diff --git a/libc/bionic/realpath.cpp b/libc/bionic/realpath.cpp
new file mode 100644
index 0000000..e43d8e2
--- /dev/null
+++ b/libc/bionic/realpath.cpp
@@ -0,0 +1,78 @@
+/*
+ * 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 <stdlib.h>
+
+#include <errno.h>
+#include <fcntl.h>
+#include <string.h>
+#include <sys/stat.h>
+
+#include "private/FdPath.h"
+#include "private/ScopedFd.h"
+
+// This function needs a 4KiB (PATH_MAX) buffer.
+// The alternative is to heap allocate and then trim, but that's 2x the code.
+// (Remember that readlink(2) won't tell you the needed size, so the multi-pass
+// algorithm isn't even an option unless you want to just guess, in which case
+// you're back needing to trim again.)
+#pragma GCC diagnostic ignored "-Wframe-larger-than="
+
+char* realpath(const char* path, char* result) {
+  // Weird special case.
+  if (!path) {
+    errno = EINVAL;
+    return nullptr;
+  }
+
+  // Get an O_PATH fd, and...
+  ScopedFd fd(open(path, O_PATH | O_CLOEXEC));
+  if (fd.get() == -1) return nullptr;
+
+  // (...remember the device/inode that we're talking about and...)
+  struct stat sb;
+  if (fstat(fd.get(), &sb) == -1) return nullptr;
+  dev_t st_dev = sb.st_dev;
+  ino_t st_ino = sb.st_ino;
+
+  // ...ask the kernel to do the hard work for us.
+  FdPath fd_path(fd.get());
+  char dst[PATH_MAX];
+  ssize_t l = readlink(fd_path.c_str(), dst, sizeof(dst) - 1);
+  if (l == -1) return nullptr;
+  dst[l] = '\0';
+
+  // What if the file was removed in the meantime? readlink(2) will have
+  // returned "/a/b/c (deleted)", and we want to return ENOENT instead.
+  if (stat(dst, &sb) == -1 || st_dev != sb.st_dev || st_ino != sb.st_ino) {
+    errno = ENOENT;
+    return nullptr;
+  }
+
+  return result ? strcpy(result, dst) : strdup(dst);
+}