[PATCH v2 0/6] tracing/boot: Add new options for tracing specific period

[Masami Hiramatsu <mhiramat@kernel.org>]

Hi,

Here is the 2nd version of the series to improve the boot-time tracing to
support kretprobe and tracing_on option. Previous version is here:

 https://lkml.kernel.org/r/159887792384.1330989.5993224243767476896.stgit@devnote2

This version fixes a build error ([1/6]) and fix a space indent issue
([5/6]).

The combination of tracing_on and kretprobe allows us to trace events
while a specific function call period. For example, the below bootconfig
will make a function callgraph in the pci_proc_init() function at boot
time.

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

Here is the example output;

# tracer: function_graph
#
# CPU  DURATION                  FUNCTION CALLS
# |     |   |                     |   |   |   |
 0)               |  pci_proc_init() {
 0)               |    proc_mkdir() {
 0)               |      proc_mkdir_data() {
 0)               |        __proc_create() {
 0)               |          _raw_read_lock() {
 0)   0.179 us    |            preempt_count_add();
 0)   0.203 us    |            do_raw_read_lock();
 0)   1.210 us    |          }
 0)               |          __xlate_proc_name() {
 0)   0.449 us    |            pde_subdir_find();
 0)   0.913 us    |          }
 0)               |          _raw_read_unlock() {
 0)   0.169 us    |            do_raw_read_unlock();
 0)   0.175 us    |            preempt_count_sub();
 0)   0.841 us    |          }
 0)               |          kmem_cache_alloc() {
 0)               |            fs_reclaim_acquire() {
 0)   0.154 us    |              __need_fs_reclaim();
 0)   0.240 us    |              fs_reclaim_acquire.part.0();
 0)   0.889 us    |            }
 0)               |            fs_reclaim_release() {
 0)   0.174 us    |              __need_fs_reclaim();
 0)   0.516 us    |            }
 0)   0.157 us    |            should_failslab();
 0)               |            rcu_read_lock_sched_held() {
 0)               |              rcu_read_lock_held_common() {
 0)   0.156 us    |                rcu_is_watching();
 0)   0.158 us    |                rcu_lockdep_current_cpu_online();
 0)   0.735 us    |              }
 0)   1.054 us    |            }
 0)   3.407 us    |          }
 0)   0.168 us    |          __raw_spin_lock_init();
 0)   7.575 us    |        }
 0)               |        proc_register() {
 0)               |          _raw_spin_lock_irqsave() {
 0)   0.187 us    |            preempt_count_add();
...


Thank you,

---

Masami Hiramatsu (6):
      kprobes: tracing/kprobes: Fix to kill kprobes on initmem after boot
      tracing/boot: Add per-instance tracing_on option support
      Documentation: tracing: Add tracing_on option to boot-time tracer
      tracing/kprobes: Support perf-style return probe
      Documentation: tracing: Add %return suffix description
      Documentation: tracing: boot: Add an example of tracing function-calls


 Documentation/trace/boottime-trace.rst |   24 ++++++++++++++++++++++++
 Documentation/trace/kprobetrace.rst    |    2 ++
 include/linux/kprobes.h                |    5 +++++
 init/main.c                            |    2 ++
 kernel/kprobes.c                       |   22 ++++++++++++++++++++++
 kernel/trace/trace_boot.c              |   10 ++++++++++
 kernel/trace/trace_kprobe.c            |   21 ++++++++++++++++++++-
 7 files changed, 85 insertions(+), 1 deletion(-)

--
Masami Hiramatsu (Linaro) <mhiramat@kernel.org>