arch/s390/lib/checksum.c

   1 /*
   2  *  arch/s390/lib/checksum.c
   3  *    S390 fast network checksum routines
   4  *
   5  *  S390 version
   6  *    Copyright (C) 1999 IBM Deutschland Entwicklung GmbH, IBM Corporation
   7  *    Author(s): Ulrich Hild        (first version),
   8  *               Martin Schwidefsky (schwidefsky@de.ibm.com),
   9  *               Denis Joseph Barrow (djbarrow@de.ibm.com,barrow_dj@yahoo.com),
  10  *
  11  * This file contains network checksum routines
  12  */
  13
  14 #include <linux/string.h>
  15 #include <linux/types.h>
  16 #include <asm/uaccess.h>
  17 #include <asm/byteorder.h>
  18 #include <asm/checksum.h>
  19
  20 /*
  21  * computes a partial checksum, e.g. for TCP/UDP fragments
  22  */
  23 unsigned int
  24 csum_partial (const unsigned char *buff, int len, unsigned int sum)
  25 {
  26           /*
  27            * Experiments with ethernet and slip connections show that buff
  28            * is aligned on either a 2-byte or 4-byte boundary.
  29            */
  30         __asm__ __volatile__ (
  31                 "    lr   2,%1\n"    /* address in gpr 2 */
  32                 "    lr   3,%2\n"    /* length in gpr 3 */
  33                 "0:  cksm %0,2\n"    /* do checksum on longs */
  34                 "    jo   0b\n"
  35                 : "+&d" (sum)
  36                 : "d" (buff), "d" (len)
  37                 : "cc", "2", "3" );
  38         return sum;
  39 }
  40
  41 /*
  42  *      Fold a partial checksum without adding pseudo headers
  43  */
  44 unsigned short csum_fold(unsigned int sum)
  45 {
  46         __asm__ __volatile__ (
  47                 "    sr   3,3\n"   /* %0 = H*65536 + L */
  48                 "    lr   2,%0\n"  /* %0 = H L, R2/R3 = H L / 0 0 */
  49                 "    srdl 2,16\n"  /* %0 = H L, R2/R3 = 0 H / L 0 */
  50                 "    alr  2,3\n"   /* %0 = H L, R2/R3 = L H / L 0 */
  51                 "    alr  %0,2\n"  /* %0 = H+L+C L+H */
  52                 "    srl  %0,16\n" /* %0 = H+L+C */
  53                 : "+d" (sum) : : "cc", "2", "3");
  54         return ((unsigned short) ~sum);
  55 }
  56