diff --git a/libc/bionic/bionic_elf_tls.cpp b/libc/bionic/bionic_elf_tls.cpp
new file mode 100644
index 0000000..55c2c31
--- /dev/null
+++ b/libc/bionic/bionic_elf_tls.cpp
@@ -0,0 +1,64 @@
+/*
+ * Copyright (C) 2019 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/bionic_elf_tls.h"
+
+#include <sys/param.h>
+
+#include "private/bionic_macros.h"
+#include "private/bionic_tls.h"
+
+void StaticTlsLayout::reserve_tcb() {
+  offset_bionic_tcb_ = reserve_type<bionic_tcb>();
+}
+
+void StaticTlsLayout::reserve_bionic_tls() {
+  offset_bionic_tls_ = reserve_type<bionic_tls>();
+}
+
+void StaticTlsLayout::finish_layout() {
+  // Round the offset up to the alignment.
+  offset_ = round_up_with_overflow_check(offset_, alignment_);
+}
+
+// The size is not required to be a multiple of the alignment. The alignment
+// must be a positive power-of-two.
+size_t StaticTlsLayout::reserve(size_t size, size_t alignment) {
+  offset_ = round_up_with_overflow_check(offset_, alignment);
+  const size_t result = offset_;
+  if (__builtin_add_overflow(offset_, size, &offset_)) overflowed_ = true;
+  alignment_ = MAX(alignment_, alignment);
+  return result;
+}
+
+size_t StaticTlsLayout::round_up_with_overflow_check(size_t value, size_t alignment) {
+  const size_t old_value = value;
+  value = __BIONIC_ALIGN(value, alignment);
+  if (value < old_value) overflowed_ = true;
+  return value;
+}