ExitProcess() and TerminateProcess(GetCurrentProcess() is the same thing ...
However, calling them from DllMain kills the injector process.
f the specified module is a DLL that is not already loaded for the calling process, the system calls the DLL's DllMain function with the DLL_PROCESS_ATTACH value. If DllMain returns TRUE, LoadLibrary returns a handle to the module.
I think the reason no one is answering you is that what you are trying to do is stupid. Killing a critical system process causes a system failure and forces Windows to reboot, CSRSS.exe is a critical system process. You need to do A LOT more homework before you're ready to do whatever it is that you are doing. http://en.wikipedia.org/wiki/Client/Server_Runtime_Subsystem