Re: [9fans] A proposal regarding # in bind

[Martin C.Atkins <martin@mca-ltd.com>]

On Tue, 25 Feb 2003 11:02:27 +0000 chris@cjl1.demon.co.uk wrote:
> Rather than rog's special special #name for acquiring the
> local device namespace I'd prefer a syscall.

Like I've said in another message, I'd prefer there to be no (user-visible)
way to mount /ur, only a way to unmount it!

>..
> Other notes:
>
> pctl(NODEVS) still allows attach to certain devices such as devpipe
> and prog.  Martin's unmount /ur would prevent an app from killing
> off any spawned threads or using pipes, which seems draconian.

Right. Now I understand the comments in another message...

How about this:
Before starting the init process, the kernel binds into init's namespace

	#/ onto /
	#smallur onto /ur
	#bigur onto /ur (BEFORE)

using the kernel's private, special version of bind, which does understand these names.

#smallur would provide names for '#|' etc, and #bigur would provide names
for the rest. Then an inheriting process could unmount bigur, but still be able
to create pipes, etc.

(NB I'm not seriously suggesting these exact names! :-)

BTW: why would my unmount /ur prevent an application from killing spawned
threads? If the application had #p mounted on /prog, then unmounting /ur wouldn't
affect that in any way.... (/ur is only used during the bind of #p etc.)

>
> [NOTE: general access to prog is a problem anyway - consider multiple
> users logged in as 'none' - any one can kill the threads of the others.]

Indeed!

Martin
--
Martin C. Atkins				martin@mca-ltd.com
Mission Critical Applications Ltd, U.K.		http://www.mca-ltd.com