willOS
willOS is a minimal 64 bits kernel (not really an Operating System because it
cannot do a lot of things currently). Some screencasts are available in this
Twitter thread.
Setting up a development environment
The following dependencies are required to build this project:
gcc(build-essential)nasmldgrub-mkrescue(part ofgrub2-common)xorriso- (optional)
qemu
This project targets x86_64 architectures, so you likely need a
cross-compilation toolchain.
Docker (recommended way)
Use Docker with the provided
Dockerfile:
$ docker build -t willos/toolchain .
$ docker run --rm -v $(pwd):/app willos/toolchain make
MacOS
Install Homebrew, then run the following commands:
$ brew install nasm
$ brew install xorriso
$ brew install qemu
You need to tap hawkw/x86_64-pc-elf to install the cross-compilation toolchain:
$ brew tap hawkw/x86_64-pc-elf
$ brew install x86_64-pc-elf-gcc
You need to tap hawkw/grub to install the GRUB utility:
$ brew tap hawkw/grub
$ brew install grub --with-x86_64-pc-elf --HEAD
Hat tip to Eliza Weisman for the taps!
Linux
See the circle-ci
config.
Building willOS
To compile the kernel (ELF 64-bit), run:
$ make kernel
To build the ISO (this is the default target), run:
$ make iso
To compile the OS in DEBUG mode, build the ISO, and start qemu with the OS
loaded, run:
$ make debug
Note: in DEBUG mode, logging uses the serial port COM1 to write various
debugging information. qemu is configured to write the output of this serial
port to /tmp/serial.log.
To compile the OS in normal mode, build the ISO, and start qemu with the OS
loaded, run:
$ make run
Early boot sequence
- The BIOS loads the bootloader (GRUB) from the ISO
- The bootloader reads the kernel executable and finds the multiboot header
- The bootloader copies the
.bootand.textsections to memory (to
addresses0x100000and0x100020) - The bootloader jumps to the entry point (at
0x100020) - Various checks are performed to make sure we can continue the boot process
- Page table and paging are configured and enabled
- Load a 64-bit Global Descriptor Table
- Reload all the data segment registers
- Call the C
kmain()function
License
willOS is released under the MIT License. See the bundled
LICENSE file for
details. In addition, some parts of this project have their own licenses
attached (either in the source files or in a LICENSE file next to them).