OpenMaidEngine/docs/engine-re.md

Native-engine reverse engineering (Ghidra + MCP)

Static RE of the unpacked AGE.EXE engine image, driving Ghidra 12.1.2 via the bethington/ghidra-mcp bridge. This is the home for decompiled native-op findings — the class of logic the scripts call but that lives compiled in the engine (decision→scene, call-script dispatch, op 0x60, the gfx command-buffer). Opcode semantics recovered here also flow into vm-map/opcodes.toml.

Related: docs/scjump-progression.md (the SCJUMP decoder that hit this wall), name-resolution.md §1 (call-script), vm-mapping-plan.md appendix (why the exe is packed + the runtime-dump route).

---

Runbook — the Ghidra + MCP loop

One-time setup (done 2026-07-07):

• MCP server: bethington/ghidra-mcp, cloned to S:\Game Hacking\ghidra-mcp. We used the prebuilt extension GhidraMCP-5.14.2.zip (installed in Ghidra via File > Install Extensions) — this skips the Maven/Java-21 build. The Python bridge runs from a venv (.venv, Python 3.11, pip install .); no uv needed. Registered in Claude Code via .mcp.json at the workspace root: {"mcpServers":{"ghidra":{"command":"S:\\Game Hacking\\ghidra-mcp\\.venv\\Scripts\\bridge-mcp-ghidra.exe","args":["--transport","stdio"]}}}.
• In Ghidra: enable the GhidraMCP plugin (File > Configure) and Tools > GhidraMCP > Start MCP Server (serves http://127.0.0.1:8089/). The bridge talks to that; Claude reaches the bridge over stdio.

Loading the engine image (IMPORTANT — the language gotcha):

• Import age-reimpl/build/engine-dump/range_00400000.bin (the module dump: 2,490,368 bytes, the full 0x400000 module image; VA→file offset = VA − 0x400000).
• Format = Raw Binary, Language = x86:LE:32:default, Image Base = 0x400000. Ghidra's language picker offers x86:LE:32:System Management Mode as the "closest" match — do NOT use it. SMM is a 16-bit segmented (segment:offset) variant for BIOS/SMRAM; it mis-decodes flat 32-bit code (it loaded with addresses like 0000:0000/0025:ffff and produced 0 functions). The plain default variant is correct and yielded 2,721 functions.
• We drove the (re)import over MCP: import_file(language="x86:LE:32:default", compiler_spec="windows", auto_analyze=false) → set_image_base(0x400000) before analysis (so absolute-address refs resolve) → run_analysis.
• Load sanity check (AGF-decoder landmark): at VA 0x474f23, CMP word ptr [ESI + 0x4], 0x4d42 (the BM/BMP-magic check) confirms the image is correctly based + decoded.
• Escalation (unused so far): bin/pe-sieve32.exe /pid <PID> /imp 3 /dmode 3 /dir <out> (run from PowerShell, not Git Bash — it mangles /flags) rebuilds the IAT into a clean PE. Only needed if raw-dump analysis is inadequate; it was fine for reading logic, so we stayed on the raw dump.

---

Master key — the opcode→handler dispatch table (2026-07-07, anchored)

The interpreter dispatches each op via a per-context handler table, fully anchored:

handler(op) = ctx[0x26c93 + op] (word index) = *(ctx + 0x9b24c + op*4) — ctx = the engine context (esi in handlers, thiscall; param_1 in the decompile of the registration routine).

The registration routine FUN_00413860 first fills 0x400 (1024) slots starting at ctx[0x26c93] with a default handler FUN_004162b0 (op 0's slot), then overrides specific opcodes: ctx[0x26c93 + op] = <handler_va>. So opcode = (word_index − 0x26c93). Cross-check: ctx[0x26e3f] = 0x427fb0 (byte offset 0x9b8fc) → op 0x26e3f − 0x26c93 = 0x1ac.

Why this matters: the Kelebek u00XXXXXX opcode names encode handler VAs from Kelebek's build, which drift in ours. This table resolves the real handler for any opcode in our image — the general fix for VA drift project-wide. To find op N's handler: read ctx[0x26c93 + N] from the FUN_00413860 decompile (or *(ctx + 0x9b24c + N*4) at runtime).

Other confirmed engine-context offsets (ctx/esi): +0x53d14 = current gfx-object index; +0x53d88 = per-object cmd-type table (stride 0x78 = 120 bytes); operand-fetch helper = call 0x41b940 (thiscall, ecx=ctx, arg = operand index → returns the operand value); FUN_00415f30(i) = a companion operand accessor.

---

Findings

op 0x1a2 (u00428010) is a GRAPHICS command-buffer op — NOT save, NOT decision→scene (2026-07-07)

The SCJUMP slice assumed u00428010 resolved a decision value to a scene. That premise is wrong, and pinning the real handler via the dispatch table above corrects two layers of confusion:

• VA-drift trap: Kelebek's u00428010 = op 0x1a2. But Kelebek's raw VA 0x428010, in our build, sits inside a different handler 0x427fb0, which is op 0x1ac (per the table: ctx[0x26e3f]=0x427fb0). Op 0x1ac is a save-path op — its handler formats %s\SAVE%2.2d.DAT (format string 0x571e70) and is multi-operand. Reading the raw VA gave the wrong opcode.
• Op 0x1a2's real handler = FUN_0042d360 (= ctx[0x26c93+0x1a2] = ctx[0x26e35]), argc 1. It: sets the current gfx-object cmd-type to 3 (*(ctx+0x53d88 + ctx[0x53d14]*0x78) = 3), fetches operand 1, formats a key with "%c%8.8x" (format string 0x5714e0) of (3, operand), and calls FUN_0042cf70(key, &operand). This is a graphics command-buffer registration op, not save and not scene-load.
• Consequence — the decision→scene premise is discredited. The FIELD snippet lookup(0x5f0ed, 0x62ccf); mov(ptr,1); lookup(0x5f0ed, 0x62ccf); u00428010(ptr) (next op 0x21b, also gfx-family) is a graphics/UI operation, not scene sequencing. So u00428010 does not resolve decision→scene. The real decision→scene mechanism is unidentified — it belongs with the call-script / script-load dispatch (name-resolution.md §1), the next target for this loop (now armed with the dispatch table to resolve the call-script handler directly).

Lesson: never analyze a native op by its Kelebek u00XXXXXX VA directly — always resolve the real handler through the dispatch table (ctx[0x26c93 + op]). The raw VA is off by whole functions.

---

op 0x03 (call-script) is a raw index into the SYS4INI file table — SOLVED (2026-07-07)

The long-deferred call-script <id> registry (name-resolution.md §1) is cracked. Resolved through the dispatch table (op 0x03 → ctx[0x26c93+3] = FUN_0041bc90), then the loader/resolver chain:

• FUN_0041bc90 (handler): fetches operand 1 (the id), bounds-checks call depth (≤ 0x26), pushes a script frame, and calls the loader.
• FUN_0040e980 (loader): opens the resource by id, reads the 0x20-byte SYS4 header, checks magic, allocates per-frame code/local buffers from the header var-counts, reads the bytecode body, and pushes a script frame (stride 0x1e = 30 dwords, indexed by ctx[0x14f45]). Returns to the caller when the callee ends.
• FUN_0044f390 (resolver — the key): record = [ctx+0x414] + id*0x50. The record is exactly the SYS4INI 80-byte layout {name[64], arc_id@0x40, file_number@0x44, offset@0x48, size@0x4c} (count = [ctx+0x40c], archive-name table = [ctx+0x410]). It tries a loose override first (CreateFileA on record.name → the mod/patch hook point), else opens archive [record.arc_id*0x100 + ctx+0x410], SetFilePointer to record.offset, size = record.size. High-byte-tagged ids (id & 0xff000000) select an alternate pack via [ctx+0x3028] — unused by the corpus (0/297 ids carry a high byte).

So call-script <id> = a direct RAW index into the SYS4INI global file table — the same table parse_sys4ini.py reads, but indexed without skipping @ placeholders (13208 records, 2 placeholders). There is no separate on-disk id→code registry; SYS4INI is the registry, and we already had it. Statically confirmed: all 297/297 distinct corpus call-script ids resolve to a .BIN script with a semantically-exact name (0x1ab→ADDITEM, 0x2ae7→MES, 0x143→BUNKI, 0x329d→CALCREVISE, 0x2add→CALCBTPARAM), 0 out-of-range, 0 pack-branch. Tooling: parse_sys4ini.py emits build/callscript-names.json (id→name); sys4load annotates call-script 0x1ab =ADDITEM.BIN; the whole build/disasm/*.asm call graph now reads by name. See name-resolution.md §1.

Companion — op 0x8f (call) is INTRA-script, not cross-script. Its handler FUN_0041fba0 sets [frame PC @+0x53d2c] = [frame codebase @+0x53d28] + operand*4 and pushes a return address on the per-frame return stack ([ctx+0x552e8]/[ctx+0x55248]). The operand is a code offset within the current script (matches header table T3, tag 0x8F = local call targets). So 0x8f is a local JSR; only 0x03 loads another script.

Follow-up (functional): the C# VM still stubs call-script. With the id→resource mapping now known, it can be implemented for real (load the target .BIN from the archive via the SYS4INI record, push a frame, run, return) — the unlock for subroutine-using scripts and, via the same path, decision→scene (scenes are just SCxxxx.BIN records loaded by their SYS4INI index).

---

op 0x215 (query-gfx-object?) is a native command-buffer op — settles the render drift as (b) (2026-07-07)

This is the canonical account of the background/sprite "drift" bug (background pinned off-centre / bottom-right, rest grey — Screenshot 2026-07-06 211353.png). It supersedes the earlier "drift = state-divergence, seed state and it's fixed" conclusion in docs/phase-a-slice-plan.md and the status memory, which are corrected to point here.

Resolved via the dispatch table (ctx[0x26c93 + 0x215]): the registration routine FUN_00413860 stores [ESI + 0x9baa0] = 0x42a0b0, so op 0x215's real handler is FUN_0042a0b0. (Kelebek's 0x421160 is VA-drift — it lands inside the unrelated FUN_00421090. Same lesson as 0x1a2: never trust a Kelebek raw VA.)

FUN_0042a0b0(ctx) does exactly two things:

1. *(ctx + 0x53d88 + ctx[0x53d14]*0x78) = 5 — writes cmd-type 5 into the current gfx-object record. A command-buffer registration side-effect, directly parallel to op 0x1a2 (FUN_0042d360) writing cmd-type 3. So 0x215 is part of the gfx command-buffer subsystem, not a pure query.
2. out = FUN_0047f280(FUN_0041b940(2)) — FUN_0041b940(2) fetches operand 2 (the bytecode handle key); FUN_0047f280 is a std::map::find over an engine-internal associative registry, returning the mapped value or 0xffffffff (not-found); FUN_00425fb0(1, out) writes it to operand 1. That registry is populated by sibling gfx ops — op 0x1a2's handler builds a "%c%8.8x" key and calls FUN_0042cf70, an open-addressing hash insert into the same kind of store.

(a) vs (b) — the verdict is (b). The value 0x215 returns is native command-buffer state: "has a gfx object already been registered under this handle?" (≥0 = existing → use its slot; -1 = new). That state lives in the engine's own registry, maintained by the gfx ops, not in the VM global bank. So seeding story-state globals cannot reproduce it — the drift is not the Phase-B state-divergence problem. Stubbing 0x215 returns a constant → label_12649's slot-select always takes one branch → every draw collapses onto slot 0 → the anchor-preserve math measures foreign-sized textures → cumulative drift.

Why the prior "state-divergence" conclusion was wrong. It was grounded in capture_gfx_objects.py, which polled the object-record array ([esi+0x53d64]) at ~2/s and saw only 3 persistent UI objects, "0 CG objects." But (i) the branch is driven by the map lookup (a different structure the poll never observed), and (ii) command-buffer records are transient — a 2/s poll can't prove CG records weren't used. Absence in that capture ≠ absence of the native path.

The fix is tractable and Frida-free. (b) does not mean an opaque native state machine. The subsystem is a modelable data structure: an object-record array (slot / geometry / cmd-type per object) plus a handle→object registry (a hash map). The gfx ops are inserts/queries/writes against these, and the inserts are bytecode-driven — so a faithful host-side model, with the gfx ops (0x1a2, 0x215, and the 0x212–0x21a family) executed instead of stubbed, rebuilds the state from the same scripts. The opcode- level summary lives in vm-map/opcodes.toml op 0x215.

---

Native walls backlog (targets for this loop)

• call-script dispatch — SOLVED (above): call-script <id> = raw SYS4INI file index.
• decision→scene — how 0x62ccf/the decision selects the next SCxxxx. Now narrower: scenes load via call-script/the same SYS4INI-index loader, so the open question is only where the decision value is turned into a scene id (a caller of SCJUMP; re-aimed away from u00428010).
• op 0x60 (u0041A270) — the rand-like value gating 1732/1755 SCJUMP decisions.
• gfx command-buffer — the 0x212–0x21a positioned-object subsystem (scjump-unrelated; the rendering drift). Understood, not unidentified (see the op 0x215 finding above): it's a native record array + a handle→object hash registry that the gfx ops insert/query/write. The drift verdict is settled — (b), a genuine native op, not state-divergence. Remaining work is implementation, not RE: model the registry + record array host-side and execute the gfx ops (0x1a2/0x215/0x212–0x21a) instead of stubbing — static, Frida-free.