From: Christoph Hellwig <hch@infradead.org>
To: Aurelien Jarno <aurelien@aurel32.net>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>,
linux-fsdevel@vger.kernel.org,
Robert Edmonds <edmonds@debian.org>,
Rob Browning <rlb@defaultvalue.org>
Subject: Re: Argument type for FS_IOC_GETFLAGS/FS_IOC_SETFLAGS ioctls
Date: Wed, 27 Nov 2013 02:15:36 -0800 [thread overview]
Message-ID: <20131127101536.GA24697@infradead.org> (raw)
In-Reply-To: <20131126200559.GH20559@hall.aurel32.net>
On Tue, Nov 26, 2013 at 09:05:59PM +0100, Aurelien Jarno wrote:
> Most of the userland code seems to pass an int to this ioctl, but a few
> others (e.g.: bup, libexplain) passes a long. While it doesn't make a
> difference on little endian machines, it does make a difference on
> 64-bit big endian machines.
>
> Could you please tell me if I am wrong in my analysis or if there is a
> actually real problem?
The problem is that as you indeed pointed out the ABI is that an int
needs to be passed. The _IOR/_IOW generate a ioctl number based on
a few inputs including the type of the argument, which is just
passed to sizeof. So the supposedly self-documenting ioctl defintions
disagree with the actual ABI.
There's nothing that can be fixed in the kernel except for better
documenting the actual ABI, and why the ioctl defintion is very misleading
in this case.
The userspace programs that were mislead by this will need to fixed.
next prev parent reply other threads:[~2013-11-27 10:15 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-11-26 20:05 Argument type for FS_IOC_GETFLAGS/FS_IOC_SETFLAGS ioctls Aurelien Jarno
2013-11-27 1:01 ` Darrick J. Wong
2013-11-27 4:00 ` Theodore Ts'o
2013-11-27 10:03 ` Aurelien Jarno
2013-11-27 13:34 ` Theodore Ts'o
2013-11-27 18:14 ` Robert Edmonds
2013-11-27 23:14 ` Aurelien Jarno
2013-11-29 0:53 ` Andreas Dilger
2013-11-29 4:54 ` Theodore Ts'o
2013-11-29 5:27 ` Dave Chinner
2013-11-29 14:22 ` Theodore Ts'o
2013-11-29 16:32 ` Rob Browning
2013-12-01 22:20 ` Dave Chinner
2013-12-02 4:52 ` Theodore Ts'o
2013-12-02 22:30 ` Dave Chinner
2013-11-29 21:55 ` Andreas Dilger
2013-12-19 18:20 ` Rob Browning
2013-12-19 23:30 ` Darrick J. Wong
2013-11-27 10:15 ` Christoph Hellwig [this message]
2014-06-30 22:51 ` Rob Browning
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