LXR linux/arch/metag/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 <linux/module.h>
  36#include <net/checksum.h>
  37
  38#include <asm/byteorder.h>
  39
  40static inline unsigned short from32to16(unsigned int x)
  41{
  42        /* add up 16-bit and 16-bit for 16+c bit */
  43        x = (x & 0xffff) + (x >> 16);
  44        /* add up carry.. */
  45        x = (x & 0xffff) + (x >> 16);
  46        return x;
  47}
  48
  49static unsigned int do_csum(const unsigned char *buff, int len)
  50{
  51        int odd;
  52        unsigned int result = 0;
  53
  54        if (len <= 0)
  55                goto out;
  56        odd = 1 & (unsigned long) buff;
  57        if (odd) {
  58#ifdef __LITTLE_ENDIAN
  59                result += (*buff << 8);
  60#else
  61                result = *buff;
  62#endif
  63                len--;
  64                buff++;
  65        }
  66        if (len >= 2) {
  67                if (2 & (unsigned long) buff) {
  68                        result += *(unsigned short *) buff;
  69                        len -= 2;
  70                        buff += 2;
  71                }
  72                if (len >= 4) {
  73                        const unsigned char *end = buff + ((unsigned)len & ~3);
  74                        unsigned int carry = 0;
  75                        do {
  76                                unsigned int w = *(unsigned int *) buff;
  77                                buff += 4;
  78                                result += carry;
  79                                result += w;
  80                                carry = (w > result);
  81                        } while (buff < end);
  82                        result += carry;
  83                        result = (result & 0xffff) + (result >> 16);
  84                }
  85                if (len & 2) {
  86                        result += *(unsigned short *) buff;
  87                        buff += 2;
  88                }
  89        }
  90        if (len & 1)
  91#ifdef __LITTLE_ENDIAN
  92                result += *buff;
  93#else
  94                result += (*buff << 8);
  95#endif
  96        result = from32to16(result);
  97        if (odd)
  98                result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);
  99out:
 100        return result;
 101}
 102EXPORT_SYMBOL(ip_fast_csum);
 103
 104/*
 105 * computes the checksum of a memory block at buff, length len,
 106 * and adds in "sum" (32-bit)
 107 *
 108 * returns a 32-bit number suitable for feeding into itself
 109 * or csum_tcpudp_magic
 110 *
 111 * this function must be called with even lengths, except
 112 * for the last fragment, which may be odd
 113 *
 114 * it's best to have buff aligned on a 32-bit boundary
 115 */
 116__wsum csum_partial(const void *buff, int len, __wsum wsum)
 117{
 118        unsigned int sum = (__force unsigned int)wsum;
 119        unsigned int result = do_csum(buff, len);
 120
 121        /* add in old sum, and carry.. */
 122        result += sum;
 123        if (sum > result)
 124                result += 1;
 125        return (__force __wsum)result;
 126}
 127EXPORT_SYMBOL(csum_partial);
 128
 129/*
 130 * this routine is used for miscellaneous IP-like checksums, mainly
 131 * in icmp.c
 132 */
 133__sum16 ip_compute_csum(const void *buff, int len)
 134{
 135        return (__force __sum16)~do_csum(buff, len);
 136}
 137EXPORT_SYMBOL(ip_compute_csum);
 138
 139/*
 140 * copy from fs while checksumming, otherwise like csum_partial
 141 */
 142__wsum
 143csum_partial_copy_from_user(const void __user *src, void *dst, int len,
 144                                                __wsum sum, int *csum_err)
 145{
 146        int missing;
 147
 148        missing = __copy_from_user(dst, src, len);
 149        if (missing) {
 150                memset(dst + len - missing, 0, missing);
 151                *csum_err = -EFAULT;
 152        } else
 153                *csum_err = 0;
 154
 155        return csum_partial(dst, len, sum);
 156}
 157EXPORT_SYMBOL(csum_partial_copy_from_user);
 158
 159/*
 160 * copy from ds while checksumming, otherwise like csum_partial
 161 */
 162__wsum
 163csum_partial_copy(const void *src, void *dst, int len, __wsum sum)
 164{
 165        memcpy(dst, src, len);
 166        return csum_partial(dst, len, sum);
 167}
 168EXPORT_SYMBOL(csum_partial_copy);
 169