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 stac();
22 asm volatile(
23 " testq %[size8],%[size8]\n"
24 " jz 4f\n"
25 "0: movq %[zero],(%[dst])\n"
26 " addq %[eight],%[dst]\n"
27 " decl %%ecx ; jnz 0b\n"
28 "4: movq %[size1],%%rcx\n"
29 " testl %%ecx,%%ecx\n"
30 " jz 2f\n"
31 "1: movb %b[zero],(%[dst])\n"
32 " incq %[dst]\n"
33 " decl %%ecx ; jnz 1b\n"
34 "2:\n"
35 ".section .fixup,\"ax\"\n"
36 "3: lea 0(%[size1],%[size8],8),%[size8]\n"
37 " jmp 2b\n"
38 ".previous\n"
39 _ASM_EXTABLE(0b,3b)
40 _ASM_EXTABLE(1b,2b)
41 : [size8] "=&c"(size), [dst] "=&D" (__d0)
42 : [size1] "r"(size & 7), "[size8]" (size / 8), "[dst]"(addr),
43 [zero] "r" (0UL), [eight] "r" (8UL));
44 clac();
45 return size;
46 }
47 EXPORT_SYMBOL(__clear_user);
48
clear_user(void __user * to,unsigned long n)49 unsigned long clear_user(void __user *to, unsigned long n)
50 {
51 if (access_ok(VERIFY_WRITE, to, n))
52 return __clear_user(to, n);
53 return n;
54 }
55 EXPORT_SYMBOL(clear_user);
56
copy_in_user(void __user * to,const void __user * from,unsigned len)57 unsigned long copy_in_user(void __user *to, const void __user *from, unsigned len)
58 {
59 if (access_ok(VERIFY_WRITE, to, len) && access_ok(VERIFY_READ, from, len)) {
60 return copy_user_generic((__force void *)to, (__force void *)from, len);
61 }
62 return len;
63 }
64 EXPORT_SYMBOL(copy_in_user);
65
66 /*
67 * Try to copy last bytes and clear the rest if needed.
68 * Since protection fault in copy_from/to_user is not a normal situation,
69 * it is not necessary to optimize tail handling.
70 */
71 __visible unsigned long
copy_user_handle_tail(char * to,char * from,unsigned len,unsigned zerorest)72 copy_user_handle_tail(char *to, char *from, unsigned len, unsigned zerorest)
73 {
74 char c;
75 unsigned zero_len;
76
77 for (; len; --len, to++) {
78 if (__get_user_nocheck(c, from++, sizeof(char)))
79 break;
80 if (__put_user_nocheck(c, to, sizeof(char)))
81 break;
82 }
83
84 for (c = 0, zero_len = len; zerorest && zero_len; --zero_len)
85 if (__put_user_nocheck(c, to++, sizeof(char)))
86 break;
87 clac();
88 return len;
89 }
90