xref: /illumos-gate/usr/src/boot/i386/libi386/biosdisk.c (revision ed093b41a93e8563e6e1e5dae0768dda2a7bcc27)
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 
30 /*
31  * BIOS disk device handling.
32  *
33  * Ideas and algorithms from:
34  *
35  * - NetBSD libi386/biosdisk.c
36  * - FreeBSD biosboot/disk.c
37  *
38  */
39 
40 #include <sys/disk.h>
41 #include <sys/limits.h>
42 #include <sys/queue.h>
43 #include <stand.h>
44 #include <machine/bootinfo.h>
45 #include <stdarg.h>
46 #include <stdbool.h>
47 
48 #include <bootstrap.h>
49 #include <btxv86.h>
50 #include <edd.h>
51 #include "disk.h"
52 #include "libi386.h"
53 
54 #define	BIOS_NUMDRIVES		0x475
55 #define	BIOSDISK_SECSIZE	512
56 #define	BUFSIZE			(1 * BIOSDISK_SECSIZE)
57 
58 #define	DT_ATAPI	0x10	/* disk type for ATAPI floppies */
59 #define	WDMAJOR		0	/* major numbers for devices we frontend for */
60 #define	WFDMAJOR	1
61 #define	FDMAJOR		2
62 #define	DAMAJOR		4
63 #define	ACDMAJOR	117
64 #define	CDMAJOR		15
65 
66 /*
67  * INT13 commands
68  */
69 #define	CMD_RESET	0x0000
70 #define	CMD_READ_CHS	0x0200
71 #define	CMD_WRITE_CHS	0x0300
72 #define	CMD_READ_PARAM	0x0800
73 #define	CMD_DRIVE_TYPE	0x1500
74 #define	CMD_CHECK_EDD	0x4100
75 #define	CMD_READ_LBA	0x4200
76 #define	CMD_WRITE_LBA	0x4300
77 #define	CMD_EXT_PARAM	0x4800
78 #define	CMD_CD_GET_STATUS 0x4b01
79 
80 #define	DISK_BIOS	0x13
81 
82 #ifdef DISK_DEBUG
83 #define	DPRINTF(fmt, args...)	printf("%s: " fmt "\n", __func__, ## args)
84 #else
85 #define	DPRINTF(fmt, args...)	((void)0)
86 #endif
87 
88 struct specification_packet {
89 	uint8_t		sp_size;
90 	uint8_t		sp_bootmedia;
91 	uint8_t		sp_drive;
92 	uint8_t		sp_controller;
93 	uint32_t	sp_lba;
94 	uint16_t	sp_devicespec;
95 	uint16_t	sp_buffersegment;
96 	uint16_t	sp_loadsegment;
97 	uint16_t	sp_sectorcount;
98 	uint16_t	sp_cylsec;
99 	uint8_t		sp_head;
100 	uint8_t		sp_dummy[16];	/* Avoid memory corruption */
101 } __packed;
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, ulong_t 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 	bd_reset_disk(0);
281 
282 	for (drive = 0; drive < MAXBDDEV; drive++) {
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 		printf("BIOS drive %c: is %s%d\n", ('A' + unit),
325 		    biosfd.dv_name, unit);
326 		STAILQ_INSERT_TAIL(&fdinfo, bd, bd_link);
327 	}
328 
329 	bcache_add_dev(unit);
330 	return (0);
331 }
332 
333 static int
334 bd_init(void)
335 {
336 	int base, unit;
337 	bdinfo_t *bd;
338 
339 	base = 0x80;
340 	for (unit = 0; unit < *(unsigned char *)PTOV(BIOS_NUMDRIVES); unit++) {
341 		/*
342 		 * Check the BIOS equipment list for number of fixed disks.
343 		 */
344 		if ((bd = calloc(1, sizeof (*bd))) == NULL)
345 			break;
346 		bd->bd_unit = base + unit;
347 		if (!bd_int13probe(bd)) {
348 			free(bd);
349 			break;
350 		}
351 		printf("BIOS drive %c: is %s%d\n", ('C' + unit),
352 		    bioshd.dv_name, unit);
353 		STAILQ_INSERT_TAIL(&hdinfo, bd, bd_link);
354 	}
355 	bcache_add_dev(unit);
356 	return (0);
357 }
358 
359 /*
360  * We can't quiz, we have to be told what device to use, so this function
361  * doesn't do anything.  Instead, the loader calls bc_add() with the BIOS
362  * device number to add.
363  */
364 static int
365 cd_init(void)
366 {
367 
368 	return (0);
369 }
370 
371 /*
372  * Information from bootable CD-ROM.
373  */
374 static int
375 bd_get_diskinfo_cd(struct bdinfo *bd)
376 {
377 	struct specification_packet bc_sp;
378 	int ret = -1;
379 
380 	(void) memset(&bc_sp, 0, sizeof (bc_sp));
381 	/* Set sp_size as per specification. */
382 	bc_sp.sp_size = sizeof (bc_sp) - sizeof (bc_sp.sp_dummy);
383 
384 	v86.ctl = V86_FLAGS;
385 	v86.addr = DISK_BIOS;
386 	v86.eax = CMD_CD_GET_STATUS;
387 	v86.edx = bd->bd_unit;
388 	v86.ds = VTOPSEG(&bc_sp);
389 	v86.esi = VTOPOFF(&bc_sp);
390 	v86int();
391 
392 	if ((v86.eax & 0xff00) == 0 &&
393 	    bc_sp.sp_drive == bd->bd_unit) {
394 		bd->bd_cyl = ((bc_sp.sp_cylsec & 0xc0) << 2) +
395 		    ((bc_sp.sp_cylsec & 0xff00) >> 8) + 1;
396 		bd->bd_sec = bc_sp.sp_cylsec & 0x3f;
397 		bd->bd_hds = bc_sp.sp_head + 1;
398 		bd->bd_sectors = (uint64_t)bd->bd_cyl * bd->bd_hds * bd->bd_sec;
399 
400 		if (bc_sp.sp_bootmedia & 0x0F) {
401 			/* Floppy or hard-disk emulation */
402 			bd->bd_sectorsize = BIOSDISK_SECSIZE;
403 			return (-1);
404 		} else {
405 			bd->bd_sectorsize = 2048;
406 			bd->bd_flags = BD_MODEEDD | BD_CDROM;
407 			ret = 0;
408 		}
409 	}
410 
411 	/*
412 	 * If this is the boot_drive, default to non-emulation bootable CD-ROM.
413 	 */
414 	if (ret != 0 && bd->bd_unit >= 0x88) {
415 		bd->bd_cyl = 0;
416 		bd->bd_hds = 1;
417 		bd->bd_sec = 15;
418 		bd->bd_sectorsize = 2048;
419 		bd->bd_flags = BD_MODEEDD | BD_CDROM;
420 		bd->bd_sectors = 0;
421 		ret = 0;
422 	}
423 
424 	/*
425 	 * Note we can not use bd_get_diskinfo_ext() nor bd_get_diskinfo_std()
426 	 * here - some systems do get hung with those.
427 	 */
428 	/*
429 	 * Still no size? use 7.961GB. The size does not really matter
430 	 * as long as it is reasonably large to make our reads to pass
431 	 * the sector count check.
432 	 */
433 	if (bd->bd_sectors == 0)
434 		bd->bd_sectors = 4173824;
435 
436 	return (ret);
437 }
438 
439 int
440 bc_add(int biosdev)
441 {
442 	bdinfo_t *bd;
443 	int nbcinfo = 0;
444 
445 	if (!STAILQ_EMPTY(&cdinfo))
446 		return (-1);
447 
448 	if ((bd = calloc(1, sizeof (*bd))) == NULL)
449 		return (-1);
450 
451 	bd->bd_unit = biosdev;
452 	if (bd_get_diskinfo_cd(bd) < 0) {
453 		free(bd);
454 		return (-1);
455 	}
456 
457 	STAILQ_INSERT_TAIL(&cdinfo, bd, bd_link);
458 	printf("BIOS CD is cd%d\n", nbcinfo);
459 	nbcinfo++;
460 	bcache_add_dev(nbcinfo);	/* register cd device in bcache */
461 	return (0);
462 }
463 
464 /*
465  * Return EDD version or 0 if EDD is not supported on this drive.
466  */
467 static int
468 bd_check_extensions(int unit)
469 {
470 	/* do not use ext calls for floppy devices */
471 	if (unit < 0x80)
472 		return (0);
473 
474 	/* Determine if we can use EDD with this device. */
475 	v86.ctl = V86_FLAGS;
476 	v86.addr = DISK_BIOS;
477 	v86.eax = CMD_CHECK_EDD;
478 	v86.edx = unit;
479 	v86.ebx = EDD_QUERY_MAGIC;
480 	v86int();
481 
482 	if (V86_CY(v86.efl) ||			/* carry set */
483 	    (v86.ebx & 0xffff) != EDD_INSTALLED) /* signature */
484 		return (0);
485 
486 	/* extended disk access functions (AH=42h-44h,47h,48h) supported */
487 	if ((v86.ecx & EDD_INTERFACE_FIXED_DISK) == 0)
488 		return (0);
489 
490 	return ((v86.eax >> 8) & 0xff);
491 }
492 
493 static void
494 bd_reset_disk(int unit)
495 {
496 	/* reset disk */
497 	v86.ctl = V86_FLAGS;
498 	v86.addr = DISK_BIOS;
499 	v86.eax = CMD_RESET;
500 	v86.edx = unit;
501 	v86int();
502 }
503 
504 /*
505  * Read CHS info. Return 0 on success, error otherwise.
506  */
507 static int
508 bd_get_diskinfo_std(struct bdinfo *bd)
509 {
510 	bzero(&v86, sizeof (v86));
511 	v86.ctl = V86_FLAGS;
512 	v86.addr = DISK_BIOS;
513 	v86.eax = CMD_READ_PARAM;
514 	v86.edx = bd->bd_unit;
515 	v86int();
516 
517 	if (V86_CY(v86.efl) && ((v86.eax & 0xff00) != 0))
518 		return ((v86.eax & 0xff00) >> 8);
519 
520 	/* return custom error on absurd sector number */
521 	if ((v86.ecx & 0x3f) == 0)
522 		return (0x60);
523 
524 	bd->bd_cyl = ((v86.ecx & 0xc0) << 2) + ((v86.ecx & 0xff00) >> 8) + 1;
525 	/* Convert max head # -> # of heads */
526 	bd->bd_hds = ((v86.edx & 0xff00) >> 8) + 1;
527 	bd->bd_sec = v86.ecx & 0x3f;
528 	bd->bd_type = v86.ebx;
529 	bd->bd_sectors = (uint64_t)bd->bd_cyl * bd->bd_hds * bd->bd_sec;
530 
531 	return (0);
532 }
533 
534 /*
535  * Read EDD info. Return 0 on success, error otherwise.
536  *
537  * Avoid stack corruption on some systems by adding extra bytes to
538  * params block.
539  */
540 static int
541 bd_get_diskinfo_ext(struct bdinfo *bd)
542 {
543 	struct disk_params {
544 		struct edd_params head;
545 		struct edd_device_path_v3 device_path;
546 		uint8_t	dummy[16];
547 	} __packed dparams;
548 	struct edd_params *params;
549 	uint64_t total;
550 
551 	params = &dparams.head;
552 	/* Get disk params */
553 	bzero(&dparams, sizeof (dparams));
554 	params->len = sizeof (struct edd_params_v3);
555 	v86.ctl = V86_FLAGS;
556 	v86.addr = DISK_BIOS;
557 	v86.eax = CMD_EXT_PARAM;
558 	v86.edx = bd->bd_unit;
559 	v86.ds = VTOPSEG(&dparams);
560 	v86.esi = VTOPOFF(&dparams);
561 	v86int();
562 
563 	if (V86_CY(v86.efl) && ((v86.eax & 0xff00) != 0))
564 		return ((v86.eax & 0xff00) >> 8);
565 
566 	/*
567 	 * Sector size must be a multiple of 512 bytes.
568 	 * An alternate test would be to check power of 2,
569 	 * powerof2(params.sector_size).
570 	 * 16K is largest read buffer we can use at this time.
571 	 */
572 	if (params->sector_size >= 512 &&
573 	    params->sector_size <= 16384 &&
574 	    (params->sector_size % BIOSDISK_SECSIZE) == 0)
575 		bd->bd_sectorsize = params->sector_size;
576 
577 	bd->bd_cyl = params->cylinders;
578 	bd->bd_hds = params->heads;
579 	bd->bd_sec = params->sectors_per_track;
580 
581 	if (params->sectors != 0) {
582 		total = params->sectors;
583 	} else {
584 		total = (uint64_t)params->cylinders *
585 		    params->heads * params->sectors_per_track;
586 	}
587 	bd->bd_sectors = total;
588 
589 	return (0);
590 }
591 
592 /*
593  * Try to detect a device supported by the legacy int13 BIOS
594  */
595 static bool
596 bd_int13probe(bdinfo_t *bd)
597 {
598 	int edd, ret;
599 
600 	bd->bd_flags &= ~BD_NO_MEDIA;
601 
602 	if ((bd->bd_flags & BD_CDROM) != 0) {
603 		return (bd_get_diskinfo_cd(bd) == 0);
604 	}
605 
606 	edd = bd_check_extensions(bd->bd_unit);
607 	if (edd == 0)
608 		bd->bd_flags |= BD_MODEINT13;
609 	else if (edd < 0x30)
610 		bd->bd_flags |= BD_MODEEDD1;
611 	else
612 		bd->bd_flags |= BD_MODEEDD3;
613 
614 	/* Default sector size */
615 	if (bd->bd_sectorsize == 0)
616 		bd->bd_sectorsize = BIOSDISK_SECSIZE;
617 
618 	/*
619 	 * Test if the floppy device is present, so we can avoid receiving
620 	 * bogus information from bd_get_diskinfo_std().
621 	 */
622 	if (bd->bd_unit < 0x80) {
623 		/* reset disk */
624 		bd_reset_disk(bd->bd_unit);
625 
626 		/* Get disk type */
627 		v86.ctl = V86_FLAGS;
628 		v86.addr = DISK_BIOS;
629 		v86.eax = CMD_DRIVE_TYPE;
630 		v86.edx = bd->bd_unit;
631 		v86int();
632 		if (V86_CY(v86.efl) || (v86.eax & 0x300) == 0)
633 			return (false);
634 	}
635 
636 	ret = 1;
637 	if (edd != 0)
638 		ret = bd_get_diskinfo_ext(bd);
639 	if (ret != 0 || bd->bd_sectors == 0)
640 		ret = bd_get_diskinfo_std(bd);
641 
642 	if (ret != 0 && bd->bd_unit < 0x80) {
643 		/* Set defaults for 1.44 floppy */
644 		bd->bd_cyl = 80;
645 		bd->bd_hds = 2;
646 		bd->bd_sec = 18;
647 		bd->bd_sectors = 2880;
648 		/* Since we are there, there most likely is no media */
649 		bd->bd_flags |= BD_NO_MEDIA;
650 		ret = 0;
651 	}
652 
653 	if (ret != 0) {
654 		if (bd->bd_sectors != 0 && edd != 0) {
655 			bd->bd_sec = 63;
656 			bd->bd_hds = 255;
657 			bd->bd_cyl =
658 			    (bd->bd_sectors + bd->bd_sec * bd->bd_hds - 1) /
659 			    bd->bd_sec * bd->bd_hds;
660 		} else {
661 			const char *dv_name;
662 
663 			if ((bd->bd_flags & BD_FLOPPY) != 0)
664 				dv_name = biosfd.dv_name;
665 			else
666 				dv_name = bioshd.dv_name;
667 
668 			printf("Can not get information about %s unit %#x\n",
669 			    dv_name, bd->bd_unit);
670 			return (false);
671 		}
672 	}
673 
674 	if (bd->bd_sec == 0)
675 		bd->bd_sec = 63;
676 	if (bd->bd_hds == 0)
677 		bd->bd_hds = 255;
678 
679 	if (bd->bd_sectors == 0)
680 		bd->bd_sectors = (uint64_t)bd->bd_cyl * bd->bd_hds * bd->bd_sec;
681 
682 	DPRINTF("unit 0x%x geometry %d/%d/%d\n", bd->bd_unit, bd->bd_cyl,
683 	    bd->bd_hds, bd->bd_sec);
684 
685 	return (true);
686 }
687 
688 static int
689 bd_count(bdinfo_list_t *bdi)
690 {
691 	bdinfo_t *bd;
692 	int i;
693 
694 	i = 0;
695 	STAILQ_FOREACH(bd, bdi, bd_link)
696 		i++;
697 	return (i);
698 }
699 
700 /*
701  * Print information about disks
702  */
703 static int
704 bd_print_common(struct devsw *dev, bdinfo_list_t *bdi, int verbose)
705 {
706 	char line[80];
707 	struct disk_devdesc devd;
708 	bdinfo_t *bd;
709 	int i, ret = 0;
710 	char drive;
711 
712 	if (STAILQ_EMPTY(bdi))
713 		return (0);
714 
715 	printf("%s devices:", dev->dv_name);
716 	if ((ret = pager_output("\n")) != 0)
717 		return (ret);
718 
719 	i = -1;
720 	STAILQ_FOREACH(bd, bdi, bd_link) {
721 		i++;
722 
723 		switch (dev->dv_type) {
724 		case DEVT_FD:
725 			drive = 'A';
726 			break;
727 		case DEVT_CD:
728 			drive = 'C' + bd_count(&hdinfo);
729 			break;
730 		default:
731 			drive = 'C';
732 			break;
733 		}
734 
735 		snprintf(line, sizeof (line),
736 		    "    %s%d:   BIOS drive %c (%s%ju X %u):\n",
737 		    dev->dv_name, i, drive + i,
738 		    (bd->bd_flags & BD_NO_MEDIA) == BD_NO_MEDIA ?
739 		    "no media, " : "",
740 		    (uintmax_t)bd->bd_sectors,
741 		    bd->bd_sectorsize);
742 		if ((ret = pager_output(line)) != 0)
743 			break;
744 
745 		if ((bd->bd_flags & BD_NO_MEDIA) == BD_NO_MEDIA)
746 			continue;
747 
748 		if (dev->dv_type != DEVT_DISK)
749 			continue;
750 
751 		devd.dd.d_dev = dev;
752 		devd.dd.d_unit = i;
753 		devd.d_slice = D_SLICENONE;
754 		devd.d_partition = D_PARTNONE;
755 		if (disk_open(&devd,
756 		    bd->bd_sectorsize * bd->bd_sectors,
757 		    bd->bd_sectorsize) == 0) {
758 			snprintf(line, sizeof (line), "    %s%d",
759 			    dev->dv_name, i);
760 			ret = disk_print(&devd, line, verbose);
761 			disk_close(&devd);
762 			if (ret != 0)
763 				break;
764 		}
765 	}
766 	return (ret);
767 }
768 
769 static int
770 fd_print(int verbose)
771 {
772 	return (bd_print_common(&biosfd, &fdinfo, verbose));
773 }
774 
775 static int
776 bd_print(int verbose)
777 {
778 	return (bd_print_common(&bioshd, &hdinfo, verbose));
779 }
780 
781 static int
782 cd_print(int verbose)
783 {
784 	return (bd_print_common(&bioscd, &cdinfo, verbose));
785 }
786 
787 /*
788  * Read disk size from partition.
789  * This is needed to work around buggy BIOS systems returning
790  * wrong (truncated) disk media size.
791  * During bd_probe() we tested if the multiplication of bd_sectors
792  * would overflow so it should be safe to perform here.
793  */
794 static uint64_t
795 bd_disk_get_sectors(struct disk_devdesc *dev)
796 {
797 	bdinfo_t *bd;
798 	struct disk_devdesc disk;
799 	uint64_t size;
800 
801 	bd = bd_get_bdinfo(&dev->dd);
802 	if (bd == NULL)
803 		return (0);
804 
805 	disk.dd.d_dev = dev->dd.d_dev;
806 	disk.dd.d_unit = dev->dd.d_unit;
807 	disk.d_slice = D_SLICENONE;
808 	disk.d_partition = D_PARTNONE;
809 	disk.d_offset = 0;
810 
811 	size = bd->bd_sectors * bd->bd_sectorsize;
812 	if (disk_open(&disk, size, bd->bd_sectorsize) == 0) {
813 		(void) disk_ioctl(&disk, DIOCGMEDIASIZE, &size);
814 		disk_close(&disk);
815 	}
816 	return (size / bd->bd_sectorsize);
817 }
818 
819 /*
820  * Attempt to open the disk described by (dev) for use by (f).
821  *
822  * Note that the philosophy here is "give them exactly what
823  * they ask for".  This is necessary because being too "smart"
824  * about what the user might want leads to complications.
825  * (eg. given no slice or partition value, with a disk that is
826  *  sliced - are they after the first BSD slice, or the DOS
827  *  slice before it?)
828  */
829 static int
830 bd_open(struct open_file *f, ...)
831 {
832 	bdinfo_t *bd;
833 	struct disk_devdesc *dev;
834 	va_list ap;
835 	int rc;
836 
837 	va_start(ap, f);
838 	dev = va_arg(ap, struct disk_devdesc *);
839 	va_end(ap);
840 
841 	bd = bd_get_bdinfo(&dev->dd);
842 	if (bd == NULL)
843 		return (EIO);
844 
845 	if ((bd->bd_flags & BD_NO_MEDIA) == BD_NO_MEDIA) {
846 		if (!bd_int13probe(bd))
847 			return (EIO);
848 		if ((bd->bd_flags & BD_NO_MEDIA) == BD_NO_MEDIA)
849 			return (EIO);
850 	}
851 	if (bd->bd_bcache == NULL)
852 		bd->bd_bcache = bcache_allocate();
853 
854 	if (bd->bd_open == 0)
855 		bd->bd_sectors = bd_disk_get_sectors(dev);
856 	bd->bd_open++;
857 
858 	rc = 0;
859 	if (dev->dd.d_dev->dv_type == DEVT_DISK) {
860 		rc = disk_open(dev, bd->bd_sectors * bd->bd_sectorsize,
861 		    bd->bd_sectorsize);
862 		if (rc != 0) {
863 			bd->bd_open--;
864 			if (bd->bd_open == 0) {
865 				bcache_free(bd->bd_bcache);
866 				bd->bd_bcache = NULL;
867 			}
868 		}
869 	}
870 	return (rc);
871 }
872 
873 static int
874 bd_close(struct open_file *f)
875 {
876 	struct disk_devdesc *dev;
877 	bdinfo_t *bd;
878 	int rc = 0;
879 
880 	dev = (struct disk_devdesc *)f->f_devdata;
881 	bd = bd_get_bdinfo(&dev->dd);
882 	if (bd == NULL)
883 		return (EIO);
884 
885 	bd->bd_open--;
886 	if (bd->bd_open == 0) {
887 		bcache_free(bd->bd_bcache);
888 		bd->bd_bcache = NULL;
889 	}
890 	if (dev->dd.d_dev->dv_type == DEVT_DISK)
891 		rc = disk_close(dev);
892 	return (rc);
893 }
894 
895 static int
896 bd_ioctl(struct open_file *f, ulong_t cmd, void *data)
897 {
898 	bdinfo_t *bd;
899 	struct disk_devdesc *dev;
900 	int rc;
901 
902 	dev = (struct disk_devdesc *)f->f_devdata;
903 	bd = bd_get_bdinfo(&dev->dd);
904 	if (bd == NULL)
905 		return (EIO);
906 
907 	if (dev->dd.d_dev->dv_type == DEVT_DISK) {
908 		rc = disk_ioctl(dev, cmd, data);
909 		if (rc != ENOTTY)
910 			return (rc);
911 	}
912 
913 	switch (cmd) {
914 	case DIOCGSECTORSIZE:
915 		*(uint32_t *)data = bd->bd_sectorsize;
916 		break;
917 	case DIOCGMEDIASIZE:
918 		*(uint64_t *)data = bd->bd_sectors * bd->bd_sectorsize;
919 		break;
920 	default:
921 		return (ENOTTY);
922 	}
923 	return (0);
924 }
925 
926 static int
927 bd_strategy(void *devdata, int rw, daddr_t dblk, size_t size,
928     char *buf, size_t *rsize)
929 {
930 	bdinfo_t *bd;
931 	struct bcache_devdata bcd;
932 	struct disk_devdesc *dev;
933 	daddr_t offset;
934 
935 	dev = (struct disk_devdesc *)devdata;
936 	bd = bd_get_bdinfo(&dev->dd);
937 	if (bd == NULL)
938 		return (EINVAL);
939 
940 	bcd.dv_strategy = bd_realstrategy;
941 	bcd.dv_devdata = devdata;
942 	bcd.dv_cache = bd->bd_bcache;
943 
944 	offset = 0;
945 	if (dev->dd.d_dev->dv_type == DEVT_DISK) {
946 
947 		offset = dev->d_offset * bd->bd_sectorsize;
948 		offset /= BIOSDISK_SECSIZE;
949 	}
950 	return (bcache_strategy(&bcd, rw, dblk + offset, size,
951 	    buf, rsize));
952 }
953 
954 static int
955 bd_realstrategy(void *devdata, int rw, daddr_t dblk, size_t size,
956     char *buf, size_t *rsize)
957 {
958 	struct disk_devdesc *dev = (struct disk_devdesc *)devdata;
959 	bdinfo_t *bd;
960 	uint64_t disk_blocks, offset, d_offset;
961 	size_t blks, blkoff, bsize, bio_size, rest;
962 	caddr_t bbuf = NULL;
963 	int rc;
964 
965 	bd = bd_get_bdinfo(&dev->dd);
966 	if (bd == NULL || (bd->bd_flags & BD_NO_MEDIA) == BD_NO_MEDIA)
967 		return (EIO);
968 
969 	/*
970 	 * First make sure the IO size is a multiple of 512 bytes. While we do
971 	 * process partial reads below, the strategy mechanism is built
972 	 * assuming IO is a multiple of 512B blocks. If the request is not
973 	 * a multiple of 512B blocks, it has to be some sort of bug.
974 	 */
975 	if (size == 0 || (size % BIOSDISK_SECSIZE) != 0) {
976 		printf("bd_strategy: %d bytes I/O not multiple of %d\n",
977 		    size, BIOSDISK_SECSIZE);
978 		return (EIO);
979 	}
980 
981 	DPRINTF("open_disk %p", dev);
982 
983 	offset = dblk * BIOSDISK_SECSIZE;
984 	dblk = offset / bd->bd_sectorsize;
985 	blkoff = offset % bd->bd_sectorsize;
986 
987 	/*
988 	 * Check the value of the size argument. We do have quite small
989 	 * heap (64MB), but we do not know good upper limit, so we check against
990 	 * INT_MAX here. This will also protect us against possible overflows
991 	 * while translating block count to bytes.
992 	 */
993 	if (size > INT_MAX) {
994 		DPRINTF("too large I/O: %zu bytes", size);
995 		return (EIO);
996 	}
997 
998 	blks = size / bd->bd_sectorsize;
999 	if (blks == 0 || (size % bd->bd_sectorsize) != 0)
1000 		blks++;
1001 
1002 	if (dblk > dblk + blks)
1003 		return (EIO);
1004 
1005 	if (rsize)
1006 		*rsize = 0;
1007 
1008 	/*
1009 	 * Get disk blocks, this value is either for whole disk or for
1010 	 * partition.
1011 	 */
1012 	d_offset = 0;
1013 	disk_blocks = 0;
1014 	if (dev->dd.d_dev->dv_type == DEVT_DISK) {
1015 		if (disk_ioctl(dev, DIOCGMEDIASIZE, &disk_blocks) == 0) {
1016 			/* DIOCGMEDIASIZE does return bytes. */
1017 			disk_blocks /= bd->bd_sectorsize;
1018 		}
1019 		d_offset = dev->d_offset;
1020 	}
1021 	if (disk_blocks == 0)
1022 		disk_blocks = bd->bd_sectors - d_offset;
1023 
1024 	/* Validate source block address. */
1025 	if (dblk < d_offset || dblk >= d_offset + disk_blocks)
1026 		return (EIO);
1027 
1028 	/*
1029 	 * Truncate if we are crossing disk or partition end.
1030 	 */
1031 	if (dblk + blks >= d_offset + disk_blocks) {
1032 		blks = d_offset + disk_blocks - dblk;
1033 		size = blks * bd->bd_sectorsize;
1034 		DPRINTF("short I/O %d", blks);
1035 	}
1036 
1037 	bio_size = min(BIO_BUFFER_SIZE, size);
1038 	while (bio_size > bd->bd_sectorsize) {
1039 		bbuf = bio_alloc(bio_size);
1040 		if (bbuf != NULL)
1041 			break;
1042 		bio_size -= bd->bd_sectorsize;
1043 	}
1044 	if (bbuf == NULL) {
1045 		bio_size = V86_IO_BUFFER_SIZE;
1046 		if (bio_size / bd->bd_sectorsize == 0)
1047 			panic("BUG: Real mode buffer is too small");
1048 
1049 		/* Use alternate 4k buffer */
1050 		bbuf = PTOV(V86_IO_BUFFER);
1051 	}
1052 	rest = size;
1053 	rc = 0;
1054 	while (blks > 0) {
1055 		int x = min(blks, bio_size / bd->bd_sectorsize);
1056 
1057 		switch (rw & F_MASK) {
1058 		case F_READ:
1059 			DPRINTF("read %d from %lld to %p", x, dblk, buf);
1060 			bsize = bd->bd_sectorsize * x - blkoff;
1061 			if (rest < bsize)
1062 				bsize = rest;
1063 
1064 			if ((rc = bd_io(dev, bd, dblk, x, bbuf, BD_RD)) != 0) {
1065 				rc = EIO;
1066 				goto error;
1067 			}
1068 
1069 			bcopy(bbuf + blkoff, buf, bsize);
1070 			break;
1071 		case F_WRITE :
1072 			DPRINTF("write %d from %lld to %p", x, dblk, buf);
1073 			if (blkoff != 0) {
1074 				/*
1075 				 * We got offset to sector, read 1 sector to
1076 				 * bbuf.
1077 				 */
1078 				x = 1;
1079 				bsize = bd->bd_sectorsize - blkoff;
1080 				bsize = min(bsize, rest);
1081 				rc = bd_io(dev, bd, dblk, x, bbuf, BD_RD);
1082 			} else if (rest < bd->bd_sectorsize) {
1083 				/*
1084 				 * The remaining block is not full
1085 				 * sector. Read 1 sector to bbuf.
1086 				 */
1087 				x = 1;
1088 				bsize = rest;
1089 				rc = bd_io(dev, bd, dblk, x, bbuf, BD_RD);
1090 			} else {
1091 				/* We can write full sector(s). */
1092 				bsize = bd->bd_sectorsize * x;
1093 			}
1094 			/*
1095 			 * Put your Data In, Put your Data out,
1096 			 * Put your Data In, and shake it all about
1097 			 */
1098 			bcopy(buf, bbuf + blkoff, bsize);
1099 			if ((rc = bd_io(dev, bd, dblk, x, bbuf, BD_WR)) != 0) {
1100 				rc = EIO;
1101 				goto error;
1102 			}
1103 			break;
1104 		default:
1105 			/* DO NOTHING */
1106 			rc = EROFS;
1107 			goto error;
1108 		}
1109 
1110 		blkoff = 0;
1111 		buf += bsize;
1112 		rest -= bsize;
1113 		blks -= x;
1114 		dblk += x;
1115 	}
1116 
1117 	if (rsize != NULL)
1118 		*rsize = size;
1119 error:
1120 	if (bbuf != PTOV(V86_IO_BUFFER))
1121 		bio_free(bbuf, bio_size);
1122 	return (rc);
1123 }
1124 
1125 static int
1126 bd_edd_io(bdinfo_t *bd, daddr_t dblk, int blks, caddr_t dest,
1127     int dowrite)
1128 {
1129 	static struct edd_packet packet;
1130 
1131 	packet.len = sizeof (struct edd_packet);
1132 	packet.count = blks;
1133 	packet.off = VTOPOFF(dest);
1134 	packet.seg = VTOPSEG(dest);
1135 	packet.lba = dblk;
1136 	v86.ctl = V86_FLAGS;
1137 	v86.addr = DISK_BIOS;
1138 	if (dowrite == BD_WR)
1139 		v86.eax = CMD_WRITE_LBA; /* maybe Write with verify 0x4302? */
1140 	else
1141 		v86.eax = CMD_READ_LBA;
1142 	v86.edx = bd->bd_unit;
1143 	v86.ds = VTOPSEG(&packet);
1144 	v86.esi = VTOPOFF(&packet);
1145 	v86int();
1146 	if (V86_CY(v86.efl))
1147 		return (v86.eax >> 8);
1148 	return (0);
1149 }
1150 
1151 static int
1152 bd_chs_io(bdinfo_t *bd, daddr_t dblk, int blks, caddr_t dest,
1153     int dowrite)
1154 {
1155 	uint32_t x, bpc, cyl, hd, sec;
1156 
1157 	bpc = bd->bd_sec * bd->bd_hds;	/* blocks per cylinder */
1158 	x = dblk;
1159 	cyl = x / bpc;			/* block # / blocks per cylinder */
1160 	x %= bpc;				/* block offset into cylinder */
1161 	hd = x / bd->bd_sec;		/* offset / blocks per track */
1162 	sec = x % bd->bd_sec;		/* offset into track */
1163 
1164 	/* correct sector number for 1-based BIOS numbering */
1165 	sec++;
1166 
1167 	if (cyl > 1023) {
1168 		/* CHS doesn't support cylinders > 1023. */
1169 		return (1);
1170 	}
1171 
1172 	v86.ctl = V86_FLAGS;
1173 	v86.addr = DISK_BIOS;
1174 	if (dowrite == BD_WR)
1175 		v86.eax = CMD_WRITE_CHS | blks;
1176 	else
1177 		v86.eax = CMD_READ_CHS | blks;
1178 	v86.ecx = ((cyl & 0xff) << 8) | ((cyl & 0x300) >> 2) | sec;
1179 	v86.edx = (hd << 8) | bd->bd_unit;
1180 	v86.es = VTOPSEG(dest);
1181 	v86.ebx = VTOPOFF(dest);
1182 	v86int();
1183 	if (V86_CY(v86.efl))
1184 		return (v86.eax >> 8);
1185 	return (0);
1186 }
1187 
1188 static void
1189 bd_io_workaround(bdinfo_t *bd)
1190 {
1191 	uint8_t buf[8 * 1024];
1192 
1193 	bd_edd_io(bd, 0xffffffff, 1, (caddr_t)buf, BD_RD);
1194 }
1195 
1196 static int
1197 bd_io(struct disk_devdesc *dev, bdinfo_t *bd, daddr_t dblk, int blks,
1198     caddr_t dest, int dowrite)
1199 {
1200 	int result, retry;
1201 
1202 	/* Just in case some idiot actually tries to read/write -1 blocks... */
1203 	if (blks < 0)
1204 		return (-1);
1205 
1206 	/*
1207 	 * Workaround for a problem with some HP ProLiant BIOS failing to work
1208 	 * out the boot disk after installation. hrs and kuriyama discovered
1209 	 * this problem with an HP ProLiant DL320e Gen 8 with a 3TB HDD, and
1210 	 * discovered that an int13h call seems to cause a buffer overrun in
1211 	 * the bios. The problem is alleviated by doing an extra read before
1212 	 * the buggy read. It is not immediately known whether other models
1213 	 * are similarly affected.
1214 	 * Loop retrying the operation a couple of times.  The BIOS
1215 	 * may also retry.
1216 	 */
1217 	if (dowrite == BD_RD && dblk >= 0x100000000)
1218 		bd_io_workaround(bd);
1219 	for (retry = 0; retry < 3; retry++) {
1220 		if (bd->bd_flags & BD_MODEEDD)
1221 			result = bd_edd_io(bd, dblk, blks, dest, dowrite);
1222 		else
1223 			result = bd_chs_io(bd, dblk, blks, dest, dowrite);
1224 
1225 		if (result == 0) {
1226 			if (bd->bd_flags & BD_NO_MEDIA)
1227 				bd->bd_flags &= ~BD_NO_MEDIA;
1228 			break;
1229 		}
1230 
1231 		bd_reset_disk(bd->bd_unit);
1232 
1233 		/*
1234 		 * Error codes:
1235 		 * 20h	controller failure
1236 		 * 31h	no media in drive (IBM/MS INT 13 extensions)
1237 		 * 80h	no media in drive, VMWare (Fusion)
1238 		 * There is no reason to repeat the IO with errors above.
1239 		 */
1240 		if (result == 0x20 || result == 0x31 || result == 0x80) {
1241 			bd->bd_flags |= BD_NO_MEDIA;
1242 			break;
1243 		}
1244 	}
1245 
1246 	if (result != 0 && (bd->bd_flags & BD_NO_MEDIA) == 0) {
1247 		if (dowrite == BD_WR) {
1248 			printf("%s%d: Write %d sector(s) from %p (0x%x) "
1249 			    "to %lld: 0x%x\n", dev->dd.d_dev->dv_name,
1250 			    dev->dd.d_unit, blks, dest, VTOP(dest), dblk,
1251 			    result);
1252 		} else {
1253 			printf("%s%d: Read %d sector(s) from %lld to %p "
1254 			    "(0x%x): 0x%x\n", dev->dd.d_dev->dv_name,
1255 			    dev->dd.d_unit, blks, dblk, dest, VTOP(dest),
1256 			    result);
1257 		}
1258 	}
1259 
1260 	return (result);
1261 }
1262 
1263 /*
1264  * Return the BIOS geometry of a given "fixed drive" in a format
1265  * suitable for the legacy bootinfo structure.  Since the kernel is
1266  * expecting raw int 0x13/0x8 values for N_BIOS_GEOM drives, we
1267  * prefer to get the information directly, rather than rely on being
1268  * able to put it together from information already maintained for
1269  * different purposes and for a probably different number of drives.
1270  *
1271  * For valid drives, the geometry is expected in the format (31..0)
1272  * "000000cc cccccccc hhhhhhhh 00ssssss"; and invalid drives are
1273  * indicated by returning the geometry of a "1.2M" PC-format floppy
1274  * disk.  And, incidentally, what is returned is not the geometry as
1275  * such but the highest valid cylinder, head, and sector numbers.
1276  */
1277 uint32_t
1278 bd_getbigeom(int bunit)
1279 {
1280 
1281 	v86.ctl = V86_FLAGS;
1282 	v86.addr = DISK_BIOS;
1283 	v86.eax = CMD_READ_PARAM;
1284 	v86.edx = 0x80 + bunit;
1285 	v86int();
1286 	if (V86_CY(v86.efl))
1287 		return (0x4f010f);
1288 	return (((v86.ecx & 0xc0) << 18) | ((v86.ecx & 0xff00) << 8) |
1289 	    (v86.edx & 0xff00) | (v86.ecx & 0x3f));
1290 }
1291 
1292 /*
1293  * Return a suitable dev_t value for (dev).
1294  *
1295  * In the case where it looks like (dev) is a SCSI disk, we allow the number of
1296  * IDE disks to be specified in $num_ide_disks.  There should be a Better Way.
1297  */
1298 int
1299 bd_getdev(struct i386_devdesc *d)
1300 {
1301 	struct disk_devdesc *dev;
1302 	bdinfo_t *bd;
1303 	int	biosdev;
1304 	int	major;
1305 	int	rootdev;
1306 	char	*nip, *cp;
1307 	int	i, unit, slice, partition;
1308 
1309 	/* XXX: Assume partition 'a'. */
1310 	slice = 0;
1311 	partition = 0;
1312 
1313 	dev = (struct disk_devdesc *)d;
1314 	bd = bd_get_bdinfo(&dev->dd);
1315 	if (bd == NULL)
1316 		return (-1);
1317 
1318 	biosdev = bd_unit2bios(d);
1319 	DPRINTF("unit %d BIOS device %d", dev->dd.d_unit, biosdev);
1320 	if (biosdev == -1)			/* not a BIOS device */
1321 		return (-1);
1322 
1323 	if (dev->dd.d_dev->dv_type == DEVT_DISK) {
1324 		if (disk_open(dev, bd->bd_sectors * bd->bd_sectorsize,
1325 		    bd->bd_sectorsize) != 0)	/* oops, not a viable device */
1326 			return (-1);
1327 		else
1328 			disk_close(dev);
1329 		slice = dev->d_slice + 1;
1330 		partition = dev->d_partition;
1331 	}
1332 
1333 	if (biosdev < 0x80) {
1334 		/* floppy (or emulated floppy) or ATAPI device */
1335 		if (bd->bd_type == DT_ATAPI) {
1336 			/* is an ATAPI disk */
1337 			major = WFDMAJOR;
1338 		} else {
1339 			/* is a floppy disk */
1340 			major = FDMAJOR;
1341 		}
1342 	} else {
1343 		/* assume an IDE disk */
1344 		major = WDMAJOR;
1345 	}
1346 	/* default root disk unit number */
1347 	unit = biosdev & 0x7f;
1348 
1349 	if (dev->dd.d_dev->dv_type == DEVT_CD) {
1350 		/*
1351 		 * XXX: Need to examine device spec here to figure out if
1352 		 * SCSI or ATAPI.  No idea on how to figure out device number.
1353 		 * All we can really pass to the kernel is what bus and device
1354 		 * on which bus we were booted from, which dev_t isn't well
1355 		 * suited to since those number don't match to unit numbers
1356 		 * very well.  We may just need to engage in a hack where
1357 		 * we pass -C to the boot args if we are the boot device.
1358 		 */
1359 		major = ACDMAJOR;
1360 		unit = 0;	/* XXX */
1361 	}
1362 
1363 	/* XXX a better kludge to set the root disk unit number */
1364 	if ((nip = getenv("root_disk_unit")) != NULL) {
1365 		i = strtol(nip, &cp, 0);
1366 		/* check for parse error */
1367 		if ((cp != nip) && (*cp == 0))
1368 			unit = i;
1369 	}
1370 
1371 	rootdev = MAKEBOOTDEV(major, slice, unit, partition);
1372 	DPRINTF("dev is 0x%x\n", rootdev);
1373 	return (rootdev);
1374 }
1375