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