1/* uaccess.c: userspace access functions
2 *
3 * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License
8 * as published by the Free Software Foundation; either version
9 * 2 of the License, or (at your option) any later version.
10 */
11
12#include <linux/mm.h>
13#include <linux/module.h>
14#include <asm/uaccess.h>
15
16/*****************************************************************************/
17/*
18 * copy a null terminated string from userspace
19 */
20long strncpy_from_user(char *dst, const char __user *src, long count)
21{
22	unsigned long max;
23	char *p, ch;
24	long err = -EFAULT;
25
26	BUG_ON(count < 0);
27
28	p = dst;
29
30#ifndef CONFIG_MMU
31	if ((unsigned long) src < memory_start)
32		goto error;
33#endif
34
35	if ((unsigned long) src >= get_addr_limit())
36		goto error;
37
38	max = get_addr_limit() - (unsigned long) src;
39	if ((unsigned long) count > max) {
40		memset(dst + max, 0, count - max);
41		count = max;
42	}
43
44	err = 0;
45	for (; count > 0; count--, p++, src++) {
46		__get_user_asm(err, ch, src, "ub", "=r");
47		if (err < 0)
48			goto error;
49		if (!ch)
50			break;
51		*p = ch;
52	}
53
54	err = p - dst; /* return length excluding NUL */
55
56 error:
57	if (count > 0)
58		memset(p, 0, count); /* clear remainder of buffer [security] */
59
60	return err;
61
62} /* end strncpy_from_user() */
63
64EXPORT_SYMBOL(strncpy_from_user);
65
66/*****************************************************************************/
67/*
68 * Return the size of a string (including the ending 0)
69 *
70 * Return 0 on exception, a value greater than N if too long
71 */
72long strnlen_user(const char __user *src, long count)
73{
74	const char __user *p;
75	long err = 0;
76	char ch;
77
78	BUG_ON(count < 0);
79
80#ifndef CONFIG_MMU
81	if ((unsigned long) src < memory_start)
82		return 0;
83#endif
84
85	if ((unsigned long) src >= get_addr_limit())
86		return 0;
87
88	for (p = src; count > 0; count--, p++) {
89		__get_user_asm(err, ch, p, "ub", "=r");
90		if (err < 0)
91			return 0;
92		if (!ch)
93			break;
94	}
95
96	return p - src + 1; /* return length including NUL */
97
98} /* end strnlen_user() */
99
100EXPORT_SYMBOL(strnlen_user);
101