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 1.3 1997/12/01 17:57:34 ralf 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
from32to16(unsigned int x)34 static 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
do_csum(const unsigned char * buff,int len)43 static 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);
97 out:
98 return result;
99 }
100
101 /*
102 * computes a partial checksum, e.g. for TCP/UDP fragments
103 */
104 /*
105 * why bother folding?
106 */
csum_partial(const void * buff,int len,__wsum sum)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
114 EXPORT_SYMBOL(csum_partial);
115
116 /*
117 * copy while checksumming, otherwise like csum_partial
118 */
csum_partial_copy_nocheck(const void * src,void * dst,int len,__wsum sum)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 }
131 EXPORT_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 */
csum_partial_copy_from_user(const void __user * src,void * dst,int len,__wsum sum,int * err_ptr)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 }
151 EXPORT_SYMBOL(csum_partial_copy_from_user);
152