[PATCH] powerpc: fix ioremap_flags() with book3e pte definition

[Kumar Gala]

On Feb 7, 2010, at 10:21 PM, Benjamin Herrenschmidt wrote:

> On Fri, 2010-02-05 at 00:53 +0800, Li Yang wrote:
>> We can't just clear the user read permission in book3e pte, because
>> that will also clear supervisor read permission.  This surely isn't
>> desired.  Fix the problem by adding the supervisor read back.
>> 
>> Signed-off-by: Li Yang <leoli at freescale.com>
>> ---
>> arch/powerpc/mm/pgtable_32.c |    5 +++++
>> 1 files changed, 5 insertions(+), 0 deletions(-)
>> 
>> diff --git a/arch/powerpc/mm/pgtable_32.c b/arch/powerpc/mm/pgtable_32.c
>> index cb96cb2..aff7c04 100644
>> --- a/arch/powerpc/mm/pgtable_32.c
>> +++ b/arch/powerpc/mm/pgtable_32.c
>> @@ -144,6 +144,11 @@ ioremap_flags(phys_addr_t addr, unsigned long size, unsigned long flags)
>> 	/* we don't want to let _PAGE_USER and _PAGE_EXEC leak out */
>> 	flags &= ~(_PAGE_USER | _PAGE_EXEC);
>> 
>> +#if defined(CONFIG_FSL_BOOKE) && defined(CONFIG_PTE_64BIT)
>> +	/* supervisor read permission has just been cleared, add back */
>> +	flags |= _PAGE_BAP_SR;
>> +#endif
>> +
> 
> So this is a bit fishy indeed. pgtable_64.c seems to have the same
> problem in fact.
> 
> It boils down to the "hack" I have in the new PTE format which consists
> of having _SR be part of _PAGE_USER. I wonder if I should change that
> instead. Kumar, what do you reckon ?
> 
> _Maybe_ an option is to have _PAGE_NO_USER that defaults to be
> ~_PAGE_USER in pte-common.h and can be set in pte-book3e.h to
> only strip out UR and UW ?

We never closed on this.  I think lets add _PAGE_NO_USER

- k