core: add code to witness when state object is accessed (ethereum#30698)

I think the core code should generally be agnostic about the witness and
the statedb layer should determine what elements need to be included in
the witness. Because code is accessed via `GetCode`, and
`GetCodeLength`, the statedb will always know when it needs to add that
code into the witness.

The edge case is block hashes, so we continue to add them manually in
the implementation of `BLOCKHASH`.

It probably makes sense to refactor statedb so we have a wrapped
implementation that accumulates the witness, but this is a simpler
change that makes ethereum#30078 less aggressive.

core/state/statedb.go

@@ -341,6 +341,9 @@ func (s *StateDB) TxIndex() int {
 func (s *StateDB) GetCode(addr common.Address) []byte {
 	stateObject := s.getStateObject(addr)
 	if stateObject != nil {
+		if s.witness != nil {
+			s.witness.AddCode(stateObject.Code())
+		}
 		return stateObject.Code()
 	}
 	return nil
@@ -349,6 +352,9 @@ func (s *StateDB) GetCode(addr common.Address) []byte {
 func (s *StateDB) GetCodeSize(addr common.Address) int {
 	stateObject := s.getStateObject(addr)
 	if stateObject != nil {
+		if s.witness != nil {
+			s.witness.AddCode(stateObject.Code())
+		}
 		return stateObject.CodeSize()
 	}
 	return 0

core/vm/evm.go

@@ -213,9 +213,6 @@ func (evm *EVM) Call(caller ContractRef, addr common.Address, input []byte, gas
 		// Initialise a new contract and set the code that is to be used by the EVM.
 		// The contract is a scoped environment for this execution context only.
 		code := evm.StateDB.GetCode(addr)
-		if witness := evm.StateDB.Witness(); witness != nil {
-			witness.AddCode(code)
-		}
 		if len(code) == 0 {
 			ret, err = nil, nil // gas is unchanged
 		} else {
@@ -283,9 +280,6 @@ func (evm *EVM) CallCode(caller ContractRef, addr common.Address, input []byte,
 		// Initialise a new contract and set the code that is to be used by the EVM.
 		// The contract is a scoped environment for this execution context only.
 		contract := NewContract(caller, AccountRef(caller.Address()), value, gas)
-		if witness := evm.StateDB.Witness(); witness != nil {
-			witness.AddCode(evm.StateDB.GetCode(addrCopy))
-		}
 		contract.SetCallCode(&addrCopy, evm.StateDB.GetCodeHash(addrCopy), evm.StateDB.GetCode(addrCopy))
 		ret, err = evm.interpreter.Run(contract, input, false)
 		gas = contract.Gas
@@ -333,9 +327,6 @@ func (evm *EVM) DelegateCall(caller ContractRef, addr common.Address, input []by
 		addrCopy := addr
 		// Initialise a new contract and make initialise the delegate values
 		contract := NewContract(caller, AccountRef(caller.Address()), nil, gas).AsDelegate()
-		if witness := evm.StateDB.Witness(); witness != nil {
-			witness.AddCode(evm.StateDB.GetCode(addrCopy))
-		}
 		contract.SetCallCode(&addrCopy, evm.StateDB.GetCodeHash(addrCopy), evm.StateDB.GetCode(addrCopy))
 		ret, err = evm.interpreter.Run(contract, input, false)
 		gas = contract.Gas
@@ -391,9 +382,6 @@ func (evm *EVM) StaticCall(caller ContractRef, addr common.Address, input []byte
 		// Initialise a new contract and set the code that is to be used by the EVM.
 		// The contract is a scoped environment for this execution context only.
 		contract := NewContract(caller, AccountRef(addrCopy), new(uint256.Int), gas)
-		if witness := evm.StateDB.Witness(); witness != nil {
-			witness.AddCode(evm.StateDB.GetCode(addrCopy))
-		}
 		contract.SetCallCode(&addrCopy, evm.StateDB.GetCodeHash(addrCopy), evm.StateDB.GetCode(addrCopy))
 		// When an error was returned by the EVM or when setting the creation code
 		// above we revert to the snapshot and consume any gas remaining. Additionally

core/vm/instructions.go

@@ -340,10 +340,6 @@ func opReturnDataCopy(pc *uint64, interpreter *EVMInterpreter, scope *ScopeConte
 
 func opExtCodeSize(pc *uint64, interpreter *EVMInterpreter, scope *ScopeContext) ([]byte, error) {
 	slot := scope.Stack.peek()
-	address := slot.Bytes20()
-	if witness := interpreter.evm.StateDB.Witness(); witness != nil {
-		witness.AddCode(interpreter.evm.StateDB.GetCode(address))
-	}
 	slot.SetUint64(uint64(interpreter.evm.StateDB.GetCodeSize(slot.Bytes20())))
 	return nil, nil
 }
@@ -383,9 +379,6 @@ func opExtCodeCopy(pc *uint64, interpreter *EVMInterpreter, scope *ScopeContext)
 	}
 	addr := common.Address(a.Bytes20())
 	code := interpreter.evm.StateDB.GetCode(addr)
-	if witness := interpreter.evm.StateDB.Witness(); witness != nil {
-		witness.AddCode(code)
-	}
 	codeCopy := getData(code, uint64CodeOffset, length.Uint64())
 	scope.Memory.Set(memOffset.Uint64(), length.Uint64(), codeCopy)