arch/microblaze/lib/checksum.c

   1 /*
   2  *
   3  * INET         An implementation of the TCP/IP protocol suite for the LINUX
   4  *              operating system.  INET is implemented using the  BSD Socket
   5  *              interface as the means of communication with the user level.
   6  *
   7  *              IP/TCP/UDP checksumming routines
   8  *
   9  * Authors:     Jorge Cwik, <jorge@laser.satlink.net>
  10  *              Arnt Gulbrandsen, <agulbra@nvg.unit.no>
  11  *              Tom May, <ftom@netcom.com>
  12  *              Andreas Schwab, <schwab@issan.informatik.uni-dortmund.de>
  13  *              Lots of code moved from tcp.c and ip.c; see those files
  14  *              for more names.
  15  *
  16  * 03/02/96     Jes Sorensen, Andreas Schwab, Roman Hodek:
  17  *              Fixed some nasty bugs, causing some horrible crashes.
  18  *              A: At some points, the sum (%0) was used as
  19  *              length-counter instead of the length counter
  20  *              (%1). Thanks to Roman Hodek for pointing this out.
  21  *              B: GCC seems to mess up if one uses too many
  22  *              data-registers to hold input values and one tries to
  23  *              specify d0 and d1 as scratch registers. Letting gcc
  24  *              choose these registers itself solves the problem.
  25  *
  26  *              This program is free software; you can redistribute it and/or
  27  *              modify it under the terms of the GNU General Public License
  28  *              as published by the Free Software Foundation; either version
  29  *              2 of the License, or (at your option) any later version.
  30  */
  31
  32 /* Revised by Kenneth Albanowski for m68knommu. Basic problem: unaligned access
  33  kills, so most of the assembly has to go. */
  34
  35 #include <net/checksum.h>
  36 #include <asm/checksum.h>
  37 #include <linux/module.h>
  38
  39 static inline unsigned short from32to16(unsigned long x)
  40 {
  41         /* add up 16-bit and 16-bit for 16+c bit */
  42         x = (x & 0xffff) + (x >> 16);
  43         /* add up carry.. */
  44         x = (x & 0xffff) + (x >> 16);
  45         return x;
  46 }
  47
  48 static unsigned int do_csum(const unsigned char *buff, int len)
  49 {
  50         int odd, count;
  51         unsigned long result = 0;
  52
  53         if (len <= 0)
  54                 goto out;
  55         odd = 1 & (unsigned long) buff;
  56         if (odd) {
  57                 result = *buff;
  58                 len--;
  59                 buff++;
  60         }
  61         count = len >> 1;               /* nr of 16-bit words.. */
  62         if (count) {
  63                 if (2 & (unsigned long) buff) {
  64                         result += *(unsigned short *) buff;
  65                         count--;
  66                         len -= 2;
  67                         buff += 2;
  68                 }
  69                 count >>= 1;            /* nr of 32-bit words.. */
  70                 if (count) {
  71                         unsigned long carry = 0;
  72                         do {
  73                                 unsigned long w = *(unsigned long *) buff;
  74                                 count--;
  75                                 buff += 4;
  76                                 result += carry;
  77                                 result += w;
  78                                 carry = (w > result);
  79                         } while (count);
  80                         result += carry;
  81                         result = (result & 0xffff) + (result >> 16);
  82                 }
  83                 if (len & 2) {
  84                         result += *(unsigned short *) buff;
  85                         buff += 2;
  86                 }
  87         }
  88         if (len & 1)
  89                 result += (*buff << 8);
  90         result = from32to16(result);
  91         if (odd)
  92                 result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);
  93 out:
  94         return result;
  95 }
  96
  97 /*
  98  *      This is a version of ip_compute_csum() optimized for IP headers,
  99  *      which always checksum on 4 octet boundaries.
 100  */
 101 __sum16 ip_fast_csum(const void *iph, unsigned int ihl)
 102 {
 103         return (__force __sum16)~do_csum(iph, ihl*4);
 104 }
 105
 106 /*
 107  * computes the checksum of a memory block at buff, length len,
 108  * and adds in "sum" (32-bit)
 109  *
 110  * returns a 32-bit number suitable for feeding into itself
 111  * or csum_tcpudp_magic
 112  *
 113  * this function must be called with even lengths, except
 114  * for the last fragment, which may be odd
 115  *
 116  * it's best to have buff aligned on a 32-bit boundary
 117  */
 118 __wsum csum_partial(const void *buff, int len, __wsum sum)
 119 {
 120         unsigned int result = do_csum(buff, len);
 121
 122         /* add in old sum, and carry.. */
 123         result += sum;
 124         if (sum > result)
 125                 result += 1;
 126         return result;
 127 }
 128 EXPORT_SYMBOL(csum_partial);
 129
 130 /*
 131  * this routine is used for miscellaneous IP-like checksums, mainly
 132  * in icmp.c
 133  */
 134 __sum16 ip_compute_csum(const unsigned char *buff, int len)
 135 {
 136         return ~do_csum(buff, len);
 137 }
 138 EXPORT_SYMBOL(ip_compute_csum);
 139
 140 /*
 141  * copy from fs while checksumming, otherwise like csum_partial
 142  */
 143 __wsum
 144 csum_partial_copy_from_user(const char __user *src, char *dst, int len,
 145                                                 int sum, int *csum_err)
 146 {
 147         if (csum_err)
 148                 *csum_err = 0;
 149         memcpy(dst, src, len);
 150         return csum_partial(dst, len, sum);
 151 }
 152 EXPORT_SYMBOL(csum_partial_copy_from_user);
 153
 154 /*
 155  * copy from ds while checksumming, otherwise like csum_partial
 156  */
 157 __wsum
 158 csum_partial_copy(const char *src, char *dst, int len, int sum)
 159 {
 160         memcpy(dst, src, len);
 161         return csum_partial(dst, len, sum);
 162 }
 163 EXPORT_SYMBOL(csum_partial_copy);