linux-kernel - Re: [PATCH] powerpc: Default to enabling STRICT_KERNEL

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Date:   Thu, 5 Oct 2017 20:57:24 +0200
From:   christophe leroy <christophe.leroy@....fr>
To:     Kees Cook <keescook@...omium.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Paul Mackerras <paulus@...ba.org>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>
Subject: Re: [PATCH] powerpc: Default to enabling STRICT_KERNEL_RWX



Le 05/10/2017 à 19:30, Kees Cook a écrit :
> On Thu, Oct 5, 2017 at 12:49 AM, Christophe LEROY
> <christophe.leroy@....fr> wrote:
>>
>>
>> Le 05/10/2017 à 05:45, Kees Cook a écrit :
>>>
>>> When available, CONFIG_KERNEL_RWX should be default-enabled.
>>
>>
>> On PPC32, this option implies deactivating BATs and/or LTLB mapping of the
>> linear kernel address space, hence a significant performance degradation.
>>
>> So at least on PPC32, it should remain unselected by default.
> 
> Alright, sounds fine to me. Would this be okay?
> 
> +       select ARCH_OPTIONAL_KERNEL_RWX_DEFAULT if !PPC64

You mean

select ARCH_OPTIONAL_KERNEL_RWX_DEFAULT if PPC64

Don't you ?

Christophe

> 
> -Kees
> 
>>
>> Christophe
>>
>>
>>>
>>> Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
>>> Cc: Paul Mackerras <paulus@...ba.org>
>>> Cc: Michael Ellerman <mpe@...erman.id.au>
>>> Cc: linuxppc-dev@...ts.ozlabs.org
>>> Signed-off-by: Kees Cook <keescook@...omium.org>
>>> ---
>>>    arch/powerpc/Kconfig | 1 +
>>>    1 file changed, 1 insertion(+)
>>>
>>> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
>>> index 809c468edab1..9a549bbfc278 100644
>>> --- a/arch/powerpc/Kconfig
>>> +++ b/arch/powerpc/Kconfig
>>> @@ -178,6 +178,7 @@ config PPC
>>>          select HAVE_ARCH_TRACEHOOK
>>>          select ARCH_HAS_STRICT_KERNEL_RWX       if ((PPC_BOOK3S_64 ||
>>> PPC32) && !RELOCATABLE && !HIBERNATION)
>>>          select ARCH_OPTIONAL_KERNEL_RWX         if
>>> ARCH_HAS_STRICT_KERNEL_RWX
>>> +       select ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
>>>          select HAVE_CBPF_JIT                    if !PPC64
>>>          select HAVE_CONTEXT_TRACKING            if PPC64
>>>          select HAVE_DEBUG_KMEMLEAK
>>>
>>
> 
> 
> 

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