re: locate the live ScriptMission/ScriptPhase without a debugger
Unblocks the phase experiment, which was stuck because '38 enemies died' could not say whether the right ones did. Chasing craft->squadron was the wrong angle: the script VM keeps that table itself, indexed by the .ssb symbol-table-2 index. Route: find the .ssb header in guest memory (0xAB840010 for a Stage 02 run), code base = filebase + 0x24, scan for a word equal to it, then VALIDATE arithmetically -- [ScriptMission+44] must equal filebase + symtab1 offset + 4. Measured 0xAB874C94, predicted 0xAB874C94, exact. A second candidate that also pointed at the code base failed that check and was discarded; without it either would have looked plausible. ScriptPhase+324 -> +4 is an array of 122 per-unit records -- exactly the size of Stage 02's symbol table 2, an independent confirmation of the index space. [ScriptMission+40] reads 1 in a phase-1 mission. The mirror at [*(0x828F35F8)+236] that three earlier runs polled reads 0, because ChangePhase only posts once the ordinal exceeds 1 -- so +40 is the real counter and is reachable from /dev/shm with no debugger. Flagged rather than asserted: the three objective squadrons read state=1 with a LIVE object pointer in a mission where nothing has been shot, which does not fit the built-in table's '1 = gone'. Reading state != 2 as destroyed would be a plausible-but-wrong inference; the encoding needs pinning first. New tool tools/re-capture/squadron_state.py, verified end to end against the manual reading.
This commit is contained in:
Sylpheed RE agent
76
docs/re/script-runtime-probe.md
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76
docs/re/script-runtime-probe.md
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# Reading the live script state — the real phase counter, and per-squadron liveness
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Status: ✅ `ScriptMission` and `ScriptPhase` located in a running mission with no
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debugger, validated arithmetically; ✅ the true phase ordinal read live;
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🟡 the per-unit `state` encoding needs care.
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This unblocks [mission-phase-membership](mission-phase-membership.md), which was
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stuck because "38 enemies died" could not say whether the *right* ones did.
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Chasing craft→squadron was the wrong angle: **the script VM already keeps that
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table**, indexed by the `.ssb` symbol-table-2 index.
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Tool: `tools/re-capture/squadron_state.py`.
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## ✅ Locating the objects, without gdb
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1. Find the **`.ssb` header** in guest memory — 20 bytes of version + code offset
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+ the two symbol-table offsets, distinctive enough to hit once. For a Stage 02
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run it sat at **`0xAB840010`**.
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2. `code base = file base + header code offset` (`0x24`) → `0xAB840034`.
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3. `[ScriptMission+24]` **is** that code base, so scan for a word equal to it.
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4. **Validate arithmetically, not by eye:** `[ScriptMission+44]` must equal
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`file base + symtab1 offset + 4`. Measured `0xAB874C94`; predicted
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`0xAB840010 + 0x34C80 + 4 = 0xAB874C94`. Exact.
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That check is what makes this trustworthy — the candidate is confirmed against a
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number taken from the file on disc, not against "it looks like a pointer". A
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second candidate that also pointed at the code base failed it and was discarded.
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```
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ScriptMission 0xBC7A2A20
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+4 ScriptPhase* = 0xBE14DD80 +20 state = 1 ("phase running")
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+24 code base = 0xAB840034 +28 pc = 0xAB84007C
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+40 PHASE ORDINAL = 1 +44 symtab1 = 0xAB874C94 ✓
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ScriptPhase 0xBE14DD80
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+196 finished = 0 +244 symtab1 = 0xAB874C94 +324 unit array = 0xBC43B560
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```
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`ScriptPhase+324` → `+4` → an array of per-unit records. It holds **122
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records — exactly the size of Stage 02's symbol table 2**, which is an
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independent confirmation that the index space is the one the bytecode uses.
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## ✅ The real phase counter reads 1 — the mirror was the wrong field
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`[ScriptMission+40]` reads **1** in a phase-1 mission. The runtime mirror at
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`[*(0x828F35F8)+236]`, which three earlier runs polled, reads **0** — because
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`ChangePhase` is only posted once the ordinal exceeds 1.
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So the mirror is not a phase readout at all in phase 1, and **`+40` is**. It is
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reachable from `/dev/shm` with no debugger, which is what made three runs of
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polling the wrong address avoidable in hindsight.
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## 🟡 The per-unit `state` encoding is not what the summary implies
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For the three phase-1 objective squadrons, early in a fresh mission:
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```
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ADN110 idx=1 obj=True state=1
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ADN111 idx=2 obj=True state=1
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ADN112 idx=5 obj=True state=1
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records with state==2 (active): 27-29 of 122
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```
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The built-in table describes `+16` as *"2 = active; 1/3/4 = gone/dead/invalid"*.
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But these three have a **live object pointer and state 1**, in a mission that has
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barely started and where nothing has been shot. So either state 1 does not mean
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"gone", or it means "not yet deployed" — **not settled**, and worth pinning
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before any conclusion is drawn from it. Reading `state != 2` as "destroyed"
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would be exactly the kind of plausible-but-wrong inference this corpus keeps
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catching.
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## What this makes possible
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The decisive phase experiment is no longer blocked on attribution: sample
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`[ScriptMission+40]` and the three squadrons' records together over a run, and a
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phase advance becomes directly observable along with the state change that caused
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it. That run has **not** been done yet.
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144
tools/re-capture/squadron_state.py
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144
tools/re-capture/squadron_state.py
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#!/usr/bin/env python3
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"""Read per-SQUADRON liveness straight out of the running ScriptPhase.
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Why this exists: the phase-1 clear condition polls three named squadrons
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(ADN110/111/112), but nothing mapped a live craft back to its roster squadron,
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so "38 enemies died" could not say whether the *right* ones died
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(mission-phase-membership.md). Chasing craft->squadron was the wrong angle --
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the script VM already keeps exactly that table.
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From the built-in disassembly (isl-builtins.md):
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[phase+324] runtime unit array
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[[phase+324]+4] -> array of per-unit record pointers
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record[idx*4] indexed by the .ssb SYMBOL TABLE 2 index
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record +4 live object (NULL = absent)
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record +16 state (2 = active; 1/3/4 = gone/dead/invalid)
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record +128 / +132 HP / max HP
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So a squadron's state is one indexed read, no attribution needed.
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Finding the ScriptPhase without a debugger:
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1. the loaded .ssb code is in guest memory -- search for a distinctive run of
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its bytes;
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2. `[phase+232]` is the code base, so scan for a word equal to that address;
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3. the candidate phase is that word's address - 232;
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4. validate: `[cand+244]` and `[cand+324]` must both be plausible pointers.
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Usage: squadron_state.py <Stage02.ssb> [names...]
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"""
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import struct
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import sys
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sys.path.insert(0, __file__.rsplit('/', 1)[0])
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import gmem
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import isl
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HDR_LEN = 20 # version, +4, code offset, symtab1, symtab2 -- distinctive
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def _fd_extents(f, size):
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# gmem.extents takes a file DESCRIPTOR, not a file object.
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return gmem.extents(f.fileno(), size)
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def _find(f, size, needle):
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out = []
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for start, end in _fd_extents(f, size):
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f.seek(start)
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remaining, base, prev = end - start, start, b''
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while remaining > 0:
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chunk = f.read(min(1 << 22, remaining))
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if not chunk:
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break
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buf = prev + chunk
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i = buf.find(needle)
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while i >= 0:
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out.append(base - len(prev) + i)
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i = buf.find(needle, i + 1)
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prev = chunk[-len(needle):]
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base += len(chunk)
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remaining -= len(chunk)
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return out
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def u32(f, va):
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off = gmem.va_to_off(va)
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if off is None:
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return None
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f.seek(off)
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b = f.read(4)
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return int.from_bytes(b, 'big') if len(b) == 4 else None
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def find_mission(f, size, ssb):
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"""Locate the live ScriptMission for this .ssb.
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1. find the .ssb HEADER in guest memory -- 20 bytes of version + offsets,
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distinctive enough that it hits once;
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2. code base = file base + the header's code offset;
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3. `[ScriptMission+24]` is that code base, so scan for a word equal to it;
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4. validate with `[+44]`, which must equal file base + symtab1 offset + 4 --
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an exact arithmetic check, not a heuristic.
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"""
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hdr = ssb[:HDR_LEN]
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code_off = struct.unpack_from('>I', ssb, 0x08)[0]
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sym1_off = struct.unpack_from('>I', ssb, 0x0C)[0]
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for off in _find(f, size, hdr):
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for filebase in gmem.off_to_vas(off):
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code_base = filebase + code_off
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want_44 = filebase + sym1_off + 4
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for poff in _find(f, size, struct.pack('>I', code_base & 0xFFFFFFFF)):
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if poff % 4:
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continue
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for pva in gmem.off_to_vas(poff):
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m = pva - 24
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if u32(f, m + 44) == want_44:
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return m, filebase
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return None, None
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def read_states(f, mission, sym2, names):
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phase = u32(f, mission + 4)
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arr = u32(f, phase + 324) if phase else None
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base = u32(f, arr + 4) if arr else None
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idx = {n: i for i, (_t, n) in sym2.items()}
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out = {'phase_ordinal': u32(f, mission + 40),
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'phase_obj': phase, 'finished': u32(f, phase + 196) if phase else None,
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'units': {}}
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active = 0
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if base:
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for i in sorted(sym2):
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rec = u32(f, base + i * 4)
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if not rec:
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continue
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if u32(f, rec + 16) == 2:
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active += 1
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for n in names:
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i = idx.get(n)
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rec = u32(f, base + i * 4) if i is not None else None
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out['units'][n] = None if not rec else {
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'idx': i, 'obj': bool(u32(f, rec + 4)), 'state': u32(f, rec + 16)}
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out['active_records'] = active
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return out
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if __name__ == '__main__':
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ssb = isl.load(sys.argv[1])
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sym2 = isl.symbols(ssb, 2)
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names = sys.argv[2:] or ['ADN110', 'ADN111', 'ADN112']
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import os
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path = gmem.mem_path()
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with open(path, 'rb', buffering=0) as f:
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size = os.path.getsize(path)
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m, fb = find_mission(f, size, ssb)
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if m is None:
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print('ScriptMission not located'); sys.exit(1)
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print('file base 0x%08X, ScriptMission 0x%08X' % (fb, m))
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r = read_states(f, m, sym2, names)
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print(' phase ordinal = %s (the REAL counter; the +236 mirror reads 0 in phase 1)'
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% r['phase_ordinal'])
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print(' ScriptPhase = 0x%08X finished=%s' % (r['phase_obj'] or 0, r['finished']))
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print(' records active = %d of %d' % (r['active_records'], len(sym2)))
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for n, v in r['units'].items():
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print(' %-10s %s' % (n, v))
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