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| 1 | +-- SPDX-License-Identifier: MPL-2.0 |
| 2 | +-- Copyright (c) 2026 Jonathan D.A. Jewell (hyperpolymath) <j.d.a.jewell@open.ac.uk> |
| 3 | +-- |
| 4 | +||| Layer-5 CAPSTONE: the end-to-end ABI soundness certificate for VeriSimiser. |
| 5 | +||| |
| 6 | +||| Every prior layer proves one face of the ABI contract in isolation: |
| 7 | +||| |
| 8 | +||| * Layer 2 (`Octad.idr`) — the *flagship* model theorem: the eight octad |
| 9 | +||| dimensions biject with `Fin 8` (`octadFinInverseL` / `octadFinInverseR`), |
| 10 | +||| and the per-dimension sidecar-isolation cross-check. |
| 11 | +||| * Layer 3 (`Invariants.idr`) — the *deeper compositional invariant*: |
| 12 | +||| read-only-ness is closed under pipeline composition, with the concrete |
| 13 | +||| `readPathPipeline` as the canonical positive control |
| 14 | +||| (`readPathIsReadOnly`). |
| 15 | +||| * Layer 4 (`FfiSeam.idr`) — the *FFI seam*: the `resultToInt` wire encoding |
| 16 | +||| is injective (`resultToIntInjective`), so distinct ABI outcomes never |
| 17 | +||| collide on the C boundary. |
| 18 | +||| |
| 19 | +||| This module ties them together. `ABISound` is a record whose fields are those |
| 20 | +||| exact proven facts, and `abiContractDischarged : ABISound` is a single |
| 21 | +||| inhabited value built ONLY from the existing exported witnesses. It is the |
| 22 | +||| capstone in the literal sense: it typechecks iff every constituent proof is |
| 23 | +||| still sound. The certificate therefore states, as one inhabited value, that |
| 24 | +||| the manifest's octad model (flagship Layer-2) + its compositional safety |
| 25 | +||| invariant (Layer-3) + the FFI wire encoding (Layer-4) are discharged |
| 26 | +||| TOGETHER as one end-to-end soundness statement — not merely module by module. |
| 27 | + |
| 28 | +module Verisimiser.ABI.Capstone |
| 29 | + |
| 30 | +import Verisimiser.ABI.Types |
| 31 | +import Verisimiser.ABI.Octad |
| 32 | +import Verisimiser.ABI.Invariants |
| 33 | +import Verisimiser.ABI.FfiSeam |
| 34 | +import Data.Fin |
| 35 | + |
| 36 | +%default total |
| 37 | + |
| 38 | +-------------------------------------------------------------------------------- |
| 39 | +-- The end-to-end soundness certificate |
| 40 | +-------------------------------------------------------------------------------- |
| 41 | + |
| 42 | +||| The conjunction of the key proven ABI facts, one field per prior layer. |
| 43 | +||| |
| 44 | +||| Each field's TYPE is the proposition; the only way to populate the record is |
| 45 | +||| to supply the real proof of that proposition, so an inhabitant of `ABISound` |
| 46 | +||| is a machine-checked certificate that the whole ABI contract holds. |
| 47 | +public export |
| 48 | +record ABISound where |
| 49 | + constructor MkABISound |
| 50 | + ||| Layer-2 flagship (octad model): the octad ≅ Fin 8 round-trip on the |
| 51 | + ||| canonical `Simulation` dimension (the eighth, index 7). Witnesses that the |
| 52 | + ||| flagship bijection theorem genuinely has inhabitants on a concrete point. |
| 53 | + flagshipOctadBijection : octadFromFin (octadToFin Simulation) = Simulation |
| 54 | + ||| Layer-2 flagship, the other round-trip direction on a concrete ordinal: |
| 55 | + ||| ordinal 7 names a dimension and survives the decode/encode round-trip. |
| 56 | + flagshipFinSurjective : octadToFin (octadFromFin 7) = 7 |
| 57 | + ||| Layer-3 deeper invariant (compositional sidecar isolation): the canonical |
| 58 | + ||| positive-control read-path pipeline is provably read-only. |
| 59 | + layer3Invariant : pipelineEffect Invariants.readPathPipeline = EReadOnly |
| 60 | + ||| Layer-4 FFI seam: the `resultToInt` wire encoding is injective, so distinct |
| 61 | + ||| ABI result codes never collide on the C boundary. |
| 62 | + ffiSeamInjective : (a, b : Result) -> resultToInt a = resultToInt b -> a = b |
| 63 | + |
| 64 | +||| THE CAPSTONE. A single inhabited value assembled entirely from the existing |
| 65 | +||| exported witnesses of Layers 2-4. If any of those prior proofs were unsound |
| 66 | +||| (or were quietly weakened), this value would fail to typecheck and the proof |
| 67 | +||| build would go red. Its existence is the end-to-end ABI soundness statement. |
| 68 | +public export |
| 69 | +abiContractDischarged : ABISound |
| 70 | +abiContractDischarged = MkABISound |
| 71 | + (octadFinInverseL Simulation) -- Layer-2 flagship, round-trip L on Simulation |
| 72 | + (octadFinInverseR 7) -- Layer-2 flagship, round-trip R on ordinal 7 |
| 73 | + readPathIsReadOnly -- Layer-3 invariant on the positive control |
| 74 | + resultToIntInjective -- Layer-4 FFI-seam injectivity |
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