Re: [PATCH v7 7/9] mm: Add address parameter to arch_validate_prot()

[Khalid Aziz]

On 08/10/2017 07:20 AM, Michael Ellerman wrote:
> Khalid Aziz <khalid.aziz@xxxxxxxxxx> writes:
>
> > A protection flag may not be valid across entire address space and
> > hence arch_validate_prot() might need the address a protection bit is
> > being set on to ensure it is a valid protection flag. For example, sparc
> > processors support memory corruption detection (as part of ADI feature)
> > flag on memory addresses mapped on to physical RAM but not on PFN mapped
> > pages or addresses mapped on to devices. This patch adds address to the
> > parameters being passed to arch_validate_prot() so protection bits can
> > be validated in the relevant context.
> >
> > Signed-off-by: Khalid Aziz <khalid.aziz@xxxxxxxxxx>
> > Cc: Khalid Aziz <khalid@xxxxxxxxxxxxxx>
> > ---
> > v7:
> > 	- new patch
> >
> >   arch/powerpc/include/asm/mman.h | 2 +-
> >   arch/powerpc/kernel/syscalls.c  | 2 +-
> >   include/linux/mman.h            | 2 +-
> >   mm/mprotect.c                   | 2 +-
> >   4 files changed, 4 insertions(+), 4 deletions(-)
> >
> > diff --git a/arch/powerpc/include/asm/mman.h b/arch/powerpc/include/asm/mman.h
> > index 30922f699341..bc74074304a2 100644
> > --- a/arch/powerpc/include/asm/mman.h
> > +++ b/arch/powerpc/include/asm/mman.h
> > @@ -40,7 +40,7 @@ static inline bool arch_validate_prot(unsigned long prot)
> >   		return false;
> >   	return true;
> >   }
> > -#define arch_validate_prot(prot) arch_validate_prot(prot)
> > +#define arch_validate_prot(prot, addr) arch_validate_prot(prot)
>
> This can be simpler, as just:
>
> #define arch_validate_prot arch_validate_prot

Hi Michael,

Thanks for reviewing!

My patch expands parameter list for arch_validate_prot() from one to two 
parameters. Existing powerpc version of arch_validate_prot() is written 
with one parameter. If I use the above #define, compilation fails with:

mm/mprotect.c: In function âdo_mprotect_pkeyâ:
mm/mprotect.c:399: error: too many arguments to function 
âarch_validate_protâ

Another way to solve it would be to add the new addr parameter to 
powerpc version of arch_validate_prot() but I chose the less disruptive 
solution of tackling it through #define and expanded the existing 
#define to include the new parameter. Make sense?

Thanks,
Khalid