Subject: [PATCH] build: add a hack for removing non-essential module info
From: Felix Fietkau <[email-masked]>

Signed-off-by: Felix Fietkau <[email-masked]>
---
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -82,7 +82,7 @@ void sort_extable(struct exception_table
 void sort_main_extable(void);
 void trim_init_extable(struct module *m);
 
-#ifdef MODULE
+#if defined(MODULE) && !defined(CONFIG_MODULE_STRIPPED)
 #define MODULE_GENERIC_TABLE(gtype,name)			\
 extern const struct gtype##_id __mod_##gtype##_table		\
   __attribute__ ((unused, alias(__stringify(name))))
@@ -93,9 +93,10 @@ extern const struct gtype##_id __mod_##g
 
 /* Generic info of form tag = "info" */
 #define MODULE_INFO(tag, info) __MODULE_INFO(tag, tag, info)
+#define MODULE_INFO_STRIP(tag, info) __MODULE_INFO_STRIP(tag, tag, info)
 
 /* For userspace: you can also call me... */
-#define MODULE_ALIAS(_alias) MODULE_INFO(alias, _alias)
+#define MODULE_ALIAS(_alias) MODULE_INFO_STRIP(alias, _alias)
 
 /*
  * The following license idents are currently accepted as indicating free
@@ -131,10 +132,10 @@ extern const struct gtype##_id __mod_##g
  * Author(s), use "Name <email>" or just "Name", for multiple
  * authors use multiple MODULE_AUTHOR() statements/lines.
  */
-#define MODULE_AUTHOR(_author) MODULE_INFO(author, _author)
+#define MODULE_AUTHOR(_author) MODULE_INFO_STRIP(author, _author)
   
 /* What your module does. */
-#define MODULE_DESCRIPTION(_description) MODULE_INFO(description, _description)
+#define MODULE_DESCRIPTION(_description) MODULE_INFO_STRIP(description, _description)
 
 #define MODULE_DEVICE_TABLE(type,name)		\
   MODULE_GENERIC_TABLE(type##_device,name)
@@ -155,7 +156,9 @@ extern const struct gtype##_id __mod_##g
 */
 
 #if defined(MODULE) || !defined(CONFIG_SYSFS)
-#define MODULE_VERSION(_version) MODULE_INFO(version, _version)
+#define MODULE_VERSION(_version) MODULE_INFO_STRIP(version, _version)
+#elif defined(CONFIG_MODULE_STRIPPED)
+#define MODULE_VERSION(_version) __MODULE_INFO_DISABLED(version)
 #else
 #define MODULE_VERSION(_version)					\
 	static struct module_version_attribute ___modver_attr = {	\
@@ -177,7 +180,7 @@ extern const struct gtype##_id __mod_##g
 /* Optional firmware file (or files) needed by the module
  * format is simply firmware file name.  Multiple firmware
  * files require multiple MODULE_FIRMWARE() specifiers */
-#define MODULE_FIRMWARE(_firmware) MODULE_INFO(firmware, _firmware)
+#define MODULE_FIRMWARE(_firmware) MODULE_INFO_STRIP(firmware, _firmware)
 
 /* Given an address, look for it in the exception tables */
 const struct exception_table_entry *search_exception_tables(unsigned long add);
--- a/include/linux/moduleparam.h
+++ b/include/linux/moduleparam.h
@@ -16,6 +16,16 @@
 /* Chosen so that structs with an unsigned long line up. */
 #define MAX_PARAM_PREFIX_LEN (64 - sizeof(unsigned long))
 
+/* This struct is here for syntactic coherency, it is not used */
+#define __MODULE_INFO_DISABLED(name)					  \
+  struct __UNIQUE_ID(name) {}
+
+#ifdef CONFIG_MODULE_STRIPPED
+#define __MODULE_INFO_STRIP(tag, name, info) __MODULE_INFO_DISABLED(name)
+#else
+#define __MODULE_INFO_STRIP(tag, name, info) __MODULE_INFO(tag, name, info)
+#endif
+
 #ifdef MODULE
 #define __MODULE_INFO(tag, name, info)					  \
 static const char __UNIQUE_ID(name)[]					  \
@@ -23,8 +33,7 @@ static const char __UNIQUE_ID(name)[]
   = __stringify(tag) "=" info
 #else  /* !MODULE */
 /* This struct is here for syntactic coherency, it is not used */
-#define __MODULE_INFO(tag, name, info)					  \
-  struct __UNIQUE_ID(name) {}
+#define __MODULE_INFO(tag, name, info) __MODULE_INFO_DISABLED(name)
 #endif
 #define __MODULE_PARM_TYPE(name, _type)					  \
   __MODULE_INFO(parmtype, name##type, #name ":" _type)
@@ -32,7 +41,7 @@ static const char __UNIQUE_ID(name)[]
 /* One for each parameter, describing how to use it.  Some files do
    multiple of these per line, so can't just use MODULE_INFO. */
 #define MODULE_PARM_DESC(_parm, desc) \
-	__MODULE_INFO(parm, _parm, #_parm ":" desc)
+	__MODULE_INFO_STRIP(parm, _parm, #_parm ":" desc)
 
 struct kernel_param;
 
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1783,6 +1783,13 @@ config MODULE_SIG_HASH
 	default "sha384" if MODULE_SIG_SHA384
 	default "sha512" if MODULE_SIG_SHA512
 
+config MODULE_STRIPPED
+	bool "Reduce module size"
+	depends on MODULES
+	help
+	  Remove module parameter descriptions, author info, version, aliases,
+	  device tables, etc.
+
 endif # MODULES
 
 config INIT_ALL_POSSIBLE
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2690,6 +2690,7 @@ static struct module *setup_load_info(st
 
 static int check_modinfo(struct module *mod, struct load_info *info, int flags)
 {
+#ifndef CONFIG_MODULE_STRIPPED
 	const char *modmagic = get_modinfo(info, "vermagic");
 	int err;
 
@@ -2716,6 +2717,7 @@ static int check_modinfo(struct module *
 		       " the quality is unknown, you have been warned.\n",
 		       mod->name);
 	}
+#endif
 
 	/* Set up license info based on the info section */
 	set_license(mod, get_modinfo(info, "license"));
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -1744,7 +1744,9 @@ static void read_symbols(char *modname)
 		symname = info.strtab + sym->st_name;
 
 		handle_modversions(mod, &info, sym, symname);
+#ifndef CONFIG_MODULE_STRIPPED
 		handle_moddevtable(mod, &info, sym, symname);
+#endif
 	}
 	if (!is_vmlinux(modname) ||
 	     (is_vmlinux(modname) && vmlinux_section_warnings))
@@ -1888,7 +1890,9 @@ static void add_header(struct buffer *b,
 	buf_printf(b, "#include <linux/vermagic.h>\n");
 	buf_printf(b, "#include <linux/compiler.h>\n");
 	buf_printf(b, "\n");
+#ifndef CONFIG_MODULE_STRIPPED
 	buf_printf(b, "MODULE_INFO(vermagic, VERMAGIC_STRING);\n");
+#endif
 	buf_printf(b, "\n");
 	buf_printf(b, "struct module __this_module\n");
 	buf_printf(b, "__attribute__((section(\".gnu.linkonce.this_module\"))) = {\n");
@@ -1905,16 +1909,20 @@ static void add_header(struct buffer *b,
 
 static void add_intree_flag(struct buffer *b, int is_intree)
 {
+#ifndef CONFIG_MODULE_STRIPPED
 	if (is_intree)
 		buf_printf(b, "\nMODULE_INFO(intree, \"Y\");\n");
+#endif
 }
 
 static void add_staging_flag(struct buffer *b, const char *name)
 {
+#ifndef CONFIG_MODULE_STRIPPED
 	static const char *staging_dir = "drivers/staging";
 
 	if (strncmp(staging_dir, name, strlen(staging_dir)) == 0)
 		buf_printf(b, "\nMODULE_INFO(staging, \"Y\");\n");
+#endif
 }
 
 /**
@@ -2007,11 +2015,13 @@ static void add_depends(struct buffer *b
 
 static void add_srcversion(struct buffer *b, struct module *mod)
 {
+#ifndef CONFIG_MODULE_STRIPPED
 	if (mod->srcversion[0]) {
 		buf_printf(b, "\n");
 		buf_printf(b, "MODULE_INFO(srcversion, \"%s\");\n",
 			   mod->srcversion);
 	}
+#endif
 }
 
 static void write_if_changed(struct buffer *b, const char *fname)
@@ -2237,7 +2247,9 @@ int main(int argc, char **argv)
 		add_staging_flag(&buf, mod->name);
 		err |= add_versions(&buf, mod);
 		add_depends(&buf, mod, modules);
+#ifndef CONFIG_MODULE_STRIPPED
 		add_moddevtable(&buf, mod);
+#endif
 		add_srcversion(&buf, mod);
 
 		sprintf(fname, "%s.mod.c", mod->name);