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installboot.c revision 1.24.12.1
      1 /*	$NetBSD: installboot.c,v 1.24.12.1 2011/11/10 14:31:39 yamt 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(void);
     57 static void	oscheck(void);
     58 static u_int	abcksum(void *);
     59 static void	setNVpref(void);
     60 static void	setIDEpar(u_int8_t *, size_t);
     61 static void	mkahdiboot(struct ahdi_root *, char *,
     62 						char *, u_int32_t);
     63 static void	mkbootblock(struct bootblock *, char *,
     64 				char *, struct disklabel *, u_int);
     65 static void	install_fd(char *, struct disklabel *);
     66 static void	install_sd(char *, struct disklabel *);
     67 static void	install_wd(char *, struct disklabel *);
     68 
     69 static struct bootblock	bootarea;
     70 static struct ahdi_root ahdiboot;
     71 static const char	mdecpath[] = PATH_MDEC;
     72 static const char	stdpath[] = PATH_STD;
     73 static const char	milanpath[] = PATH_MILAN;
     74 static int		nowrite = 0;
     75 static int		verbose = 0;
     76 static int		trackpercyl = 0;
     77 static int		secpertrack = 0;
     78 static int		milan = 0;
     79 
     80 static void
     81 usage(void)
     82 {
     83 	fprintf(stderr,
     84 		"usage: installboot [options] device\n"
     85 		"where options are:\n"
     86 		"\t-N  do not actually write anything on the disk\n"
     87 		"\t-m  use Milan boot blocks\n"
     88 		"\t-t  number of tracks per cylinder (IDE disk)\n"
     89 		"\t-u  number of sectors per track (IDE disk)\n"
     90 		"\t-v  verbose mode\n");
     91 	exit(EXIT_FAILURE);
     92 }
     93 
     94 int
     95 main(int argc, char *argv[])
     96 {
     97 	struct disklabel dl;
     98 	char		 *dn;
     99 	char		 *devchr;
    100 	int		 fd, c;
    101 
    102 	/* check OS bootversion */
    103 	oscheck();
    104 
    105 	/* parse options */
    106 	while ((c = getopt(argc, argv, "Nmt:u:v")) != -1) {
    107 		switch (c) {
    108 		  case 'N':
    109 			nowrite = 1;
    110 			break;
    111 		  case 'm':
    112 			milan = 1;
    113 			break;
    114 		  case 't':
    115 			trackpercyl = atoi(optarg);
    116 			break;
    117 		  case 'u':
    118 			secpertrack = atoi(optarg);
    119 			break;
    120 		  case 'v':
    121 			verbose = 1;
    122 			break;
    123 		  default:
    124 			usage();
    125 		}
    126 	}
    127 	argv += optind;
    128 	argc -= optind;
    129 	if (argc != 1)
    130 		usage();
    131 
    132 	/* get disk label */
    133 	dn = alloca(sizeof(_PATH_DEV) + strlen(argv[0]) + 8);
    134 	if (!strchr(argv[0], '/')) {
    135 		sprintf(dn, "%sr%s%c", _PATH_DEV, argv[0], RAW_PART + 'a');
    136 		fd = open(dn, O_RDONLY);
    137 		if (fd < 0 && errno == ENOENT) {
    138 			sprintf(dn, "%sr%s", _PATH_DEV, argv[0]);
    139 			fd = open(dn, O_RDONLY);
    140 		}
    141 	} else {
    142 		sprintf(dn, "%s", argv[0]);
    143 		fd = open(dn, O_RDONLY);
    144 	}
    145 	if (fd < 0)
    146 		err(EXIT_FAILURE, "%s", dn);
    147 	if (ioctl(fd, DIOCGDINFO, &dl))
    148 		err(EXIT_FAILURE, "%s: DIOCGDINFO", dn);
    149 	if (close(fd))
    150 		err(EXIT_FAILURE, "%s", dn);
    151 
    152 	/* Eg: in /dev/fd0c, set devchr to point to the 'f' */
    153 	devchr = strrchr(dn, '/') + 1;
    154 	if (*devchr == 'r')
    155 		++devchr;
    156 
    157 	switch (*devchr) {
    158 		case 'f': /* fd */
    159 			install_fd(dn, &dl);
    160 			break;
    161 		case 'w': /* wd */
    162 			install_wd(dn, &dl);
    163 			setNVpref();
    164 			break;
    165 		case 's': /* sd */
    166 			install_sd(dn, &dl);
    167 			setNVpref();
    168 			break;
    169 		default:
    170 			errx(EXIT_FAILURE,
    171 			     "%s: '%c': Device type not supported.",
    172 			     dn, *devchr);
    173 	}
    174 
    175 	return(EXIT_SUCCESS);
    176 }
    177 
    178 static void
    179 oscheck(void)
    180 {
    181 	struct nlist kbv[] = {
    182 		{ .n_name = "_bootversion" },
    183 		{ .n_name = NULL }
    184 	};
    185 	kvm_t		*kd_kern;
    186 	char		errbuf[_POSIX2_LINE_MAX];
    187 	u_short		kvers;
    188 	struct stat	sb;
    189 
    190 	if (stat(_PATH_UNIX, &sb) < 0) {
    191 		warnx("Cannot stat %s, no bootversion check done", _PATH_UNIX);
    192 		return;
    193 	}
    194 
    195 	kd_kern = kvm_openfiles(NULL, NULL, NULL, O_RDONLY, errbuf);
    196 	if (kd_kern == NULL)
    197 		errx(EXIT_FAILURE, "kvm_openfiles: %s", errbuf);
    198 	if (kvm_nlist(kd_kern, kbv) == -1)
    199 		errx(EXIT_FAILURE, "kvm_nlist: %s", kvm_geterr(kd_kern));
    200 	if (kbv[0].n_value == 0)
    201 		errx(EXIT_FAILURE, "%s not in namelist", kbv[0].n_name);
    202 	if (kvm_read(kd_kern, kbv[0].n_value, &kvers, sizeof(kvers)) == -1)
    203 		errx(EXIT_FAILURE, "kvm_read: %s", kvm_geterr(kd_kern));
    204 	kvm_close(kd_kern);
    205 	if (kvers != BOOTVERSION)
    206 		errx(EXIT_FAILURE, "Kern bootversion: %d, expected: %d",
    207 		    kvers, BOOTVERSION);
    208 }
    209 
    210 static void
    211 install_fd(char *devnm, struct disklabel *label)
    212 {
    213 	const char	 *machpath;
    214 	char		 *xxboot, *bootxx;
    215 	struct partition *rootpart;
    216 
    217 	if (label->d_secsize != 512)
    218 		errx(EXIT_FAILURE,
    219 		     "%s: %u: Block size not supported.", devnm,
    220 							  label->d_secsize);
    221 	if (label->d_ntracks != 2)
    222 		errx(EXIT_FAILURE,
    223 		     "%s: Single sided floppy not supported.", devnm);
    224 
    225 	if (milan)
    226 		machpath = milanpath;
    227 	else
    228 		machpath = stdpath;
    229 	xxboot = alloca(strlen(mdecpath) + strlen(machpath) + 8);
    230 	sprintf(xxboot, "%s%sfdboot", mdecpath, machpath);
    231 	bootxx = alloca(strlen(mdecpath) + strlen(machpath) + 8);
    232 	sprintf(bootxx, "%s%sbootxx", mdecpath, machpath);
    233 
    234 	/* first used partition (a, b or c) */		/* XXX */
    235 	for (rootpart = label->d_partitions; ; ++rootpart) {
    236 		if (rootpart->p_size)
    237 			break;
    238 	}
    239 	if (rootpart != label->d_partitions) {		/* XXX */
    240 		*(label->d_partitions) = *rootpart;
    241 		memset(rootpart, 0, sizeof(*rootpart));
    242 	}
    243 	label->d_partitions->p_fstype = FS_BSDFFS;	/* XXX */
    244 	label->d_npartitions = 1;
    245 	label->d_checksum = 0;
    246 	label->d_checksum = dkcksum(label);
    247 
    248 	trackpercyl = secpertrack = 0;
    249 	mkbootblock(&bootarea, xxboot, bootxx, label, 0);
    250 
    251 	if (!nowrite) {
    252 		int	fd;
    253 		if ((fd = open(devnm, O_WRONLY)) < 0)
    254 			err(EXIT_FAILURE, "%s", devnm);
    255 		if (write(fd, &bootarea, sizeof(bootarea)) != sizeof(bootarea))
    256 			err(EXIT_FAILURE, "%s", devnm);
    257 		if (close(fd))
    258 			err(EXIT_FAILURE, "%s", devnm);
    259 		if (verbose)
    260 			printf("Boot block installed on %s\n", devnm);
    261 	}
    262 }
    263 
    264 static void
    265 install_sd(char *devnm, struct disklabel *label)
    266 {
    267 	const char	 *machpath;
    268 	char		 *xxb00t, *xxboot, *bootxx;
    269 	struct disklabel rawlabel;
    270 	u_int32_t	 bbsec;
    271 	u_int		 magic;
    272 
    273 	if (label->d_partitions[0].p_size == 0)
    274 		errx(EXIT_FAILURE, "%s: No root-filesystem.", devnm);
    275 	if (label->d_partitions[0].p_fstype != FS_BSDFFS)
    276 		errx(EXIT_FAILURE, "%s: %s: Illegal root-filesystem type.",
    277 		     devnm, fstypenames[label->d_partitions[0].p_fstype]);
    278 
    279 	bbsec = readdisklabel(devnm, &rawlabel);
    280 	if (bbsec == NO_BOOT_BLOCK)
    281 		errx(EXIT_FAILURE, "%s: No NetBSD boot block.", devnm);
    282 	if (memcmp(label, &rawlabel, sizeof(*label)))
    283 		errx(EXIT_FAILURE, "%s: Invalid NetBSD boot block.", devnm);
    284 
    285 	if (milan)
    286 		machpath = milanpath;
    287 	else
    288 		machpath = stdpath;
    289 	if (bbsec) {
    290 		xxb00t = alloca(strlen(mdecpath) + strlen(machpath) + 14);
    291 		sprintf(xxb00t, "%s%ssdb00t.ahdi", mdecpath, machpath);
    292 		xxboot = alloca(strlen(mdecpath) + strlen(machpath) + 14);
    293 		sprintf(xxboot, "%s%sxxboot.ahdi", mdecpath, machpath);
    294 		magic = AHDIMAGIC;
    295 	} else {
    296 		xxb00t = NULL;
    297 		xxboot = alloca(strlen(mdecpath) + strlen(machpath) + 8);
    298 		sprintf(xxboot, "%s%ssdboot", mdecpath, machpath);
    299 		magic = NBDAMAGIC;
    300 	}
    301 	bootxx = alloca(strlen(mdecpath) + strlen(machpath) + 8);
    302 	sprintf(bootxx, "%s%sbootxx", mdecpath, machpath);
    303 
    304 	trackpercyl = secpertrack = 0;
    305 	if (xxb00t)
    306 		mkahdiboot(&ahdiboot, xxb00t, devnm, bbsec);
    307 	mkbootblock(&bootarea, xxboot, bootxx, label, magic);
    308 
    309 	if (!nowrite) {
    310 		off_t	bbo = (off_t)bbsec * AHDI_BSIZE;
    311 		int	fd;
    312 
    313 		if ((fd = open(devnm, O_WRONLY)) < 0)
    314 			err(EXIT_FAILURE, "%s", devnm);
    315 		if (lseek(fd, bbo, SEEK_SET) != bbo)
    316 			err(EXIT_FAILURE, "%s", devnm);
    317 		if (write(fd, &bootarea, sizeof(bootarea)) != sizeof(bootarea))
    318 			err(EXIT_FAILURE, "%s", devnm);
    319 		if (verbose)
    320 			printf("Boot block installed on %s (sector %d)\n",
    321 			    devnm, bbsec);
    322 		if (xxb00t) {
    323 			if (lseek(fd, (off_t)0, SEEK_SET) != 0)
    324 				err(EXIT_FAILURE, "%s", devnm);
    325 			if (write(fd, &ahdiboot, sizeof(ahdiboot)) !=
    326 			    sizeof(ahdiboot))
    327 				err(EXIT_FAILURE, "%s", devnm);
    328 			if (verbose)
    329 				printf("AHDI root  installed on %s (0)\n",
    330 				    devnm);
    331 		}
    332 		if (close(fd))
    333 			err(EXIT_FAILURE, "%s", devnm);
    334 	}
    335 }
    336 
    337 static void
    338 install_wd(char *devnm, struct disklabel *label)
    339 {
    340 	const char	 *machpath;
    341 	char		 *xxb00t, *xxboot, *bootxx;
    342 	struct disklabel rawlabel;
    343 	u_int32_t	 bbsec;
    344 	u_int		 magic;
    345 
    346 	if (label->d_partitions[0].p_size == 0)
    347 		errx(EXIT_FAILURE, "%s: No root-filesystem.", devnm);
    348 	if (label->d_partitions[0].p_fstype != FS_BSDFFS)
    349 		errx(EXIT_FAILURE, "%s: %s: Illegal root-filesystem type.",
    350 		     devnm, fstypenames[label->d_partitions[0].p_fstype]);
    351 
    352 	bbsec = readdisklabel(devnm, &rawlabel);
    353 	if (bbsec == NO_BOOT_BLOCK)
    354 		errx(EXIT_FAILURE, "%s: No NetBSD boot block.", devnm);
    355 	if (memcmp(label, &rawlabel, sizeof(*label)))
    356 		errx(EXIT_FAILURE, "%s: Invalid NetBSD boot block.", devnm);
    357 
    358 	if (milan)
    359 		machpath = milanpath;
    360 	else
    361 		machpath = stdpath;
    362 	if (bbsec) {
    363 		xxb00t = alloca(strlen(mdecpath) + strlen(machpath) + 14);
    364 		sprintf(xxb00t, "%s%swdb00t.ahdi", mdecpath, machpath);
    365 		xxboot = alloca(strlen(mdecpath) + strlen(machpath) + 14);
    366 		sprintf(xxboot, "%s%sxxboot.ahdi", mdecpath, machpath);
    367 		magic = AHDIMAGIC;
    368 	} else {
    369 		xxb00t = NULL;
    370 		xxboot = alloca(strlen(mdecpath) + strlen(machpath) + 8);
    371 		sprintf(xxboot, "%s%swdboot", mdecpath, machpath);
    372 		magic = NBDAMAGIC;
    373 	}
    374 	bootxx = alloca(strlen(mdecpath) + strlen(machpath) + 8);
    375 	sprintf(bootxx, "%s%sbootxx", mdecpath, machpath);
    376 
    377 	if (xxb00t)
    378 		mkahdiboot(&ahdiboot, xxb00t, devnm, bbsec);
    379 	mkbootblock(&bootarea, xxboot, bootxx, label, magic);
    380 
    381 	if (!nowrite) {
    382 		int	fd;
    383 		off_t	bbo;
    384 
    385 		bbo = (off_t)bbsec * AHDI_BSIZE;
    386 		if ((fd = open(devnm, O_WRONLY)) < 0)
    387 			err(EXIT_FAILURE, "%s", devnm);
    388 		if (lseek(fd, bbo, SEEK_SET) != bbo)
    389 			err(EXIT_FAILURE, "%s", devnm);
    390 		if (write(fd, &bootarea, sizeof(bootarea)) != sizeof(bootarea))
    391 			err(EXIT_FAILURE, "%s", devnm);
    392 		if (verbose)
    393 			printf("Boot block installed on %s (sector %d)\n",
    394 			    devnm, bbsec);
    395 		if (xxb00t) {
    396 			if (lseek(fd, (off_t)0, SEEK_SET) != 0)
    397 				err(EXIT_FAILURE, "%s", devnm);
    398 			if (write(fd, &ahdiboot, sizeof(ahdiboot))
    399 							!= sizeof(ahdiboot))
    400 				err(EXIT_FAILURE, "%s", devnm);
    401 			if (verbose)
    402 				printf("AHDI root installed on %s (sector 0)\n",
    403 				    devnm);
    404 		}
    405 		if (close(fd))
    406 			err(EXIT_FAILURE, "%s", devnm);
    407 	}
    408 }
    409 
    410 static void
    411 mkahdiboot(struct ahdi_root *newroot, char *xxb00t, char *devnm,
    412     u_int32_t bbsec)
    413 {
    414 	struct ahdi_root tmproot;
    415 	struct ahdi_part *pd;
    416 	int		 fd;
    417 
    418 	/* read prototype root-sector */
    419 	if ((fd = open(xxb00t, O_RDONLY)) < 0)
    420 		err(EXIT_FAILURE, "%s", xxb00t);
    421 	if (read(fd, &tmproot, sizeof(tmproot)) != sizeof(tmproot))
    422 		err(EXIT_FAILURE, "%s", xxb00t);
    423 	if (close(fd))
    424 		err(EXIT_FAILURE, "%s", xxb00t);
    425 
    426 	/* set tracks/cylinder and sectors/track */
    427 	setIDEpar(tmproot.ar_fill, sizeof(tmproot.ar_fill));
    428 
    429 	/* read current root-sector */
    430 	if ((fd = open(devnm, O_RDONLY)) < 0)
    431 		err(EXIT_FAILURE, "%s", devnm);
    432 	if (read(fd, newroot, sizeof(*newroot)) != sizeof(*newroot))
    433 		err(EXIT_FAILURE, "%s", devnm);
    434 	if (close(fd))
    435 		err(EXIT_FAILURE, "%s", devnm);
    436 
    437 	/* set bootflags */
    438 	for (pd = newroot->ar_parts; pd-newroot->ar_parts < AHDI_MAXRPD; ++pd) {
    439 		if (pd->ap_st == bbsec) {
    440 			pd->ap_flg = 0x21;	/* bootable, pref = NetBSD */
    441 			goto gotit;
    442 		}
    443 	}
    444 	errx(EXIT_FAILURE,
    445 	     "%s: NetBSD boot block not on primary AHDI partition.", devnm);
    446 
    447 gotit:	/* copy code from prototype and set new checksum */
    448 	memcpy(newroot->ar_fill, tmproot.ar_fill, sizeof(tmproot.ar_fill));
    449 	newroot->ar_checksum = 0;
    450 	newroot->ar_checksum = 0x1234 - abcksum(newroot);
    451 
    452 	if (verbose)
    453 		printf("AHDI      boot loader: %s\n", xxb00t);
    454 }
    455 
    456 static void
    457 mkbootblock(struct bootblock *bb, char *xxb, char *bxx,
    458     struct disklabel *label, u_int magic)
    459 {
    460 	int		 fd;
    461 
    462 	memset(bb, 0, sizeof(*bb));
    463 
    464 	/* set boot block magic */
    465 	bb->bb_magic = magic;
    466 
    467 	/* set disk pack label */
    468 	BBSETLABEL(bb, label);
    469 
    470 	/* set second-stage boot loader */
    471 	if ((fd = open(bxx, O_RDONLY)) < 0)
    472 		err(EXIT_FAILURE, "%s", bxx);
    473 	if (read(fd, bb->bb_bootxx, sizeof(bb->bb_bootxx))
    474 					!= sizeof(bb->bb_bootxx))
    475 		err(EXIT_FAILURE, "%s", bxx);
    476 	if (close(fd))
    477 		err(EXIT_FAILURE, "%s", bxx);
    478 
    479 	/* set first-stage bootloader */
    480 	if ((fd = open(xxb, O_RDONLY)) < 0)
    481 		err(EXIT_FAILURE, "%s", xxb);
    482 	if (read(fd, bb->bb_xxboot, sizeof(bb->bb_xxboot))
    483 					!= sizeof(bb->bb_xxboot))
    484 		err(EXIT_FAILURE, "%s", xxb);
    485 	if (close(fd))
    486 		err(EXIT_FAILURE, "%s", xxb);
    487 
    488 	/* set tracks/cylinder and sectors/track */
    489 	setIDEpar(bb->bb_xxboot, sizeof(bb->bb_xxboot));
    490 
    491 	/* set AHDI checksum */
    492 	*((u_int16_t *)bb->bb_xxboot + 255) = 0;
    493 	*((u_int16_t *)bb->bb_xxboot + 255) = 0x1234 - abcksum(bb->bb_xxboot);
    494 
    495 	if (verbose) {
    496 		printf("Primary   boot loader: %s\n", xxb);
    497 		printf("Secondary boot loader: %s\n", bxx);
    498 	}
    499 }
    500 
    501 static void
    502 setIDEpar (u_int8_t *start, size_t size)
    503 {
    504 	static const u_int8_t	mark[] = { 'N', 'e', 't', 'B', 'S', 'D' };
    505 
    506 	if ((u_int)trackpercyl > 255)
    507 		errx(EXIT_FAILURE,
    508 		     "%d: Illegal tracks/cylinder value (1..255)", trackpercyl);
    509 	if ((u_int)secpertrack > 255)
    510 		errx(EXIT_FAILURE,
    511 		     "%d: Illegal sectors/track value (1..255)", secpertrack);
    512 
    513 	if (trackpercyl || secpertrack) {
    514 		u_int8_t *p;
    515 
    516 		if (!trackpercyl)
    517 			errx(EXIT_FAILURE, "Need tracks/cylinder too.");
    518 		if (!secpertrack)
    519 			errx(EXIT_FAILURE, "Need sectors/track too.");
    520 
    521 		start += 2;
    522 		size  -= sizeof(mark) + 2;
    523 		for (p = start + size; p >= start; --p) {
    524 			if (*p != *mark)
    525 				continue;
    526 			if (!memcmp(p, mark, sizeof(mark)))
    527 				break;
    528 		}
    529 		if (p < start)
    530 			errx(EXIT_FAILURE,
    531 			     "Malformatted xxboot prototype.");
    532 
    533 		*--p = secpertrack;
    534 		*--p = trackpercyl;
    535 
    536 		if (verbose) {
    537 			printf("sectors/track  : %d\n", secpertrack);
    538 			printf("tracks/cylinder: %d\n", trackpercyl);
    539 		}
    540 	}
    541 }
    542 
    543 static void
    544 setNVpref(void)
    545 {
    546 	static const u_char	bootpref = BOOTPREF_NETBSD;
    547 	static const char	nvrdev[] = PATH_NVRAM;
    548 
    549 	if (!nowrite) {
    550 		int	fd;
    551 
    552 		if ((fd = open(nvrdev, O_RDWR)) < 0)
    553 			err(EXIT_FAILURE, "%s", nvrdev);
    554 		if (lseek(fd, (off_t)1, SEEK_SET) != 1)
    555 			err(EXIT_FAILURE, "%s", nvrdev);
    556 		if (write(fd, &bootpref, (size_t)1) != 1)
    557 			err(EXIT_FAILURE, "%s", nvrdev);
    558 		if (close(fd))
    559 			err(EXIT_FAILURE, "%s", nvrdev);
    560 		if (verbose)
    561 			printf("Boot preference set to NetBSD.\n");
    562 	}
    563 }
    564 
    565 static u_int
    566 abcksum (void *bs)
    567 {
    568 	u_int16_t sum  = 0,
    569 		  *st  = (u_int16_t *)bs,
    570 		  *end = (u_int16_t *)bs + 256;
    571 
    572 	while (st < end)
    573 		sum += *st++;
    574 	return(sum);
    575 }
    576