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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 * This file should be used only for "library" routines that may have
10 * alternative implementations on specific architectures (generally
11 * found in <asm-xx/string.h>), or get overloaded by FORTIFY_SOURCE.
12 * (Specifically, this file is built with __NO_FORTIFY.)
13 *
14 * Other helper functions should live in string_helpers.c.
15 */
16
17#define __NO_FORTIFY
18#include <linux/types.h>
19#include <linux/string.h>
20#include <linux/ctype.h>
21#include <linux/kernel.h>
22#include <linux/export.h>
23#include <linux/bug.h>
24#include <linux/errno.h>
25#include <linux/slab.h>
26
27#include <asm/unaligned.h>
28#include <asm/byteorder.h>
29#include <asm/word-at-a-time.h>
30#include <asm/page.h>
31
32#ifndef __HAVE_ARCH_STRNCASECMP
33/**
34 * strncasecmp - Case insensitive, length-limited string comparison
35 * @s1: One string
36 * @s2: The other string
37 * @len: the maximum number of characters to compare
38 */
39int strncasecmp(const char *s1, const char *s2, size_t len)
40{
41 /* Yes, Virginia, it had better be unsigned */
42 unsigned char c1, c2;
43
44 if (!len)
45 return 0;
46
47 do {
48 c1 = *s1++;
49 c2 = *s2++;
50 if (!c1 || !c2)
51 break;
52 if (c1 == c2)
53 continue;
54 c1 = tolower(c1);
55 c2 = tolower(c2);
56 if (c1 != c2)
57 break;
58 } while (--len);
59 return (int)c1 - (int)c2;
60}
61EXPORT_SYMBOL(strncasecmp);
62#endif
63
64#ifndef __HAVE_ARCH_STRCASECMP
65int strcasecmp(const char *s1, const char *s2)
66{
67 int c1, c2;
68
69 do {
70 c1 = tolower(*s1++);
71 c2 = tolower(*s2++);
72 } while (c1 == c2 && c1 != 0);
73 return c1 - c2;
74}
75EXPORT_SYMBOL(strcasecmp);
76#endif
77
78#ifndef __HAVE_ARCH_STRCPY
79char *strcpy(char *dest, const char *src)
80{
81 char *tmp = dest;
82
83 while ((*dest++ = *src++) != '\0')
84 /* nothing */;
85 return tmp;
86}
87EXPORT_SYMBOL(strcpy);
88#endif
89
90#ifndef __HAVE_ARCH_STRNCPY
91char *strncpy(char *dest, const char *src, size_t count)
92{
93 char *tmp = dest;
94
95 while (count) {
96 if ((*tmp = *src) != 0)
97 src++;
98 tmp++;
99 count--;
100 }
101 return dest;
102}
103EXPORT_SYMBOL(strncpy);
104#endif
105
106#ifndef __HAVE_ARCH_STRSCPY
107ssize_t strscpy(char *dest, const char *src, size_t count)
108{
109 const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
110 size_t max = count;
111 long res = 0;
112
113 if (count == 0 || WARN_ON_ONCE(count > INT_MAX))
114 return -E2BIG;
115
116#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
117 /*
118 * If src is unaligned, don't cross a page boundary,
119 * since we don't know if the next page is mapped.
120 */
121 if ((long)src & (sizeof(long) - 1)) {
122 size_t limit = PAGE_SIZE - ((long)src & (PAGE_SIZE - 1));
123 if (limit < max)
124 max = limit;
125 }
126#else
127 /* If src or dest is unaligned, don't do word-at-a-time. */
128 if (((long) dest | (long) src) & (sizeof(long) - 1))
129 max = 0;
130#endif
131
132 /*
133 * read_word_at_a_time() below may read uninitialized bytes after the
134 * trailing zero and use them in comparisons. Disable this optimization
135 * under KMSAN to prevent false positive reports.
136 */
137 if (IS_ENABLED(CONFIG_KMSAN))
138 max = 0;
139
140 while (max >= sizeof(unsigned long)) {
141 unsigned long c, data;
142
143 c = read_word_at_a_time(src+res);
144 if (has_zero(c, &data, &constants)) {
145 data = prep_zero_mask(c, data, &constants);
146 data = create_zero_mask(data);
147 *(unsigned long *)(dest+res) = c & zero_bytemask(data);
148 return res + find_zero(data);
149 }
150 *(unsigned long *)(dest+res) = c;
151 res += sizeof(unsigned long);
152 count -= sizeof(unsigned long);
153 max -= sizeof(unsigned long);
154 }
155
156 while (count) {
157 char c;
158
159 c = src[res];
160 dest[res] = c;
161 if (!c)
162 return res;
163 res++;
164 count--;
165 }
166
167 /* Hit buffer length without finding a NUL; force NUL-termination. */
168 if (res)
169 dest[res-1] = '\0';
170
171 return -E2BIG;
172}
173EXPORT_SYMBOL(strscpy);
174#endif
175
176/**
177 * stpcpy - copy a string from src to dest returning a pointer to the new end
178 * of dest, including src's %NUL-terminator. May overrun dest.
179 * @dest: pointer to end of string being copied into. Must be large enough
180 * to receive copy.
181 * @src: pointer to the beginning of string being copied from. Must not overlap
182 * dest.
183 *
184 * stpcpy differs from strcpy in a key way: the return value is a pointer
185 * to the new %NUL-terminating character in @dest. (For strcpy, the return
186 * value is a pointer to the start of @dest). This interface is considered
187 * unsafe as it doesn't perform bounds checking of the inputs. As such it's
188 * not recommended for usage. Instead, its definition is provided in case
189 * the compiler lowers other libcalls to stpcpy.
190 */
191char *stpcpy(char *__restrict__ dest, const char *__restrict__ src);
192char *stpcpy(char *__restrict__ dest, const char *__restrict__ src)
193{
194 while ((*dest++ = *src++) != '\0')
195 /* nothing */;
196 return --dest;
197}
198EXPORT_SYMBOL(stpcpy);
199
200#ifndef __HAVE_ARCH_STRCAT
201char *strcat(char *dest, const char *src)
202{
203 char *tmp = dest;
204
205 while (*dest)
206 dest++;
207 while ((*dest++ = *src++) != '\0')
208 ;
209 return tmp;
210}
211EXPORT_SYMBOL(strcat);
212#endif
213
214#ifndef __HAVE_ARCH_STRNCAT
215char *strncat(char *dest, const char *src, size_t count)
216{
217 char *tmp = dest;
218
219 if (count) {
220 while (*dest)
221 dest++;
222 while ((*dest++ = *src++) != 0) {
223 if (--count == 0) {
224 *dest = '\0';
225 break;
226 }
227 }
228 }
229 return tmp;
230}
231EXPORT_SYMBOL(strncat);
232#endif
233
234#ifndef __HAVE_ARCH_STRLCAT
235size_t strlcat(char *dest, const char *src, size_t count)
236{
237 size_t dsize = strlen(dest);
238 size_t len = strlen(src);
239 size_t res = dsize + len;
240
241 /* This would be a bug */
242 BUG_ON(dsize >= count);
243
244 dest += dsize;
245 count -= dsize;
246 if (len >= count)
247 len = count-1;
248 __builtin_memcpy(dest, src, len);
249 dest[len] = 0;
250 return res;
251}
252EXPORT_SYMBOL(strlcat);
253#endif
254
255#ifndef __HAVE_ARCH_STRCMP
256/**
257 * strcmp - Compare two strings
258 * @cs: One string
259 * @ct: Another string
260 */
261int strcmp(const char *cs, const char *ct)
262{
263 unsigned char c1, c2;
264
265 while (1) {
266 c1 = *cs++;
267 c2 = *ct++;
268 if (c1 != c2)
269 return c1 < c2 ? -1 : 1;
270 if (!c1)
271 break;
272 }
273 return 0;
274}
275EXPORT_SYMBOL(strcmp);
276#endif
277
278#ifndef __HAVE_ARCH_STRNCMP
279/**
280 * strncmp - Compare two length-limited strings
281 * @cs: One string
282 * @ct: Another string
283 * @count: The maximum number of bytes to compare
284 */
285int strncmp(const char *cs, const char *ct, size_t count)
286{
287 unsigned char c1, c2;
288
289 while (count) {
290 c1 = *cs++;
291 c2 = *ct++;
292 if (c1 != c2)
293 return c1 < c2 ? -1 : 1;
294 if (!c1)
295 break;
296 count--;
297 }
298 return 0;
299}
300EXPORT_SYMBOL(strncmp);
301#endif
302
303#ifndef __HAVE_ARCH_STRCHR
304/**
305 * strchr - Find the first occurrence of a character in a string
306 * @s: The string to be searched
307 * @c: The character to search for
308 *
309 * Note that the %NUL-terminator is considered part of the string, and can
310 * be searched for.
311 */
312char *strchr(const char *s, int c)
313{
314 for (; *s != (char)c; ++s)
315 if (*s == '\0')
316 return NULL;
317 return (char *)s;
318}
319EXPORT_SYMBOL(strchr);
320#endif
321
322#ifndef __HAVE_ARCH_STRCHRNUL
323/**
324 * strchrnul - Find and return a character in a string, or end of string
325 * @s: The string to be searched
326 * @c: The character to search for
327 *
328 * Returns pointer to first occurrence of 'c' in s. If c is not found, then
329 * return a pointer to the null byte at the end of s.
330 */
331char *strchrnul(const char *s, int c)
332{
333 while (*s && *s != (char)c)
334 s++;
335 return (char *)s;
336}
337EXPORT_SYMBOL(strchrnul);
338#endif
339
340/**
341 * strnchrnul - Find and return a character in a length limited string,
342 * or end of string
343 * @s: The string to be searched
344 * @count: The number of characters to be searched
345 * @c: The character to search for
346 *
347 * Returns pointer to the first occurrence of 'c' in s. If c is not found,
348 * then return a pointer to the last character of the string.
349 */
350char *strnchrnul(const char *s, size_t count, int c)
351{
352 while (count-- && *s && *s != (char)c)
353 s++;
354 return (char *)s;
355}
356
357#ifndef __HAVE_ARCH_STRRCHR
358/**
359 * strrchr - Find the last occurrence of a character in a string
360 * @s: The string to be searched
361 * @c: The character to search for
362 */
363char *strrchr(const char *s, int c)
364{
365 const char *last = NULL;
366 do {
367 if (*s == (char)c)
368 last = s;
369 } while (*s++);
370 return (char *)last;
371}
372EXPORT_SYMBOL(strrchr);
373#endif
374
375#ifndef __HAVE_ARCH_STRNCHR
376/**
377 * strnchr - Find a character in a length limited string
378 * @s: The string to be searched
379 * @count: The number of characters to be searched
380 * @c: The character to search for
381 *
382 * Note that the %NUL-terminator is considered part of the string, and can
383 * be searched for.
384 */
385char *strnchr(const char *s, size_t count, int c)
386{
387 while (count--) {
388 if (*s == (char)c)
389 return (char *)s;
390 if (*s++ == '\0')
391 break;
392 }
393 return NULL;
394}
395EXPORT_SYMBOL(strnchr);
396#endif
397
398#ifndef __HAVE_ARCH_STRLEN
399size_t strlen(const char *s)
400{
401 const char *sc;
402
403 for (sc = s; *sc != '\0'; ++sc)
404 /* nothing */;
405 return sc - s;
406}
407EXPORT_SYMBOL(strlen);
408#endif
409
410#ifndef __HAVE_ARCH_STRNLEN
411size_t strnlen(const char *s, size_t count)
412{
413 const char *sc;
414
415 for (sc = s; count-- && *sc != '\0'; ++sc)
416 /* nothing */;
417 return sc - s;
418}
419EXPORT_SYMBOL(strnlen);
420#endif
421
422#ifndef __HAVE_ARCH_STRSPN
423/**
424 * strspn - Calculate the length of the initial substring of @s which only contain letters in @accept
425 * @s: The string to be searched
426 * @accept: The string to search for
427 */
428size_t strspn(const char *s, const char *accept)
429{
430 const char *p;
431
432 for (p = s; *p != '\0'; ++p) {
433 if (!strchr(accept, *p))
434 break;
435 }
436 return p - s;
437}
438EXPORT_SYMBOL(strspn);
439#endif
440
441#ifndef __HAVE_ARCH_STRCSPN
442/**
443 * strcspn - Calculate the length of the initial substring of @s which does not contain letters in @reject
444 * @s: The string to be searched
445 * @reject: The string to avoid
446 */
447size_t strcspn(const char *s, const char *reject)
448{
449 const char *p;
450
451 for (p = s; *p != '\0'; ++p) {
452 if (strchr(reject, *p))
453 break;
454 }
455 return p - s;
456}
457EXPORT_SYMBOL(strcspn);
458#endif
459
460#ifndef __HAVE_ARCH_STRPBRK
461/**
462 * strpbrk - Find the first occurrence of a set of characters
463 * @cs: The string to be searched
464 * @ct: The characters to search for
465 */
466char *strpbrk(const char *cs, const char *ct)
467{
468 const char *sc;
469
470 for (sc = cs; *sc != '\0'; ++sc) {
471 if (strchr(ct, *sc))
472 return (char *)sc;
473 }
474 return NULL;
475}
476EXPORT_SYMBOL(strpbrk);
477#endif
478
479#ifndef __HAVE_ARCH_STRSEP
480/**
481 * strsep - Split a string into tokens
482 * @s: The string to be searched
483 * @ct: The characters to search for
484 *
485 * strsep() updates @s to point after the token, ready for the next call.
486 *
487 * It returns empty tokens, too, behaving exactly like the libc function
488 * of that name. In fact, it was stolen from glibc2 and de-fancy-fied.
489 * Same semantics, slimmer shape. ;)
490 */
491char *strsep(char **s, const char *ct)
492{
493 char *sbegin = *s;
494 char *end;
495
496 if (sbegin == NULL)
497 return NULL;
498
499 end = strpbrk(sbegin, ct);
500 if (end)
501 *end++ = '\0';
502 *s = end;
503 return sbegin;
504}
505EXPORT_SYMBOL(strsep);
506#endif
507
508#ifndef __HAVE_ARCH_MEMSET
509/**
510 * memset - Fill a region of memory with the given value
511 * @s: Pointer to the start of the area.
512 * @c: The byte to fill the area with
513 * @count: The size of the area.
514 *
515 * Do not use memset() to access IO space, use memset_io() instead.
516 */
517void *memset(void *s, int c, size_t count)
518{
519 char *xs = s;
520
521 while (count--)
522 *xs++ = c;
523 return s;
524}
525EXPORT_SYMBOL(memset);
526#endif
527
528#ifndef __HAVE_ARCH_MEMSET16
529/**
530 * memset16() - Fill a memory area with a uint16_t
531 * @s: Pointer to the start of the area.
532 * @v: The value to fill the area with
533 * @count: The number of values to store
534 *
535 * Differs from memset() in that it fills with a uint16_t instead
536 * of a byte. Remember that @count is the number of uint16_ts to
537 * store, not the number of bytes.
538 */
539void *memset16(uint16_t *s, uint16_t v, size_t count)
540{
541 uint16_t *xs = s;
542
543 while (count--)
544 *xs++ = v;
545 return s;
546}
547EXPORT_SYMBOL(memset16);
548#endif
549
550#ifndef __HAVE_ARCH_MEMSET32
551/**
552 * memset32() - Fill a memory area with a uint32_t
553 * @s: Pointer to the start of the area.
554 * @v: The value to fill the area with
555 * @count: The number of values to store
556 *
557 * Differs from memset() in that it fills with a uint32_t instead
558 * of a byte. Remember that @count is the number of uint32_ts to
559 * store, not the number of bytes.
560 */
561void *memset32(uint32_t *s, uint32_t v, size_t count)
562{
563 uint32_t *xs = s;
564
565 while (count--)
566 *xs++ = v;
567 return s;
568}
569EXPORT_SYMBOL(memset32);
570#endif
571
572#ifndef __HAVE_ARCH_MEMSET64
573/**
574 * memset64() - Fill a memory area with a uint64_t
575 * @s: Pointer to the start of the area.
576 * @v: The value to fill the area with
577 * @count: The number of values to store
578 *
579 * Differs from memset() in that it fills with a uint64_t instead
580 * of a byte. Remember that @count is the number of uint64_ts to
581 * store, not the number of bytes.
582 */
583void *memset64(uint64_t *s, uint64_t v, size_t count)
584{
585 uint64_t *xs = s;
586
587 while (count--)
588 *xs++ = v;
589 return s;
590}
591EXPORT_SYMBOL(memset64);
592#endif
593
594#ifndef __HAVE_ARCH_MEMCPY
595/**
596 * memcpy - Copy one area of memory to another
597 * @dest: Where to copy to
598 * @src: Where to copy from
599 * @count: The size of the area.
600 *
601 * You should not use this function to access IO space, use memcpy_toio()
602 * or memcpy_fromio() instead.
603 */
604void *memcpy(void *dest, const void *src, size_t count)
605{
606 char *tmp = dest;
607 const char *s = src;
608
609 while (count--)
610 *tmp++ = *s++;
611 return dest;
612}
613EXPORT_SYMBOL(memcpy);
614#endif
615
616#ifndef __HAVE_ARCH_MEMMOVE
617/**
618 * memmove - Copy one area of memory to another
619 * @dest: Where to copy to
620 * @src: Where to copy from
621 * @count: The size of the area.
622 *
623 * Unlike memcpy(), memmove() copes with overlapping areas.
624 */
625void *memmove(void *dest, const void *src, size_t count)
626{
627 char *tmp;
628 const char *s;
629
630 if (dest <= src) {
631 tmp = dest;
632 s = src;
633 while (count--)
634 *tmp++ = *s++;
635 } else {
636 tmp = dest;
637 tmp += count;
638 s = src;
639 s += count;
640 while (count--)
641 *--tmp = *--s;
642 }
643 return dest;
644}
645EXPORT_SYMBOL(memmove);
646#endif
647
648#ifndef __HAVE_ARCH_MEMCMP
649/**
650 * memcmp - Compare two areas of memory
651 * @cs: One area of memory
652 * @ct: Another area of memory
653 * @count: The size of the area.
654 */
655#undef memcmp
656__visible int memcmp(const void *cs, const void *ct, size_t count)
657{
658 const unsigned char *su1, *su2;
659 int res = 0;
660
661#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
662 if (count >= sizeof(unsigned long)) {
663 const unsigned long *u1 = cs;
664 const unsigned long *u2 = ct;
665 do {
666 if (get_unaligned(u1) != get_unaligned(u2))
667 break;
668 u1++;
669 u2++;
670 count -= sizeof(unsigned long);
671 } while (count >= sizeof(unsigned long));
672 cs = u1;
673 ct = u2;
674 }
675#endif
676 for (su1 = cs, su2 = ct; 0 < count; ++su1, ++su2, count--)
677 if ((res = *su1 - *su2) != 0)
678 break;
679 return res;
680}
681EXPORT_SYMBOL(memcmp);
682#endif
683
684#ifndef __HAVE_ARCH_BCMP
685/**
686 * bcmp - returns 0 if and only if the buffers have identical contents.
687 * @a: pointer to first buffer.
688 * @b: pointer to second buffer.
689 * @len: size of buffers.
690 *
691 * The sign or magnitude of a non-zero return value has no particular
692 * meaning, and architectures may implement their own more efficient bcmp(). So
693 * while this particular implementation is a simple (tail) call to memcmp, do
694 * not rely on anything but whether the return value is zero or non-zero.
695 */
696int bcmp(const void *a, const void *b, size_t len)
697{
698 return memcmp(a, b, len);
699}
700EXPORT_SYMBOL(bcmp);
701#endif
702
703#ifndef __HAVE_ARCH_MEMSCAN
704/**
705 * memscan - Find a character in an area of memory.
706 * @addr: The memory area
707 * @c: The byte to search for
708 * @size: The size of the area.
709 *
710 * returns the address of the first occurrence of @c, or 1 byte past
711 * the area if @c is not found
712 */
713void *memscan(void *addr, int c, size_t size)
714{
715 unsigned char *p = addr;
716
717 while (size) {
718 if (*p == (unsigned char)c)
719 return (void *)p;
720 p++;
721 size--;
722 }
723 return (void *)p;
724}
725EXPORT_SYMBOL(memscan);
726#endif
727
728#ifndef __HAVE_ARCH_STRSTR
729/**
730 * strstr - Find the first substring in a %NUL terminated string
731 * @s1: The string to be searched
732 * @s2: The string to search for
733 */
734char *strstr(const char *s1, const char *s2)
735{
736 size_t l1, l2;
737
738 l2 = strlen(s2);
739 if (!l2)
740 return (char *)s1;
741 l1 = strlen(s1);
742 while (l1 >= l2) {
743 l1--;
744 if (!memcmp(s1, s2, l2))
745 return (char *)s1;
746 s1++;
747 }
748 return NULL;
749}
750EXPORT_SYMBOL(strstr);
751#endif
752
753#ifndef __HAVE_ARCH_STRNSTR
754/**
755 * strnstr - Find the first substring in a length-limited string
756 * @s1: The string to be searched
757 * @s2: The string to search for
758 * @len: the maximum number of characters to search
759 */
760char *strnstr(const char *s1, const char *s2, size_t len)
761{
762 size_t l2;
763
764 l2 = strlen(s2);
765 if (!l2)
766 return (char *)s1;
767 while (len >= l2) {
768 len--;
769 if (!memcmp(s1, s2, l2))
770 return (char *)s1;
771 s1++;
772 }
773 return NULL;
774}
775EXPORT_SYMBOL(strnstr);
776#endif
777
778#ifndef __HAVE_ARCH_MEMCHR
779/**
780 * memchr - Find a character in an area of memory.
781 * @s: The memory area
782 * @c: The byte to search for
783 * @n: The size of the area.
784 *
785 * returns the address of the first occurrence of @c, or %NULL
786 * if @c is not found
787 */
788void *memchr(const void *s, int c, size_t n)
789{
790 const unsigned char *p = s;
791 while (n-- != 0) {
792 if ((unsigned char)c == *p++) {
793 return (void *)(p - 1);
794 }
795 }
796 return NULL;
797}
798EXPORT_SYMBOL(memchr);
799#endif
800
801static void *check_bytes8(const u8 *start, u8 value, unsigned int bytes)
802{
803 while (bytes) {
804 if (*start != value)
805 return (void *)start;
806 start++;
807 bytes--;
808 }
809 return NULL;
810}
811
812/**
813 * memchr_inv - Find an unmatching character in an area of memory.
814 * @start: The memory area
815 * @c: Find a character other than c
816 * @bytes: The size of the area.
817 *
818 * returns the address of the first character other than @c, or %NULL
819 * if the whole buffer contains just @c.
820 */
821void *memchr_inv(const void *start, int c, size_t bytes)
822{
823 u8 value = c;
824 u64 value64;
825 unsigned int words, prefix;
826
827 if (bytes <= 16)
828 return check_bytes8(start, value, bytes);
829
830 value64 = value;
831#if defined(CONFIG_ARCH_HAS_FAST_MULTIPLIER) && BITS_PER_LONG == 64
832 value64 *= 0x0101010101010101ULL;
833#elif defined(CONFIG_ARCH_HAS_FAST_MULTIPLIER)
834 value64 *= 0x01010101;
835 value64 |= value64 << 32;
836#else
837 value64 |= value64 << 8;
838 value64 |= value64 << 16;
839 value64 |= value64 << 32;
840#endif
841
842 prefix = (unsigned long)start % 8;
843 if (prefix) {
844 u8 *r;
845
846 prefix = 8 - prefix;
847 r = check_bytes8(start, value, prefix);
848 if (r)
849 return r;
850 start += prefix;
851 bytes -= prefix;
852 }
853
854 words = bytes / 8;
855
856 while (words) {
857 if (*(u64 *)start != value64)
858 return check_bytes8(start, value, 8);
859 start += 8;
860 words--;
861 }
862
863 return check_bytes8(start, value, bytes % 8);
864}
865EXPORT_SYMBOL(memchr_inv);
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 * This file should be used only for "library" routines that may have
10 * alternative implementations on specific architectures (generally
11 * found in <asm-xx/string.h>), or get overloaded by FORTIFY_SOURCE.
12 * (Specifically, this file is built with __NO_FORTIFY.)
13 *
14 * Other helper functions should live in string_helpers.c.
15 */
16
17#define __NO_FORTIFY
18#include <linux/bits.h>
19#include <linux/bug.h>
20#include <linux/ctype.h>
21#include <linux/errno.h>
22#include <linux/limits.h>
23#include <linux/linkage.h>
24#include <linux/stddef.h>
25#include <linux/string.h>
26#include <linux/types.h>
27
28#include <asm/page.h>
29#include <asm/rwonce.h>
30#include <asm/unaligned.h>
31#include <asm/word-at-a-time.h>
32
33#ifndef __HAVE_ARCH_STRNCASECMP
34/**
35 * strncasecmp - Case insensitive, length-limited string comparison
36 * @s1: One string
37 * @s2: The other string
38 * @len: the maximum number of characters to compare
39 */
40int strncasecmp(const char *s1, const char *s2, size_t len)
41{
42 /* Yes, Virginia, it had better be unsigned */
43 unsigned char c1, c2;
44
45 if (!len)
46 return 0;
47
48 do {
49 c1 = *s1++;
50 c2 = *s2++;
51 if (!c1 || !c2)
52 break;
53 if (c1 == c2)
54 continue;
55 c1 = tolower(c1);
56 c2 = tolower(c2);
57 if (c1 != c2)
58 break;
59 } while (--len);
60 return (int)c1 - (int)c2;
61}
62EXPORT_SYMBOL(strncasecmp);
63#endif
64
65#ifndef __HAVE_ARCH_STRCASECMP
66int strcasecmp(const char *s1, const char *s2)
67{
68 int c1, c2;
69
70 do {
71 c1 = tolower(*s1++);
72 c2 = tolower(*s2++);
73 } while (c1 == c2 && c1 != 0);
74 return c1 - c2;
75}
76EXPORT_SYMBOL(strcasecmp);
77#endif
78
79#ifndef __HAVE_ARCH_STRCPY
80char *strcpy(char *dest, const char *src)
81{
82 char *tmp = dest;
83
84 while ((*dest++ = *src++) != '\0')
85 /* nothing */;
86 return tmp;
87}
88EXPORT_SYMBOL(strcpy);
89#endif
90
91#ifndef __HAVE_ARCH_STRNCPY
92char *strncpy(char *dest, const char *src, size_t count)
93{
94 char *tmp = dest;
95
96 while (count) {
97 if ((*tmp = *src) != 0)
98 src++;
99 tmp++;
100 count--;
101 }
102 return dest;
103}
104EXPORT_SYMBOL(strncpy);
105#endif
106
107ssize_t sized_strscpy(char *dest, const char *src, size_t count)
108{
109 const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
110 size_t max = count;
111 long res = 0;
112
113 if (count == 0 || WARN_ON_ONCE(count > INT_MAX))
114 return -E2BIG;
115
116#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
117 /*
118 * If src is unaligned, don't cross a page boundary,
119 * since we don't know if the next page is mapped.
120 */
121 if ((long)src & (sizeof(long) - 1)) {
122 size_t limit = PAGE_SIZE - ((long)src & (PAGE_SIZE - 1));
123 if (limit < max)
124 max = limit;
125 }
126#else
127 /* If src or dest is unaligned, don't do word-at-a-time. */
128 if (((long) dest | (long) src) & (sizeof(long) - 1))
129 max = 0;
130#endif
131
132 /*
133 * read_word_at_a_time() below may read uninitialized bytes after the
134 * trailing zero and use them in comparisons. Disable this optimization
135 * under KMSAN to prevent false positive reports.
136 */
137 if (IS_ENABLED(CONFIG_KMSAN))
138 max = 0;
139
140 while (max >= sizeof(unsigned long)) {
141 unsigned long c, data;
142
143 c = read_word_at_a_time(src+res);
144 if (has_zero(c, &data, &constants)) {
145 data = prep_zero_mask(c, data, &constants);
146 data = create_zero_mask(data);
147 *(unsigned long *)(dest+res) = c & zero_bytemask(data);
148 return res + find_zero(data);
149 }
150 *(unsigned long *)(dest+res) = c;
151 res += sizeof(unsigned long);
152 count -= sizeof(unsigned long);
153 max -= sizeof(unsigned long);
154 }
155
156 while (count) {
157 char c;
158
159 c = src[res];
160 dest[res] = c;
161 if (!c)
162 return res;
163 res++;
164 count--;
165 }
166
167 /* Hit buffer length without finding a NUL; force NUL-termination. */
168 if (res)
169 dest[res-1] = '\0';
170
171 return -E2BIG;
172}
173EXPORT_SYMBOL(sized_strscpy);
174
175/**
176 * stpcpy - copy a string from src to dest returning a pointer to the new end
177 * of dest, including src's %NUL-terminator. May overrun dest.
178 * @dest: pointer to end of string being copied into. Must be large enough
179 * to receive copy.
180 * @src: pointer to the beginning of string being copied from. Must not overlap
181 * dest.
182 *
183 * stpcpy differs from strcpy in a key way: the return value is a pointer
184 * to the new %NUL-terminating character in @dest. (For strcpy, the return
185 * value is a pointer to the start of @dest). This interface is considered
186 * unsafe as it doesn't perform bounds checking of the inputs. As such it's
187 * not recommended for usage. Instead, its definition is provided in case
188 * the compiler lowers other libcalls to stpcpy.
189 */
190char *stpcpy(char *__restrict__ dest, const char *__restrict__ src);
191char *stpcpy(char *__restrict__ dest, const char *__restrict__ src)
192{
193 while ((*dest++ = *src++) != '\0')
194 /* nothing */;
195 return --dest;
196}
197EXPORT_SYMBOL(stpcpy);
198
199#ifndef __HAVE_ARCH_STRCAT
200char *strcat(char *dest, const char *src)
201{
202 char *tmp = dest;
203
204 while (*dest)
205 dest++;
206 while ((*dest++ = *src++) != '\0')
207 ;
208 return tmp;
209}
210EXPORT_SYMBOL(strcat);
211#endif
212
213#ifndef __HAVE_ARCH_STRNCAT
214char *strncat(char *dest, const char *src, size_t count)
215{
216 char *tmp = dest;
217
218 if (count) {
219 while (*dest)
220 dest++;
221 while ((*dest++ = *src++) != 0) {
222 if (--count == 0) {
223 *dest = '\0';
224 break;
225 }
226 }
227 }
228 return tmp;
229}
230EXPORT_SYMBOL(strncat);
231#endif
232
233#ifndef __HAVE_ARCH_STRLCAT
234size_t strlcat(char *dest, const char *src, size_t count)
235{
236 size_t dsize = strlen(dest);
237 size_t len = strlen(src);
238 size_t res = dsize + len;
239
240 /* This would be a bug */
241 BUG_ON(dsize >= count);
242
243 dest += dsize;
244 count -= dsize;
245 if (len >= count)
246 len = count-1;
247 __builtin_memcpy(dest, src, len);
248 dest[len] = 0;
249 return res;
250}
251EXPORT_SYMBOL(strlcat);
252#endif
253
254#ifndef __HAVE_ARCH_STRCMP
255/**
256 * strcmp - Compare two strings
257 * @cs: One string
258 * @ct: Another string
259 */
260int strcmp(const char *cs, const char *ct)
261{
262 unsigned char c1, c2;
263
264 while (1) {
265 c1 = *cs++;
266 c2 = *ct++;
267 if (c1 != c2)
268 return c1 < c2 ? -1 : 1;
269 if (!c1)
270 break;
271 }
272 return 0;
273}
274EXPORT_SYMBOL(strcmp);
275#endif
276
277#ifndef __HAVE_ARCH_STRNCMP
278/**
279 * strncmp - Compare two length-limited strings
280 * @cs: One string
281 * @ct: Another string
282 * @count: The maximum number of bytes to compare
283 */
284int strncmp(const char *cs, const char *ct, size_t count)
285{
286 unsigned char c1, c2;
287
288 while (count) {
289 c1 = *cs++;
290 c2 = *ct++;
291 if (c1 != c2)
292 return c1 < c2 ? -1 : 1;
293 if (!c1)
294 break;
295 count--;
296 }
297 return 0;
298}
299EXPORT_SYMBOL(strncmp);
300#endif
301
302#ifndef __HAVE_ARCH_STRCHR
303/**
304 * strchr - Find the first occurrence of a character in a string
305 * @s: The string to be searched
306 * @c: The character to search for
307 *
308 * Note that the %NUL-terminator is considered part of the string, and can
309 * be searched for.
310 */
311char *strchr(const char *s, int c)
312{
313 for (; *s != (char)c; ++s)
314 if (*s == '\0')
315 return NULL;
316 return (char *)s;
317}
318EXPORT_SYMBOL(strchr);
319#endif
320
321#ifndef __HAVE_ARCH_STRCHRNUL
322/**
323 * strchrnul - Find and return a character in a string, or end of string
324 * @s: The string to be searched
325 * @c: The character to search for
326 *
327 * Returns pointer to first occurrence of 'c' in s. If c is not found, then
328 * return a pointer to the null byte at the end of s.
329 */
330char *strchrnul(const char *s, int c)
331{
332 while (*s && *s != (char)c)
333 s++;
334 return (char *)s;
335}
336EXPORT_SYMBOL(strchrnul);
337#endif
338
339/**
340 * strnchrnul - Find and return a character in a length limited string,
341 * or end of string
342 * @s: The string to be searched
343 * @count: The number of characters to be searched
344 * @c: The character to search for
345 *
346 * Returns pointer to the first occurrence of 'c' in s. If c is not found,
347 * then return a pointer to the last character of the string.
348 */
349char *strnchrnul(const char *s, size_t count, int c)
350{
351 while (count-- && *s && *s != (char)c)
352 s++;
353 return (char *)s;
354}
355
356#ifndef __HAVE_ARCH_STRRCHR
357/**
358 * strrchr - Find the last occurrence of a character in a string
359 * @s: The string to be searched
360 * @c: The character to search for
361 */
362char *strrchr(const char *s, int c)
363{
364 const char *last = NULL;
365 do {
366 if (*s == (char)c)
367 last = s;
368 } while (*s++);
369 return (char *)last;
370}
371EXPORT_SYMBOL(strrchr);
372#endif
373
374#ifndef __HAVE_ARCH_STRNCHR
375/**
376 * strnchr - Find a character in a length limited string
377 * @s: The string to be searched
378 * @count: The number of characters to be searched
379 * @c: The character to search for
380 *
381 * Note that the %NUL-terminator is considered part of the string, and can
382 * be searched for.
383 */
384char *strnchr(const char *s, size_t count, int c)
385{
386 while (count--) {
387 if (*s == (char)c)
388 return (char *)s;
389 if (*s++ == '\0')
390 break;
391 }
392 return NULL;
393}
394EXPORT_SYMBOL(strnchr);
395#endif
396
397#ifndef __HAVE_ARCH_STRLEN
398size_t strlen(const char *s)
399{
400 const char *sc;
401
402 for (sc = s; *sc != '\0'; ++sc)
403 /* nothing */;
404 return sc - s;
405}
406EXPORT_SYMBOL(strlen);
407#endif
408
409#ifndef __HAVE_ARCH_STRNLEN
410size_t strnlen(const char *s, size_t count)
411{
412 const char *sc;
413
414 for (sc = s; count-- && *sc != '\0'; ++sc)
415 /* nothing */;
416 return sc - s;
417}
418EXPORT_SYMBOL(strnlen);
419#endif
420
421#ifndef __HAVE_ARCH_STRSPN
422/**
423 * strspn - Calculate the length of the initial substring of @s which only contain letters in @accept
424 * @s: The string to be searched
425 * @accept: The string to search for
426 */
427size_t strspn(const char *s, const char *accept)
428{
429 const char *p;
430
431 for (p = s; *p != '\0'; ++p) {
432 if (!strchr(accept, *p))
433 break;
434 }
435 return p - s;
436}
437EXPORT_SYMBOL(strspn);
438#endif
439
440#ifndef __HAVE_ARCH_STRCSPN
441/**
442 * strcspn - Calculate the length of the initial substring of @s which does not contain letters in @reject
443 * @s: The string to be searched
444 * @reject: The string to avoid
445 */
446size_t strcspn(const char *s, const char *reject)
447{
448 const char *p;
449
450 for (p = s; *p != '\0'; ++p) {
451 if (strchr(reject, *p))
452 break;
453 }
454 return p - s;
455}
456EXPORT_SYMBOL(strcspn);
457#endif
458
459#ifndef __HAVE_ARCH_STRPBRK
460/**
461 * strpbrk - Find the first occurrence of a set of characters
462 * @cs: The string to be searched
463 * @ct: The characters to search for
464 */
465char *strpbrk(const char *cs, const char *ct)
466{
467 const char *sc;
468
469 for (sc = cs; *sc != '\0'; ++sc) {
470 if (strchr(ct, *sc))
471 return (char *)sc;
472 }
473 return NULL;
474}
475EXPORT_SYMBOL(strpbrk);
476#endif
477
478#ifndef __HAVE_ARCH_STRSEP
479/**
480 * strsep - Split a string into tokens
481 * @s: The string to be searched
482 * @ct: The characters to search for
483 *
484 * strsep() updates @s to point after the token, ready for the next call.
485 *
486 * It returns empty tokens, too, behaving exactly like the libc function
487 * of that name. In fact, it was stolen from glibc2 and de-fancy-fied.
488 * Same semantics, slimmer shape. ;)
489 */
490char *strsep(char **s, const char *ct)
491{
492 char *sbegin = *s;
493 char *end;
494
495 if (sbegin == NULL)
496 return NULL;
497
498 end = strpbrk(sbegin, ct);
499 if (end)
500 *end++ = '\0';
501 *s = end;
502 return sbegin;
503}
504EXPORT_SYMBOL(strsep);
505#endif
506
507#ifndef __HAVE_ARCH_MEMSET
508/**
509 * memset - Fill a region of memory with the given value
510 * @s: Pointer to the start of the area.
511 * @c: The byte to fill the area with
512 * @count: The size of the area.
513 *
514 * Do not use memset() to access IO space, use memset_io() instead.
515 */
516void *memset(void *s, int c, size_t count)
517{
518 char *xs = s;
519
520 while (count--)
521 *xs++ = c;
522 return s;
523}
524EXPORT_SYMBOL(memset);
525#endif
526
527#ifndef __HAVE_ARCH_MEMSET16
528/**
529 * memset16() - Fill a memory area with a uint16_t
530 * @s: Pointer to the start of the area.
531 * @v: The value to fill the area with
532 * @count: The number of values to store
533 *
534 * Differs from memset() in that it fills with a uint16_t instead
535 * of a byte. Remember that @count is the number of uint16_ts to
536 * store, not the number of bytes.
537 */
538void *memset16(uint16_t *s, uint16_t v, size_t count)
539{
540 uint16_t *xs = s;
541
542 while (count--)
543 *xs++ = v;
544 return s;
545}
546EXPORT_SYMBOL(memset16);
547#endif
548
549#ifndef __HAVE_ARCH_MEMSET32
550/**
551 * memset32() - Fill a memory area with a uint32_t
552 * @s: Pointer to the start of the area.
553 * @v: The value to fill the area with
554 * @count: The number of values to store
555 *
556 * Differs from memset() in that it fills with a uint32_t instead
557 * of a byte. Remember that @count is the number of uint32_ts to
558 * store, not the number of bytes.
559 */
560void *memset32(uint32_t *s, uint32_t v, size_t count)
561{
562 uint32_t *xs = s;
563
564 while (count--)
565 *xs++ = v;
566 return s;
567}
568EXPORT_SYMBOL(memset32);
569#endif
570
571#ifndef __HAVE_ARCH_MEMSET64
572/**
573 * memset64() - Fill a memory area with a uint64_t
574 * @s: Pointer to the start of the area.
575 * @v: The value to fill the area with
576 * @count: The number of values to store
577 *
578 * Differs from memset() in that it fills with a uint64_t instead
579 * of a byte. Remember that @count is the number of uint64_ts to
580 * store, not the number of bytes.
581 */
582void *memset64(uint64_t *s, uint64_t v, size_t count)
583{
584 uint64_t *xs = s;
585
586 while (count--)
587 *xs++ = v;
588 return s;
589}
590EXPORT_SYMBOL(memset64);
591#endif
592
593#ifndef __HAVE_ARCH_MEMCPY
594/**
595 * memcpy - Copy one area of memory to another
596 * @dest: Where to copy to
597 * @src: Where to copy from
598 * @count: The size of the area.
599 *
600 * You should not use this function to access IO space, use memcpy_toio()
601 * or memcpy_fromio() instead.
602 */
603void *memcpy(void *dest, const void *src, size_t count)
604{
605 char *tmp = dest;
606 const char *s = src;
607
608 while (count--)
609 *tmp++ = *s++;
610 return dest;
611}
612EXPORT_SYMBOL(memcpy);
613#endif
614
615#ifndef __HAVE_ARCH_MEMMOVE
616/**
617 * memmove - Copy one area of memory to another
618 * @dest: Where to copy to
619 * @src: Where to copy from
620 * @count: The size of the area.
621 *
622 * Unlike memcpy(), memmove() copes with overlapping areas.
623 */
624void *memmove(void *dest, const void *src, size_t count)
625{
626 char *tmp;
627 const char *s;
628
629 if (dest <= src) {
630 tmp = dest;
631 s = src;
632 while (count--)
633 *tmp++ = *s++;
634 } else {
635 tmp = dest;
636 tmp += count;
637 s = src;
638 s += count;
639 while (count--)
640 *--tmp = *--s;
641 }
642 return dest;
643}
644EXPORT_SYMBOL(memmove);
645#endif
646
647#ifndef __HAVE_ARCH_MEMCMP
648/**
649 * memcmp - Compare two areas of memory
650 * @cs: One area of memory
651 * @ct: Another area of memory
652 * @count: The size of the area.
653 */
654#undef memcmp
655__visible int memcmp(const void *cs, const void *ct, size_t count)
656{
657 const unsigned char *su1, *su2;
658 int res = 0;
659
660#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
661 if (count >= sizeof(unsigned long)) {
662 const unsigned long *u1 = cs;
663 const unsigned long *u2 = ct;
664 do {
665 if (get_unaligned(u1) != get_unaligned(u2))
666 break;
667 u1++;
668 u2++;
669 count -= sizeof(unsigned long);
670 } while (count >= sizeof(unsigned long));
671 cs = u1;
672 ct = u2;
673 }
674#endif
675 for (su1 = cs, su2 = ct; 0 < count; ++su1, ++su2, count--)
676 if ((res = *su1 - *su2) != 0)
677 break;
678 return res;
679}
680EXPORT_SYMBOL(memcmp);
681#endif
682
683#ifndef __HAVE_ARCH_BCMP
684/**
685 * bcmp - returns 0 if and only if the buffers have identical contents.
686 * @a: pointer to first buffer.
687 * @b: pointer to second buffer.
688 * @len: size of buffers.
689 *
690 * The sign or magnitude of a non-zero return value has no particular
691 * meaning, and architectures may implement their own more efficient bcmp(). So
692 * while this particular implementation is a simple (tail) call to memcmp, do
693 * not rely on anything but whether the return value is zero or non-zero.
694 */
695int bcmp(const void *a, const void *b, size_t len)
696{
697 return memcmp(a, b, len);
698}
699EXPORT_SYMBOL(bcmp);
700#endif
701
702#ifndef __HAVE_ARCH_MEMSCAN
703/**
704 * memscan - Find a character in an area of memory.
705 * @addr: The memory area
706 * @c: The byte to search for
707 * @size: The size of the area.
708 *
709 * returns the address of the first occurrence of @c, or 1 byte past
710 * the area if @c is not found
711 */
712void *memscan(void *addr, int c, size_t size)
713{
714 unsigned char *p = addr;
715
716 while (size) {
717 if (*p == (unsigned char)c)
718 return (void *)p;
719 p++;
720 size--;
721 }
722 return (void *)p;
723}
724EXPORT_SYMBOL(memscan);
725#endif
726
727#ifndef __HAVE_ARCH_STRSTR
728/**
729 * strstr - Find the first substring in a %NUL terminated string
730 * @s1: The string to be searched
731 * @s2: The string to search for
732 */
733char *strstr(const char *s1, const char *s2)
734{
735 size_t l1, l2;
736
737 l2 = strlen(s2);
738 if (!l2)
739 return (char *)s1;
740 l1 = strlen(s1);
741 while (l1 >= l2) {
742 l1--;
743 if (!memcmp(s1, s2, l2))
744 return (char *)s1;
745 s1++;
746 }
747 return NULL;
748}
749EXPORT_SYMBOL(strstr);
750#endif
751
752#ifndef __HAVE_ARCH_STRNSTR
753/**
754 * strnstr - Find the first substring in a length-limited string
755 * @s1: The string to be searched
756 * @s2: The string to search for
757 * @len: the maximum number of characters to search
758 */
759char *strnstr(const char *s1, const char *s2, size_t len)
760{
761 size_t l2;
762
763 l2 = strlen(s2);
764 if (!l2)
765 return (char *)s1;
766 while (len >= l2) {
767 len--;
768 if (!memcmp(s1, s2, l2))
769 return (char *)s1;
770 s1++;
771 }
772 return NULL;
773}
774EXPORT_SYMBOL(strnstr);
775#endif
776
777#ifndef __HAVE_ARCH_MEMCHR
778/**
779 * memchr - Find a character in an area of memory.
780 * @s: The memory area
781 * @c: The byte to search for
782 * @n: The size of the area.
783 *
784 * returns the address of the first occurrence of @c, or %NULL
785 * if @c is not found
786 */
787void *memchr(const void *s, int c, size_t n)
788{
789 const unsigned char *p = s;
790 while (n-- != 0) {
791 if ((unsigned char)c == *p++) {
792 return (void *)(p - 1);
793 }
794 }
795 return NULL;
796}
797EXPORT_SYMBOL(memchr);
798#endif
799
800static void *check_bytes8(const u8 *start, u8 value, unsigned int bytes)
801{
802 while (bytes) {
803 if (*start != value)
804 return (void *)start;
805 start++;
806 bytes--;
807 }
808 return NULL;
809}
810
811/**
812 * memchr_inv - Find an unmatching character in an area of memory.
813 * @start: The memory area
814 * @c: Find a character other than c
815 * @bytes: The size of the area.
816 *
817 * returns the address of the first character other than @c, or %NULL
818 * if the whole buffer contains just @c.
819 */
820void *memchr_inv(const void *start, int c, size_t bytes)
821{
822 u8 value = c;
823 u64 value64;
824 unsigned int words, prefix;
825
826 if (bytes <= 16)
827 return check_bytes8(start, value, bytes);
828
829 value64 = value;
830#if defined(CONFIG_ARCH_HAS_FAST_MULTIPLIER) && BITS_PER_LONG == 64
831 value64 *= 0x0101010101010101ULL;
832#elif defined(CONFIG_ARCH_HAS_FAST_MULTIPLIER)
833 value64 *= 0x01010101;
834 value64 |= value64 << 32;
835#else
836 value64 |= value64 << 8;
837 value64 |= value64 << 16;
838 value64 |= value64 << 32;
839#endif
840
841 prefix = (unsigned long)start % 8;
842 if (prefix) {
843 u8 *r;
844
845 prefix = 8 - prefix;
846 r = check_bytes8(start, value, prefix);
847 if (r)
848 return r;
849 start += prefix;
850 bytes -= prefix;
851 }
852
853 words = bytes / 8;
854
855 while (words) {
856 if (*(u64 *)start != value64)
857 return check_bytes8(start, value, 8);
858 start += 8;
859 words--;
860 }
861
862 return check_bytes8(start, value, bytes % 8);
863}
864EXPORT_SYMBOL(memchr_inv);