Privsep Debugging Support: /var/crash/$programname, sysctl-Managed, Added

Debugging privsep code on OpenBSD-current just became a little easier. In this commit, Theo de Raadt (deraadt@) added a new kern.nosuidcoredump value, 3, which makes core dumps go to /var/crash/$programname (assuming the directory exists), and dumps cores named after the crashing program's PID.

Changes by:	deraadt@cvs.openbsd.org	2014/05/03 21:53:38

Modified files:
	sys/kern       : kern_sig.c 
	lib/libc/gen   : sysctl.3 
	sbin/sysctl    : sysctl.8 
	share/man/man5 : core.5 

Log message:
When kern.nosuidcoredump=3, act like =2 but try to dump cores into
the /var/crash/programname/ directory, as root. For instance,
# mkdir /var/crash/bgpd/
# chmod 700 /var/crash/bgpd/    # If you skip this step, you are a moron
# sysctl kern.nosuidcoredump=3
# bgpd
# pkill -ABRT bgpd
# ls /var/crash/bgpd/
14764.core   23207.core   6423.core
Of course, in real life the idea is that you don't kill the daemon but it
crashes and you collect parallel cores.  Careful you don't fill your /var.
Further tuneables are being considered.

Sorry to be picking on bgpd for this example.  I've watched the "too
difficult to debug privsep code" angst for far too long.
ok guenther