[PATCH v1 5/7] modpost: Create modalias for builtin modules

[Alexey Gladkov <legion@kernel.org>]

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@kernel.org>
---
 include/linux/module.h   |  4 ----
 scripts/mod/file2alias.c | 13 ++++++++++++-
 scripts/mod/modpost.c    | 21 ++++++++++++++++++---
 scripts/mod/modpost.h    |  7 ++++++-
 4 files changed, 36 insertions(+), 9 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..0fa3f031b904 100644
--- a/scripts/mod/file2alias.c
+++ b/scripts/mod/file2alias.c
@@ -1471,7 +1471,8 @@ static const struct devtable devtable[] = {
 /* Create MODULE_ALIAS() statements.
  * At this time, we cannot write the actual output C source yet,
  * so we write into the mod->dev_table_buf buffer. */
-void handle_moddevtable(struct module *mod, struct elf_info *info,
+void handle_moddevtable(struct list_head *modules,
+			struct module *mod, struct elf_info *info,
 			Elf_Sym *sym, const char *symname)
 {
 	void *symval;
@@ -1509,6 +1510,16 @@ void handle_moddevtable(struct module *mod, struct elf_info *info,
 	typelen = name - type;
 	name += strlen("__");
 
+	if (mod->is_vmlinux) {
+		struct module *builtin_mod;
+
+		builtin_mod = new_module(modname, modnamelen);
+		builtin_mod->is_vmlinux = mod->is_vmlinux;
+		builtin_mod->dump_file = MODULE_BUILTIN_FNAME;
+
+		mod = builtin_mod;
+	}
+
 	/* 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..10e1987fc0e3 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -183,7 +183,7 @@ static struct module *find_module(const char *filename, const char *modname)
 	return NULL;
 }
 
-static struct module *new_module(const char *name, size_t namelen)
+struct module *new_module(const char *name, size_t namelen)
 {
 	struct module *mod;
 
@@ -1610,7 +1610,7 @@ static void read_symbols(const char *modname)
 		symname = remove_dot(info.strtab + sym->st_name);
 
 		handle_symbol(mod, &info, sym, symname);
-		handle_moddevtable(mod, &info, sym, symname);
+		handle_moddevtable(&modules, mod, &info, sym, symname);
 	}
 
 	check_sec_ref(mod, &info);
@@ -2021,11 +2021,26 @@ 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, &modules, list) {
+		if (!mod->is_vmlinux || !mod->dump_file ||
+		    strcmp(mod->dump_file, MODULE_BUILTIN_FNAME))
+			continue;
+		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);
 }
diff --git a/scripts/mod/modpost.h b/scripts/mod/modpost.h
index 9133e4c3803f..85e48f7dd837 100644
--- a/scripts/mod/modpost.h
+++ b/scripts/mod/modpost.h
@@ -199,6 +199,10 @@ static inline bool is_valid_name(struct elf_info *elf, Elf_Sym *sym)
 	return !is_mapping_symbol(name);
 }
 
+#define MODULE_BUILTIN_FNAME "(builtin)"
+
+struct module *new_module(const char *name, size_t namelen);
+
 /* symsearch.c */
 void symsearch_init(struct elf_info *elf);
 void symsearch_finish(struct elf_info *elf);
@@ -207,7 +211,8 @@ Elf_Sym *symsearch_find_nearest(struct elf_info *elf, Elf_Addr addr,
 				Elf_Addr min_distance);
 
 /* file2alias.c */
-void handle_moddevtable(struct module *mod, struct elf_info *info,
+void handle_moddevtable(struct list_head *modules,
+			struct module *mod, struct elf_info *info,
 			Elf_Sym *sym, const char *symname);
 
 /* sumversion.c */
-- 
2.49.0