xref: /freebsd/stand/i386/libi386/biosdisk.c (revision e40139ff33b48b56a24c808b166b04b8ee6f5b21)
1 /*-
2  * Copyright (c) 1998 Michael Smith <msmith@freebsd.org>
3  * Copyright (c) 2012 Andrey V. Elsukov <ae@FreeBSD.org>
4  * All rights reserved.
5  *
6  * Redistribution and use in source and binary forms, with or without
7  * modification, are permitted provided that the following conditions
8  * are met:
9  * 1. Redistributions of source code must retain the above copyright
10  *    notice, this list of conditions and the following disclaimer.
11  * 2. Redistributions in binary form must reproduce the above copyright
12  *    notice, this list of conditions and the following disclaimer in the
13  *    documentation and/or other materials provided with the distribution.
14  *
15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
16  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
17  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
18  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
19  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
20  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
21  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
22  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
23  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
24  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
25  * SUCH DAMAGE.
26  */
27 
28 #include <sys/cdefs.h>
29 __FBSDID("$FreeBSD$");
30 
31 /*
32  * BIOS disk device handling.
33  *
34  * Ideas and algorithms from:
35  *
36  * - NetBSD libi386/biosdisk.c
37  * - FreeBSD biosboot/disk.c
38  *
39  */
40 
41 #include <sys/disk.h>
42 #include <sys/limits.h>
43 #include <sys/queue.h>
44 #include <stand.h>
45 #include <machine/bootinfo.h>
46 #include <stdarg.h>
47 #include <stdbool.h>
48 
49 #include <bootstrap.h>
50 #include <btxv86.h>
51 #include <edd.h>
52 #include "disk.h"
53 #include "libi386.h"
54 
55 #define	BIOS_NUMDRIVES		0x475
56 #define	BIOSDISK_SECSIZE	512
57 #define	BUFSIZE			(1 * BIOSDISK_SECSIZE)
58 
59 #define	DT_ATAPI	0x10	/* disk type for ATAPI floppies */
60 #define	WDMAJOR		0	/* major numbers for devices we frontend for */
61 #define	WFDMAJOR	1
62 #define	FDMAJOR		2
63 #define	DAMAJOR		4
64 #define	ACDMAJOR	117
65 #define	CDMAJOR		15
66 
67 /*
68  * INT13 commands
69  */
70 #define	CMD_RESET	0x0000
71 #define	CMD_READ_CHS	0x0200
72 #define	CMD_WRITE_CHS	0x0300
73 #define	CMD_READ_PARAM	0x0800
74 #define	CMD_DRIVE_TYPE	0x1500
75 #define	CMD_CHECK_EDD	0x4100
76 #define	CMD_READ_LBA	0x4200
77 #define	CMD_WRITE_LBA	0x4300
78 #define	CMD_EXT_PARAM	0x4800
79 #define	CMD_CD_GET_STATUS 0x4b01
80 
81 #define	DISK_BIOS	0x13
82 
83 #ifdef DISK_DEBUG
84 #define	DPRINTF(fmt, args...)	printf("%s: " fmt "\n", __func__, ## args)
85 #else
86 #define	DPRINTF(fmt, args...)	((void)0)
87 #endif
88 
89 struct specification_packet {
90 	uint8_t		sp_size;
91 	uint8_t		sp_bootmedia;
92 	uint8_t		sp_drive;
93 	uint8_t		sp_controller;
94 	uint32_t	sp_lba;
95 	uint16_t	sp_devicespec;
96 	uint16_t	sp_buffersegment;
97 	uint16_t	sp_loadsegment;
98 	uint16_t	sp_sectorcount;
99 	uint16_t	sp_cylsec;
100 	uint8_t		sp_head;
101 };
102 
103 /*
104  * List of BIOS devices, translation from disk unit number to
105  * BIOS unit number.
106  */
107 typedef struct bdinfo
108 {
109 	STAILQ_ENTRY(bdinfo)	bd_link;	/* link in device list */
110 	int		bd_unit;	/* BIOS unit number */
111 	int		bd_cyl;		/* BIOS geometry */
112 	int		bd_hds;
113 	int		bd_sec;
114 	int		bd_flags;
115 #define	BD_MODEINT13	0x0000
116 #define	BD_MODEEDD1	0x0001
117 #define	BD_MODEEDD3	0x0002
118 #define	BD_MODEEDD	(BD_MODEEDD1 | BD_MODEEDD3)
119 #define	BD_MODEMASK	0x0003
120 #define	BD_FLOPPY	0x0004
121 #define	BD_CDROM	0x0008
122 #define	BD_NO_MEDIA	0x0010
123 	int		bd_type;	/* BIOS 'drive type' (floppy only) */
124 	uint16_t	bd_sectorsize;	/* Sector size */
125 	uint64_t	bd_sectors;	/* Disk size */
126 	int		bd_open;	/* reference counter */
127 	void		*bd_bcache;	/* buffer cache data */
128 } bdinfo_t;
129 
130 #define	BD_RD		0
131 #define	BD_WR		1
132 
133 typedef STAILQ_HEAD(bdinfo_list, bdinfo) bdinfo_list_t;
134 static bdinfo_list_t fdinfo = STAILQ_HEAD_INITIALIZER(fdinfo);
135 static bdinfo_list_t cdinfo = STAILQ_HEAD_INITIALIZER(cdinfo);
136 static bdinfo_list_t hdinfo = STAILQ_HEAD_INITIALIZER(hdinfo);
137 
138 static void bd_io_workaround(bdinfo_t *);
139 static int bd_io(struct disk_devdesc *, bdinfo_t *, daddr_t, int, caddr_t, int);
140 static bool bd_int13probe(bdinfo_t *);
141 
142 static int bd_init(void);
143 static int cd_init(void);
144 static int fd_init(void);
145 static int bd_strategy(void *devdata, int flag, daddr_t dblk, size_t size,
146     char *buf, size_t *rsize);
147 static int bd_realstrategy(void *devdata, int flag, daddr_t dblk, size_t size,
148     char *buf, size_t *rsize);
149 static int bd_open(struct open_file *f, ...);
150 static int bd_close(struct open_file *f);
151 static int bd_ioctl(struct open_file *f, u_long cmd, void *data);
152 static int bd_print(int verbose);
153 static int cd_print(int verbose);
154 static int fd_print(int verbose);
155 static void bd_reset_disk(int);
156 static int bd_get_diskinfo_std(struct bdinfo *);
157 
158 struct devsw biosfd = {
159 	.dv_name = "fd",
160 	.dv_type = DEVT_FD,
161 	.dv_init = fd_init,
162 	.dv_strategy = bd_strategy,
163 	.dv_open = bd_open,
164 	.dv_close = bd_close,
165 	.dv_ioctl = bd_ioctl,
166 	.dv_print = fd_print,
167 	.dv_cleanup = NULL
168 };
169 
170 struct devsw bioscd = {
171 	.dv_name = "cd",
172 	.dv_type = DEVT_CD,
173 	.dv_init = cd_init,
174 	.dv_strategy = bd_strategy,
175 	.dv_open = bd_open,
176 	.dv_close = bd_close,
177 	.dv_ioctl = bd_ioctl,
178 	.dv_print = cd_print,
179 	.dv_cleanup = NULL
180 };
181 
182 struct devsw bioshd = {
183 	.dv_name = "disk",
184 	.dv_type = DEVT_DISK,
185 	.dv_init = bd_init,
186 	.dv_strategy = bd_strategy,
187 	.dv_open = bd_open,
188 	.dv_close = bd_close,
189 	.dv_ioctl = bd_ioctl,
190 	.dv_print = bd_print,
191 	.dv_cleanup = NULL
192 };
193 
194 static bdinfo_list_t *
195 bd_get_bdinfo_list(struct devsw *dev)
196 {
197 	if (dev->dv_type == DEVT_DISK)
198 		return (&hdinfo);
199 	if (dev->dv_type == DEVT_CD)
200 		return (&cdinfo);
201 	if (dev->dv_type == DEVT_FD)
202 		return (&fdinfo);
203 	return (NULL);
204 }
205 
206 /* XXX this gets called way way too often, investigate */
207 static bdinfo_t *
208 bd_get_bdinfo(struct devdesc *dev)
209 {
210 	bdinfo_list_t *bdi;
211 	bdinfo_t *bd = NULL;
212 	int unit;
213 
214 	bdi = bd_get_bdinfo_list(dev->d_dev);
215 	if (bdi == NULL)
216 		return (bd);
217 
218 	unit = 0;
219 	STAILQ_FOREACH(bd, bdi, bd_link) {
220 		if (unit == dev->d_unit)
221 			return (bd);
222 		unit++;
223 	}
224 	return (bd);
225 }
226 
227 /*
228  * Translate between BIOS device numbers and our private unit numbers.
229  */
230 int
231 bd_bios2unit(int biosdev)
232 {
233 	bdinfo_list_t *bdi[] = { &fdinfo, &cdinfo, &hdinfo, NULL };
234 	bdinfo_t *bd;
235 	int i, unit;
236 
237 	DPRINTF("looking for bios device 0x%x", biosdev);
238 	for (i = 0; bdi[i] != NULL; i++) {
239 		unit = 0;
240 		STAILQ_FOREACH(bd, bdi[i], bd_link) {
241 			if (bd->bd_unit == biosdev) {
242 				DPRINTF("bd unit %d is BIOS device 0x%x", unit,
243 				    bd->bd_unit);
244 				return (unit);
245 			}
246 			unit++;
247 		}
248 	}
249 	return (-1);
250 }
251 
252 int
253 bd_unit2bios(struct i386_devdesc *dev)
254 {
255 	bdinfo_list_t *bdi;
256 	bdinfo_t *bd;
257 	int unit;
258 
259 	bdi = bd_get_bdinfo_list(dev->dd.d_dev);
260 	if (bdi == NULL)
261 		return (-1);
262 
263 	unit = 0;
264 	STAILQ_FOREACH(bd, bdi, bd_link) {
265 		if (unit == dev->dd.d_unit)
266 			return (bd->bd_unit);
267 		unit++;
268 	}
269 	return (-1);
270 }
271 
272 /*
273  * Use INT13 AH=15 - Read Drive Type.
274  */
275 static int
276 fd_count(void)
277 {
278 	int drive;
279 
280 	for (drive = 0; drive < MAXBDDEV; drive++) {
281 		bd_reset_disk(drive);
282 
283 		v86.ctl = V86_FLAGS;
284 		v86.addr = DISK_BIOS;
285 		v86.eax = CMD_DRIVE_TYPE;
286 		v86.edx = drive;
287 		v86int();
288 
289 		if (V86_CY(v86.efl))
290 			break;
291 
292 		if ((v86.eax & 0x300) == 0)
293 			break;
294 	}
295 
296 	return (drive);
297 }
298 
299 /*
300  * Quiz the BIOS for disk devices, save a little info about them.
301  */
302 static int
303 fd_init(void)
304 {
305 	int unit, numfd;
306 	bdinfo_t *bd;
307 
308 	numfd = fd_count();
309 	for (unit = 0; unit < numfd; unit++) {
310 		if ((bd = calloc(1, sizeof(*bd))) == NULL)
311 			break;
312 
313 		bd->bd_sectorsize = BIOSDISK_SECSIZE;
314 		bd->bd_flags = BD_FLOPPY;
315 		bd->bd_unit = unit;
316 
317 		/* Use std diskinfo for floppy drive */
318 		if (bd_get_diskinfo_std(bd) != 0) {
319 			free(bd);
320 			break;
321 		}
322 		if (bd->bd_sectors == 0)
323 			bd->bd_flags |= BD_NO_MEDIA;
324 
325 		printf("BIOS drive %c: is %s%d\n", ('A' + unit),
326 		    biosfd.dv_name, unit);
327 
328 		STAILQ_INSERT_TAIL(&fdinfo, bd, bd_link);
329 	}
330 
331 	bcache_add_dev(unit);
332 	return (0);
333 }
334 
335 static int
336 bd_init(void)
337 {
338 	int base, unit;
339 	bdinfo_t *bd;
340 
341 	base = 0x80;
342 	for (unit = 0; unit < *(unsigned char *)PTOV(BIOS_NUMDRIVES); unit++) {
343 		/*
344 		 * Check the BIOS equipment list for number of fixed disks.
345 		 */
346 		if ((bd = calloc(1, sizeof(*bd))) == NULL)
347 			break;
348 		bd->bd_unit = base + unit;
349 		if (!bd_int13probe(bd)) {
350 			free(bd);
351 			break;
352 		}
353 
354 		printf("BIOS drive %c: is %s%d\n", ('C' + unit),
355 		    bioshd.dv_name, unit);
356 
357 		STAILQ_INSERT_TAIL(&hdinfo, bd, bd_link);
358 	}
359 	bcache_add_dev(unit);
360 	return (0);
361 }
362 
363 /*
364  * We can't quiz, we have to be told what device to use, so this function
365  * doesn't do anything.  Instead, the loader calls bc_add() with the BIOS
366  * device number to add.
367  */
368 static int
369 cd_init(void)
370 {
371 
372 	return (0);
373 }
374 
375 int
376 bc_add(int biosdev)
377 {
378 	bdinfo_t *bd;
379 	struct specification_packet bc_sp;
380 	int nbcinfo = 0;
381 
382 	if (!STAILQ_EMPTY(&cdinfo))
383                 return (-1);
384 
385         v86.ctl = V86_FLAGS;
386         v86.addr = DISK_BIOS;
387         v86.eax = CMD_CD_GET_STATUS;
388         v86.edx = biosdev;
389         v86.ds = VTOPSEG(&bc_sp);
390         v86.esi = VTOPOFF(&bc_sp);
391         v86int();
392         if ((v86.eax & 0xff00) != 0)
393                 return (-1);
394 
395 	if ((bd = calloc(1, sizeof(*bd))) == NULL)
396 		return (-1);
397 
398 	bd->bd_flags = BD_CDROM;
399 	bd->bd_unit = biosdev;
400 	bd->bd_sectorsize = 2048;
401 
402 	/*
403 	 * Ignore result from bd_int13probe(), we will use local
404 	 * workaround below.
405 	 */
406 	(void)bd_int13probe(bd);
407 
408 	if (bd->bd_cyl == 0) {
409 		bd->bd_cyl = ((bc_sp.sp_cylsec & 0xc0) << 2) +
410 		    ((bc_sp.sp_cylsec & 0xff00) >> 8) + 1;
411 	}
412 	if (bd->bd_hds == 0)
413 		bd->bd_hds = bc_sp.sp_head + 1;
414 	if (bd->bd_sec == 0)
415 		bd->bd_sec = bc_sp.sp_cylsec & 0x3f;
416 	if (bd->bd_sectors == 0)
417 		bd->bd_sectors = (uint64_t)bd->bd_cyl * bd->bd_hds * bd->bd_sec;
418 
419 	/* Still no size? use 7.961GB */
420 	if (bd->bd_sectors == 0)
421 		bd->bd_sectors = 4173824;
422 
423 	STAILQ_INSERT_TAIL(&cdinfo, bd, bd_link);
424         printf("BIOS CD is cd%d\n", nbcinfo);
425         nbcinfo++;
426         bcache_add_dev(nbcinfo);        /* register cd device in bcache */
427         return(0);
428 }
429 
430 /*
431  * Return EDD version or 0 if EDD is not supported on this drive.
432  */
433 static int
434 bd_check_extensions(int unit)
435 {
436 	/* do not use ext calls for floppy devices */
437 	if (unit < 0x80)
438 		return (0);
439 
440 	/* Determine if we can use EDD with this device. */
441 	v86.ctl = V86_FLAGS;
442 	v86.addr = DISK_BIOS;
443 	v86.eax = CMD_CHECK_EDD;
444 	v86.edx = unit;
445 	v86.ebx = EDD_QUERY_MAGIC;
446 	v86int();
447 
448 	if (V86_CY(v86.efl) ||			/* carry set */
449 	    (v86.ebx & 0xffff) != EDD_INSTALLED) /* signature */
450 		return (0);
451 
452 	/* extended disk access functions (AH=42h-44h,47h,48h) supported */
453 	if ((v86.ecx & EDD_INTERFACE_FIXED_DISK) == 0)
454 		return (0);
455 
456 	return ((v86.eax >> 8) & 0xff);
457 }
458 
459 static void
460 bd_reset_disk(int unit)
461 {
462 	/* reset disk */
463 	v86.ctl = V86_FLAGS;
464 	v86.addr = DISK_BIOS;
465 	v86.eax = CMD_RESET;
466 	v86.edx = unit;
467 	v86int();
468 }
469 
470 /*
471  * Read CHS info. Return 0 on success, error otherwise.
472  */
473 static int
474 bd_get_diskinfo_std(struct bdinfo *bd)
475 {
476 	bzero(&v86, sizeof(v86));
477 	v86.ctl = V86_FLAGS;
478 	v86.addr = DISK_BIOS;
479 	v86.eax = CMD_READ_PARAM;
480 	v86.edx = bd->bd_unit;
481 	v86int();
482 
483 	if (V86_CY(v86.efl) && ((v86.eax & 0xff00) != 0))
484 		return ((v86.eax & 0xff00) >> 8);
485 
486 	/* return custom error on absurd sector number */
487 	if ((v86.ecx & 0x3f) == 0)
488 		return (0x60);
489 
490 	bd->bd_cyl = ((v86.ecx & 0xc0) << 2) + ((v86.ecx & 0xff00) >> 8) + 1;
491 	/* Convert max head # -> # of heads */
492 	bd->bd_hds = ((v86.edx & 0xff00) >> 8) + 1;
493 	bd->bd_sec = v86.ecx & 0x3f;
494 	bd->bd_type = v86.ebx;
495 	bd->bd_sectors = (uint64_t)bd->bd_cyl * bd->bd_hds * bd->bd_sec;
496 
497 	return (0);
498 }
499 
500 /*
501  * Read EDD info. Return 0 on success, error otherwise.
502  */
503 static int
504 bd_get_diskinfo_ext(struct bdinfo *bd)
505 {
506 	struct edd_params params;
507 	uint64_t total;
508 
509 	/* Get disk params */
510 	bzero(&params, sizeof(params));
511 	params.len = sizeof(params);
512 	v86.ctl = V86_FLAGS;
513 	v86.addr = DISK_BIOS;
514 	v86.eax = CMD_EXT_PARAM;
515 	v86.edx = bd->bd_unit;
516 	v86.ds = VTOPSEG(&params);
517 	v86.esi = VTOPOFF(&params);
518 	v86int();
519 
520 	if (V86_CY(v86.efl) && ((v86.eax & 0xff00) != 0))
521 		return ((v86.eax & 0xff00) >> 8);
522 
523 	/*
524 	 * Sector size must be a multiple of 512 bytes.
525 	 * An alternate test would be to check power of 2,
526 	 * powerof2(params.sector_size).
527 	 * 16K is largest read buffer we can use at this time.
528 	 */
529 	if (params.sector_size >= 512 &&
530 	    params.sector_size <= 16384 &&
531 	    (params.sector_size % BIOSDISK_SECSIZE) == 0)
532 		bd->bd_sectorsize = params.sector_size;
533 
534 	bd->bd_cyl = params.cylinders;
535 	bd->bd_hds = params.heads;
536 	bd->bd_sec = params.sectors_per_track;
537 
538 	if (params.sectors != 0) {
539 		total = params.sectors;
540 	} else {
541 		total = (uint64_t)params.cylinders *
542 		    params.heads * params.sectors_per_track;
543 	}
544 	bd->bd_sectors = total;
545 
546 	return (0);
547 }
548 
549 /*
550  * Try to detect a device supported by the legacy int13 BIOS
551  */
552 static bool
553 bd_int13probe(bdinfo_t *bd)
554 {
555 	int edd, ret;
556 
557 	bd->bd_flags &= ~BD_NO_MEDIA;
558 
559 	edd = bd_check_extensions(bd->bd_unit);
560 	if (edd == 0)
561 		bd->bd_flags |= BD_MODEINT13;
562 	else if (edd < 0x30)
563 		bd->bd_flags |= BD_MODEEDD1;
564 	else
565 		bd->bd_flags |= BD_MODEEDD3;
566 
567 	/* Default sector size */
568 	if (bd->bd_sectorsize == 0)
569 		bd->bd_sectorsize = BIOSDISK_SECSIZE;
570 
571 	/*
572 	 * Test if the floppy device is present, so we can avoid receiving
573 	 * bogus information from bd_get_diskinfo_std().
574 	 */
575 	if (bd->bd_unit < 0x80) {
576 		/* reset disk */
577 		bd_reset_disk(bd->bd_unit);
578 
579 		/* Get disk type */
580 		v86.ctl = V86_FLAGS;
581 		v86.addr = DISK_BIOS;
582 		v86.eax = CMD_DRIVE_TYPE;
583 		v86.edx = bd->bd_unit;
584 		v86int();
585 		if (V86_CY(v86.efl) || (v86.eax & 0x300) == 0)
586 			return (false);
587 	}
588 
589 	ret = 1;
590 	if (edd != 0)
591 		ret = bd_get_diskinfo_ext(bd);
592 	if (ret != 0 || bd->bd_sectors == 0)
593 		ret = bd_get_diskinfo_std(bd);
594 
595 	if (ret != 0 && bd->bd_unit < 0x80) {
596 		/* Set defaults for 1.44 floppy */
597 		bd->bd_cyl = 80;
598 		bd->bd_hds = 2;
599 		bd->bd_sec = 18;
600 		bd->bd_sectors = 2880;
601 		/* Since we are there, there most likely is no media */
602 		bd->bd_flags |= BD_NO_MEDIA;
603 		ret = 0;
604 	}
605 
606 	if (ret != 0) {
607 		/* CD is special case, bc_add() has its own fallback. */
608 		if ((bd->bd_flags & BD_CDROM) != 0)
609 			return (true);
610 
611 		if (bd->bd_sectors != 0 && edd != 0) {
612 			bd->bd_sec = 63;
613 			bd->bd_hds = 255;
614 			bd->bd_cyl =
615 			    (bd->bd_sectors + bd->bd_sec * bd->bd_hds - 1) /
616 			    bd->bd_sec * bd->bd_hds;
617 		} else {
618 			const char *dv_name;
619 
620 			if ((bd->bd_flags & BD_FLOPPY) != 0)
621 				dv_name = biosfd.dv_name;
622 			else if ((bd->bd_flags & BD_CDROM) != 0)
623 				dv_name = bioscd.dv_name;
624 			else
625 				dv_name = bioshd.dv_name;
626 
627 			printf("Can not get information about %s unit %#x\n",
628 			    dv_name, bd->bd_unit);
629 			return (false);
630 		}
631 	}
632 
633 	if (bd->bd_sec == 0)
634 		bd->bd_sec = 63;
635 	if (bd->bd_hds == 0)
636 		bd->bd_hds = 255;
637 
638 	if (bd->bd_sectors == 0)
639 		bd->bd_sectors = (uint64_t)bd->bd_cyl * bd->bd_hds * bd->bd_sec;
640 
641 	DPRINTF("unit 0x%x geometry %d/%d/%d\n", bd->bd_unit, bd->bd_cyl,
642 	    bd->bd_hds, bd->bd_sec);
643 
644 	return (true);
645 }
646 
647 static int
648 bd_count(bdinfo_list_t *bdi)
649 {
650 	bdinfo_t *bd;
651 	int i;
652 
653 	i = 0;
654 	STAILQ_FOREACH(bd, bdi, bd_link)
655 		i++;
656 	return (i);
657 }
658 
659 /*
660  * Print information about disks
661  */
662 static int
663 bd_print_common(struct devsw *dev, bdinfo_list_t *bdi, int verbose)
664 {
665 	char line[80];
666 	struct disk_devdesc devd;
667 	bdinfo_t *bd;
668 	int i, ret = 0;
669 	char drive;
670 
671 	if (STAILQ_EMPTY(bdi))
672 		return (0);
673 
674 	printf("%s devices:", dev->dv_name);
675 	if ((ret = pager_output("\n")) != 0)
676 		return (ret);
677 
678 	i = -1;
679 	STAILQ_FOREACH(bd, bdi, bd_link) {
680 		i++;
681 
682 		switch (dev->dv_type) {
683 		case DEVT_FD:
684 			drive = 'A';
685 			break;
686 		case DEVT_CD:
687 			drive = 'C' + bd_count(&hdinfo);
688 			break;
689 		default:
690 			drive = 'C';
691 			break;
692 		}
693 
694 		snprintf(line, sizeof(line),
695 		    "    %s%d:   BIOS drive %c (%s%ju X %u):\n",
696 		    dev->dv_name, i, drive + i,
697 		    (bd->bd_flags & BD_NO_MEDIA) == BD_NO_MEDIA ?
698 		    "no media, " : "",
699 		    (uintmax_t)bd->bd_sectors,
700 		    bd->bd_sectorsize);
701 		if ((ret = pager_output(line)) != 0)
702 			break;
703 
704 		if ((bd->bd_flags & BD_NO_MEDIA) == BD_NO_MEDIA)
705 			continue;
706 
707 		if (dev->dv_type != DEVT_DISK)
708 			continue;
709 
710 		devd.dd.d_dev = dev;
711 		devd.dd.d_unit = i;
712 		devd.d_slice = D_SLICENONE;
713 		devd.d_partition = D_PARTNONE;
714 		if (disk_open(&devd,
715 		    bd->bd_sectorsize * bd->bd_sectors,
716 		    bd->bd_sectorsize) == 0) {
717 			snprintf(line, sizeof(line), "    %s%d",
718 			    dev->dv_name, i);
719 			ret = disk_print(&devd, line, verbose);
720 			disk_close(&devd);
721 			if (ret != 0)
722 				break;
723 		}
724 	}
725 	return (ret);
726 }
727 
728 static int
729 fd_print(int verbose)
730 {
731 	return (bd_print_common(&biosfd, &fdinfo, verbose));
732 }
733 
734 static int
735 bd_print(int verbose)
736 {
737 	return (bd_print_common(&bioshd, &hdinfo, verbose));
738 }
739 
740 static int
741 cd_print(int verbose)
742 {
743 	return (bd_print_common(&bioscd, &cdinfo, verbose));
744 }
745 
746 /*
747  * Read disk size from partition.
748  * This is needed to work around buggy BIOS systems returning
749  * wrong (truncated) disk media size.
750  * During bd_probe() we tested if the multiplication of bd_sectors
751  * would overflow so it should be safe to perform here.
752  */
753 static uint64_t
754 bd_disk_get_sectors(struct disk_devdesc *dev)
755 {
756 	bdinfo_t *bd;
757 	struct disk_devdesc disk;
758 	uint64_t size;
759 
760 	bd = bd_get_bdinfo(&dev->dd);
761 	if (bd == NULL)
762 		return (0);
763 
764 	disk.dd.d_dev = dev->dd.d_dev;
765 	disk.dd.d_unit = dev->dd.d_unit;
766 	disk.d_slice = D_SLICENONE;
767 	disk.d_partition = D_PARTNONE;
768 	disk.d_offset = 0;
769 
770 	size = bd->bd_sectors * bd->bd_sectorsize;
771 	if (disk_open(&disk, size, bd->bd_sectorsize) == 0) {
772 		(void) disk_ioctl(&disk, DIOCGMEDIASIZE, &size);
773 		disk_close(&disk);
774 	}
775 	return (size / bd->bd_sectorsize);
776 }
777 
778 /*
779  * Attempt to open the disk described by (dev) for use by (f).
780  *
781  * Note that the philosophy here is "give them exactly what
782  * they ask for".  This is necessary because being too "smart"
783  * about what the user might want leads to complications.
784  * (eg. given no slice or partition value, with a disk that is
785  *  sliced - are they after the first BSD slice, or the DOS
786  *  slice before it?)
787  */
788 static int
789 bd_open(struct open_file *f, ...)
790 {
791 	bdinfo_t *bd;
792 	struct disk_devdesc *dev;
793 	va_list ap;
794 	int rc;
795 
796 	va_start(ap, f);
797 	dev = va_arg(ap, struct disk_devdesc *);
798 	va_end(ap);
799 
800 	bd = bd_get_bdinfo(&dev->dd);
801 	if (bd == NULL)
802 		return (EIO);
803 
804 	if ((bd->bd_flags & BD_NO_MEDIA) == BD_NO_MEDIA) {
805 		if (!bd_int13probe(bd))
806 			return (EIO);
807 		if ((bd->bd_flags & BD_NO_MEDIA) == BD_NO_MEDIA)
808 			return (EIO);
809 	}
810 	if (bd->bd_bcache == NULL)
811 	    bd->bd_bcache = bcache_allocate();
812 
813 	if (bd->bd_open == 0)
814 		bd->bd_sectors = bd_disk_get_sectors(dev);
815 	bd->bd_open++;
816 
817 	rc = 0;
818 	if (dev->dd.d_dev->dv_type == DEVT_DISK) {
819 		rc = disk_open(dev, bd->bd_sectors * bd->bd_sectorsize,
820 		    bd->bd_sectorsize);
821 		if (rc != 0) {
822 			bd->bd_open--;
823 			if (bd->bd_open == 0) {
824 				bcache_free(bd->bd_bcache);
825 				bd->bd_bcache = NULL;
826 			}
827 		}
828 	}
829 	return (rc);
830 }
831 
832 static int
833 bd_close(struct open_file *f)
834 {
835 	struct disk_devdesc *dev;
836 	bdinfo_t *bd;
837 	int rc = 0;
838 
839 	dev = (struct disk_devdesc *)f->f_devdata;
840 	bd = bd_get_bdinfo(&dev->dd);
841 	if (bd == NULL)
842 		return (EIO);
843 
844 	bd->bd_open--;
845 	if (bd->bd_open == 0) {
846 	    bcache_free(bd->bd_bcache);
847 	    bd->bd_bcache = NULL;
848 	}
849 	if (dev->dd.d_dev->dv_type == DEVT_DISK)
850 		rc = disk_close(dev);
851 	return (rc);
852 }
853 
854 static int
855 bd_ioctl(struct open_file *f, u_long cmd, void *data)
856 {
857 	bdinfo_t *bd;
858 	struct disk_devdesc *dev;
859 	int rc;
860 
861 	dev = (struct disk_devdesc *)f->f_devdata;
862 	bd = bd_get_bdinfo(&dev->dd);
863 	if (bd == NULL)
864 		return (EIO);
865 
866 	if (dev->dd.d_dev->dv_type == DEVT_DISK) {
867 		rc = disk_ioctl(dev, cmd, data);
868 		if (rc != ENOTTY)
869 			return (rc);
870 	}
871 
872 	switch (cmd) {
873 	case DIOCGSECTORSIZE:
874 		*(uint32_t *)data = bd->bd_sectorsize;
875 		break;
876 	case DIOCGMEDIASIZE:
877 		*(uint64_t *)data = bd->bd_sectors * bd->bd_sectorsize;
878 		break;
879 	default:
880 		return (ENOTTY);
881 	}
882 	return (0);
883 }
884 
885 static int
886 bd_strategy(void *devdata, int rw, daddr_t dblk, size_t size,
887     char *buf, size_t *rsize)
888 {
889 	bdinfo_t *bd;
890 	struct bcache_devdata bcd;
891 	struct disk_devdesc *dev;
892 	daddr_t offset;
893 
894 	dev = (struct disk_devdesc *)devdata;
895 	bd = bd_get_bdinfo(&dev->dd);
896 	if (bd == NULL)
897 		return (EINVAL);
898 
899 	bcd.dv_strategy = bd_realstrategy;
900 	bcd.dv_devdata = devdata;
901 	bcd.dv_cache = bd->bd_bcache;
902 
903 	offset = 0;
904 	if (dev->dd.d_dev->dv_type == DEVT_DISK) {
905 
906 		offset = dev->d_offset * bd->bd_sectorsize;
907 		offset /= BIOSDISK_SECSIZE;
908 	}
909 	return (bcache_strategy(&bcd, rw, dblk + offset, size,
910 	    buf, rsize));
911 }
912 
913 static int
914 bd_realstrategy(void *devdata, int rw, daddr_t dblk, size_t size,
915     char *buf, size_t *rsize)
916 {
917 	struct disk_devdesc *dev = (struct disk_devdesc *)devdata;
918 	bdinfo_t *bd;
919 	uint64_t disk_blocks, offset, d_offset;
920 	size_t blks, blkoff, bsize, bio_size, rest;
921 	caddr_t bbuf = NULL;
922 	int rc;
923 
924 	bd = bd_get_bdinfo(&dev->dd);
925 	if (bd == NULL || (bd->bd_flags & BD_NO_MEDIA) == BD_NO_MEDIA)
926 		return (EIO);
927 
928 	/*
929 	 * First make sure the IO size is a multiple of 512 bytes. While we do
930 	 * process partial reads below, the strategy mechanism is built
931 	 * assuming IO is a multiple of 512B blocks. If the request is not
932 	 * a multiple of 512B blocks, it has to be some sort of bug.
933 	 */
934 	if (size == 0 || (size % BIOSDISK_SECSIZE) != 0) {
935 		printf("bd_strategy: %d bytes I/O not multiple of %d\n",
936 		    size, BIOSDISK_SECSIZE);
937 		return (EIO);
938 	}
939 
940 	DPRINTF("open_disk %p", dev);
941 
942 	offset = dblk * BIOSDISK_SECSIZE;
943 	dblk = offset / bd->bd_sectorsize;
944 	blkoff = offset % bd->bd_sectorsize;
945 
946 	/*
947 	 * Check the value of the size argument. We do have quite small
948 	 * heap (64MB), but we do not know good upper limit, so we check against
949 	 * INT_MAX here. This will also protect us against possible overflows
950 	 * while translating block count to bytes.
951 	 */
952 	if (size > INT_MAX) {
953 		DPRINTF("too large I/O: %zu bytes", size);
954 		return (EIO);
955 	}
956 
957 	blks = size / bd->bd_sectorsize;
958 	if (blks == 0 || (size % bd->bd_sectorsize) != 0)
959 		blks++;
960 
961 	if (dblk > dblk + blks)
962 		return (EIO);
963 
964 	if (rsize)
965 		*rsize = 0;
966 
967 	/*
968 	 * Get disk blocks, this value is either for whole disk or for
969 	 * partition.
970 	 */
971 	d_offset = 0;
972 	disk_blocks = 0;
973 	if (dev->dd.d_dev->dv_type == DEVT_DISK) {
974 		if (disk_ioctl(dev, DIOCGMEDIASIZE, &disk_blocks) == 0) {
975 			/* DIOCGMEDIASIZE does return bytes. */
976 			disk_blocks /= bd->bd_sectorsize;
977 		}
978 		d_offset = dev->d_offset;
979 	}
980 	if (disk_blocks == 0)
981 		disk_blocks = bd->bd_sectors - d_offset;
982 
983 	/* Validate source block address. */
984 	if (dblk < d_offset || dblk >= d_offset + disk_blocks)
985 		return (EIO);
986 
987 	/*
988 	 * Truncate if we are crossing disk or partition end.
989 	 */
990 	if (dblk + blks >= d_offset + disk_blocks) {
991 		blks = d_offset + disk_blocks - dblk;
992 		size = blks * bd->bd_sectorsize;
993 		DPRINTF("short I/O %d", blks);
994 	}
995 
996 	bio_size = min(BIO_BUFFER_SIZE, size);
997 	while (bio_size > bd->bd_sectorsize) {
998 		bbuf = bio_alloc(bio_size);
999 		if (bbuf != NULL)
1000 			break;
1001 		bio_size -= bd->bd_sectorsize;
1002 	}
1003 	if (bbuf == NULL) {
1004 		bio_size = V86_IO_BUFFER_SIZE;
1005 		if (bio_size / bd->bd_sectorsize == 0)
1006 			panic("BUG: Real mode buffer is too small");
1007 
1008 		/* Use alternate 4k buffer */
1009 		bbuf = PTOV(V86_IO_BUFFER);
1010 	}
1011 	rest = size;
1012 	rc = 0;
1013 	while (blks > 0) {
1014 		int x = min(blks, bio_size / bd->bd_sectorsize);
1015 
1016 		switch (rw & F_MASK) {
1017 		case F_READ:
1018 			DPRINTF("read %d from %lld to %p", x, dblk, buf);
1019 			bsize = bd->bd_sectorsize * x - blkoff;
1020 			if (rest < bsize)
1021 				bsize = rest;
1022 
1023 			if ((rc = bd_io(dev, bd, dblk, x, bbuf, BD_RD)) != 0) {
1024 				rc = EIO;
1025 				goto error;
1026 			}
1027 
1028 			bcopy(bbuf + blkoff, buf, bsize);
1029 			break;
1030 		case F_WRITE :
1031 			DPRINTF("write %d from %lld to %p", x, dblk, buf);
1032 			if (blkoff != 0) {
1033 				/*
1034 				 * We got offset to sector, read 1 sector to
1035 				 * bbuf.
1036 				 */
1037 				x = 1;
1038 				bsize = bd->bd_sectorsize - blkoff;
1039 				bsize = min(bsize, rest);
1040 				rc = bd_io(dev, bd, dblk, x, bbuf, BD_RD);
1041 			} else if (rest < bd->bd_sectorsize) {
1042 				/*
1043 				 * The remaining block is not full
1044 				 * sector. Read 1 sector to bbuf.
1045 				 */
1046 				x = 1;
1047 				bsize = rest;
1048 				rc = bd_io(dev, bd, dblk, x, bbuf, BD_RD);
1049 			} else {
1050 				/* We can write full sector(s). */
1051 				bsize = bd->bd_sectorsize * x;
1052 			}
1053 			/*
1054 			 * Put your Data In, Put your Data out,
1055 			 * Put your Data In, and shake it all about
1056 			 */
1057 			bcopy(buf, bbuf + blkoff, bsize);
1058 			if ((rc = bd_io(dev, bd, dblk, x, bbuf, BD_WR)) != 0) {
1059 				rc = EIO;
1060 				goto error;
1061 			}
1062 
1063 			break;
1064 		default:
1065 			/* DO NOTHING */
1066 			rc = EROFS;
1067 			goto error;
1068 		}
1069 
1070 		blkoff = 0;
1071 		buf += bsize;
1072 		rest -= bsize;
1073 		blks -= x;
1074 		dblk += x;
1075 	}
1076 
1077 	if (rsize != NULL)
1078 		*rsize = size;
1079 error:
1080 	if (bbuf != PTOV(V86_IO_BUFFER))
1081 		bio_free(bbuf, bio_size);
1082 	return (rc);
1083 }
1084 
1085 static int
1086 bd_edd_io(bdinfo_t *bd, daddr_t dblk, int blks, caddr_t dest,
1087     int dowrite)
1088 {
1089 	static struct edd_packet packet;
1090 
1091 	packet.len = sizeof(struct edd_packet);
1092 	packet.count = blks;
1093 	packet.off = VTOPOFF(dest);
1094 	packet.seg = VTOPSEG(dest);
1095 	packet.lba = dblk;
1096 	v86.ctl = V86_FLAGS;
1097 	v86.addr = DISK_BIOS;
1098 	if (dowrite == BD_WR)
1099 		v86.eax = CMD_WRITE_LBA; /* maybe Write with verify 0x4302? */
1100 	else
1101 		v86.eax = CMD_READ_LBA;
1102 	v86.edx = bd->bd_unit;
1103 	v86.ds = VTOPSEG(&packet);
1104 	v86.esi = VTOPOFF(&packet);
1105 	v86int();
1106 	if (V86_CY(v86.efl))
1107 		return (v86.eax >> 8);
1108 	return (0);
1109 }
1110 
1111 static int
1112 bd_chs_io(bdinfo_t *bd, daddr_t dblk, int blks, caddr_t dest,
1113     int dowrite)
1114 {
1115 	uint32_t x, bpc, cyl, hd, sec;
1116 
1117 	bpc = bd->bd_sec * bd->bd_hds;	/* blocks per cylinder */
1118 	x = dblk;
1119 	cyl = x / bpc;			/* block # / blocks per cylinder */
1120 	x %= bpc;				/* block offset into cylinder */
1121 	hd = x / bd->bd_sec;		/* offset / blocks per track */
1122 	sec = x % bd->bd_sec;		/* offset into track */
1123 
1124 	/* correct sector number for 1-based BIOS numbering */
1125 	sec++;
1126 
1127 	if (cyl > 1023) {
1128 		/* CHS doesn't support cylinders > 1023. */
1129 		return (1);
1130 	}
1131 
1132 	v86.ctl = V86_FLAGS;
1133 	v86.addr = DISK_BIOS;
1134 	if (dowrite == BD_WR)
1135 		v86.eax = CMD_WRITE_CHS | blks;
1136 	else
1137 		v86.eax = CMD_READ_CHS | blks;
1138 	v86.ecx = ((cyl & 0xff) << 8) | ((cyl & 0x300) >> 2) | sec;
1139 	v86.edx = (hd << 8) | bd->bd_unit;
1140 	v86.es = VTOPSEG(dest);
1141 	v86.ebx = VTOPOFF(dest);
1142 	v86int();
1143 	if (V86_CY(v86.efl))
1144 		return (v86.eax >> 8);
1145 	return (0);
1146 }
1147 
1148 static void
1149 bd_io_workaround(bdinfo_t *bd)
1150 {
1151 	uint8_t buf[8 * 1024];
1152 
1153 	bd_edd_io(bd, 0xffffffff, 1, (caddr_t)buf, BD_RD);
1154 }
1155 
1156 static int
1157 bd_io(struct disk_devdesc *dev, bdinfo_t *bd, daddr_t dblk, int blks,
1158     caddr_t dest, int dowrite)
1159 {
1160 	int result, retry;
1161 
1162 	/* Just in case some idiot actually tries to read/write -1 blocks... */
1163 	if (blks < 0)
1164 		return (-1);
1165 
1166 	/*
1167 	 * Workaround for a problem with some HP ProLiant BIOS failing to work
1168 	 * out the boot disk after installation. hrs and kuriyama discovered
1169 	 * this problem with an HP ProLiant DL320e Gen 8 with a 3TB HDD, and
1170 	 * discovered that an int13h call seems to cause a buffer overrun in
1171 	 * the bios. The problem is alleviated by doing an extra read before
1172 	 * the buggy read. It is not immediately known whether other models
1173 	 * are similarly affected.
1174 	 * Loop retrying the operation a couple of times.  The BIOS
1175 	 * may also retry.
1176 	 */
1177 	if (dowrite == BD_RD && dblk >= 0x100000000)
1178 		bd_io_workaround(bd);
1179 	for (retry = 0; retry < 3; retry++) {
1180 		if (bd->bd_flags & BD_MODEEDD)
1181 			result = bd_edd_io(bd, dblk, blks, dest, dowrite);
1182 		else
1183 			result = bd_chs_io(bd, dblk, blks, dest, dowrite);
1184 
1185 		if (result == 0) {
1186 			if (bd->bd_flags & BD_NO_MEDIA)
1187 				bd->bd_flags &= ~BD_NO_MEDIA;
1188 			break;
1189 		}
1190 
1191 		bd_reset_disk(bd->bd_unit);
1192 
1193 		/*
1194 		 * Error codes:
1195 		 * 20h	controller failure
1196 		 * 31h	no media in drive (IBM/MS INT 13 extensions)
1197 		 * 80h	no media in drive, VMWare (Fusion)
1198 		 * There is no reason to repeat the IO with errors above.
1199 		 */
1200 		if (result == 0x20 || result == 0x31 || result == 0x80) {
1201 			bd->bd_flags |= BD_NO_MEDIA;
1202 			break;
1203 		}
1204 	}
1205 
1206 	if (result != 0 && (bd->bd_flags & BD_NO_MEDIA) == 0) {
1207 		if (dowrite == BD_WR) {
1208 			printf("%s%d: Write %d sector(s) from %p (0x%x) "
1209 			    "to %lld: 0x%x\n", dev->dd.d_dev->dv_name,
1210 			    dev->dd.d_unit, blks, dest, VTOP(dest), dblk,
1211 			    result);
1212 		} else {
1213 			printf("%s%d: Read %d sector(s) from %lld to %p "
1214 			    "(0x%x): 0x%x\n", dev->dd.d_dev->dv_name,
1215 			    dev->dd.d_unit, blks, dblk, dest, VTOP(dest),
1216 			    result);
1217 		}
1218 	}
1219 
1220 	return (result);
1221 }
1222 
1223 /*
1224  * Return the BIOS geometry of a given "fixed drive" in a format
1225  * suitable for the legacy bootinfo structure.  Since the kernel is
1226  * expecting raw int 0x13/0x8 values for N_BIOS_GEOM drives, we
1227  * prefer to get the information directly, rather than rely on being
1228  * able to put it together from information already maintained for
1229  * different purposes and for a probably different number of drives.
1230  *
1231  * For valid drives, the geometry is expected in the format (31..0)
1232  * "000000cc cccccccc hhhhhhhh 00ssssss"; and invalid drives are
1233  * indicated by returning the geometry of a "1.2M" PC-format floppy
1234  * disk.  And, incidentally, what is returned is not the geometry as
1235  * such but the highest valid cylinder, head, and sector numbers.
1236  */
1237 uint32_t
1238 bd_getbigeom(int bunit)
1239 {
1240 
1241 	v86.ctl = V86_FLAGS;
1242 	v86.addr = DISK_BIOS;
1243 	v86.eax = CMD_READ_PARAM;
1244 	v86.edx = 0x80 + bunit;
1245 	v86int();
1246 	if (V86_CY(v86.efl))
1247 		return (0x4f010f);
1248 	return (((v86.ecx & 0xc0) << 18) | ((v86.ecx & 0xff00) << 8) |
1249 	    (v86.edx & 0xff00) | (v86.ecx & 0x3f));
1250 }
1251 
1252 /*
1253  * Return a suitable dev_t value for (dev).
1254  *
1255  * In the case where it looks like (dev) is a SCSI disk, we allow the number of
1256  * IDE disks to be specified in $num_ide_disks.  There should be a Better Way.
1257  */
1258 int
1259 bd_getdev(struct i386_devdesc *d)
1260 {
1261 	struct disk_devdesc *dev;
1262 	bdinfo_t *bd;
1263 	int	biosdev;
1264 	int	major;
1265 	int	rootdev;
1266 	char	*nip, *cp;
1267 	int	i, unit, slice, partition;
1268 
1269 	/* XXX: Assume partition 'a'. */
1270 	slice = 0;
1271 	partition = 0;
1272 
1273 	dev = (struct disk_devdesc *)d;
1274 	bd = bd_get_bdinfo(&dev->dd);
1275 	if (bd == NULL)
1276 		return (-1);
1277 
1278 	biosdev = bd_unit2bios(d);
1279 	DPRINTF("unit %d BIOS device %d", dev->dd.d_unit, biosdev);
1280 	if (biosdev == -1)			/* not a BIOS device */
1281 		return (-1);
1282 
1283 	if (dev->dd.d_dev->dv_type == DEVT_DISK) {
1284 		if (disk_open(dev, bd->bd_sectors * bd->bd_sectorsize,
1285 		    bd->bd_sectorsize) != 0)	/* oops, not a viable device */
1286 			return (-1);
1287 		else
1288 			disk_close(dev);
1289 		slice = dev->d_slice + 1;
1290 		partition = dev->d_partition;
1291 	}
1292 
1293 	if (biosdev < 0x80) {
1294 		/* floppy (or emulated floppy) or ATAPI device */
1295 		if (bd->bd_type == DT_ATAPI) {
1296 			/* is an ATAPI disk */
1297 			major = WFDMAJOR;
1298 		} else {
1299 			/* is a floppy disk */
1300 			major = FDMAJOR;
1301 		}
1302 	} else {
1303 		/* assume an IDE disk */
1304 		major = WDMAJOR;
1305 	}
1306 	/* default root disk unit number */
1307 	unit = biosdev & 0x7f;
1308 
1309 	if (dev->dd.d_dev->dv_type == DEVT_CD) {
1310 		/*
1311 		 * XXX: Need to examine device spec here to figure out if
1312 		 * SCSI or ATAPI.  No idea on how to figure out device number.
1313 		 * All we can really pass to the kernel is what bus and device
1314 		 * on which bus we were booted from, which dev_t isn't well
1315 		 * suited to since those number don't match to unit numbers
1316 		 * very well.  We may just need to engage in a hack where
1317 		 * we pass -C to the boot args if we are the boot device.
1318 		 */
1319 		major = ACDMAJOR;
1320 		unit = 0;       /* XXX */
1321 	}
1322 
1323 	/* XXX a better kludge to set the root disk unit number */
1324 	if ((nip = getenv("root_disk_unit")) != NULL) {
1325 		i = strtol(nip, &cp, 0);
1326 		/* check for parse error */
1327 		if ((cp != nip) && (*cp == 0))
1328 			unit = i;
1329 	}
1330 
1331 	rootdev = MAKEBOOTDEV(major, slice, unit, partition);
1332 	DPRINTF("dev is 0x%x\n", rootdev);
1333 	return (rootdev);
1334 }
1335