LXR linux/fs/hfsplus/part

   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 */
  37struct 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 */
  59struct 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 */
  74int 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}
 134