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[linux-2.6.git] / arch / ia64 / lib / csum_partial_copy.c
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 static unsigned int
108 do_csum_partial_copy_from_user (const unsigned char __user *src, unsigned char *dst,
109                                 int len, unsigned int 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 += psum;
126         /* 32+c bits -> 32 bits */
127         result = (result & 0xffffffff) + (result >> 32);
128         return result;
129 }
130
131 unsigned int
132 csum_partial_copy_from_user (const unsigned char __user *src, unsigned char *dst,
133                              int len, unsigned int sum, int *errp)
134 {
135         if (!access_ok(VERIFY_READ, src, len)) {
136                 *errp = -EFAULT;
137                 memset(dst, 0, len);
138                 return sum;
139         }
140
141         return do_csum_partial_copy_from_user(src, dst, len, sum, errp);
142 }
143
144 unsigned int
145 csum_partial_copy_nocheck(const unsigned char __user *src, unsigned char *dst,
146                           int len, unsigned int sum)
147 {
148         return do_csum_partial_copy_from_user(src, dst, len, sum, NULL);
149 }
150
151 EXPORT_SYMBOL(csum_partial_copy_nocheck);