/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2007-2009 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 "opt_geom.h"

#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/part/g_part.h>

#include "g_part_if.h"

FEATURE(geom_part_ebr,
    "GEOM partitioning class for extended boot records support");
FEATURE(geom_part_ebr_compat,
    "GEOM EBR partitioning class: backward-compatible partition names");

SYSCTL_DECL(_kern_geom_part);
static SYSCTL_NODE(_kern_geom_part, OID_AUTO, ebr, CTLFLAG_RW | CTLFLAG_MPSAFE,
    0, "GEOM_PART_EBR Extended Boot Record");

#define EBRNAMFMT       "+%08u"
#define EBRSIZE         512

struct g_part_ebr_table {
        struct g_part_table     base;
        u_char                  lba0_ebr[EBRSIZE];
};

struct g_part_ebr_entry {
        struct g_part_entry     base;
        struct dos_partition    ent;
        u_char                  ebr[EBRSIZE];
        u_int                   ebr_compat_idx;
};

static int g_part_ebr_add(struct g_part_table *, struct g_part_entry *,
    struct g_part_parms *);
static void g_part_ebr_add_alias(struct g_part_table *, struct g_provider *,
    struct g_part_entry *, const char *);
static int g_part_ebr_create(struct g_part_table *, struct g_part_parms *);
static int g_part_ebr_destroy(struct g_part_table *, struct g_part_parms *);
static void g_part_ebr_dumpconf(struct g_part_table *, struct g_part_entry *,
    struct sbuf *, const char *);
static int g_part_ebr_dumpto(struct g_part_table *, struct g_part_entry *);
static int g_part_ebr_modify(struct g_part_table *, struct g_part_entry *,
    struct g_part_parms *);
static const char *g_part_ebr_name(struct g_part_table *, struct g_part_entry *,
    char *, size_t);
static struct g_provider *g_part_ebr_new_provider(struct g_part_table *,
    struct g_geom *, struct g_part_entry *, const char *);
static int g_part_ebr_precheck(struct g_part_table *, enum g_part_ctl,
    struct g_part_parms *);
static int g_part_ebr_probe(struct g_part_table *, struct g_consumer *);
static int g_part_ebr_read(struct g_part_table *, struct g_consumer *);
static int g_part_ebr_setunset(struct g_part_table *, struct g_part_entry *,
    const char *, unsigned int);
static const char *g_part_ebr_type(struct g_part_table *, struct g_part_entry *,
    char *, size_t);
static int g_part_ebr_write(struct g_part_table *, struct g_consumer *);
static int g_part_ebr_resize(struct g_part_table *, struct g_part_entry *,
    struct g_part_parms *);

static kobj_method_t g_part_ebr_methods[] = {
        KOBJMETHOD(g_part_add,          g_part_ebr_add),
        KOBJMETHOD(g_part_add_alias,    g_part_ebr_add_alias),
        KOBJMETHOD(g_part_create,       g_part_ebr_create),
        KOBJMETHOD(g_part_destroy,      g_part_ebr_destroy),
        KOBJMETHOD(g_part_dumpconf,     g_part_ebr_dumpconf),
        KOBJMETHOD(g_part_dumpto,       g_part_ebr_dumpto),
        KOBJMETHOD(g_part_modify,       g_part_ebr_modify),
        KOBJMETHOD(g_part_name,         g_part_ebr_name),
        KOBJMETHOD(g_part_new_provider, g_part_ebr_new_provider),
        KOBJMETHOD(g_part_precheck,     g_part_ebr_precheck),
        KOBJMETHOD(g_part_probe,        g_part_ebr_probe),
        KOBJMETHOD(g_part_read,         g_part_ebr_read),
        KOBJMETHOD(g_part_resize,       g_part_ebr_resize),
        KOBJMETHOD(g_part_setunset,     g_part_ebr_setunset),
        KOBJMETHOD(g_part_type,         g_part_ebr_type),
        KOBJMETHOD(g_part_write,        g_part_ebr_write),
        { 0, 0 }
};

static struct g_part_scheme g_part_ebr_scheme = {
        "EBR",
        g_part_ebr_methods,
        sizeof(struct g_part_ebr_table),
        .gps_entrysz = sizeof(struct g_part_ebr_entry),
        .gps_minent = 1,
        .gps_defent = 1,
        .gps_maxent = INT_MAX,
};
G_PART_SCHEME_DECLARE(g_part_ebr);
MODULE_VERSION(geom_part_ebr, 0);

static struct g_part_ebr_alias {
        u_char          typ;
        int             alias;
} ebr_alias_match[] = {
        { DOSPTYP_386BSD,       G_PART_ALIAS_FREEBSD },
        { DOSPTYP_EFI,          G_PART_ALIAS_EFI },
        { DOSPTYP_FAT32,        G_PART_ALIAS_MS_FAT32 },
        { DOSPTYP_FAT32LBA,     G_PART_ALIAS_MS_FAT32LBA },
        { 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 },
};

static void ebr_set_chs(struct g_part_table *, uint32_t, u_char *, u_char *,
    u_char *);

static void
ebr_entry_decode(const char *p, struct dos_partition *ent)
{
        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);
}

static void
ebr_entry_link(struct g_part_table *table, uint32_t start, uint32_t end,
   u_char *buf)
{

        buf[0] = 0 /* dp_flag */;
        ebr_set_chs(table, start, &buf[3] /* dp_scyl */, &buf[1] /* dp_shd */,
            &buf[2] /* dp_ssect */);
        buf[4] = DOSPTYP_EXT /* dp_typ */;
        ebr_set_chs(table, end, &buf[7] /* dp_ecyl */, &buf[5] /* dp_ehd */,
            &buf[6] /* dp_esect */);
        le32enc(buf + 8, start);
        le32enc(buf + 12, end - start + 1);
}

static int
ebr_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(ebr_alias_match); i++) {
                alias = g_part_alias_name(ebr_alias_match[i].alias);
                if (strcasecmp(type, alias) == 0) {
                        *dp_typ = ebr_alias_match[i].typ;
                        return (0);
                }
        }
        return (EINVAL);
}

static void
ebr_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
ebr_align(struct g_part_table *basetable, uint32_t *start, uint32_t *size)
{
        uint32_t sectors;

        sectors = basetable->gpt_sectors;
        if (*size < 2 * sectors)
                return (EINVAL);
        if (*start % sectors) {
                *size += (*start % sectors) - sectors;
                *start -= (*start % sectors) - sectors;
        }
        if (*size % sectors)
                *size -= (*size % sectors);
        if (*size < 2 * sectors)
                return (EINVAL);
        return (0);
}

static int
g_part_ebr_add(struct g_part_table *basetable, struct g_part_entry *baseentry,
    struct g_part_parms *gpp)
{
        struct g_provider *pp;
        struct g_part_ebr_entry *entry;
        struct g_part_entry *iter;
        uint32_t start, size;
        u_int idx;

        if (gpp->gpp_parms & G_PART_PARM_LABEL)
                return (EINVAL);

        pp = LIST_FIRST(&basetable->gpt_gp->consumer)->provider;
        entry = (struct g_part_ebr_entry *)baseentry;
        start = gpp->gpp_start;
        size = gpp->gpp_size;
        if (ebr_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_index = (start / basetable->gpt_sectors) + 1;
        baseentry->gpe_offset =
            (off_t)(start + basetable->gpt_sectors) * pp->sectorsize;
        baseentry->gpe_start = start;
        baseentry->gpe_end = start + size - 1;
        entry->ent.dp_start = basetable->gpt_sectors;
        entry->ent.dp_size = size - basetable->gpt_sectors;
        ebr_set_chs(basetable, entry->ent.dp_start, &entry->ent.dp_scyl,
            &entry->ent.dp_shd, &entry->ent.dp_ssect);
        ebr_set_chs(basetable, baseentry->gpe_end, &entry->ent.dp_ecyl,
            &entry->ent.dp_ehd, &entry->ent.dp_esect);

        idx = 5;
        LIST_FOREACH(iter, &basetable->gpt_entry, gpe_entry)
                idx++;
        entry->ebr_compat_idx = idx;
        return (ebr_parse_type(gpp->gpp_type, &entry->ent.dp_typ));
}

static void
g_part_ebr_add_alias(struct g_part_table *table, struct g_provider *pp,
    struct g_part_entry *baseentry, const char *pfx)
{
        struct g_part_ebr_entry *entry;

        g_provider_add_alias(pp, "%s%s" EBRNAMFMT, pfx, g_part_separator,
            baseentry->gpe_index);
        entry = (struct g_part_ebr_entry *)baseentry;
        g_provider_add_alias(pp, "%.*s%u", (int)strlen(pfx) - 1, pfx,
            entry->ebr_compat_idx);
}

static struct g_provider *
g_part_ebr_new_provider(struct g_part_table *table, struct g_geom *gp,
    struct g_part_entry *baseentry, const char *pfx)
{
        struct g_part_ebr_entry *entry;
        struct g_provider *pp;

        pp = g_new_providerf(gp, "%s%s" EBRNAMFMT, pfx, g_part_separator,
            baseentry->gpe_index);
        entry = (struct g_part_ebr_entry *)baseentry;
        g_provider_add_alias(pp, "%.*s%u", (int)strlen(pfx) - 1, pfx,
            entry->ebr_compat_idx);
        return (pp);
}

static int
g_part_ebr_create(struct g_part_table *basetable, struct g_part_parms *gpp)
{
        char type[64];
        struct g_consumer *cp;
        struct g_provider *pp;
        uint32_t msize;
        int error;

        pp = gpp->gpp_provider;

        if (pp->sectorsize < EBRSIZE)
                return (ENOSPC);
        if (pp->sectorsize > 4096)
                return (ENXIO);

        /* Check that we have a parent and that it's a MBR. */
        if (basetable->gpt_depth == 0)
                return (ENXIO);
        cp = LIST_FIRST(&pp->consumers);
        error = g_getattr("PART::scheme", cp, &type);
        if (error != 0)
                return (error);
        if (strcmp(type, "MBR") != 0)
                return (ENXIO);
        error = g_getattr("PART::type", cp, &type);
        if (error != 0)
                return (error);
        if (strcmp(type, "ebr") != 0)
                return (ENXIO);

        msize = MIN(pp->mediasize / pp->sectorsize, UINT32_MAX);
        basetable->gpt_first = 0;
        basetable->gpt_last = msize - 1;
        basetable->gpt_entries = msize / basetable->gpt_sectors;
        return (0);
}

static int
g_part_ebr_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_ebr_dumpconf(struct g_part_table *table, struct g_part_entry *baseentry,
    struct sbuf *sb, const char *indent)
{
        struct g_part_ebr_entry *entry;

        entry = (struct g_part_ebr_entry *)baseentry;
        if (indent == NULL) {
                /* conftxt: libdisk compatibility */
                sbuf_printf(sb, " xs MBREXT 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);
        } else {
                /* confxml: scheme information */
        }
}

static int
g_part_ebr_dumpto(struct g_part_table *table, struct g_part_entry *baseentry)
{
        struct g_part_ebr_entry *entry;

        /* Allow dumping to a FreeBSD partition or Linux swap partition only. */
        entry = (struct g_part_ebr_entry *)baseentry;
        return ((entry->ent.dp_typ == DOSPTYP_386BSD ||
            entry->ent.dp_typ == DOSPTYP_LINSWP) ? 1 : 0);
}

static int
g_part_ebr_modify(struct g_part_table *basetable,
    struct g_part_entry *baseentry, struct g_part_parms *gpp)
{
        struct g_part_ebr_entry *entry;

        if (gpp->gpp_parms & G_PART_PARM_LABEL)
                return (EINVAL);

        entry = (struct g_part_ebr_entry *)baseentry;
        if (gpp->gpp_parms & G_PART_PARM_TYPE)
                return (ebr_parse_type(gpp->gpp_type, &entry->ent.dp_typ));
        return (0);
}

static int
g_part_ebr_resize(struct g_part_table *basetable,
    struct g_part_entry *baseentry, struct g_part_parms *gpp)
{
        struct g_provider *pp;

        if (baseentry != NULL)
                return (EOPNOTSUPP);
        pp = LIST_FIRST(&basetable->gpt_gp->consumer)->provider;
        basetable->gpt_last = MIN(pp->mediasize / pp->sectorsize,
            UINT32_MAX) - 1;
        return (0);
}

static const char *
g_part_ebr_name(struct g_part_table *table, struct g_part_entry *entry,
    char *buf, size_t bufsz)
{
        snprintf(buf, bufsz, EBRNAMFMT, entry->gpe_index);
        return (buf);
}

static int
g_part_ebr_precheck(struct g_part_table *table, enum g_part_ctl req,
    struct g_part_parms *gpp)
{
        /*
         * The index is a function of the start of the partition.
         * This is not something the user can override, nor is it
         * something the common code will do right. We can set the
         * index now so that we get what we need.
         */
        if (req == G_PART_CTL_ADD)
                gpp->gpp_index = (gpp->gpp_start / table->gpt_sectors) + 1;
        return (0);
}

static int
g_part_ebr_probe(struct g_part_table *table, struct g_consumer *cp)
{
        char type[64];
        struct g_provider *pp;
        u_char *buf, *p;
        int error, index, res;
        uint16_t magic;

        pp = cp->provider;

        /* Sanity-check the provider. */
        if (pp->sectorsize < EBRSIZE || pp->mediasize < pp->sectorsize)
                return (ENOSPC);
        if (pp->sectorsize > 4096)
                return (ENXIO);

        /* Check that we have a parent and that it's a MBR. */
        if (table->gpt_depth == 0)
                return (ENXIO);
        error = g_getattr("PART::scheme", cp, &type);
        if (error != 0)
                return (error);
        if (strcmp(type, "MBR") != 0)
                return (ENXIO);
        /* Check that partition has type DOSPTYP_EBR. */
        error = g_getattr("PART::type", cp, &type);
        if (error != 0)
                return (error);
        if (strcmp(type, "ebr") != 0)
                return (ENXIO);

        /* Check that there's a EBR. */
        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 < 2; index++) {
                p = buf + DOSPARTOFF + index * DOSPARTSIZE;
                if (p[0] != 0 && p[0] != 0x80)
                        goto out;
        }
        res = G_PART_PROBE_PRI_NORM;

 out:
        g_free(buf);
        return (res);
}

static int
g_part_ebr_read(struct g_part_table *basetable, struct g_consumer *cp)
{
        struct dos_partition ent[2];
        struct g_provider *pp;
        struct g_part_entry *baseentry;
        struct g_part_ebr_table *table;
        struct g_part_ebr_entry *entry;
        u_char *buf;
        off_t ofs, msize;
        u_int lba, idx;
        int error, index;

        idx = 5;
        pp = cp->provider;
        table = (struct g_part_ebr_table *)basetable;
        msize = MIN(pp->mediasize / pp->sectorsize, UINT32_MAX);

        lba = 0;
        while (1) {
                ofs = (off_t)lba * pp->sectorsize;
                buf = g_read_data(cp, ofs, pp->sectorsize, &error);
                if (buf == NULL)
                        return (error);

                ebr_entry_decode(buf + DOSPARTOFF + 0 * DOSPARTSIZE, ent + 0);
                ebr_entry_decode(buf + DOSPARTOFF + 1 * DOSPARTSIZE, ent + 1);

                /* The 3rd & 4th entries should be zeroes. */
                if (le64dec(buf + DOSPARTOFF + 2 * DOSPARTSIZE) +
                    le64dec(buf + DOSPARTOFF + 3 * DOSPARTSIZE) != 0) {
                        basetable->gpt_corrupt = 1;
                        printf("GEOM: %s: invalid entries in the EBR ignored.\n",
                            pp->name);
                }
                /*
                 * Preserve EBR, it can contain boot code or other metadata we
                 * are ignorant of.
                 */
                if (lba == 0)
                        memcpy(table->lba0_ebr, buf, sizeof(table->lba0_ebr));

                if (ent[0].dp_typ == 0) {
                        g_free(buf);
                        break;
                }

                if (ent[0].dp_typ == 5 && ent[1].dp_typ == 0) {
                        lba = ent[0].dp_start;
                        g_free(buf);
                        continue;
                }

                index = (lba / basetable->gpt_sectors) + 1;
                baseentry = (struct g_part_entry *)g_part_new_entry(basetable,
                    index, lba, lba + ent[0].dp_start + ent[0].dp_size - 1);
                baseentry->gpe_offset = (off_t)(lba + ent[0].dp_start) *
                    pp->sectorsize;
                entry = (struct g_part_ebr_entry *)baseentry;
                entry->ent = ent[0];
                memcpy(entry->ebr, buf, sizeof(entry->ebr));
                entry->ebr_compat_idx = idx++;
                g_free(buf);

                if (ent[1].dp_typ == 0)
                        break;

                lba = ent[1].dp_start;
        }

        basetable->gpt_entries = msize / basetable->gpt_sectors;
        basetable->gpt_first = 0;
        basetable->gpt_last = msize - 1;
        return (0);
}

static int
g_part_ebr_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_ebr_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_ebr_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_ebr_type(struct g_part_table *basetable, struct g_part_entry *baseentry,
    char *buf, size_t bufsz)
{
        struct g_part_ebr_entry *entry;
        int i;

        entry = (struct g_part_ebr_entry *)baseentry;
        for (i = 0; i < nitems(ebr_alias_match); i++) {
                if (ebr_alias_match[i].typ == entry->ent.dp_typ)
                        return (g_part_alias_name(ebr_alias_match[i].alias));
        }
        snprintf(buf, bufsz, "!%d", entry->ent.dp_typ);
        return (buf);
}

static int
g_part_ebr_write(struct g_part_table *basetable, struct g_consumer *cp)
{
        struct g_part_ebr_table *table;
        struct g_provider *pp;
        struct g_part_entry *baseentry, *next;
        struct g_part_ebr_entry *entry;
        u_char *buf;
        u_char *p;
        int error;

        pp = cp->provider;
        buf = g_malloc(pp->sectorsize, M_WAITOK | M_ZERO);
        table = (struct g_part_ebr_table *)basetable;

        _Static_assert(DOSPARTOFF <= sizeof(table->lba0_ebr), "");
        memcpy(buf, table->lba0_ebr, DOSPARTOFF);
        le16enc(buf + DOSMAGICOFFSET, DOSMAGIC);

        baseentry = LIST_FIRST(&basetable->gpt_entry);
        while (baseentry != NULL && baseentry->gpe_deleted)
                baseentry = LIST_NEXT(baseentry, gpe_entry);

        /* Wipe-out the first EBR when there are no slices. */
        if (baseentry == NULL) {
                error = g_write_data(cp, 0, buf, pp->sectorsize);
                goto out;
        }

        /*
         * If the first partition is not in LBA 0, we need to
         * put a "link" EBR in LBA 0.
         */
        if (baseentry->gpe_start != 0) {
                ebr_entry_link(basetable, (uint32_t)baseentry->gpe_start,
                    (uint32_t)baseentry->gpe_end, buf + DOSPARTOFF);
                error = g_write_data(cp, 0, buf, pp->sectorsize);
                if (error)
                        goto out;
        }

        do {
                entry = (struct g_part_ebr_entry *)baseentry;

                _Static_assert(DOSPARTOFF <= sizeof(entry->ebr), "");
                memcpy(buf, entry->ebr, DOSPARTOFF);

                p = buf + DOSPARTOFF;
                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);

                next = LIST_NEXT(baseentry, gpe_entry);
                while (next != NULL && next->gpe_deleted)
                        next = LIST_NEXT(next, gpe_entry);

                p += DOSPARTSIZE;
                if (next != NULL)
                        ebr_entry_link(basetable, (uint32_t)next->gpe_start,
                            (uint32_t)next->gpe_end, p);
                else
                        bzero(p, DOSPARTSIZE);

                error = g_write_data(cp, baseentry->gpe_start * pp->sectorsize,
                    buf, pp->sectorsize);
                baseentry = next;
        } while (!error && baseentry != NULL);

 out:
        g_free(buf);
        return (error);
}