linux-kernel - Re: [RFC PATCH] x86: Make sure verify

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Date:	Wed, 2 Mar 2016 17:15:32 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	Mika Penttilä <mika.penttila@...tfour.com>
Cc:	"H. Peter Anvin" <hpa@...or.com>, X86 ML <x86@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Tom Lendacky <thomas.lendacky@....com>
Subject: Re: [RFC PATCH] x86: Make sure verify_cpu has a good stack

On Wed, Mar 02, 2016 at 05:55:14PM +0200, Mika Penttilä wrote:
> > +	/* Setup a stack for verify_cpu */
> > +	movq    stack_start - __START_KERNEL_map, %rsp
> > +	subq	$__START_KERNEL_map, %rsp
> > +
>
> You subtract __START_KERNEL_map twice ?

Yes. That's not very obvious and it took me a while. I probably should
add a comment.

Want to stare at it a little bit more and try to figure it out or should
I explain?

:-)

-- 
Regards/Gruss,
    Boris.

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