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#!/usr/bin/perl -w
#
# Quick Perl program to decode and display details about
# tagged images created by mknbi, and then mount the contained
# DOS filesystem using a loop-back mount
#
# Martin Atkins, November 1998
# by hacking disnbi by
# Ken Yap, September 1998
#
#
sub getvendordata {
my ($flags) = @_;
my $vendordata = '';
my $vendorlen = ($flags & 0xff) >> 4;
if ($vendorlen > 0) {
$vendorlen *= 4;
$vendordata = unpack("A$vendorlen", substr($imageheader, $curoffset));
$curoffset += $vendorlen;
}
return ($vendordata);
}
sub decodesegmentflags {
my ($flags) = @_;
$flags >>= 24;
$flags &= 0x3;
($flags == 0) and $type = "Absolute";
($flags == 1) and $type = "Follows last segment";
($flags == 2) and $type = "Below end of memory";
($flags == 3) and $type = "Below last segment loaded";
return ($type);
}
sub onesegment
{
my ($segnum) = @_;
my ($type, $vendordata);
my ($flags, $loadaddr, $imagelen, $memlength) = unpack("V4", substr($imageheader, $curoffset));
$curoffset += 16;
print "Segment number $segnum\n";
printf "Load address:\t\t%08x\n", $loadaddr;
printf "Image length:\t\t%d\n", $imagelen;
printf "Memory length:\t\t%d\n", $memlength;
$type = &decodesegmentflags($flags);
printf "Position:\t\t$type\n";
printf "Vendor tag:\t\t%d\n", ($flags >> 8) & 0xff;
if (($vendordata = &getvendordata($flags)) ne '') {
print "Vendor data:\t\t", $vendordata, "\n";
}
print "\n";
push (@seglengths, $imagelen);
return (($flags >> 26) & 1);
}
@seglengths = ();
$#ARGV == 1 or die "Usage: mntnbi tagged-image-file dir\n";
$imagefile= $ARGV[0];
open(I, $ARGV[0]) or die "$imagefile: $!\n";
(defined($status = sysread(I, $imageheader, 512)) and $status == 512)
or die "$imagefile: Cannot read header\n";
$headerrecord = substr($imageheader, 0, 16);
($magic, $flags, $bx, $ds, $ip, $cs) = unpack("a4Vv4", $headerrecord);
$magic eq "\x36\x13\x03\x1B" or die "$imagefile: Not a tagged image file\n";
$curoffset = 16;
# Now decode the header
printf "Header location:\t%04x:%04x\n", $ds, $bx;
printf "Start address:\t\t%04x:%04x\n", $cs, $ip;
printf "Flags:\n";
print "Return to loader after execution (extension)\n" if (($flags >> 8) & 1);
if (($vendordata = &getvendordata($flags)) ne '') {
print "Vendor data:\t\t", $vendordata, "\n";
}
print "\n";
# Now decode each segment record
$segnum = 1;
do {
$lastrecord = &onesegment($segnum);
++$segnum;
} while (!$lastrecord);
if ($#seglengths != 1) {
die "This is not a DOS image $#seglengths\n";
}
$offset = 512 + $seglengths[0];
print "mounting filesystem at offset $offset in $ARGV[0] on $ARGV[1]\n";
$rc = system "mount $ARGV[0] $ARGV[1] -t msdos -o loop,offset=$offset";
print "Done\n" if ($rc == 0);
exit(0);
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