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 "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  */
  37 struct 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  */
  59 struct 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  */
  74 int 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 }