static int linker_load_obj_file()

in third/libbpf/src/linker.c [538:698]

• 140 lines of code
• 25 McCabe index (conditional complexity)

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;
}