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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * linux/fs/hfs/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}