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[Help] Preventing a mov operation to a specific address

 
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uhgdn9qi
How do I cheat?
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Joined: 08 Apr 2017
Posts: 2

PostPosted: Sat Apr 08, 2017 10:14 am    Post subject: [Help] Preventing a mov operation to a specific address Reply with quote

Hello.

I'm new to Cheat Engine, and I have a problem to which I failed to find a solution.

Preface:
The game I want to hack (GTA V) has a function in the game's map screen that highlights the object (blip) which my cursor is currently on. For example, pointing the map at a gun store would highlight the Gun Shop legend item on the right side. I want to disable that behavior, and I have found a couple of data addresses which reflect the changes I make in-game.

The opcode responsible for changing one of those values seems to be doing much more than what I want disabled. If I try to replace it with nop, the game's pause menu becomes unusable (text not appearing, etc.). It writes to quite a few more values than just the one I'm interested in.

Problem:
I'd like to write a script in the auto assembler that would prevent that 1 opcode from writing to one particular address, while letting it write normally to others.

the opcode is:
Code:
movsd [rax+rdx+38],xmm6


At first I thought I could just cmp rax+rdx+38 with the address I don't want it to write to (since it doesn't change) and make it skip the code if it matches, but that failed, and I don't know how else I could do it.
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sbryzl
Master Cheater
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Joined: 25 Jul 2016
Posts: 252

PostPosted: Sat Apr 08, 2017 11:08 am    Post subject: Reply with quote

Watch the values going through the 2 registers. If one is a base value and the other is a variable offset then you could try testing that variable value, of course it may have the same effect as testing for the address. I can think of 2 conditions that may lead to failure.
1. There are more changes necessary to accomplish the goal.
2. Testing for the location within the array does not narrow results down enough which would also be linked to changes happening elsewhere.
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uhgdn9qi
How do I cheat?
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Joined: 08 Apr 2017
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PostPosted: Sun Apr 09, 2017 2:08 am    Post subject: Reply with quote

Thanks, sbryzl, for your brilliant idea. I have made some good progress.
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