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3.3. Processor architecture

The most significant architectural changes apply to the ARM processors that implement the architectural Security Extensions. Currently these are the:

  • ARM1176JZ(F)-S™ processor

  • Cortex™-A8 processor

  • Cortex-A9 processor

  • Cortex-A9 MPCore™ processor

Each of the physical processor cores in these designs provides two virtual cores, one considered Non-secure and the other Secure, and a mechanism to robustly context switch between them, known as monitor mode. The value of the NS bit sent on the main system bus is indirectly derived from the identity of the virtual core that performed the instruction or data access. This enables trivial integration of the virtual processors into the system security mechanism; the Non-secure virtual processor can only access Non-secure system resources, but the Secure virtual processor can see all resources.

Figure 3.1. : Modes in an ARM core implementing the Security Extensions

Figure 3.1. : Modes in an ARM core implementing the Security
Extensions

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