tools/objtool/elf.c

   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 <fcntl.h>
  13 #include <stdio.h>
  14 #include <stdlib.h>
  15 #include <string.h>
  16 #include <unistd.h>
  17 #include <errno.h>
  18 #include "builtin.h"
  19
  20 #include "elf.h"
  21 #include "warn.h"
  22
  23 #define MAX_NAME_LEN 128
  24
  25 static inline u32 str_hash(const char *str)
  26 {
  27         return jhash(str, strlen(str), 0);
  28 }
  29
  30 static inline int elf_hash_bits(void)
  31 {
  32         return vmlinux ? ELF_HASH_BITS : 16;
  33 }
  34
  35 #define elf_hash_add(hashtable, node, key) \
  36         hlist_add_head(node, &hashtable[hash_min(key, elf_hash_bits())])
  37
  38 static void elf_hash_init(struct hlist_head *table)
  39 {
  40         __hash_init(table, 1U << elf_hash_bits());
  41 }
  42
  43 #define elf_hash_for_each_possible(name, obj, member, key)                      \
  44         hlist_for_each_entry(obj, &name[hash_min(key, elf_hash_bits())], member)
  45
  46 static void rb_add(struct rb_root *tree, struct rb_node *node,
  47                    int (*cmp)(struct rb_node *, const struct rb_node *))
  48 {
  49         struct rb_node **link = &tree->rb_node;
  50         struct rb_node *parent = NULL;
  51
  52         while (*link) {
  53                 parent = *link;
  54                 if (cmp(node, parent) < 0)
  55                         link = &parent->rb_left;
  56                 else
  57                         link = &parent->rb_right;
  58         }
  59
  60         rb_link_node(node, parent, link);
  61         rb_insert_color(node, tree);
  62 }
  63
  64 static struct rb_node *rb_find_first(const struct rb_root *tree, const void *key,
  65                                int (*cmp)(const void *key, const struct rb_node *))
  66 {
  67         struct rb_node *node = tree->rb_node;
  68         struct rb_node *match = NULL;
  69
  70         while (node) {
  71                 int c = cmp(key, node);
  72                 if (c <= 0) {
  73                         if (!c)
  74                                 match = node;
  75                         node = node->rb_left;
  76                 } else if (c > 0) {
  77                         node = node->rb_right;
  78                 }
  79         }
  80
  81         return match;
  82 }
  83
  84 static struct rb_node *rb_next_match(struct rb_node *node, const void *key,
  85                                     int (*cmp)(const void *key, const struct rb_node *))
  86 {
  87         node = rb_next(node);
  88         if (node && cmp(key, node))
  89                 node = NULL;
  90         return node;
  91 }
  92
  93 #define rb_for_each(tree, node, key, cmp) \
  94         for ((node) = rb_find_first((tree), (key), (cmp)); \
  95              (node); (node) = rb_next_match((node), (key), (cmp)))
  96
  97 static int symbol_to_offset(struct rb_node *a, const struct rb_node *b)
  98 {
  99         struct symbol *sa = rb_entry(a, struct symbol, node);
 100         struct symbol *sb = rb_entry(b, struct symbol, node);
 101
 102         if (sa->offset < sb->offset)
 103                 return -1;
 104         if (sa->offset > sb->offset)
 105                 return 1;
 106
 107         if (sa->len < sb->len)
 108                 return -1;
 109         if (sa->len > sb->len)
 110                 return 1;
 111
 112         sa->alias = sb;
 113
 114         return 0;
 115 }
 116
 117 static int symbol_by_offset(const void *key, const struct rb_node *node)
 118 {
 119         const struct symbol *s = rb_entry(node, struct symbol, node);
 120         const unsigned long *o = key;
 121
 122         if (*o < s->offset)
 123                 return -1;
 124         if (*o >= s->offset + s->len)
 125                 return 1;
 126
 127         return 0;
 128 }
 129
 130 struct section *find_section_by_name(const struct elf *elf, const char *name)
 131 {
 132         struct section *sec;
 133
 134         elf_hash_for_each_possible(elf->section_name_hash, sec, name_hash, str_hash(name))
 135                 if (!strcmp(sec->name, name))
 136                         return sec;
 137
 138         return NULL;
 139 }
 140
 141 static struct section *find_section_by_index(struct elf *elf,
 142                                              unsigned int idx)
 143 {
 144         struct section *sec;
 145
 146         elf_hash_for_each_possible(elf->section_hash, sec, hash, idx)
 147                 if (sec->idx == idx)
 148                         return sec;
 149
 150         return NULL;
 151 }
 152
 153 static struct symbol *find_symbol_by_index(struct elf *elf, unsigned int idx)
 154 {
 155         struct symbol *sym;
 156
 157         elf_hash_for_each_possible(elf->symbol_hash, sym, hash, idx)
 158                 if (sym->idx == idx)
 159                         return sym;
 160
 161         return NULL;
 162 }
 163
 164 struct symbol *find_symbol_by_offset(struct section *sec, unsigned long offset)
 165 {
 166         struct rb_node *node;
 167
 168         rb_for_each(&sec->symbol_tree, node, &offset, symbol_by_offset) {
 169                 struct symbol *s = rb_entry(node, struct symbol, node);
 170
 171                 if (s->offset == offset && s->type != STT_SECTION)
 172                         return s;
 173         }
 174
 175         return NULL;
 176 }
 177
 178 struct symbol *find_func_by_offset(struct section *sec, unsigned long offset)
 179 {
 180         struct rb_node *node;
 181
 182         rb_for_each(&sec->symbol_tree, node, &offset, symbol_by_offset) {
 183                 struct symbol *s = rb_entry(node, struct symbol, node);
 184
 185                 if (s->offset == offset && s->type == STT_FUNC)
 186                         return s;
 187         }
 188
 189         return NULL;
 190 }
 191
 192 struct symbol *find_symbol_containing(const struct section *sec, unsigned long offset)
 193 {
 194         struct rb_node *node;
 195
 196         rb_for_each(&sec->symbol_tree, node, &offset, symbol_by_offset) {
 197                 struct symbol *s = rb_entry(node, struct symbol, node);
 198
 199                 if (s->type != STT_SECTION)
 200                         return s;
 201         }
 202
 203         return NULL;
 204 }
 205
 206 struct symbol *find_func_containing(struct section *sec, unsigned long offset)
 207 {
 208         struct rb_node *node;
 209
 210         rb_for_each(&sec->symbol_tree, node, &offset, symbol_by_offset) {
 211                 struct symbol *s = rb_entry(node, struct symbol, node);
 212
 213                 if (s->type == STT_FUNC)
 214                         return s;
 215         }
 216
 217         return NULL;
 218 }
 219
 220 struct symbol *find_symbol_by_name(const struct elf *elf, const char *name)
 221 {
 222         struct symbol *sym;
 223
 224         elf_hash_for_each_possible(elf->symbol_name_hash, sym, name_hash, str_hash(name))
 225                 if (!strcmp(sym->name, name))
 226                         return sym;
 227
 228         return NULL;
 229 }
 230
 231 struct rela *find_rela_by_dest_range(const struct elf *elf, struct section *sec,
 232                                      unsigned long offset, unsigned int len)
 233 {
 234         struct rela *rela, *r = NULL;
 235         unsigned long o;
 236
 237         if (!sec->rela)
 238                 return NULL;
 239
 240         sec = sec->rela;
 241
 242         for_offset_range(o, offset, offset + len) {
 243                 elf_hash_for_each_possible(elf->rela_hash, rela, hash,
 244                                        sec_offset_hash(sec, o)) {
 245                         if (rela->sec != sec)
 246                                 continue;
 247
 248                         if (rela->offset >= offset && rela->offset < offset + len) {
 249                                 if (!r || rela->offset < r->offset)
 250                                         r = rela;
 251                         }
 252                 }
 253                 if (r)
 254                         return r;
 255         }
 256
 257         return NULL;
 258 }
 259
 260 struct rela *find_rela_by_dest(const struct elf *elf, struct section *sec, unsigned long offset)
 261 {
 262         return find_rela_by_dest_range(elf, sec, offset, 1);
 263 }
 264
 265 static int read_sections(struct elf *elf)
 266 {
 267         Elf_Scn *s = NULL;
 268         struct section *sec;
 269         size_t shstrndx, sections_nr;
 270         int i;
 271
 272         if (elf_getshdrnum(elf->elf, &sections_nr)) {
 273                 WARN_ELF("elf_getshdrnum");
 274                 return -1;
 275         }
 276
 277         if (elf_getshdrstrndx(elf->elf, &shstrndx)) {
 278                 WARN_ELF("elf_getshdrstrndx");
 279                 return -1;
 280         }
 281
 282         for (i = 0; i < sections_nr; i++) {
 283                 sec = malloc(sizeof(*sec));
 284                 if (!sec) {
 285                         perror("malloc");
 286                         return -1;
 287                 }
 288                 memset(sec, 0, sizeof(*sec));
 289
 290                 INIT_LIST_HEAD(&sec->symbol_list);
 291                 INIT_LIST_HEAD(&sec->rela_list);
 292
 293                 s = elf_getscn(elf->elf, i);
 294                 if (!s) {
 295                         WARN_ELF("elf_getscn");
 296                         return -1;
 297                 }
 298
 299                 sec->idx = elf_ndxscn(s);
 300
 301                 if (!gelf_getshdr(s, &sec->sh)) {
 302                         WARN_ELF("gelf_getshdr");
 303                         return -1;
 304                 }
 305
 306                 sec->name = elf_strptr(elf->elf, shstrndx, sec->sh.sh_name);
 307                 if (!sec->name) {
 308                         WARN_ELF("elf_strptr");
 309                         return -1;
 310                 }
 311
 312                 if (sec->sh.sh_size != 0) {
 313                         sec->data = elf_getdata(s, NULL);
 314                         if (!sec->data) {
 315                                 WARN_ELF("elf_getdata");
 316                                 return -1;
 317                         }
 318                         if (sec->data->d_off != 0 ||
 319                             sec->data->d_size != sec->sh.sh_size) {
 320                                 WARN("unexpected data attributes for %s",
 321                                      sec->name);
 322                                 return -1;
 323                         }
 324                 }
 325                 sec->len = sec->sh.sh_size;
 326
 327                 list_add_tail(&sec->list, &elf->sections);
 328                 elf_hash_add(elf->section_hash, &sec->hash, sec->idx);
 329                 elf_hash_add(elf->section_name_hash, &sec->name_hash, str_hash(sec->name));
 330         }
 331
 332         if (stats)
 333                 printf("nr_sections: %lu\n", (unsigned long)sections_nr);
 334
 335         /* sanity check, one more call to elf_nextscn() should return NULL */
 336         if (elf_nextscn(elf->elf, s)) {
 337                 WARN("section entry mismatch");
 338                 return -1;
 339         }
 340
 341         return 0;
 342 }
 343
 344 static int read_symbols(struct elf *elf)
 345 {
 346         struct section *symtab, *symtab_shndx, *sec;
 347         struct symbol *sym, *pfunc;
 348         struct list_head *entry;
 349         struct rb_node *pnode;
 350         int symbols_nr, i;
 351         char *coldstr;
 352         Elf_Data *shndx_data = NULL;
 353         Elf32_Word shndx;
 354
 355         symtab = find_section_by_name(elf, ".symtab");
 356         if (!symtab) {
 357                 WARN("missing symbol table");
 358                 return -1;
 359         }
 360
 361         symtab_shndx = find_section_by_name(elf, ".symtab_shndx");
 362         if (symtab_shndx)
 363                 shndx_data = symtab_shndx->data;
 364
 365         symbols_nr = symtab->sh.sh_size / symtab->sh.sh_entsize;
 366
 367         for (i = 0; i < symbols_nr; i++) {
 368                 sym = malloc(sizeof(*sym));
 369                 if (!sym) {
 370                         perror("malloc");
 371                         return -1;
 372                 }
 373                 memset(sym, 0, sizeof(*sym));
 374                 sym->alias = sym;
 375
 376                 sym->idx = i;
 377
 378                 if (!gelf_getsymshndx(symtab->data, shndx_data, i, &sym->sym,
 379                                       &shndx)) {
 380                         WARN_ELF("gelf_getsymshndx");
 381                         goto err;
 382                 }
 383
 384                 sym->name = elf_strptr(elf->elf, symtab->sh.sh_link,
 385                                        sym->sym.st_name);
 386                 if (!sym->name) {
 387                         WARN_ELF("elf_strptr");
 388                         goto err;
 389                 }
 390
 391                 sym->type = GELF_ST_TYPE(sym->sym.st_info);
 392                 sym->bind = GELF_ST_BIND(sym->sym.st_info);
 393
 394                 if ((sym->sym.st_shndx > SHN_UNDEF &&
 395                      sym->sym.st_shndx < SHN_LORESERVE) ||
 396                     (shndx_data && sym->sym.st_shndx == SHN_XINDEX)) {
 397                         if (sym->sym.st_shndx != SHN_XINDEX)
 398                                 shndx = sym->sym.st_shndx;
 399
 400                         sym->sec = find_section_by_index(elf, shndx);
 401                         if (!sym->sec) {
 402                                 WARN("couldn't find section for symbol %s",
 403                                      sym->name);
 404                                 goto err;
 405                         }
 406                         if (sym->type == STT_SECTION) {
 407                                 sym->name = sym->sec->name;
 408                                 sym->sec->sym = sym;
 409                         }
 410                 } else
 411                         sym->sec = find_section_by_index(elf, 0);
 412
 413                 sym->offset = sym->sym.st_value;
 414                 sym->len = sym->sym.st_size;
 415
 416                 rb_add(&sym->sec->symbol_tree, &sym->node, symbol_to_offset);
 417                 pnode = rb_prev(&sym->node);
 418                 if (pnode)
 419                         entry = &rb_entry(pnode, struct symbol, node)->list;
 420                 else
 421                         entry = &sym->sec->symbol_list;
 422                 list_add(&sym->list, entry);
 423                 elf_hash_add(elf->symbol_hash, &sym->hash, sym->idx);
 424                 elf_hash_add(elf->symbol_name_hash, &sym->name_hash, str_hash(sym->name));
 425         }
 426
 427         if (stats)
 428                 printf("nr_symbols: %lu\n", (unsigned long)symbols_nr);
 429
 430         /* Create parent/child links for any cold subfunctions */
 431         list_for_each_entry(sec, &elf->sections, list) {
 432                 list_for_each_entry(sym, &sec->symbol_list, list) {
 433                         char pname[MAX_NAME_LEN + 1];
 434                         size_t pnamelen;
 435                         if (sym->type != STT_FUNC)
 436                                 continue;
 437                         sym->pfunc = sym->cfunc = sym;
 438                         coldstr = strstr(sym->name, ".cold");
 439                         if (!coldstr)
 440                                 continue;
 441
 442                         pnamelen = coldstr - sym->name;
 443                         if (pnamelen > MAX_NAME_LEN) {
 444                                 WARN("%s(): parent function name exceeds maximum length of %d characters",
 445                                      sym->name, MAX_NAME_LEN);
 446                                 return -1;
 447                         }
 448
 449                         strncpy(pname, sym->name, pnamelen);
 450                         pname[pnamelen] = '\0';
 451                         pfunc = find_symbol_by_name(elf, pname);
 452
 453                         if (!pfunc) {
 454                                 WARN("%s(): can't find parent function",
 455                                      sym->name);
 456                                 return -1;
 457                         }
 458
 459                         sym->pfunc = pfunc;
 460                         pfunc->cfunc = sym;
 461
 462                         /*
 463                          * Unfortunately, -fnoreorder-functions puts the child
 464                          * inside the parent.  Remove the overlap so we can
 465                          * have sane assumptions.
 466                          *
 467                          * Note that pfunc->len now no longer matches
 468                          * pfunc->sym.st_size.
 469                          */
 470                         if (sym->sec == pfunc->sec &&
 471                             sym->offset >= pfunc->offset &&
 472                             sym->offset + sym->len == pfunc->offset + pfunc->len) {
 473                                 pfunc->len -= sym->len;
 474                         }
 475                 }
 476         }
 477
 478         return 0;
 479
 480 err:
 481         free(sym);
 482         return -1;
 483 }
 484
 485 void elf_add_rela(struct elf *elf, struct rela *rela)
 486 {
 487         struct section *sec = rela->sec;
 488
 489         list_add_tail(&rela->list, &sec->rela_list);
 490         elf_hash_add(elf->rela_hash, &rela->hash, rela_hash(rela));
 491 }
 492
 493 static int read_relas(struct elf *elf)
 494 {
 495         struct section *sec;
 496         struct rela *rela;
 497         int i;
 498         unsigned int symndx;
 499         unsigned long nr_rela, max_rela = 0, tot_rela = 0;
 500
 501         list_for_each_entry(sec, &elf->sections, list) {
 502                 if (sec->sh.sh_type != SHT_RELA)
 503                         continue;
 504
 505                 sec->base = find_section_by_name(elf, sec->name + 5);
 506                 if (!sec->base) {
 507                         WARN("can't find base section for rela section %s",
 508                              sec->name);
 509                         return -1;
 510                 }
 511
 512                 sec->base->rela = sec;
 513
 514                 nr_rela = 0;
 515                 for (i = 0; i < sec->sh.sh_size / sec->sh.sh_entsize; i++) {
 516                         rela = malloc(sizeof(*rela));
 517                         if (!rela) {
 518                                 perror("malloc");
 519                                 return -1;
 520                         }
 521                         memset(rela, 0, sizeof(*rela));
 522
 523                         if (!gelf_getrela(sec->data, i, &rela->rela)) {
 524                                 WARN_ELF("gelf_getrela");
 525                                 return -1;
 526                         }
 527
 528                         rela->type = GELF_R_TYPE(rela->rela.r_info);
 529                         rela->addend = rela->rela.r_addend;
 530                         rela->offset = rela->rela.r_offset;
 531                         symndx = GELF_R_SYM(rela->rela.r_info);
 532                         rela->sec = sec;
 533                         rela->idx = i;
 534                         rela->sym = find_symbol_by_index(elf, symndx);
 535                         if (!rela->sym) {
 536                                 WARN("can't find rela entry symbol %d for %s",
 537                                      symndx, sec->name);
 538                                 return -1;
 539                         }
 540
 541                         elf_add_rela(elf, rela);
 542                         nr_rela++;
 543                 }
 544                 max_rela = max(max_rela, nr_rela);
 545                 tot_rela += nr_rela;
 546         }
 547
 548         if (stats) {
 549                 printf("max_rela: %lu\n", max_rela);
 550                 printf("tot_rela: %lu\n", tot_rela);
 551         }
 552
 553         return 0;
 554 }
 555
 556 struct elf *elf_open_read(const char *name, int flags)
 557 {
 558         struct elf *elf;
 559         Elf_Cmd cmd;
 560
 561         elf_version(EV_CURRENT);
 562
 563         elf = malloc(sizeof(*elf));
 564         if (!elf) {
 565                 perror("malloc");
 566                 return NULL;
 567         }
 568         memset(elf, 0, offsetof(struct elf, sections));
 569
 570         INIT_LIST_HEAD(&elf->sections);
 571
 572         elf_hash_init(elf->symbol_hash);
 573         elf_hash_init(elf->symbol_name_hash);
 574         elf_hash_init(elf->section_hash);
 575         elf_hash_init(elf->section_name_hash);
 576         elf_hash_init(elf->rela_hash);
 577
 578         elf->fd = open(name, flags);
 579         if (elf->fd == -1) {
 580                 fprintf(stderr, "objtool: Can't open '%s': %s\n",
 581                         name, strerror(errno));
 582                 goto err;
 583         }
 584
 585         if ((flags & O_ACCMODE) == O_RDONLY)
 586                 cmd = ELF_C_READ_MMAP;
 587         else if ((flags & O_ACCMODE) == O_RDWR)
 588                 cmd = ELF_C_RDWR;
 589         else /* O_WRONLY */
 590                 cmd = ELF_C_WRITE;
 591
 592         elf->elf = elf_begin(elf->fd, cmd, NULL);
 593         if (!elf->elf) {
 594                 WARN_ELF("elf_begin");
 595                 goto err;
 596         }
 597
 598         if (!gelf_getehdr(elf->elf, &elf->ehdr)) {
 599                 WARN_ELF("gelf_getehdr");
 600                 goto err;
 601         }
 602
 603         if (read_sections(elf))
 604                 goto err;
 605
 606         if (read_symbols(elf))
 607                 goto err;
 608
 609         if (read_relas(elf))
 610                 goto err;
 611
 612         return elf;
 613
 614 err:
 615         elf_close(elf);
 616         return NULL;
 617 }
 618
 619 struct section *elf_create_section(struct elf *elf, const char *name,
 620                                    size_t entsize, int nr)
 621 {
 622         struct section *sec, *shstrtab;
 623         size_t size = entsize * nr;
 624         Elf_Scn *s;
 625         Elf_Data *data;
 626
 627         sec = malloc(sizeof(*sec));
 628         if (!sec) {
 629                 perror("malloc");
 630                 return NULL;
 631         }
 632         memset(sec, 0, sizeof(*sec));
 633
 634         INIT_LIST_HEAD(&sec->symbol_list);
 635         INIT_LIST_HEAD(&sec->rela_list);
 636
 637         s = elf_newscn(elf->elf);
 638         if (!s) {
 639                 WARN_ELF("elf_newscn");
 640                 return NULL;
 641         }
 642
 643         sec->name = strdup(name);
 644         if (!sec->name) {
 645                 perror("strdup");
 646                 return NULL;
 647         }
 648
 649         sec->idx = elf_ndxscn(s);
 650         sec->len = size;
 651         sec->changed = true;
 652
 653         sec->data = elf_newdata(s);
 654         if (!sec->data) {
 655                 WARN_ELF("elf_newdata");
 656                 return NULL;
 657         }
 658
 659         sec->data->d_size = size;
 660         sec->data->d_align = 1;
 661
 662         if (size) {
 663                 sec->data->d_buf = malloc(size);
 664                 if (!sec->data->d_buf) {
 665                         perror("malloc");
 666                         return NULL;
 667                 }
 668                 memset(sec->data->d_buf, 0, size);
 669         }
 670
 671         if (!gelf_getshdr(s, &sec->sh)) {
 672                 WARN_ELF("gelf_getshdr");
 673                 return NULL;
 674         }
 675
 676         sec->sh.sh_size = size;
 677         sec->sh.sh_entsize = entsize;
 678         sec->sh.sh_type = SHT_PROGBITS;
 679         sec->sh.sh_addralign = 1;
 680         sec->sh.sh_flags = SHF_ALLOC;
 681
 682
 683         /* Add section name to .shstrtab (or .strtab for Clang) */
 684         shstrtab = find_section_by_name(elf, ".shstrtab");
 685         if (!shstrtab)
 686                 shstrtab = find_section_by_name(elf, ".strtab");
 687         if (!shstrtab) {
 688                 WARN("can't find .shstrtab or .strtab section");
 689                 return NULL;
 690         }
 691
 692         s = elf_getscn(elf->elf, shstrtab->idx);
 693         if (!s) {
 694                 WARN_ELF("elf_getscn");
 695                 return NULL;
 696         }
 697
 698         data = elf_newdata(s);
 699         if (!data) {
 700                 WARN_ELF("elf_newdata");
 701                 return NULL;
 702         }
 703
 704         data->d_buf = sec->name;
 705         data->d_size = strlen(name) + 1;
 706         data->d_align = 1;
 707
 708         sec->sh.sh_name = shstrtab->len;
 709
 710         shstrtab->len += strlen(name) + 1;
 711         shstrtab->changed = true;
 712
 713         list_add_tail(&sec->list, &elf->sections);
 714         elf_hash_add(elf->section_hash, &sec->hash, sec->idx);
 715         elf_hash_add(elf->section_name_hash, &sec->name_hash, str_hash(sec->name));
 716
 717         elf->changed = true;
 718
 719         return sec;
 720 }
 721
 722 struct section *elf_create_rela_section(struct elf *elf, struct section *base)
 723 {
 724         char *relaname;
 725         struct section *sec;
 726
 727         relaname = malloc(strlen(base->name) + strlen(".rela") + 1);
 728         if (!relaname) {
 729                 perror("malloc");
 730                 return NULL;
 731         }
 732         strcpy(relaname, ".rela");
 733         strcat(relaname, base->name);
 734
 735         sec = elf_create_section(elf, relaname, sizeof(GElf_Rela), 0);
 736         free(relaname);
 737         if (!sec)
 738                 return NULL;
 739
 740         base->rela = sec;
 741         sec->base = base;
 742
 743         sec->sh.sh_type = SHT_RELA;
 744         sec->sh.sh_addralign = 8;
 745         sec->sh.sh_link = find_section_by_name(elf, ".symtab")->idx;
 746         sec->sh.sh_info = base->idx;
 747         sec->sh.sh_flags = SHF_INFO_LINK;
 748
 749         return sec;
 750 }
 751
 752 int elf_rebuild_rela_section(struct elf *elf, struct section *sec)
 753 {
 754         struct rela *rela;
 755         int nr, idx = 0, size;
 756         GElf_Rela *relas;
 757
 758         nr = 0;
 759         list_for_each_entry(rela, &sec->rela_list, list)
 760                 nr++;
 761
 762         size = nr * sizeof(*relas);
 763         relas = malloc(size);
 764         if (!relas) {
 765                 perror("malloc");
 766                 return -1;
 767         }
 768
 769         sec->changed = true;
 770         elf->changed = true;
 771
 772         sec->data->d_buf = relas;
 773         sec->data->d_size = size;
 774
 775         sec->sh.sh_size = size;
 776
 777         idx = 0;
 778         list_for_each_entry(rela, &sec->rela_list, list) {
 779                 relas[idx].r_offset = rela->offset;
 780                 relas[idx].r_addend = rela->addend;
 781                 relas[idx].r_info = GELF_R_INFO(rela->sym->idx, rela->type);
 782                 idx++;
 783         }
 784
 785         return 0;
 786 }
 787
 788 int elf_write_insn(struct elf *elf, struct section *sec,
 789                    unsigned long offset, unsigned int len,
 790                    const char *insn)
 791 {
 792         Elf_Data *data = sec->data;
 793
 794         if (data->d_type != ELF_T_BYTE || data->d_off) {
 795                 WARN("write to unexpected data for section: %s", sec->name);
 796                 return -1;
 797         }
 798
 799         memcpy(data->d_buf + offset, insn, len);
 800         elf_flagdata(data, ELF_C_SET, ELF_F_DIRTY);
 801
 802         elf->changed = true;
 803
 804         return 0;
 805 }
 806
 807 int elf_write_rela(struct elf *elf, struct rela *rela)
 808 {
 809         struct section *sec = rela->sec;
 810
 811         rela->rela.r_info = GELF_R_INFO(rela->sym->idx, rela->type);
 812         rela->rela.r_addend = rela->addend;
 813         rela->rela.r_offset = rela->offset;
 814
 815         if (!gelf_update_rela(sec->data, rela->idx, &rela->rela)) {
 816                 WARN_ELF("gelf_update_rela");
 817                 return -1;
 818         }
 819
 820         elf->changed = true;
 821
 822         return 0;
 823 }
 824
 825 int elf_write(struct elf *elf)
 826 {
 827         struct section *sec;
 828         Elf_Scn *s;
 829
 830         /* Update section headers for changed sections: */
 831         list_for_each_entry(sec, &elf->sections, list) {
 832                 if (sec->changed) {
 833                         s = elf_getscn(elf->elf, sec->idx);
 834                         if (!s) {
 835                                 WARN_ELF("elf_getscn");
 836                                 return -1;
 837                         }
 838                         if (!gelf_update_shdr(s, &sec->sh)) {
 839                                 WARN_ELF("gelf_update_shdr");
 840                                 return -1;
 841                         }
 842
 843                         sec->changed = false;
 844                 }
 845         }
 846
 847         /* Make sure the new section header entries get updated properly. */
 848         elf_flagelf(elf->elf, ELF_C_SET, ELF_F_DIRTY);
 849
 850         /* Write all changes to the file. */
 851         if (elf_update(elf->elf, ELF_C_WRITE) < 0) {
 852                 WARN_ELF("elf_update");
 853                 return -1;
 854         }
 855
 856         elf->changed = false;
 857
 858         return 0;
 859 }
 860
 861 void elf_close(struct elf *elf)
 862 {
 863         struct section *sec, *tmpsec;
 864         struct symbol *sym, *tmpsym;
 865         struct rela *rela, *tmprela;
 866
 867         if (elf->elf)
 868                 elf_end(elf->elf);
 869
 870         if (elf->fd > 0)
 871                 close(elf->fd);
 872
 873         list_for_each_entry_safe(sec, tmpsec, &elf->sections, list) {
 874                 list_for_each_entry_safe(sym, tmpsym, &sec->symbol_list, list) {
 875                         list_del(&sym->list);
 876                         hash_del(&sym->hash);
 877                         free(sym);
 878                 }
 879                 list_for_each_entry_safe(rela, tmprela, &sec->rela_list, list) {
 880                         list_del(&rela->list);
 881                         hash_del(&rela->hash);
 882                         free(rela);
 883                 }
 884                 list_del(&sec->list);
 885                 free(sec);
 886         }
 887
 888         free(elf);
 889 }