Coreboot

Building in nix-shell

Note: the following was tested and working on NixOS 21.11 (Porcupine) while compiling the QEMU target for Coreboot v4.15 as well as Coreboot master (7b168c92f6).

To build your own coreboot bios:

Create a shell.nix, and run nix-shell

# shell.nix

# NOTE we need mkShellNoCC
# mkShell would add the regular gcc, which has no ada (gnat)
# https://github.com/NixOS/nixpkgs/issues/142943

with import <nixpkgs> { };
mkShellNoCC {
  buildInputs = [
    gnat11 # gcc with ada
    #gnatboot # gnat1
    ncurses # make menuconfig
    m4 flex bison # Generate flashmap descriptor parser
    #clang
    zlib
    #acpica-tools # iasl
    pkgconfig
    qemu # test the image
  ];
  shellHook = ''
    # TODO remove?
    NIX_LDFLAGS="$NIX_LDFLAGS -lncurses"
  '';
}

Now we can build coreboot:

# clone coreboot git repository (latest master)
git clone https://review.coreboot.org/coreboot.git --depth 1
# or for a specific coreboot version (I.E. version 4.15)
git clone --branch 4.15 https://review.coreboot.org/coreboot.git --depth 1

# get 3rd party submodules in coreboot repository
cd coreboot
du -sh . # ~200 MByte
git submodule update --init --checkout --depth 1
du -sh . # ~700 MByte

# configure
# set mainboard model, chip size, ...
make menuconfig MENUCONFIG_COLOR=blackbg # blackbg = dark mode

# build toolchain for a x86 target
# Note: the i386 toolchain is used for all x86 platforms including x86_64.
# See https://doc.coreboot.org/tutorial/part1.html
# to list all targets: make help
make crossgcc-i386 CPUS=$(nproc)

# build firmware
make CPUS=$(nproc)

# test firmware
qemu-system-x86_64 -bios build/coreboot.rom -serial stdio

Skip building toolchain

We can use our system toolchain to build coreboot firmware, but this is not recommended per coreboot docs:

you can possibly use your system toolchain, but the results are not reproducible, and may have issues, so this is not recommended

To use the system toolchain, in make menuconfig, enable General Setup > Allow building with any toolchain

Building as derivation

coreboot is pretty picky about the toolchain it is built with and thus using the toolchain it comes with is the easiest path to success. There are commented Nix expressions that build coreboot here.

See also

• https://doc.coreboot.org/tutorial/part1.html
• https://www.coreboot.org/Build_HOWTO
• https://www.coreboot.org/Lesson1
• https://wiki.gentoo.org/wiki/Coreboot
• flashing the new bios image
  • https://doc.coreboot.org/flash_tutorial/
  • https://libreboot.org/docs/install/spi.html