How to view the GDTR's value ?

Question

Hi In the book "Rootkit Arsenal" page 84 (Chapter 3) mentions:

..., we can view the contents of the target machine's descriptor registers using the command with the 0x100 mask: kd> rM 0x100

and a paragraph below:

Note that the same task can be accomplished by specifying the GDTR components explicitly: kd> r gdtr ....

I run Windbg on my Win XP (inside VMWare) and choose the Kernel Debug -> Local. My problem is in case of first command, windbg errors with:

lkd> rM 0x100 ^ Operation not supported in current debug session 'rM 0x100'

and in the second command:

lkd> r gdtr ^ Bad register error in 'r gdtr'

Can anyone guide me ?

Answer 1

I think I've found the solution: Use two computers for kernel debugging instead of Local Kernel Debug. (I used VMWare and am debugging through the COM port/named pipe) I am thinking why this facility/feature (Local Kernel Debugging) is there if it's not complete ?

Answer 2

Right, you can't look at registers in a local kernel debug session. LiveKD works and you can also get the address indirectly through the PCR (!pcr).

-scott