source: bootcd/isolinux/syslinux-6.03/gpxe/src/util/modrom.pl

#!/usr/bin/perl -w

use Getopt::Std;

use constant MINROMSIZE => 8192;
use constant MAXROMSIZE => 262144;

use constant PCI_PTR_LOC => 0x18;       # from beginning of ROM
use constant PCI_HDR_SIZE => 0x18;
use constant PNP_PTR_LOC => 0x1a;       # from beginning of ROM
use constant PNP_HDR_SIZE => 0x20;
use constant PNP_CHKSUM_OFF => 0x9;     # bytes from beginning of PnP header
use constant PNP_DEVICE_OFF => 0x10;    # bytes from beginning of PnP header
use constant PCI_VEND_ID_OFF => 0x4;    # bytes from beginning of PCI header
use constant PCI_DEV_ID_OFF => 0x6;     # bytes from beginning of PCI header
use constant PCI_SIZE_OFF => 0x10;      # bytes from beginning of PCI header

use constant UNDI_PTR_LOC => 0x16;      # from beginning of ROM
use constant UNDI_HDR_SIZE => 0x16;
use constant UNDI_CHKSUM_OFF => 0x05;

use strict;

use vars qw(%opts);

use bytes;

sub getromsize ($) {
        my ($romref) = @_;
        my $i;

        print STDERR "BIOS extension ROM Image did not start with 0x55 0xAA\n"
                if (substr($$romref, 0, 2) ne "\x55\xaa");
        my $size = ord(substr($$romref, 2, 1)) * 512;
        for ($i = MINROMSIZE; $i < MAXROMSIZE and $i < $size; $i *= 2) { }
        print STDERR "$size is a strange size for a boot ROM\n"
                if ($size > 0 and $i > $size);
        return ($size);
}

sub addident ($) {
        my ($romref) = @_;

        return (0) unless (my $s = $opts{'i'});
        # include the terminating NUL byte too
        $s .= "\x00";
        my $len = length($s);
        # Put the identifier in only if the space is blank
        my $pos = length($$romref) - $len - 2;
        return (0) if (substr($$romref, $pos, $len) ne ("\xFF" x $len));
        substr($$romref, $pos, $len) = $s;
        return ($pos);
}

sub pcipnpheaders ($$) {
        my ($romref, $identoffset) = @_;
        my ($pci_hdr_offset, $pnp_hdr_offset);

        $pci_hdr_offset = unpack('v', substr($$romref, PCI_PTR_LOC, 2));
        $pnp_hdr_offset = unpack('v', substr($$romref, PNP_PTR_LOC, 2));
        # Sanity checks
        if ($pci_hdr_offset < PCI_PTR_LOC + 2
                or $pci_hdr_offset > length($$romref) - PCI_HDR_SIZE
                or $pnp_hdr_offset < PNP_PTR_LOC + 2
                or $pnp_hdr_offset > length($$romref) - PNP_HDR_SIZE
                or substr($$romref, $pci_hdr_offset, 4) ne 'PCIR'
                or substr($$romref, $pnp_hdr_offset, 4) ne '$PnP') {
                $pci_hdr_offset = $pnp_hdr_offset = 0;
        } else {
                printf "PCI header at %#x and PnP header at %#x\n",
                        $pci_hdr_offset, $pnp_hdr_offset;
        }
        if ($pci_hdr_offset > 0) {
                my ($pci_vendor_id, $pci_device_id);
                # if no -p option, just report what's there
                if (!defined($opts{'p'})) {
                        $pci_vendor_id = unpack('v', substr($$romref, $pci_hdr_offset+PCI_VEND_ID_OFF, 2));
                        $pci_device_id = unpack('v', substr($$romref, $pci_hdr_offset+PCI_DEV_ID_OFF, 2));
                        printf "PCI Vendor ID %#x Device ID %#x\n",
                                $pci_vendor_id, $pci_device_id;
                } else {
                        substr($$romref, $pci_hdr_offset + PCI_SIZE_OFF, 2)
                                = pack('v', length($$romref) / 512);
                        ($pci_vendor_id, $pci_device_id) = split(/,/, $opts{'p'});
                        substr($$romref, $pci_hdr_offset+PCI_VEND_ID_OFF, 2)
                                = pack('v', oct($pci_vendor_id)) if ($pci_vendor_id);
                        substr($$romref, $pci_hdr_offset+PCI_DEV_ID_OFF, 2)
                                = pack('v', oct($pci_device_id)) if ($pci_device_id);
                }
        }
        if ($pnp_hdr_offset > 0 and defined($identoffset)) {
                # Point to device id string at end of ROM image
                substr($$romref, $pnp_hdr_offset+PNP_DEVICE_OFF, 2)
                        = pack('v', $identoffset);
                substr($$romref, $pnp_hdr_offset+PNP_CHKSUM_OFF, 1) = "\x00";
                my $sum = unpack('%8C*', substr($$romref, $pnp_hdr_offset,
                        PNP_HDR_SIZE));
                substr($$romref, $pnp_hdr_offset+PNP_CHKSUM_OFF, 1) = chr(256 - $sum);
        }
}

sub undiheaders ($) {
        my ($romref) = @_;
        my ($undi_hdr_offset);

        $undi_hdr_offset = unpack('v', substr($$romref, UNDI_PTR_LOC, 2));
        # Sanity checks
        if ($undi_hdr_offset < UNDI_PTR_LOC + 2
                or $undi_hdr_offset > length($$romref) - UNDI_HDR_SIZE
                or substr($$romref, $undi_hdr_offset, 4) ne 'UNDI') {
                $undi_hdr_offset = 0;
        } else {
                printf "UNDI header at %#x\n", $undi_hdr_offset;
        }
        if ($undi_hdr_offset > 0) {
                substr($$romref, $undi_hdr_offset+UNDI_CHKSUM_OFF, 1) = "\x00";
                my $sum = unpack('%8C*', substr($$romref, $undi_hdr_offset,
                        UNDI_HDR_SIZE));
                substr($$romref, $undi_hdr_offset+UNDI_CHKSUM_OFF, 1) = chr(256 - $sum);
        }
}

sub writerom ($$) {
        my ($filename, $romref) = @_;

        open(R, ">$filename") or die "$filename: $!\n";
        print R $$romref;
        close(R);
}

sub checksum ($) {
        my ($romref) = @_;

        substr($$romref, 6, 1) = "\x00";
        my $sum = unpack('%8C*', $$romref);
        substr($$romref, 6, 1) = chr(256 - $sum);
        # Double check
        $sum = unpack('%8C*', $$romref);
        if ($sum != 0) {
                print "Checksum fails\n"
        } elsif ($opts{'v'}) {
                print "Checksum ok\n";
        }
}

sub makerom () {
        my ($rom, $romsize);

        getopts('3xi:p:s:v', \%opts);
        $ARGV[0] or die "Usage: $0 [-s romsize] [-i ident] [-p vendorid,deviceid] [-x] [-3] rom-file\n";
        open(R, $ARGV[0]) or die "$ARGV[0]: $!\n";
        # Read in the whole ROM in one gulp
        my $filesize = read(R, $rom, MAXROMSIZE+1);
        close(R);
        defined($filesize) and $filesize >= 3 or die "Cannot get first 3 bytes of file\n";
        print "$filesize bytes read\n" if $opts{'v'};
        # If PXE image, just fill the length field and write it out
        if ($opts{'x'}) {
                substr($rom, 2, 1) = chr((length($rom) + 511) / 512);
                &writerom($ARGV[0], \$rom);
                return;
        }
        # Size specified with -s overrides value in 3rd byte in image
        # -s 0 means round up to next 512 byte block
        if (defined($opts{'s'})) {
                if (($romsize = oct($opts{'s'})) <= 0) {
                        # NB: This roundup trick only works on powers of 2
                        $romsize = ($filesize + 511) & ~511
                }
        } else {
                $romsize = &getromsize(\$rom);
                # 0 put there by *loader.S means makerom should pick the size
                if ($romsize == 0) {
                        # Shrink romsize down to the smallest power of two that will do
                        for ($romsize = MAXROMSIZE;
                                $romsize > MINROMSIZE and $romsize >= 2*$filesize;
                                $romsize /= 2) { }
                }
        }
        if ($filesize > $romsize) {
                print STDERR "ROM size of $romsize not big enough for data, ";
                # NB: This roundup trick only works on powers of 2
                $romsize = ($filesize + 511) & ~511;
                print "will use $romsize instead\n"
        }
        # Pad with 0xFF to $romsize
        $rom .= "\xFF" x ($romsize - length($rom));
        if ($romsize >= 128 * 1024) {
                print "Warning: ROM size exceeds extension BIOS limit\n";
        }
        substr($rom, 2, 1) = chr(($romsize / 512) % 256);
        print "ROM size is $romsize\n" if $opts{'v'};
        my $identoffset = &addident(\$rom);
        &pcipnpheaders(\$rom, $identoffset);
        &undiheaders(\$rom);
        # 3c503 requires last two bytes to be 0x80
        substr($rom, MINROMSIZE-2, 2) = "\x80\x80"
                if ($opts{'3'} and $romsize == MINROMSIZE);
        &checksum(\$rom);
        &writerom($ARGV[0], \$rom);
}

sub modrom () {
        my ($rom);

        getopts('p:v', \%opts);
        $ARGV[0] or die "Usage: $0 [-p vendorid,deviceid] rom-file\n";
        open(R, $ARGV[0]) or die "$ARGV[0]: $!\n";
        # Read in the whole ROM in one gulp
        my $filesize = read(R, $rom, MAXROMSIZE+1);
        close(R);
        defined($filesize) and $filesize >= 3 or die "Cannot get first 3 bytes of file\n";
        print "$filesize bytes read\n" if $opts{'v'};
        &pcipnpheaders(\$rom);
        &undiheaders(\$rom);
        &checksum(\$rom);
        &writerom($ARGV[0], \$rom);
}

# Main routine. See how we were called and behave accordingly
if ($0 =~ m:modrom(\.pl)?$:) {
        &modrom();
} else {
        &makerom();
}
exit(0);