tracing: Add traceoff_after_boot option

Sometimes tracing is used to debug issues during the boot process. Since
the trace buffer has a limited amount of storage, it may be prudent to
disable tracing after the boot is finished, otherwise the critical
information may be overwritten.  With this option, the main tracing buffer
will be turned off at the end of the boot process.

Cc: Masami Hiramatsu <[email protected]>
Cc: Mathieu Desnoyers <[email protected]>
Cc: Borislav Petkov <[email protected]>
Link: https://lore.kernel.org/[email protected]
Signed-off-by: Steven Rostedt (Google) <[email protected]>

Author: rostedt

Documentation/admin-guide/kernel-parameters.txt

@@ -7279,6 +7279,15 @@
 			See also "Event triggers" in Documentation/trace/events.rst
 
 
+	traceoff_after_boot
+			[FTRACE] Sometimes tracing is used to debug issues
+			during the boot process. Since the trace buffer has a
+			limited amount of storage, it may be prudent to
+			disable tracing after the boot is finished, otherwise
+			the critical information may be overwritten.  With this
+			option, the main tracing buffer will be turned off at
+			the end of the boot process.
+
 	traceoff_on_warning
 			[FTRACE] enable this option to disable tracing when a
 			warning is hit. This turns off "tracing_on". Tracing can

kernel/trace/trace.c

@@ -87,6 +87,7 @@ void __init disable_tracing_selftest(const char *reason)
 static struct trace_iterator *tracepoint_print_iter;
 int tracepoint_printk;
 static bool tracepoint_printk_stop_on_boot __initdata;
+static bool traceoff_after_boot __initdata;
 static DEFINE_STATIC_KEY_FALSE(tracepoint_printk_key);
 
 /* For tracers that don't implement custom flags */
@@ -330,6 +331,13 @@ static int __init set_tracepoint_printk_stop(char *str)
 }
 __setup("tp_printk_stop_on_boot", set_tracepoint_printk_stop);
 
+static int __init set_traceoff_after_boot(char *str)
+{
+	traceoff_after_boot = true;
+	return 1;
+}
+__setup("traceoff_after_boot", set_traceoff_after_boot);
+
 unsigned long long ns2usecs(u64 nsec)
 {
 	nsec += 500;
@@ -10704,6 +10712,9 @@ __init static int late_trace_init(void)
 		tracepoint_printk = 0;
 	}
 
+	if (traceoff_after_boot)
+		tracing_off();
+
 	tracing_set_default_clock();
 	clear_boot_tracer();
 	return 0;