part_tbl.c
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/*
* linux/fs/hfsplus/part_tbl.c
*
* Copyright (C) 1996-1997 Paul H. Hargrove
* 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 (aeglos@valinor.owl.de).
*
* In function preconditions the term "valid" applied to a pointer to
* a structure means that the pointer is non-NULL and the structure it
* points to has all fields initialized to consistent values.
*
*/
#include <linux/slab.h>
#include "hfsplus_fs.h"
/* offsets to various blocks */
#define HFS_DD_BLK 0 /* Driver Descriptor block */
#define HFS_PMAP_BLK 1 /* First block of partition map */
#define HFS_MDB_BLK 2 /* Block (w/i partition) of MDB */
/* magic numbers for various disk blocks */
#define HFS_DRVR_DESC_MAGIC 0x4552 /* "ER": driver descriptor map */
#define HFS_OLD_PMAP_MAGIC 0x5453 /* "TS": old-type partition map */
#define HFS_NEW_PMAP_MAGIC 0x504D /* "PM": new-type partition map */
#define HFS_SUPER_MAGIC 0x4244 /* "BD": HFS MDB (super block) */
#define HFS_MFS_SUPER_MAGIC 0xD2D7 /* MFS MDB (super block) */
/*
* 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;
static int hfs_parse_old_pmap(struct super_block *sb, struct old_pmap *pm,
sector_t *part_start, sector_t *part_size)
{
struct hfsplus_sb_info *sbi = HFSPLUS_SB(sb);
int i;
for (i = 0; i < 42; i++) {
struct old_pmap_entry *p = &pm->pdEntry[i];
if (p->pdStart && p->pdSize &&
p->pdFSID == cpu_to_be32(0x54465331)/*"TFS1"*/ &&
(sbi->part < 0 || sbi->part == i)) {
*part_start += be32_to_cpu(p->pdStart);
*part_size = be32_to_cpu(p->pdSize);
return 0;
}
}
return -ENOENT;
}
static int hfs_parse_new_pmap(struct super_block *sb, void *buf,
struct new_pmap *pm, sector_t *part_start, sector_t *part_size)
{
struct hfsplus_sb_info *sbi = HFSPLUS_SB(sb);
int size = be32_to_cpu(pm->pmMapBlkCnt);
int buf_size = hfsplus_min_io_size(sb);
int res;
int i = 0;
do {
if (!memcmp(pm->pmPartType, "Apple_HFS", 9) &&
(sbi->part < 0 || sbi->part == i)) {
*part_start += be32_to_cpu(pm->pmPyPartStart);
*part_size = be32_to_cpu(pm->pmPartBlkCnt);
return 0;
}
if (++i >= size)
return -ENOENT;
pm = (struct new_pmap *)((u8 *)pm + HFSPLUS_SECTOR_SIZE);
if ((u8 *)pm - (u8 *)buf >= buf_size) {
res = hfsplus_submit_bio(sb,
*part_start + HFS_PMAP_BLK + i,
buf, (void **)&pm, READ);
if (res)
return res;
}
} while (pm->pmSig == cpu_to_be16(HFS_NEW_PMAP_MAGIC));
return -ENOENT;
}
/*
* Parse the partition map looking for the start and length of a
* HFS/HFS+ partition.
*/
int hfs_part_find(struct super_block *sb,
sector_t *part_start, sector_t *part_size)
{
void *buf, *data;
int res;
buf = kmalloc(hfsplus_min_io_size(sb), GFP_KERNEL);
if (!buf)
return -ENOMEM;
res = hfsplus_submit_bio(sb, *part_start + HFS_PMAP_BLK,
buf, &data, READ);
if (res)
goto out;
switch (be16_to_cpu(*((__be16 *)data))) {
case HFS_OLD_PMAP_MAGIC:
res = hfs_parse_old_pmap(sb, data, part_start, part_size);
break;
case HFS_NEW_PMAP_MAGIC:
res = hfs_parse_new_pmap(sb, buf, data, part_start, part_size);
break;
default:
res = -ENOENT;
break;
}
out:
kfree(buf);
return res;
}