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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
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}