The entry environment and parameters for the vnode and VFS operations are the same for 31-bit and 64-bit addressing. The PFS is always entered in AMODE 31, with a 31-bit parameter list address in R1 that points to a parameter list of 31-bit addresses. All calling parameters are below the 2-gigabyte line, although some of these parameters may contain 64-bit addresses of areas that are above the 2-gigabyte line.

The main consideration for 64-bit addressing is the user data buffers, which may require 64-bit addressing in the UIO, IOV, and MSGH structures. In general, the other user parameters are copied into the kernel below the 2-gigabyte line, and these copies are passed to the PFS.

The data length parameter for read and write-type operations with 64-bit addressing remains 31 bits long.