aboutsummaryrefslogtreecommitdiffstats
path: root/arch/ia64/lib/csum_partial_copy.c
blob: 118daf5a0632cc505f2f88574ab645c4b79e14a5 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
/*
 * Network Checksum & Copy routine
 *
 * Copyright (C) 1999, 2003-2004 Hewlett-Packard Co
 *	Stephane Eranian <eranian@hpl.hp.com>
 *
 * Most of the code has been imported from Linux/Alpha
 */

#include <linux/module.h>
#include <linux/types.h>
#include <linux/string.h>

#include <asm/uaccess.h>

/*
 * XXX Fixme: those 2 inlines are meant for debugging and will go away
 */
static inline unsigned
short from64to16(unsigned long x)
{
	/* add up 32-bit words for 33 bits */
	x = (x & 0xffffffff) + (x >> 32);
	/* add up 16-bit and 17-bit words for 17+c bits */
	x = (x & 0xffff) + (x >> 16);
	/* add up 16-bit and 2-bit for 16+c bit */
	x = (x & 0xffff) + (x >> 16);
	/* add up carry.. */
	x = (x & 0xffff) + (x >> 16);
	return x;
}

static inline
unsigned long do_csum_c(const unsigned char * buff, int len, unsigned int psum)
{
	int odd, count;
	unsigned long result = (unsigned long)psum;

	if (len <= 0)
		goto out;
	odd = 1 & (unsigned long) buff;
	if (odd) {
		result = *buff << 8;
		len--;
		buff++;
	}
	count = len >> 1;		/* nr of 16-bit words.. */
	if (count) {
		if (2 & (unsigned long) buff) {
			result += *(unsigned short *) buff;
			count--;
			len -= 2;
			buff += 2;
		}
		count >>= 1;		/* nr of 32-bit words.. */
		if (count) {
			if (4 & (unsigned long) buff) {
				result += *(unsigned int *) buff;
				count--;
				len -= 4;
				buff += 4;
			}
			count >>= 1;	/* nr of 64-bit words.. */
			if (count) {
				unsigned long carry = 0;
				do {
					unsigned long w = *(unsigned long *) buff;
					count--;
					buff += 8;
					result += carry;
					result += w;
					carry = (w > result);
				} while (count);
				result += carry;
				result = (result & 0xffffffff) + (result >> 32);
			}
			if (len & 4) {
				result += *(unsigned int *) buff;
				buff += 4;
			}
		}
		if (len & 2) {
			result += *(unsigned short *) buff;
			buff += 2;
		}
	}
	if (len & 1)
		result += *buff;

	result = from64to16(result);

	if (odd)
		result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);

out:
	return result;
}

/*
 * XXX Fixme
 *
 * This is very ugly but temporary. THIS NEEDS SERIOUS ENHANCEMENTS.
 * But it's very tricky to get right even in C.
 */
extern unsigned long do_csum(const unsigned char *, long);

__wsum
csum_partial_copy_from_user(const void __user *src, void *dst,
				int len, __wsum psum, int *errp)
{
	unsigned long result;

	/* XXX Fixme
	 * for now we separate the copy from checksum for obvious
	 * alignment difficulties. Look at the Alpha code and you'll be
	 * scared.
	 */

	if (__copy_from_user(dst, src, len) != 0 && errp)
		*errp = -EFAULT;

	result = do_csum(dst, len);

	/* add in old sum, and carry.. */
	result += (__force u32)psum;
	/* 32+c bits -> 32 bits */
	result = (result & 0xffffffff) + (result >> 32);
	return (__force __wsum)result;
}

EXPORT_SYMBOL(csum_partial_copy_from_user);

__wsum
csum_partial_copy_nocheck(const void *src, void *dst, int len, __wsum sum)
{
	return csum_partial_copy_from_user((__force const void __user *)src,
					   dst, len, sum, NULL);
}

EXPORT_SYMBOL(csum_partial_copy_nocheck);