From: Marc Espie <marc.espie.openbsd@gmail.com>
Subject: Re: examples/sysctl.conf
To: tech@openbsd.org
Date: Tue, 3 Dec 2024 15:02:14 +0100

On Tue, Dec 03, 2024 at 01:15:02PM +0000, Stuart Henderson wrote:
> On 2024/12/03 12:08, Marc Espie wrote:
> > I always forget about these when I need some instrumentation
> > 
> > Since the ddb knobs are already there, is there an issue to having
> > more "dangerous" sysctl(8)  that need to happen before securelevel in there ?
> > ...
> > 
> > Index: sysctl.conf
> > ===================================================================
> > RCS file: /build/data/openbsd/cvs/src/etc/examples/sysctl.conf,v
> > diff -u -p -r1.5 sysctl.conf
> > --- sysctl.conf	18 Sep 2019 08:39:06 -0000	1.5
> > +++ sysctl.conf	3 Dec 2024 11:06:31 -0000
> > @@ -25,6 +25,8 @@
> >  #ddb.panic=0			# 0=Do not drop into ddb on a kernel panic
> >  #ddb.console=1			# 1=Permit entry of ddb from the console
> >  #ddb.log=1			# 1=Log ddb output in kernel message buffer
> > +#kern.allowdt=1			# 1=Enable dtrace(8)
> > +#kern.allowkmem=1		# 1=Enable procmap(8)
> >  #fs.posix.setuid=0		# 0=Traditional BSD chown() semantics
> >  #vm.swapencrypt.enable=0	# 0=Do not encrypt pages that go to swap
> >  #vfs.nfs.iothreads=4		# Number of nfsio kernel threads
> > 
> 
> I think allowkmem would need a more strongly-worded description.
> "Allow userland access to all physical and kernel memory"?
> 

Better ?

Index: sysctl.conf
===================================================================
RCS file: /build/data/openbsd/cvs/src/etc/examples/sysctl.conf,v
diff -u -p -r1.5 sysctl.conf
--- sysctl.conf	18 Sep 2019 08:39:06 -0000	1.5
+++ sysctl.conf	3 Dec 2024 14:01:57 -0000
@@ -25,6 +25,8 @@
 #ddb.panic=0			# 0=Do not drop into ddb on a kernel panic
 #ddb.console=1			# 1=Permit entry of ddb from the console
 #ddb.log=1			# 1=Log ddb output in kernel message buffer
+#kern.allowdt=1			# 1=Enable dt(4) device for btrace(8) support
+#kern.allowkmem=1		# 1=Allow access to all memory, needed for procmap(8)
 #fs.posix.setuid=0		# 0=Traditional BSD chown() semantics
 #vm.swapencrypt.enable=0	# 0=Do not encrypt pages that go to swap
 #vfs.nfs.iothreads=4		# Number of nfsio kernel threads