linux-kernel - Re: [PATCH 2/3] c/r: Add CR

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Message-ID: <49C0A80E.1040603@cs.columbia.edu>
Date:	Wed, 18 Mar 2009 03:51:42 -0400
From:	Oren Laadan <orenl@...columbia.edu>
To:	"Serge E. Hallyn" <serue@...ibm.com>
CC:	Dave Hansen <dave@...ux.vnet.ibm.com>, containers@...ts.osdl.org,
	Dan Smith <danms@...ibm.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] c/r: Add CR_COPY() macro (v3)



Serge E. Hallyn wrote:
> Quoting Dave Hansen (dave@...ux.vnet.ibm.com):
>> On Tue, 2009-03-03 at 16:57 -0800, Dan Smith wrote:
>>> DH> Did you convince Nathan that this ends up being a good idea?
>>>
>>> Technically he hasn't seen this version, but my hopes are not high
>>> that he will change his mind.  If the feedback is that they're not
>>> liked, I'll happily remove them.
>> I just figure if Nathan feels that strongly that we'll encounter more
>> people who feel even more so.  So, I was curious if he changed his mind
>> somehow.
> 
> I maintain however that two strong advantages of moving the checkpoint
> and restart of simple registers etc into a single function are:
> 
> 	1. we won't forget to add (or accidentally lose) one or the
> 		other
> 	2. any actual special handling at checkpoint or restart, like
> 		the loading of access registers at restart on s390x,
> 		stand out
> 

I, too, think that this scheme is elegant, and at the same time I, too,
think that it obfuscates the code. Since I only touch arch-dependent code
only if I really really must, I don't have strong opinion about it ;)

However, a problem with this scheme is that checkpoint and restart
are not fully symmetric -- on restart we must sanitize the input data
before restoring the registers to that data. I'm not familiar with
s390, but it is likely that by not doing so we create a security issue.

Oren.

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