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installboot.c revision 1.13
      1 /*	$NetBSD: installboot.c,v 1.13 2002/04/12 22:11:33 leo Exp $	*/
      2 
      3 /*
      4  * Copyright (c) 1995 Waldi Ravens
      5  * All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in the
     14  *    documentation and/or other materials provided with the distribution.
     15  * 3. All advertising materials mentioning features or use of this software
     16  *    must display the following acknowledgement:
     17  *        This product includes software developed by Waldi Ravens.
     18  * 4. The name of the author may not be used to endorse or promote products
     19  *    derived from this software without specific prior written permission
     20  *
     21  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
     22  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
     23  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
     24  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
     25  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
     26  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     27  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     28  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     29  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
     30  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     31  */
     32 
     33 #include <sys/types.h>
     34 #include <sys/param.h>
     35 #include <sys/sysctl.h>
     36 #include <sys/ioctl.h>
     37 #include <unistd.h>
     38 #include <string.h>
     39 #include <stdlib.h>
     40 #include <stdio.h>
     41 #include <paths.h>
     42 #include <fcntl.h>
     43 #include <errno.h>
     44 #include <err.h>
     45 #include <limits.h>
     46 #include <nlist.h>
     47 #include <kvm.h>
     48 
     49 #define	DKTYPENAMES
     50 #define	FSTYPENAMES
     51 #include <sys/disklabel.h>
     52 #include <machine/ahdilabel.h>
     53 
     54 #include "installboot.h"
     55 
     56 static void	usage __P((void));
     57 static void	oscheck __P((void));
     58 static u_int	abcksum __P((void *));
     59 static void	setNVpref __P((void));
     60 static void	setIDEpar __P((u_int8_t *, size_t));
     61 static void	mkahdiboot __P((struct ahdi_root *, char *,
     62 						char *, daddr_t));
     63 static void	mkbootblock __P((struct bootblock *, char *,
     64 				char *, struct disklabel *, u_int));
     65 static void	install_fd __P((char *, struct disklabel *));
     66 static void	install_sd __P((char *, struct disklabel *));
     67 static void	install_wd __P((char *, struct disklabel *));
     68 
     69 static struct bootblock	bootarea;
     70 static struct ahdi_root ahdiboot;
     71 static const char	mdecpath[] = PATH_MDEC;
     72 static int		nowrite = 0;
     73 static int		verbose = 0;
     74 static int		trackpercyl = 0;
     75 static int		secpertrack = 0;
     76 
     77 static void
     78 usage ()
     79 {
     80 	fprintf(stderr,
     81 		"usage: installboot [options] device\n"
     82 		"where options are:\n"
     83 		"\t-N  do not actually write anything on the disk\n"
     84 		"\t-t  number of tracks per cylinder (IDE disk)\n"
     85 		"\t-u  number of sectors per track (IDE disk)\n"
     86 		"\t-v  verbose mode\n");
     87 	exit(EXIT_FAILURE);
     88 }
     89 
     90 int
     91 main (argc, argv)
     92 	int	argc;
     93 	char	*argv[];
     94 {
     95 	struct disklabel dl;
     96 	char		 *dn;
     97 	int		 fd, c;
     98 
     99 	/* check OS bootversion */
    100 	oscheck();
    101 
    102 	/* parse options */
    103 	while ((c = getopt(argc, argv, "Nt:u:v")) != -1) {
    104 		switch (c) {
    105 		  case 'N':
    106 			nowrite = 1;
    107 			break;
    108 		  case 't':
    109 			trackpercyl = atoi(optarg);
    110 			break;
    111 		  case 'u':
    112 			secpertrack = atoi(optarg);
    113 			break;
    114 		  case 'v':
    115 			verbose = 1;
    116 			break;
    117 		  default:
    118 			usage();
    119 		}
    120 	}
    121 	argv += optind;
    122 	argc -= optind;
    123 	if (argc != 1)
    124 		usage();
    125 
    126 	/* get disk label */
    127 	dn = alloca(sizeof(_PATH_DEV) + strlen(argv[0]) + 8);
    128 	if (!strchr(argv[0], '/')) {
    129 		sprintf(dn, "%sr%s%c", _PATH_DEV, argv[0], RAW_PART + 'a');
    130 		fd = open(dn, O_RDONLY);
    131 		if (fd < 0 && errno == ENOENT) {
    132 			sprintf(dn, "%sr%s", _PATH_DEV, argv[0]);
    133 			fd = open(dn, O_RDONLY);
    134 		}
    135 	} else {
    136 		sprintf(dn, "%s", argv[0]);
    137 		fd = open(dn, O_RDONLY);
    138 	}
    139 	if (fd < 0)
    140 		err(EXIT_FAILURE, "%s", dn);
    141 	if (ioctl(fd, DIOCGDINFO, &dl))
    142 		err(EXIT_FAILURE, "%s: DIOCGDINFO", dn);
    143 	if (close(fd))
    144 		err(EXIT_FAILURE, "%s", dn);
    145 
    146 	switch (dl.d_type) {
    147 		case DTYPE_FLOPPY:
    148 			install_fd(dn, &dl);
    149 			break;
    150 		case DTYPE_ST506:
    151 		case DTYPE_ESDI:
    152 			install_wd(dn, &dl);
    153 			setNVpref();
    154 			break;
    155 		case DTYPE_SCSI:
    156 			install_sd(dn, &dl);
    157 			setNVpref();
    158 			break;
    159 		default:
    160 			errx(EXIT_FAILURE,
    161 			     "%s: %s: Device type not supported.",
    162 			     dn, dktypenames[dl.d_type]);
    163 	}
    164 
    165 	return(EXIT_SUCCESS);
    166 }
    167 
    168 static void
    169 oscheck ()
    170 {
    171 	struct nlist	kbv[] = { { "_bootversion" },
    172 				  { NULL } };
    173 	kvm_t		*kd_kern;
    174 	char		errbuf[_POSIX2_LINE_MAX];
    175 	u_short		kvers;
    176 	struct stat	sb;
    177 
    178 	if (stat(_PATH_UNIX, &sb) < 0) {
    179 		warnx("Cannot stat %s, no bootversion check done\n",
    180 							_PATH_UNIX);
    181 		return;
    182 	}
    183 
    184 	kd_kern = kvm_openfiles(NULL, NULL, NULL, O_RDONLY, errbuf);
    185 	if (kd_kern == NULL)
    186 		errx(EXIT_FAILURE, "kvm_openfiles: %s", errbuf);
    187 	if (kvm_nlist(kd_kern, kbv) == -1)
    188 		errx(EXIT_FAILURE, "kvm_nlist: %s", kvm_geterr(kd_kern));
    189 	if (kbv[0].n_value == 0)
    190 		errx(EXIT_FAILURE, "%s not in namelist", kbv[0].n_name);
    191 	if (kvm_read(kd_kern, kbv[0].n_value, (char *)&kvers,
    192 						sizeof(kvers)) == -1)
    193 		errx(EXIT_FAILURE, "kvm_read: %s", kvm_geterr(kd_kern));
    194 	kvm_close(kd_kern);
    195 	if (kvers != BOOTVERSION)
    196 		errx(EXIT_FAILURE, "Kern bootversion: %d, expected: %d\n",
    197 					kvers, BOOTVERSION);
    198 }
    199 
    200 static void
    201 install_fd (devnm, label)
    202 	char		 *devnm;
    203 	struct disklabel *label;
    204 {
    205 	char		 *xxboot, *bootxx;
    206 	struct partition *rootpart;
    207 
    208 	if (label->d_secsize != 512)
    209 		errx(EXIT_FAILURE,
    210 		     "%s: %u: Block size not supported.", devnm,
    211 							  label->d_secsize);
    212 	if (label->d_ntracks != 2)
    213 		errx(EXIT_FAILURE,
    214 		     "%s: Single sided floppy not supported.", devnm);
    215 
    216 	xxboot = alloca(strlen(mdecpath) + 8);
    217 	sprintf(xxboot, "%sfdboot", mdecpath);
    218 	bootxx = alloca(strlen(mdecpath) + 8);
    219 	sprintf(bootxx, "%sbootxx", mdecpath);
    220 
    221 	/* first used partition (a, b or c) */		/* XXX */
    222 	for (rootpart = label->d_partitions; ; ++rootpart) {
    223 		if (rootpart->p_size)
    224 			break;
    225 	}
    226 	if (rootpart != label->d_partitions) {		/* XXX */
    227 		*(label->d_partitions) = *rootpart;
    228 		memset(rootpart, 0, sizeof(*rootpart));
    229 	}
    230 	label->d_partitions->p_fstype = FS_BSDFFS;	/* XXX */
    231 	label->d_npartitions = 1;
    232 	label->d_checksum = 0;
    233 	label->d_checksum = dkcksum(label);
    234 
    235 	trackpercyl = secpertrack = 0;
    236 	mkbootblock(&bootarea, xxboot, bootxx, label, 0);
    237 
    238 	if (!nowrite) {
    239 		int	fd;
    240 		if ((fd = open(devnm, O_WRONLY)) < 0)
    241 			err(EXIT_FAILURE, "%s", devnm);
    242 		if (write(fd, &bootarea, sizeof(bootarea)) != sizeof(bootarea))
    243 			err(EXIT_FAILURE, "%s", devnm);
    244 		if (close(fd))
    245 			err(EXIT_FAILURE, "%s", devnm);
    246 		if (verbose)
    247 			printf("Boot block installed on %s\n", devnm);
    248 	}
    249 }
    250 
    251 static void
    252 install_sd (devnm, label)
    253 	char		 *devnm;
    254 	struct disklabel *label;
    255 {
    256 	char		 *xxb00t, *xxboot, *bootxx;
    257 	struct disklabel rawlabel;
    258 	daddr_t		 bbsec;
    259 	u_int		 magic;
    260 
    261 	if (label->d_partitions[0].p_size == 0)
    262 		errx(EXIT_FAILURE, "%s: No root-filesystem.", devnm);
    263 	if (label->d_partitions[0].p_fstype != FS_BSDFFS)
    264 		errx(EXIT_FAILURE, "%s: %s: Illegal root-filesystem type.",
    265 		     devnm, fstypenames[label->d_partitions[0].p_fstype]);
    266 
    267 	bbsec = readdisklabel(devnm, &rawlabel);
    268 	if (bbsec == NO_BOOT_BLOCK)
    269 		errx(EXIT_FAILURE, "%s: No NetBSD boot block.", devnm);
    270 	if (memcmp(label, &rawlabel, sizeof(*label)))
    271 		errx(EXIT_FAILURE, "%s: Invalid NetBSD boot block.", devnm);
    272 
    273 	if (bbsec) {
    274 		xxb00t = alloca(strlen(mdecpath) + 14);
    275 		sprintf(xxb00t, "%ssdb00t.ahdi", mdecpath);
    276 		xxboot = alloca(strlen(mdecpath) + 14);
    277 		sprintf(xxboot, "%sxxboot.ahdi", mdecpath);
    278 		magic = AHDIMAGIC;
    279 	} else {
    280 		xxb00t = NULL;
    281 		xxboot = alloca(strlen(mdecpath) + 8);
    282 		sprintf(xxboot, "%ssdboot", mdecpath);
    283 		magic = NBDAMAGIC;
    284 	}
    285 	bootxx = alloca(strlen(mdecpath) + 8);
    286 	sprintf(bootxx, "%sbootxx", mdecpath);
    287 
    288 	trackpercyl = secpertrack = 0;
    289 	if (xxb00t)
    290 		mkahdiboot(&ahdiboot, xxb00t, devnm, bbsec);
    291 	mkbootblock(&bootarea, xxboot, bootxx, label, magic);
    292 
    293 	if (!nowrite) {
    294 		off_t	bbo = bbsec * AHDI_BSIZE;
    295 		int	fd;
    296 
    297 		if ((fd = open(devnm, O_WRONLY)) < 0)
    298 			err(EXIT_FAILURE, "%s", devnm);
    299 		if (lseek(fd, bbo, SEEK_SET) != bbo)
    300 			err(EXIT_FAILURE, "%s", devnm);
    301 		if (write(fd, &bootarea, sizeof(bootarea)) != sizeof(bootarea))
    302 			err(EXIT_FAILURE, "%s", devnm);
    303 		if (verbose)
    304 			printf("Boot block installed on %s (%u)\n", devnm,
    305 								    bbsec);
    306 		if (xxb00t) {
    307 			if (lseek(fd, (off_t)0, SEEK_SET) != 0)
    308 				err(EXIT_FAILURE, "%s", devnm);
    309 			if (write(fd, &ahdiboot, sizeof(ahdiboot)) != sizeof(ahdiboot))
    310 				err(EXIT_FAILURE, "%s", devnm);
    311 			if (verbose)
    312 				printf("AHDI root  installed on %s (0)\n",
    313 								devnm);
    314 		}
    315 		if (close(fd))
    316 			err(EXIT_FAILURE, "%s", devnm);
    317 	}
    318 }
    319 
    320 static void
    321 install_wd (devnm, label)
    322 	char		 *devnm;
    323 	struct disklabel *label;
    324 {
    325 	char		 *xxb00t, *xxboot, *bootxx;
    326 	struct disklabel rawlabel;
    327 	daddr_t		 bbsec;
    328 	u_int		 magic;
    329 
    330 	if (label->d_partitions[0].p_size == 0)
    331 		errx(EXIT_FAILURE, "%s: No root-filesystem.", devnm);
    332 	if (label->d_partitions[0].p_fstype != FS_BSDFFS)
    333 		errx(EXIT_FAILURE, "%s: %s: Illegal root-filesystem type.",
    334 		     devnm, fstypenames[label->d_partitions[0].p_fstype]);
    335 
    336 	bbsec = readdisklabel(devnm, &rawlabel);
    337 	if (bbsec == NO_BOOT_BLOCK)
    338 		errx(EXIT_FAILURE, "%s: No NetBSD boot block.", devnm);
    339 	if (memcmp(label, &rawlabel, sizeof(*label)))
    340 		errx(EXIT_FAILURE, "%s: Invalid NetBSD boot block.", devnm);
    341 
    342 	if (bbsec) {
    343 		xxb00t = alloca(strlen(mdecpath) + 14);
    344 		sprintf(xxb00t, "%swdb00t.ahdi", mdecpath);
    345 		xxboot = alloca(strlen(mdecpath) + 14);
    346 		sprintf(xxboot, "%sxxboot.ahdi", mdecpath);
    347 		magic = AHDIMAGIC;
    348 	} else {
    349 		xxb00t = NULL;
    350 		xxboot = alloca(strlen(mdecpath) + 8);
    351 		sprintf(xxboot, "%swdboot", mdecpath);
    352 		magic = NBDAMAGIC;
    353 	}
    354 	bootxx = alloca(strlen(mdecpath) + 8);
    355 	sprintf(bootxx, "%sbootxx", mdecpath);
    356 
    357 	if (xxb00t)
    358 		mkahdiboot(&ahdiboot, xxb00t, devnm, bbsec);
    359 	mkbootblock(&bootarea, xxboot, bootxx, label, magic);
    360 
    361 	if (!nowrite) {
    362 		int	fd;
    363 		off_t	bbo;
    364 
    365 		bbo = bbsec * AHDI_BSIZE;
    366 		if ((fd = open(devnm, O_WRONLY)) < 0)
    367 			err(EXIT_FAILURE, "%s", devnm);
    368 		if (lseek(fd, bbo, SEEK_SET) != bbo)
    369 			err(EXIT_FAILURE, "%s", devnm);
    370 		if (write(fd, &bootarea, sizeof(bootarea)) != sizeof(bootarea))
    371 			err(EXIT_FAILURE, "%s", devnm);
    372 		if (verbose)
    373 			printf("Boot block installed on %s (%u)\n", devnm,
    374 								    bbsec);
    375 		if (xxb00t) {
    376 			if (lseek(fd, (off_t)0, SEEK_SET) != 0)
    377 				err(EXIT_FAILURE, "%s", devnm);
    378 			if (write(fd, &ahdiboot, sizeof(ahdiboot))
    379 							!= sizeof(ahdiboot))
    380 				err(EXIT_FAILURE, "%s", devnm);
    381 			if (verbose)
    382 				printf("AHDI root  installed on %s (0)\n",
    383 									devnm);
    384 		}
    385 		if (close(fd))
    386 			err(EXIT_FAILURE, "%s", devnm);
    387 	}
    388 }
    389 
    390 static void
    391 mkahdiboot (newroot, xxb00t, devnm, bbsec)
    392 	struct ahdi_root *newroot;
    393 	char		 *xxb00t,
    394 			 *devnm;
    395 	daddr_t		 bbsec;
    396 {
    397 	struct ahdi_root tmproot;
    398 	struct ahdi_part *pd;
    399 	int		 fd;
    400 
    401 	/* read prototype root-sector */
    402 	if ((fd = open(xxb00t, O_RDONLY)) < 0)
    403 		err(EXIT_FAILURE, "%s", xxb00t);
    404 	if (read(fd, &tmproot, sizeof(tmproot)) != sizeof(tmproot))
    405 		err(EXIT_FAILURE, "%s", xxb00t);
    406 	if (close(fd))
    407 		err(EXIT_FAILURE, "%s", xxb00t);
    408 
    409 	/* set tracks/cylinder and sectors/track */
    410 	setIDEpar(tmproot.ar_fill, sizeof(tmproot.ar_fill));
    411 
    412 	/* read current root-sector */
    413 	if ((fd = open(devnm, O_RDONLY)) < 0)
    414 		err(EXIT_FAILURE, "%s", devnm);
    415 	if (read(fd, newroot, sizeof(*newroot)) != sizeof(*newroot))
    416 		err(EXIT_FAILURE, "%s", devnm);
    417 	if (close(fd))
    418 		err(EXIT_FAILURE, "%s", devnm);
    419 
    420 	/* set bootflags */
    421 	for (pd = newroot->ar_parts; pd-newroot->ar_parts < AHDI_MAXRPD; ++pd) {
    422 		if (pd->ap_st == bbsec) {
    423 			pd->ap_flg = 0x21;	/* bootable, pref = NetBSD */
    424 			goto gotit;
    425 		}
    426 	}
    427 	errx(EXIT_FAILURE,
    428 	     "%s: NetBSD boot block not on primary AHDI partition.", devnm);
    429 
    430 gotit:	/* copy code from prototype and set new checksum */
    431 	memcpy(newroot->ar_fill, tmproot.ar_fill, sizeof(tmproot.ar_fill));
    432 	newroot->ar_checksum = 0;
    433 	newroot->ar_checksum = 0x1234 - abcksum(newroot);
    434 
    435 	if (verbose)
    436 		printf("AHDI      boot loader: %s\n", xxb00t);
    437 }
    438 
    439 static void
    440 mkbootblock (bb, xxb, bxx, label, magic)
    441 	struct bootblock *bb;
    442 	char		 *xxb,
    443 			 *bxx;
    444 	u_int		 magic;
    445 	struct disklabel *label;
    446 {
    447 	int		 fd;
    448 
    449 	memset(bb, 0, sizeof(*bb));
    450 
    451 	/* set boot block magic */
    452 	bb->bb_magic = magic;
    453 
    454 	/* set disk pack label */
    455 	BBSETLABEL(bb, label);
    456 
    457 	/* set second-stage boot loader */
    458 	if ((fd = open(bxx, O_RDONLY)) < 0)
    459 		err(EXIT_FAILURE, "%s", bxx);
    460 	if (read(fd, bb->bb_bootxx, sizeof(bb->bb_bootxx))
    461 					!= sizeof(bb->bb_bootxx))
    462 		err(EXIT_FAILURE, "%s", bxx);
    463 	if (close(fd))
    464 		err(EXIT_FAILURE, "%s", bxx);
    465 
    466 	/* set first-stage bootloader */
    467 	if ((fd = open(xxb, O_RDONLY)) < 0)
    468 		err(EXIT_FAILURE, "%s", xxb);
    469 	if (read(fd, bb->bb_xxboot, sizeof(bb->bb_xxboot))
    470 					!= sizeof(bb->bb_xxboot))
    471 		err(EXIT_FAILURE, "%s", xxb);
    472 	if (close(fd))
    473 		err(EXIT_FAILURE, "%s", xxb);
    474 
    475 	/* set tracks/cylinder and sectors/track */
    476 	setIDEpar(bb->bb_xxboot, sizeof(bb->bb_xxboot));
    477 
    478 	/* set AHDI checksum */
    479 	*((u_int16_t *)bb->bb_xxboot + 255) = 0;
    480 	*((u_int16_t *)bb->bb_xxboot + 255) = 0x1234 - abcksum(bb->bb_xxboot);
    481 
    482 	if (verbose) {
    483 		printf("Primary   boot loader: %s\n", xxb);
    484 		printf("Secondary boot loader: %s\n", bxx);
    485 	}
    486 }
    487 
    488 static void
    489 setIDEpar (start, size)
    490 	u_int8_t	*start;
    491 	size_t		size;
    492 {
    493 	static const u_int8_t	mark[] = { 'N', 'e', 't', 'B', 'S', 'D' };
    494 
    495 	if ((u_int)trackpercyl > 255)
    496 		errx(EXIT_FAILURE,
    497 		     "%d: Illegal tracks/cylinder value (1..255)", trackpercyl);
    498 	if ((u_int)secpertrack > 255)
    499 		errx(EXIT_FAILURE,
    500 		     "%d: Illegal sectors/track value (1..255)", secpertrack);
    501 
    502 	if (trackpercyl || secpertrack) {
    503 		u_int8_t *p;
    504 
    505 		if (!trackpercyl)
    506 			errx(EXIT_FAILURE, "Need tracks/cylinder too.");
    507 		if (!secpertrack)
    508 			errx(EXIT_FAILURE, "Need sectors/track too.");
    509 
    510 		start += 2;
    511 		size  -= sizeof(mark) + 2;
    512 		for (p = start + size; p >= start; --p) {
    513 			if (*p != *mark)
    514 				continue;
    515 			if (!memcmp(p, mark, sizeof(mark)))
    516 				break;
    517 		}
    518 		if (p < start)
    519 			errx(EXIT_FAILURE,
    520 			     "Malformatted xxboot prototype.");
    521 
    522 		*--p = secpertrack;
    523 		*--p = trackpercyl;
    524 
    525 		if (verbose) {
    526 			printf("sectors/track  : %d\n", secpertrack);
    527 			printf("tracks/cylinder: %d\n", trackpercyl);
    528 		}
    529 	}
    530 }
    531 
    532 static void
    533 setNVpref ()
    534 {
    535 	static const u_char	bootpref = BOOTPREF_NETBSD;
    536 	static const char	nvrdev[] = PATH_NVRAM;
    537 
    538 	if (!nowrite) {
    539 		int	fd;
    540 
    541 		if ((fd = open(nvrdev, O_RDWR)) < 0)
    542 			err(EXIT_FAILURE, "%s", nvrdev);
    543 		if (lseek(fd, (off_t)1, SEEK_SET) != 1)
    544 			err(EXIT_FAILURE, "%s", nvrdev);
    545 		if (write(fd, &bootpref, (size_t)1) != 1)
    546 			err(EXIT_FAILURE, "%s", nvrdev);
    547 		if (close(fd))
    548 			err(EXIT_FAILURE, "%s", nvrdev);
    549 		if (verbose)
    550 			printf("Boot preference set to NetBSD.\n");
    551 	}
    552 }
    553 
    554 static u_int
    555 abcksum (bs)
    556 	void	*bs;
    557 {
    558 	u_int16_t sum  = 0,
    559 		  *st  = (u_int16_t *)bs,
    560 		  *end = (u_int16_t *)bs + 256;
    561 
    562 	while (st < end)
    563 		sum += *st++;
    564 	return(sum);
    565 }
    566