// 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
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// 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 <http://www.gnu.org/licenses/>.
package vm
import (
"fmt"
"sync/atomic"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/common/math"
"github.com/ethereum/go-ethereum/crypto"
"github.com/ethereum/go-ethereum/params"
)
// Config are the configuration options for the Interpreter
type Config struct {
// Debug enabled debugging Interpreter options
Debug bool
// EnableJit enabled the JIT VM
EnableJit bool
// ForceJit forces the JIT VM
ForceJit bool
// Tracer is the op code logger
Tracer Tracer
// NoRecursion disabled Interpreter call, callcode,
// delegate call and create.
NoRecursion bool
// Disable gas metering
DisableGasMetering 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
}
// Interpreter is used to run Ethereum based contracts and will utilise the
// passed evmironment to query external sources for state information.
// The Interpreter will run the byte code VM or JIT VM based on the passed
// configuration.
type Interpreter struct {
evm *EVM
cfg Config
gasTable params.GasTable
intPool *intPool
readOnly bool // Whether to throw on stateful modifications
returnData []byte // Last CALL's return data for subsequent reuse
}
// NewInterpreter returns a new instance of the Interpreter.
func NewInterpreter(evm *EVM, cfg Config) *Interpreter {
// 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().IsByzantium(evm.BlockNumber):
cfg.JumpTable = byzantiumInstructionSet
case evm.ChainConfig().IsHomestead(evm.BlockNumber):
cfg.JumpTable = homesteadInstructionSet
default:
cfg.JumpTable = frontierInstructionSet
}
}
return &Interpreter{
evm: evm,
cfg: cfg,
gasTable: evm.ChainConfig().GasTable(evm.BlockNumber),
intPool: newIntPool(),
}
}
func (in *Interpreter) 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. No error specific checks
// should be handled to reduce complexity and errors further down the in.
func (in *Interpreter) Run(snapshot int, contract *Contract, input []byte) (ret []byte, err error) {
// Increment the call depth which is restricted to 1024
in.evm.depth++
defer func() { in.evm.depth-- }()
// 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
}
codehash := contract.CodeHash // codehash is used when doing jump dest caching
if codehash == (common.Hash{}) {
codehash = crypto.Keccak256Hash(contract.Code)
}
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
stackCopy = newstack() // stackCopy needed for Tracer since stack is mutated by 63/64 gas rule
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
defer func() {
if err != nil && !logged && in.cfg.Debug {
in.cfg.Tracer.CaptureState(in.evm, pcCopy, op, gasCopy, cost, mem, stackCopy, 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 {
// Get the memory location of pc
op = contract.GetOp(pc)
if in.cfg.Debug {
logged = false
pcCopy = uint64(pc)
gasCopy = uint64(contract.Gas)
stackCopy = newstack()
for _, val := range stack.data {
stackCopy.push(val)
}
}
// Get the operation from the jump table matching the opcode and validate the
// stack and make sure there enough stack items available to perform the operation
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
}
}
if !in.cfg.DisableGasMetering {
// consume the gas and return an error if not enough gas is available.
// cost is explicitly set so that the capture state defer method cas 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 {
mem.Resize(memorySize)
}
if in.cfg.Debug {
in.cfg.Tracer.CaptureState(in.evm, pc, op, gasCopy, cost, mem, stackCopy, contract, in.evm.depth, err)
logged = true
}
// execute the operation
res, err := operation.execute(&pc, in.evm, 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 {
verifyIntegerPool(in.intPool)
}
// 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:
pc++
}
}
return nil, nil
}