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title: Working with coreboot upstream and Chromium


coreboot development happens in the chromiumos copy of the coreboot repo, and the resulting patch must be pushed to upstream coreboot. While this can be done in one local git checkout, many developers find it easier to use two coreboot git checkouts:

  1. Regular chromiumos checkout
  2. checkout

This document describes how to set up a upstream checkout both in tree and as a separate checkout, and how to synchronize patches between the two checkouts.

Working with coreboot and Chromium

The most familiar local coreboot checkout is the one from chromiumos. It lives under src/third_party/coreboot in the chromiumos workspace. If you followed the ChromeOS Developer guide, it lives at the full path of ~/chromiumos/src/third_party/coreboot.

Developing with coreboot

Creating an account with coreboot

  1. Create an account on Sign in with Google and fill in a username in the settings.

  2. Generate an SSH key and copy the public key into the Gerrit settings form: ssh-keygen -t ed25519 cat ~/.ssh/

  3. Add the following entry to your .ssh/config for SSH access to Gerrit:

        Port 29418
        User <username you configured on Gerrit>

Commit messages

The commit message should follow the ChromiumOS Contributing Guide, including a Signed-Off-By line which can be easily added using git commit -s. The prefix for the title should be an abbreviated path to the edited file. Use git log to check for an example.


CQ-Depend entries can be added to a commit message upstream. The CQ-Depend statement will be ignored upstream, but will take effect in the chromium gerrit. See CL dependencies.


coreboot has its own issue tracking system that can be referenced. However, development intended for ChromeOS should still utilize the same BUG field used in the Chromium Gerrit. Just like the dependencies, the bug field will be ignored by the coreboot Gerrit, but will apply downstream in the Chromium repos.

Pushing code for review upstream

Once the patch has been tested up and downstream and the appropriate commit message has been filled out, the developer can push the patch to

$ git push origin HEAD:refs/for/main

Working with coreboot out of tree(Preferred)

Creating a separate upstream coreboot checkout

Check out upstream coreboot from

   $ mkdir -p ~/devel
   $ cd ~/devel
   $ git clone ssh://

Now the local checkout is tracking origin/main on the local main branch.

Building coreboot in an upstream checkout

  1. Navigate to the top level directory of the upstream checkout bash $ cd ~/devel/coreboot
  2. Run the abuild command for the desired board (util/abuild/abuild -x -t {VENDOR}_{BOARD} --clean) bash $ util/abuild/abuild -x -t GOOGLE_SKYRIM --clean
    1. Omit --clean to preserve build artifacts/logs
    2. Output can be found at ~/devel/coreboot/coreboot-builds/{VENDOR}_{BOARD} #### Setting up a second coreboot checkout to work with chromium Assuming:
  3. there is a chromiumos coreboot checkout at ~/chromiumos/src/third_party/coreboot
  4. there is a coreboot upstream checkout at ~/devel/coreboot

you can link the two repositories using git remotes that are local to the system.

$ cd ~/devel/coreboot
$ git remote add cros-coreboot ~/chromiumos/src/third_party/coreboot
$ git fetch cros-coreboot

$ cd ~/chromiumos/src/third_party/coreboot
$ git remote add upstream_local ~/devel/coreboot
$ git fetch upstream_local

The two repositories now have remotes that track one another. This serves as the basis for cherry-picking patches back and forth or rebasing commits from one repository to the other.

Developing with two coreboot checkouts

Developers should initially work in the chromiumos tree since ChromeOS can build images to test by flashing and booting on a machine. When a commit is ready in the chromiumos tree, it's time to push to Suppose that the developer committed changes in the chromiumos coreboot repository after running repo start feature1. A fetch will bring these changes into ~/devel/coreboot in the cros-coreboot/feature1 branch: 1. Ensure you are in the working directory: bash $ cd ~/devel/coreboot 1. Fetch the repo 1. If the repositories are linked: bash $ git fetch cros-coreboot 1. If the repositories are not linked: bash $ git fetch ~/devel/coreboot 1. Expected output bash remote: Counting objects: 4204, done. remote: Compressing objects: 100% (1229/1229), done. remote: Total 2495 (delta 2069), reused 1576 (delta 1245) Receiving objects: 100% (2495/2495), 456.72 KiB | 0 bytes/s, done. Resolving deltas: 100% (2069/2069), completed with 519 local objects. From ${HOME}/chromiumos/src/third_party/coreboot * [new branch] feature1 -> cros-coreboot/feature1

Now, the developer can cherry-pick or rebase the chromiumos patches into a branch that is tracking coreboot upstream.

# To cherry-pick 1 commit
$ git cherry-pick cros-coreboot/feature1
# To cherry-pick a branch with N commits
$ git cherry-pick cros-coreboot/feature1~N..cros-coreboot/feature1

Working with coreboot in tree

Checking out coreboot in tree

$ cd ~/trunk/src/third_party/coreboot/
$ git remote add origin
$ git remote update
$ git checkout origin/main

Building coreboot in tree

  1. Setup the build system for the board you want to use: bash $ ./setup_board --board=$board

  2. Tell the build system to use the most recent coreboot tree: bash $ cros_workon-$board start coreboot coreboot-utils libpayload

  3. Build the firmware: bash $ emerge-$board coreboot coreboot-utils libpayload chromeos-bootimage

    1. Prepend FEATURES="keepwork" to the emerge command to preserve build artifacts
    2. Output can be found at /build/{BOARD}/firmware/
    3. Output images have the format image-{BOARD}.bin. Images are:
      1. image-{BOARD}.bin - Normal bootable image
      2. image-{BOARD}.serial.bin - Normal bootable image with serial console
      3. image-{BOARD}.net.bin - Debug build. Only applicable on Intel platforms