Where in the linux code is linux's instruction memory made non writable?

[yogesh.kumar]

Hi,

I am a computer science student and doing a project on trying to find bugs in the linux kernel.
For that I needed to patch the linux instruction memory while the kernel is running. I have changed the code of the linux kernel to do this.
My code runs fine just as the kernel boots but then after 1-2 seconds when I try to write in the instruction memory the kernel panics. So most probably after the kernel is booted its instruction memory is made non writable by the kernel itself (as for 1-2 seconds I am able to change the instruction memory and for that time my code runs perfectly).

So it would be a great help to me if anyone could tell me where in the linux kernel code is the kernel's instruction memory is made non-writable.

Thanks in advance
Yogesh Kumar