+++ Miroslav Benes [13/01/16 10:19 +0100]:
On Fri, 8 Jan 2016, Jessica Yu wrote:static int klp_write_object_relocations(struct module *pmod, struct klp_object *obj) { - int ret = 0; - unsigned long val; - struct klp_reloc *reloc; + int i, len, ret = 0; + char *secname; + const char *objname; if (WARN_ON(!klp_is_object_loaded(obj))) return -EINVAL; - if (WARN_ON(!obj->relocs)) - return -EINVAL; + objname = klp_is_module(obj) ? obj->name : "vmlinux"; module_disable_ro(pmod); + /* For each klp rela section for this object */ + for (i = 1; i < pmod->info->hdr->e_shnum; i++) { + if (!(pmod->info->sechdrs[i].sh_flags & SHF_RELA_LIVEPATCH)) + continue;One more thing. If the module does not specify it is a live patch module in modinfo (with MODULE_INFO(livepatch, "Y")), but it is a perfect live patch module otherwise (it calls klp_register_patch in its init function), the kernel crashes here. pmod->info is not initialized at all. This should be fixed. Perhaps the easiest would be to call klp_write_object_relocations() in klp_init_object_loaded() only if is_livepatch_module() returns true. Similar to a check for obj->relocs before.
Hm yes, that's a problem. To remedy this, I think it makes sense to require all livepatch modules to identify themselves with the modinfo attribute, since it is a very simple requirement. If some module calls klp_register_patch() and it does not have the livepatch attribute, klp_register_patch() can just return an error. We can call is_livepatch_module() at the beginning of klp_register_patch(), and proceed only if the check succeeds, since we'll then know that the required structures have been properly initialized in the module loader. What do you think? Jessica -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
