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 // 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
 /**
  * strcpy - Copy a %NUL terminated string
  * @dest: Where to copy the string to
  * @src: Where to copy the string from
  */
 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
  * 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 zeroing is desired please use strscpy_pad().
  *
  * Returns:
  * * The number of characters copied (not including the trailing %NUL)
  * * -E2BIG if count is 0 or @src was truncated.
  */
 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
 
     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
 /**
  * strcat - Append one %NUL-terminated string to another
  * @dest: The string to be appended to
  * @src: The string to append to it
  */
 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
  */
 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
 /**
  * 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;
 
     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 *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
 
 #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);

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