source: bootcd/isolinux/syslinux-6.03/bios/utils/mkdiskimage @ 26ffad7

#!/usr/bin/perl
## -----------------------------------------------------------------------
##
##   Copyright 2002-2008 H. Peter Anvin - All Rights Reserved
##   Copyright 2009-2010 Intel Corporation; author: H. Peter Anvin
##
##   This program is free software; you can redistribute it and/or modify
##   it under the terms of the GNU General Public License as published by
##   the Free Software Foundation, Inc., 53 Temple Place Ste 330,
##   Boston MA 02111-1307, USA; either version 2 of the License, or
##   (at your option) any later version; incorporated herein by reference.
##
## -----------------------------------------------------------------------

#
# Creates a blank MS-DOS formatted hard disk image
#

use bytes;
use integer;
use Fcntl;
use Errno;
use Cwd;
use IO::Handle;                 # For flush()

sub absolute_path($) {
    my($f) = @_;
    my($c);

    return $f if ( $f =~ /^\// );
    $c = cwd();
    $c = '' if ( $c eq '/' );
    return $c.'/'.$f;
}

sub is_linux() {
    return !!eval '{ '.
        'use POSIX; '.
        '($sysname, $nodename, $release, $version, $machine) = POSIX::uname(); '.
        "return \$sysname eq \'Linux\'; }";
}

sub get_random() {
    # Get a 32-bit random number
    my $rfd, $rnd;
    my $rid;

    if (open($rfd, "< /dev/urandom\0") && read($rfd, $rnd, 4) == 4) {
        $rid = unpack("V", $rnd);
    }

    close($rfd) if (defined($rfd));
    return $rid if (defined($rid));

    # This sucks but is better than nothing...
    return ($$+time()) & 0xffffffff;
}

sub get_hex_data() {
    my $mbr = '';
    my $line, $byte;
    while ( $line = <DATA> ) {
        chomp $line;
        last if ($line eq '*');
        foreach $byte ( split(/\s+/, $line) ) {
            $mbr .= chr(hex($byte));
        }
    }
    return $mbr;
}

$is_linux = is_linux();
if ( $is_linux ) {
    # IOCTL numbers
    $BLKRRPART    = 0x125f;
    $BLKGETSIZE   = 0x1260;
}

%opt = ();
@args = ();

while (defined($a = shift(@ARGV))) {
    if ( $a =~ /^\-/ ) {
        foreach $o ( split(//, substr($a,1)) ) {
            $opt{$o} = 1;
            if ($o eq 'i') {
                $id = shift(@ARGV);
            }
        }
    } else {
        push(@args, $a);
    }
}

($file,$c,$h,$s) = @args;
$c += 0;  $h += 0;  $s += 0;

$pentry = 1;
$pentry = 2 if ( $opt{'2'} );
$pentry = 3 if ( $opt{'3'} );
$pentry = 4 if ( $opt{'4'} );

if ( $opt{'z'} ) {
    $h = $h || 64;
    $s = $s || 32;
}

if ( $opt{'M'} && $h && $s ) {
    # Specify size in megabytes, not in cylinders
    $c = ($c*1024*2)/($h*$s);
}

$is_open = 0;

if ( $c == 0 && $file ne '' ) {
    $len = 0;
    if ( sysopen(OUTPUT, $file, O_RDWR, 0666) ) {
        $is_open = 1;

        if ( (@filestat = stat(OUTPUT)) && S_ISREG($filestat[2]) ) {
            $len = $filestat[7] >> 9;
        } elsif ( $is_linux && S_ISBLK($filestat[2]) ) {
            $blksize = pack("L!", 0);
            if ( ioctl(OUTPUT, $BLKGETSIZE, $blksize) == 0 ) {
                $len = unpack("L!", $blksize); # In 512-byte sectors!
            }
        }
    }

    if ( !$len ) {
        print STDERR "$0: $file: don't know how to determine the size of this device\n";
        exit 1;
    }

    $c = $len/($h*$s);
}

if ( $file eq '' || $c < 1 || $h < 1 || $h > 256 || $s < 1 || $s > 63 ) {
    print STDERR "Usage: $0 [-doFMz4][-i id] file c h s (max: 1024 256 63)\n";
    print STDERR "    -d    add DOSEMU header\n";
    print STDERR "    -o    print filesystem offset to stdout\n";
    print STDERR "    -F    format partition as FAT32\n";
    print STDERR "    -M    \"c\" argument is megabytes, calculate cylinders\n";
    print STDERR "    -z    use zipdisk geometry (h=64 s=32)\n";
    print STDERR "    -4    use partition entry 4 (standard for zipdisks)\n";
    print STDERR "    -i    specify the MBR ID\n";
    print STDERR "    -s    output a sparse file (don't allocate all blocks)\n";
    exit 1;
}

if ($c > 1024) {
    print STDERR "Warning: more than 1024 cylinders ($c).\n";
    print STDERR "Not all BIOSes will be able to boot this device.\n";
    $cc = 1024;
} else {
    $cc = $c;
}

$cylsize = $h*$s*512;

if ( !$is_open ) {
    sysopen(OUTPUT, $file, O_CREAT|O_RDWR|O_TRUNC, 0666)
        or die "$0: Cannot open: $file\n";
}
binmode OUTPUT;

# Print out DOSEMU header, if requested
if ( $opt{'d'} ) {
    $emuhdr = "DOSEMU\0" . pack("VVVV", $h, $s, $c, 128);
    $emuhdr .= "\0" x (128 - length($emuhdr));
    print OUTPUT $emuhdr;
}

# Print the MBR and partition table
$mbr = get_hex_data();
if ( length($mbr) > 440 ) {
    die "$0: Bad MBR code\n";
}

$mbr .= "\0" x (440 - length($mbr));
if (defined($id)) {
    $id = to_int($id);
} else {
    $id = get_random();
}
$mbr .= pack("V", $id);         # Offset 440: MBR ID
$mbr .= "\0\0";                 # Offset 446: actual partition table

print OUTPUT $mbr;

# Print partition table
$psize = $c*$h*$s-$s;
$bhead   = ($h > 1) ? 1 : 0;
$bsect   = 1;
$bcyl    = ($h > 1) ? 0 : 1;
$ehead   = $h-1;
$esect   = $s + ((($cc-1) & 0x300) >> 2);
$ecyl    = ($cc-1) & 0xff;
if ( $c > 1024 ) {
    $fstype = 0x0e;
} elsif ( $psize > 65536 ) {
    $fstype = 0x06;
} else {
    $fstype = 0x04;
}
for ( $i = 1 ; $i <= 4 ; $i++ ) {
    if ( $i == $pentry ) {
        print OUTPUT pack("CCCCCCCCVV", 0x80, $bhead, $bsect, $bcyl, $fstype,
                          $ehead, $esect, $ecyl, $s, $psize);
    } else {
        print OUTPUT "\0" x 16;
    }
}
print OUTPUT "\x55\xaa";

# Output blank file
$totalsize = $c*$h*$s;
$tracks    = $c*$h;

# If -s is given, try to simply use truncate...
unless ($opt{'s'} && truncate(OUTPUT, $totalsize)) {
    $track = "\0" x (512*$s);

    # Print fractional track
    print OUTPUT "\0" x (512 * ($s-1));

    for ( $i = 1 ; $i < $tracks ; $i++ ) {
        print OUTPUT $track;
    }
}

# Print mtools temp file
$n = 0;
while ( !defined($tmpdir) ) {
    $tmpdir = "/tmp/mkdiskimage.$$.".($n++);
    if ( !mkdir($tmpdir, 0700) ) {
        die "$0: Failed to make temp directory: $tmpdir\n"
            if ( $! != EEXIST );
        undef $tmpdir;
    }
}

$cfgfile = $tmpdir.'/mtools.conf';
$imglink = $tmpdir.'/disk.img';
die "$0: Failed to create symlink $imglink\n"
    if ( !symlink(absolute_path($file), $imglink) );

$header_size = ($opt{'d'} ? 128 : 0);

# Start of filesystem
$offset = $s*512 + $header_size;

# Start of partition table entry
$pstart = $header_size + 446 + 16*($pentry-1);

open(MCONFIG, "> ${cfgfile}") or die "$0: Cannot make mtools config\n";
print MCONFIG "drive z:\n";
print MCONFIG "file=\"${imglink}\"\n";
print MCONFIG "cylinders=${c}\n";
print MCONFIG "heads=${h}\n";
print MCONFIG "sectors=${s}\n";
print MCONFIG "offset=${offset}\n";
print MCONFIG "mformat_only\n";
close(MCONFIG);

# Output the filesystem offset to stdout if appropriate
if ( $opt{'o'} ) {
    print $offset, "\n";
}

$ENV{'MTOOLSRC'} = $cfgfile;
if ( $opt{'F'} ) {
    system('mformat', '-F', 'z:');
} else {
    system('mformat', 'z:');
}

# Clean up in /tmp
unlink($cfgfile);
unlink($imglink);
rmdir($tmpdir);

# MTOOLS doesn't write the bsHiddenSecs field correctly
seek(OUTPUT, $offset + 0x1c, 0);
print OUTPUT pack("V", ($offset-$header_size)>>9);

# Set the partition type
if ( $opt{'F'} ) {
    if ( $c > 1024 ) {
        $fstype = 0x0c;         # FAT32 LBA
    } else {
        $fstype = 0x0b;
    }
} else {
    if ( $c > 1024 ) {
        $fstype = 0x0e;         # FAT16 LBA
    } elsif ( $psize > 65536 ) {
        $fstype = 0x06;         # FAT16 > 32MB
    } else {
        $fstype = 0x04;         # FAT16 <= 32MB
    }
    seek(OUTPUT, $offset + 0x36, 0);
    read(OUTPUT, $fsname, 8);

    # FAT12: adjust partition type
    if ( $fsname eq 'FAT12   ' ) {
        $fstype = 0x01;         # FAT12
    }
}
seek(OUTPUT, $pstart+4, 0);
print OUTPUT pack("C", $fstype);

flush OUTPUT;

# Just in case this is a block device, try to flush the partition table
if ( $is_linux ) {
    ioctl(OUTPUT, $BLKRRPART, 0);
};

exit 0;
__END__
33 c0 fa 8e d8 8e d0 bc 0 7c 89 e6 6 57 8e c0 fb fc bf 0 6 b9 0 1 f3 a5 ea
1f 6 0 0 52 52 b4 41 bb aa 55 31 c9 30 f6 f9 cd 13 72 13 81 fb 55 aa 75 d
d1 e9 73 9 66 c7 6 8d 6 b4 42 eb 15 5a b4 8 cd 13 83 e1 3f 51 f b6 c6 40 f7
e1 52 50 66 31 c0 66 99 e8 66 0 e8 35 1 4d 69 73 73 69 6e 67 20 6f 70 65 72
61 74 69 6e 67 20 73 79 73 74 65 6d 2e d a 66 60 66 31 d2 bb 0 7c 66 52 66
50 6 53 6a 1 6a 10 89 e6 66 f7 36 f4 7b c0 e4 6 88 e1 88 c5 92 f6 36 f8 7b
88 c6 8 e1 41 b8 1 2 8a 16 fa 7b cd 13 8d 64 10 66 61 c3 e8 c4 ff be be 7d
bf be 7 b9 20 0 f3 a5 c3 66 60 89 e5 bb be 7 b9 4 0 31 c0 53 51 f6 7 80 74
3 40 89 de 83 c3 10 e2 f3 48 74 5b 79 39 59 5b 8a 47 4 3c f 74 6 24 7f 3c
5 75 22 66 8b 47 8 66 8b 56 14 66 1 d0 66 21 d2 75 3 66 89 c2 e8 ac ff 72
3 e8 b6 ff 66 8b 46 1c e8 a0 ff 83 c3 10 e2 cc 66 61 c3 e8 76 0 4d 75 6c 74
69 70 6c 65 20 61 63 74 69 76 65 20 70 61 72 74 69 74 69 6f 6e 73 2e d a 66
8b 44 8 66 3 46 1c 66 89 44 8 e8 30 ff 72 27 66 81 3e 0 7c 58 46 53 42 75
9 66 83 c0 4 e8 1c ff 72 13 81 3e fe 7d 55 aa f 85 f2 fe bc fa 7b 5a 5f 7
fa ff e4 e8 1e 0 4f 70 65 72 61 74 69 6e 67 20 73 79 73 74 65 6d 20 6c 6f
61 64 20 65 72 72 6f 72 2e d a 5e ac b4 e 8a 3e 62 4 b3 7 cd 10 3c a 75 f1
cd 18 f4 eb fd 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 
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