?  search:
summary | log | graphiclog1 | graphiclog2 | commit | commitdiff | tree | refs | edit | fork
blame | history | raw | HEAD
Merge tag 'trace-printf-v6.13' of git://git.kernel.org/pub/scm/linux/kernel/git/trace...
[drm/drm-misc.git] / tools / lib / bpf / linker.c
blobcf71d149fe26a216ab96a9f8a97e5bb6ec8cd2ea
1 // SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
2 /*
3 * BPF static linker
4 *
5 * Copyright (c) 2021 Facebook
6 */
7 #include <stdbool.h>
8 #include <stddef.h>
9 #include <stdio.h>
10 #include <stdlib.h>
11 #include <string.h>
12 #include <unistd.h>
13 #include <errno.h>
14 #include <linux/err.h>
15 #include <linux/btf.h>
16 #include <elf.h>
17 #include <libelf.h>
18 #include <fcntl.h>
19 #include "libbpf.h"
20 #include "btf.h"
21 #include "libbpf_internal.h"
22 #include "strset.h"
23 #include "str_error.h"
24
25 #define BTF_EXTERN_SEC ".extern"
26
27 struct src_sec {
28 const char *sec_name;
29 /* positional (not necessarily ELF) index in an array of sections */
30 int id;
31 /* positional (not necessarily ELF) index of a matching section in a final object file */
32 int dst_id;
33 /* section data offset in a matching output section */
34 int dst_off;
35 /* whether section is omitted from the final ELF file */
36 bool skipped;
37 /* whether section is an ephemeral section, not mapped to an ELF section */
38 bool ephemeral;
39
40 /* ELF info */
41 size_t sec_idx;
42 Elf_Scn *scn;
43 Elf64_Shdr *shdr;
44 Elf_Data *data;
45
46 /* corresponding BTF DATASEC type ID */
47 int sec_type_id;
48 };
49
50 struct src_obj {
51 const char *filename;
52 int fd;
53 Elf *elf;
54 /* Section header strings section index */
55 size_t shstrs_sec_idx;
56 /* SYMTAB section index */
57 size_t symtab_sec_idx;
58
59 struct btf *btf;
60 struct btf_ext *btf_ext;
61
62 /* List of sections (including ephemeral). Slot zero is unused. */
63 struct src_sec *secs;
64 int sec_cnt;
65
66 /* mapping of symbol indices from src to dst ELF */
67 int *sym_map;
68 /* mapping from the src BTF type IDs to dst ones */
69 int *btf_type_map;
70 };
71
72 /* single .BTF.ext data section */
73 struct btf_ext_sec_data {
74 size_t rec_cnt;
75 __u32 rec_sz;
76 void *recs;
77 };
78
79 struct glob_sym {
80 /* ELF symbol index */
81 int sym_idx;
82 /* associated section id for .ksyms, .kconfig, etc, but not .extern */
83 int sec_id;
84 /* extern name offset in STRTAB */
85 int name_off;
86 /* optional associated BTF type ID */
87 int btf_id;
88 /* BTF type ID to which VAR/FUNC type is pointing to; used for
89 * rewriting types when extern VAR/FUNC is resolved to a concrete
90 * definition
91 */
92 int underlying_btf_id;
93 /* sec_var index in the corresponding dst_sec, if exists */
94 int var_idx;
95
96 /* extern or resolved/global symbol */
97 bool is_extern;
98 /* weak or strong symbol, never goes back from strong to weak */
99 bool is_weak;
100 };
101
102 struct dst_sec {
103 char *sec_name;
104 /* positional (not necessarily ELF) index in an array of sections */
105 int id;
106
107 bool ephemeral;
108
109 /* ELF info */
110 size_t sec_idx;
111 Elf_Scn *scn;
112 Elf64_Shdr *shdr;
113 Elf_Data *data;
114
115 /* final output section size */
116 int sec_sz;
117 /* final output contents of the section */
118 void *raw_data;
119
120 /* corresponding STT_SECTION symbol index in SYMTAB */
121 int sec_sym_idx;
122
123 /* section's DATASEC variable info, emitted on BTF finalization */
124 bool has_btf;
125 int sec_var_cnt;
126 struct btf_var_secinfo *sec_vars;
127
128 /* section's .BTF.ext data */
129 struct btf_ext_sec_data func_info;
130 struct btf_ext_sec_data line_info;
131 struct btf_ext_sec_data core_relo_info;
132 };
133
134 struct bpf_linker {
135 char *filename;
136 int fd;
137 Elf *elf;
138 Elf64_Ehdr *elf_hdr;
139 bool swapped_endian;
140
141 /* Output sections metadata */
142 struct dst_sec *secs;
143 int sec_cnt;
144
145 struct strset *strtab_strs; /* STRTAB unique strings */
146 size_t strtab_sec_idx; /* STRTAB section index */
147 size_t symtab_sec_idx; /* SYMTAB section index */
148
149 struct btf *btf;
150 struct btf_ext *btf_ext;
151
152 /* global (including extern) ELF symbols */
153 int glob_sym_cnt;
154 struct glob_sym *glob_syms;
155 };
156
157 #define pr_warn_elf(fmt, ...) \
158 libbpf_print(LIBBPF_WARN, "libbpf: " fmt ": %s\n", ##__VA_ARGS__, elf_errmsg(-1))
159
160 static int init_output_elf(struct bpf_linker *linker, const char *file);
161
162 static int linker_load_obj_file(struct bpf_linker *linker, const char *filename,
163 const struct bpf_linker_file_opts *opts,
164 struct src_obj *obj);
165 static int linker_sanity_check_elf(struct src_obj *obj);
166 static int linker_sanity_check_elf_symtab(struct src_obj *obj, struct src_sec *sec);
167 static int linker_sanity_check_elf_relos(struct src_obj *obj, struct src_sec *sec);
168 static int linker_sanity_check_btf(struct src_obj *obj);
169 static int linker_sanity_check_btf_ext(struct src_obj *obj);
170 static int linker_fixup_btf(struct src_obj *obj);
171 static int linker_append_sec_data(struct bpf_linker *linker, struct src_obj *obj);
172 static int linker_append_elf_syms(struct bpf_linker *linker, struct src_obj *obj);
173 static int linker_append_elf_sym(struct bpf_linker *linker, struct src_obj *obj,
174 Elf64_Sym *sym, const char *sym_name, int src_sym_idx);
175 static int linker_append_elf_relos(struct bpf_linker *linker, struct src_obj *obj);
176 static int linker_append_btf(struct bpf_linker *linker, struct src_obj *obj);
177 static int linker_append_btf_ext(struct bpf_linker *linker, struct src_obj *obj);
178
179 static int finalize_btf(struct bpf_linker *linker);
180 static int finalize_btf_ext(struct bpf_linker *linker);
181
182 void bpf_linker__free(struct bpf_linker *linker)
183 {
184 int i;
185
186 if (!linker)
187 return;
188
189 free(linker->filename);
190
191 if (linker->elf)
192 elf_end(linker->elf);
193
194 if (linker->fd >= 0)
195 close(linker->fd);
196
197 strset__free(linker->strtab_strs);
198
199 btf__free(linker->btf);
200 btf_ext__free(linker->btf_ext);
201
202 for (i = 1; i < linker->sec_cnt; i++) {
203 struct dst_sec *sec = &linker->secs[i];
204
205 free(sec->sec_name);
206 free(sec->raw_data);
207 free(sec->sec_vars);
208
209 free(sec->func_info.recs);
210 free(sec->line_info.recs);
211 free(sec->core_relo_info.recs);
212 }
213 free(linker->secs);
214
215 free(linker->glob_syms);
216 free(linker);
217 }
218
219 struct bpf_linker *bpf_linker__new(const char *filename, struct bpf_linker_opts *opts)
220 {
221 struct bpf_linker *linker;
222 int err;
223
224 if (!OPTS_VALID(opts, bpf_linker_opts))
225 return errno = EINVAL, NULL;
226
227 if (elf_version(EV_CURRENT) == EV_NONE) {
228 pr_warn_elf("libelf initialization failed");
229 return errno = EINVAL, NULL;
230 }
231
232 linker = calloc(1, sizeof(*linker));
233 if (!linker)
234 return errno = ENOMEM, NULL;
235
236 linker->fd = -1;
237
238 err = init_output_elf(linker, filename);
239 if (err)
240 goto err_out;
241
242 return linker;
243
244 err_out:
245 bpf_linker__free(linker);
246 return errno = -err, NULL;
247 }
248
249 static struct dst_sec *add_dst_sec(struct bpf_linker *linker, const char *sec_name)
250 {
251 struct dst_sec *secs = linker->secs, *sec;
252 size_t new_cnt = linker->sec_cnt ? linker->sec_cnt + 1 : 2;
253
254 secs = libbpf_reallocarray(secs, new_cnt, sizeof(*secs));
255 if (!secs)
256 return NULL;
257
258 /* zero out newly allocated memory */
259 memset(secs + linker->sec_cnt, 0, (new_cnt - linker->sec_cnt) * sizeof(*secs));
260
261 linker->secs = secs;
262 linker->sec_cnt = new_cnt;
263
264 sec = &linker->secs[new_cnt - 1];
265 sec->id = new_cnt - 1;
266 sec->sec_name = strdup(sec_name);
267 if (!sec->sec_name)
268 return NULL;
269
270 return sec;
271 }
272
273 static Elf64_Sym *add_new_sym(struct bpf_linker *linker, size_t *sym_idx)
274 {
275 struct dst_sec *symtab = &linker->secs[linker->symtab_sec_idx];
276 Elf64_Sym *syms, *sym;
277 size_t sym_cnt = symtab->sec_sz / sizeof(*sym);
278
279 syms = libbpf_reallocarray(symtab->raw_data, sym_cnt + 1, sizeof(*sym));
280 if (!syms)
281 return NULL;
282
283 sym = &syms[sym_cnt];
284 memset(sym, 0, sizeof(*sym));
285
286 symtab->raw_data = syms;
287 symtab->sec_sz += sizeof(*sym);
288 symtab->shdr->sh_size += sizeof(*sym);
289 symtab->data->d_size += sizeof(*sym);
290
291 if (sym_idx)
292 *sym_idx = sym_cnt;
293
294 return sym;
295 }
296
297 static int init_output_elf(struct bpf_linker *linker, const char *file)
298 {
299 int err, str_off;
300 Elf64_Sym *init_sym;
301 struct dst_sec *sec;
302
303 linker->filename = strdup(file);
304 if (!linker->filename)
305 return -ENOMEM;
306
307 linker->fd = open(file, O_WRONLY | O_CREAT | O_TRUNC | O_CLOEXEC, 0644);
308 if (linker->fd < 0) {
309 err = -errno;
310 pr_warn("failed to create '%s': %s\n", file, errstr(err));
311 return err;
312 }
313
314 linker->elf = elf_begin(linker->fd, ELF_C_WRITE, NULL);
315 if (!linker->elf) {
316 pr_warn_elf("failed to create ELF object");
317 return -EINVAL;
318 }
319
320 /* ELF header */
321 linker->elf_hdr = elf64_newehdr(linker->elf);
322 if (!linker->elf_hdr) {
323 pr_warn_elf("failed to create ELF header");
324 return -EINVAL;
325 }
326
327 linker->elf_hdr->e_machine = EM_BPF;
328 linker->elf_hdr->e_type = ET_REL;
329 /* Set unknown ELF endianness, assign later from input files */
330 linker->elf_hdr->e_ident[EI_DATA] = ELFDATANONE;
331
332 /* STRTAB */
333 /* initialize strset with an empty string to conform to ELF */
334 linker->strtab_strs = strset__new(INT_MAX, "", sizeof(""));
335 if (libbpf_get_error(linker->strtab_strs))
336 return libbpf_get_error(linker->strtab_strs);
337
338 sec = add_dst_sec(linker, ".strtab");
339 if (!sec)
340 return -ENOMEM;
341
342 sec->scn = elf_newscn(linker->elf);
343 if (!sec->scn) {
344 pr_warn_elf("failed to create STRTAB section");
345 return -EINVAL;
346 }
347
348 sec->shdr = elf64_getshdr(sec->scn);
349 if (!sec->shdr)
350 return -EINVAL;
351
352 sec->data = elf_newdata(sec->scn);
353 if (!sec->data) {
354 pr_warn_elf("failed to create STRTAB data");
355 return -EINVAL;
356 }
357
358 str_off = strset__add_str(linker->strtab_strs, sec->sec_name);
359 if (str_off < 0)
360 return str_off;
361
362 sec->sec_idx = elf_ndxscn(sec->scn);
363 linker->elf_hdr->e_shstrndx = sec->sec_idx;
364 linker->strtab_sec_idx = sec->sec_idx;
365
366 sec->shdr->sh_name = str_off;
367 sec->shdr->sh_type = SHT_STRTAB;
368 sec->shdr->sh_flags = SHF_STRINGS;
369 sec->shdr->sh_offset = 0;
370 sec->shdr->sh_link = 0;
371 sec->shdr->sh_info = 0;
372 sec->shdr->sh_addralign = 1;
373 sec->shdr->sh_size = sec->sec_sz = 0;
374 sec->shdr->sh_entsize = 0;
375
376 /* SYMTAB */
377 sec = add_dst_sec(linker, ".symtab");
378 if (!sec)
379 return -ENOMEM;
380
381 sec->scn = elf_newscn(linker->elf);
382 if (!sec->scn) {
383 pr_warn_elf("failed to create SYMTAB section");
384 return -EINVAL;
385 }
386
387 sec->shdr = elf64_getshdr(sec->scn);
388 if (!sec->shdr)
389 return -EINVAL;
390
391 sec->data = elf_newdata(sec->scn);
392 if (!sec->data) {
393 pr_warn_elf("failed to create SYMTAB data");
394 return -EINVAL;
395 }
396 /* Ensure libelf translates byte-order of symbol records */
397 sec->data->d_type = ELF_T_SYM;
398
399 str_off = strset__add_str(linker->strtab_strs, sec->sec_name);
400 if (str_off < 0)
401 return str_off;
402
403 sec->sec_idx = elf_ndxscn(sec->scn);
404 linker->symtab_sec_idx = sec->sec_idx;
405
406 sec->shdr->sh_name = str_off;
407 sec->shdr->sh_type = SHT_SYMTAB;
408 sec->shdr->sh_flags = 0;
409 sec->shdr->sh_offset = 0;
410 sec->shdr->sh_link = linker->strtab_sec_idx;
411 /* sh_info should be one greater than the index of the last local
412 * symbol (i.e., binding is STB_LOCAL). But why and who cares?
413 */
414 sec->shdr->sh_info = 0;
415 sec->shdr->sh_addralign = 8;
416 sec->shdr->sh_entsize = sizeof(Elf64_Sym);
417
418 /* .BTF */
419 linker->btf = btf__new_empty();
420 err = libbpf_get_error(linker->btf);
421 if (err)
422 return err;
423
424 /* add the special all-zero symbol */
425 init_sym = add_new_sym(linker, NULL);
426 if (!init_sym)
427 return -EINVAL;
428
429 init_sym->st_name = 0;
430 init_sym->st_info = 0;
431 init_sym->st_other = 0;
432 init_sym->st_shndx = SHN_UNDEF;
433 init_sym->st_value = 0;
434 init_sym->st_size = 0;
435
436 return 0;
437 }
438
439 int bpf_linker__add_file(struct bpf_linker *linker, const char *filename,
440 const struct bpf_linker_file_opts *opts)
441 {
442 struct src_obj obj = {};
443 int err = 0;
444
445 if (!OPTS_VALID(opts, bpf_linker_file_opts))
446 return libbpf_err(-EINVAL);
447
448 if (!linker->elf)
449 return libbpf_err(-EINVAL);
450
451 err = err ?: linker_load_obj_file(linker, filename, opts, &obj);
452 err = err ?: linker_append_sec_data(linker, &obj);
453 err = err ?: linker_append_elf_syms(linker, &obj);
454 err = err ?: linker_append_elf_relos(linker, &obj);
455 err = err ?: linker_append_btf(linker, &obj);
456 err = err ?: linker_append_btf_ext(linker, &obj);
457
458 /* free up src_obj resources */
459 free(obj.btf_type_map);
460 btf__free(obj.btf);
461 btf_ext__free(obj.btf_ext);
462 free(obj.secs);
463 free(obj.sym_map);
464 if (obj.elf)
465 elf_end(obj.elf);
466 if (obj.fd >= 0)
467 close(obj.fd);
468
469 return libbpf_err(err);
470 }
471
472 static bool is_dwarf_sec_name(const char *name)
473 {
474 /* approximation, but the actual list is too long */
475 return strncmp(name, ".debug_", sizeof(".debug_") - 1) == 0;
476 }
477
478 static bool is_ignored_sec(struct src_sec *sec)
479 {
480 Elf64_Shdr *shdr = sec->shdr;
481 const char *name = sec->sec_name;
482
483 /* no special handling of .strtab */
484 if (shdr->sh_type == SHT_STRTAB)
485 return true;
486
487 /* ignore .llvm_addrsig section as well */
488 if (shdr->sh_type == SHT_LLVM_ADDRSIG)
489 return true;
490
491 /* no subprograms will lead to an empty .text section, ignore it */
492 if (shdr->sh_type == SHT_PROGBITS && shdr->sh_size == 0 &&
493 strcmp(sec->sec_name, ".text") == 0)
494 return true;
495
496 /* DWARF sections */
497 if (is_dwarf_sec_name(sec->sec_name))
498 return true;
499
500 if (strncmp(name, ".rel", sizeof(".rel") - 1) == 0) {
501 name += sizeof(".rel") - 1;
502 /* DWARF section relocations */
503 if (is_dwarf_sec_name(name))
504 return true;
505
506 /* .BTF and .BTF.ext don't need relocations */
507 if (strcmp(name, BTF_ELF_SEC) == 0 ||
508 strcmp(name, BTF_EXT_ELF_SEC) == 0)
509 return true;
510 }
511
512 return false;
513 }
514
515 static struct src_sec *add_src_sec(struct src_obj *obj, const char *sec_name)
516 {
517 struct src_sec *secs = obj->secs, *sec;
518 size_t new_cnt = obj->sec_cnt ? obj->sec_cnt + 1 : 2;
519
520 secs = libbpf_reallocarray(secs, new_cnt, sizeof(*secs));
521 if (!secs)
522 return NULL;
523
524 /* zero out newly allocated memory */
525 memset(secs + obj->sec_cnt, 0, (new_cnt - obj->sec_cnt) * sizeof(*secs));
526
527 obj->secs = secs;
528 obj->sec_cnt = new_cnt;
529
530 sec = &obj->secs[new_cnt - 1];
531 sec->id = new_cnt - 1;
532 sec->sec_name = sec_name;
533
534 return sec;
535 }
536
537 static int linker_load_obj_file(struct bpf_linker *linker, const char *filename,
538 const struct bpf_linker_file_opts *opts,
539 struct src_obj *obj)
540 {
541 int err = 0;
542 Elf_Scn *scn;
543 Elf_Data *data;
544 Elf64_Ehdr *ehdr;
545 Elf64_Shdr *shdr;
546 struct src_sec *sec;
547 unsigned char obj_byteorder;
548 unsigned char link_byteorder = linker->elf_hdr->e_ident[EI_DATA];
549 #if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
550 const unsigned char host_byteorder = ELFDATA2LSB;
551 #elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
552 const unsigned char host_byteorder = ELFDATA2MSB;
553 #else
554 #error "Unknown __BYTE_ORDER__"
555 #endif
556
557 pr_debug("linker: adding object file '%s'...\n", filename);
558
559 obj->filename = filename;
560
561 obj->fd = open(filename, O_RDONLY | O_CLOEXEC);
562 if (obj->fd < 0) {
563 err = -errno;
564 pr_warn("failed to open file '%s': %s\n", filename, errstr(err));
565 return err;
566 }
567 obj->elf = elf_begin(obj->fd, ELF_C_READ_MMAP, NULL);
568 if (!obj->elf) {
569 err = -errno;
570 pr_warn_elf("failed to parse ELF file '%s'", filename);
571 return err;
572 }
573
574 /* Sanity check ELF file high-level properties */
575 ehdr = elf64_getehdr(obj->elf);
576 if (!ehdr) {
577 err = -errno;
578 pr_warn_elf("failed to get ELF header for %s", filename);
579 return err;
580 }
581
582 /* Linker output endianness set by first input object */
583 obj_byteorder = ehdr->e_ident[EI_DATA];
584 if (obj_byteorder != ELFDATA2LSB && obj_byteorder != ELFDATA2MSB) {
585 err = -EOPNOTSUPP;
586 pr_warn("unknown byte order of ELF file %s\n", filename);
587 return err;
588 }
589 if (link_byteorder == ELFDATANONE) {
590 linker->elf_hdr->e_ident[EI_DATA] = obj_byteorder;
591 linker->swapped_endian = obj_byteorder != host_byteorder;
592 pr_debug("linker: set %s-endian output byte order\n",
593 obj_byteorder == ELFDATA2MSB ? "big" : "little");
594 } else if (link_byteorder != obj_byteorder) {
595 err = -EOPNOTSUPP;
596 pr_warn("byte order mismatch with ELF file %s\n", filename);
597 return err;
598 }
599
600 if (ehdr->e_type != ET_REL
601 || ehdr->e_machine != EM_BPF
602 || ehdr->e_ident[EI_CLASS] != ELFCLASS64) {
603 err = -EOPNOTSUPP;
604 pr_warn_elf("unsupported kind of ELF file %s", filename);
605 return err;
606 }
607
608 if (elf_getshdrstrndx(obj->elf, &obj->shstrs_sec_idx)) {
609 err = -errno;
610 pr_warn_elf("failed to get SHSTRTAB section index for %s", filename);
611 return err;
612 }
613
614 scn = NULL;
615 while ((scn = elf_nextscn(obj->elf, scn)) != NULL) {
616 size_t sec_idx = elf_ndxscn(scn);
617 const char *sec_name;
618
619 shdr = elf64_getshdr(scn);
620 if (!shdr) {
621 err = -errno;
622 pr_warn_elf("failed to get section #%zu header for %s",
623 sec_idx, filename);
624 return err;
625 }
626
627 sec_name = elf_strptr(obj->elf, obj->shstrs_sec_idx, shdr->sh_name);
628 if (!sec_name) {
629 err = -errno;
630 pr_warn_elf("failed to get section #%zu name for %s",
631 sec_idx, filename);
632 return err;
633 }
634
635 data = elf_getdata(scn, 0);
636 if (!data) {
637 err = -errno;
638 pr_warn_elf("failed to get section #%zu (%s) data from %s",
639 sec_idx, sec_name, filename);
640 return err;
641 }
642
643 sec = add_src_sec(obj, sec_name);
644 if (!sec)
645 return -ENOMEM;
646
647 sec->scn = scn;
648 sec->shdr = shdr;
649 sec->data = data;
650 sec->sec_idx = elf_ndxscn(scn);
651
652 if (is_ignored_sec(sec)) {
653 sec->skipped = true;
654 continue;
655 }
656
657 switch (shdr->sh_type) {
658 case SHT_SYMTAB:
659 if (obj->symtab_sec_idx) {
660 err = -EOPNOTSUPP;
661 pr_warn("multiple SYMTAB sections found, not supported\n");
662 return err;
663 }
664 obj->symtab_sec_idx = sec_idx;
665 break;
666 case SHT_STRTAB:
667 /* we'll construct our own string table */
668 break;
669 case SHT_PROGBITS:
670 if (strcmp(sec_name, BTF_ELF_SEC) == 0) {
671 obj->btf = btf__new(data->d_buf, shdr->sh_size);
672 err = libbpf_get_error(obj->btf);
673 if (err) {
674 pr_warn("failed to parse .BTF from %s: %s\n",
675 filename, errstr(err));
676 return err;
677 }
678 sec->skipped = true;
679 continue;
680 }
681 if (strcmp(sec_name, BTF_EXT_ELF_SEC) == 0) {
682 obj->btf_ext = btf_ext__new(data->d_buf, shdr->sh_size);
683 err = libbpf_get_error(obj->btf_ext);
684 if (err) {
685 pr_warn("failed to parse .BTF.ext from '%s': %s\n",
686 filename, errstr(err));
687 return err;
688 }
689 sec->skipped = true;
690 continue;
691 }
692
693 /* data & code */
694 break;
695 case SHT_NOBITS:
696 /* BSS */
697 break;
698 case SHT_REL:
699 /* relocations */
700 break;
701 default:
702 pr_warn("unrecognized section #%zu (%s) in %s\n",
703 sec_idx, sec_name, filename);
704 err = -EINVAL;
705 return err;
706 }
707 }
708
709 err = err ?: linker_sanity_check_elf(obj);
710 err = err ?: linker_sanity_check_btf(obj);
711 err = err ?: linker_sanity_check_btf_ext(obj);
712 err = err ?: linker_fixup_btf(obj);
713
714 return err;
715 }
716
717 static int linker_sanity_check_elf(struct src_obj *obj)
718 {
719 struct src_sec *sec;
720 int i, err;
721
722 if (!obj->symtab_sec_idx) {
723 pr_warn("ELF is missing SYMTAB section in %s\n", obj->filename);
724 return -EINVAL;
725 }
726 if (!obj->shstrs_sec_idx) {
727 pr_warn("ELF is missing section headers STRTAB section in %s\n", obj->filename);
728 return -EINVAL;
729 }
730
731 for (i = 1; i < obj->sec_cnt; i++) {
732 sec = &obj->secs[i];
733
734 if (sec->sec_name[0] == '\0') {
735 pr_warn("ELF section #%zu has empty name in %s\n", sec->sec_idx, obj->filename);
736 return -EINVAL;
737 }
738
739 if (is_dwarf_sec_name(sec->sec_name))
740 continue;
741
742 if (sec->shdr->sh_addralign && !is_pow_of_2(sec->shdr->sh_addralign)) {
743 pr_warn("ELF section #%zu alignment %llu is non pow-of-2 alignment in %s\n",
744 sec->sec_idx, (long long unsigned)sec->shdr->sh_addralign,
745 obj->filename);
746 return -EINVAL;
747 }
748 if (sec->shdr->sh_addralign != sec->data->d_align) {
749 pr_warn("ELF section #%zu has inconsistent alignment addr=%llu != d=%llu in %s\n",
750 sec->sec_idx, (long long unsigned)sec->shdr->sh_addralign,
751 (long long unsigned)sec->data->d_align, obj->filename);
752 return -EINVAL;
753 }
754
755 if (sec->shdr->sh_size != sec->data->d_size) {
756 pr_warn("ELF section #%zu has inconsistent section size sh=%llu != d=%llu in %s\n",
757 sec->sec_idx, (long long unsigned)sec->shdr->sh_size,
758 (long long unsigned)sec->data->d_size, obj->filename);
759 return -EINVAL;
760 }
761
762 switch (sec->shdr->sh_type) {
763 case SHT_SYMTAB:
764 err = linker_sanity_check_elf_symtab(obj, sec);
765 if (err)
766 return err;
767 break;
768 case SHT_STRTAB:
769 break;
770 case SHT_PROGBITS:
771 if (sec->shdr->sh_flags & SHF_EXECINSTR) {
772 if (sec->shdr->sh_size % sizeof(struct bpf_insn) != 0) {
773 pr_warn("ELF section #%zu has unexpected size alignment %llu in %s\n",
774 sec->sec_idx, (long long unsigned)sec->shdr->sh_size,
775 obj->filename);
776 return -EINVAL;
777 }
778 }
779 break;
780 case SHT_NOBITS:
781 break;
782 case SHT_REL:
783 err = linker_sanity_check_elf_relos(obj, sec);
784 if (err)
785 return err;
786 break;
787 case SHT_LLVM_ADDRSIG:
788 break;
789 default:
790 pr_warn("ELF section #%zu (%s) has unrecognized type %zu in %s\n",
791 sec->sec_idx, sec->sec_name, (size_t)sec->shdr->sh_type, obj->filename);
792 return -EINVAL;
793 }
794 }
795
796 return 0;
797 }
798
799 static int linker_sanity_check_elf_symtab(struct src_obj *obj, struct src_sec *sec)
800 {
801 struct src_sec *link_sec;
802 Elf64_Sym *sym;
803 int i, n;
804
805 if (sec->shdr->sh_entsize != sizeof(Elf64_Sym))
806 return -EINVAL;
807 if (sec->shdr->sh_size % sec->shdr->sh_entsize != 0)
808 return -EINVAL;
809
810 if (!sec->shdr->sh_link || sec->shdr->sh_link >= obj->sec_cnt) {
811 pr_warn("ELF SYMTAB section #%zu points to missing STRTAB section #%zu in %s\n",
812 sec->sec_idx, (size_t)sec->shdr->sh_link, obj->filename);
813 return -EINVAL;
814 }
815 link_sec = &obj->secs[sec->shdr->sh_link];
816 if (link_sec->shdr->sh_type != SHT_STRTAB) {
817 pr_warn("ELF SYMTAB section #%zu points to invalid STRTAB section #%zu in %s\n",
818 sec->sec_idx, (size_t)sec->shdr->sh_link, obj->filename);
819 return -EINVAL;
820 }
821
822 n = sec->shdr->sh_size / sec->shdr->sh_entsize;
823 sym = sec->data->d_buf;
824 for (i = 0; i < n; i++, sym++) {
825 int sym_type = ELF64_ST_TYPE(sym->st_info);
826 int sym_bind = ELF64_ST_BIND(sym->st_info);
827 int sym_vis = ELF64_ST_VISIBILITY(sym->st_other);
828
829 if (i == 0) {
830 if (sym->st_name != 0 || sym->st_info != 0
831 || sym->st_other != 0 || sym->st_shndx != 0
832 || sym->st_value != 0 || sym->st_size != 0) {
833 pr_warn("ELF sym #0 is invalid in %s\n", obj->filename);
834 return -EINVAL;
835 }
836 continue;
837 }
838 if (sym_bind != STB_LOCAL && sym_bind != STB_GLOBAL && sym_bind != STB_WEAK) {
839 pr_warn("ELF sym #%d in section #%zu has unsupported symbol binding %d\n",
840 i, sec->sec_idx, sym_bind);
841 return -EINVAL;
842 }
843 if (sym_vis != STV_DEFAULT && sym_vis != STV_HIDDEN) {
844 pr_warn("ELF sym #%d in section #%zu has unsupported symbol visibility %d\n",
845 i, sec->sec_idx, sym_vis);
846 return -EINVAL;
847 }
848 if (sym->st_shndx == 0) {
849 if (sym_type != STT_NOTYPE || sym_bind == STB_LOCAL
850 || sym->st_value != 0 || sym->st_size != 0) {
851 pr_warn("ELF sym #%d is invalid extern symbol in %s\n",
852 i, obj->filename);
853
854 return -EINVAL;
855 }
856 continue;
857 }
858 if (sym->st_shndx < SHN_LORESERVE && sym->st_shndx >= obj->sec_cnt) {
859 pr_warn("ELF sym #%d in section #%zu points to missing section #%zu in %s\n",
860 i, sec->sec_idx, (size_t)sym->st_shndx, obj->filename);
861 return -EINVAL;
862 }
863 if (sym_type == STT_SECTION) {
864 if (sym->st_value != 0)
865 return -EINVAL;
866 continue;
867 }
868 }
869
870 return 0;
871 }
872
873 static int linker_sanity_check_elf_relos(struct src_obj *obj, struct src_sec *sec)
874 {
875 struct src_sec *link_sec, *sym_sec;
876 Elf64_Rel *relo;
877 int i, n;
878
879 if (sec->shdr->sh_entsize != sizeof(Elf64_Rel))
880 return -EINVAL;
881 if (sec->shdr->sh_size % sec->shdr->sh_entsize != 0)
882 return -EINVAL;
883
884 /* SHT_REL's sh_link should point to SYMTAB */
885 if (sec->shdr->sh_link != obj->symtab_sec_idx) {
886 pr_warn("ELF relo section #%zu points to invalid SYMTAB section #%zu in %s\n",
887 sec->sec_idx, (size_t)sec->shdr->sh_link, obj->filename);
888 return -EINVAL;
889 }
890
891 /* SHT_REL's sh_info points to relocated section */
892 if (!sec->shdr->sh_info || sec->shdr->sh_info >= obj->sec_cnt) {
893 pr_warn("ELF relo section #%zu points to missing section #%zu in %s\n",
894 sec->sec_idx, (size_t)sec->shdr->sh_info, obj->filename);
895 return -EINVAL;
896 }
897 link_sec = &obj->secs[sec->shdr->sh_info];
898
899 /* .rel<secname> -> <secname> pattern is followed */
900 if (strncmp(sec->sec_name, ".rel", sizeof(".rel") - 1) != 0
901 || strcmp(sec->sec_name + sizeof(".rel") - 1, link_sec->sec_name) != 0) {
902 pr_warn("ELF relo section #%zu name has invalid name in %s\n",
903 sec->sec_idx, obj->filename);
904 return -EINVAL;
905 }
906
907 /* don't further validate relocations for ignored sections */
908 if (link_sec->skipped)
909 return 0;
910
911 /* relocatable section is data or instructions */
912 if (link_sec->shdr->sh_type != SHT_PROGBITS && link_sec->shdr->sh_type != SHT_NOBITS) {
913 pr_warn("ELF relo section #%zu points to invalid section #%zu in %s\n",
914 sec->sec_idx, (size_t)sec->shdr->sh_info, obj->filename);
915 return -EINVAL;
916 }
917
918 /* check sanity of each relocation */
919 n = sec->shdr->sh_size / sec->shdr->sh_entsize;
920 relo = sec->data->d_buf;
921 sym_sec = &obj->secs[obj->symtab_sec_idx];
922 for (i = 0; i < n; i++, relo++) {
923 size_t sym_idx = ELF64_R_SYM(relo->r_info);
924 size_t sym_type = ELF64_R_TYPE(relo->r_info);
925
926 if (sym_type != R_BPF_64_64 && sym_type != R_BPF_64_32 &&
927 sym_type != R_BPF_64_ABS64 && sym_type != R_BPF_64_ABS32) {
928 pr_warn("ELF relo #%d in section #%zu has unexpected type %zu in %s\n",
929 i, sec->sec_idx, sym_type, obj->filename);
930 return -EINVAL;
931 }
932
933 if (!sym_idx || sym_idx * sizeof(Elf64_Sym) >= sym_sec->shdr->sh_size) {
934 pr_warn("ELF relo #%d in section #%zu points to invalid symbol #%zu in %s\n",
935 i, sec->sec_idx, sym_idx, obj->filename);
936 return -EINVAL;
937 }
938
939 if (link_sec->shdr->sh_flags & SHF_EXECINSTR) {
940 if (relo->r_offset % sizeof(struct bpf_insn) != 0) {
941 pr_warn("ELF relo #%d in section #%zu points to missing symbol #%zu in %s\n",
942 i, sec->sec_idx, sym_idx, obj->filename);
943 return -EINVAL;
944 }
945 }
946 }
947
948 return 0;
949 }
950
951 static int check_btf_type_id(__u32 *type_id, void *ctx)
952 {
953 struct btf *btf = ctx;
954
955 if (*type_id >= btf__type_cnt(btf))
956 return -EINVAL;
957
958 return 0;
959 }
960
961 static int check_btf_str_off(__u32 *str_off, void *ctx)
962 {
963 struct btf *btf = ctx;
964 const char *s;
965
966 s = btf__str_by_offset(btf, *str_off);
967
968 if (!s)
969 return -EINVAL;
970
971 return 0;
972 }
973
974 static int linker_sanity_check_btf(struct src_obj *obj)
975 {
976 struct btf_type *t;
977 int i, n, err;
978
979 if (!obj->btf)
980 return 0;
981
982 n = btf__type_cnt(obj->btf);
983 for (i = 1; i < n; i++) {
984 struct btf_field_iter it;
985 __u32 *type_id, *str_off;
986
987 t = btf_type_by_id(obj->btf, i);
988
989 err = btf_field_iter_init(&it, t, BTF_FIELD_ITER_IDS);
990 if (err)
991 return err;
992 while ((type_id = btf_field_iter_next(&it))) {
993 if (*type_id >= n)
994 return -EINVAL;
995 }
996
997 err = btf_field_iter_init(&it, t, BTF_FIELD_ITER_STRS);
998 if (err)
999 return err;
1000 while ((str_off = btf_field_iter_next(&it))) {
1001 if (!btf__str_by_offset(obj->btf, *str_off))
1002 return -EINVAL;
1003 }
1004 }
1005
1006 return 0;
1007 }
1008
1009 static int linker_sanity_check_btf_ext(struct src_obj *obj)
1010 {
1011 int err = 0;
1012
1013 if (!obj->btf_ext)
1014 return 0;
1015
1016 /* can't use .BTF.ext without .BTF */
1017 if (!obj->btf)
1018 return -EINVAL;
1019
1020 err = err ?: btf_ext_visit_type_ids(obj->btf_ext, check_btf_type_id, obj->btf);
1021 err = err ?: btf_ext_visit_str_offs(obj->btf_ext, check_btf_str_off, obj->btf);
1022 if (err)
1023 return err;
1024
1025 return 0;
1026 }
1027
1028 static int init_sec(struct bpf_linker *linker, struct dst_sec *dst_sec, struct src_sec *src_sec)
1029 {
1030 Elf_Scn *scn;
1031 Elf_Data *data;
1032 Elf64_Shdr *shdr;
1033 int name_off;
1034
1035 dst_sec->sec_sz = 0;
1036 dst_sec->sec_idx = 0;
1037 dst_sec->ephemeral = src_sec->ephemeral;
1038
1039 /* ephemeral sections are just thin section shells lacking most parts */
1040 if (src_sec->ephemeral)
1041 return 0;
1042
1043 scn = elf_newscn(linker->elf);
1044 if (!scn)
1045 return -ENOMEM;
1046 data = elf_newdata(scn);
1047 if (!data)
1048 return -ENOMEM;
1049 shdr = elf64_getshdr(scn);
1050 if (!shdr)
1051 return -ENOMEM;
1052
1053 dst_sec->scn = scn;
1054 dst_sec->shdr = shdr;
1055 dst_sec->data = data;
1056 dst_sec->sec_idx = elf_ndxscn(scn);
1057
1058 name_off = strset__add_str(linker->strtab_strs, src_sec->sec_name);
1059 if (name_off < 0)
1060 return name_off;
1061
1062 shdr->sh_name = name_off;
1063 shdr->sh_type = src_sec->shdr->sh_type;
1064 shdr->sh_flags = src_sec->shdr->sh_flags;
1065 shdr->sh_size = 0;
1066 /* sh_link and sh_info have different meaning for different types of
1067 * sections, so we leave it up to the caller code to fill them in, if
1068 * necessary
1069 */
1070 shdr->sh_link = 0;
1071 shdr->sh_info = 0;
1072 shdr->sh_addralign = src_sec->shdr->sh_addralign;
1073 shdr->sh_entsize = src_sec->shdr->sh_entsize;
1074
1075 data->d_type = src_sec->data->d_type;
1076 data->d_size = 0;
1077 data->d_buf = NULL;
1078 data->d_align = src_sec->data->d_align;
1079 data->d_off = 0;
1080
1081 return 0;
1082 }
1083
1084 static struct dst_sec *find_dst_sec_by_name(struct bpf_linker *linker, const char *sec_name)
1085 {
1086 struct dst_sec *sec;
1087 int i;
1088
1089 for (i = 1; i < linker->sec_cnt; i++) {
1090 sec = &linker->secs[i];
1091
1092 if (strcmp(sec->sec_name, sec_name) == 0)
1093 return sec;
1094 }
1095
1096 return NULL;
1097 }
1098
1099 static bool secs_match(struct dst_sec *dst, struct src_sec *src)
1100 {
1101 if (dst->ephemeral || src->ephemeral)
1102 return true;
1103
1104 if (dst->shdr->sh_type != src->shdr->sh_type) {
1105 pr_warn("sec %s types mismatch\n", dst->sec_name);
1106 return false;
1107 }
1108 if (dst->shdr->sh_flags != src->shdr->sh_flags) {
1109 pr_warn("sec %s flags mismatch\n", dst->sec_name);
1110 return false;
1111 }
1112 if (dst->shdr->sh_entsize != src->shdr->sh_entsize) {
1113 pr_warn("sec %s entsize mismatch\n", dst->sec_name);
1114 return false;
1115 }
1116
1117 return true;
1118 }
1119
1120 static bool sec_content_is_same(struct dst_sec *dst_sec, struct src_sec *src_sec)
1121 {
1122 if (dst_sec->sec_sz != src_sec->shdr->sh_size)
1123 return false;
1124 if (memcmp(dst_sec->raw_data, src_sec->data->d_buf, dst_sec->sec_sz) != 0)
1125 return false;
1126 return true;
1127 }
1128
1129 static bool is_exec_sec(struct dst_sec *sec)
1130 {
1131 if (!sec || sec->ephemeral)
1132 return false;
1133 return (sec->shdr->sh_type == SHT_PROGBITS) &&
1134 (sec->shdr->sh_flags & SHF_EXECINSTR);
1135 }
1136
1137 static void exec_sec_bswap(void *raw_data, int size)
1138 {
1139 const int insn_cnt = size / sizeof(struct bpf_insn);
1140 struct bpf_insn *insn = raw_data;
1141 int i;
1142
1143 for (i = 0; i < insn_cnt; i++, insn++)
1144 bpf_insn_bswap(insn);
1145 }
1146
1147 static int extend_sec(struct bpf_linker *linker, struct dst_sec *dst, struct src_sec *src)
1148 {
1149 void *tmp;
1150 size_t dst_align, src_align;
1151 size_t dst_align_sz, dst_final_sz;
1152 int err;
1153
1154 /* Ephemeral source section doesn't contribute anything to ELF
1155 * section data.
1156 */
1157 if (src->ephemeral)
1158 return 0;
1159
1160 /* Some sections (like .maps) can contain both externs (and thus be
1161 * ephemeral) and non-externs (map definitions). So it's possible that
1162 * it has to be "upgraded" from ephemeral to non-ephemeral when the
1163 * first non-ephemeral entity appears. In such case, we add ELF
1164 * section, data, etc.
1165 */
1166 if (dst->ephemeral) {
1167 err = init_sec(linker, dst, src);
1168 if (err)
1169 return err;
1170 }
1171
1172 dst_align = dst->shdr->sh_addralign;
1173 src_align = src->shdr->sh_addralign;
1174 if (dst_align == 0)
1175 dst_align = 1;
1176 if (dst_align < src_align)
1177 dst_align = src_align;
1178
1179 dst_align_sz = (dst->sec_sz + dst_align - 1) / dst_align * dst_align;
1180
1181 /* no need to re-align final size */
1182 dst_final_sz = dst_align_sz + src->shdr->sh_size;
1183
1184 if (src->shdr->sh_type != SHT_NOBITS) {
1185 tmp = realloc(dst->raw_data, dst_final_sz);
1186 /* If dst_align_sz == 0, realloc() behaves in a special way:
1187 * 1. When dst->raw_data is NULL it returns:
1188 * "either NULL or a pointer suitable to be passed to free()" [1].
1189 * 2. When dst->raw_data is not-NULL it frees dst->raw_data and returns NULL,
1190 * thus invalidating any "pointer suitable to be passed to free()" obtained
1191 * at step (1).
1192 *
1193 * The dst_align_sz > 0 check avoids error exit after (2), otherwise
1194 * dst->raw_data would be freed again in bpf_linker__free().
1195 *
1196 * [1] man 3 realloc
1197 */
1198 if (!tmp && dst_align_sz > 0)
1199 return -ENOMEM;
1200 dst->raw_data = tmp;
1201
1202 /* pad dst section, if it's alignment forced size increase */
1203 memset(dst->raw_data + dst->sec_sz, 0, dst_align_sz - dst->sec_sz);
1204 /* now copy src data at a properly aligned offset */
1205 memcpy(dst->raw_data + dst_align_sz, src->data->d_buf, src->shdr->sh_size);
1206
1207 /* convert added bpf insns to native byte-order */
1208 if (linker->swapped_endian && is_exec_sec(dst))
1209 exec_sec_bswap(dst->raw_data + dst_align_sz, src->shdr->sh_size);
1210 }
1211
1212 dst->sec_sz = dst_final_sz;
1213 dst->shdr->sh_size = dst_final_sz;
1214 dst->data->d_size = dst_final_sz;
1215
1216 dst->shdr->sh_addralign = dst_align;
1217 dst->data->d_align = dst_align;
1218
1219 src->dst_off = dst_align_sz;
1220
1221 return 0;
1222 }
1223
1224 static bool is_data_sec(struct src_sec *sec)
1225 {
1226 if (!sec || sec->skipped)
1227 return false;
1228 /* ephemeral sections are data sections, e.g., .kconfig, .ksyms */
1229 if (sec->ephemeral)
1230 return true;
1231 return sec->shdr->sh_type == SHT_PROGBITS || sec->shdr->sh_type == SHT_NOBITS;
1232 }
1233
1234 static bool is_relo_sec(struct src_sec *sec)
1235 {
1236 if (!sec || sec->skipped || sec->ephemeral)
1237 return false;
1238 return sec->shdr->sh_type == SHT_REL;
1239 }
1240
1241 static int linker_append_sec_data(struct bpf_linker *linker, struct src_obj *obj)
1242 {
1243 int i, err;
1244
1245 for (i = 1; i < obj->sec_cnt; i++) {
1246 struct src_sec *src_sec;
1247 struct dst_sec *dst_sec;
1248
1249 src_sec = &obj->secs[i];
1250 if (!is_data_sec(src_sec))
1251 continue;
1252
1253 dst_sec = find_dst_sec_by_name(linker, src_sec->sec_name);
1254 if (!dst_sec) {
1255 dst_sec = add_dst_sec(linker, src_sec->sec_name);
1256 if (!dst_sec)
1257 return -ENOMEM;
1258 err = init_sec(linker, dst_sec, src_sec);
1259 if (err) {
1260 pr_warn("failed to init section '%s'\n", src_sec->sec_name);
1261 return err;
1262 }
1263 } else {
1264 if (!secs_match(dst_sec, src_sec)) {
1265 pr_warn("ELF sections %s are incompatible\n", src_sec->sec_name);
1266 return -1;
1267 }
1268
1269 /* "license" and "version" sections are deduped */
1270 if (strcmp(src_sec->sec_name, "license") == 0
1271 || strcmp(src_sec->sec_name, "version") == 0) {
1272 if (!sec_content_is_same(dst_sec, src_sec)) {
1273 pr_warn("non-identical contents of section '%s' are not supported\n", src_sec->sec_name);
1274 return -EINVAL;
1275 }
1276 src_sec->skipped = true;
1277 src_sec->dst_id = dst_sec->id;
1278 continue;
1279 }
1280 }
1281
1282 /* record mapped section index */
1283 src_sec->dst_id = dst_sec->id;
1284
1285 err = extend_sec(linker, dst_sec, src_sec);
1286 if (err)
1287 return err;
1288 }
1289
1290 return 0;
1291 }
1292
1293 static int linker_append_elf_syms(struct bpf_linker *linker, struct src_obj *obj)
1294 {
1295 struct src_sec *symtab = &obj->secs[obj->symtab_sec_idx];
1296 Elf64_Sym *sym = symtab->data->d_buf;
1297 int i, n = symtab->shdr->sh_size / symtab->shdr->sh_entsize, err;
1298 int str_sec_idx = symtab->shdr->sh_link;
1299 const char *sym_name;
1300
1301 obj->sym_map = calloc(n + 1, sizeof(*obj->sym_map));
1302 if (!obj->sym_map)
1303 return -ENOMEM;
1304
1305 for (i = 0; i < n; i++, sym++) {
1306 /* We already validated all-zero symbol #0 and we already
1307 * appended it preventively to the final SYMTAB, so skip it.
1308 */
1309 if (i == 0)
1310 continue;
1311
1312 sym_name = elf_strptr(obj->elf, str_sec_idx, sym->st_name);
1313 if (!sym_name) {
1314 pr_warn("can't fetch symbol name for symbol #%d in '%s'\n", i, obj->filename);
1315 return -EINVAL;
1316 }
1317
1318 err = linker_append_elf_sym(linker, obj, sym, sym_name, i);
1319 if (err)
1320 return err;
1321 }
1322
1323 return 0;
1324 }
1325
1326 static Elf64_Sym *get_sym_by_idx(struct bpf_linker *linker, size_t sym_idx)
1327 {
1328 struct dst_sec *symtab = &linker->secs[linker->symtab_sec_idx];
1329 Elf64_Sym *syms = symtab->raw_data;
1330
1331 return &syms[sym_idx];
1332 }
1333
1334 static struct glob_sym *find_glob_sym(struct bpf_linker *linker, const char *sym_name)
1335 {
1336 struct glob_sym *glob_sym;
1337 const char *name;
1338 int i;
1339
1340 for (i = 0; i < linker->glob_sym_cnt; i++) {
1341 glob_sym = &linker->glob_syms[i];
1342 name = strset__data(linker->strtab_strs) + glob_sym->name_off;
1343
1344 if (strcmp(name, sym_name) == 0)
1345 return glob_sym;
1346 }
1347
1348 return NULL;
1349 }
1350
1351 static struct glob_sym *add_glob_sym(struct bpf_linker *linker)
1352 {
1353 struct glob_sym *syms, *sym;
1354
1355 syms = libbpf_reallocarray(linker->glob_syms, linker->glob_sym_cnt + 1,
1356 sizeof(*linker->glob_syms));
1357 if (!syms)
1358 return NULL;
1359
1360 sym = &syms[linker->glob_sym_cnt];
1361 memset(sym, 0, sizeof(*sym));
1362 sym->var_idx = -1;
1363
1364 linker->glob_syms = syms;
1365 linker->glob_sym_cnt++;
1366
1367 return sym;
1368 }
1369
1370 static bool glob_sym_btf_matches(const char *sym_name, bool exact,
1371 const struct btf *btf1, __u32 id1,
1372 const struct btf *btf2, __u32 id2)
1373 {
1374 const struct btf_type *t1, *t2;
1375 bool is_static1, is_static2;
1376 const char *n1, *n2;
1377 int i, n;
1378
1379 recur:
1380 n1 = n2 = NULL;
1381 t1 = skip_mods_and_typedefs(btf1, id1, &id1);
1382 t2 = skip_mods_and_typedefs(btf2, id2, &id2);
1383
1384 /* check if only one side is FWD, otherwise handle with common logic */
1385 if (!exact && btf_is_fwd(t1) != btf_is_fwd(t2)) {
1386 n1 = btf__str_by_offset(btf1, t1->name_off);
1387 n2 = btf__str_by_offset(btf2, t2->name_off);
1388 if (strcmp(n1, n2) != 0) {
1389 pr_warn("global '%s': incompatible forward declaration names '%s' and '%s'\n",
1390 sym_name, n1, n2);
1391 return false;
1392 }
1393 /* validate if FWD kind matches concrete kind */
1394 if (btf_is_fwd(t1)) {
1395 if (btf_kflag(t1) && btf_is_union(t2))
1396 return true;
1397 if (!btf_kflag(t1) && btf_is_struct(t2))
1398 return true;
1399 pr_warn("global '%s': incompatible %s forward declaration and concrete kind %s\n",
1400 sym_name, btf_kflag(t1) ? "union" : "struct", btf_kind_str(t2));
1401 } else {
1402 if (btf_kflag(t2) && btf_is_union(t1))
1403 return true;
1404 if (!btf_kflag(t2) && btf_is_struct(t1))
1405 return true;
1406 pr_warn("global '%s': incompatible %s forward declaration and concrete kind %s\n",
1407 sym_name, btf_kflag(t2) ? "union" : "struct", btf_kind_str(t1));
1408 }
1409 return false;
1410 }
1411
1412 if (btf_kind(t1) != btf_kind(t2)) {
1413 pr_warn("global '%s': incompatible BTF kinds %s and %s\n",
1414 sym_name, btf_kind_str(t1), btf_kind_str(t2));
1415 return false;
1416 }
1417
1418 switch (btf_kind(t1)) {
1419 case BTF_KIND_STRUCT:
1420 case BTF_KIND_UNION:
1421 case BTF_KIND_ENUM:
1422 case BTF_KIND_ENUM64:
1423 case BTF_KIND_FWD:
1424 case BTF_KIND_FUNC:
1425 case BTF_KIND_VAR:
1426 n1 = btf__str_by_offset(btf1, t1->name_off);
1427 n2 = btf__str_by_offset(btf2, t2->name_off);
1428 if (strcmp(n1, n2) != 0) {
1429 pr_warn("global '%s': incompatible %s names '%s' and '%s'\n",
1430 sym_name, btf_kind_str(t1), n1, n2);
1431 return false;
1432 }
1433 break;
1434 default:
1435 break;
1436 }
1437
1438 switch (btf_kind(t1)) {
1439 case BTF_KIND_UNKN: /* void */
1440 case BTF_KIND_FWD:
1441 return true;
1442 case BTF_KIND_INT:
1443 case BTF_KIND_FLOAT:
1444 case BTF_KIND_ENUM:
1445 case BTF_KIND_ENUM64:
1446 /* ignore encoding for int and enum values for enum */
1447 if (t1->size != t2->size) {
1448 pr_warn("global '%s': incompatible %s '%s' size %u and %u\n",
1449 sym_name, btf_kind_str(t1), n1, t1->size, t2->size);
1450 return false;
1451 }
1452 return true;
1453 case BTF_KIND_PTR:
1454 /* just validate overall shape of the referenced type, so no
1455 * contents comparison for struct/union, and allowed fwd vs
1456 * struct/union
1457 */
1458 exact = false;
1459 id1 = t1->type;
1460 id2 = t2->type;
1461 goto recur;
1462 case BTF_KIND_ARRAY:
1463 /* ignore index type and array size */
1464 id1 = btf_array(t1)->type;
1465 id2 = btf_array(t2)->type;
1466 goto recur;
1467 case BTF_KIND_FUNC:
1468 /* extern and global linkages are compatible */
1469 is_static1 = btf_func_linkage(t1) == BTF_FUNC_STATIC;
1470 is_static2 = btf_func_linkage(t2) == BTF_FUNC_STATIC;
1471 if (is_static1 != is_static2) {
1472 pr_warn("global '%s': incompatible func '%s' linkage\n", sym_name, n1);
1473 return false;
1474 }
1475
1476 id1 = t1->type;
1477 id2 = t2->type;
1478 goto recur;
1479 case BTF_KIND_VAR:
1480 /* extern and global linkages are compatible */
1481 is_static1 = btf_var(t1)->linkage == BTF_VAR_STATIC;
1482 is_static2 = btf_var(t2)->linkage == BTF_VAR_STATIC;
1483 if (is_static1 != is_static2) {
1484 pr_warn("global '%s': incompatible var '%s' linkage\n", sym_name, n1);
1485 return false;
1486 }
1487
1488 id1 = t1->type;
1489 id2 = t2->type;
1490 goto recur;
1491 case BTF_KIND_STRUCT:
1492 case BTF_KIND_UNION: {
1493 const struct btf_member *m1, *m2;
1494
1495 if (!exact)
1496 return true;
1497
1498 if (btf_vlen(t1) != btf_vlen(t2)) {
1499 pr_warn("global '%s': incompatible number of %s fields %u and %u\n",
1500 sym_name, btf_kind_str(t1), btf_vlen(t1), btf_vlen(t2));
1501 return false;
1502 }
1503
1504 n = btf_vlen(t1);
1505 m1 = btf_members(t1);
1506 m2 = btf_members(t2);
1507 for (i = 0; i < n; i++, m1++, m2++) {
1508 n1 = btf__str_by_offset(btf1, m1->name_off);
1509 n2 = btf__str_by_offset(btf2, m2->name_off);
1510 if (strcmp(n1, n2) != 0) {
1511 pr_warn("global '%s': incompatible field #%d names '%s' and '%s'\n",
1512 sym_name, i, n1, n2);
1513 return false;
1514 }
1515 if (m1->offset != m2->offset) {
1516 pr_warn("global '%s': incompatible field #%d ('%s') offsets\n",
1517 sym_name, i, n1);
1518 return false;
1519 }
1520 if (!glob_sym_btf_matches(sym_name, exact, btf1, m1->type, btf2, m2->type))
1521 return false;
1522 }
1523
1524 return true;
1525 }
1526 case BTF_KIND_FUNC_PROTO: {
1527 const struct btf_param *m1, *m2;
1528
1529 if (btf_vlen(t1) != btf_vlen(t2)) {
1530 pr_warn("global '%s': incompatible number of %s params %u and %u\n",
1531 sym_name, btf_kind_str(t1), btf_vlen(t1), btf_vlen(t2));
1532 return false;
1533 }
1534
1535 n = btf_vlen(t1);
1536 m1 = btf_params(t1);
1537 m2 = btf_params(t2);
1538 for (i = 0; i < n; i++, m1++, m2++) {
1539 /* ignore func arg names */
1540 if (!glob_sym_btf_matches(sym_name, exact, btf1, m1->type, btf2, m2->type))
1541 return false;
1542 }
1543
1544 /* now check return type as well */
1545 id1 = t1->type;
1546 id2 = t2->type;
1547 goto recur;
1548 }
1549
1550 /* skip_mods_and_typedefs() make this impossible */
1551 case BTF_KIND_TYPEDEF:
1552 case BTF_KIND_VOLATILE:
1553 case BTF_KIND_CONST:
1554 case BTF_KIND_RESTRICT:
1555 /* DATASECs are never compared with each other */
1556 case BTF_KIND_DATASEC:
1557 default:
1558 pr_warn("global '%s': unsupported BTF kind %s\n",
1559 sym_name, btf_kind_str(t1));
1560 return false;
1561 }
1562 }
1563
1564 static bool map_defs_match(const char *sym_name,
1565 const struct btf *main_btf,
1566 const struct btf_map_def *main_def,
1567 const struct btf_map_def *main_inner_def,
1568 const struct btf *extra_btf,
1569 const struct btf_map_def *extra_def,
1570 const struct btf_map_def *extra_inner_def)
1571 {
1572 const char *reason;
1573
1574 if (main_def->map_type != extra_def->map_type) {
1575 reason = "type";
1576 goto mismatch;
1577 }
1578
1579 /* check key type/size match */
1580 if (main_def->key_size != extra_def->key_size) {
1581 reason = "key_size";
1582 goto mismatch;
1583 }
1584 if (!!main_def->key_type_id != !!extra_def->key_type_id) {
1585 reason = "key type";
1586 goto mismatch;
1587 }
1588 if ((main_def->parts & MAP_DEF_KEY_TYPE)
1589 && !glob_sym_btf_matches(sym_name, true /*exact*/,
1590 main_btf, main_def->key_type_id,
1591 extra_btf, extra_def->key_type_id)) {
1592 reason = "key type";
1593 goto mismatch;
1594 }
1595
1596 /* validate value type/size match */
1597 if (main_def->value_size != extra_def->value_size) {
1598 reason = "value_size";
1599 goto mismatch;
1600 }
1601 if (!!main_def->value_type_id != !!extra_def->value_type_id) {
1602 reason = "value type";
1603 goto mismatch;
1604 }
1605 if ((main_def->parts & MAP_DEF_VALUE_TYPE)
1606 && !glob_sym_btf_matches(sym_name, true /*exact*/,
1607 main_btf, main_def->value_type_id,
1608 extra_btf, extra_def->value_type_id)) {
1609 reason = "key type";
1610 goto mismatch;
1611 }
1612
1613 if (main_def->max_entries != extra_def->max_entries) {
1614 reason = "max_entries";
1615 goto mismatch;
1616 }
1617 if (main_def->map_flags != extra_def->map_flags) {
1618 reason = "map_flags";
1619 goto mismatch;
1620 }
1621 if (main_def->numa_node != extra_def->numa_node) {
1622 reason = "numa_node";
1623 goto mismatch;
1624 }
1625 if (main_def->pinning != extra_def->pinning) {
1626 reason = "pinning";
1627 goto mismatch;
1628 }
1629
1630 if ((main_def->parts & MAP_DEF_INNER_MAP) != (extra_def->parts & MAP_DEF_INNER_MAP)) {
1631 reason = "inner map";
1632 goto mismatch;
1633 }
1634
1635 if (main_def->parts & MAP_DEF_INNER_MAP) {
1636 char inner_map_name[128];
1637
1638 snprintf(inner_map_name, sizeof(inner_map_name), "%s.inner", sym_name);
1639
1640 return map_defs_match(inner_map_name,
1641 main_btf, main_inner_def, NULL,
1642 extra_btf, extra_inner_def, NULL);
1643 }
1644
1645 return true;
1646
1647 mismatch:
1648 pr_warn("global '%s': map %s mismatch\n", sym_name, reason);
1649 return false;
1650 }
1651
1652 static bool glob_map_defs_match(const char *sym_name,
1653 struct bpf_linker *linker, struct glob_sym *glob_sym,
1654 struct src_obj *obj, Elf64_Sym *sym, int btf_id)
1655 {
1656 struct btf_map_def dst_def = {}, dst_inner_def = {};
1657 struct btf_map_def src_def = {}, src_inner_def = {};
1658 const struct btf_type *t;
1659 int err;
1660
1661 t = btf__type_by_id(obj->btf, btf_id);
1662 if (!btf_is_var(t)) {
1663 pr_warn("global '%s': invalid map definition type [%d]\n", sym_name, btf_id);
1664 return false;
1665 }
1666 t = skip_mods_and_typedefs(obj->btf, t->type, NULL);
1667
1668 err = parse_btf_map_def(sym_name, obj->btf, t, true /*strict*/, &src_def, &src_inner_def);
1669 if (err) {
1670 pr_warn("global '%s': invalid map definition\n", sym_name);
1671 return false;
1672 }
1673
1674 /* re-parse existing map definition */
1675 t = btf__type_by_id(linker->btf, glob_sym->btf_id);
1676 t = skip_mods_and_typedefs(linker->btf, t->type, NULL);
1677 err = parse_btf_map_def(sym_name, linker->btf, t, true /*strict*/, &dst_def, &dst_inner_def);
1678 if (err) {
1679 /* this should not happen, because we already validated it */
1680 pr_warn("global '%s': invalid dst map definition\n", sym_name);
1681 return false;
1682 }
1683
1684 /* Currently extern map definition has to be complete and match
1685 * concrete map definition exactly. This restriction might be lifted
1686 * in the future.
1687 */
1688 return map_defs_match(sym_name, linker->btf, &dst_def, &dst_inner_def,
1689 obj->btf, &src_def, &src_inner_def);
1690 }
1691
1692 static bool glob_syms_match(const char *sym_name,
1693 struct bpf_linker *linker, struct glob_sym *glob_sym,
1694 struct src_obj *obj, Elf64_Sym *sym, size_t sym_idx, int btf_id)
1695 {
1696 const struct btf_type *src_t;
1697
1698 /* if we are dealing with externs, BTF types describing both global
1699 * and extern VARs/FUNCs should be completely present in all files
1700 */
1701 if (!glob_sym->btf_id || !btf_id) {
1702 pr_warn("BTF info is missing for global symbol '%s'\n", sym_name);
1703 return false;
1704 }
1705
1706 src_t = btf__type_by_id(obj->btf, btf_id);
1707 if (!btf_is_var(src_t) && !btf_is_func(src_t)) {
1708 pr_warn("only extern variables and functions are supported, but got '%s' for '%s'\n",
1709 btf_kind_str(src_t), sym_name);
1710 return false;
1711 }
1712
1713 /* deal with .maps definitions specially */
1714 if (glob_sym->sec_id && strcmp(linker->secs[glob_sym->sec_id].sec_name, MAPS_ELF_SEC) == 0)
1715 return glob_map_defs_match(sym_name, linker, glob_sym, obj, sym, btf_id);
1716
1717 if (!glob_sym_btf_matches(sym_name, true /*exact*/,
1718 linker->btf, glob_sym->btf_id, obj->btf, btf_id))
1719 return false;
1720
1721 return true;
1722 }
1723
1724 static bool btf_is_non_static(const struct btf_type *t)
1725 {
1726 return (btf_is_var(t) && btf_var(t)->linkage != BTF_VAR_STATIC)
1727 || (btf_is_func(t) && btf_func_linkage(t) != BTF_FUNC_STATIC);
1728 }
1729
1730 static int find_glob_sym_btf(struct src_obj *obj, Elf64_Sym *sym, const char *sym_name,
1731 int *out_btf_sec_id, int *out_btf_id)
1732 {
1733 int i, j, n, m, btf_id = 0;
1734 const struct btf_type *t;
1735 const struct btf_var_secinfo *vi;
1736 const char *name;
1737
1738 if (!obj->btf) {
1739 pr_warn("failed to find BTF info for object '%s'\n", obj->filename);
1740 return -EINVAL;
1741 }
1742
1743 n = btf__type_cnt(obj->btf);
1744 for (i = 1; i < n; i++) {
1745 t = btf__type_by_id(obj->btf, i);
1746
1747 /* some global and extern FUNCs and VARs might not be associated with any
1748 * DATASEC, so try to detect them in the same pass
1749 */
1750 if (btf_is_non_static(t)) {
1751 name = btf__str_by_offset(obj->btf, t->name_off);
1752 if (strcmp(name, sym_name) != 0)
1753 continue;
1754
1755 /* remember and still try to find DATASEC */
1756 btf_id = i;
1757 continue;
1758 }
1759
1760 if (!btf_is_datasec(t))
1761 continue;
1762
1763 vi = btf_var_secinfos(t);
1764 for (j = 0, m = btf_vlen(t); j < m; j++, vi++) {
1765 t = btf__type_by_id(obj->btf, vi->type);
1766 name = btf__str_by_offset(obj->btf, t->name_off);
1767
1768 if (strcmp(name, sym_name) != 0)
1769 continue;
1770 if (btf_is_var(t) && btf_var(t)->linkage == BTF_VAR_STATIC)
1771 continue;
1772 if (btf_is_func(t) && btf_func_linkage(t) == BTF_FUNC_STATIC)
1773 continue;
1774
1775 if (btf_id && btf_id != vi->type) {
1776 pr_warn("global/extern '%s' BTF is ambiguous: both types #%d and #%u match\n",
1777 sym_name, btf_id, vi->type);
1778 return -EINVAL;
1779 }
1780
1781 *out_btf_sec_id = i;
1782 *out_btf_id = vi->type;
1783
1784 return 0;
1785 }
1786 }
1787
1788 /* free-floating extern or global FUNC */
1789 if (btf_id) {
1790 *out_btf_sec_id = 0;
1791 *out_btf_id = btf_id;
1792 return 0;
1793 }
1794
1795 pr_warn("failed to find BTF info for global/extern symbol '%s'\n", sym_name);
1796 return -ENOENT;
1797 }
1798
1799 static struct src_sec *find_src_sec_by_name(struct src_obj *obj, const char *sec_name)
1800 {
1801 struct src_sec *sec;
1802 int i;
1803
1804 for (i = 1; i < obj->sec_cnt; i++) {
1805 sec = &obj->secs[i];
1806
1807 if (strcmp(sec->sec_name, sec_name) == 0)
1808 return sec;
1809 }
1810
1811 return NULL;
1812 }
1813
1814 static int complete_extern_btf_info(struct btf *dst_btf, int dst_id,
1815 struct btf *src_btf, int src_id)
1816 {
1817 struct btf_type *dst_t = btf_type_by_id(dst_btf, dst_id);
1818 struct btf_type *src_t = btf_type_by_id(src_btf, src_id);
1819 struct btf_param *src_p, *dst_p;
1820 const char *s;
1821 int i, n, off;
1822
1823 /* We already made sure that source and destination types (FUNC or
1824 * VAR) match in terms of types and argument names.
1825 */
1826 if (btf_is_var(dst_t)) {
1827 btf_var(dst_t)->linkage = BTF_VAR_GLOBAL_ALLOCATED;
1828 return 0;
1829 }
1830
1831 dst_t->info = btf_type_info(BTF_KIND_FUNC, BTF_FUNC_GLOBAL, 0);
1832
1833 /* now onto FUNC_PROTO types */
1834 src_t = btf_type_by_id(src_btf, src_t->type);
1835 dst_t = btf_type_by_id(dst_btf, dst_t->type);
1836
1837 /* Fill in all the argument names, which for extern FUNCs are missing.
1838 * We'll end up with two copies of FUNCs/VARs for externs, but that
1839 * will be taken care of by BTF dedup at the very end.
1840 * It might be that BTF types for extern in one file has less/more BTF
1841 * information (e.g., FWD instead of full STRUCT/UNION information),
1842 * but that should be (in most cases, subject to BTF dedup rules)
1843 * handled and resolved by BTF dedup algorithm as well, so we won't
1844 * worry about it. Our only job is to make sure that argument names
1845 * are populated on both sides, otherwise BTF dedup will pedantically
1846 * consider them different.
1847 */
1848 src_p = btf_params(src_t);
1849 dst_p = btf_params(dst_t);
1850 for (i = 0, n = btf_vlen(dst_t); i < n; i++, src_p++, dst_p++) {
1851 if (!src_p->name_off)
1852 continue;
1853
1854 /* src_btf has more complete info, so add name to dst_btf */
1855 s = btf__str_by_offset(src_btf, src_p->name_off);
1856 off = btf__add_str(dst_btf, s);
1857 if (off < 0)
1858 return off;
1859 dst_p->name_off = off;
1860 }
1861 return 0;
1862 }
1863
1864 static void sym_update_bind(Elf64_Sym *sym, int sym_bind)
1865 {
1866 sym->st_info = ELF64_ST_INFO(sym_bind, ELF64_ST_TYPE(sym->st_info));
1867 }
1868
1869 static void sym_update_type(Elf64_Sym *sym, int sym_type)
1870 {
1871 sym->st_info = ELF64_ST_INFO(ELF64_ST_BIND(sym->st_info), sym_type);
1872 }
1873
1874 static void sym_update_visibility(Elf64_Sym *sym, int sym_vis)
1875 {
1876 /* libelf doesn't provide setters for ST_VISIBILITY,
1877 * but it is stored in the lower 2 bits of st_other
1878 */
1879 sym->st_other &= ~0x03;
1880 sym->st_other |= sym_vis;
1881 }
1882
1883 static int linker_append_elf_sym(struct bpf_linker *linker, struct src_obj *obj,
1884 Elf64_Sym *sym, const char *sym_name, int src_sym_idx)
1885 {
1886 struct src_sec *src_sec = NULL;
1887 struct dst_sec *dst_sec = NULL;
1888 struct glob_sym *glob_sym = NULL;
1889 int name_off, sym_type, sym_bind, sym_vis, err;
1890 int btf_sec_id = 0, btf_id = 0;
1891 size_t dst_sym_idx;
1892 Elf64_Sym *dst_sym;
1893 bool sym_is_extern;
1894
1895 sym_type = ELF64_ST_TYPE(sym->st_info);
1896 sym_bind = ELF64_ST_BIND(sym->st_info);
1897 sym_vis = ELF64_ST_VISIBILITY(sym->st_other);
1898 sym_is_extern = sym->st_shndx == SHN_UNDEF;
1899
1900 if (sym_is_extern) {
1901 if (!obj->btf) {
1902 pr_warn("externs without BTF info are not supported\n");
1903 return -ENOTSUP;
1904 }
1905 } else if (sym->st_shndx < SHN_LORESERVE) {
1906 src_sec = &obj->secs[sym->st_shndx];
1907 if (src_sec->skipped)
1908 return 0;
1909 dst_sec = &linker->secs[src_sec->dst_id];
1910
1911 /* allow only one STT_SECTION symbol per section */
1912 if (sym_type == STT_SECTION && dst_sec->sec_sym_idx) {
1913 obj->sym_map[src_sym_idx] = dst_sec->sec_sym_idx;
1914 return 0;
1915 }
1916 }
1917
1918 if (sym_bind == STB_LOCAL)
1919 goto add_sym;
1920
1921 /* find matching BTF info */
1922 err = find_glob_sym_btf(obj, sym, sym_name, &btf_sec_id, &btf_id);
1923 if (err)
1924 return err;
1925
1926 if (sym_is_extern && btf_sec_id) {
1927 const char *sec_name = NULL;
1928 const struct btf_type *t;
1929
1930 t = btf__type_by_id(obj->btf, btf_sec_id);
1931 sec_name = btf__str_by_offset(obj->btf, t->name_off);
1932
1933 /* Clang puts unannotated extern vars into
1934 * '.extern' BTF DATASEC. Treat them the same
1935 * as unannotated extern funcs (which are
1936 * currently not put into any DATASECs).
1937 * Those don't have associated src_sec/dst_sec.
1938 */
1939 if (strcmp(sec_name, BTF_EXTERN_SEC) != 0) {
1940 src_sec = find_src_sec_by_name(obj, sec_name);
1941 if (!src_sec) {
1942 pr_warn("failed to find matching ELF sec '%s'\n", sec_name);
1943 return -ENOENT;
1944 }
1945 dst_sec = &linker->secs[src_sec->dst_id];
1946 }
1947 }
1948
1949 glob_sym = find_glob_sym(linker, sym_name);
1950 if (glob_sym) {
1951 /* Preventively resolve to existing symbol. This is
1952 * needed for further relocation symbol remapping in
1953 * the next step of linking.
1954 */
1955 obj->sym_map[src_sym_idx] = glob_sym->sym_idx;
1956
1957 /* If both symbols are non-externs, at least one of
1958 * them has to be STB_WEAK, otherwise they are in
1959 * a conflict with each other.
1960 */
1961 if (!sym_is_extern && !glob_sym->is_extern
1962 && !glob_sym->is_weak && sym_bind != STB_WEAK) {
1963 pr_warn("conflicting non-weak symbol #%d (%s) definition in '%s'\n",
1964 src_sym_idx, sym_name, obj->filename);
1965 return -EINVAL;
1966 }
1967
1968 if (!glob_syms_match(sym_name, linker, glob_sym, obj, sym, src_sym_idx, btf_id))
1969 return -EINVAL;
1970
1971 dst_sym = get_sym_by_idx(linker, glob_sym->sym_idx);
1972
1973 /* If new symbol is strong, then force dst_sym to be strong as
1974 * well; this way a mix of weak and non-weak extern
1975 * definitions will end up being strong.
1976 */
1977 if (sym_bind == STB_GLOBAL) {
1978 /* We still need to preserve type (NOTYPE or
1979 * OBJECT/FUNC, depending on whether the symbol is
1980 * extern or not)
1981 */
1982 sym_update_bind(dst_sym, STB_GLOBAL);
1983 glob_sym->is_weak = false;
1984 }
1985
1986 /* Non-default visibility is "contaminating", with stricter
1987 * visibility overwriting more permissive ones, even if more
1988 * permissive visibility comes from just an extern definition.
1989 * Currently only STV_DEFAULT and STV_HIDDEN are allowed and
1990 * ensured by ELF symbol sanity checks above.
1991 */
1992 if (sym_vis > ELF64_ST_VISIBILITY(dst_sym->st_other))
1993 sym_update_visibility(dst_sym, sym_vis);
1994
1995 /* If the new symbol is extern, then regardless if
1996 * existing symbol is extern or resolved global, just
1997 * keep the existing one untouched.
1998 */
1999 if (sym_is_extern)
2000 return 0;
2001
2002 /* If existing symbol is a strong resolved symbol, bail out,
2003 * because we lost resolution battle have nothing to
2004 * contribute. We already checked above that there is no
2005 * strong-strong conflict. We also already tightened binding
2006 * and visibility, so nothing else to contribute at that point.
2007 */
2008 if (!glob_sym->is_extern && sym_bind == STB_WEAK)
2009 return 0;
2010
2011 /* At this point, new symbol is strong non-extern,
2012 * so overwrite glob_sym with new symbol information.
2013 * Preserve binding and visibility.
2014 */
2015 sym_update_type(dst_sym, sym_type);
2016 dst_sym->st_shndx = dst_sec->sec_idx;
2017 dst_sym->st_value = src_sec->dst_off + sym->st_value;
2018 dst_sym->st_size = sym->st_size;
2019
2020 /* see comment below about dst_sec->id vs dst_sec->sec_idx */
2021 glob_sym->sec_id = dst_sec->id;
2022 glob_sym->is_extern = false;
2023
2024 if (complete_extern_btf_info(linker->btf, glob_sym->btf_id,
2025 obj->btf, btf_id))
2026 return -EINVAL;
2027
2028 /* request updating VAR's/FUNC's underlying BTF type when appending BTF type */
2029 glob_sym->underlying_btf_id = 0;
2030
2031 obj->sym_map[src_sym_idx] = glob_sym->sym_idx;
2032 return 0;
2033 }
2034
2035 add_sym:
2036 name_off = strset__add_str(linker->strtab_strs, sym_name);
2037 if (name_off < 0)
2038 return name_off;
2039
2040 dst_sym = add_new_sym(linker, &dst_sym_idx);
2041 if (!dst_sym)
2042 return -ENOMEM;
2043
2044 dst_sym->st_name = name_off;
2045 dst_sym->st_info = sym->st_info;
2046 dst_sym->st_other = sym->st_other;
2047 dst_sym->st_shndx = dst_sec ? dst_sec->sec_idx : sym->st_shndx;
2048 dst_sym->st_value = (src_sec ? src_sec->dst_off : 0) + sym->st_value;
2049 dst_sym->st_size = sym->st_size;
2050
2051 obj->sym_map[src_sym_idx] = dst_sym_idx;
2052
2053 if (sym_type == STT_SECTION && dst_sym) {
2054 dst_sec->sec_sym_idx = dst_sym_idx;
2055 dst_sym->st_value = 0;
2056 }
2057
2058 if (sym_bind != STB_LOCAL) {
2059 glob_sym = add_glob_sym(linker);
2060 if (!glob_sym)
2061 return -ENOMEM;
2062
2063 glob_sym->sym_idx = dst_sym_idx;
2064 /* we use dst_sec->id (and not dst_sec->sec_idx), because
2065 * ephemeral sections (.kconfig, .ksyms, etc) don't have
2066 * sec_idx (as they don't have corresponding ELF section), but
2067 * still have id. .extern doesn't have even ephemeral section
2068 * associated with it, so dst_sec->id == dst_sec->sec_idx == 0.
2069 */
2070 glob_sym->sec_id = dst_sec ? dst_sec->id : 0;
2071 glob_sym->name_off = name_off;
2072 /* we will fill btf_id in during BTF merging step */
2073 glob_sym->btf_id = 0;
2074 glob_sym->is_extern = sym_is_extern;
2075 glob_sym->is_weak = sym_bind == STB_WEAK;
2076 }
2077
2078 return 0;
2079 }
2080
2081 static int linker_append_elf_relos(struct bpf_linker *linker, struct src_obj *obj)
2082 {
2083 struct src_sec *src_symtab = &obj->secs[obj->symtab_sec_idx];
2084 int i, err;
2085
2086 for (i = 1; i < obj->sec_cnt; i++) {
2087 struct src_sec *src_sec, *src_linked_sec;
2088 struct dst_sec *dst_sec, *dst_linked_sec;
2089 Elf64_Rel *src_rel, *dst_rel;
2090 int j, n;
2091
2092 src_sec = &obj->secs[i];
2093 if (!is_relo_sec(src_sec))
2094 continue;
2095
2096 /* shdr->sh_info points to relocatable section */
2097 src_linked_sec = &obj->secs[src_sec->shdr->sh_info];
2098 if (src_linked_sec->skipped)
2099 continue;
2100
2101 dst_sec = find_dst_sec_by_name(linker, src_sec->sec_name);
2102 if (!dst_sec) {
2103 dst_sec = add_dst_sec(linker, src_sec->sec_name);
2104 if (!dst_sec)
2105 return -ENOMEM;
2106 err = init_sec(linker, dst_sec, src_sec);
2107 if (err) {
2108 pr_warn("failed to init section '%s'\n", src_sec->sec_name);
2109 return err;
2110 }
2111 } else if (!secs_match(dst_sec, src_sec)) {
2112 pr_warn("sections %s are not compatible\n", src_sec->sec_name);
2113 return -1;
2114 }
2115
2116 /* shdr->sh_link points to SYMTAB */
2117 dst_sec->shdr->sh_link = linker->symtab_sec_idx;
2118
2119 /* shdr->sh_info points to relocated section */
2120 dst_linked_sec = &linker->secs[src_linked_sec->dst_id];
2121 dst_sec->shdr->sh_info = dst_linked_sec->sec_idx;
2122
2123 src_sec->dst_id = dst_sec->id;
2124 err = extend_sec(linker, dst_sec, src_sec);
2125 if (err)
2126 return err;
2127
2128 src_rel = src_sec->data->d_buf;
2129 dst_rel = dst_sec->raw_data + src_sec->dst_off;
2130 n = src_sec->shdr->sh_size / src_sec->shdr->sh_entsize;
2131 for (j = 0; j < n; j++, src_rel++, dst_rel++) {
2132 size_t src_sym_idx, dst_sym_idx, sym_type;
2133 Elf64_Sym *src_sym;
2134
2135 src_sym_idx = ELF64_R_SYM(src_rel->r_info);
2136 src_sym = src_symtab->data->d_buf + sizeof(*src_sym) * src_sym_idx;
2137
2138 dst_sym_idx = obj->sym_map[src_sym_idx];
2139 dst_rel->r_offset += src_linked_sec->dst_off;
2140 sym_type = ELF64_R_TYPE(src_rel->r_info);
2141 dst_rel->r_info = ELF64_R_INFO(dst_sym_idx, sym_type);
2142
2143 if (ELF64_ST_TYPE(src_sym->st_info) == STT_SECTION) {
2144 struct src_sec *sec = &obj->secs[src_sym->st_shndx];
2145 struct bpf_insn *insn;
2146
2147 if (src_linked_sec->shdr->sh_flags & SHF_EXECINSTR) {
2148 /* calls to the very first static function inside
2149 * .text section at offset 0 will
2150 * reference section symbol, not the
2151 * function symbol. Fix that up,
2152 * otherwise it won't be possible to
2153 * relocate calls to two different
2154 * static functions with the same name
2155 * (rom two different object files)
2156 */
2157 insn = dst_linked_sec->raw_data + dst_rel->r_offset;
2158 if (insn->code == (BPF_JMP | BPF_CALL))
2159 insn->imm += sec->dst_off / sizeof(struct bpf_insn);
2160 else
2161 insn->imm += sec->dst_off;
2162 } else {
2163 pr_warn("relocation against STT_SECTION in non-exec section is not supported!\n");
2164 return -EINVAL;
2165 }
2166 }
2167
2168 }
2169 }
2170
2171 return 0;
2172 }
2173
2174 static Elf64_Sym *find_sym_by_name(struct src_obj *obj, size_t sec_idx,
2175 int sym_type, const char *sym_name)
2176 {
2177 struct src_sec *symtab = &obj->secs[obj->symtab_sec_idx];
2178 Elf64_Sym *sym = symtab->data->d_buf;
2179 int i, n = symtab->shdr->sh_size / symtab->shdr->sh_entsize;
2180 int str_sec_idx = symtab->shdr->sh_link;
2181 const char *name;
2182
2183 for (i = 0; i < n; i++, sym++) {
2184 if (sym->st_shndx != sec_idx)
2185 continue;
2186 if (ELF64_ST_TYPE(sym->st_info) != sym_type)
2187 continue;
2188
2189 name = elf_strptr(obj->elf, str_sec_idx, sym->st_name);
2190 if (!name)
2191 return NULL;
2192
2193 if (strcmp(sym_name, name) != 0)
2194 continue;
2195
2196 return sym;
2197 }
2198
2199 return NULL;
2200 }
2201
2202 static int linker_fixup_btf(struct src_obj *obj)
2203 {
2204 const char *sec_name;
2205 struct src_sec *sec;
2206 int i, j, n, m;
2207
2208 if (!obj->btf)
2209 return 0;
2210
2211 n = btf__type_cnt(obj->btf);
2212 for (i = 1; i < n; i++) {
2213 struct btf_var_secinfo *vi;
2214 struct btf_type *t;
2215
2216 t = btf_type_by_id(obj->btf, i);
2217 if (btf_kind(t) != BTF_KIND_DATASEC)
2218 continue;
2219
2220 sec_name = btf__str_by_offset(obj->btf, t->name_off);
2221 sec = find_src_sec_by_name(obj, sec_name);
2222 if (sec) {
2223 /* record actual section size, unless ephemeral */
2224 if (sec->shdr)
2225 t->size = sec->shdr->sh_size;
2226 } else {
2227 /* BTF can have some sections that are not represented
2228 * in ELF, e.g., .kconfig, .ksyms, .extern, which are used
2229 * for special extern variables.
2230 *
2231 * For all but one such special (ephemeral)
2232 * sections, we pre-create "section shells" to be able
2233 * to keep track of extra per-section metadata later
2234 * (e.g., those BTF extern variables).
2235 *
2236 * .extern is even more special, though, because it
2237 * contains extern variables that need to be resolved
2238 * by static linker, not libbpf and kernel. When such
2239 * externs are resolved, we are going to remove them
2240 * from .extern BTF section and might end up not
2241 * needing it at all. Each resolved extern should have
2242 * matching non-extern VAR/FUNC in other sections.
2243 *
2244 * We do support leaving some of the externs
2245 * unresolved, though, to support cases of building
2246 * libraries, which will later be linked against final
2247 * BPF applications. So if at finalization we still
2248 * see unresolved externs, we'll create .extern
2249 * section on our own.
2250 */
2251 if (strcmp(sec_name, BTF_EXTERN_SEC) == 0)
2252 continue;
2253
2254 sec = add_src_sec(obj, sec_name);
2255 if (!sec)
2256 return -ENOMEM;
2257
2258 sec->ephemeral = true;
2259 sec->sec_idx = 0; /* will match UNDEF shndx in ELF */
2260 }
2261
2262 /* remember ELF section and its BTF type ID match */
2263 sec->sec_type_id = i;
2264
2265 /* fix up variable offsets */
2266 vi = btf_var_secinfos(t);
2267 for (j = 0, m = btf_vlen(t); j < m; j++, vi++) {
2268 const struct btf_type *vt = btf__type_by_id(obj->btf, vi->type);
2269 const char *var_name;
2270 int var_linkage;
2271 Elf64_Sym *sym;
2272
2273 /* could be a variable or function */
2274 if (!btf_is_var(vt))
2275 continue;
2276
2277 var_name = btf__str_by_offset(obj->btf, vt->name_off);
2278 var_linkage = btf_var(vt)->linkage;
2279
2280 /* no need to patch up static or extern vars */
2281 if (var_linkage != BTF_VAR_GLOBAL_ALLOCATED)
2282 continue;
2283
2284 sym = find_sym_by_name(obj, sec->sec_idx, STT_OBJECT, var_name);
2285 if (!sym) {
2286 pr_warn("failed to find symbol for variable '%s' in section '%s'\n", var_name, sec_name);
2287 return -ENOENT;
2288 }
2289
2290 vi->offset = sym->st_value;
2291 }
2292 }
2293
2294 return 0;
2295 }
2296
2297 static int linker_append_btf(struct bpf_linker *linker, struct src_obj *obj)
2298 {
2299 const struct btf_type *t;
2300 int i, j, n, start_id, id, err;
2301 const char *name;
2302
2303 if (!obj->btf)
2304 return 0;
2305
2306 start_id = btf__type_cnt(linker->btf);
2307 n = btf__type_cnt(obj->btf);
2308
2309 obj->btf_type_map = calloc(n + 1, sizeof(int));
2310 if (!obj->btf_type_map)
2311 return -ENOMEM;
2312
2313 for (i = 1; i < n; i++) {
2314 struct glob_sym *glob_sym = NULL;
2315
2316 t = btf__type_by_id(obj->btf, i);
2317
2318 /* DATASECs are handled specially below */
2319 if (btf_kind(t) == BTF_KIND_DATASEC)
2320 continue;
2321
2322 if (btf_is_non_static(t)) {
2323 /* there should be glob_sym already */
2324 name = btf__str_by_offset(obj->btf, t->name_off);
2325 glob_sym = find_glob_sym(linker, name);
2326
2327 /* VARs without corresponding glob_sym are those that
2328 * belong to skipped/deduplicated sections (i.e.,
2329 * license and version), so just skip them
2330 */
2331 if (!glob_sym)
2332 continue;
2333
2334 /* linker_append_elf_sym() might have requested
2335 * updating underlying type ID, if extern was resolved
2336 * to strong symbol or weak got upgraded to non-weak
2337 */
2338 if (glob_sym->underlying_btf_id == 0)
2339 glob_sym->underlying_btf_id = -t->type;
2340
2341 /* globals from previous object files that match our
2342 * VAR/FUNC already have a corresponding associated
2343 * BTF type, so just make sure to use it
2344 */
2345 if (glob_sym->btf_id) {
2346 /* reuse existing BTF type for global var/func */
2347 obj->btf_type_map[i] = glob_sym->btf_id;
2348 continue;
2349 }
2350 }
2351
2352 id = btf__add_type(linker->btf, obj->btf, t);
2353 if (id < 0) {
2354 pr_warn("failed to append BTF type #%d from file '%s'\n", i, obj->filename);
2355 return id;
2356 }
2357
2358 obj->btf_type_map[i] = id;
2359
2360 /* record just appended BTF type for var/func */
2361 if (glob_sym) {
2362 glob_sym->btf_id = id;
2363 glob_sym->underlying_btf_id = -t->type;
2364 }
2365 }
2366
2367 /* remap all the types except DATASECs */
2368 n = btf__type_cnt(linker->btf);
2369 for (i = start_id; i < n; i++) {
2370 struct btf_type *dst_t = btf_type_by_id(linker->btf, i);
2371 struct btf_field_iter it;
2372 __u32 *type_id;
2373
2374 err = btf_field_iter_init(&it, dst_t, BTF_FIELD_ITER_IDS);
2375 if (err)
2376 return err;
2377
2378 while ((type_id = btf_field_iter_next(&it))) {
2379 int new_id = obj->btf_type_map[*type_id];
2380
2381 /* Error out if the type wasn't remapped. Ignore VOID which stays VOID. */
2382 if (new_id == 0 && *type_id != 0) {
2383 pr_warn("failed to find new ID mapping for original BTF type ID %u\n",
2384 *type_id);
2385 return -EINVAL;
2386 }
2387
2388 *type_id = obj->btf_type_map[*type_id];
2389 }
2390 }
2391
2392 /* Rewrite VAR/FUNC underlying types (i.e., FUNC's FUNC_PROTO and VAR's
2393 * actual type), if necessary
2394 */
2395 for (i = 0; i < linker->glob_sym_cnt; i++) {
2396 struct glob_sym *glob_sym = &linker->glob_syms[i];
2397 struct btf_type *glob_t;
2398
2399 if (glob_sym->underlying_btf_id >= 0)
2400 continue;
2401
2402 glob_sym->underlying_btf_id = obj->btf_type_map[-glob_sym->underlying_btf_id];
2403
2404 glob_t = btf_type_by_id(linker->btf, glob_sym->btf_id);
2405 glob_t->type = glob_sym->underlying_btf_id;
2406 }
2407
2408 /* append DATASEC info */
2409 for (i = 1; i < obj->sec_cnt; i++) {
2410 struct src_sec *src_sec;
2411 struct dst_sec *dst_sec;
2412 const struct btf_var_secinfo *src_var;
2413 struct btf_var_secinfo *dst_var;
2414
2415 src_sec = &obj->secs[i];
2416 if (!src_sec->sec_type_id || src_sec->skipped)
2417 continue;
2418 dst_sec = &linker->secs[src_sec->dst_id];
2419
2420 /* Mark section as having BTF regardless of the presence of
2421 * variables. In some cases compiler might generate empty BTF
2422 * with no variables information. E.g., when promoting local
2423 * array/structure variable initial values and BPF object
2424 * file otherwise has no read-only static variables in
2425 * .rodata. We need to preserve such empty BTF and just set
2426 * correct section size.
2427 */
2428 dst_sec->has_btf = true;
2429
2430 t = btf__type_by_id(obj->btf, src_sec->sec_type_id);
2431 src_var = btf_var_secinfos(t);
2432 n = btf_vlen(t);
2433 for (j = 0; j < n; j++, src_var++) {
2434 void *sec_vars = dst_sec->sec_vars;
2435 int new_id = obj->btf_type_map[src_var->type];
2436 struct glob_sym *glob_sym = NULL;
2437
2438 t = btf_type_by_id(linker->btf, new_id);
2439 if (btf_is_non_static(t)) {
2440 name = btf__str_by_offset(linker->btf, t->name_off);
2441 glob_sym = find_glob_sym(linker, name);
2442 if (glob_sym->sec_id != dst_sec->id) {
2443 pr_warn("global '%s': section mismatch %d vs %d\n",
2444 name, glob_sym->sec_id, dst_sec->id);
2445 return -EINVAL;
2446 }
2447 }
2448
2449 /* If there is already a member (VAR or FUNC) mapped
2450 * to the same type, don't add a duplicate entry.
2451 * This will happen when multiple object files define
2452 * the same extern VARs/FUNCs.
2453 */
2454 if (glob_sym && glob_sym->var_idx >= 0) {
2455 __s64 sz;
2456
2457 /* FUNCs don't have size, nothing to update */
2458 if (btf_is_func(t))
2459 continue;
2460
2461 dst_var = &dst_sec->sec_vars[glob_sym->var_idx];
2462 /* Because underlying BTF type might have
2463 * changed, so might its size have changed, so
2464 * re-calculate and update it in sec_var.
2465 */
2466 sz = btf__resolve_size(linker->btf, glob_sym->underlying_btf_id);
2467 if (sz < 0) {
2468 pr_warn("global '%s': failed to resolve size of underlying type: %d\n",
2469 name, (int)sz);
2470 return -EINVAL;
2471 }
2472 dst_var->size = sz;
2473 continue;
2474 }
2475
2476 sec_vars = libbpf_reallocarray(sec_vars,
2477 dst_sec->sec_var_cnt + 1,
2478 sizeof(*dst_sec->sec_vars));
2479 if (!sec_vars)
2480 return -ENOMEM;
2481
2482 dst_sec->sec_vars = sec_vars;
2483 dst_sec->sec_var_cnt++;
2484
2485 dst_var = &dst_sec->sec_vars[dst_sec->sec_var_cnt - 1];
2486 dst_var->type = obj->btf_type_map[src_var->type];
2487 dst_var->size = src_var->size;
2488 dst_var->offset = src_sec->dst_off + src_var->offset;
2489
2490 if (glob_sym)
2491 glob_sym->var_idx = dst_sec->sec_var_cnt - 1;
2492 }
2493 }
2494
2495 return 0;
2496 }
2497
2498 static void *add_btf_ext_rec(struct btf_ext_sec_data *ext_data, const void *src_rec)
2499 {
2500 void *tmp;
2501
2502 tmp = libbpf_reallocarray(ext_data->recs, ext_data->rec_cnt + 1, ext_data->rec_sz);
2503 if (!tmp)
2504 return NULL;
2505 ext_data->recs = tmp;
2506
2507 tmp += ext_data->rec_cnt * ext_data->rec_sz;
2508 memcpy(tmp, src_rec, ext_data->rec_sz);
2509
2510 ext_data->rec_cnt++;
2511
2512 return tmp;
2513 }
2514
2515 static int linker_append_btf_ext(struct bpf_linker *linker, struct src_obj *obj)
2516 {
2517 const struct btf_ext_info_sec *ext_sec;
2518 const char *sec_name, *s;
2519 struct src_sec *src_sec;
2520 struct dst_sec *dst_sec;
2521 int rec_sz, str_off, i;
2522
2523 if (!obj->btf_ext)
2524 return 0;
2525
2526 rec_sz = obj->btf_ext->func_info.rec_size;
2527 for_each_btf_ext_sec(&obj->btf_ext->func_info, ext_sec) {
2528 struct bpf_func_info_min *src_rec, *dst_rec;
2529
2530 sec_name = btf__name_by_offset(obj->btf, ext_sec->sec_name_off);
2531 src_sec = find_src_sec_by_name(obj, sec_name);
2532 if (!src_sec) {
2533 pr_warn("can't find section '%s' referenced from .BTF.ext\n", sec_name);
2534 return -EINVAL;
2535 }
2536 dst_sec = &linker->secs[src_sec->dst_id];
2537
2538 if (dst_sec->func_info.rec_sz == 0)
2539 dst_sec->func_info.rec_sz = rec_sz;
2540 if (dst_sec->func_info.rec_sz != rec_sz) {
2541 pr_warn("incompatible .BTF.ext record sizes for section '%s'\n", sec_name);
2542 return -EINVAL;
2543 }
2544
2545 for_each_btf_ext_rec(&obj->btf_ext->func_info, ext_sec, i, src_rec) {
2546 dst_rec = add_btf_ext_rec(&dst_sec->func_info, src_rec);
2547 if (!dst_rec)
2548 return -ENOMEM;
2549
2550 dst_rec->insn_off += src_sec->dst_off;
2551 dst_rec->type_id = obj->btf_type_map[dst_rec->type_id];
2552 }
2553 }
2554
2555 rec_sz = obj->btf_ext->line_info.rec_size;
2556 for_each_btf_ext_sec(&obj->btf_ext->line_info, ext_sec) {
2557 struct bpf_line_info_min *src_rec, *dst_rec;
2558
2559 sec_name = btf__name_by_offset(obj->btf, ext_sec->sec_name_off);
2560 src_sec = find_src_sec_by_name(obj, sec_name);
2561 if (!src_sec) {
2562 pr_warn("can't find section '%s' referenced from .BTF.ext\n", sec_name);
2563 return -EINVAL;
2564 }
2565 dst_sec = &linker->secs[src_sec->dst_id];
2566
2567 if (dst_sec->line_info.rec_sz == 0)
2568 dst_sec->line_info.rec_sz = rec_sz;
2569 if (dst_sec->line_info.rec_sz != rec_sz) {
2570 pr_warn("incompatible .BTF.ext record sizes for section '%s'\n", sec_name);
2571 return -EINVAL;
2572 }
2573
2574 for_each_btf_ext_rec(&obj->btf_ext->line_info, ext_sec, i, src_rec) {
2575 dst_rec = add_btf_ext_rec(&dst_sec->line_info, src_rec);
2576 if (!dst_rec)
2577 return -ENOMEM;
2578
2579 dst_rec->insn_off += src_sec->dst_off;
2580
2581 s = btf__str_by_offset(obj->btf, src_rec->file_name_off);
2582 str_off = btf__add_str(linker->btf, s);
2583 if (str_off < 0)
2584 return -ENOMEM;
2585 dst_rec->file_name_off = str_off;
2586
2587 s = btf__str_by_offset(obj->btf, src_rec->line_off);
2588 str_off = btf__add_str(linker->btf, s);
2589 if (str_off < 0)
2590 return -ENOMEM;
2591 dst_rec->line_off = str_off;
2592
2593 /* dst_rec->line_col is fine */
2594 }
2595 }
2596
2597 rec_sz = obj->btf_ext->core_relo_info.rec_size;
2598 for_each_btf_ext_sec(&obj->btf_ext->core_relo_info, ext_sec) {
2599 struct bpf_core_relo *src_rec, *dst_rec;
2600
2601 sec_name = btf__name_by_offset(obj->btf, ext_sec->sec_name_off);
2602 src_sec = find_src_sec_by_name(obj, sec_name);
2603 if (!src_sec) {
2604 pr_warn("can't find section '%s' referenced from .BTF.ext\n", sec_name);
2605 return -EINVAL;
2606 }
2607 dst_sec = &linker->secs[src_sec->dst_id];
2608
2609 if (dst_sec->core_relo_info.rec_sz == 0)
2610 dst_sec->core_relo_info.rec_sz = rec_sz;
2611 if (dst_sec->core_relo_info.rec_sz != rec_sz) {
2612 pr_warn("incompatible .BTF.ext record sizes for section '%s'\n", sec_name);
2613 return -EINVAL;
2614 }
2615
2616 for_each_btf_ext_rec(&obj->btf_ext->core_relo_info, ext_sec, i, src_rec) {
2617 dst_rec = add_btf_ext_rec(&dst_sec->core_relo_info, src_rec);
2618 if (!dst_rec)
2619 return -ENOMEM;
2620
2621 dst_rec->insn_off += src_sec->dst_off;
2622 dst_rec->type_id = obj->btf_type_map[dst_rec->type_id];
2623
2624 s = btf__str_by_offset(obj->btf, src_rec->access_str_off);
2625 str_off = btf__add_str(linker->btf, s);
2626 if (str_off < 0)
2627 return -ENOMEM;
2628 dst_rec->access_str_off = str_off;
2629
2630 /* dst_rec->kind is fine */
2631 }
2632 }
2633
2634 return 0;
2635 }
2636
2637 int bpf_linker__finalize(struct bpf_linker *linker)
2638 {
2639 struct dst_sec *sec;
2640 size_t strs_sz;
2641 const void *strs;
2642 int err, i;
2643
2644 if (!linker->elf)
2645 return libbpf_err(-EINVAL);
2646
2647 err = finalize_btf(linker);
2648 if (err)
2649 return libbpf_err(err);
2650
2651 /* Finalize strings */
2652 strs_sz = strset__data_size(linker->strtab_strs);
2653 strs = strset__data(linker->strtab_strs);
2654
2655 sec = &linker->secs[linker->strtab_sec_idx];
2656 sec->data->d_align = 1;
2657 sec->data->d_off = 0LL;
2658 sec->data->d_buf = (void *)strs;
2659 sec->data->d_type = ELF_T_BYTE;
2660 sec->data->d_size = strs_sz;
2661 sec->shdr->sh_size = strs_sz;
2662
2663 for (i = 1; i < linker->sec_cnt; i++) {
2664 sec = &linker->secs[i];
2665
2666 /* STRTAB is handled specially above */
2667 if (sec->sec_idx == linker->strtab_sec_idx)
2668 continue;
2669
2670 /* special ephemeral sections (.ksyms, .kconfig, etc) */
2671 if (!sec->scn)
2672 continue;
2673
2674 /* restore sections with bpf insns to target byte-order */
2675 if (linker->swapped_endian && is_exec_sec(sec))
2676 exec_sec_bswap(sec->raw_data, sec->sec_sz);
2677
2678 sec->data->d_buf = sec->raw_data;
2679 }
2680
2681 /* Finalize ELF layout */
2682 if (elf_update(linker->elf, ELF_C_NULL) < 0) {
2683 err = -errno;
2684 pr_warn_elf("failed to finalize ELF layout");
2685 return libbpf_err(err);
2686 }
2687
2688 /* Write out final ELF contents */
2689 if (elf_update(linker->elf, ELF_C_WRITE) < 0) {
2690 err = -errno;
2691 pr_warn_elf("failed to write ELF contents");
2692 return libbpf_err(err);
2693 }
2694
2695 elf_end(linker->elf);
2696 close(linker->fd);
2697
2698 linker->elf = NULL;
2699 linker->fd = -1;
2700
2701 return 0;
2702 }
2703
2704 static int emit_elf_data_sec(struct bpf_linker *linker, const char *sec_name,
2705 size_t align, const void *raw_data, size_t raw_sz)
2706 {
2707 Elf_Scn *scn;
2708 Elf_Data *data;
2709 Elf64_Shdr *shdr;
2710 int name_off;
2711
2712 name_off = strset__add_str(linker->strtab_strs, sec_name);
2713 if (name_off < 0)
2714 return name_off;
2715
2716 scn = elf_newscn(linker->elf);
2717 if (!scn)
2718 return -ENOMEM;
2719 data = elf_newdata(scn);
2720 if (!data)
2721 return -ENOMEM;
2722 shdr = elf64_getshdr(scn);
2723 if (!shdr)
2724 return -EINVAL;
2725
2726 shdr->sh_name = name_off;
2727 shdr->sh_type = SHT_PROGBITS;
2728 shdr->sh_flags = 0;
2729 shdr->sh_size = raw_sz;
2730 shdr->sh_link = 0;
2731 shdr->sh_info = 0;
2732 shdr->sh_addralign = align;
2733 shdr->sh_entsize = 0;
2734
2735 data->d_type = ELF_T_BYTE;
2736 data->d_size = raw_sz;
2737 data->d_buf = (void *)raw_data;
2738 data->d_align = align;
2739 data->d_off = 0;
2740
2741 return 0;
2742 }
2743
2744 static int finalize_btf(struct bpf_linker *linker)
2745 {
2746 enum btf_endianness link_endianness;
2747 LIBBPF_OPTS(btf_dedup_opts, opts);
2748 struct btf *btf = linker->btf;
2749 const void *raw_data;
2750 int i, j, id, err;
2751 __u32 raw_sz;
2752
2753 /* bail out if no BTF data was produced */
2754 if (btf__type_cnt(linker->btf) == 1)
2755 return 0;
2756
2757 for (i = 1; i < linker->sec_cnt; i++) {
2758 struct dst_sec *sec = &linker->secs[i];
2759
2760 if (!sec->has_btf)
2761 continue;
2762
2763 id = btf__add_datasec(btf, sec->sec_name, sec->sec_sz);
2764 if (id < 0) {
2765 pr_warn("failed to add consolidated BTF type for datasec '%s': %d\n",
2766 sec->sec_name, id);
2767 return id;
2768 }
2769
2770 for (j = 0; j < sec->sec_var_cnt; j++) {
2771 struct btf_var_secinfo *vi = &sec->sec_vars[j];
2772
2773 if (btf__add_datasec_var_info(btf, vi->type, vi->offset, vi->size))
2774 return -EINVAL;
2775 }
2776 }
2777
2778 err = finalize_btf_ext(linker);
2779 if (err) {
2780 pr_warn(".BTF.ext generation failed: %s\n", errstr(err));
2781 return err;
2782 }
2783
2784 opts.btf_ext = linker->btf_ext;
2785 err = btf__dedup(linker->btf, &opts);
2786 if (err) {
2787 pr_warn("BTF dedup failed: %s\n", errstr(err));
2788 return err;
2789 }
2790
2791 /* Set .BTF and .BTF.ext output byte order */
2792 link_endianness = linker->elf_hdr->e_ident[EI_DATA] == ELFDATA2MSB ?
2793 BTF_BIG_ENDIAN : BTF_LITTLE_ENDIAN;
2794 btf__set_endianness(linker->btf, link_endianness);
2795 if (linker->btf_ext)
2796 btf_ext__set_endianness(linker->btf_ext, link_endianness);
2797
2798 /* Emit .BTF section */
2799 raw_data = btf__raw_data(linker->btf, &raw_sz);
2800 if (!raw_data)
2801 return -ENOMEM;
2802
2803 err = emit_elf_data_sec(linker, BTF_ELF_SEC, 8, raw_data, raw_sz);
2804 if (err) {
2805 pr_warn("failed to write out .BTF ELF section: %s\n", errstr(err));
2806 return err;
2807 }
2808
2809 /* Emit .BTF.ext section */
2810 if (linker->btf_ext) {
2811 raw_data = btf_ext__raw_data(linker->btf_ext, &raw_sz);
2812 if (!raw_data)
2813 return -ENOMEM;
2814
2815 err = emit_elf_data_sec(linker, BTF_EXT_ELF_SEC, 8, raw_data, raw_sz);
2816 if (err) {
2817 pr_warn("failed to write out .BTF.ext ELF section: %s\n", errstr(err));
2818 return err;
2819 }
2820 }
2821
2822 return 0;
2823 }
2824
2825 static int emit_btf_ext_data(struct bpf_linker *linker, void *output,
2826 const char *sec_name, struct btf_ext_sec_data *sec_data)
2827 {
2828 struct btf_ext_info_sec *sec_info;
2829 void *cur = output;
2830 int str_off;
2831 size_t sz;
2832
2833 if (!sec_data->rec_cnt)
2834 return 0;
2835
2836 str_off = btf__add_str(linker->btf, sec_name);
2837 if (str_off < 0)
2838 return -ENOMEM;
2839
2840 sec_info = cur;
2841 sec_info->sec_name_off = str_off;
2842 sec_info->num_info = sec_data->rec_cnt;
2843 cur += sizeof(struct btf_ext_info_sec);
2844
2845 sz = sec_data->rec_cnt * sec_data->rec_sz;
2846 memcpy(cur, sec_data->recs, sz);
2847 cur += sz;
2848
2849 return cur - output;
2850 }
2851
2852 static int finalize_btf_ext(struct bpf_linker *linker)
2853 {
2854 size_t funcs_sz = 0, lines_sz = 0, core_relos_sz = 0, total_sz = 0;
2855 size_t func_rec_sz = 0, line_rec_sz = 0, core_relo_rec_sz = 0;
2856 struct btf_ext_header *hdr;
2857 void *data, *cur;
2858 int i, err, sz;
2859
2860 /* validate that all sections have the same .BTF.ext record sizes
2861 * and calculate total data size for each type of data (func info,
2862 * line info, core relos)
2863 */
2864 for (i = 1; i < linker->sec_cnt; i++) {
2865 struct dst_sec *sec = &linker->secs[i];
2866
2867 if (sec->func_info.rec_cnt) {
2868 if (func_rec_sz == 0)
2869 func_rec_sz = sec->func_info.rec_sz;
2870 if (func_rec_sz != sec->func_info.rec_sz) {
2871 pr_warn("mismatch in func_info record size %zu != %u\n",
2872 func_rec_sz, sec->func_info.rec_sz);
2873 return -EINVAL;
2874 }
2875
2876 funcs_sz += sizeof(struct btf_ext_info_sec) + func_rec_sz * sec->func_info.rec_cnt;
2877 }
2878 if (sec->line_info.rec_cnt) {
2879 if (line_rec_sz == 0)
2880 line_rec_sz = sec->line_info.rec_sz;
2881 if (line_rec_sz != sec->line_info.rec_sz) {
2882 pr_warn("mismatch in line_info record size %zu != %u\n",
2883 line_rec_sz, sec->line_info.rec_sz);
2884 return -EINVAL;
2885 }
2886
2887 lines_sz += sizeof(struct btf_ext_info_sec) + line_rec_sz * sec->line_info.rec_cnt;
2888 }
2889 if (sec->core_relo_info.rec_cnt) {
2890 if (core_relo_rec_sz == 0)
2891 core_relo_rec_sz = sec->core_relo_info.rec_sz;
2892 if (core_relo_rec_sz != sec->core_relo_info.rec_sz) {
2893 pr_warn("mismatch in core_relo_info record size %zu != %u\n",
2894 core_relo_rec_sz, sec->core_relo_info.rec_sz);
2895 return -EINVAL;
2896 }
2897
2898 core_relos_sz += sizeof(struct btf_ext_info_sec) + core_relo_rec_sz * sec->core_relo_info.rec_cnt;
2899 }
2900 }
2901
2902 if (!funcs_sz && !lines_sz && !core_relos_sz)
2903 return 0;
2904
2905 total_sz += sizeof(struct btf_ext_header);
2906 if (funcs_sz) {
2907 funcs_sz += sizeof(__u32); /* record size prefix */
2908 total_sz += funcs_sz;
2909 }
2910 if (lines_sz) {
2911 lines_sz += sizeof(__u32); /* record size prefix */
2912 total_sz += lines_sz;
2913 }
2914 if (core_relos_sz) {
2915 core_relos_sz += sizeof(__u32); /* record size prefix */
2916 total_sz += core_relos_sz;
2917 }
2918
2919 cur = data = calloc(1, total_sz);
2920 if (!data)
2921 return -ENOMEM;
2922
2923 hdr = cur;
2924 hdr->magic = BTF_MAGIC;
2925 hdr->version = BTF_VERSION;
2926 hdr->flags = 0;
2927 hdr->hdr_len = sizeof(struct btf_ext_header);
2928 cur += sizeof(struct btf_ext_header);
2929
2930 /* All offsets are in bytes relative to the end of this header */
2931 hdr->func_info_off = 0;
2932 hdr->func_info_len = funcs_sz;
2933 hdr->line_info_off = funcs_sz;
2934 hdr->line_info_len = lines_sz;
2935 hdr->core_relo_off = funcs_sz + lines_sz;
2936 hdr->core_relo_len = core_relos_sz;
2937
2938 if (funcs_sz) {
2939 *(__u32 *)cur = func_rec_sz;
2940 cur += sizeof(__u32);
2941
2942 for (i = 1; i < linker->sec_cnt; i++) {
2943 struct dst_sec *sec = &linker->secs[i];
2944
2945 sz = emit_btf_ext_data(linker, cur, sec->sec_name, &sec->func_info);
2946 if (sz < 0) {
2947 err = sz;
2948 goto out;
2949 }
2950
2951 cur += sz;
2952 }
2953 }
2954
2955 if (lines_sz) {
2956 *(__u32 *)cur = line_rec_sz;
2957 cur += sizeof(__u32);
2958
2959 for (i = 1; i < linker->sec_cnt; i++) {
2960 struct dst_sec *sec = &linker->secs[i];
2961
2962 sz = emit_btf_ext_data(linker, cur, sec->sec_name, &sec->line_info);
2963 if (sz < 0) {
2964 err = sz;
2965 goto out;
2966 }
2967
2968 cur += sz;
2969 }
2970 }
2971
2972 if (core_relos_sz) {
2973 *(__u32 *)cur = core_relo_rec_sz;
2974 cur += sizeof(__u32);
2975
2976 for (i = 1; i < linker->sec_cnt; i++) {
2977 struct dst_sec *sec = &linker->secs[i];
2978
2979 sz = emit_btf_ext_data(linker, cur, sec->sec_name, &sec->core_relo_info);
2980 if (sz < 0) {
2981 err = sz;
2982 goto out;
2983 }
2984
2985 cur += sz;
2986 }
2987 }
2988
2989 linker->btf_ext = btf_ext__new(data, total_sz);
2990 err = libbpf_get_error(linker->btf_ext);
2991 if (err) {
2992 linker->btf_ext = NULL;
2993 pr_warn("failed to parse final .BTF.ext data: %s\n", errstr(err));
2994 goto out;
2995 }
2996
2997 out:
2998 free(data);
2999 return err;
3000 }
Kernel DRM miscellaneous fixes and cross-tree changes