1 | /*
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2 | * volume_id - reads filesystem label and uuid
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3 | *
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4 | * Copyright (C) 2004 Kay Sievers <kay.sievers@vrfy.org>
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5 | *
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6 | * This library is free software; you can redistribute it and/or
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7 | * modify it under the terms of the GNU Lesser General Public
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8 | * License as published by the Free Software Foundation; either
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9 | * version 2.1 of the License, or (at your option) any later version.
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10 | *
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11 | * This library is distributed in the hope that it will be useful,
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12 | * but WITHOUT ANY WARRANTY; without even the implied warranty of
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13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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14 | * Lesser General Public License for more details.
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15 | *
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16 | * You should have received a copy of the GNU Lesser General Public
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17 | * License along with this library; if not, write to the Free Software
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18 | * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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19 | */
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20 |
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21 | #include "volume_id_internal.h"
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22 |
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23 | /* linux/msdos_fs.h says: */
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24 | #define FAT12_MAX 0xff4
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25 | #define FAT16_MAX 0xfff4
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26 | #define FAT32_MAX 0x0ffffff6
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27 |
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28 | #define FAT_ATTR_VOLUME_ID 0x08
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29 | #define FAT_ATTR_DIR 0x10
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30 | #define FAT_ATTR_LONG_NAME 0x0f
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31 | #define FAT_ATTR_MASK 0x3f
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32 | #define FAT_ENTRY_FREE 0xe5
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33 |
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34 | struct vfat_super_block {
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35 | uint8_t boot_jump[3];
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36 | uint8_t sysid[8];
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37 | uint16_t sector_size_bytes;
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38 | uint8_t sectors_per_cluster;
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39 | uint16_t reserved_sct;
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40 | uint8_t fats;
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41 | uint16_t dir_entries;
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42 | uint16_t sectors;
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43 | uint8_t media;
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44 | uint16_t fat_length;
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45 | uint16_t secs_track;
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46 | uint16_t heads;
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47 | uint32_t hidden;
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48 | uint32_t total_sect;
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49 | union {
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50 | struct fat_super_block {
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51 | uint8_t unknown[3];
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52 | uint8_t serno[4];
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53 | uint8_t label[11];
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54 | uint8_t magic[8];
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55 | uint8_t dummy2[192];
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56 | uint8_t pmagic[2];
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57 | } PACKED fat;
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58 | struct fat32_super_block {
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59 | uint32_t fat32_length;
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60 | uint16_t flags;
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61 | uint8_t version[2];
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62 | uint32_t root_cluster;
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63 | uint16_t insfo_sector;
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64 | uint16_t backup_boot;
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65 | uint16_t reserved2[6];
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66 | uint8_t unknown[3];
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67 | uint8_t serno[4];
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68 | uint8_t label[11];
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69 | uint8_t magic[8];
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70 | uint8_t dummy2[164];
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71 | uint8_t pmagic[2];
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72 | } PACKED fat32;
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73 | } PACKED type;
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74 | } PACKED;
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75 |
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76 | struct vfat_dir_entry {
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77 | uint8_t name[11];
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78 | uint8_t attr;
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79 | uint16_t time_creat;
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80 | uint16_t date_creat;
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81 | uint16_t time_acc;
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82 | uint16_t date_acc;
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83 | uint16_t cluster_high;
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84 | uint16_t time_write;
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85 | uint16_t date_write;
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86 | uint16_t cluster_low;
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87 | uint32_t size;
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88 | } PACKED;
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89 |
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90 | static uint8_t *get_attr_volume_id(struct vfat_dir_entry *dir, int count)
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91 | {
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92 | for (;--count >= 0; dir++) {
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93 | /* end marker */
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94 | if (dir->name[0] == 0x00) {
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95 | dbg("end of dir");
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96 | break;
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97 | }
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98 |
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99 | /* empty entry */
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100 | if (dir->name[0] == FAT_ENTRY_FREE)
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101 | continue;
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102 |
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103 | /* long name */
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104 | if ((dir->attr & FAT_ATTR_MASK) == FAT_ATTR_LONG_NAME)
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105 | continue;
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106 |
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107 | if ((dir->attr & (FAT_ATTR_VOLUME_ID | FAT_ATTR_DIR)) == FAT_ATTR_VOLUME_ID) {
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108 | /* labels do not have file data */
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109 | if (dir->cluster_high != 0 || dir->cluster_low != 0)
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110 | continue;
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111 |
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112 | dbg("found ATTR_VOLUME_ID id in root dir");
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113 | return dir->name;
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114 | }
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115 |
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116 | dbg("skip dir entry");
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117 | }
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118 |
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119 | return NULL;
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120 | }
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121 |
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122 | int FAST_FUNC volume_id_probe_vfat(struct volume_id *id /*,uint64_t fat_partition_off*/)
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123 | {
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124 | #define fat_partition_off ((uint64_t)0)
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125 | struct vfat_super_block *vs;
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126 | struct vfat_dir_entry *dir;
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127 | uint16_t sector_size_bytes;
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128 | uint16_t dir_entries;
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129 | uint32_t sect_count;
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130 | uint16_t reserved_sct;
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131 | uint32_t fat_size_sct;
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132 | uint32_t root_cluster;
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133 | uint32_t dir_size_sct;
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134 | uint32_t cluster_count;
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135 | uint64_t root_start_off;
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136 | uint32_t start_data_sct;
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137 | uint8_t *buf;
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138 | uint32_t buf_size;
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139 | uint8_t *label = NULL;
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140 | uint32_t next_cluster;
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141 | int maxloop;
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142 |
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143 | dbg("probing at offset 0x%llx", (unsigned long long) fat_partition_off);
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144 |
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145 | vs = volume_id_get_buffer(id, fat_partition_off, 0x200);
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146 | if (vs == NULL)
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147 | return -1;
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148 |
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149 | /* believe only that's fat, don't trust the version
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150 | * the cluster_count will tell us
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151 | */
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152 | if (memcmp(vs->sysid, "NTFS", 4) == 0)
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153 | return -1;
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154 |
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155 | if (memcmp(vs->type.fat32.magic, "MSWIN", 5) == 0)
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156 | goto valid;
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157 |
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158 | if (memcmp(vs->type.fat32.magic, "FAT32 ", 8) == 0)
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159 | goto valid;
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160 |
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161 | if (memcmp(vs->type.fat.magic, "FAT16 ", 8) == 0)
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162 | goto valid;
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163 |
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164 | if (memcmp(vs->type.fat.magic, "MSDOS", 5) == 0)
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165 | goto valid;
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166 |
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167 | if (memcmp(vs->type.fat.magic, "FAT12 ", 8) == 0)
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168 | goto valid;
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169 |
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170 | /*
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171 | * There are old floppies out there without a magic, so we check
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172 | * for well known values and guess if it's a fat volume
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173 | */
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174 |
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175 | /* boot jump address check */
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176 | if ((vs->boot_jump[0] != 0xeb || vs->boot_jump[2] != 0x90)
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177 | && vs->boot_jump[0] != 0xe9
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178 | ) {
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179 | return -1;
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180 | }
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181 |
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182 | /* heads check */
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183 | if (vs->heads == 0)
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184 | return -1;
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185 |
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186 | /* cluster size check */
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187 | if (vs->sectors_per_cluster == 0
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188 | || (vs->sectors_per_cluster & (vs->sectors_per_cluster-1))
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189 | ) {
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190 | return -1;
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191 | }
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192 |
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193 | /* media check */
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194 | if (vs->media < 0xf8 && vs->media != 0xf0)
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195 | return -1;
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196 |
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197 | /* fat count*/
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198 | if (vs->fats != 2)
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199 | return -1;
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200 |
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201 | valid:
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202 | /* sector size check */
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203 | sector_size_bytes = le16_to_cpu(vs->sector_size_bytes);
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204 | if (sector_size_bytes != 0x200 && sector_size_bytes != 0x400
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205 | && sector_size_bytes != 0x800 && sector_size_bytes != 0x1000
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206 | ) {
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207 | return -1;
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208 | }
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209 |
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210 | dbg("sector_size_bytes 0x%x", sector_size_bytes);
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211 | dbg("sectors_per_cluster 0x%x", vs->sectors_per_cluster);
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212 |
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213 | reserved_sct = le16_to_cpu(vs->reserved_sct);
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214 | dbg("reserved_sct 0x%x", reserved_sct);
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215 |
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216 | sect_count = le16_to_cpu(vs->sectors);
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217 | if (sect_count == 0)
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218 | sect_count = le32_to_cpu(vs->total_sect);
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219 | dbg("sect_count 0x%x", sect_count);
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220 |
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221 | fat_size_sct = le16_to_cpu(vs->fat_length);
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222 | if (fat_size_sct == 0)
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223 | fat_size_sct = le32_to_cpu(vs->type.fat32.fat32_length);
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224 | fat_size_sct *= vs->fats;
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225 | dbg("fat_size_sct 0x%x", fat_size_sct);
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226 |
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227 | dir_entries = le16_to_cpu(vs->dir_entries);
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228 | dir_size_sct = ((dir_entries * sizeof(struct vfat_dir_entry)) +
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229 | (sector_size_bytes-1)) / sector_size_bytes;
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230 | dbg("dir_size_sct 0x%x", dir_size_sct);
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231 |
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232 | cluster_count = sect_count - (reserved_sct + fat_size_sct + dir_size_sct);
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233 | cluster_count /= vs->sectors_per_cluster;
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234 | dbg("cluster_count 0x%x", cluster_count);
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235 |
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236 | // if (cluster_count < FAT12_MAX) {
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237 | // strcpy(id->type_version, "FAT12");
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238 | // } else if (cluster_count < FAT16_MAX) {
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239 | // strcpy(id->type_version, "FAT16");
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240 | // } else {
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241 | // strcpy(id->type_version, "FAT32");
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242 | // goto fat32;
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243 | // }
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244 | if (cluster_count >= FAT16_MAX)
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245 | goto fat32;
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246 |
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247 | /* the label may be an attribute in the root directory */
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248 | root_start_off = (reserved_sct + fat_size_sct) * sector_size_bytes;
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249 | dbg("root dir start 0x%llx", (unsigned long long) root_start_off);
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250 | dbg("expected entries 0x%x", dir_entries);
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251 |
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252 | buf_size = dir_entries * sizeof(struct vfat_dir_entry);
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253 | buf = volume_id_get_buffer(id, fat_partition_off + root_start_off, buf_size);
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254 | if (buf == NULL)
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255 | goto ret;
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256 |
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257 | label = get_attr_volume_id((struct vfat_dir_entry*) buf, dir_entries);
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258 |
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259 | vs = volume_id_get_buffer(id, fat_partition_off, 0x200);
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260 | if (vs == NULL)
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261 | return -1;
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262 |
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263 | if (label != NULL && memcmp(label, "NO NAME ", 11) != 0) {
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264 | // volume_id_set_label_raw(id, label, 11);
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265 | volume_id_set_label_string(id, label, 11);
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266 | } else if (memcmp(vs->type.fat.label, "NO NAME ", 11) != 0) {
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267 | // volume_id_set_label_raw(id, vs->type.fat.label, 11);
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268 | volume_id_set_label_string(id, vs->type.fat.label, 11);
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269 | }
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270 | volume_id_set_uuid(id, vs->type.fat.serno, UUID_DOS);
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271 | goto ret;
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272 |
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273 | fat32:
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274 | /* FAT32 root dir is a cluster chain like any other directory */
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275 | buf_size = vs->sectors_per_cluster * sector_size_bytes;
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276 | root_cluster = le32_to_cpu(vs->type.fat32.root_cluster);
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277 | start_data_sct = reserved_sct + fat_size_sct;
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278 |
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279 | next_cluster = root_cluster;
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280 | maxloop = 100;
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281 | while (--maxloop) {
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282 | uint64_t next_off_sct;
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283 | uint64_t next_off;
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284 | uint64_t fat_entry_off;
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285 | int count;
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286 |
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287 | dbg("next_cluster 0x%x", (unsigned)next_cluster);
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288 | next_off_sct = (uint64_t)(next_cluster - 2) * vs->sectors_per_cluster;
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289 | next_off = (start_data_sct + next_off_sct) * sector_size_bytes;
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290 | dbg("cluster offset 0x%llx", (unsigned long long) next_off);
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291 |
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292 | /* get cluster */
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293 | buf = volume_id_get_buffer(id, fat_partition_off + next_off, buf_size);
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294 | if (buf == NULL)
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295 | goto ret;
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296 |
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297 | dir = (struct vfat_dir_entry*) buf;
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298 | count = buf_size / sizeof(struct vfat_dir_entry);
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299 | dbg("expected entries 0x%x", count);
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300 |
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301 | label = get_attr_volume_id(dir, count);
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302 | if (label)
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303 | break;
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304 |
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305 | /* get FAT entry */
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306 | fat_entry_off = (reserved_sct * sector_size_bytes) + (next_cluster * sizeof(uint32_t));
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307 | dbg("fat_entry_off 0x%llx", (unsigned long long)fat_entry_off);
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308 | buf = volume_id_get_buffer(id, fat_partition_off + fat_entry_off, buf_size);
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309 | if (buf == NULL)
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310 | goto ret;
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311 |
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312 | /* set next cluster */
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313 | next_cluster = le32_to_cpu(*(uint32_t*)buf) & 0x0fffffff;
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314 | if (next_cluster < 2 || next_cluster > FAT32_MAX)
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315 | break;
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316 | }
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317 | if (maxloop == 0)
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318 | dbg("reached maximum follow count of root cluster chain, give up");
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319 |
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320 | vs = volume_id_get_buffer(id, fat_partition_off, 0x200);
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321 | if (vs == NULL)
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322 | return -1;
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323 |
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324 | if (label != NULL && memcmp(label, "NO NAME ", 11) != 0) {
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325 | // volume_id_set_label_raw(id, label, 11);
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326 | volume_id_set_label_string(id, label, 11);
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327 | } else if (memcmp(vs->type.fat32.label, "NO NAME ", 11) != 0) {
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328 | // volume_id_set_label_raw(id, vs->type.fat32.label, 11);
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329 | volume_id_set_label_string(id, vs->type.fat32.label, 11);
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330 | }
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331 | volume_id_set_uuid(id, vs->type.fat32.serno, UUID_DOS);
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332 |
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333 | ret:
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334 | // volume_id_set_usage(id, VOLUME_ID_FILESYSTEM);
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335 | // id->type = "vfat";
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336 |
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337 | return 0;
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338 | }
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