xref: /freebsd/sys/geom/part/g_part_mbr.c (revision 397e83df75e0fcd0d3fcb95ae4d794cb7600fc89)
1 /*-
2  * SPDX-License-Identifier: BSD-2-Clause
3  *
4  * Copyright (c) 2007, 2008 Marcel Moolenaar
5  * All rights reserved.
6  *
7  * Redistribution and use in source and binary forms, with or without
8  * modification, are permitted provided that the following conditions
9  * are met:
10  *
11  * 1. Redistributions of source code must retain the above copyright
12  *    notice, this list of conditions and the following disclaimer.
13  * 2. Redistributions in binary form must reproduce the above copyright
14  *    notice, this list of conditions and the following disclaimer in the
15  *    documentation and/or other materials provided with the distribution.
16  *
17  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
18  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
19  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
20  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
21  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
22  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27  */
28 
29 #include <sys/param.h>
30 #include <sys/bio.h>
31 #include <sys/diskmbr.h>
32 #include <sys/endian.h>
33 #include <sys/kernel.h>
34 #include <sys/kobj.h>
35 #include <sys/limits.h>
36 #include <sys/lock.h>
37 #include <sys/malloc.h>
38 #include <sys/mutex.h>
39 #include <sys/queue.h>
40 #include <sys/sbuf.h>
41 #include <sys/systm.h>
42 #include <sys/sysctl.h>
43 #include <geom/geom.h>
44 #include <geom/geom_int.h>
45 #include <geom/part/g_part.h>
46 
47 #include "g_part_if.h"
48 
49 FEATURE(geom_part_mbr, "GEOM partitioning class for MBR support");
50 
51 SYSCTL_DECL(_kern_geom_part);
52 static SYSCTL_NODE(_kern_geom_part, OID_AUTO, mbr,
53     CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
54     "GEOM_PART_MBR Master Boot Record");
55 
56 static u_int enforce_chs = 0;
57 SYSCTL_UINT(_kern_geom_part_mbr, OID_AUTO, enforce_chs,
58     CTLFLAG_RWTUN, &enforce_chs, 0, "Enforce alignment to CHS addressing");
59 
60 #define	MBRSIZE		512
61 
62 struct g_part_mbr_table {
63 	struct g_part_table	base;
64 	u_char		mbr[MBRSIZE];
65 };
66 
67 struct g_part_mbr_entry {
68 	struct g_part_entry	base;
69 	struct dos_partition ent;
70 };
71 
72 static int g_part_mbr_add(struct g_part_table *, struct g_part_entry *,
73     struct g_part_parms *);
74 static int g_part_mbr_bootcode(struct g_part_table *, struct g_part_parms *);
75 static int g_part_mbr_create(struct g_part_table *, struct g_part_parms *);
76 static int g_part_mbr_destroy(struct g_part_table *, struct g_part_parms *);
77 static void g_part_mbr_dumpconf(struct g_part_table *, struct g_part_entry *,
78     struct sbuf *, const char *);
79 static int g_part_mbr_dumpto(struct g_part_table *, struct g_part_entry *);
80 static int g_part_mbr_modify(struct g_part_table *, struct g_part_entry *,
81     struct g_part_parms *);
82 static const char *g_part_mbr_name(struct g_part_table *, struct g_part_entry *,
83     char *, size_t);
84 static int g_part_mbr_probe(struct g_part_table *, struct g_consumer *);
85 static int g_part_mbr_read(struct g_part_table *, struct g_consumer *);
86 static int g_part_mbr_setunset(struct g_part_table *, struct g_part_entry *,
87     const char *, unsigned int);
88 static const char *g_part_mbr_type(struct g_part_table *, struct g_part_entry *,
89     char *, size_t);
90 static int g_part_mbr_write(struct g_part_table *, struct g_consumer *);
91 static int g_part_mbr_resize(struct g_part_table *, struct g_part_entry *,
92     struct g_part_parms *);
93 
94 static kobj_method_t g_part_mbr_methods[] = {
95 	KOBJMETHOD(g_part_add,		g_part_mbr_add),
96 	KOBJMETHOD(g_part_bootcode,	g_part_mbr_bootcode),
97 	KOBJMETHOD(g_part_create,	g_part_mbr_create),
98 	KOBJMETHOD(g_part_destroy,	g_part_mbr_destroy),
99 	KOBJMETHOD(g_part_dumpconf,	g_part_mbr_dumpconf),
100 	KOBJMETHOD(g_part_dumpto,	g_part_mbr_dumpto),
101 	KOBJMETHOD(g_part_modify,	g_part_mbr_modify),
102 	KOBJMETHOD(g_part_resize,	g_part_mbr_resize),
103 	KOBJMETHOD(g_part_name,		g_part_mbr_name),
104 	KOBJMETHOD(g_part_probe,	g_part_mbr_probe),
105 	KOBJMETHOD(g_part_read,		g_part_mbr_read),
106 	KOBJMETHOD(g_part_setunset,	g_part_mbr_setunset),
107 	KOBJMETHOD(g_part_type,		g_part_mbr_type),
108 	KOBJMETHOD(g_part_write,	g_part_mbr_write),
109 	{ 0, 0 }
110 };
111 
112 static struct g_part_scheme g_part_mbr_scheme = {
113 	"MBR",
114 	g_part_mbr_methods,
115 	sizeof(struct g_part_mbr_table),
116 	.gps_entrysz = sizeof(struct g_part_mbr_entry),
117 	.gps_minent = NDOSPART,
118 	.gps_maxent = NDOSPART,
119 	.gps_bootcodesz = MBRSIZE,
120 };
121 G_PART_SCHEME_DECLARE(g_part_mbr);
122 MODULE_VERSION(geom_part_mbr, 0);
123 
124 static struct g_part_mbr_alias {
125 	u_char		typ;
126 	int		alias;
127 } mbr_alias_match[] = {
128 	{ DOSPTYP_386BSD,	G_PART_ALIAS_FREEBSD },
129 	{ DOSPTYP_APPLE_BOOT,	G_PART_ALIAS_APPLE_BOOT },
130 	{ DOSPTYP_APPLE_UFS,	G_PART_ALIAS_APPLE_UFS },
131 	{ DOSPTYP_EFI,		G_PART_ALIAS_EFI },
132 	{ DOSPTYP_EXT,		G_PART_ALIAS_EBR },
133 	{ DOSPTYP_EXTLBA,	G_PART_ALIAS_EBR },
134 	{ DOSPTYP_FAT16,	G_PART_ALIAS_MS_FAT16 },
135 	{ DOSPTYP_FAT32,	G_PART_ALIAS_MS_FAT32 },
136 	{ DOSPTYP_FAT32LBA,	G_PART_ALIAS_MS_FAT32LBA },
137 	{ DOSPTYP_HFS,		G_PART_ALIAS_APPLE_HFS },
138 	{ DOSPTYP_LDM,		G_PART_ALIAS_MS_LDM_DATA },
139 	{ DOSPTYP_LINLVM,	G_PART_ALIAS_LINUX_LVM },
140 	{ DOSPTYP_LINRAID,	G_PART_ALIAS_LINUX_RAID },
141 	{ DOSPTYP_LINSWP,	G_PART_ALIAS_LINUX_SWAP },
142 	{ DOSPTYP_LINUX,	G_PART_ALIAS_LINUX_DATA },
143 	{ DOSPTYP_NTFS,		G_PART_ALIAS_MS_NTFS },
144 	{ DOSPTYP_PPCBOOT,	G_PART_ALIAS_PREP_BOOT },
145 	{ DOSPTYP_VMFS,		G_PART_ALIAS_VMFS },
146 	{ DOSPTYP_VMKDIAG,	G_PART_ALIAS_VMKDIAG },
147 };
148 
149 static int
150 mbr_parse_type(const char *type, u_char *dp_typ)
151 {
152 	const char *alias;
153 	char *endp;
154 	long lt;
155 	int i;
156 
157 	if (type[0] == '!') {
158 		lt = strtol(type + 1, &endp, 0);
159 		if (type[1] == '\0' || *endp != '\0' || lt <= 0 || lt >= 256)
160 			return (EINVAL);
161 		*dp_typ = (u_char)lt;
162 		return (0);
163 	}
164 	for (i = 0; i < nitems(mbr_alias_match); i++) {
165 		alias = g_part_alias_name(mbr_alias_match[i].alias);
166 		if (strcasecmp(type, alias) == 0) {
167 			*dp_typ = mbr_alias_match[i].typ;
168 			return (0);
169 		}
170 	}
171 	return (EINVAL);
172 }
173 
174 static int
175 mbr_probe_bpb(u_char *bpb)
176 {
177 	uint16_t secsz;
178 	uint8_t clstsz;
179 
180 #define PO2(x)	((x & (x - 1)) == 0)
181 	secsz = le16dec(bpb);
182 	if (secsz < 512 || secsz > 4096 || !PO2(secsz))
183 		return (0);
184 	clstsz = bpb[2];
185 	if (clstsz < 1 || clstsz > 128 || !PO2(clstsz))
186 		return (0);
187 #undef PO2
188 
189 	return (1);
190 }
191 
192 static void
193 mbr_set_chs(struct g_part_table *table, uint32_t lba, u_char *cylp, u_char *hdp,
194     u_char *secp)
195 {
196 	uint32_t cyl, hd, sec;
197 
198 	sec = lba % table->gpt_sectors + 1;
199 	lba /= table->gpt_sectors;
200 	hd = lba % table->gpt_heads;
201 	lba /= table->gpt_heads;
202 	cyl = lba;
203 	if (cyl > 1023)
204 		sec = hd = cyl = ~0;
205 
206 	*cylp = cyl & 0xff;
207 	*hdp = hd & 0xff;
208 	*secp = (sec & 0x3f) | ((cyl >> 2) & 0xc0);
209 }
210 
211 static int
212 mbr_align(struct g_part_table *basetable, uint32_t *start, uint32_t *size)
213 {
214 	uint32_t sectors;
215 
216 	if (enforce_chs == 0)
217 		return (0);
218 	sectors = basetable->gpt_sectors;
219 	if (*size < sectors)
220 		return (EINVAL);
221 	if (start != NULL && (*start % sectors)) {
222 		*size += (*start % sectors) - sectors;
223 		*start -= (*start % sectors) - sectors;
224 	}
225 	if (*size % sectors)
226 		*size -= (*size % sectors);
227 	if (*size < sectors)
228 		return (EINVAL);
229 	return (0);
230 }
231 
232 static int
233 g_part_mbr_add(struct g_part_table *basetable, struct g_part_entry *baseentry,
234     struct g_part_parms *gpp)
235 {
236 	struct g_part_mbr_entry *entry;
237 	uint32_t start, size;
238 
239 	if (gpp->gpp_parms & G_PART_PARM_LABEL)
240 		return (EINVAL);
241 
242 	entry = (struct g_part_mbr_entry *)baseentry;
243 	start = gpp->gpp_start;
244 	size = gpp->gpp_size;
245 	if (mbr_align(basetable, &start, &size) != 0)
246 		return (EINVAL);
247 	if (baseentry->gpe_deleted)
248 		bzero(&entry->ent, sizeof(entry->ent));
249 
250 	KASSERT(baseentry->gpe_start <= start, ("%s", __func__));
251 	KASSERT(baseentry->gpe_end >= start + size - 1, ("%s", __func__));
252 	baseentry->gpe_start = start;
253 	baseentry->gpe_end = start + size - 1;
254 	entry->ent.dp_start = start;
255 	entry->ent.dp_size = size;
256 	mbr_set_chs(basetable, baseentry->gpe_start, &entry->ent.dp_scyl,
257 	    &entry->ent.dp_shd, &entry->ent.dp_ssect);
258 	mbr_set_chs(basetable, baseentry->gpe_end, &entry->ent.dp_ecyl,
259 	    &entry->ent.dp_ehd, &entry->ent.dp_esect);
260 	return (mbr_parse_type(gpp->gpp_type, &entry->ent.dp_typ));
261 }
262 
263 static int
264 g_part_mbr_bootcode(struct g_part_table *basetable, struct g_part_parms *gpp)
265 {
266 	struct g_part_mbr_table *table;
267 	uint32_t dsn;
268 
269 	if (gpp->gpp_codesize != MBRSIZE)
270 		return (ENODEV);
271 
272 	table = (struct g_part_mbr_table *)basetable;
273 	dsn = *(uint32_t *)(table->mbr + DOSDSNOFF);
274 	bcopy(gpp->gpp_codeptr, table->mbr, DOSPARTOFF);
275 	if (dsn != 0 && !gpp->gpp_skip_dsn)
276 		*(uint32_t *)(table->mbr + DOSDSNOFF) = dsn;
277 	return (0);
278 }
279 
280 static int
281 g_part_mbr_create(struct g_part_table *basetable, struct g_part_parms *gpp)
282 {
283 	struct g_provider *pp;
284 	struct g_part_mbr_table *table;
285 
286 	pp = gpp->gpp_provider;
287 	if (pp->sectorsize < MBRSIZE)
288 		return (ENOSPC);
289 
290 	basetable->gpt_first = basetable->gpt_sectors;
291 	basetable->gpt_last = MIN(pp->mediasize / pp->sectorsize,
292 	    UINT32_MAX) - 1;
293 
294 	table = (struct g_part_mbr_table *)basetable;
295 	le16enc(table->mbr + DOSMAGICOFFSET, DOSMAGIC);
296 	return (0);
297 }
298 
299 static int
300 g_part_mbr_destroy(struct g_part_table *basetable, struct g_part_parms *gpp)
301 {
302 
303 	/* Wipe the first sector to clear the partitioning. */
304 	basetable->gpt_smhead |= 1;
305 	return (0);
306 }
307 
308 static void
309 g_part_mbr_efimedia(struct g_part_mbr_table *table, struct g_part_mbr_entry *entry,
310     struct sbuf *sb)
311 {
312 	uint32_t dsn;
313 
314 	dsn = le32dec(table->mbr + DOSDSNOFF);
315 	sbuf_printf(sb, "HD(%d,MBR,%#08x,%#jx,%#jx)",
316 	    entry->base.gpe_index, dsn, (intmax_t)entry->base.gpe_start,
317 	    (intmax_t)(entry->base.gpe_end - entry->base.gpe_start + 1));
318 }
319 
320 static void
321 g_part_mbr_dumpconf(struct g_part_table *basetable, struct g_part_entry *baseentry,
322     struct sbuf *sb, const char *indent)
323 {
324 	struct g_part_mbr_entry *entry;
325 	struct g_part_mbr_table *table;
326 
327 	table = (struct g_part_mbr_table *)basetable;
328 	entry = (struct g_part_mbr_entry *)baseentry;
329 	if (indent == NULL) {
330 		/* conftxt: libdisk compatibility */
331 		sbuf_printf(sb, " xs MBR xt %u", entry->ent.dp_typ);
332 	} else if (entry != NULL) {
333 		/* confxml: partition entry information */
334 		sbuf_printf(sb, "%s<rawtype>%u</rawtype>\n", indent,
335 		    entry->ent.dp_typ);
336 		if (entry->ent.dp_flag & 0x80)
337 			sbuf_printf(sb, "%s<attrib>active</attrib>\n", indent);
338 		sbuf_printf(sb, "%s<efimedia>", indent);
339 		g_part_mbr_efimedia(table, entry, sb);
340 		sbuf_cat(sb, "</efimedia>\n");
341 	} else {
342 		/* confxml: scheme information */
343 	}
344 }
345 
346 static int
347 g_part_mbr_dumpto(struct g_part_table *table, struct g_part_entry *baseentry)
348 {
349 	struct g_part_mbr_entry *entry;
350 
351 	/* Allow dumping to a FreeBSD partition or Linux swap partition only. */
352 	entry = (struct g_part_mbr_entry *)baseentry;
353 	return ((entry->ent.dp_typ == DOSPTYP_386BSD ||
354 	    entry->ent.dp_typ == DOSPTYP_LINSWP) ? 1 : 0);
355 }
356 
357 static int
358 g_part_mbr_modify(struct g_part_table *basetable,
359     struct g_part_entry *baseentry, struct g_part_parms *gpp)
360 {
361 	struct g_part_mbr_entry *entry;
362 
363 	if (gpp->gpp_parms & G_PART_PARM_LABEL)
364 		return (EINVAL);
365 
366 	entry = (struct g_part_mbr_entry *)baseentry;
367 	if (gpp->gpp_parms & G_PART_PARM_TYPE)
368 		return (mbr_parse_type(gpp->gpp_type, &entry->ent.dp_typ));
369 	return (0);
370 }
371 
372 static int
373 g_part_mbr_resize(struct g_part_table *basetable,
374     struct g_part_entry *baseentry, struct g_part_parms *gpp)
375 {
376 	struct g_part_mbr_entry *entry;
377 	struct g_provider *pp;
378 	uint32_t size;
379 
380 	if (baseentry == NULL) {
381 		pp = LIST_FIRST(&basetable->gpt_gp->consumer)->provider;
382 		basetable->gpt_last = MIN(pp->mediasize / pp->sectorsize,
383 		    UINT32_MAX) - 1;
384 		return (0);
385 	}
386 	size = gpp->gpp_size;
387 	if (mbr_align(basetable, NULL, &size) != 0)
388 		return (EINVAL);
389 	/* XXX: prevent unexpected shrinking. */
390 	pp = baseentry->gpe_pp;
391 	if ((g_debugflags & G_F_FOOTSHOOTING) == 0 && size < gpp->gpp_size &&
392 	    pp->mediasize / pp->sectorsize > size)
393 		return (EBUSY);
394 	entry = (struct g_part_mbr_entry *)baseentry;
395 	baseentry->gpe_end = baseentry->gpe_start + size - 1;
396 	entry->ent.dp_size = size;
397 	mbr_set_chs(basetable, baseentry->gpe_end, &entry->ent.dp_ecyl,
398 	    &entry->ent.dp_ehd, &entry->ent.dp_esect);
399 	return (0);
400 }
401 
402 static const char *
403 g_part_mbr_name(struct g_part_table *table, struct g_part_entry *baseentry,
404     char *buf, size_t bufsz)
405 {
406 
407 	snprintf(buf, bufsz, "s%d", baseentry->gpe_index);
408 	return (buf);
409 }
410 
411 static int
412 g_part_mbr_probe(struct g_part_table *table, struct g_consumer *cp)
413 {
414 	char psn[8];
415 	struct g_provider *pp;
416 	u_char *buf, *p;
417 	int error, index, res, sum;
418 	uint16_t magic;
419 
420 	pp = cp->provider;
421 
422 	/* Sanity-check the provider. */
423 	if (pp->sectorsize < MBRSIZE || pp->mediasize < pp->sectorsize)
424 		return (ENOSPC);
425 	if (pp->sectorsize > 4096)
426 		return (ENXIO);
427 
428 	/* We don't nest under an MBR (see EBR instead). */
429 	error = g_getattr("PART::scheme", cp, &psn);
430 	if (error == 0 && strcmp(psn, g_part_mbr_scheme.name) == 0)
431 		return (ELOOP);
432 
433 	/* Check that there's a MBR. */
434 	buf = g_read_data(cp, 0L, pp->sectorsize, &error);
435 	if (buf == NULL)
436 		return (error);
437 
438 	/* We goto out on mismatch. */
439 	res = ENXIO;
440 
441 	magic = le16dec(buf + DOSMAGICOFFSET);
442 	if (magic != DOSMAGIC)
443 		goto out;
444 
445 	for (index = 0; index < NDOSPART; index++) {
446 		p = buf + DOSPARTOFF + index * DOSPARTSIZE;
447 		if (p[0] != 0 && p[0] != 0x80)
448 			goto out;
449 	}
450 
451 	/*
452 	 * If the partition table does not consist of all zeroes,
453 	 * assume we have a MBR. If it's all zeroes, we could have
454 	 * a boot sector. For example, a boot sector that doesn't
455 	 * have boot code -- common on non-i386 hardware. In that
456 	 * case we check if we have a possible BPB. If so, then we
457 	 * assume we have a boot sector instead.
458 	 */
459 	sum = 0;
460 	for (index = 0; index < NDOSPART * DOSPARTSIZE; index++)
461 		sum += buf[DOSPARTOFF + index];
462 	if (sum != 0 || !mbr_probe_bpb(buf + 0x0b))
463 		res = G_PART_PROBE_PRI_NORM;
464 
465  out:
466 	g_free(buf);
467 	return (res);
468 }
469 
470 static int
471 g_part_mbr_read(struct g_part_table *basetable, struct g_consumer *cp)
472 {
473 	struct dos_partition ent;
474 	struct g_provider *pp;
475 	struct g_part_mbr_table *table;
476 	struct g_part_mbr_entry *entry;
477 	u_char *buf, *p;
478 	off_t chs, msize, first;
479 	u_int sectors, heads;
480 	int error, index;
481 
482 	pp = cp->provider;
483 	table = (struct g_part_mbr_table *)basetable;
484 	first = basetable->gpt_sectors;
485 	msize = MIN(pp->mediasize / pp->sectorsize, UINT32_MAX);
486 
487 	buf = g_read_data(cp, 0L, pp->sectorsize, &error);
488 	if (buf == NULL)
489 		return (error);
490 
491 	bcopy(buf, table->mbr, sizeof(table->mbr));
492 	for (index = NDOSPART - 1; index >= 0; index--) {
493 		p = buf + DOSPARTOFF + index * DOSPARTSIZE;
494 		ent.dp_flag = p[0];
495 		ent.dp_shd = p[1];
496 		ent.dp_ssect = p[2];
497 		ent.dp_scyl = p[3];
498 		ent.dp_typ = p[4];
499 		ent.dp_ehd = p[5];
500 		ent.dp_esect = p[6];
501 		ent.dp_ecyl = p[7];
502 		ent.dp_start = le32dec(p + 8);
503 		ent.dp_size = le32dec(p + 12);
504 		if (ent.dp_typ == 0 || ent.dp_typ == DOSPTYP_PMBR)
505 			continue;
506 		if (ent.dp_start == 0 || ent.dp_size == 0)
507 			continue;
508 		sectors = ent.dp_esect & 0x3f;
509 		if (sectors > basetable->gpt_sectors &&
510 		    !basetable->gpt_fixgeom) {
511 			g_part_geometry_heads(msize, sectors, &chs, &heads);
512 			if (chs != 0) {
513 				basetable->gpt_sectors = sectors;
514 				basetable->gpt_heads = heads;
515 			}
516 		}
517 		if (ent.dp_start < first)
518 			first = ent.dp_start;
519 		entry = (struct g_part_mbr_entry *)g_part_new_entry(basetable,
520 		    index + 1, ent.dp_start, ent.dp_start + ent.dp_size - 1);
521 		entry->ent = ent;
522 	}
523 
524 	basetable->gpt_entries = NDOSPART;
525 	basetable->gpt_first = basetable->gpt_sectors;
526 	basetable->gpt_last = msize - 1;
527 
528 	if (first < basetable->gpt_first)
529 		basetable->gpt_first = 1;
530 
531 	g_free(buf);
532 	return (0);
533 }
534 
535 static int
536 g_part_mbr_setunset(struct g_part_table *table, struct g_part_entry *baseentry,
537     const char *attrib, unsigned int set)
538 {
539 	struct g_part_entry *iter;
540 	struct g_part_mbr_entry *entry;
541 	int changed;
542 
543 	if (baseentry == NULL)
544 		return (ENODEV);
545 	if (strcasecmp(attrib, "active") != 0)
546 		return (EINVAL);
547 
548 	/* Only one entry can have the active attribute. */
549 	LIST_FOREACH(iter, &table->gpt_entry, gpe_entry) {
550 		if (iter->gpe_deleted)
551 			continue;
552 		changed = 0;
553 		entry = (struct g_part_mbr_entry *)iter;
554 		if (iter == baseentry) {
555 			if (set && (entry->ent.dp_flag & 0x80) == 0) {
556 				entry->ent.dp_flag |= 0x80;
557 				changed = 1;
558 			} else if (!set && (entry->ent.dp_flag & 0x80)) {
559 				entry->ent.dp_flag &= ~0x80;
560 				changed = 1;
561 			}
562 		} else {
563 			if (set && (entry->ent.dp_flag & 0x80)) {
564 				entry->ent.dp_flag &= ~0x80;
565 				changed = 1;
566 			}
567 		}
568 		if (changed && !iter->gpe_created)
569 			iter->gpe_modified = 1;
570 	}
571 	return (0);
572 }
573 
574 static const char *
575 g_part_mbr_type(struct g_part_table *basetable, struct g_part_entry *baseentry,
576     char *buf, size_t bufsz)
577 {
578 	struct g_part_mbr_entry *entry;
579 	int i;
580 
581 	entry = (struct g_part_mbr_entry *)baseentry;
582 	for (i = 0; i < nitems(mbr_alias_match); i++) {
583 		if (mbr_alias_match[i].typ == entry->ent.dp_typ)
584 			return (g_part_alias_name(mbr_alias_match[i].alias));
585 	}
586 	snprintf(buf, bufsz, "!%d", entry->ent.dp_typ);
587 	return (buf);
588 }
589 
590 static int
591 g_part_mbr_write(struct g_part_table *basetable, struct g_consumer *cp)
592 {
593 	struct g_part_entry *baseentry;
594 	struct g_part_mbr_entry *entry;
595 	struct g_part_mbr_table *table;
596 	u_char *p;
597 	int error, index;
598 
599 	table = (struct g_part_mbr_table *)basetable;
600 	baseentry = LIST_FIRST(&basetable->gpt_entry);
601 	for (index = 1; index <= basetable->gpt_entries; index++) {
602 		p = table->mbr + DOSPARTOFF + (index - 1) * DOSPARTSIZE;
603 		entry = (baseentry != NULL && index == baseentry->gpe_index)
604 		    ? (struct g_part_mbr_entry *)baseentry : NULL;
605 		if (entry != NULL && !baseentry->gpe_deleted) {
606 			p[0] = entry->ent.dp_flag;
607 			p[1] = entry->ent.dp_shd;
608 			p[2] = entry->ent.dp_ssect;
609 			p[3] = entry->ent.dp_scyl;
610 			p[4] = entry->ent.dp_typ;
611 			p[5] = entry->ent.dp_ehd;
612 			p[6] = entry->ent.dp_esect;
613 			p[7] = entry->ent.dp_ecyl;
614 			le32enc(p + 8, entry->ent.dp_start);
615 			le32enc(p + 12, entry->ent.dp_size);
616 		} else
617 			bzero(p, DOSPARTSIZE);
618 
619 		if (entry != NULL)
620 			baseentry = LIST_NEXT(baseentry, gpe_entry);
621 	}
622 
623 	error = g_write_data(cp, 0, table->mbr, cp->provider->sectorsize);
624 	return (error);
625 }
626