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

[Russell Currey]

On Fri, 2019-05-03 at 00:37 +0000, Joel Stanley wrote:
> On Thu, 2 May 2019 at 07:42, Russell Currey <ruscur at russell.cc>
> wrote:
> > 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 <ruscur at russell.cc>
> > ---
> > 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

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