linux-kernel - Re: kexec: Clearing registers just before jumping into purgatory

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Message-ID: <52582B97.2060907@nod.at>
Date:	Fri, 11 Oct 2013 18:47:19 +0200
From:	Richard Weinberger <richard@....at>
To:	Matthew Garrett <mjg59@...f.ucam.org>
CC:	Richard Weinberger <richard.weinberger@...il.com>,
	Vivek Goyal <vgoyal@...hat.com>,
	Daniel Kiper <daniel.kiper@...cle.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>, hbabu@...ibm.com,
	"H. Peter Anvin" <hpa@...ux.intel.com>,
	Kees Cook <keescook@...omium.org>, kexec@...ts.infradead.org,
	LKML <linux-kernel@...r.kernel.org>, david.vrabel@...rix.com,
	jbeulich@...e.com, keir@....org, xen-devel@...ts.xen.org
Subject: Re: kexec: Clearing registers just before jumping into purgatory

Am 11.10.2013 18:44, schrieb Matthew Garrett:
> On Fri, Oct 11, 2013 at 06:42:36PM +0200, Richard Weinberger wrote:
>> On Fri, Oct 11, 2013 at 6:39 PM, Matthew Garrett <mjg59@...f.ucam.org> wrote:
>>> On Fri, Oct 11, 2013 at 06:33:23PM +0200, Richard Weinberger wrote:
>>>> On Fri, Oct 11, 2013 at 5:48 PM, Matthew Garrett <mjg59@...f.ucam.org> wrote:
>>>>> On Fri, Oct 11, 2013 at 11:44:50AM -0400, Vivek Goyal wrote:
>>>>>
>>>>>> Just Curious. How is it useful. IOW, what's your use case of booting a new
>>>>>> kernel and then jumping back.
>>>>>
>>>>> I'm kexecing into a kernel with a modified /dev/mem, modifying the
>>>>> original kernel and then jumping back into it.
>>>>
>>>> How do you update the original kernel?
>>>
>>> It's still in RAM, so the same way you'd modify any other arbitrary
>>> physical address?
>>
>> So, you have a tool like ksplice which patches the kernel in RAM?
> 
> I have /dev/mem and a list of addresses I want to modify.

But you still need a magic tool which create you this list.
If you have a tool which takes two kernel images and create such
a delta, fine.
I'm interested in that tool. :-)

Thanks,
//richard

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