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Cortex-A9 cant enter monitor mode

Sebastian Meisheit
Note: This was originally posted on 20th July 2012 at http://forums.arm.com

Hi,

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?

Greets
Sebastian
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  • Arm Employee Badge
    Note: This was originally posted on 20th July 2012 at http://forums.arm.com

    It sounds like the the secure-world debug has been disabled, so JTAG is restricted to doing "normal world" workloads. The "approved" approach of entering monitor mode is to use the SMC instruction, and so this should still work (although if secure debug has been disabled you won't be able to see anything happening, you'll just reappear in the normal world some time later.

    Iso
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  • Arm Employee Badge
    Note: This was originally posted on 20th July 2012 at http://forums.arm.com

    It sounds like the the secure-world debug has been disabled, so JTAG is restricted to doing "normal world" workloads. The "approved" approach of entering monitor mode is to use the SMC instruction, and so this should still work (although if secure debug has been disabled you won't be able to see anything happening, you'll just reappear in the normal world some time later.

    Iso
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