Indicating support for 64-bit virtual addressing

A PFS indicates support for 64-bit user virtual addressing during initialization with:

pfsi_addr64    Indicates the PFS supports 64-bit user virtual addresses in
               the UIO, IOV, and MSGH structures.   PfsiAddr64  in PL/X.

A user indicates 64-bit addressing to the PFS with the following fields and structures:

u_addr64       Indicates that this UIO, and any associated IOV and/or MSGH
               when present, uses 64-bit addresses.   FuioAddr64 in PL/X.
u_buff64vaddr  A 64-bit field that contains the virtual address of the area
               being passed.   FuioBuff64VAddr in PL/X.

The IOV and MSGH structures have corresponding 64-bit formats, IOV64 and MSGH64.

When an application program in AMODE 64 calls a z/OS UNIX service, 64-bit user addressing is assumed and is used by the LFS. This does not necessarily mean that the 64-bit address values are actually greater than 2 gigabytes. Most 64-bit addresses will come from C programs that have been compiled with LP64, which makes all longs and pointers 64 bits by default, regardless of whether the program's heap is above the 2-gigabyte line.