lib/string.c

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