140 lines
3.6 KiB
Go
140 lines
3.6 KiB
Go
// Copyright 2017 The go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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// The go-ethereum library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// The go-ethereum library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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// Provides support for dealing with EVM assembly instructions (e.g., disassembling them).
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package asm
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import (
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"encoding/hex"
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"fmt"
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"github.com/ethereum/go-ethereum/core/vm"
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)
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// Iterator for disassembled EVM instructions
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type instructionIterator struct {
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code []byte
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pc uint64
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arg []byte
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op vm.OpCode
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error error
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started bool
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}
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// Create a new instruction iterator.
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func NewInstructionIterator(code []byte) *instructionIterator {
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it := new(instructionIterator)
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it.code = code
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return it
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}
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// Returns true if there is a next instruction and moves on.
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func (it *instructionIterator) Next() bool {
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if it.error != nil || uint64(len(it.code)) <= it.pc {
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// We previously reached an error or the end.
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return false
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}
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if it.started {
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// Since the iteration has been already started we move to the next instruction.
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if it.arg != nil {
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it.pc += uint64(len(it.arg))
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}
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it.pc++
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} else {
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// We start the iteration from the first instruction.
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it.started = true
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}
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if uint64(len(it.code)) <= it.pc {
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// We reached the end.
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return false
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}
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it.op = vm.OpCode(it.code[it.pc])
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if it.op.IsPush() {
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a := uint64(it.op) - uint64(vm.PUSH1) + 1
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u := it.pc + 1 + a
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if uint64(len(it.code)) <= it.pc || uint64(len(it.code)) < u {
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it.error = fmt.Errorf("incomplete push instruction at %v", it.pc)
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return false
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}
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it.arg = it.code[it.pc+1 : u]
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} else {
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it.arg = nil
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}
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return true
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}
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// Returns any error that may have been encountered.
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func (it *instructionIterator) Error() error {
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return it.error
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}
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// Returns the PC of the current instruction.
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func (it *instructionIterator) PC() uint64 {
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return it.pc
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}
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// Returns the opcode of the current instruction.
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func (it *instructionIterator) Op() vm.OpCode {
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return it.op
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}
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// Returns the argument of the current instruction.
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func (it *instructionIterator) Arg() []byte {
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return it.arg
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}
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// Pretty-print all disassembled EVM instructions to stdout.
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func PrintDisassembled(code string) error {
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script, err := hex.DecodeString(code)
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if err != nil {
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return err
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}
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it := NewInstructionIterator(script)
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for it.Next() {
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if it.Arg() != nil && 0 < len(it.Arg()) {
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fmt.Printf("%06v: %v 0x%x\n", it.PC(), it.Op(), it.Arg())
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} else {
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fmt.Printf("%06v: %v\n", it.PC(), it.Op())
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}
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}
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if err := it.Error(); err != nil {
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return err
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}
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return nil
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}
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// Return all disassembled EVM instructions in human-readable format.
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func Disassemble(script []byte) ([]string, error) {
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instrs := make([]string, 0)
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it := NewInstructionIterator(script)
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for it.Next() {
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if it.Arg() != nil && 0 < len(it.Arg()) {
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instrs = append(instrs, fmt.Sprintf("%06v: %v 0x%x\n", it.PC(), it.Op(), it.Arg()))
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} else {
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instrs = append(instrs, fmt.Sprintf("%06v: %v\n", it.PC(), it.Op()))
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}
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}
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if err := it.Error(); err != nil {
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return nil, err
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}
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return instrs, nil
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}
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