From: Andi Kleen <ak@suse.de>
To: Bart Hartgers <bart@etpmod.phys.tue.nl>
Subject: Re: Segfault on the i386 enter instruction
Date: Mon, 15 May 2006 13:46:21 +0200
User-Agent: KMail/1.9.1
Cc: Tomasz Malesinski <tmal@mimuw.edu.pl>, linux-kernel@vger.kernel.org
References: <20060512131654.GB2994@duch.mimuw.edu.pl> <20060512153139.GA4852@duch.mimuw.edu.pl> <446867C4.3070108@etpmod.phys.tue.nl>
In-Reply-To: <446867C4.3070108@etpmod.phys.tue.nl>
MIME-Version: 1.0
Content-Disposition: inline
Message-Id: <200605151346.21877.ak@suse.de>
Content-Type: text/plain;
  charset="iso-8859-1"
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 870
Lines: 21


> http://groups.google.co.nz/groups?selm=7i86ni%24b7n%241%40palladium.transmeta.com

Linus' reasoning is actually outdated - on most modern x86s it is not
slower than the expanded code sequence because it will generate the
same number of macro/u-ops. But it would be still extremly ugly to 
implement, which is a good reason not to.

> And perhaps x86-64 is handled different because of the red zone (some
> memory below the stack-pointer that can be accessed legally)?

Yes, but it's only 128 bytes so it won't help for larger frames.
It will also work if you preextended the stack before, but i wouldn't
rely on it.

-Andi
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/