Messages in this thread | | | Date | Wed, 19 Feb 2014 10:28:40 -0500 | Subject | How pte_mkspecial makes zero-page COW on x86 ARCH | From | Hu Yaohui <> |
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Hi All, I read the code in do_anonymous_page of the latest linux kernel. I am pretty confused how pte_mkspecial to make the zero-page COW on x86 architecture <code> static int do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long address, pte_t *page_table, pmd_t *pmd, unsigned int flags) { ..... /* Use the zero-page for reads */ if (!(flags & FAULT_FLAG_WRITE)) { entry = pte_mkspecial(pfn_pte(my_zero_pfn(address), vma->vm_page_prot)); page_table = pte_offset_map_lock(mm, pmd, address, &ptl); if (!pte_none(*page_table)) goto unlock; goto setpte; } ...... } </code> In the previous linux kernel, this is done by pte_wrprotect to make page COW. Thanks for your time!
Best Wishes, Yaohui
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