param: Fix duplicate module prefixes

Instead of insisting each new module_param sysfs entry is unique,
handle the case where it already exists (for builtin modules).

The current code assumes that all identical prefixes are together in
the section: true for normal uses, but not necessarily so if someone
overrides MODULE_PARAM_PREFIX.  More importantly, it's not true with
the new "core_param()" code which uses "kernel" as a prefix.

This simplifies the caller for the builtin case, at a slight loss of
efficiency (we do the lookup every time to see if the directory
exists).

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 141 insertions, 120 deletions

diff --git a/kernel/params.c b/kernel/params.c
index aca07e1a050f..f27c992a4625 100644
--- a/kernel/params.c
+++ b/kernel/params.c
@@ -373,6 +373,8 @@ int param_get_string(char *buffer, struct kernel_param *kp)
 }
 
 /* sysfs output in /sys/modules/XYZ/parameters/ */
+#define to_module_attr(n) container_of(n, struct module_attribute, attr);
+#define to_module_kobject(n) container_of(n, struct module_kobject, kobj);
 
 extern struct kernel_param __start___param[], __stop___param[];
 
@@ -384,6 +386,7 @@ struct param_attribute
 
 struct module_param_attrs
 {
+        unsigned int num;
         struct attribute_group grp;
         struct param_attribute attrs[0];
 };
@@ -434,69 +437,84 @@ static ssize_t param_attr_store(struct module_attribute *mattr,
 
 #ifdef CONFIG_SYSFS
 /*
- * 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"
+ * add_sysfs_param - add a parameter to sysfs
+ * @mk: struct module_kobject
+ * @kparam: the actual parameter definition to add to sysfs
+ * @name: name of parameter
  *
- * 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).
+ * Create a kobject if for a (per-module) parameter if mp NULL, and
+ * create file in sysfs.  Returns an error on out of memory.  Always cleans up
+ * if there's an error.
  */
-static __modinit struct module_param_attrs *
-param_sysfs_setup(struct module_kobject *mk,
-                  struct kernel_param *kparam,
-                  unsigned int num_params,
-                  unsigned int name_skip)
+static __modinit int add_sysfs_param(struct module_kobject *mk,
+                                     struct kernel_param *kp,
+                                     const char *name)
 {
-        struct module_param_attrs *mp;
-        unsigned int valid_attrs = 0;
-        unsigned int i, size[2];
-        struct param_attribute *pattr;
-        struct attribute **gattr;
-        int err;
-
-        for (i=0; i<num_params; i++) {
-                if (kparam[i].perm)
-                        valid_attrs++;
+        struct module_param_attrs *new;
+        struct attribute **attrs;
+        int err, num;
+
+        /* We don't bother calling this with invisible parameters. */
+        BUG_ON(!kp->perm);
+
+        if (!mk->mp) {
+                num = 0;
+                attrs = NULL;
+        } else {
+                num = mk->mp->num;
+                attrs = mk->mp->grp.attrs;
         }
 
-        if (!valid_attrs)
-                return NULL;
-
-        size[0] = ALIGN(sizeof(*mp) +
-                        valid_attrs * sizeof(mp->attrs[0]),
-                        sizeof(mp->grp.attrs[0]));
-        size[1] = (valid_attrs + 1) * sizeof(mp->grp.attrs[0]);
-
-        mp = kzalloc(size[0] + size[1], GFP_KERNEL);
-        if (!mp)
-                return ERR_PTR(-ENOMEM);
+        /* Enlarge. */
+        new = krealloc(mk->mp,
+                       sizeof(*mk->mp) + sizeof(mk->mp->attrs[0]) * (num+1),
+                       GFP_KERNEL);
+        if (!new) {
+                kfree(mk->mp);
+                err = -ENOMEM;
+                goto fail;
+        }
+        attrs = krealloc(attrs, sizeof(new->grp.attrs[0])*(num+2), GFP_KERNEL);
+        if (!attrs) {
+                err = -ENOMEM;
+                goto fail_free_new;
+        }
 
-        mp->grp.name = "parameters";
-        mp->grp.attrs = (void *)mp + size[0];
+        /* Sysfs wants everything zeroed. */
+        memset(new, 0, sizeof(*new));
+        memset(&new->attrs[num], 0, sizeof(new->attrs[num]));
+        memset(&attrs[num], 0, sizeof(attrs[num]));
+        new->grp.name = "parameters";
+        new->grp.attrs = attrs;
+
+        /* Tack new one on the end. */
+        new->attrs[num].param = kp;
+        new->attrs[num].mattr.show = param_attr_show;
+        new->attrs[num].mattr.store = param_attr_store;
+        new->attrs[num].mattr.attr.name = (char *)name;
+        new->attrs[num].mattr.attr.mode = kp->perm;
+        new->num = num+1;
+
+        /* Fix up all the pointers, since krealloc can move us */
+        for (num = 0; num < new->num; num++)
+                new->grp.attrs[num] = &new->attrs[num].mattr.attr;
+        new->grp.attrs[num] = NULL;
+
+        mk->mp = new;
+        return 0;
 
-        pattr = &mp->attrs[0];
-        gattr = &mp->grp.attrs[0];
-        for (i = 0; i < num_params; i++) {
-                struct kernel_param *kp = &kparam[i];
-                if (kp->perm) {
-                        pattr->param = kp;
-                        pattr->mattr.show = param_attr_show;
-                        pattr->mattr.store = param_attr_store;
-                        pattr->mattr.attr.name = (char *)&kp->name[name_skip];
-                        pattr->mattr.attr.mode = kp->perm;
-                        *(gattr++) = &(pattr++)->mattr.attr;
-                }
-        }
-        *gattr = NULL;
+fail_free_new:
+        kfree(new);
+fail:
+        mk->mp = NULL;
+        return err;
+}
 
-        if ((err = sysfs_create_group(&mk->kobj, &mp->grp))) {
-                kfree(mp);
-                return ERR_PTR(err);
-        }
-        return mp;
+static void free_module_param_attrs(struct module_kobject *mk)
+{
+        kfree(mk->mp->grp.attrs);
+        kfree(mk->mp);
+        mk->mp = NULL;
 }
 
 #ifdef CONFIG_MODULES
@@ -506,21 +524,33 @@ param_sysfs_setup(struct module_kobject *mk,
  * @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]/
+ * Adds sysfs entries for module parameters under
+ * /sys/module/[mod->name]/parameters/
  */
 int module_param_sysfs_setup(struct module *mod,
                              struct kernel_param *kparam,
                              unsigned int num_params)
 {
-        struct module_param_attrs *mp;
+        int i, err;
+        bool params = false;
+
+        for (i = 0; i < num_params; i++) {
+                if (kparam[i].perm == 0)
+                        continue;
+                err = add_sysfs_param(&mod->mkobj, &kparam[i], kparam[i].name);
+                if (err)
+                        return err;
+                params = true;
+        }
 
-        mp = param_sysfs_setup(&mod->mkobj, kparam, num_params, 0);
-        if (IS_ERR(mp))
-                return PTR_ERR(mp);
+        if (!params)
+                return 0;
 
-        mod->param_attrs = mp;
-        return 0;
+        /* Create the param group. */
+        err = sysfs_create_group(&mod->mkobj.kobj, &mod->mkobj.mp->grp);
+        if (err)
+                free_module_param_attrs(&mod->mkobj);
+        return err;
 }
 
 /*
@@ -532,43 +562,55 @@ int module_param_sysfs_setup(struct module *mod,
  */
 void module_param_sysfs_remove(struct module *mod)
 {
-        if (mod->param_attrs) {
-                sysfs_remove_group(&mod->mkobj.kobj,
-                                   &mod->param_attrs->grp);
+        if (mod->mkobj.mp) {
+                sysfs_remove_group(&mod->mkobj.kobj, &mod->mkobj.mp->grp);
                 /* We are positive that no one is using any param
                  * attrs at this point.  Deallocate immediately. */
-                kfree(mod->param_attrs);
-                mod->param_attrs = NULL;
+                free_module_param_attrs(&mod->mkobj);
         }
 }
 #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)
+static void __init kernel_add_sysfs_param(const char *name,
+                                          struct kernel_param *kparam,
+                                          unsigned int name_skip)
 {
         struct module_kobject *mk;
-        int ret;
+        struct kobject *kobj;
+        int err;
 
-        mk = kzalloc(sizeof(struct module_kobject), GFP_KERNEL);
-        BUG_ON(!mk);
-
-        mk->mod = THIS_MODULE;
-        mk->kobj.kset = module_kset;
-        ret = kobject_init_and_add(&mk->kobj, &module_ktype, NULL, "%s", name);
-        if (ret) {
-                kobject_put(&mk->kobj);
-                printk(KERN_ERR "Module '%s' failed to be added to sysfs, "
-                      "error number %d\n", name, ret);
-                printk(KERN_ERR "The system will be unstable now.\n");
-                return;
+        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);
+
+                mk->mod = THIS_MODULE;
+                mk->kobj.kset = module_kset;
+                err = kobject_init_and_add(&mk->kobj, &module_ktype, NULL,
+                                           "%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;
+                }
+                /* So that exit path is even. */
+                kobject_get(&mk->kobj);
         }
-        param_sysfs_setup(mk, kparam, num_params, name_skip);
+
+        /* These should not fail at boot. */
+        err = add_sysfs_param(mk, kparam, kparam->name + name_skip);
+        BUG_ON(err);
+        err = sysfs_create_group(&mk->kobj, &mk->mp->grp);
+        BUG_ON(err);
         kobject_uevent(&mk->kobj, KOBJ_ADD);
+        kobject_put(&mk->kobj);
 }
 
 /*
@@ -579,18 +621,19 @@ static void __init kernel_param_sysfs_setup(const char *name,
  * 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.
+ * and for all who have the same, call kernel_add_sysfs_param.
  */
 static void __init param_sysfs_builtin(void)
 {
-        struct kernel_param *kp, *kp_begin = NULL;
-        unsigned int i, name_len, count = 0;
-        char modname[MODULE_NAME_LEN] = "";
+        struct kernel_param *kp;
+        unsigned int name_len;
+        char modname[MODULE_NAME_LEN];
 
-        for (i=0; i < __stop___param - __start___param; i++) {
+        for (kp = __start___param; kp < __stop___param; kp++) {
                 char *dot;
 
-                kp = &__start___param[i];
+                if (kp->perm == 0)
+                        continue;
 
                 dot = strchr(kp->name, '.');
                 if (!dot) {
@@ -599,37 +642,15 @@ static void __init param_sysfs_builtin(void)
                         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++;
+                strncpy(modname, kp->name, name_len);
+                modname[name_len] = '\0';
+                kernel_add_sysfs_param(modname, kp, name_len+1);
         }
-
-        /* 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 */
 
-#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)