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)
483 const char *sc1, *sc2;
485 for (sc1 = cs; *sc1 != '\0'; ++sc1) {
486 for (sc2 = ct; *sc2 != '\0'; ++sc2) {
493 EXPORT_SYMBOL(strpbrk);
496 #ifndef __HAVE_ARCH_STRSEP
498 * strsep - Split a string into tokens
499 * @s: The string to be searched
500 * @ct: The characters to search for
502 * strsep() updates @s to point after the token, ready for the next call.
504 * It returns empty tokens, too, behaving exactly like the libc function
505 * of that name. In fact, it was stolen from glibc2 and de-fancy-fied.
506 * Same semantics, slimmer shape. ;)
508 char *strsep(char **s, const char *ct)
516 end = strpbrk(sbegin, ct);
522 EXPORT_SYMBOL(strsep);
525 #ifndef __HAVE_ARCH_MEMSET
527 * memset - Fill a region of memory with the given value
528 * @s: Pointer to the start of the area.
529 * @c: The byte to fill the area with
530 * @count: The size of the area.
532 * Do not use memset() to access IO space, use memset_io() instead.
534 void *memset(void *s, int c, size_t count)
542 EXPORT_SYMBOL(memset);
545 #ifndef __HAVE_ARCH_MEMSET16
547 * memset16() - Fill a memory area with a uint16_t
548 * @s: Pointer to the start of the area.
549 * @v: The value to fill the area with
550 * @count: The number of values to store
552 * Differs from memset() in that it fills with a uint16_t instead
553 * of a byte. Remember that @count is the number of uint16_ts to
554 * store, not the number of bytes.
556 void *memset16(uint16_t *s, uint16_t v, size_t count)
564 EXPORT_SYMBOL(memset16);
567 #ifndef __HAVE_ARCH_MEMSET32
569 * memset32() - Fill a memory area with a uint32_t
570 * @s: Pointer to the start of the area.
571 * @v: The value to fill the area with
572 * @count: The number of values to store
574 * Differs from memset() in that it fills with a uint32_t instead
575 * of a byte. Remember that @count is the number of uint32_ts to
576 * store, not the number of bytes.
578 void *memset32(uint32_t *s, uint32_t v, size_t count)
586 EXPORT_SYMBOL(memset32);
589 #ifndef __HAVE_ARCH_MEMSET64
591 * memset64() - Fill a memory area with a uint64_t
592 * @s: Pointer to the start of the area.
593 * @v: The value to fill the area with
594 * @count: The number of values to store
596 * Differs from memset() in that it fills with a uint64_t instead
597 * of a byte. Remember that @count is the number of uint64_ts to
598 * store, not the number of bytes.
600 void *memset64(uint64_t *s, uint64_t v, size_t count)
608 EXPORT_SYMBOL(memset64);
611 #ifndef __HAVE_ARCH_MEMCPY
613 * memcpy - Copy one area of memory to another
614 * @dest: Where to copy to
615 * @src: Where to copy from
616 * @count: The size of the area.
618 * You should not use this function to access IO space, use memcpy_toio()
619 * or memcpy_fromio() instead.
621 void *memcpy(void *dest, const void *src, size_t count)
630 EXPORT_SYMBOL(memcpy);
633 #ifndef __HAVE_ARCH_MEMMOVE
635 * memmove - Copy one area of memory to another
636 * @dest: Where to copy to
637 * @src: Where to copy from
638 * @count: The size of the area.
640 * Unlike memcpy(), memmove() copes with overlapping areas.
642 void *memmove(void *dest, const void *src, size_t count)
662 EXPORT_SYMBOL(memmove);
665 #ifndef __HAVE_ARCH_MEMCMP
667 * memcmp - Compare two areas of memory
668 * @cs: One area of memory
669 * @ct: Another area of memory
670 * @count: The size of the area.
673 __visible int memcmp(const void *cs, const void *ct, size_t count)
675 const unsigned char *su1, *su2;
678 #ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
679 if (count >= sizeof(unsigned long)) {
680 const unsigned long *u1 = cs;
681 const unsigned long *u2 = ct;
683 if (get_unaligned(u1) != get_unaligned(u2))
687 count -= sizeof(unsigned long);
688 } while (count >= sizeof(unsigned long));
693 for (su1 = cs, su2 = ct; 0 < count; ++su1, ++su2, count--)
694 if ((res = *su1 - *su2) != 0)
698 EXPORT_SYMBOL(memcmp);
701 #ifndef __HAVE_ARCH_BCMP
703 * bcmp - returns 0 if and only if the buffers have identical contents.
704 * @a: pointer to first buffer.
705 * @b: pointer to second buffer.
706 * @len: size of buffers.
708 * The sign or magnitude of a non-zero return value has no particular
709 * meaning, and architectures may implement their own more efficient bcmp(). So
710 * while this particular implementation is a simple (tail) call to memcmp, do
711 * not rely on anything but whether the return value is zero or non-zero.
713 int bcmp(const void *a, const void *b, size_t len)
715 return memcmp(a, b, len);
720 #ifndef __HAVE_ARCH_MEMSCAN
722 * memscan - Find a character in an area of memory.
723 * @addr: The memory area
724 * @c: The byte to search for
725 * @size: The size of the area.
727 * returns the address of the first occurrence of @c, or 1 byte past
728 * the area if @c is not found
730 void *memscan(void *addr, int c, size_t size)
732 unsigned char *p = addr;
735 if (*p == (unsigned char)c)
742 EXPORT_SYMBOL(memscan);
745 #ifndef __HAVE_ARCH_STRSTR
747 * strstr - Find the first substring in a %NUL terminated string
748 * @s1: The string to be searched
749 * @s2: The string to search for
751 char *strstr(const char *s1, const char *s2)
761 if (!memcmp(s1, s2, l2))
767 EXPORT_SYMBOL(strstr);
770 #ifndef __HAVE_ARCH_STRNSTR
772 * strnstr - Find the first substring in a length-limited string
773 * @s1: The string to be searched
774 * @s2: The string to search for
775 * @len: the maximum number of characters to search
777 char *strnstr(const char *s1, const char *s2, size_t len)
786 if (!memcmp(s1, s2, l2))
792 EXPORT_SYMBOL(strnstr);
795 #ifndef __HAVE_ARCH_MEMCHR
797 * memchr - Find a character in an area of memory.
798 * @s: The memory area
799 * @c: The byte to search for
800 * @n: The size of the area.
802 * returns the address of the first occurrence of @c, or %NULL
805 void *memchr(const void *s, int c, size_t n)
807 const unsigned char *p = s;
809 if ((unsigned char)c == *p++) {
810 return (void *)(p - 1);
815 EXPORT_SYMBOL(memchr);
818 static void *check_bytes8(const u8 *start, u8 value, unsigned int bytes)
822 return (void *)start;
830 * memchr_inv - Find an unmatching character in an area of memory.
831 * @start: The memory area
832 * @c: Find a character other than c
833 * @bytes: The size of the area.
835 * returns the address of the first character other than @c, or %NULL
836 * if the whole buffer contains just @c.
838 void *memchr_inv(const void *start, int c, size_t bytes)
842 unsigned int words, prefix;
845 return check_bytes8(start, value, bytes);
848 #if defined(CONFIG_ARCH_HAS_FAST_MULTIPLIER) && BITS_PER_LONG == 64
849 value64 *= 0x0101010101010101ULL;
850 #elif defined(CONFIG_ARCH_HAS_FAST_MULTIPLIER)
851 value64 *= 0x01010101;
852 value64 |= value64 << 32;
854 value64 |= value64 << 8;
855 value64 |= value64 << 16;
856 value64 |= value64 << 32;
859 prefix = (unsigned long)start % 8;
864 r = check_bytes8(start, value, prefix);
874 if (*(u64 *)start != value64)
875 return check_bytes8(start, value, 8);
880 return check_bytes8(start, value, bytes % 8);
882 EXPORT_SYMBOL(memchr_inv);