Pass blob pointers safely to ETW

internal/etw/eventdatadescriptor.go

@@ -13,7 +13,7 @@ const (
 )
 
 type eventDataDescriptor struct {
-	ptr       uint64
+	ptr       ptr64
 	size      uint32
 	dataType  eventDataDescriptorType
 	reserved1 uint8
@@ -21,11 +21,8 @@ type eventDataDescriptor struct {
 }
 
 func newEventDataDescriptor(dataType eventDataDescriptorType, buffer []byte) eventDataDescriptor {
-	// Passing a pointer to Go-managed memory as part of a block of memory is
-	// risky since the GC doesn't know about it. If we find a better way to do
-	// this we should use it instead.
 	return eventDataDescriptor{
-		ptr:      uint64(uintptr(unsafe.Pointer(&buffer[0]))),
+		ptr:      ptr64{ptr: unsafe.Pointer(&buffer[0])},
 		size:     uint32(len(buffer)),
 		dataType: dataType,
 	}