Tock Core WG meeting notes 2024-11-01

Attendees

• Amit Levy
• Leon Schuermann
• Benjamin Prevor
• Brad Campbell
• Hudson Ayers
• Johnathan Van Why
• Pat Pannuto
• Alexandru Radovici

Updates

Treadmill-CI:

• GPIO tets are working, mpu_walk_region and button_test are working
• RPI5 libaries for gpio created small issues button_test
• Within one week nrf tests in tock repo

Add StreamingProcessSlice helper, based on ProcessSliceBuffer design

• https://github.com/tock/tock/pull/4208
• Adds StreamingProcessSlice wrapper for streaming data from kernel to userspace
• Based on ProcessSliceBuffer design with modified semantics
• Improves documentation and buffer handling code
• One can use StreamingProcessSlice as a receive buffer for IPC
• It's hard to test because there is no upstream ADC driver
• Amit merged the PR

PR Reviews

• Discussing a PR about capability pointers (formerly meta pointers)
• Concerns about naming conventions and potential confusion with hardware capabilities
• Discussion about whether to merge current PR and handle naming changes later
• Need for clear documentation of design and abstraction layers

EWSN Tutorial Planning

• Tutorial happening in ~5 weeks
• Expected attendees: Brad, Tyler, Anthony, and Pat
• Hardware currently in San Diego
• Total conference attendance ~130, tutorial attendance TBD
• Action items:
  • Schedule planning call for next week
  • Verify nothing is broken
  • Polish existing content
  • Brad working on nonvolatile storage driver upgrade
  • Switch to new streaming slices discussed earlier
  • Resolve infrastructure build questions
  • Consider sustainability of tutorial materials

GCC/Build System Discussion

• https://github.com/tock/libtock-c/pull/470
• Debate about printing commands during build process
• Discussion about whether to suppress command output with @ symbol
• Concerns about consistency with rest of build system

CHERI Implementation Progress

• Meta pointer PR renamed to capability pointer

x86 port progress

• Two parallel efforts for x86 external clemency:
  1. Rewriting (Bobby)
  2. Rendering necessary parts including big flags (Zane)
• Ongoing discussion about naming conventions and type definitions
• Need for TRD (technical requirements document) updates or extension

Action Items

1. Schedule EWSN tutorial planning call for next week
2. Review capability pointer PR in more depth
3. Synthesize current PR changes and identify controversial/separable parts
4. Further discussion needed on x86 kernel PR comment
5. Review TRD 104 section 3.2 regarding return values

Open Questions

• Relationship between capability pointers and IPC
• How to handle tutorial environment setup for attendees
• Definition and scope of capability pointers in non-CHERI architectures
• Whether to merge current PR and handle naming changes later