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  * Returns:
 177  * * The number of characters copied (not including the trailing %NUL)
 178  * * -E2BIG if count is 0 or @src was truncated.
 179  */
 180 ssize_t strscpy(char *dest, const char *src, size_t count)
 181 {
 182         const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
 183         size_t max = count;
 184         long res = 0;
 185
 186         if (count == 0 || WARN_ON_ONCE(count > INT_MAX))
 187                 return -E2BIG;
 188
 189 #ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
 190         /*
 191          * If src is unaligned, don't cross a page boundary,
 192          * since we don't know if the next page is mapped.
 193          */
 194         if ((long)src & (sizeof(long) - 1)) {
 195                 size_t limit = PAGE_SIZE - ((long)src & (PAGE_SIZE - 1));
 196                 if (limit < max)
 197                         max = limit;
 198         }
 199 #else
 200         /* If src or dest is unaligned, don't do word-at-a-time. */
 201         if (((long) dest | (long) src) & (sizeof(long) - 1))
 202                 max = 0;
 203 #endif
 204
 205         while (max >= sizeof(unsigned long)) {
 206                 unsigned long c, data;
 207
 208                 c = read_word_at_a_time(src+res);
 209                 if (has_zero(c, &data, &constants)) {
 210                         data = prep_zero_mask(c, data, &constants);
 211                         data = create_zero_mask(data);
 212                         *(unsigned long *)(dest+res) = c & zero_bytemask(data);
 213                         return res + find_zero(data);
 214                 }
 215                 *(unsigned long *)(dest+res) = c;
 216                 res += sizeof(unsigned long);
 217                 count -= sizeof(unsigned long);
 218                 max -= sizeof(unsigned long);
 219         }
 220
 221         while (count) {
 222                 char c;
 223
 224                 c = src[res];
 225                 dest[res] = c;
 226                 if (!c)
 227                         return res;
 228                 res++;
 229                 count--;
 230         }
 231
 232         /* Hit buffer length without finding a NUL; force NUL-termination. */
 233         if (res)
 234                 dest[res-1] = '\0';
 235
 236         return -E2BIG;
 237 }
 238 EXPORT_SYMBOL(strscpy);
 239 #endif
 240
 241 /**
 242  * strscpy_pad() - Copy a C-string into a sized buffer
 243  * @dest: Where to copy the string to
 244  * @src: Where to copy the string from
 245  * @count: Size of destination buffer
 246  *
 247  * Copy the string, or as much of it as fits, into the dest buffer.  The
 248  * behavior is undefined if the string buffers overlap.  The destination
 249  * buffer is always %NUL terminated, unless it's zero-sized.
 250  *
 251  * If the source string is shorter than the destination buffer, zeros
 252  * the tail of the destination buffer.
 253  *
 254  * For full explanation of why you may want to consider using the
 255  * 'strscpy' functions please see the function docstring for strscpy().
 256  *
 257  * Returns:
 258  * * The number of characters copied (not including the trailing %NUL)
 259  * * -E2BIG if count is 0 or @src was truncated.
 260  */
 261 ssize_t strscpy_pad(char *dest, const char *src, size_t count)
 262 {
 263         ssize_t written;
 264
 265         written = strscpy(dest, src, count);
 266         if (written < 0 || written == count - 1)
 267                 return written;
 268
 269         memset(dest + written + 1, 0, count - written - 1);
 270
 271         return written;
 272 }
 273 EXPORT_SYMBOL(strscpy_pad);
 274
 275 #ifndef __HAVE_ARCH_STRCAT
 276 /**
 277  * strcat - Append one %NUL-terminated string to another
 278  * @dest: The string to be appended to
 279  * @src: The string to append to it
 280  */
 281 #undef strcat
 282 char *strcat(char *dest, const char *src)
 283 {
 284         char *tmp = dest;
 285
 286         while (*dest)
 287                 dest++;
 288         while ((*dest++ = *src++) != '\0')
 289                 ;
 290         return tmp;
 291 }
 292 EXPORT_SYMBOL(strcat);
 293 #endif
 294
 295 #ifndef __HAVE_ARCH_STRNCAT
 296 /**
 297  * strncat - Append a length-limited, C-string to another
 298  * @dest: The string to be appended to
 299  * @src: The string to append to it
 300  * @count: The maximum numbers of bytes to copy
 301  *
 302  * Note that in contrast to strncpy(), strncat() ensures the result is
 303  * terminated.
 304  */
 305 char *strncat(char *dest, const char *src, size_t count)
 306 {
 307         char *tmp = dest;
 308
 309         if (count) {
 310                 while (*dest)
 311                         dest++;
 312                 while ((*dest++ = *src++) != 0) {
 313                         if (--count == 0) {
 314                                 *dest = '\0';
 315                                 break;
 316                         }
 317                 }
 318         }
 319         return tmp;
 320 }
 321 EXPORT_SYMBOL(strncat);
 322 #endif
 323
 324 #ifndef __HAVE_ARCH_STRLCAT
 325 /**
 326  * strlcat - Append a length-limited, C-string to another
 327  * @dest: The string to be appended to
 328  * @src: The string to append to it
 329  * @count: The size of the destination buffer.
 330  */
 331 size_t strlcat(char *dest, const char *src, size_t count)
 332 {
 333         size_t dsize = strlen(dest);
 334         size_t len = strlen(src);
 335         size_t res = dsize + len;
 336
 337         /* This would be a bug */
 338         BUG_ON(dsize >= count);
 339
 340         dest += dsize;
 341         count -= dsize;
 342         if (len >= count)
 343                 len = count-1;
 344         memcpy(dest, src, len);
 345         dest[len] = 0;
 346         return res;
 347 }
 348 EXPORT_SYMBOL(strlcat);
 349 #endif
 350
 351 #ifndef __HAVE_ARCH_STRCMP
 352 /**
 353  * strcmp - Compare two strings
 354  * @cs: One string
 355  * @ct: Another string
 356  */
 357 #undef strcmp
 358 int strcmp(const char *cs, const char *ct)
 359 {
 360         unsigned char c1, c2;
 361
 362         while (1) {
 363                 c1 = *cs++;
 364                 c2 = *ct++;
 365                 if (c1 != c2)
 366                         return c1 < c2 ? -1 : 1;
 367                 if (!c1)
 368                         break;
 369         }
 370         return 0;
 371 }
 372 EXPORT_SYMBOL(strcmp);
 373 #endif
 374
 375 #ifndef __HAVE_ARCH_STRNCMP
 376 /**
 377  * strncmp - Compare two length-limited strings
 378  * @cs: One string
 379  * @ct: Another string
 380  * @count: The maximum number of bytes to compare
 381  */
 382 int strncmp(const char *cs, const char *ct, size_t count)
 383 {
 384         unsigned char c1, c2;
 385
 386         while (count) {
 387                 c1 = *cs++;
 388                 c2 = *ct++;
 389                 if (c1 != c2)
 390                         return c1 < c2 ? -1 : 1;
 391                 if (!c1)
 392                         break;
 393                 count--;
 394         }
 395         return 0;
 396 }
 397 EXPORT_SYMBOL(strncmp);
 398 #endif
 399
 400 #ifndef __HAVE_ARCH_STRCHR
 401 /**
 402  * strchr - Find the first occurrence of a character in a string
 403  * @s: The string to be searched
 404  * @c: The character to search for
 405  *
 406  * Note that the %NUL-terminator is considered part of the string, and can
 407  * be searched for.
 408  */
 409 char *strchr(const char *s, int c)
 410 {
 411         for (; *s != (char)c; ++s)
 412                 if (*s == '\0')
 413                         return NULL;
 414         return (char *)s;
 415 }
 416 EXPORT_SYMBOL(strchr);
 417 #endif
 418
 419 #ifndef __HAVE_ARCH_STRCHRNUL
 420 /**
 421  * strchrnul - Find and return a character in a string, or end of string
 422  * @s: The string to be searched
 423  * @c: The character to search for
 424  *
 425  * Returns pointer to first occurrence of 'c' in s. If c is not found, then
 426  * return a pointer to the null byte at the end of s.
 427  */
 428 char *strchrnul(const char *s, int c)
 429 {
 430         while (*s && *s != (char)c)
 431                 s++;
 432         return (char *)s;
 433 }
 434 EXPORT_SYMBOL(strchrnul);
 435 #endif
 436
 437 #ifndef __HAVE_ARCH_STRRCHR
 438 /**
 439  * strrchr - Find the last occurrence of a character in a string
 440  * @s: The string to be searched
 441  * @c: The character to search for
 442  */
 443 char *strrchr(const char *s, int c)
 444 {
 445         const char *last = NULL;
 446         do {
 447                 if (*s == (char)c)
 448                         last = s;
 449         } while (*s++);
 450         return (char *)last;
 451 }
 452 EXPORT_SYMBOL(strrchr);
 453 #endif
 454
 455 #ifndef __HAVE_ARCH_STRNCHR
 456 /**
 457  * strnchr - Find a character in a length limited string
 458  * @s: The string to be searched
 459  * @count: The number of characters to be searched
 460  * @c: The character to search for
 461  *
 462  * Note that the %NUL-terminator is considered part of the string, and can
 463  * be searched for.
 464  */
 465 char *strnchr(const char *s, size_t count, int c)
 466 {
 467         while (count--) {
 468                 if (*s == (char)c)
 469                         return (char *)s;
 470                 if (*s++ == '\0')
 471                         break;
 472         }
 473         return NULL;
 474 }
 475 EXPORT_SYMBOL(strnchr);
 476 #endif
 477
 478 /**
 479  * skip_spaces - Removes leading whitespace from @str.
 480  * @str: The string to be stripped.
 481  *
 482  * Returns a pointer to the first non-whitespace character in @str.
 483  */
 484 char *skip_spaces(const char *str)
 485 {
 486         while (isspace(*str))
 487                 ++str;
 488         return (char *)str;
 489 }
 490 EXPORT_SYMBOL(skip_spaces);
 491
 492 /**
 493  * strim - Removes leading and trailing whitespace from @s.
 494  * @s: The string to be stripped.
 495  *
 496  * Note that the first trailing whitespace is replaced with a %NUL-terminator
 497  * in the given string @s. Returns a pointer to the first non-whitespace
 498  * character in @s.
 499  */
 500 char *strim(char *s)
 501 {
 502         size_t size;
 503         char *end;
 504
 505         size = strlen(s);
 506         if (!size)
 507                 return s;
 508
 509         end = s + size - 1;
 510         while (end >= s && isspace(*end))
 511                 end--;
 512         *(end + 1) = '\0';
 513
 514         return skip_spaces(s);
 515 }
 516 EXPORT_SYMBOL(strim);
 517
 518 #ifndef __HAVE_ARCH_STRLEN
 519 /**
 520  * strlen - Find the length of a string
 521  * @s: The string to be sized
 522  */
 523 size_t strlen(const char *s)
 524 {
 525         const char *sc;
 526
 527         for (sc = s; *sc != '\0'; ++sc)
 528                 /* nothing */;
 529         return sc - s;
 530 }
 531 EXPORT_SYMBOL(strlen);
 532 #endif
 533
 534 #ifndef __HAVE_ARCH_STRNLEN
 535 /**
 536  * strnlen - Find the length of a length-limited string
 537  * @s: The string to be sized
 538  * @count: The maximum number of bytes to search
 539  */
 540 size_t strnlen(const char *s, size_t count)
 541 {
 542         const char *sc;
 543
 544         for (sc = s; count-- && *sc != '\0'; ++sc)
 545                 /* nothing */;
 546         return sc - s;
 547 }
 548 EXPORT_SYMBOL(strnlen);
 549 #endif
 550
 551 #ifndef __HAVE_ARCH_STRSPN
 552 /**
 553  * strspn - Calculate the length of the initial substring of @s which only contain letters in @accept
 554  * @s: The string to be searched
 555  * @accept: The string to search for
 556  */
 557 size_t strspn(const char *s, const char *accept)
 558 {
 559         const char *p;
 560         const char *a;
 561         size_t count = 0;
 562
 563         for (p = s; *p != '\0'; ++p) {
 564                 for (a = accept; *a != '\0'; ++a) {
 565                         if (*p == *a)
 566                                 break;
 567                 }
 568                 if (*a == '\0')
 569                         return count;
 570                 ++count;
 571         }
 572         return count;
 573 }
 574
 575 EXPORT_SYMBOL(strspn);
 576 #endif
 577
 578 #ifndef __HAVE_ARCH_STRCSPN
 579 /**
 580  * strcspn - Calculate the length of the initial substring of @s which does not contain letters in @reject
 581  * @s: The string to be searched
 582  * @reject: The string to avoid
 583  */
 584 size_t strcspn(const char *s, const char *reject)
 585 {
 586         const char *p;
 587         const char *r;
 588         size_t count = 0;
 589
 590         for (p = s; *p != '\0'; ++p) {
 591                 for (r = reject; *r != '\0'; ++r) {
 592                         if (*p == *r)
 593                                 return count;
 594                 }
 595                 ++count;
 596         }
 597         return count;
 598 }
 599 EXPORT_SYMBOL(strcspn);
 600 #endif
 601
 602 #ifndef __HAVE_ARCH_STRPBRK
 603 /**
 604  * strpbrk - Find the first occurrence of a set of characters
 605  * @cs: The string to be searched
 606  * @ct: The characters to search for
 607  */
 608 char *strpbrk(const char *cs, const char *ct)
 609 {
 610         const char *sc1, *sc2;
 611
 612         for (sc1 = cs; *sc1 != '\0'; ++sc1) {
 613                 for (sc2 = ct; *sc2 != '\0'; ++sc2) {
 614                         if (*sc1 == *sc2)
 615                                 return (char *)sc1;
 616                 }
 617         }
 618         return NULL;
 619 }
 620 EXPORT_SYMBOL(strpbrk);
 621 #endif
 622
 623 #ifndef __HAVE_ARCH_STRSEP
 624 /**
 625  * strsep - Split a string into tokens
 626  * @s: The string to be searched
 627  * @ct: The characters to search for
 628  *
 629  * strsep() updates @s to point after the token, ready for the next call.
 630  *
 631  * It returns empty tokens, too, behaving exactly like the libc function
 632  * of that name. In fact, it was stolen from glibc2 and de-fancy-fied.
 633  * Same semantics, slimmer shape. ;)
 634  */
 635 char *strsep(char **s, const char *ct)
 636 {
 637         char *sbegin = *s;
 638         char *end;
 639
 640         if (sbegin == NULL)
 641                 return NULL;
 642
 643         end = strpbrk(sbegin, ct);
 644         if (end)
 645                 *end++ = '\0';
 646         *s = end;
 647         return sbegin;
 648 }
 649 EXPORT_SYMBOL(strsep);
 650 #endif
 651
 652 /**
 653  * sysfs_streq - return true if strings are equal, modulo trailing newline
 654  * @s1: one string
 655  * @s2: another string
 656  *
 657  * This routine returns true iff two strings are equal, treating both
 658  * NUL and newline-then-NUL as equivalent string terminations.  It's
 659  * geared for use with sysfs input strings, which generally terminate
 660  * with newlines but are compared against values without newlines.
 661  */
 662 bool sysfs_streq(const char *s1, const char *s2)
 663 {
 664         while (*s1 && *s1 == *s2) {
 665                 s1++;
 666                 s2++;
 667         }
 668
 669         if (*s1 == *s2)
 670                 return true;
 671         if (!*s1 && *s2 == '\n' && !s2[1])
 672                 return true;
 673         if (*s1 == '\n' && !s1[1] && !*s2)
 674                 return true;
 675         return false;
 676 }
 677 EXPORT_SYMBOL(sysfs_streq);
 678
 679 /**
 680  * match_string - matches given string in an array
 681  * @array:      array of strings
 682  * @n:          number of strings in the array or -1 for NULL terminated arrays
 683  * @string:     string to match with
 684  *
 685  * Return:
 686  * index of a @string in the @array if matches, or %-EINVAL otherwise.
 687  */
 688 int match_string(const char * const *array, size_t n, const char *string)
 689 {
 690         int index;
 691         const char *item;
 692
 693         for (index = 0; index < n; index++) {
 694                 item = array[index];
 695                 if (!item)
 696                         break;
 697                 if (!strcmp(item, string))
 698                         return index;
 699         }
 700
 701         return -EINVAL;
 702 }
 703 EXPORT_SYMBOL(match_string);
 704
 705 /**
 706  * __sysfs_match_string - matches given string in an array
 707  * @array: array of strings
 708  * @n: number of strings in the array or -1 for NULL terminated arrays
 709  * @str: string to match with
 710  *
 711  * Returns index of @str in the @array or -EINVAL, just like match_string().
 712  * Uses sysfs_streq instead of strcmp for matching.
 713  */
 714 int __sysfs_match_string(const char * const *array, size_t n, const char *str)
 715 {
 716         const char *item;
 717         int index;
 718
 719         for (index = 0; index < n; index++) {
 720                 item = array[index];
 721                 if (!item)
 722                         break;
 723                 if (sysfs_streq(item, str))
 724                         return index;
 725         }
 726
 727         return -EINVAL;
 728 }
 729 EXPORT_SYMBOL(__sysfs_match_string);
 730
 731 #ifndef __HAVE_ARCH_MEMSET
 732 /**
 733  * memset - Fill a region of memory with the given value
 734  * @s: Pointer to the start of the area.
 735  * @c: The byte to fill the area with
 736  * @count: The size of the area.
 737  *
 738  * Do not use memset() to access IO space, use memset_io() instead.
 739  */
 740 void *memset(void *s, int c, size_t count)
 741 {
 742         char *xs = s;
 743
 744         while (count--)
 745                 *xs++ = c;
 746         return s;
 747 }
 748 EXPORT_SYMBOL(memset);
 749 #endif
 750
 751 /**
 752  * memzero_explicit - Fill a region of memory (e.g. sensitive
 753  *                    keying data) with 0s.
 754  * @s: Pointer to the start of the area.
 755  * @count: The size of the area.
 756  *
 757  * Note: usually using memset() is just fine (!), but in cases
 758  * where clearing out _local_ data at the end of a scope is
 759  * necessary, memzero_explicit() should be used instead in
 760  * order to prevent the compiler from optimising away zeroing.
 761  *
 762  * memzero_explicit() doesn't need an arch-specific version as
 763  * it just invokes the one of memset() implicitly.
 764  */
 765 void memzero_explicit(void *s, size_t count)
 766 {
 767         memset(s, 0, count);
 768         barrier_data(s);
 769 }
 770 EXPORT_SYMBOL(memzero_explicit);
 771
 772 #ifndef __HAVE_ARCH_MEMSET16
 773 /**
 774  * memset16() - Fill a memory area with a uint16_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 uint16_t instead
 780  * of a byte.  Remember that @count is the number of uint16_ts to
 781  * store, not the number of bytes.
 782  */
 783 void *memset16(uint16_t *s, uint16_t v, size_t count)
 784 {
 785         uint16_t *xs = s;
 786
 787         while (count--)
 788                 *xs++ = v;
 789         return s;
 790 }
 791 EXPORT_SYMBOL(memset16);
 792 #endif
 793
 794 #ifndef __HAVE_ARCH_MEMSET32
 795 /**
 796  * memset32() - Fill a memory area with a uint32_t
 797  * @s: Pointer to the start of the area.
 798  * @v: The value to fill the area with
 799  * @count: The number of values to store
 800  *
 801  * Differs from memset() in that it fills with a uint32_t instead
 802  * of a byte.  Remember that @count is the number of uint32_ts to
 803  * store, not the number of bytes.
 804  */
 805 void *memset32(uint32_t *s, uint32_t v, size_t count)
 806 {
 807         uint32_t *xs = s;
 808
 809         while (count--)
 810                 *xs++ = v;
 811         return s;
 812 }
 813 EXPORT_SYMBOL(memset32);
 814 #endif
 815
 816 #ifndef __HAVE_ARCH_MEMSET64
 817 /**
 818  * memset64() - Fill a memory area with a uint64_t
 819  * @s: Pointer to the start of the area.
 820  * @v: The value to fill the area with
 821  * @count: The number of values to store
 822  *
 823  * Differs from memset() in that it fills with a uint64_t instead
 824  * of a byte.  Remember that @count is the number of uint64_ts to
 825  * store, not the number of bytes.
 826  */
 827 void *memset64(uint64_t *s, uint64_t v, size_t count)
 828 {
 829         uint64_t *xs = s;
 830
 831         while (count--)
 832                 *xs++ = v;
 833         return s;
 834 }
 835 EXPORT_SYMBOL(memset64);
 836 #endif
 837
 838 #ifndef __HAVE_ARCH_MEMCPY
 839 /**
 840  * memcpy - Copy one area of memory to another
 841  * @dest: Where to copy to
 842  * @src: Where to copy from
 843  * @count: The size of the area.
 844  *
 845  * You should not use this function to access IO space, use memcpy_toio()
 846  * or memcpy_fromio() instead.
 847  */
 848 void *memcpy(void *dest, const void *src, size_t count)
 849 {
 850         char *tmp = dest;
 851         const char *s = src;
 852
 853         while (count--)
 854                 *tmp++ = *s++;
 855         return dest;
 856 }
 857 EXPORT_SYMBOL(memcpy);
 858 #endif
 859
 860 #ifndef __HAVE_ARCH_MEMMOVE
 861 /**
 862  * memmove - Copy one area of memory to another
 863  * @dest: Where to copy to
 864  * @src: Where to copy from
 865  * @count: The size of the area.
 866  *
 867  * Unlike memcpy(), memmove() copes with overlapping areas.
 868  */
 869 void *memmove(void *dest, const void *src, size_t count)
 870 {
 871         char *tmp;
 872         const char *s;
 873
 874         if (dest <= src) {
 875                 tmp = dest;
 876                 s = src;
 877                 while (count--)
 878                         *tmp++ = *s++;
 879         } else {
 880                 tmp = dest;
 881                 tmp += count;
 882                 s = src;
 883                 s += count;
 884                 while (count--)
 885                         *--tmp = *--s;
 886         }
 887         return dest;
 888 }
 889 EXPORT_SYMBOL(memmove);
 890 #endif
 891
 892 #ifndef __HAVE_ARCH_MEMCMP
 893 /**
 894  * memcmp - Compare two areas of memory
 895  * @cs: One area of memory
 896  * @ct: Another area of memory
 897  * @count: The size of the area.
 898  */
 899 #undef memcmp
 900 __visible int memcmp(const void *cs, const void *ct, size_t count)
 901 {
 902         const unsigned char *su1, *su2;
 903         int res = 0;
 904
 905         for (su1 = cs, su2 = ct; 0 < count; ++su1, ++su2, count--)
 906                 if ((res = *su1 - *su2) != 0)
 907                         break;
 908         return res;
 909 }
 910 EXPORT_SYMBOL(memcmp);
 911 #endif
 912
 913 #ifndef __HAVE_ARCH_BCMP
 914 /**
 915  * bcmp - returns 0 if and only if the buffers have identical contents.
 916  * @a: pointer to first buffer.
 917  * @b: pointer to second buffer.
 918  * @len: size of buffers.
 919  *
 920  * The sign or magnitude of a non-zero return value has no particular
 921  * meaning, and architectures may implement their own more efficient bcmp(). So
 922  * while this particular implementation is a simple (tail) call to memcmp, do
 923  * not rely on anything but whether the return value is zero or non-zero.
 924  */
 925 #undef bcmp
 926 int bcmp(const void *a, const void *b, size_t len)
 927 {
 928         return memcmp(a, b, len);
 929 }
 930 EXPORT_SYMBOL(bcmp);
 931 #endif
 932
 933 #ifndef __HAVE_ARCH_MEMSCAN
 934 /**
 935  * memscan - Find a character in an area of memory.
 936  * @addr: The memory area
 937  * @c: The byte to search for
 938  * @size: The size of the area.
 939  *
 940  * returns the address of the first occurrence of @c, or 1 byte past
 941  * the area if @c is not found
 942  */
 943 void *memscan(void *addr, int c, size_t size)
 944 {
 945         unsigned char *p = addr;
 946
 947         while (size) {
 948                 if (*p == c)
 949                         return (void *)p;
 950                 p++;
 951                 size--;
 952         }
 953         return (void *)p;
 954 }
 955 EXPORT_SYMBOL(memscan);
 956 #endif
 957
 958 #ifndef __HAVE_ARCH_STRSTR
 959 /**
 960  * strstr - Find the first substring in a %NUL terminated string
 961  * @s1: The string to be searched
 962  * @s2: The string to search for
 963  */
 964 char *strstr(const char *s1, const char *s2)
 965 {
 966         size_t l1, l2;
 967
 968         l2 = strlen(s2);
 969         if (!l2)
 970                 return (char *)s1;
 971         l1 = strlen(s1);
 972         while (l1 >= l2) {
 973                 l1--;
 974                 if (!memcmp(s1, s2, l2))
 975                         return (char *)s1;
 976                 s1++;
 977         }
 978         return NULL;
 979 }
 980 EXPORT_SYMBOL(strstr);
 981 #endif
 982
 983 #ifndef __HAVE_ARCH_STRNSTR
 984 /**
 985  * strnstr - Find the first substring in a length-limited string
 986  * @s1: The string to be searched
 987  * @s2: The string to search for
 988  * @len: the maximum number of characters to search
 989  */
 990 char *strnstr(const char *s1, const char *s2, size_t len)
 991 {
 992         size_t l2;
 993
 994         l2 = strlen(s2);
 995         if (!l2)
 996                 return (char *)s1;
 997         while (len >= l2) {
 998                 len--;
 999                 if (!memcmp(s1, s2, l2))
1000                         return (char *)s1;
1001                 s1++;
1002         }
1003         return NULL;
1004 }
1005 EXPORT_SYMBOL(strnstr);
1006 #endif
1007
1008 #ifndef __HAVE_ARCH_MEMCHR
1009 /**
1010  * memchr - Find a character in an area of memory.
1011  * @s: The memory area
1012  * @c: The byte to search for
1013  * @n: The size of the area.
1014  *
1015  * returns the address of the first occurrence of @c, or %NULL
1016  * if @c is not found
1017  */
1018 void *memchr(const void *s, int c, size_t n)
1019 {
1020         const unsigned char *p = s;
1021         while (n-- != 0) {
1022                 if ((unsigned char)c == *p++) {
1023                         return (void *)(p - 1);
1024                 }
1025         }
1026         return NULL;
1027 }
1028 EXPORT_SYMBOL(memchr);
1029 #endif
1030
1031 static void *check_bytes8(const u8 *start, u8 value, unsigned int bytes)
1032 {
1033         while (bytes) {
1034                 if (*start != value)
1035                         return (void *)start;
1036                 start++;
1037                 bytes--;
1038         }
1039         return NULL;
1040 }
1041
1042 /**
1043  * memchr_inv - Find an unmatching character in an area of memory.
1044  * @start: The memory area
1045  * @c: Find a character other than c
1046  * @bytes: The size of the area.
1047  *
1048  * returns the address of the first character other than @c, or %NULL
1049  * if the whole buffer contains just @c.
1050  */
1051 void *memchr_inv(const void *start, int c, size_t bytes)
1052 {
1053         u8 value = c;
1054         u64 value64;
1055         unsigned int words, prefix;
1056
1057         if (bytes <= 16)
1058                 return check_bytes8(start, value, bytes);
1059
1060         value64 = value;
1061 #if defined(CONFIG_ARCH_HAS_FAST_MULTIPLIER) && BITS_PER_LONG == 64
1062         value64 *= 0x0101010101010101ULL;
1063 #elif defined(CONFIG_ARCH_HAS_FAST_MULTIPLIER)
1064         value64 *= 0x01010101;
1065         value64 |= value64 << 32;
1066 #else
1067         value64 |= value64 << 8;
1068         value64 |= value64 << 16;
1069         value64 |= value64 << 32;
1070 #endif
1071
1072         prefix = (unsigned long)start % 8;
1073         if (prefix) {
1074                 u8 *r;
1075
1076                 prefix = 8 - prefix;
1077                 r = check_bytes8(start, value, prefix);
1078                 if (r)
1079                         return r;
1080                 start += prefix;
1081                 bytes -= prefix;
1082         }
1083
1084         words = bytes / 8;
1085
1086         while (words) {
1087                 if (*(u64 *)start != value64)
1088                         return check_bytes8(start, value, 8);
1089                 start += 8;
1090                 words--;
1091         }
1092
1093         return check_bytes8(start, value, bytes % 8);
1094 }
1095 EXPORT_SYMBOL(memchr_inv);
1096
1097 /**
1098  * strreplace - Replace all occurrences of character in string.
1099  * @s: The string to operate on.
1100  * @old: The character being replaced.
1101  * @new: The character @old is replaced with.
1102  *
1103  * Returns pointer to the nul byte at the end of @s.
1104  */
1105 char *strreplace(char *s, char old, char new)
1106 {
1107         for (; *s; ++s)
1108                 if (*s == old)
1109                         *s = new;
1110         return s;
1111 }
1112 EXPORT_SYMBOL(strreplace);
1113
1114 void fortify_panic(const char *name)
1115 {
1116         pr_emerg("detected buffer overflow in %s\n", name);
1117         BUG();
1118 }
1119 EXPORT_SYMBOL(fortify_panic);