[PATCH v2 5/7] modpost: Create modalias for builtin modules

[Alexey Gladkov]

For some modules, modalias is generated using the modpost utility and
the section is added to the module file.

When a module is added inside vmlinux, modpost does not generate
modalias for such modules and the information is lost.

As a result kmod (which uses modules.builtin.modinfo in userspace)
cannot determine that modalias is handled by a builtin kernel module.

$ cat /sys/devices/pci0000:00/0000:00:14.0/modalias
pci:v00008086d0000A36Dsv00001043sd00008694bc0Csc03i30

$ modinfo xhci_pci
name:           xhci_pci
filename:       (builtin)
license:        GPL
file:           drivers/usb/host/xhci-pci
description:    xHCI PCI Host Controller Driver

Missing modalias "pci:v*d*sv*sd*bc0Csc03i30*" which will be generated by
modpost if the module is built separately.

To fix this it is necessary to generate the same modalias for vmlinux as
for the individual modules. Fortunately '.vmlinux.export.o' is already
generated from which '.modinfo' can be extracted in the same way as for
vmlinux.o.

Signed-off-by: Alexey Gladkov <legion@xxxxxxxxxx>
---

v2: As Petr Pavlu suggested, I separated the builtin modules from the external
    modules. I've also added a search for duplicate modules.

---
 include/linux/module.h   |  4 ----
 scripts/mod/file2alias.c |  5 +++++
 scripts/mod/modpost.c    | 35 +++++++++++++++++++++++++++--------
 scripts/mod/modpost.h    | 15 ++++++++++++++-
 4 files changed, 46 insertions(+), 13 deletions(-)

diff --git a/include/linux/module.h b/include/linux/module.h
index 7250b4a527ec..6225793ddcd4 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -257,14 +257,10 @@ extern void cleanup_module(void);
 	__PASTE(type,			\
 	__PASTE(__, name)))))))
 
-#ifdef MODULE
 /* Creates an alias so file2alias.c can find device table. */
 #define MODULE_DEVICE_TABLE(type, name)			\
 extern typeof(name) __mod_device_table(type, name)	\
   __attribute__ ((unused, alias(__stringify(name))))
-#else  /* !MODULE */
-#define MODULE_DEVICE_TABLE(type, name)
-#endif
 
 /* Version of form [<epoch>:]<version>[-<extra-version>].
  * Or for CVS/RCS ID version, everything but the number is stripped.
diff --git a/scripts/mod/file2alias.c b/scripts/mod/file2alias.c
index dff1799a4c79..be221923f582 100644
--- a/scripts/mod/file2alias.c
+++ b/scripts/mod/file2alias.c
@@ -1509,6 +1509,11 @@ void handle_moddevtable(struct module *mod, struct elf_info *info,
 	typelen = name - type;
 	name += strlen("__");
 
+	if (mod->is_vmlinux) {
+		mod = find_module(NULL, modname, modnamelen);
+		mod = mod ?: new_builtin_module(modname, modnamelen);
+	}
+
 	/* Handle all-NULL symbols allocated into .bss */
 	if (info->sechdrs[get_secindex(info, sym)].sh_type & SHT_NOBITS) {
 		zeros = calloc(1, sym->st_size);
diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index be89921d60b6..db3c172d4528 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -168,22 +168,26 @@ char *get_line(char **stringp)
 	return orig;
 }
 
-/* A list of all modules we processed */
+/* A list of all modules (vmlinux or *.ko) we processed */
 LIST_HEAD(modules);
 
-static struct module *find_module(const char *filename, const char *modname)
+/* A list of all builtin modules we processed */
+LIST_HEAD(builtin_modules);
+
+struct module *find_module(const char *filename, const char *name, size_t namelen)
 {
 	struct module *mod;
 
 	list_for_each_entry(mod, &modules, list) {
-		if (!strcmp(mod->dump_file, filename) &&
-		    !strcmp(mod->name, modname))
+		if ((mod->dump_file && !strcmp(mod->dump_file, filename)) &&
+		    namelen != strlen(mod->name) &&
+		    !strncmp(mod->name, name, namelen))
 			return mod;
 	}
 	return NULL;
 }
 
-static struct module *new_module(const char *name, size_t namelen)
+struct module *create_module(const char *name, size_t namelen, bool is_builtin)
 {
 	struct module *mod;
 
@@ -207,7 +211,10 @@ static struct module *new_module(const char *name, size_t namelen)
 	 */
 	mod->is_gpl_compatible = true;
 
-	list_add_tail(&mod->list, &modules);
+	if (is_builtin)
+		list_add_tail(&mod->list, &builtin_modules);
+	else
+		list_add_tail(&mod->list, &modules);
 
 	return mod;
 }
@@ -2021,11 +2028,23 @@ static void write_if_changed(struct buffer *b, const char *fname)
 static void write_vmlinux_export_c_file(struct module *mod)
 {
 	struct buffer buf = { };
+	struct module_alias *alias, *next;
 
 	buf_printf(&buf,
-		   "#include <linux/export-internal.h>\n");
+		   "#include <linux/export-internal.h>\n"
+		   "#include <linux/module.h>\n");
 
 	add_exported_symbols(&buf, mod);
+
+	list_for_each_entry(mod, &builtin_modules, list) {
+		list_for_each_entry_safe(alias, next, &mod->aliases, node) {
+			buf_printf(&buf, "MODULE_ALIAS_MODNAME(\"%s\", \"%s\");\n",
+					mod->name, alias->str);
+			list_del(&alias->node);
+			free(alias);
+		}
+	}
+
 	write_if_changed(&buf, ".vmlinux.export.c");
 	free(buf.p);
 }
@@ -2112,7 +2131,7 @@ static void read_dump(const char *fname)
 			continue;
 		}
 
-		mod = find_module(fname, modname);
+		mod = find_module(fname, modname, strlen(modname));
 		if (!mod) {
 			mod = new_module(modname, strlen(modname));
 			mod->dump_file = fname;
diff --git a/scripts/mod/modpost.h b/scripts/mod/modpost.h
index 9133e4c3803f..1d0dd4ee944a 100644
--- a/scripts/mod/modpost.h
+++ b/scripts/mod/modpost.h
@@ -107,7 +107,7 @@ struct module_alias {
 };
 
 /**
- * struct module - represent a module (vmlinux or *.ko)
+ * struct module - represent a module (vmlinux, a builtin module, or *.ko)
  *
  * @dump_file: path to the .symvers file if loaded from a file
  * @aliases: list head for module_aliases
@@ -199,6 +199,19 @@ static inline bool is_valid_name(struct elf_info *elf, Elf_Sym *sym)
 	return !is_mapping_symbol(name);
 }
 
+struct module *find_module(const char *filename, const char *name, size_t namelen);
+struct module *create_module(const char *name, size_t namelen, bool is_builtin);
+
+static inline struct module *new_module(const char *name, size_t namelen)
+{
+	return create_module(name, namelen, false);
+}
+
+static inline struct module *new_builtin_module(const char *name, size_t namelen)
+{
+	return create_module(name, namelen, true);
+}
+
 /* symsearch.c */
 void symsearch_init(struct elf_info *elf);
 void symsearch_finish(struct elf_info *elf);
-- 
2.49.0