diff mbox

[V2,2/3] arm64: mm: Add double logical invert to pte accessors

Message ID 1393328334-27285-3-git-send-email-steve.capper@linaro.org
State Accepted
Commit 84fe6826c28f69d8708bd575faed7f75e6b6f57f
Headers show

Commit Message

Steve Capper Feb. 25, 2014, 11:38 a.m. UTC 
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.

Signed-off-by: Steve Capper <steve.capper@linaro.org>
---
Changes in V2: drop the pte_isset macro, just add the !!
---
 arch/arm64/include/asm/pgtable.h | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

Comments

Catalin Marinas Feb. 28, 2014, 3:46 p.m. UTC | #1 
On Tue, Feb 25, 2014 at 11:38:53AM +0000, Steve Capper wrote:
> 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.
> 
> Signed-off-by: Steve Capper <steve.capper@linaro.org>

Applied and added cc stable as well. Thanks.
diff mbox

Patch

diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index b524dcd..aa3917c 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -136,11 +136,11 @@  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_write(pte)		(pte_val(pte) & PTE_WRITE)
+#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_WRITE))
 #define pte_exec(pte)		(!(pte_val(pte) & PTE_UXN))
 
 #define pte_valid_user(pte) \