From:	CRDGW2::CRDGW2::MRGATE::"SMTP::CRVAX.SRI.COM::RELAY-INFO-VAX"  9-NOV-1989 01:04
To:	MRGATE::"ARISIA::EVERHART"
Subj:	Re: Debugging symbionts

Message-Id:  <8911090548.AA13040@crdgw1.ge.com>
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Date:           Wed, 8 Nov 89  16:50 BST
From: Nick de Smith <"PSI%JANET.000000000040::NICK%ncdlab.ulcc.ac.uk"@NSFnet-Relay.AC.UK>
To: INFO-VAX <@NSFnet-Relay.AC.UK:INFO-VAX@crvax.sri.com>
Subject:        Re: Debugging symbionts

From: "Nick de Smith, Special Systems Group, Applied Telematics" <NICK@NCDLAB.ULCC.AC.UK>
Organization: Applied Telematics Group Ltd.
Sender: nick@ncdlab.ulcc.ac.uk

I have tried to mail "mil.navy.nwc::fidler.decnet::levine" direct, to no avail.
I therefore post this...

> 	I have gotten quite a bit of feed back on how to debug a user modified
> print symbiont under VMS 5.2, however none of them help me in getting the 
> debugger to come up on the designated terminal.

Try this...

Check:
	1) That the DBG$INPUT and DBG$OUTPUT are defined /SYSTEM
	2) That you have remembered the ":" on the end of the device name.
	3) That the device protection for target terminal for DEBUG has
	   RWLP protection access for the symbiont process. I tend to either
	   give the symbiont BYPASS+LOG_IO+PHY_IO, or to use a
		$ SET PROTECTION=W:RWLP /DEVICE DBG$INPUT
	   and	$ SET PROTECTION=W:RWLP /DEVICE DBG$OUTPUT
	   to ensure access.

DEBUG requires the ":" on the device name, else it'll run up on a non-existant
file (say, called LTA42.DAT), get an EOF, print "Normal successful completion"
to SYS$OUTPUT (which is the Job Controller mailbox), and the Job Controller
will, not surprisingly, complain about a bad format message. The PSM routines
manual explicitly says that you must not use SYS$INPUT,SYS$OUTPUT,SYS$ERROR or
SYS$COMMAND.

Note that this can crash the job controller! If you use RMS to write to MBA1:
(the JBC mailbox), when you close the file, RMS kindly writes a mailbox EOF for
you. The JBC used to crash when this happened, but I haven't tried it recently.
Almost anyone could do this. Sigh. 8-<

> 	Is this SPR time? 

Probably not!

> from the interactive terminal, the debugger comes right up on the target
> terminal.

Probably due to point 3 above (access to the device). Symbionts, by default,
have very little (!!) priv. They have SETPRV and TMPMBX (I think). Any others
have to be set explicitly in the symbiont initialise routine. If you run up on
your terminal, the symbiont will have all your privs, which will (probably in
this case) give it access to the DBG$INPUT/DBG$OUTPUT. Ho, hum...

I have included an example symbiont initialise routine (in C) at the end of this
message.

good luck, and rgds,

(-: nick :-)	Reply to: NICK@NCDLAB.ULCC.AC.UK

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Example user written symbiont initialise routine...

/*****************************************************************************************************************

					I n i t i a l i z e

 Initialize the symbiont. Set the required privileges and notify the job controller of our presence.
 Why do Americans spell "initialise" with a "z" ?

*****************************************************************************************************************/
static
Initialize()
{
	long	structure_level = SMBMSG$K_STRUCTURE_LEVEL;		/* Version we compiled against		*/
	void	Ast_Routine();						/* AST routine to service requests	*/
	long	streams = 1;						/* Single stream symbiont		*/
	long	mask[ 2 ] = { 0, 0 };					/* Bitmask of privileges to set		*/

#define	setbit( mask, bit )	(mask[ (bit) / 32 ] |= 1 << ((bit) & 31)) /* Set a bit in the specified mask	*/

	setbit( mask, PRV$V_OPER );					/* We want OPER...			*/
	setbit( mask, PRV$V_WORLD );					/* ...and WORLD privileges		*/
#ifdef	TESTING
	setbit( mask, PRV$V_BYPASS );					/* Allow DEBUG to access a terminal port */
	setbit( mask, PRV$V_LOG_IO );
	setbit( mask, PRV$V_PHY_IO );
#endif	TESTING
	ss_check( SYS$SETPRV( 1, mask, 1, 0 ) )				/* Try to set privileges		*/

	ss_check( SMB$INITIALIZE( &structure_level, Ast_Routine, &streams ) ) /* Tell the Job Controller we are here */

	return SS$_NORMAL;						/* Return success			*/
}