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Matthew Stanley
b3bfdd9330
Three-layer faithful-core fix for the exception-return contract, root-caused
live over TCP on a deterministic dbg-build repro (vblank authority vetoed
forever while the guest spun in the kernel idle loop, in_exception stuck 1):
1. Interpreter RFE backend parity: dirty-RAM RFE now calls
psx_rfe_mark_escape() exactly like the recompiled opcode and every
overlay shard (ABI v12), and dirty_ram_dispatch_inner takes a pending
escape at the committed transfer before local dirty flow can keep
interpreting the resumed code inside psx_check_interrupts' window.
2. Legacy-sentinel deliveries arm the escape too: the old blanket decline
assumed a sentinel delivery always resumes AT the sentinel, but guest
TCBs never hold the sentinel (Fix B anti-leak), so a kernel
ReturnFromException restore resumes at an approximate real PC with no
exit path armed. The take site preserves the legacy contract: a resume
landing ON the sentinel still exits through the sentinel detector.
3. Same-thread completion of a sentinel delivery via explicit RFE /
ReturnFromException converts to the legacy exit (restore interrupted
GPRs, pc=0, continue the live host chain) keyed on the structural
entry_tcb == exit_tcb test - otherwise the approximate TCB PC surfaces
up the trampoline, severs the live chain, and the run dies one hop
later on an un-re-enterable mid-function PC ("execution completed").
Validated: production build passes the previously-fatal splash transition
(frames 4717+ at 60fps, was deterministic death at 1385 x3 runs); dbg build
advances past the wedge (was frozen at exactly 1385); all runtime tests +
structural guards pass (guards extended to pin the interp RFE contract).
Known follow-up: the PSX_DEBUG_TOOLS build still loses one kernel CD event
through a third timing path at the same site - tracked as an open
foundation item; production config unaffected.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>