// 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/bits.h>#include <linux/bug.h>#include <linux/ctype.h>#include <linux/errno.h>#include <linux/limits.h>#include <linux/linkage.h>#include <linux/minmax.h>#include <linux/stddef.h>#include <linux/string.h>#include <linux/types.h> #include <asm/page.h>#include <asm/rwonce.h>#include <linux/unaligned.h>#include <asm/word-at-a-time.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_STRCASECMPint 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_STRCPYchar *strcpy(char *dest, const char *src){	char *tmp = dest; 	while ((*dest++ = *src++) != '\0')		/* nothing */;	return tmp;}EXPORT_SYMBOL(strcpy);#endif #ifdef __BIG_ENDIAN# define ALLBUTLAST_BYTE_MASK (~255ul)#else# define ALLBUTLAST_BYTE_MASK (~0ul >> 8)#endif ssize_t sized_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; #ifndef CONFIG_DCACHE_WORD_ACCESS#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))		max = min(PAGE_SIZE - ((long)src & (PAGE_SIZE - 1)), max);#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#endif 	/*	 * load_unaligned_zeropad() or 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; #ifdef CONFIG_DCACHE_WORD_ACCESS		c = load_unaligned_zeropad(src+res);#else		c = read_word_at_a_time(src+res);#endif		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);		}		count -= sizeof(unsigned long);		if (unlikely(!count)) {			c &= ALLBUTLAST_BYTE_MASK;			*(unsigned long *)(dest+res) = c;			return -E2BIG;		}		*(unsigned long *)(dest+res) = c;		res += sizeof(unsigned long);		max -= sizeof(unsigned long);	} 	while (count > 1) {		char c; 		c = src[res];		dest[res] = c;		if (!c)			return res;		res++;		count--;	} 	/* Force NUL-termination. */	dest[res] = '\0'; 	/* Return E2BIG if the source didn't stop */	return src[res] ? -E2BIG : res;}EXPORT_SYMBOL(sized_strscpy); /** * 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_STRCATchar *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_STRNCATchar *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_STRLCATsize_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_STRLENsize_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_STRNLENsize_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';

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