Article 12624 of comp.os.ms-windows.programmer.nt.kernel-mode:
Rick Jones wrote:
> 
> How does one get the Process ID and Thread ID in a driver?  I know you can
> get the current Process, and Thread structure (PsGetCurrentProcess, and
> PsGetCurrentThread), but the structure returned is not defined in the DDK
> includes.
> What is the offset to the ID's?
> 
>                                                         - Rick -

The undocumented function you are looking for is:
PsGetCurrentProcessId().
Add this definition to a header file:

NTSYSAPI
ULONG
NTAPI PsGetCurrentProcessId();

There is also a PsGetCurrentThreadId(). 


Mark