ac0ad579fd
Nothing here changes what a tool computes; it changes where tools look. - tools/re-capture: 33 censuses globbed /work/sylph_extract, a path that has existed nowhere since /work became a clone, so they matched nothing and printed empty results. They now resolve the disc through a new disc.py from $SYLPHEED_DISC and exit loudly without it (the #44 fix, generalised). Nine scripts that imported siblings from the retired Reborn checkout or an old session scratchpad now import from their own directory. unitgroup.py only needs the variable when --pak is not given. - sylpheed-xex: the loader only ever uses the XEX2 retail key. The dead devkit key and a doc comment claiming a devkit fallback that does not exist are gone; Project Sylpheed is a retail XEX2, so no XEX1 key either. - sylpheed-viewer: real_font_rasterizes looked for /tmp/sylph_extract and so always skipped. It reads $SYLPHEED_DISC now, and passes against the disc. - Comments and docs that named xenia-rs, the Reborn repository or /work/*.pe as places to look now name sylpheed.db, Canary's ppc_context.h and the flat .pe; docs/re/README.md no longer says the native Canary build does not run. Historical records keep their original paths: findings that were measured against /work/xenia-rs/sylpheed.db still say so. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
115 lines
6.0 KiB
Markdown
115 lines
6.0 KiB
Markdown
# Reverse-engineering knowledge base
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This directory is the **spec-side** of the clean-room: it records what the original
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*Project Sylpheed* binary **does** (behaviour) and how its **data is laid out**, so that
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the Rust port can be implemented **from these specs** without re-deriving anything and
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without ever copying original code.
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It exists to answer one question fast: *"do we already know how X works, and how sure are we?"*
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---
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## The one rule that matters
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> **Never document a claim more confidently than the evidence supports, and never
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> paste original code here.**
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A wrong-but-confident note is worse than no note: someone builds on it and the bug hides
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for weeks. Every entry therefore carries an explicit **confidence** and its **evidence**.
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This mirrors the project method — *measure the oracle, never infer; refute before believing.*
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### Clean-room firewall
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- ✅ Allowed: behaviour descriptions, field offsets/types, formulas, state machines,
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observed input→output pairs, and **references** to the original by address
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(`sub_821B68C0`) or to `sylpheed.db`.
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- ❌ Forbidden here and in `crates/`: pasted decompiled C/C++ or verbatim disassembled
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function bodies presented as the thing to reimplement. Cite the address; describe the
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behaviour in your own words. Disassembly is a tool for *understanding*, not a source to copy.
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---
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## Confidence levels
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| Level | Meaning | Bar to reach it |
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|-------|---------|-----------------|
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| `CONFIRMED` | Behaviour verified against ground truth. | ≥2 independent observations **or** one observation cross-checked against an oracle (canary framebuffer, a known-correct value, a second code path). |
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| `PROBABLE` | Strong single-source inference. | One clean observation, or an unambiguous static read of the disassembly. |
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| `HYPOTHESIS` | Educated guess, not yet tested. | Anything else. Must say what would confirm/refute it. |
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### The status markers
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The table above is the *confidence* scale. The markers that appear in
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`BACKLOG.md` and the `structures/` pages are a separate, and until now undefined,
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vocabulary. They mean:
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| Marker | Meaning |
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|---|---|
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| ✅ | Confirmed — verified against ground truth. |
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| 🟡 | Partial: true as far as it goes, or true under a stated assumption. |
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| ❔ | Open question. Nobody has answered it yet. |
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| 🔴 | **Refuted** — shown false — **or blocked by something the container cannot do.** |
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| ❌ | A specific claim that was tried and failed. Prefer 🔴. |
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| 🚧 | Work started and not finished. |
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**🔴 never means "we have not run it yet."** That is ❔ or 🚧. Reserve 🔴's
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"blocked" sense for a real limit of the box — no push credentials, no hardware
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Vulkan (lavapipe only), or a decision only the user can make. The box *can* run
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the emulator, script input, screenshot, read guest memory, and build and test
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Rust, so "needs a run" is never a blocker. This paragraph exists because the
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marker was undefined for 98 uses and three of them were mislabelled that way.
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**Promotion requires new evidence, not re-reading the old evidence.** A `HYPOTHESIS` that
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"looks right again" is still a `HYPOTHESIS`. Only an *independent* check promotes it.
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If evidence later contradicts an entry, **demote it and record the contradiction** — do
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not silently edit the conclusion.
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---
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## When to document
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- **Right after** a function/structure crosses from `HYPOTHESIS` to at least `PROBABLE` —
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before moving to the next code path, so the knowledge isn't lost or re-derived.
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- **Whenever confidence changes** (up or down) — append to the Evidence log, don't overwrite.
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- **Not** while it's still a pure guess with no evidence — a one-liner in the relevant
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backlog/plan is enough until there's something to stand on.
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## What to document
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- **Functions/code paths** → `docs/re/functions/<name>.md` (one file per function or tight cluster).
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- **Data structures / formats** → `docs/re/structures/<name>.md`.
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- Keep the index in [`INDEX.md`](INDEX.md) (one line each: name · confidence · one-line summary).
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Use the templates: [`_TEMPLATE.function.md`](_TEMPLATE.function.md),
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[`_TEMPLATE.structure.md`](_TEMPLATE.structure.md).
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---
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## How we find and confirm code paths (the toolchain)
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Everything joins on the **guest virtual address (PC)** — code addresses are fixed by the
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XEX load, identical across our emulator and canary.
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- **Static (cheap, try first):** `sylpheed.db` at the repository root (DuckDB: 25 676
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functions, xrefs, strings, vtables, imports; git-ignored — build it with
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`sylph-xexdb dis <ISO> --db sylpheed.db --analyze sql --quiet`, then re-stamp names with
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`tools/apply_re_symbols.sql`). Query with `tools/zq.py` — `zq.py grep <str>`,
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`zq.py xref <addr>`, `zq.py dis <lo> <hi>`, `zq.py fn <pc>`. Entry points are usually a
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**string** (`zq.py grep MSG_DEMO`) or an **import** (movie/XMA API) xref'd back to the loader.
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- **Dynamic (when static is ambiguous):** Xenia Canary, below. The `xenia-rs` probe suite
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this bullet used to recommend (`--pc-probe`, `--mem-watch`, `--lr-trace`,
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`--dump-addr`) went with that emulator when it was retired on 2026-09-16. For static
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`.rdata` reads that `--dump-addr` served, read the `.pe` directly: it is a flat VA dump,
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file offset = `VA − 0x82000000`.
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- **Oracle (correctness ground truth):** canary, in either of two builds — the **Wine
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cross-build** in `xenia-canary/build-cross/bin/Windows/Debug/` (launched by
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`run-canary-safe.sh`) or the **native Linux build** in `xenia-canary-native/` (launched by
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`run-canary-native-safe.sh`). This is the only emulator that reaches the in-game menu; our
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retired `xenia-rs` never got past the intro video. Use canary to *observe output*
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(capture its framebuffer for texture colours), not usually to instrument code — though both
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builds compile, so small C++ probes + rebuild are possible when needed.
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Run **muted, one emulator process at a time**, point it at the real ISO.
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> ⚠️ **VA-equality caveat:** join **code** by PC (fixed), but **never** assume a data VA
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> holds the same bytes across emulators — allocators differ. Compare data by content/layout.
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