linux-kernel - Re: is avoiding compat ioctls possible?

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Date:	Wed, 28 Oct 2009 04:19:04 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Dave Airlie <airlied@...il.com>
Cc:	Andi Kleen <andi@...stfloor.org>,
	LKML <linux-kernel@...r.kernel.org>,
	DRI Development Mailing List 
	<dri-devel@...ts.sourceforge.net>, Arnd Bergmann <arnd@...db.de>,
	David Miller <davem@...emloft.net>
Subject: Re: is avoiding compat ioctls possible?

On Wed, Oct 28, 2009 at 01:05:08PM +1000, Dave Airlie wrote:
> We've designed that into a/c also, we pad all 64-bit values to 64-bit
> alignment on all the
> ioctls we've added to the drm in the past couple of years. Just because of
> this particular insanity.

That's actually not needed, just use compat_*64.
> 
> Assume no mistakes are made, new ioctls designed from scratch

That seems like a bad assumption. It sounds like you already
made some.

> and reviewed to do 32/64-bit properly. The s390 was something I didn't
> know about but KMS on s390 is probably never going to be something
> that sees the light of day.

Well in theory there might be more architectures in the future
which rely on compat_ptr

> 
> I'm just amazed that compat_ioctl should be required for all new code.
> 
> DrNick on irc suggested just doing:
> if (is_compat_task()) ptr &= 0x00000000FFFFFFFF;

Such hacks often have problems on BE.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only.
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