walos

WebAssembly Language based Operating System is a toy OS using the Language-based System approach.

Processes and drivers (services) are WASM binary executed by design in a sandboxed environment. So drivers can be implemented in any language targeting WebAssembly.

Unlike generalist OS, walos ignores hardware protection (Ring0, single address space). This idea simplifies the system architecture and improves performance by avoiding context switching. Syscalls are simple function calls triggered using interfaces like WASI. On the downside, the OS is not protected against CPU side-channel attacks.

Built With

• LLVM: clang, lld, wasm-ld - Make
• WASI SDK - WASM3
• QEMU - OVMF
• Limine
• Love and insomnia

Features

• WASM runtime
• Multi loaders
  • os (EFI | BIOS)
  • efi (EFI runtime)
  • elf (Unix executable)

Planned

• Multitasking
• Trim services tree
• WASM custom section
• Multi arch x86_64, Risk-V & Arm64

Getting started

Prerequisites

OS	Needed	Optional
Debian / Ubuntu	make clang lld	qemu-system ovmf xorriso
Arch / Manjaro	make clang lld	qemu edk2-ovmf libisoburn

Setup

1. Clone

git clone https://github.com/CalmSystem/walos.git
cd walos

2. Start sample/shell as ELF binary

make run ENTRY=sample/shell LOADER=elf

• Start sample/exec with QEMU and OVMF

make run ENTRY=sample/exec

• Create a bootable ISO of sample/hello.c

make package ENTRY=sample/hello.c

• Start sample/vga with QEMU, Limine and graphics

make run ENTRY=sample/vga RUN_ISO=1 RUN_VGA=1

Known environment errors

Message	Possible solution
No rule to make target '.wasm'	ENTRY argument missing
llvm-ar: Command not found	export PATH=$PATH:/usr/lib/llvm-10/bin
Executable "wasm-ld" doesn't exist!	🔼 🔼
lld: error: unable to find library -lc	export LDPATH=/usr/lib64
/bin/sh: 1: ./run: not found	export DLINK=/lib/x86_64-linux-gnu/ld-linux-x86-64.so.2
qemu: could not load PC BIOS	export OVMF=/usr/share/ovmf/x64/OVMF.fd

Project structure

• include/ - Shared structures declarations
  • kernel/ - OS core library declarations
  • utils/ - Header only utilities
  • w/ - Common services declarations
• kernel/ - OS core library
  • libc/ - Freestanding libC
• loader/ - Boot loaders implementations
  • os/ - Standalone loader
  • efi/ - UEFI application
  • elf/ - Linux binary loader
• engine/ - WASM engine implementations
  • wasm3/ - WASM3 interpreter
• service/ - Services implementations
• sample/ - Sample entry points
  • entry.c - Makefile for *.c
  • hello.c - Print Hello world
  • vga/ - Display wasm.tga on screen and wait
  • exec/ - Run embed.c using system WASM engine
  • shell/ - Interactive shell using WAPM

Outputs

• build/ - Temporary build files
• target/ - Output files

Similar projects

• Nebulet - A microkernel that implements a WebAssembly "usermode" that runs in Ring 0
• Kwast - Rust operating system running WebAssembly as userspace in ring 0
• Etheryal - Open Source Rust kernel; Runs WASM and WASI as lightweight containers
• IncludeOS - C++ Unikernel

License

Distributed under the GPLv3 License. See LICENSE for more information.