1 // SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
2 /* Copyright (c) 2018 Facebook */
3
4 #include <endian.h>
5 #include <stdio.h>
6 #include <stdlib.h>
7 #include <string.h>
8 #include <fcntl.h>
9 #include <unistd.h>
10 #include <errno.h>
11 #include <linux/err.h>
12 #include <linux/btf.h>
13 #include <gelf.h>
14 #include "btf.h"
15 #include "bpf.h"
16 #include "libbpf.h"
17 #include "libbpf_internal.h"
18 #include "hashmap.h"
19
20 #define BTF_MAX_NR_TYPES 0x7fffffff
21 #define BTF_MAX_STR_OFFSET 0x7fffffff
22
23 static struct btf_type btf_void;
24
25 struct btf {
26 union {
27 struct btf_header *hdr;
28 void *data;
29 };
30 struct btf_type **types;
31 const char *strings;
32 void *nohdr_data;
33 __u32 nr_types;
34 __u32 types_size;
35 __u32 data_size;
36 int fd;
37 };
38
ptr_to_u64(const void * ptr)39 static inline __u64 ptr_to_u64(const void *ptr)
40 {
41 return (__u64) (unsigned long) ptr;
42 }
43
btf_add_type(struct btf * btf,struct btf_type * t)44 static int btf_add_type(struct btf *btf, struct btf_type *t)
45 {
46 if (btf->types_size - btf->nr_types < 2) {
47 struct btf_type **new_types;
48 __u32 expand_by, new_size;
49
50 if (btf->types_size == BTF_MAX_NR_TYPES)
51 return -E2BIG;
52
53 expand_by = max(btf->types_size >> 2, 16);
54 new_size = min(BTF_MAX_NR_TYPES, btf->types_size + expand_by);
55
56 new_types = realloc(btf->types, sizeof(*new_types) * new_size);
57 if (!new_types)
58 return -ENOMEM;
59
60 if (btf->nr_types == 0)
61 new_types[0] = &btf_void;
62
63 btf->types = new_types;
64 btf->types_size = new_size;
65 }
66
67 btf->types[++(btf->nr_types)] = t;
68
69 return 0;
70 }
71
btf_parse_hdr(struct btf * btf)72 static int btf_parse_hdr(struct btf *btf)
73 {
74 const struct btf_header *hdr = btf->hdr;
75 __u32 meta_left;
76
77 if (btf->data_size < sizeof(struct btf_header)) {
78 pr_debug("BTF header not found\n");
79 return -EINVAL;
80 }
81
82 if (hdr->magic != BTF_MAGIC) {
83 pr_debug("Invalid BTF magic:%x\n", hdr->magic);
84 return -EINVAL;
85 }
86
87 if (hdr->version != BTF_VERSION) {
88 pr_debug("Unsupported BTF version:%u\n", hdr->version);
89 return -ENOTSUP;
90 }
91
92 if (hdr->flags) {
93 pr_debug("Unsupported BTF flags:%x\n", hdr->flags);
94 return -ENOTSUP;
95 }
96
97 meta_left = btf->data_size - sizeof(*hdr);
98 if (!meta_left) {
99 pr_debug("BTF has no data\n");
100 return -EINVAL;
101 }
102
103 if (meta_left < hdr->type_off) {
104 pr_debug("Invalid BTF type section offset:%u\n", hdr->type_off);
105 return -EINVAL;
106 }
107
108 if (meta_left < hdr->str_off) {
109 pr_debug("Invalid BTF string section offset:%u\n", hdr->str_off);
110 return -EINVAL;
111 }
112
113 if (hdr->type_off >= hdr->str_off) {
114 pr_debug("BTF type section offset >= string section offset. No type?\n");
115 return -EINVAL;
116 }
117
118 if (hdr->type_off & 0x02) {
119 pr_debug("BTF type section is not aligned to 4 bytes\n");
120 return -EINVAL;
121 }
122
123 btf->nohdr_data = btf->hdr + 1;
124
125 return 0;
126 }
127
btf_parse_str_sec(struct btf * btf)128 static int btf_parse_str_sec(struct btf *btf)
129 {
130 const struct btf_header *hdr = btf->hdr;
131 const char *start = btf->nohdr_data + hdr->str_off;
132 const char *end = start + btf->hdr->str_len;
133
134 if (!hdr->str_len || hdr->str_len - 1 > BTF_MAX_STR_OFFSET ||
135 start[0] || end[-1]) {
136 pr_debug("Invalid BTF string section\n");
137 return -EINVAL;
138 }
139
140 btf->strings = start;
141
142 return 0;
143 }
144
btf_type_size(struct btf_type * t)145 static int btf_type_size(struct btf_type *t)
146 {
147 int base_size = sizeof(struct btf_type);
148 __u16 vlen = btf_vlen(t);
149
150 switch (btf_kind(t)) {
151 case BTF_KIND_FWD:
152 case BTF_KIND_CONST:
153 case BTF_KIND_VOLATILE:
154 case BTF_KIND_RESTRICT:
155 case BTF_KIND_PTR:
156 case BTF_KIND_TYPEDEF:
157 case BTF_KIND_FUNC:
158 return base_size;
159 case BTF_KIND_INT:
160 return base_size + sizeof(__u32);
161 case BTF_KIND_ENUM:
162 return base_size + vlen * sizeof(struct btf_enum);
163 case BTF_KIND_ARRAY:
164 return base_size + sizeof(struct btf_array);
165 case BTF_KIND_STRUCT:
166 case BTF_KIND_UNION:
167 return base_size + vlen * sizeof(struct btf_member);
168 case BTF_KIND_FUNC_PROTO:
169 return base_size + vlen * sizeof(struct btf_param);
170 case BTF_KIND_VAR:
171 return base_size + sizeof(struct btf_var);
172 case BTF_KIND_DATASEC:
173 return base_size + vlen * sizeof(struct btf_var_secinfo);
174 default:
175 pr_debug("Unsupported BTF_KIND:%u\n", btf_kind(t));
176 return -EINVAL;
177 }
178 }
179
btf_parse_type_sec(struct btf * btf)180 static int btf_parse_type_sec(struct btf *btf)
181 {
182 struct btf_header *hdr = btf->hdr;
183 void *nohdr_data = btf->nohdr_data;
184 void *next_type = nohdr_data + hdr->type_off;
185 void *end_type = nohdr_data + hdr->str_off;
186
187 while (next_type < end_type) {
188 struct btf_type *t = next_type;
189 int type_size;
190 int err;
191
192 type_size = btf_type_size(t);
193 if (type_size < 0)
194 return type_size;
195 next_type += type_size;
196 err = btf_add_type(btf, t);
197 if (err)
198 return err;
199 }
200
201 return 0;
202 }
203
btf__get_nr_types(const struct btf * btf)204 __u32 btf__get_nr_types(const struct btf *btf)
205 {
206 return btf->nr_types;
207 }
208
btf__type_by_id(const struct btf * btf,__u32 type_id)209 const struct btf_type *btf__type_by_id(const struct btf *btf, __u32 type_id)
210 {
211 if (type_id > btf->nr_types)
212 return NULL;
213
214 return btf->types[type_id];
215 }
216
btf_type_is_void(const struct btf_type * t)217 static bool btf_type_is_void(const struct btf_type *t)
218 {
219 return t == &btf_void || btf_is_fwd(t);
220 }
221
btf_type_is_void_or_null(const struct btf_type * t)222 static bool btf_type_is_void_or_null(const struct btf_type *t)
223 {
224 return !t || btf_type_is_void(t);
225 }
226
227 #define MAX_RESOLVE_DEPTH 32
228
btf__resolve_size(const struct btf * btf,__u32 type_id)229 __s64 btf__resolve_size(const struct btf *btf, __u32 type_id)
230 {
231 const struct btf_array *array;
232 const struct btf_type *t;
233 __u32 nelems = 1;
234 __s64 size = -1;
235 int i;
236
237 t = btf__type_by_id(btf, type_id);
238 for (i = 0; i < MAX_RESOLVE_DEPTH && !btf_type_is_void_or_null(t);
239 i++) {
240 switch (btf_kind(t)) {
241 case BTF_KIND_INT:
242 case BTF_KIND_STRUCT:
243 case BTF_KIND_UNION:
244 case BTF_KIND_ENUM:
245 case BTF_KIND_DATASEC:
246 size = t->size;
247 goto done;
248 case BTF_KIND_PTR:
249 size = sizeof(void *);
250 goto done;
251 case BTF_KIND_TYPEDEF:
252 case BTF_KIND_VOLATILE:
253 case BTF_KIND_CONST:
254 case BTF_KIND_RESTRICT:
255 case BTF_KIND_VAR:
256 type_id = t->type;
257 break;
258 case BTF_KIND_ARRAY:
259 array = btf_array(t);
260 if (nelems && array->nelems > UINT32_MAX / nelems)
261 return -E2BIG;
262 nelems *= array->nelems;
263 type_id = array->type;
264 break;
265 default:
266 return -EINVAL;
267 }
268
269 t = btf__type_by_id(btf, type_id);
270 }
271
272 done:
273 if (size < 0)
274 return -EINVAL;
275 if (nelems && size > UINT32_MAX / nelems)
276 return -E2BIG;
277
278 return nelems * size;
279 }
280
btf__resolve_type(const struct btf * btf,__u32 type_id)281 int btf__resolve_type(const struct btf *btf, __u32 type_id)
282 {
283 const struct btf_type *t;
284 int depth = 0;
285
286 t = btf__type_by_id(btf, type_id);
287 while (depth < MAX_RESOLVE_DEPTH &&
288 !btf_type_is_void_or_null(t) &&
289 (btf_is_mod(t) || btf_is_typedef(t) || btf_is_var(t))) {
290 type_id = t->type;
291 t = btf__type_by_id(btf, type_id);
292 depth++;
293 }
294
295 if (depth == MAX_RESOLVE_DEPTH || btf_type_is_void_or_null(t))
296 return -EINVAL;
297
298 return type_id;
299 }
300
btf__find_by_name(const struct btf * btf,const char * type_name)301 __s32 btf__find_by_name(const struct btf *btf, const char *type_name)
302 {
303 __u32 i;
304
305 if (!strcmp(type_name, "void"))
306 return 0;
307
308 for (i = 1; i <= btf->nr_types; i++) {
309 const struct btf_type *t = btf->types[i];
310 const char *name = btf__name_by_offset(btf, t->name_off);
311
312 if (name && !strcmp(type_name, name))
313 return i;
314 }
315
316 return -ENOENT;
317 }
318
btf__free(struct btf * btf)319 void btf__free(struct btf *btf)
320 {
321 if (!btf)
322 return;
323
324 if (btf->fd != -1)
325 close(btf->fd);
326
327 free(btf->data);
328 free(btf->types);
329 free(btf);
330 }
331
btf__new(__u8 * data,__u32 size)332 struct btf *btf__new(__u8 *data, __u32 size)
333 {
334 struct btf *btf;
335 int err;
336
337 btf = calloc(1, sizeof(struct btf));
338 if (!btf)
339 return ERR_PTR(-ENOMEM);
340
341 btf->fd = -1;
342
343 btf->data = malloc(size);
344 if (!btf->data) {
345 err = -ENOMEM;
346 goto done;
347 }
348
349 memcpy(btf->data, data, size);
350 btf->data_size = size;
351
352 err = btf_parse_hdr(btf);
353 if (err)
354 goto done;
355
356 err = btf_parse_str_sec(btf);
357 if (err)
358 goto done;
359
360 err = btf_parse_type_sec(btf);
361
362 done:
363 if (err) {
364 btf__free(btf);
365 return ERR_PTR(err);
366 }
367
368 return btf;
369 }
370
btf_check_endianness(const GElf_Ehdr * ehdr)371 static bool btf_check_endianness(const GElf_Ehdr *ehdr)
372 {
373 #if __BYTE_ORDER == __LITTLE_ENDIAN
374 return ehdr->e_ident[EI_DATA] == ELFDATA2LSB;
375 #elif __BYTE_ORDER == __BIG_ENDIAN
376 return ehdr->e_ident[EI_DATA] == ELFDATA2MSB;
377 #else
378 # error "Unrecognized __BYTE_ORDER__"
379 #endif
380 }
381
btf__parse_elf(const char * path,struct btf_ext ** btf_ext)382 struct btf *btf__parse_elf(const char *path, struct btf_ext **btf_ext)
383 {
384 Elf_Data *btf_data = NULL, *btf_ext_data = NULL;
385 int err = 0, fd = -1, idx = 0;
386 struct btf *btf = NULL;
387 Elf_Scn *scn = NULL;
388 Elf *elf = NULL;
389 GElf_Ehdr ehdr;
390
391 if (elf_version(EV_CURRENT) == EV_NONE) {
392 pr_warning("failed to init libelf for %s\n", path);
393 return ERR_PTR(-LIBBPF_ERRNO__LIBELF);
394 }
395
396 fd = open(path, O_RDONLY);
397 if (fd < 0) {
398 err = -errno;
399 pr_warning("failed to open %s: %s\n", path, strerror(errno));
400 return ERR_PTR(err);
401 }
402
403 err = -LIBBPF_ERRNO__FORMAT;
404
405 elf = elf_begin(fd, ELF_C_READ, NULL);
406 if (!elf) {
407 pr_warning("failed to open %s as ELF file\n", path);
408 goto done;
409 }
410 if (!gelf_getehdr(elf, &ehdr)) {
411 pr_warning("failed to get EHDR from %s\n", path);
412 goto done;
413 }
414 if (!btf_check_endianness(&ehdr)) {
415 pr_warning("non-native ELF endianness is not supported\n");
416 goto done;
417 }
418 if (!elf_rawdata(elf_getscn(elf, ehdr.e_shstrndx), NULL)) {
419 pr_warning("failed to get e_shstrndx from %s\n", path);
420 goto done;
421 }
422
423 while ((scn = elf_nextscn(elf, scn)) != NULL) {
424 GElf_Shdr sh;
425 char *name;
426
427 idx++;
428 if (gelf_getshdr(scn, &sh) != &sh) {
429 pr_warning("failed to get section(%d) header from %s\n",
430 idx, path);
431 goto done;
432 }
433 name = elf_strptr(elf, ehdr.e_shstrndx, sh.sh_name);
434 if (!name) {
435 pr_warning("failed to get section(%d) name from %s\n",
436 idx, path);
437 goto done;
438 }
439 if (strcmp(name, BTF_ELF_SEC) == 0) {
440 btf_data = elf_getdata(scn, 0);
441 if (!btf_data) {
442 pr_warning("failed to get section(%d, %s) data from %s\n",
443 idx, name, path);
444 goto done;
445 }
446 continue;
447 } else if (btf_ext && strcmp(name, BTF_EXT_ELF_SEC) == 0) {
448 btf_ext_data = elf_getdata(scn, 0);
449 if (!btf_ext_data) {
450 pr_warning("failed to get section(%d, %s) data from %s\n",
451 idx, name, path);
452 goto done;
453 }
454 continue;
455 }
456 }
457
458 err = 0;
459
460 if (!btf_data) {
461 err = -ENOENT;
462 goto done;
463 }
464 btf = btf__new(btf_data->d_buf, btf_data->d_size);
465 if (IS_ERR(btf))
466 goto done;
467
468 if (btf_ext && btf_ext_data) {
469 *btf_ext = btf_ext__new(btf_ext_data->d_buf,
470 btf_ext_data->d_size);
471 if (IS_ERR(*btf_ext))
472 goto done;
473 } else if (btf_ext) {
474 *btf_ext = NULL;
475 }
476 done:
477 if (elf)
478 elf_end(elf);
479 close(fd);
480
481 if (err)
482 return ERR_PTR(err);
483 /*
484 * btf is always parsed before btf_ext, so no need to clean up
485 * btf_ext, if btf loading failed
486 */
487 if (IS_ERR(btf))
488 return btf;
489 if (btf_ext && IS_ERR(*btf_ext)) {
490 btf__free(btf);
491 err = PTR_ERR(*btf_ext);
492 return ERR_PTR(err);
493 }
494 return btf;
495 }
496
compare_vsi_off(const void * _a,const void * _b)497 static int compare_vsi_off(const void *_a, const void *_b)
498 {
499 const struct btf_var_secinfo *a = _a;
500 const struct btf_var_secinfo *b = _b;
501
502 return a->offset - b->offset;
503 }
504
btf_fixup_datasec(struct bpf_object * obj,struct btf * btf,struct btf_type * t)505 static int btf_fixup_datasec(struct bpf_object *obj, struct btf *btf,
506 struct btf_type *t)
507 {
508 __u32 size = 0, off = 0, i, vars = btf_vlen(t);
509 const char *name = btf__name_by_offset(btf, t->name_off);
510 const struct btf_type *t_var;
511 struct btf_var_secinfo *vsi;
512 const struct btf_var *var;
513 int ret;
514
515 if (!name) {
516 pr_debug("No name found in string section for DATASEC kind.\n");
517 return -ENOENT;
518 }
519
520 ret = bpf_object__section_size(obj, name, &size);
521 if (ret || !size || (t->size && t->size != size)) {
522 pr_debug("Invalid size for section %s: %u bytes\n", name, size);
523 return -ENOENT;
524 }
525
526 t->size = size;
527
528 for (i = 0, vsi = btf_var_secinfos(t); i < vars; i++, vsi++) {
529 t_var = btf__type_by_id(btf, vsi->type);
530 var = btf_var(t_var);
531
532 if (!btf_is_var(t_var)) {
533 pr_debug("Non-VAR type seen in section %s\n", name);
534 return -EINVAL;
535 }
536
537 if (var->linkage == BTF_VAR_STATIC)
538 continue;
539
540 name = btf__name_by_offset(btf, t_var->name_off);
541 if (!name) {
542 pr_debug("No name found in string section for VAR kind\n");
543 return -ENOENT;
544 }
545
546 ret = bpf_object__variable_offset(obj, name, &off);
547 if (ret) {
548 pr_debug("No offset found in symbol table for VAR %s\n",
549 name);
550 return -ENOENT;
551 }
552
553 vsi->offset = off;
554 }
555
556 qsort(t + 1, vars, sizeof(*vsi), compare_vsi_off);
557 return 0;
558 }
559
btf__finalize_data(struct bpf_object * obj,struct btf * btf)560 int btf__finalize_data(struct bpf_object *obj, struct btf *btf)
561 {
562 int err = 0;
563 __u32 i;
564
565 for (i = 1; i <= btf->nr_types; i++) {
566 struct btf_type *t = btf->types[i];
567
568 /* Loader needs to fix up some of the things compiler
569 * couldn't get its hands on while emitting BTF. This
570 * is section size and global variable offset. We use
571 * the info from the ELF itself for this purpose.
572 */
573 if (btf_is_datasec(t)) {
574 err = btf_fixup_datasec(obj, btf, t);
575 if (err)
576 break;
577 }
578 }
579
580 return err;
581 }
582
btf__load(struct btf * btf)583 int btf__load(struct btf *btf)
584 {
585 __u32 log_buf_size = BPF_LOG_BUF_SIZE;
586 char *log_buf = NULL;
587 int err = 0;
588
589 if (btf->fd >= 0)
590 return -EEXIST;
591
592 log_buf = malloc(log_buf_size);
593 if (!log_buf)
594 return -ENOMEM;
595
596 *log_buf = 0;
597
598 btf->fd = bpf_load_btf(btf->data, btf->data_size,
599 log_buf, log_buf_size, false);
600 if (btf->fd < 0) {
601 err = -errno;
602 pr_warning("Error loading BTF: %s(%d)\n", strerror(errno), errno);
603 if (*log_buf)
604 pr_warning("%s\n", log_buf);
605 goto done;
606 }
607
608 done:
609 free(log_buf);
610 return err;
611 }
612
btf__fd(const struct btf * btf)613 int btf__fd(const struct btf *btf)
614 {
615 return btf->fd;
616 }
617
btf__get_raw_data(const struct btf * btf,__u32 * size)618 const void *btf__get_raw_data(const struct btf *btf, __u32 *size)
619 {
620 *size = btf->data_size;
621 return btf->data;
622 }
623
btf__name_by_offset(const struct btf * btf,__u32 offset)624 const char *btf__name_by_offset(const struct btf *btf, __u32 offset)
625 {
626 if (offset < btf->hdr->str_len)
627 return &btf->strings[offset];
628 else
629 return NULL;
630 }
631
btf__get_from_id(__u32 id,struct btf ** btf)632 int btf__get_from_id(__u32 id, struct btf **btf)
633 {
634 struct bpf_btf_info btf_info = { 0 };
635 __u32 len = sizeof(btf_info);
636 __u32 last_size;
637 int btf_fd;
638 void *ptr;
639 int err;
640
641 err = 0;
642 *btf = NULL;
643 btf_fd = bpf_btf_get_fd_by_id(id);
644 if (btf_fd < 0)
645 return 0;
646
647 /* we won't know btf_size until we call bpf_obj_get_info_by_fd(). so
648 * let's start with a sane default - 4KiB here - and resize it only if
649 * bpf_obj_get_info_by_fd() needs a bigger buffer.
650 */
651 btf_info.btf_size = 4096;
652 last_size = btf_info.btf_size;
653 ptr = malloc(last_size);
654 if (!ptr) {
655 err = -ENOMEM;
656 goto exit_free;
657 }
658
659 memset(ptr, 0, last_size);
660 btf_info.btf = ptr_to_u64(ptr);
661 err = bpf_obj_get_info_by_fd(btf_fd, &btf_info, &len);
662
663 if (!err && btf_info.btf_size > last_size) {
664 void *temp_ptr;
665
666 last_size = btf_info.btf_size;
667 temp_ptr = realloc(ptr, last_size);
668 if (!temp_ptr) {
669 err = -ENOMEM;
670 goto exit_free;
671 }
672 ptr = temp_ptr;
673 memset(ptr, 0, last_size);
674 btf_info.btf = ptr_to_u64(ptr);
675 err = bpf_obj_get_info_by_fd(btf_fd, &btf_info, &len);
676 }
677
678 if (err || btf_info.btf_size > last_size) {
679 err = errno;
680 goto exit_free;
681 }
682
683 *btf = btf__new((__u8 *)(long)btf_info.btf, btf_info.btf_size);
684 if (IS_ERR(*btf)) {
685 err = PTR_ERR(*btf);
686 *btf = NULL;
687 }
688
689 exit_free:
690 close(btf_fd);
691 free(ptr);
692
693 return err;
694 }
695
btf__get_map_kv_tids(const struct btf * btf,const char * map_name,__u32 expected_key_size,__u32 expected_value_size,__u32 * key_type_id,__u32 * value_type_id)696 int btf__get_map_kv_tids(const struct btf *btf, const char *map_name,
697 __u32 expected_key_size, __u32 expected_value_size,
698 __u32 *key_type_id, __u32 *value_type_id)
699 {
700 const struct btf_type *container_type;
701 const struct btf_member *key, *value;
702 const size_t max_name = 256;
703 char container_name[max_name];
704 __s64 key_size, value_size;
705 __s32 container_id;
706
707 if (snprintf(container_name, max_name, "____btf_map_%s", map_name) ==
708 max_name) {
709 pr_warning("map:%s length of '____btf_map_%s' is too long\n",
710 map_name, map_name);
711 return -EINVAL;
712 }
713
714 container_id = btf__find_by_name(btf, container_name);
715 if (container_id < 0) {
716 pr_debug("map:%s container_name:%s cannot be found in BTF. Missing BPF_ANNOTATE_KV_PAIR?\n",
717 map_name, container_name);
718 return container_id;
719 }
720
721 container_type = btf__type_by_id(btf, container_id);
722 if (!container_type) {
723 pr_warning("map:%s cannot find BTF type for container_id:%u\n",
724 map_name, container_id);
725 return -EINVAL;
726 }
727
728 if (!btf_is_struct(container_type) || btf_vlen(container_type) < 2) {
729 pr_warning("map:%s container_name:%s is an invalid container struct\n",
730 map_name, container_name);
731 return -EINVAL;
732 }
733
734 key = btf_members(container_type);
735 value = key + 1;
736
737 key_size = btf__resolve_size(btf, key->type);
738 if (key_size < 0) {
739 pr_warning("map:%s invalid BTF key_type_size\n", map_name);
740 return key_size;
741 }
742
743 if (expected_key_size != key_size) {
744 pr_warning("map:%s btf_key_type_size:%u != map_def_key_size:%u\n",
745 map_name, (__u32)key_size, expected_key_size);
746 return -EINVAL;
747 }
748
749 value_size = btf__resolve_size(btf, value->type);
750 if (value_size < 0) {
751 pr_warning("map:%s invalid BTF value_type_size\n", map_name);
752 return value_size;
753 }
754
755 if (expected_value_size != value_size) {
756 pr_warning("map:%s btf_value_type_size:%u != map_def_value_size:%u\n",
757 map_name, (__u32)value_size, expected_value_size);
758 return -EINVAL;
759 }
760
761 *key_type_id = key->type;
762 *value_type_id = value->type;
763
764 return 0;
765 }
766
767 struct btf_ext_sec_setup_param {
768 __u32 off;
769 __u32 len;
770 __u32 min_rec_size;
771 struct btf_ext_info *ext_info;
772 const char *desc;
773 };
774
btf_ext_setup_info(struct btf_ext * btf_ext,struct btf_ext_sec_setup_param * ext_sec)775 static int btf_ext_setup_info(struct btf_ext *btf_ext,
776 struct btf_ext_sec_setup_param *ext_sec)
777 {
778 const struct btf_ext_info_sec *sinfo;
779 struct btf_ext_info *ext_info;
780 __u32 info_left, record_size;
781 /* The start of the info sec (including the __u32 record_size). */
782 void *info;
783
784 if (ext_sec->len == 0)
785 return 0;
786
787 if (ext_sec->off & 0x03) {
788 pr_debug(".BTF.ext %s section is not aligned to 4 bytes\n",
789 ext_sec->desc);
790 return -EINVAL;
791 }
792
793 info = btf_ext->data + btf_ext->hdr->hdr_len + ext_sec->off;
794 info_left = ext_sec->len;
795
796 if (btf_ext->data + btf_ext->data_size < info + ext_sec->len) {
797 pr_debug("%s section (off:%u len:%u) is beyond the end of the ELF section .BTF.ext\n",
798 ext_sec->desc, ext_sec->off, ext_sec->len);
799 return -EINVAL;
800 }
801
802 /* At least a record size */
803 if (info_left < sizeof(__u32)) {
804 pr_debug(".BTF.ext %s record size not found\n", ext_sec->desc);
805 return -EINVAL;
806 }
807
808 /* The record size needs to meet the minimum standard */
809 record_size = *(__u32 *)info;
810 if (record_size < ext_sec->min_rec_size ||
811 record_size & 0x03) {
812 pr_debug("%s section in .BTF.ext has invalid record size %u\n",
813 ext_sec->desc, record_size);
814 return -EINVAL;
815 }
816
817 sinfo = info + sizeof(__u32);
818 info_left -= sizeof(__u32);
819
820 /* If no records, return failure now so .BTF.ext won't be used. */
821 if (!info_left) {
822 pr_debug("%s section in .BTF.ext has no records", ext_sec->desc);
823 return -EINVAL;
824 }
825
826 while (info_left) {
827 unsigned int sec_hdrlen = sizeof(struct btf_ext_info_sec);
828 __u64 total_record_size;
829 __u32 num_records;
830
831 if (info_left < sec_hdrlen) {
832 pr_debug("%s section header is not found in .BTF.ext\n",
833 ext_sec->desc);
834 return -EINVAL;
835 }
836
837 num_records = sinfo->num_info;
838 if (num_records == 0) {
839 pr_debug("%s section has incorrect num_records in .BTF.ext\n",
840 ext_sec->desc);
841 return -EINVAL;
842 }
843
844 total_record_size = sec_hdrlen +
845 (__u64)num_records * record_size;
846 if (info_left < total_record_size) {
847 pr_debug("%s section has incorrect num_records in .BTF.ext\n",
848 ext_sec->desc);
849 return -EINVAL;
850 }
851
852 info_left -= total_record_size;
853 sinfo = (void *)sinfo + total_record_size;
854 }
855
856 ext_info = ext_sec->ext_info;
857 ext_info->len = ext_sec->len - sizeof(__u32);
858 ext_info->rec_size = record_size;
859 ext_info->info = info + sizeof(__u32);
860
861 return 0;
862 }
863
btf_ext_setup_func_info(struct btf_ext * btf_ext)864 static int btf_ext_setup_func_info(struct btf_ext *btf_ext)
865 {
866 struct btf_ext_sec_setup_param param = {
867 .off = btf_ext->hdr->func_info_off,
868 .len = btf_ext->hdr->func_info_len,
869 .min_rec_size = sizeof(struct bpf_func_info_min),
870 .ext_info = &btf_ext->func_info,
871 .desc = "func_info"
872 };
873
874 return btf_ext_setup_info(btf_ext, ¶m);
875 }
876
btf_ext_setup_line_info(struct btf_ext * btf_ext)877 static int btf_ext_setup_line_info(struct btf_ext *btf_ext)
878 {
879 struct btf_ext_sec_setup_param param = {
880 .off = btf_ext->hdr->line_info_off,
881 .len = btf_ext->hdr->line_info_len,
882 .min_rec_size = sizeof(struct bpf_line_info_min),
883 .ext_info = &btf_ext->line_info,
884 .desc = "line_info",
885 };
886
887 return btf_ext_setup_info(btf_ext, ¶m);
888 }
889
btf_ext_setup_offset_reloc(struct btf_ext * btf_ext)890 static int btf_ext_setup_offset_reloc(struct btf_ext *btf_ext)
891 {
892 struct btf_ext_sec_setup_param param = {
893 .off = btf_ext->hdr->offset_reloc_off,
894 .len = btf_ext->hdr->offset_reloc_len,
895 .min_rec_size = sizeof(struct bpf_offset_reloc),
896 .ext_info = &btf_ext->offset_reloc_info,
897 .desc = "offset_reloc",
898 };
899
900 return btf_ext_setup_info(btf_ext, ¶m);
901 }
902
btf_ext_parse_hdr(__u8 * data,__u32 data_size)903 static int btf_ext_parse_hdr(__u8 *data, __u32 data_size)
904 {
905 const struct btf_ext_header *hdr = (struct btf_ext_header *)data;
906
907 if (data_size < offsetofend(struct btf_ext_header, hdr_len) ||
908 data_size < hdr->hdr_len) {
909 pr_debug("BTF.ext header not found");
910 return -EINVAL;
911 }
912
913 if (hdr->magic != BTF_MAGIC) {
914 pr_debug("Invalid BTF.ext magic:%x\n", hdr->magic);
915 return -EINVAL;
916 }
917
918 if (hdr->version != BTF_VERSION) {
919 pr_debug("Unsupported BTF.ext version:%u\n", hdr->version);
920 return -ENOTSUP;
921 }
922
923 if (hdr->flags) {
924 pr_debug("Unsupported BTF.ext flags:%x\n", hdr->flags);
925 return -ENOTSUP;
926 }
927
928 if (data_size == hdr->hdr_len) {
929 pr_debug("BTF.ext has no data\n");
930 return -EINVAL;
931 }
932
933 return 0;
934 }
935
btf_ext__free(struct btf_ext * btf_ext)936 void btf_ext__free(struct btf_ext *btf_ext)
937 {
938 if (!btf_ext)
939 return;
940 free(btf_ext->data);
941 free(btf_ext);
942 }
943
btf_ext__new(__u8 * data,__u32 size)944 struct btf_ext *btf_ext__new(__u8 *data, __u32 size)
945 {
946 struct btf_ext *btf_ext;
947 int err;
948
949 err = btf_ext_parse_hdr(data, size);
950 if (err)
951 return ERR_PTR(err);
952
953 btf_ext = calloc(1, sizeof(struct btf_ext));
954 if (!btf_ext)
955 return ERR_PTR(-ENOMEM);
956
957 btf_ext->data_size = size;
958 btf_ext->data = malloc(size);
959 if (!btf_ext->data) {
960 err = -ENOMEM;
961 goto done;
962 }
963 memcpy(btf_ext->data, data, size);
964
965 if (btf_ext->hdr->hdr_len <
966 offsetofend(struct btf_ext_header, line_info_len))
967 goto done;
968 err = btf_ext_setup_func_info(btf_ext);
969 if (err)
970 goto done;
971
972 err = btf_ext_setup_line_info(btf_ext);
973 if (err)
974 goto done;
975
976 if (btf_ext->hdr->hdr_len <
977 offsetofend(struct btf_ext_header, offset_reloc_len))
978 goto done;
979 err = btf_ext_setup_offset_reloc(btf_ext);
980 if (err)
981 goto done;
982
983 done:
984 if (err) {
985 btf_ext__free(btf_ext);
986 return ERR_PTR(err);
987 }
988
989 return btf_ext;
990 }
991
btf_ext__get_raw_data(const struct btf_ext * btf_ext,__u32 * size)992 const void *btf_ext__get_raw_data(const struct btf_ext *btf_ext, __u32 *size)
993 {
994 *size = btf_ext->data_size;
995 return btf_ext->data;
996 }
997
btf_ext_reloc_info(const struct btf * btf,const struct btf_ext_info * ext_info,const char * sec_name,__u32 insns_cnt,void ** info,__u32 * cnt)998 static int btf_ext_reloc_info(const struct btf *btf,
999 const struct btf_ext_info *ext_info,
1000 const char *sec_name, __u32 insns_cnt,
1001 void **info, __u32 *cnt)
1002 {
1003 __u32 sec_hdrlen = sizeof(struct btf_ext_info_sec);
1004 __u32 i, record_size, existing_len, records_len;
1005 struct btf_ext_info_sec *sinfo;
1006 const char *info_sec_name;
1007 __u64 remain_len;
1008 void *data;
1009
1010 record_size = ext_info->rec_size;
1011 sinfo = ext_info->info;
1012 remain_len = ext_info->len;
1013 while (remain_len > 0) {
1014 records_len = sinfo->num_info * record_size;
1015 info_sec_name = btf__name_by_offset(btf, sinfo->sec_name_off);
1016 if (strcmp(info_sec_name, sec_name)) {
1017 remain_len -= sec_hdrlen + records_len;
1018 sinfo = (void *)sinfo + sec_hdrlen + records_len;
1019 continue;
1020 }
1021
1022 existing_len = (*cnt) * record_size;
1023 data = realloc(*info, existing_len + records_len);
1024 if (!data)
1025 return -ENOMEM;
1026
1027 memcpy(data + existing_len, sinfo->data, records_len);
1028 /* adjust insn_off only, the rest data will be passed
1029 * to the kernel.
1030 */
1031 for (i = 0; i < sinfo->num_info; i++) {
1032 __u32 *insn_off;
1033
1034 insn_off = data + existing_len + (i * record_size);
1035 *insn_off = *insn_off / sizeof(struct bpf_insn) +
1036 insns_cnt;
1037 }
1038 *info = data;
1039 *cnt += sinfo->num_info;
1040 return 0;
1041 }
1042
1043 return -ENOENT;
1044 }
1045
btf_ext__reloc_func_info(const struct btf * btf,const struct btf_ext * btf_ext,const char * sec_name,__u32 insns_cnt,void ** func_info,__u32 * cnt)1046 int btf_ext__reloc_func_info(const struct btf *btf,
1047 const struct btf_ext *btf_ext,
1048 const char *sec_name, __u32 insns_cnt,
1049 void **func_info, __u32 *cnt)
1050 {
1051 return btf_ext_reloc_info(btf, &btf_ext->func_info, sec_name,
1052 insns_cnt, func_info, cnt);
1053 }
1054
btf_ext__reloc_line_info(const struct btf * btf,const struct btf_ext * btf_ext,const char * sec_name,__u32 insns_cnt,void ** line_info,__u32 * cnt)1055 int btf_ext__reloc_line_info(const struct btf *btf,
1056 const struct btf_ext *btf_ext,
1057 const char *sec_name, __u32 insns_cnt,
1058 void **line_info, __u32 *cnt)
1059 {
1060 return btf_ext_reloc_info(btf, &btf_ext->line_info, sec_name,
1061 insns_cnt, line_info, cnt);
1062 }
1063
btf_ext__func_info_rec_size(const struct btf_ext * btf_ext)1064 __u32 btf_ext__func_info_rec_size(const struct btf_ext *btf_ext)
1065 {
1066 return btf_ext->func_info.rec_size;
1067 }
1068
btf_ext__line_info_rec_size(const struct btf_ext * btf_ext)1069 __u32 btf_ext__line_info_rec_size(const struct btf_ext *btf_ext)
1070 {
1071 return btf_ext->line_info.rec_size;
1072 }
1073
1074 struct btf_dedup;
1075
1076 static struct btf_dedup *btf_dedup_new(struct btf *btf, struct btf_ext *btf_ext,
1077 const struct btf_dedup_opts *opts);
1078 static void btf_dedup_free(struct btf_dedup *d);
1079 static int btf_dedup_strings(struct btf_dedup *d);
1080 static int btf_dedup_prim_types(struct btf_dedup *d);
1081 static int btf_dedup_struct_types(struct btf_dedup *d);
1082 static int btf_dedup_ref_types(struct btf_dedup *d);
1083 static int btf_dedup_compact_types(struct btf_dedup *d);
1084 static int btf_dedup_remap_types(struct btf_dedup *d);
1085
1086 /*
1087 * Deduplicate BTF types and strings.
1088 *
1089 * BTF dedup algorithm takes as an input `struct btf` representing `.BTF` ELF
1090 * section with all BTF type descriptors and string data. It overwrites that
1091 * memory in-place with deduplicated types and strings without any loss of
1092 * information. If optional `struct btf_ext` representing '.BTF.ext' ELF section
1093 * is provided, all the strings referenced from .BTF.ext section are honored
1094 * and updated to point to the right offsets after deduplication.
1095 *
1096 * If function returns with error, type/string data might be garbled and should
1097 * be discarded.
1098 *
1099 * More verbose and detailed description of both problem btf_dedup is solving,
1100 * as well as solution could be found at:
1101 * https://facebookmicrosites.github.io/bpf/blog/2018/11/14/btf-enhancement.html
1102 *
1103 * Problem description and justification
1104 * =====================================
1105 *
1106 * BTF type information is typically emitted either as a result of conversion
1107 * from DWARF to BTF or directly by compiler. In both cases, each compilation
1108 * unit contains information about a subset of all the types that are used
1109 * in an application. These subsets are frequently overlapping and contain a lot
1110 * of duplicated information when later concatenated together into a single
1111 * binary. This algorithm ensures that each unique type is represented by single
1112 * BTF type descriptor, greatly reducing resulting size of BTF data.
1113 *
1114 * Compilation unit isolation and subsequent duplication of data is not the only
1115 * problem. The same type hierarchy (e.g., struct and all the type that struct
1116 * references) in different compilation units can be represented in BTF to
1117 * various degrees of completeness (or, rather, incompleteness) due to
1118 * struct/union forward declarations.
1119 *
1120 * Let's take a look at an example, that we'll use to better understand the
1121 * problem (and solution). Suppose we have two compilation units, each using
1122 * same `struct S`, but each of them having incomplete type information about
1123 * struct's fields:
1124 *
1125 * // CU #1:
1126 * struct S;
1127 * struct A {
1128 * int a;
1129 * struct A* self;
1130 * struct S* parent;
1131 * };
1132 * struct B;
1133 * struct S {
1134 * struct A* a_ptr;
1135 * struct B* b_ptr;
1136 * };
1137 *
1138 * // CU #2:
1139 * struct S;
1140 * struct A;
1141 * struct B {
1142 * int b;
1143 * struct B* self;
1144 * struct S* parent;
1145 * };
1146 * struct S {
1147 * struct A* a_ptr;
1148 * struct B* b_ptr;
1149 * };
1150 *
1151 * In case of CU #1, BTF data will know only that `struct B` exist (but no
1152 * more), but will know the complete type information about `struct A`. While
1153 * for CU #2, it will know full type information about `struct B`, but will
1154 * only know about forward declaration of `struct A` (in BTF terms, it will
1155 * have `BTF_KIND_FWD` type descriptor with name `B`).
1156 *
1157 * This compilation unit isolation means that it's possible that there is no
1158 * single CU with complete type information describing structs `S`, `A`, and
1159 * `B`. Also, we might get tons of duplicated and redundant type information.
1160 *
1161 * Additional complication we need to keep in mind comes from the fact that
1162 * types, in general, can form graphs containing cycles, not just DAGs.
1163 *
1164 * While algorithm does deduplication, it also merges and resolves type
1165 * information (unless disabled throught `struct btf_opts`), whenever possible.
1166 * E.g., in the example above with two compilation units having partial type
1167 * information for structs `A` and `B`, the output of algorithm will emit
1168 * a single copy of each BTF type that describes structs `A`, `B`, and `S`
1169 * (as well as type information for `int` and pointers), as if they were defined
1170 * in a single compilation unit as:
1171 *
1172 * struct A {
1173 * int a;
1174 * struct A* self;
1175 * struct S* parent;
1176 * };
1177 * struct B {
1178 * int b;
1179 * struct B* self;
1180 * struct S* parent;
1181 * };
1182 * struct S {
1183 * struct A* a_ptr;
1184 * struct B* b_ptr;
1185 * };
1186 *
1187 * Algorithm summary
1188 * =================
1189 *
1190 * Algorithm completes its work in 6 separate passes:
1191 *
1192 * 1. Strings deduplication.
1193 * 2. Primitive types deduplication (int, enum, fwd).
1194 * 3. Struct/union types deduplication.
1195 * 4. Reference types deduplication (pointers, typedefs, arrays, funcs, func
1196 * protos, and const/volatile/restrict modifiers).
1197 * 5. Types compaction.
1198 * 6. Types remapping.
1199 *
1200 * Algorithm determines canonical type descriptor, which is a single
1201 * representative type for each truly unique type. This canonical type is the
1202 * one that will go into final deduplicated BTF type information. For
1203 * struct/unions, it is also the type that algorithm will merge additional type
1204 * information into (while resolving FWDs), as it discovers it from data in
1205 * other CUs. Each input BTF type eventually gets either mapped to itself, if
1206 * that type is canonical, or to some other type, if that type is equivalent
1207 * and was chosen as canonical representative. This mapping is stored in
1208 * `btf_dedup->map` array. This map is also used to record STRUCT/UNION that
1209 * FWD type got resolved to.
1210 *
1211 * To facilitate fast discovery of canonical types, we also maintain canonical
1212 * index (`btf_dedup->dedup_table`), which maps type descriptor's signature hash
1213 * (i.e., hashed kind, name, size, fields, etc) into a list of canonical types
1214 * that match that signature. With sufficiently good choice of type signature
1215 * hashing function, we can limit number of canonical types for each unique type
1216 * signature to a very small number, allowing to find canonical type for any
1217 * duplicated type very quickly.
1218 *
1219 * Struct/union deduplication is the most critical part and algorithm for
1220 * deduplicating structs/unions is described in greater details in comments for
1221 * `btf_dedup_is_equiv` function.
1222 */
btf__dedup(struct btf * btf,struct btf_ext * btf_ext,const struct btf_dedup_opts * opts)1223 int btf__dedup(struct btf *btf, struct btf_ext *btf_ext,
1224 const struct btf_dedup_opts *opts)
1225 {
1226 struct btf_dedup *d = btf_dedup_new(btf, btf_ext, opts);
1227 int err;
1228
1229 if (IS_ERR(d)) {
1230 pr_debug("btf_dedup_new failed: %ld", PTR_ERR(d));
1231 return -EINVAL;
1232 }
1233
1234 err = btf_dedup_strings(d);
1235 if (err < 0) {
1236 pr_debug("btf_dedup_strings failed:%d\n", err);
1237 goto done;
1238 }
1239 err = btf_dedup_prim_types(d);
1240 if (err < 0) {
1241 pr_debug("btf_dedup_prim_types failed:%d\n", err);
1242 goto done;
1243 }
1244 err = btf_dedup_struct_types(d);
1245 if (err < 0) {
1246 pr_debug("btf_dedup_struct_types failed:%d\n", err);
1247 goto done;
1248 }
1249 err = btf_dedup_ref_types(d);
1250 if (err < 0) {
1251 pr_debug("btf_dedup_ref_types failed:%d\n", err);
1252 goto done;
1253 }
1254 err = btf_dedup_compact_types(d);
1255 if (err < 0) {
1256 pr_debug("btf_dedup_compact_types failed:%d\n", err);
1257 goto done;
1258 }
1259 err = btf_dedup_remap_types(d);
1260 if (err < 0) {
1261 pr_debug("btf_dedup_remap_types failed:%d\n", err);
1262 goto done;
1263 }
1264
1265 done:
1266 btf_dedup_free(d);
1267 return err;
1268 }
1269
1270 #define BTF_UNPROCESSED_ID ((__u32)-1)
1271 #define BTF_IN_PROGRESS_ID ((__u32)-2)
1272
1273 struct btf_dedup {
1274 /* .BTF section to be deduped in-place */
1275 struct btf *btf;
1276 /*
1277 * Optional .BTF.ext section. When provided, any strings referenced
1278 * from it will be taken into account when deduping strings
1279 */
1280 struct btf_ext *btf_ext;
1281 /*
1282 * This is a map from any type's signature hash to a list of possible
1283 * canonical representative type candidates. Hash collisions are
1284 * ignored, so even types of various kinds can share same list of
1285 * candidates, which is fine because we rely on subsequent
1286 * btf_xxx_equal() checks to authoritatively verify type equality.
1287 */
1288 struct hashmap *dedup_table;
1289 /* Canonical types map */
1290 __u32 *map;
1291 /* Hypothetical mapping, used during type graph equivalence checks */
1292 __u32 *hypot_map;
1293 __u32 *hypot_list;
1294 size_t hypot_cnt;
1295 size_t hypot_cap;
1296 /* Various option modifying behavior of algorithm */
1297 struct btf_dedup_opts opts;
1298 };
1299
1300 struct btf_str_ptr {
1301 const char *str;
1302 __u32 new_off;
1303 bool used;
1304 };
1305
1306 struct btf_str_ptrs {
1307 struct btf_str_ptr *ptrs;
1308 const char *data;
1309 __u32 cnt;
1310 __u32 cap;
1311 };
1312
hash_combine(long h,long value)1313 static long hash_combine(long h, long value)
1314 {
1315 return h * 31 + value;
1316 }
1317
1318 #define for_each_dedup_cand(d, node, hash) \
1319 hashmap__for_each_key_entry(d->dedup_table, node, (void *)hash)
1320
btf_dedup_table_add(struct btf_dedup * d,long hash,__u32 type_id)1321 static int btf_dedup_table_add(struct btf_dedup *d, long hash, __u32 type_id)
1322 {
1323 return hashmap__append(d->dedup_table,
1324 (void *)hash, (void *)(long)type_id);
1325 }
1326
btf_dedup_hypot_map_add(struct btf_dedup * d,__u32 from_id,__u32 to_id)1327 static int btf_dedup_hypot_map_add(struct btf_dedup *d,
1328 __u32 from_id, __u32 to_id)
1329 {
1330 if (d->hypot_cnt == d->hypot_cap) {
1331 __u32 *new_list;
1332
1333 d->hypot_cap += max(16, d->hypot_cap / 2);
1334 new_list = realloc(d->hypot_list, sizeof(__u32) * d->hypot_cap);
1335 if (!new_list)
1336 return -ENOMEM;
1337 d->hypot_list = new_list;
1338 }
1339 d->hypot_list[d->hypot_cnt++] = from_id;
1340 d->hypot_map[from_id] = to_id;
1341 return 0;
1342 }
1343
btf_dedup_clear_hypot_map(struct btf_dedup * d)1344 static void btf_dedup_clear_hypot_map(struct btf_dedup *d)
1345 {
1346 int i;
1347
1348 for (i = 0; i < d->hypot_cnt; i++)
1349 d->hypot_map[d->hypot_list[i]] = BTF_UNPROCESSED_ID;
1350 d->hypot_cnt = 0;
1351 }
1352
btf_dedup_free(struct btf_dedup * d)1353 static void btf_dedup_free(struct btf_dedup *d)
1354 {
1355 hashmap__free(d->dedup_table);
1356 d->dedup_table = NULL;
1357
1358 free(d->map);
1359 d->map = NULL;
1360
1361 free(d->hypot_map);
1362 d->hypot_map = NULL;
1363
1364 free(d->hypot_list);
1365 d->hypot_list = NULL;
1366
1367 free(d);
1368 }
1369
btf_dedup_identity_hash_fn(const void * key,void * ctx)1370 static size_t btf_dedup_identity_hash_fn(const void *key, void *ctx)
1371 {
1372 return (size_t)key;
1373 }
1374
btf_dedup_collision_hash_fn(const void * key,void * ctx)1375 static size_t btf_dedup_collision_hash_fn(const void *key, void *ctx)
1376 {
1377 return 0;
1378 }
1379
btf_dedup_equal_fn(const void * k1,const void * k2,void * ctx)1380 static bool btf_dedup_equal_fn(const void *k1, const void *k2, void *ctx)
1381 {
1382 return k1 == k2;
1383 }
1384
btf_dedup_new(struct btf * btf,struct btf_ext * btf_ext,const struct btf_dedup_opts * opts)1385 static struct btf_dedup *btf_dedup_new(struct btf *btf, struct btf_ext *btf_ext,
1386 const struct btf_dedup_opts *opts)
1387 {
1388 struct btf_dedup *d = calloc(1, sizeof(struct btf_dedup));
1389 hashmap_hash_fn hash_fn = btf_dedup_identity_hash_fn;
1390 int i, err = 0;
1391
1392 if (!d)
1393 return ERR_PTR(-ENOMEM);
1394
1395 d->opts.dont_resolve_fwds = opts && opts->dont_resolve_fwds;
1396 /* dedup_table_size is now used only to force collisions in tests */
1397 if (opts && opts->dedup_table_size == 1)
1398 hash_fn = btf_dedup_collision_hash_fn;
1399
1400 d->btf = btf;
1401 d->btf_ext = btf_ext;
1402
1403 d->dedup_table = hashmap__new(hash_fn, btf_dedup_equal_fn, NULL);
1404 if (IS_ERR(d->dedup_table)) {
1405 err = PTR_ERR(d->dedup_table);
1406 d->dedup_table = NULL;
1407 goto done;
1408 }
1409
1410 d->map = malloc(sizeof(__u32) * (1 + btf->nr_types));
1411 if (!d->map) {
1412 err = -ENOMEM;
1413 goto done;
1414 }
1415 /* special BTF "void" type is made canonical immediately */
1416 d->map[0] = 0;
1417 for (i = 1; i <= btf->nr_types; i++) {
1418 struct btf_type *t = d->btf->types[i];
1419
1420 /* VAR and DATASEC are never deduped and are self-canonical */
1421 if (btf_is_var(t) || btf_is_datasec(t))
1422 d->map[i] = i;
1423 else
1424 d->map[i] = BTF_UNPROCESSED_ID;
1425 }
1426
1427 d->hypot_map = malloc(sizeof(__u32) * (1 + btf->nr_types));
1428 if (!d->hypot_map) {
1429 err = -ENOMEM;
1430 goto done;
1431 }
1432 for (i = 0; i <= btf->nr_types; i++)
1433 d->hypot_map[i] = BTF_UNPROCESSED_ID;
1434
1435 done:
1436 if (err) {
1437 btf_dedup_free(d);
1438 return ERR_PTR(err);
1439 }
1440
1441 return d;
1442 }
1443
1444 typedef int (*str_off_fn_t)(__u32 *str_off_ptr, void *ctx);
1445
1446 /*
1447 * Iterate over all possible places in .BTF and .BTF.ext that can reference
1448 * string and pass pointer to it to a provided callback `fn`.
1449 */
btf_for_each_str_off(struct btf_dedup * d,str_off_fn_t fn,void * ctx)1450 static int btf_for_each_str_off(struct btf_dedup *d, str_off_fn_t fn, void *ctx)
1451 {
1452 void *line_data_cur, *line_data_end;
1453 int i, j, r, rec_size;
1454 struct btf_type *t;
1455
1456 for (i = 1; i <= d->btf->nr_types; i++) {
1457 t = d->btf->types[i];
1458 r = fn(&t->name_off, ctx);
1459 if (r)
1460 return r;
1461
1462 switch (btf_kind(t)) {
1463 case BTF_KIND_STRUCT:
1464 case BTF_KIND_UNION: {
1465 struct btf_member *m = btf_members(t);
1466 __u16 vlen = btf_vlen(t);
1467
1468 for (j = 0; j < vlen; j++) {
1469 r = fn(&m->name_off, ctx);
1470 if (r)
1471 return r;
1472 m++;
1473 }
1474 break;
1475 }
1476 case BTF_KIND_ENUM: {
1477 struct btf_enum *m = btf_enum(t);
1478 __u16 vlen = btf_vlen(t);
1479
1480 for (j = 0; j < vlen; j++) {
1481 r = fn(&m->name_off, ctx);
1482 if (r)
1483 return r;
1484 m++;
1485 }
1486 break;
1487 }
1488 case BTF_KIND_FUNC_PROTO: {
1489 struct btf_param *m = btf_params(t);
1490 __u16 vlen = btf_vlen(t);
1491
1492 for (j = 0; j < vlen; j++) {
1493 r = fn(&m->name_off, ctx);
1494 if (r)
1495 return r;
1496 m++;
1497 }
1498 break;
1499 }
1500 default:
1501 break;
1502 }
1503 }
1504
1505 if (!d->btf_ext)
1506 return 0;
1507
1508 line_data_cur = d->btf_ext->line_info.info;
1509 line_data_end = d->btf_ext->line_info.info + d->btf_ext->line_info.len;
1510 rec_size = d->btf_ext->line_info.rec_size;
1511
1512 while (line_data_cur < line_data_end) {
1513 struct btf_ext_info_sec *sec = line_data_cur;
1514 struct bpf_line_info_min *line_info;
1515 __u32 num_info = sec->num_info;
1516
1517 r = fn(&sec->sec_name_off, ctx);
1518 if (r)
1519 return r;
1520
1521 line_data_cur += sizeof(struct btf_ext_info_sec);
1522 for (i = 0; i < num_info; i++) {
1523 line_info = line_data_cur;
1524 r = fn(&line_info->file_name_off, ctx);
1525 if (r)
1526 return r;
1527 r = fn(&line_info->line_off, ctx);
1528 if (r)
1529 return r;
1530 line_data_cur += rec_size;
1531 }
1532 }
1533
1534 return 0;
1535 }
1536
str_sort_by_content(const void * a1,const void * a2)1537 static int str_sort_by_content(const void *a1, const void *a2)
1538 {
1539 const struct btf_str_ptr *p1 = a1;
1540 const struct btf_str_ptr *p2 = a2;
1541
1542 return strcmp(p1->str, p2->str);
1543 }
1544
str_sort_by_offset(const void * a1,const void * a2)1545 static int str_sort_by_offset(const void *a1, const void *a2)
1546 {
1547 const struct btf_str_ptr *p1 = a1;
1548 const struct btf_str_ptr *p2 = a2;
1549
1550 if (p1->str != p2->str)
1551 return p1->str < p2->str ? -1 : 1;
1552 return 0;
1553 }
1554
btf_dedup_str_ptr_cmp(const void * str_ptr,const void * pelem)1555 static int btf_dedup_str_ptr_cmp(const void *str_ptr, const void *pelem)
1556 {
1557 const struct btf_str_ptr *p = pelem;
1558
1559 if (str_ptr != p->str)
1560 return (const char *)str_ptr < p->str ? -1 : 1;
1561 return 0;
1562 }
1563
btf_str_mark_as_used(__u32 * str_off_ptr,void * ctx)1564 static int btf_str_mark_as_used(__u32 *str_off_ptr, void *ctx)
1565 {
1566 struct btf_str_ptrs *strs;
1567 struct btf_str_ptr *s;
1568
1569 if (*str_off_ptr == 0)
1570 return 0;
1571
1572 strs = ctx;
1573 s = bsearch(strs->data + *str_off_ptr, strs->ptrs, strs->cnt,
1574 sizeof(struct btf_str_ptr), btf_dedup_str_ptr_cmp);
1575 if (!s)
1576 return -EINVAL;
1577 s->used = true;
1578 return 0;
1579 }
1580
btf_str_remap_offset(__u32 * str_off_ptr,void * ctx)1581 static int btf_str_remap_offset(__u32 *str_off_ptr, void *ctx)
1582 {
1583 struct btf_str_ptrs *strs;
1584 struct btf_str_ptr *s;
1585
1586 if (*str_off_ptr == 0)
1587 return 0;
1588
1589 strs = ctx;
1590 s = bsearch(strs->data + *str_off_ptr, strs->ptrs, strs->cnt,
1591 sizeof(struct btf_str_ptr), btf_dedup_str_ptr_cmp);
1592 if (!s)
1593 return -EINVAL;
1594 *str_off_ptr = s->new_off;
1595 return 0;
1596 }
1597
1598 /*
1599 * Dedup string and filter out those that are not referenced from either .BTF
1600 * or .BTF.ext (if provided) sections.
1601 *
1602 * This is done by building index of all strings in BTF's string section,
1603 * then iterating over all entities that can reference strings (e.g., type
1604 * names, struct field names, .BTF.ext line info, etc) and marking corresponding
1605 * strings as used. After that all used strings are deduped and compacted into
1606 * sequential blob of memory and new offsets are calculated. Then all the string
1607 * references are iterated again and rewritten using new offsets.
1608 */
btf_dedup_strings(struct btf_dedup * d)1609 static int btf_dedup_strings(struct btf_dedup *d)
1610 {
1611 const struct btf_header *hdr = d->btf->hdr;
1612 char *start = (char *)d->btf->nohdr_data + hdr->str_off;
1613 char *end = start + d->btf->hdr->str_len;
1614 char *p = start, *tmp_strs = NULL;
1615 struct btf_str_ptrs strs = {
1616 .cnt = 0,
1617 .cap = 0,
1618 .ptrs = NULL,
1619 .data = start,
1620 };
1621 int i, j, err = 0, grp_idx;
1622 bool grp_used;
1623
1624 /* build index of all strings */
1625 while (p < end) {
1626 if (strs.cnt + 1 > strs.cap) {
1627 struct btf_str_ptr *new_ptrs;
1628
1629 strs.cap += max(strs.cnt / 2, 16);
1630 new_ptrs = realloc(strs.ptrs,
1631 sizeof(strs.ptrs[0]) * strs.cap);
1632 if (!new_ptrs) {
1633 err = -ENOMEM;
1634 goto done;
1635 }
1636 strs.ptrs = new_ptrs;
1637 }
1638
1639 strs.ptrs[strs.cnt].str = p;
1640 strs.ptrs[strs.cnt].used = false;
1641
1642 p += strlen(p) + 1;
1643 strs.cnt++;
1644 }
1645
1646 /* temporary storage for deduplicated strings */
1647 tmp_strs = malloc(d->btf->hdr->str_len);
1648 if (!tmp_strs) {
1649 err = -ENOMEM;
1650 goto done;
1651 }
1652
1653 /* mark all used strings */
1654 strs.ptrs[0].used = true;
1655 err = btf_for_each_str_off(d, btf_str_mark_as_used, &strs);
1656 if (err)
1657 goto done;
1658
1659 /* sort strings by context, so that we can identify duplicates */
1660 qsort(strs.ptrs, strs.cnt, sizeof(strs.ptrs[0]), str_sort_by_content);
1661
1662 /*
1663 * iterate groups of equal strings and if any instance in a group was
1664 * referenced, emit single instance and remember new offset
1665 */
1666 p = tmp_strs;
1667 grp_idx = 0;
1668 grp_used = strs.ptrs[0].used;
1669 /* iterate past end to avoid code duplication after loop */
1670 for (i = 1; i <= strs.cnt; i++) {
1671 /*
1672 * when i == strs.cnt, we want to skip string comparison and go
1673 * straight to handling last group of strings (otherwise we'd
1674 * need to handle last group after the loop w/ duplicated code)
1675 */
1676 if (i < strs.cnt &&
1677 !strcmp(strs.ptrs[i].str, strs.ptrs[grp_idx].str)) {
1678 grp_used = grp_used || strs.ptrs[i].used;
1679 continue;
1680 }
1681
1682 /*
1683 * this check would have been required after the loop to handle
1684 * last group of strings, but due to <= condition in a loop
1685 * we avoid that duplication
1686 */
1687 if (grp_used) {
1688 int new_off = p - tmp_strs;
1689 __u32 len = strlen(strs.ptrs[grp_idx].str);
1690
1691 memmove(p, strs.ptrs[grp_idx].str, len + 1);
1692 for (j = grp_idx; j < i; j++)
1693 strs.ptrs[j].new_off = new_off;
1694 p += len + 1;
1695 }
1696
1697 if (i < strs.cnt) {
1698 grp_idx = i;
1699 grp_used = strs.ptrs[i].used;
1700 }
1701 }
1702
1703 /* replace original strings with deduped ones */
1704 d->btf->hdr->str_len = p - tmp_strs;
1705 memmove(start, tmp_strs, d->btf->hdr->str_len);
1706 end = start + d->btf->hdr->str_len;
1707
1708 /* restore original order for further binary search lookups */
1709 qsort(strs.ptrs, strs.cnt, sizeof(strs.ptrs[0]), str_sort_by_offset);
1710
1711 /* remap string offsets */
1712 err = btf_for_each_str_off(d, btf_str_remap_offset, &strs);
1713 if (err)
1714 goto done;
1715
1716 d->btf->hdr->str_len = end - start;
1717
1718 done:
1719 free(tmp_strs);
1720 free(strs.ptrs);
1721 return err;
1722 }
1723
btf_hash_common(struct btf_type * t)1724 static long btf_hash_common(struct btf_type *t)
1725 {
1726 long h;
1727
1728 h = hash_combine(0, t->name_off);
1729 h = hash_combine(h, t->info);
1730 h = hash_combine(h, t->size);
1731 return h;
1732 }
1733
btf_equal_common(struct btf_type * t1,struct btf_type * t2)1734 static bool btf_equal_common(struct btf_type *t1, struct btf_type *t2)
1735 {
1736 return t1->name_off == t2->name_off &&
1737 t1->info == t2->info &&
1738 t1->size == t2->size;
1739 }
1740
1741 /* Calculate type signature hash of INT. */
btf_hash_int(struct btf_type * t)1742 static long btf_hash_int(struct btf_type *t)
1743 {
1744 __u32 info = *(__u32 *)(t + 1);
1745 long h;
1746
1747 h = btf_hash_common(t);
1748 h = hash_combine(h, info);
1749 return h;
1750 }
1751
1752 /* Check structural equality of two INTs. */
btf_equal_int(struct btf_type * t1,struct btf_type * t2)1753 static bool btf_equal_int(struct btf_type *t1, struct btf_type *t2)
1754 {
1755 __u32 info1, info2;
1756
1757 if (!btf_equal_common(t1, t2))
1758 return false;
1759 info1 = *(__u32 *)(t1 + 1);
1760 info2 = *(__u32 *)(t2 + 1);
1761 return info1 == info2;
1762 }
1763
1764 /* Calculate type signature hash of ENUM. */
btf_hash_enum(struct btf_type * t)1765 static long btf_hash_enum(struct btf_type *t)
1766 {
1767 long h;
1768
1769 /* don't hash vlen and enum members to support enum fwd resolving */
1770 h = hash_combine(0, t->name_off);
1771 h = hash_combine(h, t->info & ~0xffff);
1772 h = hash_combine(h, t->size);
1773 return h;
1774 }
1775
1776 /* Check structural equality of two ENUMs. */
btf_equal_enum(struct btf_type * t1,struct btf_type * t2)1777 static bool btf_equal_enum(struct btf_type *t1, struct btf_type *t2)
1778 {
1779 const struct btf_enum *m1, *m2;
1780 __u16 vlen;
1781 int i;
1782
1783 if (!btf_equal_common(t1, t2))
1784 return false;
1785
1786 vlen = btf_vlen(t1);
1787 m1 = btf_enum(t1);
1788 m2 = btf_enum(t2);
1789 for (i = 0; i < vlen; i++) {
1790 if (m1->name_off != m2->name_off || m1->val != m2->val)
1791 return false;
1792 m1++;
1793 m2++;
1794 }
1795 return true;
1796 }
1797
btf_is_enum_fwd(struct btf_type * t)1798 static inline bool btf_is_enum_fwd(struct btf_type *t)
1799 {
1800 return btf_is_enum(t) && btf_vlen(t) == 0;
1801 }
1802
btf_compat_enum(struct btf_type * t1,struct btf_type * t2)1803 static bool btf_compat_enum(struct btf_type *t1, struct btf_type *t2)
1804 {
1805 if (!btf_is_enum_fwd(t1) && !btf_is_enum_fwd(t2))
1806 return btf_equal_enum(t1, t2);
1807 /* ignore vlen when comparing */
1808 return t1->name_off == t2->name_off &&
1809 (t1->info & ~0xffff) == (t2->info & ~0xffff) &&
1810 t1->size == t2->size;
1811 }
1812
1813 /*
1814 * Calculate type signature hash of STRUCT/UNION, ignoring referenced type IDs,
1815 * as referenced type IDs equivalence is established separately during type
1816 * graph equivalence check algorithm.
1817 */
btf_hash_struct(struct btf_type * t)1818 static long btf_hash_struct(struct btf_type *t)
1819 {
1820 const struct btf_member *member = btf_members(t);
1821 __u32 vlen = btf_vlen(t);
1822 long h = btf_hash_common(t);
1823 int i;
1824
1825 for (i = 0; i < vlen; i++) {
1826 h = hash_combine(h, member->name_off);
1827 h = hash_combine(h, member->offset);
1828 /* no hashing of referenced type ID, it can be unresolved yet */
1829 member++;
1830 }
1831 return h;
1832 }
1833
1834 /*
1835 * Check structural compatibility of two FUNC_PROTOs, ignoring referenced type
1836 * IDs. This check is performed during type graph equivalence check and
1837 * referenced types equivalence is checked separately.
1838 */
btf_shallow_equal_struct(struct btf_type * t1,struct btf_type * t2)1839 static bool btf_shallow_equal_struct(struct btf_type *t1, struct btf_type *t2)
1840 {
1841 const struct btf_member *m1, *m2;
1842 __u16 vlen;
1843 int i;
1844
1845 if (!btf_equal_common(t1, t2))
1846 return false;
1847
1848 vlen = btf_vlen(t1);
1849 m1 = btf_members(t1);
1850 m2 = btf_members(t2);
1851 for (i = 0; i < vlen; i++) {
1852 if (m1->name_off != m2->name_off || m1->offset != m2->offset)
1853 return false;
1854 m1++;
1855 m2++;
1856 }
1857 return true;
1858 }
1859
1860 /*
1861 * Calculate type signature hash of ARRAY, including referenced type IDs,
1862 * under assumption that they were already resolved to canonical type IDs and
1863 * are not going to change.
1864 */
btf_hash_array(struct btf_type * t)1865 static long btf_hash_array(struct btf_type *t)
1866 {
1867 const struct btf_array *info = btf_array(t);
1868 long h = btf_hash_common(t);
1869
1870 h = hash_combine(h, info->type);
1871 h = hash_combine(h, info->index_type);
1872 h = hash_combine(h, info->nelems);
1873 return h;
1874 }
1875
1876 /*
1877 * Check exact equality of two ARRAYs, taking into account referenced
1878 * type IDs, under assumption that they were already resolved to canonical
1879 * type IDs and are not going to change.
1880 * This function is called during reference types deduplication to compare
1881 * ARRAY to potential canonical representative.
1882 */
btf_equal_array(struct btf_type * t1,struct btf_type * t2)1883 static bool btf_equal_array(struct btf_type *t1, struct btf_type *t2)
1884 {
1885 const struct btf_array *info1, *info2;
1886
1887 if (!btf_equal_common(t1, t2))
1888 return false;
1889
1890 info1 = btf_array(t1);
1891 info2 = btf_array(t2);
1892 return info1->type == info2->type &&
1893 info1->index_type == info2->index_type &&
1894 info1->nelems == info2->nelems;
1895 }
1896
1897 /*
1898 * Check structural compatibility of two ARRAYs, ignoring referenced type
1899 * IDs. This check is performed during type graph equivalence check and
1900 * referenced types equivalence is checked separately.
1901 */
btf_compat_array(struct btf_type * t1,struct btf_type * t2)1902 static bool btf_compat_array(struct btf_type *t1, struct btf_type *t2)
1903 {
1904 if (!btf_equal_common(t1, t2))
1905 return false;
1906
1907 return btf_array(t1)->nelems == btf_array(t2)->nelems;
1908 }
1909
1910 /*
1911 * Calculate type signature hash of FUNC_PROTO, including referenced type IDs,
1912 * under assumption that they were already resolved to canonical type IDs and
1913 * are not going to change.
1914 */
btf_hash_fnproto(struct btf_type * t)1915 static long btf_hash_fnproto(struct btf_type *t)
1916 {
1917 const struct btf_param *member = btf_params(t);
1918 __u16 vlen = btf_vlen(t);
1919 long h = btf_hash_common(t);
1920 int i;
1921
1922 for (i = 0; i < vlen; i++) {
1923 h = hash_combine(h, member->name_off);
1924 h = hash_combine(h, member->type);
1925 member++;
1926 }
1927 return h;
1928 }
1929
1930 /*
1931 * Check exact equality of two FUNC_PROTOs, taking into account referenced
1932 * type IDs, under assumption that they were already resolved to canonical
1933 * type IDs and are not going to change.
1934 * This function is called during reference types deduplication to compare
1935 * FUNC_PROTO to potential canonical representative.
1936 */
btf_equal_fnproto(struct btf_type * t1,struct btf_type * t2)1937 static bool btf_equal_fnproto(struct btf_type *t1, struct btf_type *t2)
1938 {
1939 const struct btf_param *m1, *m2;
1940 __u16 vlen;
1941 int i;
1942
1943 if (!btf_equal_common(t1, t2))
1944 return false;
1945
1946 vlen = btf_vlen(t1);
1947 m1 = btf_params(t1);
1948 m2 = btf_params(t2);
1949 for (i = 0; i < vlen; i++) {
1950 if (m1->name_off != m2->name_off || m1->type != m2->type)
1951 return false;
1952 m1++;
1953 m2++;
1954 }
1955 return true;
1956 }
1957
1958 /*
1959 * Check structural compatibility of two FUNC_PROTOs, ignoring referenced type
1960 * IDs. This check is performed during type graph equivalence check and
1961 * referenced types equivalence is checked separately.
1962 */
btf_compat_fnproto(struct btf_type * t1,struct btf_type * t2)1963 static bool btf_compat_fnproto(struct btf_type *t1, struct btf_type *t2)
1964 {
1965 const struct btf_param *m1, *m2;
1966 __u16 vlen;
1967 int i;
1968
1969 /* skip return type ID */
1970 if (t1->name_off != t2->name_off || t1->info != t2->info)
1971 return false;
1972
1973 vlen = btf_vlen(t1);
1974 m1 = btf_params(t1);
1975 m2 = btf_params(t2);
1976 for (i = 0; i < vlen; i++) {
1977 if (m1->name_off != m2->name_off)
1978 return false;
1979 m1++;
1980 m2++;
1981 }
1982 return true;
1983 }
1984
1985 /*
1986 * Deduplicate primitive types, that can't reference other types, by calculating
1987 * their type signature hash and comparing them with any possible canonical
1988 * candidate. If no canonical candidate matches, type itself is marked as
1989 * canonical and is added into `btf_dedup->dedup_table` as another candidate.
1990 */
btf_dedup_prim_type(struct btf_dedup * d,__u32 type_id)1991 static int btf_dedup_prim_type(struct btf_dedup *d, __u32 type_id)
1992 {
1993 struct btf_type *t = d->btf->types[type_id];
1994 struct hashmap_entry *hash_entry;
1995 struct btf_type *cand;
1996 /* if we don't find equivalent type, then we are canonical */
1997 __u32 new_id = type_id;
1998 __u32 cand_id;
1999 long h;
2000
2001 switch (btf_kind(t)) {
2002 case BTF_KIND_CONST:
2003 case BTF_KIND_VOLATILE:
2004 case BTF_KIND_RESTRICT:
2005 case BTF_KIND_PTR:
2006 case BTF_KIND_TYPEDEF:
2007 case BTF_KIND_ARRAY:
2008 case BTF_KIND_STRUCT:
2009 case BTF_KIND_UNION:
2010 case BTF_KIND_FUNC:
2011 case BTF_KIND_FUNC_PROTO:
2012 case BTF_KIND_VAR:
2013 case BTF_KIND_DATASEC:
2014 return 0;
2015
2016 case BTF_KIND_INT:
2017 h = btf_hash_int(t);
2018 for_each_dedup_cand(d, hash_entry, h) {
2019 cand_id = (__u32)(long)hash_entry->value;
2020 cand = d->btf->types[cand_id];
2021 if (btf_equal_int(t, cand)) {
2022 new_id = cand_id;
2023 break;
2024 }
2025 }
2026 break;
2027
2028 case BTF_KIND_ENUM:
2029 h = btf_hash_enum(t);
2030 for_each_dedup_cand(d, hash_entry, h) {
2031 cand_id = (__u32)(long)hash_entry->value;
2032 cand = d->btf->types[cand_id];
2033 if (btf_equal_enum(t, cand)) {
2034 new_id = cand_id;
2035 break;
2036 }
2037 if (d->opts.dont_resolve_fwds)
2038 continue;
2039 if (btf_compat_enum(t, cand)) {
2040 if (btf_is_enum_fwd(t)) {
2041 /* resolve fwd to full enum */
2042 new_id = cand_id;
2043 break;
2044 }
2045 /* resolve canonical enum fwd to full enum */
2046 d->map[cand_id] = type_id;
2047 }
2048 }
2049 break;
2050
2051 case BTF_KIND_FWD:
2052 h = btf_hash_common(t);
2053 for_each_dedup_cand(d, hash_entry, h) {
2054 cand_id = (__u32)(long)hash_entry->value;
2055 cand = d->btf->types[cand_id];
2056 if (btf_equal_common(t, cand)) {
2057 new_id = cand_id;
2058 break;
2059 }
2060 }
2061 break;
2062
2063 default:
2064 return -EINVAL;
2065 }
2066
2067 d->map[type_id] = new_id;
2068 if (type_id == new_id && btf_dedup_table_add(d, h, type_id))
2069 return -ENOMEM;
2070
2071 return 0;
2072 }
2073
btf_dedup_prim_types(struct btf_dedup * d)2074 static int btf_dedup_prim_types(struct btf_dedup *d)
2075 {
2076 int i, err;
2077
2078 for (i = 1; i <= d->btf->nr_types; i++) {
2079 err = btf_dedup_prim_type(d, i);
2080 if (err)
2081 return err;
2082 }
2083 return 0;
2084 }
2085
2086 /*
2087 * Check whether type is already mapped into canonical one (could be to itself).
2088 */
is_type_mapped(struct btf_dedup * d,uint32_t type_id)2089 static inline bool is_type_mapped(struct btf_dedup *d, uint32_t type_id)
2090 {
2091 return d->map[type_id] <= BTF_MAX_NR_TYPES;
2092 }
2093
2094 /*
2095 * Resolve type ID into its canonical type ID, if any; otherwise return original
2096 * type ID. If type is FWD and is resolved into STRUCT/UNION already, follow
2097 * STRUCT/UNION link and resolve it into canonical type ID as well.
2098 */
resolve_type_id(struct btf_dedup * d,__u32 type_id)2099 static inline __u32 resolve_type_id(struct btf_dedup *d, __u32 type_id)
2100 {
2101 while (is_type_mapped(d, type_id) && d->map[type_id] != type_id)
2102 type_id = d->map[type_id];
2103 return type_id;
2104 }
2105
2106 /*
2107 * Resolve FWD to underlying STRUCT/UNION, if any; otherwise return original
2108 * type ID.
2109 */
resolve_fwd_id(struct btf_dedup * d,uint32_t type_id)2110 static uint32_t resolve_fwd_id(struct btf_dedup *d, uint32_t type_id)
2111 {
2112 __u32 orig_type_id = type_id;
2113
2114 if (!btf_is_fwd(d->btf->types[type_id]))
2115 return type_id;
2116
2117 while (is_type_mapped(d, type_id) && d->map[type_id] != type_id)
2118 type_id = d->map[type_id];
2119
2120 if (!btf_is_fwd(d->btf->types[type_id]))
2121 return type_id;
2122
2123 return orig_type_id;
2124 }
2125
2126
btf_fwd_kind(struct btf_type * t)2127 static inline __u16 btf_fwd_kind(struct btf_type *t)
2128 {
2129 return btf_kflag(t) ? BTF_KIND_UNION : BTF_KIND_STRUCT;
2130 }
2131
2132 /*
2133 * Check equivalence of BTF type graph formed by candidate struct/union (we'll
2134 * call it "candidate graph" in this description for brevity) to a type graph
2135 * formed by (potential) canonical struct/union ("canonical graph" for brevity
2136 * here, though keep in mind that not all types in canonical graph are
2137 * necessarily canonical representatives themselves, some of them might be
2138 * duplicates or its uniqueness might not have been established yet).
2139 * Returns:
2140 * - >0, if type graphs are equivalent;
2141 * - 0, if not equivalent;
2142 * - <0, on error.
2143 *
2144 * Algorithm performs side-by-side DFS traversal of both type graphs and checks
2145 * equivalence of BTF types at each step. If at any point BTF types in candidate
2146 * and canonical graphs are not compatible structurally, whole graphs are
2147 * incompatible. If types are structurally equivalent (i.e., all information
2148 * except referenced type IDs is exactly the same), a mapping from `canon_id` to
2149 * a `cand_id` is recored in hypothetical mapping (`btf_dedup->hypot_map`).
2150 * If a type references other types, then those referenced types are checked
2151 * for equivalence recursively.
2152 *
2153 * During DFS traversal, if we find that for current `canon_id` type we
2154 * already have some mapping in hypothetical map, we check for two possible
2155 * situations:
2156 * - `canon_id` is mapped to exactly the same type as `cand_id`. This will
2157 * happen when type graphs have cycles. In this case we assume those two
2158 * types are equivalent.
2159 * - `canon_id` is mapped to different type. This is contradiction in our
2160 * hypothetical mapping, because same graph in canonical graph corresponds
2161 * to two different types in candidate graph, which for equivalent type
2162 * graphs shouldn't happen. This condition terminates equivalence check
2163 * with negative result.
2164 *
2165 * If type graphs traversal exhausts types to check and find no contradiction,
2166 * then type graphs are equivalent.
2167 *
2168 * When checking types for equivalence, there is one special case: FWD types.
2169 * If FWD type resolution is allowed and one of the types (either from canonical
2170 * or candidate graph) is FWD and other is STRUCT/UNION (depending on FWD's kind
2171 * flag) and their names match, hypothetical mapping is updated to point from
2172 * FWD to STRUCT/UNION. If graphs will be determined as equivalent successfully,
2173 * this mapping will be used to record FWD -> STRUCT/UNION mapping permanently.
2174 *
2175 * Technically, this could lead to incorrect FWD to STRUCT/UNION resolution,
2176 * if there are two exactly named (or anonymous) structs/unions that are
2177 * compatible structurally, one of which has FWD field, while other is concrete
2178 * STRUCT/UNION, but according to C sources they are different structs/unions
2179 * that are referencing different types with the same name. This is extremely
2180 * unlikely to happen, but btf_dedup API allows to disable FWD resolution if
2181 * this logic is causing problems.
2182 *
2183 * Doing FWD resolution means that both candidate and/or canonical graphs can
2184 * consists of portions of the graph that come from multiple compilation units.
2185 * This is due to the fact that types within single compilation unit are always
2186 * deduplicated and FWDs are already resolved, if referenced struct/union
2187 * definiton is available. So, if we had unresolved FWD and found corresponding
2188 * STRUCT/UNION, they will be from different compilation units. This
2189 * consequently means that when we "link" FWD to corresponding STRUCT/UNION,
2190 * type graph will likely have at least two different BTF types that describe
2191 * same type (e.g., most probably there will be two different BTF types for the
2192 * same 'int' primitive type) and could even have "overlapping" parts of type
2193 * graph that describe same subset of types.
2194 *
2195 * This in turn means that our assumption that each type in canonical graph
2196 * must correspond to exactly one type in candidate graph might not hold
2197 * anymore and will make it harder to detect contradictions using hypothetical
2198 * map. To handle this problem, we allow to follow FWD -> STRUCT/UNION
2199 * resolution only in canonical graph. FWDs in candidate graphs are never
2200 * resolved. To see why it's OK, let's check all possible situations w.r.t. FWDs
2201 * that can occur:
2202 * - Both types in canonical and candidate graphs are FWDs. If they are
2203 * structurally equivalent, then they can either be both resolved to the
2204 * same STRUCT/UNION or not resolved at all. In both cases they are
2205 * equivalent and there is no need to resolve FWD on candidate side.
2206 * - Both types in canonical and candidate graphs are concrete STRUCT/UNION,
2207 * so nothing to resolve as well, algorithm will check equivalence anyway.
2208 * - Type in canonical graph is FWD, while type in candidate is concrete
2209 * STRUCT/UNION. In this case candidate graph comes from single compilation
2210 * unit, so there is exactly one BTF type for each unique C type. After
2211 * resolving FWD into STRUCT/UNION, there might be more than one BTF type
2212 * in canonical graph mapping to single BTF type in candidate graph, but
2213 * because hypothetical mapping maps from canonical to candidate types, it's
2214 * alright, and we still maintain the property of having single `canon_id`
2215 * mapping to single `cand_id` (there could be two different `canon_id`
2216 * mapped to the same `cand_id`, but it's not contradictory).
2217 * - Type in canonical graph is concrete STRUCT/UNION, while type in candidate
2218 * graph is FWD. In this case we are just going to check compatibility of
2219 * STRUCT/UNION and corresponding FWD, and if they are compatible, we'll
2220 * assume that whatever STRUCT/UNION FWD resolves to must be equivalent to
2221 * a concrete STRUCT/UNION from canonical graph. If the rest of type graphs
2222 * turn out equivalent, we'll re-resolve FWD to concrete STRUCT/UNION from
2223 * canonical graph.
2224 */
btf_dedup_is_equiv(struct btf_dedup * d,__u32 cand_id,__u32 canon_id)2225 static int btf_dedup_is_equiv(struct btf_dedup *d, __u32 cand_id,
2226 __u32 canon_id)
2227 {
2228 struct btf_type *cand_type;
2229 struct btf_type *canon_type;
2230 __u32 hypot_type_id;
2231 __u16 cand_kind;
2232 __u16 canon_kind;
2233 int i, eq;
2234
2235 /* if both resolve to the same canonical, they must be equivalent */
2236 if (resolve_type_id(d, cand_id) == resolve_type_id(d, canon_id))
2237 return 1;
2238
2239 canon_id = resolve_fwd_id(d, canon_id);
2240
2241 hypot_type_id = d->hypot_map[canon_id];
2242 if (hypot_type_id <= BTF_MAX_NR_TYPES)
2243 return hypot_type_id == cand_id;
2244
2245 if (btf_dedup_hypot_map_add(d, canon_id, cand_id))
2246 return -ENOMEM;
2247
2248 cand_type = d->btf->types[cand_id];
2249 canon_type = d->btf->types[canon_id];
2250 cand_kind = btf_kind(cand_type);
2251 canon_kind = btf_kind(canon_type);
2252
2253 if (cand_type->name_off != canon_type->name_off)
2254 return 0;
2255
2256 /* FWD <--> STRUCT/UNION equivalence check, if enabled */
2257 if (!d->opts.dont_resolve_fwds
2258 && (cand_kind == BTF_KIND_FWD || canon_kind == BTF_KIND_FWD)
2259 && cand_kind != canon_kind) {
2260 __u16 real_kind;
2261 __u16 fwd_kind;
2262
2263 if (cand_kind == BTF_KIND_FWD) {
2264 real_kind = canon_kind;
2265 fwd_kind = btf_fwd_kind(cand_type);
2266 } else {
2267 real_kind = cand_kind;
2268 fwd_kind = btf_fwd_kind(canon_type);
2269 }
2270 return fwd_kind == real_kind;
2271 }
2272
2273 if (cand_kind != canon_kind)
2274 return 0;
2275
2276 switch (cand_kind) {
2277 case BTF_KIND_INT:
2278 return btf_equal_int(cand_type, canon_type);
2279
2280 case BTF_KIND_ENUM:
2281 if (d->opts.dont_resolve_fwds)
2282 return btf_equal_enum(cand_type, canon_type);
2283 else
2284 return btf_compat_enum(cand_type, canon_type);
2285
2286 case BTF_KIND_FWD:
2287 return btf_equal_common(cand_type, canon_type);
2288
2289 case BTF_KIND_CONST:
2290 case BTF_KIND_VOLATILE:
2291 case BTF_KIND_RESTRICT:
2292 case BTF_KIND_PTR:
2293 case BTF_KIND_TYPEDEF:
2294 case BTF_KIND_FUNC:
2295 if (cand_type->info != canon_type->info)
2296 return 0;
2297 return btf_dedup_is_equiv(d, cand_type->type, canon_type->type);
2298
2299 case BTF_KIND_ARRAY: {
2300 const struct btf_array *cand_arr, *canon_arr;
2301
2302 if (!btf_compat_array(cand_type, canon_type))
2303 return 0;
2304 cand_arr = btf_array(cand_type);
2305 canon_arr = btf_array(canon_type);
2306 eq = btf_dedup_is_equiv(d,
2307 cand_arr->index_type, canon_arr->index_type);
2308 if (eq <= 0)
2309 return eq;
2310 return btf_dedup_is_equiv(d, cand_arr->type, canon_arr->type);
2311 }
2312
2313 case BTF_KIND_STRUCT:
2314 case BTF_KIND_UNION: {
2315 const struct btf_member *cand_m, *canon_m;
2316 __u16 vlen;
2317
2318 if (!btf_shallow_equal_struct(cand_type, canon_type))
2319 return 0;
2320 vlen = btf_vlen(cand_type);
2321 cand_m = btf_members(cand_type);
2322 canon_m = btf_members(canon_type);
2323 for (i = 0; i < vlen; i++) {
2324 eq = btf_dedup_is_equiv(d, cand_m->type, canon_m->type);
2325 if (eq <= 0)
2326 return eq;
2327 cand_m++;
2328 canon_m++;
2329 }
2330
2331 return 1;
2332 }
2333
2334 case BTF_KIND_FUNC_PROTO: {
2335 const struct btf_param *cand_p, *canon_p;
2336 __u16 vlen;
2337
2338 if (!btf_compat_fnproto(cand_type, canon_type))
2339 return 0;
2340 eq = btf_dedup_is_equiv(d, cand_type->type, canon_type->type);
2341 if (eq <= 0)
2342 return eq;
2343 vlen = btf_vlen(cand_type);
2344 cand_p = btf_params(cand_type);
2345 canon_p = btf_params(canon_type);
2346 for (i = 0; i < vlen; i++) {
2347 eq = btf_dedup_is_equiv(d, cand_p->type, canon_p->type);
2348 if (eq <= 0)
2349 return eq;
2350 cand_p++;
2351 canon_p++;
2352 }
2353 return 1;
2354 }
2355
2356 default:
2357 return -EINVAL;
2358 }
2359 return 0;
2360 }
2361
2362 /*
2363 * Use hypothetical mapping, produced by successful type graph equivalence
2364 * check, to augment existing struct/union canonical mapping, where possible.
2365 *
2366 * If BTF_KIND_FWD resolution is allowed, this mapping is also used to record
2367 * FWD -> STRUCT/UNION correspondence as well. FWD resolution is bidirectional:
2368 * it doesn't matter if FWD type was part of canonical graph or candidate one,
2369 * we are recording the mapping anyway. As opposed to carefulness required
2370 * for struct/union correspondence mapping (described below), for FWD resolution
2371 * it's not important, as by the time that FWD type (reference type) will be
2372 * deduplicated all structs/unions will be deduped already anyway.
2373 *
2374 * Recording STRUCT/UNION mapping is purely a performance optimization and is
2375 * not required for correctness. It needs to be done carefully to ensure that
2376 * struct/union from candidate's type graph is not mapped into corresponding
2377 * struct/union from canonical type graph that itself hasn't been resolved into
2378 * canonical representative. The only guarantee we have is that canonical
2379 * struct/union was determined as canonical and that won't change. But any
2380 * types referenced through that struct/union fields could have been not yet
2381 * resolved, so in case like that it's too early to establish any kind of
2382 * correspondence between structs/unions.
2383 *
2384 * No canonical correspondence is derived for primitive types (they are already
2385 * deduplicated completely already anyway) or reference types (they rely on
2386 * stability of struct/union canonical relationship for equivalence checks).
2387 */
btf_dedup_merge_hypot_map(struct btf_dedup * d)2388 static void btf_dedup_merge_hypot_map(struct btf_dedup *d)
2389 {
2390 __u32 cand_type_id, targ_type_id;
2391 __u16 t_kind, c_kind;
2392 __u32 t_id, c_id;
2393 int i;
2394
2395 for (i = 0; i < d->hypot_cnt; i++) {
2396 cand_type_id = d->hypot_list[i];
2397 targ_type_id = d->hypot_map[cand_type_id];
2398 t_id = resolve_type_id(d, targ_type_id);
2399 c_id = resolve_type_id(d, cand_type_id);
2400 t_kind = btf_kind(d->btf->types[t_id]);
2401 c_kind = btf_kind(d->btf->types[c_id]);
2402 /*
2403 * Resolve FWD into STRUCT/UNION.
2404 * It's ok to resolve FWD into STRUCT/UNION that's not yet
2405 * mapped to canonical representative (as opposed to
2406 * STRUCT/UNION <--> STRUCT/UNION mapping logic below), because
2407 * eventually that struct is going to be mapped and all resolved
2408 * FWDs will automatically resolve to correct canonical
2409 * representative. This will happen before ref type deduping,
2410 * which critically depends on stability of these mapping. This
2411 * stability is not a requirement for STRUCT/UNION equivalence
2412 * checks, though.
2413 */
2414 if (t_kind != BTF_KIND_FWD && c_kind == BTF_KIND_FWD)
2415 d->map[c_id] = t_id;
2416 else if (t_kind == BTF_KIND_FWD && c_kind != BTF_KIND_FWD)
2417 d->map[t_id] = c_id;
2418
2419 if ((t_kind == BTF_KIND_STRUCT || t_kind == BTF_KIND_UNION) &&
2420 c_kind != BTF_KIND_FWD &&
2421 is_type_mapped(d, c_id) &&
2422 !is_type_mapped(d, t_id)) {
2423 /*
2424 * as a perf optimization, we can map struct/union
2425 * that's part of type graph we just verified for
2426 * equivalence. We can do that for struct/union that has
2427 * canonical representative only, though.
2428 */
2429 d->map[t_id] = c_id;
2430 }
2431 }
2432 }
2433
2434 /*
2435 * Deduplicate struct/union types.
2436 *
2437 * For each struct/union type its type signature hash is calculated, taking
2438 * into account type's name, size, number, order and names of fields, but
2439 * ignoring type ID's referenced from fields, because they might not be deduped
2440 * completely until after reference types deduplication phase. This type hash
2441 * is used to iterate over all potential canonical types, sharing same hash.
2442 * For each canonical candidate we check whether type graphs that they form
2443 * (through referenced types in fields and so on) are equivalent using algorithm
2444 * implemented in `btf_dedup_is_equiv`. If such equivalence is found and
2445 * BTF_KIND_FWD resolution is allowed, then hypothetical mapping
2446 * (btf_dedup->hypot_map) produced by aforementioned type graph equivalence
2447 * algorithm is used to record FWD -> STRUCT/UNION mapping. It's also used to
2448 * potentially map other structs/unions to their canonical representatives,
2449 * if such relationship hasn't yet been established. This speeds up algorithm
2450 * by eliminating some of the duplicate work.
2451 *
2452 * If no matching canonical representative was found, struct/union is marked
2453 * as canonical for itself and is added into btf_dedup->dedup_table hash map
2454 * for further look ups.
2455 */
btf_dedup_struct_type(struct btf_dedup * d,__u32 type_id)2456 static int btf_dedup_struct_type(struct btf_dedup *d, __u32 type_id)
2457 {
2458 struct btf_type *cand_type, *t;
2459 struct hashmap_entry *hash_entry;
2460 /* if we don't find equivalent type, then we are canonical */
2461 __u32 new_id = type_id;
2462 __u16 kind;
2463 long h;
2464
2465 /* already deduped or is in process of deduping (loop detected) */
2466 if (d->map[type_id] <= BTF_MAX_NR_TYPES)
2467 return 0;
2468
2469 t = d->btf->types[type_id];
2470 kind = btf_kind(t);
2471
2472 if (kind != BTF_KIND_STRUCT && kind != BTF_KIND_UNION)
2473 return 0;
2474
2475 h = btf_hash_struct(t);
2476 for_each_dedup_cand(d, hash_entry, h) {
2477 __u32 cand_id = (__u32)(long)hash_entry->value;
2478 int eq;
2479
2480 /*
2481 * Even though btf_dedup_is_equiv() checks for
2482 * btf_shallow_equal_struct() internally when checking two
2483 * structs (unions) for equivalence, we need to guard here
2484 * from picking matching FWD type as a dedup candidate.
2485 * This can happen due to hash collision. In such case just
2486 * relying on btf_dedup_is_equiv() would lead to potentially
2487 * creating a loop (FWD -> STRUCT and STRUCT -> FWD), because
2488 * FWD and compatible STRUCT/UNION are considered equivalent.
2489 */
2490 cand_type = d->btf->types[cand_id];
2491 if (!btf_shallow_equal_struct(t, cand_type))
2492 continue;
2493
2494 btf_dedup_clear_hypot_map(d);
2495 eq = btf_dedup_is_equiv(d, type_id, cand_id);
2496 if (eq < 0)
2497 return eq;
2498 if (!eq)
2499 continue;
2500 new_id = cand_id;
2501 btf_dedup_merge_hypot_map(d);
2502 break;
2503 }
2504
2505 d->map[type_id] = new_id;
2506 if (type_id == new_id && btf_dedup_table_add(d, h, type_id))
2507 return -ENOMEM;
2508
2509 return 0;
2510 }
2511
btf_dedup_struct_types(struct btf_dedup * d)2512 static int btf_dedup_struct_types(struct btf_dedup *d)
2513 {
2514 int i, err;
2515
2516 for (i = 1; i <= d->btf->nr_types; i++) {
2517 err = btf_dedup_struct_type(d, i);
2518 if (err)
2519 return err;
2520 }
2521 return 0;
2522 }
2523
2524 /*
2525 * Deduplicate reference type.
2526 *
2527 * Once all primitive and struct/union types got deduplicated, we can easily
2528 * deduplicate all other (reference) BTF types. This is done in two steps:
2529 *
2530 * 1. Resolve all referenced type IDs into their canonical type IDs. This
2531 * resolution can be done either immediately for primitive or struct/union types
2532 * (because they were deduped in previous two phases) or recursively for
2533 * reference types. Recursion will always terminate at either primitive or
2534 * struct/union type, at which point we can "unwind" chain of reference types
2535 * one by one. There is no danger of encountering cycles because in C type
2536 * system the only way to form type cycle is through struct/union, so any chain
2537 * of reference types, even those taking part in a type cycle, will inevitably
2538 * reach struct/union at some point.
2539 *
2540 * 2. Once all referenced type IDs are resolved into canonical ones, BTF type
2541 * becomes "stable", in the sense that no further deduplication will cause
2542 * any changes to it. With that, it's now possible to calculate type's signature
2543 * hash (this time taking into account referenced type IDs) and loop over all
2544 * potential canonical representatives. If no match was found, current type
2545 * will become canonical representative of itself and will be added into
2546 * btf_dedup->dedup_table as another possible canonical representative.
2547 */
btf_dedup_ref_type(struct btf_dedup * d,__u32 type_id)2548 static int btf_dedup_ref_type(struct btf_dedup *d, __u32 type_id)
2549 {
2550 struct hashmap_entry *hash_entry;
2551 __u32 new_id = type_id, cand_id;
2552 struct btf_type *t, *cand;
2553 /* if we don't find equivalent type, then we are representative type */
2554 int ref_type_id;
2555 long h;
2556
2557 if (d->map[type_id] == BTF_IN_PROGRESS_ID)
2558 return -ELOOP;
2559 if (d->map[type_id] <= BTF_MAX_NR_TYPES)
2560 return resolve_type_id(d, type_id);
2561
2562 t = d->btf->types[type_id];
2563 d->map[type_id] = BTF_IN_PROGRESS_ID;
2564
2565 switch (btf_kind(t)) {
2566 case BTF_KIND_CONST:
2567 case BTF_KIND_VOLATILE:
2568 case BTF_KIND_RESTRICT:
2569 case BTF_KIND_PTR:
2570 case BTF_KIND_TYPEDEF:
2571 case BTF_KIND_FUNC:
2572 ref_type_id = btf_dedup_ref_type(d, t->type);
2573 if (ref_type_id < 0)
2574 return ref_type_id;
2575 t->type = ref_type_id;
2576
2577 h = btf_hash_common(t);
2578 for_each_dedup_cand(d, hash_entry, h) {
2579 cand_id = (__u32)(long)hash_entry->value;
2580 cand = d->btf->types[cand_id];
2581 if (btf_equal_common(t, cand)) {
2582 new_id = cand_id;
2583 break;
2584 }
2585 }
2586 break;
2587
2588 case BTF_KIND_ARRAY: {
2589 struct btf_array *info = btf_array(t);
2590
2591 ref_type_id = btf_dedup_ref_type(d, info->type);
2592 if (ref_type_id < 0)
2593 return ref_type_id;
2594 info->type = ref_type_id;
2595
2596 ref_type_id = btf_dedup_ref_type(d, info->index_type);
2597 if (ref_type_id < 0)
2598 return ref_type_id;
2599 info->index_type = ref_type_id;
2600
2601 h = btf_hash_array(t);
2602 for_each_dedup_cand(d, hash_entry, h) {
2603 cand_id = (__u32)(long)hash_entry->value;
2604 cand = d->btf->types[cand_id];
2605 if (btf_equal_array(t, cand)) {
2606 new_id = cand_id;
2607 break;
2608 }
2609 }
2610 break;
2611 }
2612
2613 case BTF_KIND_FUNC_PROTO: {
2614 struct btf_param *param;
2615 __u16 vlen;
2616 int i;
2617
2618 ref_type_id = btf_dedup_ref_type(d, t->type);
2619 if (ref_type_id < 0)
2620 return ref_type_id;
2621 t->type = ref_type_id;
2622
2623 vlen = btf_vlen(t);
2624 param = btf_params(t);
2625 for (i = 0; i < vlen; i++) {
2626 ref_type_id = btf_dedup_ref_type(d, param->type);
2627 if (ref_type_id < 0)
2628 return ref_type_id;
2629 param->type = ref_type_id;
2630 param++;
2631 }
2632
2633 h = btf_hash_fnproto(t);
2634 for_each_dedup_cand(d, hash_entry, h) {
2635 cand_id = (__u32)(long)hash_entry->value;
2636 cand = d->btf->types[cand_id];
2637 if (btf_equal_fnproto(t, cand)) {
2638 new_id = cand_id;
2639 break;
2640 }
2641 }
2642 break;
2643 }
2644
2645 default:
2646 return -EINVAL;
2647 }
2648
2649 d->map[type_id] = new_id;
2650 if (type_id == new_id && btf_dedup_table_add(d, h, type_id))
2651 return -ENOMEM;
2652
2653 return new_id;
2654 }
2655
btf_dedup_ref_types(struct btf_dedup * d)2656 static int btf_dedup_ref_types(struct btf_dedup *d)
2657 {
2658 int i, err;
2659
2660 for (i = 1; i <= d->btf->nr_types; i++) {
2661 err = btf_dedup_ref_type(d, i);
2662 if (err < 0)
2663 return err;
2664 }
2665 /* we won't need d->dedup_table anymore */
2666 hashmap__free(d->dedup_table);
2667 d->dedup_table = NULL;
2668 return 0;
2669 }
2670
2671 /*
2672 * Compact types.
2673 *
2674 * After we established for each type its corresponding canonical representative
2675 * type, we now can eliminate types that are not canonical and leave only
2676 * canonical ones layed out sequentially in memory by copying them over
2677 * duplicates. During compaction btf_dedup->hypot_map array is reused to store
2678 * a map from original type ID to a new compacted type ID, which will be used
2679 * during next phase to "fix up" type IDs, referenced from struct/union and
2680 * reference types.
2681 */
btf_dedup_compact_types(struct btf_dedup * d)2682 static int btf_dedup_compact_types(struct btf_dedup *d)
2683 {
2684 struct btf_type **new_types;
2685 __u32 next_type_id = 1;
2686 char *types_start, *p;
2687 int i, len;
2688
2689 /* we are going to reuse hypot_map to store compaction remapping */
2690 d->hypot_map[0] = 0;
2691 for (i = 1; i <= d->btf->nr_types; i++)
2692 d->hypot_map[i] = BTF_UNPROCESSED_ID;
2693
2694 types_start = d->btf->nohdr_data + d->btf->hdr->type_off;
2695 p = types_start;
2696
2697 for (i = 1; i <= d->btf->nr_types; i++) {
2698 if (d->map[i] != i)
2699 continue;
2700
2701 len = btf_type_size(d->btf->types[i]);
2702 if (len < 0)
2703 return len;
2704
2705 memmove(p, d->btf->types[i], len);
2706 d->hypot_map[i] = next_type_id;
2707 d->btf->types[next_type_id] = (struct btf_type *)p;
2708 p += len;
2709 next_type_id++;
2710 }
2711
2712 /* shrink struct btf's internal types index and update btf_header */
2713 d->btf->nr_types = next_type_id - 1;
2714 d->btf->types_size = d->btf->nr_types;
2715 d->btf->hdr->type_len = p - types_start;
2716 new_types = realloc(d->btf->types,
2717 (1 + d->btf->nr_types) * sizeof(struct btf_type *));
2718 if (!new_types)
2719 return -ENOMEM;
2720 d->btf->types = new_types;
2721
2722 /* make sure string section follows type information without gaps */
2723 d->btf->hdr->str_off = p - (char *)d->btf->nohdr_data;
2724 memmove(p, d->btf->strings, d->btf->hdr->str_len);
2725 d->btf->strings = p;
2726 p += d->btf->hdr->str_len;
2727
2728 d->btf->data_size = p - (char *)d->btf->data;
2729 return 0;
2730 }
2731
2732 /*
2733 * Figure out final (deduplicated and compacted) type ID for provided original
2734 * `type_id` by first resolving it into corresponding canonical type ID and
2735 * then mapping it to a deduplicated type ID, stored in btf_dedup->hypot_map,
2736 * which is populated during compaction phase.
2737 */
btf_dedup_remap_type_id(struct btf_dedup * d,__u32 type_id)2738 static int btf_dedup_remap_type_id(struct btf_dedup *d, __u32 type_id)
2739 {
2740 __u32 resolved_type_id, new_type_id;
2741
2742 resolved_type_id = resolve_type_id(d, type_id);
2743 new_type_id = d->hypot_map[resolved_type_id];
2744 if (new_type_id > BTF_MAX_NR_TYPES)
2745 return -EINVAL;
2746 return new_type_id;
2747 }
2748
2749 /*
2750 * Remap referenced type IDs into deduped type IDs.
2751 *
2752 * After BTF types are deduplicated and compacted, their final type IDs may
2753 * differ from original ones. The map from original to a corresponding
2754 * deduped type ID is stored in btf_dedup->hypot_map and is populated during
2755 * compaction phase. During remapping phase we are rewriting all type IDs
2756 * referenced from any BTF type (e.g., struct fields, func proto args, etc) to
2757 * their final deduped type IDs.
2758 */
btf_dedup_remap_type(struct btf_dedup * d,__u32 type_id)2759 static int btf_dedup_remap_type(struct btf_dedup *d, __u32 type_id)
2760 {
2761 struct btf_type *t = d->btf->types[type_id];
2762 int i, r;
2763
2764 switch (btf_kind(t)) {
2765 case BTF_KIND_INT:
2766 case BTF_KIND_ENUM:
2767 break;
2768
2769 case BTF_KIND_FWD:
2770 case BTF_KIND_CONST:
2771 case BTF_KIND_VOLATILE:
2772 case BTF_KIND_RESTRICT:
2773 case BTF_KIND_PTR:
2774 case BTF_KIND_TYPEDEF:
2775 case BTF_KIND_FUNC:
2776 case BTF_KIND_VAR:
2777 r = btf_dedup_remap_type_id(d, t->type);
2778 if (r < 0)
2779 return r;
2780 t->type = r;
2781 break;
2782
2783 case BTF_KIND_ARRAY: {
2784 struct btf_array *arr_info = btf_array(t);
2785
2786 r = btf_dedup_remap_type_id(d, arr_info->type);
2787 if (r < 0)
2788 return r;
2789 arr_info->type = r;
2790 r = btf_dedup_remap_type_id(d, arr_info->index_type);
2791 if (r < 0)
2792 return r;
2793 arr_info->index_type = r;
2794 break;
2795 }
2796
2797 case BTF_KIND_STRUCT:
2798 case BTF_KIND_UNION: {
2799 struct btf_member *member = btf_members(t);
2800 __u16 vlen = btf_vlen(t);
2801
2802 for (i = 0; i < vlen; i++) {
2803 r = btf_dedup_remap_type_id(d, member->type);
2804 if (r < 0)
2805 return r;
2806 member->type = r;
2807 member++;
2808 }
2809 break;
2810 }
2811
2812 case BTF_KIND_FUNC_PROTO: {
2813 struct btf_param *param = btf_params(t);
2814 __u16 vlen = btf_vlen(t);
2815
2816 r = btf_dedup_remap_type_id(d, t->type);
2817 if (r < 0)
2818 return r;
2819 t->type = r;
2820
2821 for (i = 0; i < vlen; i++) {
2822 r = btf_dedup_remap_type_id(d, param->type);
2823 if (r < 0)
2824 return r;
2825 param->type = r;
2826 param++;
2827 }
2828 break;
2829 }
2830
2831 case BTF_KIND_DATASEC: {
2832 struct btf_var_secinfo *var = btf_var_secinfos(t);
2833 __u16 vlen = btf_vlen(t);
2834
2835 for (i = 0; i < vlen; i++) {
2836 r = btf_dedup_remap_type_id(d, var->type);
2837 if (r < 0)
2838 return r;
2839 var->type = r;
2840 var++;
2841 }
2842 break;
2843 }
2844
2845 default:
2846 return -EINVAL;
2847 }
2848
2849 return 0;
2850 }
2851
btf_dedup_remap_types(struct btf_dedup * d)2852 static int btf_dedup_remap_types(struct btf_dedup *d)
2853 {
2854 int i, r;
2855
2856 for (i = 1; i <= d->btf->nr_types; i++) {
2857 r = btf_dedup_remap_type(d, i);
2858 if (r < 0)
2859 return r;
2860 }
2861 return 0;
2862 }
2863