1 files changed, 626 insertions, 0 deletions

diff --git a/sys/geom/part/g_part_mbr.c b/sys/geom/part/g_part_mbr.c
new file mode 100644
index 000000000000..7d44b9e03c8d
--- /dev/null
+++ b/sys/geom/part/g_part_mbr.c
@@ -0,0 +1,626 @@
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 2007, 2008 Marcel Moolenaar
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <sys/param.h>
+#include <sys/bio.h>
+#include <sys/diskmbr.h>
+#include <sys/endian.h>
+#include <sys/kernel.h>
+#include <sys/kobj.h>
+#include <sys/limits.h>
+#include <sys/lock.h>
+#include <sys/malloc.h>
+#include <sys/mutex.h>
+#include <sys/queue.h>
+#include <sys/sbuf.h>
+#include <sys/systm.h>
+#include <sys/sysctl.h>
+#include <geom/geom.h>
+#include <geom/geom_int.h>
+#include <geom/part/g_part.h>
+
+#include "g_part_if.h"
+
+FEATURE(geom_part_mbr, "GEOM partitioning class for MBR support");
+
+SYSCTL_DECL(_kern_geom_part);
+static SYSCTL_NODE(_kern_geom_part, OID_AUTO, mbr,
+    CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
+    "GEOM_PART_MBR Master Boot Record");
+
+static u_int enforce_chs = 0;
+SYSCTL_UINT(_kern_geom_part_mbr, OID_AUTO, enforce_chs,
+    CTLFLAG_RWTUN, &enforce_chs, 0, "Enforce alignment to CHS addressing");
+
+#define	MBRSIZE		512
+
+struct g_part_mbr_table {
+	struct g_part_table	base;
+	u_char		mbr[MBRSIZE];
+};
+
+struct g_part_mbr_entry {
+	struct g_part_entry	base;
+	struct dos_partition ent;
+};
+
+static int g_part_mbr_add(struct g_part_table *, struct g_part_entry *,
+    struct g_part_parms *);
+static int g_part_mbr_bootcode(struct g_part_table *, struct g_part_parms *);
+static int g_part_mbr_create(struct g_part_table *, struct g_part_parms *);
+static int g_part_mbr_destroy(struct g_part_table *, struct g_part_parms *);
+static void g_part_mbr_dumpconf(struct g_part_table *, struct g_part_entry *,
+    struct sbuf *, const char *);
+static int g_part_mbr_dumpto(struct g_part_table *, struct g_part_entry *);
+static int g_part_mbr_modify(struct g_part_table *, struct g_part_entry *,
+    struct g_part_parms *);
+static const char *g_part_mbr_name(struct g_part_table *, struct g_part_entry *,
+    char *, size_t);
+static int g_part_mbr_probe(struct g_part_table *, struct g_consumer *);
+static int g_part_mbr_read(struct g_part_table *, struct g_consumer *);
+static int g_part_mbr_setunset(struct g_part_table *, struct g_part_entry *,
+    const char *, unsigned int);
+static const char *g_part_mbr_type(struct g_part_table *, struct g_part_entry *,
+    char *, size_t);
+static int g_part_mbr_write(struct g_part_table *, struct g_consumer *);
+static int g_part_mbr_resize(struct g_part_table *, struct g_part_entry *,
+    struct g_part_parms *);
+
+static kobj_method_t g_part_mbr_methods[] = {
+	KOBJMETHOD(g_part_add,		g_part_mbr_add),
+	KOBJMETHOD(g_part_bootcode,	g_part_mbr_bootcode),
+	KOBJMETHOD(g_part_create,	g_part_mbr_create),
+	KOBJMETHOD(g_part_destroy,	g_part_mbr_destroy),
+	KOBJMETHOD(g_part_dumpconf,	g_part_mbr_dumpconf),
+	KOBJMETHOD(g_part_dumpto,	g_part_mbr_dumpto),
+	KOBJMETHOD(g_part_modify,	g_part_mbr_modify),
+	KOBJMETHOD(g_part_resize,	g_part_mbr_resize),
+	KOBJMETHOD(g_part_name,		g_part_mbr_name),
+	KOBJMETHOD(g_part_probe,	g_part_mbr_probe),
+	KOBJMETHOD(g_part_read,		g_part_mbr_read),
+	KOBJMETHOD(g_part_setunset,	g_part_mbr_setunset),
+	KOBJMETHOD(g_part_type,		g_part_mbr_type),
+	KOBJMETHOD(g_part_write,	g_part_mbr_write),
+	{ 0, 0 }
+};
+
+static struct g_part_scheme g_part_mbr_scheme = {
+	"MBR",
+	g_part_mbr_methods,
+	sizeof(struct g_part_mbr_table),
+	.gps_entrysz = sizeof(struct g_part_mbr_entry),
+	.gps_minent = NDOSPART,
+	.gps_defent = NDOSPART,
+	.gps_maxent = NDOSPART,
+	.gps_bootcodesz = MBRSIZE,
+};
+G_PART_SCHEME_DECLARE(g_part_mbr);
+MODULE_VERSION(geom_part_mbr, 0);
+
+static struct g_part_mbr_alias {
+	u_char		typ;
+	int		alias;
+} mbr_alias_match[] = {
+	{ DOSPTYP_386BSD,	G_PART_ALIAS_FREEBSD },
+	{ DOSPTYP_APPLE_BOOT,	G_PART_ALIAS_APPLE_BOOT },
+	{ DOSPTYP_APPLE_UFS,	G_PART_ALIAS_APPLE_UFS },
+	{ DOSPTYP_EFI,		G_PART_ALIAS_EFI },
+	{ DOSPTYP_EXT,		G_PART_ALIAS_EBR },
+	{ DOSPTYP_EXTLBA,	G_PART_ALIAS_EBR },
+	{ DOSPTYP_FAT16,	G_PART_ALIAS_MS_FAT16 },
+	{ DOSPTYP_FAT32,	G_PART_ALIAS_MS_FAT32 },
+	{ DOSPTYP_FAT32LBA,	G_PART_ALIAS_MS_FAT32LBA },
+	{ DOSPTYP_HFS,		G_PART_ALIAS_APPLE_HFS },
+	{ DOSPTYP_LDM,		G_PART_ALIAS_MS_LDM_DATA },
+	{ DOSPTYP_LINLVM,	G_PART_ALIAS_LINUX_LVM },
+	{ DOSPTYP_LINRAID,	G_PART_ALIAS_LINUX_RAID },
+	{ DOSPTYP_LINSWP,	G_PART_ALIAS_LINUX_SWAP },
+	{ DOSPTYP_LINUX,	G_PART_ALIAS_LINUX_DATA },
+	{ DOSPTYP_NTFS,		G_PART_ALIAS_MS_NTFS },
+	{ DOSPTYP_PPCBOOT,	G_PART_ALIAS_PREP_BOOT },
+	{ DOSPTYP_VMFS,		G_PART_ALIAS_VMFS },
+	{ DOSPTYP_VMKDIAG,	G_PART_ALIAS_VMKDIAG },
+};
+
+static int
+mbr_parse_type(const char *type, u_char *dp_typ)
+{
+	const char *alias;
+	char *endp;
+	long lt;
+	int i;
+
+	if (type[0] == '!') {
+		lt = strtol(type + 1, &endp, 0);
+		if (type[1] == '\0' || *endp != '\0' || lt <= 0 || lt >= 256)
+			return (EINVAL);
+		*dp_typ = (u_char)lt;
+		return (0);
+	}
+	for (i = 0; i < nitems(mbr_alias_match); i++) {
+		alias = g_part_alias_name(mbr_alias_match[i].alias);
+		if (strcasecmp(type, alias) == 0) {
+			*dp_typ = mbr_alias_match[i].typ;
+			return (0);
+		}
+	}
+	return (EINVAL);
+}
+
+static int
+mbr_probe_bpb(u_char *bpb)
+{
+	uint16_t secsz;
+	uint8_t clstsz;
+
+#define PO2(x)	((x & (x - 1)) == 0)
+	secsz = le16dec(bpb);
+	if (secsz < 512 || secsz > 4096 || !PO2(secsz))
+		return (0);
+	clstsz = bpb[2];
+	if (clstsz < 1 || clstsz > 128 || !PO2(clstsz))
+		return (0);
+#undef PO2
+
+	return (1);
+}
+
+static void
+mbr_set_chs(struct g_part_table *table, uint32_t lba, u_char *cylp, u_char *hdp,
+    u_char *secp)
+{
+	uint32_t cyl, hd, sec;
+
+	sec = lba % table->gpt_sectors + 1;
+	lba /= table->gpt_sectors;
+	hd = lba % table->gpt_heads;
+	lba /= table->gpt_heads;
+	cyl = lba;
+	if (cyl > 1023)
+		sec = hd = cyl = ~0;
+
+	*cylp = cyl & 0xff;
+	*hdp = hd & 0xff;
+	*secp = (sec & 0x3f) | ((cyl >> 2) & 0xc0);
+}
+
+static int
+mbr_align(struct g_part_table *basetable, uint32_t *start, uint32_t *size)
+{
+	uint32_t sectors;
+
+	if (enforce_chs == 0)
+		return (0);
+	sectors = basetable->gpt_sectors;
+	if (*size < sectors)
+		return (EINVAL);
+	if (start != NULL && (*start % sectors)) {
+		*size += (*start % sectors) - sectors;
+		*start -= (*start % sectors) - sectors;
+	}
+	if (*size % sectors)
+		*size -= (*size % sectors);
+	if (*size < sectors)
+		return (EINVAL);
+	return (0);
+}
+
+static int
+g_part_mbr_add(struct g_part_table *basetable, struct g_part_entry *baseentry,
+    struct g_part_parms *gpp)
+{
+	struct g_part_mbr_entry *entry;
+	uint32_t start, size;
+
+	if (gpp->gpp_parms & G_PART_PARM_LABEL)
+		return (EINVAL);
+
+	entry = (struct g_part_mbr_entry *)baseentry;
+	start = gpp->gpp_start;
+	size = gpp->gpp_size;
+	if (mbr_align(basetable, &start, &size) != 0)
+		return (EINVAL);
+	if (baseentry->gpe_deleted)
+		bzero(&entry->ent, sizeof(entry->ent));
+
+	KASSERT(baseentry->gpe_start <= start, ("%s", __func__));
+	KASSERT(baseentry->gpe_end >= start + size - 1, ("%s", __func__));
+	baseentry->gpe_start = start;
+	baseentry->gpe_end = start + size - 1;
+	entry->ent.dp_start = start;
+	entry->ent.dp_size = size;
+	mbr_set_chs(basetable, baseentry->gpe_start, &entry->ent.dp_scyl,
+	    &entry->ent.dp_shd, &entry->ent.dp_ssect);
+	mbr_set_chs(basetable, baseentry->gpe_end, &entry->ent.dp_ecyl,
+	    &entry->ent.dp_ehd, &entry->ent.dp_esect);
+	return (mbr_parse_type(gpp->gpp_type, &entry->ent.dp_typ));
+}
+
+static int
+g_part_mbr_bootcode(struct g_part_table *basetable, struct g_part_parms *gpp)
+{
+	struct g_part_mbr_table *table;
+	uint32_t dsn;
+
+	if (gpp->gpp_codesize != MBRSIZE)
+		return (ENODEV);
+
+	table = (struct g_part_mbr_table *)basetable;
+	dsn = *(uint32_t *)(table->mbr + DOSDSNOFF);
+	bcopy(gpp->gpp_codeptr, table->mbr, DOSPARTOFF);
+	if (dsn != 0 && !gpp->gpp_skip_dsn)
+		*(uint32_t *)(table->mbr + DOSDSNOFF) = dsn;
+	return (0);
+}
+
+static int
+g_part_mbr_create(struct g_part_table *basetable, struct g_part_parms *gpp)
+{
+	struct g_provider *pp;
+	struct g_part_mbr_table *table;
+
+	pp = gpp->gpp_provider;
+	if (pp->sectorsize < MBRSIZE)
+		return (ENOSPC);
+
+	basetable->gpt_first = basetable->gpt_sectors;
+	basetable->gpt_last = MIN(pp->mediasize / pp->sectorsize,
+	    UINT32_MAX) - 1;
+
+	table = (struct g_part_mbr_table *)basetable;
+	le16enc(table->mbr + DOSMAGICOFFSET, DOSMAGIC);
+	return (0);
+}
+
+static int
+g_part_mbr_destroy(struct g_part_table *basetable, struct g_part_parms *gpp)
+{
+
+	/* Wipe the first sector to clear the partitioning. */
+	basetable->gpt_smhead |= 1;
+	return (0);
+}
+
+static void
+g_part_mbr_efimedia(struct g_part_mbr_table *table, struct g_part_mbr_entry *entry,
+    struct sbuf *sb)
+{
+	uint32_t dsn;
+
+	dsn = le32dec(table->mbr + DOSDSNOFF);
+	sbuf_printf(sb, "HD(%d,MBR,%#08x,%#jx,%#jx)",
+	    entry->base.gpe_index, dsn, (intmax_t)entry->base.gpe_start,
+	    (intmax_t)(entry->base.gpe_end - entry->base.gpe_start + 1));
+}
+
+static void
+g_part_mbr_dumpconf(struct g_part_table *basetable, struct g_part_entry *baseentry,
+    struct sbuf *sb, const char *indent)
+{
+	struct g_part_mbr_entry *entry;
+	struct g_part_mbr_table *table;
+
+	table = (struct g_part_mbr_table *)basetable;
+	entry = (struct g_part_mbr_entry *)baseentry;
+	if (indent == NULL) {
+		/* conftxt: libdisk compatibility */
+		sbuf_printf(sb, " xs MBR xt %u", entry->ent.dp_typ);
+	} else if (entry != NULL) {
+		/* confxml: partition entry information */
+		sbuf_printf(sb, "%s<rawtype>%u</rawtype>\n", indent,
+		    entry->ent.dp_typ);
+		if (entry->ent.dp_flag & 0x80)
+			sbuf_printf(sb, "%s<attrib>active</attrib>\n", indent);
+		sbuf_printf(sb, "%s<efimedia>", indent);
+		g_part_mbr_efimedia(table, entry, sb);
+		sbuf_cat(sb, "</efimedia>\n");
+	} else {
+		/* confxml: scheme information */
+	}
+}
+
+static int
+g_part_mbr_dumpto(struct g_part_table *table, struct g_part_entry *baseentry)
+{
+	struct g_part_mbr_entry *entry;
+
+	/* Allow dumping to a FreeBSD partition or Linux swap partition only. */
+	entry = (struct g_part_mbr_entry *)baseentry;
+	return ((entry->ent.dp_typ == DOSPTYP_386BSD ||
+	    entry->ent.dp_typ == DOSPTYP_LINSWP) ? 1 : 0);
+}
+
+static int
+g_part_mbr_modify(struct g_part_table *basetable,
+    struct g_part_entry *baseentry, struct g_part_parms *gpp)
+{
+	struct g_part_mbr_entry *entry;
+
+	if (gpp->gpp_parms & G_PART_PARM_LABEL)
+		return (EINVAL);
+
+	entry = (struct g_part_mbr_entry *)baseentry;
+	if (gpp->gpp_parms & G_PART_PARM_TYPE)
+		return (mbr_parse_type(gpp->gpp_type, &entry->ent.dp_typ));
+	return (0);
+}
+
+static int
+g_part_mbr_resize(struct g_part_table *basetable,
+    struct g_part_entry *baseentry, struct g_part_parms *gpp)
+{
+	struct g_part_mbr_entry *entry;
+	struct g_provider *pp;
+	uint32_t size;
+
+	if (baseentry == NULL) {
+		pp = LIST_FIRST(&basetable->gpt_gp->consumer)->provider;
+		basetable->gpt_last = MIN(pp->mediasize / pp->sectorsize,
+		    UINT32_MAX) - 1;
+		return (0);
+	}
+	size = gpp->gpp_size;
+	if (mbr_align(basetable, NULL, &size) != 0)
+		return (EINVAL);
+	/* XXX: prevent unexpected shrinking. */
+	pp = baseentry->gpe_pp;
+	if ((g_debugflags & G_F_FOOTSHOOTING) == 0 && size < gpp->gpp_size &&
+	    pp->mediasize / pp->sectorsize > size)
+		return (EBUSY);
+	entry = (struct g_part_mbr_entry *)baseentry;
+	baseentry->gpe_end = baseentry->gpe_start + size - 1;
+	entry->ent.dp_size = size;
+	mbr_set_chs(basetable, baseentry->gpe_end, &entry->ent.dp_ecyl,
+	    &entry->ent.dp_ehd, &entry->ent.dp_esect);
+	return (0);
+}
+
+static const char *
+g_part_mbr_name(struct g_part_table *table, struct g_part_entry *baseentry,
+    char *buf, size_t bufsz)
+{
+
+	snprintf(buf, bufsz, "s%d", baseentry->gpe_index);
+	return (buf);
+}
+
+static int
+g_part_mbr_probe(struct g_part_table *table, struct g_consumer *cp)
+{
+	char psn[8];
+	struct g_provider *pp;
+	u_char *buf, *p;
+	int error, index, res, sum;
+	uint16_t magic;
+
+	pp = cp->provider;
+
+	/* Sanity-check the provider. */
+	if (pp->sectorsize < MBRSIZE || pp->mediasize < pp->sectorsize)
+		return (ENOSPC);
+	if (pp->sectorsize > 4096)
+		return (ENXIO);
+
+	/* We don't nest under an MBR (see EBR instead). */
+	error = g_getattr("PART::scheme", cp, &psn);
+	if (error == 0 && strcmp(psn, g_part_mbr_scheme.name) == 0)
+		return (ELOOP);
+
+	/* Check that there's a MBR. */
+	buf = g_read_data(cp, 0L, pp->sectorsize, &error);
+	if (buf == NULL)
+		return (error);
+
+	/* We goto out on mismatch. */
+	res = ENXIO;
+
+	magic = le16dec(buf + DOSMAGICOFFSET);
+	if (magic != DOSMAGIC)
+		goto out;
+
+	for (index = 0; index < NDOSPART; index++) {
+		p = buf + DOSPARTOFF + index * DOSPARTSIZE;
+		if (p[0] != 0 && p[0] != 0x80)
+			goto out;
+	}
+
+	/*
+	 * If the partition table does not consist of all zeroes,
+	 * assume we have a MBR. If it's all zeroes, we could have
+	 * a boot sector. For example, a boot sector that doesn't
+	 * have boot code -- common on non-i386 hardware. In that
+	 * case we check if we have a possible BPB. If so, then we
+	 * assume we have a boot sector instead.
+	 */
+	sum = 0;
+	for (index = 0; index < NDOSPART * DOSPARTSIZE; index++)
+		sum += buf[DOSPARTOFF + index];
+	if (sum != 0 || !mbr_probe_bpb(buf + 0x0b))
+		res = G_PART_PROBE_PRI_NORM;
+
+ out:
+	g_free(buf);
+	return (res);
+}
+
+static int
+g_part_mbr_read(struct g_part_table *basetable, struct g_consumer *cp)
+{
+	struct dos_partition ent;
+	struct g_provider *pp;
+	struct g_part_mbr_table *table;
+	struct g_part_mbr_entry *entry;
+	u_char *buf, *p;
+	off_t chs, msize, first;
+	u_int sectors, heads;
+	int error, index;
+
+	pp = cp->provider;
+	table = (struct g_part_mbr_table *)basetable;
+	first = basetable->gpt_sectors;
+	msize = MIN(pp->mediasize / pp->sectorsize, UINT32_MAX);
+
+	buf = g_read_data(cp, 0L, pp->sectorsize, &error);
+	if (buf == NULL)
+		return (error);
+
+	bcopy(buf, table->mbr, sizeof(table->mbr));
+	for (index = NDOSPART - 1; index >= 0; index--) {
+		p = buf + DOSPARTOFF + index * DOSPARTSIZE;
+		ent.dp_flag = p[0];
+		ent.dp_shd = p[1];
+		ent.dp_ssect = p[2];
+		ent.dp_scyl = p[3];
+		ent.dp_typ = p[4];
+		ent.dp_ehd = p[5];
+		ent.dp_esect = p[6];
+		ent.dp_ecyl = p[7];
+		ent.dp_start = le32dec(p + 8);
+		ent.dp_size = le32dec(p + 12);
+		if (ent.dp_typ == 0 || ent.dp_typ == DOSPTYP_PMBR)
+			continue;
+		if (ent.dp_start == 0 || ent.dp_size == 0)
+			continue;
+		sectors = ent.dp_esect & 0x3f;
+		if (sectors > basetable->gpt_sectors &&
+		    !basetable->gpt_fixgeom) {
+			g_part_geometry_heads(msize, sectors, &chs, &heads);
+			if (chs != 0) {
+				basetable->gpt_sectors = sectors;
+				basetable->gpt_heads = heads;
+			}
+		}
+		if (ent.dp_start < first)
+			first = ent.dp_start;
+		entry = (struct g_part_mbr_entry *)g_part_new_entry(basetable,
+		    index + 1, ent.dp_start, ent.dp_start + ent.dp_size - 1);
+		entry->ent = ent;
+	}
+
+	basetable->gpt_entries = NDOSPART;
+	basetable->gpt_first = basetable->gpt_sectors;
+	basetable->gpt_last = msize - 1;
+
+	if (first < basetable->gpt_first)
+		basetable->gpt_first = 1;
+
+	g_free(buf);
+	return (0);
+}
+
+static int
+g_part_mbr_setunset(struct g_part_table *table, struct g_part_entry *baseentry,
+    const char *attrib, unsigned int set)
+{
+	struct g_part_entry *iter;
+	struct g_part_mbr_entry *entry;
+	int changed;
+
+	if (baseentry == NULL)
+		return (ENODEV);
+	if (strcasecmp(attrib, "active") != 0)
+		return (EINVAL);
+
+	/* Only one entry can have the active attribute. */
+	LIST_FOREACH(iter, &table->gpt_entry, gpe_entry) {
+		if (iter->gpe_deleted)
+			continue;
+		changed = 0;
+		entry = (struct g_part_mbr_entry *)iter;
+		if (iter == baseentry) {
+			if (set && (entry->ent.dp_flag & 0x80) == 0) {
+				entry->ent.dp_flag |= 0x80;
+				changed = 1;
+			} else if (!set && (entry->ent.dp_flag & 0x80)) {
+				entry->ent.dp_flag &= ~0x80;
+				changed = 1;
+			}
+		} else {
+			if (set && (entry->ent.dp_flag & 0x80)) {
+				entry->ent.dp_flag &= ~0x80;
+				changed = 1;
+			}
+		}
+		if (changed && !iter->gpe_created)
+			iter->gpe_modified = 1;
+	}
+	return (0);
+}
+
+static const char *
+g_part_mbr_type(struct g_part_table *basetable, struct g_part_entry *baseentry,
+    char *buf, size_t bufsz)
+{
+	struct g_part_mbr_entry *entry;
+	int i;
+
+	entry = (struct g_part_mbr_entry *)baseentry;
+	for (i = 0; i < nitems(mbr_alias_match); i++) {
+		if (mbr_alias_match[i].typ == entry->ent.dp_typ)
+			return (g_part_alias_name(mbr_alias_match[i].alias));
+	}
+	snprintf(buf, bufsz, "!%d", entry->ent.dp_typ);
+	return (buf);
+}
+
+static int
+g_part_mbr_write(struct g_part_table *basetable, struct g_consumer *cp)
+{
+	struct g_part_entry *baseentry;
+	struct g_part_mbr_entry *entry;
+	struct g_part_mbr_table *table;
+	u_char *p;
+	int error, index;
+
+	table = (struct g_part_mbr_table *)basetable;
+	baseentry = LIST_FIRST(&basetable->gpt_entry);
+	for (index = 1; index <= basetable->gpt_entries; index++) {
+		p = table->mbr + DOSPARTOFF + (index - 1) * DOSPARTSIZE;
+		entry = (baseentry != NULL && index == baseentry->gpe_index)
+		    ? (struct g_part_mbr_entry *)baseentry : NULL;
+		if (entry != NULL && !baseentry->gpe_deleted) {
+			p[0] = entry->ent.dp_flag;
+			p[1] = entry->ent.dp_shd;
+			p[2] = entry->ent.dp_ssect;
+			p[3] = entry->ent.dp_scyl;
+			p[4] = entry->ent.dp_typ;
+			p[5] = entry->ent.dp_ehd;
+			p[6] = entry->ent.dp_esect;
+			p[7] = entry->ent.dp_ecyl;
+			le32enc(p + 8, entry->ent.dp_start);
+			le32enc(p + 12, entry->ent.dp_size);
+		} else
+			bzero(p, DOSPARTSIZE);
+
+		if (entry != NULL)
+			baseentry = LIST_NEXT(baseentry, gpe_entry);
+	}
+
+	error = g_write_data(cp, 0, table->mbr, cp->provider->sectorsize);
+	return (error);
+}