svn commit: r319874 - head/sys/kern

[Warner Losh]

On Wed, Jun 14, 2017 at 11:04 PM, Gleb Smirnoff <glebius at freebsd.org> wrote:

> On Tue, Jun 13, 2017 at 03:06:43PM +0300, Konstantin Belousov wrote:
> K> On Mon, Jun 12, 2017 at 04:43:56PM -0700, Gleb Smirnoff wrote:
> K> > On Mon, Jun 12, 2017 at 09:11:11PM +0000, Konstantin Belousov wrote:
> K> > K> Author: kib
> K> > K> Date: Mon Jun 12 21:11:11 2017
> K> > K> New Revision: 319874
> K> > K> URL: https://svnweb.freebsd.org/changeset/base/319874
> K> > K>
> K> > K> Log:
> K> > K>   Print unimplemented syscall number to the ctty on SIGSYS, if
> enabled
> K> > K>   by the knob kern.lognosys.
> K> >
> K> > Why is it off by default?
> K> In some (non-default) situation it may cause lot of ctty output.
> K> I made the knob tunable to allow it to be set very early (init)
> K> if needed.
>
> I remember myself being a beginner UNIX user, and all this
> "bad system call, core dumped" messages were so annoyingly
> uninformative for me, and I had no idea how to track to the
> actual problem. This feature gives a lot of clue for a beginner
> user, but having it default to off, devaluates its value.
>

We can also rate limit the messages. We have the technology.

Warner

>
> To avoid possible tty spam for an application that produces ton
> of bad syscalls, but ignores SIGSYS, we can enable the feature
> for those processes, who doesn't ignore SIGSYS.
>
> --
> Totus tuus, Glebius.
>
>