linux-kernel - Re: [PATCH v2 07/20] vmcore: copy non page-size aligned head and tail pages in 2nd kernel

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Message-Id: <20130311.092719.142837234.d.hatayama@jp.fujitsu.com>
Date:	Mon, 11 Mar 2013 09:27:19 +0900 (JST)
From:	HATAYAMA Daisuke <d.hatayama@...fujitsu.com>
To:	zhangyanfei@...fujitsu.com
Cc:	vgoyal@...hat.com, ebiederm@...ssion.com, 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
Subject: Re: [PATCH v2 07/20] vmcore: copy non page-size aligned head and
 tail pages in 2nd kernel

From: Zhang Yanfei <zhangyanfei@...fujitsu.com>
Subject: Re: [PATCH v2 07/20] vmcore: copy non page-size aligned head and tail pages in 2nd kernel
Date: Sun, 10 Mar 2013 14:16:51 +0800

> 于 2013年03月02日 16:36, HATAYAMA Daisuke 写道:
<cut>
>>  		/* Update the program header offset. */
>>  		phdr_ptr->p_offset = vmcore_off;
>> -		vmcore_off = vmcore_off + phdr_ptr->p_memsz;
>> +		vmcore_off +=roundup(end,PAGE_SIZE)-rounddown(start,PAGE_SIZE);
> 
> Here the code changes phdr_ptr->p_offset to a new page-size aligned offset.
> But it seems the phdr_ptr->p_paddr is still the non page-size aligned
> physical address? Does the mismatch of a PT_LOAD segment and the physical
> memory occur?
> 
> Or, later in makedumpfile, it will check the phdr_ptr->paddr to see if it
> is page-size aligned and also phdr_ptr->p_memsz to get the real memory size,
> not including padding?
> 

No, it doesn't happen. p_offset is made page-size aligned for
requirement to user-space linear-address vs file offset. The
requirement for physical address is handled internally in vmcore_list,
which is transparent to to user-space.

Thanks.
HATAYAMA, Daisuke

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