From: David Woodhouse <dwmw2@infradead.org>
To: Andi Kleen <ak@suse.de>
Cc: Arnd Bergmann <arnd@arndb.de>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Dave Airlie <airlied@linux.ie>,
linux-arch@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH] Introduce compat_u64 and compat_s64 types
Date: Fri, 15 Jun 2007 13:47:08 +0100 [thread overview]
Message-ID: <1181911628.25228.483.camel@pmac.infradead.org> (raw)
In-Reply-To: <200706151440.10273.ak@suse.de>
On Fri, 2007-06-15 at 14:40 +0200, Andi Kleen wrote:
> > That is broken on all non-x86 architectures,
> It cannot be broken, it just might be somewhat slower
No, Andi. It's broken.
We're speaking of a 32-bit ioctl compat routine. I would say it's more
than 'convention' that the structure used by the compat_ioctl routine
actually matches the 'real' structure as it gets laid out on the 32-bit
architecture.
The 'real' structure as used by the 32-bit userspace does not have the
'packed' attribute. Thus the u64 member of the structure is aligned to 8
bytes on _all_ relevant 32-bit architectures except for i386.
By adding 'packed' in the compat_ioctl routine, you cause it to expect a
structure which does not match what userspace is using, for all non-x86
architectures. That's kind of not very compatible. I call that 'broken'.
--
dwmw2
next prev parent reply other threads:[~2007-06-15 12:47 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <200706150159.l5F1xNgM000459@hera.kernel.org>
2007-06-15 8:44 ` drm: fix radeon setparam on 32/64 bit systems David Woodhouse
2007-06-15 8:58 ` Benjamin Herrenschmidt
2007-06-15 9:28 ` Arnd Bergmann
2007-06-15 9:31 ` [PATCH] Introduce compat_u64 and compat_s64 types Arnd Bergmann
2007-06-15 9:55 ` David Miller
2007-06-15 11:55 ` Andi Kleen
2007-06-15 12:00 ` David Woodhouse
2007-06-15 12:38 ` Andi Kleen
2007-06-15 12:03 ` Arnd Bergmann
2007-06-15 12:40 ` Andi Kleen
2007-06-15 12:47 ` David Woodhouse [this message]
2007-06-15 13:19 ` Benjamin Herrenschmidt
2007-06-15 12:09 ` David Howells
2007-06-15 12:43 ` Andi Kleen
2007-06-15 12:54 ` Alan Cox
2007-06-15 12:54 ` Andi Kleen
2007-06-15 13:15 ` Alan Cox
2007-06-15 13:27 ` Andi Kleen
2007-06-15 13:32 ` David Woodhouse
2007-06-15 20:50 ` Robin Getz
2007-06-15 21:22 ` Andi Kleen
2007-06-16 8:31 ` David Woodhouse
2007-06-15 13:00 ` David Woodhouse
2007-06-15 12:11 ` Matthew Wilcox
2007-06-15 12:38 ` David Woodhouse
2007-06-15 12:42 ` Arnd Bergmann
2007-06-15 13:45 ` Matthew Wilcox
2007-06-15 13:52 ` Arnd Bergmann
2007-06-15 23:54 ` Benjamin Herrenschmidt
2007-06-15 13:16 ` Benjamin Herrenschmidt
2007-06-16 9:38 ` David Woodhouse
2007-06-16 10:26 ` Arnd Bergmann
2007-06-16 11:21 ` Arnd Bergmann
2007-06-16 11:34 ` David Woodhouse
2007-06-16 13:56 ` Matthew Wilcox
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