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Combined .com executable/DOS driver, multi-header drivers (Announce)

posted by ecm Homepage E-mail, Düsseldorf, Germany, 10.08.2010, 20:21

> Thank you for your additional useful comments which also link up with a
> private email discussion with Jack after this thread. Most helpful input -
> cheers!
[Insert generic rant about private email discussion referencing Eric Auer.] Pleased to hear my knowledge might be useful to someone (and that someone even read this old thread).

> > Even if you were to trick UPX into compressing the executable,
> Which it should be noted for anyone following / interested by this
> discussion would for completeness include recalculating UPX's CRC's etc.
Not necessarily. If the file would be accepted as .COM file (or device driver, but more unlikely because that requires the -1 dword) by UPX, you could just compress it as that without any patching necessary - but losing device driver functionality. The patching is probably aimed at UPX's decompressor only anyway, so that it would work for both formats. (See EDR-DOS stuff.)

> > This would make patching of the UPX header/decompressor necessary.
> Which it should also be noted is officially not allowed in the UPX license
> :(
Oh. Might tell that to Udo Kuhnt, his EDR-DOS BIO.SYS compressor does patch it a little. (Of course on the user's system, using a DEBUG script. How anticipatory.) The DOS.SYS uses unpatched UPX .COM file compression though, which works because the DOS.SYS file is loaded by BIO.SYS so this loader has been modified to load the file like a .COM file.

> > protects the kernel/debugger from well-intentioned users that
> > think UPX can handle everything.
> So nicely put :)
I didn't want to insult anyone, what! :-D

---
l

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