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Currently, vmtest runs a custom program as init in the guest that communicates with the host via virtio-serial. This is a lot of C code that turns out can be replaced with a shell script. In order to keep the dependencies minimal, we use BusyBox.
48 lines
2.3 KiB
ReStructuredText
48 lines
2.3 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 either a wildcard pattern (e.g.,
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``5.6.*``) that matches a kernel release hosted on Dropbox (see below) or a
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kernel build directory path starting with ``.`` or ``/``.
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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.
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The guest runs a `BusyBox <https://www.busybox.net/>`_ shell script as init
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which sets up the system and filesystem hierarchy, runs a command, and returns
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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. The `kernel configuration <config>`_ includes everything
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required to run drgn and the Linux kernel helper tests. These builds are
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hosted on `Dropbox
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<https://www.dropbox.com/sh/2mcf2xvg319qdaw/AAChpI5DJZX2VwlCgPFDdaZHa?dl=0>`_.
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They are managed via the Dropbox API by the `vmtest.manage <manage.py>`_ CLI
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and downloaded by the `vmtest.resolver <resolver.py>`_ module.
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2. The test command itself. This is just some ``setup.py`` glue, a command to
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install vmlinux where drgn can find it, and the proper invocation of the
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Python `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.resolver`` modules also have CLIs for testing
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purposes. These are subject to change.
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