1 /*
2 * User address space access functions.
3 *
4 * Copyright 1997 Andi Kleen <ak@muc.de>
5 * Copyright 1997 Linus Torvalds
6 * Copyright 2002 Andi Kleen <ak@suse.de>
7 */
8 #include <linux/module.h>
9 #include <asm/uaccess.h>
10
11 /*
12 * Zero Userspace
13 */
14
__clear_user(void __user * addr,unsigned long size)15 unsigned long __clear_user(void __user *addr, unsigned long size)
16 {
17 long __d0;
18 might_fault();
19 /* no memory constraint because it doesn't change any memory gcc knows
20 about */
21 asm volatile(
22 " testq %[size8],%[size8]\n"
23 " jz 4f\n"
24 "0: movq %[zero],(%[dst])\n"
25 " addq %[eight],%[dst]\n"
26 " decl %%ecx ; jnz 0b\n"
27 "4: movq %[size1],%%rcx\n"
28 " testl %%ecx,%%ecx\n"
29 " jz 2f\n"
30 "1: movb %b[zero],(%[dst])\n"
31 " incq %[dst]\n"
32 " decl %%ecx ; jnz 1b\n"
33 "2:\n"
34 ".section .fixup,\"ax\"\n"
35 "3: lea 0(%[size1],%[size8],8),%[size8]\n"
36 " jmp 2b\n"
37 ".previous\n"
38 _ASM_EXTABLE(0b,3b)
39 _ASM_EXTABLE(1b,2b)
40 : [size8] "=&c"(size), [dst] "=&D" (__d0)
41 : [size1] "r"(size & 7), "[size8]" (size / 8), "[dst]"(addr),
42 [zero] "r" (0UL), [eight] "r" (8UL));
43 return size;
44 }
45 EXPORT_SYMBOL(__clear_user);
46
clear_user(void __user * to,unsigned long n)47 unsigned long clear_user(void __user *to, unsigned long n)
48 {
49 if (access_ok(VERIFY_WRITE, to, n))
50 return __clear_user(to, n);
51 return n;
52 }
53 EXPORT_SYMBOL(clear_user);
54
55 /*
56 * Return the size of a string (including the ending 0)
57 *
58 * Return 0 on exception, a value greater than N if too long
59 */
60
__strnlen_user(const char __user * s,long n)61 long __strnlen_user(const char __user *s, long n)
62 {
63 long res = 0;
64 char c;
65
66 while (1) {
67 if (res>n)
68 return n+1;
69 if (__get_user(c, s))
70 return 0;
71 if (!c)
72 return res+1;
73 res++;
74 s++;
75 }
76 }
77 EXPORT_SYMBOL(__strnlen_user);
78
strnlen_user(const char __user * s,long n)79 long strnlen_user(const char __user *s, long n)
80 {
81 if (!access_ok(VERIFY_READ, s, 1))
82 return 0;
83 return __strnlen_user(s, n);
84 }
85 EXPORT_SYMBOL(strnlen_user);
86
strlen_user(const char __user * s)87 long strlen_user(const char __user *s)
88 {
89 long res = 0;
90 char c;
91
92 for (;;) {
93 if (get_user(c, s))
94 return 0;
95 if (!c)
96 return res+1;
97 res++;
98 s++;
99 }
100 }
101 EXPORT_SYMBOL(strlen_user);
102
copy_in_user(void __user * to,const void __user * from,unsigned len)103 unsigned long copy_in_user(void __user *to, const void __user *from, unsigned len)
104 {
105 if (access_ok(VERIFY_WRITE, to, len) && access_ok(VERIFY_READ, from, len)) {
106 return copy_user_generic((__force void *)to, (__force void *)from, len);
107 }
108 return len;
109 }
110 EXPORT_SYMBOL(copy_in_user);
111
112 /*
113 * Try to copy last bytes and clear the rest if needed.
114 * Since protection fault in copy_from/to_user is not a normal situation,
115 * it is not necessary to optimize tail handling.
116 */
117 unsigned long
copy_user_handle_tail(char * to,char * from,unsigned len,unsigned zerorest)118 copy_user_handle_tail(char *to, char *from, unsigned len, unsigned zerorest)
119 {
120 char c;
121 unsigned zero_len;
122
123 for (; len; --len, to++) {
124 if (__get_user_nocheck(c, from++, sizeof(char)))
125 break;
126 if (__put_user_nocheck(c, to, sizeof(char)))
127 break;
128 }
129
130 for (c = 0, zero_len = len; zerorest && zero_len; --zero_len)
131 if (__put_user_nocheck(c, to++, sizeof(char)))
132 break;
133 return len;
134 }
135