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#include <linux/module.h>
  18#include <linux/types.h>
  19
  20#include <net/checksum.h>
  21#include <asm/byteorder.h>
  22#include <asm/string.h>
  23#include <asm/uaccess.h>
  24
  25#define addc(_t,_r)                     \
  26        __asm__ __volatile__ (          \
  27"       add             %0, %1, %0\n"   \
  28"       addc            %0, %%r0, %0\n" \
  29        : "=r"(_t)                      \
  30        : "r"(_r), "0"(_t));
  31
  32static inline unsigned short from32to16(unsigned int x)
  33{
  34        /* 32 bits --> 16 bits + carry */
  35        x = (x & 0xffff) + (x >> 16);
  36        /* 16 bits + carry --> 16 bits including carry */
  37        x = (x & 0xffff) + (x >> 16);
  38        return (unsigned short)x;
  39}
  40
  41static inline unsigned int do_csum(const unsigned char * buff, int len)
  42{
  43        int odd, count;
  44        unsigned int result = 0;
  45
  46        if (len <= 0)
  47                goto out;
  48        odd = 1 & (unsigned long) buff;
  49        if (odd) {
  50                result = be16_to_cpu(*buff);
  51                len--;
  52                buff++;
  53        }
  54        count = len >> 1;               /* nr of 16-bit words.. */
  55        if (count) {
  56                if (2 & (unsigned long) buff) {
  57                        result += *(unsigned short *) buff;
  58                        count--;
  59                        len -= 2;
  60                        buff += 2;
  61                }
  62                count >>= 1;            /* nr of 32-bit words.. */
  63                if (count) {
  64                        while (count >= 4) {
  65                                unsigned int r1, r2, r3, r4;
  66                                r1 = *(unsigned int *)(buff + 0);
  67                                r2 = *(unsigned int *)(buff + 4);
  68                                r3 = *(unsigned int *)(buff + 8);
  69                                r4 = *(unsigned int *)(buff + 12);
  70                                addc(result, r1);
  71                                addc(result, r2);
  72                                addc(result, r3);
  73                                addc(result, r4);
  74                                count -= 4;
  75                                buff += 16;
  76                        }
  77                        while (count) {
  78                                unsigned int w = *(unsigned int *) buff;
  79                                count--;
  80                                buff += 4;
  81                                addc(result, w);
  82                        }
  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                result += le16_to_cpu(*buff);
  92        result = from32to16(result);
  93        if (odd)
  94                result = swab16(result);
  95out:
  96        return result;
  97}
  98
  99/*
 100 * computes a partial checksum, e.g. for TCP/UDP fragments
 101 */
 102/*
 103 * why bother folding?
 104 */
 105__wsum csum_partial(const void *buff, int len, __wsum sum)
 106{
 107        unsigned int result = do_csum(buff, len);
 108        addc(result, sum);
 109        return (__force __wsum)from32to16(result);
 110}
 111
 112EXPORT_SYMBOL(csum_partial);
 113
 114/*
 115 * copy while checksumming, otherwise like csum_partial
 116 */
 117__wsum csum_partial_copy_nocheck(const void *src, void *dst,
 118                                       int len, __wsum sum)
 119{
 120        /*
 121         * It's 2:30 am and I don't feel like doing it real ...
 122         * This is lots slower than the real thing (tm)
 123         */
 124        sum = csum_partial(src, len, sum);
 125        memcpy(dst, src, len);
 126
 127        return sum;
 128}
 129EXPORT_SYMBOL(csum_partial_copy_nocheck);
 130
 131/*
 132 * Copy from userspace and compute checksum.  If we catch an exception
 133 * then zero the rest of the buffer.
 134 */
 135__wsum csum_partial_copy_from_user(const void __user *src,
 136                                        void *dst, int len,
 137                                        __wsum sum, int *err_ptr)
 138{
 139        int missing;
 140
 141        missing = copy_from_user(dst, src, len);
 142        if (missing) {
 143                memset(dst + len - missing, 0, missing);
 144                *err_ptr = -EFAULT;
 145        }
 146                
 147        return csum_partial(dst, len, sum);
 148}
 149EXPORT_SYMBOL(csum_partial_copy_from_user);
 150