path: root/core/vm/vm.go

// 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"
    "math/big"
    "time"

    "github.com/ethereum/go-ethereum/common"
    "github.com/ethereum/go-ethereum/crypto"
    "github.com/ethereum/go-ethereum/logger"
    "github.com/ethereum/go-ethereum/logger/glog"
    "github.com/ethereum/go-ethereum/params"
)

// Vm is an EVM and implements VirtualMachine
type Vm struct {
    env Environment
}

// New returns a new Vm
func New(env Environment) *Vm {
    // init the jump table. Also prepares the homestead changes
    jumpTable.init(env.BlockNumber())

    return &Vm{env: env}
}

// Run loops and evaluates the contract's code with the given input data
func (self *Vm) Run(contract *Contract, input []byte) (ret []byte, err error) {
    self.env.SetDepth(self.env.Depth() + 1)
    defer self.env.SetDepth(self.env.Depth() - 1)

    if contract.CodeAddr != nil {
        if p := Precompiled[contract.CodeAddr.Str()]; p != nil {
            return self.RunPrecompiled(p, input, contract)
        }
    }

    // Don't bother with the execution if there's no code.
    if len(contract.Code) == 0 {
        return nil, nil
    }

    var (
        codehash = crypto.Keccak256Hash(contract.Code) // codehash is used when doing jump dest caching
        program  *Program
    )
    if EnableJit {
        // If the JIT is enabled check the status of the JIT program,
        // if it doesn't exist compile a new program in a seperate
        // goroutine or wait for compilation to finish if the JIT is
        // forced.
        switch GetProgramStatus(codehash) {
        case progReady:
            return RunProgram(GetProgram(codehash), self.env, contract, input)
        case progUnknown:
            if ForceJit {
                // Create and compile program
                program = NewProgram(contract.Code)
                perr := CompileProgram(program)
                if perr == nil {
                    return RunProgram(program, self.env, contract, input)
                }
                glog.V(logger.Info).Infoln("error compiling program", err)
            } else {
                // create and compile the program. Compilation
                // is done in a seperate goroutine
                program = NewProgram(contract.Code)
                go func() {
                    err := CompileProgram(program)
                    if err != nil {
                        glog.V(logger.Info).Infoln("error compiling program", err)
                        return
                    }
                }()
            }
        }
    }

    var (
        caller     = contract.caller
        code       = contract.Code
        instrCount = 0

        op      OpCode          // current opcode
        mem     = NewMemory()   // bound memory
        stack   = newstack()    // local stack
        statedb = self.env.Db() // current state
        // 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. Pratically much less so feasible.
        pc = uint64(0) // program counter

        // jump evaluates and checks whether the given jump destination is a valid one
        // if valid move the `pc` otherwise return an error.
        jump = func(from uint64, to *big.Int) error {
            if !contract.jumpdests.has(codehash, code, to) {
                nop := contract.GetOp(to.Uint64())
                return fmt.Errorf("invalid jump destination (%v) %v", nop, to)
            }

            pc = to.Uint64()

            return nil
        }

        newMemSize *big.Int
        cost       *big.Int
    )
    contract.Input = input

    // User defer pattern to check for an error and, based on the error being nil or not, use all gas and return.
    defer func() {
        if err != nil {
            self.log(pc, op, contract.Gas, cost, mem, stack, contract, err)
        }
    }()

    if glog.V(logger.Debug) {
        glog.Infof("running byte VM %x\n", codehash[:4])
        tstart := time.Now()
        defer func() {
            glog.Infof("byte VM %x done. time: %v instrc: %v\n", codehash[:4], time.Since(tstart), instrCount)
        }()
    }

    for ; ; instrCount++ {
        /*
            if EnableJit && it%100 == 0 {
                if program != nil && progStatus(atomic.LoadInt32(&program.status)) == progReady {
                    // move execution
                    fmt.Println("moved", it)
                    glog.V(logger.Info).Infoln("Moved execution to JIT")
                    return runProgram(program, pc, mem, stack, self.env, contract, input)
                }
            }
        */

        // Get the memory location of pc
        op = contract.GetOp(pc)
        // calculate the new memory size and gas price for the current executing opcode
        newMemSize, cost, err = calculateGasAndSize(self.env, contract, caller, op, statedb, mem, stack)
        if err != nil {
            return nil, err
        }

        // Use the calculated gas. When insufficient gas is present, use all gas and return an
        // Out Of Gas error
        if !contract.UseGas(cost) {
            return nil, OutOfGasError
        }

        // Resize the memory calculated previously
        mem.Resize(newMemSize.Uint64())
        // Add a log message
        self.log(pc, op, contract.Gas, cost, mem, stack, contract, nil)
        if opPtr := jumpTable[op]; opPtr.valid {
            if opPtr.fn != nil {
                opPtr.fn(instruction{}, &pc, self.env, contract, mem, stack)
            } else {
                switch op {
                case PC:
                    opPc(instruction{data: new(big.Int).SetUint64(pc)}, &pc, self.env, contract, mem, stack)
                case JUMP:
                    if err := jump(pc, stack.pop()); err != nil {
                        return nil, err
                    }

                    continue
                case JUMPI:
                    pos, cond := stack.pop(), stack.pop()

                    if cond.Cmp(common.BigTrue) >= 0 {
                        if err := jump(pc, pos); err != nil {
                            return nil, err
                        }

                        continue
                    }
                case RETURN:
                    offset, size := stack.pop(), stack.pop()
                    ret := mem.GetPtr(offset.Int64(), size.Int64())

                    return ret, nil
                case SUICIDE:
                    opSuicide(instruction{}, nil, self.env, contract, mem, stack)

                    fallthrough
                case STOP: // Stop the contract
                    return nil, nil
                }
            }
        } else {
            return nil, fmt.Errorf("Invalid opcode %x", op)
        }

        pc++

    }
}

// calculateGasAndSize calculates the required given the opcode and stack items calculates the new memorysize for
// the operation. This does not reduce gas or resizes the memory.
func calculateGasAndSize(env Environment, contract *Contract, caller ContractRef, op OpCode, statedb Database, mem *Memory, stack *stack) (*big.Int, *big.Int, error) {
    var (
        gas                 = new(big.Int)
        newMemSize *big.Int = new(big.Int)
    )
    err := baseCheck(op, stack, gas)
    if err != nil {
        return nil, nil, err
    }

    // stack Check, memory resize & gas phase
    switch op {
    case SWAP1, SWAP2, SWAP3, SWAP4, SWAP5, SWAP6, SWAP7, SWAP8, SWAP9, SWAP10, SWAP11, SWAP12, SWAP13, SWAP14, SWAP15, SWAP16:
        n := int(op - SWAP1 + 2)
        err := stack.require(n)
        if err != nil {
            return nil, nil, err
        }
        gas.Set(GasFastestStep)
    case DUP1, DUP2, DUP3, DUP4, DUP5, DUP6, DUP7, DUP8, DUP9, DUP10, DUP11, DUP12, DUP13, DUP14, DUP15, DUP16:
        n := int(op - DUP1 + 1)
        err := stack.require(n)
        if err != nil {
            return nil, nil, err
        }
        gas.Set(GasFastestStep)
    case LOG0, LOG1, LOG2, LOG3, LOG4:
        n := int(op - LOG0)
        err := stack.require(n + 2)
        if err != nil {
            return nil, nil, err
        }

        mSize, mStart := stack.data[stack.len()-2], stack.data[stack.len()-1]

        gas.Add(gas, params.LogGas)
        gas.Add(gas, new(big.Int).Mul(big.NewInt(int64(n)), params.LogTopicGas))
        gas.Add(gas, new(big.Int).Mul(mSize, params.LogDataGas))

        newMemSize = calcMemSize(mStart, mSize)
    case EXP:
        gas.Add(gas, new(big.Int).Mul(big.NewInt(int64(len(stack.data[stack.len()-2].Bytes()))), params.ExpByteGas))
    case SSTORE:
        err := stack.require(2)
        if err != nil {
            return nil, nil, err
        }

        var g *big.Int
        y, x := stack.data[stack.len()-2], stack.data[stack.len()-1]
        val := statedb.GetState(contract.Address(), common.BigToHash(x))

        // This checks for 3 scenario's and calculates gas accordingly
        // 1. From a zero-value address to a non-zero value         (NEW VALUE)
        // 2. From a non-zero value address to a zero-value address (DELETE)
        // 3. From a nen-zero to a non-zero                         (CHANGE)
        if common.EmptyHash(val) && !common.EmptyHash(common.BigToHash(y)) {
            // 0 => non 0
            g = params.SstoreSetGas
        } else if !common.EmptyHash(val) && common.EmptyHash(common.BigToHash(y)) {
            statedb.AddRefund(params.SstoreRefundGas)

            g = params.SstoreClearGas
        } else {
            // non 0 => non 0 (or 0 => 0)
            g = params.SstoreClearGas
        }
        gas.Set(g)
    case SUICIDE:
        if !statedb.IsDeleted(contract.Address()) {
            statedb.AddRefund(params.SuicideRefundGas)
        }
    case MLOAD:
        newMemSize = calcMemSize(stack.peek(), u256(32))
    case MSTORE8:
        newMemSize = calcMemSize(stack.peek(), u256(1))
    case MSTORE:
        newMemSize = calcMemSize(stack.peek(), u256(32))
    case RETURN:
        newMemSize = calcMemSize(stack.peek(), stack.data[stack.len()-2])
    case SHA3:
        newMemSize = calcMemSize(stack.peek(), stack.data[stack.len()-2])

        words := toWordSize(stack.data[stack.len()-2])
        gas.Add(gas, words.Mul(words, params.Sha3WordGas))
    case CALLDATACOPY:
        newMemSize = calcMemSize(stack.peek(), stack.data[stack.len()-3])

        words := toWordSize(stack.data[stack.len()-3])
        gas.Add(gas, words.Mul(words, params.CopyGas))
    case CODECOPY:
        newMemSize = calcMemSize(stack.peek(), stack.data[stack.len()-3])

        words := toWordSize(stack.data[stack.len()-3])
        gas.Add(gas, words.Mul(words, params.CopyGas))
    case EXTCODECOPY:
        newMemSize = calcMemSize(stack.data[stack.len()-2], stack.data[stack.len()-4])

        words := toWordSize(stack.data[stack.len()-4])
        gas.Add(gas, words.Mul(words, params.CopyGas))

    case CREATE:
        newMemSize = calcMemSize(stack.data[stack.len()-2], stack.data[stack.len()-3])
    case CALL, CALLCODE:
        gas.Add(gas, stack.data[stack.len()-1])

        if op == CALL {
            if !env.Db().Exist(common.BigToAddress(stack.data[stack.len()-2])) {
                gas.Add(gas, params.CallNewAccountGas)
            }
        }

        if len(stack.data[stack.len()-3].Bytes()) > 0 {
            gas.Add(gas, params.CallValueTransferGas)
        }

        x := calcMemSize(stack.data[stack.len()-6], stack.data[stack.len()-7])
        y := calcMemSize(stack.data[stack.len()-4], stack.data[stack.len()-5])

        newMemSize = common.BigMax(x, y)
    case DELEGATECALL:
        gas.Add(gas, stack.data[stack.len()-1])

        x := calcMemSize(stack.data[stack.len()-5], stack.data[stack.len()-6])
        y := calcMemSize(stack.data[stack.len()-3], stack.data[stack.len()-4])

        newMemSize = common.BigMax(x, y)
    }
    quadMemGas(mem, newMemSize, gas)

    return newMemSize, gas, nil
}

// RunPrecompile runs and evaluate the output of a precompiled contract defined in contracts.go
func (self *Vm) RunPrecompiled(p *PrecompiledAccount, input []byte, contract *Contract) (ret []byte, err error) {
    gas := p.Gas(len(input))
    if contract.UseGas(gas) {
        ret = p.Call(input)

        return ret, nil
    } else {
        return nil, OutOfGasError
    }
}

// log emits a log event to the environment for each opcode encountered. This is not to be confused with the
// LOG* opcode.
func (self *Vm) log(pc uint64, op OpCode, gas, cost *big.Int, memory *Memory, stack *stack, contract *Contract, err error) {
    if Debug || GenerateStructLogs {
        mem := make([]byte, len(memory.Data()))
        copy(mem, memory.Data())

        stck := make([]*big.Int, len(stack.Data()))
        for i, item := range stack.Data() {
            stck[i] = new(big.Int).Set(item)
        }
        storage := make(map[common.Hash][]byte)
        contract.self.EachStorage(func(k, v []byte) {
            storage[common.BytesToHash(k)] = v
        })
        self.env.AddStructLog(StructLog{pc, op, new(big.Int).Set(gas), cost, mem, stck, storage, err})
    }
}

// Environment returns the current workable state of the VM
func (self *Vm) Env() Environment {
    return self.env
}