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From: Michael Schmitz <schmitzmic@gmail.com>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: linux-m68k@vger.kernel.org, Finn Thain <fthain@linux-m68k.org>,
	linux-m68k@lists.linux-m68k.org
Subject: Re: [PATCH RFC] m68k: Handle __generic_copy_to_user faults more carefully
Date: Wed, 17 Apr 2024 20:08:14 +1200	[thread overview]
Message-ID: <e7670276-24e8-dc5e-5387-2ec4f3edd8e0@gmail.com> (raw)
In-Reply-To: <CAMuHMdV-ggmMVera8Ya4fDLCJzDXguKCOpg2i_+g98ZvAoctHA@mail.gmail.com>

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
>

  reply	other threads:[~2024-04-17  8:08 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-04-16 20:36 [PATCH RFC] m68k: Handle __generic_copy_to_user faults more carefully Michael Schmitz
2024-04-17  6:59 ` Geert Uytterhoeven
2024-04-17  8:08   ` Michael Schmitz [this message]
2024-04-17  8:16   ` Eero Tamminen
2024-04-17 16:26     ` Andreas Schwab

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