Re: [PATCH v17 1/1] arm64: mm: Handle Granule Protection Faults (GPFs)

[Suzuki K Poulose]

On 10/09/2026 18:45, Catalin Marinas wrote:
> On Mon, Sep 07, 2026 at 05:22:04PM +0100, Suzuki K Poulose wrote:
> > diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
> > index 0b52557652be6..ad00997b1a873 100644
> > --- a/arch/arm64/mm/fault.c
> > +++ b/arch/arm64/mm/fault.c
> > @@ -910,6 +910,22 @@ static int do_tag_check_fault(unsigned long far, unsigned long esr,
> >   	return 0;
> >   }
> >   
> > +static int do_gpf_ptw(unsigned long far, unsigned long esr, struct pt_regs *regs)
> > +{
> > +	const struct fault_info *inf = esr_to_fault_info(esr);
> > +
> > +	die_kernel_fault(inf->name, far, esr, regs);
> > +	return 0;
> > +}
> > +
> > +static int do_gpf(unsigned long far, unsigned long esr, struct pt_regs *regs)
> > +{
> > +	if (!is_el1_instruction_abort(esr) && fixup_exception(regs, esr))
> > +		return 0;
> > +
> > +	return 1;
> > +}
>
> If we end up with a user PC here, we correctly return 1 but only because
> fixup_exception() won't find the PC. I'd rather have this explicit with
> a user_mode() check.

Sure, I have made the condtion to:

+       if (!user_mode(regs) && !is_el1_instruction_abort(esr) &&
+           fixup_exception(regs, esr))
+               return 0;

> > +
> >   static const struct fault_info fault_info[] = {
> >   	{ do_bad,		SIGKILL, SI_KERNEL,	"ttbr address size fault"	},
> >   	{ do_bad,		SIGKILL, SI_KERNEL,	"level 1 address size fault"	},
> > @@ -946,12 +962,12 @@ static const struct fault_info fault_info[] = {
> >   	{ do_bad,		SIGKILL, SI_KERNEL,	"unknown 32"			},
> >   	{ do_alignment_fault,	SIGBUS,  BUS_ADRALN,	"alignment fault"		},
> >   	{ do_bad,		SIGKILL, SI_KERNEL,	"unknown 34"			},
> > -	{ do_bad,		SIGKILL, SI_KERNEL,	"unknown 35"			},
> > -	{ do_bad,		SIGKILL, SI_KERNEL,	"unknown 36"			},
> > -	{ do_bad,		SIGKILL, SI_KERNEL,	"unknown 37"			},
> > -	{ do_bad,		SIGKILL, SI_KERNEL,	"unknown 38"			},
> > -	{ do_bad,		SIGKILL, SI_KERNEL,	"unknown 39"			},
> > -	{ do_bad,		SIGKILL, SI_KERNEL,	"unknown 40"			},
> > +	{ do_gpf_ptw,		SIGKILL, SI_KERNEL,	"level -1 granule protection fault (translation table walk)" },
> > +	{ do_gpf_ptw,		SIGKILL, SI_KERNEL,	"level 0 granule protection fault (translation table walk)" },
> > +	{ do_gpf_ptw,		SIGKILL, SI_KERNEL,	"level 1 granule protection fault (translation table walk)" },
> > +	{ do_gpf_ptw,		SIGKILL, SI_KERNEL,	"level 2 granule protection fault (translation table walk)" },
> > +	{ do_gpf_ptw,		SIGKILL, SI_KERNEL,	"level 3 granule protection fault (translation table walk)" },
> > +	{ do_gpf,		SIGBUS,  SI_KERNEL,	"granule protection fault" },
>
> For SIGBUS, we should use BUS_OBJERR like we do for do_sea().

Good point, I have added that.
> Otherwise it looks fine to me.

Thanks, I have already added the untagged_addr() as reported by Sashiko.


> Reviewed-by: Catalin Marinas <catalin.marinas@xxxxxxx>


Cheers
Suzuki