/* 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; }