blob: d6ae30bbd7bb833356049d89bdf8d0e5ae004b0c [file] [log] [blame]
Robert Richter1ac2e6c2011-06-07 11:49:55 +02001/*
2 * User address space access functions.
3 *
4 * For licencing details see kernel-base/COPYING
5 */
6
7#include <linux/highmem.h>
8#include <linux/module.h>
9
Linus Torvalds92ae03f2012-04-06 14:32:32 -070010#include <asm/word-at-a-time.h>
11
Robert Richter1ac2e6c2011-06-07 11:49:55 +020012/*
13 * best effort, GUP based copy_from_user() that is NMI-safe
14 */
15unsigned long
16copy_from_user_nmi(void *to, const void __user *from, unsigned long n)
17{
18 unsigned long offset, addr = (unsigned long)from;
19 unsigned long size, len = 0;
20 struct page *page;
21 void *map;
22 int ret;
23
24 do {
25 ret = __get_user_pages_fast(addr, 1, 0, &page);
26 if (!ret)
27 break;
28
29 offset = addr & (PAGE_SIZE - 1);
30 size = min(PAGE_SIZE - offset, n - len);
31
32 map = kmap_atomic(page);
33 memcpy(to, map+offset, size);
34 kunmap_atomic(map);
35 put_page(page);
36
37 len += size;
38 to += size;
39 addr += size;
40
41 } while (len < n);
42
43 return len;
44}
45EXPORT_SYMBOL_GPL(copy_from_user_nmi);
Linus Torvalds92ae03f2012-04-06 14:32:32 -070046
47static inline unsigned long count_bytes(unsigned long mask)
48{
49 mask = (mask - 1) & ~mask;
50 mask >>= 7;
51 return count_masked_bytes(mask);
52}
53
54/*
55 * Do a strncpy, return length of string without final '\0'.
56 * 'count' is the user-supplied count (return 'count' if we
57 * hit it), 'max' is the address space maximum (and we return
58 * -EFAULT if we hit it).
59 */
Linus Torvalds12e993b2012-04-15 17:23:00 -070060static inline long do_strncpy_from_user(char *dst, const char __user *src, long count, unsigned long max)
Linus Torvalds92ae03f2012-04-06 14:32:32 -070061{
62 long res = 0;
63
64 /*
65 * Truncate 'max' to the user-specified limit, so that
66 * we only have one limit we need to check in the loop
67 */
68 if (max > count)
69 max = count;
70
71 while (max >= sizeof(unsigned long)) {
72 unsigned long c;
73
74 /* Fall back to byte-at-a-time if we get a page fault */
75 if (unlikely(__get_user(c,(unsigned long __user *)(src+res))))
76 break;
77 /* This can write a few bytes past the NUL character, but that's ok */
78 *(unsigned long *)(dst+res) = c;
79 c = has_zero(c);
80 if (c)
81 return res + count_bytes(c);
82 res += sizeof(unsigned long);
83 max -= sizeof(unsigned long);
84 }
85
86 while (max) {
87 char c;
88
89 if (unlikely(__get_user(c,src+res)))
90 return -EFAULT;
91 dst[res] = c;
92 if (!c)
93 return res;
94 res++;
95 max--;
96 }
97
98 /*
99 * Uhhuh. We hit 'max'. But was that the user-specified maximum
100 * too? If so, that's ok - we got as much as the user asked for.
101 */
102 if (res >= count)
Linus Torvalds12e993b2012-04-15 17:23:00 -0700103 return res;
Linus Torvalds92ae03f2012-04-06 14:32:32 -0700104
105 /*
106 * Nope: we hit the address space limit, and we still had more
107 * characters the caller would have wanted. That's an EFAULT.
108 */
109 return -EFAULT;
110}
111
112/**
113 * strncpy_from_user: - Copy a NUL terminated string from userspace.
114 * @dst: Destination address, in kernel space. This buffer must be at
115 * least @count bytes long.
116 * @src: Source address, in user space.
117 * @count: Maximum number of bytes to copy, including the trailing NUL.
118 *
119 * Copies a NUL-terminated string from userspace to kernel space.
120 *
121 * On success, returns the length of the string (not including the trailing
122 * NUL).
123 *
124 * If access to userspace fails, returns -EFAULT (some data may have been
125 * copied).
126 *
127 * If @count is smaller than the length of the string, copies @count bytes
128 * and returns @count.
129 */
130long
131strncpy_from_user(char *dst, const char __user *src, long count)
132{
133 unsigned long max_addr, src_addr;
134
135 if (unlikely(count <= 0))
136 return 0;
137
138 max_addr = current_thread_info()->addr_limit.seg;
139 src_addr = (unsigned long)src;
140 if (likely(src_addr < max_addr)) {
141 unsigned long max = max_addr - src_addr;
142 return do_strncpy_from_user(dst, src, count, max);
143 }
144 return -EFAULT;
145}
146EXPORT_SYMBOL(strncpy_from_user);