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Linux/fs/hfsplus/part_tbl.c

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  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  */
 39 struct 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  */
 61 struct 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 
 70 static 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 
 91 static 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  */
128 int 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         }
154 out:
155         kfree(buf);
156         return res;
157 }
158 

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