Back-to-back USR_SCHED, SYSCALLBUF_RESET events cause checksum divergence

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
25/100
Issue type
Bug
Clarity
Needs clarification
Activity status
Stale
Tech stack
cpp, linux
Domain
devtools, operating-systems

Research direction

Start by reproducing the unit-test sequence involving SYSCALLBUF_FLUSH, USR_SCHED, and SYSCALLBUF_RESET, then trace how checksum state and the syscallbuf byte counter are updated during recording and replay. Done means the checksum no longer diverges for this back-to-back event sequence.

Written by the indexing model from the issue text.

Description

This is relevant for checksumming at events other than syscall exit. I'm trying to checksum time-slice events in a last-ditch event to pin down #416 with checksumming, but on the unit tests we fail when the following occurs

-1018 (SYSCALLBUF_FLUSH)
-1020 (USR_SCHED)
-1016 (SYSCALLBUF_RESET)

The problem is that the syscallbuf byte counter won't be reset after we finish replaying the USR_SCHED (not until the SYSCALLBUF_RESET), but during recording it was reset when the checksum was made.

It's looking like checksumming was a fairly productive digression, but isn't going to catch #416. So I don't consider this specific issue very important.

Dominant language
C++
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Merged PRs (30d)
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