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,
 	}

internal/etw/ptr64_32.go

@@ -0,0 +1,16 @@
+// +build 386 arm
+
+package etw
+
+import (
+	"unsafe"
+)
+
+// byteptr64 defines a struct containing a pointer. The struct is guaranteed to
+// be 64 bits, regardless of the actual size of a pointer on the platform. This
+// is intended for use with certain Windows APIs that expect a pointer as a
+// ULONGLONG.
+type ptr64 struct {
+	ptr unsafe.Pointer
+	_   uint32
+}

internal/etw/ptr64_64.go

@@ -0,0 +1,15 @@
+// +build amd64 arm64
+
+package etw
+
+import (
+	"unsafe"
+)
+
+// byteptr64 defines a struct containing a pointer. The struct is guaranteed to
+// be 64 bits, regardless of the actual size of a pointer on the platform. This
+// is intended for use with certain Windows APIs that expect a pointer as a
+// ULONGLONG.
+type ptr64 struct {
+	ptr unsafe.Pointer
+}