usr/src/sys/tahoe/tahoe/in_cksum.c

/*
 * Copyright (c) 1982, 1988 Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *      @(#)in_cksum.c  7.6 (Berkeley) 12/16/90
 */

#include "sys/param.h"
#include "sys/mbuf.h"

/*
 * Checksum routine for Internet Protocol family headers (CCI Version).
 *
 * This routine is very heavily used in the network
 * code and should be modified for each CPU to be as fast as possible.
 */

#define ADDCARRY(x)  { if ((x) > 65535) (x) -= 65535; }
#define REDUCE {l_util.l = sum; sum = l_util.s[0] + l_util.s[1]; ADDCARRY(sum);}

#define ADD(n)  asm("adwc n (r10),r9")
#define MOP     asm("adwc $0,r9")
#define BOTCH   asm("addl2 r7,r9")

in_cksum(m, len)
        register struct mbuf *m;
        register int len;
{
        register u_short *w;            /* On CCI, known to be r10 */
        register int sum = 0;           /* On CCI, known to be r9 */
        register int mlen = 0;
#ifndef lint
        register int ClearCarry = 0;    /* On CCI, known to be r7; see BOTCH */
#endif
        int byte_swapped = 0;

        union {
                char    c[2];
                u_short s;
        } s_util;
        union {
                u_short s[2];
                long    l;
        } l_util;

        for (;m && len; m = m->m_next) {
                if (m->m_len == 0)
                        continue;
                w = mtod(m, u_short *);
                if (mlen == -1) {
                        /*
                         * The first byte of this mbuf is the continuation
                         * of a word spanning between this mbuf and the
                         * last mbuf.
                         *
                         * s_util.c[0] is already saved when scanning previous
                         * mbuf.  sum was REDUCEd when we found mlen == -1.
                         */
                        s_util.c[1] = *(char *)w;
                        sum += s_util.s;
                        w = (u_short *)((char *)w + 1);
                        mlen = m->m_len - 1;
                        len--;
                } else
                        mlen = m->m_len;
                if (len < mlen)
                        mlen = len;
                len -= mlen;
                /*
                 * Force to long boundary so we do longword aligned
                 * memory operations.
                 */
                if (3 & (int) w) {
                        REDUCE;
                        if ((1 & (int) w) && (mlen > 0)) {
                                sum <<= 8;
                                s_util.c[0] = *(char *)w;
                                w = (u_short *)((char *)w + 1);
                                mlen--;
                                byte_swapped = 1;
                        }
                        if ((2 & (int) w) && (mlen >= 2)) {
                                sum += *w++;
                                mlen -= 2;
                        }
                }
                /*
                 * Do as much of the checksum as possible 32 bits at at time.
                 * In fact, this loop is unrolled to make overhead from
                 * branches &c small.
                 */
                while ((mlen -= 32) >= 0) {
                        /*
                         * The loop construct clears carry for us
                         * on vaxen, however, on the CCI machine subtracting
                         * a small postive number from a larger one doesn't.
                         *
                         * Doing a bicpsw is very slow (slows down the routine
                         * by a factor of 2); explicitly adding an immediate
                         * 0 to a register is optimized out; so we fake out
                         * the optimizer and add a register whose contents
                         * is always zero.
                         */
                        BOTCH;
                        ADD(0); ADD(4); ADD(8); ADD(12);
                        ADD(16); ADD(20); ADD(24); ADD(28);
                        MOP; w += 16;
                }
                mlen += 32;
                while ((mlen -= 8) >= 0) {
                        BOTCH;
                        ADD(0); ADD(4);
                        MOP;
                        w += 4;
                }
                mlen += 8;
                if (mlen == 0 && byte_swapped == 0)
                        continue;       /* worth 1% maybe ?? */
                REDUCE;
                while ((mlen -= 2) >= 0) {
                        sum += *w++;
                }
                if (byte_swapped) {
                        sum <<= 8;
                        byte_swapped = 0;
                        if (mlen == -1) {
                                s_util.c[1] = *(char *)w;
                                sum += s_util.s;
                                mlen = 0;
                        } else
                                mlen = -1;
                } else if (mlen == -1)
                        /*
                         * This mbuf has odd number of bytes.
                         * There could be a word split betwen
                         * this mbuf and the next mbuf.
                         * Save the last byte (to prepend to next mbuf).
                         */
                        s_util.c[0] = *(char *)w;
        }
        if (len)
                printf("cksum: out of data\n");
        if (mlen == -1) {
                /* The last mbuf has odd # of bytes. Follow the
                   standard (the odd byte is shifted left by 8 bits) */
                s_util.c[1] = 0;
                sum += s_util.s;
        }
        REDUCE;
        return (~sum & 0xffff);
}