| Author | Tokens | Token Proportion | Commits | Commit Proportion |
|---|---|---|---|---|
| Andrii Nakryiko | 14037 | 97.85% | 24 | 48.00% |
| Sergei Trofimovich | 126 | 0.88% | 1 | 2.00% |
| Wang Nan | 40 | 0.28% | 7 | 14.00% |
| Martin KaFai Lau | 38 | 0.26% | 3 | 6.00% |
| Kumar Kartikeya Dwivedi | 34 | 0.24% | 2 | 4.00% |
| Hengqi Chen | 16 | 0.11% | 1 | 2.00% |
| Yonghong Song | 14 | 0.10% | 2 | 4.00% |
| Ilya Leoshkevich | 10 | 0.07% | 1 | 2.00% |
| Alyssa Ross | 10 | 0.07% | 1 | 2.00% |
| Eduard Zingerman | 5 | 0.03% | 1 | 2.00% |
| Viktor Malik | 3 | 0.02% | 1 | 2.00% |
| Jiri Olsa | 3 | 0.02% | 1 | 2.00% |
| Hechao Li | 3 | 0.02% | 1 | 2.00% |
| Song Liu | 2 | 0.01% | 1 | 2.00% |
| Stanislav Fomichev | 2 | 0.01% | 1 | 2.00% |
| Joe Stringer | 1 | 0.01% | 1 | 2.00% |
| Alexei Starovoitov | 1 | 0.01% | 1 | 2.00% |
| Total | 14345 | 50 |
// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) /* * BPF static linker * * Copyright (c) 2021 Facebook */ #include <stdbool.h> #include <stddef.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <errno.h> #include <linux/err.h> #include <linux/btf.h> #include <elf.h> #include <libelf.h> #include <fcntl.h> #include "libbpf.h" #include "btf.h" #include "libbpf_internal.h" #include "strset.h" #define BTF_EXTERN_SEC ".extern" struct src_sec { const char *sec_name; /* positional (not necessarily ELF) index in an array of sections */ int id; /* positional (not necessarily ELF) index of a matching section in a final object file */ int dst_id; /* section data offset in a matching output section */ int dst_off; /* whether section is omitted from the final ELF file */ bool skipped; /* whether section is an ephemeral section, not mapped to an ELF section */ bool ephemeral; /* ELF info */ size_t sec_idx; Elf_Scn *scn; Elf64_Shdr *shdr; Elf_Data *data; /* corresponding BTF DATASEC type ID */ int sec_type_id; }; struct src_obj { const char *filename; int fd; Elf *elf; /* Section header strings section index */ size_t shstrs_sec_idx; /* SYMTAB section index */ size_t symtab_sec_idx; struct btf *btf; struct btf_ext *btf_ext; /* List of sections (including ephemeral). Slot zero is unused. */ struct src_sec *secs; int sec_cnt; /* mapping of symbol indices from src to dst ELF */ int *sym_map; /* mapping from the src BTF type IDs to dst ones */ int *btf_type_map; }; /* single .BTF.ext data section */ struct btf_ext_sec_data { size_t rec_cnt; __u32 rec_sz; void *recs; }; struct glob_sym { /* ELF symbol index */ int sym_idx; /* associated section id for .ksyms, .kconfig, etc, but not .extern */ int sec_id; /* extern name offset in STRTAB */ int name_off; /* optional associated BTF type ID */ int btf_id; /* BTF type ID to which VAR/FUNC type is pointing to; used for * rewriting types when extern VAR/FUNC is resolved to a concrete * definition */ int underlying_btf_id; /* sec_var index in the corresponding dst_sec, if exists */ int var_idx; /* extern or resolved/global symbol */ bool is_extern; /* weak or strong symbol, never goes back from strong to weak */ bool is_weak; }; struct dst_sec { char *sec_name; /* positional (not necessarily ELF) index in an array of sections */ int id; bool ephemeral; /* ELF info */ size_t sec_idx; Elf_Scn *scn; Elf64_Shdr *shdr; Elf_Data *data; /* final output section size */ int sec_sz; /* final output contents of the section */ void *raw_data; /* corresponding STT_SECTION symbol index in SYMTAB */ int sec_sym_idx; /* section's DATASEC variable info, emitted on BTF finalization */ bool has_btf; int sec_var_cnt; struct btf_var_secinfo *sec_vars; /* section's .BTF.ext data */ struct btf_ext_sec_data func_info; struct btf_ext_sec_data line_info; struct btf_ext_sec_data core_relo_info; }; struct bpf_linker { char *filename; int fd; Elf *elf; Elf64_Ehdr *elf_hdr; /* Output sections metadata */ struct dst_sec *secs; int sec_cnt; struct strset *strtab_strs; /* STRTAB unique strings */ size_t strtab_sec_idx; /* STRTAB section index */ size_t symtab_sec_idx; /* SYMTAB section index */ struct btf *btf; struct btf_ext *btf_ext; /* global (including extern) ELF symbols */ int glob_sym_cnt; struct glob_sym *glob_syms; }; #define pr_warn_elf(fmt, ...) \ libbpf_print(LIBBPF_WARN, "libbpf: " fmt ": %s\n", ##__VA_ARGS__, elf_errmsg(-1)) static int init_output_elf(struct bpf_linker *linker, const char *file); static int linker_load_obj_file(struct bpf_linker *linker, const char *filename, const struct bpf_linker_file_opts *opts, struct src_obj *obj); static int linker_sanity_check_elf(struct src_obj *obj); static int linker_sanity_check_elf_symtab(struct src_obj *obj, struct src_sec *sec); static int linker_sanity_check_elf_relos(struct src_obj *obj, struct src_sec *sec); static int linker_sanity_check_btf(struct src_obj *obj); static int linker_sanity_check_btf_ext(struct src_obj *obj); static int linker_fixup_btf(struct src_obj *obj); static int linker_append_sec_data(struct bpf_linker *linker, struct src_obj *obj); static int linker_append_elf_syms(struct bpf_linker *linker, struct src_obj *obj); static int linker_append_elf_sym(struct bpf_linker *linker, struct src_obj *obj, Elf64_Sym *sym, const char *sym_name, int src_sym_idx); static int linker_append_elf_relos(struct bpf_linker *linker, struct src_obj *obj); static int linker_append_btf(struct bpf_linker *linker, struct src_obj *obj); static int linker_append_btf_ext(struct bpf_linker *linker, struct src_obj *obj); static int finalize_btf(struct bpf_linker *linker); static int finalize_btf_ext(struct bpf_linker *linker); void bpf_linker__free(struct bpf_linker *linker) { int i; if (!linker) return; free(linker->filename); if (linker->elf) elf_end(linker->elf); if (linker->fd >= 0) close(linker->fd); strset__free(linker->strtab_strs); btf__free(linker->btf); btf_ext__free(linker->btf_ext); for (i = 1; i < linker->sec_cnt; i++) { struct dst_sec *sec = &linker->secs[i]; free(sec->sec_name); free(sec->raw_data); free(sec->sec_vars); free(sec->func_info.recs); free(sec->line_info.recs); free(sec->core_relo_info.recs); } free(linker->secs); free(linker->glob_syms); free(linker); } struct bpf_linker *bpf_linker__new(const char *filename, struct bpf_linker_opts *opts) { struct bpf_linker *linker; int err; if (!OPTS_VALID(opts, bpf_linker_opts)) return errno = EINVAL, NULL; if (elf_version(EV_CURRENT) == EV_NONE) { pr_warn_elf("libelf initialization failed"); return errno = EINVAL, NULL; } linker = calloc(1, sizeof(*linker)); if (!linker) return errno = ENOMEM, NULL; linker->fd = -1; err = init_output_elf(linker, filename); if (err) goto err_out; return linker; err_out: bpf_linker__free(linker); return errno = -err, NULL; } static struct dst_sec *add_dst_sec(struct bpf_linker *linker, const char *sec_name) { struct dst_sec *secs = linker->secs, *sec; size_t new_cnt = linker->sec_cnt ? linker->sec_cnt + 1 : 2; secs = libbpf_reallocarray(secs, new_cnt, sizeof(*secs)); if (!secs) return NULL; /* zero out newly allocated memory */ memset(secs + linker->sec_cnt, 0, (new_cnt - linker->sec_cnt) * sizeof(*secs)); linker->secs = secs; linker->sec_cnt = new_cnt; sec = &linker->secs[new_cnt - 1]; sec->id = new_cnt - 1; sec->sec_name = strdup(sec_name); if (!sec->sec_name) return NULL; return sec; } static Elf64_Sym *add_new_sym(struct bpf_linker *linker, size_t *sym_idx) { struct dst_sec *symtab = &linker->secs[linker->symtab_sec_idx]; Elf64_Sym *syms, *sym; size_t sym_cnt = symtab->sec_sz / sizeof(*sym); syms = libbpf_reallocarray(symtab->raw_data, sym_cnt + 1, sizeof(*sym)); if (!syms) return NULL; sym = &syms[sym_cnt]; memset(sym, 0, sizeof(*sym)); symtab->raw_data = syms; symtab->sec_sz += sizeof(*sym); symtab->shdr->sh_size += sizeof(*sym); symtab->data->d_size += sizeof(*sym); if (sym_idx) *sym_idx = sym_cnt; return sym; } static int init_output_elf(struct bpf_linker *linker, const char *file) { int err, str_off; Elf64_Sym *init_sym; struct dst_sec *sec; linker->filename = strdup(file); if (!linker->filename) return -ENOMEM; linker->fd = open(file, O_WRONLY | O_CREAT | O_TRUNC | O_CLOEXEC, 0644); if (linker->fd < 0) { err = -errno; pr_warn("failed to create '%s': %d\n", file, err); return err; } linker->elf = elf_begin(linker->fd, ELF_C_WRITE, NULL); if (!linker->elf) { pr_warn_elf("failed to create ELF object"); return -EINVAL; } /* ELF header */ linker->elf_hdr = elf64_newehdr(linker->elf); if (!linker->elf_hdr) { pr_warn_elf("failed to create ELF header"); return -EINVAL; } linker->elf_hdr->e_machine = EM_BPF; linker->elf_hdr->e_type = ET_REL; #if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__ linker->elf_hdr->e_ident[EI_DATA] = ELFDATA2LSB; #elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__ linker->elf_hdr->e_ident[EI_DATA] = ELFDATA2MSB; #else #error "Unknown __BYTE_ORDER__" #endif /* STRTAB */ /* initialize strset with an empty string to conform to ELF */ linker->strtab_strs = strset__new(INT_MAX, "", sizeof("")); if (libbpf_get_error(linker->strtab_strs)) return libbpf_get_error(linker->strtab_strs); sec = add_dst_sec(linker, ".strtab"); if (!sec) return -ENOMEM; sec->scn = elf_newscn(linker->elf); if (!sec->scn) { pr_warn_elf("failed to create STRTAB section"); return -EINVAL; } sec->shdr = elf64_getshdr(sec->scn); if (!sec->shdr) return -EINVAL; sec->data = elf_newdata(sec->scn); if (!sec->data) { pr_warn_elf("failed to create STRTAB data"); return -EINVAL; } str_off = strset__add_str(linker->strtab_strs, sec->sec_name); if (str_off < 0) return str_off; sec->sec_idx = elf_ndxscn(sec->scn); linker->elf_hdr->e_shstrndx = sec->sec_idx; linker->strtab_sec_idx = sec->sec_idx; sec->shdr->sh_name = str_off; sec->shdr->sh_type = SHT_STRTAB; sec->shdr->sh_flags = SHF_STRINGS; sec->shdr->sh_offset = 0; sec->shdr->sh_link = 0; sec->shdr->sh_info = 0; sec->shdr->sh_addralign = 1; sec->shdr->sh_size = sec->sec_sz = 0; sec->shdr->sh_entsize = 0; /* SYMTAB */ sec = add_dst_sec(linker, ".symtab"); if (!sec) return -ENOMEM; sec->scn = elf_newscn(linker->elf); if (!sec->scn) { pr_warn_elf("failed to create SYMTAB section"); return -EINVAL; } sec->shdr = elf64_getshdr(sec->scn); if (!sec->shdr) return -EINVAL; sec->data = elf_newdata(sec->scn); if (!sec->data) { pr_warn_elf("failed to create SYMTAB data"); return -EINVAL; } str_off = strset__add_str(linker->strtab_strs, sec->sec_name); if (str_off < 0) return str_off; sec->sec_idx = elf_ndxscn(sec->scn); linker->symtab_sec_idx = sec->sec_idx; sec->shdr->sh_name = str_off; sec->shdr->sh_type = SHT_SYMTAB; sec->shdr->sh_flags = 0; sec->shdr->sh_offset = 0; sec->shdr->sh_link = linker->strtab_sec_idx; /* sh_info should be one greater than the index of the last local * symbol (i.e., binding is STB_LOCAL). But why and who cares? */ sec->shdr->sh_info = 0; sec->shdr->sh_addralign = 8; sec->shdr->sh_entsize = sizeof(Elf64_Sym); /* .BTF */ linker->btf = btf__new_empty(); err = libbpf_get_error(linker->btf); if (err) return err; /* add the special all-zero symbol */ init_sym = add_new_sym(linker, NULL); if (!init_sym) return -EINVAL; init_sym->st_name = 0; init_sym->st_info = 0; init_sym->st_other = 0; init_sym->st_shndx = SHN_UNDEF; init_sym->st_value = 0; init_sym->st_size = 0; return 0; } int bpf_linker__add_file(struct bpf_linker *linker, const char *filename, const struct bpf_linker_file_opts *opts) { struct src_obj obj = {}; int err = 0; if (!OPTS_VALID(opts, bpf_linker_file_opts)) return libbpf_err(-EINVAL); if (!linker->elf) return libbpf_err(-EINVAL); err = err ?: linker_load_obj_file(linker, filename, opts, &obj); err = err ?: linker_append_sec_data(linker, &obj); err = err ?: linker_append_elf_syms(linker, &obj); err = err ?: linker_append_elf_relos(linker, &obj); err = err ?: linker_append_btf(linker, &obj); err = err ?: linker_append_btf_ext(linker, &obj); /* free up src_obj resources */ free(obj.btf_type_map); btf__free(obj.btf); btf_ext__free(obj.btf_ext); free(obj.secs); free(obj.sym_map); if (obj.elf) elf_end(obj.elf); if (obj.fd >= 0) close(obj.fd); return libbpf_err(err); } static bool is_dwarf_sec_name(const char *name) { /* approximation, but the actual list is too long */ return strncmp(name, ".debug_", sizeof(".debug_") - 1) == 0; } static bool is_ignored_sec(struct src_sec *sec) { Elf64_Shdr *shdr = sec->shdr; const char *name = sec->sec_name; /* no special handling of .strtab */ if (shdr->sh_type == SHT_STRTAB) return true; /* ignore .llvm_addrsig section as well */ if (shdr->sh_type == SHT_LLVM_ADDRSIG) return true; /* no subprograms will lead to an empty .text section, ignore it */ if (shdr->sh_type == SHT_PROGBITS && shdr->sh_size == 0 && strcmp(sec->sec_name, ".text") == 0) return true; /* DWARF sections */ if (is_dwarf_sec_name(sec->sec_name)) return true; if (strncmp(name, ".rel", sizeof(".rel") - 1) == 0) { name += sizeof(".rel") - 1; /* DWARF section relocations */ if (is_dwarf_sec_name(name)) return true; /* .BTF and .BTF.ext don't need relocations */ if (strcmp(name, BTF_ELF_SEC) == 0 || strcmp(name, BTF_EXT_ELF_SEC) == 0) return true; } return false; } static struct src_sec *add_src_sec(struct src_obj *obj, const char *sec_name) { struct src_sec *secs = obj->secs, *sec; size_t new_cnt = obj->sec_cnt ? obj->sec_cnt + 1 : 2; secs = libbpf_reallocarray(secs, new_cnt, sizeof(*secs)); if (!secs) return NULL; /* zero out newly allocated memory */ memset(secs + obj->sec_cnt, 0, (new_cnt - obj->sec_cnt) * sizeof(*secs)); obj->secs = secs; obj->sec_cnt = new_cnt; sec = &obj->secs[new_cnt - 1]; sec->id = new_cnt - 1; sec->sec_name = sec_name; return sec; } static int linker_load_obj_file(struct bpf_linker *linker, const char *filename, const struct bpf_linker_file_opts *opts, struct src_obj *obj) { #if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__ const int host_endianness = ELFDATA2LSB; #elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__ const int host_endianness = ELFDATA2MSB; #else #error "Unknown __BYTE_ORDER__" #endif int err = 0; Elf_Scn *scn; Elf_Data *data; Elf64_Ehdr *ehdr; Elf64_Shdr *shdr; struct src_sec *sec; pr_debug("linker: adding object file '%s'...\n", filename); obj->filename = filename; obj->fd = open(filename, O_RDONLY | O_CLOEXEC); if (obj->fd < 0) { err = -errno; pr_warn("failed to open file '%s': %d\n", filename, err); return err; } obj->elf = elf_begin(obj->fd, ELF_C_READ_MMAP, NULL); if (!obj->elf) { err = -errno; pr_warn_elf("failed to parse ELF file '%s'", filename); return err; } /* Sanity check ELF file high-level properties */ ehdr = elf64_getehdr(obj->elf); if (!ehdr) { err = -errno; pr_warn_elf("failed to get ELF header for %s", filename); return err; } if (ehdr->e_ident[EI_DATA] != host_endianness) { err = -EOPNOTSUPP; pr_warn_elf("unsupported byte order of ELF file %s", filename); return err; } if (ehdr->e_type != ET_REL || ehdr->e_machine != EM_BPF || ehdr->e_ident[EI_CLASS] != ELFCLASS64) { err = -EOPNOTSUPP; pr_warn_elf("unsupported kind of ELF file %s", filename); return err; } if (elf_getshdrstrndx(obj->elf, &obj->shstrs_sec_idx)) { err = -errno; pr_warn_elf("failed to get SHSTRTAB section index for %s", filename); return err; } scn = NULL; while ((scn = elf_nextscn(obj->elf, scn)) != NULL) { size_t sec_idx = elf_ndxscn(scn); const char *sec_name; shdr = elf64_getshdr(scn); if (!shdr) { err = -errno; pr_warn_elf("failed to get section #%zu header for %s", sec_idx, filename); return err; } sec_name = elf_strptr(obj->elf, obj->shstrs_sec_idx, shdr->sh_name); if (!sec_name) { err = -errno; pr_warn_elf("failed to get section #%zu name for %s", sec_idx, filename); return err; } data = elf_getdata(scn, 0); if (!data) { err = -errno; pr_warn_elf("failed to get section #%zu (%s) data from %s", sec_idx, sec_name, filename); return err; } sec = add_src_sec(obj, sec_name); if (!sec) return -ENOMEM; sec->scn = scn; sec->shdr = shdr; sec->data = data; sec->sec_idx = elf_ndxscn(scn); if (is_ignored_sec(sec)) { sec->skipped = true; continue; } switch (shdr->sh_type) { case SHT_SYMTAB: if (obj->symtab_sec_idx) { err = -EOPNOTSUPP; pr_warn("multiple SYMTAB sections found, not supported\n"); return err; } obj->symtab_sec_idx = sec_idx; break; case SHT_STRTAB: /* we'll construct our own string table */ break; case SHT_PROGBITS: if (strcmp(sec_name, BTF_ELF_SEC) == 0) { obj->btf = btf__new(data->d_buf, shdr->sh_size); err = libbpf_get_error(obj->btf); if (err) { pr_warn("failed to parse .BTF from %s: %d\n", filename, err); return err; } sec->skipped = true; continue; } if (strcmp(sec_name, BTF_EXT_ELF_SEC) == 0) { obj->btf_ext = btf_ext__new(data->d_buf, shdr->sh_size); err = libbpf_get_error(obj->btf_ext); if (err) { pr_warn("failed to parse .BTF.ext from '%s': %d\n", filename, err); return err; } sec->skipped = true; continue; } /* data & code */ break; case SHT_NOBITS: /* BSS */ break; case SHT_REL: /* relocations */ break; default: pr_warn("unrecognized section #%zu (%s) in %s\n", sec_idx, sec_name, filename); err = -EINVAL; return err; } } err = err ?: linker_sanity_check_elf(obj); err = err ?: linker_sanity_check_btf(obj); err = err ?: linker_sanity_check_btf_ext(obj); err = err ?: linker_fixup_btf(obj); return err; } static int linker_sanity_check_elf(struct src_obj *obj) { struct src_sec *sec; int i, err; if (!obj->symtab_sec_idx) { pr_warn("ELF is missing SYMTAB section in %s\n", obj->filename); return -EINVAL; } if (!obj->shstrs_sec_idx) { pr_warn("ELF is missing section headers STRTAB section in %s\n", obj->filename); return -EINVAL; } for (i = 1; i < obj->sec_cnt; i++) { sec = &obj->secs[i]; if (sec->sec_name[0] == '\0') { pr_warn("ELF section #%zu has empty name in %s\n", sec->sec_idx, obj->filename); return -EINVAL; } if (is_dwarf_sec_name(sec->sec_name)) continue; if (sec->shdr->sh_addralign && !is_pow_of_2(sec->shdr->sh_addralign)) { pr_warn("ELF section #%zu alignment %llu is non pow-of-2 alignment in %s\n", sec->sec_idx, (long long unsigned)sec->shdr->sh_addralign, obj->filename); return -EINVAL; } if (sec->shdr->sh_addralign != sec->data->d_align) { pr_warn("ELF section #%zu has inconsistent alignment addr=%llu != d=%llu in %s\n", sec->sec_idx, (long long unsigned)sec->shdr->sh_addralign, (long long unsigned)sec->data->d_align, obj->filename); return -EINVAL; } if (sec->shdr->sh_size != sec->data->d_size) { pr_warn("ELF section #%zu has inconsistent section size sh=%llu != d=%llu in %s\n", sec->sec_idx, (long long unsigned)sec->shdr->sh_size, (long long unsigned)sec->data->d_size, obj->filename); return -EINVAL; } switch (sec->shdr->sh_type) { case SHT_SYMTAB: err = linker_sanity_check_elf_symtab(obj, sec); if (err) return err; break; case SHT_STRTAB: break; case SHT_PROGBITS: if (sec->shdr->sh_flags & SHF_EXECINSTR) { if (sec->shdr->sh_size % sizeof(struct bpf_insn) != 0) { pr_warn("ELF section #%zu has unexpected size alignment %llu in %s\n", sec->sec_idx, (long long unsigned)sec->shdr->sh_size, obj->filename); return -EINVAL; } } break; case SHT_NOBITS: break; case SHT_REL: err = linker_sanity_check_elf_relos(obj, sec); if (err) return err; break; case SHT_LLVM_ADDRSIG: break; default: pr_warn("ELF section #%zu (%s) has unrecognized type %zu in %s\n", sec->sec_idx, sec->sec_name, (size_t)sec->shdr->sh_type, obj->filename); return -EINVAL; } } return 0; } static int linker_sanity_check_elf_symtab(struct src_obj *obj, struct src_sec *sec) { struct src_sec *link_sec; Elf64_Sym *sym; int i, n; if (sec->shdr->sh_entsize != sizeof(Elf64_Sym)) return -EINVAL; if (sec->shdr->sh_size % sec->shdr->sh_entsize != 0) return -EINVAL; if (!sec->shdr->sh_link || sec->shdr->sh_link >= obj->sec_cnt) { pr_warn("ELF SYMTAB section #%zu points to missing STRTAB section #%zu in %s\n", sec->sec_idx, (size_t)sec->shdr->sh_link, obj->filename); return -EINVAL; } link_sec = &obj->secs[sec->shdr->sh_link]; if (link_sec->shdr->sh_type != SHT_STRTAB) { pr_warn("ELF SYMTAB section #%zu points to invalid STRTAB section #%zu in %s\n", sec->sec_idx, (size_t)sec->shdr->sh_link, obj->filename); return -EINVAL; } n = sec->shdr->sh_size / sec->shdr->sh_entsize; sym = sec->data->d_buf; for (i = 0; i < n; i++, sym++) { int sym_type = ELF64_ST_TYPE(sym->st_info); int sym_bind = ELF64_ST_BIND(sym->st_info); int sym_vis = ELF64_ST_VISIBILITY(sym->st_other); if (i == 0) { if (sym->st_name != 0 || sym->st_info != 0 || sym->st_other != 0 || sym->st_shndx != 0 || sym->st_value != 0 || sym->st_size != 0) { pr_warn("ELF sym #0 is invalid in %s\n", obj->filename); return -EINVAL; } continue; } if (sym_bind != STB_LOCAL && sym_bind != STB_GLOBAL && sym_bind != STB_WEAK) { pr_warn("ELF sym #%d in section #%zu has unsupported symbol binding %d\n", i, sec->sec_idx, sym_bind); return -EINVAL; } if (sym_vis != STV_DEFAULT && sym_vis != STV_HIDDEN) { pr_warn("ELF sym #%d in section #%zu has unsupported symbol visibility %d\n", i, sec->sec_idx, sym_vis); return -EINVAL; } if (sym->st_shndx == 0) { if (sym_type != STT_NOTYPE || sym_bind == STB_LOCAL || sym->st_value != 0 || sym->st_size != 0) { pr_warn("ELF sym #%d is invalid extern symbol in %s\n", i, obj->filename); return -EINVAL; } continue; } if (sym->st_shndx < SHN_LORESERVE && sym->st_shndx >= obj->sec_cnt) { pr_warn("ELF sym #%d in section #%zu points to missing section #%zu in %s\n", i, sec->sec_idx, (size_t)sym->st_shndx, obj->filename); return -EINVAL; } if (sym_type == STT_SECTION) { if (sym->st_value != 0) return -EINVAL; continue; } } return 0; } static int linker_sanity_check_elf_relos(struct src_obj *obj, struct src_sec *sec) { struct src_sec *link_sec, *sym_sec; Elf64_Rel *relo; int i, n; if (sec->shdr->sh_entsize != sizeof(Elf64_Rel)) return -EINVAL; if (sec->shdr->sh_size % sec->shdr->sh_entsize != 0) return -EINVAL; /* SHT_REL's sh_link should point to SYMTAB */ if (sec->shdr->sh_link != obj->symtab_sec_idx) { pr_warn("ELF relo section #%zu points to invalid SYMTAB section #%zu in %s\n", sec->sec_idx, (size_t)sec->shdr->sh_link, obj->filename); return -EINVAL; } /* SHT_REL's sh_info points to relocated section */ if (!sec->shdr->sh_info || sec->shdr->sh_info >= obj->sec_cnt) { pr_warn("ELF relo section #%zu points to missing section #%zu in %s\n", sec->sec_idx, (size_t)sec->shdr->sh_info, obj->filename); return -EINVAL; } link_sec = &obj->secs[sec->shdr->sh_info]; /* .rel<secname> -> <secname> pattern is followed */ if (strncmp(sec->sec_name, ".rel", sizeof(".rel") - 1) != 0 || strcmp(sec->sec_name + sizeof(".rel") - 1, link_sec->sec_name) != 0) { pr_warn("ELF relo section #%zu name has invalid name in %s\n", sec->sec_idx, obj->filename); return -EINVAL; } /* don't further validate relocations for ignored sections */ if (link_sec->skipped) return 0; /* relocatable section is data or instructions */ if (link_sec->shdr->sh_type != SHT_PROGBITS && link_sec->shdr->sh_type != SHT_NOBITS) { pr_warn("ELF relo section #%zu points to invalid section #%zu in %s\n", sec->sec_idx, (size_t)sec->shdr->sh_info, obj->filename); return -EINVAL; } /* check sanity of each relocation */ n = sec->shdr->sh_size / sec->shdr->sh_entsize; relo = sec->data->d_buf; sym_sec = &obj->secs[obj->symtab_sec_idx]; for (i = 0; i < n; i++, relo++) { size_t sym_idx = ELF64_R_SYM(relo->r_info); size_t sym_type = ELF64_R_TYPE(relo->r_info); if (sym_type != R_BPF_64_64 && sym_type != R_BPF_64_32 && sym_type != R_BPF_64_ABS64 && sym_type != R_BPF_64_ABS32) { pr_warn("ELF relo #%d in section #%zu has unexpected type %zu in %s\n", i, sec->sec_idx, sym_type, obj->filename); return -EINVAL; } if (!sym_idx || sym_idx * sizeof(Elf64_Sym) >= sym_sec->shdr->sh_size) { pr_warn("ELF relo #%d in section #%zu points to invalid symbol #%zu in %s\n", i, sec->sec_idx, sym_idx, obj->filename); return -EINVAL; } if (link_sec->shdr->sh_flags & SHF_EXECINSTR) { if (relo->r_offset % sizeof(struct bpf_insn) != 0) { pr_warn("ELF relo #%d in section #%zu points to missing symbol #%zu in %s\n", i, sec->sec_idx, sym_idx, obj->filename); return -EINVAL; } } } return 0; } static int check_btf_type_id(__u32 *type_id, void *ctx) { struct btf *btf = ctx; if (*type_id >= btf__type_cnt(btf)) return -EINVAL; return 0; } static int check_btf_str_off(__u32 *str_off, void *ctx) { struct btf *btf = ctx; const char *s; s = btf__str_by_offset(btf, *str_off); if (!s) return -EINVAL; return 0; } static int linker_sanity_check_btf(struct src_obj *obj) { struct btf_type *t; int i, n, err = 0; if (!obj->btf) return 0; n = btf__type_cnt(obj->btf); for (i = 1; i < n; i++) { t = btf_type_by_id(obj->btf, i); err = err ?: btf_type_visit_type_ids(t, check_btf_type_id, obj->btf); err = err ?: btf_type_visit_str_offs(t, check_btf_str_off, obj->btf); if (err) return err; } return 0; } static int linker_sanity_check_btf_ext(struct src_obj *obj) { int err = 0; if (!obj->btf_ext) return 0; /* can't use .BTF.ext without .BTF */ if (!obj->btf) return -EINVAL; err = err ?: btf_ext_visit_type_ids(obj->btf_ext, check_btf_type_id, obj->btf); err = err ?: btf_ext_visit_str_offs(obj->btf_ext, check_btf_str_off, obj->btf); if (err) return err; return 0; } static int init_sec(struct bpf_linker *linker, struct dst_sec *dst_sec, struct src_sec *src_sec) { Elf_Scn *scn; Elf_Data *data; Elf64_Shdr *shdr; int name_off; dst_sec->sec_sz = 0; dst_sec->sec_idx = 0; dst_sec->ephemeral = src_sec->ephemeral; /* ephemeral sections are just thin section shells lacking most parts */ if (src_sec->ephemeral) return 0; scn = elf_newscn(linker->elf); if (!scn) return -ENOMEM; data = elf_newdata(scn); if (!data) return -ENOMEM; shdr = elf64_getshdr(scn); if (!shdr) return -ENOMEM; dst_sec->scn = scn; dst_sec->shdr = shdr; dst_sec->data = data; dst_sec->sec_idx = elf_ndxscn(scn); name_off = strset__add_str(linker->strtab_strs, src_sec->sec_name); if (name_off < 0) return name_off; shdr->sh_name = name_off; shdr->sh_type = src_sec->shdr->sh_type; shdr->sh_flags = src_sec->shdr->sh_flags; shdr->sh_size = 0; /* sh_link and sh_info have different meaning for different types of * sections, so we leave it up to the caller code to fill them in, if * necessary */ shdr->sh_link = 0; shdr->sh_info = 0; shdr->sh_addralign = src_sec->shdr->sh_addralign; shdr->sh_entsize = src_sec->shdr->sh_entsize; data->d_type = src_sec->data->d_type; data->d_size = 0; data->d_buf = NULL; data->d_align = src_sec->data->d_align; data->d_off = 0; return 0; } static struct dst_sec *find_dst_sec_by_name(struct bpf_linker *linker, const char *sec_name) { struct dst_sec *sec; int i; for (i = 1; i < linker->sec_cnt; i++) { sec = &linker->secs[i]; if (strcmp(sec->sec_name, sec_name) == 0) return sec; } return NULL; } static bool secs_match(struct dst_sec *dst, struct src_sec *src) { if (dst->ephemeral || src->ephemeral) return true; if (dst->shdr->sh_type != src->shdr->sh_type) { pr_warn("sec %s types mismatch\n", dst->sec_name); return false; } if (dst->shdr->sh_flags != src->shdr->sh_flags) { pr_warn("sec %s flags mismatch\n", dst->sec_name); return false; } if (dst->shdr->sh_entsize != src->shdr->sh_entsize) { pr_warn("sec %s entsize mismatch\n", dst->sec_name); return false; } return true; } static bool sec_content_is_same(struct dst_sec *dst_sec, struct src_sec *src_sec) { if (dst_sec->sec_sz != src_sec->shdr->sh_size) return false; if (memcmp(dst_sec->raw_data, src_sec->data->d_buf, dst_sec->sec_sz) != 0) return false; return true; } static int extend_sec(struct bpf_linker *linker, struct dst_sec *dst, struct src_sec *src) { void *tmp; size_t dst_align, src_align; size_t dst_align_sz, dst_final_sz; int err; /* Ephemeral source section doesn't contribute anything to ELF * section data. */ if (src->ephemeral) return 0; /* Some sections (like .maps) can contain both externs (and thus be * ephemeral) and non-externs (map definitions). So it's possible that * it has to be "upgraded" from ephemeral to non-ephemeral when the * first non-ephemeral entity appears. In such case, we add ELF * section, data, etc. */ if (dst->ephemeral) { err = init_sec(linker, dst, src); if (err) return err; } dst_align = dst->shdr->sh_addralign; src_align = src->shdr->sh_addralign; if (dst_align == 0) dst_align = 1; if (dst_align < src_align) dst_align = src_align; dst_align_sz = (dst->sec_sz + dst_align - 1) / dst_align * dst_align; /* no need to re-align final size */ dst_final_sz = dst_align_sz + src->shdr->sh_size; if (src->shdr->sh_type != SHT_NOBITS) { tmp = realloc(dst->raw_data, dst_final_sz); /* If dst_align_sz == 0, realloc() behaves in a special way: * 1. When dst->raw_data is NULL it returns: * "either NULL or a pointer suitable to be passed to free()" [1]. * 2. When dst->raw_data is not-NULL it frees dst->raw_data and returns NULL, * thus invalidating any "pointer suitable to be passed to free()" obtained * at step (1). * * The dst_align_sz > 0 check avoids error exit after (2), otherwise * dst->raw_data would be freed again in bpf_linker__free(). * * [1] man 3 realloc */ if (!tmp && dst_align_sz > 0) return -ENOMEM; dst->raw_data = tmp; /* pad dst section, if it's alignment forced size increase */ memset(dst->raw_data + dst->sec_sz, 0, dst_align_sz - dst->sec_sz); /* now copy src data at a properly aligned offset */ memcpy(dst->raw_data + dst_align_sz, src->data->d_buf, src->shdr->sh_size); } dst->sec_sz = dst_final_sz; dst->shdr->sh_size = dst_final_sz; dst->data->d_size = dst_final_sz; dst->shdr->sh_addralign = dst_align; dst->data->d_align = dst_align; src->dst_off = dst_align_sz; return 0; } static bool is_data_sec(struct src_sec *sec) { if (!sec || sec->skipped) return false; /* ephemeral sections are data sections, e.g., .kconfig, .ksyms */ if (sec->ephemeral) return true; return sec->shdr->sh_type == SHT_PROGBITS || sec->shdr->sh_type == SHT_NOBITS; } static bool is_relo_sec(struct src_sec *sec) { if (!sec || sec->skipped || sec->ephemeral) return false; return sec->shdr->sh_type == SHT_REL; } static int linker_append_sec_data(struct bpf_linker *linker, struct src_obj *obj) { int i, err; for (i = 1; i < obj->sec_cnt; i++) { struct src_sec *src_sec; struct dst_sec *dst_sec; src_sec = &obj->secs[i]; if (!is_data_sec(src_sec)) continue; dst_sec = find_dst_sec_by_name(linker, src_sec->sec_name); if (!dst_sec) { dst_sec = add_dst_sec(linker, src_sec->sec_name); if (!dst_sec) return -ENOMEM; err = init_sec(linker, dst_sec, src_sec); if (err) { pr_warn("failed to init section '%s'\n", src_sec->sec_name); return err; } } else { if (!secs_match(dst_sec, src_sec)) { pr_warn("ELF sections %s are incompatible\n", src_sec->sec_name); return -1; } /* "license" and "version" sections are deduped */ if (strcmp(src_sec->sec_name, "license") == 0 || strcmp(src_sec->sec_name, "version") == 0) { if (!sec_content_is_same(dst_sec, src_sec)) { pr_warn("non-identical contents of section '%s' are not supported\n", src_sec->sec_name); return -EINVAL; } src_sec->skipped = true; src_sec->dst_id = dst_sec->id; continue; } } /* record mapped section index */ src_sec->dst_id = dst_sec->id; err = extend_sec(linker, dst_sec, src_sec); if (err) return err; } return 0; } static int linker_append_elf_syms(struct bpf_linker *linker, struct src_obj *obj) { struct src_sec *symtab = &obj->secs[obj->symtab_sec_idx]; Elf64_Sym *sym = symtab->data->d_buf; int i, n = symtab->shdr->sh_size / symtab->shdr->sh_entsize, err; int str_sec_idx = symtab->shdr->sh_link; const char *sym_name; obj->sym_map = calloc(n + 1, sizeof(*obj->sym_map)); if (!obj->sym_map) return -ENOMEM; for (i = 0; i < n; i++, sym++) { /* We already validated all-zero symbol #0 and we already * appended it preventively to the final SYMTAB, so skip it. */ if (i == 0) continue; sym_name = elf_strptr(obj->elf, str_sec_idx, sym->st_name); if (!sym_name) { pr_warn("can't fetch symbol name for symbol #%d in '%s'\n", i, obj->filename); return -EINVAL; } err = linker_append_elf_sym(linker, obj, sym, sym_name, i); if (err) return err; } return 0; } static Elf64_Sym *get_sym_by_idx(struct bpf_linker *linker, size_t sym_idx) { struct dst_sec *symtab = &linker->secs[linker->symtab_sec_idx]; Elf64_Sym *syms = symtab->raw_data; return &syms[sym_idx]; } static struct glob_sym *find_glob_sym(struct bpf_linker *linker, const char *sym_name) { struct glob_sym *glob_sym; const char *name; int i; for (i = 0; i < linker->glob_sym_cnt; i++) { glob_sym = &linker->glob_syms[i]; name = strset__data(linker->strtab_strs) + glob_sym->name_off; if (strcmp(name, sym_name) == 0) return glob_sym; } return NULL; } static struct glob_sym *add_glob_sym(struct bpf_linker *linker) { struct glob_sym *syms, *sym; syms = libbpf_reallocarray(linker->glob_syms, linker->glob_sym_cnt + 1, sizeof(*linker->glob_syms)); if (!syms) return NULL; sym = &syms[linker->glob_sym_cnt]; memset(sym, 0, sizeof(*sym)); sym->var_idx = -1; linker->glob_syms = syms; linker->glob_sym_cnt++; return sym; } static bool glob_sym_btf_matches(const char *sym_name, bool exact, const struct btf *btf1, __u32 id1, const struct btf *btf2, __u32 id2) { const struct btf_type *t1, *t2; bool is_static1, is_static2; const char *n1, *n2; int i, n; recur: n1 = n2 = NULL; t1 = skip_mods_and_typedefs(btf1, id1, &id1); t2 = skip_mods_and_typedefs(btf2, id2, &id2); /* check if only one side is FWD, otherwise handle with common logic */ if (!exact && btf_is_fwd(t1) != btf_is_fwd(t2)) { n1 = btf__str_by_offset(btf1, t1->name_off); n2 = btf__str_by_offset(btf2, t2->name_off); if (strcmp(n1, n2) != 0) { pr_warn("global '%s': incompatible forward declaration names '%s' and '%s'\n", sym_name, n1, n2); return false; } /* validate if FWD kind matches concrete kind */ if (btf_is_fwd(t1)) { if (btf_kflag(t1) && btf_is_union(t2)) return true; if (!btf_kflag(t1) && btf_is_struct(t2)) return true; pr_warn("global '%s': incompatible %s forward declaration and concrete kind %s\n", sym_name, btf_kflag(t1) ? "union" : "struct", btf_kind_str(t2)); } else { if (btf_kflag(t2) && btf_is_union(t1)) return true; if (!btf_kflag(t2) && btf_is_struct(t1)) return true; pr_warn("global '%s': incompatible %s forward declaration and concrete kind %s\n", sym_name, btf_kflag(t2) ? "union" : "struct", btf_kind_str(t1)); } return false; } if (btf_kind(t1) != btf_kind(t2)) { pr_warn("global '%s': incompatible BTF kinds %s and %s\n", sym_name, btf_kind_str(t1), btf_kind_str(t2)); return false; } switch (btf_kind(t1)) { case BTF_KIND_STRUCT: case BTF_KIND_UNION: case BTF_KIND_ENUM: case BTF_KIND_ENUM64: case BTF_KIND_FWD: case BTF_KIND_FUNC: case BTF_KIND_VAR: n1 = btf__str_by_offset(btf1, t1->name_off); n2 = btf__str_by_offset(btf2, t2->name_off); if (strcmp(n1, n2) != 0) { pr_warn("global '%s': incompatible %s names '%s' and '%s'\n", sym_name, btf_kind_str(t1), n1, n2); return false; } break; default: break; } switch (btf_kind(t1)) { case BTF_KIND_UNKN: /* void */ case BTF_KIND_FWD: return true; case BTF_KIND_INT: case BTF_KIND_FLOAT: case BTF_KIND_ENUM: case BTF_KIND_ENUM64: /* ignore encoding for int and enum values for enum */ if (t1->size != t2->size) { pr_warn("global '%s': incompatible %s '%s' size %u and %u\n", sym_name, btf_kind_str(t1), n1, t1->size, t2->size); return false; } return true; case BTF_KIND_PTR: /* just validate overall shape of the referenced type, so no * contents comparison for struct/union, and allowd fwd vs * struct/union */ exact = false; id1 = t1->type; id2 = t2->type; goto recur; case BTF_KIND_ARRAY: /* ignore index type and array size */ id1 = btf_array(t1)->type; id2 = btf_array(t2)->type; goto recur; case BTF_KIND_FUNC: /* extern and global linkages are compatible */ is_static1 = btf_func_linkage(t1) == BTF_FUNC_STATIC; is_static2 = btf_func_linkage(t2) == BTF_FUNC_STATIC; if (is_static1 != is_static2) { pr_warn("global '%s': incompatible func '%s' linkage\n", sym_name, n1); return false; } id1 = t1->type; id2 = t2->type; goto recur; case BTF_KIND_VAR: /* extern and global linkages are compatible */ is_static1 = btf_var(t1)->linkage == BTF_VAR_STATIC; is_static2 = btf_var(t2)->linkage == BTF_VAR_STATIC; if (is_static1 != is_static2) { pr_warn("global '%s': incompatible var '%s' linkage\n", sym_name, n1); return false; } id1 = t1->type; id2 = t2->type; goto recur; case BTF_KIND_STRUCT: case BTF_KIND_UNION: { const struct btf_member *m1, *m2; if (!exact) return true; if (btf_vlen(t1) != btf_vlen(t2)) { pr_warn("global '%s': incompatible number of %s fields %u and %u\n", sym_name, btf_kind_str(t1), btf_vlen(t1), btf_vlen(t2)); return false; } n = btf_vlen(t1); m1 = btf_members(t1); m2 = btf_members(t2); for (i = 0; i < n; i++, m1++, m2++) { n1 = btf__str_by_offset(btf1, m1->name_off); n2 = btf__str_by_offset(btf2, m2->name_off); if (strcmp(n1, n2) != 0) { pr_warn("global '%s': incompatible field #%d names '%s' and '%s'\n", sym_name, i, n1, n2); return false; } if (m1->offset != m2->offset) { pr_warn("global '%s': incompatible field #%d ('%s') offsets\n", sym_name, i, n1); return false; } if (!glob_sym_btf_matches(sym_name, exact, btf1, m1->type, btf2, m2->type)) return false; } return true; } case BTF_KIND_FUNC_PROTO: { const struct btf_param *m1, *m2; if (btf_vlen(t1) != btf_vlen(t2)) { pr_warn("global '%s': incompatible number of %s params %u and %u\n", sym_name, btf_kind_str(t1), btf_vlen(t1), btf_vlen(t2)); return false; } n = btf_vlen(t1); m1 = btf_params(t1); m2 = btf_params(t2); for (i = 0; i < n; i++, m1++, m2++) { /* ignore func arg names */ if (!glob_sym_btf_matches(sym_name, exact, btf1, m1->type, btf2, m2->type)) return false; } /* now check return type as well */ id1 = t1->type; id2 = t2->type; goto recur; } /* skip_mods_and_typedefs() make this impossible */ case BTF_KIND_TYPEDEF: case BTF_KIND_VOLATILE: case BTF_KIND_CONST: case BTF_KIND_RESTRICT: /* DATASECs are never compared with each other */ case BTF_KIND_DATASEC: default: pr_warn("global '%s': unsupported BTF kind %s\n", sym_name, btf_kind_str(t1)); return false; } } static bool map_defs_match(const char *sym_name, const struct btf *main_btf, const struct btf_map_def *main_def, const struct btf_map_def *main_inner_def, const struct btf *extra_btf, const struct btf_map_def *extra_def, const struct btf_map_def *extra_inner_def) { const char *reason; if (main_def->map_type != extra_def->map_type) { reason = "type"; goto mismatch; } /* check key type/size match */ if (main_def->key_size != extra_def->key_size) { reason = "key_size"; goto mismatch; } if (!!main_def->key_type_id != !!extra_def->key_type_id) { reason = "key type"; goto mismatch; } if ((main_def->parts & MAP_DEF_KEY_TYPE) && !glob_sym_btf_matches(sym_name, true /*exact*/, main_btf, main_def->key_type_id, extra_btf, extra_def->key_type_id)) { reason = "key type"; goto mismatch; } /* validate value type/size match */ if (main_def->value_size != extra_def->value_size) { reason = "value_size"; goto mismatch; } if (!!main_def->value_type_id != !!extra_def->value_type_id) { reason = "value type"; goto mismatch; } if ((main_def->parts & MAP_DEF_VALUE_TYPE) && !glob_sym_btf_matches(sym_name, true /*exact*/, main_btf, main_def->value_type_id, extra_btf, extra_def->value_type_id)) { reason = "key type"; goto mismatch; } if (main_def->max_entries != extra_def->max_entries) { reason = "max_entries"; goto mismatch; } if (main_def->map_flags != extra_def->map_flags) { reason = "map_flags"; goto mismatch; } if (main_def->numa_node != extra_def->numa_node) { reason = "numa_node"; goto mismatch; } if (main_def->pinning != extra_def->pinning) { reason = "pinning"; goto mismatch; } if ((main_def->parts & MAP_DEF_INNER_MAP) != (extra_def->parts & MAP_DEF_INNER_MAP)) { reason = "inner map"; goto mismatch; } if (main_def->parts & MAP_DEF_INNER_MAP) { char inner_map_name[128]; snprintf(inner_map_name, sizeof(inner_map_name), "%s.inner", sym_name); return map_defs_match(inner_map_name, main_btf, main_inner_def, NULL, extra_btf, extra_inner_def, NULL); } return true; mismatch: pr_warn("global '%s': map %s mismatch\n", sym_name, reason); return false; } static bool glob_map_defs_match(const char *sym_name, struct bpf_linker *linker, struct glob_sym *glob_sym, struct src_obj *obj, Elf64_Sym *sym, int btf_id) { struct btf_map_def dst_def = {}, dst_inner_def = {}; struct btf_map_def src_def = {}, src_inner_def = {}; const struct btf_type *t; int err; t = btf__type_by_id(obj->btf, btf_id); if (!btf_is_var(t)) { pr_warn("global '%s': invalid map definition type [%d]\n", sym_name, btf_id); return false; } t = skip_mods_and_typedefs(obj->btf, t->type, NULL); err = parse_btf_map_def(sym_name, obj->btf, t, true /*strict*/, &src_def, &src_inner_def); if (err) { pr_warn("global '%s': invalid map definition\n", sym_name); return false; } /* re-parse existing map definition */ t = btf__type_by_id(linker->btf, glob_sym->btf_id); t = skip_mods_and_typedefs(linker->btf, t->type, NULL); err = parse_btf_map_def(sym_name, linker->btf, t, true /*strict*/, &dst_def, &dst_inner_def); if (err) { /* this should not happen, because we already validated it */ pr_warn("global '%s': invalid dst map definition\n", sym_name); return false; } /* Currently extern map definition has to be complete and match * concrete map definition exactly. This restriction might be lifted * in the future. */ return map_defs_match(sym_name, linker->btf, &dst_def, &dst_inner_def, obj->btf, &src_def, &src_inner_def); } static bool glob_syms_match(const char *sym_name, struct bpf_linker *linker, struct glob_sym *glob_sym, struct src_obj *obj, Elf64_Sym *sym, size_t sym_idx, int btf_id) { const struct btf_type *src_t; /* if we are dealing with externs, BTF types describing both global * and extern VARs/FUNCs should be completely present in all files */ if (!glob_sym->btf_id || !btf_id) { pr_warn("BTF info is missing for global symbol '%s'\n", sym_name); return false; } src_t = btf__type_by_id(obj->btf, btf_id); if (!btf_is_var(src_t) && !btf_is_func(src_t)) { pr_warn("only extern variables and functions are supported, but got '%s' for '%s'\n", btf_kind_str(src_t), sym_name); return false; } /* deal with .maps definitions specially */ if (glob_sym->sec_id && strcmp(linker->secs[glob_sym->sec_id].sec_name, MAPS_ELF_SEC) == 0) return glob_map_defs_match(sym_name, linker, glob_sym, obj, sym, btf_id); if (!glob_sym_btf_matches(sym_name, true /*exact*/, linker->btf, glob_sym->btf_id, obj->btf, btf_id)) return false; return true; } static bool btf_is_non_static(const struct btf_type *t) { return (btf_is_var(t) && btf_var(t)->linkage != BTF_VAR_STATIC) || (btf_is_func(t) && btf_func_linkage(t) != BTF_FUNC_STATIC); } static int find_glob_sym_btf(struct src_obj *obj, Elf64_Sym *sym, const char *sym_name, int *out_btf_sec_id, int *out_btf_id) { int i, j, n, m, btf_id = 0; const struct btf_type *t; const struct btf_var_secinfo *vi; const char *name; if (!obj->btf) { pr_warn("failed to find BTF info for object '%s'\n", obj->filename); return -EINVAL; } n = btf__type_cnt(obj->btf); for (i = 1; i < n; i++) { t = btf__type_by_id(obj->btf, i); /* some global and extern FUNCs and VARs might not be associated with any * DATASEC, so try to detect them in the same pass */ if (btf_is_non_static(t)) { name = btf__str_by_offset(obj->btf, t->name_off); if (strcmp(name, sym_name) != 0) continue; /* remember and still try to find DATASEC */ btf_id = i; continue; } if (!btf_is_datasec(t)) continue; vi = btf_var_secinfos(t); for (j = 0, m = btf_vlen(t); j < m; j++, vi++) { t = btf__type_by_id(obj->btf, vi->type); name = btf__str_by_offset(obj->btf, t->name_off); if (strcmp(name, sym_name) != 0) continue; if (btf_is_var(t) && btf_var(t)->linkage == BTF_VAR_STATIC) continue; if (btf_is_func(t) && btf_func_linkage(t) == BTF_FUNC_STATIC) continue; if (btf_id && btf_id != vi->type) { pr_warn("global/extern '%s' BTF is ambiguous: both types #%d and #%u match\n", sym_name, btf_id, vi->type); return -EINVAL; } *out_btf_sec_id = i; *out_btf_id = vi->type; return 0; } } /* free-floating extern or global FUNC */ if (btf_id) { *out_btf_sec_id = 0; *out_btf_id = btf_id; return 0; } pr_warn("failed to find BTF info for global/extern symbol '%s'\n", sym_name); return -ENOENT; } static struct src_sec *find_src_sec_by_name(struct src_obj *obj, const char *sec_name) { struct src_sec *sec; int i; for (i = 1; i < obj->sec_cnt; i++) { sec = &obj->secs[i]; if (strcmp(sec->sec_name, sec_name) == 0) return sec; } return NULL; } static int complete_extern_btf_info(struct btf *dst_btf, int dst_id, struct btf *src_btf, int src_id) { struct btf_type *dst_t = btf_type_by_id(dst_btf, dst_id); struct btf_type *src_t = btf_type_by_id(src_btf, src_id); struct btf_param *src_p, *dst_p; const char *s; int i, n, off; /* We already made sure that source and destination types (FUNC or * VAR) match in terms of types and argument names. */ if (btf_is_var(dst_t)) { btf_var(dst_t)->linkage = BTF_VAR_GLOBAL_ALLOCATED; return 0; } dst_t->info = btf_type_info(BTF_KIND_FUNC, BTF_FUNC_GLOBAL, 0); /* now onto FUNC_PROTO types */ src_t = btf_type_by_id(src_btf, src_t->type); dst_t = btf_type_by_id(dst_btf, dst_t->type); /* Fill in all the argument names, which for extern FUNCs are missing. * We'll end up with two copies of FUNCs/VARs for externs, but that * will be taken care of by BTF dedup at the very end. * It might be that BTF types for extern in one file has less/more BTF * information (e.g., FWD instead of full STRUCT/UNION information), * but that should be (in most cases, subject to BTF dedup rules) * handled and resolved by BTF dedup algorithm as well, so we won't * worry about it. Our only job is to make sure that argument names * are populated on both sides, otherwise BTF dedup will pedantically * consider them different. */ src_p = btf_params(src_t); dst_p = btf_params(dst_t); for (i = 0, n = btf_vlen(dst_t); i < n; i++, src_p++, dst_p++) { if (!src_p->name_off) continue; /* src_btf has more complete info, so add name to dst_btf */ s = btf__str_by_offset(src_btf, src_p->name_off); off = btf__add_str(dst_btf, s); if (off < 0) return off; dst_p->name_off = off; } return 0; } static void sym_update_bind(Elf64_Sym *sym, int sym_bind) { sym->st_info = ELF64_ST_INFO(sym_bind, ELF64_ST_TYPE(sym->st_info)); } static void sym_update_type(Elf64_Sym *sym, int sym_type) { sym->st_info = ELF64_ST_INFO(ELF64_ST_BIND(sym->st_info), sym_type); } static void sym_update_visibility(Elf64_Sym *sym, int sym_vis) { /* libelf doesn't provide setters for ST_VISIBILITY, * but it is stored in the lower 2 bits of st_other */ sym->st_other &= ~0x03; sym->st_other |= sym_vis; } static int linker_append_elf_sym(struct bpf_linker *linker, struct src_obj *obj, Elf64_Sym *sym, const char *sym_name, int src_sym_idx) { struct src_sec *src_sec = NULL; struct dst_sec *dst_sec = NULL; struct glob_sym *glob_sym = NULL; int name_off, sym_type, sym_bind, sym_vis, err; int btf_sec_id = 0, btf_id = 0; size_t dst_sym_idx; Elf64_Sym *dst_sym; bool sym_is_extern; sym_type = ELF64_ST_TYPE(sym->st_info); sym_bind = ELF64_ST_BIND(sym->st_info); sym_vis = ELF64_ST_VISIBILITY(sym->st_other); sym_is_extern = sym->st_shndx == SHN_UNDEF; if (sym_is_extern) { if (!obj->btf) { pr_warn("externs without BTF info are not supported\n"); return -ENOTSUP; } } else if (sym->st_shndx < SHN_LORESERVE) { src_sec = &obj->secs[sym->st_shndx]; if (src_sec->skipped) return 0; dst_sec = &linker->secs[src_sec->dst_id]; /* allow only one STT_SECTION symbol per section */ if (sym_type == STT_SECTION && dst_sec->sec_sym_idx) { obj->sym_map[src_sym_idx] = dst_sec->sec_sym_idx; return 0; } } if (sym_bind == STB_LOCAL) goto add_sym; /* find matching BTF info */ err = find_glob_sym_btf(obj, sym, sym_name, &btf_sec_id, &btf_id); if (err) return err; if (sym_is_extern && btf_sec_id) { const char *sec_name = NULL; const struct btf_type *t; t = btf__type_by_id(obj->btf, btf_sec_id); sec_name = btf__str_by_offset(obj->btf, t->name_off); /* Clang puts unannotated extern vars into * '.extern' BTF DATASEC. Treat them the same * as unannotated extern funcs (which are * currently not put into any DATASECs). * Those don't have associated src_sec/dst_sec. */ if (strcmp(sec_name, BTF_EXTERN_SEC) != 0) { src_sec = find_src_sec_by_name(obj, sec_name); if (!src_sec) { pr_warn("failed to find matching ELF sec '%s'\n", sec_name); return -ENOENT; } dst_sec = &linker->secs[src_sec->dst_id]; } } glob_sym = find_glob_sym(linker, sym_name); if (glob_sym) { /* Preventively resolve to existing symbol. This is * needed for further relocation symbol remapping in * the next step of linking. */ obj->sym_map[src_sym_idx] = glob_sym->sym_idx; /* If both symbols are non-externs, at least one of * them has to be STB_WEAK, otherwise they are in * a conflict with each other. */ if (!sym_is_extern && !glob_sym->is_extern && !glob_sym->is_weak && sym_bind != STB_WEAK) { pr_warn("conflicting non-weak symbol #%d (%s) definition in '%s'\n", src_sym_idx, sym_name, obj->filename); return -EINVAL; } if (!glob_syms_match(sym_name, linker, glob_sym, obj, sym, src_sym_idx, btf_id)) return -EINVAL; dst_sym = get_sym_by_idx(linker, glob_sym->sym_idx); /* If new symbol is strong, then force dst_sym to be strong as * well; this way a mix of weak and non-weak extern * definitions will end up being strong. */ if (sym_bind == STB_GLOBAL) { /* We still need to preserve type (NOTYPE or * OBJECT/FUNC, depending on whether the symbol is * extern or not) */ sym_update_bind(dst_sym, STB_GLOBAL); glob_sym->is_weak = false; } /* Non-default visibility is "contaminating", with stricter * visibility overwriting more permissive ones, even if more * permissive visibility comes from just an extern definition. * Currently only STV_DEFAULT and STV_HIDDEN are allowed and * ensured by ELF symbol sanity checks above. */ if (sym_vis > ELF64_ST_VISIBILITY(dst_sym->st_other)) sym_update_visibility(dst_sym, sym_vis); /* If the new symbol is extern, then regardless if * existing symbol is extern or resolved global, just * keep the existing one untouched. */ if (sym_is_extern) return 0; /* If existing symbol is a strong resolved symbol, bail out, * because we lost resolution battle have nothing to * contribute. We already checked abover that there is no * strong-strong conflict. We also already tightened binding * and visibility, so nothing else to contribute at that point. */ if (!glob_sym->is_extern && sym_bind == STB_WEAK) return 0; /* At this point, new symbol is strong non-extern, * so overwrite glob_sym with new symbol information. * Preserve binding and visibility. */ sym_update_type(dst_sym, sym_type); dst_sym->st_shndx = dst_sec->sec_idx; dst_sym->st_value = src_sec->dst_off + sym->st_value; dst_sym->st_size = sym->st_size; /* see comment below about dst_sec->id vs dst_sec->sec_idx */ glob_sym->sec_id = dst_sec->id; glob_sym->is_extern = false; if (complete_extern_btf_info(linker->btf, glob_sym->btf_id, obj->btf, btf_id)) return -EINVAL; /* request updating VAR's/FUNC's underlying BTF type when appending BTF type */ glob_sym->underlying_btf_id = 0; obj->sym_map[src_sym_idx] = glob_sym->sym_idx; return 0; } add_sym: name_off = strset__add_str(linker->strtab_strs, sym_name); if (name_off < 0) return name_off; dst_sym = add_new_sym(linker, &dst_sym_idx); if (!dst_sym) return -ENOMEM; dst_sym->st_name = name_off; dst_sym->st_info = sym->st_info; dst_sym->st_other = sym->st_other; dst_sym->st_shndx = dst_sec ? dst_sec->sec_idx : sym->st_shndx; dst_sym->st_value = (src_sec ? src_sec->dst_off : 0) + sym->st_value; dst_sym->st_size = sym->st_size; obj->sym_map[src_sym_idx] = dst_sym_idx; if (sym_type == STT_SECTION && dst_sym) { dst_sec->sec_sym_idx = dst_sym_idx; dst_sym->st_value = 0; } if (sym_bind != STB_LOCAL) { glob_sym = add_glob_sym(linker); if (!glob_sym) return -ENOMEM; glob_sym->sym_idx = dst_sym_idx; /* we use dst_sec->id (and not dst_sec->sec_idx), because * ephemeral sections (.kconfig, .ksyms, etc) don't have * sec_idx (as they don't have corresponding ELF section), but * still have id. .extern doesn't have even ephemeral section * associated with it, so dst_sec->id == dst_sec->sec_idx == 0. */ glob_sym->sec_id = dst_sec ? dst_sec->id : 0; glob_sym->name_off = name_off; /* we will fill btf_id in during BTF merging step */ glob_sym->btf_id = 0; glob_sym->is_extern = sym_is_extern; glob_sym->is_weak = sym_bind == STB_WEAK; } return 0; } static int linker_append_elf_relos(struct bpf_linker *linker, struct src_obj *obj) { struct src_sec *src_symtab = &obj->secs[obj->symtab_sec_idx]; int i, err; for (i = 1; i < obj->sec_cnt; i++) { struct src_sec *src_sec, *src_linked_sec; struct dst_sec *dst_sec, *dst_linked_sec; Elf64_Rel *src_rel, *dst_rel; int j, n; src_sec = &obj->secs[i]; if (!is_relo_sec(src_sec)) continue; /* shdr->sh_info points to relocatable section */ src_linked_sec = &obj->secs[src_sec->shdr->sh_info]; if (src_linked_sec->skipped) continue; dst_sec = find_dst_sec_by_name(linker, src_sec->sec_name); if (!dst_sec) { dst_sec = add_dst_sec(linker, src_sec->sec_name); if (!dst_sec) return -ENOMEM; err = init_sec(linker, dst_sec, src_sec); if (err) { pr_warn("failed to init section '%s'\n", src_sec->sec_name); return err; } } else if (!secs_match(dst_sec, src_sec)) { pr_warn("sections %s are not compatible\n", src_sec->sec_name); return -1; } /* shdr->sh_link points to SYMTAB */ dst_sec->shdr->sh_link = linker->symtab_sec_idx; /* shdr->sh_info points to relocated section */ dst_linked_sec = &linker->secs[src_linked_sec->dst_id]; dst_sec->shdr->sh_info = dst_linked_sec->sec_idx; src_sec->dst_id = dst_sec->id; err = extend_sec(linker, dst_sec, src_sec); if (err) return err; src_rel = src_sec->data->d_buf; dst_rel = dst_sec->raw_data + src_sec->dst_off; n = src_sec->shdr->sh_size / src_sec->shdr->sh_entsize; for (j = 0; j < n; j++, src_rel++, dst_rel++) { size_t src_sym_idx, dst_sym_idx, sym_type; Elf64_Sym *src_sym; src_sym_idx = ELF64_R_SYM(src_rel->r_info); src_sym = src_symtab->data->d_buf + sizeof(*src_sym) * src_sym_idx; dst_sym_idx = obj->sym_map[src_sym_idx]; dst_rel->r_offset += src_linked_sec->dst_off; sym_type = ELF64_R_TYPE(src_rel->r_info); dst_rel->r_info = ELF64_R_INFO(dst_sym_idx, sym_type); if (ELF64_ST_TYPE(src_sym->st_info) == STT_SECTION) { struct src_sec *sec = &obj->secs[src_sym->st_shndx]; struct bpf_insn *insn; if (src_linked_sec->shdr->sh_flags & SHF_EXECINSTR) { /* calls to the very first static function inside * .text section at offset 0 will * reference section symbol, not the * function symbol. Fix that up, * otherwise it won't be possible to * relocate calls to two different * static functions with the same name * (rom two different object files) */ insn = dst_linked_sec->raw_data + dst_rel->r_offset; if (insn->code == (BPF_JMP | BPF_CALL)) insn->imm += sec->dst_off / sizeof(struct bpf_insn); else insn->imm += sec->dst_off; } else { pr_warn("relocation against STT_SECTION in non-exec section is not supported!\n"); return -EINVAL; } } } } return 0; } static Elf64_Sym *find_sym_by_name(struct src_obj *obj, size_t sec_idx, int sym_type, const char *sym_name) { struct src_sec *symtab = &obj->secs[obj->symtab_sec_idx]; Elf64_Sym *sym = symtab->data->d_buf; int i, n = symtab->shdr->sh_size / symtab->shdr->sh_entsize; int str_sec_idx = symtab->shdr->sh_link; const char *name; for (i = 0; i < n; i++, sym++) { if (sym->st_shndx != sec_idx) continue; if (ELF64_ST_TYPE(sym->st_info) != sym_type) continue; name = elf_strptr(obj->elf, str_sec_idx, sym->st_name); if (!name) return NULL; if (strcmp(sym_name, name) != 0) continue; return sym; } return NULL; } static int linker_fixup_btf(struct src_obj *obj) { const char *sec_name; struct src_sec *sec; int i, j, n, m; if (!obj->btf) return 0; n = btf__type_cnt(obj->btf); for (i = 1; i < n; i++) { struct btf_var_secinfo *vi; struct btf_type *t; t = btf_type_by_id(obj->btf, i); if (btf_kind(t) != BTF_KIND_DATASEC) continue; sec_name = btf__str_by_offset(obj->btf, t->name_off); sec = find_src_sec_by_name(obj, sec_name); if (sec) { /* record actual section size, unless ephemeral */ if (sec->shdr) t->size = sec->shdr->sh_size; } else { /* BTF can have some sections that are not represented * in ELF, e.g., .kconfig, .ksyms, .extern, which are used * for special extern variables. * * For all but one such special (ephemeral) * sections, we pre-create "section shells" to be able * to keep track of extra per-section metadata later * (e.g., those BTF extern variables). * * .extern is even more special, though, because it * contains extern variables that need to be resolved * by static linker, not libbpf and kernel. When such * externs are resolved, we are going to remove them * from .extern BTF section and might end up not * needing it at all. Each resolved extern should have * matching non-extern VAR/FUNC in other sections. * * We do support leaving some of the externs * unresolved, though, to support cases of building * libraries, which will later be linked against final * BPF applications. So if at finalization we still * see unresolved externs, we'll create .extern * section on our own. */ if (strcmp(sec_name, BTF_EXTERN_SEC) == 0) continue; sec = add_src_sec(obj, sec_name); if (!sec) return -ENOMEM; sec->ephemeral = true; sec->sec_idx = 0; /* will match UNDEF shndx in ELF */ } /* remember ELF section and its BTF type ID match */ sec->sec_type_id = i; /* fix up variable offsets */ vi = btf_var_secinfos(t); for (j = 0, m = btf_vlen(t); j < m; j++, vi++) { const struct btf_type *vt = btf__type_by_id(obj->btf, vi->type); const char *var_name = btf__str_by_offset(obj->btf, vt->name_off); int var_linkage = btf_var(vt)->linkage; Elf64_Sym *sym; /* no need to patch up static or extern vars */ if (var_linkage != BTF_VAR_GLOBAL_ALLOCATED) continue; sym = find_sym_by_name(obj, sec->sec_idx, STT_OBJECT, var_name); if (!sym) { pr_warn("failed to find symbol for variable '%s' in section '%s'\n", var_name, sec_name); return -ENOENT; } vi->offset = sym->st_value; } } return 0; } static int remap_type_id(__u32 *type_id, void *ctx) { int *id_map = ctx; int new_id = id_map[*type_id]; /* Error out if the type wasn't remapped. Ignore VOID which stays VOID. */ if (new_id == 0 && *type_id != 0) { pr_warn("failed to find new ID mapping for original BTF type ID %u\n", *type_id); return -EINVAL; } *type_id = id_map[*type_id]; return 0; } static int linker_append_btf(struct bpf_linker *linker, struct src_obj *obj) { const struct btf_type *t; int i, j, n, start_id, id; const char *name; if (!obj->btf) return 0; start_id = btf__type_cnt(linker->btf); n = btf__type_cnt(obj->btf); obj->btf_type_map = calloc(n + 1, sizeof(int)); if (!obj->btf_type_map) return -ENOMEM; for (i = 1; i < n; i++) { struct glob_sym *glob_sym = NULL; t = btf__type_by_id(obj->btf, i); /* DATASECs are handled specially below */ if (btf_kind(t) == BTF_KIND_DATASEC) continue; if (btf_is_non_static(t)) { /* there should be glob_sym already */ name = btf__str_by_offset(obj->btf, t->name_off); glob_sym = find_glob_sym(linker, name); /* VARs without corresponding glob_sym are those that * belong to skipped/deduplicated sections (i.e., * license and version), so just skip them */ if (!glob_sym) continue; /* linker_append_elf_sym() might have requested * updating underlying type ID, if extern was resolved * to strong symbol or weak got upgraded to non-weak */ if (glob_sym->underlying_btf_id == 0) glob_sym->underlying_btf_id = -t->type; /* globals from previous object files that match our * VAR/FUNC already have a corresponding associated * BTF type, so just make sure to use it */ if (glob_sym->btf_id) { /* reuse existing BTF type for global var/func */ obj->btf_type_map[i] = glob_sym->btf_id; continue; } } id = btf__add_type(linker->btf, obj->btf, t); if (id < 0) { pr_warn("failed to append BTF type #%d from file '%s'\n", i, obj->filename); return id; } obj->btf_type_map[i] = id; /* record just appended BTF type for var/func */ if (glob_sym) { glob_sym->btf_id = id; glob_sym->underlying_btf_id = -t->type; } } /* remap all the types except DATASECs */ n = btf__type_cnt(linker->btf); for (i = start_id; i < n; i++) { struct btf_type *dst_t = btf_type_by_id(linker->btf, i); if (btf_type_visit_type_ids(dst_t, remap_type_id, obj->btf_type_map)) return -EINVAL; } /* Rewrite VAR/FUNC underlying types (i.e., FUNC's FUNC_PROTO and VAR's * actual type), if necessary */ for (i = 0; i < linker->glob_sym_cnt; i++) { struct glob_sym *glob_sym = &linker->glob_syms[i]; struct btf_type *glob_t; if (glob_sym->underlying_btf_id >= 0) continue; glob_sym->underlying_btf_id = obj->btf_type_map[-glob_sym->underlying_btf_id]; glob_t = btf_type_by_id(linker->btf, glob_sym->btf_id); glob_t->type = glob_sym->underlying_btf_id; } /* append DATASEC info */ for (i = 1; i < obj->sec_cnt; i++) { struct src_sec *src_sec; struct dst_sec *dst_sec; const struct btf_var_secinfo *src_var; struct btf_var_secinfo *dst_var; src_sec = &obj->secs[i]; if (!src_sec->sec_type_id || src_sec->skipped) continue; dst_sec = &linker->secs[src_sec->dst_id]; /* Mark section as having BTF regardless of the presence of * variables. In some cases compiler might generate empty BTF * with no variables information. E.g., when promoting local * array/structure variable initial values and BPF object * file otherwise has no read-only static variables in * .rodata. We need to preserve such empty BTF and just set * correct section size. */ dst_sec->has_btf = true; t = btf__type_by_id(obj->btf, src_sec->sec_type_id); src_var = btf_var_secinfos(t); n = btf_vlen(t); for (j = 0; j < n; j++, src_var++) { void *sec_vars = dst_sec->sec_vars; int new_id = obj->btf_type_map[src_var->type]; struct glob_sym *glob_sym = NULL; t = btf_type_by_id(linker->btf, new_id); if (btf_is_non_static(t)) { name = btf__str_by_offset(linker->btf, t->name_off); glob_sym = find_glob_sym(linker, name); if (glob_sym->sec_id != dst_sec->id) { pr_warn("global '%s': section mismatch %d vs %d\n", name, glob_sym->sec_id, dst_sec->id); return -EINVAL; } } /* If there is already a member (VAR or FUNC) mapped * to the same type, don't add a duplicate entry. * This will happen when multiple object files define * the same extern VARs/FUNCs. */ if (glob_sym && glob_sym->var_idx >= 0) { __s64 sz; dst_var = &dst_sec->sec_vars[glob_sym->var_idx]; /* Because underlying BTF type might have * changed, so might its size have changed, so * re-calculate and update it in sec_var. */ sz = btf__resolve_size(linker->btf, glob_sym->underlying_btf_id); if (sz < 0) { pr_warn("global '%s': failed to resolve size of underlying type: %d\n", name, (int)sz); return -EINVAL; } dst_var->size = sz; continue; } sec_vars = libbpf_reallocarray(sec_vars, dst_sec->sec_var_cnt + 1, sizeof(*dst_sec->sec_vars)); if (!sec_vars) return -ENOMEM; dst_sec->sec_vars = sec_vars; dst_sec->sec_var_cnt++; dst_var = &dst_sec->sec_vars[dst_sec->sec_var_cnt - 1]; dst_var->type = obj->btf_type_map[src_var->type]; dst_var->size = src_var->size; dst_var->offset = src_sec->dst_off + src_var->offset; if (glob_sym) glob_sym->var_idx = dst_sec->sec_var_cnt - 1; } } return 0; } static void *add_btf_ext_rec(struct btf_ext_sec_data *ext_data, const void *src_rec) { void *tmp; tmp = libbpf_reallocarray(ext_data->recs, ext_data->rec_cnt + 1, ext_data->rec_sz); if (!tmp) return NULL; ext_data->recs = tmp; tmp += ext_data->rec_cnt * ext_data->rec_sz; memcpy(tmp, src_rec, ext_data->rec_sz); ext_data->rec_cnt++; return tmp; } static int linker_append_btf_ext(struct bpf_linker *linker, struct src_obj *obj) { const struct btf_ext_info_sec *ext_sec; const char *sec_name, *s; struct src_sec *src_sec; struct dst_sec *dst_sec; int rec_sz, str_off, i; if (!obj->btf_ext) return 0; rec_sz = obj->btf_ext->func_info.rec_size; for_each_btf_ext_sec(&obj->btf_ext->func_info, ext_sec) { struct bpf_func_info_min *src_rec, *dst_rec; sec_name = btf__name_by_offset(obj->btf, ext_sec->sec_name_off); src_sec = find_src_sec_by_name(obj, sec_name); if (!src_sec) { pr_warn("can't find section '%s' referenced from .BTF.ext\n", sec_name); return -EINVAL; } dst_sec = &linker->secs[src_sec->dst_id]; if (dst_sec->func_info.rec_sz == 0) dst_sec->func_info.rec_sz = rec_sz; if (dst_sec->func_info.rec_sz != rec_sz) { pr_warn("incompatible .BTF.ext record sizes for section '%s'\n", sec_name); return -EINVAL; } for_each_btf_ext_rec(&obj->btf_ext->func_info, ext_sec, i, src_rec) { dst_rec = add_btf_ext_rec(&dst_sec->func_info, src_rec); if (!dst_rec) return -ENOMEM; dst_rec->insn_off += src_sec->dst_off; dst_rec->type_id = obj->btf_type_map[dst_rec->type_id]; } } rec_sz = obj->btf_ext->line_info.rec_size; for_each_btf_ext_sec(&obj->btf_ext->line_info, ext_sec) { struct bpf_line_info_min *src_rec, *dst_rec; sec_name = btf__name_by_offset(obj->btf, ext_sec->sec_name_off); src_sec = find_src_sec_by_name(obj, sec_name); if (!src_sec) { pr_warn("can't find section '%s' referenced from .BTF.ext\n", sec_name); return -EINVAL; } dst_sec = &linker->secs[src_sec->dst_id]; if (dst_sec->line_info.rec_sz == 0) dst_sec->line_info.rec_sz = rec_sz; if (dst_sec->line_info.rec_sz != rec_sz) { pr_warn("incompatible .BTF.ext record sizes for section '%s'\n", sec_name); return -EINVAL; } for_each_btf_ext_rec(&obj->btf_ext->line_info, ext_sec, i, src_rec) { dst_rec = add_btf_ext_rec(&dst_sec->line_info, src_rec); if (!dst_rec) return -ENOMEM; dst_rec->insn_off += src_sec->dst_off; s = btf__str_by_offset(obj->btf, src_rec->file_name_off); str_off = btf__add_str(linker->btf, s); if (str_off < 0) return -ENOMEM; dst_rec->file_name_off = str_off; s = btf__str_by_offset(obj->btf, src_rec->line_off); str_off = btf__add_str(linker->btf, s); if (str_off < 0) return -ENOMEM; dst_rec->line_off = str_off; /* dst_rec->line_col is fine */ } } rec_sz = obj->btf_ext->core_relo_info.rec_size; for_each_btf_ext_sec(&obj->btf_ext->core_relo_info, ext_sec) { struct bpf_core_relo *src_rec, *dst_rec; sec_name = btf__name_by_offset(obj->btf, ext_sec->sec_name_off); src_sec = find_src_sec_by_name(obj, sec_name); if (!src_sec) { pr_warn("can't find section '%s' referenced from .BTF.ext\n", sec_name); return -EINVAL; } dst_sec = &linker->secs[src_sec->dst_id]; if (dst_sec->core_relo_info.rec_sz == 0) dst_sec->core_relo_info.rec_sz = rec_sz; if (dst_sec->core_relo_info.rec_sz != rec_sz) { pr_warn("incompatible .BTF.ext record sizes for section '%s'\n", sec_name); return -EINVAL; } for_each_btf_ext_rec(&obj->btf_ext->core_relo_info, ext_sec, i, src_rec) { dst_rec = add_btf_ext_rec(&dst_sec->core_relo_info, src_rec); if (!dst_rec) return -ENOMEM; dst_rec->insn_off += src_sec->dst_off; dst_rec->type_id = obj->btf_type_map[dst_rec->type_id]; s = btf__str_by_offset(obj->btf, src_rec->access_str_off); str_off = btf__add_str(linker->btf, s); if (str_off < 0) return -ENOMEM; dst_rec->access_str_off = str_off; /* dst_rec->kind is fine */ } } return 0; } int bpf_linker__finalize(struct bpf_linker *linker) { struct dst_sec *sec; size_t strs_sz; const void *strs; int err, i; if (!linker->elf) return libbpf_err(-EINVAL); err = finalize_btf(linker); if (err) return libbpf_err(err); /* Finalize strings */ strs_sz = strset__data_size(linker->strtab_strs); strs = strset__data(linker->strtab_strs); sec = &linker->secs[linker->strtab_sec_idx]; sec->data->d_align = 1; sec->data->d_off = 0LL; sec->data->d_buf = (void *)strs; sec->data->d_type = ELF_T_BYTE; sec->data->d_size = strs_sz; sec->shdr->sh_size = strs_sz; for (i = 1; i < linker->sec_cnt; i++) { sec = &linker->secs[i]; /* STRTAB is handled specially above */ if (sec->sec_idx == linker->strtab_sec_idx) continue; /* special ephemeral sections (.ksyms, .kconfig, etc) */ if (!sec->scn) continue; sec->data->d_buf = sec->raw_data; } /* Finalize ELF layout */ if (elf_update(linker->elf, ELF_C_NULL) < 0) { err = -errno; pr_warn_elf("failed to finalize ELF layout"); return libbpf_err(err); } /* Write out final ELF contents */ if (elf_update(linker->elf, ELF_C_WRITE) < 0) { err = -errno; pr_warn_elf("failed to write ELF contents"); return libbpf_err(err); } elf_end(linker->elf); close(linker->fd); linker->elf = NULL; linker->fd = -1; return 0; } static int emit_elf_data_sec(struct bpf_linker *linker, const char *sec_name, size_t align, const void *raw_data, size_t raw_sz) { Elf_Scn *scn; Elf_Data *data; Elf64_Shdr *shdr; int name_off; name_off = strset__add_str(linker->strtab_strs, sec_name); if (name_off < 0) return name_off; scn = elf_newscn(linker->elf); if (!scn) return -ENOMEM; data = elf_newdata(scn); if (!data) return -ENOMEM; shdr = elf64_getshdr(scn); if (!shdr) return -EINVAL; shdr->sh_name = name_off; shdr->sh_type = SHT_PROGBITS; shdr->sh_flags = 0; shdr->sh_size = raw_sz; shdr->sh_link = 0; shdr->sh_info = 0; shdr->sh_addralign = align; shdr->sh_entsize = 0; data->d_type = ELF_T_BYTE; data->d_size = raw_sz; data->d_buf = (void *)raw_data; data->d_align = align; data->d_off = 0; return 0; } static int finalize_btf(struct bpf_linker *linker) { LIBBPF_OPTS(btf_dedup_opts, opts); struct btf *btf = linker->btf; const void *raw_data; int i, j, id, err; __u32 raw_sz; /* bail out if no BTF data was produced */ if (btf__type_cnt(linker->btf) == 1) return 0; for (i = 1; i < linker->sec_cnt; i++) { struct dst_sec *sec = &linker->secs[i]; if (!sec->has_btf) continue; id = btf__add_datasec(btf, sec->sec_name, sec->sec_sz); if (id < 0) { pr_warn("failed to add consolidated BTF type for datasec '%s': %d\n", sec->sec_name, id); return id; } for (j = 0; j < sec->sec_var_cnt; j++) { struct btf_var_secinfo *vi = &sec->sec_vars[j]; if (btf__add_datasec_var_info(btf, vi->type, vi->offset, vi->size)) return -EINVAL; } } err = finalize_btf_ext(linker); if (err) { pr_warn(".BTF.ext generation failed: %d\n", err); return err; } opts.btf_ext = linker->btf_ext; err = btf__dedup(linker->btf, &opts); if (err) { pr_warn("BTF dedup failed: %d\n", err); return err; } /* Emit .BTF section */ raw_data = btf__raw_data(linker->btf, &raw_sz); if (!raw_data) return -ENOMEM; err = emit_elf_data_sec(linker, BTF_ELF_SEC, 8, raw_data, raw_sz); if (err) { pr_warn("failed to write out .BTF ELF section: %d\n", err); return err; } /* Emit .BTF.ext section */ if (linker->btf_ext) { raw_data = btf_ext__raw_data(linker->btf_ext, &raw_sz); if (!raw_data) return -ENOMEM; err = emit_elf_data_sec(linker, BTF_EXT_ELF_SEC, 8, raw_data, raw_sz); if (err) { pr_warn("failed to write out .BTF.ext ELF section: %d\n", err); return err; } } return 0; } static int emit_btf_ext_data(struct bpf_linker *linker, void *output, const char *sec_name, struct btf_ext_sec_data *sec_data) { struct btf_ext_info_sec *sec_info; void *cur = output; int str_off; size_t sz; if (!sec_data->rec_cnt) return 0; str_off = btf__add_str(linker->btf, sec_name); if (str_off < 0) return -ENOMEM; sec_info = cur; sec_info->sec_name_off = str_off; sec_info->num_info = sec_data->rec_cnt; cur += sizeof(struct btf_ext_info_sec); sz = sec_data->rec_cnt * sec_data->rec_sz; memcpy(cur, sec_data->recs, sz); cur += sz; return cur - output; } static int finalize_btf_ext(struct bpf_linker *linker) { size_t funcs_sz = 0, lines_sz = 0, core_relos_sz = 0, total_sz = 0; size_t func_rec_sz = 0, line_rec_sz = 0, core_relo_rec_sz = 0; struct btf_ext_header *hdr; void *data, *cur; int i, err, sz; /* validate that all sections have the same .BTF.ext record sizes * and calculate total data size for each type of data (func info, * line info, core relos) */ for (i = 1; i < linker->sec_cnt; i++) { struct dst_sec *sec = &linker->secs[i]; if (sec->func_info.rec_cnt) { if (func_rec_sz == 0) func_rec_sz = sec->func_info.rec_sz; if (func_rec_sz != sec->func_info.rec_sz) { pr_warn("mismatch in func_info record size %zu != %u\n", func_rec_sz, sec->func_info.rec_sz); return -EINVAL; } funcs_sz += sizeof(struct btf_ext_info_sec) + func_rec_sz * sec->func_info.rec_cnt; } if (sec->line_info.rec_cnt) { if (line_rec_sz == 0) line_rec_sz = sec->line_info.rec_sz; if (line_rec_sz != sec->line_info.rec_sz) { pr_warn("mismatch in line_info record size %zu != %u\n", line_rec_sz, sec->line_info.rec_sz); return -EINVAL; } lines_sz += sizeof(struct btf_ext_info_sec) + line_rec_sz * sec->line_info.rec_cnt; } if (sec->core_relo_info.rec_cnt) { if (core_relo_rec_sz == 0) core_relo_rec_sz = sec->core_relo_info.rec_sz; if (core_relo_rec_sz != sec->core_relo_info.rec_sz) { pr_warn("mismatch in core_relo_info record size %zu != %u\n", core_relo_rec_sz, sec->core_relo_info.rec_sz); return -EINVAL; } core_relos_sz += sizeof(struct btf_ext_info_sec) + core_relo_rec_sz * sec->core_relo_info.rec_cnt; } } if (!funcs_sz && !lines_sz && !core_relos_sz) return 0; total_sz += sizeof(struct btf_ext_header); if (funcs_sz) { funcs_sz += sizeof(__u32); /* record size prefix */ total_sz += funcs_sz; } if (lines_sz) { lines_sz += sizeof(__u32); /* record size prefix */ total_sz += lines_sz; } if (core_relos_sz) { core_relos_sz += sizeof(__u32); /* record size prefix */ total_sz += core_relos_sz; } cur = data = calloc(1, total_sz); if (!data) return -ENOMEM; hdr = cur; hdr->magic = BTF_MAGIC; hdr->version = BTF_VERSION; hdr->flags = 0; hdr->hdr_len = sizeof(struct btf_ext_header); cur += sizeof(struct btf_ext_header); /* All offsets are in bytes relative to the end of this header */ hdr->func_info_off = 0; hdr->func_info_len = funcs_sz; hdr->line_info_off = funcs_sz; hdr->line_info_len = lines_sz; hdr->core_relo_off = funcs_sz + lines_sz; hdr->core_relo_len = core_relos_sz; if (funcs_sz) { *(__u32 *)cur = func_rec_sz; cur += sizeof(__u32); for (i = 1; i < linker->sec_cnt; i++) { struct dst_sec *sec = &linker->secs[i]; sz = emit_btf_ext_data(linker, cur, sec->sec_name, &sec->func_info); if (sz < 0) { err = sz; goto out; } cur += sz; } } if (lines_sz) { *(__u32 *)cur = line_rec_sz; cur += sizeof(__u32); for (i = 1; i < linker->sec_cnt; i++) { struct dst_sec *sec = &linker->secs[i]; sz = emit_btf_ext_data(linker, cur, sec->sec_name, &sec->line_info); if (sz < 0) { err = sz; goto out; } cur += sz; } } if (core_relos_sz) { *(__u32 *)cur = core_relo_rec_sz; cur += sizeof(__u32); for (i = 1; i < linker->sec_cnt; i++) { struct dst_sec *sec = &linker->secs[i]; sz = emit_btf_ext_data(linker, cur, sec->sec_name, &sec->core_relo_info); if (sz < 0) { err = sz; goto out; } cur += sz; } } linker->btf_ext = btf_ext__new(data, total_sz); err = libbpf_get_error(linker->btf_ext); if (err) { linker->btf_ext = NULL; pr_warn("failed to parse final .BTF.ext data: %d\n", err); goto out; } out: free(data); return err; }
Information contained on this website is for historical information purposes only and does not indicate or represent copyright ownership.
Created with Cregit http://github.com/cregit/cregit
Version 2.0-RC1