Fold revert-on-reject into the generated step code by diegonehab · Pull Request #98 · cartesi/machine-solidity-step

diegonehab · 2026-06-10T19:54:23Z

Part of cartesi/machine-emulator#388. Companion to cartesi/machine-emulator#389, which must
be referenced for regenerating the constants and test fixtures.

Problem

The EVM verifiers had no way to accept the canonical state transition of a rejected
input. The revert hash was written by a separate setCheckpointHash-era composition,
and the substitution after a rejection was left to the caller (Dave's
revertIfNeeded, built on the in-repo AdvanceStatus.sol).

Solution

SendCmioResponse.sol is regenerated from the emulator. sendCmioResponse takes a
bytes32 revertRootHash first argument and commits it into the revert root hash leaf
via EmulatorCompat.writeRevertRootHash as part of the proof
(EmulatorCompat.getRevertRootHash/setRevertRootHash are renamed to
readRevertRootHash/writeRevertRootHash to match the emulator naming).
UArchReset.sol is regenerated with the reversion folded in. After resetting the
uarch state, reset() reads iflags.Y, conditionally reads htif.tohost, decodes
dev/cmd/reason, and on a rejected manual yield calls the new
EmulatorCompat.revertState, which replaces currentRootHash with the value read
from the revert leaf. Callers need no substitution logic, Dave's boundary transition
becomes just step and reset, and its input boundary becomes a single sendCmio
call.
AdvanceStatus.sol is deleted, its only consumer was revertIfNeeded, which the
fold makes obsolete.
EmulatorConstants.sol is regenerated. The yield reason trio is renamed from
CMIO_YIELD_MANUAL_REASON_* to HTIF_YIELD_MANUAL_REASON_*, and the HTIF field
shift/mask constants plus HTIF_DEV_YIELD and HTIF_YIELD_CMD_MANUAL are added,
all queried from the emulator (CMIO_YIELD_REASON_ADVANCE_STATE keeps its name,
Dave references it).
The generator scripts are updated for the new signatures and for prefixing
EmulatorConstants names in UArchReset.sol.

Tests

The json log parser is generalized to derive per-access sibling counts and to emit the
value followed by the leaf hash for leaf read accesses, so mixed-shape logs replay.
SendCmioResponse.t.sol passes the catalog's initial root hash as the revert root
hash, and UArchReset.t.sol additionally replays the new rejected-reset fixture, whose
final root hash is the recorded revert root hash. All 56 Foundry suites pass against
fixtures regenerated from the emulator PR (Foundry v1.4.3, as pinned by CI).

The emulator now records the revert root hash as part of send_cmio_response, so the generated SendCmioResponse.sol takes a bytes32 revertRootHash argument and writes it via EmulatorCompat.writeRevertRootHash. Rename EmulatorCompat.getRevertRootHash and setRevertRootHash to readRevertRootHash and writeRevertRootHash to match the emulator naming. Update generate_SendCmioResponse.sh for the new C++ signature and explicit-instantiation layout. Fix generate_EmulatorConstants.lua to query the renamed cartesi.HTIF_YIELD_* Lua constants and regenerate EmulatorConstants.sol, which also picks up the new UARCH_PRISTINE_STATE_HASH. The SendCmioResponse test passes the catalog's initialRootHash as the revert root hash, matching the regenerated test logs.

Regenerate UArchReset.sol from the emulator. After resetting the uarch state, reset() now reads iflags.Y and conditionally htif.tohost, decodes the dev/cmd/reason fields, and on a rejected manual yield calls the new EmulatorCompat.revertState, which replaces currentRootHash with the value read from the revert root hash leaf. Callers need no substitution logic, the boundary transition in the dispute becomes just step and reset. Delete AdvanceStatus.sol. Its only consumer was Dave's revertIfNeeded, which the fold makes obsolete. Rename the EmulatorConstants yield reason trio from CMIO_YIELD_MANUAL_REASON_* to HTIF_YIELD_MANUAL_REASON_*, matching the emulator naming now that AdvanceStatus is gone, and add the HTIF field shift and mask constants plus HTIF_DEV_YIELD and HTIF_YIELD_CMD_MANUAL, all queried from the emulator by generate_EmulatorConstants.lua. CMIO_YIELD_REASON_ADVANCE_STATE keeps its name, Dave references it. Update generate_UArchReset.sh to prefix EmulatorConstants names like the other generators. Generalize the test json parser to derive per-access sibling counts and to emit the value followed by the leaf hash for leaf read accesses, so mixed-shape logs replay. UArchReset.t.sol now also replays the rejected-reset fixture, whose final root hash is the recorded revert root hash.

mpernambuco

looks great

The core send_cmio_response can no longer fail. If verification could fail for a reachable machine state and response, there would be states for which the honest party cannot produce a log that proves the resulting state transition. The iflags.Y and response-length checks now return without touching the state, like the advance-state yield check already did. The length check also moves ahead of the revert root hash write, where it can still prevent all state changes. iflags.Y remains the first access, so a no-op log is never empty, which replay requires. The host-facing machine::send_cmio_response still refuses misuse upfront. check_pending_cmio_request takes over the dropped checks, requiring a manual yield for every response reason and a response that fits in the rx buffer, with the same error messages as before. machine::log_send_cmio_response no longer fails for any machine state or response argument and logs a no-op instead.

GCdePaula · 2026-06-15T10:59:25Z


    function sendCmioResponse(
        AccessLogs.Context memory a,
+        bytes32 revertRootHash,


At this point, in every valid call, revertRootHash == a.currentRootHash. Should we drop the revertRootHash argument and have sendCmioResponse source a.currentRootHash internally?

We'd likely need to change the send_cmio_response from C++ to match, not sure whether it's feasible. From Dave's side, either API works.

Remember that send_cmio_response was supposed to work with other generic IO requests. I am not sure what the deal there would be. So it makes sense to leave the argument there, I think.

GCdePaula · 2026-06-15T11:08:04Z

        for (uint256 i = 0; i < catalog.length; i++) {
+            // run the plain reset log and the rejected-input log, whose final
+            // root hash is the recorded revert root hash
            if (


Should we add a reset-uarch-accepted-steps.json fixture (recorded from a machine paused on an RX_ACCEPTED manual yield, with finalRootHash equals the post-reset root with no revert)? I feel we're missing this third scenario.

GCdePaula

Looks great!

Minor nit, I think commit b76bf5c's subject line is not the one you meant.

GCdePaula · 2026-06-15T20:19:23Z

+                            abi.encodePacked("reset-uarch-accepted-steps.json")
+                        )
            ) {
                continue;


In the testSendCmioResponseNoop test, there's a "found" flag, and a loud test failure if the fixture is not there. Might be a good idea to repeat the same patter here too.

The UArchReset.sol reset() generated in PR 98 now reads iflags.Y, conditionally reads htif.tohost, decodes the manual-yield reason, and reverts only when the reason is RX_REJECTED. The replay test previously exercised only the plain path (iflags.Y unset, no tohost read) and the rejected path (RX_REJECTED, reverts). This adds reset-uarch-accepted-steps.json to the filter so the third path is also replayed: iflags.Y is set, tohost is read and decoded, the reason is RX_ACCEPTED, reset does not revert, and the final root hash is the post-reset root. This addresses the review comment from GCdePaula requesting this missing scenario.

diegonehab added 3 commits April 13, 2026 15:18

feat: improve coverage

f6ac168

github-project-automation Bot added this to Machine Unit Jun 10, 2026

github-project-automation Bot moved this to Todo in Machine Unit Jun 10, 2026

diegonehab self-assigned this Jun 10, 2026

diegonehab added the enhancement New feature or request label Jun 10, 2026

diegonehab moved this from Todo to Waiting Review in Machine Unit Jun 10, 2026

diegonehab marked this pull request as draft June 10, 2026 19:56

diegonehab mentioned this pull request Jun 10, 2026

Prove revert-on-reject state transitions cartesi/machine-emulator#389

Open

chore: update emulator tag

331e86e

diegonehab requested a review from mpernambuco June 10, 2026 21:25

diegonehab marked this pull request as ready for review June 10, 2026 21:31

mpernambuco previously approved these changes Jun 10, 2026

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github-project-automation Bot moved this from Waiting Review to Waiting Merge in Machine Unit Jun 10, 2026

diegonehab dismissed mpernambuco’s stale review via e60f6eb June 12, 2026 22:22

GCdePaula reviewed Jun 15, 2026

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diegonehab force-pushed the feature/revert-root-hash branch from 30998f7 to b76bf5c Compare June 15, 2026 15:58

GCdePaula previously approved these changes Jun 15, 2026

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diegonehab dismissed GCdePaula’s stale review via 0b4a09e June 17, 2026 13:20

diegonehab force-pushed the feature/revert-root-hash branch from b76bf5c to 0b4a09e Compare June 17, 2026 13:20

diegonehab force-pushed the feature/revert-root-hash branch from 0b4a09e to f12646b Compare June 17, 2026 13:22

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Fold revert-on-reject into the generated step code#98

Fold revert-on-reject into the generated step code#98
diegonehab wants to merge 6 commits into
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feature/revert-root-hash

diegonehab commented Jun 10, 2026 •

edited

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diegonehab commented Jun 10, 2026 •

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