plugeth/eth/tracers/native/prestate.go

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// Copyright 2022 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 native
import (
"bytes"
"encoding/json"
"math/big"
"sync/atomic"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/common/hexutil"
"github.com/ethereum/go-ethereum/core/vm"
"github.com/ethereum/go-ethereum/crypto"
"github.com/ethereum/go-ethereum/eth/tracers"
"github.com/ethereum/go-ethereum/log"
)
//go:generate go run github.com/fjl/gencodec -type account -field-override accountMarshaling -out gen_account_json.go
func init() {
tracers.DefaultDirectory.Register("prestateTracer", newPrestateTracer, false)
}
type state = map[common.Address]*account
type account struct {
Balance *big.Int `json:"balance,omitempty"`
Code []byte `json:"code,omitempty"`
Nonce uint64 `json:"nonce,omitempty"`
Storage map[common.Hash]common.Hash `json:"storage,omitempty"`
}
func (a *account) exists() bool {
return a.Nonce > 0 || len(a.Code) > 0 || len(a.Storage) > 0 || (a.Balance != nil && a.Balance.Sign() != 0)
}
type accountMarshaling struct {
Balance *hexutil.Big
Code hexutil.Bytes
}
type prestateTracer struct {
noopTracer
env *vm.EVM
pre state
post state
create bool
to common.Address
gasLimit uint64 // Amount of gas bought for the whole tx
config prestateTracerConfig
interrupt atomic.Bool // Atomic flag to signal execution interruption
reason error // Textual reason for the interruption
created map[common.Address]bool
deleted map[common.Address]bool
}
type prestateTracerConfig struct {
DiffMode bool `json:"diffMode"` // If true, this tracer will return state modifications
}
func newPrestateTracer(ctx *tracers.Context, cfg json.RawMessage) (tracers.Tracer, error) {
var config prestateTracerConfig
if cfg != nil {
if err := json.Unmarshal(cfg, &config); err != nil {
return nil, err
}
}
return &prestateTracer{
pre: state{},
post: state{},
config: config,
created: make(map[common.Address]bool),
deleted: make(map[common.Address]bool),
}, nil
}
// CaptureStart implements the EVMLogger interface to initialize the tracing operation.
func (t *prestateTracer) CaptureStart(env *vm.EVM, from common.Address, to common.Address, create bool, input []byte, gas uint64, value *big.Int) {
t.env = env
t.create = create
t.to = to
t.lookupAccount(from)
t.lookupAccount(to)
t.lookupAccount(env.Context.Coinbase)
// The recipient balance includes the value transferred.
toBal := new(big.Int).Sub(t.pre[to].Balance, value)
t.pre[to].Balance = toBal
// The sender balance is after reducing: value and gasLimit.
// We need to re-add them to get the pre-tx balance.
fromBal := new(big.Int).Set(t.pre[from].Balance)
gasPrice := env.TxContext.GasPrice
consumedGas := new(big.Int).Mul(gasPrice, new(big.Int).SetUint64(t.gasLimit))
fromBal.Add(fromBal, new(big.Int).Add(value, consumedGas))
t.pre[from].Balance = fromBal
t.pre[from].Nonce--
if create && t.config.DiffMode {
t.created[to] = true
}
}
// CaptureEnd is called after the call finishes to finalize the tracing.
func (t *prestateTracer) CaptureEnd(output []byte, gasUsed uint64, err error) {
if t.config.DiffMode {
return
}
if t.create {
// Keep existing account prior to contract creation at that address
if s := t.pre[t.to]; s != nil && !s.exists() {
// Exclude newly created contract.
delete(t.pre, t.to)
}
}
}
// CaptureState implements the EVMLogger interface to trace a single step of VM execution.
func (t *prestateTracer) CaptureState(pc uint64, op vm.OpCode, gas, cost uint64, scope *vm.ScopeContext, rData []byte, depth int, err error) {
if err != nil {
return
}
// Skip if tracing was interrupted
if t.interrupt.Load() {
return
}
stack := scope.Stack
stackData := stack.Data()
stackLen := len(stackData)
caller := scope.Contract.Address()
switch {
case stackLen >= 1 && (op == vm.SLOAD || op == vm.SSTORE):
slot := common.Hash(stackData[stackLen-1].Bytes32())
t.lookupStorage(caller, slot)
case stackLen >= 1 && (op == vm.EXTCODECOPY || op == vm.EXTCODEHASH || op == vm.EXTCODESIZE || op == vm.BALANCE || op == vm.SELFDESTRUCT):
addr := common.Address(stackData[stackLen-1].Bytes20())
t.lookupAccount(addr)
if op == vm.SELFDESTRUCT {
t.deleted[caller] = true
}
case stackLen >= 5 && (op == vm.DELEGATECALL || op == vm.CALL || op == vm.STATICCALL || op == vm.CALLCODE):
addr := common.Address(stackData[stackLen-2].Bytes20())
t.lookupAccount(addr)
case op == vm.CREATE:
nonce := t.env.StateDB.GetNonce(caller)
addr := crypto.CreateAddress(caller, nonce)
t.lookupAccount(addr)
t.created[addr] = true
case stackLen >= 4 && op == vm.CREATE2:
offset := stackData[stackLen-2]
size := stackData[stackLen-3]
init, err := tracers.GetMemoryCopyPadded(scope.Memory, int64(offset.Uint64()), int64(size.Uint64()))
if err != nil {
log.Warn("failed to copy CREATE2 input", "err", err, "tracer", "prestateTracer", "offset", offset, "size", size)
return
}
inithash := crypto.Keccak256(init)
salt := stackData[stackLen-4]
addr := crypto.CreateAddress2(caller, salt.Bytes32(), inithash)
t.lookupAccount(addr)
t.created[addr] = true
}
}
func (t *prestateTracer) CaptureTxStart(gasLimit uint64) {
t.gasLimit = gasLimit
}
func (t *prestateTracer) CaptureTxEnd(restGas uint64) {
if !t.config.DiffMode {
return
}
for addr, state := range t.pre {
// The deleted account's state is pruned from `post` but kept in `pre`
if _, ok := t.deleted[addr]; ok {
continue
}
modified := false
postAccount := &account{Storage: make(map[common.Hash]common.Hash)}
newBalance := t.env.StateDB.GetBalance(addr).ToBig()
newNonce := t.env.StateDB.GetNonce(addr)
newCode := t.env.StateDB.GetCode(addr)
if newBalance.Cmp(t.pre[addr].Balance) != 0 {
modified = true
postAccount.Balance = newBalance
}
if newNonce != t.pre[addr].Nonce {
modified = true
postAccount.Nonce = newNonce
}
if !bytes.Equal(newCode, t.pre[addr].Code) {
modified = true
postAccount.Code = newCode
}
for key, val := range state.Storage {
// don't include the empty slot
if val == (common.Hash{}) {
delete(t.pre[addr].Storage, key)
}
newVal := t.env.StateDB.GetState(addr, key)
if val == newVal {
// Omit unchanged slots
delete(t.pre[addr].Storage, key)
} else {
modified = true
if newVal != (common.Hash{}) {
postAccount.Storage[key] = newVal
}
}
}
if modified {
t.post[addr] = postAccount
} else {
// if state is not modified, then no need to include into the pre state
delete(t.pre, addr)
}
}
// the new created contracts' prestate were empty, so delete them
for a := range t.created {
// the created contract maybe exists in statedb before the creating tx
if s := t.pre[a]; s != nil && !s.exists() {
delete(t.pre, a)
}
}
}
// GetResult returns the json-encoded nested list of call traces, and any
// error arising from the encoding or forceful termination (via `Stop`).
func (t *prestateTracer) GetResult() (json.RawMessage, error) {
var res []byte
var err error
if t.config.DiffMode {
res, err = json.Marshal(struct {
Post state `json:"post"`
Pre state `json:"pre"`
}{t.post, t.pre})
} else {
res, err = json.Marshal(t.pre)
}
if err != nil {
return nil, err
}
return json.RawMessage(res), t.reason
}
// Stop terminates execution of the tracer at the first opportune moment.
func (t *prestateTracer) Stop(err error) {
t.reason = err
t.interrupt.Store(true)
}
// lookupAccount fetches details of an account and adds it to the prestate
// if it doesn't exist there.
func (t *prestateTracer) lookupAccount(addr common.Address) {
if _, ok := t.pre[addr]; ok {
return
}
t.pre[addr] = &account{
Balance: t.env.StateDB.GetBalance(addr).ToBig(),
Nonce: t.env.StateDB.GetNonce(addr),
Code: t.env.StateDB.GetCode(addr),
Storage: make(map[common.Hash]common.Hash),
}
}
// lookupStorage fetches the requested storage slot and adds
// it to the prestate of the given contract. It assumes `lookupAccount`
// has been performed on the contract before.
func (t *prestateTracer) lookupStorage(addr common.Address, key common.Hash) {
if _, ok := t.pre[addr].Storage[key]; ok {
return
}
t.pre[addr].Storage[key] = t.env.StateDB.GetState(addr, key)
}