AMD PSP

[Dread2]

The AMD Platform Security Processor or AMD Secure Technology is an embedded ARM5 Cortex in all AMD CPU’s. It has been incorporated in all CPU’s since AMD family 15h, and early 16h or Jaguar. It’s responsible for DRAM initialization, TPM, hardware downcoring, SEV (Secure Encryption Virtualization), onboard crypto algorithms and AGESA. The issue with PSP is it’s vulnerabilities due to the fact it runs a separate operating system in ring0, similar to Intel ME known as Kinibi. On ME, it is Minix. What is interesting about the PSP, is it can not fully killed unlike ME. ME will assist in the boot and bootstrapping process. However it has been noted to have a secret mode known as HAP (High Assurance Platform), that is enabled by setting HAP_BIT to 1.

Sources:
https://fm.csl.sri.com/LAW/2009/dobry-law09-HAP-Challenges.pdf