linux-kernel - Re: use of setjmp/longjmp in x86 emulator.

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Message-ID: <4B936C1F.4060504@redhat.com>
Date:	Sun, 07 Mar 2010 11:04:31 +0200
From:	Avi Kivity <avi@...hat.com>
To:	Gleb Natapov <gleb@...hat.com>
CC:	"H. Peter Anvin" <hpa@...or.com>,
	Zachary Amsden <zamsden@...hat.com>,
	linux-kernel@...r.kernel.org, mingo@...e.hu, mtosatti@...hat.com
Subject: Re: use of setjmp/longjmp in x86 emulator.

On 03/02/2010 10:49 AM, Gleb Natapov wrote:
> On Mon, Mar 01, 2010 at 02:56:59PM -0800, H. Peter Anvin wrote:
>    
>> On 03/01/2010 02:31 PM, H. Peter Anvin wrote:
>>      
>>> On 03/01/2010 11:18 AM, Zachary Amsden wrote:
>>>        
>>>> It's going to be ugly to emulate segmentation, NX and write protect
>>>> support without hardware to do this checking for you, but it's just what
>>>> you have to do in this slow path - tedious, fully specified emulation.
>>>>
>>>> Just because it's tedious doesn't mean we need to use setjmp / longjmp.
>>>> Throw / catch might be effective, but it's still pretty bizarre to do
>>>> tricks like that in C.
>>>>
>>>>          
>>> Well, setjmp/longjmp really is not much more than exception handling in C.
>>>
>>>        
>> For what it's worth, I think that setjmp/longjmp is not anywhere near as
>> dangerous as people want to make it out to be.  gcc will warn for
>> dangerous uses (and a lot of non-dangerous uses), but generally the
>> difficult problems can be dealt with by moving the setjmp-protected code
>> into a separate function.
>>
>>      
> Can I consider this as ACK for something like the patch blow? :) (with
> proper x86 version of setjmp/longjmp of course).
>    

The setjmp/longjmp implementation should definitely live in arch/*/lib, 
even if kvm is the only user.

-- 
error compiling committee.c: too many arguments to function

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