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From: Jacob Moody <moody@mail.posixcafe.org>
To: 9front@9front.org
Subject: Re: [9front] [PATCH] Unmount to remove sharp devices.
Date: Wed, 25 May 2022 13:03:21 -0600	[thread overview]
Message-ID: <236719d3-a3de-fed1-bb31-8cae0ce16ea0@posixcafe.org> (raw)
In-Reply-To: <d0c23d89-d009-c7ce-8dec-6cf5249ee728@posixcafe.org>

On 5/23/22 11:37, Jacob Moody wrote:
> There was some followup discussion for this on irc that I want to
> make sure is captured here:
> The command written to /dev/drivers will change to be one of:
> chdev DEVS
> chdev -DEVS

I am having some second thoughts about this. While this syntax does replicate
chmod, I am not entirely convinced that is what we want. When
being added to /sys/src/libauth/newns:/^nsop/ you have to special case around
the ARGBEGIN block. Combine that with the fact that this decision would lock
chdev(1) from ever accepting it's own flags, it felt like this was
introducing special case cruft.
Another consideration was what the syntax would be for removing all drivers,
currently it would just be chdev '' or something similar. Which is fine but
fat fingering that would be an annoying way to kill your current namespace.
These caveats may be entirely acceptable, but I was bothered enough to attempt to find another way.

Instead, I thought perhaps a rune prefix might be best. So you end up with:

chdev ∅
for removing all drivers.

chdev ∉DEVS
For removing just the specified drivers.

chdev ∈DEVS
For removing access to all but the specified drivers.

If a prefix is not given, ∈ is assumed.

I did implement this idea, to field it for quirks,
but wanted to get some feedback before redoing man page changes.

The downsides I see here are:

1. Deviation from chmod
2. This steals three runes that could have otherwise been used for drivers
3. ∉ is a bit more involved to type then '-'

With that said, I do much prefer this interface. Another option may be
to use rune prefixes, but also provide flag synonyms to the prefixes in

There is also an unrelated quirk I stumbled across when reviewing changes.
As is currently, devshr checks for if the noattach has been set before
allowing a process to post a fd. I have changed this to check for access to devmnt/'#M',
which is what replicates the 'can mount' knob that RFNOMNT tweaks. This seems fine to me,
but should we also replicate this check over in to devsrv for consistency?


  reply	other threads:[~2022-05-25 19:05 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-05-04 14:09 Jacob Moody
2022-05-04 15:05 ` ori
2022-05-04 15:31 ` ori
2022-05-04 16:15   ` Stanley Lieber
2022-05-04 17:41   ` Lyndon Nerenberg (VE7TFX/VE6BBM)
2022-05-04 17:55     ` Jacob Moody
2022-05-05  1:59       ` Alex Musolino
2022-05-05 16:07         ` Jacob Moody
2022-05-08  2:55           ` Jacob Moody
2022-05-11 14:47             ` Jacob Moody
2022-05-11 16:11               ` Stanley Lieber
2022-05-12  4:29                 ` Jacob Moody
2022-05-12  3:18             ` ori
2022-05-12  5:10               ` Jacob Moody
2022-05-12 14:21                 ` ori
2022-05-23  5:42                   ` Jacob Moody
2022-05-23 17:06                     ` cinap_lenrek
2022-05-23 17:37                       ` Jacob Moody
2022-05-25 19:03                         ` Jacob Moody [this message]
2022-05-25 20:53                           ` hiro
2022-05-25 21:20                             ` Jacob Moody
2022-05-26  5:55                               ` Jacob Moody
2022-05-26 23:36                                 ` unobe
2022-05-27  0:33                                   ` Jacob Moody
2022-05-27  3:25                                     ` unobe
2022-05-26  3:13                             ` ori
2022-05-27  1:11                           ` Lyndon Nerenberg (VE7TFX/VE6BBM)
2022-05-27  2:25                             ` Frank D. Engel, Jr.

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