Linux preempt-rt

Check our new training course

Real-Time Linux with PREEMPT_RT

Check our new training course
with Creative Commons CC-BY-SA
lecture and lab materials

Bootlin logo

Elixir Cross Referencer

  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
// SPDX-License-Identifier: GPL-2.0-only
/*
 * Helpers for formatting and printing strings
 *
 * Copyright 31 August 2008 James Bottomley
 * Copyright (C) 2013, Intel Corporation
 */
#include <linux/bug.h>
#include <linux/kernel.h>
#include <linux/math64.h>
#include <linux/export.h>
#include <linux/ctype.h>
#include <linux/device.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/limits.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/string_helpers.h>

/**
 * string_get_size - get the size in the specified units
 * @size:	The size to be converted in blocks
 * @blk_size:	Size of the block (use 1 for size in bytes)
 * @units:	units to use (powers of 1000 or 1024)
 * @buf:	buffer to format to
 * @len:	length of buffer
 *
 * This function returns a string formatted to 3 significant figures
 * giving the size in the required units.  @buf should have room for
 * at least 9 bytes and will always be zero terminated.
 *
 */
void string_get_size(u64 size, u64 blk_size, const enum string_size_units units,
		     char *buf, int len)
{
	static const char *const units_10[] = {
		"B", "kB", "MB", "GB", "TB", "PB", "EB", "ZB", "YB"
	};
	static const char *const units_2[] = {
		"B", "KiB", "MiB", "GiB", "TiB", "PiB", "EiB", "ZiB", "YiB"
	};
	static const char *const *const units_str[] = {
		[STRING_UNITS_10] = units_10,
		[STRING_UNITS_2] = units_2,
	};
	static const unsigned int divisor[] = {
		[STRING_UNITS_10] = 1000,
		[STRING_UNITS_2] = 1024,
	};
	static const unsigned int rounding[] = { 500, 50, 5 };
	int i = 0, j;
	u32 remainder = 0, sf_cap;
	char tmp[8];
	const char *unit;

	tmp[0] = '\0';

	if (blk_size == 0)
		size = 0;
	if (size == 0)
		goto out;

	/* This is Napier's algorithm.  Reduce the original block size to
	 *
	 * coefficient * divisor[units]^i
	 *
	 * we do the reduction so both coefficients are just under 32 bits so
	 * that multiplying them together won't overflow 64 bits and we keep
	 * as much precision as possible in the numbers.
	 *
	 * Note: it's safe to throw away the remainders here because all the
	 * precision is in the coefficients.
	 */
	while (blk_size >> 32) {
		do_div(blk_size, divisor[units]);
		i++;
	}

	while (size >> 32) {
		do_div(size, divisor[units]);
		i++;
	}

	/* now perform the actual multiplication keeping i as the sum of the
	 * two logarithms */
	size *= blk_size;

	/* and logarithmically reduce it until it's just under the divisor */
	while (size >= divisor[units]) {
		remainder = do_div(size, divisor[units]);
		i++;
	}

	/* work out in j how many digits of precision we need from the
	 * remainder */
	sf_cap = size;
	for (j = 0; sf_cap*10 < 1000; j++)
		sf_cap *= 10;

	if (units == STRING_UNITS_2) {
		/* express the remainder as a decimal.  It's currently the
		 * numerator of a fraction whose denominator is
		 * divisor[units], which is 1 << 10 for STRING_UNITS_2 */
		remainder *= 1000;
		remainder >>= 10;
	}

	/* add a 5 to the digit below what will be printed to ensure
	 * an arithmetical round up and carry it through to size */
	remainder += rounding[j];
	if (remainder >= 1000) {
		remainder -= 1000;
		size += 1;
	}

	if (j) {
		snprintf(tmp, sizeof(tmp), ".%03u", remainder);
		tmp[j+1] = '\0';
	}

 out:
	if (i >= ARRAY_SIZE(units_2))
		unit = "UNK";
	else
		unit = units_str[units][i];

	snprintf(buf, len, "%u%s %s", (u32)size,
		 tmp, unit);
}
EXPORT_SYMBOL(string_get_size);

static bool unescape_space(char **src, char **dst)
{
	char *p = *dst, *q = *src;

	switch (*q) {
	case 'n':
		*p = '\n';
		break;
	case 'r':
		*p = '\r';
		break;
	case 't':
		*p = '\t';
		break;
	case 'v':
		*p = '\v';
		break;
	case 'f':
		*p = '\f';
		break;
	default:
		return false;
	}
	*dst += 1;
	*src += 1;
	return true;
}

static bool unescape_octal(char **src, char **dst)
{
	char *p = *dst, *q = *src;
	u8 num;

	if (isodigit(*q) == 0)
		return false;

	num = (*q++) & 7;
	while (num < 32 && isodigit(*q) && (q - *src < 3)) {
		num <<= 3;
		num += (*q++) & 7;
	}
	*p = num;
	*dst += 1;
	*src = q;
	return true;
}

static bool unescape_hex(char **src, char **dst)
{
	char *p = *dst, *q = *src;
	int digit;
	u8 num;

	if (*q++ != 'x')
		return false;

	num = digit = hex_to_bin(*q++);
	if (digit < 0)
		return false;

	digit = hex_to_bin(*q);
	if (digit >= 0) {
		q++;
		num = (num << 4) | digit;
	}
	*p = num;
	*dst += 1;
	*src = q;
	return true;
}

static bool unescape_special(char **src, char **dst)
{
	char *p = *dst, *q = *src;

	switch (*q) {
	case '\"':
		*p = '\"';
		break;
	case '\\':
		*p = '\\';
		break;
	case 'a':
		*p = '\a';
		break;
	case 'e':
		*p = '\e';
		break;
	default:
		return false;
	}
	*dst += 1;
	*src += 1;
	return true;
}

/**
 * string_unescape - unquote characters in the given string
 * @src:	source buffer (escaped)
 * @dst:	destination buffer (unescaped)
 * @size:	size of the destination buffer (0 to unlimit)
 * @flags:	combination of the flags.
 *
 * Description:
 * The function unquotes characters in the given string.
 *
 * Because the size of the output will be the same as or less than the size of
 * the input, the transformation may be performed in place.
 *
 * Caller must provide valid source and destination pointers. Be aware that
 * destination buffer will always be NULL-terminated. Source string must be
 * NULL-terminated as well.  The supported flags are::
 *
 *	UNESCAPE_SPACE:
 *		'\f' - form feed
 *		'\n' - new line
 *		'\r' - carriage return
 *		'\t' - horizontal tab
 *		'\v' - vertical tab
 *	UNESCAPE_OCTAL:
 *		'\NNN' - byte with octal value NNN (1 to 3 digits)
 *	UNESCAPE_HEX:
 *		'\xHH' - byte with hexadecimal value HH (1 to 2 digits)
 *	UNESCAPE_SPECIAL:
 *		'\"' - double quote
 *		'\\' - backslash
 *		'\a' - alert (BEL)
 *		'\e' - escape
 *	UNESCAPE_ANY:
 *		all previous together
 *
 * Return:
 * The amount of the characters processed to the destination buffer excluding
 * trailing '\0' is returned.
 */
int string_unescape(char *src, char *dst, size_t size, unsigned int flags)
{
	char *out = dst;

	while (*src && --size) {
		if (src[0] == '\\' && src[1] != '\0' && size > 1) {
			src++;
			size--;

			if (flags & UNESCAPE_SPACE &&
					unescape_space(&src, &out))
				continue;

			if (flags & UNESCAPE_OCTAL &&
					unescape_octal(&src, &out))
				continue;

			if (flags & UNESCAPE_HEX &&
					unescape_hex(&src, &out))
				continue;

			if (flags & UNESCAPE_SPECIAL &&
					unescape_special(&src, &out))
				continue;

			*out++ = '\\';
		}
		*out++ = *src++;
	}
	*out = '\0';

	return out - dst;
}
EXPORT_SYMBOL(string_unescape);

static bool escape_passthrough(unsigned char c, char **dst, char *end)
{
	char *out = *dst;

	if (out < end)
		*out = c;
	*dst = out + 1;
	return true;
}

static bool escape_space(unsigned char c, char **dst, char *end)
{
	char *out = *dst;
	unsigned char to;

	switch (c) {
	case '\n':
		to = 'n';
		break;
	case '\r':
		to = 'r';
		break;
	case '\t':
		to = 't';
		break;
	case '\v':
		to = 'v';
		break;
	case '\f':
		to = 'f';
		break;
	default:
		return false;
	}

	if (out < end)
		*out = '\\';
	++out;
	if (out < end)
		*out = to;
	++out;

	*dst = out;
	return true;
}

static bool escape_special(unsigned char c, char **dst, char *end)
{
	char *out = *dst;
	unsigned char to;

	switch (c) {
	case '\\':
		to = '\\';
		break;
	case '\a':
		to = 'a';
		break;
	case '\e':
		to = 'e';
		break;
	case '"':
		to = '"';
		break;
	default:
		return false;
	}

	if (out < end)
		*out = '\\';
	++out;
	if (out < end)
		*out = to;
	++out;

	*dst = out;
	return true;
}

static bool escape_null(unsigned char c, char **dst, char *end)
{
	char *out = *dst;

	if (c)
		return false;

	if (out < end)
		*out = '\\';
	++out;
	if (out < end)
		*out = '0';
	++out;

	*dst = out;
	return true;
}

static bool escape_octal(unsigned char c, char **dst, char *end)
{
	char *out = *dst;

	if (out < end)
		*out = '\\';
	++out;
	if (out < end)
		*out = ((c >> 6) & 0x07) + '0';
	++out;
	if (out < end)
		*out = ((c >> 3) & 0x07) + '0';
	++out;
	if (out < end)
		*out = ((c >> 0) & 0x07) + '0';
	++out;

	*dst = out;
	return true;
}

static bool escape_hex(unsigned char c, char **dst, char *end)
{
	char *out = *dst;

	if (out < end)
		*out = '\\';
	++out;
	if (out < end)
		*out = 'x';
	++out;
	if (out < end)
		*out = hex_asc_hi(c);
	++out;
	if (out < end)
		*out = hex_asc_lo(c);
	++out;

	*dst = out;
	return true;
}

/**
 * string_escape_mem - quote characters in the given memory buffer
 * @src:	source buffer (unescaped)
 * @isz:	source buffer size
 * @dst:	destination buffer (escaped)
 * @osz:	destination buffer size
 * @flags:	combination of the flags
 * @only:	NULL-terminated string containing characters used to limit
 *		the selected escape class. If characters are included in @only
 *		that would not normally be escaped by the classes selected
 *		in @flags, they will be copied to @dst unescaped.
 *
 * Description:
 * The process of escaping byte buffer includes several parts. They are applied
 * in the following sequence.
 *
 *	1. The character is not matched to the one from @only string and thus
 *	   must go as-is to the output.
 *	2. The character is matched to the printable and ASCII classes, if asked,
 *	   and in case of match it passes through to the output.
 *	3. The character is matched to the printable or ASCII class, if asked,
 *	   and in case of match it passes through to the output.
 *	4. The character is checked if it falls into the class given by @flags.
 *	   %ESCAPE_OCTAL and %ESCAPE_HEX are going last since they cover any
 *	   character. Note that they actually can't go together, otherwise
 *	   %ESCAPE_HEX will be ignored.
 *
 * Caller must provide valid source and destination pointers. Be aware that
 * destination buffer will not be NULL-terminated, thus caller have to append
 * it if needs. The supported flags are::
 *
 *	%ESCAPE_SPACE: (special white space, not space itself)
 *		'\f' - form feed
 *		'\n' - new line
 *		'\r' - carriage return
 *		'\t' - horizontal tab
 *		'\v' - vertical tab
 *	%ESCAPE_SPECIAL:
 *		'\"' - double quote
 *		'\\' - backslash
 *		'\a' - alert (BEL)
 *		'\e' - escape
 *	%ESCAPE_NULL:
 *		'\0' - null
 *	%ESCAPE_OCTAL:
 *		'\NNN' - byte with octal value NNN (3 digits)
 *	%ESCAPE_ANY:
 *		all previous together
 *	%ESCAPE_NP:
 *		escape only non-printable characters, checked by isprint()
 *	%ESCAPE_ANY_NP:
 *		all previous together
 *	%ESCAPE_HEX:
 *		'\xHH' - byte with hexadecimal value HH (2 digits)
 *	%ESCAPE_NA:
 *		escape only non-ascii characters, checked by isascii()
 *	%ESCAPE_NAP:
 *		escape only non-printable or non-ascii characters
 *	%ESCAPE_APPEND:
 *		append characters from @only to be escaped by the given classes
 *
 * %ESCAPE_APPEND would help to pass additional characters to the escaped, when
 * one of %ESCAPE_NP, %ESCAPE_NA, or %ESCAPE_NAP is provided.
 *
 * One notable caveat, the %ESCAPE_NAP, %ESCAPE_NP and %ESCAPE_NA have the
 * higher priority than the rest of the flags (%ESCAPE_NAP is the highest).
 * It doesn't make much sense to use either of them without %ESCAPE_OCTAL
 * or %ESCAPE_HEX, because they cover most of the other character classes.
 * %ESCAPE_NAP can utilize %ESCAPE_SPACE or %ESCAPE_SPECIAL in addition to
 * the above.
 *
 * Return:
 * The total size of the escaped output that would be generated for
 * the given input and flags. To check whether the output was
 * truncated, compare the return value to osz. There is room left in
 * dst for a '\0' terminator if and only if ret < osz.
 */
int string_escape_mem(const char *src, size_t isz, char *dst, size_t osz,
		      unsigned int flags, const char *only)
{
	char *p = dst;
	char *end = p + osz;
	bool is_dict = only && *only;
	bool is_append = flags & ESCAPE_APPEND;

	while (isz--) {
		unsigned char c = *src++;
		bool in_dict = is_dict && strchr(only, c);

		/*
		 * Apply rules in the following sequence:
		 *	- the @only string is supplied and does not contain a
		 *	  character under question
		 *	- the character is printable and ASCII, when @flags has
		 *	  %ESCAPE_NAP bit set
		 *	- the character is printable, when @flags has
		 *	  %ESCAPE_NP bit set
		 *	- the character is ASCII, when @flags has
		 *	  %ESCAPE_NA bit set
		 *	- the character doesn't fall into a class of symbols
		 *	  defined by given @flags
		 * In these cases we just pass through a character to the
		 * output buffer.
		 *
		 * When %ESCAPE_APPEND is passed, the characters from @only
		 * have been excluded from the %ESCAPE_NAP, %ESCAPE_NP, and
		 * %ESCAPE_NA cases.
		 */
		if (!(is_append || in_dict) && is_dict &&
					  escape_passthrough(c, &p, end))
			continue;

		if (!(is_append && in_dict) && isascii(c) && isprint(c) &&
		    flags & ESCAPE_NAP && escape_passthrough(c, &p, end))
			continue;

		if (!(is_append && in_dict) && isprint(c) &&
		    flags & ESCAPE_NP && escape_passthrough(c, &p, end))
			continue;

		if (!(is_append && in_dict) && isascii(c) &&
		    flags & ESCAPE_NA && escape_passthrough(c, &p, end))
			continue;

		if (flags & ESCAPE_SPACE && escape_space(c, &p, end))
			continue;

		if (flags & ESCAPE_SPECIAL && escape_special(c, &p, end))
			continue;

		if (flags & ESCAPE_NULL && escape_null(c, &p, end))
			continue;

		/* ESCAPE_OCTAL and ESCAPE_HEX always go last */
		if (flags & ESCAPE_OCTAL && escape_octal(c, &p, end))
			continue;

		if (flags & ESCAPE_HEX && escape_hex(c, &p, end))
			continue;

		escape_passthrough(c, &p, end);
	}

	return p - dst;
}
EXPORT_SYMBOL(string_escape_mem);

/*
 * Return an allocated string that has been escaped of special characters
 * and double quotes, making it safe to log in quotes.
 */
char *kstrdup_quotable(const char *src, gfp_t gfp)
{
	size_t slen, dlen;
	char *dst;
	const int flags = ESCAPE_HEX;
	const char esc[] = "\f\n\r\t\v\a\e\\\"";

	if (!src)
		return NULL;
	slen = strlen(src);

	dlen = string_escape_mem(src, slen, NULL, 0, flags, esc);
	dst = kmalloc(dlen + 1, gfp);
	if (!dst)
		return NULL;

	WARN_ON(string_escape_mem(src, slen, dst, dlen, flags, esc) != dlen);
	dst[dlen] = '\0';

	return dst;
}
EXPORT_SYMBOL_GPL(kstrdup_quotable);

/*
 * Returns allocated NULL-terminated string containing process
 * command line, with inter-argument NULLs replaced with spaces,
 * and other special characters escaped.
 */
char *kstrdup_quotable_cmdline(struct task_struct *task, gfp_t gfp)
{
	char *buffer, *quoted;
	int i, res;

	buffer = kmalloc(PAGE_SIZE, GFP_KERNEL);
	if (!buffer)
		return NULL;

	res = get_cmdline(task, buffer, PAGE_SIZE - 1);
	buffer[res] = '\0';

	/* Collapse trailing NULLs, leave res pointing to last non-NULL. */
	while (--res >= 0 && buffer[res] == '\0')
		;

	/* Replace inter-argument NULLs. */
	for (i = 0; i <= res; i++)
		if (buffer[i] == '\0')
			buffer[i] = ' ';

	/* Make sure result is printable. */
	quoted = kstrdup_quotable(buffer, gfp);
	kfree(buffer);
	return quoted;
}
EXPORT_SYMBOL_GPL(kstrdup_quotable_cmdline);

/*
 * Returns allocated NULL-terminated string containing pathname,
 * with special characters escaped, able to be safely logged. If
 * there is an error, the leading character will be "<".
 */
char *kstrdup_quotable_file(struct file *file, gfp_t gfp)
{
	char *temp, *pathname;

	if (!file)
		return kstrdup("<unknown>", gfp);

	/* We add 11 spaces for ' (deleted)' to be appended */
	temp = kmalloc(PATH_MAX + 11, GFP_KERNEL);
	if (!temp)
		return kstrdup("<no_memory>", gfp);

	pathname = file_path(file, temp, PATH_MAX + 11);
	if (IS_ERR(pathname))
		pathname = kstrdup("<too_long>", gfp);
	else
		pathname = kstrdup_quotable(pathname, gfp);

	kfree(temp);
	return pathname;
}
EXPORT_SYMBOL_GPL(kstrdup_quotable_file);

/**
 * kasprintf_strarray - allocate and fill array of sequential strings
 * @gfp: flags for the slab allocator
 * @prefix: prefix to be used
 * @n: amount of lines to be allocated and filled
 *
 * Allocates and fills @n strings using pattern "%s-%zu", where prefix
 * is provided by caller. The caller is responsible to free them with
 * kfree_strarray() after use.
 *
 * Returns array of strings or NULL when memory can't be allocated.
 */
char **kasprintf_strarray(gfp_t gfp, const char *prefix, size_t n)
{
	char **names;
	size_t i;

	names = kcalloc(n + 1, sizeof(char *), gfp);
	if (!names)
		return NULL;

	for (i = 0; i < n; i++) {
		names[i] = kasprintf(gfp, "%s-%zu", prefix, i);
		if (!names[i]) {
			kfree_strarray(names, i);
			return NULL;
		}
	}

	return names;
}
EXPORT_SYMBOL_GPL(kasprintf_strarray);

/**
 * kfree_strarray - free a number of dynamically allocated strings contained
 *                  in an array and the array itself
 *
 * @array: Dynamically allocated array of strings to free.
 * @n: Number of strings (starting from the beginning of the array) to free.
 *
 * Passing a non-NULL @array and @n == 0 as well as NULL @array are valid
 * use-cases. If @array is NULL, the function does nothing.
 */
void kfree_strarray(char **array, size_t n)
{
	unsigned int i;

	if (!array)
		return;

	for (i = 0; i < n; i++)
		kfree(array[i]);
	kfree(array);
}
EXPORT_SYMBOL_GPL(kfree_strarray);

struct strarray {
	char **array;
	size_t n;
};

static void devm_kfree_strarray(struct device *dev, void *res)
{
	struct strarray *array = res;

	kfree_strarray(array->array, array->n);
}

char **devm_kasprintf_strarray(struct device *dev, const char *prefix, size_t n)
{
	struct strarray *ptr;

	ptr = devres_alloc(devm_kfree_strarray, sizeof(*ptr), GFP_KERNEL);
	if (!ptr)
		return ERR_PTR(-ENOMEM);

	ptr->array = kasprintf_strarray(GFP_KERNEL, prefix, n);
	if (!ptr->array) {
		devres_free(ptr);
		return ERR_PTR(-ENOMEM);
	}

	ptr->n = n;
	devres_add(dev, ptr);

	return ptr->array;
}
EXPORT_SYMBOL_GPL(devm_kasprintf_strarray);

/**
 * strscpy_pad() - Copy a C-string into a sized buffer
 * @dest: Where to copy the string to
 * @src: Where to copy the string from
 * @count: Size of destination buffer
 *
 * Copy the string, or as much of it as fits, into the dest buffer.  The
 * behavior is undefined if the string buffers overlap.  The destination
 * buffer is always %NUL terminated, unless it's zero-sized.
 *
 * If the source string is shorter than the destination buffer, zeros
 * the tail of the destination buffer.
 *
 * For full explanation of why you may want to consider using the
 * 'strscpy' functions please see the function docstring for strscpy().
 *
 * Returns:
 * * The number of characters copied (not including the trailing %NUL)
 * * -E2BIG if count is 0 or @src was truncated.
 */
ssize_t strscpy_pad(char *dest, const char *src, size_t count)
{
	ssize_t written;

	written = strscpy(dest, src, count);
	if (written < 0 || written == count - 1)
		return written;

	memset(dest + written + 1, 0, count - written - 1);

	return written;
}
EXPORT_SYMBOL(strscpy_pad);

/**
 * skip_spaces - Removes leading whitespace from @str.
 * @str: The string to be stripped.
 *
 * Returns a pointer to the first non-whitespace character in @str.
 */
char *skip_spaces(const char *str)
{
	while (isspace(*str))
		++str;
	return (char *)str;
}
EXPORT_SYMBOL(skip_spaces);

/**
 * strim - Removes leading and trailing whitespace from @s.
 * @s: The string to be stripped.
 *
 * Note that the first trailing whitespace is replaced with a %NUL-terminator
 * in the given string @s. Returns a pointer to the first non-whitespace
 * character in @s.
 */
char *strim(char *s)
{
	size_t size;
	char *end;

	size = strlen(s);
	if (!size)
		return s;

	end = s + size - 1;
	while (end >= s && isspace(*end))
		end--;
	*(end + 1) = '\0';

	return skip_spaces(s);
}
EXPORT_SYMBOL(strim);

/**
 * sysfs_streq - return true if strings are equal, modulo trailing newline
 * @s1: one string
 * @s2: another string
 *
 * This routine returns true iff two strings are equal, treating both
 * NUL and newline-then-NUL as equivalent string terminations.  It's
 * geared for use with sysfs input strings, which generally terminate
 * with newlines but are compared against values without newlines.
 */
bool sysfs_streq(const char *s1, const char *s2)
{
	while (*s1 && *s1 == *s2) {
		s1++;
		s2++;
	}

	if (*s1 == *s2)
		return true;
	if (!*s1 && *s2 == '\n' && !s2[1])
		return true;
	if (*s1 == '\n' && !s1[1] && !*s2)
		return true;
	return false;
}
EXPORT_SYMBOL(sysfs_streq);

/**
 * match_string - matches given string in an array
 * @array:	array of strings
 * @n:		number of strings in the array or -1 for NULL terminated arrays
 * @string:	string to match with
 *
 * This routine will look for a string in an array of strings up to the
 * n-th element in the array or until the first NULL element.
 *
 * Historically the value of -1 for @n, was used to search in arrays that
 * are NULL terminated. However, the function does not make a distinction
 * when finishing the search: either @n elements have been compared OR
 * the first NULL element was found.
 *
 * Return:
 * index of a @string in the @array if matches, or %-EINVAL otherwise.
 */
int match_string(const char * const *array, size_t n, const char *string)
{
	int index;
	const char *item;

	for (index = 0; index < n; index++) {
		item = array[index];
		if (!item)
			break;
		if (!strcmp(item, string))
			return index;
	}

	return -EINVAL;
}
EXPORT_SYMBOL(match_string);

/**
 * __sysfs_match_string - matches given string in an array
 * @array: array of strings
 * @n: number of strings in the array or -1 for NULL terminated arrays
 * @str: string to match with
 *
 * Returns index of @str in the @array or -EINVAL, just like match_string().
 * Uses sysfs_streq instead of strcmp for matching.
 *
 * This routine will look for a string in an array of strings up to the
 * n-th element in the array or until the first NULL element.
 *
 * Historically the value of -1 for @n, was used to search in arrays that
 * are NULL terminated. However, the function does not make a distinction
 * when finishing the search: either @n elements have been compared OR
 * the first NULL element was found.
 */
int __sysfs_match_string(const char * const *array, size_t n, const char *str)
{
	const char *item;
	int index;

	for (index = 0; index < n; index++) {
		item = array[index];
		if (!item)
			break;
		if (sysfs_streq(item, str))
			return index;
	}

	return -EINVAL;
}
EXPORT_SYMBOL(__sysfs_match_string);

/**
 * strreplace - Replace all occurrences of character in string.
 * @s: The string to operate on.
 * @old: The character being replaced.
 * @new: The character @old is replaced with.
 *
 * Returns pointer to the nul byte at the end of @s.
 */
char *strreplace(char *s, char old, char new)
{
	for (; *s; ++s)
		if (*s == old)
			*s = new;
	return s;
}
EXPORT_SYMBOL(strreplace);

/**
 * memcpy_and_pad - Copy one buffer to another with padding
 * @dest: Where to copy to
 * @dest_len: The destination buffer size
 * @src: Where to copy from
 * @count: The number of bytes to copy
 * @pad: Character to use for padding if space is left in destination.
 */
void memcpy_and_pad(void *dest, size_t dest_len, const void *src, size_t count,
		    int pad)
{
	if (dest_len > count) {
		memcpy(dest, src, count);
		memset(dest + count, pad,  dest_len - count);
	} else {
		memcpy(dest, src, dest_len);
	}
}
EXPORT_SYMBOL(memcpy_and_pad);

#ifdef CONFIG_FORTIFY_SOURCE
/* These are placeholders for fortify compile-time warnings. */
void __read_overflow2_field(size_t avail, size_t wanted) { }
EXPORT_SYMBOL(__read_overflow2_field);
void __write_overflow_field(size_t avail, size_t wanted) { }
EXPORT_SYMBOL(__write_overflow_field);

void fortify_panic(const char *name)
{
	pr_emerg("detected buffer overflow in %s\n", name);
	BUG();
}
EXPORT_SYMBOL(fortify_panic);
#endif /* CONFIG_FORTIFY_SOURCE */