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

[Arne Vajhøj]

On 7/3/2017 6:36 PM, Simon Clubley wrote:
> On 2017-07-03, VAXman-  @SendSpamHere.ORG <VAXman- at SendSpamHere.ORG> wrote:
>> When in exec mode, one can invoke $CMKRNL and execute code in kernel
>> mode without possessing the privies needed for $CMKRNL because there
>> is a check for the previous mode being exec.  There's nothing similar
>> for $CMEXEC from supervisor mode.  It sure would have removed a few
>> hurdles for me when writing my DCL Debugger had that been the case.

> There's still the bit about being able to set the privilege bits
> in supervisor mode however.

I don't think S mode allows changing stuff like that.

> However, if supervisor mode lets you do that, then that would seem to
> defeat the whole point of actually _having_ a supervisor mode. :-)

Well a separate mode with a separate stack pointer is very practical
for the don't start a new process to run a program paradigm.

Arne