linux - tools/lib/bpf/linker.c

3116 lines · 81.0 KiB

1	// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
2	/*
3	* BPF static linker
4	*
5	* Copyright (c) 2021 Facebook
6	*/
7	#ifndef _GNU_SOURCE
8	#define _GNU_SOURCE
9	#endif
10
11	#include <stdbool.h>
12	#include <stddef.h>
13	#include <stdio.h>
14	#include <stdlib.h>
15	#include <string.h>
16	#include <unistd.h>
17	#include <errno.h>
18	#include <linux/err.h>
19	#include <linux/btf.h>
20	#include <elf.h>
21	#include <libelf.h>
22	#include <fcntl.h>
23	#include <sys/mman.h>
24	#include "libbpf.h"
25	#include "btf.h"
26	#include "libbpf_internal.h"
27	#include "strset.h"
28
29	#define BTF_EXTERN_SEC ".extern"
30
31	struct src_sec {
32	const char *sec_name;
33	/* positional (not necessarily ELF) index in an array of sections */
34	int id;
35	/* positional (not necessarily ELF) index of a matching section in a final object file */
36	int dst_id;
37	/* section data offset in a matching output section */
38	int dst_off;
39	/* whether section is omitted from the final ELF file */
40	bool skipped;
41	/* whether section is an ephemeral section, not mapped to an ELF section */
42	bool ephemeral;
43
44	/* ELF info */
45	size_t sec_idx;
46	Elf_Scn *scn;
47	Elf64_Shdr *shdr;
48	Elf_Data *data;
49
50	/* corresponding BTF DATASEC type ID */
51	int sec_type_id;
52	};
53
54	struct src_obj {
55	const char *filename;
56	int fd;
57	Elf *elf;
58	/* Section header strings section index */
59	size_t shstrs_sec_idx;
60	/* SYMTAB section index */
61	size_t symtab_sec_idx;
62
63	struct btf *btf;
64	struct btf_ext *btf_ext;
65
66	/* List of sections (including ephemeral). Slot zero is unused. */
67	struct src_sec *secs;
68	int sec_cnt;
69
70	/* mapping of symbol indices from src to dst ELF */
71	int *sym_map;
72	/* mapping from the src BTF type IDs to dst ones */
73	int *btf_type_map;
74	};
75
76	/* single .BTF.ext data section */
77	struct btf_ext_sec_data {
78	size_t rec_cnt;
79	__u32 rec_sz;
80	void *recs;
81	};
82
83	struct glob_sym {
84	/* ELF symbol index */
85	int sym_idx;
86	/* associated section id for .ksyms, .kconfig, etc, but not .extern */
87	int sec_id;
88	/* extern name offset in STRTAB */
89	int name_off;
90	/* optional associated BTF type ID */
91	int btf_id;
92	/* BTF type ID to which VAR/FUNC type is pointing to; used for
93	* rewriting types when extern VAR/FUNC is resolved to a concrete
94	* definition
95	*/
96	int underlying_btf_id;
97	/* sec_var index in the corresponding dst_sec, if exists */
98	int var_idx;
99
100	/* extern or resolved/global symbol */
101	bool is_extern;
102	/* weak or strong symbol, never goes back from strong to weak */
103	bool is_weak;
104	};
105
106	struct dst_sec {
107	char *sec_name;
108	/* positional (not necessarily ELF) index in an array of sections */
109	int id;
110
111	bool ephemeral;
112
113	/* ELF info */
114	size_t sec_idx;
115	Elf_Scn *scn;
116	Elf64_Shdr *shdr;
117	Elf_Data *data;
118
119	/* final output section size */
120	int sec_sz;
121	/* final output contents of the section */
122	void *raw_data;
123
124	/* corresponding STT_SECTION symbol index in SYMTAB */
125	int sec_sym_idx;
126
127	/* section's DATASEC variable info, emitted on BTF finalization */
128	bool has_btf;
129	int sec_var_cnt;
130	struct btf_var_secinfo *sec_vars;
131
132	/* section's .BTF.ext data */
133	struct btf_ext_sec_data func_info;
134	struct btf_ext_sec_data line_info;
135	struct btf_ext_sec_data core_relo_info;
136	};
137
138	struct bpf_linker {
139	char *filename;
140	int fd;
141	Elf *elf;
142	Elf64_Ehdr *elf_hdr;
143	bool swapped_endian;
144
145	/* Output sections metadata */
146	struct dst_sec *secs;
147	int sec_cnt;
148
149	struct strset strtab_strs; / STRTAB unique strings */
150	size_t strtab_sec_idx; /* STRTAB section index */
151	size_t symtab_sec_idx; /* SYMTAB section index */
152
153	struct btf *btf;
154	struct btf_ext *btf_ext;
155
156	/* global (including extern) ELF symbols */
157	int glob_sym_cnt;
158	struct glob_sym *glob_syms;
159
160	bool fd_is_owned;
161	};
162
163	#define pr_warn_elf(fmt, ...) \
164	libbpf_print(LIBBPF_WARN, "libbpf: " fmt ": %s\n", ##__VA_ARGS__, elf_errmsg(-1))
165
166	static int init_output_elf(struct bpf_linker *linker);
167
168	static int bpf_linker_add_file(struct bpf_linker *linker, int fd,
169	const char *filename);
170
171	static int linker_load_obj_file(struct bpf_linker *linker,
172	struct src_obj *obj);
173	static int linker_sanity_check_elf(struct src_obj *obj);
174	static int linker_sanity_check_elf_symtab(struct src_obj obj, struct src_sec sec);
175	static int linker_sanity_check_elf_relos(struct src_obj obj, struct src_sec sec);
176	static int linker_sanity_check_btf(struct src_obj *obj);
177	static int linker_sanity_check_btf_ext(struct src_obj *obj);
178	static int linker_fixup_btf(struct src_obj *obj);
179	static int linker_append_sec_data(struct bpf_linker linker, struct src_obj obj);
180	static int linker_append_elf_syms(struct bpf_linker linker, struct src_obj obj);
181	static int linker_append_elf_sym(struct bpf_linker linker, struct src_obj obj,
182	Elf64_Sym sym, const char sym_name, int src_sym_idx);
183	static int linker_append_elf_relos(struct bpf_linker linker, struct src_obj obj);
184	static int linker_append_btf(struct bpf_linker linker, struct src_obj obj);
185	static int linker_append_btf_ext(struct bpf_linker linker, struct src_obj obj);
186
187	static int finalize_btf(struct bpf_linker *linker);
188	static int finalize_btf_ext(struct bpf_linker *linker);
189
190	void bpf_linker__free(struct bpf_linker *linker)
191	{
192	int i;
193
194	if (!linker)
195	return;
196
197	free(linker->filename);
198
199	if (linker->elf)
200	elf_end(linker->elf);
201
202	if (linker->fd >= 0 && linker->fd_is_owned)
203	close(linker->fd);
204
205	strset__free(linker->strtab_strs);
206
207	btf__free(linker->btf);
208	btf_ext__free(linker->btf_ext);
209
210	for (i = 1; i < linker->sec_cnt; i++) {
211	struct dst_sec *sec = &linker->secs[i];
212
213	free(sec->sec_name);
214	free(sec->raw_data);
215	free(sec->sec_vars);
216
217	free(sec->func_info.recs);
218	free(sec->line_info.recs);
219	free(sec->core_relo_info.recs);
220	}
221	free(linker->secs);
222
223	free(linker->glob_syms);
224	free(linker);
225	}
226
227	struct bpf_linker bpf_linker__new(const char filename, struct bpf_linker_opts *opts)
228	{
229	struct bpf_linker *linker;
230	int err;
231
232	if (!OPTS_VALID(opts, bpf_linker_opts))
233	return errno = EINVAL, NULL;
234
235	if (elf_version(EV_CURRENT) == EV_NONE) {
236	pr_warn_elf("libelf initialization failed");
237	return errno = EINVAL, NULL;
238	}
239
240	linker = calloc(1, sizeof(*linker));
241	if (!linker)
242	return errno = ENOMEM, NULL;
243
244	linker->filename = strdup(filename);
245	if (!linker->filename) {
246	err = -ENOMEM;
247	goto err_out;
248	}
249
250	linker->fd = open(filename, O_WRONLY \| O_CREAT \| O_TRUNC \| O_CLOEXEC, 0644);
251	if (linker->fd < 0) {
252	err = -errno;
253	pr_warn("failed to create '%s': %d\n", filename, err);
254	goto err_out;
255	}
256	linker->fd_is_owned = true;
257
258	err = init_output_elf(linker);
259	if (err)
260	goto err_out;
261
262	return linker;
263
264	err_out:
265	bpf_linker__free(linker);
266	return errno = -err, NULL;
267	}
268
269	struct bpf_linker bpf_linker__new_fd(int fd, struct bpf_linker_opts opts)
270	{
271	struct bpf_linker *linker;
272	char filename[32];
273	int err;
274
275	if (fd < 0)
276	return errno = EINVAL, NULL;
277
278	if (!OPTS_VALID(opts, bpf_linker_opts))
279	return errno = EINVAL, NULL;
280
281	if (elf_version(EV_CURRENT) == EV_NONE) {
282	pr_warn_elf("libelf initialization failed");
283	return errno = EINVAL, NULL;
284	}
285
286	linker = calloc(1, sizeof(*linker));
287	if (!linker)
288	return errno = ENOMEM, NULL;
289
290	snprintf(filename, sizeof(filename), "fd:%d", fd);
291	linker->filename = strdup(filename);
292	if (!linker->filename) {
293	err = -ENOMEM;
294	goto err_out;
295	}
296
297	linker->fd = fd;
298	linker->fd_is_owned = false;
299
300	err = init_output_elf(linker);
301	if (err)
302	goto err_out;
303
304	return linker;
305
306	err_out:
307	bpf_linker__free(linker);
308	return errno = -err, NULL;
309	}
310
311	static struct dst_sec add_dst_sec(struct bpf_linker linker, const char *sec_name)
312	{
313	struct dst_sec secs = linker->secs, sec;
314	size_t new_cnt = linker->sec_cnt ? linker->sec_cnt + 1 : 2;
315
316	secs = libbpf_reallocarray(secs, new_cnt, sizeof(*secs));
317	if (!secs)
318	return NULL;
319
320	/* zero out newly allocated memory */
321	memset(secs + linker->sec_cnt, 0, (new_cnt - linker->sec_cnt) * sizeof(*secs));
322
323	linker->secs = secs;
324	linker->sec_cnt = new_cnt;
325
326	sec = &linker->secs[new_cnt - 1];
327	sec->id = new_cnt - 1;
328	sec->sec_name = strdup(sec_name);
329	if (!sec->sec_name)
330	return NULL;
331
332	return sec;
333	}
334
335	static Elf64_Sym add_new_sym(struct bpf_linker linker, size_t *sym_idx)
336	{
337	struct dst_sec *symtab = &linker->secs[linker->symtab_sec_idx];
338	Elf64_Sym syms, sym;
339	size_t sym_cnt = symtab->sec_sz / sizeof(*sym);
340
341	syms = libbpf_reallocarray(symtab->raw_data, sym_cnt + 1, sizeof(*sym));
342	if (!syms)
343	return NULL;
344
345	sym = &syms[sym_cnt];
346	memset(sym, 0, sizeof(*sym));
347
348	symtab->raw_data = syms;
349	symtab->sec_sz += sizeof(*sym);
350	symtab->shdr->sh_size += sizeof(*sym);
351	symtab->data->d_size += sizeof(*sym);
352
353	if (sym_idx)
354	*sym_idx = sym_cnt;
355
356	return sym;
357	}
358
359	static int init_output_elf(struct bpf_linker *linker)
360	{
361	int err, str_off;
362	Elf64_Sym *init_sym;
363	struct dst_sec *sec;
364
365	linker->elf = elf_begin(linker->fd, ELF_C_WRITE, NULL);
366	if (!linker->elf) {
367	pr_warn_elf("failed to create ELF object");
368	return -EINVAL;
369	}
370
371	/* ELF header */
372	linker->elf_hdr = elf64_newehdr(linker->elf);
373	if (!linker->elf_hdr) {
374	pr_warn_elf("failed to create ELF header");
375	return -EINVAL;
376	}
377
378	linker->elf_hdr->e_machine = EM_BPF;
379	linker->elf_hdr->e_type = ET_REL;
380	/* Set unknown ELF endianness, assign later from input files */
381	linker->elf_hdr->e_ident[EI_DATA] = ELFDATANONE;
382
383	/* STRTAB */
384	/* initialize strset with an empty string to conform to ELF */
385	linker->strtab_strs = strset__new(INT_MAX, "", sizeof(""));
386	if (libbpf_get_error(linker->strtab_strs))
387	return libbpf_get_error(linker->strtab_strs);
388
389	sec = add_dst_sec(linker, ".strtab");
390	if (!sec)
391	return -ENOMEM;
392
393	sec->scn = elf_newscn(linker->elf);
394	if (!sec->scn) {
395	pr_warn_elf("failed to create STRTAB section");
396	return -EINVAL;
397	}
398
399	sec->shdr = elf64_getshdr(sec->scn);
400	if (!sec->shdr)
401	return -EINVAL;
402
403	sec->data = elf_newdata(sec->scn);
404	if (!sec->data) {
405	pr_warn_elf("failed to create STRTAB data");
406	return -EINVAL;
407	}
408
409	str_off = strset__add_str(linker->strtab_strs, sec->sec_name);
410	if (str_off < 0)
411	return str_off;
412
413	sec->sec_idx = elf_ndxscn(sec->scn);
414	linker->elf_hdr->e_shstrndx = sec->sec_idx;
415	linker->strtab_sec_idx = sec->sec_idx;
416
417	sec->shdr->sh_name = str_off;
418	sec->shdr->sh_type = SHT_STRTAB;
419	sec->shdr->sh_flags = SHF_STRINGS;
420	sec->shdr->sh_offset = 0;
421	sec->shdr->sh_link = 0;
422	sec->shdr->sh_info = 0;
423	sec->shdr->sh_addralign = 1;
424	sec->shdr->sh_size = sec->sec_sz = 0;
425	sec->shdr->sh_entsize = 0;
426
427	/* SYMTAB */
428	sec = add_dst_sec(linker, ".symtab");
429	if (!sec)
430	return -ENOMEM;
431
432	sec->scn = elf_newscn(linker->elf);
433	if (!sec->scn) {
434	pr_warn_elf("failed to create SYMTAB section");
435	return -EINVAL;
436	}
437
438	sec->shdr = elf64_getshdr(sec->scn);
439	if (!sec->shdr)
440	return -EINVAL;
441
442	sec->data = elf_newdata(sec->scn);
443	if (!sec->data) {
444	pr_warn_elf("failed to create SYMTAB data");
445	return -EINVAL;
446	}
447	/* Ensure libelf translates byte-order of symbol records */
448	sec->data->d_type = ELF_T_SYM;
449
450	str_off = strset__add_str(linker->strtab_strs, sec->sec_name);
451	if (str_off < 0)
452	return str_off;
453
454	sec->sec_idx = elf_ndxscn(sec->scn);
455	linker->symtab_sec_idx = sec->sec_idx;
456
457	sec->shdr->sh_name = str_off;
458	sec->shdr->sh_type = SHT_SYMTAB;
459	sec->shdr->sh_flags = 0;
460	sec->shdr->sh_offset = 0;
461	sec->shdr->sh_link = linker->strtab_sec_idx;
462	/* sh_info should be one greater than the index of the last local
463	* symbol (i.e., binding is STB_LOCAL). But why and who cares?
464	*/
465	sec->shdr->sh_info = 0;
466	sec->shdr->sh_addralign = 8;
467	sec->shdr->sh_entsize = sizeof(Elf64_Sym);
468
469	/* .BTF */
470	linker->btf = btf__new_empty();
471	err = libbpf_get_error(linker->btf);
472	if (err)
473	return err;
474
475	/* add the special all-zero symbol */
476	init_sym = add_new_sym(linker, NULL);
477	if (!init_sym)
478	return -EINVAL;
479
480	init_sym->st_name = 0;
481	init_sym->st_info = 0;
482	init_sym->st_other = 0;
483	init_sym->st_shndx = SHN_UNDEF;
484	init_sym->st_value = 0;
485	init_sym->st_size = 0;
486
487	return 0;
488	}
489
490	static int bpf_linker_add_file(struct bpf_linker *linker, int fd,
491	const char *filename)
492	{
493	struct src_obj obj = {};
494	int err = 0;
495
496	obj.filename = filename;
497	obj.fd = fd;
498
499	err = err ?: linker_load_obj_file(linker, &obj);
500	err = err ?: linker_append_sec_data(linker, &obj);
501	err = err ?: linker_append_elf_syms(linker, &obj);
502	err = err ?: linker_append_elf_relos(linker, &obj);
503	err = err ?: linker_append_btf(linker, &obj);
504	err = err ?: linker_append_btf_ext(linker, &obj);
505
506	/* free up src_obj resources */
507	free(obj.btf_type_map);
508	btf__free(obj.btf);
509	btf_ext__free(obj.btf_ext);
510	free(obj.secs);
511	free(obj.sym_map);
512	if (obj.elf)
513	elf_end(obj.elf);
514
515	return err;
516	}
517
518	int bpf_linker__add_file(struct bpf_linker linker, const char filename,
519	const struct bpf_linker_file_opts *opts)
520	{
521	int fd, err;
522
523	if (!OPTS_VALID(opts, bpf_linker_file_opts))
524	return libbpf_err(-EINVAL);
525
526	if (!linker->elf)
527	return libbpf_err(-EINVAL);
528
529	fd = open(filename, O_RDONLY \| O_CLOEXEC);
530	if (fd < 0) {
531	err = -errno;
532	pr_warn("failed to open file '%s': %s\n", filename, errstr(err));
533	return libbpf_err(err);
534	}
535
536	err = bpf_linker_add_file(linker, fd, filename);
537	close(fd);
538	return libbpf_err(err);
539	}
540
541	int bpf_linker__add_fd(struct bpf_linker *linker, int fd,
542	const struct bpf_linker_file_opts *opts)
543	{
544	char filename[32];
545	int err;
546
547	if (!OPTS_VALID(opts, bpf_linker_file_opts))
548	return libbpf_err(-EINVAL);
549
550	if (!linker->elf)
551	return libbpf_err(-EINVAL);
552
553	if (fd < 0)
554	return libbpf_err(-EINVAL);
555
556	snprintf(filename, sizeof(filename), "fd:%d", fd);
557	err = bpf_linker_add_file(linker, fd, filename);
558	return libbpf_err(err);
559	}
560
561	int bpf_linker__add_buf(struct bpf_linker linker, void buf, size_t buf_sz,
562	const struct bpf_linker_file_opts *opts)
563	{
564	char filename[32];
565	int fd, written, ret;
566
567	if (!OPTS_VALID(opts, bpf_linker_file_opts))
568	return libbpf_err(-EINVAL);
569
570	if (!linker->elf)
571	return libbpf_err(-EINVAL);
572
573	snprintf(filename, sizeof(filename), "mem:%p+%zu", buf, buf_sz);
574
575	fd = sys_memfd_create(filename, 0);
576	if (fd < 0) {
577	ret = -errno;
578	pr_warn("failed to create memfd '%s': %s\n", filename, errstr(ret));
579	return libbpf_err(ret);
580	}
581
582	written = 0;
583	while (written < buf_sz) {
584	ret = write(fd, buf + written, buf_sz - written);
585	if (ret < 0) {
586	ret = -errno;
587	pr_warn("failed to write '%s': %s\n", filename, errstr(ret));
588	goto err_out;
589	}
590	written += ret;
591	}
592
593	ret = bpf_linker_add_file(linker, fd, filename);
594	err_out:
595	close(fd);
596	return libbpf_err(ret);
597	}
598
599	static bool is_dwarf_sec_name(const char *name)
600	{
601	/* approximation, but the actual list is too long */
602	return strncmp(name, ".debug_", sizeof(".debug_") - 1) == 0;
603	}
604
605	static bool is_ignored_sec(struct src_sec *sec)
606	{
607	Elf64_Shdr *shdr = sec->shdr;
608	const char *name = sec->sec_name;
609
610	/* no special handling of .strtab */
611	if (shdr->sh_type == SHT_STRTAB)
612	return true;
613
614	/* ignore .llvm_addrsig section as well */
615	if (shdr->sh_type == SHT_LLVM_ADDRSIG)
616	return true;
617
618	/* no subprograms will lead to an empty .text section, ignore it */
619	if (shdr->sh_type == SHT_PROGBITS && shdr->sh_size == 0 &&
620	strcmp(sec->sec_name, ".text") == 0)
621	return true;
622
623	/* DWARF sections */
624	if (is_dwarf_sec_name(sec->sec_name))
625	return true;
626
627	if (strncmp(name, ".rel", sizeof(".rel") - 1) == 0) {
628	name += sizeof(".rel") - 1;
629	/* DWARF section relocations */
630	if (is_dwarf_sec_name(name))
631	return true;
632
633	/* .BTF and .BTF.ext don't need relocations */
634	if (strcmp(name, BTF_ELF_SEC) == 0 \|\|
635	strcmp(name, BTF_EXT_ELF_SEC) == 0)
636	return true;
637	}
638
639	return false;
640	}
641
642	static struct src_sec add_src_sec(struct src_obj obj, const char *sec_name)
643	{
644	struct src_sec secs = obj->secs, sec;
645	size_t new_cnt = obj->sec_cnt ? obj->sec_cnt + 1 : 2;
646
647	secs = libbpf_reallocarray(secs, new_cnt, sizeof(*secs));
648	if (!secs)
649	return NULL;
650
651	/* zero out newly allocated memory */
652	memset(secs + obj->sec_cnt, 0, (new_cnt - obj->sec_cnt) * sizeof(*secs));
653
654	obj->secs = secs;
655	obj->sec_cnt = new_cnt;
656
657	sec = &obj->secs[new_cnt - 1];
658	sec->id = new_cnt - 1;
659	sec->sec_name = sec_name;
660
661	return sec;
662	}
663
664	static int linker_load_obj_file(struct bpf_linker *linker,
665	struct src_obj *obj)
666	{
667	int err = 0;
668	Elf_Scn *scn;
669	Elf_Data *data;
670	Elf64_Ehdr *ehdr;
671	Elf64_Shdr *shdr;
672	struct src_sec *sec;
673	unsigned char obj_byteorder;
674	unsigned char link_byteorder = linker->elf_hdr->e_ident[EI_DATA];
675	#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
676	const unsigned char host_byteorder = ELFDATA2LSB;
677	#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
678	const unsigned char host_byteorder = ELFDATA2MSB;
679	#else
680	#error "Unknown __BYTE_ORDER__"
681	#endif
682
683	pr_debug("linker: adding object file '%s'...\n", obj->filename);
684
685	obj->elf = elf_begin(obj->fd, ELF_C_READ_MMAP, NULL);
686	if (!obj->elf) {
687	pr_warn_elf("failed to parse ELF file '%s'", obj->filename);
688	return -EINVAL;
689	}
690
691	/* Sanity check ELF file high-level properties */
692	ehdr = elf64_getehdr(obj->elf);
693	if (!ehdr) {
694	pr_warn_elf("failed to get ELF header for %s", obj->filename);
695	return -EINVAL;
696	}
697
698	/* Linker output endianness set by first input object */
699	obj_byteorder = ehdr->e_ident[EI_DATA];
700	if (obj_byteorder != ELFDATA2LSB && obj_byteorder != ELFDATA2MSB) {
701	err = -EOPNOTSUPP;
702	pr_warn("unknown byte order of ELF file %s\n", obj->filename);
703	return err;
704	}
705	if (link_byteorder == ELFDATANONE) {
706	linker->elf_hdr->e_ident[EI_DATA] = obj_byteorder;
707	linker->swapped_endian = obj_byteorder != host_byteorder;
708	pr_debug("linker: set %s-endian output byte order\n",
709	obj_byteorder == ELFDATA2MSB ? "big" : "little");
710	} else if (link_byteorder != obj_byteorder) {
711	err = -EOPNOTSUPP;
712	pr_warn("byte order mismatch with ELF file %s\n", obj->filename);
713	return err;
714	}
715
716	if (ehdr->e_type != ET_REL
717	\|\| ehdr->e_machine != EM_BPF
718	\|\| ehdr->e_ident[EI_CLASS] != ELFCLASS64) {
719	err = -EOPNOTSUPP;
720	pr_warn_elf("unsupported kind of ELF file %s", obj->filename);
721	return err;
722	}
723
724	if (elf_getshdrstrndx(obj->elf, &obj->shstrs_sec_idx)) {
725	pr_warn_elf("failed to get SHSTRTAB section index for %s", obj->filename);
726	return -EINVAL;
727	}
728
729	scn = NULL;
730	while ((scn = elf_nextscn(obj->elf, scn)) != NULL) {
731	size_t sec_idx = elf_ndxscn(scn);
732	const char *sec_name;
733
734	shdr = elf64_getshdr(scn);
735	if (!shdr) {
736	pr_warn_elf("failed to get section #%zu header for %s",
737	sec_idx, obj->filename);
738	return -EINVAL;
739	}
740
741	sec_name = elf_strptr(obj->elf, obj->shstrs_sec_idx, shdr->sh_name);
742	if (!sec_name) {
743	pr_warn_elf("failed to get section #%zu name for %s",
744	sec_idx, obj->filename);
745	return -EINVAL;
746	}
747
748	data = elf_getdata(scn, 0);
749	if (!data) {
750	pr_warn_elf("failed to get section #%zu (%s) data from %s",
751	sec_idx, sec_name, obj->filename);
752	return -EINVAL;
753	}
754
755	sec = add_src_sec(obj, sec_name);
756	if (!sec)
757	return -ENOMEM;
758
759	sec->scn = scn;
760	sec->shdr = shdr;
761	sec->data = data;
762	sec->sec_idx = elf_ndxscn(scn);
763
764	if (is_ignored_sec(sec)) {
765	sec->skipped = true;
766	continue;
767	}
768
769	switch (shdr->sh_type) {
770	case SHT_SYMTAB:
771	if (obj->symtab_sec_idx) {
772	err = -EOPNOTSUPP;
773	pr_warn("multiple SYMTAB sections found, not supported\n");
774	return err;
775	}
776	obj->symtab_sec_idx = sec_idx;
777	break;
778	case SHT_STRTAB:
779	/* we'll construct our own string table */
780	break;
781	case SHT_PROGBITS:
782	if (strcmp(sec_name, BTF_ELF_SEC) == 0) {
783	obj->btf = btf__new(data->d_buf, shdr->sh_size);
784	err = libbpf_get_error(obj->btf);
785	if (err) {
786	pr_warn("failed to parse .BTF from %s: %s\n",
787	obj->filename, errstr(err));
788	return err;
789	}
790	sec->skipped = true;
791	continue;
792	}
793	if (strcmp(sec_name, BTF_EXT_ELF_SEC) == 0) {
794	obj->btf_ext = btf_ext__new(data->d_buf, shdr->sh_size);
795	err = libbpf_get_error(obj->btf_ext);
796	if (err) {
797	pr_warn("failed to parse .BTF.ext from '%s': %s\n",
798	obj->filename, errstr(err));
799	return err;
800	}
801	sec->skipped = true;
802	continue;
803	}
804
805	/* data & code */
806	break;
807	case SHT_NOBITS:
808	/* BSS */
809	break;
810	case SHT_REL:
811	/* relocations */
812	break;
813	default:
814	pr_warn("unrecognized section #%zu (%s) in %s\n",
815	sec_idx, sec_name, obj->filename);
816	err = -EINVAL;
817	return err;
818	}
819	}
820
821	err = err ?: linker_sanity_check_elf(obj);
822	err = err ?: linker_sanity_check_btf(obj);
823	err = err ?: linker_sanity_check_btf_ext(obj);
824	err = err ?: linker_fixup_btf(obj);
825
826	return err;
827	}
828
829	static int linker_sanity_check_elf(struct src_obj *obj)
830	{
831	struct src_sec *sec;
832	int i, err;
833
834	if (!obj->symtab_sec_idx) {
835	pr_warn("ELF is missing SYMTAB section in %s\n", obj->filename);
836	return -EINVAL;
837	}
838	if (!obj->shstrs_sec_idx) {
839	pr_warn("ELF is missing section headers STRTAB section in %s\n", obj->filename);
840	return -EINVAL;
841	}
842
843	for (i = 1; i < obj->sec_cnt; i++) {
844	sec = &obj->secs[i];
845
846	if (sec->sec_name[0] == '\0') {
847	pr_warn("ELF section #%zu has empty name in %s\n", sec->sec_idx, obj->filename);
848	return -EINVAL;
849	}
850
851	if (is_dwarf_sec_name(sec->sec_name))
852	continue;
853
854	if (sec->shdr->sh_addralign && !is_pow_of_2(sec->shdr->sh_addralign)) {
855	pr_warn("ELF section #%zu alignment %llu is non pow-of-2 alignment in %s\n",
856	sec->sec_idx, (long long unsigned)sec->shdr->sh_addralign,
857	obj->filename);
858	return -EINVAL;
859	}
860	if (sec->shdr->sh_addralign != sec->data->d_align) {
861	pr_warn("ELF section #%zu has inconsistent alignment addr=%llu != d=%llu in %s\n",
862	sec->sec_idx, (long long unsigned)sec->shdr->sh_addralign,
863	(long long unsigned)sec->data->d_align, obj->filename);
864	return -EINVAL;
865	}
866
867	if (sec->shdr->sh_size != sec->data->d_size) {
868	pr_warn("ELF section #%zu has inconsistent section size sh=%llu != d=%llu in %s\n",
869	sec->sec_idx, (long long unsigned)sec->shdr->sh_size,
870	(long long unsigned)sec->data->d_size, obj->filename);
871	return -EINVAL;
872	}
873
874	switch (sec->shdr->sh_type) {
875	case SHT_SYMTAB:
876	err = linker_sanity_check_elf_symtab(obj, sec);
877	if (err)
878	return err;
879	break;
880	case SHT_STRTAB:
881	break;
882	case SHT_PROGBITS:
883	if (sec->shdr->sh_flags & SHF_EXECINSTR) {
884	if (sec->shdr->sh_size % sizeof(struct bpf_insn) != 0) {
885	pr_warn("ELF section #%zu has unexpected size alignment %llu in %s\n",
886	sec->sec_idx, (long long unsigned)sec->shdr->sh_size,
887	obj->filename);
888	return -EINVAL;
889	}
890	}
891	break;
892	case SHT_NOBITS:
893	break;
894	case SHT_REL:
895	err = linker_sanity_check_elf_relos(obj, sec);
896	if (err)
897	return err;
898	break;
899	case SHT_LLVM_ADDRSIG:
900	break;
901	default:
902	pr_warn("ELF section #%zu (%s) has unrecognized type %zu in %s\n",
903	sec->sec_idx, sec->sec_name, (size_t)sec->shdr->sh_type, obj->filename);
904	return -EINVAL;
905	}
906	}
907
908	return 0;
909	}
910
911	static int linker_sanity_check_elf_symtab(struct src_obj obj, struct src_sec sec)
912	{
913	struct src_sec *link_sec;
914	Elf64_Sym *sym;
915	int i, n;
916
917	if (sec->shdr->sh_entsize != sizeof(Elf64_Sym))
918	return -EINVAL;
919	if (sec->shdr->sh_size % sec->shdr->sh_entsize != 0)
920	return -EINVAL;
921
922	if (!sec->shdr->sh_link \|\| sec->shdr->sh_link >= obj->sec_cnt) {
923	pr_warn("ELF SYMTAB section #%zu points to missing STRTAB section #%zu in %s\n",
924	sec->sec_idx, (size_t)sec->shdr->sh_link, obj->filename);
925	return -EINVAL;
926	}
927	link_sec = &obj->secs[sec->shdr->sh_link];
928	if (link_sec->shdr->sh_type != SHT_STRTAB) {
929	pr_warn("ELF SYMTAB section #%zu points to invalid STRTAB section #%zu in %s\n",
930	sec->sec_idx, (size_t)sec->shdr->sh_link, obj->filename);
931	return -EINVAL;
932	}
933
934	n = sec->shdr->sh_size / sec->shdr->sh_entsize;
935	sym = sec->data->d_buf;
936	for (i = 0; i < n; i++, sym++) {
937	int sym_type = ELF64_ST_TYPE(sym->st_info);
938	int sym_bind = ELF64_ST_BIND(sym->st_info);
939	int sym_vis = ELF64_ST_VISIBILITY(sym->st_other);
940
941	if (i == 0) {
942	if (sym->st_name != 0 \|\| sym->st_info != 0
943	\|\| sym->st_other != 0 \|\| sym->st_shndx != 0
944	\|\| sym->st_value != 0 \|\| sym->st_size != 0) {
945	pr_warn("ELF sym #0 is invalid in %s\n", obj->filename);
946	return -EINVAL;
947	}
948	continue;
949	}
950	if (sym_bind != STB_LOCAL && sym_bind != STB_GLOBAL && sym_bind != STB_WEAK) {
951	pr_warn("ELF sym #%d in section #%zu has unsupported symbol binding %d\n",
952	i, sec->sec_idx, sym_bind);
953	return -EINVAL;
954	}
955	if (sym_vis != STV_DEFAULT && sym_vis != STV_HIDDEN) {
956	pr_warn("ELF sym #%d in section #%zu has unsupported symbol visibility %d\n",
957	i, sec->sec_idx, sym_vis);
958	return -EINVAL;
959	}
960	if (sym->st_shndx == 0) {
961	if (sym_type != STT_NOTYPE \|\| sym_bind == STB_LOCAL
962	\|\| sym->st_value != 0 \|\| sym->st_size != 0) {
963	pr_warn("ELF sym #%d is invalid extern symbol in %s\n",
964	i, obj->filename);
965
966	return -EINVAL;
967	}
968	continue;
969	}
970	if (sym->st_shndx < SHN_LORESERVE && sym->st_shndx >= obj->sec_cnt) {
971	pr_warn("ELF sym #%d in section #%zu points to missing section #%zu in %s\n",
972	i, sec->sec_idx, (size_t)sym->st_shndx, obj->filename);
973	return -EINVAL;
974	}
975	if (sym_type == STT_SECTION) {
976	if (sym->st_value != 0)
977	return -EINVAL;
978	continue;
979	}
980	}
981
982	return 0;
983	}
984
985	static int linker_sanity_check_elf_relos(struct src_obj obj, struct src_sec sec)
986	{
987	struct src_sec link_sec, sym_sec;
988	Elf64_Rel *relo;
989	int i, n;
990
991	if (sec->shdr->sh_entsize != sizeof(Elf64_Rel))
992	return -EINVAL;
993	if (sec->shdr->sh_size % sec->shdr->sh_entsize != 0)
994	return -EINVAL;
995
996	/* SHT_REL's sh_link should point to SYMTAB */
997	if (sec->shdr->sh_link != obj->symtab_sec_idx) {
998	pr_warn("ELF relo section #%zu points to invalid SYMTAB section #%zu in %s\n",
999	sec->sec_idx, (size_t)sec->shdr->sh_link, obj->filename);
1000	return -EINVAL;
1001	}
1002
1003	/* SHT_REL's sh_info points to relocated section */
1004	if (!sec->shdr->sh_info \|\| sec->shdr->sh_info >= obj->sec_cnt) {
1005	pr_warn("ELF relo section #%zu points to missing section #%zu in %s\n",
1006	sec->sec_idx, (size_t)sec->shdr->sh_info, obj->filename);
1007	return -EINVAL;
1008	}
1009	link_sec = &obj->secs[sec->shdr->sh_info];
1010
1011	/* .rel<secname> -> <secname> pattern is followed */
1012	if (strncmp(sec->sec_name, ".rel", sizeof(".rel") - 1) != 0
1013	\|\| strcmp(sec->sec_name + sizeof(".rel") - 1, link_sec->sec_name) != 0) {
1014	pr_warn("ELF relo section #%zu name has invalid name in %s\n",
1015	sec->sec_idx, obj->filename);
1016	return -EINVAL;
1017	}
1018
1019	/* don't further validate relocations for ignored sections */
1020	if (link_sec->skipped)
1021	return 0;
1022
1023	/* relocatable section is data or instructions */
1024	if (link_sec->shdr->sh_type != SHT_PROGBITS && link_sec->shdr->sh_type != SHT_NOBITS) {
1025	pr_warn("ELF relo section #%zu points to invalid section #%zu in %s\n",
1026	sec->sec_idx, (size_t)sec->shdr->sh_info, obj->filename);
1027	return -EINVAL;
1028	}
1029
1030	/* check sanity of each relocation */
1031	n = sec->shdr->sh_size / sec->shdr->sh_entsize;
1032	relo = sec->data->d_buf;
1033	sym_sec = &obj->secs[obj->symtab_sec_idx];
1034	for (i = 0; i < n; i++, relo++) {
1035	size_t sym_idx = ELF64_R_SYM(relo->r_info);
1036	size_t sym_type = ELF64_R_TYPE(relo->r_info);
1037
1038	if (sym_type != R_BPF_64_64 && sym_type != R_BPF_64_32 &&
1039	sym_type != R_BPF_64_ABS64 && sym_type != R_BPF_64_ABS32) {
1040	pr_warn("ELF relo #%d in section #%zu has unexpected type %zu in %s\n",
1041	i, sec->sec_idx, sym_type, obj->filename);
1042	return -EINVAL;
1043	}
1044
1045	if (!sym_idx \|\| sym_idx * sizeof(Elf64_Sym) >= sym_sec->shdr->sh_size) {
1046	pr_warn("ELF relo #%d in section #%zu points to invalid symbol #%zu in %s\n",
1047	i, sec->sec_idx, sym_idx, obj->filename);
1048	return -EINVAL;
1049	}
1050
1051	if (link_sec->shdr->sh_flags & SHF_EXECINSTR) {
1052	if (relo->r_offset % sizeof(struct bpf_insn) != 0) {
1053	pr_warn("ELF relo #%d in section #%zu points to missing symbol #%zu in %s\n",
1054	i, sec->sec_idx, sym_idx, obj->filename);
1055	return -EINVAL;
1056	}
1057	}
1058	}
1059
1060	return 0;
1061	}
1062
1063	static int check_btf_type_id(__u32 type_id, void ctx)
1064	{
1065	struct btf *btf = ctx;
1066
1067	if (*type_id >= btf__type_cnt(btf))
1068	return -EINVAL;
1069
1070	return 0;
1071	}
1072
1073	static int check_btf_str_off(__u32 str_off, void ctx)
1074	{
1075	struct btf *btf = ctx;
1076	const char *s;
1077
1078	s = btf__str_by_offset(btf, *str_off);
1079
1080	if (!s)
1081	return -EINVAL;
1082
1083	return 0;
1084	}
1085
1086	static int linker_sanity_check_btf(struct src_obj *obj)
1087	{
1088	struct btf_type *t;
1089	int i, n, err;
1090
1091	if (!obj->btf)
1092	return 0;
1093
1094	n = btf__type_cnt(obj->btf);
1095	for (i = 1; i < n; i++) {
1096	struct btf_field_iter it;
1097	__u32 type_id, str_off;
1098
1099	t = btf_type_by_id(obj->btf, i);
1100
1101	err = btf_field_iter_init(&it, t, BTF_FIELD_ITER_IDS);
1102	if (err)
1103	return err;
1104	while ((type_id = btf_field_iter_next(&it))) {
1105	if (*type_id >= n)
1106	return -EINVAL;
1107	}
1108
1109	err = btf_field_iter_init(&it, t, BTF_FIELD_ITER_STRS);
1110	if (err)
1111	return err;
1112	while ((str_off = btf_field_iter_next(&it))) {
1113	if (!btf__str_by_offset(obj->btf, *str_off))
1114	return -EINVAL;
1115	}
1116	}
1117
1118	return 0;
1119	}
1120
1121	static int linker_sanity_check_btf_ext(struct src_obj *obj)
1122	{
1123	int err = 0;
1124
1125	if (!obj->btf_ext)
1126	return 0;
1127
1128	/* can't use .BTF.ext without .BTF */
1129	if (!obj->btf)
1130	return -EINVAL;
1131
1132	err = err ?: btf_ext_visit_type_ids(obj->btf_ext, check_btf_type_id, obj->btf);
1133	err = err ?: btf_ext_visit_str_offs(obj->btf_ext, check_btf_str_off, obj->btf);
1134	if (err)
1135	return err;
1136
1137	return 0;
1138	}
1139
1140	static int init_sec(struct bpf_linker linker, struct dst_sec dst_sec, struct src_sec *src_sec)
1141	{
1142	Elf_Scn *scn;
1143	Elf_Data *data;
1144	Elf64_Shdr *shdr;
1145	int name_off;
1146
1147	dst_sec->sec_sz = 0;
1148	dst_sec->sec_idx = 0;
1149	dst_sec->ephemeral = src_sec->ephemeral;
1150
1151	/* ephemeral sections are just thin section shells lacking most parts */
1152	if (src_sec->ephemeral)
1153	return 0;
1154
1155	scn = elf_newscn(linker->elf);
1156	if (!scn)
1157	return -ENOMEM;
1158	data = elf_newdata(scn);
1159	if (!data)
1160	return -ENOMEM;
1161	shdr = elf64_getshdr(scn);
1162	if (!shdr)
1163	return -ENOMEM;
1164
1165	dst_sec->scn = scn;
1166	dst_sec->shdr = shdr;
1167	dst_sec->data = data;
1168	dst_sec->sec_idx = elf_ndxscn(scn);
1169
1170	name_off = strset__add_str(linker->strtab_strs, src_sec->sec_name);
1171	if (name_off < 0)
1172	return name_off;
1173
1174	shdr->sh_name = name_off;
1175	shdr->sh_type = src_sec->shdr->sh_type;
1176	shdr->sh_flags = src_sec->shdr->sh_flags;
1177	shdr->sh_size = 0;
1178	/* sh_link and sh_info have different meaning for different types of
1179	* sections, so we leave it up to the caller code to fill them in, if
1180	* necessary
1181	*/
1182	shdr->sh_link = 0;
1183	shdr->sh_info = 0;
1184	shdr->sh_addralign = src_sec->shdr->sh_addralign;
1185	shdr->sh_entsize = src_sec->shdr->sh_entsize;
1186
1187	data->d_type = src_sec->data->d_type;
1188	data->d_size = 0;
1189	data->d_buf = NULL;
1190	data->d_align = src_sec->data->d_align;
1191	data->d_off = 0;
1192
1193	return 0;
1194	}
1195
1196	static struct dst_sec find_dst_sec_by_name(struct bpf_linker linker, const char *sec_name)
1197	{
1198	struct dst_sec *sec;
1199	int i;
1200
1201	for (i = 1; i < linker->sec_cnt; i++) {
1202	sec = &linker->secs[i];
1203
1204	if (strcmp(sec->sec_name, sec_name) == 0)
1205	return sec;
1206	}
1207
1208	return NULL;
1209	}
1210
1211	static bool secs_match(struct dst_sec dst, struct src_sec src)
1212	{
1213	if (dst->ephemeral \|\| src->ephemeral)
1214	return true;
1215
1216	if (dst->shdr->sh_type != src->shdr->sh_type) {
1217	pr_warn("sec %s types mismatch\n", dst->sec_name);
1218	return false;
1219	}
1220	if (dst->shdr->sh_flags != src->shdr->sh_flags) {
1221	pr_warn("sec %s flags mismatch\n", dst->sec_name);
1222	return false;
1223	}
1224	if (dst->shdr->sh_entsize != src->shdr->sh_entsize) {
1225	pr_warn("sec %s entsize mismatch\n", dst->sec_name);
1226	return false;
1227	}
1228
1229	return true;
1230	}
1231
1232	static bool sec_content_is_same(struct dst_sec dst_sec, struct src_sec src_sec)
1233	{
1234	if (dst_sec->sec_sz != src_sec->shdr->sh_size)
1235	return false;
1236	if (memcmp(dst_sec->raw_data, src_sec->data->d_buf, dst_sec->sec_sz) != 0)
1237	return false;
1238	return true;
1239	}
1240
1241	static bool is_exec_sec(struct dst_sec *sec)
1242	{
1243	if (!sec \|\| sec->ephemeral)
1244	return false;
1245	return (sec->shdr->sh_type == SHT_PROGBITS) &&
1246	(sec->shdr->sh_flags & SHF_EXECINSTR);
1247	}
1248
1249	static void exec_sec_bswap(void *raw_data, int size)
1250	{
1251	const int insn_cnt = size / sizeof(struct bpf_insn);
1252	struct bpf_insn *insn = raw_data;
1253	int i;
1254
1255	for (i = 0; i < insn_cnt; i++, insn++)
1256	bpf_insn_bswap(insn);
1257	}
1258
1259	static int extend_sec(struct bpf_linker linker, struct dst_sec dst, struct src_sec *src)
1260	{
1261	void *tmp;
1262	size_t dst_align, src_align;
1263	size_t dst_align_sz, dst_final_sz;
1264	int err;
1265
1266	/* Ephemeral source section doesn't contribute anything to ELF
1267	* section data.
1268	*/
1269	if (src->ephemeral)
1270	return 0;
1271
1272	/* Some sections (like .maps) can contain both externs (and thus be
1273	* ephemeral) and non-externs (map definitions). So it's possible that
1274	* it has to be "upgraded" from ephemeral to non-ephemeral when the
1275	* first non-ephemeral entity appears. In such case, we add ELF
1276	* section, data, etc.
1277	*/
1278	if (dst->ephemeral) {
1279	err = init_sec(linker, dst, src);
1280	if (err)
1281	return err;
1282	}
1283
1284	dst_align = dst->shdr->sh_addralign;
1285	src_align = src->shdr->sh_addralign;
1286	if (dst_align == 0)
1287	dst_align = 1;
1288	if (dst_align < src_align)
1289	dst_align = src_align;
1290
1291	dst_align_sz = (dst->sec_sz + dst_align - 1) / dst_align * dst_align;
1292
1293	/* no need to re-align final size */
1294	dst_final_sz = dst_align_sz + src->shdr->sh_size;
1295
1296	if (src->shdr->sh_type != SHT_NOBITS) {
1297	tmp = realloc(dst->raw_data, dst_final_sz);
1298	/* If dst_align_sz == 0, realloc() behaves in a special way:
1299	* 1. When dst->raw_data is NULL it returns:
1300	* "either NULL or a pointer suitable to be passed to free()" [1].
1301	* 2. When dst->raw_data is not-NULL it frees dst->raw_data and returns NULL,
1302	* thus invalidating any "pointer suitable to be passed to free()" obtained
1303	* at step (1).
1304	*
1305	* The dst_align_sz > 0 check avoids error exit after (2), otherwise
1306	* dst->raw_data would be freed again in bpf_linker__free().
1307	*
1308	* [1] man 3 realloc
1309	*/
1310	if (!tmp && dst_align_sz > 0)
1311	return -ENOMEM;
1312	dst->raw_data = tmp;
1313
1314	/* pad dst section, if it's alignment forced size increase */
1315	memset(dst->raw_data + dst->sec_sz, 0, dst_align_sz - dst->sec_sz);
1316	/* now copy src data at a properly aligned offset */
1317	memcpy(dst->raw_data + dst_align_sz, src->data->d_buf, src->shdr->sh_size);
1318
1319	/* convert added bpf insns to native byte-order */
1320	if (linker->swapped_endian && is_exec_sec(dst))
1321	exec_sec_bswap(dst->raw_data + dst_align_sz, src->shdr->sh_size);
1322	}
1323
1324	dst->sec_sz = dst_final_sz;
1325	dst->shdr->sh_size = dst_final_sz;
1326	dst->data->d_size = dst_final_sz;
1327
1328	dst->shdr->sh_addralign = dst_align;
1329	dst->data->d_align = dst_align;
1330
1331	src->dst_off = dst_align_sz;
1332
1333	return 0;
1334	}
1335
1336	static bool is_data_sec(struct src_sec *sec)
1337	{
1338	if (!sec \|\| sec->skipped)
1339	return false;
1340	/* ephemeral sections are data sections, e.g., .kconfig, .ksyms */
1341	if (sec->ephemeral)
1342	return true;
1343	return sec->shdr->sh_type == SHT_PROGBITS \|\| sec->shdr->sh_type == SHT_NOBITS;
1344	}
1345
1346	static bool is_relo_sec(struct src_sec *sec)
1347	{
1348	if (!sec \|\| sec->skipped \|\| sec->ephemeral)
1349	return false;
1350	return sec->shdr->sh_type == SHT_REL;
1351	}
1352
1353	static int linker_append_sec_data(struct bpf_linker linker, struct src_obj obj)
1354	{
1355	int i, err;
1356
1357	for (i = 1; i < obj->sec_cnt; i++) {
1358	struct src_sec *src_sec;
1359	struct dst_sec *dst_sec;
1360
1361	src_sec = &obj->secs[i];
1362	if (!is_data_sec(src_sec))
1363	continue;
1364
1365	dst_sec = find_dst_sec_by_name(linker, src_sec->sec_name);
1366	if (!dst_sec) {
1367	dst_sec = add_dst_sec(linker, src_sec->sec_name);
1368	if (!dst_sec)
1369	return -ENOMEM;
1370	err = init_sec(linker, dst_sec, src_sec);
1371	if (err) {
1372	pr_warn("failed to init section '%s'\n", src_sec->sec_name);
1373	return err;
1374	}
1375	} else {
1376	if (!secs_match(dst_sec, src_sec)) {
1377	pr_warn("ELF sections %s are incompatible\n", src_sec->sec_name);
1378	return -EINVAL;
1379	}
1380
1381	/* "license" and "version" sections are deduped */
1382	if (strcmp(src_sec->sec_name, "license") == 0
1383	\|\| strcmp(src_sec->sec_name, "version") == 0) {
1384	if (!sec_content_is_same(dst_sec, src_sec)) {
1385	pr_warn("non-identical contents of section '%s' are not supported\n", src_sec->sec_name);
1386	return -EINVAL;
1387	}
1388	src_sec->skipped = true;
1389	src_sec->dst_id = dst_sec->id;
1390	continue;
1391	}
1392	}
1393
1394	/* record mapped section index */
1395	src_sec->dst_id = dst_sec->id;
1396
1397	err = extend_sec(linker, dst_sec, src_sec);
1398	if (err)
1399	return err;
1400	}
1401
1402	return 0;
1403	}
1404
1405	static int linker_append_elf_syms(struct bpf_linker linker, struct src_obj obj)
1406	{
1407	struct src_sec *symtab = &obj->secs[obj->symtab_sec_idx];
1408	Elf64_Sym *sym = symtab->data->d_buf;
1409	int i, n = symtab->shdr->sh_size / symtab->shdr->sh_entsize, err;
1410	int str_sec_idx = symtab->shdr->sh_link;
1411	const char *sym_name;
1412
1413	obj->sym_map = calloc(n + 1, sizeof(*obj->sym_map));
1414	if (!obj->sym_map)
1415	return -ENOMEM;
1416
1417	for (i = 0; i < n; i++, sym++) {
1418	/* We already validated all-zero symbol #0 and we already
1419	* appended it preventively to the final SYMTAB, so skip it.
1420	*/
1421	if (i == 0)
1422	continue;
1423
1424	sym_name = elf_strptr(obj->elf, str_sec_idx, sym->st_name);
1425	if (!sym_name) {
1426	pr_warn("can't fetch symbol name for symbol #%d in '%s'\n", i, obj->filename);
1427	return -EINVAL;
1428	}
1429
1430	err = linker_append_elf_sym(linker, obj, sym, sym_name, i);
1431	if (err)
1432	return err;
1433	}
1434
1435	return 0;
1436	}
1437
1438	static Elf64_Sym get_sym_by_idx(struct bpf_linker linker, size_t sym_idx)
1439	{
1440	struct dst_sec *symtab = &linker->secs[linker->symtab_sec_idx];
1441	Elf64_Sym *syms = symtab->raw_data;
1442
1443	return &syms[sym_idx];
1444	}
1445
1446	static struct glob_sym find_glob_sym(struct bpf_linker linker, const char *sym_name)
1447	{
1448	struct glob_sym *glob_sym;
1449	const char *name;
1450	int i;
1451
1452	for (i = 0; i < linker->glob_sym_cnt; i++) {
1453	glob_sym = &linker->glob_syms[i];
1454	name = strset__data(linker->strtab_strs) + glob_sym->name_off;
1455
1456	if (strcmp(name, sym_name) == 0)
1457	return glob_sym;
1458	}
1459
1460	return NULL;
1461	}
1462
1463	static struct glob_sym add_glob_sym(struct bpf_linker linker)
1464	{
1465	struct glob_sym syms, sym;
1466
1467	syms = libbpf_reallocarray(linker->glob_syms, linker->glob_sym_cnt + 1,
1468	sizeof(*linker->glob_syms));
1469	if (!syms)
1470	return NULL;
1471
1472	sym = &syms[linker->glob_sym_cnt];
1473	memset(sym, 0, sizeof(*sym));
1474	sym->var_idx = -1;
1475
1476	linker->glob_syms = syms;
1477	linker->glob_sym_cnt++;
1478
1479	return sym;
1480	}
1481
1482	static bool glob_sym_btf_matches(const char *sym_name, bool exact,
1483	const struct btf *btf1, __u32 id1,
1484	const struct btf *btf2, __u32 id2)
1485	{
1486	const struct btf_type t1, t2;
1487	bool is_static1, is_static2;
1488	const char n1, n2;
1489	int i, n;
1490
1491	recur:
1492	n1 = n2 = NULL;
1493	t1 = skip_mods_and_typedefs(btf1, id1, &id1);
1494	t2 = skip_mods_and_typedefs(btf2, id2, &id2);
1495
1496	/* check if only one side is FWD, otherwise handle with common logic */
1497	if (!exact && btf_is_fwd(t1) != btf_is_fwd(t2)) {
1498	n1 = btf__str_by_offset(btf1, t1->name_off);
1499	n2 = btf__str_by_offset(btf2, t2->name_off);
1500	if (strcmp(n1, n2) != 0) {
1501	pr_warn("global '%s': incompatible forward declaration names '%s' and '%s'\n",
1502	sym_name, n1, n2);
1503	return false;
1504	}
1505	/* validate if FWD kind matches concrete kind */
1506	if (btf_is_fwd(t1)) {
1507	if (btf_kflag(t1) && btf_is_union(t2))
1508	return true;
1509	if (!btf_kflag(t1) && btf_is_struct(t2))
1510	return true;
1511	pr_warn("global '%s': incompatible %s forward declaration and concrete kind %s\n",
1512	sym_name, btf_kflag(t1) ? "union" : "struct", btf_kind_str(t2));
1513	} else {
1514	if (btf_kflag(t2) && btf_is_union(t1))
1515	return true;
1516	if (!btf_kflag(t2) && btf_is_struct(t1))
1517	return true;
1518	pr_warn("global '%s': incompatible %s forward declaration and concrete kind %s\n",
1519	sym_name, btf_kflag(t2) ? "union" : "struct", btf_kind_str(t1));
1520	}
1521	return false;
1522	}
1523
1524	if (btf_kind(t1) != btf_kind(t2)) {
1525	pr_warn("global '%s': incompatible BTF kinds %s and %s\n",
1526	sym_name, btf_kind_str(t1), btf_kind_str(t2));
1527	return false;
1528	}
1529
1530	switch (btf_kind(t1)) {
1531	case BTF_KIND_STRUCT:
1532	case BTF_KIND_UNION:
1533	case BTF_KIND_ENUM:
1534	case BTF_KIND_ENUM64:
1535	case BTF_KIND_FWD:
1536	case BTF_KIND_FUNC:
1537	case BTF_KIND_VAR:
1538	n1 = btf__str_by_offset(btf1, t1->name_off);
1539	n2 = btf__str_by_offset(btf2, t2->name_off);
1540	if (strcmp(n1, n2) != 0) {
1541	pr_warn("global '%s': incompatible %s names '%s' and '%s'\n",
1542	sym_name, btf_kind_str(t1), n1, n2);
1543	return false;
1544	}
1545	break;
1546	default:
1547	break;
1548	}
1549
1550	switch (btf_kind(t1)) {
1551	case BTF_KIND_UNKN: /* void */
1552	case BTF_KIND_FWD:
1553	return true;
1554	case BTF_KIND_INT:
1555	case BTF_KIND_FLOAT:
1556	case BTF_KIND_ENUM:
1557	case BTF_KIND_ENUM64:
1558	/* ignore encoding for int and enum values for enum */
1559	if (t1->size != t2->size) {
1560	pr_warn("global '%s': incompatible %s '%s' size %u and %u\n",
1561	sym_name, btf_kind_str(t1), n1, t1->size, t2->size);
1562	return false;
1563	}
1564	return true;
1565	case BTF_KIND_PTR:
1566	/* just validate overall shape of the referenced type, so no
1567	* contents comparison for struct/union, and allowed fwd vs
1568	* struct/union
1569	*/
1570	exact = false;
1571	id1 = t1->type;
1572	id2 = t2->type;
1573	goto recur;
1574	case BTF_KIND_ARRAY:
1575	/* ignore index type and array size */
1576	id1 = btf_array(t1)->type;
1577	id2 = btf_array(t2)->type;
1578	goto recur;
1579	case BTF_KIND_FUNC:
1580	/* extern and global linkages are compatible */
1581	is_static1 = btf_func_linkage(t1) == BTF_FUNC_STATIC;
1582	is_static2 = btf_func_linkage(t2) == BTF_FUNC_STATIC;
1583	if (is_static1 != is_static2) {
1584	pr_warn("global '%s': incompatible func '%s' linkage\n", sym_name, n1);
1585	return false;
1586	}
1587
1588	id1 = t1->type;
1589	id2 = t2->type;
1590	goto recur;
1591	case BTF_KIND_VAR:
1592	/* extern and global linkages are compatible */
1593	is_static1 = btf_var(t1)->linkage == BTF_VAR_STATIC;
1594	is_static2 = btf_var(t2)->linkage == BTF_VAR_STATIC;
1595	if (is_static1 != is_static2) {
1596	pr_warn("global '%s': incompatible var '%s' linkage\n", sym_name, n1);
1597	return false;
1598	}
1599
1600	id1 = t1->type;
1601	id2 = t2->type;
1602	goto recur;
1603	case BTF_KIND_STRUCT:
1604	case BTF_KIND_UNION: {
1605	const struct btf_member m1, m2;
1606
1607	if (!exact)
1608	return true;
1609
1610	if (btf_vlen(t1) != btf_vlen(t2)) {
1611	pr_warn("global '%s': incompatible number of %s fields %u and %u\n",
1612	sym_name, btf_kind_str(t1), btf_vlen(t1), btf_vlen(t2));
1613	return false;
1614	}
1615
1616	n = btf_vlen(t1);
1617	m1 = btf_members(t1);
1618	m2 = btf_members(t2);
1619	for (i = 0; i < n; i++, m1++, m2++) {
1620	n1 = btf__str_by_offset(btf1, m1->name_off);
1621	n2 = btf__str_by_offset(btf2, m2->name_off);
1622	if (strcmp(n1, n2) != 0) {
1623	pr_warn("global '%s': incompatible field #%d names '%s' and '%s'\n",
1624	sym_name, i, n1, n2);
1625	return false;
1626	}
1627	if (m1->offset != m2->offset) {
1628	pr_warn("global '%s': incompatible field #%d ('%s') offsets\n",
1629	sym_name, i, n1);
1630	return false;
1631	}
1632	if (!glob_sym_btf_matches(sym_name, exact, btf1, m1->type, btf2, m2->type))
1633	return false;
1634	}
1635
1636	return true;
1637	}
1638	case BTF_KIND_FUNC_PROTO: {
1639	const struct btf_param m1, m2;
1640
1641	if (btf_vlen(t1) != btf_vlen(t2)) {
1642	pr_warn("global '%s': incompatible number of %s params %u and %u\n",
1643	sym_name, btf_kind_str(t1), btf_vlen(t1), btf_vlen(t2));
1644	return false;
1645	}
1646
1647	n = btf_vlen(t1);
1648	m1 = btf_params(t1);
1649	m2 = btf_params(t2);
1650	for (i = 0; i < n; i++, m1++, m2++) {
1651	/* ignore func arg names */
1652	if (!glob_sym_btf_matches(sym_name, exact, btf1, m1->type, btf2, m2->type))
1653	return false;
1654	}
1655
1656	/* now check return type as well */
1657	id1 = t1->type;
1658	id2 = t2->type;
1659	goto recur;
1660	}
1661
1662	/* skip_mods_and_typedefs() make this impossible */
1663	case BTF_KIND_TYPEDEF:
1664	case BTF_KIND_VOLATILE:
1665	case BTF_KIND_CONST:
1666	case BTF_KIND_RESTRICT:
1667	/* DATASECs are never compared with each other */
1668	case BTF_KIND_DATASEC:
1669	default:
1670	pr_warn("global '%s': unsupported BTF kind %s\n",
1671	sym_name, btf_kind_str(t1));
1672	return false;
1673	}
1674	}
1675
1676	static bool map_defs_match(const char *sym_name,
1677	const struct btf *main_btf,
1678	const struct btf_map_def *main_def,
1679	const struct btf_map_def *main_inner_def,
1680	const struct btf *extra_btf,
1681	const struct btf_map_def *extra_def,
1682	const struct btf_map_def *extra_inner_def)
1683	{
1684	const char *reason;
1685
1686	if (main_def->map_type != extra_def->map_type) {
1687	reason = "type";
1688	goto mismatch;
1689	}
1690
1691	/* check key type/size match */
1692	if (main_def->key_size != extra_def->key_size) {
1693	reason = "key_size";
1694	goto mismatch;
1695	}
1696	if (!!main_def->key_type_id != !!extra_def->key_type_id) {
1697	reason = "key type";
1698	goto mismatch;
1699	}
1700	if ((main_def->parts & MAP_DEF_KEY_TYPE)
1701	&& !glob_sym_btf_matches(sym_name, true /exact/,
1702	main_btf, main_def->key_type_id,
1703	extra_btf, extra_def->key_type_id)) {
1704	reason = "key type";
1705	goto mismatch;
1706	}
1707
1708	/* validate value type/size match */
1709	if (main_def->value_size != extra_def->value_size) {
1710	reason = "value_size";
1711	goto mismatch;
1712	}
1713	if (!!main_def->value_type_id != !!extra_def->value_type_id) {
1714	reason = "value type";
1715	goto mismatch;
1716	}
1717	if ((main_def->parts & MAP_DEF_VALUE_TYPE)
1718	&& !glob_sym_btf_matches(sym_name, true /exact/,
1719	main_btf, main_def->value_type_id,
1720	extra_btf, extra_def->value_type_id)) {
1721	reason = "key type";
1722	goto mismatch;
1723	}
1724
1725	if (main_def->max_entries != extra_def->max_entries) {
1726	reason = "max_entries";
1727	goto mismatch;
1728	}
1729	if (main_def->map_flags != extra_def->map_flags) {
1730	reason = "map_flags";
1731	goto mismatch;
1732	}
1733	if (main_def->numa_node != extra_def->numa_node) {
1734	reason = "numa_node";
1735	goto mismatch;
1736	}
1737	if (main_def->pinning != extra_def->pinning) {
1738	reason = "pinning";
1739	goto mismatch;
1740	}
1741
1742	if ((main_def->parts & MAP_DEF_INNER_MAP) != (extra_def->parts & MAP_DEF_INNER_MAP)) {
1743	reason = "inner map";
1744	goto mismatch;
1745	}
1746
1747	if (main_def->parts & MAP_DEF_INNER_MAP) {
1748	char inner_map_name[128];
1749
1750	snprintf(inner_map_name, sizeof(inner_map_name), "%s.inner", sym_name);
1751
1752	return map_defs_match(inner_map_name,
1753	main_btf, main_inner_def, NULL,
1754	extra_btf, extra_inner_def, NULL);
1755	}
1756
1757	return true;
1758
1759	mismatch:
1760	pr_warn("global '%s': map %s mismatch\n", sym_name, reason);
1761	return false;
1762	}
1763
1764	static bool glob_map_defs_match(const char *sym_name,
1765	struct bpf_linker linker, struct glob_sym glob_sym,
1766	struct src_obj obj, Elf64_Sym sym, int btf_id)
1767	{
1768	struct btf_map_def dst_def = {}, dst_inner_def = {};
1769	struct btf_map_def src_def = {}, src_inner_def = {};
1770	const struct btf_type *t;
1771	int err;
1772
1773	t = btf__type_by_id(obj->btf, btf_id);
1774	if (!btf_is_var(t)) {
1775	pr_warn("global '%s': invalid map definition type [%d]\n", sym_name, btf_id);
1776	return false;
1777	}
1778	t = skip_mods_and_typedefs(obj->btf, t->type, NULL);
1779
1780	err = parse_btf_map_def(sym_name, obj->btf, t, true /strict/, &src_def, &src_inner_def);
1781	if (err) {
1782	pr_warn("global '%s': invalid map definition\n", sym_name);
1783	return false;
1784	}
1785
1786	/* re-parse existing map definition */
1787	t = btf__type_by_id(linker->btf, glob_sym->btf_id);
1788	t = skip_mods_and_typedefs(linker->btf, t->type, NULL);
1789	err = parse_btf_map_def(sym_name, linker->btf, t, true /strict/, &dst_def, &dst_inner_def);
1790	if (err) {
1791	/* this should not happen, because we already validated it */
1792	pr_warn("global '%s': invalid dst map definition\n", sym_name);
1793	return false;
1794	}
1795
1796	/* Currently extern map definition has to be complete and match
1797	* concrete map definition exactly. This restriction might be lifted
1798	* in the future.
1799	*/
1800	return map_defs_match(sym_name, linker->btf, &dst_def, &dst_inner_def,
1801	obj->btf, &src_def, &src_inner_def);
1802	}
1803
1804	static bool glob_syms_match(const char *sym_name,
1805	struct bpf_linker linker, struct glob_sym glob_sym,
1806	struct src_obj obj, Elf64_Sym sym, size_t sym_idx, int btf_id)
1807	{
1808	const struct btf_type *src_t;
1809
1810	/* if we are dealing with externs, BTF types describing both global
1811	* and extern VARs/FUNCs should be completely present in all files
1812	*/
1813	if (!glob_sym->btf_id \|\| !btf_id) {
1814	pr_warn("BTF info is missing for global symbol '%s'\n", sym_name);
1815	return false;
1816	}
1817
1818	src_t = btf__type_by_id(obj->btf, btf_id);
1819	if (!btf_is_var(src_t) && !btf_is_func(src_t)) {
1820	pr_warn("only extern variables and functions are supported, but got '%s' for '%s'\n",
1821	btf_kind_str(src_t), sym_name);
1822	return false;
1823	}
1824
1825	/* deal with .maps definitions specially */
1826	if (glob_sym->sec_id && strcmp(linker->secs[glob_sym->sec_id].sec_name, MAPS_ELF_SEC) == 0)
1827	return glob_map_defs_match(sym_name, linker, glob_sym, obj, sym, btf_id);
1828
1829	if (!glob_sym_btf_matches(sym_name, true /exact/,
1830	linker->btf, glob_sym->btf_id, obj->btf, btf_id))
1831	return false;
1832
1833	return true;
1834	}
1835
1836	static bool btf_is_non_static(const struct btf_type *t)
1837	{
1838	return (btf_is_var(t) && btf_var(t)->linkage != BTF_VAR_STATIC)
1839	\|\| (btf_is_func(t) && btf_func_linkage(t) != BTF_FUNC_STATIC);
1840	}
1841
1842	static int find_glob_sym_btf(struct src_obj obj, Elf64_Sym sym, const char *sym_name,
1843	int out_btf_sec_id, int out_btf_id)
1844	{
1845	int i, j, n, m, btf_id = 0;
1846	const struct btf_type *t;
1847	const struct btf_var_secinfo *vi;
1848	const char *name;
1849
1850	if (!obj->btf) {
1851	pr_warn("failed to find BTF info for object '%s'\n", obj->filename);
1852	return -EINVAL;
1853	}
1854
1855	n = btf__type_cnt(obj->btf);
1856	for (i = 1; i < n; i++) {
1857	t = btf__type_by_id(obj->btf, i);
1858
1859	/* some global and extern FUNCs and VARs might not be associated with any
1860	* DATASEC, so try to detect them in the same pass
1861	*/
1862	if (btf_is_non_static(t)) {
1863	name = btf__str_by_offset(obj->btf, t->name_off);
1864	if (strcmp(name, sym_name) != 0)
1865	continue;
1866
1867	/* remember and still try to find DATASEC */
1868	btf_id = i;
1869	continue;
1870	}
1871
1872	if (!btf_is_datasec(t))
1873	continue;
1874
1875	vi = btf_var_secinfos(t);
1876	for (j = 0, m = btf_vlen(t); j < m; j++, vi++) {
1877	t = btf__type_by_id(obj->btf, vi->type);
1878	name = btf__str_by_offset(obj->btf, t->name_off);
1879
1880	if (strcmp(name, sym_name) != 0)
1881	continue;
1882	if (btf_is_var(t) && btf_var(t)->linkage == BTF_VAR_STATIC)
1883	continue;
1884	if (btf_is_func(t) && btf_func_linkage(t) == BTF_FUNC_STATIC)
1885	continue;
1886
1887	if (btf_id && btf_id != vi->type) {
1888	pr_warn("global/extern '%s' BTF is ambiguous: both types #%d and #%u match\n",
1889	sym_name, btf_id, vi->type);
1890	return -EINVAL;
1891	}
1892
1893	*out_btf_sec_id = i;
1894	*out_btf_id = vi->type;
1895
1896	return 0;
1897	}
1898	}
1899
1900	/* free-floating extern or global FUNC */
1901	if (btf_id) {
1902	*out_btf_sec_id = 0;
1903	*out_btf_id = btf_id;
1904	return 0;
1905	}
1906
1907	pr_warn("failed to find BTF info for global/extern symbol '%s'\n", sym_name);
1908	return -ENOENT;
1909	}
1910
1911	static struct src_sec find_src_sec_by_name(struct src_obj obj, const char *sec_name)
1912	{
1913	struct src_sec *sec;
1914	int i;
1915
1916	for (i = 1; i < obj->sec_cnt; i++) {
1917	sec = &obj->secs[i];
1918
1919	if (strcmp(sec->sec_name, sec_name) == 0)
1920	return sec;
1921	}
1922
1923	return NULL;
1924	}
1925
1926	static int complete_extern_btf_info(struct btf *dst_btf, int dst_id,
1927	struct btf *src_btf, int src_id)
1928	{
1929	struct btf_type *dst_t = btf_type_by_id(dst_btf, dst_id);
1930	struct btf_type *src_t = btf_type_by_id(src_btf, src_id);
1931	struct btf_param src_p, dst_p;
1932	const char *s;
1933	int i, n, off;
1934
1935	/* We already made sure that source and destination types (FUNC or
1936	* VAR) match in terms of types and argument names.
1937	*/
1938	if (btf_is_var(dst_t)) {
1939	btf_var(dst_t)->linkage = BTF_VAR_GLOBAL_ALLOCATED;
1940	return 0;
1941	}
1942
1943	dst_t->info = btf_type_info(BTF_KIND_FUNC, BTF_FUNC_GLOBAL, 0);
1944
1945	/* now onto FUNC_PROTO types */
1946	src_t = btf_type_by_id(src_btf, src_t->type);
1947	dst_t = btf_type_by_id(dst_btf, dst_t->type);
1948
1949	/* Fill in all the argument names, which for extern FUNCs are missing.
1950	* We'll end up with two copies of FUNCs/VARs for externs, but that
1951	* will be taken care of by BTF dedup at the very end.
1952	* It might be that BTF types for extern in one file has less/more BTF
1953	* information (e.g., FWD instead of full STRUCT/UNION information),
1954	* but that should be (in most cases, subject to BTF dedup rules)
1955	* handled and resolved by BTF dedup algorithm as well, so we won't
1956	* worry about it. Our only job is to make sure that argument names
1957	* are populated on both sides, otherwise BTF dedup will pedantically
1958	* consider them different.
1959	*/
1960	src_p = btf_params(src_t);
1961	dst_p = btf_params(dst_t);
1962	for (i = 0, n = btf_vlen(dst_t); i < n; i++, src_p++, dst_p++) {
1963	if (!src_p->name_off)
1964	continue;
1965
1966	/* src_btf has more complete info, so add name to dst_btf */
1967	s = btf__str_by_offset(src_btf, src_p->name_off);
1968	off = btf__add_str(dst_btf, s);
1969	if (off < 0)
1970	return off;
1971	dst_p->name_off = off;
1972	}
1973	return 0;
1974	}
1975
1976	static void sym_update_bind(Elf64_Sym *sym, int sym_bind)
1977	{
1978	sym->st_info = ELF64_ST_INFO(sym_bind, ELF64_ST_TYPE(sym->st_info));
1979	}
1980
1981	static void sym_update_type(Elf64_Sym *sym, int sym_type)
1982	{
1983	sym->st_info = ELF64_ST_INFO(ELF64_ST_BIND(sym->st_info), sym_type);
1984	}
1985
1986	static void sym_update_visibility(Elf64_Sym *sym, int sym_vis)
1987	{
1988	/* libelf doesn't provide setters for ST_VISIBILITY,
1989	* but it is stored in the lower 2 bits of st_other
1990	*/
1991	sym->st_other &= ~0x03;
1992	sym->st_other \|= sym_vis;
1993	}
1994
1995	static int linker_append_elf_sym(struct bpf_linker linker, struct src_obj obj,
1996	Elf64_Sym sym, const char sym_name, int src_sym_idx)
1997	{
1998	struct src_sec *src_sec = NULL;
1999	struct dst_sec *dst_sec = NULL;
2000	struct glob_sym *glob_sym = NULL;
2001	int name_off, sym_type, sym_bind, sym_vis, err;
2002	int btf_sec_id = 0, btf_id = 0;
2003	size_t dst_sym_idx;
2004	Elf64_Sym *dst_sym;
2005	bool sym_is_extern;
2006
2007	sym_type = ELF64_ST_TYPE(sym->st_info);
2008	sym_bind = ELF64_ST_BIND(sym->st_info);
2009	sym_vis = ELF64_ST_VISIBILITY(sym->st_other);
2010	sym_is_extern = sym->st_shndx == SHN_UNDEF;
2011
2012	if (sym_is_extern) {
2013	if (!obj->btf) {
2014	pr_warn("externs without BTF info are not supported\n");
2015	return -ENOTSUP;
2016	}
2017	} else if (sym->st_shndx < SHN_LORESERVE) {
2018	src_sec = &obj->secs[sym->st_shndx];
2019	if (src_sec->skipped)
2020	return 0;
2021	dst_sec = &linker->secs[src_sec->dst_id];
2022
2023	/* allow only one STT_SECTION symbol per section */
2024	if (sym_type == STT_SECTION && dst_sec->sec_sym_idx) {
2025	obj->sym_map[src_sym_idx] = dst_sec->sec_sym_idx;
2026	return 0;
2027	}
2028
2029	if (strcmp(src_sec->sec_name, JUMPTABLES_SEC) == 0)
2030	goto add_sym;
2031	}
2032
2033	if (sym_bind == STB_LOCAL)
2034	goto add_sym;
2035
2036	/* find matching BTF info */
2037	err = find_glob_sym_btf(obj, sym, sym_name, &btf_sec_id, &btf_id);
2038	if (err)
2039	return err;
2040
2041	if (sym_is_extern && btf_sec_id) {
2042	const char *sec_name = NULL;
2043	const struct btf_type *t;
2044
2045	t = btf__type_by_id(obj->btf, btf_sec_id);
2046	sec_name = btf__str_by_offset(obj->btf, t->name_off);
2047
2048	/* Clang puts unannotated extern vars into
2049	* '.extern' BTF DATASEC. Treat them the same
2050	* as unannotated extern funcs (which are
2051	* currently not put into any DATASECs).
2052	* Those don't have associated src_sec/dst_sec.
2053	*/
2054	if (strcmp(sec_name, BTF_EXTERN_SEC) != 0) {
2055	src_sec = find_src_sec_by_name(obj, sec_name);
2056	if (!src_sec) {
2057	pr_warn("failed to find matching ELF sec '%s'\n", sec_name);
2058	return -ENOENT;
2059	}
2060	dst_sec = &linker->secs[src_sec->dst_id];
2061	}
2062	}
2063
2064	glob_sym = find_glob_sym(linker, sym_name);
2065	if (glob_sym) {
2066	/* Preventively resolve to existing symbol. This is
2067	* needed for further relocation symbol remapping in
2068	* the next step of linking.
2069	*/
2070	obj->sym_map[src_sym_idx] = glob_sym->sym_idx;
2071
2072	/* If both symbols are non-externs, at least one of
2073	* them has to be STB_WEAK, otherwise they are in
2074	* a conflict with each other.
2075	*/
2076	if (!sym_is_extern && !glob_sym->is_extern
2077	&& !glob_sym->is_weak && sym_bind != STB_WEAK) {
2078	pr_warn("conflicting non-weak symbol #%d (%s) definition in '%s'\n",
2079	src_sym_idx, sym_name, obj->filename);
2080	return -EINVAL;
2081	}
2082
2083	if (!glob_syms_match(sym_name, linker, glob_sym, obj, sym, src_sym_idx, btf_id))
2084	return -EINVAL;
2085
2086	dst_sym = get_sym_by_idx(linker, glob_sym->sym_idx);
2087
2088	/* If new symbol is strong, then force dst_sym to be strong as
2089	* well; this way a mix of weak and non-weak extern
2090	* definitions will end up being strong.
2091	*/
2092	if (sym_bind == STB_GLOBAL) {
2093	/* We still need to preserve type (NOTYPE or
2094	* OBJECT/FUNC, depending on whether the symbol is
2095	* extern or not)
2096	*/
2097	sym_update_bind(dst_sym, STB_GLOBAL);
2098	glob_sym->is_weak = false;
2099	}
2100
2101	/* Non-default visibility is "contaminating", with stricter
2102	* visibility overwriting more permissive ones, even if more
2103	* permissive visibility comes from just an extern definition.
2104	* Currently only STV_DEFAULT and STV_HIDDEN are allowed and
2105	* ensured by ELF symbol sanity checks above.
2106	*/
2107	if (sym_vis > ELF64_ST_VISIBILITY(dst_sym->st_other))
2108	sym_update_visibility(dst_sym, sym_vis);
2109
2110	/* If the new symbol is extern, then regardless if
2111	* existing symbol is extern or resolved global, just
2112	* keep the existing one untouched.
2113	*/
2114	if (sym_is_extern)
2115	return 0;
2116
2117	/* If existing symbol is a strong resolved symbol, bail out,
2118	* because we lost resolution battle have nothing to
2119	* contribute. We already checked above that there is no
2120	* strong-strong conflict. We also already tightened binding
2121	* and visibility, so nothing else to contribute at that point.
2122	*/
2123	if (!glob_sym->is_extern && sym_bind == STB_WEAK)
2124	return 0;
2125
2126	/* At this point, new symbol is strong non-extern,
2127	* so overwrite glob_sym with new symbol information.
2128	* Preserve binding and visibility.
2129	*/
2130	sym_update_type(dst_sym, sym_type);
2131	dst_sym->st_shndx = dst_sec->sec_idx;
2132	dst_sym->st_value = src_sec->dst_off + sym->st_value;
2133	dst_sym->st_size = sym->st_size;
2134
2135	/* see comment below about dst_sec->id vs dst_sec->sec_idx */
2136	glob_sym->sec_id = dst_sec->id;
2137	glob_sym->is_extern = false;
2138
2139	if (complete_extern_btf_info(linker->btf, glob_sym->btf_id,
2140	obj->btf, btf_id))
2141	return -EINVAL;
2142
2143	/* request updating VAR's/FUNC's underlying BTF type when appending BTF type */
2144	glob_sym->underlying_btf_id = 0;
2145
2146	obj->sym_map[src_sym_idx] = glob_sym->sym_idx;
2147	return 0;
2148	}
2149
2150	add_sym:
2151	name_off = strset__add_str(linker->strtab_strs, sym_name);
2152	if (name_off < 0)
2153	return name_off;
2154
2155	dst_sym = add_new_sym(linker, &dst_sym_idx);
2156	if (!dst_sym)
2157	return -ENOMEM;
2158
2159	dst_sym->st_name = name_off;
2160	dst_sym->st_info = sym->st_info;
2161	dst_sym->st_other = sym->st_other;
2162	dst_sym->st_shndx = dst_sec ? dst_sec->sec_idx : sym->st_shndx;
2163	dst_sym->st_value = (src_sec ? src_sec->dst_off : 0) + sym->st_value;
2164	dst_sym->st_size = sym->st_size;
2165
2166	obj->sym_map[src_sym_idx] = dst_sym_idx;
2167
2168	if (sym_type == STT_SECTION && dst_sec) {
2169	dst_sec->sec_sym_idx = dst_sym_idx;
2170	dst_sym->st_value = 0;
2171	}
2172
2173	if (sym_bind != STB_LOCAL) {
2174	glob_sym = add_glob_sym(linker);
2175	if (!glob_sym)
2176	return -ENOMEM;
2177
2178	glob_sym->sym_idx = dst_sym_idx;
2179	/* we use dst_sec->id (and not dst_sec->sec_idx), because
2180	* ephemeral sections (.kconfig, .ksyms, etc) don't have
2181	* sec_idx (as they don't have corresponding ELF section), but
2182	* still have id. .extern doesn't have even ephemeral section
2183	* associated with it, so dst_sec->id == dst_sec->sec_idx == 0.
2184	*/
2185	glob_sym->sec_id = dst_sec ? dst_sec->id : 0;
2186	glob_sym->name_off = name_off;
2187	/* we will fill btf_id in during BTF merging step */
2188	glob_sym->btf_id = 0;
2189	glob_sym->is_extern = sym_is_extern;
2190	glob_sym->is_weak = sym_bind == STB_WEAK;
2191	}
2192
2193	return 0;
2194	}
2195
2196	static int linker_append_elf_relos(struct bpf_linker linker, struct src_obj obj)
2197	{
2198	struct src_sec *src_symtab = &obj->secs[obj->symtab_sec_idx];
2199	int i, err;
2200
2201	for (i = 1; i < obj->sec_cnt; i++) {
2202	struct src_sec src_sec, src_linked_sec;
2203	struct dst_sec dst_sec, dst_linked_sec;
2204	Elf64_Rel src_rel, dst_rel;
2205	int j, n;
2206
2207	src_sec = &obj->secs[i];
2208	if (!is_relo_sec(src_sec))
2209	continue;
2210
2211	/* shdr->sh_info points to relocatable section */
2212	src_linked_sec = &obj->secs[src_sec->shdr->sh_info];
2213	if (src_linked_sec->skipped)
2214	continue;
2215
2216	dst_sec = find_dst_sec_by_name(linker, src_sec->sec_name);
2217	if (!dst_sec) {
2218	dst_sec = add_dst_sec(linker, src_sec->sec_name);
2219	if (!dst_sec)
2220	return -ENOMEM;
2221	err = init_sec(linker, dst_sec, src_sec);
2222	if (err) {
2223	pr_warn("failed to init section '%s'\n", src_sec->sec_name);
2224	return err;
2225	}
2226	} else if (!secs_match(dst_sec, src_sec)) {
2227	pr_warn("sections %s are not compatible\n", src_sec->sec_name);
2228	return -EINVAL;
2229	}
2230
2231	/* shdr->sh_link points to SYMTAB */
2232	dst_sec->shdr->sh_link = linker->symtab_sec_idx;
2233
2234	/* shdr->sh_info points to relocated section */
2235	dst_linked_sec = &linker->secs[src_linked_sec->dst_id];
2236	dst_sec->shdr->sh_info = dst_linked_sec->sec_idx;
2237
2238	src_sec->dst_id = dst_sec->id;
2239	err = extend_sec(linker, dst_sec, src_sec);
2240	if (err)
2241	return err;
2242
2243	src_rel = src_sec->data->d_buf;
2244	dst_rel = dst_sec->raw_data + src_sec->dst_off;
2245	n = src_sec->shdr->sh_size / src_sec->shdr->sh_entsize;
2246	for (j = 0; j < n; j++, src_rel++, dst_rel++) {
2247	size_t src_sym_idx, dst_sym_idx, sym_type;
2248	Elf64_Sym *src_sym;
2249
2250	src_sym_idx = ELF64_R_SYM(src_rel->r_info);
2251	src_sym = src_symtab->data->d_buf + sizeof(src_sym) src_sym_idx;
2252
2253	dst_sym_idx = obj->sym_map[src_sym_idx];
2254	dst_rel->r_offset += src_linked_sec->dst_off;
2255	sym_type = ELF64_R_TYPE(src_rel->r_info);
2256	dst_rel->r_info = ELF64_R_INFO(dst_sym_idx, sym_type);
2257
2258	if (ELF64_ST_TYPE(src_sym->st_info) == STT_SECTION) {
2259	struct src_sec *sec = &obj->secs[src_sym->st_shndx];
2260	struct bpf_insn *insn;
2261
2262	if (src_linked_sec->shdr->sh_flags & SHF_EXECINSTR) {
2263	/* calls to the very first static function inside
2264	* .text section at offset 0 will
2265	* reference section symbol, not the
2266	* function symbol. Fix that up,
2267	* otherwise it won't be possible to
2268	* relocate calls to two different
2269	* static functions with the same name
2270	* (rom two different object files)
2271	*/
2272	insn = dst_linked_sec->raw_data + dst_rel->r_offset;
2273	if (insn->code == (BPF_JMP \| BPF_CALL))
2274	insn->imm += sec->dst_off / sizeof(struct bpf_insn);
2275	else
2276	insn->imm += sec->dst_off;
2277	} else {
2278	pr_warn("relocation against STT_SECTION in non-exec section is not supported!\n");
2279	return -EINVAL;
2280	}
2281	}
2282
2283	}
2284	}
2285
2286	return 0;
2287	}
2288
2289	static Elf64_Sym find_sym_by_name(struct src_obj obj, size_t sec_idx,
2290	int sym_type, const char *sym_name)
2291	{
2292	struct src_sec *symtab = &obj->secs[obj->symtab_sec_idx];
2293	Elf64_Sym *sym = symtab->data->d_buf;
2294	int i, n = symtab->shdr->sh_size / symtab->shdr->sh_entsize;
2295	int str_sec_idx = symtab->shdr->sh_link;
2296	const char *name;
2297
2298	for (i = 0; i < n; i++, sym++) {
2299	if (sym->st_shndx != sec_idx)
2300	continue;
2301	if (ELF64_ST_TYPE(sym->st_info) != sym_type)
2302	continue;
2303
2304	name = elf_strptr(obj->elf, str_sec_idx, sym->st_name);
2305	if (!name)
2306	return NULL;
2307
2308	if (strcmp(sym_name, name) != 0)
2309	continue;
2310
2311	return sym;
2312	}
2313
2314	return NULL;
2315	}
2316
2317	static int linker_fixup_btf(struct src_obj *obj)
2318	{
2319	const char *sec_name;
2320	struct src_sec *sec;
2321	int i, j, n, m;
2322
2323	if (!obj->btf)
2324	return 0;
2325
2326	n = btf__type_cnt(obj->btf);
2327	for (i = 1; i < n; i++) {
2328	struct btf_var_secinfo *vi;
2329	struct btf_type *t;
2330
2331	t = btf_type_by_id(obj->btf, i);
2332	if (btf_kind(t) != BTF_KIND_DATASEC)
2333	continue;
2334
2335	sec_name = btf__str_by_offset(obj->btf, t->name_off);
2336	sec = find_src_sec_by_name(obj, sec_name);
2337	if (sec) {
2338	/* record actual section size, unless ephemeral */
2339	if (sec->shdr)
2340	t->size = sec->shdr->sh_size;
2341	} else {
2342	/* BTF can have some sections that are not represented
2343	* in ELF, e.g., .kconfig, .ksyms, .extern, which are used
2344	* for special extern variables.
2345	*
2346	* For all but one such special (ephemeral)
2347	* sections, we pre-create "section shells" to be able
2348	* to keep track of extra per-section metadata later
2349	* (e.g., those BTF extern variables).
2350	*
2351	* .extern is even more special, though, because it
2352	* contains extern variables that need to be resolved
2353	* by static linker, not libbpf and kernel. When such
2354	* externs are resolved, we are going to remove them
2355	* from .extern BTF section and might end up not
2356	* needing it at all. Each resolved extern should have
2357	* matching non-extern VAR/FUNC in other sections.
2358	*
2359	* We do support leaving some of the externs
2360	* unresolved, though, to support cases of building
2361	* libraries, which will later be linked against final
2362	* BPF applications. So if at finalization we still
2363	* see unresolved externs, we'll create .extern
2364	* section on our own.
2365	*/
2366	if (strcmp(sec_name, BTF_EXTERN_SEC) == 0)
2367	continue;
2368
2369	sec = add_src_sec(obj, sec_name);
2370	if (!sec)
2371	return -ENOMEM;
2372
2373	sec->ephemeral = true;
2374	sec->sec_idx = 0; /* will match UNDEF shndx in ELF */
2375	}
2376
2377	/* remember ELF section and its BTF type ID match */
2378	sec->sec_type_id = i;
2379
2380	/* fix up variable offsets */
2381	vi = btf_var_secinfos(t);
2382	for (j = 0, m = btf_vlen(t); j < m; j++, vi++) {
2383	const struct btf_type *vt = btf__type_by_id(obj->btf, vi->type);
2384	const char *var_name;
2385	int var_linkage;
2386	Elf64_Sym *sym;
2387
2388	/* could be a variable or function */
2389	if (!btf_is_var(vt))
2390	continue;
2391
2392	var_name = btf__str_by_offset(obj->btf, vt->name_off);
2393	var_linkage = btf_var(vt)->linkage;
2394
2395	/* no need to patch up static or extern vars */
2396	if (var_linkage != BTF_VAR_GLOBAL_ALLOCATED)
2397	continue;
2398
2399	sym = find_sym_by_name(obj, sec->sec_idx, STT_OBJECT, var_name);
2400	if (!sym) {
2401	pr_warn("failed to find symbol for variable '%s' in section '%s'\n", var_name, sec_name);
2402	return -ENOENT;
2403	}
2404
2405	vi->offset = sym->st_value;
2406	}
2407	}
2408
2409	return 0;
2410	}
2411
2412	static int linker_append_btf(struct bpf_linker linker, struct src_obj obj)
2413	{
2414	const struct btf_type *t;
2415	int i, j, n, start_id, id, err;
2416	const char *name;
2417
2418	if (!obj->btf)
2419	return 0;
2420
2421	start_id = btf__type_cnt(linker->btf);
2422	n = btf__type_cnt(obj->btf);
2423
2424	obj->btf_type_map = calloc(n + 1, sizeof(int));
2425	if (!obj->btf_type_map)
2426	return -ENOMEM;
2427
2428	for (i = 1; i < n; i++) {
2429	struct glob_sym *glob_sym = NULL;
2430
2431	t = btf__type_by_id(obj->btf, i);
2432
2433	/* DATASECs are handled specially below */
2434	if (btf_kind(t) == BTF_KIND_DATASEC)
2435	continue;
2436
2437	if (btf_is_non_static(t)) {
2438	/* there should be glob_sym already */
2439	name = btf__str_by_offset(obj->btf, t->name_off);
2440	glob_sym = find_glob_sym(linker, name);
2441
2442	/* VARs without corresponding glob_sym are those that
2443	* belong to skipped/deduplicated sections (i.e.,
2444	* license and version), so just skip them
2445	*/
2446	if (!glob_sym)
2447	continue;
2448
2449	/* linker_append_elf_sym() might have requested
2450	* updating underlying type ID, if extern was resolved
2451	* to strong symbol or weak got upgraded to non-weak
2452	*/
2453	if (glob_sym->underlying_btf_id == 0)
2454	glob_sym->underlying_btf_id = -t->type;
2455
2456	/* globals from previous object files that match our
2457	* VAR/FUNC already have a corresponding associated
2458	* BTF type, so just make sure to use it
2459	*/
2460	if (glob_sym->btf_id) {
2461	/* reuse existing BTF type for global var/func */
2462	obj->btf_type_map[i] = glob_sym->btf_id;
2463	continue;
2464	}
2465	}
2466
2467	id = btf__add_type(linker->btf, obj->btf, t);
2468	if (id < 0) {
2469	pr_warn("failed to append BTF type #%d from file '%s'\n", i, obj->filename);
2470	return id;
2471	}
2472
2473	obj->btf_type_map[i] = id;
2474
2475	/* record just appended BTF type for var/func */
2476	if (glob_sym) {
2477	glob_sym->btf_id = id;
2478	glob_sym->underlying_btf_id = -t->type;
2479	}
2480	}
2481
2482	/* remap all the types except DATASECs */
2483	n = btf__type_cnt(linker->btf);
2484	for (i = start_id; i < n; i++) {
2485	struct btf_type *dst_t = btf_type_by_id(linker->btf, i);
2486	struct btf_field_iter it;
2487	__u32 *type_id;
2488
2489	err = btf_field_iter_init(&it, dst_t, BTF_FIELD_ITER_IDS);
2490	if (err)
2491	return err;
2492
2493	while ((type_id = btf_field_iter_next(&it))) {
2494	int new_id = obj->btf_type_map[*type_id];
2495
2496	/* Error out if the type wasn't remapped. Ignore VOID which stays VOID. */
2497	if (new_id == 0 && *type_id != 0) {
2498	pr_warn("failed to find new ID mapping for original BTF type ID %u\n",
2499	*type_id);
2500	return -EINVAL;
2501	}
2502
2503	type_id = obj->btf_type_map[type_id];
2504	}
2505	}
2506
2507	/* Rewrite VAR/FUNC underlying types (i.e., FUNC's FUNC_PROTO and VAR's
2508	* actual type), if necessary
2509	*/
2510	for (i = 0; i < linker->glob_sym_cnt; i++) {
2511	struct glob_sym *glob_sym = &linker->glob_syms[i];
2512	struct btf_type *glob_t;
2513
2514	if (glob_sym->underlying_btf_id >= 0)
2515	continue;
2516
2517	glob_sym->underlying_btf_id = obj->btf_type_map[-glob_sym->underlying_btf_id];
2518
2519	glob_t = btf_type_by_id(linker->btf, glob_sym->btf_id);
2520	glob_t->type = glob_sym->underlying_btf_id;
2521	}
2522
2523	/* append DATASEC info */
2524	for (i = 1; i < obj->sec_cnt; i++) {
2525	struct src_sec *src_sec;
2526	struct dst_sec *dst_sec;
2527	const struct btf_var_secinfo *src_var;
2528	struct btf_var_secinfo *dst_var;
2529
2530	src_sec = &obj->secs[i];
2531	if (!src_sec->sec_type_id \|\| src_sec->skipped)
2532	continue;
2533	dst_sec = &linker->secs[src_sec->dst_id];
2534
2535	/* Mark section as having BTF regardless of the presence of
2536	* variables. In some cases compiler might generate empty BTF
2537	* with no variables information. E.g., when promoting local
2538	* array/structure variable initial values and BPF object
2539	* file otherwise has no read-only static variables in
2540	* .rodata. We need to preserve such empty BTF and just set
2541	* correct section size.
2542	*/
2543	dst_sec->has_btf = true;
2544
2545	t = btf__type_by_id(obj->btf, src_sec->sec_type_id);
2546	src_var = btf_var_secinfos(t);
2547	n = btf_vlen(t);
2548	for (j = 0; j < n; j++, src_var++) {
2549	void *sec_vars = dst_sec->sec_vars;
2550	int new_id = obj->btf_type_map[src_var->type];
2551	struct glob_sym *glob_sym = NULL;
2552
2553	t = btf_type_by_id(linker->btf, new_id);
2554	if (btf_is_non_static(t)) {
2555	name = btf__str_by_offset(linker->btf, t->name_off);
2556	glob_sym = find_glob_sym(linker, name);
2557	if (glob_sym->sec_id != dst_sec->id) {
2558	pr_warn("global '%s': section mismatch %d vs %d\n",
2559	name, glob_sym->sec_id, dst_sec->id);
2560	return -EINVAL;
2561	}
2562	}
2563
2564	/* If there is already a member (VAR or FUNC) mapped
2565	* to the same type, don't add a duplicate entry.
2566	* This will happen when multiple object files define
2567	* the same extern VARs/FUNCs.
2568	*/
2569	if (glob_sym && glob_sym->var_idx >= 0) {
2570	__s64 sz;
2571
2572	/* FUNCs don't have size, nothing to update */
2573	if (btf_is_func(t))
2574	continue;
2575
2576	dst_var = &dst_sec->sec_vars[glob_sym->var_idx];
2577	/* Because underlying BTF type might have
2578	* changed, so might its size have changed, so
2579	* re-calculate and update it in sec_var.
2580	*/
2581	sz = btf__resolve_size(linker->btf, glob_sym->underlying_btf_id);
2582	if (sz < 0) {
2583	pr_warn("global '%s': failed to resolve size of underlying type: %d\n",
2584	name, (int)sz);
2585	return -EINVAL;
2586	}
2587	dst_var->size = sz;
2588	continue;
2589	}
2590
2591	sec_vars = libbpf_reallocarray(sec_vars,
2592	dst_sec->sec_var_cnt + 1,
2593	sizeof(*dst_sec->sec_vars));
2594	if (!sec_vars)
2595	return -ENOMEM;
2596
2597	dst_sec->sec_vars = sec_vars;
2598	dst_sec->sec_var_cnt++;
2599
2600	dst_var = &dst_sec->sec_vars[dst_sec->sec_var_cnt - 1];
2601	dst_var->type = obj->btf_type_map[src_var->type];
2602	dst_var->size = src_var->size;
2603	dst_var->offset = src_sec->dst_off + src_var->offset;
2604
2605	if (glob_sym)
2606	glob_sym->var_idx = dst_sec->sec_var_cnt - 1;
2607	}
2608	}
2609
2610	return 0;
2611	}
2612
2613	static void add_btf_ext_rec(struct btf_ext_sec_data ext_data, const void *src_rec)
2614	{
2615	void *tmp;
2616
2617	tmp = libbpf_reallocarray(ext_data->recs, ext_data->rec_cnt + 1, ext_data->rec_sz);
2618	if (!tmp)
2619	return NULL;
2620	ext_data->recs = tmp;
2621
2622	tmp += ext_data->rec_cnt * ext_data->rec_sz;
2623	memcpy(tmp, src_rec, ext_data->rec_sz);
2624
2625	ext_data->rec_cnt++;
2626
2627	return tmp;
2628	}
2629
2630	static int linker_append_btf_ext(struct bpf_linker linker, struct src_obj obj)
2631	{
2632	const struct btf_ext_info_sec *ext_sec;
2633	const char sec_name, s;
2634	struct src_sec *src_sec;
2635	struct dst_sec *dst_sec;
2636	int rec_sz, str_off, i;
2637
2638	if (!obj->btf_ext)
2639	return 0;
2640
2641	rec_sz = obj->btf_ext->func_info.rec_size;
2642	for_each_btf_ext_sec(&obj->btf_ext->func_info, ext_sec) {
2643	struct bpf_func_info_min src_rec, dst_rec;
2644
2645	sec_name = btf__name_by_offset(obj->btf, ext_sec->sec_name_off);
2646	src_sec = find_src_sec_by_name(obj, sec_name);
2647	if (!src_sec) {
2648	pr_warn("can't find section '%s' referenced from .BTF.ext\n", sec_name);
2649	return -EINVAL;
2650	}
2651	dst_sec = &linker->secs[src_sec->dst_id];
2652
2653	if (dst_sec->func_info.rec_sz == 0)
2654	dst_sec->func_info.rec_sz = rec_sz;
2655	if (dst_sec->func_info.rec_sz != rec_sz) {
2656	pr_warn("incompatible .BTF.ext record sizes for section '%s'\n", sec_name);
2657	return -EINVAL;
2658	}
2659
2660	for_each_btf_ext_rec(&obj->btf_ext->func_info, ext_sec, i, src_rec) {
2661	dst_rec = add_btf_ext_rec(&dst_sec->func_info, src_rec);
2662	if (!dst_rec)
2663	return -ENOMEM;
2664
2665	dst_rec->insn_off += src_sec->dst_off;
2666	dst_rec->type_id = obj->btf_type_map[dst_rec->type_id];
2667	}
2668	}
2669
2670	rec_sz = obj->btf_ext->line_info.rec_size;
2671	for_each_btf_ext_sec(&obj->btf_ext->line_info, ext_sec) {
2672	struct bpf_line_info_min src_rec, dst_rec;
2673
2674	sec_name = btf__name_by_offset(obj->btf, ext_sec->sec_name_off);
2675	src_sec = find_src_sec_by_name(obj, sec_name);
2676	if (!src_sec) {
2677	pr_warn("can't find section '%s' referenced from .BTF.ext\n", sec_name);
2678	return -EINVAL;
2679	}
2680	dst_sec = &linker->secs[src_sec->dst_id];
2681
2682	if (dst_sec->line_info.rec_sz == 0)
2683	dst_sec->line_info.rec_sz = rec_sz;
2684	if (dst_sec->line_info.rec_sz != rec_sz) {
2685	pr_warn("incompatible .BTF.ext record sizes for section '%s'\n", sec_name);
2686	return -EINVAL;
2687	}
2688
2689	for_each_btf_ext_rec(&obj->btf_ext->line_info, ext_sec, i, src_rec) {
2690	dst_rec = add_btf_ext_rec(&dst_sec->line_info, src_rec);
2691	if (!dst_rec)
2692	return -ENOMEM;
2693
2694	dst_rec->insn_off += src_sec->dst_off;
2695
2696	s = btf__str_by_offset(obj->btf, src_rec->file_name_off);
2697	str_off = btf__add_str(linker->btf, s);
2698	if (str_off < 0)
2699	return -ENOMEM;
2700	dst_rec->file_name_off = str_off;
2701
2702	s = btf__str_by_offset(obj->btf, src_rec->line_off);
2703	str_off = btf__add_str(linker->btf, s);
2704	if (str_off < 0)
2705	return -ENOMEM;
2706	dst_rec->line_off = str_off;
2707
2708	/* dst_rec->line_col is fine */
2709	}
2710	}
2711
2712	rec_sz = obj->btf_ext->core_relo_info.rec_size;
2713	for_each_btf_ext_sec(&obj->btf_ext->core_relo_info, ext_sec) {
2714	struct bpf_core_relo src_rec, dst_rec;
2715
2716	sec_name = btf__name_by_offset(obj->btf, ext_sec->sec_name_off);
2717	src_sec = find_src_sec_by_name(obj, sec_name);
2718	if (!src_sec) {
2719	pr_warn("can't find section '%s' referenced from .BTF.ext\n", sec_name);
2720	return -EINVAL;
2721	}
2722	dst_sec = &linker->secs[src_sec->dst_id];
2723
2724	if (dst_sec->core_relo_info.rec_sz == 0)
2725	dst_sec->core_relo_info.rec_sz = rec_sz;
2726	if (dst_sec->core_relo_info.rec_sz != rec_sz) {
2727	pr_warn("incompatible .BTF.ext record sizes for section '%s'\n", sec_name);
2728	return -EINVAL;
2729	}
2730
2731	for_each_btf_ext_rec(&obj->btf_ext->core_relo_info, ext_sec, i, src_rec) {
2732	dst_rec = add_btf_ext_rec(&dst_sec->core_relo_info, src_rec);
2733	if (!dst_rec)
2734	return -ENOMEM;
2735
2736	dst_rec->insn_off += src_sec->dst_off;
2737	dst_rec->type_id = obj->btf_type_map[dst_rec->type_id];
2738
2739	s = btf__str_by_offset(obj->btf, src_rec->access_str_off);
2740	str_off = btf__add_str(linker->btf, s);
2741	if (str_off < 0)
2742	return -ENOMEM;
2743	dst_rec->access_str_off = str_off;
2744
2745	/* dst_rec->kind is fine */
2746	}
2747	}
2748
2749	return 0;
2750	}
2751
2752	int bpf_linker__finalize(struct bpf_linker *linker)
2753	{
2754	struct dst_sec *sec;
2755	size_t strs_sz;
2756	const void *strs;
2757	int err, i;
2758
2759	if (!linker->elf)
2760	return libbpf_err(-EINVAL);
2761
2762	err = finalize_btf(linker);
2763	if (err)
2764	return libbpf_err(err);
2765
2766	/* Finalize strings */
2767	strs_sz = strset__data_size(linker->strtab_strs);
2768	strs = strset__data(linker->strtab_strs);
2769
2770	sec = &linker->secs[linker->strtab_sec_idx];
2771	sec->data->d_align = 1;
2772	sec->data->d_off = 0LL;
2773	sec->data->d_buf = (void *)strs;
2774	sec->data->d_type = ELF_T_BYTE;
2775	sec->data->d_size = strs_sz;
2776	sec->shdr->sh_size = strs_sz;
2777
2778	for (i = 1; i < linker->sec_cnt; i++) {
2779	sec = &linker->secs[i];
2780
2781	/* STRTAB is handled specially above */
2782	if (sec->sec_idx == linker->strtab_sec_idx)
2783	continue;
2784
2785	/* special ephemeral sections (.ksyms, .kconfig, etc) */
2786	if (!sec->scn)
2787	continue;
2788
2789	/* restore sections with bpf insns to target byte-order */
2790	if (linker->swapped_endian && is_exec_sec(sec))
2791	exec_sec_bswap(sec->raw_data, sec->sec_sz);
2792
2793	sec->data->d_buf = sec->raw_data;
2794	}
2795
2796	/* Finalize ELF layout */
2797	if (elf_update(linker->elf, ELF_C_NULL) < 0) {
2798	err = -EINVAL;
2799	pr_warn_elf("failed to finalize ELF layout");
2800	return libbpf_err(err);
2801	}
2802
2803	/* Write out final ELF contents */
2804	if (elf_update(linker->elf, ELF_C_WRITE) < 0) {
2805	err = -EINVAL;
2806	pr_warn_elf("failed to write ELF contents");
2807	return libbpf_err(err);
2808	}
2809
2810	elf_end(linker->elf);
2811	linker->elf = NULL;
2812
2813	if (linker->fd_is_owned)
2814	close(linker->fd);
2815	linker->fd = -1;
2816
2817	return 0;
2818	}
2819
2820	static int emit_elf_data_sec(struct bpf_linker linker, const char sec_name,
2821	size_t align, const void *raw_data, size_t raw_sz)
2822	{
2823	Elf_Scn *scn;
2824	Elf_Data *data;
2825	Elf64_Shdr *shdr;
2826	int name_off;
2827
2828	name_off = strset__add_str(linker->strtab_strs, sec_name);
2829	if (name_off < 0)
2830	return name_off;
2831
2832	scn = elf_newscn(linker->elf);
2833	if (!scn)
2834	return -ENOMEM;
2835	data = elf_newdata(scn);
2836	if (!data)
2837	return -ENOMEM;
2838	shdr = elf64_getshdr(scn);
2839	if (!shdr)
2840	return -EINVAL;
2841
2842	shdr->sh_name = name_off;
2843	shdr->sh_type = SHT_PROGBITS;
2844	shdr->sh_flags = 0;
2845	shdr->sh_size = raw_sz;
2846	shdr->sh_link = 0;
2847	shdr->sh_info = 0;
2848	shdr->sh_addralign = align;
2849	shdr->sh_entsize = 0;
2850
2851	data->d_type = ELF_T_BYTE;
2852	data->d_size = raw_sz;
2853	data->d_buf = (void *)raw_data;
2854	data->d_align = align;
2855	data->d_off = 0;
2856
2857	return 0;
2858	}
2859
2860	static int finalize_btf(struct bpf_linker *linker)
2861	{
2862	enum btf_endianness link_endianness;
2863	LIBBPF_OPTS(btf_dedup_opts, opts);
2864	struct btf *btf = linker->btf;
2865	const void *raw_data;
2866	int i, j, id, err;
2867	__u32 raw_sz;
2868
2869	/* bail out if no BTF data was produced */
2870	if (btf__type_cnt(linker->btf) == 1)
2871	return 0;
2872
2873	for (i = 1; i < linker->sec_cnt; i++) {
2874	struct dst_sec *sec = &linker->secs[i];
2875
2876	if (!sec->has_btf)
2877	continue;
2878
2879	id = btf__add_datasec(btf, sec->sec_name, sec->sec_sz);
2880	if (id < 0) {
2881	pr_warn("failed to add consolidated BTF type for datasec '%s': %d\n",
2882	sec->sec_name, id);
2883	return id;
2884	}
2885
2886	for (j = 0; j < sec->sec_var_cnt; j++) {
2887	struct btf_var_secinfo *vi = &sec->sec_vars[j];
2888
2889	if (btf__add_datasec_var_info(btf, vi->type, vi->offset, vi->size))
2890	return -EINVAL;
2891	}
2892	}
2893
2894	err = finalize_btf_ext(linker);
2895	if (err) {
2896	pr_warn(".BTF.ext generation failed: %s\n", errstr(err));
2897	return err;
2898	}
2899
2900	opts.btf_ext = linker->btf_ext;
2901	err = btf__dedup(linker->btf, &opts);
2902	if (err) {
2903	pr_warn("BTF dedup failed: %s\n", errstr(err));
2904	return err;
2905	}
2906
2907	/* Set .BTF and .BTF.ext output byte order */
2908	link_endianness = linker->elf_hdr->e_ident[EI_DATA] == ELFDATA2MSB ?
2909	BTF_BIG_ENDIAN : BTF_LITTLE_ENDIAN;
2910	btf__set_endianness(linker->btf, link_endianness);
2911	if (linker->btf_ext)
2912	btf_ext__set_endianness(linker->btf_ext, link_endianness);
2913
2914	/* Emit .BTF section */
2915	raw_data = btf__raw_data(linker->btf, &raw_sz);
2916	if (!raw_data)
2917	return -ENOMEM;
2918
2919	err = emit_elf_data_sec(linker, BTF_ELF_SEC, 8, raw_data, raw_sz);
2920	if (err) {
2921	pr_warn("failed to write out .BTF ELF section: %s\n", errstr(err));
2922	return err;
2923	}
2924
2925	/* Emit .BTF.ext section */
2926	if (linker->btf_ext) {
2927	raw_data = btf_ext__raw_data(linker->btf_ext, &raw_sz);
2928	if (!raw_data)
2929	return -ENOMEM;
2930
2931	err = emit_elf_data_sec(linker, BTF_EXT_ELF_SEC, 8, raw_data, raw_sz);
2932	if (err) {
2933	pr_warn("failed to write out .BTF.ext ELF section: %s\n", errstr(err));
2934	return err;
2935	}
2936	}
2937
2938	return 0;
2939	}
2940
2941	static int emit_btf_ext_data(struct bpf_linker linker, void output,
2942	const char sec_name, struct btf_ext_sec_data sec_data)
2943	{
2944	struct btf_ext_info_sec *sec_info;
2945	void *cur = output;
2946	int str_off;
2947	size_t sz;
2948
2949	if (!sec_data->rec_cnt)
2950	return 0;
2951
2952	str_off = btf__add_str(linker->btf, sec_name);
2953	if (str_off < 0)
2954	return -ENOMEM;
2955
2956	sec_info = cur;
2957	sec_info->sec_name_off = str_off;
2958	sec_info->num_info = sec_data->rec_cnt;
2959	cur += sizeof(struct btf_ext_info_sec);
2960
2961	sz = sec_data->rec_cnt * sec_data->rec_sz;
2962	memcpy(cur, sec_data->recs, sz);
2963	cur += sz;
2964
2965	return cur - output;
2966	}
2967
2968	static int finalize_btf_ext(struct bpf_linker *linker)
2969	{
2970	size_t funcs_sz = 0, lines_sz = 0, core_relos_sz = 0, total_sz = 0;
2971	size_t func_rec_sz = 0, line_rec_sz = 0, core_relo_rec_sz = 0;
2972	struct btf_ext_header *hdr;
2973	void data, cur;
2974	int i, err, sz;
2975
2976	/* validate that all sections have the same .BTF.ext record sizes
2977	* and calculate total data size for each type of data (func info,
2978	* line info, core relos)
2979	*/
2980	for (i = 1; i < linker->sec_cnt; i++) {
2981	struct dst_sec *sec = &linker->secs[i];
2982
2983	if (sec->func_info.rec_cnt) {
2984	if (func_rec_sz == 0)
2985	func_rec_sz = sec->func_info.rec_sz;
2986	if (func_rec_sz != sec->func_info.rec_sz) {
2987	pr_warn("mismatch in func_info record size %zu != %u\n",
2988	func_rec_sz, sec->func_info.rec_sz);
2989	return -EINVAL;
2990	}
2991
2992	funcs_sz += sizeof(struct btf_ext_info_sec) + func_rec_sz * sec->func_info.rec_cnt;
2993	}
2994	if (sec->line_info.rec_cnt) {
2995	if (line_rec_sz == 0)
2996	line_rec_sz = sec->line_info.rec_sz;
2997	if (line_rec_sz != sec->line_info.rec_sz) {
2998	pr_warn("mismatch in line_info record size %zu != %u\n",
2999	line_rec_sz, sec->line_info.rec_sz);
3000	return -EINVAL;
3001	}
3002
3003	lines_sz += sizeof(struct btf_ext_info_sec) + line_rec_sz * sec->line_info.rec_cnt;
3004	}
3005	if (sec->core_relo_info.rec_cnt) {
3006	if (core_relo_rec_sz == 0)
3007	core_relo_rec_sz = sec->core_relo_info.rec_sz;
3008	if (core_relo_rec_sz != sec->core_relo_info.rec_sz) {
3009	pr_warn("mismatch in core_relo_info record size %zu != %u\n",
3010	core_relo_rec_sz, sec->core_relo_info.rec_sz);
3011	return -EINVAL;
3012	}
3013
3014	core_relos_sz += sizeof(struct btf_ext_info_sec) + core_relo_rec_sz * sec->core_relo_info.rec_cnt;
3015	}
3016	}
3017
3018	if (!funcs_sz && !lines_sz && !core_relos_sz)
3019	return 0;
3020
3021	total_sz += sizeof(struct btf_ext_header);
3022	if (funcs_sz) {
3023	funcs_sz += sizeof(__u32); /* record size prefix */
3024	total_sz += funcs_sz;
3025	}
3026	if (lines_sz) {
3027	lines_sz += sizeof(__u32); /* record size prefix */
3028	total_sz += lines_sz;
3029	}
3030	if (core_relos_sz) {
3031	core_relos_sz += sizeof(__u32); /* record size prefix */
3032	total_sz += core_relos_sz;
3033	}
3034
3035	cur = data = calloc(1, total_sz);
3036	if (!data)
3037	return -ENOMEM;
3038
3039	hdr = cur;
3040	hdr->magic = BTF_MAGIC;
3041	hdr->version = BTF_VERSION;
3042	hdr->flags = 0;
3043	hdr->hdr_len = sizeof(struct btf_ext_header);
3044	cur += sizeof(struct btf_ext_header);
3045
3046	/* All offsets are in bytes relative to the end of this header */
3047	hdr->func_info_off = 0;
3048	hdr->func_info_len = funcs_sz;
3049	hdr->line_info_off = funcs_sz;
3050	hdr->line_info_len = lines_sz;
3051	hdr->core_relo_off = funcs_sz + lines_sz;
3052	hdr->core_relo_len = core_relos_sz;
3053
3054	if (funcs_sz) {
3055	(__u32 )cur = func_rec_sz;
3056	cur += sizeof(__u32);
3057
3058	for (i = 1; i < linker->sec_cnt; i++) {
3059	struct dst_sec *sec = &linker->secs[i];
3060
3061	sz = emit_btf_ext_data(linker, cur, sec->sec_name, &sec->func_info);
3062	if (sz < 0) {
3063	err = sz;
3064	goto out;
3065	}
3066
3067	cur += sz;
3068	}
3069	}
3070
3071	if (lines_sz) {
3072	(__u32 )cur = line_rec_sz;
3073	cur += sizeof(__u32);
3074
3075	for (i = 1; i < linker->sec_cnt; i++) {
3076	struct dst_sec *sec = &linker->secs[i];
3077
3078	sz = emit_btf_ext_data(linker, cur, sec->sec_name, &sec->line_info);
3079	if (sz < 0) {
3080	err = sz;
3081	goto out;
3082	}
3083
3084	cur += sz;
3085	}
3086	}
3087
3088	if (core_relos_sz) {
3089	(__u32 )cur = core_relo_rec_sz;
3090	cur += sizeof(__u32);
3091
3092	for (i = 1; i < linker->sec_cnt; i++) {
3093	struct dst_sec *sec = &linker->secs[i];
3094
3095	sz = emit_btf_ext_data(linker, cur, sec->sec_name, &sec->core_relo_info);
3096	if (sz < 0) {
3097	err = sz;
3098	goto out;
3099	}
3100
3101	cur += sz;
3102	}
3103	}
3104
3105	linker->btf_ext = btf_ext__new(data, total_sz);
3106	err = libbpf_get_error(linker->btf_ext);
3107	if (err) {
3108	linker->btf_ext = NULL;
3109	pr_warn("failed to parse final .BTF.ext data: %s\n", errstr(err));
3110	goto out;
3111	}
3112
3113	out:
3114	free(data);
3115	return err;
3116	}