modpost: Add modinfo flag to livepatch modules

Currently, livepatch infrastructure in the kernel relies on
MODULE_INFO(livepatch, "Y") statement in a livepatch module. Then the
kernel module loader knows a module is indeed livepatch module and can
behave accordingly.

klp-convert, on the other hand relies on LIVEPATCH_* statement in the
module's Makefile for exactly the same reason.

Remove dependency on modinfo and generate MODULE_INFO flag
automatically in modpost when LIVEPATCH_* is defined in the module's
Makefile. Generate a list of all built livepatch modules based on
the .livepatch file and store it in (MODVERDIR)/livepatchmods. Give
this list as an argument for modpost which will use it to identify
livepatch modules.

As MODULE_INFO is no longer needed, remove it.

[jmoreira:
* fix modpost.c (add_livepatch_flag) to update module structure with
livepatch flag and prevent modpost from breaking due to unresolved
symbols]

[joe:
* adjust modpost.c::get_modinfo() call for v5.0 version]

Signed-off-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Joao Moreira <jmoreira@suse.de>

samples/livepatch/livepatch-sample.c

@@ -79,4 +79,3 @@ static void livepatch_exit(void)
 module_init(livepatch_init);
 module_exit(livepatch_exit);
 MODULE_LICENSE("GPL");
-MODULE_INFO(livepatch, "Y");

scripts/Makefile.modpost

@@ -65,6 +65,11 @@ MODLISTCMD := find $(MODVERDIR) -name '*.mod' | xargs -r grep -h '\.ko$$' | sort
 __modules := $(shell $(MODLISTCMD))
 modules   := $(patsubst %.o,%.ko, $(wildcard $(__modules:.ko=.o)))
 
+# find all .livepatch files listed in $(MODVERDIR)/
+ifdef CONFIG_LIVEPATCH
+$(shell find $(MODVERDIR) -name '*.livepatch' | xargs -r -I{} basename {} .livepatch > $(MODVERDIR)/livepatchmods)
+endif
+
 # Stop after building .o files if NOFINAL is set. Makes compile tests quicker
 _modpost: $(if $(KBUILD_MODPOST_NOFINAL), $(modules:.ko:.o),$(modules))
 
@@ -79,7 +84,8 @@ modpost = scripts/mod/modpost                    \
  $(if $(KBUILD_EXTMOD),-o $(modulesymfile))      \
  $(if $(CONFIG_DEBUG_SECTION_MISMATCH),,-S)      \
  $(if $(CONFIG_SECTION_MISMATCH_WARN_ONLY),,-E)  \
- $(if $(KBUILD_EXTMOD)$(KBUILD_MODPOST_WARN),-w)
+ $(if $(KBUILD_EXTMOD)$(KBUILD_MODPOST_WARN),-w) \
+ $(if $(CONFIG_LIVEPATCH),-l $(MODVERDIR)/livepatchmods)
 
 MODPOST_OPT=$(subst -i,-n,$(filter -i,$(MAKEFLAGS)))
 

scripts/mod/modpost.c

@@ -1979,10 +1979,6 @@ static void read_symbols(const char *modname)
 		license = get_next_modinfo(&info, "license", license);
 	}
 
-	/* Livepatch modules have unresolved symbols resolved by klp-convert */
-	if (get_modinfo(&info, "livepatch"))
-		mod->livepatch = 1;
-
 	for (sym = info.symtab_start; sym < info.symtab_stop; sym++) {
 		symname = remove_dot(info.strtab + sym->st_name);
 
@@ -2421,6 +2417,76 @@ static void write_dump(const char *fname)
 	free(buf.p);
 }
 
+struct livepatch_mod_list {
+	struct livepatch_mod_list *next;
+	char *livepatch_mod;
+};
+
+static struct livepatch_mod_list *load_livepatch_mods(const char *fname)
+{
+	struct livepatch_mod_list *list_iter, *list_start = NULL;
+	unsigned long size, pos = 0;
+	void *file = grab_file(fname, &size);
+	char *line;
+
+	if (!file)
+		return NULL;
+
+	while ((line = get_next_line(&pos, file, size))) {
+		list_iter = NOFAIL(malloc(sizeof(*list_iter)));
+		list_iter->next = list_start;
+		list_iter->livepatch_mod = NOFAIL(strdup(line));
+		list_start = list_iter;
+	}
+	release_file(file, size);
+
+	return list_start;
+}
+
+static void free_livepatch_mods(struct livepatch_mod_list *list_start)
+{
+	struct livepatch_mod_list *list_iter;
+
+	while (list_start) {
+		list_iter = list_start->next;
+		free(list_start->livepatch_mod);
+		free(list_start);
+		list_start = list_iter;
+	}
+}
+
+static int is_livepatch_mod(const char *modname,
+		struct livepatch_mod_list *list)
+{
+	const char *myname;
+
+	if (!list)
+		return 0;
+
+	myname = strrchr(modname, '/');
+	if (myname)
+		myname++;
+	else
+		myname = modname;
+
+	while (list) {
+		if (!strcmp(myname, list->livepatch_mod))
+			return 1;
+		list = list->next;
+	}
+	return 0;
+}
+
+static void add_livepatch_flag(struct buffer *b, struct module *mod,
+		struct livepatch_mod_list *list)
+{
+	if (is_livepatch_mod(mod->name, list)) {
+		buf_printf(b, "\nMODULE_INFO(livepatch, \"Y\");\n");
+		mod->livepatch = 1;
+	}
+}
+
+
 struct ext_sym_list {
 	struct ext_sym_list *next;
 	const char *file;
@@ -2436,8 +2502,9 @@ int main(int argc, char **argv)
 	int err;
 	struct ext_sym_list *extsym_iter;
 	struct ext_sym_list *extsym_start = NULL;
+	struct livepatch_mod_list *livepatch_mods = NULL;
 
-	while ((opt = getopt(argc, argv, "i:I:e:mnsST:o:awE")) != -1) {
+	while ((opt = getopt(argc, argv, "i:I:e:l:mnsST:o:awM:K:E")) != -1) {
 		switch (opt) {
 		case 'i':
 			kernel_read = optarg;
@@ -2454,6 +2521,9 @@ int main(int argc, char **argv)
 			extsym_iter->file = optarg;
 			extsym_start = extsym_iter;
 			break;
+		case 'l':
+			livepatch_mods = load_livepatch_mods(optarg);
+			break;
 		case 'm':
 			modversions = 1;
 			break;
@@ -2514,15 +2584,16 @@ int main(int argc, char **argv)
 		buf.pos = 0;
 
 		err |= check_modname_len(mod);
-		err |= check_exports(mod);
 		add_header(&buf, mod);
 		add_intree_flag(&buf, !external_module);
 		add_retpoline(&buf);
 		add_staging_flag(&buf, mod->name);
+		add_livepatch_flag(&buf, mod, livepatch_mods);
 		err |= add_versions(&buf, mod);
 		add_depends(&buf, mod);
 		add_moddevtable(&buf, mod);
 		add_srcversion(&buf, mod);
+		err |= check_exports(mod);
 
 		sprintf(fname, "%s.mod.c", mod->name);
 		write_if_changed(&buf, fname);
@@ -2541,6 +2612,7 @@ int main(int argc, char **argv)
 			      "Set CONFIG_SECTION_MISMATCH_WARN_ONLY=y to allow them.\n");
 		}
 	}
+	free_livepatch_mods(livepatch_mods);
 	free(buf.p);
 
 	return err;