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Commit 02ca1521 authored by Masami Hiramatsu's avatar Masami Hiramatsu Committed by Steven Rostedt
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ftrace/kprobes: Fix not to delete probes if in use 

Fix kprobe-tracer not to delete a probe if the probe is in use.
In that case, delete operation will return -EBUSY.

This bug can cause a kernel panic if enabled probes are deleted
during perf record.

(Add some probes on functions)
sh-4.2# perf probe --del probe:\*
sh-4.2# exit
(kernel panic)

This is originally reported on the fedora bugzilla:

 https://bugzilla.redhat.com/show_bug.cgi?id=742383



I've also checked that this problem doesn't happen on
tracepoints when module removing because perf event
locks target module.

$ sudo ./perf record -e xfs:\* -aR sh
sh-4.2# rmmod xfs
ERROR: Module xfs is in use
sh-4.2# exit
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.203 MB perf.data (~8862 samples) ]

Signed-off-by: default avatarMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Frank Ch. Eigler <fche@redhat.com>
Cc: stable@kernel.org
Link: http://lkml.kernel.org/r/20111004104438.14591.6553.stgit@fedora15


Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent 9d3ec7a0

kernel/trace/trace_kprobe.c

+49 −9
Original line number Diff line number Diff line
@@ -836,11 +836,17 @@ static void __unregister_trace_probe(struct trace_probe *tp) 
}



/* Unregister a trace_probe and probe_event: call with locking probe_lock */

static void unregister_trace_probe(struct trace_probe *tp)

static int unregister_trace_probe(struct trace_probe *tp)

{

	/* Enabled event can not be unregistered */

	if (trace_probe_is_enabled(tp))

		return -EBUSY;



	__unregister_trace_probe(tp);

	list_del(&tp->list);

	unregister_probe_event(tp);



	return 0;

}



/* Register a trace_probe and probe_event */
@@ -854,7 +860,9 @@ static int register_trace_probe(struct trace_probe *tp) 
	/* Delete old (same name) event if exist */

	old_tp = find_trace_probe(tp->call.name, tp->call.class->system);

	if (old_tp) {

		unregister_trace_probe(old_tp);

		ret = unregister_trace_probe(old_tp);

		if (ret < 0)

			goto end;

		free_trace_probe(old_tp);

	}
@@ -892,6 +900,7 @@ static int trace_probe_module_callback(struct notifier_block *nb, 
	mutex_lock(&probe_lock);

	list_for_each_entry(tp, &probe_list, list) {

		if (trace_probe_within_module(tp, mod)) {

			/* Don't need to check busy - this should have gone. */

			__unregister_trace_probe(tp);

			ret = __register_trace_probe(tp);

			if (ret)
@@ -1205,10 +1214,11 @@ static int create_trace_probe(int argc, char **argv) 
			return -ENOENT;

		}

		/* delete an event */

		unregister_trace_probe(tp);

		ret = unregister_trace_probe(tp);

		if (ret == 0)

			free_trace_probe(tp);

		mutex_unlock(&probe_lock);

		return 0;

		return ret;

	}



	if (argc < 2) {
@@ -1317,18 +1327,29 @@ static int create_trace_probe(int argc, char **argv) 
	return ret;

}



static void release_all_trace_probes(void)

static int release_all_trace_probes(void)

{

	struct trace_probe *tp;

	int ret = 0;



	mutex_lock(&probe_lock);

	/* Ensure no probe is in use. */

	list_for_each_entry(tp, &probe_list, list)

		if (trace_probe_is_enabled(tp)) {

			ret = -EBUSY;

			goto end;

		}

	/* TODO: Use batch unregistration */

	while (!list_empty(&probe_list)) {

		tp = list_entry(probe_list.next, struct trace_probe, list);

		unregister_trace_probe(tp);

		free_trace_probe(tp);

	}



end:

	mutex_unlock(&probe_lock);



	return ret;

}



/* Probes listing interfaces */
@@ -1380,9 +1401,13 @@ static const struct seq_operations probes_seq_op = { 


static int probes_open(struct inode *inode, struct file *file)

{

	if ((file->f_mode & FMODE_WRITE) &&

	    (file->f_flags & O_TRUNC))

		release_all_trace_probes();

	int ret;



	if ((file->f_mode & FMODE_WRITE) && (file->f_flags & O_TRUNC)) {

		ret = release_all_trace_probes();

		if (ret < 0)

			return ret;

	}



	return seq_open(file, &probes_seq_op);

}
@@ -2055,6 +2080,21 @@ static __init int kprobe_trace_self_tests_init(void) 


	ret = target(1, 2, 3, 4, 5, 6);



	/* Disable trace points before removing it */

	tp = find_trace_probe("testprobe", KPROBE_EVENT_SYSTEM);

	if (WARN_ON_ONCE(tp == NULL)) {

		pr_warning("error on getting test probe.\n");

		warn++;

	} else

		disable_trace_probe(tp, TP_FLAG_TRACE);



	tp = find_trace_probe("testprobe2", KPROBE_EVENT_SYSTEM);

	if (WARN_ON_ONCE(tp == NULL)) {

		pr_warning("error on getting 2nd test probe.\n");

		warn++;

	} else

		disable_trace_probe(tp, TP_FLAG_TRACE);



	ret = command_trace_probe("-:testprobe");

	if (WARN_ON_ONCE(ret)) {

		pr_warning("error on deleting a probe.\n");