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Commit c02c7e65 authored by Masami Hiramatsu's avatar Masami Hiramatsu Committed by Steven Rostedt
Browse files

tracing/kprobes: Use rcu_dereference_raw for tp->files 

Use rcu_dereference_raw() for accessing tp->files. Because the
write-side uses rcu_assign_pointer() for memory barrier,
the read-side also has to use rcu_dereference_raw() with
read memory barrier.

Link: http://lkml.kernel.org/r/20130513115834.6545.17022.stgit@mhiramat-M0-7522



Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Tom Zanussi <tom.zanussi@intel.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Signed-off-by: default avatarMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent 60705c89

kernel/trace/trace_kprobe.c

+37 −10
Original line number Diff line number Diff line
@@ -185,9 +185,14 @@ static struct trace_probe *find_trace_probe(const char *event, 


static int trace_probe_nr_files(struct trace_probe *tp)

{

	struct ftrace_event_file **file = tp->files;

	struct ftrace_event_file **file;

	int ret = 0;



	/*

	 * Since all tp->files updater is protected by probe_enable_lock,

	 * we don't need to lock an rcu_read_lock.

	 */

	file = rcu_dereference_raw(tp->files);

	if (file)

		while (*(file++))

			ret++;
@@ -209,9 +214,10 @@ enable_trace_probe(struct trace_probe *tp, struct ftrace_event_file *file) 
	mutex_lock(&probe_enable_lock);



	if (file) {

		struct ftrace_event_file **new, **old = tp->files;

		struct ftrace_event_file **new, **old;

		int n = trace_probe_nr_files(tp);



		old = rcu_dereference_raw(tp->files);

		/* 1 is for new one and 1 is for stopper */

		new = kzalloc((n + 2) * sizeof(struct ftrace_event_file *),

			      GFP_KERNEL);
@@ -251,11 +257,17 @@ enable_trace_probe(struct trace_probe *tp, struct ftrace_event_file *file) 
static int

trace_probe_file_index(struct trace_probe *tp, struct ftrace_event_file *file)

{

	struct ftrace_event_file **files;

	int i;



	if (tp->files) {

		for (i = 0; tp->files[i]; i++)

			if (tp->files[i] == file)

	/*

	 * Since all tp->files updater is protected by probe_enable_lock,

	 * we don't need to lock an rcu_read_lock.

	 */

	files = rcu_dereference_raw(tp->files);

	if (files) {

		for (i = 0; files[i]; i++)

			if (files[i] == file)

				return i;

	}
@@ -274,10 +286,11 @@ disable_trace_probe(struct trace_probe *tp, struct ftrace_event_file *file) 
	mutex_lock(&probe_enable_lock);



	if (file) {

		struct ftrace_event_file **new, **old = tp->files;

		struct ftrace_event_file **new, **old;

		int n = trace_probe_nr_files(tp);

		int i, j;



		old = rcu_dereference_raw(tp->files);

		if (n == 0 || trace_probe_file_index(tp, file) < 0) {

			ret = -EINVAL;

			goto out_unlock;
@@ -872,9 +885,16 @@ __kprobe_trace_func(struct trace_probe *tp, struct pt_regs *regs, 
static __kprobes void

kprobe_trace_func(struct trace_probe *tp, struct pt_regs *regs)

{

	struct ftrace_event_file **file = tp->files;

	/*

	 * Note: preempt is already disabled around the kprobe handler.

	 * However, we still need an smp_read_barrier_depends() corresponding

	 * to smp_wmb() in rcu_assign_pointer() to access the pointer.

	 */

	struct ftrace_event_file **file = rcu_dereference_raw(tp->files);



	if (unlikely(!file))

		return;



	/* Note: preempt is already disabled around the kprobe handler */

	while (*file) {

		__kprobe_trace_func(tp, regs, *file);

		file++;
@@ -925,9 +945,16 @@ static __kprobes void 
kretprobe_trace_func(struct trace_probe *tp, struct kretprobe_instance *ri,

		     struct pt_regs *regs)

{

	struct ftrace_event_file **file = tp->files;

	/*

	 * Note: preempt is already disabled around the kprobe handler.

	 * However, we still need an smp_read_barrier_depends() corresponding

	 * to smp_wmb() in rcu_assign_pointer() to access the pointer.

	 */

	struct ftrace_event_file **file = rcu_dereference_raw(tp->files);



	if (unlikely(!file))

		return;



	/* Note: preempt is already disabled around the kprobe handler */

	while (*file) {

		__kretprobe_trace_func(tp, ri, regs, *file);

		file++;