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867e359b CM |
1 | /* |
2 | * Copyright 2010 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 strlen(const char *s) | |
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 | ||
25 | /* Read the first word, but force bytes before the string to be nonzero. | |
26 | * This expression works because we know shift counts are taken mod 32. | |
27 | */ | |
28 | uint32_t v = *p | ((1 << (s_int << 3)) - 1); | |
29 | ||
30 | uint32_t bits; | |
31 | while ((bits = __insn_seqb(v, 0)) == 0) | |
32 | v = *++p; | |
33 | ||
34 | return ((const char *)p) + (__insn_ctz(bits) >> 3) - s; | |
35 | } | |
36 | EXPORT_SYMBOL(strlen); |