52c30d82a7
Round-37 anchor reframe: both engines install the SAME static .rdata vtable
0x820A183C at [0x828E1F08]. Instance VAs differ only because of ε-class
allocator divergence (audit-043). vtable bytes byte-identical; the user
prompt's "factory/registry" framing was falsified.
Phase A walkthrough (rounds A1..A8):
- A.1 canary --audit_jit_prolog_pc=0x821741C8: tid=6, r3=0xBCCC4A80 (= inner
sub-object of [0x828E1F08]'s singleton), LR=0x822F1D5C (return-from-bctrl
inside sub_822F1AA8)
- A.2 found tid=6 spawn site sub_821746B0 at PC 0x82174824 spawning
entry=sub_821748F0 ctx=BC365700/BC366DA0. sub_822F1AA8 ALSO spawns a
second thread (entry=sub_822F1EE0 ctx=BCE24A40) at PC 0x822F1B08
- A.3 sub_822F1AA8 has 2 callers, both in sub_8216EA68 (its sole caller is
sub_824AB748 = entry_point)
- A.4 ours mirror probe: sub_821746B0 enters, [0x828E2B14] gate passes,
ExCreateThread fires returning handle 0x1070 (= tid=13). Ours' tid=13
IS the same logical thread as canary's spawned silph initializer
- A.5 canary --audit_jit_prolog_pc=0x821749C0: fires only 2× on short-lived
tid=17, tid=26 (the spawned initializers — NOT tid=6)
- A.6 canary --audit_jit_prolog_pc=0x822F1AA8: fires 1× on tid=6 with
r3=0xBCE24A40 LR=0x8216EE14 (the second sub_822F1AA8 call site)
- A.7 canary --audit_jit_prolog_pc=0x824AB748 (entry_point): fires on
tid=00000006. CONFIRMS canary's tid=6 = canary's main thread.
Verdict: identical call chain entry_point → sub_8216EA68 → sub_822F1AA8 in
both engines; same controller (ε-divergent VA, byte-identical fields).
Canary's main thread stays in sub_822F1AA8's dispatcher loop firing
sub_821741C8 ~1678×/30s. Ours' main thread exits the loop and thread-joins
on the spawned initializer (tid=13), which is itself wedged on handle 0x1078
forever.
Loop exit is gated by bit 28 of [r30+0] (the controller's flag word). Same
value 0x21 at function entry in both engines. Some code between entry and
loop check sets bit 28 in ours but not in canary. Mem-watch on 0x40d09a40
shows zero guest stores in ours' 50M parallel run — setter is either a
kernel-side store, computed alias, or probe-quantum-elided JIT store.
Phase B classification: Class 3a (state-divergence on controller object).
The vtable is the same; the controller's bit 28 evolves differently during
sub_822F1AA8 setup. Class 4 (synthesis) is now less attractive since we
correctly reach the dispatcher with the right inputs — we just exit too
soon.
Phase C will need either JIT instrumentation to identify the bit-28 setter,
or a kernel-side hook to clear bit 28 on entry to the loop check site.
Findings notes:
- round-A4b-ours-spawn-gate/FINDINGS.md (spawn topology + tid mapping)
- round-A8-ours-822F1AA8-trace/FINDINGS.md (full loop structure + bit-28 gate)
New reading-error class #18: probe-output anchor misframing (singleton[VA]=X
vtable=Y was misread as "Y is canary-only vtable" when Y is the same
.rdata vtable in both engines).
Branch: iterate-2C/silph-ui-spawn-trace off master @ 229b46c.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
168 lines
7.3 KiB
Markdown
168 lines
7.3 KiB
Markdown
# Round-A1..A4 findings — canary tid=6 spawn chain & divergence frontier
|
||
|
||
## Anchor reframe (round-37 misread corrected)
|
||
|
||
The "factory/registry layer divergence at [0x828E1F08]" framing is falsified.
|
||
Both engines install the SAME static-XEX `.rdata` vtable `0x820A183C` at the
|
||
singleton's `[+0]`. The instance VAs differ only because of ε-class allocator
|
||
divergence (audit-043).
|
||
|
||
| Probe | Canary | Ours |
|
||
|----------------------------|----------------------|----------------------|
|
||
| `[0x828E1F08]` | 0xBC22C910 (heap) | 0x40111910 (heap) |
|
||
| `[[0x828E1F08]+0]` vtable | 0x820A183C | 0x820A183C (SAME) |
|
||
| `vtable[+0]` thunk | 0x82175330 | 0x82175330 (SAME) |
|
||
| `vtable[+8]` thunk | 0x82175340 → b sub_821741C8 | SAME (vtable bytes from XEX `.rdata`) |
|
||
|
||
The thunks at 0x82175330+ are 8-byte `lwz r3, 8(r3); b <real_method>`
|
||
trampolines. Slot 2 (`+0x08`) is the worker dispatch entry that round 33
|
||
identified as 471× in canary tid=6 / 0× in ours.
|
||
|
||
## A.1 — Canary dispatcher loop is in sub_822F1AA8 on tid=6
|
||
|
||
Probe `--audit_jit_prolog_pc=0x821741C8 --audit_jit_prolog_r3_bytes=256` on
|
||
canary (35 s):
|
||
|
||
- ~1678 fires of sub_821741C8 on **tid=6**
|
||
- r3 at entry = `0xBCCC4A80` (the inner sub-object of the silph::UImpl
|
||
singleton — extracted via the thunk's `lwz r3, 8(r3)`)
|
||
- LR at entry = `0x822F1D5C` (return PC after the `bctrl` at 0x822F1D58 inside
|
||
sub_822F1AA8)
|
||
- Singleton's `[+C0..+D0]` UTF-16 spells "HF Frequency" (a UI label)
|
||
|
||
The dispatch site in canary (the `bctrl`) is at PC 0x822F1D58 inside
|
||
sub_822F1AA8:
|
||
```
|
||
0x822F1D40: lwz r3, 7944(r25) ; r3 = [r25+0x1F08] = [0x828E1F08]
|
||
0x822F1D4C: lwz r11, 0(r3) ; vtable
|
||
0x822F1D50: lwz r11, 8(r11) ; vtable[+8] = thunk 0x82175340
|
||
0x822F1D54: mtctr r11
|
||
0x822F1D58: bctrl ; → 0x82175340 → b 0x821741C8
|
||
```
|
||
|
||
## A.2 — Canary tid=6 spawn site is sub_821746B0 at PC 0x82174824
|
||
|
||
Enumeration of `ExCreateThread` calls in canary (35 s, 21 unique tuples):
|
||
|
||
```
|
||
entry=821748F0 start_ctx=BC365700 lr=824AC5F0 guest_lr=82174828 ← silph dispatcher #1
|
||
entry=821748F0 start_ctx=BC366DA0 lr=824AC5F0 guest_lr=82174828 ← silph dispatcher #2
|
||
```
|
||
|
||
PC `0x82174824` is the `bl 0x82172370` (the `ExCreateThread` thunk) inside
|
||
`sub_821746B0`. The setup is:
|
||
```
|
||
0x8217480C: lis r11, 0x8217
|
||
0x82174810: li r7, 0
|
||
0x82174814: li r6, 4 ; priority
|
||
0x82174818: mr r5, r29 ; start_ctx
|
||
0x8217481C: addi r4, r11, 18672 ; r4 = 0x821748F0 (entry)
|
||
0x82174820: li r3, 0
|
||
0x82174824: bl 0x82172370 ; ExCreateThread
|
||
```
|
||
|
||
The entry `0x821748F0` is a thread main that calls `bl 0x821749C0` (the
|
||
inner dispatch).
|
||
|
||
## A.3 — sub_822F1AA8 spawns a SECOND thread at 0x822F1B08
|
||
|
||
The dispatch-loop function `sub_822F1AA8` itself ALSO spawns a thread at
|
||
PC 0x822F1B08 with entry=`sub_822F1EE0` and `start_ctx=BCE24A40`:
|
||
```
|
||
0x822F1AEC: lis r11, 0x822F
|
||
0x822F1AFC: addi r4, r11, 7904 ; r4 = 0x822F1EE0
|
||
0x822F1B08: bl 0x82172370 ; ExCreateThread
|
||
```
|
||
|
||
sub_822F1EE0 → sub_822F1F20 contains its own atomic state-machine + wait loop.
|
||
|
||
## A.3' — sub_822F1AA8 has exactly 2 callers, both in sub_8216EA68
|
||
|
||
```
|
||
source=0x8216ECCC source_func=0x8216EA68 kind=call
|
||
source=0x8216EE10 source_func=0x8216EA68 kind=call
|
||
```
|
||
|
||
So sub_8216EA68 is the only function that drives sub_822F1AA8.
|
||
|
||
## A.4 — Ours' divergence is INSIDE the spawned thread, NOT at the spawn
|
||
|
||
Mirror-probed ours at `sub_821746B0` body BB heads (parallel mode, 50M
|
||
instructions, XENIA_CACHE_PERSIST=1):
|
||
|
||
| PC | Fires | Notes |
|
||
|-------------|-------|------------------------------------------------|
|
||
| 0x821746B0 | 1 | Entry. r3=0x40ba9a80 |
|
||
| 0x821746E0 | 1 | After `bl 0x8284DCFC` (critical-section) |
|
||
| 0x82174798 | 1 | After the early `beq` (r28==0 branch) |
|
||
| 0x821747B8 | 1 | **Past the gate**: `[0x828E2B14]=0x40105000` non-NULL; `bl 0x82150EF8` returned r3=0x4024a840 (NON-NULL) |
|
||
| 0x821747D8 | 1 | After the inner `bl 0x821723F0` |
|
||
| 0x8217480C | 1 | Enters the spawn block |
|
||
| 0x82174828 | 1 | **Post-`bl ExCreateThread`**, r3=0x1070 = thread handle |
|
||
|
||
**OURS DOES SPAWN THE THREAD VIA THIS SITE.** The returned handle 0x1070 is
|
||
**tid=13's thread handle** (per round 37 final state). So **ours' tid=13 IS
|
||
the same logical thread as canary's tid=6** — spawned by the identical call
|
||
site with the same entry (0x821748F0).
|
||
|
||
## A.4 — Divergence is INSIDE the spawned thread's body
|
||
|
||
Round 37's frame trail for ours' tid=13 wedge:
|
||
`0x821CB1E0 → 0x821CBAE0 → 0x821CC454 → 0x821C4F18 → 0x82174A80`
|
||
|
||
The LAST frame `0x82174A80` is **inside sub_821749C0** (= the inner dispatch
|
||
called from sub_821748F0). It's right after the vtable dispatch at
|
||
0x82174A78 (`bctrl` on `[r30+vtable][+16]`):
|
||
|
||
```
|
||
0x82174a64: mr r3, r30 ; r3 = some object
|
||
0x82174a68: lwz r11, 0(r30)
|
||
0x82174a6c: lwz r4, 4(r29)
|
||
0x82174a70: lwz r5, 8(r31)
|
||
0x82174a74: lwz r11, 16(r11) ; r11 = vtable[+0x10]
|
||
0x82174a78: mtctr r11
|
||
0x82174a7c: bctrl ; dispatch
|
||
0x82174a80: lwz r3, 0(r29) ; ← wedge frame top (LR after bctrl)
|
||
```
|
||
|
||
So `sub_821749C0`'s vtable[+0x10] dispatch on tid=13/tid=6's `r30` object
|
||
lands at audit-049 territory in ours (chain through sub_821CB030+0x128 that
|
||
ends waiting forever on handle 0x1078). In canary, the same dispatch on the
|
||
same object SHOULD land somewhere that ultimately reaches sub_822F1AA8's
|
||
dispatch loop and runs sub_821741C8 1678× via vtable[+8].
|
||
|
||
**The object `r30` is the result of `bl 0x821CF3F0`** at PC 0x821749DC. So
|
||
sub_821CF3F0 returns a registry-lookup object; the vtable on this object's
|
||
slot +0x10 method's body determines whether the thread wedges or runs.
|
||
|
||
## Phase B classification
|
||
|
||
Class 3 — **Missing init-time precondition**. Ours reaches the spawn site,
|
||
ours' tid=13 enters the chain, ours' tid=13 enters sub_821749C0, but the
|
||
vtable[+0x10] dispatch at PC 0x82174A78 in ours lands in audit-049 territory
|
||
(wait forever on 0x1078) rather than continuing through the canonical chain
|
||
toward sub_822F1AA8's outer dispatch loop.
|
||
|
||
Possible classes to refine in next round:
|
||
- **3a**: same vtable but state-dependent — `r30`'s field at a specific offset
|
||
differs in ours vs canary, causing the method body to take a different
|
||
branch.
|
||
- **3b**: the vtable in `r30` is DIFFERENT in ours vs canary (e.g., ours has
|
||
a base-class vtable but canary has a derived-class vtable).
|
||
- **4**: synthesis fallback — spawn a SECOND thread that runs sub_822F1AA8's
|
||
dispatch loop directly, bypassing the wedged sub_821749C0 chain.
|
||
|
||
## Next probe (A.4.5)
|
||
|
||
Probe both engines at sub_821749C0 entry filtering tid=13 (ours) / tid=6
|
||
(canary), capturing:
|
||
- `r3` and `r4` at entry (the factory-output object and the ctx)
|
||
- After the `bl 0x821CF3F0` at 0x821749DC: capture r30 (= sub_821CF3F0
|
||
return — the object whose vtable is dispatched at 0x82174A78)
|
||
- At PC 0x82174A78 (the divergent bctrl): r30 + r30+0 (vtable) + vtable[+0x10]
|
||
(the dispatch target)
|
||
|
||
If ours and canary have IDENTICAL `vtable[+0x10]` targets but the method
|
||
body's behavior differs → class 3a (state divergence). If targets differ →
|
||
class 3b (vtable identity divergence).
|