Date: Sun, 31 Aug 2003 22:31:02 -0700
From: "David S. Miller" <davem@redhat.com>
To: Jamie Lokier <jamie@shareable.org>
Cc: mfedyk@matchmail.com, lm@bitmover.com, linux-kernel@vger.kernel.org
Subject: Re: x86, ARM, PARISC, PPC, MIPS and Sparc folks please run this
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On Sun, 31 Aug 2003 23:49:37 +0100
Jamie Lokier <jamie@shareable.org> wrote:

> It uses POSIX shared memory and (necessarily) MAP_SHARED, which
> doesn't constrain the mapping alignment.

That's wrong.  If a platform needs to, it should properly
align the mapping when MAP_SHARED is used on a file.

If you look in arch/sparc64/kernel/sys_sparc.c, you'll see
that when we're mmap()'ing a file and MAP_SHARED is specified,
we align things to SHMLBA.

If userspace purposefully violates this alignment attempt,
then it's at it's own peril to keep the mappings coherent,
there is simply nothing the kernel should be doing to help
out that case.
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