linux-kernel - Re: [PATCH v6 19/27] x86, boot: update comments about entries for 64bit image

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Date:	Thu, 13 Dec 2012 16:38:45 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Yinghai Lu <yinghai@...nel.org>
CC:	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...e.hu>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 19/27] x86, boot: update comments about entries for
 64bit image

On 12/13/2012 04:13 PM, Yinghai Lu wrote:
> On Thu, Dec 13, 2012 at 3:27 PM, H. Peter Anvin <hpa@...or.com> wrote:
>> On 12/13/2012 02:02 PM, Yinghai Lu wrote:
>>> +      * If we come here from a bootloader, kernel(text+data+bss+brk),
>>> +      * ramdisk, zero_page, command line could be above 4G.
>>> +      * We depend on an identity mapped page table being provided
>>> +      * that maps our entire kernel(text+data+bss+brk), and hopefully
>>> +      * all of memory.
>>
>> We should make it explicit what we depend on.  We certainly *can* depend
>> only on text+data+bss+brk ... with the dynamic page table approach we
>> can do that, and that would be most conservative; if we depend on other
>> things we should make that explicit, not just here but in boot.txt.
>
> yes, in my version, only need kernel(text+data+bss+brk) get mapped.
> aka the INIT_SIZE for decompressing.
>

It is definitely the minmum we can rely on, and so is the minimum we 
should rely on.  In fact, we don't even need .bss/.brk to be mapped, but 
we probably should require that as a matter of protocol.

	-hpa

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

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