// Copyright 2017 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 (
"errors"
"github.com/ava-labs/coreth/params"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/common/math"
)
// memoryGasCost calculates the quadratic gas for memory expansion. It does so
// only for the memory region that is expanded, not the total memory.
func memoryGasCost(mem *Memory, newMemSize uint64) (uint64, error) {
if newMemSize == 0 {
return 0, nil
}
// The maximum that will fit in a uint64 is max_word_count - 1. Anything above
// that will result in an overflow. Additionally, a newMemSize which results in
// a newMemSizeWords larger than 0xFFFFFFFF will cause the square operation to
// overflow. The constant 0x1FFFFFFFE0 is the highest number that can be used
// without overflowing the gas calculation.
if newMemSize > 0x1FFFFFFFE0 {
return 0, ErrGasUintOverflow
}
newMemSizeWords := toWordSize(newMemSize)
newMemSize = newMemSizeWords * 32
if newMemSize > uint64(mem.Len()) {
square := newMemSizeWords * newMemSizeWords
linCoef := newMemSizeWords * params.MemoryGas
quadCoef := square / params.QuadCoeffDiv
newTotalFee := linCoef + quadCoef
fee := newTotalFee - mem.lastGasCost
mem.lastGasCost = newTotalFee
return fee, nil
}
return 0, nil
}
// memoryCopierGas creates the gas functions for the following opcodes, and takes
// the stack position of the operand which determines the size of the data to copy
// as argument:
// CALLDATACOPY (stack position 2)
// CODECOPY (stack position 2)
// EXTCODECOPY (stack poition 3)
// RETURNDATACOPY (stack position 2)
func memoryCopierGas(stackpos int) gasFunc {
return func(evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
// Gas for expanding the memory
gas, err := memoryGasCost(mem, memorySize)
if err != nil {
return 0, err
}
// And gas for copying data, charged per word at param.CopyGas
words, overflow := stack.Back(stackpos).Uint64WithOverflow()
if overflow {
return 0, ErrGasUintOverflow
}
if words, overflow = math.SafeMul(toWordSize(words), params.CopyGas); overflow {
return 0, ErrGasUintOverflow
}
if gas, overflow = math.SafeAdd(gas, words); overflow {
return 0, ErrGasUintOverflow
}
return gas, nil
}
}
var (
gasCallDataCopy = memoryCopierGas(2)
gasCodeCopy = memoryCopierGas(2)
gasExtCodeCopy = memoryCopierGas(3)
gasReturnDataCopy = memoryCopierGas(2)
)
func gasSStore(evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
var (
y, x = stack.Back(1), stack.Back(0)
current = evm.StateDB.GetState(contract.Address(), common.Hash(x.Bytes32()))
)
// The legacy gas metering only takes into consideration the current state
// Legacy rules should be applied if we are in Petersburg (removal of EIP-1283)
// OR Constantinople is not active
if evm.chainRules.IsPetersburg || !evm.chainRules.IsConstantinople {
// 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 non-zero to a non-zero (CHANGE)
switch {
case current == (common.Hash{}) && y.Sign() != 0: // 0 => non 0
return params.SstoreSetGas, nil
case current != (common.Hash{}) && y.Sign() == 0: // non 0 => 0
evm.StateDB.AddRefund(params.SstoreRefundGas)
return params.SstoreClearGas, nil
default: // non 0 => non 0 (or 0 => 0)
return params.SstoreResetGas, nil
}
}
// The new gas metering is based on net gas costs (EIP-1283):
//
// 1. If current value equals new value (this is a no-op), 200 gas is deducted.
// 2. If current value does not equal new value
// 2.1. If original value equals current value (this storage slot has not been changed by the current execution context)
// 2.1.1. If original value is 0, 20000 gas is deducted.
// 2.1.2. Otherwise, 5000 gas is deducted. If new value is 0, add 15000 gas to refund counter.
// 2.2. If original value does not equal current value (this storage slot is dirty), 200 gas is deducted. Apply both of the following clauses.
// 2.2.1. If original value is not 0
// 2.2.1.1. If current value is 0 (also means that new value is not 0), remove 15000 gas from refund counter. We can prove that refund counter will never go below 0.
// 2.2.1.2. If new value is 0 (also means that current value is not 0), add 15000 gas to refund counter.
// 2.2.2. If original value equals new value (this storage slot is reset)
// 2.2.2.1. If original value is 0, add 19800 gas to refund counter.
// 2.2.2.2. Otherwise, add 4800 gas to refund counter.
value := common.Hash(y.Bytes32())
if current == value { // noop (1)
return params.NetSstoreNoopGas, nil
}
original := evm.StateDB.GetCommittedState(contract.Address(), common.Hash(x.Bytes32()))
if original == current {
if original == (common.Hash{}) { // create slot (2.1.1)
return params.NetSstoreInitGas, nil
}
if value == (common.Hash{}) { // delete slot (2.1.2b)
evm.StateDB.AddRefund(params.NetSstoreClearRefund)
}
return params.NetSstoreCleanGas, nil // write existing slot (2.1.2)
}
if original != (common.Hash{}) {
if current == (common.Hash{}) { // recreate slot (2.2.1.1)
evm.StateDB.SubRefund(params.NetSstoreClearRefund)
} else if value == (common.Hash{}) { // delete slot (2.2.1.2)
evm.StateDB.AddRefund(params.NetSstoreClearRefund)
}
}
if original == value {
if original == (common.Hash{}) { // reset to original inexistent slot (2.2.2.1)
evm.StateDB.AddRefund(params.NetSstoreResetClearRefund)
} else { // reset to original existing slot (2.2.2.2)
evm.StateDB.AddRefund(params.NetSstoreResetRefund)
}
}
return params.NetSstoreDirtyGas, nil
}
// 0. If *gasleft* is less than or equal to 2300, fail the current call.
// 1. If current value equals new value (this is a no-op), SSTORE_NOOP_GAS gas is deducted.
// 2. If current value does not equal new value:
// 2.1. If original value equals current value (this storage slot has not been changed by the current execution context):
// 2.1.1. If original value is 0, SSTORE_INIT_GAS gas is deducted.
// 2.1.2. Otherwise, SSTORE_CLEAN_GAS gas is deducted. If new value is 0, add SSTORE_CLEAR_REFUND to refund counter.
// 2.2. If original value does not equal current value (this storage slot is dirty), SSTORE_DIRTY_GAS gas is deducted. Apply both of the following clauses:
// 2.2.1. If original value is not 0:
// 2.2.1.1. If current value is 0 (also means that new value is not 0), subtract SSTORE_CLEAR_REFUND gas from refund counter. We can prove that refund counter will never go below 0.
// 2.2.1.2. If new value is 0 (also means that current value is not 0), add SSTORE_CLEAR_REFUND gas to refund counter.
// 2.2.2. If original value equals new value (this storage slot is reset):
// 2.2.2.1. If original value is 0, add SSTORE_INIT_REFUND to refund counter.
// 2.2.2.2. Otherwise, add SSTORE_CLEAN_REFUND gas to refund counter.
func gasSStoreEIP2200(evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
// If we fail the minimum gas availability invariant, fail (0)
if contract.Gas <= params.SstoreSentryGasEIP2200 {
return 0, errors.New("not enough gas for reentrancy sentry")
}
// Gas sentry honoured, do the actual gas calculation based on the stored value
var (
y, x = stack.Back(1), stack.Back(0)
current = evm.StateDB.GetState(contract.Address(), common.Hash(x.Bytes32()))
)
value := common.Hash(y.Bytes32())
if current == value { // noop (1)
return params.SstoreNoopGasEIP2200, nil
}
original := evm.StateDB.GetCommittedState(contract.Address(), common.Hash(x.Bytes32()))
if original == current {
if original == (common.Hash{}) { // create slot (2.1.1)
return params.SstoreInitGasEIP2200, nil
}
if value == (common.Hash{}) { // delete slot (2.1.2b)
evm.StateDB.AddRefund(params.SstoreClearRefundEIP2200)
}
return params.SstoreCleanGasEIP2200, nil // write existing slot (2.1.2)
}
if original != (common.Hash{}) {
if current == (common.Hash{}) { // recreate slot (2.2.1.1)
evm.StateDB.SubRefund(params.SstoreClearRefundEIP2200)
} else if value == (common.Hash{}) { // delete slot (2.2.1.2)
evm.StateDB.AddRefund(params.SstoreClearRefundEIP2200)
}
}
if original == value {
if original == (common.Hash{}) { // reset to original inexistent slot (2.2.2.1)
evm.StateDB.AddRefund(params.SstoreInitRefundEIP2200)
} else { // reset to original existing slot (2.2.2.2)
evm.StateDB.AddRefund(params.SstoreCleanRefundEIP2200)
}
}
return params.SstoreDirtyGasEIP2200, nil // dirty update (2.2)
}
func makeGasLog(n uint64) gasFunc {
return func(evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
requestedSize, overflow := stack.Back(1).Uint64WithOverflow()
if overflow {
return 0, ErrGasUintOverflow
}
gas, err := memoryGasCost(mem, memorySize)
if err != nil {
return 0, err
}
if gas, overflow = math.SafeAdd(gas, params.LogGas); overflow {
return 0, ErrGasUintOverflow
}
if gas, overflow = math.SafeAdd(gas, n*params.LogTopicGas); overflow {
return 0, ErrGasUintOverflow
}
var memorySizeGas uint64
if memorySizeGas, overflow = math.SafeMul(requestedSize, params.LogDataGas); overflow {
return 0, ErrGasUintOverflow
}
if gas, overflow = math.SafeAdd(gas, memorySizeGas); overflow {
return 0, ErrGasUintOverflow
}
return gas, nil
}
}
func gasSha3(evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
gas, err := memoryGasCost(mem, memorySize)
if err != nil {
return 0, err
}
wordGas, overflow := stack.Back(1).Uint64WithOverflow()
if overflow {
return 0, ErrGasUintOverflow
}
if wordGas, overflow = math.SafeMul(toWordSize(wordGas), params.Sha3WordGas); overflow {
return 0, ErrGasUintOverflow
}
if gas, overflow = math.SafeAdd(gas, wordGas); overflow {
return 0, ErrGasUintOverflow
}
return gas, nil
}
// pureMemoryGascost is used by several operations, which aside from their
// static cost have a dynamic cost which is solely based on the memory
// expansion
func pureMemoryGascost(evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
return memoryGasCost(mem, memorySize)
}
var (
gasReturn = pureMemoryGascost
gasRevert = pureMemoryGascost
gasMLoad = pureMemoryGascost
gasMStore8 = pureMemoryGascost
gasMStore = pureMemoryGascost
gasCreate = pureMemoryGascost
)
func gasCreate2(evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
gas, err := memoryGasCost(mem, memorySize)
if err != nil {
return 0, err
}
wordGas, overflow := stack.Back(2).Uint64WithOverflow()
if overflow {
return 0, ErrGasUintOverflow
}
if wordGas, overflow = math.SafeMul(toWordSize(wordGas), params.Sha3WordGas); overflow {
return 0, ErrGasUintOverflow
}
if gas, overflow = math.SafeAdd(gas, wordGas); overflow {
return 0, ErrGasUintOverflow
}
return gas, nil
}
func gasExpFrontier(evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
expByteLen := uint64((stack.data[stack.len()-2].BitLen() + 7) / 8)
var (
gas = expByteLen * params.ExpByteFrontier // no overflow check required. Max is 256 * ExpByte gas
overflow bool
)
if gas, overflow = math.SafeAdd(gas, params.ExpGas); overflow {
return 0, ErrGasUintOverflow
}
return gas, nil
}
func gasExpEIP158(evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
expByteLen := uint64((stack.data[stack.len()-2].BitLen() + 7) / 8)
var (
gas = expByteLen * params.ExpByteEIP158 // no overflow check required. Max is 256 * ExpByte gas
overflow bool
)
if gas, overflow = math.SafeAdd(gas, params.ExpGas); overflow {
return 0, ErrGasUintOverflow
}
return gas, nil
}
func gasCall(evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
var (
gas uint64
transfersValue = !stack.Back(2).IsZero()
address = common.Address(stack.Back(1).Bytes20())
)
if evm.chainRules.IsEIP158 {
if transfersValue && evm.StateDB.Empty(address) {
gas += params.CallNewAccountGas
}
} else if !evm.StateDB.Exist(address) {
gas += params.CallNewAccountGas
}
if transfersValue {
gas += params.CallValueTransferGas
}
memoryGas, err := memoryGasCost(mem, memorySize)
if err != nil {
return 0, err
}
var overflow bool
if gas, overflow = math.SafeAdd(gas, memoryGas); overflow {
return 0, ErrGasUintOverflow
}
evm.callGasTemp, err = callGas(evm.chainRules.IsEIP150, contract.Gas, gas, stack.Back(0))
if err != nil {
return 0, err
}
if gas, overflow = math.SafeAdd(gas, evm.callGasTemp); overflow {
return 0, ErrGasUintOverflow
}
return gas, nil
}
func gasCallCode(evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
memoryGas, err := memoryGasCost(mem, memorySize)
if err != nil {
return 0, err
}
var (
gas uint64
overflow bool
)
if stack.Back(2).Sign() != 0 {
gas += params.CallValueTransferGas
}
if gas, overflow = math.SafeAdd(gas, memoryGas); overflow {
return 0, ErrGasUintOverflow
}
evm.callGasTemp, err = callGas(evm.chainRules.IsEIP150, contract.Gas, gas, stack.Back(0))
if err != nil {
return 0, err
}
if gas, overflow = math.SafeAdd(gas, evm.callGasTemp); overflow {
return 0, ErrGasUintOverflow
}
return gas, nil
}
func gasDelegateCall(evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
gas, err := memoryGasCost(mem, memorySize)
if err != nil {
return 0, err
}
evm.callGasTemp, err = callGas(evm.chainRules.IsEIP150, contract.Gas, gas, stack.Back(0))
if err != nil {
return 0, err
}
var overflow bool
if gas, overflow = math.SafeAdd(gas, evm.callGasTemp); overflow {
return 0, ErrGasUintOverflow
}
return gas, nil
}
func gasStaticCall(evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
gas, err := memoryGasCost(mem, memorySize)
if err != nil {
return 0, err
}
evm.callGasTemp, err = callGas(evm.chainRules.IsEIP150, contract.Gas, gas, stack.Back(0))
if err != nil {
return 0, err
}
var overflow bool
if gas, overflow = math.SafeAdd(gas, evm.callGasTemp); overflow {
return 0, ErrGasUintOverflow
}
return gas, nil
}
func gasSelfdestruct(evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
var gas uint64
// EIP150 homestead gas reprice fork:
if evm.chainRules.IsEIP150 {
gas = params.SelfdestructGasEIP150
var address = common.Address(stack.Back(0).Bytes20())
if evm.chainRules.IsEIP158 {
// if empty and transfers value
if evm.StateDB.Empty(address) && evm.StateDB.GetBalance(contract.Address()).Sign() != 0 {
gas += params.CreateBySelfdestructGas
}
} else if !evm.StateDB.Exist(address) {
gas += params.CreateBySelfdestructGas
}
}
if !evm.StateDB.HasSuicided(contract.Address()) {
evm.StateDB.AddRefund(params.SelfdestructRefundGas)
}
return gas, nil
}