LXR linux/arch/parisc/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 *              MIPS specific IP/TCP/UDP checksumming routines
   7 *
   8 * Authors:     Ralf Baechle, <ralf@waldorf-gmbh.de>
   9 *              Lots of code moved from tcp.c and ip.c; see those files
  10 *              for more names.
  11 *
  12 *              This program is free software; you can redistribute it and/or
  13 *              modify it under the terms of the GNU General Public License
  14 *              as published by the Free Software Foundation; either version
  15 *              2 of the License, or (at your option) any later version.
  16 *
  17 * $Id: checksum.c,v 1.3 1997/12/01 17:57:34 ralf Exp $
  18 */
  19#include <linux/module.h>
  20#include <linux/types.h>
  21
  22#include <net/checksum.h>
  23#include <asm/byteorder.h>
  24#include <asm/string.h>
  25#include <asm/uaccess.h>
  26
  27#define addc(_t,_r)                     \
  28        __asm__ __volatile__ (          \
  29"       add             %0, %1, %0\n"   \
  30"       addc            %0, %%r0, %0\n" \
  31        : "=r"(_t)                      \
  32        : "r"(_r), "0"(_t));
  33
  34static inline unsigned short from32to16(unsigned int x)
  35{
  36        /* 32 bits --> 16 bits + carry */
  37        x = (x & 0xffff) + (x >> 16);
  38        /* 16 bits + carry --> 16 bits including carry */
  39        x = (x & 0xffff) + (x >> 16);
  40        return (unsigned short)x;
  41}
  42
  43static inline unsigned int do_csum(const unsigned char * buff, int len)
  44{
  45        int odd, count;
  46        unsigned int result = 0;
  47
  48        if (len <= 0)
  49                goto out;
  50        odd = 1 & (unsigned long) buff;
  51        if (odd) {
  52                result = be16_to_cpu(*buff);
  53                len--;
  54                buff++;
  55        }
  56        count = len >> 1;               /* nr of 16-bit words.. */
  57        if (count) {
  58                if (2 & (unsigned long) buff) {
  59                        result += *(unsigned short *) buff;
  60                        count--;
  61                        len -= 2;
  62                        buff += 2;
  63                }
  64                count >>= 1;            /* nr of 32-bit words.. */
  65                if (count) {
  66                        while (count >= 4) {
  67                                unsigned int r1, r2, r3, r4;
  68                                r1 = *(unsigned int *)(buff + 0);
  69                                r2 = *(unsigned int *)(buff + 4);
  70                                r3 = *(unsigned int *)(buff + 8);
  71                                r4 = *(unsigned int *)(buff + 12);
  72                                addc(result, r1);
  73                                addc(result, r2);
  74                                addc(result, r3);
  75                                addc(result, r4);
  76                                count -= 4;
  77                                buff += 16;
  78                        }
  79                        while (count) {
  80                                unsigned int w = *(unsigned int *) buff;
  81                                count--;
  82                                buff += 4;
  83                                addc(result, w);
  84                        }
  85                        result = (result & 0xffff) + (result >> 16);
  86                }
  87                if (len & 2) {
  88                        result += *(unsigned short *) buff;
  89                        buff += 2;
  90                }
  91        }
  92        if (len & 1)
  93                result += le16_to_cpu(*buff);
  94        result = from32to16(result);
  95        if (odd)
  96                result = swab16(result);
  97out:
  98        return result;
  99}
 100
 101/*
 102 * computes a partial checksum, e.g. for TCP/UDP fragments
 103 */
 104/*
 105 * why bother folding?
 106 */
 107__wsum csum_partial(const void *buff, int len, __wsum sum)
 108{
 109        unsigned int result = do_csum(buff, len);
 110        addc(result, sum);
 111        return (__force __wsum)from32to16(result);
 112}
 113
 114EXPORT_SYMBOL(csum_partial);
 115
 116/*
 117 * copy while checksumming, otherwise like csum_partial
 118 */
 119__wsum csum_partial_copy_nocheck(const void *src, void *dst,
 120                                       int len, __wsum sum)
 121{
 122        /*
 123         * It's 2:30 am and I don't feel like doing it real ...
 124         * This is lots slower than the real thing (tm)
 125         */
 126        sum = csum_partial(src, len, sum);
 127        memcpy(dst, src, len);
 128
 129        return sum;
 130}
 131EXPORT_SYMBOL(csum_partial_copy_nocheck);
 132
 133/*
 134 * Copy from userspace and compute checksum.  If we catch an exception
 135 * then zero the rest of the buffer.
 136 */
 137__wsum csum_partial_copy_from_user(const void __user *src,
 138                                        void *dst, int len,
 139                                        __wsum sum, int *err_ptr)
 140{
 141        int missing;
 142
 143        missing = copy_from_user(dst, src, len);
 144        if (missing) {
 145                memset(dst + len - missing, 0, missing);
 146                *err_ptr = -EFAULT;
 147        }
 148                
 149        return csum_partial(dst, len, sum);
 150}
 151EXPORT_SYMBOL(csum_partial_copy_from_user);
 152