linux-kernel - Re: [PATCH v2 11/11] powerpc/8xx: Add support for TASK

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Message-ID: <1426898829.27998.256.camel@freescale.com>
Date:	Fri, 20 Mar 2015 19:47:09 -0500
From:	Scott Wood <scottwood@...escale.com>
To:	Christophe Leroy <christophe.leroy@....fr>
CC:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	<linux-kernel@...r.kernel.org>, <linuxppc-dev@...ts.ozlabs.org>,
	"Joakim Tjernlund" <joakim.tjernlund@...nsmode.se>
Subject: Re: [PATCH v2 11/11] powerpc/8xx: Add support for TASK_SIZE greater
 than 0x80000000

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 <christophe.leroy@....fr>
> 
> ---
> 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


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