Aarch64 bare metal boot code

What this project do

Building bare metal boot code for AArch64 architecture, that's able to do:

• Booting system from ROM as a bootloader.
• Booting system from RAM as a kernel.
• Self-relocating from ROM to RAM and start executing.
• Able to boot from any Exception Level (EL3->EL0).
• Run the EL0 code in C, and request svc system call to the kernel (EL1 code) and get the result.
• Implement a system call dispatcher in EL1.

The blog that tells every details about this project here Blog.

How to build

Download the toolchain from ARM official website, and change the cross compiler in Makefile to your path:

CROSS_COMPILE=../linux/toolchain/bin/aarch64-none-linux-gnu-

And then make.

How to test

I'm using QEMU as a platform, that you can change the EL by using option virtualization and secure. And also the -bios option tell the QEMU that our firmware will run as ROM code, -kernel option means run as kernel and start from RAM.

• Start from EL3 as a ROM boot code:

qemu-system-aarch64 -M virt,virtualization=on,secure=on -cpu cortex-a57 -nographic -bios boot.bin -D log.txt -d int

• Start from EL2 as a ROM boot code:

qemu-system-aarch64 -M virt,virtualization=on,secure=off -cpu cortex-a57 -nographic -bios boot.bin -D log.txt -d int

• Start from EL1 as a ROM boot code:

qemu-system-aarch64 -M virt,virtualization=off,secure=off -cpu cortex-a57 -nographic -bios boot.bin -D log.txt -d int

• Start from EL3 as a kernel:

qemu-system-aarch64 -M virt,virtualization=on,secure=on -cpu cortex-a57 -nographic -kernel boot.elf -D log.txt -d int

• Start from EL2 as a kernel:

qemu-system-aarch64 -M virt,virtualization=on,secure=off -cpu cortex-a57 -nographic -kernel boot.elf -D log.txt -d int

• Start from EL1 as a kernel:

qemu-system-aarch64 -M virt,virtualization=off,secure=off -cpu cortex-a57 -nographic -kernel boot.elf -D log.txt -d int

Sample result:

$ qemu-system-aarch64 -M virt,virtualization=on,secure=off -cpu cortex-a57 -nographic -bios boot.bin -D log.txt -d int
Aarch64 bare metal code!
In EL2!
In EL1!
In EL0!
Enter el0_main!
System call return a correct result.
Exit el0_main!