From: Marc Gonzalez <marc.w.gonzalez@free.fr>
To: Eric Biederman <ebiederm@xmission.com>,
Stephane Graber <stgraber@ubuntu.com>,
Eric Dumazet <edumazet@google.com>,
Al Viro <viro@zeniv.linux.org.uk>
Cc: LKML <linux-kernel@vger.kernel.org>,
Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: Writing a robust core-dump handling script (wrt PID namespaces)
Date: Mon, 27 Jan 2020 11:54:50 +0100 [thread overview]
Message-ID: <bb897307-b5fc-eb1c-5fa6-2be92bb0fc9d@free.fr> (raw)
In-Reply-To: <4309685e-476c-7505-4fd4-fec7095c581d@free.fr>
On 16/01/2020 14:39, Marc Gonzalez wrote:
> I'm trying to write a robust core-dump handling script -- which eventually
> sends minidumps remotely for analysis, like Mozilla Socorro[1] but for any
> crashing process in the system.
>
> I read 'man 5 core' several times, but I'm confused about "PID namespaces".
>
> %p PID of dumped process, as seen in the PID namespace in which
> the process resides
> %P PID of dumped process, as seen in the initial PID namespace
> (since Linux 3.12)
>
> For now, I've set up :
>
> echo 5 > /proc/sys/kernel/core_pipe_limit
> echo "|/usr/sbin/coredump %P" > /proc/sys/kernel/core_pattern
>
> I used %P but I'm not sure why.
> (I used 5 somewhat at random too.)
>
> The coredump script is supposed to access /proc/$PID
>
> Should I use %P or %p or something else?
I /think/ %P is the proper option, because the /usr/sbin/coredump process
should (??) be created in the initial PID namespace.
Tangent: if a process is created in a different PID namespace, does it also
have a "global" PID, or is it "invisible" in the "root" PID namespace?
http://man7.org/linux/man-pages/man7/pid_namespaces.7.html
> A process is visible to other processes in its PID namespace, and to
> the processes in each direct ancestor PID namespace going back to the
> root PID namespace. In this context, "visible" means that one
> process can be the target of operations by another process using
> system calls that specify a process ID. Conversely, the processes in
> a child PID namespace can't see processes in the parent and further
> removed ancestor namespaces. More succinctly: a process can see
> (e.g., send signals with kill(2), set nice values with
> setpriority(2), etc.) only processes contained in its own PID
> namespace and in descendants of that namespace.
What about /proc/[pid] ? (breakpad needs these bits)
I'm still not 100% sure about how to access the /proc/[pid] directory of
a process that crashed in a new PID namespace FROM a coredump analyzer
in the root PID namespace.
Regards.
prev parent reply other threads:[~2020-01-27 10:54 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-16 13:39 Writing a robust core-dump handling script (wrt PID namespaces) Marc Gonzalez
2020-01-27 10:54 ` Marc Gonzalez [this message]
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