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https://github.com/RetroPortingToolKit/psxrecomp
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Matthew Stanley
2cbbbfc4da
Three related defects in the interp observability rings. All three share a
failure mode that is worse than an error: the tool reports an empty result
that is indistinguishable from a real finding. "total: 0" reads as proof the
events never happened.
1. callret_watch armed on `lo != 0`, making address 0 an off switch rather
than a legal window floor. `lo=0 hi=0x200000` — the obvious spelling of
"watch the whole address space" — replied ok and recorded nothing.
Measured on one build, identical but for the floor:
lo=0x00000000 hi=0x00200000 -> total 0
lo=0x00000004 hi=0x00200000 -> total 468732
Four bytes of window between an empty ring and half a million call
resolutions. This cost real time during beads-eio.3.59: an
interp->compiled call route was briefly believed absent when the ring was
simply never on.
Arm on a NON-EMPTY window (hi > lo) instead. `lo=0` is now an ordinary
floor. Note that `{"lo":"0"}` was the DOCUMENTED disarm spelling
(TCP_COMMANDS.md), so that contract is kept explicitly rather than broken:
lo=0 with no hi still disarms, and now says so in the reply. Added
`disarm=true` as the unambiguous spelling. A `lo` with no `hi` is refused
outright instead of silently inheriting the previous ceiling (usually 0,
i.e. an empty window) — that was the second way to arm nothing by accident.
2. s3_smear_watch had the same `lo`-nonzero gate, so lo=0 with a real hi
recorded nothing while answering ok. Same fix. It already cleared `hi`
whenever `hi` was omitted, so `{"lo":"0"}` naturally lands on an empty
window and still disarms — no special case needed there.
Both commands now report `armed`, and callret_watch's dump carries `armed`
plus the active window, so an empty read can always be told apart from an
unarmed one.
3. The xprobe JAL/JALR watched-target list was six guest addresses from two
specific titles COMPILED INTO the shared runtime (an MMX6 card-load flow
and a Tomba target). Every other game therefore watched nothing, silently:
the `watched` dump came back empty and gave no hint that the build was
incapable of watching anything. Same defect class as beads-eio.3.21, and
the direct reason the JAL call site was unusable while measuring
beads-eio.3.59 — only the JALR callret ring could be used there.
The list is now configured, never compiled in: `xprobe_watch` TCP command
to get/set, or PSX_XPROBE_WATCH in the environment so targets are watched
from instruction zero without a rebuild. Default EMPTY — no title is
privileged — and a read with nothing watched says so rather than looking
like a negative result. Matched on the normalised address so KSEG and
physical forms both work.
Verified against Ape Escape, headless, RelWithDebInfo:
- PSX_XPROBE_WATCH=0x8002C0E4 -> watching that target from boot
- xprobe_watch targets=<two addrs> -> count 2; the `watched` dump then
carries 41 JALR records for 0x8002C0E4 and 21 for 0x8002C14C, with full
frame/cycle/src/sp/ra context. This title could previously watch NOTHING.
- xprobe_watch targets= (empty) -> count 0 plus an explanatory note
- callret_watch lo=0 hi=0x200000 -> armed true, total 77484
- callret_watch lo=0 -> disarmed, legacy spelling named
- callret_watch lo=0x40000 -> refused, window left unchanged
- callret_watch disarm=1 -> disarmed
- s3_smear_watch lo=0 hi=0x200000 -> armed true (previously silent)
- pre-fix build, callret lo=0 hi=0x200000 -> plain ok, total 0 (the trap)
TCP_COMMANDS.md regenerated for the new command. Note the regen also picks
up rows that had drifted on master beforehand: `--check` already failed on
pristine master (index said 292, the servers register 304), which is why the
count line jumps 292 -> 305 rather than by one.