Cheat Engine

[blackzero]

I've been trying to make some trainers lately but i ran into a problem, normally with ce i just tick the zf flag for some of my cheats but i cant figure out how to program this, i've searched all over the internet on assembly programming, asked my programmer friends, and even looked through this post http://forum.cheatengine.org/viewtopic.php?p=133987&highlight=zero+flag#133987 and found nothing that is helpful, if anyone knows how i can set the zf flag in my programming pls help, thanks.

[Dark Byte]

search google for "interrupt hooking" and "debug registers"
And information on how to write a device driver for windows is also usefull

That should be enough to make a change reg on bp trainer.

[bahblah]

Since I have alot more time than Dark Byte on my hands let me explain.

Debug registers are used to set up hardware breakpoints. These breakpoints raise interrupt 1.

For the int 1 handler hooking you will need to be in kernelmode. The idea is to change the flags in your replacement handler then jmp back to the original handler.

Interrupt Handlers are stored in a IDT (interrupt descriptor table).
To retrieve the IDT you simply use the LIDT instruction (Load IDT)
You change the interrupt 1 handler to your own function while storing the original interrupt 1 handler.
To set the new IDT you simply use the SIDT instruction (Store IDT)

You need to use other instructions too so you don't create a disaster: STI, CLI (SeT Interrupt flag? CLear Interrupt flag) Anyway you'll find out in your research.

To do the actual setting of the hardware breakpoints, you have to work with debug registers 0 - 3 and 7 (6 too maybe?) All I can say is it's a good idea to use Intel Pentium's Programmers Manual or w/e


But hell. Since Cheat Engine's source is open-source, you can find alot of stuff out just by reading that nice piece of code.