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 18:52:22 Exp $
18 */
19#include <net/checksum.h>
20#include <linux/module.h>
21#include <linux/types.h>
22#include <asm/byteorder.h>
23#include <asm/string.h>
24#include <asm/uaccess.h>
25
26static inline unsigned short from32to16 (unsigned long sum)
27{
28	unsigned int result;
29	/*
30			        %0		%1
31	      hsw %1, %0	H     L		L     H
32	      add %1, %0	H     L		H+L+C H+L
33	*/
34	asm ("hsw %1, %0; add %1, %0" : "=&r" (result) : "r" (sum));
35	return result >> 16;
36}
37
38static inline unsigned int do_csum(const unsigned char * buff, int len)
39{
40	int odd, count;
41	unsigned int result = 0;
42
43	if (len <= 0)
44		goto out;
45	odd = 1 & (unsigned long) buff;
46	if (odd) {
47		result = be16_to_cpu(*buff);
48		len--;
49		buff++;
50	}
51	count = len >> 1;		/* nr of 16-bit words.. */
52	if (count) {
53		if (2 & (unsigned long) buff) {
54			result += *(unsigned short *) buff;
55			count--;
56			len -= 2;
57			buff += 2;
58		}
59		count >>= 1;		/* nr of 32-bit words.. */
60		if (count) {
61			unsigned int carry = 0;
62			do {
63				unsigned int w = *(unsigned int *) buff;
64				count--;
65				buff += 4;
66				result += carry;
67				result += w;
68				carry = (w > result);
69			} while (count);
70			result += carry;
71			result = (result & 0xffff) + (result >> 16);
72		}
73		if (len & 2) {
74			result += *(unsigned short *) buff;
75			buff += 2;
76		}
77	}
78	if (len & 1)
79		result += le16_to_cpu(*buff);
80	result = from32to16(result);
81	if (odd)
82		result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);
83out:
84	return result;
85}
86
87/*
88 *	This is a version of ip_compute_csum() optimized for IP headers,
89 *	which always checksum on 4 octet boundaries.
90 */
91__sum16 ip_fast_csum(const void *iph, unsigned int ihl)
92{
93	return (__force __sum16)~do_csum(iph,ihl*4);
94}
95
96/*
97 * this routine is used for miscellaneous IP-like checksums, mainly
98 * in icmp.c
99 */
100__sum16 ip_compute_csum(const void *buff, int len)
101{
102	return (__force __sum16)~do_csum(buff,len);
103}
104
105/*
106 * computes a partial checksum, e.g. for TCP/UDP fragments
107 */
108__wsum csum_partial(const void *buff, int len, __wsum sum)
109{
110	unsigned int result = do_csum(buff, len);
111
112	/* add in old sum, and carry.. */
113	result += (__force u32)sum;
114	if ((__force u32)sum > result)
115		result += 1;
116	return (__force __wsum)result;
117}
118
119EXPORT_SYMBOL(csum_partial);
120
121/*
122 * copy while checksumming, otherwise like csum_partial
123 */
124__wsum csum_partial_copy_nocheck(const void *src, void *dst,
125                               int len, __wsum sum)
126{
127	/*
128	 * It's 2:30 am and I don't feel like doing it real ...
129	 * This is lots slower than the real thing (tm)
130	 */
131	sum = csum_partial(src, len, sum);
132	memcpy(dst, src, len);
133
134	return sum;
135}
136
137/*
138 * Copy from userspace and compute checksum.  If we catch an exception
139 * then zero the rest of the buffer.
140 */
141__wsum csum_partial_copy_from_user (const void *src,
142					  void *dst,
143                                          int len, __wsum sum,
144                                          int *err_ptr)
145{
146	int missing;
147
148	missing = copy_from_user(dst, src, len);
149	if (missing) {
150		memset(dst + len - missing, 0, missing);
151		*err_ptr = -EFAULT;
152	}
153
154	return csum_partial(dst, len, sum);
155}
156