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
80 * strcpy - Copy a %NUL terminated string
81 * @dest: Where to copy the string to
82 * @src: Where to copy the string from
84 char *strcpy(char *dest, const char *src)
88 while ((*dest++ = *src++) != '\0')
92 EXPORT_SYMBOL(strcpy);
95 #ifndef __HAVE_ARCH_STRNCPY
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
102 * The result is not %NUL-terminated if the source exceeds
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.
109 char *strncpy(char *dest, const char *src, size_t count)
114 if ((*tmp = *src) != 0)
121 EXPORT_SYMBOL(strncpy);
124 #ifndef __HAVE_ARCH_STRLCPY
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
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.
136 size_t strlcpy(char *dest, const char *src, size_t size)
138 size_t ret = strlen(src);
141 size_t len = (ret >= size) ? size - 1 : ret;
142 memcpy(dest, src, len);
147 EXPORT_SYMBOL(strlcpy);
150 #ifndef __HAVE_ARCH_STRSCPY
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
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.
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.
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().
172 * * The number of characters copied (not including the trailing %NUL)
173 * * -E2BIG if count is 0 or @src was truncated.
175 ssize_t strscpy(char *dest, const char *src, size_t count)
177 const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
181 if (count == 0 || WARN_ON_ONCE(count > INT_MAX))
184 #ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
186 * If src is unaligned, don't cross a page boundary,
187 * since we don't know if the next page is mapped.
189 if ((long)src & (sizeof(long) - 1)) {
190 size_t limit = PAGE_SIZE - ((long)src & (PAGE_SIZE - 1));
195 /* If src or dest is unaligned, don't do word-at-a-time. */
196 if (((long) dest | (long) src) & (sizeof(long) - 1))
200 while (max >= sizeof(unsigned long)) {
201 unsigned long c, data;
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);
210 *(unsigned long *)(dest+res) = c;
211 res += sizeof(unsigned long);
212 count -= sizeof(unsigned long);
213 max -= sizeof(unsigned long);
227 /* Hit buffer length without finding a NUL; force NUL-termination. */
233 EXPORT_SYMBOL(strscpy);
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
241 * @src: pointer to the beginning of string being copied from. Must not overlap
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.
251 char *stpcpy(char *__restrict__ dest, const char *__restrict__ src);
252 char *stpcpy(char *__restrict__ dest, const char *__restrict__ src)
254 while ((*dest++ = *src++) != '\0')
258 EXPORT_SYMBOL(stpcpy);
260 #ifndef __HAVE_ARCH_STRCAT
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
266 char *strcat(char *dest, const char *src)
272 while ((*dest++ = *src++) != '\0')
276 EXPORT_SYMBOL(strcat);
279 #ifndef __HAVE_ARCH_STRNCAT
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
286 * Note that in contrast to strncpy(), strncat() ensures the result is
289 char *strncat(char *dest, const char *src, size_t count)
296 while ((*dest++ = *src++) != 0) {
305 EXPORT_SYMBOL(strncat);
308 #ifndef __HAVE_ARCH_STRLCAT
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.
315 size_t strlcat(char *dest, const char *src, size_t count)
317 size_t dsize = strlen(dest);
318 size_t len = strlen(src);
319 size_t res = dsize + len;
321 /* This would be a bug */
322 BUG_ON(dsize >= count);
328 memcpy(dest, src, len);
332 EXPORT_SYMBOL(strlcat);
335 #ifndef __HAVE_ARCH_STRCMP
337 * strcmp - Compare two strings
339 * @ct: Another string
341 int strcmp(const char *cs, const char *ct)
343 unsigned char c1, c2;
349 return c1 < c2 ? -1 : 1;
355 EXPORT_SYMBOL(strcmp);
358 #ifndef __HAVE_ARCH_STRNCMP
360 * strncmp - Compare two length-limited strings
362 * @ct: Another string
363 * @count: The maximum number of bytes to compare
365 int strncmp(const char *cs, const char *ct, size_t count)
367 unsigned char c1, c2;
373 return c1 < c2 ? -1 : 1;
380 EXPORT_SYMBOL(strncmp);
383 #ifndef __HAVE_ARCH_STRCHR
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
389 * Note that the %NUL-terminator is considered part of the string, and can
392 char *strchr(const char *s, int c)
394 for (; *s != (char)c; ++s)
399 EXPORT_SYMBOL(strchr);
402 #ifndef __HAVE_ARCH_STRCHRNUL
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
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.
411 char *strchrnul(const char *s, int c)
413 while (*s && *s != (char)c)
417 EXPORT_SYMBOL(strchrnul);
421 * strnchrnul - Find and return a character in a length limited string,
423 * @s: The string to be searched
424 * @count: The number of characters to be searched
425 * @c: The character to search for
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.
430 char *strnchrnul(const char *s, size_t count, int c)
432 while (count-- && *s && *s != (char)c)
437 #ifndef __HAVE_ARCH_STRRCHR
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
443 char *strrchr(const char *s, int c)
445 const char *last = NULL;
452 EXPORT_SYMBOL(strrchr);
455 #ifndef __HAVE_ARCH_STRNCHR
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
462 * Note that the %NUL-terminator is considered part of the string, and can
465 char *strnchr(const char *s, size_t count, int c)
475 EXPORT_SYMBOL(strnchr);
478 #ifndef __HAVE_ARCH_STRLEN
480 * strlen - Find the length of a string
481 * @s: The string to be sized
483 size_t strlen(const char *s)
487 for (sc = s; *sc != '\0'; ++sc)
491 EXPORT_SYMBOL(strlen);
494 #ifndef __HAVE_ARCH_STRNLEN
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
500 size_t strnlen(const char *s, size_t count)
504 for (sc = s; count-- && *sc != '\0'; ++sc)
508 EXPORT_SYMBOL(strnlen);
511 #ifndef __HAVE_ARCH_STRSPN
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
517 size_t strspn(const char *s, const char *accept)
521 for (p = s; *p != '\0'; ++p) {
522 if (!strchr(accept, *p))
527 EXPORT_SYMBOL(strspn);
530 #ifndef __HAVE_ARCH_STRCSPN
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
536 size_t strcspn(const char *s, const char *reject)
540 for (p = s; *p != '\0'; ++p) {
541 if (strchr(reject, *p))
546 EXPORT_SYMBOL(strcspn);
549 #ifndef __HAVE_ARCH_STRPBRK
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
555 char *strpbrk(const char *cs, const char *ct)
557 const char *sc1, *sc2;
559 for (sc1 = cs; *sc1 != '\0'; ++sc1) {
560 for (sc2 = ct; *sc2 != '\0'; ++sc2) {
567 EXPORT_SYMBOL(strpbrk);
570 #ifndef __HAVE_ARCH_STRSEP
572 * strsep - Split a string into tokens
573 * @s: The string to be searched
574 * @ct: The characters to search for
576 * strsep() updates @s to point after the token, ready for the next call.
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. ;)
582 char *strsep(char **s, const char *ct)
590 end = strpbrk(sbegin, ct);
596 EXPORT_SYMBOL(strsep);
599 #ifndef __HAVE_ARCH_MEMSET
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.
606 * Do not use memset() to access IO space, use memset_io() instead.
608 void *memset(void *s, int c, size_t count)
616 EXPORT_SYMBOL(memset);
619 #ifndef __HAVE_ARCH_MEMSET16
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
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.
630 void *memset16(uint16_t *s, uint16_t v, size_t count)
638 EXPORT_SYMBOL(memset16);
641 #ifndef __HAVE_ARCH_MEMSET32
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
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.
652 void *memset32(uint32_t *s, uint32_t v, size_t count)
660 EXPORT_SYMBOL(memset32);
663 #ifndef __HAVE_ARCH_MEMSET64
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
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.
674 void *memset64(uint64_t *s, uint64_t v, size_t count)
682 EXPORT_SYMBOL(memset64);
685 #ifndef __HAVE_ARCH_MEMCPY
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.
692 * You should not use this function to access IO space, use memcpy_toio()
693 * or memcpy_fromio() instead.
695 void *memcpy(void *dest, const void *src, size_t count)
704 EXPORT_SYMBOL(memcpy);
707 #ifndef __HAVE_ARCH_MEMMOVE
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.
714 * Unlike memcpy(), memmove() copes with overlapping areas.
716 void *memmove(void *dest, const void *src, size_t count)
736 EXPORT_SYMBOL(memmove);
739 #ifndef __HAVE_ARCH_MEMCMP
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.
747 __visible int memcmp(const void *cs, const void *ct, size_t count)
749 const unsigned char *su1, *su2;
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;
757 if (get_unaligned(u1) != get_unaligned(u2))
761 count -= sizeof(unsigned long);
762 } while (count >= sizeof(unsigned long));
767 for (su1 = cs, su2 = ct; 0 < count; ++su1, ++su2, count--)
768 if ((res = *su1 - *su2) != 0)
772 EXPORT_SYMBOL(memcmp);
775 #ifndef __HAVE_ARCH_BCMP
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.
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.
787 int bcmp(const void *a, const void *b, size_t len)
789 return memcmp(a, b, len);
794 #ifndef __HAVE_ARCH_MEMSCAN
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.
801 * returns the address of the first occurrence of @c, or 1 byte past
802 * the area if @c is not found
804 void *memscan(void *addr, int c, size_t size)
806 unsigned char *p = addr;
809 if (*p == (unsigned char)c)
816 EXPORT_SYMBOL(memscan);
819 #ifndef __HAVE_ARCH_STRSTR
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
825 char *strstr(const char *s1, const char *s2)
835 if (!memcmp(s1, s2, l2))
841 EXPORT_SYMBOL(strstr);
844 #ifndef __HAVE_ARCH_STRNSTR
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
851 char *strnstr(const char *s1, const char *s2, size_t len)
860 if (!memcmp(s1, s2, l2))
866 EXPORT_SYMBOL(strnstr);
869 #ifndef __HAVE_ARCH_MEMCHR
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.
876 * returns the address of the first occurrence of @c, or %NULL
879 void *memchr(const void *s, int c, size_t n)
881 const unsigned char *p = s;
883 if ((unsigned char)c == *p++) {
884 return (void *)(p - 1);
889 EXPORT_SYMBOL(memchr);
892 static void *check_bytes8(const u8 *start, u8 value, unsigned int bytes)
896 return (void *)start;
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.
909 * returns the address of the first character other than @c, or %NULL
910 * if the whole buffer contains just @c.
912 void *memchr_inv(const void *start, int c, size_t bytes)
916 unsigned int words, prefix;
919 return check_bytes8(start, value, bytes);
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;
928 value64 |= value64 << 8;
929 value64 |= value64 << 16;
930 value64 |= value64 << 32;
933 prefix = (unsigned long)start % 8;
938 r = check_bytes8(start, value, prefix);
948 if (*(u64 *)start != value64)
949 return check_bytes8(start, value, 8);
954 return check_bytes8(start, value, bytes % 8);
956 EXPORT_SYMBOL(memchr_inv);