xref: /illumos-gate/usr/src/cmd/fs.d/pcfs/common/pcfs_common.c (revision fdc43e978a96b43e8b78e80d9bc6f39c99a8ca83)
1 /*
2  * CDDL HEADER START
3  *
4  * The contents of this file are subject to the terms of the
5  * Common Development and Distribution License (the "License").
6  * You may not use this file except in compliance with the License.
7  *
8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9  * or http://www.opensolaris.org/os/licensing.
10  * See the License for the specific language governing permissions
11  * and limitations under the License.
12  *
13  * When distributing Covered Code, include this CDDL HEADER in each
14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15  * If applicable, add the following below this CDDL HEADER, with the
16  * fields enclosed by brackets "[]" replaced with your own identifying
17  * information: Portions Copyright [yyyy] [name of copyright owner]
18  *
19  * CDDL HEADER END
20  */
21 /*
22  * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
23  * Use is subject to license terms.
24  * Copyright (c) 2011 Gary Mills
25  * Copyright 2024 MNX Cloud, Inc.
26  */
27 
28 /*
29  * common functions used by pcfs tools.
30  */
31 #include <stdio.h>
32 #include <string.h>
33 #include <errno.h>
34 #include <err.h>
35 #include <unistd.h>
36 #include <stdlib.h>
37 #include <libintl.h>
38 #include <locale.h>
39 #include <langinfo.h>
40 #include <regex.h>
41 #include <sys/isa_defs.h>
42 #include <sys/types.h>
43 #include <sys/stat.h>
44 #include <sys/fcntl.h>
45 #include <sys/dktp/fdisk.h>
46 #include <sys/dkio.h>
47 #include <sys/fs/pc_fs.h>
48 #include <sys/fs/pc_dir.h>
49 #include <sys/fs/pc_label.h>
50 #include "pcfs_common.h"
51 #include "pcfs_bpb.h"
52 
53 /*
54  *	The assumption here is that _BIG_ENDIAN implies sparc, and
55  *	so in addition to swapping bytes we also have to construct
56  *	packed structures by hand to avoid bus errors due to improperly
57  *	aligned pointers.
58  */
59 #ifdef _BIG_ENDIAN
60 void swap_pack_grab32bpb(bpb_t *wbpb, struct _boot_sector *bsp);
61 void swap_pack_grabbpb(bpb_t *wbpb, struct _boot_sector *bsp);
62 #endif /* _BIG_ENDIAN */
63 
64 /*
65  * Validate sector size.
66  */
67 bool
is_sector_size_valid(size_t size)68 is_sector_size_valid(size_t size)
69 {
70 	if (size != 512 && size != 1024 && size != 2048 && size != 4096)
71 		return (false);
72 	return (true);
73 }
74 
75 /*
76  * Use DKIOCGMEDIAINFO to get sector size.
77  */
78 int
get_media_sector_size(int fd,size_t * sizep)79 get_media_sector_size(int fd, size_t *sizep)
80 {
81 	struct dk_minfo dkminfo;
82 
83 	if (ioctl(fd, DKIOCGMEDIAINFO, &dkminfo) != -1) {
84 		*sizep = dkminfo.dki_lbsize;
85 		return (0);
86 	}
87 	/* In case the DKIOCGMEDIAINFO is not supported, return MINBPS. */
88 	if (errno == ENOTTY) {
89 		*sizep = MINBPS;
90 		return (0);
91 	}
92 
93 	return (errno);
94 }
95 
96 /*
97  * store_16_bits
98  *	Save the lower 16 bits of a 32 bit value (v) into the provided
99  *	buffer (pointed at by *bp), and increment the buffer pointer
100  *	as well.  This way the routine can be called multiple times in
101  *	succession to fill buffers.  The value is stored in little-endian
102  *	order.
103  */
104 void
store_16_bits(uchar_t ** bp,uint32_t v)105 store_16_bits(uchar_t **bp, uint32_t v)
106 {
107 	uchar_t *l = *bp;
108 
109 	*l++ = v & 0xff;
110 	*l = (v >> 8) & 0xff;
111 	*bp += 2;
112 }
113 
114 void
read_16_bits(uchar_t * bp,uint32_t * value)115 read_16_bits(uchar_t *bp, uint32_t *value)
116 {
117 	*value = *bp++;
118 	*value += *bp << 8;
119 }
120 
121 /*
122  * store_32_bits
123  *	Save the 32 bit value (v) into the provided buffer (pointed
124  *	at by *bp), and increment the buffer pointer as well.  This way
125  *	the routine can be called multiple times in succession to fill
126  *	buffers.  The value is stored in little-endian order.
127  */
128 void
store_32_bits(uchar_t ** bp,uint32_t v)129 store_32_bits(uchar_t **bp, uint32_t v)
130 {
131 	uchar_t *l = *bp;
132 	int b;
133 
134 	for (b = 0; b < 4; b++) {
135 		*l++ = v & 0xff;
136 		v = v >> 8;
137 	}
138 	*bp += 4;
139 }
140 
141 void
read_32_bits(uchar_t * bp,uint32_t * value)142 read_32_bits(uchar_t *bp, uint32_t *value)
143 {
144 	*value = *bp++;
145 	*value += *bp++ << 8;
146 	*value += *bp++ << 16;
147 	*value += *bp++ << 24;
148 }
149 
150 /*
151  *  dump_bytes  -- display bytes as hex numbers.
152  *		   b is the pointer to the byte buffer
153  *		   n is the number of bytes in the buffer
154  */
155 /* Note: BPL = bytes to display per line */
156 #define	BPL 16
157 
158 void
dump_bytes(uchar_t * buf,int n)159 dump_bytes(uchar_t *buf, int n)
160 {
161 	int printedCount;
162 	int countdown = n;
163 	int countup = 0;
164 	int offset = 0;
165 	int byte;
166 
167 	/* Display offset, 16 bytes per line, and printable ascii version */
168 	while (countdown > 0) {
169 		printedCount = 0;
170 		(void) fprintf(stderr, "\n%06x: ", offset);
171 		/*
172 		 * Print Hex value of characters in columns on left
173 		 */
174 		for (byte = 0; byte < BPL; byte++) {
175 			if (countup + byte < n) {
176 				(void) fprintf(stderr,
177 				    "%02x ", (buf[countup + byte] & 0xff));
178 				printedCount++;
179 			} else {
180 				(void) fprintf(stderr, "   ");
181 			}
182 		}
183 		/*
184 		 * Right side has the printable character or '.' for
185 		 * unprintable for each column of the left.
186 		 */
187 		for (byte = 0; byte < BPL; byte++) {
188 			if ((countup + byte < n) &&
189 			    ((buf[countup + byte] >= ' ') &&
190 			    (buf[countup + byte] <= '~'))) {
191 				(void) fprintf(stderr, "%c",
192 				    buf[countup + byte]);
193 			} else {
194 				(void) fprintf(stderr, ".");
195 			}
196 		}
197 		countup += printedCount;
198 		offset += printedCount;
199 		countdown -= printedCount;
200 	}
201 	(void) fprintf(stderr, "\n\n");
202 }
203 
204 /*
205  *  header_for_dump  --  display simple header over what will be output.
206  */
207 void
header_for_dump(void)208 header_for_dump(void)
209 {
210 	int byte;
211 
212 	(void) fprintf(stderr, "\n        ");
213 	for (byte = 0; byte < BPL; byte++)
214 		(void) fprintf(stderr, "%02x ", byte);
215 	(void) fprintf(stderr, "\n       ");
216 	byte = 3 * BPL;
217 	while (byte-- > 0)
218 		(void) fprintf(stderr, "-");
219 }
220 
221 /*
222  *  We are basically (incorrectly) assuming that if you aren't running
223  *  on x86 the BPB has to be packed by hand AND that the bytes must
224  *  be swapped.  One or both of these assumptions may one day be invalid.
225  *  (if they aren't already :-))
226  */
227 #ifdef _BIG_ENDIAN
228 /*
229  *  swap_pack_grab{32}bpb
230  *	If not on an x86 we assume the structures making up the bpb
231  *	were not packed and that longs and shorts need to be byte swapped
232  *	(we've kept everything in host order up until now).  A new architecture
233  *	might not need to swap or might not need to pack, in which case
234  *	new routines will have to be written.  Of course if an architecture
235  *	supports both packing and little-endian host order, it can follow the
236  *	same path as the x86 code.
237  */
238 void
swap_pack_grabbpb(bpb_t * wbpb,struct _boot_sector * bsp)239 swap_pack_grabbpb(bpb_t *wbpb, struct _boot_sector *bsp)
240 {
241 	uchar_t *grabp;
242 
243 	grabp = (uchar_t *)&(bsp->bs_filler[ORIG_BPB_START_INDEX]);
244 
245 	((uchar_t *)&(wbpb->bpb.bytes_per_sector))[1] = *grabp++;
246 	((uchar_t *)&(wbpb->bpb.bytes_per_sector))[0] = *grabp++;
247 	wbpb->bpb.sectors_per_cluster = *grabp++;
248 	((uchar_t *)&(wbpb->bpb.resv_sectors))[1] = *grabp++;
249 	((uchar_t *)&(wbpb->bpb.resv_sectors))[0] = *grabp++;
250 	wbpb->bpb.num_fats = *grabp++;
251 	((uchar_t *)&(wbpb->bpb.num_root_entries))[1] = *grabp++;
252 	((uchar_t *)&(wbpb->bpb.num_root_entries))[0] = *grabp++;
253 	((uchar_t *)&(wbpb->bpb.sectors_in_volume))[1] = *grabp++;
254 	((uchar_t *)&(wbpb->bpb.sectors_in_volume))[0] = *grabp++;
255 	wbpb->bpb.media = *grabp++;
256 	((uchar_t *)&(wbpb->bpb.sectors_per_fat))[1] = *grabp++;
257 	((uchar_t *)&(wbpb->bpb.sectors_per_fat))[0] = *grabp++;
258 	((uchar_t *)&(wbpb->bpb.sectors_per_track))[1] = *grabp++;
259 	((uchar_t *)&(wbpb->bpb.sectors_per_track))[0] = *grabp++;
260 	((uchar_t *)&(wbpb->bpb.heads))[1] = *grabp++;
261 	((uchar_t *)&(wbpb->bpb.heads))[0] = *grabp++;
262 	((uchar_t *)&(wbpb->bpb.hidden_sectors))[3] = *grabp++;
263 	((uchar_t *)&(wbpb->bpb.hidden_sectors))[2] = *grabp++;
264 	((uchar_t *)&(wbpb->bpb.hidden_sectors))[1] = *grabp++;
265 	((uchar_t *)&(wbpb->bpb.hidden_sectors))[0] = *grabp++;
266 	((uchar_t *)&(wbpb->bpb.sectors_in_logical_volume))[3] = *grabp++;
267 	((uchar_t *)&(wbpb->bpb.sectors_in_logical_volume))[2] = *grabp++;
268 	((uchar_t *)&(wbpb->bpb.sectors_in_logical_volume))[1] = *grabp++;
269 	((uchar_t *)&(wbpb->bpb.sectors_in_logical_volume))[0] = *grabp++;
270 	wbpb->ebpb.phys_drive_num = *grabp++;
271 	wbpb->ebpb.reserved = *grabp++;
272 	wbpb->ebpb.ext_signature = *grabp++;
273 	((uchar_t *)&(wbpb->ebpb.volume_id))[3] = *grabp++;
274 	((uchar_t *)&(wbpb->ebpb.volume_id))[2] = *grabp++;
275 	((uchar_t *)&(wbpb->ebpb.volume_id))[1] = *grabp++;
276 	((uchar_t *)&(wbpb->ebpb.volume_id))[0] = *grabp++;
277 
278 	(void) strncpy((char *)wbpb->ebpb.volume_label, (char *)grabp, 11);
279 	grabp += 11;
280 	(void) strncpy((char *)wbpb->ebpb.type, (char *)grabp, 8);
281 }
282 
283 void
swap_pack_grab32bpb(bpb_t * wbpb,struct _boot_sector * bsp)284 swap_pack_grab32bpb(bpb_t *wbpb, struct _boot_sector *bsp)
285 {
286 	uchar_t *grabp;
287 
288 	grabp = (uchar_t *)&(bsp->bs_filler[BPB_32_START_INDEX]);
289 
290 	((uchar_t *)&(wbpb->bpb32.big_sectors_per_fat))[3] = *grabp++;
291 	((uchar_t *)&(wbpb->bpb32.big_sectors_per_fat))[2] = *grabp++;
292 	((uchar_t *)&(wbpb->bpb32.big_sectors_per_fat))[1] = *grabp++;
293 	((uchar_t *)&(wbpb->bpb32.big_sectors_per_fat))[0] = *grabp++;
294 	((uchar_t *)&(wbpb->bpb32.ext_flags))[1] = *grabp++;
295 	((uchar_t *)&(wbpb->bpb32.ext_flags))[0] = *grabp++;
296 	wbpb->bpb32.fs_vers_lo = *grabp++;
297 	wbpb->bpb32.fs_vers_hi = *grabp++;
298 	((uchar_t *)&(wbpb->bpb32.root_dir_clust))[3] = *grabp++;
299 	((uchar_t *)&(wbpb->bpb32.root_dir_clust))[2] = *grabp++;
300 	((uchar_t *)&(wbpb->bpb32.root_dir_clust))[1] = *grabp++;
301 	((uchar_t *)&(wbpb->bpb32.root_dir_clust))[0] = *grabp++;
302 	((uchar_t *)&(wbpb->bpb32.fsinfosec))[1] = *grabp++;
303 	((uchar_t *)&(wbpb->bpb32.fsinfosec))[0] = *grabp++;
304 	((uchar_t *)&(wbpb->bpb32.backupboot))[1] = *grabp++;
305 	((uchar_t *)&(wbpb->bpb32.backupboot))[0] = *grabp++;
306 	((uchar_t *)&(wbpb->bpb32.reserved[0]))[1] = *grabp++;
307 	((uchar_t *)&(wbpb->bpb32.reserved[0]))[0] = *grabp++;
308 	((uchar_t *)&(wbpb->bpb32.reserved[1]))[1] = *grabp++;
309 	((uchar_t *)&(wbpb->bpb32.reserved[1]))[0] = *grabp++;
310 	((uchar_t *)&(wbpb->bpb32.reserved[2]))[1] = *grabp++;
311 	((uchar_t *)&(wbpb->bpb32.reserved[2]))[0] = *grabp++;
312 	((uchar_t *)&(wbpb->bpb32.reserved[3]))[1] = *grabp++;
313 	((uchar_t *)&(wbpb->bpb32.reserved[3]))[0] = *grabp++;
314 	((uchar_t *)&(wbpb->bpb32.reserved[4]))[1] = *grabp++;
315 	((uchar_t *)&(wbpb->bpb32.reserved[4]))[0] = *grabp++;
316 	((uchar_t *)&(wbpb->bpb32.reserved[5]))[1] = *grabp++;
317 	((uchar_t *)&(wbpb->bpb32.reserved[5]))[0] = *grabp++;
318 }
319 #endif	/* _BIG_ENDIAN */
320 
321 char *
stat_actual_disk(const char * diskname,struct stat * info,char ** suffix)322 stat_actual_disk(const char *diskname, struct stat *info, char **suffix)
323 {
324 	char *actualdisk;
325 
326 	if (stat(diskname, info) != 0) {
327 		/*
328 		 *  Device named on command line doesn't exist.  That
329 		 *  probably means there is a partition-specifying
330 		 *  suffix attached to the actual disk name.
331 		 */
332 		if ((actualdisk = strdup(diskname)) == NULL) {
333 			(void) fprintf(stderr,
334 			    gettext("Out of memory for disk name.\n"));
335 			exit(2);
336 		}
337 		if ((*suffix = strchr(actualdisk, ':')) != NULL) {
338 			**suffix = '\0';
339 			(*suffix)++;
340 		}
341 
342 		if (stat(actualdisk, info)) {
343 			err(2, "Failed to stat disk device %s",
344 			    actualdisk);
345 		}
346 	} else {
347 		if ((actualdisk = strdup(diskname)) == NULL) {
348 			(void) fprintf(stderr,
349 			    gettext("Out of memory for disk name.\n"));
350 			exit(2);
351 		}
352 	}
353 
354 	return (actualdisk);
355 }
356 
357 extern void usage(void);
358 
359 void
bad_arg(char * option)360 bad_arg(char *option)
361 {
362 	(void) fprintf(stderr,
363 	    gettext("Unrecognized option -o %s.\n"), option);
364 	usage();
365 	exit(2);
366 }
367 
368 void
missing_arg(char * option)369 missing_arg(char *option)
370 {
371 	(void) fprintf(stderr,
372 	    gettext("Option %s requires a value.\n"), option);
373 	usage();
374 	exit(3);
375 }
376 
377 static int
parse_drvnum(char * pn)378 parse_drvnum(char *pn)
379 {
380 	int drvnum;
381 
382 	/*
383 	 * Determine logical drive to seek after.
384 	 */
385 	if ((strlen(pn) == 1) && ((*pn >= 'c') && (*pn <= 'z'))) {
386 		drvnum = *pn - 'c' + 1;
387 	} else if ((*pn >= '0') && (*pn <= '9')) {
388 		char *d;
389 		int v = 0;
390 
391 		d = pn;
392 		while ((*d != '\0') && (*d >= '0') && (*d <= '9')) {
393 			v *= 10;
394 			v += *d - '0';
395 			d++;
396 		}
397 		if ((*d != '\0') || (v > 24)) {
398 			(void) fprintf(stderr,
399 			    gettext("%s: bogus logical drive specification.\n"),
400 			    pn);
401 			return (-1);
402 		}
403 		drvnum = v;
404 	} else if (strcmp(pn, "boot") == 0) {
405 		drvnum = 99;
406 	} else {
407 		(void) fprintf(stderr,
408 		    gettext("%s: bogus logical drive specification.\n"), pn);
409 		return (-1);
410 	}
411 
412 	return (drvnum);
413 }
414 
415 /*
416  * isDosDrive()
417  *	Boolean function.  Give it the systid field for an fdisk partition
418  *	and it decides if that's a systid that describes a DOS drive.  We
419  *	use systid values defined in sys/dktp/fdisk.h.
420  */
421 static int
isDosDrive(uchar_t checkMe)422 isDosDrive(uchar_t checkMe)
423 {
424 	return ((checkMe == DOSOS12) || (checkMe == DOSOS16) ||
425 	    (checkMe == DOSHUGE) || (checkMe == FDISK_WINDOWS) ||
426 	    (checkMe == FDISK_EXT_WIN) || (checkMe == FDISK_FAT95) ||
427 	    (checkMe == DIAGPART));
428 }
429 
430 /*
431  * isDosExtended()
432  *	Boolean function.  Give it the systid field for an fdisk partition
433  *	and it decides if that's a systid that describes an extended DOS
434  *	partition.
435  */
436 static int
isDosExtended(uchar_t checkMe)437 isDosExtended(uchar_t checkMe)
438 {
439 	return ((checkMe == EXTDOS) || (checkMe == FDISK_EXTLBA));
440 }
441 
442 /*
443  * isBootPart()
444  *	Boolean function.  Give it the systid field for an fdisk partition
445  *	and it decides if that's a systid that describes a Solaris boot
446  *	partition.
447  */
448 static int
isBootPart(uchar_t checkMe)449 isBootPart(uchar_t checkMe)
450 {
451 	return (checkMe == X86BOOT);
452 }
453 
454 off64_t
findPartitionOffset(int fd,size_t bpsec,char * ldrive)455 findPartitionOffset(int fd, size_t bpsec, char *ldrive)
456 {
457 	struct ipart part[FD_NUMPART];
458 	struct mboot extmboot;
459 	struct mboot mb;
460 	diskaddr_t xstartsect;
461 	off64_t nextseek = 0;
462 	off64_t lastseek = 0;
463 	off64_t found = 0;
464 	off64_t error = -1;
465 	int logicalDriveCount = 0;
466 	int extendedPart = -1;
467 	int primaryPart = -1;
468 	int bootPart = -1;
469 	uint32_t xnumsect = 0;
470 	int drvnum;
471 	int driveIndex;
472 	int i;
473 	/*
474 	 * Count of drives in the current extended partition's
475 	 * FDISK table, and indexes of the drives themselves.
476 	 */
477 	int extndDrives[FD_NUMPART];
478 	int numDrives = 0;
479 	/*
480 	 * Count of drives (beyond primary) in master boot record's
481 	 * FDISK table, and indexes of the drives themselves.
482 	 */
483 	int extraDrives[FD_NUMPART];
484 	int numExtraDrives = 0;
485 
486 	if ((drvnum = parse_drvnum(ldrive)) < 0)
487 		return (error);
488 
489 	if (read(fd, &mb, bpsec) != (ssize_t)bpsec) {
490 		(void) fprintf(stderr,
491 		    gettext("Couldn't read a Master Boot Record\n"));
492 		return (error);
493 	}
494 
495 	if (ltohs(mb.signature) != BOOTSECSIG) {
496 		(void) fprintf(stderr,
497 		    gettext("Bad signature on master boot record (%x)\n"),
498 		    ltohs(mb.signature));
499 		return (error);
500 	}
501 
502 	/*
503 	 * Copy partition table into memory
504 	 */
505 	(void) memcpy(part, mb.parts, sizeof (part));
506 
507 	/*
508 	 * Get a summary of what is in the Master FDISK table.
509 	 * Normally we expect to find one partition marked as a DOS drive.
510 	 * This partition is the one Windows calls the primary dos partition.
511 	 * If the machine has any logical drives then we also expect
512 	 * to find a partition marked as an extended DOS partition.
513 	 *
514 	 * Sometimes we'll find multiple partitions marked as DOS drives.
515 	 * The Solaris fdisk program allows these partitions
516 	 * to be created, but Windows fdisk no longer does.  We still need
517 	 * to support these, though, since Windows does.  We also need to fix
518 	 * our fdisk to behave like the Windows version.
519 	 *
520 	 * It turns out that some off-the-shelf media have *only* an
521 	 * Extended partition, so we need to deal with that case as
522 	 * well.
523 	 *
524 	 * Only a single (the first) Extended or Boot Partition will
525 	 * be recognized.  Any others will be ignored.
526 	 */
527 	for (i = 0; i < FD_NUMPART; i++) {
528 		if (isDosDrive(part[i].systid)) {
529 			if (primaryPart < 0) {
530 				logicalDriveCount++;
531 				primaryPart = i;
532 			} else {
533 				extraDrives[numExtraDrives++] = i;
534 			}
535 			continue;
536 		}
537 		if ((extendedPart < 0) && isDosExtended(part[i].systid)) {
538 			extendedPart = i;
539 			continue;
540 		}
541 		if ((bootPart < 0) && isBootPart(part[i].systid)) {
542 			bootPart = i;
543 			continue;
544 		}
545 	}
546 
547 	if (drvnum == BOOT_PARTITION_DRIVE) {
548 		if (bootPart < 0) {
549 			(void) fprintf(stderr,
550 			    gettext("No boot partition found on drive\n"));
551 			return (error);
552 		}
553 		found = ltohi(part[bootPart].relsect) * bpsec;
554 		return (found);
555 	}
556 
557 	if (drvnum == PRIMARY_DOS_DRIVE && primaryPart >= 0) {
558 		found = ltohi(part[primaryPart].relsect) * bpsec;
559 		return (found);
560 	}
561 
562 	/*
563 	 * We are not looking for the C: drive (or there was no primary
564 	 * drive found), so we had better have an extended partition or
565 	 * extra drives in the Master FDISK table.
566 	 */
567 	if ((extendedPart < 0) && (numExtraDrives == 0)) {
568 		(void) fprintf(stderr,
569 		    gettext("No such logical drive "
570 		    "(missing extended partition entry)\n"));
571 		return (error);
572 	}
573 
574 	if (extendedPart >= 0) {
575 		nextseek = xstartsect = ltohi(part[extendedPart].relsect);
576 		xnumsect = ltohi(part[extendedPart].numsect);
577 		do {
578 			/*
579 			 *  If the seek would not cause us to change
580 			 *  position on the drive, then we're out of
581 			 *  extended partitions to examine.
582 			 */
583 			if (nextseek == lastseek)
584 				break;
585 			logicalDriveCount += numDrives;
586 			/*
587 			 *  Seek the next extended partition, and find
588 			 *  logical drives within it.
589 			 */
590 			if (lseek64(fd, nextseek * bpsec, SEEK_SET) < 0 ||
591 			    read(fd, &extmboot, sizeof (extmboot)) !=
592 			    sizeof (extmboot)) {
593 				perror(gettext("Unable to read extended "
594 				    "partition record"));
595 				return (error);
596 			}
597 			(void) memcpy(part, extmboot.parts, sizeof (part));
598 			lastseek = nextseek;
599 			if (ltohs(extmboot.signature) != MBB_MAGIC) {
600 				(void) fprintf(stderr,
601 				    gettext("Bad signature on "
602 				    "extended partition\n"));
603 				return (error);
604 			}
605 			/*
606 			 *  Count up drives, and track where the next
607 			 *  extended partition is in case we need it.  We
608 			 *  are expecting only one extended partition.  If
609 			 *  there is more than one we'll only go to the
610 			 *  first one we see, but warn about ignoring.
611 			 */
612 			numDrives = 0;
613 			for (i = 0; i < FD_NUMPART; i++) {
614 				if (isDosDrive(part[i].systid)) {
615 					extndDrives[numDrives++] = i;
616 					continue;
617 				} else if (isDosExtended(part[i].systid)) {
618 					if (nextseek != lastseek) {
619 						/*
620 						 * Already found an extended
621 						 * partition in this table.
622 						 */
623 						(void) fprintf(stderr,
624 						    gettext("WARNING: "
625 						    "Ignoring unexpected "
626 						    "additional extended "
627 						    "partition"));
628 						continue;
629 					}
630 					nextseek = xstartsect +
631 					    ltohi(part[i].relsect);
632 					continue;
633 				}
634 			}
635 		} while (drvnum > logicalDriveCount + numDrives);
636 
637 		if (drvnum <= logicalDriveCount + numDrives) {
638 			/*
639 			 * The number of logical drives we've found thus
640 			 * far is enough to get us to the one we were
641 			 * searching for.
642 			 */
643 			driveIndex = logicalDriveCount + numDrives - drvnum;
644 			found =
645 			    ltohi(part[extndDrives[driveIndex]].relsect) +
646 			    lastseek;
647 			if (found > (xstartsect + xnumsect)) {
648 				(void) fprintf(stderr,
649 				    gettext("Logical drive start sector (%d) "
650 				    "is not within the partition!\n"), found);
651 				return (error);
652 			} else {
653 				found *= bpsec;
654 			}
655 			return (found);
656 		} else {
657 			/*
658 			 * We ran out of extended dos partition
659 			 * drives.  The only hope now is to go
660 			 * back to extra drives defined in the master
661 			 * fdisk table.  But we overwrote that table
662 			 * already, so we must load it in again.
663 			 */
664 			logicalDriveCount += numDrives;
665 			(void) memcpy(part, mb.parts, sizeof (part));
666 		}
667 	}
668 	/*
669 	 *  Still haven't found the drive, is it an extra
670 	 *  drive defined in the main FDISK table?
671 	 */
672 	if (drvnum <= logicalDriveCount + numExtraDrives) {
673 		driveIndex = logicalDriveCount + numExtraDrives - drvnum;
674 		found = ltohi(part[extraDrives[driveIndex]].relsect) * bpsec;
675 		return (found);
676 	}
677 	return (error);
678 }
679