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