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Commit | Line | Data |
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442f04c3 JP |
1 | /* |
2 | * elf.c - ELF access library | |
3 | * | |
4 | * Adapted from kpatch (https://github.com/dynup/kpatch): | |
5 | * Copyright (C) 2013-2015 Josh Poimboeuf <jpoimboe@redhat.com> | |
6 | * Copyright (C) 2014 Seth Jennings <sjenning@redhat.com> | |
7 | * | |
8 | * This program is free software; you can redistribute it and/or | |
9 | * modify it under the terms of the GNU General Public License | |
10 | * as published by the Free Software Foundation; either version 2 | |
11 | * of the License, or (at your option) any later version. | |
12 | * | |
13 | * This program is distributed in the hope that it will be useful, | |
14 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
15 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
16 | * GNU General Public License for more details. | |
17 | * | |
18 | * You should have received a copy of the GNU General Public License | |
19 | * along with this program; if not, see <http://www.gnu.org/licenses/>. | |
20 | */ | |
21 | ||
22 | #include <sys/types.h> | |
23 | #include <sys/stat.h> | |
24 | #include <fcntl.h> | |
25 | #include <stdio.h> | |
26 | #include <stdlib.h> | |
27 | #include <string.h> | |
28 | #include <unistd.h> | |
29 | ||
30 | #include "elf.h" | |
31 | #include "warn.h" | |
32 | ||
33 | struct section *find_section_by_name(struct elf *elf, const char *name) | |
34 | { | |
35 | struct section *sec; | |
36 | ||
37 | list_for_each_entry(sec, &elf->sections, list) | |
38 | if (!strcmp(sec->name, name)) | |
39 | return sec; | |
40 | ||
41 | return NULL; | |
42 | } | |
43 | ||
44 | static struct section *find_section_by_index(struct elf *elf, | |
45 | unsigned int idx) | |
46 | { | |
47 | struct section *sec; | |
48 | ||
49 | list_for_each_entry(sec, &elf->sections, list) | |
50 | if (sec->idx == idx) | |
51 | return sec; | |
52 | ||
53 | return NULL; | |
54 | } | |
55 | ||
56 | static struct symbol *find_symbol_by_index(struct elf *elf, unsigned int idx) | |
57 | { | |
58 | struct section *sec; | |
59 | struct symbol *sym; | |
60 | ||
61 | list_for_each_entry(sec, &elf->sections, list) | |
042ba73f | 62 | hash_for_each_possible(sec->symbol_hash, sym, hash, idx) |
442f04c3 JP |
63 | if (sym->idx == idx) |
64 | return sym; | |
65 | ||
66 | return NULL; | |
67 | } | |
68 | ||
69 | struct symbol *find_symbol_by_offset(struct section *sec, unsigned long offset) | |
70 | { | |
71 | struct symbol *sym; | |
72 | ||
a196e171 | 73 | list_for_each_entry(sym, &sec->symbol_list, list) |
442f04c3 JP |
74 | if (sym->type != STT_SECTION && |
75 | sym->offset == offset) | |
76 | return sym; | |
77 | ||
78 | return NULL; | |
79 | } | |
80 | ||
5c51f4ae JP |
81 | struct symbol *find_symbol_containing(struct section *sec, unsigned long offset) |
82 | { | |
83 | struct symbol *sym; | |
84 | ||
85 | list_for_each_entry(sym, &sec->symbol_list, list) | |
86 | if (sym->type != STT_SECTION && | |
87 | offset >= sym->offset && offset < sym->offset + sym->len) | |
88 | return sym; | |
89 | ||
90 | return NULL; | |
91 | } | |
92 | ||
442f04c3 JP |
93 | struct rela *find_rela_by_dest_range(struct section *sec, unsigned long offset, |
94 | unsigned int len) | |
95 | { | |
96 | struct rela *rela; | |
042ba73f | 97 | unsigned long o; |
442f04c3 JP |
98 | |
99 | if (!sec->rela) | |
100 | return NULL; | |
101 | ||
042ba73f JP |
102 | for (o = offset; o < offset + len; o++) |
103 | hash_for_each_possible(sec->rela->rela_hash, rela, hash, o) | |
104 | if (rela->offset == o) | |
105 | return rela; | |
442f04c3 JP |
106 | |
107 | return NULL; | |
108 | } | |
109 | ||
110 | struct rela *find_rela_by_dest(struct section *sec, unsigned long offset) | |
111 | { | |
112 | return find_rela_by_dest_range(sec, offset, 1); | |
113 | } | |
114 | ||
115 | struct symbol *find_containing_func(struct section *sec, unsigned long offset) | |
116 | { | |
117 | struct symbol *func; | |
118 | ||
a196e171 | 119 | list_for_each_entry(func, &sec->symbol_list, list) |
442f04c3 JP |
120 | if (func->type == STT_FUNC && offset >= func->offset && |
121 | offset < func->offset + func->len) | |
122 | return func; | |
123 | ||
124 | return NULL; | |
125 | } | |
126 | ||
127 | static int read_sections(struct elf *elf) | |
128 | { | |
129 | Elf_Scn *s = NULL; | |
130 | struct section *sec; | |
131 | size_t shstrndx, sections_nr; | |
132 | int i; | |
133 | ||
134 | if (elf_getshdrnum(elf->elf, §ions_nr)) { | |
baa41469 | 135 | WARN_ELF("elf_getshdrnum"); |
442f04c3 JP |
136 | return -1; |
137 | } | |
138 | ||
139 | if (elf_getshdrstrndx(elf->elf, &shstrndx)) { | |
baa41469 | 140 | WARN_ELF("elf_getshdrstrndx"); |
442f04c3 JP |
141 | return -1; |
142 | } | |
143 | ||
144 | for (i = 0; i < sections_nr; i++) { | |
145 | sec = malloc(sizeof(*sec)); | |
146 | if (!sec) { | |
147 | perror("malloc"); | |
148 | return -1; | |
149 | } | |
150 | memset(sec, 0, sizeof(*sec)); | |
151 | ||
a196e171 JP |
152 | INIT_LIST_HEAD(&sec->symbol_list); |
153 | INIT_LIST_HEAD(&sec->rela_list); | |
042ba73f JP |
154 | hash_init(sec->rela_hash); |
155 | hash_init(sec->symbol_hash); | |
442f04c3 JP |
156 | |
157 | list_add_tail(&sec->list, &elf->sections); | |
158 | ||
159 | s = elf_getscn(elf->elf, i); | |
160 | if (!s) { | |
baa41469 | 161 | WARN_ELF("elf_getscn"); |
442f04c3 JP |
162 | return -1; |
163 | } | |
164 | ||
165 | sec->idx = elf_ndxscn(s); | |
166 | ||
167 | if (!gelf_getshdr(s, &sec->sh)) { | |
baa41469 | 168 | WARN_ELF("gelf_getshdr"); |
442f04c3 JP |
169 | return -1; |
170 | } | |
171 | ||
172 | sec->name = elf_strptr(elf->elf, shstrndx, sec->sh.sh_name); | |
173 | if (!sec->name) { | |
baa41469 | 174 | WARN_ELF("elf_strptr"); |
442f04c3 JP |
175 | return -1; |
176 | } | |
177 | ||
df968c93 PV |
178 | if (sec->sh.sh_size != 0) { |
179 | sec->data = elf_getdata(s, NULL); | |
180 | if (!sec->data) { | |
181 | WARN_ELF("elf_getdata"); | |
182 | return -1; | |
183 | } | |
184 | if (sec->data->d_off != 0 || | |
185 | sec->data->d_size != sec->sh.sh_size) { | |
186 | WARN("unexpected data attributes for %s", | |
187 | sec->name); | |
188 | return -1; | |
189 | } | |
442f04c3 | 190 | } |
df968c93 | 191 | sec->len = sec->sh.sh_size; |
442f04c3 JP |
192 | } |
193 | ||
194 | /* sanity check, one more call to elf_nextscn() should return NULL */ | |
195 | if (elf_nextscn(elf->elf, s)) { | |
196 | WARN("section entry mismatch"); | |
197 | return -1; | |
198 | } | |
199 | ||
200 | return 0; | |
201 | } | |
202 | ||
203 | static int read_symbols(struct elf *elf) | |
204 | { | |
205 | struct section *symtab; | |
206 | struct symbol *sym; | |
207 | struct list_head *entry, *tmp; | |
208 | int symbols_nr, i; | |
209 | ||
210 | symtab = find_section_by_name(elf, ".symtab"); | |
211 | if (!symtab) { | |
212 | WARN("missing symbol table"); | |
213 | return -1; | |
214 | } | |
215 | ||
216 | symbols_nr = symtab->sh.sh_size / symtab->sh.sh_entsize; | |
217 | ||
218 | for (i = 0; i < symbols_nr; i++) { | |
219 | sym = malloc(sizeof(*sym)); | |
220 | if (!sym) { | |
221 | perror("malloc"); | |
222 | return -1; | |
223 | } | |
224 | memset(sym, 0, sizeof(*sym)); | |
225 | ||
226 | sym->idx = i; | |
227 | ||
baa41469 JP |
228 | if (!gelf_getsym(symtab->data, i, &sym->sym)) { |
229 | WARN_ELF("gelf_getsym"); | |
442f04c3 JP |
230 | goto err; |
231 | } | |
232 | ||
233 | sym->name = elf_strptr(elf->elf, symtab->sh.sh_link, | |
234 | sym->sym.st_name); | |
235 | if (!sym->name) { | |
baa41469 | 236 | WARN_ELF("elf_strptr"); |
442f04c3 JP |
237 | goto err; |
238 | } | |
239 | ||
240 | sym->type = GELF_ST_TYPE(sym->sym.st_info); | |
241 | sym->bind = GELF_ST_BIND(sym->sym.st_info); | |
242 | ||
243 | if (sym->sym.st_shndx > SHN_UNDEF && | |
244 | sym->sym.st_shndx < SHN_LORESERVE) { | |
245 | sym->sec = find_section_by_index(elf, | |
246 | sym->sym.st_shndx); | |
247 | if (!sym->sec) { | |
248 | WARN("couldn't find section for symbol %s", | |
249 | sym->name); | |
250 | goto err; | |
251 | } | |
252 | if (sym->type == STT_SECTION) { | |
253 | sym->name = sym->sec->name; | |
254 | sym->sec->sym = sym; | |
255 | } | |
256 | } else | |
257 | sym->sec = find_section_by_index(elf, 0); | |
258 | ||
259 | sym->offset = sym->sym.st_value; | |
260 | sym->len = sym->sym.st_size; | |
261 | ||
262 | /* sorted insert into a per-section list */ | |
a196e171 JP |
263 | entry = &sym->sec->symbol_list; |
264 | list_for_each_prev(tmp, &sym->sec->symbol_list) { | |
442f04c3 JP |
265 | struct symbol *s; |
266 | ||
267 | s = list_entry(tmp, struct symbol, list); | |
268 | ||
269 | if (sym->offset > s->offset) { | |
270 | entry = tmp; | |
271 | break; | |
272 | } | |
273 | ||
274 | if (sym->offset == s->offset && sym->len >= s->len) { | |
275 | entry = tmp; | |
276 | break; | |
277 | } | |
278 | } | |
279 | list_add(&sym->list, entry); | |
042ba73f | 280 | hash_add(sym->sec->symbol_hash, &sym->hash, sym->idx); |
442f04c3 JP |
281 | } |
282 | ||
283 | return 0; | |
284 | ||
285 | err: | |
286 | free(sym); | |
287 | return -1; | |
288 | } | |
289 | ||
290 | static int read_relas(struct elf *elf) | |
291 | { | |
292 | struct section *sec; | |
293 | struct rela *rela; | |
294 | int i; | |
295 | unsigned int symndx; | |
296 | ||
297 | list_for_each_entry(sec, &elf->sections, list) { | |
298 | if (sec->sh.sh_type != SHT_RELA) | |
299 | continue; | |
300 | ||
301 | sec->base = find_section_by_name(elf, sec->name + 5); | |
302 | if (!sec->base) { | |
303 | WARN("can't find base section for rela section %s", | |
304 | sec->name); | |
305 | return -1; | |
306 | } | |
307 | ||
308 | sec->base->rela = sec; | |
309 | ||
310 | for (i = 0; i < sec->sh.sh_size / sec->sh.sh_entsize; i++) { | |
311 | rela = malloc(sizeof(*rela)); | |
312 | if (!rela) { | |
313 | perror("malloc"); | |
314 | return -1; | |
315 | } | |
316 | memset(rela, 0, sizeof(*rela)); | |
317 | ||
baa41469 JP |
318 | if (!gelf_getrela(sec->data, i, &rela->rela)) { |
319 | WARN_ELF("gelf_getrela"); | |
442f04c3 JP |
320 | return -1; |
321 | } | |
322 | ||
323 | rela->type = GELF_R_TYPE(rela->rela.r_info); | |
324 | rela->addend = rela->rela.r_addend; | |
325 | rela->offset = rela->rela.r_offset; | |
326 | symndx = GELF_R_SYM(rela->rela.r_info); | |
327 | rela->sym = find_symbol_by_index(elf, symndx); | |
328 | if (!rela->sym) { | |
329 | WARN("can't find rela entry symbol %d for %s", | |
330 | symndx, sec->name); | |
331 | return -1; | |
332 | } | |
042ba73f JP |
333 | |
334 | list_add_tail(&rela->list, &sec->rela_list); | |
335 | hash_add(sec->rela_hash, &rela->hash, rela->offset); | |
336 | ||
442f04c3 JP |
337 | } |
338 | } | |
339 | ||
340 | return 0; | |
341 | } | |
342 | ||
627fce14 | 343 | struct elf *elf_open(const char *name, int flags) |
442f04c3 JP |
344 | { |
345 | struct elf *elf; | |
627fce14 | 346 | Elf_Cmd cmd; |
442f04c3 JP |
347 | |
348 | elf_version(EV_CURRENT); | |
349 | ||
350 | elf = malloc(sizeof(*elf)); | |
351 | if (!elf) { | |
352 | perror("malloc"); | |
353 | return NULL; | |
354 | } | |
355 | memset(elf, 0, sizeof(*elf)); | |
356 | ||
357 | INIT_LIST_HEAD(&elf->sections); | |
358 | ||
627fce14 | 359 | elf->fd = open(name, flags); |
442f04c3 JP |
360 | if (elf->fd == -1) { |
361 | perror("open"); | |
362 | goto err; | |
363 | } | |
364 | ||
627fce14 JP |
365 | if ((flags & O_ACCMODE) == O_RDONLY) |
366 | cmd = ELF_C_READ_MMAP; | |
367 | else if ((flags & O_ACCMODE) == O_RDWR) | |
368 | cmd = ELF_C_RDWR; | |
369 | else /* O_WRONLY */ | |
370 | cmd = ELF_C_WRITE; | |
371 | ||
372 | elf->elf = elf_begin(elf->fd, cmd, NULL); | |
442f04c3 | 373 | if (!elf->elf) { |
baa41469 | 374 | WARN_ELF("elf_begin"); |
442f04c3 JP |
375 | goto err; |
376 | } | |
377 | ||
378 | if (!gelf_getehdr(elf->elf, &elf->ehdr)) { | |
baa41469 | 379 | WARN_ELF("gelf_getehdr"); |
442f04c3 JP |
380 | goto err; |
381 | } | |
382 | ||
383 | if (read_sections(elf)) | |
384 | goto err; | |
385 | ||
386 | if (read_symbols(elf)) | |
387 | goto err; | |
388 | ||
389 | if (read_relas(elf)) | |
390 | goto err; | |
391 | ||
392 | return elf; | |
393 | ||
394 | err: | |
395 | elf_close(elf); | |
396 | return NULL; | |
397 | } | |
398 | ||
627fce14 JP |
399 | struct section *elf_create_section(struct elf *elf, const char *name, |
400 | size_t entsize, int nr) | |
401 | { | |
402 | struct section *sec, *shstrtab; | |
403 | size_t size = entsize * nr; | |
404 | struct Elf_Scn *s; | |
405 | Elf_Data *data; | |
406 | ||
407 | sec = malloc(sizeof(*sec)); | |
408 | if (!sec) { | |
409 | perror("malloc"); | |
410 | return NULL; | |
411 | } | |
412 | memset(sec, 0, sizeof(*sec)); | |
413 | ||
414 | INIT_LIST_HEAD(&sec->symbol_list); | |
415 | INIT_LIST_HEAD(&sec->rela_list); | |
416 | hash_init(sec->rela_hash); | |
417 | hash_init(sec->symbol_hash); | |
418 | ||
419 | list_add_tail(&sec->list, &elf->sections); | |
420 | ||
421 | s = elf_newscn(elf->elf); | |
422 | if (!s) { | |
423 | WARN_ELF("elf_newscn"); | |
424 | return NULL; | |
425 | } | |
426 | ||
427 | sec->name = strdup(name); | |
428 | if (!sec->name) { | |
429 | perror("strdup"); | |
430 | return NULL; | |
431 | } | |
432 | ||
433 | sec->idx = elf_ndxscn(s); | |
434 | sec->len = size; | |
435 | sec->changed = true; | |
436 | ||
437 | sec->data = elf_newdata(s); | |
438 | if (!sec->data) { | |
439 | WARN_ELF("elf_newdata"); | |
440 | return NULL; | |
441 | } | |
442 | ||
443 | sec->data->d_size = size; | |
444 | sec->data->d_align = 1; | |
445 | ||
446 | if (size) { | |
447 | sec->data->d_buf = malloc(size); | |
448 | if (!sec->data->d_buf) { | |
449 | perror("malloc"); | |
450 | return NULL; | |
451 | } | |
452 | memset(sec->data->d_buf, 0, size); | |
453 | } | |
454 | ||
455 | if (!gelf_getshdr(s, &sec->sh)) { | |
456 | WARN_ELF("gelf_getshdr"); | |
457 | return NULL; | |
458 | } | |
459 | ||
460 | sec->sh.sh_size = size; | |
461 | sec->sh.sh_entsize = entsize; | |
462 | sec->sh.sh_type = SHT_PROGBITS; | |
463 | sec->sh.sh_addralign = 1; | |
464 | sec->sh.sh_flags = SHF_ALLOC; | |
465 | ||
466 | ||
467 | /* Add section name to .shstrtab */ | |
468 | shstrtab = find_section_by_name(elf, ".shstrtab"); | |
469 | if (!shstrtab) { | |
470 | WARN("can't find .shstrtab section"); | |
471 | return NULL; | |
472 | } | |
473 | ||
474 | s = elf_getscn(elf->elf, shstrtab->idx); | |
475 | if (!s) { | |
476 | WARN_ELF("elf_getscn"); | |
477 | return NULL; | |
478 | } | |
479 | ||
480 | data = elf_newdata(s); | |
481 | if (!data) { | |
482 | WARN_ELF("elf_newdata"); | |
483 | return NULL; | |
484 | } | |
485 | ||
486 | data->d_buf = sec->name; | |
487 | data->d_size = strlen(name) + 1; | |
488 | data->d_align = 1; | |
489 | ||
490 | sec->sh.sh_name = shstrtab->len; | |
491 | ||
492 | shstrtab->len += strlen(name) + 1; | |
493 | shstrtab->changed = true; | |
494 | ||
495 | return sec; | |
496 | } | |
497 | ||
498 | struct section *elf_create_rela_section(struct elf *elf, struct section *base) | |
499 | { | |
500 | char *relaname; | |
501 | struct section *sec; | |
502 | ||
503 | relaname = malloc(strlen(base->name) + strlen(".rela") + 1); | |
504 | if (!relaname) { | |
505 | perror("malloc"); | |
506 | return NULL; | |
507 | } | |
508 | strcpy(relaname, ".rela"); | |
509 | strcat(relaname, base->name); | |
510 | ||
511 | sec = elf_create_section(elf, relaname, sizeof(GElf_Rela), 0); | |
0998b7a0 | 512 | free(relaname); |
627fce14 JP |
513 | if (!sec) |
514 | return NULL; | |
515 | ||
516 | base->rela = sec; | |
517 | sec->base = base; | |
518 | ||
519 | sec->sh.sh_type = SHT_RELA; | |
520 | sec->sh.sh_addralign = 8; | |
521 | sec->sh.sh_link = find_section_by_name(elf, ".symtab")->idx; | |
522 | sec->sh.sh_info = base->idx; | |
523 | sec->sh.sh_flags = SHF_INFO_LINK; | |
524 | ||
525 | return sec; | |
526 | } | |
527 | ||
528 | int elf_rebuild_rela_section(struct section *sec) | |
529 | { | |
530 | struct rela *rela; | |
531 | int nr, idx = 0, size; | |
532 | GElf_Rela *relas; | |
533 | ||
534 | nr = 0; | |
535 | list_for_each_entry(rela, &sec->rela_list, list) | |
536 | nr++; | |
537 | ||
538 | size = nr * sizeof(*relas); | |
539 | relas = malloc(size); | |
540 | if (!relas) { | |
541 | perror("malloc"); | |
542 | return -1; | |
543 | } | |
544 | ||
545 | sec->data->d_buf = relas; | |
546 | sec->data->d_size = size; | |
547 | ||
548 | sec->sh.sh_size = size; | |
549 | ||
550 | idx = 0; | |
551 | list_for_each_entry(rela, &sec->rela_list, list) { | |
552 | relas[idx].r_offset = rela->offset; | |
553 | relas[idx].r_addend = rela->addend; | |
554 | relas[idx].r_info = GELF_R_INFO(rela->sym->idx, rela->type); | |
555 | idx++; | |
556 | } | |
557 | ||
558 | return 0; | |
559 | } | |
560 | ||
561 | int elf_write(struct elf *elf) | |
562 | { | |
563 | struct section *sec; | |
564 | Elf_Scn *s; | |
565 | ||
97dab2ae | 566 | /* Update section headers for changed sections: */ |
627fce14 JP |
567 | list_for_each_entry(sec, &elf->sections, list) { |
568 | if (sec->changed) { | |
569 | s = elf_getscn(elf->elf, sec->idx); | |
570 | if (!s) { | |
571 | WARN_ELF("elf_getscn"); | |
572 | return -1; | |
573 | } | |
97dab2ae | 574 | if (!gelf_update_shdr(s, &sec->sh)) { |
627fce14 JP |
575 | WARN_ELF("gelf_update_shdr"); |
576 | return -1; | |
577 | } | |
578 | } | |
579 | } | |
580 | ||
97dab2ae JP |
581 | /* Make sure the new section header entries get updated properly. */ |
582 | elf_flagelf(elf->elf, ELF_C_SET, ELF_F_DIRTY); | |
583 | ||
584 | /* Write all changes to the file. */ | |
627fce14 JP |
585 | if (elf_update(elf->elf, ELF_C_WRITE) < 0) { |
586 | WARN_ELF("elf_update"); | |
587 | return -1; | |
588 | } | |
589 | ||
590 | return 0; | |
591 | } | |
592 | ||
442f04c3 JP |
593 | void elf_close(struct elf *elf) |
594 | { | |
595 | struct section *sec, *tmpsec; | |
596 | struct symbol *sym, *tmpsym; | |
597 | struct rela *rela, *tmprela; | |
598 | ||
baa41469 JP |
599 | if (elf->elf) |
600 | elf_end(elf->elf); | |
601 | ||
602 | if (elf->fd > 0) | |
603 | close(elf->fd); | |
604 | ||
442f04c3 | 605 | list_for_each_entry_safe(sec, tmpsec, &elf->sections, list) { |
a196e171 | 606 | list_for_each_entry_safe(sym, tmpsym, &sec->symbol_list, list) { |
442f04c3 | 607 | list_del(&sym->list); |
042ba73f | 608 | hash_del(&sym->hash); |
442f04c3 JP |
609 | free(sym); |
610 | } | |
a196e171 | 611 | list_for_each_entry_safe(rela, tmprela, &sec->rela_list, list) { |
442f04c3 | 612 | list_del(&rela->list); |
042ba73f | 613 | hash_del(&rela->hash); |
442f04c3 JP |
614 | free(rela); |
615 | } | |
616 | list_del(&sec->list); | |
617 | free(sec); | |
618 | } | |
baa41469 | 619 | |
442f04c3 JP |
620 | free(elf); |
621 | } |