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
  32 static 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
  41 static 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);
  95 out:
  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
 112 EXPORT_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 }
 129 EXPORT_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 }
 149 EXPORT_SYMBOL(csum_partial_copy_from_user);