aboutsummaryrefslogtreecommitdiffstats
path: root/utils/isohybrid.in
blob: a0487ca08d3ee3335df99552f38c049df70ae13d (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
#!/usr/bin/perl
## -----------------------------------------------------------------------
##
##   Copyright 2002-2008 H. Peter Anvin - All Rights Reserved
##
##   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.
##
## -----------------------------------------------------------------------

#
# Post-process an ISO 9660 image generated with mkisofs/genisoimage
# to allow "hybrid booting" as a CD-ROM or as a hard disk.
#

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

# Use this fake geometry (zipdrive-style...)
$h = 64; $s = 32;

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

    if (sysopen($rfd, '/dev/urandom', O_RDONLY) &&
	sysread($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;
}


($file) = @ARGV;
open(FILE, "+< $file\0") or die "$0: cannot open $file: $!\n";
binmode FILE;

#
# First, actually figure out where mkisofs hid isolinux.bin
#
seek(FILE, 17*2048, SEEK_SET) or die "$0: $file: $!\n";
read(FILE, $boot_record, 2048) == 2048 or die "$0: $file: read error\n";
($br_sign, $br_cat_offset) = unpack("a71V", $boot_record);
if ($br_sign ne ("\0CD001\1EL TORITO SPECIFICATION" . ("\0" x 41))) {
    die "$0: $file: no boot record found\n";
}
seek(FILE, $br_cat_offset*2048, SEEK_SET) or die "$0: $file: $!\n";
read(FILE, $boot_cat, 2048) == 2048 or die "$0: $file: read error\n";

# We must have a Validation Entry followed by a Default Entry...
# no fanciness allowed for the Hybrid mode [XXX: might relax this later]
@ve = unpack("v16", $boot_cat);
$cs = 0;
for ($i = 0; $i < 16; $i++) {
    $cs += $ve[$i];
}
if ($ve[0] != 0x0001 || $ve[15] != 0xaa55 || $cs & 0xffff) {
    die "$0: $file: invalid boot catalog\n";
}
($de_boot, $de_media, $de_seg, $de_sys, $de_mbz1, $de_count, 
 $de_lba, $de_mbz2) = unpack("CCvCCvVv", substr($boot_cat, 32, 32));
if ($de_boot != 0x88 || $de_media != 0 ||
    ($de_segment != 0 && $de_segment != 0x7c0) || $de_count != 4) {
    die "$0: $file: unexpected boot catalog parameters\n";
}

# Get the total size of the image
(@imgstat = stat(FILE)) or die "$0: $file: $!\n";
$imgsize = $imgstat[7];
if (!$imgsize) {
    die "$0: $file: cannot determine length of file\n";
}
# Target image size: round up to a multiple of $h*$s*512
$cylsize = $h*$s*512;
$frac = $imgsize % $cylsize;
$padding = ($frac > 0) ? $cylsize - $frac : 0;
$imgsize += $padding;
$c = $imgsize/$cylsize;
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;
}

# Now $de_lba should contain the CD sector number for isolinux.bin
seek(FILE, 0, SEEK_SET) or die "$0: $file: $!\n";

# Print the MBR and partition table
$mbr = '';
while ( $line = <DATA> ) {
    chomp $line;
    foreach $byte ( split(/\s+/, $line) ) {
	$mbr .= chr(hex($byte));
    }
}
if ( length($mbr) > 432 ) {
    die "$0: Bad MBR code\n";
}

$mbr .= "\0" x (432 - length($mbr));

$mbr .= pack("VV", $de_lba*4, 0); # Offset 432: LBA of isolinux.bin
if (defined($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 partition table
$psize = $c*$h*$s-$s;
$bhead   = 0;
$bsect   = 1;
$bcyl    = 0;
$ehead   = $h-1;
$esect   = $s + ((($cc-1) & 0x300) >> 2);
$ecyl    = ($cc-1) & 0xff;
$fstype  = 0x83;		# Linux (any better ideas?)
$pentry  = 1;
if ( $c > 1024 ) {
    $fstype = 0x0e;
} elsif ( $psize > 65536 ) {
    $fstype = 0x06;
} else {
    $fstype = 0x04;
}
for ( $i = 1 ; $i <= 4 ; $i++ ) {
    if ( $i == $pentry ) {
	$mbr .= pack("CCCCCCCCVV", 0x80, $bhead, $bsect, $bcyl, $fstype,
		     $ehead, $esect, $ecyl, $s, $psize);
    } else {
	$mbr .= "\0" x 16;
    }
}
$mbr .= "\x55\xaa";

print FILE $mbr;

# Pad the image to a fake cylinder boundary
seek(FILE, $imgstat[7], SEEK_SET) or die "$0: $file: $!\n";
if ($padding) {
    print FILE "\0" x $padding;
}

# Done...
close(FILE);

exit 0;
__END__