1/*
2 * linux/fs/hfsplus/part_tbl.c
3 *
4 * Copyright (C) 1996-1997  Paul H. Hargrove
5 * This file may be distributed under the terms of the GNU General Public License.
6 *
7 * Original code to handle the new style Mac partition table based on
8 * a patch contributed by Holger Schemel (aeglos@valinor.owl.de).
9 *
10 * In function preconditions the term "valid" applied to a pointer to
11 * a structure means that the pointer is non-NULL and the structure it
12 * points to has all fields initialized to consistent values.
13 *
14 */
15
16#include "hfsplus_fs.h"
17
18/* offsets to various blocks */
19#define HFS_DD_BLK		0 /* Driver Descriptor block */
20#define HFS_PMAP_BLK		1 /* First block of partition map */
21#define HFS_MDB_BLK		2 /* Block (w/i partition) of MDB */
22
23/* magic numbers for various disk blocks */
24#define HFS_DRVR_DESC_MAGIC	0x4552 /* "ER": driver descriptor map */
25#define HFS_OLD_PMAP_MAGIC	0x5453 /* "TS": old-type partition map */
26#define HFS_NEW_PMAP_MAGIC	0x504D /* "PM": new-type partition map */
27#define HFS_SUPER_MAGIC		0x4244 /* "BD": HFS MDB (super block) */
28#define HFS_MFS_SUPER_MAGIC	0xD2D7 /* MFS MDB (super block) */
29
30/*
31 * The new style Mac partition map
32 *
33 * For each partition on the media there is a physical block (512-byte
34 * block) containing one of these structures.  These blocks are
35 * contiguous starting at block 1.
36 */
37struct new_pmap {
38	__be16	pmSig;		/* signature */
39	__be16	reSigPad;	/* padding */
40	__be32	pmMapBlkCnt;	/* partition blocks count */
41	__be32	pmPyPartStart;	/* physical block start of partition */
42	__be32	pmPartBlkCnt;	/* physical block count of partition */
43	u8	pmPartName[32];	/* (null terminated?) string
44				   giving the name of this
45				   partition */
46	u8	pmPartType[32];	/* (null terminated?) string
47				   giving the type of this
48				   partition */
49	/* a bunch more stuff we don't need */
50} __packed;
51
52/*
53 * The old style Mac partition map
54 *
55 * The partition map consists for a 2-byte signature followed by an
56 * array of these structures.  The map is terminated with an all-zero
57 * one of these.
58 */
59struct old_pmap {
60	__be16		pdSig;	/* Signature bytes */
61	struct 	old_pmap_entry {
62		__be32	pdStart;
63		__be32	pdSize;
64		__be32	pdFSID;
65	}	pdEntry[42];
66} __packed;
67
68/*
69 * hfs_part_find()
70 *
71 * Parse the partition map looking for the
72 * start and length of the 'part'th HFS partition.
73 */
74int hfs_part_find(struct super_block *sb,
75		  sector_t *part_start, sector_t *part_size)
76{
77	struct buffer_head *bh;
78	__be16 *data;
79	int i, size, res;
80
81	res = -ENOENT;
82	bh = sb_bread512(sb, *part_start + HFS_PMAP_BLK, data);
83	if (!bh)
84		return -EIO;
85
86	switch (be16_to_cpu(*data)) {
87	case HFS_OLD_PMAP_MAGIC:
88	  {
89		struct old_pmap *pm;
90		struct old_pmap_entry *p;
91
92		pm = (struct old_pmap *)bh->b_data;
93		p = pm->pdEntry;
94		size = 42;
95		for (i = 0; i < size; p++, i++) {
96			if (p->pdStart && p->pdSize &&
97			    p->pdFSID == cpu_to_be32(0x54465331)/*"TFS1"*/ &&
98			    (HFSPLUS_SB(sb).part < 0 || HFSPLUS_SB(sb).part == i)) {
99				*part_start += be32_to_cpu(p->pdStart);
100				*part_size = be32_to_cpu(p->pdSize);
101				res = 0;
102			}
103		}
104		break;
105	  }
106	case HFS_NEW_PMAP_MAGIC:
107	  {
108		struct new_pmap *pm;
109
110		pm = (struct new_pmap *)bh->b_data;
111		size = be32_to_cpu(pm->pmMapBlkCnt);
112		for (i = 0; i < size;) {
113			if (!memcmp(pm->pmPartType,"Apple_HFS", 9) &&
114			    (HFSPLUS_SB(sb).part < 0 || HFSPLUS_SB(sb).part == i)) {
115				*part_start += be32_to_cpu(pm->pmPyPartStart);
116				*part_size = be32_to_cpu(pm->pmPartBlkCnt);
117				res = 0;
118				break;
119			}
120			brelse(bh);
121			bh = sb_bread512(sb, *part_start + HFS_PMAP_BLK + ++i, pm);
122			if (!bh)
123				return -EIO;
124			if (pm->pmSig != cpu_to_be16(HFS_NEW_PMAP_MAGIC))
125				break;
126		}
127		break;
128	  }
129	}
130	brelse(bh);
131
132	return res;
133}
134