ftrace: Fix t_hash_start()

When the output of set_ftrace_filter is larger than PAGE_SIZE, t_hash_start() will be called the 2nd time, and then we start from the head of a hlist, which is wrong and causes some entries to be outputed twice. The worse is, if the hlist is large enough, reading set_ftrace_filter won't stop but in a dead loop. Reviewed-by: Liming Wang <liming.wang@windriver.com> Signed-off-by: Li Zefan <lizf@cn.fujitsu.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> LKML-Reference: <4A41876E.2060407@cn.fujitsu.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>

ftrace: Fix t_hash_start()
When the output of set_ftrace_filter is larger than PAGE_SIZE, t_hash_start() will be called the 2nd time, and then we start from the head of a hlist, which is wrong and causes some entries to be outputed twice. The worse is, if the hlist is large enough, reading set_ftrace_filter won't stop but in a dead loop. Reviewed-by: Liming Wang <liming.wang@windriver.com> Signed-off-by: Li Zefan <lizf@cn.fujitsu.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> LKML-Reference: <4A41876E.2060407@cn.fujitsu.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Li Zefan · Ingo Molnar
1 parent 694ce0a544
Showing 1 changed file with 11 additions and 1 deletions Side-by-side Diff
kernel/trace/ftrace.c
@@ -1417,10 +1417,20 @@
 {
 	struct ftrace_iterator *iter = m->private;
 	void *p = NULL;
+	loff_t l;
  
+	if (!(iter->flags & FTRACE_ITER_HASH))
+		*pos = 0;
+
 	iter->flags |= FTRACE_ITER_HASH;
  
-	return t_hash_next(m, p, pos);
+	iter->hidx = 0;
+	for (l = 0; l <= *pos; ) {
+		p = t_hash_next(m, p, &l);
+		if (!p)
+			break;
+	}
+	return p;
 }
  
 static int t_hash_show(struct seq_file *m, void *v)
...	...	@@ -1417,10 +1417,20 @@
1417	1417	{
1418	1418	struct ftrace_iterator *iter = m->private;
1419	1419	void *p = NULL;
	1420	+ loff_t l;
1420	1421
	1422	+ if (!(iter->flags & FTRACE_ITER_HASH))
	1423	+ *pos = 0;
	1424	+
1421	1425	iter->flags \|= FTRACE_ITER_HASH;
1422	1426
1423		- return t_hash_next(m, p, pos);
	1427	+ iter->hidx = 0;
	1428	+ for (l = 0; l <= *pos; ) {
	1429	+ p = t_hash_next(m, p, &l);
	1430	+ if (!p)
	1431	+ break;
	1432	+ }
	1433	+ return p;
1424	1434	}
1425	1435
1426	1436	static int t_hash_show(struct seq_file m, void v)