalloc_addr(addr))
		vfree(addr);
	else
		kfree(addr);
}
EXPORT_SYMBOL(kvfree);

/**
 * kvfree_sensitive - Free a data object containing sensitive information.
 * @addr: address of the data object to be freed.
 * @len: length of the data object.
 *
 * Use the special memzero_explicit() function to clear the content of a
 * kvmalloc'ed object containing sensitive data to make sure that the
 * compiler won't optimize out the data clearing.
 */
void kvfree_sensitive(const void *addr, size_t len)
{
	if (likely(!ZERO_OR_NULL_PTR(addr))) {
		memzero_explicit((void *)addr, len);
		kvfree(addr);
	}
}
EXPORT_SYMBOL(kvfree_sensitive);

void *kvrealloc(const void *p, size_t oldsize, size_t newsize, gfp_t flags)
{
	void *newp;

	if (oldsize >= newsize)
		return (void *)p;
	newp = kvmalloc(newsize, flags);
	if (!newp)
		return NULL;
	memcpy(newp, p, oldsize);
	kvfree(p);
	return newp;
}
EXPORT_SYMBOL(kvrealloc);

/**
 * __vmalloc_array - allocate memory for a virtually contiguous array.
 * @n: number of elements.
 * @size: element size.
 * @flags: the type of memory to allocate (see kmalloc).
 */
void *__vmalloc_array(size_t n, size_t size, gfp_t flags)
{
	size_t bytes;

	if (unlikely(check_mul_overflow(n, size, &bytes)))
		return NULL;
	return __vmalloc(bytes, flags);
}
EXPORT_SYMBOL(__vmalloc_array);

/**
 * vmalloc_array - allocate memory for a virtually contiguous array.
 * @n: number of elements.
 * @size: element size.
 */
void *vmalloc_array(size_t n, size_t size)
{
	return __vmalloc_array(n, size, GFP_KERNEL);
}
EXPORT_SYMBOL(vmalloc_array);

/**
 * __vcalloc - allocate and zero memory for a virtually contiguous array.
 * @n: number of elements.
 * @size: element size.
 * @flags: the type of memory to allocate (see kmalloc).
 */
void *__vcalloc(size_t n, size_t size, gfp_t flags)
{
	return __vmalloc_array(n, size, flags | __GFP_ZERO);
}
EXPORT_SYMBOL(__vcalloc);

/**
 * vcalloc - allocate and zero memory for a virtually contiguous array.
 * @n: number of elements.
 * @size: element size.
 */
void *vcalloc(size_t n, size_t size)
{
	return __vmalloc_array(n, size, GFP_KERNEL | __GFP_ZERO);
}
EXPORT_SYMBOL(vcalloc);

struct anon_vma *folio_anon_vma(struct folio *folio)
{
	unsigned long mapping = (unsigned long)folio->mapping;

	if ((mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
		return NULL;
	return (void *)(mapping - PAGE_MAPPING_ANON);
}

/**
 * folio_mapping - Find the mapping where this folio is stored.
 * @folio: The folio.
 *
 * For folios which are in the page cache, return the mapping that this
 * page belongs to.  Folios in the swap cache return the swap mapping
 * this page is stored in (which is different from the mapping for the
 * swap file or swap device where the data is stored).
 *
 * You can call this for folios which aren't in the swap cache or page
 * cache and it will return NULL.
 */
struct address_space *folio_mapping(struct folio *folio)
{
	struct address_space *mapping;

	/* This happens if someone calls flush_dcache_page on slab page */
	if (unlikely(folio_test_slab(folio)))
		return NULL;

	if (unlikely(folio_test_swapcache(folio)))
		return swap_address_space(folio->swap);

	mapping = folio->mapping;
	if ((unsigned long)mapping & PAGE_MAPPING_FLAGS)
		return NULL;

	return mapping;
}
EXPORT_SYMBOL(folio_mapping);

/**
 * folio_copy - Copy the contents of one folio to another.
 * @dst: Folio to copy to.
 * @src: Folio to copy from.
 *
 * The bytes in the folio represented by @src are copied to @dst.
 * Assumes the caller has validated that @dst is at least as large as @src.
 * Can be called in atomic context for order-0 folios, but if the folio is
 * larger, it may sleep.
 */
void folio_copy(struct folio *dst, struct folio *src)
{
	long i = 0;
	long nr = folio_nr_pages(src);

	for (;;) {
		copy_highpage(folio_page(dst, i), folio_page(src, i));
		if (++i == nr)
			break;
		cond_resched();
	}
}
EXPORT_SYMBOL(folio_copy);

int sysctl_overcommit_memory __read_mostly = OVERCOMMIT_GUESS;
int sysctl_overcommit_ratio __read_mostly = 50;
unsigned long sysctl_overcommit_kbytes __read_mostly;
int sysctl_max_map_count __read_mostly = DEFAULT_MAX_MAP_COUNT;
unsigned long sysctl_user_reserve_kbytes __read_mostly = 1UL << 17; /* 128MB */
unsigned long sysctl_admin_reserve_kbytes __read_mostly = 1UL << 13; /* 8MB */

int overcommit_ratio_handler(struct ctl_table *table, int write, void *buffer,
		size_t *lenp, loff_t *ppos)
{
	int ret;

	ret = proc_dointvec(table, write, buffer, lenp, ppos);
	if (ret == 0 && write)
		sysctl_overcommit_kbytes = 0;
	return ret;
}

static void sync_overcommit_as(struct work_struct *dummy)
{
	percpu_counter_sync(&vm_committed_as);
}

int overcommit_policy_handler(struct ctl_table *table, int write, void *buffer,
		size_t *lenp, loff_t *ppos)
{
	struct ctl_table t;
	int new_policy = -1;
	int ret;

	/*
	 * The deviation of sync_overcommit_as could be big with loose policy
	 * like OVERCOMMIT_ALWAYS/OVERCOMMIT_GUESS. When changing policy to
	 * strict OVERCOMMIT_NEVER, we need to reduce the deviation to comply
	 * with the strict "NEVER", and to avoid possible race condition (even
	 * though user usually won't too frequently do the switching to policy
	 * OVERCOMMIT_NEVER), the switch is done in the following order:
	 *	1. changing the batch
	 *	2. sync percpu count on each CPU
	 *	3. switch the policy
	 */
	if (write) {
		t = *table;
		t.data = &new_policy;
		ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
		if (ret || new_policy == -1)
			return ret;

		mm_compute_batch(new_policy);
		if (new_policy == OVERCOMMIT_NEVER)
			schedule_on_each_cpu(sync_overcommit_as);
		sysctl_overcommit_memory = new_policy;
	} else {
		ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
	}

	return ret;
}

int overcommit_kbytes_handler(struct ctl_table *table, int write, void *buffer,
		size_t *lenp, loff_t *ppos)
{
	int ret;

	ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
	if (ret == 0 && write)
		sysctl_overcommit_ratio = 0;
	return ret;
}

/*
 * Committed memory limit enforced when OVERCOMMIT_NEVER policy is used
 */
unsigned long vm_commit_limit(void)
{
	unsigned long allowed;

	if (sysctl_overcommit_kbytes)
		allowed = sysctl_overcommit_kbytes >> (PAGE_SHIFT - 10);
	else
		allowed = ((totalram_pages() - hugetlb_total_pages())
			   * sysctl_overcommit_ratio / 100);
	allowed += total_swap_pages;

	return allowed;
}

/*
 * Make sure vm_committed_as in one cacheline and not cacheline shared with
 * other variables. It can be updated by several CPUs frequently.
 */
struct percpu_counter vm_committed_as ____cacheline_aligned_in_smp;

/*
 * The global memory commitment made in the system can be a metric
 * that can be used to drive ballooning decisions when Linux is hosted
 * as a guest. On Hyper-V, the host implements a policy engine for dynamically
 * balancing memory across competing virtual machines that are hosted.
 * Several metrics drive this policy engine including the guest reported
 * memory commitment.
 *
 * The time cost of this is very low for small platforms, and for big
 * platform like a 2S/36C/72T Skylake server, in worst case where
 * vm_committed_as's spinlock is under severe contention, the time cost
 * could be about 30~40 microseconds.
 */
unsigned long vm_memory_committed(void)
{
	return percpu_counter_sum_positive(&vm_committed_as);
}
EXPORT_SYMBOL_GPL(vm_memory_committed);

/*
 * Check that a process has enough memory to allocate a new virtual
 * mapping. 0 means there is enough memory for the allocation to
 * succeed and -ENOMEM implies there is not.
 *
 * We currently support three overcommit policies, which are set via the
 * vm.overcommit_memory sysctl.  See Documentation/mm/overcommit-accounting.rst
 *
 * Strict overcommit modes added 2002 Feb 26 by Alan Cox.
 * Additional code 2002 Jul 20 by Robert Love.
 *
 * cap_sys_admin is 1 if the process has admin privileges, 0 otherwise.
 *
 * Note this is a helper function intended to be used by LSMs which
 * wish to use this logic.
 */
int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
{
	long allowed;
	unsigned long bytes_failed;

	vm_acct_memory(pages);

	/*
	 * Sometimes we want to use more memory than we have
	 */
	if (sysctl_overcommit_memory == OVERCOMMIT_ALWAYS)
		return 0;

	if (sysctl_overcommit_memory == OVERCOMMIT_GUESS) {
		if (pages > totalram_pages() + total_swap_pages)
			goto error;
		return 0;
	}

	allowed = vm_commit_limit();
	/*
	 * Reserve some for root
	 */
	if (!cap_sys_admin)
		allowed -= sysctl_admin_reserve_kbytes >> (PAGE_SHIFT - 10);

	/*
	 * Don't let a single process grow so big a user can't recover
	 */
	if (mm) {
		long reserve = sysctl_user_reserve_kbytes >> (PAGE_SHIFT - 10);

		allowed -= min_t(long, mm->total_vm / 32, reserve);
	}

	if (percpu_counter_read_positive(&vm_committed_as) < allowed)
		return 0;
error:
	bytes_failed = pages << PAGE_SHIFT;
	pr_warn_ratelimited("%s: pid: %d, comm: %s, bytes: %lu not enough memory for the allocation\n",
			    __func__, current->pid, current->comm, bytes_failed);
	vm_unacct_memory(pages);

	return -ENOMEM;
}

/**
 * get_cmdline() - copy the cmdline value to a buffer.
 * @task:     the task whose cmdline value to copy.
 * @buffer:   the buffer to copy to.
 * @buflen:   the length of the buffer. Larger cmdline values are truncated
 *            to this length.
 *
 * Return: the size of the cmdline field copied. Note that the copy does
 * not guarantee an ending NULL byte.
 */
int get_cmdline(struct task_struct *task, char *buffer, int buflen)
{
	int res = 0;
	unsigned int len;
	struct mm_struct *mm = get_task_mm(task);
	unsigned long arg_start, arg_end, env_start, env_end;
	if (!mm)
		goto out;
	if (!mm->arg_end)
		goto out_mm;	/* Shh! No looking before we're done */

	spin_lock(&mm->arg_lock);
	arg_start = mm->arg_start;
	arg_end = mm->arg_end;
	env_start = mm->env_start;
	env_end = mm->env_end;
	spin_unlock(&mm->arg_lock);

	len = arg_end - arg_start;

	if (len > buflen)
		len = buflen;

	res = access_process_vm(task, arg_start, buffer, len, FOLL_FORCE);

	/*
	 * If the nul at the end of args has been overwritten, then
	 * assume application is using setproctitle(3).
	 */
	if (res > 0 && buffer[res-1] != '\0' && len < buflen) {
		len = strnlen(buffer, res);
		if (len < res) {
			res = len;
		} else {
			len = env_end - env_start;
			if (len > buflen - res)
				len = buflen - res;
			res += access_process_vm(task, env_start,
						 buffer+res, len,
						 FOLL_FORCE);
			res = strnlen(buffer, res);
		}
	}
out_mm:
	mmput(mm);
out:
	return res;
}

int __weak memcmp_pages(struct page *page1, struct page *page2)
{
	char *addr1, *addr2;
	int ret;

	addr1 = kmap_local_page(page1);
	addr2 = kmap_local_page(page2);
	ret = memcmp(addr1, addr2, PAGE_SIZE);
	kunmap_local(addr2);
	kunmap_local(addr1);
	return ret;
}

#ifdef CONFIG_PRINTK
/**
 * mem_dump_obj - Print available provenance information
 * @object: object for which to find provenance information.
 *
 * This function uses pr_cont(), so that the caller is expected to have
 * printed out whatever preamble is appropriate.  The provenance information
 * depends on the type of object and on how much debugging is enabled.
 * For example, for a slab-cache object, the slab name is printed, and,
 * if available, the return address and stack trace from the allocation
 * and last free path of that object.
 */
void mem_dump_obj(void *object)
{
	const char *type;

	if (kmem_dump_obj(object))
		return;

	if (vmalloc_dump_obj(object))
		return;

	if (is_vmalloc_addr(object))
		type = "vmalloc memory";
	else if (virt_addr_valid(object))
		type = "non-slab/vmalloc memory";
	else if (object == NULL)
		type = "NULL pointer";
	else if (object == ZERO_SIZE_PTR)
		type = "zero-size pointer";
	else
		type = "non-paged memory";

	pr_cont(" %s\n", type);
}
EXPORT_SYMBOL_GPL(mem_dump_obj);
#endif

/*
 * A driver might set a page logically offline -- PageOffline() -- and
 * turn the page inaccessible in the hypervisor; after that, access to page
 * content can be fatal.
 *
 * Some special PFN walkers -- i.e., /proc/kcore -- read content of random
 * pages after checking PageOffline(); however, these PFN walkers can race
 * with drivers that set PageOffline().
 *
 * page_offline_freeze()/page_offline_thaw() allows for a subsystem to
 * synchronize with such drivers, achieving that a page cannot be set
 * PageOffline() while frozen.
 *
 * page_offline_begin()/page_offline_end() is used by drivers that care about
 * such races when setting a page PageOffline().
 */
static DECLARE_RWSEM(page_offline_rwsem);

void page_offline_freeze(void)
{
	down_read(&page_offline_rwsem);
}

void page_offline_thaw(void)
{
	up_read(&page_offline_rwsem);
}

void page_offline_begin(void)
{
	down_write(&page_offline_rwsem);
}
EXPORT_SYMBOL(page_offline_begin);

void page_offline_end(void)
{
	up_write(&page_offline_rwsem);
}
EXPORT_SYMBOL(page_offline_end);

#ifndef flush_dcache_folio
void flush_dcache_folio(struct folio *folio)
{
	long i, nr = folio_nr_pages(folio);

	for (i = 0; i < nr; i++)
		flush_dcache_page(folio_page(folio, i));
}
EXPORT_SYMBOL(flush_dcache_folio);
#endif