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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/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 <linux/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
107#ifdef __BIG_ENDIAN
108# define ALLBUTLAST_BYTE_MASK (~255ul)
109#else
110# define ALLBUTLAST_BYTE_MASK (~0ul >> 8)
111#endif
112
113ssize_t sized_strscpy(char *dest, const char *src, size_t count)
114{
115 const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
116 size_t max = count;
117 long res = 0;
118
119 if (count == 0 || WARN_ON_ONCE(count > INT_MAX))
120 return -E2BIG;
121
122#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
123 /*
124 * If src is unaligned, don't cross a page boundary,
125 * since we don't know if the next page is mapped.
126 */
127 if ((long)src & (sizeof(long) - 1)) {
128 size_t limit = PAGE_SIZE - ((long)src & (PAGE_SIZE - 1));
129 if (limit < max)
130 max = limit;
131 }
132#else
133 /* If src or dest is unaligned, don't do word-at-a-time. */
134 if (((long) dest | (long) src) & (sizeof(long) - 1))
135 max = 0;
136#endif
137
138 /*
139 * read_word_at_a_time() below may read uninitialized bytes after the
140 * trailing zero and use them in comparisons. Disable this optimization
141 * under KMSAN to prevent false positive reports.
142 */
143 if (IS_ENABLED(CONFIG_KMSAN))
144 max = 0;
145
146 while (max >= sizeof(unsigned long)) {
147 unsigned long c, data;
148
149 c = read_word_at_a_time(src+res);
150 if (has_zero(c, &data, &constants)) {
151 data = prep_zero_mask(c, data, &constants);
152 data = create_zero_mask(data);
153 *(unsigned long *)(dest+res) = c & zero_bytemask(data);
154 return res + find_zero(data);
155 }
156 count -= sizeof(unsigned long);
157 if (unlikely(!count)) {
158 c &= ALLBUTLAST_BYTE_MASK;
159 *(unsigned long *)(dest+res) = c;
160 return -E2BIG;
161 }
162 *(unsigned long *)(dest+res) = c;
163 res += sizeof(unsigned long);
164 max -= sizeof(unsigned long);
165 }
166
167 while (count > 1) {
168 char c;
169
170 c = src[res];
171 dest[res] = c;
172 if (!c)
173 return res;
174 res++;
175 count--;
176 }
177
178 /* Force NUL-termination. */
179 dest[res] = '\0';
180
181 /* Return E2BIG if the source didn't stop */
182 return src[res] ? -E2BIG : res;
183}
184EXPORT_SYMBOL(sized_strscpy);
185
186/**
187 * stpcpy - copy a string from src to dest returning a pointer to the new end
188 * of dest, including src's %NUL-terminator. May overrun dest.
189 * @dest: pointer to end of string being copied into. Must be large enough
190 * to receive copy.
191 * @src: pointer to the beginning of string being copied from. Must not overlap
192 * dest.
193 *
194 * stpcpy differs from strcpy in a key way: the return value is a pointer
195 * to the new %NUL-terminating character in @dest. (For strcpy, the return
196 * value is a pointer to the start of @dest). This interface is considered
197 * unsafe as it doesn't perform bounds checking of the inputs. As such it's
198 * not recommended for usage. Instead, its definition is provided in case
199 * the compiler lowers other libcalls to stpcpy.
200 */
201char *stpcpy(char *__restrict__ dest, const char *__restrict__ src);
202char *stpcpy(char *__restrict__ dest, const char *__restrict__ src)
203{
204 while ((*dest++ = *src++) != '\0')
205 /* nothing */;
206 return --dest;
207}
208EXPORT_SYMBOL(stpcpy);
209
210#ifndef __HAVE_ARCH_STRCAT
211char *strcat(char *dest, const char *src)
212{
213 char *tmp = dest;
214
215 while (*dest)
216 dest++;
217 while ((*dest++ = *src++) != '\0')
218 ;
219 return tmp;
220}
221EXPORT_SYMBOL(strcat);
222#endif
223
224#ifndef __HAVE_ARCH_STRNCAT
225char *strncat(char *dest, const char *src, size_t count)
226{
227 char *tmp = dest;
228
229 if (count) {
230 while (*dest)
231 dest++;
232 while ((*dest++ = *src++) != 0) {
233 if (--count == 0) {
234 *dest = '\0';
235 break;
236 }
237 }
238 }
239 return tmp;
240}
241EXPORT_SYMBOL(strncat);
242#endif
243
244#ifndef __HAVE_ARCH_STRLCAT
245size_t strlcat(char *dest, const char *src, size_t count)
246{
247 size_t dsize = strlen(dest);
248 size_t len = strlen(src);
249 size_t res = dsize + len;
250
251 /* This would be a bug */
252 BUG_ON(dsize >= count);
253
254 dest += dsize;
255 count -= dsize;
256 if (len >= count)
257 len = count-1;
258 __builtin_memcpy(dest, src, len);
259 dest[len] = 0;
260 return res;
261}
262EXPORT_SYMBOL(strlcat);
263#endif
264
265#ifndef __HAVE_ARCH_STRCMP
266/**
267 * strcmp - Compare two strings
268 * @cs: One string
269 * @ct: Another string
270 */
271int strcmp(const char *cs, const char *ct)
272{
273 unsigned char c1, c2;
274
275 while (1) {
276 c1 = *cs++;
277 c2 = *ct++;
278 if (c1 != c2)
279 return c1 < c2 ? -1 : 1;
280 if (!c1)
281 break;
282 }
283 return 0;
284}
285EXPORT_SYMBOL(strcmp);
286#endif
287
288#ifndef __HAVE_ARCH_STRNCMP
289/**
290 * strncmp - Compare two length-limited strings
291 * @cs: One string
292 * @ct: Another string
293 * @count: The maximum number of bytes to compare
294 */
295int strncmp(const char *cs, const char *ct, size_t count)
296{
297 unsigned char c1, c2;
298
299 while (count) {
300 c1 = *cs++;
301 c2 = *ct++;
302 if (c1 != c2)
303 return c1 < c2 ? -1 : 1;
304 if (!c1)
305 break;
306 count--;
307 }
308 return 0;
309}
310EXPORT_SYMBOL(strncmp);
311#endif
312
313#ifndef __HAVE_ARCH_STRCHR
314/**
315 * strchr - Find the first occurrence of a character in a string
316 * @s: The string to be searched
317 * @c: The character to search for
318 *
319 * Note that the %NUL-terminator is considered part of the string, and can
320 * be searched for.
321 */
322char *strchr(const char *s, int c)
323{
324 for (; *s != (char)c; ++s)
325 if (*s == '\0')
326 return NULL;
327 return (char *)s;
328}
329EXPORT_SYMBOL(strchr);
330#endif
331
332#ifndef __HAVE_ARCH_STRCHRNUL
333/**
334 * strchrnul - Find and return a character in a string, or end of string
335 * @s: The string to be searched
336 * @c: The character to search for
337 *
338 * Returns pointer to first occurrence of 'c' in s. If c is not found, then
339 * return a pointer to the null byte at the end of s.
340 */
341char *strchrnul(const char *s, int c)
342{
343 while (*s && *s != (char)c)
344 s++;
345 return (char *)s;
346}
347EXPORT_SYMBOL(strchrnul);
348#endif
349
350/**
351 * strnchrnul - Find and return a character in a length limited string,
352 * or end of string
353 * @s: The string to be searched
354 * @count: The number of characters to be searched
355 * @c: The character to search for
356 *
357 * Returns pointer to the first occurrence of 'c' in s. If c is not found,
358 * then return a pointer to the last character of the string.
359 */
360char *strnchrnul(const char *s, size_t count, int c)
361{
362 while (count-- && *s && *s != (char)c)
363 s++;
364 return (char *)s;
365}
366
367#ifndef __HAVE_ARCH_STRRCHR
368/**
369 * strrchr - Find the last occurrence of a character in a string
370 * @s: The string to be searched
371 * @c: The character to search for
372 */
373char *strrchr(const char *s, int c)
374{
375 const char *last = NULL;
376 do {
377 if (*s == (char)c)
378 last = s;
379 } while (*s++);
380 return (char *)last;
381}
382EXPORT_SYMBOL(strrchr);
383#endif
384
385#ifndef __HAVE_ARCH_STRNCHR
386/**
387 * strnchr - Find a character in a length limited string
388 * @s: The string to be searched
389 * @count: The number of characters to be searched
390 * @c: The character to search for
391 *
392 * Note that the %NUL-terminator is considered part of the string, and can
393 * be searched for.
394 */
395char *strnchr(const char *s, size_t count, int c)
396{
397 while (count--) {
398 if (*s == (char)c)
399 return (char *)s;
400 if (*s++ == '\0')
401 break;
402 }
403 return NULL;
404}
405EXPORT_SYMBOL(strnchr);
406#endif
407
408#ifndef __HAVE_ARCH_STRLEN
409size_t strlen(const char *s)
410{
411 const char *sc;
412
413 for (sc = s; *sc != '\0'; ++sc)
414 /* nothing */;
415 return sc - s;
416}
417EXPORT_SYMBOL(strlen);
418#endif
419
420#ifndef __HAVE_ARCH_STRNLEN
421size_t strnlen(const char *s, size_t count)
422{
423 const char *sc;
424
425 for (sc = s; count-- && *sc != '\0'; ++sc)
426 /* nothing */;
427 return sc - s;
428}
429EXPORT_SYMBOL(strnlen);
430#endif
431
432#ifndef __HAVE_ARCH_STRSPN
433/**
434 * strspn - Calculate the length of the initial substring of @s which only contain letters in @accept
435 * @s: The string to be searched
436 * @accept: The string to search for
437 */
438size_t strspn(const char *s, const char *accept)
439{
440 const char *p;
441
442 for (p = s; *p != '\0'; ++p) {
443 if (!strchr(accept, *p))
444 break;
445 }
446 return p - s;
447}
448EXPORT_SYMBOL(strspn);
449#endif
450
451#ifndef __HAVE_ARCH_STRCSPN
452/**
453 * strcspn - Calculate the length of the initial substring of @s which does not contain letters in @reject
454 * @s: The string to be searched
455 * @reject: The string to avoid
456 */
457size_t strcspn(const char *s, const char *reject)
458{
459 const char *p;
460
461 for (p = s; *p != '\0'; ++p) {
462 if (strchr(reject, *p))
463 break;
464 }
465 return p - s;
466}
467EXPORT_SYMBOL(strcspn);
468#endif
469
470#ifndef __HAVE_ARCH_STRPBRK
471/**
472 * strpbrk - Find the first occurrence of a set of characters
473 * @cs: The string to be searched
474 * @ct: The characters to search for
475 */
476char *strpbrk(const char *cs, const char *ct)
477{
478 const char *sc;
479
480 for (sc = cs; *sc != '\0'; ++sc) {
481 if (strchr(ct, *sc))
482 return (char *)sc;
483 }
484 return NULL;
485}
486EXPORT_SYMBOL(strpbrk);
487#endif
488
489#ifndef __HAVE_ARCH_STRSEP
490/**
491 * strsep - Split a string into tokens
492 * @s: The string to be searched
493 * @ct: The characters to search for
494 *
495 * strsep() updates @s to point after the token, ready for the next call.
496 *
497 * It returns empty tokens, too, behaving exactly like the libc function
498 * of that name. In fact, it was stolen from glibc2 and de-fancy-fied.
499 * Same semantics, slimmer shape. ;)
500 */
501char *strsep(char **s, const char *ct)
502{
503 char *sbegin = *s;
504 char *end;
505
506 if (sbegin == NULL)
507 return NULL;
508
509 end = strpbrk(sbegin, ct);
510 if (end)
511 *end++ = '\0';
512 *s = end;
513 return sbegin;
514}
515EXPORT_SYMBOL(strsep);
516#endif
517
518#ifndef __HAVE_ARCH_MEMSET
519/**
520 * memset - Fill a region of memory with the given value
521 * @s: Pointer to the start of the area.
522 * @c: The byte to fill the area with
523 * @count: The size of the area.
524 *
525 * Do not use memset() to access IO space, use memset_io() instead.
526 */
527void *memset(void *s, int c, size_t count)
528{
529 char *xs = s;
530
531 while (count--)
532 *xs++ = c;
533 return s;
534}
535EXPORT_SYMBOL(memset);
536#endif
537
538#ifndef __HAVE_ARCH_MEMSET16
539/**
540 * memset16() - Fill a memory area with a uint16_t
541 * @s: Pointer to the start of the area.
542 * @v: The value to fill the area with
543 * @count: The number of values to store
544 *
545 * Differs from memset() in that it fills with a uint16_t instead
546 * of a byte. Remember that @count is the number of uint16_ts to
547 * store, not the number of bytes.
548 */
549void *memset16(uint16_t *s, uint16_t v, size_t count)
550{
551 uint16_t *xs = s;
552
553 while (count--)
554 *xs++ = v;
555 return s;
556}
557EXPORT_SYMBOL(memset16);
558#endif
559
560#ifndef __HAVE_ARCH_MEMSET32
561/**
562 * memset32() - Fill a memory area with a uint32_t
563 * @s: Pointer to the start of the area.
564 * @v: The value to fill the area with
565 * @count: The number of values to store
566 *
567 * Differs from memset() in that it fills with a uint32_t instead
568 * of a byte. Remember that @count is the number of uint32_ts to
569 * store, not the number of bytes.
570 */
571void *memset32(uint32_t *s, uint32_t v, size_t count)
572{
573 uint32_t *xs = s;
574
575 while (count--)
576 *xs++ = v;
577 return s;
578}
579EXPORT_SYMBOL(memset32);
580#endif
581
582#ifndef __HAVE_ARCH_MEMSET64
583/**
584 * memset64() - Fill a memory area with a uint64_t
585 * @s: Pointer to the start of the area.
586 * @v: The value to fill the area with
587 * @count: The number of values to store
588 *
589 * Differs from memset() in that it fills with a uint64_t instead
590 * of a byte. Remember that @count is the number of uint64_ts to
591 * store, not the number of bytes.
592 */
593void *memset64(uint64_t *s, uint64_t v, size_t count)
594{
595 uint64_t *xs = s;
596
597 while (count--)
598 *xs++ = v;
599 return s;
600}
601EXPORT_SYMBOL(memset64);
602#endif
603
604#ifndef __HAVE_ARCH_MEMCPY
605/**
606 * memcpy - Copy one area of memory to another
607 * @dest: Where to copy to
608 * @src: Where to copy from
609 * @count: The size of the area.
610 *
611 * You should not use this function to access IO space, use memcpy_toio()
612 * or memcpy_fromio() instead.
613 */
614void *memcpy(void *dest, const void *src, size_t count)
615{
616 char *tmp = dest;
617 const char *s = src;
618
619 while (count--)
620 *tmp++ = *s++;
621 return dest;
622}
623EXPORT_SYMBOL(memcpy);
624#endif
625
626#ifndef __HAVE_ARCH_MEMMOVE
627/**
628 * memmove - Copy one area of memory to another
629 * @dest: Where to copy to
630 * @src: Where to copy from
631 * @count: The size of the area.
632 *
633 * Unlike memcpy(), memmove() copes with overlapping areas.
634 */
635void *memmove(void *dest, const void *src, size_t count)
636{
637 char *tmp;
638 const char *s;
639
640 if (dest <= src) {
641 tmp = dest;
642 s = src;
643 while (count--)
644 *tmp++ = *s++;
645 } else {
646 tmp = dest;
647 tmp += count;
648 s = src;
649 s += count;
650 while (count--)
651 *--tmp = *--s;
652 }
653 return dest;
654}
655EXPORT_SYMBOL(memmove);
656#endif
657
658#ifndef __HAVE_ARCH_MEMCMP
659/**
660 * memcmp - Compare two areas of memory
661 * @cs: One area of memory
662 * @ct: Another area of memory
663 * @count: The size of the area.
664 */
665#undef memcmp
666__visible int memcmp(const void *cs, const void *ct, size_t count)
667{
668 const unsigned char *su1, *su2;
669 int res = 0;
670
671#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
672 if (count >= sizeof(unsigned long)) {
673 const unsigned long *u1 = cs;
674 const unsigned long *u2 = ct;
675 do {
676 if (get_unaligned(u1) != get_unaligned(u2))
677 break;
678 u1++;
679 u2++;
680 count -= sizeof(unsigned long);
681 } while (count >= sizeof(unsigned long));
682 cs = u1;
683 ct = u2;
684 }
685#endif
686 for (su1 = cs, su2 = ct; 0 < count; ++su1, ++su2, count--)
687 if ((res = *su1 - *su2) != 0)
688 break;
689 return res;
690}
691EXPORT_SYMBOL(memcmp);
692#endif
693
694#ifndef __HAVE_ARCH_BCMP
695/**
696 * bcmp - returns 0 if and only if the buffers have identical contents.
697 * @a: pointer to first buffer.
698 * @b: pointer to second buffer.
699 * @len: size of buffers.
700 *
701 * The sign or magnitude of a non-zero return value has no particular
702 * meaning, and architectures may implement their own more efficient bcmp(). So
703 * while this particular implementation is a simple (tail) call to memcmp, do
704 * not rely on anything but whether the return value is zero or non-zero.
705 */
706int bcmp(const void *a, const void *b, size_t len)
707{
708 return memcmp(a, b, len);
709}
710EXPORT_SYMBOL(bcmp);
711#endif
712
713#ifndef __HAVE_ARCH_MEMSCAN
714/**
715 * memscan - Find a character in an area of memory.
716 * @addr: The memory area
717 * @c: The byte to search for
718 * @size: The size of the area.
719 *
720 * returns the address of the first occurrence of @c, or 1 byte past
721 * the area if @c is not found
722 */
723void *memscan(void *addr, int c, size_t size)
724{
725 unsigned char *p = addr;
726
727 while (size) {
728 if (*p == (unsigned char)c)
729 return (void *)p;
730 p++;
731 size--;
732 }
733 return (void *)p;
734}
735EXPORT_SYMBOL(memscan);
736#endif
737
738#ifndef __HAVE_ARCH_STRSTR
739/**
740 * strstr - Find the first substring in a %NUL terminated string
741 * @s1: The string to be searched
742 * @s2: The string to search for
743 */
744char *strstr(const char *s1, const char *s2)
745{
746 size_t l1, l2;
747
748 l2 = strlen(s2);
749 if (!l2)
750 return (char *)s1;
751 l1 = strlen(s1);
752 while (l1 >= l2) {
753 l1--;
754 if (!memcmp(s1, s2, l2))
755 return (char *)s1;
756 s1++;
757 }
758 return NULL;
759}
760EXPORT_SYMBOL(strstr);
761#endif
762
763#ifndef __HAVE_ARCH_STRNSTR
764/**
765 * strnstr - Find the first substring in a length-limited string
766 * @s1: The string to be searched
767 * @s2: The string to search for
768 * @len: the maximum number of characters to search
769 */
770char *strnstr(const char *s1, const char *s2, size_t len)
771{
772 size_t l2;
773
774 l2 = strlen(s2);
775 if (!l2)
776 return (char *)s1;
777 while (len >= l2) {
778 len--;
779 if (!memcmp(s1, s2, l2))
780 return (char *)s1;
781 s1++;
782 }
783 return NULL;
784}
785EXPORT_SYMBOL(strnstr);
786#endif
787
788#ifndef __HAVE_ARCH_MEMCHR
789/**
790 * memchr - Find a character in an area of memory.
791 * @s: The memory area
792 * @c: The byte to search for
793 * @n: The size of the area.
794 *
795 * returns the address of the first occurrence of @c, or %NULL
796 * if @c is not found
797 */
798void *memchr(const void *s, int c, size_t n)
799{
800 const unsigned char *p = s;
801 while (n-- != 0) {
802 if ((unsigned char)c == *p++) {
803 return (void *)(p - 1);
804 }
805 }
806 return NULL;
807}
808EXPORT_SYMBOL(memchr);
809#endif
810
811static void *check_bytes8(const u8 *start, u8 value, unsigned int bytes)
812{
813 while (bytes) {
814 if (*start != value)
815 return (void *)start;
816 start++;
817 bytes--;
818 }
819 return NULL;
820}
821
822/**
823 * memchr_inv - Find an unmatching character in an area of memory.
824 * @start: The memory area
825 * @c: Find a character other than c
826 * @bytes: The size of the area.
827 *
828 * returns the address of the first character other than @c, or %NULL
829 * if the whole buffer contains just @c.
830 */
831void *memchr_inv(const void *start, int c, size_t bytes)
832{
833 u8 value = c;
834 u64 value64;
835 unsigned int words, prefix;
836
837 if (bytes <= 16)
838 return check_bytes8(start, value, bytes);
839
840 value64 = value;
841#if defined(CONFIG_ARCH_HAS_FAST_MULTIPLIER) && BITS_PER_LONG == 64
842 value64 *= 0x0101010101010101ULL;
843#elif defined(CONFIG_ARCH_HAS_FAST_MULTIPLIER)
844 value64 *= 0x01010101;
845 value64 |= value64 << 32;
846#else
847 value64 |= value64 << 8;
848 value64 |= value64 << 16;
849 value64 |= value64 << 32;
850#endif
851
852 prefix = (unsigned long)start % 8;
853 if (prefix) {
854 u8 *r;
855
856 prefix = 8 - prefix;
857 r = check_bytes8(start, value, prefix);
858 if (r)
859 return r;
860 start += prefix;
861 bytes -= prefix;
862 }
863
864 words = bytes / 8;
865
866 while (words) {
867 if (*(u64 *)start != value64)
868 return check_bytes8(start, value, 8);
869 start += 8;
870 words--;
871 }
872
873 return check_bytes8(start, value, bytes % 8);
874}
875EXPORT_SYMBOL(memchr_inv);