Re: [PATCH] m68knommu: switch to using asm-generic/uaccess.h

Greg Ungerer
2020-09-09T07:58:16Z

On 9/9/20 4:56 pm, Christoph Hellwig wrote:
> On Wed, Sep 09, 2020 at 12:18:31PM +1000, Greg Ungerer wrote:
>> Switch to using the asm-generic/uaccess functions for non-MMU builds.
>> Remove all the m68knommu local specific uaccess defines and macros.
>>
>> There is nothing so special about the m68knommu targets that they cannot
>> use all of the asm-generic uaccess support. Using the asm-generic
>> uaccess definitions also resolves some of the existing problems with
>> missing __user annotations in the m68knommu specific functions.
>>
>> The elimination of all of the contents of uaccess_no.h means we can fold
>> the uaccess_mm.h back into uaccess.h - and just have the single file
>> now.
>>
>> The resulting generated code ends up being slightly smaller (by a few
>> hundred bytes) due to the compilers ability to better optimize load
>> and stores without forcing its hand with asm statements.
>>
>> Specifically trivial cases like this contrived example:
>>
>> get_user(x, ptr);
>> x++;
>> put_user(x, ptr);
>>
>> end up now being optimized to a single instruction on m68k. More
>> generally the compiler can avoid using a temporary register in many
>> cases as well.
>
> This looks great!
>
> Reviewed-by: Christoph Hellwig <hch@lst.de>

Thanks Christoph.
I'll push this into the for-next branch of the m68knommu git tree.

Regards
Greg