diff --git a/libc/include/sys/ucontext.h b/libc/include/sys/ucontext.h
new file mode 100644
index 0000000..9d264e6
--- /dev/null
+++ b/libc/include/sys/ucontext.h
@@ -0,0 +1,90 @@
+/*
+ * Copyright (C) 2014 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#ifndef _SYS_UCONTEXT_H_
+#define _SYS_UCONTEXT_H_
+
+#include <signal.h>
+#include <sys/user.h>
+
+__BEGIN_DECLS
+
+#if defined(__x86_64__)
+
+enum {
+  REG_R8 = 0,
+  REG_R9,
+  REG_R10,
+  REG_R11,
+  REG_R12,
+  REG_R13,
+  REG_R14,
+  REG_R15,
+  REG_RDI,
+  REG_RSI,
+  REG_RBP,
+  REG_RBX,
+  REG_RDX,
+  REG_RAX,
+  REG_RCX,
+  REG_RSP,
+  REG_RIP,
+  REG_EFL,
+  REG_CSGSFS,
+  REG_ERR,
+  REG_TRAPNO,
+  REG_OLDMASK,
+  REG_CR2,
+  NGREG
+};
+
+typedef long greg_t;
+typedef greg_t gregset_t[NGREG];
+
+typedef struct user_i387_struct* fpregset_t;
+
+typedef struct {
+  gregset_t gregs;
+  fpregset_t fpregs;
+  /* TODO: reserved space? */
+} mcontext_t;
+
+typedef struct ucontext {
+  unsigned long uc_flags;
+  struct ucontext* uc_link;
+  stack_t uc_stack;
+  mcontext_t uc_mcontext;
+  sigset_t uc_sigmask;
+  /* TODO: __fpregs_mem? */
+} ucontext_t;
+
+#endif /* x86_64 */
+
+__END_DECLS
+
+#endif /* _SYS_UCONTEXT_H_ */