// 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 . package vm import ( "errors" "github.com/ethereum/go-ethereum/common" "github.com/ethereum/go-ethereum/common/math" "github.com/ethereum/go-ethereum/params" ) // 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 := bigUint64(stack.Back(stackpos)) 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.BigToHash(x)) ) // 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.BigToHash(y) if current == value { // noop (1) return params.NetSstoreNoopGas, nil } original := evm.StateDB.GetCommittedState(contract.Address(), common.BigToHash(x)) 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.BigToHash(x)) ) value := common.BigToHash(y) if current == value { // noop (1) return params.SstoreNoopGasEIP2200, nil } original := evm.StateDB.GetCommittedState(contract.Address(), common.BigToHash(x)) 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 := bigUint64(stack.Back(1)) 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 := bigUint64(stack.Back(1)) 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 := bigUint64(stack.Back(2)) 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).Sign() != 0 address = common.BigToAddress(stack.Back(1)) ) 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.BigToAddress(stack.Back(0)) 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 }