[PATCH V2 1/3] arm: mm: Double logical invert for pte accessors

From: catalin.marinas@arm.com (Catalin Marinas)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH V2 1/3] arm: mm: Double logical invert for pte accessors
Date: Fri, 28 Feb 2014 15:45:41 +0000	[thread overview]
Message-ID: <20140228154540.GF13970@arm.com> (raw)
In-Reply-To: <1393328334-27285-2-git-send-email-steve.capper@linaro.org>

On Tue, Feb 25, 2014 at 11:38:52AM +0000, Steve Capper wrote:
> Long descriptors on ARM 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.
> 
> Functions such as huge_pte_write also perform a downcast to unsigned
> long (which is 32 bits).
> 
> 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>

Acked-by: Catalin Marinas <catalin.marinas@arm.com>