1 // SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
4 * resolve_btfids scans Elf object for .BTF_ids section and resolves
5 * its symbols with BTF ID values.
7 * Each symbol points to 4 bytes data and is expected to have
8 * following name syntax:
10 * __BTF_ID__<type>__<symbol>[__<id>]
14 * func - lookup BTF_KIND_FUNC symbol with <symbol> name
15 * and store its ID into the data:
17 * __BTF_ID__func__vfs_close__1:
20 * struct - lookup BTF_KIND_STRUCT symbol with <symbol> name
21 * and store its ID into the data:
23 * __BTF_ID__struct__sk_buff__1:
26 * union - lookup BTF_KIND_UNION symbol with <symbol> name
27 * and store its ID into the data:
29 * __BTF_ID__union__thread_union__1:
32 * typedef - lookup BTF_KIND_TYPEDEF symbol with <symbol> name
33 * and store its ID into the data:
35 * __BTF_ID__typedef__pid_t__1:
38 * set - store symbol size into first 4 bytes and sort following
41 * __BTF_ID__set__list:
44 * __BTF_ID__func__vfs_getattr__3:
46 * __BTF_ID__func__vfs_fallocate__4:
60 #include <linux/rbtree.h>
61 #include <linux/zalloc.h>
62 #include <linux/err.h>
64 #include <bpf/libbpf.h>
65 #include <parse-options.h>
67 #define BTF_IDS_SECTION ".BTF_ids"
68 #define BTF_ID "__BTF_ID__"
70 #define BTF_STRUCT "struct"
71 #define BTF_UNION "union"
72 #define BTF_TYPEDEF "typedef"
73 #define BTF_FUNC "func"
79 struct rb_node rb_node;
87 Elf64_Addr addr[ADDR_CNT];
93 const char *base_btf_path;
103 unsigned long idlist_addr;
107 struct rb_root structs;
108 struct rb_root unions;
109 struct rb_root typedefs;
110 struct rb_root funcs;
120 static int eprintf(int level, int var, const char *fmt, ...)
127 ret = vfprintf(stderr, fmt, args);
134 #define pr_fmt(fmt) fmt
137 #define pr_debug(fmt, ...) \
138 eprintf(1, verbose, pr_fmt(fmt), ##__VA_ARGS__)
139 #define pr_debugN(n, fmt, ...) \
140 eprintf(n, verbose, pr_fmt(fmt), ##__VA_ARGS__)
141 #define pr_debug2(fmt, ...) pr_debugN(2, pr_fmt(fmt), ##__VA_ARGS__)
142 #define pr_err(fmt, ...) \
143 eprintf(0, verbose, pr_fmt(fmt), ##__VA_ARGS__)
144 #define pr_info(fmt, ...) \
145 eprintf(0, verbose, pr_fmt(fmt), ##__VA_ARGS__)
147 static bool is_btf_id(const char *name)
149 return name && !strncmp(name, BTF_ID, sizeof(BTF_ID) - 1);
152 static struct btf_id *btf_id__find(struct rb_root *root, const char *name)
154 struct rb_node *p = root->rb_node;
159 id = rb_entry(p, struct btf_id, rb_node);
160 cmp = strcmp(id->name, name);
171 static struct btf_id*
172 btf_id__add(struct rb_root *root, char *name, bool unique)
174 struct rb_node **p = &root->rb_node;
175 struct rb_node *parent = NULL;
181 id = rb_entry(parent, struct btf_id, rb_node);
182 cmp = strcmp(id->name, name);
188 return unique ? NULL : id;
191 id = zalloc(sizeof(*id));
193 pr_debug("adding symbol %s\n", name);
195 rb_link_node(&id->rb_node, parent, p);
196 rb_insert_color(&id->rb_node, root);
201 static char *get_id(const char *prefix_end)
204 * __BTF_ID__func__vfs_truncate__0
208 int len = strlen(prefix_end);
209 int pos = sizeof("__") - 1;
215 id = strdup(prefix_end + pos);
218 * __BTF_ID__func__vfs_truncate__0
221 * cut the unique id part
223 p = strrchr(id, '_');
234 static struct btf_id *add_set(struct object *obj, char *name)
237 * __BTF_ID__set__name
241 char *id = name + sizeof(BTF_SET "__") - 1;
242 int len = strlen(name);
244 if (id >= name + len) {
245 pr_err("FAILED to parse set name: %s\n", name);
249 return btf_id__add(&obj->sets, id, true);
252 static struct btf_id *add_symbol(struct rb_root *root, char *name, size_t size)
256 id = get_id(name + size);
258 pr_err("FAILED to parse symbol name: %s\n", name);
262 return btf_id__add(root, id, false);
265 /* Older libelf.h and glibc elf.h might not yet define the ELF compression types. */
266 #ifndef SHF_COMPRESSED
267 #define SHF_COMPRESSED (1 << 11) /* Section with compressed data. */
271 * The data of compressed section should be aligned to 4
272 * (for 32bit) or 8 (for 64 bit) bytes. The binutils ld
273 * sets sh_addralign to 1, which makes libelf fail with
274 * misaligned section error during the update:
275 * FAILED elf_update(WRITE): invalid section alignment
277 * While waiting for ld fix, we fix the compressed sections
278 * sh_addralign value manualy.
280 static int compressed_section_fix(Elf *elf, Elf_Scn *scn, GElf_Shdr *sh)
282 int expected = gelf_getclass(elf) == ELFCLASS32 ? 4 : 8;
284 if (!(sh->sh_flags & SHF_COMPRESSED))
287 if (sh->sh_addralign == expected)
290 pr_debug2(" - fixing wrong alignment sh_addralign %u, expected %u\n",
291 sh->sh_addralign, expected);
293 sh->sh_addralign = expected;
295 if (gelf_update_shdr(scn, sh) == 0) {
296 pr_err("FAILED cannot update section header: %s\n",
303 static int elf_collect(struct object *obj)
311 fd = open(obj->path, O_RDWR, 0666);
313 pr_err("FAILED cannot open %s: %s\n",
314 obj->path, strerror(errno));
318 elf_version(EV_CURRENT);
320 elf = elf_begin(fd, ELF_C_RDWR_MMAP, NULL);
323 pr_err("FAILED cannot create ELF descriptor: %s\n",
329 obj->efile.elf = elf;
331 elf_flagelf(elf, ELF_C_SET, ELF_F_LAYOUT);
333 if (elf_getshdrstrndx(elf, &shdrstrndx) != 0) {
334 pr_err("FAILED cannot get shdr str ndx\n");
339 * Scan all the elf sections and look for save data
340 * from .BTF_ids section and symbols.
342 while ((scn = elf_nextscn(elf, scn)) != NULL) {
348 if (gelf_getshdr(scn, &sh) != &sh) {
349 pr_err("FAILED get section(%d) header\n", idx);
353 name = elf_strptr(elf, shdrstrndx, sh.sh_name);
355 pr_err("FAILED get section(%d) name\n", idx);
359 data = elf_getdata(scn, 0);
361 pr_err("FAILED to get section(%d) data from %s\n",
366 pr_debug2("section(%d) %s, size %ld, link %d, flags %lx, type=%d\n",
367 idx, name, (unsigned long) data->d_size,
368 (int) sh.sh_link, (unsigned long) sh.sh_flags,
371 if (sh.sh_type == SHT_SYMTAB) {
372 obj->efile.symbols = data;
373 obj->efile.symbols_shndx = idx;
374 obj->efile.strtabidx = sh.sh_link;
375 } else if (!strcmp(name, BTF_IDS_SECTION)) {
376 obj->efile.idlist = data;
377 obj->efile.idlist_shndx = idx;
378 obj->efile.idlist_addr = sh.sh_addr;
381 if (compressed_section_fix(elf, scn, &sh))
388 static int symbols_collect(struct object *obj)
395 scn = elf_getscn(obj->efile.elf, obj->efile.symbols_shndx);
399 if (gelf_getshdr(scn, &sh) != &sh)
402 n = sh.sh_size / sh.sh_entsize;
405 * Scan symbols and look for the ones starting with
406 * __BTF_ID__* over .BTF_ids section.
408 for (i = 0; i < n; i++) {
413 if (!gelf_getsym(obj->efile.symbols, i, &sym))
416 if (sym.st_shndx != obj->efile.idlist_shndx)
419 name = elf_strptr(obj->efile.elf, obj->efile.strtabidx,
422 if (!is_btf_id(name))
426 * __BTF_ID__TYPE__vfs_truncate__0
429 prefix = name + sizeof(BTF_ID) - 1;
432 if (!strncmp(prefix, BTF_STRUCT, sizeof(BTF_STRUCT) - 1)) {
434 id = add_symbol(&obj->structs, prefix, sizeof(BTF_STRUCT) - 1);
436 } else if (!strncmp(prefix, BTF_UNION, sizeof(BTF_UNION) - 1)) {
438 id = add_symbol(&obj->unions, prefix, sizeof(BTF_UNION) - 1);
440 } else if (!strncmp(prefix, BTF_TYPEDEF, sizeof(BTF_TYPEDEF) - 1)) {
442 id = add_symbol(&obj->typedefs, prefix, sizeof(BTF_TYPEDEF) - 1);
444 } else if (!strncmp(prefix, BTF_FUNC, sizeof(BTF_FUNC) - 1)) {
446 id = add_symbol(&obj->funcs, prefix, sizeof(BTF_FUNC) - 1);
448 } else if (!strncmp(prefix, BTF_SET, sizeof(BTF_SET) - 1)) {
449 id = add_set(obj, prefix);
451 * SET objects store list's count, which is encoded
452 * in symbol's size, together with 'cnt' field hence
456 id->cnt = sym.st_size / sizeof(int) - 1;
460 pr_err("FAILED unsupported prefix %s\n", prefix);
467 if (id->addr_cnt >= ADDR_CNT) {
468 pr_err("FAILED symbol %s crossed the number of allowed lists\n",
472 id->addr[id->addr_cnt++] = sym.st_value;
478 static int symbols_resolve(struct object *obj)
480 int nr_typedefs = obj->nr_typedefs;
481 int nr_structs = obj->nr_structs;
482 int nr_unions = obj->nr_unions;
483 int nr_funcs = obj->nr_funcs;
484 struct btf *base_btf = NULL;
489 if (obj->base_btf_path) {
490 base_btf = btf__parse(obj->base_btf_path, NULL);
491 err = libbpf_get_error(base_btf);
493 pr_err("FAILED: load base BTF from %s: %s\n",
494 obj->base_btf_path, strerror(-err));
499 btf = btf__parse_split(obj->btf ?: obj->path, base_btf);
500 err = libbpf_get_error(btf);
502 pr_err("FAILED: load BTF from %s: %s\n",
503 obj->btf ?: obj->path, strerror(-err));
508 nr_types = btf__type_cnt(btf);
511 * Iterate all the BTF types and search for collected symbol IDs.
513 for (type_id = 1; type_id < nr_types; type_id++) {
514 const struct btf_type *type;
515 struct rb_root *root;
520 type = btf__type_by_id(btf, type_id);
522 pr_err("FAILED: malformed BTF, can't resolve type for ID %d\n",
527 if (btf_is_func(type) && nr_funcs) {
530 } else if (btf_is_struct(type) && nr_structs) {
532 root = &obj->structs;
533 } else if (btf_is_union(type) && nr_unions) {
536 } else if (btf_is_typedef(type) && nr_typedefs) {
538 root = &obj->typedefs;
542 str = btf__name_by_offset(btf, type->name_off);
544 pr_err("FAILED: malformed BTF, can't resolve name for ID %d\n",
549 id = btf_id__find(root, str);
552 pr_info("WARN: multiple IDs found for '%s': %d, %d - using %d\n",
553 str, id->id, type_id, id->id);
568 static int id_patch(struct object *obj, struct btf_id *id)
570 Elf_Data *data = obj->efile.idlist;
571 int *ptr = data->d_buf;
574 if (!id->id && !id->is_set)
575 pr_err("WARN: resolve_btfids: unresolved symbol %s\n", id->name);
577 for (i = 0; i < id->addr_cnt; i++) {
578 unsigned long addr = id->addr[i];
579 unsigned long idx = addr - obj->efile.idlist_addr;
581 pr_debug("patching addr %5lu: ID %7d [%s]\n",
582 idx, id->id, id->name);
584 if (idx >= data->d_size) {
585 pr_err("FAILED patching index %lu out of bounds %lu\n",
590 idx = idx / sizeof(int);
597 static int __symbols_patch(struct object *obj, struct rb_root *root)
599 struct rb_node *next;
602 next = rb_first(root);
604 id = rb_entry(next, struct btf_id, rb_node);
606 if (id_patch(obj, id))
609 next = rb_next(next);
614 static int cmp_id(const void *pa, const void *pb)
616 const int *a = pa, *b = pb;
621 static int sets_patch(struct object *obj)
623 Elf_Data *data = obj->efile.idlist;
624 int *ptr = data->d_buf;
625 struct rb_node *next;
627 next = rb_first(&obj->sets);
629 unsigned long addr, idx;
634 id = rb_entry(next, struct btf_id, rb_node);
636 idx = addr - obj->efile.idlist_addr;
638 /* sets are unique */
639 if (id->addr_cnt != 1) {
640 pr_err("FAILED malformed data for set '%s'\n",
645 idx = idx / sizeof(int);
646 base = &ptr[idx] + 1;
649 pr_debug("sorting addr %5lu: cnt %6d [%s]\n",
650 (idx + 1) * sizeof(int), cnt, id->name);
652 qsort(base, cnt, sizeof(int), cmp_id);
654 next = rb_next(next);
659 static int symbols_patch(struct object *obj)
663 if (__symbols_patch(obj, &obj->structs) ||
664 __symbols_patch(obj, &obj->unions) ||
665 __symbols_patch(obj, &obj->typedefs) ||
666 __symbols_patch(obj, &obj->funcs) ||
667 __symbols_patch(obj, &obj->sets))
673 /* Set type to ensure endian translation occurs. */
674 obj->efile.idlist->d_type = ELF_T_WORD;
676 elf_flagdata(obj->efile.idlist, ELF_C_SET, ELF_F_DIRTY);
678 err = elf_update(obj->efile.elf, ELF_C_WRITE);
680 pr_err("FAILED elf_update(WRITE): %s\n",
684 pr_debug("update %s for %s\n",
685 err >= 0 ? "ok" : "failed", obj->path);
686 return err < 0 ? -1 : 0;
689 static const char * const resolve_btfids_usage[] = {
690 "resolve_btfids [<options>] <ELF object>",
694 int main(int argc, const char **argv)
696 struct object obj = {
707 struct option btfid_options[] = {
708 OPT_INCR('v', "verbose", &verbose,
709 "be more verbose (show errors, etc)"),
710 OPT_STRING(0, "btf", &obj.btf, "BTF data",
712 OPT_STRING('b', "btf_base", &obj.base_btf_path, "file",
713 "path of file providing base BTF"),
718 argc = parse_options(argc, argv, btfid_options, resolve_btfids_usage,
719 PARSE_OPT_STOP_AT_NON_OPTION);
721 usage_with_options(resolve_btfids_usage, btfid_options);
725 if (elf_collect(&obj))
729 * We did not find .BTF_ids section or symbols section,
732 if (obj.efile.idlist_shndx == -1 ||
733 obj.efile.symbols_shndx == -1) {
734 pr_debug("Cannot find .BTF_ids or symbols sections, nothing to do\n");
738 if (symbols_collect(&obj))
741 if (symbols_resolve(&obj))
744 if (symbols_patch(&obj))
750 elf_end(obj.efile.elf);