module: show version information for built-in modules in sysfs

Currently only drivers that are built as modules have their versions shown in /sys/module/<module_name>/version, but this information might also be useful for built-in drivers as well. This especially important for drivers that do not define any parameters - such drivers, if built-in, are completely invisible from userspace. This patch changes MODULE_VERSION() macro so that in case when we are compiling built-in module, version information is stored in a separate section. Kernel then uses this data to create 'version' sysfs attribute in the same fashion it creates attributes for module parameters. Signed-off-by: Dmitry Torokhov <dtor@vmware.com> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

module: show version information for built-in modules in sysfs
Currently only drivers that are built as modules have their versions shown in /sys/module/<module_name>/version, but this information might also be useful for built-in drivers as well. This especially important for drivers that do not define any parameters - such drivers, if built-in, are completely invisible from userspace. This patch changes MODULE_VERSION() macro so that in case when we are compiling built-in module, version information is stored in a separate section. Kernel then uses this data to create 'version' sysfs attribute in the same fashion it creates attributes for module parameters. Signed-off-by: Dmitry Torokhov <dtor@vmware.com> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Dmitry Torokhov · Rusty Russell
1 parent 1bae4ce27c
Showing 3 changed files with 88 additions and 11 deletions Side-by-side Diff
include/asm-generic/vmlinux.lds.h
include/linux/module.h
kernel/params.c
@@ -364,6 +364,13 @@
 		VMLINUX_SYMBOL(__start___param) = .;			\
 		*(__param)						\
 		VMLINUX_SYMBOL(__stop___param) = .;			\
+	}								\
+									\
+	/* Built-in module versions. */					\
+	__modver : AT(ADDR(__modver) - LOAD_OFFSET) {			\
+		VMLINUX_SYMBOL(__start___modver) = .;			\
+		*(__modver)						\
+		VMLINUX_SYMBOL(__stop___modver) = .;			\
 		. = ALIGN((align));					\
 		VMLINUX_SYMBOL(__end_rodata) = .;			\
 	}								\
@@ -58,6 +58,12 @@
 	void (*free)(struct module *);
 };
  
+struct module_version_attribute {
+	struct module_attribute mattr;
+	const char *module_name;
+	const char *version;
+};
+
 struct module_kobject
 {
 	struct kobject kobj;
  
@@ -161,7 +167,28 @@
   Using this automatically adds a checksum of the .c files and the
   local headers in "srcversion".
 */
+
+#ifdef MODULE
 #define MODULE_VERSION(_version) MODULE_INFO(version, _version)
+#else
+#define MODULE_VERSION(_version)					\
+	extern ssize_t __modver_version_show(struct module_attribute *,	\
+					     struct module *, char *);	\
+	static struct module_version_attribute __modver_version_attr	\
+	__used								\
+    __attribute__ ((__section__ ("__modver"),aligned(sizeof(void *)))) \
+	= {								\
+		.mattr	= {						\
+			.attr	= {					\
+				.name	= "version",			\
+				.mode	= S_IRUGO,			\
+			},						\
+			.show	= __modver_version_show,		\
+		},							\
+		.module_name	= KBUILD_MODNAME,			\
+		.version	= _version,				\
+	}
+#endif
  
 /* Optional firmware file (or files) needed by the module
  * format is simply firmware file name.  Multiple firmware
@@ -719,9 +719,7 @@
 			params[i].ops->free(params[i].arg);
 }
  
-static void __init kernel_add_sysfs_param(const char *name,
-					  struct kernel_param *kparam,
-					  unsigned int name_skip)
+static struct module_kobject * __init locate_module_kobject(const char *name)
 {
 	struct module_kobject *mk;
 	struct kobject *kobj;
  
@@ -729,10 +727,7 @@
  
 	kobj = kset_find_obj(module_kset, name);
 	if (kobj) {
-		/* We already have one.  Remove params so we can add more. */
 		mk = to_module_kobject(kobj);
-		/* We need to remove it before adding parameters. */
-		sysfs_remove_group(&mk->kobj, &mk->mp->grp);
 	} else {
 		mk = kzalloc(sizeof(struct module_kobject), GFP_KERNEL);
 		BUG_ON(!mk);
  
  
@@ -743,15 +738,36 @@
 					   "%s", name);
 		if (err) {
 			kobject_put(&mk->kobj);
-			printk(KERN_ERR "Module '%s' failed add to sysfs, "
-			       "error number %d\n", name, err);
-			printk(KERN_ERR	"The system will be unstable now.\n");
-			return;
+			printk(KERN_ERR
+				"Module '%s' failed add to sysfs, error number %d\n",
+				name, err);
+			printk(KERN_ERR
+				"The system will be unstable now.\n");
+			return NULL;
 		}
-		/* So that exit path is even. */
+
+		/* So that we hold reference in both cases. */
 		kobject_get(&mk->kobj);
 	}
  
+	return mk;
+}
+
+static void __init kernel_add_sysfs_param(const char *name,
+					  struct kernel_param *kparam,
+					  unsigned int name_skip)
+{
+	struct module_kobject *mk;
+	int err;
+
+	mk = locate_module_kobject(name);
+	if (!mk)
+		return;
+
+	/* We need to remove old parameters before adding more. */
+	if (mk->mp)
+		sysfs_remove_group(&mk->kobj, &mk->mp->grp);
+
 	/* These should not fail at boot. */
 	err = add_sysfs_param(mk, kparam, kparam->name + name_skip);
 	BUG_ON(err);
  
@@ -796,7 +812,33 @@
 	}
 }
  
+ssize_t __modver_version_show(struct module_attribute *mattr,
+			      struct module *mod, char *buf)
+{
+	struct module_version_attribute *vattr =
+		container_of(mattr, struct module_version_attribute, mattr);
  
+	return sprintf(buf, "%s\n", vattr->version);
+}
+
+extern struct module_version_attribute __start___modver[], __stop___modver[];
+
+static void __init version_sysfs_builtin(void)
+{
+	const struct module_version_attribute *vattr;
+	struct module_kobject *mk;
+	int err;
+
+	for (vattr = __start___modver; vattr < __stop___modver; vattr++) {
+		mk = locate_module_kobject(vattr->module_name);
+		if (mk) {
+			err = sysfs_create_file(&mk->kobj, &vattr->mattr.attr);
+			kobject_uevent(&mk->kobj, KOBJ_ADD);
+			kobject_put(&mk->kobj);
+		}
+	}
+}
+
 /* module-related sysfs stuff */
  
 static ssize_t module_attr_show(struct kobject *kobj,
@@ -875,6 +917,7 @@
 	}
 	module_sysfs_initialized = 1;
  
+	version_sysfs_builtin();
 	param_sysfs_builtin();
  
 	return 0;
...	...	@@ -364,6 +364,13 @@
364	364	VMLINUX_SYMBOL(__start___param) = .; \
365	365	*(__param) \
366	366	VMLINUX_SYMBOL(__stop___param) = .; \
	367	+ } \
	368	+ \
	369	+ /* Built-in module versions. */ \
	370	+ __modver : AT(ADDR(__modver) - LOAD_OFFSET) { \
	371	+ VMLINUX_SYMBOL(__start___modver) = .; \
	372	+ *(__modver) \
	373	+ VMLINUX_SYMBOL(__stop___modver) = .; \
367	374	. = ALIGN((align)); \
368	375	VMLINUX_SYMBOL(__end_rodata) = .; \
369	376	} \
...	...	@@ -58,6 +58,12 @@
58	58	void (free)(struct module );
59	59	};
60	60
	61	+struct module_version_attribute {
	62	+ struct module_attribute mattr;
	63	+ const char *module_name;
	64	+ const char *version;
	65	+};
	66	+
61	67	struct module_kobject
62	68	{
63	69	struct kobject kobj;
64	70
...	...	@@ -161,7 +167,28 @@
161	167	Using this automatically adds a checksum of the .c files and the
162	168	local headers in "srcversion".
163	169	*/
	170	+
	171	+#ifdef MODULE
164	172	#define MODULE_VERSION(_version) MODULE_INFO(version, _version)
	173	+#else
	174	+#define MODULE_VERSION(_version) \
	175	+ extern ssize_t __modver_version_show(struct module_attribute *, \
	176	+ struct module , char ); \
	177	+ static struct module_version_attribute __modver_version_attr \
	178	+ __used \
	179	+ __attribute__ ((__section__ ("__modver"),aligned(sizeof(void *)))) \
	180	+ = { \
	181	+ .mattr = { \
	182	+ .attr = { \
	183	+ .name = "version", \
	184	+ .mode = S_IRUGO, \
	185	+ }, \
	186	+ .show = __modver_version_show, \
	187	+ }, \
	188	+ .module_name = KBUILD_MODNAME, \
	189	+ .version = _version, \
	190	+ }
	191	+#endif
165	192
166	193	/* Optional firmware file (or files) needed by the module
167	194	* format is simply firmware file name. Multiple firmware
...	...	@@ -719,9 +719,7 @@
719	719	params[i].ops->free(params[i].arg);
720	720	}
721	721
722		-static void __init kernel_add_sysfs_param(const char *name,
723		- struct kernel_param *kparam,
724		- unsigned int name_skip)
	722	+static struct module_kobject * __init locate_module_kobject(const char *name)
725	723	{
726	724	struct module_kobject *mk;
727	725	struct kobject *kobj;
728	726
...	...	@@ -729,10 +727,7 @@
729	727
730	728	kobj = kset_find_obj(module_kset, name);
731	729	if (kobj) {
732		- /* We already have one. Remove params so we can add more. */
733	730	mk = to_module_kobject(kobj);
734		- /* We need to remove it before adding parameters. */
735		- sysfs_remove_group(&mk->kobj, &mk->mp->grp);
736	731	} else {
737	732	mk = kzalloc(sizeof(struct module_kobject), GFP_KERNEL);
738	733	BUG_ON(!mk);
739	734
740	735
...	...	@@ -743,15 +738,36 @@
743	738	"%s", name);
744	739	if (err) {
745	740	kobject_put(&mk->kobj);
746		- printk(KERN_ERR "Module '%s' failed add to sysfs, "
747		- "error number %d\n", name, err);
748		- printk(KERN_ERR "The system will be unstable now.\n");
749		- return;
	741	+ printk(KERN_ERR
	742	+ "Module '%s' failed add to sysfs, error number %d\n",
	743	+ name, err);
	744	+ printk(KERN_ERR
	745	+ "The system will be unstable now.\n");
	746	+ return NULL;
750	747	}
751		- /* So that exit path is even. */
	748	+
	749	+ /* So that we hold reference in both cases. */
752	750	kobject_get(&mk->kobj);
753	751	}
754	752
	753	+ return mk;
	754	+}
	755	+
	756	+static void __init kernel_add_sysfs_param(const char *name,
	757	+ struct kernel_param *kparam,
	758	+ unsigned int name_skip)
	759	+{
	760	+ struct module_kobject *mk;
	761	+ int err;
	762	+
	763	+ mk = locate_module_kobject(name);
	764	+ if (!mk)
	765	+ return;
	766	+
	767	+ /* We need to remove old parameters before adding more. */
	768	+ if (mk->mp)
	769	+ sysfs_remove_group(&mk->kobj, &mk->mp->grp);
	770	+
755	771	/* These should not fail at boot. */
756	772	err = add_sysfs_param(mk, kparam, kparam->name + name_skip);
757	773	BUG_ON(err);
758	774
...	...	@@ -796,7 +812,33 @@
796	812	}
797	813	}
798	814
	815	+ssize_t __modver_version_show(struct module_attribute *mattr,
	816	+ struct module mod, char buf)
	817	+{
	818	+ struct module_version_attribute *vattr =
	819	+ container_of(mattr, struct module_version_attribute, mattr);
799	820
	821	+ return sprintf(buf, "%s\n", vattr->version);
	822	+}
	823	+
	824	+extern struct module_version_attribute __start___modver[], __stop___modver[];
	825	+
	826	+static void __init version_sysfs_builtin(void)
	827	+{
	828	+ const struct module_version_attribute *vattr;
	829	+ struct module_kobject *mk;
	830	+ int err;
	831	+
	832	+ for (vattr = __start___modver; vattr < __stop___modver; vattr++) {
	833	+ mk = locate_module_kobject(vattr->module_name);
	834	+ if (mk) {
	835	+ err = sysfs_create_file(&mk->kobj, &vattr->mattr.attr);
	836	+ kobject_uevent(&mk->kobj, KOBJ_ADD);
	837	+ kobject_put(&mk->kobj);
	838	+ }
	839	+ }
	840	+}
	841	+
800	842	/* module-related sysfs stuff */
801	843
802	844	static ssize_t module_attr_show(struct kobject *kobj,
...	...	@@ -875,6 +917,7 @@
875	917	}
876	918	module_sysfs_initialized = 1;
877	919
	920	+ version_sysfs_builtin();
878	921	param_sysfs_builtin();
879	922
880	923	return 0;