arch/alpha/lib/checksum.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * arch/alpha/lib/checksum.c
   4  *
   5  * This file contains network checksum routines that are better done
   6  * in an architecture-specific manner due to speed..
   7  * Comments in other versions indicate that the algorithms are from RFC1071
   8  *
   9  * accelerated versions (and 21264 assembly versions ) contributed by
  10  *      Rick Gorton     <rick.gorton@alpha-processor.com>
  11  */
  12
  13 #include <linux/module.h>
  14 #include <linux/string.h>
  15
  16 #include <asm/byteorder.h>
  17
  18 static inline unsigned short from64to16(unsigned long x)
  19 {
  20         /* Using extract instructions is a bit more efficient
  21            than the original shift/bitmask version.  */
  22
  23         union {
  24                 unsigned long   ul;
  25                 unsigned int    ui[2];
  26                 unsigned short  us[4];
  27         } in_v, tmp_v, out_v;
  28
  29         in_v.ul = x;
  30         tmp_v.ul = (unsigned long) in_v.ui[0] + (unsigned long) in_v.ui[1];
  31
  32         /* Since the bits of tmp_v.sh[3] are going to always be zero,
  33            we don't have to bother to add that in.  */
  34         out_v.ul = (unsigned long) tmp_v.us[0] + (unsigned long) tmp_v.us[1]
  35                         + (unsigned long) tmp_v.us[2];
  36
  37         /* Similarly, out_v.us[2] is always zero for the final add.  */
  38         return out_v.us[0] + out_v.us[1];
  39 }
  40
  41 /*
  42  * computes the checksum of the TCP/UDP pseudo-header
  43  * returns a 16-bit checksum, already complemented.
  44  */
  45 __sum16 csum_tcpudp_magic(__be32 saddr, __be32 daddr,
  46                           __u32 len, __u8 proto, __wsum sum)
  47 {
  48         return (__force __sum16)~from64to16(
  49                 (__force u64)saddr + (__force u64)daddr +
  50                 (__force u64)sum + ((len + proto) << 8));
  51 }
  52 EXPORT_SYMBOL(csum_tcpudp_magic);
  53
  54 __wsum csum_tcpudp_nofold(__be32 saddr, __be32 daddr,
  55                           __u32 len, __u8 proto, __wsum sum)
  56 {
  57         unsigned long result;
  58
  59         result = (__force u64)saddr + (__force u64)daddr +
  60                  (__force u64)sum + ((len + proto) << 8);
  61
  62         /* Fold down to 32-bits so we don't lose in the typedef-less
  63            network stack.  */
  64         /* 64 to 33 */
  65         result = (result & 0xffffffff) + (result >> 32);
  66         /* 33 to 32 */
  67         result = (result & 0xffffffff) + (result >> 32);
  68         return (__force __wsum)result;
  69 }
  70 EXPORT_SYMBOL(csum_tcpudp_nofold);
  71
  72 /*
  73  * Do a 64-bit checksum on an arbitrary memory area..
  74  *
  75  * This isn't a great routine, but it's not _horrible_ either. The
  76  * inner loop could be unrolled a bit further, and there are better
  77  * ways to do the carry, but this is reasonable.
  78  */
  79 static inline unsigned long do_csum(const unsigned char * buff, int len)
  80 {
  81         int odd, count;
  82         unsigned long result = 0;
  83
  84         if (len <= 0)
  85                 goto out;
  86         odd = 1 & (unsigned long) buff;
  87         if (odd) {
  88                 result = *buff << 8;
  89                 len--;
  90                 buff++;
  91         }
  92         count = len >> 1;               /* nr of 16-bit words.. */
  93         if (count) {
  94                 if (2 & (unsigned long) buff) {
  95                         result += *(unsigned short *) buff;
  96                         count--;
  97                         len -= 2;
  98                         buff += 2;
  99                 }
 100                 count >>= 1;            /* nr of 32-bit words.. */
 101                 if (count) {
 102                         if (4 & (unsigned long) buff) {
 103                                 result += *(unsigned int *) buff;
 104                                 count--;
 105                                 len -= 4;
 106                                 buff += 4;
 107                         }
 108                         count >>= 1;    /* nr of 64-bit words.. */
 109                         if (count) {
 110                                 unsigned long carry = 0;
 111                                 do {
 112                                         unsigned long w = *(unsigned long *) buff;
 113                                         count--;
 114                                         buff += 8;
 115                                         result += carry;
 116                                         result += w;
 117                                         carry = (w > result);
 118                                 } while (count);
 119                                 result += carry;
 120                                 result = (result & 0xffffffff) + (result >> 32);
 121                         }
 122                         if (len & 4) {
 123                                 result += *(unsigned int *) buff;
 124                                 buff += 4;
 125                         }
 126                 }
 127                 if (len & 2) {
 128                         result += *(unsigned short *) buff;
 129                         buff += 2;
 130                 }
 131         }
 132         if (len & 1)
 133                 result += *buff;
 134         result = from64to16(result);
 135         if (odd)
 136                 result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);
 137 out:
 138         return result;
 139 }
 140
 141 /*
 142  *      This is a version of ip_compute_csum() optimized for IP headers,
 143  *      which always checksum on 4 octet boundaries.
 144  */
 145 __sum16 ip_fast_csum(const void *iph, unsigned int ihl)
 146 {
 147         return (__force __sum16)~do_csum(iph,ihl*4);
 148 }
 149 EXPORT_SYMBOL(ip_fast_csum);
 150
 151 /*
 152  * computes the checksum of a memory block at buff, length len,
 153  * and adds in "sum" (32-bit)
 154  *
 155  * returns a 32-bit number suitable for feeding into itself
 156  * or csum_tcpudp_magic
 157  *
 158  * this function must be called with even lengths, except
 159  * for the last fragment, which may be odd
 160  *
 161  * it's best to have buff aligned on a 32-bit boundary
 162  */
 163 __wsum csum_partial(const void *buff, int len, __wsum sum)
 164 {
 165         unsigned long result = do_csum(buff, len);
 166
 167         /* add in old sum, and carry.. */
 168         result += (__force u32)sum;
 169         /* 32+c bits -> 32 bits */
 170         result = (result & 0xffffffff) + (result >> 32);
 171         return (__force __wsum)result;
 172 }
 173
 174 EXPORT_SYMBOL(csum_partial);
 175
 176 /*
 177  * this routine is used for miscellaneous IP-like checksums, mainly
 178  * in icmp.c
 179  */
 180 __sum16 ip_compute_csum(const void *buff, int len)
 181 {
 182         return (__force __sum16)~from64to16(do_csum(buff,len));
 183 }
 184 EXPORT_SYMBOL(ip_compute_csum);