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 __builtin_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(addr: src+res);
159 if (has_zero(a: c, bits: &data, c: &constants)) {
160 data = prep_zero_mask(a: c, bits: data, c: &constants);
161 data = create_zero_mask(bits: data);
162 *(unsigned long *)(dest+res) = c & zero_bytemask(data);
163 return res + find_zero(mask: 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 __builtin_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 *sc;
484
485 for (sc = cs; *sc != '\0'; ++sc) {
486 if (strchr(ct, *sc))
487 return (char *)sc;
488 }
489 return NULL;
490}
491EXPORT_SYMBOL(strpbrk);
492#endif
493
494#ifndef __HAVE_ARCH_STRSEP
495/**
496 * strsep - Split a string into tokens
497 * @s: The string to be searched
498 * @ct: The characters to search for
499 *
500 * strsep() updates @s to point after the token, ready for the next call.
501 *
502 * It returns empty tokens, too, behaving exactly like the libc function
503 * of that name. In fact, it was stolen from glibc2 and de-fancy-fied.
504 * Same semantics, slimmer shape. ;)
505 */
506char *strsep(char **s, const char *ct)
507{
508 char *sbegin = *s;
509 char *end;
510
511 if (sbegin == NULL)
512 return NULL;
513
514 end = strpbrk(sbegin, ct);
515 if (end)
516 *end++ = '\0';
517 *s = end;
518 return sbegin;
519}
520EXPORT_SYMBOL(strsep);
521#endif
522
523#ifndef __HAVE_ARCH_MEMSET
524/**
525 * memset - Fill a region of memory with the given value
526 * @s: Pointer to the start of the area.
527 * @c: The byte to fill the area with
528 * @count: The size of the area.
529 *
530 * Do not use memset() to access IO space, use memset_io() instead.
531 */
532void *memset(void *s, int c, size_t count)
533{
534 char *xs = s;
535
536 while (count--)
537 *xs++ = c;
538 return s;
539}
540EXPORT_SYMBOL(memset);
541#endif
542
543#ifndef __HAVE_ARCH_MEMSET16
544/**
545 * memset16() - Fill a memory area with a uint16_t
546 * @s: Pointer to the start of the area.
547 * @v: The value to fill the area with
548 * @count: The number of values to store
549 *
550 * Differs from memset() in that it fills with a uint16_t instead
551 * of a byte. Remember that @count is the number of uint16_ts to
552 * store, not the number of bytes.
553 */
554void *memset16(uint16_t *s, uint16_t v, size_t count)
555{
556 uint16_t *xs = s;
557
558 while (count--)
559 *xs++ = v;
560 return s;
561}
562EXPORT_SYMBOL(memset16);
563#endif
564
565#ifndef __HAVE_ARCH_MEMSET32
566/**
567 * memset32() - Fill a memory area with a uint32_t
568 * @s: Pointer to the start of the area.
569 * @v: The value to fill the area with
570 * @count: The number of values to store
571 *
572 * Differs from memset() in that it fills with a uint32_t instead
573 * of a byte. Remember that @count is the number of uint32_ts to
574 * store, not the number of bytes.
575 */
576void *memset32(uint32_t *s, uint32_t v, size_t count)
577{
578 uint32_t *xs = s;
579
580 while (count--)
581 *xs++ = v;
582 return s;
583}
584EXPORT_SYMBOL(memset32);
585#endif
586
587#ifndef __HAVE_ARCH_MEMSET64
588/**
589 * memset64() - Fill a memory area with a uint64_t
590 * @s: Pointer to the start of the area.
591 * @v: The value to fill the area with
592 * @count: The number of values to store
593 *
594 * Differs from memset() in that it fills with a uint64_t instead
595 * of a byte. Remember that @count is the number of uint64_ts to
596 * store, not the number of bytes.
597 */
598void *memset64(uint64_t *s, uint64_t v, size_t count)
599{
600 uint64_t *xs = s;
601
602 while (count--)
603 *xs++ = v;
604 return s;
605}
606EXPORT_SYMBOL(memset64);
607#endif
608
609#ifndef __HAVE_ARCH_MEMCPY
610/**
611 * memcpy - Copy one area of memory to another
612 * @dest: Where to copy to
613 * @src: Where to copy from
614 * @count: The size of the area.
615 *
616 * You should not use this function to access IO space, use memcpy_toio()
617 * or memcpy_fromio() instead.
618 */
619void *memcpy(void *dest, const void *src, size_t count)
620{
621 char *tmp = dest;
622 const char *s = src;
623
624 while (count--)
625 *tmp++ = *s++;
626 return dest;
627}
628EXPORT_SYMBOL(memcpy);
629#endif
630
631#ifndef __HAVE_ARCH_MEMMOVE
632/**
633 * memmove - Copy one area of memory to another
634 * @dest: Where to copy to
635 * @src: Where to copy from
636 * @count: The size of the area.
637 *
638 * Unlike memcpy(), memmove() copes with overlapping areas.
639 */
640void *memmove(void *dest, const void *src, size_t count)
641{
642 char *tmp;
643 const char *s;
644
645 if (dest <= src) {
646 tmp = dest;
647 s = src;
648 while (count--)
649 *tmp++ = *s++;
650 } else {
651 tmp = dest;
652 tmp += count;
653 s = src;
654 s += count;
655 while (count--)
656 *--tmp = *--s;
657 }
658 return dest;
659}
660EXPORT_SYMBOL(memmove);
661#endif
662
663#ifndef __HAVE_ARCH_MEMCMP
664/**
665 * memcmp - Compare two areas of memory
666 * @cs: One area of memory
667 * @ct: Another area of memory
668 * @count: The size of the area.
669 */
670#undef memcmp
671__visible int memcmp(const void *cs, const void *ct, size_t count)
672{
673 const unsigned char *su1, *su2;
674 int res = 0;
675
676#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
677 if (count >= sizeof(unsigned long)) {
678 const unsigned long *u1 = cs;
679 const unsigned long *u2 = ct;
680 do {
681 if (get_unaligned(u1) != get_unaligned(u2))
682 break;
683 u1++;
684 u2++;
685 count -= sizeof(unsigned long);
686 } while (count >= sizeof(unsigned long));
687 cs = u1;
688 ct = u2;
689 }
690#endif
691 for (su1 = cs, su2 = ct; 0 < count; ++su1, ++su2, count--)
692 if ((res = *su1 - *su2) != 0)
693 break;
694 return res;
695}
696EXPORT_SYMBOL(memcmp);
697#endif
698
699#ifndef __HAVE_ARCH_BCMP
700/**
701 * bcmp - returns 0 if and only if the buffers have identical contents.
702 * @a: pointer to first buffer.
703 * @b: pointer to second buffer.
704 * @len: size of buffers.
705 *
706 * The sign or magnitude of a non-zero return value has no particular
707 * meaning, and architectures may implement their own more efficient bcmp(). So
708 * while this particular implementation is a simple (tail) call to memcmp, do
709 * not rely on anything but whether the return value is zero or non-zero.
710 */
711int bcmp(const void *a, const void *b, size_t len)
712{
713 return memcmp(a, b, len);
714}
715EXPORT_SYMBOL(bcmp);
716#endif
717
718#ifndef __HAVE_ARCH_MEMSCAN
719/**
720 * memscan - Find a character in an area of memory.
721 * @addr: The memory area
722 * @c: The byte to search for
723 * @size: The size of the area.
724 *
725 * returns the address of the first occurrence of @c, or 1 byte past
726 * the area if @c is not found
727 */
728void *memscan(void *addr, int c, size_t size)
729{
730 unsigned char *p = addr;
731
732 while (size) {
733 if (*p == (unsigned char)c)
734 return (void *)p;
735 p++;
736 size--;
737 }
738 return (void *)p;
739}
740EXPORT_SYMBOL(memscan);
741#endif
742
743#ifndef __HAVE_ARCH_STRSTR
744/**
745 * strstr - Find the first substring in a %NUL terminated string
746 * @s1: The string to be searched
747 * @s2: The string to search for
748 */
749char *strstr(const char *s1, const char *s2)
750{
751 size_t l1, l2;
752
753 l2 = strlen(s2);
754 if (!l2)
755 return (char *)s1;
756 l1 = strlen(s1);
757 while (l1 >= l2) {
758 l1--;
759 if (!memcmp(s1, s2, l2))
760 return (char *)s1;
761 s1++;
762 }
763 return NULL;
764}
765EXPORT_SYMBOL(strstr);
766#endif
767
768#ifndef __HAVE_ARCH_STRNSTR
769/**
770 * strnstr - Find the first substring in a length-limited string
771 * @s1: The string to be searched
772 * @s2: The string to search for
773 * @len: the maximum number of characters to search
774 */
775char *strnstr(const char *s1, const char *s2, size_t len)
776{
777 size_t l2;
778
779 l2 = strlen(s2);
780 if (!l2)
781 return (char *)s1;
782 while (len >= l2) {
783 len--;
784 if (!memcmp(s1, s2, l2))
785 return (char *)s1;
786 s1++;
787 }
788 return NULL;
789}
790EXPORT_SYMBOL(strnstr);
791#endif
792
793#ifndef __HAVE_ARCH_MEMCHR
794/**
795 * memchr - Find a character in an area of memory.
796 * @s: The memory area
797 * @c: The byte to search for
798 * @n: The size of the area.
799 *
800 * returns the address of the first occurrence of @c, or %NULL
801 * if @c is not found
802 */
803void *memchr(const void *s, int c, size_t n)
804{
805 const unsigned char *p = s;
806 while (n-- != 0) {
807 if ((unsigned char)c == *p++) {
808 return (void *)(p - 1);
809 }
810 }
811 return NULL;
812}
813EXPORT_SYMBOL(memchr);
814#endif
815
816static void *check_bytes8(const u8 *start, u8 value, unsigned int bytes)
817{
818 while (bytes) {
819 if (*start != value)
820 return (void *)start;
821 start++;
822 bytes--;
823 }
824 return NULL;
825}
826
827/**
828 * memchr_inv - Find an unmatching character in an area of memory.
829 * @start: The memory area
830 * @c: Find a character other than c
831 * @bytes: The size of the area.
832 *
833 * returns the address of the first character other than @c, or %NULL
834 * if the whole buffer contains just @c.
835 */
836void *memchr_inv(const void *start, int c, size_t bytes)
837{
838 u8 value = c;
839 u64 value64;
840 unsigned int words, prefix;
841
842 if (bytes <= 16)
843 return check_bytes8(start, value, bytes);
844
845 value64 = value;
846#if defined(CONFIG_ARCH_HAS_FAST_MULTIPLIER) && BITS_PER_LONG == 64
847 value64 *= 0x0101010101010101ULL;
848#elif defined(CONFIG_ARCH_HAS_FAST_MULTIPLIER)
849 value64 *= 0x01010101;
850 value64 |= value64 << 32;
851#else
852 value64 |= value64 << 8;
853 value64 |= value64 << 16;
854 value64 |= value64 << 32;
855#endif
856
857 prefix = (unsigned long)start % 8;
858 if (prefix) {
859 u8 *r;
860
861 prefix = 8 - prefix;
862 r = check_bytes8(start, value, bytes: prefix);
863 if (r)
864 return r;
865 start += prefix;
866 bytes -= prefix;
867 }
868
869 words = bytes / 8;
870
871 while (words) {
872 if (*(u64 *)start != value64)
873 return check_bytes8(start, value, bytes: 8);
874 start += 8;
875 words--;
876 }
877
878 return check_bytes8(start, value, bytes: bytes % 8);
879}
880EXPORT_SYMBOL(memchr_inv);
881

source code of linux/lib/string.c