[PATCH V3 3/5] arch/powerpc/mm: Nest MMU workaround for mprotect RW upgrade.

[Christoph Hellwig]

On Wed, Dec 05, 2018 at 08:39:29AM +0530, Aneesh Kumar K.V wrote:
> +pte_t ptep_modify_prot_start(struct vm_area_struct *vma, unsigned long addr,
> +			     pte_t *ptep)
> +{
> +	unsigned long pte_val;
> +
> +	/*
> +	 * Clear the _PAGE_PRESENT so that no hardware parallel update is
> +	 * possible. Also keep the pte_present true so that we don't take
> +	 * wrong fault.
> +	 */
> +	pte_val = pte_update(vma->vm_mm, addr, ptep, _PAGE_PRESENT, _PAGE_INVALID, 0);
> +
> +	return __pte(pte_val);
> +
> +}
> +EXPORT_SYMBOL(ptep_modify_prot_start);

As far as I can tell this is only called from mm/memory.c, mm/mprotect.c
and fs/proc/task_mmu.c, so there should be no need to export the
function.