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  #1  
Old 10-08-2023, 21:44
dion dion is offline
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adding more space to linear executable dos games

Hi,
i am working on an old LE exe dos game, and would like to change some opcodes. the problem is, i need more space on the code segment to make my changes. i have search the internet for tools, but i don't find any. Does anyone know something like that?
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  #2  
Old 10-09-2023, 04:00
Rufflito Rufflito is offline
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Quote:
Originally Posted by dion View Post
Hi,
i am working on an old LE exe dos game, and would like to change some opcodes. the problem is, i need more space on the code segment to make my changes. i have search the internet for tools, but i don't find any. Does anyone know something like that?
Creating code caves is trivial for PEs but if it's for a native DOS app I need to see the executable first (some very old ones impose the 640 kb limit for RAM). Consider posting it?
Or for a start you can do a google search for "code caves" if you didn't already do so.
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  #3  
Old 10-09-2023, 09:50
dion dion is offline
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Yes, i have search for code cave, but nothing for LE file.
The game was compiled with watcom c++ with dos4gw stub. It was mix of 16 and 32 bit program. The program itself is 32 bit, the loader is 16 bit.

For a reason, i would not post the file here, but there seems to be many dos4gw games out there. There is a github that make program to edit LE, but it is not implemented yet. I also see a wiki that have tutorial's title the same with this thread, but it was empty, unfortunately.
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  #4  
Old 10-09-2023, 16:05
chants chants is offline
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Is there padding between functions? Often single byte padding of 0s, int3s, nops will pad functions to align them, not sure in the old LE exes if this was common. The only key is to jump there and back making sure to not interfere with any code containing relocated addresses.
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  #5  
Old 10-09-2023, 16:22
Gregory Morse Gregory Morse is offline
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Quote:
Originally Posted by chants View Post
Is there padding between functions? Often single byte padding of 0s, int3s, nops will pad functions to align them, not sure in the old LE exes if this was common. The only key is to jump there and back making sure to not interfere with any code containing relocated addresses.
It's much better to add another new section. Then no major limits to the bytes you can add.
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  #6  
Old 10-11-2023, 00:47
sendersu sendersu is offline
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Quote:
Originally Posted by dion View Post
Hi,
i am working on an old LE exe dos game, and would like to change some opcodes. the problem is, i need more space on the code segment to make my changes. i have search the internet for tools, but i don't find any. Does anyone know something like that?
I"m wondering how did you manage to debug this kind of ancient stuff?
what kind of tools are you using
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  #7  
Old 10-11-2023, 09:47
dion dion is offline
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Originally Posted by sendersu View Post
I"m wondering how did you manage to debug this kind of ancient stuff?
what kind of tools are you using
Using dosbox debugger.
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  #8  
Old 10-11-2023, 13:48
OldieHans OldieHans is offline
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Quote:
Originally Posted by sendersu View Post
I"m wondering how did you manage to debug this kind of ancient stuff?
what kind of tools are you using
That is not the most important question here...
The most shocking question that is staring at me is, how someone (user @dion) with just 2... That is right... Someone with just TWO freaking reps can gain the VIP status in this forum while many a genuine users need to wait for a day to get their posts 'approved' by the admins...

What a huge disparity...
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  #9  
Old 11-02-2023, 21:14
dion dion is offline
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for anyone need, i put my own tool here here
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