Commit 28879787 authored by Divya Indi's avatar Divya Indi Committed by Steven Rostedt (VMware)
Browse files

tracing: Adding new functions for kernel access to Ftrace instances 

Adding 2 new functions -
1) struct trace_array *trace_array_get_by_name(const char *name);

Return pointer to a trace array with given name. If it does not exist,
create and return pointer to the new trace array.

2) int trace_array_set_clr_event(struct trace_array *tr,
const char *system ,const char *event, bool enable);

Enable/Disable events to this trace array.

Additionally,
- To handle reference counters, export trace_array_put()
- Due to introduction of the above 2 new functions, we no longer need to
  export - ftrace_set_clr_event & trace_array_create APIs.

Link: http://lkml.kernel.org/r/1574276919-11119-2-git-send-email-divya.indi@oracle.com



Signed-off-by: default avatarDivya Indi <divya.indi@oracle.com>
Reviewed-by: default avatarAruna Ramakrishna <aruna.ramakrishna@oracle.com>
Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
parent fc809bc5

include/linux/trace.h

+2 −1
Original line number Diff line number Diff line
@@ -29,7 +29,8 @@ struct trace_array; 
void trace_printk_init_buffers(void);

int trace_array_printk(struct trace_array *tr, unsigned long ip,

		const char *fmt, ...);

struct trace_array *trace_array_create(const char *name);

void trace_array_put(struct trace_array *tr);

struct trace_array *trace_array_get_by_name(const char *name);

int trace_array_destroy(struct trace_array *tr);

#endif	/* CONFIG_TRACING */

include/linux/trace_events.h

+2 −1
Original line number Diff line number Diff line
@@ -555,7 +555,8 @@ extern int trace_event_get_offsets(struct trace_event_call *call); 


int ftrace_set_clr_event(struct trace_array *tr, char *buf, int set);

int trace_set_clr_event(const char *system, const char *event, int set);



int trace_array_set_clr_event(struct trace_array *tr, const char *system,

		const char *event, bool enable);

/*

 * The double __builtin_constant_p is because gcc will give us an error

 * if we try to allocate the static variable to fmt if it is not a

kernel/trace/trace.c

+76 −20
Original line number Diff line number Diff line
@@ -301,12 +301,24 @@ static void __trace_array_put(struct trace_array *this_tr) 
	this_tr->ref--;

}



/**

 * trace_array_put - Decrement the reference counter for this trace array.

 *

 * NOTE: Use this when we no longer need the trace array returned by

 * trace_array_get_by_name(). This ensures the trace array can be later

 * destroyed.

 *

 */

void trace_array_put(struct trace_array *this_tr)

{

	if (!this_tr)

		return;



	mutex_lock(&trace_types_lock);

	__trace_array_put(this_tr);

	mutex_unlock(&trace_types_lock);

}

EXPORT_SYMBOL_GPL(trace_array_put);



int tracing_check_open_get_tr(struct trace_array *tr)

{
@@ -8437,24 +8449,15 @@ static void update_tracer_options(struct trace_array *tr) 
	mutex_unlock(&trace_types_lock);

}



struct trace_array *trace_array_create(const char *name)

static struct trace_array *trace_array_create(const char *name)

{

	struct trace_array *tr;

	int ret;



	mutex_lock(&event_mutex);

	mutex_lock(&trace_types_lock);



	ret = -EEXIST;

	list_for_each_entry(tr, &ftrace_trace_arrays, list) {

		if (tr->name && strcmp(tr->name, name) == 0)

			goto out_unlock;

	}



	ret = -ENOMEM;

	tr = kzalloc(sizeof(*tr), GFP_KERNEL);

	if (!tr)

		goto out_unlock;

		return ERR_PTR(ret);



	tr->name = kstrdup(name, GFP_KERNEL);

	if (!tr->name)
@@ -8499,8 +8502,8 @@ struct trace_array *trace_array_create(const char *name) 


	list_add(&tr->list, &ftrace_trace_arrays);



	mutex_unlock(&trace_types_lock);

	mutex_unlock(&event_mutex);

	tr->ref++;





	return tr;
@@ -8510,24 +8513,77 @@ struct trace_array *trace_array_create(const char *name) 
	kfree(tr->name);

	kfree(tr);



	return ERR_PTR(ret);

}



static int instance_mkdir(const char *name)

{

	struct trace_array *tr;

	int ret;



	mutex_lock(&event_mutex);

	mutex_lock(&trace_types_lock);



	ret = -EEXIST;

	list_for_each_entry(tr, &ftrace_trace_arrays, list) {

		if (tr->name && strcmp(tr->name, name) == 0)

			goto out_unlock;

	}



	tr = trace_array_create(name);



	ret = PTR_ERR_OR_ZERO(tr);



out_unlock:

	mutex_unlock(&trace_types_lock);

	mutex_unlock(&event_mutex);



	return ERR_PTR(ret);

	return ret;

}

EXPORT_SYMBOL_GPL(trace_array_create);



static int instance_mkdir(const char *name)

/**

 * trace_array_get_by_name - Create/Lookup a trace array, given its name.

 * @name: The name of the trace array to be looked up/created.

 *

 * Returns pointer to trace array with given name.

 * NULL, if it cannot be created.

 *

 * NOTE: This function increments the reference counter associated with the

 * trace array returned. This makes sure it cannot be freed while in use.

 * Use trace_array_put() once the trace array is no longer needed.

 *

 */

struct trace_array *trace_array_get_by_name(const char *name)

{

	return PTR_ERR_OR_ZERO(trace_array_create(name));

	struct trace_array *tr;



	mutex_lock(&event_mutex);

	mutex_lock(&trace_types_lock);



	list_for_each_entry(tr, &ftrace_trace_arrays, list) {

		if (tr->name && strcmp(tr->name, name) == 0)

			goto out_unlock;

	}



	tr = trace_array_create(name);



	if (IS_ERR(tr))

		tr = NULL;

out_unlock:

	if (tr)

		tr->ref++;



	mutex_unlock(&trace_types_lock);

	mutex_unlock(&event_mutex);

	return tr;

}

EXPORT_SYMBOL_GPL(trace_array_get_by_name);



static int __remove_instance(struct trace_array *tr)

{

	int i;



	if (tr->ref || (tr->current_trace && tr->current_trace->ref))

	/* Reference counter for a newly created trace array = 1. */

	if (tr->ref > 1 || (tr->current_trace && tr->current_trace->ref))

		return -EBUSY;



	list_del(&tr->list);

kernel/trace/trace.h

+0 −1
Original line number Diff line number Diff line
@@ -345,7 +345,6 @@ extern struct list_head ftrace_trace_arrays; 
extern struct mutex trace_types_lock;



extern int trace_array_get(struct trace_array *tr);

extern void trace_array_put(struct trace_array *tr);

extern int tracing_check_open_get_tr(struct trace_array *tr);



extern int tracing_set_time_stamp_abs(struct trace_array *tr, bool abs);

kernel/trace/trace_events.c

+26 −1
Original line number Diff line number Diff line
@@ -827,7 +827,6 @@ int ftrace_set_clr_event(struct trace_array *tr, char *buf, int set) 


	return ret;

}

EXPORT_SYMBOL_GPL(ftrace_set_clr_event);



/**

 * trace_set_clr_event - enable or disable an event
@@ -852,6 +851,32 @@ int trace_set_clr_event(const char *system, const char *event, int set) 
}

EXPORT_SYMBOL_GPL(trace_set_clr_event);



/**

 * trace_array_set_clr_event - enable or disable an event for a trace array.

 * @tr: concerned trace array.

 * @system: system name to match (NULL for any system)

 * @event: event name to match (NULL for all events, within system)

 * @enable: true to enable, false to disable

 *

 * This is a way for other parts of the kernel to enable or disable

 * event recording.

 *

 * Returns 0 on success, -EINVAL if the parameters do not match any

 * registered events.

 */

int trace_array_set_clr_event(struct trace_array *tr, const char *system,

		const char *event, bool enable)

{

	int set;



	if (!tr)

		return -ENOENT;



	set = (enable == true) ? 1 : 0;

	return __ftrace_set_clr_event(tr, NULL, system, event, set);

}

EXPORT_SYMBOL_GPL(trace_array_set_clr_event);



/* 128 should be much more than enough */

#define EVENT_BUF_SIZE		127

CRA Git | Maintained and supported by SUSTech CRA and CCSE