Add arm-nacl port.

sysdeps/nacl/dl-writev.h

@@ -0,0 +1,45 @@
+/* Message-writing for the dynamic linker.  NaCl version.
+   Copyright (C) 2015 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/uio.h>
+#include <nacl-interfaces.h>
+
+/* This is used from only one place: dl-misc.c:_dl_debug_vdprintf.
+   Hence it's in a header with the expectation it will be inlined.
+
+   This is writev, but with a constraint added and others loosened:
+
+   1. Under RTLD_PRIVATE_ERRNO, it must not clobber the private errno
+      when another thread holds the dl_load_lock.
+   2. It is not obliged to detect and report errors at all.
+   3. It's not really obliged to deliver a single atomic write
+      (though it may be preferable).  */
+
+static inline void
+_dl_writev (int fd, const struct iovec *iov, size_t niov)
+{
+  for (size_t i = 0; i < niov; ++i)
+    {
+      size_t wrote;
+      if (__nacl_irt_fdio.write (fd, iov[i].iov_base, iov[i].iov_len,
+                                 &wrote) != 0
+          || wrote != iov[i].iov_len)
+        /* The write failed, so don't bother trying any more.  */
+        break;
+    }
+}