[PATCH v10 06/10] powerpc/mm/ptdump: debugfs handler for W+X checks at runtime

@@ -371,7 +371,7 @@ config PPC_PTDUMP
 	  If you are unsure, say N.
 
 config PPC_DEBUG_WX
-	bool "Warn on W+X mappings at boot"
+	bool "Warn on W+X mappings at boot & enable manual checks at runtime"
 	depends on PPC_PTDUMP && STRICT_KERNEL_RWX
 	help
 	  Generate a warning if any W+X mappings are found at boot.

@@ -385,7 +385,9 @@ config PPC_DEBUG_WX
 	  of other unfixed kernel bugs easier.
 
 	  There is no runtime or memory usage effect of this option
-	  once the kernel has booted up - it's a one time check.
+	  once the kernel has booted up, it only automatically checks once.
+
+	  Enables the "check_wx_pages" debugfs entry for checking at runtime.
 
 	  If in doubt, say "Y".
 

@@ -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.

@@ -27,6 +27,8 @@
 
 #include "ptdump.h"
 
+static bool check_wx;
+
 /*
  * To visualise what is happening,
  *

@@ -410,6 +412,9 @@ static int ptdump_show(struct seq_file *m, void *v)
 	/* Traverse kernel page tables */
 	walk_pagetables(&st);
 	note_page(&st, 0, 0, 0, 0);
+
+	if (check_wx)
+		ptdump_check_wx();
 	return 0;
 }
 

@@ -459,6 +464,33 @@ 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)
+		check_wx = true;
+	else if (val == 0ULL)
+		check_wx = false;
+	else
+		return -EINVAL;
+
+	return 0;
+}
+
+static int check_wx_debugfs_get(void *data, u64 *val)
+{
+	*val = check_wx ? 1 : 0;
+	return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(check_wx_fops, check_wx_debugfs_get, check_wx_debugfs_set, "%llu\n");
+
+static int ptdump_check_wx_init(void)
+{
+	return debugfs_create_file("check_wx_pages", 0200, NULL,
+				   NULL, &check_wx_fops) ? 0 : -ENOMEM;
+}
+device_initcall(ptdump_check_wx_init);
 #endif
 
 static int ptdump_init(void)