utils/isohybrid.in

   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
  20 use bytes;
  21 use 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
  58 sub usage() {
  59     print STDERR "Usage: $0 [options] filename.iso\n",
  60     "Options:\n",
  61     "  -h          Number of default geometry heads\n",
  62     "  -s          Number of default geometry sectors\n",
  63     "  -entry      Specify partition entry number (1-4)\n",
  64     "  -offset     Specify partition offset (default 0)\n",
  65     "  -type       Specify partition type (default 0x17)\n",
  66     "  -id         Specify MBR ID (default random)\n",
  67     "  -forcehd0   Always assume we are loaded as disk ID 0\n",
  68     "  -ctrlhd0    Assume disk ID 0 if the Ctrl key is pressed\n",
  69     "  -partok     Allow booting from within a partition\n";
  70     exit 1;
  71 }
  72
  73 # Parse a C-style integer (decimal/octal/hex)
  74 sub doh($) {
  75     my($n) = @_;
  76     return ($n =~ /^0/) ? oct $n : $n+0;
  77 }
  78
  79 sub 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
  95 sub 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 $mbr;
 106 }
 107
 108 while ($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
 129 if (!defined($file)) {
 130     usage();
 131 }
 132
 133 open(FILE, "+< $file\0") or die "$0: cannot open $file: $!\n";
 134 binmode FILE;
 135
 136 #
 137 # First, actually figure out where mkisofs hid isolinux.bin
 138 #
 139 seek(FILE, 17*2048, SEEK_SET) or die "$0: $file: $!\n";
 140 read(FILE, $boot_record, 2048) == 2048 or die "$0: $file: read error\n";
 141 ($br_sign, $br_cat_offset) = unpack("a71V", $boot_record);
 142 if ($br_sign ne ("\0CD001\1EL TORITO SPECIFICATION" . ("\0" x 41))) {
 143     die "$0: $file: no boot record found\n";
 144 }
 145 seek(FILE, $br_cat_offset*2048, SEEK_SET) or die "$0: $file: $!\n";
 146 read(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 $cs = 0;
 152 for ($i = 0; $i < 16; $i++) {
 153     $cs += $ve[$i];
 154 }
 155 if ($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));
 160 if ($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
 166 seek(FILE, $de_lba*2048+0x40, SEEK_SET) or die "$0: $file: $!\n";
 167 read(FILE, $ibsig, 4);
 168 if ($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 = $imgstat[7];
 176 if (!$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/$cylsize);
 187 if ($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 = $c;
 193 }
 194
 195 # Preserve id when run again
 196 if (defined($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
 207 seek(FILE, 0, SEEK_SET) or die "$0: $file: $!\n";
 208
 209 for ($i = 0; $i <= $opt{'hd0'}+3*$opt{'partok'}; $i++) {
 210     $mbr = get_hex_data();
 211 }
 212 if ( length($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
 236 for ( $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
 246 print FILE $mbr;
 247
 248 # Pad the image to a fake cylinder boundary
 249 seek(FILE, $imgstat[7], SEEK_SET) or die "$0: $file: $!\n";
 250 if ($padding) {
 251     print FILE "\0" x $padding;
 252 }
 253
 254 # Done...
 255 close(FILE);
 256
 257 exit 0;
 258 __END__