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TMS320F28335: How strong is the CSM module and understanding about CSM

Han SeungJae
Intellectual 980 points

Part Number: TMS320F28335

Hello,

This is a novice student who is using the board for the first time.

Please understand that my question may be abstract or may not understand it.

I have a question about the CSM module.

when i look at the related documentation, i can set the password to check inspecting contents of memory ,
prevent to execute external memory code and leakage of memory contents through the JTAG port
This means that if user do not put the correct password in the key register, can user accept that it is never accessible?

As an additional question,

if the tms320f28335 board is connected to the PC through communication,

how can user get the authentification( using password) from the outside?

Regards,

Han

  • 0
    TI__Guru* 87155 points
    Han,

    I asked our security expert to clarify your questions.
    Please expect the reply in a day or two.

    Thanks and regards,
    Vamsi
  • 0 in reply to Vamsi Gudivada
    Intellectual 980 points
    Thanks, Vamsi.

    I will wait for your reply.

    Regards,
    Han
  • 0
    TI__Guru** 117441 points

    Hi,

    This means that if user do not put the correct password in the key register, can user accept that it is never accessible?

    That is correct for JTAG access and code running from non-secure memory. Code running from secure memory has access to content in secure memory.

    if the tms320f28335 board is connected to the PC through communication,

    how can user get the authentification( using password) from the outside?

    Not very clear on this query. You can always sent the password via any communication interface and then in your user SW running on the device, extract the password and write to KEY register to unlock the device. 

    Regards,

    Vivek Singh

  • 0 in reply to Vivek Singh
    Intellectual 980 points
    Thanks for reply, Vivek
    As far as I know, it is possible to make calls that are in secure memory when running in non-secure memory.
    I know that program counters can move to secure or non-secure memory.
    When running in secure memory, can access it in secure memory as you say.

    Is what I said right?

    Are there checking for passwords every time program counter move from unprotected memory to protected memory?
    As far as I know, I know to check the value of the key during the boot phase

    I want to know what circumstances the password (key value) is checked.

    Regards,
    Han
  • 0 in reply to Han SeungJae
    TI__Guru* 95315 points
    As far as I know, it is possible to make calls that are in secure memory when running in non-secure memory.

    In this case, access to data in secure memory will be blocked by the CSM.

    I know that program counters can move to secure or non-secure memory.

    True, but secure contents can only be accessed by code running in secure memory.

    When running in secure memory, can access it in secure memory as you say.

    Correct.

    Are there checking for passwords every time program counter move from unprotected memory to protected memory?

    It is not so much about "checking for passwords". It is that the CSM will block access to the contents in secure memory.

    I want to know what circumstances the password (key value) is checked.

    If a device is secure, the CSM will always monitor access to protected resources.