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

[leroy christophe]

Le 21/03/2015 01:47, Scott Wood a Ãcrit :
> 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@xxxxxx>
> >
> > ---
> > 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?
You are right, I didn't realise that PAGE_OFFSET was also configurable 
and could be different from 0xC0000000.
andis. (which is what is always used in the current kernel) can be used 
if CONFIG_TASK_SIZE <= 0x80000000 AND PAGE_OFFSET >= 0x80000000.
I will resubmit the patch accordingly.

Christophe

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