[리눅스커널] tracing: 부팅 과정에서 자동으로 ftrace 활성화하기

<커널: v5.10>

 

부팅 과정에서 ftrace가 초기화되면서 ftrace 로깅이 드라이버 레벨로 활성화가 되면,

구지 다음과 같은 명령어를 입력할 필요성을 못 느낍니다.

 

'echo 1 > /sys/kernel/debug/tracing/tracing_on'

 

본 페이지에 소개된 패치를 적용하면 부팅 과정에서 ftracing 로깅을 실행할 수 있습니다.

 

commit 7f75bdc9ac6a2bae4d6352d15640b331d9becfbb

Author: Austin Kim <austindh.kim@gmail.com>

Date:   Mon Sep 20 14:23:17 2021 +0900

 

    tracing: enable ftrace at boot

 

    Using 'echo 1 > /sys/kernel/debug/tracing/tracing_on',

    the ftrace is enabled. But sometimes we are in the situation where

    boot time should be measured using ftrace.

 

    With CONFIG_ENABLE_FTRACE_AT_BOOT enabled, the ftrace is enabled at boot.

 

diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig

old mode 100644

new mode 100755

index 29db703f6..9e02f297f

--- a/kernel/trace/Kconfig

+++ b/kernel/trace/Kconfig

@@ -243,6 +243,13 @@ config STACK_TRACER

 

          Say N if unsure.

 

+config ENABLE_FTRACE_AT_BOOT

+       bool "Enable ftrace at boot"

+       depends on TRACING

+       default y

+    help

+               Enable ftrace at boot

+

 config TRACE_PREEMPT_TOGGLE

        bool

        help

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c

old mode 100644

new mode 100755

index ab3cb67b8..e50fd2a8c

--- a/kernel/trace/trace_events.c

+++ b/kernel/trace/trace_events.c

@@ -3424,6 +3424,47 @@ static __init int event_trace_enable(void)

        return 0;

 }

 

+#ifdef CONFIG_ENABLE_FTRACE_AT_BOOT

+static void ftrace_events_enable(int enable)

+{

+       if (enable) {

+               trace_set_clr_event(NULL, "printk", 1);

+               trace_set_clr_event(NULL, "console", 1);

+               trace_set_clr_event(NULL, "signal_generate", 1);

+               trace_set_clr_event(NULL, "signal_deliver", 1);

+    } else {

+               tracing_off();

+               trace_set_clr_event(NULL, NULL, 0);

+    }

+}

+

+static __init int enable_ftrace_boot(void)

+{

+       struct trace_array *tr;

+       int ret = 0;

+

+       tr = top_trace_array();

+       if (!tr) {

+               pr_err("%s: Invalid tr from top_trace_array n", __func__);

+               return -ENODEV;

+       }

+

+       ret = tracing_update_buffers();

+       if (ret != 0) {

+               pr_err("%s: invalid buffer ret=%dn", __func__, ret);

+               return -ENODEV;

+       }

+

+       ftrace_events_enable(1);

+       set_tracer_flag(tr, TRACE_ITER_OVERWRITE, 0);

+

+       tracing_on();

+

+       return 0;

+}

+late_initcall(enable_ftrace_boot);

+#endif

+

 /*

  * event_trace_enable() is called from trace_event_init() first to

  * initialize events and perhaps start any events that are on the