runtime: require explicit GC layouts

src/internal/gclayout/gclayout.go

@@ -17,10 +17,15 @@ const (
 
 	sizeShift = sizeBits + 1
 
-	NoPtrs  = Layout((0 << sizeShift) | (1 << 1) | 1)
-	Pointer = Layout((1 << sizeShift) | ((unsafe.Sizeof(unsafe.Pointer(nil)) / ptrAlign) << 1) | 1)
-	String  = Layout((1 << sizeShift) | ((unsafe.Sizeof("") / ptrAlign) << 1) | 1)
-	Slice   = Layout((1 << sizeShift) | ((unsafe.Sizeof([]byte{}) / ptrAlign) << 1) | 1)
+	NoPtrs      = Layout((0 << sizeShift) | (1 << 1) | 1)
+	Pointer     = Layout((1 << sizeShift) | ((unsafe.Sizeof(unsafe.Pointer(nil)) / ptrAlign) << 1) | 1)
+	PointerPair = Layout((3 << sizeShift) | ((2 * unsafe.Sizeof(unsafe.Pointer(nil)) / ptrAlign) << 1) | 1)
+	String      = Layout((1 << sizeShift) | ((unsafe.Sizeof("") / ptrAlign) << 1) | 1)
+	Slice       = Layout((1 << sizeShift) | ((unsafe.Sizeof([]byte{}) / ptrAlign) << 1) | 1)
+
+	// Conservative is reserved for stack storage, which does not have an
+	// ordinary Go object layout.
+	Conservative = Layout(2)
 )
 
 func (l Layout) AsPtr() unsafe.Pointer { return unsafe.Pointer(l) }

src/internal/reflectlite/type.go

@@ -166,6 +166,11 @@ type RawType struct {
 	meta uint8 // metadata byte, contains kind and flags (see constants above)
 }
 
+type basicType struct {
+	RawType
+	ptrTo *RawType
+}
+
 // All types that have an element type: named, chan, slice, array, map (but not
 // pointer because it doesn't have ptrTo).
 type elemType struct {
@@ -200,6 +205,7 @@ type arrayType struct {
 	elem      *RawType
 	arrayLen  uintptr
 	slicePtr  *RawType
+	layout    unsafe.Pointer
 }
 
 type mapType struct {
@@ -208,6 +214,7 @@ type mapType struct {
 	ptrTo     *RawType
 	elem      *RawType
 	key       *RawType
+	typeInfo  unsafe.Pointer
 }
 
 // namedType is the type descriptor for named types. The numMethod field uses
@@ -243,6 +250,7 @@ type structType struct {
 	pkgpath   *byte
 	size      uint32
 	numField  uint16
+	layout    unsafe.Pointer
 	fields    [1]structField // the remaining fields are all of type structField
 	// methods methodSet follows after fields, only when numMethod & numMethodHasMethodSet != 0
 }
@@ -298,6 +306,8 @@ func pointerTo(t *RawType) *RawType {
 	}
 
 	switch t.Kind() {
+	case Bool, Int, Int8, Int16, Int32, Int64, Uint, Uint8, Uint16, Uint32, Uint64, Uintptr, Complex64, Complex128, Float32, Float64, String, UnsafePointer:
+		return (*basicType)(unsafe.Pointer(t)).ptrTo
 	case Pointer:
 		if tag := t.ptrtag(); tag < 3 {
 			return (*RawType)(unsafe.Add(unsafe.Pointer(t), 1))
@@ -306,6 +316,8 @@ func pointerTo(t *RawType) *RawType {
 		// TODO(dgryski): This is blocking https://github.com/tinygo-org/tinygo/issues/3131
 		// We need to be able to create types that match existing types to prevent typecode equality.
 		panic("reflect: cannot make *****T type")
+	case Interface, Func:
+		return (*interfaceType)(unsafe.Pointer(t)).ptrTo
 	case Struct:
 		return (*structType)(unsafe.Pointer(t)).ptrTo
 	default:
@@ -729,6 +741,7 @@ func (t *RawType) Align() int {
 }
 
 func (r *RawType) gcLayout() unsafe.Pointer {
+	r = r.underlying()
 	kind := r.Kind()
 
 	if kind < String {
@@ -736,16 +749,26 @@ func (r *RawType) gcLayout() unsafe.Pointer {
 	}
 
 	switch kind {
-	case Pointer, UnsafePointer, Chan, Map:
-		return gclayout.Pointer.AsPtr()
 	case String:
 		return gclayout.String.AsPtr()
+	case UnsafePointer, Chan, Pointer, Map:
+		return gclayout.Pointer.AsPtr()
+	case Interface, Func:
+		return gclayout.PointerPair.AsPtr()
 	case Slice:
 		return gclayout.Slice.AsPtr()
+	case Array:
+		return (*arrayType)(unsafe.Pointer(r)).layout
+	case Struct:
+		return (*structType)(unsafe.Pointer(r)).layout
+	default:
+		panic("reflect: invalid GC layout kind")
 	}
+}
 
-	// Unknown (for now); let the conservative pointer scanning handle it
-	return nil
+func (r *RawType) hashmapTypeInfo() unsafe.Pointer {
+	r = r.underlying()
+	return (*mapType)(unsafe.Pointer(r)).typeInfo
 }
 
 // FieldAlign returns the alignment if this type is used in a struct field. It

src/internal/reflectlite/value.go

@@ -1,6 +1,7 @@
 package reflectlite
 
 import (
+	"internal/gclayout"
 	"math"
 	"unsafe"
 )
@@ -1644,7 +1645,7 @@ func makeInt(flags valueFlags, bits uint64, t *RawType) Value {
 
 	ptr := unsafe.Pointer(&v.value)
 	if size > unsafe.Sizeof(uintptr(0)) {
-		ptr = alloc(size, nil)
+		ptr = alloc(size, gclayout.NoPtrs.AsPtr())
 		v.value = ptr
 	}
 
@@ -1671,7 +1672,7 @@ func makeFloat(flags valueFlags, f float64, t *RawType) Value {
 
 	ptr := unsafe.Pointer(&v.value)
 	if size > unsafe.Sizeof(uintptr(0)) {
-		ptr = alloc(size, nil)
+		ptr = alloc(size, gclayout.NoPtrs.AsPtr())
 		v.value = ptr
 	}
 
@@ -1703,7 +1704,7 @@ func makeComplex(flags valueFlags, f complex128, t *RawType) Value {
 
 	ptr := unsafe.Pointer(&v.value)
 	if size > unsafe.Sizeof(uintptr(0)) {
-		ptr = alloc(size, nil)
+		ptr = alloc(size, gclayout.NoPtrs.AsPtr())
 		v.value = ptr
 	}
 
@@ -1834,7 +1835,7 @@ func Zero(typ Type) Value {
 
 	return Value{
 		typecode: typ.(*RawType),
-		value:    alloc(size, nil),
+		value:    alloc(size, typ.(*RawType).gcLayout()),
 		flags:    valueFlagExported | valueFlagRO,
 	}
 }
@@ -1844,7 +1845,7 @@ func Zero(typ Type) Value {
 func New(typ Type) Value {
 	return Value{
 		typecode: pointerTo(typ.(*RawType)),
-		value:    alloc(typ.Size(), nil),
+		value:    alloc(typ.Size(), typ.(*RawType).gcLayout()),
 		flags:    valueFlagExported,
 	}
 }
@@ -2203,13 +2204,13 @@ func (v Value) FieldByNameFunc(match func(string) bool) Value {
 }
 
 //go:linkname hashmapMake runtime.hashmapMake
-func hashmapMake(keySize, valueSize uintptr, sizeHint uintptr, alg uint8) unsafe.Pointer
+func hashmapMake(keySize, valueSize uintptr, sizeHint uintptr, typeInfo unsafe.Pointer, alg uint8) unsafe.Pointer
 
 //go:linkname hashmapMakeReflect runtime.hashmapMakeReflect
-func hashmapMakeReflect(keySize, valueSize, sizeHint uintptr, keyType unsafe.Pointer) unsafe.Pointer
+func hashmapMakeReflect(keySize, valueSize, sizeHint uintptr, typeInfo, keyType unsafe.Pointer) unsafe.Pointer
 
 //go:linkname chanMake runtime.chanMake
-func chanMake(elementSize uintptr, bufSize uintptr) unsafe.Pointer
+func chanMake(elementSize uintptr, bufSize uintptr, elementLayout unsafe.Pointer) unsafe.Pointer
 
 // MakeMapWithSize creates a new map with the specified type and initial space
 // for approximately n elements.
@@ -2231,18 +2232,19 @@ func MakeMapWithSize(typ Type, n int) Value {
 
 	key := typ.Key().(*RawType)
 	val := typ.Elem().(*RawType)
+	typeInfo := typ.(*RawType).hashmapTypeInfo()
 
 	var m unsafe.Pointer
 
 	if key.Kind() == String {
-		m = hashmapMake(key.Size(), val.Size(), uintptr(n), hashmapAlgorithmString)
+		m = hashmapMake(key.Size(), val.Size(), uintptr(n), typeInfo, hashmapAlgorithmString)
 	} else if key.isBinary() {
-		m = hashmapMake(key.Size(), val.Size(), uintptr(n), hashmapAlgorithmBinary)
+		m = hashmapMake(key.Size(), val.Size(), uintptr(n), typeInfo, hashmapAlgorithmBinary)
 	} else {
 		// Composite key type (struct with strings, floats, etc.).
 		// Use runtime-generated hash/equal closures that walk the
 		// type structure, matching the compiler-generated functions.
-		m = hashmapMakeReflect(key.Size(), val.Size(), uintptr(n), unsafe.Pointer(key))
+		m = hashmapMakeReflect(key.Size(), val.Size(), uintptr(n), typeInfo, unsafe.Pointer(key))
 	}
 
 	return Value{
@@ -2269,7 +2271,7 @@ func MakeChan(typ Type, size int) Value {
 		panic("reflect.MakeChan: unidirectional channel type")
 	}
 	elem := typ.Elem().(*RawType)
-	ch := chanMake(elem.Size(), uintptr(size))
+	ch := chanMake(elem.Size(), uintptr(size), elem.gcLayout())
 	return Value{
 		typecode: typ.(*RawType),
 		value:    ch,

src/internal/task/task_asyncify.go

@@ -3,6 +3,7 @@
 package task
 
 import (
+	"internal/gclayout"
 	"unsafe"
 )
 
@@ -73,7 +74,7 @@ func (s *state) initialize(fn uintptr, args unsafe.Pointer, stackSize uintptr) {
 	s.args = args
 
 	// Create a stack.
-	stack := runtime_alloc(stackSize, nil)
+	stack := runtime_alloc(stackSize, gclayout.Conservative.AsPtr())
 
 	// Set up the stack canary, a random number that should be checked when
 	// switching from the task back to the scheduler. The stack canary pointer

src/internal/task/task_stack.go

@@ -3,6 +3,7 @@
 package task
 
 import (
+	"internal/gclayout"
 	"unsafe"
 )
 
@@ -36,7 +37,7 @@ func taskExit() {
 // initialize the state and prepare to call the specified function with the specified argument bundle.
 func (s *state) initialize(fn uintptr, args unsafe.Pointer, stackSize uintptr) {
 	// Create a stack.
-	stack := runtime_alloc(stackSize, nil)
+	stack := runtime_alloc(stackSize, gclayout.Conservative.AsPtr())
 
 	// Set up the stack canary, a random number that should be checked when
 	// switching from the task back to the scheduler. The stack canary pointer