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 /* Older libelf.h and glibc elf.h might not yet define the ELF compression types. */ 264 #ifndef SHF_COMPRESSED 265 #define SHF_COMPRESSED (1 << 11) /* Section with compressed data. */ 266 #endif 267 268 /* 269 * The data of compressed section should be aligned to 4 270 * (for 32bit) or 8 (for 64 bit) bytes. The binutils ld 271 * sets sh_addralign to 1, which makes libelf fail with 272 * misaligned section error during the update: 273 * FAILED elf_update(WRITE): invalid section alignment 274 * 275 * While waiting for ld fix, we fix the compressed sections 276 * sh_addralign value manualy. 277 */ 278 static int compressed_section_fix(Elf *elf, Elf_Scn *scn, GElf_Shdr *sh) 279 { 280 int expected = gelf_getclass(elf) == ELFCLASS32 ? 4 : 8; 281 282 if (!(sh->sh_flags & SHF_COMPRESSED)) 283 return 0; 284 285 if (sh->sh_addralign == expected) 286 return 0; 287 288 pr_debug2(" - fixing wrong alignment sh_addralign %u, expected %u\n", 289 sh->sh_addralign, expected); 290 291 sh->sh_addralign = expected; 292 293 if (gelf_update_shdr(scn, sh) == 0) { 294 printf("FAILED cannot update section header: %s\n", 295 elf_errmsg(-1)); 296 return -1; 297 } 298 return 0; 299 } 300 301 static int elf_collect(struct object *obj) 302 { 303 Elf_Scn *scn = NULL; 304 size_t shdrstrndx; 305 int idx = 0; 306 Elf *elf; 307 int fd; 308 309 fd = open(obj->path, O_RDWR, 0666); 310 if (fd == -1) { 311 pr_err("FAILED cannot open %s: %s\n", 312 obj->path, strerror(errno)); 313 return -1; 314 } 315 316 elf_version(EV_CURRENT); 317 318 elf = elf_begin(fd, ELF_C_RDWR_MMAP, NULL); 319 if (!elf) { 320 pr_err("FAILED cannot create ELF descriptor: %s\n", 321 elf_errmsg(-1)); 322 return -1; 323 } 324 325 obj->efile.fd = fd; 326 obj->efile.elf = elf; 327 328 elf_flagelf(elf, ELF_C_SET, ELF_F_LAYOUT); 329 330 if (elf_getshdrstrndx(elf, &shdrstrndx) != 0) { 331 pr_err("FAILED cannot get shdr str ndx\n"); 332 return -1; 333 } 334 335 /* 336 * Scan all the elf sections and look for save data 337 * from .BTF_ids section and symbols. 338 */ 339 while ((scn = elf_nextscn(elf, scn)) != NULL) { 340 Elf_Data *data; 341 GElf_Shdr sh; 342 char *name; 343 344 idx++; 345 if (gelf_getshdr(scn, &sh) != &sh) { 346 pr_err("FAILED get section(%d) header\n", idx); 347 return -1; 348 } 349 350 name = elf_strptr(elf, shdrstrndx, sh.sh_name); 351 if (!name) { 352 pr_err("FAILED get section(%d) name\n", idx); 353 return -1; 354 } 355 356 data = elf_getdata(scn, 0); 357 if (!data) { 358 pr_err("FAILED to get section(%d) data from %s\n", 359 idx, name); 360 return -1; 361 } 362 363 pr_debug2("section(%d) %s, size %ld, link %d, flags %lx, type=%d\n", 364 idx, name, (unsigned long) data->d_size, 365 (int) sh.sh_link, (unsigned long) sh.sh_flags, 366 (int) sh.sh_type); 367 368 if (sh.sh_type == SHT_SYMTAB) { 369 obj->efile.symbols = data; 370 obj->efile.symbols_shndx = idx; 371 obj->efile.strtabidx = sh.sh_link; 372 } else if (!strcmp(name, BTF_IDS_SECTION)) { 373 obj->efile.idlist = data; 374 obj->efile.idlist_shndx = idx; 375 obj->efile.idlist_addr = sh.sh_addr; 376 } 377 378 if (compressed_section_fix(elf, scn, &sh)) 379 return -1; 380 } 381 382 return 0; 383 } 384 385 static int symbols_collect(struct object *obj) 386 { 387 Elf_Scn *scn = NULL; 388 int n, i, err = 0; 389 GElf_Shdr sh; 390 char *name; 391 392 scn = elf_getscn(obj->efile.elf, obj->efile.symbols_shndx); 393 if (!scn) 394 return -1; 395 396 if (gelf_getshdr(scn, &sh) != &sh) 397 return -1; 398 399 n = sh.sh_size / sh.sh_entsize; 400 401 /* 402 * Scan symbols and look for the ones starting with 403 * __BTF_ID__* over .BTF_ids section. 404 */ 405 for (i = 0; !err && i < n; i++) { 406 char *tmp, *prefix; 407 struct btf_id *id; 408 GElf_Sym sym; 409 int err = -1; 410 411 if (!gelf_getsym(obj->efile.symbols, i, &sym)) 412 return -1; 413 414 if (sym.st_shndx != obj->efile.idlist_shndx) 415 continue; 416 417 name = elf_strptr(obj->efile.elf, obj->efile.strtabidx, 418 sym.st_name); 419 420 if (!is_btf_id(name)) 421 continue; 422 423 /* 424 * __BTF_ID__TYPE__vfs_truncate__0 425 * prefix = ^ 426 */ 427 prefix = name + sizeof(BTF_ID) - 1; 428 429 /* struct */ 430 if (!strncmp(prefix, BTF_STRUCT, sizeof(BTF_STRUCT) - 1)) { 431 obj->nr_structs++; 432 id = add_symbol(&obj->structs, prefix, sizeof(BTF_STRUCT) - 1); 433 /* union */ 434 } else if (!strncmp(prefix, BTF_UNION, sizeof(BTF_UNION) - 1)) { 435 obj->nr_unions++; 436 id = add_symbol(&obj->unions, prefix, sizeof(BTF_UNION) - 1); 437 /* typedef */ 438 } else if (!strncmp(prefix, BTF_TYPEDEF, sizeof(BTF_TYPEDEF) - 1)) { 439 obj->nr_typedefs++; 440 id = add_symbol(&obj->typedefs, prefix, sizeof(BTF_TYPEDEF) - 1); 441 /* func */ 442 } else if (!strncmp(prefix, BTF_FUNC, sizeof(BTF_FUNC) - 1)) { 443 obj->nr_funcs++; 444 id = add_symbol(&obj->funcs, prefix, sizeof(BTF_FUNC) - 1); 445 /* set */ 446 } else if (!strncmp(prefix, BTF_SET, sizeof(BTF_SET) - 1)) { 447 id = add_set(obj, prefix); 448 /* 449 * SET objects store list's count, which is encoded 450 * in symbol's size, together with 'cnt' field hence 451 * that - 1. 452 */ 453 if (id) 454 id->cnt = sym.st_size / sizeof(int) - 1; 455 } else { 456 pr_err("FAILED unsupported prefix %s\n", prefix); 457 return -1; 458 } 459 460 if (!id) 461 return -ENOMEM; 462 463 if (id->addr_cnt >= ADDR_CNT) { 464 pr_err("FAILED symbol %s crossed the number of allowed lists\n", 465 id->name); 466 return -1; 467 } 468 id->addr[id->addr_cnt++] = sym.st_value; 469 } 470 471 return 0; 472 } 473 474 static int symbols_resolve(struct object *obj) 475 { 476 int nr_typedefs = obj->nr_typedefs; 477 int nr_structs = obj->nr_structs; 478 int nr_unions = obj->nr_unions; 479 int nr_funcs = obj->nr_funcs; 480 int err, type_id; 481 struct btf *btf; 482 __u32 nr_types; 483 484 btf = btf__parse(obj->btf ?: obj->path, NULL); 485 err = libbpf_get_error(btf); 486 if (err) { 487 pr_err("FAILED: load BTF from %s: %s\n", 488 obj->path, strerror(-err)); 489 return -1; 490 } 491 492 err = -1; 493 nr_types = btf__get_nr_types(btf); 494 495 /* 496 * Iterate all the BTF types and search for collected symbol IDs. 497 */ 498 for (type_id = 1; type_id <= nr_types; type_id++) { 499 const struct btf_type *type; 500 struct rb_root *root; 501 struct btf_id *id; 502 const char *str; 503 int *nr; 504 505 type = btf__type_by_id(btf, type_id); 506 if (!type) { 507 pr_err("FAILED: malformed BTF, can't resolve type for ID %d\n", 508 type_id); 509 goto out; 510 } 511 512 if (btf_is_func(type) && nr_funcs) { 513 nr = &nr_funcs; 514 root = &obj->funcs; 515 } else if (btf_is_struct(type) && nr_structs) { 516 nr = &nr_structs; 517 root = &obj->structs; 518 } else if (btf_is_union(type) && nr_unions) { 519 nr = &nr_unions; 520 root = &obj->unions; 521 } else if (btf_is_typedef(type) && nr_typedefs) { 522 nr = &nr_typedefs; 523 root = &obj->typedefs; 524 } else 525 continue; 526 527 str = btf__name_by_offset(btf, type->name_off); 528 if (!str) { 529 pr_err("FAILED: malformed BTF, can't resolve name for ID %d\n", 530 type_id); 531 goto out; 532 } 533 534 id = btf_id__find(root, str); 535 if (id) { 536 if (id->id) { 537 pr_info("WARN: multiple IDs found for '%s': %d, %d - using %d\n", 538 str, id->id, type_id, id->id); 539 } else { 540 id->id = type_id; 541 (*nr)--; 542 } 543 } 544 } 545 546 err = 0; 547 out: 548 btf__free(btf); 549 return err; 550 } 551 552 static int id_patch(struct object *obj, struct btf_id *id) 553 { 554 Elf_Data *data = obj->efile.idlist; 555 int *ptr = data->d_buf; 556 int i; 557 558 if (!id->id) { 559 pr_err("FAILED unresolved symbol %s\n", id->name); 560 return -EINVAL; 561 } 562 563 for (i = 0; i < id->addr_cnt; i++) { 564 unsigned long addr = id->addr[i]; 565 unsigned long idx = addr - obj->efile.idlist_addr; 566 567 pr_debug("patching addr %5lu: ID %7d [%s]\n", 568 idx, id->id, id->name); 569 570 if (idx >= data->d_size) { 571 pr_err("FAILED patching index %lu out of bounds %lu\n", 572 idx, data->d_size); 573 return -1; 574 } 575 576 idx = idx / sizeof(int); 577 ptr[idx] = id->id; 578 } 579 580 return 0; 581 } 582 583 static int __symbols_patch(struct object *obj, struct rb_root *root) 584 { 585 struct rb_node *next; 586 struct btf_id *id; 587 588 next = rb_first(root); 589 while (next) { 590 id = rb_entry(next, struct btf_id, rb_node); 591 592 if (id_patch(obj, id)) 593 return -1; 594 595 next = rb_next(next); 596 } 597 return 0; 598 } 599 600 static int cmp_id(const void *pa, const void *pb) 601 { 602 const int *a = pa, *b = pb; 603 604 return *a - *b; 605 } 606 607 static int sets_patch(struct object *obj) 608 { 609 Elf_Data *data = obj->efile.idlist; 610 int *ptr = data->d_buf; 611 struct rb_node *next; 612 613 next = rb_first(&obj->sets); 614 while (next) { 615 unsigned long addr, idx; 616 struct btf_id *id; 617 int *base; 618 int cnt; 619 620 id = rb_entry(next, struct btf_id, rb_node); 621 addr = id->addr[0]; 622 idx = addr - obj->efile.idlist_addr; 623 624 /* sets are unique */ 625 if (id->addr_cnt != 1) { 626 pr_err("FAILED malformed data for set '%s'\n", 627 id->name); 628 return -1; 629 } 630 631 idx = idx / sizeof(int); 632 base = &ptr[idx] + 1; 633 cnt = ptr[idx]; 634 635 pr_debug("sorting addr %5lu: cnt %6d [%s]\n", 636 (idx + 1) * sizeof(int), cnt, id->name); 637 638 qsort(base, cnt, sizeof(int), cmp_id); 639 640 next = rb_next(next); 641 } 642 return 0; 643 } 644 645 static int symbols_patch(struct object *obj) 646 { 647 int err; 648 649 if (__symbols_patch(obj, &obj->structs) || 650 __symbols_patch(obj, &obj->unions) || 651 __symbols_patch(obj, &obj->typedefs) || 652 __symbols_patch(obj, &obj->funcs) || 653 __symbols_patch(obj, &obj->sets)) 654 return -1; 655 656 if (sets_patch(obj)) 657 return -1; 658 659 elf_flagdata(obj->efile.idlist, ELF_C_SET, ELF_F_DIRTY); 660 661 err = elf_update(obj->efile.elf, ELF_C_WRITE); 662 if (err < 0) { 663 pr_err("FAILED elf_update(WRITE): %s\n", 664 elf_errmsg(-1)); 665 } 666 667 pr_debug("update %s for %s\n", 668 err >= 0 ? "ok" : "failed", obj->path); 669 return err < 0 ? -1 : 0; 670 } 671 672 static const char * const resolve_btfids_usage[] = { 673 "resolve_btfids [<options>] <ELF object>", 674 NULL 675 }; 676 677 int main(int argc, const char **argv) 678 { 679 bool no_fail = false; 680 struct object obj = { 681 .efile = { 682 .idlist_shndx = -1, 683 .symbols_shndx = -1, 684 }, 685 .structs = RB_ROOT, 686 .unions = RB_ROOT, 687 .typedefs = RB_ROOT, 688 .funcs = RB_ROOT, 689 .sets = RB_ROOT, 690 }; 691 struct option btfid_options[] = { 692 OPT_INCR('v', "verbose", &verbose, 693 "be more verbose (show errors, etc)"), 694 OPT_STRING(0, "btf", &obj.btf, "BTF data", 695 "BTF data"), 696 OPT_BOOLEAN(0, "no-fail", &no_fail, 697 "do not fail if " BTF_IDS_SECTION " section is not found"), 698 OPT_END() 699 }; 700 int err = -1; 701 702 argc = parse_options(argc, argv, btfid_options, resolve_btfids_usage, 703 PARSE_OPT_STOP_AT_NON_OPTION); 704 if (argc != 1) 705 usage_with_options(resolve_btfids_usage, btfid_options); 706 707 obj.path = argv[0]; 708 709 if (elf_collect(&obj)) 710 goto out; 711 712 /* 713 * We did not find .BTF_ids section or symbols section, 714 * nothing to do.. 715 */ 716 if (obj.efile.idlist_shndx == -1 || 717 obj.efile.symbols_shndx == -1) { 718 if (no_fail) 719 return 0; 720 pr_err("FAILED to find needed sections\n"); 721 return -1; 722 } 723 724 if (symbols_collect(&obj)) 725 goto out; 726 727 if (symbols_resolve(&obj)) 728 goto out; 729 730 if (symbols_patch(&obj)) 731 goto out; 732 733 err = 0; 734 out: 735 if (obj.efile.elf) 736 elf_end(obj.efile.elf); 737 close(obj.efile.fd); 738 return err; 739 } 740