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Read non-secure DFAR from secure world

Jitesh Shah
Note: This was originally posted on 7th June 2012 at http://forums.arm.com

Hi,
I understand that the DFAR (Data Fault Address Register) is banked between the secure and the non-secure world.

I am writing a software where I need to access the DFAR of the non-secure world from the secure world (monitor mode). Is there a way to do that without going back to the non-secure world?
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  • Arm Employee Badge
    Note: This was originally posted on 7th June 2012 at http://forums.arm.com

    If its the same as the other banked registers, you should just have to set the SCR.NS bit.

    The SCR.NS bit controls which banked copy (secure/non-secure) of a CP15 register you access.  Monitor mode is always in the Secure world, so you can toggle the SCR.NS bit without actually changing security state.  Meaning that Monitor mode is the only mode that can access both banked copies of a CP15 register.
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  • Arm Employee Badge
    Note: This was originally posted on 7th June 2012 at http://forums.arm.com

    If its the same as the other banked registers, you should just have to set the SCR.NS bit.

    The SCR.NS bit controls which banked copy (secure/non-secure) of a CP15 register you access.  Monitor mode is always in the Secure world, so you can toggle the SCR.NS bit without actually changing security state.  Meaning that Monitor mode is the only mode that can access both banked copies of a CP15 register.
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