On Mon, 10 Sep 2012 18:20:46 -0500, Joel C. Ewing wrote: >Ways other than STCK/STCKE for getting time involve an SVC, or calling a >system service, or calling a subsystem service (CICS), where >front-ending the service is an obvious approach -- probably why the >question was raised specifically on how a hardware instruction like STCK >could be handled when there is nothing to front-end. Just replacing >what looks like an STCK in a module does carry some risk of corrupting >what is really a data field that just happens to have an "inconvenient" >value, unless Hourglass does a complete logic-flow analysis of the >module (doubtful) or allows for some manual guidance on what constitutes >data areas that shouldn't be checked. Even checking for an "STCK/STCKE" >surrounded by other instructions wouldn't be sufficient to eliminate the >possibility of a data field, since in some contexts (like target of an >EXecute), instructions themselves may be "data" and could be mixed with >other data fields. > Yup.
>To do its thing, obviously Hourglass must also front-end those other >time services and not just deal with STCK./STCKE > But don't all those services funnel through STCK[E] at the base. How else would one get the time? It would need to zap STCK[E] instructions deep within those services. Risky business. I suppose one _might_ make a TCP/IP connection to port 13 or port 37 of a known timeserver. But why ever would one do that? (I've done it to estimate clock skew, before we bought an ETR.) How does it deal with STCK[E] instructions in LPA? And with REFRPROT? And with UNIX System Services? I suppose most of these things funnel through some point in Content Supervision where they can be hooked. And the Java VM. Are there any products that checksum their load modules, perhaps with the purpose of preventing meddling with license key expiration? Does CICS still bypass Content Supervision and load its own load modules for performance reasons, as was discussed here lately? >On 09/10/2012 05:01 PM, Charles Mills wrote: >> Yow! >> What he said. -- gil ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
