SystemTap is a GPLv2 licensed system-wide tool that allows you to gather tracing and profiling data from a running Linux system. The user writes a systemtap script, which is then compiled into a Linux kernel module linked against the same kernel source it is going to run under.

The script sets events and handlers, which are called by the kernel module on the specified events triggering. For this, it uses the kprobes and uprobes (if available) interfaces in the kernel, as we saw in the Using dynamic kernel events recipe before.