1/* Create descriptor from ELF descriptor for processing file.
2   Copyright (C) 2002, 2003, 2004, 2005, 2007 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 <stdbool.h>
56#include <stddef.h>
57#include <stdlib.h>
58#include <string.h>
59#include <unistd.h>
60#include <sys/stat.h>
61
62#include "libdwP.h"
63
64
65/* Section names.  */
66static const char dwarf_scnnames[IDX_last][17] =
67{
68  [IDX_debug_info] = ".debug_info",
69  [IDX_debug_abbrev] = ".debug_abbrev",
70  [IDX_debug_aranges] = ".debug_aranges",
71  [IDX_debug_line] = ".debug_line",
72  [IDX_debug_frame] = ".debug_frame",
73  [IDX_eh_frame] = ".eh_frame",
74  [IDX_debug_loc] = ".debug_loc",
75  [IDX_debug_pubnames] = ".debug_pubnames",
76  [IDX_debug_str] = ".debug_str",
77  [IDX_debug_funcnames] = ".debug_funcnames",
78  [IDX_debug_typenames] = ".debug_typenames",
79  [IDX_debug_varnames] = ".debug_varnames",
80  [IDX_debug_weaknames] = ".debug_weaknames",
81  [IDX_debug_macinfo] = ".debug_macinfo",
82  [IDX_debug_ranges] = ".debug_ranges"
83};
84#define ndwarf_scnnames (sizeof (dwarf_scnnames) / sizeof (dwarf_scnnames[0]))
85
86
87static Dwarf *
88check_section (Dwarf *result, GElf_Ehdr *ehdr, Elf_Scn *scn, bool inscngrp)
89{
90  GElf_Shdr shdr_mem;
91  GElf_Shdr *shdr;
92
93  /* Get the section header data.  */
94  shdr = gelf_getshdr (scn, &shdr_mem);
95  if (shdr == NULL)
96    /* This should never happen.  If it does something is
97       wrong in the libelf library.  */
98    abort ();
99
100  /* Ignore any SHT_NOBITS sections.  Debugging sections should not
101     have been stripped, but in case of a corrupt file we won't try
102     to look at the missing data.  */
103  if (unlikely (shdr->sh_type == SHT_NOBITS))
104    return result;
105
106  /* Make sure the section is part of a section group only iff we
107     really need it.  If we are looking for the global (= non-section
108     group debug info) we have to ignore all the info in section
109     groups.  If we are looking into a section group we cannot look at
110     a section which isn't part of the section group.  */
111  if (! inscngrp && (shdr->sh_flags & SHF_GROUP) != 0)
112    /* Ignore the section.  */
113    return result;
114
115
116  /* We recognize the DWARF section by their names.  This is not very
117     safe and stable but the best we can do.  */
118  const char *scnname = elf_strptr (result->elf, ehdr->e_shstrndx,
119				    shdr->sh_name);
120  if (scnname == NULL)
121    {
122      /* The section name must be valid.  Otherwise is the ELF file
123	 invalid.  */
124      __libdw_seterrno (DWARF_E_INVALID_ELF);
125      free (result);
126      return NULL;
127    }
128
129
130  /* Recognize the various sections.  Most names start with .debug_.  */
131  size_t cnt;
132  for (cnt = 0; cnt < ndwarf_scnnames; ++cnt)
133    if (strcmp (scnname, dwarf_scnnames[cnt]) == 0)
134      {
135	/* Found it.  Remember where the data is.  */
136	if (unlikely (result->sectiondata[cnt] != NULL))
137	  /* A section appears twice.  That's bad.  We ignore the section.  */
138	  break;
139
140	/* Get the section data.  */
141	Elf_Data *data = elf_getdata (scn, NULL);
142	if (data != NULL && data->d_size != 0)
143	  /* Yep, there is actually data available.  */
144	  result->sectiondata[cnt] = data;
145
146	break;
147      }
148
149  return result;
150}
151
152
153/* Check whether all the necessary DWARF information is available.  */
154static Dwarf *
155valid_p (Dwarf *result)
156{
157  /* We looked at all the sections.  Now determine whether all the
158     sections with debugging information we need are there.
159
160     XXX Which sections are absolutely necessary?  Add tests if
161     necessary.  For now we require only .debug_info.  Hopefully this
162     is correct.  */
163  if (likely (result != NULL)
164      && unlikely (result->sectiondata[IDX_debug_info] == NULL))
165    {
166      __libdw_seterrno (DWARF_E_NO_DWARF);
167      free (result);
168      result = NULL;
169    }
170
171  return result;
172}
173
174
175static Dwarf *
176global_read (Dwarf *result, Elf *elf, GElf_Ehdr *ehdr)
177{
178  Elf_Scn *scn = NULL;
179
180  while (result != NULL && (scn = elf_nextscn (elf, scn)) != NULL)
181    result = check_section (result, ehdr, scn, false);
182
183  return valid_p (result);
184}
185
186
187static Dwarf *
188scngrp_read (Dwarf *result, Elf *elf, GElf_Ehdr *ehdr, Elf_Scn *scngrp)
189{
190  /* SCNGRP is the section descriptor for a section group which might
191     contain debug sections.  */
192  Elf_Data *data = elf_getdata (scngrp, NULL);
193  if (data == NULL)
194    {
195      /* We cannot read the section content.  Fail!  */
196      free (result);
197      return NULL;
198    }
199
200  /* The content of the section is a number of 32-bit words which
201     represent section indices.  The first word is a flag word.  */
202  Elf32_Word *scnidx = (Elf32_Word *) data->d_buf;
203  size_t cnt;
204  for (cnt = 1; cnt * sizeof (Elf32_Word) <= data->d_size; ++cnt)
205    {
206      Elf_Scn *scn = elf_getscn (elf, scnidx[cnt]);
207      if (scn == NULL)
208	{
209	  /* A section group refers to a non-existing section.  Should
210	     never happen.  */
211	  __libdw_seterrno (DWARF_E_INVALID_ELF);
212	  free (result);
213	  return NULL;
214	}
215
216      result = check_section (result, ehdr, scn, true);
217      if (result == NULL)
218	break;
219    }
220
221  return valid_p (result);
222}
223
224
225Dwarf *
226dwarf_begin_elf (elf, cmd, scngrp)
227     Elf *elf;
228     Dwarf_Cmd cmd;
229     Elf_Scn *scngrp;
230{
231  GElf_Ehdr *ehdr;
232  GElf_Ehdr ehdr_mem;
233
234  /* Get the ELF header of the file.  We need various pieces of
235     information from it.  */
236  ehdr = gelf_getehdr (elf, &ehdr_mem);
237  if (ehdr == NULL)
238    {
239      if (elf_kind (elf) != ELF_K_ELF)
240	__libdw_seterrno (DWARF_E_NOELF);
241      else
242	__libdw_seterrno (DWARF_E_GETEHDR_ERROR);
243
244      return NULL;
245    }
246
247
248  /* Default memory allocation size.  */
249  size_t mem_default_size = sysconf (_SC_PAGESIZE) - 4 * sizeof (void *);
250
251  /* Allocate the data structure.  */
252  Dwarf *result = (Dwarf *) calloc (1, sizeof (Dwarf) + mem_default_size);
253  if (result == NULL)
254    {
255      __libdw_seterrno (DWARF_E_NOMEM);
256      return NULL;
257    }
258
259  /* Fill in some values.  */
260  if ((BYTE_ORDER == LITTLE_ENDIAN && ehdr->e_ident[EI_DATA] == ELFDATA2MSB)
261      || (BYTE_ORDER == BIG_ENDIAN && ehdr->e_ident[EI_DATA] == ELFDATA2LSB))
262    result->other_byte_order = true;
263
264  result->elf = elf;
265
266  /* Initialize the memory handling.  */
267  result->mem_default_size = mem_default_size;
268  result->oom_handler = __libdw_oom;
269  result->mem_tail = (struct libdw_memblock *) (result + 1);
270  result->mem_tail->size = (result->mem_default_size
271			    - offsetof (struct libdw_memblock, mem));
272  result->mem_tail->remaining = result->mem_tail->size;
273  result->mem_tail->prev = NULL;
274
275
276  if (cmd == DWARF_C_READ || cmd == DWARF_C_RDWR)
277    {
278      /* If the caller provides a section group we get the DWARF
279	 sections only from this setion group.  Otherwise we search
280	 for the first section with the required name.  Further
281	 sections with the name are ignored.  The DWARF specification
282	 does not really say this is allowed.  */
283      if (scngrp == NULL)
284	return global_read (result, elf, ehdr);
285      else
286	return scngrp_read (result, elf, ehdr, scngrp);
287    }
288  else if (cmd == DWARF_C_WRITE)
289    {
290      __libdw_seterrno (DWARF_E_UNIMPL);
291      free (result);
292      return NULL;
293    }
294
295  __libdw_seterrno (DWARF_E_INVALID_CMD);
296  free (result);
297  return NULL;
298}
299INTDEF(dwarf_begin_elf)
300