xous-rs-2024/OUTLINE.md

Notes for the talk's outline

About Me

• Based in Singapore
• Hardware and software

Outline

1. Project History
2. Why a new OS?
3. What can it do?

Project History

Novena: A really open laptop

We always wanted to make a laptop. Decided to give it a shot to see what happened.

The processor in this was "relatively large" -- ARM Cortex A9

Ran Linux

Chibitronics: Programming for 8-year-olds

This had a "relatively small" processor -- ARM Cortex M0 with 4 kB RAM and 32 kB flash

We got to know this chip really well

• Bit-banged USB
• AFSK demodulation
• https://ltc.chibitronics.com/

Ran ChibiOS and a very custom program

Precursor: Secure communications device

• FPGA-based (any processor you want!)
• 16 MB RAM
• 128 MB storage

Why a new OS?

Two major markets:

• MCU
  • No MMU, maybe an MPU
  • <= 1 MB RAM
  • <= 4 MB storage
• CPU
  • MMU designed for multiple processes

  • = 64 MB RAM

  • = 256 MB storage (external)

What can it do?

• Kernel is 17 ksloc
  • 6k of that is a RISC-V disassembler for optional GDB support
• Threads
• Processes
• Tier 2 Rust support
  • libstd
• Entire project built on stable Rust

Other features

• Fully Rust
• Microkernel
• Stable channel
• Requires an MMU
• Interrupts in userspace
• Each page of memory is mapped once

Xous Organization

• Kernel is single-threaded
• Services use well-defined API calls
• All drivers provided in user space
• Each page of memory can only be lent once

How can I use it?

• Talk to system vendors -- get them to include MMUs!
• Emulation is easiest -- Renode support