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disklabel.c revision 1.1 
      1 /*-
      2  * Copyright (c) 1993
      3  *	The Regents of the University of California.  All rights reserved.
      4  *
      5  * Redistribution and use in source and binary forms, with or without
      6  * modification, are permitted provided that the following conditions
      7  * are met:
      8  * 1. Redistributions of source code must retain the above copyright
      9  *    notice, this list of conditions and the following disclaimer.
     10  * 2. Redistributions in binary form must reproduce the above copyright
     11  *    notice, this list of conditions and the following disclaimer in the
     12  *    documentation and/or other materials provided with the distribution.
     13  * 3. All advertising materials mentioning features or use of this software
     14  *    must display the following acknowledgement:
     15  *	This product includes software developed by the University of
     16  *	California, Berkeley and its contributors.
     17  * 4. Neither the name of the University nor the names of its contributors
     18  *    may be used to endorse or promote products derived from this software
     19  *    without specific prior written permission.
     20  *
     21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     31  * SUCH DAMAGE.
     32  *
     33  *	from: @(#)disklabel.c	8.1 (Berkeley) 6/11/93
     34  *	      $Id: disklabel.c,v 1.1 1994/01/26 02:03:42 brezak Exp $
     35  */
     36 
     37 #include <sys/param.h>
     38 #include <sys/disklabel.h>
     39 
     40 char *
     41 getdisklabel(buf, lp)
     42 	const char *buf;
     43 	struct disklabel *lp;
     44 {
     45 	register struct buf *bp;
     46 	struct disklabel *dlp, *elp;
     47 	char *msg = (char *)0;
     48 
     49 	elp = (struct disklabel *)(buf + DEV_BSIZE - sizeof(*dlp));
     50 	for (dlp = (struct disklabel *)buf; dlp <= elp;
     51 	    dlp = (struct disklabel *)((char *)dlp + sizeof(long))) {
     52 		if (dlp->d_magic != DISKMAGIC || dlp->d_magic2 != DISKMAGIC) {
     53 			if (msg == (char *)0)
     54 				msg = "no disk label";
     55 		} else if (dlp->d_npartitions > MAXPARTITIONS ||
     56 			   dkcksum(dlp) != 0)
     57 			msg = "disk label corrupted";
     58 		else {
     59 			*lp = *dlp;
     60 			msg = (char *)0;
     61 			break;
     62 		}
     63 	}
     64 	return (msg);
     65 }
     66 
     67 /*
     68  * Compute checksum for disk label.
     69  */
     70 dkcksum(lp)
     71 	register struct disklabel *lp;
     72 {
     73 	register u_short *start, *end;
     74 	register u_short sum = 0;
     75 
     76 	start = (u_short *)lp;
     77 	end = (u_short *)&lp->d_partitions[lp->d_npartitions];
     78 	while (start < end)
     79 		sum ^= *start++;
     80 	return (sum);
     81 }
     82