handoff: VSync/event-wedge fixes + iterate 2.A–2.BC research notes
Source changes (dormant parity infra, retained from iterate 2.AI/2.AO): - xenia-kernel/exports.rs: nt_create_event manual_reset polarity + related event wiring - xenia-gpu/mmio_region.rs: D1MODE_VBLANK_VLINE_STATUS hardcode parity Also lands the audit-runs/ analysis notes (.md/.txt/.json digests) for the iterate 2.x VSync/0x10e8/0x1004 wedge investigation. Raw trace dumps (.jsonl/.gz/.csv/.stdout) and agent worktrees (.claude/) are gitignored as regenerable local artifacts — see memory + HANDOFF for the running findings. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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MechaCat02
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audit-runs/phase-c13-game-dat-files-tbl/investigation.md
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audit-runs/phase-c13-game-dat-files-tbl/investigation.md
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# Phase C+13 investigation — NtCreateFile `game:\dat\files.tbl`
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## Predecessor state (from Phase C+12)
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Cold-vs-cold first divergence at `tid_event_idx=103862` on the
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canary tid=6 → ours tid=1 main chain:
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```
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canary: NtCreateFile(path="game:\\dat\\files.tbl") -> 0xc0000034 (STATUS_OBJECT_NAME_NOT_FOUND)
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ours: NtCreateFile(path="game:\\dat\\files.tbl") -> 0x00000000 (STATUS_SUCCESS, synth-empty stub)
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```
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Verified from the C+12 archived JSONLs:
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- `xenia-rs/audit-runs/phase-c12-NtQueryFullAttributesFile/ours-cold.jsonl`
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events 103860-103862: import.call → kernel.call → kernel.return = 0.
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- `xenia-rs/audit-runs/phase-c12-NtQueryFullAttributesFile/canary-cold-tid6-250k.jsonl`
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events 103860-103862: same import.call → kernel.call → kernel.return = `0xc0000034`.
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Canary's next event (idx 103863): `RtlNtStatusToDosError(0xc0000034) -> 2`
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(ERROR_FILE_NOT_FOUND). Sylpheed has proper NOT_FOUND handling and
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continues; the synth-empty was masking the correct branch.
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## Canary semantics (xboxkrnl_io.cc:39-111)
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`NtCreateFile_entry` is a thin wrapper:
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1. Translate the `OBJECT_ATTRIBUTES.name` ANSI_STRING to a path.
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2. Path validation: `IsValidPath` → `STATUS_OBJECT_NAME_INVALID` on
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reject.
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3. Resolve the `root_directory` handle if non-zero.
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4. Call `kernel_state()->file_system()->OpenFile(...)`.
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5. **Return the `OpenFile` status verbatim.** If the file isn't
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present in any mounted device, that's `STATUS_OBJECT_NAME_NOT_FOUND`
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(`VirtualFileSystem::ResolvePath` returns nullptr for unresolved
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paths, which `OpenFile` translates to NOT_FOUND).
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6. On success: alloc handle and write to `handle_out`.
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For `game:\dat\files.tbl` specifically: the `game:` symlink points
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to the disc device. The disc image ISO doesn't contain `dat/files.tbl`
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(disc dump omission — likely a region-specific or build-time-only
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file). `OpenFile` returns NOT_FOUND, the function returns NOT_FOUND.
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## Ours pre-fix (exports.rs `open_vfs_file`)
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`open_vfs_file` had three paths:
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1. **Empty path** (root-of-device) → synth-empty handle (special-cased
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for `NtCreateFile("game:\")` disc-validation probe).
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2. **`cache:` prefix** → host-FS-backed via `open_cache_file` (AUDIT-038).
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3. **Otherwise**: call `vfs.read_file(&path)`. On `Ok(bytes)` return
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handle. **On `Err(e)`: synth a zero-byte file and return SUCCESS.**
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The (3) `Err` branch was the synth-empty fallback. Its docstring
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acknowledged two rationales:
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> 1. Writable system partitions (`cache:`, `partition0:`, `partition1:`)
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> aren't backed by the disc — we synth so opens succeed.
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> 2. Disc files that didn't make it into the ISO rip — returning
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> NOT_FOUND would make Sylpheed's boot validator call
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> `XamShowDirtyDiscErrorUI` → dashboard exit.
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But rationale (1) was already covered by the AUDIT-038 `cache:`
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short-circuit, and rationale (2) is empirically WRONG: canary returns
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NOT_FOUND for `game:\dat\files.tbl` and Sylpheed continues — there
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is no `XamShowDirtyDiscErrorUI` event in canary's trace anywhere
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near idx 103862. The synth-empty was misleading the boot trajectory
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in a non-canary direction.
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## Fix shape
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Two surgical changes:
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1. New helper `is_disc_prefix(raw_path: &str) -> bool` that
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recognises `game:\`, `d:\`/`D:\`, and `\Device\Cdrom0\` (the
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subset of `path::DEVICE_PREFIXES` that resolves to the read-only
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disc).
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2. `open_vfs_file` captures the raw path via
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`crate::path::object_attributes_raw_name` (alongside the existing
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normalised `path`). In the `Err(e)` arm, if `is_disc_prefix(&raw_path)`,
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return `STATUS_OBJECT_NAME_NOT_FOUND` (mirroring canary). Otherwise
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keep the legacy synth-empty.
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The `cache:` short-circuit is upstream of this branch and unchanged;
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its existing NOT_FOUND-on-FILE_OPEN-miss behaviour is preserved.
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## Tests
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- `is_disc_prefix_recognises_disc_aliases` (12 assertions, mix of
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disc and non-disc prefixes including case variants).
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- `nt_create_file_game_prefix_missing_returns_not_found` — primary.
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- `nt_create_file_cdrom_prefix_missing_returns_not_found` —
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`\Device\Cdrom0\` alias.
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- `nt_create_file_non_disc_prefix_missing_still_synthesizes` —
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regression guard for `\Device\Harddisk0\Partition1\sys.bin`.
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## Risk analysis (pre-fix)
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- **Sylpheed might crash on NOT_FOUND**: REFUTED. Canary returns
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NOT_FOUND, then Sylpheed calls `RtlNtStatusToDosError` and
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continues; +712 events of further progress observed in cold-vs-cold
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(no fault, no `XamShowDirtyDiscErrorUI`).
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- **Reading-error #23 regression**: matched-prefix MUST grow, not
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shrink. Cold-vs-cold confirms 103862 → 104574 (+712); no regression.
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- **Sister-chain regression**: confirmed unchanged for all 5 sister
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chains (see `cold-vs-cold-result.md`).
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- **Stable digest shift**: expected; the synth-empty was emitting
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one extra kernel.call/return pair (synth-success path); removing
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it for disc paths drops `imports` 40447 → 40390 (-57). Phase B
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`image_loaded_sha256` is unchanged.
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