int module_frob_arch_sections()

in kernel/module-sections.c [90:159]

• 56 lines of code
• 11 McCabe index (conditional complexity)

int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs,
			      char *secstrings, struct module *mod)
{
	unsigned int num_plts = 0;
	unsigned int num_gots = 0;
	int i;

	/*
	 * Find the empty .got and .plt sections.
	 */
	for (i = 0; i < ehdr->e_shnum; i++) {
		if (!strcmp(secstrings + sechdrs[i].sh_name, ".plt"))
			mod->arch.plt.shdr = sechdrs + i;
		else if (!strcmp(secstrings + sechdrs[i].sh_name, ".got"))
			mod->arch.got.shdr = sechdrs + i;
		else if (!strcmp(secstrings + sechdrs[i].sh_name, ".got.plt"))
			mod->arch.got_plt.shdr = sechdrs + i;
	}

	if (!mod->arch.plt.shdr) {
		pr_err("%s: module PLT section(s) missing\n", mod->name);
		return -ENOEXEC;
	}
	if (!mod->arch.got.shdr) {
		pr_err("%s: module GOT section(s) missing\n", mod->name);
		return -ENOEXEC;
	}
	if (!mod->arch.got_plt.shdr) {
		pr_err("%s: module GOT.PLT section(s) missing\n", mod->name);
		return -ENOEXEC;
	}

	/* Calculate the maxinum number of entries */
	for (i = 0; i < ehdr->e_shnum; i++) {
		Elf_Rela *relas = (void *)ehdr + sechdrs[i].sh_offset;
		int num_rela = sechdrs[i].sh_size / sizeof(Elf_Rela);
		Elf_Shdr *dst_sec = sechdrs + sechdrs[i].sh_info;

		if (sechdrs[i].sh_type != SHT_RELA)
			continue;

		/* ignore relocations that operate on non-exec sections */
		if (!(dst_sec->sh_flags & SHF_EXECINSTR))
			continue;

		count_max_entries(relas, num_rela, &num_plts, &num_gots);
	}

	mod->arch.plt.shdr->sh_type = SHT_NOBITS;
	mod->arch.plt.shdr->sh_flags = SHF_EXECINSTR | SHF_ALLOC;
	mod->arch.plt.shdr->sh_addralign = L1_CACHE_BYTES;
	mod->arch.plt.shdr->sh_size = (num_plts + 1) * sizeof(struct plt_entry);
	mod->arch.plt.num_entries = 0;
	mod->arch.plt.max_entries = num_plts;

	mod->arch.got.shdr->sh_type = SHT_NOBITS;
	mod->arch.got.shdr->sh_flags = SHF_ALLOC;
	mod->arch.got.shdr->sh_addralign = L1_CACHE_BYTES;
	mod->arch.got.shdr->sh_size = (num_gots + 1) * sizeof(struct got_entry);
	mod->arch.got.num_entries = 0;
	mod->arch.got.max_entries = num_gots;

	mod->arch.got_plt.shdr->sh_type = SHT_NOBITS;
	mod->arch.got_plt.shdr->sh_flags = SHF_ALLOC;
	mod->arch.got_plt.shdr->sh_addralign = L1_CACHE_BYTES;
	mod->arch.got_plt.shdr->sh_size = (num_plts + 1) * sizeof(struct got_entry);
	mod->arch.got_plt.num_entries = 0;
	mod->arch.got_plt.max_entries = num_plts;
	return 0;
}