Re: [PATCH v2 2/2] powerpc/mm: Warn if W+X pages found on boot

On Fri, 2019-05-03 at 00:37 +0000, Joel Stanley wrote:

On Thu, 2 May 2019 at 07:42, Russell Currey [off-list ref]
wrote:

quoted

Implement code to walk all pages and warn if any are found to be
both
writable and executable.  Depends on STRICT_KERNEL_RWX enabled, and
is
behind the DEBUG_WX config option.

This only runs on boot and has no runtime performance implications.

Very heavily influenced (and in some cases copied verbatim) from
the
ARM64 code written by Laura Abbott (thanks!), since our ptdump
infrastructure is similar.

Signed-off-by: Russell Currey <redacted>
---
v2: A myriad of fixes and cleanups thanks to Christophe Leroy

 arch/powerpc/Kconfig.debug         | 19 ++++++++++++++
 arch/powerpc/include/asm/pgtable.h |  6 +++++
 arch/powerpc/mm/pgtable_32.c       |  3 +++
 arch/powerpc/mm/pgtable_64.c       |  3 +++
 arch/powerpc/mm/ptdump/ptdump.c    | 41
+++++++++++++++++++++++++++++-
 5 files changed, 71 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/Kconfig.debug

b/arch/powerpc/Kconfig.debug
index 4e00cb0a5464..9e8bcddd8b8f 100644

--- a/arch/powerpc/Kconfig.debug
+++ b/arch/powerpc/Kconfig.debug

@@ -361,6 +361,25 @@ config PPC_PTDUMP

          If you are unsure, say N.

+config PPC_DEBUG_WX

The other architectures call this DEBUG_WX, in case you wanted to
name
it the same.

I did originally, I changed it since we have PPC_PTDUMP but I don't
really care either way.  mpe can change it if he wants

quoted

+       bool "Warn on W+X mappings at boot"
+       select PPC_PTDUMP
+       help
+         Generate a warning if any W+X mappings are found at boot.