[PATCH] Builtin Module Parameters in sysfs too

Currently, only module parameters in loaded modules are exported in
/sys/modules/, while those of "modules" built into the kernel can be set by
the kernel command line, but not read or set via sysfs.

- move module parameters from /sys/modules/$(module_name)/$(parameter_name) to
  /sys/modules/$(module_name)/parameters/$(parameter_name)

- remove dummy kernel_param for exporting refcnt, add "struct module *"-based
  attribute instead

- also export module paramters for "modules" which are built into the kernel,
  so parameters are always accessible at
  /sys/modules/$(KBUILD_MODNAME)/$(parameter_name)

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> (modified)
Signed-off-by: Dominik Brodowski <linux@brodo.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 391 insertions, 0 deletions

diff --git a/kernel/params.c b/kernel/params.c
index ebb3031cd6cc..45dd451e17c1 100644
--- a/kernel/params.c
+++ b/kernel/params.c
@@ -15,11 +15,14 @@
     along with this program; if not, write to the Free Software
     Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */
+#include <linux/config.h>
 #include <linux/moduleparam.h>
 #include <linux/kernel.h>
 #include <linux/string.h>
 #include <linux/errno.h>
 #include <linux/module.h>
+#include <linux/device.h>
+#include <linux/err.h>
 
 #if 0
 #define DEBUGP printk
@@ -346,6 +349,394 @@ int param_get_string(char *buffer, struct kernel_param *kp)
 	return strlcpy(buffer, kps->string, kps->maxlen);
 }
 
+/* sysfs output in /sys/modules/XYZ/parameters/ */
+
+extern struct kernel_param __start___param[], __stop___param[];
+
+#define MAX_KBUILD_MODNAME KOBJ_NAME_LEN
+
+struct param_attribute
+{
+	struct attribute attr;
+	struct kernel_param *param;
+};
+
+struct param_kobject
+{
+	struct kobject kobj;
+
+	unsigned int num_attributes;
+	struct param_attribute attr[0];
+};
+
+#define to_param_attr(n) container_of(n, struct param_attribute, attr);
+
+static ssize_t param_attr_show(struct kobject *kobj,
+			       struct attribute *attr,
+			       char *buf)
+{
+	int count;
+	struct param_attribute *attribute = to_param_attr(attr);
+
+	if (!attribute->param->get)
+		return -EPERM;
+
+	count = attribute->param->get(buf, attribute->param);
+	if (count > 0) {
+		strcat(buf, "\n");
+		++count;
+	}
+	return count;
+}
+
+/* sysfs always hands a nul-terminated string in buf.  We rely on that. */
+static ssize_t param_attr_store(struct kobject *kobj,
+				struct attribute *attr,
+				const char *buf, size_t len)
+{
+ 	int err;
+	struct param_attribute *attribute = to_param_attr(attr);
+
+	if (!attribute->param->set)
+		return -EPERM;
+
+	err = attribute->param->set(buf, attribute->param);
+	if (!err)
+		return len;
+	return err;
+}
+
+
+static struct sysfs_ops param_sysfs_ops = {
+	.show = param_attr_show,
+	.store = param_attr_store,
+};
+
+static void param_kobj_release(struct kobject *kobj)
+{
+	kfree(container_of(kobj, struct param_kobject, kobj));
+}
+
+static struct kobj_type param_ktype = {
+	.sysfs_ops =	&param_sysfs_ops,
+	.release =	&param_kobj_release,
+};
+
+static struct kset param_kset = {
+	.subsys =	&module_subsys,
+	.ktype =	&param_ktype,
+};
+
+#ifdef CONFIG_MODULES
+#define __modinit
+#else
+#define __modinit __init
+#endif
+
+/*
+ * param_add_attribute - actually adds an parameter to sysfs
+ * @mod: owner of parameter
+ * @pk: param_kobject the attribute shall be assigned to.
+ *      One per module, one per KBUILD_MODNAME.
+ * @kp: kernel_param to be added
+ * @skip: offset where the parameter name start in kp->name.
+ * Needed for built-in modules
+ *
+ * Fill in data into appropriate &pk->attr[], and create sysfs file.
+ */
+static __modinit int param_add_attribute(struct module *mod,
+					 struct param_kobject *pk,
+					 struct kernel_param *kp,
+					 unsigned int skip)
+{
+	struct param_attribute *a;
+	int err;
+
+	a = &pk->attr[pk->num_attributes];
+	a->attr.name = (char *) &kp->name[skip];
+	a->attr.owner = mod;
+	a->attr.mode = kp->perm;
+	a->param = kp;
+	err = sysfs_create_file(&pk->kobj, &a->attr);
+	if (!err)
+		pk->num_attributes++;
+	return err;
+}
+
+/*
+ * param_sysfs_remove - remove sysfs support for one module or KBUILD_MODNAME
+ * @pk: struct param_kobject which is to be removed
+ *
+ * Called when an error in registration occurs or a module is removed
+ * from the system.
+ */
+static __modinit void param_sysfs_remove(struct param_kobject *pk)
+{
+	unsigned int i;
+	for (i = 0; i < pk->num_attributes; i++)
+		sysfs_remove_file(&pk->kobj,&pk->attr[i].attr);
+
+	/* Calls param_kobj_release */
+	kobject_unregister(&pk->kobj);
+}
+
+
+/*
+ * param_sysfs_setup - setup sysfs support for one module or KBUILD_MODNAME
+ * @mk: struct module_kobject (contains parent kobject)
+ * @kparam: array of struct kernel_param, the actual parameter definitions
+ * @num_params: number of entries in array
+ * @name_skip: offset where the parameter name start in kparam[].name. Needed for built-in "modules"
+ *
+ * Create a kobject for a (per-module) group of parameters, and create files
+ * in sysfs. A pointer to the param_kobject is returned on success,
+ * NULL if there's no parameter to export, or other ERR_PTR(err).
+ */
+static __modinit struct param_kobject *
+param_sysfs_setup(struct module_kobject *mk,
+		  struct kernel_param *kparam,
+		  unsigned int num_params,
+		  unsigned int name_skip)
+{
+	struct param_kobject *pk;
+	unsigned int valid_attrs = 0;
+	unsigned int i;
+	int err;
+
+	for (i=0; i<num_params; i++) {
+		if (kparam[i].perm)
+			valid_attrs++;
+	}
+
+	if (!valid_attrs)
+		return NULL;
+
+	pk = kmalloc(sizeof(struct param_kobject)
+		     + sizeof(struct param_attribute) * valid_attrs,
+		     GFP_KERNEL);
+	if (!pk)
+		return ERR_PTR(-ENOMEM);
+	memset(pk, 0, sizeof(struct param_kobject)
+	       + sizeof(struct param_attribute) * valid_attrs);
+
+	err = kobject_set_name(&pk->kobj, "parameters");
+	if (err)
+		goto out;
+
+	pk->kobj.kset = &param_kset;
+	pk->kobj.parent = &mk->kobj;
+	err = kobject_register(&pk->kobj);
+	if (err)
+		goto out;
+
+	for (i = 0; i < num_params; i++) {
+		if (kparam[i].perm) {
+			err = param_add_attribute(mk->mod, pk,
+						  &kparam[i], name_skip);
+			if (err)
+				goto out_unreg;
+		}
+	}
+
+	return pk;
+
+out_unreg:
+	param_sysfs_remove(pk);
+	return ERR_PTR(err);
+
+out:
+	kfree(pk);
+	return ERR_PTR(err);
+}
+
+
+#ifdef CONFIG_MODULES
+
+/*
+ * module_param_sysfs_setup - setup sysfs support for one module
+ * @mod: module
+ * @kparam: module parameters (array)
+ * @num_params: number of module parameters
+ *
+ * Adds sysfs entries for module parameters, and creates a link from
+ * /sys/module/[mod->name]/parameters to /sys/parameters/[mod->name]/
+ */
+int module_param_sysfs_setup(struct module *mod,
+			     struct kernel_param *kparam,
+			     unsigned int num_params)
+{
+	struct param_kobject *pk;
+
+	pk = param_sysfs_setup(mod->mkobj, kparam, num_params, 0);
+	if (IS_ERR(pk))
+		return PTR_ERR(pk);
+
+	mod->params_kobject = pk;
+	return 0;
+}
+
+/*
+ * module_param_sysfs_remove - remove sysfs support for one module
+ * @mod: module
+ *
+ * Remove sysfs entries for module parameters and the corresponding
+ * kobject.
+ */
+void module_param_sysfs_remove(struct module *mod)
+{
+	if (mod->params_kobject) {
+		param_sysfs_remove(mod->params_kobject);
+		mod->params_kobject = NULL;
+	}
+}
+#endif
+
+/*
+ * kernel_param_sysfs_setup - wrapper for built-in params support
+ */
+static void __init kernel_param_sysfs_setup(const char *name,
+					    struct kernel_param *kparam,
+					    unsigned int num_params,
+					    unsigned int name_skip)
+{
+	struct module_kobject *mk;
+
+	mk = kmalloc(sizeof(struct module_kobject), GFP_KERNEL);
+	memset(mk, 0, sizeof(struct module_kobject));
+
+	mk->mod = THIS_MODULE;
+	kobj_set_kset_s(mk, module_subsys);
+	kobject_set_name(&mk->kobj, name);
+	kobject_register(&mk->kobj);
+
+	/* no need to keep the kobject if no parameter is exported */
+	if (!param_sysfs_setup(mk, kparam, num_params, name_skip))
+		kobject_unregister(&mk->kobj);
+}
+
+/*
+ * param_sysfs_builtin - add contents in /sys/parameters for built-in modules
+ *
+ * Add module_parameters to sysfs for "modules" built into the kernel.
+ *
+ * The "module" name (KBUILD_MODNAME) is stored before a dot, the
+ * "parameter" name is stored behind a dot in kernel_param->name. So,
+ * extract the "module" name for all built-in kernel_param-eters,
+ * and for all who have the same, call kernel_param_sysfs_setup.
+ */
+static void __init param_sysfs_builtin(void)
+{
+	struct kernel_param *kp, *kp_begin = NULL;
+	unsigned int i, name_len, count = 0;
+	char modname[MAX_KBUILD_MODNAME + 1] = "";
+
+	for (i=0; i < __stop___param - __start___param; i++) {
+		char *dot;
+
+		kp = &__start___param[i];
+
+		/* We do not handle args without periods. */
+		dot = memchr(kp->name, '.', MAX_KBUILD_MODNAME);
+		if (!dot) {
+			DEBUGP("couldn't find period in %s\n", kp->name);
+			continue;
+		}
+		name_len = dot - kp->name;
+
+ 		/* new kbuild_modname? */
+		if (strlen(modname) != name_len
+		    || strncmp(modname, kp->name, name_len) != 0) {
+			/* add a new kobject for previous kernel_params. */
+			if (count)
+				kernel_param_sysfs_setup(modname,
+							 kp_begin,
+							 count,
+							 strlen(modname)+1);
+
+			strncpy(modname, kp->name, name_len);
+			modname[name_len] = '\0';
+			count = 0;
+			kp_begin = kp;
+		}
+		count++;
+	}
+
+	/* last kernel_params need to be registered as well */
+	if (count)
+		kernel_param_sysfs_setup(modname, kp_begin, count,
+					 strlen(modname)+1);
+}
+
+
+/* module-related sysfs stuff */
+#ifdef CONFIG_MODULES
+
+#define to_module_attr(n) container_of(n, struct module_attribute, attr);
+#define to_module_kobject(n) container_of(n, struct module_kobject, kobj);
+
+static ssize_t module_attr_show(struct kobject *kobj,
+				struct attribute *attr,
+				char *buf)
+{
+	struct module_attribute *attribute;
+	struct module_kobject *mk;
+	int ret;
+
+	attribute = to_module_attr(attr);
+	mk = to_module_kobject(kobj);
+
+	if (!attribute->show)
+		return -EPERM;
+
+	if (!try_module_get(mk->mod))
+		return -ENODEV;
+
+	ret = attribute->show(mk->mod, buf);
+
+	module_put(mk->mod);
+
+	return ret;
+}
+
+static struct sysfs_ops module_sysfs_ops = {
+	.show = module_attr_show,
+	.store = NULL,
+};
+
+#else
+static struct sysfs_ops module_sysfs_ops = {
+	.show = NULL,
+	.store = NULL,
+};
+#endif
+
+static void module_kobj_release(struct kobject *kobj)
+{
+	kfree(container_of(kobj, struct module_kobject, kobj));
+}
+
+static struct kobj_type module_ktype = {
+	.sysfs_ops =	&module_sysfs_ops,
+	.release =	&module_kobj_release,
+};
+
+decl_subsys(module, &module_ktype, NULL);
+
+/*
+ * param_sysfs_init - wrapper for built-in params support
+ */
+static int __init param_sysfs_init(void)
+{
+	subsystem_register(&module_subsys);
+	kobject_set_name(&param_kset.kobj, "parameters");
+	kset_init(&param_kset);
+
+	param_sysfs_builtin();
+
+	return 0;
+}
+__initcall(param_sysfs_init);
+
 EXPORT_SYMBOL(param_set_byte);
 EXPORT_SYMBOL(param_get_byte);
 EXPORT_SYMBOL(param_set_short);