[PATCH 4/4] ptdump: add check_wx_pages debugfs attribute

[Christophe Leroy]

Add a writable attribute in debugfs to trigger a
W^X pages check at any time.

To trigger the test, just echo any numeric value into
/sys/kernel/debug/check_wx_pages

The result is provided into dmesg.

Signed-off-by: Christophe Leroy <christophe.leroy at csgroup.eu>
---
 mm/ptdump.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/mm/ptdump.c b/mm/ptdump.c
index 03c1bdae4a43..e154099c2584 100644
--- a/mm/ptdump.c
+++ b/mm/ptdump.c
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0
 
 #include <linux/pagewalk.h>
+#include <linux/debugfs.h>
 #include <linux/ptdump.h>
 #include <linux/kasan.h>
 
@@ -163,3 +164,21 @@ void ptdump_walk_pgd(struct ptdump_state *st, struct mm_struct *mm, pgd_t *pgd)
 	/* Flush out the last page */
 	st->note_page(st, 0, -1, 0);
 }
+
+static int check_wx_debugfs_set(void *data, u64 val)
+{
+	ptdump_check_wx();
+
+	return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(check_wx_fops, NULL, check_wx_debugfs_set, "%llu\n");
+
+static int ptdump_debugfs_init(void)
+{
+	debugfs_create_file("check_wx_pages", 0200, NULL, NULL, &check_wx_fops);
+
+	return 0;
+}
+
+device_initcall(ptdump_debugfs_init);
-- 
2.41.0