SVC table

The SVC table is a system data area that contains one eight-byte entry for each system-defined or user-defined SVC instruction. Locate the SVC table as follows:

1. Find the CVTABEND field in the CVT control block. This points to the SCVT control block.
2. The SCVTSVCT field in the SCVT points to the SVC table.

Each word entry in the SVC table contains the following information:

• Byte 0, bit 0 contains the AMODE.
• Bytes 0-3 contain the SVC entry point address.
• Byte 4 contains the SVC type and authorization:

  		Type
  000.	....	is type 1
  100.	....	is type 2
  110.	....	is type 3 or 4
  001.	....	is type 6
  ....	0...	is an unauthorized SVC
  ....	1...	is an authorized SVC
  ....	.1..	is an extended SVC
  ....	..1.	is a non-preemptive SVC
  ....	...1	SVC can be assisted.

• Byte 5 contains the SVC attributes:

  		Attribute
  1...	....	SVC can be issued in access register mode.

• Byte 6 indicates which locks are to be obtained by the SVC first level interruption handler (FLIH) before the SVC routine is processed:
  • X'80' is LOCAL lock.
  • X'40' is CMS lock.
  • X'20' is SRM lock.
  • X'10' is SALLOC lock.
  • X'08' is DISP lock.