SVC      TITLE 'DMTSVC     (RSCS)      VM/370 - RELEASE 6'              00001000
*.                                                                      00002000
* MODULE NAME -                                                         00003000
*                                                                       00004000
*        DMTSVC                                                         00005000
*                                                                       00006000
* FUNCTION -                                                            00007000
*                                                                       00008000
*         THE  DMTSVC  MODULE  IS  THE  MSUP  SVC  INTERRUPT            00009000
*         HANDLER. DMTSVC  RECEIVES CONTROL  DIRECTLY ON  AN            00010000
*         SVC INTERRUPT.                                                00011000
*                                                                       00012000
* ATTRIBUTES -                                                          00013000
*                                                                       00014000
*        REUSABLE, EXECUTABLE DISABLED ONLY                             00015000
*                                                                       00016000
* ENTRY POINTS -                                                        00017000
*                                                                       00018000
*        DMTSVC -   DIRECTLY ON SVC INTERRUPT                           00019000
*                                                                       00020000
*                                                                       00021000
* ENTRY CONDITIONS -                                                    00022000
*                                                                       00023000
*        ENTERED FROM DISPATCHED PROGRAMMING UPON EXECUTION             00024000
*        OF A SVC INSTRUCTION.                                          00025000
*                                                                       00026000
*                                                                       00027000
* EXIT CONDITIONS -                                                     00028000
*                                                                       00029000
*        NORMAL -                                                       00030000
*                                                                       00031000
*        ON SVC C'F', CONTROL IS RETURNED TO THE INSTRUCTION            00032000
*        FOLLOWING THE CALLING SVC INSTRUCTION WITH SYSTEM              00033000
*        MASK DISABLED (EXCEPT FOR MACHINE CHECK).  THE                 00034000
*        EXECUTING TASK HAS BEEN UNDISPATCHED, AND ITS TASK ELEMENT     00035000
*        ADDRESS IS RETURNED IN GREG 14.                                00036000
*                                                                       00037000
*        ERROR -                                                        00038000
*                                                                       00039000
*        ON SVC OTHER THAN C'F', CONTROL IS RETURNED TO THE             00040000
*        INSTRUCTION FOLLOWING THE CALLING SVC INSTRUCTION WITH         00041000
*        SYSTEM STATUS UNMODIFIED.  THE SVC IS AN EFFECTIVE NOP.        00042000
         EJECT                                                          00043000
*                                                                       00044000
* CALLS TO OTHER ROUTINES -                                             00045000
*                                                                       00046000
*        NONE                                                           00047000
*                                                                       00048000
*                                                                       00049000
* EXTERNAL REFERENCES -                                                 00050000
*                                                                       00051000
*        NONE                                                           00052000
*                                                                       00053000
*                                                                       00054000
* TABLES / WORKAREAS -                                                  00055000
*                                                                       00056000
*        TAREA -    INTERRUPTED TASK'S SAVE AREA, TO SAVE STATUS        00057000
*        TASKE -    TASK ELEMENT, TO LOCATE TAREA                       00058000
*                                                                       00059000
*                                                                       00060000
*                                                                       00061000
* REGISTER USAGE -                                                      00062000
*                                                                       00063000
*        GPR13  =  CALLER'S TASK ELEMENT BASE                           00064000
*        GPR14  =  CALLER'S TASK SAVE AREA BASE                         00065000
*        GPR15  =  DMTSVC BASE REGISTER                                 00066000
*                                                                       00067000
* NOTES -                                                               00068000
*                                                                       00069000
*        NONE                                                           00070000
*                                                                       00071000
* OPERATION -                                                           00072000
*                                                                       00073000
*                                                                       00074000
*         THE ONLY FUNCTION OF SVC WITHIN THE RSCS SYSTEM IS            00075000
*         TO "UNDISPATCH"  (OR "FREEZE") AN  EXECUTING TASK.            00076000
*         SVC IS  NECESSARY TO  PERFORM THIS  FUNCTION SINCE            00077000
*         THE LEFT HALF OF THE ACTIVE PSW IS ACCESSABLE ONLY            00078000
*         THROUGH STORAGE  OF THE PSW  ON AN  INTERRUPT. THE            00079000
*         SVC  CODE  IS  NOT INSPECTED  BY  SUPEXT,  AND  IT            00080000
*         CURRENTLY HAS NO MEANING (SEE BELOW).                         00081000
*                                                                       00082000
*         THE RUNNING  TASK IS "UNDISPATCHED"  ON AN  SVC BY            00083000
*         MOVING THE  LEFT HALF  OF THE SVC  OLD PSW  TO THE            00084000
*         TASK  SAVE  AREA  RESUME PSW  FIELD,  STORING  THE            00085000
*         REGISTER CONTENTS  ON INTERRUPT  IN THE  TASK SAVE            00086000
*         AREA, AND SETTING THE RESUME  PSW ADDRESS FIELD TO            00087000
*         THE  CONTENTS  OF  REG.14   ON  INTERRUPT.  SUPSVC            00088000
*         RETURNS CONTROL  BY SETTING REG.14 TO  THE ADDRESS            00089000
*         OF THE  TASK ELEMENT  OF THE  "UNDISPATCHED" TASK,            00090000
*         AND  LOADING A  PSW  WITH ALL  MASK  BITS SET  OFF            00091000
*         (EXCEPT MACHINE  CHECK) AND  EXECUTION ADDRESS  AS            00092000
*         STORED IN THE SVC OLD PSW.                                    00093000
*                                                                       00094000
*                                                                       00095000
*.                                                                      00096000
         EJECT                                                          00097000
DMTSVC   CSECT                                                          00098000
         SPACE                                                          00099000
*        SUPERVISOR CALL INTERRUPT ENTRY POINT                          00100000
         USING SVECTORS,0          GET SVECTORS ADDRESSABILITY          00101000
         USING TASKE,R13           GET TASK ELEMENT ADDRESSABILITY      00102000
         SPACE                                                          00103000
         ST    R15,SSAVE           SAVE WORK REGS TEMPORARILY           00104000
         L     R15,NEWSVC+4        GET ADDRESS OF ENTRY POINT           00105000
         USING DMTSVC,R15          DEFINE ADDRESSING FOR SVC HANDLER    00106000
         CLI   OLDSVC+3,C'F'       IS IT A FREEZE REQUEST?              00107000
         BNE   SVCNOP              NOP FUNCTION IF NOT                  00108000
         L     R15,SSAVE           ALL DONE WITH LOCAL ADDRESSING       00109000
         STM   R13,R14,SSAVE       SAVE CONTENTS OF WORK REGISTERS      00110000
         L     R13,ACTIVE     REG.13 = ADDRESS OF CALLER'S TASK ELEMENT 00111000
         L     R14,TASKSAVE       REG.14 = ADDRESS OF CALLER'S TASK S/A 00112000
         SPACE                                                          00113000
         USING TAREA,R14           DEFINE TASK SAVE AREA DSECT ADDRESSA 00114000
         SPACE                                                          00115000
         MVC   TPSW(4),OLDSVC      SAVE LEFT HALF OF CALLER'S PSW       00116000
         STM   R0,R15,TGREG0       SAVE ALL OF THE CALLER'S REGISTERS   00117000
         MVC   TGREG13(8),SSAVE RESTORE REGS  13 & 14 TO CORRECT VALUES 00118000
         MVC   TPSW+4(4),TGREG14   SET REG.14 RETURN ADDR IN RESUME PSW 00119000
         SPACE                                                          00120000
         MVI   ACTIVE,X'00'        RESET ACTIVE FLAG                    00121000
         SPACE 1                                                        00122000
         MVI   NEWPSW,X'00'        SET MASK OFF FOR PSW TO BE LOADED    00123000
         MVI   NEWPSW+1,X'04'      KEY = 0, MACHINE CHECK ON, SUP MODE  00124000
         MVC   NEWPSW+5(3),OLDSVC+5 MOVE IN RETURN ADDRESS              00125000
         LPSW  NEWPSW         RETURN WITH OLD MASK IN OLDSVC FOR CALLER 00126000
         SPACE                                                          00127000
SVCNOP   EQU   *                                                        00128000
         L     R15,SSAVE           RESTORE R15                          00129000
         LPSW  OLDSVC              RESTORE PRE-SVC STATUS - NOP         00130000
         EJECT                                                          00131000
         COPY  RSSEQU                                                   00132000
         EJECT                                                          00133000
         COPY  SVECTORS                                                 00134000
         EJECT                                                          00135000
         COPY  TAREA                                                    00136000
         EJECT                                                          00137000
         COPY  TASKE                                                    00138000
         END                                                            00139000