Re: Unnecessary overhead with stack protector.

Ingo Molnar
2009-10-15T19:08:19Z

(Cc:-ed Arjan too.)

* 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.

Exactly what workload showed overhead, and how much?

Ingo