// SPDX-License-Identifier: GPL-2.0 /* * linux/lib/string.c * * Copyright (C) 1991, 1992 Linus Torvalds */ /* * This file should be used only for "library" routines that may have * alternative implementations on specific architectures (generally * found in <asm-xx/string.h>), or get overloaded by FORTIFY_SOURCE. * (Specifically, this file is built with __NO_FORTIFY.) * * Other helper functions should live in string_helpers.c. */ #define __NO_FORTIFY #include <linux/types.h> #include <linux/string.h> #include <linux/ctype.h> #include <linux/kernel.h> #include <linux/export.h> #include <linux/bug.h> #include <linux/errno.h> #include <linux/slab.h> #include <asm/unaligned.h> #include <asm/byteorder.h> #include <asm/word-at-a-time.h> #include <asm/page.h> #ifndef __HAVE_ARCH_STRNCASECMP /** * strncasecmp - Case insensitive, length-limited string comparison * @s1: One string * @s2: The other string * @len: the maximum number of characters to compare */ int strncasecmp(const char *s1, const char *s2, size_t len) { /* Yes, Virginia, it had better be unsigned */ unsigned char c1, c2; if (!len) return 0; do { c1 = *s1++; c2 = *s2++; if (!c1 || !c2) break; if (c1 == c2) continue; c1 = tolower(c1); c2 = tolower(c2); if (c1 != c2) break; } while (--len); return (int)c1 - (int)c2; } EXPORT_SYMBOL(strncasecmp); #endif #ifndef __HAVE_ARCH_STRCASECMP int strcasecmp(const char *s1, const char *s2) { int c1, c2; do { c1 = tolower(*s1++); c2 = tolower(*s2++); } while (c1 == c2 && c1 != 0); return c1 - c2; } EXPORT_SYMBOL(strcasecmp); #endif #ifndef __HAVE_ARCH_STRCPY char *strcpy(char *dest, const char *src) { char *tmp = dest; while ((*dest++ = *src++) != '\0') /* nothing */; return tmp; } EXPORT_SYMBOL(strcpy); #endif #ifndef __HAVE_ARCH_STRNCPY char *strncpy(char *dest, const char *src, size_t count) { char *tmp = dest; while (count) { if ((*tmp = *src) != 0) src++; tmp++; count--; } return dest; } EXPORT_SYMBOL(strncpy); #endif #ifndef __HAVE_ARCH_STRLCPY size_t strlcpy(char *dest, const char *src, size_t size) { size_t ret = strlen(src); if (size) { size_t len = (ret >= size) ? size - 1 : ret; __builtin_memcpy(dest, src, len); dest[len] = '\0'; } return ret; } EXPORT_SYMBOL(strlcpy); #endif #ifndef __HAVE_ARCH_STRSCPY ssize_t strscpy(char *dest, const char *src, size_t count) { const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS; size_t max = count; long res = 0; if (count == 0 || WARN_ON_ONCE(count > INT_MAX)) return -E2BIG; #ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS /* * If src is unaligned, don't cross a page boundary, * since we don't know if the next page is mapped. */ if ((long)src & (sizeof(long) - 1)) { size_t limit = PAGE_SIZE - ((long)src & (PAGE_SIZE - 1)); if (limit < max) max = limit; } #else /* If src or dest is unaligned, don't do word-at-a-time. */ if (((long) dest | (long) src) & (sizeof(long) - 1)) max = 0; #endif /* * read_word_at_a_time() below may read uninitialized bytes after the * trailing zero and use them in comparisons. Disable this optimization * under KMSAN to prevent false positive reports. */ if (IS_ENABLED(CONFIG_KMSAN)) max = 0; while (max >= sizeof(unsigned long)) { unsigned long c, data; c = read_word_at_a_time(src+res); if (has_zero(c, &data, &constants)) { data = prep_zero_mask(c, data, &constants); data = create_zero_mask(data); *(unsigned long *)(dest+res) = c & zero_bytemask(data); return res + find_zero(data); } *(unsigned long *)(dest+res) = c; res += sizeof(unsigned long); count -= sizeof(unsigned long); max -= sizeof(unsigned long); } while (count) { char c; c = src[res]; dest[res] = c; if (!c) return res; res++; count--; } /* Hit buffer length without finding a NUL; force NUL-termination. */ if (res) dest[res-1] = '\0'; return -E2BIG; } EXPORT_SYMBOL(strscpy); #endif /** * stpcpy - copy a string from src to dest returning a pointer to the new end * of dest, including src's %NUL-terminator. May overrun dest. * @dest: pointer to end of string being copied into. Must be large enough * to receive copy. * @src: pointer to the beginning of string being copied from. Must not overlap * dest. * * stpcpy differs from strcpy in a key way: the return value is a pointer * to the new %NUL-terminating character in @dest. (For strcpy, the return * value is a pointer to the start of @dest). This interface is considered * unsafe as it doesn't perform bounds checking of the inputs. As such it's * not recommended for usage. Instead, its definition is provided in case * the compiler lowers other libcalls to stpcpy. */ char *stpcpy(char *__restrict__ dest, const char *__restrict__ src); char *stpcpy(char *__restrict__ dest, const char *__restrict__ src) { while ((*dest++ = *src++) != '\0') /* nothing */; return --dest; } EXPORT_SYMBOL(stpcpy); #ifndef __HAVE_ARCH_STRCAT char *strcat(char *dest, const char *src) { char *tmp = dest; while (*dest) dest++; while ((*dest++ = *src++) != '\0') ; return tmp; } EXPORT_SYMBOL(strcat); #endif #ifndef __HAVE_ARCH_STRNCAT char *strncat(char *dest, const char *src, size_t count) { char *tmp = dest; if (count) { while (*dest) dest++; while ((*dest++ = *src++) != 0) { if (--count == 0) { *dest = '\0'; break; } } } return tmp; } EXPORT_SYMBOL(strncat); #endif #ifndef __HAVE_ARCH_STRLCAT size_t strlcat(char *dest, const char *src, size_t count) { size_t dsize = strlen(dest); size_t len = strlen(src); size_t res = dsize + len; /* This would be a bug */ BUG_ON(dsize >= count); dest += dsize; count -= dsize; if (len >= count) len = count-1; __builtin_memcpy(dest, src, len); dest[len] = 0; return res; } EXPORT_SYMBOL(strlcat); #endif #ifndef __HAVE_ARCH_STRCMP /** * strcmp - Compare two strings * @cs: One string * @ct: Another string */ int strcmp(const char *cs, const char *ct) { unsigned char c1, c2; while (1) { c1 = *cs++; c2 = *ct++; if (c1 != c2) return c1 < c2 ? -1 : 1; if (!c1) break; } return 0; } EXPORT_SYMBOL(strcmp); #endif #ifndef __HAVE_ARCH_STRNCMP /** * strncmp - Compare two length-limited strings * @cs: One string * @ct: Another string * @count: The maximum number of bytes to compare */ int strncmp(const char *cs, const char *ct, size_t count) { unsigned char c1, c2; while (count) { c1 = *cs++; c2 = *ct++; if (c1 != c2) return c1 < c2 ? -1 : 1; if (!c1) break; count--; } return 0; } EXPORT_SYMBOL(strncmp); #endif #ifndef __HAVE_ARCH_STRCHR /** * strchr - Find the first occurrence of a character in a string * @s: The string to be searched * @c: The character to search for * * Note that the %NUL-terminator is considered part of the string, and can * be searched for. */ char *strchr(const char *s, int c) { for (; *s != (char)c; ++s) if (*s == '\0') return NULL; return (char *)s; } EXPORT_SYMBOL(strchr); #endif #ifndef __HAVE_ARCH_STRCHRNUL /** * strchrnul - Find and return a character in a string, or end of string * @s: The string to be searched * @c: The character to search for * * Returns pointer to first occurrence of 'c' in s. If c is not found, then * return a pointer to the null byte at the end of s. */ char *strchrnul(const char *s, int c) { while (*s && *s != (char)c) s++; return (char *)s; } EXPORT_SYMBOL(strchrnul); #endif /** * strnchrnul - Find and return a character in a length limited string, * or end of string * @s: The string to be searched * @count: The number of characters to be searched * @c: The character to search for * * Returns pointer to the first occurrence of 'c' in s. If c is not found, * then return a pointer to the last character of the string. */ char *strnchrnul(const char *s, size_t count, int c) { while (count-- && *s && *s != (char)c) s++; return (char *)s; } #ifndef __HAVE_ARCH_STRRCHR /** * strrchr - Find the last occurrence of a character in a string * @s: The string to be searched * @c: The character to search for */ char *strrchr(const char *s, int c) { const char *last = NULL; do { if (*s == (char)c) last = s; } while (*s++); return (char *)last; } EXPORT_SYMBOL(strrchr); #endif #ifndef __HAVE_ARCH_STRNCHR /** * strnchr - Find a character in a length limited string * @s: The string to be searched * @count: The number of characters to be searched * @c: The character to search for * * Note that the %NUL-terminator is considered part of the string, and can * be searched for. */ char *strnchr(const char *s, size_t count, int c) { while (count--) { if (*s == (char)c) return (char *)s; if (*s++ == '\0') break; } return NULL; } EXPORT_SYMBOL(strnchr); #endif #ifndef __HAVE_ARCH_STRLEN size_t strlen(const char *s) { const char *sc; for (sc = s; *sc != '\0'; ++sc) /* nothing */; return sc - s; } EXPORT_SYMBOL(strlen); #endif #ifndef __HAVE_ARCH_STRNLEN size_t strnlen(const char *s, size_t count) { const char *sc; for (sc = s; count-- && *sc != '\0'; ++sc) /* nothing */; return sc - s; } EXPORT_SYMBOL(strnlen); #endif #ifndef __HAVE_ARCH_STRSPN /** * strspn - Calculate the length of the initial substring of @s which only contain letters in @accept * @s: The string to be searched * @accept: The string to search for */ size_t strspn(const char *s, const char *accept) { const char *p; for (p = s; *p != '\0'; ++p) { if (!strchr(accept, *p)) break; } return p - s; } EXPORT_SYMBOL(strspn); #endif #ifndef __HAVE_ARCH_STRCSPN /** * strcspn - Calculate the length of the initial substring of @s which does not contain letters in @reject * @s: The string to be searched * @reject: The string to avoid */ size_t strcspn(const char *s, const char *reject) { const char *p; for (p = s; *p != '\0'; ++p) { if (strchr(reject, *p)) break; } return p - s; } EXPORT_SYMBOL(strcspn); #endif #ifndef __HAVE_ARCH_STRPBRK /** * strpbrk - Find the first occurrence of a set of characters * @cs: The string to be searched * @ct: The characters to search for */ char *strpbrk(const char *cs, const char *ct) { const char *sc; for (sc = cs; *sc != '\0'; ++sc) { if (strchr(ct, *sc)) return (char *)sc; } return NULL; } EXPORT_SYMBOL(strpbrk); #endif #ifndef __HAVE_ARCH_STRSEP /** * strsep - Split a string into tokens * @s: The string to be searched * @ct: The characters to search for * * strsep() updates @s to point after the token, ready for the next call. * * It returns empty tokens, too, behaving exactly like the libc function * of that name. In fact, it was stolen from glibc2 and de-fancy-fied. * Same semantics, slimmer shape. ;) */ char *strsep(char **s, const char *ct) { char *sbegin = *s; char *end; if (sbegin == NULL) return NULL; end = strpbrk(sbegin, ct); if (end) *end++ = '\0'; *s = end; return sbegin; } EXPORT_SYMBOL(strsep); #endif #ifndef __HAVE_ARCH_MEMSET /** * memset - Fill a region of memory with the given value * @s: Pointer to the start of the area. * @c: The byte to fill the area with * @count: The size of the area. * * Do not use memset() to access IO space, use memset_io() instead. */ void *memset(void *s, int c, size_t count) { char *xs = s; while (count--) *xs++ = c; return s; } EXPORT_SYMBOL(memset); #endif #ifndef __HAVE_ARCH_MEMSET16 /** * memset16() - Fill a memory area with a uint16_t * @s: Pointer to the start of the area. * @v: The value to fill the area with * @count: The number of values to store * * Differs from memset() in that it fills with a uint16_t instead * of a byte. Remember that @count is the number of uint16_ts to * store, not the number of bytes. */ void *memset16(uint16_t *s, uint16_t v, size_t count) { uint16_t *xs = s; while (count--) *xs++ = v; return s; } EXPORT_SYMBOL(memset16); #endif #ifndef __HAVE_ARCH_MEMSET32 /** * memset32() - Fill a memory area with a uint32_t * @s: Pointer to the start of the area. * @v: The value to fill the area with * @count: The number of values to store * * Differs from memset() in that it fills with a uint32_t instead * of a byte. Remember that @count is the number of uint32_ts to * store, not the number of bytes. */ void *memset32(uint32_t *s, uint32_t v, size_t count) { uint32_t *xs = s; while (count--) *xs++ = v; return s; } EXPORT_SYMBOL(memset32); #endif #ifndef __HAVE_ARCH_MEMSET64 /** * memset64() - Fill a memory area with a uint64_t * @s: Pointer to the start of the area. * @v: The value to fill the area with * @count: The number of values to store * * Differs from memset() in that it fills with a uint64_t instead * of a byte. Remember that @count is the number of uint64_ts to * store, not the number of bytes. */ void *memset64(uint64_t *s, uint64_t v, size_t count) { uint64_t *xs = s; while (count--) *xs++ = v; return s; } EXPORT_SYMBOL(memset64); #endif #ifndef __HAVE_ARCH_MEMCPY /** * memcpy - Copy one area of memory to another * @dest: Where to copy to * @src: Where to copy from * @count: The size of the area. * * You should not use this function to access IO space, use memcpy_toio() * or memcpy_fromio() instead. */ void *memcpy(void *dest, const void *src, size_t count) { char *tmp = dest; const char *s = src; while (count--) *tmp++ = *s++; return dest; } EXPORT_SYMBOL(memcpy); #endif #ifndef __HAVE_ARCH_MEMMOVE /** * memmove - Copy one area of memory to another * @dest: Where to copy to * @src: Where to copy from * @count: The size of the area. * * Unlike memcpy(), memmove() copes with overlapping areas. */ void *memmove(void *dest, const void *src, size_t count) { char *tmp; const char *s; if (dest <= src) { tmp = dest; s = src; while (count--) *tmp++ = *s++; } else { tmp = dest; tmp += count; s = src; s += count; while (count--) *--tmp = *--s; } return dest; } EXPORT_SYMBOL(memmove); #endif #ifndef __HAVE_ARCH_MEMCMP /** * memcmp - Compare two areas of memory * @cs: One area of memory * @ct: Another area of memory * @count: The size of the area. */ #undef memcmp __visible int memcmp(const void *cs, const void *ct, size_t count) { const unsigned char *su1, *su2; int res = 0; #ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS if (count >= sizeof(unsigned long)) { const unsigned long *u1 = cs; const unsigned long *u2 = ct; do { if (get_unaligned(u1) != get_unaligned(u2)) break; u1++; u2++; count -= sizeof(unsigned long); } while (count >= sizeof(unsigned long)); cs = u1; ct = u2; } #endif for (su1 = cs, su2 = ct; 0 < count; ++su1, ++su2, count--) if ((res = *su1 - *su2) != 0) break; return res; } EXPORT_SYMBOL(memcmp); #endif #ifndef __HAVE_ARCH_BCMP /** * bcmp - returns 0 if and only if the buffers have identical contents. * @a: pointer to first buffer. * @b: pointer to second buffer. * @len: size of buffers. * * The sign or magnitude of a non-zero return value has no particular * meaning, and architectures may implement their own more efficient bcmp(). So * while this particular implementation is a simple (tail) call to memcmp, do * not rely on anything but whether the return value is zero or non-zero. */ int bcmp(const void *a, const void *b, size_t len) { return memcmp(a, b, len); } EXPORT_SYMBOL(bcmp); #endif #ifndef __HAVE_ARCH_MEMSCAN /** * memscan - Find a character in an area of memory. * @addr: The memory area * @c: The byte to search for * @size: The size of the area. * * returns the address of the first occurrence of @c, or 1 byte past * the area if @c is not found */ void *memscan(void *addr, int c, size_t size) { unsigned char *p = addr; while (size) { if (*p == (unsigned char)c) return (void *)p; p++; size--; } return (void *)p; } EXPORT_SYMBOL(memscan); #endif #ifndef __HAVE_ARCH_STRSTR /** * strstr - Find the first substring in a %NUL terminated string * @s1: The string to be searched * @s2: The string to search for */ char *strstr(const char *s1, const char *s2) { size_t l1, l2; l2 = strlen(s2); if (!l2) return (char *)s1; l1 = strlen(s1); while (l1 >= l2) { l1--; if (!memcmp(s1, s2, l2)) return (char *)s1; s1++; } return NULL; } EXPORT_SYMBOL(strstr); #endif #ifndef __HAVE_ARCH_STRNSTR /** * strnstr - Find the first substring in a length-limited string * @s1: The string to be searched * @s2: The string to search for * @len: the maximum number of characters to search */ char *strnstr(const char *s1, const char *s2, size_t len) { size_t l2; l2 = strlen(s2); if (!l2) return (char *)s1; while (len >= l2) { len--; if (!memcmp(s1, s2, l2)) return (char *)s1; s1++; } return NULL; } EXPORT_SYMBOL(strnstr); #endif #ifndef __HAVE_ARCH_MEMCHR /** * memchr - Find a character in an area of memory. * @s: The memory area * @c: The byte to search for * @n: The size of the area. * * returns the address of the first occurrence of @c, or %NULL * if @c is not found */ void *memchr(const void *s, int c, size_t n) { const unsigned char *p = s; while (n-- != 0) { if ((unsigned char)c == *p++) { return (void *)(p - 1); } } return NULL; } EXPORT_SYMBOL(memchr); #endif static void *check_bytes8(const u8 *start, u8 value, unsigned int bytes) { while (bytes) { if (*start != value) return (void *)start; start++; bytes--; } return NULL; } /** * memchr_inv - Find an unmatching character in an area of memory. * @start: The memory area * @c: Find a character other than c * @bytes: The size of the area. * * returns the address of the first character other than @c, or %NULL * if the whole buffer contains just @c. */ void *memchr_inv(const void *start, int c, size_t bytes) { u8 value = c; u64 value64; unsigned int words, prefix; if (bytes <= 16) return check_bytes8(start, value, bytes); value64 = value; #if defined(CONFIG_ARCH_HAS_FAST_MULTIPLIER) && BITS_PER_LONG == 64 value64 *= 0x0101010101010101ULL; #elif defined(CONFIG_ARCH_HAS_FAST_MULTIPLIER) value64 *= 0x01010101; value64 |= value64 << 32; #else value64 |= value64 << 8; value64 |= value64 << 16; value64 |= value64 << 32; #endif prefix = (unsigned long)start % 8; if (prefix) { u8 *r; prefix = 8 - prefix; r = check_bytes8(start, value, prefix); if (r) return r; start += prefix; bytes -= prefix; } words = bytes / 8; while (words) { if (*(u64 *)start != value64) return check_bytes8(start, value, 8); start += 8; words--; } return check_bytes8(start, value, bytes % 8); } EXPORT_SYMBOL(memchr_inv);