// SPDX-License-Identifier: GPL-2.0

  /*
   *  linux/lib/string.c
   *
   *  Copyright (C) 1991, 1992  Linus Torvalds
   */
  
  /*
   * stupid library routines.. The optimized versions should generally be found
   * as inline code in <asm-xx/string.h>
   *
   * These are buggy as well..
   *
   * * Fri Jun 25 1999, Ingo Oeser <ioe@informatik.tu-chemnitz.de>
   * -  Added strsep() which will replace strtok() soon (because strsep() is
   *    reentrant and should be faster). Use only strsep() in new code, please.
   *
   * * Sat Feb 09 2002, Jason Thomas <jason@topic.com.au>,
   *                    Matthew Hawkins <matt@mh.dropbear.id.au>
   * -  Kissed strtok() goodbye
   */
  
  #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 <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
  /**
   * strcpy - Copy a %NUL terminated string
   * @dest: Where to copy the string to
   * @src: Where to copy the string from
   */

  #undef 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
  /**

   * strncpy - Copy a length-limited, C-string

   * @dest: Where to copy the string to
   * @src: Where to copy the string from
   * @count: The maximum number of bytes to copy
   *
   * The result is not %NUL-terminated if the source exceeds
   * @count bytes.

   *
   * In the case where the length of @src is less than  that  of
   * count, the remainder of @dest will be padded with %NUL.
   *

   */

  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
  /**

   * strlcpy - Copy a C-string into a sized buffer

   * @dest: Where to copy the string to
   * @src: Where to copy the string from
   * @size: size of destination buffer
   *

   * Compatible with ``*BSD``: the result is always a valid

   * NUL-terminated string that fits in the buffer (unless,
   * of course, the buffer size is zero). It does not pad
   * out the result like strncpy() does.
   */
  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;

  		memcpy(dest, src, len);
  		dest[len] = '\0';
  	}
  	return ret;
  }
  EXPORT_SYMBOL(strlcpy);
  #endif

  #ifndef __HAVE_ARCH_STRSCPY
  /**
   * strscpy - Copy a C-string into a sized buffer
   * @dest: Where to copy the string to
   * @src: Where to copy the string from
   * @count: Size of destination buffer
   *
   * Copy the string, or as much of it as fits, into the dest buffer.
   * The routine returns the number of characters copied (not including
   * the trailing NUL) or -E2BIG if the destination buffer wasn't big enough.
   * The behavior is undefined if the string buffers overlap.
   * The destination buffer is always NUL terminated, unless it's zero-sized.
   *
   * Preferred to strlcpy() since the API doesn't require reading memory
   * from the src string beyond the specified "count" bytes, and since
   * the return value is easier to error-check than strlcpy()'s.
   * In addition, the implementation is robust to the string changing out
   * from underneath it, unlike the current strlcpy() implementation.
   *
   * Preferred to strncpy() since it always returns a valid string, and
   * doesn't unnecessarily force the tail of the destination buffer to be
   * zeroed.  If the zeroing is desired, it's likely cleaner to use strscpy()
   * with an overflow test, then just memset() the tail of the dest buffer.
   */
  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)
  		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
  
  	while (max >= sizeof(unsigned long)) {
  		unsigned long c, data;
  
  		c = *(unsigned long *)(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

  #ifndef __HAVE_ARCH_STRCAT
  /**
   * strcat - Append one %NUL-terminated string to another
   * @dest: The string to be appended to
   * @src: The string to append to it
   */

  #undef 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
  /**

   * strncat - Append a length-limited, C-string to another

   * @dest: The string to be appended to
   * @src: The string to append to it
   * @count: The maximum numbers of bytes to copy
   *

   * Note that in contrast to strncpy(), strncat() ensures the result is

   * terminated.
   */

  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
  /**

   * strlcat - Append a length-limited, C-string to another

   * @dest: The string to be appended to
   * @src: The string to append to it
   * @count: The size of the destination buffer.
   */
  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;
  	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
   */

  #undef strcmp

  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
   */

  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

  #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
   */
  char *strnchr(const char *s, size_t count, int c)
  {
  	for (; count-- && *s != '\0'; ++s)

  		if (*s == (char)c)
  			return (char *)s;

  	return NULL;
  }
  EXPORT_SYMBOL(strnchr);
  #endif

  /**

   * skip_spaces - Removes leading whitespace from @str.
   * @str: The string to be stripped.

   *

   * Returns a pointer to the first non-whitespace character in @str.

   */
  char *skip_spaces(const char *str)
  {
  	while (isspace(*str))
  		++str;
  	return (char *)str;
  }
  EXPORT_SYMBOL(skip_spaces);
  
  /**

   * strim - Removes leading and trailing whitespace from @s.

   * @s: The string to be stripped.
   *
   * Note that the first trailing whitespace is replaced with a %NUL-terminator
   * in the given string @s. Returns a pointer to the first non-whitespace
   * character in @s.
   */

  char *strim(char *s)

  {
  	size_t size;
  	char *end;
  
  	size = strlen(s);

  	if (!size)
  		return s;
  
  	end = s + size - 1;

  	while (end >= s && isspace(*end))

  		end--;
  	*(end + 1) = '\0';

  	return skip_spaces(s);

  }

  EXPORT_SYMBOL(strim);

  #ifndef __HAVE_ARCH_STRLEN
  /**
   * strlen - Find the length of a string
   * @s: The string to be sized
   */

  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
  /**
   * strnlen - Find the length of a length-limited string
   * @s: The string to be sized
   * @count: The maximum number of bytes to search
   */

  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;
  	const char *a;
  	size_t count = 0;
  
  	for (p = s; *p != '\0'; ++p) {
  		for (a = accept; *a != '\0'; ++a) {
  			if (*p == *a)
  				break;
  		}
  		if (*a == '\0')
  			return count;
  		++count;
  	}

  	return count;
  }
  
  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;
  	const char *r;
  	size_t count = 0;
  
  	for (p = s; *p != '\0'; ++p) {
  		for (r = reject; *r != '\0'; ++r) {
  			if (*p == *r)
  				return count;
  		}
  		++count;
  	}

  	return count;

  }

  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 *sc1, *sc2;

  	for (sc1 = cs; *sc1 != '\0'; ++sc1) {
  		for (sc2 = ct; *sc2 != '\0'; ++sc2) {

  			if (*sc1 == *sc2)

  				return (char *)sc1;

  		}
  	}
  	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

  /**
   * sysfs_streq - return true if strings are equal, modulo trailing newline
   * @s1: one string
   * @s2: another string
   *
   * This routine returns true iff two strings are equal, treating both
   * NUL and newline-then-NUL as equivalent string terminations.  It's
   * geared for use with sysfs input strings, which generally terminate
   * with newlines but are compared against values without newlines.
   */
  bool sysfs_streq(const char *s1, const char *s2)
  {
  	while (*s1 && *s1 == *s2) {
  		s1++;
  		s2++;
  	}
  
  	if (*s1 == *s2)
  		return true;
  	if (!*s1 && *s2 == '
  ' && !s2[1])
  		return true;
  	if (*s1 == '
  ' && !s1[1] && !*s2)
  		return true;
  	return false;
  }
  EXPORT_SYMBOL(sysfs_streq);

  /**

   * match_string - matches given string in an array
   * @array:	array of strings
   * @n:		number of strings in the array or -1 for NULL terminated arrays
   * @string:	string to match with
   *
   * Return:
   * index of a @string in the @array if matches, or %-EINVAL otherwise.
   */
  int match_string(const char * const *array, size_t n, const char *string)
  {
  	int index;
  	const char *item;
  
  	for (index = 0; index < n; index++) {
  		item = array[index];
  		if (!item)
  			break;
  		if (!strcmp(item, string))
  			return index;
  	}
  
  	return -EINVAL;
  }
  EXPORT_SYMBOL(match_string);

  /**
   * __sysfs_match_string - matches given string in an array
   * @array: array of strings
   * @n: number of strings in the array or -1 for NULL terminated arrays
   * @str: string to match with
   *
   * Returns index of @str in the @array or -EINVAL, just like match_string().
   * Uses sysfs_streq instead of strcmp for matching.
   */
  int __sysfs_match_string(const char * const *array, size_t n, const char *str)
  {
  	const char *item;
  	int index;
  
  	for (index = 0; index < n; index++) {
  		item = array[index];
  		if (!item)
  			break;
  		if (sysfs_streq(item, str))
  			return index;
  	}
  
  	return -EINVAL;
  }
  EXPORT_SYMBOL(__sysfs_match_string);

  #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

  /**
   * memzero_explicit - Fill a region of memory (e.g. sensitive
   *		      keying data) with 0s.
   * @s: Pointer to the start of the area.
   * @count: The size of the area.
   *

   * Note: usually using memset() is just fine (!), but in cases
   * where clearing out _local_ data at the end of a scope is
   * necessary, memzero_explicit() should be used instead in
   * order to prevent the compiler from optimising away zeroing.
   *

   * memzero_explicit() doesn't need an arch-specific version as
   * it just invokes the one of memset() implicitly.
   */
  void memzero_explicit(void *s, size_t count)
  {
  	memset(s, 0, count);

  	barrier_data(s);

  }
  EXPORT_SYMBOL(memzero_explicit);

  #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;

  	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_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 == 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);

  
  /**
   * strreplace - Replace all occurrences of character in string.
   * @s: The string to operate on.
   * @old: The character being replaced.
   * @new: The character @old is replaced with.
   *
   * Returns pointer to the nul byte at the end of @s.
   */
  char *strreplace(char *s, char old, char new)
  {
  	for (; *s; ++s)
  		if (*s == old)
  			*s = new;
  	return s;
  }
  EXPORT_SYMBOL(strreplace);

  
  void fortify_panic(const char *name)
  {
  	pr_emerg("detected buffer overflow in %s
  ", name);
  	BUG();
  }
  EXPORT_SYMBOL(fortify_panic);

  
  #ifdef CONFIG_STRING_SELFTEST
  #include <linux/slab.h>
  #include <linux/module.h>
  
  static __init int memset16_selftest(void)
  {
  	unsigned i, j, k;

  	u16 v, *p;
  
  	p = kmalloc(256 * 2 * 2, GFP_KERNEL);
  	if (!p)
  		return -1;

  
  	for (i = 0; i < 256; i++) {
  		for (j = 0; j < 256; j++) {
  			memset(p, 0xa1, 256 * 2 * sizeof(v));
  			memset16(p + i, 0xb1b2, j);
  			for (k = 0; k < 512; k++) {
  				v = p[k];
  				if (k < i) {
  					if (v != 0xa1a1)
  						goto fail;
  				} else if (k < i + j) {
  					if (v != 0xb1b2)
  						goto fail;
  				} else {
  					if (v != 0xa1a1)
  						goto fail;
  				}
  			}
  		}
  	}
  
  fail:
  	kfree(p);
  	if (i < 256)
  		return (i << 24) | (j << 16) | k;
  	return 0;
  }
  
  static __init int memset32_selftest(void)
  {
  	unsigned i, j, k;

  	u32 v, *p;
  
  	p = kmalloc(256 * 2 * 4, GFP_KERNEL);
  	if (!p)
  		return -1;

  
  	for (i = 0; i < 256; i++) {
  		for (j = 0; j < 256; j++) {
  			memset(p, 0xa1, 256 * 2 * sizeof(v));
  			memset32(p + i, 0xb1b2b3b4, j);
  			for (k = 0; k < 512; k++) {
  				v = p[k];
  				if (k < i) {
  					if (v != 0xa1a1a1a1)
  						goto fail;
  				} else if (k < i + j) {
  					if (v != 0xb1b2b3b4)
  						goto fail;
  				} else {
  					if (v != 0xa1a1a1a1)
  						goto fail;
  				}
  			}
  		}
  	}
  
  fail:
  	kfree(p);
  	if (i < 256)
  		return (i << 24) | (j << 16) | k;
  	return 0;
  }
  
  static __init int memset64_selftest(void)
  {
  	unsigned i, j, k;

  	u64 v, *p;
  
  	p = kmalloc(256 * 2 * 8, GFP_KERNEL);
  	if (!p)
  		return -1;

  
  	for (i = 0; i < 256; i++) {
  		for (j = 0; j < 256; j++) {
  			memset(p, 0xa1, 256 * 2 * sizeof(v));
  			memset64(p + i, 0xb1b2b3b4b5b6b7b8ULL, j);
  			for (k = 0; k < 512; k++) {
  				v = p[k];
  				if (k < i) {
  					if (v != 0xa1a1a1a1a1a1a1a1ULL)
  						goto fail;
  				} else if (k < i + j) {
  					if (v != 0xb1b2b3b4b5b6b7b8ULL)
  						goto fail;
  				} else {
  					if (v != 0xa1a1a1a1a1a1a1a1ULL)
  						goto fail;
  				}
  			}
  		}
  	}
  
  fail:
  	kfree(p);
  	if (i < 256)
  		return (i << 24) | (j << 16) | k;
  	return 0;
  }
  
  static __init int string_selftest_init(void)
  {
  	int test, subtest;
  
  	test = 1;
  	subtest = memset16_selftest();
  	if (subtest)
  		goto fail;
  
  	test = 2;
  	subtest = memset32_selftest();
  	if (subtest)
  		goto fail;
  
  	test = 3;
  	subtest = memset64_selftest();
  	if (subtest)
  		goto fail;
  
  	pr_info("String selftests succeeded
  ");
  	return 0;
  fail:
  	pr_crit("String selftest failure %d.%08x
  ", test, subtest);
  	return 0;
  }
  
  module_init(string_selftest_init);
  #endif	/* CONFIG_STRING_SELFTEST */