CheriOS-microkernel

CheriOS is a minimal microkernel that demonstrates "clean-slate" CHERI memory protection and object capabilities.

Note

CheriOS-microkernel is still in a very early state.

• The code is not well documented
• It lacks several security checks/actions (thus the model is not secure yet)
• Expect races, non-recovery on error, ...

Building CheriOS

You need a Cheri SDK (LLVM and Clang) to build CheriOS.

256-bit Cheri SDK works out of the box. 128-bit Cheri SDK is not officially supported yet (it works with minor tweaks).

The following snipset will build CheriOS for a 256-bit SDK targetting cheri-qemu (defaults).

$ git clone https://github.com/CTSRD-CHERI/cherios.git cherios
$ cd cherios
$ ./build.sh

Running CheriOS

CheriOS can run on:

• cheri-qemu
• the CHERI fpga model
• the CHERI l3 simulator

The target can be choosen by setting xxx in CMakelists.txt

The following snipset shows how to run CheriOS on cheri-qemu:

$ dd if=/dev/zero of=disk.img bs=1M count=1
$ qemu-system-cheri -M malta -kernel cherios.elf -nographic -no-reboot -m 2048 \
   -drive if=none,file=disk.img,id=drv,format=raw -device virtio-blk-device,drive=drv

Code organisation

CheriOS code is organized as follow:

• kernel: kernel (the interesting part)
• boot: boot code
• fatfs: simple FAT filesystem module
• hello: Hello World module
• include: generic includes used by several modules
• ldscripts: link scripts user by modules
• libuser: all modules are linked againt it. Provides several libc function as well as cherios-related functions
• memmgt: provides the system-wide mmap
• namespace: provides a directory of registered activations
• prga: test program
• socket: module providing a minimalistic implementation of sockets
• uart: module providing print services
• virtio-blk: VirtIO over MMIO module
• zlib: zlib module
• zlib_test: test/benchmark for the zlib module