1 /* mksdcard.c 2 ** 3 ** Copyright 2007, The Android Open Source Project 4 ** 5 ** Redistribution and use in source and binary forms, with or without 6 ** modification, are permitted provided that the following conditions are met: 7 ** * Redistributions of source code must retain the above copyright 8 ** notice, this list of conditions and the following disclaimer. 9 ** * Redistributions in binary form must reproduce the above copyright 10 ** notice, this list of conditions and the following disclaimer in the 11 ** documentation and/or other materials provided with the distribution. 12 ** * Neither the name of Google Inc. nor the names of its contributors may 13 ** be used to endorse or promote products derived from this software 14 ** without specific prior written permission. 15 ** 16 ** THIS SOFTWARE IS PROVIDED BY Google Inc. ``AS IS'' AND ANY EXPRESS OR 17 ** IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF 18 ** MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO 19 ** EVENT SHALL Google Inc. BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 20 ** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, 21 ** PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; 22 ** OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, 23 ** WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR 24 ** OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF 25 ** ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 26 */ 27 28 /* a simple and portable program used to generate a blank FAT32 image file 29 * 30 * usage: mksdcard [-l label] <size> <filename> 31 */ 32 33 #include <time.h> 34 #include <stdio.h> 35 #include <stdlib.h> 36 #include <string.h> 37 #include <errno.h> 38 #include <unistd.h> 39 40 /* believe me, you *don't* want to change these constants !! */ 41 #define BYTES_PER_SECTOR 512 42 #define RESERVED_SECTORS 32 43 #define BACKUP_BOOT_SECTOR 6 44 #define NUM_FATS 2 45 46 typedef long long Wide; /* might be something else if you don't use GCC */ 47 typedef unsigned char Byte; 48 typedef Byte* Bytes; 49 50 #define BYTE_(p,i) (((Bytes)(p))[(i)]) 51 52 #define POKEB(p,v) BYTE_(p,0) = (Byte)(v) 53 #define POKES(p,v) ( BYTE_(p,0) = (Byte)(v), BYTE_(p,1) = (Byte)((v) >> 8) ) 54 #define POKEW(p,v) ( BYTE_(p,0) = (Byte)(v), BYTE_(p,1) = (Byte)((v) >> 8), BYTE_(p,2) = (Byte)((v) >> 16), BYTE_(p,3) = (Byte)((v) >> 24) ) 55 56 static Byte s_boot_sector [ BYTES_PER_SECTOR ]; /* boot sector */ 57 static Byte s_fsinfo_sector [ BYTES_PER_SECTOR ]; /* FS Info sector */ 58 static Byte s_fat_head [ BYTES_PER_SECTOR ]; /* first FAT sector */ 59 static Byte s_zero_sector [ BYTES_PER_SECTOR ]; /* empty sector */ 60 61 /* this is the date and time when creating the disk */ 62 static int 63 get_serial_id( void ) 64 { 65 unsigned short lo, hi, mid; 66 time_t now = time(NULL); 67 struct tm tm = gmtime( &now )[0]; 68 69 lo = (unsigned short)(tm.tm_mday + ((tm.tm_mon+1) << 8) + (tm.tm_sec << 8)); 70 hi = (unsigned short)(tm.tm_min + (tm.tm_hour << 8) + (tm.tm_year + 1900)); 71 72 return lo + (hi << 16); 73 } 74 75 static int 76 get_sectors_per_cluster( Wide disk_size ) 77 { 78 Wide disk_MB = disk_size/(1024*1024); 79 80 if (disk_MB < 260) 81 return 1; 82 83 if (disk_MB < 8192) 84 return 4; 85 86 if (disk_MB < 16384) 87 return 8; 88 89 if (disk_MB < 32768) 90 return 16; 91 92 return 32; 93 } 94 95 static int 96 get_sectors_per_fat( Wide disk_size, int sectors_per_cluster ) 97 { 98 Wide divider; 99 100 /* weird computation from MS - see fatgen103.doc for details */ 101 disk_size -= RESERVED_SECTORS * BYTES_PER_SECTOR; /* don't count 32 reserved sectors */ 102 disk_size /= BYTES_PER_SECTOR; /* disk size in sectors */ 103 divider = ((256 * sectors_per_cluster) + NUM_FATS) / 2; 104 105 return (int)( (disk_size + (divider-1)) / divider ); 106 } 107 108 static void 109 boot_sector_init( Bytes boot, Bytes info, Wide disk_size, const char* label ) 110 { 111 int sectors_per_cluster = get_sectors_per_cluster(disk_size); 112 int sectors_per_fat = get_sectors_per_fat(disk_size, sectors_per_cluster); 113 int sectors_per_disk = (int)(disk_size / BYTES_PER_SECTOR); 114 int serial_id = get_serial_id(); 115 int free_count; 116 117 if (label == NULL) 118 label = "SDCARD"; 119 120 POKEB(boot, 0xeb); 121 POKEB(boot+1, 0x5a); 122 POKEB(boot+2, 0x90); 123 strcpy( (char*)boot + 3, "MSWIN4.1" ); 124 POKES( boot + 0x0b, BYTES_PER_SECTOR ); /* sector size */ 125 POKEB( boot + 0xd, sectors_per_cluster ); /* sectors per cluster */ 126 POKES( boot + 0xe, RESERVED_SECTORS ); /* reserved sectors before first FAT */ 127 POKEB( boot + 0x10, NUM_FATS ); /* number of FATs */ 128 POKES( boot + 0x11, 0 ); /* max root directory entries for FAT12/FAT16, 0 for FAT32 */ 129 POKES( boot + 0x13, 0 ); /* total sectors, 0 to use 32-bit value at offset 0x20 */ 130 POKEB( boot + 0x15, 0xF8 ); /* media descriptor, 0xF8 == hard disk */ 131 POKES( boot + 0x16, 0 ); /* Sectors per FAT for FAT12/16, 0 for FAT32 */ 132 POKES( boot + 0x18, 9 ); /* Sectors per track (whatever) */ 133 POKES( boot + 0x1a, 2 ); /* Number of heads (whatever) */ 134 POKEW( boot + 0x1c, 0 ); /* Hidden sectors */ 135 POKEW( boot + 0x20, sectors_per_disk ); /* Total sectors */ 136 137 /* extension */ 138 POKEW( boot + 0x24, sectors_per_fat ); /* Sectors per FAT */ 139 POKES( boot + 0x28, 0 ); /* FAT flags */ 140 POKES( boot + 0x2a, 0 ); /* version */ 141 POKEW( boot + 0x2c, 2 ); /* cluster number of root directory start */ 142 POKES( boot + 0x30, 1 ); /* sector number of FS information sector */ 143 POKES( boot + 0x32, BACKUP_BOOT_SECTOR ); /* sector number of a copy of this boot sector */ 144 POKEB( boot + 0x40, 0x80 ); /* physical drive number */ 145 POKEB( boot + 0x42, 0x29 ); /* extended boot signature ?? */ 146 POKEW( boot + 0x43, serial_id ); /* serial ID */ 147 strncpy( (char*)boot + 0x47, label, 11 ); /* Volume Label */ 148 memcpy( boot + 0x52, "FAT32 ", 8 ); /* FAT system type, padded with 0x20 */ 149 150 POKEB( boot + BYTES_PER_SECTOR-2, 0x55 ); /* boot sector signature */ 151 POKEB( boot + BYTES_PER_SECTOR-1, 0xAA ); 152 153 /* FSInfo sector */ 154 free_count = sectors_per_disk - 32 - 2*sectors_per_fat; 155 156 POKEW( info + 0, 0x41615252 ); 157 POKEW( info + 484, 0x61417272 ); 158 POKEW( info + 488, free_count ); /* number of free clusters */ 159 POKEW( info + 492, 3 ); /* next free clusters, 0-1 reserved, 2 is used for the root dir */ 160 POKEW( info + 508, 0xAA550000 ); 161 } 162 163 static void 164 fat_init( Bytes fat ) 165 { 166 POKEW( fat, 0x0ffffff8 ); /* reserve cluster 1, media id in low byte */ 167 POKEW( fat + 4, 0x0fffffff ); /* reserve cluster 2 */ 168 POKEW( fat + 8, 0x0fffffff ); /* end of clust chain for root dir */ 169 } 170 171 172 static int 173 write_sector( FILE* file, Bytes sector ) 174 { 175 return fwrite( sector, 1, 512, file ) != 512; 176 } 177 178 static int 179 write_empty( FILE* file, Wide count ) 180 { 181 static Byte empty[64*1024]; 182 183 count *= 512; 184 while (count > 0) { 185 int len = sizeof(empty); 186 if (len > count) 187 len = count; 188 189 if ( fwrite( empty, 1, len, file ) != (size_t)len ) 190 return 1; 191 192 count -= len; 193 } 194 return 0; 195 } 196 197 static void usage (void) 198 { 199 fprintf(stderr, "mksdcard: create a blank FAT32 image to be used with the Android emulator\n" ); 200 fprintf(stderr, "usage: mksdcard [-l label] <size> <file>\n\n"); 201 fprintf(stderr, " if <size> is a simple integer, it specifies a size in bytes\n" ); 202 fprintf(stderr, " if <size> is an integer followed by 'K', it specifies a size in KiB\n" ); 203 fprintf(stderr, " if <size> is an integer followed by 'M', it specifies a size in MiB\n" ); 204 exit(1); 205 } 206 207 int main( int argc, char** argv ) 208 { 209 Wide disk_size; 210 int sectors_per_fat; 211 int sectors_per_disk; 212 char* end; 213 const char* label = NULL; 214 FILE* f; 215 216 for ( ; argc > 1 && argv[1][0] == '-'; argc--, argv++ ) 217 { 218 char* arg = argv[1] + 1; 219 switch (arg[0]) { 220 case 'l': 221 if (arg[1] != 0) 222 arg += 2; 223 else { 224 argc--; 225 argv++; 226 if (argc <= 1) 227 usage(); 228 arg = argv[1]; 229 } 230 label = arg; 231 break; 232 233 default: 234 usage(); 235 } 236 } 237 238 if (argc != 3) 239 usage(); 240 241 disk_size = strtol( argv[1], &end, 10 ); 242 if (disk_size == 0 && errno == EINVAL) 243 usage(); 244 245 if (*end == 'K') 246 disk_size *= 1024; 247 else if (*end == 'M') 248 disk_size *= 1024*1024; 249 250 if (disk_size < 8*1024*1024) 251 fprintf(stderr, "### WARNING : SD Card images < 8 MB cannot be used with the Android emulator\n"); 252 253 sectors_per_disk = disk_size / 512; 254 sectors_per_fat = get_sectors_per_fat( disk_size, get_sectors_per_cluster( disk_size ) ); 255 256 boot_sector_init( s_boot_sector, s_fsinfo_sector, disk_size, NULL ); 257 fat_init( s_fat_head ); 258 259 f = fopen( argv[2], "wb" ); 260 if ( !f ) { 261 fprintf(stderr, "could not create file '%s', aborting...\n", argv[2] ); 262 } 263 264 /* here's the layout: 265 * 266 * boot_sector 267 * fsinfo_sector 268 * empty 269 * backup boot sector 270 * backup fsinfo sector 271 * RESERVED_SECTORS - 4 empty sectors (if backup sectors), or RESERVED_SECTORS - 2 (if no backup) 272 * first fat 273 * second fat 274 * zero sectors 275 */ 276 277 if ( write_sector( f, s_boot_sector ) ) goto FailWrite; 278 if ( write_sector( f, s_fsinfo_sector ) ) goto FailWrite; 279 if ( BACKUP_BOOT_SECTOR > 0 ) { 280 if ( write_empty( f, BACKUP_BOOT_SECTOR - 2 ) ) goto FailWrite; 281 if ( write_sector( f, s_boot_sector ) ) goto FailWrite; 282 if ( write_sector( f, s_fsinfo_sector ) ) goto FailWrite; 283 if ( write_empty( f, RESERVED_SECTORS - 2 - BACKUP_BOOT_SECTOR ) ) goto FailWrite; 284 } 285 else 286 if ( write_empty( f, RESERVED_SECTORS - 2 ) ) goto FailWrite; 287 288 if ( write_sector( f, s_fat_head ) ) goto FailWrite; 289 if ( write_empty( f, sectors_per_fat-1 ) ) goto FailWrite; 290 291 if ( write_sector( f, s_fat_head ) ) goto FailWrite; 292 if ( write_empty( f, sectors_per_fat-1 ) ) goto FailWrite; 293 294 if ( write_empty( f, sectors_per_disk - RESERVED_SECTORS - 2*sectors_per_fat ) ) goto FailWrite; 295 296 fclose(f); 297 return 0; 298 299 FailWrite: 300 fprintf(stderr, "could not write to '%s', aborting...\n", argv[2] ); 301 unlink( argv[2] ); 302 fclose(f); 303 return 1; 304 } 305
