diff --git a/libc/private/bionic_fortify.h b/libc/private/bionic_fortify.h
new file mode 100644
index 0000000..df810ca
--- /dev/null
+++ b/libc/private/bionic_fortify.h
@@ -0,0 +1,69 @@
+/*
+ * 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.
+ */
+
+#include "private/libc_logging.h"
+
+#include <poll.h> // For struct pollfd.
+#include <sys/select.h> // For struct fd_set.
+
+//
+// Common helpers.
+//
+
+static inline void __check_fd_set(const char* fn, int fd, size_t set_size) {
+  if (__predict_false(fd < 0)) {
+    __fortify_fatal("%s: file descriptor %d < 0", fn, fd);
+  }
+  if (__predict_false(fd >= FD_SETSIZE)) {
+    __fortify_fatal("%s: file descriptor %d >= FD_SETSIZE %zu", fn, fd, set_size);
+  }
+  if (__predict_false(set_size < sizeof(fd_set))) {
+    __fortify_fatal("%s: set size %zu is too small to be an fd_set", fn, set_size);
+  }
+}
+
+static inline void __check_pollfd_array(const char* fn, size_t fds_size, nfds_t fd_count) {
+  size_t pollfd_array_length = fds_size / sizeof(pollfd);
+  if (__predict_false(pollfd_array_length < fd_count)) {
+    __fortify_fatal("%s: %zu-element pollfd array too small for %u fds",
+                    fn, pollfd_array_length, fd_count);
+  }
+}
+
+static inline void __check_count(const char* fn, const char* identifier, size_t value) {
+  if (__predict_false(value > SSIZE_MAX)) {
+    __fortify_fatal("%s: %s %zu > SSIZE_MAX", fn, identifier, value);
+  }
+}
+
+static inline void __check_buffer_access(const char* fn, const char* action,
+                                         size_t claim, size_t actual) {
+  if (__predict_false(claim > actual)) {
+    __fortify_fatal("%s: prevented %zu-byte %s %zu-byte buffer", fn, claim, action, actual);
+  }
+}