core/vm: include operand in error message (#34635)

Return ErrInvalidOpCode with the executing opcode and offending
immediate for forbidden DUPN, SWAPN, and EXCHANGE operands. Extend
TestEIP8024_Execution to assert both opcode and operand for all
invalid-immediate paths.

core/vm/errors.go

@@ -76,10 +76,16 @@ func (e ErrStackOverflow) Unwrap() error {
 
 // ErrInvalidOpCode wraps an evm error when an invalid opcode is encountered.
 type ErrInvalidOpCode struct {
-	opcode OpCode
+	opcode  OpCode
+	operand *byte
 }
 
-func (e *ErrInvalidOpCode) Error() string { return fmt.Sprintf("invalid opcode: %s", e.opcode) }
+func (e *ErrInvalidOpCode) Error() string {
+	if e.operand != nil {
+		return fmt.Sprintf("invalid opcode: %s (operand: 0x%02x)", e.opcode, *e.operand)
+	}
+	return fmt.Sprintf("invalid opcode: %s", e.opcode)
+}
 
 // rpcError is the same interface as the one defined in rpc/errors.go
 // but we do not want to depend on rpc package here so we redefine it.

core/vm/instructions.go

@@ -996,7 +996,8 @@ func opDupN(pc *uint64, evm *EVM, scope *ScopeContext) ([]byte, error) {
 
 	// This range is excluded to preserve compatibility with existing opcodes.
 	if x > 90 && x < 128 {
-		return nil, &ErrInvalidOpCode{opcode: OpCode(x)}
+		operand := x
+		return nil, &ErrInvalidOpCode{opcode: DUPN, operand: &operand}
 	}
 	n := decodeSingle(x)
 
@@ -1023,7 +1024,8 @@ func opSwapN(pc *uint64, evm *EVM, scope *ScopeContext) ([]byte, error) {
 
 	// This range is excluded to preserve compatibility with existing opcodes.
 	if x > 90 && x < 128 {
-		return nil, &ErrInvalidOpCode{opcode: OpCode(x)}
+		operand := x
+		return nil, &ErrInvalidOpCode{opcode: SWAPN, operand: &operand}
 	}
 	n := decodeSingle(x)
 
@@ -1053,7 +1055,8 @@ func opExchange(pc *uint64, evm *EVM, scope *ScopeContext) ([]byte, error) {
 	// This range is excluded both to preserve compatibility with existing opcodes
 	// and to keep decode_pair’s 16-aligned arithmetic mapping valid (0–81, 128–255).
 	if x > 81 && x < 128 {
-		return nil, &ErrInvalidOpCode{opcode: OpCode(x)}
+		operand := x
+		return nil, &ErrInvalidOpCode{opcode: EXCHANGE, operand: &operand}
 	}
 	n, m := decodePair(x)
 	need := max(n, m) + 1

core/vm/instructions_test.go

@@ -1014,11 +1014,12 @@ func TestEIP8024_Execution(t *testing.T) {
 	evm := NewEVM(BlockContext{}, nil, params.TestChainConfig, Config{})
 
 	tests := []struct {
-		name       string
-		codeHex    string
-		wantErr    error
-		wantOpcode OpCode
-		wantVals   []uint64
+		name        string
+		codeHex     string
+		wantErr     error
+		wantOpcode  OpCode
+		wantOperand *byte
+		wantVals    []uint64
 	}{
 		{
 			name:    "DUPN",
@@ -1063,10 +1064,18 @@ func TestEIP8024_Execution(t *testing.T) {
 			},
 		},
 		{
-			name:       "INVALID_SWAPN_LOW",
-			codeHex:    "e75b",
-			wantErr:    &ErrInvalidOpCode{},
-			wantOpcode: SWAPN,
+			name:        "INVALID_DUPN_LOW",
+			codeHex:     "e65b",
+			wantErr:     &ErrInvalidOpCode{},
+			wantOpcode:  DUPN,
+			wantOperand: ptrToByte(0x5b),
+		},
+		{
+			name:        "INVALID_SWAPN_LOW",
+			codeHex:     "e75b",
+			wantErr:     &ErrInvalidOpCode{},
+			wantOpcode:  SWAPN,
+			wantOperand: ptrToByte(0x5b),
 		},
 		{
 			name:    "JUMP_OVER_INVALID_DUPN",
@@ -1079,10 +1088,11 @@ func TestEIP8024_Execution(t *testing.T) {
 			wantVals: []uint64{1, 0, 0},
 		},
 		{
-			name:       "INVALID_EXCHANGE",
-			codeHex:    "e852",
-			wantErr:    &ErrInvalidOpCode{},
-			wantOpcode: EXCHANGE,
+			name:        "INVALID_EXCHANGE",
+			codeHex:     "e852",
+			wantErr:     &ErrInvalidOpCode{},
+			wantOpcode:  EXCHANGE,
+			wantOperand: ptrToByte(0x52),
 		},
 		{
 			name:       "UNDERFLOW_DUPN",
@@ -1150,10 +1160,21 @@ func TestEIP8024_Execution(t *testing.T) {
 				// Fail if we don't get the error we expect.
 				switch tc.wantErr.(type) {
 				case *ErrInvalidOpCode:
-					var want *ErrInvalidOpCode
-					if !errors.As(err, &want) {
+					var got *ErrInvalidOpCode
+					if !errors.As(err, &got) {
 						t.Fatalf("expected ErrInvalidOpCode, got %v", err)
 					}
+					if got.opcode != tc.wantOpcode {
+						t.Fatalf("ErrInvalidOpCode.opcode=%s; want %s", got.opcode, tc.wantOpcode)
+					}
+					if tc.wantOperand != nil {
+						if got.operand == nil {
+							t.Fatalf("ErrInvalidOpCode.operand=nil; want 0x%02x", *tc.wantOperand)
+						}
+						if *got.operand != *tc.wantOperand {
+							t.Fatalf("ErrInvalidOpCode.operand=0x%02x; want 0x%02x", *got.operand, *tc.wantOperand)
+						}
+					}
 				case *ErrStackUnderflow:
 					var want *ErrStackUnderflow
 					if !errors.As(err, &want) {
@@ -1183,3 +1204,8 @@ func TestEIP8024_Execution(t *testing.T) {
 		})
 	}
 }
+
+func ptrToByte(v byte) *byte {
+	b := v
+	return &b
+}