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Date: Wed, 21 Feb 2007 19:08:10 -0800 (PST)
From: Davide Libenzi <davidel@xmailserver.org>
Subject: Re: [PATCH]add epoll compat code to fsl/compat.c
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To: David Miller <davem@davemloft.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>, sfr@canb.auug.org.au, Andrew Morton <akpm@linux-foundation.org>, David Woodhouse <dwmw2@infradead.org>, linux-arch@vger.kernel.org, rmk@arm.linux.org.uk, tony.luck@intel.com, ralf@linux-mips.org
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On Wed, 21 Feb 2007, David Miller wrote:

> From: Linus Torvalds <torvalds@linux-foundation.org>
> Date: Wed, 21 Feb 2007 12:36:11 -0800 (PST)
> 
> > On Wed, 21 Feb 2007, Davide Libenzi wrote:
> > > 
> > > I don't think we can safely assume that we can access a potentially 
> > > 4-bytes aligned u64 on 64 bit architectures that require compat:
> > > 
> > > 	put_user(ev.data, &events->data);
> > 
> > Oh, we can. "put_user()" and "get_user()" already have to work on totally 
> > unaligned data. If some architecture has problems with that, they have 
> > bigger issues, methinks.
> > 
> > We can't trust user pointers, and that includes not trusting them being 
> > aligned. 
> 
> Right, and on Sparc for userland they are illegal so we'll just
> SIGBUS the process if that happens.

Ahha! That's where I got fooled :) I looked at IA64 and I saw it had the 
proper unaligned case, but then I saw that SPARC was not handling the 
unaligned case.



- Davide