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

Debug Events
For each of the memory hint instructions, PLD and PLI, it is IMPLEMENTATION DEFINED whether the
instruction generates Watchpoint debug events. If either or both of the PLD and PLI instructions normally
generates Watchpoint debug events, the behavior must be:
For the PLI instruction:
— no watchpoint is generated in a situation where, if the instruction was a real fetch rather than
a hint, the real fetch would generate a Prefetch Abort exception
— in all other situations a Watchpoint debug event is generated.
For the PLD instruction:
— no watchpoint is generated in a situation where, if the instruction was a real memory access
rather than a hint, the real memory access would generate a Data Abort exception
— in all other situations a Watchpoint debug event is generated.
When watchpoint generation is conditional on the type of memory access, a memory hint instruction
is treated as generating a load access.
It is IMPLEMENTATION DEFINED whether the following cache maintenance operations generate Watchpoint
debug events:
Clean data or unified cache line by MVA to PoU, DCCMVAU
Clean data or unified cache line by MVA to PoC, DCCMVAC
Invalidate data or unified cache line by MVA to PoC, DCIMVAC
Invalidate instruction cache line by MVA to PoU, ICIMVAU
Clean and Invalidate data or unified cache line by MVA to PoC, DCCIMVAC.
When Watchpoint debug event generation by these cache maintenance operations is implemented, the
behavior must be:
the cache maintenance operation must generate a Watchpoint debug event on a DVA match,
regardless of whether the data is stored in any cache
when watchpoint generation is conditional on the type of memory access, a cache maintenance
operation is treated as generating a store access.
For regular data accesses, the size of the access is considered when determining whether a watched byte is
being accessed. The size of the access is IMPLEMENTATION DEFINED for:
memory hint instructions, PLD and PLI
cache maintenance operations.
Watchpoint debug events are precise and can be synchronous or asynchronous:
a synchronous Watchpoint debug event acts like a synchronous abort exception on the memory access
instruction itself
an asynchronous Watchpoint debug event acts like a precise asynchronous abort exception that
cancels a later instruction.
For more information, see Synchronous and Asynchronous Watchpoint debug events on page C3-18.
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