1/*
2 * INET		An implementation of the TCP/IP protocol suite for the LINUX
3 *		operating system.  INET is implemented using the  BSD Socket
4 *		interface as the means of communication with the user level.
5 *
6 *		MIPS specific IP/TCP/UDP checksumming routines
7 *
8 * Authors:	Ralf Baechle, <ralf@waldorf-gmbh.de>
9 *		Lots of code moved from tcp.c and ip.c; see those files
10 *		for more names.
11 *
12 *		This program is free software; you can redistribute it and/or
13 *		modify it under the terms of the GNU General Public License
14 *		as published by the Free Software Foundation; either version
15 *		2 of the License, or (at your option) any later version.
16 *
17 * $Id: checksum.c,v 1.1.1.1 2007/08/03 18:52:03 Exp $
18 */
19#include <linux/module.h>
20#include <linux/types.h>
21
22#include <net/checksum.h>
23#include <asm/byteorder.h>
24#include <asm/string.h>
25#include <asm/uaccess.h>
26
27#define addc(_t,_r)                     \
28	__asm__ __volatile__ (          \
29"       add             %0, %1, %0\n"   \
30"       addc            %0, %%r0, %0\n" \
31	: "=r"(_t)                      \
32	: "r"(_r), "0"(_t));
33
34static inline unsigned short from32to16(unsigned int x)
35{
36	/* 32 bits --> 16 bits + carry */
37	x = (x & 0xffff) + (x >> 16);
38	/* 16 bits + carry --> 16 bits including carry */
39	x = (x & 0xffff) + (x >> 16);
40	return (unsigned short)x;
41}
42
43static inline unsigned int do_csum(const unsigned char * buff, int len)
44{
45	int odd, count;
46	unsigned int result = 0;
47
48	if (len <= 0)
49		goto out;
50	odd = 1 & (unsigned long) buff;
51	if (odd) {
52		result = be16_to_cpu(*buff);
53		len--;
54		buff++;
55	}
56	count = len >> 1;		/* nr of 16-bit words.. */
57	if (count) {
58		if (2 & (unsigned long) buff) {
59			result += *(unsigned short *) buff;
60			count--;
61			len -= 2;
62			buff += 2;
63		}
64		count >>= 1;		/* nr of 32-bit words.. */
65		if (count) {
66			while (count >= 4) {
67				unsigned int r1, r2, r3, r4;
68				r1 = *(unsigned int *)(buff + 0);
69				r2 = *(unsigned int *)(buff + 4);
70				r3 = *(unsigned int *)(buff + 8);
71				r4 = *(unsigned int *)(buff + 12);
72				addc(result, r1);
73				addc(result, r2);
74				addc(result, r3);
75				addc(result, r4);
76				count -= 4;
77				buff += 16;
78			}
79			while (count) {
80				unsigned int w = *(unsigned int *) buff;
81				count--;
82				buff += 4;
83				addc(result, w);
84			}
85			result = (result & 0xffff) + (result >> 16);
86		}
87		if (len & 2) {
88			result += *(unsigned short *) buff;
89			buff += 2;
90		}
91	}
92	if (len & 1)
93		result += le16_to_cpu(*buff);
94	result = from32to16(result);
95	if (odd)
96		result = swab16(result);
97out:
98	return result;
99}
100
101/*
102 * computes a partial checksum, e.g. for TCP/UDP fragments
103 */
104/*
105 * why bother folding?
106 */
107__wsum csum_partial(const void *buff, int len, __wsum sum)
108{
109	unsigned int result = do_csum(buff, len);
110	addc(result, sum);
111	return (__force __wsum)from32to16(result);
112}
113
114EXPORT_SYMBOL(csum_partial);
115
116/*
117 * copy while checksumming, otherwise like csum_partial
118 */
119__wsum csum_partial_copy_nocheck(const void *src, void *dst,
120				       int len, __wsum sum)
121{
122	/*
123	 * It's 2:30 am and I don't feel like doing it real ...
124	 * This is lots slower than the real thing (tm)
125	 */
126	sum = csum_partial(src, len, sum);
127	memcpy(dst, src, len);
128
129	return sum;
130}
131EXPORT_SYMBOL(csum_partial_copy_nocheck);
132
133/*
134 * Copy from userspace and compute checksum.  If we catch an exception
135 * then zero the rest of the buffer.
136 */
137__wsum csum_partial_copy_from_user(const void __user *src,
138					void *dst, int len,
139					__wsum sum, int *err_ptr)
140{
141	int missing;
142
143	missing = copy_from_user(dst, src, len);
144	if (missing) {
145		memset(dst + len - missing, 0, missing);
146		*err_ptr = -EFAULT;
147	}
148
149	return csum_partial(dst, len, sum);
150}
151EXPORT_SYMBOL(csum_partial_copy_from_user);
152