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