This is the kernel part of the dynamic profiling/tracing framework created by Martin Pieuchot (mpi@), unfortunately the userland parts btrace(8) (and the bt(5)

This is the kernel part of the dynamic profiling/tracing framework created by Martin Pieuchot (mpi@), unfortunately the userland parts btrace(8) (and the bt(5) manual) were not linked to the build for the 6.7 release, so those manuals are not available online. Besides mailing list postings, there isn't too much available for now. But btrace(8) & bt(5) together describe a utility and language that's supposed to be compatible with Linux bpftrace (but an entirely different implementation).