rr-debugger / rr-debugger/rr

Investigate emulating SYS_futex during recording

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C++
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Description

Followup to #673. We would need to work some magic with seccomp-bpf to allow us to distinguish entry to futex from entry to other syscalls, so that we could PTRACE_SYSEMU instead of PTRACE_SYSCALL the tracee into the call. But if we got that to work, emulating futex would avoid bugs like #673 (and the even worse hell that's going to break loose when we have to deal with robust futexes), and probably more importantly, gives us more control over thread scheduling.

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start by reading issue #673 and the recording path that handles futex and other syscalls; the payload does not name specific files or tests. The work is complete when syscall entry can distinguish futex from other calls, futex can be emulated during recording, and thread scheduling gains the described control.

Written by the indexing model from the issue text.

Assessment

Tech stack
cpp, linux
Domain
devtools, operating-systems
Issue type
Feature
Difficulty
5/5
Estimated time
Over a week
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
25/100

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