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

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Message-ID: <20160302162530.GA8362@pd.tnic>
Date:	Wed, 2 Mar 2016 17:25:30 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	Brian Gerst <brgerst@...il.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 11:22:30AM -0500, Brian Gerst wrote:
> This should be: movq stack_start(%rip), %rsp

No it wouldn't. That doesn't work.

> > +       subq    $__START_KERNEL_map, %rsp
> 
> It would be better to add the offset to the initializer for
> stack_start instead of adjusting it at runtime.  That would require
> moving the existing load of stack_start from the common path to the
> secondary startup,

This is the BSP we're talking about - no secondary startup. We want to run
verify_cpu as early as possible.

-- 
Regards/Gruss,
    Boris.

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