Kernel live patching
Kernel Live Patching (KLP) allows quick fixes to the kernel space without rebooting the whole system. Since version 4.0, related patches have been accepted [1][2][3], so one can configure their kernel to enable this feature. Generally, KLP is achieved by the following steps:
- Obtain the source tree of the running kernel
- Prepare the patch against the kernel
- Apply some tools (as follows) to help transform and load the patch
Some projects provide the live patching utilities before KLP was officially supported, such as Oracle's ksplice, SuSE's #kGraft, and RedHat's #kpatch. They implemented the KLP functionality in different ways. The minimalistic functional set of patches entered mainstream kernel were derived from kpatch and kGraft.
kpatch
Installation
Install kpatchAUR for an appropriate kernel and kpatch-gitAUR for userspace tools.
You can also manually build a kernel that supports kpatch usage, by enabling CONFIG_LIVEPATCH, CONFIG_DEBUG_INFO, and CONFIG_KALLSYMS.
Usage
Once both packages are successfully built and after reboot, you may
$ export ROOTDIR=some/dir/aur/linux-kpatch/src/linux-x-y $ cd $ROOTDIR
Assume that you have done some modifications and have a patch some.patch (against the source tree after a makepkg -o, not the vanilla kernel of version x.y) in the working directory. Launch the kpatch utility,
$ kpatch-build -s $(pwd) -v $(pwd)/vmlinux some.patch
This command involves two kernel builds, the original one and the patched one, so it may take a period of time to complete. After the build is over, there should be a kpatch-some.ko module in the same directory. And then,
# insmod kpatch-some.ko
should do the trick.
For further information, please check the manpages or the GitHub repository.
kGraft
KGraft has not been tested in Arch environment.