nixpkgs/nixos/modules/testing/test-instrumentation.nix
Frédéric Christ 6aba98aefd nixos/testing: Fix tty output
Prior to this contribution, the Kernel's frame buffer output
boot log wasn't visible on the graphical console.

Now, we can also test applications with graphical output that run
during the boot process.
2024-09-05 10:54:55 +02:00

234 lines
7.9 KiB
Nix

# This module allows the test driver to connect to the virtual machine
# via a root shell attached to port 514.
{ options, config, lib, pkgs, ... }:
with lib;
let
cfg = config.testing;
qemu-common = import ../../lib/qemu-common.nix { inherit lib pkgs; };
backdoorService = {
requires = [ "dev-hvc0.device" "dev-${qemu-common.qemuSerialDevice}.device" ];
after = [ "dev-hvc0.device" "dev-${qemu-common.qemuSerialDevice}.device" ];
script =
''
export USER=root
export HOME=/root
export DISPLAY=:0.0
if [[ -e /etc/profile ]]; then
source /etc/profile
fi
# Don't use a pager when executing backdoor
# actions. Because we use a tty, commands like systemctl
# or nix-store get confused into thinking they're running
# interactively.
export PAGER=
cd /tmp
exec < /dev/hvc0 > /dev/hvc0
while ! exec 2> /dev/${qemu-common.qemuSerialDevice}; do sleep 0.1; done
echo "connecting to host..." >&2
stty -F /dev/hvc0 raw -echo # prevent nl -> cr/nl conversion
# The following line is essential since it signals to
# the test driver that the shell is ready.
# See: the connect method in the Machine class.
echo "Spawning backdoor root shell..."
# Passing the terminal device makes bash run non-interactively.
# Otherwise we get errors on the terminal because bash tries to
# setup things like job control.
# Note: calling bash explicitly here instead of sh makes sure that
# we can also run non-NixOS guests during tests. This, however, is
# mostly futureproofing as the test instrumentation is still very
# tightly coupled to NixOS.
PS1= exec ${pkgs.coreutils}/bin/env bash --norc /dev/hvc0
'';
serviceConfig.KillSignal = "SIGHUP";
};
in
{
options.testing = {
initrdBackdoor = lib.mkEnableOption ''
backdoor.service in initrd. Requires
boot.initrd.systemd.enable to be enabled. Boot will pause in
stage 1 at initrd.target, and will listen for commands from the
Machine python interface, just like stage 2 normally does. This
enables commands to be sent to test and debug stage 1. Use
machine.switch_root() to leave stage 1 and proceed to stage 2
'';
};
config = {
assertions = [
{
assertion = cfg.initrdBackdoor -> config.boot.initrd.systemd.enable;
message = ''
testing.initrdBackdoor requires boot.initrd.systemd.enable to be enabled.
'';
}
];
systemd.services.backdoor = lib.mkMerge [
backdoorService
{
wantedBy = [ "multi-user.target" ];
}
];
boot.initrd.systemd = lib.mkMerge [
{
contents."/etc/systemd/journald.conf".text = ''
[Journal]
ForwardToConsole=yes
MaxLevelConsole=debug
'';
extraConfig = config.systemd.extraConfig;
}
(lib.mkIf cfg.initrdBackdoor {
# Implemented in machine.switch_root(). Suppress the unit by
# making it a noop without removing it, which would break
# initrd-parse-etc.service
services.initrd-cleanup.serviceConfig.ExecStart = [
# Reset
""
# noop
"/bin/true"
];
services.backdoor = lib.mkMerge [
backdoorService
{
# TODO: Both stage 1 and stage 2 should use these same
# settings. But a lot of existing tests rely on
# backdoor.service having default orderings,
# e.g. systemd-boot.update relies on /boot being mounted
# as soon as backdoor starts. But it can be useful for
# backdoor to start even earlier.
wantedBy = [ "sysinit.target" ];
unitConfig.DefaultDependencies = false;
conflicts = [ "shutdown.target" "initrd-switch-root.target" ];
before = [ "shutdown.target" "initrd-switch-root.target" ];
}
];
storePaths = [
"${pkgs.coreutils}/bin/env"
];
})
];
# Prevent agetty from being instantiated on the serial device, since it
# interferes with the backdoor (writes to it will randomly fail
# with EIO). Likewise for hvc0.
systemd.services."serial-getty@${qemu-common.qemuSerialDevice}".enable = false;
systemd.services."serial-getty@hvc0".enable = false;
# Only set these settings when the options exist. Some tests (e.g. those
# that do not specify any nodes, or an empty attr set as nodes) will not
# have the QEMU module loaded and thuse these options can't and should not
# be set.
virtualisation = lib.optionalAttrs (options ? virtualisation.qemu) {
qemu = {
# Only use a serial console, no TTY.
# NOTE: optionalAttrs
# test-instrumentation.nix appears to be used without qemu-vm.nix, so
# we avoid defining consoles if not possible.
# TODO: refactor such that test-instrumentation can import qemu-vm
# or declare virtualisation.qemu.console option in a module that's always imported
consoles = [ qemu-common.qemuSerialDevice ];
package = lib.mkDefault pkgs.qemu_test;
};
};
boot.kernel.sysctl = {
"kernel.hung_task_timeout_secs" = 600;
# Panic on out-of-memory conditions rather than letting the
# OOM killer randomly get rid of processes, since this leads
# to failures that are hard to diagnose.
"vm.panic_on_oom" = lib.mkDefault 2;
};
boot.kernelParams = [
"console=${qemu-common.qemuSerialDevice}"
"console=tty0"
# Panic if an error occurs in stage 1 (rather than waiting for
# user intervention).
"panic=1" "boot.panic_on_fail"
# Using acpi_pm as a clock source causes the guest clock to
# slow down under high host load. This is usually a bad
# thing, but for VM tests it should provide a bit more
# determinism (e.g. if the VM runs at lower speed, then
# timeouts in the VM should also be delayed).
"clocksource=acpi_pm"
];
# `xwininfo' is used by the test driver to query open windows.
environment.systemPackages = [ pkgs.xorg.xwininfo ];
# Log everything to the serial console.
services.journald.extraConfig =
''
ForwardToConsole=yes
TTYPath=/dev/${qemu-common.qemuSerialDevice}
MaxLevelConsole=debug
'';
systemd.extraConfig = ''
# Don't clobber the console with duplicate systemd messages.
ShowStatus=no
# Allow very slow start
DefaultTimeoutStartSec=300
DefaultDeviceTimeoutSec=300
'';
systemd.user.extraConfig = ''
# Allow very slow start
DefaultTimeoutStartSec=300
DefaultDeviceTimeoutSec=300
'';
boot.consoleLogLevel = 7;
# Prevent tests from accessing the Internet.
networking.defaultGateway = mkOverride 150 null;
networking.nameservers = mkOverride 150 [ ];
system.requiredKernelConfig = with config.lib.kernelConfig; [
(isYes "SERIAL_8250_CONSOLE")
(isYes "SERIAL_8250")
(isEnabled "VIRTIO_CONSOLE")
];
networking.usePredictableInterfaceNames = false;
# Make it easy to log in as root when running the test interactively.
# This needs to be a file because of a quirk in systemd credentials,
# where you cannot specify an empty string as a value. systemd-sysusers
# uses credentials to set passwords on users.
users.users.root.hashedPasswordFile = mkOverride 150 "${pkgs.writeText "hashed-password.root" ""}";
services.displayManager.logToJournal = true;
services.logrotate.enable = mkOverride 150 false;
# Make sure we use the Guest Agent from the QEMU package for testing
# to reduce the closure size required for the tests.
services.qemuGuest.package = pkgs.qemu_test.ga;
# Squelch warning about unset system.stateVersion
system.stateVersion = lib.mkDefault lib.trivial.release;
};
}