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

From: Ingo Molnar
Date: Thu Sep 03 2009 - 17:18:49 EST

* H. Peter Anvin <hpa@xxxxxxxxx> 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.

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