arch/ia64/lib/csum_partial_copy.c

   1 /*
   2  * Network Checksum & Copy routine
   3  *
   4  * Copyright (C) 1999, 2003-2004 Hewlett-Packard Co
   5  *      Stephane Eranian <eranian@hpl.hp.com>
   6  *
   7  * Most of the code has been imported from Linux/Alpha
   8  */
   9
  10 #include <linux/module.h>
  11 #include <linux/types.h>
  12 #include <linux/string.h>
  13
  14 #include <asm/uaccess.h>
  15
  16 /*
  17  * XXX Fixme: those 2 inlines are meant for debugging and will go away
  18  */
  19 static inline unsigned
  20 short from64to16(unsigned long x)
  21 {
  22         /* add up 32-bit words for 33 bits */
  23         x = (x & 0xffffffff) + (x >> 32);
  24         /* add up 16-bit and 17-bit words for 17+c bits */
  25         x = (x & 0xffff) + (x >> 16);
  26         /* add up 16-bit and 2-bit for 16+c bit */
  27         x = (x & 0xffff) + (x >> 16);
  28         /* add up carry.. */
  29         x = (x & 0xffff) + (x >> 16);
  30         return x;
  31 }
  32
  33 static inline
  34 unsigned long do_csum_c(const unsigned char * buff, int len, unsigned int psum)
  35 {
  36         int odd, count;
  37         unsigned long result = (unsigned long)psum;
  38
  39         if (len <= 0)
  40                 goto out;
  41         odd = 1 & (unsigned long) buff;
  42         if (odd) {
  43                 result = *buff << 8;
  44                 len--;
  45                 buff++;
  46         }
  47         count = len >> 1;               /* nr of 16-bit words.. */
  48         if (count) {
  49                 if (2 & (unsigned long) buff) {
  50                         result += *(unsigned short *) buff;
  51                         count--;
  52                         len -= 2;
  53                         buff += 2;
  54                 }
  55                 count >>= 1;            /* nr of 32-bit words.. */
  56                 if (count) {
  57                         if (4 & (unsigned long) buff) {
  58                                 result += *(unsigned int *) buff;
  59                                 count--;
  60                                 len -= 4;
  61                                 buff += 4;
  62                         }
  63                         count >>= 1;    /* nr of 64-bit words.. */
  64                         if (count) {
  65                                 unsigned long carry = 0;
  66                                 do {
  67                                         unsigned long w = *(unsigned long *) buff;
  68                                         count--;
  69                                         buff += 8;
  70                                         result += carry;
  71                                         result += w;
  72                                         carry = (w > result);
  73                                 } while (count);
  74                                 result += carry;
  75                                 result = (result & 0xffffffff) + (result >> 32);
  76                         }
  77                         if (len & 4) {
  78                                 result += *(unsigned int *) buff;
  79                                 buff += 4;
  80                         }
  81                 }
  82                 if (len & 2) {
  83                         result += *(unsigned short *) buff;
  84                         buff += 2;
  85                 }
  86         }
  87         if (len & 1)
  88                 result += *buff;
  89
  90         result = from64to16(result);
  91
  92         if (odd)
  93                 result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);
  94
  95 out:
  96         return result;
  97 }
  98
  99 /*
 100  * XXX Fixme
 101  *
 102  * This is very ugly but temporary. THIS NEEDS SERIOUS ENHANCEMENTS.
 103  * But it's very tricky to get right even in C.
 104  */
 105 extern unsigned long do_csum(const unsigned char *, long);
 106
 107 static unsigned int
 108 do_csum_partial_copy_from_user (const unsigned char __user *src, unsigned char *dst,
 109                                 int len, unsigned int psum, int *errp)
 110 {
 111         unsigned long result;
 112
 113         /* XXX Fixme
 114          * for now we separate the copy from checksum for obvious
 115          * alignment difficulties. Look at the Alpha code and you'll be
 116          * scared.
 117          */
 118
 119         if (__copy_from_user(dst, src, len) != 0 && errp)
 120                 *errp = -EFAULT;
 121
 122         result = do_csum(dst, len);
 123
 124         /* add in old sum, and carry.. */
 125         result += psum;
 126         /* 32+c bits -> 32 bits */
 127         result = (result & 0xffffffff) + (result >> 32);
 128         return result;
 129 }
 130
 131 unsigned int
 132 csum_partial_copy_from_user (const unsigned char __user *src, unsigned char *dst,
 133                              int len, unsigned int sum, int *errp)
 134 {
 135         if (!access_ok(VERIFY_READ, src, len)) {
 136                 *errp = -EFAULT;
 137                 memset(dst, 0, len);
 138                 return sum;
 139         }
 140
 141         return do_csum_partial_copy_from_user(src, dst, len, sum, errp);
 142 }
 143
 144 unsigned int
 145 csum_partial_copy_nocheck(const unsigned char __user *src, unsigned char *dst,
 146                           int len, unsigned int sum)
 147 {
 148         return do_csum_partial_copy_from_user(src, dst, len, sum, NULL);
 149 }
 150
 151 EXPORT_SYMBOL(csum_partial_copy_nocheck);