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, void *buf,
 92		struct new_pmap *pm, 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 buf_size = hfsplus_min_io_size(sb);
 97	int res;
 98	int i = 0;
 99
100	do {
101		if (!memcmp(pm->pmPartType, "Apple_HFS", 9) &&
102		    (sbi->part < 0 || sbi->part == i)) {
103			*part_start += be32_to_cpu(pm->pmPyPartStart);
104			*part_size = be32_to_cpu(pm->pmPartBlkCnt);
105			return 0;
106		}
107
108		if (++i >= size)
109			return -ENOENT;
110
111		pm = (struct new_pmap *)((u8 *)pm + HFSPLUS_SECTOR_SIZE);
112		if ((u8 *)pm - (u8 *)buf >= buf_size) {
113			res = hfsplus_submit_bio(sb,
114						 *part_start + HFS_PMAP_BLK + i,
115						 buf, (void **)&pm, READ);
116			if (res)
117				return res;
118		}
119	} while (pm->pmSig == cpu_to_be16(HFS_NEW_PMAP_MAGIC));
120
121	return -ENOENT;
122}
123
124/*
125 * Parse the partition map looking for the start and length of a
126 * HFS/HFS+ partition.
127 */
128int hfs_part_find(struct super_block *sb,
129		sector_t *part_start, sector_t *part_size)
130{
131	void *buf, *data;
132	int res;
133
134	buf = kmalloc(hfsplus_min_io_size(sb), GFP_KERNEL);
135	if (!buf)
136		return -ENOMEM;
137
138	res = hfsplus_submit_bio(sb, *part_start + HFS_PMAP_BLK,
139				 buf, &data, READ);
140	if (res)
141		goto out;
142
143	switch (be16_to_cpu(*((__be16 *)data))) {
144	case HFS_OLD_PMAP_MAGIC:
145		res = hfs_parse_old_pmap(sb, data, part_start, part_size);
146		break;
147	case HFS_NEW_PMAP_MAGIC:
148		res = hfs_parse_new_pmap(sb, buf, data, part_start, part_size);
149		break;
150	default:
151		res = -ENOENT;
152		break;
153	}
154out:
155	kfree(buf);
156	return res;
157}