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4byte.go
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4byte.go
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// (c) 2020-2021, Ava Labs, Inc.
//
// This file is a derived work, based on the go-ethereum library whose original
// notices appear below.
//
// It is distributed under a license compatible with the licensing terms of the
// original code from which it is derived.
//
// Much love to the original authors for their work.
// **********
// 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 native
import (
"encoding/json"
"math/big"
"strconv"
"sync/atomic"
"github.com/ava-labs/subnet-evm/core/vm"
"github.com/ava-labs/subnet-evm/eth/tracers"
"github.com/ethereum/go-ethereum/common"
)
func init() {
tracers.DefaultDirectory.Register("4byteTracer", newFourByteTracer, false)
}
// fourByteTracer searches for 4byte-identifiers, and collects them for post-processing.
// It collects the methods identifiers along with the size of the supplied data, so
// a reversed signature can be matched against the size of the data.
//
// Example:
//
// > debug.traceTransaction( "0x214e597e35da083692f5386141e69f47e973b2c56e7a8073b1ea08fd7571e9de", {tracer: "4byteTracer"})
// {
// 0x27dc297e-128: 1,
// 0x38cc4831-0: 2,
// 0x524f3889-96: 1,
// 0xadf59f99-288: 1,
// 0xc281d19e-0: 1
// }
type fourByteTracer struct {
noopTracer
ids map[string]int // ids aggregates the 4byte ids found
interrupt uint32 // Atomic flag to signal execution interruption
reason error // Textual reason for the interruption
activePrecompiles []common.Address // Updated on CaptureStart based on given rules
}
// newFourByteTracer returns a native go tracer which collects
// 4 byte-identifiers of a tx, and implements vm.EVMLogger.
func newFourByteTracer(ctx *tracers.Context, _ json.RawMessage) (tracers.Tracer, error) {
t := &fourByteTracer{
ids: make(map[string]int),
}
return t, nil
}
// isPrecompiled returns whether the addr is a precompile. Logic borrowed from newJsTracer in eth/tracers/js/tracer.go
func (t *fourByteTracer) isPrecompiled(addr common.Address) bool {
for _, p := range t.activePrecompiles {
if p == addr {
return true
}
}
return false
}
// store saves the given identifier and datasize.
func (t *fourByteTracer) store(id []byte, size int) {
key := bytesToHex(id) + "-" + strconv.Itoa(size)
t.ids[key] += 1
}
// CaptureStart implements the EVMLogger interface to initialize the tracing operation.
func (t *fourByteTracer) CaptureStart(env *vm.EVM, from common.Address, to common.Address, create bool, input []byte, gas uint64, value *big.Int) {
// Update list of precompiles based on current block
rules := env.ChainConfig().AvalancheRules(env.Context.BlockNumber, env.Context.Time)
t.activePrecompiles = vm.ActivePrecompiles(rules)
// Save the outer calldata also
if len(input) >= 4 {
t.store(input[0:4], len(input)-4)
}
}
// CaptureEnter is called when EVM enters a new scope (via call, create or selfdestruct).
func (t *fourByteTracer) CaptureEnter(op vm.OpCode, from common.Address, to common.Address, input []byte, gas uint64, value *big.Int) {
// Skip if tracing was interrupted
if atomic.LoadUint32(&t.interrupt) > 0 {
return
}
if len(input) < 4 {
return
}
// primarily we want to avoid CREATE/CREATE2/SELFDESTRUCT
if op != vm.DELEGATECALL && op != vm.STATICCALL &&
op != vm.CALL && op != vm.CALLCODE {
return
}
// Skip any pre-compile invocations, those are just fancy opcodes
if t.isPrecompiled(to) {
return
}
t.store(input[0:4], len(input)-4)
}
// GetResult returns the json-encoded nested list of call traces, and any
// error arising from the encoding or forceful termination (via `Stop`).
func (t *fourByteTracer) GetResult() (json.RawMessage, error) {
res, err := json.Marshal(t.ids)
if err != nil {
return nil, err
}
return res, t.reason
}
// Stop terminates execution of the tracer at the first opportune moment.
func (t *fourByteTracer) Stop(err error) {
t.reason = err
atomic.StoreUint32(&t.interrupt, 1)
}
func bytesToHex(s []byte) string {
return "0x" + common.Bytes2Hex(s)
}