src/util/swapdevids.pl

   1 #!/usr/bin/perl -w
   2 #
   3 #       Program to reverse the device identifier IDs in the PCIR and PnP
   4 #       structures in a ROM for old non-compliant BIOSes
   5 #
   6 #       GPL, Ken Yap 2001
   7 #
   8
   9 use bytes;
  10
  11 use IO::Seekable;
  12
  13 sub swaplocs ($$$)
  14 {
  15         my ($dataref, $loc1, $loc2) = @_;
  16         my ($t);
  17
  18         $t = substr($$dataref, $loc1, 1);
  19         substr($$dataref, $loc1, 1) = substr($$dataref, $loc2, 1);
  20         substr($$dataref, $loc2, 1) = $t;
  21 }
  22
  23 sub printdevids ($$)
  24 {
  25         my ($dataref, $loc) = @_;
  26
  27         return (sprintf "%02x %02x %02x", unpack('C3', substr($$dataref, $loc, 3)));
  28 }
  29
  30 $#ARGV >= 0 or die "Usage: $0 romimage\n";
  31 $file = $ARGV[0];
  32 open(F, "+<$file") or die "$file: $!\n";
  33 binmode(F);
  34 # Handle up to 64kB ROM images
  35 $len = read(F, $data, 64*1024);
  36 defined($len) or die "$file: $!\n";
  37 substr($data, 0, 2) eq "\x55\xAA" or die "$file: Not a boot ROM image\n";
  38 ($pci, $pnp) = unpack('v2', substr($data, 0x18, 4));
  39 ($pci < $len and $pnp < $len) or die "$file: Not a PCI PnP ROM image\n";
  40 (substr($data, $pci, 4) eq 'PCIR' and substr($data, $pnp, 4) eq '$PnP')
  41         or die "$file: No PCI and PNP structures, not a PCI PNP ROM image\n";
  42 &swaplocs(\$data, $pci+13, $pci+15);
  43 &swaplocs(\$data, $pnp+18, $pnp+20);
  44 seek(F, 0, SEEK_SET) or die "$file: Cannot seek to beginning\n";
  45 print F $data;
  46 close(F);
  47 print "PCI devids now: ", &printdevids(\$data, $pci+13), "\n";
  48 print "PnP devids now: ", &printdevids(\$data, $pnp+18), "\n";
  49 exit(0);