EIP-2315: JUMPSUB for the EVM

core/vm/contract.go

@@ -83,7 +83,7 @@ func NewContract(caller ContractRef, object ContractRef, value *big.Int, gas uin
 
 func (c *Contract) validJumpdest(dest *big.Int) bool {
 	udest := dest.Uint64()
-	// PC cannot go beyond len(code) and certainly can't be bigger than 63bits.
+	// PC cannot go beyond len(code) and certainly can't be bigger than 63 bits.
 	// Don't bother checking for JUMPDEST in that case.
 	if dest.BitLen() >= 63 || udest >= uint64(len(c.Code)) {
 		return false
@@ -92,16 +92,32 @@ func (c *Contract) validJumpdest(dest *big.Int) bool {
 	if OpCode(c.Code[udest]) != JUMPDEST {
 		return false
 	}
-	// Do we have it locally already?
-	if c.analysis != nil {
-		return c.analysis.codeSegment(udest)
+	return c.isCode(udest)
+}
+
+func (c *Contract) validJumpSubdest(udest uint64) bool {
+	// PC cannot go beyond len(code) and certainly can't be bigger than 63 bits.
+	// Don't bother checking for BEGINSUB in that case.
+	if int64(udest) < 0 || udest >= uint64(len(c.Code)) {
+		return false
+	}
+	// Only BEGINSUBs allowed for destinations
+	if OpCode(c.Code[udest]) != BEGINSUB {
+		return false
 	}
-	// If we have the code hash (but no analysis), we should look into the
-	// parent analysis map and see if the analysis has been made previously
+	return c.isCode(udest)
+}
+
+// isCode returns true if the provided PC location is an actual opcode, as
+// opposed to a data-segment following a PUSHN operation.
+func (c *Contract) isCode(udest uint64) bool {
+	// Do we have a contract hash already?
 	if c.CodeHash != (common.Hash{}) {
+		// Does parent context have the analysis?
 		analysis, exist := c.jumpdests[c.CodeHash]
 		if !exist {
 			// Do the analysis and save in parent context
+			// We do not need to store it in c.analysis
 			analysis = codeBitmap(c.Code)
 			c.jumpdests[c.CodeHash] = analysis
 		}
@@ -113,7 +129,9 @@ func (c *Contract) validJumpdest(dest *big.Int) bool {
 	// in state trie. In that case, we do an analysis, and save it locally, so
 	// we don't have to recalculate it for every JUMP instruction in the execution
 	// However, we don't save it within the parent context
-	c.analysis = codeBitmap(c.Code)
+	if c.analysis == nil {
+		c.analysis = codeBitmap(c.Code)
+	}
 	return c.analysis.codeSegment(udest)
 }
 

core/vm/eips.go

@@ -33,6 +33,8 @@ func EnableEIP(eipNum int, jt *JumpTable) error {
 		enable1884(jt)
 	case 1344:
 		enable1344(jt)
+	case 2315:
+		enable2315(jt)
 	default:
 		return fmt.Errorf("undefined eip %d", eipNum)
 	}
@@ -91,3 +93,34 @@ func enable2200(jt *JumpTable) {
 	jt[SLOAD].constantGas = params.SloadGasEIP2200
 	jt[SSTORE].dynamicGas = gasSStoreEIP2200
 }
+
+// enable2315 applies EIP-2315 (Simple Subroutines)
+// - Adds opcodes that jump to and return from subroutines
+func enable2315(jt *JumpTable) {
+	// New opcode
+	jt[BEGINSUB] = operation{
+		execute:     opBeginSub,
+		constantGas: GasQuickStep,
+		minStack:    minStack(0, 0),
+		maxStack:    maxStack(0, 0),
+		valid:       true,
+	}
+	// New opcode
+	jt[JUMPSUB] = operation{
+		execute:     opJumpSub,
+		constantGas: GasSlowStep,
+		minStack:    minStack(1, 0),
+		maxStack:    maxStack(1, 0),
+		jumps:       true,
+		valid:       true,
+	}
+	// New opcode
+	jt[RETURNSUB] = operation{
+		execute:     opReturnSub,
+		constantGas: GasFastStep,
+		minStack:    minStack(0, 0),
+		maxStack:    maxStack(0, 0),
+		valid:       true,
+		jumps:       true,
+	}
+}

core/vm/errors.go

@@ -23,6 +23,9 @@ import (
 
 // List evm execution errors
 var (
+	// ErrInvalidSubroutineEntry means that a BEGINSUB was reached via iteration,
+	// as opposed to from a JUMPSUB instruction
+	ErrInvalidSubroutineEntry   = errors.New("invalid subroutine entry")
 	ErrOutOfGas                 = errors.New("out of gas")
 	ErrCodeStoreOutOfGas        = errors.New("contract creation code storage out of gas")
 	ErrDepth                    = errors.New("max call depth exceeded")
@@ -34,6 +37,8 @@ var (
 	ErrWriteProtection          = errors.New("write protection")
 	ErrReturnDataOutOfBounds    = errors.New("return data out of bounds")
 	ErrGasUintOverflow          = errors.New("gas uint64 overflow")
+	ErrInvalidRetsub            = errors.New("invalid retsub")
+	ErrReturnStackExceeded      = errors.New("return stack limit reached")
 )
 
 // ErrStackUnderflow wraps an evm error when the items on the stack less

core/vm/instructions.go

@@ -664,6 +664,39 @@ func opJumpdest(pc *uint64, interpreter *EVMInterpreter, callContext *callCtx) (
 	return nil, nil
 }
 
+func opBeginSub(pc *uint64, interpreter *EVMInterpreter, callContext *callCtx) ([]byte, error) {
+	return nil, ErrInvalidSubroutineEntry
+}
+
+func opJumpSub(pc *uint64, interpreter *EVMInterpreter, callContext *callCtx) ([]byte, error) {
+	if len(callContext.rstack.data) >= 1023 {
+		return nil, ErrReturnStackExceeded
+	}
+	pos := callContext.stack.pop()
+	if !pos.IsUint64() {
+		return nil, ErrInvalidJump
+	}
+	posU64 := pos.Uint64()
+	if !callContext.contract.validJumpSubdest(posU64) {
+		return nil, ErrInvalidJump
+	}
+	callContext.rstack.push(*pc)
+	*pc = posU64 + 1
+	interpreter.intPool.put(pos)
+	return nil, nil
+}
+
+func opReturnSub(pc *uint64, interpreter *EVMInterpreter, callContext *callCtx) ([]byte, error) {
+	if len(callContext.rstack.data) == 0 {
+		return nil, ErrInvalidRetsub
+	}
+	// Other than the check that the return stack is not empty, there is no
+	// need to validate the pc from 'returns', since we only ever push valid
+	//values onto it via jumpsub.
+	*pc = callContext.rstack.pop() + 1
+	return nil, nil
+}
+
 func opPc(pc *uint64, interpreter *EVMInterpreter, callContext *callCtx) ([]byte, error) {
 	callContext.stack.push(interpreter.intPool.get().SetUint64(*pc))
 	return nil, nil

core/vm/instructions_test.go

@@ -94,6 +94,7 @@ func testTwoOperandOp(t *testing.T, tests []TwoOperandTestcase, opFn executionFu
 	var (
 		env            = NewEVM(Context{}, nil, params.TestChainConfig, Config{})
 		stack          = newstack()
+		rstack         = newReturnStack()
 		pc             = uint64(0)
 		evmInterpreter = env.interpreter.(*EVMInterpreter)
 	)
@@ -109,7 +110,7 @@ func testTwoOperandOp(t *testing.T, tests []TwoOperandTestcase, opFn executionFu
 		expected := new(big.Int).SetBytes(common.Hex2Bytes(test.Expected))
 		stack.push(x)
 		stack.push(y)
-		opFn(&pc, evmInterpreter, &callCtx{nil, stack, nil})
+		opFn(&pc, evmInterpreter, &callCtx{nil, stack, rstack, nil})
 		actual := stack.pop()
 
 		if actual.Cmp(expected) != 0 {
@@ -211,10 +212,10 @@ func TestSAR(t *testing.T) {
 // getResult is a convenience function to generate the expected values
 func getResult(args []*twoOperandParams, opFn executionFunc) []TwoOperandTestcase {
 	var (
-		env         = NewEVM(Context{}, nil, params.TestChainConfig, Config{})
-		stack       = newstack()
-		pc          = uint64(0)
-		interpreter = env.interpreter.(*EVMInterpreter)
+		env           = NewEVM(Context{}, nil, params.TestChainConfig, Config{})
+		stack, rstack = newstack(), newReturnStack()
+		pc            = uint64(0)
+		interpreter   = env.interpreter.(*EVMInterpreter)
 	)
 	interpreter.intPool = poolOfIntPools.get()
 	result := make([]TwoOperandTestcase, len(args))
@@ -223,7 +224,7 @@ func getResult(args []*twoOperandParams, opFn executionFunc) []TwoOperandTestcas
 		y := new(big.Int).SetBytes(common.Hex2Bytes(param.y))
 		stack.push(x)
 		stack.push(y)
-		opFn(&pc, interpreter, &callCtx{nil, stack, nil})
+		opFn(&pc, interpreter, &callCtx{nil, stack, rstack, nil})
 		actual := stack.pop()
 		result[i] = TwoOperandTestcase{param.x, param.y, fmt.Sprintf("%064x", actual)}
 	}
@@ -263,7 +264,7 @@ func TestJsonTestcases(t *testing.T) {
 func opBenchmark(bench *testing.B, op executionFunc, args ...string) {
 	var (
 		env            = NewEVM(Context{}, nil, params.TestChainConfig, Config{})
-		stack          = newstack()
+		stack, rstack  = newstack(), newReturnStack()
 		evmInterpreter = NewEVMInterpreter(env, env.vmConfig)
 	)
 
@@ -281,7 +282,7 @@ func opBenchmark(bench *testing.B, op executionFunc, args ...string) {
 			a := new(big.Int).SetBytes(arg)
 			stack.push(a)
 		}
-		op(&pc, evmInterpreter, &callCtx{nil, stack, nil})
+		op(&pc, evmInterpreter, &callCtx{nil, stack, rstack, nil})
 		stack.pop()
 	}
 	poolOfIntPools.put(evmInterpreter.intPool)
@@ -498,7 +499,7 @@ func BenchmarkOpIsZero(b *testing.B) {
 func TestOpMstore(t *testing.T) {
 	var (
 		env            = NewEVM(Context{}, nil, params.TestChainConfig, Config{})
-		stack          = newstack()
+		stack, rstack  = newstack(), newReturnStack()
 		mem            = NewMemory()
 		evmInterpreter = NewEVMInterpreter(env, env.vmConfig)
 	)
@@ -509,12 +510,12 @@ func TestOpMstore(t *testing.T) {
 	pc := uint64(0)
 	v := "abcdef00000000000000abba000000000deaf000000c0de00100000000133700"
 	stack.pushN(new(big.Int).SetBytes(common.Hex2Bytes(v)), big.NewInt(0))
-	opMstore(&pc, evmInterpreter, &callCtx{mem, stack, nil})
+	opMstore(&pc, evmInterpreter, &callCtx{mem, stack, rstack, nil})
 	if got := common.Bytes2Hex(mem.GetCopy(0, 32)); got != v {
 		t.Fatalf("Mstore fail, got %v, expected %v", got, v)
 	}
 	stack.pushN(big.NewInt(0x1), big.NewInt(0))
-	opMstore(&pc, evmInterpreter, &callCtx{mem, stack, nil})
+	opMstore(&pc, evmInterpreter, &callCtx{mem, stack, rstack, nil})
 	if common.Bytes2Hex(mem.GetCopy(0, 32)) != "0000000000000000000000000000000000000000000000000000000000000001" {
 		t.Fatalf("Mstore failed to overwrite previous value")
 	}
@@ -524,7 +525,7 @@ func TestOpMstore(t *testing.T) {
 func BenchmarkOpMstore(bench *testing.B) {
 	var (
 		env            = NewEVM(Context{}, nil, params.TestChainConfig, Config{})
-		stack          = newstack()
+		stack, rstack  = newstack(), newReturnStack()
 		mem            = NewMemory()
 		evmInterpreter = NewEVMInterpreter(env, env.vmConfig)
 	)
@@ -539,15 +540,15 @@ func BenchmarkOpMstore(bench *testing.B) {
 	bench.ResetTimer()
 	for i := 0; i < bench.N; i++ {
 		stack.pushN(value, memStart)
-		opMstore(&pc, evmInterpreter, &callCtx{mem, stack, nil})
+		opMstore(&pc, evmInterpreter, &callCtx{mem, stack, rstack, nil})
 	}
 	poolOfIntPools.put(evmInterpreter.intPool)
 }
 
 func BenchmarkOpSHA3(bench *testing.B) {
 	var (
 		env            = NewEVM(Context{}, nil, params.TestChainConfig, Config{})
-		stack          = newstack()
+		stack, rstack  = newstack(), newReturnStack()
 		mem            = NewMemory()
 		evmInterpreter = NewEVMInterpreter(env, env.vmConfig)
 	)
@@ -560,7 +561,7 @@ func BenchmarkOpSHA3(bench *testing.B) {
 	bench.ResetTimer()
 	for i := 0; i < bench.N; i++ {
 		stack.pushN(big.NewInt(32), start)
-		opSha3(&pc, evmInterpreter, &callCtx{mem, stack, nil})
+		opSha3(&pc, evmInterpreter, &callCtx{mem, stack, rstack, nil})
 	}
 	poolOfIntPools.put(evmInterpreter.intPool)
 }

core/vm/interpreter.go

@@ -67,6 +67,7 @@ type Interpreter interface {
 type callCtx struct {
 	memory   *Memory
 	stack    *Stack
+	rstack   *ReturnStack
 	contract *Contract
 }
 
@@ -167,12 +168,14 @@ func (in *EVMInterpreter) Run(contract *Contract, input []byte, readOnly bool) (
 	}
 
 	var (
-		op          OpCode        // current opcode
-		mem         = NewMemory() // bound memory
-		stack       = newstack()  // local stack
+		op          OpCode             // current opcode
+		mem         = NewMemory()      // bound memory
+		stack       = newstack()       // local stack
+		returns     = newReturnStack() // local returns stack
 		callContext = &callCtx{
 			memory:   mem,
 			stack:    stack,
+			rstack:   returns,
 			contract: contract,
 		}
 		// For optimisation reason we're using uint64 as the program counter.
@@ -195,9 +198,9 @@ func (in *EVMInterpreter) Run(contract *Contract, input []byte, readOnly bool) (
 		defer func() {
 			if err != nil {
 				if !logged {
-					in.cfg.Tracer.CaptureState(in.evm, pcCopy, op, gasCopy, cost, mem, stack, contract, in.evm.depth, err)
+					in.cfg.Tracer.CaptureState(in.evm, pcCopy, op, gasCopy, cost, mem, stack, returns, contract, in.evm.depth, err)
 				} else {
-					in.cfg.Tracer.CaptureFault(in.evm, pcCopy, op, gasCopy, cost, mem, stack, contract, in.evm.depth, err)
+					in.cfg.Tracer.CaptureFault(in.evm, pcCopy, op, gasCopy, cost, mem, stack, returns, contract, in.evm.depth, err)
 				}
 			}
 		}()
@@ -279,7 +282,7 @@ func (in *EVMInterpreter) Run(contract *Contract, input []byte, readOnly bool) (
 		}
 
 		if in.cfg.Debug {
-			in.cfg.Tracer.CaptureState(in.evm, pc, op, gasCopy, cost, mem, stack, contract, in.evm.depth, err)
+			in.cfg.Tracer.CaptureState(in.evm, pc, op, gasCopy, cost, mem, stack, returns, contract, in.evm.depth, err)
 			logged = true
 		}