1#include <linux/kernel.h>
2#include <linux/export.h>
3#include <linux/uaccess.h>
4
5#include <asm/word-at-a-time.h>
6
7
8#ifdef __LITTLE_ENDIAN
9# define aligned_byte_mask(n) ((1ul << 8*(n))-1)
10#else
11# define aligned_byte_mask(n) (~0xfful << (BITS_PER_LONG - 8 - 8*(n)))
12#endif
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27static inline long do_strnlen_user(const char __user *src, unsigned long count, unsigned long max)
28{
29 const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
30 long align, res = 0;
31 unsigned long c;
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36
37 if (max > count)
38 max = count;
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44 align = (sizeof(long) - 1) & (unsigned long)src;
45 src -= align;
46 max += align;
47
48 if (unlikely(unsafe_get_user(c,(unsigned long __user *)src)))
49 return 0;
50 c |= aligned_byte_mask(align);
51
52 for (;;) {
53 unsigned long data;
54 if (has_zero(c, &data, &constants)) {
55 data = prep_zero_mask(c, data, &constants);
56 data = create_zero_mask(data);
57 return res + find_zero(data) + 1 - align;
58 }
59 res += sizeof(unsigned long);
60
61 if (unlikely(max <= sizeof(unsigned long)))
62 break;
63 max -= sizeof(unsigned long);
64 if (unlikely(unsafe_get_user(c,(unsigned long __user *)(src+res))))
65 return 0;
66 }
67 res -= align;
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73 if (res >= count)
74 return count+1;
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80 return 0;
81}
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104long strnlen_user(const char __user *str, long count)
105{
106 unsigned long max_addr, src_addr;
107
108 if (unlikely(count <= 0))
109 return 0;
110
111 max_addr = user_addr_max();
112 src_addr = (unsigned long)str;
113 if (likely(src_addr < max_addr)) {
114 unsigned long max = max_addr - src_addr;
115 long retval;
116
117 user_access_begin();
118 retval = do_strnlen_user(str, count, max);
119 user_access_end();
120 return retval;
121 }
122 return 0;
123}
124EXPORT_SYMBOL(strnlen_user);
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141long strlen_user(const char __user *str)
142{
143 unsigned long max_addr, src_addr;
144
145 max_addr = user_addr_max();
146 src_addr = (unsigned long)str;
147 if (likely(src_addr < max_addr)) {
148 unsigned long max = max_addr - src_addr;
149 long retval;
150
151 user_access_begin();
152 retval = do_strnlen_user(str, ~0ul, max);
153 user_access_end();
154 return retval;
155 }
156 return 0;
157}
158EXPORT_SYMBOL(strlen_user);
159