tools/bpf/resolve_btfids/main.c

   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  *   set8    - store symbol size into first 4 bytes and sort following
  50  *             ID list
  51  *
  52  *             __BTF_ID__set8__list:
  53  *             .zero 8
  54  *             list:
  55  *             __BTF_ID__func__vfs_getattr__3:
  56  *             .zero 4
  57  *             .word (1 << 0) | (1 << 2)
  58  *             __BTF_ID__func__vfs_fallocate__5:
  59  *             .zero 4
  60  *             .word (1 << 3) | (1 << 1) | (1 << 2)
  61  */
  62
  63 #define  _GNU_SOURCE
  64 #include <stdio.h>
  65 #include <string.h>
  66 #include <unistd.h>
  67 #include <stdlib.h>
  68 #include <libelf.h>
  69 #include <gelf.h>
  70 #include <sys/stat.h>
  71 #include <fcntl.h>
  72 #include <errno.h>
  73 #include <linux/btf_ids.h>
  74 #include <linux/rbtree.h>
  75 #include <linux/zalloc.h>
  76 #include <linux/err.h>
  77 #include <bpf/btf.h>
  78 #include <bpf/libbpf.h>
  79 #include <subcmd/parse-options.h>
  80
  81 #define BTF_IDS_SECTION ".BTF_ids"
  82 #define BTF_ID_PREFIX   "__BTF_ID__"
  83
  84 #define BTF_STRUCT      "struct"
  85 #define BTF_UNION       "union"
  86 #define BTF_TYPEDEF     "typedef"
  87 #define BTF_FUNC        "func"
  88 #define BTF_SET         "set"
  89 #define BTF_SET8        "set8"
  90
  91 #define ADDR_CNT        100
  92
  93 #if __BYTE_ORDER == __LITTLE_ENDIAN
  94 # define ELFDATANATIVE  ELFDATA2LSB
  95 #elif __BYTE_ORDER == __BIG_ENDIAN
  96 # define ELFDATANATIVE  ELFDATA2MSB
  97 #else
  98 # error "Unknown machine endianness!"
  99 #endif
 100
 101 struct btf_id {
 102         struct rb_node   rb_node;
 103         char            *name;
 104         union {
 105                 int      id;
 106                 int      cnt;
 107         };
 108         int              addr_cnt;
 109         bool             is_set;
 110         bool             is_set8;
 111         Elf64_Addr       addr[ADDR_CNT];
 112 };
 113
 114 struct object {
 115         const char *path;
 116         const char *btf;
 117         const char *base_btf_path;
 118
 119         struct {
 120                 int              fd;
 121                 Elf             *elf;
 122                 Elf_Data        *symbols;
 123                 Elf_Data        *idlist;
 124                 int              symbols_shndx;
 125                 int              idlist_shndx;
 126                 size_t           strtabidx;
 127                 unsigned long    idlist_addr;
 128                 int              encoding;
 129         } efile;
 130
 131         struct rb_root  sets;
 132         struct rb_root  structs;
 133         struct rb_root  unions;
 134         struct rb_root  typedefs;
 135         struct rb_root  funcs;
 136
 137         int nr_funcs;
 138         int nr_structs;
 139         int nr_unions;
 140         int nr_typedefs;
 141 };
 142
 143 static int verbose;
 144
 145 static int eprintf(int level, int var, const char *fmt, ...)
 146 {
 147         va_list args;
 148         int ret = 0;
 149
 150         if (var >= level) {
 151                 va_start(args, fmt);
 152                 ret = vfprintf(stderr, fmt, args);
 153                 va_end(args);
 154         }
 155         return ret;
 156 }
 157
 158 #ifndef pr_fmt
 159 #define pr_fmt(fmt) fmt
 160 #endif
 161
 162 #define pr_debug(fmt, ...) \
 163         eprintf(1, verbose, pr_fmt(fmt), ##__VA_ARGS__)
 164 #define pr_debugN(n, fmt, ...) \
 165         eprintf(n, verbose, pr_fmt(fmt), ##__VA_ARGS__)
 166 #define pr_debug2(fmt, ...) pr_debugN(2, pr_fmt(fmt), ##__VA_ARGS__)
 167 #define pr_err(fmt, ...) \
 168         eprintf(0, verbose, pr_fmt(fmt), ##__VA_ARGS__)
 169 #define pr_info(fmt, ...) \
 170         eprintf(0, verbose, pr_fmt(fmt), ##__VA_ARGS__)
 171
 172 static bool is_btf_id(const char *name)
 173 {
 174         return name && !strncmp(name, BTF_ID_PREFIX, sizeof(BTF_ID_PREFIX) - 1);
 175 }
 176
 177 static struct btf_id *btf_id__find(struct rb_root *root, const char *name)
 178 {
 179         struct rb_node *p = root->rb_node;
 180         struct btf_id *id;
 181         int cmp;
 182
 183         while (p) {
 184                 id = rb_entry(p, struct btf_id, rb_node);
 185                 cmp = strcmp(id->name, name);
 186                 if (cmp < 0)
 187                         p = p->rb_left;
 188                 else if (cmp > 0)
 189                         p = p->rb_right;
 190                 else
 191                         return id;
 192         }
 193         return NULL;
 194 }
 195
 196 static struct btf_id *
 197 btf_id__add(struct rb_root *root, char *name, bool unique)
 198 {
 199         struct rb_node **p = &root->rb_node;
 200         struct rb_node *parent = NULL;
 201         struct btf_id *id;
 202         int cmp;
 203
 204         while (*p != NULL) {
 205                 parent = *p;
 206                 id = rb_entry(parent, struct btf_id, rb_node);
 207                 cmp = strcmp(id->name, name);
 208                 if (cmp < 0)
 209                         p = &(*p)->rb_left;
 210                 else if (cmp > 0)
 211                         p = &(*p)->rb_right;
 212                 else
 213                         return unique ? NULL : id;
 214         }
 215
 216         id = zalloc(sizeof(*id));
 217         if (id) {
 218                 pr_debug("adding symbol %s\n", name);
 219                 id->name = name;
 220                 rb_link_node(&id->rb_node, parent, p);
 221                 rb_insert_color(&id->rb_node, root);
 222         }
 223         return id;
 224 }
 225
 226 static char *get_id(const char *prefix_end)
 227 {
 228         /*
 229          * __BTF_ID__func__vfs_truncate__0
 230          * prefix_end =  ^
 231          * pos        =    ^
 232          */
 233         int len = strlen(prefix_end);
 234         int pos = sizeof("__") - 1;
 235         char *p, *id;
 236
 237         if (pos >= len)
 238                 return NULL;
 239
 240         id = strdup(prefix_end + pos);
 241         if (id) {
 242                 /*
 243                  * __BTF_ID__func__vfs_truncate__0
 244                  * id =            ^
 245                  *
 246                  * cut the unique id part
 247                  */
 248                 p = strrchr(id, '_');
 249                 p--;
 250                 if (*p != '_') {
 251                         free(id);
 252                         return NULL;
 253                 }
 254                 *p = '\0';
 255         }
 256         return id;
 257 }
 258
 259 static struct btf_id *add_set(struct object *obj, char *name, bool is_set8)
 260 {
 261         /*
 262          * __BTF_ID__set__name
 263          * name =    ^
 264          * id   =         ^
 265          */
 266         char *id = name + (is_set8 ? sizeof(BTF_SET8 "__") : sizeof(BTF_SET "__")) - 1;
 267         int len = strlen(name);
 268
 269         if (id >= name + len) {
 270                 pr_err("FAILED to parse set name: %s\n", name);
 271                 return NULL;
 272         }
 273
 274         return btf_id__add(&obj->sets, id, true);
 275 }
 276
 277 static struct btf_id *add_symbol(struct rb_root *root, char *name, size_t size)
 278 {
 279         char *id;
 280
 281         id = get_id(name + size);
 282         if (!id) {
 283                 pr_err("FAILED to parse symbol name: %s\n", name);
 284                 return NULL;
 285         }
 286
 287         return btf_id__add(root, id, false);
 288 }
 289
 290 /* Older libelf.h and glibc elf.h might not yet define the ELF compression types. */
 291 #ifndef SHF_COMPRESSED
 292 #define SHF_COMPRESSED (1 << 11) /* Section with compressed data. */
 293 #endif
 294
 295 /*
 296  * The data of compressed section should be aligned to 4
 297  * (for 32bit) or 8 (for 64 bit) bytes. The binutils ld
 298  * sets sh_addralign to 1, which makes libelf fail with
 299  * misaligned section error during the update:
 300  *    FAILED elf_update(WRITE): invalid section alignment
 301  *
 302  * While waiting for ld fix, we fix the compressed sections
 303  * sh_addralign value manualy.
 304  */
 305 static int compressed_section_fix(Elf *elf, Elf_Scn *scn, GElf_Shdr *sh)
 306 {
 307         int expected = gelf_getclass(elf) == ELFCLASS32 ? 4 : 8;
 308
 309         if (!(sh->sh_flags & SHF_COMPRESSED))
 310                 return 0;
 311
 312         if (sh->sh_addralign == expected)
 313                 return 0;
 314
 315         pr_debug2(" - fixing wrong alignment sh_addralign %u, expected %u\n",
 316                   sh->sh_addralign, expected);
 317
 318         sh->sh_addralign = expected;
 319
 320         if (gelf_update_shdr(scn, sh) == 0) {
 321                 pr_err("FAILED cannot update section header: %s\n",
 322                         elf_errmsg(-1));
 323                 return -1;
 324         }
 325         return 0;
 326 }
 327
 328 static int elf_collect(struct object *obj)
 329 {
 330         Elf_Scn *scn = NULL;
 331         size_t shdrstrndx;
 332         GElf_Ehdr ehdr;
 333         int idx = 0;
 334         Elf *elf;
 335         int fd;
 336
 337         fd = open(obj->path, O_RDWR, 0666);
 338         if (fd == -1) {
 339                 pr_err("FAILED cannot open %s: %s\n",
 340                         obj->path, strerror(errno));
 341                 return -1;
 342         }
 343
 344         elf_version(EV_CURRENT);
 345
 346         elf = elf_begin(fd, ELF_C_RDWR_MMAP, NULL);
 347         if (!elf) {
 348                 close(fd);
 349                 pr_err("FAILED cannot create ELF descriptor: %s\n",
 350                         elf_errmsg(-1));
 351                 return -1;
 352         }
 353
 354         obj->efile.fd  = fd;
 355         obj->efile.elf = elf;
 356
 357         elf_flagelf(elf, ELF_C_SET, ELF_F_LAYOUT);
 358
 359         if (elf_getshdrstrndx(elf, &shdrstrndx) != 0) {
 360                 pr_err("FAILED cannot get shdr str ndx\n");
 361                 return -1;
 362         }
 363
 364         if (gelf_getehdr(obj->efile.elf, &ehdr) == NULL) {
 365                 pr_err("FAILED cannot get ELF header: %s\n",
 366                         elf_errmsg(-1));
 367                 return -1;
 368         }
 369         obj->efile.encoding = ehdr.e_ident[EI_DATA];
 370
 371         /*
 372          * Scan all the elf sections and look for save data
 373          * from .BTF_ids section and symbols.
 374          */
 375         while ((scn = elf_nextscn(elf, scn)) != NULL) {
 376                 Elf_Data *data;
 377                 GElf_Shdr sh;
 378                 char *name;
 379
 380                 idx++;
 381                 if (gelf_getshdr(scn, &sh) != &sh) {
 382                         pr_err("FAILED get section(%d) header\n", idx);
 383                         return -1;
 384                 }
 385
 386                 name = elf_strptr(elf, shdrstrndx, sh.sh_name);
 387                 if (!name) {
 388                         pr_err("FAILED get section(%d) name\n", idx);
 389                         return -1;
 390                 }
 391
 392                 data = elf_getdata(scn, 0);
 393                 if (!data) {
 394                         pr_err("FAILED to get section(%d) data from %s\n",
 395                                 idx, name);
 396                         return -1;
 397                 }
 398
 399                 pr_debug2("section(%d) %s, size %ld, link %d, flags %lx, type=%d\n",
 400                           idx, name, (unsigned long) data->d_size,
 401                           (int) sh.sh_link, (unsigned long) sh.sh_flags,
 402                           (int) sh.sh_type);
 403
 404                 if (sh.sh_type == SHT_SYMTAB) {
 405                         obj->efile.symbols       = data;
 406                         obj->efile.symbols_shndx = idx;
 407                         obj->efile.strtabidx     = sh.sh_link;
 408                 } else if (!strcmp(name, BTF_IDS_SECTION)) {
 409                         obj->efile.idlist       = data;
 410                         obj->efile.idlist_shndx = idx;
 411                         obj->efile.idlist_addr  = sh.sh_addr;
 412                 } else if (!strcmp(name, BTF_BASE_ELF_SEC)) {
 413                         /* If a .BTF.base section is found, do not resolve
 414                          * BTF ids relative to vmlinux; resolve relative
 415                          * to the .BTF.base section instead.  btf__parse_split()
 416                          * will take care of this once the base BTF it is
 417                          * passed is NULL.
 418                          */
 419                         obj->base_btf_path = NULL;
 420                 }
 421
 422                 if (compressed_section_fix(elf, scn, &sh))
 423                         return -1;
 424         }
 425
 426         return 0;
 427 }
 428
 429 static int symbols_collect(struct object *obj)
 430 {
 431         Elf_Scn *scn = NULL;
 432         int n, i;
 433         GElf_Shdr sh;
 434         char *name;
 435
 436         scn = elf_getscn(obj->efile.elf, obj->efile.symbols_shndx);
 437         if (!scn)
 438                 return -1;
 439
 440         if (gelf_getshdr(scn, &sh) != &sh)
 441                 return -1;
 442
 443         n = sh.sh_size / sh.sh_entsize;
 444
 445         /*
 446          * Scan symbols and look for the ones starting with
 447          * __BTF_ID__* over .BTF_ids section.
 448          */
 449         for (i = 0; i < n; i++) {
 450                 char *prefix;
 451                 struct btf_id *id;
 452                 GElf_Sym sym;
 453
 454                 if (!gelf_getsym(obj->efile.symbols, i, &sym))
 455                         return -1;
 456
 457                 if (sym.st_shndx != obj->efile.idlist_shndx)
 458                         continue;
 459
 460                 name = elf_strptr(obj->efile.elf, obj->efile.strtabidx,
 461                                   sym.st_name);
 462
 463                 if (!is_btf_id(name))
 464                         continue;
 465
 466                 /*
 467                  * __BTF_ID__TYPE__vfs_truncate__0
 468                  * prefix =  ^
 469                  */
 470                 prefix = name + sizeof(BTF_ID_PREFIX) - 1;
 471
 472                 /* struct */
 473                 if (!strncmp(prefix, BTF_STRUCT, sizeof(BTF_STRUCT) - 1)) {
 474                         obj->nr_structs++;
 475                         id = add_symbol(&obj->structs, prefix, sizeof(BTF_STRUCT) - 1);
 476                 /* union  */
 477                 } else if (!strncmp(prefix, BTF_UNION, sizeof(BTF_UNION) - 1)) {
 478                         obj->nr_unions++;
 479                         id = add_symbol(&obj->unions, prefix, sizeof(BTF_UNION) - 1);
 480                 /* typedef */
 481                 } else if (!strncmp(prefix, BTF_TYPEDEF, sizeof(BTF_TYPEDEF) - 1)) {
 482                         obj->nr_typedefs++;
 483                         id = add_symbol(&obj->typedefs, prefix, sizeof(BTF_TYPEDEF) - 1);
 484                 /* func */
 485                 } else if (!strncmp(prefix, BTF_FUNC, sizeof(BTF_FUNC) - 1)) {
 486                         obj->nr_funcs++;
 487                         id = add_symbol(&obj->funcs, prefix, sizeof(BTF_FUNC) - 1);
 488                 /* set8 */
 489                 } else if (!strncmp(prefix, BTF_SET8, sizeof(BTF_SET8) - 1)) {
 490                         id = add_set(obj, prefix, true);
 491                         /*
 492                          * SET8 objects store list's count, which is encoded
 493                          * in symbol's size, together with 'cnt' field hence
 494                          * that - 1.
 495                          */
 496                         if (id) {
 497                                 id->cnt = sym.st_size / sizeof(uint64_t) - 1;
 498                                 id->is_set8 = true;
 499                         }
 500                 /* set */
 501                 } else if (!strncmp(prefix, BTF_SET, sizeof(BTF_SET) - 1)) {
 502                         id = add_set(obj, prefix, false);
 503                         /*
 504                          * SET objects store list's count, which is encoded
 505                          * in symbol's size, together with 'cnt' field hence
 506                          * that - 1.
 507                          */
 508                         if (id) {
 509                                 id->cnt = sym.st_size / sizeof(int) - 1;
 510                                 id->is_set = true;
 511                         }
 512                 } else {
 513                         pr_err("FAILED unsupported prefix %s\n", prefix);
 514                         return -1;
 515                 }
 516
 517                 if (!id)
 518                         return -ENOMEM;
 519
 520                 if (id->addr_cnt >= ADDR_CNT) {
 521                         pr_err("FAILED symbol %s crossed the number of allowed lists\n",
 522                                 id->name);
 523                         return -1;
 524                 }
 525                 id->addr[id->addr_cnt++] = sym.st_value;
 526         }
 527
 528         return 0;
 529 }
 530
 531 static int symbols_resolve(struct object *obj)
 532 {
 533         int nr_typedefs = obj->nr_typedefs;
 534         int nr_structs  = obj->nr_structs;
 535         int nr_unions   = obj->nr_unions;
 536         int nr_funcs    = obj->nr_funcs;
 537         struct btf *base_btf = NULL;
 538         int err, type_id;
 539         struct btf *btf;
 540         __u32 nr_types;
 541
 542         if (obj->base_btf_path) {
 543                 base_btf = btf__parse(obj->base_btf_path, NULL);
 544                 err = libbpf_get_error(base_btf);
 545                 if (err) {
 546                         pr_err("FAILED: load base BTF from %s: %s\n",
 547                                obj->base_btf_path, strerror(-err));
 548                         return -1;
 549                 }
 550         }
 551
 552         btf = btf__parse_split(obj->btf ?: obj->path, base_btf);
 553         err = libbpf_get_error(btf);
 554         if (err) {
 555                 pr_err("FAILED: load BTF from %s: %s\n",
 556                         obj->btf ?: obj->path, strerror(-err));
 557                 goto out;
 558         }
 559
 560         err = -1;
 561         nr_types = btf__type_cnt(btf);
 562
 563         /*
 564          * Iterate all the BTF types and search for collected symbol IDs.
 565          */
 566         for (type_id = 1; type_id < nr_types; type_id++) {
 567                 const struct btf_type *type;
 568                 struct rb_root *root;
 569                 struct btf_id *id;
 570                 const char *str;
 571                 int *nr;
 572
 573                 type = btf__type_by_id(btf, type_id);
 574                 if (!type) {
 575                         pr_err("FAILED: malformed BTF, can't resolve type for ID %d\n",
 576                                 type_id);
 577                         goto out;
 578                 }
 579
 580                 if (btf_is_func(type) && nr_funcs) {
 581                         nr   = &nr_funcs;
 582                         root = &obj->funcs;
 583                 } else if (btf_is_struct(type) && nr_structs) {
 584                         nr   = &nr_structs;
 585                         root = &obj->structs;
 586                 } else if (btf_is_union(type) && nr_unions) {
 587                         nr   = &nr_unions;
 588                         root = &obj->unions;
 589                 } else if (btf_is_typedef(type) && nr_typedefs) {
 590                         nr   = &nr_typedefs;
 591                         root = &obj->typedefs;
 592                 } else
 593                         continue;
 594
 595                 str = btf__name_by_offset(btf, type->name_off);
 596                 if (!str) {
 597                         pr_err("FAILED: malformed BTF, can't resolve name for ID %d\n",
 598                                 type_id);
 599                         goto out;
 600                 }
 601
 602                 id = btf_id__find(root, str);
 603                 if (id) {
 604                         if (id->id) {
 605                                 pr_info("WARN: multiple IDs found for '%s': %d, %d - using %d\n",
 606                                         str, id->id, type_id, id->id);
 607                         } else {
 608                                 id->id = type_id;
 609                                 (*nr)--;
 610                         }
 611                 }
 612         }
 613
 614         err = 0;
 615 out:
 616         btf__free(base_btf);
 617         btf__free(btf);
 618         return err;
 619 }
 620
 621 static int id_patch(struct object *obj, struct btf_id *id)
 622 {
 623         Elf_Data *data = obj->efile.idlist;
 624         int *ptr = data->d_buf;
 625         int i;
 626
 627         /* For set, set8, id->id may be 0 */
 628         if (!id->id && !id->is_set && !id->is_set8)
 629                 pr_err("WARN: resolve_btfids: unresolved symbol %s\n", id->name);
 630
 631         for (i = 0; i < id->addr_cnt; i++) {
 632                 unsigned long addr = id->addr[i];
 633                 unsigned long idx = addr - obj->efile.idlist_addr;
 634
 635                 pr_debug("patching addr %5lu: ID %7d [%s]\n",
 636                          idx, id->id, id->name);
 637
 638                 if (idx >= data->d_size) {
 639                         pr_err("FAILED patching index %lu out of bounds %lu\n",
 640                                 idx, data->d_size);
 641                         return -1;
 642                 }
 643
 644                 idx = idx / sizeof(int);
 645                 ptr[idx] = id->id;
 646         }
 647
 648         return 0;
 649 }
 650
 651 static int __symbols_patch(struct object *obj, struct rb_root *root)
 652 {
 653         struct rb_node *next;
 654         struct btf_id *id;
 655
 656         next = rb_first(root);
 657         while (next) {
 658                 id = rb_entry(next, struct btf_id, rb_node);
 659
 660                 if (id_patch(obj, id))
 661                         return -1;
 662
 663                 next = rb_next(next);
 664         }
 665         return 0;
 666 }
 667
 668 static int cmp_id(const void *pa, const void *pb)
 669 {
 670         const int *a = pa, *b = pb;
 671
 672         return *a - *b;
 673 }
 674
 675 static int sets_patch(struct object *obj)
 676 {
 677         Elf_Data *data = obj->efile.idlist;
 678         struct rb_node *next;
 679
 680         next = rb_first(&obj->sets);
 681         while (next) {
 682                 struct btf_id_set8 *set8 = NULL;
 683                 struct btf_id_set *set = NULL;
 684                 unsigned long addr, off;
 685                 struct btf_id *id;
 686
 687                 id   = rb_entry(next, struct btf_id, rb_node);
 688                 addr = id->addr[0];
 689                 off = addr - obj->efile.idlist_addr;
 690
 691                 /* sets are unique */
 692                 if (id->addr_cnt != 1) {
 693                         pr_err("FAILED malformed data for set '%s'\n",
 694                                 id->name);
 695                         return -1;
 696                 }
 697
 698                 if (id->is_set) {
 699                         set = data->d_buf + off;
 700                         qsort(set->ids, set->cnt, sizeof(set->ids[0]), cmp_id);
 701                 } else {
 702                         set8 = data->d_buf + off;
 703                         /*
 704                          * Make sure id is at the beginning of the pairs
 705                          * struct, otherwise the below qsort would not work.
 706                          */
 707                         BUILD_BUG_ON((u32 *)set8->pairs != &set8->pairs[0].id);
 708                         qsort(set8->pairs, set8->cnt, sizeof(set8->pairs[0]), cmp_id);
 709
 710                         /*
 711                          * When ELF endianness does not match endianness of the
 712                          * host, libelf will do the translation when updating
 713                          * the ELF. This, however, corrupts SET8 flags which are
 714                          * already in the target endianness. So, let's bswap
 715                          * them to the host endianness and libelf will then
 716                          * correctly translate everything.
 717                          */
 718                         if (obj->efile.encoding != ELFDATANATIVE) {
 719                                 int i;
 720
 721                                 set8->flags = bswap_32(set8->flags);
 722                                 for (i = 0; i < set8->cnt; i++) {
 723                                         set8->pairs[i].flags =
 724                                                 bswap_32(set8->pairs[i].flags);
 725                                 }
 726                         }
 727                 }
 728
 729                 pr_debug("sorting  addr %5lu: cnt %6d [%s]\n",
 730                          off, id->is_set ? set->cnt : set8->cnt, id->name);
 731
 732                 next = rb_next(next);
 733         }
 734         return 0;
 735 }
 736
 737 static int symbols_patch(struct object *obj)
 738 {
 739         off_t err;
 740
 741         if (__symbols_patch(obj, &obj->structs)  ||
 742             __symbols_patch(obj, &obj->unions)   ||
 743             __symbols_patch(obj, &obj->typedefs) ||
 744             __symbols_patch(obj, &obj->funcs)    ||
 745             __symbols_patch(obj, &obj->sets))
 746                 return -1;
 747
 748         if (sets_patch(obj))
 749                 return -1;
 750
 751         /* Set type to ensure endian translation occurs. */
 752         obj->efile.idlist->d_type = ELF_T_WORD;
 753
 754         elf_flagdata(obj->efile.idlist, ELF_C_SET, ELF_F_DIRTY);
 755
 756         err = elf_update(obj->efile.elf, ELF_C_WRITE);
 757         if (err < 0) {
 758                 pr_err("FAILED elf_update(WRITE): %s\n",
 759                         elf_errmsg(-1));
 760         }
 761
 762         pr_debug("update %s for %s\n",
 763                  err >= 0 ? "ok" : "failed", obj->path);
 764         return err < 0 ? -1 : 0;
 765 }
 766
 767 static const char * const resolve_btfids_usage[] = {
 768         "resolve_btfids [<options>] <ELF object>",
 769         NULL
 770 };
 771
 772 int main(int argc, const char **argv)
 773 {
 774         struct object obj = {
 775                 .efile = {
 776                         .idlist_shndx  = -1,
 777                         .symbols_shndx = -1,
 778                 },
 779                 .structs  = RB_ROOT,
 780                 .unions   = RB_ROOT,
 781                 .typedefs = RB_ROOT,
 782                 .funcs    = RB_ROOT,
 783                 .sets     = RB_ROOT,
 784         };
 785         struct option btfid_options[] = {
 786                 OPT_INCR('v', "verbose", &verbose,
 787                          "be more verbose (show errors, etc)"),
 788                 OPT_STRING(0, "btf", &obj.btf, "BTF data",
 789                            "BTF data"),
 790                 OPT_STRING('b', "btf_base", &obj.base_btf_path, "file",
 791                            "path of file providing base BTF"),
 792                 OPT_END()
 793         };
 794         int err = -1;
 795
 796         argc = parse_options(argc, argv, btfid_options, resolve_btfids_usage,
 797                              PARSE_OPT_STOP_AT_NON_OPTION);
 798         if (argc != 1)
 799                 usage_with_options(resolve_btfids_usage, btfid_options);
 800
 801         obj.path = argv[0];
 802
 803         if (elf_collect(&obj))
 804                 goto out;
 805
 806         /*
 807          * We did not find .BTF_ids section or symbols section,
 808          * nothing to do..
 809          */
 810         if (obj.efile.idlist_shndx == -1 ||
 811             obj.efile.symbols_shndx == -1) {
 812                 pr_debug("Cannot find .BTF_ids or symbols sections, nothing to do\n");
 813                 err = 0;
 814                 goto out;
 815         }
 816
 817         if (symbols_collect(&obj))
 818                 goto out;
 819
 820         if (symbols_resolve(&obj))
 821                 goto out;
 822
 823         if (symbols_patch(&obj))
 824                 goto out;
 825
 826         err = 0;
 827 out:
 828         if (obj.efile.elf) {
 829                 elf_end(obj.efile.elf);
 830                 close(obj.efile.fd);
 831         }
 832         return err;
 833 }