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

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Message-ID: <CAFLxGvyDYHy-UbZhdQiGvXL=8t0aW8wABc0GRkwVRy8egKJMKw@mail.gmail.com>
Date:	Fri, 11 Oct 2013 18:42:36 +0200
From:	Richard Weinberger <richard.weinberger@...il.com>
To:	Matthew Garrett <mjg59@...f.ucam.org>
Cc:	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

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?

-- 
Thanks,
//richard
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