ftrace {
      tracing_on = 0  # off by default
      tracer = function_graph
      event.kprobes {
                start_event {
                        probes = "pci_proc_init"
                        actions = "traceon"
                }
                end_event {
                        probes = "pci_proc_init%return"
                        actions = "traceoff"
                }
        }
  }