Subject: Re: powerpc: Fix _ALIGN_* errors due to type difference.

From: "Aneesh Kumar K.V" <[email-masked]>
Date: Wed, 07 Oct 2015 14:16:38 +0530

Michael Ellerman <[email-masked]> writes:

> On Fri, 2015-02-10 at 14:33:48 UTC, "Aneesh Kumar K.V" wrote:
>> This avoid errors like
>> 
>>         unsigned int usize = 1 << 30;
>>         int size = 1 << 30;
>>         unsigned long addr = 64UL << 30 ;
>> 
>>         value = _ALIGN_DOWN(addr, usize); -> 0
>>         value = _ALIGN_DOWN(addr, size);  -> 0x1000000000
>
> Are you actually seeing that anywhere? I assume not.

I hit that in new development. So not in the current kernel.

>
>> diff --git a/arch/powerpc/boot/page.h b/arch/powerpc/boot/page.h
>> index 14eca30fef64..87c42d7d283d 100644
>> --- a/arch/powerpc/boot/page.h
>> +++ b/arch/powerpc/boot/page.h
>> @@ -22,8 +22,8 @@
>>  #define PAGE_MASK	(~(PAGE_SIZE-1))
>>  
>>  /* align addr on a size boundary - adjust address up/down if needed */
>> -#define _ALIGN_UP(addr,size)	(((addr)+((size)-1))&(~((size)-1)))
>> -#define _ALIGN_DOWN(addr,size)	((addr)&(~((size)-1)))
>> +#define _ALIGN_UP(addr, size)	(((addr)+((size)-1))&(~((typeof(addr))(size)-1)))
>> +#define _ALIGN_DOWN(addr, size)	((addr)&(~((typeof(addr))(size)-1)))
>>  
>>  /* align addr on a size boundary - adjust address up if needed */
>>  #define _ALIGN(addr,size)     _ALIGN_UP(addr,size)
>> diff --git a/arch/powerpc/include/asm/page.h b/arch/powerpc/include/asm/page.h
>> index 71294a6e976e..1dd69774a31c 100644
>> --- a/arch/powerpc/include/asm/page.h
>> +++ b/arch/powerpc/include/asm/page.h
>> @@ -240,8 +240,8 @@ extern long long virt_phys_offset;
>>  #endif
>>  
>>  /* align addr on a size boundary - adjust address up/down if needed */
>> -#define _ALIGN_UP(addr,size)	(((addr)+((size)-1))&(~((size)-1)))
>> -#define _ALIGN_DOWN(addr,size)	((addr)&(~((size)-1)))
>> +#define _ALIGN_UP(addr, size)	(((addr)+((size)-1))&(~((typeof(addr))(size)-1)))
>> +#define _ALIGN_DOWN(addr, size)	((addr)&(~((typeof(addr))(size)-1)))
>
>
> It looks like ALIGN() in kernel.h already does this right, so can we just use
> that instead for _ALIGN_UP() at least.
>

But we still can't get rid of _ALIGN_UP, because that is used in other
parts of the kernel and if you are suggesting use

#define _ALIGN_UP __ALIGN_KERNEL, IMHO that is unnecessary indirection
for no real benefit.

-aneesh