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

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Message-Id: <20141113.091709.520211949477822929.d.hatayama@jp.fujitsu.com>
Date:	Thu, 13 Nov 2014 09:17:09 +0900 (JST)
From:	HATAYAMA Daisuke <d.hatayama@...fujitsu.com>
To:	vgoyal@...hat.com
Cc:	ebiederm@...ssion.com, linux-kernel@...r.kernel.org,
	kexec@...ts.infradead.org, kumagai-atsushi@....nes.nec.co.jp,
	anderson@...hat.com
Subject: Re: [PATCH] kdump, x86: report actual value of phys_base in
 VMCOREINFO

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.

Thanks.
HATAYAMA, Daisuke

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