1#!/usr/bin/perl
2## -----------------------------------------------------------------------
3##
4##   Copyright 2002-2008 H. Peter Anvin - All Rights Reserved
5##   Copyright 2009 Intel Corporation; author: H. Peter Anvin
6##
7##   This program is free software; you can redistribute it and/or modify
8##   it under the terms of the GNU General Public License as published by
9##   the Free Software Foundation, Inc., 53 Temple Place Ste 330,
10##   Boston MA 02111-1307, USA; either version 2 of the License, or
11##   (at your option) any later version; incorporated herein by reference.
12##
13## -----------------------------------------------------------------------
14
15#
16# Post-process an ISO 9660 image generated with mkisofs/genisoimage
17# to allow "hybrid booting" as a CD-ROM or as a hard disk.
18#
19
20use bytes;
21use Fcntl;
22
23# User-specifyable options
24%opt = (
25    # Fake geometry (zipdrive-style...)
26    'h'      => 64,
27    's'      => 32,
28    # Partition number
29    'entry'  => 1,
30    # Partition offset
31    'offset' => 0,
32    # Partition type
33    'type'   => 0x17,		# "Windows hidden IFS"
34    # MBR ID
35    'id'     => undef,
36);
37
38%valid_range = (
39    'h'      => [1, 256],
40    's'      => [1, 63],
41    'entry'  => [1, 4],
42    'offset' => [0, 64],
43    'type'   => [0, 255],
44    'id'     => [0, 0xffffffff],
45    'hd0'    => [0, 2],
46    'partok' => [0, 1],
47);
48
49# Boolean options just set other options
50%bool_opt = (
51    'nohd0'    => ['hd0', 0],
52    'forcehd0' => ['hd0', 1],
53    'ctrlhd0'  => ['hd0', 2],
54    'nopartok' => ['partok', 0],
55    'partok'   => ['partok', 1],
56);
57
58sub usage() {
59    print STDERR "Usage: $0 [options] filename.iso\n",
60    "Options:\n",
61    "  -h          Number of default geometry heads\n",
62    "  -s          Number of default geometry sectors\n",
63    "  -entry      Specify partition entry number (1-4)\n",
64    "  -offset     Specify partition offset (default 0)\n",
65    "  -type       Specify partition type (default 0x17)\n",
66    "  -id         Specify MBR ID (default random)\n",
67    "  -forcehd0   Always assume we are loaded as disk ID 0\n",
68    "  -ctrlhd0    Assume disk ID 0 if the Ctrl key is pressed\n",
69    "  -partok     Allow booting from within a partition\n";
70    exit 1;
71}
72
73# Parse a C-style integer (decimal/octal/hex)
74sub doh($) {
75    my($n) = @_;
76    return ($n =~ /^0/) ? oct $n : $n+0;
77}
78
79sub get_random() {
80    # Get a 32-bit random number
81    my $rfd, $rnd;
82    my $rid;
83
84    if (open($rfd, "< /dev/urandom\0") && read($rfd, $rnd, 4) == 4) {
85	$rid = unpack("V", $rnd);
86    }
87
88    close($rfd) if (defined($rfd));
89    return $rid if (defined($rid));
90
91    # This sucks but is better than nothing...
92    return ($$+time()) & 0xffffffff;
93}
94
95sub get_hex_data() {
96    my $mbr = '';
97    my $line, $byte;
98    while ( $line = <DATA> ) {
99	chomp $line;
100	last if ($line eq '*');
101	foreach $byte ( split(/\s+/, $line) ) {
102	    $mbr .= chr(hex($byte));
103	}
104    }
105    return $mbr;
106}
107
108while ($ARGV[0] =~ /^\-(.*)$/) {
109    $o = $1;
110    shift @ARGV;
111    if (defined($bool_opt{$o})) {
112	($o, $v) = @{$bool_opt{$o}};
113	$opt{$o} = $v;
114    } elsif (exists($opt{$o})) {
115	$opt{$o} = doh(shift @ARGV);
116	if (defined($valid_range{$o})) {
117	    ($l, $h) = @{$valid_range{$o}};
118	    if ($opt{$o} < $l || $opt{$o} > $h) {
119		die "$0: valid values for the -$o parameter are $l to $h\n";
120	    }
121	}
122    } else {
123	usage();
124    }
125}
126
127($file) = @ARGV;
128
129if (!defined($file)) {
130    usage();
131}
132
133open(FILE, "+< $file\0") or die "$0: cannot open $file: $!\n";
134binmode FILE;
135
136#
137# First, actually figure out where mkisofs hid isolinux.bin
138#
139seek(FILE, 17*2048, SEEK_SET) or die "$0: $file: $!\n";
140read(FILE, $boot_record, 2048) == 2048 or die "$0: $file: read error\n";
141($br_sign, $br_cat_offset) = unpack("a71V", $boot_record);
142if ($br_sign ne ("\0CD001\1EL TORITO SPECIFICATION" . ("\0" x 41))) {
143    die "$0: $file: no boot record found\n";
144}
145seek(FILE, $br_cat_offset*2048, SEEK_SET) or die "$0: $file: $!\n";
146read(FILE, $boot_cat, 2048) == 2048 or die "$0: $file: read error\n";
147
148# We must have a Validation Entry followed by a Default Entry...
149# no fanciness allowed for the Hybrid mode [XXX: might relax this later]
150@ve = unpack("v16", $boot_cat);
151$cs = 0;
152for ($i = 0; $i < 16; $i++) {
153    $cs += $ve[$i];
154}
155if ($ve[0] != 0x0001 || $ve[15] != 0xaa55 || $cs & 0xffff) {
156    die "$0: $file: invalid boot catalog\n";
157}
158($de_boot, $de_media, $de_seg, $de_sys, $de_mbz1, $de_count, 
159 $de_lba, $de_mbz2) = unpack("CCvCCvVv", substr($boot_cat, 32, 32));
160if ($de_boot != 0x88 || $de_media != 0 ||
161    ($de_segment != 0 && $de_segment != 0x7c0) || $de_count != 4) {
162    die "$0: $file: unexpected boot catalog parameters\n";
163}
164
165# Now $de_lba should contain the CD sector number for isolinux.bin
166seek(FILE, $de_lba*2048+0x40, SEEK_SET) or die "$0: $file: $!\n";
167read(FILE, $ibsig, 4);
168if ($ibsig ne "\xfb\xc0\x78\x70") {
169    die "$0: $file: bootloader does not have a isolinux.bin hybrid signature.".
170        "Note that isolinux-debug.bin does not support hybrid booting.\n";
171}
172
173# Get the total size of the image
174(@imgstat = stat(FILE)) or die "$0: $file: $!\n";
175$imgsize = $imgstat[7];
176if (!$imgsize) {
177    die "$0: $file: cannot determine length of file\n";
178}
179# Target image size: round up to a multiple of $h*$s*512
180$h = $opt{'h'};
181$s = $opt{'s'};
182$cylsize = $h*$s*512;
183$frac = $imgsize % $cylsize;
184$padding = ($frac > 0) ? $cylsize - $frac : 0;
185$imgsize += $padding;
186$c = int($imgsize/$cylsize);
187if ($c > 1024) {
188    print STDERR "Warning: more than 1024 cylinders ($c).\n";
189    print STDERR "Not all BIOSes will be able to boot this device.\n";
190    $cc = 1024;
191} else {
192    $cc = $c;
193}
194
195# Preserve id when run again
196if (defined($opt{'id'})) {
197    $id = pack("V", doh($opt{'id'}));
198} else {
199    seek(FILE, 440, SEEK_SET) or die "$0: $file: $!\n";
200    read(FILE, $id, 4);
201    if ($id eq "\x00\x00\x00\x00") {
202	$id = pack("V", get_random());
203    }
204}
205
206# Print the MBR and partition table
207seek(FILE, 0, SEEK_SET) or die "$0: $file: $!\n";
208
209for ($i = 0; $i <= $opt{'hd0'}+3*$opt{'partok'}; $i++) {
210    $mbr = get_hex_data();
211}
212if ( length($mbr) > 432 ) {
213    die "$0: Bad MBR code\n";
214}
215
216$mbr .= "\0" x (432 - length($mbr));
217
218$mbr .= pack("VV", $de_lba*4, 0); 	# Offset 432: LBA of isolinux.bin
219$mbr .= $id;				# Offset 440: MBR ID
220$mbr .= "\0\0";				# Offset 446: actual partition table
221
222# Print partition table
223$offset  = $opt{'offset'};
224$psize   = $c*$h*$s - $offset;
225$bhead   = int($offset/$s) % $h;
226$bsect   = ($offset % $s) + 1;
227$bcyl    = int($offset/($h*$s));
228$bsect  += ($bcyl & 0x300) >> 2;
229$bcyl   &= 0xff;
230$ehead   = $h-1;
231$esect   = $s + ((($cc-1) & 0x300) >> 2);
232$ecyl    = ($cc-1) & 0xff;
233$fstype  = $opt{'type'};	# Partition type
234$pentry  = $opt{'entry'};	# Partition slot
235
236for ( $i = 1 ; $i <= 4 ; $i++ ) {
237    if ( $i == $pentry ) {
238	$mbr .= pack("CCCCCCCCVV", 0x80, $bhead, $bsect, $bcyl, $fstype,
239		     $ehead, $esect, $ecyl, $offset, $psize);
240    } else {
241	$mbr .= "\0" x 16;
242    }
243}
244$mbr .= "\x55\xaa";
245
246print FILE $mbr;
247
248# Pad the image to a fake cylinder boundary
249seek(FILE, $imgstat[7], SEEK_SET) or die "$0: $file: $!\n";
250if ($padding) {
251    print FILE "\0" x $padding;
252}
253
254# Done...
255close(FILE);
256
257exit 0;
258__END__
259