[PATCH v3 3/4] powerpc/mm/ptdump: debugfs handler for W+X checks at runtime

[Russell Currey <ruscur@russell.cc>]

Very rudimentary, just

	echo 1 > [debugfs]/check_wx_pages

and check the kernel log.  Useful for testing strict module RWX.

Also fixed a typo.

Signed-off-by: Russell Currey <ruscur@russell.cc>
---
 arch/powerpc/mm/ptdump/ptdump.c | 31 +++++++++++++++++++++++++------
 1 file changed, 25 insertions(+), 6 deletions(-)

diff --git a/arch/powerpc/mm/ptdump/ptdump.c b/arch/powerpc/mm/ptdump/ptdump.c
index 2f9ddc29c535..0547cd9f264e 100644
--- a/arch/powerpc/mm/ptdump/ptdump.c
+++ b/arch/powerpc/mm/ptdump/ptdump.c
@@ -4,7 +4,7 @@
  *
  * This traverses the kernel pagetables and dumps the
  * information about the used sections of memory to
- * /sys/kernel/debug/kernel_pagetables.
+ * /sys/kernel/debug/kernel_page_tables.
  *
  * Derived from the arm64 implementation:
  * Copyright (c) 2014, The Linux Foundation, Laura Abbott.
@@ -409,16 +409,35 @@ void ptdump_check_wx(void)
 	else
 		pr_info("Checked W+X mappings: passed, no W+X pages found\n");
 }
+
+static int check_wx_debugfs_set(void *data, u64 val)
+{
+	if (val != 1ULL)
+		return -EINVAL;
+
+	ptdump_check_wx();
+
+	return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(check_wx_fops, NULL, check_wx_debugfs_set, "%llu\n");
 #endif
 
 static int ptdump_init(void)
 {
-	struct dentry *debugfs_file;
-
 	populate_markers();
 	build_pgtable_complete_mask();
-	debugfs_file = debugfs_create_file("kernel_page_tables", 0400, NULL,
-			NULL, &ptdump_fops);
-	return debugfs_file ? 0 : -ENOMEM;
+
+	if (!debugfs_create_file("kernel_page_tables", 0400, NULL,
+				 NULL, &ptdump_fops))
+		return -ENOMEM;
+
+#ifdef CONFIG_PPC_DEBUG_WX
+	if (!debugfs_create_file("check_wx_pages", 0200, NULL,
+				 NULL, &check_wx_fops))
+		return -ENOMEM;
+#endif
+
+	return 0;
 }
 device_initcall(ptdump_init);
-- 
2.23.0