--- title: EDK2 payload in Libreboot, plus Chromebooks. x-toc-enable: true ... **IGNORE chromebook info. This is a placeholder for when Canoeboot later adds Chromebooks up to Intel Haswell series (possibly Kabylake). This is inherited from Libreboot when merging EDK2 support, and this page also contains general information.** - Chromebooks (Intel/AMD) not yet actually present in Canoeboot, at least as of Canoeboot 26.11. This page also contains general guidance about EDK2 on all boards that use it, which is nearly all boards; many non-Chromebooks have EDK2 now as the default payload, in Libreboot. **This document applies to x86-64 Chromebooks. ARM64 Chromebooks are covered by [chromebooks](chromebooks.md).** Libreboot uses EDK2 on x86 Chromebooks, and U-Boot on ARM64. This page is for the EDK2 version on x86-64. Intel ME on Chromebooks ------ Libreboot leaves the Intel ME enabled by default *on Chromebooks* - on other boards, we generally disable it by default. We initially disabled it in bulk on these Intel Chromebooks, but it was decided otherwise. Users can disable it. This may break certain functionality on specific Chromebooks, e.g. SOF (Sound Open Firmware) based audio chipsets might break. Libreboot's [Binary Blob Reduction Policy](../../news/policy.html) is quite clear: we will exclude or disable any blobs that are unnecessary for operation on a given machine - however, an exception was specified there for cases where a blob is needed for the extra functioning of critical peripherals. It was decided in the Libreboot 26.10 release that your sound card is not an essential component, but this has since changed. Upstream MrChromebox also leaves Intel ME turned on by default, on Intel Chromebooks. The ME is required for DSP signature verification on certain audio chipsets. DO NOT report issues upstream Chromebooks issues to MrChromebox or others e.g. Chrultrabook. Please only report to Libreboot's issue tracker, for whatever issues you find. We will deal with you. In discussion with ninelore on IRC for example, it was stated that the following software would not work with Intel ME disabled: * Context: * More context: Thank you also to ellyq of Chrultrabook who very politely raised this issue. You can disable the ME via `--altmedisable 1` option in ifdtool, and you should also use `--platform PLATFORM` for your specific board; check Kconfig in coreboot for what the platform string should be on your board. Note that some older IFD versions don't require a platform string. Individual ME disablement can be done by Libreboot as time goes by, subject to rigorous user testing. These Chromebooks are currently marked `release="n"` in Libreboot's build system, so binaries of them are not yet provided. We generally want Libreboot to be as close to MrChromebox as possible in terms of board behaviour, hence this policy change enacted after the 26.10 release. Build from source ----------------- x86 Chromebooks not provided as binaries yet - they were source-only in the Libreboot 26.10 release. You must [build from source](../build/). Make sure to have dependencies installed, as per that page, and then do this in lbmk: ``` ./mk -b coreboot list | grep cros_ ``` This will show all of the targets, corresponding to boards. Then pick one from the list and do e.g. ``` ./mk -b coreboot cros_byt_kip_uefi ``` This will build a target. An image will appear under `bin/`, in this example `bin/mrchromebox_byt_kip_uefi/` - a lot of testing is needed before these appear as binaries in releases. Efforts are made to ensure tight sync with upstream at all times. We more or less use the same config as MrChromebox, building everything per-board in exactly the same way; lbmk even builds EDK2 once per mainboard, to ensure that the correct build flags are used. Expect possible breakage on some newer platforms as unlike MrChromebox, we set the Intel HAP bit by default (on Intel platforms) to disable the Intel ME. Please report any issues you find to the Libreboot bug tracker. The above example target, `mrchromebox_byt_kip_uefi`, was in fact tested for the Libreboot 26.10 release. Another issue is generally the use of vendor code in MrChromebox, currently done by the latter with direct distribution of such files in a special repository. Libreboot prefers, for release binaries, to scrub these at release time and insert them on release image tarballs via `./mk inject` scripting, to avoid direct distribution of such files. This can be done in a future Libreboot release, thus enabling the distribution of pre-compiled coreboot builds for these Chromebooks. Open source BIOS/UEFI firmware ------------------------------ This document will teach you how to install Libreboot, on various Intel/AMD Chromebook laptops. Libreboot replaces proprietary BIOS/UEFI firmware, though it should be noted that Google already ships coreboot and their own payload called Depthcharge, which is all free software; the difference with Libreboot is that it replaces Depthcharge with *EDK2* (as a coreboot payload), which provides a full UEFI boot implementation that can boot regular Linux and BSD systems more easily than Depthcharge. It can also boot Windows. We provide this as the default payload since Libreboot 26.10 Ominous Olive, on nearly all x86-64 mainboards; this applies also to non-Chromebook mainboards, which are also covered by this page ostensibly written about Chromebooks. We specifically use the [MrChromebox](https://docs.mrchromebox.tech/) version of EDK2, and on Chromebooks we also use MrChromebox coreboot instead of regular coreboot. You are *strongly* advised to read MrChromebox documentation in addition to Libreboot, as Libreboot does not currently integrate any of its tooling; it only has MrChromebox coreboot and EDK2. This is to say: if using Libreboot on a Chromebook, you should refer to MrChromebox documentation for information about installation and updates. Libreboot tries to maintain sync with MrChromebox in such a way that the ROM images are interchangeable. We modify MrChromebooks in the following ways: * Added EFI GRUB build in PE32 section * Added EFI SeaBIOS CSM (CSMWrap) in PE32 section * Added Memtest86\+ in PE32 section. * Enabled iPXE by default on non-Chromebooks. This page attempts to give a brief, general overview of how to flash custom firmware on ChromeOS devices. This guide usually refers to all of them as "Chromebook"s since it's the most common form factor. Non-chromebooks are also covered for installation. These will be covered first. General EDK2 guidance ----- This applies to all boards, not just Chromebooks. Some tips: We use SMMSTORE by default. You can use this option in flashprog when updating the ROM: ``` --fmap -i COREBOOT ``` Use these options in flashprog, to flash just the COREBOOT section. This avoids overwriting SMMSTORE which contains settings, otherwise you will restore your settings to default when updating. GRUB and SeaBIOS in PE32 work like the old coreboot payloads; old Libreboot setups can be adapted easily. Our setup is made to be backward-compatible. NOW, the rest of this page pertains specifically to *Chromebooks*: Flashrom -------- A special fork of flashrom, maintained by Google, is required for flashing these Chromebook devices. See: This document assumes you’ll be using ChromeOS to do the internal flashing. ChromeOS already comes with this special fork of flashrom pre-installed. But if you are using another OS or an external flasher, you will need to compile and use the aforementioned flashrom fork. NOTE: Upstream flashrom also supports this. Specifically: `--disable-wp` is needed for disabling write protection once clearing the WP pin. Flashprog will need to have this feature added, and then this section can remove flashrom from its recommendation. Enable ChromeOS "Developer Mode" -------------------------------- Chromebooks are locked-down by default to only run ChromeOS. Most things you will want to do on these require you unlock it by enabling their [Developer Mode](https://chromium.googlesource.com/chromiumos/docs/+/HEAD/developer_mode.md). On most devices, you would press the `Escape + Refresh + Power` key combination to restart into the Recovery Mode, then press `Ctrl + D` and finally confirm enabling Developer Mode with `Enter`. On your next boot, it will show you an "OS Verification is disabled" screen. Waiting for 30 seconds or pressing `Ctrl + D` on this screen will proceed to boot into ChromeOS, which then erases all data on the device and reboots again into a clean ChromeOS installation. Before following steps to configure your device as new in the first screen, you should be able to see a “Enable debugging features” link that you should click on. A confirmation dialog displays. Click Proceed. The system reboots, use `Ctrl + D` again and displays a dialog with password prompts. Set the new root password. Click Enable. The screen displays messages indicating success or failure. Click OK. You'll see the first screen again. Follow the remaining prompts to configure your Chrome device. Once you are finished configuring your device, you’ll be giving the option to sign in; here you may use the guest account option in the bottom if you like. Now in the desktop we’ll set a password to use “sudo”: Use `Ctrl+Alt+Forward Arrow` (the one two key to the right of esc key, representing F2) to open a “Developer console” (similar to opening a tty) where the first line ends with “localhost login”. Enter root and the password you just set for it. Then you must run `chromeos-setdevpassword` and set another password, which is the one that is actually used when running “sudo”. Now use `Ctrl+Alt+Backward Arrow` (the key next to the right of esc, representing F1) to get back to the desktop. With Developer Mode enabled, you can launch a terminal emulator inside ChromeOS by pressing the `Ctrl + Alt + T` key combination. Run `shell` inside the resulting `crosh` prompt to actually get to a `bash` session where you can run programs. Most of the root file system is read-only, except for `/usr/local` and any mounted drives under `/media/removable`. Identify your device -------------------- It's more common to refer to ChromeOS boards by their codenames, and many compatible devices can share a single codename. Libreboot ROM images also use these, you should only use the one corresponding to your device's. There are a number of ways to find it, some are: - Check the "Model" on the Recovery Mode or Developer Mode screens - Visit `chrome://version` in ChromeOS and check the "Firmware Version" - Run `crossystem hwid` or `crossystem fwid` in a terminal Back up stock firmware ---------------------- The stock firmware on your device comes with some irreplaceable data that is unique to your device. This can include the serial number and hardware ID of the device, network MAC address, HDCP keys, maybe more. The stock firmware is also the only one that will properly boot and run ChromeOS. Make sure you back up the original firmware before trying to replace it. The version of flashrom in ChromeOS understands `host` as a programmer to flash firmware internally. To back up stock firmware you can run: sudo flashrom -p host -r depthcharge.rom sudo flashrom -p host -v depthcharge.rom Keep the resulting `depthcharge.rom` file safe and properly backed up on another device. If you can already boot a conventional Linux distro on your Chromebook, you may be able to use `flashrom -p linux_mtd` on that system instead. **NOTE: MrChromebox flash scripts can be used with Libreboot images. These scripts intentionally preserve the `RO_VPD` region containing MAC address and serial number.** Further note: in my testing, it looks like most Intel chromebooks don't use Intel gigabit ethernet NICs, so use of nvmutil is largely useless on these boards. Check external flashability --------------------------- If a ROM image you flash is broken, you may need to restore the stock firmware to fix the board to get internal flashing working. Refer to the [external flashing guide](spi.md), and check that the result of `flashrom -r` matches what you get when you run it from the device. Chromebooks may have 1.8V as the supply voltage for the SPI NOR chip, be extra careful about that. On newer Chromebooks, there is a root-of-trust chip providing a [Closed Case Debugging](https://chromium.googlesource.com/chromiumos/platform/ec/+/cr50_stab/docs/case_closed_debugging_gsc.md) mechanism that lets you flash externally using a special USB debugging cable. However, most boards that Libreboot supports do not have this. Disable write protection ------------------------ Chromebooks have the SPI flash chip partially write-protected by default, but thankfully this protection can be disabled by the device owner. How to do so depends on the board, refer to the [ChromiumOS documentation on Write Protection](https://chromium.googlesource.com/chromiumos/docs/+/HEAD/write_protection.md) for more info. You will usually need to do this only once for the board's lifetime, unless you manually enable it again. On most boards that Libreboot supports, write-protection is enforced by a physical screw. When screwed in, it forms an electrical connection that asserts the WP pin on the flash chip. The screw can be identified by the fact that it bridges electrical contacts, but finding and removing it might require you to disassemble most of the board. In my case as an example, my kevin board had the protection screw [here](https://av.libreboot.org/board/kevin/write_protection_screw.jpg). It was tricky for me to find it since it was one of the screws that seemed to hold the heat sink in place, which I thought made it an unlikely candidate. I recommend you leave it unscrew never the less after flashing. Newer boards have a root-of-trust chip enforcing write-protection. The [Closed Case Debugging](https://chromium.googlesource.com/chromiumos/platform/ec/+/cr50_stab/docs/case_closed_debugging_gsc.md) mechanism should be used to disable hardware write-protection. Opening the case and disconnecting the battery might also disable it. Disabling the write-protect signal doesn't directly make the chip stop protecting its data, it just allows you to disable its write-protection in software. That also needs to be done in ChromeOS afterwards: sudo flashrom -p host --wp-status sudo flashrom -p host --wp-disable sudo flashrom -p host --wp-range 0x0,0x0 The *--wp* arguments are only available on the [ChromiumOS fork of flashrom](https://sites.google.com/a/chromium.org/dev/chromium-os/packages/cros-flashrom). If you are using another OS or an external flasher, you may need to compile and use that flashrom fork to disable write-protection. There is no `lbmk` support yet for automatically building it. Have a look at MrChromebox's write protect notes linked at the bottom of this page, which has some useful guidance, also see the next sections. Prepare the ROM image --------------------- Libreboot ROM image layouts are currently incompatible with the regions that should be carried over from the stock firmware. However, the released images should still be somewhat usable, since the Chromebooks supported so far don't require any non-redistributable code to be injected by the end user. Future Libreboot versions will likely require post-processing to preserve irreplaceable data in the firmware image. For now, make sure to keep backups of the original firmware. TODO: Instructions to preserve vital data when FMAPs are compatible. Flash the ROM image ------------------- You can flash the ROM image both internally and externally. For the latter, see the [external flashing guide](spi.md) and the ChromiumOS [Closed Case Debugging](https://chromium.googlesource.com/chromiumos/platform/ec/+/cr50_stab/docs/case_closed_debugging_gsc.md) documentation if your board supports it. To flash the entire ROM image internally, run within ChromeOS: sudo flashrom -p host -w libreboot.rom sudo flashrom -p host -v libreboot.rom If you can already boot a conventional Linux distro on your Chromebook, you may be able to use `flashrom -p linux_mtd` on that system instead. Install an operating system ------------------------------------------------ EDK2 is UEFI-based. It will work perfectly with any UEFI-based operating system you throw at it. Linux and BSD will pretty much just work, but may have some quirks; check MrChromebox documentation about this. Windows can be used, and drivers may be found here: We discourage the use of Windows, but this link is provided for completeness. See also -------- * [ChromiumOS Documentation](https://chromium.googlesource.com/chromiumos/docs/+/HEAD/) * [ChromiumOS Firmware Test Manual](https://chromium.googlesource.com/chromiumos/docs/+/HEAD/firmware_test_manual.md) * [ChromiumOS Flashrom Fork Information](https://www.chromium.org/chromium-os/packages/cros-flashrom/) * [MrChromebox's Unbricking Guide](https://wiki.mrchromebox.tech/Unbricking) * [MrChromebox's Write-Protection Notes](https://wiki.mrchromebox.tech/Firmware_Write_Protect) * [Coreboot Tutorial as used in ChromeOS](https://docs.google.com/presentation/d/1eGPMu03vCxIO0a3oNX8Hmij_Qwwz6R6ViFC_1HlHOYQ/preview) [//]: # "SPDX-License-Identifier: GFDL-1.3-or-later" The Canoeboot version of this page is: