int apply_relocate_add()

in kernel/module.c [312:408]

• 79 lines of code
• 16 McCabe index (conditional complexity)

int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
		       unsigned int symindex, unsigned int relsec,
		       struct module *me)
{
	Elf_Rela *rel = (void *) sechdrs[relsec].sh_addr;
	int (*handler)(struct module *me, u32 *location, Elf_Addr v);
	Elf_Sym *sym;
	u32 *location;
	unsigned int i, type;
	Elf_Addr v;
	int res;

	pr_debug("Applying relocate section %u to %u\n", relsec,
	       sechdrs[relsec].sh_info);

	for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
		/* This is where to make the change */
		location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
			+ rel[i].r_offset;
		/* This is the symbol it is referring to */
		sym = (Elf_Sym *)sechdrs[symindex].sh_addr
			+ ELF_RISCV_R_SYM(rel[i].r_info);
		if (IS_ERR_VALUE(sym->st_value)) {
			/* Ignore unresolved weak symbol */
			if (ELF_ST_BIND(sym->st_info) == STB_WEAK)
				continue;
			pr_warn("%s: Unknown symbol %s\n",
				me->name, strtab + sym->st_name);
			return -ENOENT;
		}

		type = ELF_RISCV_R_TYPE(rel[i].r_info);

		if (type < ARRAY_SIZE(reloc_handlers_rela))
			handler = reloc_handlers_rela[type];
		else
			handler = NULL;

		if (!handler) {
			pr_err("%s: Unknown relocation type %u\n",
			       me->name, type);
			return -EINVAL;
		}

		v = sym->st_value + rel[i].r_addend;

		if (type == R_RISCV_PCREL_LO12_I || type == R_RISCV_PCREL_LO12_S) {
			unsigned int j;

			for (j = 0; j < sechdrs[relsec].sh_size / sizeof(*rel); j++) {
				unsigned long hi20_loc =
					sechdrs[sechdrs[relsec].sh_info].sh_addr
					+ rel[j].r_offset;
				u32 hi20_type = ELF_RISCV_R_TYPE(rel[j].r_info);

				/* Find the corresponding HI20 relocation entry */
				if (hi20_loc == sym->st_value
				    && (hi20_type == R_RISCV_PCREL_HI20
					|| hi20_type == R_RISCV_GOT_HI20)) {
					s32 hi20, lo12;
					Elf_Sym *hi20_sym =
						(Elf_Sym *)sechdrs[symindex].sh_addr
						+ ELF_RISCV_R_SYM(rel[j].r_info);
					unsigned long hi20_sym_val =
						hi20_sym->st_value
						+ rel[j].r_addend;

					/* Calculate lo12 */
					size_t offset = hi20_sym_val - hi20_loc;
					if (IS_ENABLED(CONFIG_MODULE_SECTIONS)
					    && hi20_type == R_RISCV_GOT_HI20) {
						offset = module_emit_got_entry(
							 me, hi20_sym_val);
						offset = offset - hi20_loc;
					}
					hi20 = (offset + 0x800) & 0xfffff000;
					lo12 = offset - hi20;
					v = lo12;

					break;
				}
			}
			if (j == sechdrs[relsec].sh_size / sizeof(*rel)) {
				pr_err(
				  "%s: Can not find HI20 relocation information\n",
				  me->name);
				return -EINVAL;
			}
		}

		res = handler(me, location, v);
		if (res)
			return res;
	}

	return 0;
}