Re: [PATCH v2 04/43] arm64: RME: Handle Granule Protection Faults (GPFs)

Suzuki K Poulose
2024-04-16T11:17:11Z

On 12/04/2024 09:42, Steven Price wrote:
> If the host attempts to access granules that have been delegated for use
> in a realm these accesses will be caught and will trigger a Granule
> Protection Fault (GPF).
>
> A fault during a page walk signals a bug in the kernel and is handled by
> oopsing the kernel. A non-page walk fault could be caused by user space
> having access to a page which has been delegated to the kernel and will
> trigger a SIGBUS to allow debugging why user space is trying to access a
> delegated page.
>
> Signed-off-by: Steven Price <steven.price@arm.com>
> ---
> arch/arm64/mm/fault.c | 29 ++++++++++++++++++++++++-----
> 1 file changed, 24 insertions(+), 5 deletions(-)
>
> diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
> index 8251e2fea9c7..91da0f446dd9 100644
> --- a/arch/arm64/mm/fault.c
> +++ b/arch/arm64/mm/fault.c
> @@ -765,6 +765,25 @@ 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)
> +{
> + const struct fault_info *inf = esr_to_fault_info(esr);
> +
> + if (!is_el1_instruction_abort(esr) && fixup_exception(regs))
> + return 0;
> +
> + arm64_notify_die(inf->name, regs, inf->sig, inf->code, far, 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" },
> @@ -802,11 +821,11 @@ static const struct fault_info fault_info[] = {
> { do_alignment_fault, SIGBUS, BUS_ADRALN, "alignment fault" },
> { do_bad, SIGKILL, SI_KERNEL, "unknown 34" },
> { do_bad, SIGKILL, SI_KERNEL, "unknown 35" },

Should this also be converted to do_gpf_ptw, "GPF at level -1", given we
support LPA2 ?

> - { 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, "Granule Protection Fault at level 0" },
> + { do_gpf_ptw, SIGKILL, SI_KERNEL, "Granule Protection Fault at level 1" },
> + { do_gpf_ptw, SIGKILL, SI_KERNEL, "Granule Protection Fault at level 2" },
> + { do_gpf_ptw, SIGKILL, SI_KERNEL, "Granule Protection Fault at level 3" },
> + { do_gpf, SIGBUS, SI_KERNEL, "Granule Protection Fault not on table walk" },
> { do_bad, SIGKILL, SI_KERNEL, "level -1 address size fault" },
> { do_bad, SIGKILL, SI_KERNEL, "unknown 42" },
> { do_translation_fault, SIGSEGV, SEGV_MAPERR, "level -1 translation fault" },

Rest looks fine to me.

Suzuki