mkfs/vbr.c

   1 /*
   2         vbr.c (09.11.10)
   3         Volume Boot Record creation code.
   4
   5         Free exFAT implementation.
   6         Copyright (C) 2011-2017  Andrew Nayenko
   7
   8         This program is free software; you can redistribute it and/or modify
   9         it under the terms of the GNU General Public License as published by
  10         the Free Software Foundation, either version 2 of the License, or
  11         (at your option) any later version.
  12
  13         This program is distributed in the hope that it will be useful,
  14         but WITHOUT ANY WARRANTY; without even the implied warranty of
  15         MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16         GNU General Public License for more details.
  17
  18         You should have received a copy of the GNU General Public License along
  19         with this program; if not, write to the Free Software Foundation, Inc.,
  20         51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  21 */
  22
  23 #include "vbr.h"
  24 #include "fat.h"
  25 #include "cbm.h"
  26 #include "uct.h"
  27 #include "rootdir.h"
  28 #include <string.h>
  29
  30 static off_t vbr_alignment(void)
  31 {
  32         return get_sector_size();
  33 }
  34
  35 static off_t vbr_size(void)
  36 {
  37         return 12 * get_sector_size();
  38 }
  39
  40 static void init_sb(struct exfat_super_block* sb)
  41 {
  42         uint32_t clusters_max;
  43         uint32_t fat_sectors;
  44
  45         clusters_max = get_volume_size() / get_cluster_size();
  46         fat_sectors = DIV_ROUND_UP((off_t) clusters_max * sizeof(cluster_t),
  47                         get_sector_size());
  48
  49         memset(sb, 0, sizeof(struct exfat_super_block));
  50         sb->jump[0] = 0xeb;
  51         sb->jump[1] = 0x76;
  52         sb->jump[2] = 0x90;
  53         memcpy(sb->oem_name, "EXFAT   ", sizeof(sb->oem_name));
  54         sb->sector_start = cpu_to_le64(get_first_sector());
  55         sb->sector_count = cpu_to_le64(get_volume_size() / get_sector_size());
  56         sb->fat_sector_start = cpu_to_le32(
  57                         fat.get_alignment() / get_sector_size());
  58         sb->fat_sector_count = cpu_to_le32(ROUND_UP(
  59                         le32_to_cpu(sb->fat_sector_start) + fat_sectors,
  60                                 1 << get_spc_bits()) -
  61                         le32_to_cpu(sb->fat_sector_start));
  62         sb->cluster_sector_start = cpu_to_le32(
  63                         get_position(&cbm) / get_sector_size());
  64         sb->cluster_count = cpu_to_le32(clusters_max -
  65                         ((le32_to_cpu(sb->fat_sector_start) +
  66                           le32_to_cpu(sb->fat_sector_count)) >> get_spc_bits()));
  67         sb->rootdir_cluster = cpu_to_le32(
  68                         (get_position(&rootdir) - get_position(&cbm)) / get_cluster_size()
  69                         + EXFAT_FIRST_DATA_CLUSTER);
  70         sb->volume_serial = cpu_to_le32(get_volume_serial());
  71         sb->version.major = 1;
  72         sb->version.minor = 0;
  73         sb->volume_state = cpu_to_le16(0);
  74         sb->sector_bits = get_sector_bits();
  75         sb->spc_bits = get_spc_bits();
  76         sb->fat_count = 1;
  77         sb->drive_no = 0x80;
  78         sb->allocated_percent = 0;
  79         sb->boot_signature = cpu_to_le16(0xaa55);
  80 }
  81
  82 static int vbr_write(struct exfat_dev* dev)
  83 {
  84         struct exfat_super_block sb;
  85         uint32_t checksum;
  86         le32_t* sector = malloc(get_sector_size());
  87         size_t i;
  88
  89         if (sector == NULL)
  90         {
  91                 exfat_error("failed to allocate sector-sized block of memory");
  92                 return 1;
  93         }
  94
  95         init_sb(&sb);
  96         if (exfat_write(dev, &sb, sizeof(struct exfat_super_block)) < 0)
  97         {
  98                 free(sector);
  99                 exfat_error("failed to write super block sector");
 100                 return 1;
 101         }
 102         checksum = exfat_vbr_start_checksum(&sb, sizeof(struct exfat_super_block));
 103
 104         memset(sector, 0, get_sector_size());
 105         sector[get_sector_size() / sizeof(sector[0]) - 1] =
 106                         cpu_to_le32(0xaa550000);
 107         for (i = 0; i < 8; i++)
 108         {
 109                 if (exfat_write(dev, sector, get_sector_size()) < 0)
 110                 {
 111                         free(sector);
 112                         exfat_error("failed to write a sector with boot signature");
 113                         return 1;
 114                 }
 115                 checksum = exfat_vbr_add_checksum(sector, get_sector_size(), checksum);
 116         }
 117
 118         memset(sector, 0, get_sector_size());
 119         for (i = 0; i < 2; i++)
 120         {
 121                 if (exfat_write(dev, sector, get_sector_size()) < 0)
 122                 {
 123                         free(sector);
 124                         exfat_error("failed to write an empty sector");
 125                         return 1;
 126                 }
 127                 checksum = exfat_vbr_add_checksum(sector, get_sector_size(), checksum);
 128         }
 129
 130         for (i = 0; i < get_sector_size() / sizeof(sector[0]); i++)
 131                 sector[i] = cpu_to_le32(checksum);
 132         if (exfat_write(dev, sector, get_sector_size()) < 0)
 133         {
 134                 free(sector);
 135                 exfat_error("failed to write checksum sector");
 136                 return 1;
 137         }
 138
 139         free(sector);
 140         return 0;
 141 }
 142
 143 const struct fs_object vbr =
 144 {
 145         .get_alignment = vbr_alignment,
 146         .get_size = vbr_size,
 147         .write = vbr_write,
 148 };