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 <linux/module.h>
  36
  37 static inline unsigned short from32to16(unsigned long x)
  38 {
  39         /* add up 16-bit and 16-bit for 16+c bit */
  40         x = (x & 0xffff) + (x >> 16);
  41         /* add up carry.. */
  42         x = (x & 0xffff) + (x >> 16);
  43         return x;
  44 }
  45
  46 static unsigned long do_csum(const unsigned char * buff, int len)
  47 {
  48         int odd, count;
  49         unsigned long result = 0;
  50
  51         if (len <= 0)
  52                 goto out;
  53         odd = 1 & (unsigned long) buff;
  54         if (odd) {
  55                 result = *buff;
  56                 len--;
  57                 buff++;
  58         }
  59         count = len >> 1;               /* nr of 16-bit words.. */
  60         if (count) {
  61                 if (2 & (unsigned long) buff) {
  62                         result += *(unsigned short *) buff;
  63                         count--;
  64                         len -= 2;
  65                         buff += 2;
  66                 }
  67                 count >>= 1;            /* nr of 32-bit words.. */
  68                 if (count) {
  69                         unsigned long carry = 0;
  70                         do {
  71                                 unsigned long w = *(unsigned long *) buff;
  72                                 count--;
  73                                 buff += 4;
  74                                 result += carry;
  75                                 result += w;
  76                                 carry = (w > result);
  77                         } while (count);
  78                         result += carry;
  79                         result = (result & 0xffff) + (result >> 16);
  80                 }
  81                 if (len & 2) {
  82                         result += *(unsigned short *) buff;
  83                         buff += 2;
  84                 }
  85         }
  86         if (len & 1)
  87                 result += (*buff << 8);
  88         result = from32to16(result);
  89         if (odd)
  90                 result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);
  91 out:
  92         return result;
  93 }
  94
  95 /*
  96  * computes the checksum of a memory block at buff, length len,
  97  * and adds in "sum" (32-bit)
  98  *
  99  * returns a 32-bit number suitable for feeding into itself
 100  * or csum_tcpudp_magic
 101  *
 102  * this function must be called with even lengths, except
 103  * for the last fragment, which may be odd
 104  *
 105  * it's best to have buff aligned on a 32-bit boundary
 106  */
 107 __wsum csum_partial(const void *buff, int len, __wsum sum)
 108 {
 109         unsigned int result = do_csum(buff, len);
 110
 111         /* add in old sum, and carry.. */
 112         result += (__force u32)sum;
 113         if ((__force u32)sum > result)
 114                 result += 1;
 115         return (__force __wsum)result;
 116 }
 117
 118 EXPORT_SYMBOL(csum_partial);
 119
 120 /*
 121  * this routine is used for miscellaneous IP-like checksums, mainly
 122  * in icmp.c
 123  */
 124 __sum16 ip_compute_csum(const void *buff, int len)
 125 {
 126         return (__force __sum16)~do_csum(buff, len);
 127 }
 128
 129 EXPORT_SYMBOL(ip_compute_csum);
 130
 131 /*
 132  * copy from fs while checksumming, otherwise like csum_partial
 133  */
 134 __wsum
 135 csum_partial_copy_from_user(const void __user *src, void *dst,
 136                             int len, __wsum sum, int *csum_err)
 137 {
 138         int rem;
 139
 140         if (csum_err)
 141                 *csum_err = 0;
 142
 143         rem = copy_from_user(dst, src, len);
 144         if (rem != 0) {
 145                 if (csum_err)
 146                         *csum_err = -EFAULT;
 147                 memset(dst + len - rem, 0, rem);
 148                 len = rem;
 149         }
 150
 151         return csum_partial(dst, len, sum);
 152 }
 153
 154 EXPORT_SYMBOL(csum_partial_copy_from_user);
 155
 156 /*
 157  * copy from ds while checksumming, otherwise like csum_partial
 158  */
 159 __wsum
 160 csum_partial_copy_nocheck(const void *src, void *dst, int len, __wsum sum)
 161 {
 162         memcpy(dst, src, len);
 163         return csum_partial(dst, len, sum);
 164 }
 165
 166 EXPORT_SYMBOL(csum_partial_copy_nocheck);