The diagram claimed the entry/ret target sits at aligned_top-8 and r15 at
aligned_top-56. The code does (top & ~15) - 8 then a -= 8 before the first
write, so entry actually lands at aligned_top-16 and r15 at aligned_top-64.
Confirmed by single-stepping the shim's ret under llmdbg: the entry slot is
at an address with %16==0, giving the required rsp%16==8 on entry. Code was
correct; only the comment was wrong (and would mislead a maintainer).
A minimal Config::exact(1) program with two actors doing a fixed number of
yield_now() calls. No I/O/timers/channels, so the instruction stream stays
centered on the naked-asm switch. Frame-pointer-friendly. Intended for
single-threaded inspection under a debugger (e.g. llmdbg).
smarm-dev