/* Test program for adding (more than SHN_LORESERVE) sections.
Copyright (C) 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 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 <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include ELFUTILS_HEADER(elf)
#include <gelf.h>
/* shstrndx is special, might overflow into section zero header sh_link. */
static int
setshstrndx (Elf *elf, size_t ndx)
{
printf ("setshstrndx: %zd\n", ndx);
GElf_Ehdr ehdr_mem;
GElf_Ehdr *ehdr = gelf_getehdr (elf, &ehdr_mem);
if (ehdr == NULL)
return -1;
if (ndx < SHN_LORESERVE)
ehdr->e_shstrndx = ndx;
else
{
ehdr->e_shstrndx = SHN_XINDEX;
Elf_Scn *zscn = elf_getscn (elf, 0);
GElf_Shdr zshdr_mem;
GElf_Shdr *zshdr = gelf_getshdr (zscn, &zshdr_mem);
if (zshdr == NULL)
return -1;
zshdr->sh_link = ndx;
if (gelf_update_shdr (zscn, zshdr) == 0)
return -1;
}
if (gelf_update_ehdr (elf, ehdr) == 0)
return -1;
return 0;
}
/* Will add nr new '.extra' sections and a new '.new_shstrtab' section
at the end. */
static void
add_sections (const char *name, size_t nr, int use_mmap, size_t sec_size)
{
printf ("add_sections '%s': %zd (sec_size: %zd)\n", name, nr, sec_size);
int fd = open (name, O_RDWR);
if (fd < 0)
{
fprintf (stderr, "Couldn't open file '%s': %s\n",
name, strerror (errno));
exit (1);
}
Elf *elf = elf_begin (fd, use_mmap ? ELF_C_RDWR_MMAP : ELF_C_RDWR, NULL);
if (elf == NULL)
{
fprintf (stderr, "Couldn't open ELF file '%s': %s\n",
name, elf_errmsg (-1));
exit (1);
}
/* We will add a new shstrtab section with two new names at the end.
Just get the current shstrtab table and add two entries '.extra'
and '.old_shstrtab' at the end of the table, so all existing indexes
are still valid. */
size_t shstrndx;
if (elf_getshdrstrndx (elf, &shstrndx) < 0)
{
printf ("cannot get shstrndx: %s\n", elf_errmsg (-1));
exit (1);
}
Elf_Scn *shstrtab_scn = elf_getscn (elf, shstrndx);
if (shstrtab_scn == NULL)
{
printf ("couldn't get shstrtab scn: %s\n", elf_errmsg (-1));
exit (1);
}
Elf_Data *shstrtab_data = elf_getdata (shstrtab_scn, NULL);
if (shstrtab_data == NULL)
{
printf ("couldn't get shstrtab data: %s\n", elf_errmsg (-1));
exit (1);
}
size_t new_shstrtab_size = (shstrtab_data->d_size
+ strlen (".extra") + 1
+ strlen (".old_shstrtab") + 1);
void *new_shstrtab_buf = malloc (new_shstrtab_size);
if (new_shstrtab_buf == NULL)
{
printf ("couldn't allocate new shstrtab data d_buf\n");
exit (1);
}
memcpy (new_shstrtab_buf, shstrtab_data->d_buf, shstrtab_data->d_size);
size_t extra_idx = shstrtab_data->d_size;
size_t old_shstrtab_idx = extra_idx + strlen (".extra") + 1;
strcpy (new_shstrtab_buf + extra_idx, ".extra");
strcpy (new_shstrtab_buf + old_shstrtab_idx, ".old_shstrtab");
/* Change the name of the old shstrtab section, because elflint
has a strict check on the name/type for .shstrtab. */
GElf_Shdr shdr_mem;
GElf_Shdr *shdr = gelf_getshdr (shstrtab_scn, &shdr_mem);
if (shdr == NULL)
{
printf ("cannot get header for old shstrtab section: %s\n",
elf_errmsg (-1));
exit (1);
}
size_t shstrtab_idx = shdr->sh_name;
shdr->sh_name = old_shstrtab_idx;
if (gelf_update_shdr (shstrtab_scn, shdr) == 0)
{
printf ("cannot update old shstrtab section header: %s\n",
elf_errmsg (-1));
exit (1);
}
void *buf;
size_t bufsz;
if (sec_size == 0)
{
buf = strdup ("extra");
bufsz = strlen ("extra") + 1;
}
else
{
buf = malloc (sec_size);
if (buf == NULL)
{
printf ("cannot allocate buffer data of %zd bytes\n", sec_size);
exit (1);
}
memset (buf, 0xAA, sec_size);
bufsz = sec_size;
}
// Add lots of .extra sections...
size_t cnt = 0;
while (cnt++ < nr)
{
Elf_Scn *scn = elf_newscn (elf);
if (scn == NULL)
{
printf ("cannot create .extra section (%zd): %s\n", cnt,
elf_errmsg (-1));
exit (1);
}
Elf_Data *data = elf_newdata (scn);
if (data == NULL)
{
printf ("couldn't create new section data (%zd): %s\n", cnt,
elf_errmsg (-1));
exit (1);
}
data->d_size = bufsz;
data->d_buf = buf;
data->d_type = ELF_T_BYTE;
data->d_align = 1;
shdr = gelf_getshdr (scn, &shdr_mem);
if (shdr == NULL)
{
printf ("cannot get header for new section (%zd): %s\n", cnt,
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 = 1;
shdr->sh_entsize = 0;
shdr->sh_size = data->d_size;
shdr->sh_name = extra_idx;
if (gelf_update_shdr (scn, shdr) == 0)
{
printf ("cannot update new section header (%zd): %s\n", cnt,
elf_errmsg (-1));
exit (1);
}
}
// Create new shstrtab section.
Elf_Scn *new_shstrtab_scn = elf_newscn (elf);
if (new_shstrtab_scn == NULL)
{
printf ("cannot create new shstrtab section: %s\n", elf_errmsg (-1));
exit (1);
}
Elf_Data *new_shstrtab_data = elf_newdata (new_shstrtab_scn);
if (new_shstrtab_data == NULL)
{
printf ("couldn't create new shstrtab section data: %s\n",
elf_errmsg (-1));
exit (1);
}
new_shstrtab_data->d_size = new_shstrtab_size;
new_shstrtab_data->d_buf = new_shstrtab_buf;
new_shstrtab_data->d_type = ELF_T_BYTE;
new_shstrtab_data->d_align = 1;
shdr = gelf_getshdr (new_shstrtab_scn, &shdr_mem);
if (shdr == NULL)
{
printf ("cannot get header for new shstrtab 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_size = new_shstrtab_size;
shdr->sh_name = shstrtab_idx;
// Finished new shstrtab section, update the header.
if (gelf_update_shdr (new_shstrtab_scn, shdr) == 0)
{
printf ("cannot update new shstrtab section header: %s\n",
elf_errmsg (-1));
exit (1);
}
// Set it as the new shstrtab section to get the names correct.
size_t new_shstrndx = elf_ndxscn (new_shstrtab_scn);
if (setshstrndx (elf, new_shstrndx) < 0)
{
printf ("cannot set shstrndx: %s\n", elf_errmsg (-1));
exit (1);
}
// Write everything to disk.
if (elf_update (elf, ELF_C_WRITE) < 0)
{
printf ("failure in elf_update: %s\n", elf_errmsg (-1));
exit (1);
}
if (elf_end (elf) != 0)
{
printf ("couldn't cleanup elf '%s': %s\n", name, elf_errmsg (-1));
exit (1);
}
if (close (fd) != 0)
{
printf ("couldn't close '%s': %s\n", name, strerror (errno));
exit (1);
}
free (buf);
free (new_shstrtab_buf);
}
int
main (int argc, char *argv[])
{
elf_version (EV_CURRENT);
/* Takes the given file, and adds the given number of sections.
Optionally using mmap and optionally using a given section size. */
if (argc < 3 || argc > 5)
{
fprintf (stderr, "addsections [--mmap] nr elf.file [sec_size]\n");
exit (1);
}
int argn = 1;
bool use_mmap = false;
if (strcmp (argv[argn], "--mmap") == 0)
{
use_mmap = true;
argn++;
}
size_t nr = atoi (argv[argn++]);
const char *file = argv[argn++];
size_t sec_size = 0;
if (argn < argc)
sec_size = atol (argv[argn++]);
add_sections (file, nr, use_mmap, sec_size);
return 0;
}