AIX Version 4.3 Differences Guide

All of the following services are exported:
unsigned long long as_att64(vmhandle_t srval, int offset)
int
as_det64(unsigned long long addr64)
vmhandle_t as_geth64(unsigned long long addr64)
vmhandle_t as_getsrval64(unsigned long long addr64)
int
as_puth64(unsigned long long addr64, vmhandle_t srval)
int
as_seth64(unsigned long long addr64, vmhandle_t srval)
int
IS64U
The address space programming model for 64-bit introduces a copy of all the
32-bit interfaces appropriately scaled for 64-bit addresses. All of the 64-bit
services work properly under a 32-bit user address space or under a kproc as
well as a 64-bit user address space:
One additional non-exported service is provided:
adspace_t *getadsp64(unsigned long addr64)
The getadsp64() service exists to provide a bridge between the 64-bit and 32-bit
services. The adspace_t returned by getadsp64() may be passed to any of the
32-bit services, and it will work properly. The one exception to the example is that
32-bit as_att() will not support attaching anywhere other than the first adspace_t.
The advantage of using getadsp64() is the performance improvement of only
computing an adspace_t once per system call.
The concept of an adspace_t really does not exist with the new 64-bit interfaces;
getadsp64() is the only exception, and it is only for use with the 32-bit interfaces
internal to the kernel. The advantage of not having an adspace_t externalized is
that the width of an adspace_t is no longer surfaced to extensions. This saves the
extensions the overhead of having to compute another adspace_t every 4 GB.
Kernel extensions writing new code to enable 64-bit support that need the
address space services, should use the new *64 services instead of the current
32-bit services. The *64 services handle all the general cases for 64-bit and
32-bit address spaces. The 32-bit services will only work for addresses less than
4 GB outside the kernel.
How to Determine if this is a 64-Bit Address Space
The IS64U macro will return true if the user address space for the current process
is 64-bits. This macro is valid only in kernel mode. If used inside the kernel, this
will return the value of U.U_64bit directly. If used outside the kernel in an
extension, this will generate a subroutine call to the new kernel service:
_as_is64(). _as_is64() will simply return the value of the variable. U.U_64bit is
managed by exec() in vm_makeme64/32. IS64U is defined in user.h.
3.2.6.3 Shared Memory Management
The shared memory code is impacted for 64-bit support since it must attach
shared memory segments at large addresses. The functions shmat() and mmap()
will behave as follows regarding segment number (ESID) allocation:
• If no fixed address is specified, then allocation takes place from the
shmat()/mmap() pool at ESIDs: 0x70000000 - 0x7FFFFFFF.
• If a fixed address is specified by the user, then the allocation will be allowed
as long as the ESID is less than 0x80000000 and is not ESID 0-2,13, or 15.
54 AIX Version 4.3 Differences Guide