linux-kernel - Re: [PATCH] [PATCH] x86: Don't clobber top of pt

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Date:	Fri, 02 Nov 2012 09:53:49 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Jan Beulich <jbeulich@...e.com>
Cc:	sqazi@...gle.com, peterz@...radead.org, tglx@...utronix.de,
	torvalds@...ux-foundation.org, hpa@...ux.intel.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] [PATCH] x86: Don't clobber top of pt_regs in nested NMI

On Fri, 2012-11-02 at 09:51 -0400, Steven Rostedt wrote:
> On Thu, 2012-11-01 at 19:53 +0000, Jan Beulich wrote:
> 
> > There doesn't appear to be anything special about these adjustments, so I
> > don't see what help would be required here - it ought to be the normal use
> > of CFI_ADJUST_CFA_OFFSET that needs adding.
> 
> This change look fine to you?
> 
> diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
> index 52edf92..7ba5342 100644
> --- a/arch/x86/kernel/entry_64.S
> +++ b/arch/x86/kernel/entry_64.S
> @@ -1796,10 +1796,12 @@ repeat_nmi:
>  
>  	/* Make another copy, this one may be modified by nested NMIs */
>  	addq $(10*8), %rsp
> +	CFI_ADJUST_CFA_OFFSET -10*8
>  	.rept 5
>  	pushq_cfi -6*8(%rsp)
>  	.endr
>  	subq $(5*8), %rsp
> +	CFI_ADJUST_CFA_OFFSET 5*8
>  
>  	CFI_DEF_CFA_OFFSET SS+8-RIP
>  end_repeat_nmi:
> 

Is that second one even needed? Or will the CFI_DEF_CFA_OFFSET SS+8-RIP
fix it?

-- Steve


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