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Commit 7bcfaf54 authored by Steven Rostedt's avatar Steven Rostedt Committed by Steven Rostedt
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tracing: Add trace_options kernel command line parameter 



Add trace_options to the kernel command line parameter to be able to
set options at early boot. For example, to enable stack dumps of
events, add the following:

  trace_options=stacktrace

This along with the trace_event option, you can get not only
traces of the events but also the stack dumps with them.

Requested-by: default avatarFrederic Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent 0d5c6e1c

Documentation/kernel-parameters.txt

+16 −0
Original line number Diff line number Diff line
@@ -2859,6 +2859,22 @@ bytes respectively. Such letter suffixes can also be entirely omitted. 
			to facilitate early boot debugging.

			See also Documentation/trace/events.txt



	trace_options=[option-list]

			[FTRACE] Enable or disable tracer options at boot.

			The option-list is a comma delimited list of options

			that can be enabled or disabled just as if you were

			to echo the option name into



			    /sys/kernel/debug/tracing/trace_options



			For example, to enable stacktrace option (to dump the

			stack trace of each event), add to the command line:



			      trace_options=stacktrace



			See also Documentation/trace/ftrace.txt "trace options"

			section.



	transparent_hugepage=

			[KNL]

			Format: [always|madvise|never]

kernel/trace/trace.c

+39 −15
Original line number Diff line number Diff line
@@ -155,6 +155,18 @@ static int __init set_ftrace_dump_on_oops(char *str) 
}

__setup("ftrace_dump_on_oops", set_ftrace_dump_on_oops);





static char trace_boot_options_buf[MAX_TRACER_SIZE] __initdata;

static char *trace_boot_options __initdata;



static int __init set_trace_boot_options(char *str)

{

	strncpy(trace_boot_options_buf, str, MAX_TRACER_SIZE);

	trace_boot_options = trace_boot_options_buf;

	return 0;

}

__setup("trace_options=", set_trace_boot_options);



unsigned long long ns2usecs(cycle_t nsec)

{

	nsec += 500;
@@ -2838,24 +2850,14 @@ static void set_tracer_flags(unsigned int mask, int enabled) 
		trace_printk_start_stop_comm(enabled);

}



static ssize_t

tracing_trace_options_write(struct file *filp, const char __user *ubuf,

			size_t cnt, loff_t *ppos)

static int trace_set_options(char *option)

{

	char buf[64];

	char *cmp;

	int neg = 0;

	int ret;

	int ret = 0;

	int i;



	if (cnt >= sizeof(buf))

		return -EINVAL;



	if (copy_from_user(&buf, ubuf, cnt))

		return -EFAULT;



	buf[cnt] = 0;

	cmp = strstrip(buf);

	cmp = strstrip(option);



	if (strncmp(cmp, "no", 2) == 0) {

		neg = 1;
@@ -2874,10 +2876,25 @@ tracing_trace_options_write(struct file *filp, const char __user *ubuf, 
		mutex_lock(&trace_types_lock);

		ret = set_tracer_option(current_trace, cmp, neg);

		mutex_unlock(&trace_types_lock);

		if (ret)

	}



	return ret;

}



static ssize_t

tracing_trace_options_write(struct file *filp, const char __user *ubuf,

			size_t cnt, loff_t *ppos)

{

	char buf[64];



	if (cnt >= sizeof(buf))

		return -EINVAL;



	if (copy_from_user(&buf, ubuf, cnt))

		return -EFAULT;



	trace_set_options(buf);



	*ppos += cnt;



	return cnt;
@@ -5133,6 +5150,13 @@ __init static int tracer_alloc_buffers(void) 


	register_die_notifier(&trace_die_notifier);



	while (trace_boot_options) {

		char *option;



		option = strsep(&trace_boot_options, ",");

		trace_set_options(option);

	}



	return 0;



out_free_cpumask: