try a factory approach

core/evm_ext.go

@@ -16,12 +16,11 @@ import (
 	"github.com/ethereum/go-ethereum/log"
 )
 
-var (
-	newEVM = vm.NewEVM
-)
+var defaultEVMFactory vm.EvmFactory
 
 func init() {
-	vm.NewEVM = NewEVM
+	defaultEVMFactory = vm.DefaultEVMFactory()
+	vm.SetDefaultEVMFactory(&evmFactory{})
 }
 
 // IsProhibited returns true if [addr] is in the prohibited list of addresses which should
@@ -34,13 +33,15 @@ func IsProhibited(addr common.Address) bool {
 	return modules.ReservedAddress(addr)
 }
 
+type evmFactory struct{}
+
 type EVM struct {
 	*vm.EVM
 
 	chainConfig *params.ChainConfig
 }
 
-func NewEVM(
+func (*evmFactory) NewEVM(
 	blockCtx vm.BlockContext, txCtx vm.TxContext, statedb vm.StateDB,
 	chainConfig vm.ChainConfig, config vm.Config,
 ) *vm.EVM {
@@ -49,7 +50,7 @@ func NewEVM(
 		// If the chainConfig is not a params.ChainConfig, then we can't use the custom
 		// EVM implementation, so we fall back to the default implementation.
 		log.Warn("ChainConfig is not a *params.ChainConfig, falling back to default EVM")
-		return newEVM(blockCtx, txCtx, statedb, chainConfig, config)
+		return defaultEVMFactory.NewEVM(blockCtx, txCtx, statedb, chainConfig, config)
 	}
 	evm := &EVM{
 		chainConfig: customChainConfig,
@@ -58,7 +59,7 @@ func NewEVM(
 	config.DeployerAllowed = evm.DeployerAllowed
 	config.CustomPrecompiles = evm.CustomPrecompiles
 
-	evm.EVM = newEVM(blockCtx, txCtx, statedb, chainConfig, config)
+	evm.EVM = defaultEVMFactory.NewEVM(blockCtx, txCtx, statedb, chainConfig, config)
 	return evm.EVM
 }
 

core/vm/evm.go

@@ -171,19 +171,9 @@ type EVM struct {
 	callGasTemp uint64
 }
 
-type ChainConfig interface {
-	IsEIP158(blockNum *big.Int) bool
-	IsSubnetEVM(timestamp uint64) bool
-	IsCancun(blockNum *big.Int, timestamp uint64) bool
-	IsPrecompileEnabled(addr common.Address, timestamp uint64) bool
-	Rules(blockNum *big.Int, timestamp uint64) params.Rules
-}
-
-var NewEVM = newEVM
-
 // NewEVM returns a new EVM. The returned EVM is not thread safe and should
 // only ever be used *once*.
-func newEVM(blockCtx BlockContext, txCtx TxContext, statedb StateDB, chainConfig ChainConfig, config Config) *EVM {
+func (*evmFactory) NewEVM(blockCtx BlockContext, txCtx TxContext, statedb StateDB, chainConfig ChainConfig, config Config) *EVM {
 	// If basefee tracking is disabled (eth_call, eth_estimateGas, etc), and no
 	// gas prices were specified, lower the basefee to 0 to avoid breaking EVM
 	// invariants (basefee < feecap)

core/vm/evm_ext.go

@@ -0,0 +1,36 @@
+package vm
+
+import (
+	"math/big"
+
+	"github.com/ava-labs/subnet-evm/params"
+	"github.com/ethereum/go-ethereum/common"
+)
+
+var defaultEVMFactory EvmFactory = &evmFactory{}
+
+type evmFactory struct{}
+
+type ChainConfig interface {
+	IsEIP158(blockNum *big.Int) bool
+	IsSubnetEVM(timestamp uint64) bool
+	IsCancun(blockNum *big.Int, timestamp uint64) bool
+	IsPrecompileEnabled(addr common.Address, timestamp uint64) bool
+	Rules(blockNum *big.Int, timestamp uint64) params.Rules
+}
+
+type EvmFactory interface {
+	NewEVM(blockCtx BlockContext, txCtx TxContext, statedb StateDB, chainConfig ChainConfig, config Config) *EVM
+}
+
+func DefaultEVMFactory() EvmFactory {
+	return defaultEVMFactory
+}
+
+func SetDefaultEVMFactory(factory EvmFactory) {
+	defaultEVMFactory = factory
+}
+
+func NewEVM(blockCtx BlockContext, txCtx TxContext, statedb StateDB, chainConfig ChainConfig, config Config) *EVM {
+	return DefaultEVMFactory().NewEVM(blockCtx, txCtx, statedb, chainConfig, config)
+}