modpost: add support for generating namespace dependencies

This patch adds an option to modpost to generate a <module>.ns_deps file
per module, containing the namespace dependencies for that module.

E.g. if the linked module my-module.ko would depend on the symbol
myfunc.MY_NS in the namespace MY_NS, the my-module.ns_deps file created
by modpost would contain the entry MY_NS to express the namespace
dependency of my-module imposed by using the symbol myfunc.

These files can subsequently be used by static analysis tools (like
coccinelle scripts) to address issues with missing namespace imports. A
later patch of this series will introduce such a script 'nsdeps' and a
corresponding make target to automatically add missing
MODULE_IMPORT_NS() definitions to the module's sources. For that it uses
the information provided in the generated .ns_deps files.

Co-developed-by: Martijn Coenen <[e-mail]>
Signed-off-by: Martijn Coenen <[e-mail]>
Reviewed-by: Greg Kroah-Hartman <[e-mail]>
Signed-off-by: Matthias Maennich <[e-mail]>
Signed-off-by: Jessica Yu <[e-mail]>

.gitignore

···
 *.lzo
 *.mod
 *.mod.c
+*.ns_deps
 *.o
 *.o.*
 *.order

Makefile

···
 		-o -name '*.ko.*' \
 		-o -name '*.dtb' -o -name '*.dtb.S' -o -name '*.dt.yaml' \
 		-o -name '*.dwo' -o -name '*.lst' \
-		-o -name '*.su' -o -name '*.mod' \
+		-o -name '*.su' -o -name '*.mod' -o -name '*.ns_deps' \
 		-o -name '.*.d' -o -name '.*.tmp' -o -name '*.mod.c' \
 		-o -name '*.lex.c' -o -name '*.tab.[ch]' \
 		-o -name '*.asn1.[ch]' \

scripts/mod/modpost.c

···
 static int sec_mismatch_fatal = 0;
 /* ignore missing files */
 static int ignore_missing_files;
+/* write namespace dependencies */
+static int write_namespace_deps;
 
 enum export {
 	export_plain,      export_unused,     export_gpl,
···
 		else
 			basename = mod->name;
 
-		if (exp->namespace &&
-		    !module_imports_namespace(mod, exp->namespace)) {
-			warn("module %s uses symbol %s from namespace %s, but does not import it.\n",
-			     basename, exp->name, exp->namespace);
+		if (exp->namespace) {
+			add_namespace(&mod->required_namespaces,
+				      exp->namespace);
+
+			if (!write_namespace_deps &&
+			    !module_imports_namespace(mod, exp->namespace)) {
+				warn("module %s uses symbol %s from namespace %s, but does not import it.\n",
+				     basename, exp->name, exp->namespace);
+			}
 		}
 
 		if (!mod->gpl_compatible)
···
 	free(buf.p);
 }
 
+static void write_namespace_deps_files(void)
+{
+	struct module *mod;
+	struct namespace_list *ns;
+	struct buffer ns_deps_buf = {};
+
+	for (mod = modules; mod; mod = mod->next) {
+		char fname[PATH_MAX];
+
+		if (mod->skip)
+			continue;
+
+		ns_deps_buf.pos = 0;
+
+		for (ns = mod->required_namespaces; ns; ns = ns->next)
+			buf_printf(&ns_deps_buf, "%s\n", ns->namespace);
+
+		if (ns_deps_buf.pos == 0)
+			continue;
+
+		sprintf(fname, "%s.ns_deps", mod->name);
+		write_if_changed(&ns_deps_buf, fname);
+	}
+}
+
 struct ext_sym_list {
 	struct ext_sym_list *next;
 	const char *file;
···
 	struct ext_sym_list *extsym_iter;
 	struct ext_sym_list *extsym_start = NULL;
 
-	while ((opt = getopt(argc, argv, "i:I:e:mnsT:o:awE")) != -1) {
+	while ((opt = getopt(argc, argv, "i:I:e:mnsT:o:awEd")) != -1) {
 		switch (opt) {
 		case 'i':
 			kernel_read = optarg;
···
 		case 'E':
 			sec_mismatch_fatal = 1;
 			break;
+		case 'd':
+			write_namespace_deps = 1;
+			break;
 		default:
 			exit(1);
 		}
···
 
 		err |= check_modname_len(mod);
 		err |= check_exports(mod);
+		if (write_namespace_deps)
+			continue;
+
 		add_header(&buf, mod);
 		add_intree_flag(&buf, !external_module);
 		add_retpoline(&buf);
···
 		sprintf(fname, "%s.mod.c", mod->name);
 		write_if_changed(&buf, fname);
 	}
+
+	if (write_namespace_deps) {
+		write_namespace_deps_files();
+		return 0;
+	}
+
 	if (dump_write)
 		write_dump(dump_write);
 	if (sec_mismatch_count && sec_mismatch_fatal)

scripts/mod/modpost.h

···
 	struct buffer dev_table_buf;
 	char	     srcversion[25];
 	int is_dot_o;
+	// Required namespace dependencies
+	struct namespace_list *required_namespaces;
 	// Actual imported namespaces
 	struct namespace_list *imported_namespaces;
 };