[PATCH 15/17] mm/ksw: add recursive corruption test

[Jinchao Wang <wangjinchao600@gmail.com>]

Introduce a test case simulating stack corruption across recursive calls.
This scenario writes to a local buffer at every recursion depth up to a
configured maximum, allowing validation that KStackWatch can detect
corruption in nested stack frames.

Signed-off-by: Jinchao Wang <wangjinchao600@gmail.com>
---
 mm/kstackwatch/kstackwatch_test.c | 32 ++++++++++++++++++++++++++++++-
 1 file changed, 31 insertions(+), 1 deletion(-)

diff --git a/mm/kstackwatch/kstackwatch_test.c b/mm/kstackwatch/kstackwatch_test.c
index 1f0d616db7c5..cb216b6ee5d7 100644
--- a/mm/kstackwatch/kstackwatch_test.c
+++ b/mm/kstackwatch/kstackwatch_test.c
@@ -146,6 +146,30 @@ static void silent_corruption_test(void)
 		silent_corruption_hapless(i);
 }
 
+/*
+ * Test Case 3: Recursive Call Corruption
+ * Check whether KStackWatch can handle corruption in a recursive call
+ * Write the local variable at every depth
+ * Configure /proc/kstackwatch to specify the corruption depth
+ * Verify that the watch is triggered
+ */
+static void recursive_corruption_test(int depth)
+{
+	u64 buffer[BUFFER_SIZE];
+
+	pr_info("KSW: test: recursive call at depth %d\n", depth);
+	pr_info("KSW: test: buffer 0x%px\n", buffer);
+	if (depth <= MAX_DEPTH)
+		recursive_corruption_test(depth + 1);
+
+	buffer[0] = depth;
+
+	/* make sure the compiler do not drop assign action */
+	barrier_data(buffer);
+
+	pr_info("KSW: test: returning from depth %d\n", depth);
+}
+
 static ssize_t test_proc_write(struct file *file, const char __user *buffer,
 			       size_t count, loff_t *pos)
 {
@@ -177,6 +201,11 @@ static ssize_t test_proc_write(struct file *file, const char __user *buffer,
 			pr_info("KSW: test: triggering silent corruption test\n");
 			silent_corruption_test();
 			break;
+		case 3:
+			pr_info("KSW: test: triggering recursive corruption test\n");
+			/* depth start with 0 */
+			recursive_corruption_test(0);
+			break;
 		default:
 			pr_err("KSW: test: Unknown test number %d\n", test_num);
 			return -EINVAL;
@@ -198,7 +227,8 @@ static ssize_t test_proc_read(struct file *file, char __user *buffer,
 		"Usage:\n"
 		"  echo 'test0' > /proc/kstackwatch_test  - Canary write test\n"
 		"  echo 'test1' > /proc/kstackwatch_test  - Canary overflow test\n"
-		"  echo 'test2' > /proc/kstackwatch_test  - Silent corruption test\n";
+		"  echo 'test2' > /proc/kstackwatch_test  - Silent corruption test\n"
+		"  echo 'test3' > /proc/kstackwatch_test  - Recursive corruption test\n";
 
 	return simple_read_from_buffer(buffer, count, pos, usage,
 				       strlen(usage));
-- 
2.43.0