breadcrumbs: - - /chromium-os/developer-library/guides - ChromiumOS > Developer Library > Guides page_name: coreboot

title: coreboot in Chromium

Introduction

coreboot is an extended firmware platform that delivers a lightning fast and secure boot experience on modern computers and embedded systems. As an Open Source project it provides auditability and maximum control over technology. Its design philosophy is to do the bare minimum necessary to ensure that hardware is usable and then pass control to a different program called the payload. coreboot reserves an area in memory to save some data after it’s finished booting, known as CBMEM. In addition to CBMEM, on X86 systems, coreboot will set up SMM. This will contain things such as the boot log and other information, tables that get passed to the payload, and ACPI tables for the OS. ChromeOS uses and actively contributes to coreboot.org. See also the coreboot documentation.

Comparison to UEFI

coreboot and UEFI both handle the initialization of the hardware, but are otherwise not similar. coreboot’s goal is to JUST initialize the hardware and then exit. UEFI is actually a firmware specification, not a specific software implementation. Intel has released an open-source implementation of the overall framework, TianoCore, but it does not come with hardware support. Most hardware running UEFI uses a proprietary implementation. coreboot does not follow the UEFI specification, but it can be used to launch a UEFI payload such as Tianocore in order to provide UEFI boot services.

The UEFI specification also defines and allows for many things that are outside of coreboot’s scope: * Boot device selection * Updating the firmware * A shell * Network communication

Use within ChromeOS

All ChromeOS devices(Chromebooks, Chromeboxes, Chromebit, etc) released from 2012 onward use coreboot for their main system firmware. ChromeOS utilizes the depthcharge payload which performs additional actions and ultimately loads the Linux kernel. See coreboot upstream for information on how to work with upstream coreboot in the chromium repo.

Upstream philosophy

ChromeOS is an upstream first project. With rare exception, all changes should be made in the upstream coreboot repository and subsequently downstreamed to the Chromium repo. See downstreaming coreboot for more information on the downstreaming process.