/* mksdcard.c
**
** Copyright 2007, The Android Open Source Project
**
** Redistribution and use in source and binary forms, with or without
** modification, are permitted provided that the following conditions are met:
** * Redistributions of source code must retain the above copyright
** notice, this list of conditions and the following disclaimer.
** * Redistributions in binary form must reproduce the above copyright
** notice, this list of conditions and the following disclaimer in the
** documentation and/or other materials provided with the distribution.
** * Neither the name of Google Inc. nor the names of its contributors may
** be used to endorse or promote products derived from this software
** without specific prior written permission.
**
** THIS SOFTWARE IS PROVIDED BY Google Inc. ``AS IS'' AND ANY EXPRESS OR
** IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
** MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
** EVENT SHALL Google Inc. BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
** PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
** OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
** WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
** OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
** ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/* a simple and portable program used to generate a blank FAT32 image file
*
* usage: mksdcard [-l label] <size> <filename>
*/
#include <time.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
/* believe me, you *don't* want to change these constants !! */
#define BYTES_PER_SECTOR 512
#define RESERVED_SECTORS 32
#define BACKUP_BOOT_SECTOR 6
#define NUM_FATS 2
typedef long long Wide; /* might be something else if you don't use GCC */
typedef unsigned char Byte;
typedef Byte* Bytes;
#define BYTE_(p,i) (((Bytes)(p))[(i)])
#define POKEB(p,v) BYTE_(p,0) = (Byte)(v)
#define POKES(p,v) ( BYTE_(p,0) = (Byte)(v), BYTE_(p,1) = (Byte)((v) >> 8) )
#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) )
static Byte s_boot_sector [ BYTES_PER_SECTOR ]; /* boot sector */
static Byte s_fsinfo_sector [ BYTES_PER_SECTOR ]; /* FS Info sector */
static Byte s_fat_head [ BYTES_PER_SECTOR ]; /* first FAT sector */
static Byte s_zero_sector [ BYTES_PER_SECTOR ]; /* empty sector */
/* this is the date and time when creating the disk */
static int
get_serial_id( void )
{
unsigned short lo, hi, mid;
time_t now = time(NULL);
struct tm tm = gmtime( &now )[0];
lo = (unsigned short)(tm.tm_mday + ((tm.tm_mon+1) << 8) + (tm.tm_sec << 8));
hi = (unsigned short)(tm.tm_min + (tm.tm_hour << 8) + (tm.tm_year + 1900));
return lo + (hi << 16);
}
static int
get_sectors_per_cluster( Wide disk_size )
{
Wide disk_MB = disk_size/(1024*1024);
if (disk_MB < 260)
return 1;
if (disk_MB < 8192)
return 4;
if (disk_MB < 16384)
return 8;
if (disk_MB < 32768)
return 16;
return 32;
}
static int
get_sectors_per_fat( Wide disk_size, int sectors_per_cluster )
{
Wide divider;
/* weird computation from MS - see fatgen103.doc for details */
disk_size -= RESERVED_SECTORS * BYTES_PER_SECTOR; /* don't count 32 reserved sectors */
disk_size /= BYTES_PER_SECTOR; /* disk size in sectors */
divider = ((256 * sectors_per_cluster) + NUM_FATS) / 2;
return (int)( (disk_size + (divider-1)) / divider );
}
static void
boot_sector_init( Bytes boot, Bytes info, Wide disk_size, const char* label )
{
int sectors_per_cluster = get_sectors_per_cluster(disk_size);
int sectors_per_fat = get_sectors_per_fat(disk_size, sectors_per_cluster);
int sectors_per_disk = (int)(disk_size / BYTES_PER_SECTOR);
int serial_id = get_serial_id();
int free_count;
if (label == NULL)
label = "SDCARD";
POKEB(boot, 0xeb);
POKEB(boot+1, 0x5a);
POKEB(boot+2, 0x90);
strcpy( (char*)boot + 3, "MSWIN4.1" );
POKES( boot + 0x0b, BYTES_PER_SECTOR ); /* sector size */
POKEB( boot + 0xd, sectors_per_cluster ); /* sectors per cluster */
POKES( boot + 0xe, RESERVED_SECTORS ); /* reserved sectors before first FAT */
POKEB( boot + 0x10, NUM_FATS ); /* number of FATs */
POKES( boot + 0x11, 0 ); /* max root directory entries for FAT12/FAT16, 0 for FAT32 */
POKES( boot + 0x13, 0 ); /* total sectors, 0 to use 32-bit value at offset 0x20 */
POKEB( boot + 0x15, 0xF8 ); /* media descriptor, 0xF8 == hard disk */
POKES( boot + 0x16, 0 ); /* Sectors per FAT for FAT12/16, 0 for FAT32 */
POKES( boot + 0x18, 9 ); /* Sectors per track (whatever) */
POKES( boot + 0x1a, 2 ); /* Number of heads (whatever) */
POKEW( boot + 0x1c, 0 ); /* Hidden sectors */
POKEW( boot + 0x20, sectors_per_disk ); /* Total sectors */
/* extension */
POKEW( boot + 0x24, sectors_per_fat ); /* Sectors per FAT */
POKES( boot + 0x28, 0 ); /* FAT flags */
POKES( boot + 0x2a, 0 ); /* version */
POKEW( boot + 0x2c, 2 ); /* cluster number of root directory start */
POKES( boot + 0x30, 1 ); /* sector number of FS information sector */
POKES( boot + 0x32, BACKUP_BOOT_SECTOR ); /* sector number of a copy of this boot sector */
POKEB( boot + 0x40, 0x80 ); /* physical drive number */
POKEB( boot + 0x42, 0x29 ); /* extended boot signature ?? */
POKEW( boot + 0x43, serial_id ); /* serial ID */
strncpy( (char*)boot + 0x47, label, 11 ); /* Volume Label */
memcpy( boot + 0x52, "FAT32 ", 8 ); /* FAT system type, padded with 0x20 */
POKEB( boot + BYTES_PER_SECTOR-2, 0x55 ); /* boot sector signature */
POKEB( boot + BYTES_PER_SECTOR-1, 0xAA );
/* FSInfo sector */
free_count = sectors_per_disk - 32 - 2*sectors_per_fat;
POKEW( info + 0, 0x41615252 );
POKEW( info + 484, 0x61417272 );
POKEW( info + 488, free_count ); /* number of free clusters */
POKEW( info + 492, 3 ); /* next free clusters, 0-1 reserved, 2 is used for the root dir */
POKEW( info + 508, 0xAA550000 );
}
static void
fat_init( Bytes fat )
{
POKEW( fat, 0x0ffffff8 ); /* reserve cluster 1, media id in low byte */
POKEW( fat + 4, 0x0fffffff ); /* reserve cluster 2 */
POKEW( fat + 8, 0x0fffffff ); /* end of clust chain for root dir */
}
static int
write_sector( FILE* file, Bytes sector )
{
return fwrite( sector, 1, 512, file ) != 512;
}
static int
write_empty( FILE* file, Wide count )
{
static Byte empty[64*1024];
count *= 512;
while (count > 0) {
int len = sizeof(empty);
if (len > count)
len = count;
if ( fwrite( empty, 1, len, file ) != (size_t)len )
return 1;
count -= len;
}
return 0;
}
static void usage (void)
{
fprintf(stderr, "mksdcard: create a blank FAT32 image to be used with the Android emulator\n" );
fprintf(stderr, "usage: mksdcard [-l label] <size> <file>\n\n");
fprintf(stderr, " if <size> is a simple integer, it specifies a size in bytes\n" );
fprintf(stderr, " if <size> is an integer followed by 'K', it specifies a size in KiB\n" );
fprintf(stderr, " if <size> is an integer followed by 'M', it specifies a size in MiB\n" );
exit(1);
}
int main( int argc, char** argv )
{
Wide disk_size;
int sectors_per_fat;
int sectors_per_disk;
char* end;
const char* label = NULL;
FILE* f;
for ( ; argc > 1 && argv[1][0] == '-'; argc--, argv++ )
{
char* arg = argv[1] + 1;
switch (arg[0]) {
case 'l':
if (arg[1] != 0)
arg += 2;
else {
argc--;
argv++;
if (argc <= 1)
usage();
arg = argv[1];
}
label = arg;
break;
default:
usage();
}
}
if (argc != 3)
usage();
disk_size = strtol( argv[1], &end, 10 );
if (disk_size == 0 && errno == EINVAL)
usage();
if (*end == 'K')
disk_size *= 1024;
else if (*end == 'M')
disk_size *= 1024*1024;
if (disk_size < 8*1024*1024)
fprintf(stderr, "### WARNING : SD Card images < 8 MB cannot be used with the Android emulator\n");
sectors_per_disk = disk_size / 512;
sectors_per_fat = get_sectors_per_fat( disk_size, get_sectors_per_cluster( disk_size ) );
boot_sector_init( s_boot_sector, s_fsinfo_sector, disk_size, NULL );
fat_init( s_fat_head );
f = fopen( argv[2], "wb" );
if ( !f ) {
fprintf(stderr, "could not create file '%s', aborting...\n", argv[2] );
}
/* here's the layout:
*
* boot_sector
* fsinfo_sector
* empty
* backup boot sector
* backup fsinfo sector
* RESERVED_SECTORS - 4 empty sectors (if backup sectors), or RESERVED_SECTORS - 2 (if no backup)
* first fat
* second fat
* zero sectors
*/
if ( write_sector( f, s_boot_sector ) ) goto FailWrite;
if ( write_sector( f, s_fsinfo_sector ) ) goto FailWrite;
if ( BACKUP_BOOT_SECTOR > 0 ) {
if ( write_empty( f, BACKUP_BOOT_SECTOR - 2 ) ) goto FailWrite;
if ( write_sector( f, s_boot_sector ) ) goto FailWrite;
if ( write_sector( f, s_fsinfo_sector ) ) goto FailWrite;
if ( write_empty( f, RESERVED_SECTORS - 2 - BACKUP_BOOT_SECTOR ) ) goto FailWrite;
}
else
if ( write_empty( f, RESERVED_SECTORS - 2 ) ) goto FailWrite;
if ( write_sector( f, s_fat_head ) ) goto FailWrite;
if ( write_empty( f, sectors_per_fat-1 ) ) goto FailWrite;
if ( write_sector( f, s_fat_head ) ) goto FailWrite;
if ( write_empty( f, sectors_per_fat-1 ) ) goto FailWrite;
if ( write_empty( f, sectors_per_disk - RESERVED_SECTORS - 2*sectors_per_fat ) ) goto FailWrite;
fclose(f);
return 0;
FailWrite:
fprintf(stderr, "could not write to '%s', aborting...\n", argv[2] );
unlink( argv[2] );
fclose(f);
return 1;
}