1 // SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) 2 3 /* 4 * resolve_btfids scans Elf object for .BTF_ids section and resolves 5 * its symbols with BTF ID values. 6 * 7 * Each symbol points to 4 bytes data and is expected to have 8 * following name syntax: 9 * 10 * __BTF_ID__<type>__<symbol>[__<id>] 11 * 12 * type is: 13 * 14 * func - lookup BTF_KIND_FUNC symbol with <symbol> name 15 * and store its ID into the data: 16 * 17 * __BTF_ID__func__vfs_close__1: 18 * .zero 4 19 * 20 * struct - lookup BTF_KIND_STRUCT symbol with <symbol> name 21 * and store its ID into the data: 22 * 23 * __BTF_ID__struct__sk_buff__1: 24 * .zero 4 25 * 26 * union - lookup BTF_KIND_UNION symbol with <symbol> name 27 * and store its ID into the data: 28 * 29 * __BTF_ID__union__thread_union__1: 30 * .zero 4 31 * 32 * typedef - lookup BTF_KIND_TYPEDEF symbol with <symbol> name 33 * and store its ID into the data: 34 * 35 * __BTF_ID__typedef__pid_t__1: 36 * .zero 4 37 * 38 * set - store symbol size into first 4 bytes and sort following 39 * ID list 40 * 41 * __BTF_ID__set__list: 42 * .zero 4 43 * list: 44 * __BTF_ID__func__vfs_getattr__3: 45 * .zero 4 46 * __BTF_ID__func__vfs_fallocate__4: 47 * .zero 4 48 */ 49 50 #define _GNU_SOURCE 51 #include <stdio.h> 52 #include <string.h> 53 #include <unistd.h> 54 #include <stdlib.h> 55 #include <libelf.h> 56 #include <gelf.h> 57 #include <sys/stat.h> 58 #include <fcntl.h> 59 #include <errno.h> 60 #include <linux/rbtree.h> 61 #include <linux/zalloc.h> 62 #include <linux/err.h> 63 #include <btf.h> 64 #include <libbpf.h> 65 #include <parse-options.h> 66 67 #define BTF_IDS_SECTION ".BTF_ids" 68 #define BTF_ID "__BTF_ID__" 69 70 #define BTF_STRUCT "struct" 71 #define BTF_UNION "union" 72 #define BTF_TYPEDEF "typedef" 73 #define BTF_FUNC "func" 74 #define BTF_SET "set" 75 76 #define ADDR_CNT 100 77 78 struct btf_id { 79 struct rb_node rb_node; 80 char *name; 81 union { 82 int id; 83 int cnt; 84 }; 85 int addr_cnt; 86 Elf64_Addr addr[ADDR_CNT]; 87 }; 88 89 struct object { 90 const char *path; 91 const char *btf; 92 93 struct { 94 int fd; 95 Elf *elf; 96 Elf_Data *symbols; 97 Elf_Data *idlist; 98 int symbols_shndx; 99 int idlist_shndx; 100 size_t strtabidx; 101 unsigned long idlist_addr; 102 } efile; 103 104 struct rb_root sets; 105 struct rb_root structs; 106 struct rb_root unions; 107 struct rb_root typedefs; 108 struct rb_root funcs; 109 110 int nr_funcs; 111 int nr_structs; 112 int nr_unions; 113 int nr_typedefs; 114 }; 115 116 static int verbose; 117 118 int eprintf(int level, int var, const char *fmt, ...) 119 { 120 va_list args; 121 int ret; 122 123 if (var >= level) { 124 va_start(args, fmt); 125 ret = vfprintf(stderr, fmt, args); 126 va_end(args); 127 } 128 return ret; 129 } 130 131 #ifndef pr_fmt 132 #define pr_fmt(fmt) fmt 133 #endif 134 135 #define pr_debug(fmt, ...) \ 136 eprintf(1, verbose, pr_fmt(fmt), ##__VA_ARGS__) 137 #define pr_debugN(n, fmt, ...) \ 138 eprintf(n, verbose, pr_fmt(fmt), ##__VA_ARGS__) 139 #define pr_debug2(fmt, ...) pr_debugN(2, pr_fmt(fmt), ##__VA_ARGS__) 140 #define pr_err(fmt, ...) \ 141 eprintf(0, verbose, pr_fmt(fmt), ##__VA_ARGS__) 142 #define pr_info(fmt, ...) \ 143 eprintf(0, verbose, pr_fmt(fmt), ##__VA_ARGS__) 144 145 static bool is_btf_id(const char *name) 146 { 147 return name && !strncmp(name, BTF_ID, sizeof(BTF_ID) - 1); 148 } 149 150 static struct btf_id *btf_id__find(struct rb_root *root, const char *name) 151 { 152 struct rb_node *p = root->rb_node; 153 struct btf_id *id; 154 int cmp; 155 156 while (p) { 157 id = rb_entry(p, struct btf_id, rb_node); 158 cmp = strcmp(id->name, name); 159 if (cmp < 0) 160 p = p->rb_left; 161 else if (cmp > 0) 162 p = p->rb_right; 163 else 164 return id; 165 } 166 return NULL; 167 } 168 169 static struct btf_id* 170 btf_id__add(struct rb_root *root, char *name, bool unique) 171 { 172 struct rb_node **p = &root->rb_node; 173 struct rb_node *parent = NULL; 174 struct btf_id *id; 175 int cmp; 176 177 while (*p != NULL) { 178 parent = *p; 179 id = rb_entry(parent, struct btf_id, rb_node); 180 cmp = strcmp(id->name, name); 181 if (cmp < 0) 182 p = &(*p)->rb_left; 183 else if (cmp > 0) 184 p = &(*p)->rb_right; 185 else 186 return unique ? NULL : id; 187 } 188 189 id = zalloc(sizeof(*id)); 190 if (id) { 191 pr_debug("adding symbol %s\n", name); 192 id->name = name; 193 rb_link_node(&id->rb_node, parent, p); 194 rb_insert_color(&id->rb_node, root); 195 } 196 return id; 197 } 198 199 static char *get_id(const char *prefix_end) 200 { 201 /* 202 * __BTF_ID__func__vfs_truncate__0 203 * prefix_end = ^ 204 * pos = ^ 205 */ 206 int len = strlen(prefix_end); 207 int pos = sizeof("__") - 1; 208 char *p, *id; 209 210 if (pos >= len) 211 return NULL; 212 213 id = strdup(prefix_end + pos); 214 if (id) { 215 /* 216 * __BTF_ID__func__vfs_truncate__0 217 * id = ^ 218 * 219 * cut the unique id part 220 */ 221 p = strrchr(id, '_'); 222 p--; 223 if (*p != '_') { 224 free(id); 225 return NULL; 226 } 227 *p = '\0'; 228 } 229 return id; 230 } 231 232 static struct btf_id *add_set(struct object *obj, char *name) 233 { 234 /* 235 * __BTF_ID__set__name 236 * name = ^ 237 * id = ^ 238 */ 239 char *id = name + sizeof(BTF_SET "__") - 1; 240 int len = strlen(name); 241 242 if (id >= name + len) { 243 pr_err("FAILED to parse set name: %s\n", name); 244 return NULL; 245 } 246 247 return btf_id__add(&obj->sets, id, true); 248 } 249 250 static struct btf_id *add_symbol(struct rb_root *root, char *name, size_t size) 251 { 252 char *id; 253 254 id = get_id(name + size); 255 if (!id) { 256 pr_err("FAILED to parse symbol name: %s\n", name); 257 return NULL; 258 } 259 260 return btf_id__add(root, id, false); 261 } 262 263 /* 264 * The data of compressed section should be aligned to 4 265 * (for 32bit) or 8 (for 64 bit) bytes. The binutils ld 266 * sets sh_addralign to 1, which makes libelf fail with 267 * misaligned section error during the update: 268 * FAILED elf_update(WRITE): invalid section alignment 269 * 270 * While waiting for ld fix, we fix the compressed sections 271 * sh_addralign value manualy. 272 */ 273 static int compressed_section_fix(Elf *elf, Elf_Scn *scn, GElf_Shdr *sh) 274 { 275 int expected = gelf_getclass(elf) == ELFCLASS32 ? 4 : 8; 276 277 if (!(sh->sh_flags & SHF_COMPRESSED)) 278 return 0; 279 280 if (sh->sh_addralign == expected) 281 return 0; 282 283 pr_debug2(" - fixing wrong alignment sh_addralign %u, expected %u\n", 284 sh->sh_addralign, expected); 285 286 sh->sh_addralign = expected; 287 288 if (gelf_update_shdr(scn, sh) == 0) { 289 printf("FAILED cannot update section header: %s\n", 290 elf_errmsg(-1)); 291 return -1; 292 } 293 return 0; 294 } 295 296 static int elf_collect(struct object *obj) 297 { 298 Elf_Scn *scn = NULL; 299 size_t shdrstrndx; 300 int idx = 0; 301 Elf *elf; 302 int fd; 303 304 fd = open(obj->path, O_RDWR, 0666); 305 if (fd == -1) { 306 pr_err("FAILED cannot open %s: %s\n", 307 obj->path, strerror(errno)); 308 return -1; 309 } 310 311 elf_version(EV_CURRENT); 312 313 elf = elf_begin(fd, ELF_C_RDWR_MMAP, NULL); 314 if (!elf) { 315 pr_err("FAILED cannot create ELF descriptor: %s\n", 316 elf_errmsg(-1)); 317 return -1; 318 } 319 320 obj->efile.fd = fd; 321 obj->efile.elf = elf; 322 323 elf_flagelf(elf, ELF_C_SET, ELF_F_LAYOUT); 324 325 if (elf_getshdrstrndx(elf, &shdrstrndx) != 0) { 326 pr_err("FAILED cannot get shdr str ndx\n"); 327 return -1; 328 } 329 330 /* 331 * Scan all the elf sections and look for save data 332 * from .BTF_ids section and symbols. 333 */ 334 while ((scn = elf_nextscn(elf, scn)) != NULL) { 335 Elf_Data *data; 336 GElf_Shdr sh; 337 char *name; 338 339 idx++; 340 if (gelf_getshdr(scn, &sh) != &sh) { 341 pr_err("FAILED get section(%d) header\n", idx); 342 return -1; 343 } 344 345 name = elf_strptr(elf, shdrstrndx, sh.sh_name); 346 if (!name) { 347 pr_err("FAILED get section(%d) name\n", idx); 348 return -1; 349 } 350 351 data = elf_getdata(scn, 0); 352 if (!data) { 353 pr_err("FAILED to get section(%d) data from %s\n", 354 idx, name); 355 return -1; 356 } 357 358 pr_debug2("section(%d) %s, size %ld, link %d, flags %lx, type=%d\n", 359 idx, name, (unsigned long) data->d_size, 360 (int) sh.sh_link, (unsigned long) sh.sh_flags, 361 (int) sh.sh_type); 362 363 if (sh.sh_type == SHT_SYMTAB) { 364 obj->efile.symbols = data; 365 obj->efile.symbols_shndx = idx; 366 obj->efile.strtabidx = sh.sh_link; 367 } else if (!strcmp(name, BTF_IDS_SECTION)) { 368 obj->efile.idlist = data; 369 obj->efile.idlist_shndx = idx; 370 obj->efile.idlist_addr = sh.sh_addr; 371 } 372 373 if (compressed_section_fix(elf, scn, &sh)) 374 return -1; 375 } 376 377 return 0; 378 } 379 380 static int symbols_collect(struct object *obj) 381 { 382 Elf_Scn *scn = NULL; 383 int n, i, err = 0; 384 GElf_Shdr sh; 385 char *name; 386 387 scn = elf_getscn(obj->efile.elf, obj->efile.symbols_shndx); 388 if (!scn) 389 return -1; 390 391 if (gelf_getshdr(scn, &sh) != &sh) 392 return -1; 393 394 n = sh.sh_size / sh.sh_entsize; 395 396 /* 397 * Scan symbols and look for the ones starting with 398 * __BTF_ID__* over .BTF_ids section. 399 */ 400 for (i = 0; !err && i < n; i++) { 401 char *tmp, *prefix; 402 struct btf_id *id; 403 GElf_Sym sym; 404 int err = -1; 405 406 if (!gelf_getsym(obj->efile.symbols, i, &sym)) 407 return -1; 408 409 if (sym.st_shndx != obj->efile.idlist_shndx) 410 continue; 411 412 name = elf_strptr(obj->efile.elf, obj->efile.strtabidx, 413 sym.st_name); 414 415 if (!is_btf_id(name)) 416 continue; 417 418 /* 419 * __BTF_ID__TYPE__vfs_truncate__0 420 * prefix = ^ 421 */ 422 prefix = name + sizeof(BTF_ID) - 1; 423 424 /* struct */ 425 if (!strncmp(prefix, BTF_STRUCT, sizeof(BTF_STRUCT) - 1)) { 426 obj->nr_structs++; 427 id = add_symbol(&obj->structs, prefix, sizeof(BTF_STRUCT) - 1); 428 /* union */ 429 } else if (!strncmp(prefix, BTF_UNION, sizeof(BTF_UNION) - 1)) { 430 obj->nr_unions++; 431 id = add_symbol(&obj->unions, prefix, sizeof(BTF_UNION) - 1); 432 /* typedef */ 433 } else if (!strncmp(prefix, BTF_TYPEDEF, sizeof(BTF_TYPEDEF) - 1)) { 434 obj->nr_typedefs++; 435 id = add_symbol(&obj->typedefs, prefix, sizeof(BTF_TYPEDEF) - 1); 436 /* func */ 437 } else if (!strncmp(prefix, BTF_FUNC, sizeof(BTF_FUNC) - 1)) { 438 obj->nr_funcs++; 439 id = add_symbol(&obj->funcs, prefix, sizeof(BTF_FUNC) - 1); 440 /* set */ 441 } else if (!strncmp(prefix, BTF_SET, sizeof(BTF_SET) - 1)) { 442 id = add_set(obj, prefix); 443 /* 444 * SET objects store list's count, which is encoded 445 * in symbol's size, together with 'cnt' field hence 446 * that - 1. 447 */ 448 if (id) 449 id->cnt = sym.st_size / sizeof(int) - 1; 450 } else { 451 pr_err("FAILED unsupported prefix %s\n", prefix); 452 return -1; 453 } 454 455 if (!id) 456 return -ENOMEM; 457 458 if (id->addr_cnt >= ADDR_CNT) { 459 pr_err("FAILED symbol %s crossed the number of allowed lists\n", 460 id->name); 461 return -1; 462 } 463 id->addr[id->addr_cnt++] = sym.st_value; 464 } 465 466 return 0; 467 } 468 469 static int symbols_resolve(struct object *obj) 470 { 471 int nr_typedefs = obj->nr_typedefs; 472 int nr_structs = obj->nr_structs; 473 int nr_unions = obj->nr_unions; 474 int nr_funcs = obj->nr_funcs; 475 int err, type_id; 476 struct btf *btf; 477 __u32 nr_types; 478 479 btf = btf__parse(obj->btf ?: obj->path, NULL); 480 err = libbpf_get_error(btf); 481 if (err) { 482 pr_err("FAILED: load BTF from %s: %s\n", 483 obj->path, strerror(-err)); 484 return -1; 485 } 486 487 err = -1; 488 nr_types = btf__get_nr_types(btf); 489 490 /* 491 * Iterate all the BTF types and search for collected symbol IDs. 492 */ 493 for (type_id = 1; type_id <= nr_types; type_id++) { 494 const struct btf_type *type; 495 struct rb_root *root; 496 struct btf_id *id; 497 const char *str; 498 int *nr; 499 500 type = btf__type_by_id(btf, type_id); 501 if (!type) { 502 pr_err("FAILED: malformed BTF, can't resolve type for ID %d\n", 503 type_id); 504 goto out; 505 } 506 507 if (btf_is_func(type) && nr_funcs) { 508 nr = &nr_funcs; 509 root = &obj->funcs; 510 } else if (btf_is_struct(type) && nr_structs) { 511 nr = &nr_structs; 512 root = &obj->structs; 513 } else if (btf_is_union(type) && nr_unions) { 514 nr = &nr_unions; 515 root = &obj->unions; 516 } else if (btf_is_typedef(type) && nr_typedefs) { 517 nr = &nr_typedefs; 518 root = &obj->typedefs; 519 } else 520 continue; 521 522 str = btf__name_by_offset(btf, type->name_off); 523 if (!str) { 524 pr_err("FAILED: malformed BTF, can't resolve name for ID %d\n", 525 type_id); 526 goto out; 527 } 528 529 id = btf_id__find(root, str); 530 if (id) { 531 if (id->id) { 532 pr_info("WARN: multiple IDs found for '%s': %d, %d - using %d\n", 533 str, id->id, type_id, id->id); 534 } else { 535 id->id = type_id; 536 (*nr)--; 537 } 538 } 539 } 540 541 err = 0; 542 out: 543 btf__free(btf); 544 return err; 545 } 546 547 static int id_patch(struct object *obj, struct btf_id *id) 548 { 549 Elf_Data *data = obj->efile.idlist; 550 int *ptr = data->d_buf; 551 int i; 552 553 if (!id->id) { 554 pr_err("FAILED unresolved symbol %s\n", id->name); 555 return -EINVAL; 556 } 557 558 for (i = 0; i < id->addr_cnt; i++) { 559 unsigned long addr = id->addr[i]; 560 unsigned long idx = addr - obj->efile.idlist_addr; 561 562 pr_debug("patching addr %5lu: ID %7d [%s]\n", 563 idx, id->id, id->name); 564 565 if (idx >= data->d_size) { 566 pr_err("FAILED patching index %lu out of bounds %lu\n", 567 idx, data->d_size); 568 return -1; 569 } 570 571 idx = idx / sizeof(int); 572 ptr[idx] = id->id; 573 } 574 575 return 0; 576 } 577 578 static int __symbols_patch(struct object *obj, struct rb_root *root) 579 { 580 struct rb_node *next; 581 struct btf_id *id; 582 583 next = rb_first(root); 584 while (next) { 585 id = rb_entry(next, struct btf_id, rb_node); 586 587 if (id_patch(obj, id)) 588 return -1; 589 590 next = rb_next(next); 591 } 592 return 0; 593 } 594 595 static int cmp_id(const void *pa, const void *pb) 596 { 597 const int *a = pa, *b = pb; 598 599 return *a - *b; 600 } 601 602 static int sets_patch(struct object *obj) 603 { 604 Elf_Data *data = obj->efile.idlist; 605 int *ptr = data->d_buf; 606 struct rb_node *next; 607 608 next = rb_first(&obj->sets); 609 while (next) { 610 unsigned long addr, idx; 611 struct btf_id *id; 612 int *base; 613 int cnt; 614 615 id = rb_entry(next, struct btf_id, rb_node); 616 addr = id->addr[0]; 617 idx = addr - obj->efile.idlist_addr; 618 619 /* sets are unique */ 620 if (id->addr_cnt != 1) { 621 pr_err("FAILED malformed data for set '%s'\n", 622 id->name); 623 return -1; 624 } 625 626 idx = idx / sizeof(int); 627 base = &ptr[idx] + 1; 628 cnt = ptr[idx]; 629 630 pr_debug("sorting addr %5lu: cnt %6d [%s]\n", 631 (idx + 1) * sizeof(int), cnt, id->name); 632 633 qsort(base, cnt, sizeof(int), cmp_id); 634 635 next = rb_next(next); 636 } 637 return 0; 638 } 639 640 static int symbols_patch(struct object *obj) 641 { 642 int err; 643 644 if (__symbols_patch(obj, &obj->structs) || 645 __symbols_patch(obj, &obj->unions) || 646 __symbols_patch(obj, &obj->typedefs) || 647 __symbols_patch(obj, &obj->funcs) || 648 __symbols_patch(obj, &obj->sets)) 649 return -1; 650 651 if (sets_patch(obj)) 652 return -1; 653 654 elf_flagdata(obj->efile.idlist, ELF_C_SET, ELF_F_DIRTY); 655 656 err = elf_update(obj->efile.elf, ELF_C_WRITE); 657 if (err < 0) { 658 pr_err("FAILED elf_update(WRITE): %s\n", 659 elf_errmsg(-1)); 660 } 661 662 pr_debug("update %s for %s\n", 663 err >= 0 ? "ok" : "failed", obj->path); 664 return err < 0 ? -1 : 0; 665 } 666 667 static const char * const resolve_btfids_usage[] = { 668 "resolve_btfids [<options>] <ELF object>", 669 NULL 670 }; 671 672 int main(int argc, const char **argv) 673 { 674 bool no_fail = false; 675 struct object obj = { 676 .efile = { 677 .idlist_shndx = -1, 678 .symbols_shndx = -1, 679 }, 680 .structs = RB_ROOT, 681 .unions = RB_ROOT, 682 .typedefs = RB_ROOT, 683 .funcs = RB_ROOT, 684 .sets = RB_ROOT, 685 }; 686 struct option btfid_options[] = { 687 OPT_INCR('v', "verbose", &verbose, 688 "be more verbose (show errors, etc)"), 689 OPT_STRING(0, "btf", &obj.btf, "BTF data", 690 "BTF data"), 691 OPT_BOOLEAN(0, "no-fail", &no_fail, 692 "do not fail if " BTF_IDS_SECTION " section is not found"), 693 OPT_END() 694 }; 695 int err = -1; 696 697 argc = parse_options(argc, argv, btfid_options, resolve_btfids_usage, 698 PARSE_OPT_STOP_AT_NON_OPTION); 699 if (argc != 1) 700 usage_with_options(resolve_btfids_usage, btfid_options); 701 702 obj.path = argv[0]; 703 704 if (elf_collect(&obj)) 705 goto out; 706 707 /* 708 * We did not find .BTF_ids section or symbols section, 709 * nothing to do.. 710 */ 711 if (obj.efile.idlist_shndx == -1 || 712 obj.efile.symbols_shndx == -1) { 713 if (no_fail) 714 return 0; 715 pr_err("FAILED to find needed sections\n"); 716 return -1; 717 } 718 719 if (symbols_collect(&obj)) 720 goto out; 721 722 if (symbols_resolve(&obj)) 723 goto out; 724 725 if (symbols_patch(&obj)) 726 goto out; 727 728 err = 0; 729 out: 730 if (obj.efile.elf) 731 elf_end(obj.efile.elf); 732 close(obj.efile.fd); 733 return err; 734 } 735