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

[Catalin Marinas]

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.

> +
>  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().

Otherwise it looks fine to me.

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