From 19c311ae7c0f4f2475617a8acb7ba7b7b4575f0e Mon Sep 17 00:00:00 2001 From: Masami Hiramatsu Date: Thu, 10 Sep 2020 17:56:06 +0900 Subject: [PATCH] Documentation: tracing: boot: Add an example of tracing function-calls Add an example of tracing function calls on a specific function. Link: https://lkml.kernel.org/r/159972816669.428528.12390560334549382316.stgit@devnote2 Signed-off-by: Masami Hiramatsu Signed-off-by: Steven Rostedt (VMware) --- Documentation/trace/boottime-trace.rst | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) diff --git a/Documentation/trace/boottime-trace.rst b/Documentation/trace/boottime-trace.rst index 9bc8ace..ab3bfd6 100644 --- a/Documentation/trace/boottime-trace.rst +++ b/Documentation/trace/boottime-trace.rst @@ -168,6 +168,26 @@ is for tracing functions starting with "user\_", and others tracing The instance node also accepts event nodes so that each instance can customize its event tracing. +With the trigger action and kprobes, you can trace function-graph while +a function is called. For example, this will trace all function calls in +the pci_proc_init():: + + ftrace { + tracing_on = 0 + tracer = function_graph + event.kprobes { + start_event { + probes = "pci_proc_init" + actions = "traceon" + } + end_event { + probes = "pci_proc_init%return" + actions = "traceoff" + } + } + } + + This boot-time tracing also supports ftrace kernel parameters via boot config. For example, following kernel parameters:: -- 2.7.4