linux-kernel - Re: [PATCH v3 01/21] vmcore: reference e_phoff member explicitly to get position of program header table

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Message-Id: <20130321.115041.225288996.d.hatayama@jp.fujitsu.com>
Date:	Thu, 21 Mar 2013 11:50:41 +0900 (JST)
From:	HATAYAMA Daisuke <d.hatayama@...fujitsu.com>
To:	ebiederm@...ssion.com, vgoyal@...hat.com
Cc:	cpw@....com, kumagai-atsushi@....nes.nec.co.jp,
	lisa.mitchell@...com, heiko.carstens@...ibm.com,
	akpm@...ux-foundation.org, kexec@...ts.infradead.org,
	linux-kernel@...r.kernel.org, zhangyanfei@...fujitsu.com
Subject: Re: [PATCH v3 01/21] vmcore: reference e_phoff member explicitly
 to get position of program header table

From: "Eric W. Biederman" <ebiederm@...ssion.com>
Subject: Re: [PATCH v3 01/21] vmcore: reference e_phoff member explicitly to get position of program header table
Date: Tue, 19 Mar 2013 14:44:16 -0700

> HATAYAMA Daisuke <d.hatayama@...fujitsu.com> writes:
> 
>> Currently, the code assumes that position of program header table is
>> next to ELF header. But future change can break the assumption on
>> kexec-tools and the 1st kernel. To avoid worst case, reference e_phoff
>> member explicitly to get position of program header table in
>> file-offset.
> 
> In principle this looks good.  However when I read this it looks like
> you are going a little too far.
> 
> You are changing not only the reading of the supplied headers, but
> you are changing the generation of the new new headers that describe
> the data provided by /proc/vmcore.
> 
> I get lost in following this after you mangle merge_note_headers.
> 
> In principle removing silly assumptions seems reasonable, but I think
> it is completely orthogonal to the task of maping vmcore mmapable.
> 
> I think it is fine to claim that the assumptions made here in vmcore are
> part of the kexec on panic ABI at this point, which would generally make
> this change unnecessary.

This was suggested by Vivek. He prefers generic one.

Vivek, do you agree to this? Or is it better to re-post this and other
clean-up patches as another one separately to this patch set?

Thanks.
HATAYAMA, Daisuke

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