linux-kernel - Re: perf_fuzzer compiled for x32 causes reboot

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Message-ID: <20140227183008.6be081b7@gandalf.local.home>
Date:	Thu, 27 Feb 2014 18:30:08 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Vince Weaver <vincent.weaver@...ne.edu>,
	Peter Zijlstra <peterz@...radead.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...hat.com>
Subject: Re: perf_fuzzer compiled for x32 causes reboot

On Thu, 27 Feb 2014 14:52:54 -0800
"H. Peter Anvin" <hpa@...or.com> wrote:

> On 02/27/2014 02:31 PM, Steven Rostedt wrote:
> > 
> > Yeah, something is getting mesed up.
> > 
> 
> What it *looks* like to me is that we try to nest the cr2 save/restore,
> which doesn't nest because it is a percpu variable.
> 
> ... except in the x86-64 case, we *ALSO* save/restore cr2 inside
> entry_64.S, which makes the stuff in do_nmi completely redundant and
> there for no good reason.

Peter, look at the code. That percpu cr2 is in a #ifdef CONFIG_X86_32
section. That is, it isn't even executed. That's i386 code. The only
place the cr2 is saved for x86_64 is in entry_64.S.

-- Steve

> 
> I would actually suggest we do the equivalent on i386 as well.
> 
> Vince, could you try this patch as an experiment?
> 
> 

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