On 2016/7/11 21:30, Kirill A. Shutemov wrote: > On Mon, Jul 11, 2016 at 06:12:30PM +0800, Xishi Qiu wrote: >> Hi, >> >> We can use mprotect to set read only or read/write. >> >> mprotect_fixup() >> vma_set_page_prot() >> vm_pgprot_modify() >> vm_get_page_prot() >> protection_map[vm_flags & (VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)] >> >> The following code shows that prots from __P001(PROT_READ) and __P010(PROT_WRITE) >> are the same, so how does it distinguish read only or read/write from mprotect? > > It doesn't. > > Write protection will be removed by fault handler on next write access to > the page. Somewhat suboptiomal, but zero page implemenation relies on this > to work properly. > Hi Kirill, I know, PAGE_READONLY and PAGE_COPY are both missed _PAGE_RW, so it will cause page fault, then we will set new prot flag from vma, right? Thanks, Xishi Qiu -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>