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kernel/linux-imx6_3.14.28/fs/hfsplus/part_tbl.c 4.22 KB
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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;
  }