Commit a4d1e688 authored by Jiaxing Wang's avatar Jiaxing Wang Committed by Steven Rostedt
Browse files

tracing: Apply tracer specific options from kernel command line. 

Currently, the trace_options parameter is only applied in
tracer_alloc_buffers() when global_trace.current_trace is nop_trace,
so a tracer specific option will not be applied even when the specific
tracer is also enabled from kernel command line. For example, the
'func_stack_trace' option can't be enabled with the following kernel
parameter:

  ftrace=function ftrace_filter=kfree trace_options=func_stack_trace

We can enable tracer specific options by simply apply the options again
if the specific tracer is also supplied from command line and started
in register_tracer().

To make trace_boot_options_buf can be parsed again, a comma and a space
is put back if they were replaced by strsep and strstrip respectively.

Also make register_tracer() be __init to access the __init data, and
in fact register_tracer is only called from __init code.

Link: http://lkml.kernel.org/r/1446599669-9294-1-git-send-email-hello.wjx@gmail.com



Signed-off-by: default avatarJiaxing Wang <hello.wjx@gmail.com>
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent 627645fd

kernel/trace/trace.c

+36 −9
Original line number Diff line number Diff line
@@ -214,12 +214,10 @@ __setup("alloc_snapshot", boot_alloc_snapshot); 




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)

{

	strlcpy(trace_boot_options_buf, str, MAX_TRACER_SIZE);

	trace_boot_options = trace_boot_options_buf;

	return 0;

}

__setup("trace_options=", set_trace_boot_options);
@@ -1223,13 +1221,15 @@ static inline int run_tracer_selftest(struct tracer *type) 


static void add_tracer_options(struct trace_array *tr, struct tracer *t);



static void __init apply_trace_boot_options(void);



/**

 * register_tracer - register a tracer with the ftrace system.

 * @type - the plugin for the tracer

 *

 * Register a new plugin tracer.

 */

int register_tracer(struct tracer *type)

int __init register_tracer(struct tracer *type)

{

	struct tracer *t;

	int ret = 0;
@@ -1288,6 +1288,9 @@ int register_tracer(struct tracer *type) 
	/* Do we want this tracer to start on bootup? */

	tracing_set_tracer(&global_trace, type->name);

	default_bootup_tracer = NULL;



	apply_trace_boot_options();



	/* disable other selftests, since this will break it. */

	tracing_selftest_disabled = true;

#ifdef CONFIG_FTRACE_STARTUP_TEST
@@ -3589,6 +3592,7 @@ static int trace_set_options(struct trace_array *tr, char *option) 
	int neg = 0;

	int ret = -ENODEV;

	int i;

	size_t orig_len = strlen(option);



	cmp = strstrip(option);
@@ -3612,9 +3616,37 @@ static int trace_set_options(struct trace_array *tr, char *option) 


	mutex_unlock(&trace_types_lock);



	/*

	 * If the first trailing whitespace is replaced with '\0' by strstrip,

	 * turn it back into a space.

	 */

	if (orig_len > strlen(option))

		option[strlen(option)] = ' ';



	return ret;

}



static void __init apply_trace_boot_options(void)

{

	char *buf = trace_boot_options_buf;

	char *option;



	while (true) {

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



		if (!option)

			break;

		if (!*option)

			continue;



		trace_set_options(&global_trace, option);



		/* Put back the comma to allow this to be called again */

		if (buf)

			*(buf - 1) = ',';

	}

}



static ssize_t

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

			size_t cnt, loff_t *ppos)
@@ -7248,12 +7280,7 @@ __init static int tracer_alloc_buffers(void) 
	INIT_LIST_HEAD(&global_trace.events);

	list_add(&global_trace.list, &ftrace_trace_arrays);



	while (trace_boot_options) {

		char *option;



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

		trace_set_options(&global_trace, option);

	}

	apply_trace_boot_options();



	register_snapshot_cmd();

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