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

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Message-ID: <EF3739D4-766E-4189-91B2-1D8F7AAA1E43@zytor.com>
Date:	Wed, 02 Mar 2016 10:25:24 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Borislav Petkov <bp@...en8.de>
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 March 2, 2016 10:15:56 AM PST, Borislav Petkov <bp@...en8.de> wrote:
>On Wed, Mar 02, 2016 at 09:53:28AM -0800, H. Peter Anvin wrote:
>> Please explain why we can't use rip-relative addressing in some
>form...
>
>We *can* do almost what Brian suggested:
>
>        movq    stack_start(%rip), %rsp
>        subq    $__START_KERNEL_map, %rsp
>
>But we still have to subtract __START_KERNEL_map.

Obviously.
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