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Message-Id: <4A16C7EF-B8B7-457C-B49C-829B44F12FFE@gmail.com>
Date: Tue, 3 Apr 2018 11:24:58 -0400
From: Josh Juran <jjuran@...il.com>
To: "Eric W. Biederman" <ebiederm@...ssion.com>
Cc: Geert Uytterhoeven <geert@...ux-m68k.org>,
Eugene Syromiatnikov <esyr@...hat.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Linux/m68k <linux-m68k@...r.kernel.org>
Subject: Re: [GIT PULL] siginfo fix for v4.16-rc5
On Apr 3, 2018, at 10:27 AM, Eric W. Biederman <ebiederm@...ssion.com> wrote:
> Geert Uytterhoeven <geert@...ux-m68k.org> writes:
>
>> On Mon, Apr 2, 2018 at 10:17 PM, Eric W. Biederman <ebiederm@...ssion.com> wrote:
>>
>>> A 2-byte alignment for 4 byte pointers. That is a new one to me.
>>
>> Not just for pointers, also for int and long.
>
> The smallest I have seen previously has been 64bit integers having
> 32bit alignment. 32bit entities having only 16bit alignment on a 32bit
> arch was simply a surprise. Even when it works there tend to be good
> reasons not to do that by default.
The 68K architecture began as 16-bit with the 68000. Rather than tightening requirements, the 68020 not only maintained compatibility with 16-bit alignment, but also forgave byte-misaligned data accesses (albeit with a performance penalty). Jumping to an odd address is still an error, though.
Josh
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