linux-kernel - Re: [Xen-devel] [PATCH 2/5] xen/x86-64: clean up warnings aboutIST-usingtraps

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Date:	Fri, 08 May 2009 16:30:39 +0100
From:	"Jan Beulich" <jbeulich@...ell.com>
To:	"Jeremy Fitzhardinge" <jeremy@...p.org>
Cc:	"Ingo Molnar" <mingo@...e.hu>,
	"the arch/x86 maintainers" <x86@...nel.org>,
	"Linus Torvalds" <torvalds@...ux-foundation.org>,
	"Xen-devel" <xen-devel@...ts.xensource.com>,
	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>
Subject: Re: [Xen-devel] [PATCH 2/5] xen/x86-64: clean up warnings	
	 aboutIST-usingtraps

>>> Jeremy Fitzhardinge <jeremy@...p.org> 08.05.09 17:23 >>>
>Jan Beulich wrote:
>>> else if (addr == (unsigned long)int3)
>>> 		addr = (unsigned long)xen_int3;
>>> -	else
>>> -		WARN_ON(val->ist != 0);
>>> +	else if (addr == (unsigned long)double_fault ||
>>> +		 addr == (unsigned long)stack_segment) {
>>>     
>>
>> I don't think you want to exclude handling stack faults: Ordinary memory
>> references using rsp or rbp as the base register will cause these instead
>> of general protection faults when the resulting effective address is non-
>> canonical.
>>   
>
>So even usermode memory accesses?  Ew.

Yes, just try it out - you'll observe them generate SIGBUS instead of SIGSEGV.

Jan

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