libelf/nlist.c

/* Extract symbol list from binary.
   Copyright (C) 1998, 1999, 2000, 2001, 2002, 2005, 2007 Red Hat, Inc.
   This file is part of Red Hat elfutils.
   Written by Ulrich Drepper <drepper@redhat.com>, 1998.

   Red Hat elfutils 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; version 2 of the License.

   Red Hat 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 Red Hat elfutils; if not, write to the Free Software Foundation,
   Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301 USA.

   In addition, as a special exception, Red Hat, Inc. gives You the
   additional right to link the code of Red Hat elfutils with code licensed
   under any Open Source Initiative certified open source license
   (http://www.opensource.org/licenses/index.php) which requires the
   distribution of source code with any binary distribution and to
   distribute linked combinations of the two.  Non-GPL Code permitted under
   this exception must only link to the code of Red Hat elfutils through
   those well defined interfaces identified in the file named EXCEPTION
   found in the source code files (the "Approved Interfaces").  The files
   of Non-GPL Code may instantiate templates or use macros or inline
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   Inc. may make changes or additions to the list of Approved Interfaces.
   Red Hat's grant of this exception is conditioned upon your not adding
   any new exceptions.  If you wish to add a new Approved Interface or
   exception, please contact Red Hat.  You must obey the GNU General Public
   License in all respects for all of the Red Hat elfutils code and other
   code used in conjunction with Red Hat elfutils except the Non-GPL Code
   covered by this exception.  If you modify this file, you may extend this
   exception to your version of the file, but you are not obligated to do
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   you must delete this exception statement from your version and license
   this file solely under the GPL without exception.

   Red Hat elfutils is an included package of the Open Invention Network.
   An included package of the Open Invention Network is a package for which
   Open Invention Network licensees cross-license their patents.  No patent
   license is granted, either expressly or impliedly, by designation as an
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#ifdef HAVE_CONFIG_H
# include <config.h>
#endif

#include <fcntl.h>
#include <gelf.h>
#include <libelf.h>
#include <nlist.h>
#include <unistd.h>

#include "libelfP.h"


struct hashentry
{
  const char *str;
  GElf_Sym sym;
};
#define TYPE struct hashentry
/* XXX Use a better hash function some day.  */
#define HASHFCT(str, len) INTUSE(elf_hash) (str)
#define COMPARE(p1, p2) strcmp ((p1)->str, (p2)->str)
#define CLASS static
#define PREFIX nlist_
#define xcalloc(n, m) calloc (n, m)
#define next_prime(s) __libelf_next_prime (s)
#include <fixedsizehash.h>


int
nlist (const char *filename, struct nlist *nl)
{
  int fd;
  Elf *elf;
  Elf_Scn *scn = NULL;
  Elf_Scn *symscn = NULL;
  GElf_Shdr shdr_mem;
  GElf_Shdr *shdr = NULL;
  Elf_Data *data;
  struct nlist_fshash *table;
  size_t nsyms;
  size_t cnt;

  /* Open the file.  */
  fd = open (filename, O_RDONLY);
  if (fd == -1)
    {
      __libelf_seterrno (ELF_E_NOFILE);
      goto fail;
    }

  /* For compatibility reasons (`nlist' existed before ELF and libelf)
     we don't expect the caller to set the ELF version.  Do this here
     if it hasn't happened yet.  */
  if (__libelf_version_initialized == 0)
    INTUSE(elf_version) (EV_CURRENT);

  /* Now get an ELF descriptor.  */
  elf = INTUSE(elf_begin) (fd, ELF_C_READ_MMAP, NULL);
  if (elf == NULL)
    goto fail_fd;

  /* Find a symbol table.  We prefer the real symbol table but if it
     does not exist use the dynamic symbol table.  */
  while ((scn = INTUSE(elf_nextscn) (elf, scn)) != NULL)
    {
      shdr = INTUSE(gelf_getshdr) (scn, &shdr_mem);
      if (shdr == NULL)
	goto fail_close;

      /* That is what we are looking for.  */
      if (shdr->sh_type == SHT_SYMTAB)
	{
	  symscn = scn;
	  break;
	}

      /* Better than nothing.  Remember this section.  */
      if (shdr->sh_type == SHT_DYNSYM)
	symscn = scn;
    }

  if (symscn == NULL)
    /* We haven't found anything.  Fail.  */
    goto fail_close;

  /* Re-get the section header in case we found only the dynamic symbol
     table.  */
  if (scn == NULL)
    shdr = INTUSE(gelf_getshdr) (symscn, &shdr_mem);
  /* SHDR->SH_LINK now contains the index of the string section.  */

  /* Get the data for the symbol section.  */
  data = INTUSE(elf_getdata) (symscn, NULL);
  if (data == NULL)
    goto fail_close;

  /* How many symbols are there?  */
  nsyms = (shdr->sh_size
	   / INTUSE(gelf_fsize) (elf, ELF_T_SYM, 1, data->d_version));

  /* Create the hash table.  */
  table = nlist_fshash_init (nsyms);
  if (table == NULL)
    {
      __libelf_seterrno (ELF_E_NOMEM);
      goto fail_close;
    }

  /* Iterate over all the symbols in the section.  */
  for (cnt = 0; cnt < nsyms; ++cnt)
    {
      struct hashentry mem;
      GElf_Sym *sym;

      /* Get the symbol.  */
      sym = INTUSE(gelf_getsym) (data, cnt, &mem.sym);
      if (sym == NULL)
	goto fail_dealloc;

      /* Get the name of the symbol.  */
      mem.str = INTUSE(elf_strptr) (elf, shdr->sh_link, sym->st_name);
      if (mem.str == NULL)
	goto fail_dealloc;

      /* Don't allow zero-length strings.  */
      if (mem.str[0] == '\0')
	continue;

      /* And add it to the hash table.  Note that we are using the
         overwrite version.  This will ensure that
	 a) global symbols are preferred over local symbols since
	    they are all located at the end
	 b) if there are multiple local symbols with the same name
	    the last one is used.
      */
      (void) nlist_fshash_overwrite (table, mem.str, 0, &mem);
    }

  /* Now it is time to look for the symbols the user asked for.
     XXX What is a `null name/null string'?  This is what the
     standard says terminates the list.  Is it a null pointer
     or a zero-length string?  We test for both...  */
  while (nl->n_name != NULL && nl->n_name[0] != '\0')
    {
      struct hashentry search;
      const struct hashentry *found;

      /* Search for a matching entry in the hash table.  */
      search.str = nl->n_name;
      found = nlist_fshash_find (table, nl->n_name, 0, &search);

      if (found != NULL)
	{
	  /* Found it.  */
	  nl->n_value = found->sym.st_value;
	  nl->n_scnum = found->sym.st_shndx;
	  nl->n_type = GELF_ST_TYPE (found->sym.st_info);
	  /* XXX What shall we fill in the next fields?  */
	  nl->n_sclass = 0;
	  nl->n_numaux = 0;
	}
      else
	{
	  /* Not there.  */
	  nl->n_value = 0;
	  nl->n_scnum = 0;
	  nl->n_type = 0;
	  nl->n_sclass = 0;
	  nl->n_numaux = 0;
	}

      /* Next search request.  */
      ++nl;
    }

  /* Free the resources.  */
  nlist_fshash_fini (table);

  /* We do not need the ELF descriptor anymore.  */
  (void) INTUSE(elf_end) (elf);

  /* Neither the file descriptor.  */
  (void) close (fd);

  return 0;

 fail_dealloc:
  nlist_fshash_fini (table);

 fail_close:
  /* We do not need the ELF descriptor anymore.  */
  (void) INTUSE(elf_end) (elf);

 fail_fd:
  /* Neither the file descriptor.  */
  (void) close (fd);

 fail:
  /* We have to set all entries to zero.  */
  while (nl->n_name != NULL && nl->n_name[0] != '\0')
    {
      nl->n_value = 0;
      nl->n_scnum = 0;
      nl->n_type = 0;
      nl->n_sclass = 0;
      nl->n_numaux = 0;

      /* Next entry.  */
      ++nl;
    }

  return -1;
}