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Calling None-Secure method directly from Secure world

rising

Hi:

    If CPU is in secure state, and calling the none-secure world method. Dose this allowed or it will generat a security fault

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  • 0 Arm Employee Badge

    For Armv8-M, Secure code can call Non-secure functions (using BLXNS instruction).

    When this happen, the return address is automatically pushed to Secure stack, the and LR (link register) is updated to a special value called FNC_RETURN (function return. When Non-secure function ended and return with FNC_RETURN, the real return address is extract from Secure stack.

    With this method, it is not possible for Non-secure world to modify the actual return address.

    regards,

    Joseph

Reply
  • 0 Arm Employee Badge

    For Armv8-M, Secure code can call Non-secure functions (using BLXNS instruction).

    When this happen, the return address is automatically pushed to Secure stack, the and LR (link register) is updated to a special value called FNC_RETURN (function return. When Non-secure function ended and return with FNC_RETURN, the real return address is extract from Secure stack.

    With this method, it is not possible for Non-secure world to modify the actual return address.

    regards,

    Joseph

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