linux-kernel - Re: [PATCH v2 05/20] ARM: LPAE: Introduce L_PTE_NOEXEC and L_PTE

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Message-ID: <AANLkTik5FcZ3rNtiwN8kYP0LZh+YqGtKP_RteoFiWa16@mail.gmail.com>
Date:	Wed, 17 Nov 2010 17:02:37 +0000
From:	Catalin Marinas <catalin.marinas@....com>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
Cc:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 05/20] ARM: LPAE: Introduce L_PTE_NOEXEC and L_PTE_NOWRITE

On 15 November 2010 18:30, Russell King - ARM Linux
<linux@....linux.org.uk> wrote:
> On Fri, Nov 12, 2010 at 06:00:25PM +0000, Catalin Marinas wrote:
>> --- a/arch/arm/include/asm/pgtable-2level.h
>> +++ b/arch/arm/include/asm/pgtable-2level.h
>> @@ -128,6 +128,8 @@
>>  #define L_PTE_USER           (1 << 8)
>>  #define L_PTE_EXEC           (1 << 9)
>>  #define L_PTE_SHARED         (1 << 10)       /* shared(v6), coherent(xsc3) */
>> +#define L_PTE_NOEXEC         (0)
>> +#define L_PTE_NOWRITE                (0)
>
> Let's not make this more complicated than it has to be.  If we need the
> inverse of WRITE and EXEC, then that's what we should change everyone to,
> not invent a new system to work along side the old system.

Question on the pgprot_noncached/writecombine/dmacoherent - in the
current implementation we pass L_PTE_EXEC on the dmacoherent macro. Do
we need to pass L_PTE_NOEXEC to the noncached/writecombine ones? I
don't see a reason for any of these to be executable but maybe we can
let the code calling them decide.

Thanks.

-- 
Catalin
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