Re: [PATCH] m68k: Use generic strncpy_from_user(), strlen_user(), and strnlen_user()

Greg Ungerer
2012-06-07T11:12:51Z

Hi Geert,

On 06/07/2012 03:46 AM, Geert Uytterhoeven wrote:
> On Wed, Jun 6, 2012 at 8:31 AM, Greg Ungerer<gerg@snapgear.com> wrote:
>> Yes, looks like that should have a "|| defined(CONFIG_CPU32)".
>> (According to the CPU32 reference manual words and long words must
>> be aligned on word boundaries.)
>>
>> I think something like CONFIG_CPU_HAS_NO_UNALIGNED makes sense.
>
> OK, doing that now...
>
> Then I saw arch/m68k/lib/memcpy.c.
>
> commit f230e80b423f6cb002015ab4771c06a53d5a2287
> ("m68k: fix memcpy to unmatched/unaligned source and dest on 68000")
>
> | The original 68000 processors cannot copy 16bit or larger quantities from
> | odd addresses. All newer members of the 68k family (including ColdFire)
> | can do this.
>
> So all Coldfires can do unaligned _reads_, but not unaligned _writes_
> (exceptions below)?

This strikes me as odd. Maybe this has been wrong all along. I need
to check further but in a little testing I did today I think it may
well be that all ColdFire support unaligned reads and writes.

>>>> I also think that the Coldfire 5272 can do unaligned accesses, but I
>>>> cannot test that at the moment.
>>
>>
>> According to the MCF5272 User Manual, "it supports misaligned data
>> accesses ...". So it looks like it does.
>>
>> Having a CONFIG_CPU_HAS_NO_UNALIGNED looks like a really good solution
>> then. We need to be able select it as required on individual CPU types.
>
> For now, I just make COLDFIRE select it, but we can move it to the individual
> CPU types later.

No matter what I find I still think this is the way to go.

Thanks
Greg

------------------------------------------------------------------------
Greg Ungerer -- Principal Engineer EMAIL: gerg@snapgear.com
SnapGear Group, McAfee PHONE: +61 7 3435 2888
8 Gardner Close, FAX: +61 7 3891 3630
Milton, QLD, 4064, Australia WEB: http://www.SnapGear.com