auto import from //depot/cupcake/@135843
diff --git a/libc/unistd/sigwait.c b/libc/unistd/sigwait.c
new file mode 100644
index 0000000..c9c2a54
--- /dev/null
+++ b/libc/unistd/sigwait.c
@@ -0,0 +1,74 @@
+/*
+ * Copyright (C) 2008 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.
+ */
+#include <errno.h>
+#include <signal.h>
+#include <string.h>
+#include <time.h>
+
+int __rt_sigtimedwait(const sigset_t *uthese, siginfo_t *uinfo, const struct timespec *uts, size_t sigsetsize);
+
+/* ok, this is really subtle: <asm/signal.h> defines sigset_t differently
+ * when you're in the kernel or in the C library.
+ *
+ * in the kernel, this is an array of 2 32-bit unsigned longs
+ * in the C library, this is a single 32-bit unsigned long
+ *
+ * moreover, the kernel implementation of rt_sigtimedwait doesn't
+ * accept anything except kernel-sized signal sets (probably a bug !)
+ *
+ * we thus need to create a fake kernel sigset !!
+ */
+
+int sigwait(const sigset_t *set, int *sig)
+{
+ int ret;
+ /* use a union to get rid of aliasing warnings */
+ union {
+ unsigned long kernel_sigset[2];
+ sigset_t dummy_sigset;
+ } u;
+
+ u.kernel_sigset[0] = *set;
+ u.kernel_sigset[1] = 0; /* no real-time signals supported ? */
+ for (;;)
+ {
+ /* __rt_sigtimedwait can return EAGAIN or EINTR, we need to loop
+ * around them since sigwait is only allowed to return EINVAL
+ */
+ ret = __rt_sigtimedwait ( &u.dummy_sigset, NULL, NULL, sizeof(u.kernel_sigset));
+ if (ret >= 0)
+ break;
+
+ if (errno != EAGAIN && errno != EINTR)
+ return errno;
+ }
+
+ *sig = ret;
+ return 0;
+}
+