Cortex-A9 cant enter monitor mode
Posted 20 July 2012 - 01:49 PM
I am using pandaboard with Cortex-A9MP (2x Cortex-A9) and connect to processor_0 by JTAG and Lauterbach hardware debugger.
When i try to change from system mode to monitor mode by change of CPSR mode bits, i get an debugger error "Emulator function blocked by device security".
When i execute the ARM instruction "smc 1", nothing happens.
The "Secure Configuration Register" and "Secure Debug Enable Register" cannot be read and are marked as "???????" by the debugger, which indicates i am in non-secure mode.
My question: What might block monitor mode access?
Posted 20 July 2012 - 01:58 PM
This post has been edited by isogen74: 20 July 2012 - 01:58 PM
Posted 20 July 2012 - 02:07 PM
In terms of the SMC #1 instruction doing nothing - I'm pretty sure it doesn't exactly what it is meant to. Sets off a SMC exception, triggering an entry to Mon mode. It is just the handler is doing an immediate (or almost immediate) return - so you end up back where you started. And you can't see this happening because Secure debug is disabled. You could prove this to yourself by looking at the CCNT to see if time has elapsed.
More generally, it is quite rare to get access to the Secure world on the easily available commercial dev boards.