Merge pull request #2613 from nspcc-dev/exec-changes-3.4.0

Exec changes for 3.4.0

pkg/core/interop/contract/call.go

@@ -14,6 +14,7 @@ import (
 	"github.com/nspcc-dev/neo-go/pkg/smartcontract/callflag"
 	"github.com/nspcc-dev/neo-go/pkg/smartcontract/manifest"
 	"github.com/nspcc-dev/neo-go/pkg/util"
+	"github.com/nspcc-dev/neo-go/pkg/vm"
 	"github.com/nspcc-dev/neo-go/pkg/vm/stackitem"
 )
 
@@ -27,7 +28,7 @@ func LoadToken(ic *interop.Context, id int32) error {
 	if !ctx.GetCallFlags().Has(callflag.ReadStates | callflag.AllowCall) {
 		return errors.New("invalid call flags")
 	}
-	tok := ctx.NEF.Tokens[id]
+	tok := ctx.GetNEF().Tokens[id]
 	if int(tok.ParamCount) > ctx.Estack().Len() {
 		return errors.New("stack is too small")
 	}
@@ -67,11 +68,11 @@ func Call(ic *interop.Context) error {
 		return fmt.Errorf("method not found: %s/%d", method, len(args))
 	}
 	hasReturn := md.ReturnType != smartcontract.VoidType
-	return callInternal(ic, cs, method, fs, hasReturn, args, !hasReturn)
+	return callInternal(ic, cs, method, fs, hasReturn, args, true)
 }
 
 func callInternal(ic *interop.Context, cs *state.Contract, name string, f callflag.CallFlag,
-	hasReturn bool, args []stackitem.Item, pushNullOnUnloading bool) error {
+	hasReturn bool, args []stackitem.Item, isDynamic bool) error {
 	md := cs.Manifest.ABI.GetMethod(name, len(args))
 	if md.Safe {
 		f &^= (callflag.WriteStates | callflag.AllowNotify)
@@ -83,12 +84,12 @@ func callInternal(ic *interop.Context, cs *state.Contract, name string, f callfl
 			}
 		}
 	}
-	return callExFromNative(ic, ic.VM.GetCurrentScriptHash(), cs, name, args, f, hasReturn, pushNullOnUnloading, false)
+	return callExFromNative(ic, ic.VM.GetCurrentScriptHash(), cs, name, args, f, hasReturn, isDynamic, false)
 }
 
 // callExFromNative calls a contract with flags using the provided calling hash.
 func callExFromNative(ic *interop.Context, caller util.Uint160, cs *state.Contract,
-	name string, args []stackitem.Item, f callflag.CallFlag, hasReturn bool, pushNullOnUnloading bool, callFromNative bool) error {
+	name string, args []stackitem.Item, f callflag.CallFlag, hasReturn bool, isDynamic bool, callFromNative bool) error {
 	for _, nc := range ic.Natives {
 		if nc.Metadata().Name == nativenames.Policy {
 			var pch = nc.(policyChecker)
@@ -123,7 +124,7 @@ func callExFromNative(ic *interop.Context, caller util.Uint160, cs *state.Contra
 	if wrapped {
 		ic.DAO = ic.DAO.GetPrivate()
 	}
-	onUnload := func(commit bool) error {
+	onUnload := func(ctx *vm.Context, commit bool) error {
 		if wrapped {
 			if commit {
 				_, err := ic.DAO.Persist()
@@ -135,8 +136,13 @@ func callExFromNative(ic *interop.Context, caller util.Uint160, cs *state.Contra
 			}
 			ic.DAO = baseDAO
 		}
-		if pushNullOnUnloading && commit {
+		if isDynamic && commit {
-			ic.VM.Context().Estack().PushItem(stackitem.Null{}) // Must use current context stack.
+			eLen := ctx.Estack().Len()
+			if eLen == 0 && ctx.NumOfReturnVals() == 0 { // No return value and none expected.
+				ic.VM.Context().Estack().PushItem(stackitem.Null{}) // Must use current context stack.
+			} else if eLen > 1 { // 1 or -1 (all) retrun values expected, but only one can be returned.
+				return errors.New("multiple return values in a cross-contract call")
+			} // All other rvcount/stack length mismatches are checked by the VM.
 		}
 		if callFromNative && !commit {
 			return fmt.Errorf("unhandled exception")

pkg/core/interop/runtime/engine.go

@@ -73,6 +73,10 @@ func Notify(ic *interop.Context) error {
 	if len(name) > MaxEventNameLen {
 		return fmt.Errorf("event name must be less than %d", MaxEventNameLen)
 	}
+	if !ic.VM.Context().IsDeployed() {
+		return errors.New("notifications are not allowed in dynamic scripts")
+	}
+
 	// But it has to be serializable, otherwise we either have some broken
 	// (recursive) structure inside or an interop item that can't be used
 	// outside of the interop subsystem anyway.

pkg/core/interop/runtime/engine_test.go

@@ -12,6 +12,7 @@ import (
 	"github.com/nspcc-dev/neo-go/pkg/core/interop"
 	"github.com/nspcc-dev/neo-go/pkg/crypto/hash"
 	"github.com/nspcc-dev/neo-go/pkg/smartcontract/callflag"
+	"github.com/nspcc-dev/neo-go/pkg/smartcontract/nef"
 	"github.com/nspcc-dev/neo-go/pkg/smartcontract/trigger"
 	"github.com/nspcc-dev/neo-go/pkg/util"
 	"github.com/nspcc-dev/neo-go/pkg/vm"
@@ -133,9 +134,12 @@ func TestLog(t *testing.T) {
 
 func TestNotify(t *testing.T) {
 	h := random.Uint160()
+	caller := random.Uint160()
+	exe, err := nef.NewFile([]byte{1})
+	require.NoError(t, err)
 	newIC := func(name string, args interface{}) *interop.Context {
 		ic := &interop.Context{VM: vm.New(), DAO: &dao.Simple{}}
-		ic.VM.LoadScriptWithHash([]byte{1}, h, callflag.NoneFlag)
+		ic.VM.LoadNEFMethod(exe, caller, h, callflag.NoneFlag, true, 0, -1, nil)
 		ic.VM.Estack().PushVal(args)
 		ic.VM.Estack().PushVal(name)
 		return ic
@@ -144,6 +148,13 @@ func TestNotify(t *testing.T) {
 		ic := newIC(string(make([]byte, MaxEventNameLen+1)), stackitem.NewArray([]stackitem.Item{stackitem.Null{}}))
 		require.Error(t, Notify(ic))
 	})
+	t.Run("dynamic script", func(t *testing.T) {
+		ic := &interop.Context{VM: vm.New(), DAO: &dao.Simple{}}
+		ic.VM.LoadScriptWithHash([]byte{1}, h, callflag.NoneFlag)
+		ic.VM.Estack().PushVal(stackitem.NewArray([]stackitem.Item{stackitem.Make(42)}))
+		ic.VM.Estack().PushVal("event")
+		require.Error(t, Notify(ic))
+	})
 	t.Run("recursive struct", func(t *testing.T) {
 		arr := stackitem.NewArray([]stackitem.Item{stackitem.Null{}})
 		arr.Append(arr)

pkg/core/interop/runtime/witness.go

@@ -41,6 +41,10 @@ func getContractGroups(v *vm.VM, ic *interop.Context, h util.Uint160) (manifest.
 	return manifest.Groups(cs.Manifest.Groups), nil
 }
 
+func (sc scopeContext) IsCalledByEntry() bool {
+	return sc.VM.Context().IsCalledByEntry()
+}
+
 func (sc scopeContext) checkScriptGroups(h util.Uint160, k *keys.PublicKey) (bool, error) {
 	groups, err := getContractGroups(sc.VM, sc.ic, h)
 	if err != nil {
@@ -69,9 +73,7 @@ func checkScope(ic *interop.Context, hash util.Uint160) (bool, error) {
 				return true, nil
 			}
 			if c.Scopes&transaction.CalledByEntry != 0 {
-				callingScriptHash := ic.VM.GetCallingScriptHash()
+				if ic.VM.Context().IsCalledByEntry() {
-				entryScriptHash := ic.VM.GetEntryScriptHash()
-				if callingScriptHash.Equals(util.Uint160{}) || callingScriptHash == entryScriptHash {
 					return true, nil
 				}
 			}

pkg/core/transaction/witness_condition.go

@@ -63,9 +63,9 @@ type WitnessCondition interface {
 type MatchContext interface {
 	GetCallingScriptHash() util.Uint160
 	GetCurrentScriptHash() util.Uint160
-	GetEntryScriptHash() util.Uint160
 	CallingScriptHasGroup(*keys.PublicKey) (bool, error)
 	CurrentScriptHasGroup(*keys.PublicKey) (bool, error)
+	IsCalledByEntry() bool
 }
 
 type (
@@ -394,8 +394,7 @@ func (c ConditionCalledByEntry) Type() WitnessConditionType {
 // Match implements the WitnessCondition interface checking whether this condition
 // matches given context.
 func (c ConditionCalledByEntry) Match(ctx MatchContext) (bool, error) {
-	entry := ctx.GetEntryScriptHash()
+	return ctx.IsCalledByEntry(), nil
-	return entry.Equals(ctx.GetCallingScriptHash()) || entry.Equals(ctx.GetCurrentScriptHash()), nil
 }
 
 // EncodeBinary implements the WitnessCondition interface allowing to serialize condition.

pkg/core/transaction/witness_condition_test.go

@@ -170,6 +170,9 @@ func (t *TestMC) GetCurrentScriptHash() util.Uint160 {
 func (t *TestMC) GetEntryScriptHash() util.Uint160 {
 	return t.entry
 }
+func (t *TestMC) IsCalledByEntry() bool {
+	return t.entry.Equals(t.calling) || t.calling.Equals(util.Uint160{})
+}
 func (t *TestMC) CallingScriptHasGroup(k *keys.PublicKey) (bool, error) {
 	res, err := t.CurrentScriptHasGroup(k)
 	return !res, err // To differentiate from current we invert the logic value.

pkg/core/transaction/witness_scope.go

@@ -13,7 +13,7 @@ type WitnessScope byte
 const (
 	// None specifies that no contract was witnessed. Only sign the transaction.
 	None WitnessScope = 0
-	// CalledByEntry means that this condition must hold: EntryScriptHash == CallingScriptHash.
+	// CalledByEntry witness is only valid in entry script and ones directly called by it.
 	// No params is needed, as the witness/permission/signature given on first invocation will
 	// automatically expire if entering deeper internal invokes. This can be default safe
 	// choice for native NEO/GAS (previously used on Neo 2 as "attach" mode).

pkg/vm/context.go

@@ -16,14 +16,10 @@ import (
 	"github.com/nspcc-dev/neo-go/pkg/vm/stackitem"
 )
 
-// Context represents the current execution context of the VM.
+// scriptContext is a part of the Context that is shared between multiple Contexts,
-type Context struct {
+// it's created when a new script is loaded into the VM while regular
-	// Instruction pointer.
+// CALL/CALLL/CALLA internal invocations reuse it.
-	ip int
+type scriptContext struct {
-
-	// The next instruction pointer.
-	nextip int
-
 	// The raw program script.
 	prog []byte
 
@@ -33,12 +29,7 @@ type Context struct {
 	// Evaluation stack pointer.
 	estack *Stack
 
-	static    *slot
+	static slot
-	local     slot
-	arguments slot
-
-	// Exception context stack.
-	tryStack Stack
 
 	// Script hash of the prog.
 	scriptHash util.Uint160
@@ -46,22 +37,43 @@ type Context struct {
 	// Caller's contract script hash.
 	callingScriptHash util.Uint160
 
+	// Caller's scriptContext, if not entry.
+	callingContext *scriptContext
+
 	// Call flags this context was created with.
 	callFlag callflag.CallFlag
 
-	// retCount specifies the number of return values.
-	retCount int
 	// NEF represents a NEF file for the current contract.
 	NEF *nef.File
-	// invTree is an invocation tree (or branch of it) for this context.
+	// invTree is an invocation tree (or a branch of it) for this context.
 	invTree *invocations.Tree
 	// onUnload is a callback that should be called after current context unloading
 	// if no exception occurs.
 	onUnload ContextUnloadCallback
 }
 
+// Context represents the current execution context of the VM.
+type Context struct {
+	// Instruction pointer.
+	ip int
+
+	// The next instruction pointer.
+	nextip int
+
+	sc *scriptContext
+
+	local     slot
+	arguments slot
+
+	// Exception context stack.
+	tryStack Stack
+
+	// retCount specifies the number of return values.
+	retCount int
+}
+
 // ContextUnloadCallback is a callback method used on context unloading from istack.
-type ContextUnloadCallback func(commit bool) error
+type ContextUnloadCallback func(ctx *Context, commit bool) error
 
 var errNoInstParam = errors.New("failed to read instruction parameter")
 
@@ -74,7 +86,9 @@ func NewContext(b []byte) *Context {
 // return value count and initial position in script.
 func NewContextWithParams(b []byte, rvcount int, pos int) *Context {
 	return &Context{
-		prog:     b,
+		sc: &scriptContext{
+			prog: b,
+		},
 		retCount: rvcount,
 		nextip:   pos,
 	}
@@ -82,7 +96,7 @@ func NewContextWithParams(b []byte, rvcount int, pos int) *Context {
 
 // Estack returns the evaluation stack of c.
 func (c *Context) Estack() *Stack {
-	return c.estack
+	return c.sc.estack
 }
 
 // NextIP returns the next instruction pointer.
@@ -92,7 +106,7 @@ func (c *Context) NextIP() int {
 
 // Jump unconditionally moves the next instruction pointer to the specified location.
 func (c *Context) Jump(pos int) {
-	if pos < 0 || pos >= len(c.prog) {
+	if pos < 0 || pos >= len(c.sc.prog) {
 		panic("instruction offset is out of range")
 	}
 	c.nextip = pos
@@ -105,11 +119,12 @@ func (c *Context) Next() (opcode.Opcode, []byte, error) {
 	var err error
 
 	c.ip = c.nextip
-	if c.ip >= len(c.prog) {
+	prog := c.sc.prog
+	if c.ip >= len(prog) {
 		return opcode.RET, nil, nil
 	}
 
-	var instrbyte = c.prog[c.ip]
+	var instrbyte = prog[c.ip]
 	instr := opcode.Opcode(instrbyte)
 	if !opcode.IsValid(instr) {
 		return instr, nil, fmt.Errorf("incorrect opcode %s", instr.String())
@@ -119,24 +134,24 @@ func (c *Context) Next() (opcode.Opcode, []byte, error) {
 	var numtoread int
 	switch instr {
 	case opcode.PUSHDATA1:
-		if c.nextip >= len(c.prog) {
+		if c.nextip >= len(prog) {
 			err = errNoInstParam
 		} else {
-			numtoread = int(c.prog[c.nextip])
+			numtoread = int(prog[c.nextip])
 			c.nextip++
 		}
 	case opcode.PUSHDATA2:
-		if c.nextip+1 >= len(c.prog) {
+		if c.nextip+1 >= len(prog) {
 			err = errNoInstParam
 		} else {
-			numtoread = int(binary.LittleEndian.Uint16(c.prog[c.nextip : c.nextip+2]))
+			numtoread = int(binary.LittleEndian.Uint16(prog[c.nextip : c.nextip+2]))
 			c.nextip += 2
 		}
 	case opcode.PUSHDATA4:
-		if c.nextip+3 >= len(c.prog) {
+		if c.nextip+3 >= len(prog) {
 			err = errNoInstParam
 		} else {
-			var n = binary.LittleEndian.Uint32(c.prog[c.nextip : c.nextip+4])
+			var n = binary.LittleEndian.Uint32(prog[c.nextip : c.nextip+4])
 			if n > stackitem.MaxSize {
 				return instr, nil, errors.New("parameter is too big")
 			}
@@ -166,13 +181,13 @@ func (c *Context) Next() (opcode.Opcode, []byte, error) {
 			return instr, nil, nil
 		}
 	}
-	if c.nextip+numtoread-1 >= len(c.prog) {
+	if c.nextip+numtoread-1 >= len(prog) {
 		err = errNoInstParam
 	}
 	if err != nil {
 		return instr, nil, err
 	}
-	parameter := c.prog[c.nextip : c.nextip+numtoread]
+	parameter := prog[c.nextip : c.nextip+numtoread]
 	c.nextip += numtoread
 	return instr, parameter, nil
 }
@@ -184,46 +199,49 @@ func (c *Context) IP() int {
 
 // LenInstr returns the number of instructions loaded.
 func (c *Context) LenInstr() int {
-	return len(c.prog)
+	return len(c.sc.prog)
 }
 
 // CurrInstr returns the current instruction and opcode.
 func (c *Context) CurrInstr() (int, opcode.Opcode) {
-	return c.ip, opcode.Opcode(c.prog[c.ip])
+	return c.ip, opcode.Opcode(c.sc.prog[c.ip])
 }
 
 // NextInstr returns the next instruction and opcode.
 func (c *Context) NextInstr() (int, opcode.Opcode) {
 	op := opcode.RET
-	if c.nextip < len(c.prog) {
+	if c.nextip < len(c.sc.prog) {
-		op = opcode.Opcode(c.prog[c.nextip])
+		op = opcode.Opcode(c.sc.prog[c.nextip])
 	}
 	return c.nextip, op
 }
 
-// Copy returns an new exact copy of c.
-func (c *Context) Copy() *Context {
-	ctx := new(Context)
-	*ctx = *c
-	return ctx
-}
-
 // GetCallFlags returns the calling flags which the context was created with.
 func (c *Context) GetCallFlags() callflag.CallFlag {
-	return c.callFlag
+	return c.sc.callFlag
 }
 
 // Program returns the loaded program.
 func (c *Context) Program() []byte {
-	return c.prog
+	return c.sc.prog
 }
 
 // ScriptHash returns a hash of the script in the current context.
 func (c *Context) ScriptHash() util.Uint160 {
-	if c.scriptHash.Equals(util.Uint160{}) {
+	if c.sc.scriptHash.Equals(util.Uint160{}) {
-		c.scriptHash = hash.Hash160(c.prog)
+		c.sc.scriptHash = hash.Hash160(c.sc.prog)
 	}
-	return c.scriptHash
+	return c.sc.scriptHash
+}
+
+// GetNEF returns NEF structure used by this context if it's present.
+func (c *Context) GetNEF() *nef.File {
+	return c.sc.NEF
+}
+
+// NumOfReturnVals returns the number of return values expected from this context.
+func (c *Context) NumOfReturnVals() int {
+	return c.retCount
 }
 
 // Value implements the stackitem.Item interface.
@@ -263,7 +281,7 @@ func (c *Context) Equals(s stackitem.Item) bool {
 }
 
 func (c *Context) atBreakPoint() bool {
-	for _, n := range c.breakPoints {
+	for _, n := range c.sc.breakPoints {
 		if n == c.nextip {
 			return true
 		}
@@ -277,12 +295,12 @@ func (c *Context) String() string {
 
 // IsDeployed returns whether this context contains a deployed contract.
 func (c *Context) IsDeployed() bool {
-	return c.NEF != nil
+	return c.sc.NEF != nil
 }
 
 // DumpStaticSlot returns json formatted representation of the given slot.
 func (c *Context) DumpStaticSlot() string {
-	return dumpSlot(c.static)
+	return dumpSlot(&c.sc.static)
 }
 
 // DumpLocalSlot returns json formatted representation of the given slot.
@@ -316,6 +334,12 @@ func (v *VM) getContextScriptHash(n int) util.Uint160 {
 	return ctx.ScriptHash()
 }
 
+// IsCalledByEntry checks parent script contexts and return true if the current one
+// is an entry script (the first loaded into the VM) or one called by it.
+func (c *Context) IsCalledByEntry() bool {
+	return c.sc.callingContext == nil || c.sc.callingContext.callingContext == nil
+}
+
 // PushContextScriptHash pushes the script hash of the
 // invocation stack element number n to the evaluation stack.
 func (v *VM) PushContextScriptHash(n int) error {

pkg/vm/interop.go

@@ -36,8 +36,9 @@ func defaultSyscallHandler(v *VM, id uint32) error {
 		return errors.New("syscall not found")
 	}
 	d := defaultVMInterops[n]
-	if !v.Context().callFlag.Has(d.RequiredFlags) {
+	ctxFlag := v.Context().sc.callFlag
-		return fmt.Errorf("missing call flags: %05b vs %05b", v.Context().callFlag, d.RequiredFlags)
+	if !ctxFlag.Has(d.RequiredFlags) {
+		return fmt.Errorf("missing call flags: %05b vs %05b", ctxFlag, d.RequiredFlags)
 	}
 	return d.Func(v)
 }

pkg/vm/json_test.go

@@ -115,7 +115,7 @@ func testSyscallHandler(v *VM, id uint32) error {
 	case 0x77777777:
 		v.Estack().PushVal(stackitem.NewInterop(new(int)))
 	case 0x66666666:
-		if !v.Context().callFlag.Has(callflag.ReadOnly) {
+		if !v.Context().sc.callFlag.Has(callflag.ReadOnly) {
 			return errors.New("invalid call flags")
 		}
 		v.Estack().PushVal(stackitem.NewInterop(new(int)))
@@ -167,14 +167,14 @@ func testFile(t *testing.T, filename string) {
 					if len(result.InvocationStack) > 0 {
 						for i, s := range result.InvocationStack {
 							ctx := vm.istack.Peek(i).Value().(*Context)
-							if ctx.nextip < len(ctx.prog) {
+							if ctx.nextip < len(ctx.sc.prog) {
 								require.Equal(t, s.InstructionPointer, ctx.nextip)
 								op, err := opcode.FromString(s.Instruction)
 								require.NoError(t, err)
-								require.Equal(t, op, opcode.Opcode(ctx.prog[ctx.nextip]))
+								require.Equal(t, op, opcode.Opcode(ctx.sc.prog[ctx.nextip]))
 							}
 							compareStacks(t, s.EStack, vm.estack)
-							compareSlots(t, s.StaticFields, ctx.static)
+							compareSlots(t, s.StaticFields, ctx.sc.static)
 						}
 					}
 
@@ -240,8 +240,8 @@ func compareStacks(t *testing.T, expected []vmUTStackItem, actual *Stack) {
 	compareItemArrays(t, expected, actual.Len(), func(i int) stackitem.Item { return actual.Peek(i).Item() })
 }
 
-func compareSlots(t *testing.T, expected []vmUTStackItem, actual *slot) {
+func compareSlots(t *testing.T, expected []vmUTStackItem, actual slot) {
-	if (actual == nil || *actual == nil) && len(expected) == 0 {
+	if actual == nil && len(expected) == 0 {
 		return
 	}
 	require.NotNil(t, actual)

pkg/vm/opcodebench_test.go

@@ -56,7 +56,7 @@ func opParamSlotsPushVM(op opcode.Opcode, param []byte, sslot int, slotloc int,
 			return nil
 		}
 		if sslot != 0 {
-			v.Context().static.init(sslot, &v.refs)
+			v.Context().sc.static.init(sslot, &v.refs)
 		}
 		if slotloc != 0 && slotarg != 0 {
 			v.Context().local.init(slotloc, &v.refs)

pkg/vm/vm.go

@@ -171,9 +171,7 @@ func (v *VM) PrintOps(out io.Writer) {
 	w := tabwriter.NewWriter(out, 0, 0, 4, ' ', 0)
 	fmt.Fprintln(w, "INDEX\tOPCODE\tPARAMETER")
 	realctx := v.Context()
-	ctx := realctx.Copy()
+	ctx := &Context{sc: realctx.sc}
-	ctx.ip = 0
-	ctx.nextip = 0
 	for {
 		cursor := ""
 		instr, parameter, err := ctx.Next()
@@ -228,7 +226,7 @@ func (v *VM) PrintOps(out io.Writer) {
 		}
 
 		fmt.Fprintf(w, "%d\t%s\t%s%s\n", ctx.ip, instr, desc, cursor)
-		if ctx.nextip >= len(ctx.prog) {
+		if ctx.nextip >= len(ctx.sc.prog) {
 			break
 		}
 	}
@@ -246,7 +244,7 @@ func getOffsetDesc(ctx *Context, parameter []byte) string {
 // AddBreakPoint adds a breakpoint to the current context.
 func (v *VM) AddBreakPoint(n int) {
 	ctx := v.Context()
-	ctx.breakPoints = append(ctx.breakPoints, n)
+	ctx.sc.breakPoints = append(ctx.sc.breakPoints, n)
 }
 
 // AddBreakPointRel adds a breakpoint relative to the current
@@ -337,31 +335,31 @@ func (v *VM) LoadNEFMethod(exe *nef.File, caller util.Uint160, hash util.Uint160
 // It should be used for calling from native contracts.
 func (v *VM) loadScriptWithCallingHash(b []byte, exe *nef.File, caller util.Uint160,
 	hash util.Uint160, f callflag.CallFlag, rvcount int, offset int, onContextUnload ContextUnloadCallback) {
-	var sl slot
-
 	v.checkInvocationStackSize()
 	ctx := NewContextWithParams(b, rvcount, offset)
 	if rvcount != -1 || v.estack.Len() != 0 {
 		v.estack = subStack(v.estack)
 	}
-	ctx.estack = v.estack
+	parent := v.Context()
+	ctx.sc.estack = v.estack
 	initStack(&ctx.tryStack, "exception", nil)
-	ctx.callFlag = f
+	ctx.sc.callFlag = f
-	ctx.static = &sl
+	ctx.sc.scriptHash = hash
-	ctx.scriptHash = hash
+	ctx.sc.callingScriptHash = caller
-	ctx.callingScriptHash = caller
+	if parent != nil {
-	ctx.NEF = exe
+		ctx.sc.callingContext = parent.sc
+	}
+	ctx.sc.NEF = exe
 	if v.invTree != nil {
 		curTree := v.invTree
-		parent := v.Context()
 		if parent != nil {
-			curTree = parent.invTree
+			curTree = parent.sc.invTree
 		}
 		newTree := &invocations.Tree{Current: ctx.ScriptHash()}
 		curTree.Calls = append(curTree.Calls, newTree)
-		ctx.invTree = newTree
+		ctx.sc.invTree = newTree
 	}
-	ctx.onUnload = onContextUnload
+	ctx.sc.onUnload = onContextUnload
 	v.istack.PushItem(ctx)
 }
 
@@ -481,7 +479,7 @@ func (v *VM) StepInto() error {
 		return nil
 	}
 
-	if ctx != nil && ctx.prog != nil {
+	if ctx != nil && ctx.sc.prog != nil {
 		op, param, err := ctx.Next()
 		if err != nil {
 			v.state = vmstate.Fault
@@ -584,7 +582,7 @@ func (v *VM) execute(ctx *Context, op opcode.Opcode, parameter []byte) (err erro
 		}
 	}()
 
-	if v.getPrice != nil && ctx.ip < len(ctx.prog) {
+	if v.getPrice != nil && ctx.ip < len(ctx.sc.prog) {
 		v.gasConsumed += v.getPrice(op, parameter)
 		if v.GasLimit >= 0 && v.gasConsumed > v.GasLimit {
 			panic("gas limit is exceeded")
@@ -610,7 +608,7 @@ func (v *VM) execute(ctx *Context, op opcode.Opcode, parameter []byte) (err erro
 
 	case opcode.PUSHA:
 		n := getJumpOffset(ctx, parameter)
-		ptr := stackitem.NewPointerWithHash(n, ctx.prog, ctx.ScriptHash())
+		ptr := stackitem.NewPointerWithHash(n, ctx.sc.prog, ctx.ScriptHash())
 		v.estack.PushItem(ptr)
 
 	case opcode.PUSHNULL:
@@ -637,7 +635,7 @@ func (v *VM) execute(ctx *Context, op opcode.Opcode, parameter []byte) (err erro
 		if parameter[0] == 0 {
 			panic("zero argument")
 		}
-		ctx.static.init(int(parameter[0]), &v.refs)
+		ctx.sc.static.init(int(parameter[0]), &v.refs)
 
 	case opcode.INITSLOT:
 		if ctx.local != nil || ctx.arguments != nil {
@@ -658,20 +656,20 @@ func (v *VM) execute(ctx *Context, op opcode.Opcode, parameter []byte) (err erro
 		}
 
 	case opcode.LDSFLD0, opcode.LDSFLD1, opcode.LDSFLD2, opcode.LDSFLD3, opcode.LDSFLD4, opcode.LDSFLD5, opcode.LDSFLD6:
-		item := ctx.static.Get(int(op - opcode.LDSFLD0))
+		item := ctx.sc.static.Get(int(op - opcode.LDSFLD0))
 		v.estack.PushItem(item)
 
 	case opcode.LDSFLD:
-		item := ctx.static.Get(int(parameter[0]))
+		item := ctx.sc.static.Get(int(parameter[0]))
 		v.estack.PushItem(item)
 
 	case opcode.STSFLD0, opcode.STSFLD1, opcode.STSFLD2, opcode.STSFLD3, opcode.STSFLD4, opcode.STSFLD5, opcode.STSFLD6:
 		item := v.estack.Pop().Item()
-		ctx.static.Set(int(op-opcode.STSFLD0), item, &v.refs)
+		ctx.sc.static.Set(int(op-opcode.STSFLD0), item, &v.refs)
 
 	case opcode.STSFLD:
 		item := v.estack.Pop().Item()
-		ctx.static.Set(int(parameter[0]), item, &v.refs)
+		ctx.sc.static.Set(int(parameter[0]), item, &v.refs)
 
 	case opcode.LDLOC0, opcode.LDLOC1, opcode.LDLOC2, opcode.LDLOC3, opcode.LDLOC4, opcode.LDLOC5, opcode.LDLOC6:
 		item := ctx.local.Get(int(op - opcode.LDLOC0))
@@ -1475,7 +1473,7 @@ func (v *VM) execute(ctx *Context, op opcode.Opcode, parameter []byte) (err erro
 			break
 		}
 
-		newEstack := v.Context().estack
+		newEstack := v.Context().sc.estack
 		if oldEstack != newEstack {
 			if oldCtx.retCount >= 0 && oldEstack.Len() != oldCtx.retCount {
 				panic(fmt.Errorf("invalid return values count: expected %d, got %d",
@@ -1631,17 +1629,19 @@ func (v *VM) unloadContext(ctx *Context) {
 		ctx.arguments.ClearRefs(&v.refs)
 	}
 	currCtx := v.Context()
-	if ctx.static != nil && (currCtx == nil || ctx.static != currCtx.static) {
+	if currCtx == nil || ctx.sc != currCtx.sc {
-		ctx.static.ClearRefs(&v.refs)
+		if ctx.sc.static != nil {
-	}
+			ctx.sc.static.ClearRefs(&v.refs)
-	if ctx.onUnload != nil {
+		}
-		err := ctx.onUnload(v.uncaughtException == nil)
+		if ctx.sc.onUnload != nil {
-		if err != nil {
+			err := ctx.sc.onUnload(ctx, v.uncaughtException == nil)
-			errMessage := fmt.Sprintf("context unload callback failed: %s", err)
+			if err != nil {
-			if v.uncaughtException != nil {
+				errMessage := fmt.Sprintf("context unload callback failed: %s", err)
-				errMessage = fmt.Sprintf("%s, uncaught exception: %s", errMessage, v.uncaughtException)
+				if v.uncaughtException != nil {
+					errMessage = fmt.Sprintf("%s, uncaught exception: %s", errMessage, v.uncaughtException)
+				}
+				panic(errors.New(errMessage))
 			}
-			panic(errors.New(errMessage))
 		}
 	}
 }
@@ -1691,17 +1691,13 @@ func (v *VM) Call(offset int) {
 // package.
 func (v *VM) call(ctx *Context, offset int) {
 	v.checkInvocationStackSize()
-	newCtx := ctx.Copy()
+	newCtx := &Context{
-	newCtx.retCount = -1
+		sc:       ctx.sc,
-	newCtx.local = nil
+		retCount: -1,
-	newCtx.arguments = nil
+		tryStack: ctx.tryStack,
-	// If memory for `elems` is reused, we can end up
+	}
-	// with an incorrect exception context state in the caller.
+	// New context -> new exception handlers.
-	newCtx.tryStack.elems = nil
+	newCtx.tryStack.elems = ctx.tryStack.elems[len(ctx.tryStack.elems):]
-	initStack(&newCtx.tryStack, "exception", nil)
-	newCtx.NEF = ctx.NEF
-	// Do not clone unloading callback, new context does not require any actions to perform on unloading.
-	newCtx.onUnload = nil
 	v.istack.PushItem(newCtx)
 	newCtx.Jump(offset)
 }
@@ -1732,7 +1728,7 @@ func calcJumpOffset(ctx *Context, parameter []byte) (int, int, error) {
 		return 0, 0, fmt.Errorf("invalid %s parameter length: %d", curr, l)
 	}
 	offset := ctx.ip + int(rOffset)
-	if offset < 0 || offset > len(ctx.prog) {
+	if offset < 0 || offset > len(ctx.sc.prog) {
 		return 0, 0, fmt.Errorf("invalid offset %d ip at %d", offset, ctx.ip)
 	}
 
@@ -1955,7 +1951,7 @@ func bytesToPublicKey(b []byte, curve elliptic.Curve) *keys.PublicKey {
 
 // GetCallingScriptHash implements the ScriptHashGetter interface.
 func (v *VM) GetCallingScriptHash() util.Uint160 {
-	return v.Context().callingScriptHash
+	return v.Context().sc.callingScriptHash
 }
 
 // GetEntryScriptHash implements the ScriptHashGetter interface.