fs/hfsplus/part_tbl.c

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