diff --git a/libdw/dwarf_getalt.c b/libdw/dwarf_getalt.c
new file mode 100644
index 0000000..3e5af15
--- /dev/null
+++ b/libdw/dwarf_getalt.c
@@ -0,0 +1,196 @@
+/* Retrieves the DWARF descriptor for debugaltlink data.
+   Copyright (C) 2014, 2018 Red Hat, Inc.
+   This file is part of elfutils.
+
+   This file is free software; you can redistribute it and/or modify
+   it under the terms of either
+
+     * the GNU Lesser General Public License as published by the Free
+       Software Foundation; either version 3 of the License, or (at
+       your option) any later version
+
+   or
+
+     * the GNU General Public License as published by the Free
+       Software Foundation; either version 2 of the License, or (at
+       your option) any later version
+
+   or both in parallel, as here.
+
+   elfutils 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
+   General Public License for more details.
+
+   You should have received copies of the GNU General Public License and
+   the GNU Lesser General Public License along with this program.  If
+   not, see <http://www.gnu.org/licenses/>.  */
+
+#ifdef HAVE_CONFIG_H
+# include <config.h>
+#endif
+
+#include "libdwP.h"
+#include "libelfP.h"
+#include "libdwelfP.h"
+#include "system.h"
+
+#include <inttypes.h>
+#include <fcntl.h>
+#include <limits.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+
+
+char *
+internal_function
+__libdw_filepath (int fd, const char *dir, const char *file)
+{
+  if (file == NULL)
+    return NULL;
+
+  if (file[0] == '/')
+    return strdup (file);
+
+  if (dir != NULL && dir[0] == '/')
+    {
+      size_t dirlen = strlen (dir);
+      size_t filelen = strlen (file);
+      size_t len = dirlen + 1 + filelen + 1;
+      char *path = malloc (len);
+      if (path != NULL)
+	{
+	  char *c = mempcpy (path, dir, dirlen);
+	  if (dir[dirlen - 1] != '/')
+	    *c++ = '/';
+	  mempcpy (c, file, filelen + 1);
+	}
+      return path;
+    }
+
+  if (fd >= 0)
+    {
+      /* strlen ("/proc/self/fd/") = 14 + strlen (<MAXINT>) = 10 + 1 = 25.  */
+      char devfdpath[25];
+      sprintf (devfdpath, "/proc/self/fd/%u", fd);
+      char *fdpath = realpath (devfdpath, NULL);
+      char *path = NULL;
+      char *fddir;
+      if (fdpath != NULL && fdpath[0] == '/'
+	  && (fddir = strrchr (fdpath, '/')) != NULL)
+	{
+	  *++fddir = '\0';
+	  size_t fdpathlen = strlen (fdpath);
+	  size_t dirlen = dir != NULL ? strlen (dir) : 0;
+	  size_t filelen = strlen (file);
+	  size_t len = fdpathlen + 1 + dirlen + 1 + filelen + 1;
+	  path = malloc (len);
+	  if (path != NULL)
+	    {
+	      char *c = mempcpy (path, fdpath, fdpathlen);
+	      if (dirlen > 0)
+		{
+		  c = mempcpy (c, dir, dirlen);
+		  if (dir[dirlen - 1] != '/')
+		    *c++ = '/';
+		}
+	      mempcpy (c, file, filelen + 1);
+	    }
+	}
+      free (fdpath);
+      return path;
+    }
+
+  return NULL;
+}
+
+static void
+find_debug_altlink (Dwarf *dbg)
+{
+  const char *altname;
+  const void *build_id;
+  ssize_t build_id_len = INTUSE(dwelf_dwarf_gnu_debugaltlink) (dbg,
+							       &altname,
+							       &build_id);
+
+  /* Couldn't even get the debugaltlink.  It probably doesn't exist.  */
+  if (build_id_len <= 0)
+    return;
+
+  const uint8_t *id = (const uint8_t *) build_id;
+  size_t id_len = build_id_len;
+  int fd = -1;
+
+  /* We only look in the standard path.  And relative to the dbg file.  */
+#define DEBUGINFO_PATH "/usr/lib/debug"
+
+  /* We don't handle very short or really large build-ids.  We need at
+     at least 3 and allow for up to 64 (normally ids are 20 long).  */
+#define MIN_BUILD_ID_BYTES 3
+#define MAX_BUILD_ID_BYTES 64
+  if (id_len >= MIN_BUILD_ID_BYTES && id_len <= MAX_BUILD_ID_BYTES)
+    {
+      /* Note sizeof a string literal includes the trailing zero.  */
+      char id_path[sizeof DEBUGINFO_PATH - 1 + sizeof "/.build-id/" - 1
+		   + 2 + 1 + (MAX_BUILD_ID_BYTES - 2) * 2 + sizeof ".debug"];
+      sprintf (&id_path[0], "%s%s", DEBUGINFO_PATH, "/.build-id/");
+      sprintf (&id_path[sizeof DEBUGINFO_PATH - 1 + sizeof "/.build-id/" - 1],
+	       "%02" PRIx8 "/", (uint8_t) id[0]);
+      for (size_t i = 1; i < id_len; ++i)
+	sprintf (&id_path[sizeof DEBUGINFO_PATH - 1 + sizeof "/.build-id/" - 1
+			  + 3 + (i - 1) * 2], "%02" PRIx8, (uint8_t) id[i]);
+      strcpy (&id_path[sizeof DEBUGINFO_PATH - 1 + sizeof "/.build-id/" - 1
+		       + 3 + (id_len - 1) * 2], ".debug");
+
+      fd = TEMP_FAILURE_RETRY (open (id_path, O_RDONLY));
+    }
+
+  /* Fall back on (possible relative) alt file path.  */
+  if (fd < 0)
+    {
+      char *altpath = __libdw_filepath (dbg->elf->fildes, NULL, altname);
+      if (altpath != NULL)
+	{
+	  fd = TEMP_FAILURE_RETRY (open (altpath, O_RDONLY));
+	  free (altpath);
+	}
+    }
+
+  if (fd >= 0)
+    {
+      Dwarf *alt = dwarf_begin (fd, O_RDONLY);
+      if (alt != NULL)
+	{
+	  dbg->alt_dwarf = alt;
+	  dbg->alt_fd = fd;
+	}
+      else
+	close (fd);
+    }
+}
+
+Dwarf *
+dwarf_getalt (Dwarf *main)
+{
+  /* Only try once.  */
+  if (main == NULL || main->alt_dwarf == (void *) -1)
+    return NULL;
+
+  if (main->alt_dwarf != NULL)
+    return main->alt_dwarf;
+
+  find_debug_altlink (main);
+
+  /* If we found nothing, make sure we don't try again.  */
+  if (main->alt_dwarf == NULL)
+    {
+      main->alt_dwarf = (void *) -1;
+      return NULL;
+    }
+
+  return main->alt_dwarf;
+}
+INTDEF (dwarf_getalt)