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

[Russell Currey <ruscur@russell.cc>]

On Wed, 2019-04-24 at 09:14 +0200, Christophe Leroy wrote:
> 
> Le 24/04/2019 à 08:39, Russell Currey a écrit :
> > 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@russell.cc>
> > ---
> >   arch/powerpc/Kconfig.debug         | 19 +++++++++++++++
> >   arch/powerpc/include/asm/pgtable.h |  5 ++++
> >   arch/powerpc/mm/pgtable_32.c       |  5 ++++
> >   arch/powerpc/mm/pgtable_64.c       |  5 ++++
> >   arch/powerpc/mm/ptdump/ptdump.c    | 38
> > ++++++++++++++++++++++++++++++
> >   5 files changed, 72 insertions(+)
> > 
> > diff --git a/arch/powerpc/Kconfig.debug
> > b/arch/powerpc/Kconfig.debug
> > index 4e00cb0a5464..a4160ff02ed4 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 DEBUG_WX
> 
> I would call it PPC_DEBUG_WX to avoid confusion.

It's the same functionality as on other architectures and is an arch-
local thing, I personally think it should be left as-is but given we
already put the PPC prefix on PTDUMP, I'll add it so it's consistent

<snip>

> > +	if (radix_enabled())
> > +		st.start_address = PAGE_OFFSET;
> > +	else
> +		st.start_address = KERN_VIRT_START;
>
> KERN_VIRT_START doesn't exist on PPC32.
> 
> Christophe
> 
Thanks a lot for the review!  Applied all your suggestions.  What
should I use on PPC32 instead?

- Russell