Add a legacy inline for mmap64.

While this was never an inline, this function alone has caused most of
the bug reports related to _FILE_OFFSET_BITS=64. Providing an inline
for it should allow a lot more code to build with _FILE_OFFSET_BITS=64
when targeting pre-L.

Test: make checkbuild
Test: built trivial cc_binary for LP32 against API 14 with
      _FILE_OFFSET_BITS=64 set
Bug: lots
Change-Id: I8479d34af4da358c11423bee43d45b59e9d4143e
diff --git a/libc/include/android/legacy_sys_mman_inlines.h b/libc/include/android/legacy_sys_mman_inlines.h
new file mode 100644
index 0000000..7171896
--- /dev/null
+++ b/libc/include/android/legacy_sys_mman_inlines.h
@@ -0,0 +1,68 @@
+/*
+ * Copyright (C) 2017 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.
+ */
+
+#pragma once
+
+#include <sys/cdefs.h>
+#include <sys/mman.h>
+#include <sys/syscall.h>
+#include <unistd.h>
+
+#if __ANDROID_API__ < __ANDROID_API_L__
+
+__BEGIN_DECLS
+
+/*
+ * While this was never an inline, this function alone has caused most of the
+ * bug reports related to _FILE_OFFSET_BITS=64. Providing an inline for it
+ * should allow a lot more code to build with _FILE_OFFSET_BITS=64 when
+ * targeting pre-L.
+ */
+static __inline void* mmap64(void* __addr, size_t __size, int __prot, int __flags, int __fd,
+                             off64_t __offset) {
+  const int __mmap2_shift = 12; // 2**12 == 4096
+  if (__offset < 0 || (__offset & ((1UL << __mmap2_shift) - 1)) != 0) {
+    errno = EINVAL;
+    return MAP_FAILED;
+  }
+
+  // prevent allocations large enough for `end - start` to overflow
+  size_t __rounded = __BIONIC_ALIGN(__size, PAGE_SIZE);
+  if (__rounded < __size || __rounded > PTRDIFF_MAX) {
+    errno = ENOMEM;
+    return MAP_FAILED;
+  }
+
+  extern void* __mmap2(void* __addr, size_t __size, int __prot, int __flags, int __fd,
+                       size_t __offset);
+  return __mmap2(__addr, __size, __prot, __flags, __fd, __offset >> __mmap2_shift);
+}
+
+__END_DECLS
+
+#endif  /* __ANDROID_API__ < __ANDROID_API_L__ */