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We currently build with CONFIG_MODULES=n for simplicity. However, this means that we don't test kernel module support at all. Let's enable module support. This requires changing how we distribute kernels. Now, the /lib/modules/$(uname -r) directory (including the vmlinux and vmlinuz) is bundled up as a tarball. We extract it, then mount it with VirtFS, and do some extra setup for device nodes. (We lose the ability to run kernel builds directly, but I've never actually used that functionality.) Signed-off-by: Omar Sandoval <osandov@osandov.com>
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, BusyBox, and
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zstd to be 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 Dropbox (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 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. Each build is
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packaged as a tarball containing ``vmlinux``, ``vmlinuz``, and kernel
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modules. These packages are 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.download <download.py>`_ module.
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2. The test command itself. This is just some ``setup.py`` glue and the proper
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invocation of the 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.download`` modules also have CLIs for testing
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purposes. These are subject to change.
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