fs/hfs/part_tbl.c

   1 /*
   2  *  linux/fs/hfs/part_tbl.c
   3  *
   4  * Copyright (C) 1996-1997  Paul H. Hargrove
   5  * (C) 2003 Ardis Technologies <roman@ardistech.com>
   6  * This file may be distributed under the terms of 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
  12 #include "hfs_fs.h"
  13
  14 /*
  15  * The new style Mac partition map
  16  *
  17  * For each partition on the media there is a physical block (512-byte
  18  * block) containing one of these structures.  These blocks are
  19  * contiguous starting at block 1.
  20  */
  21 struct new_pmap {
  22         __be16  pmSig;          /* signature */
  23         __be16  reSigPad;       /* padding */
  24         __be32  pmMapBlkCnt;    /* partition blocks count */
  25         __be32  pmPyPartStart;  /* physical block start of partition */
  26         __be32  pmPartBlkCnt;   /* physical block count of partition */
  27         u8      pmPartName[32]; /* (null terminated?) string
  28                                    giving the name of this
  29                                    partition */
  30         u8      pmPartType[32]; /* (null terminated?) string
  31                                    giving the type of this
  32                                    partition */
  33         /* a bunch more stuff we don't need */
  34 } __packed;
  35
  36 /*
  37  * The old style Mac partition map
  38  *
  39  * The partition map consists for a 2-byte signature followed by an
  40  * array of these structures.  The map is terminated with an all-zero
  41  * one of these.
  42  */
  43 struct old_pmap {
  44         __be16          pdSig;  /* Signature bytes */
  45         struct  old_pmap_entry {
  46                 __be32  pdStart;
  47                 __be32  pdSize;
  48                 __be32  pdFSID;
  49         }       pdEntry[42];
  50 } __packed;
  51
  52 /*
  53  * hfs_part_find()
  54  *
  55  * Parse the partition map looking for the
  56  * start and length of the 'part'th HFS partition.
  57  */
  58 int hfs_part_find(struct super_block *sb,
  59                   sector_t *part_start, sector_t *part_size)
  60 {
  61         struct buffer_head *bh;
  62         __be16 *data;
  63         int i, size, res;
  64
  65         res = -ENOENT;
  66         bh = sb_bread512(sb, *part_start + HFS_PMAP_BLK, data);
  67         if (!bh)
  68                 return -EIO;
  69
  70         switch (be16_to_cpu(*data)) {
  71         case HFS_OLD_PMAP_MAGIC:
  72           {
  73                 struct old_pmap *pm;
  74                 struct old_pmap_entry *p;
  75
  76                 pm = (struct old_pmap *)bh->b_data;
  77                 p = pm->pdEntry;
  78                 size = 42;
  79                 for (i = 0; i < size; p++, i++) {
  80                         if (p->pdStart && p->pdSize &&
  81                             p->pdFSID == cpu_to_be32(0x54465331)/*"TFS1"*/ &&
  82                             (HFS_SB(sb)->part < 0 || HFS_SB(sb)->part == i)) {
  83                                 *part_start += be32_to_cpu(p->pdStart);
  84                                 *part_size = be32_to_cpu(p->pdSize);
  85                                 res = 0;
  86                         }
  87                 }
  88                 break;
  89           }
  90         case HFS_NEW_PMAP_MAGIC:
  91           {
  92                 struct new_pmap *pm;
  93
  94                 pm = (struct new_pmap *)bh->b_data;
  95                 size = be32_to_cpu(pm->pmMapBlkCnt);
  96                 for (i = 0; i < size;) {
  97                         if (!memcmp(pm->pmPartType,"Apple_HFS", 9) &&
  98                             (HFS_SB(sb)->part < 0 || HFS_SB(sb)->part == i)) {
  99                                 *part_start += be32_to_cpu(pm->pmPyPartStart);
 100                                 *part_size = be32_to_cpu(pm->pmPartBlkCnt);
 101                                 res = 0;
 102                                 break;
 103                         }
 104                         brelse(bh);
 105                         bh = sb_bread512(sb, *part_start + HFS_PMAP_BLK + ++i, pm);
 106                         if (!bh)
 107                                 return -EIO;
 108                         if (pm->pmSig != cpu_to_be16(HFS_NEW_PMAP_MAGIC))
 109                                 break;
 110                 }
 111                 break;
 112           }
 113         }
 114         brelse(bh);
 115
 116         return res;
 117 }