linux-kernel - Re: [PATCH v2] use -fstack-protector-strong

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Message-ID: <CAGXu5j+0gjN118RijCinw31g51BZez_oGKFYJwq2T3=yojG_ww@mail.gmail.com>
Date:	Mon, 16 Dec 2013 16:57:08 -0800
From:	Kees Cook <keescook@...omium.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Ingo Molnar <mingo@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Nicolas Pitre <nicolas.pitre@...aro.org>,
	Ingo Molnar <mingo@...hat.com>,
	Russell King <linux@....linux.org.uk>,
	Thomas Gleixner <tglx@...utronix.de>,
	"x86@...nel.org" <x86@...nel.org>,
	Shawn Guo <shawn.guo@...aro.org>,
	Olof Johansson <olofj@...omium.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v2] use -fstack-protector-strong

On Wed, Nov 27, 2013 at 10:11 AM, Kees Cook <keescook@...omium.org> wrote:
> On Wed, Nov 27, 2013 at 9:55 AM, H. Peter Anvin <hpa@...or.com> wrote:
>> On 11/27/2013 09:54 AM, Ingo Molnar wrote:
>>>>
>>>> Looks to be 2% for defconfig. That's way better. Shall I send a v3?
>>>
>>> Well, it's better than 9%, but still almost an order of magnitude
>>> higher than the cost is today, and a lot of distros have
>>> CONFIG_CC_STACKPROTECTOR=y.
>>>
>>> So it would be nice to measure how much the instruction count goes up
>>> in some realistic system-bound test. How much does something like
>>> kernel/built-in.o increase, as per 'size' output?
>
>    text    data     bss     dec     hex filename
>  929611   90851  594496 1614958  18a46e built-in.o-gcc-4.9
>  954648   90851  594496 1639995  19063b built-in.o-gcc-4.9+strong
>
> Looks like 3% for defconfg + CONFIG_CC_STACKPROTECTOR
>
>>
>> Do we need CONFIG_CC_STACKPROTECTOR_STRONG?
>
> I'm hoping to avoid this since nearly anyone using CC_STACKPROTECTOR
> would want strong added, but as a fallback, I'm happy to implement it
> as a separate config item.

Any verdict on this? Should I go with adding ..._STRONG like we used
to have for ..._ALL, or is defaulting to -strong best?

-Kees

-- 
Kees Cook
Chrome OS Security
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