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Message-ID: <20090228071534.GB9351@elte.hu>
Date:	Sat, 28 Feb 2009 08:15:34 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
Cc:	Yinghai Lu <yinghai@...nel.org>, "H. Peter Anvin" <hpa@...or.com>,
	the arch/x86 maintainers <x86@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
Subject: Re: J


* Jeremy Fitzhardinge <jeremy@...p.org> wrote:

> Yinghai Lu wrote:
>> On Fri, Feb 27, 2009 at 5:51 PM, Jeremy Fitzhardinge <jeremy@...p.org> wrote:
>>   
>>> From: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
>>>
>>> Rather than having special purpose init_pg_table_start/end variables
>>> to delimit the kernel pagetable built by head_32.S, just use the brk
>>> mechanism to extend the bss for the new pagetable.
>>>
>>> This patch removes init_pg_table_start/end and pg0, defines __brk_base
>>> (which is page-aligned and immediately follows _end), initializes
>>> the brk region to start there, and uses it for the 32-bit pagetable.
>>>     
>> ...
>>
>>   
>>> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
>>> index c246dc4..ed02176 100644
>>> --- a/arch/x86/kernel/setup.c
>>> +++ b/arch/x86/kernel/setup.c
>>> @@ -113,8 +113,10 @@
>>>  #endif
>>>
>>>  unsigned int boot_cpu_id __read_mostly;
>>> -__initdata unsigned long _brk_start = (unsigned long)&_end;
>>> -__initdata unsigned long _brk_end = (unsigned long)&_end;
>>> +
>>> +extern char __brk_base[];
>>> +__initdata unsigned long _brk_start = (unsigned long)__brk_base;
>>> +__initdata unsigned long _brk_end = (unsigned long)&__brk_base;
>>>     
>>
>> ?
>>   
>
> What are you asking?  __brk_base is _end rounded up to a page 
> boundary, so head_32.S can use it directly for pagetable 
> allocation.  Are you flagging the '&' typo?  Something else?

it's not really a typo either (__brk_base and &__brk_base should 
be the same) - just a bit weird looking.

	Ingo
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