1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Network Checksum & Copy routine
4 *
5 * Copyright (C) 1999, 2003-2004 Hewlett-Packard Co
6 * Stephane Eranian <eranian@hpl.hp.com>
7 *
8 * Most of the code has been imported from Linux/Alpha
9 */
10
11 #include <linux/module.h>
12 #include <linux/types.h>
13 #include <linux/string.h>
14
15 #include <linux/uaccess.h>
16
17 /*
18 * XXX Fixme: those 2 inlines are meant for debugging and will go away
19 */
20 static inline unsigned
from64to16(unsigned long x)21 short from64to16(unsigned long x)
22 {
23 /* add up 32-bit words for 33 bits */
24 x = (x & 0xffffffff) + (x >> 32);
25 /* add up 16-bit and 17-bit words for 17+c bits */
26 x = (x & 0xffff) + (x >> 16);
27 /* add up 16-bit and 2-bit for 16+c bit */
28 x = (x & 0xffff) + (x >> 16);
29 /* add up carry.. */
30 x = (x & 0xffff) + (x >> 16);
31 return x;
32 }
33
34 static inline
do_csum_c(const unsigned char * buff,int len,unsigned int psum)35 unsigned long do_csum_c(const unsigned char * buff, int len, unsigned int psum)
36 {
37 int odd, count;
38 unsigned long result = (unsigned long)psum;
39
40 if (len <= 0)
41 goto out;
42 odd = 1 & (unsigned long) buff;
43 if (odd) {
44 result = *buff << 8;
45 len--;
46 buff++;
47 }
48 count = len >> 1; /* nr of 16-bit words.. */
49 if (count) {
50 if (2 & (unsigned long) buff) {
51 result += *(unsigned short *) buff;
52 count--;
53 len -= 2;
54 buff += 2;
55 }
56 count >>= 1; /* nr of 32-bit words.. */
57 if (count) {
58 if (4 & (unsigned long) buff) {
59 result += *(unsigned int *) buff;
60 count--;
61 len -= 4;
62 buff += 4;
63 }
64 count >>= 1; /* nr of 64-bit words.. */
65 if (count) {
66 unsigned long carry = 0;
67 do {
68 unsigned long w = *(unsigned long *) buff;
69 count--;
70 buff += 8;
71 result += carry;
72 result += w;
73 carry = (w > result);
74 } while (count);
75 result += carry;
76 result = (result & 0xffffffff) + (result >> 32);
77 }
78 if (len & 4) {
79 result += *(unsigned int *) buff;
80 buff += 4;
81 }
82 }
83 if (len & 2) {
84 result += *(unsigned short *) buff;
85 buff += 2;
86 }
87 }
88 if (len & 1)
89 result += *buff;
90
91 result = from64to16(result);
92
93 if (odd)
94 result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);
95
96 out:
97 return result;
98 }
99
100 /*
101 * XXX Fixme
102 *
103 * This is very ugly but temporary. THIS NEEDS SERIOUS ENHANCEMENTS.
104 * But it's very tricky to get right even in C.
105 */
106 extern unsigned long do_csum(const unsigned char *, long);
107
108 __wsum
csum_partial_copy_from_user(const void __user * src,void * dst,int len,__wsum psum,int * errp)109 csum_partial_copy_from_user(const void __user *src, void *dst,
110 int len, __wsum psum, int *errp)
111 {
112 unsigned long result;
113
114 /* XXX Fixme
115 * for now we separate the copy from checksum for obvious
116 * alignment difficulties. Look at the Alpha code and you'll be
117 * scared.
118 */
119
120 if (__copy_from_user(dst, src, len) != 0 && errp)
121 *errp = -EFAULT;
122
123 result = do_csum(dst, len);
124
125 /* add in old sum, and carry.. */
126 result += (__force u32)psum;
127 /* 32+c bits -> 32 bits */
128 result = (result & 0xffffffff) + (result >> 32);
129 return (__force __wsum)result;
130 }
131
132 EXPORT_SYMBOL(csum_partial_copy_from_user);
133
134 __wsum
csum_partial_copy_nocheck(const void * src,void * dst,int len,__wsum sum)135 csum_partial_copy_nocheck(const void *src, void *dst, int len, __wsum sum)
136 {
137 return csum_partial_copy_from_user((__force const void __user *)src,
138 dst, len, sum, NULL);
139 }
140
141 EXPORT_SYMBOL(csum_partial_copy_nocheck);
142
