Can I run Python code on Morello?

If you are running in hybrid mode, you can install the default CPython interpreter with:

pkg64 install python3

This works fine, but does not have runtime support for capabilities or fine-grained memory protection.

Building MicroPython

MicroPython is a cut-down Python interpreter, designed for embedded systems. It has a smaller range of libraries than the default CPython. There is a fully functional port of MicroPython to purecap on CheriBSD. Below are the instructions for building MicroPython natively on the CheriBSD Morello platform.

# download the source code from github
git clone
cd micropython
git fetch origin morello-dev
git switch morello-dev
cd ports/unix

# install dependencies
pkg64 install git gmake llvm-morello python3 pkgconf
pkg64c install libffi

# now build micropython
gmake CC='clang-morello -march=morello -mabi=purecap' CXX='clang++-morello -march=morello+c64 -mabi=purecap' LIBFFI_LDFLAGS='-L/usr/local/lib -lffi' submodules
gmake CC='clang-morello -march=morello -mabi=purecap' CXX='clang++-morello -march=morello+c64 -mabi=purecap' LIBFFI_LDFLAGS='-L/usr/local/lib -lffi'

# the binary is at ./build-standard/micropython

Using MicroPython

The purecap MicroPython build on Morello supports tight bounds for allocations, as demonstrated by this unsafe code below, which works in vanilla MicroPython but causes a capability protection fault on Morello.

import uctypes as uct
tiny = bytearray(1)
ptr = uct.addressof(tiny)
# create a new bytearray based on ptr
unsafe = uct.bytearray_at(ptr, 16384)
# access out-of-bounds memory
unsafe [200] = 0x1f

Further references