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

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Date:   Tue, 17 Jan 2017 10:25:29 +0000
From:   Marc Zyngier <marc.zyngier@....com>
To:     Matt Redfearn <matt.redfearn@...tec.com>,
        Arvind Yadav <arvind.yadav.cs@...il.com>, tglx@...utronix.de,
        jason@...edaemon.net
Cc:     linux-kernel@...r.kernel.org,
        Linux MIPS Mailing List <linux-mips@...ux-mips.org>
Subject: Re: [PATCH v1] irqchip: irq-mips-gic:- Handle return NULL error from
 ioremap_nocache

On 17/01/17 10:17, Matt Redfearn wrote:
> 
> 
> 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@...tec.com>
> 
> 
>>
>> 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@...il.com>
>>>> ---
>>>>   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.

Fair enough, that's your call. I'll pick that up as is.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...