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/* uaccess.c: userspace access functions
*
* Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*/
#include <linux/mm.h>
#include <asm/uaccess.h>
/*****************************************************************************/
/*
* copy a null terminated string from userspace
*/
long strncpy_from_user(char *dst, const char *src, long count)
{
unsigned long max;
char *p, ch;
long err = -EFAULT;
if (count < 0)
BUG();
p = dst;
#ifndef CONFIG_MMU
if ((unsigned long) src < memory_start)
goto error;
#endif
if ((unsigned long) src >= get_addr_limit())
goto error;
max = get_addr_limit() - (unsigned long) src;
if ((unsigned long) count > max) {
memset(dst + max, 0, count - max);
count = max;
}
err = 0;
for (; count > 0; count--, p++, src++) {
__get_user_asm(err, ch, src, "ub", "=r");
if (err < 0)
goto error;
if (!ch)
break;
*p = ch;
}
err = p - dst; /* return length excluding NUL */
error:
if (count > 0)
memset(p, 0, count); /* clear remainder of buffer [security] */
return err;
} /* end strncpy_from_user() */
/*****************************************************************************/
/*
* Return the size of a string (including the ending 0)
*
* Return 0 on exception, a value greater than N if too long
*/
long strnlen_user(const char *src, long count)
{
const char *p;
long err = 0;
char ch;
if (count < 0)
BUG();
#ifndef CONFIG_MMU
if ((unsigned long) src < memory_start)
return 0;
#endif
if ((unsigned long) src >= get_addr_limit())
return 0;
for (p = src; count > 0; count--, p++) {
__get_user_asm(err, ch, p, "ub", "=r");
if (err < 0)
return 0;
if (!ch)
break;
}
return p - src + 1; /* return length including NUL */
} /* end strnlen_user() */
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