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
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
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
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
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