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