| 1 | |
| 2 | |
| 3 | * elf.c - ELF access library
|
| 4 | *
|
| 5 | * Adapted from kpatch (https://github.com/dynup/kpatch):
|
| 6 | * Copyright (C) 2013-2015 Josh Poimboeuf <[email protected]>
|
| 7 | * Copyright (C) 2014 Seth Jennings <[email protected]>
|
| 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 <linux/interval_tree_generic.h>
|
| 20 | #include <objtool/builtin.h>
|
| 21 |
|
| 22 | #include <objtool/elf.h>
|
| 23 | #include <objtool/warn.h>
|
| 24 |
|
| 25 | static inline u32 str_hash(const char *str)
|
| 26 | {
|
| 27 | return jhash(str, strlen(str), 0);
|
| 28 | }
|
| 29 |
|
| 30 | #define __elf_table(name) (elf->name##_hash)
|
| 31 | #define __elf_bits(name) (elf->name##_bits)
|
| 32 |
|
| 33 | #define __elf_table_entry(name, key) \
|
| 34 | __elf_table(name)[hash_min(key, __elf_bits(name))]
|
| 35 |
|
| 36 | #define elf_hash_add(name, node, key) \
|
| 37 | ({ \
|
| 38 | struct elf_hash_node *__node = node; \
|
| 39 | __node->next = __elf_table_entry(name, key); \
|
| 40 | __elf_table_entry(name, key) = __node; \
|
| 41 | })
|
| 42 |
|
| 43 | static inline void __elf_hash_del(struct elf_hash_node *node,
|
| 44 | struct elf_hash_node **head)
|
| 45 | {
|
| 46 | struct elf_hash_node *cur, *prev;
|
| 47 |
|
| 48 | if (node == *head) {
|
| 49 | *head = node->next;
|
| 50 | return;
|
| 51 | }
|
| 52 |
|
| 53 | for (prev = NULL, cur = *head; cur; prev = cur, cur = cur->next) {
|
| 54 | if (cur == node) {
|
| 55 | prev->next = cur->next;
|
| 56 | break;
|
| 57 | }
|
| 58 | }
|
| 59 | }
|
| 60 |
|
| 61 | #define elf_hash_del(name, node, key) \
|
| 62 | __elf_hash_del(node, &__elf_table_entry(name, key))
|
| 63 |
|
| 64 | #define elf_list_entry(ptr, type, member) \
|
| 65 | ({ \
|
| 66 | typeof(ptr) __ptr = (ptr); \
|
| 67 | __ptr ? container_of(__ptr, type, member) : NULL; \
|
| 68 | })
|
| 69 |
|
| 70 | #define elf_hash_for_each_possible(name, obj, member, key) \
|
| 71 | for (obj = elf_list_entry(__elf_table_entry(name, key), typeof(*obj), member); \
|
| 72 | obj; \
|
| 73 | obj = elf_list_entry(obj->member.next, typeof(*(obj)), member))
|
| 74 |
|
| 75 | #define elf_alloc_hash(name, size) \
|
| 76 | ({ \
|
| 77 | __elf_bits(name) = max(10, ilog2(size)); \
|
| 78 | __elf_table(name) = mmap(NULL, sizeof(struct elf_hash_node *) << __elf_bits(name), \
|
| 79 | PROT_READ|PROT_WRITE, \
|
| 80 | MAP_PRIVATE|MAP_ANON, -1, 0); \
|
| 81 | if (__elf_table(name) == (void *)-1L) { \
|
| 82 | WARN("mmap fail " #name); \
|
| 83 | __elf_table(name) = NULL; \
|
| 84 | } \
|
| 85 | __elf_table(name); \
|
| 86 | })
|
| 87 |
|
| 88 | static inline unsigned long __sym_start(struct symbol *s)
|
| 89 | {
|
| 90 | return s->offset;
|
| 91 | }
|
| 92 |
|
| 93 | static inline unsigned long __sym_last(struct symbol *s)
|
| 94 | {
|
| 95 | return s->offset + s->len - 1;
|
| 96 | }
|
| 97 |
|
| 98 | INTERVAL_TREE_DEFINE(struct symbol, node, unsigned long, __subtree_last,
|
| 99 | __sym_start, __sym_last, static, __sym)
|
| 100 |
|
| 101 | #define __sym_for_each(_iter, _tree, _start, _end) \
|
| 102 | for (_iter = __sym_iter_first((_tree), (_start), (_end)); \
|
| 103 | _iter; _iter = __sym_iter_next(_iter, (_start), (_end)))
|
| 104 |
|
| 105 | struct symbol_hole {
|
| 106 | unsigned long key;
|
| 107 | const struct symbol *sym;
|
| 108 | };
|
| 109 |
|
| 110 | |
| 111 | * Find !section symbol where @offset is after it.
|
| 112 |
|
| 113 | static int symbol_hole_by_offset(const void *key, const struct rb_node *node)
|
| 114 | {
|
| 115 | const struct symbol *s = rb_entry(node, struct symbol, node);
|
| 116 | struct symbol_hole *sh = (void *)key;
|
| 117 |
|
| 118 | if (sh->key < s->offset)
|
| 119 | return -1;
|
| 120 |
|
| 121 | if (sh->key >= s->offset + s->len) {
|
| 122 | if (s->type != STT_SECTION)
|
| 123 | sh->sym = s;
|
| 124 | return 1;
|
| 125 | }
|
| 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(section_name, sec, name_hash, str_hash(name)) {
|
| 135 | if (!strcmp(sec->name, name))
|
| 136 | return sec;
|
| 137 | }
|
| 138 |
|
| 139 | return NULL;
|
| 140 | }
|
| 141 |
|
| 142 | static struct section *find_section_by_index(struct elf *elf,
|
| 143 | unsigned int idx)
|
| 144 | {
|
| 145 | struct section *sec;
|
| 146 |
|
| 147 | elf_hash_for_each_possible(section, sec, hash, idx) {
|
| 148 | if (sec->idx == idx)
|
| 149 | return sec;
|
| 150 | }
|
| 151 |
|
| 152 | return NULL;
|
| 153 | }
|
| 154 |
|
| 155 | static struct symbol *find_symbol_by_index(struct elf *elf, unsigned int idx)
|
| 156 | {
|
| 157 | struct symbol *sym;
|
| 158 |
|
| 159 | elf_hash_for_each_possible(symbol, sym, hash, idx) {
|
| 160 | if (sym->idx == idx)
|
| 161 | return sym;
|
| 162 | }
|
| 163 |
|
| 164 | return NULL;
|
| 165 | }
|
| 166 |
|
| 167 | struct symbol *find_symbol_by_offset(struct section *sec, unsigned long offset)
|
| 168 | {
|
| 169 | struct rb_root_cached *tree = (struct rb_root_cached *)&sec->symbol_tree;
|
| 170 | struct symbol *iter;
|
| 171 |
|
| 172 | __sym_for_each(iter, tree, offset, offset) {
|
| 173 | if (iter->offset == offset && iter->type != STT_SECTION)
|
| 174 | return iter;
|
| 175 | }
|
| 176 |
|
| 177 | return NULL;
|
| 178 | }
|
| 179 |
|
| 180 | struct symbol *find_func_by_offset(struct section *sec, unsigned long offset)
|
| 181 | {
|
| 182 | struct rb_root_cached *tree = (struct rb_root_cached *)&sec->symbol_tree;
|
| 183 | struct symbol *iter;
|
| 184 |
|
| 185 | __sym_for_each(iter, tree, offset, offset) {
|
| 186 | if (iter->offset == offset && iter->type == STT_FUNC)
|
| 187 | return iter;
|
| 188 | }
|
| 189 |
|
| 190 | return NULL;
|
| 191 | }
|
| 192 |
|
| 193 | struct symbol *find_symbol_containing(const struct section *sec, unsigned long offset)
|
| 194 | {
|
| 195 | struct rb_root_cached *tree = (struct rb_root_cached *)&sec->symbol_tree;
|
| 196 | struct symbol *iter;
|
| 197 |
|
| 198 | __sym_for_each(iter, tree, offset, offset) {
|
| 199 | if (iter->type != STT_SECTION)
|
| 200 | return iter;
|
| 201 | }
|
| 202 |
|
| 203 | return NULL;
|
| 204 | }
|
| 205 |
|
| 206 | |
| 207 | * Returns size of hole starting at @offset.
|
| 208 |
|
| 209 | int find_symbol_hole_containing(const struct section *sec, unsigned long offset)
|
| 210 | {
|
| 211 | struct symbol_hole hole = {
|
| 212 | .key = offset,
|
| 213 | .sym = NULL,
|
| 214 | };
|
| 215 | struct rb_node *n;
|
| 216 | struct symbol *s;
|
| 217 |
|
| 218 | |
| 219 | * Find the rightmost symbol for which @offset is after it.
|
| 220 |
|
| 221 | n = rb_find(&hole, &sec->symbol_tree.rb_root, symbol_hole_by_offset);
|
| 222 |
|
| 223 |
|
| 224 | if (n)
|
| 225 | return 0;
|
| 226 |
|
| 227 | |
| 228 | * @offset >= sym->offset + sym->len, find symbol after it.
|
| 229 | * When hole.sym is empty, use the first node to compute the hole.
|
| 230 | * If there is no symbol in the section, the first node will be NULL,
|
| 231 | * in which case, -1 is returned to skip the whole section.
|
| 232 |
|
| 233 | if (hole.sym)
|
| 234 | n = rb_next(&hole.sym->node);
|
| 235 | else
|
| 236 | n = rb_first_cached(&sec->symbol_tree);
|
| 237 |
|
| 238 | if (!n)
|
| 239 | return -1;
|
| 240 |
|
| 241 |
|
| 242 | s = rb_entry(n, struct symbol, node);
|
| 243 | return s->offset - offset;
|
| 244 | }
|
| 245 |
|
| 246 | struct symbol *find_func_containing(struct section *sec, unsigned long offset)
|
| 247 | {
|
| 248 | struct rb_root_cached *tree = (struct rb_root_cached *)&sec->symbol_tree;
|
| 249 | struct symbol *iter;
|
| 250 |
|
| 251 | __sym_for_each(iter, tree, offset, offset) {
|
| 252 | if (iter->type == STT_FUNC)
|
| 253 | return iter;
|
| 254 | }
|
| 255 |
|
| 256 | return NULL;
|
| 257 | }
|
| 258 |
|
| 259 | struct symbol *find_symbol_by_name(const struct elf *elf, const char *name)
|
| 260 | {
|
| 261 | struct symbol *sym;
|
| 262 |
|
| 263 | elf_hash_for_each_possible(symbol_name, sym, name_hash, str_hash(name)) {
|
| 264 | if (!strcmp(sym->name, name))
|
| 265 | return sym;
|
| 266 | }
|
| 267 |
|
| 268 | return NULL;
|
| 269 | }
|
| 270 |
|
| 271 | struct reloc *find_reloc_by_dest_range(const struct elf *elf, struct section *sec,
|
| 272 | unsigned long offset, unsigned int len)
|
| 273 | {
|
| 274 | struct reloc *reloc, *r = NULL;
|
| 275 | struct section *rsec;
|
| 276 | unsigned long o;
|
| 277 |
|
| 278 | rsec = sec->rsec;
|
| 279 | if (!rsec)
|
| 280 | return NULL;
|
| 281 |
|
| 282 | for_offset_range(o, offset, offset + len) {
|
| 283 | elf_hash_for_each_possible(reloc, reloc, hash,
|
| 284 | sec_offset_hash(rsec, o)) {
|
| 285 | if (reloc->sec != rsec)
|
| 286 | continue;
|
| 287 |
|
| 288 | if (reloc_offset(reloc) >= offset &&
|
| 289 | reloc_offset(reloc) < offset + len) {
|
| 290 | if (!r || reloc_offset(reloc) < reloc_offset(r))
|
| 291 | r = reloc;
|
| 292 | }
|
| 293 | }
|
| 294 | if (r)
|
| 295 | return r;
|
| 296 | }
|
| 297 |
|
| 298 | return NULL;
|
| 299 | }
|
| 300 |
|
| 301 | struct reloc *find_reloc_by_dest(const struct elf *elf, struct section *sec, unsigned long offset)
|
| 302 | {
|
| 303 | return find_reloc_by_dest_range(elf, sec, offset, 1);
|
| 304 | }
|
| 305 |
|
| 306 | static bool is_dwarf_section(struct section *sec)
|
| 307 | {
|
| 308 | return !strncmp(sec->name, ".debug_", 7);
|
| 309 | }
|
| 310 |
|
| 311 | static int read_sections(struct elf *elf)
|
| 312 | {
|
| 313 | Elf_Scn *s = NULL;
|
| 314 | struct section *sec;
|
| 315 | size_t shstrndx, sections_nr;
|
| 316 | int i;
|
| 317 |
|
| 318 | if (elf_getshdrnum(elf->elf, §ions_nr)) {
|
| 319 | WARN_ELF("elf_getshdrnum");
|
| 320 | return -1;
|
| 321 | }
|
| 322 |
|
| 323 | if (elf_getshdrstrndx(elf->elf, &shstrndx)) {
|
| 324 | WARN_ELF("elf_getshdrstrndx");
|
| 325 | return -1;
|
| 326 | }
|
| 327 |
|
| 328 | if (!elf_alloc_hash(section, sections_nr) ||
|
| 329 | !elf_alloc_hash(section_name, sections_nr))
|
| 330 | return -1;
|
| 331 |
|
| 332 | elf->section_data = calloc(sections_nr, sizeof(*sec));
|
| 333 | if (!elf->section_data) {
|
| 334 | perror("calloc");
|
| 335 | return -1;
|
| 336 | }
|
| 337 | for (i = 0; i < sections_nr; i++) {
|
| 338 | sec = &elf->section_data[i];
|
| 339 |
|
| 340 | INIT_LIST_HEAD(&sec->symbol_list);
|
| 341 |
|
| 342 | s = elf_getscn(elf->elf, i);
|
| 343 | if (!s) {
|
| 344 | WARN_ELF("elf_getscn");
|
| 345 | return -1;
|
| 346 | }
|
| 347 |
|
| 348 | sec->idx = elf_ndxscn(s);
|
| 349 |
|
| 350 | if (!gelf_getshdr(s, &sec->sh)) {
|
| 351 | WARN_ELF("gelf_getshdr");
|
| 352 | return -1;
|
| 353 | }
|
| 354 |
|
| 355 | sec->name = elf_strptr(elf->elf, shstrndx, sec->sh.sh_name);
|
| 356 | if (!sec->name) {
|
| 357 | WARN_ELF("elf_strptr");
|
| 358 | return -1;
|
| 359 | }
|
| 360 |
|
| 361 | if (sec->sh.sh_size != 0 && !is_dwarf_section(sec)) {
|
| 362 | sec->data = elf_getdata(s, NULL);
|
| 363 | if (!sec->data) {
|
| 364 | WARN_ELF("elf_getdata");
|
| 365 | return -1;
|
| 366 | }
|
| 367 | if (sec->data->d_off != 0 ||
|
| 368 | sec->data->d_size != sec->sh.sh_size) {
|
| 369 | WARN("unexpected data attributes for %s",
|
| 370 | sec->name);
|
| 371 | return -1;
|
| 372 | }
|
| 373 | }
|
| 374 |
|
| 375 | list_add_tail(&sec->list, &elf->sections);
|
| 376 | elf_hash_add(section, &sec->hash, sec->idx);
|
| 377 | elf_hash_add(section_name, &sec->name_hash, str_hash(sec->name));
|
| 378 |
|
| 379 | if (is_reloc_sec(sec))
|
| 380 | elf->num_relocs += sec_num_entries(sec);
|
| 381 | }
|
| 382 |
|
| 383 | if (opts.stats) {
|
| 384 | printf("nr_sections: %lu\n", (unsigned long)sections_nr);
|
| 385 | printf("section_bits: %d\n", elf->section_bits);
|
| 386 | }
|
| 387 |
|
| 388 |
|
| 389 | if (elf_nextscn(elf->elf, s)) {
|
| 390 | WARN("section entry mismatch");
|
| 391 | return -1;
|
| 392 | }
|
| 393 |
|
| 394 | return 0;
|
| 395 | }
|
| 396 |
|
| 397 | static void elf_add_symbol(struct elf *elf, struct symbol *sym)
|
| 398 | {
|
| 399 | struct list_head *entry;
|
| 400 | struct rb_node *pnode;
|
| 401 | struct symbol *iter;
|
| 402 |
|
| 403 | INIT_LIST_HEAD(&sym->pv_target);
|
| 404 | sym->alias = sym;
|
| 405 |
|
| 406 | sym->type = GELF_ST_TYPE(sym->sym.st_info);
|
| 407 | sym->bind = GELF_ST_BIND(sym->sym.st_info);
|
| 408 |
|
| 409 | if (sym->type == STT_FILE)
|
| 410 | elf->num_files++;
|
| 411 |
|
| 412 | sym->offset = sym->sym.st_value;
|
| 413 | sym->len = sym->sym.st_size;
|
| 414 |
|
| 415 | __sym_for_each(iter, &sym->sec->symbol_tree, sym->offset, sym->offset) {
|
| 416 | if (iter->offset == sym->offset && iter->type == sym->type)
|
| 417 | iter->alias = sym;
|
| 418 | }
|
| 419 |
|
| 420 | __sym_insert(sym, &sym->sec->symbol_tree);
|
| 421 | pnode = rb_prev(&sym->node);
|
| 422 | if (pnode)
|
| 423 | entry = &rb_entry(pnode, struct symbol, node)->list;
|
| 424 | else
|
| 425 | entry = &sym->sec->symbol_list;
|
| 426 | list_add(&sym->list, entry);
|
| 427 | elf_hash_add(symbol, &sym->hash, sym->idx);
|
| 428 | elf_hash_add(symbol_name, &sym->name_hash, str_hash(sym->name));
|
| 429 |
|
| 430 | |
| 431 | * Don't store empty STT_NOTYPE symbols in the rbtree. They
|
| 432 | * can exist within a function, confusing the sorting.
|
| 433 |
|
| 434 | if (!sym->len)
|
| 435 | __sym_remove(sym, &sym->sec->symbol_tree);
|
| 436 | }
|
| 437 |
|
| 438 | static int read_symbols(struct elf *elf)
|
| 439 | {
|
| 440 | struct section *symtab, *symtab_shndx, *sec;
|
| 441 | struct symbol *sym, *pfunc;
|
| 442 | int symbols_nr, i;
|
| 443 | char *coldstr;
|
| 444 | Elf_Data *shndx_data = NULL;
|
| 445 | Elf32_Word shndx;
|
| 446 |
|
| 447 | symtab = find_section_by_name(elf, ".symtab");
|
| 448 | if (symtab) {
|
| 449 | symtab_shndx = find_section_by_name(elf, ".symtab_shndx");
|
| 450 | if (symtab_shndx)
|
| 451 | shndx_data = symtab_shndx->data;
|
| 452 |
|
| 453 | symbols_nr = sec_num_entries(symtab);
|
| 454 | } else {
|
| 455 | |
| 456 | * A missing symbol table is actually possible if it's an empty
|
| 457 | * .o file. This can happen for thunk_64.o. Make sure to at
|
| 458 | * least allocate the symbol hash tables so we can do symbol
|
| 459 | * lookups without crashing.
|
| 460 |
|
| 461 | symbols_nr = 0;
|
| 462 | }
|
| 463 |
|
| 464 | if (!elf_alloc_hash(symbol, symbols_nr) ||
|
| 465 | !elf_alloc_hash(symbol_name, symbols_nr))
|
| 466 | return -1;
|
| 467 |
|
| 468 | elf->symbol_data = calloc(symbols_nr, sizeof(*sym));
|
| 469 | if (!elf->symbol_data) {
|
| 470 | perror("calloc");
|
| 471 | return -1;
|
| 472 | }
|
| 473 | for (i = 0; i < symbols_nr; i++) {
|
| 474 | sym = &elf->symbol_data[i];
|
| 475 |
|
| 476 | sym->idx = i;
|
| 477 |
|
| 478 | if (!gelf_getsymshndx(symtab->data, shndx_data, i, &sym->sym,
|
| 479 | &shndx)) {
|
| 480 | WARN_ELF("gelf_getsymshndx");
|
| 481 | goto err;
|
| 482 | }
|
| 483 |
|
| 484 | sym->name = elf_strptr(elf->elf, symtab->sh.sh_link,
|
| 485 | sym->sym.st_name);
|
| 486 | if (!sym->name) {
|
| 487 | WARN_ELF("elf_strptr");
|
| 488 | goto err;
|
| 489 | }
|
| 490 |
|
| 491 | if ((sym->sym.st_shndx > SHN_UNDEF &&
|
| 492 | sym->sym.st_shndx < SHN_LORESERVE) ||
|
| 493 | (shndx_data && sym->sym.st_shndx == SHN_XINDEX)) {
|
| 494 | if (sym->sym.st_shndx != SHN_XINDEX)
|
| 495 | shndx = sym->sym.st_shndx;
|
| 496 |
|
| 497 | sym->sec = find_section_by_index(elf, shndx);
|
| 498 | if (!sym->sec) {
|
| 499 | WARN("couldn't find section for symbol %s",
|
| 500 | sym->name);
|
| 501 | goto err;
|
| 502 | }
|
| 503 | if (GELF_ST_TYPE(sym->sym.st_info) == STT_SECTION) {
|
| 504 | sym->name = sym->sec->name;
|
| 505 | sym->sec->sym = sym;
|
| 506 | }
|
| 507 | } else
|
| 508 | sym->sec = find_section_by_index(elf, 0);
|
| 509 |
|
| 510 | elf_add_symbol(elf, sym);
|
| 511 | }
|
| 512 |
|
| 513 | if (opts.stats) {
|
| 514 | printf("nr_symbols: %lu\n", (unsigned long)symbols_nr);
|
| 515 | printf("symbol_bits: %d\n", elf->symbol_bits);
|
| 516 | }
|
| 517 |
|
| 518 |
|
| 519 | list_for_each_entry(sec, &elf->sections, list) {
|
| 520 | sec_for_each_sym(sec, sym) {
|
| 521 | char *pname;
|
| 522 | size_t pnamelen;
|
| 523 | if (sym->type != STT_FUNC)
|
| 524 | continue;
|
| 525 |
|
| 526 | if (sym->pfunc == NULL)
|
| 527 | sym->pfunc = sym;
|
| 528 |
|
| 529 | if (sym->cfunc == NULL)
|
| 530 | sym->cfunc = sym;
|
| 531 |
|
| 532 | coldstr = strstr(sym->name, ".cold");
|
| 533 | if (!coldstr)
|
| 534 | continue;
|
| 535 |
|
| 536 | pnamelen = coldstr - sym->name;
|
| 537 | pname = strndup(sym->name, pnamelen);
|
| 538 | if (!pname) {
|
| 539 | WARN("%s(): failed to allocate memory",
|
| 540 | sym->name);
|
| 541 | return -1;
|
| 542 | }
|
| 543 |
|
| 544 | pfunc = find_symbol_by_name(elf, pname);
|
| 545 | free(pname);
|
| 546 |
|
| 547 | if (!pfunc) {
|
| 548 | WARN("%s(): can't find parent function",
|
| 549 | sym->name);
|
| 550 | return -1;
|
| 551 | }
|
| 552 |
|
| 553 | sym->pfunc = pfunc;
|
| 554 | pfunc->cfunc = sym;
|
| 555 |
|
| 556 | |
| 557 | * Unfortunately, -fnoreorder-functions puts the child
|
| 558 | * inside the parent. Remove the overlap so we can
|
| 559 | * have sane assumptions.
|
| 560 | *
|
| 561 | * Note that pfunc->len now no longer matches
|
| 562 | * pfunc->sym.st_size.
|
| 563 |
|
| 564 | if (sym->sec == pfunc->sec &&
|
| 565 | sym->offset >= pfunc->offset &&
|
| 566 | sym->offset + sym->len == pfunc->offset + pfunc->len) {
|
| 567 | pfunc->len -= sym->len;
|
| 568 | }
|
| 569 | }
|
| 570 | }
|
| 571 |
|
| 572 | return 0;
|
| 573 |
|
| 574 | err:
|
| 575 | free(sym);
|
| 576 | return -1;
|
| 577 | }
|
| 578 |
|
| 579 | |
| 580 | * @sym's idx has changed. Update the relocs which reference it.
|
| 581 |
|
| 582 | static int elf_update_sym_relocs(struct elf *elf, struct symbol *sym)
|
| 583 | {
|
| 584 | struct reloc *reloc;
|
| 585 |
|
| 586 | for (reloc = sym->relocs; reloc; reloc = reloc->sym_next_reloc)
|
| 587 | set_reloc_sym(elf, reloc, reloc->sym->idx);
|
| 588 |
|
| 589 | return 0;
|
| 590 | }
|
| 591 |
|
| 592 | |
| 593 | * The libelf API is terrible; gelf_update_sym*() takes a data block relative
|
| 594 | * index value, *NOT* the symbol index. As such, iterate the data blocks and
|
| 595 | * adjust index until it fits.
|
| 596 | *
|
| 597 | * If no data block is found, allow adding a new data block provided the index
|
| 598 | * is only one past the end.
|
| 599 |
|
| 600 | static int elf_update_symbol(struct elf *elf, struct section *symtab,
|
| 601 | struct section *symtab_shndx, struct symbol *sym)
|
| 602 | {
|
| 603 | Elf32_Word shndx = sym->sec ? sym->sec->idx : SHN_UNDEF;
|
| 604 | Elf_Data *symtab_data = NULL, *shndx_data = NULL;
|
| 605 | Elf64_Xword entsize = symtab->sh.sh_entsize;
|
| 606 | int max_idx, idx = sym->idx;
|
| 607 | Elf_Scn *s, *t = NULL;
|
| 608 | bool is_special_shndx = sym->sym.st_shndx >= SHN_LORESERVE &&
|
| 609 | sym->sym.st_shndx != SHN_XINDEX;
|
| 610 |
|
| 611 | if (is_special_shndx)
|
| 612 | shndx = sym->sym.st_shndx;
|
| 613 |
|
| 614 | s = elf_getscn(elf->elf, symtab->idx);
|
| 615 | if (!s) {
|
| 616 | WARN_ELF("elf_getscn");
|
| 617 | return -1;
|
| 618 | }
|
| 619 |
|
| 620 | if (symtab_shndx) {
|
| 621 | t = elf_getscn(elf->elf, symtab_shndx->idx);
|
| 622 | if (!t) {
|
| 623 | WARN_ELF("elf_getscn");
|
| 624 | return -1;
|
| 625 | }
|
| 626 | }
|
| 627 |
|
| 628 | for (;;) {
|
| 629 |
|
| 630 | symtab_data = elf_getdata(s, symtab_data);
|
| 631 | if (t)
|
| 632 | shndx_data = elf_getdata(t, shndx_data);
|
| 633 |
|
| 634 |
|
| 635 | if (!symtab_data) {
|
| 636 | |
| 637 | * Over-allocate to avoid O(n^2) symbol creation
|
| 638 | * behaviour. The down side is that libelf doesn't
|
| 639 | * like this; see elf_truncate_section() for the fixup.
|
| 640 |
|
| 641 | int num = max(1U, sym->idx/3);
|
| 642 | void *buf;
|
| 643 |
|
| 644 | if (idx) {
|
| 645 |
|
| 646 | WARN("index out of range");
|
| 647 | return -1;
|
| 648 | }
|
| 649 |
|
| 650 |
|
| 651 | symtab_data = elf_newdata(s);
|
| 652 | if (t)
|
| 653 | shndx_data = elf_newdata(t);
|
| 654 |
|
| 655 | buf = calloc(num, entsize);
|
| 656 | if (!buf) {
|
| 657 | WARN("malloc");
|
| 658 | return -1;
|
| 659 | }
|
| 660 |
|
| 661 | symtab_data->d_buf = buf;
|
| 662 | symtab_data->d_size = num * entsize;
|
| 663 | symtab_data->d_align = 1;
|
| 664 | symtab_data->d_type = ELF_T_SYM;
|
| 665 |
|
| 666 | mark_sec_changed(elf, symtab, true);
|
| 667 | symtab->truncate = true;
|
| 668 |
|
| 669 | if (t) {
|
| 670 | buf = calloc(num, sizeof(Elf32_Word));
|
| 671 | if (!buf) {
|
| 672 | WARN("malloc");
|
| 673 | return -1;
|
| 674 | }
|
| 675 |
|
| 676 | shndx_data->d_buf = buf;
|
| 677 | shndx_data->d_size = num * sizeof(Elf32_Word);
|
| 678 | shndx_data->d_align = sizeof(Elf32_Word);
|
| 679 | shndx_data->d_type = ELF_T_WORD;
|
| 680 |
|
| 681 | mark_sec_changed(elf, symtab_shndx, true);
|
| 682 | symtab_shndx->truncate = true;
|
| 683 | }
|
| 684 |
|
| 685 | break;
|
| 686 | }
|
| 687 |
|
| 688 |
|
| 689 | if (!symtab_data->d_size) {
|
| 690 | WARN("zero size data");
|
| 691 | return -1;
|
| 692 | }
|
| 693 |
|
| 694 |
|
| 695 | max_idx = symtab_data->d_size / entsize;
|
| 696 | if (idx < max_idx)
|
| 697 | break;
|
| 698 |
|
| 699 |
|
| 700 | idx -= max_idx;
|
| 701 | }
|
| 702 |
|
| 703 |
|
| 704 | if (idx < 0) {
|
| 705 | WARN("negative index");
|
| 706 | return -1;
|
| 707 | }
|
| 708 |
|
| 709 |
|
| 710 | if ((shndx >= SHN_UNDEF && shndx < SHN_LORESERVE) || is_special_shndx) {
|
| 711 | sym->sym.st_shndx = shndx;
|
| 712 | if (!shndx_data)
|
| 713 | shndx = 0;
|
| 714 | } else {
|
| 715 | sym->sym.st_shndx = SHN_XINDEX;
|
| 716 | if (!shndx_data) {
|
| 717 | WARN("no .symtab_shndx");
|
| 718 | return -1;
|
| 719 | }
|
| 720 | }
|
| 721 |
|
| 722 | if (!gelf_update_symshndx(symtab_data, shndx_data, idx, &sym->sym, shndx)) {
|
| 723 | WARN_ELF("gelf_update_symshndx");
|
| 724 | return -1;
|
| 725 | }
|
| 726 |
|
| 727 | return 0;
|
| 728 | }
|
| 729 |
|
| 730 | static struct symbol *
|
| 731 | __elf_create_symbol(struct elf *elf, struct symbol *sym)
|
| 732 | {
|
| 733 | struct section *symtab, *symtab_shndx;
|
| 734 | Elf32_Word first_non_local, new_idx;
|
| 735 | struct symbol *old;
|
| 736 |
|
| 737 | symtab = find_section_by_name(elf, ".symtab");
|
| 738 | if (symtab) {
|
| 739 | symtab_shndx = find_section_by_name(elf, ".symtab_shndx");
|
| 740 | } else {
|
| 741 | WARN("no .symtab");
|
| 742 | return NULL;
|
| 743 | }
|
| 744 |
|
| 745 | new_idx = sec_num_entries(symtab);
|
| 746 |
|
| 747 | if (GELF_ST_BIND(sym->sym.st_info) != STB_LOCAL)
|
| 748 | goto non_local;
|
| 749 |
|
| 750 | |
| 751 | * Move the first global symbol, as per sh_info, into a new, higher
|
| 752 | * symbol index. This fees up a spot for a new local symbol.
|
| 753 |
|
| 754 | first_non_local = symtab->sh.sh_info;
|
| 755 | old = find_symbol_by_index(elf, first_non_local);
|
| 756 | if (old) {
|
| 757 |
|
| 758 | elf_hash_del(symbol, &old->hash, old->idx);
|
| 759 | elf_hash_add(symbol, &old->hash, new_idx);
|
| 760 | old->idx = new_idx;
|
| 761 |
|
| 762 | if (elf_update_symbol(elf, symtab, symtab_shndx, old)) {
|
| 763 | WARN("elf_update_symbol move");
|
| 764 | return NULL;
|
| 765 | }
|
| 766 |
|
| 767 | if (elf_update_sym_relocs(elf, old))
|
| 768 | return NULL;
|
| 769 |
|
| 770 | new_idx = first_non_local;
|
| 771 | }
|
| 772 |
|
| 773 | |
| 774 | * Either way, we will add a LOCAL symbol.
|
| 775 |
|
| 776 | symtab->sh.sh_info += 1;
|
| 777 |
|
| 778 | non_local:
|
| 779 | sym->idx = new_idx;
|
| 780 | if (elf_update_symbol(elf, symtab, symtab_shndx, sym)) {
|
| 781 | WARN("elf_update_symbol");
|
| 782 | return NULL;
|
| 783 | }
|
| 784 |
|
| 785 | symtab->sh.sh_size += symtab->sh.sh_entsize;
|
| 786 | mark_sec_changed(elf, symtab, true);
|
| 787 |
|
| 788 | if (symtab_shndx) {
|
| 789 | symtab_shndx->sh.sh_size += sizeof(Elf32_Word);
|
| 790 | mark_sec_changed(elf, symtab_shndx, true);
|
| 791 | }
|
| 792 |
|
| 793 | return sym;
|
| 794 | }
|
| 795 |
|
| 796 | static struct symbol *
|
| 797 | elf_create_section_symbol(struct elf *elf, struct section *sec)
|
| 798 | {
|
| 799 | struct symbol *sym = calloc(1, sizeof(*sym));
|
| 800 |
|
| 801 | if (!sym) {
|
| 802 | perror("malloc");
|
| 803 | return NULL;
|
| 804 | }
|
| 805 |
|
| 806 | sym->name = sec->name;
|
| 807 | sym->sec = sec;
|
| 808 |
|
| 809 | |
| 810 | sym->sym.st_info = GELF_ST_INFO(STB_LOCAL, STT_SECTION);
|
| 811 | |
| 812 | |
| 813 | |
| 814 |
|
| 815 | sym = __elf_create_symbol(elf, sym);
|
| 816 | if (sym)
|
| 817 | elf_add_symbol(elf, sym);
|
| 818 |
|
| 819 | return sym;
|
| 820 | }
|
| 821 |
|
| 822 | static int elf_add_string(struct elf *elf, struct section *strtab, char *str);
|
| 823 |
|
| 824 | struct symbol *
|
| 825 | elf_create_prefix_symbol(struct elf *elf, struct symbol *orig, long size)
|
| 826 | {
|
| 827 | struct symbol *sym = calloc(1, sizeof(*sym));
|
| 828 | size_t namelen = strlen(orig->name) + sizeof("__pfx_");
|
| 829 | char *name = malloc(namelen);
|
| 830 |
|
| 831 | if (!sym || !name) {
|
| 832 | perror("malloc");
|
| 833 | return NULL;
|
| 834 | }
|
| 835 |
|
| 836 | snprintf(name, namelen, "__pfx_%s", orig->name);
|
| 837 |
|
| 838 | sym->name = name;
|
| 839 | sym->sec = orig->sec;
|
| 840 |
|
| 841 | sym->sym.st_name = elf_add_string(elf, NULL, name);
|
| 842 | sym->sym.st_info = orig->sym.st_info;
|
| 843 | sym->sym.st_value = orig->sym.st_value - size;
|
| 844 | sym->sym.st_size = size;
|
| 845 |
|
| 846 | sym = __elf_create_symbol(elf, sym);
|
| 847 | if (sym)
|
| 848 | elf_add_symbol(elf, sym);
|
| 849 |
|
| 850 | return sym;
|
| 851 | }
|
| 852 |
|
| 853 | static struct reloc *elf_init_reloc(struct elf *elf, struct section *rsec,
|
| 854 | unsigned int reloc_idx,
|
| 855 | unsigned long offset, struct symbol *sym,
|
| 856 | s64 addend, unsigned int type)
|
| 857 | {
|
| 858 | struct reloc *reloc, empty = { 0 };
|
| 859 |
|
| 860 | if (reloc_idx >= sec_num_entries(rsec)) {
|
| 861 | WARN("%s: bad reloc_idx %u for %s with %d relocs",
|
| 862 | __func__, reloc_idx, rsec->name, sec_num_entries(rsec));
|
| 863 | return NULL;
|
| 864 | }
|
| 865 |
|
| 866 | reloc = &rsec->relocs[reloc_idx];
|
| 867 |
|
| 868 | if (memcmp(reloc, &empty, sizeof(empty))) {
|
| 869 | WARN("%s: %s: reloc %d already initialized!",
|
| 870 | __func__, rsec->name, reloc_idx);
|
| 871 | return NULL;
|
| 872 | }
|
| 873 |
|
| 874 | reloc->sec = rsec;
|
| 875 | reloc->sym = sym;
|
| 876 |
|
| 877 | set_reloc_offset(elf, reloc, offset);
|
| 878 | set_reloc_sym(elf, reloc, sym->idx);
|
| 879 | set_reloc_type(elf, reloc, type);
|
| 880 | set_reloc_addend(elf, reloc, addend);
|
| 881 |
|
| 882 | elf_hash_add(reloc, &reloc->hash, reloc_hash(reloc));
|
| 883 | reloc->sym_next_reloc = sym->relocs;
|
| 884 | sym->relocs = reloc;
|
| 885 |
|
| 886 | return reloc;
|
| 887 | }
|
| 888 |
|
| 889 | struct reloc *elf_init_reloc_text_sym(struct elf *elf, struct section *sec,
|
| 890 | unsigned long offset,
|
| 891 | unsigned int reloc_idx,
|
| 892 | struct section *insn_sec,
|
| 893 | unsigned long insn_off)
|
| 894 | {
|
| 895 | struct symbol *sym = insn_sec->sym;
|
| 896 | int addend = insn_off;
|
| 897 |
|
| 898 | if (!(insn_sec->sh.sh_flags & SHF_EXECINSTR)) {
|
| 899 | WARN("bad call to %s() for data symbol %s",
|
| 900 | __func__, sym->name);
|
| 901 | return NULL;
|
| 902 | }
|
| 903 |
|
| 904 | if (!sym) {
|
| 905 | |
| 906 | * Due to how weak functions work, we must use section based
|
| 907 | * relocations. Symbol based relocations would result in the
|
| 908 | * weak and non-weak function annotations being overlaid on the
|
| 909 | * non-weak function after linking.
|
| 910 |
|
| 911 | sym = elf_create_section_symbol(elf, insn_sec);
|
| 912 | if (!sym)
|
| 913 | return NULL;
|
| 914 |
|
| 915 | insn_sec->sym = sym;
|
| 916 | }
|
| 917 |
|
| 918 | return elf_init_reloc(elf, sec->rsec, reloc_idx, offset, sym, addend,
|
| 919 | elf_text_rela_type(elf));
|
| 920 | }
|
| 921 |
|
| 922 | struct reloc *elf_init_reloc_data_sym(struct elf *elf, struct section *sec,
|
| 923 | unsigned long offset,
|
| 924 | unsigned int reloc_idx,
|
| 925 | struct symbol *sym,
|
| 926 | s64 addend)
|
| 927 | {
|
| 928 | if (sym->sec && (sec->sh.sh_flags & SHF_EXECINSTR)) {
|
| 929 | WARN("bad call to %s() for text symbol %s",
|
| 930 | __func__, sym->name);
|
| 931 | return NULL;
|
| 932 | }
|
| 933 |
|
| 934 | return elf_init_reloc(elf, sec->rsec, reloc_idx, offset, sym, addend,
|
| 935 | elf_data_rela_type(elf));
|
| 936 | }
|
| 937 |
|
| 938 | static int read_relocs(struct elf *elf)
|
| 939 | {
|
| 940 | unsigned long nr_reloc, max_reloc = 0;
|
| 941 | struct section *rsec;
|
| 942 | struct reloc *reloc;
|
| 943 | unsigned int symndx;
|
| 944 | struct symbol *sym;
|
| 945 | int i;
|
| 946 |
|
| 947 | if (!elf_alloc_hash(reloc, elf->num_relocs))
|
| 948 | return -1;
|
| 949 |
|
| 950 | list_for_each_entry(rsec, &elf->sections, list) {
|
| 951 | if (!is_reloc_sec(rsec))
|
| 952 | continue;
|
| 953 |
|
| 954 | rsec->base = find_section_by_index(elf, rsec->sh.sh_info);
|
| 955 | if (!rsec->base) {
|
| 956 | WARN("can't find base section for reloc section %s",
|
| 957 | rsec->name);
|
| 958 | return -1;
|
| 959 | }
|
| 960 |
|
| 961 | rsec->base->rsec = rsec;
|
| 962 |
|
| 963 | nr_reloc = 0;
|
| 964 | rsec->relocs = calloc(sec_num_entries(rsec), sizeof(*reloc));
|
| 965 | if (!rsec->relocs) {
|
| 966 | perror("calloc");
|
| 967 | return -1;
|
| 968 | }
|
| 969 | for (i = 0; i < sec_num_entries(rsec); i++) {
|
| 970 | reloc = &rsec->relocs[i];
|
| 971 |
|
| 972 | reloc->sec = rsec;
|
| 973 | symndx = reloc_sym(reloc);
|
| 974 | reloc->sym = sym = find_symbol_by_index(elf, symndx);
|
| 975 | if (!reloc->sym) {
|
| 976 | WARN("can't find reloc entry symbol %d for %s",
|
| 977 | symndx, rsec->name);
|
| 978 | return -1;
|
| 979 | }
|
| 980 |
|
| 981 | elf_hash_add(reloc, &reloc->hash, reloc_hash(reloc));
|
| 982 | reloc->sym_next_reloc = sym->relocs;
|
| 983 | sym->relocs = reloc;
|
| 984 |
|
| 985 | nr_reloc++;
|
| 986 | }
|
| 987 | max_reloc = max(max_reloc, nr_reloc);
|
| 988 | }
|
| 989 |
|
| 990 | if (opts.stats) {
|
| 991 | printf("max_reloc: %lu\n", max_reloc);
|
| 992 | printf("num_relocs: %lu\n", elf->num_relocs);
|
| 993 | printf("reloc_bits: %d\n", elf->reloc_bits);
|
| 994 | }
|
| 995 |
|
| 996 | return 0;
|
| 997 | }
|
| 998 |
|
| 999 | struct elf *elf_open_read(const char *name, int flags)
|
| 1000 | {
|
| 1001 | struct elf *elf;
|
| 1002 | Elf_Cmd cmd;
|
| 1003 |
|
| 1004 | elf_version(EV_CURRENT);
|
| 1005 |
|
| 1006 | elf = malloc(sizeof(*elf));
|
| 1007 | if (!elf) {
|
| 1008 | perror("malloc");
|
| 1009 | return NULL;
|
| 1010 | }
|
| 1011 | memset(elf, 0, sizeof(*elf));
|
| 1012 |
|
| 1013 | INIT_LIST_HEAD(&elf->sections);
|
| 1014 |
|
| 1015 | elf->fd = open(name, flags);
|
| 1016 | if (elf->fd == -1) {
|
| 1017 | fprintf(stderr, "objtool: Can't open '%s': %s\n",
|
| 1018 | name, strerror(errno));
|
| 1019 | goto err;
|
| 1020 | }
|
| 1021 |
|
| 1022 | if ((flags & O_ACCMODE) == O_RDONLY)
|
| 1023 | cmd = ELF_C_READ_MMAP;
|
| 1024 | else if ((flags & O_ACCMODE) == O_RDWR)
|
| 1025 | cmd = ELF_C_RDWR;
|
| 1026 | else
|
| 1027 | cmd = ELF_C_WRITE;
|
| 1028 |
|
| 1029 | elf->elf = elf_begin(elf->fd, cmd, NULL);
|
| 1030 | if (!elf->elf) {
|
| 1031 | WARN_ELF("elf_begin");
|
| 1032 | goto err;
|
| 1033 | }
|
| 1034 |
|
| 1035 | if (!gelf_getehdr(elf->elf, &elf->ehdr)) {
|
| 1036 | WARN_ELF("gelf_getehdr");
|
| 1037 | goto err;
|
| 1038 | }
|
| 1039 |
|
| 1040 | if (read_sections(elf))
|
| 1041 | goto err;
|
| 1042 |
|
| 1043 | if (read_symbols(elf))
|
| 1044 | goto err;
|
| 1045 |
|
| 1046 | if (read_relocs(elf))
|
| 1047 | goto err;
|
| 1048 |
|
| 1049 | return elf;
|
| 1050 |
|
| 1051 | err:
|
| 1052 | elf_close(elf);
|
| 1053 | return NULL;
|
| 1054 | }
|
| 1055 |
|
| 1056 | static int elf_add_string(struct elf *elf, struct section *strtab, char *str)
|
| 1057 | {
|
| 1058 | Elf_Data *data;
|
| 1059 | Elf_Scn *s;
|
| 1060 | int len;
|
| 1061 |
|
| 1062 | if (!strtab)
|
| 1063 | strtab = find_section_by_name(elf, ".strtab");
|
| 1064 | if (!strtab) {
|
| 1065 | WARN("can't find .strtab section");
|
| 1066 | return -1;
|
| 1067 | }
|
| 1068 |
|
| 1069 | s = elf_getscn(elf->elf, strtab->idx);
|
| 1070 | if (!s) {
|
| 1071 | WARN_ELF("elf_getscn");
|
| 1072 | return -1;
|
| 1073 | }
|
| 1074 |
|
| 1075 | data = elf_newdata(s);
|
| 1076 | if (!data) {
|
| 1077 | WARN_ELF("elf_newdata");
|
| 1078 | return -1;
|
| 1079 | }
|
| 1080 |
|
| 1081 | data->d_buf = str;
|
| 1082 | data->d_size = strlen(str) + 1;
|
| 1083 | data->d_align = 1;
|
| 1084 |
|
| 1085 | len = strtab->sh.sh_size;
|
| 1086 | strtab->sh.sh_size += data->d_size;
|
| 1087 |
|
| 1088 | mark_sec_changed(elf, strtab, true);
|
| 1089 |
|
| 1090 | return len;
|
| 1091 | }
|
| 1092 |
|
| 1093 | struct section *elf_create_section(struct elf *elf, const char *name,
|
| 1094 | size_t entsize, unsigned int nr)
|
| 1095 | {
|
| 1096 | struct section *sec, *shstrtab;
|
| 1097 | size_t size = entsize * nr;
|
| 1098 | Elf_Scn *s;
|
| 1099 |
|
| 1100 | sec = malloc(sizeof(*sec));
|
| 1101 | if (!sec) {
|
| 1102 | perror("malloc");
|
| 1103 | return NULL;
|
| 1104 | }
|
| 1105 | memset(sec, 0, sizeof(*sec));
|
| 1106 |
|
| 1107 | INIT_LIST_HEAD(&sec->symbol_list);
|
| 1108 |
|
| 1109 | s = elf_newscn(elf->elf);
|
| 1110 | if (!s) {
|
| 1111 | WARN_ELF("elf_newscn");
|
| 1112 | return NULL;
|
| 1113 | }
|
| 1114 |
|
| 1115 | sec->name = strdup(name);
|
| 1116 | if (!sec->name) {
|
| 1117 | perror("strdup");
|
| 1118 | return NULL;
|
| 1119 | }
|
| 1120 |
|
| 1121 | sec->idx = elf_ndxscn(s);
|
| 1122 |
|
| 1123 | sec->data = elf_newdata(s);
|
| 1124 | if (!sec->data) {
|
| 1125 | WARN_ELF("elf_newdata");
|
| 1126 | return NULL;
|
| 1127 | }
|
| 1128 |
|
| 1129 | sec->data->d_size = size;
|
| 1130 | sec->data->d_align = 1;
|
| 1131 |
|
| 1132 | if (size) {
|
| 1133 | sec->data->d_buf = malloc(size);
|
| 1134 | if (!sec->data->d_buf) {
|
| 1135 | perror("malloc");
|
| 1136 | return NULL;
|
| 1137 | }
|
| 1138 | memset(sec->data->d_buf, 0, size);
|
| 1139 | }
|
| 1140 |
|
| 1141 | if (!gelf_getshdr(s, &sec->sh)) {
|
| 1142 | WARN_ELF("gelf_getshdr");
|
| 1143 | return NULL;
|
| 1144 | }
|
| 1145 |
|
| 1146 | sec->sh.sh_size = size;
|
| 1147 | sec->sh.sh_entsize = entsize;
|
| 1148 | sec->sh.sh_type = SHT_PROGBITS;
|
| 1149 | sec->sh.sh_addralign = 1;
|
| 1150 | sec->sh.sh_flags = SHF_ALLOC;
|
| 1151 |
|
| 1152 |
|
| 1153 | shstrtab = find_section_by_name(elf, ".shstrtab");
|
| 1154 | if (!shstrtab)
|
| 1155 | shstrtab = find_section_by_name(elf, ".strtab");
|
| 1156 | if (!shstrtab) {
|
| 1157 | WARN("can't find .shstrtab or .strtab section");
|
| 1158 | return NULL;
|
| 1159 | }
|
| 1160 | sec->sh.sh_name = elf_add_string(elf, shstrtab, sec->name);
|
| 1161 | if (sec->sh.sh_name == -1)
|
| 1162 | return NULL;
|
| 1163 |
|
| 1164 | list_add_tail(&sec->list, &elf->sections);
|
| 1165 | elf_hash_add(section, &sec->hash, sec->idx);
|
| 1166 | elf_hash_add(section_name, &sec->name_hash, str_hash(sec->name));
|
| 1167 |
|
| 1168 | mark_sec_changed(elf, sec, true);
|
| 1169 |
|
| 1170 | return sec;
|
| 1171 | }
|
| 1172 |
|
| 1173 | static struct section *elf_create_rela_section(struct elf *elf,
|
| 1174 | struct section *sec,
|
| 1175 | unsigned int reloc_nr)
|
| 1176 | {
|
| 1177 | struct section *rsec;
|
| 1178 | char *rsec_name;
|
| 1179 |
|
| 1180 | rsec_name = malloc(strlen(sec->name) + strlen(".rela") + 1);
|
| 1181 | if (!rsec_name) {
|
| 1182 | perror("malloc");
|
| 1183 | return NULL;
|
| 1184 | }
|
| 1185 | strcpy(rsec_name, ".rela");
|
| 1186 | strcat(rsec_name, sec->name);
|
| 1187 |
|
| 1188 | rsec = elf_create_section(elf, rsec_name, elf_rela_size(elf), reloc_nr);
|
| 1189 | free(rsec_name);
|
| 1190 | if (!rsec)
|
| 1191 | return NULL;
|
| 1192 |
|
| 1193 | rsec->data->d_type = ELF_T_RELA;
|
| 1194 | rsec->sh.sh_type = SHT_RELA;
|
| 1195 | rsec->sh.sh_addralign = elf_addr_size(elf);
|
| 1196 | rsec->sh.sh_link = find_section_by_name(elf, ".symtab")->idx;
|
| 1197 | rsec->sh.sh_info = sec->idx;
|
| 1198 | rsec->sh.sh_flags = SHF_INFO_LINK;
|
| 1199 |
|
| 1200 | rsec->relocs = calloc(sec_num_entries(rsec), sizeof(struct reloc));
|
| 1201 | if (!rsec->relocs) {
|
| 1202 | perror("calloc");
|
| 1203 | return NULL;
|
| 1204 | }
|
| 1205 |
|
| 1206 | sec->rsec = rsec;
|
| 1207 | rsec->base = sec;
|
| 1208 |
|
| 1209 | return rsec;
|
| 1210 | }
|
| 1211 |
|
| 1212 | struct section *elf_create_section_pair(struct elf *elf, const char *name,
|
| 1213 | size_t entsize, unsigned int nr,
|
| 1214 | unsigned int reloc_nr)
|
| 1215 | {
|
| 1216 | struct section *sec;
|
| 1217 |
|
| 1218 | sec = elf_create_section(elf, name, entsize, nr);
|
| 1219 | if (!sec)
|
| 1220 | return NULL;
|
| 1221 |
|
| 1222 | if (!elf_create_rela_section(elf, sec, reloc_nr))
|
| 1223 | return NULL;
|
| 1224 |
|
| 1225 | return sec;
|
| 1226 | }
|
| 1227 |
|
| 1228 | int elf_write_insn(struct elf *elf, struct section *sec,
|
| 1229 | unsigned long offset, unsigned int len,
|
| 1230 | const char *insn)
|
| 1231 | {
|
| 1232 | Elf_Data *data = sec->data;
|
| 1233 |
|
| 1234 | if (data->d_type != ELF_T_BYTE || data->d_off) {
|
| 1235 | WARN("write to unexpected data for section: %s", sec->name);
|
| 1236 | return -1;
|
| 1237 | }
|
| 1238 |
|
| 1239 | memcpy(data->d_buf + offset, insn, len);
|
| 1240 |
|
| 1241 | mark_sec_changed(elf, sec, true);
|
| 1242 |
|
| 1243 | return 0;
|
| 1244 | }
|
| 1245 |
|
| 1246 | |
| 1247 | * When Elf_Scn::sh_size is smaller than the combined Elf_Data::d_size
|
| 1248 | * do you:
|
| 1249 | *
|
| 1250 | * A) adhere to the section header and truncate the data, or
|
| 1251 | * B) ignore the section header and write out all the data you've got?
|
| 1252 | *
|
| 1253 | * Yes, libelf sucks and we need to manually truncate if we over-allocate data.
|
| 1254 |
|
| 1255 | static int elf_truncate_section(struct elf *elf, struct section *sec)
|
| 1256 | {
|
| 1257 | u64 size = sec->sh.sh_size;
|
| 1258 | bool truncated = false;
|
| 1259 | Elf_Data *data = NULL;
|
| 1260 | Elf_Scn *s;
|
| 1261 |
|
| 1262 | s = elf_getscn(elf->elf, sec->idx);
|
| 1263 | if (!s) {
|
| 1264 | WARN_ELF("elf_getscn");
|
| 1265 | return -1;
|
| 1266 | }
|
| 1267 |
|
| 1268 | for (;;) {
|
| 1269 |
|
| 1270 | data = elf_getdata(s, data);
|
| 1271 |
|
| 1272 | if (!data) {
|
| 1273 | if (size) {
|
| 1274 | WARN("end of section data but non-zero size left\n");
|
| 1275 | return -1;
|
| 1276 | }
|
| 1277 | return 0;
|
| 1278 | }
|
| 1279 |
|
| 1280 | if (truncated) {
|
| 1281 |
|
| 1282 | WARN("truncated; but more data\n");
|
| 1283 | return -1;
|
| 1284 | }
|
| 1285 |
|
| 1286 | if (!data->d_size) {
|
| 1287 | WARN("zero size data");
|
| 1288 | return -1;
|
| 1289 | }
|
| 1290 |
|
| 1291 | if (data->d_size > size) {
|
| 1292 | truncated = true;
|
| 1293 | data->d_size = size;
|
| 1294 | }
|
| 1295 |
|
| 1296 | size -= data->d_size;
|
| 1297 | }
|
| 1298 | }
|
| 1299 |
|
| 1300 | int elf_write(struct elf *elf)
|
| 1301 | {
|
| 1302 | struct section *sec;
|
| 1303 | Elf_Scn *s;
|
| 1304 |
|
| 1305 | if (opts.dryrun)
|
| 1306 | return 0;
|
| 1307 |
|
| 1308 |
|
| 1309 | list_for_each_entry(sec, &elf->sections, list) {
|
| 1310 | if (sec->truncate)
|
| 1311 | elf_truncate_section(elf, sec);
|
| 1312 |
|
| 1313 | if (sec_changed(sec)) {
|
| 1314 | s = elf_getscn(elf->elf, sec->idx);
|
| 1315 | if (!s) {
|
| 1316 | WARN_ELF("elf_getscn");
|
| 1317 | return -1;
|
| 1318 | }
|
| 1319 |
|
| 1320 |
|
| 1321 | if (!gelf_update_shdr(s, &sec->sh)) {
|
| 1322 | WARN_ELF("gelf_update_shdr");
|
| 1323 | return -1;
|
| 1324 | }
|
| 1325 |
|
| 1326 | mark_sec_changed(elf, sec, false);
|
| 1327 | }
|
| 1328 | }
|
| 1329 |
|
| 1330 |
|
| 1331 | elf_flagelf(elf->elf, ELF_C_SET, ELF_F_DIRTY);
|
| 1332 |
|
| 1333 |
|
| 1334 | if (elf_update(elf->elf, ELF_C_WRITE) < 0) {
|
| 1335 | WARN_ELF("elf_update");
|
| 1336 | return -1;
|
| 1337 | }
|
| 1338 |
|
| 1339 | elf->changed = false;
|
| 1340 |
|
| 1341 | return 0;
|
| 1342 | }
|
| 1343 |
|
| 1344 | void elf_close(struct elf *elf)
|
| 1345 | {
|
| 1346 | if (elf->elf)
|
| 1347 | elf_end(elf->elf);
|
| 1348 |
|
| 1349 | if (elf->fd > 0)
|
| 1350 | close(elf->fd);
|
| 1351 |
|
| 1352 | |
| 1353 | * NOTE: All remaining allocations are leaked on purpose. Objtool is
|
| 1354 | * about to exit anyway.
|
| 1355 |
|
| 1356 | }
|