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

When Monitor debug-mode is configured, abort vector catches are ignored in v6 Debug
// and v6.1 Debug, but UNPREDICTABLE in v7 Debug.
if a_match && DBGDSCR == ‘10’ then
if UInt(DBGDIDR.Version) < 3 then
a_match = FALSE;
else
UNPREDICTABLE;
return match || a_match;
Watchpoints
Debug Events
If invasive debug is enabled, the Debug_CheckDataAccess() function checks WRP matches for each data
access. If the implementation includes IMPLEMENTATION DEFINED support for watchpoint generation on
memory hint operations, or on cache maintenance operations, the function also checks for WRP matches on
the appropriate operations. If a match is found the function calls WatchpointDebugEvent(). If the debug event
is not permitted, it is ignored by the processor.
On a simple sequential execution model:
for a synchronous watchpoint, the Debug_CheckDataAccess() test is made before the data access
for an asynchronous watchpoint, the Debug_CheckDataAccess() test is made after the data access.
For more information see Synchronous and Asynchronous Watchpoint debug events on page C3-18.
The WRPMatch() function checks an individual WRP match. In ARMv7, it is IMPLEMENTATION DEFINED
whether WRP matches use eight byte lanes or four. The WRPUsesEightByteLanes() function returns TRUE if
they use eight byte lanes and FALSE if they use four. Using eight byte lanes is permitted only in ARMv7.
boolean WRPUsesEightByteLanes()
For these functions the parameters read, write, privileged and secure are determined at the point the access
is made, and not from the state of the processor at the point where WRPMatch() is executed. For swaps,
read = write =TRUE.
// Debug_CheckDataAccess()
// =======================
boolean Debug_CheckDataAccess(bits(32) address, integer size, boolean read,
boolean write, boolean privileged, boolean secure)
// Do nothing if debug disabled;
if DBGDSCR == ‘00’ then return;
match = FALSE;
// Each byte accessed by the data access is checked
for byte = address to address + size - 1
for N = 0 to UInt(DBGDIDR.WRPs)
if WRPMatch(N, byte, read, write, privileged, secure) then match = TRUE;
if match then WatchpointDebugEvent();
return;
ARM DDI 0406B Copyright © 1996-1998, 2000, 2004-2008 ARM Limited. All rights reserved. C3-35