LXR linux/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
  37static 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
  46static 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);
  91out:
  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
 118EXPORT_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
 129EXPORT_SYMBOL(ip_compute_csum);
 130
 131/*
 132 * copy from fs while checksumming, otherwise like csum_partial
 133 */
 134__wsum
 135csum_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
 154EXPORT_SYMBOL(csum_partial_copy_from_user);
 155
 156/*
 157 * copy from ds while checksumming, otherwise like csum_partial
 158 */
 159__wsum
 160csum_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
 166EXPORT_SYMBOL(csum_partial_copy_nocheck);
 167