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AM6442: Processor SDK Linux: secure boot authentication U-Boot proper -> Linux

Raimar Sandner
Prodigy 50 points

Part Number: AM6442

Tool/software:

Hello,

Upon reviewing the K3 secure boot flow image in the Processor SDK Linux (10_01_10_04) documentation, I understand that all stages are authenticated through System Firmware Authentication and Decryption Requests, as detailed in the TISCI documentation.

However, it appears that this is not the case for the transition from U-Boot proper to Linux. In reality, this stage follows a more conventional approach: the public key is embedded in the U-Boot device tree blob (which is authenticated by TISCI in the previous stage), and the signatures of the images are embedded in the FIT image that is loaded.

Is this understanding correct? Additionally, is there a specific reason why U-Boot proper does not utilize TISCI API calls for authentication?

Thank you in advance for your assistance!

Best regards,
Raimar

  • +1
    TI__Guru* 79050 points

    Hi Raimar,
    Yes, your understanding is right.
    There's change on u-boot proper verifying the kernel FIT image starting from SDK 9.x, where the generic u-boot FIT signature verification with supporting the signed configuration is used instead of TIFS TISCI API to verify the kernel FIT image.
    The rational is verifying u-boot binary with ROM/TIFS to establish SoC-level RoT secure boot which make it possible to use the generic u-boot FIT signature verification flow for the rest of secure boot chain...
    Best,
    -Hong