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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
79/**
80 * strcpy - Copy a %NUL terminated string
81 * @dest: Where to copy the string to
82 * @src: Where to copy the string from
83 */
84char *strcpy(char *dest, const char *src)
85{
86 char *tmp = dest;
87
88 while ((*dest++ = *src++) != '\0')
89 /* nothing */;
90 return tmp;
91}
92EXPORT_SYMBOL(strcpy);
93#endif
94
95#ifndef __HAVE_ARCH_STRNCPY
96/**
97 * strncpy - Copy a length-limited, C-string
98 * @dest: Where to copy the string to
99 * @src: Where to copy the string from
100 * @count: The maximum number of bytes to copy
101 *
102 * The result is not %NUL-terminated if the source exceeds
103 * @count bytes.
104 *
105 * In the case where the length of @src is less than that of
106 * count, the remainder of @dest will be padded with %NUL.
107 *
108 */
109char *strncpy(char *dest, const char *src, size_t count)
110{
111 char *tmp = dest;
112
113 while (count) {
114 if ((*tmp = *src) != 0)
115 src++;
116 tmp++;
117 count--;
118 }
119 return dest;
120}
121EXPORT_SYMBOL(strncpy);
122#endif
123
124#ifndef __HAVE_ARCH_STRLCPY
125/**
126 * strlcpy - Copy a C-string into a sized buffer
127 * @dest: Where to copy the string to
128 * @src: Where to copy the string from
129 * @size: size of destination buffer
130 *
131 * Compatible with ``*BSD``: the result is always a valid
132 * NUL-terminated string that fits in the buffer (unless,
133 * of course, the buffer size is zero). It does not pad
134 * out the result like strncpy() does.
135 */
136size_t strlcpy(char *dest, const char *src, size_t size)
137{
138 size_t ret = strlen(src);
139
140 if (size) {
141 size_t len = (ret >= size) ? size - 1 : ret;
142 memcpy(dest, src, len);
143 dest[len] = '\0';
144 }
145 return ret;
146}
147EXPORT_SYMBOL(strlcpy);
148#endif
149
150#ifndef __HAVE_ARCH_STRSCPY
151/**
152 * strscpy - Copy a C-string into a sized buffer
153 * @dest: Where to copy the string to
154 * @src: Where to copy the string from
155 * @count: Size of destination buffer
156 *
157 * Copy the string, or as much of it as fits, into the dest buffer. The
158 * behavior is undefined if the string buffers overlap. The destination
159 * buffer is always NUL terminated, unless it's zero-sized.
160 *
161 * Preferred to strlcpy() since the API doesn't require reading memory
162 * from the src string beyond the specified "count" bytes, and since
163 * the return value is easier to error-check than strlcpy()'s.
164 * In addition, the implementation is robust to the string changing out
165 * from underneath it, unlike the current strlcpy() implementation.
166 *
167 * Preferred to strncpy() since it always returns a valid string, and
168 * doesn't unnecessarily force the tail of the destination buffer to be
169 * zeroed. If zeroing is desired please use strscpy_pad().
170 *
171 * Returns:
172 * * The number of characters copied (not including the trailing %NUL)
173 * * -E2BIG if count is 0 or @src was truncated.
174 */
175ssize_t strscpy(char *dest, const char *src, size_t count)
176{
177 const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
178 size_t max = count;
179 long res = 0;
180
181 if (count == 0 || WARN_ON_ONCE(count > INT_MAX))
182 return -E2BIG;
183
184#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
185 /*
186 * If src is unaligned, don't cross a page boundary,
187 * since we don't know if the next page is mapped.
188 */
189 if ((long)src & (sizeof(long) - 1)) {
190 size_t limit = PAGE_SIZE - ((long)src & (PAGE_SIZE - 1));
191 if (limit < max)
192 max = limit;
193 }
194#else
195 /* If src or dest is unaligned, don't do word-at-a-time. */
196 if (((long) dest | (long) src) & (sizeof(long) - 1))
197 max = 0;
198#endif
199
200 while (max >= sizeof(unsigned long)) {
201 unsigned long c, data;
202
203 c = read_word_at_a_time(src+res);
204 if (has_zero(c, &data, &constants)) {
205 data = prep_zero_mask(c, data, &constants);
206 data = create_zero_mask(data);
207 *(unsigned long *)(dest+res) = c & zero_bytemask(data);
208 return res + find_zero(data);
209 }
210 *(unsigned long *)(dest+res) = c;
211 res += sizeof(unsigned long);
212 count -= sizeof(unsigned long);
213 max -= sizeof(unsigned long);
214 }
215
216 while (count) {
217 char c;
218
219 c = src[res];
220 dest[res] = c;
221 if (!c)
222 return res;
223 res++;
224 count--;
225 }
226
227 /* Hit buffer length without finding a NUL; force NUL-termination. */
228 if (res)
229 dest[res-1] = '\0';
230
231 return -E2BIG;
232}
233EXPORT_SYMBOL(strscpy);
234#endif
235
236/**
237 * stpcpy - copy a string from src to dest returning a pointer to the new end
238 * of dest, including src's %NUL-terminator. May overrun dest.
239 * @dest: pointer to end of string being copied into. Must be large enough
240 * to receive copy.
241 * @src: pointer to the beginning of string being copied from. Must not overlap
242 * dest.
243 *
244 * stpcpy differs from strcpy in a key way: the return value is a pointer
245 * to the new %NUL-terminating character in @dest. (For strcpy, the return
246 * value is a pointer to the start of @dest). This interface is considered
247 * unsafe as it doesn't perform bounds checking of the inputs. As such it's
248 * not recommended for usage. Instead, its definition is provided in case
249 * the compiler lowers other libcalls to stpcpy.
250 */
251char *stpcpy(char *__restrict__ dest, const char *__restrict__ src);
252char *stpcpy(char *__restrict__ dest, const char *__restrict__ src)
253{
254 while ((*dest++ = *src++) != '\0')
255 /* nothing */;
256 return --dest;
257}
258EXPORT_SYMBOL(stpcpy);
259
260#ifndef __HAVE_ARCH_STRCAT
261/**
262 * strcat - Append one %NUL-terminated string to another
263 * @dest: The string to be appended to
264 * @src: The string to append to it
265 */
266char *strcat(char *dest, const char *src)
267{
268 char *tmp = dest;
269
270 while (*dest)
271 dest++;
272 while ((*dest++ = *src++) != '\0')
273 ;
274 return tmp;
275}
276EXPORT_SYMBOL(strcat);
277#endif
278
279#ifndef __HAVE_ARCH_STRNCAT
280/**
281 * strncat - Append a length-limited, C-string to another
282 * @dest: The string to be appended to
283 * @src: The string to append to it
284 * @count: The maximum numbers of bytes to copy
285 *
286 * Note that in contrast to strncpy(), strncat() ensures the result is
287 * terminated.
288 */
289char *strncat(char *dest, const char *src, size_t count)
290{
291 char *tmp = dest;
292
293 if (count) {
294 while (*dest)
295 dest++;
296 while ((*dest++ = *src++) != 0) {
297 if (--count == 0) {
298 *dest = '\0';
299 break;
300 }
301 }
302 }
303 return tmp;
304}
305EXPORT_SYMBOL(strncat);
306#endif
307
308#ifndef __HAVE_ARCH_STRLCAT
309/**
310 * strlcat - Append a length-limited, C-string to another
311 * @dest: The string to be appended to
312 * @src: The string to append to it
313 * @count: The size of the destination buffer.
314 */
315size_t strlcat(char *dest, const char *src, size_t count)
316{
317 size_t dsize = strlen(dest);
318 size_t len = strlen(src);
319 size_t res = dsize + len;
320
321 /* This would be a bug */
322 BUG_ON(dsize >= count);
323
324 dest += dsize;
325 count -= dsize;
326 if (len >= count)
327 len = count-1;
328 memcpy(dest, src, len);
329 dest[len] = 0;
330 return res;
331}
332EXPORT_SYMBOL(strlcat);
333#endif
334
335#ifndef __HAVE_ARCH_STRCMP
336/**
337 * strcmp - Compare two strings
338 * @cs: One string
339 * @ct: Another string
340 */
341int strcmp(const char *cs, const char *ct)
342{
343 unsigned char c1, c2;
344
345 while (1) {
346 c1 = *cs++;
347 c2 = *ct++;
348 if (c1 != c2)
349 return c1 < c2 ? -1 : 1;
350 if (!c1)
351 break;
352 }
353 return 0;
354}
355EXPORT_SYMBOL(strcmp);
356#endif
357
358#ifndef __HAVE_ARCH_STRNCMP
359/**
360 * strncmp - Compare two length-limited strings
361 * @cs: One string
362 * @ct: Another string
363 * @count: The maximum number of bytes to compare
364 */
365int strncmp(const char *cs, const char *ct, size_t count)
366{
367 unsigned char c1, c2;
368
369 while (count) {
370 c1 = *cs++;
371 c2 = *ct++;
372 if (c1 != c2)
373 return c1 < c2 ? -1 : 1;
374 if (!c1)
375 break;
376 count--;
377 }
378 return 0;
379}
380EXPORT_SYMBOL(strncmp);
381#endif
382
383#ifndef __HAVE_ARCH_STRCHR
384/**
385 * strchr - Find the first occurrence of a character in a string
386 * @s: The string to be searched
387 * @c: The character to search for
388 *
389 * Note that the %NUL-terminator is considered part of the string, and can
390 * be searched for.
391 */
392char *strchr(const char *s, int c)
393{
394 for (; *s != (char)c; ++s)
395 if (*s == '\0')
396 return NULL;
397 return (char *)s;
398}
399EXPORT_SYMBOL(strchr);
400#endif
401
402#ifndef __HAVE_ARCH_STRCHRNUL
403/**
404 * strchrnul - Find and return a character in a string, or end of string
405 * @s: The string to be searched
406 * @c: The character to search for
407 *
408 * Returns pointer to first occurrence of 'c' in s. If c is not found, then
409 * return a pointer to the null byte at the end of s.
410 */
411char *strchrnul(const char *s, int c)
412{
413 while (*s && *s != (char)c)
414 s++;
415 return (char *)s;
416}
417EXPORT_SYMBOL(strchrnul);
418#endif
419
420/**
421 * strnchrnul - Find and return a character in a length limited string,
422 * or end of string
423 * @s: The string to be searched
424 * @count: The number of characters to be searched
425 * @c: The character to search for
426 *
427 * Returns pointer to the first occurrence of 'c' in s. If c is not found,
428 * then return a pointer to the last character of the string.
429 */
430char *strnchrnul(const char *s, size_t count, int c)
431{
432 while (count-- && *s && *s != (char)c)
433 s++;
434 return (char *)s;
435}
436
437#ifndef __HAVE_ARCH_STRRCHR
438/**
439 * strrchr - Find the last occurrence of a character in a string
440 * @s: The string to be searched
441 * @c: The character to search for
442 */
443char *strrchr(const char *s, int c)
444{
445 const char *last = NULL;
446 do {
447 if (*s == (char)c)
448 last = s;
449 } while (*s++);
450 return (char *)last;
451}
452EXPORT_SYMBOL(strrchr);
453#endif
454
455#ifndef __HAVE_ARCH_STRNCHR
456/**
457 * strnchr - Find a character in a length limited string
458 * @s: The string to be searched
459 * @count: The number of characters to be searched
460 * @c: The character to search for
461 *
462 * Note that the %NUL-terminator is considered part of the string, and can
463 * be searched for.
464 */
465char *strnchr(const char *s, size_t count, int c)
466{
467 while (count--) {
468 if (*s == (char)c)
469 return (char *)s;
470 if (*s++ == '\0')
471 break;
472 }
473 return NULL;
474}
475EXPORT_SYMBOL(strnchr);
476#endif
477
478#ifndef __HAVE_ARCH_STRLEN
479/**
480 * strlen - Find the length of a string
481 * @s: The string to be sized
482 */
483size_t strlen(const char *s)
484{
485 const char *sc;
486
487 for (sc = s; *sc != '\0'; ++sc)
488 /* nothing */;
489 return sc - s;
490}
491EXPORT_SYMBOL(strlen);
492#endif
493
494#ifndef __HAVE_ARCH_STRNLEN
495/**
496 * strnlen - Find the length of a length-limited string
497 * @s: The string to be sized
498 * @count: The maximum number of bytes to search
499 */
500size_t strnlen(const char *s, size_t count)
501{
502 const char *sc;
503
504 for (sc = s; count-- && *sc != '\0'; ++sc)
505 /* nothing */;
506 return sc - s;
507}
508EXPORT_SYMBOL(strnlen);
509#endif
510
511#ifndef __HAVE_ARCH_STRSPN
512/**
513 * strspn - Calculate the length of the initial substring of @s which only contain letters in @accept
514 * @s: The string to be searched
515 * @accept: The string to search for
516 */
517size_t strspn(const char *s, const char *accept)
518{
519 const char *p;
520
521 for (p = s; *p != '\0'; ++p) {
522 if (!strchr(accept, *p))
523 break;
524 }
525 return p - s;
526}
527EXPORT_SYMBOL(strspn);
528#endif
529
530#ifndef __HAVE_ARCH_STRCSPN
531/**
532 * strcspn - Calculate the length of the initial substring of @s which does not contain letters in @reject
533 * @s: The string to be searched
534 * @reject: The string to avoid
535 */
536size_t strcspn(const char *s, const char *reject)
537{
538 const char *p;
539
540 for (p = s; *p != '\0'; ++p) {
541 if (strchr(reject, *p))
542 break;
543 }
544 return p - s;
545}
546EXPORT_SYMBOL(strcspn);
547#endif
548
549#ifndef __HAVE_ARCH_STRPBRK
550/**
551 * strpbrk - Find the first occurrence of a set of characters
552 * @cs: The string to be searched
553 * @ct: The characters to search for
554 */
555char *strpbrk(const char *cs, const char *ct)
556{
557 const char *sc1, *sc2;
558
559 for (sc1 = cs; *sc1 != '\0'; ++sc1) {
560 for (sc2 = ct; *sc2 != '\0'; ++sc2) {
561 if (*sc1 == *sc2)
562 return (char *)sc1;
563 }
564 }
565 return NULL;
566}
567EXPORT_SYMBOL(strpbrk);
568#endif
569
570#ifndef __HAVE_ARCH_STRSEP
571/**
572 * strsep - Split a string into tokens
573 * @s: The string to be searched
574 * @ct: The characters to search for
575 *
576 * strsep() updates @s to point after the token, ready for the next call.
577 *
578 * It returns empty tokens, too, behaving exactly like the libc function
579 * of that name. In fact, it was stolen from glibc2 and de-fancy-fied.
580 * Same semantics, slimmer shape. ;)
581 */
582char *strsep(char **s, const char *ct)
583{
584 char *sbegin = *s;
585 char *end;
586
587 if (sbegin == NULL)
588 return NULL;
589
590 end = strpbrk(sbegin, ct);
591 if (end)
592 *end++ = '\0';
593 *s = end;
594 return sbegin;
595}
596EXPORT_SYMBOL(strsep);
597#endif
598
599#ifndef __HAVE_ARCH_MEMSET
600/**
601 * memset - Fill a region of memory with the given value
602 * @s: Pointer to the start of the area.
603 * @c: The byte to fill the area with
604 * @count: The size of the area.
605 *
606 * Do not use memset() to access IO space, use memset_io() instead.
607 */
608void *memset(void *s, int c, size_t count)
609{
610 char *xs = s;
611
612 while (count--)
613 *xs++ = c;
614 return s;
615}
616EXPORT_SYMBOL(memset);
617#endif
618
619#ifndef __HAVE_ARCH_MEMSET16
620/**
621 * memset16() - Fill a memory area with a uint16_t
622 * @s: Pointer to the start of the area.
623 * @v: The value to fill the area with
624 * @count: The number of values to store
625 *
626 * Differs from memset() in that it fills with a uint16_t instead
627 * of a byte. Remember that @count is the number of uint16_ts to
628 * store, not the number of bytes.
629 */
630void *memset16(uint16_t *s, uint16_t v, size_t count)
631{
632 uint16_t *xs = s;
633
634 while (count--)
635 *xs++ = v;
636 return s;
637}
638EXPORT_SYMBOL(memset16);
639#endif
640
641#ifndef __HAVE_ARCH_MEMSET32
642/**
643 * memset32() - Fill a memory area with a uint32_t
644 * @s: Pointer to the start of the area.
645 * @v: The value to fill the area with
646 * @count: The number of values to store
647 *
648 * Differs from memset() in that it fills with a uint32_t instead
649 * of a byte. Remember that @count is the number of uint32_ts to
650 * store, not the number of bytes.
651 */
652void *memset32(uint32_t *s, uint32_t v, size_t count)
653{
654 uint32_t *xs = s;
655
656 while (count--)
657 *xs++ = v;
658 return s;
659}
660EXPORT_SYMBOL(memset32);
661#endif
662
663#ifndef __HAVE_ARCH_MEMSET64
664/**
665 * memset64() - Fill a memory area with a uint64_t
666 * @s: Pointer to the start of the area.
667 * @v: The value to fill the area with
668 * @count: The number of values to store
669 *
670 * Differs from memset() in that it fills with a uint64_t instead
671 * of a byte. Remember that @count is the number of uint64_ts to
672 * store, not the number of bytes.
673 */
674void *memset64(uint64_t *s, uint64_t v, size_t count)
675{
676 uint64_t *xs = s;
677
678 while (count--)
679 *xs++ = v;
680 return s;
681}
682EXPORT_SYMBOL(memset64);
683#endif
684
685#ifndef __HAVE_ARCH_MEMCPY
686/**
687 * memcpy - Copy one area of memory to another
688 * @dest: Where to copy to
689 * @src: Where to copy from
690 * @count: The size of the area.
691 *
692 * You should not use this function to access IO space, use memcpy_toio()
693 * or memcpy_fromio() instead.
694 */
695void *memcpy(void *dest, const void *src, size_t count)
696{
697 char *tmp = dest;
698 const char *s = src;
699
700 while (count--)
701 *tmp++ = *s++;
702 return dest;
703}
704EXPORT_SYMBOL(memcpy);
705#endif
706
707#ifndef __HAVE_ARCH_MEMMOVE
708/**
709 * memmove - Copy one area of memory to another
710 * @dest: Where to copy to
711 * @src: Where to copy from
712 * @count: The size of the area.
713 *
714 * Unlike memcpy(), memmove() copes with overlapping areas.
715 */
716void *memmove(void *dest, const void *src, size_t count)
717{
718 char *tmp;
719 const char *s;
720
721 if (dest <= src) {
722 tmp = dest;
723 s = src;
724 while (count--)
725 *tmp++ = *s++;
726 } else {
727 tmp = dest;
728 tmp += count;
729 s = src;
730 s += count;
731 while (count--)
732 *--tmp = *--s;
733 }
734 return dest;
735}
736EXPORT_SYMBOL(memmove);
737#endif
738
739#ifndef __HAVE_ARCH_MEMCMP
740/**
741 * memcmp - Compare two areas of memory
742 * @cs: One area of memory
743 * @ct: Another area of memory
744 * @count: The size of the area.
745 */
746#undef memcmp
747__visible int memcmp(const void *cs, const void *ct, size_t count)
748{
749 const unsigned char *su1, *su2;
750 int res = 0;
751
752#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
753 if (count >= sizeof(unsigned long)) {
754 const unsigned long *u1 = cs;
755 const unsigned long *u2 = ct;
756 do {
757 if (get_unaligned(u1) != get_unaligned(u2))
758 break;
759 u1++;
760 u2++;
761 count -= sizeof(unsigned long);
762 } while (count >= sizeof(unsigned long));
763 cs = u1;
764 ct = u2;
765 }
766#endif
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_BCMP
776/**
777 * bcmp - returns 0 if and only if the buffers have identical contents.
778 * @a: pointer to first buffer.
779 * @b: pointer to second buffer.
780 * @len: size of buffers.
781 *
782 * The sign or magnitude of a non-zero return value has no particular
783 * meaning, and architectures may implement their own more efficient bcmp(). So
784 * while this particular implementation is a simple (tail) call to memcmp, do
785 * not rely on anything but whether the return value is zero or non-zero.
786 */
787int bcmp(const void *a, const void *b, size_t len)
788{
789 return memcmp(a, b, len);
790}
791EXPORT_SYMBOL(bcmp);
792#endif
793
794#ifndef __HAVE_ARCH_MEMSCAN
795/**
796 * memscan - Find a character in an area of memory.
797 * @addr: The memory area
798 * @c: The byte to search for
799 * @size: The size of the area.
800 *
801 * returns the address of the first occurrence of @c, or 1 byte past
802 * the area if @c is not found
803 */
804void *memscan(void *addr, int c, size_t size)
805{
806 unsigned char *p = addr;
807
808 while (size) {
809 if (*p == (unsigned char)c)
810 return (void *)p;
811 p++;
812 size--;
813 }
814 return (void *)p;
815}
816EXPORT_SYMBOL(memscan);
817#endif
818
819#ifndef __HAVE_ARCH_STRSTR
820/**
821 * strstr - Find the first substring in a %NUL terminated string
822 * @s1: The string to be searched
823 * @s2: The string to search for
824 */
825char *strstr(const char *s1, const char *s2)
826{
827 size_t l1, l2;
828
829 l2 = strlen(s2);
830 if (!l2)
831 return (char *)s1;
832 l1 = strlen(s1);
833 while (l1 >= l2) {
834 l1--;
835 if (!memcmp(s1, s2, l2))
836 return (char *)s1;
837 s1++;
838 }
839 return NULL;
840}
841EXPORT_SYMBOL(strstr);
842#endif
843
844#ifndef __HAVE_ARCH_STRNSTR
845/**
846 * strnstr - Find the first substring in a length-limited string
847 * @s1: The string to be searched
848 * @s2: The string to search for
849 * @len: the maximum number of characters to search
850 */
851char *strnstr(const char *s1, const char *s2, size_t len)
852{
853 size_t l2;
854
855 l2 = strlen(s2);
856 if (!l2)
857 return (char *)s1;
858 while (len >= l2) {
859 len--;
860 if (!memcmp(s1, s2, l2))
861 return (char *)s1;
862 s1++;
863 }
864 return NULL;
865}
866EXPORT_SYMBOL(strnstr);
867#endif
868
869#ifndef __HAVE_ARCH_MEMCHR
870/**
871 * memchr - Find a character in an area of memory.
872 * @s: The memory area
873 * @c: The byte to search for
874 * @n: The size of the area.
875 *
876 * returns the address of the first occurrence of @c, or %NULL
877 * if @c is not found
878 */
879void *memchr(const void *s, int c, size_t n)
880{
881 const unsigned char *p = s;
882 while (n-- != 0) {
883 if ((unsigned char)c == *p++) {
884 return (void *)(p - 1);
885 }
886 }
887 return NULL;
888}
889EXPORT_SYMBOL(memchr);
890#endif
891
892static void *check_bytes8(const u8 *start, u8 value, unsigned int bytes)
893{
894 while (bytes) {
895 if (*start != value)
896 return (void *)start;
897 start++;
898 bytes--;
899 }
900 return NULL;
901}
902
903/**
904 * memchr_inv - Find an unmatching character in an area of memory.
905 * @start: The memory area
906 * @c: Find a character other than c
907 * @bytes: The size of the area.
908 *
909 * returns the address of the first character other than @c, or %NULL
910 * if the whole buffer contains just @c.
911 */
912void *memchr_inv(const void *start, int c, size_t bytes)
913{
914 u8 value = c;
915 u64 value64;
916 unsigned int words, prefix;
917
918 if (bytes <= 16)
919 return check_bytes8(start, value, bytes);
920
921 value64 = value;
922#if defined(CONFIG_ARCH_HAS_FAST_MULTIPLIER) && BITS_PER_LONG == 64
923 value64 *= 0x0101010101010101ULL;
924#elif defined(CONFIG_ARCH_HAS_FAST_MULTIPLIER)
925 value64 *= 0x01010101;
926 value64 |= value64 << 32;
927#else
928 value64 |= value64 << 8;
929 value64 |= value64 << 16;
930 value64 |= value64 << 32;
931#endif
932
933 prefix = (unsigned long)start % 8;
934 if (prefix) {
935 u8 *r;
936
937 prefix = 8 - prefix;
938 r = check_bytes8(start, value, prefix);
939 if (r)
940 return r;
941 start += prefix;
942 bytes -= prefix;
943 }
944
945 words = bytes / 8;
946
947 while (words) {
948 if (*(u64 *)start != value64)
949 return check_bytes8(start, value, 8);
950 start += 8;
951 words--;
952 }
953
954 return check_bytes8(start, value, bytes % 8);
955}
956EXPORT_SYMBOL(memchr_inv);