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 9use bytes; 10 11use IO::Seekable; 12 13sub 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($$dataref, $loc2, 1) = $t; 21} 22 23sub printdevids ($$) 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 = $ARGV[0]; 32open(F, "+<$file") or die "$file: $!\n"; 33binmode(F); 34# Handle up to 64kB ROM images 35$len = read(F, $data, 64*1024); 36defined($len) or die "$file: $!\n"; 37substr($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, $pnp+20); 44seek(F, 0, SEEK_SET) or die "$file: Cannot seek to beginning\n"; 45print F $data; 46close(F); 47print "PCI devids now: ", &printdevids(\$data, $pci+13), "\n"; 48print "PnP devids now: ", &printdevids(\$data, $pnp+18), "\n"; 49exit(0); 50