Re: Unnecessary overhead with stack protector.

Andrew Morton
2009-10-26T16:37:33Z

On Mon, 26 Oct 2009 12:30:04 -0400 Chuck Ebbert <cebbert@redhat.com> wrote:

> On Wed, 21 Oct 2009 18:26:36 -0700
> Andrew Morton <akpm@linux-foundation.org> wrote:
>
> > On Thu, 15 Oct 2009 14:35:41 -0400 Dave Jones <davej@redhat.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?

oh, so someone _did_ read my email!

git show --pretty=fuller 113c5413cf9051cc50b88befdc42e3402bb92115

commit 113c5413cf9051cc50b88befdc42e3402bb92115
Author: Ingo Molnar <mingo@elte.hu>
AuthorDate: Thu Feb 14 10:36:03 2008 +0100
Commit: Thomas Gleixner <tglx@linutronix.de>
CommitDate: Mon May 26 16:15:32 2008 +0200

I think the CommitDate is when it hit mainline.