1/* Return section index of section header string table.
2   Copyright (C) 2002, 2005, 2009 Red Hat, Inc.
3   This file is part of Red Hat elfutils.
4   Written by Ulrich Drepper <drepper@redhat.com>, 2002.
5
6   Red Hat elfutils is free software; you can redistribute it and/or modify
7   it under the terms of the GNU General Public License as published by the
8   Free Software Foundation; version 2 of the License.
9
10   Red Hat elfutils is distributed in the hope that it will be useful, but
11   WITHOUT ANY WARRANTY; without even the implied warranty of
12   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
13   General Public License for more details.
14
15   You should have received a copy of the GNU General Public License along
16   with Red Hat elfutils; if not, write to the Free Software Foundation,
17   Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301 USA.
18
19   In addition, as a special exception, Red Hat, Inc. gives You the
20   additional right to link the code of Red Hat elfutils with code licensed
21   under any Open Source Initiative certified open source license
22   (http://www.opensource.org/licenses/index.php) which requires the
23   distribution of source code with any binary distribution and to
24   distribute linked combinations of the two.  Non-GPL Code permitted under
25   this exception must only link to the code of Red Hat elfutils through
26   those well defined interfaces identified in the file named EXCEPTION
27   found in the source code files (the "Approved Interfaces").  The files
28   of Non-GPL Code may instantiate templates or use macros or inline
29   functions from the Approved Interfaces without causing the resulting
30   work to be covered by the GNU General Public License.  Only Red Hat,
31   Inc. may make changes or additions to the list of Approved Interfaces.
32   Red Hat's grant of this exception is conditioned upon your not adding
33   any new exceptions.  If you wish to add a new Approved Interface or
34   exception, please contact Red Hat.  You must obey the GNU General Public
35   License in all respects for all of the Red Hat elfutils code and other
36   code used in conjunction with Red Hat elfutils except the Non-GPL Code
37   covered by this exception.  If you modify this file, you may extend this
38   exception to your version of the file, but you are not obligated to do
39   so.  If you do not wish to provide this exception without modification,
40   you must delete this exception statement from your version and license
41   this file solely under the GPL without exception.
42
43   Red Hat elfutils is an included package of the Open Invention Network.
44   An included package of the Open Invention Network is a package for which
45   Open Invention Network licensees cross-license their patents.  No patent
46   license is granted, either expressly or impliedly, by designation as an
47   included package.  Should you wish to participate in the Open Invention
48   Network licensing program, please visit www.openinventionnetwork.com
49   <http://www.openinventionnetwork.com>.  */
50
51#ifdef HAVE_CONFIG_H
52# include <config.h>
53#endif
54
55#include <assert.h>
56#include <errno.h>
57#include <gelf.h>
58#include <stddef.h>
59#include <unistd.h>
60
61#include <system.h>
62#include "libelfP.h"
63#include "common.h"
64
65
66int
67elf_getshdrstrndx (elf, dst)
68     Elf *elf;
69     size_t *dst;
70{
71  int result = 0;
72
73  if (elf == NULL)
74    return -1;
75
76  if (unlikely (elf->kind != ELF_K_ELF))
77    {
78      __libelf_seterrno (ELF_E_INVALID_HANDLE);
79      return -1;
80    }
81
82  rwlock_rdlock (elf->lock);
83
84  /* We rely here on the fact that the `elf' element is a common prefix
85     of `elf32' and `elf64'.  */
86  assert (offsetof (struct Elf, state.elf.ehdr)
87	  == offsetof (struct Elf, state.elf32.ehdr));
88  assert (sizeof (elf->state.elf.ehdr)
89	  == sizeof (elf->state.elf32.ehdr));
90  assert (offsetof (struct Elf, state.elf.ehdr)
91	  == offsetof (struct Elf, state.elf64.ehdr));
92  assert (sizeof (elf->state.elf.ehdr)
93	  == sizeof (elf->state.elf64.ehdr));
94
95  if (unlikely (elf->state.elf.ehdr == NULL))
96    {
97      __libelf_seterrno (ELF_E_WRONG_ORDER_EHDR);
98      result = -1;
99    }
100  else
101    {
102      Elf32_Word num;
103
104      num = (elf->class == ELFCLASS32
105	     ? elf->state.elf32.ehdr->e_shstrndx
106	     : elf->state.elf64.ehdr->e_shstrndx);
107
108      /* Determine whether the index is too big to fit in the ELF
109	 header.  */
110      if (unlikely (num == SHN_XINDEX))
111	{
112	  /* Yes.  Search the zeroth section header.  */
113	  if (elf->class == ELFCLASS32)
114	    {
115	      size_t offset;
116
117	      if (elf->state.elf32.scns.data[0].shdr.e32 != NULL)
118		{
119		  num = elf->state.elf32.scns.data[0].shdr.e32->sh_link;
120		  goto success;
121		}
122
123	      offset = elf->state.elf32.ehdr->e_shoff;
124
125	      if (elf->map_address != NULL
126		  && elf->state.elf32.ehdr->e_ident[EI_DATA] == MY_ELFDATA
127		  && (ALLOW_UNALIGNED
128		      || (((size_t) ((char *) elf->map_address + offset))
129			  & (__alignof__ (Elf32_Shdr) - 1)) == 0))
130		/* We can directly access the memory.  */
131		num = ((Elf32_Shdr *) (elf->map_address + offset))->sh_link;
132	      else
133		{
134		  /* We avoid reading in all the section headers.  Just read
135		     the first one.  */
136		  Elf32_Shdr shdr_mem;
137
138		  if (unlikely (pread_retry (elf->fildes, &shdr_mem,
139					     sizeof (Elf32_Shdr), offset)
140				!= sizeof (Elf32_Shdr)))
141		    {
142		      /* We must be able to read this ELF section header.  */
143		      __libelf_seterrno (ELF_E_INVALID_FILE);
144		      result = -1;
145		      goto out;
146		    }
147
148		  if (elf->state.elf32.ehdr->e_ident[EI_DATA] != MY_ELFDATA)
149		    CONVERT (shdr_mem.sh_link);
150		  num = shdr_mem.sh_link;
151		}
152	    }
153	  else
154	    {
155	      if (elf->state.elf64.scns.data[0].shdr.e64 != NULL)
156		{
157		  num = elf->state.elf64.scns.data[0].shdr.e64->sh_link;
158		  goto success;
159		}
160
161	      size_t offset = elf->state.elf64.ehdr->e_shoff;
162
163	      if (elf->map_address != NULL
164		  && elf->state.elf64.ehdr->e_ident[EI_DATA] == MY_ELFDATA
165		  && (ALLOW_UNALIGNED
166		      || (((size_t) ((char *) elf->map_address + offset))
167			  & (__alignof__ (Elf64_Shdr) - 1)) == 0))
168		/* We can directly access the memory.  */
169		num = ((Elf64_Shdr *) (elf->map_address + offset))->sh_link;
170	      else
171		{
172		  /* We avoid reading in all the section headers.  Just read
173		     the first one.  */
174		  Elf64_Shdr shdr_mem;
175
176		  if (unlikely (pread_retry (elf->fildes, &shdr_mem,
177					     sizeof (Elf64_Shdr), offset)
178				!= sizeof (Elf64_Shdr)))
179		    {
180		      /* We must be able to read this ELF section header.  */
181		      __libelf_seterrno (ELF_E_INVALID_FILE);
182		      result = -1;
183		      goto out;
184		    }
185
186		  if (elf->state.elf64.ehdr->e_ident[EI_DATA] != MY_ELFDATA)
187		    CONVERT (shdr_mem.sh_link);
188		  num = shdr_mem.sh_link;
189		}
190	    }
191	}
192
193      /* Store the result.  */
194    success:
195      *dst = num;
196    }
197
198 out:
199  rwlock_unlock (elf->lock);
200
201  return result;
202}
203INTDEF(elf_getshdrstrndx)
204/* Alias for the deprecated name.  */
205#ifndef __APPLE__
206strong_alias (elf_getshdrstrndx, elf_getshstrndx)
207#endif
208