linux-kernel - Re: [PATCHv4] arm: Preserve the user r/w register TPIDRURW on context switch and fork

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Message-ID: <519A1C64.3020807@dawncrow.de>
Date:	Mon, 20 May 2013 14:51:48 +0200
From:	André Hentschel <nerv@...ncrow.de>
To:	Jonathan Austin <jonathan.austin@....com>
CC:	"linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	Will Deacon <Will.Deacon@....com>
Subject: Re: [PATCHv4] arm: Preserve the user r/w register TPIDRURW on context
 switch and fork

Am 20.05.2013 13:03, schrieb Jonathan Austin:
> Hi André
> 
> On 18/05/13 16:02, André Hentschel wrote:
>> Am 08.05.2013 21:03, schrieb André Hentschel:
>>> From: =?UTF-8?q?Andr=C3=A9=20Hentschel?= <nerv@...ncrow.de>
>>>
> 
> This is strangely formatted for me too, and I use a different client from Will so I'm not sure that the problem is just at our end...
> 
> (Also see that the list archive has weird formatting:
> http://lists.infradead.org/pipermail/linux-arm-kernel/2013-May/167325.html )
> 
> Your first couple of patches didn't come out strangely formatted, so I'm not really sure what's going on.

I'll retry it with plain Text or something. AFAIK git should understand this =UTF= style, though.

>>> Since commit 6a1c53124aa1 the user writeable TLS register was zeroed to
>>> prevent it from being used as a covert channel between two tasks.
>>>
>>> There are more and more applications coming to WinRT, Wine could support them,
>>> but mostly they expect to have the thread environment block (TEB) in TPIDRURW.
>>>
>>> This patch preserves that register per thread instead of clearing it.
>>> Unlike the TPIDRURO, which is already switched, the TPIDRURW
>>> can be updated from userspace so needs careful treatment in the case that we
>>> modify TPIDRURW and call fork(). To avoid this we must always read
>>> TPIDRURW in copy_thread.
>>>
>>> Signed-off-by: André Hentschel <nerv@...ncrow.de>
>>> Signed-off-by: Will Deacon <will.deacon@....com>
>>> Signed-off-by: Jonathan Austin <jonathan.austin@....com>
>>>
>>
>> Hi,
>> I'm not yet very familiar with the development process here,
>> am i getting no feedback on v4 because of the mergewindow being closed?
>> Or is there another reason? Sry for being impatient.
>>
> 
> This is a feature, not a fix, so most likely it'll be included at the next merge window. For that to happen it should be in Russell's tree around the middle of this cycle.
> 
> Can you please rebase on 3.10-rc2 (when it happens) and post one more version? After that, assuming nobody else has any final comments, you could put it in to Russell's patch system...
> 
> Just as a hint - one thing you might have done to increase the chances of getting comments to clarify what's different between v3 and v4 - as a way to make life easier for reviewers you can highlight the differences between versions after the "---" (where you currently have the description of why there are so many S-o-Bs).

I'll do, thank you very much for the reply and the clarification.

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