linux-kernel - Re: [RFC PATCH v2, part4 03/39] c6x: normalize global variables exported by vmlinux.lds

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Date:	Tue, 26 Mar 2013 23:23:13 +0800
From:	Jiang Liu <liuj97@...il.com>
To:	Mark Salter <msalter@...hat.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	David Rientjes <rientjes@...gle.com>,
	Jiang Liu <jiang.liu@...wei.com>,
	Wen Congyang <wency@...fujitsu.com>,
	Mel Gorman <mgorman@...e.de>, Minchan Kim <minchan@...nel.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Michal Hocko <mhocko@...e.cz>,
	Jianguo Wu <wujianguo@...wei.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Aurelien Jacquiot <a-jacquiot@...com>,
	linux-c6x-dev@...ux-c6x.org
Subject: Re: [RFC PATCH v2, part4 03/39] c6x: normalize global variables exported
 by vmlinux.lds

On 03/26/2013 01:56 AM, Mark Salter wrote:
> On Sun, 2013-03-24 at 15:24 +0800, Jiang Liu wrote:
>> Normalize global variables exported by vmlinux.lds to conform usage
>> guidelines from include/asm-generic/sections.h.
>>
>> Use _text to mark the start of the kernel image including the head text,
>> and _stext to mark the start of the .text section.
>>
>> This patch also fixes possible bugs due to current address layout that
>> [__init_begin, __init_end] is a sub-range of [_stext, _etext] and pages
>> within range [__init_begin, __init_end] will be freed by free_initmem().
> 
> I won't have time to look at this in detail until later this week, but
> the reason for that layout is because c6x commonly stores text in flash.
> Not all of the xip support is in-tree yet, but when it is, we don't want
> to free init text.
Hi Mark,
	Thanks for reminder. It's possible to support the usage case you
have described, please take a look at arch/tile/kernel/vmlinux.lds.S.
By that way, we could only free init.data sections without freeing init.text
sections.
	Regards!
	Gerry

> 
> --Mark
> 
>>
>> Signed-off-by: Jiang Liu <jiang.liu@...wei.com>
>> Cc: Mark Salter <msalter@...hat.com>
>> Cc: Aurelien Jacquiot <a-jacquiot@...com>
>> Cc: linux-c6x-dev@...ux-c6x.org
>> Cc: linux-kernel@...r.kernel.org
>> ---
>>  arch/c6x/kernel/vmlinux.lds.S |    4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/c6x/kernel/vmlinux.lds.S b/arch/c6x/kernel/vmlinux.lds.S
>> index 1d81c4c..279d807 100644
>> --- a/arch/c6x/kernel/vmlinux.lds.S
>> +++ b/arch/c6x/kernel/vmlinux.lds.S
>> @@ -54,16 +54,15 @@ SECTIONS
>>  	}
>>  
>>  	. = ALIGN(PAGE_SIZE);
>> +	__init_begin = .;
>>  	.init :
>>  	{
>> -		_stext = .;
>>  		_sinittext = .;
>>  		HEAD_TEXT
>>  		INIT_TEXT
>>  		_einittext = .;
>>  	}
>>  
>> -	__init_begin = _stext;
>>  	INIT_DATA_SECTION(16)
>>  
>>  	PERCPU_SECTION(128)
>> @@ -74,6 +73,7 @@ SECTIONS
>>  	.text :
>>  	{
>>  		_text = .;
>> +		_stext = .;
>>  		TEXT_TEXT
>>  		SCHED_TEXT
>>  		LOCK_TEXT
> 
> 

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