Add getentropy, getrandom, <sys/random.h> [BZ #17252]

sysdeps/unix/sysv/linux/getrandom.c

@@ -0,0 +1,43 @@
+/* Implementation of the getrandom system call.
+   Copyright (C) 2016 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <sys/random.h>
+#include <errno.h>
+#include <unistd.h>
+#include <sysdep-cancel.h>
+
+#ifdef __NR_getrandom
+/* Write LENGTH bytes of randomness starting at BUFFER.  Return 0 on
+   success and -1 on failure.  */
+ssize_t
+getrandom (void *buffer, size_t length, unsigned int flags)
+{
+  return SYSCALL_CANCEL (getrandom, buffer, length, flags);
+}
+#else
+/* Always provide a definition, even if the kernel headers lack the
+   system call number. */
+ssize_t
+getrandom (void *buffer, size_t length, unsigned int flags)
+{
+  /* Ideally, we would add a cancellation point here, but we currently
+     cannot do so inside libc.  */
+  __set_errno (ENOSYS);
+  return -1;
+}
+#endif