diff --git a/src/data.rs b/src/data.rs
index ae6bf91258..7775b2e938 100644
--- a/src/data.rs
+++ b/src/data.rs
@@ -231,6 +231,45 @@ impl DerefMut for TimeSpec {
     }
 }
 
+/*
+// ABI-UNSTABLE!
+#[derive(Clone, Copy, Debug, Default)]
+#[repr(C)]
+pub struct ThreadEvent {
+    pub kind: u8,
+    pub _rsvd: [u8; size_of::<usize>() - 1],
+    pub payload: [usize; 3],
+}
+#[repr(u8)]
+#[derive(Clone, Copy, Debug)]
+pub enum ThreadEventKind {
+    Sigkill = 0,
+}
+
+impl Deref for ThreadEvent {
+    type Target = [u8];
+    fn deref(&self) -> &[u8] {
+        unsafe {
+            slice::from_raw_parts(
+                self as *const ThreadEvent as *const u8,
+                mem::size_of::<ThreadEvent>(),
+            )
+        }
+    }
+}
+
+impl DerefMut for ThreadEvent {
+    fn deref_mut(&mut self) -> &mut [u8] {
+        unsafe {
+            slice::from_raw_parts_mut(
+                self as *mut ThreadEvent as *mut u8,
+                mem::size_of::<ThreadEvent>(),
+            )
+        }
+    }
+}
+*/
+
 #[derive(Clone, Copy, Debug, Default)]
 #[repr(C)]
 pub struct PtraceEvent {
diff --git a/src/flag.rs b/src/flag.rs
index 7c569008ed..0402f4b04f 100644
--- a/src/flag.rs
+++ b/src/flag.rs
@@ -170,6 +170,17 @@ pub const O_ACCMODE: usize = O_RDONLY | O_WRONLY | O_RDWR;
 
 // The top 48 bits of PTRACE_* are reserved, for now
 
+// NOT ABI STABLE!
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+#[repr(usize)]
+pub enum ContextStatus {
+    Runnable,
+    Blocked,
+    NotYetStarted,
+    Dead,
+    Other, // reserved
+}
+
 bitflags! {
     pub struct PtraceFlags: u64 {
         /// Stop before a syscall is handled. Send PTRACE_FLAG_IGNORE to not