[PATCH v5 16/30] arm64: handle PKEY/POE faults

[Joey Gouly]

On Tue, Sep 03, 2024 at 03:50:46PM +0100, Joey Gouly wrote:
> On Thu, Aug 29, 2024 at 06:55:07PM +0100, Mark Brown wrote:
> > On Thu, Aug 22, 2024 at 04:10:59PM +0100, Joey Gouly wrote:
> > 
> > > +static bool fault_from_pkey(unsigned long esr, struct vm_area_struct *vma,
> > > +			unsigned int mm_flags)
> > > +{
> > > +	unsigned long iss2 = ESR_ELx_ISS2(esr);
> > > +
> > > +	if (!system_supports_poe())
> > > +		return false;
> > > +
> > > +	if (iss2 & ESR_ELx_Overlay)
> > > +		return true;
> > 
> > Does this need an is_data_abort() && is_instruction_abort() check?
> > Overlay doesn't appear to be defined for all exception types and it
> > wasn't clear enough to me that the callers have done this check.
> 
> The only callers are in do_page_fault(), which should only be data or
> instruction aborts. I talked with Catalin and he said it's fine to not check
> again here.
> 
> I can add a permissions check though:
> 
> commit 033270f5a9462e998b4dee11fc91b43ac7929756
> Author: Joey Gouly <joey.gouly at arm.com>
> Date:   Tue Sep 3 15:45:59 2024 +0100
> 
>     fixup! arm64: handle PKEY/POE faults
> 
> diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
> index a68055150950..f651553a8ab8 100644
> --- a/arch/arm64/mm/fault.c
> +++ b/arch/arm64/mm/fault.c
> @@ -495,6 +495,9 @@ static bool fault_from_pkey(unsigned long esr, struct vm_area_struct *vma,
>         if (!system_supports_poe())
>                 return false;
>  
> +       if (!esr_fsc_is_permission_fault(esr))
> +               return false;
> +
>         if (iss2 & ESR_ELx_Overlay)
>                 return true;
>  
> 
> 
> Since the ESR_EL1 documentation says:
> 	If a memory access generates a Data Abort for a Permission fault, then this field holds information
> 	about the fault.
> 

Sorry, I was a bit too eager with that patch.  The previous patch was bailing
out before the vma-backed checks could take place.

It should be:

commit 7b67b149f2f492e907b27521c95639f4ea208221 (HEAD -> permission_overlay_v6)
Author: Joey Gouly <joey.gouly at arm.com>
Date:   Tue Sep 3 15:45:59 2024 +0100

    fixup! arm64: handle PKEY/POE faults

diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index a68055150950..8b281cf308b3 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -495,7 +495,7 @@ static bool fault_from_pkey(unsigned long esr, struct vm_area_struct *vma,
        if (!system_supports_poe())
                return false;
 
-       if (iss2 & ESR_ELx_Overlay)
+       if (esr_fsc_is_permission_fault(esr) && (iss2 & ESR_ELx_Overlay))
                return true;
 
        return !arch_vma_access_permitted(vma,