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                 sym->alias = sym;
 379
 380                 sym->idx = i;
 381
 382                 if (!gelf_getsymshndx(symtab->data, shndx_data, i, &sym->sym,
 383                                       &shndx)) {
 384                         WARN_ELF("gelf_getsymshndx");
 385                         goto err;
 386                 }
 387
 388                 sym->name = elf_strptr(elf->elf, symtab->sh.sh_link,
 389                                        sym->sym.st_name);
 390                 if (!sym->name) {
 391                         WARN_ELF("elf_strptr");
 392                         goto err;
 393                 }
 394
 395                 if ((sym->sym.st_shndx > SHN_UNDEF &&
 396                      sym->sym.st_shndx < SHN_LORESERVE) ||
 397                     (shndx_data && sym->sym.st_shndx == SHN_XINDEX)) {
 398                         if (sym->sym.st_shndx != SHN_XINDEX)
 399                                 shndx = sym->sym.st_shndx;
 400
 401                         sym->sec = find_section_by_index(elf, shndx);
 402                         if (!sym->sec) {
 403                                 WARN("couldn't find section for symbol %s",
 404                                      sym->name);
 405                                 goto err;
 406                         }
 407                         if (GELF_ST_TYPE(sym->sym.st_info) == STT_SECTION) {
 408                                 sym->name = sym->sec->name;
 409                                 sym->sec->sym = sym;
 410                         }
 411                 } else
 412                         sym->sec = find_section_by_index(elf, 0);
 413
 414                 elf_add_symbol(elf, sym);
 415         }
 416
 417         if (stats) {
 418                 printf("nr_symbols: %lu\n", (unsigned long)symbols_nr);
 419                 printf("symbol_bits: %d\n", elf->symbol_bits);
 420         }
 421
 422         /* Create parent/child links for any cold subfunctions */
 423         list_for_each_entry(sec, &elf->sections, list) {
 424                 list_for_each_entry(sym, &sec->symbol_list, list) {
 425                         char pname[MAX_NAME_LEN + 1];
 426                         size_t pnamelen;
 427                         if (sym->type != STT_FUNC)
 428                                 continue;
 429
 430                         if (sym->pfunc == NULL)
 431                                 sym->pfunc = sym;
 432
 433                         if (sym->cfunc == NULL)
 434                                 sym->cfunc = sym;
 435
 436                         coldstr = strstr(sym->name, ".cold");
 437                         if (!coldstr)
 438                                 continue;
 439
 440                         pnamelen = coldstr - sym->name;
 441                         if (pnamelen > MAX_NAME_LEN) {
 442                                 WARN("%s(): parent function name exceeds maximum length of %d characters",
 443                                      sym->name, MAX_NAME_LEN);
 444                                 return -1;
 445                         }
 446
 447                         strncpy(pname, sym->name, pnamelen);
 448                         pname[pnamelen] = '\0';
 449                         pfunc = find_symbol_by_name(elf, pname);
 450
 451                         if (!pfunc) {
 452                                 WARN("%s(): can't find parent function",
 453                                      sym->name);
 454                                 return -1;
 455                         }
 456
 457                         sym->pfunc = pfunc;
 458                         pfunc->cfunc = sym;
 459
 460                         /*
 461                          * Unfortunately, -fnoreorder-functions puts the child
 462                          * inside the parent.  Remove the overlap so we can
 463                          * have sane assumptions.
 464                          *
 465                          * Note that pfunc->len now no longer matches
 466                          * pfunc->sym.st_size.
 467                          */
 468                         if (sym->sec == pfunc->sec &&
 469                             sym->offset >= pfunc->offset &&
 470                             sym->offset + sym->len == pfunc->offset + pfunc->len) {
 471                                 pfunc->len -= sym->len;
 472                         }
 473                 }
 474         }
 475
 476         return 0;
 477
 478 err:
 479         free(sym);
 480         return -1;
 481 }
 482
 483 static struct section *elf_create_reloc_section(struct elf *elf,
 484                                                 struct section *base,
 485                                                 int reltype);
 486
 487 int elf_add_reloc(struct elf *elf, struct section *sec, unsigned long offset,
 488                   unsigned int type, struct symbol *sym, s64 addend)
 489 {
 490         struct reloc *reloc;
 491
 492         if (!sec->reloc && !elf_create_reloc_section(elf, sec, SHT_RELA))
 493                 return -1;
 494
 495         reloc = malloc(sizeof(*reloc));
 496         if (!reloc) {
 497                 perror("malloc");
 498                 return -1;
 499         }
 500         memset(reloc, 0, sizeof(*reloc));
 501
 502         reloc->sec = sec->reloc;
 503         reloc->offset = offset;
 504         reloc->type = type;
 505         reloc->sym = sym;
 506         reloc->addend = addend;
 507
 508         list_add_tail(&reloc->list, &sec->reloc->reloc_list);
 509         elf_hash_add(reloc, &reloc->hash, reloc_hash(reloc));
 510
 511         sec->reloc->sh.sh_size += sec->reloc->sh.sh_entsize;
 512         sec->reloc->changed = true;
 513
 514         return 0;
 515 }
 516
 517 /*
 518  * Ensure that any reloc section containing references to @sym is marked
 519  * changed such that it will get re-generated in elf_rebuild_reloc_sections()
 520  * with the new symbol index.
 521  */
 522 static void elf_dirty_reloc_sym(struct elf *elf, struct symbol *sym)
 523 {
 524         struct section *sec;
 525
 526         list_for_each_entry(sec, &elf->sections, list) {
 527                 struct reloc *reloc;
 528
 529                 if (sec->changed)
 530                         continue;
 531
 532                 list_for_each_entry(reloc, &sec->reloc_list, list) {
 533                         if (reloc->sym == sym) {
 534                                 sec->changed = true;
 535                                 break;
 536                         }
 537                 }
 538         }
 539 }
 540
 541 /*
 542  * Move the first global symbol, as per sh_info, into a new, higher symbol
 543  * index. This fees up the shndx for a new local symbol.
 544  */
 545 static int elf_move_global_symbol(struct elf *elf, struct section *symtab,
 546                                   struct section *symtab_shndx)
 547 {
 548         Elf_Data *data, *shndx_data = NULL;
 549         Elf32_Word first_non_local;
 550         struct symbol *sym;
 551         Elf_Scn *s;
 552
 553         first_non_local = symtab->sh.sh_info;
 554
 555         sym = find_symbol_by_index(elf, first_non_local);
 556         if (!sym) {
 557                 WARN("no non-local symbols !?");
 558                 return first_non_local;
 559         }
 560
 561         s = elf_getscn(elf->elf, symtab->idx);
 562         if (!s) {
 563                 WARN_ELF("elf_getscn");
 564                 return -1;
 565         }
 566
 567         data = elf_newdata(s);
 568         if (!data) {
 569                 WARN_ELF("elf_newdata");
 570                 return -1;
 571         }
 572
 573         data->d_buf = &sym->sym;
 574         data->d_size = sizeof(sym->sym);
 575         data->d_align = 1;
 576         data->d_type = ELF_T_SYM;
 577
 578         sym->idx = symtab->sh.sh_size / sizeof(sym->sym);
 579         elf_dirty_reloc_sym(elf, sym);
 580
 581         symtab->sh.sh_info += 1;
 582         symtab->sh.sh_size += data->d_size;
 583         symtab->changed = true;
 584
 585         if (symtab_shndx) {
 586                 s = elf_getscn(elf->elf, symtab_shndx->idx);
 587                 if (!s) {
 588                         WARN_ELF("elf_getscn");
 589                         return -1;
 590                 }
 591
 592                 shndx_data = elf_newdata(s);
 593                 if (!shndx_data) {
 594                         WARN_ELF("elf_newshndx_data");
 595                         return -1;
 596                 }
 597
 598                 shndx_data->d_buf = &sym->sec->idx;
 599                 shndx_data->d_size = sizeof(Elf32_Word);
 600                 shndx_data->d_align = 4;
 601                 shndx_data->d_type = ELF_T_WORD;
 602
 603                 symtab_shndx->sh.sh_size += 4;
 604                 symtab_shndx->changed = true;
 605         }
 606
 607         return first_non_local;
 608 }
 609
 610 static struct symbol *
 611 elf_create_section_symbol(struct elf *elf, struct section *sec)
 612 {
 613         struct section *symtab, *symtab_shndx;
 614         Elf_Data *shndx_data = NULL;
 615         struct symbol *sym;
 616         Elf32_Word shndx;
 617
 618         symtab = find_section_by_name(elf, ".symtab");
 619         if (symtab) {
 620                 symtab_shndx = find_section_by_name(elf, ".symtab_shndx");
 621                 if (symtab_shndx)
 622                         shndx_data = symtab_shndx->data;
 623         } else {
 624                 WARN("no .symtab");
 625                 return NULL;
 626         }
 627
 628         sym = malloc(sizeof(*sym));
 629         if (!sym) {
 630                 perror("malloc");
 631                 return NULL;
 632         }
 633         memset(sym, 0, sizeof(*sym));
 634
 635         sym->idx = elf_move_global_symbol(elf, symtab, symtab_shndx);
 636         if (sym->idx < 0) {
 637                 WARN("elf_move_global_symbol");
 638                 return NULL;
 639         }
 640
 641         sym->name = sec->name;
 642         sym->sec = sec;
 643
 644         // st_name 0
 645         sym->sym.st_info = GELF_ST_INFO(STB_LOCAL, STT_SECTION);
 646         // st_other 0
 647         // st_value 0
 648         // st_size 0
 649         shndx = sec->idx;
 650         if (shndx >= SHN_UNDEF && shndx < SHN_LORESERVE) {
 651                 sym->sym.st_shndx = shndx;
 652                 if (!shndx_data)
 653                         shndx = 0;
 654         } else {
 655                 sym->sym.st_shndx = SHN_XINDEX;
 656                 if (!shndx_data) {
 657                         WARN("no .symtab_shndx");
 658                         return NULL;
 659                 }
 660         }
 661
 662         if (!gelf_update_symshndx(symtab->data, shndx_data, sym->idx, &sym->sym, shndx)) {
 663                 WARN_ELF("gelf_update_symshndx");
 664                 return NULL;
 665         }
 666
 667         elf_add_symbol(elf, sym);
 668
 669         return sym;
 670 }
 671
 672 int elf_add_reloc_to_insn(struct elf *elf, struct section *sec,
 673                           unsigned long offset, unsigned int type,
 674                           struct section *insn_sec, unsigned long insn_off)
 675 {
 676         struct symbol *sym = insn_sec->sym;
 677         int addend = insn_off;
 678
 679         if (!sym) {
 680                 /*
 681                  * Due to how weak functions work, we must use section based
 682                  * relocations. Symbol based relocations would result in the
 683                  * weak and non-weak function annotations being overlaid on the
 684                  * non-weak function after linking.
 685                  */
 686                 sym = elf_create_section_symbol(elf, insn_sec);
 687                 if (!sym)
 688                         return -1;
 689
 690                 insn_sec->sym = sym;
 691         }
 692
 693         return elf_add_reloc(elf, sec, offset, type, sym, addend);
 694 }
 695
 696 static int read_rel_reloc(struct section *sec, int i, struct reloc *reloc, unsigned int *symndx)
 697 {
 698         if (!gelf_getrel(sec->data, i, &reloc->rel)) {
 699                 WARN_ELF("gelf_getrel");
 700                 return -1;
 701         }
 702         reloc->type = GELF_R_TYPE(reloc->rel.r_info);
 703         reloc->addend = 0;
 704         reloc->offset = reloc->rel.r_offset;
 705         *symndx = GELF_R_SYM(reloc->rel.r_info);
 706         return 0;
 707 }
 708
 709 static int read_rela_reloc(struct section *sec, int i, struct reloc *reloc, unsigned int *symndx)
 710 {
 711         if (!gelf_getrela(sec->data, i, &reloc->rela)) {
 712                 WARN_ELF("gelf_getrela");
 713                 return -1;
 714         }
 715         reloc->type = GELF_R_TYPE(reloc->rela.r_info);
 716         reloc->addend = reloc->rela.r_addend;
 717         reloc->offset = reloc->rela.r_offset;
 718         *symndx = GELF_R_SYM(reloc->rela.r_info);
 719         return 0;
 720 }
 721
 722 static int read_relocs(struct elf *elf)
 723 {
 724         struct section *sec;
 725         struct reloc *reloc;
 726         int i;
 727         unsigned int symndx;
 728         unsigned long nr_reloc, max_reloc = 0, tot_reloc = 0;
 729
 730         if (!elf_alloc_hash(reloc, elf->text_size / 16))
 731                 return -1;
 732
 733         list_for_each_entry(sec, &elf->sections, list) {
 734                 if ((sec->sh.sh_type != SHT_RELA) &&
 735                     (sec->sh.sh_type != SHT_REL))
 736                         continue;
 737
 738                 sec->base = find_section_by_index(elf, sec->sh.sh_info);
 739                 if (!sec->base) {
 740                         WARN("can't find base section for reloc section %s",
 741                              sec->name);
 742                         return -1;
 743                 }
 744
 745                 sec->base->reloc = sec;
 746
 747                 nr_reloc = 0;
 748                 for (i = 0; i < sec->sh.sh_size / sec->sh.sh_entsize; i++) {
 749                         reloc = malloc(sizeof(*reloc));
 750                         if (!reloc) {
 751                                 perror("malloc");
 752                                 return -1;
 753                         }
 754                         memset(reloc, 0, sizeof(*reloc));
 755                         switch (sec->sh.sh_type) {
 756                         case SHT_REL:
 757                                 if (read_rel_reloc(sec, i, reloc, &symndx))
 758                                         return -1;
 759                                 break;
 760                         case SHT_RELA:
 761                                 if (read_rela_reloc(sec, i, reloc, &symndx))
 762                                         return -1;
 763                                 break;
 764                         default: return -1;
 765                         }
 766
 767                         reloc->sec = sec;
 768                         reloc->idx = i;
 769                         reloc->sym = find_symbol_by_index(elf, symndx);
 770                         if (!reloc->sym) {
 771                                 WARN("can't find reloc entry symbol %d for %s",
 772                                      symndx, sec->name);
 773                                 return -1;
 774                         }
 775
 776                         list_add_tail(&reloc->list, &sec->reloc_list);
 777                         elf_hash_add(reloc, &reloc->hash, reloc_hash(reloc));
 778
 779                         nr_reloc++;
 780                 }
 781                 max_reloc = max(max_reloc, nr_reloc);
 782                 tot_reloc += nr_reloc;
 783         }
 784
 785         if (stats) {
 786                 printf("max_reloc: %lu\n", max_reloc);
 787                 printf("tot_reloc: %lu\n", tot_reloc);
 788                 printf("reloc_bits: %d\n", elf->reloc_bits);
 789         }
 790
 791         return 0;
 792 }
 793
 794 struct elf *elf_open_read(const char *name, int flags)
 795 {
 796         struct elf *elf;
 797         Elf_Cmd cmd;
 798
 799         elf_version(EV_CURRENT);
 800
 801         elf = malloc(sizeof(*elf));
 802         if (!elf) {
 803                 perror("malloc");
 804                 return NULL;
 805         }
 806         memset(elf, 0, offsetof(struct elf, sections));
 807
 808         INIT_LIST_HEAD(&elf->sections);
 809
 810         elf->fd = open(name, flags);
 811         if (elf->fd == -1) {
 812                 fprintf(stderr, "objtool: Can't open '%s': %s\n",
 813                         name, strerror(errno));
 814                 goto err;
 815         }
 816
 817         if ((flags & O_ACCMODE) == O_RDONLY)
 818                 cmd = ELF_C_READ_MMAP;
 819         else if ((flags & O_ACCMODE) == O_RDWR)
 820                 cmd = ELF_C_RDWR;
 821         else /* O_WRONLY */
 822                 cmd = ELF_C_WRITE;
 823
 824         elf->elf = elf_begin(elf->fd, cmd, NULL);
 825         if (!elf->elf) {
 826                 WARN_ELF("elf_begin");
 827                 goto err;
 828         }
 829
 830         if (!gelf_getehdr(elf->elf, &elf->ehdr)) {
 831                 WARN_ELF("gelf_getehdr");
 832                 goto err;
 833         }
 834
 835         if (read_sections(elf))
 836                 goto err;
 837
 838         if (read_symbols(elf))
 839                 goto err;
 840
 841         if (read_relocs(elf))
 842                 goto err;
 843
 844         return elf;
 845
 846 err:
 847         elf_close(elf);
 848         return NULL;
 849 }
 850
 851 static int elf_add_string(struct elf *elf, struct section *strtab, char *str)
 852 {
 853         Elf_Data *data;
 854         Elf_Scn *s;
 855         int len;
 856
 857         if (!strtab)
 858                 strtab = find_section_by_name(elf, ".strtab");
 859         if (!strtab) {
 860                 WARN("can't find .strtab section");
 861                 return -1;
 862         }
 863
 864         s = elf_getscn(elf->elf, strtab->idx);
 865         if (!s) {
 866                 WARN_ELF("elf_getscn");
 867                 return -1;
 868         }
 869
 870         data = elf_newdata(s);
 871         if (!data) {
 872                 WARN_ELF("elf_newdata");
 873                 return -1;
 874         }
 875
 876         data->d_buf = str;
 877         data->d_size = strlen(str) + 1;
 878         data->d_align = 1;
 879
 880         len = strtab->sh.sh_size;
 881         strtab->sh.sh_size += data->d_size;
 882         strtab->changed = true;
 883
 884         return len;
 885 }
 886
 887 struct symbol *elf_create_undef_symbol(struct elf *elf, const char *name)
 888 {
 889         struct section *symtab, *symtab_shndx;
 890         struct symbol *sym;
 891         Elf_Data *data;
 892         Elf_Scn *s;
 893
 894         sym = malloc(sizeof(*sym));
 895         if (!sym) {
 896                 perror("malloc");
 897                 return NULL;
 898         }
 899         memset(sym, 0, sizeof(*sym));
 900
 901         sym->name = strdup(name);
 902
 903         sym->sym.st_name = elf_add_string(elf, NULL, sym->name);
 904         if (sym->sym.st_name == -1)
 905                 return NULL;
 906
 907         sym->sym.st_info = GELF_ST_INFO(STB_GLOBAL, STT_NOTYPE);
 908         // st_other 0
 909         // st_shndx 0
 910         // st_value 0
 911         // st_size 0
 912
 913         symtab = find_section_by_name(elf, ".symtab");
 914         if (!symtab) {
 915                 WARN("can't find .symtab");
 916                 return NULL;
 917         }
 918
 919         s = elf_getscn(elf->elf, symtab->idx);
 920         if (!s) {
 921                 WARN_ELF("elf_getscn");
 922                 return NULL;
 923         }
 924
 925         data = elf_newdata(s);
 926         if (!data) {
 927                 WARN_ELF("elf_newdata");
 928                 return NULL;
 929         }
 930
 931         data->d_buf = &sym->sym;
 932         data->d_size = sizeof(sym->sym);
 933         data->d_align = 1;
 934         data->d_type = ELF_T_SYM;
 935
 936         sym->idx = symtab->sh.sh_size / sizeof(sym->sym);
 937
 938         symtab->sh.sh_size += data->d_size;
 939         symtab->changed = true;
 940
 941         symtab_shndx = find_section_by_name(elf, ".symtab_shndx");
 942         if (symtab_shndx) {
 943                 s = elf_getscn(elf->elf, symtab_shndx->idx);
 944                 if (!s) {
 945                         WARN_ELF("elf_getscn");
 946                         return NULL;
 947                 }
 948
 949                 data = elf_newdata(s);
 950                 if (!data) {
 951                         WARN_ELF("elf_newdata");
 952                         return NULL;
 953                 }
 954
 955                 data->d_buf = &sym->sym.st_size; /* conveniently 0 */
 956                 data->d_size = sizeof(Elf32_Word);
 957                 data->d_align = 4;
 958                 data->d_type = ELF_T_WORD;
 959
 960                 symtab_shndx->sh.sh_size += 4;
 961                 symtab_shndx->changed = true;
 962         }
 963
 964         sym->sec = find_section_by_index(elf, 0);
 965
 966         elf_add_symbol(elf, sym);
 967
 968         return sym;
 969 }
 970
 971 struct section *elf_create_section(struct elf *elf, const char *name,
 972                                    unsigned int sh_flags, size_t entsize, int nr)
 973 {
 974         struct section *sec, *shstrtab;
 975         size_t size = entsize * nr;
 976         Elf_Scn *s;
 977
 978         sec = malloc(sizeof(*sec));
 979         if (!sec) {
 980                 perror("malloc");
 981                 return NULL;
 982         }
 983         memset(sec, 0, sizeof(*sec));
 984
 985         INIT_LIST_HEAD(&sec->symbol_list);
 986         INIT_LIST_HEAD(&sec->reloc_list);
 987
 988         s = elf_newscn(elf->elf);
 989         if (!s) {
 990                 WARN_ELF("elf_newscn");
 991                 return NULL;
 992         }
 993
 994         sec->name = strdup(name);
 995         if (!sec->name) {
 996                 perror("strdup");
 997                 return NULL;
 998         }
 999
1000         sec->idx = elf_ndxscn(s);
1001         sec->changed = true;
1002
1003         sec->data = elf_newdata(s);
1004         if (!sec->data) {
1005                 WARN_ELF("elf_newdata");
1006                 return NULL;
1007         }
1008
1009         sec->data->d_size = size;
1010         sec->data->d_align = 1;
1011
1012         if (size) {
1013                 sec->data->d_buf = malloc(size);
1014                 if (!sec->data->d_buf) {
1015                         perror("malloc");
1016                         return NULL;
1017                 }
1018                 memset(sec->data->d_buf, 0, size);
1019         }
1020
1021         if (!gelf_getshdr(s, &sec->sh)) {
1022                 WARN_ELF("gelf_getshdr");
1023                 return NULL;
1024         }
1025
1026         sec->sh.sh_size = size;
1027         sec->sh.sh_entsize = entsize;
1028         sec->sh.sh_type = SHT_PROGBITS;
1029         sec->sh.sh_addralign = 1;
1030         sec->sh.sh_flags = SHF_ALLOC | sh_flags;
1031
1032         /* Add section name to .shstrtab (or .strtab for Clang) */
1033         shstrtab = find_section_by_name(elf, ".shstrtab");
1034         if (!shstrtab)
1035                 shstrtab = find_section_by_name(elf, ".strtab");
1036         if (!shstrtab) {
1037                 WARN("can't find .shstrtab or .strtab section");
1038                 return NULL;
1039         }
1040         sec->sh.sh_name = elf_add_string(elf, shstrtab, sec->name);
1041         if (sec->sh.sh_name == -1)
1042                 return NULL;
1043
1044         list_add_tail(&sec->list, &elf->sections);
1045         elf_hash_add(section, &sec->hash, sec->idx);
1046         elf_hash_add(section_name, &sec->name_hash, str_hash(sec->name));
1047
1048         elf->changed = true;
1049
1050         return sec;
1051 }
1052
1053 static struct section *elf_create_rel_reloc_section(struct elf *elf, struct section *base)
1054 {
1055         char *relocname;
1056         struct section *sec;
1057
1058         relocname = malloc(strlen(base->name) + strlen(".rel") + 1);
1059         if (!relocname) {
1060                 perror("malloc");
1061                 return NULL;
1062         }
1063         strcpy(relocname, ".rel");
1064         strcat(relocname, base->name);
1065
1066         sec = elf_create_section(elf, relocname, 0, sizeof(GElf_Rel), 0);
1067         free(relocname);
1068         if (!sec)
1069                 return NULL;
1070
1071         base->reloc = sec;
1072         sec->base = base;
1073
1074         sec->sh.sh_type = SHT_REL;
1075         sec->sh.sh_addralign = 8;
1076         sec->sh.sh_link = find_section_by_name(elf, ".symtab")->idx;
1077         sec->sh.sh_info = base->idx;
1078         sec->sh.sh_flags = SHF_INFO_LINK;
1079
1080         return sec;
1081 }
1082
1083 static struct section *elf_create_rela_reloc_section(struct elf *elf, struct section *base)
1084 {
1085         char *relocname;
1086         struct section *sec;
1087
1088         relocname = malloc(strlen(base->name) + strlen(".rela") + 1);
1089         if (!relocname) {
1090                 perror("malloc");
1091                 return NULL;
1092         }
1093         strcpy(relocname, ".rela");
1094         strcat(relocname, base->name);
1095
1096         sec = elf_create_section(elf, relocname, 0, sizeof(GElf_Rela), 0);
1097         free(relocname);
1098         if (!sec)
1099                 return NULL;
1100
1101         base->reloc = sec;
1102         sec->base = base;
1103
1104         sec->sh.sh_type = SHT_RELA;
1105         sec->sh.sh_addralign = 8;
1106         sec->sh.sh_link = find_section_by_name(elf, ".symtab")->idx;
1107         sec->sh.sh_info = base->idx;
1108         sec->sh.sh_flags = SHF_INFO_LINK;
1109
1110         return sec;
1111 }
1112
1113 static struct section *elf_create_reloc_section(struct elf *elf,
1114                                          struct section *base,
1115                                          int reltype)
1116 {
1117         switch (reltype) {
1118         case SHT_REL:  return elf_create_rel_reloc_section(elf, base);
1119         case SHT_RELA: return elf_create_rela_reloc_section(elf, base);
1120         default:       return NULL;
1121         }
1122 }
1123
1124 static int elf_rebuild_rel_reloc_section(struct section *sec)
1125 {
1126         struct reloc *reloc;
1127         int idx = 0;
1128         void *buf;
1129
1130         /* Allocate a buffer for relocations */
1131         buf = malloc(sec->sh.sh_size);
1132         if (!buf) {
1133                 perror("malloc");
1134                 return -1;
1135         }
1136
1137         sec->data->d_buf = buf;
1138         sec->data->d_size = sec->sh.sh_size;
1139         sec->data->d_type = ELF_T_REL;
1140
1141         idx = 0;
1142         list_for_each_entry(reloc, &sec->reloc_list, list) {
1143                 reloc->rel.r_offset = reloc->offset;
1144                 reloc->rel.r_info = GELF_R_INFO(reloc->sym->idx, reloc->type);
1145                 if (!gelf_update_rel(sec->data, idx, &reloc->rel)) {
1146                         WARN_ELF("gelf_update_rel");
1147                         return -1;
1148                 }
1149                 idx++;
1150         }
1151
1152         return 0;
1153 }
1154
1155 static int elf_rebuild_rela_reloc_section(struct section *sec)
1156 {
1157         struct reloc *reloc;
1158         int idx = 0;
1159         void *buf;
1160
1161         /* Allocate a buffer for relocations with addends */
1162         buf = malloc(sec->sh.sh_size);
1163         if (!buf) {
1164                 perror("malloc");
1165                 return -1;
1166         }
1167
1168         sec->data->d_buf = buf;
1169         sec->data->d_size = sec->sh.sh_size;
1170         sec->data->d_type = ELF_T_RELA;
1171
1172         idx = 0;
1173         list_for_each_entry(reloc, &sec->reloc_list, list) {
1174                 reloc->rela.r_offset = reloc->offset;
1175                 reloc->rela.r_addend = reloc->addend;
1176                 reloc->rela.r_info = GELF_R_INFO(reloc->sym->idx, reloc->type);
1177                 if (!gelf_update_rela(sec->data, idx, &reloc->rela)) {
1178                         WARN_ELF("gelf_update_rela");
1179                         return -1;
1180                 }
1181                 idx++;
1182         }
1183
1184         return 0;
1185 }
1186
1187 static int elf_rebuild_reloc_section(struct elf *elf, struct section *sec)
1188 {
1189         switch (sec->sh.sh_type) {
1190         case SHT_REL:  return elf_rebuild_rel_reloc_section(sec);
1191         case SHT_RELA: return elf_rebuild_rela_reloc_section(sec);
1192         default:       return -1;
1193         }
1194 }
1195
1196 int elf_write_insn(struct elf *elf, struct section *sec,
1197                    unsigned long offset, unsigned int len,
1198                    const char *insn)
1199 {
1200         Elf_Data *data = sec->data;
1201
1202         if (data->d_type != ELF_T_BYTE || data->d_off) {
1203                 WARN("write to unexpected data for section: %s", sec->name);
1204                 return -1;
1205         }
1206
1207         memcpy(data->d_buf + offset, insn, len);
1208         elf_flagdata(data, ELF_C_SET, ELF_F_DIRTY);
1209
1210         elf->changed = true;
1211
1212         return 0;
1213 }
1214
1215 int elf_write_reloc(struct elf *elf, struct reloc *reloc)
1216 {
1217         struct section *sec = reloc->sec;
1218
1219         if (sec->sh.sh_type == SHT_REL) {
1220                 reloc->rel.r_info = GELF_R_INFO(reloc->sym->idx, reloc->type);
1221                 reloc->rel.r_offset = reloc->offset;
1222
1223                 if (!gelf_update_rel(sec->data, reloc->idx, &reloc->rel)) {
1224                         WARN_ELF("gelf_update_rel");
1225                         return -1;
1226                 }
1227         } else {
1228                 reloc->rela.r_info = GELF_R_INFO(reloc->sym->idx, reloc->type);
1229                 reloc->rela.r_addend = reloc->addend;
1230                 reloc->rela.r_offset = reloc->offset;
1231
1232                 if (!gelf_update_rela(sec->data, reloc->idx, &reloc->rela)) {
1233                         WARN_ELF("gelf_update_rela");
1234                         return -1;
1235                 }
1236         }
1237
1238         elf->changed = true;
1239
1240         return 0;
1241 }
1242
1243 int elf_write(struct elf *elf)
1244 {
1245         struct section *sec;
1246         Elf_Scn *s;
1247
1248         /* Update changed relocation sections and section headers: */
1249         list_for_each_entry(sec, &elf->sections, list) {
1250                 if (sec->changed) {
1251                         s = elf_getscn(elf->elf, sec->idx);
1252                         if (!s) {
1253                                 WARN_ELF("elf_getscn");
1254                                 return -1;
1255                         }
1256                         if (!gelf_update_shdr(s, &sec->sh)) {
1257                                 WARN_ELF("gelf_update_shdr");
1258                                 return -1;
1259                         }
1260
1261                         if (sec->base &&
1262                             elf_rebuild_reloc_section(elf, sec)) {
1263                                 WARN("elf_rebuild_reloc_section");
1264                                 return -1;
1265                         }
1266
1267                         sec->changed = false;
1268                         elf->changed = true;
1269                 }
1270         }
1271
1272         /* Make sure the new section header entries get updated properly. */
1273         elf_flagelf(elf->elf, ELF_C_SET, ELF_F_DIRTY);
1274
1275         /* Write all changes to the file. */
1276         if (elf_update(elf->elf, ELF_C_WRITE) < 0) {
1277                 WARN_ELF("elf_update");
1278                 return -1;
1279         }
1280
1281         elf->changed = false;
1282
1283         return 0;
1284 }
1285
1286 void elf_close(struct elf *elf)
1287 {
1288         struct section *sec, *tmpsec;
1289         struct symbol *sym, *tmpsym;
1290         struct reloc *reloc, *tmpreloc;
1291
1292         if (elf->elf)
1293                 elf_end(elf->elf);
1294
1295         if (elf->fd > 0)
1296                 close(elf->fd);
1297
1298         list_for_each_entry_safe(sec, tmpsec, &elf->sections, list) {
1299                 list_for_each_entry_safe(sym, tmpsym, &sec->symbol_list, list) {
1300                         list_del(&sym->list);
1301                         hash_del(&sym->hash);
1302                         free(sym);
1303                 }
1304                 list_for_each_entry_safe(reloc, tmpreloc, &sec->reloc_list, list) {
1305                         list_del(&reloc->list);
1306                         hash_del(&reloc->hash);
1307                         free(reloc);
1308                 }
1309                 list_del(&sec->list);
1310                 free(sec);
1311         }
1312
1313         free(elf);
1314 }