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part_tbl.c
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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 ([email protected]).
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, 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, 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 }
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