eth/tracers: add withLog to callTracer (#25991)

In some cases, it is desirable to capture what is triggered by each trace, when using the `callTracer`. For example: call `USDT.transfer` will trigger a `Transfer(from, to, value)` event.

This PR adds the option to capture logs to the call tracer, by specifying `{"withLog": true}` in the tracerconfig. 
Any logs belonging to failed/reverted call-scopes are removed from the output, to prevent interpretation mistakes.

Signed-off-by: Delweng <delweng@gmail.com>
Co-authored-by: Sina Mahmoodi <itz.s1na@gmail.com>

eth/tracers/native/call.go

@@ -36,6 +36,12 @@ func init() {
 	register("callTracer", newCallTracer)
 }
 
+type callLog struct {
+	Address common.Address `json:"address"`
+	Topics  []common.Hash  `json:"topics"`
+	Data    hexutil.Bytes  `json:"data"`
+}
+
 type callFrame struct {
 	Type     vm.OpCode      `json:"-"`
 	From     common.Address `json:"from"`
@@ -47,6 +53,7 @@ type callFrame struct {
 	Error    string         `json:"error,omitempty" rlp:"optional"`
 	Revertal string         `json:"revertReason,omitempty"`
 	Calls    []callFrame    `json:"calls,omitempty" rlp:"optional"`
+	Logs     []callLog      `json:"logs,omitempty" rlp:"optional"`
 	// Placed at end on purpose. The RLP will be decoded to 0 instead of
 	// nil if there are non-empty elements after in the struct.
 	Value *big.Int `json:"value,omitempty" rlp:"optional"`
@@ -56,6 +63,10 @@ func (f callFrame) TypeString() string {
 	return f.Type.String()
 }
 
+func (f callFrame) failed() bool {
+	return len(f.Error) > 0
+}
+
 func (f *callFrame) capture(output []byte, err error) {
 	output = common.CopyBytes(output)
 	if err == nil {
@@ -98,6 +109,7 @@ type callTracer struct {
 
 type callTracerConfig struct {
 	OnlyTopCall bool `json:"onlyTopCall"` // If true, call tracer won't collect any subcalls
+	WithLog     bool `json:"withLog"`     // If true, call tracer will collect event logs
 }
 
 // newCallTracer returns a native go tracer which tracks
@@ -137,10 +149,38 @@ func (t *callTracer) CaptureEnd(output []byte, gasUsed uint64, _ time.Duration,
 
 // CaptureState implements the EVMLogger interface to trace a single step of VM execution.
 func (t *callTracer) CaptureState(pc uint64, op vm.OpCode, gas, cost uint64, scope *vm.ScopeContext, rData []byte, depth int, err error) {
+	// Only logs need to be captured via opcode processing
+	if !t.config.WithLog {
+		return
+	}
+	// Avoid processing nested calls when only caring about top call
+	if t.config.OnlyTopCall && depth > 0 {
+		return
+	}
+	switch op {
+	case vm.LOG0, vm.LOG1, vm.LOG2, vm.LOG3, vm.LOG4:
+		size := int(op - vm.LOG0)
+
+		stack := scope.Stack
+		stackData := stack.Data()
+
+		// Don't modify the stack
+		mStart := stackData[len(stackData)-1]
+		mSize := stackData[len(stackData)-2]
+		topics := make([]common.Hash, size)
+		for i := 0; i < size; i++ {
+			topic := stackData[len(stackData)-2-(i+1)]
+			topics[i] = common.Hash(topic.Bytes32())
+		}
+
+		data := scope.Memory.GetCopy(int64(mStart.Uint64()), int64(mSize.Uint64()))
+		log := callLog{Address: scope.Contract.Address(), Topics: topics, Data: hexutil.Bytes(data)}
+		t.callstack[len(t.callstack)-1].Logs = append(t.callstack[len(t.callstack)-1].Logs, log)
+	}
 }
 
 // CaptureFault implements the EVMLogger interface to trace an execution fault.
-func (t *callTracer) CaptureFault(pc uint64, op vm.OpCode, gas, cost uint64, _ *vm.ScopeContext, depth int, err error) {
+func (t *callTracer) CaptureFault(pc uint64, op vm.OpCode, gas, cost uint64, scope *vm.ScopeContext, depth int, err error) {
 }
 
 // CaptureEnter is called when EVM enters a new scope (via call, create or selfdestruct).
@@ -191,6 +231,10 @@ func (t *callTracer) CaptureTxStart(gasLimit uint64) {
 
 func (t *callTracer) CaptureTxEnd(restGas uint64) {
 	t.callstack[0].GasUsed = t.gasLimit - restGas
+	if t.config.WithLog {
+		// Logs are not emitted when the call fails
+		clearFailedLogs(&t.callstack[0], false)
+	}
 }
 
 // GetResult returns the json-encoded nested list of call traces, and any
@@ -211,3 +255,16 @@ func (t *callTracer) Stop(err error) {
 	t.reason = err
 	atomic.StoreUint32(&t.interrupt, 1)
 }
+
+// clearFailedLogs clears the logs of a callframe and all its children
+// in case of execution failure.
+func clearFailedLogs(cf *callFrame, parentFailed bool) {
+	failed := cf.failed() || parentFailed
+	// Clear own logs
+	if failed {
+		cf.Logs = nil
+	}
+	for i := range cf.Calls {
+		clearFailedLogs(&cf.Calls[i], failed)
+	}
+}

eth/tracers/native/gen_callframe_json.go

@@ -26,6 +26,7 @@ func (c callFrame) MarshalJSON() ([]byte, error) {
 		Error      string         `json:"error,omitempty" rlp:"optional"`
 		Revertal   string         `json:"revertReason,omitempty"`
 		Calls      []callFrame    `json:"calls,omitempty" rlp:"optional"`
+		Logs       []callLog      `json:"logs,omitempty" rlp:"optional"`
 		Value      *hexutil.Big   `json:"value,omitempty" rlp:"optional"`
 		TypeString string         `json:"type"`
 	}
@@ -40,6 +41,7 @@ func (c callFrame) MarshalJSON() ([]byte, error) {
 	enc.Error = c.Error
 	enc.Revertal = c.Revertal
 	enc.Calls = c.Calls
+	enc.Logs = c.Logs
 	enc.Value = (*hexutil.Big)(c.Value)
 	enc.TypeString = c.TypeString()
 	return json.Marshal(&enc)
@@ -58,6 +60,7 @@ func (c *callFrame) UnmarshalJSON(input []byte) error {
 		Error    *string         `json:"error,omitempty" rlp:"optional"`
 		Revertal *string         `json:"revertReason,omitempty"`
 		Calls    []callFrame     `json:"calls,omitempty" rlp:"optional"`
+		Logs     []callLog       `json:"logs,omitempty" rlp:"optional"`
 		Value    *hexutil.Big    `json:"value,omitempty" rlp:"optional"`
 	}
 	var dec callFrame0
@@ -94,6 +97,9 @@ func (c *callFrame) UnmarshalJSON(input []byte) error {
 	if dec.Calls != nil {
 		c.Calls = dec.Calls
 	}
+	if dec.Logs != nil {
+		c.Logs = dec.Logs
+	}
 	if dec.Value != nil {
 		c.Value = (*big.Int)(dec.Value)
 	}