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

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Message-ID: <20160302224047.GN8362@pd.tnic>
Date:	Wed, 2 Mar 2016 23:40:47 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Brian Gerst <brgerst@...il.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 02:32:54PM -0800, H. Peter Anvin wrote:
> I'm trying to think of any reason why we couldn't simply have a symbol
> at the top of the initial stack? Then a simple leaq would suffice;
> this is for the BSP after all.

That should be simpler. And we do games like that already in the trampoline:

        # Setup stack
        movl    $rm_stack_end, %esp

...

GLOBAL(rm_stack)
        .space  2048
GLOBAL(rm_stack_end)

-- 
Regards/Gruss,
    Boris.

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