From mboxrd@z Thu Jan  1 00:00:00 1970
From: Al Viro <viro-3bDd1+5oDREiFSDQTTA3OLVCufUGDwFn@public.gmane.org>
Subject: Re: [PATCHv10 man-pages 5/5] execveat.2: initial man page for
 execveat(2)
Date: Fri, 9 Jan 2015 22:57:43 +0000
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On Fri, Jan 09, 2015 at 05:42:52PM -0500, Rich Felker wrote:

> Here's a very simple way it could work -- it could put the O_PATH fd
> on a previously-unused fd number, and put a special flag on the fd,
> like FD_CLOEXEC, but that causes the kernel to close it whenever it's
> opened. The pathname passed could then simply be /dev/fd/%d or
> /proc/self/fd/%d, and although this is presently dependent on /proc
> being mounted, virtual /dev/fd/* could someday be something completely
> independent of procfs. The kernel keeps all the freedom to choose how
> to pass the name to the interpreter. I'm not proposing any kernel
> API/ABI lock-in and I'm with you in opposing such lock-in.

Huh?  open() on procfs symlinks does *NOT* work the way - the symlink is
traversed and after that point there is no information whatsoever how we
got to that vfsmount/dentry pair.  I can imagine several kludges that would
work, but they are unspeakably ugly, and do_last() is already far too
convoluted as it is.