Re: [PATCH v1] irqchip: irq-mips-gic:- Handle return NULL error from ioremap_nocache

[Matt Redfearn]

On 17/01/17 10:10, Arvind Yadav wrote:
> Hi Matt,
>
> Please Acknowledge this.
>
> Regards
> Arvind Yadav

Hi Arvind,

Acked-by: Matt Redfearn <matt.redfearn@xxxxxxxxxx>


> On Monday 09 January 2017 02:30 PM, Marc Zyngier wrote:
> > On 09/01/17 08:08, Arvind Yadav wrote:
> > > Here, If ioremap_nocache will fail. It will return NULL.
> > > Kernel can run into a NULL-pointer dereference.
> > > This error check will avoid NULL pointer dereference.
> > >
> > > Signed-off-by: Arvind Yadav <arvind.yadav.cs@xxxxxxxxx>
> > > ---
> > >   drivers/irqchip/irq-mips-gic.c | 2 ++
> > >   1 file changed, 2 insertions(+)
> > >
> > > diff --git a/drivers/irqchip/irq-mips-gic.c 
> > > b/drivers/irqchip/irq-mips-gic.c
> > > index c01c09e..eeea2e8 100644
> > > --- a/drivers/irqchip/irq-mips-gic.c
> > > +++ b/drivers/irqchip/irq-mips-gic.c
> > > @@ -979,6 +979,8 @@ static void __init __gic_init(unsigned long 
> > > gic_base_addr,
> > >       __gic_base_addr = gic_base_addr;
> > >         gic_base = ioremap_nocache(gic_base_addr, gic_addrspace_size);
> > > +    if (!gic_base)
> > > +        panic("Failed to map GIC memory");
> > So you're replacing a panic due to dereferencing a NULL pointer with
> > another panic -- not much progress here. I appreciate that the message
> > is a bit more explicit, but is there something slightly less drastic we
> > could do? Like returning an error code and see if the kernel otherwise
> > recovers (possibly with reduced functionality)?

Marc, there's really not much that can be done without the GIC 
initializing sucessfully. This should not happen if platform code / 
device tree is set up correctly, so an explicit panic if that is not the 
case is helpful.

Thanks,
Matt

> > >         gicconfig = gic_read(GIC_REG(SHARED, GIC_SH_CONFIG));
> > >       gic_shared_intrs = (gicconfig & GIC_SH_CONFIG_NUMINTRS_MSK) >>
> > Thanks,
> >
> >     M.