Official Go implementation of the Ethereum protocol
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go-ethereum/core/state/access_events.go

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// Copyright 2021 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 state
import (
"maps"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/common/math"
"github.com/ethereum/go-ethereum/params"
"github.com/ethereum/go-ethereum/trie/utils"
"github.com/holiman/uint256"
)
// mode specifies how a tree location has been accessed
// for the byte value:
// * the first bit is set if the branch has been edited
// * the second bit is set if the branch has been read
type mode byte
const (
AccessWitnessReadFlag = mode(1)
AccessWitnessWriteFlag = mode(2)
)
var zeroTreeIndex uint256.Int
// AccessEvents lists the locations of the state that are being accessed
// during the production of a block.
type AccessEvents struct {
branches map[branchAccessKey]mode
chunks map[chunkAccessKey]mode
pointCache *utils.PointCache
}
func NewAccessEvents(pointCache *utils.PointCache) *AccessEvents {
return &AccessEvents{
branches: make(map[branchAccessKey]mode),
chunks: make(map[chunkAccessKey]mode),
pointCache: pointCache,
}
}
// Merge is used to merge the access events that were generated during the
// execution of a tx, with the accumulation of all access events that were
// generated during the execution of all txs preceding this one in a block.
func (ae *AccessEvents) Merge(other *AccessEvents) {
for k := range other.branches {
ae.branches[k] |= other.branches[k]
}
for k, chunk := range other.chunks {
ae.chunks[k] |= chunk
}
}
// Keys returns, predictably, the list of keys that were touched during the
// buildup of the access witness.
func (ae *AccessEvents) Keys() [][]byte {
// TODO: consider if parallelizing this is worth it, probably depending on len(ae.chunks).
keys := make([][]byte, 0, len(ae.chunks))
for chunk := range ae.chunks {
basePoint := ae.pointCache.Get(chunk.addr[:])
key := utils.GetTreeKeyWithEvaluatedAddress(basePoint, &chunk.treeIndex, chunk.leafKey)
keys = append(keys, key)
}
return keys
}
func (ae *AccessEvents) Copy() *AccessEvents {
cpy := &AccessEvents{
branches: maps.Clone(ae.branches),
chunks: maps.Clone(ae.chunks),
pointCache: ae.pointCache,
}
return cpy
}
// AddAccount returns the gas to be charged for each of the currently cold
// member fields of an account.
func (ae *AccessEvents) AddAccount(addr common.Address, isWrite bool) uint64 {
var gas uint64
gas += ae.touchAddressAndChargeGas(addr, zeroTreeIndex, utils.BasicDataLeafKey, isWrite)
gas += ae.touchAddressAndChargeGas(addr, zeroTreeIndex, utils.CodeHashLeafKey, isWrite)
return gas
}
// MessageCallGas returns the gas to be charged for each of the currently
// cold member fields of an account, that need to be touched when making a message
// call to that account.
func (ae *AccessEvents) MessageCallGas(destination common.Address) uint64 {
var gas uint64
gas += ae.touchAddressAndChargeGas(destination, zeroTreeIndex, utils.BasicDataLeafKey, false)
return gas
}
// ValueTransferGas returns the gas to be charged for each of the currently
// cold balance member fields of the caller and the callee accounts.
func (ae *AccessEvents) ValueTransferGas(callerAddr, targetAddr common.Address) uint64 {
var gas uint64
gas += ae.touchAddressAndChargeGas(callerAddr, zeroTreeIndex, utils.BasicDataLeafKey, true)
gas += ae.touchAddressAndChargeGas(targetAddr, zeroTreeIndex, utils.BasicDataLeafKey, true)
return gas
}
// ContractCreateCPreheck charges access costs before
// a contract creation is initiated. It is just reads, because the
// address collision is done before the transfer, and so no write
// are guaranteed to happen at this point.
func (ae *AccessEvents) ContractCreatePreCheckGas(addr common.Address) uint64 {
var gas uint64
gas += ae.touchAddressAndChargeGas(addr, zeroTreeIndex, utils.BasicDataLeafKey, false)
gas += ae.touchAddressAndChargeGas(addr, zeroTreeIndex, utils.CodeHashLeafKey, false)
return gas
}
// ContractCreateInitGas returns the access gas costs for the initialization of
// a contract creation.
func (ae *AccessEvents) ContractCreateInitGas(addr common.Address) uint64 {
var gas uint64
gas += ae.touchAddressAndChargeGas(addr, zeroTreeIndex, utils.BasicDataLeafKey, true)
gas += ae.touchAddressAndChargeGas(addr, zeroTreeIndex, utils.CodeHashLeafKey, true)
return gas
}
// AddTxOrigin adds the member fields of the sender account to the access event list,
// so that cold accesses are not charged, since they are covered by the 21000 gas.
func (ae *AccessEvents) AddTxOrigin(originAddr common.Address) {
ae.touchAddressAndChargeGas(originAddr, zeroTreeIndex, utils.BasicDataLeafKey, true)
ae.touchAddressAndChargeGas(originAddr, zeroTreeIndex, utils.CodeHashLeafKey, false)
}
// AddTxDestination adds the member fields of the sender account to the access event list,
// so that cold accesses are not charged, since they are covered by the 21000 gas.
func (ae *AccessEvents) AddTxDestination(addr common.Address, sendsValue bool) {
ae.touchAddressAndChargeGas(addr, zeroTreeIndex, utils.BasicDataLeafKey, sendsValue)
ae.touchAddressAndChargeGas(addr, zeroTreeIndex, utils.CodeHashLeafKey, false)
}
// SlotGas returns the amount of gas to be charged for a cold storage access.
func (ae *AccessEvents) SlotGas(addr common.Address, slot common.Hash, isWrite bool) uint64 {
treeIndex, subIndex := utils.StorageIndex(slot.Bytes())
return ae.touchAddressAndChargeGas(addr, *treeIndex, subIndex, isWrite)
}
// touchAddressAndChargeGas adds any missing access event to the access event list, and returns the cold
// access cost to be charged, if need be.
func (ae *AccessEvents) touchAddressAndChargeGas(addr common.Address, treeIndex uint256.Int, subIndex byte, isWrite bool) uint64 {
stemRead, selectorRead, stemWrite, selectorWrite, selectorFill := ae.touchAddress(addr, treeIndex, subIndex, isWrite)
var gas uint64
if stemRead {
gas += params.WitnessBranchReadCost
}
if selectorRead {
gas += params.WitnessChunkReadCost
}
if stemWrite {
gas += params.WitnessBranchWriteCost
}
if selectorWrite {
gas += params.WitnessChunkWriteCost
}
if selectorFill {
gas += params.WitnessChunkFillCost
}
return gas
}
// touchAddress adds any missing access event to the access event list.
func (ae *AccessEvents) touchAddress(addr common.Address, treeIndex uint256.Int, subIndex byte, isWrite bool) (bool, bool, bool, bool, bool) {
branchKey := newBranchAccessKey(addr, treeIndex)
chunkKey := newChunkAccessKey(branchKey, subIndex)
// Read access.
var branchRead, chunkRead bool
if _, hasStem := ae.branches[branchKey]; !hasStem {
branchRead = true
ae.branches[branchKey] = AccessWitnessReadFlag
}
if _, hasSelector := ae.chunks[chunkKey]; !hasSelector {
chunkRead = true
ae.chunks[chunkKey] = AccessWitnessReadFlag
}
// Write access.
var branchWrite, chunkWrite, chunkFill bool
if isWrite {
if (ae.branches[branchKey] & AccessWitnessWriteFlag) == 0 {
branchWrite = true
ae.branches[branchKey] |= AccessWitnessWriteFlag
}
chunkValue := ae.chunks[chunkKey]
if (chunkValue & AccessWitnessWriteFlag) == 0 {
chunkWrite = true
ae.chunks[chunkKey] |= AccessWitnessWriteFlag
}
// TODO: charge chunk filling costs if the leaf was previously empty in the state
}
return branchRead, chunkRead, branchWrite, chunkWrite, chunkFill
}
type branchAccessKey struct {
addr common.Address
treeIndex uint256.Int
}
func newBranchAccessKey(addr common.Address, treeIndex uint256.Int) branchAccessKey {
var sk branchAccessKey
sk.addr = addr
sk.treeIndex = treeIndex
return sk
}
type chunkAccessKey struct {
branchAccessKey
leafKey byte
}
func newChunkAccessKey(branchKey branchAccessKey, leafKey byte) chunkAccessKey {
var lk chunkAccessKey
lk.branchAccessKey = branchKey
lk.leafKey = leafKey
return lk
}
// CodeChunksRangeGas is a helper function to touch every chunk in a code range and charge witness gas costs
func (ae *AccessEvents) CodeChunksRangeGas(contractAddr common.Address, startPC, size uint64, codeLen uint64, isWrite bool) uint64 {
// note that in the case where the copied code is outside the range of the
// contract code but touches the last leaf with contract code in it,
// we don't include the last leaf of code in the AccessWitness. The
// reason that we do not need the last leaf is the account's code size
// is already in the AccessWitness so a stateless verifier can see that
// the code from the last leaf is not needed.
if (codeLen == 0 && size == 0) || startPC > codeLen {
return 0
}
endPC := startPC + size
if endPC > codeLen {
endPC = codeLen
}
if endPC > 0 {
endPC -= 1 // endPC is the last bytecode that will be touched.
}
var statelessGasCharged uint64
for chunkNumber := startPC / 31; chunkNumber <= endPC/31; chunkNumber++ {
treeIndex := *uint256.NewInt((chunkNumber + 128) / 256)
subIndex := byte((chunkNumber + 128) % 256)
gas := ae.touchAddressAndChargeGas(contractAddr, treeIndex, subIndex, isWrite)
var overflow bool
statelessGasCharged, overflow = math.SafeAdd(statelessGasCharged, gas)
if overflow {
panic("overflow when adding gas")
}
}
return statelessGasCharged
}
// BasicDataGas adds the account's basic data to the accessed data, and returns the
// amount of gas that it costs.
// Note that an access in write mode implies an access in read mode, whereas an
// access in read mode does not imply an access in write mode.
func (ae *AccessEvents) BasicDataGas(addr common.Address, isWrite bool) uint64 {
return ae.touchAddressAndChargeGas(addr, zeroTreeIndex, utils.BasicDataLeafKey, isWrite)
}
// CodeHashGas adds the account's code hash to the accessed data, and returns the
// amount of gas that it costs.
// in write mode. If false, the charged gas corresponds to an access in read mode.
// Note that an access in write mode implies an access in read mode, whereas an access in
// read mode does not imply an access in write mode.
func (ae *AccessEvents) CodeHashGas(addr common.Address, isWrite bool) uint64 {
return ae.touchAddressAndChargeGas(addr, zeroTreeIndex, utils.CodeHashLeafKey, isWrite)
}