xref: /freebsd/sys/geom/part/g_part_ebr.c (revision a18eacbefdfa1085ca3db829e86ece78cd416493)
1 /*-
2  * Copyright (c) 2007-2009 Marcel Moolenaar
3  * All rights reserved.
4  *
5  * Redistribution and use in source and binary forms, with or without
6  * modification, are permitted provided that the following conditions
7  * are met:
8  *
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 ``AS IS'' AND ANY EXPRESS OR
16  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
19  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25  */
26 
27 #include "opt_geom.h"
28 
29 #include <sys/cdefs.h>
30 __FBSDID("$FreeBSD$");
31 
32 #include <sys/param.h>
33 #include <sys/bio.h>
34 #include <sys/diskmbr.h>
35 #include <sys/endian.h>
36 #include <sys/kernel.h>
37 #include <sys/kobj.h>
38 #include <sys/limits.h>
39 #include <sys/lock.h>
40 #include <sys/malloc.h>
41 #include <sys/mutex.h>
42 #include <sys/queue.h>
43 #include <sys/sbuf.h>
44 #include <sys/systm.h>
45 #include <sys/sysctl.h>
46 #include <geom/geom.h>
47 #include <geom/part/g_part.h>
48 
49 #include "g_part_if.h"
50 
51 FEATURE(geom_part_ebr,
52     "GEOM partitioning class for extended boot records support");
53 #if defined(GEOM_PART_EBR_COMPAT)
54 FEATURE(geom_part_ebr_compat,
55     "GEOM EBR partitioning class: backward-compatible partition names");
56 #endif
57 
58 #define	EBRSIZE		512
59 
60 struct g_part_ebr_table {
61 	struct g_part_table	base;
62 #ifndef GEOM_PART_EBR_COMPAT
63 	u_char		ebr[EBRSIZE];
64 #endif
65 };
66 
67 struct g_part_ebr_entry {
68 	struct g_part_entry	base;
69 	struct dos_partition	ent;
70 };
71 
72 static int g_part_ebr_add(struct g_part_table *, struct g_part_entry *,
73     struct g_part_parms *);
74 static int g_part_ebr_create(struct g_part_table *, struct g_part_parms *);
75 static int g_part_ebr_destroy(struct g_part_table *, struct g_part_parms *);
76 static void g_part_ebr_dumpconf(struct g_part_table *, struct g_part_entry *,
77     struct sbuf *, const char *);
78 static int g_part_ebr_dumpto(struct g_part_table *, struct g_part_entry *);
79 #if defined(GEOM_PART_EBR_COMPAT)
80 static void g_part_ebr_fullname(struct g_part_table *, struct g_part_entry *,
81     struct sbuf *, const char *);
82 #endif
83 static int g_part_ebr_modify(struct g_part_table *, struct g_part_entry *,
84     struct g_part_parms *);
85 static const char *g_part_ebr_name(struct g_part_table *, struct g_part_entry *,
86     char *, size_t);
87 static int g_part_ebr_precheck(struct g_part_table *, enum g_part_ctl,
88     struct g_part_parms *);
89 static int g_part_ebr_probe(struct g_part_table *, struct g_consumer *);
90 static int g_part_ebr_read(struct g_part_table *, struct g_consumer *);
91 static int g_part_ebr_setunset(struct g_part_table *, struct g_part_entry *,
92     const char *, unsigned int);
93 static const char *g_part_ebr_type(struct g_part_table *, struct g_part_entry *,
94     char *, size_t);
95 static int g_part_ebr_write(struct g_part_table *, struct g_consumer *);
96 static int g_part_ebr_resize(struct g_part_table *, struct g_part_entry *,
97     struct g_part_parms *);
98 
99 static kobj_method_t g_part_ebr_methods[] = {
100 	KOBJMETHOD(g_part_add,		g_part_ebr_add),
101 	KOBJMETHOD(g_part_create,	g_part_ebr_create),
102 	KOBJMETHOD(g_part_destroy,	g_part_ebr_destroy),
103 	KOBJMETHOD(g_part_dumpconf,	g_part_ebr_dumpconf),
104 	KOBJMETHOD(g_part_dumpto,	g_part_ebr_dumpto),
105 #if defined(GEOM_PART_EBR_COMPAT)
106 	KOBJMETHOD(g_part_fullname,	g_part_ebr_fullname),
107 #endif
108 	KOBJMETHOD(g_part_modify,	g_part_ebr_modify),
109 	KOBJMETHOD(g_part_name,		g_part_ebr_name),
110 	KOBJMETHOD(g_part_precheck,	g_part_ebr_precheck),
111 	KOBJMETHOD(g_part_probe,	g_part_ebr_probe),
112 	KOBJMETHOD(g_part_read,		g_part_ebr_read),
113 	KOBJMETHOD(g_part_resize,	g_part_ebr_resize),
114 	KOBJMETHOD(g_part_setunset,	g_part_ebr_setunset),
115 	KOBJMETHOD(g_part_type,		g_part_ebr_type),
116 	KOBJMETHOD(g_part_write,	g_part_ebr_write),
117 	{ 0, 0 }
118 };
119 
120 static struct g_part_scheme g_part_ebr_scheme = {
121 	"EBR",
122 	g_part_ebr_methods,
123 	sizeof(struct g_part_ebr_table),
124 	.gps_entrysz = sizeof(struct g_part_ebr_entry),
125 	.gps_minent = 1,
126 	.gps_maxent = INT_MAX,
127 };
128 G_PART_SCHEME_DECLARE(g_part_ebr);
129 
130 static struct g_part_ebr_alias {
131 	u_char		typ;
132 	int		alias;
133 } ebr_alias_match[] = {
134 	{ DOSPTYP_386BSD,	G_PART_ALIAS_FREEBSD },
135 	{ DOSPTYP_NTFS,		G_PART_ALIAS_MS_NTFS },
136 	{ DOSPTYP_FAT32,	G_PART_ALIAS_MS_FAT32 },
137 	{ DOSPTYP_LINSWP,	G_PART_ALIAS_LINUX_SWAP },
138 	{ DOSPTYP_LINUX,	G_PART_ALIAS_LINUX_DATA },
139 	{ DOSPTYP_LINLVM,	G_PART_ALIAS_LINUX_LVM },
140 	{ DOSPTYP_LINRAID,	G_PART_ALIAS_LINUX_RAID },
141 };
142 
143 static void ebr_set_chs(struct g_part_table *, uint32_t, u_char *, u_char *,
144     u_char *);
145 
146 static void
147 ebr_entry_decode(const char *p, struct dos_partition *ent)
148 {
149 	ent->dp_flag = p[0];
150 	ent->dp_shd = p[1];
151 	ent->dp_ssect = p[2];
152 	ent->dp_scyl = p[3];
153 	ent->dp_typ = p[4];
154 	ent->dp_ehd = p[5];
155 	ent->dp_esect = p[6];
156 	ent->dp_ecyl = p[7];
157 	ent->dp_start = le32dec(p + 8);
158 	ent->dp_size = le32dec(p + 12);
159 }
160 
161 static void
162 ebr_entry_link(struct g_part_table *table, uint32_t start, uint32_t end,
163    u_char *buf)
164 {
165 
166 	buf[0] = 0 /* dp_flag */;
167 	ebr_set_chs(table, start, &buf[3] /* dp_scyl */, &buf[1] /* dp_shd */,
168 	    &buf[2] /* dp_ssect */);
169 	buf[4] = 5 /* dp_typ */;
170 	ebr_set_chs(table, end, &buf[7] /* dp_ecyl */, &buf[5] /* dp_ehd */,
171 	    &buf[6] /* dp_esect */);
172 	le32enc(buf + 8, start);
173 	le32enc(buf + 12, end - start + 1);
174 }
175 
176 static int
177 ebr_parse_type(const char *type, u_char *dp_typ)
178 {
179 	const char *alias;
180 	char *endp;
181 	long lt;
182 	int i;
183 
184 	if (type[0] == '!') {
185 		lt = strtol(type + 1, &endp, 0);
186 		if (type[1] == '\0' || *endp != '\0' || lt <= 0 || lt >= 256)
187 			return (EINVAL);
188 		*dp_typ = (u_char)lt;
189 		return (0);
190 	}
191 	for (i = 0;
192 	    i < sizeof(ebr_alias_match) / sizeof(ebr_alias_match[0]); i++) {
193 		alias = g_part_alias_name(ebr_alias_match[i].alias);
194 		if (strcasecmp(type, alias) == 0) {
195 			*dp_typ = ebr_alias_match[i].typ;
196 			return (0);
197 		}
198 	}
199 	return (EINVAL);
200 }
201 
202 
203 static void
204 ebr_set_chs(struct g_part_table *table, uint32_t lba, u_char *cylp, u_char *hdp,
205     u_char *secp)
206 {
207 	uint32_t cyl, hd, sec;
208 
209 	sec = lba % table->gpt_sectors + 1;
210 	lba /= table->gpt_sectors;
211 	hd = lba % table->gpt_heads;
212 	lba /= table->gpt_heads;
213 	cyl = lba;
214 	if (cyl > 1023)
215 		sec = hd = cyl = ~0;
216 
217 	*cylp = cyl & 0xff;
218 	*hdp = hd & 0xff;
219 	*secp = (sec & 0x3f) | ((cyl >> 2) & 0xc0);
220 }
221 
222 static int
223 g_part_ebr_add(struct g_part_table *basetable, struct g_part_entry *baseentry,
224     struct g_part_parms *gpp)
225 {
226 	struct g_geom *gp;
227 	struct g_provider *pp;
228 	struct g_part_ebr_entry *entry;
229 	uint32_t start, size, sectors;
230 
231 	if (gpp->gpp_parms & G_PART_PARM_LABEL)
232 		return (EINVAL);
233 
234 	gp = basetable->gpt_gp;
235 	pp = LIST_FIRST(&gp->consumer)->provider;
236 	sectors = basetable->gpt_sectors;
237 
238 	entry = (struct g_part_ebr_entry *)baseentry;
239 
240 	start = gpp->gpp_start;
241 	size = gpp->gpp_size;
242 	if (size < 2 * sectors)
243 		return (EINVAL);
244 	if (start % sectors) {
245 		size = size - sectors + (start % sectors);
246 		start = start - (start % sectors) + sectors;
247 	}
248 	if (size % sectors)
249 		size = size - (size % sectors);
250 	if (size < 2 * sectors)
251 		return (EINVAL);
252 
253 	if (baseentry->gpe_deleted)
254 		bzero(&entry->ent, sizeof(entry->ent));
255 
256 	KASSERT(baseentry->gpe_start <= start, ("%s", __func__));
257 	KASSERT(baseentry->gpe_end >= start + size - 1, ("%s", __func__));
258 	baseentry->gpe_index = (start / sectors) + 1;
259 	baseentry->gpe_offset = (off_t)(start + sectors) * pp->sectorsize;
260 	baseentry->gpe_start = start;
261 	baseentry->gpe_end = start + size - 1;
262 	entry->ent.dp_start = sectors;
263 	entry->ent.dp_size = size - sectors;
264 	ebr_set_chs(basetable, entry->ent.dp_start, &entry->ent.dp_scyl,
265 	    &entry->ent.dp_shd, &entry->ent.dp_ssect);
266 	ebr_set_chs(basetable, baseentry->gpe_end, &entry->ent.dp_ecyl,
267 	    &entry->ent.dp_ehd, &entry->ent.dp_esect);
268 	return (ebr_parse_type(gpp->gpp_type, &entry->ent.dp_typ));
269 }
270 
271 static int
272 g_part_ebr_create(struct g_part_table *basetable, struct g_part_parms *gpp)
273 {
274 	char type[64];
275 	struct g_consumer *cp;
276 	struct g_provider *pp;
277 	uint32_t msize;
278 	int error;
279 
280 	pp = gpp->gpp_provider;
281 
282 	if (pp->sectorsize < EBRSIZE)
283 		return (ENOSPC);
284 	if (pp->sectorsize > 4096)
285 		return (ENXIO);
286 
287 	/* Check that we have a parent and that it's a MBR. */
288 	if (basetable->gpt_depth == 0)
289 		return (ENXIO);
290 	cp = LIST_FIRST(&pp->consumers);
291 	error = g_getattr("PART::scheme", cp, &type);
292 	if (error != 0)
293 		return (error);
294 	if (strcmp(type, "MBR") != 0)
295 		return (ENXIO);
296 	error = g_getattr("PART::type", cp, &type);
297 	if (error != 0)
298 		return (error);
299 	if (strcmp(type, "ebr") != 0)
300 		return (ENXIO);
301 
302 	msize = MIN(pp->mediasize / pp->sectorsize, UINT32_MAX);
303 	basetable->gpt_first = 0;
304 	basetable->gpt_last = msize - 1;
305 	basetable->gpt_entries = msize / basetable->gpt_sectors;
306 	return (0);
307 }
308 
309 static int
310 g_part_ebr_destroy(struct g_part_table *basetable, struct g_part_parms *gpp)
311 {
312 
313 	/* Wipe the first sector to clear the partitioning. */
314 	basetable->gpt_smhead |= 1;
315 	return (0);
316 }
317 
318 static void
319 g_part_ebr_dumpconf(struct g_part_table *table, struct g_part_entry *baseentry,
320     struct sbuf *sb, const char *indent)
321 {
322 	struct g_part_ebr_entry *entry;
323 
324 	entry = (struct g_part_ebr_entry *)baseentry;
325 	if (indent == NULL) {
326 		/* conftxt: libdisk compatibility */
327 		sbuf_printf(sb, " xs MBREXT xt %u", entry->ent.dp_typ);
328 	} else if (entry != NULL) {
329 		/* confxml: partition entry information */
330 		sbuf_printf(sb, "%s<rawtype>%u</rawtype>\n", indent,
331 		    entry->ent.dp_typ);
332 		if (entry->ent.dp_flag & 0x80)
333 			sbuf_printf(sb, "%s<attrib>active</attrib>\n", indent);
334 	} else {
335 		/* confxml: scheme information */
336 	}
337 }
338 
339 static int
340 g_part_ebr_dumpto(struct g_part_table *table, struct g_part_entry *baseentry)
341 {
342 	struct g_part_ebr_entry *entry;
343 
344 	/* Allow dumping to a FreeBSD partition or Linux swap partition only. */
345 	entry = (struct g_part_ebr_entry *)baseentry;
346 	return ((entry->ent.dp_typ == DOSPTYP_386BSD ||
347 	    entry->ent.dp_typ == DOSPTYP_LINSWP) ? 1 : 0);
348 }
349 
350 #if defined(GEOM_PART_EBR_COMPAT)
351 static void
352 g_part_ebr_fullname(struct g_part_table *table, struct g_part_entry *entry,
353     struct sbuf *sb, const char *pfx)
354 {
355 	struct g_part_entry *iter;
356 	u_int idx;
357 
358 	idx = 5;
359 	LIST_FOREACH(iter, &table->gpt_entry, gpe_entry) {
360 		if (iter == entry)
361 			break;
362 		idx++;
363 	}
364 	sbuf_printf(sb, "%.*s%u", (int)strlen(pfx) - 1, pfx, idx);
365 }
366 #endif
367 
368 static int
369 g_part_ebr_modify(struct g_part_table *basetable,
370     struct g_part_entry *baseentry, struct g_part_parms *gpp)
371 {
372 	struct g_part_ebr_entry *entry;
373 
374 	if (gpp->gpp_parms & G_PART_PARM_LABEL)
375 		return (EINVAL);
376 
377 	entry = (struct g_part_ebr_entry *)baseentry;
378 	if (gpp->gpp_parms & G_PART_PARM_TYPE)
379 		return (ebr_parse_type(gpp->gpp_type, &entry->ent.dp_typ));
380 	return (0);
381 }
382 
383 static int
384 g_part_ebr_resize(struct g_part_table *basetable,
385     struct g_part_entry *baseentry, struct g_part_parms *gpp)
386 {
387 	struct g_provider *pp;
388 
389 	if (baseentry != NULL)
390 		return (EOPNOTSUPP);
391 	pp = LIST_FIRST(&basetable->gpt_gp->consumer)->provider;
392 	basetable->gpt_last = MIN(pp->mediasize / pp->sectorsize,
393 	    UINT32_MAX) - 1;
394 	return (0);
395 }
396 
397 static const char *
398 g_part_ebr_name(struct g_part_table *table, struct g_part_entry *entry,
399     char *buf, size_t bufsz)
400 {
401 
402 	snprintf(buf, bufsz, "+%08u", entry->gpe_index);
403 	return (buf);
404 }
405 
406 static int
407 g_part_ebr_precheck(struct g_part_table *table, enum g_part_ctl req,
408     struct g_part_parms *gpp)
409 {
410 #if defined(GEOM_PART_EBR_COMPAT)
411 	if (req == G_PART_CTL_DESTROY)
412 		return (0);
413 	return (ECANCELED);
414 #else
415 	/*
416 	 * The index is a function of the start of the partition.
417 	 * This is not something the user can override, nor is it
418 	 * something the common code will do right. We can set the
419 	 * index now so that we get what we need.
420 	 */
421 	if (req == G_PART_CTL_ADD)
422 		gpp->gpp_index = (gpp->gpp_start / table->gpt_sectors) + 1;
423 	return (0);
424 #endif
425 }
426 
427 static int
428 g_part_ebr_probe(struct g_part_table *table, struct g_consumer *cp)
429 {
430 	char type[64];
431 	struct g_provider *pp;
432 	u_char *buf, *p;
433 	int error, index, res;
434 	uint16_t magic;
435 
436 	pp = cp->provider;
437 
438 	/* Sanity-check the provider. */
439 	if (pp->sectorsize < EBRSIZE || pp->mediasize < pp->sectorsize)
440 		return (ENOSPC);
441 	if (pp->sectorsize > 4096)
442 		return (ENXIO);
443 
444 	/* Check that we have a parent and that it's a MBR. */
445 	if (table->gpt_depth == 0)
446 		return (ENXIO);
447 	error = g_getattr("PART::scheme", cp, &type);
448 	if (error != 0)
449 		return (error);
450 	if (strcmp(type, "MBR") != 0)
451 		return (ENXIO);
452 	/* Check that partition has type DOSPTYP_EBR. */
453 	error = g_getattr("PART::type", cp, &type);
454 	if (error != 0)
455 		return (error);
456 	if (strcmp(type, "ebr") != 0)
457 		return (ENXIO);
458 
459 	/* Check that there's a EBR. */
460 	buf = g_read_data(cp, 0L, pp->sectorsize, &error);
461 	if (buf == NULL)
462 		return (error);
463 
464 	/* We goto out on mismatch. */
465 	res = ENXIO;
466 
467 	magic = le16dec(buf + DOSMAGICOFFSET);
468 	if (magic != DOSMAGIC)
469 		goto out;
470 
471 	for (index = 0; index < 2; index++) {
472 		p = buf + DOSPARTOFF + index * DOSPARTSIZE;
473 		if (p[0] != 0 && p[0] != 0x80)
474 			goto out;
475 	}
476 	res = G_PART_PROBE_PRI_NORM;
477 
478  out:
479 	g_free(buf);
480 	return (res);
481 }
482 
483 static int
484 g_part_ebr_read(struct g_part_table *basetable, struct g_consumer *cp)
485 {
486 	struct dos_partition ent[2];
487 	struct g_provider *pp;
488 	struct g_part_entry *baseentry;
489 	struct g_part_ebr_table *table;
490 	struct g_part_ebr_entry *entry;
491 	u_char *buf;
492 	off_t ofs, msize;
493 	u_int lba;
494 	int error, index;
495 
496 	pp = cp->provider;
497 	table = (struct g_part_ebr_table *)basetable;
498 	msize = MIN(pp->mediasize / pp->sectorsize, UINT32_MAX);
499 
500 	lba = 0;
501 	while (1) {
502 		ofs = (off_t)lba * pp->sectorsize;
503 		buf = g_read_data(cp, ofs, pp->sectorsize, &error);
504 		if (buf == NULL)
505 			return (error);
506 
507 		ebr_entry_decode(buf + DOSPARTOFF + 0 * DOSPARTSIZE, ent + 0);
508 		ebr_entry_decode(buf + DOSPARTOFF + 1 * DOSPARTSIZE, ent + 1);
509 
510 		/* The 3rd & 4th entries should be zeroes. */
511 		if (le64dec(buf + DOSPARTOFF + 2 * DOSPARTSIZE) +
512 		    le64dec(buf + DOSPARTOFF + 3 * DOSPARTSIZE) != 0) {
513 			basetable->gpt_corrupt = 1;
514 			printf("GEOM: %s: invalid entries in the EBR ignored.\n",
515 			    pp->name);
516 		}
517 #ifndef GEOM_PART_EBR_COMPAT
518 		/* Save the first EBR, it can contain a boot code */
519 		if (lba == 0)
520 			bcopy(buf, table->ebr, sizeof(table->ebr));
521 #endif
522 		g_free(buf);
523 
524 		if (ent[0].dp_typ == 0)
525 			break;
526 
527 		if (ent[0].dp_typ == 5 && ent[1].dp_typ == 0) {
528 			lba = ent[0].dp_start;
529 			continue;
530 		}
531 
532 		index = (lba / basetable->gpt_sectors) + 1;
533 		baseentry = (struct g_part_entry *)g_part_new_entry(basetable,
534 		    index, lba, lba + ent[0].dp_start + ent[0].dp_size - 1);
535 		baseentry->gpe_offset = (off_t)(lba + ent[0].dp_start) *
536 		    pp->sectorsize;
537 		entry = (struct g_part_ebr_entry *)baseentry;
538 		entry->ent = ent[0];
539 
540 		if (ent[1].dp_typ == 0)
541 			break;
542 
543 		lba = ent[1].dp_start;
544 	}
545 
546 	basetable->gpt_entries = msize / basetable->gpt_sectors;
547 	basetable->gpt_first = 0;
548 	basetable->gpt_last = msize - 1;
549 	return (0);
550 }
551 
552 static int
553 g_part_ebr_setunset(struct g_part_table *table, struct g_part_entry *baseentry,
554     const char *attrib, unsigned int set)
555 {
556 	struct g_part_entry *iter;
557 	struct g_part_ebr_entry *entry;
558 	int changed;
559 
560 	if (baseentry == NULL)
561 		return (ENODEV);
562 	if (strcasecmp(attrib, "active") != 0)
563 		return (EINVAL);
564 
565 	/* Only one entry can have the active attribute. */
566 	LIST_FOREACH(iter, &table->gpt_entry, gpe_entry) {
567 		if (iter->gpe_deleted)
568 			continue;
569 		changed = 0;
570 		entry = (struct g_part_ebr_entry *)iter;
571 		if (iter == baseentry) {
572 			if (set && (entry->ent.dp_flag & 0x80) == 0) {
573 				entry->ent.dp_flag |= 0x80;
574 				changed = 1;
575 			} else if (!set && (entry->ent.dp_flag & 0x80)) {
576 				entry->ent.dp_flag &= ~0x80;
577 				changed = 1;
578 			}
579 		} else {
580 			if (set && (entry->ent.dp_flag & 0x80)) {
581 				entry->ent.dp_flag &= ~0x80;
582 				changed = 1;
583 			}
584 		}
585 		if (changed && !iter->gpe_created)
586 			iter->gpe_modified = 1;
587 	}
588 	return (0);
589 }
590 
591 static const char *
592 g_part_ebr_type(struct g_part_table *basetable, struct g_part_entry *baseentry,
593     char *buf, size_t bufsz)
594 {
595 	struct g_part_ebr_entry *entry;
596 	int i;
597 
598 	entry = (struct g_part_ebr_entry *)baseentry;
599 	for (i = 0;
600 	    i < sizeof(ebr_alias_match) / sizeof(ebr_alias_match[0]); i++) {
601 		if (ebr_alias_match[i].typ == entry->ent.dp_typ)
602 			return (g_part_alias_name(ebr_alias_match[i].alias));
603 	}
604 	snprintf(buf, bufsz, "!%d", entry->ent.dp_typ);
605 	return (buf);
606 }
607 
608 static int
609 g_part_ebr_write(struct g_part_table *basetable, struct g_consumer *cp)
610 {
611 #ifndef GEOM_PART_EBR_COMPAT
612 	struct g_part_ebr_table *table;
613 #endif
614 	struct g_provider *pp;
615 	struct g_part_entry *baseentry, *next;
616 	struct g_part_ebr_entry *entry;
617 	u_char *buf;
618 	u_char *p;
619 	int error;
620 
621 	pp = cp->provider;
622 	buf = g_malloc(pp->sectorsize, M_WAITOK | M_ZERO);
623 #ifndef GEOM_PART_EBR_COMPAT
624 	table = (struct g_part_ebr_table *)basetable;
625 	bcopy(table->ebr, buf, DOSPARTOFF);
626 #endif
627 	le16enc(buf + DOSMAGICOFFSET, DOSMAGIC);
628 
629 	baseentry = LIST_FIRST(&basetable->gpt_entry);
630 	while (baseentry != NULL && baseentry->gpe_deleted)
631 		baseentry = LIST_NEXT(baseentry, gpe_entry);
632 
633 	/* Wipe-out the first EBR when there are no slices. */
634 	if (baseentry == NULL) {
635 		error = g_write_data(cp, 0, buf, pp->sectorsize);
636 		goto out;
637 	}
638 
639 	/*
640 	 * If the first partition is not in LBA 0, we need to
641 	 * put a "link" EBR in LBA 0.
642 	 */
643 	if (baseentry->gpe_start != 0) {
644 		ebr_entry_link(basetable, (uint32_t)baseentry->gpe_start,
645 		    (uint32_t)baseentry->gpe_end, buf + DOSPARTOFF);
646 		error = g_write_data(cp, 0, buf, pp->sectorsize);
647 		if (error)
648 			goto out;
649 	}
650 
651 	do {
652 		entry = (struct g_part_ebr_entry *)baseentry;
653 
654 		p = buf + DOSPARTOFF;
655 		p[0] = entry->ent.dp_flag;
656 		p[1] = entry->ent.dp_shd;
657 		p[2] = entry->ent.dp_ssect;
658 		p[3] = entry->ent.dp_scyl;
659 		p[4] = entry->ent.dp_typ;
660 		p[5] = entry->ent.dp_ehd;
661 		p[6] = entry->ent.dp_esect;
662 		p[7] = entry->ent.dp_ecyl;
663 		le32enc(p + 8, entry->ent.dp_start);
664 		le32enc(p + 12, entry->ent.dp_size);
665 
666 		next = LIST_NEXT(baseentry, gpe_entry);
667 		while (next != NULL && next->gpe_deleted)
668 			next = LIST_NEXT(next, gpe_entry);
669 
670 		p += DOSPARTSIZE;
671 		if (next != NULL)
672 			ebr_entry_link(basetable, (uint32_t)next->gpe_start,
673 			    (uint32_t)next->gpe_end, p);
674 		else
675 			bzero(p, DOSPARTSIZE);
676 
677 		error = g_write_data(cp, baseentry->gpe_start * pp->sectorsize,
678 		    buf, pp->sectorsize);
679 #ifndef GEOM_PART_EBR_COMPAT
680 		if (baseentry->gpe_start == 0)
681 			bzero(buf, DOSPARTOFF);
682 #endif
683 		baseentry = next;
684 	} while (!error && baseentry != NULL);
685 
686  out:
687 	g_free(buf);
688 	return (error);
689 }
690