Toggling bits in FLAGS ?

[Slugsnack]

I was curious as to how I might read and write bits from the EFLAGS register after a certain instruction had executed (at a given virtual address).

I was thinking GetThreadContext/SetThreadContext, have I got my head turned in the right direction ?

[jj2007]

pushfd
pop eax
bt eax, n

[Slugsnack]

Thanks, I have not come across bit instructions like this before so I'll need to do a bit of reading  ::)

Do you have any idea how I could do this for another thread without "hooking" it with a JMP ?

[jj2007]

OllyDbg shows the flags.

[Slugsnack]

Yeap, that's exactly what I want to reproduce.  Olly is able to step onto any instruction and then you can change flag states at that point.  I was hoping to do the same thing but not sure how to go about doing it.