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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
101struct 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
114struct 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
143static int verbose;
144
145static 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
172static bool is_btf_id(const char *name)
173{
174 return name && !strncmp(name, BTF_ID_PREFIX, sizeof(BTF_ID_PREFIX) - 1);
175}
176
177static 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
196static struct btf_id *
197btf_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
226static 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
259static 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
277static 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 */
305static 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
328static 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
429static 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
531static 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;
615out:
616 btf__free(base_btf);
617 btf__free(btf);
618 return err;
619}
620
621static 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
651static 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
668static int cmp_id(const void *pa, const void *pb)
669{
670 const int *a = pa, *b = pb;
671
672 return *a - *b;
673}
674
675static 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
737static 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
767static const char * const resolve_btfids_usage[] = {
768 "resolve_btfids [<options>] <ELF object>",
769 NULL
770};
771
772int 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;
827out:
828 if (obj.efile.elf) {
829 elf_end(obj.efile.elf);
830 close(obj.efile.fd);
831 }
832 return err;
833}
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
78struct 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
89struct 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
116static int verbose;
117
118int 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
143static bool is_btf_id(const char *name)
144{
145 return name && !strncmp(name, BTF_ID, sizeof(BTF_ID) - 1);
146}
147
148static 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
167static struct btf_id*
168btf_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
197static char *get_id(const char *prefix_end)
198{
199 /*
200 * __BTF_ID__func__vfs_truncate__0
201 * prefix_end = ^
202 */
203 char *p, *id = strdup(prefix_end + sizeof("__") - 1);
204
205 if (id) {
206 /*
207 * __BTF_ID__func__vfs_truncate__0
208 * id = ^
209 *
210 * cut the unique id part
211 */
212 p = strrchr(id, '_');
213 p--;
214 if (*p != '_') {
215 free(id);
216 return NULL;
217 }
218 *p = '\0';
219 }
220 return id;
221}
222
223static struct btf_id *add_symbol(struct rb_root *root, char *name, size_t size)
224{
225 char *id;
226
227 id = get_id(name + size);
228 if (!id) {
229 pr_err("FAILED to parse symbol name: %s\n", name);
230 return NULL;
231 }
232
233 return btf_id__add(root, id, false);
234}
235
236/*
237 * The data of compressed section should be aligned to 4
238 * (for 32bit) or 8 (for 64 bit) bytes. The binutils ld
239 * sets sh_addralign to 1, which makes libelf fail with
240 * misaligned section error during the update:
241 * FAILED elf_update(WRITE): invalid section alignment
242 *
243 * While waiting for ld fix, we fix the compressed sections
244 * sh_addralign value manualy.
245 */
246static int compressed_section_fix(Elf *elf, Elf_Scn *scn, GElf_Shdr *sh)
247{
248 int expected = gelf_getclass(elf) == ELFCLASS32 ? 4 : 8;
249
250 if (!(sh->sh_flags & SHF_COMPRESSED))
251 return 0;
252
253 if (sh->sh_addralign == expected)
254 return 0;
255
256 pr_debug2(" - fixing wrong alignment sh_addralign %u, expected %u\n",
257 sh->sh_addralign, expected);
258
259 sh->sh_addralign = expected;
260
261 if (gelf_update_shdr(scn, sh) == 0) {
262 printf("FAILED cannot update section header: %s\n",
263 elf_errmsg(-1));
264 return -1;
265 }
266 return 0;
267}
268
269static int elf_collect(struct object *obj)
270{
271 Elf_Scn *scn = NULL;
272 size_t shdrstrndx;
273 int idx = 0;
274 Elf *elf;
275 int fd;
276
277 fd = open(obj->path, O_RDWR, 0666);
278 if (fd == -1) {
279 pr_err("FAILED cannot open %s: %s\n",
280 obj->path, strerror(errno));
281 return -1;
282 }
283
284 elf_version(EV_CURRENT);
285
286 elf = elf_begin(fd, ELF_C_RDWR_MMAP, NULL);
287 if (!elf) {
288 pr_err("FAILED cannot create ELF descriptor: %s\n",
289 elf_errmsg(-1));
290 return -1;
291 }
292
293 obj->efile.fd = fd;
294 obj->efile.elf = elf;
295
296 elf_flagelf(elf, ELF_C_SET, ELF_F_LAYOUT);
297
298 if (elf_getshdrstrndx(elf, &shdrstrndx) != 0) {
299 pr_err("FAILED cannot get shdr str ndx\n");
300 return -1;
301 }
302
303 /*
304 * Scan all the elf sections and look for save data
305 * from .BTF_ids section and symbols.
306 */
307 while ((scn = elf_nextscn(elf, scn)) != NULL) {
308 Elf_Data *data;
309 GElf_Shdr sh;
310 char *name;
311
312 idx++;
313 if (gelf_getshdr(scn, &sh) != &sh) {
314 pr_err("FAILED get section(%d) header\n", idx);
315 return -1;
316 }
317
318 name = elf_strptr(elf, shdrstrndx, sh.sh_name);
319 if (!name) {
320 pr_err("FAILED get section(%d) name\n", idx);
321 return -1;
322 }
323
324 data = elf_getdata(scn, 0);
325 if (!data) {
326 pr_err("FAILED to get section(%d) data from %s\n",
327 idx, name);
328 return -1;
329 }
330
331 pr_debug2("section(%d) %s, size %ld, link %d, flags %lx, type=%d\n",
332 idx, name, (unsigned long) data->d_size,
333 (int) sh.sh_link, (unsigned long) sh.sh_flags,
334 (int) sh.sh_type);
335
336 if (sh.sh_type == SHT_SYMTAB) {
337 obj->efile.symbols = data;
338 obj->efile.symbols_shndx = idx;
339 obj->efile.strtabidx = sh.sh_link;
340 } else if (!strcmp(name, BTF_IDS_SECTION)) {
341 obj->efile.idlist = data;
342 obj->efile.idlist_shndx = idx;
343 obj->efile.idlist_addr = sh.sh_addr;
344 }
345
346 if (compressed_section_fix(elf, scn, &sh))
347 return -1;
348 }
349
350 return 0;
351}
352
353static int symbols_collect(struct object *obj)
354{
355 Elf_Scn *scn = NULL;
356 int n, i, err = 0;
357 GElf_Shdr sh;
358 char *name;
359
360 scn = elf_getscn(obj->efile.elf, obj->efile.symbols_shndx);
361 if (!scn)
362 return -1;
363
364 if (gelf_getshdr(scn, &sh) != &sh)
365 return -1;
366
367 n = sh.sh_size / sh.sh_entsize;
368
369 /*
370 * Scan symbols and look for the ones starting with
371 * __BTF_ID__* over .BTF_ids section.
372 */
373 for (i = 0; !err && i < n; i++) {
374 char *tmp, *prefix;
375 struct btf_id *id;
376 GElf_Sym sym;
377 int err = -1;
378
379 if (!gelf_getsym(obj->efile.symbols, i, &sym))
380 return -1;
381
382 if (sym.st_shndx != obj->efile.idlist_shndx)
383 continue;
384
385 name = elf_strptr(obj->efile.elf, obj->efile.strtabidx,
386 sym.st_name);
387
388 if (!is_btf_id(name))
389 continue;
390
391 /*
392 * __BTF_ID__TYPE__vfs_truncate__0
393 * prefix = ^
394 */
395 prefix = name + sizeof(BTF_ID) - 1;
396
397 /* struct */
398 if (!strncmp(prefix, BTF_STRUCT, sizeof(BTF_STRUCT) - 1)) {
399 obj->nr_structs++;
400 id = add_symbol(&obj->structs, prefix, sizeof(BTF_STRUCT) - 1);
401 /* union */
402 } else if (!strncmp(prefix, BTF_UNION, sizeof(BTF_UNION) - 1)) {
403 obj->nr_unions++;
404 id = add_symbol(&obj->unions, prefix, sizeof(BTF_UNION) - 1);
405 /* typedef */
406 } else if (!strncmp(prefix, BTF_TYPEDEF, sizeof(BTF_TYPEDEF) - 1)) {
407 obj->nr_typedefs++;
408 id = add_symbol(&obj->typedefs, prefix, sizeof(BTF_TYPEDEF) - 1);
409 /* func */
410 } else if (!strncmp(prefix, BTF_FUNC, sizeof(BTF_FUNC) - 1)) {
411 obj->nr_funcs++;
412 id = add_symbol(&obj->funcs, prefix, sizeof(BTF_FUNC) - 1);
413 /* set */
414 } else if (!strncmp(prefix, BTF_SET, sizeof(BTF_SET) - 1)) {
415 id = add_symbol(&obj->sets, prefix, sizeof(BTF_SET) - 1);
416 /*
417 * SET objects store list's count, which is encoded
418 * in symbol's size, together with 'cnt' field hence
419 * that - 1.
420 */
421 if (id)
422 id->cnt = sym.st_size / sizeof(int) - 1;
423 } else {
424 pr_err("FAILED unsupported prefix %s\n", prefix);
425 return -1;
426 }
427
428 if (!id)
429 return -ENOMEM;
430
431 if (id->addr_cnt >= ADDR_CNT) {
432 pr_err("FAILED symbol %s crossed the number of allowed lists",
433 id->name);
434 return -1;
435 }
436 id->addr[id->addr_cnt++] = sym.st_value;
437 }
438
439 return 0;
440}
441
442static int symbols_resolve(struct object *obj)
443{
444 int nr_typedefs = obj->nr_typedefs;
445 int nr_structs = obj->nr_structs;
446 int nr_unions = obj->nr_unions;
447 int nr_funcs = obj->nr_funcs;
448 int err, type_id;
449 struct btf *btf;
450 __u32 nr;
451
452 btf = btf__parse(obj->btf ?: obj->path, NULL);
453 err = libbpf_get_error(btf);
454 if (err) {
455 pr_err("FAILED: load BTF from %s: %s",
456 obj->path, strerror(err));
457 return -1;
458 }
459
460 err = -1;
461 nr = btf__get_nr_types(btf);
462
463 /*
464 * Iterate all the BTF types and search for collected symbol IDs.
465 */
466 for (type_id = 1; type_id <= nr; type_id++) {
467 const struct btf_type *type;
468 struct rb_root *root;
469 struct btf_id *id;
470 const char *str;
471 int *nr;
472
473 type = btf__type_by_id(btf, type_id);
474 if (!type) {
475 pr_err("FAILED: malformed BTF, can't resolve type for ID %d\n",
476 type_id);
477 goto out;
478 }
479
480 if (btf_is_func(type) && nr_funcs) {
481 nr = &nr_funcs;
482 root = &obj->funcs;
483 } else if (btf_is_struct(type) && nr_structs) {
484 nr = &nr_structs;
485 root = &obj->structs;
486 } else if (btf_is_union(type) && nr_unions) {
487 nr = &nr_unions;
488 root = &obj->unions;
489 } else if (btf_is_typedef(type) && nr_typedefs) {
490 nr = &nr_typedefs;
491 root = &obj->typedefs;
492 } else
493 continue;
494
495 str = btf__name_by_offset(btf, type->name_off);
496 if (!str) {
497 pr_err("FAILED: malformed BTF, can't resolve name for ID %d\n",
498 type_id);
499 goto out;
500 }
501
502 id = btf_id__find(root, str);
503 if (id) {
504 id->id = type_id;
505 (*nr)--;
506 }
507 }
508
509 err = 0;
510out:
511 btf__free(btf);
512 return err;
513}
514
515static int id_patch(struct object *obj, struct btf_id *id)
516{
517 Elf_Data *data = obj->efile.idlist;
518 int *ptr = data->d_buf;
519 int i;
520
521 if (!id->id) {
522 pr_err("FAILED unresolved symbol %s\n", id->name);
523 return -EINVAL;
524 }
525
526 for (i = 0; i < id->addr_cnt; i++) {
527 unsigned long addr = id->addr[i];
528 unsigned long idx = addr - obj->efile.idlist_addr;
529
530 pr_debug("patching addr %5lu: ID %7d [%s]\n",
531 idx, id->id, id->name);
532
533 if (idx >= data->d_size) {
534 pr_err("FAILED patching index %lu out of bounds %lu\n",
535 idx, data->d_size);
536 return -1;
537 }
538
539 idx = idx / sizeof(int);
540 ptr[idx] = id->id;
541 }
542
543 return 0;
544}
545
546static int __symbols_patch(struct object *obj, struct rb_root *root)
547{
548 struct rb_node *next;
549 struct btf_id *id;
550
551 next = rb_first(root);
552 while (next) {
553 id = rb_entry(next, struct btf_id, rb_node);
554
555 if (id_patch(obj, id))
556 return -1;
557
558 next = rb_next(next);
559 }
560 return 0;
561}
562
563static int cmp_id(const void *pa, const void *pb)
564{
565 const int *a = pa, *b = pb;
566
567 return *a - *b;
568}
569
570static int sets_patch(struct object *obj)
571{
572 Elf_Data *data = obj->efile.idlist;
573 int *ptr = data->d_buf;
574 struct rb_node *next;
575
576 next = rb_first(&obj->sets);
577 while (next) {
578 unsigned long addr, idx;
579 struct btf_id *id;
580 int *base;
581 int cnt;
582
583 id = rb_entry(next, struct btf_id, rb_node);
584 addr = id->addr[0];
585 idx = addr - obj->efile.idlist_addr;
586
587 /* sets are unique */
588 if (id->addr_cnt != 1) {
589 pr_err("FAILED malformed data for set '%s'\n",
590 id->name);
591 return -1;
592 }
593
594 idx = idx / sizeof(int);
595 base = &ptr[idx] + 1;
596 cnt = ptr[idx];
597
598 pr_debug("sorting addr %5lu: cnt %6d [%s]\n",
599 (idx + 1) * sizeof(int), cnt, id->name);
600
601 qsort(base, cnt, sizeof(int), cmp_id);
602
603 next = rb_next(next);
604 }
605 return 0;
606}
607
608static int symbols_patch(struct object *obj)
609{
610 int err;
611
612 if (__symbols_patch(obj, &obj->structs) ||
613 __symbols_patch(obj, &obj->unions) ||
614 __symbols_patch(obj, &obj->typedefs) ||
615 __symbols_patch(obj, &obj->funcs) ||
616 __symbols_patch(obj, &obj->sets))
617 return -1;
618
619 if (sets_patch(obj))
620 return -1;
621
622 elf_flagdata(obj->efile.idlist, ELF_C_SET, ELF_F_DIRTY);
623
624 err = elf_update(obj->efile.elf, ELF_C_WRITE);
625 if (err < 0) {
626 pr_err("FAILED elf_update(WRITE): %s\n",
627 elf_errmsg(-1));
628 }
629
630 pr_debug("update %s for %s\n",
631 err >= 0 ? "ok" : "failed", obj->path);
632 return err < 0 ? -1 : 0;
633}
634
635static const char * const resolve_btfids_usage[] = {
636 "resolve_btfids [<options>] <ELF object>",
637 NULL
638};
639
640int main(int argc, const char **argv)
641{
642 bool no_fail = false;
643 struct object obj = {
644 .efile = {
645 .idlist_shndx = -1,
646 .symbols_shndx = -1,
647 },
648 .structs = RB_ROOT,
649 .unions = RB_ROOT,
650 .typedefs = RB_ROOT,
651 .funcs = RB_ROOT,
652 .sets = RB_ROOT,
653 };
654 struct option btfid_options[] = {
655 OPT_INCR('v', "verbose", &verbose,
656 "be more verbose (show errors, etc)"),
657 OPT_STRING(0, "btf", &obj.btf, "BTF data",
658 "BTF data"),
659 OPT_BOOLEAN(0, "no-fail", &no_fail,
660 "do not fail if " BTF_IDS_SECTION " section is not found"),
661 OPT_END()
662 };
663 int err = -1;
664
665 argc = parse_options(argc, argv, btfid_options, resolve_btfids_usage,
666 PARSE_OPT_STOP_AT_NON_OPTION);
667 if (argc != 1)
668 usage_with_options(resolve_btfids_usage, btfid_options);
669
670 obj.path = argv[0];
671
672 if (elf_collect(&obj))
673 goto out;
674
675 /*
676 * We did not find .BTF_ids section or symbols section,
677 * nothing to do..
678 */
679 if (obj.efile.idlist_shndx == -1 ||
680 obj.efile.symbols_shndx == -1) {
681 if (no_fail)
682 return 0;
683 pr_err("FAILED to find needed sections\n");
684 return -1;
685 }
686
687 if (symbols_collect(&obj))
688 goto out;
689
690 if (symbols_resolve(&obj))
691 goto out;
692
693 if (symbols_patch(&obj))
694 goto out;
695
696 err = 0;
697out:
698 if (obj.efile.elf)
699 elf_end(obj.efile.elf);
700 close(obj.efile.fd);
701 return err;
702}