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

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Message-ID: <alpine.LFD.0.999.0711051035090.15101@woody.linux-foundation.org>
Date:	Mon, 5 Nov 2007 10:36:50 -0800 (PST)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	"H. Peter Anvin" <hpa@...or.com>
cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Mikael Petterson <mikpe@...uu.se>,
	Eric Biederman <ebiederm@...ssion.com>,
	Jeremy Fitzhardinge <jeremy@...p.org>
Subject: Re: [GIT PULL] x86 setup: correct booting on 486 (revised)



On Mon, 5 Nov 2007, H. Peter Anvin wrote:
> 
> Well, the 32-bit code needs to set up its own stack, and only it knows where
> it wants its stack; we don't guarantee that the stack is valid when we enter
> the 32-bit code and we're entering with both INT and NMI disabled (requiring a
> stack would probably break all existing users of the 32-bit entrypoint.)

I agree. But it would be nice if some basic instructions still worked: as 
is, you cannot even do things like reloading %eflags, because the only way 
to do that requires a stack.

> However, that being said, doing so is trivial, and it might help some
> debugging hack; anything that makes debugging easier is a Good Thing[TM].

Yeah. Even if it was just re-using the boot-time stack area temporarily, 
just to give code the choice to use a common set of instructions.

			Linus
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