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.  The
 163  * behavior is undefined if the string buffers overlap.  The destination
 164  * buffer is always NUL terminated, unless it's zero-sized.
 165  *
 166  * Preferred to strlcpy() since the API doesn't require reading memory
 167  * from the src string beyond the specified "count" bytes, and since
 168  * the return value is easier to error-check than strlcpy()'s.
 169  * In addition, the implementation is robust to the string changing out
 170  * from underneath it, unlike the current strlcpy() implementation.
 171  *
 172  * Preferred to strncpy() since it always returns a valid string, and
 173  * doesn't unnecessarily force the tail of the destination buffer to be
 174  * zeroed.  If zeroing is desired please use strscpy_pad().
 175  *
 176  * Return: The number of characters copied (not including the trailing
 177  *         %NUL) or -E2BIG if the destination buffer wasn't big enough.
 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 /**
 241  * strscpy_pad() - Copy a C-string into a sized buffer
 242  * @dest: Where to copy the string to
 243  * @src: Where to copy the string from
 244  * @count: Size of destination buffer
 245  *
 246  * Copy the string, or as much of it as fits, into the dest buffer.  The
 247  * behavior is undefined if the string buffers overlap.  The destination
 248  * buffer is always %NUL terminated, unless it's zero-sized.
 249  *
 250  * If the source string is shorter than the destination buffer, zeros
 251  * the tail of the destination buffer.
 252  *
 253  * For full explanation of why you may want to consider using the
 254  * 'strscpy' functions please see the function docstring for strscpy().
 255  *
 256  * Return: The number of characters copied (not including the trailing
 257  *         %NUL) or -E2BIG if the destination buffer wasn't big enough.
 258  */
 259 ssize_t strscpy_pad(char *dest, const char *src, size_t count)
 260 {
 261         ssize_t written;
 262
 263         written = strscpy(dest, src, count);
 264         if (written < 0 || written == count - 1)
 265                 return written;
 266
 267         memset(dest + written + 1, 0, count - written - 1);
 268
 269         return written;
 270 }
 271 EXPORT_SYMBOL(strscpy_pad);
 272
 273 #ifndef __HAVE_ARCH_STRCAT
 274 /**
 275  * strcat - Append one %NUL-terminated string to another
 276  * @dest: The string to be appended to
 277  * @src: The string to append to it
 278  */
 279 #undef strcat
 280 char *strcat(char *dest, const char *src)
 281 {
 282         char *tmp = dest;
 283
 284         while (*dest)
 285                 dest++;
 286         while ((*dest++ = *src++) != '\0')
 287                 ;
 288         return tmp;
 289 }
 290 EXPORT_SYMBOL(strcat);
 291 #endif
 292
 293 #ifndef __HAVE_ARCH_STRNCAT
 294 /**
 295  * strncat - Append a length-limited, C-string to another
 296  * @dest: The string to be appended to
 297  * @src: The string to append to it
 298  * @count: The maximum numbers of bytes to copy
 299  *
 300  * Note that in contrast to strncpy(), strncat() ensures the result is
 301  * terminated.
 302  */
 303 char *strncat(char *dest, const char *src, size_t count)
 304 {
 305         char *tmp = dest;
 306
 307         if (count) {
 308                 while (*dest)
 309                         dest++;
 310                 while ((*dest++ = *src++) != 0) {
 311                         if (--count == 0) {
 312                                 *dest = '\0';
 313                                 break;
 314                         }
 315                 }
 316         }
 317         return tmp;
 318 }
 319 EXPORT_SYMBOL(strncat);
 320 #endif
 321
 322 #ifndef __HAVE_ARCH_STRLCAT
 323 /**
 324  * strlcat - Append a length-limited, C-string to another
 325  * @dest: The string to be appended to
 326  * @src: The string to append to it
 327  * @count: The size of the destination buffer.
 328  */
 329 size_t strlcat(char *dest, const char *src, size_t count)
 330 {
 331         size_t dsize = strlen(dest);
 332         size_t len = strlen(src);
 333         size_t res = dsize + len;
 334
 335         /* This would be a bug */
 336         BUG_ON(dsize >= count);
 337
 338         dest += dsize;
 339         count -= dsize;
 340         if (len >= count)
 341                 len = count-1;
 342         memcpy(dest, src, len);
 343         dest[len] = 0;
 344         return res;
 345 }
 346 EXPORT_SYMBOL(strlcat);
 347 #endif
 348
 349 #ifndef __HAVE_ARCH_STRCMP
 350 /**
 351  * strcmp - Compare two strings
 352  * @cs: One string
 353  * @ct: Another string
 354  */
 355 #undef strcmp
 356 int strcmp(const char *cs, const char *ct)
 357 {
 358         unsigned char c1, c2;
 359
 360         while (1) {
 361                 c1 = *cs++;
 362                 c2 = *ct++;
 363                 if (c1 != c2)
 364                         return c1 < c2 ? -1 : 1;
 365                 if (!c1)
 366                         break;
 367         }
 368         return 0;
 369 }
 370 EXPORT_SYMBOL(strcmp);
 371 #endif
 372
 373 #ifndef __HAVE_ARCH_STRNCMP
 374 /**
 375  * strncmp - Compare two length-limited strings
 376  * @cs: One string
 377  * @ct: Another string
 378  * @count: The maximum number of bytes to compare
 379  */
 380 int strncmp(const char *cs, const char *ct, size_t count)
 381 {
 382         unsigned char c1, c2;
 383
 384         while (count) {
 385                 c1 = *cs++;
 386                 c2 = *ct++;
 387                 if (c1 != c2)
 388                         return c1 < c2 ? -1 : 1;
 389                 if (!c1)
 390                         break;
 391                 count--;
 392         }
 393         return 0;
 394 }
 395 EXPORT_SYMBOL(strncmp);
 396 #endif
 397
 398 #ifndef __HAVE_ARCH_STRCHR
 399 /**
 400  * strchr - Find the first occurrence of a character in a string
 401  * @s: The string to be searched
 402  * @c: The character to search for
 403  *
 404  * Note that the %NUL-terminator is considered part of the string, and can
 405  * be searched for.
 406  */
 407 char *strchr(const char *s, int c)
 408 {
 409         for (; *s != (char)c; ++s)
 410                 if (*s == '\0')
 411                         return NULL;
 412         return (char *)s;
 413 }
 414 EXPORT_SYMBOL(strchr);
 415 #endif
 416
 417 #ifndef __HAVE_ARCH_STRCHRNUL
 418 /**
 419  * strchrnul - Find and return a character in a string, or end of string
 420  * @s: The string to be searched
 421  * @c: The character to search for
 422  *
 423  * Returns pointer to first occurrence of 'c' in s. If c is not found, then
 424  * return a pointer to the null byte at the end of s.
 425  */
 426 char *strchrnul(const char *s, int c)
 427 {
 428         while (*s && *s != (char)c)
 429                 s++;
 430         return (char *)s;
 431 }
 432 EXPORT_SYMBOL(strchrnul);
 433 #endif
 434
 435 #ifndef __HAVE_ARCH_STRRCHR
 436 /**
 437  * strrchr - Find the last occurrence of a character in a string
 438  * @s: The string to be searched
 439  * @c: The character to search for
 440  */
 441 char *strrchr(const char *s, int c)
 442 {
 443         const char *last = NULL;
 444         do {
 445                 if (*s == (char)c)
 446                         last = s;
 447         } while (*s++);
 448         return (char *)last;
 449 }
 450 EXPORT_SYMBOL(strrchr);
 451 #endif
 452
 453 #ifndef __HAVE_ARCH_STRNCHR
 454 /**
 455  * strnchr - Find a character in a length limited string
 456  * @s: The string to be searched
 457  * @count: The number of characters to be searched
 458  * @c: The character to search for
 459  *
 460  * Note that the %NUL-terminator is considered part of the string, and can
 461  * be searched for.
 462  */
 463 char *strnchr(const char *s, size_t count, int c)
 464 {
 465         while (count--) {
 466                 if (*s == (char)c)
 467                         return (char *)s;
 468                 if (*s++ == '\0')
 469                         break;
 470         }
 471         return NULL;
 472 }
 473 EXPORT_SYMBOL(strnchr);
 474 #endif
 475
 476 /**
 477  * skip_spaces - Removes leading whitespace from @str.
 478  * @str: The string to be stripped.
 479  *
 480  * Returns a pointer to the first non-whitespace character in @str.
 481  */
 482 char *skip_spaces(const char *str)
 483 {
 484         while (isspace(*str))
 485                 ++str;
 486         return (char *)str;
 487 }
 488 EXPORT_SYMBOL(skip_spaces);
 489
 490 /**
 491  * strim - Removes leading and trailing whitespace from @s.
 492  * @s: The string to be stripped.
 493  *
 494  * Note that the first trailing whitespace is replaced with a %NUL-terminator
 495  * in the given string @s. Returns a pointer to the first non-whitespace
 496  * character in @s.
 497  */
 498 char *strim(char *s)
 499 {
 500         size_t size;
 501         char *end;
 502
 503         size = strlen(s);
 504         if (!size)
 505                 return s;
 506
 507         end = s + size - 1;
 508         while (end >= s && isspace(*end))
 509                 end--;
 510         *(end + 1) = '\0';
 511
 512         return skip_spaces(s);
 513 }
 514 EXPORT_SYMBOL(strim);
 515
 516 #ifndef __HAVE_ARCH_STRLEN
 517 /**
 518  * strlen - Find the length of a string
 519  * @s: The string to be sized
 520  */
 521 size_t strlen(const char *s)
 522 {
 523         const char *sc;
 524
 525         for (sc = s; *sc != '\0'; ++sc)
 526                 /* nothing */;
 527         return sc - s;
 528 }
 529 EXPORT_SYMBOL(strlen);
 530 #endif
 531
 532 #ifndef __HAVE_ARCH_STRNLEN
 533 /**
 534  * strnlen - Find the length of a length-limited string
 535  * @s: The string to be sized
 536  * @count: The maximum number of bytes to search
 537  */
 538 size_t strnlen(const char *s, size_t count)
 539 {
 540         const char *sc;
 541
 542         for (sc = s; count-- && *sc != '\0'; ++sc)
 543                 /* nothing */;
 544         return sc - s;
 545 }
 546 EXPORT_SYMBOL(strnlen);
 547 #endif
 548
 549 #ifndef __HAVE_ARCH_STRSPN
 550 /**
 551  * strspn - Calculate the length of the initial substring of @s which only contain letters in @accept
 552  * @s: The string to be searched
 553  * @accept: The string to search for
 554  */
 555 size_t strspn(const char *s, const char *accept)
 556 {
 557         const char *p;
 558         const char *a;
 559         size_t count = 0;
 560
 561         for (p = s; *p != '\0'; ++p) {
 562                 for (a = accept; *a != '\0'; ++a) {
 563                         if (*p == *a)
 564                                 break;
 565                 }
 566                 if (*a == '\0')
 567                         return count;
 568                 ++count;
 569         }
 570         return count;
 571 }
 572
 573 EXPORT_SYMBOL(strspn);
 574 #endif
 575
 576 #ifndef __HAVE_ARCH_STRCSPN
 577 /**
 578  * strcspn - Calculate the length of the initial substring of @s which does not contain letters in @reject
 579  * @s: The string to be searched
 580  * @reject: The string to avoid
 581  */
 582 size_t strcspn(const char *s, const char *reject)
 583 {
 584         const char *p;
 585         const char *r;
 586         size_t count = 0;
 587
 588         for (p = s; *p != '\0'; ++p) {
 589                 for (r = reject; *r != '\0'; ++r) {
 590                         if (*p == *r)
 591                                 return count;
 592                 }
 593                 ++count;
 594         }
 595         return count;
 596 }
 597 EXPORT_SYMBOL(strcspn);
 598 #endif
 599
 600 #ifndef __HAVE_ARCH_STRPBRK
 601 /**
 602  * strpbrk - Find the first occurrence of a set of characters
 603  * @cs: The string to be searched
 604  * @ct: The characters to search for
 605  */
 606 char *strpbrk(const char *cs, const char *ct)
 607 {
 608         const char *sc1, *sc2;
 609
 610         for (sc1 = cs; *sc1 != '\0'; ++sc1) {
 611                 for (sc2 = ct; *sc2 != '\0'; ++sc2) {
 612                         if (*sc1 == *sc2)
 613                                 return (char *)sc1;
 614                 }
 615         }
 616         return NULL;
 617 }
 618 EXPORT_SYMBOL(strpbrk);
 619 #endif
 620
 621 #ifndef __HAVE_ARCH_STRSEP
 622 /**
 623  * strsep - Split a string into tokens
 624  * @s: The string to be searched
 625  * @ct: The characters to search for
 626  *
 627  * strsep() updates @s to point after the token, ready for the next call.
 628  *
 629  * It returns empty tokens, too, behaving exactly like the libc function
 630  * of that name. In fact, it was stolen from glibc2 and de-fancy-fied.
 631  * Same semantics, slimmer shape. ;)
 632  */
 633 char *strsep(char **s, const char *ct)
 634 {
 635         char *sbegin = *s;
 636         char *end;
 637
 638         if (sbegin == NULL)
 639                 return NULL;
 640
 641         end = strpbrk(sbegin, ct);
 642         if (end)
 643                 *end++ = '\0';
 644         *s = end;
 645         return sbegin;
 646 }
 647 EXPORT_SYMBOL(strsep);
 648 #endif
 649
 650 /**
 651  * sysfs_streq - return true if strings are equal, modulo trailing newline
 652  * @s1: one string
 653  * @s2: another string
 654  *
 655  * This routine returns true iff two strings are equal, treating both
 656  * NUL and newline-then-NUL as equivalent string terminations.  It's
 657  * geared for use with sysfs input strings, which generally terminate
 658  * with newlines but are compared against values without newlines.
 659  */
 660 bool sysfs_streq(const char *s1, const char *s2)
 661 {
 662         while (*s1 && *s1 == *s2) {
 663                 s1++;
 664                 s2++;
 665         }
 666
 667         if (*s1 == *s2)
 668                 return true;
 669         if (!*s1 && *s2 == '\n' && !s2[1])
 670                 return true;
 671         if (*s1 == '\n' && !s1[1] && !*s2)
 672                 return true;
 673         return false;
 674 }
 675 EXPORT_SYMBOL(sysfs_streq);
 676
 677 /**
 678  * match_string - matches given string in an array
 679  * @array:      array of strings
 680  * @n:          number of strings in the array or -1 for NULL terminated arrays
 681  * @string:     string to match with
 682  *
 683  * Return:
 684  * index of a @string in the @array if matches, or %-EINVAL otherwise.
 685  */
 686 int match_string(const char * const *array, size_t n, const char *string)
 687 {
 688         int index;
 689         const char *item;
 690
 691         for (index = 0; index < n; index++) {
 692                 item = array[index];
 693                 if (!item)
 694                         break;
 695                 if (!strcmp(item, string))
 696                         return index;
 697         }
 698
 699         return -EINVAL;
 700 }
 701 EXPORT_SYMBOL(match_string);
 702
 703 /**
 704  * __sysfs_match_string - matches given string in an array
 705  * @array: array of strings
 706  * @n: number of strings in the array or -1 for NULL terminated arrays
 707  * @str: string to match with
 708  *
 709  * Returns index of @str in the @array or -EINVAL, just like match_string().
 710  * Uses sysfs_streq instead of strcmp for matching.
 711  */
 712 int __sysfs_match_string(const char * const *array, size_t n, const char *str)
 713 {
 714         const char *item;
 715         int index;
 716
 717         for (index = 0; index < n; index++) {
 718                 item = array[index];
 719                 if (!item)
 720                         break;
 721                 if (sysfs_streq(item, str))
 722                         return index;
 723         }
 724
 725         return -EINVAL;
 726 }
 727 EXPORT_SYMBOL(__sysfs_match_string);
 728
 729 #ifndef __HAVE_ARCH_MEMSET
 730 /**
 731  * memset - Fill a region of memory with the given value
 732  * @s: Pointer to the start of the area.
 733  * @c: The byte to fill the area with
 734  * @count: The size of the area.
 735  *
 736  * Do not use memset() to access IO space, use memset_io() instead.
 737  */
 738 void *memset(void *s, int c, size_t count)
 739 {
 740         char *xs = s;
 741
 742         while (count--)
 743                 *xs++ = c;
 744         return s;
 745 }
 746 EXPORT_SYMBOL(memset);
 747 #endif
 748
 749 /**
 750  * memzero_explicit - Fill a region of memory (e.g. sensitive
 751  *                    keying data) with 0s.
 752  * @s: Pointer to the start of the area.
 753  * @count: The size of the area.
 754  *
 755  * Note: usually using memset() is just fine (!), but in cases
 756  * where clearing out _local_ data at the end of a scope is
 757  * necessary, memzero_explicit() should be used instead in
 758  * order to prevent the compiler from optimising away zeroing.
 759  *
 760  * memzero_explicit() doesn't need an arch-specific version as
 761  * it just invokes the one of memset() implicitly.
 762  */
 763 void memzero_explicit(void *s, size_t count)
 764 {
 765         memset(s, 0, count);
 766         barrier_data(s);
 767 }
 768 EXPORT_SYMBOL(memzero_explicit);
 769
 770 #ifndef __HAVE_ARCH_MEMSET16
 771 /**
 772  * memset16() - Fill a memory area with a uint16_t
 773  * @s: Pointer to the start of the area.
 774  * @v: The value to fill the area with
 775  * @count: The number of values to store
 776  *
 777  * Differs from memset() in that it fills with a uint16_t instead
 778  * of a byte.  Remember that @count is the number of uint16_ts to
 779  * store, not the number of bytes.
 780  */
 781 void *memset16(uint16_t *s, uint16_t v, size_t count)
 782 {
 783         uint16_t *xs = s;
 784
 785         while (count--)
 786                 *xs++ = v;
 787         return s;
 788 }
 789 EXPORT_SYMBOL(memset16);
 790 #endif
 791
 792 #ifndef __HAVE_ARCH_MEMSET32
 793 /**
 794  * memset32() - Fill a memory area with a uint32_t
 795  * @s: Pointer to the start of the area.
 796  * @v: The value to fill the area with
 797  * @count: The number of values to store
 798  *
 799  * Differs from memset() in that it fills with a uint32_t instead
 800  * of a byte.  Remember that @count is the number of uint32_ts to
 801  * store, not the number of bytes.
 802  */
 803 void *memset32(uint32_t *s, uint32_t v, size_t count)
 804 {
 805         uint32_t *xs = s;
 806
 807         while (count--)
 808                 *xs++ = v;
 809         return s;
 810 }
 811 EXPORT_SYMBOL(memset32);
 812 #endif
 813
 814 #ifndef __HAVE_ARCH_MEMSET64
 815 /**
 816  * memset64() - Fill a memory area with a uint64_t
 817  * @s: Pointer to the start of the area.
 818  * @v: The value to fill the area with
 819  * @count: The number of values to store
 820  *
 821  * Differs from memset() in that it fills with a uint64_t instead
 822  * of a byte.  Remember that @count is the number of uint64_ts to
 823  * store, not the number of bytes.
 824  */
 825 void *memset64(uint64_t *s, uint64_t v, size_t count)
 826 {
 827         uint64_t *xs = s;
 828
 829         while (count--)
 830                 *xs++ = v;
 831         return s;
 832 }
 833 EXPORT_SYMBOL(memset64);
 834 #endif
 835
 836 #ifndef __HAVE_ARCH_MEMCPY
 837 /**
 838  * memcpy - Copy one area of memory to another
 839  * @dest: Where to copy to
 840  * @src: Where to copy from
 841  * @count: The size of the area.
 842  *
 843  * You should not use this function to access IO space, use memcpy_toio()
 844  * or memcpy_fromio() instead.
 845  */
 846 void *memcpy(void *dest, const void *src, size_t count)
 847 {
 848         char *tmp = dest;
 849         const char *s = src;
 850
 851         while (count--)
 852                 *tmp++ = *s++;
 853         return dest;
 854 }
 855 EXPORT_SYMBOL(memcpy);
 856 #endif
 857
 858 #ifndef __HAVE_ARCH_MEMMOVE
 859 /**
 860  * memmove - Copy one area of memory to another
 861  * @dest: Where to copy to
 862  * @src: Where to copy from
 863  * @count: The size of the area.
 864  *
 865  * Unlike memcpy(), memmove() copes with overlapping areas.
 866  */
 867 void *memmove(void *dest, const void *src, size_t count)
 868 {
 869         char *tmp;
 870         const char *s;
 871
 872         if (dest <= src) {
 873                 tmp = dest;
 874                 s = src;
 875                 while (count--)
 876                         *tmp++ = *s++;
 877         } else {
 878                 tmp = dest;
 879                 tmp += count;
 880                 s = src;
 881                 s += count;
 882                 while (count--)
 883                         *--tmp = *--s;
 884         }
 885         return dest;
 886 }
 887 EXPORT_SYMBOL(memmove);
 888 #endif
 889
 890 #ifndef __HAVE_ARCH_MEMCMP
 891 /**
 892  * memcmp - Compare two areas of memory
 893  * @cs: One area of memory
 894  * @ct: Another area of memory
 895  * @count: The size of the area.
 896  */
 897 #undef memcmp
 898 __visible int memcmp(const void *cs, const void *ct, size_t count)
 899 {
 900         const unsigned char *su1, *su2;
 901         int res = 0;
 902
 903         for (su1 = cs, su2 = ct; 0 < count; ++su1, ++su2, count--)
 904                 if ((res = *su1 - *su2) != 0)
 905                         break;
 906         return res;
 907 }
 908 EXPORT_SYMBOL(memcmp);
 909 #endif
 910
 911 #ifndef __HAVE_ARCH_BCMP
 912 /**
 913  * bcmp - returns 0 if and only if the buffers have identical contents.
 914  * @a: pointer to first buffer.
 915  * @b: pointer to second buffer.
 916  * @len: size of buffers.
 917  *
 918  * The sign or magnitude of a non-zero return value has no particular
 919  * meaning, and architectures may implement their own more efficient bcmp(). So
 920  * while this particular implementation is a simple (tail) call to memcmp, do
 921  * not rely on anything but whether the return value is zero or non-zero.
 922  */
 923 #undef bcmp
 924 int bcmp(const void *a, const void *b, size_t len)
 925 {
 926         return memcmp(a, b, len);
 927 }
 928 EXPORT_SYMBOL(bcmp);
 929 #endif
 930
 931 #ifndef __HAVE_ARCH_MEMSCAN
 932 /**
 933  * memscan - Find a character in an area of memory.
 934  * @addr: The memory area
 935  * @c: The byte to search for
 936  * @size: The size of the area.
 937  *
 938  * returns the address of the first occurrence of @c, or 1 byte past
 939  * the area if @c is not found
 940  */
 941 void *memscan(void *addr, int c, size_t size)
 942 {
 943         unsigned char *p = addr;
 944
 945         while (size) {
 946                 if (*p == c)
 947                         return (void *)p;
 948                 p++;
 949                 size--;
 950         }
 951         return (void *)p;
 952 }
 953 EXPORT_SYMBOL(memscan);
 954 #endif
 955
 956 #ifndef __HAVE_ARCH_STRSTR
 957 /**
 958  * strstr - Find the first substring in a %NUL terminated string
 959  * @s1: The string to be searched
 960  * @s2: The string to search for
 961  */
 962 char *strstr(const char *s1, const char *s2)
 963 {
 964         size_t l1, l2;
 965
 966         l2 = strlen(s2);
 967         if (!l2)
 968                 return (char *)s1;
 969         l1 = strlen(s1);
 970         while (l1 >= l2) {
 971                 l1--;
 972                 if (!memcmp(s1, s2, l2))
 973                         return (char *)s1;
 974                 s1++;
 975         }
 976         return NULL;
 977 }
 978 EXPORT_SYMBOL(strstr);
 979 #endif
 980
 981 #ifndef __HAVE_ARCH_STRNSTR
 982 /**
 983  * strnstr - Find the first substring in a length-limited string
 984  * @s1: The string to be searched
 985  * @s2: The string to search for
 986  * @len: the maximum number of characters to search
 987  */
 988 char *strnstr(const char *s1, const char *s2, size_t len)
 989 {
 990         size_t l2;
 991
 992         l2 = strlen(s2);
 993         if (!l2)
 994                 return (char *)s1;
 995         while (len >= l2) {
 996                 len--;
 997                 if (!memcmp(s1, s2, l2))
 998                         return (char *)s1;
 999                 s1++;
1000         }
1001         return NULL;
1002 }
1003 EXPORT_SYMBOL(strnstr);
1004 #endif
1005
1006 #ifndef __HAVE_ARCH_MEMCHR
1007 /**
1008  * memchr - Find a character in an area of memory.
1009  * @s: The memory area
1010  * @c: The byte to search for
1011  * @n: The size of the area.
1012  *
1013  * returns the address of the first occurrence of @c, or %NULL
1014  * if @c is not found
1015  */
1016 void *memchr(const void *s, int c, size_t n)
1017 {
1018         const unsigned char *p = s;
1019         while (n-- != 0) {
1020                 if ((unsigned char)c == *p++) {
1021                         return (void *)(p - 1);
1022                 }
1023         }
1024         return NULL;
1025 }
1026 EXPORT_SYMBOL(memchr);
1027 #endif
1028
1029 static void *check_bytes8(const u8 *start, u8 value, unsigned int bytes)
1030 {
1031         while (bytes) {
1032                 if (*start != value)
1033                         return (void *)start;
1034                 start++;
1035                 bytes--;
1036         }
1037         return NULL;
1038 }
1039
1040 /**
1041  * memchr_inv - Find an unmatching character in an area of memory.
1042  * @start: The memory area
1043  * @c: Find a character other than c
1044  * @bytes: The size of the area.
1045  *
1046  * returns the address of the first character other than @c, or %NULL
1047  * if the whole buffer contains just @c.
1048  */
1049 void *memchr_inv(const void *start, int c, size_t bytes)
1050 {
1051         u8 value = c;
1052         u64 value64;
1053         unsigned int words, prefix;
1054
1055         if (bytes <= 16)
1056                 return check_bytes8(start, value, bytes);
1057
1058         value64 = value;
1059 #if defined(CONFIG_ARCH_HAS_FAST_MULTIPLIER) && BITS_PER_LONG == 64
1060         value64 *= 0x0101010101010101ULL;
1061 #elif defined(CONFIG_ARCH_HAS_FAST_MULTIPLIER)
1062         value64 *= 0x01010101;
1063         value64 |= value64 << 32;
1064 #else
1065         value64 |= value64 << 8;
1066         value64 |= value64 << 16;
1067         value64 |= value64 << 32;
1068 #endif
1069
1070         prefix = (unsigned long)start % 8;
1071         if (prefix) {
1072                 u8 *r;
1073
1074                 prefix = 8 - prefix;
1075                 r = check_bytes8(start, value, prefix);
1076                 if (r)
1077                         return r;
1078                 start += prefix;
1079                 bytes -= prefix;
1080         }
1081
1082         words = bytes / 8;
1083
1084         while (words) {
1085                 if (*(u64 *)start != value64)
1086                         return check_bytes8(start, value, 8);
1087                 start += 8;
1088                 words--;
1089         }
1090
1091         return check_bytes8(start, value, bytes % 8);
1092 }
1093 EXPORT_SYMBOL(memchr_inv);
1094
1095 /**
1096  * strreplace - Replace all occurrences of character in string.
1097  * @s: The string to operate on.
1098  * @old: The character being replaced.
1099  * @new: The character @old is replaced with.
1100  *
1101  * Returns pointer to the nul byte at the end of @s.
1102  */
1103 char *strreplace(char *s, char old, char new)
1104 {
1105         for (; *s; ++s)
1106                 if (*s == old)
1107                         *s = new;
1108         return s;
1109 }
1110 EXPORT_SYMBOL(strreplace);
1111
1112 void fortify_panic(const char *name)
1113 {
1114         pr_emerg("detected buffer overflow in %s\n", name);
1115         BUG();
1116 }
1117 EXPORT_SYMBOL(fortify_panic);