core/vm, eth: Add support for javascript trace functions

1 files changed, 300 insertions, 0 deletions

diff --git a/internal/ethapi/tracer.go b/internal/ethapi/tracer.go
new file mode 100644
index 000000000..27af1166b
--- /dev/null
+++ b/internal/ethapi/tracer.go
@@ -0,0 +1,300 @@
+// Copyright 2016 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 ethapi
+
+import (
+	"errors"
+	"fmt"
+	"math/big"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core/vm"
+	"github.com/robertkrimen/otto"
+)
+
+// fakeBig is used to provide an interface to Javascript for 'big.NewInt'
+type fakeBig struct{}
+
+// NewInt creates a new big.Int with the specified int64 value.
+func (fb *fakeBig) NewInt(x int64) *big.Int {
+	return big.NewInt(x)
+}
+
+// OpCodeWrapper provides a JavaScript-friendly wrapper around OpCode, to convince Otto to treat it
+// as an object, instead of a number.
+type opCodeWrapper struct {
+	op vm.OpCode
+}
+
+// toNumber returns the ID of this opcode as an integer
+func (ocw *opCodeWrapper) toNumber() int {
+	return int(ocw.op)
+}
+
+// toString returns the string representation of the opcode
+func (ocw *opCodeWrapper) toString() string {
+	return ocw.op.String()
+}
+
+// isPush returns true if the op is a Push
+func (ocw *opCodeWrapper) isPush() bool {
+	return ocw.op.IsPush()
+}
+
+// toValue returns an otto.Value for the opCodeWrapper
+func (ocw *opCodeWrapper) toValue(vm *otto.Otto) otto.Value {
+	value, _ := vm.ToValue(ocw)
+	obj := value.Object()
+	obj.Set("toNumber", ocw.toNumber)
+	obj.Set("toString", ocw.toString)
+	obj.Set("isPush", ocw.isPush)
+	return value
+}
+
+// memoryWrapper provides a JS wrapper around vm.Memory
+type memoryWrapper struct {
+	memory *vm.Memory
+}
+
+// slice returns the requested range of memory as a byte slice
+func (mw *memoryWrapper) slice(begin, end int64) []byte {
+	return mw.memory.Get(begin, end-begin)
+}
+
+// getUint returns the 32 bytes at the specified address interpreted
+// as an unsigned integer
+func (mw *memoryWrapper) getUint(addr int64) *big.Int {
+	ret := big.NewInt(0)
+	ret.SetBytes(mw.memory.GetPtr(addr, 32))
+	return ret
+}
+
+// toValue returns an otto.Value for the memoryWrapper
+func (mw *memoryWrapper) toValue(vm *otto.Otto) otto.Value {
+	value, _ := vm.ToValue(mw)
+	obj := value.Object()
+	obj.Set("slice", mw.slice)
+	obj.Set("getUint", mw.getUint)
+	return value
+}
+
+// stackWrapper provides a JS wrapper around vm.Stack
+type stackWrapper struct {
+	stack *vm.Stack
+}
+
+// peek returns the nth-from-the-top element of the stack.
+func (sw *stackWrapper) peek(idx int) *big.Int {
+	return sw.stack.Data()[len(sw.stack.Data())-idx-1]
+}
+
+// length returns the length of the stack
+func (sw *stackWrapper) length() int {
+	return len(sw.stack.Data())
+}
+
+// toValue returns an otto.Value for the stackWrapper
+func (sw *stackWrapper) toValue(vm *otto.Otto) otto.Value {
+	value, _ := vm.ToValue(sw)
+	obj := value.Object()
+	obj.Set("peek", sw.peek)
+	obj.Set("length", sw.length)
+	return value
+}
+
+// dbWrapper provides a JS wrapper around vm.Database
+type dbWrapper struct {
+	db vm.Database
+}
+
+// getBalance retrieves an account's balance
+func (dw *dbWrapper) getBalance(addr common.Address) *big.Int {
+	return dw.db.GetBalance(addr)
+}
+
+// getNonce retrieves an account's nonce
+func (dw *dbWrapper) getNonce(addr common.Address) uint64 {
+	return dw.db.GetNonce(addr)
+}
+
+// getCode retrieves an account's code
+func (dw *dbWrapper) getCode(addr common.Address) []byte {
+	return dw.db.GetCode(addr)
+}
+
+// getState retrieves an account's state data for the given hash
+func (dw *dbWrapper) getState(addr common.Address, hash common.Hash) common.Hash {
+	return dw.db.GetState(addr, hash)
+}
+
+// exists returns true iff the account exists
+func (dw *dbWrapper) exists(addr common.Address) bool {
+	return dw.db.Exist(addr)
+}
+
+// toValue returns an otto.Value for the dbWrapper
+func (dw *dbWrapper) toValue(vm *otto.Otto) otto.Value {
+	value, _ := vm.ToValue(dw)
+	obj := value.Object()
+	obj.Set("getBalance", dw.getBalance)
+	obj.Set("getNonce", dw.getNonce)
+	obj.Set("getCode", dw.getCode)
+	obj.Set("getState", dw.getState)
+	obj.Set("exists", dw.exists)
+	return value
+}
+
+// JavascriptTracer provides an implementation of Tracer that evaluates a
+// Javascript function for each VM execution step.
+type JavascriptTracer struct {
+	vm          *otto.Otto             // Javascript VM instance
+	traceobj    *otto.Object           // User-supplied object to call
+	log         map[string]interface{} // (Reusable) map for the `log` arg to `step`
+	logvalue    otto.Value             // JS view of `log`
+	opcode      *opCodeWrapper         // Wrapper around the opcode
+	opcodevalue otto.Value             // JS view of 'opcode'
+	memory      *memoryWrapper         // Wrapper around the VM memory
+	memvalue    otto.Value             // JS view of `memory`
+	stack       *stackWrapper          // Wrapper around the VM stack
+	stackvalue  otto.Value             // JS view of `stack`
+	db          *dbWrapper             // Wrapper around the VM environment
+	dbvalue     otto.Value             // JS view of `db`
+	err         error                  // Error, if one has occurred
+}
+
+// NewJavascriptTracer instantiates a new JavascriptTracer instance.
+// code specifies a Javascript snippet, which must evaluate to an expression
+// returning an object with 'step' and 'result' functions.
+func NewJavascriptTracer(code string) (*JavascriptTracer, error) {
+	vm := otto.New()
+	vm.Interrupt = make(chan func(), 1)
+
+	// Set up builtins for this environment
+	vm.Set("big", &fakeBig{})
+
+	jstracer, err := vm.Object("(" + code + ")")
+	if err != nil {
+		return nil, err
+	}
+
+	// Check the required functions exist
+	step, err := jstracer.Get("step")
+	if err != nil {
+		return nil, err
+	}
+	if !step.IsFunction() {
+		return nil, fmt.Errorf("Trace object must expose a function step()")
+	}
+
+	result, err := jstracer.Get("result")
+	if err != nil {
+		return nil, err
+	}
+	if !result.IsFunction() {
+		return nil, fmt.Errorf("Trace object must expose a function result()")
+	}
+
+	// Create the persistent log object
+	log := make(map[string]interface{})
+	logvalue, _ := vm.ToValue(log)
+
+	// Create persistent wrappers for memory and stack
+	opcode := &opCodeWrapper{}
+	mem := &memoryWrapper{}
+	stack := &stackWrapper{}
+	db := &dbWrapper{}
+
+	return &JavascriptTracer{
+		vm:          vm,
+		traceobj:    jstracer,
+		log:         log,
+		logvalue:    logvalue,
+		opcode:      opcode,
+		opcodevalue: opcode.toValue(vm),
+		memory:      mem,
+		memvalue:    mem.toValue(vm),
+		stack:       stack,
+		stackvalue:  stack.toValue(vm),
+		db:          db,
+		dbvalue:     db.toValue(vm),
+		err:         nil,
+	}, nil
+}
+
+// Stop terminates execution of any JavaScript
+func (jst *JavascriptTracer) Stop(err error) {
+	jst.vm.Interrupt <- func() {
+		panic(err)
+	}
+}
+
+// callSafely executes a method on a JS object, catching any panics and
+// returning them as error objects.
+func (jst *JavascriptTracer) callSafely(method string, argumentList ...interface{}) (ret interface{}, err error) {
+	defer func() {
+		if caught := recover(); caught != nil {
+			switch caught := caught.(type) {
+			case error:
+				err = caught
+			case string:
+				err = errors.New(caught)
+			case fmt.Stringer:
+				err = errors.New(caught.String())
+			default:
+				panic(caught)
+			}
+		}
+	}()
+
+	value, err := jst.traceobj.Call(method, argumentList...)
+	ret, _ = value.Export()
+	return ret, err
+}
+
+// CaptureState implements the Tracer interface to trace a single step of VM execution
+func (jst *JavascriptTracer) CaptureState(env vm.Environment, pc uint64, op vm.OpCode, gas, cost *big.Int, memory *vm.Memory, stack *vm.Stack, contract *vm.Contract, depth int, err error) {
+	if jst.err == nil {
+		jst.opcode.op = op
+		jst.memory.memory = memory
+		jst.stack.stack = stack
+		jst.db.db = env.Db()
+
+		jst.log["pc"] = pc
+		jst.log["op"] = jst.opcodevalue
+		jst.log["gas"] = gas.Int64()
+		jst.log["gasPrice"] = cost.Int64()
+		jst.log["memory"] = jst.memvalue
+		jst.log["stack"] = jst.stackvalue
+		jst.log["depth"] = depth
+		jst.log["account"] = contract.Address()
+		jst.log["err"] = err
+
+		_, err := jst.callSafely("step", jst.logvalue, jst.dbvalue)
+		if err != nil {
+			jst.err = err
+		}
+	}
+}
+
+// GetResult calls the Javascript 'result' function and returns its value, or any accumulated error
+func (jst *JavascriptTracer) GetResult() (result interface{}, err error) {
+	if jst.err != nil {
+		return nil, jst.err
+	}
+
+	return jst.callSafely("result")
+}