From 551bd6e7214acd8671c7577923206744281303a0 Mon Sep 17 00:00:00 2001
From: Martin Holst Swende <martin@swende.se>
Date: Mon, 1 Nov 2021 19:06:33 +0100
Subject: [PATCH] eth/tracers: invoke enter/exit on 0-value calls to inex
 accounts (#23828)

---
 core/vm/evm.go              | 11 ++++--
 eth/tracers/tracers_test.go | 79 +++++++++++++++++++++++++++++++++++++
 2 files changed, 87 insertions(+), 3 deletions(-)

diff --git a/core/vm/evm.go b/core/vm/evm.go
index 3b4bd69d7..07e961915 100644
--- a/core/vm/evm.go
+++ b/core/vm/evm.go
@@ -182,9 +182,14 @@ func (evm *EVM) Call(caller ContractRef, addr common.Address, input []byte, gas
 	if !evm.StateDB.Exist(addr) {
 		if !isPrecompile && evm.chainRules.IsEIP158 && value.Sign() == 0 {
 			// Calling a non existing account, don't do anything, but ping the tracer
-			if evm.Config.Debug && evm.depth == 0 {
-				evm.Config.Tracer.CaptureStart(evm, caller.Address(), addr, false, input, gas, value)
-				evm.Config.Tracer.CaptureEnd(ret, 0, 0, nil)
+			if evm.Config.Debug {
+				if evm.depth == 0 {
+					evm.Config.Tracer.CaptureStart(evm, caller.Address(), addr, false, input, gas, value)
+					evm.Config.Tracer.CaptureEnd(ret, 0, 0, nil)
+				} else {
+					evm.Config.Tracer.CaptureEnter(CALL, caller.Address(), addr, input, gas, value)
+					evm.Config.Tracer.CaptureExit(ret, 0, nil)
+				}
 			}
 			return nil, gas, nil
 		}
diff --git a/eth/tracers/tracers_test.go b/eth/tracers/tracers_test.go
index 32c09b1a7..f2333b87b 100644
--- a/eth/tracers/tracers_test.go
+++ b/eth/tracers/tracers_test.go
@@ -120,6 +120,85 @@ type callTracerTest struct {
 	Result  *callTrace    `json:"result"`
 }
 
+// TestZeroValueToNotExitCall tests the calltracer(s) on the following:
+// Tx to A, A calls B with zero value. B does not already exist.
+// Expected: that enter/exit is invoked and the inner call is shown in the result
+func TestZeroValueToNotExitCall(t *testing.T) {
+	var to = common.HexToAddress("0x00000000000000000000000000000000deadbeef")
+	privkey, err := crypto.HexToECDSA("0000000000000000deadbeef00000000000000000000000000000000deadbeef")
+	if err != nil {
+		t.Fatalf("err %v", err)
+	}
+	signer := types.NewEIP155Signer(big.NewInt(1))
+	tx, err := types.SignNewTx(privkey, signer, &types.LegacyTx{
+		GasPrice: big.NewInt(0),
+		Gas:      50000,
+		To:       &to,
+	})
+	if err != nil {
+		t.Fatalf("err %v", err)
+	}
+	origin, _ := signer.Sender(tx)
+	txContext := vm.TxContext{
+		Origin:   origin,
+		GasPrice: big.NewInt(1),
+	}
+	context := vm.BlockContext{
+		CanTransfer: core.CanTransfer,
+		Transfer:    core.Transfer,
+		Coinbase:    common.Address{},
+		BlockNumber: new(big.Int).SetUint64(8000000),
+		Time:        new(big.Int).SetUint64(5),
+		Difficulty:  big.NewInt(0x30000),
+		GasLimit:    uint64(6000000),
+	}
+	var code = []byte{
+		byte(vm.PUSH1), 0x0, byte(vm.DUP1), byte(vm.DUP1), byte(vm.DUP1), // in and outs zero
+		byte(vm.DUP1), byte(vm.PUSH1), 0xff, byte(vm.GAS), // value=0,address=0xff, gas=GAS
+		byte(vm.CALL),
+	}
+	var alloc = core.GenesisAlloc{
+		to: core.GenesisAccount{
+			Nonce: 1,
+			Code:  code,
+		},
+		origin: core.GenesisAccount{
+			Nonce:   0,
+			Balance: big.NewInt(500000000000000),
+		},
+	}
+	_, statedb := tests.MakePreState(rawdb.NewMemoryDatabase(), alloc, false)
+	// Create the tracer, the EVM environment and run it
+	tracer, err := New("callTracer", new(Context))
+	if err != nil {
+		t.Fatalf("failed to create call tracer: %v", err)
+	}
+	evm := vm.NewEVM(context, txContext, statedb, params.MainnetChainConfig, vm.Config{Debug: true, Tracer: tracer})
+	msg, err := tx.AsMessage(signer, nil)
+	if err != nil {
+		t.Fatalf("failed to prepare transaction for tracing: %v", err)
+	}
+	st := core.NewStateTransition(evm, msg, new(core.GasPool).AddGas(tx.Gas()))
+	if _, err = st.TransitionDb(); err != nil {
+		t.Fatalf("failed to execute transaction: %v", err)
+	}
+	// Retrieve the trace result and compare against the etalon
+	res, err := tracer.GetResult()
+	if err != nil {
+		t.Fatalf("failed to retrieve trace result: %v", err)
+	}
+	have := new(callTrace)
+	if err := json.Unmarshal(res, have); err != nil {
+		t.Fatalf("failed to unmarshal trace result: %v", err)
+	}
+	wantStr := `{"type":"CALL","from":"0x682a80a6f560eec50d54e63cbeda1c324c5f8d1b","to":"0x00000000000000000000000000000000deadbeef","value":"0x0","gas":"0x7148","gasUsed":"0x2d0","input":"0x","output":"0x","calls":[{"type":"CALL","from":"0x00000000000000000000000000000000deadbeef","to":"0x00000000000000000000000000000000000000ff","value":"0x0","gas":"0x6cbf","gasUsed":"0x0","input":"0x","output":"0x"}]}`
+	want := new(callTrace)
+	json.Unmarshal([]byte(wantStr), want)
+	if !jsonEqual(have, want) {
+		t.Error("have != want")
+	}
+}
+
 func TestPrestateTracerCreate2(t *testing.T) {
 	unsignedTx := types.NewTransaction(1, common.HexToAddress("0x00000000000000000000000000000000deadbeef"),
 		new(big.Int), 5000000, big.NewInt(1), []byte{})