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SubjectRe: [v2 PATCH 1/2] powerpc32: adds handling of _PAGE_RO

Le 18/12/2014 03:14, Scott Wood a écrit :
> On Wed, 2014-12-17 at 10:14 +0100, Christophe Leroy wrote:
>> Some powerpc like the 8xx don't have a RW bit in PTE bits but a RO (Read Only) bit.
>> This patch implements the handling of a _PAGE_RO flag to be used in place of _PAGE_RW
>>
>> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
>>
>> ---
>> v2 is a complete rework compared to v1
>>
>> arch/powerpc/include/asm/pgtable-ppc32.h | 11 ++++++-----
>> arch/powerpc/include/asm/pgtable.h | 10 +++++++---
>> arch/powerpc/include/asm/pte-common.h | 27 ++++++++++++++++++---------
>> arch/powerpc/mm/gup.c | 2 ++
>> arch/powerpc/mm/mem.c | 2 +-
>> arch/powerpc/mm/pgtable_32.c | 24 ++++++++++++++++++++----
>> 6 files changed, 54 insertions(+), 22 deletions(-)
>>
>> diff --git a/arch/powerpc/include/asm/pgtable-ppc32.h b/arch/powerpc/include/asm/pgtable-ppc32.h
>> index 543bb8e..64ed9e1 100644
>> --- a/arch/powerpc/include/asm/pgtable-ppc32.h
>> +++ b/arch/powerpc/include/asm/pgtable-ppc32.h
>> @@ -125,7 +125,7 @@ extern int icache_44x_need_flush;
>> #ifndef __ASSEMBLY__
>>
>> #define pte_clear(mm, addr, ptep) \
>> - do { pte_update(ptep, ~_PAGE_HASHPTE, 0); } while (0)
>> + do { pte_update(ptep, ~_PAGE_HASHPTE, _PAGE_RO); } while (0)
> Is this really necessary? It's already clearing the valid bit.
>
> Likewise in several other places that set or check for _PAGE_RO on pages
> for which no access is permitted.
>
>
You are right, this is not needed. I needed it because I had defined
pte_none() as requiring _PAGE_RO set. But we can keep value 0 as
pte_none. Taken into account in v3

Christophe


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