From a779a482fb9b9f8fcdf8b2519c789b4b9bb5dd05 Mon Sep 17 00:00:00 2001
From: Felix Fietkau <nbd@nbd.name>
Date: Fri, 7 Jul 2017 16:56:48 +0200
Subject: build: add a hack for removing non-essential module info

Signed-off-by: Felix Fietkau <nbd@nbd.name>
---
 include/linux/module.h      | 13 ++++++++-----
 include/linux/moduleparam.h | 15 ++++++++++++---
 init/Kconfig                |  7 +++++++
 kernel/module.c             |  5 ++++-
 scripts/mod/modpost.c       | 12 ++++++++++++
 5 files changed, 43 insertions(+), 9 deletions(-)

--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -164,6 +164,7 @@ extern void cleanup_module(void);
 
 /* 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)
@@ -233,12 +234,12 @@ extern void cleanup_module(void);
  * 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)
 
-#ifdef MODULE
+#if defined(MODULE) && !defined(CONFIG_MODULE_STRIPPED)
 /* Creates an alias so file2alias.c can find device table. */
 #define MODULE_DEVICE_TABLE(type, name)					\
 extern typeof(name) __mod_##type##__##name##_device_table		\
@@ -265,7 +266,9 @@ extern typeof(name) __mod_##type##__##na
  */
 
 #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)					\
 	MODULE_INFO(version, _version);					\
@@ -288,7 +291,7 @@ extern typeof(name) __mod_##type##__##na
 /* 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)
 
 #define MODULE_IMPORT_NS(ns)	MODULE_INFO(import_ns, __stringify(ns))
 
--- a/include/linux/moduleparam.h
+++ b/include/linux/moduleparam.h
@@ -20,6 +20,16 @@
 /* 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
+
 #define __MODULE_INFO(tag, name, info)					  \
 	static const char __UNIQUE_ID(name)[]				  \
 		__used __section(".modinfo") __aligned(1)		  \
@@ -31,7 +41,7 @@
 /* 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/kernel/module/Kconfig
+++ b/kernel/module/Kconfig
@@ -389,4 +389,11 @@ config MODULES_TREE_LOOKUP
 	def_bool y
 	depends on PERF_EVENTS || TRACING || CFI_CLANG
 
+config MODULE_STRIPPED
+	bool "Reduce module size"
+	depends on MODULES
+	help
+	  Remove module parameter descriptions, author info, version, aliases,
+	  device tables, etc.
+
 endif # MODULES
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@@ -997,6 +997,7 @@ size_t modinfo_attrs_count = ARRAY_SIZE(
 
 static const char vermagic[] = VERMAGIC_STRING;
 
+#if defined(CONFIG_MODVERSIONS) || !defined(CONFIG_MODULE_STRIPPED)
 int try_to_force_load(struct module *mod, const char *reason)
 {
 #ifdef CONFIG_MODULE_FORCE_LOAD
@@ -1008,6 +1009,7 @@ int try_to_force_load(struct module *mod
 	return -ENOEXEC;
 #endif
 }
+#endif
 
 /* Parse tag=value strings from .modinfo section */
 char *module_next_tag_pair(char *string, unsigned long *secsize)
@@ -2075,9 +2077,11 @@ static void module_augment_kernel_taints
 
 static int check_modinfo(struct module *mod, struct load_info *info, int flags)
 {
-	const char *modmagic = get_modinfo(info, "vermagic");
 	int err;
 
+#ifndef CONFIG_MODULE_STRIPPED
+	const char *modmagic = get_modinfo(info, "vermagic");
+
 	if (flags & MODULE_INIT_IGNORE_VERMAGIC)
 		modmagic = NULL;
 
@@ -2091,6 +2095,7 @@ static int check_modinfo(struct module *
 		       info->name, modmagic, vermagic);
 		return -ENOEXEC;
 	}
+#endif
 
 	err = check_modinfo_livepatch(mod, info);
 	if (err)
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -1666,7 +1666,9 @@ static void read_symbols(const char *mod
 		symname = remove_dot(info.strtab + sym->st_name);
 
 		handle_symbol(mod, &info, sym, symname);
+#ifndef CONFIG_MODULE_STRIPPED
 		handle_moddevtable(mod, &info, sym, symname);
+#endif
 	}
 
 	check_sec_ref(mod, &info);
@@ -1839,8 +1841,10 @@ static void add_header(struct buffer *b,
 	buf_printf(b, "BUILD_SALT;\n");
 	buf_printf(b, "BUILD_LTO_INFO;\n");
 	buf_printf(b, "\n");
+#ifndef CONFIG_MODULE_STRIPPED
 	buf_printf(b, "MODULE_INFO(vermagic, VERMAGIC_STRING);\n");
 	buf_printf(b, "MODULE_INFO(name, KBUILD_MODNAME);\n");
+#endif
 	buf_printf(b, "\n");
 	buf_printf(b, "__visible struct module __this_module\n");
 	buf_printf(b, "__section(\".gnu.linkonce.this_module\") = {\n");
@@ -1854,8 +1858,10 @@ static void add_header(struct buffer *b,
 	buf_printf(b, "\t.arch = MODULE_ARCH_INIT,\n");
 	buf_printf(b, "};\n");
 
+#ifndef CONFIG_MODULE_STRIPPED
 	if (!external_module)
 		buf_printf(b, "\nMODULE_INFO(intree, \"Y\");\n");
+#endif
 
 	buf_printf(b,
 		   "\n"
@@ -1863,8 +1869,10 @@ static void add_header(struct buffer *b,
 		   "MODULE_INFO(retpoline, \"Y\");\n"
 		   "#endif\n");
 
+#ifndef CONFIG_MODULE_STRIPPED
 	if (strstarts(mod->name, "drivers/staging"))
 		buf_printf(b, "\nMODULE_INFO(staging, \"Y\");\n");
+#endif
 
 	if (strstarts(mod->name, "tools/testing"))
 		buf_printf(b, "\nMODULE_INFO(test, \"Y\");\n");
@@ -1974,11 +1982,13 @@ 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_buf(struct buffer *b, const char *fname)
@@ -2061,7 +2071,9 @@ static void write_mod_c_file(struct modu
 	add_exported_symbols(&buf, mod);
 	add_versions(&buf, mod);
 	add_depends(&buf, mod);
+#ifndef CONFIG_MODULE_STRIPPED
 	add_moddevtable(&buf, mod);
+#endif
 	add_srcversion(&buf, mod);
 
 	ret = snprintf(fname, sizeof(fname), "%s.mod.c", mod->name);
