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#include <linux/module.h>
18#include <linux/types.h>
19
20#include <net/checksum.h>
21#include <asm/byteorder.h>
22#include <asm/string.h>
23#include <asm/uaccess.h>
24
25#define addc(_t,_r)                     \
26	__asm__ __volatile__ (          \
27"       add             %0, %1, %0\n"   \
28"       addc            %0, %%r0, %0\n" \
29	: "=r"(_t)                      \
30	: "r"(_r), "0"(_t));
31
32static inline unsigned short from32to16(unsigned int x)
33{
34	/* 32 bits --> 16 bits + carry */
35	x = (x & 0xffff) + (x >> 16);
36	/* 16 bits + carry --> 16 bits including carry */
37	x = (x & 0xffff) + (x >> 16);
38	return (unsigned short)x;
39}
40
41static inline unsigned int do_csum(const unsigned char * buff, int len)
42{
43	int odd, count;
44	unsigned int result = 0;
45
46	if (len <= 0)
47		goto out;
48	odd = 1 & (unsigned long) buff;
49	if (odd) {
50		result = be16_to_cpu(*buff);
51		len--;
52		buff++;
53	}
54	count = len >> 1;		/* nr of 16-bit words.. */
55	if (count) {
56		if (2 & (unsigned long) buff) {
57			result += *(unsigned short *) buff;
58			count--;
59			len -= 2;
60			buff += 2;
61		}
62		count >>= 1;		/* nr of 32-bit words.. */
63		if (count) {
64			while (count >= 4) {
65				unsigned int r1, r2, r3, r4;
66				r1 = *(unsigned int *)(buff + 0);
67				r2 = *(unsigned int *)(buff + 4);
68				r3 = *(unsigned int *)(buff + 8);
69				r4 = *(unsigned int *)(buff + 12);
70				addc(result, r1);
71				addc(result, r2);
72				addc(result, r3);
73				addc(result, r4);
74				count -= 4;
75				buff += 16;
76			}
77			while (count) {
78				unsigned int w = *(unsigned int *) buff;
79				count--;
80				buff += 4;
81				addc(result, w);
82			}
83			result = (result & 0xffff) + (result >> 16);
84		}
85		if (len & 2) {
86			result += *(unsigned short *) buff;
87			buff += 2;
88		}
89	}
90	if (len & 1)
91		result += le16_to_cpu(*buff);
92	result = from32to16(result);
93	if (odd)
94		result = swab16(result);
95out:
96	return result;
97}
98
99/*
100 * computes a partial checksum, e.g. for TCP/UDP fragments
101 */
102/*
103 * why bother folding?
104 */
105__wsum csum_partial(const void *buff, int len, __wsum sum)
106{
107	unsigned int result = do_csum(buff, len);
108	addc(result, sum);
109	return (__force __wsum)from32to16(result);
110}
111
112EXPORT_SYMBOL(csum_partial);
113
114/*
115 * copy while checksumming, otherwise like csum_partial
116 */
117__wsum csum_partial_copy_nocheck(const void *src, void *dst,
118				       int len, __wsum sum)
119{
120	/*
121	 * It's 2:30 am and I don't feel like doing it real ...
122	 * This is lots slower than the real thing (tm)
123	 */
124	sum = csum_partial(src, len, sum);
125	memcpy(dst, src, len);
126
127	return sum;
128}
129EXPORT_SYMBOL(csum_partial_copy_nocheck);
130
131/*
132 * Copy from userspace and compute checksum.  If we catch an exception
133 * then zero the rest of the buffer.
134 */
135__wsum csum_partial_copy_from_user(const void __user *src,
136					void *dst, int len,
137					__wsum sum, int *err_ptr)
138{
139	int missing;
140
141	missing = copy_from_user(dst, src, len);
142	if (missing) {
143		memset(dst + len - missing, 0, missing);
144		*err_ptr = -EFAULT;
145	}
146
147	return csum_partial(dst, len, sum);
148}
149EXPORT_SYMBOL(csum_partial_copy_from_user);
150