From: Baruch Siach <baruch@tkos.co.il>
Date: Fri, 29 Sep 2017 10:06:52 +0300
Subject: [PATCH] Fix build with musl and older Linux kernel

The musl libc carries its own copy of Linux system calls. When building
with Linux headers older than v3.17, musl provides SYS_getrandom
definition, but not GRND_NONBLOCK. This causes build failure for
libressl and openntpd:

getentropy_linux.c: In function 'getentropy_getrandom':
getentropy_linux.c:205:42: error: 'GRND_NONBLOCK' undeclared (first use in this function)
   ret = syscall(SYS_getrandom, buf, len, GRND_NONBLOCK);
                                          ^~~~~~~~~~~~~

Define GRND_NONBLOCK locally when its definition is missing to fix the
build. There should be no run-time effect. Older kernels return ENOSYS
for unsupported syscall().

[ from upstream pull request with file location changed ]
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
---
Upstream status: https://github.com/libressl-portable/openbsd/pull/82

diff -Nuar libressl-2.5.5-orig/crypto/compat/getentropy_linux.c libressl-2.5.5/crypto/compat/getentropy_linux.c
--- libressl-2.5.5-orig/crypto/compat/getentropy_linux.c	2017-07-09 13:59:48.000000000 +0300
+++ libressl-2.5.5/crypto/compat/getentropy_linux.c	2017-09-29 10:03:32.447958829 +0300
@@ -194,6 +194,11 @@
 }
 
 #ifdef SYS_getrandom
+
+#ifndef GRND_NONBLOCK
+#define GRND_NONBLOCK   0x0001
+#endif
+
 static int
 getentropy_getrandom(void *buf, size_t len)
 {