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/*

 *  arch/s390/lib/checksum.c

 *    S390 fast network checksum routines

 *

 *  S390 version

 *    Copyright (C) 1999 IBM Deutschland Entwicklung GmbH, IBM Corporation

 *    Author(s): Ulrich Hild        (first version),

 *               Martin Schwidefsky (schwidefsky@de.ibm.com),

 *               Denis Joseph Barrow (djbarrow@de.ibm.com,barrow_dj@yahoo.com),

 *

 * This file contains network checksum routines

 */

#include <linux/string.h>

#include <linux/types.h>

#include <asm/uaccess.h>

#include <asm/byteorder.h>

#include <asm/checksum.h>

/*

 * computes a partial checksum, e.g. for TCP/UDP fragments

 */

unsigned int

csum_partial (const unsigned char *buff, int len, unsigned int sum)

{

        register_pair rp;

          /*

           * Experiments with ethernet and slip connections show that buff

           * is aligned on either a 2-byte or 4-byte boundary.

           */

        rp.subreg.even = (unsigned long) buff;

        rp.subreg.odd = (unsigned long) len;

        __asm__ __volatile__ (

                "0:  cksm %0,%1\n"    /* do checksum on longs */

                "    jo   0b\n"

                : "+&d" (sum), "+&a" (rp) : : "cc" );

        return sum;

}

/*

 *      Fold a partial checksum without adding pseudo headers

 */

unsigned short csum_fold(unsigned int sum)

{

        register_pair rp;

        __asm__ __volatile__ (

                "    slr  %N1,%N1\n" /* %0 = H L */

                "    lr   %1,%0\n"   /* %0 = H L, %1 = H L 0 0 */

                "    srdl %1,16\n"   /* %0 = H L, %1 = 0 H L 0 */

                "    alr  %1,%N1\n"  /* %0 = H L, %1 = L H L 0 */

                "    alr  %0,%1\n"   /* %0 = H+L+C L+H */

                "    srl  %0,16\n"   /* %0 = H+L+C */

                : "+&d" (sum), "=d" (rp) : : "cc" );

        return ((unsigned short) ~sum);

}