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Message-ID: <45339BEF.6020206@innova-card.com>
Date:	Mon, 16 Oct 2006 16:49:19 +0200
Reply-To: Franck <vagabon.xyz@gmail.com>
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To:	Franck <vagabon.xyz@gmail.com>
CC:	Thiemo Seufer <ths@networkno.de>,
	Atsushi Nemoto <anemo@mba.ocn.ne.jp>, ralf@linux-mips.org,
	linux-mips@linux-mips.org
Subject: Re: [PATCH 6/7] setup.c: clean up initrd related code
References: <11607431461469-git-send-email-fbuihuu@gmail.com> <1160743146503-git-send-email-fbuihuu@gmail.com> <45333CC1.3090704@innova-card.com> <20061016090923.GB25607@networkno.de> <453395CB.4040106@innova-card.com>
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From:	Franck Bui-Huu <vagabon.xyz@gmail.com>
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Franck Bui-Huu wrote:
> Thiemo Seufer wrote:
>> Franck Bui-Huu wrote:
>>> Atsushi,
>>>
>>> Franck Bui-Huu wrote:
>>>> Signed-off-by: Franck Bui-Huu <fbuihuu@gmail.com>
>>>> ---
>>> [snip]
>>>> @@ -176,24 +174,34 @@ static unsigned long __init init_initrd(
>>> [snip]
>>>>  	end = (unsigned long)&_end;
>>>>  	tmp = PAGE_ALIGN(end) - sizeof(u32) * 2;
>>>>  	if (tmp < end)
>>>>  		tmp += PAGE_SIZE;
>>>>  
>>> Any idea on what is this code for ?
>>> It seems that a minimum gap is needed betweend the end of kernel
>>> code and initrd but I don't see why...
>> AFAIR the bootmem map is placed there.
>>
> 
> boot_mem_map[] seems to be located in bss.
> 

ok I think I got it...

Actually sizeof(u32) * 2 is the place reserved for the initrd header
and this header is right before initrd itself.

	initrd_header[0] -> magic number
	initrd_header[1] -> size of initrd
		initrd start
		    ...
		initrd end

and initrd start must be PAGE_SIZE aligned, surely because we free it
with a page granularity.

		Franck