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 void insn_to_reloc_sym_addend(struct section *sec, unsigned long offset,
 266                               struct reloc *reloc)
 267 {
 268         if (sec->sym) {
 269                 reloc->sym = sec->sym;
 270                 reloc->addend = offset;
 271                 return;
 272         }
 273
 274         /*
 275          * The Clang assembler strips section symbols, so we have to reference
 276          * the function symbol instead:
 277          */
 278         reloc->sym = find_symbol_containing(sec, offset);
 279         if (!reloc->sym) {
 280                 /*
 281                  * Hack alert.  This happens when we need to reference the NOP
 282                  * pad insn immediately after the function.
 283                  */
 284                 reloc->sym = find_symbol_containing(sec, offset - 1);
 285         }
 286
 287         if (reloc->sym)
 288                 reloc->addend = offset - reloc->sym->offset;
 289 }
 290
 291 static int read_sections(struct elf *elf)
 292 {
 293         Elf_Scn *s = NULL;
 294         struct section *sec;
 295         size_t shstrndx, sections_nr;
 296         int i;
 297
 298         if (elf_getshdrnum(elf->elf, &sections_nr)) {
 299                 WARN_ELF("elf_getshdrnum");
 300                 return -1;
 301         }
 302
 303         if (elf_getshdrstrndx(elf->elf, &shstrndx)) {
 304                 WARN_ELF("elf_getshdrstrndx");
 305                 return -1;
 306         }
 307
 308         for (i = 0; i < sections_nr; i++) {
 309                 sec = malloc(sizeof(*sec));
 310                 if (!sec) {
 311                         perror("malloc");
 312                         return -1;
 313                 }
 314                 memset(sec, 0, sizeof(*sec));
 315
 316                 INIT_LIST_HEAD(&sec->symbol_list);
 317                 INIT_LIST_HEAD(&sec->reloc_list);
 318
 319                 s = elf_getscn(elf->elf, i);
 320                 if (!s) {
 321                         WARN_ELF("elf_getscn");
 322                         return -1;
 323                 }
 324
 325                 sec->idx = elf_ndxscn(s);
 326
 327                 if (!gelf_getshdr(s, &sec->sh)) {
 328                         WARN_ELF("gelf_getshdr");
 329                         return -1;
 330                 }
 331
 332                 sec->name = elf_strptr(elf->elf, shstrndx, sec->sh.sh_name);
 333                 if (!sec->name) {
 334                         WARN_ELF("elf_strptr");
 335                         return -1;
 336                 }
 337
 338                 if (sec->sh.sh_size != 0) {
 339                         sec->data = elf_getdata(s, NULL);
 340                         if (!sec->data) {
 341                                 WARN_ELF("elf_getdata");
 342                                 return -1;
 343                         }
 344                         if (sec->data->d_off != 0 ||
 345                             sec->data->d_size != sec->sh.sh_size) {
 346                                 WARN("unexpected data attributes for %s",
 347                                      sec->name);
 348                                 return -1;
 349                         }
 350                 }
 351                 sec->len = sec->sh.sh_size;
 352
 353                 list_add_tail(&sec->list, &elf->sections);
 354                 elf_hash_add(elf->section_hash, &sec->hash, sec->idx);
 355                 elf_hash_add(elf->section_name_hash, &sec->name_hash, str_hash(sec->name));
 356         }
 357
 358         if (stats)
 359                 printf("nr_sections: %lu\n", (unsigned long)sections_nr);
 360
 361         /* sanity check, one more call to elf_nextscn() should return NULL */
 362         if (elf_nextscn(elf->elf, s)) {
 363                 WARN("section entry mismatch");
 364                 return -1;
 365         }
 366
 367         return 0;
 368 }
 369
 370 static int read_symbols(struct elf *elf)
 371 {
 372         struct section *symtab, *symtab_shndx, *sec;
 373         struct symbol *sym, *pfunc;
 374         struct list_head *entry;
 375         struct rb_node *pnode;
 376         int symbols_nr, i;
 377         char *coldstr;
 378         Elf_Data *shndx_data = NULL;
 379         Elf32_Word shndx;
 380
 381         symtab = find_section_by_name(elf, ".symtab");
 382         if (!symtab) {
 383                 WARN("missing symbol table");
 384                 return -1;
 385         }
 386
 387         symtab_shndx = find_section_by_name(elf, ".symtab_shndx");
 388         if (symtab_shndx)
 389                 shndx_data = symtab_shndx->data;
 390
 391         symbols_nr = symtab->sh.sh_size / symtab->sh.sh_entsize;
 392
 393         for (i = 0; i < symbols_nr; i++) {
 394                 sym = malloc(sizeof(*sym));
 395                 if (!sym) {
 396                         perror("malloc");
 397                         return -1;
 398                 }
 399                 memset(sym, 0, sizeof(*sym));
 400                 sym->alias = sym;
 401
 402                 sym->idx = i;
 403
 404                 if (!gelf_getsymshndx(symtab->data, shndx_data, i, &sym->sym,
 405                                       &shndx)) {
 406                         WARN_ELF("gelf_getsymshndx");
 407                         goto err;
 408                 }
 409
 410                 sym->name = elf_strptr(elf->elf, symtab->sh.sh_link,
 411                                        sym->sym.st_name);
 412                 if (!sym->name) {
 413                         WARN_ELF("elf_strptr");
 414                         goto err;
 415                 }
 416
 417                 sym->type = GELF_ST_TYPE(sym->sym.st_info);
 418                 sym->bind = GELF_ST_BIND(sym->sym.st_info);
 419
 420                 if ((sym->sym.st_shndx > SHN_UNDEF &&
 421                      sym->sym.st_shndx < SHN_LORESERVE) ||
 422                     (shndx_data && sym->sym.st_shndx == SHN_XINDEX)) {
 423                         if (sym->sym.st_shndx != SHN_XINDEX)
 424                                 shndx = sym->sym.st_shndx;
 425
 426                         sym->sec = find_section_by_index(elf, shndx);
 427                         if (!sym->sec) {
 428                                 WARN("couldn't find section for symbol %s",
 429                                      sym->name);
 430                                 goto err;
 431                         }
 432                         if (sym->type == STT_SECTION) {
 433                                 sym->name = sym->sec->name;
 434                                 sym->sec->sym = sym;
 435                         }
 436                 } else
 437                         sym->sec = find_section_by_index(elf, 0);
 438
 439                 sym->offset = sym->sym.st_value;
 440                 sym->len = sym->sym.st_size;
 441
 442                 rb_add(&sym->sec->symbol_tree, &sym->node, symbol_to_offset);
 443                 pnode = rb_prev(&sym->node);
 444                 if (pnode)
 445                         entry = &rb_entry(pnode, struct symbol, node)->list;
 446                 else
 447                         entry = &sym->sec->symbol_list;
 448                 list_add(&sym->list, entry);
 449                 elf_hash_add(elf->symbol_hash, &sym->hash, sym->idx);
 450                 elf_hash_add(elf->symbol_name_hash, &sym->name_hash, str_hash(sym->name));
 451
 452                 /*
 453                  * Don't store empty STT_NOTYPE symbols in the rbtree.  They
 454                  * can exist within a function, confusing the sorting.
 455                  */
 456                 if (!sym->len)
 457                         rb_erase(&sym->node, &sym->sec->symbol_tree);
 458         }
 459
 460         if (stats)
 461                 printf("nr_symbols: %lu\n", (unsigned long)symbols_nr);
 462
 463         /* Create parent/child links for any cold subfunctions */
 464         list_for_each_entry(sec, &elf->sections, list) {
 465                 list_for_each_entry(sym, &sec->symbol_list, list) {
 466                         char pname[MAX_NAME_LEN + 1];
 467                         size_t pnamelen;
 468                         if (sym->type != STT_FUNC)
 469                                 continue;
 470
 471                         if (sym->pfunc == NULL)
 472                                 sym->pfunc = sym;
 473
 474                         if (sym->cfunc == NULL)
 475                                 sym->cfunc = sym;
 476
 477                         coldstr = strstr(sym->name, ".cold");
 478                         if (!coldstr)
 479                                 continue;
 480
 481                         pnamelen = coldstr - sym->name;
 482                         if (pnamelen > MAX_NAME_LEN) {
 483                                 WARN("%s(): parent function name exceeds maximum length of %d characters",
 484                                      sym->name, MAX_NAME_LEN);
 485                                 return -1;
 486                         }
 487
 488                         strncpy(pname, sym->name, pnamelen);
 489                         pname[pnamelen] = '\0';
 490                         pfunc = find_symbol_by_name(elf, pname);
 491
 492                         if (!pfunc) {
 493                                 WARN("%s(): can't find parent function",
 494                                      sym->name);
 495                                 return -1;
 496                         }
 497
 498                         sym->pfunc = pfunc;
 499                         pfunc->cfunc = sym;
 500
 501                         /*
 502                          * Unfortunately, -fnoreorder-functions puts the child
 503                          * inside the parent.  Remove the overlap so we can
 504                          * have sane assumptions.
 505                          *
 506                          * Note that pfunc->len now no longer matches
 507                          * pfunc->sym.st_size.
 508                          */
 509                         if (sym->sec == pfunc->sec &&
 510                             sym->offset >= pfunc->offset &&
 511                             sym->offset + sym->len == pfunc->offset + pfunc->len) {
 512                                 pfunc->len -= sym->len;
 513                         }
 514                 }
 515         }
 516
 517         return 0;
 518
 519 err:
 520         free(sym);
 521         return -1;
 522 }
 523
 524 void elf_add_reloc(struct elf *elf, struct reloc *reloc)
 525 {
 526         struct section *sec = reloc->sec;
 527
 528         list_add_tail(&reloc->list, &sec->reloc_list);
 529         elf_hash_add(elf->reloc_hash, &reloc->hash, reloc_hash(reloc));
 530 }
 531
 532 static int read_rel_reloc(struct section *sec, int i, struct reloc *reloc, unsigned int *symndx)
 533 {
 534         if (!gelf_getrel(sec->data, i, &reloc->rel)) {
 535                 WARN_ELF("gelf_getrel");
 536                 return -1;
 537         }
 538         reloc->type = GELF_R_TYPE(reloc->rel.r_info);
 539         reloc->addend = 0;
 540         reloc->offset = reloc->rel.r_offset;
 541         *symndx = GELF_R_SYM(reloc->rel.r_info);
 542         return 0;
 543 }
 544
 545 static int read_rela_reloc(struct section *sec, int i, struct reloc *reloc, unsigned int *symndx)
 546 {
 547         if (!gelf_getrela(sec->data, i, &reloc->rela)) {
 548                 WARN_ELF("gelf_getrela");
 549                 return -1;
 550         }
 551         reloc->type = GELF_R_TYPE(reloc->rela.r_info);
 552         reloc->addend = reloc->rela.r_addend;
 553         reloc->offset = reloc->rela.r_offset;
 554         *symndx = GELF_R_SYM(reloc->rela.r_info);
 555         return 0;
 556 }
 557
 558 static int read_relocs(struct elf *elf)
 559 {
 560         struct section *sec;
 561         struct reloc *reloc;
 562         int i;
 563         unsigned int symndx;
 564         unsigned long nr_reloc, max_reloc = 0, tot_reloc = 0;
 565
 566         list_for_each_entry(sec, &elf->sections, list) {
 567                 if ((sec->sh.sh_type != SHT_RELA) &&
 568                     (sec->sh.sh_type != SHT_REL))
 569                         continue;
 570
 571                 sec->base = find_section_by_index(elf, sec->sh.sh_info);
 572                 if (!sec->base) {
 573                         WARN("can't find base section for reloc section %s",
 574                              sec->name);
 575                         return -1;
 576                 }
 577
 578                 sec->base->reloc = sec;
 579
 580                 nr_reloc = 0;
 581                 for (i = 0; i < sec->sh.sh_size / sec->sh.sh_entsize; i++) {
 582                         reloc = malloc(sizeof(*reloc));
 583                         if (!reloc) {
 584                                 perror("malloc");
 585                                 return -1;
 586                         }
 587                         memset(reloc, 0, sizeof(*reloc));
 588                         switch (sec->sh.sh_type) {
 589                         case SHT_REL:
 590                                 if (read_rel_reloc(sec, i, reloc, &symndx))
 591                                         return -1;
 592                                 break;
 593                         case SHT_RELA:
 594                                 if (read_rela_reloc(sec, i, reloc, &symndx))
 595                                         return -1;
 596                                 break;
 597                         default: return -1;
 598                         }
 599
 600                         reloc->sec = sec;
 601                         reloc->idx = i;
 602                         reloc->sym = find_symbol_by_index(elf, symndx);
 603                         if (!reloc->sym) {
 604                                 WARN("can't find reloc entry symbol %d for %s",
 605                                      symndx, sec->name);
 606                                 return -1;
 607                         }
 608
 609                         elf_add_reloc(elf, reloc);
 610                         nr_reloc++;
 611                 }
 612                 max_reloc = max(max_reloc, nr_reloc);
 613                 tot_reloc += nr_reloc;
 614         }
 615
 616         if (stats) {
 617                 printf("max_reloc: %lu\n", max_reloc);
 618                 printf("tot_reloc: %lu\n", tot_reloc);
 619         }
 620
 621         return 0;
 622 }
 623
 624 struct elf *elf_open_read(const char *name, int flags)
 625 {
 626         struct elf *elf;
 627         Elf_Cmd cmd;
 628
 629         elf_version(EV_CURRENT);
 630
 631         elf = malloc(sizeof(*elf));
 632         if (!elf) {
 633                 perror("malloc");
 634                 return NULL;
 635         }
 636         memset(elf, 0, offsetof(struct elf, sections));
 637
 638         INIT_LIST_HEAD(&elf->sections);
 639
 640         elf_hash_init(elf->symbol_hash);
 641         elf_hash_init(elf->symbol_name_hash);
 642         elf_hash_init(elf->section_hash);
 643         elf_hash_init(elf->section_name_hash);
 644         elf_hash_init(elf->reloc_hash);
 645
 646         elf->fd = open(name, flags);
 647         if (elf->fd == -1) {
 648                 fprintf(stderr, "objtool: Can't open '%s': %s\n",
 649                         name, strerror(errno));
 650                 goto err;
 651         }
 652
 653         if ((flags & O_ACCMODE) == O_RDONLY)
 654                 cmd = ELF_C_READ_MMAP;
 655         else if ((flags & O_ACCMODE) == O_RDWR)
 656                 cmd = ELF_C_RDWR;
 657         else /* O_WRONLY */
 658                 cmd = ELF_C_WRITE;
 659
 660         elf->elf = elf_begin(elf->fd, cmd, NULL);
 661         if (!elf->elf) {
 662                 WARN_ELF("elf_begin");
 663                 goto err;
 664         }
 665
 666         if (!gelf_getehdr(elf->elf, &elf->ehdr)) {
 667                 WARN_ELF("gelf_getehdr");
 668                 goto err;
 669         }
 670
 671         if (read_sections(elf))
 672                 goto err;
 673
 674         if (read_symbols(elf))
 675                 goto err;
 676
 677         if (read_relocs(elf))
 678                 goto err;
 679
 680         return elf;
 681
 682 err:
 683         elf_close(elf);
 684         return NULL;
 685 }
 686
 687 struct section *elf_create_section(struct elf *elf, const char *name,
 688                                    unsigned int sh_flags, size_t entsize, int nr)
 689 {
 690         struct section *sec, *shstrtab;
 691         size_t size = entsize * nr;
 692         Elf_Scn *s;
 693         Elf_Data *data;
 694
 695         sec = malloc(sizeof(*sec));
 696         if (!sec) {
 697                 perror("malloc");
 698                 return NULL;
 699         }
 700         memset(sec, 0, sizeof(*sec));
 701
 702         INIT_LIST_HEAD(&sec->symbol_list);
 703         INIT_LIST_HEAD(&sec->reloc_list);
 704
 705         s = elf_newscn(elf->elf);
 706         if (!s) {
 707                 WARN_ELF("elf_newscn");
 708                 return NULL;
 709         }
 710
 711         sec->name = strdup(name);
 712         if (!sec->name) {
 713                 perror("strdup");
 714                 return NULL;
 715         }
 716
 717         sec->idx = elf_ndxscn(s);
 718         sec->len = size;
 719         sec->changed = true;
 720
 721         sec->data = elf_newdata(s);
 722         if (!sec->data) {
 723                 WARN_ELF("elf_newdata");
 724                 return NULL;
 725         }
 726
 727         sec->data->d_size = size;
 728         sec->data->d_align = 1;
 729
 730         if (size) {
 731                 sec->data->d_buf = malloc(size);
 732                 if (!sec->data->d_buf) {
 733                         perror("malloc");
 734                         return NULL;
 735                 }
 736                 memset(sec->data->d_buf, 0, size);
 737         }
 738
 739         if (!gelf_getshdr(s, &sec->sh)) {
 740                 WARN_ELF("gelf_getshdr");
 741                 return NULL;
 742         }
 743
 744         sec->sh.sh_size = size;
 745         sec->sh.sh_entsize = entsize;
 746         sec->sh.sh_type = SHT_PROGBITS;
 747         sec->sh.sh_addralign = 1;
 748         sec->sh.sh_flags = SHF_ALLOC | sh_flags;
 749
 750
 751         /* Add section name to .shstrtab (or .strtab for Clang) */
 752         shstrtab = find_section_by_name(elf, ".shstrtab");
 753         if (!shstrtab)
 754                 shstrtab = find_section_by_name(elf, ".strtab");
 755         if (!shstrtab) {
 756                 WARN("can't find .shstrtab or .strtab section");
 757                 return NULL;
 758         }
 759
 760         s = elf_getscn(elf->elf, shstrtab->idx);
 761         if (!s) {
 762                 WARN_ELF("elf_getscn");
 763                 return NULL;
 764         }
 765
 766         data = elf_newdata(s);
 767         if (!data) {
 768                 WARN_ELF("elf_newdata");
 769                 return NULL;
 770         }
 771
 772         data->d_buf = sec->name;
 773         data->d_size = strlen(name) + 1;
 774         data->d_align = 1;
 775
 776         sec->sh.sh_name = shstrtab->len;
 777
 778         shstrtab->len += strlen(name) + 1;
 779         shstrtab->changed = true;
 780
 781         list_add_tail(&sec->list, &elf->sections);
 782         elf_hash_add(elf->section_hash, &sec->hash, sec->idx);
 783         elf_hash_add(elf->section_name_hash, &sec->name_hash, str_hash(sec->name));
 784
 785         elf->changed = true;
 786
 787         return sec;
 788 }
 789
 790 static struct section *elf_create_rel_reloc_section(struct elf *elf, struct section *base)
 791 {
 792         char *relocname;
 793         struct section *sec;
 794
 795         relocname = malloc(strlen(base->name) + strlen(".rel") + 1);
 796         if (!relocname) {
 797                 perror("malloc");
 798                 return NULL;
 799         }
 800         strcpy(relocname, ".rel");
 801         strcat(relocname, base->name);
 802
 803         sec = elf_create_section(elf, relocname, 0, sizeof(GElf_Rel), 0);
 804         free(relocname);
 805         if (!sec)
 806                 return NULL;
 807
 808         base->reloc = sec;
 809         sec->base = base;
 810
 811         sec->sh.sh_type = SHT_REL;
 812         sec->sh.sh_addralign = 8;
 813         sec->sh.sh_link = find_section_by_name(elf, ".symtab")->idx;
 814         sec->sh.sh_info = base->idx;
 815         sec->sh.sh_flags = SHF_INFO_LINK;
 816
 817         return sec;
 818 }
 819
 820 static struct section *elf_create_rela_reloc_section(struct elf *elf, struct section *base)
 821 {
 822         char *relocname;
 823         struct section *sec;
 824
 825         relocname = malloc(strlen(base->name) + strlen(".rela") + 1);
 826         if (!relocname) {
 827                 perror("malloc");
 828                 return NULL;
 829         }
 830         strcpy(relocname, ".rela");
 831         strcat(relocname, base->name);
 832
 833         sec = elf_create_section(elf, relocname, 0, sizeof(GElf_Rela), 0);
 834         free(relocname);
 835         if (!sec)
 836                 return NULL;
 837
 838         base->reloc = sec;
 839         sec->base = base;
 840
 841         sec->sh.sh_type = SHT_RELA;
 842         sec->sh.sh_addralign = 8;
 843         sec->sh.sh_link = find_section_by_name(elf, ".symtab")->idx;
 844         sec->sh.sh_info = base->idx;
 845         sec->sh.sh_flags = SHF_INFO_LINK;
 846
 847         return sec;
 848 }
 849
 850 struct section *elf_create_reloc_section(struct elf *elf,
 851                                          struct section *base,
 852                                          int reltype)
 853 {
 854         switch (reltype) {
 855         case SHT_REL:  return elf_create_rel_reloc_section(elf, base);
 856         case SHT_RELA: return elf_create_rela_reloc_section(elf, base);
 857         default:       return NULL;
 858         }
 859 }
 860
 861 static int elf_rebuild_rel_reloc_section(struct section *sec, int nr)
 862 {
 863         struct reloc *reloc;
 864         int idx = 0, size;
 865         GElf_Rel *relocs;
 866
 867         /* Allocate a buffer for relocations */
 868         size = nr * sizeof(*relocs);
 869         relocs = malloc(size);
 870         if (!relocs) {
 871                 perror("malloc");
 872                 return -1;
 873         }
 874
 875         sec->data->d_buf = relocs;
 876         sec->data->d_size = size;
 877
 878         sec->sh.sh_size = size;
 879
 880         idx = 0;
 881         list_for_each_entry(reloc, &sec->reloc_list, list) {
 882                 relocs[idx].r_offset = reloc->offset;
 883                 relocs[idx].r_info = GELF_R_INFO(reloc->sym->idx, reloc->type);
 884                 idx++;
 885         }
 886
 887         return 0;
 888 }
 889
 890 static int elf_rebuild_rela_reloc_section(struct section *sec, int nr)
 891 {
 892         struct reloc *reloc;
 893         int idx = 0, size;
 894         GElf_Rela *relocs;
 895
 896         /* Allocate a buffer for relocations with addends */
 897         size = nr * sizeof(*relocs);
 898         relocs = malloc(size);
 899         if (!relocs) {
 900                 perror("malloc");
 901                 return -1;
 902         }
 903
 904         sec->data->d_buf = relocs;
 905         sec->data->d_size = size;
 906
 907         sec->sh.sh_size = size;
 908
 909         idx = 0;
 910         list_for_each_entry(reloc, &sec->reloc_list, list) {
 911                 relocs[idx].r_offset = reloc->offset;
 912                 relocs[idx].r_addend = reloc->addend;
 913                 relocs[idx].r_info = GELF_R_INFO(reloc->sym->idx, reloc->type);
 914                 idx++;
 915         }
 916
 917         return 0;
 918 }
 919
 920 int elf_rebuild_reloc_section(struct elf *elf, struct section *sec)
 921 {
 922         struct reloc *reloc;
 923         int nr;
 924
 925         sec->changed = true;
 926         elf->changed = true;
 927
 928         nr = 0;
 929         list_for_each_entry(reloc, &sec->reloc_list, list)
 930                 nr++;
 931
 932         switch (sec->sh.sh_type) {
 933         case SHT_REL:  return elf_rebuild_rel_reloc_section(sec, nr);
 934         case SHT_RELA: return elf_rebuild_rela_reloc_section(sec, nr);
 935         default:       return -1;
 936         }
 937 }
 938
 939 int elf_write_insn(struct elf *elf, struct section *sec,
 940                    unsigned long offset, unsigned int len,
 941                    const char *insn)
 942 {
 943         Elf_Data *data = sec->data;
 944
 945         if (data->d_type != ELF_T_BYTE || data->d_off) {
 946                 WARN("write to unexpected data for section: %s", sec->name);
 947                 return -1;
 948         }
 949
 950         memcpy(data->d_buf + offset, insn, len);
 951         elf_flagdata(data, ELF_C_SET, ELF_F_DIRTY);
 952
 953         elf->changed = true;
 954
 955         return 0;
 956 }
 957
 958 int elf_write_reloc(struct elf *elf, struct reloc *reloc)
 959 {
 960         struct section *sec = reloc->sec;
 961
 962         if (sec->sh.sh_type == SHT_REL) {
 963                 reloc->rel.r_info = GELF_R_INFO(reloc->sym->idx, reloc->type);
 964                 reloc->rel.r_offset = reloc->offset;
 965
 966                 if (!gelf_update_rel(sec->data, reloc->idx, &reloc->rel)) {
 967                         WARN_ELF("gelf_update_rel");
 968                         return -1;
 969                 }
 970         } else {
 971                 reloc->rela.r_info = GELF_R_INFO(reloc->sym->idx, reloc->type);
 972                 reloc->rela.r_addend = reloc->addend;
 973                 reloc->rela.r_offset = reloc->offset;
 974
 975                 if (!gelf_update_rela(sec->data, reloc->idx, &reloc->rela)) {
 976                         WARN_ELF("gelf_update_rela");
 977                         return -1;
 978                 }
 979         }
 980
 981         elf->changed = true;
 982
 983         return 0;
 984 }
 985
 986 int elf_write(struct elf *elf)
 987 {
 988         struct section *sec;
 989         Elf_Scn *s;
 990
 991         /* Update section headers for changed sections: */
 992         list_for_each_entry(sec, &elf->sections, list) {
 993                 if (sec->changed) {
 994                         s = elf_getscn(elf->elf, sec->idx);
 995                         if (!s) {
 996                                 WARN_ELF("elf_getscn");
 997                                 return -1;
 998                         }
 999                         if (!gelf_update_shdr(s, &sec->sh)) {
1000                                 WARN_ELF("gelf_update_shdr");
1001                                 return -1;
1002                         }
1003
1004                         sec->changed = false;
1005                 }
1006         }
1007
1008         /* Make sure the new section header entries get updated properly. */
1009         elf_flagelf(elf->elf, ELF_C_SET, ELF_F_DIRTY);
1010
1011         /* Write all changes to the file. */
1012         if (elf_update(elf->elf, ELF_C_WRITE) < 0) {
1013                 WARN_ELF("elf_update");
1014                 return -1;
1015         }
1016
1017         elf->changed = false;
1018
1019         return 0;
1020 }
1021
1022 void elf_close(struct elf *elf)
1023 {
1024         struct section *sec, *tmpsec;
1025         struct symbol *sym, *tmpsym;
1026         struct reloc *reloc, *tmpreloc;
1027
1028         if (elf->elf)
1029                 elf_end(elf->elf);
1030
1031         if (elf->fd > 0)
1032                 close(elf->fd);
1033
1034         list_for_each_entry_safe(sec, tmpsec, &elf->sections, list) {
1035                 list_for_each_entry_safe(sym, tmpsym, &sec->symbol_list, list) {
1036                         list_del(&sym->list);
1037                         hash_del(&sym->hash);
1038                         free(sym);
1039                 }
1040                 list_for_each_entry_safe(reloc, tmpreloc, &sec->reloc_list, list) {
1041                         list_del(&reloc->list);
1042                         hash_del(&reloc->hash);
1043                         free(reloc);
1044                 }
1045                 list_del(&sec->list);
1046                 free(sec);
1047         }
1048
1049         free(elf);
1050 }