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Commit ac1adc55 authored by Tom Zanussi's avatar Tom Zanussi Committed by Ingo Molnar
Browse files

tracing/filters: add filter_mutex to protect filter predicates 



This patch adds a filter_mutex to prevent the filter predicates from
being accessed concurrently by various external functions.

It's based on a previous patch by Li Zefan:
        "[PATCH 7/7] tracing/filters: make filter preds RCU safe"

v2 changes:

- fixed wrong value returned in a add_subsystem_pred() failure case
  noticed by Li Zefan.

[ Impact: fix trace filter corruption/crashes on parallel access ]

Signed-off-by: default avatarTom Zanussi <tzanussi@gmail.com>
Reviewed-by: default avatarLi Zefan <lizf@cn.fujitsu.com>
Tested-by: default avatarLi Zefan <lizf@cn.fujitsu.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: paulmck@linux.vnet.ibm.com
LKML-Reference: <1239946028.6639.13.camel@tropicana>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 46de405f

kernel/trace/trace.h

+3 −1
Original line number Diff line number Diff line
@@ -757,13 +757,15 @@ struct filter_pred { 
};



extern void filter_free_pred(struct filter_pred *pred);

extern void filter_print_preds(struct filter_pred **preds, int n_preds,

extern void filter_print_preds(struct ftrace_event_call *call,

			       struct trace_seq *s);

extern int filter_parse(char **pbuf, struct filter_pred *pred);

extern int filter_add_pred(struct ftrace_event_call *call,

			   struct filter_pred *pred);

extern void filter_disable_preds(struct ftrace_event_call *call);

extern void filter_free_subsystem_preds(struct event_subsystem *system);

extern void filter_print_subsystem_preds(struct event_subsystem *system,

					 struct trace_seq *s);

extern int filter_add_subsystem_pred(struct event_subsystem *system,

				     struct filter_pred *pred);

kernel/trace/trace_events.c

+2 −2
Original line number Diff line number Diff line
@@ -488,7 +488,7 @@ event_filter_read(struct file *filp, char __user *ubuf, size_t cnt, 


	trace_seq_init(s);



	filter_print_preds(call->preds, call->n_preds, s);

	filter_print_preds(call, s);

	r = simple_read_from_buffer(ubuf, cnt, ppos, s->buffer, s->len);



	kfree(s);
@@ -558,7 +558,7 @@ subsystem_filter_read(struct file *filp, char __user *ubuf, size_t cnt, 


	trace_seq_init(s);



	filter_print_preds(system->preds, system->n_preds, s);

	filter_print_subsystem_preds(system, s);

	r = simple_read_from_buffer(ubuf, cnt, ppos, s->buffer, s->len);



	kfree(s);

kernel/trace/trace_events_filter.c

+70 −20
Original line number Diff line number Diff line
@@ -22,10 +22,13 @@ 
#include <linux/uaccess.h>

#include <linux/module.h>

#include <linux/ctype.h>

#include <linux/mutex.h>



#include "trace.h"

#include "trace_output.h"



static DEFINE_MUTEX(filter_mutex);



static int filter_pred_64(struct filter_pred *pred, void *event)

{

	u64 *addr = (u64 *)(event + pred->offset);
@@ -112,7 +115,7 @@ int filter_match_preds(struct ftrace_event_call *call, void *rec) 
}

EXPORT_SYMBOL_GPL(filter_match_preds);



void filter_print_preds(struct filter_pred **preds, int n_preds,

static void __filter_print_preds(struct filter_pred **preds, int n_preds,

				 struct trace_seq *s)

{

	char *field_name;
@@ -138,6 +141,21 @@ void filter_print_preds(struct filter_pred **preds, int n_preds, 
	}

}



void filter_print_preds(struct ftrace_event_call *call, struct trace_seq *s)

{

	mutex_lock(&filter_mutex);

	__filter_print_preds(call->preds, call->n_preds, s);

	mutex_unlock(&filter_mutex);

}



void filter_print_subsystem_preds(struct event_subsystem *system,

				  struct trace_seq *s)

{

	mutex_lock(&filter_mutex);

	__filter_print_preds(system->preds, system->n_preds, s);

	mutex_unlock(&filter_mutex);

}



static struct ftrace_event_field *

find_event_field(struct ftrace_event_call *call, char *name)

{
@@ -180,7 +198,7 @@ static int filter_set_pred(struct filter_pred *dest, 
	return 0;

}



void filter_disable_preds(struct ftrace_event_call *call)

static void __filter_disable_preds(struct ftrace_event_call *call)

{

	int i;
@@ -190,6 +208,13 @@ void filter_disable_preds(struct ftrace_event_call *call) 
		call->preds[i]->fn = filter_pred_none;

}



void filter_disable_preds(struct ftrace_event_call *call)

{

	mutex_lock(&filter_mutex);

	__filter_disable_preds(call);

	mutex_unlock(&filter_mutex);

}



int init_preds(struct ftrace_event_call *call)

{

	struct filter_pred *pred;
@@ -223,7 +248,7 @@ int init_preds(struct ftrace_event_call *call) 
}

EXPORT_SYMBOL_GPL(init_preds);



void filter_free_subsystem_preds(struct event_subsystem *system)

static void __filter_free_subsystem_preds(struct event_subsystem *system)

{

	struct ftrace_event_call *call;

	int i;
@@ -241,18 +266,25 @@ void filter_free_subsystem_preds(struct event_subsystem *system) 
			continue;



		if (!strcmp(call->system, system->name))

			filter_disable_preds(call);

			__filter_disable_preds(call);

	}

}



static int __filter_add_pred(struct ftrace_event_call *call,

void filter_free_subsystem_preds(struct event_subsystem *system)

{

	mutex_lock(&filter_mutex);

	__filter_free_subsystem_preds(system);

	mutex_unlock(&filter_mutex);

}



static int filter_add_pred_fn(struct ftrace_event_call *call,

			      struct filter_pred *pred,

			      filter_pred_fn_t fn)

{

	int idx, err;



	if (call->n_preds && !pred->compound)

		filter_disable_preds(call);

		__filter_disable_preds(call);



	if (call->n_preds == MAX_FILTER_PRED)

		return -ENOSPC;
@@ -276,7 +308,8 @@ static int is_string_field(const char *type) 
	return 0;

}



int filter_add_pred(struct ftrace_event_call *call, struct filter_pred *pred)

static int __filter_add_pred(struct ftrace_event_call *call,

			     struct filter_pred *pred)

{

	struct ftrace_event_field *field;

	filter_pred_fn_t fn;
@@ -293,7 +326,7 @@ int filter_add_pred(struct ftrace_event_call *call, struct filter_pred *pred) 
			return -EINVAL;

		fn = filter_pred_string;

		pred->str_len = field->size;

		return __filter_add_pred(call, pred, fn);

		return filter_add_pred_fn(call, pred, fn);

	} else {

		if (pred->str_len)

			return -EINVAL;
@@ -316,7 +349,18 @@ int filter_add_pred(struct ftrace_event_call *call, struct filter_pred *pred) 
		return -EINVAL;

	}



	return __filter_add_pred(call, pred, fn);

	return filter_add_pred_fn(call, pred, fn);

}



int filter_add_pred(struct ftrace_event_call *call, struct filter_pred *pred)

{

	int err;



	mutex_lock(&filter_mutex);

	err = __filter_add_pred(call, pred);

	mutex_unlock(&filter_mutex);



	return err;

}



int filter_add_subsystem_pred(struct event_subsystem *system,
@@ -324,20 +368,27 @@ int filter_add_subsystem_pred(struct event_subsystem *system, 
{

	struct ftrace_event_call *call;



	mutex_lock(&filter_mutex);



	if (system->n_preds && !pred->compound)

		filter_free_subsystem_preds(system);

		__filter_free_subsystem_preds(system);



	if (!system->n_preds) {

		system->preds = kzalloc(MAX_FILTER_PRED * sizeof(pred),

					GFP_KERNEL);

		if (!system->preds)

		if (!system->preds) {

			mutex_unlock(&filter_mutex);

			return -ENOMEM;

		}

	}



	if (system->n_preds == MAX_FILTER_PRED)

	if (system->n_preds == MAX_FILTER_PRED) {

		mutex_unlock(&filter_mutex);

		return -ENOSPC;

	}



	system->preds[system->n_preds] = pred;

	system->n_preds++;



	list_for_each_entry(call, &ftrace_events, list) {

		int err;
@@ -348,17 +399,16 @@ int filter_add_subsystem_pred(struct event_subsystem *system, 
		if (strcmp(call->system, system->name))

			continue;



		if (!find_event_field(call, pred->field_name))

			continue;



		err = filter_add_pred(call, pred);

		err = __filter_add_pred(call, pred);

		if (err == -ENOMEM) {

			system->preds[system->n_preds] = NULL;

			system->n_preds--;

			mutex_unlock(&filter_mutex);

			return err;

		}

	}



	system->n_preds++;

	mutex_unlock(&filter_mutex);



	return 0;

}