The tracing system can be used in a wide variety of debugging scenarios, but one of the most common tracers used is the function tracer. It instruments every kernel function with an NOP call that is replaced and used to trace the kernel functions when a trace point is enabled.

To enable the function tracer in the kernel, use the CONFIG_FUNCTION_TRACER and CONFIG_FUNCTION_GRAPH_TRACER configuration variables.

The kernel tracing system is controlled via a tracing file in the debug filesystem, which is mounted by default on Yocto's default images. If not, you can mount it with the following:

$ mount -t debugfs nodev /sys/kernel/debug  

We can list the available tracers in our kernel by executing the following:

$ cat /sys/kernel/debug/tracing/available_tracers
function_graph function nop