core, core/vm, cmd/disasm: unify procedures for disassembling evm code (#3530)

core/asm/asm.go

@@ -0,0 +1,139 @@
+// 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 <http://www.gnu.org/licenses/>.
+
+// Provides support for dealing with EVM assembly instructions (e.g., disassembling them).
+package asm
+
+import (
+	"encoding/hex"
+	"fmt"
+
+	"github.com/ethereum/go-ethereum/core/vm"
+)
+
+// Iterator for disassembled EVM instructions
+type instructionIterator struct {
+	code    []byte
+	pc      uint64
+	arg     []byte
+	op      vm.OpCode
+	error   error
+	started bool
+}
+
+// Create a new instruction iterator.
+func NewInstructionIterator(code []byte) *instructionIterator {
+	it := new(instructionIterator)
+	it.code = code
+	return it
+}
+
+// Returns true if there is a next instruction and moves on.
+func (it *instructionIterator) Next() bool {
+	if it.error != nil || uint64(len(it.code)) <= it.pc {
+		// We previously reached an error or the end.
+		return false
+	}
+
+	if it.started {
+		// Since the iteration has been already started we move to the next instruction.
+		if it.arg != nil {
+			it.pc += uint64(len(it.arg))
+		}
+		it.pc++
+	} else {
+		// We start the iteration from the first instruction.
+		it.started = true
+	}
+
+	if uint64(len(it.code)) <= it.pc {
+		// We reached the end.
+		return false
+	}
+
+	it.op = vm.OpCode(it.code[it.pc])
+	if it.op.IsPush() {
+		a := uint64(it.op) - uint64(vm.PUSH1) + 1
+		u := it.pc + 1 + a
+		if uint64(len(it.code)) <= it.pc || uint64(len(it.code)) < u {
+			it.error = fmt.Errorf("incomplete push instruction at %v", it.pc)
+			return false
+		}
+		it.arg = it.code[it.pc+1 : u]
+	} else {
+		it.arg = nil
+	}
+	return true
+}
+
+// Returns any error that may have been encountered.
+func (it *instructionIterator) Error() error {
+	return it.error
+}
+
+// Returns the PC of the current instruction.
+func (it *instructionIterator) PC() uint64 {
+	return it.pc
+}
+
+// Returns the opcode of the current instruction.
+func (it *instructionIterator) Op() vm.OpCode {
+	return it.op
+}
+
+// Returns the argument of the current instruction.
+func (it *instructionIterator) Arg() []byte {
+	return it.arg
+}
+
+// Pretty-print all disassembled EVM instructions to stdout.
+func PrintDisassembled(code string) error {
+	script, err := hex.DecodeString(code)
+	if err != nil {
+		return err
+	}
+
+	it := NewInstructionIterator(script)
+	for it.Next() {
+		if it.Arg() != nil && 0 < len(it.Arg()) {
+			fmt.Printf("%06v: %v 0x%x\n", it.PC(), it.Op(), it.Arg())
+		} else {
+			fmt.Printf("%06v: %v\n", it.PC(), it.Op())
+		}
+	}
+	if err := it.Error(); err != nil {
+		return err
+	}
+	return nil
+}
+
+// Return all disassembled EVM instructions in human-readable format.
+func Disassemble(script []byte) ([]string, error) {
+	instrs := make([]string, 0)
+
+	it := NewInstructionIterator(script)
+	for it.Next() {
+		if it.Arg() != nil && 0 < len(it.Arg()) {
+			instrs = append(instrs, fmt.Sprintf("%06v: %v 0x%x\n", it.PC(), it.Op(), it.Arg()))
+		} else {
+			instrs = append(instrs, fmt.Sprintf("%06v: %v\n", it.PC(), it.Op()))
+		}
+	}
+	if err := it.Error(); err != nil {
+		return nil, err
+	}
+	return instrs, nil
+}