linux-kernel - Re: Unnecessary overhead with stack protector.

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Message-ID: <20091026123004.297a0a25@katamari.usersys.redhat.com>
Date:	Mon, 26 Oct 2009 12:30:04 -0400
From:	Chuck Ebbert <cebbert@...hat.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Dave Jones <davej@...hat.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>, esandeen@...hat.com
Subject: Re: Unnecessary overhead with stack protector.

On Wed, 21 Oct 2009 18:26:36 -0700
Andrew Morton <akpm@...ux-foundation.org> wrote:

> On Thu, 15 Oct 2009 14:35:41 -0400 Dave Jones <davej@...hat.com> wrote:
> 
> > 113c5413cf9051cc50b88befdc42e3402bb92115 introduced a change that
> > made CC_STACKPROTECTOR_ALL not-selectable if someone enables CC_STACKPROTECTOR.
> > 
> > We've noticed in Fedora that this has introduced noticable overhead on
> > some functions, including those which don't even have any on-stack variables.
> > 
> > According to the gcc manpage, -fstack-protector will protect functions with
> > as little as 8 bytes of stack usage. So we're introducing a huge amount
> > of overhead, to close a small amount of vulnerability (the >0 && <8 case).
> > 
> > The overhead as it stands right now means this whole option is unusable for
> > a distro kernel without reverting the above commit.
> > 
> 
> This looks like a fairly serious problem to me, but I'm confused by the
> commit ID.  February 2008 - is this correct?
> 

That date is pure fiction AFAICT. And the Mercurial kernel repo says May 2008...
Is there some way to get the date a change was merged into the official tree as
opposed to the date it was created in some other tree?
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