WINDOWS INTERNALS: SECURE CALLS - THE BRIDGE BETWEEN THE NT KERNEL AND SECURE KERNEL

Summary from the TLDR InfoSec newsletter

Secure Calls are a mechanism in Windows that allows the “regular” (NT) kernel, residing in virtual trust level (VTL) 0, to communicate with the secure kernel (SK) operating in VTL 1. Secure calls are implemented as a hypercall with the hypervisor brokering the connection. In this post, the author reverse-engineers the secure call process and structure and introduces a tool for making secure calls with user-supplied arguments.