[Info-vax] How dangerous is it to be able to get into DCL supervisor mode

[osuvman50 at gmail.com]

On Wednesday, July 5, 2017 at 4:04:45 PM UTC-4, Robert A. Brooks wrote:
> On 7/5/2017 1:42 PM, Bob Koehler wrote:
> > In article <ojj3gf$ola$1 at dont-email.me>, David Froble <davef at tsoft-inc.com> writes:
> >>
> >> My memory, remember, we're talking over 30 years, is that if the conditions for
> >> an exception handler were met, whatever they are, then the exception handler(s)
> >> will be invoked.
> > 
> >     There are many situations in which VMS will skip user mode handlers.
> > 
> >     For example, if you stop a process with STOP, user mode handlers get
> >     skipped.  We had a utility program that would do a force exit on the
> >     process instead.
> 
> Which is why folks will frequently use an image rundown handler, which is created
> by calling img$add_privileged_vector_entry().  See the Internal and Data Structures
> manual for details.
> 
> -- 
> 
>                        -- Rob

I had written a cool program for VAX/VMS, circa 1988, that added a permanent
routine to the CTL$GL_USRUNDWN rundown vector.  The Alpha changed the format of
all that and learning the new scheme would have taken more time than I wanted
to devote to it.