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1 // SPDX-License-Identifier: GPL-2.0
5 * Copyright (C) 1991, 1992 Linus Torvalds
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.)
14 * Other helper functions should live in string_helpers.c.
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>
27 #include <asm/unaligned.h>
28 #include <asm/byteorder.h>
29 #include <asm/word-at-a-time.h>
32 #ifndef __HAVE_ARCH_STRNCASECMP
34 * strncasecmp - Case insensitive, length-limited string comparison
36 * @s2: The other string
37 * @len: the maximum number of characters to compare
39 int strncasecmp(const char *s1
, const char *s2
, size_t len
)
41 /* Yes, Virginia, it had better be unsigned */
59 return (int)c1
- (int)c2
;
61 EXPORT_SYMBOL(strncasecmp
);
64 #ifndef __HAVE_ARCH_STRCASECMP
65 int strcasecmp(const char *s1
, const char *s2
)
72 } while (c1
== c2
&& c1
!= 0);
75 EXPORT_SYMBOL(strcasecmp
);
78 #ifndef __HAVE_ARCH_STRCPY
79 char *strcpy(char *dest
, const char *src
)
83 while ((*dest
++ = *src
++) != '\0')
87 EXPORT_SYMBOL(strcpy
);
90 #ifndef __HAVE_ARCH_STRNCPY
91 char *strncpy(char *dest
, const char *src
, size_t count
)
96 if ((*tmp
= *src
) != 0)
103 EXPORT_SYMBOL(strncpy
);
106 #ifndef __HAVE_ARCH_STRLCPY
107 size_t strlcpy(char *dest
, const char *src
, size_t size
)
109 size_t ret
= strlen(src
);
112 size_t len
= (ret
>= size
) ? size
- 1 : ret
;
113 memcpy(dest
, src
, len
);
118 EXPORT_SYMBOL(strlcpy
);
121 #ifndef __HAVE_ARCH_STRSCPY
122 ssize_t
strscpy(char *dest
, const char *src
, size_t count
)
124 const struct word_at_a_time constants
= WORD_AT_A_TIME_CONSTANTS
;
128 if (count
== 0 || WARN_ON_ONCE(count
> INT_MAX
))
131 #ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
133 * If src is unaligned, don't cross a page boundary,
134 * since we don't know if the next page is mapped.
136 if ((long)src
& (sizeof(long) - 1)) {
137 size_t limit
= PAGE_SIZE
- ((long)src
& (PAGE_SIZE
- 1));
142 /* If src or dest is unaligned, don't do word-at-a-time. */
143 if (((long) dest
| (long) src
) & (sizeof(long) - 1))
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.
152 if (IS_ENABLED(CONFIG_KMSAN
))
155 while (max
>= sizeof(unsigned long)) {
156 unsigned long c
, data
;
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
);
165 *(unsigned long *)(dest
+res
) = c
;
166 res
+= sizeof(unsigned long);
167 count
-= sizeof(unsigned long);
168 max
-= sizeof(unsigned long);
182 /* Hit buffer length without finding a NUL; force NUL-termination. */
188 EXPORT_SYMBOL(strscpy
);
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
196 * @src: pointer to the beginning of string being copied from. Must not overlap
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.
206 char *stpcpy(char *__restrict__ dest
, const char *__restrict__ src
);
207 char *stpcpy(char *__restrict__ dest
, const char *__restrict__ src
)
209 while ((*dest
++ = *src
++) != '\0')
213 EXPORT_SYMBOL(stpcpy
);
215 #ifndef __HAVE_ARCH_STRCAT
216 char *strcat(char *dest
, const char *src
)
222 while ((*dest
++ = *src
++) != '\0')
226 EXPORT_SYMBOL(strcat
);
229 #ifndef __HAVE_ARCH_STRNCAT
230 char *strncat(char *dest
, const char *src
, size_t count
)
237 while ((*dest
++ = *src
++) != 0) {
246 EXPORT_SYMBOL(strncat
);
249 #ifndef __HAVE_ARCH_STRLCAT
250 size_t strlcat(char *dest
, const char *src
, size_t count
)
252 size_t dsize
= strlen(dest
);
253 size_t len
= strlen(src
);
254 size_t res
= dsize
+ len
;
256 /* This would be a bug */
257 BUG_ON(dsize
>= count
);
263 memcpy(dest
, src
, len
);
267 EXPORT_SYMBOL(strlcat
);
270 #ifndef __HAVE_ARCH_STRCMP
272 * strcmp - Compare two strings
274 * @ct: Another string
276 int strcmp(const char *cs
, const char *ct
)
278 unsigned char c1
, c2
;
284 return c1
< c2
? -1 : 1;
290 EXPORT_SYMBOL(strcmp
);
293 #ifndef __HAVE_ARCH_STRNCMP
295 * strncmp - Compare two length-limited strings
297 * @ct: Another string
298 * @count: The maximum number of bytes to compare
300 int strncmp(const char *cs
, const char *ct
, size_t count
)
302 unsigned char c1
, c2
;
308 return c1
< c2
? -1 : 1;
315 EXPORT_SYMBOL(strncmp
);
318 #ifndef __HAVE_ARCH_STRCHR
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
324 * Note that the %NUL-terminator is considered part of the string, and can
327 char *strchr(const char *s
, int c
)
329 for (; *s
!= (char)c
; ++s
)
334 EXPORT_SYMBOL(strchr
);
337 #ifndef __HAVE_ARCH_STRCHRNUL
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
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.
346 char *strchrnul(const char *s
, int c
)
348 while (*s
&& *s
!= (char)c
)
352 EXPORT_SYMBOL(strchrnul
);
356 * strnchrnul - Find and return a character in a length limited string,
358 * @s: The string to be searched
359 * @count: The number of characters to be searched
360 * @c: The character to search for
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.
365 char *strnchrnul(const char *s
, size_t count
, int c
)
367 while (count
-- && *s
&& *s
!= (char)c
)
372 #ifndef __HAVE_ARCH_STRRCHR
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
378 char *strrchr(const char *s
, int c
)
380 const char *last
= NULL
;
387 EXPORT_SYMBOL(strrchr
);
390 #ifndef __HAVE_ARCH_STRNCHR
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
397 * Note that the %NUL-terminator is considered part of the string, and can
400 char *strnchr(const char *s
, size_t count
, int c
)
410 EXPORT_SYMBOL(strnchr
);
413 #ifndef __HAVE_ARCH_STRLEN
414 size_t strlen(const char *s
)
418 for (sc
= s
; *sc
!= '\0'; ++sc
)
422 EXPORT_SYMBOL(strlen
);
425 #ifndef __HAVE_ARCH_STRNLEN
426 size_t strnlen(const char *s
, size_t count
)
430 for (sc
= s
; count
-- && *sc
!= '\0'; ++sc
)
434 EXPORT_SYMBOL(strnlen
);
437 #ifndef __HAVE_ARCH_STRSPN
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
443 size_t strspn(const char *s
, const char *accept
)
447 for (p
= s
; *p
!= '\0'; ++p
) {
448 if (!strchr(accept
, *p
))
453 EXPORT_SYMBOL(strspn
);
456 #ifndef __HAVE_ARCH_STRCSPN
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
462 size_t strcspn(const char *s
, const char *reject
)
466 for (p
= s
; *p
!= '\0'; ++p
) {
467 if (strchr(reject
, *p
))
472 EXPORT_SYMBOL(strcspn
);
475 #ifndef __HAVE_ARCH_STRPBRK
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
481 char *strpbrk(const char *cs
, const char *ct
)
485 for (sc
= cs
; *sc
!= '\0'; ++sc
) {
491 EXPORT_SYMBOL(strpbrk
);
494 #ifndef __HAVE_ARCH_STRSEP
496 * strsep - Split a string into tokens
497 * @s: The string to be searched
498 * @ct: The characters to search for
500 * strsep() updates @s to point after the token, ready for the next call.
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. ;)
506 char *strsep(char **s
, const char *ct
)
514 end
= strpbrk(sbegin
, ct
);
520 EXPORT_SYMBOL(strsep
);
523 #ifndef __HAVE_ARCH_MEMSET
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.
530 * Do not use memset() to access IO space, use memset_io() instead.
532 void *memset(void *s
, int c
, size_t count
)
540 EXPORT_SYMBOL(memset
);
543 #ifndef __HAVE_ARCH_MEMSET16
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
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.
554 void *memset16(uint16_t *s
, uint16_t v
, size_t count
)
562 EXPORT_SYMBOL(memset16
);
565 #ifndef __HAVE_ARCH_MEMSET32
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
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.
576 void *memset32(uint32_t *s
, uint32_t v
, size_t count
)
584 EXPORT_SYMBOL(memset32
);
587 #ifndef __HAVE_ARCH_MEMSET64
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
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.
598 void *memset64(uint64_t *s
, uint64_t v
, size_t count
)
606 EXPORT_SYMBOL(memset64
);
609 #ifndef __HAVE_ARCH_MEMCPY
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.
616 * You should not use this function to access IO space, use memcpy_toio()
617 * or memcpy_fromio() instead.
619 void *memcpy(void *dest
, const void *src
, size_t count
)
628 EXPORT_SYMBOL(memcpy
);
631 #ifndef __HAVE_ARCH_MEMMOVE
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.
638 * Unlike memcpy(), memmove() copes with overlapping areas.
640 void *memmove(void *dest
, const void *src
, size_t count
)
660 EXPORT_SYMBOL(memmove
);
663 #ifndef __HAVE_ARCH_MEMCMP
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.
671 __visible
int memcmp(const void *cs
, const void *ct
, size_t count
)
673 const unsigned char *su1
, *su2
;
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
;
681 if (get_unaligned(u1
) != get_unaligned(u2
))
685 count
-= sizeof(unsigned long);
686 } while (count
>= sizeof(unsigned long));
691 for (su1
= cs
, su2
= ct
; 0 < count
; ++su1
, ++su2
, count
--)
692 if ((res
= *su1
- *su2
) != 0)
696 EXPORT_SYMBOL(memcmp
);
699 #ifndef __HAVE_ARCH_BCMP
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.
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.
711 int bcmp(const void *a
, const void *b
, size_t len
)
713 return memcmp(a
, b
, len
);
718 #ifndef __HAVE_ARCH_MEMSCAN
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.
725 * returns the address of the first occurrence of @c, or 1 byte past
726 * the area if @c is not found
728 void *memscan(void *addr
, int c
, size_t size
)
730 unsigned char *p
= addr
;
733 if (*p
== (unsigned char)c
)
740 EXPORT_SYMBOL(memscan
);
743 #ifndef __HAVE_ARCH_STRSTR
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
749 char *strstr(const char *s1
, const char *s2
)
759 if (!memcmp(s1
, s2
, l2
))
765 EXPORT_SYMBOL(strstr
);
768 #ifndef __HAVE_ARCH_STRNSTR
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
775 char *strnstr(const char *s1
, const char *s2
, size_t len
)
784 if (!memcmp(s1
, s2
, l2
))
790 EXPORT_SYMBOL(strnstr
);
793 #ifndef __HAVE_ARCH_MEMCHR
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.
800 * returns the address of the first occurrence of @c, or %NULL
803 void *memchr(const void *s
, int c
, size_t n
)
805 const unsigned char *p
= s
;
807 if ((unsigned char)c
== *p
++) {
808 return (void *)(p
- 1);
813 EXPORT_SYMBOL(memchr
);
816 static void *check_bytes8(const u8
*start
, u8 value
, unsigned int bytes
)
820 return (void *)start
;
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.
833 * returns the address of the first character other than @c, or %NULL
834 * if the whole buffer contains just @c.
836 void *memchr_inv(const void *start
, int c
, size_t bytes
)
840 unsigned int words
, prefix
;
843 return check_bytes8(start
, value
, bytes
);
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;
852 value64
|= value64
<< 8;
853 value64
|= value64
<< 16;
854 value64
|= value64
<< 32;
857 prefix
= (unsigned long)start
% 8;
862 r
= check_bytes8(start
, value
, prefix
);
872 if (*(u64
*)start
!= value64
)
873 return check_bytes8(start
, value
, 8);
878 return check_bytes8(start
, value
, bytes
% 8);
880 EXPORT_SYMBOL(memchr_inv
);