Google dictates that Chromebooks use Coreboot as the HLOS bootloader.
Coreboot replaces the XBL in the Qualcomm LA boot stack for Chromebook distributions.
Coreboot provides all code from PBL to HLOS entry-point.
Bulk of this code is OSS, though provisions are made to allow a vendor
(e.g. Qualcomm) to protect IP (e.g. DRAM initialization and training)
through the use of binary blobs, while implementing the boot stack.
Major components of the Coreboot project that will be used include:
Coreboot, Vboot, Libpayload, Depthcharge and ARM Trusted Firmware.
Provide bootloader stack to SDM845.LC.1.0 project. All code from PBL to HLOS entry-point is included here.