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>
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;
86 Elf64_Addr addr[ADDR_CNT];
101 unsigned long idlist_addr;
105 struct rb_root structs;
106 struct rb_root unions;
107 struct rb_root typedefs;
108 struct rb_root funcs;
118 static int eprintf(int level, int var, const char *fmt, ...)
125 ret = vfprintf(stderr, fmt, args);
132 #define pr_fmt(fmt) fmt
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__)
145 static bool is_btf_id(const char *name)
147 return name && !strncmp(name, BTF_ID, sizeof(BTF_ID) - 1);
150 static struct btf_id *btf_id__find(struct rb_root *root, const char *name)
152 struct rb_node *p = root->rb_node;
157 id = rb_entry(p, struct btf_id, rb_node);
158 cmp = strcmp(id->name, name);
169 static struct btf_id*
170 btf_id__add(struct rb_root *root, char *name, bool unique)
172 struct rb_node **p = &root->rb_node;
173 struct rb_node *parent = NULL;
179 id = rb_entry(parent, struct btf_id, rb_node);
180 cmp = strcmp(id->name, name);
186 return unique ? NULL : id;
189 id = zalloc(sizeof(*id));
191 pr_debug("adding symbol %s\n", name);
193 rb_link_node(&id->rb_node, parent, p);
194 rb_insert_color(&id->rb_node, root);
199 static char *get_id(const char *prefix_end)
202 * __BTF_ID__func__vfs_truncate__0
206 int len = strlen(prefix_end);
207 int pos = sizeof("__") - 1;
213 id = strdup(prefix_end + pos);
216 * __BTF_ID__func__vfs_truncate__0
219 * cut the unique id part
221 p = strrchr(id, '_');
232 static struct btf_id *add_set(struct object *obj, char *name)
235 * __BTF_ID__set__name
239 char *id = name + sizeof(BTF_SET "__") - 1;
240 int len = strlen(name);
242 if (id >= name + len) {
243 pr_err("FAILED to parse set name: %s\n", name);
247 return btf_id__add(&obj->sets, id, true);
250 static struct btf_id *add_symbol(struct rb_root *root, char *name, size_t size)
254 id = get_id(name + size);
256 pr_err("FAILED to parse symbol name: %s\n", name);
260 return btf_id__add(root, id, false);
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. */
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
275 * While waiting for ld fix, we fix the compressed sections
276 * sh_addralign value manualy.
278 static int compressed_section_fix(Elf *elf, Elf_Scn *scn, GElf_Shdr *sh)
280 int expected = gelf_getclass(elf) == ELFCLASS32 ? 4 : 8;
282 if (!(sh->sh_flags & SHF_COMPRESSED))
285 if (sh->sh_addralign == expected)
288 pr_debug2(" - fixing wrong alignment sh_addralign %u, expected %u\n",
289 sh->sh_addralign, expected);
291 sh->sh_addralign = expected;
293 if (gelf_update_shdr(scn, sh) == 0) {
294 printf("FAILED cannot update section header: %s\n",
301 static int elf_collect(struct object *obj)
309 fd = open(obj->path, O_RDWR, 0666);
311 pr_err("FAILED cannot open %s: %s\n",
312 obj->path, strerror(errno));
316 elf_version(EV_CURRENT);
318 elf = elf_begin(fd, ELF_C_RDWR_MMAP, NULL);
320 pr_err("FAILED cannot create ELF descriptor: %s\n",
326 obj->efile.elf = elf;
328 elf_flagelf(elf, ELF_C_SET, ELF_F_LAYOUT);
330 if (elf_getshdrstrndx(elf, &shdrstrndx) != 0) {
331 pr_err("FAILED cannot get shdr str ndx\n");
336 * Scan all the elf sections and look for save data
337 * from .BTF_ids section and symbols.
339 while ((scn = elf_nextscn(elf, scn)) != NULL) {
345 if (gelf_getshdr(scn, &sh) != &sh) {
346 pr_err("FAILED get section(%d) header\n", idx);
350 name = elf_strptr(elf, shdrstrndx, sh.sh_name);
352 pr_err("FAILED get section(%d) name\n", idx);
356 data = elf_getdata(scn, 0);
358 pr_err("FAILED to get section(%d) data from %s\n",
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,
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;
378 if (compressed_section_fix(elf, scn, &sh))
385 static int symbols_collect(struct object *obj)
392 scn = elf_getscn(obj->efile.elf, obj->efile.symbols_shndx);
396 if (gelf_getshdr(scn, &sh) != &sh)
399 n = sh.sh_size / sh.sh_entsize;
402 * Scan symbols and look for the ones starting with
403 * __BTF_ID__* over .BTF_ids section.
405 for (i = 0; i < n; i++) {
410 if (!gelf_getsym(obj->efile.symbols, i, &sym))
413 if (sym.st_shndx != obj->efile.idlist_shndx)
416 name = elf_strptr(obj->efile.elf, obj->efile.strtabidx,
419 if (!is_btf_id(name))
423 * __BTF_ID__TYPE__vfs_truncate__0
426 prefix = name + sizeof(BTF_ID) - 1;
429 if (!strncmp(prefix, BTF_STRUCT, sizeof(BTF_STRUCT) - 1)) {
431 id = add_symbol(&obj->structs, prefix, sizeof(BTF_STRUCT) - 1);
433 } else if (!strncmp(prefix, BTF_UNION, sizeof(BTF_UNION) - 1)) {
435 id = add_symbol(&obj->unions, prefix, sizeof(BTF_UNION) - 1);
437 } else if (!strncmp(prefix, BTF_TYPEDEF, sizeof(BTF_TYPEDEF) - 1)) {
439 id = add_symbol(&obj->typedefs, prefix, sizeof(BTF_TYPEDEF) - 1);
441 } else if (!strncmp(prefix, BTF_FUNC, sizeof(BTF_FUNC) - 1)) {
443 id = add_symbol(&obj->funcs, prefix, sizeof(BTF_FUNC) - 1);
445 } else if (!strncmp(prefix, BTF_SET, sizeof(BTF_SET) - 1)) {
446 id = add_set(obj, prefix);
448 * SET objects store list's count, which is encoded
449 * in symbol's size, together with 'cnt' field hence
453 id->cnt = sym.st_size / sizeof(int) - 1;
455 pr_err("FAILED unsupported prefix %s\n", prefix);
462 if (id->addr_cnt >= ADDR_CNT) {
463 pr_err("FAILED symbol %s crossed the number of allowed lists\n",
467 id->addr[id->addr_cnt++] = sym.st_value;
473 static int symbols_resolve(struct object *obj)
475 int nr_typedefs = obj->nr_typedefs;
476 int nr_structs = obj->nr_structs;
477 int nr_unions = obj->nr_unions;
478 int nr_funcs = obj->nr_funcs;
483 btf = btf__parse(obj->btf ?: obj->path, NULL);
484 err = libbpf_get_error(btf);
486 pr_err("FAILED: load BTF from %s: %s\n",
487 obj->path, strerror(-err));
492 nr_types = btf__get_nr_types(btf);
495 * Iterate all the BTF types and search for collected symbol IDs.
497 for (type_id = 1; type_id <= nr_types; type_id++) {
498 const struct btf_type *type;
499 struct rb_root *root;
504 type = btf__type_by_id(btf, type_id);
506 pr_err("FAILED: malformed BTF, can't resolve type for ID %d\n",
511 if (btf_is_func(type) && nr_funcs) {
514 } else if (btf_is_struct(type) && nr_structs) {
516 root = &obj->structs;
517 } else if (btf_is_union(type) && nr_unions) {
520 } else if (btf_is_typedef(type) && nr_typedefs) {
522 root = &obj->typedefs;
526 str = btf__name_by_offset(btf, type->name_off);
528 pr_err("FAILED: malformed BTF, can't resolve name for ID %d\n",
533 id = btf_id__find(root, str);
536 pr_info("WARN: multiple IDs found for '%s': %d, %d - using %d\n",
537 str, id->id, type_id, id->id);
551 static int id_patch(struct object *obj, struct btf_id *id)
553 Elf_Data *data = obj->efile.idlist;
554 int *ptr = data->d_buf;
558 pr_err("FAILED unresolved symbol %s\n", id->name);
562 for (i = 0; i < id->addr_cnt; i++) {
563 unsigned long addr = id->addr[i];
564 unsigned long idx = addr - obj->efile.idlist_addr;
566 pr_debug("patching addr %5lu: ID %7d [%s]\n",
567 idx, id->id, id->name);
569 if (idx >= data->d_size) {
570 pr_err("FAILED patching index %lu out of bounds %lu\n",
575 idx = idx / sizeof(int);
582 static int __symbols_patch(struct object *obj, struct rb_root *root)
584 struct rb_node *next;
587 next = rb_first(root);
589 id = rb_entry(next, struct btf_id, rb_node);
591 if (id_patch(obj, id))
594 next = rb_next(next);
599 static int cmp_id(const void *pa, const void *pb)
601 const int *a = pa, *b = pb;
606 static int sets_patch(struct object *obj)
608 Elf_Data *data = obj->efile.idlist;
609 int *ptr = data->d_buf;
610 struct rb_node *next;
612 next = rb_first(&obj->sets);
614 unsigned long addr, idx;
619 id = rb_entry(next, struct btf_id, rb_node);
621 idx = addr - obj->efile.idlist_addr;
623 /* sets are unique */
624 if (id->addr_cnt != 1) {
625 pr_err("FAILED malformed data for set '%s'\n",
630 idx = idx / sizeof(int);
631 base = &ptr[idx] + 1;
634 pr_debug("sorting addr %5lu: cnt %6d [%s]\n",
635 (idx + 1) * sizeof(int), cnt, id->name);
637 qsort(base, cnt, sizeof(int), cmp_id);
639 next = rb_next(next);
644 static int symbols_patch(struct object *obj)
648 if (__symbols_patch(obj, &obj->structs) ||
649 __symbols_patch(obj, &obj->unions) ||
650 __symbols_patch(obj, &obj->typedefs) ||
651 __symbols_patch(obj, &obj->funcs) ||
652 __symbols_patch(obj, &obj->sets))
658 elf_flagdata(obj->efile.idlist, ELF_C_SET, ELF_F_DIRTY);
660 err = elf_update(obj->efile.elf, ELF_C_WRITE);
662 pr_err("FAILED elf_update(WRITE): %s\n",
666 pr_debug("update %s for %s\n",
667 err >= 0 ? "ok" : "failed", obj->path);
668 return err < 0 ? -1 : 0;
671 static const char * const resolve_btfids_usage[] = {
672 "resolve_btfids [<options>] <ELF object>",
676 int main(int argc, const char **argv)
678 bool no_fail = false;
679 struct object obj = {
690 struct option btfid_options[] = {
691 OPT_INCR('v', "verbose", &verbose,
692 "be more verbose (show errors, etc)"),
693 OPT_STRING(0, "btf", &obj.btf, "BTF data",
695 OPT_BOOLEAN(0, "no-fail", &no_fail,
696 "do not fail if " BTF_IDS_SECTION " section is not found"),
701 argc = parse_options(argc, argv, btfid_options, resolve_btfids_usage,
702 PARSE_OPT_STOP_AT_NON_OPTION);
704 usage_with_options(resolve_btfids_usage, btfid_options);
708 if (elf_collect(&obj))
712 * We did not find .BTF_ids section or symbols section,
715 if (obj.efile.idlist_shndx == -1 ||
716 obj.efile.symbols_shndx == -1) {
719 pr_err("FAILED to find needed sections\n");
723 if (symbols_collect(&obj))
726 if (symbols_resolve(&obj))
729 if (symbols_patch(&obj))
735 elf_end(obj.efile.elf);