initial darwin
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*);
+
