From: Jeremy Fitzhardinge <jeremy@goop.org>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: mingo@redhat.com, linux-kernel@vger.kernel.org,
jeremy.fitzhardinge@citrix.com, stable@kernel.org,
tglx@linutronix.de, mingo@elte.hu,
linux-tip-commits@vger.kernel.org, Tejun Heo <tj@kernel.org>
Subject: Re: [tip:x86/asm] x86/i386: Make sure stack-protector segment base is cache aligned
Date: Thu, 03 Sep 2009 14:28:27 -0700 [thread overview]
Message-ID: <4AA034FB.1030400@goop.org> (raw)
In-Reply-To: <4AA031DE.2070109@zytor.com>
On 09/03/09 14:15, H. Peter Anvin 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.
>
I'm assuming that stack-protector has fairly serious performance impact
anyway, so a bit of extra entry/exit cost is acceptable. But I agree
that there's no point in making it gratuitously bad.
J
next prev parent reply other threads:[~2009-09-03 21:28 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-09-03 19:27 [PATCH] x86/i386: make sure stack-protector segment base is cache aligned Jeremy Fitzhardinge
2009-09-03 19:47 ` Eric Dumazet
2009-09-03 20:41 ` Jeremy Fitzhardinge
2009-09-03 21:07 ` Eric Dumazet
2009-09-03 21:31 ` Jeremy Fitzhardinge
2009-09-04 7:58 ` [tip:x86/asm] x86/i386: Put aligned stack-canary in percpu shared_aligned section tip-bot for Jeremy Fitzhardinge
2009-09-03 20:03 ` [tip:x86/asm] x86/i386: Make sure stack-protector segment base is cache aligned tip-bot for Jeremy Fitzhardinge
2009-09-03 20:26 ` H. Peter Anvin
2009-09-03 20:45 ` Jeremy Fitzhardinge
2009-09-03 21:15 ` H. Peter Anvin
2009-09-03 21:18 ` Ingo Molnar
2009-09-03 21:21 ` H. Peter Anvin
2009-09-04 14:15 ` Arjan van de Ven
2009-09-04 15:59 ` Jeremy Fitzhardinge
2009-09-04 16:06 ` H. Peter Anvin
2009-09-03 21:28 ` Jeremy Fitzhardinge [this message]
2009-09-04 2:51 ` Tejun Heo
2009-09-04 2:59 ` Tejun Heo
2009-09-04 3:35 ` H. Peter Anvin
2009-09-04 3:47 ` Tejun Heo
2009-09-04 3:51 ` H. Peter Anvin
2009-09-04 5:06 ` Tejun Heo
2009-09-04 5:12 ` Ingo Molnar
2009-09-04 16:04 ` Jeremy Fitzhardinge
2009-09-04 16:09 ` Tejun Heo
2009-09-04 16:13 ` H. Peter Anvin
2009-09-04 16:01 ` Jeremy Fitzhardinge
2009-09-04 16:52 ` H. Peter Anvin
2009-09-04 16:57 ` Jeremy Fitzhardinge
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