linux-kernel - Re: [PATCHv2] arm64: Fix R/O permissions in mark_rodata

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Message-ID: <CAKv+Gu9qoZBJRzmKvi_MrbUJgqqwvC+y=v_vUap+m1FW==Tb9w@mail.gmail.com>
Date:	Tue, 17 Nov 2015 10:56:10 +0100
From:	Ard Biesheuvel <ard.biesheuvel@...aro.org>
To:	Laura Abbott <labbott@...hat.com>
Cc:	Laura Abbott <labbott@...oraproject.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCHv2] arm64: Fix R/O permissions in mark_rodata_ro

On 16 November 2015 at 23:50, Laura Abbott <labbott@...hat.com> wrote:
> On 11/14/2015 11:38 PM, Ard Biesheuvel wrote:
>>
>> On 12 November 2015 at 21:21, Laura Abbott <labbott@...oraproject.org>
>> wrote:
>>>
>>> The permissions in mark_rodata_ro trigger a build error
>>> with STRICT_MM_TYPECHECKS. Fix this by introducing
>>> PAGE_KERNEL_ROX for the same reasons as PAGE_KERNEL_RO.
>>
>>
>> Forgive the bikeshedding but perhaps PAGE_KERNEL_EXEC_RO is more
>> consistent?
>>
>
> powerpc was using PAGE_KERNEL_ROX so I went with that. Blame powerpc ;)
>

OK, in that case, let's keep PAGE_KERNEL_ROX

>>>
>>>  From Ard:
>>>
>>> "PAGE_KERNEL_EXEC has PTE_WRITE set as well, making the range
>>> writeable under the ARMv8.1 DBM feature, that manages the
>>> dirty bit in hardware (writing to a page with the PTE_RDONLY
>>> and PTE_WRITE bits both set will clear the PTE_RDONLY bit in that case)"
>>>
>>> Signed-off-by: Laura Abbott <labbott@...oraproject.org>
>>
>>
>> Acked-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
>>
>
> Thanks,
> Laura
>
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