Introduce a test that performs stack writes in recursive calls to exercise
stack watch at a specific recursion depth.

Signed-off-by: Jinchao Wang <wangjinchao600@gmail.com>
---
 mm/kstackwatch/test.c | 22 +++++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)

diff --git a/mm/kstackwatch/test.c b/mm/kstackwatch/test.c
index 012692c97a50..203fff4bec92 100644
--- a/mm/kstackwatch/test.c
+++ b/mm/kstackwatch/test.c
@@ -18,6 +18,7 @@
 static struct dentry *test_file;
 
 #define BUFFER_SIZE 32
+#define MAX_DEPTH 6
 
 static void test_watch_fire(void)
 {
@@ -46,6 +47,21 @@ static void test_canary_overflow(void)
 	pr_info("exit of %s\n", __func__);
 }
 
+static void test_recursive_depth(int depth)
+{
+	u64 buffer[BUFFER_SIZE];
+
+	pr_info("entry of %s depth:%d\n", __func__, depth);
+
+	if (depth < MAX_DEPTH)
+		test_recursive_depth(depth + 1);
+
+	buffer[0] = depth;
+	barrier_data(buffer);
+
+	pr_info("exit of %s depth:%d\n", __func__, depth);
+}
+
 static ssize_t test_dbgfs_write(struct file *file, const char __user *buffer,
 				size_t count, loff_t *pos)
 {
@@ -71,6 +87,9 @@ static ssize_t test_dbgfs_write(struct file *file, const char __user *buffer,
 		case 1:
 			test_canary_overflow();
 			break;
+		case 2:
+			test_recursive_depth(0);
+			break;
 		default:
 			pr_err("Unknown test number %d\n", test_num);
 			return -EINVAL;
@@ -92,7 +111,8 @@ static ssize_t test_dbgfs_read(struct file *file, char __user *buffer,
 		"Usage:\n"
 		"echo test{i} > /sys/kernel/debug/kstackwatch/test\n"
 		" test0 - test watch fire\n"
-		" test1 - test canary overflow\n";
+		" test1 - test canary overflow\n"
+		" test2 - test recursive func\n";
 
 	return simple_read_from_buffer(buffer, count, ppos, usage,
 				       strlen(usage));
-- 
2.43.0