1 // SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
5 * Copyright (c) 2021 Facebook
14 #include <linux/err.h>
15 #include <linux/btf.h>
22 #include "libbpf_internal.h"
27 /* positional (not necessarily ELF) index in an array of sections */
29 /* positional (not necessarily ELF) index of a matching section in a final object file */
31 /* section data offset in a matching output section */
33 /* whether section is omitted from the final ELF file */
35 /* whether section is an ephemeral section, not mapped to an ELF section */
44 /* corresponding BTF DATASEC type ID */
52 /* Section header strings section index */
53 size_t shstrs_sec_idx;
54 /* SYMTAB section index */
55 size_t symtab_sec_idx;
58 struct btf_ext *btf_ext;
60 /* List of sections (including ephemeral). Slot zero is unused. */
64 /* mapping of symbol indices from src to dst ELF */
66 /* mapping from the src BTF type IDs to dst ones */
70 /* single .BTF.ext data section */
71 struct btf_ext_sec_data {
79 /* positional (not necessarily ELF) index in an array of sections */
88 /* final output section size */
90 /* final output contents of the section */
93 /* corresponding STT_SECTION symbol index in SYMTAB */
96 /* section's DATASEC variable info, emitted on BTF finalization */
99 struct btf_var_secinfo *sec_vars;
101 /* section's .BTF.ext data */
102 struct btf_ext_sec_data func_info;
103 struct btf_ext_sec_data line_info;
104 struct btf_ext_sec_data core_relo_info;
113 /* Output sections metadata */
114 struct dst_sec *secs;
117 struct strset *strtab_strs; /* STRTAB unique strings */
118 size_t strtab_sec_idx; /* STRTAB section index */
119 size_t symtab_sec_idx; /* SYMTAB section index */
122 struct btf_ext *btf_ext;
125 #define pr_warn_elf(fmt, ...) \
126 libbpf_print(LIBBPF_WARN, "libbpf: " fmt ": %s\n", ##__VA_ARGS__, elf_errmsg(-1))
128 static int init_output_elf(struct bpf_linker *linker, const char *file);
130 static int linker_load_obj_file(struct bpf_linker *linker, const char *filename, struct src_obj *obj);
131 static int linker_sanity_check_elf(struct src_obj *obj);
132 static int linker_sanity_check_elf_symtab(struct src_obj *obj, struct src_sec *sec);
133 static int linker_sanity_check_elf_relos(struct src_obj *obj, struct src_sec *sec);
134 static int linker_sanity_check_btf(struct src_obj *obj);
135 static int linker_sanity_check_btf_ext(struct src_obj *obj);
136 static int linker_fixup_btf(struct src_obj *obj);
137 static int linker_append_sec_data(struct bpf_linker *linker, struct src_obj *obj);
138 static int linker_append_elf_syms(struct bpf_linker *linker, struct src_obj *obj);
139 static int linker_append_elf_relos(struct bpf_linker *linker, struct src_obj *obj);
140 static int linker_append_btf(struct bpf_linker *linker, struct src_obj *obj);
141 static int linker_append_btf_ext(struct bpf_linker *linker, struct src_obj *obj);
143 static int finalize_btf(struct bpf_linker *linker);
144 static int finalize_btf_ext(struct bpf_linker *linker);
146 void bpf_linker__free(struct bpf_linker *linker)
153 free(linker->filename);
156 elf_end(linker->elf);
161 strset__free(linker->strtab_strs);
163 btf__free(linker->btf);
164 btf_ext__free(linker->btf_ext);
166 for (i = 1; i < linker->sec_cnt; i++) {
167 struct dst_sec *sec = &linker->secs[i];
173 free(sec->func_info.recs);
174 free(sec->line_info.recs);
175 free(sec->core_relo_info.recs);
182 struct bpf_linker *bpf_linker__new(const char *filename, struct bpf_linker_opts *opts)
184 struct bpf_linker *linker;
187 if (!OPTS_VALID(opts, bpf_linker_opts))
190 if (elf_version(EV_CURRENT) == EV_NONE) {
191 pr_warn_elf("libelf initialization failed");
195 linker = calloc(1, sizeof(*linker));
201 err = init_output_elf(linker, filename);
208 bpf_linker__free(linker);
212 static struct dst_sec *add_dst_sec(struct bpf_linker *linker, const char *sec_name)
214 struct dst_sec *secs = linker->secs, *sec;
215 size_t new_cnt = linker->sec_cnt ? linker->sec_cnt + 1 : 2;
217 secs = libbpf_reallocarray(secs, new_cnt, sizeof(*secs));
221 /* zero out newly allocated memory */
222 memset(secs + linker->sec_cnt, 0, (new_cnt - linker->sec_cnt) * sizeof(*secs));
225 linker->sec_cnt = new_cnt;
227 sec = &linker->secs[new_cnt - 1];
228 sec->id = new_cnt - 1;
229 sec->sec_name = strdup(sec_name);
236 static Elf64_Sym *add_new_sym(struct bpf_linker *linker, size_t *sym_idx)
238 struct dst_sec *symtab = &linker->secs[linker->symtab_sec_idx];
239 Elf64_Sym *syms, *sym;
240 size_t sym_cnt = symtab->sec_sz / sizeof(*sym);
242 syms = libbpf_reallocarray(symtab->raw_data, sym_cnt + 1, sizeof(*sym));
246 sym = &syms[sym_cnt];
247 memset(sym, 0, sizeof(*sym));
249 symtab->raw_data = syms;
250 symtab->sec_sz += sizeof(*sym);
251 symtab->shdr->sh_size += sizeof(*sym);
252 symtab->data->d_size += sizeof(*sym);
260 static int init_output_elf(struct bpf_linker *linker, const char *file)
266 linker->filename = strdup(file);
267 if (!linker->filename)
270 linker->fd = open(file, O_WRONLY | O_CREAT | O_TRUNC, 0644);
271 if (linker->fd < 0) {
273 pr_warn("failed to create '%s': %d\n", file, err);
277 linker->elf = elf_begin(linker->fd, ELF_C_WRITE, NULL);
279 pr_warn_elf("failed to create ELF object");
284 linker->elf_hdr = elf64_newehdr(linker->elf);
285 if (!linker->elf_hdr) {
286 pr_warn_elf("failed to create ELF header");
290 linker->elf_hdr->e_machine = EM_BPF;
291 linker->elf_hdr->e_type = ET_REL;
292 #if __BYTE_ORDER == __LITTLE_ENDIAN
293 linker->elf_hdr->e_ident[EI_DATA] = ELFDATA2LSB;
294 #elif __BYTE_ORDER == __BIG_ENDIAN
295 linker->elf_hdr->e_ident[EI_DATA] = ELFDATA2MSB;
297 #error "Unknown __BYTE_ORDER"
301 /* initialize strset with an empty string to conform to ELF */
302 linker->strtab_strs = strset__new(INT_MAX, "", sizeof(""));
303 if (libbpf_get_error(linker->strtab_strs))
304 return libbpf_get_error(linker->strtab_strs);
306 sec = add_dst_sec(linker, ".strtab");
310 sec->scn = elf_newscn(linker->elf);
312 pr_warn_elf("failed to create STRTAB section");
316 sec->shdr = elf64_getshdr(sec->scn);
320 sec->data = elf_newdata(sec->scn);
322 pr_warn_elf("failed to create STRTAB data");
326 str_off = strset__add_str(linker->strtab_strs, sec->sec_name);
330 sec->sec_idx = elf_ndxscn(sec->scn);
331 linker->elf_hdr->e_shstrndx = sec->sec_idx;
332 linker->strtab_sec_idx = sec->sec_idx;
334 sec->shdr->sh_name = str_off;
335 sec->shdr->sh_type = SHT_STRTAB;
336 sec->shdr->sh_flags = SHF_STRINGS;
337 sec->shdr->sh_offset = 0;
338 sec->shdr->sh_link = 0;
339 sec->shdr->sh_info = 0;
340 sec->shdr->sh_addralign = 1;
341 sec->shdr->sh_size = sec->sec_sz = 0;
342 sec->shdr->sh_entsize = 0;
345 sec = add_dst_sec(linker, ".symtab");
349 sec->scn = elf_newscn(linker->elf);
351 pr_warn_elf("failed to create SYMTAB section");
355 sec->shdr = elf64_getshdr(sec->scn);
359 sec->data = elf_newdata(sec->scn);
361 pr_warn_elf("failed to create SYMTAB data");
365 str_off = strset__add_str(linker->strtab_strs, sec->sec_name);
369 sec->sec_idx = elf_ndxscn(sec->scn);
370 linker->symtab_sec_idx = sec->sec_idx;
372 sec->shdr->sh_name = str_off;
373 sec->shdr->sh_type = SHT_SYMTAB;
374 sec->shdr->sh_flags = 0;
375 sec->shdr->sh_offset = 0;
376 sec->shdr->sh_link = linker->strtab_sec_idx;
377 /* sh_info should be one greater than the index of the last local
378 * symbol (i.e., binding is STB_LOCAL). But why and who cares?
380 sec->shdr->sh_info = 0;
381 sec->shdr->sh_addralign = 8;
382 sec->shdr->sh_entsize = sizeof(Elf64_Sym);
385 linker->btf = btf__new_empty();
386 err = libbpf_get_error(linker->btf);
390 /* add the special all-zero symbol */
391 init_sym = add_new_sym(linker, NULL);
395 init_sym->st_name = 0;
396 init_sym->st_info = 0;
397 init_sym->st_other = 0;
398 init_sym->st_shndx = SHN_UNDEF;
399 init_sym->st_value = 0;
400 init_sym->st_size = 0;
405 int bpf_linker__add_file(struct bpf_linker *linker, const char *filename)
407 struct src_obj obj = {};
413 err = err ?: linker_load_obj_file(linker, filename, &obj);
414 err = err ?: linker_append_sec_data(linker, &obj);
415 err = err ?: linker_append_elf_syms(linker, &obj);
416 err = err ?: linker_append_elf_relos(linker, &obj);
417 err = err ?: linker_append_btf(linker, &obj);
418 err = err ?: linker_append_btf_ext(linker, &obj);
420 /* free up src_obj resources */
421 free(obj.btf_type_map);
423 btf_ext__free(obj.btf_ext);
434 static bool is_dwarf_sec_name(const char *name)
436 /* approximation, but the actual list is too long */
437 return strncmp(name, ".debug_", sizeof(".debug_") - 1) == 0;
440 static bool is_ignored_sec(struct src_sec *sec)
442 Elf64_Shdr *shdr = sec->shdr;
443 const char *name = sec->sec_name;
445 /* no special handling of .strtab */
446 if (shdr->sh_type == SHT_STRTAB)
449 /* ignore .llvm_addrsig section as well */
450 if (shdr->sh_type == SHT_LLVM_ADDRSIG)
453 /* no subprograms will lead to an empty .text section, ignore it */
454 if (shdr->sh_type == SHT_PROGBITS && shdr->sh_size == 0 &&
455 strcmp(sec->sec_name, ".text") == 0)
459 if (is_dwarf_sec_name(sec->sec_name))
462 if (strncmp(name, ".rel", sizeof(".rel") - 1) == 0) {
463 name += sizeof(".rel") - 1;
464 /* DWARF section relocations */
465 if (is_dwarf_sec_name(name))
468 /* .BTF and .BTF.ext don't need relocations */
469 if (strcmp(name, BTF_ELF_SEC) == 0 ||
470 strcmp(name, BTF_EXT_ELF_SEC) == 0)
477 static struct src_sec *add_src_sec(struct src_obj *obj, const char *sec_name)
479 struct src_sec *secs = obj->secs, *sec;
480 size_t new_cnt = obj->sec_cnt ? obj->sec_cnt + 1 : 2;
482 secs = libbpf_reallocarray(secs, new_cnt, sizeof(*secs));
486 /* zero out newly allocated memory */
487 memset(secs + obj->sec_cnt, 0, (new_cnt - obj->sec_cnt) * sizeof(*secs));
490 obj->sec_cnt = new_cnt;
492 sec = &obj->secs[new_cnt - 1];
493 sec->id = new_cnt - 1;
494 sec->sec_name = sec_name;
499 static int linker_load_obj_file(struct bpf_linker *linker, const char *filename, struct src_obj *obj)
501 #if __BYTE_ORDER == __LITTLE_ENDIAN
502 const int host_endianness = ELFDATA2LSB;
503 #elif __BYTE_ORDER == __BIG_ENDIAN
504 const int host_endianness = ELFDATA2MSB;
506 #error "Unknown __BYTE_ORDER"
515 pr_debug("linker: adding object file '%s'...\n", filename);
517 obj->filename = filename;
519 obj->fd = open(filename, O_RDONLY);
522 pr_warn("failed to open file '%s': %d\n", filename, err);
525 obj->elf = elf_begin(obj->fd, ELF_C_READ_MMAP, NULL);
528 pr_warn_elf("failed to parse ELF file '%s'", filename);
532 /* Sanity check ELF file high-level properties */
533 ehdr = elf64_getehdr(obj->elf);
536 pr_warn_elf("failed to get ELF header for %s", filename);
539 if (ehdr->e_ident[EI_DATA] != host_endianness) {
541 pr_warn_elf("unsupported byte order of ELF file %s", filename);
544 if (ehdr->e_type != ET_REL
545 || ehdr->e_machine != EM_BPF
546 || ehdr->e_ident[EI_CLASS] != ELFCLASS64) {
548 pr_warn_elf("unsupported kind of ELF file %s", filename);
552 if (elf_getshdrstrndx(obj->elf, &obj->shstrs_sec_idx)) {
554 pr_warn_elf("failed to get SHSTRTAB section index for %s", filename);
559 while ((scn = elf_nextscn(obj->elf, scn)) != NULL) {
560 size_t sec_idx = elf_ndxscn(scn);
561 const char *sec_name;
563 shdr = elf64_getshdr(scn);
566 pr_warn_elf("failed to get section #%zu header for %s",
571 sec_name = elf_strptr(obj->elf, obj->shstrs_sec_idx, shdr->sh_name);
574 pr_warn_elf("failed to get section #%zu name for %s",
579 data = elf_getdata(scn, 0);
582 pr_warn_elf("failed to get section #%zu (%s) data from %s",
583 sec_idx, sec_name, filename);
587 sec = add_src_sec(obj, sec_name);
594 sec->sec_idx = elf_ndxscn(scn);
596 if (is_ignored_sec(sec)) {
601 switch (shdr->sh_type) {
603 if (obj->symtab_sec_idx) {
605 pr_warn("multiple SYMTAB sections found, not supported\n");
608 obj->symtab_sec_idx = sec_idx;
611 /* we'll construct our own string table */
614 if (strcmp(sec_name, BTF_ELF_SEC) == 0) {
615 obj->btf = btf__new(data->d_buf, shdr->sh_size);
616 err = libbpf_get_error(obj->btf);
618 pr_warn("failed to parse .BTF from %s: %d\n", filename, err);
624 if (strcmp(sec_name, BTF_EXT_ELF_SEC) == 0) {
625 obj->btf_ext = btf_ext__new(data->d_buf, shdr->sh_size);
626 err = libbpf_get_error(obj->btf_ext);
628 pr_warn("failed to parse .BTF.ext from '%s': %d\n", filename, err);
644 pr_warn("unrecognized section #%zu (%s) in %s\n",
645 sec_idx, sec_name, filename);
651 err = err ?: linker_sanity_check_elf(obj);
652 err = err ?: linker_sanity_check_btf(obj);
653 err = err ?: linker_sanity_check_btf_ext(obj);
654 err = err ?: linker_fixup_btf(obj);
659 static bool is_pow_of_2(size_t x)
661 return x && (x & (x - 1)) == 0;
664 static int linker_sanity_check_elf(struct src_obj *obj)
669 if (!obj->symtab_sec_idx) {
670 pr_warn("ELF is missing SYMTAB section in %s\n", obj->filename);
673 if (!obj->shstrs_sec_idx) {
674 pr_warn("ELF is missing section headers STRTAB section in %s\n", obj->filename);
678 for (i = 1; i < obj->sec_cnt; i++) {
681 if (sec->sec_name[0] == '\0') {
682 pr_warn("ELF section #%zu has empty name in %s\n", sec->sec_idx, obj->filename);
686 if (sec->shdr->sh_addralign && !is_pow_of_2(sec->shdr->sh_addralign))
688 if (sec->shdr->sh_addralign != sec->data->d_align)
691 if (sec->shdr->sh_size != sec->data->d_size)
694 switch (sec->shdr->sh_type) {
696 err = linker_sanity_check_elf_symtab(obj, sec);
703 if (sec->shdr->sh_flags & SHF_EXECINSTR) {
704 if (sec->shdr->sh_size % sizeof(struct bpf_insn) != 0)
711 err = linker_sanity_check_elf_relos(obj, sec);
715 case SHT_LLVM_ADDRSIG:
718 pr_warn("ELF section #%zu (%s) has unrecognized type %zu in %s\n",
719 sec->sec_idx, sec->sec_name, (size_t)sec->shdr->sh_type, obj->filename);
727 static int linker_sanity_check_elf_symtab(struct src_obj *obj, struct src_sec *sec)
729 struct src_sec *link_sec;
733 if (sec->shdr->sh_entsize != sizeof(Elf64_Sym))
735 if (sec->shdr->sh_size % sec->shdr->sh_entsize != 0)
738 if (!sec->shdr->sh_link || sec->shdr->sh_link >= obj->sec_cnt) {
739 pr_warn("ELF SYMTAB section #%zu points to missing STRTAB section #%zu in %s\n",
740 sec->sec_idx, (size_t)sec->shdr->sh_link, obj->filename);
743 link_sec = &obj->secs[sec->shdr->sh_link];
744 if (link_sec->shdr->sh_type != SHT_STRTAB) {
745 pr_warn("ELF SYMTAB section #%zu points to invalid STRTAB section #%zu in %s\n",
746 sec->sec_idx, (size_t)sec->shdr->sh_link, obj->filename);
750 n = sec->shdr->sh_size / sec->shdr->sh_entsize;
751 sym = sec->data->d_buf;
752 for (i = 0; i < n; i++, sym++) {
753 int sym_type = ELF64_ST_TYPE(sym->st_info);
754 int sym_bind = ELF64_ST_BIND(sym->st_info);
755 int sym_vis = ELF64_ST_VISIBILITY(sym->st_other);
758 if (sym->st_name != 0 || sym->st_info != 0
759 || sym->st_other != 0 || sym->st_shndx != 0
760 || sym->st_value != 0 || sym->st_size != 0) {
761 pr_warn("ELF sym #0 is invalid in %s\n", obj->filename);
766 if (sym_bind != STB_LOCAL && sym_bind != STB_GLOBAL && sym_bind != STB_WEAK) {
767 pr_warn("ELF sym #%d in section #%zu has unsupported symbol binding %d\n",
768 i, sec->sec_idx, sym_bind);
771 if (sym_vis != STV_DEFAULT && sym_vis != STV_HIDDEN) {
772 pr_warn("ELF sym #%d in section #%zu has unsupported symbol visibility %d\n",
773 i, sec->sec_idx, sym_vis);
776 if (sym->st_shndx == 0) {
777 if (sym_type != STT_NOTYPE || sym_bind == STB_LOCAL
778 || sym->st_value != 0 || sym->st_size != 0) {
779 pr_warn("ELF sym #%d is invalid extern symbol in %s\n",
786 if (sym->st_shndx < SHN_LORESERVE && sym->st_shndx >= obj->sec_cnt) {
787 pr_warn("ELF sym #%d in section #%zu points to missing section #%zu in %s\n",
788 i, sec->sec_idx, (size_t)sym->st_shndx, obj->filename);
791 if (sym_type == STT_SECTION) {
792 if (sym->st_value != 0)
801 static int linker_sanity_check_elf_relos(struct src_obj *obj, struct src_sec *sec)
803 struct src_sec *link_sec, *sym_sec;
807 if (sec->shdr->sh_entsize != sizeof(Elf64_Rel))
809 if (sec->shdr->sh_size % sec->shdr->sh_entsize != 0)
812 /* SHT_REL's sh_link should point to SYMTAB */
813 if (sec->shdr->sh_link != obj->symtab_sec_idx) {
814 pr_warn("ELF relo section #%zu points to invalid SYMTAB section #%zu in %s\n",
815 sec->sec_idx, (size_t)sec->shdr->sh_link, obj->filename);
819 /* SHT_REL's sh_info points to relocated section */
820 if (!sec->shdr->sh_info || sec->shdr->sh_info >= obj->sec_cnt) {
821 pr_warn("ELF relo section #%zu points to missing section #%zu in %s\n",
822 sec->sec_idx, (size_t)sec->shdr->sh_info, obj->filename);
825 link_sec = &obj->secs[sec->shdr->sh_info];
827 /* .rel<secname> -> <secname> pattern is followed */
828 if (strncmp(sec->sec_name, ".rel", sizeof(".rel") - 1) != 0
829 || strcmp(sec->sec_name + sizeof(".rel") - 1, link_sec->sec_name) != 0) {
830 pr_warn("ELF relo section #%zu name has invalid name in %s\n",
831 sec->sec_idx, obj->filename);
835 /* don't further validate relocations for ignored sections */
836 if (link_sec->skipped)
839 /* relocatable section is data or instructions */
840 if (link_sec->shdr->sh_type != SHT_PROGBITS && link_sec->shdr->sh_type != SHT_NOBITS) {
841 pr_warn("ELF relo section #%zu points to invalid section #%zu in %s\n",
842 sec->sec_idx, (size_t)sec->shdr->sh_info, obj->filename);
846 /* check sanity of each relocation */
847 n = sec->shdr->sh_size / sec->shdr->sh_entsize;
848 relo = sec->data->d_buf;
849 sym_sec = &obj->secs[obj->symtab_sec_idx];
850 for (i = 0; i < n; i++, relo++) {
851 size_t sym_idx = ELF64_R_SYM(relo->r_info);
852 size_t sym_type = ELF64_R_TYPE(relo->r_info);
854 if (sym_type != R_BPF_64_64 && sym_type != R_BPF_64_32) {
855 pr_warn("ELF relo #%d in section #%zu has unexpected type %zu in %s\n",
856 i, sec->sec_idx, sym_type, obj->filename);
860 if (!sym_idx || sym_idx * sizeof(Elf64_Sym) >= sym_sec->shdr->sh_size) {
861 pr_warn("ELF relo #%d in section #%zu points to invalid symbol #%zu in %s\n",
862 i, sec->sec_idx, sym_idx, obj->filename);
866 if (link_sec->shdr->sh_flags & SHF_EXECINSTR) {
867 if (relo->r_offset % sizeof(struct bpf_insn) != 0) {
868 pr_warn("ELF relo #%d in section #%zu points to missing symbol #%zu in %s\n",
869 i, sec->sec_idx, sym_idx, obj->filename);
878 static int check_btf_type_id(__u32 *type_id, void *ctx)
880 struct btf *btf = ctx;
882 if (*type_id > btf__get_nr_types(btf))
888 static int check_btf_str_off(__u32 *str_off, void *ctx)
890 struct btf *btf = ctx;
893 s = btf__str_by_offset(btf, *str_off);
901 static int linker_sanity_check_btf(struct src_obj *obj)
909 n = btf__get_nr_types(obj->btf);
910 for (i = 1; i <= n; i++) {
911 t = btf_type_by_id(obj->btf, i);
913 err = err ?: btf_type_visit_type_ids(t, check_btf_type_id, obj->btf);
914 err = err ?: btf_type_visit_str_offs(t, check_btf_str_off, obj->btf);
922 static int linker_sanity_check_btf_ext(struct src_obj *obj)
929 /* can't use .BTF.ext without .BTF */
933 err = err ?: btf_ext_visit_type_ids(obj->btf_ext, check_btf_type_id, obj->btf);
934 err = err ?: btf_ext_visit_str_offs(obj->btf_ext, check_btf_str_off, obj->btf);
941 static int init_sec(struct bpf_linker *linker, struct dst_sec *dst_sec, struct src_sec *src_sec)
949 dst_sec->sec_idx = 0;
951 /* ephemeral sections are just thin section shells lacking most parts */
952 if (src_sec->ephemeral)
955 scn = elf_newscn(linker->elf);
958 data = elf_newdata(scn);
961 shdr = elf64_getshdr(scn);
966 dst_sec->shdr = shdr;
967 dst_sec->data = data;
968 dst_sec->sec_idx = elf_ndxscn(scn);
970 name_off = strset__add_str(linker->strtab_strs, src_sec->sec_name);
974 shdr->sh_name = name_off;
975 shdr->sh_type = src_sec->shdr->sh_type;
976 shdr->sh_flags = src_sec->shdr->sh_flags;
978 /* sh_link and sh_info have different meaning for different types of
979 * sections, so we leave it up to the caller code to fill them in, if
984 shdr->sh_addralign = src_sec->shdr->sh_addralign;
985 shdr->sh_entsize = src_sec->shdr->sh_entsize;
987 data->d_type = src_sec->data->d_type;
990 data->d_align = src_sec->data->d_align;
996 static struct dst_sec *find_dst_sec_by_name(struct bpf_linker *linker, const char *sec_name)
1001 for (i = 1; i < linker->sec_cnt; i++) {
1002 sec = &linker->secs[i];
1004 if (strcmp(sec->sec_name, sec_name) == 0)
1011 static bool secs_match(struct dst_sec *dst, struct src_sec *src)
1013 if (dst->shdr->sh_type != src->shdr->sh_type) {
1014 pr_warn("sec %s types mismatch\n", dst->sec_name);
1017 if (dst->shdr->sh_flags != src->shdr->sh_flags) {
1018 pr_warn("sec %s flags mismatch\n", dst->sec_name);
1021 if (dst->shdr->sh_entsize != src->shdr->sh_entsize) {
1022 pr_warn("sec %s entsize mismatch\n", dst->sec_name);
1029 static bool sec_content_is_same(struct dst_sec *dst_sec, struct src_sec *src_sec)
1031 if (dst_sec->sec_sz != src_sec->shdr->sh_size)
1033 if (memcmp(dst_sec->raw_data, src_sec->data->d_buf, dst_sec->sec_sz) != 0)
1038 static int extend_sec(struct dst_sec *dst, struct src_sec *src)
1041 size_t dst_align = dst->shdr->sh_addralign;
1042 size_t src_align = src->shdr->sh_addralign;
1043 size_t dst_align_sz, dst_final_sz;
1047 if (dst_align < src_align)
1048 dst_align = src_align;
1050 dst_align_sz = (dst->sec_sz + dst_align - 1) / dst_align * dst_align;
1052 /* no need to re-align final size */
1053 dst_final_sz = dst_align_sz + src->shdr->sh_size;
1055 if (src->shdr->sh_type != SHT_NOBITS) {
1056 tmp = realloc(dst->raw_data, dst_final_sz);
1059 dst->raw_data = tmp;
1061 /* pad dst section, if it's alignment forced size increase */
1062 memset(dst->raw_data + dst->sec_sz, 0, dst_align_sz - dst->sec_sz);
1063 /* now copy src data at a properly aligned offset */
1064 memcpy(dst->raw_data + dst_align_sz, src->data->d_buf, src->shdr->sh_size);
1067 dst->sec_sz = dst_final_sz;
1068 dst->shdr->sh_size = dst_final_sz;
1069 dst->data->d_size = dst_final_sz;
1071 dst->shdr->sh_addralign = dst_align;
1072 dst->data->d_align = dst_align;
1074 src->dst_off = dst_align_sz;
1079 static bool is_data_sec(struct src_sec *sec)
1081 if (!sec || sec->skipped)
1083 /* ephemeral sections are data sections, e.g., .kconfig, .ksyms */
1086 return sec->shdr->sh_type == SHT_PROGBITS || sec->shdr->sh_type == SHT_NOBITS;
1089 static bool is_relo_sec(struct src_sec *sec)
1091 if (!sec || sec->skipped || sec->ephemeral)
1093 return sec->shdr->sh_type == SHT_REL;
1096 static int linker_append_sec_data(struct bpf_linker *linker, struct src_obj *obj)
1100 for (i = 1; i < obj->sec_cnt; i++) {
1101 struct src_sec *src_sec;
1102 struct dst_sec *dst_sec;
1104 src_sec = &obj->secs[i];
1105 if (!is_data_sec(src_sec))
1108 dst_sec = find_dst_sec_by_name(linker, src_sec->sec_name);
1110 dst_sec = add_dst_sec(linker, src_sec->sec_name);
1113 err = init_sec(linker, dst_sec, src_sec);
1115 pr_warn("failed to init section '%s'\n", src_sec->sec_name);
1119 if (!secs_match(dst_sec, src_sec)) {
1120 pr_warn("ELF sections %s are incompatible\n", src_sec->sec_name);
1124 /* "license" and "version" sections are deduped */
1125 if (strcmp(src_sec->sec_name, "license") == 0
1126 || strcmp(src_sec->sec_name, "version") == 0) {
1127 if (!sec_content_is_same(dst_sec, src_sec)) {
1128 pr_warn("non-identical contents of section '%s' are not supported\n", src_sec->sec_name);
1131 src_sec->skipped = true;
1132 src_sec->dst_id = dst_sec->id;
1137 /* record mapped section index */
1138 src_sec->dst_id = dst_sec->id;
1140 if (src_sec->ephemeral)
1143 err = extend_sec(dst_sec, src_sec);
1151 static int linker_append_elf_syms(struct bpf_linker *linker, struct src_obj *obj)
1153 struct src_sec *symtab = &obj->secs[obj->symtab_sec_idx];
1154 Elf64_Sym *sym = symtab->data->d_buf, *dst_sym;
1155 int i, n = symtab->shdr->sh_size / symtab->shdr->sh_entsize;
1156 int str_sec_idx = symtab->shdr->sh_link;
1158 obj->sym_map = calloc(n + 1, sizeof(*obj->sym_map));
1162 for (i = 0; i < n; i++, sym++) {
1163 struct src_sec *src_sec = NULL;
1164 struct dst_sec *dst_sec = NULL;
1165 const char *sym_name;
1169 /* We already validated all-zero symbol #0 and we already
1170 * appended it preventively to the final SYMTAB, so skip it.
1175 sym_name = elf_strptr(obj->elf, str_sec_idx, sym->st_name);
1177 pr_warn("can't fetch symbol name for symbol #%d in '%s'\n", i, obj->filename);
1181 if (sym->st_shndx && sym->st_shndx < SHN_LORESERVE) {
1182 src_sec = &obj->secs[sym->st_shndx];
1183 if (src_sec->skipped)
1185 dst_sec = &linker->secs[src_sec->dst_id];
1187 /* allow only one STT_SECTION symbol per section */
1188 if (ELF64_ST_TYPE(sym->st_info) == STT_SECTION && dst_sec->sec_sym_idx) {
1189 obj->sym_map[i] = dst_sec->sec_sym_idx;
1194 name_off = strset__add_str(linker->strtab_strs, sym_name);
1198 dst_sym = add_new_sym(linker, &dst_sym_idx);
1202 dst_sym->st_name = name_off;
1203 dst_sym->st_info = sym->st_info;
1204 dst_sym->st_other = sym->st_other;
1205 dst_sym->st_shndx = src_sec ? dst_sec->sec_idx : sym->st_shndx;
1206 dst_sym->st_value = (src_sec ? src_sec->dst_off : 0) + sym->st_value;
1207 dst_sym->st_size = sym->st_size;
1209 obj->sym_map[i] = dst_sym_idx;
1211 if (ELF64_ST_TYPE(sym->st_info) == STT_SECTION && dst_sym) {
1212 dst_sec->sec_sym_idx = dst_sym_idx;
1213 dst_sym->st_value = 0;
1221 static int linker_append_elf_relos(struct bpf_linker *linker, struct src_obj *obj)
1223 struct src_sec *src_symtab = &obj->secs[obj->symtab_sec_idx];
1224 struct dst_sec *dst_symtab = &linker->secs[linker->symtab_sec_idx];
1227 for (i = 1; i < obj->sec_cnt; i++) {
1228 struct src_sec *src_sec, *src_linked_sec;
1229 struct dst_sec *dst_sec, *dst_linked_sec;
1230 Elf64_Rel *src_rel, *dst_rel;
1233 src_sec = &obj->secs[i];
1234 if (!is_relo_sec(src_sec))
1237 /* shdr->sh_info points to relocatable section */
1238 src_linked_sec = &obj->secs[src_sec->shdr->sh_info];
1239 if (src_linked_sec->skipped)
1242 dst_sec = find_dst_sec_by_name(linker, src_sec->sec_name);
1244 dst_sec = add_dst_sec(linker, src_sec->sec_name);
1247 err = init_sec(linker, dst_sec, src_sec);
1249 pr_warn("failed to init section '%s'\n", src_sec->sec_name);
1252 } else if (!secs_match(dst_sec, src_sec)) {
1253 pr_warn("sections %s are not compatible\n", src_sec->sec_name);
1257 /* shdr->sh_link points to SYMTAB */
1258 dst_sec->shdr->sh_link = linker->symtab_sec_idx;
1260 /* shdr->sh_info points to relocated section */
1261 dst_linked_sec = &linker->secs[src_linked_sec->dst_id];
1262 dst_sec->shdr->sh_info = dst_linked_sec->sec_idx;
1264 src_sec->dst_id = dst_sec->id;
1265 err = extend_sec(dst_sec, src_sec);
1269 src_rel = src_sec->data->d_buf;
1270 dst_rel = dst_sec->raw_data + src_sec->dst_off;
1271 n = src_sec->shdr->sh_size / src_sec->shdr->sh_entsize;
1272 for (j = 0; j < n; j++, src_rel++, dst_rel++) {
1273 size_t src_sym_idx = ELF64_R_SYM(src_rel->r_info);
1274 size_t sym_type = ELF64_R_TYPE(src_rel->r_info);
1275 Elf64_Sym *src_sym, *dst_sym;
1278 src_sym_idx = ELF64_R_SYM(src_rel->r_info);
1279 src_sym = src_symtab->data->d_buf + sizeof(*src_sym) * src_sym_idx;
1281 dst_sym_idx = obj->sym_map[src_sym_idx];
1282 dst_sym = dst_symtab->raw_data + sizeof(*dst_sym) * dst_sym_idx;
1283 dst_rel->r_offset += src_linked_sec->dst_off;
1284 sym_type = ELF64_R_TYPE(src_rel->r_info);
1285 dst_rel->r_info = ELF64_R_INFO(dst_sym_idx, sym_type);
1287 if (ELF64_ST_TYPE(src_sym->st_info) == STT_SECTION) {
1288 struct src_sec *sec = &obj->secs[src_sym->st_shndx];
1289 struct bpf_insn *insn;
1291 if (src_linked_sec->shdr->sh_flags & SHF_EXECINSTR) {
1292 /* calls to the very first static function inside
1293 * .text section at offset 0 will
1294 * reference section symbol, not the
1295 * function symbol. Fix that up,
1296 * otherwise it won't be possible to
1297 * relocate calls to two different
1298 * static functions with the same name
1299 * (rom two different object files)
1301 insn = dst_linked_sec->raw_data + dst_rel->r_offset;
1302 if (insn->code == (BPF_JMP | BPF_CALL))
1303 insn->imm += sec->dst_off / sizeof(struct bpf_insn);
1305 insn->imm += sec->dst_off;
1307 pr_warn("relocation against STT_SECTION in non-exec section is not supported!\n");
1318 static struct src_sec *find_src_sec_by_name(struct src_obj *obj, const char *sec_name)
1320 struct src_sec *sec;
1323 for (i = 1; i < obj->sec_cnt; i++) {
1324 sec = &obj->secs[i];
1326 if (strcmp(sec->sec_name, sec_name) == 0)
1333 static Elf64_Sym *find_sym_by_name(struct src_obj *obj, size_t sec_idx,
1334 int sym_type, const char *sym_name)
1336 struct src_sec *symtab = &obj->secs[obj->symtab_sec_idx];
1337 Elf64_Sym *sym = symtab->data->d_buf;
1338 int i, n = symtab->shdr->sh_size / symtab->shdr->sh_entsize;
1339 int str_sec_idx = symtab->shdr->sh_link;
1342 for (i = 0; i < n; i++, sym++) {
1343 if (sym->st_shndx != sec_idx)
1345 if (ELF64_ST_TYPE(sym->st_info) != sym_type)
1348 name = elf_strptr(obj->elf, str_sec_idx, sym->st_name);
1352 if (strcmp(sym_name, name) != 0)
1361 static int linker_fixup_btf(struct src_obj *obj)
1363 const char *sec_name;
1364 struct src_sec *sec;
1370 n = btf__get_nr_types(obj->btf);
1371 for (i = 1; i <= n; i++) {
1372 struct btf_var_secinfo *vi;
1375 t = btf_type_by_id(obj->btf, i);
1376 if (btf_kind(t) != BTF_KIND_DATASEC)
1379 sec_name = btf__str_by_offset(obj->btf, t->name_off);
1380 sec = find_src_sec_by_name(obj, sec_name);
1382 /* record actual section size, unless ephemeral */
1384 t->size = sec->shdr->sh_size;
1386 /* BTF can have some sections that are not represented
1387 * in ELF, e.g., .kconfig and .ksyms, which are used
1388 * for special extern variables. Here we'll
1389 * pre-create "section shells" for them to be able to
1390 * keep track of extra per-section metadata later
1391 * (e.g., BTF variables).
1393 sec = add_src_sec(obj, sec_name);
1397 sec->ephemeral = true;
1398 sec->sec_idx = 0; /* will match UNDEF shndx in ELF */
1401 /* remember ELF section and its BTF type ID match */
1402 sec->sec_type_id = i;
1404 /* fix up variable offsets */
1405 vi = btf_var_secinfos(t);
1406 for (j = 0, m = btf_vlen(t); j < m; j++, vi++) {
1407 const struct btf_type *vt = btf__type_by_id(obj->btf, vi->type);
1408 const char *var_name = btf__str_by_offset(obj->btf, vt->name_off);
1409 int var_linkage = btf_var(vt)->linkage;
1412 /* no need to patch up static or extern vars */
1413 if (var_linkage != BTF_VAR_GLOBAL_ALLOCATED)
1416 sym = find_sym_by_name(obj, sec->sec_idx, STT_OBJECT, var_name);
1418 pr_warn("failed to find symbol for variable '%s' in section '%s'\n", var_name, sec_name);
1422 vi->offset = sym->st_value;
1429 static int remap_type_id(__u32 *type_id, void *ctx)
1432 int new_id = id_map[*type_id];
1434 /* Error out if the type wasn't remapped. Ignore VOID which stays VOID. */
1435 if (new_id == 0 && *type_id != 0) {
1436 pr_warn("failed to find new ID mapping for original BTF type ID %u\n", *type_id);
1440 *type_id = id_map[*type_id];
1445 static int linker_append_btf(struct bpf_linker *linker, struct src_obj *obj)
1447 const struct btf_type *t;
1448 int i, j, n, start_id, id;
1453 start_id = btf__get_nr_types(linker->btf) + 1;
1454 n = btf__get_nr_types(obj->btf);
1456 obj->btf_type_map = calloc(n + 1, sizeof(int));
1457 if (!obj->btf_type_map)
1460 for (i = 1; i <= n; i++) {
1461 t = btf__type_by_id(obj->btf, i);
1463 /* DATASECs are handled specially below */
1464 if (btf_kind(t) == BTF_KIND_DATASEC)
1467 id = btf__add_type(linker->btf, obj->btf, t);
1469 pr_warn("failed to append BTF type #%d from file '%s'\n", i, obj->filename);
1473 obj->btf_type_map[i] = id;
1476 /* remap all the types except DATASECs */
1477 n = btf__get_nr_types(linker->btf);
1478 for (i = start_id; i <= n; i++) {
1479 struct btf_type *dst_t = btf_type_by_id(linker->btf, i);
1481 if (btf_type_visit_type_ids(dst_t, remap_type_id, obj->btf_type_map))
1485 /* append DATASEC info */
1486 for (i = 1; i < obj->sec_cnt; i++) {
1487 struct src_sec *src_sec;
1488 struct dst_sec *dst_sec;
1489 const struct btf_var_secinfo *src_var;
1490 struct btf_var_secinfo *dst_var;
1492 src_sec = &obj->secs[i];
1493 if (!src_sec->sec_type_id || src_sec->skipped)
1495 dst_sec = &linker->secs[src_sec->dst_id];
1497 /* Mark section as having BTF regardless of the presence of
1498 * variables. In some cases compiler might generate empty BTF
1499 * with no variables information. E.g., when promoting local
1500 * array/structure variable initial values and BPF object
1501 * file otherwise has no read-only static variables in
1502 * .rodata. We need to preserve such empty BTF and just set
1503 * correct section size.
1505 dst_sec->has_btf = true;
1507 t = btf__type_by_id(obj->btf, src_sec->sec_type_id);
1508 src_var = btf_var_secinfos(t);
1510 for (j = 0; j < n; j++, src_var++) {
1511 void *sec_vars = dst_sec->sec_vars;
1513 sec_vars = libbpf_reallocarray(sec_vars,
1514 dst_sec->sec_var_cnt + 1,
1515 sizeof(*dst_sec->sec_vars));
1519 dst_sec->sec_vars = sec_vars;
1520 dst_sec->sec_var_cnt++;
1522 dst_var = &dst_sec->sec_vars[dst_sec->sec_var_cnt - 1];
1523 dst_var->type = obj->btf_type_map[src_var->type];
1524 dst_var->size = src_var->size;
1525 dst_var->offset = src_sec->dst_off + src_var->offset;
1532 static void *add_btf_ext_rec(struct btf_ext_sec_data *ext_data, const void *src_rec)
1536 tmp = libbpf_reallocarray(ext_data->recs, ext_data->rec_cnt + 1, ext_data->rec_sz);
1539 ext_data->recs = tmp;
1541 tmp += ext_data->rec_cnt * ext_data->rec_sz;
1542 memcpy(tmp, src_rec, ext_data->rec_sz);
1544 ext_data->rec_cnt++;
1549 static int linker_append_btf_ext(struct bpf_linker *linker, struct src_obj *obj)
1551 const struct btf_ext_info_sec *ext_sec;
1552 const char *sec_name, *s;
1553 struct src_sec *src_sec;
1554 struct dst_sec *dst_sec;
1555 int rec_sz, str_off, i;
1560 rec_sz = obj->btf_ext->func_info.rec_size;
1561 for_each_btf_ext_sec(&obj->btf_ext->func_info, ext_sec) {
1562 struct bpf_func_info_min *src_rec, *dst_rec;
1564 sec_name = btf__name_by_offset(obj->btf, ext_sec->sec_name_off);
1565 src_sec = find_src_sec_by_name(obj, sec_name);
1567 pr_warn("can't find section '%s' referenced from .BTF.ext\n", sec_name);
1570 dst_sec = &linker->secs[src_sec->dst_id];
1572 if (dst_sec->func_info.rec_sz == 0)
1573 dst_sec->func_info.rec_sz = rec_sz;
1574 if (dst_sec->func_info.rec_sz != rec_sz) {
1575 pr_warn("incompatible .BTF.ext record sizes for section '%s'\n", sec_name);
1579 for_each_btf_ext_rec(&obj->btf_ext->func_info, ext_sec, i, src_rec) {
1580 dst_rec = add_btf_ext_rec(&dst_sec->func_info, src_rec);
1584 dst_rec->insn_off += src_sec->dst_off;
1585 dst_rec->type_id = obj->btf_type_map[dst_rec->type_id];
1589 rec_sz = obj->btf_ext->line_info.rec_size;
1590 for_each_btf_ext_sec(&obj->btf_ext->line_info, ext_sec) {
1591 struct bpf_line_info_min *src_rec, *dst_rec;
1593 sec_name = btf__name_by_offset(obj->btf, ext_sec->sec_name_off);
1594 src_sec = find_src_sec_by_name(obj, sec_name);
1596 pr_warn("can't find section '%s' referenced from .BTF.ext\n", sec_name);
1599 dst_sec = &linker->secs[src_sec->dst_id];
1601 if (dst_sec->line_info.rec_sz == 0)
1602 dst_sec->line_info.rec_sz = rec_sz;
1603 if (dst_sec->line_info.rec_sz != rec_sz) {
1604 pr_warn("incompatible .BTF.ext record sizes for section '%s'\n", sec_name);
1608 for_each_btf_ext_rec(&obj->btf_ext->line_info, ext_sec, i, src_rec) {
1609 dst_rec = add_btf_ext_rec(&dst_sec->line_info, src_rec);
1613 dst_rec->insn_off += src_sec->dst_off;
1615 s = btf__str_by_offset(obj->btf, src_rec->file_name_off);
1616 str_off = btf__add_str(linker->btf, s);
1619 dst_rec->file_name_off = str_off;
1621 s = btf__str_by_offset(obj->btf, src_rec->line_off);
1622 str_off = btf__add_str(linker->btf, s);
1625 dst_rec->line_off = str_off;
1627 /* dst_rec->line_col is fine */
1631 rec_sz = obj->btf_ext->core_relo_info.rec_size;
1632 for_each_btf_ext_sec(&obj->btf_ext->core_relo_info, ext_sec) {
1633 struct bpf_core_relo *src_rec, *dst_rec;
1635 sec_name = btf__name_by_offset(obj->btf, ext_sec->sec_name_off);
1636 src_sec = find_src_sec_by_name(obj, sec_name);
1638 pr_warn("can't find section '%s' referenced from .BTF.ext\n", sec_name);
1641 dst_sec = &linker->secs[src_sec->dst_id];
1643 if (dst_sec->core_relo_info.rec_sz == 0)
1644 dst_sec->core_relo_info.rec_sz = rec_sz;
1645 if (dst_sec->core_relo_info.rec_sz != rec_sz) {
1646 pr_warn("incompatible .BTF.ext record sizes for section '%s'\n", sec_name);
1650 for_each_btf_ext_rec(&obj->btf_ext->core_relo_info, ext_sec, i, src_rec) {
1651 dst_rec = add_btf_ext_rec(&dst_sec->core_relo_info, src_rec);
1655 dst_rec->insn_off += src_sec->dst_off;
1656 dst_rec->type_id = obj->btf_type_map[dst_rec->type_id];
1658 s = btf__str_by_offset(obj->btf, src_rec->access_str_off);
1659 str_off = btf__add_str(linker->btf, s);
1662 dst_rec->access_str_off = str_off;
1664 /* dst_rec->kind is fine */
1671 int bpf_linker__finalize(struct bpf_linker *linker)
1673 struct dst_sec *sec;
1681 err = finalize_btf(linker);
1685 /* Finalize strings */
1686 strs_sz = strset__data_size(linker->strtab_strs);
1687 strs = strset__data(linker->strtab_strs);
1689 sec = &linker->secs[linker->strtab_sec_idx];
1690 sec->data->d_align = 1;
1691 sec->data->d_off = 0LL;
1692 sec->data->d_buf = (void *)strs;
1693 sec->data->d_type = ELF_T_BYTE;
1694 sec->data->d_size = strs_sz;
1695 sec->shdr->sh_size = strs_sz;
1697 for (i = 1; i < linker->sec_cnt; i++) {
1698 sec = &linker->secs[i];
1700 /* STRTAB is handled specially above */
1701 if (sec->sec_idx == linker->strtab_sec_idx)
1704 /* special ephemeral sections (.ksyms, .kconfig, etc) */
1708 sec->data->d_buf = sec->raw_data;
1711 /* Finalize ELF layout */
1712 if (elf_update(linker->elf, ELF_C_NULL) < 0) {
1714 pr_warn_elf("failed to finalize ELF layout");
1718 /* Write out final ELF contents */
1719 if (elf_update(linker->elf, ELF_C_WRITE) < 0) {
1721 pr_warn_elf("failed to write ELF contents");
1725 elf_end(linker->elf);
1734 static int emit_elf_data_sec(struct bpf_linker *linker, const char *sec_name,
1735 size_t align, const void *raw_data, size_t raw_sz)
1742 name_off = strset__add_str(linker->strtab_strs, sec_name);
1746 scn = elf_newscn(linker->elf);
1749 data = elf_newdata(scn);
1752 shdr = elf64_getshdr(scn);
1756 shdr->sh_name = name_off;
1757 shdr->sh_type = SHT_PROGBITS;
1759 shdr->sh_size = raw_sz;
1762 shdr->sh_addralign = align;
1763 shdr->sh_entsize = 0;
1765 data->d_type = ELF_T_BYTE;
1766 data->d_size = raw_sz;
1767 data->d_buf = (void *)raw_data;
1768 data->d_align = align;
1774 static int finalize_btf(struct bpf_linker *linker)
1776 struct btf *btf = linker->btf;
1777 const void *raw_data;
1781 /* bail out if no BTF data was produced */
1782 if (btf__get_nr_types(linker->btf) == 0)
1785 for (i = 1; i < linker->sec_cnt; i++) {
1786 struct dst_sec *sec = &linker->secs[i];
1791 id = btf__add_datasec(btf, sec->sec_name, sec->sec_sz);
1793 pr_warn("failed to add consolidated BTF type for datasec '%s': %d\n",
1798 for (j = 0; j < sec->sec_var_cnt; j++) {
1799 struct btf_var_secinfo *vi = &sec->sec_vars[j];
1801 if (btf__add_datasec_var_info(btf, vi->type, vi->offset, vi->size))
1806 err = finalize_btf_ext(linker);
1808 pr_warn(".BTF.ext generation failed: %d\n", err);
1812 err = btf__dedup(linker->btf, linker->btf_ext, NULL);
1814 pr_warn("BTF dedup failed: %d\n", err);
1818 /* Emit .BTF section */
1819 raw_data = btf__get_raw_data(linker->btf, &raw_sz);
1823 err = emit_elf_data_sec(linker, BTF_ELF_SEC, 8, raw_data, raw_sz);
1825 pr_warn("failed to write out .BTF ELF section: %d\n", err);
1829 /* Emit .BTF.ext section */
1830 if (linker->btf_ext) {
1831 raw_data = btf_ext__get_raw_data(linker->btf_ext, &raw_sz);
1835 err = emit_elf_data_sec(linker, BTF_EXT_ELF_SEC, 8, raw_data, raw_sz);
1837 pr_warn("failed to write out .BTF.ext ELF section: %d\n", err);
1845 static int emit_btf_ext_data(struct bpf_linker *linker, void *output,
1846 const char *sec_name, struct btf_ext_sec_data *sec_data)
1848 struct btf_ext_info_sec *sec_info;
1853 if (!sec_data->rec_cnt)
1856 str_off = btf__add_str(linker->btf, sec_name);
1861 sec_info->sec_name_off = str_off;
1862 sec_info->num_info = sec_data->rec_cnt;
1863 cur += sizeof(struct btf_ext_info_sec);
1865 sz = sec_data->rec_cnt * sec_data->rec_sz;
1866 memcpy(cur, sec_data->recs, sz);
1869 return cur - output;
1872 static int finalize_btf_ext(struct bpf_linker *linker)
1874 size_t funcs_sz = 0, lines_sz = 0, core_relos_sz = 0, total_sz = 0;
1875 size_t func_rec_sz = 0, line_rec_sz = 0, core_relo_rec_sz = 0;
1876 struct btf_ext_header *hdr;
1880 /* validate that all sections have the same .BTF.ext record sizes
1881 * and calculate total data size for each type of data (func info,
1882 * line info, core relos)
1884 for (i = 1; i < linker->sec_cnt; i++) {
1885 struct dst_sec *sec = &linker->secs[i];
1887 if (sec->func_info.rec_cnt) {
1888 if (func_rec_sz == 0)
1889 func_rec_sz = sec->func_info.rec_sz;
1890 if (func_rec_sz != sec->func_info.rec_sz) {
1891 pr_warn("mismatch in func_info record size %zu != %u\n",
1892 func_rec_sz, sec->func_info.rec_sz);
1896 funcs_sz += sizeof(struct btf_ext_info_sec) + func_rec_sz * sec->func_info.rec_cnt;
1898 if (sec->line_info.rec_cnt) {
1899 if (line_rec_sz == 0)
1900 line_rec_sz = sec->line_info.rec_sz;
1901 if (line_rec_sz != sec->line_info.rec_sz) {
1902 pr_warn("mismatch in line_info record size %zu != %u\n",
1903 line_rec_sz, sec->line_info.rec_sz);
1907 lines_sz += sizeof(struct btf_ext_info_sec) + line_rec_sz * sec->line_info.rec_cnt;
1909 if (sec->core_relo_info.rec_cnt) {
1910 if (core_relo_rec_sz == 0)
1911 core_relo_rec_sz = sec->core_relo_info.rec_sz;
1912 if (core_relo_rec_sz != sec->core_relo_info.rec_sz) {
1913 pr_warn("mismatch in core_relo_info record size %zu != %u\n",
1914 core_relo_rec_sz, sec->core_relo_info.rec_sz);
1918 core_relos_sz += sizeof(struct btf_ext_info_sec) + core_relo_rec_sz * sec->core_relo_info.rec_cnt;
1922 if (!funcs_sz && !lines_sz && !core_relos_sz)
1925 total_sz += sizeof(struct btf_ext_header);
1927 funcs_sz += sizeof(__u32); /* record size prefix */
1928 total_sz += funcs_sz;
1931 lines_sz += sizeof(__u32); /* record size prefix */
1932 total_sz += lines_sz;
1934 if (core_relos_sz) {
1935 core_relos_sz += sizeof(__u32); /* record size prefix */
1936 total_sz += core_relos_sz;
1939 cur = data = calloc(1, total_sz);
1944 hdr->magic = BTF_MAGIC;
1945 hdr->version = BTF_VERSION;
1947 hdr->hdr_len = sizeof(struct btf_ext_header);
1948 cur += sizeof(struct btf_ext_header);
1950 /* All offsets are in bytes relative to the end of this header */
1951 hdr->func_info_off = 0;
1952 hdr->func_info_len = funcs_sz;
1953 hdr->line_info_off = funcs_sz;
1954 hdr->line_info_len = lines_sz;
1955 hdr->core_relo_off = funcs_sz + lines_sz;
1956 hdr->core_relo_len = core_relos_sz;
1959 *(__u32 *)cur = func_rec_sz;
1960 cur += sizeof(__u32);
1962 for (i = 1; i < linker->sec_cnt; i++) {
1963 struct dst_sec *sec = &linker->secs[i];
1965 sz = emit_btf_ext_data(linker, cur, sec->sec_name, &sec->func_info);
1976 *(__u32 *)cur = line_rec_sz;
1977 cur += sizeof(__u32);
1979 for (i = 1; i < linker->sec_cnt; i++) {
1980 struct dst_sec *sec = &linker->secs[i];
1982 sz = emit_btf_ext_data(linker, cur, sec->sec_name, &sec->line_info);
1992 if (core_relos_sz) {
1993 *(__u32 *)cur = core_relo_rec_sz;
1994 cur += sizeof(__u32);
1996 for (i = 1; i < linker->sec_cnt; i++) {
1997 struct dst_sec *sec = &linker->secs[i];
1999 sz = emit_btf_ext_data(linker, cur, sec->sec_name, &sec->core_relo_info);
2009 linker->btf_ext = btf_ext__new(data, total_sz);
2010 err = libbpf_get_error(linker->btf_ext);
2012 linker->btf_ext = NULL;
2013 pr_warn("failed to parse final .BTF.ext data: %d\n", err);