Revert "Revert "Attempt to use arc4random where getauxval(AT_RANDOM) is used.""
This reverts commit 60d052dda600f26fdb6180ac1a2c53e97df5a58a.
Bug: http://b/27729263
Change-Id: I7f32dc9f9a1f21fda3213f10da940821e1bdd63f
diff --git a/libc/private/bionic_arc4random.h b/libc/private/bionic_arc4random.h
new file mode 100644
index 0000000..d26a4e7
--- /dev/null
+++ b/libc/private/bionic_arc4random.h
@@ -0,0 +1,45 @@
+/*
+ * Copyright (C) 2016 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 _PRIVATE_BIONIC_ARC4RANDOM_H_
+#define _PRIVATE_BIONIC_ARC4RANDOM_H_
+
+#include <stddef.h>
+
+#include "private/KernelArgumentBlock.h"
+
+/*
+ * arc4random aborts if it's unable to fetch entropy, which is always the case
+ * for init on devices without getrandom(2), since /dev/random hasn't been
+ * created yet. Provide a wrapper function that falls back to AT_RANDOM if
+ * we don't have getrandom and /dev/urandom is missing.
+ */
+
+void __libc_safe_arc4random_buf(void* buf, size_t n, KernelArgumentBlock& args);
+
+#endif