From c9c98bc5cc2ab4e0d5c9ad58286fa7e1670dfded Mon Sep 17 00:00:00 2001 From: Oliver O'Halloran Date: Fri, 28 Jul 2017 01:35:53 +1000 Subject: [PATCH] powerpc/mm: Fix pmd/pte_devmap() on non-leaf entries The Radix MMU translation tree as defined in ISA v3.0 contains two different types of entry, directories and leaves. Leaves are identified by _PAGE_PTE being set. The formats of the two entries are different, with the directory entries containing no spare bits for use by software. In particular the bit we use for _PAGE_DEVMAP is not reserved for software, and is part of the NLB (Next Level Base) field, essentially the address of the next level in the tree. Note that the Linux pte_t is not == _PAGE_PTE. A huge page pmd entry (or devmap!) is also a leaf and so has _PAGE_PTE set, even though we use a pmd_t for it in Linux. The fix is to ensure that the pmd/pte_devmap() confirm they are looking at a leaf entry (_PAGE_PTE) as well as checking _PAGE_DEVMAP. Fixes: ebd31197931d ("powerpc/mm: Add devmap support for ppc64") Signed-off-by: Oliver O'Halloran Tested-by: Laurent Vivier Tested-by: Jose Ricardo Ziviani Reviewed-by: Suraj Jitindar Singh Reviewed-by: Aneesh Kumar K.V [mpe: Add a comment in the code and flesh out change log] Signed-off-by: Michael Ellerman --- arch/powerpc/include/asm/book3s/64/pgtable.h | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h index d1da415e283c..818a58fc3f4f 100644 --- a/arch/powerpc/include/asm/book3s/64/pgtable.h +++ b/arch/powerpc/include/asm/book3s/64/pgtable.h @@ -608,9 +608,17 @@ static inline pte_t pte_mkdevmap(pte_t pte) return __pte(pte_val(pte) | _PAGE_SPECIAL|_PAGE_DEVMAP); } +/* + * This is potentially called with a pmd as the argument, in which case it's not + * safe to check _PAGE_DEVMAP unless we also confirm that _PAGE_PTE is set. + * That's because the bit we use for _PAGE_DEVMAP is not reserved for software + * use in page directory entries (ie. non-ptes). + */ static inline int pte_devmap(pte_t pte) { - return !!(pte_raw(pte) & cpu_to_be64(_PAGE_DEVMAP)); + u64 mask = cpu_to_be64(_PAGE_DEVMAP | _PAGE_PTE); + + return (pte_raw(pte) & mask) == mask; } static inline pte_t pte_modify(pte_t pte, pgprot_t newprot) -- 2.20.1