Page table entries on ARM64 are 64 bits, and some pte functions such as
pte_dirty return a bitwise-and of a flag with the pte value. If the
flag to be tested resides in the upper 32 bits of the pte, then we run
into the danger of the result being dropped if downcast.
For example:
gather_stats(page, md, pte_dirty(*pte), 1);
where pte_dirty(*pte) is downcast to an int.
This patch adds a double logical invert to all the pte_ accessors to
ensure predictable downcasting.
Cc: <stable@vger.kernel.org>
Signed-off-by: Catalin Marinas <catalin.mari...@arm.com>
[steve.cap...@linaro.org: rebased patch to leave pte_write alone to
allow for merge with 3.13 stable]
Signed-off-by: Steve Capper <steve.cap...@linaro.org>
---
This is a rebase of:
84fe682 arm64: mm: Add double logical invert to pte accessors
It was CC stable, but had a merge conflict around pte_write when
applied to 3.13-stable.
I've fixed the merge conflict for 3.13 and given it a quick test.
---
arch/arm64/include/asm/pgtable.h | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index 7f2b60a..2c121f7 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -136,10 +136,10 @@ extern struct page *empty_zero_page;
/*
* The following only work if pte_present(). Undefined behaviour otherwise.
*/
-#define pte_present(pte) (pte_val(pte) & (PTE_VALID | PTE_PROT_NONE))
-#define pte_dirty(pte) (pte_val(pte) & PTE_DIRTY)
-#define pte_young(pte) (pte_val(pte) & PTE_AF)
-#define pte_special(pte) (pte_val(pte) & PTE_SPECIAL)
+#define pte_present(pte) (!!(pte_val(pte) & (PTE_VALID | PTE_PROT_NONE)))
+#define pte_dirty(pte) (!!(pte_val(pte) & PTE_DIRTY))
+#define pte_young(pte) (!!(pte_val(pte) & PTE_AF))
+#define pte_special(pte) (!!(pte_val(pte) & PTE_SPECIAL))
#define pte_write(pte) (!(pte_val(pte) & PTE_RDONLY))
#define pte_exec(pte) (!(pte_val(pte) & PTE_UXN))
--
1.8.1.4
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