System Control
ARM DDI 0500D
Copyright © 2013-2014 ARM. All rights reserved.
4-243
ID021414
Non-Confidential
Table 4-218
shows how the LL bits in the Status field encode the lookup level associated with
the MMU fault.
To access the DFSR:
MRC p15, 0, <Rt>, c5, c0, 0; Read DFSR into Rt
MCR p15, 0, <Rt>, c5, c0, 0; Write Rt to DFSR
4.5.49
Instruction Fault Status Register
The IFSR characteristics are:
Purpose
Holds status information about the last instruction fault.
Usage constraints
This register is accessible as follows:
Configurations
IFSR (NS) is architecturally mapped to AArch64 register IFSR32_EL2.
See
Instruction Fault Status Register, EL2
on page 4-98
.
There are separate Secure and Non-secure copies of this register.
Attributes
IFSR is a 32-bit register.
There are two formats for this register. The current translation table format determines which
format of the register is used. This section describes:
•
IFSR when using the Short-descriptor translation table format
.
•
IFSR when using the Long-descriptor translation table format
on page 4-244
.
IFSR when using the Short-descriptor translation table format
Figure 4-123
shows the IFSR bit assignments when using the Short-descriptor translation table
format.
Figure 4-123 IFSR bit assignments for Short-descriptor translation table format
Table 4-218 Encodings of LL bits associated with the MMU fault
Bits
Meaning
0b00
Reserved
0b01
Level 1
0b10
Level 2
0b11
Level 3
EL0
(NS)
EL0
(S)
EL1
(NS)
EL1
(S)
EL2
EL3
(SCR.NS = 1)
EL3
(SCR.NS = 0)
-
-
RW
RW
RW
RW
RW
31
13 12 11 10 9 8
4 3
0
RES
0
0
ExT
FS[4]
RES
0
FS[3:0]
RES
0