SPTM/MIE deep dive: sptm.t8160 820.22 -> 820.40.24 (+64 KiB)

- docs/SPTM-MIE-27.2.md: separate SPTM firmware changed (kernel __DATA_SPTM
  is not the monitor); new DART GAPF race, GMMU TLBI verification, iommu
  refcount, Dekker locks, hibernation handoff/latch checks; TXM build-only;
  Exclave +229 KB; MIE SK tag-page check unchanged (210 insns, relocated)
- candidate directions: DART unganged-GAPF race, hibernation handoff page
  count, SK tag-page aliasing, dangling tag storage; no working bypass
- correct the earlier claim that SPTM was unchanged
- tools: fw_diff, string_xref, func_string_diff

README.md

@@ -145,7 +145,7 @@ Kernel R/W feasibility for the high/critical entries is in [docs/KERNEL-RW-ASSES
 
 112507 reachability was re-measured on the target (iPhone19,7, iOS 27.0.1) with the new `kern.ipc.lifecycle` module and an `armed` counter in `kern.ipc`: `mach_port_request_notification` returns -300 (MIG_TYPE_ERROR) for every type/right combination tried, 0 armed out of 12,288 registrations. The request table is never armed, so the race is not reachable from an unentitled app; the earlier "survived the interleaving" line is retracted. Details in [docs/KERNEL-RW-ASSESSMENT.md](docs/KERNEL-RW-ASSESSMENT.md).
 
-**iOS 27.2 firmware diff (27.0.1 vs 27.2, iPhone19,7):** [docs/IOS27.2-KERNEL-DIFF.md](docs/IOS27.2-KERNEL-DIFF.md). The update carries 162 advisory CVEs; 93 of 303 common kexts changed text size. Confirmed fix sites: 112705 clamps `NumberOfTemporalLayers` to 0…7 (`iNumberOfTemporalLayers <= 7` assertion), 113910 adds `chunk %u produced %lld of %lld expected bytes`, 112507 adds `ipr != NULL` / `table != NULL` in `ipc_misc.c`. `__DATA_SPTM` is byte-identical across both builds; the PPL/SPTM/MIE string and code surface is unchanged, so no bypass for those three is fixed in 27.2.
+**iOS 27.2 firmware diff (27.0.1 vs 27.2, iPhone19,7):** [docs/IOS27.2-KERNEL-DIFF.md](docs/IOS27.2-KERNEL-DIFF.md). The update carries 162 advisory CVEs; 93 of 303 common kexts changed text size. Confirmed fix sites: 112705 clamps `NumberOfTemporalLayers` to 0…7 (`iNumberOfTemporalLayers <= 7` assertion), 113910 adds `chunk %u produced %lld of %lld expected bytes`, 112507 adds `ipr != NULL` / `table != NULL` in `ipc_misc.c`. The kernel's `__DATA_SPTM` segment is byte-identical, but the separate `sptm.t8160` firmware changed from SPTM-820.0.22 to **820.40.24** (+64 KiB: DART/IOMMU, TLBI and hibernation hardening, not in the CVE list). MIE/MTE policy in SPTM/XNU is unchanged. See [docs/SPTM-MIE-27.2.md](docs/SPTM-MIE-27.2.md) for the deep dive and candidate bypass directions.
 
 ## Module semantics