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Which component will program TZASC?

Sahil

I have read in one ARM document

The TrustZone Address Space Controller (TZASC) is an AXI component which partitions its slave address range into a number of memory regions. The TZASC can be programmed by Secure software to configure these regions as Secure or Non-secure,
and will reject Non-secure transactions to a region that is configured as Secure.

In the highlighted statement it is written that "secure software" will we configuring TZASC.

I want to know that if secure software also includes "Trusted OS" or only Code running in EL3/monitor mode can configure the TZASC.

Thanks

Sahil

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    Hi Sahil,

    my long experience is with ARMv7-A Architecture.
    In ARMv7-A both monitor mode and supervisor mode runs in PL1, and both modes (in secure world) can be used for configuring the TZASC.

    In ARMv8-A, ARM completely changed the Previlige Level classification, and the monitor mode runs in EL3, while the supervisor mode runs in EL1. Anyway, both modes have previliged access in the secure side, so I would say that might be possible to configure the TZASC also in both modes.

    Sandro 

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    Hi Sahil,

    my long experience is with ARMv7-A Architecture.
    In ARMv7-A both monitor mode and supervisor mode runs in PL1, and both modes (in secure world) can be used for configuring the TZASC.

    In ARMv8-A, ARM completely changed the Previlige Level classification, and the monitor mode runs in EL3, while the supervisor mode runs in EL1. Anyway, both modes have previliged access in the secure side, so I would say that might be possible to configure the TZASC also in both modes.

    Sandro 

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