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We don't specifically need BusyBox; we just need a reasonable Linux userspace, which we can assume is already available on the host, whether it's coreutils+util-linux, BusyBox, or something else. Signed-off-by: Omar Sandoval <osandov@osandov.com>
53 lines
2.6 KiB
ReStructuredText
53 lines
2.6 KiB
ReStructuredText
drgn VM Testing
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===============
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drgn has a significant amount of code (both core and in helpers) which is
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dependent on the Linux kernel version. This code is tested on multiple Linux
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kernel versions in a virtual machine. These tests can be run on all supported
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kernels with ``python3 setup.py test -K``. This requires QEMU and zstd to be
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installed.
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Tests can also be run on specific kernels with ``-k``. This takes a
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comma-separated list of kernels which are wildcard patterns (e.g., ``5.6.*``)
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matching a kernel release hosted on GitHub (see below).
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Architecture
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------------
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The goal of vmtest is to run tests in the same userspace environment as the
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host, but with a different kernel. The host runs the virtual machine with `QEMU
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<https://www.qemu.org/>`_ (see the `vmtest.vm <vm.py>`_ module).
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The guest mounts the host's root filesystem as its own root filesystem via
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`VirtFS <https://www.linux-kvm.org/page/VirtFS>`_. It is mounted read-only for
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safety. To support modifications, the guest uses `OverlayFS
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<https://www.kernel.org/doc/Documentation/filesystems/overlayfs.txt>`_ to
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overlay a read-write tmpfs over the VirtFS root. It also mounts the kernel
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modules and vmlinux via VirtFS.
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The guest runs an init shell script which sets up the system and filesystem
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hierarchy, runs a command, and returns the exit status via `virtio-serial
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<https://fedoraproject.org/wiki/Features/VirtioSerial>`_.
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This infrastructure is all generic. The drgn-specific parts are:
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1. The kernel builds. These are configured with a minimal configuration
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including everything required to run drgn and the Linux kernel helper tests.
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Each build is packaged as a tarball containing ``vmlinux``, ``vmlinuz``, and
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kernel modules. These packages are built by the `vmtest.kbuild <kbuild.py>`_
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module. They are hosted in a `GitHub release
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<https://github.com/osandov/drgn/releases/tag/vmtest-assets>`_ which is
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managed via the GitHub API by the `vmtest.manage <manage.py>`_ CLI. New
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kernel releases are built and uploaded by a `GitHub Actions workflow
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<../.github/workflows/vmtest-build.yml>`_. The packages are downloaded by
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the `vmtest.download <download.py>`_ module.
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2. A `kernel module <../tests/linux_kernel/kmod>`_ for testing drgn
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functionality that cannot be tested through userspace APIs.
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3. The test command itself. This is just some ``setup.py`` glue to build the
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test kernel module and run the VM with the proper invocation of the Python
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`unittest command line interface
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<https://docs.python.org/3/library/unittest.html#test-discovery>`_.
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The ``vmtest.vm`` and ``vmtest.download`` modules also have CLIs for testing
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purposes. These are subject to change.
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