Cheat Engine

[LongBeardedLion]

I mean calling a game function in c++. But the new _asm should be only specifically changed when im calling the function. I dont want the function to have its code permanently altered. Only when i call it i want it to have a specific _asm code.

This is my code that calls the game function, it works perfectly:

[Csimbi]

Local variables in a function only exists while that function runs. Plus, there may be multiple instances.
Register are pretty volatile as all processing goes through them; you need to change them at the right moment else is might not even be holding the right variable.
So, I think you will want to inject a permanent piece of code (into the game) anyway that determines a) whether the change is required and if yes, b) get the value that should be loaded into ESI and lastly, c) load the value into ESI.

[LongBeardedLion]

Thanks CSimba

That sounds like a good way to go. Could you please just give me an hint of how to alter a eventual ESI value in the midst of my function?

Where do i put it?
Cause i have no idea.

Also i was thinking, what if i do a 3 process method:

1- Hook/detour the function, change the code to something that i want. This i know how to do.

2- Call the function (will call the function but now it has the hook with my new code).

3- After the call is finished, hook again the function and overwrite it again with its original code.

All these three processes will run quickly one after the other. So basically it will change the code of the function, call function, and change back to what it was.

? IS this a good practice? Or its stupid and doesnt make any sense?

[Csimbi]

In your hook, allocate space for two variables and register them both.
One is a flag, the second is the value.
In your hook you will do something like:

[LongBeardedLion]

Thanks Csimbi,

[Csimbi]

That seems to redirect code from 0x4B0820 to ourFunct just tine.
At least, by reading the code above, that's the impression I get.
Note: you did not save the original instructions - you should restore it after ESC is hit in MainThread.
Declare and initialize a DWORD for flag, make it a global var.
Declare and initialize a DWORD for value, make it a global var.

Add this to the loop in MainThread:
if (GetAsyncKeyState(VK_MENU)) flag = 1 else flag = 0;
Make sure value takes an input somewhere (another hotkey)?

What's with mov esi,ecx?
I thought your value was in ESI.
- the conditional jump has no label to jump to.
- it seems you don't pop the stack at the end of ourFunct.

Replace everything in ourFunct with a single NOP just to test that it the jump is actually correct (it does step into ourFunct).
Then, put the contents back and fixed those two things I mentioned above and then it should work.

[LongBeardedLion]

Sorry i think there is a bit of a confusion here. I shouldnt have not posted the code for hook, i distracted you from the problem and the real code. I think you confused it with the original function for calling. They are completely different things.

The last code i posted that you commented on your last answer is not the function im using, that is just an example that i used to show you my code for a hook/detour, so that i can show what i have done in the past when i wanted to change _asm, that i cant use right now because im calling a function, not injecting code. So that is different than the first code i showed you, that is used to calling the function (and that im trying to somehow use it and at the same time change the _asm of the function that is called by it).

The 1st code in the original post, is used solely to call a function, and the problem is there is no way, that i know, to alter _asm code in there.

The 2nd code i posted is a detour/hook, and that alone does not ever call the function. It simply overwrites the code and makes it jump, when the function is called by the game (not by user artificially).

In other words the difference between 1 and 2, is that 1 is calling the function externally/indirectly/artificially. While 2 is not calling the function just altering its code that sits there waiting for the game to call it.

I know this is confusing, and i dont know what else i can do to explain it better. Sorry if this is a mess.

So the same problem persists.

If i use the 1st code that calls the function, i have no way to alter its _asm, that i know. I dont know where in the 1st solution should i write the _asm. Whereas in the 2nd code the function is never called, because its just a detour, it was just an example, because i wanted to say that maybe i should somehow combine both, and try to alter the _asm first, and then call the function?

This can be solved if i know where in my 1st code, in the original post, can i insert _asm code that alters the instructions.

In my 2nd code whatever i do with the flags and _asm will not call the function.

However your idea to make a [flag] in my still beginner notions, would maybe solve the problem. If only i could assign the [flag] to a random address in memory, that is checked everytime the function is called. So that when i call the function artificially, i write to that address in [flag] the value of 1, so when the function is called (artificially), it will check the value in [flag], and it will know it is an artificial call, meaning its a call from the dll, and not any other calls made by the game, so it will then execute our code, and in this case change our ESI to the value that we need, and then set the flag again back to 0, so that when the function is called by the game in the natural circumstances, the ESI will get its natural values not our artificial value.
Does this make any sense?
What do you think?

[Csimbi]

Well, yes, in principle, the code changing ESI has to run as part of the original function, whenever it's called - and that's only possible if you hook it and redirect it to your won cave.
As for what happens in there, yes, you need to be able to control the variables from the outside.

Here's an idea: do it in CE's AA first and see what actually happens there.
Then, try to do the same with your own code.

[LongBeardedLion]

I made a huge progress. Image below.

I was able to make an injection and write to a specific empty address the number 1, so thats the flag.

But the problem is, in my _asm im not being able to type the address where i make the flag. So it never makes the comparison. I tried editing the code and writting the address manually and then it works. So now i only need to figure out how to make the address pass into that _asm function.

chunk of the code that matters:

[Csimbi]

You could pass the flag and the value as a parameter, yes.
But be sure you pass the pointers, not the current values of these.
(You will check/use the current values at the pointer every time the function runs.)

[LongBeardedLion]

Thanks CSIMBI

I made it work finally.
With a lot of stubborness and with your help i was able to make it.
Is there anyway i can upvote you?
This is what i wrote in the assembly to make it work: