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/arch/v850/lib/checksum.c

https://bitbucket.org/evzijst/gittest
C | 154 lines | 95 code | 13 blank | 46 comment | 11 complexity | af28c5440669002a9445ea30b394761d MD5 | raw file
  1/*
  2 * INET		An implementation of the TCP/IP protocol suite for the LINUX
  3 *		operating system.  INET is implemented using the  BSD Socket
  4 *		interface as the means of communication with the user level.
  5 *
  6 *		MIPS specific IP/TCP/UDP checksumming routines
  7 *
  8 * Authors:	Ralf Baechle, <ralf@waldorf-gmbh.de>
  9 *		Lots of code moved from tcp.c and ip.c; see those files
 10 *		for more names.
 11 *
 12 *		This program is free software; you can redistribute it and/or
 13 *		modify it under the terms of the GNU General Public License
 14 *		as published by the Free Software Foundation; either version
 15 *		2 of the License, or (at your option) any later version.
 16 *
 17 * $Id: checksum.c,v 1.1 2002/09/28 14:58:40 gerg Exp $
 18 */
 19#include <net/checksum.h>
 20#include <linux/module.h>
 21#include <linux/types.h>
 22#include <asm/byteorder.h>
 23#include <asm/string.h>
 24#include <asm/uaccess.h>
 25
 26static inline unsigned short from32to16 (unsigned long sum)
 27{
 28	unsigned int result;
 29	/*
 30			        %0		%1
 31	      hsw %1, %0	H     L		L     H
 32	      add %1, %0	H     L		H+L+C H+L
 33	*/
 34	asm ("hsw %1, %0; add %1, %0" : "=&r" (result) : "r" (sum));
 35	return result >> 16;
 36}
 37
 38static inline unsigned int do_csum(const unsigned char * buff, int len)
 39{
 40	int odd, count;
 41	unsigned int result = 0;
 42
 43	if (len <= 0)
 44		goto out;
 45	odd = 1 & (unsigned long) buff;
 46	if (odd) {
 47		result = be16_to_cpu(*buff);
 48		len--;
 49		buff++;
 50	}
 51	count = len >> 1;		/* nr of 16-bit words.. */
 52	if (count) {
 53		if (2 & (unsigned long) buff) {
 54			result += *(unsigned short *) buff;
 55			count--;
 56			len -= 2;
 57			buff += 2;
 58		}
 59		count >>= 1;		/* nr of 32-bit words.. */
 60		if (count) {
 61			unsigned int carry = 0;
 62			do {
 63				unsigned int w = *(unsigned int *) buff;
 64				count--;
 65				buff += 4;
 66				result += carry;
 67				result += w;
 68				carry = (w > result);
 69			} while (count);
 70			result += carry;
 71			result = (result & 0xffff) + (result >> 16);
 72		}
 73		if (len & 2) {
 74			result += *(unsigned short *) buff;
 75			buff += 2;
 76		}
 77	}
 78	if (len & 1)
 79		result += le16_to_cpu(*buff);
 80	result = from32to16(result);
 81	if (odd)
 82		result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);
 83out:
 84	return result;
 85}
 86
 87/*
 88 *	This is a version of ip_compute_csum() optimized for IP headers,
 89 *	which always checksum on 4 octet boundaries.
 90 */
 91unsigned short ip_fast_csum(unsigned char * iph, unsigned int ihl)
 92{
 93	return ~do_csum(iph,ihl*4);
 94}
 95
 96/*
 97 * this routine is used for miscellaneous IP-like checksums, mainly
 98 * in icmp.c
 99 */
100unsigned short ip_compute_csum(const unsigned char * buff, int len)
101{
102	return ~do_csum(buff,len);
103}
104
105/*
106 * computes a partial checksum, e.g. for TCP/UDP fragments
107 */
108unsigned int csum_partial(const unsigned char *buff, int len, unsigned int sum)
109{
110	unsigned int result = do_csum(buff, len);
111
112	/* add in old sum, and carry.. */
113	result += sum;
114	if(sum > result)
115		result += 1;
116	return result;
117}
118
119EXPORT_SYMBOL(csum_partial);
120
121/*
122 * copy while checksumming, otherwise like csum_partial
123 */
124unsigned int csum_partial_copy(const unsigned char *src, unsigned char *dst,
125                               int len, unsigned int sum)
126{
127	/*
128	 * It's 2:30 am and I don't feel like doing it real ...
129	 * This is lots slower than the real thing (tm)
130	 */
131	sum = csum_partial(src, len, sum);
132	memcpy(dst, src, len);
133
134	return sum;
135}
136
137/*
138 * Copy from userspace and compute checksum.  If we catch an exception
139 * then zero the rest of the buffer.
140 */
141unsigned int csum_partial_copy_from_user (const unsigned char *src, unsigned char *dst,
142                                          int len, unsigned int sum,
143                                          int *err_ptr)
144{
145	int missing;
146
147	missing = copy_from_user(dst, src, len);
148	if (missing) {
149		memset(dst + len - missing, 0, missing);
150		*err_ptr = -EFAULT;
151	}
152		
153	return csum_partial(dst, len, sum);
154}