linux-kernel - Re: [PATCH] x86: Allow kernel_map_pages_in

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Date:	Tue, 22 Jul 2014 18:35:01 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Stuart Hayes <stuart.w.hayes@...il.com>
Cc:	tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
	x86@...nel.org, linux-kernel@...r.kernel.org, bpetkov@...e.com,
	matt.fleming@...el.com
Subject: Re: [PATCH] x86: Allow kernel_map_pages_in_pgd() to work when NX is
 disabled

On Tue, Jul 08, 2014 at 05:31:12PM -0500, Stuart Hayes wrote:
> The function kernel_map_pages_in_pgd() will not map pages if NX is
> disabled, which causes a lot of problems booting in EFI mode
> (efi_map_region() and other functions depend on this).  This patch
> just makes sure that the NX flag doesn't get set in the page tables
> if NX is disabled, rather than not mapping the pages at all.
> 
> Signed-off-by: Stuart Hayes <stuart.w.hayes@...il.com>
> ---
> --- linux-3.16-rc3/arch/x86/mm/pageattr.c.orig	2014-07-02 12:04:49.244288159 -0400
> +++ linux-3.16-rc3/arch/x86/mm/pageattr.c	2014-07-02 12:05:55.808290437 -0400
> @@ -1862,10 +1862,7 @@ int kernel_map_pages_in_pgd(pgd_t *pgd,
>  		.flags = 0,
>  	};
>  
> -	if (!(__supported_pte_mask & _PAGE_NX))
> -		goto out;

arch/x86/mm/pageattr.c: In function ‘kernel_map_pages_in_pgd’:
arch/x86/mm/pageattr.c:1873:1: warning: label ‘out’ defined but not used [-Wunused-label]

> -
> -	if (!(page_flags & _PAGE_NX))
> +	if ((!(__supported_pte_mask & _PAGE_NX)) || !(page_flags & _PAGE_NX))
>  		cpa.mask_clr = __pgprot(_PAGE_NX);
>  
>  	cpa.mask_set = __pgprot(_PAGE_PRESENT | page_flags);
> 
> --
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> 

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
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