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1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * elf.c - ELF access library
4 *
5 * Adapted from kpatch (https://github.com/dynup/kpatch):
6 * Copyright (C) 2013-2015 Josh Poimboeuf <jpoimboe@redhat.com>
7 * Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>
8 */
9
10#include <sys/types.h>
11#include <sys/stat.h>
12#include <sys/mman.h>
13#include <fcntl.h>
14#include <stdio.h>
15#include <stdlib.h>
16#include <string.h>
17#include <unistd.h>
18#include <errno.h>
19#include <objtool/builtin.h>
20
21#include <objtool/elf.h>
22#include <objtool/warn.h>
23
24#define MAX_NAME_LEN 128
25
26static inline u32 str_hash(const char *str)
27{
28 return jhash(str, strlen(str), 0);
29}
30
31#define __elf_table(name) (elf->name##_hash)
32#define __elf_bits(name) (elf->name##_bits)
33
34#define elf_hash_add(name, node, key) \
35 hlist_add_head(node, &__elf_table(name)[hash_min(key, __elf_bits(name))])
36
37#define elf_hash_for_each_possible(name, obj, member, key) \
38 hlist_for_each_entry(obj, &__elf_table(name)[hash_min(key, __elf_bits(name))], member)
39
40#define elf_alloc_hash(name, size) \
41({ \
42 __elf_bits(name) = max(10, ilog2(size)); \
43 __elf_table(name) = mmap(NULL, sizeof(struct hlist_head) << __elf_bits(name), \
44 PROT_READ|PROT_WRITE, \
45 MAP_PRIVATE|MAP_ANON, -1, 0); \
46 if (__elf_table(name) == (void *)-1L) { \
47 WARN("mmap fail " #name); \
48 __elf_table(name) = NULL; \
49 } \
50 __elf_table(name); \
51})
52
53static bool symbol_to_offset(struct rb_node *a, const struct rb_node *b)
54{
55 struct symbol *sa = rb_entry(a, struct symbol, node);
56 struct symbol *sb = rb_entry(b, struct symbol, node);
57
58 if (sa->offset < sb->offset)
59 return true;
60 if (sa->offset > sb->offset)
61 return false;
62
63 if (sa->len < sb->len)
64 return true;
65 if (sa->len > sb->len)
66 return false;
67
68 sa->alias = sb;
69
70 return false;
71}
72
73static int symbol_by_offset(const void *key, const struct rb_node *node)
74{
75 const struct symbol *s = rb_entry(node, struct symbol, node);
76 const unsigned long *o = key;
77
78 if (*o < s->offset)
79 return -1;
80 if (*o >= s->offset + s->len)
81 return 1;
82
83 return 0;
84}
85
86struct section *find_section_by_name(const struct elf *elf, const char *name)
87{
88 struct section *sec;
89
90 elf_hash_for_each_possible(section_name, sec, name_hash, str_hash(name)) {
91 if (!strcmp(sec->name, name))
92 return sec;
93 }
94
95 return NULL;
96}
97
98static struct section *find_section_by_index(struct elf *elf,
99 unsigned int idx)
100{
101 struct section *sec;
102
103 elf_hash_for_each_possible(section, sec, hash, idx) {
104 if (sec->idx == idx)
105 return sec;
106 }
107
108 return NULL;
109}
110
111static struct symbol *find_symbol_by_index(struct elf *elf, unsigned int idx)
112{
113 struct symbol *sym;
114
115 elf_hash_for_each_possible(symbol, sym, hash, idx) {
116 if (sym->idx == idx)
117 return sym;
118 }
119
120 return NULL;
121}
122
123struct symbol *find_symbol_by_offset(struct section *sec, unsigned long offset)
124{
125 struct rb_node *node;
126
127 rb_for_each(node, &offset, &sec->symbol_tree, symbol_by_offset) {
128 struct symbol *s = rb_entry(node, struct symbol, node);
129
130 if (s->offset == offset && s->type != STT_SECTION)
131 return s;
132 }
133
134 return NULL;
135}
136
137struct symbol *find_func_by_offset(struct section *sec, unsigned long offset)
138{
139 struct rb_node *node;
140
141 rb_for_each(node, &offset, &sec->symbol_tree, symbol_by_offset) {
142 struct symbol *s = rb_entry(node, struct symbol, node);
143
144 if (s->offset == offset && s->type == STT_FUNC)
145 return s;
146 }
147
148 return NULL;
149}
150
151struct symbol *find_symbol_containing(const struct section *sec, unsigned long offset)
152{
153 struct rb_node *node;
154
155 rb_for_each(node, &offset, &sec->symbol_tree, symbol_by_offset) {
156 struct symbol *s = rb_entry(node, struct symbol, node);
157
158 if (s->type != STT_SECTION)
159 return s;
160 }
161
162 return NULL;
163}
164
165struct symbol *find_func_containing(struct section *sec, unsigned long offset)
166{
167 struct rb_node *node;
168
169 rb_for_each(node, &offset, &sec->symbol_tree, symbol_by_offset) {
170 struct symbol *s = rb_entry(node, struct symbol, node);
171
172 if (s->type == STT_FUNC)
173 return s;
174 }
175
176 return NULL;
177}
178
179struct symbol *find_symbol_by_name(const struct elf *elf, const char *name)
180{
181 struct symbol *sym;
182
183 elf_hash_for_each_possible(symbol_name, sym, name_hash, str_hash(name)) {
184 if (!strcmp(sym->name, name))
185 return sym;
186 }
187
188 return NULL;
189}
190
191struct reloc *find_reloc_by_dest_range(const struct elf *elf, struct section *sec,
192 unsigned long offset, unsigned int len)
193{
194 struct reloc *reloc, *r = NULL;
195 unsigned long o;
196
197 if (!sec->reloc)
198 return NULL;
199
200 sec = sec->reloc;
201
202 for_offset_range(o, offset, offset + len) {
203 elf_hash_for_each_possible(reloc, reloc, hash,
204 sec_offset_hash(sec, o)) {
205 if (reloc->sec != sec)
206 continue;
207
208 if (reloc->offset >= offset && reloc->offset < offset + len) {
209 if (!r || reloc->offset < r->offset)
210 r = reloc;
211 }
212 }
213 if (r)
214 return r;
215 }
216
217 return NULL;
218}
219
220struct reloc *find_reloc_by_dest(const struct elf *elf, struct section *sec, unsigned long offset)
221{
222 return find_reloc_by_dest_range(elf, sec, offset, 1);
223}
224
225static int read_sections(struct elf *elf)
226{
227 Elf_Scn *s = NULL;
228 struct section *sec;
229 size_t shstrndx, sections_nr;
230 int i;
231
232 if (elf_getshdrnum(elf->elf, §ions_nr)) {
233 WARN_ELF("elf_getshdrnum");
234 return -1;
235 }
236
237 if (elf_getshdrstrndx(elf->elf, &shstrndx)) {
238 WARN_ELF("elf_getshdrstrndx");
239 return -1;
240 }
241
242 if (!elf_alloc_hash(section, sections_nr) ||
243 !elf_alloc_hash(section_name, sections_nr))
244 return -1;
245
246 for (i = 0; i < sections_nr; i++) {
247 sec = malloc(sizeof(*sec));
248 if (!sec) {
249 perror("malloc");
250 return -1;
251 }
252 memset(sec, 0, sizeof(*sec));
253
254 INIT_LIST_HEAD(&sec->symbol_list);
255 INIT_LIST_HEAD(&sec->reloc_list);
256
257 s = elf_getscn(elf->elf, i);
258 if (!s) {
259 WARN_ELF("elf_getscn");
260 return -1;
261 }
262
263 sec->idx = elf_ndxscn(s);
264
265 if (!gelf_getshdr(s, &sec->sh)) {
266 WARN_ELF("gelf_getshdr");
267 return -1;
268 }
269
270 sec->name = elf_strptr(elf->elf, shstrndx, sec->sh.sh_name);
271 if (!sec->name) {
272 WARN_ELF("elf_strptr");
273 return -1;
274 }
275
276 if (sec->sh.sh_size != 0) {
277 sec->data = elf_getdata(s, NULL);
278 if (!sec->data) {
279 WARN_ELF("elf_getdata");
280 return -1;
281 }
282 if (sec->data->d_off != 0 ||
283 sec->data->d_size != sec->sh.sh_size) {
284 WARN("unexpected data attributes for %s",
285 sec->name);
286 return -1;
287 }
288 }
289 sec->len = sec->sh.sh_size;
290
291 if (sec->sh.sh_flags & SHF_EXECINSTR)
292 elf->text_size += sec->len;
293
294 list_add_tail(&sec->list, &elf->sections);
295 elf_hash_add(section, &sec->hash, sec->idx);
296 elf_hash_add(section_name, &sec->name_hash, str_hash(sec->name));
297 }
298
299 if (stats) {
300 printf("nr_sections: %lu\n", (unsigned long)sections_nr);
301 printf("section_bits: %d\n", elf->section_bits);
302 }
303
304 /* sanity check, one more call to elf_nextscn() should return NULL */
305 if (elf_nextscn(elf->elf, s)) {
306 WARN("section entry mismatch");
307 return -1;
308 }
309
310 return 0;
311}
312
313static void elf_add_symbol(struct elf *elf, struct symbol *sym)
314{
315 struct list_head *entry;
316 struct rb_node *pnode;
317
318 sym->type = GELF_ST_TYPE(sym->sym.st_info);
319 sym->bind = GELF_ST_BIND(sym->sym.st_info);
320
321 sym->offset = sym->sym.st_value;
322 sym->len = sym->sym.st_size;
323
324 rb_add(&sym->node, &sym->sec->symbol_tree, symbol_to_offset);
325 pnode = rb_prev(&sym->node);
326 if (pnode)
327 entry = &rb_entry(pnode, struct symbol, node)->list;
328 else
329 entry = &sym->sec->symbol_list;
330 list_add(&sym->list, entry);
331 elf_hash_add(symbol, &sym->hash, sym->idx);
332 elf_hash_add(symbol_name, &sym->name_hash, str_hash(sym->name));
333
334 /*
335 * Don't store empty STT_NOTYPE symbols in the rbtree. They
336 * can exist within a function, confusing the sorting.
337 */
338 if (!sym->len)
339 rb_erase(&sym->node, &sym->sec->symbol_tree);
340}
341
342static int read_symbols(struct elf *elf)
343{
344 struct section *symtab, *symtab_shndx, *sec;
345 struct symbol *sym, *pfunc;
346 int symbols_nr, i;
347 char *coldstr;
348 Elf_Data *shndx_data = NULL;
349 Elf32_Word shndx;
350
351 symtab = find_section_by_name(elf, ".symtab");
352 if (symtab) {
353 symtab_shndx = find_section_by_name(elf, ".symtab_shndx");
354 if (symtab_shndx)
355 shndx_data = symtab_shndx->data;
356
357 symbols_nr = symtab->sh.sh_size / symtab->sh.sh_entsize;
358 } else {
359 /*
360 * A missing symbol table is actually possible if it's an empty
361 * .o file. This can happen for thunk_64.o. Make sure to at
362 * least allocate the symbol hash tables so we can do symbol
363 * lookups without crashing.
364 */
365 symbols_nr = 0;
366 }
367
368 if (!elf_alloc_hash(symbol, symbols_nr) ||
369 !elf_alloc_hash(symbol_name, symbols_nr))
370 return -1;
371
372 for (i = 0; i < symbols_nr; i++) {
373 sym = malloc(sizeof(*sym));
374 if (!sym) {
375 perror("malloc");
376 return -1;
377 }
378 memset(sym, 0, sizeof(*sym));
379 sym->alias = sym;
380
381 sym->idx = i;
382
383 if (!gelf_getsymshndx(symtab->data, shndx_data, i, &sym->sym,
384 &shndx)) {
385 WARN_ELF("gelf_getsymshndx");
386 goto err;
387 }
388
389 sym->name = elf_strptr(elf->elf, symtab->sh.sh_link,
390 sym->sym.st_name);
391 if (!sym->name) {
392 WARN_ELF("elf_strptr");
393 goto err;
394 }
395
396 if ((sym->sym.st_shndx > SHN_UNDEF &&
397 sym->sym.st_shndx < SHN_LORESERVE) ||
398 (shndx_data && sym->sym.st_shndx == SHN_XINDEX)) {
399 if (sym->sym.st_shndx != SHN_XINDEX)
400 shndx = sym->sym.st_shndx;
401
402 sym->sec = find_section_by_index(elf, shndx);
403 if (!sym->sec) {
404 WARN("couldn't find section for symbol %s",
405 sym->name);
406 goto err;
407 }
408 if (GELF_ST_TYPE(sym->sym.st_info) == STT_SECTION) {
409 sym->name = sym->sec->name;
410 sym->sec->sym = sym;
411 }
412 } else
413 sym->sec = find_section_by_index(elf, 0);
414
415 elf_add_symbol(elf, sym);
416 }
417
418 if (stats) {
419 printf("nr_symbols: %lu\n", (unsigned long)symbols_nr);
420 printf("symbol_bits: %d\n", elf->symbol_bits);
421 }
422
423 /* Create parent/child links for any cold subfunctions */
424 list_for_each_entry(sec, &elf->sections, list) {
425 list_for_each_entry(sym, &sec->symbol_list, list) {
426 char pname[MAX_NAME_LEN + 1];
427 size_t pnamelen;
428 if (sym->type != STT_FUNC)
429 continue;
430
431 if (sym->pfunc == NULL)
432 sym->pfunc = sym;
433
434 if (sym->cfunc == NULL)
435 sym->cfunc = sym;
436
437 coldstr = strstr(sym->name, ".cold");
438 if (!coldstr)
439 continue;
440
441 pnamelen = coldstr - sym->name;
442 if (pnamelen > MAX_NAME_LEN) {
443 WARN("%s(): parent function name exceeds maximum length of %d characters",
444 sym->name, MAX_NAME_LEN);
445 return -1;
446 }
447
448 strncpy(pname, sym->name, pnamelen);
449 pname[pnamelen] = '\0';
450 pfunc = find_symbol_by_name(elf, pname);
451
452 if (!pfunc) {
453 WARN("%s(): can't find parent function",
454 sym->name);
455 return -1;
456 }
457
458 sym->pfunc = pfunc;
459 pfunc->cfunc = sym;
460
461 /*
462 * Unfortunately, -fnoreorder-functions puts the child
463 * inside the parent. Remove the overlap so we can
464 * have sane assumptions.
465 *
466 * Note that pfunc->len now no longer matches
467 * pfunc->sym.st_size.
468 */
469 if (sym->sec == pfunc->sec &&
470 sym->offset >= pfunc->offset &&
471 sym->offset + sym->len == pfunc->offset + pfunc->len) {
472 pfunc->len -= sym->len;
473 }
474 }
475 }
476
477 return 0;
478
479err:
480 free(sym);
481 return -1;
482}
483
484static struct section *elf_create_reloc_section(struct elf *elf,
485 struct section *base,
486 int reltype);
487
488int elf_add_reloc(struct elf *elf, struct section *sec, unsigned long offset,
489 unsigned int type, struct symbol *sym, int addend)
490{
491 struct reloc *reloc;
492
493 if (!sec->reloc && !elf_create_reloc_section(elf, sec, SHT_RELA))
494 return -1;
495
496 reloc = malloc(sizeof(*reloc));
497 if (!reloc) {
498 perror("malloc");
499 return -1;
500 }
501 memset(reloc, 0, sizeof(*reloc));
502
503 reloc->sec = sec->reloc;
504 reloc->offset = offset;
505 reloc->type = type;
506 reloc->sym = sym;
507 reloc->addend = addend;
508
509 list_add_tail(&reloc->list, &sec->reloc->reloc_list);
510 elf_hash_add(reloc, &reloc->hash, reloc_hash(reloc));
511
512 sec->reloc->sh.sh_size += sec->reloc->sh.sh_entsize;
513 sec->reloc->changed = true;
514
515 return 0;
516}
517
518int elf_add_reloc_to_insn(struct elf *elf, struct section *sec,
519 unsigned long offset, unsigned int type,
520 struct section *insn_sec, unsigned long insn_off)
521{
522 struct symbol *sym;
523 int addend;
524
525 if (insn_sec->sym) {
526 sym = insn_sec->sym;
527 addend = insn_off;
528
529 } else {
530 /*
531 * The Clang assembler strips section symbols, so we have to
532 * reference the function symbol instead:
533 */
534 sym = find_symbol_containing(insn_sec, insn_off);
535 if (!sym) {
536 /*
537 * Hack alert. This happens when we need to reference
538 * the NOP pad insn immediately after the function.
539 */
540 sym = find_symbol_containing(insn_sec, insn_off - 1);
541 }
542
543 if (!sym) {
544 WARN("can't find symbol containing %s+0x%lx", insn_sec->name, insn_off);
545 return -1;
546 }
547
548 addend = insn_off - sym->offset;
549 }
550
551 return elf_add_reloc(elf, sec, offset, type, sym, addend);
552}
553
554static int read_rel_reloc(struct section *sec, int i, struct reloc *reloc, unsigned int *symndx)
555{
556 if (!gelf_getrel(sec->data, i, &reloc->rel)) {
557 WARN_ELF("gelf_getrel");
558 return -1;
559 }
560 reloc->type = GELF_R_TYPE(reloc->rel.r_info);
561 reloc->addend = 0;
562 reloc->offset = reloc->rel.r_offset;
563 *symndx = GELF_R_SYM(reloc->rel.r_info);
564 return 0;
565}
566
567static int read_rela_reloc(struct section *sec, int i, struct reloc *reloc, unsigned int *symndx)
568{
569 if (!gelf_getrela(sec->data, i, &reloc->rela)) {
570 WARN_ELF("gelf_getrela");
571 return -1;
572 }
573 reloc->type = GELF_R_TYPE(reloc->rela.r_info);
574 reloc->addend = reloc->rela.r_addend;
575 reloc->offset = reloc->rela.r_offset;
576 *symndx = GELF_R_SYM(reloc->rela.r_info);
577 return 0;
578}
579
580static int read_relocs(struct elf *elf)
581{
582 struct section *sec;
583 struct reloc *reloc;
584 int i;
585 unsigned int symndx;
586 unsigned long nr_reloc, max_reloc = 0, tot_reloc = 0;
587
588 if (!elf_alloc_hash(reloc, elf->text_size / 16))
589 return -1;
590
591 list_for_each_entry(sec, &elf->sections, list) {
592 if ((sec->sh.sh_type != SHT_RELA) &&
593 (sec->sh.sh_type != SHT_REL))
594 continue;
595
596 sec->base = find_section_by_index(elf, sec->sh.sh_info);
597 if (!sec->base) {
598 WARN("can't find base section for reloc section %s",
599 sec->name);
600 return -1;
601 }
602
603 sec->base->reloc = sec;
604
605 nr_reloc = 0;
606 for (i = 0; i < sec->sh.sh_size / sec->sh.sh_entsize; i++) {
607 reloc = malloc(sizeof(*reloc));
608 if (!reloc) {
609 perror("malloc");
610 return -1;
611 }
612 memset(reloc, 0, sizeof(*reloc));
613 switch (sec->sh.sh_type) {
614 case SHT_REL:
615 if (read_rel_reloc(sec, i, reloc, &symndx))
616 return -1;
617 break;
618 case SHT_RELA:
619 if (read_rela_reloc(sec, i, reloc, &symndx))
620 return -1;
621 break;
622 default: return -1;
623 }
624
625 reloc->sec = sec;
626 reloc->idx = i;
627 reloc->sym = find_symbol_by_index(elf, symndx);
628 if (!reloc->sym) {
629 WARN("can't find reloc entry symbol %d for %s",
630 symndx, sec->name);
631 return -1;
632 }
633
634 list_add_tail(&reloc->list, &sec->reloc_list);
635 elf_hash_add(reloc, &reloc->hash, reloc_hash(reloc));
636
637 nr_reloc++;
638 }
639 max_reloc = max(max_reloc, nr_reloc);
640 tot_reloc += nr_reloc;
641 }
642
643 if (stats) {
644 printf("max_reloc: %lu\n", max_reloc);
645 printf("tot_reloc: %lu\n", tot_reloc);
646 printf("reloc_bits: %d\n", elf->reloc_bits);
647 }
648
649 return 0;
650}
651
652struct elf *elf_open_read(const char *name, int flags)
653{
654 struct elf *elf;
655 Elf_Cmd cmd;
656
657 elf_version(EV_CURRENT);
658
659 elf = malloc(sizeof(*elf));
660 if (!elf) {
661 perror("malloc");
662 return NULL;
663 }
664 memset(elf, 0, offsetof(struct elf, sections));
665
666 INIT_LIST_HEAD(&elf->sections);
667
668 elf->fd = open(name, flags);
669 if (elf->fd == -1) {
670 fprintf(stderr, "objtool: Can't open '%s': %s\n",
671 name, strerror(errno));
672 goto err;
673 }
674
675 if ((flags & O_ACCMODE) == O_RDONLY)
676 cmd = ELF_C_READ_MMAP;
677 else if ((flags & O_ACCMODE) == O_RDWR)
678 cmd = ELF_C_RDWR;
679 else /* O_WRONLY */
680 cmd = ELF_C_WRITE;
681
682 elf->elf = elf_begin(elf->fd, cmd, NULL);
683 if (!elf->elf) {
684 WARN_ELF("elf_begin");
685 goto err;
686 }
687
688 if (!gelf_getehdr(elf->elf, &elf->ehdr)) {
689 WARN_ELF("gelf_getehdr");
690 goto err;
691 }
692
693 if (read_sections(elf))
694 goto err;
695
696 if (read_symbols(elf))
697 goto err;
698
699 if (read_relocs(elf))
700 goto err;
701
702 return elf;
703
704err:
705 elf_close(elf);
706 return NULL;
707}
708
709static int elf_add_string(struct elf *elf, struct section *strtab, char *str)
710{
711 Elf_Data *data;
712 Elf_Scn *s;
713 int len;
714
715 if (!strtab)
716 strtab = find_section_by_name(elf, ".strtab");
717 if (!strtab) {
718 WARN("can't find .strtab section");
719 return -1;
720 }
721
722 s = elf_getscn(elf->elf, strtab->idx);
723 if (!s) {
724 WARN_ELF("elf_getscn");
725 return -1;
726 }
727
728 data = elf_newdata(s);
729 if (!data) {
730 WARN_ELF("elf_newdata");
731 return -1;
732 }
733
734 data->d_buf = str;
735 data->d_size = strlen(str) + 1;
736 data->d_align = 1;
737
738 len = strtab->len;
739 strtab->len += data->d_size;
740 strtab->changed = true;
741
742 return len;
743}
744
745struct symbol *elf_create_undef_symbol(struct elf *elf, const char *name)
746{
747 struct section *symtab, *symtab_shndx;
748 struct symbol *sym;
749 Elf_Data *data;
750 Elf_Scn *s;
751
752 sym = malloc(sizeof(*sym));
753 if (!sym) {
754 perror("malloc");
755 return NULL;
756 }
757 memset(sym, 0, sizeof(*sym));
758
759 sym->name = strdup(name);
760
761 sym->sym.st_name = elf_add_string(elf, NULL, sym->name);
762 if (sym->sym.st_name == -1)
763 return NULL;
764
765 sym->sym.st_info = GELF_ST_INFO(STB_GLOBAL, STT_NOTYPE);
766 // st_other 0
767 // st_shndx 0
768 // st_value 0
769 // st_size 0
770
771 symtab = find_section_by_name(elf, ".symtab");
772 if (!symtab) {
773 WARN("can't find .symtab");
774 return NULL;
775 }
776
777 s = elf_getscn(elf->elf, symtab->idx);
778 if (!s) {
779 WARN_ELF("elf_getscn");
780 return NULL;
781 }
782
783 data = elf_newdata(s);
784 if (!data) {
785 WARN_ELF("elf_newdata");
786 return NULL;
787 }
788
789 data->d_buf = &sym->sym;
790 data->d_size = sizeof(sym->sym);
791 data->d_align = 1;
792 data->d_type = ELF_T_SYM;
793
794 sym->idx = symtab->len / sizeof(sym->sym);
795
796 symtab->len += data->d_size;
797 symtab->changed = true;
798
799 symtab_shndx = find_section_by_name(elf, ".symtab_shndx");
800 if (symtab_shndx) {
801 s = elf_getscn(elf->elf, symtab_shndx->idx);
802 if (!s) {
803 WARN_ELF("elf_getscn");
804 return NULL;
805 }
806
807 data = elf_newdata(s);
808 if (!data) {
809 WARN_ELF("elf_newdata");
810 return NULL;
811 }
812
813 data->d_buf = &sym->sym.st_size; /* conveniently 0 */
814 data->d_size = sizeof(Elf32_Word);
815 data->d_align = 4;
816 data->d_type = ELF_T_WORD;
817
818 symtab_shndx->len += 4;
819 symtab_shndx->changed = true;
820 }
821
822 sym->sec = find_section_by_index(elf, 0);
823
824 elf_add_symbol(elf, sym);
825
826 return sym;
827}
828
829struct section *elf_create_section(struct elf *elf, const char *name,
830 unsigned int sh_flags, size_t entsize, int nr)
831{
832 struct section *sec, *shstrtab;
833 size_t size = entsize * nr;
834 Elf_Scn *s;
835
836 sec = malloc(sizeof(*sec));
837 if (!sec) {
838 perror("malloc");
839 return NULL;
840 }
841 memset(sec, 0, sizeof(*sec));
842
843 INIT_LIST_HEAD(&sec->symbol_list);
844 INIT_LIST_HEAD(&sec->reloc_list);
845
846 s = elf_newscn(elf->elf);
847 if (!s) {
848 WARN_ELF("elf_newscn");
849 return NULL;
850 }
851
852 sec->name = strdup(name);
853 if (!sec->name) {
854 perror("strdup");
855 return NULL;
856 }
857
858 sec->idx = elf_ndxscn(s);
859 sec->len = size;
860 sec->changed = true;
861
862 sec->data = elf_newdata(s);
863 if (!sec->data) {
864 WARN_ELF("elf_newdata");
865 return NULL;
866 }
867
868 sec->data->d_size = size;
869 sec->data->d_align = 1;
870
871 if (size) {
872 sec->data->d_buf = malloc(size);
873 if (!sec->data->d_buf) {
874 perror("malloc");
875 return NULL;
876 }
877 memset(sec->data->d_buf, 0, size);
878 }
879
880 if (!gelf_getshdr(s, &sec->sh)) {
881 WARN_ELF("gelf_getshdr");
882 return NULL;
883 }
884
885 sec->sh.sh_size = size;
886 sec->sh.sh_entsize = entsize;
887 sec->sh.sh_type = SHT_PROGBITS;
888 sec->sh.sh_addralign = 1;
889 sec->sh.sh_flags = SHF_ALLOC | sh_flags;
890
891 /* Add section name to .shstrtab (or .strtab for Clang) */
892 shstrtab = find_section_by_name(elf, ".shstrtab");
893 if (!shstrtab)
894 shstrtab = find_section_by_name(elf, ".strtab");
895 if (!shstrtab) {
896 WARN("can't find .shstrtab or .strtab section");
897 return NULL;
898 }
899 sec->sh.sh_name = elf_add_string(elf, shstrtab, sec->name);
900 if (sec->sh.sh_name == -1)
901 return NULL;
902
903 list_add_tail(&sec->list, &elf->sections);
904 elf_hash_add(section, &sec->hash, sec->idx);
905 elf_hash_add(section_name, &sec->name_hash, str_hash(sec->name));
906
907 elf->changed = true;
908
909 return sec;
910}
911
912static struct section *elf_create_rel_reloc_section(struct elf *elf, struct section *base)
913{
914 char *relocname;
915 struct section *sec;
916
917 relocname = malloc(strlen(base->name) + strlen(".rel") + 1);
918 if (!relocname) {
919 perror("malloc");
920 return NULL;
921 }
922 strcpy(relocname, ".rel");
923 strcat(relocname, base->name);
924
925 sec = elf_create_section(elf, relocname, 0, sizeof(GElf_Rel), 0);
926 free(relocname);
927 if (!sec)
928 return NULL;
929
930 base->reloc = sec;
931 sec->base = base;
932
933 sec->sh.sh_type = SHT_REL;
934 sec->sh.sh_addralign = 8;
935 sec->sh.sh_link = find_section_by_name(elf, ".symtab")->idx;
936 sec->sh.sh_info = base->idx;
937 sec->sh.sh_flags = SHF_INFO_LINK;
938
939 return sec;
940}
941
942static struct section *elf_create_rela_reloc_section(struct elf *elf, struct section *base)
943{
944 char *relocname;
945 struct section *sec;
946
947 relocname = malloc(strlen(base->name) + strlen(".rela") + 1);
948 if (!relocname) {
949 perror("malloc");
950 return NULL;
951 }
952 strcpy(relocname, ".rela");
953 strcat(relocname, base->name);
954
955 sec = elf_create_section(elf, relocname, 0, sizeof(GElf_Rela), 0);
956 free(relocname);
957 if (!sec)
958 return NULL;
959
960 base->reloc = sec;
961 sec->base = base;
962
963 sec->sh.sh_type = SHT_RELA;
964 sec->sh.sh_addralign = 8;
965 sec->sh.sh_link = find_section_by_name(elf, ".symtab")->idx;
966 sec->sh.sh_info = base->idx;
967 sec->sh.sh_flags = SHF_INFO_LINK;
968
969 return sec;
970}
971
972static struct section *elf_create_reloc_section(struct elf *elf,
973 struct section *base,
974 int reltype)
975{
976 switch (reltype) {
977 case SHT_REL: return elf_create_rel_reloc_section(elf, base);
978 case SHT_RELA: return elf_create_rela_reloc_section(elf, base);
979 default: return NULL;
980 }
981}
982
983static int elf_rebuild_rel_reloc_section(struct section *sec)
984{
985 struct reloc *reloc;
986 int idx = 0;
987 void *buf;
988
989 /* Allocate a buffer for relocations */
990 buf = malloc(sec->sh.sh_size);
991 if (!buf) {
992 perror("malloc");
993 return -1;
994 }
995
996 sec->data->d_buf = buf;
997 sec->data->d_size = sec->sh.sh_size;
998 sec->data->d_type = ELF_T_REL;
999
1000 idx = 0;
1001 list_for_each_entry(reloc, &sec->reloc_list, list) {
1002 reloc->rel.r_offset = reloc->offset;
1003 reloc->rel.r_info = GELF_R_INFO(reloc->sym->idx, reloc->type);
1004 if (!gelf_update_rel(sec->data, idx, &reloc->rel)) {
1005 WARN_ELF("gelf_update_rel");
1006 return -1;
1007 }
1008 idx++;
1009 }
1010
1011 return 0;
1012}
1013
1014static int elf_rebuild_rela_reloc_section(struct section *sec)
1015{
1016 struct reloc *reloc;
1017 int idx = 0;
1018 void *buf;
1019
1020 /* Allocate a buffer for relocations with addends */
1021 buf = malloc(sec->sh.sh_size);
1022 if (!buf) {
1023 perror("malloc");
1024 return -1;
1025 }
1026
1027 sec->data->d_buf = buf;
1028 sec->data->d_size = sec->sh.sh_size;
1029 sec->data->d_type = ELF_T_RELA;
1030
1031 idx = 0;
1032 list_for_each_entry(reloc, &sec->reloc_list, list) {
1033 reloc->rela.r_offset = reloc->offset;
1034 reloc->rela.r_addend = reloc->addend;
1035 reloc->rela.r_info = GELF_R_INFO(reloc->sym->idx, reloc->type);
1036 if (!gelf_update_rela(sec->data, idx, &reloc->rela)) {
1037 WARN_ELF("gelf_update_rela");
1038 return -1;
1039 }
1040 idx++;
1041 }
1042
1043 return 0;
1044}
1045
1046static int elf_rebuild_reloc_section(struct elf *elf, struct section *sec)
1047{
1048 switch (sec->sh.sh_type) {
1049 case SHT_REL: return elf_rebuild_rel_reloc_section(sec);
1050 case SHT_RELA: return elf_rebuild_rela_reloc_section(sec);
1051 default: return -1;
1052 }
1053}
1054
1055int elf_write_insn(struct elf *elf, struct section *sec,
1056 unsigned long offset, unsigned int len,
1057 const char *insn)
1058{
1059 Elf_Data *data = sec->data;
1060
1061 if (data->d_type != ELF_T_BYTE || data->d_off) {
1062 WARN("write to unexpected data for section: %s", sec->name);
1063 return -1;
1064 }
1065
1066 memcpy(data->d_buf + offset, insn, len);
1067 elf_flagdata(data, ELF_C_SET, ELF_F_DIRTY);
1068
1069 elf->changed = true;
1070
1071 return 0;
1072}
1073
1074int elf_write_reloc(struct elf *elf, struct reloc *reloc)
1075{
1076 struct section *sec = reloc->sec;
1077
1078 if (sec->sh.sh_type == SHT_REL) {
1079 reloc->rel.r_info = GELF_R_INFO(reloc->sym->idx, reloc->type);
1080 reloc->rel.r_offset = reloc->offset;
1081
1082 if (!gelf_update_rel(sec->data, reloc->idx, &reloc->rel)) {
1083 WARN_ELF("gelf_update_rel");
1084 return -1;
1085 }
1086 } else {
1087 reloc->rela.r_info = GELF_R_INFO(reloc->sym->idx, reloc->type);
1088 reloc->rela.r_addend = reloc->addend;
1089 reloc->rela.r_offset = reloc->offset;
1090
1091 if (!gelf_update_rela(sec->data, reloc->idx, &reloc->rela)) {
1092 WARN_ELF("gelf_update_rela");
1093 return -1;
1094 }
1095 }
1096
1097 elf->changed = true;
1098
1099 return 0;
1100}
1101
1102int elf_write(struct elf *elf)
1103{
1104 struct section *sec;
1105 Elf_Scn *s;
1106
1107 /* Update changed relocation sections and section headers: */
1108 list_for_each_entry(sec, &elf->sections, list) {
1109 if (sec->changed) {
1110 s = elf_getscn(elf->elf, sec->idx);
1111 if (!s) {
1112 WARN_ELF("elf_getscn");
1113 return -1;
1114 }
1115 if (!gelf_update_shdr(s, &sec->sh)) {
1116 WARN_ELF("gelf_update_shdr");
1117 return -1;
1118 }
1119
1120 if (sec->base &&
1121 elf_rebuild_reloc_section(elf, sec)) {
1122 WARN("elf_rebuild_reloc_section");
1123 return -1;
1124 }
1125
1126 sec->changed = false;
1127 elf->changed = true;
1128 }
1129 }
1130
1131 /* Make sure the new section header entries get updated properly. */
1132 elf_flagelf(elf->elf, ELF_C_SET, ELF_F_DIRTY);
1133
1134 /* Write all changes to the file. */
1135 if (elf_update(elf->elf, ELF_C_WRITE) < 0) {
1136 WARN_ELF("elf_update");
1137 return -1;
1138 }
1139
1140 elf->changed = false;
1141
1142 return 0;
1143}
1144
1145void elf_close(struct elf *elf)
1146{
1147 struct section *sec, *tmpsec;
1148 struct symbol *sym, *tmpsym;
1149 struct reloc *reloc, *tmpreloc;
1150
1151 if (elf->elf)
1152 elf_end(elf->elf);
1153
1154 if (elf->fd > 0)
1155 close(elf->fd);
1156
1157 list_for_each_entry_safe(sec, tmpsec, &elf->sections, list) {
1158 list_for_each_entry_safe(sym, tmpsym, &sec->symbol_list, list) {
1159 list_del(&sym->list);
1160 hash_del(&sym->hash);
1161 free(sym);
1162 }
1163 list_for_each_entry_safe(reloc, tmpreloc, &sec->reloc_list, list) {
1164 list_del(&reloc->list);
1165 hash_del(&reloc->hash);
1166 free(reloc);
1167 }
1168 list_del(&sec->list);
1169 free(sec);
1170 }
1171
1172 free(elf);
1173}