lwext4/ext4_mbr.c

   1 /*
   2  * Copyright (c) 2015 Grzegorz Kostka (kostka.grzegorz@gmail.com)
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  *
   9  * - Redistributions of source code must retain the above copyright
  10  *   notice, this list of conditions and the following disclaimer.
  11  * - Redistributions in binary form must reproduce the above copyright
  12  *   notice, this list of conditions and the following disclaimer in the
  13  *   documentation and/or other materials provided with the distribution.
  14  * - The name of the author may not be used to endorse or promote products
  15  *   derived from this software without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  18  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  19  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  20  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  21  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  22  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  23  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  24  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  26  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27  */
  28
  29 /** @addtogroup lwext4
  30  * @{
  31  */
  32 /**
  33  * @file  ext4_mbr.c
  34  * @brief Master boot record parser
  35  */
  36
  37 #include "ext4_config.h"
  38 #include "ext4_types.h"
  39 #include "ext4_debug.h"
  40 #include "ext4_mbr.h"
  41
  42 #include <inttypes.h>
  43 #include <string.h>
  44
  45 #define MBR_SIGNATURE 0xAA55
  46
  47 struct ext4_part_entry {
  48         uint8_t status;
  49         uint8_t chs1[3];
  50         uint8_t type;
  51         uint8_t chs2[3];
  52         uint32_t first_lba;
  53         uint32_t sectors;
  54 } __attribute__((packed));
  55
  56 struct ext4_mbr {
  57         uint8_t bootstrap[446];
  58         struct ext4_part_entry part_entry[4];
  59         uint16_t signature;
  60 } __attribute__((packed));
  61
  62
  63 int ext4_mbr_scan(struct ext4_blockdev *parent, struct ext4_mbr_bdevs *bdevs)
  64 {
  65         int r;
  66         size_t i;
  67
  68         ext4_dbg(DEBUG_MBR, DBG_INFO "ext4_mbr_scan\n");
  69         memset(bdevs, 0, sizeof(struct ext4_mbr_bdevs));
  70         r = ext4_block_init(parent);
  71         if (r != EOK)
  72                 return r;
  73
  74         r = ext4_block_readbytes(parent, 0, parent->bdif->ph_bbuf, 512);
  75         if (r != EOK) {
  76                 goto blockdev_fini;
  77         }
  78
  79         const struct ext4_mbr *mbr = (void *)parent->bdif->ph_bbuf;
  80
  81         if (to_le16(mbr->signature) != MBR_SIGNATURE) {
  82                 ext4_dbg(DEBUG_MBR, DBG_ERROR "ext4_mbr_scan: unknown "
  83                          "signature: 0x%x\n", to_le16(mbr->signature));
  84                 r = ENOENT;
  85                 goto blockdev_fini;
  86         }
  87
  88         /*Show bootstrap code*/
  89         ext4_dbg(DEBUG_MBR, "mbr_part: bootstrap:");
  90         for (i = 0; i < sizeof(mbr->bootstrap); ++i) {
  91                 if (!(i & 0xF))
  92                                 ext4_dbg(DEBUG_MBR | DEBUG_NOPREFIX, "\n");
  93                 ext4_dbg(DEBUG_MBR | DEBUG_NOPREFIX, "%02x, ", mbr->bootstrap[i]);
  94         }
  95
  96         ext4_dbg(DEBUG_MBR | DEBUG_NOPREFIX, "\n\n");
  97         for (i = 0; i < 4; ++i) {
  98                 const struct ext4_part_entry *pe = &mbr->part_entry[i];
  99                 ext4_dbg(DEBUG_MBR, "mbr_part: %d\n", (int)i);
 100                 ext4_dbg(DEBUG_MBR, "\tstatus: 0x%x\n", pe->status);
 101                 ext4_dbg(DEBUG_MBR, "\ttype 0x%x:\n", pe->type);
 102                 ext4_dbg(DEBUG_MBR, "\tfirst_lba: 0x%"PRIx32"\n", pe->first_lba);
 103                 ext4_dbg(DEBUG_MBR, "\tsectors: 0x%"PRIx32"\n", pe->sectors);
 104
 105                 if (!pe->sectors)
 106                         continue; /*Empty entry*/
 107
 108                 if (pe->type != 0x83)
 109                         continue; /*Unsupported entry. 0x83 - linux native*/
 110
 111                 bdevs->partitions[i].bdif = parent->bdif;
 112                 bdevs->partitions[i].part_offset =
 113                         (uint64_t)pe->first_lba * parent->bdif->ph_bsize;
 114                 bdevs->partitions[i].part_size =
 115                         (uint64_t)pe->sectors * parent->bdif->ph_bsize;
 116         }
 117
 118         blockdev_fini:
 119         ext4_block_fini(parent);
 120         return r;
 121 }
 122
 123 /**
 124  * @}
 125  */
 126