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

From: Christophe Leroy
Date: Wed Oct 17 2018 - 07:14:21 EST

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>
arch/powerpc/include/asm/nohash/pte-book3e.h | 14 ++++++++++++++
1 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 @@

+static inline pte_t pte_mkprivileged(pte_t pte)
+ return __pte((pte_val(pte) & ~_PAGE_USER) | _PAGE_PRIVILEGED);
+#define pte_mkprivileged pte_mkprivileged
+static inline pte_t pte_mkuser(pte_t pte)
+ return __pte((pte_val(pte) & ~_PAGE_PRIVILEGED) | _PAGE_USER);
+#define pte_mkuser pte_mkuser
#endif /* __KERNEL__ */

But there's also a use of pte_pgprot() in mm/memory.c, and I think that
is also broken now that we don't add PAGE_KERNEL back in.

Aneesh is going to do a patch to make pte_pgprot() only mask the PFN
which is what other arches do.

Yes I saw it, that's ok for me.



From: Christophe Leroy <christophe.leroy@xxxxxx>
Date: Wed, 17 Oct 2018 05:56:25 +0000
Subject: [PATCH] powerpc/mm: don't use pte_pgprot() in ioremap_prot()

pte_pgprot() filters out some required flags like _PAGE_PRESENT.

This patch replaces pte_pgprot() by __pgprot(pte_val())
in ioremap_prot()

Fixes: 26973fa5ac0e ("powerpc/mm: use pte helpers in generic code")
Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxx>
arch/powerpc/mm/pgtable_32.c | 3 ++-
arch/powerpc/mm/pgtable_64.c | 4 ++--
2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/mm/pgtable_32.c b/arch/powerpc/mm/pgtable_32.c
index 5877f5aa8f5d..a606e2f4937b 100644
--- a/arch/powerpc/mm/pgtable_32.c
+++ b/arch/powerpc/mm/pgtable_32.c
@@ -122,7 +122,8 @@ ioremap_prot(phys_addr_t addr, unsigned long size,
unsigned long flags)
pte = pte_exprotect(pte);
pte = pte_mkprivileged(pte);

- return __ioremap_caller(addr, size, pte_pgprot(pte),
+ return __ioremap_caller(addr, size, __pgprot(pte_val(pte)),
+ __builtin_return_address(0));

diff --git a/arch/powerpc/mm/pgtable_64.c b/arch/powerpc/mm/pgtable_64.c
index fb1375c07e8c..836bf436cabb 100644
--- a/arch/powerpc/mm/pgtable_64.c
+++ b/arch/powerpc/mm/pgtable_64.c
@@ -245,8 +245,8 @@ void __iomem * ioremap_prot(phys_addr_t addr,
unsigned long size,
pte = pte_mkprivileged(pte);

if (ppc_md.ioremap)
- return ppc_md.ioremap(addr, size, pte_pgprot(pte), caller);
- return __ioremap_caller(addr, size, pte_pgprot(pte), caller);
+ return ppc_md.ioremap(addr, size, __pgprot(pte_val(pte)), caller);
+ return __ioremap_caller(addr, size, __pgprot(pte_val(pte)), caller);