Re: [PATCH RFC] m68k: Handle __generic_copy_to_user faults more carefully

Michael Schmitz
2024-04-17T08:08:20Z

Hi Geert,

Am 17.04.2024 um 18:59 schrieb Geert Uytterhoeven:
> Hi Michael,
>
> On Tue, Apr 16, 2024 at 10:36 PM Michael Schmitz <schmitzmic@gmail.com> wrote:
>> I have tested this fault scenario with a transfer beginning
>> at a single byte at the end of a mapped page only, which IMO
>> does violate m68k alignment rules. I cannot remember ever
>> seeing such faults reported from conforming software before.
>
> 68020+ does support unaligned data accesses, so IMHO such transfers
> are valid. For compatibility with 68000/68008/68010/68012, data is
> recommended to be 2-byte aligned.
> Instructions must always be aligned to 2 bytes, though.

Thanks - won't test this with two bytes offset from the page end then.

Unaligned access allowed means this is a valid fault scenario and Finn's
fix is necessary...

Cheers,

Michael

>
> Gr{oetje,eeting}s,
>
> Geert
>