1/*	$NetBSD: mbr.c,v 1.6 2021/05/17 20:21:05 mrg Exp $	*/
2
3/*
4 * Copyright (C) 1995, 1996 Wolfgang Solfrank.
5 * Copyright (C) 1995, 1996 TooLs GmbH.
6 * All rights reserved.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
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 * 3. All advertising materials mentioning features or use of this software
17 *    must display the following acknowledgement:
18 *	This product includes software developed by TooLs GmbH.
19 * 4. The name of TooLs GmbH may not be used to endorse or promote products
20 *    derived from this software without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY TOOLS GMBH ``AS IS'' AND ANY EXPRESS OR
23 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
24 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
25 * IN NO EVENT SHALL TOOLS GMBH BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
26 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
27 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
28 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
29 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
30 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
31 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
32 */
33
34#include <sys/param.h>
35#include <sys/bootblock.h>
36
37#include <lib/libkern/libkern.h>
38#include <lib/libsa/byteorder.h>
39#include <lib/libsa/stand.h>
40
41#include "mbr.h"
42
43static int find_mbr_part(struct of_dev *, uint32_t, char *,
44    struct disklabel *, uint32_t, uint8_t, int);
45static void make_dos_label(struct disklabel *, uint32_t);
46
47/*
48 * Find a valid MBR disklabel.
49 */
50int
51search_mbr_label(struct of_dev *devp, u_long off, char *buf,
52    struct disklabel *lp, u_long off0)
53{
54	static uint8_t fat_types[] = {
55		MBR_PTYPE_FAT12, MBR_PTYPE_FAT16S, MBR_PTYPE_FAT16B,
56		MBR_PTYPE_FAT32, MBR_PTYPE_FAT32L, MBR_PTYPE_FAT16L
57	};
58	size_t read;
59	uint32_t poff;
60	int i;
61
62	/* Find a disklabel in a NetBSD or 386BSD partition. */
63	poff = find_mbr_part(devp, off, buf, lp, 0, MBR_PTYPE_NETBSD, 0);
64#ifdef COMPAT_386BSD_MBRPART
65	if (poff == 0) {
66		poff = find_mbr_part(devp, off, buf, lp, 0,
67		    MBR_PTYPE_386BSD, 0);
68		if (poff != 0)
69			printf("WARNING: old BSD partition ID!\n");
70	}
71#endif
72	if (poff != 0) {
73		if (strategy(devp, F_READ, poff + LABELSECTOR, DEV_BSIZE,
74		    buf, &read) == 0 && read == DEV_BSIZE)
75			if (getdisklabel(buf, lp) == NULL)
76				return 0;
77	}
78
79	/*
80	 * No BSD partition with a valid disklabel found, so try to
81	 * construct a label from a DOS partition.
82	 */
83	for (i = 0; i < sizeof(fat_types); i++) {
84		poff = find_mbr_part(devp, off, buf, lp, 0, fat_types[i], 0);
85		if (poff != 0) {
86			make_dos_label(lp, poff);
87			return 0;
88		}
89	}
90
91	return ERDLAB;
92}
93
94static int
95find_mbr_part(struct of_dev *devp, uint32_t off, char *buf,
96    struct disklabel *lp, uint32_t off0, uint8_t ptype, int recursion)
97{
98	size_t read;
99	struct mbr_partition *p;
100	int i;
101	uint32_t poff;
102
103	if (strategy(devp, F_READ, off, DEV_BSIZE, buf, &read)
104	    || read != DEV_BSIZE)
105		return 0;
106
107	if (*(uint16_t *)&buf[MBR_MAGIC_OFFSET] != sa_htole16(MBR_MAGIC))
108		return 0;
109
110	if (recursion++ <= 1)
111		off0 += off;
112
113	for (p = (struct mbr_partition *)(buf + MBR_PART_OFFSET), i = 0;
114	     i < MBR_PART_COUNT; i++, p++) {
115		if (p->mbrp_type == ptype) {
116			recursion--;
117			return sa_le32toh(p->mbrp_start) + off0;
118		}
119		else if (p->mbrp_type == MBR_PTYPE_EXT) {
120			poff = find_mbr_part(devp, sa_le32toh(p->mbrp_start),
121			    buf, lp, off0, ptype, recursion);
122			if (poff != 0) {
123				recursion--;
124				return poff;
125			}
126			if (strategy(devp, F_READ, off, DEV_BSIZE, buf, &read)
127			    || read != DEV_BSIZE) {
128				recursion--;
129				return 0;
130			}
131		}
132	}
133
134	return 0;
135}
136
137static void
138make_dos_label(struct disklabel *lp, uint32_t poff)
139{
140	int i;
141
142	/* clear all partitions */
143	lp->d_npartitions = RAW_PART + 1;
144	for (i = 0; i < MAXPARTITIONS; i++) {
145		lp->d_partitions[i].p_size = 0;
146		lp->d_partitions[i].p_offset = 0;
147		lp->d_partitions[i].p_fstype = 0;
148	}
149
150	/* set DOS partition as root partition */
151	lp->d_partitions[0].p_offset = poff;
152	lp->d_partitions[0].p_fstype = FS_MSDOS;
153
154	/* disklabel is valid */
155	lp->d_magic = lp->d_magic2 = DISKMAGIC;
156	lp->d_checksum = 0;
157	lp->d_checksum = dkcksum(lp);
158}
159