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                 /*
 384                  * A missing symbol table is actually possible if it's an empty
 385                  * .o file.  This can happen for thunk_64.o.
 386                  */
 387                 return 0;
 388         }
 389
 390         symtab_shndx = find_section_by_name(elf, ".symtab_shndx");
 391         if (symtab_shndx)
 392                 shndx_data = symtab_shndx->data;
 393
 394         symbols_nr = symtab->sh.sh_size / symtab->sh.sh_entsize;
 395
 396         for (i = 0; i < symbols_nr; i++) {
 397                 sym = malloc(sizeof(*sym));
 398                 if (!sym) {
 399                         perror("malloc");
 400                         return -1;
 401                 }
 402                 memset(sym, 0, sizeof(*sym));
 403                 sym->alias = sym;
 404
 405                 sym->idx = i;
 406
 407                 if (!gelf_getsymshndx(symtab->data, shndx_data, i, &sym->sym,
 408                                       &shndx)) {
 409                         WARN_ELF("gelf_getsymshndx");
 410                         goto err;
 411                 }
 412
 413                 sym->name = elf_strptr(elf->elf, symtab->sh.sh_link,
 414                                        sym->sym.st_name);
 415                 if (!sym->name) {
 416                         WARN_ELF("elf_strptr");
 417                         goto err;
 418                 }
 419
 420                 sym->type = GELF_ST_TYPE(sym->sym.st_info);
 421                 sym->bind = GELF_ST_BIND(sym->sym.st_info);
 422
 423                 if ((sym->sym.st_shndx > SHN_UNDEF &&
 424                      sym->sym.st_shndx < SHN_LORESERVE) ||
 425                     (shndx_data && sym->sym.st_shndx == SHN_XINDEX)) {
 426                         if (sym->sym.st_shndx != SHN_XINDEX)
 427                                 shndx = sym->sym.st_shndx;
 428
 429                         sym->sec = find_section_by_index(elf, shndx);
 430                         if (!sym->sec) {
 431                                 WARN("couldn't find section for symbol %s",
 432                                      sym->name);
 433                                 goto err;
 434                         }
 435                         if (sym->type == STT_SECTION) {
 436                                 sym->name = sym->sec->name;
 437                                 sym->sec->sym = sym;
 438                         }
 439                 } else
 440                         sym->sec = find_section_by_index(elf, 0);
 441
 442                 sym->offset = sym->sym.st_value;
 443                 sym->len = sym->sym.st_size;
 444
 445                 rb_add(&sym->sec->symbol_tree, &sym->node, symbol_to_offset);
 446                 pnode = rb_prev(&sym->node);
 447                 if (pnode)
 448                         entry = &rb_entry(pnode, struct symbol, node)->list;
 449                 else
 450                         entry = &sym->sec->symbol_list;
 451                 list_add(&sym->list, entry);
 452                 elf_hash_add(elf->symbol_hash, &sym->hash, sym->idx);
 453                 elf_hash_add(elf->symbol_name_hash, &sym->name_hash, str_hash(sym->name));
 454
 455                 /*
 456                  * Don't store empty STT_NOTYPE symbols in the rbtree.  They
 457                  * can exist within a function, confusing the sorting.
 458                  */
 459                 if (!sym->len)
 460                         rb_erase(&sym->node, &sym->sec->symbol_tree);
 461         }
 462
 463         if (stats)
 464                 printf("nr_symbols: %lu\n", (unsigned long)symbols_nr);
 465
 466         /* Create parent/child links for any cold subfunctions */
 467         list_for_each_entry(sec, &elf->sections, list) {
 468                 list_for_each_entry(sym, &sec->symbol_list, list) {
 469                         char pname[MAX_NAME_LEN + 1];
 470                         size_t pnamelen;
 471                         if (sym->type != STT_FUNC)
 472                                 continue;
 473
 474                         if (sym->pfunc == NULL)
 475                                 sym->pfunc = sym;
 476
 477                         if (sym->cfunc == NULL)
 478                                 sym->cfunc = sym;
 479
 480                         coldstr = strstr(sym->name, ".cold");
 481                         if (!coldstr)
 482                                 continue;
 483
 484                         pnamelen = coldstr - sym->name;
 485                         if (pnamelen > MAX_NAME_LEN) {
 486                                 WARN("%s(): parent function name exceeds maximum length of %d characters",
 487                                      sym->name, MAX_NAME_LEN);
 488                                 return -1;
 489                         }
 490
 491                         strncpy(pname, sym->name, pnamelen);
 492                         pname[pnamelen] = '\0';
 493                         pfunc = find_symbol_by_name(elf, pname);
 494
 495                         if (!pfunc) {
 496                                 WARN("%s(): can't find parent function",
 497                                      sym->name);
 498                                 return -1;
 499                         }
 500
 501                         sym->pfunc = pfunc;
 502                         pfunc->cfunc = sym;
 503
 504                         /*
 505                          * Unfortunately, -fnoreorder-functions puts the child
 506                          * inside the parent.  Remove the overlap so we can
 507                          * have sane assumptions.
 508                          *
 509                          * Note that pfunc->len now no longer matches
 510                          * pfunc->sym.st_size.
 511                          */
 512                         if (sym->sec == pfunc->sec &&
 513                             sym->offset >= pfunc->offset &&
 514                             sym->offset + sym->len == pfunc->offset + pfunc->len) {
 515                                 pfunc->len -= sym->len;
 516                         }
 517                 }
 518         }
 519
 520         return 0;
 521
 522 err:
 523         free(sym);
 524         return -1;
 525 }
 526
 527 void elf_add_reloc(struct elf *elf, struct reloc *reloc)
 528 {
 529         struct section *sec = reloc->sec;
 530
 531         list_add_tail(&reloc->list, &sec->reloc_list);
 532         elf_hash_add(elf->reloc_hash, &reloc->hash, reloc_hash(reloc));
 533 }
 534
 535 static int read_rel_reloc(struct section *sec, int i, struct reloc *reloc, unsigned int *symndx)
 536 {
 537         if (!gelf_getrel(sec->data, i, &reloc->rel)) {
 538                 WARN_ELF("gelf_getrel");
 539                 return -1;
 540         }
 541         reloc->type = GELF_R_TYPE(reloc->rel.r_info);
 542         reloc->addend = 0;
 543         reloc->offset = reloc->rel.r_offset;
 544         *symndx = GELF_R_SYM(reloc->rel.r_info);
 545         return 0;
 546 }
 547
 548 static int read_rela_reloc(struct section *sec, int i, struct reloc *reloc, unsigned int *symndx)
 549 {
 550         if (!gelf_getrela(sec->data, i, &reloc->rela)) {
 551                 WARN_ELF("gelf_getrela");
 552                 return -1;
 553         }
 554         reloc->type = GELF_R_TYPE(reloc->rela.r_info);
 555         reloc->addend = reloc->rela.r_addend;
 556         reloc->offset = reloc->rela.r_offset;
 557         *symndx = GELF_R_SYM(reloc->rela.r_info);
 558         return 0;
 559 }
 560
 561 static int read_relocs(struct elf *elf)
 562 {
 563         struct section *sec;
 564         struct reloc *reloc;
 565         int i;
 566         unsigned int symndx;
 567         unsigned long nr_reloc, max_reloc = 0, tot_reloc = 0;
 568
 569         list_for_each_entry(sec, &elf->sections, list) {
 570                 if ((sec->sh.sh_type != SHT_RELA) &&
 571                     (sec->sh.sh_type != SHT_REL))
 572                         continue;
 573
 574                 sec->base = find_section_by_index(elf, sec->sh.sh_info);
 575                 if (!sec->base) {
 576                         WARN("can't find base section for reloc section %s",
 577                              sec->name);
 578                         return -1;
 579                 }
 580
 581                 sec->base->reloc = sec;
 582
 583                 nr_reloc = 0;
 584                 for (i = 0; i < sec->sh.sh_size / sec->sh.sh_entsize; i++) {
 585                         reloc = malloc(sizeof(*reloc));
 586                         if (!reloc) {
 587                                 perror("malloc");
 588                                 return -1;
 589                         }
 590                         memset(reloc, 0, sizeof(*reloc));
 591                         switch (sec->sh.sh_type) {
 592                         case SHT_REL:
 593                                 if (read_rel_reloc(sec, i, reloc, &symndx))
 594                                         return -1;
 595                                 break;
 596                         case SHT_RELA:
 597                                 if (read_rela_reloc(sec, i, reloc, &symndx))
 598                                         return -1;
 599                                 break;
 600                         default: return -1;
 601                         }
 602
 603                         reloc->sec = sec;
 604                         reloc->idx = i;
 605                         reloc->sym = find_symbol_by_index(elf, symndx);
 606                         if (!reloc->sym) {
 607                                 WARN("can't find reloc entry symbol %d for %s",
 608                                      symndx, sec->name);
 609                                 return -1;
 610                         }
 611
 612                         elf_add_reloc(elf, reloc);
 613                         nr_reloc++;
 614                 }
 615                 max_reloc = max(max_reloc, nr_reloc);
 616                 tot_reloc += nr_reloc;
 617         }
 618
 619         if (stats) {
 620                 printf("max_reloc: %lu\n", max_reloc);
 621                 printf("tot_reloc: %lu\n", tot_reloc);
 622         }
 623
 624         return 0;
 625 }
 626
 627 struct elf *elf_open_read(const char *name, int flags)
 628 {
 629         struct elf *elf;
 630         Elf_Cmd cmd;
 631
 632         elf_version(EV_CURRENT);
 633
 634         elf = malloc(sizeof(*elf));
 635         if (!elf) {
 636                 perror("malloc");
 637                 return NULL;
 638         }
 639         memset(elf, 0, offsetof(struct elf, sections));
 640
 641         INIT_LIST_HEAD(&elf->sections);
 642
 643         elf_hash_init(elf->symbol_hash);
 644         elf_hash_init(elf->symbol_name_hash);
 645         elf_hash_init(elf->section_hash);
 646         elf_hash_init(elf->section_name_hash);
 647         elf_hash_init(elf->reloc_hash);
 648
 649         elf->fd = open(name, flags);
 650         if (elf->fd == -1) {
 651                 fprintf(stderr, "objtool: Can't open '%s': %s\n",
 652                         name, strerror(errno));
 653                 goto err;
 654         }
 655
 656         if ((flags & O_ACCMODE) == O_RDONLY)
 657                 cmd = ELF_C_READ_MMAP;
 658         else if ((flags & O_ACCMODE) == O_RDWR)
 659                 cmd = ELF_C_RDWR;
 660         else /* O_WRONLY */
 661                 cmd = ELF_C_WRITE;
 662
 663         elf->elf = elf_begin(elf->fd, cmd, NULL);
 664         if (!elf->elf) {
 665                 WARN_ELF("elf_begin");
 666                 goto err;
 667         }
 668
 669         if (!gelf_getehdr(elf->elf, &elf->ehdr)) {
 670                 WARN_ELF("gelf_getehdr");
 671                 goto err;
 672         }
 673
 674         if (read_sections(elf))
 675                 goto err;
 676
 677         if (read_symbols(elf))
 678                 goto err;
 679
 680         if (read_relocs(elf))
 681                 goto err;
 682
 683         return elf;
 684
 685 err:
 686         elf_close(elf);
 687         return NULL;
 688 }
 689
 690 struct section *elf_create_section(struct elf *elf, const char *name,
 691                                    unsigned int sh_flags, size_t entsize, int nr)
 692 {
 693         struct section *sec, *shstrtab;
 694         size_t size = entsize * nr;
 695         Elf_Scn *s;
 696         Elf_Data *data;
 697
 698         sec = malloc(sizeof(*sec));
 699         if (!sec) {
 700                 perror("malloc");
 701                 return NULL;
 702         }
 703         memset(sec, 0, sizeof(*sec));
 704
 705         INIT_LIST_HEAD(&sec->symbol_list);
 706         INIT_LIST_HEAD(&sec->reloc_list);
 707
 708         s = elf_newscn(elf->elf);
 709         if (!s) {
 710                 WARN_ELF("elf_newscn");
 711                 return NULL;
 712         }
 713
 714         sec->name = strdup(name);
 715         if (!sec->name) {
 716                 perror("strdup");
 717                 return NULL;
 718         }
 719
 720         sec->idx = elf_ndxscn(s);
 721         sec->len = size;
 722         sec->changed = true;
 723
 724         sec->data = elf_newdata(s);
 725         if (!sec->data) {
 726                 WARN_ELF("elf_newdata");
 727                 return NULL;
 728         }
 729
 730         sec->data->d_size = size;
 731         sec->data->d_align = 1;
 732
 733         if (size) {
 734                 sec->data->d_buf = malloc(size);
 735                 if (!sec->data->d_buf) {
 736                         perror("malloc");
 737                         return NULL;
 738                 }
 739                 memset(sec->data->d_buf, 0, size);
 740         }
 741
 742         if (!gelf_getshdr(s, &sec->sh)) {
 743                 WARN_ELF("gelf_getshdr");
 744                 return NULL;
 745         }
 746
 747         sec->sh.sh_size = size;
 748         sec->sh.sh_entsize = entsize;
 749         sec->sh.sh_type = SHT_PROGBITS;
 750         sec->sh.sh_addralign = 1;
 751         sec->sh.sh_flags = SHF_ALLOC | sh_flags;
 752
 753
 754         /* Add section name to .shstrtab (or .strtab for Clang) */
 755         shstrtab = find_section_by_name(elf, ".shstrtab");
 756         if (!shstrtab)
 757                 shstrtab = find_section_by_name(elf, ".strtab");
 758         if (!shstrtab) {
 759                 WARN("can't find .shstrtab or .strtab section");
 760                 return NULL;
 761         }
 762
 763         s = elf_getscn(elf->elf, shstrtab->idx);
 764         if (!s) {
 765                 WARN_ELF("elf_getscn");
 766                 return NULL;
 767         }
 768
 769         data = elf_newdata(s);
 770         if (!data) {
 771                 WARN_ELF("elf_newdata");
 772                 return NULL;
 773         }
 774
 775         data->d_buf = sec->name;
 776         data->d_size = strlen(name) + 1;
 777         data->d_align = 1;
 778
 779         sec->sh.sh_name = shstrtab->len;
 780
 781         shstrtab->len += strlen(name) + 1;
 782         shstrtab->changed = true;
 783
 784         list_add_tail(&sec->list, &elf->sections);
 785         elf_hash_add(elf->section_hash, &sec->hash, sec->idx);
 786         elf_hash_add(elf->section_name_hash, &sec->name_hash, str_hash(sec->name));
 787
 788         elf->changed = true;
 789
 790         return sec;
 791 }
 792
 793 static struct section *elf_create_rel_reloc_section(struct elf *elf, struct section *base)
 794 {
 795         char *relocname;
 796         struct section *sec;
 797
 798         relocname = malloc(strlen(base->name) + strlen(".rel") + 1);
 799         if (!relocname) {
 800                 perror("malloc");
 801                 return NULL;
 802         }
 803         strcpy(relocname, ".rel");
 804         strcat(relocname, base->name);
 805
 806         sec = elf_create_section(elf, relocname, 0, sizeof(GElf_Rel), 0);
 807         free(relocname);
 808         if (!sec)
 809                 return NULL;
 810
 811         base->reloc = sec;
 812         sec->base = base;
 813
 814         sec->sh.sh_type = SHT_REL;
 815         sec->sh.sh_addralign = 8;
 816         sec->sh.sh_link = find_section_by_name(elf, ".symtab")->idx;
 817         sec->sh.sh_info = base->idx;
 818         sec->sh.sh_flags = SHF_INFO_LINK;
 819
 820         return sec;
 821 }
 822
 823 static struct section *elf_create_rela_reloc_section(struct elf *elf, struct section *base)
 824 {
 825         char *relocname;
 826         struct section *sec;
 827
 828         relocname = malloc(strlen(base->name) + strlen(".rela") + 1);
 829         if (!relocname) {
 830                 perror("malloc");
 831                 return NULL;
 832         }
 833         strcpy(relocname, ".rela");
 834         strcat(relocname, base->name);
 835
 836         sec = elf_create_section(elf, relocname, 0, sizeof(GElf_Rela), 0);
 837         free(relocname);
 838         if (!sec)
 839                 return NULL;
 840
 841         base->reloc = sec;
 842         sec->base = base;
 843
 844         sec->sh.sh_type = SHT_RELA;
 845         sec->sh.sh_addralign = 8;
 846         sec->sh.sh_link = find_section_by_name(elf, ".symtab")->idx;
 847         sec->sh.sh_info = base->idx;
 848         sec->sh.sh_flags = SHF_INFO_LINK;
 849
 850         return sec;
 851 }
 852
 853 struct section *elf_create_reloc_section(struct elf *elf,
 854                                          struct section *base,
 855                                          int reltype)
 856 {
 857         switch (reltype) {
 858         case SHT_REL:  return elf_create_rel_reloc_section(elf, base);
 859         case SHT_RELA: return elf_create_rela_reloc_section(elf, base);
 860         default:       return NULL;
 861         }
 862 }
 863
 864 static int elf_rebuild_rel_reloc_section(struct section *sec, int nr)
 865 {
 866         struct reloc *reloc;
 867         int idx = 0, size;
 868         GElf_Rel *relocs;
 869
 870         /* Allocate a buffer for relocations */
 871         size = nr * sizeof(*relocs);
 872         relocs = malloc(size);
 873         if (!relocs) {
 874                 perror("malloc");
 875                 return -1;
 876         }
 877
 878         sec->data->d_buf = relocs;
 879         sec->data->d_size = size;
 880
 881         sec->sh.sh_size = size;
 882
 883         idx = 0;
 884         list_for_each_entry(reloc, &sec->reloc_list, list) {
 885                 relocs[idx].r_offset = reloc->offset;
 886                 relocs[idx].r_info = GELF_R_INFO(reloc->sym->idx, reloc->type);
 887                 idx++;
 888         }
 889
 890         return 0;
 891 }
 892
 893 static int elf_rebuild_rela_reloc_section(struct section *sec, int nr)
 894 {
 895         struct reloc *reloc;
 896         int idx = 0, size;
 897         GElf_Rela *relocs;
 898
 899         /* Allocate a buffer for relocations with addends */
 900         size = nr * sizeof(*relocs);
 901         relocs = malloc(size);
 902         if (!relocs) {
 903                 perror("malloc");
 904                 return -1;
 905         }
 906
 907         sec->data->d_buf = relocs;
 908         sec->data->d_size = size;
 909
 910         sec->sh.sh_size = size;
 911
 912         idx = 0;
 913         list_for_each_entry(reloc, &sec->reloc_list, list) {
 914                 relocs[idx].r_offset = reloc->offset;
 915                 relocs[idx].r_addend = reloc->addend;
 916                 relocs[idx].r_info = GELF_R_INFO(reloc->sym->idx, reloc->type);
 917                 idx++;
 918         }
 919
 920         return 0;
 921 }
 922
 923 int elf_rebuild_reloc_section(struct elf *elf, struct section *sec)
 924 {
 925         struct reloc *reloc;
 926         int nr;
 927
 928         sec->changed = true;
 929         elf->changed = true;
 930
 931         nr = 0;
 932         list_for_each_entry(reloc, &sec->reloc_list, list)
 933                 nr++;
 934
 935         switch (sec->sh.sh_type) {
 936         case SHT_REL:  return elf_rebuild_rel_reloc_section(sec, nr);
 937         case SHT_RELA: return elf_rebuild_rela_reloc_section(sec, nr);
 938         default:       return -1;
 939         }
 940 }
 941
 942 int elf_write_insn(struct elf *elf, struct section *sec,
 943                    unsigned long offset, unsigned int len,
 944                    const char *insn)
 945 {
 946         Elf_Data *data = sec->data;
 947
 948         if (data->d_type != ELF_T_BYTE || data->d_off) {
 949                 WARN("write to unexpected data for section: %s", sec->name);
 950                 return -1;
 951         }
 952
 953         memcpy(data->d_buf + offset, insn, len);
 954         elf_flagdata(data, ELF_C_SET, ELF_F_DIRTY);
 955
 956         elf->changed = true;
 957
 958         return 0;
 959 }
 960
 961 int elf_write_reloc(struct elf *elf, struct reloc *reloc)
 962 {
 963         struct section *sec = reloc->sec;
 964
 965         if (sec->sh.sh_type == SHT_REL) {
 966                 reloc->rel.r_info = GELF_R_INFO(reloc->sym->idx, reloc->type);
 967                 reloc->rel.r_offset = reloc->offset;
 968
 969                 if (!gelf_update_rel(sec->data, reloc->idx, &reloc->rel)) {
 970                         WARN_ELF("gelf_update_rel");
 971                         return -1;
 972                 }
 973         } else {
 974                 reloc->rela.r_info = GELF_R_INFO(reloc->sym->idx, reloc->type);
 975                 reloc->rela.r_addend = reloc->addend;
 976                 reloc->rela.r_offset = reloc->offset;
 977
 978                 if (!gelf_update_rela(sec->data, reloc->idx, &reloc->rela)) {
 979                         WARN_ELF("gelf_update_rela");
 980                         return -1;
 981                 }
 982         }
 983
 984         elf->changed = true;
 985
 986         return 0;
 987 }
 988
 989 int elf_write(struct elf *elf)
 990 {
 991         struct section *sec;
 992         Elf_Scn *s;
 993
 994         /* Update section headers for changed sections: */
 995         list_for_each_entry(sec, &elf->sections, list) {
 996                 if (sec->changed) {
 997                         s = elf_getscn(elf->elf, sec->idx);
 998                         if (!s) {
 999                                 WARN_ELF("elf_getscn");
1000                                 return -1;
1001                         }
1002                         if (!gelf_update_shdr(s, &sec->sh)) {
1003                                 WARN_ELF("gelf_update_shdr");
1004                                 return -1;
1005                         }
1006
1007                         sec->changed = false;
1008                 }
1009         }
1010
1011         /* Make sure the new section header entries get updated properly. */
1012         elf_flagelf(elf->elf, ELF_C_SET, ELF_F_DIRTY);
1013
1014         /* Write all changes to the file. */
1015         if (elf_update(elf->elf, ELF_C_WRITE) < 0) {
1016                 WARN_ELF("elf_update");
1017                 return -1;
1018         }
1019
1020         elf->changed = false;
1021
1022         return 0;
1023 }
1024
1025 void elf_close(struct elf *elf)
1026 {
1027         struct section *sec, *tmpsec;
1028         struct symbol *sym, *tmpsym;
1029         struct reloc *reloc, *tmpreloc;
1030
1031         if (elf->elf)
1032                 elf_end(elf->elf);
1033
1034         if (elf->fd > 0)
1035                 close(elf->fd);
1036
1037         list_for_each_entry_safe(sec, tmpsec, &elf->sections, list) {
1038                 list_for_each_entry_safe(sym, tmpsym, &sec->symbol_list, list) {
1039                         list_del(&sym->list);
1040                         hash_del(&sym->hash);
1041                         free(sym);
1042                 }
1043                 list_for_each_entry_safe(reloc, tmpreloc, &sec->reloc_list, list) {
1044                         list_del(&reloc->list);
1045                         hash_del(&reloc->hash);
1046                         free(reloc);
1047                 }
1048                 list_del(&sec->list);
1049                 free(sec);
1050         }
1051
1052         free(elf);
1053 }