arch/v850/lib/checksum.c

   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
  26 static 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
  38 static 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);
  83 out:
  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  */
  91 unsigned 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  */
 100 unsigned 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  */
 108 unsigned 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
 119 EXPORT_SYMBOL(csum_partial);
 120
 121 /*
 122  * copy while checksumming, otherwise like csum_partial
 123  */
 124 unsigned 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  */
 141 unsigned int csum_partial_copy_from_user (const unsigned char *src,
 142                                           unsigned char *dst,
 143                                           int len, unsigned int sum,
 144                                           int *err_ptr)
 145 {
 146         int missing;
 147
 148         missing = copy_from_user(dst, src, len);
 149         if (missing) {
 150                 memset(dst + len - missing, 0, missing);
 151                 *err_ptr = -EFAULT;
 152         }
 153
 154         return csum_partial(dst, len, sum);
 155 }