2014-07-08 22:31:13

by stuart hayes

Subject: [PATCH] x86: Allow kernel_map_pages_in_pgd() to work when NX is disabled

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 <[email protected]>
---
--- 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;
-
- 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);

2014-07-22 16:35:07

by Borislav Petkov

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 <[email protected]>
> ---
> --- 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.
--