Re: Upstart 0.5.0, /proc, and telinit

Jeff Oliver Mon, 23 Feb 2009 19:07:07 -0800

First off, I would say that there is no need to mount /proc, if its not necessary. For the most part, job files, wouldn't even require /proc to be mounted. Following on from that logic, there is only 1 place, that I can see, that actually attempts to use a /proc file, when upstart changes the oom_adj value. So, first check to see if the job file is even changing that value, if not, /proc is not needed and skip that step. Second, if it does need /proc, then what? You could simply fail the job, quietly ignore the error, or mount proc? I guess that part is up for debate yet.

It should not use system(), it opens itself up for other problems.

Jeff

Garrett Cooper wrote:

On Mon, Feb 23, 2009 at 2:14 PM, Adam Sampson <[email protected]> wrote:

Scott James Remnant <[email protected]> writes:

Nobody has supplied a patch.

Well, here's what I'm using happily, but I suspect a little more finesse
would be useful. ;)

http://offog.org/darcs/garstow/sys/upstart/files/mountproc.diff


Uh, that will almost certainly fail if it can't allocate a shell
because system(3) calls execve(2) and allocates a shell.

Using mount(2), like so, would be better:

#include <string.h>          /* For strerror(3). */
#include <errno.h>
#include <sys/mount.h>
#include <linux/kernel.h> /* For panic(2). */

/* ... */

if (mount("none", "/proc", "proc", 0, NULL) < 0) {
    /* Change to OOM support not available, etc for this instead of a panic? */
    panic ("Failed to mount /proc: %s\n", strerror(errno));
}

    You'll potentially need to do similar for /dev and /dev/console
(we currently do that, but I'm not sure if /dev/console is needed...).
Combined with proper calls to fstab(5) with getent, this should be
solved properly in less than 30 lines.
Cheers,
-Garrett

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Re: Upstart 0.5.0, /proc, and telinit

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