From: Arnd Bergmann <arnd@arndb.de>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Valdis.Kletnieks@vt.edu, "H.J. Lu" <hjl.tools@gmail.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Christoph Hellwig <hch@infradead.org>,
LKML <linux-kernel@vger.kernel.org>, Ingo Molnar <mingo@elte.hu>,
Thomas Gleixner <tglx@linutronix.de>,
Richard Kuo <rkuo@codeaurora.org>,
Mark Salter <msalter@redhat.com>, Jonas Bonn <jonas@southpole.se>,
Tobias Klauser <tklauser@distanz.ch>
Subject: Re: RFD: x32 ABI system call numbers
Date: Sun, 04 Sep 2011 17:17:59 +0200 [thread overview]
Message-ID: <3546423.kFMPx0aPCi@wuerfel> (raw)
In-Reply-To: <4E62638E.40308@zytor.com>
On Saturday 03 September 2011 10:27:42 H. Peter Anvin wrote:
> On 09/03/2011 10:16 AM, Valdis.Kletnieks@vt.edu wrote:
> >>
> >> The complexity of changing that would be enormous.
> >
> > Oh, I know changing the x86-32 ABI is impossible - I meant changing the
> > decision to emulate that ABI (as opposed to emulating the x86-64 ABI, or a
> > variant thereof, or something else). Or are we already commited to that
> > route, even if we're still trying to figure out what syscalls to include?
> >
>
> About ioctl in particular, the ABI has dependencies into almost every
> single driver in the Linux kernel. It is hard-coded in the kernel that
> there are two paths -- native and compat. Since pointers are going to
> be 4 bytes, it means we have to use the compat path.
>
> We may be able to cheat a little bit since we encode the argument sizes
> in the ioctl numbers; this solves the case of PPGETTIME/PPSETTIME for
> example (in fact, this ioctl looks currently broken in compat mode!)
> However, at some point the sheer number of data types that can be
> consumed by ioctl is a real concern, so changing the ones we really care
> about -- like timespec/timeval -- while leaving the rest intact so we
> can use the compat path as a general rule would be highly useful.
The ppdev ioctls are indeed missing in user space, and they are
an example for a different problem than the one I meant.
We really have a number of different cases that we will have to
deal with in different ways:
* different layout and ioctl code due to padding on x86-32,
x32 is compatible:
DRM_IOCTL_RADEON_SETPARAM
DRM_IOCTL_UPDATE_DRAW32
EXT4_IOC32_GROUP_ADD
* different layout due to padding on x86-32, but same ioctl code:
RAW_SETBIND
RAW_GETBIND
* uses time_t, different ioctl code:
PPPIOCGIDLE32
VIDIOC_DQBUF32
VIDIOC_QBUF32
VIDIOC_QUERYBUF32
VIDIOC_DQEVENT32
* uses time_t, same ioctl code:
VIDEO_GET_EVENT
LPSETTIMEOUT
* Different alignment, three different ioctl numbers:
FS_IOC_RESVSP_32
FS_IOC_RESVSP64_32
* manually checks if compat_task:
input/evdev
* Very complex, no easy solution:
XFS_IOC_*
* Only needed for x86-32, not for x32:
sys_quotactl
* Data structures embed time values, not an ioctl
sys_sendmsg (cmsg)
sys_recvmsg (cmsg)
sys_mq_*
sys_semtimedop
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.
Arnd
next prev parent reply other threads:[~2011-09-04 15:18 UTC|newest]
Thread overview: 94+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-08-26 23:00 RFD: x32 ABI system call numbers H. Peter Anvin
2011-08-26 23:13 ` Linus Torvalds
2011-08-26 23:39 ` H. Peter Anvin
2011-08-27 0:36 ` Linus Torvalds
2011-08-27 0:43 ` Linus Torvalds
2011-08-27 0:53 ` H. Peter Anvin
2011-08-27 1:18 ` Linus Torvalds
2011-08-27 1:35 ` H. Peter Anvin
2011-08-27 1:45 ` Linus Torvalds
2011-08-27 1:12 ` H. Peter Anvin
2011-08-27 1:42 ` Linus Torvalds
2011-08-29 19:01 ` Geert Uytterhoeven
2011-08-29 19:03 ` H. Peter Anvin
2011-08-30 1:17 ` Ted Ts'o
2011-08-30 1:48 ` Linus Torvalds
2011-08-30 2:16 ` Kyle Moffett
2011-08-30 4:45 ` H. Peter Anvin
2011-08-30 7:06 ` Geert Uytterhoeven
2011-08-30 12:18 ` Arnd Bergmann
2011-08-30 7:09 ` Andi Kleen
2011-08-30 9:56 ` Alan Cox
2011-08-30 7:00 ` Geert Uytterhoeven
2011-09-20 18:37 ` Jan Engelhardt
2011-09-06 20:40 ` Florian Weimer
2011-08-27 0:57 ` H. Peter Anvin
2011-08-27 4:40 ` Christoph Hellwig
2011-08-29 15:04 ` Arnd Bergmann
2011-08-29 18:31 ` H. Peter Anvin
2011-08-30 12:09 ` Arnd Bergmann
2011-08-30 16:35 ` H. Peter Anvin
2011-08-31 16:14 ` Arnd Bergmann
2011-08-31 16:25 ` H. Peter Anvin
2011-08-31 16:39 ` Arnd Bergmann
2011-08-31 16:48 ` Linus Torvalds
2011-08-31 19:18 ` Arnd Bergmann
2011-08-31 19:44 ` H. Peter Anvin
2011-08-31 19:54 ` Alan Cox
2011-08-31 20:02 ` H. Peter Anvin
2011-08-31 20:55 ` Arnd Bergmann
2011-08-31 20:58 ` H. Peter Anvin
2011-08-31 19:49 ` Geert Uytterhoeven
2011-08-31 16:46 ` Linus Torvalds
2011-08-31 17:05 ` H.J. Lu
2011-09-03 2:56 ` H.J. Lu
2011-09-03 3:04 ` Linus Torvalds
2011-09-03 4:02 ` H.J. Lu
2011-09-03 4:29 ` H. Peter Anvin
2011-09-03 4:44 ` H.J. Lu
2011-09-03 5:16 ` H. Peter Anvin
2011-09-03 14:11 ` H.J. Lu
2011-09-03 5:29 ` H. Peter Anvin
2011-09-03 8:41 ` Arnd Bergmann
2011-09-03 14:04 ` Valdis.Kletnieks
2011-09-03 16:40 ` H. Peter Anvin
2011-09-03 17:16 ` Valdis.Kletnieks
2011-09-03 17:22 ` H.J. Lu
2011-09-03 17:28 ` H. Peter Anvin
2011-09-03 17:27 ` H. Peter Anvin
2011-09-04 13:51 ` Valdis.Kletnieks
2011-09-04 15:17 ` Arnd Bergmann [this message]
2011-09-04 17:08 ` Linus Torvalds
2011-09-04 18:40 ` H.J. Lu
2011-09-04 19:06 ` Arnd Bergmann
2011-09-04 19:31 ` H.J. Lu
2011-09-04 21:13 ` Arnd Bergmann
2011-09-04 21:25 ` H.J. Lu
2011-09-04 21:41 ` Arnd Bergmann
2011-09-04 22:13 ` H.J. Lu
2011-09-05 7:48 ` Arnd Bergmann
2011-09-05 15:11 ` H.J. Lu
2011-09-05 17:21 ` Arnd Bergmann
2011-09-05 19:34 ` H.J. Lu
2011-09-05 19:54 ` H.J. Lu
2011-09-05 19:59 ` H. Peter Anvin
2011-09-05 20:27 ` Arnd Bergmann
2011-09-09 21:02 ` H.J. Lu
2011-09-04 20:11 ` H. Peter Anvin
2011-09-04 19:31 ` richard -rw- weinberger
2011-09-04 19:32 ` H.J. Lu
2011-09-03 14:15 ` H.J. Lu
2011-08-31 17:09 ` H. Peter Anvin
2011-08-31 17:19 ` Linus Torvalds
2011-08-31 17:38 ` H. Peter Anvin
2011-09-01 11:35 ` Arnd Bergmann
2011-10-01 19:38 ` Jonas Bonn
2012-02-08 21:36 ` 64-bit time on 32-bit systems H. Peter Anvin
2011-09-01 13:30 ` RFD: x32 ABI system call numbers Avi Kivity
2011-09-01 14:13 ` H. Peter Anvin
2011-09-02 0:49 ` Pedro Alves
2011-09-02 1:51 ` H. Peter Anvin
2011-09-02 8:02 ` Arnd Bergmann
2011-09-02 8:42 ` Pedro Alves
2011-09-01 6:08 ` Jonas Bonn
2011-09-02 6:17 ` Andy Lutomirski
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