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

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Message-ID: <CAGXu5j+6_M65pDoJjx1NEUw8SkfpGjH=yhswt-RW=_W97=kkzQ@mail.gmail.com>
Date:	Wed, 27 Nov 2013 10:11:28 -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 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.

-Kees

-- 
Kees Cook
Chrome OS Security
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