diff --git a/libelf/elf_update.c b/libelf/elf_update.c
new file mode 100644
index 0000000..8ce0782
--- /dev/null
+++ b/libelf/elf_update.c
@@ -0,0 +1,222 @@
+/* Update data structures for changes and write them out.
+   Copyright (C) 1999, 2000, 2001, 2002, 2004, 2005, 2006, 2015 Red Hat, Inc.
+   This file is part of elfutils.
+   Contributed by Ulrich Drepper <drepper@redhat.com>, 1999.
+
+   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 <libelf.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+
+#include "libelfP.h"
+
+
+static off_t
+write_file (Elf *elf, off_t size, int change_bo, size_t shnum)
+{
+  int class = elf->class;
+
+  /* Check the mode bits now, before modification might change them.  */
+  struct stat st;
+  if (unlikely (fstat (elf->fildes, &st) != 0))
+    {
+      __libelf_seterrno (ELF_E_WRITE_ERROR);
+      return -1;
+    }
+
+  /* Adjust the size in any case.  We do this even if we use `write'.
+     We cannot do this if this file is in an archive.  We also don't
+     do it *now* if we are shortening the file since this would
+     prevent programs to use the data of the file in generating the
+     new file.  We truncate the file later in this case.  */
+  if (elf->parent == NULL
+      && (elf->maximum_size == ~((size_t) 0)
+	  || (size_t) size > elf->maximum_size)
+      && unlikely (ftruncate (elf->fildes, size) != 0))
+    {
+      __libelf_seterrno (ELF_E_WRITE_ERROR);
+      return -1;
+    }
+
+  /* Try to map the file if this isn't done yet.  */
+  if (elf->map_address == NULL && elf->cmd == ELF_C_WRITE_MMAP)
+    {
+      elf->map_address = mmap (NULL, size, PROT_READ | PROT_WRITE,
+			       MAP_SHARED, elf->fildes, 0);
+      if (unlikely (elf->map_address == MAP_FAILED))
+	elf->map_address = NULL;
+      else
+	elf->flags |= ELF_F_MMAPPED;
+    }
+
+  if (elf->map_address != NULL)
+    {
+      /* When using mmap we want to make sure the file content is
+	 really there. Only using ftruncate might mean the file is
+	 extended, but space isn't allocated yet.  This might cause a
+	 SIGBUS once we write into the mmapped space and the disk is
+	 full.  In glibc posix_fallocate is required to extend the
+	 file and allocate enough space even if the underlying
+	 filesystem would normally return EOPNOTSUPP.  But other
+	 implementations might not work as expected.  And the glibc
+	 fallback case might fail (with unexpected errnos) in some cases.
+	 So we only report an error when the call fails and errno is
+	 ENOSPC. Otherwise we ignore the error and treat it as just hint.  */
+      if (elf->parent == NULL
+	  && (elf->maximum_size == ~((size_t) 0)
+	      || (size_t) size > elf->maximum_size)
+	  && unlikely (posix_fallocate (elf->fildes, 0, size) != 0))
+	if (errno == ENOSPC)
+	  {
+	    __libelf_seterrno (ELF_E_WRITE_ERROR);
+	    return -1;
+	  }
+
+      /* The file is mmaped.  */
+      if ((class == ELFCLASS32
+	   ? __elf32_updatemmap (elf, change_bo, shnum)
+	   : __elf64_updatemmap (elf, change_bo, shnum)) != 0)
+	/* Some problem while writing.  */
+	size = -1;
+    }
+  else
+    {
+      /* The file is not mmaped.  */
+      if ((class == ELFCLASS32
+	   ? __elf32_updatefile (elf, change_bo, shnum)
+	   : __elf64_updatefile (elf, change_bo, shnum)) != 0)
+	/* Some problem while writing.  */
+	size = -1;
+    }
+
+  /* Reduce the file size if necessary.  */
+  if (size != -1
+      && elf->parent == NULL
+      && elf->maximum_size != ~((size_t) 0)
+      && (size_t) size < elf->maximum_size
+      && unlikely (ftruncate (elf->fildes, size) != 0))
+    {
+      __libelf_seterrno (ELF_E_WRITE_ERROR);
+      size = -1;
+    }
+
+  /* POSIX says that ftruncate and write may clear the S_ISUID and S_ISGID
+     mode bits.  So make sure we restore them afterwards if they were set.
+     This is not atomic if someone else chmod's the file while we operate.  */
+  if (size != -1
+      && unlikely (st.st_mode & (S_ISUID | S_ISGID))
+      /* fchmod ignores the bits we cannot change.  */
+      && unlikely (fchmod (elf->fildes, st.st_mode) != 0))
+    {
+      __libelf_seterrno (ELF_E_WRITE_ERROR);
+      size = -1;
+    }
+
+  if (size != -1 && elf->parent == NULL)
+    elf->maximum_size = size;
+
+  return size;
+}
+
+
+off_t
+elf_update (Elf *elf, Elf_Cmd cmd)
+{
+  size_t shnum;
+  off_t size;
+  int change_bo = 0;
+
+  if (cmd != ELF_C_NULL
+      && cmd != ELF_C_WRITE
+      && unlikely (cmd != ELF_C_WRITE_MMAP))
+    {
+      __libelf_seterrno (ELF_E_INVALID_CMD);
+      return -1;
+    }
+
+  if (elf == NULL)
+    return -1;
+
+  if (elf->kind != ELF_K_ELF)
+    {
+      __libelf_seterrno (ELF_E_INVALID_HANDLE);
+      return -1;
+    }
+
+  rwlock_wrlock (elf->lock);
+
+  /* Make sure we have an ELF header.  */
+  if (elf->state.elf.ehdr == NULL)
+    {
+      __libelf_seterrno (ELF_E_WRONG_ORDER_EHDR);
+      size = -1;
+      goto out;
+    }
+
+  /* Determine the number of sections.  */
+  shnum = (elf->state.elf.scns_last->cnt == 0
+	   ? 0
+	   : 1 + elf->state.elf.scns_last->data[elf->state.elf.scns_last->cnt - 1].index);
+
+  /* Update the ELF descriptor.  First, place the program header.  It
+     will come right after the ELF header.  The count the size of all
+     sections and finally place the section table.  */
+  size = (elf->class == ELFCLASS32
+	  ? __elf32_updatenull_wrlock (elf, &change_bo, shnum)
+	  : __elf64_updatenull_wrlock (elf, &change_bo, shnum));
+  if (likely (size != -1)
+      /* See whether we actually have to write out the data.  */
+      && (cmd == ELF_C_WRITE || cmd == ELF_C_WRITE_MMAP))
+    {
+      if (elf->cmd != ELF_C_RDWR
+	  && elf->cmd != ELF_C_RDWR_MMAP
+	  && elf->cmd != ELF_C_WRITE
+	  && unlikely (elf->cmd != ELF_C_WRITE_MMAP))
+	{
+	  __libelf_seterrno (ELF_E_UPDATE_RO);
+	  size = -1;
+	}
+      else if (unlikely (elf->fildes == -1))
+	{
+	  /* We closed the file already.  */
+	  __libelf_seterrno (ELF_E_FD_DISABLED);
+	  size = -1;
+	}
+      else
+	size = write_file (elf, size, change_bo, shnum);
+    }
+
+ out:
+  rwlock_unlock (elf->lock);
+
+  return size;
+}