linux-kernel - Re: [PATCH] kdump, x86: report actual value of phys

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Message-ID: <20141113090657.2578f087@hananiah.suse.cz>
Date:	Thu, 13 Nov 2014 09:06:57 +0100
From:	Petr Tesarik <ptesarik@...e.cz>
To:	HATAYAMA Daisuke <d.hatayama@...fujitsu.com>
Cc:	vgoyal@...hat.com, kumagai-atsushi@....nes.nec.co.jp,
	anderson@...hat.com, kexec@...ts.infradead.org,
	ebiederm@...ssion.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kdump, x86: report actual value of phys_base in
 VMCOREINFO

On Thu, 13 Nov 2014 09:17:09 +0900 (JST)
HATAYAMA Daisuke <d.hatayama@...fujitsu.com> wrote:

> From: Vivek Goyal <vgoyal@...hat.com>
> Subject: Re: [PATCH] kdump, x86: report actual value of phys_base in VMCOREINFO
> Date: Wed, 12 Nov 2014 17:12:05 -0500
> 
> > On Wed, Nov 12, 2014 at 03:40:42PM +0900, HATAYAMA Daisuke wrote:
> >> Currently, VMCOREINFO note information reports the virtual address of
> >> phys_base that is assigned to symbol phys_base. But this doesn't make
> >> sense because to refer to value of the phys_base, it's necessary to
> >> get the value of phys_base itself we are now about to refer to.
> >> 
> > 
> > Hi Hatayama,
> > 
> > /proc/vmcore ELF headers have virtual address information and using
> > that you should be able to read actual value of phys_base. gdb deals
> > with virtual addresses all the time and can read value of any symbol
> > using those headers.
> > 
> > So I am not sure what's the need for exporting actual value of
> > phys_base.
> > 
> 
> Sorry, my logic in the patch description was wrong. For /proc/vmcore,
> there's enough information for makedumpdile to get phys_base. It's
> correct. The problem here is that other crash dump mechanisms that run
> outside Linux kernel independently don't have information to get
> phys_base.

Yes, but these mechanisms won't be able to read VMCOREINFO either, will
they?

Petr T
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