path: root/core/vm/evm.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 (
    "math/big"
    "sync/atomic"
    "time"

    "github.com/dexon-foundation/dexon/common"
    "github.com/dexon-foundation/dexon/core/state"
    "github.com/dexon-foundation/dexon/crypto"
    "github.com/dexon-foundation/dexon/params"
)

// emptyCodeHash is used by create to ensure deployment is disallowed to already
// deployed contract addresses (relevant after the account abstraction).
var emptyCodeHash = crypto.Keccak256Hash(nil)

type (
    // CanTransferFunc is the signature of a transfer guard function
    CanTransferFunc func(StateDB, common.Address, *big.Int) bool
    // TransferFunc is the signature of a transfer function
    TransferFunc func(StateDB, common.Address, common.Address, *big.Int)
    // GetHashFunc returns the nth block hash in the blockchain
    // and is used by the BLOCKHASH EVM op code.
    GetHashFunc func(uint64) common.Hash
    // StateAtFunc returns the statedb given a root hash.
    StateAtNumberFunc func(uint64) (*state.StateDB, error)
    // GetRoundHeightFunc returns the round height.
    GetRoundHeightFunc func(uint64) (uint64, bool)
)

// run runs the given contract and takes care of running precompiles with a fallback to the byte code interpreter.
func run(evm *EVM, contract *Contract, input []byte, readOnly bool) ([]byte, error) {
    if contract.CodeAddr != nil {
        if o := OracleContracts[*contract.CodeAddr]; o != nil {
            return RunOracleContract(o(), evm, input, contract)
        }
        precompiles := PrecompiledContractsHomestead
        if evm.ChainConfig().IsByzantium(evm.BlockNumber) {
            precompiles = PrecompiledContractsByzantium
        }
        if p := precompiles[*contract.CodeAddr]; p != nil {
            return RunPrecompiledContract(p, input, contract)
        }
    }
    for _, interpreter := range evm.interpreters {
        if interpreter.CanRun(contract.Code) {
            if evm.interpreter != interpreter {
                // Ensure that the interpreter pointer is set back
                // to its current value upon return.
                defer func(i Interpreter) {
                    evm.interpreter = i
                }(evm.interpreter)
                evm.interpreter = interpreter
            }
            return interpreter.Run(contract, input, readOnly)
        }
    }
    return nil, ErrNoCompatibleInterpreter
}

// Context provides the EVM with auxiliary information. Once provided
// it shouldn't be modified.
type Context struct {
    // CanTransfer returns whether the account contains
    // sufficient ether to transfer the value
    CanTransfer CanTransferFunc
    // Transfer transfers ether from one account to the other
    Transfer TransferFunc
    // GetHash returns the hash corresponding to n
    GetHash GetHashFunc
    // StateAtNumber returns the statedb given a root hash.
    StateAtNumber StateAtNumberFunc
    // GetRoundHeight returns the round height.
    GetRoundHeight GetRoundHeightFunc

    // Message information
    Origin   common.Address // Provides information for ORIGIN
    GasPrice *big.Int       // Provides information for GASPRICE

    // Block information
    Coinbase    common.Address // Provides information for COINBASE
    GasLimit    uint64         // Provides information for GASLIMIT
    BlockNumber *big.Int       // Provides information for NUMBER
    Time        *big.Int       // Provides information for TIME
    Randomness  []byte         // Provides information for RAND
    Difficulty  *big.Int       // Provides information for DIFFICULTY
    Round       *big.Int       // Current round number.

    RandCallIndex uint64 // Number of times opRand is called
}

// EVM is the Ethereum Virtual Machine base object and provides
// the necessary tools to run a contract on the given state with
// the provided context. It should be noted that any error
// generated through any of the calls should be considered a
// revert-state-and-consume-all-gas operation, no checks on
// specific errors should ever be performed. The interpreter makes
// sure that any errors generated are to be considered faulty code.
//
// The EVM should never be reused and is not thread safe.
type EVM struct {
    // Context provides auxiliary blockchain related information
    Context
    // StateDB gives access to the underlying state
    StateDB StateDB
    // Depth is the current call stack
    depth int

    // chainConfig contains information about the current chain
    chainConfig *params.ChainConfig
    // chain rules contains the chain rules for the current epoch
    chainRules params.Rules
    // virtual machine configuration options used to initialise the
    // evm.
    vmConfig Config
    // global (to this context) ethereum virtual machine
    // used throughout the execution of the tx.
    interpreters []Interpreter
    interpreter  Interpreter
    // abort is used to abort the EVM calling operations
    // NOTE: must be set atomically
    abort int32
    // callGasTemp holds the gas available for the current call. This is needed because the
    // available gas is calculated in gasCall* according to the 63/64 rule and later
    // applied in opCall*.
    callGasTemp uint64
}

// NewEVM returns a new EVM. The returned EVM is not thread safe and should
// only ever be used *once*.
func NewEVM(ctx Context, statedb StateDB, chainConfig *params.ChainConfig, vmConfig Config) *EVM {
    evm := &EVM{
        Context:      ctx,
        StateDB:      statedb,
        vmConfig:     vmConfig,
        chainConfig:  chainConfig,
        chainRules:   chainConfig.Rules(ctx.BlockNumber),
        interpreters: make([]Interpreter, 0, 1),
    }

    if chainConfig.IsEWASM(ctx.BlockNumber) {
        // to be implemented by EVM-C and Wagon PRs.
        // if vmConfig.EWASMInterpreter != "" {
        //  extIntOpts := strings.Split(vmConfig.EWASMInterpreter, ":")
        //  path := extIntOpts[0]
        //  options := []string{}
        //  if len(extIntOpts) > 1 {
        //    options = extIntOpts[1..]
        //  }
        //  evm.interpreters = append(evm.interpreters, NewEVMVCInterpreter(evm, vmConfig, options))
        // } else {
        //  evm.interpreters = append(evm.interpreters, NewEWASMInterpreter(evm, vmConfig))
        // }
        panic("No supported ewasm interpreter yet.")
    }

    // vmConfig.EVMInterpreter will be used by EVM-C, it won't be checked here
    // as we always want to have the built-in EVM as the failover option.
    evm.interpreters = append(evm.interpreters, NewEVMInterpreter(evm, vmConfig))
    evm.interpreter = evm.interpreters[0]

    return evm
}

// Cancel cancels any running EVM operation. This may be called concurrently and
// it's safe to be called multiple times.
func (evm *EVM) Cancel() {
    atomic.StoreInt32(&evm.abort, 1)
}

// Interpreter returns the current interpreter
func (evm *EVM) Interpreter() Interpreter {
    return evm.interpreter
}

// Call executes the contract associated with the addr with the given input as
// parameters. It also handles any necessary value transfer required and takes
// the necessary steps to create accounts and reverses the state in case of an
// execution error or failed value transfer.
func (evm *EVM) Call(caller ContractRef, addr common.Address, input []byte, gas uint64, value *big.Int) (ret []byte, leftOverGas uint64, err error) {
    if evm.vmConfig.NoRecursion && evm.depth > 0 {
        return nil, gas, nil
    }

    // Fail if we're trying to execute above the call depth limit
    if evm.depth > int(params.CallCreateDepth) {
        return nil, gas, ErrDepth
    }
    // Fail if we're trying to transfer more than the available balance
    if !evm.Context.CanTransfer(evm.StateDB, caller.Address(), value) {
        return nil, gas, ErrInsufficientBalance
    }

    var (
        to       = AccountRef(addr)
        snapshot = evm.StateDB.Snapshot()
    )
    if !evm.StateDB.Exist(addr) {
        precompiles := PrecompiledContractsHomestead
        if evm.ChainConfig().IsByzantium(evm.BlockNumber) {
            precompiles = PrecompiledContractsByzantium
        }
        if precompiles[addr] == nil && OracleContracts[addr] == nil &&
            evm.ChainConfig().IsEIP158(evm.BlockNumber) && value.Sign() == 0 {
            // Calling a non existing account, don't do anything, but ping the tracer
            if evm.vmConfig.Debug && evm.depth == 0 {
                evm.vmConfig.Tracer.CaptureStart(caller.Address(), addr, false, input, gas, value)
                evm.vmConfig.Tracer.CaptureEnd(ret, 0, 0, nil)
            }
            return nil, gas, nil
        }
        evm.StateDB.CreateAccount(addr)
    }
    evm.Transfer(evm.StateDB, caller.Address(), to.Address(), value)
    // 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, to, value, gas)
    contract.SetCallCode(&addr, evm.StateDB.GetCodeHash(addr), evm.StateDB.GetCode(addr))

    // Even if the account has no code, we need to continue because it might be a precompile
    start := time.Now()

    // Capture the tracer start/end events in debug mode
    if evm.vmConfig.Debug && evm.depth == 0 {
        evm.vmConfig.Tracer.CaptureStart(caller.Address(), addr, false, input, gas, value)

        defer func() { // Lazy evaluation of the parameters
            evm.vmConfig.Tracer.CaptureEnd(ret, gas-contract.Gas, time.Since(start), err)
        }()
    }
    ret, err = run(evm, contract, input, false)

    // 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
    // when we're in homestead this also counts for code storage gas errors.
    if err != nil {
        evm.StateDB.RevertToSnapshot(snapshot)
        if err != errExecutionReverted {
            contract.UseGas(contract.Gas)
        }
    }
    return ret, contract.Gas, err
}

// CallCode executes the contract associated with the addr with the given input
// as parameters. It also handles any necessary value transfer required and takes
// the necessary steps to create accounts and reverses the state in case of an
// execution error or failed value transfer.
//
// CallCode differs from Call in the sense that it executes the given address'
// code with the caller as context.
func (evm *EVM) CallCode(caller ContractRef, addr common.Address, input []byte, gas uint64, value *big.Int) (ret []byte, leftOverGas uint64, err error) {
    if evm.vmConfig.NoRecursion && evm.depth > 0 {
        return nil, gas, nil
    }

    // Fail if we're trying to execute above the call depth limit
    if evm.depth > int(params.CallCreateDepth) {
        return nil, gas, ErrDepth
    }
    // Fail if we're trying to transfer more than the available balance
    if !evm.CanTransfer(evm.StateDB, caller.Address(), value) {
        return nil, gas, ErrInsufficientBalance
    }

    var (
        snapshot = evm.StateDB.Snapshot()
        to       = AccountRef(caller.Address())
    )
    // 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, to, value, gas)
    contract.SetCallCode(&addr, evm.StateDB.GetCodeHash(addr), evm.StateDB.GetCode(addr))

    ret, err = run(evm, contract, input, false)
    if err != nil {
        evm.StateDB.RevertToSnapshot(snapshot)
        if err != errExecutionReverted {
            contract.UseGas(contract.Gas)
        }
    }
    return ret, contract.Gas, err
}

// DelegateCall executes the contract associated with the addr with the given input
// as parameters. It reverses the state in case of an execution error.
//
// DelegateCall differs from CallCode in the sense that it executes the given address'
// code with the caller as context and the caller is set to the caller of the caller.
func (evm *EVM) DelegateCall(caller ContractRef, addr common.Address, input []byte, gas uint64) (ret []byte, leftOverGas uint64, err error) {
    if evm.vmConfig.NoRecursion && evm.depth > 0 {
        return nil, gas, nil
    }
    // Fail if we're trying to execute above the call depth limit
    if evm.depth > int(params.CallCreateDepth) {
        return nil, gas, ErrDepth
    }

    var (
        snapshot = evm.StateDB.Snapshot()
        to       = AccountRef(caller.Address())
    )

    // Initialise a new contract and make initialise the delegate values
    contract := NewContract(caller, to, nil, gas).AsDelegate()
    contract.SetCallCode(&addr, evm.StateDB.GetCodeHash(addr), evm.StateDB.GetCode(addr))

    ret, err = run(evm, contract, input, false)
    if err != nil {
        evm.StateDB.RevertToSnapshot(snapshot)
        if err != errExecutionReverted {
            contract.UseGas(contract.Gas)
        }
    }
    return ret, contract.Gas, err
}

// StaticCall executes the contract associated with the addr with the given input
// as parameters while disallowing any modifications to the state during the call.
// Opcodes that attempt to perform such modifications will result in exceptions
// instead of performing the modifications.
func (evm *EVM) StaticCall(caller ContractRef, addr common.Address, input []byte, gas uint64) (ret []byte, leftOverGas uint64, err error) {
    if evm.vmConfig.NoRecursion && evm.depth > 0 {
        return nil, gas, nil
    }
    // Fail if we're trying to execute above the call depth limit
    if evm.depth > int(params.CallCreateDepth) {
        return nil, gas, ErrDepth
    }

    var (
        to       = AccountRef(addr)
        snapshot = evm.StateDB.Snapshot()
    )
    // 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, to, new(big.Int), gas)
    contract.SetCallCode(&addr, evm.StateDB.GetCodeHash(addr), evm.StateDB.GetCode(addr))

    // We do an AddBalance of zero here, just in order to trigger a touch.
    // This doesn't matter on Mainnet, where all empties are gone at the time of Byzantium,
    // but is the correct thing to do and matters on other networks, in tests, and potential
    // future scenarios
    evm.StateDB.AddBalance(addr, bigZero)

    // 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
    // when we're in Homestead this also counts for code storage gas errors.
    ret, err = run(evm, contract, input, true)
    if err != nil {
        evm.StateDB.RevertToSnapshot(snapshot)
        if err != errExecutionReverted {
            contract.UseGas(contract.Gas)
        }
    }
    return ret, contract.Gas, err
}

type codeAndHash struct {
    code []byte
    hash common.Hash
}

func (c *codeAndHash) Hash() common.Hash {
    if c.hash == (common.Hash{}) {
        c.hash = crypto.Keccak256Hash(c.code)
    }
    return c.hash
}

// create creates a new contract using code as deployment code.
func (evm *EVM) create(caller ContractRef, codeAndHash *codeAndHash, gas uint64, value *big.Int, address common.Address) ([]byte, common.Address, uint64, error) {
    // Depth check execution. Fail if we're trying to execute above the
    // limit.
    if evm.depth > int(params.CallCreateDepth) {
        return nil, common.Address{}, gas, ErrDepth
    }
    if !evm.CanTransfer(evm.StateDB, caller.Address(), value) {
        return nil, common.Address{}, gas, ErrInsufficientBalance
    }
    nonce := evm.StateDB.GetNonce(caller.Address())
    evm.StateDB.SetNonce(caller.Address(), nonce+1)

    // Ensure there's no existing contract already at the designated address
    contractHash := evm.StateDB.GetCodeHash(address)
    if evm.StateDB.GetNonce(address) != 0 || (contractHash != (common.Hash{}) && contractHash != emptyCodeHash) {
        return nil, common.Address{}, 0, ErrContractAddressCollision
    }
    // Create a new account on the state
    snapshot := evm.StateDB.Snapshot()
    evm.StateDB.CreateAccount(address)
    if evm.ChainConfig().IsEIP158(evm.BlockNumber) {
        evm.StateDB.SetNonce(address, 1)
    }
    evm.Transfer(evm.StateDB, caller.Address(), address, value)

    // 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(address), value, gas)
    contract.SetCodeOptionalHash(&address, codeAndHash)

    if evm.vmConfig.NoRecursion && evm.depth > 0 {
        return nil, address, gas, nil
    }

    if evm.vmConfig.Debug && evm.depth == 0 {
        evm.vmConfig.Tracer.CaptureStart(caller.Address(), address, true, codeAndHash.code, gas, value)
    }
    start := time.Now()

    ret, err := run(evm, contract, nil, false)

    // check whether the max code size has been exceeded
    maxCodeSizeExceeded := evm.ChainConfig().IsEIP158(evm.BlockNumber) && len(ret) > params.MaxCodeSize
    // if the contract creation ran successfully and no errors were returned
    // calculate the gas required to store the code. If the code could not
    // be stored due to not enough gas set an error and let it be handled
    // by the error checking condition below.
    if err == nil && !maxCodeSizeExceeded {
        createDataGas := uint64(len(ret)) * params.CreateDataGas
        if contract.UseGas(createDataGas) {
            evm.StateDB.SetCode(address, ret)
        } else {
            err = ErrCodeStoreOutOfGas
        }
    }

    // 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
    // when we're in homestead this also counts for code storage gas errors.
    if maxCodeSizeExceeded || (err != nil && (evm.ChainConfig().IsHomestead(evm.BlockNumber) || err != ErrCodeStoreOutOfGas)) {
        evm.StateDB.RevertToSnapshot(snapshot)
        if err != errExecutionReverted {
            contract.UseGas(contract.Gas)
        }
    }
    // Assign err if contract code size exceeds the max while the err is still empty.
    if maxCodeSizeExceeded && err == nil {
        err = errMaxCodeSizeExceeded
    }
    if evm.vmConfig.Debug && evm.depth == 0 {
        evm.vmConfig.Tracer.CaptureEnd(ret, gas-contract.Gas, time.Since(start), err)
    }
    return ret, address, contract.Gas, err

}

// Create creates a new contract using code as deployment code.
func (evm *EVM) Create(caller ContractRef, code []byte, gas uint64, value *big.Int) (ret []byte, contractAddr common.Address, leftOverGas uint64, err error) {
    contractAddr = crypto.CreateAddress(caller.Address(), evm.StateDB.GetNonce(caller.Address()))
    return evm.create(caller, &codeAndHash{code: code}, gas, value, contractAddr)
}

// Create2 creates a new contract using code as deployment code.
//
// The different between Create2 with Create is Create2 uses sha3(0xff ++ msg.sender ++ salt ++ sha3(init_code))[12:]
// instead of the usual sender-and-nonce-hash as the address where the contract is initialized at.
func (evm *EVM) Create2(caller ContractRef, code []byte, gas uint64, endowment *big.Int, salt *big.Int) (ret []byte, contractAddr common.Address, leftOverGas uint64, err error) {
    codeAndHash := &codeAndHash{code: code}
    contractAddr = crypto.CreateAddress2(caller.Address(), common.BigToHash(salt), codeAndHash.Hash().Bytes())
    return evm.create(caller, codeAndHash, gas, endowment, contractAddr)
}

// ChainConfig returns the environment's chain configuration
func (evm *EVM) ChainConfig() *params.ChainConfig { return evm.chainConfig }

// IsBlockProposer returns whether or not we are a block proposer.
func (evm *EVM) IsBlockProposer() bool { return evm.vmConfig.IsBlockProposer }