[Karmic] SRU-fix: Fix nx_enable reporting

[Andy Whitcroft]

On Tue, Nov 10, 2009 at 01:43:27PM +0100, Stefan Bader wrote:
> As described in the patch, we got a regression in proposed which was
> caused by a SRU update. Though fixing the message fir 64bit it caused
> 32bit non-PAE suddenly to believe it had nx protection. Which then
> caused sleep problems (for the computer, not the programmer :)).
> I guess after being involved in testing, I should get two other ACKs
> for it and then respin, proposed. Thanks.
> 
> -Stefan

> From cf0516662862b64f42ae167d50894d1152d27743 Mon Sep 17 00:00:00 2001
> From: Kees Cook <kees.cook at canonical.com>
> Date: Mon, 9 Nov 2009 13:58:54 -0800
> Subject: [PATCH] UBUNTU: SAUCE: Fix nx_enable reporting
> 
> BugLink: https://bugs.launchpad.net/bugs/454285
> Submitted upstream.
> 
> This fixes a regression caused by
> 
> commit 8bf095f8b62c5fdfe55a8c95be775ea62be7bc10
> Author: Kees Cook <kees at ubuntu.com>
> Date:   Sun Oct 18 09:16:44 2009 -0700
>     UBUNTU: SAUCE: [x86] fix report of cs-limit nx-emulation
> 
> The _PAGE_NX is 0 when compiled for 32bit without PAE, so the previous
> attempt to fix the misleading message on 64bit caused 32bit non-PAE to
> break (discovered by having problems on suspend/resume).
> 
> Signed-off-by: Kees Cook <kees.cook at canonical.com>
> Tested-by: Stefan Bader <stefan.bader at canonical.com>
> ---
>  arch/x86/mm/init.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
> index 817fa01..6654c44 100644
> --- a/arch/x86/mm/init.c
> +++ b/arch/x86/mm/init.c
> @@ -77,7 +77,7 @@ static void __init set_nx(void)
>  #else
>  static inline void set_nx(void)
>  {
> -	nx_enabled = ( (__supported_pte_mask & _PAGE_NX) == _PAGE_NX );
> +	nx_enabled = _PAGE_NX && ((__supported_pte_mask & _PAGE_NX) == _PAGE_NX);
>  }
>  #endif

The issue was that _PAGE_NX went to 0 when on i386 non-pae.  Such that
the expression became true inadvertantly:

  __support_pte_mask & 0 == 0

The change looks appropriate to fix that.

Acked-by: Andy Whitcroft <apw at canonical.com>

-apw