Commit e248491a authored by Jiri Olsa's avatar Jiri Olsa Committed by Steven Rostedt
Browse files

ftrace: Add enable/disable ftrace_ops control interface 

Adding a way to temporarily enable/disable ftrace_ops. The change
follows the same way as 'global' ftrace_ops are done.

Introducing 2 global ftrace_ops - control_ops and ftrace_control_list
which take over all ftrace_ops registered with FTRACE_OPS_FL_CONTROL
flag. In addition new per cpu flag called 'disabled' is also added to
ftrace_ops to provide the control information for each cpu.

When ftrace_ops with FTRACE_OPS_FL_CONTROL is registered, it is
set as disabled for all cpus.

The ftrace_control_list contains all the registered 'control' ftrace_ops.
The control_ops provides function which iterates ftrace_control_list
and does the check for 'disabled' flag on current cpu.

Adding 3 inline functions:
  ftrace_function_local_disable/ftrace_function_local_enable
  - enable/disable the ftrace_ops on current cpu
  ftrace_function_local_disabled
  - get disabled ftrace_ops::disabled value for current cpu

Link: http://lkml.kernel.org/r/1329317514-8131-2-git-send-email-jolsa@redhat.com



Acked-by: default avatarFrederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: default avatarJiri Olsa <jolsa@redhat.com>
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent 5b349261

include/linux/ftrace.h

+66 −0
Original line number Diff line number Diff line
@@ -31,16 +31,33 @@ ftrace_enable_sysctl(struct ctl_table *table, int write, 


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



/*

 * FTRACE_OPS_FL_* bits denote the state of ftrace_ops struct and are

 * set in the flags member.

 *

 * ENABLED - set/unset when ftrace_ops is registered/unregistered

 * GLOBAL  - set manualy by ftrace_ops user to denote the ftrace_ops

 *           is part of the global tracers sharing the same filter

 *           via set_ftrace_* debugfs files.

 * DYNAMIC - set when ftrace_ops is registered to denote dynamically

 *           allocated ftrace_ops which need special care

 * CONTROL - set manualy by ftrace_ops user to denote the ftrace_ops

 *           could be controled by following calls:

 *             ftrace_function_local_enable

 *             ftrace_function_local_disable

 */

enum {

	FTRACE_OPS_FL_ENABLED		= 1 << 0,

	FTRACE_OPS_FL_GLOBAL		= 1 << 1,

	FTRACE_OPS_FL_DYNAMIC		= 1 << 2,

	FTRACE_OPS_FL_CONTROL		= 1 << 3,

};



struct ftrace_ops {

	ftrace_func_t			func;

	struct ftrace_ops		*next;

	unsigned long			flags;

	int __percpu			*disabled;

#ifdef CONFIG_DYNAMIC_FTRACE

	struct ftrace_hash		*notrace_hash;

	struct ftrace_hash		*filter_hash;
@@ -97,6 +114,55 @@ int register_ftrace_function(struct ftrace_ops *ops); 
int unregister_ftrace_function(struct ftrace_ops *ops);

void clear_ftrace_function(void);



/**

 * ftrace_function_local_enable - enable controlled ftrace_ops on current cpu

 *

 * This function enables tracing on current cpu by decreasing

 * the per cpu control variable.

 * It must be called with preemption disabled and only on ftrace_ops

 * registered with FTRACE_OPS_FL_CONTROL. If called without preemption

 * disabled, this_cpu_ptr will complain when CONFIG_DEBUG_PREEMPT is enabled.

 */

static inline void ftrace_function_local_enable(struct ftrace_ops *ops)

{

	if (WARN_ON_ONCE(!(ops->flags & FTRACE_OPS_FL_CONTROL)))

		return;



	(*this_cpu_ptr(ops->disabled))--;

}



/**

 * ftrace_function_local_disable - enable controlled ftrace_ops on current cpu

 *

 * This function enables tracing on current cpu by decreasing

 * the per cpu control variable.

 * It must be called with preemption disabled and only on ftrace_ops

 * registered with FTRACE_OPS_FL_CONTROL. If called without preemption

 * disabled, this_cpu_ptr will complain when CONFIG_DEBUG_PREEMPT is enabled.

 */

static inline void ftrace_function_local_disable(struct ftrace_ops *ops)

{

	if (WARN_ON_ONCE(!(ops->flags & FTRACE_OPS_FL_CONTROL)))

		return;



	(*this_cpu_ptr(ops->disabled))++;

}



/**

 * ftrace_function_local_disabled - returns ftrace_ops disabled value

 *                                  on current cpu

 *

 * This function returns value of ftrace_ops::disabled on current cpu.

 * It must be called with preemption disabled and only on ftrace_ops

 * registered with FTRACE_OPS_FL_CONTROL. If called without preemption

 * disabled, this_cpu_ptr will complain when CONFIG_DEBUG_PREEMPT is enabled.

 */

static inline int ftrace_function_local_disabled(struct ftrace_ops *ops)

{

	WARN_ON_ONCE(!(ops->flags & FTRACE_OPS_FL_CONTROL));

	return *this_cpu_ptr(ops->disabled);

}



extern void ftrace_stub(unsigned long a0, unsigned long a1);



#else /* !CONFIG_FUNCTION_TRACER */

kernel/trace/ftrace.c

+104 −7
Original line number Diff line number Diff line
@@ -62,6 +62,8 @@ 
#define FTRACE_HASH_DEFAULT_BITS 10

#define FTRACE_HASH_MAX_BITS 12



#define FL_GLOBAL_CONTROL_MASK (FTRACE_OPS_FL_GLOBAL | FTRACE_OPS_FL_CONTROL)



/* ftrace_enabled is a method to turn ftrace on or off */

int ftrace_enabled __read_mostly;

static int last_ftrace_enabled;
@@ -89,12 +91,14 @@ static struct ftrace_ops ftrace_list_end __read_mostly = { 
};



static struct ftrace_ops *ftrace_global_list __read_mostly = &ftrace_list_end;

static struct ftrace_ops *ftrace_control_list __read_mostly = &ftrace_list_end;

static struct ftrace_ops *ftrace_ops_list __read_mostly = &ftrace_list_end;

ftrace_func_t ftrace_trace_function __read_mostly = ftrace_stub;

static ftrace_func_t __ftrace_trace_function_delay __read_mostly = ftrace_stub;

ftrace_func_t __ftrace_trace_function __read_mostly = ftrace_stub;

ftrace_func_t ftrace_pid_function __read_mostly = ftrace_stub;

static struct ftrace_ops global_ops;

static struct ftrace_ops control_ops;



static void

ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip);
@@ -168,6 +172,32 @@ static void ftrace_test_stop_func(unsigned long ip, unsigned long parent_ip) 
}

#endif



static void control_ops_disable_all(struct ftrace_ops *ops)

{

	int cpu;



	for_each_possible_cpu(cpu)

		*per_cpu_ptr(ops->disabled, cpu) = 1;

}



static int control_ops_alloc(struct ftrace_ops *ops)

{

	int __percpu *disabled;



	disabled = alloc_percpu(int);

	if (!disabled)

		return -ENOMEM;



	ops->disabled = disabled;

	control_ops_disable_all(ops);

	return 0;

}



static void control_ops_free(struct ftrace_ops *ops)

{

	free_percpu(ops->disabled);

}



static void update_global_ops(void)

{

	ftrace_func_t func;
@@ -259,6 +289,26 @@ static int remove_ftrace_ops(struct ftrace_ops **list, struct ftrace_ops *ops) 
	return 0;

}



static void add_ftrace_list_ops(struct ftrace_ops **list,

				struct ftrace_ops *main_ops,

				struct ftrace_ops *ops)

{

	int first = *list == &ftrace_list_end;

	add_ftrace_ops(list, ops);

	if (first)

		add_ftrace_ops(&ftrace_ops_list, main_ops);

}



static int remove_ftrace_list_ops(struct ftrace_ops **list,

				  struct ftrace_ops *main_ops,

				  struct ftrace_ops *ops)

{

	int ret = remove_ftrace_ops(list, ops);

	if (!ret && *list == &ftrace_list_end)

		ret = remove_ftrace_ops(&ftrace_ops_list, main_ops);

	return ret;

}



static int __register_ftrace_function(struct ftrace_ops *ops)

{

	if (ftrace_disabled)
@@ -270,15 +320,20 @@ static int __register_ftrace_function(struct ftrace_ops *ops) 
	if (WARN_ON(ops->flags & FTRACE_OPS_FL_ENABLED))

		return -EBUSY;



	/* We don't support both control and global flags set. */

	if ((ops->flags & FL_GLOBAL_CONTROL_MASK) == FL_GLOBAL_CONTROL_MASK)

		return -EINVAL;



	if (!core_kernel_data((unsigned long)ops))

		ops->flags |= FTRACE_OPS_FL_DYNAMIC;



	if (ops->flags & FTRACE_OPS_FL_GLOBAL) {

		int first = ftrace_global_list == &ftrace_list_end;

		add_ftrace_ops(&ftrace_global_list, ops);

		add_ftrace_list_ops(&ftrace_global_list, &global_ops, ops);

		ops->flags |= FTRACE_OPS_FL_ENABLED;

		if (first)

			add_ftrace_ops(&ftrace_ops_list, &global_ops);

	} else if (ops->flags & FTRACE_OPS_FL_CONTROL) {

		if (control_ops_alloc(ops))

			return -ENOMEM;

		add_ftrace_list_ops(&ftrace_control_list, &control_ops, ops);

	} else

		add_ftrace_ops(&ftrace_ops_list, ops);
@@ -302,11 +357,23 @@ static int __unregister_ftrace_function(struct ftrace_ops *ops) 
		return -EINVAL;



	if (ops->flags & FTRACE_OPS_FL_GLOBAL) {

		ret = remove_ftrace_ops(&ftrace_global_list, ops);

		if (!ret && ftrace_global_list == &ftrace_list_end)

			ret = remove_ftrace_ops(&ftrace_ops_list, &global_ops);

		ret = remove_ftrace_list_ops(&ftrace_global_list,

					     &global_ops, ops);

		if (!ret)

			ops->flags &= ~FTRACE_OPS_FL_ENABLED;

	} else if (ops->flags & FTRACE_OPS_FL_CONTROL) {

		ret = remove_ftrace_list_ops(&ftrace_control_list,

					     &control_ops, ops);

		if (!ret) {

			/*

			 * The ftrace_ops is now removed from the list,

			 * so there'll be no new users. We must ensure

			 * all current users are done before we free

			 * the control data.

			 */

			synchronize_sched();

			control_ops_free(ops);

		}

	} else

		ret = remove_ftrace_ops(&ftrace_ops_list, ops);
@@ -3873,6 +3940,36 @@ ftrace_ops_test(struct ftrace_ops *ops, unsigned long ip) 


#endif /* CONFIG_DYNAMIC_FTRACE */



static void

ftrace_ops_control_func(unsigned long ip, unsigned long parent_ip)

{

	struct ftrace_ops *op;



	if (unlikely(trace_recursion_test(TRACE_CONTROL_BIT)))

		return;



	/*

	 * Some of the ops may be dynamically allocated,

	 * they must be freed after a synchronize_sched().

	 */

	preempt_disable_notrace();

	trace_recursion_set(TRACE_CONTROL_BIT);

	op = rcu_dereference_raw(ftrace_control_list);

	while (op != &ftrace_list_end) {

		if (!ftrace_function_local_disabled(op) &&

		    ftrace_ops_test(op, ip))

			op->func(ip, parent_ip);



		op = rcu_dereference_raw(op->next);

	};

	trace_recursion_clear(TRACE_CONTROL_BIT);

	preempt_enable_notrace();

}



static struct ftrace_ops control_ops = {

	.func = ftrace_ops_control_func,

};



static void

ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip)

{

kernel/trace/trace.h

+2 −0
Original line number Diff line number Diff line
@@ -288,6 +288,8 @@ struct tracer { 
/* for function tracing recursion */

#define TRACE_INTERNAL_BIT		(1<<11)

#define TRACE_GLOBAL_BIT		(1<<12)

#define TRACE_CONTROL_BIT		(1<<13)



/*

 * Abuse of the trace_recursion.

 * As we need a way to maintain state if we are tracing the function

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