OVMF

OVMF is a project by TianoCore that targets accurate emulation of real UEFI hardware in virtual environments.

OVMF is part of why this whole project exists; without it LensorOS would need to be tested on real hardware at every step... Suffice to say I'm very grateful.

Due to OVMF depending on the (humongous) EDK2 code-base to create the OVMF images that are required for QEMU to run, I provide some pre-built images so everybody that wants to emulate LensorOS doesn't have to build EDK2 + OVMF from source.

If you would prefer to build OVMF anyway, due to trying to target a different architecture or just the ones included being out of date, here are the resources needed to build them yourself:

• EDK2 Source from GitHub
  • This includes OVMF, as well as about 30 other packages. We will only be using two of them:
    • MdeModulePkg
    • OvmfPkg
  • EDK2 has a slightly convoluted build system, but it's nothing too bad if you made it through the cross compiler. I found the following resources immensely helpful for the initial EDK2 build (all links wayback machined for posterity):
    • EDK2 Common Instructions
    • Using EDK2 with Native GCC

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Building OVMF from Source

Warning: This requires over a GiB of hard-drive space.

As with most large builds, utilize the make -j flag to allow for more jobs to happen at once (multi-threading). The general consensus is to pick somewhere around the amount of CPU cores you have. Whichever you pick, more jobs happening at once means faster builds (and with large ones like the ones upcoming, you will definitely want them to be sped up).

Before you do anything, ensure the following pre-requisites are installed:

sudo apt install build-essential uuid-dev iasl git gcc-5 nasm python3-distutils

To begin, you must obtain the EDK2 source code. This can be done through GitHub, SourceForge, etc. For this example, I'll show obtaining it from GitHub onto a Unix-like system into a directory $HOME/EDK2/.

cd $HOME
mkdir -p EDK2
cd EDK2
git clone https://github.com/tianocore/edk2.git
cd edk2
git submodule update --init

Next, compile the build tools that EDK2 uses to build itself, then setup a basic configuration, then re-build the tools once more :^).

cd $HOME/EDK2/edk2
make -C BaseTools
. edksetup.sh
make -C BaseTools

For EDK2 to work properly, it needs to be told where a few things are installed on the system (namely, it's BaseTools directory).

cd $HOME/EDK2/edk2
export EDK_TOOLS_PATH=$HOME/EDK2/edk2/BaseTools
. edksetup.sh BaseTools

Once the build tools have been built and setup correctly, configuration files should have been made in the $HOME/EDK2/edk2/Conf directory.
Find the following lines within target.txt:

• "TARGET = DEBUG"
• "TARGET_ARCH = IA32"
• "TOOL_CHAIN_TAG = VS2015x86"

Replace them with the following:

• "TARGET = DEBUG RELEASE"
• "TARGET_ARCH = X64"
• "TOOL_CHAIN_TAG = GCC5"

You may be tempted (like me), to try out different versions of GCC, but it turns out GCC5 is EDK2's way of saying GCC5 or greater.

To build MdeModulePkg, a dependency of OvmfPkg, run the following one-liner:

cd $HOME/EDK2/edk2 && build -p MdeModulePkg/MdeModulePkg.dsc

With MdeModulePkg built, we can move on to building OvmfPkg to get our .fd files that are necessary for QEMU to boot into a UEFI environment:

cd $HOME/EDK2/edk2 && build -p OvmfPkg/OvmfPkgX64.dsc

A specific size, x, of OVMF.fd may be defined by appending the following to the above build command:

-DFD_SIZE_IN_KB=x

The included OVMF binaries are built using -DFD_SIZE_IN_KB=2048 for a 2MiB image.

With that, you have successfully built OVMF from source! Congratulations.
Within the Build sub-directory you should be able to find two files within OvmfX64/FV/:

• OVMF_CODE.fd
• OVMF_VARS.fd

These can be copied to LensorOS/OVMFbin/ and, if correctly renamed, will be used by QEMU to boot from when the run batch/shell script is used.