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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)72 copy_user_handle_tail(char *to, char *from, unsigned len)
73 {
74 	for (; len; --len, to++) {
75 		char c;
76 
77 		if (__get_user_nocheck(c, from++, sizeof(char)))
78 			break;
79 		if (__put_user_nocheck(c, to, sizeof(char)))
80 			break;
81 	}
82 	clac();
83 
84 	/* If the destination is a kernel buffer, we always clear the end */
85 	if (!__addr_ok(to))
86 		memset(to, 0, len);
87 	return len;
88 }
89