x86: NX bit handling in change_page_attr()
This patch fixes a bug of change_page_attr/change_page_attr_addr on Intel x86_64 CPUs. After changing page attribute to be executable with these functions, the page remains un-executable on Intel x86_64 CPU. Because on Intel x86_64 CPU, only if the "NX" bits of all four level page tables are cleared, the corresponding page is executable (refer to section 4.13.2 of Intel 64 and IA-32 Architectures Software Developer's Manual). So, the bug is fixed through clearing the "NX" bit of PMD when splitting the huge PMD. Signed-off-by: Huang Ying <ying.huang@intel.com> Cc: Andi Kleen <ak@suse.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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@ -148,6 +148,7 @@ __change_page_attr(unsigned long address, unsigned long pfn, pgprot_t prot,
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split = split_large_page(address, prot, ref_prot2);
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if (!split)
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return -ENOMEM;
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pgprot_val(ref_prot2) &= ~_PAGE_NX;
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set_pte(kpte, mk_pte(split, ref_prot2));
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kpte_page = split;
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}
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