x86: add code to dump the (kernel) page tables for visual inspection by kernel developers

This patch adds code to the kernel to have an (optional)
/proc/kernel_page_tables debug file that basically dumps the kernel
pagetables; this allows us kernel developers to verify that nothing fishy is
going on and that the various mappings are set up correctly. This was quite
useful in finding various change_page_attr() bugs, and is very likely to be
useful in the future as well.

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Cc: mingo@elte.hu
Cc: tglx@tglx.de
Cc: hpa@zytor.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 12 insertions, 0 deletions

diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
index 702eb39901c..cb7002eca88 100644
--- a/arch/x86/Kconfig.debug
+++ b/arch/x86/Kconfig.debug
@@ -54,6 +54,18 @@ config DEBUG_PER_CPU_MAPS
 
           Say N if unsure.
 
+config X86_PTDUMP
+        bool "Export kernel pagetable layout to userspace via debugfs"
+        depends on X86_64
+        select DEBUG_FS
+        help
+          Say Y here if you want to show the kernel pagetable layout in a
+          debugfs file. This information is only useful for kernel developers
+          who are working in architecture specific areas of the kernel.
+          It is probably not a good idea to enable this feature in a production
+          kernel.
+          If in doubt, say "N"
+
 config DEBUG_RODATA
         bool "Write protect kernel read-only data structures"
         default y