arch/frv/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  *              IP/TCP/UDP checksumming routines
   7  *
   8  * Authors:     Jorge Cwik, <jorge@laser.satlink.net>
   9  *              Arnt Gulbrandsen, <agulbra@nvg.unit.no>
  10  *              Tom May, <ftom@netcom.com>
  11  *              Andreas Schwab, <schwab@issan.informatik.uni-dortmund.de>
  12  *              Lots of code moved from tcp.c and ip.c; see those files
  13  *              for more names.
  14  *
  15  * 03/02/96     Jes Sorensen, Andreas Schwab, Roman Hodek:
  16  *              Fixed some nasty bugs, causing some horrible crashes.
  17  *              A: At some points, the sum (%0) was used as
  18  *              length-counter instead of the length counter
  19  *              (%1). Thanks to Roman Hodek for pointing this out.
  20  *              B: GCC seems to mess up if one uses too many
  21  *              data-registers to hold input values and one tries to
  22  *              specify d0 and d1 as scratch registers. Letting gcc choose these
  23  *      registers itself solves the problem.
  24  *
  25  *              This program is free software; you can redistribute it and/or
  26  *              modify it under the terms of the GNU General Public License
  27  *              as published by the Free Software Foundation; either version
  28  *              2 of the License, or (at your option) any later version.
  29  */
  30
  31 /* Revised by Kenneth Albanowski for m68knommu. Basic problem: unaligned access kills, so most
  32    of the assembly has to go. */
  33
  34 #include <net/checksum.h>
  35 #include <asm/checksum.h>
  36 #include <linux/module.h>
  37
  38 static inline unsigned short from32to16(unsigned long x)
  39 {
  40         /* add up 16-bit and 16-bit for 16+c bit */
  41         x = (x & 0xffff) + (x >> 16);
  42         /* add up carry.. */
  43         x = (x & 0xffff) + (x >> 16);
  44         return x;
  45 }
  46
  47 static unsigned long do_csum(const unsigned char * buff, int len)
  48 {
  49         int odd, count;
  50         unsigned long result = 0;
  51
  52         if (len <= 0)
  53                 goto out;
  54         odd = 1 & (unsigned long) buff;
  55         if (odd) {
  56                 result = *buff;
  57                 len--;
  58                 buff++;
  59         }
  60         count = len >> 1;               /* nr of 16-bit words.. */
  61         if (count) {
  62                 if (2 & (unsigned long) buff) {
  63                         result += *(unsigned short *) buff;
  64                         count--;
  65                         len -= 2;
  66                         buff += 2;
  67                 }
  68                 count >>= 1;            /* nr of 32-bit words.. */
  69                 if (count) {
  70                         unsigned long carry = 0;
  71                         do {
  72                                 unsigned long w = *(unsigned long *) buff;
  73                                 count--;
  74                                 buff += 4;
  75                                 result += carry;
  76                                 result += w;
  77                                 carry = (w > result);
  78                         } while (count);
  79                         result += carry;
  80                         result = (result & 0xffff) + (result >> 16);
  81                 }
  82                 if (len & 2) {
  83                         result += *(unsigned short *) buff;
  84                         buff += 2;
  85                 }
  86         }
  87         if (len & 1)
  88                 result += (*buff << 8);
  89         result = from32to16(result);
  90         if (odd)
  91                 result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);
  92 out:
  93         return result;
  94 }
  95
  96 /*
  97  * computes the checksum of a memory block at buff, length len,
  98  * and adds in "sum" (32-bit)
  99  *
 100  * returns a 32-bit number suitable for feeding into itself
 101  * or csum_tcpudp_magic
 102  *
 103  * this function must be called with even lengths, except
 104  * for the last fragment, which may be odd
 105  *
 106  * it's best to have buff aligned on a 32-bit boundary
 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  * this routine is used for miscellaneous IP-like checksums, mainly
 123  * in icmp.c
 124  */
 125 unsigned short ip_compute_csum(const unsigned char * buff, int len)
 126 {
 127         return ~do_csum(buff, len);
 128 }
 129
 130 EXPORT_SYMBOL(ip_compute_csum);
 131
 132 /*
 133  * copy from fs while checksumming, otherwise like csum_partial
 134  */
 135 unsigned int
 136 csum_partial_copy_from_user(const char __user *src, char *dst,
 137                             int len, int sum, int *csum_err)
 138 {
 139         int rem;
 140
 141         if (csum_err)
 142                 *csum_err = 0;
 143
 144         rem = copy_from_user(dst, src, len);
 145         if (rem != 0) {
 146                 if (csum_err)
 147                         *csum_err = -EFAULT;
 148                 memset(dst + len - rem, 0, rem);
 149                 len = rem;
 150         }
 151
 152         return csum_partial(dst, len, sum);
 153 }
 154
 155 EXPORT_SYMBOL(csum_partial_copy_from_user);
 156
 157 /*
 158  * copy from ds while checksumming, otherwise like csum_partial
 159  */
 160 unsigned int
 161 csum_partial_copy(const char *src, char *dst, int len, int sum)
 162 {
 163         memcpy(dst, src, len);
 164         return csum_partial(dst, len, sum);
 165 }
 166
 167 EXPORT_SYMBOL(csum_partial_copy);