To begin with the aim of introducing coreboot for arm64 qemu, the first task I had to accomplish was to set up a qemu aarch64 environment to work on. In this post, I will talk about building qemu and then booting a kernel that allows us to begin experimentation with this architecture.
To begin building qemu, we need a few packages:
Next, we need a qemu version which support aarch64, so I installed qemu 2.3.0. Here you can also do :
sudo apt-get install build-dep qemu
Since I was building it on a mac, I was required to do a brew install qemu (again, v2.3.0). For mac, it is recommended to use actual gcc rather than the existing ‘gcc’ which is symbolic-linked to llvm-gcc (x86_64-apple-darwin13.4.0/4.9.2/). Going with the innate gcc kept giving me pains, so I downloaded gcc 4.9.2, created a manual link and used it for my build. Moving on, we now need some of the source code;
git clone git://git.qemu.org/qemu.git qemu.git cd qemu.git ./configure --target-list=aarch64-softmmu
The last command will usually return an error, saying DTC (libfdt) not present. The problem is that qemu tries to search for dtc binaries in qemu/dtc. Even if you install dtc using sudo apt-get install device-tree-compiler, we keep getting this error. So probably you need to have the binaries in qemu/dtc. Doing this in the repo will fix it.
git submodule update --init dtc
Then, run the ./configure command again. The output can be found here. We then have to run a make command,
This gives the following ouput. After this successful build, we have an executable ./qemu-system-aarch64 in qemu.git/aarch64-softmmu. I then used a prebuilt kernel image that has a combined initial RAM disk (initrd) and a basic root file-system. It can be downloaded from here.
Then finally, we run this kernel in our generated aarch64 system to find the linux boot sequence and eventually a log in prompt.
qemu-system-aarch64 -machine virt -cpu cortex-a57 -machine type=virt -nographic -smp 1 -m 2048 -kernel ~/Downloads/aarch64-linux-3.15rc2-buildroot.img --append "console=ttyAMA0"
The boot sequence results as
Welcome to Buildroot buildroot login: root # ls # uname -a Linux buildroot 3.15.0-rc2ajb-00069-g1aae31c #39 SMP Thu Apr 24 11:48:57 BST 2014 aarch64 GNU/Linux
This gives us an aarch64 qemu environment with linux on which we can begin building coreboot.
With the development platform ready, I now begin my actual work on building coreboot for qemu arm64. For this week, I look at the ( now obsolete ) foundation-armv8 patchset and begin my development. The first task would be to create an appropriate media structure / functions that I would use.