Using dynamic kernel events

Although dynamic tracing is a very useful feature, custom kernel modules is not a user-friendly interface. Fortunately, the Linux kernel has been extended with the support of kprobe events, which allow us to set kprobes probes using a debugfs interface.

Getting ready

To make use of this feature, we need to configure our kernel with the CONFIG_KPROBE_EVENT configuration variable.

How to do it...

The debugfs interface adds probes via the /sys/kernel/debug/tracing/kprobe_events file. For example, to add a kprobe called example_probe to the do_sys_open function, you can execute the following command:

# echo 'p:example_probe do_sys_open dfd=%r0 filename=%r1 flags=%r2 mode=%r3' > /sys/kernel/debug/tracing/kprobe_events

The probe will print the function's argument list, according to the function's declaration arguments as seen in the funcion's definition below:

long do_sys_open(int dfd, const char __user *filename, int flags, umode_t mode);

You can then manage kprobes...