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

Application Level Programmers’ Model
Use of HandlerBase
ThumbEE handlers are entered by reference to a HandlerBase address, defined by the TEEHBR. See
ThumbEE Handler Base Register (TEEHBR) on page A2-71. Table A2-13 shows how the handlers are
arranged in relation to the value of HandlerBase:
The IndexCheck occurs when a CHKA instruction detects an index out of range. For more information, see
CHKA on page A9-15.
The NullCheck occurs when any memory access instruction is executed with a value of 0 in the base register.
For more information, see Null checking on page A9-3.
Note
Offset from HandlerBase Name Value stored
Table A2-13 Access to ThumbEE handlers
-0x0008 IndexCheck Branch to IndexCheck handler
-0x0004 NullCheck Branch to NullCheck handler
+0x0000 Handler_00 Implementation of Handler_00
+0x0020 Handler_01 Implementation of Handler_01
... ... ...
+(0x0000 + 32n) Handler_ Implementation of Handler_
... ... Implementation of additional handlers
Checks are similar to conditional branches, with the added property that they clear the IT bits when taken.
Other handlers are called using explicit handler call instructions. For details see the following sections:
HB, HBL on page A9-16
HBLP on page A9-17
HBP on page A9-18.
A2-72 Copyright © 1996-1998, 2000, 2004-2008 ARM Limited. All rights reserved. ARM DDI 0406B