Linux Late Launch Kernel¶
Summary¶
The Linux kernel will be extended to make it function as the late launch kernel for both AMD (Secure Loader) and Intel TXT (Measured Launch Environment).
Background¶
The late launch process provides a means to measure a target execution environment and then jump into the environment as presribed by the CPU's late launch protocol. This process provides a means by which to a establish a hardware-based Root of Trust for Measurement (RTM). The implementation here will provide a means to launch the Linux kernel as an RTM envrionment to enable building trust in a platform's launch.
Approach¶
A preliminary approach is as follows, * Create a late-launch landing zone (LZ) in 64k real code section of Linux kernel header * Sanitize any CPU state passed through late launch * Verify LZ signature with pubkey * Verify measurement from LZ signature against CRTM * (AMD) Create/Setup TPM Event log * Extend hash of pubkey into PCR 18, record in event log * This aligns to TXT's DA scheme * Parse Linux header to detect relevant details about kernel * DEV/DMAR protect remainder of Linux kernel * Extend hash of Linux kernel into PCR 17, record in event log * Prepare and then handoff to Linux kernel proper * Need to support Legacy/CSM and UEFI environments * Add a new start/launch path to Linux kernel * Secure rendezvous APUs * Process system state passed up from LZ * e.g. memory map, etc. * Setup Linux state for handover to mainline start up * Jump into mainline start up