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 */
 19static inline unsigned
 20short 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
 33static inline
 34unsigned 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
 95out:
 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 */
105extern unsigned long do_csum(const unsigned char *, long);
106
107__wsum
108csum_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
131EXPORT_SYMBOL(csum_partial_copy_from_user);
132
133__wsum
134csum_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
140EXPORT_SYMBOL(csum_partial_copy_nocheck);