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1/*
2 * linux/lib/string.c
3 *
4 * Copyright (C) 1991, 1992 Linus Torvalds
5 */
6
7/*
8 * stupid library routines.. The optimized versions should generally be found
9 * as inline code in <asm-xx/string.h>
10 *
11 * These are buggy as well..
12 *
13 * * Fri Jun 25 1999, Ingo Oeser <ioe@informatik.tu-chemnitz.de>
14 * - Added strsep() which will replace strtok() soon (because strsep() is
15 * reentrant and should be faster). Use only strsep() in new code, please.
16 *
17 * * Sat Feb 09 2002, Jason Thomas <jason@topic.com.au>,
18 * Matthew Hawkins <matt@mh.dropbear.id.au>
19 * - Kissed strtok() goodbye
20 */
21
22#include <linux/types.h>
23#include <linux/string.h>
24#include <linux/ctype.h>
25#include <linux/kernel.h>
26#include <linux/export.h>
27#include <linux/bug.h>
28#include <linux/errno.h>
29
30#include <asm/byteorder.h>
31#include <asm/word-at-a-time.h>
32#include <asm/page.h>
33
34#ifndef __HAVE_ARCH_STRNCASECMP
35/**
36 * strncasecmp - Case insensitive, length-limited string comparison
37 * @s1: One string
38 * @s2: The other string
39 * @len: the maximum number of characters to compare
40 */
41int strncasecmp(const char *s1, const char *s2, size_t len)
42{
43 /* Yes, Virginia, it had better be unsigned */
44 unsigned char c1, c2;
45
46 if (!len)
47 return 0;
48
49 do {
50 c1 = *s1++;
51 c2 = *s2++;
52 if (!c1 || !c2)
53 break;
54 if (c1 == c2)
55 continue;
56 c1 = tolower(c1);
57 c2 = tolower(c2);
58 if (c1 != c2)
59 break;
60 } while (--len);
61 return (int)c1 - (int)c2;
62}
63EXPORT_SYMBOL(strncasecmp);
64#endif
65
66#ifndef __HAVE_ARCH_STRCASECMP
67int strcasecmp(const char *s1, const char *s2)
68{
69 int c1, c2;
70
71 do {
72 c1 = tolower(*s1++);
73 c2 = tolower(*s2++);
74 } while (c1 == c2 && c1 != 0);
75 return c1 - c2;
76}
77EXPORT_SYMBOL(strcasecmp);
78#endif
79
80#ifndef __HAVE_ARCH_STRCPY
81/**
82 * strcpy - Copy a %NUL terminated string
83 * @dest: Where to copy the string to
84 * @src: Where to copy the string from
85 */
86#undef strcpy
87char *strcpy(char *dest, const char *src)
88{
89 char *tmp = dest;
90
91 while ((*dest++ = *src++) != '\0')
92 /* nothing */;
93 return tmp;
94}
95EXPORT_SYMBOL(strcpy);
96#endif
97
98#ifndef __HAVE_ARCH_STRNCPY
99/**
100 * strncpy - Copy a length-limited, C-string
101 * @dest: Where to copy the string to
102 * @src: Where to copy the string from
103 * @count: The maximum number of bytes to copy
104 *
105 * The result is not %NUL-terminated if the source exceeds
106 * @count bytes.
107 *
108 * In the case where the length of @src is less than that of
109 * count, the remainder of @dest will be padded with %NUL.
110 *
111 */
112char *strncpy(char *dest, const char *src, size_t count)
113{
114 char *tmp = dest;
115
116 while (count) {
117 if ((*tmp = *src) != 0)
118 src++;
119 tmp++;
120 count--;
121 }
122 return dest;
123}
124EXPORT_SYMBOL(strncpy);
125#endif
126
127#ifndef __HAVE_ARCH_STRLCPY
128/**
129 * strlcpy - Copy a C-string into a sized buffer
130 * @dest: Where to copy the string to
131 * @src: Where to copy the string from
132 * @size: size of destination buffer
133 *
134 * Compatible with *BSD: the result is always a valid
135 * NUL-terminated string that fits in the buffer (unless,
136 * of course, the buffer size is zero). It does not pad
137 * out the result like strncpy() does.
138 */
139size_t strlcpy(char *dest, const char *src, size_t size)
140{
141 size_t ret = strlen(src);
142
143 if (size) {
144 size_t len = (ret >= size) ? size - 1 : ret;
145 memcpy(dest, src, len);
146 dest[len] = '\0';
147 }
148 return ret;
149}
150EXPORT_SYMBOL(strlcpy);
151#endif
152
153#ifndef __HAVE_ARCH_STRSCPY
154/**
155 * strscpy - Copy a C-string into a sized buffer
156 * @dest: Where to copy the string to
157 * @src: Where to copy the string from
158 * @count: Size of destination buffer
159 *
160 * Copy the string, or as much of it as fits, into the dest buffer.
161 * The routine returns the number of characters copied (not including
162 * the trailing NUL) or -E2BIG if the destination buffer wasn't big enough.
163 * The behavior is undefined if the string buffers overlap.
164 * The destination buffer is always NUL terminated, unless it's zero-sized.
165 *
166 * Preferred to strlcpy() since the API doesn't require reading memory
167 * from the src string beyond the specified "count" bytes, and since
168 * the return value is easier to error-check than strlcpy()'s.
169 * In addition, the implementation is robust to the string changing out
170 * from underneath it, unlike the current strlcpy() implementation.
171 *
172 * Preferred to strncpy() since it always returns a valid string, and
173 * doesn't unnecessarily force the tail of the destination buffer to be
174 * zeroed. If the zeroing is desired, it's likely cleaner to use strscpy()
175 * with an overflow test, then just memset() the tail of the dest buffer.
176 */
177ssize_t strscpy(char *dest, const char *src, size_t count)
178{
179 const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
180 size_t max = count;
181 long res = 0;
182
183 if (count == 0)
184 return -E2BIG;
185
186#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
187 /*
188 * If src is unaligned, don't cross a page boundary,
189 * since we don't know if the next page is mapped.
190 */
191 if ((long)src & (sizeof(long) - 1)) {
192 size_t limit = PAGE_SIZE - ((long)src & (PAGE_SIZE - 1));
193 if (limit < max)
194 max = limit;
195 }
196#else
197 /* If src or dest is unaligned, don't do word-at-a-time. */
198 if (((long) dest | (long) src) & (sizeof(long) - 1))
199 max = 0;
200#endif
201
202 while (max >= sizeof(unsigned long)) {
203 unsigned long c, data;
204
205 c = *(unsigned long *)(src+res);
206 if (has_zero(c, &data, &constants)) {
207 data = prep_zero_mask(c, data, &constants);
208 data = create_zero_mask(data);
209 *(unsigned long *)(dest+res) = c & zero_bytemask(data);
210 return res + find_zero(data);
211 }
212 *(unsigned long *)(dest+res) = c;
213 res += sizeof(unsigned long);
214 count -= sizeof(unsigned long);
215 max -= sizeof(unsigned long);
216 }
217
218 while (count) {
219 char c;
220
221 c = src[res];
222 dest[res] = c;
223 if (!c)
224 return res;
225 res++;
226 count--;
227 }
228
229 /* Hit buffer length without finding a NUL; force NUL-termination. */
230 if (res)
231 dest[res-1] = '\0';
232
233 return -E2BIG;
234}
235EXPORT_SYMBOL(strscpy);
236#endif
237
238#ifndef __HAVE_ARCH_STRCAT
239/**
240 * strcat - Append one %NUL-terminated string to another
241 * @dest: The string to be appended to
242 * @src: The string to append to it
243 */
244#undef strcat
245char *strcat(char *dest, const char *src)
246{
247 char *tmp = dest;
248
249 while (*dest)
250 dest++;
251 while ((*dest++ = *src++) != '\0')
252 ;
253 return tmp;
254}
255EXPORT_SYMBOL(strcat);
256#endif
257
258#ifndef __HAVE_ARCH_STRNCAT
259/**
260 * strncat - Append a length-limited, C-string to another
261 * @dest: The string to be appended to
262 * @src: The string to append to it
263 * @count: The maximum numbers of bytes to copy
264 *
265 * Note that in contrast to strncpy(), strncat() ensures the result is
266 * terminated.
267 */
268char *strncat(char *dest, const char *src, size_t count)
269{
270 char *tmp = dest;
271
272 if (count) {
273 while (*dest)
274 dest++;
275 while ((*dest++ = *src++) != 0) {
276 if (--count == 0) {
277 *dest = '\0';
278 break;
279 }
280 }
281 }
282 return tmp;
283}
284EXPORT_SYMBOL(strncat);
285#endif
286
287#ifndef __HAVE_ARCH_STRLCAT
288/**
289 * strlcat - Append a length-limited, C-string to another
290 * @dest: The string to be appended to
291 * @src: The string to append to it
292 * @count: The size of the destination buffer.
293 */
294size_t strlcat(char *dest, const char *src, size_t count)
295{
296 size_t dsize = strlen(dest);
297 size_t len = strlen(src);
298 size_t res = dsize + len;
299
300 /* This would be a bug */
301 BUG_ON(dsize >= count);
302
303 dest += dsize;
304 count -= dsize;
305 if (len >= count)
306 len = count-1;
307 memcpy(dest, src, len);
308 dest[len] = 0;
309 return res;
310}
311EXPORT_SYMBOL(strlcat);
312#endif
313
314#ifndef __HAVE_ARCH_STRCMP
315/**
316 * strcmp - Compare two strings
317 * @cs: One string
318 * @ct: Another string
319 */
320#undef strcmp
321int strcmp(const char *cs, const char *ct)
322{
323 unsigned char c1, c2;
324
325 while (1) {
326 c1 = *cs++;
327 c2 = *ct++;
328 if (c1 != c2)
329 return c1 < c2 ? -1 : 1;
330 if (!c1)
331 break;
332 }
333 return 0;
334}
335EXPORT_SYMBOL(strcmp);
336#endif
337
338#ifndef __HAVE_ARCH_STRNCMP
339/**
340 * strncmp - Compare two length-limited strings
341 * @cs: One string
342 * @ct: Another string
343 * @count: The maximum number of bytes to compare
344 */
345int strncmp(const char *cs, const char *ct, size_t count)
346{
347 unsigned char c1, c2;
348
349 while (count) {
350 c1 = *cs++;
351 c2 = *ct++;
352 if (c1 != c2)
353 return c1 < c2 ? -1 : 1;
354 if (!c1)
355 break;
356 count--;
357 }
358 return 0;
359}
360EXPORT_SYMBOL(strncmp);
361#endif
362
363#ifndef __HAVE_ARCH_STRCHR
364/**
365 * strchr - Find the first occurrence of a character in a string
366 * @s: The string to be searched
367 * @c: The character to search for
368 */
369char *strchr(const char *s, int c)
370{
371 for (; *s != (char)c; ++s)
372 if (*s == '\0')
373 return NULL;
374 return (char *)s;
375}
376EXPORT_SYMBOL(strchr);
377#endif
378
379#ifndef __HAVE_ARCH_STRCHRNUL
380/**
381 * strchrnul - Find and return a character in a string, or end of string
382 * @s: The string to be searched
383 * @c: The character to search for
384 *
385 * Returns pointer to first occurrence of 'c' in s. If c is not found, then
386 * return a pointer to the null byte at the end of s.
387 */
388char *strchrnul(const char *s, int c)
389{
390 while (*s && *s != (char)c)
391 s++;
392 return (char *)s;
393}
394EXPORT_SYMBOL(strchrnul);
395#endif
396
397#ifndef __HAVE_ARCH_STRRCHR
398/**
399 * strrchr - Find the last occurrence of a character in a string
400 * @s: The string to be searched
401 * @c: The character to search for
402 */
403char *strrchr(const char *s, int c)
404{
405 const char *last = NULL;
406 do {
407 if (*s == (char)c)
408 last = s;
409 } while (*s++);
410 return (char *)last;
411}
412EXPORT_SYMBOL(strrchr);
413#endif
414
415#ifndef __HAVE_ARCH_STRNCHR
416/**
417 * strnchr - Find a character in a length limited string
418 * @s: The string to be searched
419 * @count: The number of characters to be searched
420 * @c: The character to search for
421 */
422char *strnchr(const char *s, size_t count, int c)
423{
424 for (; count-- && *s != '\0'; ++s)
425 if (*s == (char)c)
426 return (char *)s;
427 return NULL;
428}
429EXPORT_SYMBOL(strnchr);
430#endif
431
432/**
433 * skip_spaces - Removes leading whitespace from @str.
434 * @str: The string to be stripped.
435 *
436 * Returns a pointer to the first non-whitespace character in @str.
437 */
438char *skip_spaces(const char *str)
439{
440 while (isspace(*str))
441 ++str;
442 return (char *)str;
443}
444EXPORT_SYMBOL(skip_spaces);
445
446/**
447 * strim - Removes leading and trailing whitespace from @s.
448 * @s: The string to be stripped.
449 *
450 * Note that the first trailing whitespace is replaced with a %NUL-terminator
451 * in the given string @s. Returns a pointer to the first non-whitespace
452 * character in @s.
453 */
454char *strim(char *s)
455{
456 size_t size;
457 char *end;
458
459 size = strlen(s);
460 if (!size)
461 return s;
462
463 end = s + size - 1;
464 while (end >= s && isspace(*end))
465 end--;
466 *(end + 1) = '\0';
467
468 return skip_spaces(s);
469}
470EXPORT_SYMBOL(strim);
471
472#ifndef __HAVE_ARCH_STRLEN
473/**
474 * strlen - Find the length of a string
475 * @s: The string to be sized
476 */
477size_t strlen(const char *s)
478{
479 const char *sc;
480
481 for (sc = s; *sc != '\0'; ++sc)
482 /* nothing */;
483 return sc - s;
484}
485EXPORT_SYMBOL(strlen);
486#endif
487
488#ifndef __HAVE_ARCH_STRNLEN
489/**
490 * strnlen - Find the length of a length-limited string
491 * @s: The string to be sized
492 * @count: The maximum number of bytes to search
493 */
494size_t strnlen(const char *s, size_t count)
495{
496 const char *sc;
497
498 for (sc = s; count-- && *sc != '\0'; ++sc)
499 /* nothing */;
500 return sc - s;
501}
502EXPORT_SYMBOL(strnlen);
503#endif
504
505#ifndef __HAVE_ARCH_STRSPN
506/**
507 * strspn - Calculate the length of the initial substring of @s which only contain letters in @accept
508 * @s: The string to be searched
509 * @accept: The string to search for
510 */
511size_t strspn(const char *s, const char *accept)
512{
513 const char *p;
514 const char *a;
515 size_t count = 0;
516
517 for (p = s; *p != '\0'; ++p) {
518 for (a = accept; *a != '\0'; ++a) {
519 if (*p == *a)
520 break;
521 }
522 if (*a == '\0')
523 return count;
524 ++count;
525 }
526 return count;
527}
528
529EXPORT_SYMBOL(strspn);
530#endif
531
532#ifndef __HAVE_ARCH_STRCSPN
533/**
534 * strcspn - Calculate the length of the initial substring of @s which does not contain letters in @reject
535 * @s: The string to be searched
536 * @reject: The string to avoid
537 */
538size_t strcspn(const char *s, const char *reject)
539{
540 const char *p;
541 const char *r;
542 size_t count = 0;
543
544 for (p = s; *p != '\0'; ++p) {
545 for (r = reject; *r != '\0'; ++r) {
546 if (*p == *r)
547 return count;
548 }
549 ++count;
550 }
551 return count;
552}
553EXPORT_SYMBOL(strcspn);
554#endif
555
556#ifndef __HAVE_ARCH_STRPBRK
557/**
558 * strpbrk - Find the first occurrence of a set of characters
559 * @cs: The string to be searched
560 * @ct: The characters to search for
561 */
562char *strpbrk(const char *cs, const char *ct)
563{
564 const char *sc1, *sc2;
565
566 for (sc1 = cs; *sc1 != '\0'; ++sc1) {
567 for (sc2 = ct; *sc2 != '\0'; ++sc2) {
568 if (*sc1 == *sc2)
569 return (char *)sc1;
570 }
571 }
572 return NULL;
573}
574EXPORT_SYMBOL(strpbrk);
575#endif
576
577#ifndef __HAVE_ARCH_STRSEP
578/**
579 * strsep - Split a string into tokens
580 * @s: The string to be searched
581 * @ct: The characters to search for
582 *
583 * strsep() updates @s to point after the token, ready for the next call.
584 *
585 * It returns empty tokens, too, behaving exactly like the libc function
586 * of that name. In fact, it was stolen from glibc2 and de-fancy-fied.
587 * Same semantics, slimmer shape. ;)
588 */
589char *strsep(char **s, const char *ct)
590{
591 char *sbegin = *s;
592 char *end;
593
594 if (sbegin == NULL)
595 return NULL;
596
597 end = strpbrk(sbegin, ct);
598 if (end)
599 *end++ = '\0';
600 *s = end;
601 return sbegin;
602}
603EXPORT_SYMBOL(strsep);
604#endif
605
606/**
607 * sysfs_streq - return true if strings are equal, modulo trailing newline
608 * @s1: one string
609 * @s2: another string
610 *
611 * This routine returns true iff two strings are equal, treating both
612 * NUL and newline-then-NUL as equivalent string terminations. It's
613 * geared for use with sysfs input strings, which generally terminate
614 * with newlines but are compared against values without newlines.
615 */
616bool sysfs_streq(const char *s1, const char *s2)
617{
618 while (*s1 && *s1 == *s2) {
619 s1++;
620 s2++;
621 }
622
623 if (*s1 == *s2)
624 return true;
625 if (!*s1 && *s2 == '\n' && !s2[1])
626 return true;
627 if (*s1 == '\n' && !s1[1] && !*s2)
628 return true;
629 return false;
630}
631EXPORT_SYMBOL(sysfs_streq);
632
633/**
634 * match_string - matches given string in an array
635 * @array: array of strings
636 * @n: number of strings in the array or -1 for NULL terminated arrays
637 * @string: string to match with
638 *
639 * Return:
640 * index of a @string in the @array if matches, or %-EINVAL otherwise.
641 */
642int match_string(const char * const *array, size_t n, const char *string)
643{
644 int index;
645 const char *item;
646
647 for (index = 0; index < n; index++) {
648 item = array[index];
649 if (!item)
650 break;
651 if (!strcmp(item, string))
652 return index;
653 }
654
655 return -EINVAL;
656}
657EXPORT_SYMBOL(match_string);
658
659#ifndef __HAVE_ARCH_MEMSET
660/**
661 * memset - Fill a region of memory with the given value
662 * @s: Pointer to the start of the area.
663 * @c: The byte to fill the area with
664 * @count: The size of the area.
665 *
666 * Do not use memset() to access IO space, use memset_io() instead.
667 */
668void *memset(void *s, int c, size_t count)
669{
670 char *xs = s;
671
672 while (count--)
673 *xs++ = c;
674 return s;
675}
676EXPORT_SYMBOL(memset);
677#endif
678
679/**
680 * memzero_explicit - Fill a region of memory (e.g. sensitive
681 * keying data) with 0s.
682 * @s: Pointer to the start of the area.
683 * @count: The size of the area.
684 *
685 * Note: usually using memset() is just fine (!), but in cases
686 * where clearing out _local_ data at the end of a scope is
687 * necessary, memzero_explicit() should be used instead in
688 * order to prevent the compiler from optimising away zeroing.
689 *
690 * memzero_explicit() doesn't need an arch-specific version as
691 * it just invokes the one of memset() implicitly.
692 */
693void memzero_explicit(void *s, size_t count)
694{
695 memset(s, 0, count);
696 barrier_data(s);
697}
698EXPORT_SYMBOL(memzero_explicit);
699
700#ifndef __HAVE_ARCH_MEMCPY
701/**
702 * memcpy - Copy one area of memory to another
703 * @dest: Where to copy to
704 * @src: Where to copy from
705 * @count: The size of the area.
706 *
707 * You should not use this function to access IO space, use memcpy_toio()
708 * or memcpy_fromio() instead.
709 */
710void *memcpy(void *dest, const void *src, size_t count)
711{
712 char *tmp = dest;
713 const char *s = src;
714
715 while (count--)
716 *tmp++ = *s++;
717 return dest;
718}
719EXPORT_SYMBOL(memcpy);
720#endif
721
722#ifndef __HAVE_ARCH_MEMMOVE
723/**
724 * memmove - Copy one area of memory to another
725 * @dest: Where to copy to
726 * @src: Where to copy from
727 * @count: The size of the area.
728 *
729 * Unlike memcpy(), memmove() copes with overlapping areas.
730 */
731void *memmove(void *dest, const void *src, size_t count)
732{
733 char *tmp;
734 const char *s;
735
736 if (dest <= src) {
737 tmp = dest;
738 s = src;
739 while (count--)
740 *tmp++ = *s++;
741 } else {
742 tmp = dest;
743 tmp += count;
744 s = src;
745 s += count;
746 while (count--)
747 *--tmp = *--s;
748 }
749 return dest;
750}
751EXPORT_SYMBOL(memmove);
752#endif
753
754#ifndef __HAVE_ARCH_MEMCMP
755/**
756 * memcmp - Compare two areas of memory
757 * @cs: One area of memory
758 * @ct: Another area of memory
759 * @count: The size of the area.
760 */
761#undef memcmp
762__visible int memcmp(const void *cs, const void *ct, size_t count)
763{
764 const unsigned char *su1, *su2;
765 int res = 0;
766
767 for (su1 = cs, su2 = ct; 0 < count; ++su1, ++su2, count--)
768 if ((res = *su1 - *su2) != 0)
769 break;
770 return res;
771}
772EXPORT_SYMBOL(memcmp);
773#endif
774
775#ifndef __HAVE_ARCH_MEMSCAN
776/**
777 * memscan - Find a character in an area of memory.
778 * @addr: The memory area
779 * @c: The byte to search for
780 * @size: The size of the area.
781 *
782 * returns the address of the first occurrence of @c, or 1 byte past
783 * the area if @c is not found
784 */
785void *memscan(void *addr, int c, size_t size)
786{
787 unsigned char *p = addr;
788
789 while (size) {
790 if (*p == c)
791 return (void *)p;
792 p++;
793 size--;
794 }
795 return (void *)p;
796}
797EXPORT_SYMBOL(memscan);
798#endif
799
800#ifndef __HAVE_ARCH_STRSTR
801/**
802 * strstr - Find the first substring in a %NUL terminated string
803 * @s1: The string to be searched
804 * @s2: The string to search for
805 */
806char *strstr(const char *s1, const char *s2)
807{
808 size_t l1, l2;
809
810 l2 = strlen(s2);
811 if (!l2)
812 return (char *)s1;
813 l1 = strlen(s1);
814 while (l1 >= l2) {
815 l1--;
816 if (!memcmp(s1, s2, l2))
817 return (char *)s1;
818 s1++;
819 }
820 return NULL;
821}
822EXPORT_SYMBOL(strstr);
823#endif
824
825#ifndef __HAVE_ARCH_STRNSTR
826/**
827 * strnstr - Find the first substring in a length-limited string
828 * @s1: The string to be searched
829 * @s2: The string to search for
830 * @len: the maximum number of characters to search
831 */
832char *strnstr(const char *s1, const char *s2, size_t len)
833{
834 size_t l2;
835
836 l2 = strlen(s2);
837 if (!l2)
838 return (char *)s1;
839 while (len >= l2) {
840 len--;
841 if (!memcmp(s1, s2, l2))
842 return (char *)s1;
843 s1++;
844 }
845 return NULL;
846}
847EXPORT_SYMBOL(strnstr);
848#endif
849
850#ifndef __HAVE_ARCH_MEMCHR
851/**
852 * memchr - Find a character in an area of memory.
853 * @s: The memory area
854 * @c: The byte to search for
855 * @n: The size of the area.
856 *
857 * returns the address of the first occurrence of @c, or %NULL
858 * if @c is not found
859 */
860void *memchr(const void *s, int c, size_t n)
861{
862 const unsigned char *p = s;
863 while (n-- != 0) {
864 if ((unsigned char)c == *p++) {
865 return (void *)(p - 1);
866 }
867 }
868 return NULL;
869}
870EXPORT_SYMBOL(memchr);
871#endif
872
873static void *check_bytes8(const u8 *start, u8 value, unsigned int bytes)
874{
875 while (bytes) {
876 if (*start != value)
877 return (void *)start;
878 start++;
879 bytes--;
880 }
881 return NULL;
882}
883
884/**
885 * memchr_inv - Find an unmatching character in an area of memory.
886 * @start: The memory area
887 * @c: Find a character other than c
888 * @bytes: The size of the area.
889 *
890 * returns the address of the first character other than @c, or %NULL
891 * if the whole buffer contains just @c.
892 */
893void *memchr_inv(const void *start, int c, size_t bytes)
894{
895 u8 value = c;
896 u64 value64;
897 unsigned int words, prefix;
898
899 if (bytes <= 16)
900 return check_bytes8(start, value, bytes);
901
902 value64 = value;
903#if defined(CONFIG_ARCH_HAS_FAST_MULTIPLIER) && BITS_PER_LONG == 64
904 value64 *= 0x0101010101010101ULL;
905#elif defined(CONFIG_ARCH_HAS_FAST_MULTIPLIER)
906 value64 *= 0x01010101;
907 value64 |= value64 << 32;
908#else
909 value64 |= value64 << 8;
910 value64 |= value64 << 16;
911 value64 |= value64 << 32;
912#endif
913
914 prefix = (unsigned long)start % 8;
915 if (prefix) {
916 u8 *r;
917
918 prefix = 8 - prefix;
919 r = check_bytes8(start, value, prefix);
920 if (r)
921 return r;
922 start += prefix;
923 bytes -= prefix;
924 }
925
926 words = bytes / 8;
927
928 while (words) {
929 if (*(u64 *)start != value64)
930 return check_bytes8(start, value, 8);
931 start += 8;
932 words--;
933 }
934
935 return check_bytes8(start, value, bytes % 8);
936}
937EXPORT_SYMBOL(memchr_inv);
938
939/**
940 * strreplace - Replace all occurrences of character in string.
941 * @s: The string to operate on.
942 * @old: The character being replaced.
943 * @new: The character @old is replaced with.
944 *
945 * Returns pointer to the nul byte at the end of @s.
946 */
947char *strreplace(char *s, char old, char new)
948{
949 for (; *s; ++s)
950 if (*s == old)
951 *s = new;
952 return s;
953}
954EXPORT_SYMBOL(strreplace);
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * linux/lib/string.c
4 *
5 * Copyright (C) 1991, 1992 Linus Torvalds
6 */
7
8/*
9 * This file should be used only for "library" routines that may have
10 * alternative implementations on specific architectures (generally
11 * found in <asm-xx/string.h>), or get overloaded by FORTIFY_SOURCE.
12 * (Specifically, this file is built with __NO_FORTIFY.)
13 *
14 * Other helper functions should live in string_helpers.c.
15 */
16
17#define __NO_FORTIFY
18#include <linux/types.h>
19#include <linux/string.h>
20#include <linux/ctype.h>
21#include <linux/kernel.h>
22#include <linux/export.h>
23#include <linux/bug.h>
24#include <linux/errno.h>
25#include <linux/slab.h>
26
27#include <asm/unaligned.h>
28#include <asm/byteorder.h>
29#include <asm/word-at-a-time.h>
30#include <asm/page.h>
31
32#ifndef __HAVE_ARCH_STRNCASECMP
33/**
34 * strncasecmp - Case insensitive, length-limited string comparison
35 * @s1: One string
36 * @s2: The other string
37 * @len: the maximum number of characters to compare
38 */
39int strncasecmp(const char *s1, const char *s2, size_t len)
40{
41 /* Yes, Virginia, it had better be unsigned */
42 unsigned char c1, c2;
43
44 if (!len)
45 return 0;
46
47 do {
48 c1 = *s1++;
49 c2 = *s2++;
50 if (!c1 || !c2)
51 break;
52 if (c1 == c2)
53 continue;
54 c1 = tolower(c1);
55 c2 = tolower(c2);
56 if (c1 != c2)
57 break;
58 } while (--len);
59 return (int)c1 - (int)c2;
60}
61EXPORT_SYMBOL(strncasecmp);
62#endif
63
64#ifndef __HAVE_ARCH_STRCASECMP
65int strcasecmp(const char *s1, const char *s2)
66{
67 int c1, c2;
68
69 do {
70 c1 = tolower(*s1++);
71 c2 = tolower(*s2++);
72 } while (c1 == c2 && c1 != 0);
73 return c1 - c2;
74}
75EXPORT_SYMBOL(strcasecmp);
76#endif
77
78#ifndef __HAVE_ARCH_STRCPY
79char *strcpy(char *dest, const char *src)
80{
81 char *tmp = dest;
82
83 while ((*dest++ = *src++) != '\0')
84 /* nothing */;
85 return tmp;
86}
87EXPORT_SYMBOL(strcpy);
88#endif
89
90#ifndef __HAVE_ARCH_STRNCPY
91char *strncpy(char *dest, const char *src, size_t count)
92{
93 char *tmp = dest;
94
95 while (count) {
96 if ((*tmp = *src) != 0)
97 src++;
98 tmp++;
99 count--;
100 }
101 return dest;
102}
103EXPORT_SYMBOL(strncpy);
104#endif
105
106#ifndef __HAVE_ARCH_STRLCPY
107size_t strlcpy(char *dest, const char *src, size_t size)
108{
109 size_t ret = strlen(src);
110
111 if (size) {
112 size_t len = (ret >= size) ? size - 1 : ret;
113 memcpy(dest, src, len);
114 dest[len] = '\0';
115 }
116 return ret;
117}
118EXPORT_SYMBOL(strlcpy);
119#endif
120
121#ifndef __HAVE_ARCH_STRSCPY
122ssize_t strscpy(char *dest, const char *src, size_t count)
123{
124 const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
125 size_t max = count;
126 long res = 0;
127
128 if (count == 0 || WARN_ON_ONCE(count > INT_MAX))
129 return -E2BIG;
130
131#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
132 /*
133 * If src is unaligned, don't cross a page boundary,
134 * since we don't know if the next page is mapped.
135 */
136 if ((long)src & (sizeof(long) - 1)) {
137 size_t limit = PAGE_SIZE - ((long)src & (PAGE_SIZE - 1));
138 if (limit < max)
139 max = limit;
140 }
141#else
142 /* If src or dest is unaligned, don't do word-at-a-time. */
143 if (((long) dest | (long) src) & (sizeof(long) - 1))
144 max = 0;
145#endif
146
147 /*
148 * read_word_at_a_time() below may read uninitialized bytes after the
149 * trailing zero and use them in comparisons. Disable this optimization
150 * under KMSAN to prevent false positive reports.
151 */
152 if (IS_ENABLED(CONFIG_KMSAN))
153 max = 0;
154
155 while (max >= sizeof(unsigned long)) {
156 unsigned long c, data;
157
158 c = read_word_at_a_time(src+res);
159 if (has_zero(c, &data, &constants)) {
160 data = prep_zero_mask(c, data, &constants);
161 data = create_zero_mask(data);
162 *(unsigned long *)(dest+res) = c & zero_bytemask(data);
163 return res + find_zero(data);
164 }
165 *(unsigned long *)(dest+res) = c;
166 res += sizeof(unsigned long);
167 count -= sizeof(unsigned long);
168 max -= sizeof(unsigned long);
169 }
170
171 while (count) {
172 char c;
173
174 c = src[res];
175 dest[res] = c;
176 if (!c)
177 return res;
178 res++;
179 count--;
180 }
181
182 /* Hit buffer length without finding a NUL; force NUL-termination. */
183 if (res)
184 dest[res-1] = '\0';
185
186 return -E2BIG;
187}
188EXPORT_SYMBOL(strscpy);
189#endif
190
191/**
192 * stpcpy - copy a string from src to dest returning a pointer to the new end
193 * of dest, including src's %NUL-terminator. May overrun dest.
194 * @dest: pointer to end of string being copied into. Must be large enough
195 * to receive copy.
196 * @src: pointer to the beginning of string being copied from. Must not overlap
197 * dest.
198 *
199 * stpcpy differs from strcpy in a key way: the return value is a pointer
200 * to the new %NUL-terminating character in @dest. (For strcpy, the return
201 * value is a pointer to the start of @dest). This interface is considered
202 * unsafe as it doesn't perform bounds checking of the inputs. As such it's
203 * not recommended for usage. Instead, its definition is provided in case
204 * the compiler lowers other libcalls to stpcpy.
205 */
206char *stpcpy(char *__restrict__ dest, const char *__restrict__ src);
207char *stpcpy(char *__restrict__ dest, const char *__restrict__ src)
208{
209 while ((*dest++ = *src++) != '\0')
210 /* nothing */;
211 return --dest;
212}
213EXPORT_SYMBOL(stpcpy);
214
215#ifndef __HAVE_ARCH_STRCAT
216char *strcat(char *dest, const char *src)
217{
218 char *tmp = dest;
219
220 while (*dest)
221 dest++;
222 while ((*dest++ = *src++) != '\0')
223 ;
224 return tmp;
225}
226EXPORT_SYMBOL(strcat);
227#endif
228
229#ifndef __HAVE_ARCH_STRNCAT
230char *strncat(char *dest, const char *src, size_t count)
231{
232 char *tmp = dest;
233
234 if (count) {
235 while (*dest)
236 dest++;
237 while ((*dest++ = *src++) != 0) {
238 if (--count == 0) {
239 *dest = '\0';
240 break;
241 }
242 }
243 }
244 return tmp;
245}
246EXPORT_SYMBOL(strncat);
247#endif
248
249#ifndef __HAVE_ARCH_STRLCAT
250size_t strlcat(char *dest, const char *src, size_t count)
251{
252 size_t dsize = strlen(dest);
253 size_t len = strlen(src);
254 size_t res = dsize + len;
255
256 /* This would be a bug */
257 BUG_ON(dsize >= count);
258
259 dest += dsize;
260 count -= dsize;
261 if (len >= count)
262 len = count-1;
263 memcpy(dest, src, len);
264 dest[len] = 0;
265 return res;
266}
267EXPORT_SYMBOL(strlcat);
268#endif
269
270#ifndef __HAVE_ARCH_STRCMP
271/**
272 * strcmp - Compare two strings
273 * @cs: One string
274 * @ct: Another string
275 */
276int strcmp(const char *cs, const char *ct)
277{
278 unsigned char c1, c2;
279
280 while (1) {
281 c1 = *cs++;
282 c2 = *ct++;
283 if (c1 != c2)
284 return c1 < c2 ? -1 : 1;
285 if (!c1)
286 break;
287 }
288 return 0;
289}
290EXPORT_SYMBOL(strcmp);
291#endif
292
293#ifndef __HAVE_ARCH_STRNCMP
294/**
295 * strncmp - Compare two length-limited strings
296 * @cs: One string
297 * @ct: Another string
298 * @count: The maximum number of bytes to compare
299 */
300int strncmp(const char *cs, const char *ct, size_t count)
301{
302 unsigned char c1, c2;
303
304 while (count) {
305 c1 = *cs++;
306 c2 = *ct++;
307 if (c1 != c2)
308 return c1 < c2 ? -1 : 1;
309 if (!c1)
310 break;
311 count--;
312 }
313 return 0;
314}
315EXPORT_SYMBOL(strncmp);
316#endif
317
318#ifndef __HAVE_ARCH_STRCHR
319/**
320 * strchr - Find the first occurrence of a character in a string
321 * @s: The string to be searched
322 * @c: The character to search for
323 *
324 * Note that the %NUL-terminator is considered part of the string, and can
325 * be searched for.
326 */
327char *strchr(const char *s, int c)
328{
329 for (; *s != (char)c; ++s)
330 if (*s == '\0')
331 return NULL;
332 return (char *)s;
333}
334EXPORT_SYMBOL(strchr);
335#endif
336
337#ifndef __HAVE_ARCH_STRCHRNUL
338/**
339 * strchrnul - Find and return a character in a string, or end of string
340 * @s: The string to be searched
341 * @c: The character to search for
342 *
343 * Returns pointer to first occurrence of 'c' in s. If c is not found, then
344 * return a pointer to the null byte at the end of s.
345 */
346char *strchrnul(const char *s, int c)
347{
348 while (*s && *s != (char)c)
349 s++;
350 return (char *)s;
351}
352EXPORT_SYMBOL(strchrnul);
353#endif
354
355/**
356 * strnchrnul - Find and return a character in a length limited string,
357 * or end of string
358 * @s: The string to be searched
359 * @count: The number of characters to be searched
360 * @c: The character to search for
361 *
362 * Returns pointer to the first occurrence of 'c' in s. If c is not found,
363 * then return a pointer to the last character of the string.
364 */
365char *strnchrnul(const char *s, size_t count, int c)
366{
367 while (count-- && *s && *s != (char)c)
368 s++;
369 return (char *)s;
370}
371
372#ifndef __HAVE_ARCH_STRRCHR
373/**
374 * strrchr - Find the last occurrence of a character in a string
375 * @s: The string to be searched
376 * @c: The character to search for
377 */
378char *strrchr(const char *s, int c)
379{
380 const char *last = NULL;
381 do {
382 if (*s == (char)c)
383 last = s;
384 } while (*s++);
385 return (char *)last;
386}
387EXPORT_SYMBOL(strrchr);
388#endif
389
390#ifndef __HAVE_ARCH_STRNCHR
391/**
392 * strnchr - Find a character in a length limited string
393 * @s: The string to be searched
394 * @count: The number of characters to be searched
395 * @c: The character to search for
396 *
397 * Note that the %NUL-terminator is considered part of the string, and can
398 * be searched for.
399 */
400char *strnchr(const char *s, size_t count, int c)
401{
402 while (count--) {
403 if (*s == (char)c)
404 return (char *)s;
405 if (*s++ == '\0')
406 break;
407 }
408 return NULL;
409}
410EXPORT_SYMBOL(strnchr);
411#endif
412
413#ifndef __HAVE_ARCH_STRLEN
414size_t strlen(const char *s)
415{
416 const char *sc;
417
418 for (sc = s; *sc != '\0'; ++sc)
419 /* nothing */;
420 return sc - s;
421}
422EXPORT_SYMBOL(strlen);
423#endif
424
425#ifndef __HAVE_ARCH_STRNLEN
426size_t strnlen(const char *s, size_t count)
427{
428 const char *sc;
429
430 for (sc = s; count-- && *sc != '\0'; ++sc)
431 /* nothing */;
432 return sc - s;
433}
434EXPORT_SYMBOL(strnlen);
435#endif
436
437#ifndef __HAVE_ARCH_STRSPN
438/**
439 * strspn - Calculate the length of the initial substring of @s which only contain letters in @accept
440 * @s: The string to be searched
441 * @accept: The string to search for
442 */
443size_t strspn(const char *s, const char *accept)
444{
445 const char *p;
446
447 for (p = s; *p != '\0'; ++p) {
448 if (!strchr(accept, *p))
449 break;
450 }
451 return p - s;
452}
453EXPORT_SYMBOL(strspn);
454#endif
455
456#ifndef __HAVE_ARCH_STRCSPN
457/**
458 * strcspn - Calculate the length of the initial substring of @s which does not contain letters in @reject
459 * @s: The string to be searched
460 * @reject: The string to avoid
461 */
462size_t strcspn(const char *s, const char *reject)
463{
464 const char *p;
465
466 for (p = s; *p != '\0'; ++p) {
467 if (strchr(reject, *p))
468 break;
469 }
470 return p - s;
471}
472EXPORT_SYMBOL(strcspn);
473#endif
474
475#ifndef __HAVE_ARCH_STRPBRK
476/**
477 * strpbrk - Find the first occurrence of a set of characters
478 * @cs: The string to be searched
479 * @ct: The characters to search for
480 */
481char *strpbrk(const char *cs, const char *ct)
482{
483 const char *sc1, *sc2;
484
485 for (sc1 = cs; *sc1 != '\0'; ++sc1) {
486 for (sc2 = ct; *sc2 != '\0'; ++sc2) {
487 if (*sc1 == *sc2)
488 return (char *)sc1;
489 }
490 }
491 return NULL;
492}
493EXPORT_SYMBOL(strpbrk);
494#endif
495
496#ifndef __HAVE_ARCH_STRSEP
497/**
498 * strsep - Split a string into tokens
499 * @s: The string to be searched
500 * @ct: The characters to search for
501 *
502 * strsep() updates @s to point after the token, ready for the next call.
503 *
504 * It returns empty tokens, too, behaving exactly like the libc function
505 * of that name. In fact, it was stolen from glibc2 and de-fancy-fied.
506 * Same semantics, slimmer shape. ;)
507 */
508char *strsep(char **s, const char *ct)
509{
510 char *sbegin = *s;
511 char *end;
512
513 if (sbegin == NULL)
514 return NULL;
515
516 end = strpbrk(sbegin, ct);
517 if (end)
518 *end++ = '\0';
519 *s = end;
520 return sbegin;
521}
522EXPORT_SYMBOL(strsep);
523#endif
524
525#ifndef __HAVE_ARCH_MEMSET
526/**
527 * memset - Fill a region of memory with the given value
528 * @s: Pointer to the start of the area.
529 * @c: The byte to fill the area with
530 * @count: The size of the area.
531 *
532 * Do not use memset() to access IO space, use memset_io() instead.
533 */
534void *memset(void *s, int c, size_t count)
535{
536 char *xs = s;
537
538 while (count--)
539 *xs++ = c;
540 return s;
541}
542EXPORT_SYMBOL(memset);
543#endif
544
545#ifndef __HAVE_ARCH_MEMSET16
546/**
547 * memset16() - Fill a memory area with a uint16_t
548 * @s: Pointer to the start of the area.
549 * @v: The value to fill the area with
550 * @count: The number of values to store
551 *
552 * Differs from memset() in that it fills with a uint16_t instead
553 * of a byte. Remember that @count is the number of uint16_ts to
554 * store, not the number of bytes.
555 */
556void *memset16(uint16_t *s, uint16_t v, size_t count)
557{
558 uint16_t *xs = s;
559
560 while (count--)
561 *xs++ = v;
562 return s;
563}
564EXPORT_SYMBOL(memset16);
565#endif
566
567#ifndef __HAVE_ARCH_MEMSET32
568/**
569 * memset32() - Fill a memory area with a uint32_t
570 * @s: Pointer to the start of the area.
571 * @v: The value to fill the area with
572 * @count: The number of values to store
573 *
574 * Differs from memset() in that it fills with a uint32_t instead
575 * of a byte. Remember that @count is the number of uint32_ts to
576 * store, not the number of bytes.
577 */
578void *memset32(uint32_t *s, uint32_t v, size_t count)
579{
580 uint32_t *xs = s;
581
582 while (count--)
583 *xs++ = v;
584 return s;
585}
586EXPORT_SYMBOL(memset32);
587#endif
588
589#ifndef __HAVE_ARCH_MEMSET64
590/**
591 * memset64() - Fill a memory area with a uint64_t
592 * @s: Pointer to the start of the area.
593 * @v: The value to fill the area with
594 * @count: The number of values to store
595 *
596 * Differs from memset() in that it fills with a uint64_t instead
597 * of a byte. Remember that @count is the number of uint64_ts to
598 * store, not the number of bytes.
599 */
600void *memset64(uint64_t *s, uint64_t v, size_t count)
601{
602 uint64_t *xs = s;
603
604 while (count--)
605 *xs++ = v;
606 return s;
607}
608EXPORT_SYMBOL(memset64);
609#endif
610
611#ifndef __HAVE_ARCH_MEMCPY
612/**
613 * memcpy - Copy one area of memory to another
614 * @dest: Where to copy to
615 * @src: Where to copy from
616 * @count: The size of the area.
617 *
618 * You should not use this function to access IO space, use memcpy_toio()
619 * or memcpy_fromio() instead.
620 */
621void *memcpy(void *dest, const void *src, size_t count)
622{
623 char *tmp = dest;
624 const char *s = src;
625
626 while (count--)
627 *tmp++ = *s++;
628 return dest;
629}
630EXPORT_SYMBOL(memcpy);
631#endif
632
633#ifndef __HAVE_ARCH_MEMMOVE
634/**
635 * memmove - Copy one area of memory to another
636 * @dest: Where to copy to
637 * @src: Where to copy from
638 * @count: The size of the area.
639 *
640 * Unlike memcpy(), memmove() copes with overlapping areas.
641 */
642void *memmove(void *dest, const void *src, size_t count)
643{
644 char *tmp;
645 const char *s;
646
647 if (dest <= src) {
648 tmp = dest;
649 s = src;
650 while (count--)
651 *tmp++ = *s++;
652 } else {
653 tmp = dest;
654 tmp += count;
655 s = src;
656 s += count;
657 while (count--)
658 *--tmp = *--s;
659 }
660 return dest;
661}
662EXPORT_SYMBOL(memmove);
663#endif
664
665#ifndef __HAVE_ARCH_MEMCMP
666/**
667 * memcmp - Compare two areas of memory
668 * @cs: One area of memory
669 * @ct: Another area of memory
670 * @count: The size of the area.
671 */
672#undef memcmp
673__visible int memcmp(const void *cs, const void *ct, size_t count)
674{
675 const unsigned char *su1, *su2;
676 int res = 0;
677
678#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
679 if (count >= sizeof(unsigned long)) {
680 const unsigned long *u1 = cs;
681 const unsigned long *u2 = ct;
682 do {
683 if (get_unaligned(u1) != get_unaligned(u2))
684 break;
685 u1++;
686 u2++;
687 count -= sizeof(unsigned long);
688 } while (count >= sizeof(unsigned long));
689 cs = u1;
690 ct = u2;
691 }
692#endif
693 for (su1 = cs, su2 = ct; 0 < count; ++su1, ++su2, count--)
694 if ((res = *su1 - *su2) != 0)
695 break;
696 return res;
697}
698EXPORT_SYMBOL(memcmp);
699#endif
700
701#ifndef __HAVE_ARCH_BCMP
702/**
703 * bcmp - returns 0 if and only if the buffers have identical contents.
704 * @a: pointer to first buffer.
705 * @b: pointer to second buffer.
706 * @len: size of buffers.
707 *
708 * The sign or magnitude of a non-zero return value has no particular
709 * meaning, and architectures may implement their own more efficient bcmp(). So
710 * while this particular implementation is a simple (tail) call to memcmp, do
711 * not rely on anything but whether the return value is zero or non-zero.
712 */
713int bcmp(const void *a, const void *b, size_t len)
714{
715 return memcmp(a, b, len);
716}
717EXPORT_SYMBOL(bcmp);
718#endif
719
720#ifndef __HAVE_ARCH_MEMSCAN
721/**
722 * memscan - Find a character in an area of memory.
723 * @addr: The memory area
724 * @c: The byte to search for
725 * @size: The size of the area.
726 *
727 * returns the address of the first occurrence of @c, or 1 byte past
728 * the area if @c is not found
729 */
730void *memscan(void *addr, int c, size_t size)
731{
732 unsigned char *p = addr;
733
734 while (size) {
735 if (*p == (unsigned char)c)
736 return (void *)p;
737 p++;
738 size--;
739 }
740 return (void *)p;
741}
742EXPORT_SYMBOL(memscan);
743#endif
744
745#ifndef __HAVE_ARCH_STRSTR
746/**
747 * strstr - Find the first substring in a %NUL terminated string
748 * @s1: The string to be searched
749 * @s2: The string to search for
750 */
751char *strstr(const char *s1, const char *s2)
752{
753 size_t l1, l2;
754
755 l2 = strlen(s2);
756 if (!l2)
757 return (char *)s1;
758 l1 = strlen(s1);
759 while (l1 >= l2) {
760 l1--;
761 if (!memcmp(s1, s2, l2))
762 return (char *)s1;
763 s1++;
764 }
765 return NULL;
766}
767EXPORT_SYMBOL(strstr);
768#endif
769
770#ifndef __HAVE_ARCH_STRNSTR
771/**
772 * strnstr - Find the first substring in a length-limited string
773 * @s1: The string to be searched
774 * @s2: The string to search for
775 * @len: the maximum number of characters to search
776 */
777char *strnstr(const char *s1, const char *s2, size_t len)
778{
779 size_t l2;
780
781 l2 = strlen(s2);
782 if (!l2)
783 return (char *)s1;
784 while (len >= l2) {
785 len--;
786 if (!memcmp(s1, s2, l2))
787 return (char *)s1;
788 s1++;
789 }
790 return NULL;
791}
792EXPORT_SYMBOL(strnstr);
793#endif
794
795#ifndef __HAVE_ARCH_MEMCHR
796/**
797 * memchr - Find a character in an area of memory.
798 * @s: The memory area
799 * @c: The byte to search for
800 * @n: The size of the area.
801 *
802 * returns the address of the first occurrence of @c, or %NULL
803 * if @c is not found
804 */
805void *memchr(const void *s, int c, size_t n)
806{
807 const unsigned char *p = s;
808 while (n-- != 0) {
809 if ((unsigned char)c == *p++) {
810 return (void *)(p - 1);
811 }
812 }
813 return NULL;
814}
815EXPORT_SYMBOL(memchr);
816#endif
817
818static void *check_bytes8(const u8 *start, u8 value, unsigned int bytes)
819{
820 while (bytes) {
821 if (*start != value)
822 return (void *)start;
823 start++;
824 bytes--;
825 }
826 return NULL;
827}
828
829/**
830 * memchr_inv - Find an unmatching character in an area of memory.
831 * @start: The memory area
832 * @c: Find a character other than c
833 * @bytes: The size of the area.
834 *
835 * returns the address of the first character other than @c, or %NULL
836 * if the whole buffer contains just @c.
837 */
838void *memchr_inv(const void *start, int c, size_t bytes)
839{
840 u8 value = c;
841 u64 value64;
842 unsigned int words, prefix;
843
844 if (bytes <= 16)
845 return check_bytes8(start, value, bytes);
846
847 value64 = value;
848#if defined(CONFIG_ARCH_HAS_FAST_MULTIPLIER) && BITS_PER_LONG == 64
849 value64 *= 0x0101010101010101ULL;
850#elif defined(CONFIG_ARCH_HAS_FAST_MULTIPLIER)
851 value64 *= 0x01010101;
852 value64 |= value64 << 32;
853#else
854 value64 |= value64 << 8;
855 value64 |= value64 << 16;
856 value64 |= value64 << 32;
857#endif
858
859 prefix = (unsigned long)start % 8;
860 if (prefix) {
861 u8 *r;
862
863 prefix = 8 - prefix;
864 r = check_bytes8(start, value, prefix);
865 if (r)
866 return r;
867 start += prefix;
868 bytes -= prefix;
869 }
870
871 words = bytes / 8;
872
873 while (words) {
874 if (*(u64 *)start != value64)
875 return check_bytes8(start, value, 8);
876 start += 8;
877 words--;
878 }
879
880 return check_bytes8(start, value, bytes % 8);
881}
882EXPORT_SYMBOL(memchr_inv);