linux-kernel - Re: [PATCH RFC] x86: add brk allocation for very, very early allocations

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Message-ID: <49A83C52.5050801@zytor.com>
Date:	Fri, 27 Feb 2009 11:17:38 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
CC:	Yinghai Lu <yinghai@...nel.org>, Ingo Molnar <mingo@...e.hu>,
	the arch/x86 maintainers <x86@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RFC] x86: add brk allocation for very, very early allocations

Jeremy Fitzhardinge wrote:
> 
> unsigned int boot_cpu_id __read_mostly;
> +__initdata unsigned long _brk_start, _brk_end;
> 

Better yet, initialize _brk_start and _brk_end statically:

extern const char _end[];
__initdata unsigned long _brk_start = (unsigned long)&_end;
__initdata unsigned long _brk_end   = (unsigned long)&_end;

That way it's available from the first instruction, and we can fully
remove the x86-32 init_pg_tables_end and replace it with _brk_end (thus
putting the initial page tables in the brk.)

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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