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