Assembling error in IDA Pro 6.1

Question

I need to modify a DLL. I need to patch

cmp     byte_1075A02C, 0

To

mov     byte_1075A02C, 1

I tried to use the Patch->Assemble command in IDA Pro, and i have a "Invalid Operand" message.

Anyone have any idea why a have this message please ?

The cmp byte_1075A02C, 0 is equal to : 80 3D 2C A0 75 10 00 But what is the mov byte_1075A02C, 1 equivalent ?

Tanks a lot for your helps :)

Answer 1

That should be

C6 05 2C A0 75 10 01

Answer 2

For a quick general solution, you could always try an online assembler such as this one. The syntax for this instruction is mov byte ptr [0x1075A02C], 1. Try it!

Different x86 assemblers use slightly different syntax, so I recommend familiarizing yourself with one and sticking to it.