From: "H. Peter Anvin" <hpa@zytor.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Ingo Molnar <mingo@elte.hu>,
linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
Peter Zijlstra <a.p.zijlstra@chello.nl>
Subject: Re: [PATCH][GIT PULL][v3.3] x86: Test saved %rip in NMI to determine nested NMI
Date: Sun, 19 Feb 2012 12:45:09 -0800 [thread overview]
Message-ID: <4F415F55.6050902@zytor.com> (raw)
In-Reply-To: <1329683679.1561.20.camel@acer.local.home>
On 02/19/2012 12:34 PM, Steven Rostedt wrote:
> On Sun, 2012-02-19 at 05:46 -0800, hpanvin@gmail.com wrote:
>> Vsyscall page, not vdso...
>
> Peter,
>
> My original patch was to check the %cs register against __KERNEL_CS, but
> IIRC, you said that userspace can change that register to anything it
> wanted before doing a long jump or something. Is this true for x86_64 as
> well? I guess it would be because x86_64 can support 32bit apps.
>
> Anyway, I'll add a check that makes sure that the RIP is less than the
> FIXADDR sections as well.
>
User space can change %cs, but it can never set it to __KERNEL_CS;
specifically user space can never set the bottom two bits in CS to zero.
So this should be a better test.
(Now, doing the test that way plays havoc with the braindamage knows as
Xen paravirt, but I don't think it's subject to this particular NMI code.)
-hpa
next prev parent reply other threads:[~2012-02-19 20:45 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-02-19 2:06 [PATCH][GIT PULL][v3.3] x86: Test saved %rip in NMI to determine nested NMI Steven Rostedt
2012-02-19 12:56 ` Ingo Molnar
2012-02-19 13:46 ` hpanvin@gmail.com
2012-02-19 13:48 ` Ingo Molnar
2012-02-19 20:34 ` Steven Rostedt
2012-02-19 20:45 ` H. Peter Anvin [this message]
2012-02-19 21:00 ` Steven Rostedt
2012-02-19 14:57 ` Steven Rostedt
2012-02-20 8:10 ` Ingo Molnar
2012-02-20 14:41 ` Steven Rostedt
2012-02-20 15:34 ` Ingo Molnar
2012-02-20 17:07 ` H. Peter Anvin
2012-02-19 21:43 ` [PATCH v2][GIT PULL][v3.3] x86: Test saved %cs " Steven Rostedt
2012-02-20 11:47 ` [tip:x86/urgent] x86/nmi: Test saved %cs in NMI to determine nested NMI case tip-bot for Steven Rostedt
2012-02-20 16:51 ` Steven Rostedt
2012-02-27 21:29 ` Greg KH
2012-02-20 18:03 ` Linus Torvalds
2012-02-20 18:26 ` Steven Rostedt
2012-02-21 22:08 ` [tip:x86/urgent] x86: Specify a size for the cmp in the NMI handler tip-bot for Steven Rostedt
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