Re: [tip:x86/asm] x86/i386: Make sure stack-protector segment base is cache aligned

Ingo Molnar
2009-09-03T21:18:42Z

* H. Peter Anvin <hpa@zytor.com> wrote:

> On 09/03/2009 01:45 PM, Jeremy Fitzhardinge wrote:
> >
> > Two problems:
> >
> > * gcc generates %gs: references for stack-protector, but we use %fs
> > for percpu data (because restoring %fs is faster if it's a null
> > selector; TLS uses %gs). I guess we could use %fs if
> > !CONFIG_CC_STACKPROTECTOR, or %gs if we are using it (though that
> > has some fiddly ramifications for things like ptrace).
>
> Well, by touching two segments we're getting the worst of both
> worlds, so at least assuming some significant number of real-world
> deployments use CC_STACKPROTECTOR, we really don't want to
> pessimize that case too much.

Fedora has stackprotector enabled so it's used in a widespread way.

Ingo