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Subject: Submission for mod-computers-vax
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Date: Tue, 17-Feb-87 03:10:28 EST
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Posted: Tue Feb 17 03:10:28 1987
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Path: umnd-cs!umn-cs!moll
From: moll@umn-cs.UUCP
Newsgroups: mod.computers.vax
Subject: Re: Correction to Privelege Query
Message-ID: <31000002@umn-cs.UUCP>
Date: 16 Feb 87 18:44:00 GMT
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Nf-From: umn-cs!moll    Feb 16 12:44:00 1987
Posted: Mon Feb 16 12:44:00 1987


> [...] indicating that only NETMBX and TMPMBX were in
> effect.  No error was detected on the call to SYS$SETPRV in the subroutine
> that tried to raise the priv to SYSNAM.  I don't know why.

I've been away from VMS for awhile, but doesn't SETPRV normally refuse
to set unauthorized bits without returning an error?

I have never been able to get privileges to work for a sharable image.
As far as I can tell, the image privilege mask for the process is set
when the original (calling) image is activated without regard to the
privileges of the shareable (called) image.  I called the Dec hotline
and asked if there was some way to install a shareable subroutine with
privilege and they said no.

This makes sense to me since image privileges would have to change across
a subroutine call when the image activator is already long gone.  If anyone
does know how to get this to work, I'd like to hear about it.  I'm not
completely sure of my facts here, I'm just saying that I couldn't make it
work.

I think there may be a harder solution, though.  The linker manual mentions
the possibility of creating known images which can be called by unprivileged
code, yet operate in a privileged access mode (Kernel or Exec).  I think
the idea is that the user code calls the routine with a CMKRNL instruction
rather than an ordinary subroutine call.  This would cause an interrupt to
the kernel which, if the call wasn't a recognized system service call,
would look through some table (ISD's?) looking for such a routine to
dispatch to.  Anybody out there ever create such a beast?  Can anybody
point to the proper documentation (the linker manual gives it about three
lines)?