z/OS UNIX System Services File System Interface Reference
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VFS server considerations for 64-bit addressing

z/OS UNIX System Services File System Interface Reference
SA23-2285-00

For a server that is entirely 31-bit, no changes are required.

For v_op calls in AMODE 31:
  • A server may set FuioAddr64 and use 64-bit addressing within the UIO to address its own buffers for the v_rdwr, v_readdir, and v_readlink operations.
  • The UIO itself and all the calling parameters must be 31-bit addressable.
For v_op calls in AMODE 64:
  • The server must set FuioAddr64 appropriately to indicate whether a 31-bit or a 64-bit buffer address is being passed.
  • Register 1 and the parameter list must all be 64-bit addresses; the parameters themselves may be above or below 2 gigabytes.
  • BPX1 callers must use the BPX4 entry names.
Parent topic: VFS servers

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