supervision - discussion about system services, daemon supervision, init, runlevel management, and tools such as s6 and runit
 help / color / mirror / Atom feed
From: Guillermo <gdiazhartusch@gmail.com>
To: supervision <supervision@list.skarnet.org>
Subject: Re: runit SIGPWR support
Date: Tue, 25 Feb 2020 15:38:15 -0300	[thread overview]
Message-ID: <CADQ2Nw9hu0tt2_XkF2-3D9z2d0JyAah0Eog=YkXxBMLtCAru7w@mail.gmail.com> (raw)
In-Reply-To: <00e1ad14-3bd4-c9ec-8f18-a33a1ba37bb6@NTLWorld.COM>

El mar., 25 feb. 2020 a las 6:08, Jonathan de Boyne Pollard escribió:
>
> Laurent Bercot:
> >  Of course, but once the fd is closed, /dev/console should not have
> > any impact on the process, so would a kbrequest still reach it?
>
> Yes.

Also, I tested it :) I added an open2("/dev/tty0", O_RDONLY |
O_NOCTTY) + ioctl() + fd_close() sequence to s6-linux-init.c right
after the reboot(RB_DISABLE_CAD) call, specifying SIGQUIT as the
argument of the KDSIGACCEPT ioctl (to use a signal 'divertable' by
s6-2.9.0.1's s6-svscan), and the SIGQUIT handler does get called
indeed when I press Alt + Up Arrow.

The file descriptor specified in the ioctl() call, as far as I can
tell, is only used by the kernel to check permissions. The ioctl is
allowed if the FD corresponds to the process' control terminal, or if
the process has CAP_KILL or CAP_SYS_TTY_CONFIG capabilities. But the
kernel just seems to record the PID of the invoking process and the
requested signal number. (vt_ioctl() in drivers/tty/vt/vt_ioctl.c).

> First: This is a kernel virtual terminal thing not a console
> thing.  Strictly speaking, it is doing it wrongly to access it through
> the console device, which is not necessarily a KVT.

Yeah, I overlooked this. I suppose it'll work on /dev/console as long
as it is a kernel virtual terminal, but it won't always be the case.
sysvinit and systemd use /dev/tty0 for the ioctl (and sysvinit falls
back to its standard input if that fails), so I used that for the
(second) test.

G.


  reply	other threads:[~2020-02-25 18:38 UTC|newest]

Thread overview: 64+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <1beb6e35-d4be-60b8-fc52-af666c4fffe3@gmx.com>
2020-02-12 14:25 ` innerspacepilot
2020-02-12 21:54   ` Colin Booth
2020-02-12 22:16     ` Dewayne Geraghty
2020-02-14  9:38     ` Jeff
2020-02-14 12:38       ` Steve Litt
2020-02-15 10:47       ` fungal-net
2020-02-14 10:08     ` Jeff
2020-02-14 10:46     ` Jeff
2020-02-14 12:29       ` innerspacepilot
2020-02-14 12:45         ` Steve Litt
     [not found]           ` <CALZWFRLvtofWfP4kzxJ8_8_K3nzebPjCR-NsJ2MU22cSuaOLng@mail.gmail.com>
     [not found]             ` <20200214182241.15614126@mydesk.domain.cxm>
2020-02-17 19:46               ` Cameron Nemo
2020-02-23 16:11                 ` Jeff
2020-02-17 14:39         ` Jeff
2020-02-14 14:02       ` Casper Ti. Vector
2020-02-17 14:45     ` Jeff
2020-02-17 14:50       ` Jeff
2020-02-14 13:15   ` Casper Ti. Vector
2020-02-14 13:39     ` innerspacepilot
2020-02-14 13:57       ` Casper Ti. Vector
2020-02-14 14:06         ` innerspacepilot
2020-02-14 14:25           ` Casper Ti. Vector
2020-02-14 18:30       ` Laurent Bercot
2020-02-17 10:00         ` innerspacepilot
2020-02-17 15:13           ` Jeff
2020-02-18  9:39             ` Laurent Bercot
2020-02-20 20:39               ` Serge E. Hallyn
2020-02-23 16:51               ` Jeff
2020-02-23 23:53                 ` Laurent Bercot
2020-02-24  6:31                   ` innerspacepilot
2020-02-24 10:23                     ` Laurent Bercot
2020-02-24 13:00                       ` Jeff
2020-02-24 19:53                         ` Laurent Bercot
2020-02-24 13:12                       ` innerspacepilot
2020-02-24 15:26                         ` Serge E. Hallyn
2020-02-26  8:07                           ` innerspacepilot
2020-02-28  6:39                             ` Jan Braun
2020-02-28  9:45                               ` Alex Suykov
2020-02-28 23:50                                 ` fungal-net
2020-02-29 13:44                                 ` Jonathan de Boyne Pollard
2020-02-29 18:20                             ` Guillermo
2020-03-06 20:07                               ` innerspacepilot
2020-03-06 20:09                               ` innerspacepilot
2020-02-25  8:39                       ` Jonathan de Boyne Pollard
2020-02-24 21:13                   ` Guillermo
2020-02-24 22:25                     ` Laurent Bercot
2020-02-24 22:49                       ` Laurent Bercot
2020-02-24 23:08                         ` Guillermo
2020-02-25  1:48                           ` Laurent Bercot
2020-02-25  9:08                             ` Jonathan de Boyne Pollard
2020-02-25 18:38                               ` Guillermo [this message]
2020-03-16 12:49                               ` Jeff
2020-03-16 17:13                               ` Jeff
2020-02-24 23:03                       ` Guillermo
2020-03-16 12:31                       ` Jeff
2020-03-16 18:03                         ` Laurent Bercot
2020-02-23 17:31               ` Jeff
2020-02-24  0:33                 ` Laurent Bercot
2020-02-14 19:08   ` John W Higgins
2020-02-14 23:18     ` Laurent Bercot
2020-02-14 23:38       ` John W Higgins
2020-02-15  2:15         ` Laurent Bercot
2020-04-14 16:57 Maxim Vetsalo
  -- strict thread matches above, loose matches on Subject: below --
2020-01-23 20:44 innerspacepilot
2020-01-31  4:39 ` Colin Booth

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to='CADQ2Nw9hu0tt2_XkF2-3D9z2d0JyAah0Eog=YkXxBMLtCAru7w@mail.gmail.com' \
    --to=gdiazhartusch@gmail.com \
    --cc=supervision@list.skarnet.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).