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Xous Core

Core files for the Xous microkernel operating system.

You might find this wiki handy, as well as the Xous Book.

This repository contains everything necessary to build the Xous kernel from source. It consists of the following projects:

  • kernel: core memory manager, irq manager, and syscallhandler
  • loader: initial loader used to start the kernel
  • tools: programs used to construct a final boot image
  • docs: documentation on various aspects of Xous
  • emulation: Renode scripts used to emulate Xous
  • xous-rs: userspace library


  • Xous requires its own Rust target, riscv32imac-unknown-xous-elf. If you run cargo xtask from the command line, you should be prompted to install the target automatically if it does not already exist.
  • You may need to remove the target/ directory before building, if rustc continues to behave like it can't find the xous target even after it is installed.
  • If you plan on doing USB firmware updates, you'll need progressbar2 (updates) and pyusb (updates). Note that pyusb has name space conflicts with similarly named packages, so if updates aren't working you may need to create a venv or uninstall conflicting packages.
  • If you are doing development on the digital signatures with the Python helper scripts, you will need: pycryptodome (signing - PEM read), cryptography (signing - x509 read), pynacl (signing - ed25519 signatures) (most users won't need this).
  • Some system packages are needed, which can be installed with sudo apt install libssl-dev libxkbcommon-dev or similar
  • If you receive an error about feature resolver is required, try installing a newer version of rustc and cargo via rustup

Quickstart using Hosted Mode

You can try out Xous in a "hosted mode" wherein programs are compiled for your native platform and are run locally as processes within your current operating system. System calls are replaced with network calls to a kernel that simply shuffles messages around.

Xous uses the xtask convention, where various complex build commands are stored under cargo xtask. This allows for us to create arbitrarily complex build sequences without resorting to make (which is platform-dependent), sh (which requires a lot of external tooling), or another build system.

To build a set of sample programs and run them all using the kernel for communication, clone this repository and run:

cargo xtask run

This will build several servers and a "shell" program to control them all. Most notably, a graphics-server will appear and kernel messages will begin scrolling in your terminal.

Quickstart using an emulator

Xous uses Renode as the preferred emulator, because it is easy to extend the hardware peripherals without recompiling the entire emulator.

Download Renode and ensure it is in your path. For now, you need to download the nightly build, until DecodedOperation is included in the release.

Then, build Xous:

cargo xtask renode-image

This will compile everything in release mode for RISC-V, compile the tools require to package it all up, then create an image file.

Finally, run Renode and specify the xous-release.resc REnode SCript:

renode emulation/xous-release.resc

Renode will start emulation automatically, and will run the same set of programs as in "Hosted mode".

Generating a hardware image

To build for real hardware, you must specify an .svd file. This file is generated by the SoC build process and describes a single Betrusted core. These addresses will change as hardware is modified, so if you distribute a modified Betrusted core, you should be sure to distribute the .svd file.

We have included a reference version of the gateware and its SVD file in the precursors directory, so you can compile a gateware for the reference image using this command:

cargo xtask hw-image precursors/soc.svd

The resulting images are in your target directory (typically target/riscv32imac-unknown-xous-elf/release/) with the names xous.img (for the kernel) and loader.bin (for its bootloader). The corresponding gateware is in precursors/soc_csr.bin. These can be written to your device by following the update guide.