blob: 2e4e4b02c37a62cd593f3a59645898d946d95ffb [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
Linus Torvalds92ae03f2012-04-06 14:32:32 -070047/*
48 * Do a strncpy, return length of string without final '\0'.
49 * 'count' is the user-supplied count (return 'count' if we
50 * hit it), 'max' is the address space maximum (and we return
51 * -EFAULT if we hit it).
52 */
Linus Torvalds12e993b2012-04-15 17:23:00 -070053static inline long do_strncpy_from_user(char *dst, const char __user *src, long count, unsigned long max)
Linus Torvalds92ae03f2012-04-06 14:32:32 -070054{
55 long res = 0;
56
57 /*
58 * Truncate 'max' to the user-specified limit, so that
59 * we only have one limit we need to check in the loop
60 */
61 if (max > count)
62 max = count;
63
64 while (max >= sizeof(unsigned long)) {
Linus Torvalds07497082012-04-28 14:27:38 -070065 unsigned long c, mask;
Linus Torvalds92ae03f2012-04-06 14:32:32 -070066
67 /* Fall back to byte-at-a-time if we get a page fault */
68 if (unlikely(__get_user(c,(unsigned long __user *)(src+res))))
69 break;
Linus Torvalds07497082012-04-28 14:27:38 -070070 mask = has_zero(c);
71 if (mask) {
72 mask = (mask - 1) & ~mask;
73 mask >>= 7;
74 *(unsigned long *)(dst+res) = c & mask;
75 return res + count_masked_bytes(mask);
76 }
Linus Torvalds92ae03f2012-04-06 14:32:32 -070077 *(unsigned long *)(dst+res) = c;
Linus Torvalds92ae03f2012-04-06 14:32:32 -070078 res += sizeof(unsigned long);
79 max -= sizeof(unsigned long);
80 }
81
82 while (max) {
83 char c;
84
85 if (unlikely(__get_user(c,src+res)))
86 return -EFAULT;
87 dst[res] = c;
88 if (!c)
89 return res;
90 res++;
91 max--;
92 }
93
94 /*
95 * Uhhuh. We hit 'max'. But was that the user-specified maximum
96 * too? If so, that's ok - we got as much as the user asked for.
97 */
98 if (res >= count)
Linus Torvalds12e993b2012-04-15 17:23:00 -070099 return res;
Linus Torvalds92ae03f2012-04-06 14:32:32 -0700100
101 /*
102 * Nope: we hit the address space limit, and we still had more
103 * characters the caller would have wanted. That's an EFAULT.
104 */
105 return -EFAULT;
106}
107
108/**
109 * strncpy_from_user: - Copy a NUL terminated string from userspace.
110 * @dst: Destination address, in kernel space. This buffer must be at
111 * least @count bytes long.
112 * @src: Source address, in user space.
113 * @count: Maximum number of bytes to copy, including the trailing NUL.
114 *
115 * Copies a NUL-terminated string from userspace to kernel space.
116 *
117 * On success, returns the length of the string (not including the trailing
118 * NUL).
119 *
120 * If access to userspace fails, returns -EFAULT (some data may have been
121 * copied).
122 *
123 * If @count is smaller than the length of the string, copies @count bytes
124 * and returns @count.
125 */
126long
127strncpy_from_user(char *dst, const char __user *src, long count)
128{
129 unsigned long max_addr, src_addr;
130
131 if (unlikely(count <= 0))
132 return 0;
133
134 max_addr = current_thread_info()->addr_limit.seg;
135 src_addr = (unsigned long)src;
136 if (likely(src_addr < max_addr)) {
137 unsigned long max = max_addr - src_addr;
138 return do_strncpy_from_user(dst, src, count, max);
139 }
140 return -EFAULT;
141}
142EXPORT_SYMBOL(strncpy_from_user);