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5916700c KS |
1 | /* |
2 | * Copyright 2013 Tilera Corporation. All Rights Reserved. | |
3 | * | |
4 | * This program is free software; you can redistribute it and/or | |
5 | * modify it under the terms of the GNU General Public License | |
6 | * as published by the Free Software Foundation, version 2. | |
7 | * | |
8 | * This program is distributed in the hope that it will be useful, but | |
9 | * WITHOUT ANY WARRANTY; without even the implied warranty of | |
10 | * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or | |
11 | * NON INFRINGEMENT. See the GNU General Public License for | |
12 | * more details. | |
13 | */ | |
14 | ||
15 | #include <linux/types.h> | |
16 | #include <linux/string.h> | |
17 | #include <linux/module.h> | |
18 | ||
19 | size_t strnlen(const char *s, size_t count) | |
20 | { | |
21 | /* Get an aligned pointer. */ | |
22 | const uintptr_t s_int = (uintptr_t) s; | |
23 | const uint32_t *p = (const uint32_t *)(s_int & -4); | |
24 | size_t bytes_read = sizeof(*p) - (s_int & (sizeof(*p) - 1)); | |
25 | size_t len; | |
26 | uint32_t v, bits; | |
27 | ||
28 | /* Avoid page fault risk by not reading any bytes when count is 0. */ | |
29 | if (count == 0) | |
30 | return 0; | |
31 | ||
32 | /* Read first word, but force bytes before the string to be nonzero. */ | |
33 | v = *p | ((1 << ((s_int << 3) & 31)) - 1); | |
34 | ||
35 | while ((bits = __insn_seqb(v, 0)) == 0) { | |
36 | if (bytes_read >= count) { | |
37 | /* Read COUNT bytes and didn't find the terminator. */ | |
38 | return count; | |
39 | } | |
40 | v = *++p; | |
41 | bytes_read += sizeof(v); | |
42 | } | |
43 | ||
44 | len = ((const char *) p) + (__insn_ctz(bits) >> 3) - s; | |
45 | return (len < count ? len : count); | |
46 | } | |
47 | EXPORT_SYMBOL(strnlen); |