ARM Architecture Reference Manual ARMv7-A and ARMv7-R edition

ARMv4 and ARMv5 Differences
MRC p15,0,,c5,c0,1 ; Read CP15 Instruction Region Access Permissions Register
MCR p15,0,,c5,c0,1 ; Write CP15 Instruction Region Access Permissions Register
c5, Memory Region Extended Access Permissions Registers (DEAPR and IEAPR)
The two Memory Region Extended Access Permissions Registers are:
The Data or unified Extended Access Permissions Register, DEAPR.
The Instruction Extended Access Permissions Register, IEAPR. The IEAPR is implemented only
when the processor implements separate data and instruction memory protection region definitions.
Whether an implementation includes Extended Access Permissions Registers is IMPLEMENTATION DEFINED.
A Memory Region Extended Access Permissions Registers hold the access permission bits AP[3:0] for each
of the eight memory protection regions.
The format of a Memory Region Access Permissions Register is:
31 28 27 24 23 20 19 16 15 12 11 8 7 4 3 0
AP7 AP6 AP5 AP4 AP3 AP2 AP1 AP0
APn, bits [4n+3:4n], for n = 0 to 7
Access permission bits AP[3:0] for memory protection region n.
For details of the significance of these bits see Table H-11 on page AppxH-29.
If the implementation does not permit the requested type of access, it signals an abort to the processor.
Accessing the Memory Region Extended Access Permissions Registers
To access the Memory Region Extended Access Permissions Registers you read or write the CP15 registers
with set to 0, set to c5, set to c0, and set as follows:
2 if there is only a single set of protection regions
when there are separate memory protection regions for data and instructions:
— 2 to access the Data Region Extended Access Permissions Register
— 3 to access the Instruction Region Extended Access Permissions Register.
For example:
MRC p15,0,,c5,c0,2 ; Read CP15 Data or unified Region Extended Access Permissions Register
MCR p15,0,,c5,c0,2 ; Write CP15 Data or unified Region Extended Access Permissions Register
MRC p15,0,,c5,c0,3 ; Read CP15 Instruction Region Extended Access Permissions Register
MCR p15,0,,c5,c0,3 ; Write CP15 Instruction Region Extended Access Permissions Register
AppxH-46 Copyright © 1996-1998, 2000, 2004-2008 ARM Limited. All rights reserved. ARM DDI 0406B