diff --git a/src/libthread/Darwin-ucontext.h b/src/libthread/Darwin-ucontext.h
new file mode 100644
index 0000000..c7915ff
--- /dev/null
+++ b/src/libthread/Darwin-ucontext.h
@@ -0,0 +1,24 @@
+typedef struct ucontext ucontext_t;
+struct ucontext
+{
+	ulong	pc;		/* lr */
+	ulong	cr;		/* mfcr */
+	ulong	ctr;		/* mfcr */
+	ulong	xer;		/* mfcr */
+	ulong	sp;		/* callee saved: r1 */
+	ulong	toc;		/* callee saved: r2 */
+	ulong	r3;		/* first arg to function, return register: r3 */
+	ulong	gpr[19];	/* callee saved: r13-r31 */
+// XXX: currently do not save vector registers or floating-point state
+//	ulong	pad;
+//	uvlong	fpr[18];	/* callee saved: f14-f31 */
+//	ulong	vr[4*12];	/* callee saved: v20-v31, 256-bits each */
+};
+
+void makecontext(ucontext_t*, void(*)(void), int, ...);
+void getcontext(ucontext_t*);
+int setcontext(ucontext_t*);
+int swapcontext(ucontext_t*, ucontext_t*);
+int __setlabel(ucontext_t*);
+void __gotolabel(ucontext_t*);
+