[PATCH natty] UBUNTU: SAUCE: nx-emu: further clarify dmesg reporting

[Tim Gardner]

On 03/30/2011 04:06 PM, Kees Cook wrote:
> When booting a 32bit non-PAE kernel on a CPU that supports hardware NX,
> dmesg did not indicate that NX emulation was being used. This changes
> the dmesg reporting to be more clear. Warnings about lacking hardware
> NX remain, and the state of NX-emulation is reported when enabled.
>
> BugLink: https://launchpad.net/bugs/745181
>
> Signed-off-by: Kees Cook<kees.cook at canonical.com>
> ---
>   arch/x86/mm/setup_nx.c |   28 +++++++++++++++++-----------
>   1 files changed, 17 insertions(+), 11 deletions(-)
>
> diff --git a/arch/x86/mm/setup_nx.c b/arch/x86/mm/setup_nx.c
> index 4323de4..90c9eff 100644
> --- a/arch/x86/mm/setup_nx.c
> +++ b/arch/x86/mm/setup_nx.c
> @@ -40,19 +40,12 @@ void __cpuinit x86_configure_nx(void)
>
>   void __init x86_report_nx(void)
>   {
> +	int nx_emulation = 0;
> +
>   	if (!cpu_has_nx) {
> -#ifdef CONFIG_X86_32
> -		if (!disable_nx)
> -			printk(KERN_INFO "NX (Execute Disable) protection: "
> -			       "approximated by x86 segment limits\n");
> -		else
> -			printk(KERN_INFO "NX (Execute Disable) protection: "
> -			       "approximation disabled by kernel command "
> -			       "line option\n");
> -#else
>   		printk(KERN_NOTICE "Notice: NX (Execute Disable) protection "
>   		       "missing in CPU!\n");
> -#endif
> +		nx_emulation = 1;
>   	} else {
>   #if defined(CONFIG_X86_64) || defined(CONFIG_X86_PAE)
>   		if (disable_nx) {
> @@ -65,7 +58,20 @@ void __init x86_report_nx(void)
>   #else
>   		/* 32bit non-PAE kernel, NX cannot be used */
>   		printk(KERN_NOTICE "Notice: NX (Execute Disable) protection "
> -		       "cannot be enabled: non-PAE kernel!\n");
> +		       "cannot be enabled in hardware: non-PAE kernel!\n");
> +		nx_emulation = 1;
> +#endif
> +	}
> +
> +	if (nx_emulation) {
> +#ifdef CONFIG_X86_32
> +		if (!disable_nx)
> +			printk(KERN_INFO "NX (Execute Disable) protection: "
> +			       "approximated by x86 segment limits\n");
> +		else
> +			printk(KERN_INFO "NX (Execute Disable) protection: "
> +			       "approximation disabled by kernel command "
> +			       "line option\n");
>   #endif
>   	}
>   }

Possible strings before patch:

Notice: NX (Execute Disable) protection missing in CPU!
NX (Execute Disable) protection: disabled by kernel command line option
NX (Execute Disable) protection: active
Notice: NX (Execute Disable) protection cannot be enabled: non-PAE kernel!

Possible strings after patch:

Notice: NX (Execute Disable) protection missing in CPU!
NX (Execute Disable) protection: disabled by kernel command line option
NX (Execute Disable) protection: active
Notice: NX (Execute Disable) protection cannot be enabled in hardware: 
non-PAE kernel!
NX (Execute Disable) protection: approximated by x86 segment limits
NX (Execute Disable) protection: approximation disabled by kernel 
command line option

This is simple enough stuff. I assume this patch is in the merge window 
pipeline? 'Cause its churny enough that it'll be a pain to resolve if it 
doesn't make it upstream intact.

applied to Natty

rtg
-- 
Tim Gardner tim.gardner at canonical.com