part_tbl.c

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/*
 *  linux/fs/hfs/part_tbl.c
 *
 * Copyright (C) 1996-1997  Paul H. Hargrove
 * (C) 2003 Ardis Technologies <[email protected]>
 * This file may be distributed under the terms of the GNU General Public License.
 *
 * Original code to handle the new style Mac partition table based on
 * a patch contributed by Holger Schemel ([email protected]).
 */

#include "hfs_fs.h"

/*
 * The new style Mac partition map
 *
 * For each partition on the media there is a physical block (512-byte
 * block) containing one of these structures.  These blocks are
 * contiguous starting at block 1.
 */
struct new_pmap {
    __be16  pmSig;      /* signature */
    __be16  reSigPad;   /* padding */
    __be32  pmMapBlkCnt;    /* partition blocks count */
    __be32  pmPyPartStart;  /* physical block start of partition */
    __be32  pmPartBlkCnt;   /* physical block count of partition */
    u8  pmPartName[32]; /* (null terminated?) string
                   giving the name of this
                   partition */
    u8  pmPartType[32]; /* (null terminated?) string
                   giving the type of this
                   partition */
    /* a bunch more stuff we don't need */
} __packed;

/*
 * The old style Mac partition map
 *
 * The partition map consists for a 2-byte signature followed by an
 * array of these structures.  The map is terminated with an all-zero
 * one of these.
 */
struct old_pmap {
    __be16      pdSig;  /* Signature bytes */
    struct  old_pmap_entry {
        __be32  pdStart;
        __be32  pdSize;
        __be32  pdFSID;
    }   pdEntry[42];
} __packed;

/*
 * hfs_part_find()
 *
 * Parse the partition map looking for the
 * start and length of the 'part'th HFS partition.
 */
int hfs_part_find(struct super_block *sb,
          sector_t *part_start, sector_t *part_size)
{
    struct buffer_head *bh;
    __be16 *data;
    int i, size, res;

    res = -ENOENT;
    bh = sb_bread512(sb, *part_start + HFS_PMAP_BLK, data);
    if (!bh)
        return -EIO;

    switch (be16_to_cpu(*data)) {
    case HFS_OLD_PMAP_MAGIC:
      {
        struct old_pmap *pm;
        struct old_pmap_entry *p;

        pm = (struct old_pmap *)bh->b_data;
        p = pm->pdEntry;
        size = 42;
        for (i = 0; i < size; p++, i++) {
            if (p->pdStart && p->pdSize &&
                p->pdFSID == cpu_to_be32(0x54465331)/*"TFS1"*/ &&
                (HFS_SB(sb)->part < 0 || HFS_SB(sb)->part == i)) {
                *part_start += be32_to_cpu(p->pdStart);
                *part_size = be32_to_cpu(p->pdSize);
                res = 0;
            }
        }
        break;
      }
    case HFS_NEW_PMAP_MAGIC:
      {
        struct new_pmap *pm;

        pm = (struct new_pmap *)bh->b_data;
        size = be32_to_cpu(pm->pmMapBlkCnt);
        for (i = 0; i < size;) {
            if (!memcmp(pm->pmPartType,"Apple_HFS", 9) &&
                (HFS_SB(sb)->part < 0 || HFS_SB(sb)->part == i)) {
                *part_start += be32_to_cpu(pm->pmPyPartStart);
                *part_size = be32_to_cpu(pm->pmPartBlkCnt);
                res = 0;
                break;
            }
            brelse(bh);
            bh = sb_bread512(sb, *part_start + HFS_PMAP_BLK + ++i, pm);
            if (!bh)
                return -EIO;
            if (pm->pmSig != cpu_to_be16(HFS_NEW_PMAP_MAGIC))
                break;
        }
        break;
      }
    }
    brelse(bh);

    return res;
}