linux-kernel - Re: [PATCH v6 2/8] vmcore: allocate buffer for ELF headers on page-size alignment

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Date:	Fri, 17 May 2013 09:08:08 +0900
From:	HATAYAMA Daisuke <d.hatayama@...fujitsu.com>
To:	Vivek Goyal <vgoyal@...hat.com>
CC:	ebiederm@...ssion.com, akpm@...ux-foundation.org, cpw@....com,
	kumagai-atsushi@....nes.nec.co.jp, lisa.mitchell@...com,
	kexec@...ts.infradead.org, linux-kernel@...r.kernel.org,
	zhangyanfei@...fujitsu.com, jingbai.ma@...com, linux-mm@...ck.org,
	riel@...hat.com, walken@...gle.com, hughd@...gle.com,
	kosaki.motohiro@...fujitsu.com
Subject: Re: [PATCH v6 2/8] vmcore: allocate buffer for ELF headers on page-size
 alignment

(2013/05/17 1:51), Vivek Goyal wrote:
> On Wed, May 15, 2013 at 06:05:51PM +0900, HATAYAMA Daisuke wrote:
>
> [..]
>> @@ -398,9 +403,7 @@ static int __init process_ptload_program_headers_elf64(char *elfptr,
>>   	phdr_ptr = (Elf64_Phdr*)(elfptr + sizeof(Elf64_Ehdr)); /* PT_NOTE hdr */
>>
>>   	/* First program header is PT_NOTE header. */
>> -	vmcore_off = sizeof(Elf64_Ehdr) +
>> -			(ehdr_ptr->e_phnum) * sizeof(Elf64_Phdr) +
>> -			phdr_ptr->p_memsz; /* Note sections */
>> +	vmcore_off = elfsz + roundup(phdr_ptr->p_memsz, PAGE_SIZE);
>>
>>   	for (i = 0; i < ehdr_ptr->e_phnum; i++, phdr_ptr++) {
>>   		if (phdr_ptr->p_type != PT_LOAD)
>> @@ -435,9 +438,7 @@ static int __init process_ptload_program_headers_elf32(char *elfptr,
>>   	phdr_ptr = (Elf32_Phdr*)(elfptr + sizeof(Elf32_Ehdr)); /* PT_NOTE hdr */
>>
>>   	/* First program header is PT_NOTE header. */
>> -	vmcore_off = sizeof(Elf32_Ehdr) +
>> -			(ehdr_ptr->e_phnum) * sizeof(Elf32_Phdr) +
>> -			phdr_ptr->p_memsz; /* Note sections */
>> +	vmcore_off = elfsz + roundup(phdr_ptr->p_memsz, PAGE_SIZE);
>
> Hmm.., so we are rounding up ELF note data size too here. I think this belongs
> in some other patch as in this patch we are just rounding up the elf
> headers.
>
> This might create read problems too as we have not taking care of this
> rounding when adding note to vc_list and it might happen that we are
> reading wrong data at a particular offset.
>
> So may be this rounding up we should do in later patches when we take
> care of copying ELF notes data to second kernel.
>
> Vivek
>

This is my careless fault. They should have been in 6/7.

-- 
Thanks.
HATAYAMA, Daisuke

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