From 8aaf7d913a382291f2770e6ce72a8919d5441bef Mon Sep 17 00:00:00 2001
From: Kent Overstreet <kent.overstreet@gmail.com>
Date: Tue, 15 Aug 2017 17:19:06 -0600
Subject: [PATCH] urandom fallback

---
 include/linux/random.h |  9 +++++++++
 linux/sched.c          | 14 ++++++++++++++
 2 files changed, 23 insertions(+)

diff --git a/include/linux/random.h b/include/linux/random.h
index bd3dc61b..95a15d05 100644
--- a/include/linux/random.h
+++ b/include/linux/random.h
@@ -10,10 +10,19 @@
 #include <sys/syscall.h>
 #include <linux/bug.h>
 
+#ifdef __NR_getrandom
 static inline int getrandom(void *buf, size_t buflen, unsigned int flags)
 {
 	 return syscall(SYS_getrandom, buf, buflen, flags);
 }
+#else
+extern int urandom_fd;
+
+static inline int getrandom(void *buf, size_t buflen, unsigned int flags)
+{
+	return read(urandom_fd, buf, buflen);
+}
+#endif
 
 static inline void get_random_bytes(void *buf, int nbytes)
 {
diff --git a/linux/sched.c b/linux/sched.c
index 898ccb19..cc614b12 100644
--- a/linux/sched.c
+++ b/linux/sched.c
@@ -179,3 +179,17 @@ static void sched_init(void)
 	rcu_init();
 	rcu_register_thread();
 }
+
+#ifndef __NR_getrandom
+#include <fcntl.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+int urandom_fd;
+
+__attribute__((constructor(101)))
+static void rand_init(void)
+{
+	urandom_fd = open("/dev/urandom", O_RDONLY);
+	BUG_ON(urandom_fd < 0);
+}
+#endif