Re: [RFC PATCH v6 01/20] iommu/arm-smmu: change IOMMU_EXEC to IOMMU_NOEXEC

Will Deacon
2014-06-16T15:04:12Z

On Thu, Jun 05, 2014 at 06:03:09PM +0100, Antonios Motakis wrote:
> Exposing the XN flag of the SMMU driver as IOMMU_NOEXEC instead of
> IOMMU_EXEC makes it enforceable, since for IOMMUs that don't support
> the XN flag pages will always be executable.
>
> Signed-off-by: Antonios Motakis <a.motakis@virtualopensystems.com>
> ---
> drivers/iommu/arm-smmu.c | 2 +-
> include/linux/iommu.h | 2 +-
> 2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
> index 647c3c7..d5a2200 100644
> --- a/drivers/iommu/arm-smmu.c
> +++ b/drivers/iommu/arm-smmu.c
> @@ -1294,7 +1294,7 @@ static int arm_smmu_alloc_init_pte(struct arm_smmu_device *smmu, pmd_t *pmd,
> }
>
> /* If no access, create a faulting entry to avoid TLB fills */
> - if (prot & IOMMU_EXEC)
> + if (!(prot & IOMMU_NOEXEC))
> pteval &= ~ARM_SMMU_PTE_XN;

It's probably simpler to change the logic so that we initialise pteval
without XN set, then set it if IOMMU_NOEXEC is set (rather than set it
by default, then clear it if NOEXEC is not set).

Will