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. */
66 static 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
87 static Dwarf *
check_section(Dwarf * result,GElf_Ehdr * ehdr,Elf_Scn * scn,bool inscngrp)88 check_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. */
154 static Dwarf *
valid_p(Dwarf * result)155 valid_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
175 static Dwarf *
global_read(Dwarf * result,Elf * elf,GElf_Ehdr * ehdr)176 global_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
187 static Dwarf *
scngrp_read(Dwarf * result,Elf * elf,GElf_Ehdr * ehdr,Elf_Scn * scngrp)188 scngrp_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
225 Dwarf *
dwarf_begin_elf(elf,cmd,scngrp)226 dwarf_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 }
299 INTDEF(dwarf_begin_elf)
300