Fix Cannon `StateHash` computation

cannon/mipsevm/evm_test.go

@@ -15,7 +15,6 @@ import (
 	"github.com/ethereum/go-ethereum/common/hexutil"
 	"github.com/ethereum/go-ethereum/core/state"
 	"github.com/ethereum/go-ethereum/core/vm"
-	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/eth/tracers/logger"
 	"github.com/stretchr/testify/require"
 
@@ -92,7 +91,9 @@ func (m *MIPSEVM) Step(t *testing.T, stepWitness *StepWitness) []byte {
 	logs := m.evmState.Logs()
 	require.Equal(t, 1, len(logs), "expecting a log with post-state")
 	evmPost := logs[0].Data
-	require.Equal(t, crypto.Keccak256Hash(evmPost), postHash, "logged state must be accurate")
+
+	stateHash := (StateWitness)(evmPost).StateHash()
+	require.Equal(t, stateHash, postHash, "logged state must be accurate")
 
 	m.env.StateDB.RevertToSnapshot(snap)
 	t.Logf("EVM step took %d gas, and returned stateHash %s", startingGas-leftOverGas, postHash)

cannon/mipsevm/state.go

@@ -78,8 +78,8 @@ const (
 func (sw StateWitness) StateHash() common.Hash {
 	hash := crypto.Keccak256Hash(sw)
 	offset := 32*2 + 4*6
-	exited := sw[offset]
-	exitCode := sw[offset+1]
+	exitCode := sw[offset]
+	exited := sw[offset+1]
 	status := vmStatus(exited == 1, exitCode)
 	hash[0] = status
 	return hash