[RFC PATCH v3 2/6] module: preserve Elf information for livepatch modules

@@ -281,6 +281,21 @@ void *__symbol_get(const char *symbol);
 void *__symbol_get_gpl(const char *symbol);
 #define symbol_get(x) ((typeof(&x))(__symbol_get(VMLINUX_SYMBOL_STR(x))))
 
+struct load_info {
+	Elf_Ehdr *hdr;
+	unsigned long len;
+	Elf_Shdr *sechdrs;
+	char *secstrings, *strtab;
+	unsigned long symoffs, stroffs;
+	struct _ddebug *debug;
+	unsigned int num_debug;
+	bool sig_ok;
+	struct {
+		unsigned int sym, str, mod, vers, info, pcpu;
+	} index;
+};
+
+
 /* modules using other modules: kdb wants to see this. */
 struct module_use {
 	struct list_head source_list;

@@ -455,7 +470,11 @@ struct module {
 #endif
 
 #ifdef CONFIG_LIVEPATCH
+	bool klp; /* Is this a livepatch module? */
 	bool klp_alive;
+
+	/* Elf information */
+	struct load_info *info;
 #endif
 
 #ifdef CONFIG_MODULE_UNLOAD

@@ -798,4 +817,16 @@ static inline bool module_sig_ok(struct module *module)
 }
 #endif	/* CONFIG_MODULE_SIG */
 
+#ifdef CONFIG_LIVEPATCH
+static inline bool is_livepatch_module(struct module *mod)
+{
+	return mod->klp;
+}
+#else
+static inline bool is_livepatch_module(struct module *mod)
+{
+	return false;
+}
+#endif /* CONFIG_LIVEPATCH */
+
 #endif /* _LINUX_MODULE_H */

@@ -294,20 +294,6 @@ int unregister_module_notifier(struct notifier_block *nb)
 }
 EXPORT_SYMBOL(unregister_module_notifier);
 
-struct load_info {
-	Elf_Ehdr *hdr;
-	unsigned long len;
-	Elf_Shdr *sechdrs;
-	char *secstrings, *strtab;
-	unsigned long symoffs, stroffs;
-	struct _ddebug *debug;
-	unsigned int num_debug;
-	bool sig_ok;
-	struct {
-		unsigned int sym, str, mod, vers, info, pcpu;
-	} index;
-};
-
 /* We require a truly strong try_module_get(): 0 means failure due to
    ongoing or failed initialization etc. */
 static inline int strong_try_module_get(struct module *mod)

@@ -1966,6 +1952,89 @@ static void module_enable_nx(const struct module *mod) { }
 static void module_disable_nx(const struct module *mod) { }
 #endif
 
+#ifdef CONFIG_LIVEPATCH
+/*
+ * copy_module_elf - preserve Elf information about a module
+ *
+ * Copy relevant Elf information from the load_info struct.
+ * Note: not all fields from the original load_info are
+ * copied into mod->info.
+ */
+static int copy_module_elf(struct module *mod, struct load_info *info)
+{
+	unsigned int size;
+	int ret = 0;
+
+	mod->info = kmalloc(sizeof(*info), GFP_KERNEL);
+	if (mod->info == NULL)
+		return -ENOMEM;
+
+	/* Elf header */
+	size = sizeof(Elf_Ehdr);
+	mod->info->hdr = kmalloc(size, GFP_KERNEL);
+	if (mod->info->hdr == NULL) {
+		ret = -ENOMEM;
+		goto free_info;
+	}
+	memcpy(mod->info->hdr, info->hdr, size);
+
+	/* Elf section header table */
+	size = sizeof(Elf_Shdr) * info->hdr->e_shnum;
+	mod->info->sechdrs = kmalloc(size, GFP_KERNEL);
+	if (mod->info->sechdrs == NULL) {
+		ret = -ENOMEM;
+		goto free_hdr;
+	}
+	memcpy(mod->info->sechdrs, info->sechdrs, size);
+
+	/* Elf section name string table */
+	size = info->sechdrs[info->hdr->e_shstrndx].sh_size;
+	mod->info->secstrings = kmalloc(size, GFP_KERNEL);
+	if (mod->info->secstrings == NULL) {
+		ret = -ENOMEM;
+		goto free_sechdrs;
+	}
+	memcpy(mod->info->secstrings, info->secstrings, size);
+
+	/* Elf section indices */
+	memcpy(&mod->info->index, &info->index, sizeof(info->index));
+
+	/*
+	 * Update symtab's sh_addr to point to a valid
+	 * symbol table, as the temporary symtab in module
+	 * init memory will be freed
+	 */
+	mod->info->sechdrs[mod->info->index.sym].sh_addr = (unsigned long)mod->core_symtab;
+
+	return ret;
+
+free_sechdrs:
+	kfree(mod->info->sechdrs);
+free_hdr:
+	kfree(mod->info->hdr);
+free_info:
+	kfree(mod->info);
+	return ret;
+}
+
+static void free_module_elf(struct module *mod)
+{
+	kfree(mod->info->sechdrs);
+	kfree(mod->info->hdr);
+	kfree(mod->info->secstrings);
+	kfree(mod->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);

@@ -2004,6 +2073,10 @@ 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. */

@@ -2119,6 +2192,10 @@ static int simplify_symbols(struct module *mod, const struct load_info *info)
 			       (long)sym[i].st_value);
 			break;
 
+		case SHN_LIVEPATCH:
+			/* klp symbols are resolved by livepatch */
+			break;
+
 		case SHN_UNDEF:
 			ksym = resolve_symbol_wait(mod, info, name);
 			/* Ok if resolved.  */

@@ -2167,6 +2244,10 @@ static int apply_relocations(struct module *mod, const struct load_info *info)
 		if (!(info->sechdrs[infosec].sh_flags & SHF_ALLOC))
 			continue;
 
+		/* klp 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);

@@ -2385,6 +2466,8 @@ static char elf_type(const Elf_Sym *sym, const struct load_info *info)
 		return 'U';
 	if (sym->st_shndx == SHN_ABS || sym->st_shndx == info->index.pcpu)
 		return 'a';
+	if (sym->st_shndx == SHN_LIVEPATCH)
+		return 'k';
 	if (sym->st_shndx >= SHN_LORESERVE)
 		return '?';
 	if (sechdrs[sym->st_shndx].sh_flags & SHF_EXECINSTR)

@@ -2462,7 +2545,7 @@ 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;

@@ -2505,7 +2588,7 @@ 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];

@@ -2672,6 +2755,24 @@ static int copy_module_from_user(const void __user *umod, unsigned long len,
 	return 0;
 }
 
+#ifdef CONFIG_LIVEPATCH
+static int check_livepatch_modinfo(struct module *mod, struct load_info *info)
+{
+	mod->klp = get_modinfo(info, "livepatch") ? true : false;
+
+	return 0;
+}
+#else
+static int check_livepatch_modinfo(struct module *mod, struct load_info *info)
+{
+	if (get_modinfo(info, "livepatch"))
+		return -EINVAL;
+
+	return 0;
+}
+#endif
+
+
 /* Sets info->hdr and info->len. */
 static int copy_module_from_fd(int fd, struct load_info *info)
 {

@@ -2855,6 +2956,10 @@ static int check_modinfo(struct module *mod, struct load_info *info, int flags)
 			"is unknown, you have been warned.\n", mod->name);
 	}
 
+	err = check_livepatch_modinfo(mod, info);
+	if (err)
+		return -ENOEXEC;
+
 	/* Set up license info based on the info section */
 	set_license(mod, get_modinfo(info, "license"));
 

@@ -3511,6 +3616,16 @@ static int load_module(struct load_info *info, const char __user *uargs,
 	if (err < 0)
 		goto bug_cleanup;
 
+	/*
+	 * Save sechdrs, indices, and other data from
+	 * load_info for livepatch modules
+	 */
+	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);
 

@@ -3519,6 +3634,8 @@ 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);