Linux Kernel Hacking

1.0: Livepatch

Patching kernel functions in memory on a live machine. Taken from samples/livepatch.

This livepatch kernel module creates a replacement for cmdline_proc_show() from fs/proc/cmdline.c to simply print a message out instead of the usual cmdline.

To use:

• Check the output of cat /proc/cmdline
• Build with make, and load into the kernel with insmod livepatch-sample.ko
• Check the output again of cat /proc/cmdline
• Disable the livepatch with echo 0 | sudo tee /sys/kernel/livepatch/livepatch-sample/enabled
• Unload from the kernel with rmmod livepatch-sample.ko

Tested on Ubuntu 20.04 running under Vagrant.