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

5 files changed, 213 insertions, 162 deletions

diff --git a/core/asm.go b/core/asm.go
deleted file mode 100644
index b2e47b5e9..000000000
--- a/core/asm.go
+++ /dev/null
@@ -1,64 +0,0 @@
-// Copyright 2014 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 core
-
-import (
-	"fmt"
-	"math/big"
-
-	"github.com/ethereum/go-ethereum/common"
-	"github.com/ethereum/go-ethereum/core/vm"
-)
-
-func Disassemble(script []byte) (asm []string) {
-	pc := new(big.Int)
-	for {
-		if pc.Cmp(big.NewInt(int64(len(script)))) >= 0 {
-			return
-		}
-
-		// Get the memory location of pc
-		val := script[pc.Int64()]
-		// Get the opcode (it must be an opcode!)
-		op := vm.OpCode(val)
-
-		asm = append(asm, fmt.Sprintf("%04v: %v", pc, op))
-
-		switch op {
-		case vm.PUSH1, vm.PUSH2, vm.PUSH3, vm.PUSH4, vm.PUSH5, vm.PUSH6, vm.PUSH7, vm.PUSH8,
-			vm.PUSH9, vm.PUSH10, vm.PUSH11, vm.PUSH12, vm.PUSH13, vm.PUSH14, vm.PUSH15,
-			vm.PUSH16, vm.PUSH17, vm.PUSH18, vm.PUSH19, vm.PUSH20, vm.PUSH21, vm.PUSH22,
-			vm.PUSH23, vm.PUSH24, vm.PUSH25, vm.PUSH26, vm.PUSH27, vm.PUSH28, vm.PUSH29,
-			vm.PUSH30, vm.PUSH31, vm.PUSH32:
-			pc.Add(pc, common.Big1)
-			a := int64(op) - int64(vm.PUSH1) + 1
-			if int(pc.Int64()+a) > len(script) {
-				return
-			}
-
-			data := script[pc.Int64() : pc.Int64()+a]
-			if len(data) == 0 {
-				data = []byte{0}
-			}
-			asm = append(asm, fmt.Sprintf("%04v: 0x%x", pc, data))
-
-			pc.Add(pc, big.NewInt(a-1))
-		}
-
-		pc.Add(pc, common.Big1)
-	}
-}
diff --git a/core/asm/asm.go b/core/asm/asm.go
new file mode 100644
index 000000000..5fe827e7c
--- /dev/null
+++ b/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
+}
diff --git a/core/asm/asm_test.go b/core/asm/asm_test.go
new file mode 100644
index 000000000..92b26b67a
--- /dev/null
+++ b/core/asm/asm_test.go
@@ -0,0 +1,74 @@
+// 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/>.
+
+package asm
+
+import (
+	"testing"
+
+	"encoding/hex"
+)
+
+// Tests disassembling the instructions for valid evm code
+func TestInstructionIteratorValid(t *testing.T) {
+	cnt := 0
+	script, _ := hex.DecodeString("61000000")
+
+	it := NewInstructionIterator(script)
+	for it.Next() {
+		cnt++
+	}
+
+	if err := it.Error(); err != nil {
+		t.Errorf("Expected 2, but encountered error %v instead.", err)
+	}
+	if cnt != 2 {
+		t.Errorf("Expected 2, but got %v instead.", cnt)
+	}
+}
+
+// Tests disassembling the instructions for invalid evm code
+func TestInstructionIteratorInvalid(t *testing.T) {
+	cnt := 0
+	script, _ := hex.DecodeString("6100")
+
+	it := NewInstructionIterator(script)
+	for it.Next() {
+		cnt++
+	}
+
+	if it.Error() == nil {
+		t.Errorf("Expected an error, but got %v instead.", cnt)
+	}
+}
+
+// Tests disassembling the instructions for empty evm code
+func TestInstructionIteratorEmpty(t *testing.T) {
+	cnt := 0
+	script, _ := hex.DecodeString("")
+
+	it := NewInstructionIterator(script)
+	for it.Next() {
+		cnt++
+	}
+
+	if err := it.Error(); err != nil {
+		t.Errorf("Expected 0, but encountered error %v instead.", err)
+	}
+	if cnt != 0 {
+		t.Errorf("Expected 0, but got %v instead.", cnt)
+	}
+}
diff --git a/core/vm/asm.go b/core/vm/asm.go
deleted file mode 100644
index d7dbde5e8..000000000
--- a/core/vm/asm.go
+++ /dev/null
@@ -1,61 +0,0 @@
-// Copyright 2014 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 vm
-
-import (
-	"fmt"
-	"math/big"
-
-	"github.com/ethereum/go-ethereum/common"
-)
-
-// Disassemble disassembles the byte code and returns the string
-// representation (human readable opcodes).
-func Disassemble(script []byte) (asm []string) {
-	pc := new(big.Int)
-	for {
-		if pc.Cmp(big.NewInt(int64(len(script)))) >= 0 {
-			return
-		}
-
-		// Get the memory location of pc
-		val := script[pc.Int64()]
-		// Get the opcode (it must be an opcode!)
-		op := OpCode(val)
-
-		asm = append(asm, fmt.Sprintf("%v", op))
-
-		switch op {
-		case PUSH1, PUSH2, PUSH3, PUSH4, PUSH5, PUSH6, PUSH7, PUSH8, PUSH9, PUSH10, PUSH11, PUSH12, PUSH13, PUSH14, PUSH15, PUSH16, PUSH17, PUSH18, PUSH19, PUSH20, PUSH21, PUSH22, PUSH23, PUSH24, PUSH25, PUSH26, PUSH27, PUSH28, PUSH29, PUSH30, PUSH31, PUSH32:
-			pc.Add(pc, common.Big1)
-			a := int64(op) - int64(PUSH1) + 1
-			if int(pc.Int64()+a) > len(script) {
-				return nil
-			}
-
-			data := script[pc.Int64() : pc.Int64()+a]
-			if len(data) == 0 {
-				data = []byte{0}
-			}
-			asm = append(asm, fmt.Sprintf("0x%x", data))
-
-			pc.Add(pc, big.NewInt(a-1))
-		}
-
-		pc.Add(pc, common.Big1)
-	}
-}
diff --git a/core/vm/disasm.go b/core/vm/disasm.go
deleted file mode 100644
index 2bfea5cbd..000000000
--- a/core/vm/disasm.go
+++ /dev/null
@@ -1,37 +0,0 @@
-// Copyright 2015 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 vm
-
-import "fmt"
-
-func Disasm(code []byte) []string {
-	var out []string
-	for pc := uint64(0); pc < uint64(len(code)); pc++ {
-		op := OpCode(code[pc])
-		out = append(out, op.String())
-
-		switch op {
-		case PUSH1, PUSH2, PUSH3, PUSH4, PUSH5, PUSH6, PUSH7, PUSH8, PUSH9, PUSH10, PUSH11, PUSH12, PUSH13, PUSH14, PUSH15, PUSH16, PUSH17, PUSH18, PUSH19, PUSH20, PUSH21, PUSH22, PUSH23, PUSH24, PUSH25, PUSH26, PUSH27, PUSH28, PUSH29, PUSH30, PUSH31, PUSH32:
-			a := uint64(op) - uint64(PUSH1) + 1
-			out = append(out, fmt.Sprintf("0x%x", code[pc+1:pc+1+a]))
-
-			pc += a
-		}
-	}
-
-	return out
-}