Line data Source code
1 : /* Create descriptor from ELF descriptor for processing file.
2 : Copyright (C) 2002-2011, 2014, 2015, 2017, 2018 Red Hat, Inc.
3 : This file is part of elfutils.
4 :
5 : This file is free software; you can redistribute it and/or modify
6 : it under the terms of either
7 :
8 : * the GNU Lesser General Public License as published by the Free
9 : Software Foundation; either version 3 of the License, or (at
10 : your option) any later version
11 :
12 : or
13 :
14 : * the GNU General Public License as published by the Free
15 : Software Foundation; either version 2 of the License, or (at
16 : your option) any later version
17 :
18 : or both in parallel, as here.
19 :
20 : elfutils is distributed in the hope that it will be useful, but
21 : WITHOUT ANY WARRANTY; without even the implied warranty of
22 : MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
23 : General Public License for more details.
24 :
25 : You should have received copies of the GNU General Public License and
26 : the GNU Lesser General Public License along with this program. If
27 : not, see <http://www.gnu.org/licenses/>. */
28 :
29 : #ifdef HAVE_CONFIG_H
30 : # include <config.h>
31 : #endif
32 :
33 : #include <assert.h>
34 : #include <stdbool.h>
35 : #include <stddef.h>
36 : #include <stdlib.h>
37 : #include <stdio.h>
38 : #include <string.h>
39 : #include <unistd.h>
40 : #include <sys/types.h>
41 : #include <sys/stat.h>
42 : #include <fcntl.h>
43 : #include <endian.h>
44 :
45 : #include "libelfP.h"
46 : #include "libdwP.h"
47 :
48 :
49 : /* Section names. (Note .debug_str_offsets is the largest 19 chars.) */
50 : static const char dwarf_scnnames[IDX_last][19] =
51 : {
52 : [IDX_debug_info] = ".debug_info",
53 : [IDX_debug_types] = ".debug_types",
54 : [IDX_debug_abbrev] = ".debug_abbrev",
55 : [IDX_debug_addr] = ".debug_addr",
56 : [IDX_debug_aranges] = ".debug_aranges",
57 : [IDX_debug_line] = ".debug_line",
58 : [IDX_debug_line_str] = ".debug_line_str",
59 : [IDX_debug_frame] = ".debug_frame",
60 : [IDX_debug_loc] = ".debug_loc",
61 : [IDX_debug_loclists] = ".debug_loclists",
62 : [IDX_debug_pubnames] = ".debug_pubnames",
63 : [IDX_debug_str] = ".debug_str",
64 : [IDX_debug_str_offsets] = ".debug_str_offsets",
65 : [IDX_debug_macinfo] = ".debug_macinfo",
66 : [IDX_debug_macro] = ".debug_macro",
67 : [IDX_debug_ranges] = ".debug_ranges",
68 : [IDX_debug_rnglists] = ".debug_rnglists",
69 : [IDX_gnu_debugaltlink] = ".gnu_debugaltlink"
70 : };
71 : #define ndwarf_scnnames (sizeof (dwarf_scnnames) / sizeof (dwarf_scnnames[0]))
72 :
73 : static Dwarf *
74 274801 : check_section (Dwarf *result, size_t shstrndx, Elf_Scn *scn, bool inscngrp)
75 : {
76 : GElf_Shdr shdr_mem;
77 : GElf_Shdr *shdr;
78 :
79 : /* Get the section header data. */
80 274801 : shdr = gelf_getshdr (scn, &shdr_mem);
81 274801 : if (shdr == NULL)
82 : /* We may read /proc/PID/mem with only program headers mapped and section
83 : headers out of the mapped pages. */
84 : goto err;
85 :
86 : /* Ignore any SHT_NOBITS sections. Debugging sections should not
87 : have been stripped, but in case of a corrupt file we won't try
88 : to look at the missing data. */
89 274801 : if (unlikely (shdr->sh_type == SHT_NOBITS))
90 : return result;
91 :
92 : /* Make sure the section is part of a section group only iff we
93 : really need it. If we are looking for the global (= non-section
94 : group debug info) we have to ignore all the info in section
95 : groups. If we are looking into a section group we cannot look at
96 : a section which isn't part of the section group. */
97 262427 : if (! inscngrp && (shdr->sh_flags & SHF_GROUP) != 0)
98 : /* Ignore the section. */
99 : return result;
100 :
101 :
102 : /* We recognize the DWARF section by their names. This is not very
103 : safe and stable but the best we can do. */
104 262427 : const char *scnname = elf_strptr (result->elf, shstrndx,
105 262427 : shdr->sh_name);
106 262427 : if (scnname == NULL)
107 : {
108 : /* The section name must be valid. Otherwise is the ELF file
109 : invalid. */
110 1 : err:
111 1 : Dwarf_Sig8_Hash_free (&result->sig8_hash);
112 1 : __libdw_seterrno (DWARF_E_INVALID_ELF);
113 1 : free (result);
114 1 : return NULL;
115 : }
116 :
117 : /* Recognize the various sections. Most names start with .debug_. */
118 : size_t cnt;
119 : bool gnu_compressed = false;
120 4270657 : for (cnt = 0; cnt < ndwarf_scnnames; ++cnt)
121 : {
122 4309198 : size_t dbglen = strlen (dwarf_scnnames[cnt]);
123 4309198 : size_t scnlen = strlen (scnname);
124 4309198 : if (strncmp (scnname, dwarf_scnnames[cnt], dbglen) == 0
125 38583 : && (dbglen == scnlen
126 542 : || (scnlen == dbglen + 4
127 427 : && strstr (scnname, ".dwo") == scnname + dbglen)))
128 : break;
129 4270739 : else if (scnname[0] == '.' && scnname[1] == 'z'
130 594 : && (strncmp (&scnname[2], &dwarf_scnnames[cnt][1],
131 : dbglen - 1) == 0
132 82 : && (scnlen == dbglen + 1
133 0 : || (scnlen == dbglen + 5
134 0 : && strstr (scnname,
135 0 : ".dwo") == scnname + dbglen + 1))))
136 : {
137 : gnu_compressed = true;
138 : break;
139 : }
140 : }
141 :
142 262426 : if (cnt >= ndwarf_scnnames)
143 : /* Not a debug section; ignore it. */
144 : return result;
145 :
146 38541 : if (unlikely (result->sectiondata[cnt] != NULL))
147 : /* A section appears twice. That's bad. We ignore the section. */
148 : return result;
149 :
150 : /* We cannot know whether or not a GNU compressed section has already
151 : been uncompressed or not, so ignore any errors. */
152 38541 : if (gnu_compressed)
153 82 : elf_compress_gnu (scn, 0, 0);
154 :
155 38541 : if ((shdr->sh_flags & SHF_COMPRESSED) != 0)
156 : {
157 298 : if (elf_compress (scn, 0, 0) < 0)
158 : {
159 : /* It would be nice if we could fail with a specific error.
160 : But we don't know if this was an essential section or not.
161 : So just continue for now. See also valid_p(). */
162 : return result;
163 : }
164 : }
165 :
166 : /* Get the section data. */
167 38541 : Elf_Data *data = elf_getdata (scn, NULL);
168 38541 : if (data == NULL)
169 : goto err;
170 :
171 38541 : if (data->d_buf == NULL || data->d_size == 0)
172 : /* No data actually available, ignore it. */
173 : return result;
174 :
175 : /* We can now read the section data into results. */
176 38535 : result->sectiondata[cnt] = data;
177 :
178 38535 : return result;
179 : }
180 :
181 :
182 : /* Helper function to set debugdir field. We want to cache the dir
183 : where we found this Dwarf ELF file to locate alt and dwo files. */
184 : char *
185 6028 : __libdw_debugdir (int fd)
186 : {
187 : /* strlen ("/proc/self/fd/") = 14 + strlen (<MAXINT>) = 10 + 1 = 25. */
188 : char devfdpath[25];
189 6028 : sprintf (devfdpath, "/proc/self/fd/%u", fd);
190 6028 : char *fdpath = realpath (devfdpath, NULL);
191 : char *fddir;
192 6028 : if (fdpath != NULL && fdpath[0] == '/'
193 5770 : && (fddir = strrchr (fdpath, '/')) != NULL)
194 : {
195 5770 : *++fddir = '\0';
196 5770 : return fdpath;
197 : }
198 : return NULL;
199 : }
200 :
201 :
202 : /* Check whether all the necessary DWARF information is available. */
203 : static Dwarf *
204 5650 : valid_p (Dwarf *result)
205 : {
206 : /* We looked at all the sections. Now determine whether all the
207 : sections with debugging information we need are there.
208 :
209 : Require at least one section that can be read "standalone". */
210 5650 : if (likely (result != NULL)
211 5649 : && unlikely (result->sectiondata[IDX_debug_info] == NULL
212 : && result->sectiondata[IDX_debug_line] == NULL
213 : && result->sectiondata[IDX_debug_frame] == NULL))
214 : {
215 99 : Dwarf_Sig8_Hash_free (&result->sig8_hash);
216 99 : __libdw_seterrno (DWARF_E_NO_DWARF);
217 99 : free (result);
218 99 : result = NULL;
219 : }
220 :
221 : /* For dwarf_location_attr () we need a "fake" CU to indicate
222 : where the "fake" attribute data comes from. This is a block
223 : inside the .debug_loc or .debug_loclists section. */
224 5551 : if (result != NULL && result->sectiondata[IDX_debug_loc] != NULL)
225 : {
226 5268 : result->fake_loc_cu = (Dwarf_CU *) calloc (1, sizeof (Dwarf_CU));
227 5268 : if (unlikely (result->fake_loc_cu == NULL))
228 : {
229 0 : Dwarf_Sig8_Hash_free (&result->sig8_hash);
230 0 : __libdw_seterrno (DWARF_E_NOMEM);
231 0 : free (result);
232 0 : result = NULL;
233 : }
234 : else
235 : {
236 5268 : result->fake_loc_cu->sec_idx = IDX_debug_loc;
237 5268 : result->fake_loc_cu->dbg = result;
238 : result->fake_loc_cu->startp
239 5268 : = result->sectiondata[IDX_debug_loc]->d_buf;
240 : result->fake_loc_cu->endp
241 5268 : = (result->sectiondata[IDX_debug_loc]->d_buf
242 5268 : + result->sectiondata[IDX_debug_loc]->d_size);
243 : }
244 : }
245 :
246 5650 : if (result != NULL && result->sectiondata[IDX_debug_loclists] != NULL)
247 : {
248 45 : result->fake_loclists_cu = (Dwarf_CU *) calloc (1, sizeof (Dwarf_CU));
249 45 : if (unlikely (result->fake_loclists_cu == NULL))
250 : {
251 0 : Dwarf_Sig8_Hash_free (&result->sig8_hash);
252 0 : __libdw_seterrno (DWARF_E_NOMEM);
253 0 : free (result->fake_loc_cu);
254 0 : free (result);
255 0 : result = NULL;
256 : }
257 : else
258 : {
259 45 : result->fake_loclists_cu->sec_idx = IDX_debug_loclists;
260 45 : result->fake_loclists_cu->dbg = result;
261 : result->fake_loclists_cu->startp
262 45 : = result->sectiondata[IDX_debug_loclists]->d_buf;
263 : result->fake_loclists_cu->endp
264 45 : = (result->sectiondata[IDX_debug_loclists]->d_buf
265 45 : + result->sectiondata[IDX_debug_loclists]->d_size);
266 : }
267 : }
268 :
269 : /* For DW_OP_constx/GNU_const_index and DW_OP_addrx/GNU_addr_index
270 : the dwarf_location_attr () will need a "fake" address CU to
271 : indicate where the attribute data comes from. This is a just
272 : inside the .debug_addr section, if it exists. */
273 5650 : if (result != NULL && result->sectiondata[IDX_debug_addr] != NULL)
274 : {
275 39 : result->fake_addr_cu = (Dwarf_CU *) calloc (1, sizeof (Dwarf_CU));
276 39 : if (unlikely (result->fake_addr_cu == NULL))
277 : {
278 0 : Dwarf_Sig8_Hash_free (&result->sig8_hash);
279 0 : __libdw_seterrno (DWARF_E_NOMEM);
280 0 : free (result->fake_loc_cu);
281 0 : free (result->fake_loclists_cu);
282 0 : free (result);
283 0 : result = NULL;
284 : }
285 : else
286 : {
287 39 : result->fake_addr_cu->sec_idx = IDX_debug_addr;
288 39 : result->fake_addr_cu->dbg = result;
289 : result->fake_addr_cu->startp
290 39 : = result->sectiondata[IDX_debug_addr]->d_buf;
291 : result->fake_addr_cu->endp
292 39 : = (result->sectiondata[IDX_debug_addr]->d_buf
293 39 : + result->sectiondata[IDX_debug_addr]->d_size);
294 : }
295 : }
296 :
297 5650 : if (result != NULL)
298 5550 : result->debugdir = __libdw_debugdir (result->elf->fildes);
299 :
300 5650 : return result;
301 : }
302 :
303 :
304 : static Dwarf *
305 5650 : global_read (Dwarf *result, Elf *elf, size_t shstrndx)
306 : {
307 5650 : Elf_Scn *scn = NULL;
308 :
309 286101 : while (result != NULL && (scn = elf_nextscn (elf, scn)) != NULL)
310 274801 : result = check_section (result, shstrndx, scn, false);
311 :
312 5650 : return valid_p (result);
313 : }
314 :
315 :
316 : static Dwarf *
317 0 : scngrp_read (Dwarf *result, Elf *elf, size_t shstrndx, Elf_Scn *scngrp)
318 : {
319 : GElf_Shdr shdr_mem;
320 0 : GElf_Shdr *shdr = gelf_getshdr (scngrp, &shdr_mem);
321 0 : if (shdr == NULL)
322 : {
323 0 : Dwarf_Sig8_Hash_free (&result->sig8_hash);
324 0 : __libdw_seterrno (DWARF_E_INVALID_ELF);
325 0 : free (result);
326 0 : return NULL;
327 : }
328 :
329 0 : if ((shdr->sh_flags & SHF_COMPRESSED) != 0
330 0 : && elf_compress (scngrp, 0, 0) < 0)
331 : {
332 0 : Dwarf_Sig8_Hash_free (&result->sig8_hash);
333 0 : __libdw_seterrno (DWARF_E_COMPRESSED_ERROR);
334 0 : free (result);
335 0 : return NULL;
336 : }
337 :
338 : /* SCNGRP is the section descriptor for a section group which might
339 : contain debug sections. */
340 0 : Elf_Data *data = elf_getdata (scngrp, NULL);
341 0 : if (data == NULL)
342 : {
343 : /* We cannot read the section content. Fail! */
344 0 : Dwarf_Sig8_Hash_free (&result->sig8_hash);
345 0 : free (result);
346 0 : return NULL;
347 : }
348 :
349 : /* The content of the section is a number of 32-bit words which
350 : represent section indices. The first word is a flag word. */
351 0 : Elf32_Word *scnidx = (Elf32_Word *) data->d_buf;
352 : size_t cnt;
353 0 : for (cnt = 1; cnt * sizeof (Elf32_Word) <= data->d_size; ++cnt)
354 : {
355 0 : Elf_Scn *scn = elf_getscn (elf, scnidx[cnt]);
356 0 : if (scn == NULL)
357 : {
358 : /* A section group refers to a non-existing section. Should
359 : never happen. */
360 0 : Dwarf_Sig8_Hash_free (&result->sig8_hash);
361 0 : __libdw_seterrno (DWARF_E_INVALID_ELF);
362 0 : free (result);
363 0 : return NULL;
364 : }
365 :
366 0 : result = check_section (result, shstrndx, scn, true);
367 0 : if (result == NULL)
368 : break;
369 : }
370 :
371 0 : return valid_p (result);
372 : }
373 :
374 :
375 : Dwarf *
376 5650 : dwarf_begin_elf (Elf *elf, Dwarf_Cmd cmd, Elf_Scn *scngrp)
377 : {
378 : GElf_Ehdr *ehdr;
379 : GElf_Ehdr ehdr_mem;
380 :
381 : /* Get the ELF header of the file. We need various pieces of
382 : information from it. */
383 5650 : ehdr = gelf_getehdr (elf, &ehdr_mem);
384 5650 : if (ehdr == NULL)
385 : {
386 0 : if (elf_kind (elf) != ELF_K_ELF)
387 0 : __libdw_seterrno (DWARF_E_NOELF);
388 : else
389 0 : __libdw_seterrno (DWARF_E_GETEHDR_ERROR);
390 :
391 : return NULL;
392 : }
393 :
394 :
395 : /* Default memory allocation size. */
396 5650 : size_t mem_default_size = sysconf (_SC_PAGESIZE) - 4 * sizeof (void *);
397 5650 : assert (sizeof (struct Dwarf) < mem_default_size);
398 :
399 : /* Allocate the data structure. */
400 5650 : Dwarf *result = (Dwarf *) calloc (1, sizeof (Dwarf) + mem_default_size);
401 5650 : if (unlikely (result == NULL)
402 5650 : || unlikely (Dwarf_Sig8_Hash_init (&result->sig8_hash, 11) < 0))
403 : {
404 0 : free (result);
405 0 : __libdw_seterrno (DWARF_E_NOMEM);
406 0 : return NULL;
407 : }
408 :
409 : /* Fill in some values. */
410 5650 : if ((BYTE_ORDER == LITTLE_ENDIAN && ehdr->e_ident[EI_DATA] == ELFDATA2MSB)
411 : || (BYTE_ORDER == BIG_ENDIAN && ehdr->e_ident[EI_DATA] == ELFDATA2LSB))
412 78 : result->other_byte_order = true;
413 :
414 5650 : result->elf = elf;
415 5650 : result->alt_fd = -1;
416 :
417 : /* Initialize the memory handling. */
418 5650 : result->mem_default_size = mem_default_size;
419 5650 : result->oom_handler = __libdw_oom;
420 5650 : result->mem_tail = (struct libdw_memblock *) (result + 1);
421 5650 : result->mem_tail->size = (result->mem_default_size
422 5650 : - offsetof (struct libdw_memblock, mem));
423 5650 : result->mem_tail->remaining = result->mem_tail->size;
424 5650 : result->mem_tail->prev = NULL;
425 :
426 5650 : if (cmd == DWARF_C_READ || cmd == DWARF_C_RDWR)
427 : {
428 : /* All sections are recognized by name, so pass the section header
429 : string index along to easily get the section names. */
430 : size_t shstrndx;
431 5650 : if (elf_getshdrstrndx (elf, &shstrndx) != 0)
432 : {
433 0 : Dwarf_Sig8_Hash_free (&result->sig8_hash);
434 0 : __libdw_seterrno (DWARF_E_INVALID_ELF);
435 0 : free (result);
436 0 : return NULL;
437 : }
438 :
439 : /* If the caller provides a section group we get the DWARF
440 : sections only from this setion group. Otherwise we search
441 : for the first section with the required name. Further
442 : sections with the name are ignored. The DWARF specification
443 : does not really say this is allowed. */
444 5650 : if (scngrp == NULL)
445 5650 : return global_read (result, elf, shstrndx);
446 : else
447 0 : return scngrp_read (result, elf, shstrndx, scngrp);
448 : }
449 0 : else if (cmd == DWARF_C_WRITE)
450 : {
451 0 : Dwarf_Sig8_Hash_free (&result->sig8_hash);
452 0 : __libdw_seterrno (DWARF_E_UNIMPL);
453 0 : free (result);
454 0 : return NULL;
455 : }
456 :
457 0 : Dwarf_Sig8_Hash_free (&result->sig8_hash);
458 0 : __libdw_seterrno (DWARF_E_INVALID_CMD);
459 0 : free (result);
460 0 : return NULL;
461 : }
462 : INTDEF(dwarf_begin_elf)
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