From: "H. Peter Anvin" <hpa@zytor.com>
To: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>,
Rusty Russell <rusty@rustcorp.com.au>, Andi Kleen <ak@suse.de>,
Chris Wright <chrisw@sous-sol.org>,
Zachary Amsden <zach@vmware.com>,
Andrew Morton <akpm@linux-foundation.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
lkml - Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [RFC PATCH 3/3] boot bzImages under paravirt
Date: Fri, 04 May 2007 09:43:31 -0700 [thread overview]
Message-ID: <463B62B3.1030408@zytor.com> (raw)
In-Reply-To: <463B5B90.20308@goop.org>
Jeremy Fitzhardinge wrote:
> H. Peter Anvin wrote:
>> In 32-bit mode? Surely you're joking, Mr. Feynman!
>>
>
> Right, yes.
>
>> What's worse, reloading segments here might be highly unsafe, if the
>> memory previously occupied by the GDT has been overwritten. Keep in
>> mind the GDT is touched on a segment *load*, not on a segment *access*;
>> in areas such as booting that can be a huge difference.
>>
>
> Yep, suits me. I'm happy for the code to assume that at least %cs and
> %ds are sane; I guess %ss too. We could copy %ds into %[efg]s if we
> want to be sure (since I could imagine a bootloader leaving them in a
> less defined state).
No, we shouldn't. %es should be assumed set up (this is 32-bit code,
after all!), and %fs and %gs should not be used.
> But if the gdt could be missing altogether, then, yes, we should not
> touch them at all.
Exactly. Not relying on a set-up GDT is the safest option, IMNSHO.
-hpa
next prev parent reply other threads:[~2007-05-04 16:44 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-05-04 12:59 [RFC PATCH 1/3] Replace paravirt_probe with "platform type" boot header field Rusty Russell
2007-05-04 13:02 ` [RFC PATCH 2/3] lguest: Boot with virtual == physical to get closer to native Linux Rusty Russell
2007-05-04 13:07 ` [RFC PATCH 3/3] boot bzImages under paravirt Rusty Russell
2007-05-04 14:38 ` Eric W. Biederman
2007-05-04 14:55 ` Rusty Russell
2007-05-04 15:49 ` H. Peter Anvin
2007-05-04 15:15 ` Jeremy Fitzhardinge
2007-05-04 15:45 ` H. Peter Anvin
2007-05-04 16:13 ` Jeremy Fitzhardinge
2007-05-04 16:43 ` H. Peter Anvin [this message]
2007-05-04 16:57 ` Eric W. Biederman
2007-05-04 17:07 ` H. Peter Anvin
2007-05-04 17:30 ` Eric W. Biederman
2007-05-04 18:22 ` Jeremy Fitzhardinge
2007-05-04 18:48 ` Eric W. Biederman
2007-05-04 18:55 ` Jeremy Fitzhardinge
2007-05-04 19:21 ` Eric W. Biederman
2007-05-04 16:46 ` Eric W. Biederman
2007-05-04 17:25 ` Jeremy Fitzhardinge
2007-05-04 17:27 ` H. Peter Anvin
2007-05-04 17:36 ` Eric W. Biederman
2007-05-04 17:44 ` H. Peter Anvin
2007-05-04 18:25 ` Jeremy Fitzhardinge
2007-05-04 14:01 ` [RFC PATCH 1/3] Replace paravirt_probe with "platform type" boot header field Eric W. Biederman
2007-05-04 14:18 ` Rusty Russell
2007-05-04 14:23 ` Eric W. Biederman
2007-05-04 15:52 ` H. Peter Anvin
2007-05-04 16:48 ` Eric W. Biederman
2007-05-04 17:13 ` H. Peter Anvin
2007-05-04 18:30 ` Eric W. Biederman
2007-05-04 18:55 ` H. Peter Anvin
2007-05-04 19:10 ` Eric W. Biederman
2007-05-04 19:14 ` H. Peter Anvin
2007-05-04 19:31 ` Eric W. Biederman
2007-05-04 19:19 ` H. Peter Anvin
2007-05-04 15:10 ` Eric W. Biederman
2007-05-04 15:53 ` H. Peter Anvin
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