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Commit b0fc494f authored by Steven Rostedt's avatar Steven Rostedt Committed by Thomas Gleixner
Browse files

ftrace: add ftrace_enabled sysctl to disable mcount function 



This patch adds back the sysctl ftrace_enabled. This time it is
defaulted to on, if DYNAMIC_FTRACE is configured. When ftrace_enabled
is disabled, the ftrace function is set to the stub return.

If DYNAMIC_FTRACE is also configured, on ftrace_enabled = 0,
the registered ftrace functions will all be set to jmps, but no more
new calls to ftrace recording (used to find the ftrace calling sites)
will be called.

Signed-off-by: default avatarSteven Rostedt <srostedt@redhat.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 3d083395

include/linux/ftrace.h

+6 −0
Original line number Diff line number Diff line
@@ -5,6 +5,12 @@ 


#include <linux/linkage.h>



extern int ftrace_enabled;

extern int

ftrace_enable_sysctl(struct ctl_table *table, int write,

		     struct file *filp, void __user *buffer, size_t *lenp,

		     loff_t *ppos);



typedef void (*ftrace_func_t)(unsigned long ip, unsigned long parent_ip);



struct ftrace_ops {

kernel/sysctl.c

+11 −0
Original line number Diff line number Diff line
@@ -46,6 +46,7 @@ 
#include <linux/nfs_fs.h>

#include <linux/acpi.h>

#include <linux/reboot.h>

#include <linux/ftrace.h>



#include <asm/uaccess.h>

#include <asm/processor.h>
@@ -455,6 +456,16 @@ static struct ctl_table kern_table[] = { 
		.mode		= 0644,

		.proc_handler	= &proc_dointvec,

	},

#ifdef CONFIG_FTRACE

	{

		.ctl_name	= CTL_UNNUMBERED,

		.procname	= "ftrace_enabled",

		.data		= &ftrace_enabled,

		.maxlen		= sizeof(int),

		.mode		= 0644,

		.proc_handler	= &ftrace_enable_sysctl,

	},

#endif

#ifdef CONFIG_KMOD

	{

		.ctl_name	= KERN_MODPROBE,

kernel/trace/ftrace.c

+107 −18
Original line number Diff line number Diff line
@@ -20,12 +20,24 @@ 
#include <linux/hardirq.h>

#include <linux/ftrace.h>

#include <linux/module.h>

#include <linux/sysctl.h>

#include <linux/hash.h>

#include <linux/list.h>



#include "trace.h"



#ifdef CONFIG_DYNAMIC_FTRACE

# define FTRACE_ENABLED_INIT 1

#else

# define FTRACE_ENABLED_INIT 0

#endif



int ftrace_enabled = FTRACE_ENABLED_INIT;

static int last_ftrace_enabled = FTRACE_ENABLED_INIT;



static DEFINE_SPINLOCK(ftrace_lock);

static DEFINE_MUTEX(ftrace_sysctl_lock);



static struct ftrace_ops ftrace_list_end __read_mostly =

{

	.func = ftrace_stub,
@@ -78,6 +90,7 @@ static int notrace __register_ftrace_function(struct ftrace_ops *ops) 
	smp_wmb();

	ftrace_list = ops;



	if (ftrace_enabled) {

		/*

		 * For one func, simply call it directly.

		 * For more than one func, call the chain.
@@ -86,6 +99,7 @@ static int notrace __register_ftrace_function(struct ftrace_ops *ops) 
			ftrace_trace_function = ops->func;

		else

			ftrace_trace_function = ftrace_list_func;

	}



	spin_unlock(&ftrace_lock);
@@ -120,10 +134,12 @@ static int notrace __unregister_ftrace_function(struct ftrace_ops *ops) 


	*p = (*p)->next;



	if (ftrace_enabled) {

		/* If we only have one func left, then call that directly */

		if (ftrace_list == &ftrace_list_end ||

		    ftrace_list->next == &ftrace_list_end)

			ftrace_trace_function = ftrace_list->func;

	}



 out:

	spin_unlock(&ftrace_lock);
@@ -263,6 +279,7 @@ static void notrace ftrace_startup(void) 
		goto out;

	__unregister_ftrace_function(&ftrace_shutdown_ops);



	if (ftrace_enabled)

		ftrace_run_startup_code();

 out:

	mutex_unlock(&ftraced_lock);
@@ -275,6 +292,7 @@ static void notrace ftrace_shutdown(void) 
	if (ftraced_suspend)

		goto out;



	if (ftrace_enabled)

		ftrace_run_shutdown_code();



	__register_ftrace_function(&ftrace_shutdown_ops);
@@ -282,6 +300,24 @@ static void notrace ftrace_shutdown(void) 
	mutex_unlock(&ftraced_lock);

}



static void notrace ftrace_startup_sysctl(void)

{

	mutex_lock(&ftraced_lock);

	/* ftraced_suspend is true if we want ftrace running */

	if (ftraced_suspend)

		ftrace_run_startup_code();

	mutex_unlock(&ftraced_lock);

}



static void notrace ftrace_shutdown_sysctl(void)

{

	mutex_lock(&ftraced_lock);

	/* ftraced_suspend is true if ftrace is running */

	if (ftraced_suspend)

		ftrace_run_shutdown_code();

	mutex_unlock(&ftraced_lock);

}



static cycle_t		ftrace_update_time;

static unsigned long	ftrace_update_cnt;

unsigned long		ftrace_update_tot_cnt;
@@ -341,8 +377,9 @@ static int notrace ftraced(void *ignore) 
		/* check once a second */

		schedule_timeout(HZ);



		mutex_lock(&ftrace_sysctl_lock);

		mutex_lock(&ftraced_lock);

		if (ftraced_trigger && !ftraced_suspend) {

		if (ftrace_enabled && ftraced_trigger && !ftraced_suspend) {

			ftrace_record_suspend++;

			ftrace_update_code();

			usecs = nsecs_to_usecs(ftrace_update_time);
@@ -360,6 +397,7 @@ static int notrace ftraced(void *ignore) 
			ftrace_record_suspend--;

		}

		mutex_unlock(&ftraced_lock);

		mutex_unlock(&ftrace_sysctl_lock);



		ftrace_shutdown_replenish();
@@ -391,6 +429,8 @@ core_initcall(ftrace_shutdown_init); 
#else

# define ftrace_startup()	  do { } while (0)

# define ftrace_shutdown()	  do { } while (0)

# define ftrace_startup_sysctl()  do { } while (0)

# define ftrace_shutdown_sysctl() do { } while (0)

#endif /* CONFIG_DYNAMIC_FTRACE */



/**
@@ -406,9 +446,15 @@ core_initcall(ftrace_shutdown_init); 
 */

int register_ftrace_function(struct ftrace_ops *ops)

{

	int ret;



	mutex_lock(&ftrace_sysctl_lock);

	ftrace_startup();



	return __register_ftrace_function(ops);

	ret = __register_ftrace_function(ops);

	mutex_unlock(&ftrace_sysctl_lock);



	return ret;

}



/**
@@ -421,10 +467,53 @@ int unregister_ftrace_function(struct ftrace_ops *ops) 
{

	int ret;



	mutex_lock(&ftrace_sysctl_lock);

	ret = __unregister_ftrace_function(ops);



	if (ftrace_list == &ftrace_list_end)

		ftrace_shutdown();



	mutex_unlock(&ftrace_sysctl_lock);



	return ret;

}



notrace int

ftrace_enable_sysctl(struct ctl_table *table, int write,

		     struct file *filp, void __user *buffer, size_t *lenp,

		     loff_t *ppos)

{

	int ret;



	mutex_lock(&ftrace_sysctl_lock);



	ret  = proc_dointvec(table, write, filp, buffer, lenp, ppos);



	if (ret || !write || (last_ftrace_enabled == ftrace_enabled))

		goto out;



	last_ftrace_enabled = ftrace_enabled;



	if (ftrace_enabled) {



		ftrace_startup_sysctl();



		/* we are starting ftrace again */

		if (ftrace_list != &ftrace_list_end) {

			if (ftrace_list->next == &ftrace_list_end)

				ftrace_trace_function = ftrace_list->func;

			else

				ftrace_trace_function = ftrace_list_func;

		}



	} else {

		/* stopping ftrace calls (just send to ftrace_stub) */

		ftrace_trace_function = ftrace_stub;



		ftrace_shutdown_sysctl();

	}



 out:

	mutex_unlock(&ftrace_sysctl_lock);

	return ret;

}