Add __libc_arc4random_unlimited_entropy.
Let the caller know when libc has an entropy source and arc4random is safe.
This is useful for the callers that want entropy, but don't absolutely need it.
Bug: http://b/27729263
Test: booted angler-userdebug w/ safestack
Change-Id: Iab3050bd19f23518e1676629573eebc656ba1090
diff --git a/libc/private/bionic_arc4random.h b/libc/private/bionic_arc4random.h
index d26a4e7..b51f818 100644
--- a/libc/private/bionic_arc4random.h
+++ b/libc/private/bionic_arc4random.h
@@ -39,7 +39,12 @@
* 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);
+/*
+ * Return true if libc has an unlimited entropy source (something other than
+ * AT_RANDOM), and arc4random* calls will always succeed.
+ */
+bool __libc_arc4random_has_unlimited_entropy();
+
#endif