1/*
2 * Network Checksum & Copy routine
3 *
4 * Copyright (C) 1999, 2003-2004 Hewlett-Packard Co
5 *	Stephane Eranian <eranian@hpl.hp.com>
6 *
7 * Most of the code has been imported from Linux/Alpha
8 */
9
10#include <linux/module.h>
11#include <linux/types.h>
12#include <linux/string.h>
13
14#include <asm/uaccess.h>
15
16/*
17 * XXX Fixme: those 2 inlines are meant for debugging and will go away
18 */
19static inline unsigned
20short from64to16(unsigned long x)
21{
22	/* add up 32-bit words for 33 bits */
23	x = (x & 0xffffffff) + (x >> 32);
24	/* add up 16-bit and 17-bit words for 17+c bits */
25	x = (x & 0xffff) + (x >> 16);
26	/* add up 16-bit and 2-bit for 16+c bit */
27	x = (x & 0xffff) + (x >> 16);
28	/* add up carry.. */
29	x = (x & 0xffff) + (x >> 16);
30	return x;
31}
32
33static inline
34unsigned long do_csum_c(const unsigned char * buff, int len, unsigned int psum)
35{
36	int odd, count;
37	unsigned long result = (unsigned long)psum;
38
39	if (len <= 0)
40		goto out;
41	odd = 1 & (unsigned long) buff;
42	if (odd) {
43		result = *buff << 8;
44		len--;
45		buff++;
46	}
47	count = len >> 1;		/* nr of 16-bit words.. */
48	if (count) {
49		if (2 & (unsigned long) buff) {
50			result += *(unsigned short *) buff;
51			count--;
52			len -= 2;
53			buff += 2;
54		}
55		count >>= 1;		/* nr of 32-bit words.. */
56		if (count) {
57			if (4 & (unsigned long) buff) {
58				result += *(unsigned int *) buff;
59				count--;
60				len -= 4;
61				buff += 4;
62			}
63			count >>= 1;	/* nr of 64-bit words.. */
64			if (count) {
65				unsigned long carry = 0;
66				do {
67					unsigned long w = *(unsigned long *) buff;
68					count--;
69					buff += 8;
70					result += carry;
71					result += w;
72					carry = (w > result);
73				} while (count);
74				result += carry;
75				result = (result & 0xffffffff) + (result >> 32);
76			}
77			if (len & 4) {
78				result += *(unsigned int *) buff;
79				buff += 4;
80			}
81		}
82		if (len & 2) {
83			result += *(unsigned short *) buff;
84			buff += 2;
85		}
86	}
87	if (len & 1)
88		result += *buff;
89
90	result = from64to16(result);
91
92	if (odd)
93		result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);
94
95out:
96	return result;
97}
98
99/*
100 * XXX Fixme
101 *
102 * This is very ugly but temporary. THIS NEEDS SERIOUS ENHANCEMENTS.
103 * But it's very tricky to get right even in C.
104 */
105extern unsigned long do_csum(const unsigned char *, long);
106
107__wsum
108csum_partial_copy_from_user(const void __user *src, void *dst,
109				int len, __wsum psum, int *errp)
110{
111	unsigned long result;
112
113	/* XXX Fixme
114	 * for now we separate the copy from checksum for obvious
115	 * alignment difficulties. Look at the Alpha code and you'll be
116	 * scared.
117	 */
118
119	if (__copy_from_user(dst, src, len) != 0 && errp)
120		*errp = -EFAULT;
121
122	result = do_csum(dst, len);
123
124	/* add in old sum, and carry.. */
125	result += (__force u32)psum;
126	/* 32+c bits -> 32 bits */
127	result = (result & 0xffffffff) + (result >> 32);
128	return (__force __wsum)result;
129}
130
131EXPORT_SYMBOL(csum_partial_copy_from_user);
132
133__wsum
134csum_partial_copy_nocheck(const void *src, void *dst, int len, __wsum sum)
135{
136	return csum_partial_copy_from_user((__force const void __user *)src,
137					   dst, len, sum, NULL);
138}
139
140EXPORT_SYMBOL(csum_partial_copy_nocheck);
141