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
   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 (aeglos@valinor.owl.de).
  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 */
  39struct 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 */
  61struct 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
  70static 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
  91static int hfs_parse_new_pmap(struct super_block *sb, struct new_pmap *pm,
  92                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 res;
  97        int i = 0;
  98
  99        do {
 100                if (!memcmp(pm->pmPartType, "Apple_HFS", 9) &&
 101                    (sbi->part < 0 || sbi->part == i)) {
 102                        *part_start += be32_to_cpu(pm->pmPyPartStart);
 103                        *part_size = be32_to_cpu(pm->pmPartBlkCnt);
 104                        return 0;
 105                }
 106
 107                if (++i >= size)
 108                        return -ENOENT;
 109
 110                res = hfsplus_submit_bio(sb->s_bdev,
 111                                         *part_start + HFS_PMAP_BLK + i,
 112                                         pm, READ);
 113                if (res)
 114                        return res;
 115        } while (pm->pmSig == cpu_to_be16(HFS_NEW_PMAP_MAGIC));
 116
 117        return -ENOENT;
 118}
 119
 120/*
 121 * Parse the partition map looking for the start and length of a
 122 * HFS/HFS+ partition.
 123 */
 124int hfs_part_find(struct super_block *sb,
 125                sector_t *part_start, sector_t *part_size)
 126{
 127        void *data;
 128        int res;
 129
 130        data = kmalloc(HFSPLUS_SECTOR_SIZE, GFP_KERNEL);
 131        if (!data)
 132                return -ENOMEM;
 133
 134        res = hfsplus_submit_bio(sb->s_bdev, *part_start + HFS_PMAP_BLK,
 135                                 data, READ);
 136        if (res)
 137                goto out;
 138
 139        switch (be16_to_cpu(*((__be16 *)data))) {
 140        case HFS_OLD_PMAP_MAGIC:
 141                res = hfs_parse_old_pmap(sb, data, part_start, part_size);
 142                break;
 143        case HFS_NEW_PMAP_MAGIC:
 144                res = hfs_parse_new_pmap(sb, data, part_start, part_size);
 145                break;
 146        default:
 147                res = -ENOENT;
 148                break;
 149        }
 150out:
 151        kfree(data);
 152        return res;
 153}
 154