From: Jeremy Fitzhardinge <jeremy@goop.org>
To: Avi Kivity <avi@redhat.com>
Cc: Sergio Luis <eeeesti@gmail.com>, Ingo Molnar <mingo@elte.hu>,
"Rafael J. Wysocki" <rjw@sisk.pl>, Pavel Machek <pavel@suse.cz>,
Linux-kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: x86: asm doubt
Date: Mon, 16 Mar 2009 09:20:39 -0700 [thread overview]
Message-ID: <49BE7C57.6060100@goop.org> (raw)
In-Reply-To: <49BE5E4E.1070209@redhat.com>
Avi Kivity wrote:
> Jeremy Fitzhardinge wrote:
>> In 32-bit mode, moving to a segment register can fault if the
>> underlying GDT/LDT entry is invalid. In 64-bit mode, segment
>> registers are mostly decorative and have no function, and moving
>> arbitrary values into them doesn't fault, making the exception
>> catching unnecessary.
>
> 64-bit mode will in fact fault if an access is made outside the
> GDT/LDT, or of the descriptor is invalid.
Oh, I didn't think it bothered. I guess I'm conflating that with the
fact that it doesn't apply any of the segment properties to memory
accesses. Anyway, in that case the 64-bit code should definitely be
using the standard segment accessors.
J
prev parent reply other threads:[~2009-03-16 16:20 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-03-15 14:16 x86: asm doubt Sergio Luis
2009-03-15 16:41 ` Jeremy Fitzhardinge
2009-03-16 13:12 ` Sergio Luis
2009-03-16 14:12 ` Avi Kivity
2009-03-16 16:20 ` Jeremy Fitzhardinge [this message]
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