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bf3c2d6d RV |
1 | #include <linux/compiler.h> |
2 | #include <linux/export.h> | |
2922585b DM |
3 | #include <linux/uaccess.h> |
4 | #include <linux/kernel.h> | |
5 | #include <linux/errno.h> | |
6 | ||
7 | #include <asm/byteorder.h> | |
36126f8f | 8 | #include <asm/word-at-a-time.h> |
2922585b DM |
9 | |
10 | #ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS | |
11 | #define IS_UNALIGNED(src, dst) 0 | |
12 | #else | |
13 | #define IS_UNALIGNED(src, dst) \ | |
14 | (((long) dst | (long) src) & (sizeof(long) - 1)) | |
15 | #endif | |
16 | ||
17 | /* | |
18 | * Do a strncpy, return length of string without final '\0'. | |
19 | * 'count' is the user-supplied count (return 'count' if we | |
20 | * hit it), 'max' is the address space maximum (and we return | |
21 | * -EFAULT if we hit it). | |
22 | */ | |
23 | static inline long do_strncpy_from_user(char *dst, const char __user *src, long count, unsigned long max) | |
24 | { | |
36126f8f | 25 | const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS; |
2922585b DM |
26 | long res = 0; |
27 | ||
28 | /* | |
29 | * Truncate 'max' to the user-specified limit, so that | |
30 | * we only have one limit we need to check in the loop | |
31 | */ | |
32 | if (max > count) | |
33 | max = count; | |
34 | ||
35 | if (IS_UNALIGNED(src, dst)) | |
36 | goto byte_at_a_time; | |
37 | ||
38 | while (max >= sizeof(unsigned long)) { | |
36126f8f | 39 | unsigned long c, data; |
2922585b DM |
40 | |
41 | /* Fall back to byte-at-a-time if we get a page fault */ | |
9fd4470f | 42 | if (unlikely(unsafe_get_user(c,(unsigned long __user *)(src+res)))) |
2922585b | 43 | break; |
2922585b | 44 | *(unsigned long *)(dst+res) = c; |
36126f8f LT |
45 | if (has_zero(c, &data, &constants)) { |
46 | data = prep_zero_mask(c, data, &constants); | |
47 | data = create_zero_mask(data); | |
48 | return res + find_zero(data); | |
2922585b DM |
49 | } |
50 | res += sizeof(unsigned long); | |
51 | max -= sizeof(unsigned long); | |
52 | } | |
53 | ||
54 | byte_at_a_time: | |
55 | while (max) { | |
56 | char c; | |
57 | ||
9fd4470f | 58 | if (unlikely(unsafe_get_user(c,src+res))) |
2922585b DM |
59 | return -EFAULT; |
60 | dst[res] = c; | |
61 | if (!c) | |
62 | return res; | |
63 | res++; | |
64 | max--; | |
65 | } | |
66 | ||
67 | /* | |
68 | * Uhhuh. We hit 'max'. But was that the user-specified maximum | |
69 | * too? If so, that's ok - we got as much as the user asked for. | |
70 | */ | |
71 | if (res >= count) | |
72 | return res; | |
73 | ||
74 | /* | |
75 | * Nope: we hit the address space limit, and we still had more | |
76 | * characters the caller would have wanted. That's an EFAULT. | |
77 | */ | |
78 | return -EFAULT; | |
79 | } | |
80 | ||
81 | /** | |
82 | * strncpy_from_user: - Copy a NUL terminated string from userspace. | |
83 | * @dst: Destination address, in kernel space. This buffer must be at | |
84 | * least @count bytes long. | |
85 | * @src: Source address, in user space. | |
86 | * @count: Maximum number of bytes to copy, including the trailing NUL. | |
87 | * | |
88 | * Copies a NUL-terminated string from userspace to kernel space. | |
89 | * | |
90 | * On success, returns the length of the string (not including the trailing | |
91 | * NUL). | |
92 | * | |
93 | * If access to userspace fails, returns -EFAULT (some data may have been | |
94 | * copied). | |
95 | * | |
96 | * If @count is smaller than the length of the string, copies @count bytes | |
97 | * and returns @count. | |
98 | */ | |
99 | long strncpy_from_user(char *dst, const char __user *src, long count) | |
100 | { | |
101 | unsigned long max_addr, src_addr; | |
102 | ||
103 | if (unlikely(count <= 0)) | |
104 | return 0; | |
105 | ||
106 | max_addr = user_addr_max(); | |
107 | src_addr = (unsigned long)src; | |
108 | if (likely(src_addr < max_addr)) { | |
109 | unsigned long max = max_addr - src_addr; | |
9fd4470f LT |
110 | long retval; |
111 | ||
112 | user_access_begin(); | |
113 | retval = do_strncpy_from_user(dst, src, count, max); | |
114 | user_access_end(); | |
115 | return retval; | |
2922585b DM |
116 | } |
117 | return -EFAULT; | |
118 | } | |
119 | EXPORT_SYMBOL(strncpy_from_user); |