Re: Crash on FSL Book3E due to pte_pgprot()? (was Re: [PATCH v3 12/24] powerpc/mm: use pte helpers in generic code)

[Aneesh Kumar K.V]

On 10/17/18 4:42 PM, Christophe Leroy wrote:
> On 10/17/2018 10:32 AM, Michael Ellerman wrote:
> > Christophe Leroy <christophe.leroy@xxxxxx> writes:
> > > On 10/17/2018 12:59 AM, Michael Ellerman wrote:
> > ...
> > > > The question is what's the right way to fix it? Should pte_pgprot() not
> > > > be filtering those bits out on book3e?
> > >
> > > I think we should not use pte_pggrot() for that then. What about the
> > > below fix ?
> >
> > Thanks, that almost works.
> >
> > pte_mkprivileged() also needs to not strip _PAGE_BAP_SR.
>
> Oops, I missed it allthough I knew it. Patch below.
>
> From: Christophe Leroy <christophe.leroy@xxxxxx>
> Date: Wed, 17 Oct 2018 10:46:24 +0000
> Subject: [PATCH] powerpc/book3e: redefine pte_mkprivileged() and 
> pte_mkuser()
> To: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>, Paul Mackerras 
> <paulus@xxxxxxxxx>, Michael Ellerman <mpe@xxxxxxxxxxxxxx>
> Cc: linux-kernel@xxxxxxxxxxxxxxx, linuxppc-dev@xxxxxxxxxxxxxxxx
>
> Book3e defines both _PAGE_USER and _PAGE_PRIVILEGED, so the nohash
> default pte_mkprivileged() and pte_mkuser() are not usable.
>
> This patch redefines them for book3e.
>
> Fixes: a0da4bc166f2 ("powerpc/mm: Allow platforms to redefine some 
> helpers")
> Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxx>
> ---
>  Âarch/powerpc/include/asm/nohash/pte-book3e.h | 14 ++++++++++++++
>  Â1 file changed, 14 insertions(+)
>
> diff --git a/arch/powerpc/include/asm/nohash/pte-book3e.h 
> b/arch/powerpc/include/asm/nohash/pte-book3e.h
> index 58eef8cb569d..fb4297dff3e2 100644
> --- a/arch/powerpc/include/asm/nohash/pte-book3e.h
> +++ b/arch/powerpc/include/asm/nohash/pte-book3e.h
> @@ -109,5 +109,19 @@
>  Â#define PAGE_READONLYÂÂÂ __pgprot(_PAGE_BASE | _PAGE_USER)
>  Â#define PAGE_READONLY_XÂÂÂ __pgprot(_PAGE_BASE | _PAGE_USER | _PAGE_EXEC)
>
> +static inline pte_t pte_mkprivileged(pte_t pte)
> +{
> +ÂÂÂ return __pte((pte_val(pte) & ~_PAGE_USER) | _PAGE_PRIVILEGED);
> +}
> +
> +#define pte_mkprivileged pte_mkprivileged
> +
> +static inline pte_t pte_mkuser(pte_t pte)
> +{
> +ÂÂÂ return __pte((pte_val(pte) & ~_PAGE_PRIVILEGED) | _PAGE_USER);
> +}
> +
> +#define pte_mkuser pte_mkuser
> +

I was build testing a similar patch. We would need to put #ifndef 
__ASSEMBLY__ around it.



-aneesh