arch/ia64/lib/csum_partial_copy.c

   1 /*
   2  * Network Checksum & Copy routine
   3  *
   4  * Copyright (C) 1999 Hewlett-Packard Co
   5  * Copyright (C) 1999 Stephane Eranian <eranian@hpl.hp.com>
   6  *
   7  * Most of the code has been imported from Linux/Alpha
   8  */
   9
  10 #include <linux/types.h>
  11 #include <linux/string.h>
  12
  13 #include <asm/uaccess.h>
  14
  15 /*
  16  * XXX Fixme: those 2 inlines are meant for debugging and will go away
  17  */
  18 static inline unsigned
  19 short from64to16(unsigned long x)
  20 {
  21         /* add up 32-bit words for 33 bits */
  22         x = (x & 0xffffffff) + (x >> 32);
  23         /* add up 16-bit and 17-bit words for 17+c bits */
  24         x = (x & 0xffff) + (x >> 16);
  25         /* add up 16-bit and 2-bit for 16+c bit */
  26         x = (x & 0xffff) + (x >> 16);
  27         /* add up carry.. */
  28         x = (x & 0xffff) + (x >> 16);
  29         return x;
  30 }
  31
  32 static inline
  33 unsigned long do_csum_c(const unsigned char * buff, int len, unsigned int psum)
  34 {
  35         int odd, count;
  36         unsigned long result = (unsigned long)psum;
  37
  38         if (len <= 0)
  39                 goto out;
  40         odd = 1 & (unsigned long) buff;
  41         if (odd) {
  42                 result = *buff << 8;
  43                 len--;
  44                 buff++;
  45         }
  46         count = len >> 1;               /* nr of 16-bit words.. */
  47         if (count) {
  48                 if (2 & (unsigned long) buff) {
  49                         result += *(unsigned short *) buff;
  50                         count--;
  51                         len -= 2;
  52                         buff += 2;
  53                 }
  54                 count >>= 1;            /* nr of 32-bit words.. */
  55                 if (count) {
  56                         if (4 & (unsigned long) buff) {
  57                                 result += *(unsigned int *) buff;
  58                                 count--;
  59                                 len -= 4;
  60                                 buff += 4;
  61                         }
  62                         count >>= 1;    /* nr of 64-bit words.. */
  63                         if (count) {
  64                                 unsigned long carry = 0;
  65                                 do {
  66                                         unsigned long w = *(unsigned long *) buff;
  67                                         count--;
  68                                         buff += 8;
  69                                         result += carry;
  70                                         result += w;
  71                                         carry = (w > result);
  72                                 } while (count);
  73                                 result += carry;
  74                                 result = (result & 0xffffffff) + (result >> 32);
  75                         }
  76                         if (len & 4) {
  77                                 result += *(unsigned int *) buff;
  78                                 buff += 4;
  79                         }
  80                 }
  81                 if (len & 2) {
  82                         result += *(unsigned short *) buff;
  83                         buff += 2;
  84                 }
  85         }
  86         if (len & 1)
  87                 result += *buff;
  88
  89         result = from64to16(result);
  90
  91         if (odd)
  92                 result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);
  93
  94 out:
  95         return result;
  96 }
  97
  98 /*
  99  * XXX Fixme
 100  *
 101  * This is very ugly but temporary. THIS NEEDS SERIOUS ENHANCEMENTS.
 102  * But it's very tricky to get right even in C.
 103  */
 104 extern unsigned long do_csum(const unsigned char *, int);
 105
 106 static unsigned int
 107 do_csum_partial_copy_from_user (const char *src, char *dst, int len,
 108                                 unsigned int psum, int *errp)
 109 {
 110         const unsigned char *psrc = src;
 111         unsigned long result;
 112         int cplen = len;
 113         int r = 0;
 114
 115         /* XXX Fixme
 116          * for now we separate the copy from checksum for obvious
 117          * alignment difficulties. Look at the Alpha code and you'll be
 118          * scared.
 119          */
 120
 121         while ( cplen-- ) r |=__get_user(*dst++,psrc++);
 122
 123         if ( r && errp ) *errp = r;
 124
 125         result = do_csum(src, len);
 126
 127         /* add in old sum, and carry.. */
 128         result += psum;
 129         /* 32+c bits -> 32 bits */
 130         result = (result & 0xffffffff) + (result >> 32);
 131         return result;
 132 }
 133
 134 unsigned int
 135 csum_partial_copy_from_user(const char *src, char *dst, int len,
 136                             unsigned int sum, int *errp)
 137 {
 138         if (!access_ok(src, len, VERIFY_READ)) {
 139                 *errp = -EFAULT;
 140                 memset(dst, 0, len);
 141                 return sum;
 142         }
 143
 144         return do_csum_partial_copy_from_user(src, dst, len, sum, errp);
 145 }
 146
 147 unsigned int
 148 csum_partial_copy_nocheck(const char *src, char *dst, int len, unsigned int sum)
 149 {
 150         return do_csum_partial_copy_from_user(src, dst, len, sum, NULL);
 151 }
 152
 153 unsigned int
 154 csum_partial_copy (const char *src, char *dst, int len, unsigned int sum)
 155 {
 156         unsigned int ret;
 157         int error = 0;
 158
 159         ret = do_csum_partial_copy_from_user(src, dst, len, sum, &error);
 160         if (error)
 161                 printk("csum_partial_copy_old(): tell mingo to convert me!\n");
 162
 163         return ret;
 164 }
 165