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SubjectRe: [PATCH] Enable mprotect on huge pages
"Zhang, Yanmin" <yanmin_zhang@linux.intel.com> wrote:
>
> From: Zhang, Yanmin <yanmin.zhang@intel.com>
>
> 2.6.16-rc3 uses hugetlb on-demand paging, but it doesn_t support hugetlb
> mprotect. My patch against 2.6.16-rc3 enables this capability.
>

Well I suppose that makes sense. It does assume that the normal pte
protection-changing APIs do the right thing on all architectures which
implement huge pages. That's quite possibly the case, but we should
confirm that.

> +
> +void hugetlb_change_protection(struct vm_area_struct *vma,
> + unsigned long address, unsigned long end, pgprot_t newprot)
> +{
> + struct mm_struct *mm = vma->vm_mm;
> + unsigned long start = address;
> + pte_t *ptep;
> + pte_t pte;
> +
> + BUG_ON(address >= end);
> + flush_cache_range(vma, address, end);
> +
> + spin_lock(&mm->page_table_lock);
> + for (; address < end; address += HPAGE_SIZE) {
> + ptep = huge_pte_offset(mm, address);
> + if (!ptep)
> + continue;
> + if (pte_present(*ptep)) {
> + pte = ptep_get_and_clear(mm, address, ptep);
> + pte = pte_modify(pte, newprot);
> + set_huge_pte_at(mm, addr, ptep, pte);
> + lazy_mmu_prot_update(pte);
> + }
> + }
> + spin_unlock(&mm->page_table_lock);
> +
> + flush_tlb_range(vma, start, end);
> +}

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