evm.go

// Copyright 2018 The go-hpb Authors
// Modified based on go-ethereum, which Copyright (C) 2014 The go-ethereum Authors.
//
// The go-hpb 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-hpb 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-hpb. If not, see <http://www.gnu.org/licenses/>.

package evm

import (
	"github.com/hpb-project/go-hpb/vmcore"
	"math/big"
	"sync/atomic"
	"time"

	"github.com/hpb-project/go-hpb/blockchain/types"
	"github.com/hpb-project/go-hpb/common"
	"github.com/hpb-project/go-hpb/common/crypto"
	"github.com/hpb-project/go-hpb/common/log"
	"github.com/hpb-project/go-hpb/config"
	"github.com/hpb-project/go-hpb/consensus"
)

// 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 func(vmcore.StateDB, common.Address, *big.Int) bool
	TransferFunc    func(vmcore.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
)

func (evm *EVM) ActivePrecompiles() map[common.Address]PrecompiledContract {
	switch num := evm.BlockNumber.Uint64(); {
	case num > consensus.StageNumberNewPrecompiledContract:
		return PrecompiledContractsIstanbul
	default:
		return PrecompiledContractsByzantium
	}
}

// run runs the given contract and takes care of running precompiles with a fallback to the byte code interpreter.
func run(evm *EVM, snapshot int, contract *Contract, input []byte) ([]byte, error) {
	if contract.CodeAddr != nil {
		precompiles := evm.ActivePrecompiles()
		if p := precompiles[*contract.CodeAddr]; p != nil {
			return RunPrecompiledContract(p, input, contract)
		}
	}
	return evm.interpreter.Run(snapshot, contract, input)
}

// Context provides the EVM with auxiliary information. Once provided
// it shouldn't be modified.
type Context struct {
	// CanTransfer returns whether the account contains
	// sufficient hpber to transfer the value
	CanTransfer CanTransferFunc
	// Transfer transfers hpber from one account to the other
	Transfer TransferFunc
	// GetHash returns the hash corresponding to n
	GetHash GetHashFunc

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

	// Block information
	Miner       common.Address // Provides information for COINBASE
	GasLimit    *big.Int       // Provides information for GASLIMIT
	BlockNumber *big.Int       // Provides information for NUMBER
	Time        *big.Int       // Provides information for TIME
	Difficulty  *big.Int       // Provides information for DIFFICULTY
	Random      []byte
}

// EVM is the Hpb 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 vmcore.StateDB
	// Depth is the current call stack
	depth int

	// chainConfig contains information about the current chain
	chainConfig *config.ChainConfig
	// virtual machine configuration options used to initialise the
	// evm.
	vmConfig Config
	// global (to this context) hpb virtual machine
	// used throughout the execution of the tx.
	interpreter *Interpreter
	// abort is used to abort the EVM calling operations
	// NOTE: must be set atomically
	abort     int32
	StateDiff []*vmcore.State_Diff
	depthid   [config.CallCreateDepth]int
}

// ChainContext supports retrieving headers and consensus parameters from the
// current blockchain to be used during transaction processing.
type ChainContext interface {
	// Engine retrieves the chain's consensus engine.
	Engine() consensus.Engine

	// GetHeader returns the hash corresponding to their hash.
	GetHeader(common.Hash, uint64) *types.Header
}

// GetHashFn returns a GetHashFunc which retrieves header hashes by number
func GetHashFn(ref *types.Header, chain ChainContext) func(n uint64) common.Hash {
	return func(n uint64) common.Hash {
		for header := chain.GetHeader(ref.ParentHash, ref.Number.Uint64()-1); header != nil; header = chain.GetHeader(header.ParentHash, header.Number.Uint64()-1) {
			if header.Number.Uint64() == n {
				return header.Hash()
			}
		}

		return common.Hash{}
	}
}

// CanTransfer checks wether there are enough funds in the address' account to make a transfer.
// This does not take the necessary gas in to account to make the transfer valid.
func CanTransfer(db vmcore.StateDB, addr common.Address, amount *big.Int) bool {
	return db.GetBalance(addr).Cmp(amount) >= 0
}

// Transfer subtracts amount from sender and adds amount to recipient using the given Db
func Transfer(db vmcore.StateDB, sender, recipient common.Address, amount *big.Int) {
	db.SubBalance(sender, amount)
	db.AddBalance(recipient, amount)
}

// NewEVM retutrns a new EVM . The returned EVM is not thread safe and should
// only ever be used *once*.
func NewEVM(ctx Context, statedb vmcore.StateDB, chainConfig *config.ChainConfig, vmConfig Config) *EVM {
	evm := &EVM{
		Context:     ctx,
		StateDB:     statedb,
		vmConfig:    vmConfig,
		chainConfig: chainConfig,
	}

	evm.interpreter = NewInterpreter(evm, vmConfig)
	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)
}

// Cancelled returns true if Cancel has been called
func (evm *EVM) Cancelled() bool {
	return atomic.LoadInt32(&evm.abort) == 1
}

// 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 vmcore.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(config.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       = vmcore.AccountRef(addr)
		snapshot = evm.StateDB.Snapshot()
	)
	if !evm.StateDB.Exist(addr) {
		precompiles := evm.ActivePrecompiles()
		if precompiles[addr] == nil && 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)

	// 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(startGas uint64, startTime time.Time) { // Lazy evaluation of the parameters
			evm.vmConfig.Tracer.CaptureEnd(ret, startGas-gas, time.Since(startTime), err)
		}(gas, time.Now())
	}

	// initialise a new contract and set the code that is to be used by the
	// E 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, snapshot, contract, input)
	// 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)
		}
	} else {
		log.Debug("EVM Transfer", "caller", caller.Address(), "to", to.Address(), "value", value.String())

		statediff := &vmcore.State_Diff{
			From:     caller.Address(),
			To:       to.Address(),
			Tvalue:   value.String(),
			Gaslimit: gas,
			Depth:    evm.depth,
			Id:       evm.depthid[evm.depth],
		}
		evm.depthid[evm.depth]++
		evm.StateDiff = append(evm.StateDiff, statediff)
	}
	gas = contract.Gas
	return ret, contract.Gas, err
}

func (evm *EVM) InnerCall(caller vmcore.ContractRef, addr common.Address, input []byte) (ret []byte, err error) {
	if evm.vmConfig.NoRecursion && evm.depth > 0 {
		return nil, nil
	}

	// Fail if we're trying to execute above the call depth limit
	if evm.depth > int(config.CallCreateDepth) {
		return nil, ErrDepth
	}

	var (
		to       = vmcore.AccountRef(addr)
		snapshot = evm.StateDB.Snapshot()
	)
	if !evm.StateDB.Exist(addr) {
		precompiles := evm.ActivePrecompiles()
		if precompiles[addr] == nil {
			return nil, nil
		}
		evm.StateDB.CreateAccount(addr)
	}

	// initialise a new contract and set the code that is to be used by the
	// E The contract is a scoped environment for this execution context
	// only.
	contract := NewContract(caller, to, big.NewInt(0), 49999986000000000)
	contract.SetCallCode(&addr, evm.StateDB.GetCodeHash(addr), evm.StateDB.GetCode(addr))
	ret, err = run(evm, snapshot, contract, input)
	if err != nil {
		evm.StateDB.RevertToSnapshot(snapshot)
	}

	return ret, 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 vmcore.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(config.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       = vmcore.AccountRef(caller.Address())
	)
	// initialise a new contract and set the code that is to be used by the
	// E The contract is a scoped evmironment 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, snapshot, contract, input)
	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 vmcore.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(config.CallCreateDepth) {
		return nil, gas, ErrDepth
	}

	var (
		snapshot = evm.StateDB.Snapshot()
		to       = vmcore.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, snapshot, contract, input)
	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 vmcore.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(config.CallCreateDepth) {
		return nil, gas, ErrDepth
	}
	// 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 !evm.interpreter.readOnly {
		evm.interpreter.readOnly = true
		defer func() { evm.interpreter.readOnly = false }()
	}

	var (
		to       = vmcore.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))

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

// Create creates a new contract using code as deployment code.
func (evm *EVM) Create(caller vmcore.ContractRef, code []byte, gas uint64, value *big.Int) (ret []byte, contractAddr common.Address, leftOverGas uint64, err error) {

	// Depth check execution. Fail if we're trying to execute above the
	// limit.
	if evm.depth > int(config.CallCreateDepth) {
		return nil, common.Address{}, gas, ErrDepth
	}
	if !evm.CanTransfer(evm.StateDB, caller.Address(), value) {
		return nil, common.Address{}, gas, ErrInsufficientBalance
	}
	// Ensure there's no existing contract already at the designated address
	nonce := evm.StateDB.GetNonce(caller.Address())
	evm.StateDB.SetNonce(caller.Address(), nonce+1)

	contractAddr = crypto.CreateAddress(caller.Address(), nonce)
	contractHash := evm.StateDB.GetCodeHash(contractAddr)
	if evm.StateDB.GetNonce(contractAddr) != 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(contractAddr)
	evm.StateDB.SetNonce(contractAddr, 1)
	evm.Transfer(evm.StateDB, caller.Address(), contractAddr, value)

	// initialise a new contract and set the code that is to be used by the
	// E The contract is a scoped evmironment for this execution context
	// only.
	contract := NewContract(caller, vmcore.AccountRef(contractAddr), value, gas)

	contract.SetCallCode(&contractAddr, crypto.Keccak256Hash(code), code)
	if evm.vmConfig.NoRecursion && evm.depth > 0 {
		return nil, contractAddr, gas, nil
	}
	if evm.vmConfig.Debug && evm.depth == 0 {
		evm.vmConfig.Tracer.CaptureStart(caller.Address(), contractAddr, true, code, gas, value)
	}

	start := time.Now()

	ret, err = run(evm, snapshot, contract, nil)

	// check whether the max code size has been exceeded
	maxCodeSizeExceeded := len(ret) > config.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)) * config.CreateDataGas
		if contract.UseGas(createDataGas) {
			evm.StateDB.SetCode(contractAddr, 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.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, contractAddr, contract.Gas, err
}

func (evm *EVM) Create2(caller vmcore.ContractRef, code []byte, gas uint64, value *big.Int, salt *big.Int) (ret []byte, contractAddr common.Address, leftOverGas uint64, err error) {

	if evm.depth > int(config.CallCreateDepth) {
		return nil, common.Address{}, gas, ErrDepth
	}
	if !evm.CanTransfer(evm.StateDB, caller.Address(), value) {
		return nil, common.Address{}, gas, ErrInsufficientBalance
	}
	// Ensure there's no existing contract already at the designated address
	nonce := evm.StateDB.GetNonce(caller.Address())
	evm.StateDB.SetNonce(caller.Address(), nonce+1)
	codeHash := crypto.Keccak256Hash(code)
	contractAddr = common.BytesToAddress(crypto.Keccak256([]byte{0xff}, caller.Address().Bytes(), common.BigToHash(salt).Bytes(), codeHash.Bytes())[12:])
	contractHash := evm.StateDB.GetCodeHash(contractAddr)
	if evm.StateDB.GetNonce(contractAddr) != 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(contractAddr)
	evm.StateDB.SetNonce(contractAddr, 1)
	evm.Transfer(evm.StateDB, caller.Address(), contractAddr, value)

	// initialise a new contract and set the code that is to be used by the
	// E The contract is a scoped evmironment for this execution context
	// only.
	contract := NewContract(caller, vmcore.AccountRef(contractAddr), value, gas)

	contract.SetCallCode(&contractAddr, codeHash, code)
	if evm.vmConfig.NoRecursion && evm.depth > 0 {
		return nil, contractAddr, gas, nil
	}
	ret, err = run(evm, snapshot, contract, nil)

	// check whether the max code size has been exceeded
	maxCodeSizeExceeded := len(ret) > config.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)) * config.CreateDataGas
		if contract.UseGas(createDataGas) {
			evm.StateDB.SetCode(contractAddr, 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.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
	}
	return ret, contractAddr, contract.Gas, err
}

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

// Interpreter returns the EVM interpreter
func (evm *EVM) Interpreter() *Interpreter { return evm.interpreter }
func (evm *EVM) GetStateDiff() []*vmcore.State_Diff {
	return evm.StateDiff
}

func (evm *EVM) GetCoinbase() common.Address {
	return evm.Miner
}

func (evm *EVM) GetStateDB() vmcore.StateDB {
	return evm.StateDB
}

func (evm *EVM) GetOrigin() common.Address {
	return evm.Context.Origin
}