From: Al Viro <viro@ZenIV.linux.org.uk>
To: David Howells <dhowells@redhat.com>
Cc: "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com>,
Jeff Layton <jlayton@redhat.com>,
lkml <linux-kernel@vger.kernel.org>,
Linux API <linux-api@vger.kernel.org>,
linux-man <linux-man@vger.kernel.org>
Subject: Re: Revised statx(2) man page for review [and AT_EMPTY_PATH question]
Date: Wed, 26 Apr 2017 16:53:00 +0100 [thread overview]
Message-ID: <20170426155259.GY29622@ZenIV.linux.org.uk> (raw)
In-Reply-To: <14390.1493206508@warthog.procyon.org.uk>
On Wed, Apr 26, 2017 at 12:35:08PM +0100, David Howells wrote:
> AT_EMPTY_PATH wasn't there back in 2010. I could eliminate the:
>
> statx(fd, NULL, 0, ...);
>
> option in favour of:
>
> statx(fd, "", AT_EMPTY_PATH, ...);
>
> Any thoughts either way, Al?
>
> It would seem that AT_EMPTY_PATH should be redundant, though, since you can
> just set the pathname pointer to NULL.
NULL pathname pointer means an error for a lot of existing syscalls, so
if you want to turn them into wrappers for ...at() ones at libc level,
you'd need to do special-casing of NULL both kernel-side and in libc wrappers.
Requiring "" + AT_EMPTY_PATH means a single dereference of userland pointer.
OTOH, that's not a terrible burden...
prev parent reply other threads:[~2017-04-26 15:53 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-25 11:14 Revised statx(2) man page for review Michael Kerrisk (man-pages)
2017-04-25 18:50 ` Silvan Jegen
2017-04-25 19:40 ` Michael Kerrisk (man-pages)
2017-04-25 20:06 ` Dmitry V. Levin
2017-04-26 5:42 ` Michael Kerrisk (man-pages)
2017-04-26 10:43 ` G. Branden Robinson
2017-04-26 11:35 ` Revised statx(2) man page for review [and AT_EMPTY_PATH question] David Howells
2017-04-26 12:13 ` Michael Kerrisk (man-pages)
2017-04-26 15:10 ` David Howells
2017-04-26 19:08 ` Michael Kerrisk (man-pages)
2017-04-26 15:53 ` Al Viro [this message]
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