diff --git a/libelf/gelf_update_dyn.c b/libelf/gelf_update_dyn.c
new file mode 100644
index 0000000..5c515d2
--- /dev/null
+++ b/libelf/gelf_update_dyn.c
@@ -0,0 +1,107 @@
+/* Update information in dynamic table at the given index.
+   Copyright (C) 2000, 2001, 2002, 2005, 2009, 2014, 2015 Red Hat, Inc.
+   This file is part of elfutils.
+   Written by Ulrich Drepper <drepper@redhat.com>, 2000.
+
+   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 <gelf.h>
+#include <string.h>
+
+#include "libelfP.h"
+
+
+int
+gelf_update_dyn (Elf_Data *data, int ndx, GElf_Dyn *src)
+{
+  Elf_Data_Scn *data_scn = (Elf_Data_Scn *) data;
+  Elf_Scn *scn;
+  int result = 0;
+
+  if (data == NULL)
+    return 0;
+
+  if (unlikely (data_scn->d.d_type != ELF_T_DYN))
+    {
+      /* The type of the data better should match.  */
+      __libelf_seterrno (ELF_E_DATA_MISMATCH);
+      return 0;
+    }
+
+  scn = data_scn->s;
+  rwlock_wrlock (scn->elf->lock);
+
+  if (scn->elf->class == ELFCLASS32)
+    {
+      Elf32_Dyn *dyn;
+
+      /* There is the possibility that the values in the input are
+	 too large.  */
+      if (unlikely (src->d_tag < -0x80000000ll)
+	  || unlikely (src->d_tag > 0x7fffffffll)
+	  || unlikely (src->d_un.d_val > 0xffffffffull))
+	{
+	  __libelf_seterrno (ELF_E_INVALID_DATA);
+	  goto out;
+	}
+
+      /* Check whether we have to resize the data buffer.  */
+      if (INVALID_NDX (ndx, Elf32_Dyn, &data_scn->d))
+	{
+	  __libelf_seterrno (ELF_E_INVALID_INDEX);
+	  goto out;
+	}
+
+      dyn = &((Elf32_Dyn *) data_scn->d.d_buf)[ndx];
+
+      dyn->d_tag = src->d_tag;
+      dyn->d_un.d_val = src->d_un.d_val;
+    }
+  else
+    {
+      /* Check whether we have to resize the data buffer.  */
+      if (INVALID_NDX (ndx, Elf64_Dyn, &data_scn->d))
+	{
+	  __libelf_seterrno (ELF_E_INVALID_INDEX);
+	  goto out;
+	}
+
+      ((Elf64_Dyn *) data_scn->d.d_buf)[ndx] = *src;
+    }
+
+  result = 1;
+
+  /* Mark the section as modified.  */
+  scn->flags |= ELF_F_DIRTY;
+
+ out:
+  rwlock_unlock (scn->elf->lock);
+
+  return result;
+}