linux-kernel - Re: RFD: x32 ABI system call numbers

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Date:	Sun, 4 Sep 2011 10:08:50 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	"H. Peter Anvin" <hpa@...or.com>, Valdis.Kletnieks@...edu,
	"H.J. Lu" <hjl.tools@...il.com>,
	Christoph Hellwig <hch@...radead.org>,
	LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Richard Kuo <rkuo@...eaurora.org>,
	Mark Salter <msalter@...hat.com>,
	Jonas Bonn <jonas@...thpole.se>,
	Tobias Klauser <tklauser@...tanz.ch>
Subject: Re: RFD: x32 ABI system call numbers

On Sun, Sep 4, 2011 at 8:17 AM, Arnd Bergmann <arnd@...db.de> wrote:
>
> For a lot of these cases, the best option is to change the
> kernel headers to use new definitions on x32 before someone
> tries to ship a distro, especially when the ioctl command code
> is fixed. In case of the XFS ioctls, I think the only sane
> way is define the x32 ABI to match the 64 bit ABI completely,
> while for RAW_GETBIND and VIDEO_GET_EVENT it's probably enough
> to make x32 match x86-32.

Ack, ack, ack.

If we make the x32 ioctl system call first do "regular" ioctl, and
then fall back to the compat ones if that fails, x32 can mix and
match. It's not pretty, but I think it's better than the alternative
(which would be to have to use one r the other and add lots of new
compat handling).

Of course, we could also just have "compat_ioctl()" fall back to
native mode in general, and not make a x32 special case.

                     Linus
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