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_STRSCPY
107 ssize_t strscpy(char *dest, const char *src, size_t count)
109 const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
113 if (count == 0 || WARN_ON_ONCE(count > INT_MAX))
116 #ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
118 * If src is unaligned, don't cross a page boundary,
119 * since we don't know if the next page is mapped.
121 if ((long)src & (sizeof(long) - 1)) {
122 size_t limit = PAGE_SIZE - ((long)src & (PAGE_SIZE - 1));
127 /* If src or dest is unaligned, don't do word-at-a-time. */
128 if (((long) dest | (long) src) & (sizeof(long) - 1))
133 * read_word_at_a_time() below may read uninitialized bytes after the
134 * trailing zero and use them in comparisons. Disable this optimization
135 * under KMSAN to prevent false positive reports.
137 if (IS_ENABLED(CONFIG_KMSAN))
140 while (max >= sizeof(unsigned long)) {
141 unsigned long c, data;
143 c = read_word_at_a_time(src+res);
144 if (has_zero(c, &data, &constants)) {
145 data = prep_zero_mask(c, data, &constants);
146 data = create_zero_mask(data);
147 *(unsigned long *)(dest+res) = c & zero_bytemask(data);
148 return res + find_zero(data);
150 *(unsigned long *)(dest+res) = c;
151 res += sizeof(unsigned long);
152 count -= sizeof(unsigned long);
153 max -= sizeof(unsigned long);
167 /* Hit buffer length without finding a NUL; force NUL-termination. */
173 EXPORT_SYMBOL(strscpy);
177 * stpcpy - copy a string from src to dest returning a pointer to the new end
178 * of dest, including src's %NUL-terminator. May overrun dest.
179 * @dest: pointer to end of string being copied into. Must be large enough
181 * @src: pointer to the beginning of string being copied from. Must not overlap
184 * stpcpy differs from strcpy in a key way: the return value is a pointer
185 * to the new %NUL-terminating character in @dest. (For strcpy, the return
186 * value is a pointer to the start of @dest). This interface is considered
187 * unsafe as it doesn't perform bounds checking of the inputs. As such it's
188 * not recommended for usage. Instead, its definition is provided in case
189 * the compiler lowers other libcalls to stpcpy.
191 char *stpcpy(char *__restrict__ dest, const char *__restrict__ src);
192 char *stpcpy(char *__restrict__ dest, const char *__restrict__ src)
194 while ((*dest++ = *src++) != '\0')
198 EXPORT_SYMBOL(stpcpy);
200 #ifndef __HAVE_ARCH_STRCAT
201 char *strcat(char *dest, const char *src)
207 while ((*dest++ = *src++) != '\0')
211 EXPORT_SYMBOL(strcat);
214 #ifndef __HAVE_ARCH_STRNCAT
215 char *strncat(char *dest, const char *src, size_t count)
222 while ((*dest++ = *src++) != 0) {
231 EXPORT_SYMBOL(strncat);
234 #ifndef __HAVE_ARCH_STRLCAT
235 size_t strlcat(char *dest, const char *src, size_t count)
237 size_t dsize = strlen(dest);
238 size_t len = strlen(src);
239 size_t res = dsize + len;
241 /* This would be a bug */
242 BUG_ON(dsize >= count);
248 __builtin_memcpy(dest, src, len);
252 EXPORT_SYMBOL(strlcat);
255 #ifndef __HAVE_ARCH_STRCMP
257 * strcmp - Compare two strings
259 * @ct: Another string
261 int strcmp(const char *cs, const char *ct)
263 unsigned char c1, c2;
269 return c1 < c2 ? -1 : 1;
275 EXPORT_SYMBOL(strcmp);
278 #ifndef __HAVE_ARCH_STRNCMP
280 * strncmp - Compare two length-limited strings
282 * @ct: Another string
283 * @count: The maximum number of bytes to compare
285 int strncmp(const char *cs, const char *ct, size_t count)
287 unsigned char c1, c2;
293 return c1 < c2 ? -1 : 1;
300 EXPORT_SYMBOL(strncmp);
303 #ifndef __HAVE_ARCH_STRCHR
305 * strchr - Find the first occurrence of a character in a string
306 * @s: The string to be searched
307 * @c: The character to search for
309 * Note that the %NUL-terminator is considered part of the string, and can
312 char *strchr(const char *s, int c)
314 for (; *s != (char)c; ++s)
319 EXPORT_SYMBOL(strchr);
322 #ifndef __HAVE_ARCH_STRCHRNUL
324 * strchrnul - Find and return a character in a string, or end of string
325 * @s: The string to be searched
326 * @c: The character to search for
328 * Returns pointer to first occurrence of 'c' in s. If c is not found, then
329 * return a pointer to the null byte at the end of s.
331 char *strchrnul(const char *s, int c)
333 while (*s && *s != (char)c)
337 EXPORT_SYMBOL(strchrnul);
341 * strnchrnul - Find and return a character in a length limited string,
343 * @s: The string to be searched
344 * @count: The number of characters to be searched
345 * @c: The character to search for
347 * Returns pointer to the first occurrence of 'c' in s. If c is not found,
348 * then return a pointer to the last character of the string.
350 char *strnchrnul(const char *s, size_t count, int c)
352 while (count-- && *s && *s != (char)c)
357 #ifndef __HAVE_ARCH_STRRCHR
359 * strrchr - Find the last occurrence of a character in a string
360 * @s: The string to be searched
361 * @c: The character to search for
363 char *strrchr(const char *s, int c)
365 const char *last = NULL;
372 EXPORT_SYMBOL(strrchr);
375 #ifndef __HAVE_ARCH_STRNCHR
377 * strnchr - Find a character in a length limited string
378 * @s: The string to be searched
379 * @count: The number of characters to be searched
380 * @c: The character to search for
382 * Note that the %NUL-terminator is considered part of the string, and can
385 char *strnchr(const char *s, size_t count, int c)
395 EXPORT_SYMBOL(strnchr);
398 #ifndef __HAVE_ARCH_STRLEN
399 size_t strlen(const char *s)
403 for (sc = s; *sc != '\0'; ++sc)
407 EXPORT_SYMBOL(strlen);
410 #ifndef __HAVE_ARCH_STRNLEN
411 size_t strnlen(const char *s, size_t count)
415 for (sc = s; count-- && *sc != '\0'; ++sc)
419 EXPORT_SYMBOL(strnlen);
422 #ifndef __HAVE_ARCH_STRSPN
424 * strspn - Calculate the length of the initial substring of @s which only contain letters in @accept
425 * @s: The string to be searched
426 * @accept: The string to search for
428 size_t strspn(const char *s, const char *accept)
432 for (p = s; *p != '\0'; ++p) {
433 if (!strchr(accept, *p))
438 EXPORT_SYMBOL(strspn);
441 #ifndef __HAVE_ARCH_STRCSPN
443 * strcspn - Calculate the length of the initial substring of @s which does not contain letters in @reject
444 * @s: The string to be searched
445 * @reject: The string to avoid
447 size_t strcspn(const char *s, const char *reject)
451 for (p = s; *p != '\0'; ++p) {
452 if (strchr(reject, *p))
457 EXPORT_SYMBOL(strcspn);
460 #ifndef __HAVE_ARCH_STRPBRK
462 * strpbrk - Find the first occurrence of a set of characters
463 * @cs: The string to be searched
464 * @ct: The characters to search for
466 char *strpbrk(const char *cs, const char *ct)
470 for (sc = cs; *sc != '\0'; ++sc) {
476 EXPORT_SYMBOL(strpbrk);
479 #ifndef __HAVE_ARCH_STRSEP
481 * strsep - Split a string into tokens
482 * @s: The string to be searched
483 * @ct: The characters to search for
485 * strsep() updates @s to point after the token, ready for the next call.
487 * It returns empty tokens, too, behaving exactly like the libc function
488 * of that name. In fact, it was stolen from glibc2 and de-fancy-fied.
489 * Same semantics, slimmer shape. ;)
491 char *strsep(char **s, const char *ct)
499 end = strpbrk(sbegin, ct);
505 EXPORT_SYMBOL(strsep);
508 #ifndef __HAVE_ARCH_MEMSET
510 * memset - Fill a region of memory with the given value
511 * @s: Pointer to the start of the area.
512 * @c: The byte to fill the area with
513 * @count: The size of the area.
515 * Do not use memset() to access IO space, use memset_io() instead.
517 void *memset(void *s, int c, size_t count)
525 EXPORT_SYMBOL(memset);
528 #ifndef __HAVE_ARCH_MEMSET16
530 * memset16() - Fill a memory area with a uint16_t
531 * @s: Pointer to the start of the area.
532 * @v: The value to fill the area with
533 * @count: The number of values to store
535 * Differs from memset() in that it fills with a uint16_t instead
536 * of a byte. Remember that @count is the number of uint16_ts to
537 * store, not the number of bytes.
539 void *memset16(uint16_t *s, uint16_t v, size_t count)
547 EXPORT_SYMBOL(memset16);
550 #ifndef __HAVE_ARCH_MEMSET32
552 * memset32() - Fill a memory area with a uint32_t
553 * @s: Pointer to the start of the area.
554 * @v: The value to fill the area with
555 * @count: The number of values to store
557 * Differs from memset() in that it fills with a uint32_t instead
558 * of a byte. Remember that @count is the number of uint32_ts to
559 * store, not the number of bytes.
561 void *memset32(uint32_t *s, uint32_t v, size_t count)
569 EXPORT_SYMBOL(memset32);
572 #ifndef __HAVE_ARCH_MEMSET64
574 * memset64() - Fill a memory area with a uint64_t
575 * @s: Pointer to the start of the area.
576 * @v: The value to fill the area with
577 * @count: The number of values to store
579 * Differs from memset() in that it fills with a uint64_t instead
580 * of a byte. Remember that @count is the number of uint64_ts to
581 * store, not the number of bytes.
583 void *memset64(uint64_t *s, uint64_t v, size_t count)
591 EXPORT_SYMBOL(memset64);
594 #ifndef __HAVE_ARCH_MEMCPY
596 * memcpy - Copy one area of memory to another
597 * @dest: Where to copy to
598 * @src: Where to copy from
599 * @count: The size of the area.
601 * You should not use this function to access IO space, use memcpy_toio()
602 * or memcpy_fromio() instead.
604 void *memcpy(void *dest, const void *src, size_t count)
613 EXPORT_SYMBOL(memcpy);
616 #ifndef __HAVE_ARCH_MEMMOVE
618 * memmove - Copy one area of memory to another
619 * @dest: Where to copy to
620 * @src: Where to copy from
621 * @count: The size of the area.
623 * Unlike memcpy(), memmove() copes with overlapping areas.
625 void *memmove(void *dest, const void *src, size_t count)
645 EXPORT_SYMBOL(memmove);
648 #ifndef __HAVE_ARCH_MEMCMP
650 * memcmp - Compare two areas of memory
651 * @cs: One area of memory
652 * @ct: Another area of memory
653 * @count: The size of the area.
656 __visible int memcmp(const void *cs, const void *ct, size_t count)
658 const unsigned char *su1, *su2;
661 #ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
662 if (count >= sizeof(unsigned long)) {
663 const unsigned long *u1 = cs;
664 const unsigned long *u2 = ct;
666 if (get_unaligned(u1) != get_unaligned(u2))
670 count -= sizeof(unsigned long);
671 } while (count >= sizeof(unsigned long));
676 for (su1 = cs, su2 = ct; 0 < count; ++su1, ++su2, count--)
677 if ((res = *su1 - *su2) != 0)
681 EXPORT_SYMBOL(memcmp);
684 #ifndef __HAVE_ARCH_BCMP
686 * bcmp - returns 0 if and only if the buffers have identical contents.
687 * @a: pointer to first buffer.
688 * @b: pointer to second buffer.
689 * @len: size of buffers.
691 * The sign or magnitude of a non-zero return value has no particular
692 * meaning, and architectures may implement their own more efficient bcmp(). So
693 * while this particular implementation is a simple (tail) call to memcmp, do
694 * not rely on anything but whether the return value is zero or non-zero.
696 int bcmp(const void *a, const void *b, size_t len)
698 return memcmp(a, b, len);
703 #ifndef __HAVE_ARCH_MEMSCAN
705 * memscan - Find a character in an area of memory.
706 * @addr: The memory area
707 * @c: The byte to search for
708 * @size: The size of the area.
710 * returns the address of the first occurrence of @c, or 1 byte past
711 * the area if @c is not found
713 void *memscan(void *addr, int c, size_t size)
715 unsigned char *p = addr;
718 if (*p == (unsigned char)c)
725 EXPORT_SYMBOL(memscan);
728 #ifndef __HAVE_ARCH_STRSTR
730 * strstr - Find the first substring in a %NUL terminated string
731 * @s1: The string to be searched
732 * @s2: The string to search for
734 char *strstr(const char *s1, const char *s2)
744 if (!memcmp(s1, s2, l2))
750 EXPORT_SYMBOL(strstr);
753 #ifndef __HAVE_ARCH_STRNSTR
755 * strnstr - Find the first substring in a length-limited string
756 * @s1: The string to be searched
757 * @s2: The string to search for
758 * @len: the maximum number of characters to search
760 char *strnstr(const char *s1, const char *s2, size_t len)
769 if (!memcmp(s1, s2, l2))
775 EXPORT_SYMBOL(strnstr);
778 #ifndef __HAVE_ARCH_MEMCHR
780 * memchr - Find a character in an area of memory.
781 * @s: The memory area
782 * @c: The byte to search for
783 * @n: The size of the area.
785 * returns the address of the first occurrence of @c, or %NULL
788 void *memchr(const void *s, int c, size_t n)
790 const unsigned char *p = s;
792 if ((unsigned char)c == *p++) {
793 return (void *)(p - 1);
798 EXPORT_SYMBOL(memchr);
801 static void *check_bytes8(const u8 *start, u8 value, unsigned int bytes)
805 return (void *)start;
813 * memchr_inv - Find an unmatching character in an area of memory.
814 * @start: The memory area
815 * @c: Find a character other than c
816 * @bytes: The size of the area.
818 * returns the address of the first character other than @c, or %NULL
819 * if the whole buffer contains just @c.
821 void *memchr_inv(const void *start, int c, size_t bytes)
825 unsigned int words, prefix;
828 return check_bytes8(start, value, bytes);
831 #if defined(CONFIG_ARCH_HAS_FAST_MULTIPLIER) && BITS_PER_LONG == 64
832 value64 *= 0x0101010101010101ULL;
833 #elif defined(CONFIG_ARCH_HAS_FAST_MULTIPLIER)
834 value64 *= 0x01010101;
835 value64 |= value64 << 32;
837 value64 |= value64 << 8;
838 value64 |= value64 << 16;
839 value64 |= value64 << 32;
842 prefix = (unsigned long)start % 8;
847 r = check_bytes8(start, value, prefix);
857 if (*(u64 *)start != value64)
858 return check_bytes8(start, value, 8);
863 return check_bytes8(start, value, bytes % 8);
865 EXPORT_SYMBOL(memchr_inv);