LXR linux/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
  18static 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}
  52EXPORT_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}
  70EXPORT_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 */
  79static 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);
 137out:
 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}
 149EXPORT_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
 174EXPORT_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}
 184EXPORT_SYMBOL(ip_compute_csum);
 185