core,eth: call frame tracing (ethereum#23087)

This change introduces 2 new optional methods; `enter()` and `exit()` for js tracers, and makes `step()` optiona. The two new methods are invoked when entering and exiting a call frame (but not invoked for the outermost scope, which has it's own methods). Currently these are the data fields passed to each of them:

    enter: type (opcode), from, to, input, gas, value
    exit: output, gasUsed, error

The PR also comes with a re-write of the callTracer. As a backup we keep the previous tracing script under the name `callTracerLegacy`. Behaviour of both tracers are equivalent for the most part, although there are some small differences (improvements), where the new tracer is more correct / has more information.

Author: s1na

core/vm/access_list_tracer.go

@@ -166,6 +166,11 @@ func (*AccessListTracer) CaptureFault(env *EVM, pc uint64, op OpCode, gas, cost
 
 func (*AccessListTracer) CaptureEnd(output []byte, gasUsed uint64, t time.Duration, err error) {}
 
+func (*AccessListTracer) CaptureEnter(typ OpCode, from common.Address, to common.Address, input []byte, gas uint64, value *big.Int) {
+}
+
+func (*AccessListTracer) CaptureExit(output []byte, gasUsed uint64, err error) {}
+
 // AccessList returns the current accesslist maintained by the tracer.
 func (a *AccessListTracer) AccessList() types.AccessList {
 	return a.list.accessList()

core/vm/evm.go

@@ -203,11 +203,19 @@ func (evm *EVM) Call(caller ContractRef, addr common.Address, input []byte, gas
 	evm.Context.Transfer(evm.StateDB, caller.Address(), addr, value)
 
 	// Capture the tracer start/end events in debug mode
-	if evm.Config.Debug && evm.depth == 0 {
-		evm.Config.Tracer.CaptureStart(evm, caller.Address(), addr, false, input, gas, value)
-		defer func(startGas uint64, startTime time.Time) { // Lazy evaluation of the parameters
-			evm.Config.Tracer.CaptureEnd(ret, startGas-gas, time.Since(startTime), err)
-		}(gas, time.Now())
+	if evm.Config.Debug {
+		if evm.depth == 0 {
+			evm.Config.Tracer.CaptureStart(evm, caller.Address(), addr, false, input, gas, value)
+			defer func(startGas uint64, startTime time.Time) { // Lazy evaluation of the parameters
+				evm.Config.Tracer.CaptureEnd(ret, startGas-gas, time.Since(startTime), err)
+			}(gas, time.Now())
+		} else {
+			// Handle tracer events for entering and exiting a call frame
+			evm.Config.Tracer.CaptureEnter(CALL, caller.Address(), addr, input, gas, value)
+			defer func(startGas uint64) {
+				evm.Config.Tracer.CaptureExit(ret, startGas-gas, err)
+			}(gas)
+		}
 	}
 
 	if isPrecompile {
@@ -269,6 +277,14 @@ func (evm *EVM) CallCode(caller ContractRef, addr common.Address, input []byte,
 	}
 	var snapshot = evm.StateDB.Snapshot()
 
+	// Invoke tracer hooks that signal entering/exiting a call frame
+	if evm.Config.Debug {
+		evm.Config.Tracer.CaptureEnter(CALLCODE, caller.Address(), addr, input, gas, value)
+		defer func(startGas uint64) {
+			evm.Config.Tracer.CaptureExit(ret, startGas-gas, err)
+		}(gas)
+	}
+
 	// It is allowed to call precompiles, even via delegatecall
 	if p, isPrecompile := evm.precompile(addr); isPrecompile {
 		ret, gas, err = RunPrecompiledContract(p, input, gas)
@@ -305,6 +321,14 @@ func (evm *EVM) DelegateCall(caller ContractRef, addr common.Address, input []by
 	}
 	var snapshot = evm.StateDB.Snapshot()
 
+	// Invoke tracer hooks that signal entering/exiting a call frame
+	if evm.Config.Debug {
+		evm.Config.Tracer.CaptureEnter(DELEGATECALL, caller.Address(), addr, input, gas, nil)
+		defer func(startGas uint64) {
+			evm.Config.Tracer.CaptureExit(ret, startGas-gas, err)
+		}(gas)
+	}
+
 	// It is allowed to call precompiles, even via delegatecall
 	if p, isPrecompile := evm.precompile(addr); isPrecompile {
 		ret, gas, err = RunPrecompiledContract(p, input, gas)
@@ -350,6 +374,14 @@ func (evm *EVM) StaticCall(caller ContractRef, addr common.Address, input []byte
 	// future scenarios
 	evm.StateDB.AddBalance(addr, big0)
 
+	// Invoke tracer hooks that signal entering/exiting a call frame
+	if evm.Config.Debug {
+		evm.Config.Tracer.CaptureEnter(STATICCALL, caller.Address(), addr, input, gas, nil)
+		defer func(startGas uint64) {
+			evm.Config.Tracer.CaptureExit(ret, startGas-gas, err)
+		}(gas)
+	}
+
 	if p, isPrecompile := evm.precompile(addr); isPrecompile {
 		ret, gas, err = RunPrecompiledContract(p, input, gas)
 	} else {
@@ -389,7 +421,7 @@ func (c *codeAndHash) Hash() common.Hash {
 }
 
 // create creates a new contract using code as deployment code.
-func (evm *EVM) create(caller ContractRef, codeAndHash *codeAndHash, gas uint64, value *big.Int, address common.Address) ([]byte, common.Address, uint64, error) {
+func (evm *EVM) create(caller ContractRef, codeAndHash *codeAndHash, gas uint64, value *big.Int, address common.Address, typ OpCode) ([]byte, common.Address, uint64, error) {
 	// Depth check execution. Fail if we're trying to execute above the
 	// limit.
 	if evm.depth > int(params.CallCreateDepth) {
@@ -427,9 +459,14 @@ func (evm *EVM) create(caller ContractRef, codeAndHash *codeAndHash, gas uint64,
 		return nil, address, gas, nil
 	}
 
-	if evm.Config.Debug && evm.depth == 0 {
-		evm.Config.Tracer.CaptureStart(evm, caller.Address(), address, true, codeAndHash.code, gas, value)
+	if evm.Config.Debug {
+		if evm.depth == 0 {
+			evm.Config.Tracer.CaptureStart(evm, caller.Address(), address, true, codeAndHash.code, gas, value)
+		} else {
+			evm.Config.Tracer.CaptureEnter(typ, caller.Address(), address, codeAndHash.code, gas, value)
+		}
 	}
+
 	start := time.Now()
 
 	ret, err := evm.interpreter.Run(contract, nil, false)
@@ -467,16 +504,20 @@ func (evm *EVM) create(caller ContractRef, codeAndHash *codeAndHash, gas uint64,
 		}
 	}
 
-	if evm.Config.Debug && evm.depth == 0 {
-		evm.Config.Tracer.CaptureEnd(ret, gas-contract.Gas, time.Since(start), err)
+	if evm.Config.Debug {
+		if evm.depth == 0 {
+			evm.Config.Tracer.CaptureEnd(ret, gas-contract.Gas, time.Since(start), err)
+		} else {
+			evm.Config.Tracer.CaptureExit(ret, gas-contract.Gas, err)
+		}
 	}
 	return ret, address, contract.Gas, err
 }
 
 // Create creates a new contract using code as deployment code.
 func (evm *EVM) Create(caller ContractRef, code []byte, gas uint64, value *big.Int) (ret []byte, contractAddr common.Address, leftOverGas uint64, err error) {
 	contractAddr = crypto.CreateAddress(caller.Address(), evm.StateDB.GetNonce(caller.Address()))
-	return evm.create(caller, &codeAndHash{code: code}, gas, value, contractAddr)
+	return evm.create(caller, &codeAndHash{code: code}, gas, value, contractAddr, CREATE)
 }
 
 // Create2 creates a new contract using code as deployment code.
@@ -486,7 +527,7 @@ func (evm *EVM) Create(caller ContractRef, code []byte, gas uint64, value *big.I
 func (evm *EVM) Create2(caller ContractRef, code []byte, gas uint64, endowment *big.Int, salt *uint256.Int) (ret []byte, contractAddr common.Address, leftOverGas uint64, err error) {
 	codeAndHash := &codeAndHash{code: code}
 	contractAddr = crypto.CreateAddress2(caller.Address(), salt.Bytes32(), codeAndHash.Hash().Bytes())
-	return evm.create(caller, codeAndHash, gas, endowment, contractAddr)
+	return evm.create(caller, codeAndHash, gas, endowment, contractAddr, CREATE2)
 }
 
 // ChainConfig returns the environment's chain configuration

core/vm/instructions.go

@@ -791,6 +791,10 @@ func opSuicide(pc *uint64, interpreter *EVMInterpreter, scope *ScopeContext) ([]
 	balance := interpreter.evm.StateDB.GetBalance(scope.Contract.Address())
 	interpreter.evm.StateDB.AddBalance(beneficiary.Bytes20(), balance)
 	interpreter.evm.StateDB.Suicide(scope.Contract.Address())
+	if interpreter.cfg.Debug {
+		interpreter.cfg.Tracer.CaptureEnter(SELFDESTRUCT, scope.Contract.Address(), beneficiary.Bytes20(), []byte{}, 0, balance)
+		interpreter.cfg.Tracer.CaptureExit([]byte{}, 0, nil)
+	}
 	return nil, nil
 }
 

core/vm/logger.go

@@ -106,6 +106,8 @@ func (s *StructLog) ErrorString() string {
 type Tracer interface {
 	CaptureStart(env *EVM, from common.Address, to common.Address, create bool, input []byte, gas uint64, value *big.Int)
 	CaptureState(env *EVM, pc uint64, op OpCode, gas, cost uint64, scope *ScopeContext, rData []byte, depth int, err error)
+	CaptureEnter(typ OpCode, from common.Address, to common.Address, input []byte, gas uint64, value *big.Int)
+	CaptureExit(output []byte, gasUsed uint64, err error)
 	CaptureFault(env *EVM, pc uint64, op OpCode, gas, cost uint64, scope *ScopeContext, depth int, err error)
 	CaptureEnd(output []byte, gasUsed uint64, t time.Duration, err error)
 }
@@ -225,6 +227,11 @@ func (l *StructLogger) CaptureEnd(output []byte, gasUsed uint64, t time.Duration
 	}
 }
 
+func (l *StructLogger) CaptureEnter(typ OpCode, from common.Address, to common.Address, input []byte, gas uint64, value *big.Int) {
+}
+
+func (l *StructLogger) CaptureExit(output []byte, gasUsed uint64, err error) {}
+
 // StructLogs returns the captured log entries.
 func (l *StructLogger) StructLogs() []StructLog { return l.logs }
 
@@ -342,3 +349,8 @@ func (t *mdLogger) CaptureEnd(output []byte, gasUsed uint64, tm time.Duration, e
 	fmt.Fprintf(t.out, "\nOutput: `0x%x`\nConsumed gas: `%d`\nError: `%v`\n",
 		output, gasUsed, err)
 }
+
+func (t *mdLogger) CaptureEnter(typ OpCode, from common.Address, to common.Address, input []byte, gas uint64, value *big.Int) {
+}
+
+func (t *mdLogger) CaptureExit(output []byte, gasUsed uint64, err error) {}

core/vm/logger_json.go

@@ -87,3 +87,8 @@ func (l *JSONLogger) CaptureEnd(output []byte, gasUsed uint64, t time.Duration,
 	}
 	l.encoder.Encode(endLog{common.Bytes2Hex(output), math.HexOrDecimal64(gasUsed), t, errMsg})
 }
+
+func (l *JSONLogger) CaptureEnter(typ OpCode, from common.Address, to common.Address, input []byte, gas uint64, value *big.Int) {
+}
+
+func (l *JSONLogger) CaptureExit(output []byte, gasUsed uint64, err error) {}