linux-kernel - Re: [Xen-devel] kasan_map_early

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Date:	Wed, 04 Mar 2015 17:36:17 +0300
From:	Andrey Ryabinin <a.ryabinin@...sung.com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Cc:	"Luis R. Rodriguez" <mcgrof@...e.com>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	Rusty Russell <rusty@...tcorp.com.au>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Andy Lutomirski <luto@...capital.net>,
	Chris Wright <chrisw@...s-sol.org>,
	xen-devel@...ts.xenproject.org,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	virtualization@...ts.linux-foundation.org,
	Alok Kataria <akataria@...are.com>
Subject: Re: [Xen-devel] kasan_map_early_shadow() on Xen

On 03/03/2015 07:02 PM, Konrad Rzeszutek Wilk wrote:
> On Tue, Mar 03, 2015 at 06:38:20PM +0300, Andrey Ryabinin wrote:
>> On 03/03/2015 05:16 PM, Konrad Rzeszutek Wilk wrote:
>>> On Tue, Mar 03, 2015 at 04:15:06PM +0300, Andrey Ryabinin wrote:
>>>> On 03/03/2015 12:40 PM, Luis R. Rodriguez wrote:
>>>>> Andrey,
>>>>>
>>>>> I believe that on Xen we should disable kasan, would like confirmation
>>>>
>>>> I guess Xen guests won't work with kasan because Xen guests doesn't setup shadow
>>>> (kasan_map_early_shadow() is not called in xen guests).
>>>>
>>>> Disabling kasan for Xen in Kconfig is undesirable because that will disable kasan
>>>> for allmodconfig and allyesconfig builds, but I don't see other option for now.
>>>
>>> Was there an bug reported for this? It would be good to CC the maintainers
>>> of Xen on that sort of thing.
>>>
>>
>> There was no report for this. I just looked at Xen code because of this Luis's mail
>> and I don't see how it could work with kasan.
> 
> Ahh.
>> Fixing this might be not trivial. We need to setup shadow memory before any kasan instrumented
>> function will run.
>> This is like with -fstack-protector (you need to setup gdt before calling any stack protected function).
> 
> If it is like that - then just using what had to be implemented
> for the stack protection as a template ought to pave most of the
> work?
> 

Probably. I think I could make this work.
However, I won't be able to work on this until the end of the next week.
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