Provide a way in CMCP hook to access ECB control block to pass data to created ECB

The CMCP hook introduced in APAR PJ42117 did not provide a consistent way to update control block information in order to pass data to a created ECBs. This new hook is called from different places from CP segments and at each place the control block (IDSXFC) for new ECB is pointed by different base register. This makes it difficult to set data for new ECB from CMCP hook.

Additionally, the CMCP hook is not being invoked during FORKC processing in CCE4 copy member. Below is the piece of code from CCE4 copy member where user exit is being invoked but the call to hook is missing.

FORKFFG DS 0H @PJ25589
LG R9,CPMPAR @PJ25589 ZTPF11
LG R6,CPMCHD Get the child address @PJ25589 ZTPF11
UXITC CHECK=CMCP,NOTACTIVE=FORKOUT Go is exit not active @PJ33393
* *
* Call User Exit to allow the user to pass any *
* other ECB information from the parent ECB to the child ECB *
* *
* User Exit expects: R9 = Parent ECB *
* R2 = Pointer to 4 byte User *
* data field *
* R6 = Child ECB *
* *
LARL R2,CCE4PRM PASS POINTER TO 4 BYTE LOCATION ZTPF11
OC PGMNM,PGMNM Is this for Posix fork? @PJ28765
JNZ NOTPFORK0 No, bypass call to Posix. @PJ28765
SLR R2,R2 Indicate Posix fork() @PJ28765
NOTPFORK0 DS 0H @PJ28765
UXITC XP=CMCP WHERE USER CAN STORE DATA TO PASS ZTPF11
J FORKOUT ZTPF11
SPACE 1 ZTPF11
CCE4PRM DC F'3' ZTPF11
SPACE 1 @411.073
FORKOUT DS 0H @PJ25589
OC PGMNM,PGMNM Is this for Posix fork?
JNZ NOTPFORK2 No, bypass call to Posix.
CLNKC RTN=CPMPFRK2,TYPE=LOCAL
J FORK_RTN