linux-kernel - Re: [GIT PULL] x86 setup: correct booting on 486 (revised)

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Message-ID: <m1zlxr5mik.fsf@ebiederm.dsl.xmission.com>
Date:	Tue, 06 Nov 2007 10:09:23 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Jeremy Fitzhardinge <jeremy@...p.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Mikael Petterson <mikpe@...uu.se>
Subject: Re: [GIT PULL] x86 setup: correct booting on 486 (revised)

"H. Peter Anvin" <hpa@...or.com> writes:

> Jeremy Fitzhardinge wrote:
>> H. Peter Anvin wrote:
>>> .notes : {
>>>     *(.note.*)
>>>     . = ALIGN(4);
>>>     LONG(0);
>>>     LONG(0);
>>>     LONG(0);
>>> }
>>>
>>> Am I missing something?
>>
>> Oh, I suppose, but I never much liked putting data-definition into the
>> linker script.
>>
>
> I think it should be sparsely used, but stuff like simple end markers is pretty
> much what it's good for.
>
> The main reason I want to avoid adding another header field is that the header
> is a finite resource; one of the many poor decisions in its original design was
> using a 2-byte jump at the top, so address 0x281 is the end of the universe.

That was fixed long ago (by having a 4 byte reserved field in the middle) that
we can do a two byte jump and then do a farther jump from there to the 16bit
code.  So as long as we actually use discipline and really reserve
the field for a further jump there should be no need for 0x281 being the end
of the universe.

Eric
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