linux/lib/string.c

// 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/stddef.h>
#include <linux/string.h>
#include <linux/types.h>

#include <asm/page.h>
#include <asm/rwonce.h>
#include <asm/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)
{ … }
EXPORT_SYMBOL(…);
#endif

#ifndef __HAVE_ARCH_STRCASECMP
int strcasecmp(const char *s1, const char *s2)
{ … }
EXPORT_SYMBOL(…);
#endif

#ifndef __HAVE_ARCH_STRCPY
char *strcpy(char *dest, const char *src)
{ … }
EXPORT_SYMBOL(…);
#endif

#ifndef __HAVE_ARCH_STRNCPY
char *strncpy(char *dest, const char *src, size_t count)
{ … }
EXPORT_SYMBOL(…);
#endif

ssize_t sized_strscpy(char *dest, const char *src, size_t count)
{ … }
EXPORT_SYMBOL(…);

/**
 * 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)
{ … }
EXPORT_SYMBOL(…);

#ifndef __HAVE_ARCH_STRCAT
char *strcat(char *dest, const char *src)
{ … }
EXPORT_SYMBOL(…);
#endif

#ifndef __HAVE_ARCH_STRNCAT
char *strncat(char *dest, const char *src, size_t count)
{ … }
EXPORT_SYMBOL(…);
#endif

#ifndef __HAVE_ARCH_STRLCAT
size_t strlcat(char *dest, const char *src, size_t count)
{ … }
EXPORT_SYMBOL(…);
#endif

#ifndef __HAVE_ARCH_STRCMP
/**
 * strcmp - Compare two strings
 * @cs: One string
 * @ct: Another string
 */
int strcmp(const char *cs, const char *ct)
{ … }
EXPORT_SYMBOL(…);
#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)
{ … }
EXPORT_SYMBOL(…);
#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)
{ … }
EXPORT_SYMBOL(…);
#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)
{ … }
EXPORT_SYMBOL(…);
#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)
{ … }

#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)
{ … }
EXPORT_SYMBOL(…);
#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)
{ … }
EXPORT_SYMBOL(…);
#endif

#ifndef __HAVE_ARCH_STRLEN
size_t strlen(const char *s)
{ … }
EXPORT_SYMBOL(…);
#endif

#ifndef __HAVE_ARCH_STRNLEN
size_t strnlen(const char *s, size_t count)
{ … }
EXPORT_SYMBOL(…);
#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)
{ … }
EXPORT_SYMBOL(…);
#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)
{ … }
EXPORT_SYMBOL(…);
#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)
{ … }
EXPORT_SYMBOL(…);
#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)
{ … }
EXPORT_SYMBOL(…);
#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)
{ … }
EXPORT_SYMBOL(…);
#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)
{ … }
EXPORT_SYMBOL(…);
#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)
{ … }
EXPORT_SYMBOL(…);
#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)
{ … }
EXPORT_SYMBOL(…);
#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)
{ … }
EXPORT_SYMBOL(…);
#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)
{ … }
EXPORT_SYMBOL(…);
#endif

static void *check_bytes8(const u8 *start, u8 value, unsigned int bytes)
{ … }

/**
 * 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)
{ … }
EXPORT_SYMBOL(…);