Hello Mercury 13,
Yes, the FreeDOS kernel is compressed with UPX --- but there are some
preprocessing and postprocessing steps done to the uncompressed kernel
code, before and after it is passed through UPX.
Bart Oldeman's utils/exeflat.c program in the kernel sources is
responsible for doing these processing steps and wrapping the call to UPX.
I think it _might_ be feasible to write a program to reverse what
utils/exeflat.c does, to allow UPX to decompress the image, though of
course this will need some work. Part of the reversal process will
involve restoring the .exe header and relocation(s) which were created
by UPX and removed by exeflat.
(Anyway, I think compressing programs is useful, if FreeDOS is likely to
be used in resource-constrained situations. Floppy disks were not only
slow --- they also had quite limited capacity. (-: )
Thank you!
--
https://github.com/tkchia/
On 07/10/2018 03:18 PM, Mercury Thirteen via Freedos-devel wrote:
I agree... not sure why the FreeDOS kernel folks felt that was necessary. Maybe
a size limitation of the bootloader?
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-------- Original Message --------
On Jul 10, 2018, 12:47 AM, Ralf Quint wrote:
On 7/9/2018 7:43 PM, Mercury Thirteen via Freedos-devel wrote:
So, I've been looking into de-UPXing the kernel image and keep getting
told by the UPX binary that the image "wasn't compressed by UPX". Is
there anything special I have to do to convince it otherwise? Was the
kernel in fact not compressed by UPX? I'm using the latest UPX on
Linux Mint 19, if that helps.
What would be the purpose of using UPX today? It made kind of sense back
in the days of slow data media (floppy disks) but nowadays, there just
isn't IMHO any valid reason to do that anymore.
Ralf
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