tests/fillfile.c - platform/external/elfutils.git - Git at Google

 /* Test program for changing data in one section (but not others) with gaps.
    Copyright (C) 2017 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 the GNU General Public License as published by
    the Free Software Foundation; either version 3 of the License, or
    (at your option) any later version.

    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 a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */


 #ifdef HAVE_CONFIG_H
 # include <config.h>
 #endif

 #include <errno.h>
 #include <fcntl.h>
 #include <inttypes.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>

 #include ELFUTILS_HEADER(elf)
 #include <gelf.h>


 /* Index of last string added.  Returned by add_string ().  */
 static size_t stridx = 0;

 /* Adds a string and returns the offset in the section.  */
 static size_t
 add_strtab_entry (Elf_Scn *strtab, const char *str)
 {
   size_t lastidx = stridx;
   size_t size = strlen (str) + 1;

   Elf_Data *data = elf_newdata (strtab);
   if (data == NULL)
     {
       printf ("cannot create data SHSTRTAB section: %s\n", elf_errmsg (-1));
       exit (1);
     }

   data->d_buf = (char *) str; /* Discards const, but we will not change. */
   data->d_type = ELF_T_BYTE;
   data->d_size = size;
   data->d_align = 1;
   data->d_version = EV_CURRENT;

   stridx += size;
   printf ("add_string: '%s', stridx: %zd, lastidx: %zd\n",
 	  str, stridx, lastidx);
   return lastidx;
 }

 static Elf_Scn *
 create_strtab (Elf *elf)
 {
   // Create strtab section.
   Elf_Scn *scn = elf_newscn (elf);
   if (scn == NULL)
     {
       printf ("cannot create strings section: %s\n", elf_errmsg (-1));
       exit (1);
     }

   // Add an empty string to the table as NUL entry for section zero.
   add_strtab_entry (scn, "");

   GElf_Shdr shdr_mem;
   GElf_Shdr *shdr = gelf_getshdr (scn, &shdr_mem);
   if (shdr == NULL)
     {
       printf ("cannot get header for new strtab section: %s\n",
 	      elf_errmsg (-1));
       exit (1);
     }

   shdr->sh_type = SHT_STRTAB;
   shdr->sh_flags = 0;
   shdr->sh_addr = 0;
   shdr->sh_link = SHN_UNDEF;
   shdr->sh_info = SHN_UNDEF;
   shdr->sh_addralign = 1;
   shdr->sh_entsize = 0;
   shdr->sh_name = add_strtab_entry (scn, ".strtab");

   // We have to store the section strtab index in the ELF header.
   // So sections have actual names.
   GElf_Ehdr ehdr_mem;
   GElf_Ehdr *ehdr = gelf_getehdr (elf, &ehdr_mem);
   if (ehdr == NULL)
     {
       printf ("cannot get ELF header: %s\n", elf_errmsg (-1));
       exit (1);
     }

   int ndx = elf_ndxscn (scn);
   ehdr->e_shstrndx = ndx;

   if (gelf_update_ehdr (elf, ehdr) == 0)
     {
       printf ("cannot update ELF header: %s\n", elf_errmsg (-1));
       exit (1);
     }

   // Finished strtab section, update the header.
   if (gelf_update_shdr (scn, shdr) == 0)
     {
       printf ("cannot update STRTAB section header: %s\n", elf_errmsg (-1));
       exit (1);
     }

   return scn;
 }

 static char sec_data[] = { 1, 2, 3, 4, 5 };
 static char new_data[] = { 5, 4, 3, 2, 1 };

 static void
 add_data_section (Elf *elf, Elf_Scn *strtab, const char *sname)
 {
   printf ("Add data section %s\n", sname);
   Elf_Scn *scn = elf_newscn (elf);
   if (scn == NULL)
     {
       printf ("cannot create strings section: %s\n", elf_errmsg (-1));
       exit (1);
     }

   GElf_Shdr shdr_mem;
   GElf_Shdr *shdr = gelf_getshdr (scn, &shdr_mem);
   if (shdr == NULL)
     {
       printf ("cannot get header for new %s section: %s\n",
 	      sname, elf_errmsg (-1));
       exit (1);
     }

   shdr->sh_type = SHT_PROGBITS;
   shdr->sh_flags = 0;
   shdr->sh_addr = 0;
   shdr->sh_link = SHN_UNDEF;
   shdr->sh_info = SHN_UNDEF;
   shdr->sh_addralign = 128;  // Large alignment to force gap between sections.
   shdr->sh_entsize = 1;
   shdr->sh_name = add_strtab_entry (strtab, sname);

   if (gelf_update_shdr (scn, shdr) == 0)
     {
       printf ("cannot update %s section header: %s\n", sname, elf_errmsg (-1));
       exit (1);
     }

   /* Add some data, but less than alignment. */
   Elf_Data *data = elf_newdata (scn);
   if (data == NULL)
     {
       printf ("cannot update %s section header: %s\n", sname, elf_errmsg (-1));
       exit (1);
     }
   data->d_buf = sec_data;
   data->d_size = 5;
 }

 static void
 check_data (const char *sname, Elf_Data *data, char *buf)
 {
   printf ("check data %s [", sname);
   for (int i = 0; i < 5; i++)
     printf ("%d%s", buf[i], i < 4 ? "," : "");
   printf ("]\n");
   if (data == NULL || data->d_buf == NULL)
     {
       printf ("No data in section %s\n", sname);
       exit (1);
     }

   if (data->d_size != 5 || memcmp (data->d_buf, buf, 5) != 0)
     {
       printf ("Wrong data in section %s [", sname);
       for (size_t i = 0; i < data->d_size; i++)
 	printf ("%d%s", ((char *)data->d_buf)[i],
 		i < data->d_size - 1 ? "," : "");
       printf ("]\n");
       exit(1);
     }
 }

 static void
 check_elf (const char *fname, int class, int use_mmap)
 {
   printf ("\nfname: %s\n", fname);
   stridx = 0; // Reset strtab strings index

   int fd = open (fname, O_RDWR | O_CREAT | O_TRUNC, 0666);
   if (fd == -1)
     {
       printf ("cannot open `%s': %s\n", fname, strerror (errno));
       exit (1);
     }

   Elf *elf = elf_begin (fd, use_mmap ? ELF_C_WRITE_MMAP : ELF_C_WRITE, NULL);
   if (elf == NULL)
     {
       printf ("cannot create ELF descriptor: %s\n", elf_errmsg (-1));
       exit (1);
     }

   // Create an ELF header.
   if (gelf_newehdr (elf, class) == 0)
     {
       printf ("cannot create ELF header: %s\n", elf_errmsg (-1));
       exit (1);
     }

   GElf_Ehdr ehdr_mem;
   GElf_Ehdr *ehdr = gelf_getehdr (elf, &ehdr_mem);
   if (ehdr == NULL)
     {
       printf ("cannot get ELF header: %s\n", elf_errmsg (-1));
       exit (1);
     }

   // Initialize header.
   ehdr->e_ident[EI_DATA] = class == ELFCLASS64 ? ELFDATA2LSB : ELFDATA2MSB;
   ehdr->e_ident[EI_OSABI] = ELFOSABI_GNU;
   ehdr->e_type = ET_NONE;
   ehdr->e_machine = EM_X86_64;
   ehdr->e_version = EV_CURRENT;

   if (gelf_update_ehdr (elf, ehdr) == 0)
     {
       printf ("cannot update ELF header: %s\n", elf_errmsg (-1));
       exit (1);
     }

   Elf_Scn *strtab = create_strtab (elf);
   add_data_section (elf, strtab, ".data1");
   add_data_section (elf, strtab, ".data2");
   add_data_section (elf, strtab, ".data3");
   add_data_section (elf, strtab, ".data4");

   // Write everything to disk.
   if (elf_update (elf, ELF_C_WRITE) < 0)
     {
       printf ("failure in elf_update(WRITE): %s\n", elf_errmsg (-1));
       exit (1);
     }

   if (elf_end (elf) != 0)
     {
       printf ("failure in elf_end: %s\n", elf_errmsg (-1));
       exit (1);
     }

   close (fd);

   /* Reread the ELF from disk now.  */
   printf ("Rereading %s\n", fname);
   fd = open (fname, O_RDWR, 0666);
   if (fd == -1)
     {
       printf ("cannot (re)open `%s': %s\n", fname, strerror (errno));
       exit (1);
     }

   elf = elf_begin (fd, use_mmap ? ELF_C_RDWR_MMAP : ELF_C_RDWR, NULL);
   if (elf == NULL)
     {
       printf ("cannot create ELF descriptor read-only: %s\n", elf_errmsg (-1));
       exit (1);
     }

   /* We are going to change some data (in-place), but want the layout
      to stay exactly the same. */
   elf_flagelf (elf, ELF_C_SET, ELF_F_LAYOUT);

   size_t shdrstrndx;
   if (elf_getshdrstrndx (elf, &shdrstrndx) != 0)
     {
       printf ("cannot get shdr str ndx\n");
       exit (1);
     }
   printf ("shdrstrndx: %zd\n", shdrstrndx);

   // Get third data section and change it.
   Elf_Scn *checkscn = NULL;
   Elf_Scn *scn = elf_nextscn (elf, NULL);
   while (scn != NULL)
     {
       GElf_Shdr shdr_mem;
       GElf_Shdr *shdr = gelf_getshdr (scn, &shdr_mem);
       if (shdr == NULL)
 	{
 	  printf ("cannot get header for section: %s\n", elf_errmsg (-1));
 	  exit (1);
 	}
       const char *sname = elf_strptr (elf, shdrstrndx, shdr->sh_name);
       if (sname != NULL && strcmp (".data3", sname) == 0)
 	checkscn = scn;

       // Get all data, but don't really use it
       // (this triggered the original bug).
       Elf_Data *data = elf_getdata (scn, NULL);
       if (data != NULL && data->d_buf != NULL && data->d_size == 0)
 	{
 	  printf ("Bad data...n");
 	  exit (1);
 	}
       scn = elf_nextscn (elf, scn);
     }

   if (checkscn == NULL)
     {
       printf ("ELF file doesn't have a .data3 section\n");
       exit (1);
     }

   Elf_Data *data = elf_getdata (checkscn, NULL);
   check_data (".data3", data, sec_data);
   memcpy (data->d_buf, new_data, 5);
   elf_flagdata (data, ELF_C_SET, ELF_F_DIRTY);

   // Write everything to disk.
   if (elf_update (elf, ELF_C_WRITE) < 0)
     {
       printf ("failure in elf_update(WRITE): %s\n", elf_errmsg (-1));
       exit (1);
     }

   if (elf_end (elf) != 0)
     {
       printf ("failure in elf_end: %s\n", elf_errmsg (-1));
       exit (1);
     }

   close (fd);

   // And read it in one last time.
   printf ("Rereading %s again\n", fname);
   fd = open (fname, O_RDONLY, 0666);
   if (fd == -1)
     {
       printf ("cannot open `%s' read-only: %s\n", fname, strerror (errno));
       exit (1);
     }

   elf = elf_begin (fd, use_mmap ? ELF_C_READ_MMAP : ELF_C_READ, NULL);
   if (elf == NULL)
     {
       printf ("cannot create ELF descriptor read-only: %s\n", elf_errmsg (-1));
       exit (1);
     }

   // Get all .data sections and check them.
   Elf_Scn *scn1 = NULL;
   Elf_Scn *scn2 = NULL;
   Elf_Scn *scn3 = NULL;
   Elf_Scn *scn4 = NULL;
   scn = elf_nextscn (elf, NULL);
   while (scn != NULL)
     {
       GElf_Shdr shdr_mem;
       GElf_Shdr *shdr = gelf_getshdr (scn, &shdr_mem);
       if (shdr == NULL)
 	{
 	  printf ("cannot get header for section: %s\n", elf_errmsg (-1));
 	  exit (1);
 	}
       const char *sname = elf_strptr (elf, shdrstrndx, shdr->sh_name);
       if (sname != NULL && strcmp (".data1", sname) == 0)
 	scn1 = scn;
       else if (sname != NULL && strcmp (".data2", sname) == 0)
 	scn2 = scn;
       else if (sname != NULL && strcmp (".data3", sname) == 0)
 	scn3 = scn;
       else if (sname != NULL && strcmp (".data4", sname) == 0)
 	scn4 = scn;
       scn = elf_nextscn (elf, scn);
     }

   if (scn1 == NULL)
     {
       printf ("ELF file doesn't have a .data1 section\n");
       exit (1);
     }
   data = elf_getdata (scn1, NULL);
   check_data (".data1", data, sec_data);

   if (scn2 == NULL)
     {
       printf ("ELF file doesn't have a .data2 section\n");
       exit (1);
     }
   data = elf_getdata (scn2, NULL);
   check_data (".data2", data, sec_data);

   if (scn3 == NULL)
     {
       printf ("ELF file doesn't have a .data3 section\n");
       exit (1);
     }
   data = elf_getdata (scn3, NULL);
   check_data (".data3", data, new_data);

   if (scn4 == NULL)
     {
       printf ("ELF file doesn't have a .data4 section\n");
       exit (1);
     }
   data = elf_getdata (scn4, NULL);
   check_data (".data4", data, sec_data);

   if (elf_end (elf) != 0)
     {
       printf ("failure in elf_end: %s\n", elf_errmsg (-1));
       exit (1);
     }

   close (fd);

   unlink (fname);
 }

 int
 main (int argc __attribute__ ((unused)),
       char *argv[] __attribute__ ((unused)))
 {
   elf_version (EV_CURRENT);

   elf_fill (0xA);

   check_elf ("fill.elf.32", ELFCLASS32, 0);
   check_elf ("fill.elf.32.mmap", ELFCLASS32, 1);
   check_elf ("fill.elf.64", ELFCLASS64, 0);
   check_elf ("fill.elf.64.mmap", ELFCLASS64, 1);

   return 0;
 }
	/* Test program for changing data in one section (but not others) with gaps.
	Copyright (C) 2017 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 the GNU General Public License as published by
	the Free Software Foundation; either version 3 of the License, or
	(at your option) any later version.

	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 a copy of the GNU General Public License
	along with this program. If not, see <http://www.gnu.org/licenses/>. */


	#ifdef HAVE_CONFIG_H
	# include <config.h>
	#endif

	#include <errno.h>
	#include <fcntl.h>
	#include <inttypes.h>
	#include <stdio.h>
	#include <stdlib.h>
	#include <string.h>
	#include <unistd.h>

	#include ELFUTILS_HEADER(elf)
	#include <gelf.h>


	/* Index of last string added. Returned by add_string (). */
	static size_t stridx = 0;

	/* Adds a string and returns the offset in the section. */
	static size_t
	add_strtab_entry (Elf_Scn strtab, const char str)
	{
	size_t lastidx = stridx;
	size_t size = strlen (str) + 1;

	Elf_Data *data = elf_newdata (strtab);
	if (data == NULL)
	{
	printf ("cannot create data SHSTRTAB section: %s\n", elf_errmsg (-1));
	exit (1);
	}

	data->d_buf = (char ) str; / Discards const, but we will not change. */
	data->d_type = ELF_T_BYTE;
	data->d_size = size;
	data->d_align = 1;
	data->d_version = EV_CURRENT;

	stridx += size;
	printf ("add_string: '%s', stridx: %zd, lastidx: %zd\n",
	str, stridx, lastidx);
	return lastidx;
	}

	static Elf_Scn *
	create_strtab (Elf *elf)
	{
	// Create strtab section.
	Elf_Scn *scn = elf_newscn (elf);
	if (scn == NULL)
	{
	printf ("cannot create strings section: %s\n", elf_errmsg (-1));
	exit (1);
	}

	// Add an empty string to the table as NUL entry for section zero.
	add_strtab_entry (scn, "");

	GElf_Shdr shdr_mem;
	GElf_Shdr *shdr = gelf_getshdr (scn, &shdr_mem);
	if (shdr == NULL)
	{
	printf ("cannot get header for new strtab section: %s\n",
	elf_errmsg (-1));
	exit (1);
	}

	shdr->sh_type = SHT_STRTAB;
	shdr->sh_flags = 0;
	shdr->sh_addr = 0;
	shdr->sh_link = SHN_UNDEF;
	shdr->sh_info = SHN_UNDEF;
	shdr->sh_addralign = 1;
	shdr->sh_entsize = 0;
	shdr->sh_name = add_strtab_entry (scn, ".strtab");

	// We have to store the section strtab index in the ELF header.
	// So sections have actual names.
	GElf_Ehdr ehdr_mem;
	GElf_Ehdr *ehdr = gelf_getehdr (elf, &ehdr_mem);
	if (ehdr == NULL)
	{
	printf ("cannot get ELF header: %s\n", elf_errmsg (-1));
	exit (1);
	}

	int ndx = elf_ndxscn (scn);
	ehdr->e_shstrndx = ndx;

	if (gelf_update_ehdr (elf, ehdr) == 0)
	{
	printf ("cannot update ELF header: %s\n", elf_errmsg (-1));
	exit (1);
	}

	// Finished strtab section, update the header.
	if (gelf_update_shdr (scn, shdr) == 0)
	{
	printf ("cannot update STRTAB section header: %s\n", elf_errmsg (-1));
	exit (1);
	}

	return scn;
	}

	static char sec_data[] = { 1, 2, 3, 4, 5 };
	static char new_data[] = { 5, 4, 3, 2, 1 };

	static void
	add_data_section (Elf elf, Elf_Scn strtab, const char *sname)
	{
	printf ("Add data section %s\n", sname);
	Elf_Scn *scn = elf_newscn (elf);
	if (scn == NULL)
	{
	printf ("cannot create strings section: %s\n", elf_errmsg (-1));
	exit (1);
	}

	GElf_Shdr shdr_mem;
	GElf_Shdr *shdr = gelf_getshdr (scn, &shdr_mem);
	if (shdr == NULL)
	{
	printf ("cannot get header for new %s section: %s\n",
	sname, elf_errmsg (-1));
	exit (1);
	}

	shdr->sh_type = SHT_PROGBITS;
	shdr->sh_flags = 0;
	shdr->sh_addr = 0;
	shdr->sh_link = SHN_UNDEF;
	shdr->sh_info = SHN_UNDEF;
	shdr->sh_addralign = 128; // Large alignment to force gap between sections.
	shdr->sh_entsize = 1;
	shdr->sh_name = add_strtab_entry (strtab, sname);

	if (gelf_update_shdr (scn, shdr) == 0)
	{
	printf ("cannot update %s section header: %s\n", sname, elf_errmsg (-1));
	exit (1);
	}

	/* Add some data, but less than alignment. */
	Elf_Data *data = elf_newdata (scn);
	if (data == NULL)
	{
	printf ("cannot update %s section header: %s\n", sname, elf_errmsg (-1));
	exit (1);
	}
	data->d_buf = sec_data;
	data->d_size = 5;
	}

	static void
	check_data (const char sname, Elf_Data data, char *buf)
	{
	printf ("check data %s [", sname);
	for (int i = 0; i < 5; i++)
	printf ("%d%s", buf[i], i < 4 ? "," : "");
	printf ("]\n");
	if (data == NULL \|\| data->d_buf == NULL)
	{
	printf ("No data in section %s\n", sname);
	exit (1);
	}

	if (data->d_size != 5 \|\| memcmp (data->d_buf, buf, 5) != 0)
	{
	printf ("Wrong data in section %s [", sname);
	for (size_t i = 0; i < data->d_size; i++)
	printf ("%d%s", ((char *)data->d_buf)[i],
	i < data->d_size - 1 ? "," : "");
	printf ("]\n");
	exit(1);
	}
	}

	static void
	check_elf (const char *fname, int class, int use_mmap)
	{
	printf ("\nfname: %s\n", fname);
	stridx = 0; // Reset strtab strings index

	int fd = open (fname, O_RDWR \| O_CREAT \| O_TRUNC, 0666);
	if (fd == -1)
	{
	printf ("cannot open `%s': %s\n", fname, strerror (errno));
	exit (1);
	}

	Elf *elf = elf_begin (fd, use_mmap ? ELF_C_WRITE_MMAP : ELF_C_WRITE, NULL);
	if (elf == NULL)
	{
	printf ("cannot create ELF descriptor: %s\n", elf_errmsg (-1));
	exit (1);
	}

	// Create an ELF header.
	if (gelf_newehdr (elf, class) == 0)
	{
	printf ("cannot create ELF header: %s\n", elf_errmsg (-1));
	exit (1);
	}

	GElf_Ehdr ehdr_mem;
	GElf_Ehdr *ehdr = gelf_getehdr (elf, &ehdr_mem);
	if (ehdr == NULL)
	{
	printf ("cannot get ELF header: %s\n", elf_errmsg (-1));
	exit (1);
	}

	// Initialize header.
	ehdr->e_ident[EI_DATA] = class == ELFCLASS64 ? ELFDATA2LSB : ELFDATA2MSB;
	ehdr->e_ident[EI_OSABI] = ELFOSABI_GNU;
	ehdr->e_type = ET_NONE;
	ehdr->e_machine = EM_X86_64;
	ehdr->e_version = EV_CURRENT;

	if (gelf_update_ehdr (elf, ehdr) == 0)
	{
	printf ("cannot update ELF header: %s\n", elf_errmsg (-1));
	exit (1);
	}

	Elf_Scn *strtab = create_strtab (elf);
	add_data_section (elf, strtab, ".data1");
	add_data_section (elf, strtab, ".data2");
	add_data_section (elf, strtab, ".data3");
	add_data_section (elf, strtab, ".data4");

	// Write everything to disk.
	if (elf_update (elf, ELF_C_WRITE) < 0)
	{
	printf ("failure in elf_update(WRITE): %s\n", elf_errmsg (-1));
	exit (1);
	}

	if (elf_end (elf) != 0)
	{
	printf ("failure in elf_end: %s\n", elf_errmsg (-1));
	exit (1);
	}

	close (fd);

	/* Reread the ELF from disk now. */
	printf ("Rereading %s\n", fname);
	fd = open (fname, O_RDWR, 0666);
	if (fd == -1)
	{
	printf ("cannot (re)open `%s': %s\n", fname, strerror (errno));
	exit (1);
	}

	elf = elf_begin (fd, use_mmap ? ELF_C_RDWR_MMAP : ELF_C_RDWR, NULL);
	if (elf == NULL)
	{
	printf ("cannot create ELF descriptor read-only: %s\n", elf_errmsg (-1));
	exit (1);
	}

	/* We are going to change some data (in-place), but want the layout
	to stay exactly the same. */
	elf_flagelf (elf, ELF_C_SET, ELF_F_LAYOUT);

	size_t shdrstrndx;
	if (elf_getshdrstrndx (elf, &shdrstrndx) != 0)
	{
	printf ("cannot get shdr str ndx\n");
	exit (1);
	}
	printf ("shdrstrndx: %zd\n", shdrstrndx);

	// Get third data section and change it.
	Elf_Scn *checkscn = NULL;
	Elf_Scn *scn = elf_nextscn (elf, NULL);
	while (scn != NULL)
	{
	GElf_Shdr shdr_mem;
	GElf_Shdr *shdr = gelf_getshdr (scn, &shdr_mem);
	if (shdr == NULL)
	{
	printf ("cannot get header for section: %s\n", elf_errmsg (-1));
	exit (1);
	}
	const char *sname = elf_strptr (elf, shdrstrndx, shdr->sh_name);
	if (sname != NULL && strcmp (".data3", sname) == 0)
	checkscn = scn;

	// Get all data, but don't really use it
	// (this triggered the original bug).
	Elf_Data *data = elf_getdata (scn, NULL);
	if (data != NULL && data->d_buf != NULL && data->d_size == 0)
	{
	printf ("Bad data...n");
	exit (1);
	}
	scn = elf_nextscn (elf, scn);
	}

	if (checkscn == NULL)
	{
	printf ("ELF file doesn't have a .data3 section\n");
	exit (1);
	}

	Elf_Data *data = elf_getdata (checkscn, NULL);
	check_data (".data3", data, sec_data);
	memcpy (data->d_buf, new_data, 5);
	elf_flagdata (data, ELF_C_SET, ELF_F_DIRTY);

	// Write everything to disk.
	if (elf_update (elf, ELF_C_WRITE) < 0)
	{
	printf ("failure in elf_update(WRITE): %s\n", elf_errmsg (-1));
	exit (1);
	}

	if (elf_end (elf) != 0)
	{
	printf ("failure in elf_end: %s\n", elf_errmsg (-1));
	exit (1);
	}

	close (fd);

	// And read it in one last time.
	printf ("Rereading %s again\n", fname);
	fd = open (fname, O_RDONLY, 0666);
	if (fd == -1)
	{
	printf ("cannot open `%s' read-only: %s\n", fname, strerror (errno));
	exit (1);
	}

	elf = elf_begin (fd, use_mmap ? ELF_C_READ_MMAP : ELF_C_READ, NULL);
	if (elf == NULL)
	{
	printf ("cannot create ELF descriptor read-only: %s\n", elf_errmsg (-1));
	exit (1);
	}

	// Get all .data sections and check them.
	Elf_Scn *scn1 = NULL;
	Elf_Scn *scn2 = NULL;
	Elf_Scn *scn3 = NULL;
	Elf_Scn *scn4 = NULL;
	scn = elf_nextscn (elf, NULL);
	while (scn != NULL)
	{
	GElf_Shdr shdr_mem;
	GElf_Shdr *shdr = gelf_getshdr (scn, &shdr_mem);
	if (shdr == NULL)
	{
	printf ("cannot get header for section: %s\n", elf_errmsg (-1));
	exit (1);
	}
	const char *sname = elf_strptr (elf, shdrstrndx, shdr->sh_name);
	if (sname != NULL && strcmp (".data1", sname) == 0)
	scn1 = scn;
	else if (sname != NULL && strcmp (".data2", sname) == 0)
	scn2 = scn;
	else if (sname != NULL && strcmp (".data3", sname) == 0)
	scn3 = scn;
	else if (sname != NULL && strcmp (".data4", sname) == 0)
	scn4 = scn;
	scn = elf_nextscn (elf, scn);
	}

	if (scn1 == NULL)
	{
	printf ("ELF file doesn't have a .data1 section\n");
	exit (1);
	}
	data = elf_getdata (scn1, NULL);
	check_data (".data1", data, sec_data);

	if (scn2 == NULL)
	{
	printf ("ELF file doesn't have a .data2 section\n");
	exit (1);
	}
	data = elf_getdata (scn2, NULL);
	check_data (".data2", data, sec_data);

	if (scn3 == NULL)
	{
	printf ("ELF file doesn't have a .data3 section\n");
	exit (1);
	}
	data = elf_getdata (scn3, NULL);
	check_data (".data3", data, new_data);

	if (scn4 == NULL)
	{
	printf ("ELF file doesn't have a .data4 section\n");
	exit (1);
	}
	data = elf_getdata (scn4, NULL);
	check_data (".data4", data, sec_data);

	if (elf_end (elf) != 0)
	{
	printf ("failure in elf_end: %s\n", elf_errmsg (-1));
	exit (1);
	}

	close (fd);

	unlink (fname);
	}

	int
	main (int argc __attribute__ ((unused)),
	char *argv[] __attribute__ ((unused)))
	{
	elf_version (EV_CURRENT);

	elf_fill (0xA);

	check_elf ("fill.elf.32", ELFCLASS32, 0);
	check_elf ("fill.elf.32.mmap", ELFCLASS32, 1);
	check_elf ("fill.elf.64", ELFCLASS64, 0);
	check_elf ("fill.elf.64.mmap", ELFCLASS64, 1);

	return 0;
	}