I got a bug report concerning my sqlite-fts4 project running on PPC64 and s390x architectures.
\nThe s390x is an IBM mainframe architecture, which I found glamorous!
\nThe bug related to those machines being big-endian v.s. my software being tested on little-endian machines. My first attempt at fixing it (see this TIL) turned out not to be correct. I really needed a way to test agaist an emulated s390x machine with big-endian byte order.
\nI figured out how to do that using Docker for Mac and QEMU.
\nThis is the first command to run. It does something magical to your Docker installation:
\ndocker run --rm --privileged multiarch/qemu-user-static:register --reset\nThe qemu-user-static README says:
\n\n\n\n
multiarch/qemu-user-staticandmultiarch/qemu-user-static:registerimages execute the register script that registers below kind of/proc/sys/fs/binfmt_misc/qemu-$archfiles for all supported processors except the current one in it when running the container.
It continues:
\n\n\nThe
\n--resetoption is implemented at the register script that executes find/proc/sys/fs/binfmt_misc -type f -name 'qemu-*' -exec sh -c 'echo -1 > {}' \\;to removebinfmt_miscentry files before register the entry.
I don't understand what this means. But running this command was essential for the next command to work.
\nHaving run that command, the following command drops you into a shell in an emulated s390x machine running Ubuntu Focal:
\ndocker run -it multiarch/ubuntu-core:s390x-focal /bin/bash\nUsing -focal gives you Python 3.8. I previously tried s390x-bionic but that gave me Python 3.6.
You don't actually get Python until you install it, like so:
\napt-get -y update && apt-get -y install python3\nThis will take a while. I think it's slower because the hardware is being emulated.
\nNow you can check the Python version and confirm that the byte order is big-endian like this:
\nroot@ea63e288ce49:/# python3 --version\nPython 3.8.10\nroot@ea63e288ce49:/# python3 -c 'import sys; print(sys.byteorder)'\nbig\nI figured out the following recipe for running this in GitHub Actions.
\nIn this example I'm cloning my sqlite-fts4 repo and running the tests in it as well:
name: QEMU to run s390x-focal\n\non:\n push:\n workflow_dispatch:\n\njobs:\n one:\n runs-on: ubuntu-latest\n steps:\n - name: Setup multiarch/qemu-user-static\n run: |\n docker run --rm --privileged multiarch/qemu-user-static:register --reset\n - name: ubuntu-core:s390x-focal\n uses: docker://multiarch/ubuntu-core:s390x-focal\n with:\n args: >\n bash -c\n \"uname -a &&\n lscpu | grep Endian &&\n apt-get -y update &&\n apt-get -y install python3 git python3.8-venv &&\n python3 --version &&\n python3 -c 'import sys; print(sys.byteorder)' &&\n git clone https://github.com/simonw/sqlite-fts4 &&\n cd sqlite-fts4 &&\n python3 -m venv venv &&\n source venv/bin/activate &&\n pip install -e '.[test]' &&\n pytest\n \"