lib/string.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *  linux/lib/string.c
   4  *
   5  *  Copyright (C) 1991, 1992  Linus Torvalds
   6  */
   7
   8 /*
   9  * stupid library routines.. The optimized versions should generally be found
  10  * as inline code in <asm-xx/string.h>
  11  *
  12  * These are buggy as well..
  13  *
  14  * * Fri Jun 25 1999, Ingo Oeser <ioe@informatik.tu-chemnitz.de>
  15  * -  Added strsep() which will replace strtok() soon (because strsep() is
  16  *    reentrant and should be faster). Use only strsep() in new code, please.
  17  *
  18  * * Sat Feb 09 2002, Jason Thomas <jason@topic.com.au>,
  19  *                    Matthew Hawkins <matt@mh.dropbear.id.au>
  20  * -  Kissed strtok() goodbye
  21  */
  22
  23 #include <linux/types.h>
  24 #include <linux/string.h>
  25 #include <linux/ctype.h>
  26 #include <linux/kernel.h>
  27 #include <linux/export.h>
  28 #include <linux/bug.h>
  29 #include <linux/errno.h>
  30 #include <linux/slab.h>
  31
  32 #include <asm/byteorder.h>
  33 #include <asm/word-at-a-time.h>
  34 #include <asm/page.h>
  35
  36 #ifndef __HAVE_ARCH_STRNCASECMP
  37 /**
  38  * strncasecmp - Case insensitive, length-limited string comparison
  39  * @s1: One string
  40  * @s2: The other string
  41  * @len: the maximum number of characters to compare
  42  */
  43 int strncasecmp(const char *s1, const char *s2, size_t len)
  44 {
  45         /* Yes, Virginia, it had better be unsigned */
  46         unsigned char c1, c2;
  47
  48         if (!len)
  49                 return 0;
  50
  51         do {
  52                 c1 = *s1++;
  53                 c2 = *s2++;
  54                 if (!c1 || !c2)
  55                         break;
  56                 if (c1 == c2)
  57                         continue;
  58                 c1 = tolower(c1);
  59                 c2 = tolower(c2);
  60                 if (c1 != c2)
  61                         break;
  62         } while (--len);
  63         return (int)c1 - (int)c2;
  64 }
  65 EXPORT_SYMBOL(strncasecmp);
  66 #endif
  67
  68 #ifndef __HAVE_ARCH_STRCASECMP
  69 int strcasecmp(const char *s1, const char *s2)
  70 {
  71         int c1, c2;
  72
  73         do {
  74                 c1 = tolower(*s1++);
  75                 c2 = tolower(*s2++);
  76         } while (c1 == c2 && c1 != 0);
  77         return c1 - c2;
  78 }
  79 EXPORT_SYMBOL(strcasecmp);
  80 #endif
  81
  82 #ifndef __HAVE_ARCH_STRCPY
  83 /**
  84  * strcpy - Copy a %NUL terminated string
  85  * @dest: Where to copy the string to
  86  * @src: Where to copy the string from
  87  */
  88 #undef strcpy
  89 char *strcpy(char *dest, const char *src)
  90 {
  91         char *tmp = dest;
  92
  93         while ((*dest++ = *src++) != '\0')
  94                 /* nothing */;
  95         return tmp;
  96 }
  97 EXPORT_SYMBOL(strcpy);
  98 #endif
  99
 100 #ifndef __HAVE_ARCH_STRNCPY
 101 /**
 102  * strncpy - Copy a length-limited, C-string
 103  * @dest: Where to copy the string to
 104  * @src: Where to copy the string from
 105  * @count: The maximum number of bytes to copy
 106  *
 107  * The result is not %NUL-terminated if the source exceeds
 108  * @count bytes.
 109  *
 110  * In the case where the length of @src is less than  that  of
 111  * count, the remainder of @dest will be padded with %NUL.
 112  *
 113  */
 114 char *strncpy(char *dest, const char *src, size_t count)
 115 {
 116         char *tmp = dest;
 117
 118         while (count) {
 119                 if ((*tmp = *src) != 0)
 120                         src++;
 121                 tmp++;
 122                 count--;
 123         }
 124         return dest;
 125 }
 126 EXPORT_SYMBOL(strncpy);
 127 #endif
 128
 129 #ifndef __HAVE_ARCH_STRLCPY
 130 /**
 131  * strlcpy - Copy a C-string into a sized buffer
 132  * @dest: Where to copy the string to
 133  * @src: Where to copy the string from
 134  * @size: size of destination buffer
 135  *
 136  * Compatible with ``*BSD``: the result is always a valid
 137  * NUL-terminated string that fits in the buffer (unless,
 138  * of course, the buffer size is zero). It does not pad
 139  * out the result like strncpy() does.
 140  */
 141 size_t strlcpy(char *dest, const char *src, size_t size)
 142 {
 143         size_t ret = strlen(src);
 144
 145         if (size) {
 146                 size_t len = (ret >= size) ? size - 1 : ret;
 147                 memcpy(dest, src, len);
 148                 dest[len] = '\0';
 149         }
 150         return ret;
 151 }
 152 EXPORT_SYMBOL(strlcpy);
 153 #endif
 154
 155 #ifndef __HAVE_ARCH_STRSCPY
 156 /**
 157  * strscpy - Copy a C-string into a sized buffer
 158  * @dest: Where to copy the string to
 159  * @src: Where to copy the string from
 160  * @count: Size of destination buffer
 161  *
 162  * Copy the string, or as much of it as fits, into the dest buffer.
 163  * The routine returns the number of characters copied (not including
 164  * the trailing NUL) or -E2BIG if the destination buffer wasn't big enough.
 165  * The behavior is undefined if the string buffers overlap.
 166  * The destination buffer is always NUL terminated, unless it's zero-sized.
 167  *
 168  * Preferred to strlcpy() since the API doesn't require reading memory
 169  * from the src string beyond the specified "count" bytes, and since
 170  * the return value is easier to error-check than strlcpy()'s.
 171  * In addition, the implementation is robust to the string changing out
 172  * from underneath it, unlike the current strlcpy() implementation.
 173  *
 174  * Preferred to strncpy() since it always returns a valid string, and
 175  * doesn't unnecessarily force the tail of the destination buffer to be
 176  * zeroed.  If the zeroing is desired, it's likely cleaner to use strscpy()
 177  * with an overflow test, then just memset() the tail of the dest buffer.
 178  */
 179 ssize_t strscpy(char *dest, const char *src, size_t count)
 180 {
 181         const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
 182         size_t max = count;
 183         long res = 0;
 184
 185         if (count == 0)
 186                 return -E2BIG;
 187
 188 #ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
 189         /*
 190          * If src is unaligned, don't cross a page boundary,
 191          * since we don't know if the next page is mapped.
 192          */
 193         if ((long)src & (sizeof(long) - 1)) {
 194                 size_t limit = PAGE_SIZE - ((long)src & (PAGE_SIZE - 1));
 195                 if (limit < max)
 196                         max = limit;
 197         }
 198 #else
 199         /* If src or dest is unaligned, don't do word-at-a-time. */
 200         if (((long) dest | (long) src) & (sizeof(long) - 1))
 201                 max = 0;
 202 #endif
 203
 204         while (max >= sizeof(unsigned long)) {
 205                 unsigned long c, data;
 206
 207                 c = read_word_at_a_time(src+res);
 208                 if (has_zero(c, &data, &constants)) {
 209                         data = prep_zero_mask(c, data, &constants);
 210                         data = create_zero_mask(data);
 211                         *(unsigned long *)(dest+res) = c & zero_bytemask(data);
 212                         return res + find_zero(data);
 213                 }
 214                 *(unsigned long *)(dest+res) = c;
 215                 res += sizeof(unsigned long);
 216                 count -= sizeof(unsigned long);
 217                 max -= sizeof(unsigned long);
 218         }
 219
 220         while (count) {
 221                 char c;
 222
 223                 c = src[res];
 224                 dest[res] = c;
 225                 if (!c)
 226                         return res;
 227                 res++;
 228                 count--;
 229         }
 230
 231         /* Hit buffer length without finding a NUL; force NUL-termination. */
 232         if (res)
 233                 dest[res-1] = '\0';
 234
 235         return -E2BIG;
 236 }
 237 EXPORT_SYMBOL(strscpy);
 238 #endif
 239
 240 #ifndef __HAVE_ARCH_STRCAT
 241 /**
 242  * strcat - Append one %NUL-terminated string to another
 243  * @dest: The string to be appended to
 244  * @src: The string to append to it
 245  */
 246 #undef strcat
 247 char *strcat(char *dest, const char *src)
 248 {
 249         char *tmp = dest;
 250
 251         while (*dest)
 252                 dest++;
 253         while ((*dest++ = *src++) != '\0')
 254                 ;
 255         return tmp;
 256 }
 257 EXPORT_SYMBOL(strcat);
 258 #endif
 259
 260 #ifndef __HAVE_ARCH_STRNCAT
 261 /**
 262  * strncat - Append a length-limited, C-string to another
 263  * @dest: The string to be appended to
 264  * @src: The string to append to it
 265  * @count: The maximum numbers of bytes to copy
 266  *
 267  * Note that in contrast to strncpy(), strncat() ensures the result is
 268  * terminated.
 269  */
 270 char *strncat(char *dest, const char *src, size_t count)
 271 {
 272         char *tmp = dest;
 273
 274         if (count) {
 275                 while (*dest)
 276                         dest++;
 277                 while ((*dest++ = *src++) != 0) {
 278                         if (--count == 0) {
 279                                 *dest = '\0';
 280                                 break;
 281                         }
 282                 }
 283         }
 284         return tmp;
 285 }
 286 EXPORT_SYMBOL(strncat);
 287 #endif
 288
 289 #ifndef __HAVE_ARCH_STRLCAT
 290 /**
 291  * strlcat - Append a length-limited, C-string to another
 292  * @dest: The string to be appended to
 293  * @src: The string to append to it
 294  * @count: The size of the destination buffer.
 295  */
 296 size_t strlcat(char *dest, const char *src, size_t count)
 297 {
 298         size_t dsize = strlen(dest);
 299         size_t len = strlen(src);
 300         size_t res = dsize + len;
 301
 302         /* This would be a bug */
 303         BUG_ON(dsize >= count);
 304
 305         dest += dsize;
 306         count -= dsize;
 307         if (len >= count)
 308                 len = count-1;
 309         memcpy(dest, src, len);
 310         dest[len] = 0;
 311         return res;
 312 }
 313 EXPORT_SYMBOL(strlcat);
 314 #endif
 315
 316 #ifndef __HAVE_ARCH_STRCMP
 317 /**
 318  * strcmp - Compare two strings
 319  * @cs: One string
 320  * @ct: Another string
 321  */
 322 #undef strcmp
 323 int strcmp(const char *cs, const char *ct)
 324 {
 325         unsigned char c1, c2;
 326
 327         while (1) {
 328                 c1 = *cs++;
 329                 c2 = *ct++;
 330                 if (c1 != c2)
 331                         return c1 < c2 ? -1 : 1;
 332                 if (!c1)
 333                         break;
 334         }
 335         return 0;
 336 }
 337 EXPORT_SYMBOL(strcmp);
 338 #endif
 339
 340 #ifndef __HAVE_ARCH_STRNCMP
 341 /**
 342  * strncmp - Compare two length-limited strings
 343  * @cs: One string
 344  * @ct: Another string
 345  * @count: The maximum number of bytes to compare
 346  */
 347 int strncmp(const char *cs, const char *ct, size_t count)
 348 {
 349         unsigned char c1, c2;
 350
 351         while (count) {
 352                 c1 = *cs++;
 353                 c2 = *ct++;
 354                 if (c1 != c2)
 355                         return c1 < c2 ? -1 : 1;
 356                 if (!c1)
 357                         break;
 358                 count--;
 359         }
 360         return 0;
 361 }
 362 EXPORT_SYMBOL(strncmp);
 363 #endif
 364
 365 #ifndef __HAVE_ARCH_STRCHR
 366 /**
 367  * strchr - Find the first occurrence of a character in a string
 368  * @s: The string to be searched
 369  * @c: The character to search for
 370  */
 371 char *strchr(const char *s, int c)
 372 {
 373         for (; *s != (char)c; ++s)
 374                 if (*s == '\0')
 375                         return NULL;
 376         return (char *)s;
 377 }
 378 EXPORT_SYMBOL(strchr);
 379 #endif
 380
 381 #ifndef __HAVE_ARCH_STRCHRNUL
 382 /**
 383  * strchrnul - Find and return a character in a string, or end of string
 384  * @s: The string to be searched
 385  * @c: The character to search for
 386  *
 387  * Returns pointer to first occurrence of 'c' in s. If c is not found, then
 388  * return a pointer to the null byte at the end of s.
 389  */
 390 char *strchrnul(const char *s, int c)
 391 {
 392         while (*s && *s != (char)c)
 393                 s++;
 394         return (char *)s;
 395 }
 396 EXPORT_SYMBOL(strchrnul);
 397 #endif
 398
 399 #ifndef __HAVE_ARCH_STRRCHR
 400 /**
 401  * strrchr - Find the last occurrence of a character in a string
 402  * @s: The string to be searched
 403  * @c: The character to search for
 404  */
 405 char *strrchr(const char *s, int c)
 406 {
 407         const char *last = NULL;
 408         do {
 409                 if (*s == (char)c)
 410                         last = s;
 411         } while (*s++);
 412         return (char *)last;
 413 }
 414 EXPORT_SYMBOL(strrchr);
 415 #endif
 416
 417 #ifndef __HAVE_ARCH_STRNCHR
 418 /**
 419  * strnchr - Find a character in a length limited string
 420  * @s: The string to be searched
 421  * @count: The number of characters to be searched
 422  * @c: The character to search for
 423  */
 424 char *strnchr(const char *s, size_t count, int c)
 425 {
 426         for (; count-- && *s != '\0'; ++s)
 427                 if (*s == (char)c)
 428                         return (char *)s;
 429         return NULL;
 430 }
 431 EXPORT_SYMBOL(strnchr);
 432 #endif
 433
 434 /**
 435  * skip_spaces - Removes leading whitespace from @str.
 436  * @str: The string to be stripped.
 437  *
 438  * Returns a pointer to the first non-whitespace character in @str.
 439  */
 440 char *skip_spaces(const char *str)
 441 {
 442         while (isspace(*str))
 443                 ++str;
 444         return (char *)str;
 445 }
 446 EXPORT_SYMBOL(skip_spaces);
 447
 448 /**
 449  * strim - Removes leading and trailing whitespace from @s.
 450  * @s: The string to be stripped.
 451  *
 452  * Note that the first trailing whitespace is replaced with a %NUL-terminator
 453  * in the given string @s. Returns a pointer to the first non-whitespace
 454  * character in @s.
 455  */
 456 char *strim(char *s)
 457 {
 458         size_t size;
 459         char *end;
 460
 461         size = strlen(s);
 462         if (!size)
 463                 return s;
 464
 465         end = s + size - 1;
 466         while (end >= s && isspace(*end))
 467                 end--;
 468         *(end + 1) = '\0';
 469
 470         return skip_spaces(s);
 471 }
 472 EXPORT_SYMBOL(strim);
 473
 474 #ifndef __HAVE_ARCH_STRLEN
 475 /**
 476  * strlen - Find the length of a string
 477  * @s: The string to be sized
 478  */
 479 size_t strlen(const char *s)
 480 {
 481         const char *sc;
 482
 483         for (sc = s; *sc != '\0'; ++sc)
 484                 /* nothing */;
 485         return sc - s;
 486 }
 487 EXPORT_SYMBOL(strlen);
 488 #endif
 489
 490 #ifndef __HAVE_ARCH_STRNLEN
 491 /**
 492  * strnlen - Find the length of a length-limited string
 493  * @s: The string to be sized
 494  * @count: The maximum number of bytes to search
 495  */
 496 size_t strnlen(const char *s, size_t count)
 497 {
 498         const char *sc;
 499
 500         for (sc = s; count-- && *sc != '\0'; ++sc)
 501                 /* nothing */;
 502         return sc - s;
 503 }
 504 EXPORT_SYMBOL(strnlen);
 505 #endif
 506
 507 #ifndef __HAVE_ARCH_STRSPN
 508 /**
 509  * strspn - Calculate the length of the initial substring of @s which only contain letters in @accept
 510  * @s: The string to be searched
 511  * @accept: The string to search for
 512  */
 513 size_t strspn(const char *s, const char *accept)
 514 {
 515         const char *p;
 516         const char *a;
 517         size_t count = 0;
 518
 519         for (p = s; *p != '\0'; ++p) {
 520                 for (a = accept; *a != '\0'; ++a) {
 521                         if (*p == *a)
 522                                 break;
 523                 }
 524                 if (*a == '\0')
 525                         return count;
 526                 ++count;
 527         }
 528         return count;
 529 }
 530
 531 EXPORT_SYMBOL(strspn);
 532 #endif
 533
 534 #ifndef __HAVE_ARCH_STRCSPN
 535 /**
 536  * strcspn - Calculate the length of the initial substring of @s which does not contain letters in @reject
 537  * @s: The string to be searched
 538  * @reject: The string to avoid
 539  */
 540 size_t strcspn(const char *s, const char *reject)
 541 {
 542         const char *p;
 543         const char *r;
 544         size_t count = 0;
 545
 546         for (p = s; *p != '\0'; ++p) {
 547                 for (r = reject; *r != '\0'; ++r) {
 548                         if (*p == *r)
 549                                 return count;
 550                 }
 551                 ++count;
 552         }
 553         return count;
 554 }
 555 EXPORT_SYMBOL(strcspn);
 556 #endif
 557
 558 #ifndef __HAVE_ARCH_STRPBRK
 559 /**
 560  * strpbrk - Find the first occurrence of a set of characters
 561  * @cs: The string to be searched
 562  * @ct: The characters to search for
 563  */
 564 char *strpbrk(const char *cs, const char *ct)
 565 {
 566         const char *sc1, *sc2;
 567
 568         for (sc1 = cs; *sc1 != '\0'; ++sc1) {
 569                 for (sc2 = ct; *sc2 != '\0'; ++sc2) {
 570                         if (*sc1 == *sc2)
 571                                 return (char *)sc1;
 572                 }
 573         }
 574         return NULL;
 575 }
 576 EXPORT_SYMBOL(strpbrk);
 577 #endif
 578
 579 #ifndef __HAVE_ARCH_STRSEP
 580 /**
 581  * strsep - Split a string into tokens
 582  * @s: The string to be searched
 583  * @ct: The characters to search for
 584  *
 585  * strsep() updates @s to point after the token, ready for the next call.
 586  *
 587  * It returns empty tokens, too, behaving exactly like the libc function
 588  * of that name. In fact, it was stolen from glibc2 and de-fancy-fied.
 589  * Same semantics, slimmer shape. ;)
 590  */
 591 char *strsep(char **s, const char *ct)
 592 {
 593         char *sbegin = *s;
 594         char *end;
 595
 596         if (sbegin == NULL)
 597                 return NULL;
 598
 599         end = strpbrk(sbegin, ct);
 600         if (end)
 601                 *end++ = '\0';
 602         *s = end;
 603         return sbegin;
 604 }
 605 EXPORT_SYMBOL(strsep);
 606 #endif
 607
 608 /**
 609  * sysfs_streq - return true if strings are equal, modulo trailing newline
 610  * @s1: one string
 611  * @s2: another string
 612  *
 613  * This routine returns true iff two strings are equal, treating both
 614  * NUL and newline-then-NUL as equivalent string terminations.  It's
 615  * geared for use with sysfs input strings, which generally terminate
 616  * with newlines but are compared against values without newlines.
 617  */
 618 bool sysfs_streq(const char *s1, const char *s2)
 619 {
 620         while (*s1 && *s1 == *s2) {
 621                 s1++;
 622                 s2++;
 623         }
 624
 625         if (*s1 == *s2)
 626                 return true;
 627         if (!*s1 && *s2 == '\n' && !s2[1])
 628                 return true;
 629         if (*s1 == '\n' && !s1[1] && !*s2)
 630                 return true;
 631         return false;
 632 }
 633 EXPORT_SYMBOL(sysfs_streq);
 634
 635 /**
 636  * match_string - matches given string in an array
 637  * @array:      array of strings
 638  * @n:          number of strings in the array or -1 for NULL terminated arrays
 639  * @string:     string to match with
 640  *
 641  * Return:
 642  * index of a @string in the @array if matches, or %-EINVAL otherwise.
 643  */
 644 int match_string(const char * const *array, size_t n, const char *string)
 645 {
 646         int index;
 647         const char *item;
 648
 649         for (index = 0; index < n; index++) {
 650                 item = array[index];
 651                 if (!item)
 652                         break;
 653                 if (!strcmp(item, string))
 654                         return index;
 655         }
 656
 657         return -EINVAL;
 658 }
 659 EXPORT_SYMBOL(match_string);
 660
 661 /**
 662  * __sysfs_match_string - matches given string in an array
 663  * @array: array of strings
 664  * @n: number of strings in the array or -1 for NULL terminated arrays
 665  * @str: string to match with
 666  *
 667  * Returns index of @str in the @array or -EINVAL, just like match_string().
 668  * Uses sysfs_streq instead of strcmp for matching.
 669  */
 670 int __sysfs_match_string(const char * const *array, size_t n, const char *str)
 671 {
 672         const char *item;
 673         int index;
 674
 675         for (index = 0; index < n; index++) {
 676                 item = array[index];
 677                 if (!item)
 678                         break;
 679                 if (sysfs_streq(item, str))
 680                         return index;
 681         }
 682
 683         return -EINVAL;
 684 }
 685 EXPORT_SYMBOL(__sysfs_match_string);
 686
 687 #ifndef __HAVE_ARCH_MEMSET
 688 /**
 689  * memset - Fill a region of memory with the given value
 690  * @s: Pointer to the start of the area.
 691  * @c: The byte to fill the area with
 692  * @count: The size of the area.
 693  *
 694  * Do not use memset() to access IO space, use memset_io() instead.
 695  */
 696 void *memset(void *s, int c, size_t count)
 697 {
 698         char *xs = s;
 699
 700         while (count--)
 701                 *xs++ = c;
 702         return s;
 703 }
 704 EXPORT_SYMBOL(memset);
 705 #endif
 706
 707 /**
 708  * memzero_explicit - Fill a region of memory (e.g. sensitive
 709  *                    keying data) with 0s.
 710  * @s: Pointer to the start of the area.
 711  * @count: The size of the area.
 712  *
 713  * Note: usually using memset() is just fine (!), but in cases
 714  * where clearing out _local_ data at the end of a scope is
 715  * necessary, memzero_explicit() should be used instead in
 716  * order to prevent the compiler from optimising away zeroing.
 717  *
 718  * memzero_explicit() doesn't need an arch-specific version as
 719  * it just invokes the one of memset() implicitly.
 720  */
 721 void memzero_explicit(void *s, size_t count)
 722 {
 723         memset(s, 0, count);
 724         barrier_data(s);
 725 }
 726 EXPORT_SYMBOL(memzero_explicit);
 727
 728 #ifndef __HAVE_ARCH_MEMSET16
 729 /**
 730  * memset16() - Fill a memory area with a uint16_t
 731  * @s: Pointer to the start of the area.
 732  * @v: The value to fill the area with
 733  * @count: The number of values to store
 734  *
 735  * Differs from memset() in that it fills with a uint16_t instead
 736  * of a byte.  Remember that @count is the number of uint16_ts to
 737  * store, not the number of bytes.
 738  */
 739 void *memset16(uint16_t *s, uint16_t v, size_t count)
 740 {
 741         uint16_t *xs = s;
 742
 743         while (count--)
 744                 *xs++ = v;
 745         return s;
 746 }
 747 EXPORT_SYMBOL(memset16);
 748 #endif
 749
 750 #ifndef __HAVE_ARCH_MEMSET32
 751 /**
 752  * memset32() - Fill a memory area with a uint32_t
 753  * @s: Pointer to the start of the area.
 754  * @v: The value to fill the area with
 755  * @count: The number of values to store
 756  *
 757  * Differs from memset() in that it fills with a uint32_t instead
 758  * of a byte.  Remember that @count is the number of uint32_ts to
 759  * store, not the number of bytes.
 760  */
 761 void *memset32(uint32_t *s, uint32_t v, size_t count)
 762 {
 763         uint32_t *xs = s;
 764
 765         while (count--)
 766                 *xs++ = v;
 767         return s;
 768 }
 769 EXPORT_SYMBOL(memset32);
 770 #endif
 771
 772 #ifndef __HAVE_ARCH_MEMSET64
 773 /**
 774  * memset64() - Fill a memory area with a uint64_t
 775  * @s: Pointer to the start of the area.
 776  * @v: The value to fill the area with
 777  * @count: The number of values to store
 778  *
 779  * Differs from memset() in that it fills with a uint64_t instead
 780  * of a byte.  Remember that @count is the number of uint64_ts to
 781  * store, not the number of bytes.
 782  */
 783 void *memset64(uint64_t *s, uint64_t v, size_t count)
 784 {
 785         uint64_t *xs = s;
 786
 787         while (count--)
 788                 *xs++ = v;
 789         return s;
 790 }
 791 EXPORT_SYMBOL(memset64);
 792 #endif
 793
 794 #ifndef __HAVE_ARCH_MEMCPY
 795 /**
 796  * memcpy - Copy one area of memory to another
 797  * @dest: Where to copy to
 798  * @src: Where to copy from
 799  * @count: The size of the area.
 800  *
 801  * You should not use this function to access IO space, use memcpy_toio()
 802  * or memcpy_fromio() instead.
 803  */
 804 void *memcpy(void *dest, const void *src, size_t count)
 805 {
 806         char *tmp = dest;
 807         const char *s = src;
 808
 809         while (count--)
 810                 *tmp++ = *s++;
 811         return dest;
 812 }
 813 EXPORT_SYMBOL(memcpy);
 814 #endif
 815
 816 #ifndef __HAVE_ARCH_MEMMOVE
 817 /**
 818  * memmove - Copy one area of memory to another
 819  * @dest: Where to copy to
 820  * @src: Where to copy from
 821  * @count: The size of the area.
 822  *
 823  * Unlike memcpy(), memmove() copes with overlapping areas.
 824  */
 825 void *memmove(void *dest, const void *src, size_t count)
 826 {
 827         char *tmp;
 828         const char *s;
 829
 830         if (dest <= src) {
 831                 tmp = dest;
 832                 s = src;
 833                 while (count--)
 834                         *tmp++ = *s++;
 835         } else {
 836                 tmp = dest;
 837                 tmp += count;
 838                 s = src;
 839                 s += count;
 840                 while (count--)
 841                         *--tmp = *--s;
 842         }
 843         return dest;
 844 }
 845 EXPORT_SYMBOL(memmove);
 846 #endif
 847
 848 #ifndef __HAVE_ARCH_MEMCMP
 849 /**
 850  * memcmp - Compare two areas of memory
 851  * @cs: One area of memory
 852  * @ct: Another area of memory
 853  * @count: The size of the area.
 854  */
 855 #undef memcmp
 856 __visible int memcmp(const void *cs, const void *ct, size_t count)
 857 {
 858         const unsigned char *su1, *su2;
 859         int res = 0;
 860
 861         for (su1 = cs, su2 = ct; 0 < count; ++su1, ++su2, count--)
 862                 if ((res = *su1 - *su2) != 0)
 863                         break;
 864         return res;
 865 }
 866 EXPORT_SYMBOL(memcmp);
 867 #endif
 868
 869 #ifndef __HAVE_ARCH_MEMSCAN
 870 /**
 871  * memscan - Find a character in an area of memory.
 872  * @addr: The memory area
 873  * @c: The byte to search for
 874  * @size: The size of the area.
 875  *
 876  * returns the address of the first occurrence of @c, or 1 byte past
 877  * the area if @c is not found
 878  */
 879 void *memscan(void *addr, int c, size_t size)
 880 {
 881         unsigned char *p = addr;
 882
 883         while (size) {
 884                 if (*p == c)
 885                         return (void *)p;
 886                 p++;
 887                 size--;
 888         }
 889         return (void *)p;
 890 }
 891 EXPORT_SYMBOL(memscan);
 892 #endif
 893
 894 #ifndef __HAVE_ARCH_STRSTR
 895 /**
 896  * strstr - Find the first substring in a %NUL terminated string
 897  * @s1: The string to be searched
 898  * @s2: The string to search for
 899  */
 900 char *strstr(const char *s1, const char *s2)
 901 {
 902         size_t l1, l2;
 903
 904         l2 = strlen(s2);
 905         if (!l2)
 906                 return (char *)s1;
 907         l1 = strlen(s1);
 908         while (l1 >= l2) {
 909                 l1--;
 910                 if (!memcmp(s1, s2, l2))
 911                         return (char *)s1;
 912                 s1++;
 913         }
 914         return NULL;
 915 }
 916 EXPORT_SYMBOL(strstr);
 917 #endif
 918
 919 #ifndef __HAVE_ARCH_STRNSTR
 920 /**
 921  * strnstr - Find the first substring in a length-limited string
 922  * @s1: The string to be searched
 923  * @s2: The string to search for
 924  * @len: the maximum number of characters to search
 925  */
 926 char *strnstr(const char *s1, const char *s2, size_t len)
 927 {
 928         size_t l2;
 929
 930         l2 = strlen(s2);
 931         if (!l2)
 932                 return (char *)s1;
 933         while (len >= l2) {
 934                 len--;
 935                 if (!memcmp(s1, s2, l2))
 936                         return (char *)s1;
 937                 s1++;
 938         }
 939         return NULL;
 940 }
 941 EXPORT_SYMBOL(strnstr);
 942 #endif
 943
 944 #ifndef __HAVE_ARCH_MEMCHR
 945 /**
 946  * memchr - Find a character in an area of memory.
 947  * @s: The memory area
 948  * @c: The byte to search for
 949  * @n: The size of the area.
 950  *
 951  * returns the address of the first occurrence of @c, or %NULL
 952  * if @c is not found
 953  */
 954 void *memchr(const void *s, int c, size_t n)
 955 {
 956         const unsigned char *p = s;
 957         while (n-- != 0) {
 958                 if ((unsigned char)c == *p++) {
 959                         return (void *)(p - 1);
 960                 }
 961         }
 962         return NULL;
 963 }
 964 EXPORT_SYMBOL(memchr);
 965 #endif
 966
 967 static void *check_bytes8(const u8 *start, u8 value, unsigned int bytes)
 968 {
 969         while (bytes) {
 970                 if (*start != value)
 971                         return (void *)start;
 972                 start++;
 973                 bytes--;
 974         }
 975         return NULL;
 976 }
 977
 978 /**
 979  * memchr_inv - Find an unmatching character in an area of memory.
 980  * @start: The memory area
 981  * @c: Find a character other than c
 982  * @bytes: The size of the area.
 983  *
 984  * returns the address of the first character other than @c, or %NULL
 985  * if the whole buffer contains just @c.
 986  */
 987 void *memchr_inv(const void *start, int c, size_t bytes)
 988 {
 989         u8 value = c;
 990         u64 value64;
 991         unsigned int words, prefix;
 992
 993         if (bytes <= 16)
 994                 return check_bytes8(start, value, bytes);
 995
 996         value64 = value;
 997 #if defined(CONFIG_ARCH_HAS_FAST_MULTIPLIER) && BITS_PER_LONG == 64
 998         value64 *= 0x0101010101010101ULL;
 999 #elif defined(CONFIG_ARCH_HAS_FAST_MULTIPLIER)
1000         value64 *= 0x01010101;
1001         value64 |= value64 << 32;
1002 #else
1003         value64 |= value64 << 8;
1004         value64 |= value64 << 16;
1005         value64 |= value64 << 32;
1006 #endif
1007
1008         prefix = (unsigned long)start % 8;
1009         if (prefix) {
1010                 u8 *r;
1011
1012                 prefix = 8 - prefix;
1013                 r = check_bytes8(start, value, prefix);
1014                 if (r)
1015                         return r;
1016                 start += prefix;
1017                 bytes -= prefix;
1018         }
1019
1020         words = bytes / 8;
1021
1022         while (words) {
1023                 if (*(u64 *)start != value64)
1024                         return check_bytes8(start, value, 8);
1025                 start += 8;
1026                 words--;
1027         }
1028
1029         return check_bytes8(start, value, bytes % 8);
1030 }
1031 EXPORT_SYMBOL(memchr_inv);
1032
1033 /**
1034  * strreplace - Replace all occurrences of character in string.
1035  * @s: The string to operate on.
1036  * @old: The character being replaced.
1037  * @new: The character @old is replaced with.
1038  *
1039  * Returns pointer to the nul byte at the end of @s.
1040  */
1041 char *strreplace(char *s, char old, char new)
1042 {
1043         for (; *s; ++s)
1044                 if (*s == old)
1045                         *s = new;
1046         return s;
1047 }
1048 EXPORT_SYMBOL(strreplace);
1049
1050 void fortify_panic(const char *name)
1051 {
1052         pr_emerg("detected buffer overflow in %s\n", name);
1053         BUG();
1054 }
1055 EXPORT_SYMBOL(fortify_panic);