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Tock Core Notes 2021-10-08

doc/wg/core/notes/core-notes-2021-10-08.md

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Tock Core Notes 2021-10-08

Attendees

  • Amit Levy
  • Leon Schuermann
  • Alexandru Radovici
  • Hudson Ayers
  • Jett Rink
  • Philip Levis
  • Gabe Marcano
  • Johnathan Van Why
  • Vadim Sukhomlinov
  • Brad Campbell

Updates

  • Brad: Hard/impossible to get debug printing traits for everything, but does work for printing the memory map. PR is open and updated.
  • Phil: Using autogenerated registers for OpenTitan. Plan to keep them separate files for now (since they change often). Eventually merge them into the driver file once stabilized.
    • No longer just constants, actually generating the register macro now.
  • Jett: Going to update the time HIL to remove the 'a lifetime.

AppID

  • https://github.com/tock/tock/blob/appid/doc/reference/trd-appid.md
  • End of section 4.
  • Challenge: generate compiled binary, then want to include TBF header. Integrity protection needs to cover code binary and headers, but not the credentials header.
  • Header has length. Need to pick some length, then compute header value and then insert in TBF header.
  • Should an app be signable serially? Or do all signatures have to happen at once?
  • Do signatures stack? Or does the second signature sign the previous signature?
    • Idea: signature 2 signs over previous signature. Benefit would be could add an arbitrary number of signatures.
  • Verifier decides how to handle if there are multiple signatures.
  • Examples would help with why multiple signatures.
    • Do Tock users want to do this?
    • Work on use cases.
  • Idea: put signature/credentials in a "container" separate from TBF.
  • Idea: put signatures at the end, perhaps as some sort of list.
  • Various technical implementations proposed and discussed.
  • note: ARM MPU requires power of 2, appending to the binary would today double the length.
  • Signatures could be large (kilobytes) so reserving space could add a fair bit of speculative overhead.

UART HIL

PR Merges

  • To squash or not to squash?