From 1a8583de72e12e139e9c7fbcfc026c2cbf410519 Mon Sep 17 00:00:00 2001
From: glass <glass@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>
Date: Sun, 10 Feb 2019 08:21:33 +0000
Subject: [PATCH] random.c: use getrandom() if available.

getrandom() is supported by glibc 2.25 or later.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@67043 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
---
 configure.ac |  1 +
 random.c     | 26 ++++++++++++++++++++++++++
 2 files changed, 27 insertions(+)

diff --git a/configure.ac b/configure.ac
index cc9df54c0d..b9fd9ff728 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1826,6 +1826,7 @@ AC_CHECK_FUNCS(getpgid)
 AC_CHECK_FUNCS(getpgrp)
 AC_CHECK_FUNCS(getpriority)
 AC_CHECK_FUNCS(getpwnam_r)
+AC_CHECK_FUNCS(getrandom)
 AC_CHECK_FUNCS(getresgid)
 AC_CHECK_FUNCS(getresuid)
 AC_CHECK_FUNCS(getrlimit)
diff --git a/random.c b/random.c
index 77a8fc7b04..704f78d44d 100644
--- a/random.c
+++ b/random.c
@@ -390,6 +390,32 @@ fill_random_bytes_syscall(void *seed, size_t size, int unused)
     CryptGenRandom(prov, size, seed);
     return 0;
 }
+#elif defined HAVE_GETRANDOM
+#include <sys/random.h>
+
+static int
+fill_random_bytes_syscall(void *seed, size_t size, int need_secure)
+{
+    static rb_atomic_t try_syscall = 1;
+    if (try_syscall) {
+	ssize_t ret;
+	size_t offset = 0;
+	int flags = 0;
+	if (!need_secure)
+	    flags = GRND_NONBLOCK;
+	do {
+	    errno = 0;
+	    ret = getrandom(((char*)seed) + offset, size - offset, flags);
+	    if (ret == -1) {
+		ATOMIC_SET(try_syscall, 0);
+		return -1;
+	    }
+	    offset += (size_t)ret;
+	} while(offset < size);
+	return 0;
+    }
+    return -1;
+}
 #elif defined __linux__ && defined __NR_getrandom
 #include <linux/random.h>