Architecture Overview

VyomaOS is a four-layer operating system where the kernel handles hardware, and everything else runs through a Rust supervisor that manages WebAssembly applications.

System stack

Linux 5.10 kernel (allnoconfig, 2.3 MB)
  |
Rust supervisor (PID 1, ~2.9 MB static musl)
  |-- Manifest parser (TOML capabilities)
  |-- Concurrent scheduler (one thread per app)
  |-- IPC broker (route @<app>: messages)
  |-- Framebuffer driver (DRM/virtio-gpu)
  |-- TTY input router (raw mode)
  |-- Process manager (ps, kill, restart)
  |
Wasmtime runtime (WASI Preview 2)
  |
WASM apps (wasm32-wasip2 binaries, 1-10 KB each)

Design decisions

Capability-secure by default

The supervisor does not filter app syscalls. It only wires up the WASI imports declared in each app's vyoma.toml. This means:

• No network = true declaration = no network interface exists for the app
• No filesystem = true declaration = no /data mount exists
• No seccomp, AppArmor, or SELinux layer needed

Deterministic binaries

WASM bytecode is byte-identical across builds and hosts. Unlike ELF binaries that vary by libc and architecture, WASM apps produce the same output everywhere. This enables reproducible deployments.

Minimal kernel

The Linux kernel is compiled with allnoconfig plus only the drivers VyomaOS needs:

• virtio (block, network, GPU, console)
• 9P filesystem (host-VM file sharing)
• DRM (framebuffer for display)
• fbcon (early console output)

No networking stack, no USB drivers, no excess filesystem drivers.

Supervisor-side IPC

Apps never communicate directly. The supervisor brokers all messages, which:

• Centralizes routing logic
• Enables monitoring and debugging
• Allows message filtering and rate limiting
• Supports future features like message logging

Supervisor subsystems

The supervisor is organized into focused modules:

Subsystem	Purpose
runtime/	WasmRuntime trait + Wasmtime/wasm3 adapters
hal/	Hardware Abstraction Layer (GPIO, I2C, SPI, UART, ADC)
profile/	Platform profile loader (desktop, mobile, IoT, MCU)
ota/	A/B slot OTA update manager
observability/	Structured heartbeat and metrics emitter
capability/	Peripheral capability enforcer
display/	Framebuffer driver and VYOMA_DRAW parser
font/	Scalable font rendering via fontdue
image/	PNG image loading via lodepng
chrome/	Window decorations and compositor

Build system

Docker-based hermetic builds ensure reproducibility:

make build    # kernel + supervisor + apps + rootfs

The Makefile orchestrates:

1. Linux kernel compilation
2. Supervisor compilation (x86_64-unknown-linux-musl)
3. WASM app compilation (wasm32-wasip2)
4. Rootfs packaging (initramfs.cpio.gz)
5. Data disk creation (ext4, 64 MB)

Multi-platform support

Six platform profiles target different hardware:

Platform	Target	Runtime	RAM
desktop-full	x86-64	Wasmtime JIT	512 MB
mobile	ARM64	Wasmtime JIT	256 MB
server-headless	ARM64/x86-64	Wasmtime JIT	1 GB
iot-edge	ARM64 SBC	WAMR AOT	4 MB
robotics-rt	ARM64	WAMR AOT	8 MB
mcu-minimal	ARM Cortex-M4	wasm3	128 KB