Linux kernel: Difference between revisions
Copy edit |
m Update Nix code for out-of-tree kernel modules according to changes made during a PR review by Aleksanaa in https://github.com/NixOS/nixpkgs/pull/334445 |
||
| (14 intermediate revisions by 9 users not shown) | |||
| Line 28: | Line 28: | ||
nix-repl> pkgs.linuxPackages | nix-repl> pkgs.linuxPackages | ||
pkgs.linuxPackages pkgs. | pkgs.linuxPackages pkgs.linuxPackages_custom | ||
pkgs.linuxPackages-libre pkgs. | pkgs.linuxPackages-libre pkgs.linuxPackages_custom_tinyconfig_kernel | ||
pkgs.linuxPackages-rt pkgs. | pkgs.linuxPackages-rt pkgs.linuxPackages_hardened | ||
pkgs.linuxPackages- | pkgs.linuxPackages-rt_latest pkgs.linuxPackages_latest | ||
pkgs. | pkgs.linuxPackagesFor pkgs.linuxPackages_latest-libre | ||
pkgs. | pkgs.linuxPackages_4_14 pkgs.linuxPackages_latest_hardened | ||
pkgs. | pkgs.linuxPackages_4_19 pkgs.linuxPackages_latest_xen_dom0 | ||
pkgs. | pkgs.linuxPackages_4_19_hardened pkgs.linuxPackages_latest_xen_dom0_hardened | ||
pkgs. | pkgs.linuxPackages_4_9 pkgs.linuxPackages_lqx | ||
pkgs. | pkgs.linuxPackages_5_10 pkgs.linuxPackages_rpi0 | ||
pkgs. | pkgs.linuxPackages_5_10_hardened pkgs.linuxPackages_rpi02w | ||
pkgs.linuxPackages_5_4 pkgs.linuxPackages_testing | pkgs.linuxPackages_5_15 pkgs.linuxPackages_rpi1 | ||
pkgs. | pkgs.linuxPackages_5_15_hardened pkgs.linuxPackages_rpi2 | ||
pkgs. | pkgs.linuxPackages_5_18 pkgs.linuxPackages_rpi3 | ||
pkgs. | pkgs.linuxPackages_5_19 pkgs.linuxPackages_rpi4 | ||
pkgs. | pkgs.linuxPackages_5_4 pkgs.linuxPackages_rt_5_10 | ||
pkgs. | pkgs.linuxPackages_5_4_hardened pkgs.linuxPackages_rt_5_15 | ||
pkgs. | pkgs.linuxPackages_6_0 pkgs.linuxPackages_rt_5_4 | ||
pkgs.linuxPackages_6_1 pkgs.linuxPackages_rt_6_1 | |||
pkgs.linuxPackages_6_1_hardened pkgs.linuxPackages_testing | |||
pkgs.linuxPackages_6_2 pkgs.linuxPackages_testing_bcachefs | |||
pkgs.linuxPackages_6_3 pkgs.linuxPackages_xanmod | |||
pkgs.linuxPackages_6_4 pkgs.linuxPackages_xanmod_latest | |||
pkgs.linuxPackages_6_5 pkgs.linuxPackages_xanmod_stable | |||
pkgs.linuxPackages_6_6 pkgs.linuxPackages_xen_dom0 | |||
pkgs.linuxPackages_6_6_hardened pkgs.linuxPackages_xen_dom0_hardened | |||
pkgs.linuxPackages_6_7 pkgs.linuxPackages_zen | |||
pkgs.linuxPackages_6_8 | |||
</syntaxhighlight> | </syntaxhighlight> | ||
| Line 86: | Line 95: | ||
} | } | ||
</nowiki>}} | </nowiki>}} | ||
=== Enable SysRq === | |||
The Linux kernel is known<ref>https://github.com/hakavlad/nohang?tab=readme-ov-file#what-is-the-problem</ref> to not handle out-of-memory situation properly and can freeze for a long time, often leaving no option but doing a hard reboot. The [https://en.wikipedia.org/wiki/Magic_SysRq_key SysRq shortcuts] can be used to trigger a more graceful reboot. However, most keys are disabled by default on NixOS. To enable: | |||
{{file|/etc/nixos/configuration.nix|nix|<nowiki> | |||
{ | |||
boot.kernel.sysctl."kernel.sysrq" = 1; | |||
} | |||
</nowiki>}} | |||
Useful shortcuts, triggered using {{ic|Alt+SysRq+<key>}}: | |||
* {{ic|h}}: Print help to the system log. | |||
* {{ic|f}}: Trigger the kernel oom killer. | |||
* {{ic|s}}: Sync data to disk before triggering the reset options below. | |||
* {{ic|e}}: SIGTERM all processes except PID 0. | |||
* {{ic|i}}: SIGKILL all processes except PID 0. | |||
* {{ic|b}}: Reboot the system. | |||
Check <code>journalctl</code> to see if you are triggering the shortcuts correctly, which might be different for your keyboard, as noted in the Wikipedia page. | |||
Also see {{nixos:option|services.earlyoom.enable}} and {{nixos:option|systemd.oomd.enable}}. | |||
=== Custom configuration === | === Custom configuration === | ||
| Line 140: | Line 172: | ||
version = "4.19.60"; | version = "4.19.60"; | ||
modDirVersion = "4.19.60"; | modDirVersion = "4.19.60"; | ||
}; | |||
}); | }); | ||
} | } | ||
| Line 150: | Line 182: | ||
{{bc|note: keeping build directory '/tmp/nix-build-linux-config-4.19.0-mptcp_v0.94.1.drv-0'}} | {{bc|note: keeping build directory '/tmp/nix-build-linux-config-4.19.0-mptcp_v0.94.1.drv-0'}} | ||
== Embedded Linux Cross-compile | == Embedded Linux Cross-compile == | ||
To configure and cross-compile Linux kernels for embedded development, often distributed separately instead of using the stock kernel, you can setup a development environment as shown below: | |||
{{file|shell.nix|nix|3=let | |||
let | |||
pkgs = import <nixpkgs> { }; | pkgs = import <nixpkgs> { }; | ||
in | in | ||
| Line 179: | Line 210: | ||
exec bash | exec bash | ||
''; | ''; | ||
}).env | }).env}} | ||
Clone the kernel sources, enter the environment using {{ic|nix-shell}}, and then do development normally. | |||
== make menuconfig == | == make menuconfig == | ||
| Line 246: | Line 276: | ||
=== Packaging out-of-tree kernel modules === | === Packaging out-of-tree kernel modules === | ||
There are a couple of steps that you will most likely need to do a couple of things. Here is an annotated example: | There are a couple of steps that you will most likely need to do a couple of things. Here is an annotated example: | ||
< | <syntaxhighlight lang="nix"> | ||
{ stdenv, lib, fetchFromGitHub, kernel, kmod }: | { stdenv, lib, fetchFromGitHub, kernel, kmod }: | ||
stdenv.mkDerivation rec { | stdenv.mkDerivation rec { | ||
pname = "v4l2loopback-dc"; | |||
version = "1.6"; | version = "1.6"; | ||
| Line 257: | Line 287: | ||
repo = "droidcam"; | repo = "droidcam"; | ||
rev = "v${version}"; | rev = "v${version}"; | ||
hash = "1d9qpnmqa3pfwsrpjnxdz76ipk4w37bbxyrazchh4vslnfc886fx"; | |||
}; | }; | ||
| Line 270: | Line 300: | ||
]; | ]; | ||
meta = | meta = { | ||
description = "A kernel module to create V4L2 loopback devices"; | description = "A kernel module to create V4L2 loopback devices"; | ||
homepage = "https://github.com/aramg/droidcam"; | homepage = "https://github.com/aramg/droidcam"; | ||
license = licenses.gpl2; | license = lib.licenses.gpl2; | ||
maintainers = [ maintainers.makefu ]; | maintainers = [ lib.maintainers.makefu ]; | ||
platforms = platforms.linux; | platforms = lib.platforms.linux; | ||
}; | }; | ||
} | } | ||
</ | </syntaxhighlight> | ||
1. For kernel modules it is necessary to disable <code>pic</code> in compiler hardenings as the kernel need different compiler flags. | 1. For kernel modules it is necessary to disable <code>pic</code> in compiler hardenings as the kernel need different compiler flags. | ||
| Line 359: | Line 389: | ||
and the module will be automatically loaded after a reboot. If you want instead to load it at stage 1 (before the root is even mounted), you need to add it to <code>boot.initrd.availableKernelModules</code> and <code>boot.initrd.kernelModules</code>. | and the module will be automatically loaded after a reboot. If you want instead to load it at stage 1 (before the root is even mounted), you need to add it to <code>boot.initrd.availableKernelModules</code> and <code>boot.initrd.kernelModules</code>. | ||
Note that if you don't reboot, you can still load manually the module using <code>modprobe yourmodulename></code>, and to automatically enable a module during configuration switch/reboot, you can put <code>modprobe yourmodulename || true</code> inside the script of a systemctl service (it is for example what does wireguard). | Note that if you don't reboot, you can still load manually the module using <code>modprobe <yourmodulename></code>, and to automatically enable a module during configuration switch/reboot, you can put <code>modprobe yourmodulename || true</code> inside the script of a systemctl service (it is for example what does wireguard). | ||
Finally, if you want to define some options by default (used when you load manually a module using <code>modprobe</code>, or when the system boots), you can specify them in: | Finally, if you want to define some options by default (used when you load manually a module using <code>modprobe</code>, or when the system boots), you can specify them in: | ||
| Line 393: | Line 423: | ||
Save the following as <code>shell.nix</code> for your nix-shell: | Save the following as <code>shell.nix</code> for your nix-shell: | ||
< | <syntaxhighlight lang="nix"> | ||
{ pkgs ? import <nixpkgs> {} }: | { pkgs ? import <nixpkgs> {} }: | ||
let | let | ||
| Line 402: | Line 432: | ||
# the override is optional if you need for example more build dependencies | # the override is optional if you need for example more build dependencies | ||
nativeBuildInputs = old.nativeBuildInputs ++ [ pkgs.gllvm ]; | nativeBuildInputs = old.nativeBuildInputs ++ [ pkgs.gllvm ]; | ||
} | }) | ||
</ | </syntaxhighlight> | ||
Then you can run the following commands (in the nix-shell <code>$makeFlags</code> will contain | Then you can run the following commands (in the nix-shell <code>$makeFlags</code> will contain | ||
| Line 519: | Line 549: | ||
After packaging the kernel module you can add it to your system just like an out-of-tree kernel module, it will replace the default module provided by the linux package because it has the same name: | After packaging the kernel module you can add it to your system just like an out-of-tree kernel module, it will replace the default module provided by the linux package because it has the same name: | ||
< | <syntaxhighlight lang="nix"> | ||
{pkgs, config, ...}: | {pkgs, config, ...}: | ||
let | let | ||
| Line 531: | Line 561: | ||
(amdgpu-kernel-module.overrideAttrs (_: { | (amdgpu-kernel-module.overrideAttrs (_: { | ||
patches = [ ./patches/amdgpu-foo-bar.patch ]; | patches = [ ./patches/amdgpu-foo-bar.patch ]; | ||
}) | })) | ||
]; | ]; | ||
} | } | ||
</ | </syntaxhighlight> | ||
== Troubleshooting == | == Troubleshooting == | ||