Re: Unnecessary overhead with stack protector.

[Ingo Molnar]

(Cc:-ed Arjan too.)

* Dave Jones <davej@xxxxxxxxxx> 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
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