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

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
+	bool "Warn on W+X mappings at boot"
+	select PPC_PTDUMP