Coreboot

Building in nix-shell

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
    #bison # generate parsers
    #flex
    #clang
    zlib
    #acpica-tools # iasl
    pkgconfig
    qemu # test the image
  ];
  shellHook = ''
    # TODO remove?
    NIX_LDFLAGS="$NIX_LDFLAGS -lncurses"
  '';
}

Now we can build coreboot:

git clone https://review.coreboot.org/coreboot.git --depth 1
cd coreboot
du -sh . # 200 MByte
git submodule update --init --checkout --depth 1
du -sh . # 700 MByte

# configure
# set mainboard, flash size, ...
make menuconfig

# build toolchain
# this can take some hours
make crossgcc CPUS=$(nproc)

# build firmware
make

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

Compiler version

gcc (provided by clang) and gnat (the GNU Ada compiler) must have the same version

gcc --version
gnat --version

For example, both have version 10.3.0

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