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// Copyright 2014 The go-ethereum Authors
// This file is part of the go-ethereum library.
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// GNU Lesser General Public License for more details.
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <>.
package vm
import (
// Config are the configuration options for the Interpreter
type Config struct {
// Debug enabled debugging Interpreter options
Debug bool
// Tracer is the op code logger
Tracer Tracer
// NoRecursion disabled Interpreter call, callcode,
// delegate call and create.
NoRecursion bool
// Enable recording of SHA3/keccak preimages
EnablePreimageRecording bool
// JumpTable contains the EVM instruction table. This
// may be left uninitialised and will be set to the default
// table.
JumpTable [256]operation
// Type of the EWASM interpreter
EWASMInterpreter string
// Type of the EVM interpreter
EVMInterpreter string
// Interpreter is used to run Ethereum based contracts and will utilise the
// passed environment to query external sources for state information.
// The Interpreter will run the byte code VM based on the passed
// configuration.
type Interpreter interface {
// Run loops and evaluates the contract's code with the given input data and returns
// the return byte-slice and an error if one occurred.
Run(contract *Contract, input []byte, static bool) ([]byte, error)
// CanRun tells if the contract, passed as an argument, can be
// run by the current interpreter. This is meant so that the
// caller can do something like:
// ```golang
// for _, interpreter := range interpreters {
// if interpreter.CanRun(contract.code) {
// interpreter.Run(contract.code, input)
// }
// }
// ```
CanRun([]byte) bool
// keccakState wraps sha3.state. In addition to the usual hash methods, it also supports
// Read to get a variable amount of data from the hash state. Read is faster than Sum
// because it doesn't copy the internal state, but also modifies the internal state.
type keccakState interface {
Read([]byte) (int, error)
// EVMInterpreter represents an EVM interpreter
type EVMInterpreter struct {
evm *EVM
cfg Config
gasTable params.GasTable
intPool *intPool
hasher keccakState // Keccak256 hasher instance shared across opcodes
hasherBuf common.Hash // Keccak256 hasher result array shared aross opcodes
readOnly bool // Whether to throw on stateful modifications
returnData []byte // Last CALL's return data for subsequent reuse
// NewEVMInterpreter returns a new instance of the Interpreter.
func NewEVMInterpreter(evm *EVM, cfg Config) *EVMInterpreter {
// We use the STOP instruction whether to see
// the jump table was initialised. If it was not
// we'll set the default jump table.
if !cfg.JumpTable[STOP].valid {
switch {
case evm.ChainConfig().IsConstantinople(evm.BlockNumber):
cfg.JumpTable = constantinopleInstructionSet
case evm.ChainConfig().IsByzantium(evm.BlockNumber):
cfg.JumpTable = byzantiumInstructionSet
case evm.ChainConfig().IsHomestead(evm.BlockNumber):
cfg.JumpTable = homesteadInstructionSet
cfg.JumpTable = frontierInstructionSet
return &EVMInterpreter{
evm: evm,
cfg: cfg,
gasTable: evm.ChainConfig().GasTable(evm.BlockNumber),
func (in *EVMInterpreter) enforceRestrictions(op OpCode, operation operation, stack *Stack) error {
if in.evm.chainRules.IsByzantium {
if in.readOnly {
// If the interpreter is operating in readonly mode, make sure no
// state-modifying operation is performed. The 3rd stack item
// for a call operation is the value. Transferring value from one
// account to the others means the state is modified and should also
// return with an error.
if operation.writes || (op == CALL && stack.Back(2).BitLen() > 0) {
return errWriteProtection
return nil
// Run loops and evaluates the contract's code with the given input data and returns
// the return byte-slice and an error if one occurred.
// It's important to note that any errors returned by the interpreter should be
// considered a revert-and-consume-all-gas operation except for
// errExecutionReverted which means revert-and-keep-gas-left.
func (in *EVMInterpreter) Run(contract *Contract, input []byte, readOnly bool) (ret []byte, err error) {
if in.intPool == nil {
in.intPool = poolOfIntPools.get()
defer func() {
in.intPool = nil
// Increment the call depth which is restricted to 1024
defer func() { in.evm.depth-- }()
// Make sure the readOnly is only set if we aren't in readOnly yet.
// This makes also sure that the readOnly flag isn't removed for child calls.
if readOnly && !in.readOnly {
in.readOnly = true
defer func() { in.readOnly = false }()
// Reset the previous call's return data. It's unimportant to preserve the old buffer
// as every returning call will return new data anyway.
in.returnData = nil
// Don't bother with the execution if there's no code.
if len(contract.Code) == 0 {
return nil, nil
var (
op OpCode // current opcode
mem = NewMemory() // bound memory
stack = newstack() // local stack
// For optimisation reason we're using uint64 as the program counter.
// It's theoretically possible to go above 2^64. The YP defines the PC
// to be uint256. Practically much less so feasible.
pc = uint64(0) // program counter
cost uint64
// copies used by tracer
pcCopy uint64 // needed for the deferred Tracer
gasCopy uint64 // for Tracer to log gas remaining before execution
logged bool // deferred Tracer should ignore already logged steps
contract.Input = input
// Reclaim the stack as an int pool when the execution stops
defer func() { in.intPool.put( }()
if in.cfg.Debug {
defer func() {
if err != nil {
if !logged {
in.cfg.Tracer.CaptureState(in.evm, pcCopy, op, gasCopy, cost, mem, stack, contract, in.evm.depth, err)
} else {
in.cfg.Tracer.CaptureFault(in.evm, pcCopy, op, gasCopy, cost, mem, stack, contract, in.evm.depth, err)
// The Interpreter main run loop (contextual). This loop runs until either an
// explicit STOP, RETURN or SELFDESTRUCT is executed, an error occurred during
// the execution of one of the operations or until the done flag is set by the
// parent context.
for atomic.LoadInt32(&in.evm.abort) == 0 {
if in.cfg.Debug {
// Capture pre-execution values for tracing.
logged, pcCopy, gasCopy = false, pc, contract.Gas
// Get the operation from the jump table and validate the stack to ensure there are
// enough stack items available to perform the operation.
op = contract.GetOp(pc)
operation := in.cfg.JumpTable[op]
if !operation.valid {
return nil, fmt.Errorf("invalid opcode 0x%x", int(op))
if err := operation.validateStack(stack); err != nil {
return nil, err
// If the operation is valid, enforce and write restrictions
if err := in.enforceRestrictions(op, operation, stack); err != nil {
return nil, err
var memorySize uint64
// calculate the new memory size and expand the memory to fit
// the operation
if operation.memorySize != nil {
memSize, overflow := bigUint64(operation.memorySize(stack))
if overflow {
return nil, errGasUintOverflow
// memory is expanded in words of 32 bytes. Gas
// is also calculated in words.
if memorySize, overflow = math.SafeMul(toWordSize(memSize), 32); overflow {
return nil, errGasUintOverflow
// consume the gas and return an error if not enough gas is available.
// cost is explicitly set so that the capture state defer method can get the proper cost
cost, err = operation.gasCost(in.gasTable, in.evm, contract, stack, mem, memorySize)
if err != nil || !contract.UseGas(cost) {
return nil, ErrOutOfGas
if memorySize > 0 {
if in.cfg.Debug {
in.cfg.Tracer.CaptureState(in.evm, pc, op, gasCopy, cost, mem, stack, contract, in.evm.depth, err)
logged = true
// execute the operation
res, err := operation.execute(&pc, in, contract, mem, stack)
// verifyPool is a build flag. Pool verification makes sure the integrity
// of the integer pool by comparing values to a default value.
if verifyPool {
// if the operation clears the return data (e.g. it has returning data)
// set the last return to the result of the operation.
if operation.returns {
in.returnData = res
switch {
case err != nil:
return nil, err
case operation.reverts:
return res, errExecutionReverted
case operation.halts:
return res, nil
case !operation.jumps:
return nil, nil
// CanRun tells if the contract, passed as an argument, can be
// run by the current interpreter.
func (in *EVMInterpreter) CanRun(code []byte) bool {
return true