[PATCH 1/4] powerpc/prom: avoid endian conversions for linux, memory-limit node

[Hari Bathini]

On Friday 04 August 2017 09:21 AM, Michael Ellerman wrote:
> Hari Bathini <hbathini at linux.vnet.ibm.com> writes:
>
>> As linux,memory-limit node is set and also later used by the kernel,
>> avoid endian conversions for this property.
>>
>> Fixes: 493adffcb43f ("powerpc: Make prom_init.c endian safe")
>> Cc: stable at vger.kernel.org # 3.12+
>> Cc: Anton Blanchard <anton at ozlabs.org>
>> Cc: Benjamin Herrenschmidt <benh at kernel.crashing.org>
>> Signed-off-by: Hari Bathini <hbathini at linux.vnet.ibm.com>
>> ---
>>   arch/powerpc/kernel/prom_init.c |    3 +--
>>   1 file changed, 1 insertion(+), 2 deletions(-)
> As Ben said, this is not OK. The flat device tree is a data
> structure with a specified format[1], we don't violate the spec just to
> avoid an endian swap.
>
> Is there an actual bug you're trying to solve?

Yep. While retrieving this property in prom.c, no endian conversion is 
being done.
It was broken for a while. Let me do the endian swap in prom.c while 
retrieving..

Thanks
Hari

> [1]: https://www.devicetree.org/
>
>> diff --git a/arch/powerpc/kernel/prom_init.c b/arch/powerpc/kernel/prom_init.c
>> index 613f79f..723df83 100644
>> --- a/arch/powerpc/kernel/prom_init.c
>> +++ b/arch/powerpc/kernel/prom_init.c
>> @@ -3180,9 +3180,8 @@ unsigned long __init prom_init(unsigned long r3, unsigned long r4,
>>   	 * Fill in some infos for use by the kernel later on
>>   	 */
>>   	if (prom_memory_limit) {
>> -		__be64 val = cpu_to_be64(prom_memory_limit);
>>   		prom_setprop(prom.chosen, "/chosen", "linux,memory-limit",
>> -			     &val, sizeof(val));
>> +			     &prom_memory_limit, sizeof(prom_memory_limit));
>>   	}
>>   #ifdef CONFIG_PPC64
>>   	if (prom_iommu_off)