1/* user_fixup.c: Fix up user copy faults.
2 *
3 * Copyright (C) 2004 David S. Miller <davem@redhat.com>
4 */
5
6#include <linux/compiler.h>
7#include <linux/kernel.h>
8#include <linux/string.h>
9#include <linux/errno.h>
10#include <linux/module.h>
11
12#include <asm/uaccess.h>
13
14/* Calculating the exact fault address when using
15 * block loads and stores can be very complicated.
16 *
17 * Instead of trying to be clever and handling all
18 * of the cases, just fix things up simply here.
19 */
20
21static unsigned long compute_size(unsigned long start, unsigned long size, unsigned long *offset)
22{
23	unsigned long fault_addr = current_thread_info()->fault_address;
24	unsigned long end = start + size;
25
26	if (fault_addr < start || fault_addr >= end) {
27		*offset = 0;
28	} else {
29		*offset = fault_addr - start;
30		size = end - fault_addr;
31	}
32	return size;
33}
34
35unsigned long copy_from_user_fixup(void *to, const void __user *from, unsigned long size)
36{
37	unsigned long offset;
38
39	size = compute_size((unsigned long) from, size, &offset);
40	if (likely(size))
41		memset(to + offset, 0, size);
42
43	return size;
44}
45EXPORT_SYMBOL(copy_from_user_fixup);
46
47unsigned long copy_to_user_fixup(void __user *to, const void *from, unsigned long size)
48{
49	unsigned long offset;
50
51	return compute_size((unsigned long) to, size, &offset);
52}
53EXPORT_SYMBOL(copy_to_user_fixup);
54
55unsigned long copy_in_user_fixup(void __user *to, void __user *from, unsigned long size)
56{
57	unsigned long fault_addr = current_thread_info()->fault_address;
58	unsigned long start = (unsigned long) to;
59	unsigned long end = start + size;
60
61	if (fault_addr >= start && fault_addr < end)
62		return end - fault_addr;
63
64	start = (unsigned long) from;
65	end = start + size;
66	if (fault_addr >= start && fault_addr < end)
67		return end - fault_addr;
68
69	return size;
70}
71EXPORT_SYMBOL(copy_in_user_fixup);
72