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