runtime: support Pinner.Pin for string type

For #65286

Change-Id: I1a04f151ac78c8c09a37d2cb7f782b2b61ad3290

Author: qiulaidongfeng

src/runtime/pinner.go

@@ -107,14 +107,20 @@ func pinnerGetPtr(i *any) unsafe.Pointer {
 	if etyp == nil {
 		panic(errorString("runtime.Pinner: argument is nil"))
 	}
-	if kind := etyp.Kind_ & kindMask; kind != kindPtr && kind != kindUnsafePointer {
-		panic(errorString("runtime.Pinner: argument is not a pointer: " + toRType(etyp).string()))
+	var data unsafe.Pointer
+	kind := etyp.Kind_ & kindMask
+	switch kind {
+	case kindPtr, kindUnsafePointer:
+	case kindString:
+		data = unsafe.Pointer(unsafe.StringData(*(*string)(e.data)))
+	default:
+		panic(errorString("runtime.Pinner: argument is not a pointer or string: " + toRType(etyp).string()))
 	}
 	if inUserArenaChunk(uintptr(e.data)) {
 		// Arena-allocated objects are not eligible for pinning.
 		panic(errorString("runtime.Pinner: object was allocated into an arena"))
 	}
-	return e.data
+	return data
 }
 
 // isPinned checks if a Go pointer is pinned.

src/runtime/pinner_test.go

@@ -538,3 +538,21 @@ func TestPinnerConstStringData(t *testing.T) {
 		t.Fatal("not marked as pinned")
 	}
 }
+
+func TestPinnerPinString(t *testing.T) {
+	var pinner runtime.Pinner
+	heapStr := getHeapStr()
+	pinner.Pin(heapStr)
+	addr := unsafe.Pointer(unsafe.StringData(heapStr))
+	if !runtime.IsPinned(addr) {
+		t.Fatal("not marked as pinned")
+	}
+	pinner.Unpin()
+	if runtime.IsPinned(addr) {
+		t.Fatal("still marked as pinned")
+	}
+}
+
+func getHeapStr() string {
+	return string(byte(fastrand()))
+}