Converting 8088 Depackers to x86

[emmanuel-marty]

Converting 8088 Depackers to x86

[emmanuel-marty]

From a first glance, the most likely issue is that you aren't handling offsets >= 64K. You kept the 'mov dh,cl' on line 97 which will only copy 8 high bits, which means the offsets will still be limited to < 64K. You should probably do something like mov edx, ecx / shl ecx,8 . Same with the minmatch 3/4 offset comparisons below, the cmp dh,07DH should be a cmp edx,07D00H, cmp dh,05H should be cmp edx,0500H and cmp dx,0080H a cmp edx,80H (or equivalent shorter code forms).

I will look further and do some tests, but that would be my first guess!

Note that you can limit the max offsets by using -w 65535 or somesuch on the apultra command line, just for quickly testing if the offset sizes are the issue. I wouldn't recommend actually using that in production, as it would grealy limit compression of your large exes, but just for testing.

[emmanuel-marty]

Ok, the code below seems to work with large files (I took your code and put in the changes in my previous message, plus a xor edx,edx instead of dh,dh in the code handling 7O+1M commands). If you optimize for size there are probably some opportunities to reduce this down. Let me know if that works :)

aplib_x86_small_fixed.zip

[odzhan]

Thanks for the prompt response and help. It appears to be working fine now! :)