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

[Khalid Aziz]

On 08/14/2017 11:02 PM, Michael Ellerman wrote:
> Khalid Aziz <khalid.aziz@xxxxxxxxxx> writes:
>
> > 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?
>
> Yes, it makes sense. But it's a bit gross.
>
> At first glance it looks like our arch_validate_prot() has an incorrect
> signature.
>
> I'd prefer you just updated it to have the correct signature, I think
> you'll have to change one more line in do_mmap2(). So it's not very
> intrusive.

Thanks, Michael. I can do that.

--
Khalid