Subject: Re: [PATCH v2 11/11] powerpc/8xx: Add support for TASK_SIZE greater than 0x80000000

From: Scott Wood <[email-masked]>
Date: Fri, 20 Mar 2015 19:47:09 -0500

On Tue, 2015-01-20 at 10:57 +0100, Christophe Leroy wrote:
> By default, TASK_SIZE is set to 0x80000000 for PPC_8xx, which is most likely
> sufficient for most cases. However, kernel configuration allows to set TASK_SIZE
> to another value, so the 8xx shall handle it.
> 
> Signed-off-by: Christophe Leroy <[email-masked]>
> 
> ---
> v2: no change
> 
>  arch/powerpc/kernel/head_8xx.S | 25 +++++++++++++++++++------
>  1 file changed, 19 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/head_8xx.S b/arch/powerpc/kernel/head_8xx.S
> index ead6448..92a6456 100644
> --- a/arch/powerpc/kernel/head_8xx.S
> +++ b/arch/powerpc/kernel/head_8xx.S
> @@ -48,6 +48,19 @@
>  	mtspr	spr, reg
>  #endif
>  
> +/* Macro to test if an address is a kernel address */
> +#if CONFIG_TASK_SIZE <= 0x80000000
> +#define IS_KERNEL(tmp, addr)		\
> +	andis.	tmp, addr, 0x8000	/* Address >= 0x80000000 */
> +#define BRANCH_UNLESS_KERNEL(label)	beq	label
> +#else

This works if CONFIG_TASK_SIZE == 0x80000000, but what if it's less, and
you have a kernel address < 0x80000000?

-Scott