From:	SMTP%"RELAY-INFO-VAX@CRVAX.SRI.COM" 26-MAY-1994 13:29:41.07
To:	EVERHART
CC:	
Subj:	Accessing the intrusion database

Date: Thu, 26 May 1994 17:23:13 +0300 (CET-DST)
From: "All thoughts, all passions, all delights..." <SEMUSCHIN@DECUS.DECUS.DE>
To:   info-vax@sri.com
Message-Id: <940526172313.8581@DECUS.DECUS.DE>
Subject: Accessing the intrusion database

Hi Joel,

I just revided my opinion about syncronisation of access to intrusion database.
I isn't spinlock. It is mutex. If you'll link sys$system:sys.stb to get the map
( link/noexe/map=sys/full ) for readability, you would find there besides
CIA$GQ_INTRUDER another CIA symbol: CIA$GL_MUTEX. It is a mutex used by CIA.EXE
(program, that actually will executed, when you issue show intr|del/intr).
You could lock that resource using sch$lockr (for read) and sch$lockw (for
write) and then unlock it with sch$unlock. All mentioned SCH$ routines take
MUTEX as they first parameter (address in R0) and PCB as the second one 
(address in R4). They are described in Black Book 8.5 Mutual Exclusion 
Semaphores (mutexes). So what you actually need to do is:

   $cmkrnl
   acquire the mutex in appropriate mode (read/write)
   read/modify intrusion database
   free mutex

To write kernel mode you could read some articles in Digital Systems Journal
(former VAX Professional) or Hitchhicker's Guide to Vms by Bruce Ellis
ISBN 1-878956-00-0 (some parts of this book were published in VAX Profesional).
However tasks, you intend to do on kernel stack not very sophisticated,
and reading of all above mentioned books will not insure you 100%,
so if you nave a VAX that could be crashed some times during the day ...

Many happy minutes with SDA ...

				... and happy hacking

					= Seva

PS
a properly written exception handler could save your system from crashes
caused by some dumb/typo mistakes.

+-----------------------------------+------------------------------------------+
| V.Semuschin                       |                                          |
| SONY Deutschland GmbH             |                                          |
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| It's not a trick, it's my opinion |                                          |
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