[RFC PATCH v4 2/6] module: preserve Elf information for livepatch modules

@@ -324,6 +324,15 @@ struct module_layout {
 #define __module_layout_align
 #endif
 
+#ifdef CONFIG_LIVEPATCH
+struct klp_modinfo {
+	Elf_Ehdr hdr;
+	Elf_Shdr *sechdrs;
+	char *secstrings;
+	unsigned int symndx;
+};
+#endif
+
 struct module {
 	enum module_state state;
 

@@ -455,7 +464,11 @@ struct module {
 #endif
 
 #ifdef CONFIG_LIVEPATCH
+	bool klp; /* Is this a livepatch module? */
 	bool klp_alive;
+
+	/* Elf information */
+	struct klp_modinfo *klp_info;
 #endif
 
 #ifdef CONFIG_MODULE_UNLOAD

@@ -629,6 +642,18 @@ static inline bool module_requested_async_probing(struct module *module)
 	return module && module->async_probe_requested;
 }
 
+#ifdef CONFIG_LIVEPATCH
+static inline bool is_livepatch_module(struct module *mod)
+{
+	return mod->klp;
+}
+#else /* !CONFIG_LIVEPATCH */
+static inline bool is_livepatch_module(struct module *mod)
+{
+	return false;
+}
+#endif /* CONFIG_LIVEPATCH */
+
 #else /* !CONFIG_MODULES... */
 
 /* Given an address, look for it in the exception tables. */

@@ -1970,6 +1970,82 @@ static void module_enable_nx(const struct module *mod) { }
 static void module_disable_nx(const struct module *mod) { }
 #endif
 
+#ifdef CONFIG_LIVEPATCH
+/*
+ * Persist Elf information about a module. Copy the Elf header,
+ * section header table, section string table, and symtab section
+ * index from info to mod->klp_info.
+ */
+static int copy_module_elf(struct module *mod, struct load_info *info)
+{
+	unsigned int size, symndx;
+	int ret = 0;
+
+	size = sizeof(*mod->klp_info);
+	mod->klp_info = kmalloc(size, GFP_KERNEL);
+	if (mod->klp_info == NULL)
+		return -ENOMEM;
+
+	/* Elf header */
+	size = sizeof(Elf_Ehdr);
+	memcpy(&mod->klp_info->hdr, info->hdr, size);
+
+	/* Elf section header table */
+	size = sizeof(Elf_Shdr) * info->hdr->e_shnum;
+	mod->klp_info->sechdrs = kmalloc(size, GFP_KERNEL);
+	if (mod->klp_info->sechdrs == NULL) {
+		ret = -ENOMEM;
+		goto free_info;
+	}
+	memcpy(mod->klp_info->sechdrs, info->sechdrs, size);
+
+	/* Elf section name string table */
+	size = info->sechdrs[info->hdr->e_shstrndx].sh_size;
+	mod->klp_info->secstrings = kmalloc(size, GFP_KERNEL);
+	if (mod->klp_info->secstrings == NULL) {
+		ret = -ENOMEM;
+		goto free_sechdrs;
+	}
+	memcpy(mod->klp_info->secstrings, info->secstrings, size);
+
+	/* Elf symbol section index */
+	symndx = info->index.sym;
+	mod->klp_info->symndx = symndx;
+
+	/*
+	 * For livepatch modules, core_symtab is a complete copy
+	 * of the original symbol table. Adjust sh_addr to point
+	 * to core_symtab since the copy of the symtab in module
+	 * init memory is freed at the end of do_init_module().
+	 */
+	mod->klp_info->sechdrs[symndx].sh_addr = (unsigned long) mod->core_symtab;
+
+	return ret;
+
+free_sechdrs:
+	kfree(mod->klp_info->sechdrs);
+free_info:
+	kfree(mod->klp_info);
+	return ret;
+}
+
+static void free_module_elf(struct module *mod)
+{
+	kfree(mod->klp_info->sechdrs);
+	kfree(mod->klp_info->secstrings);
+	kfree(mod->klp_info);
+}
+#else /* !CONFIG_LIVEPATCH */
+static int copy_module_elf(struct module *mod, struct load_info *info)
+{
+	return 0;
+}
+
+static void free_module_elf(struct module *mod)
+{
+}
+#endif /* CONFIG_LIVEPATCH */
+
 void __weak module_memfree(void *module_region)
 {
 	vfree(module_region);

@@ -2008,6 +2084,10 @@ static void free_module(struct module *mod)
 	/* Free any allocated parameters. */
 	destroy_params(mod->kp, mod->num_kp);
 
+	/* Free Elf information if it was saved */
+	if (is_livepatch_module(mod))
+		free_module_elf(mod);
+
 	/* Now we can delete it from the lists */
 	mutex_lock(&module_mutex);
 	/* Unlink carefully: kallsyms could be walking list. */

@@ -2123,6 +2203,10 @@ static int simplify_symbols(struct module *mod, const struct load_info *info)
 			       (long)sym[i].st_value);
 			break;
 
+		case SHN_LIVEPATCH:
+			/* Livepatch symbols are resolved by livepatch */
+			break;
+
 		case SHN_UNDEF:
 			ksym = resolve_symbol_wait(mod, info, name);
 			/* Ok if resolved.  */

@@ -2171,6 +2255,10 @@ static int apply_relocations(struct module *mod, const struct load_info *info)
 		if (!(info->sechdrs[infosec].sh_flags & SHF_ALLOC))
 			continue;
 
+		/* Livepatch relocation sections are applied by livepatch */
+		if (info->sechdrs[i].sh_flags & SHF_RELA_LIVEPATCH)
+			continue;
+
 		if (info->sechdrs[i].sh_type == SHT_REL)
 			err = apply_relocate(info->sechdrs, info->strtab,
 					     info->index.sym, i, mod);

@@ -2466,7 +2554,7 @@ static void layout_symtab(struct module *mod, struct load_info *info)
 
 	/* Compute total space required for the core symbols' strtab. */
 	for (ndst = i = 0; i < nsrc; i++) {
-		if (i == 0 ||
+		if (i == 0 || is_livepatch_module(mod) ||
 		    is_core_symbol(src+i, info->sechdrs, info->hdr->e_shnum,
 				   info->index.pcpu)) {
 			strtab_size += strlen(&info->strtab[src[i].st_name])+1;

@@ -2509,7 +2597,7 @@ static void add_kallsyms(struct module *mod, const struct load_info *info)
 	mod->core_strtab = s = mod->core_layout.base + info->stroffs;
 	src = mod->symtab;
 	for (ndst = i = 0; i < mod->num_symtab; i++) {
-		if (i == 0 ||
+		if (i == 0 || is_livepatch_module(mod) ||
 		    is_core_symbol(src+i, info->sechdrs, info->hdr->e_shnum,
 				   info->index.pcpu)) {
 			dst[ndst] = src[i];

@@ -2676,6 +2764,23 @@ static int copy_module_from_user(const void __user *umod, unsigned long len,
 	return 0;
 }
 
+#ifdef CONFIG_LIVEPATCH
+static int find_livepatch_modinfo(struct module *mod, struct load_info *info)
+{
+	mod->klp = get_modinfo(info, "livepatch") ? true : false;
+
+	return 0;
+}
+#else /* !CONFIG_LIVEPATCH */
+static int find_livepatch_modinfo(struct module *mod, struct load_info *info)
+{
+	if (get_modinfo(info, "livepatch"))
+		return -ENOEXEC;
+
+	return 0;
+}
+#endif /* CONFIG_LIVEPATCH */
+
 /* Sets info->hdr and info->len. */
 static int copy_module_from_fd(int fd, struct load_info *info)
 {

@@ -2859,6 +2964,10 @@ static int check_modinfo(struct module *mod, struct load_info *info, int flags)
 			"is unknown, you have been warned.\n", mod->name);
 	}
 
+	err = find_livepatch_modinfo(mod, info);
+	if (err)
+		return err;
+
 	/* Set up license info based on the info section */
 	set_license(mod, get_modinfo(info, "license"));
 

@@ -3222,6 +3331,12 @@ static noinline int do_init_module(struct module *mod)
 	 */
 	current->flags &= ~PF_USED_ASYNC;
 
+#ifdef CONFIG_KALLSYMS
+	/* Make symtab and strtab available prior to module init call */
+	mod->num_symtab = mod->core_num_syms;
+	mod->symtab = mod->core_symtab;
+	mod->strtab = mod->core_strtab;
+#endif
 	do_mod_ctors(mod);
 	/* Start the module */
 	if (mod->init != NULL)

@@ -3266,11 +3381,6 @@ static noinline int do_init_module(struct module *mod)
 	/* Drop initial reference. */
 	module_put(mod);
 	trim_init_extable(mod);
-#ifdef CONFIG_KALLSYMS
-	mod->num_symtab = mod->core_num_syms;
-	mod->symtab = mod->core_symtab;
-	mod->strtab = mod->core_strtab;
-#endif
 	mod_tree_remove_init(mod);
 	disable_ro_nx(&mod->init_layout);
 	module_arch_freeing_init(mod);

@@ -3522,6 +3632,13 @@ static int load_module(struct load_info *info, const char __user *uargs,
 	if (err < 0)
 		goto bug_cleanup;
 
+	/* For livepatch modules, save Elf info from load_info struct */
+	if (is_livepatch_module(mod)) {
+		err = copy_module_elf(mod, info);
+		if (err < 0)
+			goto sysfs_cleanup;
+	}
+
 	/* Get rid of temporary copy. */
 	free_copy(info);
 

@@ -3530,6 +3647,8 @@ static int load_module(struct load_info *info, const char __user *uargs,
 
 	return do_init_module(mod);
 
+ sysfs_cleanup:
+	mod_sysfs_teardown(mod);
  bug_cleanup:
 	/* module_bug_cleanup needs module_mutex protection */
 	mutex_lock(&module_mutex);