src/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_misc.h>
  40 #include <ext4_errno.h>
  41 #include <ext4_debug.h>
  42
  43 #include <ext4_mbr.h>
  44
  45 #include <inttypes.h>
  46 #include <string.h>
  47
  48 #define MBR_SIGNATURE 0xAA55
  49
  50 #pragma pack(push, 1)
  51
  52 struct ext4_part_entry {
  53         uint8_t status;
  54         uint8_t chs1[3];
  55         uint8_t type;
  56         uint8_t chs2[3];
  57         uint32_t first_lba;
  58         uint32_t sectors;
  59 };
  60
  61 struct ext4_mbr {
  62         uint8_t bootstrap[446];
  63         struct ext4_part_entry part_entry[4];
  64         uint16_t signature;
  65 };
  66
  67 #pragma pack(pop)
  68
  69 int ext4_mbr_scan(struct ext4_blockdev *parent, struct ext4_mbr_bdevs *bdevs)
  70 {
  71         int r;
  72         size_t i;
  73
  74         ext4_dbg(DEBUG_MBR, DBG_INFO "ext4_mbr_scan\n");
  75         memset(bdevs, 0, sizeof(struct ext4_mbr_bdevs));
  76         r = ext4_block_init(parent);
  77         if (r != EOK)
  78                 return r;
  79
  80         r = ext4_block_readbytes(parent, 0, parent->bdif->ph_bbuf, 512);
  81         if (r != EOK) {
  82                 goto blockdev_fini;
  83         }
  84
  85         const struct ext4_mbr *mbr = (void *)parent->bdif->ph_bbuf;
  86
  87         if (to_le16(mbr->signature) != MBR_SIGNATURE) {
  88                 ext4_dbg(DEBUG_MBR, DBG_ERROR "ext4_mbr_scan: unknown "
  89                          "signature: 0x%x\n", to_le16(mbr->signature));
  90                 r = ENOENT;
  91                 goto blockdev_fini;
  92         }
  93
  94         /*Show bootstrap code*/
  95         ext4_dbg(DEBUG_MBR, "mbr_part: bootstrap:");
  96         for (i = 0; i < sizeof(mbr->bootstrap); ++i) {
  97                 if (!(i & 0xF))
  98                                 ext4_dbg(DEBUG_MBR | DEBUG_NOPREFIX, "\n");
  99                 ext4_dbg(DEBUG_MBR | DEBUG_NOPREFIX, "%02x, ", mbr->bootstrap[i]);
 100         }
 101
 102         ext4_dbg(DEBUG_MBR | DEBUG_NOPREFIX, "\n\n");
 103         for (i = 0; i < 4; ++i) {
 104                 const struct ext4_part_entry *pe = &mbr->part_entry[i];
 105                 ext4_dbg(DEBUG_MBR, "mbr_part: %d\n", (int)i);
 106                 ext4_dbg(DEBUG_MBR, "\tstatus: 0x%x\n", pe->status);
 107                 ext4_dbg(DEBUG_MBR, "\ttype 0x%x:\n", pe->type);
 108                 ext4_dbg(DEBUG_MBR, "\tfirst_lba: 0x%"PRIx32"\n", pe->first_lba);
 109                 ext4_dbg(DEBUG_MBR, "\tsectors: 0x%"PRIx32"\n", pe->sectors);
 110
 111                 if (!pe->sectors)
 112                         continue; /*Empty entry*/
 113
 114                 if (pe->type != 0x83)
 115                         continue; /*Unsupported entry. 0x83 - linux native*/
 116
 117                 bdevs->partitions[i].bdif = parent->bdif;
 118                 bdevs->partitions[i].part_offset =
 119                         (uint64_t)pe->first_lba * parent->bdif->ph_bsize;
 120                 bdevs->partitions[i].part_size =
 121                         (uint64_t)pe->sectors * parent->bdif->ph_bsize;
 122         }
 123
 124         blockdev_fini:
 125         ext4_block_fini(parent);
 126         return r;
 127 }
 128
 129 int ext4_mbr_write(struct ext4_blockdev *parent, struct ext4_mbr_parts *parts)
 130 {
 131         int r;
 132         uint64_t disk_size;
 133         uint32_t division_sum = parts->division[0] + parts->division[1] +
 134                                 parts->division[2] + parts->division[3];
 135
 136         if (division_sum > 100)
 137                 return EINVAL;
 138
 139         ext4_dbg(DEBUG_MBR, DBG_INFO "ext4_mbr_write\n");
 140         r = ext4_block_init(parent);
 141         if (r != EOK)
 142                 return r;
 143
 144         disk_size = parent->part_size;
 145
 146         /*Calculate CHS*/
 147         uint32_t k = 16;
 148         while ((k < 256) && ((disk_size / k / 63) > 1024))
 149                 k *= 2;
 150
 151         if (k == 256)
 152                 --k;
 153
 154         const uint32_t cyl_size = 63 * k;
 155         const uint32_t cyl_count = disk_size / cyl_size;
 156
 157         struct ext4_mbr *mbr = (void *)parent->bdif->ph_bbuf;
 158         memset(mbr, 0, sizeof(struct ext4_mbr));
 159
 160
 161         uint32_t cyl_it = 0;
 162         for (int i = 0; i < 4; ++i) {
 163                 uint32_t cyl_part = cyl_count * parts->division[i] / 100;
 164                 if (!cyl_part)
 165                         continue;
 166
 167                 uint32_t part_start = cyl_it * cyl_size;
 168                 uint32_t part_size = cyl_part * cyl_size;
 169
 170                 if (i == 0) {
 171                         part_start += 63;
 172                         part_size -= 63 * parent->bdif->ph_bsize;
 173                 }
 174
 175                 uint32_t cyl_end = cyl_part + cyl_it - 1;
 176
 177                 mbr->part_entry[i].status = 0;
 178                 mbr->part_entry[i].chs1[0] = i ? 0 : 1;;
 179                 mbr->part_entry[i].chs1[1] = (cyl_it >> 2) + 1;
 180                 mbr->part_entry[i].chs1[2] = cyl_it;
 181                 mbr->part_entry[i].type = 0x83;
 182                 mbr->part_entry[i].chs2[0] = k - 1;
 183                 mbr->part_entry[i].chs2[1] = (cyl_end >> 2) + 63;
 184                 mbr->part_entry[i].chs2[2] = cyl_end;
 185
 186                 mbr->part_entry[i].first_lba = part_start;
 187                 mbr->part_entry[i].sectors = part_size / parent->bdif->ph_bsize;
 188
 189                 cyl_it += cyl_part;
 190         }
 191
 192         mbr->signature = MBR_SIGNATURE;
 193         r = ext4_block_writebytes(parent, 0, parent->bdif->ph_bbuf, 512);
 194         if (r != EOK)
 195                 goto blockdev_fini;
 196
 197
 198         blockdev_fini:
 199         ext4_block_fini(parent);
 200         return r;
 201 }
 202
 203 /**
 204  * @}
 205  */
 206