diff --git a/libmango/include-user/mango/handle.h b/libmango/include-user/mango/handle.h
index b515384..ef71805 100644
--- a/libmango/include-user/mango/handle.h
+++ b/libmango/include-user/mango/handle.h
@@ -12,5 +12,11 @@ extern kern_status_t kern_handle_transfer(
 	kern_handle_t dest_handle,
 	unsigned int mode,
 	kern_handle_t *out_handle);
+extern kern_status_t kern_handle_control(
+	kern_handle_t task,
+	kern_handle_t handle,
+	uint32_t set_mask,
+	uint32_t clear_mask,
+	uint32_t *out_flags);
 
 #endif
diff --git a/libmango/include/mango/syscall.h b/libmango/include/mango/syscall.h
index f20a8cf..fc388a1 100644
--- a/libmango/include/mango/syscall.h
+++ b/libmango/include/mango/syscall.h
@@ -51,5 +51,6 @@
 #define SYS_FUTEX_WAKE                  48
 #define SYS_KERN_OBJECT_QUERY           49
 #define SYS_TASK_DUPLICATE              50
+#define SYS_KERN_HANDLE_CONTROL         51
 
 #endif
diff --git a/libmango/include/mango/types.h b/libmango/include/mango/types.h
index 9b6ac21..109e96d 100644
--- a/libmango/include/mango/types.h
+++ b/libmango/include/mango/types.h
@@ -28,6 +28,12 @@
 #define THREAD_CFG_FSBASE            0x20001u
 #define THREAD_CFG_GSBASE            0x20002u
 
+/* user-defined flags that can be set on handles */
+#define KERN_HANDLE_FLAG0            0x10000000UL
+#define KERN_HANDLE_FLAG1            0x20000000UL
+#define KERN_HANDLE_FLAG2            0x40000000UL
+#define KERN_HANDLE_FLAG3            0x80000000UL
+
 /* maximum number of handles that can be sent in a single message */
 #define KERN_MSG_MAX_HANDLES         64