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Why set Trusted Firmware BL2 as Secure-EL1?

Emmy

Hi,

   I am studying Juno board trusted firmware.

   I'm not clear why is trusted firmware BL2 set to secure-EL1 instead of EL3.

   Thanks for your attention!

Emmy

  • 0 Arm Employee Badge

    Hi,

    I think largely because running everything at EL3 isn't a good design philosophy. Generally the code is partitioned so that it runs at the lowest privilege level needed to perform its function.

    Note that BL1 (now called AP_BL1), which does run at EL3, is typically executed from internal ROM which will have space constraints, so there's a good reason why the functionality of this boot stage is reduced to what is necessary,

    Hope that helps

    MarkN.

  • 0 in reply to Mark Nicholson

    Hi MarkN,

         I'm clear.   

         Thank you!

    Emmy