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Message-Id: <5092D31C020000780008EB6B@nat28.tlf.novell.com>
Date: Thu, 01 Nov 2012 19:53:00 +0000
From: "Jan Beulich" <jbeulich@...e.com>
To: <rostedt@...dmis.org>, <sqazi@...gle.com>
Cc: <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
>>> Steven Rostedt <rostedt@...dmis.org> 11/01/12 2:04 AM >>>
>On Mon, 2012-10-01 at 17:29 -0700, Salman Qazi wrote:
>> @@ -1826,12 +1832,15 @@ repeat_nmi:
>> * is benign for the non-repeat case, where 1 was pushed just above
>> * to this very stack slot).
>> */
>> - movq $1, 5*8(%rsp)
>> + movq $1, 10*8(%rsp)
>>
>> /* Make another copy, this one may be modified by nested NMIs */
>> + addq $(10*8), %rsp
>
>This breaks the CFI magic.
>
>> .rept 5
>> - pushq_cfi 4*8(%rsp)
>> + pushq_cfi -6*8(%rsp)
>> .endr
>> + subq $(5*8), %rsp
>
>So does this.
>
>This needs to be annotated correctly before I can push it out. But the
>good news is, I stressed tested this change, and it all works out.
>
>Jan, can you help out here?
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.
Jan
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