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 reloc *find_reloc_by_dest_range(const struct elf *elf, struct section *sec,
 232                                      unsigned long offset, unsigned int len)
 233 {
 234         struct reloc *reloc, *r = NULL;
 235         unsigned long o;
 236
 237         if (!sec->reloc)
 238                 return NULL;
 239
 240         sec = sec->reloc;
 241
 242         for_offset_range(o, offset, offset + len) {
 243                 elf_hash_for_each_possible(elf->reloc_hash, reloc, hash,
 244                                        sec_offset_hash(sec, o)) {
 245                         if (reloc->sec != sec)
 246                                 continue;
 247
 248                         if (reloc->offset >= offset && reloc->offset < offset + len) {
 249                                 if (!r || reloc->offset < r->offset)
 250                                         r = reloc;
 251                         }
 252                 }
 253                 if (r)
 254                         return r;
 255         }
 256
 257         return NULL;
 258 }
 259
 260 struct reloc *find_reloc_by_dest(const struct elf *elf, struct section *sec, unsigned long offset)
 261 {
 262         return find_reloc_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->reloc_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
 438                         if (sym->pfunc == NULL)
 439                                 sym->pfunc = sym;
 440
 441                         if (sym->cfunc == NULL)
 442                                 sym->cfunc = sym;
 443
 444                         coldstr = strstr(sym->name, ".cold");
 445                         if (!coldstr)
 446                                 continue;
 447
 448                         pnamelen = coldstr - sym->name;
 449                         if (pnamelen > MAX_NAME_LEN) {
 450                                 WARN("%s(): parent function name exceeds maximum length of %d characters",
 451                                      sym->name, MAX_NAME_LEN);
 452                                 return -1;
 453                         }
 454
 455                         strncpy(pname, sym->name, pnamelen);
 456                         pname[pnamelen] = '\0';
 457                         pfunc = find_symbol_by_name(elf, pname);
 458
 459                         if (!pfunc) {
 460                                 WARN("%s(): can't find parent function",
 461                                      sym->name);
 462                                 return -1;
 463                         }
 464
 465                         sym->pfunc = pfunc;
 466                         pfunc->cfunc = sym;
 467
 468                         /*
 469                          * Unfortunately, -fnoreorder-functions puts the child
 470                          * inside the parent.  Remove the overlap so we can
 471                          * have sane assumptions.
 472                          *
 473                          * Note that pfunc->len now no longer matches
 474                          * pfunc->sym.st_size.
 475                          */
 476                         if (sym->sec == pfunc->sec &&
 477                             sym->offset >= pfunc->offset &&
 478                             sym->offset + sym->len == pfunc->offset + pfunc->len) {
 479                                 pfunc->len -= sym->len;
 480                         }
 481                 }
 482         }
 483
 484         return 0;
 485
 486 err:
 487         free(sym);
 488         return -1;
 489 }
 490
 491 void elf_add_reloc(struct elf *elf, struct reloc *reloc)
 492 {
 493         struct section *sec = reloc->sec;
 494
 495         list_add_tail(&reloc->list, &sec->reloc_list);
 496         elf_hash_add(elf->reloc_hash, &reloc->hash, reloc_hash(reloc));
 497 }
 498
 499 static int read_rel_reloc(struct section *sec, int i, struct reloc *reloc, unsigned int *symndx)
 500 {
 501         if (!gelf_getrel(sec->data, i, &reloc->rel)) {
 502                 WARN_ELF("gelf_getrel");
 503                 return -1;
 504         }
 505         reloc->type = GELF_R_TYPE(reloc->rel.r_info);
 506         reloc->addend = 0;
 507         reloc->offset = reloc->rel.r_offset;
 508         *symndx = GELF_R_SYM(reloc->rel.r_info);
 509         return 0;
 510 }
 511
 512 static int read_rela_reloc(struct section *sec, int i, struct reloc *reloc, unsigned int *symndx)
 513 {
 514         if (!gelf_getrela(sec->data, i, &reloc->rela)) {
 515                 WARN_ELF("gelf_getrela");
 516                 return -1;
 517         }
 518         reloc->type = GELF_R_TYPE(reloc->rela.r_info);
 519         reloc->addend = reloc->rela.r_addend;
 520         reloc->offset = reloc->rela.r_offset;
 521         *symndx = GELF_R_SYM(reloc->rela.r_info);
 522         return 0;
 523 }
 524
 525 static int read_relocs(struct elf *elf)
 526 {
 527         struct section *sec;
 528         struct reloc *reloc;
 529         int i;
 530         unsigned int symndx;
 531         unsigned long nr_reloc, max_reloc = 0, tot_reloc = 0;
 532
 533         list_for_each_entry(sec, &elf->sections, list) {
 534                 if ((sec->sh.sh_type != SHT_RELA) &&
 535                     (sec->sh.sh_type != SHT_REL))
 536                         continue;
 537
 538                 sec->base = find_section_by_index(elf, sec->sh.sh_info);
 539                 if (!sec->base) {
 540                         WARN("can't find base section for reloc section %s",
 541                              sec->name);
 542                         return -1;
 543                 }
 544
 545                 sec->base->reloc = sec;
 546
 547                 nr_reloc = 0;
 548                 for (i = 0; i < sec->sh.sh_size / sec->sh.sh_entsize; i++) {
 549                         reloc = malloc(sizeof(*reloc));
 550                         if (!reloc) {
 551                                 perror("malloc");
 552                                 return -1;
 553                         }
 554                         memset(reloc, 0, sizeof(*reloc));
 555                         switch (sec->sh.sh_type) {
 556                         case SHT_REL:
 557                                 if (read_rel_reloc(sec, i, reloc, &symndx))
 558                                         return -1;
 559                                 break;
 560                         case SHT_RELA:
 561                                 if (read_rela_reloc(sec, i, reloc, &symndx))
 562                                         return -1;
 563                                 break;
 564                         default: return -1;
 565                         }
 566
 567                         reloc->sec = sec;
 568                         reloc->idx = i;
 569                         reloc->sym = find_symbol_by_index(elf, symndx);
 570                         if (!reloc->sym) {
 571                                 WARN("can't find reloc entry symbol %d for %s",
 572                                      symndx, sec->name);
 573                                 return -1;
 574                         }
 575
 576                         elf_add_reloc(elf, reloc);
 577                         nr_reloc++;
 578                 }
 579                 max_reloc = max(max_reloc, nr_reloc);
 580                 tot_reloc += nr_reloc;
 581         }
 582
 583         if (stats) {
 584                 printf("max_reloc: %lu\n", max_reloc);
 585                 printf("tot_reloc: %lu\n", tot_reloc);
 586         }
 587
 588         return 0;
 589 }
 590
 591 struct elf *elf_open_read(const char *name, int flags)
 592 {
 593         struct elf *elf;
 594         Elf_Cmd cmd;
 595
 596         elf_version(EV_CURRENT);
 597
 598         elf = malloc(sizeof(*elf));
 599         if (!elf) {
 600                 perror("malloc");
 601                 return NULL;
 602         }
 603         memset(elf, 0, offsetof(struct elf, sections));
 604
 605         INIT_LIST_HEAD(&elf->sections);
 606
 607         elf_hash_init(elf->symbol_hash);
 608         elf_hash_init(elf->symbol_name_hash);
 609         elf_hash_init(elf->section_hash);
 610         elf_hash_init(elf->section_name_hash);
 611         elf_hash_init(elf->reloc_hash);
 612
 613         elf->fd = open(name, flags);
 614         if (elf->fd == -1) {
 615                 fprintf(stderr, "objtool: Can't open '%s': %s\n",
 616                         name, strerror(errno));
 617                 goto err;
 618         }
 619
 620         if ((flags & O_ACCMODE) == O_RDONLY)
 621                 cmd = ELF_C_READ_MMAP;
 622         else if ((flags & O_ACCMODE) == O_RDWR)
 623                 cmd = ELF_C_RDWR;
 624         else /* O_WRONLY */
 625                 cmd = ELF_C_WRITE;
 626
 627         elf->elf = elf_begin(elf->fd, cmd, NULL);
 628         if (!elf->elf) {
 629                 WARN_ELF("elf_begin");
 630                 goto err;
 631         }
 632
 633         if (!gelf_getehdr(elf->elf, &elf->ehdr)) {
 634                 WARN_ELF("gelf_getehdr");
 635                 goto err;
 636         }
 637
 638         if (read_sections(elf))
 639                 goto err;
 640
 641         if (read_symbols(elf))
 642                 goto err;
 643
 644         if (read_relocs(elf))
 645                 goto err;
 646
 647         return elf;
 648
 649 err:
 650         elf_close(elf);
 651         return NULL;
 652 }
 653
 654 struct section *elf_create_section(struct elf *elf, const char *name,
 655                                    size_t entsize, int nr)
 656 {
 657         struct section *sec, *shstrtab;
 658         size_t size = entsize * nr;
 659         Elf_Scn *s;
 660         Elf_Data *data;
 661
 662         sec = malloc(sizeof(*sec));
 663         if (!sec) {
 664                 perror("malloc");
 665                 return NULL;
 666         }
 667         memset(sec, 0, sizeof(*sec));
 668
 669         INIT_LIST_HEAD(&sec->symbol_list);
 670         INIT_LIST_HEAD(&sec->reloc_list);
 671
 672         s = elf_newscn(elf->elf);
 673         if (!s) {
 674                 WARN_ELF("elf_newscn");
 675                 return NULL;
 676         }
 677
 678         sec->name = strdup(name);
 679         if (!sec->name) {
 680                 perror("strdup");
 681                 return NULL;
 682         }
 683
 684         sec->idx = elf_ndxscn(s);
 685         sec->len = size;
 686         sec->changed = true;
 687
 688         sec->data = elf_newdata(s);
 689         if (!sec->data) {
 690                 WARN_ELF("elf_newdata");
 691                 return NULL;
 692         }
 693
 694         sec->data->d_size = size;
 695         sec->data->d_align = 1;
 696
 697         if (size) {
 698                 sec->data->d_buf = malloc(size);
 699                 if (!sec->data->d_buf) {
 700                         perror("malloc");
 701                         return NULL;
 702                 }
 703                 memset(sec->data->d_buf, 0, size);
 704         }
 705
 706         if (!gelf_getshdr(s, &sec->sh)) {
 707                 WARN_ELF("gelf_getshdr");
 708                 return NULL;
 709         }
 710
 711         sec->sh.sh_size = size;
 712         sec->sh.sh_entsize = entsize;
 713         sec->sh.sh_type = SHT_PROGBITS;
 714         sec->sh.sh_addralign = 1;
 715         sec->sh.sh_flags = SHF_ALLOC;
 716
 717
 718         /* Add section name to .shstrtab (or .strtab for Clang) */
 719         shstrtab = find_section_by_name(elf, ".shstrtab");
 720         if (!shstrtab)
 721                 shstrtab = find_section_by_name(elf, ".strtab");
 722         if (!shstrtab) {
 723                 WARN("can't find .shstrtab or .strtab section");
 724                 return NULL;
 725         }
 726
 727         s = elf_getscn(elf->elf, shstrtab->idx);
 728         if (!s) {
 729                 WARN_ELF("elf_getscn");
 730                 return NULL;
 731         }
 732
 733         data = elf_newdata(s);
 734         if (!data) {
 735                 WARN_ELF("elf_newdata");
 736                 return NULL;
 737         }
 738
 739         data->d_buf = sec->name;
 740         data->d_size = strlen(name) + 1;
 741         data->d_align = 1;
 742
 743         sec->sh.sh_name = shstrtab->len;
 744
 745         shstrtab->len += strlen(name) + 1;
 746         shstrtab->changed = true;
 747
 748         list_add_tail(&sec->list, &elf->sections);
 749         elf_hash_add(elf->section_hash, &sec->hash, sec->idx);
 750         elf_hash_add(elf->section_name_hash, &sec->name_hash, str_hash(sec->name));
 751
 752         elf->changed = true;
 753
 754         return sec;
 755 }
 756
 757 static struct section *elf_create_rel_reloc_section(struct elf *elf, struct section *base)
 758 {
 759         char *relocname;
 760         struct section *sec;
 761
 762         relocname = malloc(strlen(base->name) + strlen(".rel") + 1);
 763         if (!relocname) {
 764                 perror("malloc");
 765                 return NULL;
 766         }
 767         strcpy(relocname, ".rel");
 768         strcat(relocname, base->name);
 769
 770         sec = elf_create_section(elf, relocname, sizeof(GElf_Rel), 0);
 771         free(relocname);
 772         if (!sec)
 773                 return NULL;
 774
 775         base->reloc = sec;
 776         sec->base = base;
 777
 778         sec->sh.sh_type = SHT_REL;
 779         sec->sh.sh_addralign = 8;
 780         sec->sh.sh_link = find_section_by_name(elf, ".symtab")->idx;
 781         sec->sh.sh_info = base->idx;
 782         sec->sh.sh_flags = SHF_INFO_LINK;
 783
 784         return sec;
 785 }
 786
 787 static struct section *elf_create_rela_reloc_section(struct elf *elf, struct section *base)
 788 {
 789         char *relocname;
 790         struct section *sec;
 791
 792         relocname = malloc(strlen(base->name) + strlen(".rela") + 1);
 793         if (!relocname) {
 794                 perror("malloc");
 795                 return NULL;
 796         }
 797         strcpy(relocname, ".rela");
 798         strcat(relocname, base->name);
 799
 800         sec = elf_create_section(elf, relocname, sizeof(GElf_Rela), 0);
 801         free(relocname);
 802         if (!sec)
 803                 return NULL;
 804
 805         base->reloc = sec;
 806         sec->base = base;
 807
 808         sec->sh.sh_type = SHT_RELA;
 809         sec->sh.sh_addralign = 8;
 810         sec->sh.sh_link = find_section_by_name(elf, ".symtab")->idx;
 811         sec->sh.sh_info = base->idx;
 812         sec->sh.sh_flags = SHF_INFO_LINK;
 813
 814         return sec;
 815 }
 816
 817 struct section *elf_create_reloc_section(struct elf *elf,
 818                                          struct section *base,
 819                                          int reltype)
 820 {
 821         switch (reltype) {
 822         case SHT_REL:  return elf_create_rel_reloc_section(elf, base);
 823         case SHT_RELA: return elf_create_rela_reloc_section(elf, base);
 824         default:       return NULL;
 825         }
 826 }
 827
 828 static int elf_rebuild_rel_reloc_section(struct section *sec, int nr)
 829 {
 830         struct reloc *reloc;
 831         int idx = 0, size;
 832         GElf_Rel *relocs;
 833
 834         /* Allocate a buffer for relocations */
 835         size = nr * sizeof(*relocs);
 836         relocs = malloc(size);
 837         if (!relocs) {
 838                 perror("malloc");
 839                 return -1;
 840         }
 841
 842         sec->data->d_buf = relocs;
 843         sec->data->d_size = size;
 844
 845         sec->sh.sh_size = size;
 846
 847         idx = 0;
 848         list_for_each_entry(reloc, &sec->reloc_list, list) {
 849                 relocs[idx].r_offset = reloc->offset;
 850                 relocs[idx].r_info = GELF_R_INFO(reloc->sym->idx, reloc->type);
 851                 idx++;
 852         }
 853
 854         return 0;
 855 }
 856
 857 static int elf_rebuild_rela_reloc_section(struct section *sec, int nr)
 858 {
 859         struct reloc *reloc;
 860         int idx = 0, size;
 861         GElf_Rela *relocs;
 862
 863         /* Allocate a buffer for relocations with addends */
 864         size = nr * sizeof(*relocs);
 865         relocs = malloc(size);
 866         if (!relocs) {
 867                 perror("malloc");
 868                 return -1;
 869         }
 870
 871         sec->data->d_buf = relocs;
 872         sec->data->d_size = size;
 873
 874         sec->sh.sh_size = size;
 875
 876         idx = 0;
 877         list_for_each_entry(reloc, &sec->reloc_list, list) {
 878                 relocs[idx].r_offset = reloc->offset;
 879                 relocs[idx].r_addend = reloc->addend;
 880                 relocs[idx].r_info = GELF_R_INFO(reloc->sym->idx, reloc->type);
 881                 idx++;
 882         }
 883
 884         return 0;
 885 }
 886
 887 int elf_rebuild_reloc_section(struct elf *elf, struct section *sec)
 888 {
 889         struct reloc *reloc;
 890         int nr;
 891
 892         sec->changed = true;
 893         elf->changed = true;
 894
 895         nr = 0;
 896         list_for_each_entry(reloc, &sec->reloc_list, list)
 897                 nr++;
 898
 899         switch (sec->sh.sh_type) {
 900         case SHT_REL:  return elf_rebuild_rel_reloc_section(sec, nr);
 901         case SHT_RELA: return elf_rebuild_rela_reloc_section(sec, nr);
 902         default:       return -1;
 903         }
 904 }
 905
 906 int elf_write_insn(struct elf *elf, struct section *sec,
 907                    unsigned long offset, unsigned int len,
 908                    const char *insn)
 909 {
 910         Elf_Data *data = sec->data;
 911
 912         if (data->d_type != ELF_T_BYTE || data->d_off) {
 913                 WARN("write to unexpected data for section: %s", sec->name);
 914                 return -1;
 915         }
 916
 917         memcpy(data->d_buf + offset, insn, len);
 918         elf_flagdata(data, ELF_C_SET, ELF_F_DIRTY);
 919
 920         elf->changed = true;
 921
 922         return 0;
 923 }
 924
 925 int elf_write_reloc(struct elf *elf, struct reloc *reloc)
 926 {
 927         struct section *sec = reloc->sec;
 928
 929         if (sec->sh.sh_type == SHT_REL) {
 930                 reloc->rel.r_info = GELF_R_INFO(reloc->sym->idx, reloc->type);
 931                 reloc->rel.r_offset = reloc->offset;
 932
 933                 if (!gelf_update_rel(sec->data, reloc->idx, &reloc->rel)) {
 934                         WARN_ELF("gelf_update_rel");
 935                         return -1;
 936                 }
 937         } else {
 938                 reloc->rela.r_info = GELF_R_INFO(reloc->sym->idx, reloc->type);
 939                 reloc->rela.r_addend = reloc->addend;
 940                 reloc->rela.r_offset = reloc->offset;
 941
 942                 if (!gelf_update_rela(sec->data, reloc->idx, &reloc->rela)) {
 943                         WARN_ELF("gelf_update_rela");
 944                         return -1;
 945                 }
 946         }
 947
 948         elf->changed = true;
 949
 950         return 0;
 951 }
 952
 953 int elf_write(struct elf *elf)
 954 {
 955         struct section *sec;
 956         Elf_Scn *s;
 957
 958         /* Update section headers for changed sections: */
 959         list_for_each_entry(sec, &elf->sections, list) {
 960                 if (sec->changed) {
 961                         s = elf_getscn(elf->elf, sec->idx);
 962                         if (!s) {
 963                                 WARN_ELF("elf_getscn");
 964                                 return -1;
 965                         }
 966                         if (!gelf_update_shdr(s, &sec->sh)) {
 967                                 WARN_ELF("gelf_update_shdr");
 968                                 return -1;
 969                         }
 970
 971                         sec->changed = false;
 972                 }
 973         }
 974
 975         /* Make sure the new section header entries get updated properly. */
 976         elf_flagelf(elf->elf, ELF_C_SET, ELF_F_DIRTY);
 977
 978         /* Write all changes to the file. */
 979         if (elf_update(elf->elf, ELF_C_WRITE) < 0) {
 980                 WARN_ELF("elf_update");
 981                 return -1;
 982         }
 983
 984         elf->changed = false;
 985
 986         return 0;
 987 }
 988
 989 void elf_close(struct elf *elf)
 990 {
 991         struct section *sec, *tmpsec;
 992         struct symbol *sym, *tmpsym;
 993         struct reloc *reloc, *tmpreloc;
 994
 995         if (elf->elf)
 996                 elf_end(elf->elf);
 997
 998         if (elf->fd > 0)
 999                 close(elf->fd);
1000
1001         list_for_each_entry_safe(sec, tmpsec, &elf->sections, list) {
1002                 list_for_each_entry_safe(sym, tmpsym, &sec->symbol_list, list) {
1003                         list_del(&sym->list);
1004                         hash_del(&sym->hash);
1005                         free(sym);
1006                 }
1007                 list_for_each_entry_safe(reloc, tmpreloc, &sec->reloc_list, list) {
1008                         list_del(&reloc->list);
1009                         hash_del(&reloc->hash);
1010                         free(reloc);
1011                 }
1012                 list_del(&sec->list);
1013                 free(sec);
1014         }
1015
1016         free(elf);
1017 }