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
6 * the GNU General Public License.
7 *
8 * Original code to handle the new style Mac partition table based on
9 * a patch contributed by Holger Schemel (aeglos@valinor.owl.de).
10 *
11 * In function preconditions the term "valid" applied to a pointer to
12 * a structure means that the pointer is non-NULL and the structure it
13 * points to has all fields initialized to consistent values.
14 *
15 */
16
17 #include <linux/slab.h>
18 #include "hfsplus_fs.h"
19
20 /* offsets to various blocks */
21 #define HFS_DD_BLK 0 /* Driver Descriptor block */
22 #define HFS_PMAP_BLK 1 /* First block of partition map */
23 #define HFS_MDB_BLK 2 /* Block (w/i partition) of MDB */
24
25 /* magic numbers for various disk blocks */
26 #define HFS_DRVR_DESC_MAGIC 0x4552 /* "ER": driver descriptor map */
27 #define HFS_OLD_PMAP_MAGIC 0x5453 /* "TS": old-type partition map */
28 #define HFS_NEW_PMAP_MAGIC 0x504D /* "PM": new-type partition map */
29 #define HFS_SUPER_MAGIC 0x4244 /* "BD": HFS MDB (super block) */
30 #define HFS_MFS_SUPER_MAGIC 0xD2D7 /* MFS MDB (super block) */
31
32 /*
33 * The new style Mac partition map
34 *
35 * For each partition on the media there is a physical block (512-byte
36 * block) containing one of these structures. These blocks are
37 * contiguous starting at block 1.
38 */
39 struct new_pmap {
40 __be16 pmSig; /* signature */
41 __be16 reSigPad; /* padding */
42 __be32 pmMapBlkCnt; /* partition blocks count */
43 __be32 pmPyPartStart; /* physical block start of partition */
44 __be32 pmPartBlkCnt; /* physical block count of partition */
45 u8 pmPartName[32]; /* (null terminated?) string
46 giving the name of this
47 partition */
48 u8 pmPartType[32]; /* (null terminated?) string
49 giving the type of this
50 partition */
51 /* a bunch more stuff we don't need */
52 } __packed;
53
54 /*
55 * The old style Mac partition map
56 *
57 * The partition map consists for a 2-byte signature followed by an
58 * array of these structures. The map is terminated with an all-zero
59 * one of these.
60 */
61 struct old_pmap {
62 __be16 pdSig; /* Signature bytes */
63 struct old_pmap_entry {
64 __be32 pdStart;
65 __be32 pdSize;
66 __be32 pdFSID;
67 } pdEntry[42];
68 } __packed;
69
70 static int hfs_parse_old_pmap(struct super_block *sb, struct old_pmap *pm,
71 sector_t *part_start, sector_t *part_size)
72 {
73 struct hfsplus_sb_info *sbi = HFSPLUS_SB(sb);
74 int i;
75
76 for (i = 0; i < 42; i++) {
77 struct old_pmap_entry *p = &pm->pdEntry[i];
78
79 if (p->pdStart && p->pdSize &&
80 p->pdFSID == cpu_to_be32(0x54465331)/*"TFS1"*/ &&
81 (sbi->part < 0 || sbi->part == i)) {
82 *part_start += be32_to_cpu(p->pdStart);
83 *part_size = be32_to_cpu(p->pdSize);
84 return 0;
85 }
86 }
87
88 return -ENOENT;
89 }
90
91 static int hfs_parse_new_pmap(struct super_block *sb, void *buf,
92 struct new_pmap *pm, sector_t *part_start, sector_t *part_size)
93 {
94 struct hfsplus_sb_info *sbi = HFSPLUS_SB(sb);
95 int size = be32_to_cpu(pm->pmMapBlkCnt);
96 int buf_size = hfsplus_min_io_size(sb);
97 int res;
98 int i = 0;
99
100 do {
101 if (!memcmp(pm->pmPartType, "Apple_HFS", 9) &&
102 (sbi->part < 0 || sbi->part == i)) {
103 *part_start += be32_to_cpu(pm->pmPyPartStart);
104 *part_size = be32_to_cpu(pm->pmPartBlkCnt);
105 return 0;
106 }
107
108 if (++i >= size)
109 return -ENOENT;
110
111 pm = (struct new_pmap *)((u8 *)pm + HFSPLUS_SECTOR_SIZE);
112 if ((u8 *)pm - (u8 *)buf >= buf_size) {
113 res = hfsplus_submit_bio(sb,
114 *part_start + HFS_PMAP_BLK + i,
115 buf, (void **)&pm, REQ_OP_READ);
116 if (res)
117 return res;
118 }
119 } while (pm->pmSig == cpu_to_be16(HFS_NEW_PMAP_MAGIC));
120
121 return -ENOENT;
122 }
123
124 /*
125 * Parse the partition map looking for the start and length of a
126 * HFS/HFS+ partition.
127 */
128 int hfs_part_find(struct super_block *sb,
129 sector_t *part_start, sector_t *part_size)
130 {
131 void *buf, *data;
132 int res;
133
134 buf = kmalloc(hfsplus_min_io_size(sb), GFP_KERNEL);
135 if (!buf)
136 return -ENOMEM;
137
138 res = hfsplus_submit_bio(sb, *part_start + HFS_PMAP_BLK,
139 buf, &data, REQ_OP_READ);
140 if (res)
141 goto out;
142
143 switch (be16_to_cpu(*((__be16 *)data))) {
144 case HFS_OLD_PMAP_MAGIC:
145 res = hfs_parse_old_pmap(sb, data, part_start, part_size);
146 break;
147 case HFS_NEW_PMAP_MAGIC:
148 res = hfs_parse_new_pmap(sb, buf, data, part_start, part_size);
149 break;
150 default:
151 res = -ENOENT;
152 break;
153 }
154 out:
155 kfree(buf);
156 return res;
157 }
158
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