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