I would have  bigger question - why an SVC at all? SVC's are limited
resources. If you will only be working when a server a/s is up, it would make
more sense to use a PC.

On Sat, 31 Dec 2011 12:53:42 -0600 Dave Day <david...@consolidated.net> wrote:

:>Peter,
:>
:>The SVC in question has but one purpose.  To generate a system trace
:>>>table entry.  The code within the SVC clears r15, and then branches r14.
:>> Having an SVC that is like that is surely a bad idea if used in a customer
:>> shop
:>> in production where malicious use of that SVC could compromise system
:>> serviceability.
:>
:>    I don't understand your comment.  Unless by malicious use you mean that 
:>the SVC would be executed over and over, just driving up overhead?
:>
:>    I honestly don't see that happening.  The code to execute the SVC is 
:>supplied by me, within a macro.  The SVC number will be supplied by my 
:>server code in my vendor table.  The code dropped out by the macro  checks 
:>that my vendor entry is there, and that the SVC number is not 00's.  And, I 
:>would expect anyone assembling the macro into their code would certainly 
:>control the logic flow with some kind of parm setting/flag byte convention. 
:>If one of my customers ships their code to their customer with my code 
:>embedded, and without any check on its execution, it wouldn't do anything 
:>without my server being there, and up and running.  And, if my server is 
:>there, it would be pretty easy to identify the fact that the code in 
:>question is executing this SVC without any controls on it.
:>
:>I can't see any need to set a slip, or find it using IPCS in a dump.
:>> That strikes me as a bit short-sighted unless this will never be used in a
:>> customer shop.
:>
:>    Why is that short-sighted?  Why would I ever set a slip on a BR R14?  If 
:>I need to know where the code is located in a dump, I can get the number 
:>from my own data area, compute the offset into the SVC table, and then go 
:>get it from that table.

--
Binyamin Dissen <bdis...@dissensoftware.com>
http://www.dissensoftware.com

Director, Dissen Software, Bar & Grill - Israel


Should you use the mailblocks package and expect a response from me,
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I very rarely bother responding to challenge/response systems,
especially those from irresponsible companies.

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