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Monitor stack  pointer configuration in non secure mode

naveen venugopal
Note: This was originally posted on 28th December 2011 at http://forums.arm.com

Hi

Please help me to understand whether the monitor stack pointer has to be configured in the non secure mode in the boot sequence.
I understand that all the other stack pointers(usr, svc, fiq ,irq ) has to be configured for the non secure area.

But should i configure the monitor stack pointer also in non secure mode????
Please help
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  • Arm Employee Badge
    Note: This was originally posted on 3rd January 2012 at http://forums.arm.com

    Simple answer is - no.

    You have a "Secure Monitor" which is a bit of software responsible for switching between the Secure and Normal worlds.  The "Secure Monitor" software executes mainly in "Monitor mode".  When the processor is "Monitor mode" it is ALWAYS in the Secure world.

    To initialize any of the Monitor mode registers (lr_mon, sp_min, spsr_mon) you need to be in Monitor mode.  Whenever you are in Monitor mode you are in the Secure world.

    As something said, the boot code for the Secure world will be responsible for setting up Monitor mode/Secure Monitor.  The Normal world code should not need to do anything related to the Monitor.
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  • Arm Employee Badge
    Note: This was originally posted on 3rd January 2012 at http://forums.arm.com

    Simple answer is - no.

    You have a "Secure Monitor" which is a bit of software responsible for switching between the Secure and Normal worlds.  The "Secure Monitor" software executes mainly in "Monitor mode".  When the processor is "Monitor mode" it is ALWAYS in the Secure world.

    To initialize any of the Monitor mode registers (lr_mon, sp_min, spsr_mon) you need to be in Monitor mode.  Whenever you are in Monitor mode you are in the Secure world.

    As something said, the boot code for the Secure world will be responsible for setting up Monitor mode/Secure Monitor.  The Normal world code should not need to do anything related to the Monitor.
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