Commit 752be5c5 authored by Masami Hiramatsu (Google)'s avatar Masami Hiramatsu (Google) Committed by Steven Rostedt (Google)
Browse files

tracing/eprobe: Add eprobe filter support 

Add the filter option to the event probe. This is useful if user wants
to derive a new event based on the condition of the original event.

E.g.
 echo 'e:egroup/stat_runtime_4core sched/sched_stat_runtime \
        runtime=$runtime:u32 if cpu < 4' >> ../dynamic_events

Then it can filter the events only on first 4 cores.
Note that the fields used for 'if' must be the fields in the original
events, not eprobe events.

Link: https://lkml.kernel.org/r/165932114513.2850673.2592206685744598080.stgit@devnote2



Cc: Tzvetomir Stoyanov <tz.stoyanov@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: default avatarMasami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
parent f76349cf

kernel/trace/trace_eprobe.c

+96 −8
Original line number Diff line number Diff line
@@ -26,6 +26,9 @@ struct trace_eprobe { 
	/* tracepoint event */

	const char *event_name;



	/* filter string for the tracepoint */

	char *filter_str;



	struct trace_event_call *event;



	struct dyn_event	devent;
@@ -664,14 +667,15 @@ static struct event_trigger_data * 
new_eprobe_trigger(struct trace_eprobe *ep, struct trace_event_file *file)

{

	struct event_trigger_data *trigger;

	struct event_filter *filter = NULL;

	struct eprobe_data *edata;

	int ret;



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

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

	if (!trigger || !edata) {

		kfree(edata);

		kfree(trigger);

		return ERR_PTR(-ENOMEM);

		ret = -ENOMEM;

		goto error;

	}



	trigger->flags = EVENT_TRIGGER_FL_PROBE;
@@ -686,13 +690,25 @@ new_eprobe_trigger(struct trace_eprobe *ep, struct trace_event_file *file) 
	trigger->cmd_ops = &event_trigger_cmd;



	INIT_LIST_HEAD(&trigger->list);

	RCU_INIT_POINTER(trigger->filter, NULL);



	if (ep->filter_str) {

		ret = create_event_filter(file->tr, file->event_call,

					ep->filter_str, false, &filter);

		if (ret)

			goto error;

	}

	RCU_INIT_POINTER(trigger->filter, filter);



	edata->file = file;

	edata->ep = ep;

	trigger->private_data = edata;



	return trigger;

error:

	free_event_filter(filter);

	kfree(edata);

	kfree(trigger);

	return ERR_PTR(ret);

}



static int enable_eprobe(struct trace_eprobe *ep,
@@ -726,6 +742,7 @@ static int disable_eprobe(struct trace_eprobe *ep, 
{

	struct event_trigger_data *trigger = NULL, *iter;

	struct trace_event_file *file;

	struct event_filter *filter;

	struct eprobe_data *edata;



	file = find_event_file(tr, ep->event_system, ep->event_name);
@@ -752,6 +769,10 @@ static int disable_eprobe(struct trace_eprobe *ep, 
	/* Make sure nothing is using the edata or trigger */

	tracepoint_synchronize_unregister();



	filter = rcu_access_pointer(trigger->filter);



	if (filter)

		free_event_filter(filter);

	kfree(edata);

	kfree(trigger);
@@ -927,12 +948,62 @@ static int trace_eprobe_tp_update_arg(struct trace_eprobe *ep, const char *argv[ 
	return ret;

}



static int trace_eprobe_parse_filter(struct trace_eprobe *ep, int argc, const char *argv[])

{

	struct event_filter *dummy;

	int i, ret, len = 0;

	char *p;



	if (argc == 0) {

		trace_probe_log_err(0, NO_EP_FILTER);

		return -EINVAL;

	}



	/* Recover the filter string */

	for (i = 0; i < argc; i++)

		len += strlen(argv[i]) + 1;



	ep->filter_str = kzalloc(len, GFP_KERNEL);

	if (!ep->filter_str)

		return -ENOMEM;



	p = ep->filter_str;

	for (i = 0; i < argc; i++) {

		ret = snprintf(p, len, "%s ", argv[i]);

		if (ret < 0)

			goto error;

		if (ret > len) {

			ret = -E2BIG;

			goto error;

		}

		p += ret;

		len -= ret;

	}

	p[-1] = '\0';



	/*

	 * Ensure the filter string can be parsed correctly. Note, this

	 * filter string is for the original event, not for the eprobe.

	 */

	ret = create_event_filter(top_trace_array(), ep->event, ep->filter_str,

				  true, &dummy);

	free_event_filter(dummy);

	if (ret)

		goto error;



	return 0;

error:

	kfree(ep->filter_str);

	ep->filter_str = NULL;

	return ret;

}



static int __trace_eprobe_create(int argc, const char *argv[])

{

	/*

	 * Argument syntax:

	 *      e[:[GRP/][ENAME]] SYSTEM.EVENT [FETCHARGS]

	 * Fetch args:

	 *      e[:[GRP/][ENAME]] SYSTEM.EVENT [FETCHARGS] [if FILTER]

	 * Fetch args (no space):

	 *  <name>=$<field>[:TYPE]

	 */

	const char *event = NULL, *group = EPROBE_EVENT_SYSTEM;
@@ -942,8 +1013,8 @@ static int __trace_eprobe_create(int argc, const char *argv[]) 
	char buf1[MAX_EVENT_NAME_LEN];

	char buf2[MAX_EVENT_NAME_LEN];

	char gbuf[MAX_EVENT_NAME_LEN];

	int ret = 0;

	int i;

	int ret = 0, filter_idx = 0;

	int i, filter_cnt;



	if (argc < 2 || argv[0][0] != 'e')

		return -ECANCELED;
@@ -973,6 +1044,15 @@ static int __trace_eprobe_create(int argc, const char *argv[]) 
		event = buf1;

	}



	for (i = 2; i < argc; i++) {

		if (!strcmp(argv[i], "if")) {

			filter_idx = i + 1;

			filter_cnt = argc - filter_idx;

			argc = i;

			break;

		}

	}



	mutex_lock(&event_mutex);

	event_call = find_and_get_event(sys_name, sys_event);

	ep = alloc_event_probe(group, event, event_call, argc - 2);
@@ -988,6 +1068,14 @@ static int __trace_eprobe_create(int argc, const char *argv[]) 
		goto error;

	}



	if (filter_idx) {

		trace_probe_log_set_index(filter_idx);

		ret = trace_eprobe_parse_filter(ep, filter_cnt, argv + filter_idx);

		if (ret)

			goto parse_error;

	} else

		ep->filter_str = NULL;



	argc -= 2; argv += 2;

	/* parse arguments */

	for (i = 0; i < argc && i < MAX_TRACE_ARGS; i++) {

kernel/trace/trace_probe.h

+2 −1
Original line number Diff line number Diff line
@@ -445,7 +445,8 @@ extern int traceprobe_define_arg_fields(struct trace_event_call *event_call, 
	C(SAME_PROBE,		"There is already the exact same probe event"),\

	C(NO_EVENT_INFO,	"This requires both group and event name to attach"),\

	C(BAD_ATTACH_EVENT,	"Attached event does not exist"),\

	C(BAD_ATTACH_ARG,	"Attached event does not have this field"),

	C(BAD_ATTACH_ARG,	"Attached event does not have this field"),\

	C(NO_EP_FILTER,		"No filter rule after 'if'"),



#undef C

#define C(a, b)		TP_ERR_##a