Snap hangs when accessing a special /dev/file (/dev/vcio) [ubuntu-core 16 / RaspberryPi2]

[Loïc Minier]

There is a GPIO interface
<https://github.com/snapcore/snapd/blob/master/interfaces/builtin/gpio.go> and
it was going through some fixes a couple of weeks ago as it would only work
when first connected, but not after a reboot.

On Mon, Nov 7, 2016 at 8:53 AM, Didier Roche <didrocks at ubuntu.com> wrote:

> Le 06/11/2016 à 11:50, Jacques Supcik a écrit :
>
> Dear community.
>
> I have a program <https://gitlab.com/telecom-tower/tower>, written in go,
> and running on a raspberry Pi 2, which displays messages on a LED panel.
> The panel <https://www.adafruit.com/product/2294> is made of "neo pixels"
> and is connected to the GPIO of the raspberry Pi. Internally, it uses the
> DMA and PWM to generate and accurate signals.
>
> The program currently runs well on a Raspbian system and I would like to
> move to ubuntu-core. I was able to build the snap and to deploy it on a
> raspberry Pi 2 running Core version 16. I installed the snap with
> "--dangerous", but as soon as the system configure the DMA/PWM/GPIO, it
> just freezes.
>
> I installed snappy-debug to check the logs and this is what I get:
>
> = AppArmor =
> Time: Nov  6 09:28:45
> Log: apparmor="DENIED" operation="open" profile="snap.telecom-tower.daemon"
> name="/dev/vcio" pid=4441 comm="tower" requested_mask="r" denied_mask="r"
> fsuid=0 ouid=0
> File: /dev/vcio (read)
>
> = Seccomp =
> Time: Nov  6 09:28:45
> Log: auid=4294967295 uid=0 gid=0 ses=4294967295 pid=4441 comm="tower"
> exe="/snap/telecom-tower/x1/bin/tower" sig=31 arch=40000028 14(mknod)
> compat=0 ip=0x76e3aaf6 code=0x0
> Syscall: mknod
>
> Note that if I scp the binary file and run on ubuntu core as root, then
> the program runs fine. (I don't install the snap, I just run the binary
> from the home directory.)
>
> Does someone have an idea about what I can do to make my snap run?
>
> Thank you very much in advance for your support.
>
>
> Hey Jacques,
>
> I think we did discuss about GPIO support in confined mode, but there is
> no interface for this today AFAIK (CCing Jamie who can confirm and maybe
> give a path/ETA forward).
>
> Meanwhile, you can still install your snap in devmode to bypass security,
> and that should do it in your case, mind confirming?
> Cheers,
> Didier
>
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>


-- 
- Loïc
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