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 19size_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} 36EXPORT_SYMBOL(strlen); 37